Antioxidant defenses in the preterm lung: role for hypoxia-inducible factors in BPD?

Toxicology and Applied Pharmacology 203 (2005) 177 – 188 www.elsevier.com/locate/ytaap

Review

Antioxidant defenses in the preterm lung: role for hypoxia-inducible factors in BPD? Tiina M. Asikainen*, Carl W. White Department of Pediatrics, National Jewish Medical and Research Center, Denver, CO 80206, USA Received 7 June 2004; accepted 22 July 2004 Available online 27 October 2004

Abstract Pulmonary antioxidants and their therapeutic implications have been extensively studied during past decades. The purpose of this review is to briefly summarize the key findings of these studies as well as to elaborate on some novel approaches with respect to potential preventive treatments for neonatal chronic lung disease bronchopulmonary dysplasia (BPD). Such new ideas include, for example, modification of transcription factors governing the hypoxic response pathways, important in angiogenesis, cell survival, and glycolytic responses. The fundamental strategy behind that approach is that fetal lung normally develops under hypoxic conditions and that this hypoxic, growth-favoring environment is interrupted by a premature birth. Importantly, during fetal lung development, alveolar development appears to be dependent on vascular development. Therefore, enhancement of signaling factors that occur during hypoxic fetal life (dcontinued fetal life ex uteroT), including angiogenic responses, could potentially lead to improved lung growth and thereby alleviate the alveolar and vascular hypoplasia characteristic of BPD. D 2004 Elsevier Inc. All rights reserved. Keywords: Prematurity; Respiratory distress syndrome; Bronchopulmonary dysplasia; Hypoxia-inducible factors; Antioxidant enzymes; Vascular endothelial growth factor

Contents Background . . . . . . . . . . Lung development . . . . . Oxygen-induced lung injury Antioxidant defenses . . . .

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Abbreviations: Ang-1 to -4, angiopoietin 1 to 4; AOE(s), antioxidant enzyme(s); ARD-1, HIF acetylase; ARNT, aryl hydrocarbon nuclear translocator; BPD, bronchopulmonary dysplasia; CAT, catalase; CTAD and NTAD, C- and N-terminal transactivation domain, respectively; CuZnSOD, copper/zinc SOD; DFO, deferoxamine; DMOG, dimethyloxaloylglycine; ECSOD, extracellular SOD; EPO, erythropoietin; ET-1, endothelin 1; FIH, factor inhibiting HIF; Flt-1, fms-like tyrosine kinase 1; g-GCL, gamma glutamate-cysteine ligase; Glut-1, glucose transporter 1; G6PDH, glucose 6-phosphate dehydrogenase; GPx, glutathione peroxidase; GR, glutathione reductase; GSH, glutathione; g-GT, gamma glutamyl transpeptidase; HIF-1a and HIF-2a, hypoxia-inducible factor 1 and 2 alpha, respectively; HK-II, hexokinase II; HO, heme oxygenase; HRE, hypoxia response element; IGF-1, insulin-like growth factor 1; KDR/Flk-1, kinase insert domaincontaining receptor/fetal liver kinase 1; MnSOD, manganese SOD; NOS-2, nitric oxide synthase 2; PDGF, platelet derived growth factor; PECAM-1, platelet endothelial cell adhesion molecule 1; PHD(s), prolyl 4-hydroxylase(s); pVHL, product of von Hippel–Lindau factor; RDS, respiratory distress syndrome; ROS, reactive oxygen species; SOD, superoxide dismutase; Tie-2, angiopoietin receptor; TPx, thioredoxin peroxidase; TR, thioredoxin reductase; Trx, thioredoxin; Ub, ubiquitin; VEGF, vascular endothelial growth factor; XOR, xanthine oxidoreductase. * Corresponding author. Department of Pediatrics, National Jewish Medical and Research Center, Room D-301, 1400 Jackson Street, Denver, CO 80206. Fax: +1 303 398 1851. E-mail address: [email protected] (T.M. Asikainen). 0041-008X/$ - see front matter D 2004 Elsevier Inc. All rights reserved. doi:10.1016/j.taap.2004.07.008

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Pulmonary antioxidant defenses during development . . . . . . . . Pulmonary antioxidant defenses in hyperoxia . . . . . . . . . . . . Respiratory distress syndrome and bronchopulmonary dysplasia . . Antioxidant therapy . . . . . . . . . . . . . . . . . . . . . . . . . Role of hypoxia-inducible factors and novel approaches to consider development of BPD. . . . . . . . . . . . . . . . . . . . . . . . . Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Background

Oxygen-induced lung injury

Lung development

Oxygen toxicity to cells is mediated through reactive oxygen and nitrogen species (ROS and RNS, respectively) that are generated endogenously by several mechanisms under both physiological and pathological conditions (Fig. 1) (Freeman and Crapo, 1982; Kinnula et al., 1995; Radi, 2004). Furthermore, in hyperoxia, superoxide production from the mitochondrial respiratory chain is amplified (Freeman and Crapo, 1981). Some experimental data also suggest functional roles for optimal levels of ROS in, for example, signaling pathways regulating cell proliferation and differentiation (Finkel, 1998; Thannickal and Fanburg, 2000). The anatomical location of lung tissue brings it into direct contact with inhaled oxygen, making the lung cells primary targets for oxygen-induced injury. The degree of oxygen-induced damage depends on oxygen concentration and length of exposure, as has previously been described in detail (Crapo, 1986; Crapo et al., 1980). In general, oxygen concentrations more than 95% for over 3–7 days are lethal for adult animals (Frank, 1991) that die with signs of progressive respiratory distress (Crapo et al., 1980). Briefly, the characteristic morphological changes that occur in a distinct temporal sequence include accumulation of inflammatory cells into the intravascular and interstitial spaces, damage to capillary endothelium leading to pericapillary edema, morphological changes in type I and II pneumocytes with progressive loss of type I cells, and a reactive hyperplasia of type II cells (reviewed also in Asikainen and White, 2004). Most species, however, can endure sublethal concentrations of oxygen, that is, 50–85% oxygen, for extended periods of time, usually several weeks (Coursin et al., 1987; Holm et al., 1987). Though these animals outlive exposure to sublethal hyperoxia, they still develop a lung injury, the histopathological manifestations of which closely resemble those caused by lethal hyperoxia. Clinically, the main difference is with respect to onset and progression of lung injury. Histopathologically, exposure to sublethal oxygen concentrations is different from lethal hyperoxia in that it is characterized by increased proliferation of type II pneumocytes and fibroblasts, and by increased deposition of collagen into the interstitium, leading to interstitial fibrosis and development of secondary pulmonary hypertension

Lung growth involves five stages commencing in the fetus and continuing postnatally. Several factors, including genetic, developmental, and environmental, play a role in lung development, and a disturbance in any of these can lead to various pulmonary abnormalities. The main stages of human lung development consist of (1) embryonic [(0–7 gestational weeks (gest. wk)], (2) pseudoglandular (7–17 gest. wk), (3) canalicular (17–27 gest. wk), (4) saccular (28–36 gest. wk), and (5) alveolar phase (36 gest. wk to 3 years postnatally) (Burri, 1984; Inselman and Mellins, 1981). The capacity for pulmonary respiration is one of the main determinants for survival of a preterm neonate. This usually occurs in the canalicular period after 24 gestational weeks, when the blood–gas barrier has been formed and surfactant synthesis begins. The preterm babies born in the late canalicular or early saccular stage are at risk for developing respiratory distress syndrome (RDS), bronchopulmonary dysplasia (BPD), and lung hypoplasia, the pathogenesis of all of which are multifactorial (Jobe and Bancalari, 2001). The lung develops as an evagination from the ventral wall of the primitive foregut endoderm. Epithelial cells of the primitive foregut invade the surrounding mesenchyme and branch forming the tracheobronchial tree. Simultaneously, the pulmonary arteries derive from the sixth aortic arches and accompany the branching airways (Burri, 1984). The mature lung vasculature develops by both vasculogenesis (formation of new blood vessels from angioblasts) and angiogenesis (sprouting of new vessels from existing ones). During recent years, several investigations have been directed at discovering factors governing lung vascular development (Stenmark and Gebb, 2003). For example, pulmonary vessel development is dependent on epithelial–mesenchymal interactions (Gebb and Shannon, 2000; Shannon and Hyatt, 2004). Further, experimental studies have shown that angiogenesis and alveolarization are interlocked processes such that inhibition of angiogenesis leads to impaired development of alveoli and alveolar hypoplasia (Jakkula et al., 2000).

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Fig. 1. The most important intra- and extracellular (I and E, respectively) sources of free radicals and enzymatic and non-enzymatic antioxidant defense mechanisms (antioxidant defenses shown in bold). CAT, catalase; CuZnSOD, copper–zinc superoxide dismutase; Cys, cysteine; ECSOD, extracellular superoxide dismutase; g-GCL, gamma glutamate-cysteine ligase; Gly, glycine; G6PDH, glucose 6-phosphate dehydrogenase; GPx, glutathione peroxidase; GR, glutathione reductase; GS, glutathione synthetase; GSH, reduced glutathione; GSSG, oxidized glutathione; g-GT, gamma glutamyl transpeptidase; H2O2, hydrogen peroxide; HO-1, hemeoxygenase 1; MnSOD, manganese superoxide dismutase; NADP, nicotinamide adenine dinucleotide phosphate; NO, nitric oxide; O2 , superoxide; OH , hydroxyl radical; ONOO , peroxynitrite; TPx, thioredoxin peroxidase; TR, thioredoxin reductase; Trx, thioredoxin; Trx-S2, oxidized thioredoxin; Trx-(SH)2, reduced thioredoxin; XOR, xanthine oxidoreductase; *, in phagocytic cells; **, in neutrophils.

S

S

S

(Crapo, 1986; Crapo et al., 1980; Jones et al., 1985; Wilson et al., 1985). Antioxidant defenses To avoid ROS-induced injury to tissues, a complex antioxidant system, consisting of both enzymatic and nonenzymatic defenses, has evolved (Fig. 1). Traditionally, antioxidants have been defined as substances that prevent the formation of ROS or other oxidants, scavenge them, or repair the damage that they cause (Sies, 1991). The most important antioxidant defenses include (a) classical antioxidant enzymes (AOEs), such as the manganese, copper– zinc, and extracellular superoxide dismutases (MnSOD, CuZnSOD, ECSOD, respectively), glutathione and thio-

redoxin peroxidases (GPx and TPx, respectively) and their associated reductases glutathione and thioredoxin reductases (GR and TR, respectively), (b) glutathione (GSH) and thioredoxin (Trx), (c) heme oxygenases (HOs), and (d) numerous small molecular weight antioxidants, including vitamins C and E (Deneke, 2000; Halliwell, 1996; Holmgren, 2000; Kinnula and Crapo, 2003). The continuous production of ROS has to be counterbalanced with a similar rate of their consumption by antioxidants. Potential for ROS-mediated toxicity exists if the production of ROS exceeds the antioxidant capacity of the cell, called oxidative stress (Freeman and Crapo, 1982; Kinnula et al., 1995; Sies, 1991). Some agents, such as nitric oxide, can act as both a radical producer and an antioxidant (for review, see Radi, 2004).

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Table 1 A summary of studies exploring the developmental profiles of pulmonary antioxidants in various species during ontogenesis Antioxidant

Species

Gestational age

Result

Reference

CuZnSOD, GPx-1 G6PDH, MnSOD, CAT, CuZnSOD, GPx MnSOD, GPx CuZnSOD MnSOD, CAT, CuZnSOD, GPx TPx-1, TPx-2 SOD, CAT, GPx MnSOD, CAT, GPx CuZnSOD SOD, CAT, GPx SOD, CAT, GPx MnSOD, CuZnSOD Trx, TPx-1, TR SOD CuZnSOD MnSOD, CuZnSOD SODs, CAT, GPx MnSOD, CAT, CuZnSOD, GPx g-GCL GPx

Mouse Rat Rat Rat Rat Rat Guinea pig Guinea pig Guinea pig Guinea pig Lamb Baboon Baboon Human Human Human Human Human Human Human

3. trimester 3. trimester 3. trimester 3. trimester 3. trimester 3. trimester, pp 3. trimester, pp 3. trimester, pp 3. trimester 3. trimester 3. trimester 3. trimester 3. trimester 2.-3. trimester 2-3. trimester 2.-3. trimester 2.-3. trimester 2.-3. trimester 2.-3. trimester 2.-3. trimester

Increased Increased Unchanged Increased Increased Increased, Decreased or increased Increased Increased, Decreased Decreased Increased Increased Increased or decreased Unchanged Increased Unchanged Increased Increased or unchanged Increased or unchanged Unchanged Unchanged

de Haan et al., 1994 Tanswell and Freeman, 1984 Clerch and Massaro, 1992a Hass and Massaro, 1987 Hayashibe et al., 1990 Kim et al., 2001 Rickett and Kelly, 1990 Yuan et al., 1996 Yuan et al., 1996 Sosenko and Frank, 1987 Walther et al., 1991 Morton et al., 1999 Das et al., 1999, 2001 Autor et al., 1976 Strange et al., 1988 Dobashi et al., 1993 McElroy et al., 1992 Asikainen et al., 1998, 2001 Levonen et al., 2000 Fryer et al., 1986

CAT, catalase; CuZnSOD, copper/zinc superoxide dismutase; g-GCL, gamma glutamate-cysteine ligase; G6PDH, glucose 6-phosphate dehydrogenase; GPx, glutathione peroxidase; MnSOD, manganese superoxide dismutase; pp, postpartum; SOD, superoxide dismutase; TPx, thioredoxin peroxidase; TR, thioredoxin reductase; Trx, thioredoxin.

Pulmonary antioxidant defenses during development The maturation of pulmonary surfactant system during the third trimester is of critical importance to the potential survival of a very preterm neonate. Importantly, the expression of most AOEs is enhanced during that same period of time (Table 1), as if in preparation for the imminent birth. The variation of results with the same enzymes in Table 1 may relate to whether the authors studied mRNA, immunoreactive protein, or enzyme activity levels, and may also be due to differences in methodology. In addition, the level at which AOEs are regulated in late gestation varies between enzymes (Clerch and Massaro, 1992a). Moreover, the developmentally regulated, redox-sensitive mRNA-bind-

ing proteins for MnSOD and CAT add another layer of complexity to the regulation of AOEs during development (Clerch and Massaro, 1992b; Fazzone et al., 1993). Pulmonary antioxidant defenses in hyperoxia The regulation of pulmonary AOEs in hyperoxia differs between animal species (Table 2) and also among different age groups within the same species (Frank, 1991; Yam et al., 1978). For example, term newborn pups of mice, rats, and rabbits are capable of increasing AOE activities when challenged with hyperoxia and subsequently survive for longer periods of time than adults of the same species (Frank, 1991). However, neonatal guinea pigs and hamsters show no

Table 2 A summary of studies characterizing the expression of pulmonary antioxidant enzymes in preterm and term neonates of various species in hyperoxia Antioxidant

Species

Neonate

Result

Reference

SOD, GPx, GR, GSH, G6PDH SOD, CAT, GPx MnSOD, CAT, GPx CuZnSOD CuZnSOD, CAT, GPx SOD, CAT, GPx SOD, CAT, GPx SOD, CAT, GPx, G6PDH MnSOD, CuZnSOD MnSOD Trx, TPx, TR MnSOD MnSOD, CuZnSOD MnSOD

Rat Rat, mouse, rabbit Rat Rat Guinea pig Guinea pig Rabbit Baboon Baboon Baboon Human Human Human

Term Term Term Preterm Term Preterm Preterm Preterm Preterm Preterm Preterm, term Preterm Preterm

Increased Increased Increased Increased Unchanged Increased Unchanged Decreased/unchanged Increased Increased or unchanged Unchanged or increased Unchanged Increased

Yam et al., 1978 Frank et al., 1978 Clerch and Massaro, 1992a Chen et al., 1994 Frank et al., 1978 Sosenko and Frank, 1987 Frank and Sosenko, 1991 Morton et al., 1999 Clerch et al., 1996 Das et al., 1999, 2001 Asikainen et al., 2001 Strange et al., 1990 Dobashi et al., 1993

CAT, catalase; CuZnSOD, copper/zinc superoxide dismutase; g-GCL, gamma glutamate-cysteine ligase; G6PDH, glucose 6-phosphate dehydrogenase; GPx, glutathione peroxidase; MnSOD, manganese superoxide dismutase; pp, postpartum; SOD, superoxide dismutase; TPx, thioredoxin peroxidase; TR, thioredoxin reductase; Trx, thioredoxin.

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surfactant system. RDS is characterized by decreased lung volumes and impaired gas exchange resulting in hypoxemia and necessitating the use of ventilatory therapy with inhaled, higher than atmospheric concentrations of oxygen. Oxygen treatment, however, is a dual blessing. Although it is often life-saving, it leaves the neonates at further risk of developing other complications, such as BPD, also called chronic lung disease of infancy (Jobe and Bancalari, 2001). The body of data from several extensive investigations supports the role of oxygen toxicity in the pathogenesis of BPD (Coalson et al., 1992; Crapo, 1986; Frank, 1992; Margraf et al., 1991; Pitka¨nen et al., 1990; Saugstad, 1998; Smith et al., 1993; Varsila et al., 1995). In addition to inhaled oxygen treatment, preterm and term babies with hypoxemic respiratory failure and persistent pulmonary hypertension are often treated with inhaled nitric oxide, a selective pulmonary vasodilator, to improve oxygenation (Kinsella et al., 1999). When first described nearly 40 years ago, BPD was described as oxygen dependency for over 28 days and persistent increased densities on chest radiographs (Northway et al., 1967). Thereafter, the definition has been modified due to altered clinical course and histopathological findings in dthe modern BPDT (Bancalari et al., 2003; Jobe and Bancalari, 2001; Shennan et al., 1988). One hundred percent oxygen is no longer used in the treatment of these babies unless necessary for survival. With the use of lower oxygen concentrations coupled with less traumatic ventilatory techniques, the histopathological features of BPD have also changed. Nevertheless, lung injury still develops but the hallmarks of the new BPD are vascular and alveolar

adaptive increases in AOE expression in hyperoxia and die as the respective parent animals (Frank, 1991). Indeed, numerous experimental models have demonstrated the importance of increased expression of AOEs, especially that of the mitochondrial MnSOD, to the development of tolerance to hyperoxia (Clerch and Massaro, 1993; Tsan et al., 1990; White and Ghezzi, 1989). This appears logical, as the mitochondrial respiratory chain is the main source of superoxide production in hyperoxia (Freeman and Crapo, 1981). Respiratory distress syndrome and bronchopulmonary dysplasia As summarized in Table 2, preterm neonates of some, but not all, species show rapid increases in expression of AOEs when challenged with hyperoxia and develop a relative tolerance to hyperoxia (Chen et al., 1994; Sosenko and Frank, 1987). With respect to human and other primate preterm neonates, both increased and unchanged levels of AOEs have been found (Table 2). The lack of AOEs due to developmental regulation as well as the possible inability to upregulate them in response to hyperoxia may play a critical role in the development of oxygen-induced lung injury in the preterm neonates. In addition to AOEs, other antioxidants, such as GSH, are lower in preterm neonates as compared with term infants (Jain et al., 1995). The preterm baby encounters relative oxidative stress at birth when exposed to several-fold higher oxygen concentrations than in utero. In addition, many very preterm babies are affected by RDS (previously also called hyaline membrane disease) due to immaturity of the pulmonary

Table 3 Clinical investigations assessing the effects of various antioxidants and steroids in preventing bronchopulmonary dysplasia in human preterm neonates Compound

Weight/gestational week

Route of administration

Result

Reference

Glucocorticoids Corticosteroids

Varying gestational ages Varying gestational ages

Maternal i.v.

Crowley, 2000 Halliday and Ehrenkranz, 2001

TRH F corticosteroids

b30 gestation wk

Maternal

Reduced mortality, RDS, and IVH Decreased BPD and death, increased GI complications, possible severe adverse neurological effects No effect on RDS, BPD, or death

rhCuZnSOD

b1300 g

i.t.

NAC Selenium Vitamin A

b1000 g b1500 g b800 g

i.v. i.v., p.o. i.m.

Vitamin E

b1500 g

p.o., i.m.

Nitric oxide

b34 gestation wk

Inhaled

No effect on death or BPD, but improved long-term pulmonary and neurological outcome No effect on BPD or death No effect on oxygen dependency Corrected vitamin A deficiency and modestly decreased the risk of BPD No effect on BPD or death Improved oxygenation, decreased* or unchanged** incidence of BPD and death

Ballard et al., 1998, Crowther et al., 2004 Davis et al., 1997, 2000, 2003, Suresh et al., 2001 Ahola et al., 2003 Darlow and Graham, 2000 Tyson et al., 1999 Darlow et al., 2000 Watts et al., 1991, Ehrenkranz et al., 1982 Finer and Barrington, 2001, Kinsella et al., 1999**, Schreiber et al., 2003*

BPD, bronchopulmonary dysplasia; GI, gastrointestinal; i.m., intra muscular; i.t., intra tracheal; i.v., intra venous; IVH, intraventricular hemorrhage; NAC, N-acetylcysteine; p.o., per orum; rhCuZnSOD, recombinant copper/zinc superoxide dismutase; RDS, respiratory distress syndrome; TRH, thyrotropin releasing hormone.

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Fig. 2. The most important signaling pathways regulated by HIFs. Ang-1 to -4, angiopoietin 1 to 4; Flt-1, fms-like tyrosine kinase 1; EPO, erythropoietin; ET-1, endothelin 1; Glut-1, glucose transporter 1; HIFs, hypoxia-inducible factors 1a and 2a; HK-II, hexokinase II; IGF-2, insulin-like growth factor; IGFbp-1 to -3, IGF binding protein 1 to 3; KDR/Flk-1, kinase insert domain-containing receptor/fetal liver kinase 1; LDH-A, lactate dehydrogenase A; NOS-2, nitric oxide synthase 2; PDGF, platelet derived growth factor; PI3K, phosphatidyl inositol 3-kinase; Tie-2, angiopoietin receptor; VEGF, vascular endothelial growth factor.

hypoplasia rather than massive interstitial fibrosis (Abman, 2001; Coalson et al., 1999).

Role of hypoxia-inducible factors and novel approaches to consider in future treatment or prevention regimens for development of BPD

Antioxidant therapy Pulmonary antioxidants and their therapeutic implications have been extensively studied during past decades (for reviews on topic, see Asikainen and White, in press; Chang et al., 2003; Davis, 1998; Jankov et al., 2001). An ideal antioxidant therapeutic agent, either natural or synthetic, should have good bioavailability, and it should be potent in penetrating to site of action and efficient in scavenging appropriate radical species. The agent should be stable, nontoxic, nonimmunogenic, and preferably inexpensive. Importantly, it should allow essential developmental and healing processes to proceed. Classical antioxidant therapy to prevent or ameliorate BPD has been based on the assumption that a preterm neonate is deficient in AOEs because of (a) developmental regulation of AOEs, (b) inability to upregulate AOEs in response to hyperoxia, and (c) overpowering oxidative stress due to treatment of the clinical condition. Toward this goal, several types of antioxidants, including, for example, classical AOEs, catalytic antioxidants and antibodies, thiol-based antioxidants, vitamins, and lazaroids, have been tested in experimental models both in vitro and in vivo (Asikainen and White, in press). Some of these approaches have also been tested in clinical trials (Table 3). Out of the potential therapies listed in Table 3, antenatal glucocorticoid treatment to hasten surfactant maturation remains the only clearly favorable therapy routinely given in the case of impending labor. Inhaled nitric oxide treatment also carries many advantageous effects in improving oxygenation in preterm and term neonates with persistent pulmonary hypertension (Kinsella and Abman, 2000) and recently has also been associated with decreased incidence of BPD and death (Schreiber et al., 2003).

Modification of certain transcription and growth factors may provide a valuable tool for enhancing vascular and alveolar development in the preterm lung. One group of such potential transcription factors is the hypoxia-inducible factors (HIFs). HIFs have also been called master regulators because of their involvement in several important pathways (Fig. 2), such as angiogenic, glycolytic, and survival pathways (Bruick, 2003; Pugh and Ratcliffe, 2003; Semenza, 1998; Sowter et al., 2003). Fetal lung develops under hypoxic conditions and hypoxia favors fetal lung growth ex vivo as compared with ambient oxygen tension (Stenmark and Gebb, 2003). In addition to the HIFs, other factors important for lung development, such as Rho–Rho kinase, are activated by hypoxia (McMurtry et al., 2003). Further, nuclear HIF-1a DNA binding is higher in 3% oxygen versus 21% or 95% oxygen in fetal rat lung epithelial cells (Haddad and Land, 2000). Based on this background, a premature birth could be anticipated to cause a rapid degradation of HIFs and other factors. In fact, several angiogenic growth factors, all downstream targets of HIFs (Fig. 2), appear altered in lungs of patients with RDS and BPD. For example, human preterm neonates with RDS have diminished levels of pulmonary vascular endothelial growth factor (VEGF) as compared with age-matched controls (Lassus et al., 2001). In addition, some, but not all, studies report decreased platelet endothelial cell adhesion molecule 1 (PECAM-1), VEGF, fms-like tyrosine kinase 1, (Flt-1, also called VEGF receptor 1), and angiopoietin receptor Tie-2 in the lungs of human or baboon newborns with BPD (Bhatt et al., 2001; Coalson et al., 1999; Lassus et al., 2001; Maniscalco et al., 2002). Pulmonary insulin-like growth factor 1 (IGF-1) and

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its receptor (IGF-1R), which are important for normal fetal lung vascularization (Han et al., 2003), are upregulated in human patients with BPD (Chetty et al., 2004). However, although the above studies link reduced protein levels of several important angiogenic factors with RDS or BPD, a direct causal relationship has not been demonstrated and in some cases the changes may be a result of another injury altering cellular populations or phenotypes. During human fetal development, HIF-1a mRNA is expressed at highest levels in the brain, heart, kidney, and lungs (Madan et al., 2002), but HIF proteins have not been assessed. Gene ablation models have confirmed that HIFs are critical for fetal development. Complete genetic inactivation of Hif1a (Iyer et al., 1998; Yu et al., 1999) or Epas1 (encoding HIF-2a) (Compernolle et al., 2002; Scortegagna et al., 2003) leads to embryonic lethality at midgestation or at term. The homozygous Hif1a knockout mice die with cardiovascular malformations, mesenchymal cell death, and neural tube defects (Iyer et al., 1998). The heterozygous Hif1a mice develop normally but show abnormal adaptive responses to chronic hypoxia (Yu et al., 1999). Two different knockout mouse models have been developed for Epas1 (Compernolle et al., 2002; Scortegagna et al., 2003). Fifty percent of the Epas1 null mutant mice generated by Compernolle et al. die of cardiac failure at E13.5 and the surviving mice succumb to respiratory failure soon after term birth. The latter group manifests abnormal surfactant production and reduced VEGF levels in alveolar epithelial cells (Compernolle et al., 2002). The homozygous Epas1 mouse by Scortegagna et al. show reduced embryonic survival and reduced life span from 3 weeks of postnatal age onward. These mice develop a multiorgan failure consistent with mitochondrial disease (Scortegagna et al., 2003). The phenotype of Epas1 / mouse model exhibits striking similarities to that of Sod2 / (Sod2 encodes MnSOD), with shared pathological features, such as increased embryonic lethality, decreased life span, cardiac hypertrophy, hepatic steatosis, retinopathy, and anemia (Lebovitz et al., 1996; Li et al., 1995; Scortegagna et al., 2003). Interestingly, Epas1 / mice show increased oxidative stress in tissues, yet the gene expression of AOE including MnSOD, CuZnSOD, CAT, and GPx is diminished when compared with wild-type mice. However, in transfection analyses, HIF-2a could transactivate the promoters of these AOEs. Furthermore, some pathological features of Epas1 / mice could be partially rescued by treatment with manganese tetrakis-(4-benzoic acid) porphyrin (MnTBAP), a catalytic antioxidant (Scortegagna et al., 2003). Moreover, the activity of redox-sensitive HIF can be induced by oxidative stress (Lando et al., 2000; Wang et al., 1995). These data suggest a possible role for HIF-2a as a modifier of expression of AOEs. HIF-1 is a heterodimer composed of the helix-loop-helix/ Per-Arnt-Sim protein HIF-1a and the aryl hydrocarbon nuclear translocator (ARNT), also known as HIF-1h (Lando et al., 2000). ARNT serves as a dimerization partner for

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Fig. 3. Regulation of HIF stability. (A) The stability of the HIF-1a subunit is regulated by PHD, FIH, and ARD enzymes that hydroxylate or acetylate certain amino acids in the ODD or CTAD of HIF-1a. The hydroxylated or acetylated HIF-1a is recognized by pVHL leading to ubiquitination of HIF1a and destruction by the proteosomal pathway. PHD enzymes require certain cosubstrates and cofactors, such as oxygen, 2-OG, iron, and ascorbate, for full activity. (B) The activity of PHD enzymes is inhibited in hypoxia and in response to pharmacological inhibitors such as iron chelator DFO or 2-OG analog DMOG. This leads to stabilization and subsequent translocation of HIF-1a into the nucleus where it dimerizes with ARNT and transcriptional enhancer p300. HIF-1 complex then binds to HREs of target genes promoting their transcription. ARD-1, HIF acetylase; ARNT, aryl hydrocarbon receptor nuclear translocator; CTAD and NTAD, C- and Nterminal transactivation domain, respectively; DFO, deferoxamine, DMOG, dimethyloxaloylglycine; FIH, factor inhibiting HIF; HIF, hypoxia-inducible factor; HRE; hypoxia response element; 2-OG, 2-oxoglutarate; PHD, prolyl 4-hydroxylase; pVHL, product of von Hippel–Lindau factor; Ub, ubiquitin.

HIF-1a and HIF-2a, as well as for other mammalian proteins (Gradin et al., 1996). HIF-1a and HIF-2a proteins are regulated by oxygen concentrations such that their levels increase with decreasing oxygen (O’Rourke et al., 1999; Wiesener et al., 1998). Stabilized and activated HIF-1a accumulates in the nucleus, binds to ARNT, and then binds

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to specific DNA sequences called hypoxia response elements (HRE) of target genes leading to increased transcription of hypoxia-inducible genes (Jiang et al., 1997). The stability of HIFs is governed by enzymes called HIF prolyl 4-hydroxylases (PHDs, also called P4Hs), which require certain substrates and cofactors, such as oxygen, 2oxoglutarate, iron, and ascorbate, for full activity (Hirsila¨ et al., 2003) (Fig. 3). When active, the HIF–PHDs hydroxylate certain proline residues on the oxygen-dependent degradation domain of HIF-1a (Hirsila¨ et al., 2003; Ivan et al., 2001; Jaakkola et al., 2001). Another enzyme called factor inhibiting HIF (FIH) can hydroxylate an asparagine residue on the C-terminal transactivation domain of HIF-1a thereby preventing interaction with transcriptional cofactors (Koivunen et al., 2004; Lando et al., 2002). The product of von Hippel–Lindau tumor suppressor gene (pVHL) recognizes the hydroxylated HIF-1a subunits and targets them for polyubiquitination followed by proteosomal destruction (Cockman et al., 2000; Huang et al., 1998; Salceda and Caro, 1997). ARD-1-mediated acetylation of a proline residue on the HIF-1a subunit can further augment the interaction of pVHL and HIF-1a, thereby enhancing proteosomal destruction pathway (Jeong et al., 2002). In addition, some level of nuclear-mitochondrial cross-talk also appears to influence regulation of HIF stability, as other experimental data show that a functional electron transport chain is required for HIF-1a stabilization in hypoxia (Chandel et al., 2000; Schroedl et al., 2002). Could HIFs be pharmacologically stabilized with the goal of improved angiogenesis and alveolarization in the preterm lung (dcontinued fetal life ex uteroT)? Stabilization of HIFs could be brought about by, for example, (1) inhibition of HIF–PHD, FIH, and ARD-1 enzymes, and (2) interference with pVHL tagging and proteosomal degradation pathway. For example, nonspecific inhibitors of collagen PHDs, such as dimethyloxaloylglycine (DMOG, a 2-oxoglutarate analog), also express varying degrees of HIF–PHD inhibitory activity as demonstrated by stabilization of HIF-1a (Jaakkola et al., 2001). Further, HIF–PHD activity can be decreased by deferoxamine (DFO, an iron chelator), but this approach too is very nonspecific and also toxic (deLemos et al., 1990). To improve specificity and reduce toxicity, small molecular weight PHD inhibitors, which stabilize HIF-1a and drive expression of VEGF, have been developed (Ivan et al., 2002). As an example from the latter alternative for HIF stabilization, HIF peptides that interfere with the proteosomal degradation pathway have been used successfully to stabilize endogenous HIF (Willam et al., 2002). However, stabilization of HIFs and potentiation of angiogenesis might not only be exclusively beneficial but could also carry associated untoward effects and risks in the form of, for example, hemangiomas and other tumors as well as other structurally or functionally abnormal vasculature. On the other hand, angiogenesis is a carefully orchestrated series of steps requiring multiple growth factors, receptors, and cell types, and therefore angiogenesis induced by HIF stabilization

would be expected to result in a more balanced outcome as compared with single agent stimuli. For example, vessels formed by VEGF only are leaky and tortuous (reviewed in Carmeliet, 2000). Furthermore, overexpression of VEGF only during fetal development may result in disruption of pulmonary vascular assembly as well as altered epithelial branching morphogenesis (Akeson et al., 2003). Transgenic mice that express VEGF alone in the skin have an increased number of blood vessels with excessive permeability (Larcher et al., 1998). When angiopoietin 1 (Ang-1) is combined with VEGF, the vessels formed are less leaky but not uniform in size (Thurston et al., 1999). However, in another transgenic model overexpressing HIF-1a, the mice also have increased skin vascularization but no abnormal permeability (Elson et al., 2001).

Conclusions Despite advances in neonatal critical care, including less traumatic ventilatory techniques and reduced oxygen concentrations, BPD still affects approximately one-third of very-low-birth-weight preterm babies and thus is associated with significant morbidity and some mortality. Major longterm efforts have been directed at finding antioxidant and other treatments to prevent or mitigate BPD, but not many of these have proven themselves noticeably beneficial and without significant untoward effects in clinical practice. More novel approaches are therefore warranted. Pre- and postnatal lung development is an intricate process involving numerous factors and pathways, and, therefore, it is possible that single therapeutic factors are insufficient for successful treatment of a preterm baby at risk for developing BPD. On the other hand, certain transcription factors, such as HIFs, govern multiple important pathways involving angiogenesis, glycolysis, and survival pathways. Pharmacological stabilization of HIFs after premature birth could potentially lead to increased expression of several growth factors important for pulmonary angiogenesis and alveolarization, and thus alleviate BPD. Studies using various neonatal experimental models will show whether this approach holds future promise as treatment for BPD. Acknowledgments This work was financially supported by Academy of Finland (T.M.A) and NIH U01 HL56263 (C.W.W). References Abman, S.H., 2001. Bronchopulmonary dysplasia: ba vascular hypothesisQ. Am. J. Respir. Crit. Care Med. 164, 1755 – 1756. Ahola, T., Lapatto, R., Raivio, K.O., Selander, B., Stigson, L., Jonsson, B., Jonsbo, F., Esberg, G., Stovring, S., Kjartansson, S., Stiris, T., Lossius, K., Virkola, K., Fellman, V., 2003. N-acetylcysteine does not prevent

T.M. Asikainen, C.W. White / Toxicology and Applied Pharmacology 203 (2005) 177–188 bronchopulmonary dysplasia in immature infants: a randomized controlled trial. J. Pediatr. 143, 713 – 719. Akeson, A.L., Greenberg, J.M., Cameron, J.E., Thompson, F.Y., Brooks, S.K., Wiginton, D., Whitsett, J.A., 2003. Temporal and spatial regulation of VEGF-A controls vascular patterning in the embryonic lung. Dev. Biol. 264, 443 – 455. Asikainen, T.M., White, C.W., 2004. Antioxidant therapy for lung injury. In: Notter, R.H., Finkelstein, J.N., Holm, B.A. (Eds.), Lung Injury: Mechanisms, Pathophysiology, and Therapy. Marcel&Decker, New York. (in press). Asikainen, T.M., White, C.W., 2004. Pulmonary antioxidant defenses in the preterm newborn with respiratory distress and bronchopulmonary dysplasia in evolution: implications for antioxidant therapy. Antioxid. Redox Signal. 6, 155 – 167. Asikainen, T.M., Raivio, K.O., Saksela, M., Kinnula, V.L., 1998. Expression and developmental profile of antioxidant enzymes in human lung and liver. Am. J. Respir. Cell Mol. Biol. 19, 942 – 949. Asikainen, T.M., Heikkil7, P., Kaarteenaho-Wiik, R., Kinnula, V.L., Raivio, K.O., 2001. Cell-specific expression of manganese superoxide dismutase protein in the lungs of patients with respiratory distress syndrome, chronic lung disease, or persistent pulmonary hypertension. Pediatr. Pulmonol. 32, 193 – 200. Autor, A.P., Frank, L., Roberts, R.J., 1976. Developmental characteristics of pulmonary superoxide dismutase: relationship to idiopathic respiratory distress syndrome. Pediatr. Res. 10, 154 – 158. Ballard, R.A., Ballard, P.L., Cnaan, A., Pinto-Martin, J., Davis, D.J., Padbury, J.F., Phibbs, R.H., Parer, J.T., Hart, M.C., Mannino, F.L., Sawai, S.K., 1998. Antenatal thyrotropin-releasing hormone to prevent lung disease in preterm infants. North American Thyrotropin-Releasing Hormone Study Group. N. Engl. J. Med. 338, 493 – 498. Bancalari, E., Claure, N., Sosenko, I.R., 2003. Bronchopulmonary dysplasia: changes in pathogenesis, epidemiology and definition. Semin. Neonatol. 8, 63 – 71. Bhatt, A.J., Pryhuber, G.S., Huyck, H., Watkins, R.H., Metlay, L.A., Maniscalco, W.M., 2001. Disrupted pulmonary vasculature and decreased vascular endothelial growth factor, Flt-1, and TIE-2 in human infants dying with bronchopulmonary dysplasia. Am. J. Respir. Crit. Care Med. 164, 1971 – 1980. Bruick, R.K., 2003. Oxygen sensing in the hypoxic response pathway: regulation of the hypoxia-inducible transcription factor. Genes Dev. 17, 2614 – 2623. Burri, P.H., 1984. Fetal and postnatal development of the lung. Annu. Rev. Physiol. 46, 617 – 628. Carmeliet, P., 2000. VEGF gene therapy: stimulating angiogenesis or angioma-genesis? Nat. Med. 6, 1102 – 1103. Chandel, N.S., McClintock, D.S., Feliciano, C.E., Wood, T.M., Melendez, J.A., Rodriguez, A.M., Schumacker, P.T., 2000. Reactive oxygen species generated at mitochondrial complex III stabilize hypoxiainducible factor-1alpha during hypoxia: a mechanism of O2 sensing. J. Biol. Chem. 275, 25130 – 25138. Chang, L.Y., Subramaniam, M., Yoder, B.A., Day, B.J., Ellison, M.C., Sunday, M.E., Crapo, J.D., 2003. A catalytic antioxidant attenuates alveolar structural remodeling in bronchopulmonary dysplasia. Am. J. Respir. Crit. Care Med. 167, 57 – 64. Chen, Y., Whitney, P.L., Frank, L., 1994. Comparative responses of premature versus full-term newborn rats to prolonged hyperoxia. Pediatr. Res. 35, 233 – 237. Chetty, A., Andersson, S., Lassus, P., Nielsen, H.C., 2004. Insulin-like growth factor-1 (IGF-1) and IGF-1 receptor (IGF-1R) expression in human lung in RDS and BPD. Pediatr. Pulmonol. 37, 128 – 136. Clerch, L.B., Massaro, D., 1992a. Rat lung antioxidant enzymes: differences in perinatal gene expression and regulation. Am. J. Physiol. Lung Cell. Mol. Physiol. 263, L466 – L470. Clerch, L.B., Massaro, D., 1992b. Oxidation–reduction-sensitive binding of lung protein to rat catalase mRNA. J. Biol. Chem. 267, 2853 – 2855. Clerch, L.B., Massaro, D., 1993. Tolerance of rats to hyperoxia. Lung antioxidant enzyme gene expression. J. Clin. Invest. 91, 499 – 508.

185

Clerch, L.B., Wright, A.E., Coalson, J.J., 1996. Lung manganese superoxide dismutase protein expression increases in the baboon model of bronchopulmonary dysplasia and is regulated at a posttranscriptional level. Pediatr. Res. 39, 253 – 258. Coalson, J.J., Winter, V.T., Gerstmann, D.R., Idell, S., King, R.J., Delemos, R.A., 1992. Pathophysiologic, morphometric, and biochemical studies of the premature baboon with bronchopulmonary dysplasia. Am. Rev. Respir. Dis. 145, 872 – 881. Coalson, J.J., Winter, V.T., Siler-Khodr, T., Yoder, B.A., 1999. Neonatal chronic lung disease in extremely immature baboons. Am. J. Respir. Crit. Care Med. 160, 1333 – 1346. Cockman, M.E., Masson, N., Mole, D.R., Jaakkola, P., Chang, G.W., Clifford, S.C., Maher, E.R., Pugh, C.W., Ratcliffe, P.J., Maxwell, P.H., 2000. Hypoxia inducible factor-alpha binding and ubiquitylation by the von Hippel–Lindau tumor suppressor protein. J. Biol. Chem. 275, 25733 – 25741. Compernolle, V., Brusselmans, K., Acker, T., Hoet, P., Tjwa, M., Beck, H., Plaisance, S., Dor, Y., Keshet, E., Lupu, F., Nemery, B., Dewerchin, M., Van Veldhoven, P., Plate, K., Moons, L., Collen, D., Carmeliet, P., 2002. Loss of HIF-2alpha and inhibition of VEGF impair fetal lung maturation, whereas treatment with VEGF prevents fatal respiratory distress in premature mice. Nat. Med. 8, 702 – 710. Coursin, D.B., Cihla, H.P., Will, J.A., McCreary, J.L., 1987. Adaptation to chronic hyperoxia. Biochemical effects and the response to subsequent lethal hyperoxia. Am. Rev. Respir. Dis. 135, 1002 – 1006. Crapo, J.D., 1986. Morphologic changes in pulmonary oxygen toxicity. Annu. Rev. Physiol. 48, 721 – 731. Crapo, J.D., Barry, B.E., Foscue, H.A., Shelburne, J., 1980. Structural and biochemical changes in rat lungs occurring during exposures to lethal and adaptive doses of oxygen. Am. Rev. Respir. Dis. 122, 123 – 143. Crowley, P., 2000. Prophylactic corticosteroids for preterm birth. Cochrane Database Syst. Rev. 2, CD000065. Crowther, C., Alfirevic, Z., Haslam, R., 2004. Thyrotropin-releasing hormone added to corticosteroids for women at risk of preterm birth for preventing neonatal respiratory disease. Cochrane Database Syst. Rev. 2, CD000019. Darlow, B.A., Graham, P.J., 2000. Vitamin A supplementation for preventing morbidity and mortality in very low birthweight infants. Cochrane Database Syst. Rev. 2, CD000501. Darlow, B.A., Winterbourn, C.C., Inder, T.E., Graham, P.J., Harding, J.E., Weston, P.J., Austin, N.C., Elder, D.E., Mogridge, N., Buss, I.H., Sluis, K.B., 2000. The effect of selenium supplementation on outcome in very low birth weight infants: a randomized controlled trial. The New Zealand Neonatal Study Group. J. Pediatr. 136, 473 – 480. Das, K.C., Guo, X.L., White, C.W., 1999. Induction of thioredoxin and thioredoxin reductase gene expression in lungs of newborn primates by oxygen. Am. J. Physiol. Lung Cell. Mol. Physiol. 276, L530 – L539. Das, K.C., Pahl, P.M., Guo, X.L., White, C.W., 2001. Induction of peroxiredoxin gene expression by oxygen in lungs of newborn primates. Am. J. Respir. Cell Mol. Biol. 25, 226 – 232. Davis, J.M., 1998. Superoxide dismutase: a role in the prevention of chronic lung disease. Biol. Neonate 1, 29 – 34. Davis, J.M., Rosenfeld, W.N., Richter, S.E., Parad, M.R., Gewolb, I.H., Spitzer, A.R., Carlo, W.A., Couser, R.J., Price, A., Flaster, E., Kassem, N., Edwards, L., Tierney, J., Horowitz, S., 1997. Safety and pharmacokinetics of multiple doses of recombinant human CuZn superoxide dismutase administered intratracheally to premature neonates with respiratory distress syndrome. Pediatrics 100, 24 – 30. Davis, J.M., Richter, S.E., Biswas, S., Rosenfeld, W.N., Parton, L., Gewolb, I.H., Parad, R., Carlo, W., Couser, R.J., Baumgart, S., Atluru, V., Salerno, L., Kassem, N., 2000. Long-term follow-up of premature infants treated with prophylactic, intratracheal recombinant human CuZn superoxide dismutase. J. Perinatol. 20, 213 – 216. Davis, J.M., Parad, R.B., Michele, T., Allred, E., Price, A., Rosenfeld, W., 2003. Pulmonary outcome at 1 year corrected age in premature infants treated at birth with recombinant human CuZn superoxide dismutase. Pediatrics 111, 469 – 476.

186

T.M. Asikainen, C.W. White / Toxicology and Applied Pharmacology 203 (2005) 177–188

de Haan, J.B., Tymms, M.J., Cristiano, F., Kola, I., 1994. Expression of copper/zinc superoxide dismutase and glutathione peroxidase in organs of developing mouse embryos, fetuses, and neonates. Pediatr. Res. 35, 188 – 196. deLemos, R.A., Roberts, R.J., Coalson, J.J., deLemos, J.A., Null, D.M.J., Gerstmann, D.R., 1990. Toxic effects associated with the administration of deferoxamine in the premature baboon with hyaline membrane disease. Am. J. Dis. Child. 144, 915 – 919. Deneke, S.M., 2000. Thiol-based antioxidants. Curr. Top. Cell. Regul. 36, 151 – 180. Dobashi, K., Asayama, K., Hayashibe, H., Munim, A., Kawaoi, A., Morikawa, M., Nakazawa, S., 1993. Immunohistochemical study of copper-zinc and manganese superoxide dismutases in the lungs of human fetuses and newborn infants: developmental profile and alterations in hyaline membrane disease and bronchopulmonary dysplasia. Virchows Arch. A. Pathol. Anat. Histopathol. 423, 177 – 184. Ehrenkranz, R.A., Ablow, R.C., Warshaw, J.B., 1982. Effect of vitamin E on the development of oxygen-induced lung injury in neonates. Ann. N. Y. Acad. Sci. 393, 452 – 466. Elson, D.A., Thurston, G., Huang, L.E., Ginzinger, D.G., McDonald, D.M., Johnson, R.S., Arbeit, J.M., 2001. Induction of hypervascularity without leakage or inflammation in transgenic mice overexpressing hypoxia-inducible factor-1alpha. Genes Dev. 15, 2520 – 2532. Fazzone, H., Wangner, A., Clerch, L.B., 1993. Rat lung contains a developmentally regulated manganese superoxide dismutase mRNAbinding protein. J. Clin. Invest. 92, 1278 – 1281. Finer, N.N., Barrington, K.J., 2001. Nitric oxide for respiratory failure in infants born at or near term. Cochrane Database Syst. Rev., CD000399. Finkel, T., 1998. Oxygen radicals and signaling. Curr. Opin. Cell Biol. 10, 248 – 253. Frank, L., 1991. Developmental aspects of experimental pulmonary oxygen toxicity. Free Radical Biol. Med. 11, 463 – 494. Frank, L., 1992. Antioxidants, nutrition, and bronchopulmonary dysplasia. Clin. Perinatol. 19, 541 – 562. Frank, L., Sosenko, I.R., 1991. Failure of premature rabbits to increase antioxidant enzymes during hyperoxic exposure: increased susceptibility to pulmonary oxygen toxicity compared with term rabbits. Pediatr. Res. 29, 292 – 296. Frank, L., Bucher, J.R., Roberts, R.J., 1978. Oxygen toxicity in neonatal and adult animals of various species. J. Appl. Physiol. 45, 699 – 704. Freeman, B.A., Crapo, J.D., 1981. Hyperoxia increases oxygen radical production in rat lungs and lung mitochondria. J. Biol. Chem. 256, 10986 – 10992. Freeman, B.A., Crapo, J.D., 1982. Biology of disease: free radicals and tissue injury. Lab. Invest. 47, 412 – 426. Fryer, A.A., Hume, R., Strange, R.C., 1986. The development of glutathione S-transferase and glutathione peroxidase activities in human lung. Biochim. Biophys. Acta 883, 448 – 453. Gebb, S.A., Shannon, J.M., 2000. Tissue interactions mediate early events in pulmonary vasculogenesis. Dev. Dyn. 217, 159 – 169. Gradin, K., McGuire, J., Wenger, R.H., Kvietikova, I., Whitelaw, M.L., Toftgard, R., Tora, L., Gassmann, M., Poellinger, L., 1996. Functional interference between hypoxia and dioxin signal transduction pathways: competition for recruitment of the Arnt transcription factor. Mol. Cell. Biol. 16, 5221 – 5231. Haddad, J.J., Land, S.C., 2000. O2-evoked regulation of HIF-1alpha and NF-kappaB in perinatal lung epithelium requires glutathione biosynthesis. Am. J. Physiol.: Lung Cell. Mol. Physiol. 278, L492 – L503. Halliday, H.L., Ehrenkranz, R.A., 2001. Early postnatal (b96 hours) corticosteroids for preventing chronic lung disease in preterm infants. Cochrane Database Syst. Rev. 1, CD001146. Halliwell, B., 1996. Antioxidants in human health and disease. Annu. Rev. Nutr. 16, 33 – 50. Han, R.N., Post, M., Tanswell, A.K., Lye, S.J., 2003. Insulin-like growth factor-I receptor-mediated vasculogenesis/angiogenesis in human lung development. Am. J. Respir. Cell Mol. Biol. 28, 159 – 169.

Hass, M.A., Massaro, D., 1987. Developmental regulation of rat lung Cu,Zn-superoxide dismutase. Biochem. J. 246, 697 – 703. Hayashibe, H., Asayama, K., Dobashi, K., Kato, K., 1990. Prenatal development of antioxidant enzymes in rat lung, kidney, and heart: marked increase in immunoreactive superoxide dismutases, glutathione peroxidase, and catalase in the kidney. Pediatr. Res. 27, 472 – 475. Hirsil7, M., Koivunen, P., Gqnzler, V., Kivirikko, K.I., Myllyharju, J., 2003. Characterization of the human prolyl 4-hydroxylases that modify the hypoxia-inducible factor. J. Biol. Chem. 278, 30772 – 30780. Holm, B.A., Notter, R.H., Leary, J.F., Matalon, S., 1987. Alveolar epithelial changes in rabbits after a 21-day exposure to 60% O2. J. Appl. Physiol. 62, 2230 – 2236. Holmgren, A., 2000. Antioxidant function of thioredoxin and glutaredoxin systems. Antioxid. Redox Signal. 2, 811 – 820. Huang, L.E., Gu, J., Schau, M., Bunn, H.F., 1998. Regulation of hypoxiainducible factor 1alpha is mediated by an O2-dependent degradation domain via the ubiquitin–proteasome pathway. Proc. Natl. Acad. Sci. U.S.A. 95, 7987 – 7992. Inselman, L.S., Mellins, R.B., 1981. Growth and development of the lung. J. Pediatr. 98, 1 – 15. Ivan, M., Kondo, K., Yang, H., Kim, W., Valiando, J., Ohh, M., Salic, A., Asara, J.M., Lane, W.S., Kaelin Jr., W.G., 2001. HIFalpha targeted for VHL-mediated destruction by proline hydroxylation: implications for O2 sensing. Science 292, 464 – 468. Ivan, M., Haberberger, T., Gervasi, D.C., Michelson, K.S., Gqnzler, V., Kondo, K., Yang, H., Sorokina, I., Conaway, R.C., Conaway, J.W., Kaelin Jr., W.G., 2002. Biochemical purification and pharmacological inhibition of a mammalian prolyl hydroxylase acting on hypoxiainducible factor. Proc. Natl. Acad. Sci. U.S.A. 99, 13459 – 13464. Iyer, N.V., Kotch, L.E., Agani, F., Leung, S.W., Laughner, E., Wenger, R.H., Gassmann, M., Gearhart, J.D., Lawler, A.M., Yu, A.Y., Semenza, G.L., 1998. Cellular and developmental control of O2 homeostasis by hypoxia-inducible factor 1 alpha. Genes Dev. 12, 149 – 162. Jaakkola, P., Mole, D.R., Tian, Y.M., Wilson, M.I., Gielbert, J., Gaskell, S.J., Kriegsheim, A., Hebestreit, H.F., Mukherji, M., Schofield, C.J., Maxwell, P.H., Pugh, C.W., Ratcliffe, P.J., 2001. Targeting of HIF-alpha to the von Hippel–Lindau ubiquitylation complex by O2-regulated prolyl hydroxylation. Science 292, 468 – 472. Jain, A., Mehta, T., Auld, P.A., Rodrigues, J., Ward, R.F., Schwartz, M.K., Martensson, J., 1995. Glutathione metabolism in newborns: evidence for glutathione deficiency in plasma, bronchoalveolar lavage fluid, and lymphocytes in prematures. Pediatr. Pulmonol. 20, 160 – 166. Jakkula, M., Le Cras, T.D., Gebb, S., Hirth, K.P., Tuder, R.M., Voelkel, N.F., Abman, S.H., 2000. Inhibition of angiogenesis decreases alveolarization in the developing rat lung. Am. J. Physiol. Lung Cell. Mol. Physiol. 279, L600 – L607. Jankov, R.P., Negus, A., Tanswell, A.K., 2001. Antioxidants as therapy in the newborn: some words of caution. Pediatr. Res. 50, 681 – 687. Jeong, J.W., Bae, M.K., Ahn, M.Y., Kim, S.H., Sohn, T.K., Bae, M.H., Yoo, M.A., Song, E.J., Lee, K.J., Kim, K.W., 2002. Regulation and destabilization of HIF-1alpha by ARD1-mediated acetylation. Cell 111, 709 – 720. Jiang, B.H., Zheng, J.Z., Leung, S.W., Roe, R., Semenza, G.L., 1997. Transactivation and inhibitory domains of hypoxia-inducible factor 1alpha. Modulation of transcriptional activity by oxygen tension. J. Biol. Chem. 272, 19253 – 19260. Jobe, A.H., Bancalari, E., 2001. Bronchopulmonary dysplasia. Am. J. Respir. Crit. Care Med. 163, 1723 – 1729. Jones, R., Zapol, W.M., Reid, L., 1985. Oxygen toxicity and restructuring of pulmonary arteries—a morphometric study. The response to 4 weeks’ exposure to hyperoxia and return to breathing air. Am. J. Pathol. 121, 212 – 223. Kim, H.S., Kang, S.W., Rhee, S.G., Clerch, L.B., 2001. Rat lung peroxiredoxins I and II are differentially regulated during development and by hyperoxia. Am. J. Physiol. Lung Cell. Mol. Physiol. 280, L1212 – L1217.

T.M. Asikainen, C.W. White / Toxicology and Applied Pharmacology 203 (2005) 177–188 Kinnula, V.L., Crapo, J.D., 2003. Superoxide dismutases in the lung and human lung diseases. Am. J. Respir. Crit. Care Med. 167, 1600 – 1619. Kinnula, V.L., Crapo, J.D., Raivio, K.O., 1995. Generation and disposal of reactive oxygen metabolites in the lung. Lab. Invest. 73, 3 – 19. Kinsella, J.P., Abman, S.H., 2000. Inhaled nitric oxide: current and future uses in neonates. Semin. Perinatol. 24, 387 – 395. Kinsella, J.P., Walsh, W.F., Bose, C.L., Gerstmann, D.R., Labella, J.J., Sardesai, S., Walsh-Sukys, M.C., McCaffrey, M.J., Cornfield, D.N., Bhutani, V.K., Cutter, G.R., Baier, M., Abman, S.H., 1999. Inhaled nitric oxide in premature neonates with severe hypoxaemic respiratory failure: a randomised controlled trial. Lancet 354, 1061 – 1065. Koivunen, P., Hirsila¨, M., Gu¨nzler, V., Kivirikko, K.I., Myllyharju, J., 2004. Catalytic properties of the asparaginyl hydroxylase (FIH) in the oxygen sensing pathway are distinct from those of its prolyl 4-hydroxylases. J. Biol. Chem. 279, 9899 – 9904. Lando, D., Pongratz, I., Poellinger, L., Whitelaw, M.L., 2000. A redox mechanism controls differential DNA binding activities of hypoxiainducible factor (HIF) 1alpha and the HIF-like factor. J. Biol. Chem. 275, 4618 – 4627. Lando, D., Peet, D.J., Whelan, D.A., Gorman, J.J., Whitelaw, M.L., 2002. Asparagine hydroxylation of the HIF transactivation domain: a hypoxic switch. Science 295, 858 – 861. Larcher, F., Murillas, R., Bolontrade, M., Conti, C.J., Jorcano, J.L., 1998. VEGF/VPF overexpression in skin of transgenic mice induces angiogenesis, vascular hyperpermeability and accelerated tumor development. Oncogene 17, 303 – 311. Lassus, P., Turanlahti, M., Heikkil7, P., Andersson, L.C., Nupponen, I., Sarnesto, A., Andersson, S., 2001. Pulmonary vascular endothelial growth factor and Flt-1 in fetuses, in acute and chronic lung disease, and in persistent pulmonary hypertension of the newborn. Am. J. Respir. Crit. Care Med. 164, 1981 – 1987. Lebovitz, R.M., Zhang, H., Vogel, H., Cartwright, J.J., Dionne, L., Lu, N., Huang, S., Matzuk, M.M., 1996. Neurodegeneration, myocardial injury, and perinatal death in mitochondrial superoxide diamutase-deficient mice. Proc. Natl. Acad. Sci. U.S.A. 93, 9782 – 9787. Levonen, A.L., Lapatto, R., Saksela, M., Raivio, K.O., 2000. Expression of gamma-glutamylcysteine synthetase during development. Pediatr. Res. 47, 266 – 270. Li, Y., Huang, T.T., Carlson, E.J., Melov, S., Ursell, P.C., Olson, J.L., Noble, L.J., Yoshimura, M.P., Berger, C., Chan, P.H., Wallace, D.C., Epstein, C.J., 1995. Dilated cardiomyopathy and neonatal lethality in mutant mice lacking manganese superoxide dismutase. Nat. Genet. 11, 376 – 381. Madan, A., Varma, S., Cohen, H.J., 2002. Developmental stage-specific expression of the alpha and beta subunits of the HIF-1 protein in the mouse and human fetus. Mol. Genet. Metab. 75, 244 – 249. Maniscalco, W.M., Watkins, R.H., Pryhuber, G.S., Bhatt, A., Shea, C., Huyck, H., 2002. Angiogenic factors and alveolar vasculature: development and alterations by injury in very premature baboons. Am. J. Physiol. Lung Cell. Mol. Physiol. 282, L811 – L823. Margraf, L.R., Tomashefski Jr., J.F., Bruce, M.C., Dahms, B.B., 1991. Morphometric analysis of the lung in bronchopulmonary dysplasia. Am. Rev. Respir. Dis. 143, 391 – 400. McElroy, M.C., Postle, A.D., Kelly, F.J., 1992. Catalase, superoxide dismutase and glutathione peroxidase activities of lung and liver during human development. Biochim. Biophys. Acta 15, 153 – 158. McMurtry, I.F., Bauer, N.R., Fagan, K.A., Nagaoka, T., Gebb, S.A., Oka, M., 2003. Hypoxia and Rho/Rho-kinase signaling. Lung development versus hypoxic pulmonary hypertension. Adv. Exp. Med. Biol. 543, 127 – 137. Morton, R.L., Das, K.C., Guo, X.L., Ikle, D.N., White, C.W., 1999. Effect of oxygen on lung superoxide dismutase activities in premature baboons with bronchopulmonary dysplasia. Am. J. Physiol. Lung Cell. Mol. Physiol. 276, L64 – L74. Northway, W.J., Rosan, R.C., Porter, D.Y., 1967. Pulmonary disease following respirator therapy of hyaline-membrane disease, bronchopulmonary dysplasia. N. Engl. J. Med. 276, 357 – 368.

187

O’Rourke, J.F., Tian, Y.M., Ratcliffe, P.J., Pugh, C.W., 1999. Oxygenregulated and transactivating domains in endothelial PAS protein 1: comparison with hypoxia-inducible factor-1alpha. J. Biol. Chem. 274, 2060 – 2071. Pitk7nen, O.M., Hallman, M., Andersson, S.M., 1990. Correlation of free oxygen radical-induced lipid peroxidation with outcome in very low birth weight infants. J. Pediatr. 116, 760 – 764. Pugh, C.W., Ratcliffe, P.J., 2003. Regulation of angiogenesis by hypoxia: role of the HIF system. Nat. Med. 9, 677 – 684. Radi, R., 2004. Nitric oxide, oxidants, and protein tyrosine nitration. Proc. Natl. Acad. Sci. U.S.A. 101, 4003 – 4008. Rickett, G.M., Kelly, F.J., 1990. Developmental expression of antioxidant enzymes in guinea pig lung and liver. Development 108, 331 – 336. Salceda, S., Caro, J., 1997. Hypoxia-inducible factor 1alpha (HIF-1alpha) protein is rapidly degraded by the ubiquitin–proteasome system under normoxic conditions. Its stabilization by hypoxia depends on redoxinduced changes. J. Biol. Chem. 272, 22642 – 22647. Saugstad, O.D., 1998. Chronic lung disease: the role of oxidative stress. Biol. Neonate 1, 21 – 28. Schreiber, M.D., Gin-Mestan, K., Marks, J.D., Huo, D., Lee, G., Srisuparp, P., 2003. Inhaled nitric oxide in premature infants with the respiratory distress syndrome. N. Engl. J. Med. 349, 2099 – 2107. Schroedl, C., McClintock, D.S., Budinger, G.R., Chandel, N.S., 2002. Hypoxic but not anoxic stabilization of HIF-1alpha requires mitochondrial reactive oxygen species. Am. J. Physiol. Lung Cell. Mol. Physiol. 283, L922 – L931. Scortegagna, M., Ding, K., Oktay, Y., Gaur, A., Thurmond, F., Yan, L.J., Marck, B.T., Matsumoto, A.M., Shelton, J.M., Richardson, J.A., Bennett, M.J., Garcia, J.A., 2003. Multiple organ pathology, metabolic abnormalities and impaired homeostasis of reactive oxygen species in Epas1 / mice. Nat. Genet. 35, 331 – 340. Semenza, G.L., 1998. Hypoxia-inducible factor 1: master regulator of O2 homeostasis. Curr. Opin. Genet. Dev. 8, 588 – 594. Shannon, J.M., Hyatt, B.A., 2004. Epithelial–mesenchymal interactions in the developing lung. Annu. Rev. Physiol. 66, 625 – 645. Shennan, A.T., Dunn, M.S., Ohlsson, A., Lennox, K., Hoskins, E.M., 1988. Abnormal pulmonary outcomes in premature infants: prediction from oxygen requirement in the neonatal period. Pediatrics 82, 527 – 532. Sies, H., 1991. Oxidative stress: from basic research to clinical application. Am. J. Med. 91, 31S – 38S. Smith, C.V., Hansen, T.N., Martin, N.E., McMicken, H.W., Elliott, S.J., 1993. Oxidant stress responses in premature infants during exposure to hyperoxia. Pediatr. Res. 34, 360 – 365. Sosenko, I.R., Frank, L., 1987. Guinea pig lung development: antioxidant enzymes and premature survival in high O2. Am. J. Physiol., Regul. 252, R693 – R698. Sowter, H.M., Raval, R., Moore, J., Ratcliffe, P.J., Harris, A.L., 2003. Predominant role of hypoxia-inducible transcription factor (Hif)-1alpha versus HIF-2alpha in regulation of the transcriptional response to hypoxia. Cancer Res. 63, 6130 – 6134. Stenmark, K.R., Gebb, S.A., 2003. Lung vascular development: breathing new life into an old problem. Am. J. Respir. Cell Mol. Biol. 28, 133 – 137. Strange, R.C., Cotton, W., Fryer, A.A., Drew, R., Bradwell, A.R., Marshall, T., Collins, M.F., Bell, J., Hume, R., 1988. Studies on the expression of Cu,Zn superoxide dismutase in human tissues during development. Biochim. Biophys. Acta 964, 260 – 265. Strange, R.C., Cotton, W., Fryer, A.A., Jones, P., Bell, J., Hume, R., 1990. Lipid peroxidation and expression of copper–zinc and manganese superoxide dismutase in lungs of premature infants with hyaline membrane disease and bronchopulmonary dysplasia. J. Lab. Clin. Med. 116, 666 – 673. Suresh, G.K., Davis, J.M., Soll, R.F., 2001. Superoxide dismutase for preventing chronic lung disease in mechanically ventilated preterm infants. Cochrane Database Syst. Rev., CD001968.

188

T.M. Asikainen, C.W. White / Toxicology and Applied Pharmacology 203 (2005) 177–188

Tanswell, A.K., Freeman, B.A., 1984. Pulmonary antioxidant enzyme maturation in the fetal and neonatal rat. I. Developmental profiles. Pediatr. Res. 18, 584 – 587. Thannickal, V.J., Fanburg, B.L., 2000. Reactive oxygen species in cell signaling. Am. J. Physiol. Lung Cell. Mol. Physiol. 279, L1005 – L1028. Thurston, G., Suri, C., Smith, K., McClain, J., Sato, T.N., Yancopoulos, G.D., McDonald, D.M., 1999. Leakage-resistant blood vessels in mice transgenically overexpressing angiopoietin-1. Science 286, 2511 – 2514. Tsan, M.F., White, J.E., Santana, T.A., Lee, C.Y., 1990. Tracheal insufflation of tumor necrosis factor protects rats against oxygen toxicity. J. Appl. Physiol. 68, 1211 – 1219. Tyson, J.E., Wright, L.L., Oh, W., Kennedy, K.A., Mele, L., Ehrenkranz, R.A., Stoll, B.J., Lemons, J.A., Stevenson, D.K., Bauer, C.R., Korones, S.B., Fanaroff, A.A., 1999. Vitamin A supplementation for extremelylow-birth-weight infants. National Institute of Child Health and Human Development Neonatal Research Network. N. Engl. J. Med. 340, 1962 – 1968. Varsila, E., Pesonen, E., Andersson, S., 1995. Early protein oxidation in the neonatal lung is related to development of chronic lung disease. Acta Paediatr. 84, 1296 – 1299. Walther, F.J., Wade, A.B., Warburton, D., Forman, H.J., 1991. Ontogeny of antioxidant enzymes in the fetal lamb lung. Exp. Lung Res. 17, 39 – 45. Wang, G.L., Jiang, B.H., Semenza, G.L., 1995. Effect of altered redox states on expression and DNA-binding activity of hypoxia-inducible factor 1. Biochem. Biophys. Res. Commun. 212, 550 – 556. Watts, J.L., Milner, R., Zipursky, A., Paes, B., Ling, E., Gill, G., Fletcher, B., Rand, C., 1991. Failure of supplementation with vitamin E to

prevent bronchopulmonary dysplasia in infants less than 1500 g birth weight. Eur. Respir. J. 4, 188 – 190. White, C.W., Ghezzi, P., 1989. Protection against pulmonary oxygen toxicity by interleukin-1 and tumor necrosis factor: role of antioxidant enzymes and effect of cyclooxygenase inhibitors. Biotherapy 1, 361 – 367. Wiesener, M.S., Turley, H., Allen, W.E., Willam, C., Eckardt, K.U., Talks, K.L., Wood, S.M., Gatter, K.C., Harris, A.L., Pugh, C.W., Ratcliffe, P.J., Maxwell, P.H., 1998. Induction of endothelial PAS domain protein1 by hypoxia: characterization and comparison with hypoxia-inducible factor-1alpha. Blood 92, 2260 – 2268. Willam, C., Masson, N., Tian, Y.M., Mahmood, S.A., Wilson, M.I., Bicknell, R., Eckardt, K.U., Maxwell, P.H., Ratcliffe, P.J., Pugh, C.W., 2002. Peptide blockade of HIFalpha degradation modulates cellular metabolism and angiogenesis. Proc. Natl. Acad. Sci. U.S.A. 99, 10423 – 10428. Wilson, W.L., Mullen, M., Olley, P.M., Rabinovitch, M., 1985. Hyperoxiainduced pulmonary vascular and lung abnormalities in young rats and potential for recovery. Pediatr. Res. 19, 1059 – 1067. Yam, J., Frank, L., Roberts, R.J., 1978. Oxygen toxicity: comparison of lung biochemical responses in neonatal and adult rats. Pediatr. Res. 12, 115 – 119. Yu, A.Y., Shimoda, L.A., Iyer, N.V., Huso, D.L., Sun, X., McWilliams, R., Beaty, T., Sham, J.S., Wiener, C.M., Sylvester, J.T., Semenza, G.L., 1999. Impaired physiological responses to chronic hypoxia in mice partially deficient for hypoxia-inducible factor 1alpha. J. Clin. Invest. 103, 691 – 696. Yuan, H.T., Bingle, C.D., Kelly, F.J., 1996. Differential patterns of antioxidant enzyme mRNA expression in guinea pig lung and liver during development. Biochim. Biophys. Acta 1, 163 – 171.