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Pre-eclampsia—A Workshop Report
Placenta (2004), 25, Supplement A, Trophoblast Research, Vol. 18, S112–S114 doi:10.1016/j.placenta.2004.01.018
Pre-eclampsia—A Workshop Report F. Lyall a,* and R. Seufert b a
Maternal and Fetal Medicine Section, Institute of Medical Genetics, University of Glasgow, Yorkhill, Glasgow, Scotland G3 8SJ, UK; b Department of Obstetrics and Gynaecology, Johannes Gutenberg University, Langenbeckstraße 1, D55101 Mainz, Germany
INTRODUCTION The aims of this workshop on pre-eclampsia were two-fold. The first half aimed to provide an update on the influence of oxygen and oxidative stress on the development of preeclampsia. The session, with four speakers, was chaired by Fiona Lyall. The second part of the workshop was more clinically orientated addressing new patho-physiological and clinical findings. This session also had four speakers and was chaired by Rudi Seufert.
OXIDATIVE STRESS IN PRE-ECLAMPSIA Maarten Raijmakers (St Thomas’ Hospital, London) discussed placental detoxification and oxidative stress in pre-eclampsia. The glutathione/glutathione dependent enzyme system is one the most important protective systems [1]. Glutathione S-transferases (GSTs) provide protection against xenobiotics and metabolize breakdown products produced in vivo by oxidative stress. In eukaryotes the GST family is comprised of membrane-bound transferases and a family of seven soluble proteins, also referred to as cytosolic GSTs. GST Alpha, Pi, Mu and Theta (GSTA, GSTP, GSTM and GSTT, respectively) are primarily expressed in humans in a tissue specific manner. GST alpha is the main isoform in liver, whereas GSTPi is predominantly expressed in placenta and embryonic and fetal tissues [2]. Steegers et al. were the first to link GSTs with complications of pregnancy [3]. The placenta provides protection against noxious compounds for both mother and child. In contrast placental oxidative stress contributes to the development of pre-eclampsia. Although placental and decidual expression of GSTP is lower in women with preeclampsia, overall GST enzyme activity is similar in normotensive and pre-eclamptic pregnancies [1]. In contrast, glutathione levels and glutathione peroxidase enzyme activity were higher in women with pre-eclampsia [4] which is probably due to a compensatory antioxidant response. The higher levels of GST enzymes, GPX enzyme activity and glutathione levels in decidual tissue as compared to placental levels may indicate an unforeseen role in detoxification for decidual tissue. A polymorphism in the GSTP gene was found to be a risk factor for pre-eclampsia [5]. The prevalence of this polymor*
To whom correspondence should be addressed; E-mail: gqta01@ udcf.gla.ac.uk 0143-4004/$–see front matter
phism in the GSTP gene was also higher in fathers and offspring of women who developed pre-eclampsia compared to controls [6]. Leslie Myatt (University of Cincinnati, USA) followed with a discussion on the role of nitrotyrosine in the placenta in pre-eclampsia. Pregnancy is a state of oxidative stress and this is exacerbated in certain pregnancy pathologies including pre-eclampsia. This increased oxidative stress is associated with endothelial and vascular dysfunction in the placenta and increased apoptosis and deportation of trophoblast. Oxidative stress may arise from increased production of reactive oxygen species, such as superoxide and nitric oxide. These may interact to produce peroxynitrite (ONOO) a powerful longlived pro-oxidant whose production and action can be determined by its ability to nitrate tyrosine residues on proteins producing nitrotyrosine residues. Nitration of proteins in turn alters protein function. This group demonstrated the presence of nitrotyrosine residues in the placenta from pregnancies complicated by pre-eclampsia and pre-gestational diabetes in association with altered vascular reactivity [7,8]. To determine a cause and effect relationship, nitrated proteins were identified in the placenta and these include phospho p38 MAP kinase and p53, the tumour suppressor gene. Nitration of phospho p38 MAP kinase appears to reduce catalytic activity. 2D gel electrophoresis has revealed differences in protein expression that may be related to altered placental function in pathologic pregnancies.
THE MATERNAL SYSTEMIC INFLAMMATORY RESPONSE IN PRE-ECLAMPSIA Chris Redman (University of Oxford, UK) next discussed the maternal systemic inflammatory response in pre-eclampsia in relation to oxidative stress. This work was performed in collaboration with Ian Sargent (Oxford). Oxidative stress and inflammatory responses are related, perhaps inseparable phenomena [9]. This is because reactive oxygen species are widely used as second messengers to propagate proinflammatory signals. These interrelationships imply that antioxidants, such as the anti-oxidant vitamins that are now being tested as prophylaxis for pre-eclampsia, are anti-inflammatory agents. This group has shown that normal pregnancy is characterized by a systemic inflammatory response which intensifies in the third trimester. In parallel, there are also 2004 IFPA and Elsevier Ltd. All rights reserved.
Lyall and Seufert: Pre-eclampsia
increased circulating markers of systemic oxidative stress. In pre-eclampsia these changes are on average more intense. It is proposed that the endothelial dysfunction and other elements of the pre-eclampsia syndrome are consequences of the systemic inflammatory processes [10]. It is probable that there are multiple causes for these responses in normal and pre-eclamptic pregnancies. The group’s evidence points to a major role for syncytiotrophoblast debris shed into the maternal circulation. This debris, including whole cell fragments, subcellular syncytial fragments (STBM), soluble cytokeratin, and soluble placental DNA and RNA, is generated during renewal of the syncytial surface of the placenta. They are all significantly increased in preeclampsia and have the potential to be pro-inflammatory. The group have demonstrated that monocytes are associated with syncytiotrophobast antigen peripheral blood in vivo. Although there is no apparent increase in the proportion of peripheral blood monocytes binding STBM in pre-eclampsia, this may be because STBM binding is increased, but the activated monocytes are rapidly cleared from the circulation or that the primary site of clearance is in the reticuloendothelial system, such as the liver. There is clear evidence that monocytes are activated by STBM in vitro. For example STBM stimulate peripheral blood mononuclear cells from non-pregnant women to produce more TNF, IL-12 or IL-18. In summary, a systemic inflammatory response and oxidative stress are inseparable processes. Normal pregnancy is characterized by systemic inflammation and, on average, in pre-eclampsia these responses are more intense. Placental debris could be the cause accounting for the link between the maternal syndrome and the essential placental origins of pre-eclampsia.
HIGH ALTITUDE PREGNANCY AS A MODEL FOR CHRONIC HYPOXIA Stacy Zamudio (New Jersey Medical School, USA) expanded the topic by discussing a model of chronic placental hypoxia. The incidence of pre-eclampsia is increased 2–4 fold in women residing at high altitude (HA >2700 m), supporting the idea that placental hypoxia contributes to the development of pre-eclampsia [11]. Neither failed trophoblast invasion nor placental hypoxia alone are sufficient to explain pre-eclampsia. Many features of pre-eclampsia are present in normal pregnancy at HA but pre-eclampsia does not result [12,13]. This speaker proposed that the in vivo model pregnancy at HA may permit separation of the effects of hypoxia from unique, causal features of pre-eclampsia. Among the ‘normal’ effects of HA are increased villous angiogenesis. Changes in gene expression in normal placentae from high versus low altitude were examined. Four functional gene groups involved in response to hypoxia were targeted; markers of hypoxia, angiogenesis, trophoblast invasion and growth regulation [14]. The preliminary results suggest that markers of tissue remodelling are increased in the normal HA placenta and growth factors may be reduced.
S113
The preliminary data pertinent to three causal hypotheses were discussed. Isabella Caniggia found specific defects in the oxygen-sensitive regulatory pathway HIF-1, in pre-eclamptic but not in HA placentae [15]. Fiona Lyall found that expression of haemoxygenase-2, which helps to maintain basal placental vascular tone, was reduced in both pre-eclampsia and in normal HA placental endothelial cells [16]. She also found that VCAM-1, a marker of endothelial cell activation, which is increased in pre-eclampsia [17] was not increased in HA compared with low altitude pregnancy. Stacy Zamudio concluded that use of the HA model to examine the specific factors associated with pre-eclampsia, as well as broader analyses using powerful technologies such as gene array, may permit us to separate the non-pathological effects of chronic hypoxia from those pathological features uniquely associated with the etiology of pre-eclampsia.
CLINICAL ASPECTS OF PRE-ECLAMPSIA The second part of the workshop was more clinically orientated addressing new patho-physiological and clinical findings. H. Mu¨nteferring (University of Mainz, Germany) reviewed the pathomorphological features of the placenta in preeclampsia. He confirmed that neither conventional macroscopic nor microscopic examinations of the fetal part of the placenta allow a morphological diagnosis of pre-eclampsia. Those changes that are found are obviously not suitable for describing the degree of seriousness of pre-eclampsia even when quantitative methods are used. In the feto-placental border, these changes are defective invasion of the extravillous cytotrophoblast, hyperplastic arterio-arteriolopathy, acute atherosclerosis and fibrinoid necrosis of endothelium. In the fetal part of placenta, changes include infarctions/fibrin deposits, obliterative angiopathy, stromal fibrosis/fibrinoid degeneration, syncytiotrophoblastic nodes (Tenney–Parker phenomenon) and disturbances of maturation of the villi. Rudi Seufert (Johannes Gutenberg University, Mainz) discussed experimental models for pre-eclampsia. Experimental models can simulate single clinical features. For example, chronic reduction of uteroplacental blood flow in gravid rats by aortic banding below Aa. renalis leads to hypertension and proteinuria. The group studied isometrical contractions and relaxations of isolated vessels from A. mesenterica superior and from A. carotis induced by norepinephrine, angiotensin II and acetylcholine. Reduced uteroplacental blood flow significantly increased vasoreactivity of isolated vessels, while endothelium denudation and incubation with indomethacin normalized the increased contractions. Inhibition of NOsynthesis by N-nitro-arginine increased vasoreactivity. It was speculated that de novo synthesis of local endothelial derived vasoconstrictive prostaglandins may increase local vasoreactivity. Incubation of fresh serum from gravid animals with reduced uteroplacental blood flow caused significantly increased contractions of isolated vessels and superoxide production, while gravid and non-gravid control serum did not.
S114
F. Bahlmann (University of Heidelberg, Germany) next discussed Doppler velocity and ultrasound in pre-eclampsia along with prediction and clinical guidelines. Two thirds of women with pre-eclampsia could be detected by colour-coded Doppler sonography of the uterine artery. Therefore this could be performed as a non-invasive screening method between 19 and 22 weeks of gestation. The compensatory phase of the fetus can be recognized by typical Doppler and ultrasound findings including increased pulsatility in the feto-placental unit, decreased pulsatility in the middle cerebral artery, decreased amniotic fluid and small placental volume. In the decompensatory phase, progressive haemodynamic deterioration of the fetus occurs with impairment of myocardial function which could be detected by abnormal venous Doppler waveforms, occurrence of fetal heart rate abnormalities and worsening of the biophysical profile. Only cases with retrograde end diastolic flow velocities of the umbilical artery the Ductus venosus flow pattern show an increased pulsatility of the Ductus venous with absent or retrograde flow during atrial contraction reflecting increased pressure in the right atrium and venous system. This speaker concluded that combining multivessel Doppler, cardiotocography and biophysical profile with serial evaluation will maximize the precision of fetal assessment and therefore optimize the timing of delivery. Finally Susanne Strand (University of Heidelberg) discussed placenta-derived CD95-ligand and its role in apoptosis and liver damage in HELLP syndrome. CD95-mediated apoptosis of liver cells is a major pathogenic mechanism in liver disease. The interaction of CD-95 with its ligand CD-95L is a prerequisite for induction of apoptosis and thus the source of CD-95L is critical for understanding the pathomechansim of liver damage. This group investigated the role of the CD95system in causing liver damage in HELLP syndrome. Apoptosis in the liver of HELLP patients and cytotoxic activity for primary human hepatocytes in HELLP serum were typical features. Inhibition of CD-95 signalling reduced the cytotoxic activity of HELLP serum. In addition, cytotoxic activity increased as HELLP syndrome developed. Furthermore, CD95L was found to be produced in the placenta and extracts of placenta were cytotoxic for human hepatocytes. Injection of mouse placenta extract in mice induced liver damage which could be prevented by blocking CD-95L. This speaker suggested that CD-95L derived from the placenta acts systemically and is probably the cause of liver damage in HELLP syndrome. In summary the speakers provided an excellent overview of oxidative stress in pre-eclampsia and emphasized that future
Placenta (2004), Vol. 25, Supplement A, Trophoblast Research, Vol. 18
clinical therapies may come about through furthering our understanding of the processes involved.
REFERENCES [1] Hayes JD, Pulford DJ. The glutathione S-transferase supergene family: regulation of GST and the contribution of the isoenzymes to cancer chemoprotection and drug resistance. Crit Rev Biochem Mol Biol 1995; 30:445–600. [2] Zusterzeel PLM, Peters WHM, De Bruyn MA, Knapen MFCM, Merkus HWJM, Steegers EAP. Glutathione S-transferase isoenzymes in decidua and placenta of preeclamptic pregnancies. Obstet Gynecol 1999; 94:1033–8. [3] Steegers EAP, Mulder TPJ, Bisseling JGA, Delemarre FMC, Peters WHM. Glutathione S-transferase alpha as marker for hepatocellular damage in pre-eclampsia and HELLP syndrome. Lancet 1995; 345:1571–2. [4] Knapen MFCM, Peters WHM, Mulder TPJ, Merkus HMWM, Jansen JBMJ, Steegers EAP. Glutathione and glutathione-related enzymes in decidua and placenta of controls and women with pre-eclampsia. Placenta 1999;20:541–6. [5] Zusterzeel PLM, Visser W, Peters WHM, Merkus HWJM, Nelen WLDM, Steegers EAP. Polymorphism in the glutathione S-transferase P1 gene and risk for preeclampsia. Obstet Gynecol 2000;96:50–4. [6] Zusterzeel PLM, te Morsche RHM, Raijmakers MTM, Roes EM, Peters WHM, Steegers EAP. Paternal contribution to the risk for pre-eclampsia. J Med Genet 2002;39:44–5. [7] Myatt L, Rosenfield RB, Eis ALW, Brockman DE, Greer IA, Lyall F. Nitrotyrosine residues in placenta. Evidence of peroxynitrite formation and action. Hypertension 1996;28:488–93. [8] Kossenjans W, Eis A, Sahay R, Brockman D, Myatt L. Role of peroxynitrite in altered fetal-placental vascular reactivity in diabetes or preeclampsia. Am J Physiol Heart Circ Physiol 2000; 278:H1311–H1319. [9] Hensley K, Robinson KA, Gabbita SP et al. Reactive oxygen species, cell signaling, and cell injury. Free Radic Biol Med 2000;28:1456–62. [10] Redman CWG, Sargent IL. Pre-eclampsia as an inflammatory response. In: Critchley H, Walker JJ, Poston L., editors. Proceedings of RCOG Study Group 2004 in press. [11] Palmer SK, Moore LG, Young DA, Cregger B, Berman JC, Zamudio S. Increased preeclampsia and altered blood pressure course during normal pregnancy at high (3100 m) altitude in Colorado. Am J Obstet Gynecol 1999;180:1161–8. [12] Zamudio S. The placenta at high altitude. High Alt Med Biol 2003; 4:171–91. [13] Tissot van Patot M, Grilli A, Chapman P, Blanford C, Broad E, Tyson W et al. Increased fetal and maternal angiogenesis and decreased remodeling of uteroplacental arteries in high (3100 m) vs. low (1600 m) altitude placentas. Placenta 2003;24:326–35. [14] Caniggia I, Soleymanlou N, Jurisica I, Zamudio S. Targeted analysis of differences in placental gene expression resulting from chronic (altitudeinduced) hypoxia. Placenta 2003;24:A21. [15] Caniggia I, Wu Y, Zamudio S. Overexpression of Hif-1 in placentae from high altitude pregnancies. Placenta 2002;23:A49. [16] Lyall F, Myatt L, Cousins F, Barber A, Zamudio S. Abnormal expression of hemeoxygenase in placentae from high altitude pregnancies. J Soc Gynecol Investig 2002;9(suppl):223A. [17] Lyall F, Cousins F, Duffie L, Zamudio S. VCAM-1 concentrations are reduced in the maternal circulation in high altitude pregnancies. J Soc Gynecol Investig 2003;10(suppl):308A.
Pre-eclampsia—A Workshop Report F. Lyall a,* and R. Seufert b a
Maternal and Fetal Medicine Section, Institute of Medical Genetics, University of Glasgow, Yorkhill, Glasgow, Scotland G3 8SJ, UK; b Department of Obstetrics and Gynaecology, Johannes Gutenberg University, Langenbeckstraße 1, D55101 Mainz, Germany
INTRODUCTION The aims of this workshop on pre-eclampsia were two-fold. The first half aimed to provide an update on the influence of oxygen and oxidative stress on the development of preeclampsia. The session, with four speakers, was chaired by Fiona Lyall. The second part of the workshop was more clinically orientated addressing new patho-physiological and clinical findings. This session also had four speakers and was chaired by Rudi Seufert.
OXIDATIVE STRESS IN PRE-ECLAMPSIA Maarten Raijmakers (St Thomas’ Hospital, London) discussed placental detoxification and oxidative stress in pre-eclampsia. The glutathione/glutathione dependent enzyme system is one the most important protective systems [1]. Glutathione S-transferases (GSTs) provide protection against xenobiotics and metabolize breakdown products produced in vivo by oxidative stress. In eukaryotes the GST family is comprised of membrane-bound transferases and a family of seven soluble proteins, also referred to as cytosolic GSTs. GST Alpha, Pi, Mu and Theta (GSTA, GSTP, GSTM and GSTT, respectively) are primarily expressed in humans in a tissue specific manner. GST alpha is the main isoform in liver, whereas GSTPi is predominantly expressed in placenta and embryonic and fetal tissues [2]. Steegers et al. were the first to link GSTs with complications of pregnancy [3]. The placenta provides protection against noxious compounds for both mother and child. In contrast placental oxidative stress contributes to the development of pre-eclampsia. Although placental and decidual expression of GSTP is lower in women with preeclampsia, overall GST enzyme activity is similar in normotensive and pre-eclamptic pregnancies [1]. In contrast, glutathione levels and glutathione peroxidase enzyme activity were higher in women with pre-eclampsia [4] which is probably due to a compensatory antioxidant response. The higher levels of GST enzymes, GPX enzyme activity and glutathione levels in decidual tissue as compared to placental levels may indicate an unforeseen role in detoxification for decidual tissue. A polymorphism in the GSTP gene was found to be a risk factor for pre-eclampsia [5]. The prevalence of this polymor*
To whom correspondence should be addressed; E-mail: gqta01@ udcf.gla.ac.uk 0143-4004/$–see front matter
phism in the GSTP gene was also higher in fathers and offspring of women who developed pre-eclampsia compared to controls [6]. Leslie Myatt (University of Cincinnati, USA) followed with a discussion on the role of nitrotyrosine in the placenta in pre-eclampsia. Pregnancy is a state of oxidative stress and this is exacerbated in certain pregnancy pathologies including pre-eclampsia. This increased oxidative stress is associated with endothelial and vascular dysfunction in the placenta and increased apoptosis and deportation of trophoblast. Oxidative stress may arise from increased production of reactive oxygen species, such as superoxide and nitric oxide. These may interact to produce peroxynitrite (ONOO) a powerful longlived pro-oxidant whose production and action can be determined by its ability to nitrate tyrosine residues on proteins producing nitrotyrosine residues. Nitration of proteins in turn alters protein function. This group demonstrated the presence of nitrotyrosine residues in the placenta from pregnancies complicated by pre-eclampsia and pre-gestational diabetes in association with altered vascular reactivity [7,8]. To determine a cause and effect relationship, nitrated proteins were identified in the placenta and these include phospho p38 MAP kinase and p53, the tumour suppressor gene. Nitration of phospho p38 MAP kinase appears to reduce catalytic activity. 2D gel electrophoresis has revealed differences in protein expression that may be related to altered placental function in pathologic pregnancies.
THE MATERNAL SYSTEMIC INFLAMMATORY RESPONSE IN PRE-ECLAMPSIA Chris Redman (University of Oxford, UK) next discussed the maternal systemic inflammatory response in pre-eclampsia in relation to oxidative stress. This work was performed in collaboration with Ian Sargent (Oxford). Oxidative stress and inflammatory responses are related, perhaps inseparable phenomena [9]. This is because reactive oxygen species are widely used as second messengers to propagate proinflammatory signals. These interrelationships imply that antioxidants, such as the anti-oxidant vitamins that are now being tested as prophylaxis for pre-eclampsia, are anti-inflammatory agents. This group has shown that normal pregnancy is characterized by a systemic inflammatory response which intensifies in the third trimester. In parallel, there are also 2004 IFPA and Elsevier Ltd. All rights reserved.
Lyall and Seufert: Pre-eclampsia
increased circulating markers of systemic oxidative stress. In pre-eclampsia these changes are on average more intense. It is proposed that the endothelial dysfunction and other elements of the pre-eclampsia syndrome are consequences of the systemic inflammatory processes [10]. It is probable that there are multiple causes for these responses in normal and pre-eclamptic pregnancies. The group’s evidence points to a major role for syncytiotrophoblast debris shed into the maternal circulation. This debris, including whole cell fragments, subcellular syncytial fragments (STBM), soluble cytokeratin, and soluble placental DNA and RNA, is generated during renewal of the syncytial surface of the placenta. They are all significantly increased in preeclampsia and have the potential to be pro-inflammatory. The group have demonstrated that monocytes are associated with syncytiotrophobast antigen peripheral blood in vivo. Although there is no apparent increase in the proportion of peripheral blood monocytes binding STBM in pre-eclampsia, this may be because STBM binding is increased, but the activated monocytes are rapidly cleared from the circulation or that the primary site of clearance is in the reticuloendothelial system, such as the liver. There is clear evidence that monocytes are activated by STBM in vitro. For example STBM stimulate peripheral blood mononuclear cells from non-pregnant women to produce more TNF, IL-12 or IL-18. In summary, a systemic inflammatory response and oxidative stress are inseparable processes. Normal pregnancy is characterized by systemic inflammation and, on average, in pre-eclampsia these responses are more intense. Placental debris could be the cause accounting for the link between the maternal syndrome and the essential placental origins of pre-eclampsia.
HIGH ALTITUDE PREGNANCY AS A MODEL FOR CHRONIC HYPOXIA Stacy Zamudio (New Jersey Medical School, USA) expanded the topic by discussing a model of chronic placental hypoxia. The incidence of pre-eclampsia is increased 2–4 fold in women residing at high altitude (HA >2700 m), supporting the idea that placental hypoxia contributes to the development of pre-eclampsia [11]. Neither failed trophoblast invasion nor placental hypoxia alone are sufficient to explain pre-eclampsia. Many features of pre-eclampsia are present in normal pregnancy at HA but pre-eclampsia does not result [12,13]. This speaker proposed that the in vivo model pregnancy at HA may permit separation of the effects of hypoxia from unique, causal features of pre-eclampsia. Among the ‘normal’ effects of HA are increased villous angiogenesis. Changes in gene expression in normal placentae from high versus low altitude were examined. Four functional gene groups involved in response to hypoxia were targeted; markers of hypoxia, angiogenesis, trophoblast invasion and growth regulation [14]. The preliminary results suggest that markers of tissue remodelling are increased in the normal HA placenta and growth factors may be reduced.
S113
The preliminary data pertinent to three causal hypotheses were discussed. Isabella Caniggia found specific defects in the oxygen-sensitive regulatory pathway HIF-1, in pre-eclamptic but not in HA placentae [15]. Fiona Lyall found that expression of haemoxygenase-2, which helps to maintain basal placental vascular tone, was reduced in both pre-eclampsia and in normal HA placental endothelial cells [16]. She also found that VCAM-1, a marker of endothelial cell activation, which is increased in pre-eclampsia [17] was not increased in HA compared with low altitude pregnancy. Stacy Zamudio concluded that use of the HA model to examine the specific factors associated with pre-eclampsia, as well as broader analyses using powerful technologies such as gene array, may permit us to separate the non-pathological effects of chronic hypoxia from those pathological features uniquely associated with the etiology of pre-eclampsia.
CLINICAL ASPECTS OF PRE-ECLAMPSIA The second part of the workshop was more clinically orientated addressing new patho-physiological and clinical findings. H. Mu¨nteferring (University of Mainz, Germany) reviewed the pathomorphological features of the placenta in preeclampsia. He confirmed that neither conventional macroscopic nor microscopic examinations of the fetal part of the placenta allow a morphological diagnosis of pre-eclampsia. Those changes that are found are obviously not suitable for describing the degree of seriousness of pre-eclampsia even when quantitative methods are used. In the feto-placental border, these changes are defective invasion of the extravillous cytotrophoblast, hyperplastic arterio-arteriolopathy, acute atherosclerosis and fibrinoid necrosis of endothelium. In the fetal part of placenta, changes include infarctions/fibrin deposits, obliterative angiopathy, stromal fibrosis/fibrinoid degeneration, syncytiotrophoblastic nodes (Tenney–Parker phenomenon) and disturbances of maturation of the villi. Rudi Seufert (Johannes Gutenberg University, Mainz) discussed experimental models for pre-eclampsia. Experimental models can simulate single clinical features. For example, chronic reduction of uteroplacental blood flow in gravid rats by aortic banding below Aa. renalis leads to hypertension and proteinuria. The group studied isometrical contractions and relaxations of isolated vessels from A. mesenterica superior and from A. carotis induced by norepinephrine, angiotensin II and acetylcholine. Reduced uteroplacental blood flow significantly increased vasoreactivity of isolated vessels, while endothelium denudation and incubation with indomethacin normalized the increased contractions. Inhibition of NOsynthesis by N-nitro-arginine increased vasoreactivity. It was speculated that de novo synthesis of local endothelial derived vasoconstrictive prostaglandins may increase local vasoreactivity. Incubation of fresh serum from gravid animals with reduced uteroplacental blood flow caused significantly increased contractions of isolated vessels and superoxide production, while gravid and non-gravid control serum did not.
S114
F. Bahlmann (University of Heidelberg, Germany) next discussed Doppler velocity and ultrasound in pre-eclampsia along with prediction and clinical guidelines. Two thirds of women with pre-eclampsia could be detected by colour-coded Doppler sonography of the uterine artery. Therefore this could be performed as a non-invasive screening method between 19 and 22 weeks of gestation. The compensatory phase of the fetus can be recognized by typical Doppler and ultrasound findings including increased pulsatility in the feto-placental unit, decreased pulsatility in the middle cerebral artery, decreased amniotic fluid and small placental volume. In the decompensatory phase, progressive haemodynamic deterioration of the fetus occurs with impairment of myocardial function which could be detected by abnormal venous Doppler waveforms, occurrence of fetal heart rate abnormalities and worsening of the biophysical profile. Only cases with retrograde end diastolic flow velocities of the umbilical artery the Ductus venosus flow pattern show an increased pulsatility of the Ductus venous with absent or retrograde flow during atrial contraction reflecting increased pressure in the right atrium and venous system. This speaker concluded that combining multivessel Doppler, cardiotocography and biophysical profile with serial evaluation will maximize the precision of fetal assessment and therefore optimize the timing of delivery. Finally Susanne Strand (University of Heidelberg) discussed placenta-derived CD95-ligand and its role in apoptosis and liver damage in HELLP syndrome. CD95-mediated apoptosis of liver cells is a major pathogenic mechanism in liver disease. The interaction of CD-95 with its ligand CD-95L is a prerequisite for induction of apoptosis and thus the source of CD-95L is critical for understanding the pathomechansim of liver damage. This group investigated the role of the CD95system in causing liver damage in HELLP syndrome. Apoptosis in the liver of HELLP patients and cytotoxic activity for primary human hepatocytes in HELLP serum were typical features. Inhibition of CD-95 signalling reduced the cytotoxic activity of HELLP serum. In addition, cytotoxic activity increased as HELLP syndrome developed. Furthermore, CD95L was found to be produced in the placenta and extracts of placenta were cytotoxic for human hepatocytes. Injection of mouse placenta extract in mice induced liver damage which could be prevented by blocking CD-95L. This speaker suggested that CD-95L derived from the placenta acts systemically and is probably the cause of liver damage in HELLP syndrome. In summary the speakers provided an excellent overview of oxidative stress in pre-eclampsia and emphasized that future
Placenta (2004), Vol. 25, Supplement A, Trophoblast Research, Vol. 18
clinical therapies may come about through furthering our understanding of the processes involved.
REFERENCES [1] Hayes JD, Pulford DJ. The glutathione S-transferase supergene family: regulation of GST and the contribution of the isoenzymes to cancer chemoprotection and drug resistance. Crit Rev Biochem Mol Biol 1995; 30:445–600. [2] Zusterzeel PLM, Peters WHM, De Bruyn MA, Knapen MFCM, Merkus HWJM, Steegers EAP. Glutathione S-transferase isoenzymes in decidua and placenta of preeclamptic pregnancies. Obstet Gynecol 1999; 94:1033–8. [3] Steegers EAP, Mulder TPJ, Bisseling JGA, Delemarre FMC, Peters WHM. Glutathione S-transferase alpha as marker for hepatocellular damage in pre-eclampsia and HELLP syndrome. Lancet 1995; 345:1571–2. [4] Knapen MFCM, Peters WHM, Mulder TPJ, Merkus HMWM, Jansen JBMJ, Steegers EAP. Glutathione and glutathione-related enzymes in decidua and placenta of controls and women with pre-eclampsia. Placenta 1999;20:541–6. [5] Zusterzeel PLM, Visser W, Peters WHM, Merkus HWJM, Nelen WLDM, Steegers EAP. Polymorphism in the glutathione S-transferase P1 gene and risk for preeclampsia. Obstet Gynecol 2000;96:50–4. [6] Zusterzeel PLM, te Morsche RHM, Raijmakers MTM, Roes EM, Peters WHM, Steegers EAP. Paternal contribution to the risk for pre-eclampsia. J Med Genet 2002;39:44–5. [7] Myatt L, Rosenfield RB, Eis ALW, Brockman DE, Greer IA, Lyall F. Nitrotyrosine residues in placenta. Evidence of peroxynitrite formation and action. Hypertension 1996;28:488–93. [8] Kossenjans W, Eis A, Sahay R, Brockman D, Myatt L. Role of peroxynitrite in altered fetal-placental vascular reactivity in diabetes or preeclampsia. Am J Physiol Heart Circ Physiol 2000; 278:H1311–H1319. [9] Hensley K, Robinson KA, Gabbita SP et al. Reactive oxygen species, cell signaling, and cell injury. Free Radic Biol Med 2000;28:1456–62. [10] Redman CWG, Sargent IL. Pre-eclampsia as an inflammatory response. In: Critchley H, Walker JJ, Poston L., editors. Proceedings of RCOG Study Group 2004 in press. [11] Palmer SK, Moore LG, Young DA, Cregger B, Berman JC, Zamudio S. Increased preeclampsia and altered blood pressure course during normal pregnancy at high (3100 m) altitude in Colorado. Am J Obstet Gynecol 1999;180:1161–8. [12] Zamudio S. The placenta at high altitude. High Alt Med Biol 2003; 4:171–91. [13] Tissot van Patot M, Grilli A, Chapman P, Blanford C, Broad E, Tyson W et al. Increased fetal and maternal angiogenesis and decreased remodeling of uteroplacental arteries in high (3100 m) vs. low (1600 m) altitude placentas. Placenta 2003;24:326–35. [14] Caniggia I, Soleymanlou N, Jurisica I, Zamudio S. Targeted analysis of differences in placental gene expression resulting from chronic (altitudeinduced) hypoxia. Placenta 2003;24:A21. [15] Caniggia I, Wu Y, Zamudio S. Overexpression of Hif-1 in placentae from high altitude pregnancies. Placenta 2002;23:A49. [16] Lyall F, Myatt L, Cousins F, Barber A, Zamudio S. Abnormal expression of hemeoxygenase in placentae from high altitude pregnancies. J Soc Gynecol Investig 2002;9(suppl):223A. [17] Lyall F, Cousins F, Duffie L, Zamudio S. VCAM-1 concentrations are reduced in the maternal circulation in high altitude pregnancies. J Soc Gynecol Investig 2003;10(suppl):308A.