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Role of Reduced Nitric Oxide in Liver Cell Apoptosis Inhibition During Liver Damage
Archives of Medical Research
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(2018)
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REVIEW ARTICLE
Roles of Reduced Nitric Oxide in Liver Cell Apoptosis Inhibition During Liver Damage Ying-yi Wang,a,1 Meng-ting Chen,a,1 Hui-min Hong,a,1 Ying Wang,a Qian Li,a Hui Liu,a Mei-wen Yang,b Fen-fang Hong,c and Shu-long Yanga b
a Department of Physiology, College of Medicine, Nanchang University, Nanchang, China Department of Nurse, The Affiliated Hospital of Jiangxi Academy of Medical Science, Nanchang, Jiangxi, China c Department of Experimental Teaching Center, Nanchang University, Nanchang, China
Received for publication June 27, 2018; accepted September 14, 2018 (ARCMED:2018_126).
Hepatic injury is a major event in liver surgery and may lead to liver cell apoptosis. Nitric oxide (NO) is an unstable, carbon-centered radical with a short half-time and a key role in molecular signaling. Increasing evidence demonstrates that NO plays an important role in the liver cell apoptosis caused by hepatic ischemia reperfusion (IR) injury and other liver damage. Our recent article summarized the association between elevated nitric oxide levels and hepatic cell apoptosis during liver injury. This article reviews the newest research progress for the relationship between decreased nitric oxide levels and hepatic cell apoptosis inhibition during liver injury. It is shown that decreased NO level can influence liver apoptosis by promoting or inhibiting the signaling pathway involving the caspase family, BCL-2, mitochondria, oxidative stress, death receptors, and mitogen activated protein kinases, etc. This review outlines the literature basis for clinical application of anti-apoptosis treatment to relieve organ injury following liver surgery. NO-related drugs appear to be helpful in clinical treatment of liver diseases. Ó 2018 IMSS. Published by Elsevier Inc. Key Words: Reduced nitric oxide, Apoptosis inhibition, Liver damage.
Introduction Apoptosis is an autonomous cell death controlled by its relative genes. There is some overexpression of oncogenes and anti-oncogenes, and death receptoreligand binding and excessive inflammatory cytokines occurred in damaged liver cells. These factors may activate a series of signaling pathways that lead to liver cell apoptosis, including caspase pathway, Bcl-2 gene family, oxidative stress, etc. Increasing evidence demonstrates that nitric oxide (NO) plays an important role in liver cell apoptosis caused by hepatic ischemia reperfusion (IR) injury and other liver damage. In China, the morbidity and mortality of liver disease, which is one of
1
These authors contributed equally to this work. Address reprint requests to: Shu-long Yang, Department of Physiology, College of Medicine, Nanchang University, Nanchang, China; Phone/FAX: (þ86) (791) 886360556; Address reprint requests to: Fen-fang Hong, Department of Experimental Teaching Center, Nanchang University, Xuefu Road 999, Honggutan New District, Nanchang City 330031, Jiangxi province, China. Phone: (þ86)18970965319; FAX: (þ86)791-83827051; E-mail: [email protected] or [email protected]
the major diseases that threaten human health, are very high. Recently, we reviewed the association between elevated nitric oxide levels and hepatic cell apoptosis during liver injury (1). In this paper, we further summarize the newest research progress for the relationship between decreased NO levels and liver cell apoptosis inhibition during liver injury. Apoptotic Signal Transduction Pathways Exist Invariably in Damaged Liver Apoptotic signal transduction pathways in damaged liver are as follows: a) caspases, b) Bcl-2 gene family, c) death receptor, d) mitochondrial, e) oxidative stress, f) mitogen activated protein kinase (MAPK), g) PI3K/Akt, h) NF-k kB. They can be activated to induce liver cell apoptosis upon the overexpression of some oncogenes and antioncogenes, death receptoreligand binding, and expression of excessive inflammatory cytokines. The Source of NO and Its Biological Role in Liver Injury NO is an important biological messenger and effector molecule that has been extensively researched and gradually
0188-4409/$ - see front matter. Copyright Ó 2018 IMSS. Published by Elsevier Inc. https://doi.org/10.1016/j.arcmed.2018.09.001
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understood in recent decades. Endogenously, nitric oxide synthase (NOS) synthesizes NO using L-arginine as a substrate. There are three NOS isoforms in humans, namely neuronal (nNOS), endothelial (eNOS), and inducible (iNOS). nNOS and eNOS are Ca2þ-dependent, their activation requires binding to the kinase binding sites of calmodulin. These NO synthases are mainly distributed in endothelial cells, platelets, and brain and adrenal cells. Their effects include smooth muscle relaxation, inhibition of platelet aggregation and adhesion, and nerve signal transduction. Conversely, iNOS is Ca2þindependent; its activation depends on some external factors, such as bacteria, viruses, interferon, proinflammatory cytokines, etc., of which endotoxin is the main iNOS inducer. Evidently, when macrophages and neutrophils were activated, iNOS was overexpressed to produce an immediate NO increase, which may kill bacteria, parasites, and tumor cells and result in cell necrosis (2). NO has various biological functions. As an endotheliumderived vasodilator, it can antagonize endothelin vasoconstriction, improve liver microcirculatory function, and inhibit leukocyte adhesion. Furthermore, as an antioxidant, it can reduce hepatotoxicity by alleviating liver cell injury caused by superoxide anion free radicals. In addition, NO can inhibit expressions of adhesion molecule MHC- II and ICAM-1 in macrophages, subsequently reducing liver inflammation. However, hepatocytes and Kupffer cells can produce a large quantity of NO via iNOS; elevated NO level is toxic to liver due to depression of mitochondrial respiratory chain function, liver cell glucose metabolism, and synthesis of liver cell protein and DNA. Thus, ultimate NO action on liver injury appears to be dependent on the net outcome of protection and aggravation effects. NO Level Decrease and Hepatic Cell Apoptosis Inhibition NO level decrease and hepatic cell apoptosis inhibition induced by caspases pathway. Cell apoptosis is a cascade amplification reaction where the substrate is hydrolyzed irreversibly and limitedly by caspase. At least 14 caspases are currently known. Caspase molecules have high homology and similar structures, and all are cysteine proteases. Caspases can be divided into two categories based on function: one is cell processing, such as pro-IL-1b and pro-IL-1d, the other is cell apoptosis, including caspase 2, 3, 6, 7, 8, 9, and 10, which are subdivided into starter enzymes, such as caspase 8, 9, and 10, and effector enzymes, such as caspase 3, 6, and 7. These subdivisions play a role in the upstream and downstream regulation, respectively, of death signal transduction. The starter enzymes stimulate apoptosis signals and initiate the cell suicide process, and the effector enzymes are specific executors that complete the hydrolysis of specific protein substrates. Peritonitis from sepsis (3), arsenic (4), lipopolysaccharide (LPS) (5), and alcohol (6) can increase NO level and caspase expressions upregulate in liver cells, leading to liver injury and
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hepatocyte apoptosis. However, pretreatment with deprenyl (3), diallyl trisulfide (4), genistein (5), and microencapsulated protein-1 (6) counteracted liver damage caused by the above factors, with decreased levels of NO and caspase. The protective effects of these drugs on liver cells were also demonstrated by histopathological check. These results suggested that apoptosis inhibition and NO decrease were involved in the drugs actions. Similarly, 20 ,40 -Dihydroxy60 -methoxy-30 ,50 -dimethylchalcone (DMC) was demonstrated to eliminate H2O2-induced oxidative liver damage and decrease NO level and caspase 3 expression (7) This effectively counteracted the loss of cell viability. The protective effect of coenzyme Q10 on rat liver injury induced by acetaminophen is related to its significant reduction of iNOS, NF-kB, caspase 3, and p53 overexpression in liver tissue (8). Da Rosa DP (9) found that antioxidants may downregulate expressions of iNOS, caspase 3, and caspase 6; thus, it can protect the liver from liver inflammation and apoptosis induced by intermittent hypoxia. Kwon AH, et al. (10) studied the mechanism for the protective effects of plasma fibronectins (pFn) on endotoxic shock in rats with partial hepatectomy. The results showed that in the pFn treatment group, NO serum level was significantly lower than the control group; similarly, caspase 3 and caspase 8 activity was significantly inhibited, and the degree of hepatic cell necrosis and apoptosis decreased. In a recent study, one of the protective effects of Se against Cd-induced injury was the reduction of NO production and decreased expression of caspase 3 (11). Similarly, the preventive effects of indigofera oblongifolia leaf extract (IOLE) on lead acetate (PbAc)-induced hepatotoxicity in adult male Wistar rats were also achieved by reducing NO production and decreasing caspase 3 expression (12). It was found that punicalagin significantly and dose-dependently reduced NO, iNOS, and caspase 3 and 9 activities (13). Furthermore, punicalagin also protected rat liver against cyclophosphamide toxicity by inhibiting oxidative/nitrosative stress, inflammation and apoptosis. The above studies confirmed that decreased caspase expressions and lower NO level can effectively reduce liver cell apoptosis and confer a protective effect on the liver. The drugs mentioned above mostly achieved this protective effect by inhibiting caspase 3, which is the most important terminal enzyme in the process of apoptosis. In the process of developing new drugs, this may be a key mechanism worthy of special attention. The relationship between caspase alterations and decreased NO level still needs further exploration. Whether the protective effects of multi-acting drugs, which significantly reduced the levels of various caspases in liver cells, were better than that of other drugs, such as DMC, Se, IOLE that only affected one caspase, is still worthy of further study. Reduced no level and inhibition of liver cell apoptosis mediated by imbalanced Bax/Bcl-2 ratio. Recent studies
Reduced Nitric Oxide Involves in Liver Cell Apoptosis Inhibition
have shown that procyanidin B2 exerted its effects via antiinflammation and antioxidation, downregulation of iNOS expression, inhibition of Bax upregulation and Bcl xl downregulation, indicating that procyanidin B2 can reduce cell apoptosis (14). These findings suggest that procyanidin B2 may prevent CCl4-induced apoptosis injury. Acteoside (15), cyclo-trans-4-l-hydroxyprolyl-l-serine (JBP485) (16), and emblica officinalis gaertn (17) all have a protective effect against liver injury in mice. Their underlying mechanisms may include decreasing NO content, downregulating Bax protein expression, and increasing Bcl-2 protein expression, which inhibits mice liver cell apoptosis. Tsuchihashi S et al reported that FK330 (FR260330), a novel iNOS inhibitor, can prevent IR injury in rat liver during transplantation and decrease the Bax/Bcl-2 ratio to prevent liver cell apoptosis (18). These studies suggested that the NO and Bax/Bcl-2 ratio reduction could inhibit liver cell apoptosis to a certain extent. The fact that iNOS inhibitors reduced Bax/Bcl-2 ratio confirms the correlation between NO reduction and Bax/Bcl-2 ratio reduction. In another study, tormentic acid (TA) (19) reduced TNF a by inhibiting NF-k KB activity; furthermore, it decreased NO and iNOS levels and increased Bcl-2 expression, which lead to the an imbalanced Bax/Bcl-2 ratio. Thus, the protective effects of tormentic acid in liver may be superior to other drugs with a single effect. NO level reduction and inhibition of liver cell apoptosis induced by oxidative stress. Several studies have confirmed that oxidative stress plays an important role in liver injury, and many drugs reduce hepatic cell apoptosis by inhibiting oxidative stress pathway (20e22). Kocak FE, et al. (20) pretreated liver IR injury rats with 2.5 or 5 mg/kg of simvastatin (SV). Their results showed that 5.0 mg/kg SV reduced liver injury and cell apoptosis. Compared to the IR control group, the levels of malonyldialdehyde (MDA) and NO in the 5.0 mg/kg SV group were decreased, whereas glutathione peroxidase, catalase, and superoxide dismutase (SOD) activity were significantly increased. These results may guide clinical practice. However, the doseeresponse relationship still needs to be established. It was shown that melatonin (21) and cisplatin (22) can reduce NO production, reduce oxidized glutathione (GSSG), and increase glutathione (GSH) to inhibit cell apoptosis. IL-4 (23) can downregulate iNOS mRNA expression and reduce GSH consumption, thereby inhibiting the cell apoptosis. It is clear that antioxidants, such as procyanidin B2 (14), caffeic acid phenethyl ester (CAPE) (24) and artichoke leaf extract (25), play a positive role in inhibiting liver cell apoptosis. For example, a-lipoic acid (26), a powerful antioxidant, attenuates the hepatotoxic effects of nanocopper particles through improved oxidative status in male rats. In addition, citrus aurantium peel extract (27), tea polyphenols (28), and tangeretin (29) have potential protective
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effects against liver apotosis. These different types of drugs influence the apoptosis of liver cells, not only by oxidative stress, but also through other pathways. Furthermore, the influences of different drugs on liver injury is based on different conditions. Until now it has been unclear whether the efficacy of drugs with many pathways are better than drugs with only a single pathway affecting apoptosis. The issue needs further investigation. NO decrease and inhibition of liver cell apoptosis mediated by the mitochondrial pathway. Cytochrome c is regulated by Bax and Bcl-2, whose release is the key event of apoptosis and also the main apoptosis pathway driven by mitochondria. Other mitochondria-mediated apoptosis pathways are as follows: gamma rays or ceramide disrupting electron transfer link and mitochondrial energy metabolism, release of O2 free radicals and death-promoting factors, alteration of mitochondrial membrane permeability, and pressured cytoskeleton resulting from mitochondrial hyperosmolar state. All these pathways promote cell apoptosis. Livers from myocardial death wild-type and iNOS gene knockout type mice were transplanted into wild-type receptor mice, and mitochondria depolarization was detected through confocal microscopy in vivo. The results showed that iNOS and 3-nitro-tyrosine complex increased in the liver after transplant from myocardial death wildtype mice, but eNOS did not change. Compared to the control group, liver injury and loss of function from the myocardial death group were more severe. In liver from the donor mice with myocardial death and iNOS gene knockout type, NO production decreased, mitochondrial depolarization was reduced, ATP production was relieved, liver cell apoptosis was inhibited, and liver function improved (30). Grossini E found that levosimendan can inhibit liver cell apoptosis. One of its mechanisms is inhibition of nitric oxide synthase activation and decreased NO release. Another mechanism is inhibition of mitochondrial ATP sensitive potassium channel (mitoKATP) opening, reduced ATP consumption, and prevention of liver cell apoptosis (31). Treatment with geraniol reduced histological scores, fibrosis, and apoptosis in liver, preserved hepatic mitochondrial function—evidenced by reduced mitochondrial reactive oxygen species formation—enhanced adenosine triphosphate formation and membrane integrity, restored mitochondrial electron transport chain enzyme activity, increased mitochondrial DNA content, and downregulated iNOS expression in livers of rats fed a methioninecholine-deficient (MCD) diet. These results indicate that NO is closely related to apoptosis mediated by the mitochondrial pathway (32). NO level decline and mitogen activated protein kinase family inhibition. MAPKs are intracellular serine/threonine
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protein kinases, which include four subfamilies: extracellular signal regulated protein kinase (ERK), c-Jun N-terminal kinase (JNK), p38 mitogen activated protein kinase (p38 MAPK), and ERK5. MAPK’s signal transduction pathway exists in most cells, and it plays a vital role in the extracellular signal transduction to the cell and its nucleus and the process of cell biological response. Under physiological circumstances, ERK, JNK, and P38 MAPK can promote cell differentiation; however, in stress conditions, ERK may present an antiapoptotic effects, whereas JNK and P38 may promote apoptosis. Some scholars have observed that LPS-induced rat liver toxicity is mainly due to perturbation of the redox reaction balance and accumulation of oxidation products. Suberoylanilide hydroxamic acid (SAHA) administered simultaneously with LPS improved the survival rate of LPS-induced shock mice. SAHA neutralized LPSinduced oxidation reaction products, such as thiobarbituric acid reactive substances, nitrite and NO metabolites, and it also reversed the LPS-induced reduction of antioxidant enzymes and glutathione. These results demonstrated that SAHA can inhibit oxidationereduction reaction enzymes, apoptosis signal-regulating kinase, and p38 MAPK together with JNK, and thus reduce LPS-induced liver apoptosis (33). Using D-galactosamine induced acute liver failure in Wistar rats. Ganai AA et al., found that genistein reduced NO level in the liver by inhibiting iNOS expression and inhibited phosphorylation of MAPKs to achieve its hepatoprotective effect, illustrating the potential therapeutic properties of genistein for liver diseases (34). Furthermore, it is found that tangeretin pretreatment significantly improved liver function tests (ALT and AST) and diminished histopathologic structural damage in liver tissue. Regarding the MAPK pathway, tangeretin attenuated the cisplatin-induced increase in phospho-p38, phospho-c-Jun N-terminal kinase (p-JNK) and phospho-extracellular signal-regulated kinase (pERK1/2) in liver tissues (29). These results indicated that NO level decline is closely related to MAPK inhibition. NO level reduction and Fas death receptor-mediated liver apoptosis inhibition. Fas are apoptosis-promoting genes whose effects are contrary to the apoptosis related gene Bcl-2. As a member of the tumor necrosis factor receptor (TNFR) family, Fas is a transmembrane glycoprotein gene product. After binding FasL or Fas antibody, Fas directly activates apoptotic gene products and induces apoptosis, which is mediated by special intracellular proteins. The protective effect of H2S on hepatic IR injury in rats imparted by reducing serum inflammatory substances and inhibiting apoptosis related proteins, such as Fas and Fas ligand (35). Additionally, hydrogen sulfide can effectively inhibit the caspase 3 activity and cell
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apoptosis, but it is unclear which is the primary mechanism. NO level reduction and liver cell apoptosis inhibition mediated by NF-kB pathway. NF-kB is widely present in a variety of liver cells and involved in many physiological and pathological processes through regulation of gene transcription. In fulminant hepatic failure and arsenic poisoning induced liver injury, it has been confirmed that NF-kB is elevated to varying levels in liver tissue (5,36). There are NF-kB inhibition phenomenon involved in the liverprotection mechanisms of a-lipoic acid, astaxanthin original B2, genistein, and allicin. It was suggested that the antiapoptotic process of hepatic cells is related to the NFkB pathway (5,14,34,37). Another study showed that coenzyme Q10 significantly downregulated acetaminopheninduced iNOS overexpression, reduced NF-kB level in liver tissue, and inhibited hepatocyte apoptosis (8). Coenzyme Q10 was demonstrated to have multiple action mechanisms, suggesting that it prevents acetaminophen-induced acute liver toxicity and has important significance for guiding the clinical treatment of liver injury. It was found that punicalagin significantly and dose-dependently reduced the elevations of serum alanine aminotransferase and nuclear factor-kB p65 and liver toxicity (13). A study from Murugesan P, et al. showed that administration of BI113823 reduced iNOS expression and injury score and attenuated NF-kB activation and apoptosis in the liver (38). Double effects of NO on liver cell apoptosis. Prince JM, (39) cultured adult rat hepatocytes in medium containing various concentrations of the NO donor S-nitrosoglutathione and found that the apoptosis rate in the control group was 47.9 2.9% (mean standard error); the NO donor showed a biphasic response: 200 and 500 mmol S-nitrosoglutathione group apoptosis rate was only 14.4 0.4%, significantly lower than the control group and the 1000 mmol S-nitrosoglutathione group. The apoptosis rate in the nitrosoglutathione group was 82.6%, which was significantly higher than that in the control group. Similarly, Wang K, et al. (40) studies have shown that endogenous NO inhibits liver cell apoptosis and exogenous NO donors play a dual role in liver cell apoptosis; specifically, low concentrations produce inhibition and high concentrations promote apoptosis. It is suggested that low concentration of an NO donor can activate the iNOSeAktesurvivin axis and inhibit apoptosis. In contrast, high concentrations of NO donors can activate CHOP through p38 MAPK and upregulate TRAIL receptor DR5, thereby inhibiting the survivin gene and promoting apoptosis. In summary, the effect of NO on liver cell apoptosis is not simply inhibition or promotion. Given that most experimental designs are limited to narrow drug concentrations, this ambiguity is not surprising.
Reduced Nitric Oxide Involves in Liver Cell Apoptosis Inhibition
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Table 1. Different drugs mentioned in the paper and its effects on NO level and liver cell apoptosis and underlying mechanisms during liver injury
NO level
Liver cell apoptosis
Caspases[ Caspases[ ①Caspases[ ②NF-kB[ Caspases[ CaspasesY CaspasesY CaspasesY CaspasesY Caspase-3Y
[ [ [ [ Y Y Y Y Y
[ [ [ [ Y Y Y Y Y
①Caspase-3Y ②NF-kBY ③p53Y Caspase-3,6Y Caspase-3,8Y
Y Y Y
Y Y Y
Caspase-3Y Caspase-3Y ①Caspase-3,9Y ②NF-kBY ③p65Y
Y Y Y
Y Y Y
①Inhibiting Bax[ and bcl-xlY ②Antixidation ③NF-kBY BaxYBcl-2[ BaxYBcl-2[ BaxYBcl-2[ Bax/Bcl-2Y ①Bcl-2[ ②NF-kBY
Y
Y
Y Y Y Y Y
Y Y Y Y Y
Y
Y
Y Y Y Y Y Y Y Y Y
Y Y Y Y Y Y Y Y Y
(21) (22) (23) (24) (25) (26) (27) (28) (29)
Depolarization of mitochondriaY, consumption of ATPY Opening of the mitochondrial ATP sensitive potassium channel Y, consumption of ATPY Mitochondrial reactive oxygen species formationY, mitochondrial electron transport chain enzyme activity [, mitochondrial RNA content [
Y
Y
(30)
Y
Y
(31)
Y
Y
(32)
①p38 MAPKYJNKY ②Axidation reduction reaction enzymeY ①Phosphorylation of MAPKsY ②NF-kBY
Y
Y
LPS
(33)
Y
Y
D-galactosamine
(34)
①Fas, Fas ligandY ②caspase-3Y
Y
Y
Ischemia reperfusion
(35)
NF-kB[ NF-kBY NF-kBY
[ Y Y
[ Y Y
Pretreatment Caspases pathway Peritonitis with sepsis Arsenic Lipopolysaccharide Alcohol Deprenyl Trisulfide Genistein Microencapsulated protein-1 20 ,40 -dihydroxy-60 -methoxy-30 , 50 -dimethylchalcone Coenzyme Q10 Antioxidants Plasma fibronectins Se Indigofera oblongifolia leaf extract Punicalagin Imbalance of bax-bcl ratio Procyanidin B2 Acteoside TBP485 Emblica officinalis gaertn FK330 Tormentic acid Oxidative stress Simvastatin Melatonin Cisplatin IL-4 Caffeic acid phenethyl ester Artichoke leaf extract a-lipoic acid Citrus aurantium peel extract Tea polyphenols Tangeretin Mitochondrial pathway Knocking out iNOS gene Levosimendan Geraniol
Mitogen activated protein kinase family Suberoylanilide hydroxamic acid Genstein Fas death receptor Hydrogen sulfide NF-kB pathway Arsenic Allicin BI113823
Mechanism
MDAY, SODY, glutathione peroxidase[, catalase[ GSSGY, GSH[ GSSGY, GSH[ Consumption of GSHY Oxidative stressY Oxidative stressY Oxidative stressY Oxidative stressY Oxidative stressY ①Oxidative stressY ②Phosphorylation of p38 MAPK, JNK, EPKY
Revulsanta
Reference
(3) (4) (5) (6) (3) (4) (5) (6) (7)
H2O2 Acetaminophen Intermittent hypohios Endotoxic shock with partial hepatectomy Cd Lead acetate
(8) (9) (10)
Carbon tetrachloride
(14)
(11) (12) (13)
(15) (16) (17) (18) (19) Ischemia reperfusion
(20)
(36) (37) (38) (continued on next page)
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Table 1 (continued ) Pretreatment
Mechanism
Double effect s-nitrosoglutathione Endogenous nitric oxide Exogenous nitric oxide
NO level
Liver cell apoptosis
Y [ Y Y [
Y [ Y Y [
Revulsanta
200 or 500 mmol/L 1000 mmol/L
Reference
(39) (40)
Low concentration High concentration
a
The level of liver cell apoptosis was evaluated by pathological specimens. Revulsant is used to induce liver injury. Comprehensive list of drugs in the review and their effects on NO level and liver cell apoptosis.
Conclusion In general, NO can both inhibit and promote the liver cell apoptosis. Here we have reviewed recent literature concerning the mechanisms underlying the relationship between NO level reduction and liver cell apoptosis inhibition. This improves our understanding of NO’s role in liver cell apoptosis injury and provides a reliable basis for further exploration of the dual effects of NO on hepatic cell apoptosis and clinical treatment of liver diseases. We have also produced a Table 1, which includes all drugs and their protective mechanisms that were mentioned in this review. Overall, the most important mechanisms involved in hepatic cell apoptosis inhibition are: caspases pathway, Bax/Bcl2 ratio imbalance, and oxidative stress. Therefore, antioxidants and drugs decreasing Bax can inhibit liver cell apoptosis; however, which of these drugs can present a notable effect in vivo requires further research. For example, experiments comparing the protective effects of different antioxidants would be beneficial. Although these recent studies have made some progress in understanding the relationship between NO level decrease and liver cell apoptosis damage, the exact mechanisms awaits further study.
Acknowledgments This work was supported by the National Natural Science Foundation of China (No. 81660151, 81660751, 81260504), the Key Research and Development Program of Jiangxi Province of China (No. 20161BBG70067), and Jiangxi Provincial Natural Science Foundation of China (No 20171BAB205085). Conflict of Interest: There is no conflict of interest associated with any of the authors or other coauthors in this manuscript.
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Reduced Nitric Oxide Involves in Liver Cell Apoptosis Inhibition 20. Kocak FE, Kucuk A, Ozyigit F, et al. Protective effects of simvastatin administered in the experimental hepatic ischemia-reperfusion injury rat model. J Surg Res 2015;199:393e401. 21. Abdel Moneim AE, Ortiz F, Leonardo-Mendonca RC, et al. Protective effects of melatonin against oxidative damage induced by Egyptian cobra (Naja haje) crude venom in rats. Acta Trop 2015;143:58e65. 22. Dkhil MA, Al-Quraishy S, Aref AM, et al. The potential role of Azadirachta indica treatment on cisplatin-induced hepatotoxicity and oxidative stress in female rats. Oxid Med Cell Longev 2013;2013:741817. 23. Zhang NN, Huang NY, Zhou XK, et al. Protective effects of IL-4 on Bacillus Calmette-Guerin and lipopolysaccharide induced immunological liver injury in mice. Inflamm Res 2012;61:17e26. 24. Chu J, Zhang X, Jin L, et al. Protective effects of caffeic acid phenethyl ester against acute radiation-induced hepatic injury in rats. Environ Toxicol Pharmacol 2015;39:683e689. 25. El Morsy EM, Kamel R. Protective effect of artichoke leaf extract against paracetamol-induced hepatotoxicity in rats. Pharm Biol 2015;53:167e173. 26. Khalaf AA, Zaki AR, Galal MK, et al. The potential protective effect of alpha-lipoic acid against nanocopper particle-induced hepatotoxicity in male rats. Hum Exp Toxicol 2017;36:881e891. 27. Lim SW, Lee DR, Choi BK, et al. Protective effects of a polymethoxy flavonoids-rich Citrus aurantium peel extract on liver fibrosis induced by bile duct ligation in mice. Asian Pac J Trop Med 2016;9:1158e1164. 28. Tao J, Shen X, Ai Y, et al. Tea polyphenols protect against ischemia/ reperfusion-induced liver injury in mice through anti-oxidative and anti-apoptotic properties. Exp Ther Med 2016;12:3433e3439. 29. Omar HA, Mohamed WR, Arab HH, et al. Tangeretin Alleviates Cisplatin-Induced Acute Hepatic Injury in Rats: Targeting MAPKs and Apoptosis. PLoS One 2016;11:e0151649. 30. Liu Q, Rehman H, Krishnasamy Y, et al. Improvement of liver injury and survival by JNK2 and iNOS deficiency in liver transplants from cardiac death mice. J Hepatol 2015;63:68e74.
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31. Grossini E, Bellofatto K, Farruggio S, et al. Levosimendan inhibits peroxidation in hepatocytes by modulating apoptosis/autophagy interplay. PLoS One 2015;10:e0124742. 32. Chen J, Fan X, Zhou L, et al. Treatment with geraniol ameliorates methionine-choline-deficient diet-induced non-alcoholic steatohepatitis in rats. J Gastroenterol Hepatol 2016;31:1357e1365. 33. Zhao Y, Zhou P, Liu B, et al. Protective effect of suberoylanilide hydroxamic acid against lipopolysaccharide-induced liver damage in rodents. J Surg Res 2015;194:544e550. 34. Ganai AA, Khan AA, Malik ZA, et al. Genistein modulates the expression of NF-kappaB and MAPK (p-38 and ERK1/2), thereby attenuating d-Galactosamine induced fulminant hepatic failure in Wistar rats. Toxicol Appl Pharmacol 2015;283:139e146. 35. Kang K, Zhao M, Jiang H, et al. Role of hydrogen sulfide in hepatic ischemia-reperfusion-induced injury in rats. Liver Transpl 2009;15: 1306e1314. 36. Chen EQ, Bai L, Gong DY, et al. Employment of digital gene expression profiling to identify potential pathogenic and therapeutic targets of fulminant hepatic failure. J Transl Med 2015;13:22. 37. Tanaka Y, Kaibori M, Miki H, et al. Alpha-lipoic acid exerts a liverprotective effect in acute liver injury rats. J Surg Res 2015;193: 675e683. 38. Murugesan P, Jung B, Lee D, et al. Kinin B1 Receptor Inhibition With BI113823 Reduces Inflammatory Response, Mitigates Organ Injury, and Improves Survival Among Rats With Severe Sepsis. J Infect Dis 2016;213:532e540. 39. Prince JM, Vodovotz Y, Baun MJ, et al. The nitric oxide donor S-nitrosoglutathione reduces apoptotic primary liver cell loss in a threedimensional perfusion bioreactor culture model developed for liver support. Tissue Eng Part A 2010;16:861e866. 40. Wang K, Brems JJ, Gamelli RL, et al. iNOS/NO signaling regulates apoptosis induced by glycochenodeoxycholate in hepatocytes. Cell Signal 2011;23:1677e1685.
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REVIEW ARTICLE
Roles of Reduced Nitric Oxide in Liver Cell Apoptosis Inhibition During Liver Damage Ying-yi Wang,a,1 Meng-ting Chen,a,1 Hui-min Hong,a,1 Ying Wang,a Qian Li,a Hui Liu,a Mei-wen Yang,b Fen-fang Hong,c and Shu-long Yanga b
a Department of Physiology, College of Medicine, Nanchang University, Nanchang, China Department of Nurse, The Affiliated Hospital of Jiangxi Academy of Medical Science, Nanchang, Jiangxi, China c Department of Experimental Teaching Center, Nanchang University, Nanchang, China
Received for publication June 27, 2018; accepted September 14, 2018 (ARCMED:2018_126).
Hepatic injury is a major event in liver surgery and may lead to liver cell apoptosis. Nitric oxide (NO) is an unstable, carbon-centered radical with a short half-time and a key role in molecular signaling. Increasing evidence demonstrates that NO plays an important role in the liver cell apoptosis caused by hepatic ischemia reperfusion (IR) injury and other liver damage. Our recent article summarized the association between elevated nitric oxide levels and hepatic cell apoptosis during liver injury. This article reviews the newest research progress for the relationship between decreased nitric oxide levels and hepatic cell apoptosis inhibition during liver injury. It is shown that decreased NO level can influence liver apoptosis by promoting or inhibiting the signaling pathway involving the caspase family, BCL-2, mitochondria, oxidative stress, death receptors, and mitogen activated protein kinases, etc. This review outlines the literature basis for clinical application of anti-apoptosis treatment to relieve organ injury following liver surgery. NO-related drugs appear to be helpful in clinical treatment of liver diseases. Ó 2018 IMSS. Published by Elsevier Inc. Key Words: Reduced nitric oxide, Apoptosis inhibition, Liver damage.
Introduction Apoptosis is an autonomous cell death controlled by its relative genes. There is some overexpression of oncogenes and anti-oncogenes, and death receptoreligand binding and excessive inflammatory cytokines occurred in damaged liver cells. These factors may activate a series of signaling pathways that lead to liver cell apoptosis, including caspase pathway, Bcl-2 gene family, oxidative stress, etc. Increasing evidence demonstrates that nitric oxide (NO) plays an important role in liver cell apoptosis caused by hepatic ischemia reperfusion (IR) injury and other liver damage. In China, the morbidity and mortality of liver disease, which is one of
1
These authors contributed equally to this work. Address reprint requests to: Shu-long Yang, Department of Physiology, College of Medicine, Nanchang University, Nanchang, China; Phone/FAX: (þ86) (791) 886360556; Address reprint requests to: Fen-fang Hong, Department of Experimental Teaching Center, Nanchang University, Xuefu Road 999, Honggutan New District, Nanchang City 330031, Jiangxi province, China. Phone: (þ86)18970965319; FAX: (þ86)791-83827051; E-mail: [email protected] or [email protected]
the major diseases that threaten human health, are very high. Recently, we reviewed the association between elevated nitric oxide levels and hepatic cell apoptosis during liver injury (1). In this paper, we further summarize the newest research progress for the relationship between decreased NO levels and liver cell apoptosis inhibition during liver injury. Apoptotic Signal Transduction Pathways Exist Invariably in Damaged Liver Apoptotic signal transduction pathways in damaged liver are as follows: a) caspases, b) Bcl-2 gene family, c) death receptor, d) mitochondrial, e) oxidative stress, f) mitogen activated protein kinase (MAPK), g) PI3K/Akt, h) NF-k kB. They can be activated to induce liver cell apoptosis upon the overexpression of some oncogenes and antioncogenes, death receptoreligand binding, and expression of excessive inflammatory cytokines. The Source of NO and Its Biological Role in Liver Injury NO is an important biological messenger and effector molecule that has been extensively researched and gradually
0188-4409/$ - see front matter. Copyright Ó 2018 IMSS. Published by Elsevier Inc. https://doi.org/10.1016/j.arcmed.2018.09.001
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understood in recent decades. Endogenously, nitric oxide synthase (NOS) synthesizes NO using L-arginine as a substrate. There are three NOS isoforms in humans, namely neuronal (nNOS), endothelial (eNOS), and inducible (iNOS). nNOS and eNOS are Ca2þ-dependent, their activation requires binding to the kinase binding sites of calmodulin. These NO synthases are mainly distributed in endothelial cells, platelets, and brain and adrenal cells. Their effects include smooth muscle relaxation, inhibition of platelet aggregation and adhesion, and nerve signal transduction. Conversely, iNOS is Ca2þindependent; its activation depends on some external factors, such as bacteria, viruses, interferon, proinflammatory cytokines, etc., of which endotoxin is the main iNOS inducer. Evidently, when macrophages and neutrophils were activated, iNOS was overexpressed to produce an immediate NO increase, which may kill bacteria, parasites, and tumor cells and result in cell necrosis (2). NO has various biological functions. As an endotheliumderived vasodilator, it can antagonize endothelin vasoconstriction, improve liver microcirculatory function, and inhibit leukocyte adhesion. Furthermore, as an antioxidant, it can reduce hepatotoxicity by alleviating liver cell injury caused by superoxide anion free radicals. In addition, NO can inhibit expressions of adhesion molecule MHC- II and ICAM-1 in macrophages, subsequently reducing liver inflammation. However, hepatocytes and Kupffer cells can produce a large quantity of NO via iNOS; elevated NO level is toxic to liver due to depression of mitochondrial respiratory chain function, liver cell glucose metabolism, and synthesis of liver cell protein and DNA. Thus, ultimate NO action on liver injury appears to be dependent on the net outcome of protection and aggravation effects. NO Level Decrease and Hepatic Cell Apoptosis Inhibition NO level decrease and hepatic cell apoptosis inhibition induced by caspases pathway. Cell apoptosis is a cascade amplification reaction where the substrate is hydrolyzed irreversibly and limitedly by caspase. At least 14 caspases are currently known. Caspase molecules have high homology and similar structures, and all are cysteine proteases. Caspases can be divided into two categories based on function: one is cell processing, such as pro-IL-1b and pro-IL-1d, the other is cell apoptosis, including caspase 2, 3, 6, 7, 8, 9, and 10, which are subdivided into starter enzymes, such as caspase 8, 9, and 10, and effector enzymes, such as caspase 3, 6, and 7. These subdivisions play a role in the upstream and downstream regulation, respectively, of death signal transduction. The starter enzymes stimulate apoptosis signals and initiate the cell suicide process, and the effector enzymes are specific executors that complete the hydrolysis of specific protein substrates. Peritonitis from sepsis (3), arsenic (4), lipopolysaccharide (LPS) (5), and alcohol (6) can increase NO level and caspase expressions upregulate in liver cells, leading to liver injury and
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hepatocyte apoptosis. However, pretreatment with deprenyl (3), diallyl trisulfide (4), genistein (5), and microencapsulated protein-1 (6) counteracted liver damage caused by the above factors, with decreased levels of NO and caspase. The protective effects of these drugs on liver cells were also demonstrated by histopathological check. These results suggested that apoptosis inhibition and NO decrease were involved in the drugs actions. Similarly, 20 ,40 -Dihydroxy60 -methoxy-30 ,50 -dimethylchalcone (DMC) was demonstrated to eliminate H2O2-induced oxidative liver damage and decrease NO level and caspase 3 expression (7) This effectively counteracted the loss of cell viability. The protective effect of coenzyme Q10 on rat liver injury induced by acetaminophen is related to its significant reduction of iNOS, NF-kB, caspase 3, and p53 overexpression in liver tissue (8). Da Rosa DP (9) found that antioxidants may downregulate expressions of iNOS, caspase 3, and caspase 6; thus, it can protect the liver from liver inflammation and apoptosis induced by intermittent hypoxia. Kwon AH, et al. (10) studied the mechanism for the protective effects of plasma fibronectins (pFn) on endotoxic shock in rats with partial hepatectomy. The results showed that in the pFn treatment group, NO serum level was significantly lower than the control group; similarly, caspase 3 and caspase 8 activity was significantly inhibited, and the degree of hepatic cell necrosis and apoptosis decreased. In a recent study, one of the protective effects of Se against Cd-induced injury was the reduction of NO production and decreased expression of caspase 3 (11). Similarly, the preventive effects of indigofera oblongifolia leaf extract (IOLE) on lead acetate (PbAc)-induced hepatotoxicity in adult male Wistar rats were also achieved by reducing NO production and decreasing caspase 3 expression (12). It was found that punicalagin significantly and dose-dependently reduced NO, iNOS, and caspase 3 and 9 activities (13). Furthermore, punicalagin also protected rat liver against cyclophosphamide toxicity by inhibiting oxidative/nitrosative stress, inflammation and apoptosis. The above studies confirmed that decreased caspase expressions and lower NO level can effectively reduce liver cell apoptosis and confer a protective effect on the liver. The drugs mentioned above mostly achieved this protective effect by inhibiting caspase 3, which is the most important terminal enzyme in the process of apoptosis. In the process of developing new drugs, this may be a key mechanism worthy of special attention. The relationship between caspase alterations and decreased NO level still needs further exploration. Whether the protective effects of multi-acting drugs, which significantly reduced the levels of various caspases in liver cells, were better than that of other drugs, such as DMC, Se, IOLE that only affected one caspase, is still worthy of further study. Reduced no level and inhibition of liver cell apoptosis mediated by imbalanced Bax/Bcl-2 ratio. Recent studies
Reduced Nitric Oxide Involves in Liver Cell Apoptosis Inhibition
have shown that procyanidin B2 exerted its effects via antiinflammation and antioxidation, downregulation of iNOS expression, inhibition of Bax upregulation and Bcl xl downregulation, indicating that procyanidin B2 can reduce cell apoptosis (14). These findings suggest that procyanidin B2 may prevent CCl4-induced apoptosis injury. Acteoside (15), cyclo-trans-4-l-hydroxyprolyl-l-serine (JBP485) (16), and emblica officinalis gaertn (17) all have a protective effect against liver injury in mice. Their underlying mechanisms may include decreasing NO content, downregulating Bax protein expression, and increasing Bcl-2 protein expression, which inhibits mice liver cell apoptosis. Tsuchihashi S et al reported that FK330 (FR260330), a novel iNOS inhibitor, can prevent IR injury in rat liver during transplantation and decrease the Bax/Bcl-2 ratio to prevent liver cell apoptosis (18). These studies suggested that the NO and Bax/Bcl-2 ratio reduction could inhibit liver cell apoptosis to a certain extent. The fact that iNOS inhibitors reduced Bax/Bcl-2 ratio confirms the correlation between NO reduction and Bax/Bcl-2 ratio reduction. In another study, tormentic acid (TA) (19) reduced TNF a by inhibiting NF-k KB activity; furthermore, it decreased NO and iNOS levels and increased Bcl-2 expression, which lead to the an imbalanced Bax/Bcl-2 ratio. Thus, the protective effects of tormentic acid in liver may be superior to other drugs with a single effect. NO level reduction and inhibition of liver cell apoptosis induced by oxidative stress. Several studies have confirmed that oxidative stress plays an important role in liver injury, and many drugs reduce hepatic cell apoptosis by inhibiting oxidative stress pathway (20e22). Kocak FE, et al. (20) pretreated liver IR injury rats with 2.5 or 5 mg/kg of simvastatin (SV). Their results showed that 5.0 mg/kg SV reduced liver injury and cell apoptosis. Compared to the IR control group, the levels of malonyldialdehyde (MDA) and NO in the 5.0 mg/kg SV group were decreased, whereas glutathione peroxidase, catalase, and superoxide dismutase (SOD) activity were significantly increased. These results may guide clinical practice. However, the doseeresponse relationship still needs to be established. It was shown that melatonin (21) and cisplatin (22) can reduce NO production, reduce oxidized glutathione (GSSG), and increase glutathione (GSH) to inhibit cell apoptosis. IL-4 (23) can downregulate iNOS mRNA expression and reduce GSH consumption, thereby inhibiting the cell apoptosis. It is clear that antioxidants, such as procyanidin B2 (14), caffeic acid phenethyl ester (CAPE) (24) and artichoke leaf extract (25), play a positive role in inhibiting liver cell apoptosis. For example, a-lipoic acid (26), a powerful antioxidant, attenuates the hepatotoxic effects of nanocopper particles through improved oxidative status in male rats. In addition, citrus aurantium peel extract (27), tea polyphenols (28), and tangeretin (29) have potential protective
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effects against liver apotosis. These different types of drugs influence the apoptosis of liver cells, not only by oxidative stress, but also through other pathways. Furthermore, the influences of different drugs on liver injury is based on different conditions. Until now it has been unclear whether the efficacy of drugs with many pathways are better than drugs with only a single pathway affecting apoptosis. The issue needs further investigation. NO decrease and inhibition of liver cell apoptosis mediated by the mitochondrial pathway. Cytochrome c is regulated by Bax and Bcl-2, whose release is the key event of apoptosis and also the main apoptosis pathway driven by mitochondria. Other mitochondria-mediated apoptosis pathways are as follows: gamma rays or ceramide disrupting electron transfer link and mitochondrial energy metabolism, release of O2 free radicals and death-promoting factors, alteration of mitochondrial membrane permeability, and pressured cytoskeleton resulting from mitochondrial hyperosmolar state. All these pathways promote cell apoptosis. Livers from myocardial death wild-type and iNOS gene knockout type mice were transplanted into wild-type receptor mice, and mitochondria depolarization was detected through confocal microscopy in vivo. The results showed that iNOS and 3-nitro-tyrosine complex increased in the liver after transplant from myocardial death wildtype mice, but eNOS did not change. Compared to the control group, liver injury and loss of function from the myocardial death group were more severe. In liver from the donor mice with myocardial death and iNOS gene knockout type, NO production decreased, mitochondrial depolarization was reduced, ATP production was relieved, liver cell apoptosis was inhibited, and liver function improved (30). Grossini E found that levosimendan can inhibit liver cell apoptosis. One of its mechanisms is inhibition of nitric oxide synthase activation and decreased NO release. Another mechanism is inhibition of mitochondrial ATP sensitive potassium channel (mitoKATP) opening, reduced ATP consumption, and prevention of liver cell apoptosis (31). Treatment with geraniol reduced histological scores, fibrosis, and apoptosis in liver, preserved hepatic mitochondrial function—evidenced by reduced mitochondrial reactive oxygen species formation—enhanced adenosine triphosphate formation and membrane integrity, restored mitochondrial electron transport chain enzyme activity, increased mitochondrial DNA content, and downregulated iNOS expression in livers of rats fed a methioninecholine-deficient (MCD) diet. These results indicate that NO is closely related to apoptosis mediated by the mitochondrial pathway (32). NO level decline and mitogen activated protein kinase family inhibition. MAPKs are intracellular serine/threonine
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protein kinases, which include four subfamilies: extracellular signal regulated protein kinase (ERK), c-Jun N-terminal kinase (JNK), p38 mitogen activated protein kinase (p38 MAPK), and ERK5. MAPK’s signal transduction pathway exists in most cells, and it plays a vital role in the extracellular signal transduction to the cell and its nucleus and the process of cell biological response. Under physiological circumstances, ERK, JNK, and P38 MAPK can promote cell differentiation; however, in stress conditions, ERK may present an antiapoptotic effects, whereas JNK and P38 may promote apoptosis. Some scholars have observed that LPS-induced rat liver toxicity is mainly due to perturbation of the redox reaction balance and accumulation of oxidation products. Suberoylanilide hydroxamic acid (SAHA) administered simultaneously with LPS improved the survival rate of LPS-induced shock mice. SAHA neutralized LPSinduced oxidation reaction products, such as thiobarbituric acid reactive substances, nitrite and NO metabolites, and it also reversed the LPS-induced reduction of antioxidant enzymes and glutathione. These results demonstrated that SAHA can inhibit oxidationereduction reaction enzymes, apoptosis signal-regulating kinase, and p38 MAPK together with JNK, and thus reduce LPS-induced liver apoptosis (33). Using D-galactosamine induced acute liver failure in Wistar rats. Ganai AA et al., found that genistein reduced NO level in the liver by inhibiting iNOS expression and inhibited phosphorylation of MAPKs to achieve its hepatoprotective effect, illustrating the potential therapeutic properties of genistein for liver diseases (34). Furthermore, it is found that tangeretin pretreatment significantly improved liver function tests (ALT and AST) and diminished histopathologic structural damage in liver tissue. Regarding the MAPK pathway, tangeretin attenuated the cisplatin-induced increase in phospho-p38, phospho-c-Jun N-terminal kinase (p-JNK) and phospho-extracellular signal-regulated kinase (pERK1/2) in liver tissues (29). These results indicated that NO level decline is closely related to MAPK inhibition. NO level reduction and Fas death receptor-mediated liver apoptosis inhibition. Fas are apoptosis-promoting genes whose effects are contrary to the apoptosis related gene Bcl-2. As a member of the tumor necrosis factor receptor (TNFR) family, Fas is a transmembrane glycoprotein gene product. After binding FasL or Fas antibody, Fas directly activates apoptotic gene products and induces apoptosis, which is mediated by special intracellular proteins. The protective effect of H2S on hepatic IR injury in rats imparted by reducing serum inflammatory substances and inhibiting apoptosis related proteins, such as Fas and Fas ligand (35). Additionally, hydrogen sulfide can effectively inhibit the caspase 3 activity and cell
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apoptosis, but it is unclear which is the primary mechanism. NO level reduction and liver cell apoptosis inhibition mediated by NF-kB pathway. NF-kB is widely present in a variety of liver cells and involved in many physiological and pathological processes through regulation of gene transcription. In fulminant hepatic failure and arsenic poisoning induced liver injury, it has been confirmed that NF-kB is elevated to varying levels in liver tissue (5,36). There are NF-kB inhibition phenomenon involved in the liverprotection mechanisms of a-lipoic acid, astaxanthin original B2, genistein, and allicin. It was suggested that the antiapoptotic process of hepatic cells is related to the NFkB pathway (5,14,34,37). Another study showed that coenzyme Q10 significantly downregulated acetaminopheninduced iNOS overexpression, reduced NF-kB level in liver tissue, and inhibited hepatocyte apoptosis (8). Coenzyme Q10 was demonstrated to have multiple action mechanisms, suggesting that it prevents acetaminophen-induced acute liver toxicity and has important significance for guiding the clinical treatment of liver injury. It was found that punicalagin significantly and dose-dependently reduced the elevations of serum alanine aminotransferase and nuclear factor-kB p65 and liver toxicity (13). A study from Murugesan P, et al. showed that administration of BI113823 reduced iNOS expression and injury score and attenuated NF-kB activation and apoptosis in the liver (38). Double effects of NO on liver cell apoptosis. Prince JM, (39) cultured adult rat hepatocytes in medium containing various concentrations of the NO donor S-nitrosoglutathione and found that the apoptosis rate in the control group was 47.9 2.9% (mean standard error); the NO donor showed a biphasic response: 200 and 500 mmol S-nitrosoglutathione group apoptosis rate was only 14.4 0.4%, significantly lower than the control group and the 1000 mmol S-nitrosoglutathione group. The apoptosis rate in the nitrosoglutathione group was 82.6%, which was significantly higher than that in the control group. Similarly, Wang K, et al. (40) studies have shown that endogenous NO inhibits liver cell apoptosis and exogenous NO donors play a dual role in liver cell apoptosis; specifically, low concentrations produce inhibition and high concentrations promote apoptosis. It is suggested that low concentration of an NO donor can activate the iNOSeAktesurvivin axis and inhibit apoptosis. In contrast, high concentrations of NO donors can activate CHOP through p38 MAPK and upregulate TRAIL receptor DR5, thereby inhibiting the survivin gene and promoting apoptosis. In summary, the effect of NO on liver cell apoptosis is not simply inhibition or promotion. Given that most experimental designs are limited to narrow drug concentrations, this ambiguity is not surprising.
Reduced Nitric Oxide Involves in Liver Cell Apoptosis Inhibition
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Table 1. Different drugs mentioned in the paper and its effects on NO level and liver cell apoptosis and underlying mechanisms during liver injury
NO level
Liver cell apoptosis
Caspases[ Caspases[ ①Caspases[ ②NF-kB[ Caspases[ CaspasesY CaspasesY CaspasesY CaspasesY Caspase-3Y
[ [ [ [ Y Y Y Y Y
[ [ [ [ Y Y Y Y Y
①Caspase-3Y ②NF-kBY ③p53Y Caspase-3,6Y Caspase-3,8Y
Y Y Y
Y Y Y
Caspase-3Y Caspase-3Y ①Caspase-3,9Y ②NF-kBY ③p65Y
Y Y Y
Y Y Y
①Inhibiting Bax[ and bcl-xlY ②Antixidation ③NF-kBY BaxYBcl-2[ BaxYBcl-2[ BaxYBcl-2[ Bax/Bcl-2Y ①Bcl-2[ ②NF-kBY
Y
Y
Y Y Y Y Y
Y Y Y Y Y
Y
Y
Y Y Y Y Y Y Y Y Y
Y Y Y Y Y Y Y Y Y
(21) (22) (23) (24) (25) (26) (27) (28) (29)
Depolarization of mitochondriaY, consumption of ATPY Opening of the mitochondrial ATP sensitive potassium channel Y, consumption of ATPY Mitochondrial reactive oxygen species formationY, mitochondrial electron transport chain enzyme activity [, mitochondrial RNA content [
Y
Y
(30)
Y
Y
(31)
Y
Y
(32)
①p38 MAPKYJNKY ②Axidation reduction reaction enzymeY ①Phosphorylation of MAPKsY ②NF-kBY
Y
Y
LPS
(33)
Y
Y
D-galactosamine
(34)
①Fas, Fas ligandY ②caspase-3Y
Y
Y
Ischemia reperfusion
(35)
NF-kB[ NF-kBY NF-kBY
[ Y Y
[ Y Y
Pretreatment Caspases pathway Peritonitis with sepsis Arsenic Lipopolysaccharide Alcohol Deprenyl Trisulfide Genistein Microencapsulated protein-1 20 ,40 -dihydroxy-60 -methoxy-30 , 50 -dimethylchalcone Coenzyme Q10 Antioxidants Plasma fibronectins Se Indigofera oblongifolia leaf extract Punicalagin Imbalance of bax-bcl ratio Procyanidin B2 Acteoside TBP485 Emblica officinalis gaertn FK330 Tormentic acid Oxidative stress Simvastatin Melatonin Cisplatin IL-4 Caffeic acid phenethyl ester Artichoke leaf extract a-lipoic acid Citrus aurantium peel extract Tea polyphenols Tangeretin Mitochondrial pathway Knocking out iNOS gene Levosimendan Geraniol
Mitogen activated protein kinase family Suberoylanilide hydroxamic acid Genstein Fas death receptor Hydrogen sulfide NF-kB pathway Arsenic Allicin BI113823
Mechanism
MDAY, SODY, glutathione peroxidase[, catalase[ GSSGY, GSH[ GSSGY, GSH[ Consumption of GSHY Oxidative stressY Oxidative stressY Oxidative stressY Oxidative stressY Oxidative stressY ①Oxidative stressY ②Phosphorylation of p38 MAPK, JNK, EPKY
Revulsanta
Reference
(3) (4) (5) (6) (3) (4) (5) (6) (7)
H2O2 Acetaminophen Intermittent hypohios Endotoxic shock with partial hepatectomy Cd Lead acetate
(8) (9) (10)
Carbon tetrachloride
(14)
(11) (12) (13)
(15) (16) (17) (18) (19) Ischemia reperfusion
(20)
(36) (37) (38) (continued on next page)
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Table 1 (continued ) Pretreatment
Mechanism
Double effect s-nitrosoglutathione Endogenous nitric oxide Exogenous nitric oxide
NO level
Liver cell apoptosis
Y [ Y Y [
Y [ Y Y [
Revulsanta
200 or 500 mmol/L 1000 mmol/L
Reference
(39) (40)
Low concentration High concentration
a
The level of liver cell apoptosis was evaluated by pathological specimens. Revulsant is used to induce liver injury. Comprehensive list of drugs in the review and their effects on NO level and liver cell apoptosis.
Conclusion In general, NO can both inhibit and promote the liver cell apoptosis. Here we have reviewed recent literature concerning the mechanisms underlying the relationship between NO level reduction and liver cell apoptosis inhibition. This improves our understanding of NO’s role in liver cell apoptosis injury and provides a reliable basis for further exploration of the dual effects of NO on hepatic cell apoptosis and clinical treatment of liver diseases. We have also produced a Table 1, which includes all drugs and their protective mechanisms that were mentioned in this review. Overall, the most important mechanisms involved in hepatic cell apoptosis inhibition are: caspases pathway, Bax/Bcl2 ratio imbalance, and oxidative stress. Therefore, antioxidants and drugs decreasing Bax can inhibit liver cell apoptosis; however, which of these drugs can present a notable effect in vivo requires further research. For example, experiments comparing the protective effects of different antioxidants would be beneficial. Although these recent studies have made some progress in understanding the relationship between NO level decrease and liver cell apoptosis damage, the exact mechanisms awaits further study.
Acknowledgments This work was supported by the National Natural Science Foundation of China (No. 81660151, 81660751, 81260504), the Key Research and Development Program of Jiangxi Province of China (No. 20161BBG70067), and Jiangxi Provincial Natural Science Foundation of China (No 20171BAB205085). Conflict of Interest: There is no conflict of interest associated with any of the authors or other coauthors in this manuscript.
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