TNF-alpha but not IL-1alpha is correlated with PGE1-dependent protection against acute D-galactosamine-induced liver injury.

BACKGROUND: Prostaglandin E1 (PGE1) treatment of humans and rodents during acute hepatic failure ameliorates different parameters of hepatic dysfunction. PURPOSE: To investigate whether prevention of acute liver injury induced by D-galactosamine (D-GalN) with preadministration of PGE1 is correlated with a change in the concentration of two proinflammatory cytokines, as tumour necrosis factor-alpha (TNF-alpha) and interleukin (IL)-1alpha, and/or nitrite+nitrate (NOx), as nitric oxide-related end products in serum. RESULTS: D-GalN significantly increased alanine aminotransferase (ALT) and TNF-alpha concentration in serum 5 and 10 mins, respectively, after treatment compared with the control group (P< or =0.05). D-GalN did not change the IL-1alpha concentration at any time during the study. Preadministration of PGE1 to D-GalN-treated rats significantly reduced the ALT content and increased significantly the TNF-alpha concentration in serum 1, 2.5, 5 and 10 mins after D-GalN treatment compared with the D-GalN group (P< or =0.05). Nitric oxide was not involved in either the toxic effect due to D-GalN or the protection observed with PGE1 against D-GalN toxicity. CONCLUSIONS: Acute liver injury induced by D-GalN is correlated with an increased TNF-alpha release. Preadministration of PGE1 to D-GalN-treated rats exerted a priming effect on inflammatory cells to release enhanced levels of TNF-alpha but not IL-1alpha. These findings indicate that stimulation of TNF-alpha release may be involved in the acute D-GalN-induced liver injury and also in PGE1 protection from hepatotoxicity in clinical and experimental studies.     

The nitric oxide pathway--evidence and mechanisms for protection against liver ischaemia reperfusion injury

Ischaemia reperfusion (IR) injury is a clinical entity with a major contribution to the morbidity and mortality of liver surgery and transplantation. A central pathway of protection against IR injury utilizes nitric oxide (NO). Nitric oxide synthase (NOS) enzymes manufacture NO from L-arginine. NO generated by the endothelial NOS (eNOS) isoform protects against liver IR injury, whereas inducible NOS (iNOS)-derived NO may have either a protective or a deleterious effect during the early phase of IR injury, depending on the length of ischaemia, length of reperfusion and experimental model. In late phase hepatic IR injury, iNOS-derived NO plays a protective role. In addition to NOS consumption of L-arginine during NO synthesis, this amino acid may also be metabolized by arginase, an enzyme whose release is increased during prolonged ischaemia, and therefore diverts L-arginine away from NOS metabolism leading to a drop in the rate of NO synthesis. NO most commonly acts through the soluble guanylyl cyclase-cyclic GMP- protein kinase G pathway to ameliorate hepatic IR injury. Both endogenously generated and exogenously administered NO donors protect against liver IR injury. The beneficial effects of NO on liver IR are not, however, universal, and certain conditions, such as steatosis, may influence the protective effects of NO. In this review, the evidence for, and mechanisms of these protective actions of NO are discussed, and areas in need of further research are highlighted.     

Inhibition of inducible nitric oxide synthase protects against liver injury induced by mycobacterial infection and endotoxins

BACKGROUND/AIMS: Bacillus Calmette Guerin (BCG) infection causes hepatic injury following granuloma formation and secretion of cytokines which render mice highly sensitive to endotoxin-mediated hepatotoxicity. This work investigates the role of inducible nitric oxide synthase (iNOS) in liver damage induced by BCG and endotoxins in BCG-infected mice. METHODS: Liver injury and cytokine activation induced by BCG and by LPS upon BCG infection (BCG/LPS) were compared in wild-type and iNOS-/- mice. RESULTS: iNOS-/- mice infected with living BCG are protected from hepatic injury when compared to wild-type mice which express iNOS protein in macrophages forming hepatic granulomas. In addition, iNOS-/- mice show a decrease in BCG-induced IFN-gamma serum levels. LPS challenge in BCG-infected mice strongly activates iNOS in the liver and spleen of wild-type mice which show important liver damage associated with a dramatic increase in TNF and IL-6 and also Th1 type cytokines. In contrast, iNOS-/- mice are protected from liver injury after BCG/LPS challenge and their TNF, IL-6 and Th1 type cytokine serum levels raise moderately. CONCLUSIONS: These results demonstrate that nitric oxide (NO) from iNOS is involved in hepatotoxicity induced by both mycobacterial infection and endotoxin effects upon BCG infection and that inhibition of NO from iNOS protects from liver injuries.     

诱导型一氧化氮合酶在ConA诱发T细胞介导的小鼠肝损害中的表达

目的观察诱导型一氧化氮合酶（ｉＮＯＳ）在刀豆素Ａ（ＣｏｎＡ）诱发Ｔ细胞介导的小鼠肝损害中的表达及意义。方法应用黄递酶染色（ＮＡＤＰＨ－ｄ）技术观察ｉＮＯＳ表达。结果ＣｏｎＡ造成肝损害后，血浆中亚硝酸盐（ＮＯ－２）较正常对照组（ＰＢＳ组）显著升高，以Ｌ－ＮＡＭＥ抑制ＮＯ合成，肝细胞损害反而加重，且肝组织内丙二醛（ＭＤＡ）增加，肝窦内血细胞聚集加重；在ＣｏｎＡ造成肝损害时可见肝实质细胞表达ｉＮＯＳ，且越靠近中央静脉的肝细胞表达越多，推测这是肝细胞对缺血缺氧而产生的一种自身反映；用环孢霉素Ａ（ＣＳＡ）预先抑制Ｔ细胞活化，则未发现肝细胞表达ｉＮＯＳ。结论在ＣｏｎＡ性肝损害中，肝实质细胞通过启动自身的ＮＯ生物合成机制参与了炎症应答，并通过消除氧自由基和抑制血细胞在肝窦内聚集而起一定的保护作用，这一生物过程很可能是肝细胞参与机体免疫应答的一部分。     

Carvedilol action is dependent on endogenous production of nitric oxide

BACKGROUND: Carvedilol is known to be an adrenoreceptor blocker and free radical scavenger, used in hypertension and cardiac failure. However, its therapeutic actions cannot be fully explained by these mechanisms. In these studies, we tested the hypothesis that carvedilol action is associated with the synthesis/release of nitric oxide (NO). METHODS: Male Wistar rats (n = 22), 9 weeks old, were anesthetized with an intraperitoneal injection of sodium pentobarbital. Mean arterial pressure and arterial NO levels were monitored throughout the experiments. Carvedilol (1 mg/kg, intravenously [iv]) effects were evaluated before and after NO synthase (NOS) inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME, 5 mg/kg, iv). RESULTS: Carvedilol induced a significant decrease in basal arterial pressure (from 126.6 +/- 4.3 mm Hg to 75.9 +/- 3.0 mm Hg, P < .001) and significant increase in NO levels (from 17.9 +/- 1.7 micromol/L to 32.2 +/- 2.5 micromol/L, P < .001). After administration of L-NAME the arterial pressure increased (129.9 +/- 5.0 mm Hg, P < .001) with concomitant decrease in NO levels (13.4 +/- 1.6 micromol/L, P < .01). The second carvedilol administration (post-L-NAME) did not affect either arterial pressure (108.3 +/- 8.0 mm Hg) or NO levels (22.1 +/- 1.3 micromol/L). CONCLUSIONS: Our results suggest that the carvedilol-induced decrease of blood pressure is associated with an increase of plasma NO levels. Furthermore, NOS inhibition results in impairment of carvedilol hemodynamic effects and plasma NO levels. Therefore, these results are consistent with the hypothesis that the hemodynamic effect of carvedilol is in part dependent on endogenous NO production.     

Protection against acetaminophen-induced liver injury and lethality by interleukin 10: role of inducible nitric oxide synthase

Mechanistic study of idiosyncratic drug-induced hepatitis (DIH) continues to be a challenging problem because of the lack of animal models. The inability to produce this type of hepatotoxicity in animals, and its relative rarity in humans, may be linked to the production of anti-inflammatory factors that prevent drug-protein adducts from causing liver injury by immune and nonimmune mechanisms. We tested this hypothesis by using a model of acetaminophen (APAP)-induced liver injury in mice. After APAP treatment, a significant increase was observed in serum levels of interleukin (IL)-4, IL-10, and IL-13, cytokines that regulate inflammatory mediator production and cell-mediated autoimmunity. When IL-10 knockout (KO) mice were treated with APAP, most of these mice died within 24 to 48 hours from liver injury. This increased susceptibility to APAP-induced liver injury appeared to correlate with an elevated expression of liver proinflammatory cytokines, tumor necrosis factor (TNF)-alpha, and IL-1, as well as inducible nitric oxide synthase (iNOS). In this regard, mice lacking both IL-10 and iNOS genes were protected from APAP-induced liver injury and lethality when compared with IL-10 KO mice. All strains, including wild-type animals, generated similar amounts of liver APAP-protein adducts, indicating that the increased susceptibility of IL-10 KO mice to APAP hepatotoxicity was not caused by an enhanced formation of APAP-protein adducts. In conclusion, these findings suggest that an important feature of the normal response to drug-induced liver injury may be the increased expression of anti-inflammatory factors such as IL-10. Certain polymorphisms of these factors may have a role in determining the susceptibility of individuals to idiosyncratic DIH.     

一氧化氮在ConA诱发小鼠急性肝损害中的作用

目的：观察一氧化氮（NO）在刀豆素（ConA）诱发急性小鼠肝损害中的作用。方法：25只昆明小鼠随机分为5组，ConA(40mg/kg)自小鼠尾静脉注入复制急性肝损害，为ConA组；应用ConA前半小时，给予NO合成的抑制剂（L-NAME，5mg/只），为LN组；应用ConA前半小时，给予NO合成底物（L-精氮酸），为L-精氮酸组；单独给予L-NAME(5mg/只)者为L-NAME组；对照组只给予尾静脉注射生理盐水。各组8小时后取血分别测定丙氮酸转氮酶（ALT），取肝组织测定亚硝酸盐（NO2^-）和丙二醛（MDA）含量。结果：ConA造成肝损害后，肝组织中亚硝酸盐（NO2^-）较对照组显著升高；以L-NAME抑制NO合成，肝组织中NO2^-含量下降，肝细胞损害反而加重，且肝组织MDA增加，肝窦内血细胞淤集加重；L-精氮酸组未见明显的肝脏保护作用。结论：在ConA性肝损害中，NO通过消除氧自由基和抑制血细胞在肝窦内淤而发挥一定的保护作用。     

Monocyte production of nitric oxide (NO) in severe acute pancreatitis

To clarify the correlation between the kinetics of nitric oxide (NO) production and the occurrence of organ dysfunction in acute pancreatitis, we examined the production of NO₂ and NO₃ by monocytes in five patients with severe pancreatitis and organ dysfunction (four males and one female, aged 24–52 years: group S), and compared the results with those in five patients with mild pancreatitis (three males and two females, aged 24–52 years: group M) and 12 healthy volunteers (9 males and three females, aged 25–44: group C). The time course of induced NO production by cultured monocytes obtained from these subjects was also examined, using a NO-sensitive electrode. The levels of NO₂ and NO₃ production by monocytes in vitro, with or without stimulation, were significantly higher (P<0.05), the time required for NO production by cultured monocytes was significantly shorter (P<0.01), and the duration of NO production by monocytes was significantly longer (P<0.01), in group S compared with the other groups. These findings indicate that, in patients with severe acute pancreatitis, the NO-producing mechanism of monocytes is not only primed but also triggered. Further-more, it seems that NO production by monocytes is directly correlated with the incidence of organ dysfunction.     

Role of neuronal nitric oxide synthase and inducible nitric oxide synthase in intestinal injury in neonatal rats

AIM: To investigate the dynamic change and role of neuronal nitric oxide synthase (nNOS) and inducible nitric oxide synthase (iNOS) in neonatal rat with intestinal injury and to define whether necrotizing enterocolitis (NEC) is associated with the levels of nitric oxide synthase (NOS) in the mucosa of the affected intestine tissue. METHODS: Wistar rats less than 24 h in age received an intraperitoneal injection with 5 mg/kg lipopolysaccharide (IPS). Ileum tissues were collected at 1, 3, 6, 12 and 24 h following LPS challenge for histological evaluation of NEC and for measurements of nNOS and iNOS. The correlation between the degree of intestinal injury and levels of NOS was determined. RESULTS: The LPS-injected pups showed a significant increase in injury scores versus the control. The expression of nNOS protein and mRNA was diminished after LPS injection. There was a negative significant correlation between the nNOS protein and the grade of median intestinal injury within 24 h. The expression of iNOS protein and mRNA was significantly increased in the peak of intestinal injury. CONCLUSION: nNOS and iNOS play different roles in LPS-induced intestinal injury. Caution should be exerted concerning potential therapeutic uses of NOS inhibitors in NEC.     

一氧化氮和自由基对大鼠急性肝损伤的作用

目的用硫代乙酰胺（ＴＡＡ）诱发大鼠急性肝损伤,观察肝损伤过程中一氧化氮与自由基的变化．方法实验Ⅰ：大鼠２４只分为４组,一组为正常组,其余３组为损伤组．ＴＡＡ６００ｍｇ／ｋｇｓｃ２４,４８,７２ｈ测定内毒素及ＮＯ３－／ＮＯ２－,ＡＬＴ,ＡＳＴ含量．取肝组织匀浆,测定蛋白含量．脂质过氧化物歧化酶（ＳＯＤ）及谷胱甘肽过氧化物酶（ＧＳＨＰＸ）活性,并观察肝组织学变化．实验Ⅱ：大鼠３２只分为４组,Ａ组为正常组,Ｂ,Ｃ,Ｄ组ＴＡＡ６００ｍｇ／ｋｇｓｃ;同时给予Ｂ组生理盐水０４ｍＬ／ｋｇ,Ｃ组７５％ＬＡｒｇ３００ｍｇ／ｋｇ,Ｄ组２５％ＬＮＮＡ１０ｍｇ／ｋｇ．２４ｈ后重复注射１次．２４ｈ后按实验Ⅰ取血、肝组织,测定有关指标．结果大鼠注射ＬＡｒｇ后,ＮＯ的合成增多,转氨酶及肝组织损伤程度明显降低,注射ＬＮＮＡ组大鼠肝损伤程度加重,肝组织自由基的测定表明,抑制肝损伤大鼠ＮＯ合成,肝组织ＬＰＯ含量增高而ＳＯＤ,ＧＳＰＨＸ活性降低,ＳＯＤ,ＧＳＨＰＸ协同作用可清除体内自由基．结论抑制ＮＯ的生物合成,自由基水平增高,从而加重了肝损伤     

Increase in TNF-alpha and inducible nitric oxide synthase-expressing dendritic cells in psoriasis and reduction with efalizumab (anti-CD11a)

We find that CD11c(+) cells with many markers of dendritic cells (DCs) are a major cell type in the skin lesions of psoriasis. These CD11c(+) cells, which are evident in both epidermis and dermis, are the sites for the expression of two mediators of inflammation, inducible nitric oxide synthase (iNOS) and TNF-alpha in diseased skin. These cells express HLA-DR, CD40, and CD86, lack the Langerin and CD14 markers of Langerhans cells and monocytes, respectively, and to a significant extent express the DC maturation markers DC-LAMP and CD83. Treatment of psoriasis with efalizumab (anti-CD11a, Raptiva) strongly reduces infiltration by these DCs in patients responding to this agent. Disease activity after therapy was more related to DC infiltrates and iNOS mRNA levels than T cell infiltrates, and CD11c(+) cells responded more quickly to therapy than epidermal keratinocytes. Our results suggest that a type of DC, which resembles murine "Tip-DCs" that can accumulate during infection, has proinflammatory effects in psoriasis through nitric oxide and TNF-alpha production, and can be an important target for suppressive therapies.     

Temporal expression of hepatic inducible nitric oxide synthase in liver cirrhosis

AIM: Nitric oxide (NO) has been implicated in the pathogenesis of liver cirrhosis. We have found inducible nitric oxide synthase (iNOS) can be induced in hepatocytes of cirrhotic liver. This study further investigated the temporal expression and activity of hepatic iNOS in cirrhosis development. METHODS: Cirrhosis was induced in rats by chronic bile duet ligatjon (BDL). At different time points after the operation, samples were collected to examine NO concentration, liver function, and morphological changes. Hepatocytes were isolated for determination of iNOS mRNA, protein and enzymatic activity. RESULTS: Histological examination showed early cirrhosis 1-2 wk after BDL, with advanced cirrhosis at 3-4 wk. Bilirubin increased dramatically 3 d after BDL, but decreased by 47% on d 14. Three weeks after BDL, it elevated again. Systemic NO concentration did not increase significantly until 4 wk after BDL, when ascites developed. Hepatocyte iNOS mRNA expression was identified 3 d after BDL, and enhanced with time to 3 wk, but reduced thereafter. iNOS protein showed a similar pattern to mRNA expression. iNOS activity decreased from d 3 to d 7, but increased again thereafter till d 21. CONCLUSION: Hepatic iNOS can be induced in the early stage, which increases with time as cirrhosis develops. lts enzymatic activity is significantly correlated with protein expression and histological alterations of the liver, but not with systemic NO levels, nor with absolute values of liver function markers.     

Protection against liver injury by PGE1 or anti-TNF-alpha is associated with a reduction of TNF-R1 expression in hepatocytes

BACKGROUND: Tumour necrosis factor-alpha (TNF-5) has been shown to exacerbate or protect against liver injury in different experimental models. In a previous study, we observed that enhancement of TNF-alpha expression in hepatocytes by prostaglandin E1 (PGE1) pre-administration induced iNOS expression and cytoprotection against experimental liver injury in rats. Nevertheless, the reduction of TNF-alpha bioactivity by anti-TNF-alpha antibodies also reduced liver injury by D-GalN. The purpose of the present study was to evaluate whether protection by PGE1 or anti-TNF-alpha was related to a common effect on the membrane-bound TNF-alpha receptor expression. METHODS: Liver injury was induced in male Wistar rats by intraperitoneal injection of D-galactosamine (D-GalN) (1 g/kg). PGE1 or anti-TNF-alpha was administered at 30 or 60 min before D-GalN, respectively. Liver injury was evaluated by alanine aminotransferase (ALT) activity in serum and histological examination in liver sections. TNF-alpha was determined by ELISA in serum. The expression of TNF-alpha receptor type 1 (TNF-R1) and TNF-alpha receptor type 2 (TNF-R2) in hepatocytes was assessed by immunohistochemistry and immunoprecipitation + Western-blot analysis. RESULTS: PGE1 or anti-TNF-alpha reduced liver injury induced by D-GalN. Although PGE1 enhanced and anti-TNF-alpha reduced TNF-alpha concentration in serum, both protective treatments reduced the expression of TNF-R1 in hepatocytes. TNF-R2 was not detected in our experimental conditions. CONCLUSIONS: Our study showed that reduction of liver injury by PGE1 or anti-TNF-alpha antibodies was related to a reduction of TNF-R1 expression in hepatocytes.     

Lipoxygenase products regulate nitric oxide and inducible nitric oxide synthase production in interleukin-1beta stimulated vascular smooth muscle cells.

In cultured vascular smooth muscle cells (VSMCs), interleukin-1beta (IL-1beta) stimulates inducible nitric oxide synthase (iNOS) expression and nitric oxide (NO) production. IL-1beta also activates phospholipase A2 (PLA2), and induces lipoxygenase (LOX) and cyclooxygenase-2 (COX-2). The present study investigated whether these metabolites are involved in the regulation of IL-1beta-induced NO production and iNOS expression. Pretreatment with ONO-RS-082, the secretory PLA2 (sPLA2) inhibitor, at 1 to 10 micromol/l reduced IL-1beta-stimulated nitrite production and iNOS expression. Nordihydroguaiaretic acid (NDGA, 1 to 10 micromol/l), the LOX inhibitor, also reduced IL-1beta (10 ng/ml)-stimulated nitrite production and iNOS expression in a dose-dependent manner. Exogenous 12(S)-hydroxyeicosatetraenoic acids (HETE) enhanced the IL-1beta-stimulated nitrite production and iNOS expression. On the other hand, the COX inhibitors, indomethacin and NS-398, had little effect on nitrite production or iNOS expression. These results suggest that LOX products play important roles in the regulation of stimulus-induced NO production in VSMCs.     

Heme oxygenase-1 pathway is involved in delayed protection induced by heat stress against cardiac ischemia-reperfusion injury

Previous studies have shown that heme oxygenase-1 (HO-1), a heat stress protein (HSP32), has a beneficial effect on the ischemic myocardium. The purpose of the present study was to explore whether HO-1 is involved in delayed cardioprotection provided by heat stress in vivo. Sprague--Dawley rats were pretreated with whole body hyperthermia (rectal 42 degrees C) for 15 min followed by ischemia-reperfusion 24 h later. Ischemia-reperfusion injury was induced by 45 min of coronary artery occlusion followed by a 3-h reperfusion. Myocardial injury degree was evaluated by measurement of infarct size and serum creatine kinase (CK) activity. The expression of HO-1 mRNA and protein in myocardial tissues were measured. Pretreatment with hyperthemia significantly reduced infarct size and CK release during reperfusion, which was completely blocked by pretreatment with ZnPP-9, an inhibitor of HO and methylene blue, an inhibitor of soluble guanylate cyclase. Heat stress also significantly increased the expression of HO-1 mRNA and protein, and the effect was not affected by pretreatment with methylene blue. The present results suggest that the HO-1 pathway is involved in the mediation of delayed cardioprotection by heat stress in rats.