| Background:Nonsteroidal anti-inflammatory drugs(NSAIDs) are extensively used for treatment of a variety of rheumatoid disorders, including osteoarthritis, rheumatoid arthritis, ankylosing spondylitis, NSAIDs-liver injury can cause a variety of side effects and liver injury is a common phenomenon particularly. Clinical manifestations from minor abnormal liver function to severe hepatic failure which leading to death. The most frequent cause of NSAIDs hepatic injury is diclofenac (Dcf). Hepatocellular damage of diclofenac is acute hepatitis. The pathogenesis of dicl-ofenac remains elusive. Previous studies showed the involvement of oxidative stress, energy depletion, mitochondrial dysfunction and nitric oxide (NO). nitric oxide is a effector molecules which has variety of biological activity in vivo, nitric oxide is enzymatic product of nitric oxide synthase(NOS), that catalyze the oxidation of one of the guanidine of L-arginine (L-Arg). endothelial nitric oxide synthase (eNOS) and inducible nitric oxide synthase (iNOS) are mainly in the liver tissue. More and more attention were concentrated on the role of NO in liver disease recently.The effect of NO in liver disease has been controversial. Previous studies showed APAP and endotoxin can increases levels of nitric oxide and expression of iNOS. Mice lacking inducible nitric oxide synthase activity (iNOS) or iNOS knockout mice can protected against hepatocellular killing after simulated ischemia/reperfusion and APAP injection.The effective drug therapies are still unavailable at present except antidote N-acetylcysteine, protection hepatocytes medicines and support, nutrition.The emergency liver transplantation is considered as the only effective treatment that radically improves the outcome of acute liver failure by NSAIDs. Dexamethasone is a glucocorticoid, which has effect of anti-inflammatory, anti-endotoxin, immunosuppression, anti-shock etc. Previous studies showed dexamethasone protected against experimental liver injury induced by certain toxins such as carbon tetracholride, D-galactosamine(D-GalN) and concanavalin A,etc. The hepatoprotective mechanisms of dexamethasone may be related to inhibition of NO overproduction and oxidative tissue damage. Therefore, the aim of the present study was to investigate both the effect and mechanism. of nitric oxid on dcf-induced liver injury in rats. Meanwhile, to investigate the protective effect and related mechanisms of dexamethasone on acute hepatic injury induced by diclofenac in rats.Objective:To investigate the effect and mechanism of nitric oxide on Dcf-induced liver injury in rats; and to investigate the influence of dexamethasoneMethods:Rats were randomly divided into normal control group, model model group with Dcf, treatment groups with dexamethasone(Dex10mg/kg) and N-nitro-L-arginine methyl ester (L-NAME10mg/kg). Dcf(100mg/kg) was intraperitoneally administered to establish a drug-induced liver injury model,Dex was intraperitoneally administered1h before Dcf injection, L-NAME was intraperitoneal injected10min before Dcf administered,24hours after Dcf injection,analyze serum alanine aminotransferase (ALT), aspartate aminotransferase (AST) and total bilirubin(TBil) values. Liver tissue slices from each rats were prepared for pathology, detect Nitric oxide levels in serum and liver tissue homogenates,evaluation and detect the activity of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px),the content of malondialdehyde (MDA),glutathion (GSH) and myeloperoxidase(MPO) in liver tissue were also determined.The isolated liver mitochondria were prepared to perform all the experiments.Detect the activity of succinodehydrogenase (SDH) and adenosine triphosphatase (ATPase) in liver mitochondria.Detect mitochondrial membrane potential(MMP),mitochondrial swelling,mitochondrial NAD(P)H.and immunocyto chemical detection Bcl-2,TUNEL.Bax and cytochromeC positive cells. Immunohis-tochemical SP methods were used to investigate the expression of endothelial nitric oxide synthase (eNOS) and inducible NOS (iNOS).Results:Administration of diclofenac in24h interval resulted in an obvious liver injury and inflammation in rats,as indicated by the elevation of serum alanine transaminasefold, aspartate aminotransferase and total bilirubin(p<0.01),24h after diclofenac administration,widespread areas of necrosis and inflammation in the liver were showed. Swelling and hydropic degeneration of hepatocytes, vacuolar degeneration and a moderate infiltration of neutrophil and monocytes in the portal area and hepatic lobuli were observed. Which reflected biochemical and pathological changes in diclofenac-induced liver injury. Total NO production in serum and tissue homogenates were increased (p<0.01) in diclofenac-administered rats:The immunoreactivity with iNOS in the liver of normal control group was negative,24h after diclofenac injection, staining of iNOS was expressed in CL hepatocytes, Administration of diclofenac in24h interval resulted in an obvious values of SOD,GSH and GSH-PX decreased, while MDA and MPO increased in model group compared to normal group, with a significant difference (P<0.05or P<0.01), the uptake of R123by liver mitochondria in model group was lessen that in normal group.and the sensitivity to high level of calcium-induced swelling was also decreased, mitochondrial NAD(P)H level was also decreased.SDH and ATPase activity was also decreased (P<0.05or P<0.01).Positive cells Bcl-2staining were significantly decreased, positive cells in Bax,cytochrome C and TUNEL staining were significantly increased,L-NAME and Dex decreased the ALT,AST levels by (36.3%,54.3%,57.3%,53.8%)The expression of iNOS and NO levels in the serum and tissue homogenates both were inhibited in rats by L-NAME and Dex, The content of homogenate MDA,MPO decreased evidently,(P<0.05or P<0.01). Whereas the content of SOD,GSH and GSH-Px increased in rats that were Pretreatment with L-NAME and Dex,(P<0.05or P<0.01).The uptake of R123by liver mitochondria in model group were significantly increased,the sensitivity to high level of calcium-induced swelling was increased, mitochondria NAD(P)H level and SDH,ATPase activity were also increased in groups retreatment with L-NAME and Dex,(P<0.05or P<0.01).L-NAME and Dex increase positive cells in Bcl-2staining, decrease positive cells in Bax, cytochrome C and TUNEL staining.Conclusion:NO(iNOS/NOsystem)contributes to the damage in Dcf-induced liver injury via free oxygen radicals mitochondrial dysfunction and cell apoptosis. Dex protect the liver against the injurious effects of Dcf and the function may be correlated to prevent Dcf-induced NO overproduction by iNOS. |
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