Modulation of liver oxidant-antioxidant system by ischemic preconditioning during ischemia／reperfusion injury in rats

AIM: To investigate effects of ischemic pre-conditioning on the liver endogenous oxidant-antioxidant system during ischemia/reperfusion injury.METHODS: Twenty-four male Sprague-Dawley rats were randomly divided into sham-operated (Sham), ischemia/reperfusion (I/R), ischemic pre-conditioning plus ischemia/reperfusion (IPC) groups. Serum ALT, AST and hyaluronic acid levels were assayed and pathologic alterations observed. Liver malondialdehyde (MDA) contents,endogenous antioxidant enzymes, superoxidase dismutase (SOD), catalase (CAT), gultathionine peroxidase (GSH-Px)activities, neutrophils accumulation marker, myeloperoxidase (MPO) activities were measured respectively.RESULTS: Compared with I/R group, sinusoidal endothelial cells as well as hepatocytes damages, as assessed biochemically and histochemically, were improved significantly in IPC group; neutrophils infiltration was also markedly reduced. In IPC group, liver peroxidation, as measured by MDA contents, was significantly decreased when compared with I/R group; endogenous antioxidant enzymes, SOD, CAT and GSH-Px activities were markedly higher than that in I/R group.CONCLUSION: Ischemic pre-conditioning exerts protective effects on both hepatic sinusoidal endothelial cells and hepatocytes during liver I/R injury. Its mechanisms may involve dimunition of neutrophils infiltration and modulation of the imbalance of endogenous oxidant-antioxidant system in the organism.

Effects of PPARg agonist pioglitazone on rat hepatic fibrosis

AIM: To investigate effects of pioglitazone on rat hepatic fibrosis and to explore its mechanism. METHODS: Rat hepatic fibrosis was induced by carbontet. achloride (CCI4). Forty Sprague-Dawley rats were divided randomly into 4 groups: control, model, and two treatment (PⅠ, PⅡ) groups. Except for rats in control group, all rats were given subcutaneous injection of 400 mL/L CCI4, twice a wk for 8 wk. Rats in PⅠ and PⅡ groups were also treated with pioglitazone of 3 mg/kg, daily via gastrogavage beginning on the 1^st day and at the end of the 2^nd week, administration of CCI4 respectively. Liver functions (ALT, AST), serum fibrotic markers (HA, LN, PCIII) and hepatic hydroxyproline (HP) concentration were determined respectively. Histochemical staining of formalin-fixed liver sections with HE, Masson-Trichrome, and immunohistochemical staining for m-smooth muscle actin (α-SMA) were performed. Modified Knodell and Chevallier semi-quantitative scoring system (SSS) was used to evaluate necroinflammatory activity and fibrosis degree. RESULTS: Compared with model group, pioglitazone significantly reduced the serum levels of ALT, AST, HA, LN and PCⅢ (P<0.05 or <0.01). The HP concentrations in PⅠ(210.90±24.07 μg/g), and PⅡ (257.36±30.55 μg/g) groups were also lower than those in model group (317.80±36.44) μg/g) (P<0.01). Histologic examination showed that PⅠ and PⅡ groups had milder hepatocellular degeneration, necrosis and infiltration of inflammatory cells, and thinner or less fibrotic septa than did model group. The scores for necroinflammation in P (2.80±1.03), and PⅡ (3.00±1.05) groups were significantly reduced as compared with model group (4.88±2.30) (P<0.05 or <0.01); the fibrosis scores in PⅠ (3.40±1.65), and PⅡ (4.60±1.35) groups were also markedly lower than those in model group (7.00±3.21) (P<0.05 or <0.01). Immunohistochemical staining showed that expression of α-SMA in PⅠ and PⅡ groups was ameliorated dramatically compared with model group. CONCLUSION: PPARγ, agonist pioglitazone greatly retards the progression of rat hepatic fibrosis induced by CCI4 through inhibition of HSC activation and amelioration of hepatocyte necroinflammation in rats.