Effects Of Wy14643 On Hepatic Ischemia-reperfusion Injury In Rats

Objective Peroxisome proliferator-activated receptor-α(PPAR-α) is one of the three subtypes of the nuclear receptor PPAR family. There are many studies indicate that PPARαprobably protect against important organs ischemia/reperfusion injury in recent years. Wy14643 is a selective PPAR-αagonist, which protects against important organs ischemia-reperfusion injury associated with inhibiting of oxidative stress and inflammatory response. But effects of different doses of Wy14643 on liver partial ischemia-reperfusion injury have not been reported. The purpose of this study was to investigate the effects of different doses of Wy14643 on liver partial ischemia/reperfusion injury in rats and its mechanism.Methods Male Sprague-Dawley rats (weighing 220 - 280g) were used in these experiments. An atraumatic clip was used to prevent blood supply to the left lateral and median lobes of the liver for setting up liver partial ischemia/reperfusion injury model. The color of ischemia liver from bright red to dark red after vascular occlusion indicates that ischemia is successed. Rats were randomly divided into five experimental groups each containing six rats. Sham group (G1, n=6): a sham operation was performed (except for liver I/R); I/R-untreated group (G2, n=6): rats underwent liver ischemia for 90 min followed by reperfusion for 4h; I/R+Wy14643 groups (G3, G4, G5; n=6): after the same surgical procedure as in group 2, animals were pretreated with Wy14643 at the dose of 1, 5 and 10mg/kg 1h before ischemia, respectively. Hepatic ischemia/reperfusion (I/R) was induced by clamping blood supply to the left lateral and median lobes of the liver for 90 min, and atraumatic clamp was removed for 4 h reperfusion. Blood samples and liver ischemia tissues were obtained at the end of reperfusion to assess serum and hepatic tissue homogenate aminotransferase (ALT), aspartate aminotransferase (AST), myeloperoxidase (MPO), serum interleukin-1β(IL-1β) and tumor necrosis factor alpha (TNF-α), as well as activity of superoxide dismutase (SOD) and content of malondialdehyde (MDA) in the hepatic tissue homogenate. The liver slices were also observed under microscope and electron microscope. Finally, all data were expressed as mean±SD. The statistical significance of differences between groups was analyzed using the one-way analysis of variance (ANOVA) and methods of LSD with the SPSS11.5 for windows XP statistical software package. The P values less than 0.05 were considered statistically significant.Results Compared with sham group, the I/R group showed more ischemia/reperfusion induced injury. Serum ALT, AST and MPO activities and TNF-α, IL-1βlevels increased significantly(P<0.01). ALT, AST and MPO activities and MDA level in liver tissue homogenate increased(P<0.01). However SOD activity in liver tissue homogenate was lower in I/R group than sham group(P<0.01). Serum ALT, AST and MPO activities in G3, G4 group and G5 group were all lower than those in I/R group (P<0.01 or P<0.05). Serum TNF-αand IL-1βlevels in G4 group and G5 group were lower than those in I/R group(P<0.01). Alough the serum TNF-αand IL-1βin G3 group also decreased , there were no significant difference(P>0.05). Liver tissue homogenate ALT, AST and MPO activities in G3, G4 group and G5 group were all lower than those in I/R group (P<0.01 or P<0.05). Alough SOD activity in G4 group and G5 group significantly increased in liver tissue homogenate, MDA content was markedly decreased (P<0.01 or P<0.05).With the staining of HE, it can be found under microscope that the main pathologic changes of I/R liver tissue were sinusoidal stretch and congestion and hepatocytes degeneration while cells necrosis were relatively seldom. In I/R group, there were obviously congestion and stretch in sinusoids. Hepatocytes degeneration and some necrosis were seen, and the structure of hepatic cords was destroyed. There were relieve in the G3 group and G5 group. The manifestation in G4 group was similar to the G3 group and G5 group. Under electron microscope it was showed that the occluded liver tissue from the I/R group was markedly damaged with mitochondrion swollen, vacuolar degenerationand, and mitochondrial crista destruction, marked decrease of rough endoplasmic reticulum and nucleus structure destruction compared with sham group. It was demonstrated that hepatic injury was a significant amelioration in Pretreatment groups with 1,5 and 10mg/kg Wy14643.Conclusion All data demonstrated that Wy14643 pretreatment exerts significant protection against liver partial ischemia / reperfusion injury in rats. The protective effects are possibly associated with enhancement of anti-oxidant and inhibition inflammation response. In addition, the protective effects may be associated with doses of Wy14643.