Abstract:

BACKGROUND: Curcumin pre-conditioning can alleviate liver injury induced by limb ischemia/reperfusion (I/R), but whether curcumin post-conditioning has protective effect against liver cold I/R injury and its mechanism are still poorly studied.

OBJECTIVE: To investigate the effects of curcumin post-conditioning on hepatocyte apoptosis in rats with liver cold I/R injury in rats.

METHODS: Eighty adult male Sprague-Dawley rats were randomly divided into four groups (n=20 per group) by using a random number table: sham group, I/R group, curcumin post-conditioning group (I/R+Cur group), and dexamethasone group (I/R+Dex group). The liver blood flow was completely blocked. Then the splenic vein and the adrenal vein were used as the inflow and outflow tracts to inject 0 ^oC compound Ringer lactate solution followed by cold perfusion for 30 minutes. After stopping cold perfusion, the proximal splenic vein and the right adrenal vein were ligated to remove the spleen, and then the blood flow in the liver restored. The cold I/R model was successfully established. After 30 minutes of cold ischemia, 60 mg/kg curcumin was injected into the rat tail vein in the I/R+Cur group, 0.5 mg/kg dexamethasone was injected into the rat tail vein in the I/R+Dex group, and the same amount of saline was injected in the other groups. Blood sample was taken from the carotid artery at 6 hours after reperfusion. Serum levels of aspartate aminotransferase and alanine transferase were detected. Then the rats were sacrificed to detect malondialdehyde level in liver tissue, observe liver pathological changes by hematoxylin-eosin staining, measure hepatocyte apoptosis index by Hoechst 33258 staining, detect expression of Bcl-2 and Bax protein by western blot, expression of caspase-9 mRNA by RT-PCR, and levels of tumor necrosis factor-α and interleukin-1β by ELISA.

RESULTS AND CONCLUSION: Compared with the sham group, aspartate aminotransferase, alanine transferase, malondialdehyde levels and apoptosis index in the I/R group increased significantly (P < 0.05). Hematoxylin-eosin staining showed a large number of inflammatory cells infiltrated in the hepatic sinusoids, eosinophilic changes of hepatocytes, cytoplasmic loosening, balloon-like changes of hepatocytes, occasional patchy necrosis, and scattered punctate necrosis foci in the I/R group. The I/R group had significantly decreased expression of Bcl-2, and increased expression of Bax (P < 0.05), Caspase-9 mRNA, tumor necrosis factor-α and interleukin-1β (P < 0.05). Compared with the I/R group, aspartate aminotransferase, alanine transferase, malondialdehyde levels and apoptosis index in the I/R+Cur group decreased significantly (P < 0.05). Hematoxylin-eosin staining showed that inflammatory infiltration in the hepatic sinusoids decreased significantly, eosinophilic and balloon-like hepatocytes decreased significantly, but occasionally a small amount of scattered punctate necrosis was observed in the I/R+Cur group. There was significantly increased Bcl-2 expression, and significantly decreased Bax (P < 0.05), Caspase-9 mRNA, tumor necrosis factor-α and interleukin-1β (P < 0.05). No significant differences were observed between I/R+Cur group and I/R+Dex group (P > 0.05). In a word, curcumin-post conditioning can alleviate liver injury induced by cold I/R in rats. Its mechanism may be related to down-regulation of Bcl-2/Bax ratio, inhibition of caspase-9 mRNA expression, and reduction of the release of tumor necrosis factor-α and interleukin-1β, therefore playing an anti-apoptotic role in liver protection.

Key words: curcumin, post-conditioning, liver, cold ischemia-reperfusion, Bcl-2, Bax