Effects of sizofiran on endotoxin-enhanced cold ischemia-reperfusion injury of the rat liver

Kupffer cells (KC), resident macrophages of the liver, have been strongly implicated in lipopolysaccharide (LPS)-induced liver graft injury. However, our recent study showed that sizofiran (schizophyllan glucan) (SPG), which activates KC, did not influence cold ischemia-reperfusion liver injury of LPS-exposed rats. Here we investigated some mechanisms by which SPG does not aggravate LPS-enhanced cold ischemia-reperfusion rat liver injury. Control and SPG-treated rats were exposed to LPS for 2 h prior to hepatectomy. The livers were cold-preserved in University of Wisconsin solution followed by reperfusion with Krebs-Henseleit buffer. We found that SPG dramatically inhibited LPS-induced increases of tumor necrosis factor-alpha (TNF-alpha) in the plasma and bile in vivo. Moreover, LPS-induced TNF-alpha release into the washout solution after cold ischemia was also abrogated by SPG pretreatment. However, SPG increased TNF-alpha release into the perfusate after reperfusion. On the other hand, SPG completely abolished expression of c-myc protooncogene, which is known to sensitize cells to TNF-alpha cytotoxicity. In conclusion, inhibition of both TNF-alpha release after LPS challenge and c-myc expression may explain why activation of KC with SPG does not aggravate endotoxin-enhanced cold ischemia-reperfusion liver injury.