Expression of Cytokine Genes during Liver Regeneration after Partial Hepatectomy in Rats

Abstract In the present study to demonstrate the relationship between cytokines and liver regeneration we investigated by Northern blot hybridization the cytokine gene induction in the regenerating liver and several other organs (spleen, lung, and kidney) in the rat after partial hepatectomy (PH). We also examined whether Kupffer cells and the spleen are involved in the induction of cytokine mRNA in the regenerating liver. Both IL-1α and β mRNA increased transiently 1 2 to 1 hr after PH in nonparenchymal cells (NPC) of the regenerating liver; they reached a maximum before the peak of hepatocyte DNA synthesis. PH also induced a slight, but significant, gene expression of IL-1 in lung and kidney in the early postoperative period. TNF-αmRNA increased gradually in the spleen, but not the liver, of partially hepatectomized rats at 3 to 12 hr and then reached a peak at 24 hr after PH. IL-6 transcripts were not detected in the regenerating liver, spleen, lung, or kidney during liver regeneration. In contrast, no cytokine gene expression was induced in any of these four organs during the first 3 days after sham operation or unilateral nephrectomy. When Kupffer cell activity was suppressed by gadolinium chloride pretreatment, or when splenectomy was performed 24 hr before PH, the constitutive IL-1α and β mRNA expressions in NPC of the normal rat liver were completely suppressed. In conclusion, the present study demonstrates, for the first time, the specific kinetics of cytokine gene expression in the liver, spleen, lung, and kidney after PH. Further studies on the role of cytokine gene induction should contribute to an understanding of the pathophysiology of liver regeneration.