Role of Kupffer Cells in Vasoregulatory Gene Expression During Endotoxemia

Abstract

Although hepatic microcirculatory dysfunction occurs during endotoxemia, the mechanism responsible for this remains unclear. Since Kupffer cells provide signals that regulate hepatic response in inflammation, this study was designed to investigate the role of Kupffer cells in the imbalance in the expression of vasoactive mediators. Endotoxemia was induced by intraperitoneal E. coli endotoxin (LPS, 1 mg/kg body weight). Kupffer cells were inactivated with gadolinium chloride (<TEX>$GdCl_3$</TEX>, 7.5 mg/kg body weight, intravenously) 2 days prior to LPS exposure. Liver samples were taken 6 h following LPS exposure for RT-PCR analysis of mRNA for genes of interest: endothelin (ET-1), its receptors <TEX>$ET_A$</TEX> and <TEX>$ET_B$</TEX>, inducible nitric oxide synthase (iNOS), heme oxygenase (HO-1), and tumor necrosis factor-<TEX>$\alpha$</TEX> (TNF-<TEX>$\alpha$</TEX>). mRNA levels for iNOS and TNF-<TEX>$\alpha$</TEX> were significantly increased 31.8-fold and 26.7-fold in LPS-treated animals, respectively. This increase was markedly attenuated by <TEX>$GdCl_3$</TEX>, HO-1 expression significantly increased in LPS-treated animals, with no significant difference between saline and <TEX>$GdCl_3$</TEX> groups. ET-1 was increased by LPS. mRNA levels for <TEX>$ET_A$</TEX> receptor showed no change, whereas <TEX>$ET_B$</TEX> transcripts increased in LPS-treated animals. The increase in <TEX>$ET_B$</TEX> transcripts was potentiated by <TEX>$GdCl_3$</TEX>. We conclude that activation of Kupffer cells plays an important role in the imbalanced hepatic vasoregulatory gene expression induced by endotoxin.