Killed Escherichia coli stimulates macrophage-mediated alterations in hepatocellular function during in vitro coculture: a mechanism of altered liver function in sepsis

Abstract

Hepatic dysfunction is a poorly understood and highly lethal component of multiple-system organ failure. Both in vivo and in vitro studies of "liver" function have generally neglected hepatocyte-Kupffer cell interactions. In the following experiments, isolated hepatocytes were cocultivated with unstimulated peritoneal cells, predominately macrophages, which served as a readily available Kupffer cell analog. Coculture of hepatocytes with peritoneal cells resulted in little or no change in [3H]leucine incorporation into hepatocyte protein. When gentamicin-killed Escherichia coli cells (GKEC) were added to coculture, there was a marked decrease in hepatocyte [3H]leucine incorporation. In contrast, GKEC added to hepatocytes alone had no effect. Kinetic data revealed an 8-h delay before any significant decrease in leucine incorporation into hepatocyte protein after the addition of GKEC to the coculture. The maximal decrease in hepatocyte [3H]leucine incorporation occurred 24 h after GKEC were added. The decrease observed 24 h after GKEC were added disappeared almost completely after 48 h of coculture. Similar alterations in cocultured hepatocyte protein synthesis were observed after the addition of phorbol myristate acetate, lipopolysaccharide, or muramyl dipeptide, a component of bacterial peptidoglycan. Hepatocyte viability by trypan blue exclusion was unchanged, and gross morphology by light or electron microscopy was unaffected. We propose that during sepsis, macrophages (Kupffer cells) respond to circulating microbial products and mediate alterations in hepatocyte function. These experiments underscore the important role of Kupffer cell function in attempts to understand hepatic malfunction in multiple-system organ failure.