Endotoxin stimulates gene expression of ROS-eliminating pathways in rat hepatic endothelial and Kupffer cells.
Reactive oxygen species (ROS) are mediators of cellular injury and play a putative role in the onset of hepatic damage during endotoxemia or sepsis. It has been suggested that induction of glucose-6-phosphate (G-6-P) dehydrogenase, the key enzyme of the hexose monophosphate shunt (HMS), may support ROS-producing or ROS-eliminating pathways in hepatic endothelial and Kupffer cells during endotoxemia. The aim of the study was to assess in vivo lipopolysaccharide (LPS)-induced alterations in rat gene expression of selected enzymes that are in functional relationship with the HMS. mRNA levels and activities of glucose transporter GLUT-1, Mn- and CuZn-dependent superoxide dismutases (Mn-SOD and CuZn-SOD), and Se-dependent glutathione peroxidase (Se-GPX) were determined. Cellular extracts were analyzed 7 or 22 h after injection of LPS (Escherichia coli, 2 mg/kg ip) or injection of saline. Exposure to LPS for 7 or 22 h caused a 10- to 25-fold increase in GLUT-1 mRNA levels in endothelial and Kupffer cells. In parenchymal cells, GLUT-1 mRNA expression was low, and LPS caused no marked changes. Cellular levels of Mn-SOD mRNA were 20-40 times greater in all hepatic cells from LPS-treated animals than in cells from control rats. LPS at 22 h increased Mn-SOD activity by 45% in endothelial cells but caused no significant changes in Kupffer or parenchymal cells. Message levels and enzyme activities of CuZn-SOD and Se-GPX were significantly elevated 22 h after LPS injection in endothelial cells only. Thus LPS results in marked upregulation of functionally related genes in hepatic cells. In endothelial cells, the simultaneous upregulation of GLUT-1, G-6-P dehydrogenase, Mn-SOD, CuZn-SOD, and Se-GPX may represent an important mechanism for accelerated elimination of ROS released from activated sinusoidal phagocytes. In Kupffer cells, upregulated GLUT-1 and G-6-P dehydrogenase, together with constitutively present SOD and lack of upregulated Se-GPX, suggest an elevated capacity to produce O2- and H2O2 that is consistent with primed bacterial killing.
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Department of Anatomy, Cell Biology, and Injury Sciences, New Jersey Medical School, Newark 07103, USA.
D000818:Animals; D004727:Endothelium / Q000166:cytology / Q000378:metabolism; D004731:Endotoxins / Q000494:pharmacology*; D015870:Gene Expression / Q000187:drug effects*; D051272:Glucose Transporter Type 1; D005979:Glutathione Peroxidase / Q000235:genetics; D007728:Kupffer Cells / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000494:pharmacology; D008099:Liver / Q000166:cytology / Q000378:metabolism*; D008297:Male; D009004:Monosaccharide Transport Proteins / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism*; D012643:Selenium / Q000502:physiology; D013482:Superoxide Dismutase / Q000235:genetics
D004731:Endotoxins; D051272:Glucose Transporter Type 1; D008070:Lipopolysaccharides; D009004:Monosaccharide Transport Proteins; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; C495679:Slc2a1 protein, rat; D005979:Glutathione Peroxidase; D013482:Superoxide Dismutase; D012643:Selenium