Endotoxin stimulates hydrogen peroxide detoxifying activity in rat hepatic endothelial cells

• Published in: Hepatology (Baltimore, Md.) Vol. 24; no. 3; pp. 691 - 696
• Main Authors: Spolarics, Z, Stein, D S, Garcia, Z C
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01.09.1996
• ISSN: 0270-9139; 1527-3350
• DOI: 10.1002/hep.510240336

The study aimed to assess the effect of lipopolysaccharide (LPS) in vivo (from Escherichia coli, 2 mg/kg body weight intraperitoneally) on the production and elimination of hydrogen peroxide (H2O2) in rat hepatic endothelial and Kupffer cells. Twenty‐two hours after the injection of LPS, hepatic cells were isolated by collagenase and pronase digestion followed by centrifugal elutriation, and cell‐ associated H2O2 was determined by flow cytometry analysis using 2′,7′‐ dichloroflorescin diacetate (DCF‐diacetate). LPS treatment did not alter the basal or phorbol myristate acetate‐stimulated levels of H2O2‐ related fluorescence in endothelial cells; however, it doubled phorbol myristate acetate‐stimulated fluorescence in Kupffer cells. Administration of varying concentrations of H202 (range, 10−7 ‐ 10−4 mol/L) in vitro caused a significantly delayed increase in fluorescence in endothelial cells from endotoxemic rats as compared with cells from saline‐injected animals. The 50% effective concentration of H2O2 was found at 1.1 × 10−6 and 8.1 × 10−6 mol/L on endothelial cells after saline and LPS treatment, respectively. No differences were detected in H2O2‐stimulated fluorescence between resting and LPS‐stimulated Kupffer cells. Administration of varying glucose concentrations in vitro significantly decreased the H2O2‐ stimulated fluorescence in endothelial and Kupffer cells from LPS‐ injected animals. Inhibition of nitric oxide synthase by in vitro administration of NG‐monomethyl‐L‐arginine (L‐NNMMA) did not alter the H2O2‐ or phorbol myristate acetate‐stimulated responses in endothelial and Kupffer cells. As shown earlier, LPS stimulates the gene expression of GLUT1 glucose transporter, glucose‐6‐phosphate dehydrogenase (G6PD), superoxide dismutases, and glutathione peroxidase in hepatic endothelial cells. The present data indicate that the LPS‐induced metabolic alterations are accompanied by an increased H2O2‐detoxifying capacity in hepatic endothelial cells. This may represent a protective mechanism against exogenous oxidative stress caused by activated hepatic phagocytes during inflammation. Our observations are consistent with primed production of reactive oxygen species (ROS) in LPS‐activated Kupffer cells.