Clearance of bacterial lipopolysaccharides and lipid A by the liver and the role of argininosuccinate synthase.
The liver is thought to be involved in the systemic clearance and detoxification of lipopolysaccharide (LPS). Argininosuccinate synthase (AS), a liver cytosolic urea cycle enzyme, has been found to bind to and inactivate LPS and lipid A. To elucidate the participation of AS in the clearance of LPS by liver and hepatocytes, we investigated the correlation between AS content and the removal of lipid A and LPS in vivo and in vitro, tracing levels of biological activity. A hepatotoxic model in which mice were injected with CCl(4) revealed a significant reduction in lipid A clearance along with liver failure on day 1; total body clearance was changed to 0.534 ml/min from 1.42 ml/min. AS content in liver concomitantly decreased to about half and AS leaked to blood at about 6 microg/ml. Total body clearance of i.v. injected AS was estimated at 0.083 ml/min, which predicted about 24-h leakage of AS after CCl(4) injection. The treatment also reduced the clearance of R-type LPSs to a lesser degree the larger its polysaccharide portion. S-type LPS, which has a large O-antigen polysaccharide, exhibited enhancement of clearance on CCl(4) treatment. When pretreated in vitro with AS and injected into normal mice, lipid A and R-type LPS showed a similar pattern of clearance of residual activities to the untreated forms, but S-type LPS exhibited enhancement of clearance. Comparison between different strains of mice revealed a correlation of AS content in liver and lipid A clearance, where the higher AS strain C3H/He mice showed a more rapid clearance than the lower AS strains C57BL/6 and BALB/c. Primary spheroid cultures of hepatocytes treated with 0.1 microM dexamethasone and 1 microM glucagon showed about a 2-fold increase in AS amount and a more rapid clearance of LPS from culture medium than untreated cells. These results suggest that AS in hepatocytes may be involved in the process of lipid A and LPS clearance and the extracellular leakage of AS may also participate in the systemic detoxification.
Satoh
Motonobu
M
Department of Medicinal Chemistry, Faculty of Pharmaceutical Sciences, Teikyo University, Sagamihara, Kanagawa, Japan. moto-sth@pharm.teikyo-u.ac.jp
Ando
Shingo
S
Shinoda
Takehiro
T
Yamazaki
Masatoshi
M
D000818:Animals; D001124:Argininosuccinate Synthase / Q000096:biosynthesis* / Q000378:metabolism; D002251:Carbon Tetrachloride / Q000008:administration & dosage / Q000633:toxicity; D018929:Cell Culture Techniques; D002461:Cell Line, Transformed; D056486:Chemical and Drug Induced Liver Injury / Q000097:blood / Q000382:microbiology / Q000503:physiopathology; D004926:Escherichia coli; D022781:Hepatocytes / Q000201:enzymology*; D008050:Lipid A / Q000097:blood / Q000493:pharmacokinetics*; D008070:Lipopolysaccharides / Q000097:blood / Q000493:pharmacokinetics*; D008099:Liver / Q000201:enzymology*; D008297:Male; D008657:Metabolic Clearance Rate; D051379:Mice; D011110:Polymorphism, Genetic; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D008050:Lipid A; D008070:Lipopolysaccharides; D014409:Tumor Necrosis Factor-alpha; D002251:Carbon Tetrachloride; D001124:Argininosuccinate Synthase