Reorientation of macrophage mediator production in endotoxin tolerance.
During endotoxin shock macrophages produce arachidonic acid (AA) metabolites, nitric oxide (NO) and interleukin 6 (IL-6). In contrast, macrophages from endotoxin tolerant rats become hyporesponsive to LPS-induced AA metabolites production. However the role of NO and IL-6 during endotoxin tolerance is not known. Therefore, we evaluated the production of the AA metabolite 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha), IL-6 and NO (by nitrite measurement) by peritoneal macrophages from endotoxin tolerant rats. Since pertussis toxin (PT) sensitive guanine nucleotide binding regulatory (Gi) protein activity is altered during endotoxin tolerance, we also studied the effect of PT on the regulation of the above mediators synthesis. Endotoxin tolerance was induced in rats by intraperitoneal injection of a sublethal dose of Salmonella enteritidis lipopolysaccharide (LPS, 100 micrograms/kg ip). Peritoneal macrophages were harvested 24 hours after LPS injection and stimulated in vitro with LPS (50 micrograms/ml) for determination of NO activity by nitrite, 6-keto-PGF1 alpha and IL-6 production. In macrophages collected from vehicle-pretreated rats (control) LPS stimulates all three mediators. In vivo pretreatment with LPS induced a desensitization of macrophages to LPS-induced 6-keto-PGF1 alpha production compared to control macrophages (p < 0.001). LPS-stimulated IL-6 synthesis was also partially, but not completely, reduced in tolerant macrophages (p < 0.001 versus control).(ABSTRACT TRUNCATED AT 250 WORDS)
Department of Physiology, Medical University of South Carolina, Charleston 29425, USA.
B
B
Zingarelli
H
H
Chen
A P
AP
Caputi
P V
PV
Halushka
J A
JA
Cook
D015121:6-Ketoprostaglandin F1 alpha / Q000096:biosynthesis; D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism; D004361:Drug Tolerance / Q000502:physiology; D004731:Endotoxins / Q000633:toxicity*; D019204:GTP-Binding Proteins / Q000378:metabolism; D066298:In Vitro Techniques; D015850:Interleukin-6 / Q000096:biosynthesis; D008070:Lipopolysaccharides / Q000633:toxicity; D008264:Macrophages / Q000187:drug effects* / Q000502:physiology*; D008297:Male; D009569:Nitric Oxide / Q000096:biosynthesis; D037342:Pertussis Toxin; D051381:Rats; D010566:Virulence Factors, Bordetella / Q000633:toxicity
D004731:Endotoxins; D015850:Interleukin-6; D008070:Lipopolysaccharides; D010566:Virulence Factors, Bordetella; D016718:Arachidonic Acid; D009569:Nitric Oxide; D015121:6-Ketoprostaglandin F1 alpha; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins