title: Dissociation of TNF-alpha from endotoxin-induced nitric oxide and acute-phase hypotension.
abstract: We tested the concept that tumor necrosis factor-alpha (TNF-alpha) or platelet-activating factor (PAF) mediated Escherichia coli endotoxin lipopolysaccharide (LPS)-induced upregulation of nitric oxide (NO) and acute-phase hypotension (APH) in the rat. LPS (0.5 mg/kg i.v.) given to rats treated with saline or nonimmune goat-derived gamma-globulin (immunoglobulin G, 22 mg/kg i.m.) produced APH and increased plasma concentrations of TNF-alpha and nitrate and nitrite anions (reactive nitrogen intermediates; RNI) and NO in ex vivo incubates of polymorphonuclear neutrophils (PMN) and inducible NO synthase (iNOS) mRNA in PMN. Pretreatment of rats with a polyclonal TNF-alpha antibody (TNF-Ab, 22 mg/kg i.m.) abolished LPS-mediated increases in plasma TNF-alpha but failed to inhibit APH or the NO system. TNF-alpha (8.2 micrograms/kg i.v.) produced transient hypertension and sustained tachycardia and increased plasma TNF-alpha and PMN iNOS mRNA but not RNI. LPS and TNF-alpha decreased spontaneous and calcimycin (Ca2+ ionophore, 1 microM)- and PAF (1 microM)-mediated increases in head-space NO production by rings of mesenteric artery incubated ex vivo. TNF-Ab abolished all effects of TNF-alpha. PAF (25, 50, and 100 ng/kg) produced APH without increasing plasma TNF-alpha, RNI, or PMN iNOS mRNA. The PAF receptor antagonist BN-50730 (80 micrograms/kg i.v.) abolished PAF-induced APH and attenuated LPS-induced increases in RNI. We conclude that 1) LPS produces parallel but unrelated changes in TNF-alpha and RNI in plasma and PMN during the APH of endotoxemia; and 2) endogenous TNF-alpha is not required for LPS-mediated induction of iNOS mRNA, and PAF mediates LPS-induced APH.
authors.affiliation: Department of Medicine, Louisiana State University Medical Center, New Orleans 70112, USA.
authors.forename: J
authors.initials: J
authors.lastname: Xie
authors.forename: K O
authors.initials: KO
authors.lastname: Joseph
authors.forename: G J
authors.initials: GJ
authors.lastname: Bagby
authors.forename: T D
authors.initials: TD
authors.lastname: Giles
authors.forename: S S
authors.initials: SS
authors.lastname: Greenberg
mesh_terms: D000818:Animals; D001381:Azepines / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D004731:Endotoxins / Q000633:toxicity*; D004790:Enzyme Induction; D004926:Escherichia coli; D006339:Heart Rate / Q000187:drug effects; D007022:Hypotension / Q000139:chemically induced / Q000503:physiopathology*; D007074:Immunoglobulin G / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000633:toxicity*; D008297:Male; D008638:Mesenteric Arteries / Q000187:drug effects / Q000502:physiology / Q000503:physiopathology*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology / Q000503:physiopathology*; D009504:Neutrophils / Q000187:drug effects / Q000502:physiology*; D009569:Nitric Oxide / Q000096:biosynthesis; D019001:Nitric Oxide Synthase / Q000096:biosynthesis*; D010972:Platelet Activating Factor / Q000494:pharmacology; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley; D058924:Thienopyridines; D013997:Time Factors; D014158:Transcription, Genetic / Q000187:drug effects; D014230:Triazoles / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis / Q000502:physiology*
chemical_list: D001381:Azepines; D004731:Endotoxins; D007074:Immunoglobulin G; D008070:Lipopolysaccharides; D010972:Platelet Activating Factor; D010975:Platelet Aggregation Inhibitors; D012333:RNA, Messenger; D058924:Thienopyridines; D014230:Triazoles; D014409:Tumor Necrosis Factor-alpha; C066686:BN 50730; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase