TNF potentiates PAF-induced pulmonary vasoconstriction in the rat: role of neutrophils and thromboxane A2.
Both tumor necrosis factor (TNF) and platelet-activating factor (PAF) are released during sepsis and are important mediators of septic lung injury. I investigated the interactions of TNF and PAF on vasoactive responses in the pulmonary circulation. In isolated rat lungs perfused with a cell- and plasma-free physiological salt solution, PAF (0.01- and 0.1-micrograms boluses) caused transient dose-dependent pulmonary arterial and venous constrictions. In vivo pretreatment of the rats with TNF (0.02 or 0.2 mg/kg i.v.) 1 h before lung isolation increased lung myeloperoxidase activity and markedly enhanced PAF-induced pulmonary vasoconstriction without affecting the pressor responses to angiotensin II or hypoxia. In contrast, pretreatment with lipopolysaccharide (10 mg/kg), which increased lung myeloperoxidase to the same extent as TNF, caused only a modest enhancement of PAF-induced vasoconstriction associated with reduced pressor responses to angiotensin II and hypoxia. Ex vivo perfusion of isolated lungs with TNF for 1 h did not affect PAF vasoconstriction. The TNF-induced potentiation of PAF vasoconstriction was not altered by depletion of circulating neutrophils with vinblastine but was blocked by Dazmegrel, a thromboxane synthase inhibitor. Thus, TNF potentiates PAF-induced pulmonary vasoconstriction by an in vivo mechanism that is neutrophil independent but thromboxane dependent. This TNF-PAF interaction likely contributes to the development of pulmonary hypertension during sepsis.
Chang
S W
SW
Department of Medicine, Northwestern University Medical School, Chicago, Illinois.
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D004357:Drug Synergism; D007093:Imidazoles / Q000494:pharmacology; D066298:In Vitro Techniques; D008070:Lipopolysaccharides / Q000494:pharmacology; D008297:Male; D009503:Neutropenia / Q000503:physiopathology; D009504:Neutrophils / Q000502:physiology*; D010972:Platelet Activating Factor / Q000494:pharmacology*; D011652:Pulmonary Circulation / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013928:Thromboxane A2 / Q000502:physiology*; D013930:Thromboxane-A Synthase / Q000037:antagonists & inhibitors; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D014661:Vasoconstriction / Q000187:drug effects
D007093:Imidazoles; D008070:Lipopolysaccharides; D010972:Platelet Activating Factor; D014409:Tumor Necrosis Factor-alpha; C039242:dazmegrel; D013928:Thromboxane A2; D013930:Thromboxane-A Synthase