Effects of bafilomycin A1 on functional capabilities of LPS-activated alveolar macrophages.
Resident alveolar macrophages (m phi) possess plasmalemmal vacuolar-type H(+)-ATPase (V-ATPase) that plays a crucial role in regulation of intracellular pH (pHi). To assess the importance of this V-ATPase to m phi effector functions, resident alveolar m phi from rabbits were activated with E. coli-derived lipopolysaccharide (LPS) and exposed to bafilomycin A1, a specific inhibitor of V-ATPase. Bafilomycin caused a significant cytosolic acidification in both the absence and presence of CO2-HCO3-, and in both unstimulated and activated m phi. Superoxide production and Fc receptor-mediated phagocytosis also were reduced in bafilomycin-treated m phi. Similar effects were elicited by acidifying the cytoplasm in the absence of bafilomycin, by lowering extracellular pH (pHo) from 7.4 to 6.5-6.6. Thus, the effects of bafilomycin on phagocytosis and superoxide production probably were related to cytosolic acidification, secondary to blockade of V-ATPase-mediated H+ extrusion across the plasma membrane. Conversely, bafilomycin significantly increased TNF-alpha release. This effect cannot be explained by a bafilomycin-induced acidosis because acidic pHo significantly reduced TNF-alpha release. The results demonstrate that V-ATPase activity is an important determinant of the effector functions of LPS-activated m phi.
Department of Internal Medicine, University of Texas Medical Branch, Galveston 77555-0561.
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Bidani
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Heming
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D000935:Antifungal Agents / Q000494:pharmacology*; D001992:Bronchoalveolar Lavage Fluid / Q000166:cytology; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D004926:Escherichia coli; D005452:Fluoresceins; D006863:Hydrogen-Ion Concentration; D008070:Lipopolysaccharides / Q000494:pharmacology*; D018942:Macrolides; D008262:Macrophage Activation / Q000187:drug effects* / Q000502:physiology*; D016676:Macrophages, Alveolar / Q000187:drug effects* / Q000201:enzymology / Q000502:physiology*; D010587:Phagocytosis / Q000187:drug effects; D006180:Proton-Translocating ATPases / Q000037:antagonists & inhibitors / Q000378:metabolism; D011817:Rabbits; D012680:Sensitivity and Specificity; D013268:Stimulation, Chemical; D013481:Superoxides / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D014617:Vacuoles / Q000201:enzymology
D000900:Anti-Bacterial Agents; D000935:Antifungal Agents; D005452:Fluoresceins; D008070:Lipopolysaccharides; D018942:Macrolides; D014409:Tumor Necrosis Factor-alpha; D013481:Superoxides; C040929:bafilomycin A1; D000255:Adenosine Triphosphate; D006180:Proton-Translocating ATPases