title: Evidence for pH sensitivity of tumor necrosis factor-alpha release by alveolar macrophages.
abstract: Alveolar macrophages (m phi) participate in inflammatory and immune responses in acidic microenvironments such as the interstitial fluids of tumors and abscesses. Two plasmalemmal H+ extruders interact to control the acid-base status of alveolar m phi, namely a V-type H+ pump (V-ATPase) and a Na+/H+ exchanger. The present study examined the effects of extracellular pH (pHo) and H+ transport inhibitors on tumor necrosis factor-alpha (TNF-alpha) release induced by endotoxin (lipopolysaccharide) in rabbit alveolar m phi. The amount and activity of TNF-alpha in m phi-conditioned media were determined by enzyme-linked immunosorbent assay and L929 fibroblast bioassay, respectively. TNF-alpha release was suppressed progressively at lower pHo values (< or = 7.0). Also, bafilomycin A1 (a specific inhibitor of V-ATPases) significantly reduced the amount and activity of TNF-alpha in m phi-conditioned media (pHo 7.4). However, bafilomycin caused a significant increase in the nonspecific cytotoxicity (i.e. bioactivity insensitive to TNF-alpha antibody) of m phi-conditioned media. The effects of bafilomycin specifically on TNF-alpha release followed a time course similar to that of acidic pHo, suggesting that both treatments acted on similar events in the lipopolysaccharide signal transduction pathway. Amiloride (an inhibitor of Na+ transporters including the Na+/H+ exchanger) also suppressed TNF-alpha release but displayed a time course of action different from the acidic pHo or bafilomycin.
authors.affiliation: Department of Internal Medicine, Shriners Burns Institute, University of Texas Medical Branch, Galveston 77555-0561, USA.
authors.forename: A
authors.initials: A
authors.lastname: Bidani
authors.forename: C Z
authors.initials: CZ
authors.lastname: Wang
authors.forename: S J
authors.initials: SJ
authors.lastname: Saggi
authors.forename: T A
authors.initials: TA
authors.lastname: Heming
mesh_terms: D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002470:Cell Survival / Q000187:drug effects; D006863:Hydrogen-Ion Concentration; D018942:Macrolides; D016676:Macrophages, Alveolar / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology*; D008297:Male; D006180:Proton-Translocating ATPases / Q000037:antagonists & inhibitors; D011817:Rabbits; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*; D025262:Vacuolar Proton-Translocating ATPases
chemical_list: D000900:Anti-Bacterial Agents; D018942:Macrolides; D014409:Tumor Necrosis Factor-alpha; D000584:Amiloride; C040929:bafilomycin A1; D025262:Vacuolar Proton-Translocating ATPases; D006180:Proton-Translocating ATPases