Evidence for pH sensitivity of tumor necrosis factor-α release by alveolar macrophages
Evidence for pH sensitivity of tumor necrosis factor-α release by alveolar macrophages
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作者：
Bidani, A;Wang, CZ;Heming, TA
肺泡巨噬细胞（m phi）参与肿瘤和脓肿间质液等酸性微环境中的炎症和免疫反应。本研究探讨了胞外pH（pH(o)）和H+转运抑制剂对内毒素（脂多糖）诱导的兔肺泡m φ肿瘤坏死因子- α (tnf - α)释放的影响。采用酶联免疫吸附法和L929成纤维细胞生物测定法测定培养基中tnf - α的含量和活性。在较低的pH值(0)下（小于或等于7.0），tnf - α的释放逐渐被抑制。此外，巴菲霉素A(l) （V-ATPases的特异性抑制剂）显著降低了pH(o) 7.4培养基中tnf - α的数量和活性。然而，巴非霉素引起非特异性细胞毒性（即对tnf - α抗体不敏感的生物活性）的显著增加。巴菲霉素对tnf - α释放的特异性影响遵循与酸性pH(0)相似的时间过程，这表明两种处理在脂多糖信号转导途径中作用于相似的事件。Amiloride（一种Na+转运体的抑制剂，包括Na+/H+交换器）也抑制tnf - α的释放，但其作用的时间过程与酸性pH(0)或巴菲霉素不同。
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 (pH(o)) 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 pH(o), values (less than or equal to 7.0). Also, bafilomycin A(l) (a specific inhibitor of V-ATPases) significantly reduced the amount and activity of TNF-alpha in m phi-conditioned media (pH(o) 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 pH(o), 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 pH(o) or bafilomycin.