- 期刊
Effects of Indomethacin on Intracellular pH and Na^+/H^+ Exchanger in the Human Monocytes
並列摘要
The ability to maintain optimal intracellular pH (pH_i) is an essential requirement for all cells. Na^+-H^+ exchanger (NHE), a ubiquitously expressed transmembrane protein, has been found widely as a major acid extruder in many different cell types, including human monocytes. We therefore investigated the mechanism of the active pH_i recovery from intracellular acidosis (induced by NH_4Cl prepulse) using intracellular 2',7'-bis (2-carboxethyl)-5(6)-carboxyl-fluorescein (BCECF) fluorescence in cultured human monocytes. Indomethacin is a potent, nonselective inhibitor of cyclooxygenases. Due to its toxicity, the clinical use of indomethacin as an analgesic-antipyretic agent is limited. However, it has recently been found that indomethacin can effectively treat many inflammatory/immune disorders. In this study, we further investigated the effect of indomethacin on the pH_i and explored the underlying mechanism. In HEPES (nominally HCO_3^- free) Tyrode solution, a pH_i recovery from induced intracellular acidosis could be blocked completely by 30μM HOE 694, a specific NHE1 inhibitor, or by removing [Na^+]_o. Therefore, in the present study, we provided functional evidence, physiologically and pharmacologically, that the HCO_3^--independent acid extruder was mostly likely the NHE1 which was involved in acid extrusion in the human monocytes. Moreover, indomethacin (1μM-1mM) decreased pH_i levels in a concentration-dependent manner and significantly suppressed the activity of the NHE1, suggesting that indomethacin-induced intracellular acidosis is caused both by the inhibition of NHE1 activity and the non-specified NHE1-independent acidifying mechanism. In conclusion, our present study demonstrates that NHE1 exists functionally in human monocytes, and the indomethacin-induced pH_i decreasing is summation effects on NHE1-dependent and-independent mechanism.
參考文獻
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