title: Effects of Indomethacin on Intracellular pH and Na⁺/H⁺ Exchanger in the Human Monocytes.
abstract: 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 NH₄Cl 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 pHi and explored the underlying mechanism. In HEPES (nominally HCO₃⁻-free) Tyrode solution, a pH(i) recovery from induced intracellular acidosis could be blocked completely by 30 μM HOE 694, a specific NHE1 inhibitor, or by removing [Na⁺]₀. Therefore, in the present study, we provided functional evidence, physiologically and pharmacologically, that the HCO₃⁻-independent acid extruder was mostly likely the NHE1 which was involved in acid extrusion in the human monocytes. Moreover, indomethacin (1 μM-1 mM) 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 pHi decreasing is summation effects on NHE1-dependent and -independent mechanism.
authors.affiliation: Division of Cardiovascular Surgery, Department of Surgery, Tri-Service General Hospital, National Defense Medical Center, Taipei 11490, Taiwan, Republic of China.|Graduate Institute of Medical Sciences, National Defense Medical Center, Taipei 11490, Taiwan, Republic of China.
authors.forename: Yi-Ting
authors.initials: YT
authors.lastname: Tsai
authors.affiliation: Division of Cardiovascular Surgery, Department of Surgery, Tri-Service General Hospital, National Defense Medical Center, Taipei 11490, Taiwan, Republic of China.
authors.forename: Chung-Yi
authors.initials: CY
authors.lastname: Lee
authors.affiliation: Department of Pharmacology, National Defense Medical Center, Taipei 11490, Taiwan, Republic of China.
authors.forename: Chao-Chin
authors.initials: CC
authors.lastname: Chuang
authors.affiliation: Graduate Institute of Aerospace and Undersea Medicine of Tri-Service General Hospital, National Defense Medical Center, Taipei 11490, Taiwan, Republic of China.
authors.forename: Hsueh-Ju
authors.initials: HJ
authors.lastname: Lin
authors.affiliation: Department of Pharmacology, National Defense Medical Center, Taipei 11490, Taiwan, Republic of China.
authors.forename: Ching-Hsia
authors.initials: CH
authors.lastname: Wu
authors.affiliation: Department of Pharmacology, National Defense Medical Center, Taipei 11490, Taiwan, Republic of China.
authors.forename: Yu-Zhe
authors.initials: YZ
authors.lastname: Yang
authors.affiliation: Division of Cardiovascular Surgery, Department of Surgery, Tri-Service General Hospital, National Defense Medical Center, Taipei 11490, Taiwan, Republic of China.|Graduate Institute of Medical Sciences, National Defense Medical Center, Taipei 11490, Taiwan, Republic of China.|Department of Pharmacology, National Defense Medical Center, Taipei 11490, Taiwan, Republic of China.
authors.forename: Chien-Sung
authors.initials: CS
authors.lastname: Tsai
authors.affiliation: Graduate Institute of Medical Sciences, National Defense Medical Center, Taipei 11490, Taiwan, Republic of China.|Department of Pharmacology, National Defense Medical Center, Taipei 11490, Taiwan, Republic of China.
authors.forename: Shih-Hurng
authors.initials: SH
authors.lastname: Loh
mesh_terms: D027682:Cation Transport Proteins / Q000037:antagonists & inhibitors; D002478:Cells, Cultured; D006146:Guanidines / Q000494:pharmacology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007213:Indomethacin / Q000494:pharmacology*; D009000:Monocytes / Q000187:drug effects* / Q000378:metabolism; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013450:Sulfones / Q000494:pharmacology
chemical_list: D027682:Cation Transport Proteins; D006146:Guanidines; C490998:SLC9A1 protein, human; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers; D013450:Sulfones; C074107:3-methylsulfonyl-4-piperidinobenzoyl guanidine; D007213:Indomethacin