Cellular mechanisms of inhibition of superoxide anion generation in rat neutrophils by the synthetic isoquinoline DMDI
作者:Jih-Pyang Wang、Ling-Chu Chang、Shue-Ling Raung、Mei-Feng Hsu、Chi-Ming Chen
DOI:10.1016/s0014-2999(01)01536-9
日期:2002.1
This study was undertaken to assess the cellular localization of the inhibitory effect of a chemically synthetic isoquinoline compound 1-(3', 4'-dimethoxybenzyl)-6,7-dichloroisoquinoline (DMDI) on the formyl-methionyl-leucyl-phenylalanine (fMLP)-induced respiratory burst in rat neutrophils. The DMDI concentration dependently inhibited the superoxide anion (0;) generation and 02 Consumption (IC50 12.2 +/- 4.9 and 15.2 +/- 8.4 muM, respectively) of neutrophils. DMDI did not scavenge the O-2(.-) generated during the autoxidation of dihydroxyfumaric acid in a cell-free system. DMDI did not elevate cellular cyclic AMP levels. Inhibition of O-2(.-) generation by DMDI in neutrophils was not reversed by a cyclic AMP-dependent protein kinase inhibitor, (8R,9S,11S)-(-)-9-hydroxy-9-hexoxycarbonyl-8-methyl-2,3,9, 10-tetrahydro-8,11-epoxy-1H,8H,11H-2,7b, 11a-triazadibenzo[a,g]cycloocta[cde]trinden-1-one (KT5720). The DMDI concentration dependently inhibited the late plateau phase but not the initial spike of fMLP-induced [Ca2+](i) changes in the presence of extracellular Ca2+. However, DMDI had no effect on the fMLP-induced [Ca2+](i) changes in the absence of extracellular Ca2+. In addition, DMDI did not affect the fMLP-stimulated phosphatidylinositol 3-kinase (PI3-kinase) activation. DMDI produced a concentration-dependent reduction in the formation of phosphatidic acid and phosphatidylethanol in the presence of ethanol from fMLP-stimulated neutrophils (IC50 13.3 +/- 4.0 and 9.4 +/- 4.3 muM, respectively). On the basis of the immunoblot analysis of the phosphorylation of the mitogen-activated protein (MAP) kinase, DMDI attenuated the fMLP-stimulated MAP kinase phosphorylation in a similar concentration range. Collectively, these results indicate that the inhibition of the respiratory burst by DMDI in rat neutrophils is mediated through the blockade of phospholipase D and MAP kinase signaling pathways. (C) 2002 Elsevier Science B.V. All rights reserved.