| Abstrakt: |
The cell activation inhibitor CI‐959 [5‐methoxy‐3‐(1‐methylethoxy)‐N‐1H‐tetrazol‐5‐ylbenzo[b]thiophene‐2‐carboxamide, monosodium salt] was evaluated for its effects on human neutrophil functions. CI‐959 inhibited spontaneous migration and chemotaxis toward N‐formyl–methionyl‐l‐leucyl‐l‐phenylalanine (fMLP) with 50% inhibition (IC50) values of 3.6 and 3.1 μM, respectively. CI‐959 also inhibited superoxide anion generation in response to C5a, fMLP, serum‐opsonized zymosan (SOZ), concanavalin A (Con A), and calcium ionophore A23187 with IC50values of 2.5, 4.7, 14.5, 5.4, and 14.8 μM, respectively. In comparison, CI‐959 inhibited myeloperoxidase release in response to C5a, fMLP, SOZ, and Con A with IC50values of 11.6, 16.1, 7.5, and <1.0 μM, respectively, while inhibiting the response to A23187 by only 5.5% at 100 μM. At concentrations up to 100 μM, CI‐959 had no effect on the respiratory burst or degranulation in response to L‐α‐1,2‐dioctanoylglycerol (DiC8) or phorbol 12‐myristate 13‐acetate (PMA). In addition, the compound inhibited leukotriene B4release stimulated by fMLP and SOZ (IC50values 4.0 and 2.5 μM, respectively), while having less activity against the A23187‐stimulated response (IC50>100 μM). These results demonstrate that CI‐959 inhibits cellular responses to stimuli that mobilize intracellular calcium. For cellular responses to ionophore‐mediated calcium influx, only oxygen radical production was inhibited by CI‐959. CI‐959 was further evaluated for its effects on neutrophil stimulus‐response coupling. At 100 μM, CI‐959 had no effect on human neutrophil phospholipase C or protein kinase C. CI‐959 inhibited fMLP‐stimulated intracellular calcium mobilization and calcium influx with IC50values of 16.7 and 3.1 μM, respectively, and exhibited less potent calmodulin antagonist activity (IC50= 90.5 μM). These results indicate that CI‐959 may exert its stimulus‐ and response‐specific inhibitory effects on neutrophil functions, in part, through inhibition of calcium‐regulated signalling mechanisms. J. Leukoc. Biol.55: 443–451; 1994. |
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