Genistein inhibits lysosomal enzyme release by suppressing Ca2+ influx in HL-60 granulocytes

The tyrosine kinase inhibitor genistein (5-200 mu M) suppressed Ca2+-depend ent fMLP (1 mu M) and ATP (100 mu M)-induced release of the lysosomal enzym e, beta-glucuronidase from neutrophil-like HL-60 granulocytes. Agonist-indu ced Ca2+ mobilization resulted from the release of intracellular Ca2+ store s and the influx of extracellular Ca2+. Genistein (200 mu M) suppressed fML P (1 mu M) and ATP (100 mu M)-induced Ca2+ mobilization, by 30-40%. Ca2+ re lease from intracellular stores was unaffected by genistein, however, genis tein abolished agonist-induced Ca2+ (Mn2+) influx. Consistent with these fi ndings, genistein (200 mu M) or removal of extracellular Ca2+ (EGTA 1 mM), inhibited Ca2+-dependent agonist-induced beta-glucuronidase release by simi lar extents (about 50%). In the absence of extracellular Ca2+, genistein ha d a small additional inhibitory effect on fMLP and ATP-induced beta-glucuro nidase release, suggesting an additional inhibitory site of action. Geniste in also abolished store-operated (thapsigargin-induced) Ca2+ (Mn2+) influx. Neither fMLP nor ATP increased the rate of Mn2+ influx induced by thapsiga rgin (0.5 mu M). These data indicate that agonist-induced Ca2+ influx and s tore-operated Ca2+ influx occur via the same genistein-sensitive pathway. A ctivation of this pathway supports approximately 50% of lysosomal enzyme re lease induced by either fMLP or ATP from HL-60 granulocytes.