Calcium signalling is altered in myeloid cells with a deficiency in NADPH oxidase activity

The relation of O-2(.-)-production and Ca2+ homeostasis was investigated in PLB-985 cell lines and neutrophilic granulocytes from peripheral blood. In differentiated wild-type PLB-985 cells, a high level of O-2(.-)-production was associated with a significant decrease in the membrane potential and the inhibition of capacitative Ca2+ entry. These correlations were not observed in gp91(phox -/-) cells or in cells transfected with a non-functional mutant of gp91(phox) (Thr341Lys). Membrane depolarization and inhibition of Ca2+ entry reappeared in cells transfected with wild-type gp91(phox). These experiments demonstrate that inhibition of Ca2+ entry depends on the presence of a functional NADPH oxidase. The Ca2+ signal induced by stimulation of chemotactic receptors also showed remarkable differences: [Ca2+](ic) in the sustained phase was higher in gp91(phox-/-) than in wild-type cells. Alteration of the Ca2+ signal was reproduced by treating peripheral blood neutrophils with the NADPH oxidase inhibitor diphenylene-iodonium. It is concluded that the deficiency in O-2(.-)-production is accompanied by significant alterations of Ca2+ homeostasis in myeloid cells.