Accelerated calcium influx and hyperactivation of neutrophils in chronic granulomatous disease.
The relationship between activation of NADPH-oxidase, alterations in membrane potential and triggering of Ca2+ fluxes in human phagocytes has been investigated using neutrophils from four subjects with chronic granulomatous disease (CGD). Cytosolic Ca2+ and membrane potential were measured by spectrofluorimetry, and net efflux and influx of Ca2+ by radiometric procedures. Exposure of normal neutrophils to the chemotactic tripeptide, N-formyl-L-methionyl-L-leucyl-L-phenylalanine (FMLP; 1 microM) was accompanied by an abrupt increase in cytosolic Ca2+ coincident with membrane depolarization and efflux of the cation. These events terminated at around 30 s after the addition of FMLP and were followed by membrane repolarization and store-operated influx of Ca2+, both of which were superimposable and complete after about 5 min. Activation of CGD neutrophils was also accompanied by an increase in cytosolic Ca2+, which, in spite of an efficient efflux response, was prolonged in relation to that observed in normal cells. This prolonged increase in cytosolic Ca2+ in activated CGD neutrophils occurred in the setting of trivial membrane depolarization and accelerated influx of Ca2+, and was associated with hyperactivity of the cells according to excessive release of elastase and increased activity of phospholipase A2. Treatment of CGD neutrophils with the type 4 phosphodiesterase inhibitor, rolipram (1 microM) restored Ca2+ homeostasis and attenuated the increase in elastase release. These findings support the involvement of NADPH-oxidase in regulating membrane potential and Ca2+ influx in activated neutrophils, and may explain the disordered inflammatory responses and granuloma formation which are characteristic of CGD.
Tintinger
G R
GR
Medical Research Council Unit for Inflammationand Immunity, Department of Immunology, Institute for Pathology, University of Pretoria, Pretoria, South Africa.
Theron
A J
AJ
Steel
H C
HC
Anderson
R
R
D000293:Adolescent; D000328:Adult; D002118:Calcium / Q000276:immunology* / Q000378:metabolism; D005260:Female; D006105:Granulomatous Disease, Chronic / Q000097:blood / Q000276:immunology*; D006801:Humans; D008297:Male; D019255:NADPH Oxidases / Q000097:blood / Q000276:immunology; D018375:Neutrophil Activation; D009504:Neutrophils / Q000276:immunology*; D010587:Phagocytosis
D019255:NADPH Oxidases; D002118:Calcium