Reversible activation of the neutrophil superoxide generating system by hexachlorocyclohexane: correlation with effects on a subcellular superoxide-generating fraction.
gamma-Hexachlorocyclohexane was found to exert profound effects on the phosphatidylinositol cycle, cytosolic calcium level, and the respiratory burst of human neutrophils. Exposure of neutrophils prelabelled with 32P to 4 X 10(-4) M gamma-hexachlorocyclohexane almost tripled radioactivity in phosphatidic acid and correspondingly decreased radioactivity in phosphatidylinositol 4,5 bisphosphate. Under similar conditions, gamma-hexachlorocyclohexane evoked the generation of superoxide at a rate of over 11 nmol/min/10(6) cells and more than doubled cytosolic-free calcium concentration as monitored by Quin-2 fluorescence. Because intermediates of the phosphatidylinositol cycle, via increases in available calcium levels or activated protein kinase C, are considered potential second messengers for activation of the NADPH-dependent O-2-generating system, we compared neutrophil responses to gamma-hexachlorocyclohexane with responses to phorbol myristate acetate, an activator of protein kinase C with well known effects on neutrophils. Like phorbol myristate acetate, gamma-hexachlorocyclohexane induced neutrophil degranulation but was not an effective chemotactic stimulus. The ability of gamma-hexachlorocyclohexane to induce a pattern of oxidative activation in neutrophil cytoplasts similar to that in intact cells indicated that concurrent degranulation was not required for sustained O-2 generation in response to this agent. When neutrophils or neutrophil cytoplasts exposed to gamma-hexachlorocyclohexane were centrifuged and resuspended in stimulus-free medium, O-2 generation ceased entirely but could be reinitiated by addition of the same stimulus. This finding was in contrast to the continued O-2 production by phorbol myristate acetate-stimulated neutrophils similarly washed and resuspended in stimulus-free medium. Unlike subcellular fractions of phorbol myristate acetate-stimulated neutrophils, corresponding fractions prepared from gamma-hexachlorocyclohexane-stimulated neutrophils contained almost no detectable NADPH-dependent O-2-generating activity. Subcellular oxidase activity was not recovered when cells and membrane fractions were continuously exposed to gamma-hexachlorocyclohexane during disruption and fractionation after cell stimulation, nor could it be induced by the addition of the stimulus to the subcellular fractions. Thus, the stimulus dependence of continuous neutrophil superoxide release evoked by gamma-hexachlorocyclohexane does not merely reflect a physical interaction of the agonist with the enzyme system involved.(ABSTRACT TRUNCATED AT 400 WORDS)
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Siakotos
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Gabig
D002118:Calcium / Q000378:metabolism; D002634:Chemotaxis, Leukocyte / Q000187:drug effects; D003593:Cytoplasm / Q000187:drug effects / Q000378:metabolism; D003594:Cytoplasmic Granules / Q000201:enzymology; D001556:Hexachlorocyclohexane / Q000494:pharmacology*; D006801:Humans; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism / Q000502:physiology; D019255:NADPH Oxidases; D009504:Neutrophils / Q000378:metabolism*; D010743:Phospholipids / Q000378:metabolism; D013347:Subcellular Fractions / Q000502:physiology; D013481:Superoxides / Q000096:biosynthesis*
D010743:Phospholipids; D013481:Superoxides; D001556:Hexachlorocyclohexane; D009247:NADH, NADPH Oxidoreductases; D019255:NADPH Oxidases; C022709:superoxide-forming enzyme; D002118:Calcium