Age-related events in human active T lymphocytes: changes in the phosphoinositidase C activity.
Since PHA-stimulated active T lymphocytes from aged humans showed changes in the metabolic pattern of inositol lipids in comparison with young subjects, we studied the possible role of phosphoinositidase C (PIC) in the generation of this phenomenon. The breakdown of exogenous [3H]phosphatidylinositol 4,5-bisphosphate was found to be optimal at neutral pH and Ca++ concentrations close to millimolar levels. Under these conditions PIC activity of resting lymphocytes did not differ in aged and young subjects, while, after short periods of PHA stimulation (up to 4 hr) the substrate hydrolysis was lower and delayed in the elderly group in comparison with that of controls. Our findings support the hypothesis that the age-related default of this enzyme, responsible for the age-related changes in the inositol lipid pathway of this peculiar subpopulation, could be involved, as a primary event, in the mechanisms leading to the reduced proliferative response of aged active T lymphocytes.
Di Pietro
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Istituto di Morfologia Umana Normale, Università di Chieti, Italy.
Rana
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RA
Sciscio
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Marmiroli
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Billi
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Cataldi
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Cocco
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D000328:Adult; D000367:Age Factors; D000368:Aged; D000375:Aging / Q000502:physiology*; D002118:Calcium / Q000494:pharmacology; D002478:Cells, Cultured; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008213:Lymphocyte Activation; D010727:Phosphoric Diester Hydrolases / Q000097:blood*; D013601:T-Lymphocytes / Q000201:enzymology* / Q000276:immunology
D010727:Phosphoric Diester Hydrolases; C021491:glycerophosphoinositol glycerophosphodiesterase; D002118:Calcium