ELEVATED SUPEROXIDE GENERATION IN MONONUCLEAR PHAGOCYTES BY TREATMENTWITH 1-ALPHA HYDROXYVITAMIN D-3 - CHANGES IN KINETICS AND IN OXIDASE CYTOSOLIC FACTOR P47

The effect of 1 alpha-hydroxyvitamin D-3 (1 alpha OHD3) treatment on t he superoxide production of phagocytic cells in patients undergoing co ntinuous ambulatory peritoneal dialysis (CAPD) was studied, A 3-day tr eatment of CAPD patients with 3 mu g per day of 1 alpha OHD3 (high-dos e treatment) significantly increased NADPH oxidase and killing activit ies in peritoneal macrophages and peripheral blood monocytes (P<0.001) as compared with low-dose (0.25 mu g/day of 1 alpha OHD3) treatment o r nontreatment, The high oxidase activity observed in macrophages and monocytes after the treatment with 1 alpha OHD3, correlated significan tly to the increase in the amount of the cytosolic factor p47 of the N ADPH oxidase as detected by western blotting analysis. Superoxide prod uction by the peripheral blood neutrophils of these patients only slig htly increased with 1 alpha OHD3 treatment, and the amount of p47 was not affected by 1 alpha OHD3 administration, In order to evaluate the significance of the oxidase cytosolic factor in dictating oxidase acti vity, a reconstitution of NADPH oxidase was conducted by mixing macrop hage cytosols and membranes in a cell-free system, The addition of mac rophage cytosol from patients on high-dose treatment to macrophage mem branes from patients in all of the categories of treatment resulted in significantly higher (P<0.001) superoxide production as opposed to th e macrophage cytosol from nontreated patients. These results suggest t hat 1,25(OH)(2)D-3 causes an increase in NADPH oxidase activity in the peritoneal macrophages and monocytes of CAPD patients by inducing syn thesis and elevating the amount of the cytosolic factor p47. The incre ased killing of staphylococci by these cells is probably due to the el evation of superoxide generation, which is the major mechanism for the killing of invasive pathogens.