Elevated superoxide generation in mononuclear phagocytes by treatment with 1 alpha hydroxyvitamin D3: changes in kinetics and in oxidase cytosolic factor p47.

The effect of 1 alpha-hydroxyvitamin D3 (1 alpha OHD3) treatment on the superoxide production of phagocytic cells in patients undergoing continuous ambulatory peritoneal dialysis (CAPD) was studied. A 3-day treatment of CAPD patients with 3 micrograms per day of 1 alpha OHD3 (high-dose treatment) significantly increased NADPH oxidase and killing activities in peritoneal macrophages and peripheral blood monocytes (P < 0.001) as compared with low-dose (0.25 microgram/day of 1 alpha OHD3) treatment or nontreatment. The high oxidase activity observed in macrophages and monocytes after the treatment with 1 alpha OHD3, correlated significantly to the increase in the amount of the cytosolic factor p47 of the NADPH oxidase as detected by western blotting analysis. Superoxide production by the peripheral blood neutrophils of these patients only slightly 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 activity, a reconstitution of NADPH oxidase was conducted by mixing macrophage cytosols and membranes in a cell-free system. The addition of macrophage cytosol from patients on high-dose treatment to macrophage membranes from patients in all of the categories of treatment resulted in significantly higher (P < 0.001) superoxide production as opposed to the macrophage cytosol from nontreated patients. These results suggest that 1,25(OH)2D3 causes an increase in NADPH oxidase activity in the peritoneal macrophages and monocytes of CAPD patients by inducing synthesis and elevating the amount of the cytosolic factor p47.(ABSTRACT TRUNCATED AT 250 WORDS)