Vitamin D therapy modulates cytokine secretion in patients with renal failure

In studies in vitro calcitriol (1,25-dihydroxyvitamin D3) inhibits lymphocyte proliferation and modulates several monocyte functions, including the secretion of prostaglandins and monokines. However its effects on monokine production in vivo are not known. Therefore we studied the secretion of interleukin (IL)-1, IL-6 and tumor necrosis factor (TNF) by peripheral blood mononuclear cells (PBMC) from 7 patients on periodic hemodialysis, before and after oral treatment with calcitriol (0.5 microgram daily) for 1 month. Calcitriol therapy resulted in significant increases in the phorbol myristate acetate (PMA)-induced secretion of IL-1 and IL-6 (p = 0.04 and 0.03, respectively). This was a transient effect, observable by day 7 of therapy, but no longer evident by day 30. However, calcitriol induced a progressive reduction of TNF secretion (down to 53% of control values by day 30, p = 0.02). There were no correlations between the individual changes in calcium/PTH and cytokine release. These results show that doses of calcitriol within the therapeutic range induce marked changes in cytokine secretion by PBMC from uremic patients.