CALCITRIOL MODULATES IN-VIVO AND IN-VITRO CYTOKINE PRODUCTION - A ROLE FOR INTRACELLULAR CALCIUM

Background Several immunomodulatory properties of calcitriol are curre ntly known, however, only little information is available regarding th e in vivo and in vitro effects of calcitriol on cytokine production in chronic renal failure. Methods. To study the in vitro effect of calci triol on lipopolysaccharide (LPS)-induced cytokine production, periphe ral blood mononuclear cells (PBMC, 2.5 ml/ml) from 12 chronic dialytic (KD), 15 undialyzed chronic renal failure (CRF) patients and 10 norma l subjects (N) were incubated at 37 degrees for 12 hours with 100 ng o f LPS (E. coil and P. maltofilia). Increasing doses of calcitriol from 10(-10) to 10(-9) M were added and cell associated TNF-alpha and IL-1 beta were determined by immunoreactive tests after three freeze-thaw cycles. The intradialytic TNF-alpha and IL-1 beta production were eval uated in vivo in 12 HD patients before and after three months of intra venous calcitriol treatment (6 mu g/week). Intracellular calcium [Ca+](i) was determined on PBMC with a cytofluorimetric assay using FLUO-3 AM as the indicator. Results. In vitro, TNF-alpha increased from 3.6 +/- 1.9 pg/cell to 1797 +/- 337 in N, from 4.5 +/- 1.7 to 1724 +/- 232 in CRF and from 3.4 +/- 2.3 to 1244 +/- 553 in HD after the LPS stimu lus. The production of TNF-alpha was inhibited by calcitriol in a dose -dependent manner [LPS + Vit.D-3, 100 ng, 2.9 +/- 2.1 in N, 3.7 +/- 1. 9 in CRF and 3.4 +- 1.7 in HD; LPS + Vit.D-3 50 ng, 263 +/- 296 (N), 6 .73 +/- 11(CRF), 38 +/- 28 (HD); LPS + Vit.D-3 25 ng = 873 +/- 583 (N) , 325 +/- 483 (CRF), 588 +/- 507 (KD); LPS + Vit.D-3 12.5 ng, 954 +/- 483 (N), 912 +/- 510 (CRF), 875 +/- 527 (HD)]. Comparable data were ob served on IL-1 beta production. In vivo, the intradialytic TNF-alpha i ncrease (from 8.5 +/- 2.3 to 19 +/- 5.6 pg/2.5 x 10(6) cell) during he modialysis was markedly reduced after calcitriol therapy (from 6.6 +/- 3.1 to 11 +/- 4.7). [Ca++](i) decreased from 105 +/- 25 to 72 +/- 18 nM (P < 0.05) and a positive correlation between cytokine levels and [ Ca++](i) was found (r = 0.79; P < 0.001). Conclusions. The in vitro in crease of cell-associated cytokine after LPS challenge was inhibited b y calcitriol in a dose-dependent manner. These data suggest a possible in vivo modulatory effect of calcitriol therapy on cytokine productio n in hemodialysis.