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Background The active form of vitamin D, 1,25(OH) 2 D 3 , exerts important effects on proliferation and differentiation of many cell types, and immunoregulatory activities in particular on T cell-mediated immunity. Aim The aim of this study was to investigate whether KH 1060, a vitamin D analogue, could decrease tumor necrosis factor-alpha (TNF-α) levels in patients with inflammatory bowel disease (IBD). Methods PBMC proliferation was determined by [ 3 H]thymidine incorporation. TNF-α levels were measured by ELISA kit; VDR, Bcl-2 and Bax protein levels with Western blot analysis. Results KH 1060 inhibited PBMC proliferation and decreased TNF-α levels in IBD patients and this effect was synergistic with anti-TNF-α. VDR protein levels were significantly increased by PBMC treatment with KH 1060 or anti-TNF-α or their combination in ulcerative colitis (UC) patients, and decreased in Crohn's disease (CD) patients, treating the cells with KH 1060. In UC patients an increase in Bcl-2 and Bax levels was observed incubating, PBMC with KH 1060 or anti-TNF-α or their combination. In CD patients a slight decrease in Bcl-2 levels was registered when anti-TNF alone or in association with KH 1060 was used. Bax protein levels were slightly increased in the presence of KH 1060 alone or in combination with anti-TNF. Conclusion This study shows that KH 1060 acts as an immunomodulator on PBMC, acting as TNF-α inhibitor. This finding provides strong evidence that vitamin D status could be an important regulator of immunity IBD.

The aim of this study was to investigate whether the vitamin D analogue KH 1060 could exert a suppressive action on Tumor necrosis factor-alpha (TNF-alpha). The chimeric anti-TNF-alpha monoclonal antibody (anti-TNF), alone or in combination with KH 1060, was also used. KH 1060 (0.01, 0.1, 1 nM) significantly inhibited cell proliferation, determined after 5 days by [3H]thymidine incorporation, when peripheral blood mononuclear cells (PBMC), obtained from healthy subjects, were stimulated with phytohaemagglutinin (PHA) and incubated for 24 h in the absence and in the presence of lipopolysaccharide (LPS). In the same experimental conditions, anti-TNF exerted a significant inhibition on PBMC proliferation, at the lowest doses (0.001, 0.01 microg/ml) in the absence of LPS, and at 0.001, 1, 10 microg/ml in its presence. A synergistic inhibition was registered combining KH 1060 and anti-TNF, at well-defined concentrations. 0.1 nM KH 1060 produced a significant decrease in TNF-alpha levels, determined by ELISA, although less remarkable than in the presence of anti-TNF. This decrease was synergistic, associating 0.1 nM KH 1060 and 0.1 microg/ml anti-TNF. VDR protein levels were increased by 0.1 nM KH 1060, 0.1 microg/ml anti-TNF or their combination. The protein levels of two oncogenes, Bax and Bcl-2, remained unchanged, when PBMC were incubated with KH 1060, anti-TNF or their combination in the absence of LPS, while, in its presence, an increase was registered. The demonstrated anti-TNF-alpha effect of KH 1060 may suggest for this compound an immunosuppressive action and the possibility to synergistically act with other drugs.