Vitamin D Derivatives Induce Apoptosis and Downregulate ICAM-1 Levels in Peripheral Blood Mononuclear Cells of Inflammatory Bowel Disease Patients

Background: Lymphocytes are crucial in the pathogenesis of inflammatory bowel disease (IBD) and are an important target for drug development. Our aim was to verify whether 2 vitamin D derivatives, 1,25-dihydroxyvitamin D 3 [1,25(OH) 2 D 3 ] and EB 1089, could induce cell apoptosis and affect cell-cell interaction by regulating adhesion molecule levels. Methods: Peripheral blood mononuclear cell (PBMC) proliferation was studied by [ 3 H]thymidine incorporation and apoptosis was determined using an enzyme-linked immunosorbent assay (ELISA) kit. (Poly(ADP-ribose)polymerase (PARP) cleavage, caspase-3, and ICAM-1 protein levels were determined by Western blot analysis. Results: Our results indicate that 1,25(OH) 2 D 3 or EB 1089 or anti-TNF-a (infliximab) induce apoptosis in PBMC obtained from healthy subjects. In IBD patients apoptosis is induced by vitamin D derivatives and by anti-TNF-a only in CD patients. Caspase-3 activation and PARP cleavage are registered when PBMC were treated with vitamin D derivatives. ICAM-1 levels remarkably increase when PBMC was incubated with lipopolysaccharide (LPS) or TNF-a. The treatment with the vitamin D derivatives, alone or in combination with LPS or TNF-a, significantly decreases ICAM- 1 levels both in healthy subjects and IBD patients. In HUVEC cocultured with PBMC, previously incubated with LPS or TNF-a associated with 1,25(OH) 2 D 3 , ICAM-1 levels decrease both in healthy subjects and IBD patients. Conclusions: 1,25(OH) 2 D 3 and EB 1089 inhibit PBMC proliferation, induce apoptosis in PBMC of healthy subjects and IBD patients, and affect ICAM- 1 expression on PBMC and on HUVEC cocultured with PBMC, suggesting that the ICAM- 1 downregulation could provide a new target for controlling the recruitment of leukocytes at the sites of inflammation in IBD.