Background: In addition to its role in calcium homeostasis and bone mineralization, vitamin D is involved in immune defence, cardiovascular function, inflammation and angiogenesis, and these pleiotropic effects are of interested in the treatment of chronic kidney disease. Here we investigated the effects of paricalcitol, a nonhypercalcemic vitamin D analogue, on human peripheral blood mononuclear cell proliferation and signaling, and on angiogenesis. These effects were compared with those of a known inhibitor of angiogenesis pertaining to the vitamin D axis, the vitamin D-binding protein-derived Gc-macrophage activating factor (GcMAF).
Methods: Since the effects of vitamin D receptor agonists are associated with polymorphisms of the gene coding for the receptor, we measured the effects of both compounds on mononuclear cells harvested from subjects harboring different BsmI polymorphisms.
Results: Paricalcitol inhibited mononuclear cell viability with the bb genotype showing the highest effect. GcMAF, on the contrary, stimulated cell proliferation, with the bb genotype showing the highest stimulatory effect. Both compounds stimulated 3'-5'-cyclic adenosine monophosphate formation in mononuclear cells with the highest effect on the bb genotype. Paricalcitol and GcMAF inhibited the angiogenesis induced by proinflammatory prostaglandin E1.
Conclusions: Polymorphisms of the vitamin D receptor gene, known to be associated with the highest responses to vitamin D receptor agonists, are also associated with the highest responses to GcMAF. These results highlight the role of the vitamin D axis in chronic kidney disease, an axis which includes vitamin D, its receptor and vitamin D-binding protein-derived GcMAF.