Effect of Vitamin D on Peripheral Blood Mononuclear Cells from Patients with Psoriasis Vulgaris and Psoriatic Arthritis

BACKGROUND Psoriasis, a chronic skin disease with or without joint inflammation, has increased circulating proinflammatory cytokine levels. Vitamin D is involved in calcium homeostasis, bone formation, osteoclastogenesis and osteoclast activity, as well as regulation of immune response. We aimed to study osteoclast differentiation and cytokine secretion of peripheral blood mononuclear cells (PBMCs) from patients with psoriasis vulgaris and psoriatic arthritis, in response to 1,25(OH)2D3. METHODS Serum levels of bone turnover markers were measured by ELISA in patients with psoriasis vulgaris and psoriatic arthritis, and healthy controls. PBMCs were isolated and cultured with or without RANKL/M-CSF and 1,25(OH)2D3. Osteoclast differentiation and cytokine secretion were assessed. RESULTS Psoriatic arthritis patients had lower osteocalcin, as well as higher C-telopeptide of type I collagen and cathepsin K serum levels compared with psoriasis vulgaris patients and controls. RANKL/M-CSF-stimulated PBMCs from psoriatic arthritis patients produced higher proinflammatory cytokine levels and had a differential secretion profile in response to 1,25(OH)2D3, compared with psoriasis vulgaris and control PBMCs. CONCLUSIONS Our data confirmed altered bone turnover in psoriatic arthritis patients, and demonstrated increased osteoclastogenic potential and proinflammatory cytokine secretion capacity of these PBMCs compared with psoriasis vulgaris and controls. 1,25(OH)2D3 abrogated these effects.