Preventive Role of Vitamin D in Silica-Induced Skin Fibrosis: A Study in Relation to Oxidative Stress and Pro-Inflammatory Cytokines

The protective effects of vitamin D analogue calcipotriol in silica-induced skin fibrosis were studied in the present study. Male BALB / c mice were divided into four groups; Control, Vitamin D, Silica and Silica+Vitamin D. Silica was administered as a single intradermal injection (40 µg / µL, dissolved in normal saline; particle size 1 - 5 µm) in the hind limbs of animals in Silica & Silica+Vitamin D group. Vitamin D group animals received topical application of 100µL of vitamin D solution (10-7M in Ethanol) daily for 12 weeks. Silica+Vitamin D group animals received co-treatment of silica and vitamin D as described for other groups. After 12 weeks of treatment, dermal thickness and hydroxyproline content of treated sections were measured. The TNF-α and IL-6 levels were measured in serum of all treated animals. The silica-induced oxidative stress was measured in terms of lipid peroxidation in skin tissue. Antioxidant defence system was assessed in terms of levels of reduced glutathione, superoxide dismutase, catalase, glutathione peroxidase and glutathione reductase. A significant increase in the dermal thickness and hydroxyproline content was observed after silica treatment (931 ± 57.98 to 1804.61 ± 146.20 µm)(p < 0.05). Vitamin D co-treatment reduced dermal thickness and hydroxyproline content compared to Silica group (p < 0.05). Similarly a decrease in TNF-α and IL-6 levels were also observed after vitamin D treatment. A significant reduction in oxidative stress in terms of lipid peroxidation (4.92 ± 0.70 to 2.40 ± 0.31 nmol / mg protein). Therefore, present study suggested that vitamin D could be an effective agent against silica-induced skin fibrosis and oxidative stress.