Association of vitamin D status and its molecular pathway with oxidative DNA damage and clinical manifestations in patients with systemic sclerosis

Systemic sclerosis (scleroderma) is a rare autoimmune disease characterized by the progressive fibrosis of the skin and internal organs. Increased oxidative macromolecule damage has been reported in scleroderma. Oxidative DNA damage is prominent due to its cytotoxic and mutagenic effects. Since vitamin D deficiency is a common problem in scleroderma, vitamin D replacement is an important contributor during treatment. Following the demonstration of vitamin D's antioxidant potential, the need to clarify the relationship between vitamin D and oxidative DNA damage in scleroderma has arisen. Hereby, oxidative DNA damage in scleroderma was comprehensively evaluated by measuring three stable damage products (8-OH-dG, S-cdA, R-cdA) by liquid chromatography-tandem mass spectrometry (LC-MS/MS); serum vitamin D levels were determined by ultra-performance liquid chromatography high-resolution mass spectrometry (UPLC-HRMS) and vitamin D receptor (VDR) gene expression and four polymorphisms in this gene (rs2228570, rs1544410, rs7975232, rs731236) were analyzed by RT-PCR and compared with healthy individuals. In the prospective part, post-replacement DNA damage and VDR expression of the patients receiving vitamin D were re-evaluated. All DNA damage products were increased in scleroderma compared to healthy individuals; vitamin D and VDR expression were found to be low (p<0.05). All DNA damage products showed a trend towards reduction following the replacement. The decrease in 8-OH-dG, as a gold marker of DNA damage, and increment in VDR expression reached statistical significance (p<0.05). The effectiveness of vitamin D in scleroderma patients with organ involvement has been demonstrated by attenuated 8- OH-dG after replacement in patients with lung, joint, and gastrointestinal system involvement. This is the first study to comprehensively examine DNA damage in scleroderma and evaluate the effects of vitamin D on DNA damage by a clinical prospective design.