Oxidative DNA Damage and Repair Dynamics in Multiple Sclerosis: Insights from Comet Assay Kinetics, Base Excision Repair Gene Expression, and Genotype Analysis

Multiple sclerosis (MS) is a neuroinflammatory disease where oxidative stress and DNA damage may influence disease progression. We investigated whether defects in base excision repair (BER) pathways contribute to MS by combining functional DNA repair assays, gene expression profiling, and genotype analysis. We collected peripheral blood mononuclear cells from 70 MS patients and 61 healthy controls. These cells were subjected to tert-butyl hydroperoxide (TBH)-induced oxidative stress, and comet assay kinetics were measured over a period of 60 min. Additionally, we quantified the mRNA expression of nine key BER genes and genotyped selected polymorphisms related to DNA repair capacity. Samples from MS patients exhibited significantly higher levels of TBH-induced DNA lesions and displayed a distinct repair trajectory over time, as indicated by area-under-the-curve (AUC) analyses (<i>p</i> < 0.001). The transcripts of <i>MBD4</i> and <i>NTHL1</i> were notably reduced in MS patients compared to those in the controls (<i>p</i> < 0.0001). A logistic regression analysis revealed an association between the specific BER-related single nucleotide polymorphisms (SNPs) rs3087404, rs4135054, and rs1052133 and ineffective DNA repair. Subset analyses of B cells, CD4⁺ cells, and CD8⁺ cells further supported the presence of altered repair kinetics in MS, even though some subsets exhibited similar baseline lesion levels. Our findings suggest that impaired oxidative DNA repair is present in MS, likely driven by functional deficits in repair kinetics and alterations in the expression of BER genes and polymorphisms. This integrated approach highlights DNA repair pathways as potential therapeutic or prognostic targets in MS.