Impaired Oxidative DNA Lesions Repair Kinetics in Multiple Sclerosis: Combined Assessment of Functional Capacity, Gene Expression, and Genetic Variants in the Base Excision Repair Pathway
Beata Filipek1, Anna Macieja2, Aleksandra Binda3, Elzbieta Miller4, Mariola Swiderek-Matysiak1, Mariusz Stasiolek1, Ireneusz Majsterek3, Tomasz Poplawski2
1Norbert Barlicki Memorial Teaching Hospital No. 1 of the Medical University of Lodz, 2Department of Microbiology and Pharmaceutical Biochemistry, 3Department of Clinical Chemistry and Biochemistry, 4⁵ Department of Neurological Rehabilitation, Medical University of Lodz
Objective:
We sought to determine whether compromised base excision repair (BER) mechanisms contribute to MS development by simultaneously examining repair function, transcript abundance, and polymorphic variation.
Background:
Neuroinflammatory processes in MS generate reactive oxygen species that inflict substantial DNA damage. Cellular responses to oxidative damage depend heavily on BER, which removes modified bases and restores genomic integrity. Deficiencies in BER could permit the accumulation of mutagenic lesions, potentially accelerating neurodegeneration, yet functional impact of BER in MS remains poorly characterized.
Design/Methods:
We isolated PBMCs from 70 MS patients and 61 controls, challenged them with 7µM tert-butylhydroperoxide, and tracked DNA damage resolution over 60minutes using alkaline single-cell gel electrophoresis. Transcript levels for nine BER components (OGG1, MBD4, APEX1, APEX2, PARP1, PARP2, LIG3, NTHL1, MUTYH) were measured via real-time PCR with dual housekeeping normalization. For genotyping SNPs we used real-time PCR. To assess cell-specific responses, we purified B lymphocytes, CD4⁺helper cells, and CD8⁺cytotoxic cells and repeated kinetic measurements in each subset.
Results:
Following oxidative challenge, MS-derived cells displayed a substantially greater lesion burden than controls (p<0.001). Longitudinal analysis demonstrated that while control cells restored baseline integrity within 1 hour, MS cells exhibited persistent damage (group effect:F=41.61, p<0.0001; group×time:F=12.49, p<0.0001). At the transcriptional level, MBD4 and NTHL1 expression was reduced in MS (both p<0.0001). Regression modeling identified three SNPs conferring altered repair phenotypes:rs3087404(SMUG1), rs4135054(TDG), and rs1052133(OGG1) showed independent associations with MS after covariate adjustment. All three purified lymphocyte lineages exhibited abnormal repair trajectories in MS (B cells:F=3.93, p=0.006; CD4⁺:F=6.27, p<0.001; CD8⁺:F=5.73, p=0.0002), though initial damage levels were comparable in specific subsets.
Conclusions:
We present converging evidence that MS involves systemic BER dysfunction, showed by slower lesion resolution, diminished glycosylase expression, and risk-associated genetic architecture. Future investigations should establish whether restoring BER capacity can modify disease trajectory and whether genotype-directed interventions offer superior outcomes in carriers of high-risk alleles.
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