Modulation of Paraoxonase 1 Activity and Asymmetric Dimethylarginine by Immunomodulatory Therapies in Multiple Sclerosis.

Background: Neurodegeneration is present from the earliest stages of multiple sclerosis [MS], and oxidative stress together with mitochondrial dysfunction are key contributors to neuronal injury and disease progression. Objective: To investigate the role of the antioxidant enzyme paraoxonase 1 (PON1) and serum asymmetric dimethylarginine (ADMA) levels in MS across different disease subtypes and immunomodulatory treatments. Methods: Serum lipid levels and PON1 activity were measured and compared by disease subtype and treatment in a single-center MS cohort (N = 262; CIS = 10, RRMS = 208, PPMS = 19, SPMS = 25; 110 untreated, 152 treated) and in 91 healthy controls. ADMA levels were assessed in sera from 79 MS patients (19 untreated, 60 treated) and 31 age-matched controls. Results: Median serum paraoxonase (PON) and arylesterase (ARE) activity levels were 83.8 and 127.2 IU/L in MS patients versus 85.9 and 136.9 IU/L in controls, with no significant difference for PON (p = 0.191) but a significant reduction in ARE [p = 0.003]. PON activity differed significantly among disease subtypes (p = 0.023), with the highest levels in CIS. PON and ARE activity also varied across treatment groups (p = 0.038 and p = 0.034, respectively), with longitudinal analysis indicating a measurable effect of immunomodulatory therapy on PON activity at 10 years (p = 0.0136). Significant differences in enzyme activity were observed between untreated and interferon-treated patients (PON p = 0.0055, ARE p = 0.0001), with trends toward differences in ARE under natalizumab and fingolimod. ADMA levels were lower in MS patients than controls (p < 0.0001) and differed among treatment subgroups (natalizumab, dimethyl fumarate, glatiramer acetate, untreated RRMS). Conclusions: PON1 activity and ADMA levels differ between MS subgroups and under immunomodulatory treatments. Long-term therapy was associated with increased PON1 activity, while highly effective immunomodulators reduced ADMA levels. These changes may contribute to the treatment-related reduction in disease activity and attenuation of neurodegenerative processes in MS.