Nitric oxide involvement in the disability and active disease of multiple sclerosis: Systematic review and meta-analysis.

BACKGROUND: Multiple sclerosis (MS) is a chronic and immune-mediated disease of unknown etiology and leading to a physical and cognitive disability. Different studies suggest that nitrosative stress may play a pivotal role in the pathogenesis and disability in MS. Besides, reports evaluated NO and their metabolites, expressed by nitrite and nitrate (NOx) levels of MS patients compared with other pathologies, but did not evaluate disability and relapse/remission phases.

OBJECTIVE: Thus, this study aimed to conduct a systematic review and meta-analysis of NOx levels in MS patients in relapse/remission phases and its involvement in patient disability.

METHODS: The protocol was registered in PROSPERO (CRD42022327161). We used GRADE to estimate the articles' quality and evaluated the publication bias using Egger's and Begg's tests.

RESULTS: Here, through a search in the Pubmed, Scopus, and EMBASE databases, 5.276 studies were found, and after the selection process, 20 studies were included in this systematic review and meta-analysis. The studies included data from 1.474 MS patients and 1.717 healthy controls, 1.010 RRMS and 221 primary progressive MS (PPMS).

CONCLUSION: NOx levels are increased in relapsing-remitting MS (RRMS) patients in the relapse phase. Also, NOx levels were increased in MS patients with higher disability. However, further studies are still needed to control lifestyle habits, pain, and MS treatment effects in biased NOx levels.