Could tear endothelin-1 levels be associated with disability in multiple sclerosis?

Background: Endothelin-1 (ET-1) is a potent vasoconstrictor substance mainly secreted by endothelial cells. Increased ET-1 levels in plasma or cerebrospinal fluid (CSF) have been identified in multiple sclerosis (MS). We aimed to analyze tear ET-1 levels; visual evoked potential (VEP) and disability scores in patients with MS and in healthy controls. Methods: Adult patients (18-65 year-old) diagnosed with MS according to the McDonald criteria, and healthy controls were recruited for the study. Demographic features, VEP, and tear ET-1 levels were evaluated. Disability in the MS group was assessed and grouped by EDSS score (<3 vs. ≥3). The EDSS score in healthy controls was zero. Results: Both in the total number of patients overall and in the patients with EDSS score <3, tear ET-1 levels were higher in the MS group than that in the controls (p<0.001). In the MS group, the ET-1 level was higher in the patients with EDSS score ≥3 than in those with EDSS score <3 (p<0.001). The tear ET-1 level was positively correlated with age and EDSS score in the MS group (p<0.001). Conclusion: To the best of our knowledge, there is no study in the literature that measures tear ET-1 levels in MS and examines their relationship with EDSS score and VEP. Higher tear ET-1 levels seem to be associated with disability and abnormal VEP in MS. Tear ET-1 measurement may be a simple new noninvasive marker indicating the disability in the patients with MS in the future.