Plasma Cystine as a Marker of Acute Stroke Severity

<b>Background/Objectives</b>: The amino acid cysteine (Cys) plays an important role in the neuronal injury process in stroke. Cys is present in blood plasma in various forms. The relationship between Cys and its forms and the severity of acute stroke has not been sufficiently studied. We investigated the levels of total Cys and two of its forms (reduced Cys and its disulfide (cystine, CysS)) in blood plasma and their influence on stroke severity in patients at admission. <b>Methods</b>: A total of 210 patients (39-59 years old) with ischemic stroke and intracerebral or subarachnoid hemorrhage were examined. The contents of the different forms of Cys were determined in the first 10-72 h. Stroke severity was estimated using the National Institutes of Health Stroke Scale (NIHSS) and the modified Rankin Scale (mRs). <b>Results</b>: CysS levels < 54 μM were associated with severe (NIHSS > 13) neurological deficit (ischemic stroke: RR = 5.58 and <i>p</i> = 0.0021; hemorrhagic stroke: RR = 3.56 and <i>p</i> = 0.0003). Smoking and high levels of total Cys and other thiols (glutathione and homocysteine) appear to be factors determining this relationship. <b>Conclusions</b>: Low CysS levels may serve as a potential biomarker of acute stroke severity.