Abstracts

Rationale: Early poststroke seizures (EPS) occur in 5-10% of stroke patients, more commonly after intracerebral hemorrhage than infarction. EPS are thought to result from cellular biochemical dysfunction leading to electrically irritable tissue. The molecular mechanisms of EPS remain obscure. Pleiotropic effects of nitric oxide proved to be important in stroke. We hypothesized that disorders of brain nitrergic system may play a role in the development of EPS. Methods: In 48 patients with the first-ever stroke (hemorrhagic/ ischemic: 22/26, in each group 50% with EPS) and 10 age-and gender matched controls we studied CSF levels of nitric oxide metabolites, nitrates, and nitrites (NOx), nitric oxide synthase (NOS) activity, products of nitrosative stress, immunoglobulins, and autoantibodies to nitrated proteins in the CSF of patients during the first day after stroke onset. NOS activity was assayed by conversion of radiolabeled arginine to citrulline, NOx levels - using a fluorescent probe diaminonaphtalene. The activity of lactate dehydrogenase (LDH) was assayed by a fluorometric method. Binding of nitrotyrosine-BSA with liquor proteins was assayed by ELISA with the use of a monoclonal antinitrotyrosine antibody.Results: There was a significant increase of NOx level in CSF of ischemic stroke (IS) patients without EPS (5,5 0,64 vs. 2,2 0,43 mol/l in controls, P<0.01). This phenomenon is believed to reflect compensatory activation of endothelial NOS (eNOS) in cerebral vessels to ensure vasodilatation. Since patients with EPS did not demonstrate NOx increase (2,6 0,40 mol/l,), we hypothesized that an eNOS defect can underlie EPS after ischemic event. Hemorrhagic stroke (HS) patients with and without EPS demonstrated NOx levels similar to the controls. However, the activity of NOS, virtually absent in the control group, was significant in CSF of patients with HS (p<0.001 vs controls, p< 0.05 in patients with EPS vs without EPS). As release of LDH into the CSF after HS was also significantly higher as compared to controls and correlated with NOS activity (r=0.72, p<0.05) we suggested that NOS is released into CSF from damaged brain cells or cells penetrating damaged blood-brain barrier. In the CSF of stroke patients, the content of immunoglobulins (Ig) of G, M, and A classes was significantly elevated. This increase was more pronounced in patients with HS. Binding to nitrotyrosine-BSA was increased in IS and was substantially higher in HS. Structural modifications of proteins induced by nitrosative stress stimulate the immune response, which develops in the CSF at the early stage of stroke. Conclusions: The mechanisms of EPS are different in IS and HS. Early seizures in IS are related to the impaired ability to urgently increase eNOS activity in response to an ischemic situation and to provide an effective vasodilatation. Mechanisms of EPS in HS are associated with the BBB damage. Nitrosative stress and stimulation of the immune response might contribute to both mechanisms and should be further investigated.