Neurotoxic effects of exogenous tissue-type plasminogen activator on the normal brain

2005 Fiscal Year Final Research Report Summary

• Project/Area Number: 14571313
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Cerebral neurosurgery
• Research Institution: Yamaguchi University
• Principal Investigator: SUZUKI Michiyasu Yamaguchi University, Faculty of Medicine, Professor, 医学部, 教授 (80196873)
• Co-Investigator(Kenkyū-buntansha): FUJISAWA Hirosuke Yamaguchi University, Faculty of Medicine, Assistant Professor, 医学部, 講師 (50238565) ; FUJII Masami Yamaguchi University, Hospital, Associate Professor, 医学部附属病院, 助教授 (90181320) ; MAEKAWA Tsuyoshi Yamaguchi University, Faculty of Medicine, Professor, 医学部, 教授 (60034972)
• Project Period (FY): 2002 – 2005
• Keywords: tissue-type plasminogen activator / neurotoxicity / excitatory amino acid / nitric oxide / microdialysis / rat / blood-brain barrier / immunohistochemistry

Research Abstract

Thrombolytic therapy with intravenous and intra-arterial administration of tissue-type plasminogen activator (tPA) has been established for the treatment of acute ischemic stroke. tPA has also been suggested to have neurotoxic effects. The purpose of this study was to examine tPA-induced neurotoxicity after perfusion into the cortex via a microdialysis probe. Adult male Wistar rats were divided into three groups : (a)high-dose (30 μmol/l) tPA group ; (b)low-dose (15μ mol/l) tPA ; (c)control (physiological saline) group. The volume of the lesion was quantified histologically by image analysis of hematoxylin and eosin (HE)-stained sections. tPA-induced blood-brain barrier (BBB) disruption was evaluated by intravenous injection of Evans blue. Injury of the basal lamina was evaluated by immunohistochemistry using an anti-laminin antibody. Sequential changes in nitric oxide (NO) synthesis following tPA perfusion was also investigated. In the control group, no structural change was observed except for the probe tract. In both tPA groups, a pale lesion was produced around the probe, and microscopically, neurons showed necrotic changes. The volume of the lesions was significantly higher in the high-dose tPA group. Marked and extensive extravasation of Evans blue was observed in the rtPA-perfused animals. Laminin immunoreactivity of blood vessels in the tPA-induced lesions was lost. The level of NO end-products was increased markedly after tPA perfusion. These results provide evidence of direct neurotoxicity of tPA, and also suggest that tPA causes BBB disruption and injury of the basal lamina, thereby increasing edema formation.