1. ¹Neuroprotection Research Laboratory, Departments of Neurology and Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts, USA
2. ²Stroke and Neurovascular Regulation Laboratory, Departments of Neurology and Neurosurgery, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts, USA
3. ³Cardiovascular Research Center, Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts, USA
4. ⁴Cardiovascular Division, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA

Correspondence: MA Moskowitz, Stroke and Neurovascular Regulation Laboratory, Departments of Neurology and Neurosurgery, MGH East 149-6403, Charlestown, MA 02129, USA. E-mail: moskowitz@helix.mgh.harvard.edu

Received 29 July 2004; Revised 12 November 2004; Accepted 24 November 2004; Published online 16 February 2005.

Abstract

Previous studies have shown that 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) protect the brain against ischemic injury by upregulating endothelial nitric oxide synthase (eNOS). Here, we tested the hypothesis that statins provide additional beneficial effects by also upregulating endogenous tissue plasminogen activator (tPA) and enhancing clot lysis in a mouse model of embolic focal ischemia. Heterologous blood clots (0.2 mm) were injected into the distal internal carotid artery to occlude blood flow in the middle cerebral artery territory after long-term (14 days) simvastatin, atorvastatin or vehicle treatment. Ischemic lesion volume, neurologic deficits, as well as residual blood clots were measured at 22 h. Reverse transcription-polymerase chain reaction assessed mRNA levels of eNOS, tPA, and the endogenous plasminogen activator inhibitor PAI-1. Ischemic lesion volumes and neurologic deficits were significantly reduced in wild-type mice by both simvastatin and atorvastatin. Statins increased eNOS and tPA mRNA levels but did not change mRNA levels of PAI-1. In eNOS knockout mice, atorvastatin reduced the volume of ischemic tissue and improved neurologic outcomes after arterial occlusion by blood clot emboli. In contrast, statins did not have protective effects in tPA knockout mice after embolic focal ischemia, but only in a filament model where focal ischemia was achieved via mechanical occlusion. These results suggest that statins protect against stroke by multiple mechanisms involving both eNOS and tPA. The involvement of each pathway may be revealed depending on the choice of experimental stroke model.