Phosphodiesterase 5 Inhibition Attenuates Cerebral Vasospasm and Improves Functional Recovery After Experimental Subarachnoid Hemorrhage

Abstract BACKGROUND Cerebral vasospasm is an independent predictor of poor outcome after subarachnoid hemorrhage (SAH). The nitric oxide–cyclic guanosine monophosphate (NO-cGMP) vasodilatory pathway is strongly implicated in its pathophysiology. Preliminary studies suggest that phosphodiesterase 5 (...

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Bibliographic Details
Published inNeurosurgery Vol. 70; no. 1; pp. 178 - 187
Main Authors Han, Byung Hee, Vellimana, Ananth Kesav, Zhou, Meng-Liang, Milner, Eric, Zipfel, Gregory Joseph
Format Journal Article
LanguageEnglish
Published Hagerstown, MD Oxford University Press 01.01.2012
Lippincott Williams & Wilkins
Wolters Kluwer Health, Inc
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Summary:Abstract BACKGROUND Cerebral vasospasm is an independent predictor of poor outcome after subarachnoid hemorrhage (SAH). The nitric oxide–cyclic guanosine monophosphate (NO-cGMP) vasodilatory pathway is strongly implicated in its pathophysiology. Preliminary studies suggest that phosphodiesterase 5 (PDE5), an enzyme that degrades cGMP, may play a role because the PDE5 inhibitor sildenafil was found to reduce vasospasm after SAH. However, several questions that are critical when considering translational studies remain unanswered. OBJECTIVE To elucidate the mechanism of action of sildenafil against vasospasm and to assess whether sildenafil attenuates SAH-induced neuronal cell death, improves functional outcome after SAH, or causes significant physiological side effects when administered at therapeutically relevant doses. METHODS SAH was induced via endovascular perforation in male C57BL6 mice. Beginning 2 hours later, mice received sildenafil citrate (0.7, 2 or 5 mg/kg orally twice daily) or vehicle. Neurological outcome was assessed daily. Vasospasm was determined on post-SAH day 3. Brain PDE5 expression and activity, cGMP content, neuronal cell death, arterial blood pressure, and intracranial pressure were examined. RESULTS We found that PDE5 activity (but not expression) is increased after SAH, leading to decreased cGMP levels. Sildenafil attenuates this increase in PDE5 activity and restores cGMP levels after SAH. Post-SAH initiation of sildenafil was found to decrease vasospasm and neuronal cell death and markedly improve neurological outcome without causing significant physiological side effects. CONCLUSION Sildenafil, a US Food and Drug Administration–approved drug with a proven track record of safety in humans, is a promising new therapy for vasospasm and neurological deficits after SAH.
ISSN:0148-396X
1524-4040
DOI:10.1227/NEU.0b013e31822ec2b0