Research ReportOral l-Citrulline administration improves memory deficits following transient brain ischemia through cerebrovascular protection

•Oral citrulline administration inhibits cerebrovascular injury following brain ischemia.•The cerebrovascular protection by citrulline is associated with increased eNOS expression.•The cerebrovascular protection by citrulline elicits inhibition of neuronal death.•Oral citrulline administration finally improves memory deficits following brain ischemia.

l-citrulline (l-Cit) is known to increase nitric oxide (NO) production via the increase of l-arginine (l-Arg) concentration in the blood and improve endothelial dysfunction in cardiovascular diseases. However, little is known about the effects of l-Cit on cerebrovascular dysfunction. Here we showed that oral l-Cit administration prevents cerebrovascular injury following cerebral ischemia using a 20-min bilateral common carotid artery occlusion (BCCAO) mouse model. After BCCAO ischemia, mice were treated with l-Cit (50, 75, or 100 mg/kg p.o.) for 10 days once a day. l-Cit administration not only prevented neuronal cell death but also prevented capillary loss in the hippocampal region following brain ischemia. The cerebrovascular protective effect of l-Cit was associated with the restoration of endothelial nitric oxide synthase (eNOS) expression in the hippocampus. In addition, we devised a novel protocol to analyze NOx− (NO2− and NO3−) productions following l-Arg infusion using in vivo microdialysis and revealed that decreased l-Arg-induced NOx− levels were improved in the hippocampus of BCCAO mice following repeated l-Cit administration. Finally, memory deficits following brain ischemia were improved by oral administration of l-Cit. In summary, l-Cit is a potential therapeutic agent that protects cerebrovascular injury and in turn prevents neuronal cell death. Thereby, oral l-Cit administration improves cognitive deficits following brain ischemia.