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.