Puerarin provides a neuroprotection against transient cerebral ischemia by attenuating autophagy at the ischemic penumbra in neurons but not in astrocytes

Abstract

Puerarin is an isoflavone derived from the Chinese medical herb of Radix puerariae (kudzu root), and has been widely used in the treatment for ischemic stroke in China. However, its underlying pharmacological mechanisms are still not understood. This study was to investigate the efficacy of puerarin on autophagy in the ischemic penumbra after cerebral stroke. A model of cerebral stroke in Sprague-Dawley rats was prepared by middle cerebral artery occlusion (MCAO); rats were then randomly divided into 5 groups: MCAO+Pue group (rats were treated with puerarin), MCAO+Pue+Tat-Beclin-1 group (rats were administrated with both puerarin and autophagy inducer Tat-Beclin-1), MCAO+Tat-Beclin-1 group (rats were treated with Tat-Beclin-1), MCAO+saline group (rats were administrated with the same volume of physiological saline), and sham surgery group. The autophagy levels in infarct penumbra were evaluated by western blotting, real-time PCR and immunofluorescence 14days after the insult. Meanwhile, the neurological deficit score, brain water content and infarct volume were assessed. The results illustrated that the cerebral infarct volume, cerebral edema and neurological deficiency were significantly alleviated by puerarin treatment. Western blotting and the quantitative PCR revealed that the autophagy level in the penumbra was markedly reduced by puerarin administration. However, these effects of puerarin could be counteracted by Tat-Beclin-1. Additionally, double immunofluorescence showed that neuronal autophagy was markedly attenuated by puerarin treatment, whereas astrocytic autophagy was only mildly reduced. Our study suggests that puerarin could confer a neuroprotection against cerebral ischemia, and this biological function is associated with attenuating autophagy in neurons but not in astrocytes.