Quercetin attenuates neuronal cells damage in a middle cerebral artery occlusion animal model

Abstract

Cerebral ischemia is a neurological disorder with high mortality. Quercetin is a flavonoid compound that is abundant in vegetables and fruits. It exerts anti-inflammatory and anti-apoptotic effects. This study investigated the neuroprotective effects of quercetin in focal cerebral ischemia. Male Sprague-Dawley rats were subjected to middle cerebral artery occlusion (MCAO) to induce focal cerebral ischemia. Quercetin or vehicle was injected 30 min before the onset of ischemia. A neurological function test, brain edema measurement, and 2,3,5-triphenyltetrazolium chloride staining were performed to elucidate the neuroprotective effects of quercetin. Western blot analysis was performed to observe caspase-3 and poly ADP-ribose polymerase (PARP) protein expression. MCAO leads to severe neuronal deficits and increases brain edema and infarct volume. However, quercetin administration attenuated the MCAO-induced neuronal deficits and neuronal degeneration. We observed increases in caspase-3 and PARP protein levels in MCAO-operated animals injected with vehicle, whereas quercetin administration attenuated these increases in MCAO injury. This study reveals the neuroprotective effect of quercetin in an MCAO-induced animal model and demonstrates the regulation of caspase-3 and PARP expression by quercetin treatment. These results suggest that quercetin exerts a neuroprotective effect through preventing the MCAO-induced activation of apoptotic pathways affecting caspase-3 and PARP expression.

Keywords: PARP; caspase-3; neuroprotection; quercetin.

Fig. 1.

Neurobehavioral scores (A) and edema measurement (B) in vehicle + sham, quercetin + sham, vehicle + middle cerebral artery occlusion (MCAO), and quercetin + MCAO animals. Quercetin attenuated the neurological deficits and edema value induced by ischemic stroke. Data (n=4) are represented as the mean ± S.E.M. *P<0.01, **P<0.05 vs. vehicle + sham animals, #P<0.05 vs. vehicle + MCAO animals.

Fig. 2.

Representative photograph of TTC staining (A) and infarct volume (B) in vehicle + sham, quercetin + sham, vehicle + middle cerebral artery occlusion (MCAO), and quercetin + MCAO animals. The ischemic area remained white, while the intact area was stained red (A). Infarct volume was calculated by the ratio of the infarction area to the total section area (B). Quercetin attenuated the MCAO-induced infarct region. Data (n=4) are represented as the mean ± S.E.M. *P<0.01, **P<0.05 vs. vehicle + sham animals, #P<0.05 vs. vehicle + MCAO animals.

Fig. 3.

Representative photograph of Hematoxylin and Eosin staining in vehicle + sham, quercetin + sham, vehicle + middle cerebral artery occlusion (MCAO), and quercetin + MCAO animals. Arrows indicate shrunken and condensed nuclei and open arrows indicate swelled and vacuolated forms. Scale bar=100 µm.

Fig. 4.

Representative photos of Fluoro-Jade B and DAPI staining in the cerebral cortex of vehicle + sham, quercetin + sham, vehicle + middle cerebral artery occlusion (MCAO), and quercetin + MCAO animals. Many cells positive for Fluro-Jade B staining were observed in animals with MCAO injury, while quercetin decreased the number of Fluro-Jade B positive cells (A and B). Scale bar: 100 µm. Data (n=4) are shown as the mean ± S.E.M. *P<0.01, **P<0.05 vs. vehicle + sham animals, #P<0.05 vs. vehicle + MCAO animals.

Fig. 5.

Western blot analysis (A–C) of PARP and caspase-3 in the cerebral cortex of vehicle + sham, quercetin + sham, vehicle + middle cerebral artery occlusion (MCAO), and quercetin + MCAO animals. Densitometric analysis is represented as a ratio of PARP (B) and caspase-3 (C) staining intensity to actin intensity. Data (n=4) are shown as the mean ± S.E.M. *P<0.01, **P<0.05 vs. vehicle + sham animals, #P<0.05 vs. vehicle + MCAO animals.