Ropinirole induces neuroprotection following reperfusion-promoted mitochondrial dysfunction after focal cerebral ischemia in Wistar rats

Abstract

Stroke is characterized by an initial ischemia followed by a reperfusion that promotes cascade of damage referred to as primary injury. The loss of mitochondrial function after ischemia, which is characterized by oxidative stress and activation of apoptotic factors is considered to play a crucial role in the proliferation of secondary injury and subsequent brain neuronal cell death. Dopamine D2 receptor agonist, Ropinirole, has been found to promote neuroprotection in Parkinson´s disease and restless leg syndrome. The current study was designed to test its efficacy in preclinical model of stroke. Previously it has been demonstrated that Ropinirole mediates its neuroprotection via mitochondrial pathways. Assuming this, we investigated the effect of Ropinirole on mitochondrial dysfunction, we have shown the positive effect of Ropinirole administration on behavioral deficits and mitochondrial health in an ischemic stroke injury model of transient middle cerebral artery occlusion (tMCAO). Male Wistar rats underwent transient middle cerebral artery occlusion and then received the Ropinirole (10 mg and 20 mg/kg b.w.) at 6 h, 12 and 18 h post occlusion. Behavioral assessment for functional deficits included grip strength, motor coordination and gait analysis. Our findings revealed a significant improvement with Ropinirole treatment in tMCAO animals. Staining of isolated brain slices from Ropinirole-treated rats with 2, 3,5-triphenyltetrazolium chloride (TTC) showed a reduction in the infarct area in comparison to the vehicle group, indicating the presence of an increased number of viable mitochondria. Ropinirole treatment was also able to attenuate mitochondrial reactive oxygen species (ROS) production, as well as block the mitochondrial permeability transition pore (mPTP), in the tMCAO injury model. In addition, it was also able to ameliorate the altered mitochondrial membrane potential and respiration ratio in the ischemic animals, thereby suggesting that Ropinirole has a positive effect on mitochondrial bioenergetics. Ropinirole inhibited the translocation of cytochrome c from mitochondria to cytosol reduces the downstream apoptotic processes. In conclusion, these results demonstrate that Ropinirole treatment is beneficial in preserving the mitochondrial functions that are altered in cerebral ischemic injury and thus can help in defining better therapies.