Risperidone Enhances The Vulnerability To Stroke In Hypertensive Rats

Background-Stroke is the second most common cause of death and major cause of disability worldwide. Risperidone is an atypical antipsychotic drug. Clinical studies indicated that risperidone may increase the risk of stroke. While, the possible mechanisms were not explained and animal models were not copied successfully to this side-effect. The present work was designed to affirm whether risperidone could enhances the vulnerability to stroke in hypertensive rats and find out the possible mechanisms.Methods-Experiment 1: Effect of risperidone on brain ischemia after MCAO and on survival time of rats. Forty eight male SHR-SPs at the age of 20-22 weeks were divided randomly into 3 groups, and received risperidone of 0, 0.8 mg/kg, and 2.4 mg/kg respectively. One month later, their body weights were recorded, and their SBP was measured using tail-cuff plethysmography until they were all carried out MCAO. The percentage of infarct area in hemisphere was calculated. The activity of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and the levels of malondialdehyde (MDA) were determined. Cerebral ultramicroscopic structure morphology was observed using electron microscope before and after MCAO respectively. Thirty eight male WKYs at the age of 20-22 weeks carried out the same protocol as SHR-SPs above except for one group of 0.8 mg/kg. Twenty male SHRs at the age of 20-22 weeks received risperidone of 0 and 2.4 mg/kg respectively for 1 month only for body weights, SBP and infarct area analysis. Another forty five male SHR-SPs received risperidone as SHR-SPs above, only for life-long treatment. Rats were observed twice daily (at 8 AM and 6 PM) and the survival time (from birth to death) of every rat was recorded.Experiment 2: Effect of risperidone on proinflammatory cytokines and apoptosis in the cerebral cortex nerve cells. First, primary cultures of cortical microglias from WKYs were prepared. Expression of Interleukin-6 (IL-6) and tumor necrosis factor-a (TNF-a) was examined by ELISA kits in quiescent microglias and LPS-induced microglias of WKYs at the dosage of 0, 0.3, 1, 3, 30μM. Second, effect of risperidone on neurotoxic potential in normal cerebral cortex neurons from SHR-SPs and WKYs was examined by MTT at the dosages of 0, 30, 60, 90, 120, 150μM, and was further assessed by flow cytometry at the dosages of 0, 30, 60, 90 to affirm the doses, at which there was no significant neurotoxic potential. Third, effect of risperidone on already apoptotic neurons was examined by MTT in oxygen-glucose deprivation model and hydrogen peroxide model from WKYs and SHR-SPs, and was further assessed by flow cytometry and TUNEL in hydrogen peroxide model from WKYs, SHRs and SHR-SPs to test whether effect of risperidone on already apoptotic neurons is different with the increase of the blood pressure in three rat models. At last, the expression of Bax, Bcl-2 and caspase-8 was examined by western blot for 3 times independently in cerebral cortex neurons from SHR-SPs administrated with risperidone in a series of dosages of 0, 30, 60, 90μM.Results-1-month treatment of risperidone increased the infarct area induced by MCAO in SHR-SPs dose-dependently (from 14.8%±1.5% in control rats to 19.3%±2.7% and 21.3%±1.9% in rats receiving 0.8 and 2.4 mg/kg/d risperidone, respectively; p=0.0263 and p=0.0001 respectively). Similar findings were observed in SHRs but not in WKYs. Risperidone did not influence the body weight and SBP in SHR-SPs, SHRs and WKYs, the activity of SOD, GSH-Px and the level of MDA, measured in ischemic brain tissue after MCAO in SHR-SPs and WKYs, and the expression of IL-6 and TNF-a in quiescent microglias and in LPS-induced microglias of WKYs.Life-long treatment of risperidone decreased the survival time of SHR-SPs at a dose of 2.4 mg/kg/d (318±53 vs. 362±53 days in the control rats; P=0.0472, log rank test), but not at lower dose of 0.8 mg/kg/d (379±58 vs. 362±53 days in the control rats; P=0.3368, log rank test). Death was nearly all caused by stroke due to stroke symptom or brain morphology observationAt the dose of 30, 60, 90μM, risperidone did not have neurotoxic potential in normal cerebral cortex neurons in SHR-SPs and WKYs examined by MTT and in WKYs, SHRs and SHR-SPs examined by flow cytometry. Risperidone decreased the neuron absorbance dose-dependently examined by MTT from WKYs and SHR-SPs. Both in oxygen-glucose deprivation model and in hydrogen peroxide model, the absorbance decreased faster in SHR-SPs than in WKYs. Similar findings were observed by flow cytometry and by TUNEL in hydrogen peroxide model. The apoptosis rate increased dose-dependently and more faster in SHRs, most faster in SHR-SPs than in WKYs.Risperidone aggravated the damage of cerebral ultramicroscopic structure in WKYs and in SHR-SPs, especially in SHR-SPs. The similar results were found in the cerebral morphology after MCAO. In detail, Risperidone increased capillary endothelial vacuoles and edema around of capillary, made the mitochondrions distent, ridge lost and membrane ruptured, induced the chromatin accumulated and the lysosome formation.Risperisone increased the expression of Bax dose-dependently (from 1±0.15 in control group to 1.79±0.21, 2.30±0.30 and 2.89±0.35 in groups receiving 30, 60 and 90μM risperidone, respectively; p=0.0395, p=0.0063 and p=0.0012, respectively) No similar results were found in expression of Bcl-2 and caspase-8.Conclusions-risperidone can enhance the vulnerability to stroke in hypertensive rats by neuron apoptosis and endothelium injury. The neuron apoptosis is aggravated by mitochondria pathway through increased Bax, and the injury of brain microvessel endothelium make the lumen constricted and vessel wall vulnerable..