Roles Of Bradykinin B1 And B2 Receptors In Cerebral Ischemia/Reperfusion Injury In Experimental Diabetic Rats

Part ? Dynamic changes of B1R and B2R expression posterior to cerebral ischemia/reperfusion in non-diabetic and diabetic ratsObjective:To investigate the dynamic changes of B1R and B2R expression after cerebral ischemia/reperfusion in non-diabetic and diabetic rats.Methods:Type 2 diabetes rat model was induced by peritoneal injection of low dose streptozotocin combined with high glucose and fat diets, the left MCA ischemia/reperfusion model was established with suture method. RT-qPCR was used to detect the mRNA expressions of BIR and B2R at sham,3h,6h,12h,24h,72h, and 7d of reperfusion in brain tissues of non-diabetic and diabetic rats; western blot was used to observe the protein expressions of BIR and B2R at sham,12h,24h and 72h of reperfusion in brain tissues of non-diabetic and diabetic rats.Results:Both B1R and B2R mRNA were obviously upregulated after cerebral ischemia in non-diabetics and diabetics. Compared with non-doabetics, B1R mRNA expressions in diabetics during cerebral I/R elevated much earlier and faster and maintained at a higher level in a longer period of time while B2R mRNA had no significant difference within the first 12h of reperfusion but relatively decreased afterward. Western blot illustrated a similar trend in the protein expressions of B1R and B2R after cerebral ischemia except for a delayed peak time. Conclusion:Cerebral I/R in non-diabetics induced a more prominent B2R expression while diabetics exhibited more noticeable B1R upregulation after cerebral I/R.Part ? Effects of B1R and B2R in cerebral ischemia/reperfusion in diabetic ratsObjective:To explore the roles of B1R and B2R at acute phase after cerebral ischemia/reperfusion in diabetic rats.Methods:A total of 127 diabetic rats were randomly divided into four groups, including sham group, saline-treated group, B1R antagonist-treated group and B2R antagonist-treated group. All interventions were administrated via tail vein at the beginning of reperfusion and twenty-four hours after cerebral I/R, neurological deficiency was evaluated by neurological severity scores (NSS); infarct volume was observed by TTC staining; brain edema was detected by wet and dry weight; cell apoptosis and degeneration were determined by TUNEL and Fluoro-Jade C staining; the disrupture and associated protein expressions of blood-brain-barrier were analyzed by Evans blue extravasation and Western blot; microglial activation and expressions of inflammatory cytokines were compared by immuno-histochemistry and RT-qPCR.Results:Blockade of BIR (Lys-(des-Arg9-Leu8)-Bradykinin,300 nmol/kg) at the onset of reperfusion in DM rats not only reduced infarct volume, neurological severity scores, brain edema, cell apoptosis and neuron degeneration, but also attenuated blood-brain barrier (BBB) disruption and post-ischemic inflammation. On the contrary, B2R inhibitor (bradyzide,1 nmol/kg) deteriorated the brain damage and neurological deficits, meanwhile exacerbated the BBB penetrability and tissue inflammation.Conclusion:BIR and B2R exhibited detrimental and neuro-protective effects respectively after cerebral I/R in diabetic rats through regulating the BBB permeability and focal inflammatory response.