Bradykinin B1 Receptor Abolishes The Neuroprotective Effect Of Bradykinin B2 Receptor After Organophosphate-induced Toxicity

Organophosphates (OPs)are used as pesticides and also as chemical warfare nerve agents. The main mechanism of OP action is acetylcholinesterase inhibition. This inhibition directly or indirectly produces impairment of brain function and disruption of the blood brain barrier (BBB). The peptides of kallikrein-kinin system bradykinin (BK) and des-Arg⁹-bradykinin through its respectively receptors B2 bradykinin receptor (B2BKR) and B1 bradykinin receptor (B1BKR) play different roles in neuron survival and can increase BBB permeation. However, the role of these receptors has never been tested in OPs poisoning events. Therefore, the aims of this study were to investigate the effects of B1BKR and B2BKR activation on the neurotoxicity caused by Diisopropylfluorophosphate (DFP), and characterize one BBB model using immortalized human brain micro vascular endothelial cells. Our results have shown that after exposure of 200µM DFP for 10 min, the functional neuron outcome measured as population spikes decreased to values below 40% and  BK at 1µM superfused 30 min after DFP induced-toxicity triggered a neuroprotective cascade via B2BKR. However this neuroprotection was abolished by 1µM of the B1BKR agonist Lys-des-Arg⁹-BK (LDBK). MEK/MAPK was involved on B1BKR exerted effects since the MEK inhibition abolished the deleterious effect of LDBK. Experiments using the HBMVEC have shown B2BKR expression, acetylcholinesterase activity and no change in cell viability using DFP concentrations reaching 400 µM. These results demonstrated a neuroprotective role of B2BKR and deleterious actions of B1BKR in neurons after DFP injury, besides HBMVEC could be used to study the effects of these receptors in our BBB model.