ENOS uncoupling in the cerebellum after BBB disruption by exposure to Phoneutria nigriventer spider venom. (15th September 2015) - Soares, Edilene Siqueira
Abstract: Numerous studies have shown that the venom of Phoneutria nigriventer (PNV) armed-spider causes excitotoxic signals and blood–brain barrier breakdown (BBBb) in rats. Nitric oxide (NO) is a signaling molecule which has a role in endothelium homeostasis and vascular health. The present study investigated the relevance of endothelial NO synthase (eNOS) uncoupling to clinical neurotoxic evolution induced by PNV. eNOS immunoblotting of cerebellum lysates processed through low-temperature SDS-PAGE revealed significant increased monomerization of the enzyme at critical periods of severe envenoming (1–2 h), whereas eNOS dimerization reversal paralleled to amelioration of animals condition (5–72 h). Moreover, eNOS uncoupling was accompanied by increased expression in calcium-sensing calmodulin protein and calcium-binding calbindin-D28 protein in cerebellar neurons. It is known that greater eNOS monomers than dimers implies the inability of eNOS to produce NO leading to superoxide production and endothelial/vascular barrier dysfunction. We suggest that transient eNOS deactivation and disturbances in calcium handling reduce NO production and enhance production of free radicals thus contributing to endothelial dysfunction in the cerebellum of envenomed rats. In addition, eNOS uncoupling compromises the enzyme capacity to respond to shear stress contributing to perivascular edema and it is one of the mechanisms involved in the BBBb promoted by PNV. Highlights: Phoneutria nigriventer venom (PNV) affected eNOS monomer/dimer ratio. PNV induced eNOS uncoupling during periods of severe envenoming in the cerebellum of rats. eNOS recoupling progressed in parallel with periods of recovery from neurotoxic conditions in rats. PNV altered calmodulin, calbindin-D28 and eNOS expression. Transient PNV-induced eNOS uncoupling may contribute to endothelial dysfunction.