ConBr, A Lectin Purified from the Seeds of Canavalia brasiliensis, Protects Against Ischemia in Organotypic Culture of Rat Hippocampus: Potential Implication of Voltage-Gated Calcium Channels.

Abstract

Lectins are proteins that bind cellular glycans and can modulate various neuronal functions. We have evaluated the neuroprotective effect of ConBr, a lectin purified from the seeds of Canavalia brasiliensis in a model of rat organotypic hippocampal cultures (OHCs) exposed to oxygen and glucose deprivation (OGD). OGD for 15min followed by 24h re-oxygenation significantly increased cell death, caused mitochondrial depolarization and increased reactive oxygen species (ROS) in CA1 region of OHCs. ConBr (0.1μg/mL) added during the re-oxygenation period counteracted cell death, mitochondrial depolarization and overproduction of ROS induced by OGD. Moreover, ConBr restored the levels of Akt and ERK1 phosphorylation that were reduced by OGD. Modulation of intracellular Ca2+ by ConBr was evaluated in isolated hippocampal neurons loaded with the fluorescent calcium dye Fluo-4/AM. ConBr (0.1 and 1µg/mL) reduced by 25-30 % the Ca2+ increment induced by 70mM K+. A sub effective concentration of ConBr (0.01µg/mL) together with a sub effective concentration of the L-type calcium channel antagonist nifedipine (0.3µM) conferred a synergic neuroprotective effect in OHCs subjected to OGD. In conclusion, ConBr provides OHCs neuroprotection against OGD. The mechanism was not fully addressed but it may involve modulation of L-type voltage-gated Ca2+ channels by ConBr.