Critical role of large-conductance calcium- and voltage-activated potassium channels in leptin-induced neuroprotection of N-methyl-d-aspartate-exposed cortical neurons

Abstract

In the present study, the neuroprotective effects of the adipokine leptin, and the molecular mechanism involved, have been studied in rat and mice cortical neurons exposed to N-methyl-d-aspartate (NMDA) in vitro. In rat cortical neurons, leptin elicited neuroprotective effects against NMDA-induced cell death, which were concentration-dependent (10–100ng/ml) and largest when the adipokine was preincubated for 2h before the neurotoxic stimulus. In both rat and mouse cortical neurons, leptin-induced neuroprotection was fully antagonized by paxilline (Pax, 0.01–1μM) and iberiotoxin (Ibtx, 1–100nM), with EC50s of 38±10nM and 5±2nM for Pax and Ibtx, respectively, close to those reported for Pax- and Ibtx-induced Ca2+- and voltage-activated K+ channels (Slo1 BK channels) blockade; the BK channel opener NS1619 (1–30μM) induced a concentration-dependent protection against NMDA-induced excitotoxicity. Moreover, cortical neurons from mice lacking one or both alleles coding for Slo1 BK channel pore-forming subunits were insensitive to leptin-induced neuroprotection. Finally, leptin exposure dose-dependently (10–100ng/ml) increased intracellular Ca2+ levels in rat cortical neurons. In conclusion, our results suggest that Slo1 BK channel activation following increases in intracellular Ca2+ levels is a critical step for leptin-induced neuroprotection in NMDA-exposed cortical neurons in vitro, thus highlighting leptin-based intervention via BK channel activation as a potential strategy to counteract neurodegenerative diseases.