VDAC activation inhibits hippocampal plasticity via NLRP3 inflammasome & caspase-1: modulation by allopregnanolone enantiomers

Voltage-dependent anion channels (VDACs) are the most abundant proteins in the outer mitochondrial membrane (OMM) and key regulators of mitochondrial function under physiological and pathological conditions. These channels are modulated by multiple agents and are known binding sites for neuroactive steroids (NAS) including allopregnanolone (AlloP). Using erastin, an agent that promotes VDAC activation by preventing inhibition by tubulin, we assessed the impact of VDAC activation on hippocampal function. Brief erastin administration had no effect on basal transmission but completely inhibited induction of long-term potentiation (LTP) in the Schaffer collateral pathway of rat hippocampal slices. This LTP inhibition was prevented by VBIT-4, an agent that inhibits VDAC oligomerization. VDAC-mediated LTP inhibition was also prevented by inhibitors of the NLRP3 inflammasome and caspase-1, downstream effectors of VDACs, but not by inhibition of cGAS-STING, narrowing the neuroinflammatory pathways involved. Similarly, effects of erastin were prevented by AlloP and at lower concentrations by its unnatural enantiomer ( ent -AlloP), an agent that unlike AlloP has little effect on GABA A receptors. Erastin also inhibited memory formation in a hippocampal-dependent form of one-trial learning and these effects were prevented by VBIT-4 and ent -AlloP, but not by a non-sedating dose of AlloP. These results have relevance for understanding the role of VDACs as mediators of neuronal stress and for the further development of NAS as neurotherapeutics and modulators of cellular stress.