Inhibition of Cx43 mediates protective effects on hypoxic/reoxygenated human neuroblastoma cells

Olfactory Ensheathing Cells (OECs), a special population of glial cells, are able to synthesise several trophic factors exerting a neuroprotective action and promoting growth and functional recovery in both in vitro and in vivo models. In the present work, we investigated the neuroprotective effects of OEC Conditioned Medium (OEC-CM) on a human neuron-like cell line (SH-SY5Y neuroblastoma cell line), under normoxic and hypoxic conditions. In addition, we also focused our attention on the role of Connexins (Cxs) in the neuroprotective processes. Our results confirmed OEC-CM-mediated neuroprotection as shown by cell adherence, proliferation and cellular viability analyses. Reduced Connexin 43 (Cx43) levels in OEC-CM compared to unconditioned cells in hypoxic conditions prompted us to investigate the role of Cx43-Gap Junctions (GJs) and Cx43-hemichannels (HCs) in hypoxic-reoxygenation injury using carbenoxolone (non-selective GJ inhibitor), ioxynil octanoato (selective Cx43-GJ inhibitor) and Gap19 (selective Cx43-HC inhibitor). We found that Cx43-GJ and Cx43-HC inhibitors are able to protect SH-SY5Y and allow to these cultures to overcome the injury. Our findings support the hypothesis that both OEC-CM and the inhibition of Cx43-GJs and Cx43-HCs offer a neuroprotective effect by reducing Cx43-mediated cell-to-cell and cell-toextracellular environment communications.