Cardiac arrest victims may experience transient brain hypoperfusion leading to delayed death of hippocampal CA1 neurons and cognitive impairment. We prevented this in adult rats by inhibiting the expression of transient receptor potential melastatin 7 (TRPM7), a transient receptor potential channel that is essential for embryonic development, is necessary for cell survival and trace ion homeostasis in vitro, and whose global deletion in mice is lethal. TRPM7 was suppressed in CA1 neurons by intrahippocampal injections of viral vectors bearing shRNA specific for TRPM7. This had no ill effect on animal survival, neuronal and dendritic morphology, neuronal excitability, or synaptic plasticity, as exemplified by robust long-term potentiation (LTP). However, TRPM7 suppression made neurons resistant to ischemic death after brain ischemia and preserved neuronal morphology and function. Also, it prevented ischemia-induced deficits in LTP and preserved performance in fear-associated and spatial-navigational memory tasks. Thus, regional suppression of TRPM7 is feasible, well tolerated and inhibits delayed neuronal death in vivo.
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We thank M. Aarts and W. Czerwinski for technical information, J.C. Roder for advice on MWM testing, and A. Fleig, C. Montell, A. Scharenberg and E. Lo for a critical review of the manuscript. This work was supported by grants from the Canadian Institute of Health Research (MOP68939 and MOP89720 to M.T. and MOP15514 to J.F.M.), the US National Institutes of Health (NS048956 to M.T.), the Canadian Stroke Networks (M.T., J.F.M. and M.F.J.) and the Krembil Seed fund (M.T.). H.-S.S. is a recipient of Postdoctoral Fellowship Awards from the Heart and Stroke Foundation of Canada Focus on Stroke Training Initiative Program.
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Sun, HS., Jackson, M., Martin, L. et al. Suppression of hippocampal TRPM7 protein prevents delayed neuronal death in brain ischemia. Nat Neurosci 12, 1300–1307 (2009). https://doi.org/10.1038/nn.2395
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