Abstract Body: Background: Emerging evidence implicates post-stroke cognitive impairment as a major contributor to long-term disability. Therefore, optimal therapeutic targets reduce acute ischemic injury and enhance post-stroke brain function. Strong data demonstrates that TRPM2 channel activity increases post-stroke deficits. By reducing the expression level of TRPM2 within neurons cognitive deficits at the sub-acute stage can be mitigated. A potent TRPM2 antagonist tat-M2NX has shown to rescue LTP after a delayed administration.

Hypothesis: Knockout of neuron-specific TRPM2 channel expression enhances functional recovery following MCAO.

Methods: Transient MCAO (60 min) was performed on adult (8-10 week) male and female TRPM2 neuron-specific KO (TRPM2fl/fl, CaMKII Cre) and TRPM2 floxed controls (TRPM2fl/fl). Hemispheric infarct volume analyzed from MRI (T2) images 3 days post-injury by a blinded investigator. Additionally, an AAV9-CamKII-cre-GFP was administered 7 days post stroke in TRPM2 fl/fl mice as was the tat-M2NX was administered 29 days post injury via I.V. injection in WT mice. Extracellular field recordings of CA1 neurons were performed in acute hippocampal slices prepared both 7 and 30 days after recovery from MCAO to analyze synaptic plasticity (LTP).

Results: We observed that neuronal-specific TRPM2 channel knockout does not reduce acute ischemic injury (infarct volume) in male or female animals. Consistent with the hypothesis that neuronal TRPM2 channels contribute to ischemia-induced synaptic dysfunction, recordings obtained in brain slices from neuronal TRPM2 channel KO mice (TRPM2fl/fl-CaMKIICRE) mice 7 days after recovery from 60 min MCAo exhibited intact hippocampal plasticity compared to control TRPM2fl/fl mice not expressing CRE. Male sham control mice exhibit robust LTP of 163+10.4% (n=5) compared to 147+1.0% (n=8) in TRPM2fl/fl mice after MCAO at 7 days. Neuronal KO exhibited 191+12.1% (n=4). Similarly, female mice had LTP of 124+8.0 (n=3) in TRPM2fl/fl mice after MCAO whereas neuronal KO exhibited 208+6.8% (n=5, p<0.05 ANOVA compared to TRPM2fl/flMCAO). Delayed AAV9-cre administration rescued LTP from 119+4.3 (n=5) to 176.9+9.4 (n=5). Delayed administration of tat-M2NX after MCAO rescued LTP 185+20.4% (n=5) compared to tat-SCR 118+5.4% (n=5).

Conclusion: Our data highlight that TRPM2 channels expressed in neurons contribute to both acute and subacute injury following transient ischemic stroke as well subacute functional recovery.