Abstract 17443: Inhibition of the Calcineurin Interaction Site on TRPV1 Reduces Myocardial Infarct Size in Rats

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Introduction: With recent public concerns of opioid overuse, misuse and addiction along with the heightened FDA restrictions on opioid prescribing, non-opioid cardiac-safe pain therapeutics for those with cardiovascular disease is needed. The transient receptor potential vanilloid 1 (TRPV1), a mediator of heat, pain and noxious stimuli, mediates nociception. While blocking TRPV1 reduces pain, the finding preconditioning-induced cardioprotection is lost in TRPV1 knockout mice or by TRPV1 inhibition indicates a dual role for TRPV1 both in protection from cardiac injury and in pain signaling. Hypothesis: We tested whether a peptide corresponding to a calcineurin interaction site on TRPV1 could separate the functions of TRPV1 by reducing myocardial injury while providing pain control. Methods: The peptide was synthesized using a Liberty peptide synthesizer and conjugated to TAT for intracellular entry. Male Sprague-Dawley rats 8 weeks of age were used for both isolated heart and in vivo studies consisting of 30 minutes of ischemia followed by reperfusion. Infarct size was assessed by triphenyltetrazolium staining. Results: Testing the peptide using a calcineurin activity assay kit in vitro showed the peptide inhibited calcineurin activity vs. TAT control (0.46±0.03* vs. 0.77±0.02, nmol phosphate, n=3/group, *P<0.05). Further, peptide treatment of isolated hearts (1μM, infused over 10 minutes prior to ischemia) reduced infarct size and creatine phosphokinase (CPK) release when compared to TAT-treated hearts (Infarct size: 19±3%* vs. 53±4%, %infarct/left ventricle; CPK: 69±22* vs. 459±132, n=6/group, *P<0.01). In an in vivo myocardial ischemia-reperfusion model, the peptide (1mg/kg), given subcutaneously to the abdominal skin prior to ischemia, reduced infarct size compared to control (50±2*% vs. 66±1%, *P<0.001). Initial evidence also suggests that the peptide provides analgesia in pain models. Conclusions: Our results suggest a peptide blocking the calcineurin interaction site of TRPV1 reduces myocardial infarct size. Therefore, disrupting specific protein-protein interactions between calcineurin and TRPV1 may provide a novel strategy to design non-opioid therapeutics for cardioprotection, while also providing pain relief.