Abstract P290: RhoA Protects Against Myocardial Ischemia/Reperfusion Injury

2011 ◽  
Vol 109 (suppl_1) ◽  
Author(s):  
Sunny Y Xiang ◽  
Shigeki Miyamoto ◽  
Davy Vanhoutte ◽  
Jeffery D Molkentin ◽  
Gerald W Dorn ◽  
...  
Keyword(s):  
Infarct Size ◽  
Contractile Function ◽  
Ex Vivo ◽  
Myocardial Infarct ◽  
Ischemia Reperfusion ◽  
Small Gtpase ◽  
Myocardial Infarct Size ◽  
Rhoa Signaling

The small GTPase RhoA has established effects on cytoskeletal dynamics and gene expression but its role in regulating cardiac physiology and disease remains elusive. To characterize the in vivo role of RhoA signaling in cardiomyocytes, we generated conditional cardiac-specific RhoA transgenic mice (CA-RhoA) with 2–5 fold increases in RhoA activation in the adult heart. CA-RhoA mice show no overt cardiomyopathy but when challenged by in vivo or ex vivo I/R, these mice exhibit strikingly increased tolerance to injury. Compared to control mice, myocardial infarct size in CA-RhoA mice is reduced by 60–70% (20% vs. 50%, ex vivo; 10% vs. 37%, in vivo) and recovery of contractile function is significantly improved. Protein kinase D (PKD) is robustly activated in CA-RhoA hearts and inhibiting PKD reverses the cardioprotection afforded by RhoA. Both RhoA and PKD are also activated during I/R and blocking PKD augments I/R injury in WT mouse hearts. To further confirm that RhoA and PKD play a protective role during I/R, cardiac-specific RhoA knockout mice generated in the Molkentin laboratory were tested and demonstrated to show decreased tolerance to I/R injury, manifests as increased infarct size (42% vs. 23%) and lactate dehydrogenase release relative to control mice. This was accompanied by attenuated PKD activation during I/R. Taken together, our data indicates that RhoA signaling in adult cardiomyocytes promotes survival and reveals an unexpected role of PKD as a downstream mediator of RhoA and on cardioprotection against I/R.

Abstract 2894: Essential Role of ERK 1/2 in Sildenafil-Induced Early and Delayed Cardioprotection in Mice

Circulation ◽  
2008 ◽  
Vol 118 (suppl_18) ◽  
Author(s):  
Anindita das ◽  
Lei Xi ◽  
Fadi N Salloum ◽  
Yuan J Rao ◽  
Rakesh C Kukreja
Keyword(s):  
South Carolina ◽  
Infarct Size ◽  
Myocardial Infarct ◽  
Ischemia Reperfusion ◽  
Critical Role ◽  
Heart Association ◽  
Myocardial Infarct Size ◽  
Western Blots ◽  
Delayed Cardioprotection

Background: Sildenafil (SIL), a potent inhibitor of phosphodiesterase-5 induces powerful protection against myocardial ischemia-reperfusion (I-R) injury through activation of protein kinase G (PKG). However, the downstream targets of PKG in SIL-induced cardioprotection remain unclear. We hypothesized that PKG-dependent activation of survival kinase, ERK may play a critical role in SIL-induced cardioprotection in mice. Methods & Results: Ventricular myocytes were isolated from adult male ICR mice and exposed to 40 min of simulated ischemia (SI) with/without 1 hr pre-incubation of SIL (1 μM). Myocyte necrosis and apoptosis were determined after 1 hr or 18 hrs of reoxygenation (RO) using trypan blue or TUNEL assay, respectively. Pretreatment with SIL protected cardiomyocytes after SI-RO (necrosis 18.5±0.5% and apoptosis 6.6±0.7%; n=4, p<0.001) as compared with controls (necrosis 42.1±1.8% and apoptosis 23.3±0.9%). Co-incubation of PD98059 (20 μM), a selective ERK1/2 inhibitor blocked both anti-necrotic and anti-apoptotic protection in cardiomyocytes. Furthermore, intra-coronary infusion of SIL (1 μM) in Langendorff isolated mouse hearts 10 min prior to zero-flow global I (20 min) and R (30 min) significantly reduced myocardial infarct size (from 29.4±2.4% to 16.0±3.0%; p<0.05, n=6). Co-treatment of PD98059 abrogated SIL-induced protection (33.0±5.9; n=4). To evaluate the role of ERK1/2 in delayed cardioprotection, mice were treated with saline or SIL (0.7 mg/kg i.p.) 24 hours before global I-R in Langendorff mode. PD98059 (1 mg/kg) was administered (i.p.) 30 min before the treatment of SIL. Infarct size was reduced from 27.6±3.3% in saline-treated controls to 6.9±1.2% in SIL-treated mice (P<0.05, n=6). The delayed protective effect of SIL was also abolished by PD98059 (22.5±2.3%). Western Blots revealed that SIL significantly increased phosphorylation of ERK1/2 which was blocked by PKG inhibitor, KT5823 in the heart and adult myocytes. Selective knockdown of PKG in cardiomyocytes with short hairpin RNA of PKG also blocked the phosphorylation of ERK1/2. Conclusion: SIL-induced cardioprotection involves the activation and phosphorylation of ERK which appear to be intimately linked with a PKG-dependent survival pathway. This research has received full or partial funding support from the American Heart Association, AHA Mid-Atlantic Affiliate (Maryland, North Carolina, South Carolina, Virginia & Washington, DC).

Abstract 1568: Loss of Ischemic Postconditioning in the Mouse Hearts Lacking Adenosine A 1 or Bradykinin B 2 Receptors

Circulation ◽  
2007 ◽  
Vol 116 (suppl_16) ◽  
Author(s):  
Lei Xi ◽  
Anindita Das ◽  
Zhi-Qing Zhao ◽  
Vanessa F Merino ◽  
Michael Bader ◽  
...  
Keyword(s):  
Infarct Size ◽  
G Protein ◽  
Contractile Function ◽  
Gene Knockout ◽  
Myocardial Infarct ◽  
Membrane Receptors ◽  
Ischemic Postconditioning ◽  
Myocardial Infarct Size ◽  
G Protein Coupled

Background: Ischemic postconditioning (PostC) is a recently described cardioprotective modality against reperfusion injury, through a series of brief episodes of reperfusion/ischemia at the very onset of reperfusion. It has been well recognized that PostC can activate cellular signaling cascade, in which the role of G protein-coupled membrane receptors serving as upstream triggers of PostC remains to be established. Hence the goal of this study was to determine a definitive role of adenosine A 1 receptors (A1) and bradykinin B 1 or B 2 receptors (B1 or B2) in PostC, using gene knockout (KO) mice. Methods & Results: The hearts isolated from adult male C57BL/6J wild-type mice (C57-WT) or A1, B1, or B2 KO mice (n=7–9 per group) were subjected to 20 min of zero-flow global ischemia and 30 min of reperfusion with or without PostC in a Langendorff isolated, buffer-perfused heart model. PostC, consisted of 6 cycles of 10 sec of reperfusion and 10 sec of ischemia, significantly reduced myocardial infarct size (22.8±3.1%, Mean±SEM) as compared with C57-WT controls (35.1±2.8%, P<0.05). As shown in Figure below, the infarct-limiting protection of PostC was absent in A1-KO (34.9±2.7%) or B2-KO (33.3±1.7%) and was partially attenuated in B1-KO (25.6±2.9%) mice, as compared with the corresponding non-PostC controls under same genetic background (P>0.05). However, cardiac contractile function and coronary flow at the end of reperfusion were not significantly altered by PostC. Conclusion: PostC-induced infarct size reduction in globally ischemic mouse hearts is triggered by activation of multiple G protein-coupled membrane receptors, which include A1, B2, and, to a lesser extent, B1 receptors.

PAR-2 activation at the time of reperfusion salvages myocardium via an ERK1/2 pathway in in vivo rat hearts

2007 ◽  
Vol 293 (5) ◽  
pp. H2845-H2852 ◽  
Author(s):  
Rong Jiang ◽  
Amanda Zatta ◽  
Hajime Kin ◽  
Ningping Wang ◽  
James G. Reeves ◽  
...  
Keyword(s):  
Infarct Size ◽  
Kinase Inhibitor ◽  
Myocardial Infarct ◽  
Ischemia Reperfusion ◽  
Myocardial Infarct Size ◽  
Protective Effects ◽  
Rat Hearts ◽  
Sparing Effect ◽  
Myocardial Ischemia Reperfusion

Protease-activated receptor-2 (PAR-2) may have proinflammatory effects in some tissues and protective effects in other tissues. The role of PAR-2 in in vivo myocardial ischemia-reperfusion has not yet been determined. This study tested the hypothesis that PAR-2 activation with the PAR-2 agonist peptide SLIGRL (PAR-2 AP) reduces myocardial infarct size when given at reperfusion in vivo, and this cardioprotection involves the ERK1/2 pathway. Anesthetized rats were randomly assigned to the following groups with 30 min of regional ischemia and 3 h reperfusion: 1) control with saline; 2) vehicle (DMSO); 3) PAR-2 AP, 1 mg/kg given intravenously 5 min before reperfusion; 4) scrambled peptide (SP), 1 mg/kg; 5) the ERK1/2 inhibitor PD-98059 (PD), 0.3 mg/kg given 10 min before reperfusion; 6) the phosphatidylinositol 3-kinase inhibitor LY-294002 (LY), 0.3 mg/kg given 10 min before reperfusion; 7) PD + PAR-2 AP, 0.3 mg/kg PD given 5 min before PAR-2 AP; 8) LY + PAR-2 AP, 0.3 mg/kg LY given 5 min before PAR-2 AP; 9) chelerythrine (Chel) alone, 5 mg/kg given 10 min before reperfusion; and 10) Chel + PAR-2 AP, Chel was given 5 min before PAR-2 AP (10 min before reperfusion). Activation of ERK1/2, ERK5, Akt, and the downstream targets of ERK1/2 [P90 RSK and bcl-xl/bcl-2-associated death promoter (BAD)] was determined by Western blot analysis in separate experiments. PAR-2 AP significantly reduced infarct size compared with control (36 ± 2% vs. 53 ± 1%, P < 0.05), and SP had no effect on infarct size (53 ± 3%). PAR-2 AP significantly increased phosphorylation of ERK1/2, p90RSK, and BAD but not Akt or ERK5. Accordingly, the infarct-size sparing effect of PAR-2 AP was abolished by PD (PAR-2 AP, 36 ± 2% vs. PD + PAR-2 AP, 50 ± 1%; P < 0.05) and by Chel (Chel + PAR-2 AP, 58 ± 2%) but not by LY (PAR-2 AP, 36 ± 2% vs. LY + PAR-2 AP, 38 ± 3%; P > 0.05). Therefore, PAR-2 activation is cardioprotective in the in vivo rat heart ischemia-reperfusion model, and this protection involves the ERK1/2 pathway and PKC.

scholarly journals Loss of Protein Kinase Novel 1 (PKN1) is associated with mild systolic and diastolic contractile dysfunction, increased phospholamban Thr17 phosphorylation, and exacerbated ischaemia-reperfusion injury

2017 ◽  
Vol 114 (1) ◽  
pp. 138-157 ◽  
Author(s):  
Asvi A Francois ◽  
Kofo Obasanjo-Blackshire ◽  
James E Clark ◽  
Andrii Boguslavskyi ◽  
Mark R Holt ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Infarct Size ◽  
Cell Injury ◽  
Contractile Function ◽  
Myocardial Infarct ◽  
Neonatal Rat ◽  
Myocardial Infarct Size ◽  
Ischaemia Reperfusion ◽  
Sirna Knockdown

Abstract Aims PKN1 is a stress-responsive protein kinase acting downstream of small GTP-binding proteins of the Rho/Rac family. The aim was to determine its role in endogenous cardioprotection. Methods and results Hearts from PKN1 knockout (KO) or wild type (WT) littermate control mice were perfused in Langendorff mode and subjected to global ischaemia and reperfusion (I/R). Myocardial infarct size was doubled in PKN1 KO hearts compared to WT hearts. PKN1 was basally phosphorylated on the activation loop Thr778 PDK1 target site which was unchanged during I/R. However, phosphorylation of p42/p44-MAPK was decreased in KO hearts at baseline and during I/R. In cultured neonatal rat ventricular cardiomyocytes (NRVM) and NRVM transduced with kinase dead (KD) PKN1 K644R mutant subjected to simulated ischaemia/reperfusion (sI/R), PhosTag® gel analysis showed net dephosphorylation of PKN1 during sI and early R despite Thr778 phosphorylation. siRNA knockdown of PKN1 in NRVM significantly decreased cell survival and increased cell injury by sI/R which was reversed by WT- or KD-PKN1 expression. Confocal immunofluorescence analysis of PKN1 in NRVM showed increased localization to the sarcoplasmic reticulum (SR) during sI. GC-MS/MS and immunoblot analysis of PKN1 immunoprecipitates following sI/R confirmed interaction with CamKIIδ. Co-translocation of PKN1 and CamKIIδ to the SR/membrane fraction during sI correlated with phospholamban (PLB) Thr17 phosphorylation. siRNA knockdown of PKN1 in NRVM resulted in increased basal CamKIIδ activation and increased PLB Thr17 phosphorylation only during sI. In vivo PLB Thr17 phosphorylation, Sarco-Endoplasmic Reticulum Ca2+ ATPase (SERCA2) expression and Junctophilin-2 (Jph2) expression were also basally increased in PKN1 KO hearts. Furthermore, in vivo P-V loop analysis of the beat-to-beat relationship between rate of LV pressure development or relaxation and end diastolic P (EDP) showed mild but significant systolic and diastolic dysfunction with preserved ejection fraction in PKN1 KO hearts. Conclusion Loss of PKN1 in vivo significantly reduces endogenous cardioprotection and increases myocardial infarct size following I/R injury. Cardioprotection by PKN1 is associated with reduced CamKIIδ-dependent PLB Thr17 phosphorylation at the SR and therefore may stabilize the coupling of SR Ca2+ handling and contractile function, independent of its kinase activity.

Coronary endothelial P-selectin in pathogenesis of myocardial ischemia-reperfusion injury

1998 ◽  
Vol 275 (5) ◽  
pp. H1865-H1872 ◽  
Author(s):  
Anthony J. Palazzo ◽  
Steven P. Jones ◽  
Donald C. Anderson ◽  
D. Neil Granger ◽  
David J. Lefer
Keyword(s):  
Myocardial Ischemia ◽  
Infarct Size ◽  
Ischemia Reperfusion Injury ◽  
Myocardial Infarct ◽  
Ischemia Reperfusion ◽  
Myocardial Infarct Size ◽  
Wild Type ◽  
Area At Risk ◽  
Myocardial Ischemia Reperfusion

We investigated in vivo coronary P-selectin expression and its pathophysiological consequences in a murine model of myocardial ischemia-reperfusion (MI/R) using wild-type and P-selectin deficient (−/−) mice. Coronary P-selectin expression [μg monoclonal antibody (MAb)/g tissue] was measured using a radiolabeled MAb method after 30 min of myocardial ischemia and 20 min of reperfusion. P-selectin expression in wild-type mice was significantly ( P< 0.01) elevated in the ischemic zone (0.070 ± 0.010) compared with the nonischemic zone (0.037 ± 0.008). Myocardial P-selectin expression was nearly undetectable in P-selectin −/− mice after MI/R. Furthermore, myocardial infarct size (% of area at risk) after 30 min of myocardial ischemia and 120 min of reperfusion was 42.5 ± 4.4 in wild-type mice and 24.4 ± 4.0 in P-selectin −/− mice ( P < 0.05). In additional experiments of prolonged myocardial ischemia (60 min) and reperfusion (120 min), myocardial infarct size was similar in P-selectin −/− mice and wild-type mice. Our results clearly demonstrate the involvement of coronary P-selectin in the development of myocardial infarction after MI/R.

Abstract 411: Endogenous miRNA Induced By Ischemic Preconditioning Reduces Myocardial Infarct Size following Ischemia/Reperfusion In Mice

Circulation ◽  
2007 ◽  
Vol 116 (suppl_16) ◽  
Author(s):  
Chang Yin ◽  
Fadi N Salloum ◽  
Rakesh C Kukreja
Keyword(s):  
Infarct Size ◽  
Ischemic Preconditioning ◽  
Myocardial Infarct ◽  
Ischemia Reperfusion ◽  
Protective Role ◽  
Coronary Artery Ligation ◽  
Myocardial Infarct Size ◽  
Artery Ligation ◽  
Buffer Control

BACKGROUND: Due to its short length (~24 nt) and non-coding nature, microRNA (miRNA) used to be regarded as “evolutionary transcriptional debris”. Recent evidence suggests that miRNA is a novel regulator for transcription and translation. It is known that brief episodes of ischemia during ischemic preconditioning (IPC) trigger complex genetic pro-survival program that results in modulation of several key proteins involved in protection against I/R injury. We hypothesized that miRNA synthesized during IPC is the potential mediator of such protection. METHODS / RESULTS : Hearts were isolated from 3 groups (n = 6/group) of adult ICR mice and subjected to the following treatments in Langendorff mode: 120 min of perfusion with Krebs-Henseleit buffer (control); 30 min global ischemia followed by 1 hr reperfusion (I/R); 2 cycles of 30 sec ischemia and 90 sec reperfusion followed by 30 min ischemia and 1 hr reperfusion (IPC). Infarct size (IS) was measured by triphenyl tetrazolium staining. IPC in the Langendorff model reduced IS from 29.7 ± 2.1% in the I/R hearts to 9.1 ± 1.8 % in the IPC group. This protection was associated with a significant induction of miRNA-1 (162 ± 13%), miRNA-21 (118 ± 6%), and miRNA-24 (46 ± 12%). To test its protective role, miRNA was extracted from 6 hearts following the IPC protocol; and then injected in vivo into the left ventricle wall in another group of 6 mice. Forty-eight hrs later, these mice were subjected to I/R injury in vivo by left coronary artery ligation for 30 min followed by reperfusion for 24 hr. In addition, a subset of mice was treated with miRNA inhibitors (methylated antisense miRNA) in conjunction with miRNA from IPC hearts. The results show that miRNA extracted from the IPC hearts reproduced a protective phenotype with significantly lower infarction (18.8 ± 2.5 %) in vivo as compared to saline-treated control (37.5 ± 2.2%). This protective effect was totally abolished by specific inhibitors of miRNA-1 and miRNA-21 (IS: 43.7 ± 2.1%). CONCLUSION : miRNA extracted from preconditioned hearts shows a protective role against I/R injury. The detection of miRNA in preconditioned hearts offers a novel strategy in cardioprotection. Further studies are needed to identify the gene targets by which miRNA generate protective phenotype.

Loss of Sema4D Signaling in Platelets Impairs the Formation and Stability of Arterial Thrombi In Vivo and Reduces Myocardial Infarct Size.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 3631-3631 ◽  
Author(s):  
Li Zhu ◽  
Timothy J. Stalker ◽  
Tao Wang ◽  
Hong Jiang ◽  
Atushi Kumanogoh ◽  
...  
Keyword(s):  
Infarct Size ◽  
Platelet Function ◽  
Ischemia Reperfusion Injury ◽  
Thrombus Formation ◽  
Infarct Volume ◽  
Myocardial Infarct ◽  
Ischemia Reperfusion ◽  
Myocardial Infarct Size ◽  
Cremaster Muscle

Abstract Contact-dependent signaling between platelets helps to promote thrombus growth and stability. One mechanism for contact-dependent signaling involves the binding of cell surface ligands to corresponding receptors on the surface of adjacent cells. In our efforts to identify novel participants in this process, we have recently reported that platelets express on their surface the semaphorin family member, sema4D, and its two known receptors, CD72 and plexin-B1 (Zhu, et al, PNAS, 2007). We have also shown that although their initial tail bleeding time is normal, platelets from sema4D(−/−) mice have a defect in collagen-induced signaling and platelet aggregation in vitro. In the present studies, we used matched sema4D(−/−) and wild type (WT) mice to examine the consequences of impaired sema4D signaling in models of platelet function in vivo. In the first model, irradiated Rose Bengal dye was used to produce an arteriolar injury in an exteriorized cremaster muscle. Platelets were identified with a fluorescent CD41 antibody and detected in real time using digital microscopy. The results showed that thrombus formation occurred in all of the mice that were tested, but while stable occlusion was observed in approximately half of the control mice, none of the sema4D(−/−) mice developed stable occlusions during the period of observation (p&lt;0.02). Similarly, when a laser was used to produce a focal injury in cremaster muscle arterioles, both the initial rate of platelet accumulation and the peak extent of accumulation were approximately 50% lower in the sema4D(−/−) mice than in the matched controls. To test the contribution of sema4D to platelet responses in a larger artery, the right common carotid was injured by transient exposure to FeCl3 and changes in flow were measured using a Doppler probe. The results showed that the time to occlusion was 35% greater in the sema4D(−/−) mice than in controls (p&lt;0.02). Furthermore, stable occlusion occurred in only 9 of 16 (56%) sema4D(−/−) mice Vs. 7 of 9 (78%) WT mice. Finally, myocardial infarct size was measured in an ischemia/reperfusion injury model 48 hrs after transient ligation of the left anterior descending coronary artery. Although infarction occurred in all cases, infarct volume was 56% smaller in the sema4D(−/−) mice than the matched controls (p&lt;0.01). In summary, these results show that there is a substantial impairment of platelet function in vivo in mice that lack sema4D. This impairment was observed in both arterioles and arteries using several different methods to evoke platelet activation. When combined with our earlier observations, the results show that signaling by sema4D and its receptors provides a novel mechanism to promote thrombus growth and stability.

Sustained exogenous administration of Met5-enkephalin protects against infarction in vivo

2003 ◽  
Vol 285 (6) ◽  
pp. H2463-H2470 ◽  
Author(s):  
Koh Kuzume ◽  
Roger A. Wolff ◽  
Kazuhiko Amakawa ◽  
Kazuyo Kuzume ◽  
Donna M. Van Winkle
Keyword(s):  
Infarct Size ◽  
Opioid Receptor ◽  
Myocardial Infarct ◽  
Ischemia Reperfusion ◽  
Opioid Peptide ◽  
Opioid Antagonist ◽  
Myocardial Infarct Size ◽  
Endogenous Opioid ◽  
Area At Risk

The opioid antagonist naloxone abolishes infarct limitation by myocardial ischemic preconditioning, suggesting that one or more endogenous opioid peptides can mediate cardiac protection against ischemic damage. We tested the hypothesis that the naturally occurring opioid peptide Met5-enkephalin (ME) modulates myocardial infarct size in vivo. Experiments were conducted in barbiturate-anesthetized open-chest rabbits subjected to regional myocardial ischemia-reperfusion. ME was administered via osmotic minipump for 24 h. Infarct size was assessed with tetrazolium and is expressed as a percentage of the area at risk. Exogenous ME reduced the amount of the risk zone infarcted by ∼60% compared with saline-treated controls. ME-induced protection was sensitive to opioid receptor blockade with naloxone [NAL 50 ± 2% vs. ME + NAL 39 ± 3%, P = not significant (NS)] and also to blockade of sarcolemmal and mitochondrial ATP-sensitive K+ (KATP) channels [5-hydroxydecanoate (5-HD) 33 ± 3% vs. ME + 5-HD 43 ± 8%, P = NS; and HMR-1098 60 ± 3% vs. ME + HMR-1098 54 ± 7%, P = NS]. We conclude that ME limits ischemic injury in vivo by an opioid receptor-mediated mechanism that involves both sarcolemmal and mitochondrial KATP channels.

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

Circulation ◽  
2014 ◽  
Vol 130 (suppl_2) ◽  
Author(s):  
Eric R Gross ◽  
Nir Qvit ◽  
Garrett J Gross ◽  
Daria Mochly-Rosen
Keyword(s):  
Infarct Size ◽  
Transient Receptor Potential ◽  
Myocardial Infarct ◽  
Ischemia Reperfusion ◽  
In Vivo Studies ◽  
Transient Receptor Potential Vanilloid ◽  
Myocardial Infarct Size ◽  
Interaction Site ◽  
Calcineurin Activity

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.

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