Calpain inhibition improves collateral-dependent perfusion in a hypercholesterolemic swine model of chronic myocardial ischemia

Calpain inhibition decreases oxidative stress via mitochondrial regulation in a swine model of chronic myocardial ischemia

INTRODUCTION

Calpain overexpression is implicated in mitochondrial damage leading to tissue oxidative stress and myocardial ischemic injury. The aim of this study was to determine the effects of calpain inhibition (CI) on mitochondrial impairment and oxidative stress in a swine model of chronic myocardial ischemia and metabolic syndrome.

METHODS

Yorkshire swine were fed a high-fat diet for 4 weeks to induce metabolic syndrome then underwent placement of an ameroid constrictor to the left circumflex artery. Three weeks later, animals received: no drug (control, "CON"; n= 7); a low-dose calpain inhibitor (0.12 mg/kg; "LCI", n= 7); or high-dose calpain inhibitor (0.25 mg/kg; "HCI", n=7). Treatment continued for 5 weeks, followed by tissue harvest. Cardiac tissue was assayed for protein carbonyl content, as well as antioxidant and mitochondrial protein expression. Reactive oxygen species (ROS) and mitochondrial respiration was measured in H9c2 cells following exposure to normoxia or hypoxia (1%) for 24 h with or without CI.

RESULTS

In ischemic myocardial tissue, CI was associated with decreased total oxidative stress compared to control. CI was also associated with increased expression of mitochondrial proteins superoxide dismutase 1, SDHA, and pyruvate dehydrogenase compared to control. 100 nM of calpain inhibitor decreased ROS levels and respiration in both normoxic and hypoxic H9c2 cardiomyoblasts.

CONCLUSIONS

In the setting of metabolic syndrome, CI improves oxidative stress in chronically ischemic myocardial tissue. Decreased oxidative stress may be via modulation of mitochondrial proteins involved in free radical scavenging and production.

One Billion hiPSC-Cardiomyocytes: Upscaling Engineered Cardiac Tissues to Create High Cell Density Therapies for Clinical Translation in Heart Regeneration

Despite the overwhelming use of cellularized therapeutics in cardiac regenerative engineering, approaches to biomanufacture engineered cardiac tissues (ECTs) at clinical scale remain limited. This study aims to evaluate the impact of critical biomanufacturing decisions-namely cell dose, hydrogel composition, and size-on ECT formation and function-through the lens of clinical translation. ECTs were fabricated by mixing human induced pluripotent stem-cell-derived cardiomyocytes (hiPSC-CMs) and human cardiac fibroblasts into a collagen hydrogel to engineer meso-(3 × 9 mm), macro- (8 × 12 mm), and mega-ECTs (65 × 75 mm). Meso-ECTs exhibited a hiPSC-CM dose-dependent response in structure and mechanics, with high-density ECTs displaying reduced elastic modulus, collagen organization, prestrain development, and active stress generation. Scaling up, cell-dense macro-ECTs were able to follow point stimulation pacing without arrhythmogenesis. Finally, we successfully fabricated a mega-ECT at clinical scale containing 1 billion hiPSC-CMs for implantation in a swine model of chronic myocardial ischemia to demonstrate the technical feasibility of biomanufacturing, surgical implantation, and engraftment. Through this iterative process, we define the impact of manufacturing variables on ECT formation and function as well as identify challenges that must still be overcome to successfully accelerate ECT clinical translation.

Preclinical models of congestive heart failure, advantages, and limitations for application in clinical practice

Congestive heart failure (CHF) has increased over the years, in part because of recent progress in the management of chronic diseases, thus contributing to the maintenance of an increasingly aging population. CHF represents an unresolved health problem and therefore the establishment of animal models that recapitulates the complexity of CHF will become a critical element to be addressed, representing a serious challenge given the complexity of the pathogenesis of CHF itself, which is further compounded by methodological biases that depend on the animal species in use. Animal models of CHF have been developed in many different species, with different surgical procedures, all with promising results but, for the moment, unable to fully recapitulate the human disease. Large animal models often provide a more promising reality, with all the difficulties that their use entails, and which limit their performance to fewer laboratories, the costly of animal housing, animal handling, specialized facilities, skilled methodological training, and reproducibility as another important limiting factor when considering a valid animal model versus potentially better performing alternatives. In this review we will discuss the different animal models of CHF, their advantages and, above all, the limitations of each procedure with respect to effectiveness of results in terms of clinical application.

Efficacy of leupeptin in treating ischemia in a rat hind limb model

Prolonged tourniquet use can lead to tissue ischemia and can cause progressive muscle and nerve injuries. Such injuries are accompanied by calpain activation and subsequent Wallerian-like degeneration. Several known inhibitors, including leupeptin, are known to impede the activity of calpain and associated tissue damage. We hypothesize that employment of leupeptin in a rat model of prolonged hind limb ischemia can mitigate muscle and nerve injuries. Sprague-Dawley rats (n = 10) weighing between 300-400 g were employed in this study. Their left hind limbs were subjected to blood flow occlusion for a period of 2-h using a neonatal blood pressure cuff. Five rats were given twice weekly intramuscular leupeptin injections, while the other five received saline. After 2 weeks, the animals were euthanized, their sciatic nerves and gastrocnemius muscles were harvested, fixed, stained, and analyzed using NIH Image J software. The administration of leupeptin resulted in larger gastrocnemius muscle fiber cross-sectional areas for the right (non-tourniquet applied) hindlimb as compared to that treated with the saline (p = 0.0110). However, no statistically significant differences were found between these two groups for the injured left hindlimb (p = 0.1440). With regards to the sciatic nerve cross-sectional areas and sciatic functional index, no differences were detected between the leupeptin and control treated groups for both the healthy and injured hindlimbs. This research provides new insights on how to employ leupeptin to inhibit the degenerative effects of calpain and preserve tissues following ischemia resulting from orthopedic or plastic surgery procedures.

Calpain inhibition decreases myocardial fibrosis in chronically ischemic hypercholesterolemic swine

OBJECTIVES

Calpain activation during ischemia is known to play critical roles in myocardial remodeling. We hypothesize that calpain inhibition (CI) may serve to reverse and/or prevent fibrosis in chronically ischemic myocardium.

METHODS

Yorkshire swine were fed a high-cholesterol diet for 4 weeks followed by placement of an ameroid constrictor on the left circumflex artery to induce myocardial ischemia. 3 weeks later, animals received either: no drug; high-cholesterol control group (CON; n = 8); low-dose CI (0.12 mg/kg; LCI, n = 9); or high-dose CI (0.25 mg/kg; HCI, n = 8). The high-cholesterol diet and CI were continued for 5 weeks, after which myocardial tissue was harvested. Tissue samples were analyzed by western blot for changes in protein content.

RESULTS

In the setting of hypercholesterolemia and chronic myocardial ischemia, CI decreased the expression of collagen in ischemic and nonischemic myocardial tissue. This reduced collagen content was associated with a corresponding decrease in Jak/STAT/MCP-1 signaling pathway, suggesting a role for Jak 2 signaling in calpain activity. CI also decreases the expression of focal adhesion proteins (vinculin) and stabilizes the expression of cytoskeletal and structural proteins (N-cadherin, α-fodrin, desmin, vimentin, filamin, troponin-I). CI had no significant effect on metabolic and hemodynamic parameters.

CONCLUSIONS

Calpain inhibition may be a beneficial medical therapy to decrease collagen formation in patients with coronary artery disease and associated comorbidities.

Coronary microvascular adaptations distal to epicardial artery stenosis

Until recently, epicardial coronary stenosis has been considered the primary outcome of coronary heart disease, and clinical interventions have been dedicated primarily to the identification and removal of flow-limiting stenoses. However, a growing body of literature indicates that both epicardial stenosis and microvascular dysfunction contribute to damaging myocardial ischemia. In this review, we discuss the coexistence of macro- and microvascular disease, and how the structure and function of the distal microcirculation is impacted by the hemodynamic consequences of an epicardial, flow-limiting stenosis. Mechanisms of endothelial dysfunction as well as alterations of smooth muscle function in the coronary microcirculation distal to stenosis are discussed. Risk factors including diabetes, metabolic syndrome, and aging exacerbate microvascular dysfunction in the myocardium distal to a stenosis, and our current understanding of the role of these factors in limiting collateralization and angiogenesis of the ischemic myocardium is presented. Importantly, exercise training has been shown to promote collateral growth and improve microvascular function distal to stenosis; thus, the current literature reporting the mechanisms that underlie the beneficial effects of exercise training in the microcirculation distal to epicardial stenosis is reviewed. We also discuss recent studies of therapeutic interventions designed to improve microvascular function and stimulate angiogenesis in clinically relevant animal models of epicardial stenosis and microvascular disease. Finally, microvascular adaptation to removal of epicardial stenosis is considered.

Extracellular Vesicles Promote Arteriogenesis in Chronically Ischemic Myocardium in the Setting of Metabolic Syndrome

Background

Ischemic heart disease continues to be a leading cause of mortality in patients. Extracellular vesicles (EVs) provide a potential for treatment that may induce collateral vessel growth to increase myocardial perfusion.

Methods and Results

Nineteen male Yorkshire pigs were given a high‐fat diet for 4 weeks, then underwent placement of an ameroid constrictor on the left circumflex artery to induce chronic myocardial ischemia. Two weeks later, the pigs received either intramyocardial vehicle (n=6), EVs (high‐fat diet with myocardial EV injection [HVM]; n=8), or HVM and calpain inhibition (n=5). Five weeks later, myocardial function, perfusion, coronary vascular density, and cell signaling were examined. Perfusion in the collateral‐dependent myocardium was increased during rapid ventricular pacing in the HVM group in both nonischemic (P=0.04) and ischemic areas of the ventricle (P=0.05). Cardiac output and stroke volume were significantly improved in the HVM group compared with the control group during ventricular pacing (P=0.006). Increased arteriolar density was seen in the HVM group in both nonischemic and ischemic myocardium (P=0.003 for both). However, no significant changes in the capillary density were observed between the control, HVM, and HVM and calpain inhibition groups (P=0.07). The group that received EVs with oral calpain inhibition had neither increased vessel density (P>0.99) nor improvement in blood flow or cardiac function (P=0.48) when compared with the control group.

Conclusions

These findings suggest that EVs promote angiogenesis in areas of chronic myocardial ischemia and improve cardiac function under conditions of diet‐induced metabolic syndrome.

Increased coronary arteriolar contraction to serotonin in juvenile pigs with metabolic syndrome

Metabolic syndrome (MetS) is associated with alterations in coronary vascular smooth muscle and endothelial function. The current study examined the contractile response of the isolated coronary arterioles to serotonin in pigs with and without MetS and investigated the signaling pathways responsible for serotonin-induced vasomotor tone. The MetS pigs (8-weeks old) were fed with a hyper-caloric, fat/cholesterol diet and the control animals (lean) were fed with a regular diet for 12 weeks (n = 6/group). The coronary arterioles (90–180 μm in diameter) were dissected from the harvested pig myocardial tissues and the in vitro coronary arteriolar response to serotonin was measured in the presence of pharmacological inhibitors. The protein expressions of phospholipase A2 (PLA₂), TXA₂ synthase, and the thromboxane-prostanoid (TP) receptor in the pigs’ left ventricular tissue samples were measured using Western blotting. Serotonin (10⁻⁹–10⁻⁵ M) induced dose-dependent contractions of coronary-resistant arterioles in both non-MetS control (lean) and MetS pigs. This effect was more pronounced in the MetS vessels compared with those of non-MetS controls (lean, P < 0.05]. Serotonin-induced contraction of the MetS vessels was significantly inhibited in the presence of the selective PLA₂ inhibitor quinacrine (10⁻⁶ M), the COX inhibitor indomethacin (10⁻⁵ M), and the TP receptor antagonist SQ29548 (10⁻⁶ M), respectively (P < 0.05). MetS exhibited significant increases in tissue levels of TXA₂ synthase and TP receptors (P < 0.05 vs. lean), respectively. MetS is associated with increased contractile response of porcine coronary arterioles to serotonin, which is in part via upregulation/activation of PLA₂, COX, and subsequent TXA₂, suggesting that alteration of vasomotor function may occur at an early stage of MetS and juvenile obesity.

Enhanced coronary arteriolar contraction to vasopressin in patients with diabetes after cardiac surgery

OBJECTIVE

Cardioplegic arrest (CP) and cardiopulmonary bypass (CPB) are associated with vasomotor dysfunction of coronary arterioles in patients with diabetes (DM) undergoing cardiac surgery. We hypothesized that DM may up-regulate vasopressin receptor expression and alter the contractile response of coronary arterioles to vasopressin in the setting of CP/CPB.

METHODS

Right atrial tissue samples of patients with DM and without (ND) (n = 8 in each group) undergoing cardiac surgery were harvested before and after CP/CPB. The isolated coronary arterioles (80-150 μm) dissected from the harvested right atrial tissue samples were cannulated and pressurized (40 mm Hg) in a no-flow state. The changes in diameter were measured with video microscopy. The protein expression/localization of vasopressin 1A receptors (V1A) and vasopressin 1B receptors (V1B) in the atrial tissue were measured by immune-blotting and immunohistochemistry.

RESULTS

The pre-CP/CPB contractile responses of the coronary arterioles to vasopressin were significantly increased post-CP/CPB in both the ND and DM groups. This effect was more pronounced in the vessels from patients in the DM group than that of vessels from patients in the ND group (P < .05). Vasopressin-induced contractile response of the coronary arterioles was inhibited in the presence of the specific V1A antagonist SR 49059 (10-7 M) in both ND and DM vessels (P < .05). The post-CP/CPB protein levels of V1A were significantly increased compared with pre-CP/CPB values in both the ND and DM groups (P < .05), whereas this increase was greater in DM than that of ND (P < .05). Immunohistochemistry staining further indicates that V1B were mainly expressed in the myocardium but not in vascular smooth muscle.

CONCLUSIONS

CP/CPB and DM are both associated with up-regulation in V1 receptor expression/localization in human myocardium. Vasopressin may induce coronary arteriolar constriction via V1A. This alteration may lead to increased coronary arteriolar spasm in patients with DM undergoing CP/CPB and cardiac surgery.

Extracellular Vesicle Injection Improves Myocardial Function and Increases Angiogenesis in a Swine Model of Chronic Ischemia

BACKGROUND

Mesenchymal stem cell-derived extracellular vesicles (EVs) are believed to be cardioprotective in myocardial infarct. The objective of this study was to examine the effects of human mesenchymal cell-derived EV injection on cardiac function, myocardial blood flow, and vessel density in the setting of chronic myocardial ischemia.

METHODS AND RESULTS

Twenty-three Yorkshire swine underwent placement of an ameroid constrictor on their left circumflex artery. Two weeks later, the animals were split into 2 groups: the control group (CON; n=7) and the EV myocardial injection group (MVM; n=10). The MVM group underwent myocardial injection of 50 μg of EVs in 2 mL 0.9% saline into the ischemic myocardium. Five weeks later, the pigs underwent a harvest procedure, and the left ventricular myocardium was analyzed. Absolute blood flow and the ischemic/nonischemic myocardial perfusion ratio were increased in the ischemic myocardium in the MVM group compared with the CON group. Pigs in the MVM group had increased capillary and arteriolar density in the ischemic myocardial tissue compared with CON pigs. There was an increase in expression of the phospho-mitogen-activated protein kinase/mitogen-activated protein kinase ratio, the phospho-endothelial nitric oxide synthase/endothelial nitric oxide synthase ratio, and total protein kinase B in the MVM group compared with CON. There was an increase in cardiac output and stroke volume in the MVM group compared with CON.

CONCLUSIONS

In the setting of chronic myocardial ischemia, myocardial injection of human mesenchymal cell-derived EVs increases blood flow to ischemic myocardial tissue by induction of capillary and arteriolar growth via activation of the protein kinase B/endothelial nitric oxide synthase and mitogen-activated protein kinase signaling pathways resulting in increased cardiac output and stroke volume.

Mechanisms of I/R-Induced Endothelium-Dependent Vasodilator Dysfunction

Ischemia/reperfusion (I/R) induces leukocyte/endothelial cell adhesive interactions (LECA) in postcapillary venules and impaired endothelium-dependent, NO-mediated dilatory responses (EDD) in upstream arterioles. A large body of evidence has implicated reactive oxygen species, adherent leukocytes, and proteases in postischemic EDD dysfunction in conduit arteries. However, arterioles represent the major site for the regulation of vascular resistance but have received less attention with regard to the mechanisms underlying their reduced responsiveness to EDD stimuli in I/R. Even though leukocytes do not roll along, adhere to, or emigrate across arteriolar endothelium in postischemic intestine, recent work indicates that I/R-induced venular LECA is causally linked to EDD in arterioles. An emerging body of evidence suggests that I/R-induced EDD in arterioles occurs by a mechanism that is triggered by LECA in postcapillary venules and involves the formation of signals in the interstitium elicited by the proteolytic activity of emigrated leukocytes. This activity releases matricryptins from or exposes matricryptic sites in the extracellular matrix that interact with the integrin α_vβ₃ to induce mast cell chymase-dependent formation of angiotensin II (Ang II). Subsequent activation of NAD(P)H oxidase by Ang II leads to the formation of oxidants which inactivate NO and leads to eNOS uncoupling, resulting in arteriolar EDD dysfunction. This work establishes new links between LECA in postcapillary venules, signals generated in the interstitium by emigrated leukocytes, mast cell degranulation, and impaired EDD in upstream arterioles. These fundamentally important findings have enormous implications for our understanding of blood flow dysregulation in conditions characterized by I/R.

Novel molecular targets for coronary angiogenesis and ischemic heart disease

Coronary artery disease (CAD) is the number one cause of death among men and women in the USA. Genetic predisposition and environmental factors lead to the development of atherosclerotic plaques in the vessel walls of the coronary arteries, resulting in decreased myocardial perfusion. Treatment includes a combination of revascularization procedures and medical therapy. Because of the high surgical risk of many of the patients undergoing revascularization procedures, medical therapies to reduce ischemic disease are an area of active research. Small molecule, cytokine, endothelial progenitor cell, stem cell, gene, and mechanical therapies show promise in increasing the collateral growth of blood vessels, thereby reducing myocardial ischemia.

Diabetes and Cardioplegia

Cardiac surgery with cardiopulmonary bypass and cardioplegic arrest is associated with injury to the vasculature and microcirculation leading to coronary microvascular dysfunction, permeability changes and cardiac dysfunction. In the setting of cardiopulmonary bypass with cardioplegia, poorly-controlled diabetes is associated with significant changes in endothelium-dependent and independent vascular dysfunction, vascular reactivity, vascular permeability, protein expression, cell death, coronary/peripheral microcirculation and reduced vasomotor tone leading to hypotension and impaired endothelial function. The gene expression profiles after cardiopulmonary bypass with cardioplegic arrest is quantitatively and qualitatively different in patients with diabetes. Gene expression profiling capitalizing on the differences between patients with and without diabetes is a good place to identify potential medical targets.

Calpain inhibition decreases inflammatory protein expression in vessel walls in a model of chronic myocardial ischemia

BACKGROUND

Emerging data suggest a link between calpain activation and the enhanced inflammatory response of the cardiovascular system. We hypothesize that calpain activation associates with altered inflammatory protein expression in correlation with the proinflammatory profile of the myocardium. Our pig hypercholesterolemic model with chronic myocardial ischemia was treated with calpain inhibitors to establish their potential to improve cardiac function.

METHODS

Yorkshire swine, fed a high cholesterol diet for 4 weeks then underwent placement of an ameroid constrictor on the left circumflex artery. Two weeks later, animals received either no drug (high-cholesterol control group, n = 8), a low dose of calpain inhibitors (0.12 mg/kg, n = 9), or a high dose of calpain inhibitors (0.25 mg/kg; n = 8). The high-cholesterol diet and calpain inhibitors were continued for 5 weeks, after which the pig was euthanized. The left ventricular myocardial tissue (ischemic and nonischemic) was harvested and analyzed for inflammatory protein expression. Data were statistically analyzed via the Kruskal-Wallis and Dunn post hoc test.

RESULTS

Calpain inhibitor treatment coincides with increased expression of IKB-α and decreased expression of macrophages, NFkB, IL-1, and tumor necrosis factor (TNF)-α in the ischemic myocardial tissue as compared with the control group. An NFkB array revealed decreased expression of IRF5, JNK1/2, JNK2, CD18, NFkB p65, c-Rel, Sharpin, TNF R1, TNF R2, and DR5 in the ischemic myocardium of the group treated with a high dose of calpain inhibitors compared with the control.

CONCLUSION

Calpain activation in metabolic syndrome is a potential contributor to cardiac dysfunction in metabolic disorders with ischemic background. We suggest that calpain inhibition downregulates NFkB signaling in the vessel walls, which might be useful for improving myocardial blood flow in ischemic conditions.

Calpain inhibition modulates glycogen synthase kinase 3β pathways in ischemic myocardium: A proteomic and mechanistic analysis

BACKGROUND

Calpain inhibition has an enhancing effect on myocardial perfusion and improves myocardial density by inhibiting glycogen synthase kinase 3β (GSK-3β) and up-regulating downstream signaling pathways, including the insulin/PI3K and WNT/β-catenin pathways, in a pig model of chronic myocardial ischemia in the setting of metabolic syndrome.

METHODS

Pigs were fed a high-fat diet for 4 weeks, then underwent placement of an ameroid constrictor to the left circumflex artery. Three weeks later, the animals received no drug (high-cholesterol controls [HCC]), a high-dose calpain inhibitor (HCI), a low-dose calpain inhibitor (LCI), or a GSK-3β inhibitor (GSK-3βI). The diets and drug regimens were continued for 5 weeks and the myocardial tissue was harvested.

RESULTS

Calpain and GSK-3β inhibition caused an increase in myocardial perfusion ratios at rest and during pacing compared with controls. Pigs in the LCI and HCI groups had increased vessel density in the ischemic myocardium, and pigs in the GSK-3βI group had increased vessel density in the ischemic and nonischemic myocardium compared with the HCC group. Calpain inhibition modulates proteins involved in the insulin/PI3K and WNT/β-catenin pathways. Quantitative proteomics revealed that calpain and GSK-3β inhibition significantly modulated the expression of proteins enriched in cytoskeletal regulation, metabolism, respiration, and calcium-binding pathways.

CONCLUSIONS

In the setting of metabolic syndrome, calpain or GSK-3β inhibition increases vessel density in both ischemic and nonischemic myocardial tissue. Calpain inhibition may exert these effects through the inhibition of GSK-3β and up-regulation of downstream signaling pathways, including the insulin/PI3K and WNT/β-catenin pathways.

Glycogen Synthase Kinase 3β Inhibition Improves Myocardial Angiogenesis and Perfusion in a Swine Model of Metabolic Syndrome

BACKGROUND

Inhibition of glycogen synthase kinase 3β (GSK-3β) has been reported to be cardioprotective during stressful conditions.

METHODS AND RESULTS

Pigs were fed a high-fat diet for 4 weeks to develop metabolic syndrome, then underwent placement of an ameroid constrictor to their left circumflex artery to induce chronic myocardial ischemia. Two weeks later, animals received either: no drug (high cholesterol control group [HCC]) or a GSK-3β inhibitor (GSK-3β inhibited group [GSK-3βI]), which were continued for 5 weeks, followed by myocardial tissue harvest. Coronary blood flow and vessel density were significantly increased in the GSK-3βI group compared to the HCC group. Expression levels of the following proteins were greater in the GSK-3βI group compared to the HCC group: vascular endothelial growth factor receptor 1 , vascular endothelial cadherin, γ-catenin, β-catenin, protein kinase B, phosphorylated forkhead box O1, and superoxide dismutase 2.

CONCLUSIONS

In the setting of metabolic syndrome, inhibition of GSK-3β increases blood flow and vessel density in chronically ischemic myocardium. We identified several angiogenic, cell survival, and differentiation pathways that include β-catenin signaling and AKT/FOXO1, through which GSK-3β appears to improve vessel density and blood flow. These results may provide a potential mechanism for medical therapy of patients suffering from coronary artery disease and metabolic syndrome.

Role of Calpain in Pathogenesis of Human Disease Processes

Calpains are a 15-member class of calcium activated nonlysosomal neutral proteases which are involved in a broad range of cellular function. Calpains are usually localized to the cytosol and within mitochondria. Calpastatin is an endogenous protein that specifically binds to and inhibits calpain. Overactivation of calpain has been implicated in a number of disease processes of the brain, eyes, heart, lungs, pancreas, kidneys, vascular system and skeletal muscle. Therefore, calpain may serve as a potential therapeutic target for a wide variety of disease processes. This review briefly outlines the current literature regarding the involvement of calpain overactivation in the pathogenesis of almost every organ in the body.

Calpains and Coronary Vascular Disease

Despite many advances in percutaneous and surgical interventions in the treatment of coronary artery disease (CAD), up to one-third of patients are still either not candidates or receive suboptimal revascularization. Calpains are a class of calcium-activated non-lysosomal cysteine proteases that serve as a proteolytic unit for cellular homeostasis. Uncontrolled activation of calpain has been found to be involved in the pathogenesis of myocardial reperfusion injury, cardiac hypertrophy, myocardial stunning and cardiac ischemia. Inhibition of calpains has been shown to significantly attenuate myocardial stunning and reduced infarct size after ischemia-reperfusion. Calpain inhibition therefore serves as a potential medical therapy for patients suffering from a number of diseases, including CAD.