Preserved coronary endothelial function by inhibition of delta protein kinase C in a porcine acute myocardial infarction model.

BACKGROUND: Previous studies demonstrate impairment of endothelial-dependent vasodilation after ischemia/reperfusion (I/R). Though we have demonstrated that inhibition of delta protein kinase C (delta PKC) at reperfusion reduces myocyte damage and improves cardiac function in a porcine acute myocardial infarction (AMI) model, impact of the selective delta PKC inhibitor on epicardial coronary endothelial function remains unknown. METHODS: Either delta PKC inhibitor (delta V1-1, n=5) or saline (n=5) was infused into the left anterior descending artery at the last 1 min of the 30-min ischemia by balloon occlusion. In vivo responses to bradykinin (endothelium-dependent vasodilator) or nitroglycerin (endothelium-independent vasodilator) were analyzed at 24 h after I/R using intravascular ultrasound. Vascular responses were calculated as the ratio of vessel area at each time point (30, 60, 90 and 120 s after the infusion), divided by values at baseline (before the infusion). RESULTS: In control pigs, endothelial-dependent vasodilation following bradykinin infusion in infarct-related epicardial coronary artery was impaired, whereas in delta PKC inhibitor-treated pigs the endothelial-dependent vasodilation was preserved. Nitroglycerin infusion caused similar vasodilatory responses in the both groups. CONCLUSIONS: This is the first demonstration that a delta PKC inhibitor preserves vasodilator capacity in epicardial coronary arteries in an in vivo porcine AMI model. Because endothelial dysfunction correlates with worse outcome in patients with AMI, this preserved endothelial function in epicardial coronary arteries might result in a better clinical outcome.

Mast cells and epsilonPKC: a role in cardiac remodeling in hypertension-induced heart failure.

Heart failure (HF) is a chronic syndrome in which pathological cardiac remodeling is an integral part of the disease and mast cell (MC) degranulation-derived mediators have been suggested to play a role in its progression. Protein kinase C (PKC) signaling is a key event in the signal transduction pathway of MC degranulation. We recently found that inhibition of epsilonPKC slows down the progression of hypertension-induced HF in salt-sensitive Dahl rats fed a high-salt diet. We therefore determined whether epsilonPKC inhibition affects MC degranulation in this model. Six week-old male Dahl rats were fed with a high-salt diet to induce systemic hypertension, which resulted in concentric left ventricular hypertrophy at the age of 11 weeks, followed by myocardial dilatation and HF at the age of 17 weeks. We administered epsilonV1-2, an epsilonPKC-selective inhibitor peptide (3 mg/kg/day), deltaV1-1, a deltaPKC-selective inhibitor peptide (3 mg/kg/day), TAT (negative control; at equimolar concentration; 1.6 mg/kg/day) or olmesartan (angiotensin receptor blocker [ARB] as a positive control; 3 mg/kg/day) between 11 weeks and 17 weeks. Treatment with epsilonV1-2 attenuated cardiac MC degranulation without affecting MC density, myocardial fibrosis, microvessel patency, vascular thickening and cardiac inflammation in comparison to TAT- or deltaV1-1-treatment. Treatment with ARB also attenuated MC degranulation and cardiac remodeling, but to a lesser extent when compared to epsilonV1-2. Finally, epsilonV1-2 treatment inhibited MC degranulation in isolated peritoneal MCs. Together, our data suggest that epsilonPKC inhibition attenuates pathological remodeling in hypertension-induced HF, at least in part, by preventing cardiac MC degranulation.

Alteration of gene expression during progression of hypertension-induced cardiac dysfunction in rats.

Hypertension induced by high-salt diet in Dahl salt-sensitive rats leads to compensatory cardiac hypertrophy by approximately 11 wk, cardiac dysfunction at approximately 17 wk, and death from cardiac dysfunction at approximately 21 wk. It is unclear what molecular hallmarks distinguish the compensatory hypertrophy from the decompensated cardiac dysfunction phase. Here we compared the gene expression in rat cardiac tissue from the compensatory hypertrophic phase (11 wk, n = 6) with the cardiac dysfunction phase (17 wk, n = 6) and with age-matched normotensive controls. Messenger RNA levels of 93 genes, selected based on predicted association with cardiac dysfunction, were measured by quantitative real-time PCR. In the hypertrophic phase, the expression of three genes, atrial natriuretic peptide (ANP; P = 0.0089), brain natriuretic peptide (P = 0.0012), and endothelin-1 precursor (P = 0.028), significantly increased, whereas there was decreased expression of 24 other genes including SOD2 (P = 0.0148), sarco(endo)plasmic reticulum Ca(2+)-ATPase 2a (P = 0.0002), and ryanodine receptor 2 (P = 0.0319). In the subsequent heart cardiac dysfunction phase, the expression of an additional 20 genes including inducible nitric oxide synthase (NOS; P = 0.0135), angiotensin I-converting enzyme (P = 0.0082), and IL-1beta (P < 0.0001) increased, whereas the expression of seven genes decreased compared with those of age-matched controls. Furthermore, the expression of 22 genes, including prepro-endothelin-1, ANP, angiotensin I-converting enzyme, beta(1)-adrenergic receptor, SOD2, and endothelial NOS, significantly changed in the cardiac dysfunction phase compared with the compensatory hypertrophic phase. Finally, principal component analysis successfully segregated animals with decompensatory cardiac dysfunction from controls, as well as from animals at the compensated hypertrophy phase, suggesting that we have identified molecular markers for each stage of the disease.

Pharmacological inhibition of epsilon-protein kinase C attenuates cardiac fibrosis and dysfunction in hypertension-induced heart failure.

Studies on genetically manipulated mice suggest a role for epsilon-protein kinase C (epsilonPKC) in cardiac hypertrophy and in heart failure. The potential clinical relevance of these findings was tested here using a pharmacological inhibitor of epsilonPKC activity during the progression to heart failure in hypertensive Dahl rats. Dahl rats, fed an 8% high-salt diet from the age of 6 weeks, exhibited compensatory cardiac hypertrophy by 11 weeks, followed by heart failure at approximately 17 weeks and death by the age of approximately 20 weeks (123+/-3 days). Sustained treatment between weeks 11 and 17 with the selective epsilonPKC inhibitor epsilonV1-2 or with an angiotensin II receptor blocker olmesartan prolonged animal survival by approximately 5 weeks (epsilonV1-2: 154+/-7 days; olmesartan: 149+/-5 days). These treatments resulted in improved fractional shortening (epsilonV1-2: 58+/-2%; olmesartan: 53+/-2%; saline: 41+/-6%) and decreased cardiac parenchymal fibrosis when measured at 17 weeks without lowering blood pressure at any time during the treatment. Combined treatment with epsilonV1-2, together with olmesartan, prolonged animal survival by 5 weeks (37 days) relative to olmesartan alone (from 160+/-5 to 197+/-14 days, respectively) and by approximately 11 weeks (74 days) on average relative to saline-treated animals, suggesting that the pathway inhibited by epsilonPKC inhibition is not identical to the olmesartan-induced effect. These data suggest that an epsilonPKC-selective inhibitor such as epsilonV1-2 may have a potential in augmenting current therapeutic strategies for the treatment of heart failure in humans.

Reduction of infracardiac intestinal activity by a small amount of soda water in technetium-99m tetrofosmin myocardial perfusion scintigraphy with adenosine stress.

BACKGROUND: In technetium (Tc)-99m myocardial perfusion imaging (MPI), intestinal activity often interferes with the assessment of myocardial perfusion of the inferior wall. We examined whether a small amount of soda water prevents intestinal activity and improves image quality of the inferior wall in Tc-99m tetrofosmin MPI. METHODS AND RESULTS: Ninety-five patients referred for 1-day rest/stress Tc-99m tetrofosmin MPI were assigned to one of two groups automatically, according to the date when they underwent MPI: the soda water group (n = 63) ingested 100 mL soda water just before image acquisition after adenosine stress, and the control group (n = 32) underwent no intervention. The frequency of intestinal activity was assessed visually on planar images. The inferior myocardial wall and the abdominal activity adjacent to the myocardium were assessed quantitatively on three different planar images during stress, and the mean inferior wall-to-abdomen (I/A) count ratio was calculated. The frequency of intestinal activity was 69.8% in the soda water group, and 90.6% in the control group (P = .038). The I/A count ratio was significantly higher in the soda water group than in the control group (1.98 +/- 0.51 vs 1.50 +/- 0.35, respectively, P < .0001, +/- SD). CONCLUSIONS: The intake of 100 mL of soda water improves intestinal activity and improves the image quality of the inferior wall.

Sustained pharmacological inhibition of deltaPKC protects against hypertensive encephalopathy through prevention of blood-brain barrier breakdown in rats.

Hypertensive encephalopathy is a potentially fatal condition associated with cerebral edema and the breakdown of the blood-brain barrier (BBB). The molecular pathways leading to this condition, however, are unknown. We determined the role of deltaPKC, which is thought to regulate microvascular permeability, in the development of hypertensive encephalopathy using deltaV1-1 - a selective peptide inhibitor of deltaPKC. As a model of hypertensive encephalopathy, Dahl salt-sensitive rats were fed an 8% high-salt diet from 6 weeks of age and then were infused s.c. with saline, control TAT peptide, or deltaV1-1 using osmotic minipumps. The mortality rate and the behavioral symptoms of hypertensive encephalopathy decreased significantly in the deltaV1-1-treated group relative to the control-treated group, and BBB permeability was reduced by more than 60%. Treatment with deltaV1-1 was also associated with decreased deltaPKC accumulation in capillary endothelial cells and in the endfeet of capillary astrocytes, which suggests decreased microvasculature disruption. Treatment with deltaV1-1 prevented hypertension-induced tight junction disruption associated with BBB breakdown, which suggests that deltaPKC may specifically act to dysregulate tight junction components. Together, these results suggest that deltaPKC plays a role in the development of hypertension-induced encephalopathy and may be a therapeutic target for the prevention of BBB disruption.

Pharmacological inhibition of epsilon PKC suppresses chronic inflammation in murine cardiac transplantation model.

Epsilon protein kinase C (epsilonPKC) plays pivotal roles in myocardial infarction and in heart failure. Although cardiac transplantation is a well-established therapy for severe heart failure, allograft rejection and host inflammatory responses limit graft function and reduce life expectancy. Here we determined whether sustained epsilonPKC inhibition beginning 3 days after transplantation suppress allograft rejection and improve cardiac transplantation using a murine heterotopic transplantation model. Hearts of FVB mice (H-2(q)) were transplanted into C57BL/6 mice (H-2(b)). Delivery of the epsilonPKC inhibitor, TAT(47-57)-epsilonV1-2 (epsilonV1-2, n=9, 20 mg/kg/day), or the carrier control peptide, TAT(47-57) (TAT, n=8), by osmotic pump began 3 days after transplantation and continued for the remaining 4 weeks. epsilonV1-2 treatment significantly improved the beating score throughout the treatment. Infiltration of macrophages and T cells into the cardiac grafts was significantly reduced and parenchymal fibrosis was decreased in animals treated with epsilonV1-2 as compared with control treatment. Finally, the rise in pro-fibrotic cytokine, TGF-beta and monocyte recruiting chemokine MCP-1 levels was almost abolished by epsilonV1-2 treatment, whereas the rise in PDGF-BB level was unaffected. These data suggest that epsilonPKC activity contributes to the chronic immune response in cardiac allograft and that an epsilonPKC-selective inhibitor, such as epsilonV1-2, could augment current therapeutic strategies to suppress inflammation and prolong graft survival in humans.

Impaired perfusion after myocardial infarction is due to reperfusion-induced deltaPKC-mediated myocardial damage.

OBJECTIVE: To improve myocardial flow during reperfusion after acute myocardial infarction and to elucidate the molecular and cellular basis that impedes it. According to the AHA/ACC recommendation, an ideal reperfusion treatment in patients with acute myocardial infarction (AMI) should not only focus on restoring flow in the occluded artery, but should aim to reduce microvascular damage to improve blood flow in the infarcted myocardium. METHODS: Transgenic mouse hearts expressing the deltaPKC (protein kinase C) inhibitor, deltaV1-1, in their myocytes only were treated with or without the deltaPKC inhibitor after ischemia in an ex vivo AMI model. deltaV1-1 or vehicle was also delivered at reperfusion in an in vivo porcine model of AMI. Microvascular dysfunction was assessed by physiological and histological measurements. RESULTS: deltaPKC inhibition in the endothelial cells improved myocardial perfusion in the transgenic mice. In the porcine in vivo AMI model, coronary flow reserve (CFR), which is impaired for 6 days following infarction, was improved immediately following a one-minute treatment at the end of the ischemic period with the deltaPKC-selective inhibitor, deltaV1-1 ( approximately 250 ng/kg), and was completely corrected by 24 h. Myocardial contrast echocardiography, electron microscopy studies, and TUNEL staining demonstrated deltaPKC-mediated microvascular damage. epsilonPKC-induced preconditioning, which also reduces infarct size by >60%, did not improve microvascular function. CONCLUSIONS: These data suggest that deltaPKC activation in the microvasculature impairs blood flow in the infarcted tissue after restoring flow in the occluded artery and that AMI patients with no-reflow may therefore benefit from treatment with a deltaPKC inhibitor given in conjunction with removal of the coronary occlusion.

Isodicentric Philadelphia chromosome in acute lymphoblastic leukemia with der(7;12)(q10;q10).

We describe here the first case of acute lymphoblastic leukemia (ALL) with an isodicentric Philadelphia [idic(Ph)] chromosome. A 35-year-old man was diagnosed as ALL because of the infiltration of CD10(+)CD19(+)CD33(+)CD34(+) lymphoblasts in the bone marrow and the expression of p190-type BCR/ABL fusion transcript. Chromosome analysis showed 45,XY,der(7;12)(q10;q10),der(9)t(9;22)(q34;q11),idic der(22)t(9;22)(q34;q11). The idic(Ph) chromosome was spindle-shaped and supposed to be formed by two Ph chromosomes joined at their q terminals, whereas idic(Ph) chromosomes in chronic myelogenous leukemia (CML) have been shown to be fused at the satellite regions of p arms. The results indicate that the structure of idic(Ph) chromosomes appears to be different between ALL and CML. The patient did not respond to any chemotherapy and could not achieve remission. This chromosome aberration in ALL may suggest poor prognosis as observed in some cases of CML. Furthermore, considering other three reported cases, der(7;12)(q10;q10) may be one of the recurrent translocations in ALL.

Protein kinase C delta (deltaPKC)-annexin V interaction: a required step in deltaPKC translocation and function.

Protein kinase C (PKC) plays a critical role in diseases such as cancer, stroke, and cardiac ischemia, and participates in a variety of signal transduction pathways such as apoptosis, cell proliferation, and tumor suppression. Though much is known about PKC downstream signaling events, the mechanisms of regulation of PKC activation and subsequent translocation have not been elucidated. Protein-protein interactions regulate and determine the specificity of many cellular signaling events. Such a specific protein-protein interaction is described here between deltaPKC and annexin V. We demonstrate, at physiologically relevant conditions, that a transient interaction between annexin V and deltaPKC occurs in cells after deltaPKC stimulation, but before deltaPKC translocates to the particulate fraction. Evidence of deltaPKC-annexin V binding is provided also by FRET and by in vitro binding studies. Dissociation of the deltaPKC-annexin V complex requires ATP and microtubule integrity. Furthermore, depletion of endogenous annexin V, but not annexin IV, with siRNA inhibits deltaPKC translocation following PKC stimulation. A rationally designed eight amino acid peptide, corresponding to the interaction site for deltaPKC on annexin V, inhibits deltaPKC translocation and deltaPKC-mediated function as evidenced by its protective effect in a model of myocardial infarction. Our data indicate that translocation of deltaPKC is not simply a diffusion-driven process, but is instead a multi-step event regulated by protein-protein interactions. We show that following cell activation, deltaPKC-annexin V binding is a transient and an essential step in the function of deltaPKC, thus identifying a new role for annexin V in PKC signaling and a new step in PKC activation.

Epsilon protein kinase C as a potential therapeutic target for the ischemic heart.

Ischemic heart disease is the leading cause of morbidity and mortality in the western world. Ischemic damage can occur by acute myocardial infarction, stable angina, cardiac stunning, and myocardial hibernation. In addition, 'scheduled' ischemic events, occurring during cardiac surgery, heart transplantation, and elective angioplasty, can also result in cardiac damage. Ischemic or pharmacological preconditioning can decrease the extent of damage to the myocardium. Although the mechanism of preconditioning-mediated cardioprotection is not fully understood, epsilonPKC has been implicated as a critical mediator of this process in animal studies. The use of isozyme-specific pharmacological tools has permitted a better elucidation of the upstream stimuli and the downstream transducers of epsilonPKC in the pathways leading to cardioprotection. While little is known about the role of epsilonPKC in these pathways in humans, animal studies suggest a potential therapeutic role of epsilonPKC. This review will focus on the role of epsilonPKC in cardiac protection and on the signal transduction cascades that have been implicated in this protection.

Inhibition of heart transplant injury and graft coronary artery disease after prolonged organ ischemia by selective protein kinase C regulators.

OBJECTIVE: Transplanted hearts subjected to prolonged ischemia develop ischemia-reperfusion injury and graft coronary artery disease. To determine the effect of delta-protein kinase C and -protein kinase C on ischemia-reperfusion injury and the resulting graft coronary artery disease induced by prolonged ischemia, we used a delta-protein kinase C-selective inhibitor peptide and an -protein kinase C-selective activator peptide after 30 or 120 minutes of ischemia. METHODS: Hearts of piebald viral glaxo (PVG) rats were heterotopically transplanted into allogeneic August Copenhagen Irish (ACI) rats. After cardioplegic arrest of the donor heart, -protein kinase C activator was injected antegrade into the coronary arteries. Hearts were procured and bathed in -protein kinase C activator, and before reperfusion, delta-protein kinase C inhibitor was injected into the recipient inferior vena cava. Controls were treated with saline. To analyze ischemia-reperfusion injury, grafts were procured at 4 hours after transplantation and analyzed for superoxide generation; myeloperoxidase activity; tumor necrosis factor alpha, interleukin 1beta, and monocyte/macrophage chemoattractant protein 1 production; and cardiomyocyte apoptosis by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling and caspase 2, 3, 8, and 9 activity. To analyze graft coronary artery disease, another set of animals underwent equal ischemic times and treatment strategies and then after 90 days were analyzed for graft coronary artery disease indexes. RESULTS: All measures of ischemia-reperfusion injury and graft coronary artery disease after 120 minutes of ischemia in the saline-treated group were significantly increased relative to those observed after 30 minutes of ischemia. It is important to note that all ischemia-reperfusion injury parameters and graft coronary artery disease indexes decreased significantly in the protein kinase C regulator-treated group in comparison to saline-treated controls; additionally, these values were equivalent to those in saline-treated controls with 30 minutes of ischemia. CONCLUSIONS: Combined treatment with -protein kinase C activator and delta-protein kinase C inhibitor reduces ischemia-reperfusion injury and decreases the resulting graft coronary artery disease induced by prolonged ischemia.

Cardioprotection by epsilon-protein kinase C activation from ischemia: continuous delivery and antiarrhythmic effect of an epsilon-protein kinase C-activating peptide.

BACKGROUND: We previously showed that a selective activator peptide of epsilon-protein kinase C (PKC), psi(epsilon)RACK, conferred cardioprotection against ischemia-reperfusion when delivered ex vivo before the ischemic event. Here, we tested whether in vivo continuous systemic delivery of psi(epsilon)RACK confers sustained cardioprotection against ischemia-reperfusion in isolated mouse hearts and whether psi(epsilon)RACK treatment reduces infarct size or lethal arrhythmias in porcine hearts in vivo. METHODS AND RESULTS: After psi(epsilon)RACK was systemically administered in mice either acutely or continuously, hearts were subjected to ischemia-reperfusion in an isolated perfused model. Whereas psi(epsilon)RACK-induced cardioprotection lasted 1 hour after a single intraperitoneal injection, continuous treatment with psi(epsilon)RACK induced a sustained preconditioned state during the 10 days of delivery. There was no desensitization to the therapeutic effect, no downregulation of epsilonPKC, and no adverse effects after sustained psi(epsilon)RACK delivery. Porcine hearts were subjected to ischemia-reperfusion in vivo, and psi(epsilon)RACK was administered by intracoronary injection during the first 10 minutes of ischemia. psi(epsilon)RACK treatment reduced infarct size (34+/-2% versus 14+/-1%, control versus psi(epsilon)RACK) and resulted in fewer cases of ventricular fibrillation during ischemia-reperfusion (87.5% versus 50%, control versus psi(epsilon)RACK). CONCLUSIONS: The epsilonPKC activator psi(epsilon)RACK induced cardioprotection both in vivo and ex vivo, reduced the incidence of lethal arrhythmia during ischemia-reperfusion, and did not cause desensitization or downregulation of epsilonPKC after sustained delivery. Thus, psi(epsilon)RACK may be useful for patients with ischemic heart disease. In addition, the psi(epsilon)RACK peptide should be a useful pharmacological agent for animal studies in which systemic and sustained modulation of epsilonPKC in vivo is needed.

Suppression of graft coronary artery disease by a brief treatment with a selective epsilonPKC activator and a deltaPKC inhibitor in murine cardiac allografts.

BACKGROUND: Inhibiting delta protein kinase C (deltaPKC) during reperfusion and activating epsilon PKC (epsilonPKC) before ischemia each limits cardiac ischemic injury. Here, we examined whether limiting ischemia-reperfusion injury inhibits graft coronary artery disease (GCAD) and improves murine cardiac allografting. METHODS AND RESULTS: Hearts of FVB mice (H-2q) were transplanted into C57BL/6 mice (H-2b). epsilonPKC activator (psiepsilonRACK) was injected intraperitoneally (20 nmol) into donor mice 20 minutes before procurement. Hearts were then perfused with psiepsilonRACK (1.5 nmol) through the inferior vena cava (IVC) and subsequently submerged in psiepsilonRACK (0.5 micromol/L) for 20 minutes at 4 degrees C. Before reperfusion, the peritoneal cavity of recipients was irrigated with deltaPKC inhibitor (deltaV1-1, 300 nmol); control animals were treated with normal saline. The total ischemic time to the organ was 50 minutes. Two hours after transplantation, production of inflammatory cytokines and adhesion molecules, cardiomyocyte apoptosis, and caspase-3 and caspase-9 (but not caspase-8) activities were significantly reduced in the PKC regulator-treated group. Fas ligand levels (but not Fas) were also significantly reduced in this group. Importantly, GCAD indices, production of inflammatory cytokines, and adhesion molecules were significantly decreased and cardiac allograft function was significantly better as measured up to 30 days after transplantation. CONCLUSIONS: An epsilonPKC activator and a deltaPKC inhibitor together reduced GCAD. Clinically, these PKC isozyme regulators may be useful for organ preservation and prevention of ischemia-reperfusion injury and graft coronary artery disease in cardiac transplantation.

Protein kinase Cdelta activation induces apoptosis in response to cardiac ischemia and reperfusion damage: a mechanism involving BAD and the mitochondria.

Heart attacks caused by occlusion of coronary arteries are often treated by mechanical or enzymatic removal of the occlusion and reperfusion of the ischemic heart. It is now recognized that reperfusion per se contributes to myocardial damage, and there is a great interest in identifying the molecular basis of this damage. We recently showed that inhibiting protein kinase Cdelta (PKCdelta) protects the heart from ischemia and reperfusion-induced damage. Here, we demonstrate that PKCdelta activity and mitochondrial translocation at the onset of reperfusion mediates apoptosis by facilitating the accumulation and dephosphorylation of the pro-apoptotic BAD (Bcl-2-associated death promoter), dephosphorylation of Akt, cytochrome c release, PARP (poly(ADP-ribose) polymerase) cleavage, and DNA laddering. Our data suggest that PKCdelta activation has a critical proapoptotic role in cardiac responses following ischemia and reperfusion.

Inhibition of delta-protein kinase C protects against reperfusion injury of the ischemic heart in vivo.

BACKGROUND: Current treatment for acute myocardial infarction (AMI) focuses on reestablishing blood flow (reperfusion). Paradoxically, reperfusion itself may cause additional injury to the heart. We previously found that delta-protein kinase C (deltaPKC) inhibition during simulated ischemia/reperfusion in isolated rat hearts is cardioprotective. We focus here on the role for deltaPKC during reperfusion only, using an in vivo porcine model of AMI. METHODS AND RESULTS: An intracoronary application of a selective deltaPKC inhibitor to the heart at the time of reperfusion reduced infarct size, improved cardiac function, inhibited troponin T release, and reduced apoptosis. Using 31P NMR in isolated perfused mouse hearts, we found a faster recovery of ATP levels in hearts treated with the deltaPKC inhibitor during reperfusion only. CONCLUSIONS: Reperfusion injury after cardiac ischemia is mediated, at least in part, by deltaPKC activation. This study suggests that including a deltaPKC inhibitor at reperfusion may improve the outcome for patients with AMI.

Reinduction of T-type calcium channels by endothelin-1 in failing hearts in vivo and in adult rat ventricular myocytes in vitro.

BACKGROUND: In ventricular myocardium, the T-type Ca2+ current (ICa,T), which is temporarily observed during fetal and neonatal periods, has been shown to reappear in failing/remodeling hearts. However, its pathophysiological regulation has not been elucidated. METHODS AND RESULTS: We utilized Dahl salt-sensitive (DS) rats with hypertension at the stage of concentric left ventricular (LV) hypertrophy (11 weeks old, LVH) and at the heart failure stage (16 to 18 weeks old, CHF). Some were treated with bosentan (100 mg/kg per day) during the period from LVH to CHF. In LVH, neither the presence of ICa,T (measured in the freshly isolated LV myocytes) nor an increase in alpha-1G mRNA expression were detected. This condition was associated with increases in tissue angiotensin II (AII) but not with endothelin (ET)-1 peptides. In contrast, in CHF, when the tissue AII remained elevated and ET-1 de novo increased, ICa,T was recorded in most of the cells (-0.87+/-0.18 pA/pF at -30 mV, P<0.01 versus LVH). This was associated with a significant increase in the alpha-1G mRNA level. The chronic bosentan treatment eliminated both the elevation of alpha-1G mRNA level and ICa,T from the cells, whereas it did not affect the cell size and membrane capacitance. In addition, 48-hour exposure to ET-1 but not AII induced ICa,T in normal adult myocytes in culture from Sprague-Dawley rats. CONCLUSIONS: ICa,T channels reappear in failing but not in hypertrophied LV cardiomyocytes in a manner depending on the tissue ET-1 activation.

Additive protection of the ischemic heart ex vivo by combined treatment with delta-protein kinase C inhibitor and epsilon-protein kinase C activator.

BACKGROUND: Protein kinase C (PKC) plays a major role in cardioprotection from ischemia/reperfusion injury. Using an HIV-1 Tat protein-derived peptide to mediate rapid and efficient transmembrane delivery of peptide regulators of PKC translocation and function, we examined the cardioprotective effect of selective delta-PKC inhibitor (deltaV1-1) and epsilon-PKC activator (psi(epsilon)RACK) peptides for ischemia/reperfusion damage in isolated perfused rat hearts. Furthermore, we examined the protective effects of these PKC isozymes in isolated perfused hearts subjected to ischemia/reperfusion damage using transgenic mice expressing these peptides specifically in their cardiomyocytes. METHODS AND RESULTS: In isolated perfused rat hearts, administration of deltaV1-1 but not psi(epsilon)RACK during reperfusion improved cardiac function and decreased creatine phosphokinase release. In contrast, pretreatment with psi(epsilon)RACK but not deltaV1-1, followed by a 10-minute washout before ischemia/reperfusion, also improved cardiac function and decreased creatine phosphokinase release. Furthermore, administration of psi(epsilon)RACK before ischemia followed by deltaV1-1 during reperfusion only conferred greater cardioprotective effects than that obtained by each peptide treatment alone. Both the delta-PKC inhibitor and epsilon-PKC activator conferred cardioprotection against ischemia/reperfusion injury in transgenic mice expressing these peptides in the heart, and coexpression of both peptides conferred greater cardioprotective effects than that obtained by the expression of each peptide alone. CONCLUSIONS: delta-PKC inhibitor prevents reperfusion injury, and epsilon-PKC activator mimics ischemic preconditioning. Furthermore, treatment with both peptides confers additive cardioprotective effects. Therefore, these peptides mediate cardioprotection by regulating ischemia/reperfusion damage at distinct time points.

Tissue angiotensin II during progression or ventricular hypertrophy to heart failure in hypertensive rats; differential effects on PKC epsilon and PKC beta.

The protein kinase C (PKC) family has been implicated as second messengers in mechanosensitive modulation of cardiac hypertrophy. However, little information is available on the role of expression and activation of specific cardiac PKC isozymes during development of left ventricular hypertrophy (LVH) and failure (LVF). Dahl salt-sensitive rats fed an 8% salt diet developed systemic hypertension and concentric LVH at 11 weeks of age that is followed by left ventricle (LV) dilatation and global hypokinesis at 17 weeks. Among several PKC isozymes expressed in the LV myocardium, only PKC epsilon showed a 94% increase at the LVH stage. At the LVF stage, however, PKC epsilon returned to the control level, whereas PKC beta I and beta II increased by 158% and 155%, respectively. Hearts were studied at each stage using the Langendorff set-up, and a LV balloon was inflated to achieve an equivalent diastolic wall stress. Following mechanical stretch, PKC epsilon was significantly activated in LVH myocardium in which tissue angiotensin II levels were increased by 59%. Pre-treatment with valsartan, an AT(1)-receptor blocker, abolished the stretch-mediated PKC epsilon activation. Mechanical stretch no longer induced PKC epsilon activation in LVF. Chronic administration of valsartan blunted the progression of LVF and inhibited the increase in PKC beta. Mechanosensitive PKC epsilon activation is augmented and therefore may contribute to the development of compensatory hypertrophy. This effect was dependent on activation of tissue angiotensin II. However, this compensatory mechanism becomes inactive in LVF, where PKC beta may participate in the progression to cardiac dysfunction and LV remodeling.