To date, measurements of the activity of aldehyde dehydrogenase-2 (ALDH2), a critical mitochondrial enzyme for eliminating certain cytotoxic aldehydes in the body and a promising target for drug development, have been largely limited to in vitro methods. Recent advancements in magnetic resonance spectroscopy (MRS) of hyperpolarized 13C-labeled substrates now provide a method to detect and image in vivo metabolic pathways with signal-to-noise ratio gains greater than 10,000 fold over conventional MRS techniques. However aldehydes, due to their toxicity and short T1 relaxation times, are generally poor targets for such 13C-labeled studies. In this work, we show that dynamic magnetic resonance spectroscopic imaging of hyperpolarized [1-13C]pyruvate and its conversion to [1-13C]lactate can provide an indirect in vivo measurement of ALDH2 activity via the concentration of NADH, a co-factor common to both the reduction of pyruvate to lactate and the oxidation of acetaldehyde to acetate. Results from a rat liver ethanol model (n = 9) show that changes in 13C-lactate labeling following the bolus injection of hyperpolarized pyruvate are highly correlated with changes in ALDH2 activity (R2=0.76).
hyperpolarized 13C; ALDH2 activity; liver; ethanol; pyruvate; lactate; NADH
Inflammation enhances the peripheral analgesic efficacy of opioid drugs, but the mechanisms involved in this phenomenon have not been fully elucidated. Crotalphine (CRP), a peptide that was first isolated from South American rattlesnake C.d. terrificus venom, induces a potent and long-lasting anti-nociceptive effect that is mediated by the activation of peripheral opioid receptors. Because the high efficacy of CRP is only observed in the presence of inflammation, we aimed to elucidate the mechanisms involved in the CRP anti-nociceptive effect induced by inflammation. Using real-time RT-PCR, western blot analysis and ELISA assays, we demonstrate that the intraplantar injection of prostaglandin E2 (PGE2) increases the mRNA and protein levels of the µ- and κ-opioid receptors in the dorsal root ganglia (DRG) and paw tissue of rats within 3 h of the injection. Using conformation state-sensitive antibodies that recognize activated opioid receptors, we show that PGE2, alone does not increase the activation of these opioid receptors but that in the presence of PGE2, the activation of specific opioid receptors by CRP and selective µ- and κ-opioid receptor agonists (positive controls) increases. Furthermore, PGE2 down-regulated the expression and activation of the δ-opioid receptor. CRP increased the level of activated mitogen-activated protein kinases in cultured DRG neurons, and this increase was dependent on the activation of protein kinase Cζ. This CRP effect was much more prominent when the cells were pretreated with PGE2. These results indicate that the expression and activation of peripheral opioid receptors by opioid-like drugs can be up- or down-regulated in the presence of an acute injury and that acute tissue injury enhances the efficacy of peripheral opioids.
Activation of PKCε confers protection against neuronal ischemia/reperfusion. Since activation of PKCε leads to its translocation to multiple intracellular sites, a mitochondrial-selective PKCε activator was used to test the importance of mitochondrial activation to the neuroprotective effect of PKCε. PKCε can regulate key cytoprotective mitochondrial functions including electron transport chain activity, reactive oxygen species (ROS) generation, mitochondrial permeability transition, and detoxification of reactive aldehydes. We tested the ability of mitochondrial selective activation of PKCε to protect primary brain cell cultures or mice subjected to ischemic stroke. Pre-treatment with either general PKCε activator peptide, ψεRACK, or mitochondrial-selective PKCε activator, ψεHSP90, reduced cell death induced by simulated ischemia/reperfusion in neurons, astrocytes, and mixed neuronal cultures. The protective effects of both ψεRACK and ψεHSP90 were blocked by the PKCε antagonist, εV1–2, indicating protection requires PKCε interaction with its anchoring protein, εRACK. Further supporting a mitochondrial mechanism for PKCε, neuroprotection by ψεHSP90 was associated with a marked delay in mitochondrial membrane depolarization and significantly attenuated ROS generation during ischemia. Importantly, ψεHSP90 reduced infarct size and reduced neurological deficit in C57/BL6 mice subjected to middle cerebral artery occlusion and 24 hours of reperfusion. Thus selective activation of mitochondrial PKCε preserves mitochondrial function in vitro and improves outcome in vivo, suggesting potential therapeutic value clinically when brain ischemia is anticipated, including neurosurgery and cardiac surgery.
mitochondria; astrocytes; acute stroke; cell culture; animal models
Huntington’s disease (HD) is the result of expression of a mutated Huntingtin protein (mtHtt), and is associated with a variety of cellular dysfunctions including excessive mitochondrial fission. Here, we tested whether inhibition of excessive mitochondrial fission prevents mtHtt-induced pathology. We developed a selective inhibitor (P110-TAT) of the mitochondrial fission protein dynamin-related protein 1 (DRP1). We found that P110-TAT inhibited mtHtt-induced excessive mitochondrial fragmentation, improved mitochondrial function, and increased cell viability in HD cell culture models. P110-TAT treatment of fibroblasts from patients with HD and patients with HD with iPS cell–derived neurons reduced mitochondrial fragmentation and corrected mitochondrial dysfunction. P110-TAT treatment also reduced the extent of neurite shortening and cell death in iPS cell–derived neurons in patients with HD. Moreover, treatment of HD transgenic mice with P110-TAT reduced mitochondrial dysfunction, motor deficits, neuropathology, and mortality. We found that p53, a stress gene involved in HD pathogenesis, binds to DRP1 and mediates DRP1-induced mitochondrial and neuronal damage. Furthermore, P110-TAT treatment suppressed mtHtt-induced association of p53 with mitochondria in multiple HD models. These data indicate that inhibition of DRP1-dependent excessive mitochondrial fission with a P110-TAT–like inhibitor may prevent or slow the progression of HD.
Ischemia and reperfusion (IR) injury remains a major cause of morbidity and mortality and multiple molecular and cellular pathways have been implicated in this injury. We determined whether acute inhibition of excessive mitochondrial fission at the onset of reperfusion improves mitochondrial dysfunction and cardiac contractility postmyocardial infarction in rats.
Methods and Results
We used a selective inhibitor of the fission machinery, P110, which we have recently designed. P110 treatment inhibited the interaction of fission proteins Fis1/Drp1, decreased mitochondrial fission, and improved bioenergetics in three different rat models of IR, including primary cardiomyocytes, ex vivo heart model, and an in vivo myocardial infarction model. Drp1 transiently bound to the mitochondria following IR injury and P110 treatment blocked this Drp1 mitochondrial association. Compared with control treatment, P110 (1 μmol/L) decreased infarct size by 28±2% and increased adenosine triphosphate levels by 70+1% after IR relative to control IR in the ex vivo model. Intraperitoneal injection of P110 (0.5 mg/kg) at the onset of reperfusion in an in vivo model resulted in improved mitochondrial oxygen consumption by 68% when measured 3 weeks after ischemic injury, improved cardiac fractional shortening by 35%, reduced mitochondrial H2O2 uncoupling state by 70%, and improved overall mitochondrial functions.
Together, we show that excessive mitochondrial fission at reperfusion contributes to long‐term cardiac dysfunction in rats and that acute inhibition of excessive mitochondrial fission at the onset of reperfusion is sufficient to result in long‐term benefits as evidenced by inhibiting cardiac dysfunction 3 weeks after acute myocardial infarction.
cardiac myocytes; Drp1; heart; mitochondria; protein‐protein interaction inhibitor
Metastasis is the major reason for breast cancer-related deaths. Although there is a host of indirect evidence for a role of PKCα in primary breast cancer growth, its role in the molecular pathways leading to metastasis have not been comprehensively studied. By treating mice with αV5-3, a novel peptide inhibitor selective for PKCα, we were able to determine how PKCα regulates metastasis of mammary cancer cells using a syngeneic and orthotopic model. The primary tumor growth was not affected by αV5-3 treatment. However, the mortality rate was reduced and metastasis in the lung decreased by more than 90% in the αV5-3-treated mice relative to the control-treated mice. αV5-3 treatment reduced intravasation by reducing MMP-9 activities. αV5-3 treatment also reduced lung seeding of tumor cells and decreased cell migration, effects that were accompanied by a reduction in NFκB-activity and cell surface levels of the CXCL12 receptor, CXCR4. αV5-3 treatment caused no apparent toxicity in non-tumor bearing naïve mice. Rather, inhibiting PKCα protected against liver damage and increased the number of immune cells in tumor-bearing mice. Importantly, αV5-3 showed superior efficacy relative to anti-CXCR4 antibody in reducing metastasis, in vivo. Together, these data show that pharmacological inhibition of PKCα effectively reduces mammary cancer metastasis by targeting intravasation and lung seeding steps in the metastatic process and suggest that PKCα-specific inhibitors, such as αV5-3, can be used to study the mechanistic roles of PKCα specifically and may provide a safe and effective treatment for the prevention of lung metastasis of breast cancer patients.
bioluminescence; mammary cancer; metastasis and protein kinase C
The balance between endothelial nitric oxide synthase (eNOS)-derived nitric oxide (NO) and reactive oxygen species (ROS) production determines endothelial-mediated vascular homeostasis. Activation of protein kinase C (PKC) has been linked to imbalance of the eNOS/ROS system, which leads to endothelial dysfunction. We previously found that selective inhibition of delta PKC (δPKC) or selective activation of epsilon PKC (εPKC) reduces oxidative damage in the heart following myocardial infarction. In this study we determined the effect of these PKC isozymes in the survival of coronary endothelial cells (CVEC). We demonstrate here that serum deprivation of CVEC increased eNOS-mediated ROS levels, activated caspase-3, reduced Akt phosphorylation and cell number. Treatment with either the δPKC inhibitor, δV1-1, or the εPKC activator, ψεRACK, inhibited these effects, restoring cell survival through inhibition of eNOS activity. The decrease in eNOS activity coincided with specific de-phosphorylation of eNOS at Ser1179, and eNOS phosphorylation at Thr497 and Ser116. Furthermore, δV1-1 or ψεRACK induced physical association of eNOS with caveolin-1, an additional marker of eNOS inhibition, and restored Akt activation by inhibiting its nitration. Together our data demonstrate that 1) in endothelial dysfunction, ROS and reactive nitrogen species (RNS) formation result from uncontrolled eNOS activity mediated by activation of δPKC or inhibition of εPKC 2) inhibition of δPKC or activation of εePKC correct the perturbed phosphorylation state of eNOS, thus increasing cell survival. Since endothelial health ensures better tissue perfusion and oxygenation, treatment with a δPKC inhibitor and/or an εPKC activator in diseases of endothelial dysfunction should be considered.
Protein kinase C (PKC) has been a tantalizing target for drug discovery ever since it was first identified as the receptor for the tumor promoter phorbol ester in 19821. Although initial therapeutic efforts focused on cancer, additional diseases, including diabetic complications, heart failure, myocardial infarction, pain and bipolar disease were targeted as researchers developed a better understanding of the roles that PKC’s eight conventional and novel isozymes play in health and disease. Unfortunately, both academic and pharmaceutical efforts have yet to result in the approval of a single new drug that specifically targets PKC. Why does PKC remain an elusive drug target? This review will provide a short account of some of the efforts, challenges and opportunities in developing PKC modulators to address unmet clinical needs.
Maintaining cerebrovascular function is a priority for reducing damage following acute ischemic events such as stroke, and under chronic stress in diseases such as hypertension. Ischemic episodes lead to endothelial cell damage, deleterious inflammatory responses, and altered neuronal and astrocyte regulation of vascular function. These, in turn, can lead to impaired cerebral blood flow and compromised blood–brain barrier function, promoting microvascular collapse, edema, hemorrhagic transformation, and worsened neurological recovery. Multiple studies demonstrate that protein kinase C (PKC), a widely expressed serine/threonine kinase, is involved in mediating arterial tone and microvascular function. However, there is no clear understanding about the role of individual PKC isozymes. We show that intraperitoneal injection of δV1-1–TAT47–57 (0.2 mg/kg in 1 mL), an isozymespecific peptide inhibitor of δPKC, improved microvascular pathology, increased the number of patent microvessels by 92% compared to control-treated animals, and increased cerebral blood flow by 26% following acute focal ischemia induced by middle cerebral artery occlusion in normotensive rats. In addition, acute delivery of δV1-1–TAT47–57 in hypertensive Dahl rats increased cerebral blood flow by 12%, and sustained delivery δV1-1–TAT47–57 (5 uL/h, 1 mM), reduced infarct size by 25% following an acute stroke induced by MCA occlusion for 90 min. Together, these findings demonstrate that δPKC is an important therapeutic target for protection of microvascular structure and function under both acute and chronic conditions of cerebrovascular stress.
Cerebral blood flow; Hypertension; Microvasculature; Protein kinase C; Stroke; Vasculature
Ning, S., Budas, G. R., Churchill, E. N., Chen, C., Knox, S. J. and Mochly-Rosen, D. Mitigation of Radiation-Induced Dermatitis by Activation of Aldehyde Dehydrogenase 2 Using Topical Alda-1 in Mice.
Radiation-induced dermatitis is a debilitating clinical problem in cancer patients undergoing cancer radiation therapy. It is also a possible outcome of exposure to high levels of radiation due to accident or hostile activity. We report that activation of aldehyde dehydrogenase 2 (ALDH2) enzymatic activity using the allosteric agonist, Alda-1, significantly reduced 4-hydroxynonenal adducts accumulation, delayed the onset of radiation dermatitis and substantially reduced symptoms in a clinically-relevant model of radiation-induced dermatitis. Importantly, Alda-1 did not radioprotect tumors in mice. Rather, it increased the sensitivity of the tumors to radiation therapy. This is the first report of reactive aldehydes playing a role in the intrinsic radiosensitivity of normal and tumor tissues. Our findings suggest that ALDH2 represents a novel target for the treatment of radiation dermatitis without reducing the benefit of radiotherapy.
Protein kinase C (PKC) ε, a member of the novel PKC family, plays key roles in mitogenesis and survival in normal and cancer cells. PKCε is frequently overexpressed in epithelial cancers, particularly in lung cancer. Using a shRNA approach, here we established that PKCε is required for non-small cell lung carcinoma (NSCLC) growth in vitro as well as tumor growth when inoculated into athymic mice. Moreover, sustained delivery of a PKCε selective inhibitor peptide, εV1-2, reduced xenograft growth in mice. Both RNAi depletion and pharmacological inhibition of PKCε caused a marked elevation in the number of apoptotic cells in NSCLC tumors. PKCε-depleted NSCLC cells show elevated expression of pro-apoptotic proteins of the Bcl-2 family, caspase recruitment domain (CARD)-containing proteins, and TNF ligands/receptor superfamily members. Moreover, a Gene Set Enrichment Analysis (GSEA) revealed that a vast majority of the genes changed in PKCε-depleted cells were also deregulated in human NSCLC. Our results strongly suggest that PKCε is required for NSCLC cell survival and maintenance of NSCLC tumor growth. Therefore, PKCε may represent an attractive therapeutic target for NSCLC.
PKCε; non-small cell lung carcinoma; tumorigenesis; cell survival; apoptotic genes
The physiological effects of ethanol are dependent upon the amount and duration of consumption. Chronic excessive consumption can lead to diseases such as liver cirrhosis, and cardiac arrhythmias, while chronic moderate consumption can have therapeutic effects on the cardiovascular system. Recently, it has also been observed that acute administration of ethanol to animals prior to an ischemic event provides significant protection to the heart. This review focuses on the different modalities of chronic vs. acute ethanol consumption and discusses recent evidence for a protective effect of acute ethanol exposure and the possible use of ethanol as a therapeutic agent.
PKC; ethanol; ischemic preconditioning; ischemia; reperfusion; cardiac protection
Nitroglycerin, which helps impaired cardiac function as it is converted to nitric oxide, is used worldwide to treat patients with various ischemic and congestive cardiac diseases, including angina pectoris. Nevertheless, after continuous treatment, the benefits of nitroglycerin are limited by the development of tolerance to the drug. Nitroglycerin tolerance is a result of inactivation of aldehyde dehydrogenase 2 (ALDH2), an enzyme essential for cardioprotection in animals subjected to myocardial infarction (MI). Here we tested the hypothesis that the tolerance that develops as a result of sustained nitroglycerin treatment increases cardiac injury by subsequent MI. In a rat model of MI, 16 hours of prior, sustained nitroglycerin treatment (7.2 mg/kg/day) resulted in infarcts that were twice as large as those in untreated control animals and in diminished cardiac function at 3 days and 2 weeks after the MI. We also sought to identify a potential treatment to protect against this increased cardiac damage. Nitroglycerin inhibited ALDH2 activity in vitro, an effect that was blocked by Alda-1, an activator of ALDH2. Co-administration of Alda-1 (16 mg/kg/day) with the nitroglycerin prevented the nitroglycerin-induced increase in cardiac dysfunction after MI in rats, at least in part by enhancing metabolism of reactive aldehyde adducts that impair normal protein functions. If our animal studies showing that nitroglycerin tolerance increases cardiac injury upon ischemic insult are corroborated in humans, activators of ALDH2 such as Alda-1 may help to protect MI patients from this nitroglycerin-induced increase in cardiac injury, while maintaining the cardiac benefits of the increased nitric oxide concentrations produced by nitroglycerin.
To assess aldehyde dehydrogenase (ALDH) expression in adult human and murine submandibular gland (SMG) stem cells and to determine the effect of ALDH3 activation in SMG stem cell enrichment.
Adult human and murine SMG stem cells were selected by cell surface markers (CD34 for human and c-Kit for mouse) and characterized for various other stem cell surface markers by flow cytometry and ALDH isozymes expression by quantitative reverse transcriptase PCR. Sphere formation and bromodeoxyuridine (BrdUrd) incorporation assays were used on selected cells to confirm their renewal capacity and three-dimensional (3D) collagen matrix culture was applied to observe differentiation. To determine whether ALDH3 activation would increase stem cell yield, adult mice were infused with a novel ALDH3 activator (Alda-89) or with vehicle followed by quantification of c-Kit+/CD90+ SMG stem cells and BrdUrd+ salispheres.
More than 99% of CD34+ huSMG stem cells stained positive for c-Kit, CD90 and 70% colocalized with CD44, Nestin. Similarly, 73.8% c-Kit+ mSMG stem cells colocalized with Sca-1, whereas 80.7% with CD90. Functionally, these cells formed BrdUrd+ salispheres, which differentiated into acinar- and ductal-like structures when cultured in 3D collagen. Both adult human and murine SMG stem cells showed higher expression of ALDH3 than in their non–stem cells and 84% of these cells have measurable ALDH1 activity. Alda-89 infusion in adult mice significantly increased c-Kit+/CD90+ SMG population and BrdUrd+ sphere formation compared with control.
This is the first study to characterize expression of different ALDH isozymes in SMG stem cells. In vivo activation of ALDH3 can increase SMG stem cell yield, thus providing a novel means for SMG stem cell enrichment for future stem cell therapy.
PKCδ is generally known as a pro-apoptotic and anti-proliferative enzyme in human prostate cancer cells.
Here, we investigated the role of PKCδ on the growth of PC-3 human prostate cancer cells in vivo and in vitro.
We found that sustained treatment with a specific PKCδ activator (ψδ receptor for active C kinase, ψδRACK) increased growth of PC-3 xenografts. There was increased levels of HIF-1α, vascular endothelial growth factor and CD31-positive cells in PC-3 xenografts, representative of increased tumor angiogenesis. Mechanistically, PKCδ activation increased the levels of reactive oxygen species (ROS) by binding to and phosphorylating NADPH oxidase, which induced its activity. Also, PKCδ-induced activation of NADPH oxidase increased the level of HIF-1α.
Our results using tumors from the PC-3 xenograft model suggest that PKCδ activation increases angiogenic activity in androgen-independent PC-3 prostate cancer cells by increasing NADPH oxidase activity and HIF-1α levels and thus may partly be responsible for increased angiogenesis in advanced prostate cancer.
angiogenesis; HIF-1α; NADPH oxidase; prostate cancer; protein kinase C
Emerging evidence showed that resistin induces vascular smooth muscle cell (VSMC) migration, a critical step to initiating vascular restenosis. Mechanistically, adhesion molecule expression and cytoskeletal rearrangement have been observed in this progress. Given that matrix metalloproteinases (MMPs) also regulates cell migration, we hypothesized that MMPs may mediate resistin-induced VSMC migration.
Materials and Methods
Human VSMCs were treated with recombinant human resistin at physiological (10 ng/mL) and pathological (40 ng/mL) concentrations for 24 hours. Cell migration was determinate by Boyden chamber assay. MMP and TIMP mRNA and protein levels were measured with real-time PCR and ELISA. MMP enzymatic activity was measured by zymography on precast gels. In another experiment, neutralizing antibodies against MMP-2 and MMP-9 were co-incubated with resistin in cultured VSMCs. The regulation of MMP by protein kinase C (PKC) was determined by εV1–2, a selective PKCε inhibitor.
Resistin-induced SMC migration was confirmed by Boyden chamber assay. 40ng/mL Resistin increased SMC migration by 3.7 fold. Molecularly, resistin stimulated MMP-2 and - MMP9 mRNA and protein expressions. In contrast, the TIMP-1 and TIMP-2 mRNA levels were inhibited by resistin. Neutralizing antibodies against MMP-2 and MMP-9 effectively reversed VSMC migration. Furthermore, resistin activated PKCε and selective PKCε inhibitor suppressed resistin-induced MMP expression, activity and cell migration.
Our study confirmed that resistin increases vascular smooth muscle cell migration in vitro. Mechanistically, resistin-stimulated cell migration was associated with increased MMP expression and activity, which was dependent on PKCε activation.
diabetes mellitus; obesity; resistin; smooth muscle cell migration; restenosis
Exercise training is a well-known coadjuvant in heart failure treatment; however, the molecular mechanisms underlying its beneficial effects remain elusive. Despite the primary cause, heart failure is often preceded by two distinct phenomena: mitochondria dysfunction and cytosolic protein quality control disruption. The objective of the study was to determine the contribution of exercise training in regulating cardiac mitochondria metabolism and cytosolic protein quality control in a post-myocardial infarction-induced heart failure (MI-HF) animal model. Our data demonstrated that isolated cardiac mitochondria from MI-HF rats displayed decreased oxygen consumption, reduced maximum calcium uptake and elevated H2O2 release. These changes were accompanied by exacerbated cardiac oxidative stress and proteasomal insufficiency. Declined proteasomal activity contributes to cardiac protein quality control disruption in our MI-HF model. Using cultured neonatal cardiomyocytes, we showed that either antimycin A or H2O2 resulted in inactivation of proteasomal peptidase activity, accumulation of oxidized proteins and cell death, recapitulating our in vivo model. Of interest, eight weeks of exercise training improved cardiac function, peak oxygen uptake and exercise tolerance in MI-HF rats. Moreover, exercise training restored mitochondrial oxygen consumption, increased Ca2+-induced permeability transition and reduced H2O2 release in MI-HF rats. These changes were followed by reduced oxidative stress and better cardiac protein quality control. Taken together, our findings uncover the potential contribution of mitochondrial dysfunction and cytosolic protein quality control disruption to heart failure and highlight the positive effects of exercise training in re-establishing cardiac mitochondrial physiology and protein quality control, reinforcing the importance of this intervention as a non-pharmacological tool for heart failure therapy.
Vascular restenosis, an overreaction of biological response to injury, is initialized by thrombosis and inflammation. This response is characterized by increased smooth muscle cell migration and proliferation. Available pharmacological treatments include anticoagulants, antiplatelet agents, immunosuppressants and antiproliferation agents. Protein kinase C (PKC), a large family of serine/threonine kinases, has been shown to participate in various pathological stages of restenosis. Consequently, PKC inhibitors are expected to exert a wide range of pharmacological activities therapeutically beneficial for restenosis. In this review, the roles of PKC isozymes in platelets, leukocytes, endothelial cells and smooth muscle cells are discussed, with emphasis given to smooth muscle cells. We will describe cellular and animal studies assessing prevention of restenosis with PKC inhibitors, particularly targeting -alpha, -beta, -delta and -zeta isozymes. The delivery strategy, efficacy and safety of such PKC regulators will also be discussed.
protein kinase C; smooth muscle cell; migration; proliferation; vascular restenosis
Acute myocardial infarction and its sequelae are leading causes of morbidity and mortality worldwide. Nitroglycerin remains a first-line treatment for angina pectoris and acute myocardial infarction. Nitroglycerin achieves its benefit by giving rise to nitric oxide, which causes vasodilation and increases blood flow to the myocardium. However, continuous delivery of nitroglycerin results in tolerance, limiting the use of this drug. Nitroglycerin tolerance is due, at least in part, to inactivation of aldehyde dehydrogenase 2 (ALDH2), an enzyme that converts nitroglycerin to the vasodilator, nitric oxide. We have recently found that, in addition to nitroglycerin’s effect on the vasculature, sustained treatment with nitroglycerin negatively affects cardiomyocyte viability following ischemia, thus resulting in increased infarct size in a myocardial infarction model in animals. Co-administration of Alda-1, an activator of ALDH2, with nitroglycerin improves metabolism of reactive aldehyde adducts and prevents the nitroglycerin-induced increase in cardiac dysfunction following myocardial infarction. In this review, we describe the molecular mechanisms associated with the benefits and risks of nitroglycerin administration in myocardial infarction. (167 of 200).
aldehyde dehydrogenase; nitric oxide; nitroglycerin tolerance; cardiomyocyte; cell death
Cardiac excitability and electrical activity are determined by the sum of individual ion channels, gap junctions and exchanger activities. Electrophysiological remodeling during heart disease involves changes in membrane properties of cardiomyocytes and is related to higher prevalence of arrhythmia-associated morbidity and mortality. Pharmacological and genetic manipulation of cardiac cells as well as animal models of cardiovascular diseases are used to identity changes in electrophysiological properties and the molecular mechanisms associated with the disease. Protein kinase C (PKC) and several other kinases play a pivotal role in cardiac electrophysiological remodeling. Therefore, identifying specific therapies that regulate these kinases is the main focus of current research. PKC, a family of serine/threonine kinases, has been implicated as potential signaling nodes associated with biochemical and biophysical stress in cardiovascular diseases. Thus, the role of PKC isozymes in regulating cardiac excitability has been a subject of great attention. In this review, we describe the role of PKC isozymes that are involved in cardiac excitability and discuss both genetic and pharmacological tools that were used, their attributes and limitations. Selective and effective pharmacological interventions to normalize cardiac electrical activities and correct cardiac arrhythmias will be of great clinical benefit.
Activation of ε protein kinase C (εPKC) protects hearts from ischemic injury. However, some of the mechanism(s) of εPKC mediated cardioprotection are still unclear. Identification of εPKC targets may aid to elucidate εPKC–mediated cardioprotective mechanisms. Previous studies, using a combination of εPKC transgenic mice and difference in gel electrophoresis (DIGE), identified a number of proteins involved in glucose metabolism, whose expression was modified by εPKC. These studies, were accompanied by metabolomic analysis, and suggested that increased glucose oxidation may be responsible for the cardioprotective effect of εPKC. However, whether these εPKC-mediated alterations were due to differences in protein expression or phosphorylation was not determined.
Methods and Results
Here, we used an εPKC-specific activator peptide, ψεRACK, in combination with phosphoproteomics to identify εPKC targets, and identified proteins whose phosphorylation was altered by selective activation of εPKC most of the identified proteins were mitochondrial proteins and analysis of the mitochondrial phosphoproteome, led to the identification of 55 spots, corresponding to 37 individual proteins, which were exclusively phosphorylated, in the presence of ψεRACK. The majority of the proteins identified were proteins involved in glucose and lipid metabolism, components of the respiratory chain as well as mitochondrial heat shock proteins.
In summary the protective effect of εPKC during ischemia involves phosphorylation of several mitochondrial proteins involved in glucose, lipid metabolism and oxidative phosphorylation. Regulation of these metabolic pathways by εPKC phosphorylation may lead to εPKC-mediated cardioprotection induced by ψεRACK.
εPKC; ischemia; phosphorylation; mitochondria
We previously found that in the hearts of hypertensive Dahl salt-sensitive rats, βIIPKC levels increase during the transition from compensated cardiac hypertrophy to cardiac dysfunction. Here we showed that a six-week treatment of these hypertensive rats with a βIIPKC-specific inhibitor, βIIV5-3, prolonged their survival by at least six weeks, suppressed myocardial fibrosis and inflammation, and delayed the transition from compensated hypertrophy to cardiac dysfunction. In addition, changes in the levels of the Ca2+-handling proteins, SERCA2 and the Na+/Ca2+ exchanger, as well as troponin I phosphorylation, seen in the control-treated hypertensive rats were not observed in the βIIPKC-treated rats, suggesting that βIIPKC contributes to the regulation of calcium levels in the myocardium. In contrast, treatment with the selective inhibitor of βIPKC, an alternative spliced form of βIIPKC, had no beneficial effects in these rats. We also found that βIIV5-3, but not βIV5-3, improved calcium handling in isolated rat cardiomyocytes and enhanced contractility in isolated rat hearts. In conclusion, our data using an in vivo model of cardiac dysfunction (late-phase hypertrophy), suggest that βIIPKC contributes to the pathology associated with heart failure and thus an inhibitor of βIIPKC may be a potential treatment for this disease.
β-adrenergic receptors (β-ARs) modulate cardiotoxicity/cardioprotection through crosstalk with multiple signaling pathways. We have previously shown that β2-ARs are cardioprotective during exposure to oxidative stress induced by doxorubicin (DOX). DOX cardiotoxicity is mediated in part through a Ca2+-dependent opening of the mitochondrial permeability transition (MPT), however the signals linking a cell surface receptor like the β2-AR to regulators of mitochondrial function are not clear. The objective of this study was to assess mechanisms of crosstalk between β2-ARs and mitochondrial cell death pathways.
Methods and Results
DOX administered to WT mice resulted in no acute mortality, however 85% of β2-/- mice died within 30 min. Several pro- and anti-survival pathways were altered. The pro-survival kinase, εPKC, was decreased by 64% in β2-/- after DOX vs WT (p<0.01); the εPKC activator ψεRACK partially rescued these mice (47% reduction in mortality). Activity of the pro-survival kinase Akt decreased by 76% in β2-/- after DOX vs WT (p<0.01). The α1-antagonist prazosin restored Akt activity to normal and also partially reversed the mortality (45%). Deletion of the β2-AR increased rate of Ca2+ release by 75% and peak [Ca2+]i by 20% respectively in isolated cardiomyocytes; the Ca2+ channel blocker verapamil also partially rescued the β2-/- (26%). Mitochondrial architecture was disrupted and complex I and II activities decreased by 40.9% and 34.6% respectively after DOX only in β2-/-. The MPT blocker cyclosporine reduced DOX mortality by 41% and prazosin plus cyclosporine acted synergistically to decrease mortality by 85%.
β2-ARs activate pro-survival kinases and attenuate mitochondrial dysfunction during oxidative stress; absence of β2-ARs enhances cardiotoxicity via negative regulation of survival kinases and enhancement of intracellular Ca2+, thus predisposing the mitochondria to opening of the MPT.
Adrenergic receptors; cardiomyopathy; mitochondria; signal transduction; protein kinases
Cardiac hypertrophy is a complex adaptive response to mechanical and neurohumoral stimuli and under continual stressor, it contributes to maladaptive responses, heart failure and death. Protein kinase C (PKC) and several other kinases play a role in the maladaptative cardiac responses, including cardiomyocyte hypertrophy, myocardial fibrosis and inflammation. Identifying specific therapies that regulate these kinases is a major focus of current research. PKC, a family of serine/threonine kinases, has emerged as potential mediators of hypertrophic stimuli associated with neurohumoral hyperactivity in heart failure. In this review, we describe the role of PKC isozymes that are involved in cardiac hypertrophy and heart failure.
PKC signaling pathways; cardiac remodeling; heart failure