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

Mast cells: a novel therapeutic avenue for cardiovascular diseases?

Mast cells are tissue-resident immune cells strategically located in different compartments of the normal human heart (the myocardium, pericardium, aortic valve, and close to nerves) as well as in atherosclerotic plaques. Cardiac mast cells produce a broad spectrum of vasoactive and proinflammatory mediators, which have potential roles in inflammation, angiogenesis, lymphangiogenesis, tissue remodelling, and fibrosis. Mast cells release preformed mediators (e.g. histamine, tryptase, and chymase) and de novo synthesized mediators (e.g. cysteinyl leukotriene C4 and prostaglandin D2), as well as cytokines and chemokines, which can activate different resident immune cells (e.g. macrophages) and structural cells (e.g. fibroblasts and endothelial cells) in the human heart and aorta. The transcriptional profiles of various mast cell populations highlight their potential heterogeneity and distinct gene and proteome expression. Mast cell plasticity and heterogeneity enable these cells the potential for performing different, even opposite, functions in response to changing tissue contexts. Human cardiac mast cells display significant differences compared with mast cells isolated from other organs. These characteristics make cardiac mast cells intriguing, given their dichotomous potential roles of inducing or protecting against cardiovascular diseases. Identification of cardiac mast cell subpopulations represents a prerequisite for understanding their potential multifaceted roles in health and disease. Several new drugs specifically targeting human mast cell activation are under development or in clinical trials. Mast cells and/or their subpopulations can potentially represent novel therapeutic targets for cardiovascular disorders.

Mast Cells in Cardiac Remodeling: Focus on the Right Ventricle

In response to various stressors, cardiac chambers undergo structural remodeling. Long-term exposure of the right ventricle (RV) to pressure or volume overload leads to its maladaptive remodeling, associated with RV failure and increased mortality. While left ventricular adverse remodeling is well understood and therapeutic options are available or emerging, RV remodeling remains underexplored, and no specific therapies are currently available. Accumulating evidence implicates the role of mast cells in RV remodeling. Mast cells produce and release numerous inflammatory mediators, growth factors and proteases that can adversely affect cardiac cells, thus contributing to cardiac remodeling. Recent experimental findings suggest that mast cells might represent a potential therapeutic target. This review examines the role of mast cells in cardiac remodeling, with a specific focus on RV remodeling, and explores the potential efficacy of therapeutic interventions targeting mast cells to mitigate adverse RV remodeling.

An Update on Protein Kinases as Therapeutic Targets-Part I: Protein Kinase C Activation and Its Role in Cancer and Cardiovascular Diseases

Protein kinases are one of the most significant drug targets in the human proteome, historically harnessed for the treatment of cancer, cardiovascular disease, and a growing number of other conditions, including autoimmune and inflammatory processes. Since the approval of the first kinase inhibitors in the late 1990s and early 2000s, the field has grown exponentially, comprising 98 approved therapeutics to date, 37 of which were approved between 2016 and 2021. While many of these small-molecule protein kinase inhibitors that interact orthosterically with the protein kinase ATP binding pocket have been massively successful for oncological indications, their poor selectively for protein kinase isozymes have limited them due to toxicities in their application to other disease spaces. Thus, recent attention has turned to the use of alternative allosteric binding mechanisms and improved drug platforms such as modified peptides to design protein kinase modulators with enhanced selectivity and other pharmacological properties. Herein we review the role of different protein kinase C (PKC) isoforms in cancer and cardiovascular disease, with particular attention to PKC-family inhibitors. We discuss translational examples and carefully consider the advantages and limitations of each compound (Part I). We also discuss the recent advances in the field of protein kinase modulators, leverage molecular docking to model inhibitor-kinase interactions, and propose mechanisms of action that will aid in the design of next-generation protein kinase modulators (Part II).

Involvement of Polyamines From Cardiac Mast Cells in Myocardial Remodeling Induced by Pressure Overload Through Mitochondrial Permeability Transition Pore Opening

Objective

Polyamines mainly contain spermine (SPM), spermidine (SPD), and putrescine (PUT). Many research results suggest that polyamines participate in cell proliferation, differentiation, and the regulation of gene expression, and have a close relationship with the occurrence and development of many diseases. However, the role and possible mechanisms of action of polyamines from cardiac mast cells in myocardial remodeling induced by pressure overload remain to be elucidated.

Methods

Pressure overload was induced by abdominal aortic constriction (AAC). Toluidine blue staining was used to visualize mast cells in cardiac tissue. The polyamine content of cardiac tissue was analyzed using high-performance liquid chromatography. Opening of the mitochondrial permeability transition pore (MPTP) was determined by the Ca²⁺-induced swelling of isolated cardiac mitochondria, measured as a reduction in A₅₂₀.

Results

Compared with sham rats, the cardiac mast cell density, the polyamine content (PUT, SPB, and SPM), and myocardial MPTP opening in rats with AAC were significantly increased (P < 0.05), and were accompanied by increased myocardial fibrosis and heart weight/body weight ratio. Intraperitoneal injection of polyamines mimicked these results, and these effects were reversed by cromolyn sodium, a mast cell stabilizer (P < 0.05). Myocardial MPTP opening increased in rats with AAC (P < 0.05), and the three polyamines also increased myocardial MPTP opening (P < 0.05).

Conclusion

Mast cell-derived polyamines are involved in pressure overload-induced myocardial remodeling by increasing opening of the MPTP.

Diabetic Aldehyde Dehydrogenase 2 Mutant (ALDH2*2) Mice Are More Susceptible to Cardiac Ischemic-Reperfusion Injury Due to 4-Hydroxy-2-Nonenal Induced Coronary Endothelial Cell Damage

Background

Aldehyde dehydrogenase‐2 (ALDH2), a mitochondrial enzyme, detoxifies reactive aldehydes such as 4‐hydroxy‐2‐nonenal (4HNE). A highly prevalent E487K mutation in ALDH2 (ALDH2*2) in East Asian people with intrinsic low ALDH2 activity is implicated in diabetic complications. 4HNE‐induced cardiomyocyte dysfunction was studied in diabetic cardiac damage; however, coronary endothelial cell (CEC) injury in myocardial ischemia‐reperfusion injury (IRI) in diabetic mice has not been studied. Therefore, we hypothesize that the lack of ALDH2 activity exacerbates 4HNE‐induced CEC dysfunction which leads to cardiac damage in ALDH2*2 mutant diabetic mice subjected to myocardial IRI.

Methods and Results

Three weeks after diabetes mellitus (DM) induction, hearts were subjected to IRI either in vivo via left anterior descending artery occlusion and release or ex vivo IRI by using the Langendorff system. The cardiac performance was assessed by conscious echocardiography in mice or by inserting a balloon catheter in the left ventricle in the ex vivo model. Just 3 weeks of DM led to an increase in cardiac 4HNE protein adducts and, cardiac dysfunction, and a decrease in the number of CECs along with reduced myocardial ALDH2 activity in ALDH2*2 mutant diabetic mice compared with their wild‐type counterparts. Systemic pretreatment with Alda‐1 (10 mg/kg per day), an activator of both ALDH2 and ALDH2*2, led to a reduction in myocardial infarct size and dysfunction, and coronary perfusion pressure upon cardiac IRI by increasing CEC population and coronary arteriole opening.

Conclusions

Low ALDH2 activity exacerbates 4HNE‐mediated CEC injury and thereby cardiac dysfunction in diabetic mouse hearts subjected to IRI, which can be reversed by ALDH2 activation.

B-arrestin-2 Signaling Is Important to Preserve Cardiac Function During Aging

Experiments reported here tested the hypothesis that β-arrestin-2 is an important element in the preservation of cardiac function during aging. We tested this hypothesis by aging β-arrestin-2 knock-out (KO) mice, and wild-type equivalent (WT) to 12-16months. We developed the rationale for these experiments on the basis that angiotensin II (ang II) signaling at ang II receptor type 1 (AT1R), which is a G-protein coupled receptor (GPCR) promotes both G-protein signaling as well as β-arrestin-2 signaling. β-arrestin-2 participates in GPCR desensitization, internalization, but also acts as a scaffold for adaptive signal transduction that may occur independently or in parallel to G-protein signaling. We have previously reported that biased ligands acting at the AT1R promote β-arrestin-2 signaling increasing cardiac contractility and reducing maladaptations in a mouse model of dilated cardiomyopathy. Although there is evidence that ang II induces maladaptive senescence in the cardiovascular system, a role for β-arrestin-2 signaling has not been studied in aging. By echocardiography, we found that compared to controls aged KO mice exhibited enlarged left atria and left ventricular diameters as well as depressed contractility parameters with preserved ejection fraction. Aged KO also exhibited depressed relaxation parameters when compared to WT controls at the same age. Moreover, cardiac dysfunction in aged KO mice was correlated with alterations in the phosphorylation of myofilament proteins, such as cardiac myosin binding protein-C, and myosin regulatory light chain. Our evidence provides novel insights into a role for β-arrestin-2 as an important signaling mechanism that preserves cardiac function during aging.

Innate Immune Cells and Hypertension: Neutrophils and Neutrophil Extracellular Traps (NETs)

Uncontrolled immune system activation amplifies end-organ injury in hypertension. Nonetheless, the exact mechanisms initiating this exacerbated inflammatory response, thereby contributing to further increases in blood pressure (BP), are still being revealed. While participation of lymphoid-derived immune cells has been well described in the hypertension literature, the mechanisms by which myeloid-derived innate immune cells contribute to T cell activation, and subsequent BP elevation, remains an active area of investigation. In this article, we critically analyze the literature to understand how monocytes, macrophages, dendritic cells, and polymorphonuclear leukocytes, including mast cells, eosinophils, basophils, and neutrophils, contribute to hypertension and hypertension-associated end-organ injury. The most abundant leukocytes, neutrophils, are indisputably increased in hypertension. However, it is unknown how (and why) they switch from critical first responders of the innate immune system, and homeostatic regulators of BP, to tissue-damaging, pro-hypertensive mediators. We propose that myeloperoxidase-derived pro-oxidants, neutrophil elastase, neutrophil extracellular traps (NETs), and interactions with other innate and adaptive immune cells are novel mechanisms that could contribute to the inflammatory cascade in hypertension. We further posit that the gut microbiota serves as a set point for neutropoiesis and their function. Finally, given that hypertension appears to be a key risk factor for morbidity and mortality in COVID-19 patients, we put forth evidence that neutrophils and NETs cause cardiovascular injury post-coronavirus infection, and thus may be proposed as an intriguing therapeutic target for high-risk individuals. © 2021 American Physiological Society. Compr Physiol 11:1575-1589, 2021.

Innate Immunity Effector Cells as Inflammatory Drivers of Cardiac Fibrosis

Despite relevant advances made in therapies for cardiovascular diseases (CVDs), they still represent the first cause of death worldwide. Cardiac fibrosis and excessive extracellular matrix (ECM) remodeling are common end-organ features in diseased hearts, leading to tissue stiffness, impaired myocardial functional, and progression to heart failure. Although fibrosis has been largely recognized to accompany and complicate various CVDs, events and mechanisms driving and governing fibrosis are still not entirely elucidated, and clinical interventions targeting cardiac fibrosis are not yet available. Immune cell types, both from innate and adaptive immunity, are involved not just in the classical response to pathogens, but they take an active part in "sterile" inflammation, in response to ischemia and other forms of injury. In this context, different cell types infiltrate the injured heart and release distinct pro-inflammatory cytokines that initiate the fibrotic response by triggering myofibroblast activation. The complex interplay between immune cells, fibroblasts, and other non-immune/host-derived cells is now considered as the major driving force of cardiac fibrosis. Here, we review and discuss the contribution of inflammatory cells of innate immunity, including neutrophils, macrophages, natural killer cells, eosinophils and mast cells, in modulating the myocardial microenvironment, by orchestrating the fibrogenic process in response to tissue injury. A better understanding of the time frame, sequences of events during immune cells infiltration, and their action in the injured inflammatory heart environment, may provide a rationale to design new and more efficacious therapeutic interventions to reduce cardiac fibrosis.

Analysis of mast cells and myocardial fibrosis in autopsied patients with hypertensive heart disease

OBJECTIVE

To analyze the percentage of collagen fibers and mast cell density in the left ventricular myocardium of autopsied patients with and without hypertensive heart disease.

METHODS

Thirty fragments of left ventricular myocardium were obtained from individuals autopsied at the Clinical Hospital of the Federal University of Triângulo Mineiro (UFTM) in the period from 1987 to 2017. Individuals were divided into two groups: those with hypertensive heart disease (HD) and those with no heart disease (ND). Subjects were also assessed according to age, gender and race (white and non-white). Collagen fibers were quantified by computed morphometry and mast cell density was assessed by immunohistochemical methods.

RESULTS

There were significantly more collagen fibers in the left ventricle in the HD group than in the ND group (p<0.001). Mast cell density was significantly higher in the left ventricle of individuals with HD immunolabeled with anti-chymase and anti-tryptase antibodies (p=0.02) and also of those immunolabeled only with anti-tryptase antibodies (p=0.03). Analyzing the HD group, there was a significant positive correlation between the percentage of collagen fibers in the left ventricle and mast cell density immunolabeled by anti-chymase and anti-tryptase antibodies (p=0.04) and also mast cell density immunolabeled only with anti-tryptase antibodies (p=0.02).

CONCLUSIONS

Mast cells are involved in the development of hypertensive heart disease, contributing to the remodeling of collagen fibers in this disease.

Mast Cells in Cardiac Fibrosis: New Insights Suggest Opportunities for Intervention

Mast cells (MC) are innate immune cells present in virtually all body tissues with key roles in allergic disease and host defense. MCs recognize damage-associated molecular patterns (DAMPs) through expression of multiple receptors including Toll-like receptors and the IL-33 receptor ST2. MCs can be activated to degranulate and release pre-formed mediators, to synthesize and secrete cytokines and chemokines without degranulation, and/or to produce lipid mediators. MC numbers are generally increased at sites of fibrosis. They are potent, resident, effector cells producing mediators that regulate the fibrotic process. The nature of the secretory products produced by MCs depend on micro-environmental signals and can be both pro- and anti-fibrotic. MCs have been repeatedly implicated in the pathogenesis of cardiac fibrosis and in angiogenic responses in hypoxic tissues, but these findings are controversial. Several rodent studies have indicated a protective role for MCs. MC-deficient mice have been reported to have poorer outcomes after coronary artery ligation and increased cardiac function upon MC reconstitution. In contrast, MCs have also been implicated as key drivers of fibrosis. MC stabilization during a hypertensive rat model and an atrial fibrillation mouse model rescued associated fibrosis. Discrepancies in the literature could be related to problems with mouse models of MC deficiency. To further complicate the issue, mice generally have a much lower density of MCs in their cardiac tissue than humans, and as such comparing MC deficient and MC containing mouse models is not necessarily reflective of the role of MCs in human disease. In this review, we will evaluate the literature regarding the role of MCs in cardiac fibrosis with an emphasis on what is known about MC biology, in this context. MCs have been well-studied in allergic disease and multiple pharmacological tools are available to regulate their function. We will identify potential opportunities to manipulate human MC function and the impact of their mediators with a view to preventing or reducing harmful fibrosis. Important therapeutic opportunities could arise from increased understanding of the impact of such potent, resident immune cells, with the ability to profoundly alter long term fibrotic processes.

Mast cell tryptase - Marker and maker of cardiovascular diseases

Mast cells are tissue-resident cells, which have been proposed to participate in various inflammatory diseases, among them the cardiovascular diseases (CVDs). For mast cells to be able to contribute to an inflammatory process, they need to be activated to exocytose their cytoplasmic secretory granules. The granules contain a vast array of highly bioactive effector molecules, the neutral protease tryptase being the most abundant protein among them. The released tryptase may act locally in the inflamed cardiac or vascular tissue, so contributing directly to the pathogenesis of CVDs. Moreover, a fraction of the released tryptase reaches the systemic circulation, thereby serving as a biomarker of mast cell activation. Actually, increased levels of circulating tryptase have been found to associate with CVDs. Here we review the biological relevance of the circulating tryptase as a biomarker of mast cell activity in CVDs, with special emphasis on the relationship between activation of mast cells in their tissue microenvironments and the pathophysiological pathways of CVDs. Based on the available in vitro and in vivo studies, we highlight the potential molecular mechanisms by which tryptase may contribute to the pathogenesis of CVDs. Finally, the synthetic and natural inhibitors of tryptase are reviewed for their potential utility as therapeutic agents in CVDs.

Protein kinase C and cardiac dysfunction: a review

Heart failure (HF) is a physiological state in which cardiac output is insufficient to meet the needs of the body. It is a clinical syndrome characterized by impaired ability of the left ventricle to either fill or eject blood efficiently. HF is a disease of multiple aetiologies leading to progressive cardiac dysfunction and it is the leading cause of deaths in both developed and developing countries. HF is responsible for about 73,000 deaths in the UK each year. In the USA, HF affects 5.8 million people and 550,000 new cases are diagnosed annually. Cardiac remodelling (CD), which plays an important role in pathogenesis of HF, is viewed as stress response to an index event such as myocardial ischaemia or imposition of mechanical load leading to a series of structural and functional changes in the viable myocardium. Protein kinase C (PKC) isozymes are a family of serine/threonine kinases. PKC is a central enzyme in the regulation of growth, hypertrophy, and mediators of signal transduction pathways. In response to circulating hormones, activation of PKC triggers a multitude of intracellular events influencing multiple physiological processes in the heart, including heart rate, contraction, and relaxation. Recent research implicates PKC activation in the pathophysiology of a number of cardiovascular disease states. Few reports are available that examine PKC in normal and diseased human hearts. This review describes the structure, functions, and distribution of PKCs in the healthy and diseased heart with emphasis on the human heart and, also importantly, their regulation in heart failure.

Monoamine oxidase-dependent endoplasmic reticulum-mitochondria dysfunction and mast cell degranulation lead to adverse cardiac remodeling in diabetes

Monoamine oxidase (MAO) inhibitors ameliorate contractile function in diabetic animals, but the mechanisms remain unknown. Equally elusive is the interplay between the cardiomyocyte alterations induced by hyperglycemia and the accompanying inflammation. Here we show that exposure of primary cardiomyocytes to high glucose and pro-inflammatory stimuli leads to MAO-dependent increase in reactive oxygen species that causes permeability transition pore opening and mitochondrial dysfunction. These events occur upstream of endoplasmic reticulum (ER) stress and are abolished by the MAO inhibitor pargyline, highlighting the role of these flavoenzymes in the ER/mitochondria cross-talk. In vivo, streptozotocin administration to mice induced oxidative changes and ER stress in the heart, events that were abolished by pargyline. Moreover, MAO inhibition prevented both mast cell degranulation and altered collagen deposition, thereby normalizing diastolic function. Taken together, these results elucidate the mechanisms underlying MAO-induced damage in diabetic cardiomyopathy and provide novel evidence for the role of MAOs in inflammation and inter-organelle communication. MAO inhibitors may be considered as a therapeutic option for diabetic complications as well as for other disorders in which mast cell degranulation is a dominant phenomenon.

The protective role of liquiritin in high fructose-induced myocardial fibrosis via inhibiting NF-κB and MAPK signaling pathway

Diabetic cardiomyopathy has been known as an important complication of diabetes and characterized by persistent diastolic dysfunction, resulting in myocardial fibrosis, which is associated inflammatory response and oxidative stress. Liquiritin is a major constituent of Glycyrrhiza Radix, possessing various pharmacological activities and exhibiting various positive biological effects, including anti-cancer, anti-oxidative and neuroprotective effects. Here, we investigated the anti-inflammatory properties and protective effects of lquiritin in high fructose-induced mice and cardiomyocytes to clarify the potential mechanism. The mice were divided into the control mice, 30% high fructose-induced mice, 10mg/kg liquiritin-treaed mice after fructose feeding and 20mg/kg liquiritin-treaed mice after fructose feeding. Liquiritin effectively reduced the lipid accumulation and insulin resistance induced by fructose feeding. In comparison to high fructose-feeding control mice, liquiritin-treated mice developed less myocardial fibrosis with lower expression of Collagen type I, Collagen type II and alpha smooth muscle-actin (α-SMA). In addition, liquiritin significantly reduced the inflammatory cytokine release and NF-κB phosphorylation through IKKα/IκBα signaling pathway suppression. Further, Mitogen-activated protein kinases (MAPKs), including p38, ERK1/2 and JNK, was up-regulated for fructose stimulation, which was inactivated by liquiritin treatment in vivo and in vitro studies. Our data indicates that liquiritin has a protective effect against high fructose-induced myocardial fibrosis via suppression of NF-κB and MAPKs signaling pathways, and liquiritin may be a promising candidate for diabetes-related myocardial fibrosis treatment.

Cardiovascular symptoms in patients with systemic mast cell activation disease

Traditionally, mast cell activation disease (MCAD) has been considered as just one rare (neoplastic) disease, mastocytosis, focused on the mast cell (MC) mediators tryptase and histamine and the suggestive, blatant symptoms of flushing and anaphylaxis. Recently another form of MCAD, the MC activation syndrome, has been recognized featuring inappropriate MC activation with little to no neoplasia and likely much more heterogeneously clonal and far more prevalent than mastocytosis. Increasing expertise and appreciation has been established for the truly very large menagerie of MC mediators and their complex patterns of release, engendering complex, nebulous presentations of chronic and acute illness best characterized as multisystem polymorbidity of generally inflammatory ± allergic theme. We describe the pathogenesis of MCAD with a particular focus on clinical cardiovascular symptoms and the therapeutic options for MC mediator-induced cardiovascular symptoms.

Periostin expression induced by oxidative stress contributes to myocardial fibrosis in a rat model of high salt-induced hypertension

Periostin is an extracellular matrix protein involved in fibrosis. The present study investigated the importance of periostin in hypertension-induced myocardial fibrosis. Rats were randomly divided into either the normal group (0.4% NaCl diet; n=8) or hypertension group (8% NaCl diet; n=8). For 36 weeks, the blood pressure and heart rate of the rats were monitored. At week 36, the hearts were extracted for further analysis. Masson's staining and western blotting were performed to determine the levels of periostin protein expression, oxidative stress and fibrosis. In addition, fibroblasts were isolated from adult rats and cultured in vitro, and following treatment with angiotensin II (Ang II) and N-acetyl-L-cysteine (NAC), western blotting, immunofluorescence and 2′,7′ dichlorodihydrofluorescin staining were performed to examine reactive oxygen species production, and periostin and α-smooth muscle actin (α-SMA) expression levels. The results demonstrated that periostin expression and oxidative stress were increased in hypertensive hearts compared with normal hearts. The in vitro experiments demonstrated that Ang II upregulated the expression levels of periostin and α-SMA compared with the control, whereas, pretreatment with NAC inhibited oxidative stress, periostin and α-SMA expression in fibroblasts. In conclusion, the results of the current study suggested that oxidative stress-induced periostin is involved in myocardial fibrosis and hypertension. The present study demonstrated that periostin inhibition may be a promising approach for the inhibition of hypertension-induced cardiac remodeling.

Ultrasound assisted synthesis of imidazolium salts: an efficient way to ionic liquids

In this study a straightforward and efficient approach concerning synthesis of 1,3-diazole derivatives under ultrasound (US) irradiation as well as under conventional thermal heating (TH) is presented. N-alkylation under US irradiation may be considered environmentally friendly in terms of higher yields, smaller amounts of solvent used and an overall energy efficiency due to a substantial reduction of reaction times. A comparative study of ultrasound vs. conventional conditions has been performed. Overall, the use of US proved to be more efficient than TH. A possible explanation concerning the different behavior of imidazole and benzimidazole in the N1-alkylation reactions under US irradiation was proposed.

Uncovering the cathepsin system in heart failure patients submitted to Left Ventricular Assist Device (LVAD) implantation

Background

In end-stage heart failure (HF), the implantation of a left ventricular assist device (LVAD) is able to induce reverse remodeling. Cellular proteases, such as cathepsins, are involved in the progression of HF. The aim of this study was to evaluate the role of cathepsin system in HF patients supported by LVAD, in order to determine their involvement in cardiac remodeling.

Methods

The expression of cysteine (CatB, CatK, CatL, CatS) and serine cathepsin (CatG), and relative inhibitors (Cystatin B, C and SerpinA3, respectively) was determined in cardiac biopsies of 22 patients submitted to LVAD (pre-LVAD) and compared with: 1) control stable chronic HF patients on medical therapy at the moment of heart transplantation without prior LVAD (HT, n = 7); 2) patients supported by LVAD at the moment of transplantation (post-LVAD, n = 6).

Results

The expression of cathepsins and their inhibitors was significantly higher in pre-LVAD compared to the HT group and LVAD induced a further increase in the cathepsin system. Significant positive correlations were observed between cardiac expression of cathepsins and their inhibitors as well as inflammatory cytokines. In the pre-LVAD group, a relationship of cathepsins with dilatative etiology and length of hospitalization was found.

Conclusions

A parallel activation of cathepsins and their inhibitors was observed after LVAD support. The possible clinical importance of these modifications is confirmed by their relation with patients’ outcome. A better discovery of these pathways could add more insights into the cardiac remodeling during HF.

Histological characterization of mast cell chymase in patients with pulmonary hypertension and chronic obstructive pulmonary disease

Our previous findings demonstrated an increase in pulmonary mast cells (MCs) in idiopathic pulmonary arterial hypertension (IPAH). Also, literature suggests a potential role for MCs in chronic obstructive pulmonary disease (COPD). However, a comprehensive investigation of lungs from patients is still needed. We systematically investigated the presence/expression of MCs/MC chymase in the lungs of IPAH and COPD patients by (immuno)histochemistry and subsequent quantification. We found that total and perivascular chymase-positive MCs were significantly higher in IPAH patients than in donors. In addition, chymase-positive MCs were located in proximity to regions with prominent expression of big-endothelin-1 in the pulmonary vessels of IPAH patients. Total and perivascular MCs around resistant vessels were augmented and a significant majority of them were degranulated (activated) in COPD patients. While the total chymase-positive MC count tended to increase in COPD patients, the perivascular number was significantly enhanced in all vessel sizes analyzed. Surprisingly, MC and chymase-positive MC numbers positively correlated with better lung function in COPD. Our findings suggest that activated MCs, possibly by releasing chymase, may contribute to pulmonary vascular remodeling in IPAH. Pulmonary MCs/chymase may have compartment-specific (vascular vs. airway) functions in COPD. Future studies should elucidate the mechanisms of MC accumulation and the role of MC chymase in pathologies of these severe lung diseases.

Protein Kinase C Epsilon Contributes to NADPH Oxidase Activation in a Pre-Eclampsia Lymphoblast Cell Model

Pre-eclampsia is a pregnancy-specific disorder characterised by hypertension and proteinuria, which in severe cases results in multi-system disturbances. The maternal syndrome is associated with a pro-inflammatory state, consisting of leukocyte activation, which is thought to contribute to the widespread endothelial dysfunction. We previously showed increased activation of NADPH oxidase in pre-eclampsia, in both neutrophils and B-lymphoblast cell lines (B-LCLs). In this study, the mechanism by which NADPH oxidase activity is increased in pre-eclampsia was further investigated. NADPH oxidase activity was found to be increased in phorbol-12-myristate-13-acetate (PMA) stimulated B-LCLs isolated from women with pre-eclampsia. This correlated with an increase in protein kinase C (PKC) substrate phosphorylation, p47-phox phosphorylation (a regulatory component of NADPH oxidase) and p47-phox directed-kinase activity. Using ion exchange and hydroxyapatite chromatography we identified a major peak of PMA regulated p47-phox kinase activity. Chromatography fractions were probed for PKC isoforms. We found the major peak of p47-phox kinase activity could not be separated from the elution profile of PKC epsilon. Using a peptide inhibitor of PKC epsilon, PMA-induced reactive oxygen species (ROS) production could be reduced to that of a normal B-LCL. These data suggest a pro-inflammatory role for PKC epsilon in the pathogenesis of pre-eclampsia.

Mast cell inhibition attenuates myocardial damage, adverse remodeling, and dysfunction during fulminant myocarditis in the rat

BACKGROUND

Myocarditis is a life-threatening heart disease characterized by myocardial inflammation, necrosis, and chronic fibrosis. While mast cell inhibition has been suggested to prevent fibrosis in rat myocarditis, little is known about its effectiveness in attenuating cardiac remodeling and dysfunction in myocarditis. Thus, we sought to test the hypothesis that mast cell inhibition will attenuate the inflammatory reaction and associated left ventricular (LV) remodeling and dysfunction after fulminant autoimmune myocarditis. Methods and

RESULTS

To induce experimental autoimmune myocarditis, we immunized 30 rats with porcine cardiac myosin (PCM) twice at a 7-day interval. On day 8 animals were randomized into treatment with either an intraperitoneal (IP) injection of 25mg/kg of cromolyn sodium (n = 13) or an equivalent volume (∼0.5 mL IP) of normal saline (n = 11). All animals were scanned by serial echocardiography studies before treatment (baseline echocardiogram) and after 20 days of cromolyn sodium (28 days after immunization). Furthermore, serial cardiac magnetic resonance was performed in a subgroup of 12 animals. After 20 days of treatment (28 days from first immunization), hearts were harvested for histopathological analysis. By echocardiography, cromolyn sodium prevented LV dilatation and attenuated LV dysfunction, compared with controls. Postmortem analysis of hearts showed that cromolyn sodium reduced myocardial fibrosis, as well as the number and size of cardiac mast cells in the inflamed myocardium, compared with controls.

CONCLUSIONS

Our study suggests that mast cell inhibition with cromolyn sodium attenuates adverse LV remodeling and dysfunction in myocarditis. This mechanism-based therapy is clinically relevant and could improve the outcome of patients at risk for inflammatory cardiomyopathy and heart failure.

βIIPKC and εPKC isozymes as potential pharmacological targets in cardiac hypertrophy and heart failure

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 is involved in cardiac hypertrophy and heart failure. This article is part of a special issue entitled "Key Signaling Molecules in Hypertrophy and Heart Failure".

Pharmacological inhibition of βIIPKC is cardioprotective in late-stage hypertrophy

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 6weeks, suppressed myocardial fibrosis and inflammation, and delayed the transition from compensated hypertrophy to cardiac dysfunction. In addition, changes in the levels of the Ca(2+)-handling proteins, SERCA2 and the Na(+)/Ca(2+) exchanger, as well as troponin I phosphorylation, seen in the control-treated hypertensive rats were not observed in the βΙΙPKC-treated rats, suggesting that βΙΙPKC 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.

Involvement of mast cells in monocrotaline-induced pulmonary hypertension in rats

BACKGROUND

Mast cells (MCs) are implicated in inflammation and tissue remodeling. Accumulation of lung MCs is described in pulmonary hypertension (PH); however, whether MC degranulation and c-kit, a tyrosine kinase receptor critically involved in MC biology, contribute to the pathogenesis and progression of PH has not been fully explored.

METHODS

Pulmonary MCs of idiopathic pulmonary arterial hypertension (IPAH) patients and monocrotaline-injected rats (MCT-rats) were examined by histochemistry and morphometry. Effects of the specific c-kit inhibitor PLX and MC stabilizer cromolyn sodium salt (CSS) were investigated in MCT-rats both by the preventive and therapeutic approaches. Hemodynamic and right ventricular hypertrophy measurements, pulmonary vascular morphometry and analysis of pulmonary MC localization/counts/activation were performed in animal model studies.

RESULTS

There was a prevalence of pulmonary MCs in IPAH patients and MCT-rats as compared to the donors and healthy rats, respectively. Notably, the perivascular MCs were increased and a majority of them were degranulated in lungs of IPAH patients and MCT-rats (p < 0.05 versus donor and control, respectively). In MCT-rats, the pharmacological inhibitions of MC degranulation and c-kit with CSS and PLX, respectively by a preventive approach (treatment from day 1 to 21 of MCT-injection) significantly attenuated right ventricular systolic pressure (RVSP) and right ventricular hypertrophy (RVH). Moreover, vascular remodeling, as evident from the significantly decreased muscularization and medial wall thickness of distal pulmonary vessels, was improved. However, treatments with CSS and PLX by a therapeutic approach (from day 21 to 35 of MCT-injection) neither improved hemodynamics and RVH nor vascular remodeling.

CONCLUSIONS

The accumulation and activation of perivascular MCs in the lungs are the histopathological features present in clinical (IPAH patients) and experimental (MCT-rats) PH. Moreover, the accumulation and activation of MCs in the lungs contribute to the development of PH in MCT-rats. Our findings reveal an important pathophysiological insight into the role of MCs in the pathogenesis of PH in MCT-rats.

Cardiomyocyte lipids impair β-adrenergic receptor function via PKC activation

Normal hearts have increased contractility in response to catecholamines. Because several lipids activate PKCs, we hypothesized that excess cellular lipids would inhibit cardiomyocyte responsiveness to adrenergic stimuli. Cardiomyocytes treated with saturated free fatty acids, ceramide, and diacylglycerol had reduced cellular cAMP response to isoproterenol. This was associated with increased PKC activation and reduction of β-adrenergic receptor (β-AR) density. Pharmacological and genetic PKC inhibition prevented both palmitate-induced β-AR insensitivity and the accompanying reduction in cell surface β-ARs. Mice with excess lipid uptake due to either cardiac-specific overexpression of anchored lipoprotein lipase, PPARγ, or acyl-CoA synthetase-1 or high-fat diet showed reduced inotropic responsiveness to dobutamine. This was associated with activation of protein kinase C (PKC)α or PKCδ. Thus, several lipids that are increased in the setting of lipotoxicity can produce abnormalities in β-AR responsiveness. This can be attributed to PKC activation and reduced β-AR levels.

Highly Specific Modulators of Protein Kinase C Localization: Applications to Heart Failure

Heart failure (HF) in which the blood supply does not match the body's needs, affects 10% of the population over 65 years old. The protein kinase C (PKC) family of kinases has a key role in normal and disease states. Here we discuss the role of PKC in HF and focus on the use of specific PKC regulators to identify the mechanism leading to this Pathology and potential leads for therapeutics.

Translocation of protein kinase C isoforms is involved in propofol-induced endothelial nitric oxide synthase activation

BACKGROUND

Previous studies have indicated that protein kinase C (PKC) may enhance endothelial nitric oxide synthase (eNOS) activation, although the detailed mechanism(s) remains unclear. In this study, we investigated the roles of PKC isoforms in regulating propofol-induced eNOS activation in human umbilical vein endothelial cells (HUVECs).

METHODS

We applied western blot (WB) analysis to investigate the effects of propofol on Ser(1177) phosphorylation-dependent eNOS activation in HUVECs. Nitrite (NO(2)(-)) accumulation was measured using the Griess assay. The phosphatidylinositol 3-kinase/Akt (PI3K/Akt) pathway was examined by WB assay. Propofol-induced translocation of individual PKC isoforms in subcellular fractions in HUVECs was analysed using WB assay.

RESULTS

In HUVECs, protocol treatment (1-100 microM) for 10 min induced a concentration-dependent increase in phosphorylation of eNOS at Ser(1177). The NO production was also increased accordingly. PKC inhibitors, bisindolylmaleimide I (0.1-1 microM), and staurosporine (20 and 100 nM), effectively blocked propofol-induced eNOS activation and NO production. Further analyses in fractionated endothelial lysate showed that short-term propofol treatment (50 microM) led to translocation of PKC-alpha, PKC-delta, PKC-zeta, PKC-eta, and PKC-epsilon from cytosolic to membrane fractions, which could also be inhibited by both PKC inhibitors. These data revealed that the differential redistribution of these isozymes is indispensable for propofol-induced eNOS activation. In addition, Akt was not phosphorylated in response to propofol at Ser(473) or Thr(308).

CONCLUSIONS

Propofol induces the Ser(1177) phosphorylation-dependent eNOS activation through the drug-stimulated translocation of PKC isoforms to distinct intracellular sites in HUVECs, which is independent of PI3K/Akt-independent pathway.

Effects of benzylidenecyclopentanone analogues of curcumin on histamine release from mast cells

Curcumin reportedly has anti-allergic effects and can inhibit the release of histamine from mast cells. In the present study, fourteen benzylidenecyclopentanone analogues of curcumin were studied for their effects on histamine release from rat basophilic leukemia (RBL-2H3) cells. After screening, four selected compounds: 2,5-bis(4-hydroxybenzylidene)cyclopentanone; 2,5-bis(4-hydroxy-3-methoxybenzylidene)cyclopentanone; 2,5-bis(4-hydroxy-3,5-dimethylbenzylidene) cyclopentanone; and 2,5-bis(4-hydroxy-3,5-diethylbenzylidene)cyclopentanone were studied for their concentration-dependent effects on histamine release and Ca(2+) uptake. In RBL-2H3 cells and rat peritoneal mast cells stimulated with antigen or compound 48/80, respectively, the methoxy-hydroxy analogue was more potent than curcumin in inhibiting histamine release. In contrast, the inhibitory effects of methyl/ethyl analogues were less potent than those of curcumin. Moreover, these compounds abrogated histamine release induced by increased intracellular Ca(2+) concentrations in response to stimulants such as thapsigargin and ionomycin. These compounds also showed potent inhibitory effects on (45)Ca(2+) uptake in RBL-2H3 cells. The mechanism of the inhibitory effects of these curcumin analogues on histamine release appeared to be related to blockade of Ca(2+) signaling events. These results provide useful information to guide the development of new synthetic compounds for the treatment of allergic and inflammatory diseases related to histamine or mast cells.

PARP inhibition delays transition of hypertensive cardiopathy to heart failure in spontaneously hypertensive rats

AIMS

Oxidative stress followed by abnormal signalling can play a critical role in the development of long-term, high blood pressure-induced cardiac remodelling in heart failure (HF). Since oxidative stress-induced poly(ADP-ribose)polymerase (PARP) activation and cell death have been observed in several experimental models, we investigated the possibility that inhibition of nuclear PARP improves cardiac performance and delays transition from hypertensive cardiopathy to HF in a spontaneously hypertensive rat (SHR) model of HF.

METHODS AND RESULTS

SHRs were divided into two groups: one received no treatment (SHR-C) and the other (SHR-L) received 5 mg/kg/day L-2286 (PARP-inhibitor) orally for 46 weeks. A third group was a normotensive age-matched control group (CFY) and a fourth was a normotensive age-matched group receiving L-2286 treatment 5 mg/kg/day (CFY+L). At the beginning of the study, systolic function was similar in both CFY and SHR groups. In the SHR-C group at the end of the study, eccentric hypertrophy with poor left ventricular (LV) systolic function was observed, while PARP inhibitor treatment preserved systolic LV function. Due to these favourable changes, the survival rate of SHRs was significantly improved (P < 0.01) by the administration of the PARP inhibitor (L-2286). The PARP inhibitor used did not affect the elevated blood pressure of SHR rats, but moderated the level of plasma-BNP (P < 0.01) and favourably influenced all the measured gravimetric parameters (P < 0.05) and the extent of myocardial fibrosis (P < 0.05). The inhibition of PARP increased the phosporylation of Akt-1/GSK-3beta (P < 0.01), ERK 1/2 (P < 0.01), and PKC epsilon (P < 0.01), and decreased the phosphorylation of JNK (P < 0.05), p-38 MAPK (P < 0.01), PKC pan betaII and PKC zeta/lambda (P < 0.01), and PKC alpha/betaII and delta (P < 0.05).

CONCLUSION

These data demonstrate that chronic inhibition of PARP induces long-term favourable changes in the most important signalling pathways related to oxidative stress. PARP inhibition also prevents remodelling, preserves systolic function, and delays transition of hypertensive cardiopathy to HF in SHRs.

Protein kinase C in heart failure: a therapeutic target?

Heart failure (HF) afflicts about 5 million people and causes 300,000 deaths a year in the United States alone. An integral part of the pathogenesis of HF is cardiac remodelling, and the signalling events that regulate it are a subject of intense research. Cardiac remodelling is the sum of responses of the heart to causes of HF, such as ischaemia, myocardial infarction, volume and pressure overload, infection, inflammation, and mechanical injury. These responses, including cardiomyocyte hypertrophy, myocardial fibrosis, and inflammation, involve numerous cellular and structural changes and ultimately result in a progressive decline in cardiac performance. Pharmacological and genetic manipulation of cultured heart cells and animal models of HF and the analysis of cardiac samples from patients with HF are all used to identify the molecular and cellular mechanisms leading to the disease. Protein kinase C (PKC) isozymes, a family of serine-threonine protein kinase enzymes, were found to regulate a number of cardiac responses, including those associated with HF. In this review, we describe the PKC isozymes that play critical roles in specific aspects of cardiac remodelling and dysfunction in HF.