Cardiac hypertrophy induced by sustained β-adrenoreceptor activation: pathophysiological aspects

The protective effect of Macrostemonoside T from Allium macrostemon Bunge against Isoproterenol-Induced myocardial injury via the PI3K/Akt/mTOR signaling pathway

Myocardial injury (MI) signifies a pathological aspect of cardiovascular diseases (CVDs) such as coronary artery disease, diabetic cardiomyopathy, and myocarditis. Macrostemonoside T (MST) has been isolated from Allium macrostemon Bunge (AMB), a key traditional Chinese medicine (TCM) used for treating chest stuffiness and pains. Although MST has demonstrated considerable antioxidant activity in vitro, its protective effect against MI remains unexplored. To investigate MST's effects in both in vivo and in vitro models of isoproterenol (ISO)-induced MI and elucidate its underlying molecular mechanisms. This study established an ISO-induced MI model in rats and assessed H9c2 cytotoxicity to examine MST's impact on MI. Various assays, including histopathological staining, TUNEL staining, immunohistochemical staining, DCFH-DA staining, JC-1 staining, ELISA technique, and Western blot (WB), were utilized to explore the potential molecular mechanisms of MI protection. In vivo experiments demonstrated that ISO caused myocardial fiber disorders, elevated cardiac enzyme levels, and apoptosis. However, pretreatment with MST significantly mitigated these detrimental changes. In vitro experiments revealed that MST boosted antioxidant enzyme levels and suppressed malondialdehyde (MDA) production in H9c2 cells. Concurrently, MST inhibited ISO-induced reactive oxygen species (ROS) production and mitigated the decline in mitochondrial membrane potential, thereby reducing the apoptosis rate. Moreover, pretreatment with MST elevated the expression levels of p-PI3K, p-Akt, and p-mTOR, indicating activation of the PI3K/Akt/mTOR signaling pathway and consequent protection against MI. MST attenuated ISO-induced MI in rats by impeding apoptosis through activation of the PI3K/Akt/mTOR signaling pathway. This study presents potential avenues for the development of precursor drugs for CVDs.

Adipocyte-released adipomes in Chagas cardiomyopathy: Impact on cardiac metabolic and immune regulation

Chronic Trypanosoma cruzi infection leads to Chagas cardiomyopathy (CCM), with varying manifestations such as inflammatory hypertrophic cardiomyopathy, arrhythmias, and dilated cardiomyopathy. The factors responsible for the increasing risk of progression to CCM are not fully understood. Previous studies link adipocyte loss to CCM progression, but the mechanism triggering CCM pathogenesis remains unexplored. Our study uncovers that T. cruzi infection triggers adipocyte apoptosis, leading to the release of extracellular vesicles named "adipomes". We developed an innovative method to isolate intact adipomes from infected mice's adipose tissue and plasma, showing they carry unique lipid cargoes. Large and Small adipomes, particularly plasma-derived infection-associated L-adipomes (P-ILA), regulate immunometabolic signaling and induce cardiomyopathy. P-ILA treatment induces hypertrophic cardiomyopathy in wild-type mice and worsens cardiomyopathy severity in post-acute-infected mice by regulating adipogenic/lipogenic and mitochondrial functions. These findings highlight adipomes' pivotal role in promoting inflammation and impairing myocardial function during cardiac remodeling in CD.

The isoproterenol-induced myocardial fibrosis: A biochemical and histological investigation

The isoproterenol (ISO)-induced myocardial fibrosis is considered a reliable and repeatable experimental model characterized by a relatively low mortality rate. Although is well-known that ISO stimulates the β1 adrenergic receptors at the myocardial level, a high degree of heterogeneity emerges around the doses and duration of the treatment generating unclear results. Therefore, we propose to gain insights into the progression of ISO-induced myocardial fibrosis, in order to critically analyze and optimize the experimental model. Male Wistar rats (12-14-week-old) were submitted to subcutaneous injection of ISO, in particular, two doses were selected: the commonly used dose of 5 mg/kg and a lower dose of 1 mg/kg, administered for 3 and 6 days. Biochemical and histological examinations were conducted either immediately after the last administration or after a recovering period of 7 or 14 days from the initial administration. Noteworthy, from our investigation emerged that even the lower dose of ISO was able to induce the maximal biochemical and histological alterations, suggesting that lower doses should be considered to control the progression of the damage more precisely and to identify a prodromic phase in which intervention with pharmacological or nutraceutical tools can be effectively attempted.

The JMJD family of histone demethylase and their intimate links to cardiovascular disease

The incidence rate and mortality rate of cardiovascular disease rank first in the world. It is associated with various high-risk factors, and there is no single cause. Epigenetic modifications, such as DNA methylation or histone modification, actively participate in the initiation and development of cardiovascular diseases. Histone lysine methylation is a type of histone post-translational modification. The human Jumonji C domain (JMJD) protein family consists of more than 30 members. JMJD proteins participate in many key nuclear processes and play a key role in the specific regulation of gene expression, DNA damage and repair, and DNA replication. Importantly, increasing evidence shows that JMJD proteins are abnormally expressed in cardiovascular diseases, which may be a potential mechanism for the occurrence and development of these diseases. Here, we discuss the key roles of JMJD proteins in various common cardiovascular diseases. This includes histone lysine demethylase, which has been studied in depth, and less-studied JMJD members. Furthermore, we focus on the epigenetic changes induced by each JMJD member, summarize recent research progress, and evaluate their relationship with cardiovascular diseases and therapeutic potential.

Association of ARRDC3 and NFIA variants with bovine congestive heart failure in feedlot cattle

BACKGROUND

Bovine congestive heart failure (BCHF) has become increasingly prevalent among feedlot cattle in the Western Great Plains of North America with up to 7% mortality in affected herds. BCHF is an untreatable complex condition involving pulmonary hypertension that culminates in right ventricular failure and death. Genes associated with BCHF in feedlot cattle have not been previously identified. Our aim was to search for genomic regions associated with this disease.

METHODS

A retrospective, matched case-control design with 102 clinical BCHF cases and their unaffected pen mates was used in a genome-wide association study. Paired nominal data from approximately 560,000 filtered single nucleotide polymorphisms (SNPs) were analyzed with McNemar's test.

RESULTS

Two independent genomic regions were identified as having the most significant association with BCHF: the arrestin domain-containing protein 3 gene ( ARRDC3), and the nuclear factor IA gene ( NFIA, mid- p-values, 1x10 -8 and 2x10 -7, respectively). Animals with two copies of risk alleles at either gene were approximately eight-fold more likely to have BCHF than their matched pen mates with either one or zero risk alleles at both genes (CI 95 = 3-17). Further, animals with two copies of risk alleles at both genes were 28-fold more likely to have BCHF than all others ( p-value = 1×10 -7, CI 95 = 4-206). A missense variant in ARRDC3 (C182Y) represents a potential functional variant since the C182 codon is conserved among all other jawed vertebrate species observed. A two-SNP test with markers in both genes showed 29% of 273 BCHF cases had homozygous risk genotypes in both genes, compared to 2.5% in 198 similar unaffected feedlot cattle. This and other DNA tests may be useful for identifying feedlot animals with the highest risk for BCHF in the environments described here.

CONCLUSIONS

Although pathogenic roles for variants in the ARRDC3 and NFIA genes are unknown, their discovery facilitates classifying animals by genetic risk and allows cattle producers to make informed decisions for selective breeding and animal health management.

Association of ARRDC3 and NFIA variants with bovine congestive heart failure in feedlot cattle

Background

Bovine congestive heart failure (BCHF) has become increasingly prevalent among feedlot cattle in the Western Great Plains of North America with up to 7% mortality in affected herds. BCHF is an untreatable complex condition involving pulmonary hypertension that culminates in right ventricular failure and death. Genes associated with BCHF in feedlot cattle have not been previously identified. Our aim was to search for genomic regions associated with this disease.

Methods

A retrospective, matched case-control design with 102 clinical BCHF cases and their unaffected pen mates was used in a genome-wide association study. Paired nominal data from approximately 560,000 filtered single nucleotide polymorphisms (SNPs) were analyzed with McNemar's test.

Results

Two independent genomic regions were identified as having the most significant association with BCHF: the arrestin domain-containing protein 3 gene ( ARRDC3), and the nuclear factor IA gene ( NFIA, mid- p-values, 1x10 -8 and 2x10 -7, respectively). Animals with two copies of risk alleles at either gene were approximately eight-fold more likely to have BCHF than their matched pen mates with either one or zero risk alleles at both genes (CI 95 = 3-17). Further, animals with two copies of risk alleles at both genes were 28-fold more likely to have BCHF than all others ( p-value = 1×10 -7, CI 95 = 4-206). A missense variant in ARRDC3 (C182Y) represents a potential functional variant since the C182 codon is conserved among all other jawed vertebrate species observed. A two-SNP test with markers in both genes showed 29% of 273 BCHF cases had homozygous risk genotypes in both genes, compared to 2.5% in 198 similar unaffected feedlot cattle. This and other DNA tests may be useful for identifying feedlot animals with the highest risk for BCHF in the environments described here.

Conclusions

Although pathogenic roles for variants in the ARRDC3 and NFIA genes are unknown, their discovery facilitates classifying animals by genetic risk and allows cattle producers to make informed decisions for selective breeding and animal health management.

Pharmacological inhibition of ICOS attenuates the protective effect of exercise on cardiac fibrosis induced by isoproterenol

AIMS

To investigate the cardioprotective mechanism of exercise or exercise combined with inducible costimulatory molecules (ICOS) monoclonal antibody (mAb) therapy against isoproterenol (ISO)-induced cardiac remodeling.

MAIN METHODS

Totally 24 male C57BL/6J mice were randomly divided into four groups: the control group (normal saline treatment), ISO group (subcutaneous injection of isoproterenol, 10 mg/kg/day, once daily for 5 consecutive days), the exercise with subcutaneous ISO injection group (EPI), and the exercise with injected with ISO and ICOS mAb group (EPII). The mice in EPI and EPII group were trained on a small animal treadmill for 4 weeks (13 m/min, 0% grade, 60min/day).

KEY FINDINGS

Exercise significantly attenuated CD45+, Mac-2 inflammatory cell infiltration, cardiac fibrosis and inhibited the RIPK1/RIPK3/MLKL/CaMKII and cardiomyocyte pyroptosis pathways to counter ISO-induced severe cardiac injury. The administration of the ICOS mAb may inhibit the cardioprotection of exercise against ISO-induced heart damage. Compared to those in EPI, our data showed that the increasing levels of myocardial fibrosis, the leukocyte infiltration of cardiac tissue and proteins expression of cardiac myocyte necrosis and pyroptosis signaling pathways in the EPII group.

SIGNIFICANCE

Our results demonstrated that exercise decreased leukocyte infiltration in heart, inhibited the cardiomyocyte pyroptosis and necroptosis signaling pathways, and attenuated inflammatory responses to alleviate ISO-induced cardiac fibrosis. However, the antifibrotic effects of combined treatment with exercise and ICOS mAb intervention did not exhibit synergistic enhancement.

S14-Phosphorylated RPN6 Mediates Proteasome Activation by PKA and Alleviates Proteinopathy

BACKGROUND

A better understanding of the regulation of proteasome activities can facilitate the search for new therapeutic strategies. A cell culture study shows that PKA (cAMP-dependent protein kinase or protein kinase A) activates the 26S proteasome by pS14-Rpn6 (serine14-phosphorylated Rpn6), but this discovery and its physiological significance remain to be established in vivo.

METHODS

Male and female mice with Ser14 of Rpn6 (regulatory particle non-ATPase 6) mutated to Ala (S14A [Rpn6/Psmd11S14A]) or Asp (S14D) to respectively block or mimic pS14-Rpn6 were created and used along with cells derived from them. cAMP/PKA were manipulated pharmacologically. Ubiquitin-proteasome system functioning was evaluated with the GFPdgn (green fluorescence protein with carboxyl fusion of the CL1 degron) reporter mouse and proteasomal activity assays. Impact of S14A and S14D on proteotoxicity was tested in mice and cardiomyocytes overexpressing the misfolded protein R120G-CryAB (R120G [arginine120 to glycine missense mutant alpha B-crystallin]).

RESULTS

PKA activation increased pS14-Rpn6 and 26S proteasome activities in wild-type but not S14A embryonic fibroblasts (mouse embryonic fibroblasts), adult cardiomyocytes, and mouse hearts. Basal 26S proteasome activities were significantly greater in S14D myocardium and adult mouse cardiomyocytes than in wild-type counterparts. S14D::GFPdgn mice displayed significantly lower myocardial GFPdgn protein but not mRNA levels than GFPdgn mice. In R120G mice, a classic model of cardiac proteotoxicity, basal myocardial pS14-Rpn6 was significantly lower compared with nontransgenic littermates, which was not always associated with reduction of other phosphorylated PKA substrates. Cultured S14D neonatal cardiomyocytes displayed significantly faster proteasomal degradation of R120G than wild-type neonatal cardiomyocytes. Compared with R120G mice, S14D/S14D::R120G mice showed significantly greater myocardial proteasome activities, lower levels of total and K48-linked ubiquitin conjugates, and of aberrant CryAB (alpha B-crystallin) protein aggregates, less fetal gene reactivation, and cardiac hypertrophy, and delays in cardiac malfunction.

CONCLUSIONS

This study establishes in animals that pS14-Rpn6 mediates the activation of 26S proteasomes by PKA and that the reduced pS14-Rpn6 is a key pathogenic factor in cardiac proteinopathy, thereby identifying a new therapeutic target to reduce cardiac proteotoxicity.

Risk assessment of bisphenol analogues towards mortality, heart rate and stress-mediated gene expression in cladocerans Moina micrura

Bisphenol A (BPA) is a well-known endocrine-disrupting compound that causes several toxic effects on human and aquatic organisms. The restriction of BPA in several applications has increased the substituted toxic chemicals such as bisphenol F (BPF) and bisphenol S (BPS). A native tropical freshwater cladoceran, Moina micrura, was used as a bioindicator to assess the adverse effects of bisphenol analogues at molecular, organ, individual and population levels. Bisphenol analogues significantly upregulated the expressions of stress-related genes, which are the haemoglobin and glutathione S-transferase genes, but the sex determination genes such as doublesex and juvenile hormone analogue genes were not significantly different. The results show that bisphenol analogues affect the heart rate and mortality rate of M. micrura. The 48-h lethal concentration (LC₅₀) values based on acute toxicity for BPA, BPF and BPS were 611.6 µg L^-1, 632.0 µg L^-1 and 819.1 µg L^-1, respectively. The order of toxicity based on the LC₅₀ and predictive non-effect concentration values were as follows: BPA > BPF > BPS. Furthermore, the incorporated method combining the responses throughout the organisation levels can comprehensively interpret the toxic effects of bisphenol analogues, thus providing further understanding of the toxicity mechanisms. Moreover, the output of this study produces a comprehensive ecotoxicity assessment, which provides insights for the legislators regarding exposure management and mitigation of bisphenol analogues in riverine ecosystems.

Natriuretic peptides potentiate cardiac hypertrophic response to noradrenaline in rats

Excessive activation of the sympathetic nervous system is involved in cardiovascular damage including cardiac hypertrophy. Natriuretic peptides are assumed to exert protective actions for the heart, alleviating hypertrophy and/or fibrosis of the myocardium. In contrast to this assumption, we show in the present study that both atrial and C-type natriuretic peptides (ANP and CNP) potentiate cardiac hypertrophic response to noradrenaline (NA) in rats. Nine-week-old male Wistar rats were continuously infused with subcutaneous 30 micro-g/h NA without or with persistent intravenous administration of either 1.0 micro-g/h ANP or CNP for 14 days. Blood pressure (BP) was recorded under an unrestrained condition by a radiotelemetry system. Cardiac hypertrophic response to NA was evaluated by heart weight/body weight (HW/BW) ratio and microscopic measurement of myocyte size of the left ventricle. Mean BP levels at the light and dark cycles rose by about 20mmHg following NA infusion for 14 days, with slight increases in HW/BW ratio and ventricular myocyte size. Infusions of ANP and CNP had no significant effects on mean BP in NA-infused rats, while two natriuretic peptides potentiated cardiac hypertrophic response to NA. Cardiac hypertrophy induced by co-administration of NA and ANP was attenuated by treatment with prazosin or atenolol. In summary, both ANP and CNP potentiated cardiac hypertrophic effect of continuously infused NA in rats, suggesting a possible pro-hypertrophic action of natriuretic peptides on the heart.

Regression of cardiac hypertrophy in health and disease: mechanisms and therapeutic potential

Left ventricular hypertrophy is a leading risk factor for cardiovascular morbidity and mortality. Although reverse ventricular remodelling was long thought to be irreversible, evidence from the past three decades indicates that this process is possible with many existing heart disease therapies. The regression of pathological hypertrophy is associated with improved cardiac function, quality of life and long-term health outcomes. However, less than 50% of patients respond favourably to most therapies, and the reversibility of remodelling is influenced by many factors, including age, sex, BMI and disease aetiology. Cardiac hypertrophy also occurs in physiological settings, including pregnancy and exercise, although in these cases, hypertrophy is associated with normal or improved ventricular function and is completely reversible postpartum or with cessation of training. Studies over the past decade have identified the molecular features of hypertrophy regression in health and disease settings, which include modulation of protein synthesis, microRNAs, metabolism and protein degradation pathways. In this Review, we summarize the evidence for hypertrophy regression in patients with current first-line pharmacological and surgical interventions. We further discuss the molecular features of reverse remodelling identified in cell and animal models, highlighting remaining knowledge gaps and the essential questions for future investigation towards the goal of designing specific therapies to promote regression of pathological hypertrophy.

Ser14-RPN6 Phosphorylation Mediates the Activation of 26S Proteasomes by cAMP and Protects against Cardiac Proteotoxic Stress in Mice

Background

A better understanding of the regulation of proteasome activities can facilitate the search for new therapeutic strategies. A cell culture study shows that cAMP-dependent protein kinase (PKA) activates the 26S proteasome by phosphorylating Ser14 of RPN6 (pS14-RPN6), but this discovery and its physiological significance remain to be established in vivo .

Methods

Male and female mice with Ser14 of Rpn6 mutated to Ala (S14A) or Asp (S14D) to respectively block or mimic pS14-Rpn6 were created and used along with cells derived from them. cAMP/PKA were manipulated pharmacologically. Ubiquitin-proteasome system (UPS) functioning was evaluated with the GFPdgn reporter mouse and proteasomal activity assays. Impact of S14A and S14D on proteotoxicity was tested in mice and cardiomyocytes overexpressing the misfolded protein R120G-CryAB (R120G).

Results

PKA activation increased pS14-Rpn6 and 26S proteasome activities in wild-type (WT) but not S14A embryonic fibroblasts (MEFs), adult cardiomyocytes (AMCMs), and mouse hearts. Basal 26S proteasome activities were significantly greater in S14D myocardium and AMCMs than in WT counterparts. S14D::GFPdgn mice displayed significantly lower myocardial GFPdgn protein but not mRNA levels than GFPdgn mice. In R120G mice, a classic model of cardiac proteotoxicity, basal myocardial pS14-Rpn6 was significantly lower compared with non- transgenic littermates, which was not always associated with reduction of other phosphorylated PKA substrates. Cultured S14D neonatal cardiomyocytes displayed significantly faster proteasomal degradation of R120G than WT neonatal cardiomyocytes. Compared with R120G mice, S14D/S14D::R120G mice showed significantly greater myocardial proteasome activities, lower levels of total and K48-linked ubiquitin conjugates and of aberrant CryAB protein aggregates, less reactivation of fetal genes and cardiac hypertrophy, and delays in cardiac malfunction.

Conclusions

This study establishes in animals that pS14-Rpn6 mediates the activation of 26S proteasomes by PKA and that the reduced pS14-Rpn6 is a key pathogenic factor in cardiac proteinopathy, thereby identifies a new therapeutic target to reduce cardiac proteotoxicity.

Aurintricarboxylic acid protects isoproterenol induced left ventricular hypertrophy by modulating TWEAK signaling

BACKGROUND

Cardiac hypertrophy is regarded as a compensation mechanism to overcome the increased workload. Aurintricarboxylic acid (ATA) is a derivative of quinomethanes and a selective inhibitor of TWEAK/Fn14 pathway. In this study, we investigated the effect of ATA on isoproterenol (ISO)-induced pathological cardiac hypertrophy.

METHODS

Cardiac hypertrophy in H9C2 cells was induced using ISO 20 μM dissolved in PBS. H9C2 cells were treated with ATA (5 µM, 10 µM, 20 µM) followed by ISO stimulation for 24 h. Male SD rats were injected ISO (5 mg/kg/day, s.c) for 21 days and followed by treatment with ATA (10 mg/kg, i.p.) for 14 days. Cardiac functions were assessed. After sacrifice, hearts were subjected to histopathological and western blot analysis.

RESULTS

In in-vitro results, upon ATA treatment, ICC results showed significant decrease in TWEAK and ANP expression. In in-vivo results, echocardiography showed significant restoration of cardiac function in ATA treated rats. Histopathological analysis showed a significant decrease in left ventricular wall thickness, cardiomyocytes width and reduced fibrosis in ATA treated rats. Western blotting showed decreased expression of the cardiac hypertrophy maker ANP, inflammatory markers including TWEAK and apoptotic markers after ATA treatment.

CONCLUSION

These findings suggested that the TWEAK/Fn14 pathway could be a potential target for therapeutic exploration in ISO induced cardiac hypertrophy. ATA, as an inhibitor of this pathway, exerted significant cardioprotective effect against ISO-induced cardiac hypertrophy in rats.

GDH promotes isoprenaline-induced cardiac hypertrophy by activating mTOR signaling via elevation of α-ketoglutarate level

Numerous studies reveal that metabolism dysfunction contributes to the development of pathological cardiac hypertrophy. While the abnormal lipid and glucose utilization in cardiomyocytes responding to hypertrophic stimuli have been extensively studied, the alteration and implication of glutaminolysis are rarely discussed. In the present work, we provide the first evidence that glutamate dehydrogenase (GDH), an enzyme that catalyzes conversion of glutamate into ɑ-ketoglutarate (AKG), participates in isoprenaline (ISO)-induced cardiac hypertrophy through activating mammalian target of rapamycin (mTOR) signaling. The expression and activity of GDH were enhanced in cultured cardiomyocytes and rat hearts following ISO treatment. Overexpression of GDH, but not its enzymatically inactive mutant, provoked cardiac hypertrophy. In contrast, GDH knockdown could relieve ISO-triggered hypertrophic responses. The intracellular AKG level was elevated by ISO or GDH overexpression, which led to increased phosphorylation of mTOR and downstream effector ribosomal protein S6 kinase (S6K). Exogenous supplement of AKG also resulted in mTOR activation and cardiomyocyte hypertrophy. However, incubation with rapamycin, an mTOR inhibitor, attenuated hypertrophic responses in cardiomyocytes. Furthermore, GDH silencing protected rats from ISO-induced cardiac hypertrophy. These findings give a further insight into the role of GDH in cardiac hypertrophy and suggest it as a potential target for hypertrophy-related cardiomyopathy.

Epigenetic Reader Bromodomain Containing Protein 2 Facilitates Pathological Cardiac Hypertrophy via Regulating the Expression of Citrate Cycle Genes

The bromodomain and extra-terminal domain proteins (BETs) family serve as epigenetic “readers”, which recognize the acetylated histones and recruit transcriptional regulator complexes to chromatin, eventually regulating gene transcription. Accumulating evidences demonstrate that pan BET inhibitors (BETi) confer protection against pathological cardiac hypertrophy, a precursor progress for developing heart failure. However, the roles of BET family members, except BRD4, remain unknown in pathological cardiac hypertrophy. The present study identified BRD2 as a novel regulator in cardiac hypertrophy, with a distinct mechanism from BRD4. BRD2 expression was elevated in cardiac hypertrophy induced by β-adrenergic agonist isoprenaline (ISO) in vivo and in vitro. Overexpression of BRD2 upregulated the expression of hypertrophic biomarkers and increased cell surface area, whereas BRD2 knockdown restrained ISO-induced cardiomyocyte hypertrophy. In vivo, rats received intramyocardial injection of adeno-associated virus (AAV) encoding siBRD2 significantly reversed ISO-induced pathological cardiac hypertrophy, cardiac fibrosis, and cardiac function dysregulation. The bioinformatic analysis of whole-genome sequence data demonstrated that a majority of metabolic genes, in particular those involved in TCA cycle, were under regulation by BRD2. Real-time PCR results confirmed that the expressions of TCA cycle genes were upregulated by BRD2, but were downregulated by BRD2 silencing in ISO-treated cardiomyocytes. Results of mitochondrial oxygen consumption rate (OCR) and ATP production measurement demonstrated that BRD2 augmented cardiac metabolism during cardiac hypertrophy. In conclusion, the present study revealed that BRD2 could facilitate cardiac hypertrophy through upregulating TCA cycle genes. Strategies targeting inhibition of BRD2 might suggest therapeutic potential for pathological cardiac hypertrophy and heart failure.

Plantago asiatica L. seeds extract protects against cardiomyocyte injury in isoproterenol- induced cardiac hypertrophy by inhibiting excessive autophagy and apoptosis in mice

BACKGROUND

Cardiac hypertrophy is the early stage of many heart diseases, such as coronary heart disease, hypertension, valvular dysfunction and cardiomyopathy. Cardiomyocyte autophagy and apoptosis play an important role in the process of cardiac hypertrophic response. Plantago asiatica L. seeds extract (PASE) is prepared from a traditional herbal medicine in Asia with tremendous pharmacological activities. However, whether PASE could relieve cardiac hypertrophy has not been elucidated. The present study is aimed to investigate the effect of PASE on cardiac hypertrophy and explore its potential underlying mechanism.

METHODS

Cardiac hypertrophy was induced in C57BL/6 mice by subcutaneous injection of isoproterenol (ISO) for two weeks. Meanwhile, the mice were intraperitoneally injected with PASE at dosages of 20, 40 and 80 mg/kg/day. Cardiac hypertrophy was evaluated by echocardiographic examination, haematoxylin and eosin staining and quantitative real-time polymerase chain reaction. Expressions of proteins involved in autophagy and apoptosis such as Beclin1, p62, LC3II, Bax, Bcl-2 and Cleaved-caspase-3 were detected by western blot analysis. Western blot, transient transfection, acridine orange staining, TUNEL staining and autophagy inducer were used to observe the effect and explore the mechanism of PASE on cardiomyocyte and H9c2 cells with excessive autophagy and apoptosis induced by ISO.

RESULTS

ISO induction for two weeks disturbed the myocardial contractility and cardiac function of left ventricles of mice. PASE treated mice showed significantly improved cardiac function indexes, including EF, FS, SV and CO, compared with the ISO group. Treatment with PASE also decreased the heart weight/body weight ratio and cardiomyocyte size, and downregulated the mRNA and protein expressions of hypertrophic markers ANP, BNP, and β-MHC. Furthermore, the changes of autophagy and apoptosis markers, such as LC3II, Beclin1, p62, Bcl-2, Bax and Cleaved-caspase-3 induced by ISO were resumed by PASE treatment. Consistently, PASE demonstrated similar effects on ISO-induced H9c2 cells as it did in vivo. In addition, PASE could counteract the increased autophagy induced by the autophagy inducer, rapamycin.

CONCLUSION

PASE attenuated ISO-induced cardiac hypertrophy in mice by inhibiting excessive autophagy and apoptosis in cardiomyocytes. The novel findings may pave the way for the clinical usage of PASE for the prevention of heart diseases related with cardiac hypertrophy.

Increased β-adrenergic stimulation augments vascular smooth muscle cell calcification via PKA/CREB signalling

In chronic kidney disease (CKD), hyperphosphatemia promotes medial vascular calcification, a process augmented by osteogenic transdifferentiation of vascular smooth muscle cells (VSMCs). VSMC function is regulated by sympathetic innervation, and these cells express α- and β-adrenergic receptors. The present study explored the effects of β2-adrenergic stimulation by isoproterenol on VSMC calcification. Experiments were performed in primary human aortic VSMCs treated with isoproterenol during control or high phosphate conditions. As a result, isoproterenol dose dependently up-regulated the expression of osteogenic markers core-binding factor α-1 (CBFA1) and tissue-nonspecific alkaline phosphatase (ALPL) in VSMCs. Furthermore, prolonged isoproterenol exposure augmented phosphate-induced calcification of VSMCs. Isoproterenol increased the activation of PKA and CREB, while knockdown of the PKA catalytic subunit α (PRKACA) or of CREB1 genes was able to suppress the pro-calcific effects of isoproterenol in VSMCs. β2-adrenergic receptor silencing or inhibition with the selective antagonist ICI 118,551 blocked isoproterenol-induced osteogenic signalling in VSMCs. The present observations imply a pro-calcific effect of β2-adrenergic overstimulation in VSMCs, which is mediated, at least partly, by PKA/CREB signalling. These observations may support a link between sympathetic overactivity in CKD and vascular calcification.

Post-translational modifications talk and crosstalk to class IIa histone deacetylases

Epigenetic modifications, such as histone or DNA modifications are key regulators of gene transcription and changes are often associated with maladaptive processes underlying cardiovascular disease. Epigenetic regulators therefore likely play a crucial role in cardiomyocyte homeostasis and facilitate the cellular adaption to various internal and external stimuli, responding to different intercellular and extracellular cues. Class IIa histone deacetylases are a class of epigenetic regulators that possess a myriad of post-transcriptional modification sites that modulate their activity in response to oxidative stress, altered catecholamine signalling or changes in the cellular metabolism. This review summaries the known reversible, post-translational modifications (PTMs) of class IIa histone deacetylases (HDACs) that ultimately drive transcriptional changes in homeostasis and disease. We also highlight the idea of a crosstalk of various PTMs on class IIa HDACs potentially leading to compensatory or synergistic effects on the class IIa HDAC-regulated cell behavior.

An Original Aspirin-Containing Carbonic Anhydrase 9 Inhibitor Overcomes Hypoxia-Induced Drug Resistance to Enhance the Efficacy of Myocardial Protection

PURPOSE

Hypoxic microenvironment plays a vital role in myocardial ischemia injury, generally leading to the resistance of chemotherapeutic drugs. This induces an intriguing study on mechanism exploration and prodrug design to overcome the hypoxia-induced drug resistance.

METHODS

In this study, we hypothesized that the overexpression of carbonic anhydrase 9 (CAIX) in myocardial cells is closely related to the drug resistance. Herein, bioinformatics analysis, gene knockdown, and overexpression assay certificated the correlation between CAIX overexpression and hypoxia. An original aspirin-containing CAIX inhibitor AcAs has been developed.

RESULTS

Based on the downregulation of CAIX level, both in vitro and in vivo, AcAs can overcome the acquired resistance and more effectively attenuate myocardial ischemia and hypoxia injury than that of aspirin. CAIX inhibitor is believed to recover the extracellular pH value so as to ensure the stable effect of aspirin.

CONCLUSION

Results indicate great potential of CAIX inhibitor for further application in myocardial hypoxia injury therapy.

Periplocymarin protects against myocardial fibrosis induced by β-adrenergic activation in mice

Periplocymarin is an effective component of Periplocae Cortex, which was wildly used as an ingredient in Traditional Chinese Medicine. Our group previously reported that periplocymarin exerted cardiotonic role via promoting calcium influx. However, its exact role in the pathogenesis of myocardial fibrosis has not been elucidated yet. The present study was aimed at determining the potential effect and underlying mechanism of periplocymarin in isoproterenol (ISO)-induced myocardial fibrosis. C57BL/6 mice were subcutaneously injected with ISO (5 mg/kg/day) or saline for 1 week. The early-to-atrial wave ratio (E/A ratio) measured by echocardiography revealed that ISO-induced heart stiffness was remarkably reversed by administration of periplocymarin (5 mg/kg/day). Masson trichrome staining exhibited that treatment of periplocymarin reduced the excessive deposition of extracellular matrix (ECM). Further investigations employing real-time PCR and western blot demonstrated that periplocymarin suppressed the expression of fibrosis related genes (Col1a1, Col3a1, Acta2 and Tgfb1) and proteins (Collagen I, Collagen III, α-SMA and TGF-β1) induced by ISO. Metabolomics analysis demonstrated that periplocymarin ameliorated the disorders triggered by ISO and many of the differential metabolic substances were involved in amino acid, glucose and lipid metabolism. Further analysis using network pharmacology revealed that three key genes, namely NOS2, NOS3 and Ptgs2, may be the potential targets of periplocymarin and responsible for the disorders. Validation using heart tissues showed that the mRNA expression of NOS3 was decreased while Ptgs2 was increased upon ISO treatment, which were reversed by periplocymarin. Moreover, the expression of COX-2 (Ptgs2 encoded protein) was consistent with the aspect of Ptgs2 mRNA, while eNOS (NOS3 encoded protein) expression was unchanged. In vitro studies exhibited that periplocymarin exerts anti-fibrotic function via regulating at least eNOS and COX-2 in cardiomyocyte. Taken together, periplocymarin protects against myocardial fibrosis induced by β-adrenergic activation, the potential mechanism was that periplocymarin targeted on, at least eNOS and COX-2, to improve the metabolic processes of cardiomyocyte and thus attenuated the myocardial fibrosis. Our study highlighted that periplocymarin is a potential therapeutic agent for the prevention of myocardial fibrosis.

CaMKII and PKA-dependent phosphorylation co-regulate nuclear localization of HDAC4 in adult cardiomyocytes

Nuclear histone deacetylase 4 (HDAC4) represses MEF2-mediated transcription, implicated in the development of heart failure. CaMKII-dependent phosphorylation drives nucleus-to-cytoplasm HDAC4 shuttling, but protein kinase A (PKA) is also linked to HDAC4 translocation. However, the interplay of CaMKII and PKA in regulating adult cardiomyocyte HDAC4 translocation is unclear. Here we sought to determine the interplay of PKA- and CaMKII-dependent HDAC4 phosphorylation and translocation in adult mouse, rabbit and human ventricular myocytes. Confocal imaging and protein analyses revealed that inhibition of CaMKII-but not PKA, PKC or PKD-raised nucleo-to-cytoplasmic HDAC4 fluorescence ratio (F_Nuc/F_Cyto) by ~ 50%, indicating baseline CaMKII activity that limits HDAC4 nuclear localization. Further CaMKII activation (via increased extracellular [Ca²⁺], high pacing frequencies, angiotensin II or overexpression of CaM or CaMKIIδC) led to significant HDAC4 nuclear export. In contrast, PKA activation by isoproterenol or forskolin drove HDAC4 into the nucleus (raising F_Nuc/F_Cyto by > 60%). These PKA-mediated effects were abolished in cells pretreated with PKA inhibitors and in cells expressing mutant HDAC4 in S265/266A mutant. In physiological conditions where both kinases are active, PKA-dependent nuclear accumulation of HDAC4 was predominant in the very early response, while CaMKII-dependent HDAC4 export prevailed upon prolonged stimuli. This orchestrated co-regulation was shifted in failing cardiomyocytes, where CaMKII-dependent effects predominated over PKA-dependent response. Importantly, human cardiomyocytes showed similar CaMKII- and PKA-dependent HDAC4 shifts. Collectively, CaMKII limits nuclear localization of HDAC4, while PKA favors HDAC4 nuclear retention and S265/266 is essential for PKA-mediated regulation. These pathways thus compete in HDAC4 nuclear localization and transcriptional regulation in cardiac signaling.

Mechanisms Underlying the Cardioprotection of YangXinDingJi Capsule against Myocardial Ischemia in Rats

Background

YangXinDingJi (YXDJ) capsule is one of traditional Chinese medicines (TCMs) derived from Zhigancao decoction, which is usually used for the treatment of cardiovascular disease in China. Aim of the Study. Cardiovascular events are one of the leading causes of death worldwide. Myocardial ischemia (MI) severely reduces myocyte longevity and function. The YangXinDingJi (YXDJ) capsule has been used in the treatment of clinical cardiac disease in China. Nevertheless, the underlying cellular mechanisms for the benefits to heart function resulting from the use of this capsule are still unclear. The aim of this study was to evaluate the protective effects of the YXDJ on isoprenaline-induced MI in rats and to clarify its underlying myocardial protective mechanisms based on L-type calcium channels and myocardial contractility.

Materials and Methods

Rats were randomly divided into five groups with ten rats in each group: (1) control; (2) ISO-induced model; (3) high-dose YXDJ (2.8 g/kg/day intraperitoneally for five days), (4) low-dose YXDJ (1.4 g/kg/day for five days); and (5) verapamil (n = 10 in each group). Isoproterenol (ISO) was injected subcutaneously for two consecutive days to induce the rat model of MI. Heart and biochemical parameters were obtained. The patch-clamp technique was used to observe the regulatory effects of YXDJ on the L-type calcium current (I_Ca-L) in isolated cardiomyocytes. An IonOptix MyoCam detection system was used to observe the contractility of YXDJ on isolated cardiomyocytes.

Results

YXDJ caused a significant improvement in pathological heart morphology and alleviated oxidative stress and inflammatory responses. Exposure to YXDJ caused a decrease in blockade of I_Ca-L in a concentration-dependent manner.

Conclusions

The results indicate that YXDJ significantly inhibited inflammatory cytokine expressions, oxidative stress, and L-type Ca²⁺ channels, and decreased contractility in isolated rat cardiomyocytes. These findings may be relevant to the cardioprotective efficacy of YXDJ.

Key Player in Cardiac Hypertrophy, Emphasizing the Role of Toll-Like Receptor 4

Toll-like receptor 4 (TLR4), a key pattern recognition receptor, initiates the innate immune response and leads to chronic and acute inflammation. In the past decades, accumulating evidence has implicated TLR4-mediated inflammatory response in regulation of myocardium hypertrophic remodeling, indicating that regulation of the TLR4 signaling pathway may be an effective strategy for managing cardiac hypertrophy's pathophysiology. Given TLR4's significance, it is imperative to review the molecular mechanisms and roles underlying TLR4 signaling in cardiac hypertrophy. Here, we comprehensively review the current knowledge of TLR4-mediated inflammatory response and its interaction ligands and co-receptors, as well as activation of various intracellular signaling. We also describe the associated roles in promoting immune cell infiltration and inflammatory mediator secretion, that ultimately cause cardiac hypertrophy. Finally, we provide examples of some of the most promising drugs and new technologies that have the potential to attenuate TLR4-mediated inflammatory response and prevent or reverse the ominous cardiac hypertrophy outcomes.

Isoproterenol Triggers ROS/P53/S100-A9 Positive Feedback to Aggravate Myocardial Damage Associated with Complement Activation

Negative feelings caused by external stress can continually agonize adrenergic receptors via promoting catecholamine secretion, causing cardiovascular disease. This study examines the mechanism by which persistent β-adrenergic receptor agonism induces myocardial injury. A rat model of cardiac injury was herein established using isoproterenol (5 mg/kg, continuous intraperitoneal injection for 3 days), and multiomics technology combined with metabolomics and proteomics was used to explore the mechanism by which persistent β-adrenergic receptor agonism induces myocardial injury. The mechanism underlying this phenomenon was further verified at the cellular level. Isoproterenol-induced persistent β-adrenergic receptor agonism promoted the release of reactive oxygen species, and P53, S100-A9, and complement 3 were shown to be involved in complement system activation pathways. Our data have demonstrated that isoproterenol could trigger ROS/P53/S100-A9 positive feedback to aggravate myocardial damage associated with complement activation.

Cardiomyocyte Proteome Remodeling due to Isoproterenol-Induced Cardiac Hypertrophy during the Compensated Phase

PURPOSE

Although the pathophysiological response of cardiac tissue to pro-hypertrophic stimulus is well characterized, a comprehensive characterization of the molecular events underlying the pathological hypertrophy in cardiomyocytes during the early compensated cardiac hypertrophy is currently lacking.

EXPERIMENTAL DESIGN

A quantitative label-free proteomic analysis of cardiomyocytes isolated was conducted from mice treated subcutaneously with isoproterenol (ISO) during 7 days in comparison with cardiomyocytes from control animals (CT).

RESULTS

Canonical pathway analysis of dysregulated proteins indicated that ISO-hypertrophy drives the activation of actin cytoskeleton and integrin-linked kinase (ILK) signaling, and inhibition of the sirtuin signaling. Alteration in cardiac contractile function and calcium signaling are predicted as downstream effects of ISO-hypertrophy probably due to the upregulation of key elements such as myosin-7 (MYH7). Confocal microscopy corroborated that indeed ISO-treatment led to increased abundance of MYH7. Potential early markers for cardiac hypertrophy as APBB1, GOLGA4, HOOK1, KATNA1, KIFBP, MAN2B2, and SLC16A1 are also reported.

CONCLUSIONS AND CLINICAL RELEVANCE

The data consist in a complete molecular mapping of ISO-induced compensated cardiac hypertrophy model at cardiomyocyte level. Marker candidates reported may assist early diagnosis of cardiac hypertrophy and ultimately heart failure.

[6]-Gingerol Ameliorates ISO-Induced Myocardial Fibrosis by Reducing Oxidative Stress, Inflammation, and Apoptosis through Inhibition of TLR4/MAPKs/NF-κB Pathway

SCOPE

[6]-Gingerol is one of the primary pungent constituents of ginger. While [6]-gingerol has many pharmacological effects, its benefits for myocardial fibrosis, including its exact role and underlying mechanisms, remain largely unexplored. The present study is designed to characterize the cardio-protective effects of [6]-gingerol in myocardial fibrosis mice and possible underlying mechanisms.

METHODS AND RESULTS

Mice are subcutaneously injected with isoproterenol (ISO, 10 mg kg^-1 ) and gavaged with [6]-gingerol (10, 20 mg kg^-1 day^-1 ) for 14 days. Pathological alterations, fibrosis, oxidative stress, inflammation response, and apoptosis are examined. In ISO-induced myocardial fibrosis, [6]-gingerol treatment decreases the J-point, heart rate, cardiac weight index, left ventricle weight index, creatine kinase (CK), and lactate dehydrogenase serum levels, calcium concentration, reactive oxygen species, malondialdehyde, and glutathione disulfide (GSSG), and increases levels of superoxide dismutase, catalase, glutathione, and GSH/GSSG. Further, [6]-gingerol improved ISO-induced morphological pathologies, inhibited inflammation and apoptosis, and suppressed the toll-like receptor-4 (TLR4)/mitogen-activated protein kinases (MAPKs)/nuclear factor κB (NF-κB) signaling pathways.

CONCLUSION

The protective effect of [6]-gingerol in mice with ISO-induced myocardial fibrosis may be related to the inhibition of oxidative stress, inflammation, and apoptosis, potentially through the TLR4/MAPKs/NF-κB signaling pathway.

The Role of Oxidative Stress in Cardiac Disease: From Physiological Response to Injury Factor

Reactive oxygen species (ROS) are highly reactive chemical species containing oxygen, controlled by both enzymatic and nonenzymatic antioxidant defense systems. In the heart, ROS play an important role in cell homeostasis, by modulating cell proliferation, differentiation, and excitation-contraction coupling. Oxidative stress occurs when ROS production exceeds the buffering capacity of the antioxidant defense systems, leading to cellular and molecular abnormalities, ultimately resulting in cardiac dysfunction. In this review, we will discuss the physiological sources of ROS in the heart, the mechanisms of oxidative stress-related myocardial injury, and the implications of experimental studies and clinical trials with antioxidant therapies in cardiovascular diseases.

In Mice Subjected to Chronic Stress, Exogenous cBIN1 Preserves Calcium-Handling Machinery and Cardiac Function

Heart failure is an important, and growing, cause of morbidity and mortality. Half of patients with heart failure have preserved ejection fraction, for whom therapeutic options are limited. Here we report that cardiac bridging integrator 1 gene therapy to maintain subcellular membrane compartments within cardiomyocytes can stabilize intracellular distribution of calcium-handling machinery, preserving diastolic function in hearts stressed by chronic beta agonist stimulation and pressure overload. This study identifies that maintenance of intracellular architecture and, in particular, membrane microdomains at t-tubules, is important in the setting of sympathetic stress. Stabilization of membrane microdomains may be a pathway for future therapeutic development.

Binge Alcohol Exposure in Adolescence Impairs Normal Heart Growth

Background

Approximately 1 in 6 adolescents report regular binge alcohol consumption, and we hypothesize it affects heart growth during this period.

Methods and Results

Adolescent, genetically diverse, male Wistar rats were gavaged with water or ethanol once per day for 6 days. In vivo structure and function were assessed before and after exposure. Binge alcohol exposure in adolescence significantly impaired normal cardiac growth but did not affect whole‐body growth during adolescence, therefore this pathology was specific to the heart. Binge rats also exhibited signs of accelerated pathological growth (concentric cellular hypertrophy and thickening of the myocardial wall), suggesting a global reorientation from physiologic to pathologic growth. Binge rats compensated for their smaller filling volumes by increasing systolic function and sympathetic stimulation. Consequently, binge alcohol exposure increased PKA (protein kinase A) phosphorylation of troponin I, inducing myofilament calcium desensitization. Binge alcohol also impaired in vivo relaxation and increased titin‐based cellular stiffness due to titin phosphorylation by PKCα (protein kinase C α). Mechanistically, alcohol inhibited extracellular signal‐related kinase activity, a nodal signaling kinase activating physiology hypertrophy. Thus, binge alcohol exposure depressed genes involved in growth. These cardiac structural alterations from binge alcohol exposure persisted through adolescence even after cessation of ethanol exposure.

Conclusions

Alcohol negatively impacts function in the adult heart, but the adolescent heart is substantially more sensitive to its effects. This difference is likely because adolescent binge alcohol impedes the normal rapid physiological growth and reorients it towards pathological hypertrophy. Many adolescents regularly binge alcohol, and here we report a novel pathological consequence as well as mechanisms involved.

The role and molecular mechanism of epigenetics in cardiac hypertrophy

Cardiac hypertrophy is a significant risk factor for cardiovascular disease, including heart failure, arrhythmia, and sudden death. Cardiac hypertrophy involves both embryonic gene expression and transcriptional reprogramming, which are tightly regulated by epigenetic mechanisms. An increasing number of studies have demonstrated that epigenetics plays an influential role in the occurrence and development of cardiac hypertrophy. Here, we summarize the latest research progress on epigenetics in cardiac hypertrophy involving DNA methylation, histone modification, and non-coding RNA, to help understand the mechanism of epigenetics in cardiac hypertrophy. The expression of both embryonic and functional genes can be precisely regulated by epigenetic mechanisms during cardiac hypertrophy, providing a substantial number of therapeutic targets. Thus, epigenetic treatment is expected to become a novel therapeutic strategy for cardiac hypertrophy. According to the research performed to date, epigenetic mechanisms associated with cardiac hypertrophy remain far from completely understood. Therefore, epigenetic mechanisms require further exploration to improve the prevention, diagnosis, and treatment of cardiac hypertrophy.

The proarrhythmic features of pathological cardiac hypertrophy in neonatal rat ventricular cardiomyocyte cultures

Different factors may trigger arrhythmias in diseased hearts, including fibrosis, cardiomyocyte hypertrophy, hypoxia, and inflammation. This makes it difficult to establish the relative contribution of each of them to the occurrence of arrhythmias. Accordingly, in this study, we used an in vitro model of pathological cardiac hypertrophy (PCH) to investigate its proarrhythmic features and the underlying mechanisms independent of fibrosis or other PCH-related processes. Neonatal rat ventricular cardiomyocyte (nr-vCMC) monolayers were treated with phorbol 12-myristate 13-acetate (PMA) to create an in vitro model of PCH. The electrophysiological properties of PMA-treated and control monolayers were analyzed by optical mapping at day 9 of culture. PMA treatment led to a significant increase in cell size and total protein content. It also caused a reduction in sarcoplasmic/endoplasmic reticulum Ca²⁺ ATPase 2 level (32%) and an increase in natriuretic peptide A (42%) and α1-skeletal muscle actin (34%) levels, indicating that the hypertrophic response induced by PMA was, indeed, pathological in nature. PMA-treated monolayers showed increases in action potential duration (APD) and APD dispersion, and a decrease in conduction velocity (CV; APD₃₀ of 306 ± 39 vs. 148 ± 18 ms, APD₃₀ dispersion of 85 ± 19 vs. 22 ± 7 and CV of 10 ± 4 vs. 21 ± 2 cm/s in controls). Upon local 1-Hz stimulation, 53.6% of the PMA-treated cultures showed focal tachyarrhythmias based on triggered activity (n = 82), while the control group showed 4.3% tachyarrhythmias (n = 70). PMA-treated nr-vCMC cultures may, thus, represent a well-controllable in vitro model for testing new therapeutic interventions targeting specific aspects of hypertrophy-associated arrhythmias.NEW & NOTEWORTHY Phorbol 12-myristate 13-acetate (PMA) treatment of neonatal rat ventricular cardiomyocytes (nr-vCMCs) led to induction of many significant features of pathological cardiac hypertrophy (PCH), including action potential duration prolongation and dispersion, which provided enough time and depolarizing force for formation of early afterdepolarization (EAD)-induced focal tachyarrhythmias. PMA-treated nr-vCMCs represent a well-controllable in vitro model, which mostly resembles to moderate left ventricular hypertrophy (LVH) rather than severe LVH, in which generation of a reentry is the putative mechanism of its arrhythmias.

Role of CyPA in cardiac hypertrophy and remodeling

Pathological cardiac hypertrophy is a complex process and eventually develops into heart failure, in which the heart responds to various intrinsic or external stress, involving increased interstitial fibrosis, cell death and cardiac dysfunction. Studies have shown that oxidative stress is an important mechanism for this maladaptation. Cyclophilin A (CyPA) is a member of the cyclophilin (CyPs) family. Many cells secrete CyPA to the outside of the cells in response to oxidative stress. CyPA from blood vessels and the heart itself participate in a variety of signaling pathways to regulate the production of reactive oxygen species (ROS) and mediate inflammation, promote cardiomyocyte hypertrophy and proliferation of cardiac fibroblasts, stimulate endothelial injury and vascular smooth muscle hyperplasia, and promote the dissolution of extracellular matrix (ECM) by activating matrix metalloproteinases (MMPs). The events triggered by CyPA cause a decline of diastolic and systolic function and finally lead to the occurrence of heart failure. This article aims to introduce the role and mechanism of CyPA in cardiac hypertrophy and remodeling, and highlights its potential role as a disease biomarker and therapeutic target.

Isosteviol prevents the development of isoprenaline‑induced myocardial hypertrophy

Isosteviol sodium (STVNa), which is a derivate of the natural sweet-tasting glycoside stevioside, has recently been developed and it has been determined that this compound exhibits neuro- and cardio-protective properties. In the current study, whether STVNa interferes with the development of cardiac hypertrophy, which is induced by isoprenaline (Iso), was investigated in an experimental rat model. Rats were treated with a vehicle (0.9% NaCl; control), isoprenaline (Iso; 5 mg/kg) or Iso (5 mg/kg) with STVNa (4 mg/kg; Iso + STVNa). Cardiomyocytes were isolated using enzymatic dissociation and were treated with 5 µM Iso for 24 h and co-treated with 5 µM STVNa. Brain natriuretic peptide (BNP) mRNA expression was determined using PCR analysis. Cell surface area, intracellular reactive oxygen species (ROS), mitochondrial transmembrane potential (ΔΨm), cytoplasmic Ca²⁺ and Ca²⁺ and contractile function were examined using a laser scanning confocal microscope. The current study demonstrated that STVNa inhibited Iso-induced cardiac hypertrophy by inhibiting cardiomyocyte size. STVNa significantly reduced cell surface area and decreased BNP mRNA expression in ventricular cardiomyocyte Iso-induced hypertrophy. STVNa was also revealed to restore ΔΨm and reduce ROS generation and intracellular Ca²⁺ concentration when compared with the Iso-treated group. Additionally, STVNa preserved Ca²⁺ transients in hypertrophic cardiomyocytes. In conclusion, the present study demonstrated that STVNa protects against Iso-induced myocardial hypertrophy by reducing oxidative stress, restoring ΔΨm and maintaining Ca²⁺ homeostasis.

The contribution of phosphodiesterases to cardiac dysfunction in rats with metabolic syndrome induced by a high-carbohydrate diet

Metabolic syndrome (MetS) is a cluster of risk factors, including insulin resistance among others, underlying the development of diabetes and (or) cardiovascular diseases. Studies show a close relationship between cardiac dysfunction and abnormal cAMP catabolism, which contributes to pathological remodelling. Stimulating the synthesis of cAMP via suppression of phosphodiesterases (PDEs) has positive therapeutic effects. Therefore, we examined the role of PDEs on cardiac dysfunction in high-carbohydrate diet-induced MetS rats. We first demonstrated significantly high expression levels of PDE3 and PDE4, the most highly expressed subtypes, together with depressed cAMP levels in heart tissue from MetS rats. Second, we demonstrated the activity of these PDEs by using either their basal or PDE inhibitor-induced intracellular levels of cAMP and Ca²⁺, the transient intracellular Ca²⁺ changes under electrical stimulation, isometric contractions in papillary muscle strips and some key signalling proteins (such as RyR2, PLN, PP1A, and PKA) are responsible for the Ca²⁺ homeostasis in isolated cardiomyocytes from MetS rats. The clear recovery in decreased basal cAMP levels, increased protein expression levels of PDE3 and PDE4, and positive responses in the altered Ca²⁺ homeostasis to PDE inhibitors as seen in our study can provide important insights about the roles of activated PDEs in depressed contractile activity in hearts from MetS rats.

Protective effect of histone methyltransferase NSD3 on ISO-induced cardiac hypertrophy

Nuclear receptor-binding SET domain 3 (NSD3) is a lysine methyltransferase that plays important roles in multiple biological activities; however; its potential roles in the cardiovascular system remain unknown. In this study, we found that NSD3 expression is reduced by isoproterenol (ISO) stimuli both in vitro and in vivo. Overexpression of NSD3 attenuates ISO-induced cardiomyocyte hypertrophy. Mechanistically, ISO treatment decreases H3K27me2/3 modifications on the atrial natriuretic factor (ANF) promoter by suppressing NSD3 and inhibits the association between NSD3 and bromodomain-containing protein 4 (BRD4), thus suppressing the BRD4-mediated H3K27ac modifications, which ultimately promote ANF transcription and cardiomyocyte hypertrophy. In conclusion, NSD3 decreases ANF expression and, thereby, attenuates ISO-induced cardiomyocyte hypertrophy.

Chrysophanol attenuated isoproterenol-induced cardiac hypertrophy by inhibiting Janus kinase 2/signal transducer and activator of transcription 3 signaling pathway

Cardiac hypertrophy is a common pathological change found in various cardiovascular diseases. Although it has long been recognized as an important risk factor responsible for heart failure, there is still a lack of effective treatments in clinic. Chrysophanol is a natural compound with multiple biological activities and protective roles in the cardiovascular system. However, its potential effect on cardiac hypertrophy remains unclear. In the current study, we found that chrysophanol could protect against isoproterenol (ISO)-induced cardiac hypertrophy both in vitro and in vivo. Increase of cell surface and hypertrophic marker expression induced by ISO in neonatal rat cardiomyocytes was downregulated by chrysophanol. Moreover, chrysophanol ameliorated the abnormal changes of cardiac structure and function in rats subjected to ISO injection, as shown by echocardiography and morphometry measurements. Further mechanistical investigation demonstrated that chrysophanol inhibited phosphorylation of Janus kinase 2 (JAK2) and signal transducer and activator of transcription 3 (STAT3) induced by ISO. Nuclear translocation of STAT3 and transcription of downstream genes promoted by ISO treatment were also remarkably suppressed by chrysophanol. Taken together, our findings revealed that chrysophanol attenuated ISO-induced cardiac hypertrophy by inhibiting JAK2/STAT3 signaling pathway. Chrysophanol may be a potential candidate compound for the prevention and treatment of hypertrophy-related cardiomyopathy.

Myofibroblast β2 adrenergic signaling amplifies cardiac hypertrophy in mice

Abnormal β-adrenergic signaling plays a central role in human heart failure. In mice, chronic β-adrenergic receptor (βAR) stimulation elicits cardiac hypertrophy. It has been reported that cultured cardiac fibroblasts express βAR; however, the functional in vivo requirement of βAR signaling in cardiac fibroblasts during the development of cardiac hypertrophy remains elusive. β2AR null mice exhibited attenuated hypertrophic responses to chronic βAR stimulation upon continuous infusion of an agonist, isoprenaline (ISO), compared to those in wildtype controls, suggesting that β2AR activation in the heart induces pro-hypertrophic effects in mice. Since β2AR signaling is protective in cardiomyocytes, we focused on β2AR signaling in cardiac myofibroblasts. To determine whether β2AR signaling in myofibroblasts affects cardiac hypertrophy, we generated myofibroblast-specific transgenic mice (TG) with the catalytic subunit of protein kinase A (PKAcα) using Cre-loxP system. Myofibroblast-specific PKAcα overexpression resulted in enhanced heart weight normalized to body weight ratio, associated with an enlargement of cardiomyocytes at 12 weeks of age, indicating that myofibroblast-specific activation of PKA mediates cardiac hypertrophy in mice. Neonatal rat cardiomyocytes stimulated with conditioned media from TG cardiac fibroblasts likewise exhibited significantly more growth than those from controls. Thus, β2AR signaling in myofibroblasts plays a substantial role in ISO-induced cardiac hypertrophy, possibly due to a paracrine effect. β2AR signaling in cardiac myofibroblasts may represent a promising target for development of novel therapies for cardiac hypertrophy.

AdipoRon prevents l-thyroxine or isoproterenol-induced cardiac hypertrophy through regulating the AMPK-related pathway

Cardiac hypertrophy is a risk factor which can intrigue heart failure. In the present study, we explored whether AdipoRon attenuates isoprenaline (ISO) or l-thyroxine-induced cardiac hypertrophy in Sprague-Dawley (SD) rats and whether the anti-hypertrophy effect is mediated by AMPK-related pathway. Here, cardiac hypertrophy was induced by injection of l-thyroxine or ISO in SD rats. In the treatment group, AdipoRon was co-administered. We examined the effects of AdipoRon on cardiac hypertrophy and hypertrophy signaling pathway. The weight of SD rats was recorded every day. Rats were killed for collection of blood and heart under anesthesia. The left heart weight and heart weight were weighed. Paraffin-embedded heart tissue regions (4 μm) were stained with hematoxylin and eosin or Masson to detect left heart hypertrophy and myocardial fibrosis. The serum BNP levels were determined by using an enzyme-linked immunosorbent assay. The mRNA levels of ANP, BNP, PGC-1α, and ERRα were evaluated by real-time PCR analysis. The protein expression levels of PGC-1α, ERRα, and pAMPK/AMPK were determined by western blot analysis. The results showed that AdipoRon significantly reversed heart weight (HW)/body weight (BW) ratio, left ventricular (LV)/BW ratio, serum BNP level and the mRNA level of ANP and BNP induced by ISO or l-thyroxine. ISO or l-thyroxine reduced both the mRNA level and protein level of ERRα and PGC-1α, and also reduced the protein level of pAMPK/AMPK. However, AdipoRon reversed ISO or l-thyroxine-induced changes of pAMPK/AMPK, ERRα, and PGC-1α. Our data indicated that the effects of AdipoRon are mediated partly by activating AMPK-related pathway, and AdipoRon plays a potential role in the prevention of cardiac hypertrophy.

Adrenergic Regulation of Drp1-Driven Mitochondrial Fission in Cardiac Physio-Pathology

Abnormal mitochondrial morphology, especially fragmented mitochondria, and mitochondrial dysfunction are hallmarks of a variety of human diseases including heart failure (HF). Although emerging evidence suggests a link between mitochondrial fragmentation and cardiac dysfunction, it is still not well described which cardiac signaling pathway regulates mitochondrial morphology and function under pathophysiological conditions such as HF. Mitochondria change their shape and location via the activity of mitochondrial fission and fusion proteins. This mechanism is suggested as an important modulator for mitochondrial and cellular functions including bioenergetics, reactive oxygen species (ROS) generation, spatiotemporal dynamics of Ca²⁺ signaling, cell growth, and death in the mammalian cell- and tissue-specific manners. Recent reports show that a mitochondrial fission protein, dynamin-like/related protein 1 (DLP1/Drp1), is post-translationally modified via cell signaling pathways, which control its subcellular localization, stability, and activity in cardiomyocytes/heart. In this review, we summarize the possible molecular mechanisms for causing post-translational modifications (PTMs) of DLP1/Drp1 in cardiomyocytes, and further discuss how these PTMs of DLP1/Drp1 mediate abnormal mitochondrial morphology and mitochondrial dysfunction under adrenergic signaling activation that contributes to the development and progression of HF.

JMJD3 inhibition protects against isoproterenol-induced cardiac hypertrophy by suppressing β-MHC expression

Jumonji domain-containing protein D3 (JMJD3), a histone 3 lysine 27 (H3K27) demethylase, has been extensively studied for their participation in development, cellular physiology and a variety of diseases. However, its potential roles in cardiovascular system remain unknown. In this study, we found that JMJD3 played a pivotal role in the process of cardiac hypertrophy. JMJD3 expression was elevated by isoproterenol (ISO) stimuli both in vitro and in vivo. Overexpression of wild-type JMJD3, but not the demethylase-defective mutant, promoted cardiomyocyte hypertrophy, as implied by increased cardiomyocyte surface area and the expression of hypertrophy marker genes. In contrary, JMJD3 silencing or its inhibitor GSK-J4 suppressed ISO-induced cardiac hypertrophy. Mechanistically, JMJD3 was recruited to demethylate H3K27me3 at the promoter of β-MHC to promote its expression and cardiac hypertrophy. Thus, our results reveal that JMJD3 may be a key epigenetic regulator of β-MHC expression in cardiomyocytes and a potential therapeutic target for cardiac hypertrophy.

Myocardial hypertrophy associated with long-term phenylpropanolamine use in a dog

CASE DESCRIPTION A 9-year-old spayed female Dalmatian was examined because of progressive pelvic limb paraparesis. CLINICAL FINDINGS The dog had a history of chronic urinary incontinence and had been treated with phenylpropanolamine (PPA) for almost 8.5 years. Intervertebral disk disease at T12-13 was diagnosed, and a hemilaminectomy was performed. Three days after surgery, the dog developed a ventricular tachyarrhythmia. Severe left and mild right ventricular hypertrophy were detected by echocardiography. TREATMENT AND OUTCOME The arrhythmia was controlled with sotalol. Phenylpropanolamine administration was discontinued immediately before surgery and was not resumed. Heart rate and rhythm and blood pressure were within reference limits, and the ventricular hypertrophy had almost completely resolved 5 months later. Sotalol administration was discontinued. Shortly after the 5-month recheck evaluation, PPA administration was resumed, albeit at a lower dosage than that before surgery, for control of urinary incontinence. At the 10-month recheck evaluation, the dog was hypertensive and ventricular hypertrophy had recurred. Discontinuation of PPA administration was recommended but not heeded. The dog developed marked azotemia 1.5 years after surgery, which was managed by the referring veterinarian, and was subsequently lost to follow-up. CLINICAL RELEVANCE The fact that the ventricular hypertrophy almost completely resolved when PPA administration was discontinued and then recurred after it was resumed strongly suggested the drug was an important contributing factor to the cardiac disease of this patient. Patients receiving PPA on a long-term basis should be frequently monitored for cardiac disease, and use of other adrenergic receptor agonists should be avoided in such patients.

Myocardial Strain and Stiffness Parameters as a Novel Target of Antihypertensive Treatment

In the review, the clinical significance of increased myocardial stiffness and strain impairment in the settings of arterial hypertension is considered. The mechanisms of increasing myocardial stiffness as a part of hypertensive heart disease are presented. Particular attention is paid to the role of the sympathetic nervous system activation as one of the triggers that induce the connective tissue alteration of cardiac interstitium. The possibilities of echocardiography in the early noninvasive detection of myocardial strain abnormalities are discussed. New ultrasound parameters for describing stiffness properties of the heart are presented. From the evidence-based medicine point of view, the prognostic significance of increasing myocardial stiffness as a risk factor of the adverse cardiovascular events, as well as the possibility of its management with different antihypertensive drugs, is considered. Finally, there are presented clinical trials data, indicating high potential of the highly selective ^1-adrenoblocker bisoprolol for of correction myocardial stiffness and strain impairment.

Effect of β-adrenergic receptor agents on cardiac structure and function and whole-body gene expression in Daphnia magna

Propranolol (PRO), a human β-AR (β-adrenergic receptor) antagonist, is considered to result in specific effects in a non-target species, D. magna, based on our previous studies. The present study investigated the effects of β-AR agents, including an antagonist and agonist using pharmacologically relevant endpoints as well as a more holistic gene expression approach to reveal the impacts and potential mode of actions (MOAs) in the model non-target species. Results show that the responses in cardiac endpoints and gene expression in D. magna are partially similar but distinguishable from the observations in different organisms. No effect was observed on heart size growth in PRO and isoprenaline (ISO) exposure. The contraction capacity of the heart was decreased in ISO exposure, and the heart rate was decreased in PRO exposure. Time-series exposures showed different magnitudes of effect on heart rate and gene expression dependent on the type of chemical exposure. Significant enrichment of gene families involved in protein metabolism and biotransformation was observed within the differentially expressed genes, and we also observed differential expression in juvenile hormone-inducible proteins in ISO and PRO exposure, which is suspected of having endocrine disruption potential. Taken together, deviation between the effects of PRO and ISO in D. magna and other organisms suggests dissimilarity in MOAs or attributes of target bio-molecules between species. Additionally, PRO and ISO may act as endocrine disruptors based on the gene expression observation. Results in the present study confirm that it is challenging to predict ecological impact of active pharmaceutical ingredients (APIs) based on the available data acquired through human-focused studies. Furthermore, the present study provided unique data and a case study on the impact of APIs in a non-target organism.

Dimethyl fumarate interferes with MyD88-dependent toll-like receptor signalling pathway in isoproterenol-induced cardiac hypertrophy model

Objectives

To investigate the effect of dimethyl fumarate (DMF) on Toll-like receptor (TLR) signalling pathway in isoproterenol (ISO)-induced cardiac hypertrophy in rats.

Methods

Sixty adult male Sprague-Dawley rats were randomly allocated into three groups. group I: rats received the vehicles only; group II: rats were treated with ISO (5 mg/kg per day S.C.) to induce cardiac hypertrophy for 7 days; and group III: rats were given DMF (25 mg/kg per 12 h P.O.) for 28 days, and at the last 7 days, they were treated with ISO (5 mg/kg per day S.C.).

Key findings

Pretreatment with DMF decreased heart-to-body weight ratio, heart rate and blood pressure and improved the electrocardiographic patterns when compared with ISO group. DMF exhibited cardioprotective effect as evidenced by the reduction in cardiac troponin I, creatine kinase-MB and atrial natriuretic peptide levels. Moreover, DMF alleviated the changed oxidative stress and inflammatory biochemical markers through its anti-inflammatory and antioxidant effects. DMF interfered with TLR signalling pathway, evidenced by decreased levels of the TLR adaptor protein MyD88 and p-ERK1/2 and increased p-Akt level.

Conclusions

Dimethyl fumarate exerted cardioprotective effect against ISO-induced cardiac hypertrophy. This effect is suggested to be through interfering with TLR signalling pathway.

Protocatechuic aldehyde protects against isoproterenol-induced cardiac hypertrophy via inhibition of the JAK2/STAT3 signaling pathway

Protocatechuic aldehyde (PCA) is a natural compound found in the Chinese herb Salvia miltiorrhiza. It has been shown to possess multiple biological activities and to protect the cardiovascular system against oxidative stress, inflammation, and atherosclerosis. However, the potential effects of PCA on cardiac hypertrophy remain to be investigated. In this study, we showed that isoproterenol treatment (ISO, 10 μM for 24 h) induced significant hypertrophy in cultured neonatal rat cardiomyocytes, as manifested by enlargement of cell surface area (1.74-fold greater than that of the control, p < 0.05) and upregulation of hypertrophic gene markers (2.44- to 2.75-fold increase in ANF and β-MHC protein expression, p < 0.05). These ISO-induced hypertrophic responses were attenuated by PCA (50-200 μM, p < 0.05). Furthermore, intragastric administration of PCA (10-100 mg/kg/day) ameliorated cardiac hypertrophy in ISO-treated rats (1.5 mg/kg/day, s.c., for 7 days). PCA inhibited the abnormal changes in echocardiographic parameters and suppressed ISO-induced increase in cardiomyocyte cross-sectional area and collagen content (p < 0.05). It also ameliorated ISO-mediated elevation of HW/BW, LVW/BW, and HW/TL ratios (p < 0.05). Mechanistically, ISO facilitated JAK2 and STAT3 phosphorylation, increased STAT3 nuclear translocation, and enhanced STAT3 transcriptional activity. All these changes were attenuated by PCA. Taken together, these findings showed that PCA could protect against cardiac hypertrophy induced by ISO possibly via inhibition of the JAK2/STAT3 signaling pathway, suggesting the potential of PCA as a therapeutic candidate for hypertrophy-associated heart diseases.

2-Methoxyestradiol protects against pressure overload-induced left ventricular hypertrophy

Numerous experimental studies have supported the evidence that 2-methoxyestradiol (2 ME) is a biologically active metabolite that mediates multiple effects on the cardiovascular system, largely independent of the estrogen receptor. 2 ME is a major cytochrome P450 1B1 (CYP1B1) metabolite and has been reported to have vasoprotective and anti-inflammatory actions. However, whether 2 ME would prevent cardiac hypertrophy induced by abdominal aortic constriction (AAC) has not been investigated yet. Therefore, the overall objectives of the present study were to elucidate the potential antihypertrophic effect of 2 ME and explore the mechanism(s) involved. Our results showed that 2 ME significantly inhibited AAC-induced left ventricular hypertrophy using echocardiography. The antihypertrophic effect of 2 ME was associated with a significant inhibition of CYP1B1 and mid-chain hydroxyeicosatetraenoic acids. Based on proteomics data, the protective effect of 2 ME is linked to the induction of antioxidant and anti-inflammatory proteins in addition to the modulation of proteins involved in myocardial energy metabolism. In vitro, 2 ME has shown a direct antihypertrophic effect through mitogen-activated protein kinases- and nuclear factor-κB-dependent mechanisms. The present work shows a strong evidence that 2 ME protects against left ventricular hypertrophy. Our data suggest the potential of repurposing 2 ME as a selective CYP1B1 inhibitor for the treatment of heart failure.

Age-, Gender-, and in Vivo Different Doses of Isoproterenol Modify in Vitro Aortic Vasoreactivity and Circulating VCAM-1

Different human-like cardiomyopathies associated to β-adrenergic stimulation are experimentally modeled in animals through variations in dose, route, and duration of administration of different cardiotoxic drugs. However, associated changes in the vasculature and their relation to systemic inflammation, and the influence of cardiovascular diseases risk factors (gender and age) upon them are seldom analyzed. Here we studied the effect of age and gender on the vasoreactivity of aortas from mice subjected to in vivo repeated β-adrenergic stimulation with different doses of isoproterenol (ISO) in association with circulating inflammatory cytokines. Young (2 months) and old (18 months) male and female mice received 0 (control), 5, 40, 80 or 160 μg/g/d of ISO (7 days, s.c.). IL-1α, IL-4 and vascular cell adhesion molecule-1 (VCAM-1) were quantified in plasma. In vitro, norepinephrine-induced vasoconstriction and acetylcholine-induced relaxation were measured in aortas. No differences in contraction, relaxation, IL-1α, and IL-4 were found between control young males and females. Age decreased contraction in males and relaxation was lower in females and abolished in males. VCAM-1 was higher in young males than in females and increased in old mice. Vasoconstriction in ISO-treated mice results as a bell-shaped curve on contraction in young and old males, with lower values in the latter. In females, ISO-160 increased contraction in young females but decreased it in old females. Vasorelaxation was reduced in ISO-treated young males and females. ISO-80 and 160 reduced vasorelaxation in old females, and intermediate doses relaxed aortas from old males. VCAM-1 was higher in young and old males with ISO-80 and 160; while VCAM-1 was higher only with ISO-160 in old females. Our results demonstrate that repeated β-adrenergic stimulation modifies vascular reactivity depending on gender, age, and dose. Females were less sensitive to alterations in vasoreactivity, and young females required a higher amount of the adrenergic stimuli than old females to show vascular alterations. Changes were independent of IL-1α and IL-4. VCAM-1 only changed in old females stimulated with ISO 160. Our results highlight the relevance of considering and comparing in the same study females and aged organisms to improve the accuracy of applications to clinical studies.