Markers Atrial Natriuretic Peptide Research Articles

Fibroblast growth factor 20 ameliorates cardiac hypertrophy via activation ErbB2

Fibroblast growth factor 20 (FGF20) is a member of the fibroblast growth factor family and involved in embryonic development and cardiac repair. This study aimed to explore the role of FGF20 in cardiac hypertrophy and the underlying molecular mechanisms. FGF20 improved cardiac hypertrophy in vivo and in vitro. Furthermore, FGF20 increased expression of erythroblastic leukemia viral oncogene homolog 2 (ErbB2), which was negatively correlated with expression of the cardiac hypertrophy markers atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP). In addition, FGF20 effectively protected cardiomyocytes against apoptosis and oxidative stress. To further investigate whether protective effect of FGF20 is mediated by ErbB2, neonatal rat cardiomyocytes (NRCMs) were treated with lapatinib, an inhibitor of ErbB2. Lapatinib largely abrogated the anti-hypertrophic effect of FGF20, accompanied by increases in cardiomyocyte apoptosis and oxidative stress. In summary, this study reveals that FGF20 prevents cardiac hypertrophy by inhibiting apoptosis and oxidative stress via activating ErbB2 and may be a promising therapeutic strategy for cardiac hypertrophy.

Exercise-induced cardiac mitochondrial reorganization and enhancement in spontaneously hypertensive rats.

The myocardium is a highly oxidative tissue in which mitochondria are essential to supply the energy required to maintain pump function. When pathological hypertrophy develops, energy consumption augments and jeopardizes mitochondrial capacity. We explored the cardiac consequences of chronic swimming training, focusing on the mitochondrial network, in spontaneously hypertensive rats (SHR). Male adult SHR were randomized to sedentary or trained (T: 8-week swimming protocol). Blood pressure and echocardiograms were recorded, and hearts were removed at the end of the training period to perform molecular, imaging, or isolated mitochondria studies. Swimming improved cardiac midventricular shortening and decreased the pathological hypertrophic marker atrial natriuretic peptide. Oxidative stress was reduced, and even more interesting, mitochondrial spatial distribution, dynamics, function, and ATP were significantly improved in the myocardium of T rats. In the signaling pathway triggered by training, we detected an increase in the phosphorylation level of both AKT and glycogen synthase kinase-3 β, key downstream targets of insulin-like growth factor 1 signaling that are crucially involved in mitochondria biogenesis and integrity. Aerobic exercise training emerges as an effective approach to improve pathological cardiac hypertrophy and bioenergetics in hypertension-induced cardiac hypertrophy.

Evaluation of Tyrosine Kinase Inhibitors Loaded Injectable Hydrogels for Improving Connexin43 Gap Junction Intercellular Communication.

Myocardial infarction (MI) is one of the leading causes of death in the developed world, and the loss of cardiomyocytes plays a critical role in the pathogenesis of heart failure. Implicated in this process is a decrease in gap junction intercellular communication due to remodeling of Connexin43 (Cx43). We previously identified that intraperitoneal injection of the Pyk2 inhibitor PF4618433 reduced infarct size, maintained Cx43 at the intercalated disc in left ventricle hypertrophic myocytes, and improved cardiac function in an MI animal model of heart failure. With the emergence of injectable hydrogels as a therapeutic toward the regeneration of cardiac tissue after MI, here, we provide proof of concept that the release of tyrosine kinase inhibitors from hydrogels could have beneficial effects on cardiomyocytes. We developed an injectable hydrogel consisting of thiolated hyaluronic acid and P123-maleimide micelles that can incorporate PF4618433 as well as the Src inhibitor Saracatinib and achieved sustained release (of note, Src activates Pyk2). Using neonatal rat ventricular myocytes in the presence of a phorbol ester, endothelin-1, or phenylephrine to stimulate cardiac hypertrophy, the release of PF4618433 from the hydrogel had the same ability to decrease Cx43 tyrosine phosphorylation and maintain Cx43 localization at the plasma membrane as when directly added to the growth media. Additional beneficial effects included decreases in apoptosis, the hypertrophic marker atrial natriuretic peptide (ANP), and serine kinases upregulated in hypertrophy. Finally, the presence of both PF4618433 and Saracatinib further decreased the level of ANP and apoptosis than each inhibitor alone, suggesting that a combinatorial approach may be most beneficial. These findings provide the groundwork to test if tyrosine kinase inhibitor release from hydrogels will have a beneficial effect in an animal model of MI-induced heart failure.

Programmable siRNA pro-drugs that activate RNAi activity in response to specific cellular RNA biomarkers

Since Paul Ehrlich’s introduction of the “magic bullet” concept in 1908, drug developers have been seeking new ways to target drug activity to diseased cells while limiting effects on normal tissues. In recent years, it has been proposed that coupling riboswitches capable of detecting RNA biomarkers to small interfering RNAs (siRNAs) to create siRNA pro-drugs could selectively activate RNA interference (RNAi) activity in specific cells. However, this concept has not been achieved previously. We report here that we have accomplished this goal, validating a simple and programmable new design that functions reliably in mammalian cells. We show that these conditionally activated siRNAs (Cond-siRNAs) can switch RNAi activity against different targets between clearly distinguished OFF and ON states in response to different cellular RNA biomarkers. Notably, in a rat cardiomyocyte cell line (H9C2), one version of our construct demonstrated biologically meaningful inhibition of a heart-disease-related target gene protein phosphatase 3 catalytic subunit alpha (PPP3CA) in response to increased expression of the pathological marker atrial natriuretic peptide (NPPA) messenger RNA (mRNA). Our results demonstrate the ability of synthetic riboswitches to regulate gene expression in mammalian cells, opening a new path for development of programmable siRNA pro-drugs.

Combined deletion of PR-domain containing 16 (Prdm16) in cardiomyocyte and non-cardiomyocyte lineages results in spontaneous early-onset lethality and progressive left ventricular dysfunction in mice

Abstract Introduction PR-domain containing 16 (Prdm16) has an asymmetric expression pattern in the developing cardiovascular system, including ventricular myocardium, endocardium and arterial endothelial and smooth muscle cell (SMC) layers. Heterozygous PRDM16 mutations in humans have been linked with early-onset cardiomyopathy resulting in heart failure. Myocardial PRDM16-deficiency has been suggested as the culprit for this cardiomyopathy, however embryonic Prdm16 deletion in cardiomyocytes or their progenitors in mice only results in symptomatic cardiac defects upon metabolic stress or ageing. This suggests that Prdm16 loss in other cell types has an important co-contribution in the early heart phenotype seen in patients with causal PRDM16 variants. Purpose To investigate the adjuvant role of non-cardiomyocytes to the heart phenotype caused by Prdm16 deficiency, we used a conditional mouse model in which deletion of Prdm16 occurs in all cells expressing an Sm22-driven Cre recombinase which has a combined activity in cardiomyocyte and non-cardiomyocyte lineages in the heart, including SMCs and pericytes. Methods Mice carrying two Prdm16 alleles with a floxed exon 9 (Prdm16fl/fl) were intercrossed with the Sm22-Cre driver line. Offspring of Sm22Cre+; Prdm16fl/fl and Sm22Cre−; Prdm16fl/fl breeding pairs was monitored for Mendelian inheritance and for signs of (progressive) cardiac dysfunction by echocardiography at 5 and 16 weeks of age. Hearts were isolated and analyzed for RNA expression levels of cardiac stress markers Atrial and Brain Natriuretic Peptide (ANP and BNP) via quantitative RT-PCR and histologically for the appearance of fibrosis through Sirius red-staining. Results Genotyping at 5 weeks of age showed a loss of 60.4% of Sm22Cre+; Prdm16fl/fl offspring. Mice surviving at 5 weeks spontaneously developed signs of left ventricular diastolic and systolic dysfunction, the latter shown by a significantly reduced ejection fraction (EF; 37±3% vs. 61±3% in control Sm22Cre−; Prdm16fl/fl littermates). Cardiac expression levels of ANP and BNP were significantly increased (728-fold and 36-fold, respectively) in Sm22Cre+; Prdm16fl/fl mice which also showed perivascular fibrosis compared to control littermates. At 16 weeks of age, this aberrant cardiac phenotype further progressed (EF: 32±3% vs. 57±4%; ANP: 2,541-fold increase; BNP: 129-fold increase) and in addition to perivascular fibrosis, hearts also showed interstitial fibrosis (Sirius red+ area: 17±2% vs. 3.0±0.4% in control littermates). Conclusion Unlike recently reported mice with a Prdm16 deficiency in cardiomyocytes or their (precursor) lineages, mice with a combined loss of Prdm16 in the cardiomyocytes and certain non-cardiomyocyte lineages feature early mortality and (progressive) signs of severe heart failure. Therefore, Prdm16 expressed by non-cardiomyocytes is indispensable for proper cardiac function and its loss in these cell types co-determines the aberrant cardiac phenotype. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Fonds voor Wetenschappelijk Onderzoek Strategic Basic Research pre-doctoral fellowship (1S25817N)KU Leuven Research Coordination grant (C14/19/095)

Mechanisms of Systolic Cardiac Dysfunction in PP2A, PP5 and PP2AxPP5 Double Transgenic Mice.

As part of our ongoing studies on the potential pathophysiological role of serine/threonine phosphatases (PP) in the mammalian heart, we have generated transgenic mice with cardiac muscle cell-specific overexpression of PP2Acα (PP2A) and PP5 (PP5). For further studies we crossbred PP2A and PP5 mice to obtain PP2AxPP5 double transgenic mice (PP2AxPP5, DT) and compared them with littermate wild-type mice (WT) serving as a control. The mortality of DT mice was greatly enhanced vs. other genotypes. Cardiac fibrosis was noted histologically and mRNA levels of collagen 1α, collagen 3α and fibronectin 1 were augmented in DT. DT and PP2A mice exhibited an increase in relative heart weight. The ejection fraction (EF) was reduced in PP2A and DT but while the EF of PP2A was nearly normalized after β-adrenergic stimulation by isoproterenol, it was almost unchanged in DT. Moreover, left atrial preparations from DT were less sensitive to isoproterenol treatment both under normoxic conditions and after hypoxia. In addition, levels of the hypertrophy markers atrial natriuretic peptide and B-type natriuretic peptide as well as the inflammation markers interleukin 6 and nuclear factor kappa B were increased in DT. PP2A enzyme activity was enhanced in PP2A vs. WT but similar to DT. This was accompanied by a reduced phosphorylation state of phospholamban at serine-16. Fittingly, the relaxation times in left atria from DT were prolonged. In summary, cardiac co-overexpression of PP2A and PP5 were detrimental to animal survival and cardiac function, and the mechanism may involve dephosphorylation of important regulatory proteins but also fibrosis and inflammation.

Fatty acid-binding protein 4 silencing protects against lipopolysaccharide-induced cardiomyocyte hypertrophy and apoptosis by inhibiting the Toll-like receptor 4-nuclear factor-κB pathway.

ObjectiveTo explore the effects and potential mechanisms of fatty acid-binding protein 4 (FABP4) in a lipopolysaccharide (LPS)-induced in vitro septic cardiomyopathy model.MethodsRat cardiomyocyte H9c2 cells were transfected with small interfering RNA (siRNA) against FABP4 (siFABP4), then induced with LPS. The following parameters were measured: cell viability, lactate dehydrogenase release, cardiac hypertrophy and related marker expression, apoptosis, inflammatory cytokine release and expression, and the activation of Toll-like receptor 4 (TLR4) and nuclear factor-κB (NF-κB) pathways.ResultsLPS increased the mRNA and protein expression of FABP4 in H9c2 cells. FABP4 silencing by siFABP4 significantly inhibited LPS-induced cardiac hypertrophy and reduced the mRNA expression of the myocardial hypertrophy markers atrial natriuretic peptide and brain natriuretic peptide. siFABP4 also attenuated LPS-induced increase in TUNEL-positive apoptotic cells, caspase-3 and caspase-9 activities, and the release and expression of proinflammatory cytokines. Mechanistically, we found that FABP4 silencing inhibited the mRNA and protein expression of TLR4 and suppressed the NF-kappa B signaling pathway, as evidenced by reduced nuclear NF-κB p65 and increased cytoplasmic I-κBα expression in LPS-stimulated H9c2 cells.ConclusionFABP4 silencing reduces LPS-induced cardiomyocyte hypertrophy and apoptosis by down-regulating the TLR4/NF-κB axis.

Comparative studies on regional variations in PM2.5 in the induction of myocardial hypertrophy in mice

Exposure to fine particulate matter (PM2.5) has been indicated to be related to an increased risk of cardiovascular diseases (CVDs) in sensitive people. However, the underlying mechanisms of PM2.5-induced CVDs are poorly understood. In the present study, PM2.5 samples were collected during winter from four cities (Taiyuan, Beijing, Hangzhou, and Guangzhou) in China. Ten-month-old C57BL/6 female mice were exposed to PM2.5 suspension at a dosage of 3 mg·kg−1 (b. w.) every other day for 4 weeks by oropharyngeal aspiration. PM2.5 from Taiyuan increased the blood pressure and the thicknesses of the left ventricular anterior and posterior walls, decreased the ratio of nucleus to cytoplasm in cardiomyocytes and reduced the systolic function of the heart in mice. Further investigation revealed that PM2.5 from Taiyuan induced lung inflammatory cytokines with up-regulated expressions of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6). The mRNA expression levels of myocardial hypertrophy markers atrial natriuretic peptide and the β isoform of myosin heavy chain (ANP and β-MHC), matrix metalloproteinase 2 (MMP2), MMP9, and inflammatory cytokines TNF-α and IL-6 in the myocardium were significantly increased after exposure to PM2.5 of Taiyuan. Furthermore, PM2.5 from Taiyuan activated the IL-6/JAK2/STAT3/β-MHC signaling pathway in the myocardium. The correlation between the PM2.5 components and myocardial hypertrophy markers suggested that Zinc (Zn) and acenaphthene (AC) are related to the changes in ANP and β-MHC at the transcriptional level, respectively. The above results indicated that PM2.5 exposure induced myocardial hypertrophy in older mice, which might be related to the critical contributions of Zn and AC in PM2.5. The present study provides new insights into the mechanism of myocardial hypertrophy after PM2.5 exposure.

Increased cholinergic activity under conditions of low estrogen leads to adverse cardiac remodeling.

Cholinesterase inhibitors are used in postmenopausal women for the treatment of neurodegenerative diseases. Despite their widespread use in the clinical practice, little is known about the impact of augmented cholinergic signaling on cardiac function under reduced estrogen conditions. To address this gap, we subjected a genetically engineered murine model of systemic vesicular acetylcholine transporter overexpression (Chat-ChR2) to ovariectomy and evaluated cardiac parameters. Left-ventricular function was similar between Chat-ChR2 and wild-type (WT) mice. Following ovariectomy, WT mice showed signs of cardiac hypertrophy. Conversely, ovariectomized (OVX) Chat-ChR2 mice evolved to cardiac dilation and failure. Transcript levels for cardiac stress markers atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP) were similarly upregulated in WT/OVX and Chat-ChR2/OVX mice. 17β-Estradiol (E2) treatment normalized cardiac parameters in Chat-ChR2/OVX to the Chat-ChR2/SHAM levels, providing a link between E2 status and the aggravated cardiac response in this model. To investigate the cellular basis underlying the cardiac alterations, ventricular myocytes were isolated and their cellular area and contractility were assessed. Myocytes from WT/OVX mice were wider than WT/SHAM, an indicative of concentric hypertrophy, but their fractional shortening was similar. Conversely, Chat-ChR2/OVX myocytes were elongated and presented contractile dysfunction. E2 treatment again prevented the structural and functional changes in Chat-ChR2/OVX myocytes. We conclude that hypercholinergic mice under reduced estrogen conditions do not develop concentric hypertrophy, a critical compensatory adaptation, evolving toward cardiac dilation and failure. This study emphasizes the importance of understanding the consequences of cholinesterase inhibition, used clinically to treat dementia, for cardiac function in postmenopausal women.

ANO1 relieves pressure overload-induced myocardial fibrosis in mice by inhibiting TGF-β/Smad3 signaling pathway.

The aim of this study was to measure the expression of anoctamin 1 (ANO1) in myocardial tissues of mice with pressure overload-induced myocardial fibrosis, and to further investigate the effect of ANO1 on myocardial fibrosis in mice and its mechanism. A total of 40 male C57/B6 mice aged 6-8 weeks old were divided into 2 groups using a random number table, namely sham operation group (Sham group, n=20) and thoracic aortic constriction group (TAC group, n=20). Meanwhile, 20 ANO1 transgenic (TG) mice aged 6-8 weeks old were enrolled for TAC as TAC + ANO1 TG group. At 8 weeks after TAC, ejection fraction (EF%) and fraction shortening (FS%) in each group of mice were detected via echocardiography. Western blotting and immunofluorescence staining assays were conducted to measure the protein expression of ANO1 in myocardial tissues of mice in each group. The pathological changes in myocardial tissues of mice were evaluated through hematoxylin-eosin (H&E) staining. Reverse Transcription-Polymerase Chain Reaction (RT-PCR) assay was performed to measure the messenger ribonucleic acid (mRNA) expression levels of hypertrophy markers atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) in myocardial tissues of mice in each group. The deposition of collagen fibers in heart tissues was determined by Masson staining assay. Terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end labeling (TUNEL) staining assay was carried out to detect the apoptosis of myocardial cells and fibroblasts in heart tissues. Additionally, the protein expressions of oxidative stress markers superoxide dismutase 1 (SOD1) and 4-hydroxynonenal (4-HNE) in myocardial tissues were detected as well. Finally, Western blotting was employed to detect the effect of ANO1 overexpression on the expression of transforming growth factor-β (TGF-β)/Smad3 signaling pathway-related proteins in myocardial tissues of mice. At 8 weeks after TAC, ANO1 expression was overtly reduced in myocardial tissues of mice (p<0.05). Echocardiographic results showed that ANO1 overexpression significantly alleviated TAC-induced cardiac function deterioration in mice (p<0.05). The mRNA expression levels of ANP and BNP in myocardial tissues of TAC + ANO1 TG group were evidently lower than those in TAC group (p<0.05). Meanwhile, myocardial interstitial collagen deposition was significantly ameliorated in TAC + ANO1 TG group compared with TAC group (p<0.05). ANO1 overexpression notably mitigated the apoptosis of myocardial cells and oxidative stress in mice with cardiac pressure overload (p<0.05). Western blotting results further indicated that after overexpression of ANO1, the protein levels of TGF-β and phosphorylated Smad3 (p-Smad3) were significantly inhibited in mice undergoing TAC (p<0.05). In the case of cardiac pressure overload in mice, ANO1 is lowly expressed in myocardial tissues. Meanwhile, its overexpression is able to attenuate pressure overload-induced myocardial fibrosis in mice by repressing the TGF-β/smad3 signaling pathway. All our findings indicate that ANO1 can serve as a potential gene target for the treatment of myocardial fibrosis in the future.

The Expression of microRNA in Adult Rat Heart with Isoproterenol-Induced Cardiac Hypertrophy.

Cardiac hypertrophy is a common pathological condition and an independent risk factor that triggers cardiovascular morbidity. As an important epigenetic regulator, miRNA is widely involved in many biological processes. In this study, miRNAs expressed in rat hearts that underwent isoprenaline-induced cardiac hypertrophy were identified using high-throughput sequencing, and functional verification of typical miRNAs was performed using rat primary cardiomyocytes. A total of 623 miRNAs were identified, of which 33 were specifically expressed in cardiac hypertrophy rats. The enriched pathways of target genes of differentially expressed miRNAs included the FoxO signaling pathway, dopaminergic synapse, Wnt signaling pathway, MAPK (mitogen-activated protein kinase) signaling pathway, and Hippo signaling pathway. Subsequently, miR-144 was the most differentially expressed miRNA and was subsequently selected for in vitro validation. Inhibition of miR-144 expression in primary myocardial cells caused up-regulation of cardiac hypertrophy markers atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP). The dual luciferase reporter system showed that ANP may be a target gene of miR-144. Long non-coding RNA myocardial infarction associated transcript (LncMIAT) is closely related to heart disease, and here, we were the first to discover that LncMIAT may act as an miR-144 sponge in isoproterenol-induced cardiac hypertrophy. Taken together, these results enriched the understanding of miRNA in regulating cardiac hypertrophy and provided a reference for preventing and treating cardiac hypertrophy.

Taurine attenuates isoproterenol-induced H9c2 cardiomyocytes hypertrophy by improving antioxidative ability and inhibiting calpain-1-mediated apoptosis.

Pathological cardiac hypertrophy is ultimately accompanied by cardiomyocyte apoptosis. Apoptosis mainly related to calpain-1-mediated apoptotic pathways. Studies had proved that taurine can maintain heart health through antioxidation and antiapoptotic functions, but the effect of taurine on cardiachypertrophy is still unclear. This study aimed to determine whether taurine could inhibit calpain-1-mediated mitochondria-dependent apoptotic pathways in isoproterenol (ISO)-induced hypertrophic cardiomyocytes. We found that taurine could inhibit the increase in cell surface area and reduce the protein expression levels of the hypertrophic markers atrial natriuretic peptide, brain natriuretic polypeptide, and β-myosin heavy chain. Taurine also reduced ROS, intracellular Ca2+ overload and mitochondrial membrane potential. Moreover, taurine inhibited cardiomyocyte apoptosis by decreasing the protein expression of calpain-1, Bax, t-Bid, cytosolic cytochrome c, Apaf-1, cleaved caspase-9 and cleaved caspase-3 and by enhancing calpastatin and Bcl-2 protein expression. Calpain-1 small interfering RNA transfection results showed similar antiapoptotic effects as the taurine prevention group. However, compared with the two treatments, taurine inhibited the expression of cleaved caspase-9 more significantly. Therefore, we believe that taurine prevents ISO-induced H9c2 cardiomyocyte hypertrophy by inhibiting oxidative stress, intracellular Ca2+ overload, the calpain-1-mediated mitochondria-dependent apoptotic pathway and cleaved caspase-9 levels.

Cymbopogon Proximus Essential Oil Protects Rats against Isoproterenol-Induced Cardiac Hypertrophy and Fibrosis.

Cardiac hypertrophy is an independent risk factor of many cardiovascular diseases. Several cardiovascular protective properties of Cymbopogon proximus have been reported. However, no reports investigating the direct effect of C. proximus essential oil on the heart are available. The goal of this study was to explore the cardioprotective effect of C. proximus on cardiac hypertrophy and fibrosis. Male albino rats were administered C. proximus essential oil in the presence or absence of hypertrophic agonist isoproterenol. Cardiac hypertrophy and fibrosis were assessed using real-time polymerase chain reaction (PCR) and histological examination. Pre- treatment of rats with C. proximus decreased the ratio of heart weight to body weight and gene expression of hypertrophy markers atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and β-myosin heavy chain (β-MHC), which were induced by isoproterenol. Moreover, C. proximus prevented the increase in gene expression of fibrosis markers procollagen I and procollagen III and alleviated the collagen volume fraction caused by isoproterenol. The pre- treatment with C. proximus essential oil conferred cardio-protection against isoproterenol- induced cardiac hypertrophy and fibrosis.

Cardiac iron overload promotes ferroptosis and cardiac dysfunction in mice with sickle cell disease

Ferroptosis is a recently defined form of iron‐dependent, non‐apoptotic programmed cell death that is characterized by accumulation of lipid peroxides. Although ferroptosis was first identified in cancer cells, recent studies have demonstrated its implications in a wide range of physiological disorders such as ischemic and hemorrhagic stroke, Alzheimer’s disease, and epilepsy. Notably, there is a significant association between iron loading and heart failure. For example, cardiomyopathy is the leading cause of mortality in thalassemia and accounts for 30% of mortality in iron overload sickle cell disease (SCD). However, the underlying mechanisms of iron‐induced cardiotoxicity are not well understood. Although cell death mechanisms such as apoptosis and necrosis have been recognized in the context of heart disease, the role of ferroptosis in cardiac damage is largely unexplored. Here we hypothesized that cardiac iron overload promotes ferroptosis and cardiac dysfunction in the Townes mouse model of SCD. To test our hypothesis, we determined and compared iron levels, cardiotoxicity and ferroptotic markers between sickling HbSS (homozygous for the human βS globin gene) and their non‐sickling heterozygous HbAS littermates. First, we observed an increase in systemic and tissue iron levels in HbSS mice. We also found increased expression of the cardiotoxic markers ANP (atrial natriuretic peptide) and BNP (brain natriuretic peptide). These results were associated with an upregulation of the ferroptotic marker, Ptgs2, and increased levels of lipid peroxidation, a characteristic of ferroptosis, in the cardiac tissue of HbSS mice. However, no differences were found in caspase‐3 levels, suggesting that cardiotoxicity does not result from apoptotic mechanisms. To distinguish between the effects of the sickling gene and iron loading, we induced iron overload in non‐sickling mice by iron dextran treatment, an established model of secondary iron overload. Similar to our findings in sickling mice, we demonstrated that induced iron overload displayed increased lipid peroxidation and cardiac damage, consistent with cardiac ferroptosis. Finally, inhibition of ferroptosis, either by chelating excess iron (using an iron chelator deferoxamine) or by inhibiting lipid peroxidation (using ferrostatin‐1, a lipid radical scavenger), improved cardiac dysfunction in sickling mice. These findings suggest a novel mechanism of cardiac cell death in SCD and could provide potential protective targets against iron‐induced cardiotoxicity.

The effect and mechanism of heat shock protein 47 on streptozotocin-induced diabetic cardiomyopathy

Objective: To investigate the effect and specific mechanism of heat shock protein 47 (HSP47) on streptozotocin (STZ)-induced diabetic cardiomyopathy (DCM). Methods: A mouse model of type 1 diabetic cardiomyopathy was established by intraperitoneal injection of STZ. After 8 weeks of successful modeling, HSP47 was overexpressed by tail vein injection, and the heart of the mouse was harvested after 6 weeks. Hematoxylin-eosin (HE) staining and Sirius red (PSR) staining were used to detect the cross-sectional area of myocardial cells and myocardial fibrosis, respectively. Immunofluorescence staining with α-smooth muscle actin (α-SMA) and collagen Ⅰ was used to detect the degree of fibrosis activation. The expression level of fibrosis-related proteins was determined by Western blot. Results: The expression level of HSP47 in the myocardium of the diabetic group up-regulated (2.014±0.264 vs 1.004±0.064, P<0.001). The area of myocardial cells in the diabetic group was increased compared with the control group [(235.3±20.7) μm(2) vs (172.8±13.6) μm(2), P<0.001] and the cross-sectional area of myocardial cells in the HSP47 overexpression-diabetes group was further increased [(302.2±41.0) μm(2) vs (235.3±20.7) μm(2), P=0.009], while the mRNA levels of mouse cardiac hypertrophic markers atrial natriuretic peptide (ANP), type B brain natriuretic peptide (BNP), myosin heavy chain β (β-MHC) further upregulated (all P<0.001). Compared with the control group, the myocardial fibrosis content in the diabetic group increased [(7.333±1.127)% vs (4.837±0.775)%, P=0.002] and the left ventricular fibrosis content of the HSP47 overexpressing diabetic group further increased [(9.175±1.008)% vs (7.333±1.127)%, P=0.025] and the mRNA levels of fibrosis index collagenⅠ, collagen Ⅲ, connective tissue growth factor (CTGF) and transforming growth factor β (TGFβ) further up-regulated (all P<0.001). Immunofluorescence results showed that compared with the control group, the expression of collagenⅠ up-regulated in the endothelial stroma of the diabetic group and the content of collagenⅠ in the HSP47 over-expressing diabetic group was higher (P<0.001). Western blot results indicated that the phosphorylation level of Smad3 and the protein levels of α-SMA and TGFβ in HSP47 overexpressing diabetic group increased, compared with those of diabetic group (all P<0.001). Conclusion: HSP47 ameliorates STZ-induced diabetic myocardial fibrosis by activating the TGFβ/Smad3 signaling pathway.

Sinomenine's protective role and mechanism in stress load-induced heart failure.

This study is designed to investigate the effects and mechanisms of sinomenine (Sin) in stress load-induced heart failure in mice. We used aortic constriction (AB) to cause pressure overload as our heart failure model. Sin was received in mice as the treatment group. Cardiac function and structural changes were detected using echocardiography. Heart-lung mass ratios were measured. The serum levels of IL-10 and IL-17 proteins were detected by using ELISA, cardiac hypertrophy markers atrial natriuretic peptide (ANP), myocardial I and III collagen mRNA levels were detected by RT-PCR. Myocardial type I and III collagen protein levels were detected by Western blotting. Sin significantly improved stress load-induced heart failure (P<0.05), reduced the heart-lung mass ratio, ANP, collagen-I and -III mRNA and protein levels (P<0.05); Sin can enhance the ratio of IL-10/IL-17. Sin may be a promising drug target to improve heart failure. Its role is related to reduce serum ANP levels, inhibit the mRNA and protein level of type I and III collagen and enhance the ratio of IL-10/IL-17.

TRPC3 deficiency attenuates high salt-induced cardiac hypertrophy by alleviating cardiac mitochondrial dysfunction

Long-term high salt intake leads to cardiac hypertrophy, but the mechanism remains elusive. Transient receptor potential channel, canonical 3(TRPC3), located in mitochondria, regulates mitochondrial calcium and reactive oxygen species(ROS) production. Herein, we investigated whether TRPC3 participates in high salt-induced cardiac hypertrophy by impairing cardiac mitochondrial function. High salt treatment increased the expression of mitochondrial TRPC3 in cardiomyocytes, accompanied by enhanced mitochondrial calcium uptake and elevated ROS production. Inhibition of TRPC3 significantly reduced high salt-induced ROS generation, promoted ATP production by stimulating oxidative phosphorylation, and increased enzyme activity in mitochondria in cardiomyocytes. Additionally, TRPC3 deficiency inhibited high salt-induced cardiac hypertrophy in vivo. A long-term high salt diet increased cardiac mitochondrial TRPC3 expression, elevated expression of cardiac hypertrophic markers atrial natriuretic peptide (ANP),brain natriuretic peptide (BNP) and β-myosin heavy chain (β-MHC) and decreased ATP production and mitochondrial complex I and II enzyme activity in a TRPC3-dependent manner. TRPC3 deficiency antagonises high salt diet-mediated cardiac hypertrophy by ameliorating TRPC3-mediated cardiac mitochondrial dysfunction. TRPC3 may therefore represent a novel target for preventing high salt-induced cardiac damage.

Arbutin Attenuates Isoproterenol-Induced Cardiac Hypertrophy by Inhibiting TLR-4/NF-κB Pathway in Mice.

Arbutin is a glycoside reported for its anti-oxidant, anti-inflammatory and anti-tumor properties. However, the cardioprotective effect of Arbutin is not well established. The study aims to understand the effect of arbutin on isoproterenol (ISO)-induced cardiac hypertrophy in mice. The animals were pretreated with Arbutin for a week and ISO was administered for 10 days and then sacrificed. Cardiac injury markers such as creatinine kinase and lactate dehydrogenase concentrations were measured in the serum. The mRNA expression of cardiac hypertrophy markers namely atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) were measured using qRT-PCR. The levels of pro-inflammatory cytokines TNF-α and IL-6 were quantified by ELISA in isolated tissues and serum. Other tissue anti-oxidant parameters such as GST, GSH, SOD and TBARS were also measured. TUNEL assay was performed to detect apoptosis. Histology studies were performed using H & E and Masson trichome staining. Immunoblot analysis was used to quantify the protein expression of TLR-4 and NF-κB. ISO-alone-treated group showed significant increase in CK-MB, LDH along with increase in hypertrophic markers ANP and BNP, TNF-α and IL-6 levels in serum and tissues andincreased cardiomyocyte apoptosis. Anti-oxidant parameters were significantly decreased and TLR-4 and NF-κB protein expression was found to be upregulated in comparison to the control group. Pretreatment with Arbutin-exhibited significant inhibition of TLR-4/NF-κB pathway with decreased levels of pro-inflammatory cytokines and enhanced myocardial anti-oxidant status. Our study demonstrated that pretreatment with Arbutin exhibits marked protective effects on ISO-induced cardiac hypertrophy in mice. Thus, Arbutin may be used as potential pharmacological interventions in the management of cardiac hypertrophy.

Aconitine ameliorates cardiomyocyte hypertrophy induced by angiotensin Ⅱ

This paper was aimed to investigate the inhibitory effect of aconitine(AC) on angiotensin Ⅱ(Ang Ⅱ)-induced H9 c2 cell hypertrophy and explore its mechanism of action. The model of hypertrophy was induced by Ang Ⅱ(1×10-6 mol·L-1),and cardiomyocytes were incubated with different concentrations of AC. Western blot was used to quantify the protein expression levels of atrial natriuretic peptide(ANP),brain natriuretic peptide(BNP),β-myosin heavy chain(β-MHC),and α-smooth muscle actin(α-SMA). Real-time quantitative PCR(qRT-PCR) was used to quantify the mRNA expression levels of cardiac hypertrophic markers ANP,BNP and β-MHC. In addition,the fluorescence intensity of the F-actin marker,an important component of myofibrils,was detected by using laser confocal microscope. AC could significantly reverse the increase of total protein content in H9 c2 cells induced by Ang Ⅱ; qRT-PCR results showed that AC could significantly inhibit the ANP,BNP and β-MHC mRNA up-regulation induced by AngⅡ. Western blot results showed that AC could significantly inhibit the ANP,BNP and β-MHC protein up-regulation induced by AngⅡ. In addition,F-actin expression induced by Ang Ⅱ could be inhibited by AC,and multiple indicators of cardiomyocyte hypertrophy induced by Ang Ⅱ could be down-regulated,indicating that AC may inhibit cardiac hypertrophy by inhibiting the expression of hypertrophic factors,providing new clues for exploring the cardiovascular protection of AC.

Cardiomyocyte specific overexpression of a 37 amino acid domain of regulator of G protein signalling 2 inhibits cardiac hypertrophy and improves function in response to pressure overload in mice

Regulator of G protein signalling 2 (RGS2) is known to play a protective role in maladaptive cardiac hypertrophy and heart failure via its ability to inhibit Gq- and Gs- mediated GPCR signalling. We previously demonstrated that RGS2 can also inhibit protein translation and can thereby attenuate cell growth. This G protein-independent inhibitory effect has been mapped to a 37 amino acid domain (RGS2eb) within RGS2 that binds to eukaryotic initiation factor 2B (eIF2B). When expressed in neonatal rat cardiomyocytes, RGS2eb attenuates both protein synthesis and hypertrophy induced by Gq- and Gs- activating agents. In the current study, we investigated the potential cardioprotective role of RGS2eb by determining whether RGS2eb transgenic (RGS2eb TG) mice with cardiomyocyte specific overexpression of RGS2eb show resistance to the development of hypertrophy in comparison to wild-type (WT) controls. Using transverse aortic constriction (TAC) in a pressure-overload hypertrophy model, we demonstrated that cardiac hypertrophy was inhibited in RGS2eb TG mice compared to WT controls following four weeks of TAC. Expression of the hypertrophic markers atrial natriuretic peptide (ANP) and β-myosin heavy chain (MHC-β) was also reduced in RGS2eb TG compared to WT TAC animals. Furthermore, cardiac function in RGS2eb TG TAC mice was significantly improved compared to WT TAC mice. Notably, cardiomyocyte cell size was significantly decreased in TG compared to WT TAC mice. These results suggest that RGS2 may limit pathological cardiac hypertrophy at least in part via the function of its eIF2B-binding domain.