Overexpression of macrophage migration inhibitory factor protects against pressure overload-induced cardiac hypertrophy through regulating the miR-29b-3p/HBP1 axis.

Cardiac hypertrophy is an adaptive response to stressors such as high cardiac workload, which might lead to abnormal cardiac function and heart failure. Previous studies have indicated that macrophage migration inhibitory factor (MIF) might play a protective role in cardiac hypertrophy. Here, we aimed to illustrate the mechanism of MIF in protecting against pressure overload-induced cardiac hypertrophy. Transverse aortic constriction (TAC) mouse model was established and we found that overexpression of MIF protected against pressure overload-induced cardiac hypotrophy in TAC treated mice, as evidenced by significantly decreased the heart weight. In addition, transthoracic echocardiography showed that overexpression of MIF restored ejection fraction in TAC-treated mice. While TAC treatment resulted in a much larger cardiomyocyte size in mice, MIF overexpression notably decreased the cardiomyocyte size. Next, we demonstrated that MIF overexpression promoted the expression of miR-29b-3p which further downregulated the expression of its downstream target HMG box protein 1 (HBP1). Overexpression of HBP1 reversed the effect of MIF in alleviating Ang-II induced oxidative stress in cardiomyocytes. In conclusion, our findings suggest that MIF could attenuate pressure overload-induced cardiac hypertrophy through regulating the miR-29b-3p/HBP1 axis.

TNIP3 protects against pathological cardiac hypertrophy by stabilizing STAT1.

Pathological cardiac hypertrophy is one of the major risk factors of heart failure and other cardiovascular diseases. However, the mechanisms underlying pathological cardiac hypertrophy remain largely unknown. Here, we identified the first evidence that TNFAIP3 interacting protein 3 (TNIP3) was a negative regulator of pathological cardiac hypertrophy. We observed a significant upregulation of TNIP3 in mouse hearts subjected to transverse aortic constriction (TAC) surgery and in primary neonatal rat cardiomyocytes stimulated by phenylephrine (PE). In Tnip3-deficient mice, cardiac hypertrophy was aggravated after TAC surgery. Conversely, cardiac-specific Tnip3 transgenic (TG) mice showed a notable reversal of the same phenotype. Accordingly, TNIP3 alleviated PE-induced cardiomyocyte enlargement in vitro. Mechanistically, RNA-sequencing and interactome analysis were combined to identify the signal transducer and activator of transcription 1 (STAT1) as a potential target to clarify the molecular mechanism of TNIP3 in pathological cardiac hypertrophy. Via immunoprecipitation and Glutathione S-transferase assay, we found that TNIP3 could interact with STAT1 directly and suppress its degradation by suppressing K48-type ubiquitination in response to hypertrophic stimulation. Remarkably, preservation effect of TNIP3 on cardiac hypertrophy was blocked by STAT1 inhibitor Fludaradbine or STAT1 knockdown. Our study found that TNIP3 serves as a novel suppressor of pathological cardiac hypertrophy by promoting STAT1 stability, which suggests that TNIP3 could be a promising therapeutic target of pathological cardiac hypertrophy and heart failure.

Aspirin and Celecoxib Regulate Notch1/Hes1 Pathway to Prevent Pressure Overload-Induced Myocardial Hypertrophy.

This study aimed to investigate the molecular mechanisms underlying the protective effects of cyclooxygenase (cox) inhibitors against myocardial hypertrophy.Rat H9c2 cardiomyocytes were induced by mechanical stretching. SD rats underwent transverse aortic constriction to induce pressure overload myocardial hypertrophy. Rats were subjected to echocardiography and tail arterial pressure in 12W. qPCR and western blot were used to detect the expression of Notch-related signaling. The inflammatory factors were tested by ELISA in serum, heart tissue, and cell culture supernatant.Compared with control, levels of pro-inflammatory cytokines IL-6, TNF-α, and IL-1ß were increased and anti-inflammatory cytokine IL-10 was reduced in myocardial tissues and serum of rat models. Levels of Notch1 and Hes1 were reduced in myocardial tissues. However, cox inhibitor treatment (aspirin and celecoxib), the improvement of exacerbated myocardial hypertrophy, fibrosis, dysfunction, and inflammation was parallel to the activation of Notch1/Hes1 pathway. Moreover, in vitro experiments showed that, in cardiomyocyte H9c2 cells, application of ~20% mechanical stretching activated inflammatory mediators (IL-6, TNF-α, and IL-1ß) and hypertrophic markers (ANP and BNP). Moreover, expression levels of Notch1 and Hes1 were decreased. These changes were effectively alleviated by aspirin and celecoxib.Cox inhibitors may protect heart from hypertrophy and inflammation possibly via the Notch1/Hes1 signaling pathway.

MiR-378 Inhibits Angiotensin II-Induced Cardiomyocyte Hypertrophy by Targeting AKT2.

Cardiomyocyte hypertrophy plays a crucial role in heart failure development, potentially leading to sudden cardiac arrest and death. Previous studies suggest that micro-ribonucleic acids (miRNAs) show promise for the early diagnosis and treatment of cardiomyocyte hypertrophy.To investigate the miR-378 expression in the cardiomyocyte hypertrophy model, reverse transcription-polymerase chain reaction (RT-qPCR), Western blot, and immunofluorescence tests were conducted in angiotensin II (Ang II)-induced H9c2 cells and Ang II-induced mouse model of cardiomyocyte hypertrophy. The functional interaction between miR-378 and AKT2 was studied by dual-luciferase reporter, RNA pull-down, Western blot, and RT-qPCR assays.The results of RT-qPCR analysis showed the downregulated expression of miR-378 in both the cell and animal models of cardiomyocyte hypertrophy. It was observed that the introduction of the miR-378 mimic inhibited the hypertrophy of cardiomyocytes induced by Ang II. Furthermore, the co-transfection of AKT2 expression vector partially mitigated the negative impact of miR-378 overexpression on Ang II-induced cardiomyocytes. Molecular investigations provided evidence that miR-378 negatively regulated AKT2 expression by interacting with the 3' untranslated region (UTR) of AKT2 mRNA.Decreased miR-378 expression and AKT2 activation are linked to Ang II-induced cardiomyocyte hypertrophy. Targeting miR-378/AKT2 axis offers therapeutic opportunity to alleviate cardiomyocyte hypertrophy.

Cell size induced bias of current density in hypertrophic cardiomyocytes.

Alterations in ion channel expression and function known as "electrical remodeling" contribute to the development of hypertrophy and to the emergence of arrhythmias and sudden cardiac death. However, comparing current density values - an electrophysiological parameter commonly utilized to assess ion channel function - between normal and hypertrophied cells may be flawed when current amplitude does not scale with cell size. Even more, common routines to study equally sized cells or to discard measurements when large currents do not allow proper voltage-clamp control may introduce a selection bias and thereby confound direct comparison. To test a possible dependence of current density on cell size and shape, we employed whole-cell patch-clamp recording of voltage-gated sodium and calcium currents in Langendorff-isolated ventricular cardiomyocytes and Purkinje myocytes, as well as in cardiomyocytes derived from trans-aortic constriction operated mice. Here, we describe a distinct inverse relationship between voltage-gated sodium and calcium current densities and cell capacitance both in normal and hypertrophied cells. This inverse relationship was well fit by an exponential function and may be due to physiological adaptations that do not scale proportionally with cell size or may be explained by a selection bias. Our study emphasizes the need to consider cell size bias when comparing current densities in cardiomyocytes of different sizes, particularly in hypertrophic cells. Conventional comparisons based solely on mean current density may be inadequate for groups with unequal cell size or non-proportional current amplitude and cell size scaling.

Histone methyltransferase MLL4 protects against pressure overload-induced heart failure via a THBS4-mediated protection in ER stress.

Pressure overload-induced pathological cardiac hypertrophy eventually leads to heart failure (HF). Unfortunately, lack of effective targeted therapies for HF remains a challenge in clinical management. Mixed-lineage leukemia 4 (MLL4) is a member of the SET family of histone methyltransferase enzymes, which possesses histone H3 lysine 4 (H3K4)-specific methyltransferase activity. However, whether and how MLL4 regulates cardiac function is not reported in adult HF. Here we report that MLL4 is required for endoplasmic reticulum (ER) stress homeostasis of cardiomyocytes and protective against pressure overload-induced cardiac hypertrophy and HF. We observed that MLL4 is increased in the heart tissue of HF mouse model and HF patients. The cardiomyocyte-specific deletion of Mll4 (Mll4-cKO) in mice leads to aggravated ER stress and cardiac dysfunction following pressure overloading. MLL4 knockdown neonatal rat cardiomyocytes (NRCMs) also display accelerated decompensated ER stress and hypertrophy induced by phenylephrine (PE). The combined analysis of Cleavage Under Targets and Tagmentation sequencing (CUT&Tag-seq) and RNA sequencing (RNA-seq) data reveals that, silencing of Mll4 alters the chromatin landscape for H3K4me1 modification and gene expression patterns in NRCMs. Interestingly, the deficiency of MLL4 results in a marked reduction of H3K4me1 and H3K27ac occupations on Thrombospondin-4 (Thbs4) gene loci, as well as Thbs4 gene expression. Mechanistically, MLL4 acts as a transcriptional activator of Thbs4 through mono-methylation of H3K4 and further regulates THBS4-dependent ER stress response, ultimately plays a role in HF. Our study indicates that pharmacologically targeting MLL4 and ER stress might be a valid therapeutic approach to protect against cardiac hypertrophy and HF.

miR-31-5p suppresses myocardial hypertrophy by targeting Nfatc2ip.

Cardiac hypertrophy, worldwide known as an adaptive functional compensatory state of myocardial stress, is mainly believed to proceed to severe heart diseases, even to sudden death. Emerging studies have explored the microRNA alteration during hypertrophy. However, the mechanisms of microRNAs involved in cardiac hypertrophy are still uncertain. We studied young rats to establish abdominal aorta coarctation (AAC) for 4 weeks. With the significant downregulated cardiac function and upregulated hypertrophic biomarkers, AAC-induced rats showed enlarged myocardiocytes and alterations in microRNAs, especially downregulated miR-31-5p. miR-31-5p targets the 3'UTR of Nfatc2ip and inhibits myocardial hypertrophy in vitro and in vivo. Furthermore, we verified that Nfatc2ip is necessary and sufficient for cardiac hypertrophy in neonatal rat cardiomyocytes. Moreover, we found miR-31-5p inhibited the colocalization of Nfatc2ip and hypertrophic gene ß-Mhc. Luciferase assay and ChiP-qPCR test demonstrated that Nfatc2ip binded to the core-promoter of ß-Mhc and enhanced its transcriptional activity. Above all, our study found a new pathway, mir-31-5p/Nfatc2ip/ß-Mhc, which is involved in cardiac hypertrophy, suggesting a potential target for intervention of cardiac hypertrophy.

Semaglutide ameliorates cardiac remodeling in male mice by optimizing energy substrate utilization through the Creb5/NR4a1 axis.

Semaglutide, a glucagon-like peptide-1 receptor agonist, is clinically used as a glucose-lowering and weight loss medication due to its effects on energy metabolism. In heart failure, energy production is impaired due to altered mitochondrial function and increased glycolysis. However, the impact of semaglutide on cardiomyocyte metabolism under pressure overload remains unclear. Here we demonstrate that semaglutide improves cardiac function and reduces hypertrophy and fibrosis in a mouse model of pressure overload-induced heart failure. Semaglutide preserves mitochondrial structure and function under chronic stress. Metabolomics reveals that semaglutide reduces mitochondrial damage, lipid accumulation, and ATP deficiency by promoting pyruvate entry into the tricarboxylic acid cycle and increasing fatty acid oxidation. Transcriptional analysis shows that semaglutide regulates myocardial energy metabolism through the Creb5/NR4a1 axis in the PI3K/AKT pathway, reducing NR4a1 expression and its translocation to mitochondria. NR4a1 knockdown ameliorates mitochondrial dysfunction and abnormal glucose and lipid metabolism in the heart. These findings suggest that semaglutide may be a therapeutic agent for improving cardiac remodeling by modulating energy metabolism.

Deleting the ribosomal prolyl hydroxylase OGFOD1 protects mice against diet-induced obesity and insulin resistance.

Type 2 diabetes predisposes patients to heart disease, which is the primary cause of death across the globe. Type 2 diabetes often accompanies obesity and is defined by insulin resistance and abnormal glucose handling. Insulin resistance impairs glucose uptake and results in hyperglycemia, which damages tissues such as kidneys, liver, and heart. 2-oxoglutarate (2-OG)- and iron-dependent oxygenases (2-OGDOs), a family of enzymes regulating various aspects of cellular physiology, have been studied for their role in obesity and diet-induced insulin resistance. However, nothing is known of the 2-OGDO family member 2-oxoglutarate and iron-dependent prolyl hydroxylase domain containing protein 1 (OGFOD1) in this setting. OGFOD1 deletion leads to protection in cardiac ischemia-reperfusion injury and cardiac hypertrophy, which are two cardiac events that can lead to heart failure. Considering the remarkable correlation between heart disease and diabetes, the cardioprotection observed in OGFOD1-knockout mice led us to challenge these knockouts with high-fat diet. Wildtype mice fed a high-fat diet developed diet-induced obesity, insulin resistance, and glucose intolerance, but OGFOD1 knockout mice fed this same diet were resistant to diet-induced obesity and insulin resistance. These results support OGFOD1 down-regulation as a strategy for preventing obesity and insulin handling defects.

ERK3 is involved in regulating cardiac fibroblast function.

ERK3/MAPK6 activates MAP kinase-activated protein kinase (MK)-5 in selected cell types. Male MK5 haplodeficient mice show reduced hypertrophy and attenuated increase in Col1a1 mRNA in response to increased cardiac afterload. In addition, MK5 deficiency impairs cardiac fibroblast function. This study determined the effect of reduced ERK3 on cardiac hypertrophy following transverse aortic constriction (TAC) and fibroblast biology in male mice. Three weeks post-surgery, ERK3, but not ERK4 or p38α, co-immunoprecipitated with MK5 from both sham and TAC heart lysates. The increase in left ventricular mass and myocyte diameter was lower in TAC-ERK3+/- than TAC-ERK3+/+ hearts, whereas ERK3 haploinsufficiency did not alter systolic or diastolic function. Furthermore, the TAC-induced increase in Col1a1 mRNA abundance was diminished in ERK3+/- hearts. ERK3 immunoreactivity was detected in atrial and ventricular fibroblasts but not myocytes. In both quiescent fibroblasts and "activated" myofibroblasts isolated from adult mouse heart, siRNA-mediated knockdown of ERK3 reduced the TGF-ß-induced increase in Col1a1 mRNA. In addition, intracellular type 1 collagen immunoreactivity was reduced following ERK3 depletion in quiescent fibroblasts but not myofibroblasts. Finally, knocking down ERK3 impaired motility in both atrial and ventricular myofibroblasts. These results suggest that ERK3 plays an important role in multiple aspects of cardiac fibroblast biology.

Supersulfide catabolism participates in maladaptive remodeling of cardiac cells.

The atrophic myocardium resulting from mechanical unloading and nutritional deprivation is considered crucial as maladaptive remodeling directly associated with heart failure, as well as interstitial fibrosis. Conversely, myocardial hypertrophy resulting from hemodynamic loading is perceived as compensatory stress adaptation. We previously reported the abundant presence of highly redox-active polysulfide molecules, termed supersulfide, with two or more sulfur atoms catenated in normal hearts, and the supersulfide catabolism in pathologic hearts after myocardial infarction correlated with worsened prognosis of heart failure. However, the impact of supersulfide on myocardial remodeling remains unclear. Here, we investigated the involvement of supersulfide metabolism in cardiomyocyte remodeling, using a model of adenosine 5'-triphosphate (ATP) receptor-stimulated atrophy and endothelin-1 receptor-stimulated hypertrophy in neonatal rat cardiomyocytes. Results revealed contrasting changes in intracellular supersulfide and its catabolite, hydrogen sulfide (H2S), between cardiomyocyte atrophy and hypertrophy. Stimulation of cardiomyocytes with ATP decreased supersulfide activity, while H2S accumulation itself did not affect cardiomyocyte atrophy. This supersulfide catabolism was also involved in myofibroblast formation of neonatal rat cardiac fibroblasts. Thus, unraveling supersulfide metabolism during myocardial remodeling may lead to the development of novel therapeutic strategies to improve heart failure.

Effect of electroacupuncture on myocardial transient receptor potential channels in mice with myocardial hypertrophy. / ç”µé’ˆå¯¹å¿ƒè‚Œè‚¥åŽšå°é¼ å¿ƒè‚Œç»„ç»‡çž¬æ—¶å—ä½“ç”µä½é€šé“çš„å½±å“.

OBJECTIVES: To observe the effect of electroacupuncture (EA) at "Neiguan"(PC6) on cardiac function, cardiac morphology and transient receptor potential channel (TRPC) protein expressions in myocardial tissue of mice with myocardial hypertrophy, so as to explore its mechanisms underlying improvement of myocardial hypertrophy. METHODS: Forty-five male C57BL/6 mice were randomly divided into control, model and EA groups (15 mice/group). The myocardial hypertrophy model was established by subcutaneous injection of isoproterenol hydrochloride (15 mg·kg-1·d-1) for 14 days. The mice of the control group received subcutaneous injection of same amount of normal saline. The mice of the EA group received EA stimulation (frequency of 2 Hz, intensity of 1 mA) of bilateral PC6 for 20 min each time, once a day for 14 consecutive days. After the intervention, the body weight, tibia length and heart weight were measured. The left ventricular ejection fraction (EF), fractional shortening index (FS), left ventricular end-systolic volume (LVEV), left ventricular end-systolic internal diameter (LVID) and left ventricular posterior wall thickness (LVPW) were measured by using echocardiography for evaluating the cardiac function. The mean number and surface area of myocardial cells was detected by wheat germ agglutinin (WGA) staining, and changes of the cardiac morphology were observed under light microscopy after HE staining. The expression levels of TRPC1, TRPC3, TRPC4 and TRPC6 (TRPC1/3/4/6) in the myocardial tissue were detected by real-time quantitative PCR (qPCR) and Western blot, separately. RESULTS: Compared with the control group, the heart-body weight ratio(P<0.05) and heart-weight-to-tibia-length ratio (P<0.01), LVEV and LVID levels, the relative surface area, left ventricular area ratio, and the expression levels of cardiac TRPC1/3/4/6 were significantly increased (P<0.01, P<0.05), while the EF, FS, LVPW, number of cardiomyocytes, and the left ventricular posterior wall ratio were obviously decreased (P<0.01, P<0.05) in the model group. In comparison with the model group, the heart/body weight ratio, heart-weight-to-tibia-length ratio, LVEV and LVID levels, relative surface area, left ventricular area ratio, and the expression levels of cardiac TRPC1/3/4/6 were significantly decreased (P<0.01, P<0.05), while the EF, FS, LVPW, number of cardiomyocytes and left ventricular posterior wall ratio were significantly increased (P<0.01, P<0.05) in the EA group. H.E. staining showed disordered arrangement of cardiomyocytes and obvious myocardial interstitial inflammatory cell infiltration in the model group, and evident reduction of degree of cardiac fibrosis and interstitial edema in the EA group. CONCLUSIONS: EA of PC6 can improve the cardiac function and cardiac morphology in mice with myocardial hypertrophy, which may be related to its functions in down-regulating the expression of transient receptor potential channels.

Canonical and Noncanonical Contribution of Thyroid Hormone Receptor Isoforms Alpha and Beta to Cardiac Hypertrophy and Heart Rate in Male Mice.

Background: Stimulation of ventricular hypertrophy and heart rate are two major cardiac effects of thyroid hormone (TH). The aim of this study was to determine in vivo which TH receptor (TR)-α or ß-and which mode of TR action-canonical gene expression or DNA-binding independent noncanonical action-mediate these effects. Methods: We compared global TRα and TRß knockout mice (TRαKO; TRßKO) with wild-type (WT) mice to determine the TR isoform responsible for T3 effects. The relevance of TR DNA binding was studied in mice with a mutation in the DNA-binding domain that selectively abrogates DNA binding and canonical TR action (TRαGS; TRßGS). Hearts were studied with echocardiography at baseline and after 7 weeks of T3 treatment. Gene expression was measured with real-time polymerase chain reaction. Heart rate was recorded with radiotelemetry transmitters for 7 weeks in untreated, hypothyroid, and T3-treated mice. Results: T3 induced ventricular hypertrophy in WT and TRßKO mice, but not in TRαKO mice. Hypertrophy was also induced in TRαGS mice. Thus, hypertrophy is mostly mediated by noncanonical TRα action. Similarly, repression of Mhy7 occurred in WT and TRαGS mice. Basal heart rate was largely dependent on canonical TRα action. But responsiveness to hypothyroidism and T3 treatment as well as expression of pacemaker gene Hcn2 were still preserved in TRαKO mice, demonstrating that TRß could compensate for absence of TRα. Conclusions: T3-induced cardiac hypertrophy could be attributed to noncanonical TRα action, whereas heart rate regulation was mediated by canonical TRα action. TRß could substitute for canonical but not noncanonical TRα action.

UCP1-dependent brown adipose activation accelerates cardiac metabolic remodeling and reduces initial hypertrophic and fibrotic responses to pathological stress.

Brown adipose tissue (BAT) is correlated to cardiovascular health in rodents and humans, but the physiological role of BAT in the initial cardiac remodeling at the onset of stress is unknown. Activation of BAT via 48 h cold (16°C) in mice following transverse aortic constriction (TAC) reduced cardiac gene expression for LCFA uptake and oxidation in male mice and accelerated the onset of cardiac metabolic remodeling, with an early isoform shift of carnitine palmitoyltransferase 1 (CPT1) toward increased CPT1a, reduced entry of long chain fatty acid (LCFA) into oxidative metabolism (0.59 ± 0.02 vs. 0.72 ± 0.02 in RT TAC hearts, p < .05) and increased carbohydrate oxidation with altered glucose transporter content. BAT activation with TAC reduced early hypertrophic expression of ß-MHC by 61% versus RT-TAC and reduced pro-fibrotic TGF-ß1 and COL3α1 expression. While cardiac natriuretic peptide expression was yet to increase at only 3 days TAC, Nppa and Nppb expression were elevated in Cold TAC versus RT TAC hearts 2.7- and 2.4-fold, respectively. Eliminating BAT thermogenic activation with UCP1 KO mice eliminated differences between Cold TAC and RT TAC hearts, confirming effects of BAT activation rather than autonomous cardiac responses to cold. Female responses to BAT activation were blunted, with limited UCP1 changes with cold, partly due to already activated BAT in females at RT compared to thermoneutrality. These data reveal a previously unknown physiological mechanism of UCP1-dependent BAT activation in attenuating early cardiac hypertrophic and profibrotic signaling and accelerating remodeled metabolic activity in the heart at the onset of cardiac stress.

Ultrasensitive Proteomics of Trace Cardiac Tissues with Anchor-Nanoparticles.

Pathological cardiac hypertrophy is a complex process that often leads to heart failure. Label-free proteomics has emerged as an important platform to reveal protein variations and to elucidate the mechanisms of cardiac hypertrophy. Endomyocardial biopsy is a minimally invasive technique for sampling cardiac tissue, but it yields only limited amounts of an ethically permissible specimen. After regular pathological examination, the remaining trace samples pose significant challenges for effective protein extraction and mass spectrometry analysis. Herein, we developed trace cardiac tissue proteomics based on the anchor-nanoparticles (TCPA) method. We identified an average of 6666 protein groups using ∼50 µg of myocardial interventricular septum samples by TCPA. We then applied TCPA to acquire proteomics from patients' cardiac samples both diagnosed as hypertrophic hearts and myocarditis controls and identified significant alterations in pathways such as regulation of actin cytoskeleton, oxidative phosphorylation, and cGMP-PKG signaling pathway. Moreover, we found multiple lipid metabolic pathways to be dysregulated in transthyretin cardiac amyloidosis compared to other types of cardiac hypertrophy. TCPA offers a new technique for studying pathological cardiac hypertrophy and can serve as a platform toolbox for proteomic research in other cardiac diseases.

Metformin induction of heat shock factor 1 activation and the mitochondrial unfolded protein response alleviate cardiac remodeling in spontaneously hypertensive rats.

Heart failure and cardiac remodeling are both characterized by mitochondrial dysfunction. Healthy mitochondria are required for adequate contractile activity and appropriate regulation of cell survival. In the mammalian heart, enhancement of the mitochondrial unfolded protein response (UPRmt) is cardioprotective under pressure overload conditions. We explored the UPRmt and the underlying regulatory mechanism in terms of hypertension-induced cardiac remodeling and the cardioprotective effect of metformin. Male spontaneously hypertensive rats and angiotensin II-treated neonatal rat cardiomyocytes were used to induce cardiac hypertrophy. The results showed that hypertension induced the formation of aberrant mitochondria, characterized by a reduced mtDNA/nDNA ratio and swelling, as well as lower levels of mitochondrial complexes I to V and inhibition of the expression of one protein subunit of each of complexes I to IV. Such changes eventually enlarged cardiomyocytes and increased cardiac fibrosis. Metformin treatment increased the mtDNA/nDNA ratio and regulated the UPRmt, as indicated by increased expression of activating transcription factor 5, Lon protease 1, and heat shock protein 60, and decreased expression of C/EBP homologous protein. Thus, metformin improved mitochondrial ultrastructure and function in spontaneously hypertensive rats. In vitro analyses revealed that metformin reduced the high levels of angiotensin II-induced mitochondrial reactive oxygen species in such animals and stimulated nuclear translocation of heat shock factor 1 (HSF1). Moreover, HSF1 small-interfering RNA reduced the metformin-mediated improvements in mitochondrial morphology and the UPRmt by suppressing hypertrophic signals and cardiomyocyte apoptosis. These results suggest that HSF1/UPRmt signaling contributes to the beneficial effects of metformin. Metformin-mediated targeting of mitochondrial protein homeostasis and modulation of HSF1 levels have potential therapeutic implications in terms of cardiac remodeling.

The mechanism of 14-3-3η in thyroxine induced mitophagy in cardiomyocytes.

Hyperthyroidism is becoming increasingly important as an independent risk factor for cardiovascular disease, eventually resulting in cardiac hypertrophy and heart failure. The 14-3-3 protein family subtypes regulate many cellular processes in eukaryotes by interacting with a diverse array of client proteins. Considering that the 14-3-3η protein protects cardiomyocytes by affecting mitochondrial function, exploring the biological influence and molecular mechanisms by which 14-3-3η alleviates the cardiac hypertrophy of hyperthyroidism is imperative. In vivo and in vitro, RT-PCR, Western blot, and Mitochondrial tracking assay were performed to understand the molecular mechanism of thyroxine-induced cardiomyocyte hypertrophy. HE staining, transmission electron microscopy, and immunofluorescence were used to observe intuitively changes of hearts and cardiomyocytes. The in vivo and in vitro results indicated that overexpression of the 14-3-3η ameliorated thyroxine-induced cardiomyocyte hypertrophy, whereas knockdown of the 14-3-3η protein aggravated thyroxine-induced cardiomyocyte hypertrophy. Additionally, overexpression of the 14-3-3η protein reduces thyroxine-induced mitochondrial damage and mitophagy in cardiomyocytes. Overexpression of 14-3-3η protein improves excessive mitophagy in the myocardium caused by thyroxine and thus prevents cardiac hypertrophy.

MICU3 Regulates Mitochondrial Calcium and Cardiac Hypertrophy.

BACKGROUND: Calcium (Ca2+) uptake by mitochondria occurs via the mitochondrial Ca2+ uniporter. Mitochondrial Ca2+ uniporter exists as a complex, regulated by 3 MICU (mitochondrial Ca2+ uptake) proteins localized in the intermembrane space: MICU1, MICU2, and MICU3. Although MICU3 is present in the heart, its role is largely unknown. METHODS: We used CRISPR-Cas9 to generate a mouse with global deletion of MICU3 and an adeno-associated virus (AAV9) to overexpress MICU3 in wild-type mice. We examined the role of MICU3 in regulating mitochondrial calcium ([Ca2+]m) in ex vivo hearts using an optical method following adrenergic stimulation in perfused hearts loaded with a Ca2+-sensitive fluorophore. Additionally, we studied how deletion and overexpression of MICU3, respectively, impact cardiac function in vivo by echocardiography and the molecular composition of the mitochondrial Ca2+ uniporter complex via Western blot, immunoprecipitation, and Blue native-PAGE analysis. Finally, we measured MICU3 expression in failing human hearts. RESULTS: MICU3 knock out hearts and cardiomyocytes exhibited a significantly smaller increase in [Ca2+]m than wild-type hearts following acute isoproterenol infusion. In contrast, heart with overexpression of MICU3 exhibited an enhanced increase in [Ca2+]m compared with control hearts. Echocardiography analysis showed no significant difference in cardiac function in knock out MICU3 mice relative to wild-type mice at baseline. However, mice with overexpression of MICU3 exhibited significantly reduced ejection fraction and fractional shortening compared with control mice. We observed a significant increase in the ratio of heart weight to tibia length in hearts with overexpression of MICU3 compared with controls, consistent with hypertrophy. We also found a significant decrease in MICU3 protein and expression in failing human hearts. CONCLUSIONS: Our results indicate that increased and decreased expression of MICU3 enhances and reduces, respectively, the uptake of [Ca2+]m in the heart. We conclude that MICU3 plays an important role in regulating [Ca2+]m physiologically, and overexpression of MICU3 is sufficient to induce cardiac hypertrophy, making MICU3 a possible therapeutic target.

Changes in cardiovascular arachidonic acid metabolism in experimental models of menopause and implications on postmenopausal cardiac hypertrophy.

Menopause is a normal stage in the human female aging process characterized by the cessation of menstruation and the ovarian production of estrogen and progesterone hormones. Menopause is associated with an increased risk of several different diseases. Cardiovascular diseases are generally less common in females than in age-matched males. However, this female advantage is lost after menopause. Cardiac hypertrophy is a disease characterized by increased cardiac size that develops as a response to chronic overload or stress. Similar to other cardiovascular diseases, the risk of cardiac hypertrophy significantly increases after menopause. However, the exact underlying mechanisms are not yet fully elucidated. Several studies have shown that surgical or chemical induction of menopause in experimental animals is associated with cardiac hypertrophy, or aggravates cardiac hypertrophy induced by other stressors. Arachidonic acid (AA) released from the myocardial phospholipids is metabolized by cardiac cytochrome P450 (CYP), cyclooxygenase (COX), and lipoxygenase (LOX) enzymes to produce several eicosanoids. AA-metabolizing enzymes and their respective metabolites play an important role in the pathogenesis of cardiac hypertrophy. Menopause is associated with changes in the cardiovascular levels of CYP, COX, and LOX enzymes and the levels of their metabolites. It is possible that these changes might play a role in the increased risk of cardiac hypertrophy after menopause.

Downregulation of HHATL promotes cardiac hypertrophy via activation of SHH/DRP1.

HHATL, previously implicated in cardiac hypertrophy in the zebrafish model, has emerged as a prioritized HCM risk gene. We identified six rare mutations in HHATL, present in 6.94 % of nonsarcomeric HCM patients (5/72). Moreover, a decrease of HHATL in the heart tissue from HCM patients and cardiac hypertrophy mouse model using transverse aortic constriction was observed. Despite this, the precise pathogenic mechanisms underlying HHATL-associated cardiac hypertrophy remain elusive. In this study, we observed that HHATL downregulation in H9C2 cells resulted in elevated expression of hypertrophic markers and reactive oxygen species (ROS), culminating in cardiac hypertrophy and mitochondrial dysfunction. Notably, the bioactive form of SHH, SHHN, exhibited a significant increase, while the mitochondrial fission protein dynamin-like GTPase (DRP1) decreased upon HHATL depletion. Intervention with the SHH inhibitor RU-SKI 43 or DRP1 overexpression effectively prevented Hhatl-depletion-induced cardiac hypertrophy, mitigating disruptions in mitochondrial morphology and membrane potential through the SHH/DRP1 axis. In summary, our findings suggest that HHATL depletion activates SHH signaling, reducing DRP1 levels and thereby promoting the expression of hypertrophic markers, ROS generation, and mitochondrial dysfunction, ultimately leading to cardiac hypertrophy. This study provides additional compelling evidence supporting the association of HHATL with cardiac hypertrophy.