Metoprolol alleviates arginine vasopressin-induced cardiomyocyte hypertrophy by upregulating the AKT1-SERCA2 cascade in H9C2 cells

L-arginine alleviates heat stress-induced mammary gland injury through modulating CASTOR1-mTORC1 axis mediated mitochondrial homeostasis

As global warming intensifies, extreme heat is becoming increasingly frequent. These extreme heatwaves have decreased the milk production of dairy animals such as cows and goats and have caused significant damage to the entire dairy industry. It is known that heat stress (HS) can induce the apoptosis and autophagy of mammary epithelial cells (MECs), leading to a decrease in lactating MECs. L-arginine can effectively attenuate HS-induced decreases in milk yield, but the exact mechanisms are not fully understood. In this study, we found that HS upregulated the arginine sensor CASTOR1 in mouse MECs. Arginine activated mTORC1 activity through CASTOR1 and promoted mitochondrial biogenesis through the mTORC1/PGC-1α/NRF1 pathway. Moreover, arginine inhibited mitophagy through the CASTOR1/PINK1/Parkin pathway. Mitochondrial homeostasis ensures ATP synthesis and a stable cellular redox state for MECs under HS, further alleviating HS-induced damage and improving the lactation performance of MECs. In conclusion, these findings reveal the molecular mechanisms by which L-arginine relieves HS-induced mammary gland injury, and suggest that the intake of arginine-based feeds or feed additives is a promising method to increase the milk yield of dairy animals in extreme heat conditions.

M-type pyruvate kinase 2 (PKM2) tetramerization alleviates the progression of right ventricle failure by regulating oxidative stress and mitochondrial dynamics

BACKGROUND

Right ventricle failure (RVF) is a progressive heart disease that has yet to be fully understood at the molecular level. Elevated M-type pyruvate kinase 2 (PKM2) tetramerization alleviates heart failure, but detailed molecular mechanisms remain unclear.

OBJECTIVE

We observed changes in PKM2 tetramerization levels during the progression of right heart failure and in vitro cardiomyocyte hypertrophy and explored the causal relationship between altered PKM2 tetramerization and the imbalance of redox homeostasis in cardiomyocytes, as well as its underlying mechanisms. Ultimately, our goal was to propose rational intervention strategies for the treatment of RVF.

METHOD

We established RVF in Sprague Dawley (SD) rats by intraperitoneal injection of monocrotaline (MCT). The pulmonary artery pressure and right heart function of rats were assessed using transthoracic echocardiography combined with right heart catheterization. TEPP-46 was used both in vivo and in vitro to promote PKM2 tetramerization.

RESULTS

We observed that oxidative stress and mitochondrial disorganization were associated with increased apoptosis in the right ventricular tissue of RVF rats. Quantitative proteomics revealed that PKM2 was upregulated during RVF and negatively correlated with the cardiac function. Facilitating PKM2 tetramerization promoted mitochondrial network formation and alleviated oxidative stress and apoptosis during cardiomyocyte hypertrophy. Moreover, enhancing PKM2 tetramer formation improved cardiac mitochondrial morphology, mitigated oxidative stress and alleviated heart failure.

CONCLUSION

Disruption of PKM2 tetramerization contributed to RVF by inducing mitochondrial fragmentation, accumulating ROS, and finally promoted the progression of cardiomyocyte apoptosis. Facilitating PKM2 tetramerization holds potential as a promising therapeutic approach for RVF.

Comparison of the Protective Effects of Nebivolol and Metoprolol against LPS-Induced Injury in H9c2 Cardiomyoblasts

Here, we, for the first time, compared the cardioprotective effects of third-generation vasodilating beta-blocker nebivolol (Neb) and conventional beta-blocker metoprolol (Met) on LPS-induced injury in H9c2 cardiomyoblasts. Our findings denoted that Neb and Met pretreatment diminish LPS-mediated cytotoxicity and oxidative stress. Concomitantly, LPS-triggered inflammatory cytokines activation was significantly suppressed by Neb but not by Met. Pretreatment with either Neb or Met alleviated LPS-mediated mitochondrial impairment by enhancing the expression of genes related to its biogenesis such as PGC-1α, NRF1, and TFAM. On the contrary, Neb but not Met-upregulated mitochondrial fusion-related genes such as OPA, and MFN2. In summary, our findings suggest that Neb and Met treatment significantly ameliorated the LPS-induced cytotoxicity and oxidative stress. Additionally, these findings suggest that Neb but not Met significantly down-regulates LPS-induced proinflammatory factors, probably by enhancing mitochondrial biogenesis and fusion.

Melatonin activates the Mst1-Nrf2 signaling to alleviate cardiac hypertrophy in pulmonary arterial hypertension

Among pulmonary arterial hypertension (PAH) patients, right ventricular (RV) functioning has been considered a major determining factor for cardiac capacity and survival. However, despite the recognition of the clinical importance for preserving RV functioning, no effective treatments are currently available for RV failure. This study aims to suggest one such possible treatment, through investigating the cardio-protective capabilities of the anti-oxidant, melatonin (Mel), for treating adverse RV remodeling in PAH, along with its underlying mechanisms. Arginine vasopressin induced neonatal rat cardiomyocyte hypertrophy in vitro; in vivo, PAH was induced in rats through intraperitoneal monocrotaline (MCT) injections, and Mel was administered intraperitoneally 24 h prior to MCT. Mel reduced rat cardiomyocyte hypertrophy and mitochondrial oxidative stress in vitro by activating the Mst1-Nrf2 pathway, which were all reversed upon siRNA knockdown of Mst1. Likewise, in vivo, Mel pre-treatment significantly ameliorated MCT-induced deterioration in cardiac function, RV hypertrophy, fibrosis and dilation. These beneficial effects were also associated with Mst1-Nrf2 pathway up regulation and its associated reduction in oxidative stress, as evidenced by the decrease in RV malondialdehyde content. Notably, results from Mel treatment were similar, or even superior, to those obtained from N-acetyl cysteine (NAC), which has already been-confirmed as an anti-oxidative treatment for PAH. By contrast, co-treatment with the Mst1 inhibitor XMU-MP-1 reversed all of those Mel-associated beneficial effects. Our findings thus identified Mel as a potent cardio-protective agent against the onset of maladaptive RV remodeling, through enhancement of the anti-oxidative response via Mst1-Nrf2 pathway activation.

Downregulation of CASTOR1 Inhibits Heat-Stress-Induced Apoptosis and Promotes Casein and Lipid Synthesis in Mammary Epithelial Cells

Heat stress is one of the most important factors limiting the milk yields of dairy animals. This decline can be attributed to the heat-stress-induced apoptosis of mammary epithelial cells (MECs). The cytosolic arginine sensor for mTORC1 subunit 1 (CASTOR1) is a crucial upstream regulator of the mechanistic target of rapamycin complex 1 (mTORC1) signaling, which has close connections with apoptosis. However, the specific roles of CASTOR1 in regulating the apoptosis and lactation of MECs are still obscure. In the present study, we found that heat stress promotes apoptosis and CASTOR1's expression in HC11 cells. Downregulation of CASTOR1 inhibits heat-stress-induced apoptosis through a ROS-independent pathway. In addition, silencing of CASTOR1 promotes cell proliferation, cell cycle progression, and milk component synthesis, and overexpressing of CASTOR1 reverses these observations. Furthermore, we found that silencing of CASTOR1 contributes to the nuclear transport of SREBP1 and promotes lipid synthesis. This study demonstrates the pivotal roles of CASTOR1 in heat-stress-induced apoptosis and milk component synthesis in MECs.

Metoprolol Protects Against Arginine Vasopressin-Induced Cellular Senescence in H9C2 Cardiomyocytes by Regulating the Sirt1/p53/p21 Axis

Cardiomyocyte senescence is involved in the pathological mechanism of cardiac diseases. Metoprolol is a β1 receptor blocker used for the treatment of hypertension. Recent studies show that Metoprolol can protect cardiomyocytes against ischemia injury. The present study aims to investigate the protective effects of Metoprolol against arginine vasopressin (AVP)-induced cellular senescence in cultured cardiomyocytes. The cell proliferation assay and cytotoxicity lactate dehydrogenase assay showed that the highest tolerated dosage of Metoprolol in H9C2 cardiomyocytes was optimized as 10 µM. The enzyme-linked immunosorbent assay showed that Metoprolol significantly ameliorated the elevated level of the DNA oxidation product 8-hydroxy-2 deoxyguanosine. Metoprolol also decreased the percentage of senescence-associated β-galactosidase positive cells and improved the telomerase activity under AVP exposure. Moreover, treatment with Metoprolol ameliorated the decreased intracellular nicotinamide phosphoribosyltransferase activity, nicotinamide adenine dinucleotide/nicotinamide adenine dinucleotide phosphate (NAD⁺/NADPH) ratio, and Sirtuin1 activity in cardiomyocytes by AVP. Finally, Metoprolol was able to downregulate the AVP-induced expression of acetylated p53 and p21. Taken together, our data reveal that Metoprolol protected the cardiomyocytes from AVP-induced senescence.

Regulation of the Immune Microenvironment by an NLRP3 Inhibitor Contributes to Attenuation of Acute Right Ventricular Failure in Rats with Pulmonary Arterial Hypertension

Background

Right heart failure is the terminal stage of PAH. When PAH patients suffer from pulmonary infection or puerperal infection heart failure often rapidly develops. Low dose of lipopolysaccharide induces rapid right ventricular failure in rats with pulmonary arterial hypertension.

Purpose

The objective of this study was to investigate whether the NLRP3 inflammasome mediates disturbance of the ventricular immune microenvironment of PAH rats and promotes right ventricular failure.

Methods

Intraperitoneal injection of monocrotaline was used to induce PAH in rats. Right ventricular function was measured via echocardiography before and after the rats were treated with lipopolysaccharide and MCC950. The degree of immune microenvironment disturbance in right ventricular tissue was measured with a rat chemokine and cytokine antibody array, Western blot, flow cytometry and quantitative real-time PCR analysis.

Results

After the rats were injected with LPS, they exhibited right ventricular dysfunction and a significant increase in right ventricular tissue inflammation with elevated M1 macrophage proportion. Administration of MCC950 suppressed inflammation and improved right ventricular function. The number of M1 macrophages was decreased after MCC950 treatment. NLRP3 inflammasome inhibition ameliorated LPS-induced changes in the immune microenvironment in the right heart and right ventricular dysfunction in rats with PAH.

Conclusion

Selective inhibition of NLRP3 pathway interfered the interaction between hypertrophic cardiomyocytes and macrophages in the initial stage of inflammation and maintained the immune microenvironment balance, eventually contributing to attenuation of LPS-induced acute heart failure in PAH rats.

Genome-wide analysis of the mouse LIM gene family reveals its roles in regulating pathological cardiac hypertrophy

LIM-domain proteins have been shown to be associated with heart development and diseases. Systematic studies of LIM family members at the genome-wide level, which are crucial to further understand their functions in cardiac hypertrophy, are currently lacking. Here, 70 LIM genes were identified and characterised in mice. The expression patterns of LIM genes differ greatly during cardiac development and in the case of hypertrophy. Both Crip2 and Xirp2 are differentially expressed in cardiac hypertrophy and during heart failure. In addition, the hypertrophic state of cardiomyocytes is controlled by the relative expression levels of Crip2 and Xirp2. This study provides a foundation for further understanding of the special roles of LIM proteins in mammalian cardiac development and hypertrophy.

Whole Genome Level Analysis of the Wnt and DIX Gene Families in Mice and Their Coordination Relationship in Regulating Cardiac Hypertrophy

The Wnt signaling pathway is an evolutionarily conserved signaling pathway that plays essential roles in embryonic development, organogenesis, and many other biological activities. Both Wnt proteins and DIX proteins are important components of Wnt signaling. Systematic studies of Wnt and DIX families at the genome-wide level may provide a comprehensive landscape to elucidate their functions and demonstrate their relationships, but they are currently lacking. In this report, we describe the correlations between mouse Wnt and DIX genes in family expansion, molecular evolution, and expression levels in cardiac hypertrophy at the genome-wide scale. We observed that both the Wnt and DIX families underwent more expansion than the overall average in the evolutionarily early stage. In addition, mirrortree analyses suggested that Wnt and DIX were co-evolved protein families. Collectively, these results would help to elucidate the evolutionary characters of Wnt and DIX families and demonstrate their correlations in mediating cardiac hypertrophy.

Tannic acid alleviates lipopolysaccharide‑induced H9C2 cell apoptosis by suppressing reactive oxygen species‑mediated endoplasmic reticulum stress

Sepsis-induced myocardial dysfunction is one of the features of multiple organ dysfunction in sepsis, which is associated with extremely high mortality and is characterized by impaired myocardial compliance. To date, there are few effective treatment options available to cure sepsis. Tannic acid (TA) is reportedly protective during sepsis; however, the underlying mechanisms by which TA protects against septic heart injury remain elusive. The present study investigated the potential effects and underlying mechanisms of TA in alleviating lipopolysaccharide (LPS)-induced H9C2 cardiomyocyte cell apoptosis. H9C2 cells were treated with LPS (15 µg/ml), TA (10 µM) and TA + LPS; control cells were treated with medium only. Apoptosis was measured using flow cytometry, reverse transcription-quantitative PCR (RT-qPCR) and western blot analysis. Additionally, the levels of cellular reactive oxygen species (ROS), malondialdehyde and nicotinamide adenine dinucleotide phosphate were evaluated. Western blotting and RT-qPCR were also employed to detect the expression levels of endoplasmic reticulum (ER) stress-associated functional proteins. The present findings demonstrated that TA reduced the degree of LPS-induced H9C2 cell injury, including inhibition of ROS production and ER stress (ERS)-associated apoptosis. ERS-associated functional proteins, including activating transcription factor 6, protein kinase-like ER kinase, inositol-requiring enzyme 1, spliced X box-binding protein 1 and C/EBP-homologous protein were suppressed in response to TA treatment. Furthermore, the expression levels of ERS-associated apoptotic proteins, including c-Jun N-terminal kinase, Bax, cytochrome c, caspase-3, caspase-12 and caspase-9 were reduced following treatment with TA. Additionally, the protective effects of TA on LPS-induced H9C2 cells were partially inhibited following treatment with the ROS inhibitor N-acetylcysteine, which demonstrated that ROS mediated ERS-associated apoptosis and TA was able to decrease ROS-mediated ERS-associated apoptosis. Collectively, the present findings demonstrated that the protective effects of TA against LPS-induced H9C2 cell apoptosis may be associated with the amelioration of ROS-mediated ERS. These findings may assist the development of potential novel therapeutic methods to inhibit the progression of myocardial cell injury.

Neurohormonal activation induces intracellular iron deficiency and mitochondrial dysfunction in cardiac cells

Background

Iron deficiency (ID) is common in patients with heart failure (HF) and is associated with poor outcomes, yet its role in the pathophysiology of HF is not well-defined. We sought to determine the consequences of HF neurohormonal activation in iron homeostasis and mitochondrial function in cardiac cells.

Methods

HF was induced in C57BL/6 mice by using isoproterenol osmotic pumps and embryonic rat heart-derived H9c2 cells were subsequently challenged with Angiotensin II and/or Norepinephrine. The expression of several genes and proteins related to intracellular iron metabolism were assessed by Real time-PCR and immunoblotting, respectively. The intracellular iron levels were also determined. Mitochondrial function was analyzed by studying the mitochondrial membrane potential, the accumulation of radical oxygen species (ROS) and the adenosine triphosphate (ATP) production.

Results

Hearts from isoproterenol-stimulated mice showed a decreased in both mRNA and protein levels of iron regulatory proteins, transferrin receptor 1, ferroportin 1 and hepcidin compared to control mice. Furthermore, mitoferrin 2 and mitochondrial ferritin were also downregulated in the hearts from HF mice. Similar data regarding these key iron regulatory molecules were found in the H9c2 cells challenged with neurohormonal stimuli. Accordingly, a depletion of intracellular iron levels was found in the stimulated cells compared to non-stimulated cells, as well as in the hearts from the isoproterenol-induced HF mice. Finally, neurohormonal activation impaired mitochondrial function as indicated by the accumulation of ROS, the impaired mitochondrial membrane potential and the decrease in the ATP levels in the cardiac cells.

Conclusions

HF characteristic neurohormonal activation induced changes in the regulation of key molecules involved in iron homeostasis, reduced intracellular iron levels and impaired mitochondrial function. The current results suggest that iron could be involved in the pathophysiology of HF.