Autophagy and Myocardial Remodeling

Effect of Dendrobine on Cardiac Dysfunction in Rats with Myocardial Infarction by Regulating Autophagy

Aim: To observe Dendrobine (Den) on rats with post-myocardial infarction cardiac dysfunction and mechanism. Materials: Dividing 27 rats as Sham, Model and Den groups, rats treated with two weeks of drug had their cardiac function and structure measured by ultrasound; their myocardial pathological changes observed by HE and Masson staining and observe apoptosis cell number by TUNEL staining; their serum activities of LDH and CK-MB detected by ELISA; myocardial autophagy protein expressions detected by WB and immunohistochemistry. Results: Model group displayed decreased cardiac function levels, enlarged area of myocardial fibrosis, more serum activities of LDH and CK-MB, increased myocardial tissue structural damage and apoptosis cell number, downregulated LAMP2 expression, and up-regulated expressions of Beclin1, LC3-II/LC3-I rate, and P62. To rat victims of myocardial infarction, Den improved cardiac function, reduced area of myocardial fibrosis, compromised activities of serum LDH and CK-MB, and relieved damage in myocardial structure, decreased apoptosis cell number in myocardial tissue, up-regulated the expressions of Beclin1, LAMP2 and LC3-II, and down-regulated P62 to promote the autophagy in myocardium damaged by myocardial infarction. Conclusion: Den alleviates post-myocardial infarction cardiac dysfunction through improvement of autophagosomes formation and autophagic flux via Beclin1/LAMP2 pathway.

Exosomes and Exosomal Cargos: A Promising World for Ventricular Remodeling Following Myocardial Infarction

Exosomes are a pluripotent group of extracellular nanovesicles secreted by all cells that mediate intercellular communications. The effective information within exosomes is primarily reflected in exosomal cargos, including proteins, lipids, DNAs, and non-coding RNAs (ncRNAs), the most intensively studied molecules. Cardiac resident cells (cardiomyocytes, fibroblasts, and endothelial cells) and foreign cells (infiltrated immune cells, cardiac progenitor cells, cardiosphere-derived cells, and mesenchymal stem cells) are involved in the progress of ventricular remodeling (VR) following myocardial infarction (MI) via transferring exosomes into target cells. Here, we summarize the pathological mechanisms of VR following MI, including cardiac myocyte hypertrophy, cardiac fibrosis, inflammation, pyroptosis, apoptosis, autophagy, angiogenesis, and metabolic disorders, and the roles of exosomal cargos in these processes, with a focus on proteins and ncRNAs. Continued research in this field reveals a novel diagnostic and therapeutic strategy for VR.

Integrating pharmacological evaluation and computational identification for deciphering the action mechanism of Yunpi-Huoxue-Sanjie formula alleviates diabetic cardiomyopathy

Background: Yunpi-Huoxue-Sanjie (YP-SJ) formula is a Chinese herbal formula with unique advantages for the treatment of diabetic cardiovascular complications, such as Diabetic cardiomyopathy (DCM). However, potential targets and molecular mechanisms remain unclear. Therefore, our research was designed to evaluate rat myocardial morphology, fat metabolism and oxidative stress to verify myocardial protective effect of YP-SJ formula in vivo. And then to explore and validate its probable mechanism through network pharmacology and experiments in vitro and in vivo.

Methods: In this study, DCM rats were randomly divided into five groups: control group, model group, and three YP-SJ formula groups (low-dose, middle-dose, and high-dose groups). Experimental rats were treated with 6 g/kg/d, 12 g/kg/d and 24 g/kg/d YP-SJ formula by gavage for 10 weeks, respectively. Cardiac function of rats was measured by high-resolution small-animal imaging system. The cells were divided into control group, high glucose group, high glucose + control serum group, high glucose + dosed serum group, high glucose + NC-siRNA group, high glucose + siRNA-FoxO1 group. The extent of autophagy was measured by flow cytometry, immunofluorescence, and western blotting.

Results: It was found that YP-SJ formula could effectively improve cardiac systolic function in DCM rats. We identified 46 major candidate YP-SJ formula targets that are closely related to the progression of DCM. Enrichment analysis revealed key targets of YP-SJ formula related to environmental information processing, organic systems, and the metabolic occurrence of reactive oxygen species. Meanwhile, we verified that YP-SJ formula can increase the expression of forkhead box protein O1 (FoxO1), autophagy-related protein 7 (Atg7), Beclin 1, and light chain 3 (LC3), and decrease the expression of phosphorylated FoxO1 in vitro and in vivo. The results showed that YP-SJ formula could activate the FoxO1 signaling pathway associated with DCM rats. Further experiments showed that YP-SJ formula could improve cardiac function by regulating autophagy.

Conclusion: YP-SJ formula treats DCM by modulating targets that play a key role in autophagy, improving myocardial function through a multi-component, multi-level, multi-target, multi-pathway, and multi-mechanism approach.

Mitochondrial Pathobiology and Metabolic Remodeling in Progression to Overt Systolic Heart Failure

The mitochondria are mostly abundant in the heart, a beating organ of high- energy demands. Their function extends beyond being a power plant of the cell including redox balance, ion homeostasis and metabolism. They are dynamic organelles that are tethered to neighboring structures, especially the endoplasmic reticulum. Together, they constitute a functional unit implicated in complex physiological and pathophysiological processes. Their topology in the cell, the cardiac myocyte in particular, places them at the hub of signaling and calcium homeostasis, making them master regulators of cell survival or cell death. Perturbations in mitochondrial function play a central role in the pathophysiology of myocardial remodeling and progression of heart failure. In this minireview, we summarize important pathophysiological mechanisms, pertaining to mitochondrial morphology, dynamics and function, which take place in compensated hypertrophy and in progression to overt systolic heart failure. Published work in the last few years has expanded our understanding of these important mechanisms; a key prerequisite to identifying therapeutic strategies targeting mitochondrial dysfunction in heart failure.

Melatonin ameliorates pressure overload-induced cardiac hypertrophy by attenuating Atg5-dependent autophagy and activating the Akt/mTOR pathway

Cardiac hypertrophy, including hypertension and valvular dysfunction, is a pathological feature of many cardiac diseases that ultimately leads to heart failure. Melatonin confers a protective role against pathological cardiac hypertrophy, but the underlying mechanisms remain elusive. In the present study, we hypothesized that melatonin protects against pressure overload-induced cardiac hypertrophy by attenuating Atg5-dependent autophagy and activating the Akt/mTOR pathway. Male C57BL/6 mice that received adenovirus carrying cardiac-specific Atg5 (under the cTNT promoter; Ad-cTNT-Atg5) underwent transverse aortic constriction (TAC) or sham operation and received an intraperitoneal injection of melatonin (10 mg/kg/d), vehicle or LY294002 (10 mg/kg/d) for 8 weeks. Melatonin treatment for 8 weeks markedly attenuated cardiac hypertrophy and restored impaired cardiac function, as indicated by a decreased HW/BW ratio, reduced cell cross-sectional area and fibrosis, downregulated the mRNA levels of ANP, BNP, and β-MHC and ameliorated adverse effects on the LVEF and LVFS. Melatonin treatment also inhibited apoptosis and alleviated autophagy dysfunction. Furthermore, melatonin inhibited Akt/mTOR pathway activation, while these effects were blocked by LY294002. In addition, the effect of melatonin regulation on TAC-induced autophagy dysfunction was inhibited by LY294002 or cardiac-specific Atg5 overexpression. As expected, Akt/mTOR pathway inhibition or cardiac-specific Atg5 overexpression restrained melatonin alleviation of pressure overload-induced cardiac hypertrophy. These results demonstrated that melatonin ameliorated pressure overload-induced cardiac hypertrophy by attenuating Atg5-dependent autophagy and activating the Akt/mTOR pathway.

HIF-1α/BNIP3 signaling pathway-induced-autophagy plays protective role during myocardial ischemia-reperfusion injury

OBJECTIVE

The study was established to inquire into the protective effect of the HIF-1α (Hypoxia-inducible factor-1α)/ BNIP3(Bcl-2/adenovirus E1B 19-kDa interacting protein) signal path-induced-autophagy during myocardial ischemia/ reperfusion (I/R) and oxygen-glucose deprivation/recovery (OGD/R) injury in heart-derived H9C2 cells as well as its potential underlying mechanism.

METHODS

Immediate myocardial I/R in SD (Spraque Dawley) rats and cytotoxicity of OGD/R injury on H9C2 cells with and without inhibitors or agonists of HIF-1α and BNIP3 were evaluated. Expression of mitochondrial autophagic protein were detected by Western blot and immunofluorescence. And the mitochondrial autophagosome were detected using Transmission Electron Microscope (TEM).

RESULTS

I/R and OGD/R injury increased the expression level of HIF-1α, activated the downstream BNIP3 and subsequently triggered mitochondria-dependent autophagy. Up-regulation the expression of HIF-1α and BNIP3 may promote the cardiac myocytes of SD rats of I/R injure and OGD/R injury-induced autophagy of H9C2 cells. Moreover, down-regulation the expression of HIF-1α or BNIP3-siRNA decreased H9C2 cells autophagy under OGD/R injury.

CONCLUSIONS

Together, our studies indicated that HIF-1α synchronization regulate BNIP3 during OGD/R injury-induced autophagy in H9C2 cells, though BNIP3-induced autophagy acting as a survival mechanism.

Morphological Stages of Mitochondrial Vacuolar Degeneration in Phenylephrine-Stressed Cardiac Myocytes and in Animal Models and Human Heart Failure

Background and objectives: Derangements in mitochondrial integrity and function constitute an important pathophysiological feature in the pathogenesis of heart failure (HF) and play an important role in myocardial remodeling and systolic dysfunction. In systolic HF, we and others have shown an imbalance in mitochondrial dynamics toward mitochondrial fission and fragmentation with evidence of mitophagy, mitochondrial vacuolar degeneration, and impairment in mitochondrial oxidative capacity. The morphological stages of mitochondrial vacuolar degeneration have not been defined. We sought to elucidate the progressive stages of mitochondrial vacuolar degeneration, which would serve as a measure to define, morphologically, the severity of mitochondrial damage. Materials and Methods: Transmission electron microscopy was used to study mitochondrial morphology and pathology in phenylephrine-stressed cardiac myocytes in vitro and in left ventricular myocardium from a rat model of pressure overload induced systolic dysfunction and from patients with systolic HF. Results: In phenylephrine-stressed cardiomyocytes for two hours, alterations in mitochondrial cristae morphology (Stage A) and loss and dissolution of mitochondrial cristae in one (Stage B) or multiple (early Stage B→C) mitochondrion area(s) were evident in the earliest stages of mitochondrial vacuolar degeneration. Mitochondrial swelling and progressive dissolution of mitochondrial cristae (advanced Stage B→C), followed by complete loss and dissolution of mitochondrial cristae and permeabilization and destruction of inner mitochondrial membrane (Stage C) then outer mitochondrial membrane rupture (Stage D) constituted advanced stages of mitochondrial vacuolar degeneration. Similar morphological changes in mitochondrial vacuolar degeneration were seen in vivo in animal models and in patients with systolic HF; where about 60-70% of the mitochondria are mainly observed in stages B→C and fewer in stages C and D. Conclusion: Mitochondrial vacuolar degeneration is a prominent mitochondrial morphological feature seen in HF. Defining the progressive stages of mitochondrial vacuolar degeneration would serve as a measure to assess morphologically the severity of mitochondrial damage.