Sequential changes in autophagy in diabetic cardiac fibrosis

Kinase Inhibitors Involved in the Regulation of Autophagy: Molecular Concepts and Clinical Implications

All cells and intracellular components are remodeled and recycled in order to replace the old and damaged cells. Autophagy is a process by which damaged, and unwanted cells are degraded in the lysosomes. There are three different types of autophagy: macroautophagy, microautophagy, and chaperone-mediated autophagy. Autophagy has an effect on adaptive and innate immunity, suppression of any tumour, and the elimination of various microbial pathogens. The process of autophagy has both positive and negative effects, and this pertains to any specific disease or its stage of progression. Autophagy involves various processes which are controlled by various signaling pathways, such as Jun N-terminal kinase, GSK3, ERK1, Leucine-rich repeat kinase 2, and PTEN-induced putative kinase 1 and parkin RBR E3. Protein kinases are also important for the regulation of autophagy as they regulate the process of autophagy either by activation or inhibition. The present review discusses the kinase catalyzed phosphorylated reactions, the kinase inhibitors, types of protein kinase inhibitors and their binding properties to protein kinase domains, the structures of active and inactive kinases, and the hydrophobic spine structures in active and inactive protein kinase domains. The intervention of autophagy by targeting specific kinases may form the mainstay of treatment of many diseases and lead the road to future drug discovery.

The role of autophagy in cardiovascular pathology

Macroautophagy/autophagy is a conserved catabolic recycling pathway in which cytoplasmic components are sequestered, degraded, and recycled to survive various stress conditions. Autophagy dysregulation has been observed and linked with the development and progression of several pathologies, including cardiovascular diseases, the leading cause of death in the developed world. In this review, we aim to provide a broad understanding of the different molecular factors that govern autophagy regulation and how these mechanisms are involved in the development of specific cardiovascular pathologies, including ischemic and reperfusion injury, myocardial infarction, cardiac hypertrophy, cardiac remodeling, and heart failure.

Human apoCIII transgenic mice with epicardial adipose tissue inflammation and PRESERVATION of the cardiac plexus

Hypertriglyceridemia is a result of the increase in the serum levels of lipoproteins, which are responsible for the transport of triglycerides and can be caused by genetic and/or metabolic factors. Animal models which either express or lack genes related to changes in the lipoproteins profile are useful to understand lipid metabolism. Apolipoprotein CIII (apoCIII) is an important modulator of hepatic production and peripheral removal of triglycerides. Mice that overexpress the apoCIII gene become hypertriglyceridemic, showing high concentrations of free fatty acids in the blood. Since hypertriglyceridemia is related to atherosclerosis, and the latter refers to cardiac alterations, this study aimed at evaluating the morphological, morphometric and quantitative profiles of the cardiac plexus, as well as the morphometric and histopathological aspects of the epicardial adipose tissue in human apoCIII transgenic mice. Therefore, 8-12-month-old male C57BL/6 mice that overexpressed human apoCIII (CIII) and their respective controls were used. Our results showed that overexpression of human apoCIII did not modify morphological or quantitative parameters of cardiac plexus neurons; however, age increased both, the area and the number of such cells. Furthermore, there was a direct correlation of this dyslipidemia to the thickening of periganglionar type 1 collagens. On the other hand, this overexpression caused epicardial adipose tissue inflammation and an increase in the area of the adipocytes, thus, favoring the recruitment of inflammatory cells in this tissue. In conclusion, this overexpression is harmful since it is related to an increase in cardiac adiposity, as well as to a predisposition to an inflammatory environment in the epicardial fat and to the incidence of cardiovascular diseases.

Dietary EPA Increases Rat Mortality in Diabetes Mellitus, A Phenomenon Which Is Compensated by Green Tea Extract

Diabetes is characterized by a high mortality rate which is often associated with heart failure. Green tea and eicosapentaenoic acid (EPA) are known to lessen some of the harmful impacts of diabetes and to exert cardio-protection. The aim of the study was to determine the effects of EPA, green tea extract (GTE), and a combination of both on the cardiac consequences of diabetes mellitus, induced in Wistar rats by injection of a low dose of streptozotocin (33 mg/kg) combined with a high fat diet. Cardiac mechanical function, coronary reactivity, and parameters of oxidative stress, inflammation, and energy metabolism were evaluated. In the context of diabetes, GTE alone limited several diabetes-related symptoms such as inflammation. It also slightly improved coronary reactivity and considerably enhanced lipid metabolism. EPA alone caused the rapid death of the animals, but this effect was negated by the addition of GTE in the diet. EPA and GTE combined enhanced coronary reactivity considerably more than GTE alone. In a context of significant oxidative stress such as during diabetes mellitus, EPA enrichment constitutes a risk factor for animal survival. It is essential to associate it with the antioxidants contained in GTE in order to decrease mortality rate and preserve cardiac function.

Hyperphosphatemia Promotes Senescence of Myoblasts by Impairing Autophagy Through Ilk Overexpression, A Possible Mechanism Involved in Sarcopenia

In mammalians, advancing age is associated with sarcopenia, the progressive and involuntary loss of muscle mass and strength. Hyperphosphatemia is an aging-related condition involved in several pathologies. The aim of this work was to assess whether hyperphosphatemia plays a role in the age-related loss of mass muscle and strength by inducing cellular senescence in murine myoblasts and to explore the intracellular mechanism involved in this effect. Cultured mouse C2C12 cells were treated with 10 mM beta-glycerophosphate (BGP] at different periods of time to induce hyperphosphatemia. BGP promoted cellular senescence after 24 h of treatment, assessed by the increased expression of p53, acetylated-p53 and p21 and senescence associated β-galactosidase activity. In parallel, BGP increased ILK expression and activity, followed by mTOR activation and autophagy reduction. Knocking-down ILK expression increased autophagy and protected cells from senescence induced by hyperphosphatemia. BGP also reduced the proliferative capacity of cultured myoblasts. Old mice (24-months-old] presented higher serum phosphate concentration, lower forelimb strength, higher expression of p53 and ILK and less autophagy in vastus muscle than young mice (5-months-old]. In conclusion, we propose that hyperphosphatemia induces senescence in cultured myoblasts through ILK overexpression, reducing their proliferative capacity, which could be a mechanism involved in the development of sarcopenia, since old mice showed loss of muscular strength correlated with high serum phosphate concentration and increased levels of ILK and p53.

Proteostasis in epicardial versus subcutaneous adipose tissue in heart failure subjects with and without diabetes

BACKGROUND

Cardiovascular diseases (CVDs) are leading cause of death and primary cause of morbidity and mortality in diabetic population. Epicardial adipose tissue (EAT) covers the heart's surface and is a source of biomolecules regulating heart and blood vessel physiology. The protective activation of the unfolded protein response (UPR) and autophagy allows the cardiomyocyte reticular network to restore energy and/or nutrient homeostasis and to avoid cell death. However, an excessive or prolonged UPR activation can trigger cell death. UPR activation is an early event of diabetic cardiomyopathies and deregulated autophagy is associated with CVDs.

RESULTS

An upregulation of UPR markers (glucose-regulated protein 78 KDa, glucose-regulated protein 94 KDa, inositol-requiring enzyme 1α, protein kinase RNA-like ER kinase and CCAAT/-enhancer-binding protein homologous protein (CHOP) gene) in EAT compared to subcutaneous adipose tissue (SAT), was observed as well as the UPR-related apoptosis marker caspase-4/procaspase-4 ratio but not in CHOP protein levels. Additionally, levels of ubiquitin and ubiquitinated proteins were decreased in EAT. Moreover, upregulation of autophagy markers (5' adenosine monophosphate-activated protein kinase, mechanistic target of rapamycin, Beclin 1, microtubule-associated protein light chain 3-II, lysosome-associated membrane protein 2, and PTEN-induced putative kinase 1) was observed, as well as an increase in the apoptotic Bim but not the ratio between Bim and the anti-apoptotic Bcl-2 in EAT. Diabetic patients show alterations in UPR activation markers but not in autophagy or apoptosis markers.

CONCLUSION

UPR and autophagy are increased in EAT compared to SAT, opening doors to the identification of early biomarkers for cardiomyopathies and novel therapeutic targets.

An Intervention Target for Myocardial Fibrosis: Autophagy

Myocardial fibrosis (MF) is the result of metabolic imbalance of collagen synthesis and metabolism, which is widespread in various cardiovascular diseases. Autophagy is a lysosomal degradation pathway which is highly conserved. In recent years, research on autophagy has been increasing and the researchers have also become cumulatively aware of the specified association between autophagy and MF. This review highlights the role of autophagy in MF and the potential effects through the administration of medicine.

Myocardial stress and autophagy: mechanisms and potential therapies

Autophagy is a ubiquitous cellular catabolic process responsive to energy stress. Research over the past decade has revealed that cardiomyocyte autophagy is a prominent homeostatic pathway, important in adaptation to altered myocardial metabolic demand. The cellular machinery of autophagy involves targeted direction of macromolecules and organelles for lysosomal degradation. Activation of autophagy has been identified as cardioprotective in some settings (that is, ischaemia and ischaemic preconditioning). In other situations, sustained autophagy has been linked with cardiopathology (for example, sustained pressure overload and heart failure). Perturbation of autophagy in diabetic cardiomyopathy has also been observed and is associated with both adaptive and maladaptive responses to stress. Emerging research findings indicate that various forms of selective autophagy operate in parallel to manage various types of catabolic cellular cargo including mitochondria, large proteins, glycogen, and stored lipids. In this Review, induction of autophagy associated with cardiac benefit or detriment is considered. The various static and dynamic approaches used to measure autophagy are critiqued, and current inconsistencies in the understanding of autophagy regulation in the heart are highlighted. The prospects for pharmacological intervention to achieve therapeutic manipulation of autophagic processes are also discussed.

Paris Saponin II induced apoptosis via activation of autophagy in human lung cancer cells

Paris Saponin II (PSII) has been shown anticancer activity against several cancer lines through the pro-apoptotic pathway. The aim of the study was to investigate the relationship between apoptosis and autophagy taking part in the anti-cancer mechanisms of PSII. In this study, PSII induced autophagy and apoptosis in dose- and time-dependent manners. Meanwhile, it induced autophagy as early as 2 h after exposure to 1 μM of PSII accompanying with apoptosis. Blockade of autophagy with chloroquine (CQ) attenuated apoptosis, while regulation of reactive oxygen species (ROS) by N-acetyl cysteine (NAC), gallic acid (GA) and H2O2 could not influence autophagy. In addition, PSII induced apoptosis via activation of autophagy, which might be associated with the activation of JNK and inhibition of PI3K/AKT/mTOR pathway. All in all, our research increased the understanding of the role of PSII regulating autophagy and apoptosis, which would hopefully provide prospective strategies for cancer therapy.