Synergistic cardiac pathological hypertrophy induced by high-salt diet in IGF-IIRα cardiac-specific transgenic rats

Mitophagy in Doxorubicin-Induced Cardiotoxicity: Insights into Molecular Biology and Novel Therapeutic Strategies

Doxorubicin is a chemotherapeutic drug utilized for solid tumors and hematologic malignancies, but its clinical application is hampered by life-threatening cardiotoxicity, including cardiac dilation and heart failure. Mitophagy, a cargo-specific form of autophagy, is specifically used to eliminate damaged mitochondria in autophagosomes through hydrolytic degradation following fusion with lysosomes. Recent advances have unveiled a major role for defective mitophagy in the etiology of DOX-induced cardiotoxicity. Moreover, specific interventions targeting this mechanism to preserve mitochondrial function have emerged as potential therapeutic strategies to attenuate DOX-induced cardiotoxicity. However, clinical translation is challenging because of the unclear mechanisms of action and the potential for pharmacological adverse effects. This review aims to offer fresh perspectives on the role of mitophagy in the development of DOX-induced cardiotoxicity and investigate potential therapeutic strategies that focus on this mechanism to improve clinical management.

Enhanced IGF-IIRα Expression Exacerbates Lipopolysaccharide-Induced Cardiac Inflammation, Hypertrophy, and Apoptosis Through Calcineurin Activation

Cardiovascular disease is one of the leading causes of death worldwide and has a high prevalence. Insulin-like growth factor-II receptor α (IGF-IIRα) acts as a stress-inducible negative regulator. This study focused on the substantial impact of heightened expression of IGF-IIRα in cardiac myoblasts and its association with the exacerbation of cardiac dysfunction. Using lipopolysaccharide (LPS)-induced H9c2 cardiac myoblasts as a model for sepsis, we aimed to elucidate the molecular interactions between IGF-IIRα and LPS in exacerbating cardiac injury. Our findings demonstrated a synergistic induction of cardiac inflammation and hypertrophy by LPS stimulation and IGF-IIRα overexpression, leading to decreased cell survival. Excessive calcineurin activity, triggered by this combined condition, was identified as a key factor exacerbating the negative effects on cell survival. Cellular changes such as cell enlargement, disrupted actin filaments, and upregulation of hypertrophy-related and inflammation-related proteins contributed to the overall hypertrophic and inflammatory responses. Overexpression of IGF-IIRα also exacerbated apoptosis induced by LPS in H9c2 cardiac myoblasts. Inhibiting calcineurin in LPS-treated H9c2 cardiac myoblasts with IGF-IIRα overexpression effectively reversed the detrimental effects, reducing cell damage and mitigating apoptosis-related cardiac mechanisms. Our study suggests that under sepsis-like conditions in the heart with IGF-IIRα overexpression, hyperactivation of calcineurin worsens cardiac damage. Suppressing IGF-IIRα and calcineurin expression could be a potential intervention to alleviate the impact of the illness and improve cardiac function.

Cardiac-specific overexpression of insulin-like growth factor II receptor-α interferes with the regulation of calcium homeostasis in the heart under hyperglycemic conditions

BACKGROUND

Diabetic cardiomyopathy is a progressive disease caused by inexplicit mechanisms, and a novel factor, insulin-like growth factor II receptor-α (IGF-IIRα), may contribute to aggravating its pathogenesis. We hypothesized that IGF-IIRα could intensify diabetic heart injury.

METHODS AND RESULTS

To demonstrate the potential role of IGF-IIRα in the diabetic heart, we used (SD-TG [IGF-IIRα]) transgenic rat model with cardiac-specific overexpression of IGF-IIRα, along with H9c2 cells, to study the effects of IGF-IIRα in the heart under hyperglycemic conditions. IGF-IIRα was found to remodel calcium homeostasis and intracellular Ca2+ overload-induced autophagy disturbance in the heart during diabetes. IGF-IIRα overexpression induced intracellular Ca2+ alteration by downregulating phosphorylated phospholamban/sarcoplasmic/endoplasmic reticulum calcium-ATPase 2a (PLB/SERCA2a), resulting in the suppression of Ca2+ uptake into the endoplasmic reticulum. Additionally, IGF-IIRα itself contributed to Ca2+ withdrawal from the endoplasmic reticulum by increasing the expression of CaMKIIδ in the active form. Furthermore, alterations in Ca2+ homeostasis significantly dysregulated autophagy in the heart during diabetes.

CONCLUSIONS

Our study reveals the novel role of IGF-IIRα in regulating cardiac intracellular Ca2+ homeostasis and its related autophagy interference, which contribute to the development of diabetic cardiomyopathy. In future, the present study findings have implications in the development of appropriate therapy to reduce diabetic cardiomyopathy.

Insulin-like growth factor II receptor alpha overexpression in heart aggravates hyperglycemia-induced cardiac inflammation and myocardial necrosis

Diabetes-induced cardiovascular complications are mainly associated with high morbidity and mortality in patients with diabetes. Insulin-like growth factor II receptor α (IGF-IIRα) is a cardiac risk factor. In this study, we hypothesized IGF-IIRα could also deteriorate diabetic heart injury. The results presented that both in vivo transgenic Sprague-Dawley rat model with specific IGF-IIRα overexpression in the heart and in vitro myocardium H9c2 cells were used to investigate the negative function of IGF-IIRα in diabetic hearts. The results showed that IGF-IIRα overexpression aided hyperglycemia in creating more myocardial injury. Pro-inflammatory factors, such as Tumor necrosis factor-alpha, Interleukin-6, Cyclooxygenase-2, Inducible nitric oxide synthase, and Nuclear factor-kappaB inflammatory cascade, are enhanced in the diabetic myocardium with cardiac-specific IGF-IIRα overexpression. Correspondingly, IGF-IIRα overexpression in the diabetic myocardium also reduced the PI3K-AKT survival axis and activated mitochondrial-dependent apoptosis. Finally, both ejection fraction and fractional shortening were be significantly decrease in diabetic rats with cardiac-specific IGF-IIRα overexpression. Overall, all results provid clear evidence that IGF-IIRα can enhance cardiac damage and is a harmful factor to the heart under high-blood glucose conditions. However, the pathophysiology of IGF-IIRα under different stresses and its downstream regulation in the heart still require further research.

Overexpression of cardiac-specific IGF-IIRα accelerates the development of liver dysfunction through STZ-induced diabetic hepatocyte damage in transgenic rats

This study reports the effect of cardiac-specific insulin-like growth factor-II receptor α (IGF-IIRα) overexpression on the development of liver dysfunction in transgenic rats via STZ-induced diabetic hepatocyte damage. The cardio-hepatic syndrome comprises a number of heart and liver illnesses in which an acute or chronic disease in one organ can lead to acute or chronic disease in the other. However, the molecular mechanism involved in such a set of conditions is unclear. In this study, we developed a transgenic rat model with cardiac-specific overexpression of IGF-IIRα, which is a supplementary splicing variant of insulin-like growth factor-II receptor (IGF-IIR), expressed in pathological hearts, to investigate the relationship between late fetal gene expression in diabetic hearts and their influence on diabetic hepatopathy. STZ (55 mg/kg) was intraperitoneally delivered into IGF-IIR overexpressed transgenic (TG) and non-transgenic (NTG) animal models developed in Sprague-Dawley (SD) rats after an overnight fast. The relationship among IGF-IIRα overexpression and hepatocyte damages have been determined based on the complexity of damage in the liver. Our findings revealed that overexpression of the cardiac-specific IGF-IIRα enhances diabetes-induced morphological alterations and hepatic inflammation in the livers. The diabetic transgenic rats demonstrated the development of pathological conditions such as thick collagen fiber deposition, bridging fibrosis, and elevation of α-SMA and MMP1 related liver fibrosis mechanisms. Our data suggest that IGF-IIRα overexpression in the heart during a pathological state may worsen diabetic hepatopathy in rats.

Angiotensin II Receptor Blocker Irbesartan Enhanced SIRT1 longevity Signaling Replaces the Mitochondrial Biogenetic Survival Pathway to Attenuate Hypertension-Induced Heart Apoptosis

Background: The present study investigated whether angiotensin II type 1 receptor blocker irbesartan (ARB) and partial agonist of PPAR-γ prevents heart apoptosis by suppressing cardiac Fas/FasL-mediated to mitochondria-mediated apoptosis in the hearts of hypertensive rat model. Methods: Cardiac function using echocardiography, H&E staining, TUNEL assay, and Western blotting were measured in the excised hearts from three groups, i.e., an untreated hypertensive group (SHR), an ARB-treated hypertensive group (50 mg/kg/day, S.C., SHR-ARB), and untreated normotensive Wistar-Kyoto rats (WKY). Results: Fas Ligand, Fas death receptors, FADD, active caspase-8, active caspase-3 (Fas/FasL-mediated apoptotic pathway), as well as Bax, cytochrome c, active caspase-9 and -3 (mitochondria-mediated apoptotic pathway), IGF-II, and p-JNK were decreased in SHR-ARB group when compared with the SHR group. SIRT1, PGC-1α, Bcl2, and Bcl-xL (SIRT1/PGC-1α pro-survival pathway) were increased in the SHR-ARB group when compared with the SHR group. Conclusions: Our findings suggested that the ARB might prevent cardiac Fas/FasL-mediated to mitochondria-mediated apoptosis pathway in the hypertensive model associated with IGF-II, p-JNK deactivation, and SIRT1/PGC-1α pro-survival pathway upregulation. ARB prevents hypertension-enhanced cardiac apoptosis via enhancing SIRT1 longevity signaling and enhances the mitochondrial biogenetic survival pathway.

Perturbed ER homeostasis by IGF-IIRα promotes cardiac damage under stresses

The heart is a very dynamic pumping organ working perpetually to maintain a constant blood supply to the whole body to transport oxygen and nutrients. Unfortunately, it is also subjected to various stresses based on physiological or pathological conditions, particularly more vulnerable to damages caused by oxidative stress. In this study, we investigate the molecular mechanism and contribution of IGF-IIRα in endoplasmic reticulum stress induction in the heart under doxorubicin-induced cardiotoxicity. Using in vitro H9c2 cells, in vivo transgenic rat cardiac tissues, siRNAs against CHOP, chemical ER chaperone PBA, and western blot experiments, we found that IGF-IIRα overexpression enhanced ER stress markers ATF4, ATF6, IRE1α, and PERK which were further aggravated by DOX treatment. This was accompanied by a significant perturbation in stress-associated MAPKs such as p38 and JNK. Interestingly, PARKIN, a stress responsive cellular protective mediator was significantly downregulated by IGF-IIRα concomitant with decreased expression of ER chaperone GRP78. Furthermore, ER stress-associated pro-apoptotic factor CHOP was increased considerably in a dose-dependent manner followed by elevated c-caspase-12 and c-caspase-3 activities. Conversely, treatment of H9c2 cells with chemical ER chaperone PBA or siRNA against CHOP abolished the IGF-IIRα-induced ER stress responses. Altogether, these findings suggested that IGF-IIRα contributes to ER stress induction and inhibits cellular stress coping proteins while increasing pro-apoptotic factors feeding into a cardio myocyte damage program that eventually paves the way to heart failure.

Physical exercise prevents age-related heart dysfunction induced by high-salt intake and heart salt-specific overexpression in Drosophila

A long-term high-salt intake (HSI) seems to accelerate cardiac aging and age-related diseases, but the molecular mechanism is still not entirely clear. Exercise is an effective way to delay cardiac aging. However, it remains unclear whether long-term exercise (LTE) can protect heart from aging induced by high-salt stress. In this study, heart CG2196(salt) specific overexpression (HSSO) and RNAi (HSSR) was constructed by using the UAS/hand-Gal4 system in Drosophila. Flies were given exercise and a high-salt diet intervention from 1 to 5 weeks of age. Results showed that HSSR and LTE remarkably prevented heart from accelerated age-related defects caused by HSI and HSSO, and these defects included a marked increase in heart period, arrhythmia index, malondialdehyde (MDA) level, salt expression, and dTOR expression, and a marked decrease in fractional shortening, SOD activity level, dFOXO expression, PGC-1α expression, and the number of mitochondria and myofibrils. The combination of HSSR and LTE could better protect the aging heart from the damage of HSI. Therefore, current evidences suggested that LTE resisted HSI-induced heart presenility via blocking CG2196(salt)/TOR/oxidative stress and activating dFOXO/PGC-1α. LTE also reversed heart presenility induced by cardiac-salt overexpression via activating dFOXO/PGC-1α and blocking TOR/oxidative stress.

IGF IIRα-triggered pathological manifestations in the heart aggravate renal inflammation in STZ-induced type-I diabetes rats

Pathological manifestations in either heart or kidney impact the function of the other and form the basis for the development of cardiorenal syndrome. However, the mechanism or factors involved in such scenario are not completely elucidated. In our study, to find the correlation between late fetal gene expression in diabetic hearts and their influence on diabetic nephropathy, we created a rat model with cardiac specific overexpression of IGF-IIRα, which is an alternative splicing variant of IGFIIR, expressed in pathological hearts. In this study, transgenic rats over expressing cardiac specific IGF-IIRα and non-transgenic animal models established in SD rats were administered with single dose of streptozotocin (STZ, 55 mg/Kg) to induce Type I diabetes. The correlation between IGF-IIRα and kidney damages were further determined based on their intensity of damage in the kidneys. The results show that cardiac specific overexpression of IGF-IIRα elevates the diabetes associated inflammation and morphological changes in the kidneys. The diabetic transgenic rats showed advancement in the pathological features such a renal tubular damage, collagen accumulation and enhancement in STAT3 associated mechanism of renal fibrosis. The results therefore show that that IGF-IIRα expression in the heart during pathological condition may worsen symptoms of diabetic nephropathy in rats.

Development of Magnetic Torque Stimulation (MTS) Utilizing Rotating Uniform Magnetic Field for Mechanical Activation of Cardiac Cells

Regulation of cell signaling through physical stimulation is an emerging topic in biomedicine. Background: While recent advances in biophysical technologies show capabilities for spatiotemporal stimulation, interfacing those tools with biological systems for intact signal transfer and noncontact stimulation remains challenging. Here, we describe the use of a magnetic torque stimulation (MTS) system combined with engineered magnetic particles to apply forces on the surface of individual cells. MTS utilizes an externally rotating magnetic field to induce a spin on magnetic particles and generate torsional force to stimulate mechanotransduction pathways in two types of human heart cells—cardiomyocytes and cardiac fibroblasts. Methods: The MTS system operates in a noncontact mode with two magnets separated (60 mm) from each other and generates a torque of up to 15 pN µm across the entire area of a 35-mm cell culture dish. The MTS system can mechanically stimulate both types of human heart cells, inducing maturation and hypertrophy. Results: Our findings show that application of the MTS system under hypoxic conditions induces not only nuclear localization of mechanoresponsive YAP proteins in human heart cells but also overexpression of hypertrophy markers, including β-myosin heavy chain (βMHC), cardiotrophin-1 (CT-1), microRNA-21 (miR-21), and transforming growth factor beta-1 (TGFβ-1). Conclusions: These results have important implications for the applicability of the MTS system to diverse in vitro studies that require remote and noninvasive mechanical regulation.

Endurance exercise protects aging Drosophila from high-salt diet (HSD)-induced climbing capacity decline and lifespan decrease by enhancing antioxidant capacity

A high-salt diet (HSD) is a major cause of many chronic and age-related defects such as myocardial hypertrophy, locomotor impairment and mortality. Exercise training can efficiently prevent and treat many chronic and age-related diseases. However, it remains unclear whether endurance exercise can resist HSD-induced impairment of climbing capacity and longevity in aging individuals. In our study, flies were given exercise training and fed a HSD from 1-week old to 5-weeks old. Overexpression or knockdown of salt and dFOXO were built by UAS/Gal4 system. The results showed that a HSD, salt gene overexpression and dFOXO knockdown significantly reduced climbing endurance, climbing index, survival, dFOXO expression and SOD activity level, and increased malondialdehyde level in aging flies. Inversely, in a HSD aging flies, endurance exercise and dFOXO overexpression significantly increased their climbing ability, lifespan and antioxidant capacity, but they did not significantly change the salt gene expression. Overall, current results indicated that a HSD accelerated the age-related decline of climbing capacity and mortality via upregulating salt expression and inhibiting the dFOXO/SOD pathway. Increased dFOXO/SOD pathway activity played a key role in mediating endurance exercise resistance to the low salt tolerance-induced impairment of climbing capacity and longevity in aging DrosophilaThis article has an associated First Person interview with the first author of the paper.