High glucose-induced Ca2+ overload and oxidative stress contribute to apoptosis of cardiac cells through mitochondrial dependent and independent pathways

Recent Progression of Pathogenesis and Treatment for Diabetic Cataracts

Background: Cataracts are still the main cause of blindness worldwide. The incidence of cataracts in the diabetic population is 3-5 times higher than in healthy people. With the increasing incidence of diabetes and the development of aging, as well as the higher risk of surgical and postoperative complications of diabetic patients undergoing surgery, it is still necessary to study the occurrence and development mechanism of diabetic cataracts as well as potential therapeutic targets and therapeutic drugs.Methods: A retrospective review of the literature from PubMed (2017-2024).Results: We summarized the the current literature on the molecular mechanism and prevention and treatment of diabetic cataracts.Conclusions: The aqueous humor metabolism changes, oxidative stress, reactive oxygen species generation increase, the conversion of polyol pathway, as well as non-coding RNA expression changes play important roles in diabetic cataract and these processes is closely linked with each other. Inhibitors or drugs target to these processes, such as aldose reductase inhibitors, antioxidants, natural flavonoid compounds, as well as nanotechnology-based therapeutic product, have shown promising prospects in the prevention and treatment of diabetic cataract.

Enhancing the therapeutic efficacy of mesenchymal stem cell transplantation in diabetes: Amelioration of mitochondrial dysfunction-induced senescence

Mesenchymal stem cell (MSC) transplantation offers significant potential for the treatment of diabetes mellitus (DM) and its complications. However, hyperglycemic conditions can induce senescence and dysfunction in both transplanted and resident MSCs, thereby limiting their therapeutic potential. Mitochondrial dysfunction and oxidative stress are key contributors to this process in MSCs exposed to hyperglycemia. As such, strategies aimed at mitigating mitochondrial dysfunction could enhance the therapeutic efficacy of MSC transplantation in DM. In this review, we provide an updated overview of how mitochondrial dysfunction mediates MSC senescence. We present experimental evidence for the molecular mechanisms behind high glucose-induced mitochondrial dysfunction in MSCs, which include impairment of mitochondrial biogenesis, mitochondrial calcium regulation, the mitochondrial antioxidant system, mitochondrial fusion-fission dynamics, mitophagy, and intercellular mitochondrial transfer. Furthermore, we propose potential pharmacological candidates that could improve the efficacy of MSC transplantation by enhancing mitochondrial function in patients with DM and related complications.

Calpain inhibition decreases oxidative stress via mitochondrial regulation in a swine model of chronic myocardial ischemia

INTRODUCTION

Calpain overexpression is implicated in mitochondrial damage leading to tissue oxidative stress and myocardial ischemic injury. The aim of this study was to determine the effects of calpain inhibition (CI) on mitochondrial impairment and oxidative stress in a swine model of chronic myocardial ischemia and metabolic syndrome.

METHODS

Yorkshire swine were fed a high-fat diet for 4 weeks to induce metabolic syndrome then underwent placement of an ameroid constrictor to the left circumflex artery. Three weeks later, animals received: no drug (control, "CON"; n= 7); a low-dose calpain inhibitor (0.12 mg/kg; "LCI", n= 7); or high-dose calpain inhibitor (0.25 mg/kg; "HCI", n=7). Treatment continued for 5 weeks, followed by tissue harvest. Cardiac tissue was assayed for protein carbonyl content, as well as antioxidant and mitochondrial protein expression. Reactive oxygen species (ROS) and mitochondrial respiration was measured in H9c2 cells following exposure to normoxia or hypoxia (1%) for 24 h with or without CI.

RESULTS

In ischemic myocardial tissue, CI was associated with decreased total oxidative stress compared to control. CI was also associated with increased expression of mitochondrial proteins superoxide dismutase 1, SDHA, and pyruvate dehydrogenase compared to control. 100 nM of calpain inhibitor decreased ROS levels and respiration in both normoxic and hypoxic H9c2 cardiomyoblasts.

CONCLUSIONS

In the setting of metabolic syndrome, CI improves oxidative stress in chronically ischemic myocardial tissue. Decreased oxidative stress may be via modulation of mitochondrial proteins involved in free radical scavenging and production.

Rare variants in CAPN2 increase risk for isolated hypoplastic left heart syndrome

Hypoplastic left heart syndrome (HLHS) is a severe congenital heart defect (CHD) characterized by hypoplasia of the left ventricle and aorta along with stenosis or atresia of the aortic and mitral valves. HLHS represents only ∼4%-8% of all CHDs but accounts for ∼25% of deaths. HLHS is an isolated defect (i.e., iHLHS) in 70% of families, the vast majority of which are simplex. Despite intense investigation, the genetic basis of iHLHS remains largely unknown. We performed exome sequencing on 331 families with iHLHS aggregated from four independent cohorts. A Mendelian-model-based analysis demonstrated that iHLHS was not due to single, large-effect alleles in genes previously reported to underlie iHLHS or CHD in >90% of families in this cohort. Gene-based association testing identified increased risk for iHLHS associated with variation in CAPN2 (p = 1.8 × 10-5), encoding a protein involved in functional adhesion. Functional validation studies in a vertebrate animal model (Xenopus laevis) confirmed CAPN2 is essential for cardiac ventricle morphogenesis and that in vivo loss of calpain function causes hypoplastic ventricle phenotypes and suggest that human CAPN2707C>T and CAPN21112C>T variants, each found in multiple individuals with iHLHS, are hypomorphic alleles. Collectively, our findings show that iHLHS is typically not a Mendelian condition, demonstrate that CAPN2 variants increase risk of iHLHS, and identify a novel pathway involved in HLHS pathogenesis.

CDN1163, a SERCA activator, causes intracellular Ca2+ leak, mitochondrial hyperpolarization and cell cycle arrest in mouse neuronal N2A cells

OBJECTIVE

Activity or expression of sarcoplasmic/endoplasmic reticulum Ca2+ ATPase (SERCA) is diminished in some disease states such as cardiac failure and diabetes mellitus. A newly developed activator of SERCA, CDN1163, reportedly rescued or alleviated pathological conditions attributed to dysfunctional SERCA. We examined whether CDN1163 could relieve mouse neuronal N2A cell growth inhibition caused by cyclopiazonic acid (CPA, SERCA inhibitor). We also examined how CDN1163 affected cytosolic Ca2+, mitochondrial Ca2+ and mitochondrial membrane potential.

METHODS

Cell viability was measured by MTT assay and trypan blue exclusion test. Cytosolic Ca2+, mitochondrial Ca2+ and mitochondrial membrane potential were measured using fura 2, Rhod-2 and JC-1, respectively, as fluorescent probes.

RESULTS

CDN1163 (10 μM) itself suppressed cell proliferation, and did not alleviate CPA's inhibitory effect (and vice versa). Cell cycle was arrested at the G1 phase after CDN1163 treatment. CDN1163 treatment caused a slow yet persistent cytosolic [Ca2+] elevation partly due to Ca2+ release from an internal store other than the CPA-sensitive endoplasmic reticulum (ER). Treatment with CDN1163 for 3 h raised mitochondrial Ca2+ level and such increase was suppressed by MCU-i4 (an inhibitor of mitochondria Ca2+ uniporter, MCU), suggesting Ca2+ entered the mitochondrial matrix through MCU. Treatment of cells with CDN1163 up to 2 days resulted in mitochondrial hyperpolarization.

CONCLUSION

CDN1163 caused internal Ca2+ leak, cytosolic Ca2+ overload, mitochondrial Ca2+ elevation and hyperpolarization, cell cycle arrest and cell growth inhibition.

SGLT1: A Potential Drug Target for Cardiovascular Disease

SGLT1 and SGLT2 are the two main members of the sodium-glucose cotransporters (SGLTs), which are mainly responsible for glucose reabsorption in the body. In recent years, many large clinical trials have shown that SGLT2 inhibitors have cardiovascular protection for diabetic and non-diabetic patients independent of lowering blood glucose. However, SGLT2 was barely detected in the hearts of humans and animals, while SGLT1 was highly expressed in myocardium. As SGLT2 inhibitors also have a moderate inhibitory effect on SGLT1, the cardiovascular protection of SGLT2 inhibitors may be due to SGLT1 inhibition. SGLT1 expression is associated with pathological processes such as cardiac oxidative stress, inflammation, fibrosis, and cell apoptosis, as well as mitochondrial dysfunction. The purpose of this review is to summarize the protective effects of SGLT1 inhibition on hearts in various cell types, including cardiomyocytes, endothelial cells, and fibroblasts in preclinical studies, and to highlight the underlying molecular mechanisms of protection against cardiovascular diseases. Selective SGLT1 inhibitors could be considered a class of drugs for cardiac-specific therapy in the future.

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.

Effects of High-Intensity Interval Training and Continuous Training on Exercise Capacity, Heart Rate Variability and Isolated Hearts in Diabetic Rats

BACKGROUND

High-intensity interval training (HIIT) has been suggested as an alternative for continuous training (CT) in people with diabetes mellitus (DM) due to its short duration and potential to improve adherence to exercise. However, data on its impact on heart rate variability (HRV) are scarce.

OBJECTIVES

To assess and compare the effects of HIIT and CT on exercise capacity, HRV and isolated hearts in diabetic rats.

METHODS

DM (intravenous streptozotocin, 45 mg.kg -1 ) and control (C) animals performed 20 sessions (5 days/week, 50 min, for 4 weeks) of CT on a treadmill (70% of maximal exercise capacity) or HIIT (cycles of 1:1min at 50% and 90% of maximal exercise capacity). HRV was assessed by continuous electrocardiogram, and cardiac function assessed in isolated perfused hearts. For data analysis, we used the framework of the multivariate covariance generalized linear model or one-way ANOVA followed by Tukey's test, considering p<0.05 as significant.

RESULTS

Higher exercise capacity (m/min) was achieved in HIIT (DM-HIIT: 36.5 [IQR 30.0-41.3]; C-HIIT: 41.5 [37.8-44.5], both n=10) compared to CT (DM-CT: 29.0 [23.8-33.0]; C-CT: 32.0 [29.5-37.0], both n=10) (p<0.001). Heart rate (bpm) was lower in DM compared to controls (p<0.001) both in vivo (DM-HIIT:348±51, C-HIIT:441±66, DM-CT:361±70, C-CT:437±38) and in isolated hearts. There were no differences in HRV between the groups. Maximum and minimal dP/dt were reduced in DM, except +dP/dt in DM-HIIT vs. C-HIIT (mean difference: 595.5±250.3, p=0.190).

CONCLUSION

Short-term HIIT promotes greater improvement in exercise performance compared to CT, including in DM, without causing significant changes in HRV.

Ion drugs for precise orthotopic tumor management by in situ the generation of toxic ion and drug pools

Background: Asymmetric intracellular and extracellular ionic gradients are critical to the survivability of mammalian cells. Given the importance of manganese (Mn²⁺), calcium (Ca²⁺), and bicarbonate (HCO₃ ^-) ions, any alteration of the ion-content balance could induce a series of cellular responses. HCO₃ ^- plays an indispensable role for Mn-mediated Fenton-like reaction, but this is difficult to achieve because bicarbonates are tightly regulated by live cells, and are limited in anticancer efficacy. Methods: A responsive and biodegradable biomineral, Mn-doped calcium carbonate integrated with dexamethasone phosphate (DEX) (Mn:CaCO₃-DEX), was reported to enable synergistic amplification of tumor oxidative stress, reduce inflammation, and induce Ca-overload cell apoptosis by elevating the intracellular and extracellular ionic gradients. Results: Under the acidic environment in tumor region, the ions (Mn²⁺, CO₃ ^2-, Ca²⁺) were released by the degradation of Mn:CaCO₃-DEX and then escalated oxidative stresses by triggering a HCO₃ ^--indispensable Mn-based Fenton-like reaction and breaking Ca²⁺ ion homeostasis to cause oxidative stress in cells and calcification. The released anti-inflammatory and antitumor drug, DEX, could alleviate the inflammatory environment. The investigations in vitro and in vivo demonstrated that the synergistic oncotherapy could effectively inhibit the growth of subcutaneous tumors and orthotopic liver tumors. Notably, normal cells showed greater tolerance of the synergistic influences. Conclusion: As an ion drug, Mn:CaCO₃-DEX is an excellent potential diagnostic agent for precise orthotopic tumor management by the generation in situ of toxic ion and drug pools in the environment of tumor region, with synergistic effects of enhanced chemodynamic therapy, calcification, and anti-inflammation effects.

Calpain-Mediated Mitochondrial Damage: An Emerging Mechanism Contributing to Cardiac Disease

Calpains belong to the family of calcium-dependent cysteine proteases expressed ubiquitously in mammals and many other organisms. Activation of calpain is observed in diseased hearts and is implicated in cardiac cell death, hypertrophy, fibrosis, and inflammation. However, the underlying mechanisms remain incompletely understood. Recent studies have revealed that calpains target and impair mitochondria in cardiac disease. The objective of this review is to discuss the role of calpains in mediating mitochondrial damage and the underlying mechanisms, and to evaluate whether targeted inhibition of mitochondrial calpain is a potential strategy in treating cardiac disease. We expect to describe the wealth of new evidence surrounding calpain-mediated mitochondrial damage to facilitate future mechanistic studies and therapy development for cardiac disease.

Activation of Ca2+/Calmodulin-Dependent Protein Kinase II (CaMKII) with Lidocaine Provokes Pyroptosis of Glioblastoma Cells

The study examines the problem whether pyroptosis of U87-MG glioblastoma cells can result from activation of Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) by a local anesthetic. Glioblastoma cells exposed to various concentrations of typical local anesthetic lidocaine demonstrated augmented cytosolic flux of Ca²⁺, while suppression of CaMKII expression with the corresponding siRNA significantly inhibited this effect in cells treated with 2 mM lidocaine. Lidocaine up-regulated the expression of mRNA caspase-3 and gasdermin GSDME proteins, whereas silencing of CaMKII gene with siRNA significantly moderated this effect. In addition, lidocaine inhibited proliferation of U87-MG cells, and this effect was prevented by silencing CaMKII gene. Thus, lidocaine activated protein kinase CaMKII, which phosphorylated TRPV1 ion channels and induced calcium overload of U87-MG glioblastoma cells, thereby provoking their pyroptosis.

Effects of Bergamot Polyphenols on Mitochondrial Dysfunction and Sarcoplasmic Reticulum Stress in Diabetic Cardiomyopathy

Cardiovascular disease is the leading cause of death and disability in the Western world. In order to safeguard the structure and the functionality of the myocardium, it is extremely important to adequately support the cardiomyocytes. Two cellular organelles of cardiomyocytes are essential for cell survival and to ensure proper functioning of the myocardium: mitochondria and the sarcoplasmic reticulum. Mitochondria are responsible for the energy metabolism of the myocardium, and regulate the processes that can lead to cell death. The sarcoplasmic reticulum preserves the physiological concentration of the calcium ion, and triggers processes to protect the structural and functional integrity of the proteins. The alterations of these organelles can damage myocardial functioning. A proper nutritional balance regarding the intake of macronutrients and micronutrients leads to a significant improvement in the symptoms and consequences of heart disease. In particular, the Mediterranean diet, characterized by a high consumption of plant-based foods, small quantities of red meat, and high quantities of olive oil, reduces and improves the pathological condition of patients with heart failure. In addition, nutritional support and nutraceutical supplementation in patients who develop heart failure can contribute to the protection of the failing myocardium. Since polyphenols have numerous beneficial properties, including anti-inflammatory and antioxidant properties, this review gathers what is known about the beneficial effects of polyphenol-rich bergamot fruit on the cardiovascular system. In particular, the role of bergamot polyphenols in mitochondrial and sarcoplasmic dysfunctions in diabetic cardiomyopathy is reported.

Exaggerated activities of TRPM7 underlie bupivacaine-induced neurotoxicity in the SH-SY5Y cells preconditioned with high glucose

Hyperglycemia is considered a risk factor for the enhancement of local anesthetic-induced neurotoxicity. Transient receptor potential melastatin 7 (TRPM7), a kinase-coupled cation channel, has been implicated in a variety of neuropathological processes, including intracellular calcium disturbance and high glucose-induced neuropathy. In this study, we investigated whether TRPM7-related pathophysiology is involved in bupivacaine-induced neurotoxicity in SH-SY5Y cells and how hyperglycemia acts as a risk factor. For initial neurotoxicity evaluation, it was confirmed that cell damage and apoptosis induced by acute exposure to bupivacaine were dependent on its concentration and glucose preconditioning. High glucose preconditioning facilitated the bupivacaine-induced fast and temporary rise in intracellular free calcium concentration ([Ca²⁺ ]_i ), which was attributed to both calcium influx through TRPM7 and calcium store release. Additionally, bupivacaine was shown to increase TRPM7-like currents, particularly in cells preconditioned with high glucose. Bupivacaine-induced neurotoxicity in hyperglycemia was correlated with extracellular signal-regulated kinase (ERK), but not protein kinase B (AKT) activation. Inhibition of TRPM7 and ERK activity alleviates bupivacaine neurotoxicity. These results suggest that therapeutically targeting TRPM7-related pathophysiological changes could be a potential strategy for treating local anesthetic-induced neurotoxicity exacerbated by hyperglycemia.

Hyperglycaemia-Induced Contractile Dysfunction and Apoptosis in Cardiomyocyte-Like Pulsatile Cells Derived from Mouse Embryonic Stem Cells

Hyperglycaemia, a key metabolic abnormality in diabetes mellitus, is implicated in pathological cardiogenesis during embryological development. However, the underlying mechanisms and potential therapeutic targets remain unknown. We, therefore, studied the effect of hyperglycaemia on mouse embryonic stem cell (mESC) cardiac differentiation. The mESCs were differentiated via embryoid body (EB) formation and cultured under conditions with baseline (25 mM) or high (50 mM) glucose. Time-lapse microscopy images of pulsatile mESCs and Ca²⁺ transients were recorded. Biomarkers of cellular changes were detected using immunocytochemistry, terminal deoxynucleotidyl transferase dUTP nick-end labelling (TUNEL) assay, and Western blot analyses. Differentiated, spontaneously beating mESCs stained positive for cardiac troponin T, α-actinin 2, myosin heavy chain, and connexin 43. Hyperglycaemia decreased the EB diameter and number of beating EBs as well as the cellular amplitude of contraction, the Ca²⁺ transient, and the contractile response to caffeine (1 mM), but had no effect on the expression of the sarco-endoplasmic reticulum calcium transport ATPase 2 (SERCA 2). Furthermore, hyperglycaemia decreased the expression of B cell lymphoma 2 (Bcl-2) and increased the expression of cytoplasmic cytochrome c and the number of TUNEL-positive cells, but had no effect on the expression of one of the mitochondrial fusion regulatory proteins, optic atrophy protein 1 (OPA1). Overall, hyperglycaemia suppressed the mESC cardiomyocyte-like differentiation and induced contractile dysfunction. The results are consistent with mechanisms involving abnormal Ca²⁺ handling and mitochondrial-dependent apoptosis, factors which represent potential therapeutic targets in developmental diabetic cardiac disease.

Sirtuins: To Be or Not To Be in Diabetic Cardiomyopathy

Diabetic cardiomyopathy is the leading cause of death among people with diabetes. Despite its severity and poor prognosis, there are currently no approved specific drugs to prevent or even treat diabetic cardiomyopathy. There is a need to understand the pathogenic mechanisms underlying the development of diabetic cardiomyopathy to design new therapeutic strategies. These mechanisms are complex and intricate and include metabolic dysregulation, inflammation, oxidative stress, fibrosis, and apoptosis. Sirtuins, a group of deacetylase enzymes, play an important role in all these processes and are, therefore, potential molecular targets for treating this disease. In this review, we discuss the role of sirtuins in the heart, focusing on their contribution to the pathogenesis of diabetic cardiomyopathy and how their modulation could be therapeutically useful.

Preventing Myocardial Injury Following Non-Cardiac Surgery: A Potential Role for Preoperative Antioxidant Therapy with Ubiquinone

Over 240 million non-cardiac operations occur each year and are associated with a 15-20% incidence of adverse perioperative cardiovascular events. Unfortunately, preoperative therapies that have been useful for chronic ischemic heart diseases, such as coronary artery revascularization, antiplatelet agents, and beta-blockers have failed to improve outcomes. In a pre-clinical swine model of ischemic heart disease, we showed that daily administration of ubiquinone (coenzyme Q₁₀, CoQ₁₀) enhances the antioxidant status of mitochondria within chronically ischemic heart tissue, potentially via a PGC1α-dependent mechanism. In a randomized controlled trial, among high-risk patients undergoing elective vascular surgery, we showed that NT Pro-BNP levels are an important means of risk-stratification during the perioperative period and can be lowered with administration of CoQ₁₀ (400 mg/day) for 3 days prior to surgery. The review provides background information for the role of oxidant stress and inflammation during high-risk operations and the potential novel application of ubiquinone as a preoperative antioxidant therapy that might reduce perioperative adverse cardiovascular outcomes.

Hyperglycemia Induces Generation of Reactive Oxygen Species and Accelerates Apoptotic Cell Death in Salivary Gland Cells

INTRODUCTION

Type-2 diabetes mellitus (T2DM) is associated with several systemic vascular symptoms and xerostomia. It is considered that hyperglycemia-induced polyuria and dehydration cause decreased body-water volume, leading to decreased saliva secretion and, ultimately, xerostomia. In T2DM, increased production of reactive oxygen species (ROS) causes tissue damage to vascular endothelial cells as well as epithelial tissue, including pancreas and cornea. Hence, a similar phenomenon may occur in other tissues and glands in a hyperglycemic environment.

METHODS

Salivary gland tissue injury was examined, using T2DM model mouse (db/db). Transferase-mediated dUTP nick-end labeling (TUNEL) was conducted to evaluate tissue injury. The levels of malondialdehyde (MDA) and 8-hydroxy-2'-deoxyguanosine, Bax/Bcl-2 ratio were measured as indicator of oxidative stress. Moreover, in vitro ROS production and cell injury was evaluated by mouse salivary gland-derived normal cells under high-glucose condition culture.

RESULTS

In vivo and in vitro analysis showed a higher percentage of TUNEL-positive cells and higher levels of MDA and 8-hydroxy-2'-deoxyguanosine in salivary gland tissue of db/db mice. This suggests damage of saliva secretion-associated lipids and DNA by hyperglycemic-induced oxidative stress. To analyze the mechanism by which hyperglycemia promotes ROS production, mouse salivary gland-derived cells were isolated. The cell culture with high-glucose medium enhanced ROS production and promotes apoptotic and necrotic cell death.

CONCLUSION

These findings suggest a novel mechanism whereby hyperglycemic-induced ROS production promotes salivary gland injury, resulting in hyposalivation.

Melatonin alleviates angiotensin-II-induced cardiac hypertrophy via activating MICU1 pathway

Mitochondrial calcium uptake 1 (MICU1) is a pivotal molecule in maintaining mitochondrial homeostasis under stress conditions. However, it is unclear whether MICU1 attenuates mitochondrial stress in angiotensin II (Ang-II)-induced cardiac hypertrophy or if it has a role in the function of melatonin. Here, small-interfering RNAs against MICU1 or adenovirus-based plasmids encoding MICU1 were delivered into left ventricles of mice or incubated with neonatal murine ventricular myocytes (NMVMs) for 48 h. MICU1 expression was depressed in hypertrophic myocardia and MICU1 knockdown aggravated Ang-II-induced cardiac hypertrophy in vivo and in vitro. In contrast, MICU1 upregulation decreased cardiomyocyte susceptibility to hypertrophic stress. Ang-II administration, particularly in NMVMs with MICU1 knockdown, led to significantly increased reactive oxygen species (ROS) overload, altered mitochondrial morphology, and suppressed mitochondrial function, all of which were reversed by MICU1 supplementation. Moreover, peroxisome proliferator-activated receptor gamma coactivator 1-α (PGC-1α)/MICU1 expression in hypertrophic myocardia increased with melatonin. Melatonin ameliorated excessive ROS generation, promoted mitochondrial function, and attenuated cardiac hypertrophy in control but not MICU1 knockdown NMVMs or mice. Collectively, our results demonstrate that MICU1 attenuates Ang-II-induced cardiac hypertrophy by inhibiting mitochondria-derived oxidative stress. MICU1 activation may be the mechanism underlying melatonin-induced protection against myocardial hypertrophy.

High glucose induces phosphorylation and oxidation of mitochondrial proteins in renal tubular cells: A proteomics approach

Mitochondrial dysfunction has been thought to play roles in the pathogenesis of diabetic nephropathy (DN). However, precise mechanisms underlying mitochondrial dysfunction in DN remained unclear. Herein, mitochondria were isolated from renal tubular cells after exposure to normal glucose (5.5 mM glucose), high glucose (25 mM glucose), or osmotic control (5.5 mM glucose + 19.5 mM mannitol) for 96 h. Comparative proteomic analysis revealed six differentially expressed proteins among groups that were subsequently identified by tandem mass spectrometry (nanoLC-ESI-ETD MS/MS) and confirmed by Western blotting. Several various types of post-translational modifications (PTMs) were identified in all of these identified proteins. Interestingly, phosphorylation and oxidation were most abundant in mitochondrial proteins whose levels were exclusively increased in high glucose condition. The high glucose-induced increases in phosphorylation and oxidation of mitochondrial proteins were successfully confirmed by various assays including MS/MS analyses. Moreover, high glucose also increased levels of phosphorylated ezrin, intracellular ATP and ROS, all of which could be abolished by a p38 MAPK inhibitor (SB239063), implicating a role of p38 MAPK-mediated phosphorylation in high glucose-induced mitochondrial dysfunction. These data indicate that phosphorylation and oxidation of mitochondrial proteins are, at least in part, involved in mitochondrial dysfunction in renal tubular cells during DN.

A novel form of glycolytic metabolism-dependent cardioprotection revealed by PKCα and β inhibition

KEY POINTS

Acute hyperglycaemia at the time of a heart attack worsens the outcome for the patient. Acute hyperglycaemia is not limited to diabetic patients and can be due to a stress response in non-diabetics. This study suggests that the damaging cardiac effects of hyperglycaemia can be reversed by selective PKC inhibition. If PKCα/β isoforms are inhibited, then high glucose itself becomes protective against ischaemic damage. Selective PKC inhibition may therefore be a useful therapeutic tool to limit the damage that can occur during a heart attack by stress-induced hyperglycaemia.

ABSTRACT

Hyperglycaemia has a powerful association with adverse prognosis for patients with acute coronary syndromes (ACS). Previous work shows that high glucose prevents ischaemic preconditioning and causes electrical and mechanical disruption via protein kinase C α/β (PKCα/β) activation. The present study aimed to: (i) determine whether the adverse clinical association of hyperglycaemia in ACS can be replicated in preclinical cellular models of ACS and (ii) determine the importance of PKCα/β activation to the deleterious effect of glucose. Freshly isolated rat, guinea pig or rabbit cardiomyocytes were exposed to simulated ischaemia after incubation in the presence of normal (5 mm) or high (20 mm) glucose in the absence or presence of small molecule or tat-peptide-linked PKCαβ inhibitors. In each of the four conditions, the following hallmarks of cardioprotection were recorded using electrophysiology or fluorescence imaging: cardiomyocyte contraction and survival, action potential stability and time to failure, intracellular calcium and ATP, mitochondrial depolarization, ischaemia-sensitive leak current, and time to K_ir 6.2 opening. High glucose alone resulted in decreased cardiomyocyte contraction and survival; however, it also imparted cardioprotection in the presence of PKCα/β inhibitors. This cardioprotective phenotype displayed improvements in all of the measured parameters and decreased myocardium damage during whole heart coronary ligation experiments. High glucose is deleterious to cellular and whole-heart models of simulated ischaemia, in keeping with the clinical association of hyperglycaemia with an adverse outcome in ACS. PKCαβ inhibition revealed high glucose to show a cardioprotective phenotype in this setting. The results of the present study suggest the potential for the therapeutic application of PKCαβ inhibition in ACS associated with hyperglycaemia.

Trolox prevents high glucose-induced apoptosis in rat myocardial H9c2 cells by regulating GLUT-4 and antioxidant defense mechanism

Redox imbalance due to hyperglycemia is a causative factor for an increased generation of reactive oxygen species (ROS) that leads to mitochondrial dysfunction and the release of cytochrome-c. The aim of the present study is to elucidate the functional role of oxidative stress (OS) in the induction of apoptosis in H9c2 cells in the hyperglycemic state through glucose transporter-4 (GLUT-4) regulation and antioxidant status. H9c2 cells were incubated with 15, 24, and 33 mM glucose for 24, 48, and 72 hr to induce hyperglycemic stress. Hyperglycemic episodes have significantly influenced GLUT-4 mRNA regulation, depleted glutathione (GSH) and its associated enzymes, reduced cellular antioxidant enzymes (AOEs), caused nuclear condensation, and induced apoptosis by activating caspase-9 and 3 and annexin V binding in a concentration and duration-dependent manner. Trolox pretreatment significantly enhanced the GLUT-4 mRNA and antioxidant defense mechanism, suppressed nuclear condensation, and prevented cytochrome-c release, thereby reducing mitochondrial-dependent apoptosis. The present study shows that the toxic effect of high glucose is significantly regulated and that OS induction can be prevented through a water-soluble vitamin E analog "Trolox" treatment.

Puerarin prevents diabetic cardiomyopathy in vivo and in vitro by inhibition of inflammation

Diabetic cardiomyopathy (DCM) is one of the chief diabetes mellitus complications. Inflammation factors may be one reason for the damage from DM. The purpose of this research is to study the potential protective effects of puerarin on DM and the possible mechanisms of action related to NF-κB signal pathway. Following administration of puerarin to the disease model rat, several changes were observed including the changes of serum biochemical index, improved diastolic dysfunction, and enhanced endogenous antioxidant enzymes activities, further NF-κB signaling activation. Puerarin showed cardio-protective effects on DCM by inhibiting inflammation, and it might be a potential candidate for the treatment of DCM.

Hesperidin-CAMKIV interaction and its impact on cell proliferation and apoptosis in the human hepatic carcinoma and neuroblastoma cells

Calcium/calmodulin-dependent protein kinase IV (CAMKIV) is a key regulatory molecule of cell signaling, and thereby controls its growth and proliferation, including expression of certain genes. The overexpression of CAMKIV is directly associated with the development of different types of cancers. Hesperidin is abundantly found in citrus fruits and exhibits wide range of pharmacological activities including anti-inflammatory, antibacterial and anticancerous effects. We have investigated binding mechanism of hesperidin with the CAMKIV using molecular docking methods followed by fluorescence quenching and isothermal titration calorimetric assays. An appreciable binding affinity of hesperidin was observed with CAMKIV during fluorescence quenching and isothermal titration calorimetric studies. Efficacy of hesperidin to inhibit the growth of human hepatic carcinoma (HepG2) and neuroblastoma (SH-SY5Y) cancer cell lines were investigated. Hesperidin has significantly reduced the proliferation of HepG2 and SH-SY5Y cells and induces apoptosis by activating the caspase-3-dependent intrinsic pathway through the upregulation of proapoptotic Bax protein. Hesperidin treatment reduces the mitochondrial membrane potential of HepG2 and SH-SY5Y cells. All these observations clearly anticipated hesperidin a potent inhibitor of CAMKIV which may be further exploited a newer therapeutic approach for the management of different cancer types.

PI3-kinase/Akt pathway-regulated membrane transportation of acid-sensing ion channel 1a/Calcium ion influx/endoplasmic reticulum stress activation on PDGF-induced HSC Activation

Acid-sensing ion channel 1a (ASIC1a) allows Na⁺ and Ca²⁺ flow into cells. It is expressed during inflammation, in tumour and ischaemic tissue, in the central nervous system and non-neuronal injury environments. Endoplasmic reticulum stress (ERS) is caused by the accumulation of misfolded proteins that interferes with intracellular calcium homoeostasis. Our recent reports showed ASIC1a and ERS are involved in liver fibrosis progression, particularly in hepatic stellate cell (HSC) activation. In this study, we investigated the roles of ASIC1a and ERS in activated HSC. We found that ASIC1a and ERS-related proteins were up-regulated in carbon tetrachloride (CCl₄ )-induced fibrotic mouse liver tissues, and in patient liver tissues with hepatocellular carcinoma with severe liver fibrosis. The results show silencing ASIC1a reduced the expression of ERS-related biomarkers GRP78, Caspase12 and IREI-XBP1. And, ERS inhibition by 4-PBA down-regulated the high expression of ASIC1a induced by PDGF, suggesting an interactive relationship. In PDGF-induced HSCs, ASIC1a was activated and migrated to the cell membrane, leading to extracellular calcium influx and ERS, which was mediated by PI3K/AKT pathway. Our work shows PDGF-activated ASIC1a via the PI3K/AKT pathway, induced ERS and promoted liver fibrosis progression.

High glucose induced calcium overload via impairment of SERCA/PLN pathway and mitochondrial dysfunction leads to oxidative stress in H9c2 cells and amelioration with ferulic acid

Oxidative stress and associated complications are the major pathological concerns of diabetic cardiomyopathy (DC). We aim to elucidate the mechanisms by which high glucose (HG) induced alteration in calcium homeostasis and evaluation of the beneficial effect of two concentrations (10 and 25 μm) of ferulic acid (FA). HG was induced in H9c2 cardiomyoblast by treating with glucose (33 mm) for 48 h, and FA was co-treated. Intracellular calcium ([Ca²⁺ ]i) overload was found increased significantly with HG. For elucidation of mechanism, the SERCA pathway and mitochondrial integrity (transmembrane potential and permeability transition pore) were explored. Then, we assessed oxidative stress, and cell injury with brain natriuretic peptide (BNP), atrial natriuretic peptide (ANP), and lactate dehydrogenase (LDH) release. HG caused significant [Ca²⁺ ]i overload through downregulation of SERCA2/1, pPLN, and pPKA C-α; and upregulation of PLN and PKA C-α and alteration in the integrity of mitochondria with HG. The [Ca²⁺ ]i overload in turn caused oxidative stress via generation of reactive oxygen species, lipid peroxidation, and protein carbonylation. This resulted in cell injury which was evident with significant release of BNP, ANP, and LDH. FA co-treatment was effective to mitigate all pathological changes caused by HG. From the overall results, we conclude that [Ca²⁺ ]i overload via SERCA pathway and altered mitochondrial integrity is the main cause for oxidative stress during HG. Based on our result, we report that FA could be an attractive nutraceutical for DC.

Synthesis and evaluation of isoprenylation-resveratrol dimer derivatives against Alzheimer's disease

A series of resveratrol dimer derivatives against Alzheimer's disease (AD) was obtained by structural modification and transformation using resveratrol as substrate. Biological analysis revealed that these derivatives had moderate inhibitory activity against human monoamine oxidase B (hMAO-B). In particular, 3 and 7 showed the better inhibitory activity for hMAO-B (IC50 = 3.91 ± 0.23 μM, 0.90 ± 0.01 μM) respectively. Compound 3 (IC50 = 46.95 ± 0.21 μM for DPPH, 1.43 and 1.74 trolox equivalent by ABTS and FRAP method respectively), and 7 (IC50 = 35.33 ± 0.15 μM for DPPH, 1.70 and 1.97 trolox equivalent by ABTS method and FRAP method respectively) have excellent antioxidant effects. Cellular assay shown that 3 and 7 had lower toxicity and were resistant to neurotoxicity induced by oxidative toxins (H2O2, rotenone and oligomycin-A). More importantly, the selected compounds have neuroprotective effects against ROS generation, H2O2-induced apoptosis and a significant in vitro anti-inflammatory activity. The results of the parallel artificial membrane permeability assay for blood-brain barrier indicated that 3 and 7 would be predominant to cross the blood-brain barrier. In this study, mouse microglia BV2 cells were used to establish cell oxidative stress injury model with H2O2 and to explore the protective effect and mechanism of 3 and 7. In general, 3 and 7 can be considered candidates for potential treatment of AD.

In Vivo Monitoring of Calpain Activity by Forster Resonance Energy Transfer

Calpains are a 15-member class of calcium-activated nonlysosomal neutral proteases. They are involved in many cellular processes and are highly upregulated in pathological conditions. Some are ubiquitously expressed (CAPN1, CAPN2, CAPN4, CAPN5, CAPN7, and CAPN10), but others are thought to be localized in specific tissues. The monitoring of in vivo calpain activity is required for physiological, pathological, and therapeutic evaluations. This past decade, a tool for monitoring calpain activity in such conditions was developed using Forster resonance energy transfer (FRET). Studies showed that the level of calpain activity correlates with a decrease in FRET between the two fluorescent proteins. This chapter describes the methodologies from the design of the construct to the imaging procedure and analysis to evaluate ubiquitous calpain activity in vivo.

Bromine inhalation mimics ischemia-reperfusion cardiomyocyte injury and calpain activation in rats

Halogens are widely used, highly toxic chemicals that pose a potential threat to humans because of their abundance. Halogens such as bromine (Br₂) cause severe pulmonary and systemic injuries; however, the mechanisms of their toxicity are largely unknown. Here, we demonstrated that Br₂ and reactive brominated species produced in the lung and released in blood reach the heart and cause acute cardiac ultrastructural damage and dysfunction in rats. Br₂-induced cardiac damage was demonstrated by acute (3-24 h) increases in circulating troponin I, heart-type fatty acid-binding protein, and NH₂-terminal pro-brain natriuretic peptide. Transmission electron microscopy demonstrated acute (3-24 h) cardiac contraction band necrosis, disruption of z-disks, and mitochondrial swelling and disorganization. Echocardiography and hemodynamic analysis revealed left ventricular (LV) systolic and diastolic dysfunction at 7 days. Plasma and LV tissue had increased levels of brominated fatty acids. 2-Bromohexadecanal (Br-HDA) injected into the LV cavity of a normal rat caused acute LV enlargement with extensive disruption of the sarcomeric architecture and mitochondrial damage. There was extensive infiltration of neutrophils and increased myeloperoxidase levels in the hearts of Br_2- or Br₂ reactant-exposed rats. Increased bromination of sarco(endo)plasmic reticulum Ca²⁺-ATPase (SERCA) and increased phosphalamban after Br₂ inhalation decreased cardiac SERCA activity by 70%. SERCA inactivation was accompanied by increased Ca²⁺-sensitive LV calpain activity. The calpain-specific inhibitor MDL28170 administered within 1 h after exposure significantly decreased calpain activity and acute mortality. Bromine inhalation and formation of reactive brominated species caused acute cardiac injury and myocardial damage that can lead to heart failure. NEW & NOTEWORTHY The present study defines left ventricular systolic and diastolic dysfunction due to cardiac injury after bromine (Br₂) inhalation. A calpain-dependent mechanism was identified as a potential mediator of cardiac ultrastructure damage. This study not only highlights the importance of monitoring acute cardiac symptoms in victims of Br₂ exposure but also defines calpains as a potential target to treat Br₂-induced toxicity.

Empagliflozin Ammeliorates High Glucose Induced-Cardiac Dysfuntion in Human iPSC-Derived Cardiomyocytes

Empagliflozin, a sodium-glucose co-transporter (SGLT) inhibitor, reduces heart failure and sudden cardiac death but the underlying mechanisms remain elusive. In cardiomyocytes, SGLT1 and SGLT2 expression is upregulated in diabetes mellitus, heart failure, and myocardial infarction. We hypothesise that empagliflozin exerts direct effects on cardiomyocytes that attenuate diabetic cardiomyopathy. To test this hypothesis, cardiomyocytes derived from human induced pluripotent stem cells (hiPSCs) were used to test the potential effects of empagliflozin on neutralization of cardiac dysfunction induced by diabetic-like cultures. Our results indicated that insulin-free high glucose culture significantly increased the size of and NPPB, SGLT1 and SGLT2 expression of hiPSC-derived cardiomyocytes. In addition, high glucose-treated hiPSC-derived cardiomyocytes exhibited reduced contractility regardless of the increased calcium transient capacity. Interestingly, application of empagliflozin before or after high glucose treatment effectively reduced the high glucose-induced cardiac abnormalities. Since application of empagliflozin did not significantly alter viability or glycolytic capacity of the hiPSC-derived cardiomyocytes, it is plausible that empagliflozin exerts its effects via the down-regulation of SGLT1, SGLT2 and GLUT1 expression. These observations provide supportive evidence that may help explain its unexpected benefit observed in the EMPA-REG trial.

Proteomics of the Rat Myocardium during Development of Type 2 Diabetes Mellitus Reveals Progressive Alterations in Major Metabolic Pathways

Congestive heart failure and poor clinical outcome after myocardial infarction are known complications in patients with type-2 diabetes mellitus (T2DM). Protein alterations may be involved in the mechanisms underlying these disarrays in the diabetic heart. Here we map proteins involved in intracellular metabolic pathways in the Zucker diabetic fatty rat heart as T2DM develops using MS based proteomics. The prediabetic state only induced minor pathway changes, whereas onset and late T2DM caused pronounced perturbations. Two actin-associated proteins, ARPC2 and TPM3, were up-regulated at the prediabetic state indicating increased actin dynamics. All differentially regulated proteins involved in fatty acid metabolism, both peroxisomal and mitochondrial, were up-regulated at late T2DM, whereas enzymes of branched chain amino acid degradation were all down-regulated. At both onset and late T2DM, two members of the serine protease inhibitor superfamily, SERPINA3K and SERPINA3L, were down-regulated. Furthermore, we found alterations in proteins involved in clearance of advanced glycation end-products and lipotoxicity, DCXR and CBR1, at both onset and late T2DM. These proteins deserve elucidation with regard to their role in T2DM pathogenesis and their respective role in the deterioration of the diabetic heart. Data are available via ProteomeXchange with identifiers PXD009538, PXD009554, and PXD009555.

MCU-knockdown attenuates high glucose-induced inflammation through regulating MAPKs/NF-κB pathways and ROS production in HepG2 cells

Mitochondrial Ca2+ is a key regulator of organelle physiology and the excessive increase in mitochondrial calcium is associated with the oxidative stress. In the present study, we investigated the molecular mechanisms linking mitochondrial calcium to inflammatory and coagulative responses in hepatocytes exposed to high glucose (HG) (33mM glucose). Treatment of HepG2 cells with HG for 24 h induced insulin resistance, as demonstrated by an impairment of insulin-stimulated Akt phosphorylation. HepG2 treatment with HG led to an increase in mitochondrial Ca2+ uptake, while cytosolic calcium remained unchanged. Inhibition of MCU by lentiviral-mediated shRNA prevented mitochondrial calcium uptake and downregulated the inflammatory (TNF-α, IL-6) and coagulative (PAI-1 and FGA) mRNA expression in HepG2 cells exposed to HG. The protection from HG-induced inflammation by MCU inhibition was accompanied by a decrease in the generation of reactive oxygen species (ROS). Importantly, MCU inhibition in HepG2 cells abrogated the phosphorylation of p38, JNK and IKKα/IKKβ in HG treated cells. Taken together, these data suggest that MCU inhibition may represent a promising therapy for prevention of deleterious effects of obesity and metabolic diseases.

Protective Effect of Water Extracted Spirulina maxima on Glutamate-induced Neuronal Cell Death in Mouse Hippocampal HT22 Cell

Introduction:

Spirulina maxima was used as important nutritional source in the Aztec civilization because it is rich in proteins and vitamins. It contains various antioxidants such as phycocyanin and flavonoids. Based on abundant antioxidants, S. maxima is known to possess anti-inflammatory effect, especially on neuronal cells.

Materials and Methods:

S. maxima was extracted in water and contain of phycocyanin was identified by high-performance liquid chromatography. Cell viability test was performed with treatment of S. maxima extract. After, oxidative stress-related mechanisms were evaluated by detecting the accumulation of reactive oxygen species (ROS) and Ca²⁺ influx, and decrease of mitochondrial membrane potential (MMP) level. Then, the glutathione (GSH) related assays were conducted.

Results:

The water extracted S. maxima exerted the neuroprotective activity by attenuating the ROS and Ca²⁺ formation, maintaining the MMP level, and protecting the activity of the antioxidant enzymes by increasing reduced GSH against oxidative stress compared to control.

Conclusion:

The results suggested that water extracted S. maxima showed powerful neuroprotective effect through the mechanism related to antioxidant activity, able to preventing the radical-mediated cell death.

SUMMARY

Water extracted Spirulina maxima contains C-phycocyanin

Water extracted Spirulina maxima exerts neuroprotective effect on HT22 cell

To investigate the protective mechanisms, reactive oxygen species, Ca²⁺, mitochondrial membrane potential, Glutathione-related assays were performed.

Abbreviations used: ROS: Reactive oxygen species; MMP: Mitochondrial membrane potential; GSH: Glutathione; GSSG: Glutathione disulfide, oxidized glutathione; GPx: Glutathione peroxidase; GR: Glutathione reductase; DMEM: Dulbecco's modified Eagle's medium; FBS: Fetal bovine serum; DCF-DA: 2',7'-dichlorofluorescein diacetate; PBS: Phosphate buffered serum; Rho 123: Rhodamine 123; NADPH: Nicotinamide adenine dinucleotide phosphate; DTNB: 5,5'-dithiobis-2-nitrobenzoic acid, Ellman's reagent; GSSG-R: Glutathione disulfide reductase; MTT: 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide; DMSO: Dimethyl sulfoxide; HPLC: High-performance liquid chromatography.

Spirulina platensis prevents high glucose-induced oxidative stress mitochondrial damage mediated apoptosis in cardiomyoblasts

The current study was undertaken to study the effect of Spirulina platensis (Spirulina) extract on enhanced oxidative stress during high glucose induced cell death in H9c2 cells. H9c2 cultured under high glucose (33 mM) conditions resulted in a noteworthy increase in oxidative stress (free radical species) accompanied by loss of mitochondrial membrane potential, release of cytochrome c, increase in caspase activity and pro-apoptotic protein (Bax). Spirulina extract (1 μg/mL), considerably inhibited increased ROS and RNS levels, reduction in cytochrome c release, raise in mitochondrial membrane potential, decreased the over expression of proapoptotic protein Bax and suppressed the Bax/Bcl2 ratio with induced apoptosis without affecting cell viability. Overall results suggest that Spirulina extract plays preventing role against enhanced oxidative stress during high glucose induced apoptosis in cardiomyoblasts as well as related dysfunction in H9c2 cells.

Palmitic Acid-Induced Podocyte Apoptosis via the Reactive Oxygen Species-Dependent Mitochondrial Pathway

BACKGROUND/AIMS

Chronic kidney disease (CKD) is often accompanied by hyperlipidemia, which accelerates progression of the disease. Podocyte injury can lead to dysfunction of the glomerular filtration barrier, which is associated with proteinuria, a risk marker for the progression of CKD. Our previous studies demonstrated that palmitic acid (PA) can induce podocyte apoptosis; however, the underlying mechanisms are unclear. In the present study, we investigated the specific molecular mechanisms of PA-induced apoptosis in cultured podocytes.

METHODS

We cultured mouse podocytes and treated them with PA. Then, cell viability was measured using the Cell Counting Kit-8 colorimetric assay, lipid uptake was assessed by Oil Red O staining and boron-dipyrromethene staining, apoptosis was measured by flow cytometry, mitochondrial injury was assessed by JC-1 staining and transmission electron microscopy, and mitochondrial production of reactive oxygen species (ROS) was evaluated by fluorescence microscopy using the MitoSOX Red reagent. The effects of PA on the mitochondria-mediated caspase activation pathway were investigated by examining the expression of caspase-8, cleaved caspase-9, cleaved caspase-3, cleaved poly (ADP-ribose) polymerase (PARP), B-cell lymphoma 2 (Bcl-2), Bax, Bid, cytochrome c, and Fas-associated protein with death domain (FADD) using western blotting. The translocation of Bax and cytochrome c were detected by immunofluorescence.

RESULTS

PA treatment significantly increased lipid accumulation and induced podocyte apoptosis. We investigated whether the two primary apoptosis signaling pathways (death receptor-mediated pathway and mitochondria-mediated pathway) were involved in the execution of PA-induced podocyte apoptosis, and found that the levels of FADD, caspase-8, and Bid did not significantly change during this process. Meanwhile, PA treatment induced an increase in Bax protein expression and a decrease in Bcl-2 protein expression, with Bax translocation to the mitochondria. Furthermore, PA treatment induced mitochondrial impairment, and triggered the release of cytochrome c from the mitochondria to cytosol, with a concomitant dose-dependent increase in the levels of cleaved caspase-9, cleaved caspase-3, and PARP. Meanwhile, PA treatment increased mitochondrial production of ROS, and the mitochondria-targeted antioxidant mitoTEMPO significantly ameliorated PA-induced podocyte apoptosis.

CONCLUSION

Our findings indicated that PA induced caspase-dependent podocyte apoptosis through the mitochondrial pathway, and mitochondrial ROS production participated in this process, thus potentially contributing to podocyte injury.

Cardioprotection by exenatide: A novel mechanism via improving mitochondrial function involving the GLP-1 receptor/cAMP/PKA pathway

Accumulating evidence suggests that glucagon-like peptide-1 (GLP-1) and its analogues exert cardioprotective effects via modulating cardiomyocyte metabolism. Mitochondria play a pivotal role in the regulation of cell metabolism. It was hypothesized that treatment with exenatide, a GLP-1 analogue, may exert cardioprotective effects by improving mitochondrial function in an in vitro model of hypoxia/reoxygenation (H/R). H9c2 cells were employed to establish an in vitro model of H/R. Exenatide was added to the cells for 30 min prior to exposure to hypoxia. The GLP-1 receptor antagonist exendin‑(9‑39), the cyclic adenosine monophosphate (cAMP) inhibitor Rp-cAMPS and the protein kinase A (PKA) inhibitor H-89 were added to the cells for 10 min prior to treatment with exenatide. The release of lactate dehydrogenase (LDH) and creatine kinase-MB (CK-MB) and cardiomyocyte apoptosis were evaluated. The characteristics of mitochondrial morphology and functions, including ATP synthesis, membrane potential (ΔΨm), mitochondrial permeability transition pore (mPTP), mitochondrial ATPase activity and oxidative stress, were determined. the mitochondrial uncoupling protein-3 (UCP-3) and nuclear respiratory factor-1 (Nrf-1) were also investigated by western blot analysis. Exenatide pretreatment significantly decreased LDH and CK-MB release and cardiomyocyte apoptosis in H9c2 cells subjected to H/R. More importantly, to the best of our knowledge, this is the first report of exenatide pretreatment decreasing mitochondrial abnormalities and reducing oxidative stress, while enhancing ATP synthesis, mitochondrial ATPase activity and ΔΨm in H9c2 cells subjected to H/R. Exenatide pretreatment also decreased mitochondrial calcium overload and inhibited the opening of mPTP in H9c2 cells subjected to H/R. Furthermore, exenatide pretreatment upregulated UCP-3 and Nrf-1 expression in H9c2 cells subjected to H/R. However, the abovementioned observed effects of exenatide were all abolished when exenatide was co-administered with exendin‑(9‑39), Rp-cAMPS and̸or H-89. Therefore, the GLP-1 analogue exenatide was found to exert cardioprotective effects in an in vitro model of H/R, and this cardioprotection may be attributed to the improvement of mitochondrial function. These effects are most likely associated with the activation of the GLP-1 receptor/cAMP/PKA signaling pathway.

Epoxyeicosatrienoic Acid Inhibits the Apoptosis of Cerebral Microvascular Smooth Muscle Cells by Oxygen Glucose Deprivation via Targeting the JNK/c-Jun and mTOR Signaling Pathways

As a component of the neurovascular unit, cerebral smooth muscle cells (CSMCs) are an important mediator in the development of cerebral vascular diseases such as stroke. Epoxyeicosatrienoic acids (EETs) are the products of arachidonic acid catalyzed by cytochrome P450 epoxygenase. EETs are shown to exert neuroprotective effects. In this article, the role of EET in the growth and apoptosis of CSMCs and the underlying mechanisms under oxygen glucose deprivation (OGD) conditions were addressed. The viability of CMSCs was decreased significantly in the OGD group, while different subtypes of EETs, especially 14,15-EET, could increase the viability of CSMCs under OGD conditions. RAPA (serine/threonine kinase Mammalian Target of Rapamycin), a specific mTOR inhibitor, could elevate the level of oxygen free radicals in CSMCs as well as the anti-apoptotic effects of 14,15-EET under OGD conditions. However, SP600125, a specific JNK (c-Jun N-terminal protein kinase) pathway inhibitor, could attenuate oxygen free radicals levels in CSMCs as well as the anti-apoptotic effects of 14,15-EET under OGD conditions. These results strongly suggest that EETs exert protective functions during the growth and apoptosis of CSMCs, via the JNK/c-Jun and mTOR signaling pathways in vitro. We are the first to disclose the beneficial roles and underlying mechanism of 14,15-EET in CSMC under OGD conditions.

Klotho protects the heart from hyperglycemia-induced injury by inactivating ROS and NF-κB-mediated inflammation both in vitro and in vivo

Cardiac inflammation and oxidative stress play a key role in the pathogenesis of diabetic cardiomyopathy (DCM). The anti-aging protein Klotho has been found to protect cells from inflammation and oxidative stress. The current study aimed to explore the cardioprotective effects of Klotho on DCM and the underlying mechanisms. H9c2 cells and neonatal cardiomyocytes were incubated with 33mM glucose in the presence or absence of Klotho. Klotho pretreatment effectively inhibited high glucose-induced inflammation, ROS generation, apoptosis, mitochondrial dysfunction, fibrosis and hypertrophy in both H9c2 cells and neonatal cardiomyocytes. In STZ-induced type 1 diabetic mice, intraperitoneal injection of Klotho at 0.01mg/kg per 48h for 3months completely suppressed cardiac inflammatory cytokines and oxidative stress and prevented cardiac cell death and remodeling, which subsequently improved cardiac dysfunction without affecting hyperglycemia. This study revealed that Klotho may exert its protective effects by augmenting nuclear factor erythroid 2-related factor 2 (Nrf2) expression and inactivating nuclear factor κB (NF-κB) activation both in vitro and in vivo. Thus, this work demonstrated for the first time that the anti-aging protein Klotho may be a potential therapeutic agent to treat DCM by inhibiting oxidative stress and inflammation. We also demonstrated the critical roles of the Nrf2 and NF-κB pathways in diabetes-stimulated cardiac injuries and indicated that they may be key therapeutic targets for diabetic complications.

Evidence of vanillin binding to CAMKIV explains the anti-cancer mechanism in human hepatic carcinoma and neuroblastoma cells

Human calcium/calmodulin-dependent protein kinase IV (CAMKIV) is a member of Ser/Thr kinase family, and is associated with different types of cancer and neurodegenerative diseases. Vanillin is a natural compound, a primary component of the extract of the vanilla bean which possesses varieties of pharmacological features including anti-oxidant, anti-inflammatory, anti-bacterial and anti-tumor. Here, we have investigated the binding mechanism and affinity of vanillin to the CAMKIV which is being considered as a potential drug target for cancer and neurodegenerative diseases. We found that vanillin binds strongly to the active site cavity of CAMKIV and stabilized by a large number of non-covalent interactions. We explored the utility of vanillin as anti-cancer agent and found that it inhibits the proliferation of human hepatocyte carcinoma (HepG2) and neuroblastoma (SH-SY5Y) cells in a dose-dependent manner. Furthermore, vanillin treatment resulted into the significant reduction in the mitochondrial membrane depolarization and ROS production that eventually leads to apoptosis in HepG2 and SH-SY5Y cancer cells. These findings may offer a novel therapeutic approach by targeting the CAMKIV using natural product and its derivative with a minimal side effect.

Neuroprotective effect of dual specificity phosphatase 6 against glutamate-induced cytotoxicity in mouse hippocampal neurons

Dual specificity phosphatase 6 (DUSP6), a member of the dual specificity protein phosphatase subfamily, can inactivate ERK1/2. However, its possible role in glutamate-induced oxidative cytotoxicity effects is not clear.Here, we aimed to investigate whether DUSP6 was neuroprotective against glutamate-induced cytotoxicity in HT22 mouse hippocampal cells and primary cultured hippocampal neurons (pc-HNeu). HT22 and pc-HNeu cells were treated with varying concentrations of glutamate (from 0.05mM to 5.0mM) and DUSP6 protein expression were detected by western blotting. DUSP6-overexpressing HT22 and pc-HNeu cells were generated by transfection with DUSP6-overexpressing plasmid. The effects of DUSP6 overexpression on glutamate-induced cytotoxicity, cell death, cell apoptosis, and cell autophagy were determined by cell proliferation assays, flow cytometry, transmission electron microscopy, and western blotting. Glutamate treatment from 0.5mM to 5.0mM downregulated DUSP6 protein expression in both HT22 and pc-HNeu cells. DUSP6 overexpression ameliorated glutamate-induced cell death, apoptosis, and autophagy in both HT22 and pc-HNeu cells. Furthermore, ERK1/2 phosphorylation was decreased by DUSP6 overexpression. In conclusion, DUSP6 has neuroprotective effects against glutamate-induced cytotoxicity in HT22 and pc-HNeu cells. Targeting DUSP6 may be a useful strategy to prevent neuronal death in neurodegenerative diseases including AD.

Increased Intracellular Reactive Oxygen Species Mediates the Anti-Cancer Effects of WZ35 via Activating Mitochondrial Apoptosis Pathway in Prostate Cancer Cells

BACKGROUND

The limited treatment option for recurrent prostate cancer and eventual resistant to conventional chemotherapy drugs has fueled continued interest in finding new anti-neoplastic agents. WZ35, a chemical analog of curcumin, had been demonstrated to have high chemical stability and potential anticancer effects in gastric cancer cells. The present study aimed to investigate the anti-prostate cancer effects of WZ35 in vitro and in vivo as well as the underlying mechanism.

METHODS

Two prostate cancer cell lines RM-1 and DU145 were utilized to test the anti-cancer effects of WZ35 and the underlying mechanism. MTT assay was used to assess the cytotoxic effect of WZ35. Cell cycle distribution, apoptosis, alteration of ROS, and [Ca²⁺ ]_i level were evaluated using flow cytometry. Western blotting assay was applied to measure the levels of proteins associated with apoptosis and cell cycle. Immunofluorescence staining and Electron micrographs were used to evaluate activation of mitochondrial apoptosis pathway. Tumor models in nude mice were induced by injection of RM-1 prostate cancer cells to test the in vivo anticancer action of WZ35.

RESULTS

Our results showed that WZ35 treatment induced loss of cell viability, cell apoptosis, and G2/M cycle arrest in both RM-1 and DU145 cells, coupled with ROS overproduction, intracellular calcium surge, and activation of mitochondrial apoptosis pathway in RM-1 cells. Interestingly, all above changes induced by WZ35 were completely reversed by ROS blockage. In addition, prevention of [Ca²⁺ ]_i elevation by BAPTA/AM also inhibited activation of mitochondrial apoptosis pathway induced by WZ35. In vivo studies, WZ35 treatment significantly inhibited RM-1 homograft tumor growth along with increased ROS accumulation, mitochondrial disruption, and cell apoptosis in tumor tissues.

CONCLUSIONS

In conclusion, this work provides a novel anticancer candidate for the treatment of prostate cancer and demonstrated that increased ROS mediate the anti-cancer effects of WZ35 via activating mitochondrial apoptosis pathway. Importantly, this work also reveals that targeting ROS generation might be an effective strategy in human androgen-resistant prostate cancer treatment. Prostate 77:489-504, 2017. © 2016 Wiley Periodicals, Inc.

Salvianolic acid B attenuates oxidized low-density lipoprotein-induced endothelial cell apoptosis through inhibition of oxidative stress, p53, and caspase-3 pathways

OBJECTIVE

To investigate the effect of salvianolic acid B (Sal B) on oxidized low-density lipoprotein (ox-LDL)-induced human umbilical vein endothelial cells (HUVECs) apoptosis and the possible mechanism.

METHODS

HUVECs were divided into 6 groups, including control group, ox-LDL group, vitamin C group (positive control), and 5, 10 and 20 μg/mL Sal B groups. Cell viability of HUVECs was determined by 3-(4,5-dimethylthiazol- 2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The anti-apoptotic effect of Sal B was tested by Hoechst 33258 staining and Annexin V/propidium iodide flflow cytometry analysis. Apoptosis-related genes (p53, Bcl-2 and Bax) expression and caspase-3 activity were also determined. Oxidative stress markers malondialdehyde (MDA) and superoxide dismutase (SOD) were determined by the corresponding kits.

RESULTS

In HUVECs, ox-LDL signifificantly reduced cell viability and induced apoptosis (P<0.05 or P<0.01), however, Sal B diminished the effects of ox-LDL in a dose-dependent manner (P<0.05). Moreover, 10 and 20 μg/mL Sal B reduced the expression levels of p53, increased the Bcl-2/Bax ratio and inhibited the caspase-3 activity in ox-LDL-treated HUVECs (P<0.05). In addition, 5, 10 and 20 μg/mL Sal B signifificantly enhanced the activity of SOD, while decreased the level of MDA in the HUVECs which treated with ox-LDL (P<0.05).

CONCLUSION

Sal B exhibited anti-apoptotic effects in ox-LDL-induced endothelial cell injury by suppressing oxidative stress, p53, and caspase-3.

Butein provides neuroprotective and anti-neuroinflammatory effects through Nrf2/ARE-dependent haem oxygenase 1 expression by activating the PI3K/Akt pathway

BACKGROUND AND PURPOSE

Butein, 3,4,2',4'-tetrahydroxychalcone, has various pharmacological effects. However, no study has demonstrated the specific neurobiological mechanisms of the effects of butein in neuronal cells. The present study examined the role of butein as an antioxidative and anti-inflammatory inducer of haem oxygenase 1 (HO1) in mouse hippocampal HT22, BV2 microglial and primary mouse hippocampus neurons.

EXPERIMENTAL APPROACH

We investigated the neuroprotective effects of butein on glutamate-induced HT22 cell and primary mouse hippocampal neuron death and its anti-neuroinflammatory effects on LPS-induced activation of BV2 cells. We elucidated the underlying mechanisms by assessing the involvement of NF-κB, HO1, nuclear factor-E2-related factor 2 (Nrf2) and Akt signalling.

KEY RESULTS

Butein decreased cellular oxidative injury and the production of ROS in glutamate-treated HT22 cells and primary mouse hippocampal neurons. Furthermore, butein suppressed LPS-induced pro-inflammatory enzymes and mediators in BV2 microglia. Butein inhibited IL-6, IL-1β and TNF-α production and mRNA expression. In addition, butein decreased NO and PGE2 production and inducible NOS and COX-2 expression through the NF-κB signalling pathway. Butein up-regulated Nrf2/ARE-mediated HO1 expression through the PI3K/Akt pathway and this was positively associated with its cytoprotective effects and anti-neuroinflammatory actions.

CONCLUSION AND IMPLICATIONS

Our results indicate that butein effectively prevents glutamate-induced oxidative damage and LPS-induced activation and that the induction of HO1 by butein through the PI3K/Akt pathway and Nrf2 activation appears to play a pivotal role in its effects on neuronal cells. Our results provide evidence for the neuroprotective properties of butein.

Activation of Na+/K+-ATPase attenuates high glucose-induced H9c2 cell apoptosis via suppressing ROS accumulation and MAPKs activities by DRm217

Hyperglycemia is one of the major factors responsible for the myocardial apoptosis and dysfunction in diabetes. Many studies have proved that there is a close relationship between decreased Na⁺/K⁺-ATPase activity and diabetic cardiomyopathy. However, the effect of directly activated Na⁺/K⁺-ATPase on high glucose-induced myocardial injury is still unknown. Here we found that DRm217, a Na⁺/K⁺-ATPase's DR-region specific monoclonal antibody and direct activator, could prevent high glucose-induced H9c2 cell injury, reactive oxygen species (ROS) release, and mitochondrial dysfunction. High glucose-treatment decreased Na⁺/K⁺-ATPase activity and increased intracellular Ca²⁺ level, whereas DRm217 increased Na⁺/K⁺-ATPase activity and alleviated Ca²⁺ overload. Inhibition of Ca²⁺ overload or closing sodium calcium exchanger (NCX channel) could reverse high glucose-induced ROS increasing and cell injury. In addition, DRm217 could significantly attenuate high glucose-induced p38, JNK and ERK1/2 phosphorylation, which were involved in high glucose-induced cell injury and ROS accumulation. Our findings suggest that DRm217 may protect against the deleterious effects of high glucose in the heart. Prevention of high glucose-induced myocardial cell injury by specific Na⁺/K⁺-ATPase activator may be an attractive therapeutic option.

Expression of the mitochondrial calcium uniporter in cardiac myocytes improves impaired mitochondrial calcium handling and metabolism in simulated hyperglycemia

Diabetic cardiomyopathy is associated with metabolic changes, including decreased glucose oxidation (Gox) and increased fatty acid oxidation (FAox), which result in cardiac energetic deficiency. Diabetic hyperglycemia is a pathophysiological mechanism that triggers multiple maladaptive phenomena. The mitochondrial Ca²⁺ uniporter (MCU) is the channel responsible for Ca²⁺ uptake in mitochondria, and free mitochondrial Ca²⁺ concentration ([Ca²⁺]_m) regulates mitochondrial metabolism. Experiments with cardiac myocytes (CM) exposed to simulated hyperglycemia revealed reduced [Ca²⁺]_m and MCU protein levels. Therefore, we investigated whether returning [Ca²⁺]_m to normal levels in CM by MCU expression could lead to normalization of Gox and FAox with no detrimental effects. Mouse neonatal CM were exposed for 72 h to normal glucose [5.5 mM glucose + 19.5 mM mannitol (NG)], high glucose [25 mM glucose (HG)], or HG + adenoviral MCU expression. Gox and FAox, [Ca²⁺]_m, MCU levels, pyruvate dehydrogenase (PDH) activity, oxidative stress, mitochondrial membrane potential, and apoptosis were assessed. [Ca²⁺]_m and MCU protein levels were reduced after 72 h of HG. Gox was decreased and FAox was increased in HG, PDH activity was decreased, phosphorylated PDH levels were increased, and mitochondrial membrane potential was reduced. MCU expression returned these parameters toward NG levels. Moreover, increased oxidative stress and apoptosis were reduced in HG by MCU expression. We also observed reduced MCU protein levels and [Ca²⁺]_m in hearts from type 1 diabetic mice. Thus we conclude that HG-induced metabolic alterations can be reversed by restoration of MCU levels, resulting in return of [Ca²⁺]_m to normal levels.

Effect of 8-hydroxyquinoline and derivatives on human neuroblastoma SH-SY5Y cells under high glucose

8-Hydroxyquinoline and derivatives exhibit multifunctional properties, including antioxidant, antineurodegenerative, anticancer, anti-inflammatory and antidiabetic activities. In biological systems, elevation of intracellular calcium can cause calpain activation, leading to cell death. Here, the effect of 8-hydroxyquinoline and derivatives (5-chloro-7-iodo-8-hydroxyquinoline or clioquinol and 8-hydroxy-5-nitroquinoline or nitroxoline) on calpain-dependent (calpain-calpastatin) pathways in human neuroblastoma (SH-SY5Y) cells was investigated. 8-Hydroxyquinoline and derivatives ameliorated high glucose toxicity in SH-SY5Y cells. The investigated compounds, particularly clioquinol, attenuated the increased expression of calpain, even under high-glucose conditions. 8-Hydroxyquinoline and derivatives thus adversely affected the promotion of neuronal cell death by high glucose via the calpain-calpastatin signaling pathways. These findings support the beneficial effects of 8-hydroxyquinolines for further therapeutic development.

Post-operative atrial fibrillation is associated with a pre-existing structural and electrical substrate in human right atrial myocardium

Background

Post-operative atrial fibrillation (POAF) is a major health economic burden. However, the precise mechanisms in POAF remain unclear. In other forms of AF, sites of high dominant frequency (DF) in sinus rhythm (SR) may harbour ‘AF nests’. We studied AF inducibility in relation to substrate changes using epicardial electrograms and cardiomyocyte calcium handling in the atria of AF naïve patients.

Method

Bipolar electrograms were recorded from the lateral right atrial (RA) wall in 34 patients undergoing coronary surgery using a high-density array in sinus rhythm (NSR). RA burst pacing at 200/500/1000 ms cycle lengths (CL) was performed, recording episodes of AF > 30 s. Co-localised RA tissue was snap frozen for RNA and protein extraction.

Results

Electrograms prolonged during AF (76.64 ± 29.35 ms) vs. NSR/pacing (p < 0.001). Compared to NSR, electrogram amplitude was reduced during AF and during pacing at 200 ms CL (p < 0.001). Electrogram DF was significantly lower in AF (75.87 ± 23.63 Hz) vs. NSR (89.33 ± 25.99 Hz) (p < 0.05), and NSR DF higher in AF inducible patients at the site of AF initiation (p < 0.05). Structurally, POAF atrial myocardium demonstrated reduced sarcolipin gene (p = 0.0080) and protein (p = 0.0242) expression vs. NSR. Phospholamban gene and protein expression was unchanged. SERCA2a protein expression remained unchanged, but MYH6 (p = 0.0297) and SERCA2A (p = 0.0343) gene expression was reduced in POAF.

Conclusions

Human atrial electrograms prolong and reduce in amplitude in induced peri-operative AF vs. NSR or pacing. In those sustaining AF, high DF sites in NSR may indicate ‘AF nests’. This electrical remodelling is accompanied by structural remodelling with altered expression of cardiomyocyte calcium handling detectable before POAF. These novel upstream substrate changes offer a novel mechanism and manifestation of human POAF.