Arsenite retards the cardiac differentiation of rat cardiac myoblast H9c2 cells

Facile Fabrication of Three-Dimensional Hydrogel Film with Complex Tissue Morphology

In this study, we proposed a simple and easy method for fabricating a three-dimensional (3D) structure that can recapitulate the morphology of a tissue surface and deliver biological molecules into complex-shaped target tissues. To fabricate the 3D hydrogel film structure, we utilized a direct tissue casting method that can recapitulate tissue structure in micro-/macroscale using polydimethylsiloxane (PDMS). A replica 3D negative mold was manufactured by a polyurethane acrylate (PUA)-based master mold. Then, we poured the catechol-conjugated alginate (ALG-C) solution into the mold and evaporated it to form a dried film, followed by crosslinking the film using calcium chloride. The ALG-C hydrogel film had a tensile modulus of 725.2 ± 123.4 kPa and maintained over 95% of initial weight after 1 week without significant degradation. The ALG-C film captured over 4.5 times as much macromolecule (FITC-dextran) compared to alginate film (ALG). The cardiomyoblast cells exhibited high cell viability over 95% on ALG-C film. Moreover, the ALG-C film had about 70% of surface-bound lentivirus (1% in ALG film), which finally exhibited much higher viral transfection efficiency of GFP protein to C2C12 cells on the film than ALG film. In conclusion, we demonstrated a 3D film structure of biofunctionalized hydrogel for substrate-mediated drug delivery, and this approach could be utilized to recapitulate the complex-shaped tissues.

A Novel Titin Truncation Variant Linked to Familial Dilated Cardiomyopathy Found in a Japanese Family and Its Functional Analysis in Genome-Edited Model Cells

Dilated cardiomyopathy (DCM) is a common cause of heart failure. TTN, which encodes titin protein, is a representative causative gene of DCM, and is presented mainly as a truncation variant. However, TTN truncation variants are also found in healthy individuals, and it is therefore important to evaluate the pathogenicity of each variant. In this study, we analyzed 67 cardiomyopathy-associated genes in a male Japanese patient who was hospitalized for recurrent severe heart failure and identified a novel truncation variant, TTN Ser17456Arg fs*14. This TTN truncation variant was located in the A-band region. Moreover, the patient's mother with heart failure harbored the same variant, whereas the father and brother without heart failure did not harbor the variant. To examine the functional changes associated with the truncation variant, H9c2 cells were subjected to genome editing to generate cells with a homologous truncation variant. The cells were differentiated using all-trans-retinoic acid, and the mRNA expression of skeletal actin and cardiac actin were found to be increased and decreased, respectively, consistent with known changes in patients with DCM or heart failure. In contrast, another cell with the titin truncation variant used as a control showed no changes in heart failure-related genes. In summary, we found a novel TTN truncation variant in familial DCM patients and confirmed its functional changes using a relatively simple cell model. The novel truncation variant was identified as a pathogenic and disease-causing mutation.

Ferritinophagy-mediated ferroptosis is involved in sepsis-induced cardiac injury

Ferroptosis is a reactive oxygen species (ROS)- and iron-dependent form of regulated cell death (RCD), playing critical roles in organ injury and targeting therapy of cancers. Previous studies have demonstrated that ferroptosis participates in the development of cardiomyopathy including cardiac hypertrophy, diabetic cardiomyopathy and doxorubicin-induced cardiotoxicity. However, the role of ferroptosis in sepsis-induced cardiac injury remains unclear. This study aimed to explore the role and underlying mechanism of ferroptosis on lipopolysaccharide (LPS)-induced cardiac injury. Mice were injected with LPS (10 mg/kg) for 12 h to generate experimental sepsis. Ferrostatin-1 (Fer-1) and Dexrazoxane (DXZ) were used to suppress ferroptosis of mice with sepsis-induced cardiac injury. LPS increased the levels of ferroptotic markers involving prostaglandin endoperoxide synthase 2 (PTGS2), malonaldehyde (MDA) and lipid ROS, apart from resulting in obvious mitochondria damage, which were alleviated by Fer-1 and DXZ. In vitro experiments showed that Fer-1 inhibited LPS-induced lipid peroxidation and injury of H9c2 myofibroblasts while erastin and sorafenib aggravated LPS-induced ferroptosis. Additionally, Fer-1 and DXZ improved survival rate and cardiac function of mice with sepsis. Mechanistically, LPS increased the expression of nuclear receptor coactivator 4 (NCOA4) and the level of intracellular Fe²⁺ but decreased the level of ferritin. NCOA4 could directly interact with ferritin and degrade it in a ferritinophagy-dependent manner, which subsequently released a great amount of iron. Cytoplasmic Fe²⁺ further activated the expression of siderofexin (SFXN1) on mitochondrial membrane, which in turn transported cytoplasmic Fe²⁺ into mitochondria, giving rise to the production of mitochondrial ROS and ferroptosis. Based on these findings, we concluded that ferritinophagy-mediated ferroptosis is one of the critical mechanisms contributing to sepsis-induced cardiac injury. Targeting ferroptosis in cardiomyocytes may be a therapeutic strategy for preventing sepsis in the future.

Tanshinone IIA promotes cardiac differentiation and improves cell motility by modulating the Wnt/β‑catenin signaling pathway

Although the cardiovascular pharmacological actions of Tanshinone IIA (TanIIA) have been extensively studied, research on its roles in cardiac regeneration is still insufficient. The present study employed the cardiac myoblast cell line H9c2 to evaluate the possible roles of TanIIA in cardiac regeneration. It was found that certain concentration of TanIIA inhibited cell proliferation by suppressing the expression of proteins related to the cell cycle [cyclin dependent kinase (CDK)4, CDK6 and cyclin D1] and proliferation [c-Myc, octamer-binding transcription factor 4 (Oct4) and proliferating cell nuclear antigen (PCNA)] without inducing apoptosis. In this process, the expression of cardiac troponin in the treated cells was significantly increased and the migration of the treated cells toward the wound area was significantly enhanced. Meanwhile, TanIIA inhibited the canonical signaling pathway through increasing the expression of glycogen synthase kinase 3β (GSK-3β) and adenomatous polyposis coli (APC) and increased the expression of Wnt11 and Wnt5a in the noncanonical Wnt signaling pathway. Following β-catenin agonist WAY-262611 intervention, the effect of TanIIA on the promotion of cardiac differentiation and improved cell migration was significantly reduced. In conclusion, it was hypothesized that TanIIA could promote cardiac differentiation and improve cell motility by modulating the Wnt/β-catenin signaling pathway. These results suggest that TanIIA may play beneficial roles in myocardial regeneration following stem cell transplantation.

Withaferin A inhibits apoptosis via activated Akt-mediated inhibition of oxidative stress

Withaferin A (WFA), a withanolide derived from medicinal plant Withania somnifera, possesses anti-tumorigenic and immunomodulatory activities against various cancer cells. However, the role of WFA in myocardial ischemia reperfusion (MI/R) injury remains unclear. In the present study, we determined whether WFA may regulate cardiac ischemia reperfusion injury and elucidate the underlying mechanisms. We demonstrated that WFA enhanced H9c2 cells survival ability against simulated ischemia/reperfusion (SI/R) or hydrogen peroxide (H₂O₂)-induced cell apoptosis. In addition, the enhanced oxidative stress induced by SI/R was inhibited by WFA. Among the multiple antioxidant molecules determined, antioxidants SOD2, SOD3, Prdx-1 was obviously upregulated by WFA. When Akt inhibitor IV was administrated, WFA's suppression effect on oxidative stress was obviously abolished. Additional experiments demonstrated that WFA successfully inhibited H₂O₂ induced upregulation of SOD2, SOD3, and Prdx-1, ameliorated cardiomyocyte caspase-3 activity via an Akt dependent manner. Collectively, these results support the therapeutic potential of WFA against cardiac ischemia reperfusion injury and highlight the application of WFA in cardiovascular diseases holding great promise for the future.

Kolaviron attenuated arsenic acid induced-cardiorenal dysfunction via regulation of ROS, C-reactive proteins (CRP), cardiac troponin I (CTnI) and BCL2

Arsenic acid is one of the abundant environmental pollutants present in soil, water and the air. Undoubtedly, it has found its way to the food chain in which humans and animals are the final targets thereby causing arrays of disease conditions including cardiovascular and renal dysfunction. Hence, the use of phytochemicals present in medicinal plants has gained global acceptance as chemotherapeutic agents that can prevent, ameliorate, reverse or treat diseases. From our study, arsenic acid intoxication led to significant increase in heart rate (HR), QRS, together with prolonged QT and QTc interval. However, Kolaviron (KV) at the dosage of 100 and 200 mg/kg body weight reversed the aforementioned electrocardiographic (ECG) changes. KV pre-treatment also ameliorated cardiorenal dysfunction via significant reduction in cardiac and renal markers of oxidative stress such as malondialdehyde, hydrogen peroxide generation, myeloperoxidase activity and nitric oxide contents. Immunohistochemistry revealed expressions of renal C-reactive proteins (CRP) and expressions of anti-apoptotic protein BCL2 in KV treated rats. Furthermore, cardiac troponin I (CTnI) expressions were lower in KV treated rats. Taken together, KV mitigated arsenic-acid induced cardiovascular dysfunction via up-regulation of antioxidant defense system and down-regulation of inflammatory and apoptotic signaling pathways.

Antioxidants Protect against Arsenic Induced Mitochondrial Cardio-Toxicity

Arsenic is a potent cardiovascular toxicant associated with numerous biomarkers of cardiovascular diseases in exposed human populations. Arsenic is also a carcinogen, yet arsenic trioxide is used as a therapeutic agent in the treatment of acute promyelotic leukemia (APL). The therapeutic use of arsenic is limited due to its severe cardiovascular side effects. Many of the toxic effects of arsenic are mediated by mitochondrial dysfunction and related to arsenic's effect on oxidative stress. Therefore, we investigated the effectiveness of antioxidants against arsenic induced cardiovascular dysfunction. A growing body of evidence suggests that antioxidant phytonutrients may ameliorate the toxic effects of arsenic on mitochondria by scavenging free radicals. This review identifies 21 antioxidants that can effectively reverse mitochondrial dysfunction and oxidative stress in cardiovascular cells and tissues. In addition, we propose that antioxidants have the potential to improve the cardiovascular health of millions of people chronically exposed to elevated arsenic concentrations through contaminated water supplies or used to treat certain types of leukemias. Importantly, we identify conceptual gaps in research and development of new mito-protective antioxidants and suggest avenues for future research to improve bioavailability of antioxidants and distribution to target tissues in order reduce arsenic-induced cardiovascular toxicity in a real-world context.

Comparative proteomic analysis reveals heart toxicity induced by chronic arsenic exposure in rats

Arsenic is a widespread metalloid in the environment, which poses a broad spectrum of adverse effects on human health. However, a global view of arsenic-induced heart toxicity is still lacking, and the underlying molecular mechanisms remain unclear. By performing a comparative quantitative proteomic analysis, the present study aims to investigate the alterations of proteome profile in rat heart after long-term exposure to arsenic. As a result, we found that the abundance of 81 proteins were significantly altered by arsenic treatment (35 up-regulated and 46 down-regulated). Among these, 33 proteins were specifically associated with cardiovascular system development and function, including heart development, heart morphology, cardiac contraction and dilation, and other cardiovascular functions. It is further proposed that the aberrant regulation of 14 proteins induced by arsenic would disturb cardiac contraction and relaxation, impair heart morphogenesis and development, and induce thrombosis in rats, which is mediated by the Akt/p38 MAPK signaling pathway. Overall, these findings will augment our knowledge of the involved mechanisms and develop useful biomarkers for cardiotoxicity induced by environmental arsenic exposure.

IL-6 Activates PI3K and PKCζ Signaling and Determines Cardiac Differentiation in Rat Embryonic H9c2 Cells

INTRODUCTION

IL-6 influences several biological processes, including cardiac stem cell and cardiomyocyte physiology. Although JAK-STAT3 activation is the defining feature of IL-6 signaling, signaling molecules such as PI3K, PKCs, and ERK1/2 are also activated and elicit different responses. Moreover, most studies on the specific role of these signaling molecules focus on the adult heart, and few studies are available on the biological effects evoked by IL-6 in embryonic cardiomyocytes.

AIM

The aim of this study was to clarify the biological response of embryonic heart derived cells to IL-6 by analyzing the morphological modifications and the signaling cascades evoked by the cytokine in H9c2 cells.

RESULTS

IL-6 stimulation determined the terminal differentiation of H9c2 cells, as evidenced by the increased expression of cardiac transcription factors (NKX2.5 and GATA4), structural proteins (α-myosin heavy chain and cardiac Troponin T) and the gap junction protein Connexin 43. This process was mediated by the rapid modulation of PI3K, Akt, PTEN, and PKCζ phosphorylation levels. PI3K recruitment was an upstream event in the signaling cascade and when PI3K was inhibited, IL-6 failed to modify PKCζ, PTEN, and Akt phosphorylation. Blocking PKCζ activity affected only PTEN and Akt. Finally, the overexpression of a constitutively active form of PKCζ in H9c2 cells largely mimicked the morphological and molecular effects evoked by IL-6.

CONCLUSIONS

This study demonstrated that IL-6 induces the cardiac differentiation of H9c2 embryonic cells though a signaling cascade that involves PI3K, PTEN, and PKCζ activities.

Arsenic trioxide alters the differentiation of mouse embryonic stem cell into cardiomyocytes

Chronic arsenic exposure is associated with increased morbidity and mortality for cardiovascular diseases. Arsenic increases myocardial infarction mortality in young adulthood, suggesting that exposure during foetal life correlates with cardiac alterations emerging later. Here, we investigated the mechanisms of arsenic trioxide (ATO) cardiomyocytes disruption during their differentiation from mouse embryonic stem cells. Throughout 15 days of differentiation in the presence of ATO (0.1, 0.5, 1.0 μM) we analysed: the expression of i) marker genes of mesoderm (day 4), myofibrillogenic commitment (day 7) and post-natal-like cardiomyocytes (day 15); ii) sarcomeric proteins and their organisation; iii) Connexin 43 and iv) the kinematics contractile properties of syncytia. The higher the dose used, the earlier the stage of differentiation affected (mesoderm commitment, 1.0 μM). At 0.5 or 1.0 μM the expression of cardiomyocyte marker genes is altered. Even at 0.1 μM, ATO leads to reduction and skewed ratio of sarcomeric proteins and to a rarefied distribution of Connexin 43 cardiac junctions. These alterations contribute to the dysruption of the sarcomere and syncytium organisation and to the impairment of kinematic parameters of cardiomyocyte function. This study contributes insights into the mechanistic comprehension of cardiac diseases caused by in utero arsenic exposure.

Cardiomyoblast (h9c2) differentiation on tunable extracellular matrix microenvironment

Extracellular matrices (ECM) obtained from in vitro-cultured cells have been given much attention, but its application in cardiac tissue engineering is still limited. This study investigates cardiomyogenic potential of fibroblast-derived matrix (FDM) as a novel ECM platform over gelatin or fibronectin, in generating cardiac cell lineages derived from H9c2 cardiomyoblasts. As characterized through SEM and AFM, FDM exhibits unique surface texture and biomechanical property. Immunofluorescence also found fibronectin, collagen, and laminin in the FDM. Cells on FDM showed a more circular shape and slightly less proliferation in a growth medium. After being cultured in a differentiation medium for 7 days, H9c2 cells on FDM differentiated into cardiomyocytes, as identified by stronger positive markers, such as α-actinin and cTnT, along with more elevated gene expression of Myl2 and Tnnt compared to the cells on gelatin and fibronectin. The gap junction protein connexin 43 was also significantly upregulated for the cells differentiated on FDM. A successive work enabled matrix stiffness tunable; FDM crosslinked by 2wt% genipin increased the stiffness up to 8.5 kPa, 100 times harder than that of natural FDM. The gene expression of integrin subunit α5 was significantly more upregulated on FDM than on crosslinked FDM (X-FDM), whereas no difference was observed for β1 expression. Interestingly, X-FDM showed a much greater effect on the cardiomyoblast differentiation into cardiomyocytes over natural one. This study strongly indicates that FDM can be a favorable ECM microenvironment for cardiomyogenesis of H9c2 and that tunable mechanical compliance induced by crosslinking further provides a valuable insight into the role of matrix stiffness on cardiomyogenesis.

Arsenic inhibits hedgehog signaling during P19 cell differentiation

Arsenic is a toxicant found in ground water around the world, and human exposure mainly comes from drinking water or from crops grown in areas containing arsenic in soils or water. Epidemiological studies have shown that arsenic exposure during development decreased intellectual function, reduced birth weight, and altered locomotor activity, while in vitro studies have shown that arsenite decreased muscle and neuronal cell differentiation. The sonic hedgehog (Shh) signaling pathway plays an important role during the differentiation of both neurons and skeletal muscle. The purpose of this study was to investigate whether arsenic can disrupt Shh signaling in P19 mouse embryonic stem cells, leading to changes muscle and neuronal cell differentiation. P19 embryonic stem cells were exposed to 0, 0.25, or 0.5 μM of sodium arsenite for up to 9 days during cell differentiation. We found that arsenite exposure significantly reduced transcript levels of genes in the Shh pathway in both a time and dose-dependent manner. This included the Shh ligand, which was decreased 2- to 3-fold, the Gli2 transcription factor, which was decreased 2- to 3-fold, and its downstream target gene Ascl1, which was decreased 5-fold. GLI2 protein levels and transcriptional activity were also reduced. However, arsenic did not alter GLI2 primary cilium accumulation or nuclear translocation. Moreover, additional extracellular SHH rescued the inhibitory effects of arsenic on cellular differentiation due to an increase in GLI binding activity. Taken together, we conclude that arsenic exposure affected Shh signaling, ultimately decreasing the expression of the Gli2 transcription factor. These results suggest a mechanism by which arsenic disrupts cell differentiation.