All-trans retinoic acid prevents angiotensin II- and mechanical stretch-induced reactive oxygen species generation and cardiomyocyte apoptosis

Region and cell-type resolved multi-omic altas of the heart

The heart is a vital muscular organ in vertebrate animals, responsible for maintaining blood circulation through rhythmic contraction. Although previous studies have investigated the heart proteome, the full hierarchical molecular network at cell-type and region resolved level, illustrating the specialized roles and crosstalk among different cell types and regions, remains unclear. Here, we presented an atlas of cell-type resolved proteome for mouse heart and region resolved proteome for both mouse and human hearts. In-depth proteomic analysis identified 11,794 proteins across four cell types and 11,995 proteins across six regions of the mouse heart. To further illustrate protein expression patterns in both physiological and pathological conditions, we conducted proteomic analysis on human heart samples from four regions with dilated cardiomyopathy (DCM). We quantified 8,201 proteins in DCM tissue and 8,316 proteins in adjacent unaffected myocardium (AUM) tissue across the four human heart regions. Notably, we found that the retinoic acid synthesis pathway was significantly enriched in the DCM-affected left ventricle, and functional experiments demonstrated that all-trans retinoic acid (atRA) efficiently rescued Ang II-induced myocardial hypertrophy and transverse aorta constriction (TAC)- induced heart failure. In conclusion, our datasets uncovered the functional features of different cell types and their synergistic cooperation centered by cell-type specific transcription factors (ctsTF) in different regions, while these TF-TG (target gene) axes were significantly altered in DCM. Additionally, atRA was demonstrated to be an efficient treatment for heart failure. This work presented a panoramic heart proteome map, offering a valuable resource for future cardiovascular research.

Co-delivery of retinoic acid and miRNA by functional Au nanoparticles for improved survival and CT imaging tracking of MSCs in pulmonary fibrosis therapy

Mesenchymal stem cells (MSCs) have emerged as promising candidates for idiopathic pulmonary fibrosis (IPF) therapy. Increasing the MSC survival rate and deepening the understanding of the behavior of transplanted MSCs are of great significance for improving the efficacy of MSC-based IPF treatment. Therefore, dual-functional Au-based nanoparticles (Au@PEG@PEI@TAT NPs, AuPPT) were fabricated by sequential modification of cationic polymer polyetherimide (PEI), polyethylene glycol (PEG), and transactivator of transcription (TAT) penetration peptide on AuNPs, to co-deliver retinoic acid (RA) and microRNA (miRNA) for simultaneously enhancing MSC survive and real-time imaging tracking of MSCs during IPF treatment. AuPPT NPs, with good drug loading and cellular uptake abilities, could efficiently deliver miRNA and RA to protect MSCs from reactive oxygen species and reduce their expression of apoptosis executive protein Caspase 3, thus prolonging the survival time of MSC after transplantation. In the meantime, the intracellular accumulation of AuPPT NPs enhanced the computed tomography imaging contrast of transplanted MSCs, allowing them to be visually tracked in vivo. This study establishes an Au-based dual-functional platform for drug delivery and cell imaging tracking, which provides a new strategy for MSC-related IPF therapy.

Exploring the molecular biology of ischemic cardiomyopathy based on ferroptosis‑related genes

Ischemic cardiomyopathy (ICM) is a serious cardiac disease with a very high mortality rate worldwide, which causes myocardial ischemia and hypoxia as the main damage. Further understanding of the underlying pathological processes of cardiomyocyte injury is key to the development of cardioprotective strategies. Ferroptosis is an iron-dependent form of regulated cell death characterized by the accumulation of lipid hydroperoxides to lethal levels, resulting in oxidative damage to the cell membrane. The current understanding of the role and regulation of ferroptosis in ICM is still limited, especially in the absence of evidence from large-scale transcriptomic data. Through comprehensive bioinformatics analysis of human ICM transcriptome data obtained from the Gene Expression Omnibus database, the present study identified differentially expressed ferroptosis-related genes (DEFRGs) in ICM. Subsequently, their potential biological mechanisms and cross-talk were analyzed, and hub genes were identified by constructing protein-protein interaction networks. Ferroptosis features such as reactive oxygen species generation, changes in ferroptosis marker proteins, iron ion aggregation and lipid oxidation, were identified in the H9c2 anoxic reoxygenation injury model. Finally, the diagnostic ability of Gap junction alpha-1 (GJA1), Solute carrier family 40 member 1 (SLC40A1), Alpha-synuclein (SNCA) were identified through receiver operating characteristic curves and the expression of DEFRGs was verified in an in vitro model. Furthermore, potential drugs (retinoic acid) that could regulate ICM ferroptosis were predicted based on key DEFRGs. The present article presents new insights into the role of ferroptosis in ICM, investigating the regulatory role of ferroptosis in the pathological process of ICM and advocating for ferroptosis as a potential novel therapeutic target for ICM based on evidence from the ICM transcriptome.

Mitochondrial Dynamics: Working with the Cytoskeleton and Intracellular Organelles to Mediate Mechanotransduction

Cells are constantly exposed to various mechanical environments; therefore, it is important that they are able to sense and adapt to changes. It is known that the cytoskeleton plays a critical role in mediating and generating extra- and intracellular forces and that mitochondrial dynamics are crucial for maintaining energy homeostasis. Nevertheless, the mechanisms by which cells integrate mechanosensing, mechanotransduction, and metabolic reprogramming remain poorly understood. In this review, we first discuss the interaction between mitochondrial dynamics and cytoskeletal components, followed by the annotation of membranous organelles intimately related to mitochondrial dynamic events. Finally, we discuss the evidence supporting the participation of mitochondria in mechanotransduction and corresponding alterations in cellular energy conditions. Notable advances in bioenergetics and biomechanics suggest that the mechanotransduction system composed of mitochondria, the cytoskeletal system, and membranous organelles is regulated through mitochondrial dynamics, which may be a promising target for further investigation and precision therapies.

Retinoic Acid Has Neuroprotective effects by Modulating Thioredoxin in Ischemic Brain Damage and Glutamate-exposed Neurons

Ischemic stroke is a neurological disorder that causes pathological changes by increasing oxidative stress. Retinoic acid is one of the metabolites of vitamin A. It regulates oxidative stress and exerts neuroprotective effects. Thioredoxin is a small redox protein with antioxidant activity. The aim of this study was to investigate whether retinoic acid modulates the expression of thioredoxin in ischemic brain injury. Cerebral ischemia was induced by middle cerebral artery occlusion (MCAO) surgery and retinoic acid (5 mg/kg) or vehicle was administered to adult male rats for four days prior to surgery. MCAO induced neurological deficits and increased oxidative stress and retinoic acid attenuated these changes. Retinoic acid ameliorated the MCAO-induced decrease in thioredoxin expression. MCAO decreases the interaction between thioredoxin and apoptosis signal-regulating kinase 1 (ASK1), and retinoic acid treatment alleviates this decrease. Glutamate (5 mM) exposure induced cell death and decreased thioredoxin expression in cultured neurons. Retinoic acid treatment attenuated these changes in a dose-dependent manner. Retinoic acid prevented the decrease of bcl-2 expression and the increase of bax expression caused by glutamate exposure. Moreover, retinoic acid attenuated the increases in caspase-3, cleaved caspase-3, and cytochrome c in glutamate-exposed neurons. However, the mitigation effects of retinoic acid were lower in thioredoxin siRNA-transfected neurons than in non-transfected neurons. These results demonstrate that retinoic acid regulates oxidative stress and thioredoxin expression, maintains the interaction between thioredoxin and ASK1, and modulates apoptosis-associated proteins. Taken together, these results suggest that retinoic acid has neuroprotective effects by regulating thioredoxin expression and modulating apoptotic pathway.

Relationship between disorders of the intestinal microbiota and heart failure in infants with congenital heart disease

Purpose

There is a close relationship between the intestinal microbiota and heart failure, but no study has assessed this relationship in infants with congenital heart disease. This study aimed to explore the relationship between heart failure and intestinal microbiota in infants with congenital heart disease.

Methods

Twenty-eight infants with congenital heart disease with heart failure admitted to a provincial children’s hospital from September 2021 to December 2021 were enrolled in this study. A total of 22 infants without heart disease and matched for age, sex, and weight were selected as controls. Faecal samples were collected from every participant and subjected to 16S rDNA gene sequencing.

Results

The composition of the intestinal microbiota was significantly disordered in infants with heart failure caused by congenital heart disease compared with that in infants without heart disease. At the phylum level, the most abundant bacteria in the heart failure group were Firmicutes, Actinobacteria, Proteobacteria, and Bacteroidetes, and the most abundant bacteria in the control group were Firmicutes, Proteobacteria, Actinobacteria, and Bacteroidetes. At the genus level, the most abundant bacteria in the heart failure group were Enterococcus, Bifidobacterium, Subdoligranulum, Shigella, and Streptococcus, and the most abundant bacteria in the control group were Bifidobacterium, Blautia, Bacteroides, Streptococcus, and Ruminococcus. The alpha and beta diversities of the gut bacterial community in the heart failure group were significantly lower than those in the control group (p<0.05). Compared with the control group, retinol metabolism was significantly downregulated in the heart failure group.

Conclusion

Heart failure in infants with congenital heart disease caused intestinal microbiota disorder, which was characterised by an increase in pathogenic bacteria, a decrease in beneficial bacteria, and decreases in diversity and richness. The significant downregulation of retinol metabolism in the intestinal microbiota of infants with heart failure may be related to the progression of heart failure, and further study of the underlying mechanism is needed.

Role of Nutrients and Foods in Attenuation of Cardiac Remodeling through Oxidative Stress Pathways

Cardiac remodeling is defined as a group of molecular, cellular, and interstitial changes that manifest clinically as changes in the heart’s size, mass, geometry, and function after different injuries. Importantly, remodeling is associated with increased risk of ventricular dysfunction and heart failure. Therefore, strategies to attenuate this process are critical. Reactive oxygen species and oxidative stress play critical roles in remodeling. Importantly, antioxidative dietary compounds potentially have protective properties against remodeling. Therefore, this review evaluates the role of nutrients and food as modulators of cardiac remodeling.

Comprehending Cardiac Dysfunction by Oxidative Stress: Untargeted Metabolomics of In Vitro Samples

Cardiovascular diseases (CVDs) are noncommunicable diseases known for their complex etiology and high mortality rate. Oxidative stress (OS), a condition in which the release of free radical exceeds endogenous antioxidant capacity, is pivotal in CVC, such as myocardial infarction, ischemia/reperfusion, and heart failure. Due to the lack of information about the implications of OS on cardiovascular conditions, several methodologies have been applied to investigate the causes and consequences, and to find new ways of diagnosis and treatment as well. In the present study, cardiac dysfunction was evaluated by analyzing cells’ alterations with untargeted metabolomics, after simulation of an oxidative stress condition using hydrogen peroxide (H₂O₂) in H9c2 myocytes. Optimizations of H₂O₂ concentration, cell exposure, and cell recovery times were performed through MTT assays. Intracellular metabolites were analyzed right after the oxidative stress (oxidative stress group) and after 48 h of cell recovery (recovery group) by ultra-high-performance liquid chromatography coupled to mass spectrometry (UHPLC-MS) in positive and negative ESI ionization mode. Significant alterations were found in pathways such as “alanine, aspartate and glutamate metabolism”, “glycolysis”, and “glutathione metabolism”, mostly with increased metabolites (upregulated). Furthermore, our results indicated that the LC-MS method is effective for studying metabolism in cardiomyocytes and generated excellent fit (R²Y > 0.987) and predictability (Q² > 0.84) values.

Role of cellular retinol-binding protein, type 1 and retinoid homeostasis in the adult mouse heart: A multi-omic approach

The main active metabolite of Vitamin A, all-trans retinoic acid (RA), is required for proper cellular function and tissue organization. Heart development has a well-defined requirement for RA, but there is limited research on the role of RA in the adult heart. Homeostasis of RA includes regulation of membrane receptors, chaperones, enzymes, and nuclear receptors. Cellular retinol-binding protein, type 1 (CRBP1), encoded by retinol-binding protein, type 1 (Rbp1), regulates RA homeostasis by delivering vitamin A to enzymes for RA synthesis and protecting it from non-specific oxidation. In this work, a multi-omics approach was used to characterize the effect of CRBP1 loss using the Rbp1^-/- mouse. Retinoid homeostasis was disrupted in Rbp1^-/- mouse heart tissue, as seen by a 33% and 24% decrease in RA levels in the left and right ventricles, respectively, compared to wild-type mice (WT). To further inform on the effect of disrupted RA homeostasis, we conducted high-throughput targeted metabolomics. A total of 222 metabolite and metabolite combinations were analyzed, with 33 having differential abundance between Rbp1^-/- and WT hearts. Additionally, we performed global proteome profiling to further characterize the impact of CRBP1 loss in adult mouse hearts. More than 2606 unique proteins were identified, with 340 proteins having differential expression between Rbp1^-/- and WT hearts. Pathway analysis performed on metabolomic and proteomic data revealed pathways related to cellular metabolism and cardiac metabolism were the most disrupted in Rbp1^-/- mice. Together, these studies characterize the effect of CRBP1 loss and reduced RA in the adult heart.

All-Trans Retinoic Acid Attenuates Transmissible Gastroenteritis Virus-Induced Apoptosis in IPEC-J2 Cells via Inhibiting ROS-Mediated P38MAPK Signaling Pathway

Transmissible gastroenteritis virus (TGEV) can cause diarrhea, dehydration, and high mortality in piglets, which is closely related to intestinal epithelial cell apoptosis caused by TGEV infection. All-trans retinoic acid (ATRA) is the active metabolite of vitamin A, which has antioxidant and anti-apoptotic properties. However, it is unknown whether ATRA can attenuate TGEV-induced IPEC-J2 cells apoptosis. Therefore, we investigated the protective effects of ATRA on TGEV-induced apoptosis of IPEC-J2 cells and explored the potential molecular mechanism. Our results indicated that TGEV infection caused IPEC-J2 cells damage and apoptosis. However, ATRA treatment attenuated TGEV-induced IPEC-J2 cells damage by upregulating the mRNA expressions of ZO-1, Occludin, and Mucin-1. ATRA treatment also attenuated TGEV-induced apoptosis in IPEC-J2 cells by downregulating the expression of Caspase-3, which is related to the inhibition of death receptor (Fas and Caspase-8) and mitochondrial (Bax, Bcl-2, and Caspase-9) pathways. Moreover, ATRA treatment prevented TGEV-induced ROS and MDA production and the upregulation of P₃₈MAPK phosphorylation level, which is related to the increase in the activities of antioxidant enzymes (SOD, CAT, and T-AOC) and the mRNA abundance of antioxidant-related genes (GPX1, GPX2, SOD1, CAT, GCLC, and GCLM). In addition, treatment of TGEV-infected IPEC-J2 cells with the ROS inhibitors (NAC) significantly reduced the protein levels of p-P₃₈MAPK, Fas, Bax, and Cleaved-caspase-3 and the percentage of apoptotic cells. Our results indicated that ATRA attenuated TGEV-induced apoptosis in IPEC-J2 cells via improving the antioxidant capacity, thereby inhibiting the cell damage. the mechanism of which is associated with the inhibition of ROS-mediated P₃₈MAPK signaling pathway.

Activation of the M3AChR and Notch1/HSF1 Signaling Pathway by Choline Alleviates Angiotensin II-Induced Cardiomyocyte Apoptosis

Angiotensin II- (Ang II-) induced cardiac hypertrophy and apoptosis are major characteristics of early-stage heart failure. Choline exerts cardioprotective effects; however, its effects on Ang II-induced cardiomyocyte apoptosis are unclear. In this study, the role and underlying mechanism of choline in regulating Ang II-induced cardiomyocyte apoptosis were investigated using a model of cardiomyocyte apoptosis, which was induced by exposing neonatal rat cardiomyocytes to Ang II (10⁻⁶ M, 48 h). Choline promoted heat shock transcription factor 1 (HSF1) nuclear translocation and the intracellular domain of Notch1 (NICD) expression. Consequently, choline attenuated Ang II-induced increases in mitochondrial reactive oxygen species (mtROS) and promotion of proapoptotic protein release from mitochondria, including cytochrome c, Omi/high-temperature requirement protein A2, and second mitochondrial activator of caspases/direct inhibitor of apoptosis-binding protein with low P. The reversion of these events attenuated Ang II-induced increases in cardiomyocyte size and numbers of terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick end labeling-positive cells, presumably via type 3 muscarinic acetylcholine receptor (M3AChR). Indeed, downregulation of M3AChR or Notch1 blocked choline-mediated upregulation of NICD and nuclear HSF1 expression, as well as inhibited mitochondrial apoptosis pathway and cardiomyocyte apoptosis, indicating that M3AChR and Notch1/HSF1 activation confer the protective effects of choline. In vivo studies were performed in parallel, in which rats were infused with Ang II for 4 weeks to induce cardiac apoptosis. The results showed that choline alleviated cardiac remodeling and apoptosis of Ang II-infused rats in a manner related to activation of the Notch1/HSF1 pathway, consistent with the in vitro findings. Taken together, our results reveal that choline impedes oxidative damage and cardiomyocyte apoptosis by activating M3AChR and Notch1/HSF1 antioxidant signaling, and suggest a novel role for the Notch1/HSF1 signaling pathway in the modulation of cardiomyocyte apoptosis.

Untangling the Cooperative Role of Nuclear Receptors in Cardiovascular Physiology and Disease

The heart is the first organ to acquire its physiological function during development, enabling it to supply the organism with oxygen and nutrients. Given this early commitment, cardiomyocytes were traditionally considered transcriptionally stable cells fully committed to contractile function. However, growing evidence suggests that the maintenance of cardiac function in health and disease depends on transcriptional and epigenetic regulation. Several studies have revealed that the complex transcriptional alterations underlying cardiovascular disease (CVD) manifestations such as myocardial infarction and hypertrophy is mediated by cardiac retinoid X receptors (RXR) and their partners. RXRs are members of the nuclear receptor (NR) superfamily of ligand-activated transcription factors and drive essential biological processes such as ion handling, mitochondrial biogenesis, and glucose and lipid metabolism. RXRs are thus attractive molecular targets for the development of effective pharmacological strategies for CVD treatment and prevention. In this review, we summarize current knowledge of RXR partnership biology in cardiac homeostasis and disease, providing an up-to-date view of the molecular mechanisms and cellular pathways that sustain cardiomyocyte physiology.

The multi-faceted role of retinoid X receptor in cardiovascular diseases

Retinoid X receptors (RXRs) are members of ligand-dependent transcription factors whose effects on a diversity of cellular processes, including cellular proliferation, the immune response, and lipid and glucose metabolism. Knock out of RXRα causes a hypoplasia of the myocardium which is lethal during fetal life. In addition, the heart maintains a well-orchestrated balances in utilizing fatty acids (FAs) and other substrates to meet the high energy requirements. As the master transcriptional regulators of lipid metabolism, RXRs become particularly important for the energy needs of the heart. Accumulating evidence suggested that RXRs may exert direct beneficial effects in the heart both through heterodimerization with other nuclear receptors (NRs) and homodimerization, thus standing as suitable targets for treating in cardiovascular diseases. Although compounds that target RXRs are promising drugs, their use is limited by toxicity. A better understanding of the structural biology of RXRs in cardiovascular disease should enable the rational design of more selective nuclear receptor modulators to overcome these problems. Here, this review summarizes a brief overview of RXRs structure and versatility of RXR action in the control of cardiovascular diseases. And we also discussed the therapeutic potential of RXR ligand.

Oxidative Stress, Kinase Activity and Inflammatory Implications in Right Ventricular Hypertrophy and Heart Failure under Hypobaric Hypoxia

High altitude (hypobaric hypoxia) triggers several mechanisms to compensate for the decrease in oxygen bioavailability. One of them is pulmonary artery vasoconstriction and its subsequent pulmonary arterial remodeling. These changes can lead to pulmonary hypertension and the development of right ventricular hypertrophy (RVH), right heart failure (RHF) and, ultimately to death. The aim of this review is to describe the most recent molecular pathways involved in the above conditions under this type of hypobaric hypoxia, including oxidative stress, inflammation, protein kinases activation and fibrosis, and the current therapeutic approaches for these conditions. This review also includes the current knowledge of long-term chronic intermittent hypobaric hypoxia. Furthermore, this review highlights the signaling pathways related to oxidative stress (Nox-derived O₂^.- and H₂O₂), protein kinase (ERK5, p38α and PKCα) activation, inflammatory molecules (IL-1β, IL-6, TNF-α and NF-kB) and hypoxia condition (HIF-1α). On the other hand, recent therapeutic approaches have focused on abolishing hypoxia-induced RVH and RHF via attenuation of oxidative stress and inflammatory (IL-1β, MCP-1, SDF-1 and CXCR-4) pathways through phytotherapy and pharmacological trials. Nevertheless, further studies are necessary.

Experimental models of cardiac physiology and pathology

Experimental models of cardiac disease play a key role in understanding the pathophysiology of the disease and developing new therapies. The features of the experimental models should reflect the clinical phenotype, which can have a wide spectrum of underlying mechanisms. We review characteristics of commonly used experimental models of cardiac physiology and pathophysiology in all translational steps including in vitro, small animal, and large animal models. Understanding their characteristics and relevance to clinical disease is the key for successful translation to effective therapies.

Rosuvastatin and retinoic acid may act as 'pleiotropic agents' against β-adrenergic agonist-induced acute myocardial injury through modulation of multiple signalling pathways

Cardiovascular disorders constitute the principal cause of deaths worldwide and will continue as the major disease-burden by the year 2060. A significant proportion of heart failures occur because of use and misuse of drugs and most of the investigational agents fail to achieve any clinical relevance. Here, we investigated rosuvastatin and retinoic acid for their "pharmacological pleiotropy" against high dose β-adrenergic agonist (isoproterenol)-induced acute myocardial insult. Rats were pretreated with rosuvastatin and/or retinoic acid for seven days and the myocardial injury was induced by administering isoproterenol on the seventh and eighth day. After induction, rats were anaesthetized for electrocardiography, then sacrificed and different samples were collected/stored for various downstream assays. Myocardial injury with isoproterenol resulted in increased cardiac mass, decreased R-wave amplitude, increased QRS and QT durations; elevated levels of cardiac markers like cTnI, CK-MB, ALT and AST; increased lipid peroxidation, protein carbonylation and tissue nitric oxide levels; decreased endogenous antioxidants like SOD, CAT, GR, GST, GPx and total antioxidant activity; increased inflammatory markers like TNF-α and IL-6; decreased the mRNA expression of Nrf2 and Bcl-2; increased the mRNA expression of Bax, eNOS and iNOS genes. Pretreatment with rosuvastatin and/or retinoic acid mitigated many of the above biochemical and pathological alterations. Our results demonstrate that rosuvastatin and retinoic acid exert cardioprotective effects and may act as potential agents in the prevention of β-adrenergic agonist-induced acute myocardial injury in rats. Cardioprotective potential of rosuvastatin and retinoic acid could be attributed to their influence on the redox pathways, immunomodulation, membrane stability, Nrf2 preservation, iNOS and Bax expression levels. Thus, they may act directly or indirectly at various steps, the breakpoints, in the pathophysiological cascade responsible for cardiac injury. Our study gives insights about the pharmacological pleiotropism of rosuvastatin and retinoic acid.

The Pleiotropic Role of Retinoic Acid/Retinoic Acid Receptors Signaling: From Vitamin A Metabolism to Gene Rearrangements in Acute Promyelocytic Leukemia

The family of retinoic acid receptors (RARs: RARα, -β, and -γ) has remarkable pleiotropy characteristics, since the retinoic acid/RARs pathway is involved in numerous biological processes not only during embryonic development, but also in the postnatal phase and during adulthood. In this review, we trace the roles of RA/RARs signaling in the immune system (where this pathway has both an immunosuppressive role or is involved in the inflammatory response), in hematopoiesis (enhancing hematopoietic stem cell self-renewal, progenitor cells differentiation or maintaining the bone marrow microenvironment homeostasis), and in bone remodeling (where this pathway seems to have controversial effects on bone formation or osteoclast activation). Moreover, in this review is shown the involvement of RAR genes in multiple chromosomal rearrangements generating different fusion genes in hematological neoplasms, with a particular focus on acute promyelocytic leukemia and its variant subtypes. The effect of different RARs fusion proteins on leukemic transformation, on patients’ outcome, and on therapy response is also discussed.

Apocynin Ameliorates Pressure Overload-Induced Cardiac Remodeling by Inhibiting Oxidative Stress and Apoptosis

Oxidative stress plays an important role in pressure overload-induced cardiac remodeling. The purpose of this study was to determine whether apocynin, a nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitor, attenuates pressure overload-induced cardiac remodeling in rats. After abdominal aorta constriction, the surviving rats were randomly divided into four groups: sham group, abdominal aorta constriction group, apocynin group, captopril group. Left ventricular pathological changes were studied using Masson’s trichrome staining. Metalloproteinase-2 (MMP-2) levels in the left ventricle were analyzed by western blot and gelatin zymography. Oxidative stress and apoptotic index were also examined in cardiomyocytes using dihydroethidium and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL), respectively. Our results showed that abdominal aorta constriction significantly caused excess collagen deposition and cardiac insult. Treatment with apocynin significantly inhibited deposition of collagen and reduced the level of MMP-2. Furthermore, apocynin also decreased the NADPH oxidase activity, reactive oxygen species production and cardiomyocyte apoptotic index. Interestingly, apocynin only inhibited NADPH oxidase activity without affecting its expression or the level of angiotension II in the left ventricle. In conclusion, apocynin reduced collagen deposition, oxidative stress, and inhibited apoptosis, ultimately ameliorating cardiac remodeling by mechanisms that are independent of the renin-angiotensin system.

All-trans-retinoic acid-mediated cytoprotection in LLC-PK1 renal epithelial cells is coupled to p-ERK activation in a ROS-independent manner

Although all-trans-retinoic acid (ATRA) provides protection against a variety of conditions in vivo, particularly ischemia, the molecular mechanisms underpinning these effects remain unclear. The present studies were designed to assess potential mechanisms by which ATRA affords cytoprotection against renal toxicants in LLC-PK₁ cells. Pretreatment of LLC-PK₁ cells with ATRA (25 μM) for 24 h afforded cytoprotection against oncotic cell death induced by p-aminophenol (PAP), 2-(glutathion-S-yl)hydroquinone (MGHQ), and iodoacetamide but not against apoptotic cell death induced by cisplatin. Inhibition of protein synthesis with cycloheximide blunted ATRA protection, indicating essential cell survival pathways must be engaged before toxicant exposure to provide cytoprotection. Interestingly, ATRA did not prevent the PAP-induced generation of reactive oxygen species (ROS) nor did it alter glutathione levels. Moreover, ATRA had no significant effect on Nrf2 protein expression, and the Nrf2 inducers sulforaphane and MG132 did not influence ATRA cytoprotection, suggesting cytoprotective pathways beyond those that influence ROS levels contribute to ATRA protection. In contrast, ATRA rapidly (15 min) induced levels of the cellular stress kinases p-ERK and p-AKT at concentrations of ATRA (10 and 25 μM) required for cytoprotection. Consistent with a role for p-ERK in ATRA-mediated cytoprotection, inhibition of p-ERK with PD98059 reduced the ability of ATRA to afford protection against PAP toxicity. Collectively, these data suggest that p-ERK and its downstream targets, independent of ROS and antioxidant signaling, are important contributors to the cytoprotective effects of ATRA against oncotic cell death.

2-Aminobutyric acid modulates glutathione homeostasis in the myocardium

A previous report showed that the consumption of glutathione through oxidative stress activates the glutathione synthetic pathway, which is accompanied by production of ophthalmic acid from 2-aminobutyric acid (2-AB). We conducted a comprehensive quantification of serum metabolites using gas chromatography-mass spectrometry in patients with atrial septal defect to find clues for understanding myocardial metabolic regulation, and demonstrated that circulating 2-AB levels reflect hemodynamic changes. However, the metabolism and pathophysiological role of 2-AB remains unclear. We revealed that 2-AB is generated by an amino group transfer reaction to 2-oxobutyric acid, a byproduct of cysteine biosynthesis from cystathionine. Because cysteine is a rate-limiting substrate for glutathione synthesis, we hypothesized that 2-AB reflects glutathione compensation against oxidative stress. A murine cardiomyopathy model induced by doxorubicin supported our hypothesis, i.e., increased reactive oxygen species are accompanied by 2-AB accumulation and compensatory maintenance of myocardial glutathione levels. Intriguingly, we also found that 2-AB increases intracellular glutathione levels by activating AMPK and exerts protective effects against oxidative stress. Finally, we demonstrated that oral administration of 2-AB efficiently raises both circulating and myocardial glutathione levels and protects against doxorubicin-induced cardiomyopathy in mice. This is the first study to demonstrate that 2-AB modulates glutathione homeostasis in the myocardium.

Loss of myocardial retinoic acid receptor α induces diastolic dysfunction by promoting intracellular oxidative stress and calcium mishandling in adult mice

Retinoic acid receptor (RAR) has been implicated in pathological stimuli-induced cardiac remodeling. To determine whether the impairment of RARα signaling directly contributes to the development of heart dysfunction and the involved mechanisms, tamoxifen-induced myocardial specific RARα deletion (RARαKO) mice were utilized. Echocardiographic and cardiac catheterization studies showed significant diastolic dysfunction after 16wks of gene deletion. However, no significant differences were observed in left ventricular ejection fraction (LVEF), between RARαKO and wild type (WT) control mice. DHE staining showed increased intracellular reactive oxygen species (ROS) generation in the hearts of RARαKO mice. Significantly increased NOX2 (NADPH oxidase 2) and NOX4 levels and decreased SOD1 and SOD2 levels were observed in RARαKO mouse hearts, which were rescued by overexpression of RARα in cardiomyocytes. Decreased SERCA2a expression and phosphorylation of phospholamban (PLB), along with decreased phosphorylation of Akt and Ca²⁺/calmodulin-dependent protein kinase II δ (CaMKII δ) was observed in RARαKO mouse hearts. Ca²⁺ reuptake and cardiomyocyte relaxation were delayed by RARα deletion. Overexpression of RARα or inhibition of ROS generation or NOX activation prevented RARα deletion-induced decrease in SERCA2a expression/activation and delayed Ca²⁺ reuptake. Moreover, the gene and protein expression of RARα was significantly decreased in aged or metabolic stressed mouse hearts. RARα deletion accelerated the development of diastolic dysfunction in streptozotocin (STZ)-induced type 1 diabetic mice or in high fat diet fed mice. In conclusion, myocardial RARα deletion promoted diastolic dysfunction, with a relative preserved LVEF. Increased oxidative stress have an important role in the decreased expression/activation of SERCA2a and Ca²⁺ mishandling in RARαKO mice, which are major contributing factors in the development of diastolic dysfunction. These data suggest that impairment of cardiac RARα signaling may be a novel mechanism that is directly linked to pathological stimuli-induced diastolic dysfunction.

Retinoic acid and sodium butyrate suppress the cardiac expression of hypertrophic markers and proinflammatory mediators in Npr1 gene-disrupted haplotype mice

The objective of the present study was to examine the genetically determined differences in the natriuretic peptide receptor-A (NPRA) gene (Npr1) copies affecting the expression of cardiac hypertrophic markers, proinflammatory mediators, and matrix metalloproteinases (MMPs) in a gene-dose-dependent manner. We determined whether stimulation of Npr1 by all-trans retinoic acid (RA) and histone deacetylase (HDAC) inhibitor sodium butyric acid (SB) suppress the expression of cardiac disease markers. In the present study, we utilized Npr1 gene-disrupted heterozygous (Npr1(+/-), 1-copy), wild-type (Npr1(+/+), 2-copy), gene-duplicated (Npr1(++/+), 3-copy) mice, which were treated intraperitoneally with RA, SB, and a combination of RA/SB, a hybrid drug (HB) for 2 wk. Untreated 1-copy mice showed significantly increased heart weight-body weight (HW/BW) ratio, blood pressure, hypertrophic markers, including beta-myosin heavy chain (β-MHC) and proto-oncogenes (c-fos and c-jun), proinflammatory mediator nuclear factor kappa B (NF-κB), and MMPs (MMP-2, MMP-9) compared with 2-copy and 3-copy mice. The heterozygous (haplotype) 1-copy mice treated with RA, SB, or HB, exhibited significant reduction in the expression of β-MHC, c-fos, c-jun, NF-κB, MMP-2, and MMP-9. In drug-treated animals, the activity and expression levels of HDAC were significantly reduced and histone acetyltransferase activity and expression levels were increased. The drug treatments significantly increased the fractional shortening and reduced the systolic and diastolic parameters of the Npr1(+/-) mice hearts. Together, the present results demonstrate that a decreased Npr1 copy number enhanced the expression of hypertrophic markers, proinflammatory mediators, and MMPs, whereas an increased Npr1 repressed the cardiac disease markers in a gene-dose-dependent manner.

Jia-Shen decoction-medicated serum inhibits angiotensin-II induced cardiac fibroblast proliferation via the TGF-β1/Smad signaling pathway

Jia-Shen decoction (JSD) is a traditional Chinese medicine, which is used widely to treat chronic heart failure. However, the underlying mechanism remains to be elucidated. The present study aimed to investigate the mechanism underlying the effects of JSD on cardiac fibroblast (CF) proliferation and differentiation. The CFs were obtained from the hearts of neonatal (1‑3‑day old) Sprague‑Dawley rats and treated with JSD-medicated serum (JSDS) with or without angiotensin II (Ang II). Cell proliferation was assessed using Cell Counting Kit‑8 reagent. In addition, the mRNA expression levels of transforming growth factor‑β1 (TGF‑β1) and phosphorylated small mothers against decapentaplegic (p‑Smad)2/3 and their protein expression levels were analyzed. CF proliferation was significantly increased in the Ang II‑treated group, compared with the control group (P<0.05). The expression levels of collagen, α‑smooth muscle actin, TGF‑β1 and p‑Smad2/3 were also increased in the Ang II‑treated group (P<0.05). Following JSDS treatment, the increased levels of collagen and cell proliferation were inhibited, and the increased expression levels of p‑Smad2 and p‑Smad3 were also inhibited (P<0.05). These data suggested that JSDS may inhibit CF proliferation via attenuating the TGF‑β1/Smad signaling pathway.

20-Hydroxyeicosatetraenoic Acid Is a Key Mediator of Angiotensin II-induced Apoptosis in Cardiac Myocytes

Cardiomyocyte apoptosis is involved in a variety of cardiac stresses, including ischemia-reperfusion injury, heart failure, and cardiomyopathy. Both Angiotensin II (Ang II) and 20-hydroxyeicosatetraenoic acid (20-HETE) induce apoptosis in cardiomyocytes. Here, we examined the relationship between 20-HETE and Ang II in cardiomyocyte apoptosis. Apoptosis was examined using flow cytometry in primary cultured rat cardiomyocytes treated with control, Ang II, and Ang II plus HET0016 (a 20-HETE formation inhibitor). The results demonstrated that the treatment of cardiomyocytes with Ang II or 20-HETE significantly increased the percentage of apoptotic cells and that Ang II-induced apoptosis was markedly attenuated by HET0016 or losartan (an AT1 receptor antagonist). In apoptotic mechanism experiments, Ang II or 20-HETE treatment significantly reduced mitochondrial membrane potential, indicating that a mitochondria-dependent mechanism is involved. Ang II-induced alteration in mitochondrial membrane potential was significantly attenuated by HET0016. Treatment of cardiomyocytes with Ang II also increased superoxide production, and this effect of Ang II was attenuated by HET0016. Treatment of cardiomyocytes with Ang II significantly increased CYP4A1 expression and 20-HETE production, as measured by Western blot, real-time RT-PCR, and mass spectrometric analysis. All results suggest that 20-HETE may play a key role in Ang II-induced apoptosis in cardiomyocytes by a mitochondrial superoxide-dependent pathway.

Propofol ameliorates hyperglycemia-induced cardiac hypertrophy and dysfunction via heme oxygenase-1/signal transducer and activator of transcription 3 signaling pathway in rats

OBJECTIVES

Heme oxygenase-1 is inducible in cardiomyocytes in response to stimuli such as oxidative stress and plays critical roles in combating cardiac hypertrophy and injury. Signal transducer and activator of transcription 3 plays a pivotal role in heme oxygenase-1-mediated protection against liver and lung injuries under oxidative stress. We hypothesized that propofol, an anesthetic with antioxidant capacity, may attenuate hyperglycemia-induced oxidative stress in cardiomyocytes via enhancing heme oxygenase-1 activation and ameliorate hyperglycemia-induced cardiac hypertrophy and apoptosis via heme oxygenase-1/signal transducer and activator of transcription 3 signaling and improve cardiac function in diabetes.

DESIGN

Treatment study.

SETTING

Research laboratory.

SUBJECTS

Sprague-Dawley rats.

INTERVENTIONS

In vivo and in vitro treatments.

MEASUREMENTS AND MAIN RESULTS

At 8 weeks of streptozotocin-induced type 1 diabetes in rats, myocardial 15-F2t-isoprostane was significantly increased, accompanied by cardiomyocyte hypertrophy and apoptosis and impaired left ventricular function that was coincident with reduced heme oxygenase-1 activity and signal transducer and activator of transcription 3 activation despite an increase in heme oxygenase-1 protein expression as compared to control. Propofol infusion (900 μg/kg/min) for 45 minutes significantly improved cardiac function with concomitantly enhanced heme oxygenase-1 activity and signal transducer and activator of transcription activation. Similar to the changes seen in diabetic rat hearts, high glucose (25 mmol/L) exposure for 48 hours led to cardiomyocyte hypertrophy and apoptosis, both in primary cultured neonatal rat cardiomyocytes and in H9c2 cells compared to normal glucose (5.5 mmol/L). Hypertrophy was accompanied by increased reactive oxygen species and malondialdehyde production and caspase-3 activity. Propofol, similar to the heme oxygenase-1 inducer cobalt protoporphyrin, significantly increased cardiomyocyte heme oxygenase-1 and p-signal transducer and activator of transcription protein expression and heme oxygenase-1 activity and attenuated high-glucose-mediated cardiomyocyte hypertrophy and apoptosis and reduced reactive oxygen species and malondialdehyde production (p < 0.05). These protective effects of propofol were abolished by heme oxygenase-1 inhibition with zinc protoporphyrin and by heme oxygenase-1 or signal transducer and activator of transcription 3 gene knockdown.

CONCLUSIONS

Heme oxygenase-1/signal transducer and activator of transcription 3 signaling plays a critical role in propofol-mediated amelioration of hyperglycemia-induced cardiomyocyte hypertrophy and apoptosis, whereby propofol improves cardiac function in diabetic rats.

Downregulation of Reactive Oxygen Species in Apoptosis

Generation of reactive oxygen species (ROS) by diverse anti-cancer drugs or phytochemicals has been closely related with the induction of apoptosis in cancers. Also, the downregulation of ROS by these chemicals has been found to block initiation of carcinogenesis. Therefore, modulation of ROS by phytochemicals emerges as a crucial mechanism to regulate apoptosis in cancer prevention or therapy. This review summarizes the current understanding of the selected chemical compounds and related cellular components that modulate ROS during apoptotic process. Metformin, quercetin, curcumin, vitamin C, and other compounds have been shown to downregulate ROS in the cellular apoptotic process, and some of them even induce apoptosis in cancer cells. The cellular components mediating the downregulation of ROS include nuclear factor erythroid 2-related factor 2 antioxidant signaling pathway, thioredoxin, catalase, glutathione, heme oxygenase-1, and uncoupling proteins. The present review provides information on the relationship between these compounds and the cellular components in modulating ROS in apoptotic cancer cells.

Non-classical Transcriptional Activity of Retinoic Acid

It has long been established that the transcriptional activity of retinoic acid (RA) is mediated by members of the nuclear receptor family of ligand-activated transcription factors termed RA receptors (RARs). More recent observations have established that RA also activates an additional nuclear receptor, PPARβ/δ. Partitioning RA between RARs and PPARβ/δ is governed by different intracellular lipid-binding proteins: cellular RA binding protein 2 (CRABP2) delivers RA to nuclear RARs and a fatty acid binding protein (FABP5) delivers the hormone from the cytosol to nuclear PPARβ/δ. Consequently, RA signals through RARs in CRABP2-expressing cells, but activates PPARβ/δ in cells that express a high level of FABP5. RA elicits different and sometimes opposing responses in cells that express different FABP5/CRABP2 ratios because PPARβ/δ and RARs regulate the expression of distinct sets of genes. An overview of the observations that led to the discovery of this non-classical activity of RA are presented here, along with a discussion of evidence demonstrating the involvement of the dual transcriptional activities of RA in regulating energy homeostasis, insulin responses, and adipocyte and neuron differentiation.

All-trans retinoic acid protects against doxorubicin-induced cardiotoxicity by activating the ERK2 signalling pathway

BACKGROUND AND PURPOSE

Doxorubicin is a powerful antineoplastic agent for treating a wide range of cancers. However, doxorubicin cardiotoxicity of the heart has largely limited its clinical use. All-trans retinoic acid (ATRA) plays an important role in many cardiac biological processes, but its protective effects on doxorubicin-induced cardiotoxicity remain unknown. Here, we studied the effect of ATRA on doxorubicin cardiotoxicity and the underlying mechanisms.

EXPERIMENTAL APPROACHES

Cellular viability assays, Western blotting and mitochondrial respiration analyses were employed to evaluate the cellular response to ATRA in H9c2 cells and primary cardiomyocytes. Quantitative PCR and gene knockdown were performed to investigate the underlying molecular mechanisms of ATRA's effects on doxorubicin cardiotoxicity.

KEY RESULTS

ATRA significantly inhibited doxorubicin-induced apoptosis in H9c2 cells and primary cardiomyocytes. ATRA was more effective against doxorubicin cardiotoxicity than resveratrol and dexrazoxane. ATRA also suppressed reactive oxygen species generation and restored expression levels of mRNA and proteins in the phase II detoxifying enzyme system: nuclear factor-E2-related factor 2, manganese superoxide dismutase, haem oxygenase-1, and mitochondrial function (mitochondrial membrane integrity, mitochondrial DNA copy numbers and mitochondrial respiration capacity, biogenesis and dynamics). Both a ERK1/2 inhibitor (U0126) and ERK2 siRNA, but not ERK1 siRNA, abolished the protective effect of ATRA against doxorubicin-induced toxicity in H9c2 cells. Remarkably, ATRA did not compromise the anticancer efficacy of doxorubicin in gastric carcinoma cells.

CONCLUSIONS AND IMPLICATIONS

ATRA protected cardiomyocytes against doxorubicin-induced toxicity, by activating the ERK2 pathway, without compromising its anticancer efficacy. Therefore, ATRA is a promising candidate as a cardioprotective agent against doxorubicin cardiotoxicity.

Protective effect of Danggui (Radix Angelicae Sinensis) on angiotensin II-induced apoptosis in H9c2 cardiomyoblast cells

BACKGROUND

Danggui (Radix Angelicae Sinensis) is an herb often used in Traditional Chinese medicine. It is used to promote blood flow and has been used in the treatment of myocardial ischemia-reperfusion injury in animal models. Angiotensin II (Ang II) has been shown to play important roles in mediating cardiovascular diseases, and may cause cardiac hypertrophy and apoptosis. This study aimed to investigate whether Danggui has protective effects on Ang II-induced apoptosis in H9c2 cardiomyoblast cells and study the mechanisms involved.

METHODS

We evaluated the effect of Danggui on Ang II-induced apoptosis in an in vitro model. H9c2 cardiomyoblast cells were cultured in serum-free medium for 4 hr, then treated with Danggui (50, 100 μg/ml) 1 hr pre- or post-Ang II treatment. After a further 23 hr of culture, cells were harvested for analyses with assays for apoptosis markers and cell signaling pathways.

RESULTS

Our results showed that Ang II induced upregulation of pro-apoptotic Bad, instability of the mitochondria membrane potential, cytochrome c release, caspase-9 and caspase-3 activation and cardiomyocyte apoptosis. Pre- or post-treatment with Danggui reversed all of the above Ang II-induced apoptotic effects in H9c2 cells. Furthermore, the JNK (SP600125) inhibitor completely blocked Danggui inhibition of caspase-3 activation in Ang II-treated H9c2 cells.

CONCLUSIONS

Our results showed that Danggui either pre-treatment or post-treatment highly attenuated the Ang II-induced apoptosis in cardiomyoblast cells. The findings demonstrated that the anti-apoptosis effect of Danggui is mediated by JNK and PI3k inhibitors.

Protective role of retinoid X receptor in H9c2 cardiomyocytes from hypoxia/reoxygenation injury in rats

BACKGROUND

Retinoid X receptor (RXR) plays a central role in the regulation of intracellular receptor signaling pathways. The activation of RXR has protective effect on H2O2-induced apoptosis of H9c2 ventricular cells in rats. But the protective effect and mechanism of activating RXR in cardiomyocytes against hypoxia/reoxygenation (H/R)-induced oxidative iniury are still unclear.

METHODS

The model of H/R injury was established through hypoxia for 2 hours and reoxygenation for 4 hours in H9c2 cardiomyocytes of rats. 9-cis-retinoic acid (9-cis RA) was obtained as an RXR agonist, and HX531 as an RXR antagonist. Cultured cardiomyocytes were randomly divided into four groups: sham group, H/R group, H/R+9-cis RA -pretreated group (100 nmol/L 9-cis RA), and H/R+9-cis RA+HX531-pretreated group (2.5 μmol/L HX531). The cell viability was measured by MTT, apoptosis rate of cardiomyocytes by flow cytometry analysis, and mitochondrial membrane potential (ΔΨm) by JC-1 fluorescent probe, and protein expressions of Bcl-2, Bax and cleaved caspase-9 with Western blotting. All measurement data were expressed as mean±standard deviation, and analyzed using one-way ANOVA and the Dunnett test. Differences were considered significant when P was <0.05.

RESULTS

Pretreatment with RXR agonist enhanced cell viability, reduced apoptosis ratio, and stabled ΔΨm. Dot blotting experiments showed that under H/R stress conditions, Bcl-2 protein level decreased, while Bax and cleaved caspase-9 were increased. 9-cis RA administration before H/R stress prevented these effects, but the protective effects of activating RXR on cardiomyocytes against H/R induced oxidative injury were abolished when pretreated with RXR pan-antagonist HX531.

CONCLUSION

The activation of RXR has protective effects against H/R injury in H9c2 cardiomyocytes of rats through attenuating signaling pathway of mitochondria apoptosis.

All-trans retinoic acid stimulates gene expression of the cardioprotective natriuretic peptide system and prevents fibrosis and apoptosis in cardiomyocytes of obese ob/ob mice

In hypertensive rodents, retinoic acid (RA) prevents adverse cardiac remodelling and improves myocardial infarction outcome, but its role in obesity-related changes of cardiac tissue are unclear. We hypothesized that all-trans RA (ATRA) treatment will improve the cardioprotective oxytocin-natriuretic peptides (OT-NP) system, preventing apoptosis and collagen accumulation in hearts of ob/ob mice, a mouse model of obesity and insulin resistance. Female 9-week-old B6.V-Lep/J ob/ob mice (n = 16) were divided into 2 groups: 1 group (n = 8) treated with 100 μg of ATRA dissolved in 100 μL of corn oil (vehicle) delivered daily (∼2 μg·g body weight(-1)·day(-1)) by stomach intubation for 16 days, and 1 group (n = 8) that received the vehicle alone. A group of nonobese littermate mice (n = 9) served as controls. Ob/ob mice exhibited obesity, hyperglycaemia, and downregulation of the cardiac OT-NP system, including the mRNA for the transcription factor GATA4, OT receptor and brain NP, and the protein expression for endothelial nitric oxide synthase. Hearts from ob/ob mice also demonstrated increased apoptosis and collagen accumulation. ATRA treatment induced weight loss and decreased adipocytes diameter in the visceral fat, thus reducing visceral obesity, which is associated with a high risk for cardiovascular disease. RA treatment was associated with a reduction in hyperglycemia and a normalization of the OT-NP system's expression in the hearts of ob/ob mice. Furthermore, ATRA treatment prevented apoptosis and collagen accumulation in hearts of ob/ob mice. The present study indicates that ATRA treatment was effective in restoring the cardioprotective OT-NP system and in preventing abnormal cardiac remodelling in the ob/ob mice.

Involvement of retinoic acid-induced peroxiredoxin 6 expression in recovery of noise-induced temporary hearing threshold shifts

All-trans retinoic acid (ATRA) is reported to reduce hair cell loss and hearing deterioration caused by noise-induced hearing loss (NIHL). The present study investigates the involvement of peroxiredoxin 6 (Prdx 6) in ATRA-mediated protection of temporary threshold shift of hearing. Mice fed with ATRA before or after exposure to white noise showed a faster recovery than untreated controls within 1 week, with a concomitant increase of cochlear Prdx 6 expression. Treatment of mouse auditory cells with ATRA induced Prdx 6 expression. A putative retinoic acid (RA)-response element (RARE) was identified in a murine Prdx 6 promoter region. Prdx 6 promoter activities were elevated in wild-type reporter plasmid-transfected cells, whereas no significant change in activity was in those with RARE-disrupted mutant reporter. RA receptor α (RARα) functions as a transactivator of Prdx 6 gene expression. These findings suggest that ATRA-induced Prdx 6 expression may be associated with rapid recovery from temporary NIHL.

Mitochondrial reactive oxygen species (ROS) as signaling molecules of intracellular pathways triggered by the cardiac renin-angiotensin II-aldosterone system (RAAS)

Mitochondria represent major sources of basal reactive oxygen species (ROS) production of the cardiomyocyte. The role of ROS as signaling molecules that mediate different intracellular pathways has gained increasing interest among physiologists in the last years. In our lab, we have been studying the participation of mitochondrial ROS in the intracellular pathways triggered by the renin-angiotensin II-aldosterone system (RAAS) in the myocardium during the past few years. We have demonstrated that acute activation of cardiac RAAS induces mitochondrial ATP-dependent potassium channel (mitoK_ATP) opening with the consequent enhanced production of mitochondrial ROS. These oxidant molecules, in turn, activate membrane transporters, as sodium/hydrogen exchanger (NHE-1) and sodium/bicarbonate cotransporter (NBC) via the stimulation of the ROS-sensitive MAPK cascade. The stimulation of such effectors leads to an increase in cardiac contractility. In addition, it is feasible to suggest that a sustained enhanced production of mitochondrial ROS induced by chronic cardiac RAAS, and hence, chronic NHE-1 and NBC stimulation, would also result in the development of cardiac hypertrophy.

Endoplasmic reticulum stress and C/EBP homologous protein-induced Bax translocation are involved in angiotensin II-induced apoptosis in cultured neonatal rat cardiomyocytes

The aim of this study was to identify the roles and potential mechanisms of endoplasmic reticulum stress (ER stress), proapoptotic transcription factor C/EBP homologous protein (CHOP) and Bax in angiotensin II (Ang II)-induced cardiomyocyte apoptosis. Cultured neonatal rat cardiomyocytes were incubated with Ang II or antisense CHOP oligonucleotide which was used to inhibit CHOP expression. Expressions of ER chaperone immunoglobulin heavy chain-binding protein (BiP), CHOP and cytochrome c were examined by Western blotting. Mitochondrial membrane potential (MMP) was detected by a spectrofluorimeter. Apoptosis was analyzed with flow cytometry. Bax translocation was determined by double-labeling of immunofluorescence and Western blotting. Our results showed that Ang II-induced cardiomyocyte apoptosis was associated with the upregulations of BiP and CHOP, Bax translocation, MMP deplorization and cytochrome c release. These above effects were suppressed by antisense CHOP oligonucleotide. Furthermore, BiP and CHOP expressions, reactive oxygen species (ROS) production and cardiomyocyte apoptosis, which were upregulated by Ang II, were depressed by the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitor apocynin. From our results, ROS, ER stress and CHOP-mediated Bax translocation may be involved in Ang II-induced cardiomyocyte apoptosis.

Mechanobiology in cardiac physiology and diseases

Mechanosensitivity is essential for heart function just as for all other cells and organs in the body, and it is involved in both normal physiology and diseases processes of the cardiovascular system. In this review, we have outlined the relationship between mechanosensitivity and heart physiology, including the Frank-Starling law of the heart and mechanoelectric feedback. We then focused on molecules involved in mechanotransduction, particularly mechanosensitive ion channels. We have also discussed the involvement of mechanosensitivity in heart diseases, such as arrhythmias, hypertrophy and ischaemic heart disease. Finally, mechanobiology in cardiogenesis is described with regard to regenerative medicine.

Retinoic acid protects cardiomyocytes from high glucose-induced apoptosis through inhibition of NF-κB signaling pathway

We have previously shown that retinoic acid (RA) has protective effects on high glucose (HG)-induced cardiomyocyte apoptosis. To further elucidate the molecular mechanisms of RA effects, we determined the interaction between nuclear factor (NF)-κB and RA signaling. HG induced a sustained phosphorylation of IKK/IκBα and transcriptional activation of NF-κB in cardiomyocytes. Activated NF-κB signaling has an important role in HG-induced cardiomyocyte apoptosis and gene expression of interleukin-6 (IL-6), tumor necrosis factor (TNF)-α, and monocyte chemoattractant protein-1 (MCP-1). All-trans RA (ATRA) and LGD1069, through activation of RAR/RXR-mediated signaling, inhibited the HG-mediated effects in cardiomyocytes. The inhibitory effect of RA on NF-κB activation was mediated through inhibition of IKK/IκBα phosphorylation. ATRA and LGD1069 treatment promoted protein phosphatase 2A (PP2A) activity, which was significantly suppressed by HG stimulation. The RA effects on IKK and IκBα were blocked by okadaic acid or silencing the expression of PP2Ac-subunit, indicating that the inhibitory effect of RA on NF-κB is regulated through activation of PP2A and subsequent dephosphorylation of IKK/IκBα. Moreover, ATRA and LGD1069 reversed the decreased PP2A activity and inhibited the activation of IKK/IκBα and gene expression of MCP-1, IL-6, and TNF-α in the hearts of Zucker diabetic fatty rats. In summary, our findings suggest that the suppressed activation of PP2A contributed to sustained activation of NF-κB in HG-stimulated cardiomyocytes; and that the protective effect of RA on hyperglycemia-induced cardiomyocyte apoptosis and inflammatory responses is partially regulated through activation of PP2A and suppression of NF-κB-mediated signaling and downstream targets.

Relaxant effect of all-trans-retinoic acid via NO-sGC-cGMP pathway and calcium-activated potassium channels in rat mesenteric artery

Intraperitoneal injection of all-trans-retinoic acid (ATRA) results in a reduction of blood pressure in spontaneously hypertensive rats. However, the mechanisms involved in this effect are not clear. We hypothesized that ATRA may relax resistance arteries. In this study, we found that ATRA relaxed phenylephrine-preconstricted mesenteric arterial rings, which were abrogated by the removal of the endothelium. Pretreatment of endothelium-intact arterial rings with an inhibitor of endothelial nitric oxide (NO) synthase, N(G)-nitro-l-arginine methyl ester (l-NAME), or soluble guanylyl cyclase, 1H-[1,2,4]-oxadiazole-[4,3-α]-quinoxaline-1-one, reduced the vasorelaxant effect of ATRA. Incubation of mesenteric arterial rings with ATRA increased the production of NO and cGMP, which were blocked by N(G)-nitro-l-arginine methyl ester. The vasorelaxant effect of ATRA was markedly attenuated in the presence of an inhibitor of big conductance calcium-activated potassium channels (charybdotoxin), but not with an inhibitor of voltage-dependent potassium channel (4-aminopyridine) or ATP-sensitive potassium channel (glibenclamide). Activation of retinoic acid receptors (RARs) with CH55 or retinoic X receptors (RXRs) with LGD1069 induced the vasorelaxation of phenylephrine-preconstricted mesenteric arterial rings. The RAR (BMS493) and RXR (UVI3003) antagonists blocked the ATRA-induced vasorelaxation. The vasorelaxant effect ATRA is physiologically relevant because the intravenous infusion of ATRA decreased blood pressure in normotensive rats. We conclude that ATRA relaxes resistance vessels via both RARs and RXRs receptors that are mediated by the endothelium-dependent NO-cGMP pathway, which may participate in the control of blood pressure.

Association of all-trans retinoic acid treatment with the renin-angiotensin aldosterone system expression in glomerulosclerosis rats

BACKGROUND AND OBJECTIVE

All-trans retinoic acid (ATRA), a promising therapeutic agent, has been confirmed in animal experiments as playing a protective role against renal diseases. The renin-angiotensin aldosterone system (RAAS) plays a key role in the pathogenesis of renal diseases, and RAAS inhibitors can prevent the progression of kidney diseases. In our previous study, we found that ATRA could play a protective role against glomerulosclerosis (GS) lesions in rats, and its effect was similar to RAAS inhibitors. However, whether ATRA treatment was associated with RAAS expression was not clear.

METHODS

Six-week-old male Wistar rats were divided into three groups: sham operation group (SHO), glomerulosclerosis model group without treatment (GS) and GS model group treated with ATRA (GA). At the end of 13 weeks, the relevant samples were collected and analyzed.

RESULTS

The mRNA and protein expression of angiotensin-converting enzyme 1 (ACE1) in the GS group was notably higher when compared with the SHO group. However, mRNA and protein expression of ACE1 in the ATRA treatment group was markedly down-regulated when compared with the GS group. Angiotensin-converting enzyme 2 (ACE2) expression (mRNA or protein) in the GS group was reduced compared with that in the SHO group, and ATRA markedly increased the mRNA and protein expression of ACE2 compared with the GS group. The levels of protein expression of angiotensin I and angiotensin II were significantly up-regulated in the GS group compared with those in the SHO group, and ATRA reduced their expression in the GA group when compared with the GS group.

CONCLUSION

ATRA is associated with RAAS expression in GS rats, but its detailed mechanism needs to be elucidated by further research.

Glutathione peroxidase 3, a new retinoid target gene, is crucial for human skeletal muscle precursor cell survival

Protection of satellite cells from cytotoxic damages is crucial to ensure efficient adult skeletal muscle regeneration and to improve therapeutic efficacy of cell transplantation in degenerative skeletal muscle diseases. It is therefore important to identify and characterize molecules and their target genes that control the viability of muscle stem cells. Recently, we demonstrated that high aldehyde dehydrogenase activity is associated with increased viability of human myoblasts. In addition to its detoxifying activity, aldehyde dehydrogenase can also catalyze the irreversible oxidation of vitamin A to retinoic acid; therefore, we examined whether retinoic acid is important for myoblast viability. We showed that when exposed to oxidative stress induced by hydrogen peroxide, adherent human myoblasts entered apoptosis and lost their capacity for adhesion. Pre-treatment with retinoic acid reduced the cytotoxic damage ex vivo and enhanced myoblast survival in transplantation assays. The effects of retinoic acid were maintained in dystrophic myoblasts derived from facioscapulohumeral patients. RT-qPCR analysis of antioxidant gene expression revealed glutathione peroxidase 3 (Gpx3), a gene encoding an antioxidant enzyme, as a potential retinoic acid target gene in human myoblasts. Knockdown of Gpx3 using short interfering RNA induced elevation in reactive oxygen species and cell death. The anti-cytotoxic effects of retinoic acid were impaired in GPx3-inactivated myoblasts, which indicates that GPx3 regulates the antioxidative effects of retinoic acid. Therefore, retinoid status and GPx3 levels may have important implications for the viability of human muscle stem cells.

High glucose-induced repression of RAR/RXR in cardiomyocytes is mediated through oxidative stress/JNK signaling

The biological actions of retinoids are mediated by nuclear retinoic acid receptors (RARs) and retinoid X receptors (RXRs). We have recently reported that decreased expression of RARα and RXRα has an important role in high glucose (HG)-induced cardiomyocyte apoptosis. However, the regulatory mechanisms of HG effects on RARα and RXRα remain unclear. Using neonatal cardiomyocytes, we found that ligand-induced promoter activity of RAR and RXR was significantly suppressed by HG. HG promoted protein destabilization and serine-phosphorylation of RARα and RXRα. Proteasome inhibitor MG132 blocked the inhibitory effect of HG on RARα and RXRα. Inhibition of intracellular reactive oxidative species (ROS) abolished the HG effect. In contrast, H(2)O(2) stimulation suppressed the expression and ligand-induced promoter activity of RARα and RXRα. HG promoted phosphorylation of ERK1/2, JNK and p38 MAP kinases, which was abrogated by an ROS inhibitor. Inhibition of JNK, but not ERK and p38 activity, reversed HG effects on RARα and RXRα. Activation of JNK by over expressing MKK7 and MEKK1, resulted in significant downregulation of RARα and RXRα. Ligand-induced promoter activity of RARα and RXRα was also suppressed by overexpression of MEKK1. HG-induced cardiomyocyte apoptosis was potentiated by activation of JNK, and prevented by all-trans retinoic acid and inhibition of JNK. Silencing the expression of RARα and RXRα activated the JNK pathway. In conclusion, HG-induced oxidative stress and activation of the JNK pathway negatively regulated expression/activation of RAR and RXR. The impaired RAR/RXR signaling and oxidative stress/JNK pathway forms a vicious circle, which significantly contributes to hyperglycemia induced cardiomyocyte apoptosis.

13-cis-Retinoic acid specific down-regulation of angiotensin type 1 receptor in rat liver epithelial and aortic smooth muscle cells

Transcriptional repression through cis- and trans-acting factors enabling an alternate approach to control angiotensin type 1 receptor (AT1 or AGTR1 as listed in the MGI database) expression has not been studied. In previous investigations, treatment with retinoic acid was found to be associated with enhanced insulin sensitivity. In our previous study, expression of AT1 was found to be inversely correlated with intracellular glucose concentrations. Therefore, we hypothesized that 13-cis-retinoic acid (13cRA), an antioxidant, enhances insulin-sensitive glucose-mediated down-regulation of the AT1. In this study, we used continuously passaged rat liver epithelial cells. Our study shows that cells exposed to 13cRA specifically down-regulated the AT1 protein in a dose- and time-dependent manner, independently of any change in receptor affinity. Down-regulation of the AT1 expression leads to reduced AngII-mediated intracellular calcium release, a hallmark of receptor-mediated intracellular signaling. Similarly with receptor down-regulation, we observed a significant reduction in AT1 mRNA; however, the AT1 down-regulation was independent of insulin-sensitive glucose uptake and retinoic acid receptor activation (RAR/RXR). Treatment with 13cRA resulted in phosphorylation of p42/p44 MAP kinases in these cells. Subsequent studies using MEK inhibitor PD98059 prevented 13cRA-mediated AT1 down-regulation and restored AngII-mediated intracellular calcium response. Furthermore, 13cRA-mediated inhibitory effects on AT1 were validated in primary rat aortic smooth muscle cells. In summary, our results demonstrate for the first time that 13cRA has a glucose- and RAR/RXR-independent mechanism for transcriptional inhibition of AT1, suggesting its therapeutic potential in systems in which AT1 expression is deregulated in insulin-sensitive and -insensitive tissues.

Cardiomyocyte-expressed farnesoid-X-receptor is a novel apoptosis mediator and contributes to myocardial ischaemia/reperfusion injury

AIMS

Emerging evidence indicates that nuclear receptors play a critical regulatory role in cardiovascular physiology/pathology. Recently, farnesoid-X-receptor (FXR), a member of the metabolic nuclear receptor superfamily, has been demonstrated to be expressed in vascular cells, with important roles in vascular physiology/pathology. However, the potential cardiac function of FXR remains unclear. We investigated the cardiac expression and biological function of FXR.

METHODS AND RESULTS

Farnesoid-X-receptor was detected in both isolated neonatal rat cardiac myocytes and fibroblasts. Natural and synthetic FXR agonists upregulated cardiac FXR expression, stimulated myocyte apoptosis, and reduced myocyte viability dose- and time-dependently. Mechanistic studies demonstrated that FXR agonists disrupted mitochondria, characterized by mitochondrial permeability transition pores activation, mitochondrial potential dissipation, cytochrome c release, and both caspase-9 and -3 activation. Such mitochondrial apoptotic responses were abolished by siRNA-mediated silencing of endogenous FXR or pharmacological inhibition of mitochondrial death signalling. Furthermore, low levels of FXR were detected in the adult mouse heart, with significant (∼2.0-fold) upregulation after myocardial ischaemia/reperfusion (MI/R). Pharmacological inhibition or genetic ablation of FXR significantly reduced myocardial apoptosis by 29.0-53.4%, decreased infarct size by 23.4-49.7%, and improved cardiac function in ischaemic/reperfused myocardium.

CONCLUSION

These results demonstrate that nuclear receptor FXR acts as a novel functional receptor in cardiac tissue, regulates apoptosis in cardiomyocytes, and contributes to MI/R injury.

Acute effects of all-trans-retinoic acid in ischemic injury

All-trans-retinoic acid (ATRA) is a vitamin A derivative that is important in neuronal patterning, survival, and neurite outgrowth. Neuroprotective effects of ATRA in ischemia have been demonstrated but its effects on glial swelling are not known. We investigated the relatively acute effects of ATRA on cell swelling in ischemic injury and on key features hypothesized to contribute to cell swelling including increased reactive oxygen species/reactive nitrogen species (ROS/RNS), depolarization of the inner mitochondrial membrane potential (ΔΨm), and increased intracellular calcium ([Ca2+]i). C6 glial cultures were subjected to 5 hr oxygen-glucose deprivation (OGD). ATRA was added to separate groups after the end of OGD. OGD increased cell volume by 43%, determined at 90 min after the end of OGD, but this increase was significantly attenuated by ATRA. OGD induced an increase in ROS/RNS production in the whole cell and mitochondria, as assessed by the fluorescent dyes CM-H2DCFDA and MitoTracker CM-H2-XROS at the end of OGD. The increase in mitochondrial ROS, but not cellular ROS, was significantly attenuated by ATRA. OGD also induced a 67% decline in mitochondrial ΔΨm but this decline was significantly attenuated by ATRA. OGD-induced increase in [Ca2+]i was also significantly attenuated by ATRA. Taken together with our previous results where calcium channel blockers reduced cell swelling, the effects of ATRA in attenuating swelling are possibly mediated through its effects in regulating [Ca2+]i. Considering the paucity of agents in attenuating brain edema in ischemia, ATRA has the potential to reduce brain edema and associated neural damage in ischemic injury.

MicroRNA-20a inhibits stress-induced cardiomyocyte apoptosis involving its novel target Egln3/PHD3

Excessive stress, e.g. due to biomechanical overload or ischemia/reperfusion is a potent inductor of cardiomyocyte apoptosis, which contributes to maladaptive remodeling. Despite substantial progress in the understanding of the molecular pathophysiology, many components of the signaling pathways underlying remodeling in general and apoptosis in particular still remain unknown. Recent evidence suggests that microRNAs (miRs) play an important role in the heart's response to increased cardiac stress. To identify novel modulators of stress-dependent remodeling, we conducted a genome-wide miR-screen of mechanically stretched neonatal rat cardiomyocytes (NRCM). Out of 351 miRs, eight were significantly regulated by biomechanical stress, including microRNA-20a, which is part of the miR17-92 cluster. Interestingly, further expression analyses also revealed upregulation of microRNA-20a in an in vitro hypoxia/"reperfusion" model. Given the potential apoptosis-modulating properties of the miR17-92 cluster, we subjected NRCM to hypoxia and subsequent reoxygenation. AdmiR-20a significantly inhibited hypoxia-mediated apoptosis in a dose-dependent fashion, while targeted knockdown of miR-20a in NRCM induced cardiomyocyte apoptosis. Mechanistically, the antiapoptotic effect of miR-20a appears to be mediated through direct targeting and subsequent downregulation of the proapoptotic factor Egln3. Thus, miR-20a is upregulated in acute biomechanical stress as well as hypoxia and inhibits apoptosis in cardiomyocytes. These properties reveal miR-20a as a cardioprotective micro-RNA and a potential target for novel therapeutic strategies to prevent cardiac remodeling.

Corneal endothelial autocrine trophic factor VIP in a mechanism-based strategy to enhance human donor cornea preservation for transplantation

Vasoactive intestinal peptide (VIP) and ciliary neurotrophic factor (CNTF) are identified as autocrines of human corneal endothelial (CE) cells working in concert to maintain the differentiated state and promote the survival of the corneal endothelium. From VIP gene knockdown study, endogenous VIP is shown to maintain the level of the differentiation marker, the adhesion molecule N-cadherin, CE cell size, shape, and retention, in situ in the human donor corneoscleral explants. Exogenous VIP protects the corneal endothelium against the killing effect of oxidative stress, in part by upholding ATP levels in CE cells dying of oxidative stress-induced injury, allowing them to die of an apoptotic death instead of an acute necrotic one. The switch from the acute necrosis to the programmed cell death (apoptosis) may have allowed the injured CE cell to be rescued by the VIP-upregulated pathways, including those of Bcl-2 and N-cadherin, and resulted in long-term CE cell survival. The endogenous VIP in CE cells is upregulated by CNTF, which is released by CE cells surviving the oxidative stress. The CNTF receptor (CNTFRα) is expressed in CE cells in human donor corneoscleral explant and gradually becomes lost during corneal storage. VIP treatment (10(-8) M, 37 °C, 30 min) prior to storage of freshly dissected human donor corneoscleral explants increases their CE cell CNTFRα level and responsiveness to CNTF in upregulating the gap junctional protein connexin-43 expression. VIP treatment of both fresh and preserved corneoscleral explants reduces CE damage in the corneoscleral explants and in the corneal buttons trephined from them. CE cell loss is a critical risk factor in corneal graft failure at any time in the life of the graft, which can be as late as 5-10 years after an initially successful transplant. A new procedure, Descemet's stripping automated endothelial keratoplasty (DSAEK), which is superior to the traditional full thickness transplantation in many aspects, nevertheless subjects the corneal endothelium to extensive mechanical forces, resulting in even more pronounced CE cell loss than the traditional technique. Whereas it is known that cells transduce mechanical stress through N-cadherin, stimulation of the N-cadherin pathway increases the anti-apoptotic protein Bcl-2 expression. Since N-cadherin and Bcl-2 in the corneal endothelium are both upregulated by VIP, we aim to strengthen the CE sheet by VIP treatments of the corneoscleral explants for full thickness traditional corneal transplantation and pre-cut corneas for DSAEK.