Hydrogen Sulfide Promotes Cardiomyocyte Proliferation and Heart Regeneration via ROS Scavenging

Hydrogen sulfide and ferroptosis inhibition underlies the dietary restriction-induced protection against cyclophosphamide cystitis

Dietary restriction (DR) has emerged as a potential therapeutic intervention for various pathological conditions. This study investigated the effects of DR on cyclophosphamide-induced cystitis in mice. Animals were subjected to controlled food restriction for 1 week prior to cyclophosphamide administration. We evaluated changes in body weight, bladder pathology, redox status, and ferroptotic parameters. DR significantly attenuated cyclophosphamide-induced cystitis severity, as evidenced by reduced bladder weight, decreased lipid peroxidation, and diminished ferroptotic markers in bladder tissue. Mechanistic investigations revealed that DR upregulated hepatic hydrogen sulfide (H2S)-synthesizing enzymes and enhanced H2S production. Inhibition of H2S-synthesizing enzymes with DL-propargylglycine (PAG) and aminooxyacetic acid (AOAA) exacerbated cyclophosphamide-induced cystitis, whereas administration of diallyl trisulfide (DATS), an H2S donor, markedly ameliorated bladder pathology. In vitro studies demonstrated that H2S donors, NaHS and DATS, protected against cyclophosphamide metabolite acrolein (ACR)-induced urothelial cell death by suppressing oxidative stress, as indicated by reduced p38 MAPK activation and protein carbonylation. These findings suggest that DR confers protection against cyclophosphamide-induced cystitis through the induction of endogenous H2S production and inhibition of ferroptosis. Our study provides additional evidence supporting the health-promoting effects of DR as well as novel mechanistic insights into the beneficial effects of DR. Given H2S has anti-inflammatory and anti-oxidative properties and that oxidative stress and ferroptosis underlie various diseases, our finding could have broader implications.

Cell cycle arrest of cardiomyocytes in the context of cardiac regeneration

The limited capacity of adult mammalian cardiomyocytes to undergo cell division and proliferation is one of the key factors contributing to heart failure. In newborn mice, cardiac proliferation occurs during a brief window, but this proliferative capacity diminishes by 7 days after birth. Current studies on cardiac regeneration focused on elucidating changes in regulatory factors within the heart before and after this proliferative window, aiming to determine whether potential association between these factors and cell cycle arrest in cardiomyocytes. Facilitating the re-entry of cardiomyocytes into the cell cycle or reversing their exit from it represents a critical strategy for cardiac regeneration. This paper provides an overview of the role of cell cycle arrest in cardiac regeneration, briefly describes cardiomyocyte proliferation and cardiac regeneration, and systematically summarizes the regulation of the cell cycle arrest in cardiomyocytes, and the potential metabolic mechanisms underlying cardiomyocyte cycle arrest. Additionally, we highlight the development of cardiovascular disease drugs targeting cardiomyocyte cell cycle regulation and their status in clinical treatment. Our goal is to outline strategies for promoting cardiac regeneration and repair following cardiac injury, while also pointing toward future research directions that may offer new technologies and prospects for treating cardiovascular diseases, such as myocardial infarction, arrhythmia and heart failure.

The Dual Role of Exogenous Hydrogen Sulfide (H2S) in Intestinal Barrier Mitochondrial Function: Insights into Cytoprotection and Cytotoxicity Under Non-Stressed Conditions

Hydrogen sulfide (H2S) is a critical gasotransmitter that plays a dual role in physiological and pathological processes, particularly in the gastrointestinal tract. While physiological levels of H2S exert cytoprotective effects, excessive concentrations can lead to toxicity, oxidative stress, and inflammation. The aim of this study was to investigate the dose-dependent effects of exogenous H2S on mitochondrial functions and biogenesis in intestinal epithelial cells under non-stressed conditions. Using a Caco-2 monolayer model, we evaluated the impact of sodium hydrosulfide (NaHS) at concentrations ranging from 1 × 10-7 M to 5 × 10-3 M on mitochondrial metabolism, redox balance, antioxidant defense, inflammatory responses, autophagy/mitophagy, and apoptosis. Our results demonstrated a biphasic response: low-to-moderate H2S concentrations (1 × 10-7 M-1.5 × 10-3 M) enhance mitochondrial biogenesis through PGC-1α activation, upregulating TFAM and COX-4 expression, and increasing the mtDNA copy number. In contrast, higher concentrations (2 × 10-3-5 × 10-3 M) impair mitochondrial function, induce oxidative stress, and promote apoptosis. These effects are associated with elevated reactive oxygen species (ROS) production, dysregulation of antioxidant enzymes, and COX-2-mediated inflammation. H2S-induced autophagy/mitophagy is a protective mechanism at intermediate concentrations but fails to mitigate mitochondrial damage at toxic levels. This study underscores the delicate balance between the cytoprotective and cytotoxic effects of exogenous H2S in intestinal cells, helping to develop new therapeutic approaches for gastrointestinal disorders.

Sustained-Release H2S Nanospheres Regulate the Inflammatory Microenvironment of Wounds, Promote Angiogenesis and Collagen Deposition, and Accelerate Diabetic Wound Healing

Diabetic wounds are blocked in the inflammatory stage, growth factors are degraded, and blood vessels are difficult to regenerate, leading to continuous necrosis and nonhealing of the wound. Hydrogen sulfide (H2S) plays an important role in the pathophysiological process of wound healing and has a long history of treating skin diseases. Although the sulfide salt solution is the preferred donor of exogenous H2S, its rapid release rate, excess production, and difficulty in accurately controlling the dose limit its use. Herein, we developed H2S sustained-release nanospheres NaHS@MS@LP for the treatment of diabetic wounds. NaHS@MS@LP nanosphere was composed of a NaHS-loaded mesoporous silicon core and a DSPE-PEG liposome outer membrane. When NaHS@MS@LP nanospheres were used to treat the wound of diabetic rats, mesoporous silicon was delivered into the cells and the loaded NaHS slowly released H2S through hydrolysis, participating in all stages of wound healing. In conclusion, NaHS@MS@LP nanospheres regulated the inflammatory microenvironment of wound skin by inducing the transformation of macrophages into M2 type and promoted angiogenesis and collagen deposition to accelerate wound healing in diabetic rats. Our findings provide strategies for the treatment of chronic wounds, including but not limited to diabetic wounds.

Molecular regulation of cardiomyocyte functions by exogenous hydrogen sulphide in Atlantic salmon (Salmo salar)

Hydrogen sulphide (H2S) is known to regulate various physiological processes, but its role in fish cardiac function, especially at the molecular level, is poorly understood. This study examined the molecular functions of exogenous H2S, using sodium hydrosulphide (NaHS) as a donor, on Atlantic salmon cardiomyocytes. NaHS concentrations of 10 to 160 μM showed limited cytotoxicity and no impact on cell proliferation, though higher doses increased ATP activity. Menadione and NaHS administered separately or sequentially differentially regulated the expression of antioxidant response and sulphide detoxification genes. Transcriptomic analysis over 24, 48, 72, and 120 h revealed differential gene expression related to metabolic recovery. Enriched Gene Ontology terms at 24 h included processes like cell signalling and lipid metabolism, shifting to lipid metabolism and ribosomal processes by 48 h. By 120 h, xenobiotic metabolism and RNA synthesis were prominent. The study highlights NaHS-induced metabolic adjustments, particularly in lipid metabolism, in Atlantic salmon cardiomyocytes.

Regenerative therapies for myocardial infarction: exploring the critical role of energy metabolism in achieving cardiac repair

Cardiovascular diseases are the most lethal diseases worldwide, of which myocardial infarction is the leading cause of death. After myocardial infarction, in order to ensure normal blood supply to the heart, the remaining cardiomyocytes compensate for the loss of cardiomyocytes mainly by working at high capacity rather than by proliferating to produce new cardiomyocytes. This is partly due to the extremely limited ability of the adult heart to repair itself. A growing body of research suggests that the loss of cardiac regenerative capacity is closely related to metabolic shifts in energy sources. Currently, a large number of studies have focused on changes in metabolic levels before and after the proliferation window of cardiomyocytes, so it is crucial to search for relevant factors in metabolic pathways to regulate the cell cycle in cardiomyocyte progression. This paper presents a review of the role of myocardial energy metabolism in regenerative repair after cardiac injury. It aims to elucidate the effects of myocardial metabolic shifts on cardiomyocyte proliferation in adult mammals and to point out directions for cardiac regeneration research and clinical treatment of myocardial infarction.

Tert promotes cardiac regenerative repair after MI through alleviating ROS-induced DNA damage response in cardiomyocyte

Telomerase reverse transcriptase (Tert) has been found to have a protective effect on telomeric DNA, but whether it could improve the repair of reactive oxygen species (ROS)-induced DNA damage and promote myocardial regenerative repair after myocardial infarction (MI) by protecting telomeric DNA is unclear. The immunofluorescence staining with TEL-CY3 and the TeloTAGGG Telomerase PCR ELISA kit were used to show the telomere length and telomerase activity. The heart-specific Tert-deletion homozygotes were generated by using commercial Cre tool mice and flox heterozygous mice for mating. We measured the telomere length and telomerase activity of mouse cardiomyocytes (CMs) at different days of age, and the results showed that they were negatively correlated with age. Overexpressed Tert could enhance telomerase activity and lengthen telomeres, thereby repairing the DNA damage induced by ROS and promoting CM proliferation in vitro. The in vivo results indicated that enhanced Tert could significantly improve cardiac function and prognosis by alleviating CM DNA damage and promoting angiogenesis post-MI. In terms of mechanism, DNA pulldown assay was used to identify that nuclear ribonucleoprotein A2B1 (hnRNPA2B1) could be an upstream regulator of Tert in CMs. Overexpressed Tert could activate the NF-κB signaling pathway in CMs and bind to the VEGF promoter in the endothelium to increase the VEGF level. Further immunoblotting showed that Tert protected DNA from ROS-induced damage by inhibiting ATM phosphorylation and blocking the Chk1/p53/p21 pathway activation. HnRNPA2B1-activated Tert could repair the ROS-induced telomeric DNA damage to induce the cell cycle re-entry in CMs and enhance the interaction between CMs and endothelium, thus achieving cardiac regenerative repair after MI.

PEX3 promotes regenerative repair after myocardial injury in mice through facilitating plasma membrane localization of ITGB3

The peroxisome is a versatile organelle that performs diverse metabolic functions. PEX3, a critical regulator of the peroxisome, participates in various biological processes associated with the peroxisome. Whether PEX3 is involved in peroxisome-related redox homeostasis and myocardial regenerative repair remains elusive. We investigate that cardiomyocyte-specific PEX3 knockout (Pex3-KO) results in an imbalance of redox homeostasis and disrupts the endogenous proliferation/development at different times and spatial locations. Using Pex3-KO mice and myocardium-targeted intervention approaches, the effects of PEX3 on myocardial regenerative repair during both physiological and pathological stages are explored. Mechanistically, lipid metabolomics reveals that PEX3 promotes myocardial regenerative repair by affecting plasmalogen metabolism. Further, we find that PEX3-regulated plasmalogen activates the AKT/GSK3β signaling pathway via the plasma membrane localization of ITGB3. Our study indicates that PEX3 may represent a novel therapeutic target for myocardial regenerative repair following injury.

A fluorescent probe for detecting H2O2 and delivering H2S in lysosomes and its application in maintaining the redox environments

Hydrogen peroxide (H2O2) is a reactive oxygen species (ROS) that can be used as a marker for the occurrence of oxidative stress in the organism. Lysosomes serve as intracellular digestive sites, and when the concentration of H2O2 in them is abnormal, lysosomal function is often impaired, leading to the development of diseases. Hydrogen sulfide (H2S) acts as a gaseous signaling molecule that scavenges H2O2 from cells and tissues, thereby maintaining the redox environment of the body. However, most of the reported hydrogen peroxide fluorescent probes so far can only detect H2O2, but cannot maintain the intracellular redox environment. In this paper, an H2O2 fluorescent probe LN-HOD with lysosomal targeting properties was designed and synthesized by combining the H2O2 recognition site with a naphthylamine fluorophore via a thiocarbamate moiety. The probe has the advantages of large Stokes shift (110 nm), high sensitivity and good H2S release capability. The probe LN-HOD can be used to detect H2O2 in cells, zebrafish and plant roots. In addition, LN-HOD detects changes in the concentration of H2O2 in plant roots when Arabidopsis is stressed by cadmium ion (Cd2+). And through its ability to release H2S, it can help to remove excess H2O2 and maintain the redox environment in cells, zebrafish and plant roots. The present work provides new ideas for the detection and assisted removal of H2O2, which contributes to the in-depth study of the cellular microenvironment in organisms.

Hydrogen Sulfide Promotes Postnatal Cardiomyocyte Proliferation by Upregulating SIRT1 Signaling Pathway

Hydrogen sulfide (H2S) has been identified as a novel gasotransmitter and a substantial antioxidant that can activate various cellular targets to regulate physiological and pathological processes in mammals. However, under physiological conditions, it remains unclear whether it is involved in regulating cardiomyocyte (CM) proliferation during postnatal development in mice. This study mainly aimed to evaluate the role of H2S in postnatal CM proliferation and its regulating molecular mechanisms. We found that sodium hydrosulfide (NaHS, the most widely used H2S donor, 50-200 μM) increased neonatal mouse primary CM proliferation in a dose-dependent manner in vitro. Consistently, exogenous administration of H2S also promoted CM proliferation and increased the total number of CMs at postnatal 7 and 14 days in vivo. Moreover, we observed that the protein expression of SIRT1 was significantly upregulated after NaHS treatment. Inhibition of SIRT1 with EX-527 or si-SIRT1 decreased CM proliferation, while enhancement of the activation of SIRT1 with SRT1720 promoted CM proliferation. Meanwhile, pharmacological and genetic blocking of SIRT1 repressed the effect of NaHS on CM proliferation. Taken together, these results reveal that H2S plays a promotional role in proliferation of CMs in vivo and in vitro and SIRT1 is required for H2S-mediated CM proliferation, which indicates that H2S may be a potential modulator for heart development in postnatal time window.

Recent advances in pyroptosis, liver disease, and traditional Chinese medicine: A review

In recent years, the incidence of liver disease has increased, becoming a major cause of death. Various liver diseases are intricately linked to pyroptosis, which is one of the most common forms of programmed cell death. As a powerful weapon in the fight against liver diseases, traditional Chinese medicine (TCM) can affect pyroptosis via a number of routes, including the classical, nucleotide oligomerization domain-like receptors protein 3/caspase-1/gasdermin D (GSDMD) pathway, the nonclassical lipopolysaccharide/caspase-11/GSDMD pathway, the ROS/caspase-3/gasdermin E pathway, the caspase-9/caspase-3/GSDMD pathway, and the Apaf-1/caspase-11/caspase-3 pathway. In this review, we provide an overview of pyroptosis, the interplay between pyroptosis and liver diseases, and the mechanisms through which TCM regulates pyroptosis in liver diseases. The information used in the text was collected and compiled from the databases of PubMed, Web of Science, Scopus, CNKI, and Wanfang Data up to June 2023. The search was not limited with regard to the language and country of the articles. Research and review articles were included, and papers with duplicate results or unrelated content were excluded. We examined the current understanding of the relationship between pyroptosis and liver diseases as well as the advances in TCM interventions to provide a resource for the identification of potential targets for TCM in the treatment of liver diseases.

P16INK4a Regulates ROS-Related Autophagy and CDK4/6-Mediated Proliferation: A New Target of Myocardial Regeneration Therapy

Neonatal mice achieve complete cardiac repair through endogenous myocardial regeneration after apical resection (AR), but this capacity is rapidly lost 7 days after birth. As an upstream inhibitor of cyclin-dependent kinase 4/6- (CDK4/6-) mediated cell cycle activity, p16^INK4a is widely involved in regulating tumor and senescence. Given that p16^INK4a had a significant negative regulation on cell proliferation, targeting cardiomyocytes (CMs) to inhibit p16^INK4a seems to be a promising attempt at myocardial regeneration therapy. The p16^INK4a expression was upregulated during perimyocardial regeneration time. Knockdown of p16^INK4a stimulated CM proliferation, while p16^INK4a overexpression had the opposite effect. In addition, p16^INK4a knockdown prolonged the proliferation time window of newborn myocardium. And p16^INK4a overexpression inhibited cell cycle activity and deteriorated myocardial regeneration after AR. The quantitative proteomic analysis showed that p16^INK4a knockdown mediated the cell cycle progression and intervened in energy metabolism homeostasis. Mechanistically, overexpression of p16^INK4a causes abnormal accumulation of reactive oxygen species (ROS) to induce autophagy, while scavenging ROS with N-acetylcysteine can alleviate autophagy and regulate p16^INK4a, CDK4/6, and CyclinD1 in a covering manner. And the effect of inhibiting the proliferation of p16^INK4a-activated CMs was significantly blocked by the CDK4/6 inhibitor Palbociclib. In summary, p16^INK4a regulated CM proliferation progression through CDK4/6 and ROS-related autophagy to jointly affect myocardial regeneration repair. Our study revealed that p16^INK4a might be a potential therapeutic target for myocardial regeneration after injury.

Construction of a Band-Aid Like Cardiac Patch for Myocardial Infarction with Controllable H2 S Release

Excessive or persistent inflammation incites cardiomyocytes necrosis by generating reactive oxygen species in myocardial infarction (MI). Hydrogen sulfide (H2 S), a gaseous signal molecule, can quickly permeate cells and tissues, growing concerned for its cardioprotective effects. However, short resident time and strong side effects greatly restrict its application. Herein, a complex scaffold (AAB) is first developed to slowly release H2 S for myocardial protection by integrating alginate modified with 2-aminopyridine-5-thiocarboxamide (H2 S donor) into albumin electrospun fibers. Next, a band-aid like patch is constructed based on AAB (center) and nanocomposite scaffold which comprises albumin scaffold and black phosphorus nanosheets (BPNSs). With near-infrared laser (808 nm), thermal energy generated by BPNSs can locally change the molecular structure of fibrous scaffold, thereby attaching patch to the myocardium. In this study, it is also demonstrated that AAB can enhance regenerative M2 macrophage and attenuate inflammatory polarization of macrophages via reduction in intracellular ROS. Eventually, this engineered cardiac patch can relieve inflammation and promote angiogenesis after MI, and thereby recover heart function, providing a promising therapeutic strategy for MI treatment.

Polystyrene microplastics-induced cardiotoxicity in chickens via the ROS-driven NF-κB-NLRP3-GSDMD and AMPK-PGC-1α axes

Microplastics (MPs) pollution is getting increasingly prominent, and its dangers have attracted widespread attention. The heart is the central hub of the organism's survival, and the mechanism of MPs-induced heart injury in chickens is unknown. Here, we investigated the effects of 5 μm polystyrene microplastics (PS-MPs) on the heart and primary cardiomyocytes of chickens at varied concentrations. We observed that PS-MPs caused severe pathological damage and ultrastructural changes in heart, induced myocardial pyroptosis, inflammatory cell infiltration and mitochondrial lesions. PS-MPs evoked abnormal antioxidant enzyme content and ROS overproduction. Detailed mechanistic investigation indicated that PS-MPs triggered pyroptosis via NF-κB-NLRP3-GSDMD axis and exacerbated myocardial inflammation (NLRP3, Caspase-1, IL-1β, IL-18, ASC, GSDMD, NF-κB, COX-2, iNOS and IL-6 overexpression). Additionally, PS-MPs induced mitochondrial damage (TFAM, OPA1, MFN1 and MFN2 down-expression, DRP1 and Fis1 overexpression) and energy metabolism disorders (HK2, PKM2, PDHX and LDH up-regulation) by inhibiting AMPK-PGC-1α pathway. Interestingly, NAC alleviated these aberrant manifestations in vitro. We suggested that PS-MPs driven alterations in NF-κB-NLRP3-GSDMD and AMPK-PGC-1α pathways via ROS overload, which in turn triggered oxidative stress, myocardial pyroptosis, inflammation, mitochondrial and energy metabolism dysfunction. This provided theoretical bases for protecting chickens from toxic injury by MPs.

LPA2 Contributes to Vascular Endothelium Homeostasis and Cardiac Remodeling After Myocardial Infarction

RATIONALE

Myocardial infarction (MI) is one of the most dangerous adverse cardiovascular events. Our previous study found that lysophosphatidic acid (LPA) is increased in human peripheral blood after MI, and LPA has a protective effect on the survival and proliferation of various cell types. However, the role of LPA and its receptors in MI is less understood.

OBJECTIVES

To study the unknown role of LPA and its receptors in heart during MI.

METHODS AND RESULTS

In this study, we found that mice also had elevated LPA level in peripheral blood, as well as increased cardiac expression of its receptor LPA₂ in the early stages after MI. With adult and neonate MI models in global Lpar2 knockout (Lpar2-KO) mice, we found Lpar2 deficiency increased vascular leak leading to disruption of its homeostasis, so as to impaired heart function and increased early mortality. Histological examination revealed larger scar size, increased fibrosis, and reduced vascular density in the heart of Lpar2-KO mice. Furthermore, Lpar2-KO also attenuated blood flow recovery after femoral artery ligation with decreased vascular density in gastrocnemius. Our study revealed that Lpar2 was mainly expressed and altered in cardiac endothelial cells during MI, and use of endothelial-specific Lpar2 knockout mice phenocopied the global knockout mice. Additionally, adenovirus-Lpar2 and pharmacologically activated LPA₂ significantly improved heart function, reduced scar size, increased vascular formation, and alleviated early mortality by maintaining vascular homeostasis owing to protecting vessels from leakage. Mechanistic studies demonstrated that LPA-LPA₂ signaling could promote endothelial cell proliferation through PI3K-Akt/PLC-Raf1-Erk pathway and enhanced endothelial cell tube formation via PKD1-CD36 signaling.

CONCLUSIONS

Our results indicate that endothelial LPA-LPA₂ signaling promotes angiogenesis and maintains vascular homeostasis, which is vital for restoring blood flow and repairing tissue function in ischemic injuries. Targeting LPA-LPA₂ signal might have clinical therapeutic potential to protect the heart from ischemic injury.

Metabolic Regulation of Cardiac Regeneration

The mortality due to heart diseases remains highest in the world every year, with ischemic cardiomyopathy being the prime cause. The irreversible loss of cardiomyocytes following myocardial injury leads to compromised contractility of the remaining myocardium, adverse cardiac remodeling, and ultimately heart failure. The hearts of adult mammals can hardly regenerate after cardiac injury since adult cardiomyocytes exit the cell cycle. Nonetheless, the hearts of early neonatal mammals possess a stronger capacity for regeneration. To improve the prognosis of patients with heart failure and to find the effective therapeutic strategies for it, it is essential to promote endogenous regeneration of adult mammalian cardiomyocytes. Mitochondrial metabolism maintains normal physiological functions of the heart and compensates for heart failure. In recent decades, the focus is on the changes in myocardial energy metabolism, including glucose, fatty acid, and amino acid metabolism, in cardiac physiological and pathological states. In addition to being a source of energy, metabolites are becoming key regulators of gene expression and epigenetic patterns, which may affect heart regeneration. However, the myocardial energy metabolism during heart regeneration is majorly unknown. This review focuses on the role of energy metabolism in cardiac regeneration, intending to shed light on the strategies for manipulating heart regeneration and promoting heart repair after cardiac injury.

Sphingosine 1-phosphate and its regulatory role in vascular endothelial cells

Sphingosine 1-phosphate (S1P) is a bioactive metabolite of sphingomyelin. S1P activates a series of signaling cascades by acting on its receptors S1PR1-3 on endothelial cells (ECs), which plays an important role in endothelial barrier maintenance, anti-inflammation, antioxidant and angiogenesis, and thus is considered as a potential therapeutic biomarker for ischemic stroke, sepsis, idiopathic pulmonary fibrosis, cancers, type 2 diabetes and cardiovascular diseases. We presently review the levels of S1P in those vascular and vascular-related diseases. Plasma S1P levels were reduced in various inflammation-related diseases such as atherosclerosis and sepsis, but were increased in other diseases including type 2 diabetes, neurodegeneration, cerebrovascular damages such as acute ischemic stroke, Alzheimer's disease, vascular dementia, angina, heart failure, idiopathic pulmonary fibrosis, community-acquired pneumonia, and hepatocellular carcinoma. Then, we highlighted the molecular mechanism by which S1P regulated EC biology including vascular development and angiogenesis, inflammation, permeability, and production of reactive oxygen species (ROS), nitric oxide (NO) and hydrogen sulfide (H₂S), which might provide new ways for exploring the pathogenesis and implementing individualized therapy strategies for those diseases.

Signaling Integration of Hydrogen Sulfide and Iron on Cellular Functions

Significance: Hydrogen sulfide (H₂S) is an endogenous signaling molecule, regulating numerous physiological functions from vasorelaxation to neuromodulation. Iron is a well-known bioactive metal ion, being the central component of hemoglobin for oxygen transportation and participating in biomolecule degradation, redox balance, and enzymatic actions. The interplay between H₂S and iron metabolisms and functions impacts significantly on the fate and wellness of different types of cells. Recent Advances: Iron level in vivo affects the production of H₂S via nonenzymatic reactions. On the contrary, H₂S quenches excessive iron inside the cells and regulates the redox status of iron. Critical Issues: Abnormal metabolisms of both iron and H₂S are associated with various conditions and diseases such as iron overload, anemia, oxidative stress, and cardiovascular and neurodegenerative diseases. The molecular mechanisms for the interactions between H₂S and iron are unsettled yet. Here we review signaling links of the production, metabolism, and their respective and integrative functions of H₂S and iron in normalcy and diseases. Future Directions: Physiological and pathophysiological importance of H₂S and iron as well as their therapeutic applications should be evaluated jointly, not separately. Future investigation should expand from iron-rich cells and tissues to the others, in which H₂S and iron interaction has not received due attention. Antioxid. Redox Signal. 36, 275-293.

DR1 Activation Inhibits the Proliferation of Vascular Smooth Muscle Cells through Increasing Endogenous H2S in Diabetes

Tissue ischemia and hypoxia caused by the abnormal proliferation of smooth muscle cells (SMCs) in the diabetic state is an important pathological basis for diabetic microangiopathy. Studies in recent years have shown that the chronic complications of diabetes are related to the decrease of endogenous hydrogen sulfide (H₂S) in diabetic patients, and it has been proven that H₂S can inhibit the proliferation of vascular SMCs (VSMCs). Our study showed that the endogenous H₂S content and the expression of cystathionine gamma-lyase (CSE), which is the key enzyme of H₂S production, were decreased in arterial SMCs of diabetic mice. The expression of PCNA and Cyclin D1 was increased, and the expression of p21 was decreased in the diabetic state. After administration of dopamine 1-like receptors (DR1) agonist SKF38393 and exogenous H₂S donor NaHS, the expression of CSE was increased and the change in proliferation-related proteins caused by diabetes was reversed. It was further verified by cell experiments that SKF38393 activated calmodulin (CaM) by increasing the intracellular calcium ([Ca²⁺]_i) concentration, which activated the CSE/H₂S pathway, enhancing the H₂S content in vivo. We also found that SKF38393 and NaHS inhibited insulin-like growth factor-1 (IGF-1)/IGF-1R and heparin-binding EGF-like growth factor (HB-EGF)/EGFR, as well as their downstream PI3K/Akt, JAK2/STAT3 and ERK1/2 pathways. Taken together, our results suggest that DR1 activation up-regulates the CSE/H₂S system by increasing Ca²⁺-CaM binding, which inhibits the IGF-1/IGF-1R and HB-EGF/EGFR pathways, thereby decreasing their downstream PI3K/Akt, JAK2/STAT3 and ERK1/2 pathways to achieve the effect of inhibiting HG-induced VSMCs proliferation.

Cardioprotective effects of hydrogen sulfide in attenuating myocardial ischemia‑reperfusion injury (Review)

Ischemic heart disease is one of the major causes of cardiovascular‑related mortality worldwide. Myocardial ischemia can be attenuated by reperfusion that restores the blood supply. However, injuries occur during blood flow restoration that induce cardiac dysfunction, which is known as myocardial ischemia‑reperfusion injury (MIRI). Hydrogen sulfide (H₂S), the third discovered endogenous gasotransmitter in mammals (after NO and CO), participates in various pathophysiological processes. Previous in vitro and in vivo research have revealed the protective role of H₂S in the cardiovascular system that render it useful in the protection of the myocardium against MIRI. The cardioprotective effects of H₂S in attenuating MIRI are summarized in the present review.

Fibrosis, the Bad Actor in Cardiorenal Syndromes: Mechanisms Involved

Cardiorenal syndrome is a term that defines the complex bidirectional nature of the interaction between cardiac and renal disease. It is well established that patients with kidney disease have higher incidence of cardiovascular comorbidities and that renal dysfunction is a significant threat to the prognosis of patients with cardiac disease. Fibrosis is a common characteristic of organ injury progression that has been proposed not only as a marker but also as an important driver of the pathophysiology of cardiorenal syndromes. Due to the relevance of fibrosis, its study might give insight into the mechanisms and targets that could potentially be modulated to prevent fibrosis development. The aim of this review was to summarize some of the pathophysiological pathways involved in the fibrotic damage seen in cardiorenal syndromes, such as inflammation, oxidative stress and endoplasmic reticulum stress, which are known to be triggers and mediators of fibrosis.

Dexmedetomidine Protects Human Cardiomyocytes Against Ischemia-Reperfusion Injury Through α2-Adrenergic Receptor/AMPK-Dependent Autophagy

Background: Ischemia-reperfusion injury (I/R) strongly affects the prognosis of children with complicated congenital heart diseases (CHDs) who undergo long-term cardiac surgical processes. Recently, the α2-adrenergic receptor agonist Dexmedetomidine (Dex) has been reported to protect cardiomyocytes (CMs) from I/R in cellular models and adult rodent models. However, whether and how Dex may protect human CMs in young children remains largely unknown. Methods and Results: Human ventricular tissue from tetralogy of Fallot (TOF) patients and CMs derived from human-induced pluripotent stem cells (iPSC-CMs) were used to assess whether and how Dex protects human CMs from I/R. The results showed that when pretreated with Dex, the apoptosis marker-TUNEL and cleaved caspase 3 in the ventricular tissue were significantly reduced. In addition, the autophagy marker LC3II was significantly increased compared with that of the control group. When exposed to the hypoxia/reoxygenation process, iPSC-CMs pretreated with Dex also showed reduced TUNEL and cleaved caspase 3 and increased LC3II. When the autophagy inhibitor (3-methyladenine, 3-MA) was applied to the iPSC-CMs, the protective effect of Dex on the CMs was largely blocked. In addition, when the fusion of autophagosomes with lysosomes was blocked by Bafilomycin A1, the degradation of p62 induced by Dex during the autophagy process was suspended. Moreover, when pretreated with Dex, both the human ventricle and the iPSC-CMs expressed more AMP-activated protein kinase (AMPK) and phospho AMPK (pAMPK) during the I/R process. After AMPK knockout or the use of an α2-adrenergic receptor antagonist-yohimbine, the protection of Dex and its enhancement of autophagy were inhibited. Conclusion: Dex protects young human CMs from I/R injury, and α2-adrenergic receptor/AMPK-dependent autophagy plays an important role during this process. Dex may have a therapeutic effect for children with CHD who undergo long-term cardiac surgical processes.

Macrophage Polarization in Cardiac Tissue Repair Following Myocardial Infarction

Cardiovascular disease is the leading cause of mortality and morbidity around the globe, creating a substantial socio-economic burden as a result. Myocardial infarction is a significant contributor to the detrimental impact of cardiovascular disease. The death of cardiomyocytes following myocardial infarction causes an immune response which leads to further destruction of tissue, and subsequently, results in the formation of non-contractile scar tissue. Macrophages have been recognized as important regulators and participants of inflammation and fibrosis following myocardial infarction. Macrophages are generally classified into two distinct groups, namely, classically activated, or M1 macrophages, and alternatively activated, or M2 macrophages. The phenotypic profile of cardiac macrophages, however, is much more diverse and should not be reduced to these two subsets. In this review, we describe the phenotypes and functions of macrophages which are present in the healthy, as well as the infarcted heart, and analyze them with respect to M1 and M2 polarization states. Furthermore, we discuss therapeutic strategies which utilize macrophage polarization towards an anti-inflammatory or reparative phenotype for the treatment of myocardial infarction.

Endothelium-dependent remote signaling in ischemia and reperfusion: Alterations in the cardiometabolic continuum

Intact endothelial function plays a fundamental role for the maintenance of cardiovascular (CV) health. The endothelium is also involved in remote signaling pathway-mediated protection against ischemia/reperfusion (I/R) injury. However, the transfer of these protective signals into clinical practice has been hampered by the complex metabolic alterations frequently observed in the cardiometabolic continuum, which affect redox balance and inflammatory pathways. Despite recent advances in determining the distinct roles of hyperglycemia, insulin resistance (InR), hyperinsulinemia, and ultimately diabetes mellitus (DM), which define the cardiometabolic continuum, our understanding of how these conditions modulate endothelial signaling remains challenging. It is widely accepted that endothelial cells (ECs) undergo functional changes within the cardiometabolic continuum. Beyond vascular tone and platelet-endothelium interaction, endothelial dysfunction may have profound negative effects on outcome during I/R. In this review, we summarize the current knowledge of the influence of hyperglycemia, InR, hyperinsulinemia, and DM on endothelial function and redox balance, their influence on remote protective signaling pathways, and their impact on potential therapeutic strategies to optimize protective heterocellular signaling.

Age-Related Pathways in Cardiac Regeneration: A Role for lncRNAs?

Aging imposes a barrier for tissue regeneration. In the heart, aging leads to a severe rearrangement of the cardiac structure and function and to a subsequent increased risk of heart failure. An intricate network of distinct pathways contributes to age-related alterations during healthy heart aging and account for a higher susceptibility of heart disease. Our understanding of the systemic aging process has already led to the design of anti-aging strategies or to the adoption of protective interventions. Nevertheless, our understanding of the molecular determinants operating during cardiac aging or repair remains limited. Here, we will summarize the molecular and physiological alterations that occur during aging of the heart, highlighting the potential role for long non-coding RNAs (lncRNAs) as novel and valuable targets in cardiac regeneration/repair.