Isthmin-1 alleviates cardiac ischemia/reperfusion injury through cGMP-PKG signaling pathway.

AIMS: Ischemia/reperfusion (I/R) injury is an important complication of reperfusion therapy for acute myocardial infarction, extremely compromising the cardiac benefits of revascularization, however, specific and efficient treatment for cardiac I/R injury is still lacking. Isthmin-1 (ISM1) is a novel adipokine, and plays indispensable roles in regulating glycolipid metabolism and cell survival. The present study aims to investigate the potential role and molecular mechanism of ISM1 in cardiac I/R injury using gain- and loss-of-function approaches. METHODS AND RESULTS: Cardiac-specific ISM1 overexpression and silence were achieved using an adeno-associated virus serotype 9 system, and then these mice were subjected to I/R surgery, followed by biochemical test, echocardiography and histopathologic examinations, etc. Meanwhile, neonatal rat cardiomyocytes (NRCMs) with ISM1 silence or overexpression also received simulated I/R (sI/R) injury to further verify its role in vitro. The potential downstream pathways and molecular targets of ISM1 were screened by RNA-sequencing. We also treated injured mice and NRCMs with recombinant ISM1 (rISM1) to explore whether supplementation with ISM1 was sufficient to protect against I/R injury. Furthermore, acute myocardial infarction patients with percutaneous coronary intervention (PCI) and paired healthy controls were included to reveal the clinical relevance of circulating ISM1. Cardiac-specific ISM1 silencing aggravated while ISM1 overexpression alleviated I/R-induced acute cardiac injury and cardiac remodeling and dysfunction. Mechanistically, ISM1 targeted αvß5 integrin to facilitate the nuclear accumulation of nuclear transcription factor Y subunit alpha, transcriptionally increased soluble guanylyl cyclase beta subunit expression, and eventually enhanced cGMP generation. Besides, we confirmed that treatment with rISM1 before or after reperfusion could confer cardioprotective effects in mice. Clinically, lower ISM1 levels post-PCI was associated with worse outcome in patients. CONCLUSION: ISM1 can protect against cardiac I/R injury through cGMP-PKG signaling pathway, and it is a promising therapeutic and predictive target of cardiac I/R injury.

IRX2 regulates angiotensin II-induced cardiac fibrosis by transcriptionally activating EGR1 in male mice.

Cardiac fibrosis is a common feature of chronic heart failure. Iroquois homeobox (IRX) family of transcription factors plays important roles in heart development; however, the role of IRX2 in cardiac fibrosis has not been clarified. Here we report that IRX2 expression is significantly upregulated in the fibrotic hearts. Increased IRX2 expression is mainly derived from cardiac fibroblast (CF) during the angiotensin II (Ang II)-induced fibrotic response. Using two CF-specific Irx2-knockout mouse models, we show that deletion of Irx2 in CFs protect against pathological fibrotic remodelling and improve cardiac function in male mice. In contrast, Irx2 gain of function in CFs exaggerate fibrotic remodelling. Mechanistically, we find that IRX2 directly binds to the promoter of the early growth response factor 1 (EGR1) and subsequently initiates the transcription of several fibrosis-related genes. Our study provides evidence that IRX2 regulates the EGR1 pathway upon Ang II stimulation and drives cardiac fibrosis.

Tisp40 prevents cardiac ischemia/reperfusion injury through the hexosamine biosynthetic pathway in male mice.

The hexosamine biosynthetic pathway (HBP) produces uridine diphosphate N-acetylglucosamine (UDP-GlcNAc) to facilitate O-linked GlcNAc (O-GlcNAc) protein modifications, and subsequently enhance cell survival under lethal stresses. Transcript induced in spermiogenesis 40 (Tisp40) is an endoplasmic reticulum membrane-resident transcription factor and plays critical roles in cell homeostasis. Here, we show that Tisp40 expression, cleavage and nuclear accumulation are increased by cardiac ischemia/reperfusion (I/R) injury. Global Tisp40 deficiency exacerbates, whereas cardiomyocyte-restricted Tisp40 overexpression ameliorates I/R-induced oxidative stress, apoptosis and acute cardiac injury, and modulates cardiac remodeling and dysfunction following long-term observations in male mice. In addition, overexpression of nuclear Tisp40 is sufficient to attenuate cardiac I/R injury in vivo and in vitro. Mechanistic studies indicate that Tisp40 directly binds to a conserved unfolded protein response element (UPRE) of the glutamine-fructose-6-phosphate transaminase 1 (GFPT1) promoter, and subsequently potentiates HBP flux and O-GlcNAc protein modifications. Moreover, we find that I/R-induced upregulation, cleavage and nuclear accumulation of Tisp40 in the heart are mediated by endoplasmic reticulum stress. Our findings identify Tisp40 as a cardiomyocyte-enriched UPR-associated transcription factor, and targeting Tisp40 may develop effective approaches to mitigate cardiac I/R injury.

Mapping current research and identifying hotspots of ferroptosis in cardiovascular diseases.

Objective: Ferroptosis is a unique cell death depended on iron metabolism disorder which is different from previous apoptosis-regulated cell death. Early studies have proposed that ferroptosis is closely associated with multiple cardiovascular diseases (CVDs). However, the relationship of ferroptosis and CVDs has not been summarized by using bibliometric analysis. We intended to illustrate the development of ferroptosis in CVDs over the past years and provide relevant valuable information. Materials and methods: The authoritative database of Web of Science Core Collection was collected for retrieving ferroptosis studies in CVDs. In this work, statistical and visualization analysis were conducted using VOSviewer and Citespace. Results: A total of 263 studies were included in the final study. From the perspective of the overall literature, the study maintains an increased trend year by year and most manuscripts belonged to original article. China was the most productive country with the utmost scientific research output, as well as the institutions and authors, followed by Germany and the United States of America (USA). Jun Peng from China contributes to the most publications. Collaborative efforts between institutes and authors were limited and there was little widespread cooperation. In addition, burst keywords analysis discovered that ischemia-reperfusion (I/R) injury, heart failure (HF), and atherosclerosis were the top three research directions of ferroptosis in CVDs. The burst investigation and timeline views also indicated that endothelial injury and gut microbiota may also serve as new research topics in the future. Conclusion: This study provided comprehensive and specific information about the most influential articles on ferroptosis in CVDs. The relationship between ferroptosis and CVDs had attracted the scholar's concerns especially in China. Cooperations and communications between countries and institutions should be emphasized and future directions can be concentrated on endothelial disorder and gut microbiota.

Fibronectin type III domain-containing 5 improves aging-related cardiac dysfunction in mice.

Aging is an important risk factor for cardiovascular diseases, and aging-related cardiac dysfunction serves as a major determinant of morbidity and mortality in elderly populations. Our previous study has identified fibronectin type III domain-containing 5 (FNDC5) and its cleaved form, irisin, as the cardioprotectant against doxorubicin-induced cardiomyopathy. Herein, aging or matched young mice were overexpressed with FNDC5 by adeno-associated virus serotype 9 (AAV9) vectors, or subcutaneously infused with irisin to uncover the role of FNDC5 in aging-related cardiac dysfunction. To verify the involvement of nucleotide-binding oligomerization domain-like receptor with a pyrin domain 3 (NLRP3) and AMP-activated protein kinase α (AMPKα), Nlrp3 or Ampkα2 global knockout mice were used. Besides, young mice were injected with AAV9-FNDC5 and maintained for 12 months to determine the preventive effect of FNDC5. Moreover, neonatal rat cardiomyocytes were stimulated with tumor necrosis factor-α (TNF-α) to examine the role of FNDC5 in vitro. We found that FNDC5 was downregulated in aging hearts. Cardiac-specific overexpression of FNDC5 or irisin infusion significantly suppressed NLRP3 inflammasome and cardiac inflammation, thereby attenuating aging-related cardiac remodeling and dysfunction. In addition, irisin treatment also inhibited cellular senescence in TNF-α-stimulated cardiomyocytes in vitro. Mechanistically, FNDC5 activated AMPKα through blocking the lysosomal degradation of glucagon-like peptide-1 receptor. More importantly, FNDC5 gene transfer in early life could delay the onset of cardiac dysfunction during aging process. We prove that FNDC5 improves aging-related cardiac dysfunction by activating AMPKα, and it might be a promising therapeutic target to support cardiovascular health in elderly populations.

Cellular Senescence in Cardiovascular Diseases: A Systematic Review.

Aging is a prominent risk factor for cardiovascular diseases, which is the leading cause of death around the world. Recently, cellular senescence has received potential attention as a promising target in preventing cardiovascular diseases, including acute myocardial infarction, atherosclerosis, cardiac aging, pressure overload-induced hypertrophy, heart regeneration, hypertension, and abdominal aortic aneurysm. Here, we discuss the mechanisms underlying cellular senescence and describe the involvement of senescent cardiovascular cells (including cardiomyocytes, endothelial cells, vascular smooth muscle cells, fibroblasts/myofibroblasts and T cells) in age-related cardiovascular diseases. Then, we highlight the targets (SIRT1 and mTOR) that regulating cellular senescence in cardiovascular disorders. Furthermore, we review the evidence that senescent cells can exert both beneficial and detrimental implications in cardiovascular diseases on a context-dependent manner. Finally, we summarize the emerging pro-senescent or anti-senescent interventions and discuss their therapeutic potential in preventing cardiovascular diseases.

Osteocrin, a novel myokine, prevents diabetic cardiomyopathy via restoring proteasomal activity.

Proteasomal activity is compromised in diabetic hearts that contributes to proteotoxic stresses and cardiac dysfunction. Osteocrin (OSTN) acts as a novel exercise-responsive myokine and is implicated in various cardiac diseases. Herein, we aim to investigate the role and underlying molecular basis of OSTN in diabetic cardiomyopathy (DCM). Mice received a single intravenous injection of the cardiotrophic adeno-associated virus serotype 9 to overexpress OSTN in the heart and then were exposed to intraperitoneal injections of streptozotocin (STZ, 50 mg/kg) for consecutive 5 days to generate diabetic models. Neonatal rat cardiomyocytes were isolated and stimulated with high glucose to verify the role of OSTN in vitro. OSTN expression was reduced by protein kinase B/forkhead box O1 dephosphorylation in diabetic hearts, while its overexpression significantly attenuated cardiac injury and dysfunction in mice with STZ treatment. Besides, OSTN incubation prevented, whereas OSTN silence aggravated cardiomyocyte apoptosis and injury upon hyperglycemic stimulation in vitro. Mechanistically, OSTN treatment restored protein kinase G (PKG)-dependent proteasomal function, and PKG or proteasome inhibition abrogated the protective effects of OSTN in vivo and in vitro. Furthermore, OSTN replenishment was sufficient to prevent the progression of pre-established DCM and had synergistic cardioprotection with sildenafil. OSTN protects against DCM via restoring PKG-dependent proteasomal activity and it is a promising therapeutic target to treat DCM.

Endothelial ERG alleviates cardiac fibrosis via blocking endothelin-1-dependent paracrine mechanism.

Cardiac endothelium communicates closely with adjacent cardiac cells by multiple cytokines and plays critical roles in regulating fibroblasts proliferation, activation, and collagen synthesis during cardiac fibrosis. E26 transformation-specific (ETS)-related gene (ERG) belongs to the ETS transcriptional factor family and is required for endothelial cells (ECs) homeostasis and cardiac development. This study aims at investigating the potential role and molecular basis of ERG in fibrotic remodeling within the adult heart. We observed that ERG was abundant in murine hearts, especially in cardiac ECs, but decreased during cardiac fibrosis. ERG knockdown within murine hearts caused spontaneously cardiac fibrosis and dysfunction, accompanied by the activation of multiple Smad-dependent and independent pathways. However, the direct silence of ERG in cardiac fibroblasts did not affect the expression of fibrotic markers. Intriguingly, ERG knockdown in human umbilical vein endothelial cells (HUVECs) promoted the secretion of endothelin-1 (ET-1), which subsequently accelerated the proliferation, phenotypic transition, and collagen synthesis of cardiac fibroblasts in a paracrine manner. Suppressing ET-1 with either a neutralizing antibody or a receptor blocker abolished ERG knockdown-mediated deleterious effect in vivo and in vitro. This pro-fibrotic effect was also negated by RGD (Arg-Gly-Asp)-peptide magnetic nanoparticles target delivery of ET-1 small interfering RNA to ECs in mice. More importantly, we proved that endothelial ERG overexpression notably prevented pressure overload-induced cardiac fibrosis. Collectively, endothelial ERG alleviates cardiac fibrosis via blocking ET-1-dependent paracrine mechanism and it functions as a candidate for treating cardiac fibrosis. • ERG is abundant in murine hearts, especially in cardiac ECs, but decreased during fibrotic remodeling. • ERG knockdown causes spontaneously cardiac fibrosis and dysfunction. • ERG silence in HUVECs promotes the secretion of endothelin-1, which in turn activates cardiac fibroblasts in a paracrine manner. • Endothelial ERG overexpression prevents pressure overload-induced cardiac fibrosis.

Significant reduction of humoral response to SARS-CoV-2 4 months after the diagnosis of COVID-19.

A commentary on "Humoral immune response to SARS-CoV-2 in Iceland".

Fibronectin type III domain-containing 5 in cardiovascular and metabolic diseases: a promising biomarker and therapeutic target.

Cardiovascular and metabolic diseases are the leading causes of death and disability worldwide and impose a tremendous socioeconomic burden on individuals as well as the healthcare system. Fibronectin type III domain-containing 5 (FNDC5) is a widely distributed transmembrane glycoprotein that can be proteolytically cleaved and secreted as irisin to regulate glycolipid metabolism and cardiovascular homeostasis. In this review, we present the current knowledge on the predictive and therapeutic role of FNDC5 in a variety of cardiovascular and metabolic diseases, such as hypertension, atherosclerosis, ischemic heart disease, arrhythmia, metabolic cardiomyopathy, cardiac remodeling, heart failure, diabetes mellitus, and obesity.

Matrine attenuates pathological cardiac fibrosis via RPS5/p38 in mice.

Pathological cardiac fibrosis is a common feature in multiple cardiovascular diseases that contributes to the occurrence of heart failure and life-threatening arrhythmias. Our previous study demonstrated that matrine could attenuate doxorubicin-induced oxidative stress and cardiomyocyte apoptosis. In this study, we investigated the effect of matrine on cardiac fibrosis. Mice received aortic banding (AB) operation or continuous injection of isoprenaline (ISO) to generate pathological cardiac fibrosis and then were exposed to matrine lavage (200 mg·kg-1·d-1) or an equal volume of vehicle as the control. We found that matrine lavage significantly attenuated AB or ISO-induced fibrotic remodeling and cardiac dysfunction. We also showed that matrine (200 µmol/L) significantly inhibited the proliferation, migration, collagen production, and phenotypic transdifferentiation of cardiac fibroblasts. Mechanistically, matrine suppressed p38 activation in vivo and in vitro, and overexpression of constitutively active p38 completely abolished the protective effects of matrine. We also demonstrated that ribosomal protein S5 (RPS5) upregulation was responsible for matrine-mediated inhibition on p38 and fibrogenesis. More importantly, matrine was capable of ameliorating preexisting cardiac fibrosis in mice. In conclusion, matrine treatment attenuates cardiac fibrosis by regulating RPS5/p38 signaling in mice, and it might be a promising therapeutic agent for treating pathological cardiac fibrosis.

A brief overview about the physiology of fibronectin type III domain-containing 5.

Fibronectin type III domain-containing 5 (FNDC5) is a widely distributed transmembrane glycoprotein and can be proteolytically cleaved as irisin that has multiple benefits on human diseases. In this review, we will focus on the synthesis, cleavage, distribution, elimination, single nucleotide polymorphisms, protein structure and glycosylated modification of FNDC5 or the cleaved form irisin, and also summarize a brief knowledge on their biological functions.

Toll-like receptor 5 deficiency diminishes doxorubicin-induced acute cardiotoxicity in mice.

Rationale: Clinical application of doxorubicin (DOX) is limited by its toxic cardiovascular side effects. Our previous study found that toll-like receptor (TLR) 5 deficiency attenuated cardiac fibrosis in mice. However, the role of TLR5 in DOX-induced cardiotoxicity remains unclear. Methods: To further investigate this, TLR5-deficient mice were subjected to a single intraperitoneal injection of DOX to mimic an acute model. Results: Here, we reported that TLR5 expression was markedly increased in response to DOX injection. Moreover, TLR5 deficiency exerted potent protective effects against DOX-related cardiac injury, whereas activation of TLR5 by flagellin exacerbated DOX injection-induced cardiotoxicity. Mechanistically, the effects of TLR5 were largely attributed to direct interaction with spleen tyrosine kinase to activate NADPH oxidase (NOX) 2, increasing the production of superoxide and subsequent activation of p38. The toxic effects of TLR5 activation in DOX-related acute cardiac injury were abolished by NOX2 deficiency in mice. Our further study showed that neutralizing antibody-mediated TLR5 depletion also attenuated DOX-induced acute cardiotoxicity. Conclusion: These findings suggest that TLR5 deficiency attenuates DOX-induced cardiotoxicity in mice, and targeting TLR5 may provide feasible therapies for DOX-induced acute cardiotoxicity.

Meteorin-like protein attenuates doxorubicin-induced cardiotoxicity via activating cAMP/PKA/SIRT1 pathway.

Meteorin-like (METRNL) protein is a newly identified myokine that functions to modulate energy expenditure and inflammation in adipose tissue. Herein, we aim to investigate the potential role and molecular basis of METRNL in doxorubicin (DOX)-induced cardiotoxicity. METRNL was found to be abundantly expressed in cardiac muscle under physiological conditions that was decreased upon DOX exposure. Cardiac-specific overexpression of METRNL by adeno-associated virus serotype 9 markedly improved oxidative stress, apoptosis, cardiac dysfunction and survival status in DOX-treated mice. Conversely, knocking down endogenous METRNL by an intramyocardial injection of adenovirus exacerbated DOX-induced cardiotoxicity and death. Meanwhile, METRNL overexpression attenuated, while METRNL silence promoted oxidative damage and apoptosis in DOX-treated H9C2 cells. Systemic METRNL depletion by a neutralizing antibody aggravated DOX-related cardiac injury and dysfunction in vivo, which were notably alleviated by METRNL overexpression within the cardiomyocytes. Besides, we detected robust METRNL secretion from isolated rodent hearts and cardiomyocytes, but to a less extent in those with DOX treatment. And the beneficial effects of METRNL in H9C2 cells disappeared after the incubation with a METRNL neutralizing antibody. Mechanistically, METRNL activated SIRT1 via the cAMP/PKA pathway, and its antioxidant and antiapoptotic capacities were blocked by SIRT1 deficiency. More importantly, METRNL did not affect the tumor-killing action of DOX in 4T1 breast cancer cells and tumor-bearing mice. Collectively, cardiac-derived METRNL activates SIRT1 via cAMP/PKA signaling axis in an autocrine manner, which ultimately improves DOX-elicited oxidative stress, apoptosis and cardiac dysfunction. Targeting METRNL may provide a novel therapeutic strategy for the prevention of DOX-associated cardiotoxicity.

Osteocrin attenuates inflammation, oxidative stress, apoptosis, and cardiac dysfunction in doxorubicin-induced cardiotoxicity.

BACKGROUND: Inflammation, oxidative stress, and apoptosis contribute to the evolution of doxorubicin (DOX)-induced cardiotoxicity. Osteocrin (OSTN) is a novel secretory peptide mainly derived from the bone and skeletal muscle, and plays critical roles in regulating bone growth and physical endurance. Inspiringly, OSTN was also reported to be abundant in the myocardium that functioned as a therapeutic agent against cardiac rupture and congestive heart failure in mice after myocardial infarction. Herein, we investigated the role and potential mechanism of OSTN in DOX-induced cardiotoxicity. METHODS: Cardiac-restrict OSTN overexpression was performed by the intravenous injection of a cardiotropic AAV9 vector, and subsequently the mice received 15 mg/kg DOX injection (i.p., once) to induce acute cardiac injury. Besides, H9C2 cell lines were used to assess the possible role of OSTN in vitro by incubating with recombinant human OSTN or small interfering RNA against Ostn (siOstn). To clarify the involvement of protein kinase G (PKG), KT5823 and siPkg were used in vivo and in vitro. Mice were also administrated intraperitoneally with 5 mg/kg DOX weekly for consecutive 3 weeks at a cumulative dose of 15 mg/kg to mimic the cardiotoxic effects upon chronic DOX exposure. RESULTS: OSTN treatment notably attenuated, whereas OSTN silence exacerbated inflammation, oxidative stress, and cardiomyocyte apoptosis in DOX-treated H9C2 cells. Besides, cardiac-restrict OSTN-overexpressed mice showed an alleviated cardiac injury and malfunction upon DOX injection. Mechanistically, we found that OSTN activated PKG, while PKG inhibition abrogated the beneficial effect of OSTN in vivo and in vitro. As expected, OSTN overexpression also improved cardiac function and survival rate in mice after chronic DOX treatment. CONCLUSIONS: OSTN protects against DOX-elicited inflammation, oxidative stress, apoptosis, and cardiac dysfunction via activating PKG, and cardiac gene therapy with OSTN provides a novel therapeutic strategy against DOX-induced cardiotoxicity.

Geniposide protects against sepsis-induced myocardial dysfunction through AMPKα-dependent pathway.

Uncontrolled inflammatory response and subsequent cardiomyocytes loss (apoptosis and pyroptosis) are closely involved in sepsis-induced myocardial dysfunction. Our previous study has found that geniposide (GE) can protect the murine hearts against obesity-induced inflammation. However, the effect of GE on sepsis-related cardiac dysfunction is still unknown. Mice were exposed to lipopolysaccharide (LPS) to generate sepsis-induced myocardial dysfunction. And 50 mg/kg GE was used to treat mice for consecutive 7 days. Our results showed that GE treatment significantly improved survival rate and cardiac function, and suppressed myocardial inflammatory response, as well as myocardial loss in LPS-treated mice. Those effects of GE were largely abolished in NOD-like receptor protein 3 (NLRP3)-deficient mice. Further detection revealed that the inhibition of NLRP3 inflammasome activation depended on the reduction of p47phox by GE. GE treatment restored the phosphorylation and activity of AMP-activated protein kinase α (AMPKα) in the hearts of sepsis mice, and knockout of AMPKα abolished the protection of GE against reactive oxygen species (ROS) accumulation, NLRP3 inflammasome activation and cardiomyocytes loss in sepsis mice. In conclusion, our findings revealed that GE activated AMPKα to suppress myocardial ROS accumulation, thus blocking NLRP3 inflammasome-mediated cardiomyocyte apoptosis and pyroptosis and improving cardiac function in mice with sepsis.

FNDC5 alleviates oxidative stress and cardiomyocyte apoptosis in doxorubicin-induced cardiotoxicity via activating AKT.

Oxidative stress and cardiomyocyte apoptosis play critical roles in doxorubicin (DOX)-induced cardiotoxicity. Previous studies indicated that fibronectin type III domain-containing 5 (FNDC5) and its cleaved form, irisin, could preserve mitochondrial function and attenuate oxidative damage as well as cell apoptosis, however, its role in DOX-induced cardiotoxicity remains unknown. Our present study aimed to investigate the role and underlying mechanism of FNDC5 on oxidative stress and cardiomyocyte apoptosis in DOX-induced cardiotoxicity. Cardiomyocyte-specific FNDC5 overexpression was achieved using an adeno-associated virus system, and then the mice were exposed to a single intraperitoneal injection of DOX (15 mg/kg) to generate DOX-induced cardiotoxicity. Herein, we found that FNDC5 expression was downregulated in DOX-treated murine hearts and cardiomyocytes. Fndc5 deficiency resulted in increased oxidative damage and apoptosis in H9C2 cells under basal conditions, imitating the phenotype of DOX-induced cardiomyopathy in vitro, conversely, FNDC5 overexpression or irisin treatment alleviated DOX-induced oxidative stress and cardiomyocyte apoptosis in vivo and in vitro. Mechanistically, we identified that FNDC5/Irisin activated AKT/mTOR signaling and decreased DOX-induced cardiomyocyte apoptosis, and moreover, we provided direct evidence that the anti-oxidant effect of FNDC5/Irisin was mediated by the AKT/GSK3ß/FYN/Nrf2 axis in an mTOR-independent manner. And we also demonstrated that heat shock protein 20 was responsible for the activation of AKT caused by FNDC5/Irisin. In line with the data in acute model, we also found that FNDC5/Irisin exerted beneficial effects in chronic model of DOX-induced cardiotoxicity (5 mg/kg, i.p., once a week for three times, the total cumulative dose is 15 mg/kg) in mice. Based on these findings, we supposed that FNDC5/Irisin was a potential therapeutic agent against DOX-induced cardiotoxicity.

Protection against Doxorubicin-Induced Cytotoxicity by Geniposide Involves AMPKα Signaling Pathway.

Oxidative stress and cardiomyocyte apoptosis play critical roles in the development of doxorubicin- (DOX-) induced cardiotoxicity. Our previous study found that geniposide (GE) could inhibit cardiac oxidative stress and apoptosis of cardiomyocytes but its role in DOX-induced heart injury remains unknown. Our study is aimed at investigating whether GE could protect against DOX-induced heart injury. The mice were subjected to a single intraperitoneal injection of DOX (15 mg/kg) to induce cardiomyopathy model. To explore the protective effects, GE was orally given for 10 days. The morphological examination and biochemical analysis were used to evaluate the effects of GE. H9C2 cells were used to verify the protective role of GE in vitro. GE treatment alleviated heart dysfunction and attenuated cardiac oxidative stress and cell loss induced by DOX in vivo and in vitro. GE could activate AMP-activated protein kinase α (AMPKα) in vivo and in vitro. Moreover, inhibition of AMPKα could abolish the protective effects of GE against DOX-induced oxidative stress and apoptosis. GE could protect against DOX-induced heart injury via activation of AMPKα. GE has therapeutic potential for the treatment of DOX cardiotoxicity.

TLR9 is essential for HMGB1-mediated post-myocardial infarction tissue repair through affecting apoptosis, cardiac healing, and angiogenesis.

The poor prognosis of patients with acute myocardial infarction is partially attributed to a large number of cardiomyocyte apoptosis, necrosis, limited cardiac healing and angiogenesis, and cardiac dysfunction. Immune cells dysfunction leads to nonhealing or poor healing of wounds after acute myocardial infarction. Toll-like receptor 9 (TLR9) as an essential part of the innate immune system plays a vital role in regulating cardiomyocyte survival and wound healing. During hypoxia, High Mobility Group Box 1 (HMGB1), as the typical damage-associated molecular patterns (DAMPs) or alarmin, is rapidly released extracellularly and translocates from the nucleus to bind with cytoplasmic TLR9. However, the mechanism by which TLR9 interacts with HMGB1 and regulates myocardial damage remains unclear. Our current study found that the survival rate of TLR9KO mice with a higher rate of cardiac rupture was significantly lower than that in WT mice after 28 days post-operation. The effect of TLR9 knockout on insufficient wound healing in experimental MI was caused by a diminished number of myofibroblast and defective matrix synthetic capability. Moreover, the increased myocardial apoptotic cells and decreased angiogenic capacity were found in TLR9 knockout mice after MI. The results showed contrary in Recombinant Human High Mobility Group Box 1 (rhHMGB1) treated WT mice and similarity after applying rhHMGB1 in TLR9KO mice. This study demonstrates that TLR9 is essential for the repair of infarcted myocardium and interaction of HMGB1 and TLR9 is involved in the survival of myocardial cells, wound healing, and angiogenesis after myocardial infarction.