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.

CTRP3 protected against doxorubicin-induced cardiac dysfunction, inflammation and cell death via activation of Sirt1.

BACKGROUND: Inflammation and myocytes apoptosis play critical roles in the development of doxorubicin (DOX)-induced cardiotoxicity. Our previous study found that C1q/tumour necrosis factor-related protein-3 (CTRP3) could inhibit cardiac inflammation and apoptosis of myocytes but its role in DOX-induced heart injury remains largely unknown. Our study aimed to investigate whether CTRP3 protected against DOX-induced heart injury and the underlying mechanism. METHODS: We overexpressed CTRP3 in the hearts using an adeno-associated virus system. The mice were subjected to a single intraperitoneal injection of DOX (15mg/kg) to induce short-term model for cardiomyopathy. The morphological examination and biochemical analysis were used to evaluate the effects of CTRP3. H9C2 cells were used to verify the protective role of CTRP3 in vitro. RESULTS: Myocardial CTRP3 protein levels were reduced in DOX-treated mice. Cardiac specific-overexpression of CTRP3 preserved heart dysfunction, and attenuated cardiac inflammation and cell loss induced by DOX in vivo and in vitro. CTRP3 could activate silent information regulator 1 (Sirt1) in vivo and in vitro. Moreover, specific inhibitor of Sirt1 and the silence of Sirt1 could abolish the protective effects of CTRP3 against DOX-induced inflammation and apoptosis. CONCLUSION: CTRP3 protected against DOX-induced heart injury via activation of Sirt1. CTRP3 has therapeutic potential for the treatment of DOX cardiotoxicity.

Pioglitazone Alleviates Cardiac Fibrosis and Inhibits Endothelial to Mesenchymal Transition Induced by Pressure Overload.

BACKGROUND/AIMS: Cardiac fibrosis, characterized by an unbalanced production and degradation of extracellular matrix components, is a common pathophysiology of multiple cardiovascular diseases. Recent studies suggested that endothelial to mesenchymal transition (EndMT) could be a source of activated fibroblasts and contribute to cardiac fibrosis. Here, the role of pioglitazone (PIO) in cardiac fibrosis and EndMT was elaborated. METHODS: Male C57BL/6 mice were subjected to aortic banding (AB), which was used to construct a model of pressure overload-induced cardiac hypertrophy. PIO and GW9662 was given for 4 weeks to detect the effects of PIO on EndMT. RESULTS: Our results showed PIO treatment attenuated cardiac hypertrophy, dysfunction and fibrosis response to pressure overload. Mechanistically, PIO suppressed the TGF-ß/Smad signaling pathway activated by 4-week AB surgery. Moreover, PIO dramatically inhibited EndMT in vivo and in vitro stimulated by pressure overload or TGF-ß. A selective antagonist of PPAR-γ, GW9662, neutralized the anti-fibrotic effect and abolished the inhibitory effect of EndMT during the treatment of PIO. CONCLUSION: Our data implied that PIO exerts an alleviative effect on cardiac fibrosis via inhibition of the TGF-ß/Smad signaling pathway and EndMT by activating PPAR-γ.

T-bet deficiency attenuates cardiac remodelling in rats.

Previous studies have suggested the involvement of CD4 + T lymphocytes in cardiac remodelling. T-bet can direct Th1 lineage commitment. This study aimed to investigate the functional significance of T-bet in cardiac remodelling induced by pressure overload using T-bet global knockout rats. Increased T-bet levels were observed in rodent and human hypertrophied hearts. T-bet deficiency resulted in a less severe hypertrophic phenotype in rats. CD4 + T-lymphocyte reconstitution in T-bet-/- rats resulted in aggravated cardiac remodelling. T-cell homing molecule expression and cytokine secretion were altered in T-bet-deficient rat hearts. Administration of exogenous interferon-γ (IFN-γ) offset T-bet deficiency-mediated cardioprotection. Cardiomyocytes cultured in T-bet-/- CD4 + T-cell-conditioned media showed a reduced hypertrophic response after hypertrophic stimuli, which was abolished by an IFN-γ-neutralizing antibody. Taken together, our findings show that T-bet deficiency attenuates pressure overload-induced cardiac remodelling in rats. Specifically, targeting T-bet in T cells may be of great importance for the treatment of pathological cardiac remodelling and heart failure.

A77 1726 (leflunomide) blocks and reverses cardiac hypertrophy and fibrosis in mice.

T-cell infiltration and the subsequent increased intracardial chronic inflammation play crucial roles in the development of cardiac hypertrophy and heart failure (HF). A77 1726, the active metabolite of leflunomide, has been reported to have powerful anti-inflammatory and T cell-inhibiting properties. However, the effect of A77 1726 on cardiac hypertrophy remains completely unknown. Herein, we found that A77 1726 treatment attenuated pressure overload or angiotensin II (Ang II)-induced cardiac hypertrophy in vivo, as well as agonist-induced hypertrophic response of cardiomyocytes in vitro In addition, we showed that A77 1726 administration prevented induction of cardiac fibrosis by inhibiting cardiac fibroblast (CF) transformation into myofibroblast. Surprisingly, we found that the protective effect of A77 1726 was not dependent on its T lymphocyte-inhibiting property. A77 1726 suppressed the activation of protein kinase B (AKT) signaling pathway, and overexpression of constitutively active AKT completely abolished A77 1726-mediated cardioprotective effects in vivo and in vitro Pretreatment with siRNA targetting Fyn (si Fyn) blunted the protective effect elicited by A77 1726 in vitro More importantly, A77 1726 was capable of blocking pre-established cardiac hypertrophy in mice. In conclusion, A77 1726 attenuated cardiac hypertrophy and cardiac fibrosis via inhibiting FYN/AKT signaling pathway.

CTRP3 attenuates cardiac dysfunction, inflammation, oxidative stress and cell death in diabetic cardiomyopathy in rats.

AIMS/HYPOTHESIS: Oxidative stress, inflammation and cell death are closely involved in the development of diabetic cardiomyopathy (DCM). C1q/tumour necrosis factor-related protein-3 (CTRP3) has anti-inflammatory properties but its role in DCM remains largely unknown. The aims of this study were to determine whether CTRP3 could attenuate DCM and to clarify the underlying mechanisms. METHODS: Streptozotocin (STZ) was injected intraperitoneally to induce diabetes in Sprague-Dawley rats. Cardiomyocyte-specific CTRP3 overexpression was achieved using an adeno-associated virus system 12 weeks after STZ injection. RESULTS: CTRP3 expression was significantly decreased in diabetic rat hearts. Knockdown of CTRP3 in cardiomyocytes at baseline resulted in increased oxidative injury, inflammation and apoptosis in vitro. Cardiomyocyte-specific overexpression of CTRP3 decreased oxidative stress and inflammation, attenuated myocyte death and improved cardiac function in rats treated with STZ. CTRP3 significantly activated AMP-activated protein kinase α (AMPKα) and Akt (protein kinase B) in H9c2 cells. CTRP3 protected against high-glucose-induced oxidative stress, inflammation and apoptosis in vitro. AMPKα deficiency abolished the protective effects of CTRP3 in vitro and in vivo. Furthermore, we found that CTRP3 activated AMPKα via the cAMP-exchange protein directly activated by cAMP (EPAC)-mitogen-activated protein kinase kinase (MEK) pathway. CONCLUSIONS/INTERPRETATION: CTRP3 protected against DCM via activation of the AMPKα pathway. CTRP3 has therapeutic potential for the treatment of DCM.

Arctiin protects against cardiac hypertrophy through inhibiting MAPKs and AKT signaling pathways.

PURPOSE: The mitogen-activated protein kinases (MAPKs) and protein kinase B (AKT) pathways have emerged as essential intracellular signaling pathways in eukaryotic cells, particularly as regulators of cardiac hypertrophy. Previous studies indicated that arctiin, an active ingredient of biennial dried ripe burdock, could exhibit potent anti-inflammatory and anti-allergic activities via down-regulating the activation of MAPKs and AKT pathways. However, little is known about its effects on cardiac hypertrophy. Therefore, the present study aimed to explore whether arctiin could attenuate cardiac hypertrophy. GENERAL METHODS: Arctiin (80 mg/kg) was administered by oral gavage once daily for 3 weeks from 1 week after surgery. Then, the mice were subjected to either chronic pressure overload generated by aortic banding (AB) or sham surgery (control group). Cardiac function was assessed by echocardiography. FINDINGS: The results indicated that arctiin attenuated cardiac hypertrophy induced by AB, and suppressed cardiac fibrosis and accumulation of collagen in vivo. Arctiin also inhibit the activation of MAPKs and AKT occurs in response to hypertrophic stimuli. Arctiin attenuated phenylephrine-induced hypertrophy of myocytes in vitro. CONCLUSIONS: In conclusion, arctiin can improve cardiac function and prevent the development of cardiac hypertrophy by blocking the MAPKs and AKT signaling pathways.

S100a8/9 (S100 Calcium Binding Protein a8/9) Promotes Cardiac Hypertrophy Via Upregulation of FGF23 (Fibroblast Growth Factor 23) in Mice.

BACKGROUND: S100a8/9 (S100 calcium binding protein a8/9) belongs to the S100 family and has gained a lot of interest as a critical regulator of inflammatory response. Our previous study found that S100a8/9 homolog promoted aortic valve sclerosis in mice with chronic kidney disease. However, the role of S100a8/9 in pressure overload-induced cardiac hypertrophy remains unclear. The present study was to explore the role of S100a8/9 in cardiac hypertrophy. METHODS AND RESULTS: Cardiomyocyte-specific S100a9 loss or gain of function was achieved using an adeno-associated virus system, and the model of cardiac hypertrophy was established by aortic banding-induced pressure overload. The results indicate that S100a8/9 expression was increased in response to pressure overload. S100a9 deficiency alleviated pressure overload-induced hypertrophic response, whereas S100a9 overexpression accelerated cardiac hypertrophy. S100a9-overexpressed mice showed increased FGF23 (fibroblast growth factor 23) expression in the hearts after exposure to pressure overload, which activated calcineurin/NFAT (nuclear factor of activated T cells) signaling in cardiac myocytes and thus promoted hypertrophic response. A specific antibody that blocks FGFR4 (FGF receptor 4) largely abolished the prohypertrophic response of S100a9 in mice. CONCLUSIONS: In conclusion, S100a8/9 promoted the development of cardiac hypertrophy in mice. Targeting S100a8/9 may be a promising therapeutic approach to treat cardiac hypertrophy.

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.

Underlying the Mechanisms of Doxorubicin-Induced Acute Cardiotoxicity: Oxidative Stress and Cell Death.

Cancer is a destructive disease that causes high levels of morbidity and mortality. Doxorubicin (DOX) is a highly efficient antineoplastic chemotherapeutic drug, but its use places survivors at risk for cardiotoxicity. Many studies have demonstrated that multiple factors are involved in DOX-induced acute cardiotoxicity. Among them, oxidative stress and cell death predominate. In this review, we provide a comprehensive overview of the mechanisms underlying the source and effect of free radicals and dependent cell death pathways induced by DOX. Hence, we attempt to explain the cellular mechanisms of oxidative stress and cell death that elicit acute cardiotoxicity and provide new insights for researchers to discover potential therapeutic strategies to prevent or reverse doxorubicin-induced cardiotoxicity.

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.

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.

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.

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.

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.

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.

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.

C1q-tumour necrosis factor-related protein-3 exacerbates cardiac hypertrophy in mice.

AIMS: C1q-tumour necrosis factor-related protein-3 (CTRP3) is an adipokine and a paralog of adiponectin. Our previous study showed that CTRP3 attenuated diabetes-related cardiomyopathy. However, the precise role of CTRP3 in cardiac hypertrophy remains unclear. This study was aimed to clarify the role of CTRP3 involved in cardiac hypertrophy. METHODS AND RESULTS: Cardiomyocyte-specific CTRP3 overexpression was achieved using an adeno-associated virus system, and cardiac CTRP3 expression was knocked down using gene delivery of specific short hairpin RNAs in vivo. CTRP3 expression was upregulated in murine hypertrophic hearts and failing human hearts. Increased CTRP3 was mainly derived from cardiomyocytes and induced by the production of reactive oxygen species (ROS) during the hypertrophic response. CTRP3-overexpressing mice exhibited exacerbated cardiac hypertrophy and cardiac dysfunction in response to pressure overload. Conversely, Ctrp3 deficiency in the heart resulted in an alleviated hypertrophic phenotype. CTRP3 induced hypertrophy in cardiomyocytes, which could be blocked by the addition of CTRP3 antibody in the media. Detection of signalling pathways showed that pressure overload-induced activation of the transforming growth factor ß-activated kinase 1 (TAK1)-c-Jun N-terminal kinase (JNK) pathway was enhanced by CTRP3 overexpression and inhibited by CTRP3 disruption. Furthermore, we found that CTRP3 lost its pro-hypertrophic effects in cardiomyocyte-specific Tak1 knockout mice. Protein kinase A (PKA) was involved in the activation of TAK1 by CTRP3. CONCLUSION: In conclusion, our results suggest that CTRP3 promotes pressure overload-induced cardiac hypertrophy via activation of the TAK1-JNK axis.