Pressure Overload-induced Cardiac Dysfunction Research Articles

MicroRNA-27 attenuates pressure overload-Induced cardiac hypertrophy and dysfunction by targeting galectin-3

Cardiac hypertrophy is an adaptive response to hemodynamic stress to compensate for cardiac dysfunction. MicroRNAs can regulate cardiac function and play a vital role in the regulation of cardiac hypertrophy. In the current study, in vivo and vitro hypertrophy models are established to explore the role of miR-27b and to elucidate the underlying mechanism in cardiac hypertrophy. Expression of miR-27b was down-regulated in mice with cardiac hypertrophy. The cardiac function of the mice with cardiac hypertrophy could be restored with the overexpression of miR-27b, this is observed in terms of decreasing LVEDd, LVESd, and increasing LVFS, LVEF. This study also predicted and confirmed that galectin-3 is a target gene of miR-27b. Depletion of galectin-3 significantly attenuated hypertrophy of hearts in both in vitro and in vivo tests. In conclusion, MiR-27b be used to exert a protective role against cardiac dysfunction and hypertrophy by decreasing the expression level of galectin-3. The methodology suggested in this study provides a novel therapeutic strategy against cardiac hypertrophy.

Chronic activation of hexosamine biosynthesis in the heart triggers pathological cardiac remodeling

The hexosamine biosynthetic pathway (HBP) plays critical roles in nutrient sensing, stress response, and cell growth. However, its contribution to cardiac hypertrophic growth and heart failure remains incompletely understood. Here, we show that the HBP is induced in cardiomyocytes during hypertrophic growth. Overexpression of Gfat1 (glutamine:fructose-6-phosphate amidotransferase 1), the rate-limiting enzyme of HBP, promotes cardiomyocyte growth. On the other hand, Gfat1 inhibition significantly blunts phenylephrine-induced hypertrophic growth in cultured cardiomyocytes. Moreover, cardiac-specific overexpression of Gfat1 exacerbates pressure overload-induced cardiac hypertrophy, fibrosis, and cardiac dysfunction. Conversely, deletion of Gfat1 in cardiomyocytes attenuates pathological cardiac remodeling in response to pressure overload. Mechanistically, persistent upregulation of the HBP triggers decompensated hypertrophy through activation of mTOR while Gfat1 deficiency shows cardioprotection and a concomitant decrease in mTOR activity. Taken together, our results reveal that chronic upregulation of the HBP under hemodynamic stress induces pathological cardiac hypertrophy and heart failure through persistent activation of mTOR.

B38-CAP is a bacteria-derived ACE2-like enzyme that suppresses hypertension and cardiac dysfunction

Angiotensin-converting enzyme 2 (ACE2) is critically involved in cardiovascular physiology and pathology, and is currently clinically evaluated to treat acute lung failure. Here we show that the B38-CAP, a carboxypeptidase derived from Paenibacillus sp. B38, is an ACE2-like enzyme to decrease angiotensin II levels in mice. In protein 3D structure analysis, B38-CAP homolog shares structural similarity to mammalian ACE2 with low sequence identity. In vitro, recombinant B38-CAP protein catalyzed the conversion of angiotensin II to angiotensin 1–7, as well as other known ACE2 target peptides. Treatment with B38-CAP suppressed angiotensin II-induced hypertension, cardiac hypertrophy, and fibrosis in mice. Moreover, B38-CAP inhibited pressure overload-induced pathological hypertrophy, myocardial fibrosis, and cardiac dysfunction in mice. Our data identify the bacterial B38-CAP as an ACE2-like carboxypeptidase, indicating that evolution has shaped a bacterial carboxypeptidase to a human ACE2-like enzyme. Bacterial engineering could be utilized to design improved protein drugs for hypertension and heart failure.

Fibroblast growth factor-inducible 14 mediates macrophage infiltration in heart to promote pressure overload-induced cardiac dysfunction

AimsHeart failure (HF) is characterized by compromised cardiac structure and function. Previous work has identified a link between upregulation of pro-inflammatory cytokines and HF. Tumor necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK) is a pro-inflammatory cytokine, which binds to fibroblast growth factor inducible 14 (Fn14), a ubiquitously expressed cell-surface receptor. The objective of this study was to investigate the role of TWEAK/Fn14 pathway in promoting cardiac inflammation under non ischemic stress conditions. Main methodsWild type (WT) and Fn14 knock out (Fn14−/−) mice were subjected to pressure overload [transaortic constriction (TAC)] for 1 or 6 weeks. A subset of WT TAC animals were treated with the Fn14 antagonist L524-0366. Cardiac function was measured by echocardiography. Cardiac fibrosis and macrophage infiltration were quantified using immunohistochemistry and flow cytometry, respectively. Cardiac fibroblasts were isolated for quantifying TWEAK-induced chemokine release. Key findingsFn14−/− mice displayed improved cardiac function, reduced fibrosis and lower macrophage infiltration in heart compared to WT following TAC. L524-0366 mitigated maladaptive remodeling with TAC. TWEAK induced secretion of the pro-inflammatory chemokine, monocyte chemoattractant protein 1 from WT but not Fn14−/− fibroblasts in vitro, in part through activation of non-canonical NF-κB signaling. Finally, Fn14 expression was increased in mouse following TAC and in human failing hearts. SignificanceOur findings support an important role for the TWEAK/Fn14 promoting macrophage infiltration and fibrosis in heart under non-ischemic stress, with potential for therapeutic intervention to improve cardiac function in the setting of HF.

TASK-1 and TASK-3 channels modulate pressure overload-induced cardiac remodeling and dysfunction.

Tandem pore domain acid-sensitive K+ (TASK) channels are present in cardiac tissue; however, their contribution to cardiac pathophysiology is not well understood. Here, we investigate the role of TASK-1 and TASK-3 in the pathogenesis of cardiac dysfunction using both human tissue and mouse models of genetic TASK channel loss of function. Compared with normal human cardiac tissue, TASK-1 gene expression is reduced in association with either cardiac hypertrophy alone or combined cardiac hypertrophy and heart failure. In a pressure overload cardiomyopathy model, TASK-1 global knockout (TASK-1 KO) mice have both reduced cardiac hypertrophy and preserved cardiac function compared with wild-type mice. In contrast to the TASK-1 KO mouse pressure overload response, TASK-3 global knockout (TASK-3 KO) mice develop cardiac hypertrophy and a delayed onset of cardiac dysfunction compared with wild-type mice. The cardioprotective effects observed in TASK-1 KO mice are associated with pressure overload-induced augmentation of AKT phosphorylation and peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) expression, with consequent augmentation of cardiac energetics and fatty acid oxidation. The protective effects of TASK-1 loss of function are associated with an enhancement of physiologic hypertrophic signaling and preserved metabolic functions. These findings may provide a rationale for TASK-1 channel inhibition in the treatment of cardiac dysfunction.NEW & NOTEWORTHY The role of tandem pore domain acid-sensitive K+ (TASK) channels in cardiac function is not well understood. This study demonstrates that TASK channel gene expression is associated with the onset of human cardiac hypertrophy and heart failure. TASK-1 and TASK-3 strongly affect the development of pressure overload cardiomyopathies in genetic models of TASK-1 and TASK-3 loss of function. The effects of TASK-1 loss of function were associated with enhanced AKT phosphorylation and expression of peroxisome proliferator-activated receptor-γ coactivator-1 (PGC-1) transcription factor. These data suggest that TASK channels influence the development of cardiac hypertrophy and dysfunction in response to injury.

Sodium (±)-5-bromo-2-(α-hydroxypentyl) benzoate ameliorates pressure overload-induced cardiac hypertrophy and dysfunction through inhibiting autophagy.

Sodium (±)‐5‐bromo‐2‐(a‐hydroxypentyl) benzoate (generic name: brozopine, BZP) has been reported to protect against stroke‐induced brain injury and was approved for Phase II clinical trials for treatment of stroke‐related brain damage by the China Food and Drug Administration (CFDA). However, the role of BZP in cardiac diseases, especially in pressure overload‐induced cardiac hypertrophy and heart failure, remains to be investigated. In the present study, angiotensin II stimulation and transverse aortic constriction were employed to induce cardiomyocyte hypertrophy in vitro and in vivo, respectively, prior to the assessment of myocardial cell autophagy. We observed that BZP administration ameliorated cardiomyocyte hypertrophy and excessive autophagic activity. Further results indicated that AMP‐activated protein kinase (AMPK)‐mediated activation of the mammalian target of rapamycin (mTOR) pathway likely played a role in regulation of autophagy by BZP after Ang II stimulation. The activation of AMPK with metformin reversed the BZP‐induced suppression of autophagy. Finally, for the first time, we demonstrated that BZP could protect the heart from pressure overload‐induced hypertrophy and dysfunction, and this effect is associated with its inhibition of maladaptive cardiomyocyte autophagy through the AMPK‐mTOR signalling pathway. These findings indicated that BZP may serve as a promising compound for treatment of pressure overload‐induced cardiac remodelling and heart failure.

Wnt5a-Mediated Neutrophil Recruitment Has an Obligatory Role in Pressure Overload–Induced Cardiac Dysfunction

Although the complex roles of macrophages in myocardial injury are widely appreciated, the function of neutrophils in nonischemic cardiac pathology has received relatively little attention. To examine the regulation and function of neutrophils in pressure overload-induced cardiac hypertrophy, mice underwent treatment with Ly6G antibody to deplete neutrophils and then were subjected to transverse aortic constriction. Neutrophil depletion diminished transverse aortic constriction-induced hypertrophy and inflammation and preserved cardiac function. Myeloid deficiency of Wnt5a, a noncanonical Wnt, suppressed neutrophil infiltration to the hearts of transverse aortic constriction-treated mice and produced a phenotype that was similar to the neutropenic conditions. Conversely, mice overexpressing Wnt5a in myeloid cells displayed greater hypertrophic growth, inflammation, and cardiac dysfunction. Neutrophil depletion reversed the Wnt5a overexpression-induced cardiac pathology and eliminated differences in cardiac parameters between wild-type and myeloid-specific Wnt5a transgenic mice. These findings reveal that Wnt5a-regulated neutrophil infiltration has a critical role in pressure overload-induced heart failure.

Involvement of microRNA-23b-5p in the promotion of cardiac hypertrophy and dysfunction via the HMGB2 signaling pathway

The processes involved in the progression of myocardial cells towards hypertrophy and its gradual transition to heart failure represent a multifactorial health disorder. The aim of this study was to identify the molecular mechanism(s) underlying the abnormal overexpression of miR-23b-5p and its involvement in the promotion of cardiac hypertrophy and dysfunction via HMGB2. A type 9 recombinant adeno-associated virus (rAAV9) was employed to manipulate miR-23b-5p expression under conditions of thoracic aortic constriction (TAC)-/angiotensin-II (Ang-II)-induced cardiac dysfunction. Cardiac structures and functions were assessed by echocardiography and invasive pressure-volume analysis. HMGB2 expression under conditions of cardiac hypertrophy was detected by western blotting. The biochemical relationship between miR-23b-5p and HMGB2 was verified using a luciferase reporter vector, lentiviral construct comprising the miR-23b-5p mimic sequence, and microRNA inhibitor (miR-inhibitor). The expression levels of miR-23b-5p were increased in the hearts under conditions of both Ang-II- and TAC-induced cardiac hypertrophy. The results of the luciferase activity analysis showed that HMGB2 is a supposed target of miR-23b-5p. miR-23b-5p overexpression in vivo aggravated pressure overload-induced cardiac hypertrophy and dysfunction, whereas the miR-inhibitor increased HMGB2 expression and reversed these effects. In the present study, we observed that miR-23b-5p mediates and is involved in the aggravation of cardiac hypertrophy and dysfunction via the HMGB2 signaling pathway.

CXCR3 regulates CD4+ T cell cardiotropism in pressure overload-induced cardiac dysfunction.

Heart failure (HF) is associated in humans and mice with increased circulating levels of CXCL9 and CXCL10, chemokine ligands of the CXCR3 receptor, predominantly expressed on CD4+ Th1 cells. Chemokine engagement of receptors is required for T cell integrin activation and recruitment to sites of inflammation. Th1 cells drive adverse cardiac remodeling in pressure overload-induced cardiac dysfunction, and mice lacking the integrin ligand ICAM-1 show defective T cell recruitment to the heart. Here, we show that CXCR3+ T cells infiltrate the heart in humans and mice with pressure overload-induced cardiac dysfunction. Genetic deletion of CXCR3 disrupts CD4+ T cell heart infiltration and prevents adverse cardiac remodeling. We demonstrate that cardiac fibroblasts and cardiac myeloid cells that include resident and infiltrated macrophages are the source of CXCL9 and CXCL10, which mechanistically promote Th1 cell adhesion to ICAM-1 under shear conditions in a CXCR3-dependent manner. To our knowledge, our findings identify a previously unrecognized role for CXCR3 in Th1 cell recruitment into the heart in pressure overload-induced cardiac dysfunction.

Lin28a Regulates Pathological Cardiac Hypertrophic Growth through Pck2‐mediated Enhancement of Anabolic Synthesis

During pathological hypertrophy, the heart undergoes extensive metabolic changes prior to the onset of structural remodeling, yet, it remains largely unexplored whether and how this metabolic remodeling could contribute to cardiac hypertrophic growth. Here, we identified the RNA‐binding protein Lin28a as a critical regulator of pathological cardiac hypertrophy and metabolic re‐patterning. Cardiac‐specific deletion of Lin28a attenuated pressure overload‐induced hypertrophic growth, cardiac dysfunction and alterations in cardiac transcriptome. Mechanistically, Lin28a directly bound to mitochondrial phosphoenolpyruvate carboxykinase 2 (Pck2) mRNA and positively modulated its level. Manipulation of Pck2 expression phenocopied hypertrophic growth phenotypes of manipulating Lin28a expression. Epistatic analysis demonstrated that Pck2 mediated, at least in part, the role of Lin28a in cardiac hypertrophic growth. Furthermore, metabolomic analyses highlighted role for Lin28a and Pck2 in promoting cardiac anabolic biosynthesis required for cell growth. Thus, our study revealed a critical role of Lin28a in the regulation of pathological cardiac hypertrophic growth through Pck2‐mediated regulation of cardiac metabolism.Support or Funding InformationThis study was supported by AHA 13SDG17060010, Ellison Medical Foundation (EMF) AGNS‐13 1064‐, and NIH/NHLBI R01HL128331 to L.Q., NIH/NHLBI R00 HL109079, R56HL133081, and American Heart Association (AHA) 15GRNT25530005 to J.L.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Rituximab prevents and reverses cardiac remodeling by depressing B cell function in mice

B lymphocytes have been shown to contribute to autoimmune diseases via producing antibodies and proinflammatory cytokines. Depletion of B cells by blocking CD20 can inhibit these diseases. Here we examined whether an antibody against CD20, rituximab (RTX) (Rituxan@), used clinically in oncology could have similar anti-inflammatory effects in cardiac remodeling and heart failure (HF) in mice. Cardiac remodeling was established by pressure overload induced by transverse aortic constriction (TAC). Wild-type (WT) male C57BL/6 J mice were subjected to pressure overload by using transverse aortic constriction and then received RTX for 4 weeks. Administration of RTX markedly improves in vivo heart function, and suppressed heart chamber dilation, myocyte hypertrophy, fibrosis and oxidative stress in mice after TAC operation. RTX treatment also reversed established hypertrophic remodeling induced by TAC. Moreover, TAC-induced activation of multiple signaling pathways including calcineurin A, ERK1/2, STAT3, TGFβ/Smad2/3 and IKKα/β/NF-kB were remarkably attenuated in RTX-treated hearts compared with controls. These inhibitory effects of RTX were associated with inhibition of proinflammatory cytokine expression and Th2 cytokine-mediated IgG production from B cells. In conclusion, this study identifies that administration of RTX can inhibit pressure overload-induced cardiac remodeling and dysfunction in mice, and suggest that RTX may be a promising drug for treating hypertrophic disease.

Role of the PRC2-Six1-miR-25 signaling axis in heart failure

The reduced expression of cardiac sarco-endoplasmic reticulum Ca2+ ATPase (SERCA2a) is a hallmark of heart failure. We previously showed that miR-25 is a crucial transcriptional regulator of SERCA2a in the heart. However, the precise mechanism of cardiac miR-25 regulation is largely unknown. Literatures suggested that miR-25 is regulated by the transcriptional co-factor, sine oculis homeobox homolog 1 (Six1), which in turn is epigenetically regulated by polycomb repressive complex 2 (PRC 2) in cardiac progenitor cells. Therefore, we aimed to investigate whether Six1 and PRC2 are indeed involved in the regulation of the miR-25 level in the setting of heart failure. Six1 was up-regulated in the failing hearts of humans and mice. Overexpression of Six1 led to adverse cardiac remodeling, whereas knock-down of Six1 attenuated pressure overload-induced cardiac dysfunction. The adverse effects of Six1 were ameliorated by knock-down of miR-25. The epigenetic repression on the Six1 promoter by PRC2 was significantly reduced in failing hearts. Epigenetic repression of Six1 is relieved through a reduction of PRC2 activity in heart failure. Six1 up-regulates miR-25, which is followed by reduction of cardiac SERCA2a expression. Collectively, these data showed that the PRC2-Six1-miR-25 signaling axis is involved in heart failure. Our finding introduces new insight into potential treatments of heart failure.

Novel role of mitochondrial GTPases 1 in pathological cardiac hypertrophy

While most mitochondrial proteins are encoded in the nucleus and translated on cytosolic/endoplasmic reticulum ribosomes, proteins encoded by mitochondrial DNA are translated on mitochondrial ribosomes. Mitochondrial GTPases 1 (MTG1) regulates mitochondrial ribosome assembly and translation, but its impact on cardiac adaptation to stress is unknown. Here, we found that MTG1 is dramatically elevated in hearts of dilated cardiomyopathy patients and in mice exposed to left ventricular pressure overload (AB). To examine the role of MTG1 in cardiac hypertrophy and heart failure, MTG1 loss/gain of function studies were performed in cultured cardiomyocytes and mice exposed to hypertrophic stress. MTG1 shRNA and adenoviral overexpression studies indicated that MTG1 expression attenuates angiotensin II-induced hypertrophy in cultured cardiomyocytes, while MTG1 KO mice exhibited no observable cardiac phenotype under basal conditions. MTG1 deficiency significantly exacerbated AB-induced cardiac hypertrophy, expression of hypertrophic stress markers, fibrosis, and LV dysfunction in comparison to WT mice. Conversely, transgenic cardiac MTG1 expression attenuated AB-induced hypertrophy and LV dysfunction. Mechanistically, MTG1 preserved mitochondrial respiratory chain complex activity during pressure overload, which further attenuated ROS generation. Moreover, we demonstrated that TAK1, P38 and JNK1/2 activity is downregulated in the MTG1 overexpression group. Importantly, dampening oxidative stress with N-acetylcysteine (NAC) lowered hypertrophy in MTG1 KO to WT levels. Collectively, our data indicate that MTG1 protects against pressure overload-induced cardiac hypertrophy and dysfunction by preserving mitochondrial function and reducing oxidative stress and downstream TAK1 stress signaling.

Sensitization of the Angiotensin II AT1 Receptor Contributes to RKIP-Induced Symptoms of Heart Failure.

Inhibition of the G-protein-coupled receptor kinase 2 (GRK2) is an emerging treatment approach for heart failure. Therefore, cardio-protective mechanisms induced by GRK2 inhibition are under investigation. We compared two different GRK2 inhibitors, i.e., (i) the dual-specific GRK2 and raf kinase inhibitor protein, RKIP, and (ii) the dominant-negative GRK2-K220R mutant. We found that RKIP induced a strong sensitization of Gq/11-dependent, heart failure-promoting angiotensin II AT1 receptor signaling. The AT1-sensitizing function of RKIP was mediated by the RKIP-GRK2 interaction because the RKIP-S153V mutant, which does not interact with GRK2, had no effect on AT1-stimulated signaling. In contrast, GRK2-K220R significantly inhibited the AT1-stimulated signal. The in vivo relevance of these major differences between two different approaches of GRK2 inhibition was analyzed by generation of transgenic mice with myocardium-specific expression of RKIP and GRK2-K220R. Our results showed that a moderately increased cardiac protein level of RKIP was sufficient to induce major symptoms of heart failure in aged, 8-months-old RKIP-transgenic mice in two different genetic backgrounds. In contrast, GRK2-K220R protected against chronic pressure overload-induced cardiac dysfunction. The AT1 receptor contributed to RKIP-induced heart failure because treatment with the AT1 receptor antagonist, losartan, retarded symptoms of heart failure in RKIP-transgenic mice. Thus, sensitization of the heart failure-promoting AT1 receptor by the RKIP-GRK2 interaction contributes to heart failure whereas dominant-negative GRK2-K220R is cardioprotective. Because RKIP is up-regulated on cardiac biopsy specimens of heart failure patients, the deduced heart failure-promoting mechanism of RKIP could also be relevant for the human disease.

Mitoquinone ameliorates pressure overload-induced cardiac fibrosis and left ventricular dysfunction in mice

Increasing evidence indicates that mitochondrial-associated redox signaling contributes to the pathophysiology of heart failure (HF). The mitochondrial-targeted antioxidant, mitoquinone (MitoQ), is capable of modifying mitochondrial signaling and has shown beneficial effects on HF-dependent mitochondrial dysfunction. However, the potential therapeutic impact of MitoQ-based mitochondrial therapies for HF in response to pressure overload is reliant upon demonstration of improved cardiac contractile function and suppression of deleterious cardiac remodeling. Using a new (patho)physiologically relevant model of pressure overload-induced HF we tested the hypothesis that MitoQ is capable of ameliorating cardiac contractile dysfunction and suppressing fibrosis. To test this C57BL/6J mice were subjected to left ventricular (LV) pressure overload by ascending aortic constriction (AAC) followed by MitoQ treatment (2 µmol) for 7 consecutive days. Doppler echocardiography showed that AAC caused severe LV dysfunction and hypertrophic remodeling. MitoQ attenuated pressure overload-induced apoptosis, hypertrophic remodeling, fibrosis and LV dysfunction. Profibrogenic transforming growth factor-β1 (TGF-β1) and NADPH oxidase 4 (NOX4, a major modulator of fibrosis related redox signaling) expression increased markedly after AAC. MitoQ blunted TGF-β1 and NOX4 upregulation and the downstream ACC-dependent fibrotic gene expressions. In addition, MitoQ prevented Nrf2 downregulation and activation of TGF-β1-mediated profibrogenic signaling in cardiac fibroblasts (CF). Finally, MitoQ ameliorated the dysregulation of cardiac remodeling-associated long noncoding RNAs (lncRNAs) in AAC myocardium, phenylephrine-treated cardiomyocytes, and TGF-β1-treated CF. The present study demonstrates for the first time that MitoQ improves cardiac hypertrophic remodeling, fibrosis, LV dysfunction and dysregulation of lncRNAs in pressure overload hearts, by inhibiting the interplay between TGF-β1 and mitochondrial associated redox signaling.

Rosmarinic acid alleviates cardiomyocyte apoptosis via cardiac fibroblast in doxorubicin-induced cardiotoxicity.

Cardiomyocyte apoptosis is a key event in the process of doxorubicin (DOX)-induced cardiotoxicity. Our previous study found that rosmarinic acid (RA) could attenuate pressure overload-induced cardiac dysfunction via cardiac fibroblasts (CFs), however its effect in DOX-induced cardiotoxicity remains unknown. In the present study, mice were subjected to a single intraperitoneal injection of DOX (15mg/kg) to generate DOX-induced cardiotoxicity. Histological examination, echocardiography, and molecular markers were used to evaluate the effects of RA. Neonatal rat cardiomyocytes (CMs) and CFs were used to verify the protective effect of RA in vitro. Conditioned medium derived from RA-treated CFs were prepared to illustrate the effect of RA on paracrine interplay between CFs and CMs. We found that RA significantly alleviated DOX-induced cardiomyocyte apoptosis and cardiac dysfunction in vivo, which, however, had almost negligible beneficial effect on DOX directly induced cardiomyocyte apoptosis in vitro. Mechanistically, CFs-derived Fas L was responsible for DOX-induced cardiomyocyte apoptosis, and RA treatment could decrease Fas L expression in CFs and its release to the conditioned medium by suppressing nuclear factor of activated T cells (NFAT) activation and metalloproteinase 7 (MMP7) expression, and exerted the anti-apoptotic effect on CMs via CFs. Ionomycin, and activator of NFAT, abrogated RA-mediated protective effect on cardiomyocyte apoptosis and cardiac dysfunction. In summary, RA alleviated cardiomyocyte apoptosis by inhibiting the expression and release of Fas L in CFs via a paracrine manner, moreover, NFAT as well as MMP7 inhibition were responsible for the suppression of Fas L. RA could be a powerful new therapeutic agent to mitigate cardiomyocyte apoptosis, thereby improving DOX-induced cardiotoxicity.

Comparison of different chemically modified inhibitors of miR-199b in vivo

MicroRNAs (miRNAs) have recently received great attention for their regulatory roles in diverse cellular processes and for their contribution to several human pathologies. Modulation of miRNAs in vivo provides beneficial therapeutic strategies for the treatment of many diseases, as evidenced by various preclinical studies. However, specific issues regarding the in vivo use of miRNA inhibitors (antimiRs) such as organ-specific delivery, optimal dosing and formulation of the best chemistry to obtain efficient miRNA inhibition remain to be addressed. Here, we aimed at comparing the in vivo efficacy of different chemistry-based antimiR oligonucleotides to inhibit cardiac expression of miR-199b, a highly promising therapeutic target for the treatment of pressure overload-induced cardiac dysfunction. For this purpose, four different designs of oligonucleotides to inhibit miR-199b were initially developed. Systemic administration to wildtype mice on three consecutive days was followed by organ harvesting, seven days after the first injection, in order to quantify the dose-dependent changes in miR-199b expression levels. When comparing the efficiency of each inhibitor at the highest applied dose we observed that the antagomir was the only inhibitor inducing complete inhibition of miR-199b in the heart. LNA reduced expression in the heart by 50 percent while the Zen-AMO and F/MOE chemistries failed to repress miR-199b expression in the heart at any given dose, in vivo. Further optimization was achieved by subjecting the antagomir and LNA nucleotides to additional chemical modifications. Interestingly, antagomir modification by replacing the cholesterol moiety from the 3′ to the 5′ end of the molecule significantly improved the inhibitory capacity, as reflected by a 75 percent downregulation of miR-199b expression already at a concentration of 5 mg/kg/day. Similar results could be obtained with a LNA-RNA molecule but upon administration of 80 mg/kg/day. These findings show that, from all the chemistries tested by us, an antagomir carrying the cholesterol group at the 5′ end was the most efficient inhibitor of miR-199b in the heart, in vivo. Moreover, our data also emphasize the importance of chemistry optimization and best dose range finding to achieve the greatest efficacy in miRNA inhibition in vivo.

Focal selective chemo-ablation of spinal cardiac afferent nerve by resiniferatoxin protects the heart from pressure overload-induced hypertrophy

Resiniferatoxin (RTX), a selective transient receptor potential vanilloid 1 (TRPV1) receptor agonist, can eliminate TRPV1+ primary sensory afferents and blunt cardiac sympathetic afferent reflex for a relatively long period. The present study determined the effects of intrathecal RTX administration on transverse aortic constriction (TAC)-induced cardiac dysfunction and cardiac remodeling in rats. Five days before TAC, RTX (2 μg/10 μl) was injected intrathecally into the T2/T3 interspace of rats. Cardiac sympathetic nerve activities (CSNAs) and cardiac structure and function were determined eight weeks after TAC. Intrathecal RTX administration abolished TRPV1 expression in the dorsal horn and reduced over-activated CSNA in the TAC rat model. Hemodynamic analysis revealed that RTX reduced left ventricular end-diastolic pressure, indicating the improvement of cardiac compliance. Histologic analysis, real-time reverse transcription-polymerase chain reaction, and Western blots showed that RTX prevented TAC-induced cardiac hypertrophy, cardiac fibrosis, and cardiac apoptosis and reduced the expression of apoptotic proteins and myocardial mRNAs. In conclusion, these results demonstrate that focal chemo-ablation of TRPV1+ afferents in the spinal cord protects the heart from pressure overload-induced cardiac remodeling and cardiac dysfunction, which suggest a novel promising therapeutic method for cardiac hypertrophy and diastolic dysfunction.

The two-pore domain potassium channel TREK-1 mediates cardiac fibrosis and diastolic dysfunction.

Cardiac two-pore domain potassium channels (K2P) exist in organisms from Drosophila to humans; however, their role in cardiac function is not known. We identified a K2P gene, CG8713 (sandman), in a Drosophila genetic screen and show that sandman is critical to cardiac function. Mice lacking an ortholog of sandman, TWIK-related potassium channel (TREK-1, also known Kcnk2), exhibit exaggerated pressure overload-induced concentric hypertrophy and alterations in fetal gene expression, yet retain preserved systolic and diastolic cardiac function. While cardiomyocyte-specific deletion of TREK-1 in response to in vivo pressure overload resulted in cardiac dysfunction, TREK-1 deletion in fibroblasts prevented deterioration in cardiac function. The absence of pressure overload-induced dysfunction in TREK-1-KO mice was associated with diminished cardiac fibrosis and reduced activation of JNK in cardiomyocytes and fibroblasts. These findings indicate a central role for cardiac fibroblast TREK-1 in the pathogenesis of pressure overload-induced cardiac dysfunction and serve as a conceptual basis for its inhibition as a potential therapy.

Ufm1-Specific Ligase Ufl1 Regulates Endoplasmic Reticulum Homeostasis and Protects Against Heart Failure.

Defects in protein homeostasis are sufficient to provoke cardiac remodeling and dysfunction. Although posttranslational modifications by ubiquitin and ubiquitin-like proteins are emerging as an important regulatory mechanism of protein function, the role of Ufm1 (ubiquitin-fold modifier 1)-a novel ubiquitin-like protein-has not been explored in either the normal or stressed heart. Western blotting revealed that Ufl1 (Ufm1-specific E3 ligase 1)-an enzyme essential for Ufm1 modification-was increased in hypertrophic mouse hearts but reduced in the failing hearts of patients with dilated cardiomyopathy. To determine the functional role of Ufl1 in the heart, we generated a cardiac-specific knockout mouse and showed that Ufl1-deficient mice developed age-dependent cardiomyopathy and heart failure, as indicated by elevated cardiac fetal gene expression, increased fibrosis, and impaired cardiac contractility. When challenged with pressure overload, Ufl1-deficient hearts exhibited remarkably greater hypertrophy, exacerbated fibrosis, and worsened cardiac contractility compared with control counterparts. Transcriptome analysis identified that genes associated with the endoplasmic reticulum (ER) function were dysregulated in Ufl1-deficient hearts. Biochemical analysis revealed that excessive ER stress preceded and deteriorated along with the development of cardiomyopathy in Ufl1-deficient hearts. Mechanistically, Ufl1 depletion impaired (PKR-like ER-resident kinase) signaling and aggravated cardiomyocyte cell death after ER stress. Administration of the chemical ER chaperone tauroursodeoxycholic acid to Ufl1-deficient mice alleviated ER stress and attenuated pressure overload-induced cardiac dysfunction. Our results advance a novel concept that the Ufm1 system is essential for cardiac homeostasis through regulation of ER function and that upregulation of myocardial Ufl1 could be protective against heart failure.