JMJD6 protects against isoproterenol-induced cardiac hypertrophy via inhibition of NF-κB activation by demethylating R149 of the p65 subunit.

Histone modification plays an important role in pathological cardiac hypertrophy and heart failure. In this study we investigated the role of a histone arginine demethylase, Jumonji C domain-containing protein 6 (JMJD6) in pathological cardiac hypertrophy. Cardiac hypertrophy was induced in rats by subcutaneous injection of isoproterenol (ISO, 1.2 mg·kg-1·d-1) for a week. At the end of the experiment, the rats underwent echocardiography, followed by euthanasia and heart collection. We found that JMJD6 levels were compensatorily increased in ISO-induced hypertrophic cardiac tissues, but reduced in patients with heart failure with reduced ejection fraction (HFrEF). Furthermore, we demonstrated that JMJD6 overexpression significantly attenuated ISO-induced hypertrophy in neonatal rat cardiomyocytes (NRCMs) evidenced by the decreased cardiomyocyte surface area and hypertrophic genes expression. Cardiac-specific JMJD6 overexpression in rats protected the hearts against ISO-induced cardiac hypertrophy and fibrosis, and rescued cardiac function. Conversely, depletion of JMJD6 by single-guide RNA (sgRNA) exacerbated ISO-induced hypertrophic responses in NRCMs. We revealed that JMJD6 interacted with NF-κB p65 in cytoplasm and reduced nuclear levels of p65 under hypertrophic stimulation in vivo and in vitro. Mechanistically, JMJD6 bound to p65 and demethylated p65 at the R149 residue to inhibit the nuclear translocation of p65, thus inactivating NF-κB signaling and protecting against pathological cardiac hypertrophy. In addition, we found that JMJD6 demethylated histone H3R8, which might be a new histone substrate of JMJD6. These results suggest that JMJD6 may be a potential target for therapeutic interventions in cardiac hypertrophy and heart failure.

MicroRNA-214 contributes to Ang II-induced cardiac hypertrophy by targeting SIRT3 to provoke mitochondrial malfunction.

Reduction of expression and activity of sirtuin 3 (SIRT3) contributes to the pathogenesis of cardiomyopathy via inducing mitochondrial injury and energy metabolism disorder. However, development of effective ways and agents to modulate SIRT3 remains a big challenge. In this study we explored the upstream suppressor of SIRT3 in angiotensin II (Ang II)-induced cardiac hypertrophy in mice. We first found that SIRT3 deficiency exacerbated Ang II-induced cardiac hypertrophy, and resulted in the development of spontaneous heart failure. Since miRNAs play crucial roles in the pathogenesis of cardiac hypertrophy, we performed miRNA sequencing on myocardium tissues from Ang II-infused Sirt3-/- and wild type mice, and identified microRNA-214 (miR-214) was significantly up-regulated in Ang II-infused mice. Similar results were also obtained in Ang II-treated neonatal mouse cardiomyocytes (NMCMs). Using dual-luciferase reporter assay we demonstrated that SIRT3 was a direct target of miR-214. Overexpression of miR-214 in vitro and in vivo decreased the expression of SIRT3, which resulted in extensive mitochondrial damages, thereby facilitating the onset of hypertrophy. In contrast, knockdown of miR-214 counteracted Ang II-induced detrimental effects via restoring SIRT3, and ameliorated mitochondrial morphology and respiratory activity. Collectively, these results demonstrate that miR-214 participates in Ang II-induced cardiac hypertrophy by directly suppressing SIRT3, and subsequently leading to mitochondrial malfunction, suggesting the potential of miR-214 as a promising intervention target for antihypertrophic therapy.

sFRP1 protects H9c2 cardiac myoblasts from doxorubicin-induced apoptosis by inhibiting the Wnt/PCP-JNK pathway.

Doxorubicin (Dox) is an effective chemotherapy drug against a wide range of cancers, including both hematological and solid tumors. However, the serious cardiotoxic effect restricted its clinical application. We previously have illuminated the protective role of canonical Wnt/ß-catenin signaling in Dox-induced cardiotoxicity. Secreted frizzled-related protein 1 (sFRP1) is one of the endogenous inhibitors of both canonical and noncanonical Wnt signaling. In this study, we investigated the relationship between sFRP1 and noncanonical Wnt/PCP-JNK (Wnt/planar cell polarity-c-Jun N-terminal kinase) pathway in Dox-induced cardiotoxicity in vitro and in vivo. We showed that treatment of H9c2 cardiac myoblasts with Dox (1 µM) time-dependently suppressed cell viability accompanied by significantly decreased sFRP1 protein level and increased Wnt/PCP-JNK signaling. Pretreatment with SP600125, the Wnt/PCP-JNK signaling inhibitor, attenuated Dox-induced apoptosis of H9c2 cells. Overexpression of sFRP1 protected H9c2 cells from Dox-induced apoptosis by inhibiting the Wnt/PCP-JNK pathway. After intraperitoneal injection of a cumulative dose of 15 mg/kg Dox, rats displayed significant cardiac dysfunction; their heart showed inhibited Wnt/ß-catenin signaling and activated Wnt/PCP-JNK signaling. These results suggest that sFRP1 may be a novel target for Dox-induced cardiotoxicity.