Pulmonary arterial hypertension (PAH) is a fatal disease whose molecular mechanism is unknown. The trimethylation of lysine 36 on histone 3 (H3K36me3) catalyzed by SETD2 and the modification of N6-methyladenine (m6A) mRNA mediated by METTL14 play important roles in a variety of normal and pathological biological processes. However, the role of these epigenetic controls in the pathogenesis of PAH remains unclear. In this study, the expression of SETD2 and METTL14 was elevated in pulmonary artery smooth muscle cells (PASMCs) of hypoxia-induced PAH mice. We further constructed a mouse model with SETD2 specific knockout in smooth muscle cells (SETD2SM22α Cre). Our results suggest that the lack of SETD2 in SMCs protected mice from hypoxia-induced PAH and significantly reduced right ventricular systolic pressure (RVSP), right ventricular/left ventricular plus septum [RV/(LV+S)] weight ratio, and pulmonary median width. In addition, the absence of SETD2 in SMCs alleviates the level of METTL14 expression and the m6A RNA methylation level in PAH SMCs. These results obtained from mice suggest that strategies that target the inhibition of SETD2/METTL14 activity may be a viable treatment for PAH in a clinical setting.

Both the Notch1 and Keap1–Nrf2 signaling pathways have cardioprotective effects, but the role of Notch1–Nrf2 crosstalk in myocardial ischemia–reperfusion injury is unclear. In this study, we established hypoxia–reoxygenation in neonate rat myocardial cells and employed γ-secretase inhibitor and curcumin to inhibit and activate the Notch1 and Keap1–Nrf2 signaling pathways, respectively. We found that the combined action of the Notch1 and Keap1–Nrf2 signaling pathways significantly increased cardiomyocyte viability, inhibited cardiomyocyte apoptosis, reduced the formation of reactive oxygen species, and increased antioxidant activities. In conclusion, these findings suggest that Notch1–Nrf2 crosstalk exerts myocardial protection by reducing the formation of reactive oxygen species.

Background: Myocardial ischemia/reperfusion injury is associated with adverse cardiovascular outcomes after acute myocardial infarction. However, the molecular mechanism of ischemia/reperfusion injury remains unclear. Mitochondria dysfunction is a participant in and regulator of myocardial ischemia-reperfusion injury. However, the molecular mechanisms involved in this process are not yet fully understood. We previously reported that Notch1 can reduce mitochondrial lysis, reduce myocardial infarct size, and inhibit ventricular remodeling. Herein, we explore the role of the downstream target Notch1 in mitochondrial regulation. Methods: This study constructs an ischemic/reperfusion injury rat model and a hypoxia/reoxygenation cell model. The expression of PTEN is detected by real-time PCR, Western blot, and immunofluorescence staining. Cell viability is analyzed with CCK-8. Apoptosis level is detected via the TUNEL assay, and mitochondrial fission/fusion is analyzed with MitoTracker Green staining. Cardiac troponin I (cTnI), lactate dehydrogenase (LDH), superoxide dismutase (SOD), and CK levels of creatine kinase-MB (CK) are measured with ELISA kits. Results: We found that PETN-Pink1-Parkin signaling is inhibited by Notch1 I/R in injured neonatal cardiomyocytes and hearts, i.e., via the inhibition of mitochondrial dysfunction and fragmentation. With the recure of PTEN or Pink1, the protective effect of Notch1 was largely diminished. Conclusion: These results suggest that N1ICD acts protectively against ischemic reperfusion injury by suppressing PTEN-Pink1-mediated mitochondrial dysfunction and fragmentation.

Histone lysine methylation plays an important role in the regulation of ventricular remodelling. NSD2 is involved in many types of tumours through enhancing H3K36me2 expression. However, the role of NSD2 in the regulation of histone lysine methylation during ventricular remodelling remains unclear. In this study, we established cardiac hypertrophy model in C57BL/6 mice by transverse aortic constriction and found that histone lysine methylation participated in ventricular remodelling regulation via the up‐regulation of H3K27me2 and H3K36me2 expression. In addition, we constructed transgenic C57BL/6 mice with conditional knockout of NSD2 (NSD2^−/−) in the myocardium. NSD2^−/− C57BL/6 mice had milder ventricular remodelling and significantly improved cardiac function compared with wild‐type mice, and the expression of H3K36me2 but not H3K27me2 was down‐regulated. In conclusion, NSD2 promotes ventricular remodelling mediated by the regulation of H3K36me2.

Increased expression and activity of cardiac and circulating cathepsin D and soluble fms‐like tyrosine kinase‐1 (sFlt‐1) have been demonstrated to induce and promote peripartum cardiomyopathy (PPCM) via promoting cleavage of 23‐kD prolactin (PRL) to 16‐kD PRL and neutralizing vascular endothelial growth factor (VEGF), respectively. We hypothesized that activation of Hes1 is proposed to suppress cathepsin D via activating Stat3, leading to alleviated development of PPCM. In the present study, we aimed to investigate the role of Notch1/Hes1 pathway in PPCM. Pregnant mice between prenatal 3 days and postpartum 3 weeks were fed with LY‐411575 (a notch inhibitor, 10 mg/kg/d). Ventricular function and pathology were evaluated by echocardiography and histological analysis. Western blotting analysis was used to examine the expression at the protein level. The results found that inhibition of Notch1 significantly promoted postpartum ventricular dilatation, myocardial hypertrophy and myocardial interstitial fibrosis and suppressed myocardial angiogenesis. Western blotting analysis showed that inhibition of Notch1 markedly increased cathepsin D and sFlt‐1, reduced Hes1, phosphorylated Stat3 (p‐Stat3), VEGFA and PDGFB, and promoted cleavage of 23k‐D PRL to 16‐kD PRL. Collectively, inhibition of Notch1/Hes1 pathway induced and promoted PPCM via increasing the expressions of cathepsin D and sFlt‐1. Notch1/Hes1 was a promising target for prevention and therapeutic regimen of PPCM.

Pulmonary arterial hypertension (PAH) is characterized by pathological vascular remodeling driven by pulmonary artery smooth muscle cell (PASMC) proliferation. While METTL14-mediated N6-methyladenosine (m⁶A) RNA modification has been implicated in PAH, the upstream regulators and downstream effectors linking m⁶A to PASMC dysregulation remain unclear. This study investigates the role of SETD2, a histone methyltransferase, in driving METTL14-dependent m⁶A modifications to promote PAH via Piezo1 and transglutaminase 2 (TGM2). C57BL/6 mice were subjected to hypoxia, and pulmonary artery smooth muscle cells (PASMCs) were periodically stretched to establish PAH models in vivo and in vitro. The epigenetic regulation of METTL14 by SETD2-mediated H3K36me3 was investigated by chromatin immunoprecipitation (ChIP). Methylated RNA immunoprecipitation sequence (MeRIP-seq), RNA-seq, and dual-luciferase reporter gene data were used to determine whether METTL14 enhances the expression of Piezo1 in an m⁶A-dependent manner. To analyze comparisons between multiple datasets, one-way ANOVA was used. METTL14 overexpression increased PASMC proliferation by 1.45-fold (vs. controls) and elevated global m⁶A levels by 1.73-fold in total RNA and 1.43-fold in poly A + RNA. SETD2-driven H3K36me3 histone modification upregulated METTL14 expression by 1.76-fold, amplifying m⁶A deposition. In hypoxia-induced PAH mice, METTL14 overexpression exacerbated hemodynamic severity, increasing right ventricular systolic pressure (RVSP) by 29% and mean pulmonary arterial pressure (mPAP) by 33% (vs. hypoxia alone). SETD2 knockout in PASMCs reduced RVSP by 24%, mPAP by 28%, and pulmonary artery media thickness (PAMT) by 29%, while decreasing m⁶A levels by 48%. Piezo1 mRNA stability increased by 2.36-fold via METTL14-mediated m⁶A modification at adenosine 1080, elevating Piezo1 protein expression by 3.58-fold in PASMCs. Piezo1 overexpression increased intracellular Ca²⁺ influx, driving TGM2 activity by 1.79-fold and restoring PASMC proliferation despite SETD2 deficiency. This study identifies a novel SETD2/H3K36me3/METTL14/m⁶A axis that stabilizes Piezo1 mRNA, promoting Ca²⁺-dependent TGM2 activation and PASMC proliferation in PAH. Targeting this pathway-via SETD2, METTL14, or Piezo1 inhibition-may offer therapeutic potential to ameliorate vascular remodeling in PAH.