Proximal telomeric decompaction due to telomere shortening drives FOXC1-dependent myocardial senescence.

Telomeres, TTAGGGn DNA repeat sequences located at the ends of eukaryotic chromosomes, play a pivotal role in aging and are targets of DNA damage response. Although we and others have demonstrated presence of short telomeres in genetic cardiomyopathic and heart failure cardiomyocytes, little is known about the role of telomere lengths in cardiomyocyte. Here, we demonstrate that in heart failure patient cardiomyocytes, telomeres are shortened compared to healthy controls. We generated isogenic human induced pluripotent stem cell derived cardiomyocytes (hiPSC-CMs) with short telomeres (sTL-CMs) and normal telomeres (nTL-CMs) as model. Compared to nTL-CMs, short telomeres result in cardiac dysfunction and expression of senescent markers. Using Hi-C and RNASeq, we observe that short telomeres induced TAD insulation decrease near telomeric ends and this correlated with a transcription upregulation in sTL-CMs. FOXC1, a key transcription factor involved in early cardiogenesis, was upregulated in sTL-CMs and its protein levels were negatively correlated with telomere lengths in heart failure patients. Overexpression of FOXC1 induced hiPSC-CM aging, mitochondrial and contractile dysfunction; knockdown of FOXC1 rescued these phenotypes. Overall, the work presented demonstrate that increased chromatin accessibility due to telomere shortening resulted in the induction of FOXC1-dependent expression network responsible for contractile dysfunction and myocardial senescence.

The Imbalance of p53-Park7 Signaling Axis Induces Iron Homeostasis Dysfunction in Doxorubicin-Challenged Cardiomyocytes.

Doxorubicin (DOX)-induced cardiotoxicity (DoIC) is a major side effect for cancer patients. Recently, ferroptosis, triggered by iron overload, is demonstrated to play a role in DoIC. How iron homeostasis is dysregulated in DoIC remains to be elucidated. Here, the authors demonstrate that DOX challenge exhibits reduced contractile function and induction of ferroptosis-related phenotype in cardiomyocytes, evidenced by iron overload, lipid peroxide accumulation, and mitochondrial dysfunction. Compared to Ferric ammonium citrate (FAC) induced secondary iron overload, DOX-challenged cardiomyocytes show a dysfunction of iron homeostasis, with decreased cytoplasmic and mitochondrial iron-sulfur (FeS) cluster-mediated aconitase activity and abnormal expression of iron homeostasis-related proteins. Mechanistically, mass spectrometry analysis identified DOX-treatment induces p53-dependent degradation of Parkinsonism associated deglycase (Park7) which results in iron homeostasis dysregulation. Park7 counteracts iron overload by regulating iron regulatory protein family transcription while blocking mitochondrial iron uptake. Knockout of p53 or overexpression of Park7 in cardiomyocytes remarkably restores the activity of FeS cluster and iron homeostasis, inhibits ferroptosis, and rescues cardiac function in DOX treated animals. These results demonstrate that the iron homeostasis plays a key role in DoIC ferroptosis. Targeting of the newly identified p53-Park7 signaling axis may provide a new approach to prevent DoIC.

p53-Dependent Mitochondrial Compensation in Heart Failure With Preserved Ejection Fraction.

Background Heart failure with preserved ejection fraction (HFpEF) accounts for 50% of patients with heart failure. Clinically, HFpEF prevalence shows age and gender biases. Although the majority of patients with HFpEF are elderly, there is an emergence of young patients with HFpEF. A better understanding of the underlying pathogenic mechanism is urgently needed. Here, we aimed to determine the role of aging in the pathogenesis of HFpEF. Methods and Results HFpEF dietary regimen (high-fat diet + Nω-Nitro-L-arginine methyl ester hydrochloride) was used to induce HFpEF in wild type and telomerase RNA knockout mice (second-generation and third-generation telomerase RNA component knockout), an aging murine model. First, both male and female animals develop HFpEF equally. Second, cardiac wall thickening preceded diastolic dysfunction in all HFpEF animals. Third, accelerated HFpEF onset was observed in second-generation telomerase RNA component knockout (at 6 weeks) and third-generation telomerase RNA component knockout (at 4 weeks) compared with wild type (8 weeks). Fourth, we demonstrate that mitochondrial respiration transitioned from compensatory state (normal basal yet loss of maximal respiratory capacity) to dysfunction (loss of both basal and maximal respiratory capacity) in a p53 dosage dependent manner. Last, using myocardial-specific p53 knockout animals, we demonstrate that loss of p53 activation delays the development of HFpEF. Conclusions Here we demonstrate that p53 activation plays a role in the pathogenesis of HFpEF. We show that short telomere animals exhibit a basal level of p53 activation, mitochondria upregulate mtDNA encoded genes as a mean to compensate for blocked mitochondrial biogenesis, and loss of myocardial p53 delays HFpEF onset in high fat diet + Nω-Nitro-L-arginine methyl ester hydrochloride challenged murine model.

Generation of two induced pluripotent stem cell lines, SHIPMi001-A from a patient with hypertrophic cardiomyopathy caused by MYBPC3 gene mutation and SHIPMi002-A from a healthy male individual.

Hypertrophic cardiomyopathy is a hereditary disease with high incidence of sudden death and heart failure. Myosin-binding protein C3 (MYBPC3) is the most commonly mutation gene. Here, we report the establishment of two human induced pluripotent stem cell (iPSC) lines: one from a patient carrying a heterozygous c.1377delC mutation in MYBPC3 (c.1377delC: p.L460Wfs) and one from a healthy donor. The generated iPSC lines showed comparable pluripotent genes, demonstrated the capacity to differentiate into derivatives of all three germ layers and normal karyotypes. These lines are valuable for the mechanism research and drug development of hypertrophic cardiomyopathy.

Targeting of CAT and VCAM1 as Novel Therapeutic Targets for DMD Cardiomyopathy.

Duchenne muscular dystrophy (DMD) related cardiomyopathy is the leading cause of early mortality in DMD patients. There is an urgent need to gain a better understanding of the disease molecular pathogenesis and develop effective therapies to prevent the onset of heart failure. In the present study, we used DMD human induced pluripotent stem cells (DMD-hiPSCs) derived cardiomyocytes (CMs) as a platform to explore the active compounds in commonly used Chinese herbal medicine (CHM) herbs. Single CHM herb (DaH, ZK, and CQZ) reduced cell beating rate, decreased cellular ROS accumulation, and improved structure of DMD hiPSC-CMs. Cross-comparison of transcriptomic profiling data and active compound library identified nine active chemicals targeting ROS neutralizing Catalase (CAT) and structural protein vascular cell adhesion molecule 1 (VCAM1). Treatment with Quecetin, Kaempferol, and Vitamin C, targeting CAT, conferred ROS protection and improved contraction; treatment with Hesperidin and Allicin, targeting VCAM1, induced structure enhancement via induction of focal adhesion. Lastly, overexpression of CAT or VCAM1 in DMD hiPSC-CMs reconstituted efficacious effects and conferred increase in cardiomyocyte function. Together, our results provide a new insight in treating DMD cardiomyopathy via targeting of CAT and VCAM1, and serves as an example of translating Bed to Bench back to Bed using a muti-omics approach.

Catalytic oxidation removal of manganese from groundwater by iron-manganese co-oxide filter films under anaerobic conditions.

Although dissolved oxygen (DO) is a key factor for the removal of manganese (Mn) from aqueous solutions, this study presents an efficient method for Mn removal without any DO consumption. We demonstrate the feasibility of using an iron (Fe)-Mn co-oxide filter film to continuously remove Mn from groundwater under anaerobic conditions. A pilot-scale filter equipped with Fe-Mn co-oxide filter media (120 cm high) was adapted to explore the Mn removal performance under three DO levels (6-7 mg/L, 1-2 mg/L, and 0-0.2 mg/L). The Fe-Mn co-oxide filter exhibited a higher Mn removal performance under anaerobic conditions (no DO consumption) than under the other two DO conditions. The morphology, structure, and Mn valence changes of the Fe-Mn co-oxide filter film were studied using scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), Brunauer Emmett Teller (BET) theory, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The Fe-Mn co-oxide filter film under anaerobic conditions had a large contact surface area and large pore volume, and thus possessed more adsorption sites and reaction channels for Mn removal. By considering all of the characterization and reaction data reported in this study, we conclude that H2O ligands, hydrogen bonding (-OH), and vacant sites affect the transformation of Mn, thus play important roles in the continuous removal of Mn under anaerobic conditions. This discovery presents a new and effective approach for Mn removal during groundwater treatment.