Anti-signal recognition particle antibodies induce cardiac diastolic dysfunction via oxidative stress injury.

Objectives: Anti-signal recognition particle (SRP) antibodies, markers of immune-mediated necrotising myopathy, are reportedly related to cardiac involvement; however, whether they are pathogenic to the myocardium remains unclear. We aimed, therefore, to explore the pathogenicity of anti-SRP antibodies against the myocardium through in vivo and in vitro studies. Methods: Total immunoglobulin G (IgG), purified from patients with positive anti-SRP antibodies, was passively transferred into C57BL/6 mice. Cardiac function was evaluated via echocardiography and the ventricular pressure-volume loop; cardiac histological changes were analysed using haematoxylin-eosin staining, picrosirius red staining, immunofluorescence and immunohistochemistry. Additionally, reactive oxygen species (ROS) formation was evaluated by dihydroethidium (DHE) staining; mitochondrial morphology and function were evaluated using transmission electron microscopy and seahorse mitochondrial respiration assay, respectively. The myositis cohort at our centre was subsequently reviewed in terms of cardiac assessments. Results: After the passive transfer of total IgG from patients with positive anti-SRP antibodies, C57BL/6 mice developed significant left ventricular diastolic dysfunction (LVDD). Transcriptomic analysis and corresponding experiments revealed increased oxidative stress and mitochondrial damage in the hearts of the experimental mice. Cardiomyocytes exposed to anti-SRP-specific IgG, however, recovered normal mitochondrial metabolism after treatment with N-acetylcysteine, an ROS scavenger. Moreover, patients positive for anti-SRP antibodies manifested worse diastolic but equivalent systolic function compared to their counterparts after propensity score matching. Conclusion: Anti-SRP antibodies may play a pathogenic role in the development of LVDD by promoting ROS production and subsequent myocardial mitochondrial impairment. The inhibition of oxidative stress was effective in reversing anti-SRP antibody-induced LVDD.

Cellular Membrane-Engineered Nanovesicles as a Three-Stage Booster to Target the Lesion Core.

The lesion core is the area with the most serious injury and vigorous repair. Existing nanocarriers are difficult to break through the targeted delivery to the lesion core for precise treatment in the intracellular and extracellular microenvironment. Herein, a cellular membrane-engineered nanovesicle (CMEV) with a hierarchical structure is constructed using the double emulsion-extrusion method by integrating a neutrophil membrane, functional antibody, and gelled drug-loaded core as a three-stage booster to target the lesion core and deliver catestatin (CST), a small therapeutic peptide, for ischemic cardiomyopathy therapy. By coating the neutrophil membrane outside the shell, CMEV is endowed with the function of neutrophil-like migration to achieve the first stage of tissue targeting. Based on the specific anchoring to injured myocardium, a myosin light chain 3 (MLC3) antibody is embedded to fulfill the second stage of CMEV accumulation in the lesion core. The gelled core containing CST-sodium alginate (NaAlg) with a pH-responsive shell is prepared by ionic cross-linking to accomplish the third stage of precise CST administration. Triggered by the microenvironment, NaAlg electrostatically adheres to the lesion core for sustained release, enhancing the efficacy of CST in improving cardiomyocyte apoptosis, excessive fibrosis, macrophage polarization, and angiogenesis. Thus, the "three-stage booster" nanovesicle significantly ameliorates cardiac function and adverse remodeling to treat ischemic cardiomyopathy.

Catestatin Protects Against Diastolic Dysfunction by Attenuating Mitochondrial Reactive Oxygen Species Generation.

Background Catestatin has been reported as a pleiotropic cardioprotective peptide. Heart failure with preserved ejection fraction (HFpEF) was considered a heterogeneous syndrome with a complex cause. We sought to investigate the role of catestatin in HFpEF and diastolic dysfunction. METHODS AND RESULTS Administration of recombinant catestatin (1.5 mg/kg/d) improved diastolic dysfunction and left ventricular chamber stiffness in transverse aortic constriction mice with deoxycorticosterone acetate pellet implantation, as reflected by Doppler tissue imaging and pressure-volume loop catheter. Less cardiac hypertrophy and myocardial fibrosis was observed, and transcriptomic analysis revealed downregulation of mitochondrial electron transport chain components after catestatin treatment. Catestatin reversed mitochondrial structural and respiratory chain component abnormality, decreased mitochondrial proton leak, and reactive oxygen species generation in myocardium. Excessive oxidative stress induced by Ru360 abolished catestatin treatment effects on HFpEF-like cardiomyocytes in vitro, indicating the beneficial role of catestatin in HFpEF as a mitochondrial ETC modulator. The serum concentration of catestatin was tested among 81 patients with HFpEF and 76 non-heart failure controls. Compared with control subjects, serum catestatin concentration was higher in patients with HFpEF and positively correlated with E velocity to mitral annular e' velocity ratio, indicating a feedback compensation role of catestatin in HFpEF. Conclusions Catestatin protects against diastolic dysfunction in HFpEF through attenuating mitochondrial electron transport chain-derived reactive oxygen species generation. Serum catestatin concentration is elevated in patients with HFpEF, probably as a relatively insufficient but self-compensatory mechanism.

Nuclear Tkt promotes ischemic heart failure via the cleaved Parp1/Aif axis.

Transketolase (Tkt), an enzyme in pentose phosphate pathway, has been reported to regulate genome instability and cell survival in cancers. Yet, the role of Tkt after myocardial ischemic injury remains to be elucidated. Label-free proteomics revealed dramatic elevation of Tkt in murine hearts after myocardial infarction (MI). Lentivirus-mediated Tkt knockdown ameliorated cardiomyocyte apoptosis and preserved the systolic function after myocardial ischemic injury. In contrast, Tkt overexpression led to the opposite effects. Inducible conditional cardiomyocyte Tkt-knockout mice were generated, and cardiomyocyte-expressed Tkt was found to play an intrinsic role in the ischemic heart failure of these model mice. Furthermore, through luciferase assay and chromatin immunoprecipitation, Tkt was shown to be a direct target of transcription factor Krüppel-like factor 5 (Klf5). In cardiomyocytes under ischemic stress, Tkt redistributed into the nucleus. By binding with the full-length poly(ADP-ribose) polymerase 1 (Parp1), facilitating its cleavage, and activating apoptosis inducible factor (Aif) subsequently, nuclear Tkt demonstrated its non-metabolic functions. Overall, our study confirmed that elevated nuclear Tkt plays a noncanonical role in promoting cardiomyocyte apoptosis via the cleaved Parp1/Aif pathway, leading to the deterioration of cardiac dysfunction.