Background: Inflammation is a prominent feature of arrhythmogenic cardiomyopathy (ACM), but whether it contributes to the disease phenotype is not known. Methods: To define the role of inflammation in the pathogenesis of ACM, we characterized nuclear factor-κB signaling in ACM models in vitro and in vivo and in cardiac myocytes from patient induced pluripotent stem cells. Results: Activation of nuclear factor-κB signaling, indicated by increased expression and nuclear accumulation of phospho-RelA/p65, occurred in both an in vitro model of ACM (expression of JUP ^2157del2 in neonatal rat ventricular myocytes) and a robust murine model of ACM (homozygous knock-in of mutant desmoglein-2 [ Dsg2 ^{mut/mu t} ]) that recapitulates the cardiac manifestations seen in patients with ACM. Bay 11-7082, a small-molecule inhibitor of nuclear factor-κB signaling, prevented the development of ACM disease features in vitro (abnormal redistribution of intercalated disk proteins, myocyte apoptosis, release of inflammatory cytokines) and in vivo (myocardial necrosis and fibrosis, left ventricular contractile dysfunction, electrocardiographic abnormalities). Hearts of Dsg2 ^mut/mut mice expressed markedly increased levels of inflammatory cytokines and chemotactic molecules that were attenuated by Bay 11-7082. Salutary effects of Bay 11-7082 correlated with the extent to which production of selected cytokines had been blocked. Nuclear factor-κB signaling was also activated in cardiac myocytes derived from a patient with ACM. These cells produced and secreted abundant inflammatory cytokines under basal conditions, and this was also greatly reduced by Bay 11-7082. Conclusions: Inflammatory signaling is activated in ACM and drives key features of the disease. Targeting inflammatory pathways may be an effective new mechanism-based therapy for ACM.

Inhibition of pulmonary fibrosis (PF) by restoring sarco/endoplasmic reticulum calcium ATPase 2a isoform (SERCA2a) expression using targeted gene therapy may be a potentially powerful new treatment approach for PF. Here, we found that SERCA2a expression was significantly decreased in lung samples from patients with PF and in the bleomycin (BLM) mouse model of PF. In the BLM-induced PF model, intratracheal aerosolized adeno-associated virus serotype 1 (AAV1) encoding for human SERCA2a (AAV1.hSERCA2a) reduces lung fibrosis and associated vascular remodeling. SERCA2a gene therapy also decreases right ventricular pressure and hypertrophy in both prevention and curative protocols. In vitro, we observed that SERCA2a overexpression inhibits fibroblast proliferation, migration, and fibroblast-to-myofibroblast transition induced by transforming growth factor β (TGF-β1). Thus, pro-fibrotic gene expression is prevented by blocking nuclear factor κB (NF-κB)/interleukin-6 (IL-6)-induced signal transducer and activator of transcription 3 (STAT3) activation. This effect is signaled toward an inhibitory mechanism of small mother against decapentaplegic (SMAD)/TGF-β signaling through the repression of OTU deubiquitinase, ubiquitin aldehyde binding 1 (OTUB1) and Forkhead box M1 (FOXM1). Interestingly, this cross-inhibition leads to an increase of SKI and SnoN expression, an auto-inhibitory feedback loop of TGF-β signaling. Collectively, our results demonstrate that SERCA2a gene transfer attenuates bleomycin (BLM)-induced PF by blocking the STAT3/FOXM1 pathway and promoting the SNON/SKI Axis. Thus, SERCA2a gene therapy may be a potential therapeutic target for PF.

Background: Autoimmunity is increasingly recognized as a key contributing factor in heart muscle diseases. The functional features of cardiac autoimmunity in humans remain undefined because of the challenge of studying immune responses in situ. We previously described a subset of c-mesenchymal epithelial transition factor (c-Met)–expressing (c-Met ⁺ ) memory T lymphocytes that preferentially migrate to cardiac tissue in mice and humans. Methods: In-depth phenotyping of peripheral blood T cells, including c-Met ⁺ T cells, was undertaken in groups of patients with inflammatory and noninflammatory cardiomyopathies, patients with noncardiac autoimmunity, and healthy controls. Validation studies were carried out using human cardiac tissue and in an experimental model of cardiac inflammation. Results: We show that c-Met ⁺ T cells are selectively increased in the circulation and in the myocardium of patients with inflammatory cardiomyopathies. The phenotype and function of c-Met ⁺ T cells are distinct from those of c-Met–negative (c-Met ⁻ ) T cells, including preferential proliferation to cardiac myosin and coproduction of multiple cytokines (interleukin-4, interleukin-17, and interleukin-22). Furthermore, circulating c-Met ⁺ T cell subpopulations in different heart muscle diseases identify distinct and overlapping mechanisms of heart inflammation. In experimental autoimmune myocarditis, elevations in autoantigen-specific c-Met ⁺ T cells in peripheral blood mark the loss of immune tolerance to the heart. Disease development can be halted by pharmacologic c-Met inhibition, indicating a causative role for c-Met ⁺ T cells. Conclusions: Our study demonstrates that the detection of circulating c-Met ⁺ T cells may have use in the diagnosis and monitoring of adaptive cardiac inflammation and definition of new targets for therapeutic intervention when cardiac autoimmunity causes or contributes to progressive cardiac injury.