Arrhythmogenic cardiomyopathy (AC) is a genetic disease causing arrhythmia and sudden cardiac death with only symptomatic therapy available at present. Mutations of desmosomal proteins, including desmoglein-2 (Dsg2) and plakoglobin (Pg), are the major cause of AC and have been shown to lead to impaired gap junction function. Recent data indicated the involvement of anti-Dsg2 autoantibodies in AC pathogenesis. We applied a peptide to stabilize Dsg2 binding similar to a translational approach to pemphigus, which is caused by anti-desmoglein autoantibodies. We provide evidence that stabilization of Dsg2 binding by a linking peptide (Dsg2-LP) is efficient to rescue arrhythmia in an AC mouse model immediately upon perfusion. Dsg2-LP, designed to cross-link Dsg2 molecules in proximity to the known binding pocket, stabilized Dsg2-mediated interactions on the surface of living cardiomyocytes as revealed by atomic force microscopy and induced Dsg2 oligomerization. Moreover, Dsg2-LP rescued disrupted cohesion induced by siRNA-mediated Pg or Dsg2 depletion or l-tryptophan, which was applied to impair overall cadherin binding. Dsg2-LP rescued connexin-43 mislocalization and conduction irregularities in response to impaired cardiomyocyte cohesion. These results demonstrate that stabilization of Dsg2 binding by Dsg2-LP can serve as a novel approach to treat arrhythmia in patients with AC.

Arrhythmogenic cardiomyopathy (AC) is a heritable, potentially lethal disease without a causal therapy. AC is characterized by focal cardiomyocyte death followed by inflammation and progressive formation of connective tissue. The pathomechanisms leading to structural disease onset and progression, however, are not fully elucidated. Recent studies revealed that dysregulation of autophagy and endoplasmic/sarcoplasmic reticulum (ER/SR) stress plays an important role in cardiac pathophysiology. We therefore examined the temporal and spatial expression patterns of autophagy and ER/SR stress indicators in murine AC models by qRT-PCR, immunohistochemistry, in situ hybridization and electron microscopy. Cardiomyocytes overexpressing the autophagy markers LC3 and SQSTM1/p62 and containing prominent autophagic vacuoles were detected next to regions of inflammation and fibrosis during onset and chronic disease progression. mRNAs of the ER stress markers Chop and sXbp1 were elevated in both ventricles at disease onset. During chronic disease progression Chop mRNA was upregulated in right ventricles. In addition, reduced Ryr2 mRNA expression together with often drastically enlarged ER/SR cisternae further indicated SR dysfunction during this disease phase. Our observations support the hypothesis that locally altered autophagy and enhanced ER/SR stress play a role in AC pathogenesis both at the onset and during chronic progression.

Neuroinflammation plays a dual role in brain health supporting defense and repair, but causes neurotoxicity when persistent. Microglia and astrocytes coordinate these responses through cytokine signaling and extracellular vesicles (EVs), though their vesicle-mediated communication remains unclear. This study investigated whether EVs from activated microglia (ABEVs) influence astrocyte polarization and inflammatory signaling. BV-2 microglial cells were activated with lipopolysaccharide (LPS), and microvesicle (ABMVs) and exosome (ABEXs) EVs were isolated via sequential ultracentrifugation. Primary mouse astrocytes were treated with LPS, ABMVs, or ABEXs, and expression of reactive astrocyte markers (C3, Serpina3n, S100a10, Sphk1) and inflammatory mediators (Lcn2, Il-1β, Ccl2, Ccl5, Cxcl10) was quantified, and EV protein cargo was analyzed by mass spectrometry and proteomics. LPS-treated astrocytes exhibited increased C3 and Serpina3n and decreased S100a10, consistent with reactive polarization. ABEXs mimicked this effect, significantly inducing C3, Serpina3n, and Sphk1, whereas ABMVs had a weaker influence. ABEXs also upregulated Lcn2 and Il-1β, partially reproducing microglial inflammatory effects. Proteomic profiling revealed marked cargo differences: ABEXs exhibited 16 upregulated proteins linked to NOD-like receptor signaling compared to non-activated BEXs, and 165 proteins associated with ribosome biogenesis and spliceosome pathways compared to ABMVs, indicating subtype-specific signaling potential. Collectively, our findings demonstrate that microglia-derived EVs modulate astrocytic polarization and cytokine profiles in a cargo-dependent manner, emphasizing their importance in interglial communication and revealing novel targets for neuroinflammatory modulation.

Desmoglein-2 mutations are detected in 5–10% of patients with arrhythmogenic right ventricular cardiomyopathy (ARVC). Endurance training accelerates the development of the ARVC phenotype, leading to earlier arrhythmic events. Homozygous Dsg2 mutant mice develop a severe ARVC-like phenotype. The phenotype of heterozygous mutant (Dsg2^mt/wt) or haploinsufficient (Dsg2^0/wt) mice is still not well understood. To assess the effects of age and endurance swim training, we studied cardiac morphology and function in sedentary one-year-old Dsg2^mt/wt and Dsg2^0/wt mice and in young Dsg2^mt/wt mice exposed to endurance swim training. Cardiac structure was only occasionally affected in aged Dsg2^0/wt and Dsg2^mt/wt mice manifesting as small fibrotic foci and displacement of Connexin 43. Endurance swim training increased the right ventricular (RV) diameter and decreased RV function in Dsg2^mt/wt mice but not in wild types. Dsg2^mt/wt hearts showed increased ventricular activation times and pacing-induced ventricular arrhythmia without obvious fibrosis or inflammation. Preload-reducing therapy during training prevented RV enlargement and alleviated the electrophysiological phenotype. Taken together, endurance swim training induced features of ARVC in young adult Dsg2^mt/wt mice. Prolonged ventricular activation times in the hearts of trained Dsg2^mt/wt mice are therefore a potential mechanism for increased arrhythmia risk. Preload-reducing therapy prevented training-induced ARVC phenotype pointing to beneficial treatment options in human patients.