Type 2 T-Cell Responses against Distinct Epitopes of the Desmoglein 3 Ectodomain in Pemphigus Vulgaris

JAK1/2 Inhibitors Alleviate the Damage of Intercellular Adhesion by Reducing Endoplasmic Reticulum Stress-Induced Apoptosis in Pemphigus Vulgaris

Pemphigus vulgaris (PV), a severe autoimmune disease with high morbidity and mortality, necessitates innovative therapies to improve outcomes while minimising the adverse effects of conventional immunosuppressants. Immunohistochemical analysis revealed elevated phosphorylated Janus kinase (p-JAK)1 and p-JAK2 expression in PV lesions, complemented by transcriptome data showing JAK/STAT pathway dysregulation. Using a PV acantholysis model, we demonstrated that Ruxolitinib, a JAK1/2 inhibitor, significantly reduced keratinocyte apoptosis, enhanced cell adhesion, and alleviated endoplasmic reticulum (ER) stress. Additionally, Ruxolitinib mitigated tunicamycin-induced ER stress and apoptosis in HaCaT cells. These findings establish a crucial role for JAK1/2 in PV pathogenesis, demonstrating that their inhibition alleviates ER stress, reduces apoptosis, and improves cell adhesion. Our results provide a theoretical foundation for the clinical application of JAK inhibitors in PV treatment.

Epitomic profiling and functional characteristics of pemphigus vulgaris autoantibody binding to keratinocyte M3 muscarinic acetylcholine receptor

Patients with pemphigus vulgaris (PV) develop IgG autoantibodies (AuAbs) binding to keratinocyte desmogleins (Dsg), acetylcholine (ACh) receptors, mitochondrial proteins, and some other self-antigens. In this study, we identified linear and discontinuous peptide tetrameric epitope segments (ES) of M3 muscarinic ACh receptor (M3AR) targeted by different anti-M3AR AuAbs. As positive controls, we identified Dsg1 and Dsg3 ES targeted by PV sera. Healthy individuals also possessed natural antibodies targeting M3AR, Dsg1 and Dsg3 epitopes that were different from those targeted by AuAbs produced by patients with PV. The two targeted M3AR pentameric ES encompass the 10 amino acids-long epitope LSEPTITFGT included the tetramer TFGT containing Thr235 which is a part of the ACh-binding pocket. Previously, it has been demonstrated that the anti-M3AR AuAb produces an agonist-like effect on downstream signaling, but its long-term effect is receptor desensitization. In this study, we compared the functional consequences of binding anti-M3AR AuAbs that target the ACh-binding pocket with that of AuAbs that target M3AR outside of its ACh-binding pocket. While the former AuAbs induced a very high elevation of phospholipase C, inositol triphosphate and diacylglycerol, which represents an agonist-like effect, the latter AuAbs produced a much weaker signaling response. These results indicate that patients with PV develop two types of anti-M3AR AuAbs. One type attaches to orthosteric, i.e., ACh-binding, site and elicits a strong signaling response comparable to that induced by a full pharmacologic agonist, whereas another type binds to an allosteric site and elicits submaximal signaling response comparable to that induced by a partial (allosteric) agonist.

Meeting report - Alpine desmosome disease meeting 2024: advances and emerging topics in desmosomes and related diseases

Desmosomes are adhesive cell contacts abundant in tissues exposed to mechanical strain, such as the stratified and simple epithelia of the epidermis and mucous membranes, as well as the myocardium. Besides their role in mechanical cell cohesion, desmosomes also modulate pathways important for tissue differentiation, wound healing and immune responses. Dysfunctional desmosomes, resulting from pathogenic variants in genes encoding desmosomal components, autoantibodies targeting desmosomal adhesion molecules or inflammation, cause the life-threatening diseases arrhythmogenic cardiomyopathy and pemphigus and contribute to the pathogenesis of inflammatory bowel diseases. The Alpine Desmosome Disease Meeting 2024 (ADDM 2024), held in Grainau, Germany in October 2024, connected international researchers from basic sciences with clinical experts from dermatology, cardiology, gastroenterology and surgery. The participants discussed recent advances, identified hot topics in desmosome biology and disease and provided new concepts for pathogenesis and treatment approaches.

Pemphigus: trigger and predisposing factors

Pemphigus is a life-threatening autoimmune blistering disease affecting skin and mucous membranes. Despite its etiopathogenesis remains largely unknown, several trigger and predisposing factors have been reported. Pemphigus is caused by autoantibodies that target desmoglein 1 and desmoglein 3, impacting desmosome function. However, circulating autoantibodies are often the consequence of a precipitating factor that occurs in predisposed individuals. This review aims to describe and discuss almost all trigger and predisposing factors reported as possible or probable cause of the disease. Among the reported trigger factors that may induce or exacerbate pemphigus, we have found of particular interest: drug intake (especially thiol- and phenol-containing compounds), vaccines, infections, as well as some reports about pregnancy, radiations, emotional stress, pesticides and physical trauma. Moreover, we discuss the possible role of food intake in pemphigus onset and particular attention is given to dietary factors containing thiol, phenol and tannin compounds. A trigger factor is "the straw that breaks the camel's back," and often acts together with predisposing factors. Here we discuss how pemphigus onset may be influenced by genetic susceptibility and comorbidities like thyroid diseases, malignancies and other autoimmune disorders. To identify other hitherto unknown trigger and predisposing factors, well designed prospective studies are needed. In this context, future research should explore their connection with the aim to advance our understanding of pemphigus pathogenesis.