Bullous Pemphigoid IgG Induces Cell Dysfunction and Enhances the Motility of Epidermal Keratinocytes via Rac1/Proteasome Activation

EGF-Induced Macropinocytosis Promotes NAV1-Dependent Internalization of Occludin in Keratinocytes

Epidermal keratinocytes form the outermost layer of the skin and serve as a pivotal barrier against external insults. This barrier, however, can be compromised in conditions such as atopic dermatitis (AD), where both genetic and environmental factors contribute to its disruption. Recent studies have indicated that macropinocytosis, a non-selective endocytic process, is involved in the internalization of barrier proteins. In this study, we explored the role of macropinocytosis in differentiated keratinocytes and its potential impact on skin barrier integrity in AD. Our results demonstrated that epidermal growth factor (EGF), but not the type 2 cytokines IL-4 and IL-13, significantly promoted macropinocytosis in differentiated HaCaT keratinocytes. EGF stimulation increased the uptake of 70 kDa dextran and induced the internalization of occludin, a component of tight junction proteins. Furthermore, enhanced macropinocytosis was observed in the epidermis of a mouse model of AD, accompanied by elevated EGF expression in the skin, indicating that the AD skin microenvironment may drive this process. NAV1 was identified as a critical regulator of EGF-induced macropinocytosis, as its knockdown significantly impaired this process. Transcriptome analysis of NAV1-knockdown cells further revealed changes in the expression of Rho family GTPases, including CDC42 and MMP14, suggesting that NAV1 modulates macropinocytosis through Rho-dependent pathways. These findings provide new insights into the regulation of macropinocytosis in keratinocytes and its potential contribution to the barrier dysfunction observed in AD.

Single cell transcriptome profiling reveals pathogenesis of bullous pemphigoid

Bullous pemphigoid (BP) triggers profound functional changes in both immune and non-immune cells in the skin and circulation, though the underlying mechanisms remain unclear. In this study, we conduct single-cell transcriptome analysis of lesional and non-lesional skin, as well as blood samples from BP patients. In lesional skin, non-immune cells upregulate pathways related to metabolism, wound healing, immune activation, and cell migration. LAMP3+DCs from cDC2 show stronger pro-inflammatory signatures than those from cDC1, and VEGFA+ mast cells, crucial for BP progression, are predominantly in lesional skin. As BP patients transition from active to remission stages, blood B cell function shifts from differentiation and memory formation to increased type 1 interferon signaling and reduced IL-4 response. Blood CX3CR1+ ZNF683+ and LAG3+ exhausted T cells exhibit the highest TCR expansion among clones shared with skin CD8+T cells, suggesting their role in fueling skin CD8+T cell clonal expansion. Clinical BP severity correlates positively with blood NK cell IFN-γ production and negatively with amphiregulin (AREG) production. NK cell-derived AREG mitigates IFN-γ-induced keratinocyte apoptosis, suggesting a crucial balance between AREG and IFN-γ in BP progression. These findings highlight functional shifts in BP pathology and suggest potential therapeutic targets.

Targeting antibody-mediated complement-independent mechanism in bullous pemphigoid with diacerein

BACKGROUND

Bullous pemphigoid (BP) is an antibody-mediated blistering disease predominantly affecting the elderly. The pathogenesis involves both complement-dependent and complement-independent mechanisms. The therapeutic potential of targeting complement-independent mechanism has not yet been determined. The mainstay of treatment, corticosteroid, has many side effects, indicating the needs of better treatments.

OBJECTIVE

We tempted to establish an in vitro model of BP which resembles complement-independent mechanism and to examine the therapeutic potential of a novel anti-inflammatory agent, diacerein.

METHODS

Cultured HaCaT cells were treated with purified antibodies from BP patients, with or without diacerein to measure the cell interface presence of BP180, protein kinase C, and the production of proinflammatory cytokines. An open-label, randomized, phase 2 trial was conducted to compare topical diacerein and clobetasol ointments in patients with mild-to-moderate BP (NCT03286582).

RESULTS

The reduced presentation of BP180 at cell interface after treating with BP autoantibodies was noticed in immunofluorescence and western blotting studies. The phenomenon was restored by diacerein. Diacerein also reduced the autoantibody-induced increase of pro-inflammatory cytokines. Reciprocal changes of BP180 and protein kinase C at the cell interface were found after treating with BP autoantibodies. This phenomenon was also reversed by diacerein in a dose-dependent manner. The phase 2 trial showed that topical diacerein reduced the clinical symptoms which were comparable to those of topical clobetasol.

CONCLUSION

Diacerein inhibited BP autoantibody-induced reduction of BP180 and production of proinflammatory cytokines in vitro and showed therapeutic potential in patients with BP. It is a novel drug worthy of further investigations.

Adaptive and innate immune pathogenesis of bullous pemphigoid: A review

Bullous pemphigoid (BP) is an autoimmune blistering disease that primarily affects elderly individuals. The presentation of BP is heterogeneous, typically manifesting as microscopic subepidermal separation with a mixed inflammatory infiltrate. The mechanism of pemphigoid development is unclear. B cells play a major role in pathogenic autoantibody production, and T cells, type II inflammatory cytokines, eosinophils, mast cells, neutrophils, and keratinocytes are also implicated in the pathogenesis of BP. Here, we review the roles of and crosstalk between innate and adaptive immune cells in BP.

Genetic polymorphism of glutathione S-transferases (GSTM1, GSTT1, and GSTP1) in patients with bullous pemphigoid in a Polish population

Introduction. Bullous pemphigoid (BP) is one of the most common bullous diseases with an autoimmune background. The etiology and pathogenesis of BP are believed to be influenced not only by environmental, genetic, and immunological factors as well as by oxidative stress. BP is observed more frequently in elderly patients. Additionally, more potent oxidative stress is observed just in old age. Glutathione S-transferases (GSTs) play key roles in the detoxification of xenobiotics, metabolism of endogenous substrates, and the defense against oxidative stress. The present study examines whether polymorphism of genes encoding three selected GSTs (GSTM1, GSTT1, and GSTP1) might be associated with a higher risk for BP.

Materials and methods. The study involved 71 patients with BP and 100 healthy volunteers from a Polish population. The presence of the deletion type polymorphism for GSTM1 and GSTT1 was confirmed by multiplex PCR. The Ile105Val GSTP1 polymorphism was analyzed by PCR-RFLP.

Results. It was observed that the combination of GSTM1 null/GSTT1 null/GSTP1 Ile/Val, Val/Val genotypes occurred more frequently in patients with BP (8.5%) than in controls (4.0%). The odds ratio for carriers of GSTM1 null/GSTT1 null/ GSTP1 Ile/Val, Val/Val genotypes was 2.22 (95% CI 0.60–8.16; p = 0.3727), but was not statistically significant.

Conclusions. The combination of GSTM1 null, GSTT1 null, GSTP1 Ile/Val, Val/Val genotypes might be related to a greater risk of BP in a Polish population. However, future studies including more individuals are required to confirm this.

Evolving Mechanisms in the Pathophysiology of Pemphigus Vulgaris: A Review Emphasizing the Role of Desmoglein 3 in Regulating p53 and the Yes-Associated Protein

The immunobullous condition Pemphigus Vulgaris (PV) is caused by autoantibodies targeting the adhesion proteins of desmosomes, leading to blistering in the skin and mucosal membrane. There is still no cure to the disease apart from the use of corticosteroids and immunosuppressive agents. Despite numerous investigations, the pathological mechanisms of PV are still incompletely understood, though the etiology is thought to be multifactorial. Thus, further understanding of the molecular basis underlying this disease process is vital to develop targeted therapies. Ample studies have highlighted the role of Desmoglein-3 (DSG3) in the initiation of disease as DSG3 serves as a primary target of PV autoantibodies. DSG3 is a pivotal player in mediating outside-in signaling involved in cell junction remodeling, cell proliferation, differentiation, migration or apoptosis, thus validating its biological function in tissue integrity and homeostasis beyond desmosome adhesion. Recent studies have uncovered new activities of DSG3 in regulating p53 and the yes-associated protein (YAP), with the evidence of dysregulation of these pathways demonstrated in PV. The purpose of this review is to summarize the earlier and recent advances highlighting our recent findings related to PV pathogenesis that may pave the way for future research to develop novel specific therapies in curing this disease.

Tyrosine Kinases in Autoimmune and Inflammatory Skin Diseases

Tyrosine kinases relay signals from diverse leukocyte antigen receptors, innate immune receptors, and cytokine receptors, and therefore mediate the recruitment and activation of various leukocyte populations. Non-receptor tyrosine kinases of the Jak, Src, Syk, and Btk families play major roles in various immune-mediated disorders, and small-molecule tyrosine kinase inhibitors are emerging novel therapeutics in a number of those diseases. Autoimmune and inflammatory skin diseases represent a broad spectrum of immune-mediated diseases. Genetic and pharmacological studies in humans and mice support the role of tyrosine kinases in several inflammatory skin diseases. Atopic dermatitis and psoriasis are characterized by an inflammatory microenvironment which activates cytokine receptors coupled to the Jak-Stat signaling pathway. Jak kinases are also implicated in alopecia areata and vitiligo, skin disorders mediated by cytotoxic T lymphocytes. Genetic studies indicate a critical role for Src-family kinases and Syk in animal models of autoantibody-mediated blistering skin diseases. Here, we review the various tyrosine kinase signaling pathways and their role in various autoimmune and inflammatory skin diseases. Special emphasis will be placed on identification of potential therapeutic targets, as well as on ongoing preclinical and clinical studies for the treatment of inflammatory skin diseases by small-molecule tyrosine kinase inhibitors.

New Insights Into the Pathogenesis of Bullous Pemphigoid: 2019 Update

There are several lines of evidence indicating that the physiopathological bases of bullous pemphigoid (BP), the most common subepidermal autoimmune bullous disease, are hallmarked by the production of autoantibodies directed against the hemidesmosomal anchoring proteins BP180 and BP230. In contrast to the robustness of the latter assumption, the multifaceted complexity of upstream and downstream mechanisms implied in the pathogenesis of BP remains an area of intense speculation. So far, an imbalance between T regulatory cells and autoreactive T helper (Th) cells has been regarded as the main pathogenic factor triggering the autoimmune response in BP patients. However, the contributory role of signaling pathways fostering the B cell stimulation, such as Toll-like receptor activation, as well as that of ancillary inflammatory mechanisms responsible for blister formation, such as Th17 axis stimulation and the activation of the coagulation cascade, are still a matter of debate. In the same way, the pathomechanisms implied in the loss of dermal-epidermal adhesion secondary to autoantibodies binding are not fully understood. Herein, we review in detail the current concepts and controversies on the complex pathogenesis of BP, shedding light on the most recent theories emerging from the literature.