| dc.description.abstract | Pemphigus Vulgaris (PV) is a life-threatening mucocutaneous blistering autoimmune disease caused by autoantibodies targeting desmoglein-3/1 (Dsg3/1). Despite many studies, the pathogenesis of PV remains incompletely understood. Dsg3 also acts as a vital signalling molecule involvement of various pathways has been identified by others and our group. In the meantime, our recent studies found that Dsg3 regulates yes-associated protein (YAP) and constrains reactive oxygen species (ROS). Here we hypothesised that disruption of Dsg3 in PV may have an effect on YAP and ROS in keratinocytes with PV treatment; therefore, PV IgG targeting Dsg3 may cause oxidative stress and disruption of cell-cell junctions accompanied by YAP dysregulation in cells that lead to the pathogenesis of pemphigus acantholysis. The purpose of this study is to investigate the role of Dsg3 disruption played in the YAP and ROS dysregulation underlying the PV disease. Firstly, this study uncovers aberrant YAP expression in PV blisters and the perilesional regions (Chapter 3). In vitro studies revealed that PV sera or the pathogenic anti-Dsg3 monoclonal antibody (AK23) evoked ROS overproduction with concomitant YAP cytoplasmic accumulation in keratinocytes, with a similar effect being detectable in cells treated with hydrogen peroxide (H2O2) along with the reduction of Dsg3 and α-Catenin, a negative regulator of YAP (Chapter 4). In Chapter 5, the rescue studies were conducted in four different ways. First, YAP depletion caused augmented expression of Dsg3 and α-Catenin that could abolish the pathogenic effect of AK23. Correspondingly, an inverse effect was observed in cells with forced expression of exogenous GFP-YAP or YAP-S127A that rendered intercellular junction assembly. Secondly, ectopic α-Catenin, the negative regulator of YAP, by transfection of α-Catenin-GFP which elicited YAP cytoplasmic translocation. Lastly, antioxidants and inhibitors of the MAPK pathways, including p38MAPK, suppressed H2O2-induced YAP augmentation, coupled with enhanced cell-cell adhesion and integrity. Importantly, the beneficial effect of antioxidants was also reproducible in primary keratinocytes treated with PV sera. However, in Chapter 6, YAP was subjected to Verteporfin (VP), with its photodynamic property and was mainly used for cancer treatment, and also identified recently as a YAP inhibitor, leading to a drastic reduction of YAP, accompanied by diminished expression of desmosomal proteins and the Dsg3/phospho-YAP (p-YAP) complex, with concurrent disintegration of cell junctions. In conclusion, this study suggests that oxidative stress coupled with YAP dysregulation is likely attributed to PV blistering, implying antioxidants might be beneficial in the treatment of PV. These results advance our knowledge of PV pathogenesis and the understanding of how Dsg3 and YAP interplay with ROS and regulate junction integrity and epithelial homeostasis. Most importantly, these findings may suggest some potential of clinical implications for diagnosis and the development of novel therapeutic strategies to treat this devastating autoimmune blistering disease. | en_US |
