Project description:The vascular endothelial barrier, which supports balanced plasma solute and macromolecule composition, controls hemostasis, and limits leukocyte extravasation at homeostasis, is frequently disrupted in inflammation associated with sepsis and other critical illness. Monoclonal gammopathy-associated idiopathic systemic capillary leak syndrome (ISCLS, Clarkson disease) is a rare and devastating disorder characterized by relapsing-remitting episodes of spontaneous, profound microvascular hyper-permeability. A loss of function (LOF) mutation (G628R) in the mono ADP-ribosyltransferase PARP15, a protein of unknown function that is absent in mice, is associated with ISCLS and correlates with clinical markers of severe vascular leakage. In vascular endothelial cells, PARP15 suppresses cytokine-induced barrier disruption by ADP-ribosylating the scaffold protein JNK-interacting protein 3 (JIP3) and inhibiting p38 MAP kinase activation. Mice expressing human wild type (WT) PARP15 have curtailed inflammation-associated vascular leakage compared to mice expressing PARP15(G628R) in a p38-dependent fashion. Thus, PARP15 is essential for vascular endothelial barrier function under inflammatory stress.
Project description:TDP-43 is a DNA/RNA-binding protein that regulates gene expression and its malfunction in neurons has been causally associated with multiple neurodegenerative disorders. Although progress has been made in understanding the functions of TDP-43 in neurons, little is known about its role in endothelial cells (ECs), angiogenesis and vascular function. Using inducible EC-specific TDP-43 knockout mice, we show that TDP-43 is required for sprouting angiogenesis, vascular barrier integrity and blood vessel stability. Postnatal EC-specific deletion of TDP-43 leads to retinal hypovascularization due to defects in vessel sprouting associated with reduced EC proliferation and migration. In mature blood vessels, loss of TDP-43 disrupts the blood-brain barrier and triggers vascular degeneration. These vascular defects are associated with an inflammatory response in the central-nervous system with activation of microglia and astrocytes. Mechanistically, deletion of TDP-43 disrupts fibronectin matrix around sprouting vessels and reduces -catenin signaling in ECs. Together, our results indicate that TDP-43 is essential for the formation of a stable and mature vasculature.
Project description:The skin epidermis provides a vital barrier for preventing transepidermal water loss (TEWL) and environmental stimuli. However, the molecular mechanisms ensuring barrier integrity remain not fully understood. RORα is a nuclear receptor highly expressed in the epidermis of normal skin. However, its epidermal expression is significantly reduced in the lesions of multiple inflammatory skin diseases. In this study, using mice with epidermis-specific Rora gene deletion (RoraEKO), we have demonstrated the central roles of RORα in stabilizing skin barrier function. Albeit the lack of spontaneous skin lesion or dermatitis, RoraEKO mice exhibited elevated TEWL rate and skin features indicating barrier dysfunction. The histological and lipidomic analysis uncovered low levels of cornified envelope proteins and aberrant ceramide composition in the RoraEKO epidermis, implying disturbed late epidermal differentiation. In parallel, RNA-seq analysis revealed altered transcription levels of gene clusters related to “keratinization” and “lipid metabolism” in RORα deficient epidermis. Importantly, epidermal Rora ablation greatly amplified percutaneous allergic inflammatory responses to oxazolone in a mouse allergic contact dermatitis (ACD) model. Our results substantiated the essence of epidermal RORα in maintaining late keratinocyte differentiation and normal barrier function while suppressing cutaneous inflammation.
Project description:Increased endothelial permeability and failure to repair is the hallmark of several vascular diseases including acute lung injury (ALI). However, little is known about the intrinsic pathways that activate endothelial cell (EC) regenerative programs and thereby tissue repair. Studies have invoked a crucial role of sphingosine-1-phosphate (S1P) in resolving endothelial hyperpermeability through activation of the G-protein coupled receptor, sphingosine-1-phosphate receptor 1 (S1PR1). Here, we addressed mechanisms of generation of S1PR1+ EC, which may prevent endothelial injury. Studies were made using inducible EC-S1PR1-/- (iEC-S1PR1-/-) mice and S1PR1-GFP reporter mice to trace the generation of S1PR1+ EC. We observed in a mouse model of endotoxemia that S1P generation induced the programming of S1PR1lo to S1PR1+ EC, which comprised 80% of lung EC. The transition of these cells was required for reestablishing the endothelial barrier. We also observed that conditional deletion of S1PR1 in EC increased vascular permeability. RNA-seq analysis of S1PR1+ EC showed enrichment of genes regulating S1P synthesis and transport, sphingosine kinase 1 (SPHK1) and SPNS2, respectively. The activation of transcription factors EGR1 and STAT3 were essential for transcribing SPHK1 and SPNS2, respectively, to increase S1P production that served to amplify S1PR1+ EC transition. Transplantation of S1PR1+ EC into injured lung vasculature restored endothelial integrity. Our findings show that generation of a S1PR1+ EC population activates the endothelial regenerative program mediating vascular endothelial repair, thus raising the possibility of harnessing this pathway to restore vascular homeostasis in inflammatory injury.