Granzyme K mediates IL-23-dependent inflammation and keratinocyte proliferation in psoriasis.

Psoriasis is an inflammatory disease with systemic manifestations that most commonly presents as itchy, erythematous, scaly plaques on extensor surfaces. Activation of the IL-23/IL-17 pro-inflammatory signaling pathway is a hallmark of psoriasis and its inhibition is key to clinical management. Granzyme K (GzmK) is an immune cell-secreted serine protease elevated in inflammatory and proliferative skin conditions. In the present study, human psoriasis lesions exhibited elevated GzmK levels compared to non-lesional psoriasis and healthy control skin. In an established murine model of imiquimod (IMQ)-induced psoriasis, genetic loss of GzmK significantly reduced disease severity, as determined by delayed plaque formation, decreased erythema and desquamation, reduced epidermal thickness, and inflammatory infiltrate. Molecular characterization in vitro revealed that GzmK contributed to macrophage secretion of IL-23 as well as PAR-1-dependent keratinocyte proliferation. These findings demonstrate that GzmK enhances IL-23-driven inflammation as well as keratinocyte proliferation to exacerbate psoriasis severity.

Granzyme K contributes to endothelial microvascular damage and leakage during skin inflammation.

BACKGROUND: Granzyme K (GzmK) is a serine protease with minimal presence in healthy tissues while abundant in inflamed tissues. Initially thought to play an exclusive role in immune-mediated cell death, extracellular GzmK can also promote inflammation. OBJECTIVES: To evaluate the role of GzmK in the pathogenesis of atopic dermatitis (AD), the most common inflammatory skin disease. METHODS: A panel of human AD and control samples was analysed to determine if GzmK is elevated. Next, to determine a pathological role for GzmK in AD-like skin inflammation, oxazolone-induced dermatitis was induced in GzmK-/- and wild-type (WT) mice. RESULTS: In human lesional AD samples, there was an increase in the number of GzmK+ cells compared with healthy controls. GzmK-/- mice exhibited reduced overall disease severity characterized by reductions in scaling, erosions and erythema. Surprisingly, the presence of GzmK did not notably increase the overall pro-inflammatory response or epidermal barrier permeability in WT mice; rather, GzmK impaired angiogenesis, increased microvascular damage and microhaemorrhage. Mechanistically, GzmK contributed to vessel damage through cleavage of syndecan-1, a key structural component of the glycocalyx, which coats the luminal surface of vascular endothelia. CONCLUSIONS: GzmK may provide a potential therapeutic target for skin conditions associated with persistent inflammation, vasculitis and pathological angiogenesis.

Informing a Canadian Skin Science Trainee Program Based on the State of Trainee Programs Offered by International Academic Societies.

BACKGROUND: For dermatology to effectively address the ever-growing medical needs, longstanding communication barriers across investigators working in different research pillars and practicing clinicians must be improved. To address this problem, trainee-specific programs are now evolving to align their educational landscape across basic science, translational and clinical research programs. OBJECTIVES: To establish a Skin Investigation Network of Canada (SkIN Canada) training roadmap for the career and skill development of future clinicians, clinican scientists and basic scientists in Canada. This Working Group aims to strengthen and harmonize collaborations and capacity across the skin research community. METHODS: The Working Group conducted a search of established international academic societies which offered trainee programs with mandates similar to SkIN Canada. Societies' program items and meetings were evaluated by use of an interview survey and/or the collection of publicly available data. Program logistics, objectives and feedback were assessed for commonalities and factors reported or determined to improve trainee experience. RESULTS: Through the various factors explored, the Working Group discovered the need for increasing program accessibility, creating opportunities for soft skill development, emphasizing the importance of current challenges, collecting and responding to feedback, and improving knowledge sharing to bridge pillars of skin research. CONCLUSIONS: Although improvements have been made to trainee education in recent years, a plurality of approaches exist and many of the underlying roadblocks remain unresolved. To establish fundamental clinician-basic scientist collaboration and training efforts, this Working Group highlights important factors to include and consider in building a trainee program and emphasizes the importance of trainee education.

Sulfaphenazole reduces thermal and pressure injury severity through rapid restoration of tissue perfusion.

Pressure injuries, also known as pressure ulcers, are regions of localized damage to the skin and/or underlying tissue. Repeated rounds of ischemia-reperfusion (I/R) have a major causative role for tissue damage in pressure injury. Ischemia prevents oxygen/nutrient supply, and restoration of blood flow induces a burst of reactive oxygen species that damages blood vessels, surrounding tissues and can halt blood flow return. Minimizing the consequences of repeated I/R is expected to provide a protective effect against pressure injury. Sulfaphenazole (SP), an off patent sulfonamide antibiotic, is a potent CYP 2C6 and CYP 2C9 inhibitor, functioning to decrease post-ischemic vascular dysfunction and increase blood flow. The therapeutic effect of SP on pressure injury was therefore investigated in apolipoprotein E knockout mice, a model of aging susceptible to ischemic injury, which were subjected to repeated rounds of I/R-induced skin injury. SP reduced overall severity, improved wound closure and increased wound tensile strength compared to vehicle-treated controls. Saliently, SP restored tissue perfusion in and around the wound rapidly to pre-injury levels, decreased tissue hypoxia, and reduced both inflammation and fibrosis. SP also demonstrated bactericidal activity through enhanced M1 macrophage activity. The efficacy of SP in reducing thermal injury severity was also demonstrated. SP is therefore a potential therapeutic option for pressure injury and other ischemic skin injuries.

Noncytotoxic Roles of Granzymes in Health and Disease.

Granzymes are serine proteases previously believed to play exclusive and somewhat redundant roles in lymphocyte-mediated target cell death. However, recent studies have challenged this paradigm. Distinct substrate profiles and functions have since emerged for each granzyme while their dysregulated proteolytic activities have been linked to diverse pathologies.

Granzyme B mediates impaired healing of pressure injuries in aged skin.

Pressure injuries (PIs), also known as bedsores or pressure ulcers, are a major cause of death and morbidity in the elderly. The serine protease, Granzyme B (GzmB), contributes to skin aging and impaired wound healing. Aging is a major risk factor for PIs; thus, the role of GzmB in PI pathogenesis was investigated. GzmB levels in human PI tissue and wound fluids were markedly elevated. A causative role for GzmB was assessed in GzmB knockout (GzmB-/-) and wild-type (WT) mice using a murine model of PI. An apolipoprotein E knockout (ApoE-/-) model of aging and vascular dysfunction was also utilized to assess GzmB in a relevant age-related model better resembling tissue perfusion in the elderly. PI severity displayed no difference between young GzmB-/- and WT mice. However, in aged mice, PI severity was reduced in mice lacking GzmB. Mechanistically, GzmB increased vascular wall inflammation and impaired extracellular matrix remodeling. Together, GzmB is an important contributor to age-dependent impaired PI healing.

Granzyme B Contributes to Barrier Dysfunction in Oxazolone-Induced Skin Inflammation through E-Cadherin and FLG Cleavage.

Atopic dermatitis (AD) is the most common inflammatory skin condition. Skin barrier dysfunction is of major importance in AD because it facilitates allergen sensitization and systemic allergic responses. Long regarded as a pro-apoptotic protease, emerging studies indicate granzyme B (GzmB) to have extracellular roles involving the proteolytic cleavage of extracellular matrix, cell adhesion proteins, and basement membrane proteins. Minimally expressed in normal skin, GzmB is elevated in AD and is positively correlated with disease severity and pruritus. We hypothesized that GzmB contributes to AD through extracellular protein cleavage. A causative role for GzmB was assessed in an oxazolone-induced murine model of dermatitis, comparing GzmB-/- mice with wild-type mice, showing significant reductions in inflammation, epidermal thickness, and lesion formation in GzmB-/- mice. Topical administration of a small-molecule GzmB inhibitor reduced disease severity compared with vehicle-treated controls. Mechanistically, GzmB impaired epithelial barrier function through E-cadherin and FLG cleavage. GzmB proteolytic activity contributes to impaired epidermal barrier function and represents a valid therapeutic target for AD.

Proteases in Pemphigoid Diseases.

Pemphigoid diseases are a subgroup of autoimmune skin diseases characterized by widespread tense blisters. Standard of care typically involves immunosuppressive treatments, which may be insufficient and are often associated with significant adverse events. As such, a deeper understanding of the pathomechanism(s) of pemphigoid diseases is necessary in order to identify improved therapeutic approaches. A major initiator of pemphigoid diseases is the accumulation of autoantibodies against proteins at the dermal-epidermal junction (DEJ), followed by protease activation at the lesion. The contribution of proteases to pemphigoid disease pathogenesis has been investigated using a combination of in vitro and in vivo models. These studies suggest proteolytic degradation of anchoring proteins proximal to the DEJ is crucial for dermal-epidermal separation and blister formation. In addition, proteases can also augment inflammation, expose autoantigenic cryptic epitopes, and/or provoke autoantigen spreading, which are all important in pemphigoid disease pathology. The present review summarizes and critically evaluates the current understanding with respect to the role of proteases in pemphigoid diseases.

Granzyme K Expressed by Classically Activated Macrophages Contributes to Inflammation and Impaired Remodeling.

Granzyme K (GzmK), traditionally described as a pro-apoptotic, granule-secreted serine protease, has been proposed to promote inflammation. Found at low levels in the plasma of healthy individuals, GzmK is markedly elevated in response to sepsis and infection. In this study we investigated the role of GzmK in inflammation and remodeling in response to thermal injury. In human burn tissue, GzmK was elevated compared with normal skin, with expression predominantly found in macrophages. GzmK was expressed and secreted by cultured human classically activated macrophages. To assess the role of GzmK in response to skin wounding, wild-type or GzmK-/- mice were subjected to grade 2 thermal injury. GzmK-/- mice exhibited improved wound closure, matrix organization, and tensile strength compared with wild-type mice. Reduced proinflammatory IL-6, ICAM-1, VCAM-1, and MCP-1 expressions were observed at 3 days after injury. Additionally, GzmK induced IL-6 expression in keratinocytes and skin fibroblasts that was dependent on PAR-1 activation. Re-epithelialization showed the greatest degree of improvement of all healing parameters, suggesting that keratinocytes are sensitive to GzmK-mediated proteolysis. In support, keratinocytes, but not skin fibroblasts, exposed to GzmK showed impaired wound healing in vitro. In summary, GzmK influences wound healing by augmenting inflammation and impeding epithelialization.