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Pterygium is often associated with chronic ultraviolet (UV) radiation exposure and characterized by the overgrowth of conjunctiva and extracellular matrix (ECM) remodeling. Notably, several studies in the skin have demonstrated that chronic UV radiation can upregulate Granzyme B (GrB) expression and increase ECM degradation. The aim of this study was to compare GrB expression between pterygium and healthy controls and to further link this GrB expression to mast cells. Post-mortem pterygium tissues and conjunctival tissues from age-matched controls were used to assess GrB expression via immunofluorescence and microscopy. We found a significantly higher density of GrB+ cells from pterygium specimens compared to healthy controls. Furthermore, many of the GrB+ cells in pterygium specimens co-expressed tryptase, a mast cell marker. These findings suggest a role for conjunctival mast cell-secreted GrB in the pathogenesis of pterygium and highlight GrB as a possible therapeutic target in delaying or halting pterygium progression. [ABSTRACT FROM AUTHOR]

Age-related macular degeneration (AMD), a prevalent and progressive degenerative disease of the macula, is the leading cause of blindness in elderly individuals in developed countries. The advanced stages include neovascular AMD (nAMD), characterized by choroidal neovascularization (CNV), leading to subretinal fibrosis and permanent vision loss. Despite the efficacy of anti-vascular endothelial growth factor (VEGF) therapy in stabilizing or improving vision in nAMD, the development of subretinal fibrosis following CNV remains a significant concern. In this review, we explore multifaceted aspects of subretinal fibrosis in nAMD, focusing on its clinical manifestations, risk factors, and underlying pathophysiology. We also outline the potential sources of myofibroblast precursors and inflammatory mechanisms underlying their recruitment and transdifferentiation. Special attention is given to the potential role of mast cells in CNV and subretinal fibrosis, with a focus on putative mast cell mediators, tryptase and granzyme B. We summarize our findings on the role of GzmB in CNV and speculate how GzmB may be involved in the pathological transition from CNV to subretinal fibrosis in nAMD. Finally, we discuss the advantages and drawbacks of animal models of subretinal fibrosis and pinpoint potential therapeutic targets for subretinal fibrosis. [ABSTRACT FROM AUTHOR]

Objective: To gain insights into how proteases signal to connective tissues cells in the periodontium. Background: The connective tissue degradation observed in periodontitis is largely due to matrix metalloproteinase (MMP) release by gingival fibroblasts. Granzyme B (GzmB) is a serine protease whose role in periodontitis is undefined. Methods: Human gingival crevicular fluid (GCF) samples were obtained from sites with periodontal disease and healthy control sites. GzmB was quantified in the GCF ([GzmB]GCF) by ELISA. Gingival fibroblasts (GF) were cultured in the presence or absence of recombinant GzmB. Culture supernatants were analyzed by ELISA to quantify GzmB‐induced release of interstitial collagenase (MMP‐1). In some experiments, cells were pre‐treated with the inhibitor PD98059 to block MEK/ERK signaling. The protease‐activated receptor‐1 (PAR‐1) was blocked with ATAP‐2 neutralizing antibody prior to GzmB stimulation. Systemic MMP‐1 levels were measured in plasma from wild‐type (WT) and granzyme‐B‐knockout (GzmB−/−) mice. Results: The [GzmB]GCF in human samples was ~4–5 fold higher at sites of periodontal disease (gingivitis/periodontitis) compared to healthy control sites, suggesting an association between GzmB and localized matrix degradation. GzmB induced a ~4–5‐fold increase in MMP‐1 secretion by cultured fibroblasts. GzmB induced phosphorylation of Erk1/2, which was abrogated by PD98059. GzmB‐induced upregulation of MMP‐1 secretion was also reduced by PD98059. Blockade of PAR‐1 function by ATAP‐2 abrogated the increase in MMP‐1 secretion by GF. Circulating MMP‐1 was similar in WT and GzmB−/− mice, suggesting that GzmB's effects on MMP‐1 release are not reflected systemically. Conclusion: These data point to a novel GzmB‐driven signaling pathway in fibroblasts in which MMP‐1 secretion is upregulated in a PAR1‐ and Erk1/2‐dependent manner. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Interferon-α (IFN-α) is essential for antiviral immunity, but in the absence of matrix metalloproteinase-12 (MMP-12) or IκBα (encoded by NFKBIA) we show that IFN-α is retained in the cytosol of virus-infected cells and is not secreted. Our findings suggest that activated IκBα mediates the export of IFN-α from virus-infected cells and that the inability of cells in [Mmp12.sup.-/-] but not wild-type mice to express IκBα and thus export IFN-α makes coxsackievirus type B3 infection lethal and renders respiratory syncytial virus more pathogenic. We show here that after macrophage secretion, MMP-12 is transported into virus-infected cells. In HeLa cells MMP-12 is also translocated to the nucleus, where it binds to the NFKBIA promoter, driving transcription. We also identified dual-regulated substrates that are repressed both by MMP-12 binding to the substrate's gene exons and by MMP-12-mediated cleavage of the substrate protein itself. Whereas intracellular MMP-12 mediates NFKBIA transcription, leading to IFN-α secretion and host protection, extra cellular MMP-12 cleaves off the IFN-α receptor 2 binding site of systemic IFN-α, preventing an unchecked immune response. Consistent with an unexpected role for MMP-12 in clearing systemic IFN-α, treatment of coxsackievirus type B3-infected wild-type mice with a membrane-impermeable MMP-12 inhibitor elevates systemic IFN-α levels and reduces viral replication in pancreas while sparing intracellular MMP-12. These findings suggest that inhibiting extra cellular MMP-12 could be a new avenue for the development of antiviral treatments., Interferons (1) and macrophages are important in antiviral immunity (2). MMP-12 (ref. 3; also known as macrophage metalloelastase) is a secreted protease that degrades extra cellular matrix during inflammatory tissue [...]