Upregulation of cathepsin S in psoriatic keratinocytes

Cathepsin S: A key drug target and signalling hub in immune system diseases

The lysosomal cysteine protease cathepsin S supports host defence by promoting the maturation of MHC class-II proteins. In contrast, increased cathepsin S activity mediates tissue destructive immune responses in autoimmune and inflammatory diseases. Therefore, cathepsin S is a key target in drug discovery programs. Here, we critically reviewed the specific mechanisms by which cathepsin S mediates autoimmune and hyperinflammatory responses to identify new targets for therapeutic immunomodulation. To this end, we performed literature review utilizing PubMed, drug database of US FDA, European Medicines Agency and the Drug-Gene Interaction Database. Cathepsin S destroys T cell epitopes and reduces endogenous antigen diversity, impairing negative selection of autoreactive T cells that could recognize these epitopes. Moreover, cathepsin S critically regulates inflammatory disease severity by generating proinflammatory molecules (PAR-1, PAR-2, IL-36γ, Fractalkine, Endostatin, Ephrin-B2), inactivating anti-inflammatory mediators (SLPI) and degrading molecules involved in antimicrobial and immunomodulatory responses (surfactant protein-A, LL-37, beta-defensins), inter-endothelial/-epithelial barrier function, gene repair and energy homeostasis. These pathways could be targeted by repositioning of existing drugs. These findings suggest that inhibiting cathepsin S or a specific downstream target of cathepsin S by repositioning of existing drugs could be a promising strategy for treating autoimmune and inflammatory diseases. Current cathepsin S inhibitors in clinical trials face challenges, highlighting the need for innovative inhibitors that function effectively in various cellular compartments with differing pH levels, without targeting the shared catalytic site of cysteine cathepsins.

Beyond the classic players: Mas-related G protein-coupled receptor member X2 role in pruritus and skin diseases

Chronic spontaneous urticaria (CSU), atopic dermatitis (AD), psoriasis and rosacea are highly prevalent inflammatory skin conditions which impose a significant burden on patients' quality of life. Their pathophysiology is likely multifactorial, involving genetic, immune and environmental factors. Recent advancements in the field have demonstrated the key role of mast cells (MC) in the pathophysiology of these conditions. The Mas-related G protein-coupled receptor X2 (MRGPRX2) has emerged as a promising non-IgE-mediated MC activation receptor. MRGPRX2 is predominately expressed on MC and activated by endogenous and exogenous ligands, leading to MC degranulation and release of various pro-inflammatory mediators. Mounting evidence on the presence of endogenous MRGPRX2 agonists (substance P, cortistatin-14, LL37, PAMP-12 and VIP) and its high expression among patients with CSU, AD, rosacea, psoriasis and chronic pruritus emphasizes the pathogenic role of MRGPRX2 in these conditions. Despite the currently available treatments, there remains a pressing need for novel drug targets and treatment options for these chronic inflammatory skin conditions. Here, we reviewed the pathogenic role of MRGPRX2 and its potential as a novel therapeutic target and provided an update on future research directions.

Advances in psoriasis research: From pathogenesis to therapeutics

Psoriasis is a chronic inflammatory condition affecting approximately 2 % to 3 % of the global population. The pathogenesis of psoriasis is complex, involving immune dysregulation, hyperproliferation and angiogenesis. It is a multifactorial disease which is influenced by genetic and environmental factors. The development of various therapeutic agents, such as JAK inhibitors, small molecules, and biologics with potential anti-psoriatic properties was possible with the vast understanding of the pathogenesis of psoriasis. Various signalling pathways, including NF-κB, JAK-STAT, S1P, PDE-4, and A3AR that are involved in the pathogenesis of psoriasis as well as the preclinical models utilised in the research of psoriasis have been highlighted in this review. The review also focuses on technological advancements that have contributed to a better understanding of psoriasis. Then, the molecules targeting the respective signalling pathways that are still under clinical trials or recently approved as well as the latest breakthroughs in therapeutic and drug delivery approaches that can contribute to the improvement in the management of psoriasis are highlighted in this review. This review provides an extensive understanding of the current state of research in psoriasis, giving rise to opportunities for researchers to discover future therapeutic breakthroughs and personalised interventions. Efficient treatment options for individuals with psoriasis can be achieved by an extensive understanding of pathogenesis, therapeutic agents, and novel drug delivery strategies.

In silico approaches for better understanding cysteine cathepsin-glycosaminoglycan interactions

Cysteine cathepsins constitute the largest cathepsin family, with 11 proteases in human that are present primarily within acidic endosomal and lysosomal compartments. They are involved in the turnover of intracellular and extracellular proteins. They are synthesized as inactive procathepsins that are converted to mature active forms. Cathepsins play important roles in physiological and pathological processes and, therefore, receive increasing attention as potential therapeutic targets. Their maturation and activity can be regulated by glycosaminoglycans (GAGs), long linear negatively charged polysaccharides composed of recurring dimeric units. In this review, we summarize recent computational progress in the field of (pro)cathepsin-GAG complexes analyses.

20S constitutive proteasome, 20S immunoproteasome, and cathepsin S are high-sensitivity and independent markers of immunological activity in relapsing-remitting type of multiple sclerosis

Research on the markers of autoimmune response in multiple sclerosis (MS) is still of great importance. The aim of our study was the evaluation of plasma 20S constitutive proteasome, 20S immunoproteasome, and cathepsin S concentrations as potential biomarkers of a relapsing-remitting type of MS (RRMS). Surface plasmon resonance imaging (SPRI) biosensors were used for the evaluation of protein concentrations. Plasma 20S constitutive proteasome, 20S immunoproteasome, and cathepsin S concentrations were significantly higher in RRMS patients compared to the control group. All three parameters were characterized by excellent usefulness in differentiating MS patients from healthy individuals (AUC equal to or close to 1.000). The plasma concentration of analyzed parameters was not correlated with severity of disability in the course of RRMS (EDSS value), the number of years from the first MS symptoms, the number of years from MS diagnosis, or the number of relapses within the 24-month observational period. Our study has shown that plasma concentrations of 20S constitutive proteasome, 20S immunoproteasome, and cathepsin S have promising potential in differentiating RRMS patients from healthy individuals. All of the analyzed parameters were found to be independent of the time of MS relapse and the severity of neurological symptoms. Hence, their potential as highly sensitive and independent circulating markers of RRMS suggests a stronger association with immunological activity (inflammatory processes) than with the severity of the disease.

Tick cysteine protease inhibitors suppress immune responses in mannan-induced psoriasis-like inflammation

Protease inhibitors regulate various biological processes and prevent host tissue/organ damage. Specific inhibition/regulation of proteases is clinically valuable for treating several diseases. Psoriasis affects the skin in the limbs and scalp of the body, and the contribution of cysteine and serine proteases to the development of skin inflammation is well documented. Cysteine protease inhibitors from ticks have high specificity, selectivity, and affinity to their target proteases and are efficient immunomodulators. However, their potential therapeutic effect on psoriasis pathogenesis remains to be determined. Therefore, we tested four tick cystatins (Sialostatin L, Sialostatin L2, Iristatin, and Mialostatin) in the recently developed, innate immunity-dependent mannan-induced psoriasis model. We explored the effects of protease inhibitors on clinical symptoms and histological features. In addition, the number and percentage of immune cells (dendritic cells, neutrophils, macrophages, and γδT cells) by flow cytometry, immunofluorescence/immunohistochemistry and, the expression of pro-inflammatory cytokines (TNF-a, IL-6, IL-22, IL-23, and IL-17 family) by qPCR were analyzed using skin, spleen, and lymph node samples. Tick protease inhibitors have significantly decreased psoriasis symptoms and disease manifestations but had differential effects on inflammatory responses and immune cell populations, suggesting different modes of action of these inhibitors on psoriasis-like inflammation. Thus, our study demonstrates, for the first time, the usefulness of tick-derived protease inhibitors for treating skin inflammation in patients.

Insights into Autophagic Machinery and Lysosomal Function in Cells Involved in the Psoriatic Immune-Mediated Inflammatory Cascade

Impaired autophagy, due to the dysfunction of lysosomal organelles, contributes to maladaptive responses by pathways central to the immune system. Deciphering the immune-inflammatory ecosystem is essential, but remains a major challenge in terms of understanding the mechanisms responsible for autoimmune diseases. Accumulating evidence implicates a role that is played by a dysfunctional autophagy-lysosomal pathway (ALP) and an immune niche in psoriasis (Ps), one of the most common chronic skin diseases, characterized by the co-existence of autoimmune and autoinflammatory responses. The dysregulated autophagy associated with the defective lysosomal system is only one aspect of Ps pathogenesis. It probably cannot fully explain the pathomechanism involved in Ps, but it is likely important and should be seriously considered in Ps research. This review provides a recent update on discoveries in the field. Also, it sheds light on how the dysregulation of intracellular pathways, coming from modulated autophagy and endolysosomal trafficking, characteristic of key players of the disease, i.e., skin-resident cells, as well as circulating immune cells, may be responsible for immune impairment and the development of Ps.

Computational Modeling and Evaluation of Potential mRNA and Peptide-Based Vaccine against Marburg Virus (MARV) to Provide Immune Protection against Hemorrhagic Fever

A hemorrhagic fever caused by the Marburg virus (MARV) belongs to the Filoviridae family and has been classified as a risk group 4 pathogen. To this day, there are no approved effective vaccinations or medications available to prevent or treat MARV infections. Reverse vaccinology-based approach was formulated to prioritize B and T cell epitopes utilizing a numerous immunoinformatics tools. Potential epitopes were systematically screened based on various parameters needed for an ideal vaccine such as allergenicity, solubility, and toxicity. The most suitable epitopes capable of inducing immune response were shortlisted. Epitopes with population coverage of 100% and fulfilling set parameters were selected for docking with human leukocyte antigen molecules, and binding affinity of each peptide was analyzed. Finally, 4 CTL and HTL each while 6 B cell 16-mers were used for designing multiepitope subunit (MSV) and mRNA vaccine joined via suitable linkers. Immune simulations were used to validate the constructed vaccine's capacity to induce a robust immune response whereas molecular dynamics simulations were used to confirm epitope-HLA complex stability. Based on these parameter's studies, both the vaccines constructed in this study offer a promising choice against MARV but require further experimental verification. This study provides a rationale point to begin with the development of an efficient vaccine against Marburg virus; however, the findings need further experimental validation to confirm the computational finding of this study.

Transcriptome profiling in psoriasis: NB-UVB treatment-associated transcriptional changes and modulation of autoinflammation in perilesional skin in early-phase disease

BACKGROUND

Psoriasis is a chronic inflammatory skin condition. It is widely treated with phototherapy using narrowband ultraviolet B (NB-UVB). The therapeutic mechanisms of NB-UVB, however, remain unclear, particularly in the early phases of the disease.

OBJECTIVE

To investigate the mechanisms underlying the effects of NB-UVB on psoriasis in a model of perilesional psoriasis.

METHODS

Psoriatic patients that received NB-UVB treatment and were evaluated with the psoriasis area and severity index were included in the study. Skin biopsies obtained before and after treatment were subjected to RNA sequencing (RNA-seq) and Ingenuity Pathway Analyses for genome-wide transcriptome profiling to gain further insights into the signaling pathways underlying the improvement of psoriasis with therapeutic intervention.

RESULTS

Our findings revealed that NB-UVB treatment may exert its effects by suppressing nuclear factor kappa B, which leads to upregulation of the sirtuin signaling pathway, as well as by decreasing the function of major upstream regulators associated with proinflammatory and inflammatory cytokines, which blocks the expression of downstream toll-like receptors. Psoriasis improvement after NB-UVB treatment was associated with decreased expression of NFKBIZ, SERPINB4, ATG13, and CTSS and increased expression of SKP1 gene. Our results also highlighted the expression of proposed genes associated with the modulation of autoinflammation.

CONCLUSIONS

To the best of our knowledge, this is the first study to apply advanced molecular techniques to explore the effects of phototherapy on psoriasis in the early-phase, providing new insights into the disease pathogenesis and novel genetic information for the development of new therapeutic modalities and potential treatment targets.

Identification and pharmacological modification of resistance mechanisms to protoporphyrin-mediated photodynamic therapy in human cutaneous squamous cell carcinoma cell lines

BACKGROUND

Photodynamic therapy (PDT) is clinically approved to treat neoplastic skin diseases such as precursors of cutaneous squamous cell carcinoma (cSCC). In PDT, 5-aminolevulinic acid (5-ALA) drives the selective formation of the endogenous photosensitizer protoporphyrin IX (PpIX). Although 5-ALA PDT is clinically highly effective, resistance might occur due to decreased accumulation of PpIX in certain tumors. Such resistance may be caused by any fundamental step of PpIX accumulation: 5-ALA uptake, PpIX synthesis and PpIX efflux.

METHODS

We investigated PpIX accumulation and photodynamically induced cell death in PDT refractory SCC-13, PDT susceptible A431, and normal human epidermal keratinocytes (NHEK). Expression of genes associated with cellular PpIX kinetics was investigated on mRNA and protein level. PpIX accumulation and cell death upon illumination were pharmacologically manipulated using drugs targeting 5-ALA uptake, PpIX synthesis or efflux.

RESULTS

The experiments indicate that taurine transporter (SLC6A6) is the major pathway for 5-ALA uptake in cSCC cells, while being less important in NHEK. Downregulation of PpIX synthesis enzymes in SCC-13 was counteracted by methotrexate (MTX) treatment, which restored PpIX formation and cell death. PpIX efflux inhibitors targeting ABC transporters led to significantly increased PpIX accumulation in SCC-13, thereby fully overcoming resistance.

CONCLUSIONS

The results indicate a conserved threshold for PpIX accumulation with respect to PDT-resistance. Cells showed increased viability after PDT at PpIX concentrations below 1.5 nM. Selective uptake of 5-ALA via taurine transporter SLC6A6 in cutaneous tumor cells is novel but unrelated to resistance. MTX can partially abrogate resistance by PpIX synthesis enzyme induction, while efflux mechanisms via ABC transporters seem the main driving force and promising drug targets.

Potential Immunogenic Activity of Computationally Designed mRNA- and Peptide-Based Prophylactic Vaccines against MERS, SARS-CoV, and SARS-CoV-2: A Reverse Vaccinology Approach

The continued emergence of human coronaviruses (hCoVs) in the last few decades has posed an alarming situation and requires advanced cross-protective strategies against these pandemic viruses. Among these, Middle East Respiratory Syndrome coronavirus (MERS-CoV), Severe Acute Respiratory Syndrome coronavirus (SARS-CoV), and Severe Acute Respiratory Syndrome coronavirus-2 (SARS-CoV-2) have been highly associated with lethality in humans. Despite the challenges posed by these viruses, it is imperative to develop effective antiviral therapeutics and vaccines for these human-infecting viruses. The proteomic similarity between the receptor-binding domains (RBDs) among the three viral species offers a potential target for advanced cross-protective vaccine designs. In this study, putative immunogenic epitopes including Cytotoxic T Lymphocytes (CTLs), Helper T Lymphocytes (HTLs), and Beta-cells (B-cells) were predicted for each RBD-containing region of the three highly pathogenic hCoVs. This was followed by the structural organization of peptide- and mRNA-based prophylactic vaccine designs. The validated 3D structures of these epitope-based vaccine designs were subjected to molecular docking with human TLR4. Furthermore, the CTL and HTL epitopes were processed for binding with respective human Lymphocytes Antigens (HLAs). In silico cloning designs were obtained for the prophylactic vaccine designs and may be useful in further experimental designs. Additionally, the epitope-based vaccine designs were evaluated for immunogenic activity through immune simulation. Further studies may clarify the safety and efficacy of these prophylactic vaccine designs through experimental testing against these human-pathogenic coronaviruses.

Overexpression of cathepsin S exacerbates lupus pathogenesis through upregulation TLR7 and IFN-α in transgenic mice

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease that affects multiple organs. Recent studies suggest relevance between cysteine protease cathepsin S (CTSS) expression and SLE. To investigate the mechanism of CTSS in SLE, CTSS-overexpressing transgenic (TG) mice were generated, and induced lupus-like symptoms. Eight months later, the TG mice spontaneously developed typical SLE symptoms regardless of the inducement. Furthermore, we observed increased toll-like receptor 7 (TLR7) expression with increased monocyte and neutrophil populations in the TG mice. In conclusion, overexpression of CTSS in mice influences TLR7 expression, autoantibodies and IFN-α, which leads to an autoimmune reaction and exacerbates lupus-like symptoms.

Skullcapflavone II Suppresses TNF-α/IFN-γ-Induced TARC, MDC, and CTSS Production in HaCaT Cells

Skullcapflavone II (SFII), a flavonoid derived from Scutellaria baicalensis, has been reported to have anti-inflammatory properties. However, its therapeutic potential for skin inflammatory diseases and its mechanism are unknown. Therefore, this study aimed to investigate the effect of SFII on TNF-α/IFN-γ-induced atopic dermatitis (AD)-associated cytokines, such as thymus- and activation-regulated chemokine (TARC) and macrophage-derived chemokine (MDC). Co-stimulation with TNF-α/IFN-γ in HaCaT cells is a well-established model for induction of pro-inflammatory cytokines. We treated cells with SFII prior to TNF-α/IFN-γ-stimulation and confirmed that it significantly inhibited TARC and MDC expression at the mRNA and protein levels. Additionally, SFII also inhibited the expression of cathepsin S (CTSS), which is associated with itching in patients with AD. Using specific inhibitors, we demonstrated that STAT1, NF-κB, and p38 MAPK mediate TNF-α/IFN-γ-induced TARC and MDC, as well as CTSS expression. Finally, we confirmed that SFII significantly suppressed TNF-α/IFN-γ-induced phosphorylation of STAT1, NF-κB, and p38 MAPK. Taken together, our study indicates that SFII inhibits TNF-α/IFN-γ-induced TARC, MDC, and CTSS expression by regulating STAT1, NF-κB, and p38 MAPK signaling pathways.

Unlocking the Non-IgE-Mediated Pseudo-Allergic Reaction Puzzle with Mas-Related G-Protein Coupled Receptor Member X2 (MRGPRX2)

Mas-related G-protein coupled receptor member X2 (MRGPRX2) is a class A GPCR expressed on mast cells. Mast cells are granulated tissue-resident cells known for host cell response, allergic response, and vascular homeostasis. Immunoglobulin E receptor (FcεRI)-mediated mast cell activation is a well-studied and recognized mechanism of allergy and hypersensitivity reactions. However, non-IgE-mediated mast cell activation is less explored and is not well recognized. After decades of uncertainty, MRGPRX2 was discovered as the receptor responsible for non-IgE-mediated mast cells activation. The puzzle of non-IgE-mediated pseudo-allergic reaction is unlocked by MRGPRX2, evidenced by a plethora of reported endogenous and exogenous MRGPRX2 agonists. MRGPRX2 is exclusively expressed on mast cells and exhibits varying affinity for many molecules such as antimicrobial host defense peptides, neuropeptides, and even US Food and Drug Administration-approved drugs. The discovery of MRGPRX2 has changed our understanding of mast cell biology and filled the missing link of the underlying mechanism of drug-induced MC degranulation and pseudo-allergic reactions. These non-canonical characteristics render MRGPRX2 an intriguing player in allergic diseases. In the present article, we reviewed the emerging role of MRGPRX2 as a non-IgE-mediated mechanism of mast cell activation in pseudo-allergic reactions. We have presented an overview of mast cells, their receptors, structural insight into MRGPRX2, MRGPRX2 agonists and antagonists, the crucial role of MRGPRX2 in pseudo-allergic reactions, current challenges, and the future research direction.

A domain-based vaccine construct against SARS-CoV-2, the causative agent of COVID-19 pandemic: development of self-amplifying mRNA and peptide vaccines

Introduction: Coronavirus disease 2019 (COVID-19) is undoubtedly the most challenging pandemic in the current century with more than 293,241 deaths worldwide since its emergence in late 2019 (updated May 13, 2020). COVID-19 is caused by a novel emerged coronavirus named severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Today, the world needs crucially to develop a prophylactic vaccine scheme for such emerged and emerging infectious pathogens. Methods: In this study, we have targeted spike (S) glycoprotein, as an important surface antigen to identify its B- and T-cell immunodominant regions. We have conducted a multi-method B-cell epitope (BCE) prediction approach using different predictor algorithms to discover the most potential BCEs. Besides, we sought among a pool of MHC class I and II-associated peptide binders provided by the IEDB server through the strict cut-off values. To design a broad-coverage vaccine, we carried out a population coverage analysis for a set of candidate T-cell epitopes and based on the HLA allele frequency in the top most-affected countries by COVID-19 (update 02 April 2020). Results: The final determined B- and T-cell epitopes were mapped on the S glycoprotein sequence, and three potential hub regions covering the largest number of overlapping epitopes were identified for the vaccine designing (I531-N711; T717-C877; and V883-E973). Here, we have designed two domain-based constructs to be produced and delivered through the recombinant protein- and gene-based approaches, including (i) an adjuvanted domain-based protein vaccine construct (DPVC), and (ii) a self-amplifying mRNA vaccine (SAMV) construct. The safety, stability, and immunogenicity of the DPVC were validated using the integrated sequential (i.e. allergenicity, autoimmunity, and physicochemical features) and structural (i.e. molecular docking between the vaccine and human Toll-like receptors (TLRs) 4 and 5) analysis. The stability of the docked complexes was evaluated using the molecular dynamics (MD) simulations. Conclusion: These rigorous in silico validations supported the potential of the DPVC and SAMV to promote both innate and specific immune responses in preclinical studies.

Mas-related G protein-coupled receptor X2 and its activators in dermatologic allergies

The Mas-related G protein-coupled receptor X2 (MRGPRX2) is a multiligand receptor responding to various exogenous and endogenous stimuli. Being highly expressed on skin mast cells, MRGPRX2 triggers their degranulation and release of proinflammatory mediators, and it promotes multicellular signaling cascades, such as itch induction and transmission in sensory neurons. The expression of MRGPRX2 by skin mast cells and the levels of the MRGPRX2 agonists (eg, substance P, major basic protein, eosinophil peroxidase) are upregulated in the serum and/or skin of patients with inflammatory and pruritic skin diseases, such as chronic spontaneous urticaria or atopic dermatitis. Therefore, MRGPRX2 and its agonists might be potential biomarkers for the progression of cutaneous inflammatory diseases and the response to treatment. In addition, they may represent promising targets for prevention and treatment of signs and symptoms in patients with skin diseases or drug reactions. To assess this possibility, this review explores the role and relevance of MRGPRX2 and its activators in cutaneous inflammatory disorders and chronic pruritus.

Single-Cell Profiling Reveals Divergent, Globally Patterned Immune Responses in Murine Skin Inflammation

Inflammatory response heterogeneity has impeded high-resolution dissection of diverse immune cell populations during activation. We characterize mouse cutaneous immune cells by single-cell RNA sequencing, after inducing inflammation using imiquimod and oxazolone dermatitis models. We identify 13 CD45⁺ subpopulations, which broadly represent most functionally characterized immune cell types. Oxazolone pervasively upregulates Jak2/Stat3 expression across T cells and antigen-presenting cells (APCs). Oxazolone also induces Il4/Il13 expression in newly infiltrating basophils, and Il4ra and Ccl24, most prominently in APCs. In contrast, imiquimod broadly upregulates Il17/Il22 and Ccl4/Ccl5. A comparative analysis of single-cell inflammatory transcriptional responses reveals that APC response to oxazolone is tightly restricted by cell identity, whereas imiquimod enforces shared programs on multiple APC populations in parallel. These global molecular patterns not only contrast immune responses on a systems level but also suggest that the mechanisms of new sources of inflammation can eventually be deduced by comparison to known signatures.

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Oxazolone pervasively upregulates Jak2/Stat3 expression across T cells and APCs

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Il4/Il13 induction in skin by oxazolone is dominated by infiltrating basophils

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Imiquimod broadly increases Il17/Il22 and Ccl4/Ccl5, extending to non-T cells

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Oxazolone induces more highly compartmentalized immune cell responses than imiquimod

Expression of elastolytic cathepsins in human skin and their involvement in age-dependent elastin degradation

BACKGROUND

Skin ageing is associated with structure-functional changes in the extracellular matrix, which is in part caused by proteolytic degradation. Since cysteine cathepsins are major matrix protein-degrading proteases, we investigated the age-dependent expression of elastolytic cathepsins K, S, and V in human skin, their in vitro impact on the integrity of the elastic fibre network, their cleavage specificities, and the release of bioactive peptides.

METHODS

Cathepsin-mediated degradation of human skin elastin samples was assessed from young to very old human donors using immunohistochemical and biochemical assays, scanning electron microscopy, and mass spectrometry.

RESULTS

Elastin samples derived from patients between 10 and 86 years of age were analysed and showed an age-dependent deterioration of the fibre structure from a dense network of thinner fibrils into a beaded and porous mesh. Reduced levels of cathepsins K, S, and V were observed in aged skin with a predominant epidermal expression. Cathepsin V was the most potent elastase followed by cathepsin K and S. Biomechanical analysis of degraded elastin fibres corroborated the destructive activity of cathepsins. Mass spectrometric determination of the cleavage sites in elastin revealed that all three cathepsins predominantly cleaved in hydrophobic domains. The degradation of elastin was efficiently inhibited by an ectosteric inhibitor. Furthermore, the degradation of elastin fibres resulted in the release of bioactive peptides, which have previously been associated with various pathologies.

CONCLUSION

Cathepsins are powerful elastin-degrading enzymes and capable of generating a multitude of elastokines. They may represent a viable target for intervention strategies to reduce skin ageing.

Characteristics of Pruritus according to Morphological Phenotype of Psoriasis and Association with Neuropeptides and Interleukin-31

Background

Pruritus is a common symptom in psoriasis. However, few studies have assessed the characteristics of pruritus according to morphological phenotypes of psoriasis.

Objective

To investigate the characteristics of pruritus according to morphological phenotypes of psoriasis and to assess the association with inflammatory mediators related to pruritus.

Methods

Psoriasis patients were divided into 2 groups according to clinical phenotype: eruptive inflammatory (EI) and chronic stable (CS). Clinical data of pruritus were assessed by an itch questionnaire. Serum neuropeptides and cytokines including substance P, histamine, vasoactive intestinal peptide, neuropeptide Y, calcitonin gene-related peptide and interleukin-31 (IL-31) were quantitatively measured.

Results

In total, 50 patients with psoriasis (30 male, 20 female; mean age, 45.7 years) were studied (EI, n=15 and CS, n=35). Pruritus was reported by 80% of EI and CS patients. There were no significant differences in prevalence of pruritus, pruritus intensity, severity of psoriasis, serum neuropeptides, or IL-31 between the 2 groups.

Conclusion

The morphological phenotype does not seem to be an important factor affecting the prevalence and characteristics of pruritus in psoriasis.

A novel cathepsin L inhibitor prevents the progression of idiopathic pulmonary fibrosis

In previous work, the target of asperphenamate as a natural product was successfully determined as cathepsin by the natural product consensus pharmacophore strategy. In order to develop accurate SAR (structure-activity relationship) of asperphenamate-type cathepsin inhibitor, we chose several novel analogs with heterocyclic moiety to perform further study. The molecular simulation showed that 4-pyridyl derivative 3 with the greatest cathepsin inhibitory activity presented new interaction modes with protein utilizing its B-ring moiety. And then molecular dynamics (MD) simulation further revealed that 3 and cathepsin kept stable interaction in the binding site, which validated the molecular docking results. In view that cathepsins play an important role in fibrosis and some cathepsin inhibitors display the therapeutic ability for fibrosis, we investigated the anti-fibrotic effect of 3in vitro and in vivo. The results indicated that 3 displayed the strongest inhibitory effect on the formation of α-SMA and collagen I as the protein markers of fibrosis among all tested derivatives. Further in vivo assay confirmed that 3 indeed showed significant inhibitory ability against pulmonary fibrosis by the method of H&E and Masson staining as well as immunohistochemical staining for characteristic α-SMA proteins.

Biomechanical Factors in Psoriatic Disease: Defective Repair Exertion as a Potential Cause. Hypothesis Presentation and Literature Review

Joining main clinical manifestations of psoriatic skin disorder are inflammatory arthritis and nail lesions. Repetitive microdamage has been postulated as a main triggering factor in lesions of psoriatic arthritis. This concept of psoriatic disease might also be admissible for triggering nail lesions because the nail is a frequently traumatized structure. Here, we aimed to describe the conjectural injury mechanisms of nail complex with regard to acting biomechanical factors. Tissue repair response to physical microdamage may be altered in psoriatic disease. It is plausible to consider that a defective repair process in the dysregulated prepsoriatic tissue may lead to innate immune activation and further development of autoinflammatory lesions, although excessive inflammation is known to impair wound healing. Recently published data have revealed the importance of mechanosensitive Wingless-type (Wnt) signaling in the pathophysiology of psoriasis and ankylosing spondylitis. The Wnt signaling system is involved in morphogenesis, repair, and regeneration as a biologic process main regulator. Wnt5a seems to be a dominating mediator in both psoriatic plaques and during the spondylitis process that might also be a linking molecule of psoriatic response to mechanical stress. Future studies should focus on complex responsive interactions of tissue repair regulators regarded in psoriatic disease.

Cathepsin S acts via protease-activated receptor 2 to activate sensory neurons and induce itch-like behaviour

Chronic itch is a debilitating condition characterised by excessive scratching and is a symptom frequently reported in skin diseases such as atopic dermatitis. It has been proposed that release of the cysteine protease Cathepsin S (CatS) from skin keratinocytes or immune cells resident in or infiltrating the skin could act as a pruritogen in chronic itch conditions. CatS is known to activate protease-activated receptor 2 (PAR2). We therefore hypothesised that enzymatic activation of neuronally expressed PAR2 by CatS was responsible for activation of sensory neurons and transmission of itch signals. Intradermally-injected human recombinant (hr)-CatS or the PAR2 agonist, SLIGRL-NH2 behaved as pruritogens by causing scratching behaviour in mice. Hr-CatS-induced scratching behaviour was prevented by CatS inhibitors and PAR2 antagonists and reduced by 50% in TRPV1-/- mice compared with wild-type mice, whilst no significant reduction in scratching behaviour was observed in TRPA1-/- mice. Cultured dorsal root ganglion (DRG) cells showed an increase in [Ca2+]i following incubation with hr-CatS, and the percentage of neurons that responded to hr-CatS decreased in the presence of a PAR2 antagonist or in cultures of neurons from TRPV1-/- mice. Taken together, our results indicate CatS acts as a pruritogen via PAR2 activation in TRPV1-expressing sensory neurons.

Multi-omics integration reveals molecular networks and regulators of psoriasis

BACKGROUND

Psoriasis is a complex multi-factorial disease, involving both genetic susceptibilities and environmental triggers. Genome-wide association studies (GWAS) and epigenome-wide association studies (EWAS) have been carried out to identify genetic and epigenetic variants that are associated with psoriasis. However, these loci cannot fully explain the disease pathogenesis.

METHODS

To achieve a comprehensive mechanistic understanding of psoriasis, we conducted a systems biology study, integrating multi-omics datasets including GWAS, EWAS, tissue-specific transcriptome, expression quantitative trait loci (eQTLs), gene networks, and biological pathways to identify the key genes, processes, and networks that are genetically and epigenetically associated with psoriasis risk.

RESULTS

This integrative genomics study identified both well-characterized (e.g., the IL17 pathway in both GWAS and EWAS) and novel biological processes (e.g., the branched chain amino acid catabolism process in GWAS and the platelet and coagulation pathway in EWAS) involved in psoriasis. Finally, by utilizing tissue-specific gene regulatory networks, we unraveled the interactions among the psoriasis-associated genes and pathways in a tissue-specific manner and detected potential key regulatory genes in the psoriasis networks.

CONCLUSIONS

The integration and convergence of multi-omics signals provide deeper and comprehensive insights into the biological mechanisms associated with psoriasis susceptibility.

High Expression of Human Cathepsin S by Recombinant Pichia pastoris with Cod Skin as an Organic Co-Nitrogen Source

Human cathepsin S production by recombinant Pichia pastoris using cod skin as the co-nitrogen source was investigated in this study. The addition of carbon sources of glycerol in the fed-batch phase and of methanol in the induction stage was also investigated. A new approach to the highly expression of human cathepsin S was developed using 90 g/L of cod skin (wet weight). After 24 h of the initial fermentation, 4% glycerol (v/v, glycerol/culture) was added once to enhance the cell density (OD600) in the cultivation. Then, adding and maintaining methanol at 0.5% (v/v, methanol/cultivation) after about 48 h of fermentation achieved a high expression of human cathepsin S in a 5-L bioreactor. The results demonstrate that the maximum activity of human cathepsin S in the fermentation supernatant reached 7,152 U/L after 96 h of methanol induction. The methylotrophic yeast P. pastoris grown in the medium containing cod skin (90 g/L) as the co-nitrogen source provided a 21% higher cell density (OD600) and 18.3% higher human cathepsin S yield than P. pastoris grown in BMGY medium. For the first time, human cathepsin S was successfully expressed by P. pastoris with cod skin as the co-nitrogen source. The glycerol fed-batch controlling strategy and method of maintaining methanol at a constant concentration of 0.5% (v/v, methanol/cultivation) in the induction stage was efficient for P. pastoris growth and the expression of human cathepsin S.

RNA-Seq Analysis of IL-1B and IL-36 Responses in Epidermal Keratinocytes Identifies a Shared MyD88-Dependent Gene Signature

IL-36 cytokines have recently emerged as mediators of inflammation in autoimmune conditions including psoriasis vulgaris (PsV) and generalized pustular psoriasis (GPP). This study used RNA-seq to profile the transcriptome of primary epidermal keratinocytes (KCs) treated with IL-1B, IL-36A, IL-36B, or IL-36G. We identified some early IL-1B-specific responses (8 h posttreatment), but nearly all late IL-1B responses were replicated by IL-36 cytokines (24 h posttreatment). Type I and II interferon genes exhibited time-dependent response patterns, with early induction (8 h) followed by no response or repression (24 h). Altogether, we identified 225 differentially expressed genes (DEGs) with shared responses to all 4 cytokines at both time points (8 and 24 h). These involved upregulation of ligands (IL1A, IL1B, and IL36G) and activating proteases (CTSS) but also upregulation of inhibitors such as IL1RN and IL36RN. Shared IL-1B/IL-36 DEGs overlapped significantly with genes altered in PsV and GPP skin lesions, as well as genes near GWAS loci linked to autoimmune and autoinflammatory diseases (e.g., PsV, psoriatic arthritis, inflammatory bowel disease, and primary biliary cholangitis). Inactivation of MyD88 adapter protein using CRISPR/Cas9 completely abolished expression responses of such DEGs to IL-1B and IL-36G stimulation. These results provide a global view of IL-1B and IL-36 expression responses in epidermal KCs with fine-scale characterization of time-dependent and cytokine-specific response patterns. Our findings support an important role for IL-1B and IL-36 in autoimmune or autoinflammatory conditions and show that MyD88 adaptor protein mediates shared IL-1B/IL-36 responses.

Mrgprs activation is required for chronic itch conditions in mice

Introduction

Chronic itch has been drawing much attention due to its clinical significance and the complexity of its mechanisms. To facilitate the development of anti-itch strategies, it is necessary to investigate the key players in itch sensation under chronic itch conditions. Several members of the Mrgpr family were identified as itch receptors that detect cutaneous pruritogens in primary sensory neurons. However, the role of Mrgprs in chronic itch conditions has not been well described.

Methods

Scratching behaviors of WT and Mrgpr-clusterΔ^-/- mice were examined in dry skin model and contact dermatitis model to examine the role of Mrgpr genes in mediating chronic itch sensation. Scratching behaviors of the mice were also examined in allergic itch model. Real-time PCR were performed to examine the expression level of MrgprA3 and MrgprC11 under naïve and dry skin conditions. The MrgprA3⁺ itch-sensing fibers were labeled by tdTomato fluorescence in Mrgpra3^GFP-Cre; ROSA26^tdTomato mice, and the morphology and density of those fibers in the epidermis were analyzed under dry skin condition.

Results

We showed that deleting a cluster of Mrgpr genes in mice reduced scratching behavior severely under two chronic itch conditions, namely dry skin and contact dermatitis, and the allergic itch condition. Moreover, the gene expressions of itch receptors MrgprA3 and MrgprC11 in dorsal root ganglia (DRG) were upregulated significantly under dry skin condition. Consistently, the percentage of MrgprA3⁺ itch-sensing neurons was increased as well. We also observed hyperinnervation of MrgprA3⁺ itch-sensing fibers in the epidermis of the skin under dry skin condition.

Discussion

We demonstrate that Mrgprs play important roles in mediating chronic itch and allergic itch. These findings enrich our knowledge of itch mechanism and may lead to the development of novel therapeutic approach to combat itch.

Models in the Research Process of Psoriasis

Psoriasis is an ancient, universal chronic skin disease with a significant geographical variability, with the lowest incidence rate at the equator, increasing towards the poles. Insights into the mechanisms responsible for psoriasis have generated an increasing number of druggable targets and molecular drugs. The development of relevant in vitro and in vivo models of psoriasis is now a priority and an important step towards its cure. In this review, we summarize the current cellular and animal systems suited to the study of psoriasis. We discuss the strengths and limitations of the various models and the lessons learned. We conclude that, so far, there is no one model that can meet all of the research needs. Therefore, the choice model system will depend on the questions being addressed.

Cathepsin S inhibition suppresses autoimmune-triggered inflammatory responses in macrophages

In several types of antigen-presenting cells (APCs), Cathepsin S (CatS) plays a crucial role in the regulation of MHC class II surface expression and consequently influences antigen (Ag) presentation of APCs to CD4⁺ T cells. During the assembly of MHC class II-Ag peptide complexes, CatS cleaves the invariant chain p10 (Lip10) - a fragment of the MHC class II-associated invariant chain peptide. In this report, we used a selective, high-affinity CatS inhibitor to suppress the proteolytic activity of CatS in lymphoid and myeloid cells. CatS inhibition resulted in a concentration-dependent Lip10 accumulation in B cells from both healthy donors and patients with systemic lupus erythematosus (SLE). Furthermore, CatS inhibition led to a decreased MHC class II expression on B cells, monocytes, and proinflammatory macrophages. In SLE patient-derived peripheral blood mononuclear cells, CatS inhibition led to a suppressed secretion of IL-6, TNFα, and IL-10. In a second step, we tested the effect of CatS inhibition on macrophages being exposed to patient-derived autoantibodies against C1q (anti-C1q) that are known to be associated with severe lupus nephritis. As shown previously, those SLE patient-derived high-affinity anti-C1q bound to immobilized C1q induce a proinflammatory phenotype in macrophages. Using this human in vitro model of autoimmunity, we found that CatS inhibition reduces the inflammatory responses of macrophages as demonstrated by a decreased secretion of proinflammatory cytokines, the downregulation of MHC class II and CD80. In summary, we can show that the used CatS inhibitor is able to block Lip10 degradation in healthy donor- and SLE patient-derived B cells and inhibits the induction of proinflammatory macrophages. Thus, CatS inhibition seems to be a promising future treatment of SLE.

Cathepsin K Inhibitors for Osteoporosis: Biology, Potential Clinical Utility, and Lessons Learned

Cathepsin K is a cysteine protease member of the cathepsin lysosomal protease family. Although cathepsin K is highly expressed in osteoclasts, lower levels of cathepsin K are also found in a variety of other tissues. Secretion of cathepsin K from the osteoclast into the sealed osteoclast-bone cell interface results in efficient degradation of type I collagen. The absence of cathepsin K activity in humans results in pycnodysostosis, characterized by increased bone mineral density and fractures. Pharmacologic cathepsin K inhibition leads to continuous increases in bone mineral density for ≤5 years of treatment and improves bone strength at the spine and hip. Compared with other antiresorptive agents, cathepsin K inhibition is nearly equally efficacious for reducing biochemical markers of bone resorption but comparatively less active for reducing bone formation markers. Despite multiple efforts to develop cathepsin K inhibitors, potential concerns related to off-target effects of the inhibitors against other cathepsins and cathepsin K inhibition at nonbone sites, including skin and perhaps cardiovascular and cerebrovascular sites, prolonged the regulatory approval process. A large multinational randomized, double-blind phase III study of odanacatib in postmenopausal women with osteoporosis was recently completed. Although that study demonstrated clinically relevant reductions in fractures at multiple sites, odanacatib was ultimately withdrawn from the regulatory approval process after it was found to be associated with an increased risk of cerebrovascular accidents. Nonetheless, the underlying biology and clinical effects of cathepsin K inhibition remain of considerable interest and could guide future therapeutic approaches for osteoporosis.

Cathepsin S is the major activator of the psoriasis-associated proinflammatory cytokine IL-36γ

The proinflammatory cytokine IL-36γ is highly expressed in epithelial cells and is a pivotal mediator of epithelial inflammation. In particular, IL-36γ is strongly associated with the inflammatory skin disease psoriasis. As with other IL-1 cytokines, IL-36γ is expressed as an inactive precursor and must be processed by specific proteases to become bioactive. Our aim therefore was to identify protease/s capable of IL-36γ activation and explore the importance of this activation in psoriasis. Using a keratinocyte-based activity assay in conjunction with small-molecule inhibitors and siRNA gene silencing, cathepsin S was identified as the major IL-36γ-activating protease expressed by epithelial cells. Interestingly, cathepsin S activity was strongly up-regulated in samples extracted from psoriasis patients relative to healthy controls. In addition, IL-36γ-Ser18, identified as the main product of cathepsin S-dependent IL-36γ cleavage, induced psoriasiform changes in human skin-equivalent models. Together, these data provide important mechanistic insights into the activation of IL-36γ and highlight that cathepsin S-mediated activation of IL-36γ may be important in the development of numerous IL-36γ-driven pathologies, in addition to psoriasis.

Early Activation of Th2/Th22 Inflammatory and Pruritogenic Pathways in Acute Canine Atopic Dermatitis Skin Lesions

Determining inflammation and itch pathway activation in patients with atopic dermatitis (AD) is fraught with the inability to precisely assess the age of skin lesions, thus affecting the analysis of time-dependent mediators. To characterize inflammatory events occurring during early experimental acute AD lesions, biopsy samples were collected 6, 24, and 48 hours after epicutaneous application of Dermatophagoides farinae house dust mites to sensitized atopic dogs. The skin transcriptome was assessed using a dog-specific microarray and quantitative PCR. Acute canine AD skin lesions had a significant up-regulation of genes encoding T helper (Th) 2 (e.g., IL4, IL5, IL13, IL31, and IL33), Th9 (IL9), and Th22 (IL22) cytokines as well as Th2-promoting chemokines such as CCL5 and CCL17. Proinflammatory (e.g., IL6, LTB, and IL18) cytokines were also up-regulated. Other known pruritogenic pathways were also activated: there was significant up-regulation of genes encoding proteases cathepsin S (CTSS), mast cell chymase (CMA1), tryptase (TPS1) and mastin, neuromedin-B (NMB), nerve growth factor (NGF), and leukotriene-synthesis enzymes (ALOX5, ALOX5AP, and LTA4H). Experimental acute canine house dust mite-induced AD lesions exhibit an activation of innate and adaptive immune responses and pruritogenic pathways similar to those seen in humans with acute AD, thereby validating this model to test innovative therapeutics modalities for this disease.

A bioavailable cathepsin S nitrile inhibitor abrogates tumor development

Background

Cathepsin S has been implicated in a variety of malignancies with genetic ablation studies demonstrating a key role in tumor invasion and neo-angiogenesis. Thus, the application of cathepsin S inhibitors may have clinical utility in the treatment of cancer. In this investigation, we applied a cell-permeable dipeptidyl nitrile inhibitor of cathepsin S, originally developed to target cathepsin S in inflammatory diseases, in both in vitro and in vivo tumor models.

Methods

Validation of cathepsin S selectivity was carried out by assaying fluorogenic substrate turnover using recombinant cathepsin protease. Complete kinetic analysis was carried out and true K_i values calculated. Abrogation of tumour invasion using murine MC38 and human MCF7 cell lines were carried out in vitro using a transwell migration assay. Effect on endothelial tube formation was evaluated using primary HUVEC cells. The effect of inhibitor in vivo on MC38 and MCF7 tumor progression was evaluated using cells propagated in C57BL/6 and BALB/c mice respectively. Subsequent immunohistochemical staining of proliferation (Ki67) and apoptosis (TUNEL) was carried out on MCF7 tumors.

Results

We confirmed that this inhibitor was able to selectively target cathepsin S over family members K, V, L and B. The inhibitor also significantly reduced MC38 and MCF7 cell invasion and furthermore, significantly reduced HUVEC endothelial tubule formation in vitro. In vivo analysis revealed that the compound could significantly reduce tumor volume in murine MC38 syngeneic and MCF7 xenograft models. Immunohistochemical analysis of MCF7 tumors revealed cathepsin S inhibitor treatment significantly reduced proliferation and increased apoptosis.

Conclusions

In summary, these results highlight the characterisation of this nitrile cathepsin S inhibitor using in vitro and in vivo tumor models, presenting a compound which may be used to further dissect the role of cathepsin S in cancer progression and may hold therapeutic potential.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-016-0513-7) contains supplementary material, which is available to authorized users.

A novel approach for reliable detection of cathepsin S activities in mouse antigen presenting cells

Cathepsin S (CTSS) is a eukaryotic protease mostly expressed in professional antigen presenting cells (APCs). Since CTSS activity regulation plays a role in the pathogenesis of various autoimmune diseases like multiple sclerosis, atherosclerosis, Sjögren's syndrome and psoriasis as well as in cancer progression, there is an ongoing interest in the reliable detection of cathepsin S activity. Various applications have been invented for specific detection of this enzyme. However, most of them have only been shown to be suitable for human samples, do not deliver quantitative results or the experimental procedure requires technical equipment that is not commonly available in a standard laboratory. We have tested a fluorogen substrate, Mca-GRWPPMGLPWE-Lys(Dnp)-DArg-NH2, that has been described to specifically detect CTSS activities in human APCs for its potential use for mouse samples. We have modified the protocol and thereby offer a cheap, easy, reproducible and quick activity assay to detect CTSS activities in mouse APCs. Since most of basic research on CTSS is performed in mice, this method closes a gap and offers a possibility for reliable and quantitative CTSS activity detection that can be performed in almost every laboratory.

Redefining the concept of protease-activated receptors: cathepsin S evokes itch via activation of Mrgprs

Sensory neurons expressing Mas-related G protein coupled receptors (Mrgprs) mediate histamine-independent itch. We show that the cysteine protease cathepsin S activates MrgprC11 and evokes receptor-dependent scratching in mice. In contrast to its activation of conventional protease-activated receptors, cathepsin S mediated activation of MrgprC11 did not involve the generation of a tethered ligand. We demonstrate further that different cysteine proteases selectively activate specific mouse and human Mrgpr family members. This expansion of our understanding by which proteases interact with GPCRs redefines the concept of what constitutes a protease-activated receptor. The findings also implicate proteases as ligands to members of this orphan receptor family while providing new insights into how cysteine proteases contribute to itch.

Cysteine cathepsins: their role in tumor progression and recent trends in the development of imaging probes

Papain-like cysteine proteases bear an enormous potential as drug discovery targets for both infectious and systemic human diseases. The considerable progress in this field over the last two decades has also raised interest in the visualization of these enzymes in their native context, especially with regard to tumor imaging. After a short introduction to structure and general functions of human cysteine cathepsins, we highlight their importance for drug discovery and development and provide a critical update on the current state of knowledge toward their involvement in tumor progression, with a special emphasis on their role in therapy response. In accordance with a radiopharmaceutical point of view, the main focus of this review article will be the discussion of recently developed fluorescence and radiotracer-based imaging agents together with related molecular probes.

Protease-activated receptors and itch

Protease-activated receptors (PARs) have been implicated in a variety of physiological functions, as well as somatosensation and particularly itch and pain. Considerable attention has focused on PARs following the finding they are upregulated in the skin of atopic dermatitis patients. The present review focuses on recent studies showing that PARs are critically involved in itch and sensitization of itch. PARs are expressed by diverse cell types including primary sensory neurons, keratinocytes, and immune cells and are activated by proteases that expose a tethered ligand. Endogenous proteases are also released from diverse cell types including keratinocytes and immune cells. Exogenous proteases released from certain plants and insects contacting the skin can also induce itch. Increased levels of proteases in the skin contribute to inflammation that is often accompanied by chronic itch which is not predominantly mediated by histamine. The neural pathway signaling itch induced by activation of PARs is distinct from that mediating histamine-induced itch. In addition, there is evidence that PARs play an important role in sensitization of itch signaling under conditions of chronic itch. These recent findings suggest that PARs and other molecules involved in the itch-signaling pathway are good targets to develop novel treatments for most types of chronic itch that are poorly treated with antihistamines.

Increased immunoreactivity of cathepsins in the rat esophagus under chronic acid reflux esophagitis

We have designed a stable rat chronic acid reflux esophagitis (RE) model. In gastrointestinal lesions, several lysosomal cathepsins are known to participate in epithelial permeability in cell-cell connections, such as tight junctions in ulcerative colitis. However, very few studies have focused on the distribution of cathepsins in the esophageal multilayer squamous epithelium. Therefore to clarify the role of cathepsins in RE, we investigated their immunohistological localization in the esophageal epithelium under normal conditions and after RE. Of the cathepsins examined (cathepsins B, C, D, F, H, L, S, and X), granular immunoreactivity for cathepsins B, C, D and L was observed in the control esophageal epithelia; although, their distribution differed depending on the enzyme examined. In the RE model, immunoreactivity of these cathepsins was increased in esophageal epithelial cells and activated macrophages. The immunoreactivity for cathepsins F, H, S and X was barely detectable in the control esophageal epithelium. However, in the RE model, we noticed a slight increase in the expression of cathepsins H and X in the epithelial cells. Furthermore, activated macrophages of the RE model possessed intense immunoreactivity for these cathepsins, which may have been related to esophageal inflammatory mechanisms.

Differential expression of cathepsins K, S and V between young and aged Caucasian women skin epidermis

Cutaneous aging translates drastic structural and functional alterations in the extracellular matrix (ECM). Multiple mechanisms are involved, including changes in protease levels. We investigated the age-related protein expression and activity of cysteine cathepsins and the expression of two endogenous protein inhibitors in young and aged Caucasian women skin epidermis. Immunofluorescence studies indicate that the expression of cathepsins K, S and V, as well as cystatins A and M/E within keratinocytes is reduced in photoprotected skin of aged women. Furthermore, the overall endopeptidase activity of cysteine cathepsins in epidermis lysates decreased with age. Albeit dermal elastic fiber and laminin expression is reduced in aged skin, staining of nidogen-1, a key protein in BM assembly that is sensitive to proteolysis by cysteine, metallo- and serine proteases, has a similar pattern in both young and aged skin. Since cathepsins contribute to the hydrolysis and turnover of ECM/basement membrane components, the abnormal protein degradation and deposition during aging process may be related in part to a decline of lysosomal/endosomal cathepsin K, S and V activity.

Synthesis of proline analogues as potent and selective cathepsin S inhibitors

Cathepsin S is a potential target of autoimmune disease. A series of proline derived compounds were synthesized and evaluated as cathepsin S inhibitors. We discovered potent cathepsin S inhibitors through structure-activity relationship studies of proline analogues. In particular, compound 19-(S) showed promising in vitro/vivo pharmacological activities and properties as a selective cathepsin S inhibitor.

Cleavage of nidogen-1 by cathepsin S impairs its binding to basement membrane partners

Cathepsin S (catS), which is expressed in normal human keratinocytes and localized close to the dermal-epidermal junction (DEJ) degrades some of major basement membrane (BM) constituents. Among them, catS readily hydrolyzed in a time and dose dependent manner human nidogen-1 (nid-1) and nidogen-2, which are key proteins in the BM structure. CatS preferentially cleaved nid-1 at both acid and neutral pH. Hydrolysis of nid-1 was hampered in murine ctss^−/− spleen lysates pretreated with inhibitors of other classes of proteases. Nid-1 was cleaved within its G2 and G3 globular domains that are both involved in interactions with other BM components. Binding assays with soluble and immobilized ligands indicated that catS altered the formation of complexes between nid-1 and other BM components. Assuming that the cleavage of nid-1 impairs its ability to crosslink with BM partners and perturbs the viscoelastic properties of BM matrix, these data indicate that catS may participate in BM proteolysis, in addition to already identified proteases.