Increased Cathepsin S activity associated with decreased protease inhibitory capacity contributes to altered tear proteins in Sjögren's Syndrome patients

Rational design of humanized antibody inhibitors for cathepsin S

Cathepsin S (CTSS) is involved in pathogenesis of many human diseases. Inhibitors blocking its protease activity hold therapeutic potential. In comparison to small-molecule inhibitors, monoclonal antibodies capable of inhibiting CTSS enzymatic activity may possess advantageous pharmacological properties. Here we designed and produced inhibitory antibodies targeting human CTSS by genetically fusing the propeptide of procathepsin S (proCTSS) with antibodies in clinic. The resulting antibody fusions in full-length or fragment antigen-binding format could be stably expressed and potently inhibit CTSS proteolytic activity in high specificity. These fusion antibodies not only demonstrate a new approach for facile synthesis of antibody inhibitors against CTSS, but also represent novel anti-CTSS therapeutic candidates.

The Potential Utility of Salivary and Tear Proteomics to Discriminate Sjögren's Disease from Non-Sjögren's Sicca

Sjögren's Disease (SjD) is an autoimmune disorder associated with decreased saliva and/or tear secretions, resulting in patients reporting dryness in the mouth and eyes. Serum autoantibodies directed against the Ro60/SS-A and La/SS-B autoantigens are a distinctive feature of the disease. Analysis of the saliva and tear proteomes represents one promising alternative method of both classifying and monitoring the condition, and research into salivary and tear proteomics in patients with SjD, with and without sicca, has shown its efficacy and practicality in both clinical and research settings. Studies analyzing the saliva proteomics of SjD patients have generally shown an overexpression of proteins involved in T-cell activation, the immune response, β-2 microglobulin, and the recruitment of pro-inflammatory agents. These studies also show a decrease in or downregulation of proteins involved in salivary secretion. Studies analyzing the tear proteomics of patients with SjD have generally indicated an upregulation of proteins involved with TNF-α signaling, B-cell survival, and the recruitment of pro-inflammatory agents. Studies also note the differential expression of tear protein folding as a hallmark of ocular involvement in this condition. These findings help to elucidate the biochemical relationship between the proteomes of saliva/tear fluids and the general pathophysiology of the gland involved with the pathogenesis of this condition, giving further credence to the potential role of salivary and tear proteomics in the future of diagnosis and treatment for patients with SjD.

Advances in mesenchymal stem cell-derived extracellular vesicles therapy for Sjogren's syndrome-related dry eye disease

Sjogren's syndrome (SS) is a chronic autoimmune disorder that affects exocrine glands, particularly lacrimal glands, leading to dry eye disease (DED). DED is a common ocular surface disease that affects millions of people worldwide, causing discomfort, visual impairment, and even blindness in severe cases. However, there is no definitive cure for DED, and existing treatments primarily relieve symptoms. Consequently, there is an urgent need for innovative therapeutic strategies based on the pathophysiology of DED. Mesenchymal stem cells (MSCs) have emerged as a promising therapeutic tool for various autoimmune disorders, including SS-related DED (SS-DED). A particularly intriguing facet of MSCs is their ability to produce extracellular vesicles (EVs), which contain various bioactive components such as proteins, lipids, and nucleic acids. These molecules play a key role in facilitating communication between cells and modulating a wide range of biological processes. Importantly, MSC-derived EVs (MSC-EVs) have therapeutic properties similar to those of their parent cells, including immunomodulatory, anti-inflammatory, and regenerative properties. In addition, MSC-EVs offer several notable advantages over intact MSCs, including lower immunogenicity, reduced risk of tumorigenicity, and greater convenience in terms of storage and transport. In this review, we elucidate the underlying mechanisms of SS-DED and discuss the relevant mechanisms and targets of MSC-EVs in treating SS-DED. In addition, we comprehensively review the broader landscape of EV application in autoimmune and corneal diseases. This review focuses on the efficacy of MSC-EVs in treating SS-DED, a field of study that holds considerable appeal due to its multifaceted regulation of immune responses and regenerative functions.

A randomized, double-blind, placebo-controlled, parallel group study on the effects of a cathepsin S inhibitor in primary Sjögren's syndrome

OBJECTIVES

Primary SS (pSS) is a chronic autoimmune disorder characterized by mucosal dryness and systemic symptoms. We tested the effects of inhibition of cathepsin S using the potent and selective inhibitor RO5459072 on disease activity and symptoms of pSS.

METHODS

This was a randomized, double-blind, placebo-controlled, parallel-group, Phase IIA study to investigate the effects of RO5459072 (100 mg twice daily; 200 mg per day). Seventy-five patients with pSS were randomized 1:1 to receive either RO5459072 or placebo for 12 weeks. The primary outcome was the proportion of patients with a ≥3 point reduction from baseline in EULAR SS Disease Activity Index (ESSDAI) score. We also investigated the effects of RO5459072 on quality of life, exocrine gland function, biomarkers related to SS, and safety and tolerability.

RESULTS

The proportion of patients showing an improvement in ESSDAI score was not significantly different between the RO5459072 and placebo arms. No clinically meaningful treatment effects were observed in favour of RO5459072 for all secondary outcomes. Analysis of soluble biomarkers indicated target engagement between RO5459072 and cathepsin S. There were modest decreases in the number of circulating B cells and T cells in the RO5459072 group, although these did not reach significance. RO5459072 was safe and well-tolerated.

CONCLUSIONS

There was no clinically relevant improvement in ESSDAI score (primary endpoint), and no apparent benefit in favour of RO5459072 in any of the secondary clinical endpoints. Further work is needed in order to understand the mechanisms of MHC-II-mediated immune stimulation in pSS.

TRIAL REGISTRATION

ClinicalTrials.gov; NCT02701985.

Review of genes potentially related to hyposecretion in male non-obese diabetic (NOD) mice, a Sjögren's syndrome model

BACKGROUND

Sjögren's syndrome (SS) is known to cause dry eyes and mouth due to inflammation of the lacrimal and salivary glands. However, some reports imply that other factors trigger dry eyes and mouth. We previously investigated various factors using RNA-sequencing analysis of lacrimal glands from male non-obese diabetic (NOD) mice, an SS model. In this review, we described (1) the exocrine features of male and female NOD mice, (2) the up- and down-regulated genes in the lacrimal glands of male NOD mice as revealed by our RNA-sequencing data, and (3) comparisons between these genes and data in the Salivary Gland Gene Expression Atlas.

HIGHLIGHTS

Male NOD mice exhibit a steady worsening of lacrimal hyposecretion and dacryoadenitis, whereas females exhibit a complex pathophysiological condition that includes diabetic disease, salivary hyposecretion, and sialadenitis. Ctss, an up-regulated gene, is a potential inducer of lacrimal hyposecretion and is also expressed in salivary glands. Two other up-regulated genes, Ccl5 and Cxcl13, may worsen the inflammation of SS in both the lacrimal and salivary glands. The genes Esp23, Obp1a, and Spc25 were detected as down-regulated, but judging the relationship between these genes and hyposecretion is difficult as only limited information is available. Another down-regulated gene, Arg1, is involved in lacrimal hyposecretion, and it also has the potential to cause salivary hyposecretion in NOD mice.

CONCLUSION

In NOD mice, males may be better than females at evaluating the pathophysiology of SS. Some regulated genes revealed by our RNA-sequencing data might be potential therapeutic targets for SS.

Cathepsin S (CTSS) activity in health and disease - A treasure trove of untapped clinical potential

Amongst the lysosomal cysteine cathepsin family of proteases, cathepsin S (CTSS) holds particular interest due to distinctive properties including a normal restricted expression profile, inducible upregulation and activity at a broad pH range. Consequently, while CTSS is well-established as a member of the proteolytic cocktail within the lysosome, degrading unwanted and damaged proteins, it has increasingly been shown to mediate a number of distinct, more selective roles including antigen processing and antigen presentation, and cleavage of substrates both intra and extracellularly. Increasingly, aberrant CTSS expression has been demonstrated in a variety of conditions and disease states, marking it out as both a biomarker and potential therapeutic target. This review seeks to contextualise CTSS within the cysteine cathepsin family before providing an overview of the broad range of pathologies in which roles for CTSS have been identified. Additionally, current clinical progress towards specific inhibitors is detailed, updating the position of the field in exploiting this most unique of proteases.

Tear Biomarkers in Alzheimer's and Parkinson's Diseases, and Multiple Sclerosis: Implications for Diagnosis (Systematic Review)

Biological material is one of the most important aspects that allow for the correct diagnosis of the disease, and tears are an interesting subject of research because of the simplicity of collection, as the well as the relation to the components similar to other body fluids. In this review, biomarkers for Alzheimer's disease (AD), Parkinson's disease (PD), and multiple sclerosis (MS) in tears are investigated and analyzed. Records were obtained from the PubMed and Google Scholar databases in a timeline of 2015-2022. The keywords were: tear film/tear biochemistry/tear biomarkers + diseases (AD, PD, or MS). The recent original studies were analyzed, discussed, and biomarkers present in tears that can be used for the diagnosis and management of AD, PD, and MS diseases were shown. α-synTotal and α-synOligo, lactoferrin, norepinephrine, adrenaline, epinephrine, dopamine, α-2-macroglobulin, proteins involved in immune response, lipid metabolism and oxidative stress, apolipoprotein superfamily, and others were shown to be biomarkers in PD. For AD as potential biomarkers, there are: lipocalin-1, lysozyme-C, and lacritin, amyloid proteins, t-Tau, p-Tau; for MS there are: oligoclonal bands, lipids containing choline, free carnitine, acylcarnitines, and some amino acids. Information systematized in this review provides interesting data and new insight to help improve clinical outcomes for patients with neurodegenerative disorders.

Proteases and Their Potential Role as Biomarkers and Drug Targets in Dry Eye Disease and Ocular Surface Dysfunction

Dry eye disease (DED) is a multifactorial disorder that leads to ocular discomfort, visual disturbance, and tear film instability. DED is accompanied by an increase in tear osmolarity and ocular surface inflammation. The diagnosis and treatment of DED still present significant challenges. Therefore, novel biomarkers and treatments are of great interest. Proteases are present in different tissues on the ocular surface. In a healthy eye, proteases are highly regulated. However, dysregulation occurs in various pathologies, including DED. With this review, we provide an overview of the implications of different families of proteases in the development and severity of DED, along with studies involving protease inhibitors as potential therapeutic tools. Even though further research is needed, this review aims to give suggestions for identifying novel biomarkers and developing new protease inhibitors.

Updates in diagnostics, treatments, and correlations between oral and ocular manifestations of Sjogren's syndrome

Sjogren's syndrome (SS) is characterized as an autoimmune disorder targeting secretory glands, including the lacrimal and salivary glands, causing dry eye and dry mouth predominantly in women over the age of 40. In this review, we summarize recent advancements in SS diagnostics, treatments, and our understanding of correlations between oral and ocular manifestations of SS. Google Scholar and PubMed databases were utilized to search peer-reviewed papers since 2016 on SS diagnosis, treatment, and correlations between oral and ocular manifestations. For diagnostics, we discuss the updated SS classification criteria by the American College of Rheumatology/European League Against Rheumatism (ACR/EULAR), new biomarkers, and compare studies of current diagnostic methods with alternative technologies. For treatments, we discuss topical, systemic, and surgical treatment developments in the management of oral and ocular symptoms of SS as there is still no cure for the disorder. Finally, we report studies that directly suggest correlations between the ocular surface disease and oral disease in SS, as well as shared abnormalities in the microbiome and cytokine expression that may be correlated. We conclude by stating limitations to our review as well as paths moving forward. Elucidating correlations between oral and ocular manifestations may be the key to furthering our understanding of SS pathogenesis as well as defining new standards for diagnosis and treatment.

Mucopolysaccharidosis Type IVA: Extracellular Matrix Biomarkers in Cardiovascular Disease

Cardiovascular disease (CVD) in Mucopolysaccharidosis Type IVA (Morquio A), signified by valvular disease and cardiac hypertrophy, is the second leading cause of death and remains untouched by current therapies. Enzyme replacement therapy (ERT) is the gold-standard treatment for MPS disorders including Morquio A. Early administration of ERT improves outcomes of patients from childhood to adulthood while posing new challenges including prognosis of CVD and ERT's negligible effect on cardiovascular health. Thus, having accurate biomarkers for CVD could be critical. Here we show that cathepsin S (CTSS) and elastin (ELN) can be used as biomarkers of extracellular matrix remodeling in Morquio A disease. We found in a cohort of 54 treatment naïve Morquio A patients and 74 normal controls that CTSS shows promising attributes as a biomarker in young Morquio A children. On the other hand, ELN shows promising attributes as a biomarker in adolescent and adult Morquio A. Plasma/urine keratan sulfate (KS), and urinary glycosaminoglycan (GAG) levels were significantly higher in Morquio A patients (p < 0.001) which decreased with age of patients. CTSS levels did not correlate with patients' phenotypic severity but differed significantly between patients (median range 5.45-8.52 ng/mL) and normal controls (median range 9.61-15.9 ng/mL; p < 0.001). We also studied α -2-macroglobulin (A2M), C-reactive protein (CRP), and circulating vascular cell adhesion molecule-1 (sVCAM-1) in a subset of samples to understand the relation between ECM biomarkers and the severity of CVD in Morquio A patients. Our experiments revealed that CRP and sVCAM-1 levels were lower in Morquio A patients compared to normal controls. We also observed a strong inverse correlation between urine/plasma KS and CRP (p = 0.013 and p = 0.022, respectively) in Morquio A patients as well as a moderate correlation between sVCAM-1 and CTSS in Morquio A patients at all ages (p = 0.03). As the first study to date investigating CTSS and ELN levels in Morquio A patients and in the normal population, our results establish a starting point for more elaborate studies in larger populations to understand how CTSS and ELN levels correlate with Morquio A severity.

Single-cell transcriptional profiling of murine conjunctival immune cells reveals distinct populations expressing homeostatic and regulatory genes

Immune cells in the exposed conjunctiva mucosa defend against environmental and microbial stresses. Expression profiling by single-cell RNA sequencing was performed to identify conjunctival immune cell populations expressing homeostatic and regulatory genes. Fourteen distinct clusters were identified, including myeloid cells (neutrophils, monocytes, macrophages), dendritic cells (DC), and lymphoid cells (B, T, γδT, ILC2, and NK) lineages. Novel neutrophil [lipocalin (Lcn2) high and low), and MHCII^lo macrophage (MP) clusters were identified. More than half of the cells map to myeloid and dendritic cell populations with differential expression profiles that include genes with homeostatic and regulatory functions: Serpinb2 (MHCII^lo macrophage), Apoe (monocyte), Cd209a (macrophage), Cst3 (cDC1), and IL4i1 in migratory DC (mDC). ILC2 expresses the goblet cell trophic factor IL-13. Suppressed inflammatory and activated anti-inflammatory/regulatory pathways were observed in certain myeloid and DC populations. Confocal immunolocalization of identity markers showed mDC (CCR7, FASCIN1) located on or within the conjunctival epithelium. Monocyte, macrophage, cDC1 and IL-13/IL-5⁺ ILC2 were located below the conjunctival epithelium and goblet cells. This study found distinct immune cell populations in the conjunctiva and identified cells expressing genes with known homeostatic and immunoregulatory functions.

Tear miRNAs Identified in a Murine Model of Sjögren’s Syndrome as Potential Diagnostic Biomarkers and Indicators of Disease Mechanism

Objective

The tear miRNAome of the male NOD mouse, a model of ocular symptoms of Sjögren’s syndrome (SS), was analyzed to identify unique miRNAs.

Methods

Male NOD mice, aged 12-14 weeks, were used to identify tear miRNAs associated with development of autoimmune dacryoadenitis. Age- and sex-matched male BALB/c mice served as healthy controls while age-matched female NOD mice that do not develop the autoimmune dacryoadenitis characteristic of SS were used as additional controls. Total RNA was isolated from stimulated tears pooled from 5 mice per sample and tear miRNAs were sequenced and analyzed. Putative miRNA hits were validated in additional mouse cohorts as well as in tears of SS patients versus patients with another form of dry eye disease, meibomian gland disease (MGD) using qRT-PCR. The pathways influenced by the validated hits were identified using Ingenuity Pathway Analysis.

Results

In comparison to tears from both healthy (male BALB/c) and additional control (female NOD) mice, initial analy1sis identified 7 upregulated and 7 downregulated miRNAs in male NOD mouse tears. Of these, 8 were validated by RT-qPCR in tears from additional mouse cohorts. miRNAs previously implicated in SS pathology included mmu-miR-146a/b-5p, which were significantly downregulated, as well as mmu-miR-150-5p and mmu-miR-181a-5p, which were upregulated in male NOD mouse tears. All other validated hits including the upregulated miR-181b-5p and mmu-miR-203-3p, as well as the downregulated mmu-miR-322-5p and mmu-miR-503-5p, represent novel putative indicators of autoimmune dacryoadenitis in SS. When compared to tears from patients with MGD, miRNAs hsa-miR-203a-3p, hsa-miR-181a-5p and hsa-miR-181b-5p were also significantly increased in tears of SS patients.

Conclusions

A panel of differentially expressed miRNAs were identified in tears of male NOD mice, with some preliminary validation in SS patients, including some never previously linked to SS. These may have potential utility as indicators of ocular symptoms of SS; evaluation of the pathways influenced by these dysregulated miRNAs may also provide further insights into SS pathogenesis.

Cathepsin S is a novel target for age-related dry eye

Cathepsin S (Ctss) is a protease that is proinflammatory on epithelial cells. The purpose of this study was to investigate the role of Ctss in age-related dry eye disease. Ctss^-/- mice [in a C57BL/6 (B6) background] of different ages were compared to B6 mice. Ctss activity in tears and lacrimal gland (LG) lysates was measured. The corneal barrier function was investigated in naïve mice or after topical administration of Ctss eye drops 5X/day for two days. Eyes were collected, and conjunctival goblet cell density was measured in PAS-stained sections. Immunoreactivity of the tight junction proteins, ZO-1 and occludin, was investigated in primary human cultured corneal epithelial cells (HCEC) without or with Ctss, with or without a Ctss inhibitor. A significant increase in Ctss activity was observed in the tears and LG lysates in aged B6 compared to young mice. This was accompanied by higher Ctss transcripts and protein expression in LG and spleen. Compared to B6, 12 and 24-month-old Ctss^-/- mice did not display age-related corneal barrier disruption and goblet cell loss. Treatment of HCEC with Ctss for 48 h disrupted occludin and ZO-1 immunoreactivity compared to control cells. This was prevented by the Ctss inhibitor LY3000328 or Ctss-heat inactivation. Topical reconstitution of Ctss in Ctss^-/- mice for two days disrupted corneal barrier function. Aging on the ocular surface is accompanied by increased expression and activity of the protease Ctss. Our results suggest that cathepsin S modulation might be a novel target for age-related dry eye disease.

Mass spectrometry analysis of human tear fluid biomarkers specific for ocular and systemic diseases in the context of 3P medicine

Over the last two decades, a large number of non-communicable/chronic disorders reached an epidemic level on a global scale such as diabetes mellitus type 2, cardio-vascular disease, several types of malignancies, neurological and eye pathologies-all exerted system's enormous socio-economic burden to primary, secondary, and tertiary healthcare. The paradigm change from reactive to predictive, preventive, and personalized medicine (3PM/PPPM) has been declared as an essential transformation of the overall healthcare approach to benefit the patient and society at large. To this end, specific biomarker panels are instrumental for a cost-effective predictive approach of individualized prevention and treatments tailored to the person. The source of biomarkers is crucial for specificity and reliability of diagnostic tests and treatment targets. Furthermore, any diagnostic approach preferentially should be noninvasive to increase availability of the biomaterial, and to decrease risks of potential complications as well as concomitant costs. These requirements are clearly fulfilled by tear fluid, which represents a precious source of biomarker panels. The well-justified principle of a "sick eye in a sick body" makes comprehensive tear fluid biomarker profiling highly relevant not only for diagnostics of eye pathologies but also for prediction, prognosis, and treatment monitoring of systemic diseases. One prominent example is the Sicca syndrome linked to a cascade of severe complications that include dry eye, neurologic, and oncologic diseases. In this review, protein profiles in tear fluid are highlighted and corresponding biomarkers are exemplified for several relevant pathologies, including dry eye disease, diabetic retinopathy, cancers, and neurological disorders. Corresponding analytical approaches such as sample pre-processing, differential proteomics, electrophoretic techniques, high-performance liquid chromatography (HPLC), enzyme-linked immuno-sorbent assay (ELISA), microarrays, and mass spectrometry (MS) methodology are detailed. Consequently, we proposed the overall strategies based on the tear fluid biomarkers application for 3P medicine practice. In the context of 3P medicine, tear fluid analytical pathways are considered to predict disease development, to target preventive measures, and to create treatment algorithms tailored to individual patient profiles.

Targeting lysosomes in human disease: from basic research to clinical applications

In recent years, accumulating evidence has elucidated the role of lysosomes in dynamically regulating cellular and organismal homeostasis. Lysosomal changes and dysfunction have been correlated with the development of numerous diseases. In this review, we interpreted the key biological functions of lysosomes in four areas: cellular metabolism, cell proliferation and differentiation, immunity, and cell death. More importantly, we actively sought to determine the characteristic changes and dysfunction of lysosomes in cells affected by these diseases, the causes of these changes and dysfunction, and their significance to the development and treatment of human disease. Furthermore, we outlined currently available targeting strategies: (1) targeting lysosomal acidification; (2) targeting lysosomal cathepsins; (3) targeting lysosomal membrane permeability and integrity; (4) targeting lysosomal calcium signaling; (5) targeting mTOR signaling; and (6) emerging potential targeting strategies. Moreover, we systematically summarized the corresponding drugs and their application in clinical trials. By integrating basic research with clinical findings, we discussed the current opportunities and challenges of targeting lysosomes in human disease.

Immunobiology of T Cells in Sjögren's Syndrome

Sjögren's syndrome (SjS) is a systemic autoimmune disease marked by xerostomia (dry mouth), keratoconjunctivitis sicca (eye dryness), and other systematic disorders. Its pathogenesis involves an inflammatory process that is characterized by lymphocytic infiltration into exocrine glands and other tissues. Although the development of ectopic lymphoid tissue and overproduction of autoantibodies by hyperactive B cells suggest that they may promote SjS development, treatment directed towards them fails to induce significant laboratory or clinical improvement. T cells are overwhelming infiltrators in most phases of the disease, and the involvement of multiple T cell subsets of suggests the extraordinary complexity of SjS pathogenesis. The factors, including various cellular subtypes and molecules, regulate the activation and suppression of T cells. T cell activation induces inflammatory cell infiltration, B cell activation, tissue damage, and metabolic changes in SjS. Knowledge of the pathways that link these T cell subtypes and regulation of their activities are not completely understood. This review comprehensively summarizes the research progress and our understanding of T cells in SjS, including CD4⁺ T cells, CD8⁺ T_RM cells, and innate T cells, to provide insights into for clinical treatment.

Phenylephrine increases tear cathepsin S secretion in healthy murine lacrimal gland acinar cells through an alternative secretory pathway

Little is known about the relationship between stimulation of lacrimal gland (LG) tear protein secretion by parasympathetic versus sympathetic nerves, particularly whether the spectrum of tear proteins evoked through each innervation pathway varies. We have previously shown that activity and abundance of cathepsin S (CTSS), a cysteine protease, is greatly increased in tears of Sjögren's syndrome (SS) patients and in tears from the male NOD mouse of autoimmune dacryoadenitis that recapitulates SS-associated dry eye disease. Beyond the increased synthesis of CTSS detected in the diseased NOD mouse LG, increased tear CTSS secretion in NOD mouse tears was recently linked to increased exocytosis from a novel endolysosomal secretory pathway. Here, we have compared secretion and trafficking of CTSS in healthy mouse LG acinar cells stimulated with either the parasympathetic acetylcholine receptor agonist, carbachol (CCh), or the sympathetic α₁-adrenergic agonist, phenylephrine (PE). In situ secretion studies show that PE significantly increases CTSS activity and protein in tears relative to CCh stimulation by 1.2-fold (***, p = 0.0009) and ∼5-fold (*, p-0.0319), respectively. A similar significant increase in CTSS activity with PE relative to CCh is observed when cultured LGAC are stimulated in vitro. CCh stimulation significantly elevates intracellular [Ca²⁺], an effect associated with increases in the size of Rab3D-enriched vesicles consistent with compound fusion, and subsequently decreases in their intensity of labeling consistent with their exocytosis. PE stimulation induces a lower [Ca²⁺] response and has minimal effects on Rab3D-enriched SV diameter or the intensity of Rab3D-enriched SV labeling. LG deficient in Rab3D exhibit a higher sensitivity to PE stimulation, and secrete more CTSS activity. Significant increases in the colocalization of endolysosomal vesicle markers (Lamp1, Lamp2, Rab7) with the subapical actin suggestive of fusion of endolysosomal vesicles at the apical membrane occur both with CCh and PE stimulation, but PE demonstrates increased colocalization. In conclusion, the α₁-adrenergic agonist, PE, increases CTSS secretion into tears through a pathway independent of the exocytosis of Rab3D-enriched mature SV, possibly representing an alternative endolysosomal secretory pathway.

Ocular Surface Biomarkers

ABSTRACT

Sjögren syndrome (SS) is a chronic inflammatory autoimmune disease of the lacrimal and salivary glands. Salivary gland biopsy is still one of the most valuable and acceptable diagnostic tests for SS, which however, is an invasive test. Therefore, noninvasive diagnostic biomarkers with high specificity and sensitivity are required for the diagnosis and assessment of SS. Because ophthalmological testing constitutes to an important part for the diagnosis of SS. Tears harbor biomarkers with a high potential to be used for differential diagnosis and assessment of treatment in many systemic disorders, including SS. This review aims to summarize recent advances in the identification of tear biomarkers of SS, trying to identify reliable, sensitive, and specific biomarkers that can be used to guide treatment decisions.

Cysteine Cathepsins and Their Prognostic and Therapeutic Relevance in Leukemia

Cysteine cathepsins are lysosomal proteases that require Cys-His ion pair in their catalytic site for enzymatic activity. While their aberrant expression and oncogenic functions have been widely reported in solid tumors, recent findings suggest that these proteases also play an important role in the pathogenesis of hematological malignancies. In this review, we summarize the potential clinical implications of cysteine cathepsins as diagnostic and prognostic markers in leukemia, and present evidences which supports the utility of these proteases as potential therapeutic targets in hematological malignancies. We also highlight the available information on the expression patterns, regulation, and potential functions of cysteine cathepsins in normal hematopoiesis and hematological malignancies. In hematopoiesis, cysteine cathepsins play a variety of physiological roles including regulation of hematopoietic stem cell adhesion in the bone marrow, trafficking, and maturation. They are also involved in several functions of immune cells which include the selection of lymphocytes in the thymus, antigen processing, and presentation. However, the expression of cysteine cathepsins is dysregulated in hematological malignancies where they have been shown to play diverse functions. Interestingly, several pieces of evidence over the past few years have demonstrated overexpression of cathepsins in leukemia and their association with worst survival outcomes in patients. Strategies aimed at altering the expression, activity, and subcellular localization of these cathepsins are emerging as potential therapeutic modalaties in the management of hematological malignancies. Recent findings also suggest the involvement of these proteases in modulating the immune response in leukemia and lymphomas.

The ocular surface immune system through the eyes of aging

Since the last century, advances in healthcare, housing, and education have led to an increase in life expectancy. Longevity is accompanied by a higher prevalence of age-related diseases, such as cancer, autoimmunity, diabetes, and infection, and part of this increase in disease incidence relates to the significant changes that aging brings about in the immune system. The eye is not spared by aging either, presenting with age-related disorders of its own, and interestingly, many of these diseases have immune pathophysiology. Being delicate organs that must be exposed to the environment in order to capture light, the eyes are endowed with a mucosal environment that protects them, the so-called ocular surface. As in other mucosal sites, immune responses at the ocular surface need to be swift and potent to eliminate threats but are at the same time tightly controlled to prevent excessive inflammation and bystander damage. This review will detail how aging affects the mucosal immune response of the ocular surface as a whole and how this process relates to the higher incidence of ocular surface disease in the elderly.

Tear Proteases and Protease Inhibitors: Potential Biomarkers and Disease Drivers in Ocular Surface Disease

Tears are highly concentrated in proteins relative to other biofluids, and a notable fraction of tear proteins are proteases and protease inhibitors. These components are present in a delicate equilibrium that maintains ocular surface homeostasis in response to physiological and temporal cues. Dysregulation of the activity of protease and protease inhibitors in tears occurs in ocular surface diseases including dry eye and infection, and ocular surface conditions including wound healing after refractive surgery and contact lens (CL) wear. Measurement of these changes can provide general information regarding ocular surface health and, increasingly, has the potential to give specific clues regarding disease diagnosis and guidance for treatment. Here, we review three major categories of tear proteases (matrix metalloproteinases, cathepsins, and plasminogen activators [PAs]) and their endogenous inhibitors (tissue inhibitors of metalloproteinases, cystatins, and PA inhibitors), and the changes in these factors associated with dry eye, infection and allergy, refractive surgery, and CLs. We highlight suggestions for development of these and other protease/protease inhibitor biomarkers in this promising field.

Cathepsin S as a potential therapeutic target for chronic pain

Chronic pain is a distressing yet poorly-treated condition that can arise as a result of diseases and injuries to the nervous system. The development of more efficacious therapies for chronic pain is essential and requires advances in our understanding of its underlying mechanisms. Clinical and preclinical evidence has demonstrated that immune responses play a crucial role in chronic pain. The lysosomal cysteine protease cathepsin S (CatS) plays a key role in such immune response. Here we discuss the preclinical evidence for the mechanistic importance of extracellular CatS in chronic pain focussing on studies utilising drugs and other pharmacological tools that target CatS activity. We also consider the use of CatS inhibitors as potential novel antihyperalgesics, highlighting that the route and timing of delivery would need to be tailored to the initial cause of pain in order to ensure the most effective use of such drugs.

•

Cathepsin S plays a key extracellular role in the underlying mechanisms of chronic pain

•

Pharmacological tools provide crucial evidence for this role and the therapeutic potential of targeting Cathepsin S

•

The route of delivery and timing of cathepsin S inhibitor administration should be tailored to specific causes of chronic pain

Oxidative damage of lysosomes in regulated cell death systems: Pathophysiology and pharmacologic interventions

Lysosomes are small specialized organelles containing a variety of different hydrolase enzymes that are responsible for degradation of all macromolecules, entering the cells through the endosomal system or originated from the internal sources. This allows for transport and recycling of nutrients and internalization of surface proteins for antigen presentation as well as maintaining cellular homeostasis. Lysosomes are also important storage compartments for metal ions and nutrients. The integrity of lysosomal membrane is central to maintaining their normal function, but like other cellular membranes, lysosomal membrane is subject to damage mediated by reactive oxygen species. This results in spillage of lysosomal enzymes into the cytoplasm, leading to proteolytic damage to cellular systems and organelles. Several forms of lysosomal dependent cell death have been identified in diseases. Examination of these events are important for finding treatment strategies relevant to cancer or neurodegenerative diseases as well as autoimmune deficiencies. In this review, we have examined the current literature on involvement of lysosomes in induction of programed cell death and have provided an extensive list of therapeutic approaches that can modulate cell death. Exploitation of these mechanisms can lead to novel therapies for cancer and neurodegenerative diseases.

Small RNA Deep Sequencing Identifies a Unique miRNA Signature Released in Serum Exosomes in a Mouse Model of Sjögren's Syndrome

Sjögren's Syndrome (SS) is an autoimmune disease characterized by lymphocytic infiltration and loss of function of moisture-producing exocrine glands as well as systemic inflammation. SS diagnosis is cumbersome, subjective and complicated by manifestation of symptoms that overlap with those of other rheumatic and ocular diseases. Definitive diagnosis averages 4–5 years and this delay may lead to irreversible tissue damage. Thus, there is an urgent need for diagnostic biomarkers for earlier detection of SS. Extracellular vesicles called exosomes carry functional small non-coding RNAs which play a critical role in maintaining cellular homeostasis via transcriptional and translational regulation of mRNA. Alterations in levels of specific exosomal miRNAs may be predictive of disease status. Here, we have assessed serum exosomal RNA using next generation sequencing in a discovery cohort of the NOD mouse, a model of early-intermediate SS, to identify dysregulated miRNAs that may be indicative of SS. We found five miRNAs upregulated in serum exosomes of NOD mice with an adjusted p < 0.05—miRNA-127-3p, miRNA-409-3p, miRNA-410-3p, miRNA-541-5p, and miRNA-540-5p. miRNAs 127-3p and 541-5p were also statistically significantly upregulated in a validation cohort of NOD mice. Pathway analysis and existing literature indicates that differential expression of these miRNAs may dysregulate pathways involved in inflammation. Future studies will apply these findings in a human cohort to understand how they are correlated with manifestations of SS as well as understanding their functional role in systemic autoimmunity specific to SS.

Emerging drugs for primary Sjögren's syndrome

Introduction: Primary Sjögren's syndrome (pSS) is an autoimmune systemic disease characterized by a complex and not yet completely elucidated etiopathogenesis, where autoimmune manifestations coexist with different degree of lymphoproliferation, resulting in multiple possible scenarios extremely heterogeneous from patient to patient. Although considerable progress has been made in the identifications of potential novel therapeutic targets in recent years, the biological complexity of pSS, combined to such heterogeneous clinical manifestations, makes the treatment of pSS, even today, a great challenge. Areas covered: A therapy specifically approved for pSS is still lacking. In recent years, several novel promising agents are being tested in pSS. Based on a deep revision of drugs evaluated for pSS therapy, it is striking that several clinical trials, some of them testing very promising agents, failed. Expert opinion: a renewal of clinical trial design, including the definition of novel inclusion criteria and outcome measures, together with the development of a stratification model of pSS patients and the advance in the definition of pathogenetic mechanisms underlying peculiar pSS subsets, represent preliminary and crucial steps to overcome the current therapeutic impasse in pSS.

Cathepsin S: investigating an old player in lung disease pathogenesis, comorbidities, and potential therapeutics

Dysregulated expression and activity of cathepsin S (CTSS), a lysosomal protease and a member of the cysteine cathepsin protease family, is linked to the pathogenesis of multiple diseases, including a number of conditions affecting the lungs. Extracellular CTSS has potent elastase activity and by processing cytokines and host defense proteins, it also plays a role in the regulation of inflammation. CTSS has also been linked to G-coupled protein receptor activation and possesses an important intracellular role in major histocompatibility complex class II antigen presentation. Modulated CTSS activity is also associated with pulmonary disease comorbidities, such as cancer, cardiovascular disease, and diabetes. CTSS is expressed in a wide variety of immune cells and is biologically active at neutral pH. Herein, we review the significance of CTSS signaling in pulmonary diseases and associated comorbidities. We also discuss CTSS as a plausible therapeutic target and describe recent and current clinical trials examining CTSS inhibition as a means for treatment.

Cysteine cathepsins as therapeutic targets in inflammatory diseases

Introduction: Cysteine cathepsins are involved in the development and progression of numerous inflammation-associated diseases such as cancer, arthritis, bone and immune disorders. Consequently, there is a drive to progress research efforts focused on cathepsin use in diagnostics and as therapeutic targets in disease.Areas covered: This review discusses the potential of cysteine cathepsins as therapeutic targets in inflammation-associated diseases and recent advances in preclinical and clinical research. We describe direct targeting of cathepsins for treatment purposes and their indirect use in diagnostics.Expert opinion: The targeting of cysteine cathepsins has not translated into the clinic; this failure is attributed to off- and on-target side effects and/or the lack of companion biomarkers. This field now embraces developments in diagnostic imaging, the activation of prodrugs and antibody-drug conjugates for targeted drug delivery. The future lies in improved molecular tools and therapeutic concepts that will find a wide spectrum of uses in diagnostic and therapeutic applications.

Melatonin attenuates epidermal growth factor-induced cathepsin S expression in ARPE-19 cells: Implications for proliferative vitreoretinopathy

Abnormal proliferation and motility of retinal pigment epithelial cells leads to proliferative vitreoretinopathy (PVR). Melatonin is a known effective antitumour and anti-invasive agent, but whether it affects the formation and underlying mechanisms of PVR remains unclear. In this study, the results of the MTT assay, colony formation and propidium iodide (PI) staining with flow cytometry revealed that melatonin dose dependently inhibited epidermal growth factor (EGF)-induced proliferation of human ARPE-19 cells. Furthermore, melatonin reduced EGF-induced motility by suppressing cathepsin S (CTSS) expression. Pretreatment with ZFL (a CTSS inhibitor) or overexpression of CTSS (pCMV-CTSS) significantly inhibited EGF-induced cell motility when combined with melatonin. Epidermal growth factor induced the phosphorylation of AKT(S473)/mTOR (S2448) and transcription factor (c-Jun/Sp1) signaling pathways. Pretreatment of LY294002 (a PI3K inhibitor) or rapamycin (an mTOR inhibitor) markedly reduced EGF-induced motility and p-AKT/p-mTOR/c-Jun/Sp1 expression when combined with melatonin. Taken together, these data indicate that melatonin inhibited EGF-induced proliferation and motility of human ARPE-19 cells by activating the AKT/mTOR pathway, which is dependent on CTSS modulation of c-Jun/Sp1 signalling. Melatonin may be a promising therapeutic drug against PVR.

Lysosomes as a therapeutic target

Lysosomes are membrane-bound organelles with roles in processes involved in degrading and recycling cellular waste, cellular signalling and energy metabolism. Defects in genes encoding lysosomal proteins cause lysosomal storage disorders, in which enzyme replacement therapy has proved successful. Growing evidence also implicates roles for lysosomal dysfunction in more common diseases including inflammatory and autoimmune disorders, neurodegenerative diseases, cancer and metabolic disorders. With a focus on lysosomal dysfunction in autoimmune disorders and neurodegenerative diseases - including lupus, rheumatoid arthritis, multiple sclerosis, Alzheimer disease and Parkinson disease - this Review critically analyses progress and opportunities for therapeutically targeting lysosomal proteins and processes, particularly with small molecules and peptide drugs.

Differential effects of specific cathepsin S inhibition in biocompartments from patients with primary Sjögren syndrome

OBJECTIVE

Primary Sjögren syndrome (pSS) is characterized by T and B cell infiltration of exocrine glands. The cysteine protease cathepsin S (CatS) is crucially involved in MHCII processing and T cell stimulation, and elevated levels have been found in patients with RA, psoriasis and pSS. However, little is known about the functional characteristics and mechanisms of SS-A- and SS-B-specific T cells in pSS patients. We herein investigated the inhibition of CatS activity in different biocompartments of pSS patients including antigen-specific T cell responses.

METHODS

Ex vivo CatS activity was assessed in tears, plasma and saliva of 15 pSS patients and 13 healthy controls (HC) and in the presence or absence of the specific CatS inhibitor RO5459072. In addition, antigen (SS-A (60kD), SS-B, influenza H3N2, tetanus toxoid and SEB)-specific T cell responses were examined using ex vivo IFN-γ/IL-17 Dual ELISPOT and Bromdesoxyuridin (BrdU) proliferation assays in the presence or absence of RO5459072. Supernatants were analysed for IL-1β, IL-6, IL-10, TNF-α, IL-21, IL-22 and IL-23, using conventional ELISA.

RESULTS

CatS activity was significantly elevated in tear fluid, but not other biocompartments, was inversely associated with exocrinic function in pSS patients and could significantly be suppressed by RO5459072. Moreover, CatS inhibition by RO5459072 led to strong and dose-dependent suppression of SS-A/SS-B-specific T cell effector functions and cytokine secretion by CD14+ monocytes. However, RO5459072 was incapable of suppressing SS-A/SS-B-induced secretion of cytokines in CD14+ monocytes when T cells were absent, confirming a CatS/MHCII-mediated mechanism of suppression.

CONCLUSION

CatS activity in tear fluid seems to be a relevant biomarker for pSS disease activity. Conversely, CatS inhibition diminishes T cell and associated monokine responses towards relevant autoantigens in pSS. Thus, CatS inhibition may represent a promising novel treatment strategy in pSS.

Inhibition of Cathepsin S Reduces Lacrimal Gland Inflammation and Increases Tear Flow in a Mouse Model of Sjögren's Syndrome

Cathepsin S (CTSS) is highly increased in Sjögren's syndrome (SS) patients tears and in tears and lacrimal glands (LG) of male non-obese diabetic (NOD) mice, a murine model of SS. To explore CTSS's utility as a therapeutic target for mitigating ocular manifestations of SS in sites where CTSS is increased in disease, the tears and the LG (systemically), the peptide-based inhibitor, Z-FL-COCHO (Z-FL), was administered to 14-15 week male NOD mice. Systemic intraperitoneal (i.p.) injection for 2 weeks significantly reduced CTSS activity in tears, LG and spleen, significantly reduced total lymphocytic infiltration into LG, reduced CD3+ and CD68+ cell abundance within lymphocytic infiltrates, and significantly increased stimulated tear secretion. Topical administration of Z-FL to a different cohort of 14-15 week male NOD mice for 6 weeks significantly reduced only tear CTSS while not affecting LG and spleen CTSS and attenuated the disease-progression related reduction of basal tear secretion, while not significantly impacting lymphocytic infiltration of the LG. These findings suggest that CTSS inhibitors administered either topically or systemically can mitigate aspects of the ocular manifestations of SS.

Oligomeric α-synuclein is increased in basal tears of Parkinson's patients

Aim: Secretion of proteins into basal tears of Parkinson's disease (PD) patients may be altered by changes in nerve function. Materials & methods: Oligomeric α-Syn_Oligo and total α-Syn_Total, CCL-2, DJ-1, LF and MMP-9 were measured in basal tears from 93 PD patients and 82 age- and sex-equivalent healthy controls. Results: α-Syn_Total was decreased (p = 0.0043), whereas α-Syn_Oligo (p < 0.0001) and the ratio of α-Syn_Oligo/α-Syn_Total (p < 0.0001) were increased in basal tears from PD patients compared with healthy controls. Area under receiver-operating curves of α-Syn_Oligo and α-Syn_Oligo/α-Syn_Total contents were 0.70 (95% confidence limits: 0.621-0.774) and 0.72 (95% confidence limits: 0.642-0.792). Conclusion: PD patient basal tears may contain biomarkers that can be assayed noninvasively and inexpensively.

Berunda Polypeptides: Biheaded Rapamycin Carriers for Subcutaneous Treatment of Autoimmune Dry Eye Disease

The USFDA-approved immunosuppressive drug rapamycin (Rapa), despite its potency, is limited by poor bioavailability and a narrow therapeutic index. In this study, we sought to improve bioavailability of Rapa with subcutaneous (SC) administration and to test its therapeutic feasibility and practicality in a murine model of Sjögren's syndrome (SS), a systemic autoimmune disease with no approved therapies. To improve its therapeutic index, we formulated Rapa with a carrier termed FAF, a fusion of the human cytosolic FK506-binding protein 12 (FKBP12) and an elastin-like polypeptide (ELP). The resulting 97 kDa FAF (i) has minimal burst release, (ii) is "humanized", (iii) is biodegradable, (iv) solubilizes two Rapa per FAF, and (v) avoids organic solvents or amphiphilic carriers. Demonstrating high stability, FAF remained soluble and monodisperse with a hydrodynamic radius of 8 nm at physiological temperature. A complete pharmacokinetic (PK) analysis of FAF revealed that the bioavailability of SC FAF was 60%, with significantly higher blood concentration during the elimination phase compared to IV FAF. The plasma concentration of Rapa delivered by FAF was 8-fold higher with a significantly increased plasma-to-whole blood ratio relative to free Rapa, 24 h after injection. To evaluate therapeutic effects, FAF-Rapa was administered SC every other day for 2 weeks to male non-obese diabetic (NOD) mice, which develop an SS-like autoimmune-mediated lacrimal gland (LG) inflammation and other characteristic features of SS. Both FAF-Rapa and free Rapa exhibited immunomodulatory effects by significantly suppressing lymphocytic infiltration, gene expression of IFN-γ, MHC II, type I collagen and IL-12a, and cathepsin S (CTSS) activity in LG compared to controls. Serum chemistry and histopathological analyses in major organs revealed no apparent toxicity of FAF-Rapa. Given its improved PK and equipotent therapeutic efficacy compared to free Rapa, FAF-Rapa is of further interest for systemic treatments for autoimmune diseases like SS.

Association of autoimmunity and cancer: An emphasis on proteolytic enzymes

Cancer and autoimmune diseases are the two devastating conditions that together constitute a leading health problem worldwide. The rising burden of these disorders in the developing world demands a multifaceted approach to address the challenges it poses. Understanding the root causes and specific molecular mechanisms by which the progression of the diseases takes place is need of the hour. A strong inflammatory background and common developmental pathways, such as activation of immune cells, proliferation, increased cell survival and migration which are controlled by growth factors and inflammatory cytokines have been considered as the critical culprits in the progression and complications of these disorders. Enzymes are the potential immune modulators which regulate various inflammatory events and can break the circulating immune complexes via macrophages production. In the current manuscript, we have uncovered the possible role of proteolytic enzymes in the pathogenesis and progression of cancer and autoimmune diseases. In the light of the available scientific literature, we advocate in-depth comprehensive studies which will shed light towards the role of proteolytic enzymes in the modulation of inflammatory responses in cancer and autoimmune diseases together.

Review of Biomarkers in Ocular Matrices: Challenges and Opportunities

Biomarkers provide a powerful and dynamic approach to improve our understanding of the mechanisms underlying ocular diseases with applications in diagnosis, disease modulation or for predicting and monitoring of clinical response to treatment. Defined as measurable indicator of normal or pathological processes, biomarker evaluation has been used extensively in drug development within clinical settings to better comprehend effectiveness of treatment in ocular diseases. Biomarkers in the eye have the advantage of access to multiple ocular matrices via minimally invasive methods. Repeat sampling for biomarker assessment has enabled reproducible objective measures of disease process or biological responses to a drug treatment. This review describes the usage of biomarkers with respect to four commonly sampled ocular matrices in clinic: tears, conjunctiva, aqueous humor and vitreous. Issues that affect the evaluation of biomarkers are discussed along with opportunities to leverage biomarkers such that ultimately, they can be used for customized targeted therapy.

Cathepsin S Alters the Expression of Pro-Inflammatory Cytokines and MMP-9, Partially through Protease-Activated Receptor-2, in Human Corneal Epithelial Cells

Cathepsin S (CTSS) activity is increased in tears of Sjögren’s syndrome (SS) patients. This elevated CTSS may contribute to ocular surface inflammation. Human corneal epithelial cells (HCE-T cells) were treated with recombinant human CTSS at activity comparable to that in SS patient tears for 2, 4, 8, and 24 h. Acute CTSS significantly increased HCE-T cell gene and protein expression of interleukin 6 (IL-6), interleukin 8 (IL-8), tumor necrosis factor-α (TNF-α), and interleukin-1β (IL-1β) from 2 to 4 h, while matrix metalloproteinase 9 (MMP-9), CTSS, and protease-activated receptor-2 (PAR-2) were increased by chronic CTSS (24 h). To investigate whether the increased pro-inflammatory cytokines and proteases were induced by CTSS activation of PAR-2, HCE-T cells were transfected with PAR-2 siRNA, reducing cellular PAR-2 by 45%. Cells with reduced PAR-2 expression showed significantly reduced release of IL-6, TNF-α, IL-1β, and MMP-9 into culture medium in response to acute CTSS, while IL-6, TNF-α, and MMP-9 were reduced in culture medium, and IL-6 and MMP-9 in cell lysates, after chronic CTSS. Moreover, cells with reduced PAR-2 expression showed reduced ability of chronic CTSS to induce gene expression of pro-inflammatory cytokines and proteases. CTSS activation of PAR-2 may represent a potential therapeutic target for amelioration of ocular surface inflammation in SS patients.

Molecular Regulatory Mechanism of Exocytosis in the Salivary Glands

Every day, salivary glands produce about 0.5 to 1.5 L of saliva, which contains salivary proteins that are essential for oral health. The contents of saliva, 0.3% proteins (1.5 to 4.5 g) in fluid, help prevent oral infections, provide lubrication, aid digestion, and maintain oral health. Acinar cells in the lobular salivary glands secrete prepackaged secretory granules that contain salivary components such as amylase, mucins, and immunoglobulins. Despite the important physiological functions of salivary proteins, we know very little about the regulatory mechanisms of their secretion via exocytosis, which is a process essential for the secretion of functional proteins, not only in salivary glands, but also in other secretory organs, including lacrimal and mammary glands, the pancreas, and prostate. In this review, we discuss recent findings that elucidate exocytosis by exocrine glands, especially focusing on the salivary glands, in physiological and pathological conditions.

Longitudinal analysis of tear cathepsin S activity levels in male non-obese diabetic mice suggests its potential as an early stage biomarker of Sjögren's Syndrome

CONTEXT

Cathepsin S (CTSS) activity is elevated in Sjögren's Syndrome (SS) patient tears.

OBJECTIVE

To evaluate longitudinal expression of tear and tissue CTSS activity relative to other disease indicators in Non-Obese Diabetic (NOD) mice.

METHODS

CTSS activity was measured in tears and lacrimal glands (LG) from male 1-6 month (M) NOD and 1 and 6 M BALB/c mice. Lymphocytic infiltration was quantified by histopathology, while disease-related proteins (Rab3D, CTSS, collagen 1) were quantified using q-PCR and immunofluorescence.

RESULTS

In NOD LG, lymphocytic infiltration was noted by 2 M and established by 3 M (p < 0.01). IFN-ɣ, TNF-α, and MHC II expression were increased by 2 M (p < 0.01). Tear CTSS activity was significantly elevated at 2 M (p < 0.001) to a maximum of 10.1-fold by 6 M (p < 0.001). CTSS activity in LG lysates was significantly elevated by 2 M (p < 0.001) to a maximum of 14-fold by 3 M (p < 0.001). CTSS and Rab3D immunofluorescence were significantly increased and decreased maximally in LG acini by 3 M and 2 M, respectively. Comparable changes were not detected between 1 and 6 M BALB/c mouse LG, although Collagen 1 was decreased by 6 M in LG of both strains.

CONCLUSION

Tear CTSS activity is elevated with other early disease indicators, suggesting potential as an early stage biomarker for SS.