Lysosomal Cysteine Protease Cathepsin Research Articles

Cathepsin B Deficiency Improves Memory Deficits and Reduces Amyloid-β in hAβPP Mouse Models Representing the Major Sporadic Alzheimer's Disease Condition.

The lysosomal cysteine protease cathepsin B (CTSB) has been suggested as a biomarker for Alzheimer's disease (AD) because elevated serum CTSB in AD patients has been found to correlate with cognitive dysfunction. Furthermore, CTSB gene knockout (KO) in non-transgenic and transgenic AD animal models showed that elimination of CTSB improved memory deficits. However, conflicting CTSB KO results on amyloid-β (Aβ) pathology in transgenic AD models have been reported. The conflict is resolved here as likely being due to the different hAβPP transgenes used in the different AD mouse models. CTSB gene KO reduced wild-type (Wt) β-secretase activity, brain Aβ, pyroglutamate-Aβ, amyloid plaque, and memory deficits in models that used cDNA transgenes expressing hAβPP isoform 695. But in models that used mutated mini transgenes expressing hAβPP isoforms 751 and 770, CTSB KO had no effect on Wt β-secretase activity and slightly increased brain Aβ. All models expressed the AβPP transgenes in neurons. These conflicting results in Wt β-secretase activity models can be explained by hAβPP isoform specific cellular expression, proteolysis, and subcellular processing. CTSB KO had no effect on Swedish mutant (Swe) β-secretase activity in hAβPP695 and hAβPP751/770 models. Different proteolytic sensitivities for hAβPP with Wt versus Swe β-secretase site sequences may explain the different CTSB β-secretase effects in hAβPP695 models. But since the vast majority of sporadic AD patients have Wt β-secretase activity, the CTSB effects on Swe β-secretase activity are of little importance to the general AD population. As neurons naturally produce and process hAβPP isoform 695 and not the 751 and 770 isoforms, only the hAβPP695 Wt models mimic the natural neuronal hAβPP processing and Aβ production occurring in most AD patients. Significantly, these CTSB KO findings in the hAβPP695 Wt models demonstrate that CTSB participates in memory deficits and production of pyroglutamate-Aβ (pyroglu-Aβ), which provide rationale for future investigation of CTSB inhibitors in AD therapeutics development.

Intracellular Construction of Cathepsin B-Guided Gadolinium Nanoparticles for Enhanced T2 -Weighted MR Tumor Imaging.

Magnetic resonance imaging (MRI) is a superior and noninvasive imaging technique with unlimited tissue penetration depth and superb spatiotemporal resolution, however, using intracellular self-assembly of Gd-containing nanoparticles to enhance the T2 -weighted MR contrast of cancer cells in vivo for precise tumor MRI is rarely reported. The lysosomal cysteine protease cathepsin B (CTSB) is regarded as an attractive biomarker for the early diagnosis of cancers and metastasis. Herein, taking advantage of a biocompatible condensation reaction, a "smart" Gd-based CTSB-responsive small molecular contrast agent VC-Gd-CBT is developed, which can self-assemble into large intracellular Gd-containing nanoparticles by glutathione reduction and CTSB cleavage to enhance the T2 -weighted MR contrast of CTSB-overexpressing MDA-MB-231 cells at 9.4T. In vivo T2 -weighted MRI studies using MDA-MB-231 murine xenografts show that the T2 -weighted MR contrast change of tumors in VC-Gd-CBT-injected mice is distinctly larger than the mice injected with the commercial agent gadopentetate dimeglumine, or co-injected with CTSB inhibitor and VC-Gd-CBT, indicating that the accumulation of self-assembled Gd-containing nanoparticles at tumor sites effectively enhances the T2 -weighted MR tumor imaging. Hence, this CTSB-targeted small molecule VC-Gd-CBT has the potential to be employed as a T2 contrast agent for the clinical diagnosis of cancers at an early stage.

Brief Report: Intracellular Cystatin B Levels Are Altered in HIV-Infected Participants With Respect to Neurocognitive Status and Antiretroviral Therapy.

With advances in HIV treatment, people with HIV (PWH) are living longer but experience aging-related comorbidities, including cognitive deficits, at higher rates than the general population. Previous studies have shown alterations in lysosomal proteins in blood from PWH with severe dementia. However, these markers have not been evaluated in PWH with milder neurocognitive impairment. We sought to determine whether levels of the lysosomal cysteine protease cathepsin B (CatB) and its endogenous inhibitor cystatin B (CysB) were altered in PWH with neurocognitive impairment and whether antiretroviral therapy (ART) further influenced these levels. Peripheral blood mononuclear cells were obtained from the tenofovir arm of a multicenter clinical trial in which ART-naive, HIV+ participants received treatment for 48 weeks (ACTG A5303, NCT01400412). PWH were divided by neurocognitive status (eg, with or without neurocognitive impairment) before ART initiation. Intracellular levels of CatB and CysB were measured in T cells and monocytes by means of flow cytometry. Levels of CysB were significantly decreased in both CD4 + T cells and CD8 + T cells after 48 weeks of ART in HIV+ participants without neurocognitive impairment but not in participants with neurocognitive impairment. Levels of CysB were increased in CD14 + monocytes from the participants with neurocognitive impairment after ART. Levels of CysB and CatB positively correlated regardless of HIV, neurocognitive status, or exposure to ART. These findings suggest that CysB has the potential to provide mechanistic insight into HIV-associated neurocognitive disorders or provide a molecular target for systemic monitoring or treatment of neurocognitive impairment in the context of ART and should be investigated further.

Coprophagy Prevention Decreases the Reproductive Performance and Granulosa Cell Apoptosis via Regulation of CTSB Gene in Rabbits.

Coprophagy is an instinctive behavior in rabbit with important effects on growth and reproductive performance. The underlying mechanism of this effect in rabbit is unknown. Here, we used Elizabeth circle as a coprophagy preventing model in female rabbits and assess feed intake, growth, and reproductive performance. We found that preventing coprophagy did not affect feed intake but decreased body weight and weight of several organs and tissues and resulted in complete reproductive failure during the late pregnancy period, accompanied by reduced levels of plasma progesterone. RNA-seq analysis of rabbit ovarian tissues revealed that preventing coprophagy affected significantly 241 genes (DEGs), with the large majority being downregulated. Bioinformatic analyses revealed that those DEGs are mostly involved in apoptosis, immune response, and metabolic pathways. Among DEGs, the lysosomal cysteine protease cathepsin B (CTSB) was significantly downregulated in the coprophagy prevention group. Further studies using siRNA and adenovirus overexpression systems revealed that CTSB promotes the proliferation of rabbit granulosa cells (GCS) and prevents apoptosis. Measurement of transcripts coding for proteins related to apoptosis revealed a minor transcriptomic effect of CTSB, indicating that its effect is likely post-transcriptional. Overexpression of CTSB increased secretion of progesterone and estradiol, partly via upregulation of CYP19A1 while inhibition of CTSB decreased progesterone secretion partly via downregulation of the StAR gene. In conclusion, our study demonstrated the detrimental effect on reproduction by preventing coprophagy with a main role for this response played by CTSB on the granulosa cells of the ovary.

Extracellular cathepsin Z signals through the α5 integrin and augments NLRP3 inflammasome activation

Respiratory silicosis is a preventable occupational disease that develops secondary to the aspiration of crystalline silicon dioxide (silica) into the lungs, activation of the NLRP3 inflammasome, and IL-1β production. Cathepsin Z has been associated with the development of inflammation and IL-1β production; however, the mechanism of how cathepsin Z leads to IL-1β production is unknown. Here, the requirement for cathepsin Z in silicosis was determined using WT mice and mice deficient in cathepsin Z. The activation of the NLRP3 inflammasome in macrophages was studied using WT and cathepsin Z-deficient bone marrow-derived murine dendritic cells and the human monocytic cell line THP-1. The cells were activated with silica, and IL-1β release was determined using enzyme-linked immunosorbent assay or IL-1β bioassays. The relative contribution of the active domain or integrin-binding domain of cathepsin Z was studied using recombinant cathepsin Z constructs and the α5 integrin neutralizing antibody. We report that the lysosomal cysteine protease cathepsin Z potentiates the development of inflammation associated with respiratory silicosis by augmenting NLRP3 inflammasome-derived IL-1β expression in response to silica. The secreted cathepsin Z functions nonproteolytically via the internal integrin-binding domain to impact caspase-1 activation and the production of active IL-1β through integrin α5 without affecting the transcription levels of NLRP3 inflammasome components. This work reveals a regulatory pathway for the NLRP3 inflammasome that occurs in an outside-in fashion and provides a link between extracellular cathepsin Z and inflammation. Furthermore, it reveals a level of NLRP3 inflammasome regulation that has previously only been found downstream of extracellular pathogens.

1239-P: Evidence of Altered Alpha- and Beta-Cell Lysosomes prior to Onset of Type 1 Diabetes

Autophagic degradation is a dynamic recycling process that contributes to cellular homeostasis and mitigation of cellular stress. While there are multiple forms of -phagic degradation processes, a common endpoint is the final degradation step in the lumen of the acidic lysosomes. Post-mitotic cells, including beta cells, can accumulate tertiary lysosomes called telolysosomes which contain oxidized proteins and lipids that are not completely digested. We recently found that autophagy is impaired in the beta cells of individuals with T1D and also in islets of diabetic NOD mice. We also observed a significant increase in the number of autophagosomes, and telolysosomes in the beta cells of autoantibody positive organ donors when compared to nondiabetic organ donors. We now also find a 1.5-fold increase in the number of telolysosomes in the alpha cells of autoantibody positive donors when compared to nondiabetic organ donors (p=0.03). This was mirrored by our previous observation of globally increased lysosome numbers across the islets of pre-diabetic NOD mice, suggesting that these lysosomes may be dysfunctional. To test this, we performed a lysosomal enzyme activity assay to analyze the lysosomal cysteine protease Cathepsin H (a T1D susceptibility locus). Interestingly, we found that the activity of Cathepsin H was increased by ~2-fold in islets of pre-diabetic NOD mice when compared to NOR controls (p=0.02). Taken together, these data suggest a compensatory hyperactivation of the lysosomal enzyme Cathepsin H in the islets of pre-diabetic NOD mice, potentially as a mechanism to rid the cell of degradation-resistant oxidized proteins and lipids whose accumulation in lysosomes might lead to the presence of telolysosomes. Disclosure C. Muralidharan: None. J. Crowder: None. A. K. Linnemann: None. Funding Network for Pancreatic Organ Donors with Diabetes (nPOD; RRID:SCR_014641); JDRF (nPOD: 5-SRA-2018-557-Q-R); The Leona M. and Harry B. Helmsley Charitable Trust (2018PG-T1D053)

Inhibition of Cathepsin S Restores TGF-β-induced Epithelial-to-mesenchymal Transition and Tight Junction Turnover in Glioblastoma Cells.

Background: Invasive growth is one of the most typical features of aggressive types of malignant cancer, including glioblastoma. Lysosomal cysteine protease-cathepsin S (CTSS), has been reported to be involved in invasive growth and distant metastasis of cancer cells. However, the underlying mechanisms remained elusive.Methods: U87 and U251 human glioblastoma cell lines were applied in this study. Cell migration and invasion ability were measured by wound healing assay and transwell assay. Western blot was employed to detect the expression levels of proteins. Immunofluorescence assays of cells and tissues were used to visualize the localization and expression of proteins. The SPSS software was used for statistical analysis.Results: Our results showed that the high expression of CTSS was link with the grades of glioma tissues. The CTSS inhibitor-Z-FL-COCHO (ZFL), could attenuate TGF-β-induced invasive growth as proven by wound healing and transwell assays. Furthermore, inhibition of CTSS could reverse TGF-β-induced epithelial-to-mesenchymal transition (EMT) and restore TGF-β-triggered tight junction proteins turnover, thus decreasing glioblastoma cell mobility. We also observed that TGF-β could change the morphology of glioblastoma cells, redistribute intermediate-filament, vimentin, which was highly relevant to mesenchymal type cells and enhanced mobility. However, inhibition of CTSS could significantly restore this transformation. Our results proved that PI3K/AKT/mTOR pathway was significantly suppressed in the TGF-β+ZFL (CTSS inhibitor) groups, and AKT activator-SC79, could reverse the anti-invasion effect of CTSS, indicating an important role of PI3K/AKT/mTOR pathway in this process.Conclusion: Z-FL-COCHO (ZFL), a CTSS inhibitor, could reverse TGF-β-induced EMT and change of tight junction proteins via PI3K/AKT/mTOR pathway.

Targeting lysosomal cysteine protease cathepsin S reveals immunomodulatory therapeutic strategy for oxaliplatin-induced peripheral neuropathy

Rationale: Oxaliplatin-induced peripheral neuropathy (OIPN) is a common adverse effect that causes delayed treatment and poor prognosis among colorectal cancer (CRC) patients. However, its mechanism remains elusive, and no effective treatment is available.Methods: We employed a prospective cohort study of adult patients with pathologically confirmed stage III CRC receiving adjuvant chemotherapy with an oxaliplatin-based regimen for investigating OIPN. To further validate the clinical manifestations and identify a potential therapeutic strategy, animal models, and in vitro studies on the mechanism of OIPN were applied.Results: Our work found that (1) consistent with clinical findings, OIPN was observed in animal models. Targeting the enzymatic activity of cathepsin S (CTSS) by pharmacological blockade and gene deficiency strategy alleviates the manifestations of OIPN. (2) Oxaliplatin treatment increases CTSS expression by enhancing cytosol translocation of interferon response factor 1 (IRF1), which then facilitates STIM-dependent store-operated Ca2+ entry homeostasis. (3) The cytokine array demonstrated an increase in anti-inflammatory cytokines and suppression of proinflammatory cytokines in mice treated with RJW-58. (4) Mechanistically, inhibiting CTSS facilitated olfactory receptors transcription factor 1 release from P300/CBP binding, which enhanced binding to the interleukin-10 (IL-10) promoter region, driving IL-10 downstream signaling pathway. (5) Serum CTSS expression is increased in CRC patients with oxaliplatin-induced neurotoxicity.Conclusions: We highlighted the critical role of CTSS in OIPN, which provides a therapeutic strategy for the common adverse side effects of oxaliplatin.

Cathepsin B is a mediator of organelle-specific initiation of ferroptosis

Ferroptosis is a type of non-apoptotic regulated cell death that involves excessive iron accumulation and subsequent lipid peroxidation. Although the antioxidant mechanisms of ferroptosis have been extensively studied recently, little is known about the interactions between the different organelles that control ferroptosis. Here, we show that the translocation of lysosomal cysteine protease cathepsin B (CTSB) into the nucleus is an important molecular event that mediates organelle-specific initiation of ferroptosis in human pancreatic cancer cells. Iron-dependent lysosomal membrane permeability triggers the release of CTSB from the lysosome to nucleus during ferroptosis. Mechanistically, nuclear CTSB accumulation causes DNA damage and subsequent activation of the stimulator of interferon response CGAMP interactor 1 (STING1/STING)-dependent DNA sensor pathway, which ultimately leads to autophagy-dependent ferroptosis. Consequently, the genetic inhibition of CTSB-dependent STING1 activation by RNAi prevents ferroptosis in cell culture and animal models. These new findings not only enhance our understanding of the mechanism by which organelles specifically trigger ferroptosis, but also may provide a potential way to enhance the anticancer activity of ferroptosis therapy.

Changes in the activity of lysosomal cysteine proteases of plasma mononuclear and polymorphonuclear blood leukocytes in Alzheimer’s disease

Aim. To study the level of activity of lysosomal cysteine proteases (cathepsins H, B, L) in blood plasma and fractionated leukocytes (polymorphonuclear and mononuclear) in patients with Alzheimer’s disease in comparison with similar indicators in persons without signs of neurodegeneration as a possible marker of Alzheimer’s disease development and diagnosis. Materials and methods. The spectrofluorimetric study of cathepsins B, L, H activity level in plasma and fractionated leukocytes was conducted in 22 patients diagnosed with Alzheimer’s disease in comparison with the same indicators in 22 patients matched by sex, age and associated diseases with patients of the observation group, but having no signs of neurodegeneration. Results. The activity of all three enzymes, and especially cathepsin H, increased significantly in blood plasma. A significant increase is also noted in the activity of cathepsins H, B, and L in homogenates of fractionated leukocytes. At the same time, in both polymorphonuclear and mononuclear leukocytes the greatest degree of changes is demonstrated by the activity of cathepsin B, and the least is the activity of cathepsin L. Given the available data on an increased cathepsin B activity in the cerebrospinal fluid of patients with Alzheimer’s disease, we can assume a correlation between the state of lysosomal proteases activity in the Central nervous system and in the peripheral blood cells. Conclusion. Alzheimer’s disease is associated with increased activity of cysteine cathepsins in plasma, polymorphonuclear and mononuclear leukocytes of peripheral blood, which can be considered as one of the possible markers of development and diagnosis of the disease.

HMGB1 mediates homocysteine-induced endothelial cells pyroptosis via cathepsin V-dependent pathway

Endothelial cells injury and pro-inflammation cytokines release are the initial steps of hyperhomocysteinemia (HHcy)-associated vascular inflammation. Pyroptosis is a newly identified pro-inflammation form of programmed cell death, causing cell lysis and IL-1β release, and characterized by the caspases-induced cleavage of its effector molecule gasdermins (GSDMs). However, the effect of homocysteine (Hcy) on endothelial cells pyroptosis and the underlying mechanisms have not been fully defined. We have previously reported that Hcy induces vascular endothelial inflammation accompanied by the increase of high mobility group box-1 protein (HMGB1) and lysosomal cysteine protease cathepsin V in endothelial cells, and other studies have shown that HMGB1 or cathepsins are involved in activation of NLRP3 inflammasome and caspase-1. Here, we investigated the role of HMGB1 and cathepsin V in the process of Hcy-induced pyroptosis. We observed an increase in plasma IL-1β levels in HHcy patients and mice models, cathepsin V inhibitor reduced the plasma IL-1β levels and cleavage of GSDMD full-length into GSDMD N-terminal in the thoracic aorta of hyperhomocysteinemia mice. Using cultured HUVECs, we observed that Hcy promoted GSDMD N-terminal expression, silencing GSDMD or HMGB1 rescued Hcy-induced pyroptosis. HMGB1 also increased GSDMD N-terminal expression, and silencing cathepsin V reversed HMGB1-induced pyroptosis. HMGB1 could increase lysosome permeability, and silencing cathepsin V attenuated HMGB1-induced activation of caspase-1. In conclusion, this study has delineated a novel mechanism that HMGB1 mediated Hcy-induced endothelial cells pyroptosis partly via cathepsin V-dependent pathway.

Cathepsin B inhibition blocks neurite outgrowth in cultured neurons by regulating lysosomal trafficking and remodeling.

Lysosomes are known to mediate neurite outgrowth in neurons. However, the principal lysosomal molecule controlling that outgrowth is unclear. We studied primary mouse neurons in vitro and found that they naturally develop neurite outgrowths over time and as they did so the lysosomal cysteine protease cathepsin B (CTSB) mRNA levels dramatically increased. Surprisingly, we found that treating those neurons with CA-074Me, which inhibits CTSB, prevented neurites. As that compound also inhibits another protease, we evaluated a N2a neuronal cell line in which the CTSB gene was deleted (CTSB knockout, KO) using CRISPR technology and induced their neurite outgrowth by treatment with retinoic acid. We found that CTSB KO N2a cells failed to produce neurite outgrowths but the wild-type (WT) did. CA-074Me is a cell permeable prodrug of CA-074, which is cell impermeable and a specific CTSB inhibitor. Neurite outgrowth was and was not suppressed in WT N2a cells treated with CA-074Me and CA-074, respectively. Lysosome-associated membrane glycoprotein 2-positive lysosomes traffic to the plasma cell membrane in WT but not in CTSB KO N2 a cells. Interestingly, no obvious differences between WT and CTSB KO N2a cells were found in neurite outgrowth regulatory proteins, PI3K/AKT, ERK/MAPK, cJUN, and CREB. These findings show that intracellular CTSB controls neurite outgrowth and that it does so through regulation of lysosomal trafficking and remodeling in neurons. This adds valuable information regarding the physiological function of CTSB in neural development.

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.

Expression and Clinical Implications of Cysteine Cathepsins in Gallbladder Carcinoma.

Background: Gallbladder carcinoma (GBC) exhibits poor prognosis due to its detection at an advanced stage. Upregulation of lysosomal cysteine proteases cathepsin L (CTSL) and cathepsin B (CTSB) has been implicated in several tumorigenic processes. However, no such information in GBC was available. Therefore, the present study was planned to investigate the expression and clinical significance of these cathepsins in GBC.Methods: Activities of CTSL and CTSB were assayed in the gallbladder (GB) tissues obtained from GBC patients (n = 43) and control subjects (n = 69). Protein and mRNA levels were quantified using immunohistochemistry and real-time PCR (qPCR), respectively. Finally, serum levels of CTSL and CTSB were estimated by ELISA. Receiver operating characteristic (ROC) curve analysis was used for the assessment of sensitivity, specificity, and diagnostic accuracy of these cysteine cathepsins in GBC. The association of combined CTSL and CTSB activity with overall survival was assessed using Kaplan Meier survival analysis.Results: The expression and activity of both CTSL and CTSB were significantly increased (p < 0.050) in tumors of GBC patients as compared to controls. Enzymatic activity of CTSL+B and CTSB exhibited a strong positive association with tumor stage and lymph node involvement in GBC (p < 0.050). Interestingly, the elevated activity of combined CTSL+B was also associated with increased mortality in these patients. Furthermore, significantly enhanced levels of serum CTSL and CTSB were also observed in GBC (p < 0.050) as compared to controls. ROC analysis revealed high diagnostic significance of serum CTSB and CTSL for distinguishing GBC patients from controls with an area under the curve (AUC) of 82 and 77%, respectively.Conclusion: This study, for the first time, demonstrates the clinical significance of CTSL and CTSB overexpression in GBC. Our findings may help improve the clinical management of this carcinoma.

Lysosomal cysteine protease cathepsin S is involved in cancer cell motility by regulating store-operated Ca2+ entry

Cathepsin S (CTSS), a lysosomal cysteine protease, has been reported to be associated with extracellular matrix (ECM) degradation, thus promoting cell migration and invasion, but whether CTSS regulates other intracellular mechanisms during metastasis remains unknown. The expression of CTSS was knocked down using siRNA transfection, and enzymatic activity was inhibited by the highly-selective CTSS inhibitor RJW-58. The results of in vitro functional assays, western blot analysis, and an in vivo colonization model demonstrated that CTSS was positively related to cellular adhesive ability. Moreover, both CTSS knockdown and inhibition significantly decreased Ca2+ influx via store-operated Ca2+ entry (SOCE) without changing STIM1 and Orai1 expression levels, while RJW-58 dose-dependently reduced the activation of the Ca2+-dependent downstream effectors, NFAT1 and Rac1. The results of immunoprecipitation assays demonstrated that CTSS could bind to STIM1, which was reversed by CTSS inhibition. In addition, confocal microscopy and super-resolution imaging showed that CTSS inhibition led to STIM1 puncta accumulation in the endoplasmic reticulum and reduced the interaction between active STIM1 and EB1. In conclusion, we have demonstrated for the first time that the lysosomal cysteine protease, CTSS, plays an important role in mediating Ca2+ homeostasis by regulating STIM1 trafficking, which leads to the suppression of cell migration and invasion.

Cathepsin S in the spinal microglia facilitates morphine-induced antinociceptive tolerance in rats

Microglia-derived lysosomal cysteine protease cathepsin S (CatS) is increasingly recognized as important mediators to exaggerate nociceptive signaling. However, the patterns and functional roles of CatS in morphine tolerance have never been investigated. Here, we showed that mature form of CatS was exclusively upregulated in the spinal microglia following chronic morphine treatment. Pharmacological blockade of CatS before each morphine treatment prolonged the efficacy of morphine analgesia. Correspondingly, inhibition of CatS suppressed activation of spinal microglia and phosphorylated p38 MAPK. Finally, intrathecal injection of selective microglia inhibitor minocycline reduced upregulation of mature CatS induced by chronic morphine treatment. Our data provide novel insight into the cellular mechanisms underlying morphine antinociceptive tolerance and highlight CatS as a therapeutic target for preventing morphine tolerance.

Characterization of cathepsin C from orange-spotted grouper, Epinephelus coioides involved in SGIV infection

The lysosomal cysteine protease cathepsin C plays a pivotal role in regulation of inflammatory and immune responses. However, the function of fish cathepsin C in virus replication remains largely unknown. In this study, cathepsin C gene (Ec-CC) was cloned and characterized from orange-spotted grouper, Epinephelus coioides. The full-length Ec-CC cDNA was composed of 2077 bp. It contained an open reading frame (ORF) of 1374 bp and encoded a 458-amino acid protein which shared 89% identity to cathepsin C from bicolor damselfish (Stegastes partitus). Amino acid alignment analysis showed that Ec-CC contained an N-terminal signal peptide, the propeptide region and the mature peptide. RT-PCR analysis showed that Ec-CC transcript was expressed in all the examined tissues which abundant in spleen and head kidney. After challenged with Singapore grouper iridovirus (SGIV) stimulation, the relative expression of EC-CC was significantly increased at 24 h post-infection. Subcellular localization analysis revealed that Ec-CC was distributed mainly in the cytoplasm. Further studies showed that overexpression of Ec-CC in vitro significantly delayed the cytopathic effect (CPE) progression evoked by SGIV and inhibited the viral genes transcription. Moreover, overexpression of Ec-CC significantly increased the expression of proinflammatory cytokines during SGIV infection. Taken together, our results demonstrated that Ec-CC might play a functional role in SGIV infection by regulating the inflammation response.

Cathepsin B and S as markers for cardiovascular risk and all-cause mortality in patients with stable coronary heart disease during 10 years: a CLARICOR trial sub-study

Background and aimsThe lysosomal cysteine proteases cathepsin B and S have been implicated in the atherosclerotic process. The present paper investigates the association between serum levels of cathepsin B and S and cardiovascular events and mortality in patients with stable coronary heart disease. MethodsThe CLARICOR trial is a randomised, placebo-controlled trial investigating the effect of clarithromycin versus placebo in patients with stable coronary heart disease. The outcome was time to either a cardiovascular event or all-cause mortality. The placebo group was used as discovery sample and the clarithromycin group as replication sample: n = 1998, n = 1979; mean age (years) 65, 65; 31%, 30% women; follow-up for 10 years; number of composite outcomes n = 1204, n = 1220; respectively. We used a pre-defined multivariable Cox regression model adjusting for inflammation, established cardiovascular risk factors, kidney function, and use of cardiovascular drugs. ResultsCathepsin B was associated with an increased risk of the composite outcome in both samples after multivariable adjustment (discovery: multivariable ratio (HR) per standard deviation increase 1.12, 95% confidence interval (CI) 1.05–1.19, p < 0.001, replication; HR 1.14, 95% CI 1.07–1.21, p < 0.001). There was no significant association between cathepsin S and the composite outcome in either the discovery or replication sample after multivariable adjustment (p>0.45). Secondary analyses suggest that cathepsin B was predominantly associated with mortality rather than specific cardiovascular events. ConclusionsCathepsin B, but not serum cathepsin S, was associated with an increased risk of cardiovascular events in patients with stable coronary heart disease. The clinical implications of our findings remain to be established.

Consequences of cathepsin C inactivation for membrane exposure of proteinase 3, the target antigen in autoimmune vasculitis

Membrane-bound proteinase 3 (PR3m) is the main target antigen of anti-neutrophil cytoplasmic autoantibodies (ANCA) in granulomatosis with polyangiitis, a systemic small-vessel vasculitis. Binding of ANCA to PR3m triggers neutrophil activation with the secretion of enzymatically active PR3 and related neutrophil serine proteases, thereby contributing to vascular damage. PR3 and related proteases are activated from pro-forms by the lysosomal cysteine protease cathepsin C (CatC) during neutrophil maturation. We hypothesized that pharmacological inhibition of CatC provides an effective measure to reduce PR3m and therefore has implications as a novel therapeutic approach in granulomatosis with polyangiitis. We first studied neutrophilic PR3 from 24 patients with Papillon-Lefèvre syndrome (PLS), a genetic form of CatC deficiency. PLS neutrophil lysates showed a largely reduced but still detectable (0.5-4%) PR3 activity when compared with healthy control cells. Despite extremely low levels of cellular PR3, the amount of constitutive PR3m expressed on the surface of quiescent neutrophils and the typical bimodal membrane distribution pattern were similar to what was observed in healthy neutrophils. However, following cell activation, there was no significant increase in the total amount of PR3m on PLS neutrophils, whereas the total amount of PR3m on healthy neutrophils was significantly increased. We then explored the effect of pharmacological CatC inhibition on PR3 stability in normal neutrophils using a potent cell-permeable CatC inhibitor and a CD34+ hematopoietic stem cell model. Human CD34+ hematopoietic stem cells were treated with the inhibitor during neutrophil differentiation over 10 days. We observed strong reductions in PR3m, cellular PR3 protein, and proteolytic PR3 activity, whereas neutrophil differentiation was not compromised.

Abstract 2653: Cell proliferation and Cathepsin L expression are inversely correlated in bladder cancer progression and patient survival

Abstract In 2017 there will be an estimated 79,000 new cases of bladder cancer (UBC) resulting in 16,870 deaths. A better understanding of UBC progression and prognostic factors could improve patient management. UBC anatomic stage is determined by depth of invasion. Stage 0 is non-invasive, Stage 1 invades the sub-mucosa, Stage 2 invades the detrusor muscle, Stage 3 invades perivesical fat, and Stage 4 invades local or distant organs. 70-80% of UBCs are superficial, but can recur locally and be multifocal. Muscle invasive bladder cancers (MIBCs) can metastasize to pelvic lymph nodes or distant organs. To better understand the molecular mechanisms of UBC progression we measured cell proliferation utilizing the molecular marker of proliferating cells Ki 67 (Dako) and immunohistochemically detected expression of the lysosomal cysteine proteinase Cathepsin L (Abcam) in archived surgical specimens from 145 UBC patients. A board certified pathologist diagnosed and graded each histologic specimen and marked three areas for photography and image analysis. Clinical information and follow-up was obtained from existing medical records and the Kentucky Cancer Registry. IRB approval for the study was obtained from St. Elizabeth Healthcare who also donated the FFPE surgical specimens. We hypothesized that the % of proliferating tumor cells would increase with loss of cell differentiation and that Cathepsin L expression would increase with depth of tumor invasion into and beyond the detrusor muscle. Patients with high grade tumors (Grades 3 and 4) had a poor survival compared to patients with low grade tumors (p &amp;lt; 0.0001) and patients with MIBC (Stages 2-4) had a poorer survival that patients with superficial tumors (Stages 0 - 1) (p &amp;lt; 0.0001, HR = 18.63). Cell proliferation as determined by % of Ki 67 labeled nuclei was highly correlated with stage and grade (p &amp;lt;0.0001). In contrast Cathepsin L expression measured either semi-quantitatively by histoscore (area X intensity of stain) or quantitatively by computer assisted image analysis was negatively correlated with stage, grade, and Ki 67 labeling (p &amp;lt;0.0001). Recently multiple subtypes of MIBC have been identified, including basal tumors with squamous differentiation and luminal tumors. The highest rate of cell proliferation and the lowest expression of Cathepsin L in our data set were found in MIBC with squamous differentiation. Ki 67 labeling in UBC was highly prognostic of poor patient survival (p = 0.0003), whereas Cathepsin L expression as measured either by histoscore or image analysis was highly prognostic of good patient survival (p &amp;lt; 0.0001). Since Cathepsin L is encoded by the CTSL gene located on chromosome 9, these data are consistent with published reports of frequent genetic loss and mutations of chromosome 9 in UBC. These data also strongly support the value of UBC cell proliferation as a prognostic marker for stratifying UBC patients. Citation Format: Larry E. Douglass, Michelle C. Robillard, Dan Stelzer, Mariah Dooley, James A. Deddens, Julia H. Carter. Cell proliferation and Cathepsin L expression are inversely correlated in bladder cancer progression and patient survival [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2653.