Impact of circulating cathepsin K on the coronary calcification and the clinical outcome in chronic kidney disease patients

The many roles of cathepsins in restenosis

Drug-eluting stents (DES) and dual antiplatelet regimens have significantly improved the clinical management of ischemic heart disease; however, the drugs loaded with DES in clinical practice are mostly paclitaxel or rapamycin derivatives, which target symptoms of post implantation proliferation and inflammation, leading to delayed re-endothelialization and neo-atherosclerosis. Along with the treatments already in place, there is a need for novel strategies to lessen the negative clinical outcomes of DES delays as well as a need for greater understanding of their pathobiological mechanisms. This review concentrates on the function of cathepsins (Cats) in the inflammatory response and granulation tissue formation that follow Cat-induced damage to the vasculature scaffold, as well as the functions of Cats in intimal hyperplasia, which is characterized by the migration and proliferation of smooth muscle cells, and endothelial denudation, re-endothelialization, and/or neo-endothelialization. Additionally, Cats can alter essential neointima formation and immune response inside scaffolds, and if Cats are properly controlled in vivo, they may improve scaffold biocompatibility. This unique profile of functions could lead to an original concept for a cathepsin-based coronary intervention treatment as an adjunct to stent placement.

Overview of multifunctional cysteinyl cathepsins in atherosclerosis-based cardiovascular disease: from insights into molecular functions to clinical implications

Cysteinyl cathepsins (CTSs) are widely known to have a proteolysis function that mediates recycling of unwanted proteins in endosomes and lysosomes, and investigation of CTSs has greatly improved with advances in live-imaging techniques both in vivo and in vitro, leading to three key findings. (1) CTSs are relocated from the lysosomes to other cellular spaces (i.e., cytosol, nucleus, nuclear membrane, plasma membrane, and extracellular milieu). (2) In addition to acidic cellular compartments, CTSs also exert biological activity in neutral environments. (3) CTSs also exert multiple nontraditional functions in, for example, extracellular matrix metabolism, cell signaling transduction, protein processing/trafficking, and cellular events. Various stimuli regulate the expression and activities of CTSs in vivo and vitro-e.g., inflammatory cytokines, oxidative stress, neurohormones, and growth factors. Accumulating evidence has confirmed the participation of CTSs in vascular diseases characterized by atherosclerosis, plaque rupture, thrombosis, calcification, aneurysm, restenosis/in-stent-restenosis, and neovasel formation. Circulating and tissue CTSs are promising as biomarkers and as a diagnostic imaging tool in patients with atherosclerosis-based cardiovascular disease (ACVD), and pharmacological interventions with their specific and non-specific inhibitors, and cardiovascular drugs might have potential for the therapeutic targeting of CTSs in animals. This review focuses on the update findings on CTS biology and the involvement of CTSs in the initiation and progression of ACVD and discusses the potential use of CTSs as biomarkers and small-molecule targets to prevent deleterious nontraditional functions in ACVD.

Cathepsin K in Pathological Conditions and New Therapeutic and Diagnostic Perspectives

Cathepsin K (CatK) is a part of the family of cysteine proteases involved in many important processes, including the degradation activity of collagen 1 and elastin in bone resorption. Changes in levels of CatK are associated with various pathological conditions, primarily related to bone and cartilage degradation, such as pycnodysostosis (associated with CatK deficiency), osteoporosis, and osteoarthritis (associated with CatK overexpression). Recently, the increased secretion of CatK is being highly correlated to vascular inflammation, hypersensitivity pneumonitis, Wegener granulomatosis, berylliosis, tuberculosis, as well as with tumor progression. Due to the wide spectrum of diseases in which CatK is involved, the design and validation of active site-specific inhibitors has been a subject of keen interest in pharmaceutical companies in recent decades. In this review, we summarized the molecular background of CatK and its involvement in various diseases, as well as its clinical significance for diagnosis and therapy.

Cathepsin K Deficiency Prevented Kidney Damage and Dysfunction in Response to 5/6 Nephrectomy Injury in Mice With or Without Chronic Stress

Background:

Chronic psychological stress is a risk factor for kidney disease, including kidney dysfunction and hypertension. Lysosomal CatK (cathepsin K) participates in various human pathobiologies. We investigated the role of CatK in kidney remodeling and hypertension in response to 5/6 nephrectomy injury in mice with or without chronic stress.

Methods:

Male 7-week-old WT (wild type; CatK^+/+) and CatK-deficient (CatK^−/−) mice that were or were not subjected to chronic stress underwent 5/6 nephrectomy. At 8 weeks post-stress/surgery, the stress was observed to have accelerated injury-induced glomerulosclerosis, proteinuria, and blood pressure elevation.

Results:

Compared with the nonstressed mice, the stressed mice showed increased levels of TLR (Toll-like receptor)-2/4, p22^phox, gp91^phox, CatK, MMP (matrix metalloproteinase)-2/9, collagen type I and III genes, PPAR-γ (peroxisome proliferator-activated receptor-gamma), NLRP-3 (NOD-like receptor thermal protein domain associated protein 3), p21, p16, and cleaved caspase-8 proteins, podocyte foot process effacement, macrophage accumulation, apoptosis, and decreased levels of Bcl-2 (B cell lymphoma 2) and Sirt1, as well as decreased glomerular desmin expression in the kidneys. These harmful changes were retarded by the genetic or pharmacological inhibition of CatK. Consistently, CatK inhibition ameliorated 5/6 nephrectomy–related kidney injury and dysfunction. In mesangial cells, CatK silencing or overexpression, respectively, reduced or increased the PPAR-γ and cleaved caspase-8 protein levels, providing evidence and a mechanistic explanation of CatK’s involvement in PPAR-γ/caspase-8–mediated cell apoptosis in response to superoxide and stressed serum.

Conclusions:

These results demonstrate that CatK plays an essential role in kidney remodeling and hypertension in response to 5/6 nephrectomy or stress, possibly via a reduction of glomerular inflammation, apoptosis, and fibrosis, suggesting a novel therapeutic strategy for controlling kidney injury in mice under chronic psychological stress conditions.

Abdominal Aortic Calcification and Cardiovascular Outcomes in Chronic Kidney Disease: Findings from KNOW-CKD Study

To investigate the association between abdominal aortic calcification score (AACS) assessed by plain radiograph of the lateral abdomen and the risk of cardiovascular (CV) events in patients with pre-dialysis chronic kidney disease (CKD), a total of 2090 pre-dialysis CKD patients from the Korean Cohort Study for Outcome in Patients with Chronic Kidney Disease (KNOW-CKD) were categorized by AACS into 0, 1–2, 3–4, 5–6, and ≥7. The primary outcome of the study was the composite CV events, defined as a composite of non-fatal CV events and all-cause death. The risk of composite CV events was significantly higher in the subjects with AACS ≥ 7 (adjusted hazard ratio (HR) 1.888, 95% confidence interval (CI) 1.219 to 2.923), compared to that of the subjects with AACS 0. The risks of fatal and non-fatal CV events (adjusted HR 1.052, 95% CI 1.030 to 1.073) and all-cause death (adjusted HR 1.949, 95% CI 1.073 to 3.539) were also significantly higher in the subjects with AACS ≥ 7. In conclusion, AACS assessed by plain radiograph is independently associated with adverse CV outcomes in patients with pre-dialysis CKD. A simple radiographic examination of the lateral abdomen may help CV risk stratification in this population.

Urine peptidome analysis in cardiorenal syndrome reflects molecular processes

The cardiorenal syndrome (CRS) is defined as the confluence of heart-kidney dysfunction. This study investigates the molecular differences at the level of the urinary peptidome between CRS patients and controls and their association to disease pathophysiology. The urinary peptidome of CRS patients (n = 353) was matched for age and sex with controls (n = 356) at a 1:1 ratio. Changes in the CRS peptidome versus controls were identified after applying the Mann-Whitney test, followed by correction for multiple testing. Proteasix tool was applied to investigate predicted proteases involved in CRS-associated peptide generation. Overall, 559 differentially excreted urinary peptides were associated with CRS patients. Of these, 193 peptides were specifically found in CRS when comparing with heart failure and chronic kidney disease urinary peptide profiles. Proteasix predicted 18 proteases involved in > 1% of proteolytic cleavage events including multiple forms of MMPs, proprotein convertases, cathepsins and kallikrein 4. Forty-four percent of the cleavage events were produced by 3 proteases including MMP13, MMP9 and MMP2. Pathway enrichment analysis supported that ECM-related pathways, fibrosis and inflammation were represented. Collectively, our study describes the changes in urinary peptides of CRS patients and potential proteases involved in their generation, laying the basis for further validation.

Cathepsin-K is a potential cardiovascular risk biomarker in prevalent hemodialysis patients

PURPOSE

Cardiovascular (CV) disease remains the leading cause of mortality among end-stage kidney disease (ESKD) patients. Cathepsin-K (CatK), a small cysteine protease involved in bone and extracellular matrix remodeling, has recently emerged as a key-factor in the pathogenesis of various conditions predisposing to CV disease, including atherosclerosis, obesity, diabetes, and vascular calcification. In this pilot prospective study, we aimed at evaluating the clinical significance and the predictive power of CatK in a small cohort of hemodialysis (HD) patients.

METHODS

Cathepsin-K was measured in 54 prevalent HD patients and in 30 controls together with routine parameters. Patients were then followed up to 26 months and the time of cardiovascular death (endpoint of the study prospective phase) recorded.

RESULTS

CatK levels were increased in the HD cohort as compared with controls (p < 0.001). In HD patients, CatK was also independently correlated to PTH (β = 0.368; p = 0.001), alkaline phosphatase (β = 0.383; p < 0.001), C-reactive protein (β = 0.260; p = 0.01), and white cell count (β = - 0.219; p = 0.02). After baseline assessment, patients were followed for CV death (mean follow-up 24.8 ± 3.1 months). Kaplan-Meier analysis showed a worsen survival (log-rank p = 0.04) in HD patients with CatK levels > 440 pg/mL (best ROC-derived cut-off with 69.6% sensitivity and 79.8% specificity) with a crude HR (Mantel-Haenszel) of CV death of 3.46 (95% CI 1.89-13.44).

CONCLUSIONS

In prevalent HD patients, altered CatK levels may reflect mineral dysmetabolism and inflammation, and predict CV death in the mid-term. These preliminary findings prompt the rationale for further investigations on larger cohorts to validate CatK as a biomarker for improving CV risk stratification in ESKD.

Increased circulating Cathepsin-K levels reflect PTH control in chronic hemodialysis patients

BACKGROUND

Mineral bone disease (MBD) is remarkably frequent among chronic hemodialysis (HD) patients. In this setting, deranged PTH levels portend an adjunctive risk of worsen outcomes. Various evidence exists demonstrating that PTH strongly induces Cathepsin-K, a cysteine protease mainly found in lysosomes of osteoclasts and macrophages which promotes bone and extracellular matrix remodelling. Cathepsin-K levels are altered in various bone disorders, systemic inflammation and even in non-advanced CKD. In this study, we tested the hypothesis of an association between Cathepsin-K, uremic-MBD and circulating PTH levels in a cohort of chronic HD patients.

METHODS

We measured Cathepsin-K in 85 stable chronic HD patients and dialysis vintage > 6 months by a commercially available ELISA kit and we collected routine clinical parameters, including intact PTH. Patients were further stratified according to their "on- target" or "off-target" PTH status.

RESULTS

Cathepsin-K levels were significantly higher in HD patients than in healthy controls (p < 0.0001) and were independently associated with alkaline phosphatase (β = 0.37; p < 0.001), PTH (β = 0.30; p = 0.02) and C-reactive protein (β = 0.24; p = 0.008) levels. Cathepsin-K was also higher in patients with off-target PTH as compared to those with controlled PTH levels (230 [40-420] vs. 3250 [820-4205] pg/mL; p < 0.0001). At ROC analyses, Cathepsin-K levels were able to identify off-target PTH and parathyroidectomized patients (AUCs 0.85 [95% CI 0.71-0.98] and 0.97 [95% CI 0.92-0.99], respectively).

CONCLUSION

In chronic HD patients, Cathepsin-K associates with PTH levels, raising the intriguing hypothesis that this protein represents a causal link between mineral and inflammatory complications and could be tested as a candidate biomarker of MBD severity and PTH balance.

Cysteinyl cathepsins in cardiovascular diseases

Cysteinyl cathepsins are lysosomal/endosomal proteases that mediate bulk protein degradation in these intracellular acidic compartments. Yet, studies indicate that these proteases also appear in the nucleus, nuclear membrane, cytosol, plasma membrane, and extracellular space. Patients with cardiovascular diseases (CVD) show increased levels of cathepsins in the heart, aorta, and plasma. Plasma cathepsins often serve as biomarkers or risk factors of CVD. In aortic diseases, such as atherosclerosis and abdominal aneurysms, cathepsins play pathogenic roles, but many of the same cathepsins are cardioprotective in hypertensive, hypertrophic, and infarcted hearts. During the development of CVD, cathepsins are regulated by inflammatory cytokines, growth factors, hypertensive stimuli, oxidative stress, and many others. Cathepsin activities in inflammatory molecule activation, immunity, cell migration, cholesterol metabolism, neovascularization, cell death, cell signaling, and tissue fibrosis all contribute to CVD and are reviewed in this article in memory of Dr. Nobuhiko Katunuma for his contribution to the field.

Elastolytic activity of cysteine cathepsins K, S, and V promotes vascular calcification

Elastin plays an important role in maintaining blood vessel integrity. Proteolytic degradation of elastin in the vascular system promotes the development of atherosclerosis, including blood vessel calcification. Cysteine cathepsins have been implicated in this process, however, their role in disease progression and associated complications remains unclear. Here, we showed that the degradation of vascular elastin by cathepsins (Cat) K, S, and V directly stimulates the mineralization of elastin and that mineralized insoluble elastin fibers were ~25–30% more resistant to CatK, S, and V degradation when compared to native elastin. Energy dispersive X-ray spectroscopy investigations showed that insoluble elastin predigested by CatK, S, or V displayed an elemental percentage in calcium and phosphate up to 8-fold higher when compared to non-digested elastin. Cathepsin-generated elastin peptides increased the calcification of MOVAS-1 cells acting through the ERK1/2 pathway by 34–36%. We made similar observations when cathepsin-generated elastin peptides were added to ex vivo mouse aorta rings. Altogether, our data suggest that CatK-, S-, and V-mediated elastolysis directly accelerates the mineralization of the vascular matrix by the generation of nucleation points in the elastin matrix and indirectly by elastin-derived peptides stimulating the calcification by vascular smooth muscle cells. Both processes inversely protect against further extracellular matrix degradation.

Cathepsin K activity controls cardiotoxin-induced skeletal muscle repair in mice

BACKGROUND

Cathepsin K (CatK) is a widely expressed cysteine protease that has gained attention because of its enzymatic and non-enzymatic functions in signalling. Here, we examined whether CatK-deficiency (CatK^-/- ) would mitigate injury-related skeletal muscle remodelling and fibrosis in mice, with a special focus on inflammation and muscle cell apoptosis.

METHODS

Cardiotoxin (CTX, 20 μM/200 μL) was injected into the left gastrocnemius muscle of male wild-type (CatK^+/+ ) and CatK^-/- mice, and the mice were processed for morphological and biochemical studies.

RESULTS

On post-injection Day 14, CatK deletion ameliorated muscle interstitial fibrosis and remodelling and performance. At an early time point (Day 3), CatK^-/- reduced the lesion macrophage and leucocyte contents and cell apoptosis, the mRNA levels of monocyte chemoattractant protein-1, toll-like receptor-2 and toll-like receptor-4, and the gelatinolytic activity related to matrix metalloproteinase-2/-9. CatK deletion also restored the protein levels of caspase-3 and cleaved caspase-8 and the ratio of the BAX to the Bcl-2. Moreover, CatK deficiency protected muscle fibre laminin and desmin disorder in response to CTX injury. These beneficial muscle effects were mimicked by CatK-specific inhibitor treatment. In vitro experiments demonstrated that pharmacological CatK inhibition reduced the apoptosis of C2C12 mouse myoblasts and the levels of BAX and caspase-3 proteins induced by CTX.

CONCLUSIONS

These results demonstrate that CatK plays an essential role in skeletal muscle loss and fibrosis in response to CTX injury, possibly via a reduction of inflammation and cell apoptosis, suggesting a novel therapeutic strategy for the control of skeletal muscle diseases by regulating CatK activity.

Cysteine Protease Cathepsins in Atherosclerotic Cardiovascular Diseases

Atherosclerotic cardiovascular disease (ASCVD) is an inflammatory disease characterized by extensive arterial wall matrix protein degradation. Cysteine protease cathepsins play a pivotal role in extracellular matrix (ECM) remodeling and have been implicated in the development and progression of atherosclerosis-based cardiovascular diseases. An imbalance in expression between cathepsins (such as cathepsins S, K, L, C) and their inhibitor cystatin C may favor proteolysis of ECM in the pathogenesis of cardiovascular disease such as atherosclerosis, aneurysm formation, restenosis, and neovascularization. New insights into cathepsin functions have been made possible by the generation of knock-out mice and by the application of specific inhibitors. Inflammatory cytokines regulate the expression and activities of cathepsins in cultured vascular cells and macrophages. In addition, evaluations of the possibility of cathepsins as a diagnostic tool revealed that the circulating levels of cathepsin S, K, and L, and their endogenous inhibitor cystatin C could be promising biomarkers in the diagnosis of coronary artery disease, aneurysm, adiposity, peripheral arterial disease, and coronary artery calcification. In this review, we summarize the available information regarding the mechanistic contributions of cathepsins to ASCVD.

Impact of serum albumin levels on long-term outcomes in patients undergoing percutaneous coronary intervention

Epidemiological studies have demonstrated an association between low serum albumin levels and both coronary artery disease (CAD) and mortality. However, the long-term clinical impact of low serum albumin level in patients with CAD undergoing percutaneous coronary intervention (PCI) has not yet been fully investigated. We studied 2860 all-comer patients with CAD who underwent their first PCI and had data available for pre-procedural serum albumin between 2000 and 2011. Patients were assigned to tertiles based on pre-procedural albumin levels. We evaluated the incidence of major adverse cardiac events (MACE), including all-cause death and nonfatal myocardial infarction. Mean albumin level was 4.0 ± 0.5 g/dL. Lower albumin levels were associated with older age, lower body mass index (BMI), and higher prevalences of female sex, ACS and chronic kidney disease (CKD). During the median follow-up period of 7.4 years, Kaplan-Meier curves showed ongoing divergence in rates of MACE among albumin tertiles (albumin <3.8 g/dl: 44.3% vs. 3.8-4.1 g/dl: 38.0% vs. >4.1 g/dl: 22.9%; log-rank p < 0.0001). After adjusting for established cardiovascular risk factors including age, acute coronary syndrome, BMI and CKD, serum albumin levels were significantly associated with incidence of MACE (HR 1.74 per 1-g/dl decrease, 95% CI 1.34-2.26, p < 0.0001) and all-cause mortality (HR 1.74, 95% CI 1.30-2.33, p = 0.0002). Pre-PCI low serum albumin level was associated with worse long-term outcomes, independent of traditional risk factors. Assessing albumin levels may allow risk stratification in patients with CAD undergoing PCI.

Brain natriuretic peptide as a potential novel marker of salt-sensitivity in chronic kidney disease patients without cardiac dysfunction

Although the renin-angiotensin system (RAS) is counter-balanced by a salt-sensitive mechanism in the hypertensive state, both are reported to be up-regulated in chronic kidney disease (CKD) patients. We conducted this study to evaluate the associations among the RAS, renal function, hypertension, and atherosclerosis, as well as to identify markers for salt-sensitivity. A total of 213 pre-dialysis CKD patients with preserved cardiac function (EF >50 %) were enrolled. Their renal and cardiac biochemical markers and plasma renin activity (PRA) were measured, and echocardiography and carotid artery ultrasound were performed. Their salt intake was estimated by the NaCl excretion from a 24-h collected urine sample. The PRA was higher in patients with hypertension (p = 0.018), and had a significant negative correlation with the eGFR (r = -0.23, p = 0.0067). Importantly, the PRA had a strong negative correlation with the brain natriuretic peptide (BNP) level (r = -0.28, p = 0.017) regardless of whether the patients were being treated with RAS inhibitors. The BNP level was related to the renal functions (eGFR: p = 0.001, ACR: p = 0.009). There was a significant positive correlation between the BNP level and carotid intima-media thickness (p < 0.001). A multivariate analysis revealed that older age and an excess of NaCl excretion were independent predictors of BNP elevation (p = 0.02 and 0.003, respectively). Our analysis revealed details of the counterbalance between BNP and PRA, as well as identifying that excess salt intake is a predictor of BNP elevation. These results indicate that the BNP could be a possible valuable marker for salt sensitivity, and that high salt sensitivity could facilitate atherosclerosis in CKD patients.

Axillary artery cannulation provides balanced cerebral oxygenation

Deterioration of cerebral performance remains a major problem after cardiac surgery. Axillary artery cannulation can improve clinical outcome, but some experimental series show a malperfusion of the right hemisphere. The aim of our clinical study was to analyze the intraoperative investigation of cerebral oxygenation in two different arterial cannulation sites by use of near-infrared spectroscopic oximetry (NIRO). We compared retrospectively the cerebral saturation of 20 patients with aortic cannulation (group AoC) and 20 patients with right axillary artery cannulation (group AxC) during either valve, coronary artery bypass graft (CABG), combined procedures, or aortic surgery. Patients were monitored with bihemispheric NIRO (NIRO-200, Hamamatsu, Herrsching, Germany). The oxygenation data were calculated as tissue oxygenation index (TOI). And the cardiopulmonary bypass time was considered with special regard to potentially dangerous phases for cerebral desaturation like the starting of the extracorporeal circulation (ECC), cross-clamping, rewarming phase, aortic declamping, and stopping of ECC. Patients were then postoperatively evaluated by a standardized neurological examination. During the entire CPB time and the specific phases potentially at risk for cerebral desaturation, no statistically significant drop of cerebral oxygenation (>20 % for >60 s) was detected after aortic and right axillary artery cannulation, respectively. Furthermore, no significant difference in TOI was found comparing the left and right hemisphere in each group. Postoperatively 2 transient confusional syndromes (CS) were observed after aortic and 3 CS after axillary artery cannulation. Right axillary artery cannulation provides balanced cerebral oxygenation in both hemispheres during extracorporeal circulation and its specific phases potentially at risk for cerebral malperfusion. It might therefore reduce the risk of neurological injury by reduction of solid embolization and maintenance of balanced cerebral oxygenation.