Cystatin C deficiency increases elastic lamina degradation and aortic dilatation in apolipoprotein E-null mice

Association of biological age with health outcomes and its modifiable factors

Identifying the clinical implications and modifiable and unmodifiable factors of aging requires the measurement of biological age (BA) and age gap. Leveraging the biomedical traits involved with physical measures, biochemical assays, genomic data, and cognitive functions from the healthy participants in the UK Biobank, we establish an integrative BA model consisting of multi-dimensional indicators. Accelerated aging (age gap >3.2 years) at baseline is associated incident circulatory diseases, related chronic disorders, all-cause, and cause-specific mortality. We identify 35 modifiable factors for age gap (p < 4.81 × 10-4 ), where pulmonary functions, body mass, hand grip strength, basal metabolic rate, estimated glomerular filtration rate, and C-reactive protein show the most significant associations. Genetic analyses replicate the possible associations between age gap and health-related outcomes and further identify CST3 as an essential gene for biological aging, which is highly expressed in the brain and is associated with immune and metabolic traits. Our study profiles the landscape of biological aging and provides insights into the preventive strategies and therapeutic targets for aging.

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.

Association between Serum Cystatin C levels and long‐term cardiovascular outcomes and all-cause mortality in older patients with obstructive sleep apnea

Background and Aims: To investigate the association between obstructive sleep apnea (OSA) severity and baseline serum cystatin C (Cys-C) concentration and to explore the association between baseline serum Cys-C and long-term cardiovascular outcomes and mortality in older patients with OSA.

Methods: Between January 2015 and October 2017, a total of 1107 consecutive eligible older patients (≥60 years) with OSA were included in this multicenter, prospective cohort study, and baseline demographics, clinical characteristics, sleep parameters, and follow-up outcomes were collected. Participants were divided into different groups based on baseline serum Cys-C levels. The primary end point was major adverse cardiovascular events (MACE) and the secondary end point was all-cause mortality. The correlation between OSA severity and baseline serum Cys-C was evaluated by Spearman correlation analysis. Multivariate Cox regression was used to analyze the association between Cys-C and the incidence of MACE and mortality.

Results: Participants included 672 men and 435 women, with a median age of 66 (range, 60–96) years. At baseline, apnea–hypopnea index (AHI) (r = 0.128, p &lt; 0.05), oxygen desaturation index (ODI) (r = 0.116, p &lt; 0.05), and the lowest pulse oxygen saturation (LSpO2) (r = −0.097, p &lt; 0.05) were correlated with serum Cys-C concentration. During the median follow-up period of 42 months, 97 patients (8.8%) experienced MACE and 40 patients (3.6%) experienced death. The association between serum Cys-C levels and the risk of MACE and all-cause mortality was slow rising shaped. The multivariable Cox regression analysis showed patients with a serum Cys-C concentration of ≥1.14 mg/L had higher risks of MACE (HR = 5.30, 95% CI: 2.28–12.30, p &lt; 0.05) and all-cause mortality (HR = 9.66, 95% CI: 2.09–44.72, p &lt; 0.05) compared with patients with serum Cys-C of ≤0.81 mg/L in older patients with OSA. The receiver-operating characteristic curve showed baseline serum Cys-C levels exhibited moderately capable of identifying patients with a long-term risk of clinical adverse events (MACE and mortality).

Conclusion: OSA severity was positively correlated with serum Cys-C concentration. High levels of Cys-C were independently associated with increased risks of MACE and all-cause mortality in older patients with OSA, suggesting that lowering Cys-C levels should be considered as a therapeutic target, and monitoring serum Cys-C may be beneficial to the favorable prognosis of older patients with OSA.

The HDL Proteome Watch: Compilation of studies leads to new insights on HDL function

PURPOSE OF REVIEW

High density lipoproteins (HDL) are a heterogeneous family of particles that contain distinct complements of proteins that define their function. Thus, it is important to accurately and sensitively identify proteins associated with HDL. Here we highlight the HDL Proteome Watch Database which tracks proteomics studies from different laboratories across the world.

RECENT FINDINGS

In 45 published reports, almost 1000 individual proteins have been detected in preparations of HDL. Of these, 251 have been identified in at least three different laboratories. The known functions of these consensus HDL proteins go well beyond traditionally recognized roles in lipid transport with many proteins pointing to HDL functions in innate immunity, inflammation, cell adhesion, hemostasis and protease regulation, and even vitamin and metal binding.

SUMMARY

The HDL proteome derived across multiple studies using various methodologies provides confidence in protein identifications that can offer interesting new insights into HDL function. We also point out significant issues that will require additional study going forward.

Association Between CST3 Gene Polymorphisms and Large-Artery Atherosclerotic Stroke

Objective: Cystatin C, a marker of atherosclerosis, is encoded by CST3. We aimed to evaluate whether two single-nucleotide polymorphisms (SNPs) of CST3 are correlated with large-artery atherosclerotic stroke (LAAS) and prognosis.

Methods: This subgroup analysis of the Third China National Stroke Registry (CNSR-III) enrolled acute ischemic stroke (AIS) patients within 7 days from August 2015 to March 2018 in China. rs13038305 and rs911119 of CST3 were selected based on the strong association with cystatin C concentration.

Results: Two loci of CST3 (rs13038305 and rs911119) were analyzed in 3,833 ischemic stroke patients. Carriers of T allele in rs13038305 and C allele in rs911119 tend to have lower serum cystatin C levels (p < 0.05). Compared with C/C as a reference in rs13038305, odds ratio (OR) of T/T was 0.486, 95% CI 0.237–0.994, p = 0.048. Per C allele of rs13038305 also showed an increased level of low-density lipoprotein cholesterol (LDL-C), β (95% CI) was 1.335 (1.008–1.250), p = 0.044. No correlation was found between the selected SNPs and stroke prognosis (functional outcome, recurrence, and mortality).

Conclusions: Carriers of the T allele in rs13038305 tend to have a lower proportion of LAAS. rs13038305 and rs911119 polymorphisms were likely to affect cystatin C concentration independently of kidney function.

Serum Cystatin C Predicts Stroke Clinical Outcomes at 1 Year Independent of Renal Function

Objective: Serum cystatin C (CysC) is a sensitive marker of renal function to predict cardiovascular diseases. We aimed to investigate the predictive value of CysC for clinical outcomes independent of renal function in patients with acute ischemic stroke (AIS).

Methods: We measured serum CysC levels in 10,256 AIS patients from Third China National Stroke Registry (CNSR-III). The primary outcome was a combination of all-cause mortality and major disability (modified Rankin scale score, 3–6). Secondary outcomes included stroke recurrence and combined vascular events at 1 year. Outcomes were analyzed using logistic regression and Cox proportional hazards models, respectively.

Results: The median CysC of included patients was 0.95 mg/l (interquartile range, 0.83–1.10 mg/l). A U-shaped association was observed between CysC and primary outcome (all-cause mortality or major disability) [quartile (Q)1 vs. Q2: adjusted odds ratio (aOR) 1.29, 95% CI 1.06–1.58, p = 0.012; Q3 vs. Q2: aOR 1.12, 95% CI 0.93–1.35, p = 0.242; Q4 vs. Q2: aOR 1.35, 95% CI 1.10–1.65, p = 0.004]. A similar trend also existed in “preserved renal function” patients. Adding CysC to a model containing conventional risk factors improved the model performance with integrated discrimination improvement (IDI) of 0.13% (p = 0.016) and net reclassification index (NRI) of 13.10% (p <0.001) for primary outcome. No significant association was observed for stroke recurrence or combined vascular event rate in different CysC quartiles.

Conclusions: CysC showed a U-shaped correlation with 1-year stroke clinical outcome, suggesting that serum CysC may not only be a simple candidate marker of renal function.

Beta-2-Microglobulin is an Independent Risk Factor for Asymptomatic Carotid Atherosclerosis in Patients with Primary Aldosteronism

Aim: To identify the association between serum beta-2-microglobulin (B2M) or cystatin C (CysC) and asymptomatic carotid atherosclerosis in patients with primary aldosteronism (PA).

Methods: In this cross-sectional study, 265 subjects were enrolled, including 83 patients with PA, 91 with essential hypertension (EH), and 91 normotensive (NT) controls. B2M, CysC, plasma renin activity (PRA), and plasma aldosterone concentration (PAC) were measured, and the aldosterone-to-renin ratio (ARR) was calculated. Carotid intima-media thickness (cIMT), increased cIMT, and presence of carotid plaque or carotid stenosis ＜50% in the carotid artery were measuredvia ultrasonography to evaluate the degree of asymptomatic carotid atherosclerosis.

Results: CIMT increased in the NT, EH, and PA groups (0.60 (0.50, 0.80) mm vs. 0.80 (0.60, 1.00) mm vs. 0.90 (0.70, 1.10) mm,P＜0.01), so as the prevalence of increased cIMT and presence of carotid plaque (bothP＜0.05). The B2M and CysC levels exhibited the same trend (B2M: 1.60±0.34 mg/L, 1.80±0.41 mg/L, 1.98±0.64 mg/L,P＜0.05; CysC: 0.76±0.12 mg/L, 0.88±0.17 mg/L, 0.94±0.23 mg/L,P＜0.05). B2M, CysC, PAC, and ARR were all positively associated with cIMT (allP＜0.01) in the PA group. After adjusting for potential confounders, B2M, PAC, but not CysC or ARR were independently associated with increased cIMT and presence of carotid plaque and carotid stenosis ＜50%, respectively. The receiver operating characteristic (ROC) curve analysis revealed that B2M and PAC demonstrated significant predictive ability for increased cIMT and presence of carotid plaque and carotid stenosis ＜50%.

Conclusion: B2M is an independent risk factor for asymptomatic carotid atherosclerosis in patients with PA.

Transforming growth factor-β1 inhibits interleukin-1β-induced expression of inflammatory genes and Cathepsin S activity in human vascular smooth muscle cells

OBJECTIVE AND DESIGN

This study investigated the opposite mechanisms by which IL-1β and TGF-β1 modulated the inflammatory and migratory phenotypes in cultured human intimal vascular smooth muscle cells vSMCs.

MATERIALS AND TREATMENT

Primary human vSMCs, obtained from twelve hypertensive patients who underwent carotid endarterectomy, were incubated for 24 hours with either 40 pM TGF-β1, or 1 nmol/L IL-1β, or their combination in presence or absence of anti-TGF-β neutralizing antibody.

METHODS

The expression levels of matrix metalloproteases and their inhibitors, and the elastolytic enzyme cathepsin S (CTSS) and its inhibitor cystatin C were evaluated with RT-PCR. CTSS activity was measured by fluorometry.

RESULTS

TGF-β1 reversed IL-1β-induced expression of iNOS, CXCL6, IL1R1, MMP12, and CTSS, while upregulated TIMP2 expression. Furthermore, anti-TGF-β neutralizing antibody abrogated TGF-β effects. Combination with IL-1β and TGF-β1 induced the expression of IL1α, IL1β, IL1R1, and CTSS, but suppressed CST3 expression. CTSS expression in the combination treatment was higher than that of cells treated with anti-TGF-β antibodies alone. Moreover, IL-1β-induced CTSS enzymatic activity was reduced when human vSMCs were co-treated with TGF-β, whereas this reduction was abrogated by anti-TGF-β neutralizing antibody.

CONCLUSION

TGF-β1 abrogated IL-1β-induced expression of inflammatory genes and elastolytic activity in cultured human vSMCs. Thus, TGF-β1 can play a crucial role in impairing IL-1β-induced vascular inflammation and damage involved in the etiology of cardiovascular diseases.

Prognostic value of cystatin C in patients with acute coronary syndrome: A systematic review and meta-analysis

BACKGROUND

Circulating cystatin C has been considered as an independent predictor of cardiovascular and all-cause mortality in the general population. The purpose of this study was to evaluate the prognostic value of baseline circulating cystatin C levels in patients with acute coronary syndrome (ACS) through meta-analysis.

METHODS

Prospective studies about the relationship between the level of cystatin C and the prognosis of ACS patients were searched on PubMed, Web of science, Cochrane Library and Embase databases from the establishment of the databases to July 2020. The prognostic values included in this analysis covered all-cause mortality, major adverse cardiovascular events (MACE) and recurrent myocardial infarction. The effect index between cystatin C level and ACS risk was carried out by hazard ratio (HR). Stata 15.0 software was used for statistical analysis. The quality of the included literature was evaluated according to Newcastle-Ottawa Scale (NOS).

RESULTS

A total of 10 studies were included in this meta-analysis. The results showed that high cystatin C levels significantly predicted the all-cause mortality of ACS, HR = 2.53 (95%CI: 1.72 ~ 3.72). High cystatin C level significantly predicted MACE of patients with ACS, HR = 3.24 (95%CI: 1.30 ~ 8.07). However, it had no significant predictive significance for recurrent myocardial infarction, HR = 1.71 (95%CI:0.99 ~ 2.97).

CONCLUSION

Our meta-analysis showed that high cystatin C levels were significantly associated with the death risk and MACE in ACS patients. Therefore, cystatin C can be included in the risk stratification model to guide the treatment of high-risk ACS patients.

Activating transcription factor 3 is a potential target and a new biomarker for the prognosis of atherosclerosis

ATF3 (activating transcription factor 3) is a member of the mammalian activation transcription factor/cAMP-responsive element-binding (CREB) family. It plays a role in inflammation and innate immunity, and suggests that ATF3 is associated with atherosclerosis. In our study, we analyzed datasets of atherosclerosis from the NCBI-GEO (Gene Expression Omnibus) database and found that expression levels of ATF3 were lower in macrophages from ruptured atherosclerotic plaques than from stable atherosclerotic plaques. Expression levels of ATF3 correlated with the stability of atherosclerotic plaques. KEGG analysis of different expression genes (DEGs) between ruptured and stable atherosclerotic plaques was performed by Metascape database. The PI3K-AKT pathway may be a potential pathway of the formation of ruptured atherosclerotic plaques. High-fat diet-induced atherosclerosis apoE-/- mice were divided into two groups: a model group and an ATF3 overexpression (OE)-group. Tests on atherosclerotic plaques in the aortic root suggested that absence of ATF3 and increase of macrophages may be risk factors for the formation of ruptured atherosclerotic plaques. We found decreased areas of lesions in aortic roots and branches of aortic arch, as well as increased lesional content of macrophages as well as TUNEL-positive areas. Consistent with these results, we found reduced degradation and incidence of elastic plate cracks accompanied by suppressed MMPs expression and transduction pathway protein PI3K/AKT activation. These data suggest that ATF3 is a signaling molecule that mediates the progression and stability of atherosclerotic plaques. ATF3 could be a potential new biomarker for the prognosis of atherosclerosis and may be a therapeutic target to reduce atherosclerosis.

Reduced Nhe1 (Na+-H+ Exchanger-1) Function Protects ApoE-Deficient Mice From Ang II (Angiotensin II)-Induced Abdominal Aortic Aneurysms

IgE-mediated activation of Nhe1 (Na⁺-H⁺ exchanger-1) induces aortic cell extracellular acidification and promotes cell apoptosis. A pH-sensitive probe pHrodo identified acidic regions at positions of macrophage accumulation, IgE expression, and cell apoptosis in human and mouse abdominal aortic aneurysm (AAA) lesions. Ang II (angiotensin II)-induced AAA in Nhe1-insufficient Apoe^-/-Nhe1^+/- mice and Apoe^-/-Nhe1^+/+ littermates tested Nhe1 activity in experimental AAA, because Nhe1^-/- mice develop ataxia and epileptic-like seizures and die early. Nhe1 insufficiency reduced AAA incidence and size, lesion macrophage and T-cell accumulation, collagen deposition, elastin fragmentation, cell apoptosis, smooth muscle cell loss, and MMP (matrix metalloproteinase) activity. Nhe1 insufficiency also reduced blood pressure and the plasma apoptosis marker TCTP (translationally controlled tumor protein) but did not affect plasma IgE. While pHrodo localized the acidic regions to macrophage clusters, IgE expression, and cell apoptosis in AAA lesions from Apoe^-/-Nhe1^+/+ mice, such acidic areas were much smaller in lesions from Apoe^-/-Nhe1^+/- mice. Nhe1-FcεR1 colocalization in macrophages from AAA lesions support a role of IgE-mediated Nhe1 activation. Gelatin zymography, immunoblot, and real-time polymerase chain reaction analyses demonstrated that Nhe1 insufficiency reduced the MMP activity, cysteinyl cathepsin expression, IgE-induced apoptosis, and NF-κB activation in macrophages and blocked IgE-induced adhesion molecule expression in endothelial cells. A near-infrared fluorescent probe (LS662) together with fluorescence reflectance imaging of intact aortas showed reduced acidity in AAA lesions from Nhe-1-insufficient mice. This study revealed extracellular acidity at regions rich in macrophages, IgE expression, and cell apoptosis in human and mouse AAA lesions and established a direct role of Nhe1 in AAA pathogenesis.

Serum cystatin C is associated with carotid atherosclerosis in patients with acute ischemic stroke

BACKGROUND

Accumulating studies have shown that cystatin C may play important roles in the pathogenesis of arteriosclerosis. However, the association between serum cystatin C and the characteristics of carotid plaques has not been elucidated. Furthermore, the diagnostic value of serum cystatin C in carotid stenosis has not been studied.

METHODS

Serum cystatin C in 156 patients with acute ischemic stroke (AIS) in the carotid artery was measured by ELISA. Intima-media thickness (IMT), stenosis of the symptomatic common carotid artery (CCA), extra/intracranial internal carotid artery (ICA) stenosis, and plaque characteristics were measured and recorded. Receiver operating characteristic (ROC) curves were used to assess the diagnostic value of serum cystatin C in carotid stenosis.

RESULTS

One hundred fifty-six patients were divided into two groups based on their cystatin C levels. The degree of arteriosclerosis, the severity of plaques, and stenosis of the symptomatic CCA were significantly higher in the patients with high cystatin C levels. In addition, the rate of unstable plaques was significantly higher in those with high cystatin C. Serum cystatin C levels of 1.075 and 1.125 mg/L had diagnostic value in distinguishing stenosis of CCA and extracranial ICA, respectively.

CONCLUSIONS

Higher cystatin C levels were strongly correlated with symptomatic CCA stenosis and the rate of unstable plaques. Analysis of cystatin C levels may be useful for the identification of CCA stenosis and extracranial ICA in patients with AIS.

Increased Rate of Retinal Pigment Epithelial Cell Migration and Pro-Angiogenic Potential Ensuing From Reduced Cystatin C Expression

Purpose

Variant B precursor cysteine protease inhibitor cystatin C, a known recessive risk factor for developing exudative age-related macular degeneration (AMD), presents altered intracellular trafficking and reduced secretion from retinal pigment epithelial (RPE) cells. Because cystatin C inhibits multiple extracellular matrix (ECM)-degrading cathepsins, this study evaluated the role of this mutation in inducing ECM-related functional changes in RPE cellular behavior.

Methods

Induced pluripotent stem cells gene-edited bi-allelically by CRISPR/Cas9 to express the AMD-linked cystatin C variant were differentiated to RPE cells and assayed for their ability to degrade fluorescently labeled ECM proteins. Cellular migration and adhesion on multiple ECM proteins, differences in transepithelial resistance and polarized protein secretion were tested. Vessel formation induced by gene edited cells-conditioned media was quantified using primary human dermal microvascular epithelial cells.

Results

Variant B cystatin C-expressing induced pluripotent stem cells-derived RPE cells displayed a significantly higher rate of laminin and fibronectin degradation 3 days after seeding on fluorescently labeled ECM (P < 0.05). Migration on matrigel, collagen IV and fibronectin was significantly faster for edited cells compared with wild-type (WT) cells. Both edited and WT cells displayed polarized secretion of cystatin C, but transepithelial resistance was lower in gene-edited cells after 6 weeks culture, with significantly lower expression of tight junction protein claudin-3. Media conditioned by gene-edited cells stimulated formation of significantly longer microvascular tubes (P < 0.05) compared with WT-conditioned media.

Conclusions

Reduced levels of cystatin C lead to changes in the RPE ability to degrade, adhere, and migrate supporting increased invasiveness and angiogenesis relevant for AMD pathology.

Pathogenic mechanisms and the potential of drug therapies for aortic aneurysm

Aortic aneurysm is a permanent focal dilation of the aorta. It is usually an asymptomatic disease but can lead to sudden death due to aortic rupture. Aortic aneurysm-related mortalities are estimated at ∼200,000 deaths per year worldwide. Because no pharmacological treatment has been found to be effective so far, surgical repair remains the only treatment for aortic aneurysm. Aortic aneurysm results from changes in the aortic wall structure due to loss of smooth muscle cells and degradation of the extracellular matrix and can form in different regions of the aorta. Research over the past decade has identified novel contributors to aneurysm formation and progression. The present review provides an overview of cellular and noncellular factors as well as enzymes that process extracellular matrix and regulate cellular functions (e.g., matrix metalloproteinases, granzymes, and cathepsins) in the context of aneurysm pathogenesis. An update of clinical trials focusing on therapeutic strategies to slow abdominal aortic aneurysm growth and efforts underway to develop effective pharmacological treatments is also provided.

Association Between Cystatin C and Cardiac Function and Long-Term Prognosis in Patients with Chronic Heart Failure

Background

The aim of this study was to investigate the association between cystatin C and cardiac function and long-term prognosis in patients with chronic heart failure (CHF).

Material/Methods

We selected 418 CHF patients admitted to our hospital as subjects. Patients were divided into 3 groups according to the cystatin C level (Quantile 1 group: 0.65–1.04 mg/L, Quantile 2 group: 1.05–1.35 mg/L, and Quantile 3 group: 1.36–7.84 mg/L), and patients were followed up for 5 years. We used odds ratio (OR) and 95% confidence interval (CI) to compare the results.

Results

The cystatin C and NT-ProBNP level in the cardiac function grade (NYHA) class IV group were higher than those in the class III group (P<0.05). Pearson correlation analysis showed that there was a positive correlation between cystatin C and NT-ProBNP log₁₀ transform in CHF patients (r=0.411). During 5-year follow-up, 231 patients died and the 5-year all-cause mortality rate was 55.26% (231/418). There was a significant difference in 5-year all-cause mortality among the 3 groups (P for trend=0.010). After adjusting for potential confounders by multivariate regression analysis, the Quantile 2 group vs. Quantile 1 group were OR=0.83, 95% CI 0.51 to 1.35, P=0.448, and the Quantile 3 group vs. Quantile 1 group were OR=1.71, 95% CI. 1.04 to 2.82, P=0.034. Curve fitting showed that cystatin C was positively correlated with 5-year all-cause mortality in CHF patients.

Conclusions

Cystatin C was positively correlated with cardiac function and NT-ProBNP in CHF patients. Cystatin C could be used as a serological index to evaluate the long-term prognosis of CHF patients.

Cystatin C for Risk Stratification in Patients After an Acute Coronary Syndrome

Background

Cystatin C (Cys‐C) is a marker of renal function that has shown prognostic value for cardiovascular risk stratification across different patient populations. The incremental value of Cys‐C beyond established cardiac and renal biomarkers remains incompletely explored.

Methods and Results

SOLID‐TIMI 52 (Stabilization of Plaques Using Darapladib‐Thrombolysis in Myocardial Infarction 52; http://www.clinicaltrials.gov, NCT01000727) randomized patients ≤30 days post–acute coronary syndrome were treated with darapladib or placebo. The association between Cys‐C and long‐term risk (median follow‐up 2.5 years) was assessed in 4965 individuals with adjustments made for clinical variables and other risk markers (eg, estimated glomerular filtration rate, high‐sensitivity troponin I, brain‐type natriuretic peptide, and fibroblast growth factor‐23). The prespecified outcome of interest was cardiovascular death (CVD) or heart failure hospitalization. Cys‐C was strongly correlated with creatinine (r=0.60) and estimated glomerular filtration rate (r=−0.68), moderately correlated with fibroblast growth factor‐23 (r=0.39), and weakly correlated with brain‐type natriuretic peptide (r=0.28) and high‐sensitivity troponin I (r=0.06) (all P<0.0001). After multivariate adjustment, increasing concentration of Cys‐C (per SD of log‐transformed Cys‐C) was significantly associated with a 28% higher hazard of CVD or heart failure hospitalization (hazard ratio [HR] 1.28, 95% confidence interval [CI] 1.12‐1.46, P<0.001), including CVD (HR 1.24, 95% CI 1.04‐1.47, P=0.01) and heart failure hospitalization (HR 1.42, 95% CI 1.19‐1.69, P<0.001). Cys‐C was also associated with a higher hazard of CVD, myocardial infarction, or stroke (HR 1.15, 95% CI 1.04‐1.28, P<0.01), including myocardial infarction (HR 1.17, 95% CI 1.02‐1.33, P=0.02). The addition of Cys‐C to a fully adjusted model without estimated glomerular filtration rate improved the C‐statistic from 0.80 to 0.81 (P=0.03) for CVD or heart failure hospitalization. In contrast, the addition of estimated glomerular filtration rate to a fully adjusted model without Cys‐C failed to improve model discrimination (P=0.17).

Conclusions

Cys‐C is associated with the risk of adverse outcomes in patients after acute coronary syndrome. This relationship is independent of established and novel biomarkers of the cardiorenal axis.

Soluble Expression of Recombinant Human Cystatin C and Comparison of the Ni Column and Magnetic Bead Purification

Cystatin C, also known as γ-trace or post-γ-globulin, is a cysteine protease inhibitor from the cystatin superfamily. It is usually used as a marker of the glomerular filtration rate owing to its low molecular weight and constant secretion. The recently available methods for cystatin C preparation have low outputs. Hence, a productive preparation system is urgently required. In this study, a 6 × His-tag coupled with a thrombin cleavage site was fused to the C-terminus of cystatin C, and the protein was well expressed in Escherichia coli after optimization. Then, two different systems were used to obtain no-tag cystatin C: a traditional nickel (Ni)-column system and a subtly Ni magnetic bead system. The column system was more commonly used, and the magnetic bead system was more convenient. Cystatin C (purity > 97%) was successfully obtained, and the yields in both the systems were higher than those in previous studies. Further, the proper folding status and bioactivity of recombinant cystatin C were confirmed using the papain inhibition assay, dynamic light scattering, and circular dichroism spectroscopy.

Renal Biomarker and Angiostatic Mediator? Cystatin C as a Negative Regulator of Vascular Endothelial Cell Homeostasis and Angiogenesis

See Article by Li et al.

Plasma Cystatin B Association With Abdominal Aortic Aneurysms and Need for Later Surgical Repair: A Sub-study of the VIVA Trial

OBJECTIVE/BACKGROUND

The development of an abdominal aortic aneurysm (AAA) involves extensive extracellular matrix remodelling, leading to aortic wall weakening. This process is mediated by proteases, including cysteinyl cathepsins. Cystatins are their endogenous inhibitors. This study tested whether plasma cystatin B levels in patients with AAA differed from those of healthy controls.

METHODS

Plasma samples from patients with AAA and age matched controls were selected from the Viborg Vascular (VIVA) screening trial for AAA. Enzyme linked immunosorbent assay determined plasma cystatin B. T-test, logistic regression, Pearson's correlation and Cox regression tested whether plasma cystatin B correlates with AAA size and growth rate, or serves as a marker for AAA.

RESULTS

Plasma cystatin B levels were significantly higher in patients with AAA than in controls (p < 0.001). Logistic regression analysis showed that cystatin B tertile at baseline was associated with the presence of AAA before (odds ratio [OR] 1.656; p < 0.001) and after adjustment for peripheral arterial disease (PAD), chronic obstructive pulmonary disease (COPD), and previous ischaemic events (OR 1.526; p < 0.001). A t-test showed a significant association between cystatin B and PAD at screening, hospital diagnosis of COPD, previous atherosclerotic events, and use of low dose aspirin. Pearson's correlation test showed positive and significant associations between cystatin B and AAA size (r = 0.15; p < 0.001). Cox regression test showed that plasma cystatin B tertile at baseline was associated with later AAA surgical repair before (hazard ratio [HR] 1.387; p < 0.001) and after adjustment for PAD, COPD, previous ischaemic event, and maximum infrarenal aortic diameter (HR 1.523; p < 0.001).

CONCLUSION

In contrast to prior studies that showed that cystatin C is negatively associated with AAA development, this study demonstrated a positive association between cystatin B and AAA size and associations between cystatin B tertile at baseline and AAA presence and need for later surgical repair. It is possible that these two cystatins inhibit cathepsin activity and participate in AAA with different mechanisms.

MicroRNA regulation of extracellular matrix components in the process of atherosclerotic plaque destabilization

The process of atherosclerotic plaque destabilization, leading to myocardial infarction, is still not fully understood. The pathway - composed of structural and regulatory proteins of the extracellular matrix (ECM) such as collagen, elastin, small leucine-rich proteoglycans, metalloproteinases, cathepsins and serine proteases - is one potential way of atherosclerotic plaque destabilization. The expression of these proteins is controlled by different microRNA molecules. The goal of this paper is to summarize the current investigations and knowledge about ECM in the process of atherosclerotic plaque destabilization, giving special attention to epigenetic expression regulation by microRNA.

Cathepsin B aggravates coxsackievirus B3-induced myocarditis through activating the inflammasome and promoting pyroptosis

Cathepsin B (CatB) is a cysteine proteolytic enzyme widely expressed in various cells and mainly located in the lysosomes. It contributes to the pathogenesis and development of many diseases. However, the role of CatB in viral myocarditis (VMC) has never been elucidated. Here we generated the VMC model by intraperitoneal injection of coxsackievirus B3 (CVB3) into mice. At day 7 and day 28, we found CatB was significantly activated in hearts from VMC mice. Compared with the wild-type mice receiving equal amount of CVB3, genetic ablation of CatB (Ctsb^-/-) significantly improved survival, reduced inflammatory cell infiltration, decreased serum level of cardiac troponin I, and ameliorated cardiac dysfunction, without altering virus titers in hearts. Conversely, genetic deletion of cystatin C (Cstc^-/-), which markedly enhanced CatB levels in hearts, distinctly increased the severity of VMC. Furthermore, compared with the control, we found the inflammasome was activated in the hearts of wild-type mice with VMC, which was attenuated in the hearts of Ctsb^-/- mice but was further enhanced in Cstc^-/- mice. Consistently, the inflammasome-initiated pyroptosis was reduced in Ctsb^-/- mice hearts and further increased in Cstc^-/- mice. These results suggest that CatB aggravates CVB3-induced VMC probably through activating the inflammasome and promoting pyroptosis. This finding might provide a novel strategy for VMC treatment.

Severe VMC could lead to sudden cardiac death especially in youths, and is also the most common cause of secondary dilated cardiomyopathy. However, we still lack effective and specific clinical treatments currently. Therefore, further exploration of the pathogenesis and new therapeutic targets are urgently needed. Our results implied that CatB, a cysteine protease mainly located in the lysosome, is activated in the hearts of mice with VMC induced by intraperitoneal injection of CVB3. Genetic deletion of CatB significantly improves survival, attenuates cardiac inflammation, decreases serum cardiac troponin I levels and alleviates cardiac dysfunction, without altering virus titers in hearts. However, ablation of its main endogenous inhibitor, cystatin C, distinctly exaggerates the disease severity. Mechanistically, we found that CatB influences VMC probably by activating the NLRP3 inflammasome and promoting caspase-1-induced pyroptosis. This may provide a potential new therapeutic strategy for VMC.

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.

Association of serum cystatin C levels with mortality in patients with acute type A aortic dissection

Increased serum cystatin C levels are related to the prognosis of cardiovascular diseases. This study aims to investigate the effect of admission serum cystatin C levels on short- and long-term mortality in patients with acute type A aortic dissection (ATAAD). From 2010 to 2014, 136 consecutive patients with ATAAD were enrolled and followed up. Clinical data and laboratory assays including were measured. During a median follow-up of 198.7 days, the short-term mortality (30-days) was 20.6%, whereas the long-term death rate was 10.2%. We identified that the expression of cystatin C and high-sensitivity C-reactive protein (hs-CRP) in the dying patients was higher than in the surviving patients (P < 0.01). Hs-CRP (HR = 1.41, 95% CI: 1.03–2.59, P = 0.037) was an independent risk factor of short-term death determined by univariate and multivariate Cox analyses. No impact of cystatin C was observed on the short-term mortality. For long-term mortality, cystatin C (HR = 1.49, 95% CI: 1.10–7.36, P = 0.013) was identified as an independent predictor at above the cut-off value ≥ 1.10 mg/L. ROC analysis showed the AUC values of cystatin C and hs-CRP were 0.772 (95% CI, 0.692–0.839) and 0.640 (95% CI, 0.574–0.739), respectively, in the prediction of long-term death. The combined AUC value of cystatin C and hs-CRP was 0.883 (95% CI, 0.826–0.935; P < 0.01). Taken together, high cystatin C levels (≥ 1.10 mg/L) on admission are independently associated with the long-term mortality in patients with ATAAD.

Decreased cathepsin K levels in human atherosclerotic plaques are associated with plaque instability

Investigating the determinants and dynamics of atherosclerotic plaque instability is a key area of current cardiovascular research. Extracellular matrix degradation from excessive proteolysis induced by enzymes such as cathepsin K (Cat K) is implicated in the pathogenesis of unstable plaques. The current study assessed the expression of Cat K in human unstable atherosclerotic plaques. Specimens of popliteal arteries with atherosclerotic plaques were classified as stable (<40% lipid core plaque area; n=6) or unstable (≥40% lipid core plaque area; n=14) based on histopathological examinations of hematoxylin and eosin stained sections. The expression of Cat K and cystatin C (Cys C) were assessed by immunohistochemical examination and levels of Cat K mRNA were detected by semi-quantitative reverse transcriptase polymerase chain reaction. Morphological changes including a larger lipid core, endothelial proliferation with foam cells and destruction of internal elastic lamina were observed in unstable atherosclerotic plaques. In unstable plaques, the expression of Cat K protein and mRNA was upregulated, whereas Cys C protein expression was downregulated. The interplay between Cat K and Cys C may underlie the progression of plaques from stable to unstable and the current study indicated that Cat K and Cys C are potential targets for preventing and treating vulnerable atherosclerotic plaque ruptures.

Cystatin C as a potential therapeutic mediator against Parkinson's disease via VEGF-induced angiogenesis and enhanced neuronal autophagy in neurovascular units

Cystatin C (CYS C, Cst3) is an endogenous cysteine protease inhibitor that plays neuroprotective roles in neurodegenerative diseases. We aimed to explore the association of CYS C with Parkinson’s disease (PD) models and investigate its involvement in the role of neurovascular units (NVUs) in PD neuro-pathogenesis. We used A53T α-synuclein (SNCA) transgenic mice and 6-hydroxydopamine-lesioned DAergic PC12 cells as experimental PD models to investigate the mechanisms behind this association. The injections of CYS C were administered to the right substantia nigra (SN) of A53T SNCA transgenic mice to measure the effects of CYS C in transgenic A53T SNCA mice. To explore the angiogenesis in vivo and in vitro, we used the chick embryo chorioallantoic membrane (CAM) assay and tube formation (TF) assay. We found that CYS C has a neuroprotective effect in this in vivo PD model. We observed increased VEGF, NURR1 and autophagy markers LC3B and decreased SNCA and apoptosis marker cleaved CASP3 in different brain regions of CYS C-treated A53T SNCA transgenic mice. In vitro, we observed that CYS C-induced VEGF, a secreted protein, attenuated 6-OHDA-lesioned DAergic PC12 cell degeneration by regulating p-PKC-α/p-ERK1/2-Nurr1 signaling and inducing autophagy. VEGF-mediated angiogenesis was markedly enhanced in the conditioned media of 6-OHDA-lesioned PC12 cells with CYS C-overexpression, whereas blockage of autophagy in CYS C-overexpressing PC12 cells significantly downregulated VEGF expression and the associated angiogenesis. Our data indicate that CYS C displays dual neuronal–vascular functions, promoting PC12 cell survival and angiogenesis via regulating the level of secreted VEGF in NVUs. Our study provides evidence that may aid in the development of an alternative approach for the treatment of PD through modulation of CYS C-mediated neuronal-vascular pathways.

Serum creatinine and cystatin C provide conflicting evidence of acute kidney injury following acute ingestion of potassium permanganate and oxalic acid

AIM

Acute kidney injury (AKI) is common following deliberate self-poisoning with a combination washing powder containing oxalic acid (H₂C₂O₄) and potassium permanganate (KMnO₄). Early and rapid increases in serum creatinine (sCr) follow severe poisoning. We investigated the relationship of these increases with direct nephrotoxicity in an ongoing multicenter prospective cohort study in Sri Lanka exploring AKI following poisoning.

METHODS

Multiple measures of change in kidney function were evaluated in 48 consenting patients who had serial sCr and serum cystatin C (sCysC) data available.

RESULTS

Thirty-eight (38/48, 79%) patients developed AKI (AKIN criteria). Twenty-eight (58%) had AKIN stage 2 or 3. Initial increases in urine creatinine (uCr) excretion were followed by a substantial loss of renal function. The AKIN stage 2 and 3 (AKIN2/3) group had very rapid rises in sCr (a median of 118% at 24 h and by 400% at 72 h post ingestion). We excluded the possibility that the rapid rise resulted from the assay used or muscle damage. In contrast, the average sCysC increase was 65% by 72 h.

CONCLUSIONS

In most AKI, sCysC increases to the same extent but more rapidly than sCr, as sCysC has a shorter half-life. This suggests either a reduction in Cystatin C production or, conversely, that the rapid early rise of sCr results from increased production of creatine and creatinine to meet energy demands following severe oxidative stress mediated by H₂C₂O₄ and KMnO₄. Increased early creatinine excretion supports the latter explanation, since creatinine excretion usually decreases transiently in AKIN2/3 from other causes.

Cystatin C-Adiponectin Complex in Plasma Associates with Coronary Plaque Instability

Aim: Adiponectin (APN) is an adipocyte-derived bioactive molecule with antiatherogenic properties. We previously reported that cystatin C (CysC) abolished the anti-atherogenic effects of APN. We aimed to elucidate the clinical significance of CysC–APN complex in patients with coronary artery disease (CAD).

Methods: We enrolled 43 stable CAD male patients to examine the relationship between CysC–APN complex and coronary plaque characteristics. Serum was immunoprecipitated by the anti-APN antibody and immunoblotted by the anti-CysC antibody to demonstrate the presence of CysC–APN complexes in vivo. To confirm their binding in vitro, HEK293T cell lysates overexpressing myc-APN and FLAG-CysC were immunoprecipitated with an anti-myc or anti-FLAG antibody, followed by immunoblotting with an anti-APN or anti-CysC antibody.

Results: CysC was identified as a specific co-immunoprecipitant with APN by the anti-APN antibody in human serum. In vitro, FLAG-CysC was co-immunoprecipitated with myc-APN by the antimyc antibody and myc-APN was co-immunoprecipitated with FLAG-CysC by the anti-FLAG antibody. Among CAD patients, serum CysC–APN complex levels negatively correlated with fibrotic components of coronary plaques and positively correlated with either necrotic or lipidic plus necrotic components. Plaque burden negatively correlated with serum APN levels but not serum CysC–APN complex levels. Serum CysC levels had no association with plaque characteristics. In multivariate analysis, CysC–APN complex levels were identified as the strongest negative factor for fibrotic components and the strongest positive factor for both necrotic and lipidic plus necrotic components.

Conclusion: Measuring serum CysC–APN complex levels is helpful for evaluating coronary plaque instability in CAD patients.

Plasma Cathepsin S and Cathepsin S/Cystatin C Ratios Are Potential Biomarkers for COPD

Purpose. This study aimed to examine whether plasma levels of cathepsin S or its inhibitor, cystatin C, may serve as biomarkers for COPD. Patients and Methods. We measured anthropometrics and performed pulmonary function tests and chest CT scans on 94 patients with COPD and 31 subjects with productive cough but no airflow obstruction (“at risk”; AR). In these subjects and in 52 healthy nonsmokers (NS) and 66 healthy smokers (HS) we measured plasma concentrations of cathepsin S and cystatin C using an ELISA. Data were analyzed using simple and logistic regression and receiver operating characteristic analyses. Results. Cathepsin S and cystatin C plasma levels were significantly higher in the COPD and AR groups than in the NS and HS groups (p < 0.01). Among the COPD patients and AR subjects, plasma cathepsin S levels and cathepsin S/cystatin C ratios, but not cystatin C levels, were negatively related to severe airflow limitation (% FEV₁ predicted < 50%; p = 0.005) and severe emphysema as assessed by low attenuation area (LAA) score on chest CT scans (LAA ≥ 8.0; p = 0.001). Conclusion. Plasma cathepsin S and cathepsin S/cystatin C ratios may serve as potential biomarkers for COPD.

Arterial indices and serum cystatin C level in individuals with occupational wide band noise exposure

BACKGROUND

Chronic exposure to noise is known to cause a wide range of health problems including extracellular matrix (ECM) proliferation and involvement of cardiovascular system. There are a few studies to investigate noise-induced vascular changes using noninvasive methods. In this study we used carotid artery intima-media thickness (CIMT) and aortic augmentation as indices of arterial properties and cystatin C as a serum biomarker relating to ECM metabolism.

MATERIALS AND METHODS

Ninety-three male participants were included in this study from aeronautic technicians: 39 with and 54 without a history of wide band noise (WBN) exposure. For better discrimination, the participants were divided into the two age groups: <40 and >40 years old. Adjusted aortic augmentation index (AI) for a heart rate equal to 75 beats per minute (AIx@HR75) were calculated using pulse wave analysis (PWA). CIMT was measured in 54 participants who accepted to undergo Doppler ultrasonography. Serum cystatin C was also measured.

RESULTS

Among younger individuals the mean CIMT was 0.85 ± 0.09 mm and 0.75 ± 0.22 mm in the in the exposed and the control groups respectively. Among older individuals CIMT had a mean of 1.04 ± 0.22 mm vs. 1.00 ± 0.25 mm for the exposed vs. the control group. However, in both age groups the difference was not significant at the 0.05 level. A comparison of AIx@HR75 between exposure group and control group both in younger age group (5.46 ± 11.22 vs. 8.56 ± 8.66) and older age group (17.55 ± 10.07 vs. 16.61 ± 5.77) revealed no significant difference. We did not find any significant correlation between CIMT and AIx@HR75 in exposed group (r = 0.314, P value = 0.145) but the correlation was significant in control group (r = 0.455, P value = 0.019). Serum cystatin C level was significantly lower in individuals with WBN exposure compared to controls (441.10 ± 104.70 ng/L vs. 616.89 ± 136.14, P value < 0.001) both in younger and older groups.

CONCLUSION

We could not find any evidence for the association of WBN exposure with arterial properties, but cystatin C was significantly lower in the exposed group.

Plasma cystatin C and neutrophil gelatinase-associated lipocalin in relation to coronary atherosclerosis on intravascular ultrasound and cardiovascular outcome: Impact of kidney function (ATHEROREMO-IVUS study)

BACKGROUND AND AIMS

We investigated whether plasma cystatin C (CysC) and neutrophil gelatinase-associated lipocalin (NGAL) are associated with intravascular ultrasound (IVUS)-derived characteristics of coronary atherosclerosis and 1-year adverse coronary events in patients with normal and mildly-to-moderately impaired kidney function.

METHODS

Between 2008 and 2011, virtual histology (VH)-IVUS of a non-culprit coronary artery was performed in 581 patients undergoing coronary angiography. Creatinine, CysC and NGAL were measured in pre-procedural blood samples. Presence of VH-IVUS-derived thin-cap fibroatheroma (TCFA) lesions, lesions with plaque burden (PB)≥70% and lesions with minimal luminal area (MLA)≤4 mm² was assessed. Major adverse coronary events (MACE) comprised the composite of all-cause mortality, acute coronary syndrome, or unplanned coronary revascularization. Analyses were stratified using eGFR_Cr of 90 ml/min/1.73 m² as the cut-off.

RESULTS

In patients with normal kidney function, those with higher CysC levels had fewer lesions with PB ≥ 70% and fewer VH-TCFA lesions (adjusted odds ratios (ORs) and 95% confidence intervals (CIs): 0.46 [0.30-0.69] and 0.59 [0.44-0.83], respectively, per standard deviation (SD) ln[ng/mL] CysC). Those with higher NGAL levels also had fewer lesions with PB ≥ 70% (adjusted OR [95% CI]:0.49 [0.29-0.82]) In patients with impaired kidneys, no differences in high-risk lesions were observed for CysC or NGAL. However, those with higher CysC had higher risk of MACE (hazard ratio (HR):1.4, 95% CI [1.03-1.92]). This was not the case in patients with normal kidney function. NGAL did not influence risk of MACE.

CONCLUSIONS

Mild-to-moderate kidney dysfunction modifies the relationship between CysC and high-risk coronary lesions. This has not been established before, and offers an explanation for the difference in findings between experimental and epidemiologic studies.

Differential cathepsin responses to inhibitor-induced feedback: E-64 and cystatin C elevate active cathepsin S and suppress active cathepsin L in breast cancer cells

Cathepsins are powerful proteases, once referred to as the lysosomal cysteine proteases, that have been implicated in breast cancer invasion and metastasis, but pharmaceutical inhibitors have suffered failures in clinical trials due to adverse side effects. Scientific advancement from lysosomotropic to cell impermeable cathepsin inhibitors have improved efficacy in treating disease, but off-target effects have still been problematic, motivating a need to better understand cellular feedback and responses to treatment with cathepsin inhibitors. To address this need, we investigated effects of E-64 and cystatin C, two broad spectrum cathepsin inhibitors, on cathepsin levels intra- and extracellularly in MDA-MB-231 breast cancer cells. Cathepsins S and L had opposing responses to both E-64 and cystatin C inhibitor treatments with paradoxically elevated amounts of active cathepsin S, but decreased amounts of active cathepsin L, as determined by multiplex cathepsin zymography. This indicated cellular feedback to selectively sustain the amounts of active cathepsin S even in the presence of inhibitors with subnanomolar inhibitory constant values. These differences were identified in cellular locations of cathepsins L and S, trafficking for secretion, co-localization with endocytosed inhibitors, and longer protein turnover time for cathepsin S compared to cathepsin L. Together, this work demonstrates that previously underappreciated cellular compensation and compartmentalization mechanisms may sustain elevated amounts of some active cathepsins while diminishing others after inhibitor treatment. This can confound predictions based solely on inhibitor kinetics, and must be better understood to effectively deploy therapies and dosing strategies that target cathepsins to prevent cancer progression.

Autophagy dysfunction and regulatory cystatin C in macrophage death of atherosclerosis

Autophagy dysfunction in mouse atherosclerosis models has been associated with increased lipid accumulation, apoptosis and inflammation. Expression of cystatin C (CysC) is decreased in human atheroma, and CysC deficiency enhances atherosclerosis in mice. Here, we first investigated the association of autophagy and CysC expression levels with atheroma plaque severity in human atherosclerotic lesions. We found that autophagy proteins Atg5 and LC3β in advanced human carotid atherosclerotic lesions are decreased, while markers of dysfunctional autophagy p62/SQSTM1 and ubiquitin are increased together with elevated levels of lipid accumulation and apoptosis. The expressions of LC3β and Atg5 were positively associated with CysC expression. Second, we investigated whether CysC expression is involved in autophagy in atherosclerotic apoE-deficient mice, demonstrating that CysC deficiency (CysC(-/-) ) in these mice results in reduction of Atg5 and LC3β levels and induction of apoptosis. Third, macrophages isolated from CysC(-/-) mice displayed increased levels of p62/SQSTM1 and higher sensitivity to 7-oxysterol-mediated lysosomal membrane destabilization and apoptosis. Finally, CysC treatment minimized oxysterol-mediated cellular lipid accumulation. We conclude that autophagy dysfunction is a characteristic of advanced human atherosclerotic lesions and is associated with reduced levels of CysC. The deficiency of CysC causes autophagy dysfunction and apoptosis in macrophages and apoE-deficient mice. The results indicate that CysC plays an important regulatory role in combating cell death via the autophagic pathway in atherosclerosis.

Endothelial cells and cathepsins: Biochemical and biomechanical regulation

Cathepsins are mechanosensitive proteases that are regulated not only by biochemical factors, but are also responsive to biomechanical forces in the cardiovascular system that regulate their expression and activity to participate in cardiovascular tissue remodeling. Their elastinolytic and collagenolytic activity have been implicated in atherosclerosis, abdominal aortic aneurysms, and in heart valve disease, all of which are lined by endothelial cells that are the mechanosensitive monolayer of cells that sense and respond to fluid shear stress as the blood flows across the surfaces of the arteries and valve leaflets. Inflammatory cytokine signaling is integrated with biomechanical signaling pathways by the endothelial cells to transcribe, translate, and activate either the cysteine cathepsins to remodel the tissue or to express their inhibitors to maintain healthy cardiovascular tissue structure. Other cardiovascular diseases should now be included in the study of the cysteine cathepsin activation because of the additional biochemical cues they provide that merges with the already existing hemodynamics driving cardiovascular disease. Sickle cell disease causes a chronic inflammation including elevated TNFα and increased numbers of circulating monocytes that alter the biochemical stimulation while the more viscous red blood cells due to the sickling of hemoglobin alters the hemodynamics and is associated with accelerated elastin remodeling causing pediatric strokes. HIV-mediated cardiovascular disease also occurs earlier in than the broader population and the influence of HIV-proteins and antiretrovirals on endothelial cells must be considered to understand these accelerated mechanisms in order to identify new therapeutic targets for prevention.

Influence of Selective Biochemical and Morphological Agents on Natural History of Aneurysm of Abdominal Aorta Development

BACKGROUND The development of abdominal aortic aneurysm (AAA) is probably influenced by many factors. The role of some of these factors, such as intraluminal thrombus (ILT) or cystatin C serum levels, remains controversial. Proving their influence could have therapeutic implications for some patients with AAA. Associations between the rate of increase in diameter of an aneurysm and ILT, as well as other factors, including biochemical factors (C-Reactive Protein - CRP, cystatin C), age, sex, and comorbidities, could predict disease progression in individual patients. MATERIAL AND METHODS Seventy patients with small AAA were included into the study. The patients were followed using ultrasound and CT imaging. We evaluated aneurysm dimensions and aneurysm wall thickness, as well as ILT and its dimensions, aneurysm wall morphology, CRP, and cystatin C. RESULTS We observed significant growth of AAA and thinning of aneurysmal wall. Aneurysms over 4 cm grew significantly faster in the second year of observation. ILT grew together with AAA size. Age, sex, smoking, dyslipidemias, or controlled arterial hypertension had no influence on aneurysm progression rate. Changes in serum of CRP concentration did not reach statistical significance, but cystatin C levels did. CONCLUSIONS Presence and size of ILT, wall thickness, and cystatin C levels may be considered in prediction of AAA progression. ILT might exert a protective influence on the risk of aneurysm rupture. However, larger aneurysms containing larger thrombi grow faster and their walls undergo more rapid degradation, which in turn increases the risk of rupture. This matter requires further studies.

Muscadine grape skin extract can antagonize Snail-cathepsin L-mediated invasion, migration and osteoclastogenesis in prostate and breast cancer cells

To develop new and effective chemopreventive agents against bone metastasis, we assessed the effects of muscadine grape skin extract (MSKE), whose main bioactive component is anthocyanin, on bone turnover, using prostate and breast cancer cell models overexpressing Snail transcription factor. MSKE has been shown previously to promote apoptosis in prostate cancer cells without affecting normal prostate epithelial cells. Snail is overexpressed in prostate and breast cancer, and is associated with increased invasion, migration and bone turnover/osteoclastogenesis. Cathepsin L (CatL) is a cysteine cathepsin protease that is overexpressed in cancer and involved in bone turnover. Snail overexpression in prostate (LNCaP, ARCaP-E) and breast (MCF-7) cancer cells led to increased CatL expression/activity and phosphorylated STAT-3 (pSTAT-3), compared to Neo vector controls, while the reverse was observed in C4-2 (the aggressive subline of LNCaP) cells with Snail knockdown. Moreover, CatL expression was higher in prostate and breast tumor tissue compared to normal tissue. MSKE decreased Snail and pSTAT3 expression, and abrogated Snail-mediated CatL activity, migration and invasion. Additionally, Snail overexpression promoted osteoclastogenesis, which was significantly inhibited by the MSKE as effectively as Z-FY-CHO, a CatL-specific inhibitor, or osteoprotegerin, a receptor activator of nuclear factor kappa B ligand (RANKL) antagonist. Overall, these novel findings suggest that Snail regulation of CatL may occur via STAT-3 signaling and can be antagonized by MSKE, leading to decreased cell invasion, migration and bone turnover. Therefore, inhibition using a natural product such as MSKE could potentially be a promising bioactive compound for bone metastatic cancer.

Cystatin C is a disease-associated protein subject to multiple regulation

A protease inhibitor, cystatin C (Cst C), is a secreted cysteine protease inhibitor abundantly expressed in body fluids. Clinically, it is mostly used to measure glomerular filtration rate as a marker for kidney function due to its relatively small molecular weight and easy detection. However, recent findings suggest that Cst C is regulated at both transcriptional and post‐translational levels, and Cst C production from haematopoietic cell lineages contributes significantly to the systematic pools of Cst C. Furthermore, Cst C is directly linked to many pathologic processes through various mechanisms. Thus fluctuation of Cst C levels might have serious clinical implications rather than a mere reflection of kidney functions. Here, we summarize the pathophysiological roles of Cst C dependent and independent on its inhibition of proteases, outline its change of expression by various stimuli, and elucidate the regulatory mechanisms to control this disease‐related protease inhibitor. Finally, we discuss the clinical implications of these findings for translational gains.

Cathepsin G activity lowers plasma LDL and reduces atherosclerosis

Cathepsin G (CatG), a serine protease present in mast cells and neutrophils, can produce angiotensin-II (Ang-II) and degrade elastin. Here we demonstrate increased CatG expression in smooth muscle cells (SMCs), endothelial cells (ECs), macrophages, and T cells from human atherosclerotic lesions. In low-density lipoprotein (LDL) receptor-deficient (Ldlr(-/-)) mice, the absence of CatG reduces arterial wall elastin degradation and attenuates early atherosclerosis when mice consume a Western diet for 3months. When mice consume this diet for 6months, however, CatG deficiency exacerbates atherosclerosis in aortic arch without affecting lesion inflammatory cell content or extracellular matrix accumulation, but raises plasma total cholesterol and LDL levels without affecting high-density lipoprotein (HDL) or triglyceride levels. Patients with atherosclerosis also have significantly reduced plasma CatG levels that correlate inversely with total cholesterol (r=-0.535, P<0.0001) and LDL cholesterol (r=-0.559, P<0.0001), but not with HDL cholesterol (P=0.901) or triglycerides (P=0.186). Such inverse correlations with total cholesterol (r=-0.504, P<0.0001) and LDL cholesterol (r=-0.502, P<0.0001) remain significant after adjusting for lipid lowering treatments among this patient population. Human CatG degrades purified human LDL, but not HDL. This study suggests that CatG promotes early atherogenesis through its elastinolytic activity, but suppresses late progression of atherosclerosis by degrading LDL without affecting HDL or triglycerides.

Comparison of estimated GFR equations based on serum cystatin C alone and in combination with serum creatinine in patients with coronary artery disease

OBJECTIVE

Several new equations (GFRCKD-EPI-cr, GFRCKD-EPI-CysC, GFRCKD-EPI Cr+CysC) are used for the calculation of estimated GFR (eGFR) to evaluate renal function. These equations explicitly demonstrate the association of coronary artery disease (CAD) and severe renal impairment cases. However, these equations are considered insufficient to explain the relation with normal or mildly impaired eGFR and CAD. Our hypothesis was to indicate the inversely proportional relationship of eGFR values, calculated by the different equations, with the presence of CAD in patients with normal or mildly impaired renal function.

METHODS

Eighty-eight patients who underwent elective coronary angiographic intervention were enrolled into the study. The study population was divided into two groups based on angiographic documents: patients with normal coronary arteries (CAD-) and patients with CAD (CAD +). These patients were stable and decided to implement angiography for the purpose of suspicion about CAD and control. Since it is thought that eGFR equations based on creatinine are inadequate to determine chronic kidney disease (CKD) and overestimate CKD diagnosis, cystatin C-based equations are considered an alternative. Due to the potential effects of inflammatory events of the markers used in equations, patients with diabetes mellitus, severe CKD, and inflammatory bowel disease were excluded from the study.

RESULTS

The average age of all participants was 51.93±9.31 (32-65 years); 80.7% (n=71) was male. A statistical difference was found between the CAD (-) group and the CAD (+) group in terms of the variables of age (45.46±8.48 vs. 54.95±8.11, p<0.001), gender (67.9% vs. 86.7%, male, p=0.037), cystatin C values (1.37±0.34 vs. 0.85±0.39, p<0.001), and GFR equations defined by the Chronic Kidney Disease Epidemiology: GFRCKD-EPI-cr (85.86±14.20 vs. 79.45±10.25, p=0.018), GFRCKD-EPI-CysC (58.61±21.87 vs. 100.82±32.00, p<0.001), and GFRCKD-EPI Cr+CysC (68.29±13.49 vs. 90.75±18.34, p<0.001). After adjustment of the variables in multiple regression analyses, only age (OR, 1.199; 95% CI, 1.077 to 1.335, p=0.001), gender (OR, 8.252; 95% CI, 0.223 to 55.659, p=0.030), and the GFRCKD-EPI-CysC equation (OR, 1.059; 95% CI, 1.028 to 1.090, p<0.001) were detected as predictors for presence of CAD.

CONCLUSION

GFR equations based on cystatin C or combined with creatinine may have superiority to GFR equations based on creatinine alone in CAD patients. However, the impact of different variables on the GFRCKD-EPI-CysC equation should not be ignored in specific groups, such as CAD.

Developmental regulation of synthesis and dimerization of the amyloidogenic protease inhibitor cystatin C in the hematopoietic system

The cysteine protease inhibitor cystatin C is thought to be secreted by most cells and eliminated in the kidneys, so its concentration in plasma is diagnostic of kidney function. Low extracellular cystatin C is linked to pathologic protease activity in cancer, arthritis, atherosclerosis, aortic aneurism, and emphysema. Cystatin C forms non-inhibitory dimers and aggregates by a mechanism known as domain swapping, a property that reportedly protects against Alzheimer disease but can also cause amyloid angiopathy. Despite these clinical associations, little is known about the regulation of cystatin C production, dimerization, and secretion. We show that hematopoietic cells are major contributors to extracellular cystatin C levels in healthy mice. Among these cells, macrophages and dendritic cells (DC) are the predominant producers of cystatin C. Both cell types synthesize monomeric and dimeric cystatin C in vivo, but only secrete monomer. Dimerization occurs co-translationally in the endoplasmic reticulum and is regulated by the levels of reactive oxygen species (ROS) derived from mitochondria. Drugs or stimuli that reduce the intracellular concentration of ROS inhibit cystatin C dimerization. The extracellular concentration of inhibitory cystatin C is thus partly dependent on the abundance of macrophages and DC, and the ROS levels. These results have implications for the diagnostic use of serum cystatin C as a marker of kidney function during inflammatory processes that induce changes in DC or macrophage abundance. They also suggest an important role for macrophages, DC, and ROS in diseases associated with the protease inhibitory activity or amyloidogenic properties of cystatin C.

Molecular biology of atherosclerosis

At least 468 individual genes have been manipulated by molecular methods to study their effects on the initiation, promotion, and progression of atherosclerosis. Most clinicians and many investigators, even in related disciplines, find many of these genes and the related pathways entirely foreign. Medical schools generally do not attempt to incorporate the relevant molecular biology into their curriculum. A number of key signaling pathways are highly relevant to atherogenesis and are presented to provide a context for the gene manipulations summarized herein. The pathways include the following: the insulin receptor (and other receptor tyrosine kinases); Ras and MAPK activation; TNF-α and related family members leading to activation of NF-κB; effects of reactive oxygen species (ROS) on signaling; endothelial adaptations to flow including G protein-coupled receptor (GPCR) and integrin-related signaling; activation of endothelial and other cells by modified lipoproteins; purinergic signaling; control of leukocyte adhesion to endothelium, migration, and further activation; foam cell formation; and macrophage and vascular smooth muscle cell signaling related to proliferation, efferocytosis, and apoptosis. This review is intended primarily as an introduction to these key signaling pathways. They have become the focus of modern atherosclerosis research and will undoubtedly provide a rich resource for future innovation toward intervention and prevention of the number one cause of death in the modern world.

How to understand the association between cystatin C levels and cardiovascular disease: Imbalance, counterbalance, or consequence?

The association of cystatin C with renal function has been studied for more than 25 years. Cystatin C has been described to have a better diagnostic performance than creatinine to assess renal function, particularly to detect small reductions in glomerular filtration rate. Recently, cystatin C has emerged as a strong predictor of incident or recurrent cardiovascular events and adverse outcomes in patients without kidney disease. Furthermore, it has been suggested that cystatin C concentrations are directly related to both inflammation and atherosclerosis. Nevertheless, the link between inflammation, atherogenesis, cardiovascular risk, and cystatin C is still poorly understood. This brief report discusses recent data, contrasting findings and possible mechanisms involved in this interaction.

Cysteine protease cathepsins and matrix metalloproteinases in the development of abdominal aortic aneurysms

Both cysteine protease cathepsins and matrix metalloproteinases are implicated in the pathogenesis of abdominal aortic aneurysms (AAAs) in humans and animals. Blood and aortic tissues from humans or animals with AAAs contain much higher levels of these proteases, and often lower levels of their endogenous inhibitors, than do blood and aortic tissues from healthy subjects. Protease- and protease inhibitor-deficient mice and synthetic protease inhibitors have affirmed that cysteinyl cathepsins and matrix metalloproteinases both participate directly in AAA development in several experimental model systems. Here, we summarize our current understanding of how proteases contribute to the pathogenesis of AAA, and discuss whether proteases or their inhibitors may serve as diagnostic biomarkers or potential therapeutic targets for this common human arterial disease.

Relevance of increased serum cystatin C to vascular alterations in obese children

OBJECTIVE

Epidemiological studies report a positive relationship between serum cystatin C and cardiovascular outcomes in adults. Here, we tested the relevance of cystatin C as a biomarker for early vascular alterations in severely obese children.

METHODS

Two hundred nineteen obese (140 girls; age = 11.7 ± 2.7 years, BMI Z-score = 4.7 ± 1.2 SD) and 262 non-obese children (129 girls; age = 11.6 ± 0.6 years, body mass index [BMI] Z-score = 0.1 ± 1.0 SD). Serum cystatin C was measured by immunonephelometry. Intima media thickness (IMT), incremental elastic modulus, and flow-mediated and glyceryl-trinitrate-mediated dilations were determined at the common carotid artery and the brachial artery in obese children.

RESULTS

Obese children had significantly higher serum cystatin C than normal weight controls (0.86 ± 0.01 vs. 0.80 ± 0.01, P < 0.0001). In obese children, serum cystatin C correlates positively with BMI and the homeostasis model assessment index and negatively with the quantitative insulin sensitivity check index and adiponectin. A positive relationship was found between serum cystatin C and carotid IMT (r = 0.23, P = 0.0005), which remained significant in multivariate models adjusted for BMI (P = 0.01) and adiponectin with a trend towards significance (P = 0.05).

CONCLUSION

This study positions cystatin C and adiponectin as covariables associated with arterial wall thickness in obese children. Although the underlying pathophysiology linking cystatin C to early vascular disease remains to be deciphered, cystatin C may represent a novel adipose tissue-derived biomarker implicated in obesity-related comorbidities early in life.

Cysteinyl cathepsins: multifunctional enzymes in cardiovascular disease

Until recently, the role of lysosomal cysteine protease cathepsins in intracellular protein degradation was believed to be mainly restricted to scavenging. However, recent studies have revealed nontraditional roles for cysteine protease cathepsins in the extracellular space during the development and progression of cardiovascular disease. Although the precise mechanisms are unknown, data from animal studies suggest that members of the cathepsin family, like other extracellular proteases, contribute to extracellular matrix protein remodeling and interstitial matrix degradation, as well as to cell signaling and cell apoptosis in heart disease. Inflammatory cytokines and hormones regulate the expression and secretion of cathepsins in cultured cardiovascular cells and macrophages. Serum levels of cathepsins L, S, and K and their endogenous inhibitor cystatin C may be useful predictive biomarkers in patients with coronary artery disease and cardiac disease. Furthermore, in vivo pharmacological intervention with a synthetic cathepsin inhibitor and cardiovascular drugs (including statins and angiotensin II type 1 receptor antagonists) has the potential for pharmacologic targeting of cathepsins in cardiovascular disease. This review focuses on cathepsin biology (structure, synthesis, processing, activation, secretion, activity regulation, and function) and the involvement of cysteinyl cathepsins in the pathogenesis of several heart and vessel diseases, especially with respect to their potential application as diagnostic and prognostic markers and drug targets to prevent inappropriate proteolysis in cardiovascular disease.

Deficiency of cathepsin S attenuates angiotensin II-induced abdominal aortic aneurysm formation in apolipoprotein E-deficient mice

AIMS

Abdominal aortic aneurysm (AAA) is characterized by extensive aortic wall matrix degradation that contributes to the remodelling and eventual rupture of the arterial wall. Elastinolytic cathepsin S (Cat S) is highly expressed in human aneurysmal lesions, but whether it contributes to the pathogenesis of AAA remains unknown.

METHODS AND RESULTS

AAAs were induced in apolipoprotein E (ApoE) and Cat S compound mutant (Apoe(-/-)Ctss(-/-)) mice and in ApoE-deficient Cat S wild-type littermates (Apoe(-/-)Ctss(+/+)) by chronic angiotensin II infusion, and AAA lesions were analysed after 28 days. We found that Cat S expression increased significantly in mouse AAA lesions. The AAA incidence in Apoe(-/-)Ctss(-/-) mice was much lower than that in Apoe(-/-)Ctss(+/+) mice (10 vs. 80%). Cat S deficiency significantly reduced external and luminal abdominal aortic diameters, medial elastin fragmentation, and adventitia collagen content. Cat S deficiency reduced aortic lesion expression and the activity of matrix metalloproteinase (MMP)-2, MMP-9, and Cat K, but not the activity of other major cathepsins, such as Cat B and Cat L. Absence of Cat S significantly reduced AAA lesion media smooth muscle cell (SMC) apoptosis, lesion adventitia microvessel content, and inflammatory cell accumulation and proliferation. In vitro studies proved that Cat S helps promote SMC apoptosis, angiogenesis, monocyte and T-cell transmigration, and T-cell proliferation--all of which are essential to AAA pathogenesis.

CONCLUSIONS

These data provide direct evidence that Cat S plays an important role in AAA formation and suggest that Cat S is a new therapeutic target for human AAA.