Cystatin C loaded in brain-derived extracellular vesicles rescues synapses after ischemic insult in vitro and in vivo

Synaptic loss is an early event in the penumbra area after an ischemic stroke. Promoting synaptic preservation in this area would likely improve functional neurological recovery. We aimed to detect proteins involved in endogenous protection mechanisms of synapses in the penumbra after stroke and to analyse potential beneficial effects of these candidates for a prospective stroke treatment. For this, we performed Liquid Chromatography coupled to Mass Spectrometry (LC-MS)-based proteomics of synaptosomes isolated from the ipsilateral hemispheres of mice subjected to experimental stroke at different time points (24 h, 4 and 7 days) and compared them to sham-operated mice. Proteomic analyses indicated that, among the differentially expressed proteins between the two groups, cystatin C (CysC) was significantly increased at 24 h and 4 days following stroke, before returning to steady-state levels at 7 days, thus indicating a potential transient and intrinsic rescue mechanism attempt of neurons. When CysC was applied to primary neuronal cultures subjected to an in vitro model of ischemic damage, this treatment significantly improved the preservation of synaptic structures. Notably, similar effects were observed when CysC was loaded into brain-derived extracellular vesicles (BDEVs). Finally, when CysC contained in BDEVs was administered intracerebroventricularly to stroked mice, it significantly increased the expression of synaptic markers such as SNAP25, Homer-1, and NCAM in the penumbra area compared to the group supplied with empty BDEVs. Thus, we show that CysC-loaded BDEVs promote synaptic protection after ischemic damage in vitro and in vivo, opening the possibility of a therapeutic use in stroke patients.

Copper interaction with cystatin C: effects on protein structure and oligomerization

Human cystatin C (hCC), a small secretory protein, has gained attention beyond its classical role as a cysteine protease inhibitor owing to its potential involvement in neurodegenerative disorders. This study investigates the interaction between copper(II) ions [Cu(II)] and hCC, specifically targeting histidine residues known to participate in metal binding. Through various analytical techniques, including mutagenesis, circular dichroism, fluorescence assays, gel filtration chromatography, and electron microscopy, we evaluated the impact of Cu(II) ions on the structure and oligomerization of hCC. The results show that Cu(II) does not influence the secondary and tertiary structure of the studied hCC variants but affects their stability. To explore the Cu(II)-binding site, nuclear magnetic resonance (NMR) and X-ray studies were conducted. NMR experiments revealed notable changes in signal intensities and linewidths within the region 86His-Asp-Gln-Pro-His90, suggesting its involvement in Cu(II) coordination. Both histidine residues from this fragment were found to serve as a primary anchor of Cu(II) in solution, depending on the structural context and the presence of other Cu(II)-binding agents. The presence of Cu(II) led to significant destabilization and altered thermal stability of the wild-type and H90A variant, confirming differentiation between His residues in Cu(II) binding. In conclusion, this study provides valuable insights into the interaction between Cu(II) and hCC, elucidating the impact of copper ions on protein stability and identifying potential Cu(II)-binding residues. Understanding these interactions enhances our knowledge of the role of copper in neurodegenerative disorders and may facilitate the development of therapeutic strategies targeting copper-mediated processes in protein aggregation and associated pathologies.

Cystatin C: immunoregulation role in macrophages infected with Porphyromonas gingivalis

Background

Periodontitis is a chronic infectious disease, characterized by an exacerbated inflammatory response and a progressive loss of the supporting tissues of the teeth. Porphyromonas gingivalis is a key etiologic agent in periodontitis. Cystatin C is an antimicrobial salivary peptide that inhibits the growth of P. gingivalis. This study aimed to evaluate the antimicrobial activity of this peptide and its effect on cytokine production, nitric oxide (NO) release, reactive oxygen species (ROS) production, and programmed cell death in human macrophages infected with P. gingivalis.

Methods

Monocyte-derived macrophages generated from peripheral blood were infected with P. gingivalis (MOI 1:10) and stimulated with cystatin C (2.75 µg/ml) for 24 h. The intracellular localization of P. gingivalis and cystatin C was determined by immunofluorescence and transmission electron microscopy (TEM). The intracellular antimicrobial activity of cystatin C in macrophages was assessed by counting Colony Forming Units (CFU). ELISA assay was performed to assess inflammatory (TNFα, IL-1β) and anti-inflammatory (IL-10) cytokines. The production of nitrites and ROS was analyzed by Griess reaction and incubation with 2',7'-dichlorodihydrofluorescein diacetate (H2DCFDA), respectively. Programmed cell death was assessed with the TUNEL assay, Annexin-V, and caspase activity was also determined.

Results

Our results showed that cystatin C inhibits the extracellular growth of P. gingivalis. In addition, this peptide is internalized in the infected macrophage, decreases the intracellular bacterial load, and reduces the production of inflammatory cytokines and NO. Interestingly, peptide treatment increased ROS production and substantially decreased bacterial-induced macrophage apoptosis.

Conclusions

Cystatin C has antimicrobial and immuno-regulatory activity in macrophages infected with P. gingivalis. These findings highlight the importance of understanding the properties of cystatin C for its possible therapeutic use against oral infections such as periodontitis.

Modification of Association of Cystatin C With Kidney and Cardiovascular Outcomes by Obesity

RATIONALE & OBJECTIVE

Cystatin C-based estimated glomerular filtration rate (eGFRcys) has stronger associations with adverse clinical outcomes than creatinine-based eGFR (eGFRcr). Obesity may be associated with higher cystatin C levels, independent of kidney function, but it is unknown whether obesity modifies associations of eGFRcys with kidney and cardiovascular outcomes.

STUDY DESIGN

Cohort study.

SETTING & PARTICIPANTS

27,249 US adults in the Reasons for Geographic and Racial Differences in Stroke Study.

PREDICTORS

eGFRcys, eGFRcr, waist circumference, and body mass index (BMI).

OUTCOME

All-cause mortality, kidney failure, incident atherosclerotic cardiovascular disease (ASCVD), and incident heart failure (HF).

ANALYTICAL APPROACH

Multivariable Cox and Fine-Gray models with multiplicative interaction terms were constructed to investigate whether waist circumference quartiles or BMI categories modified associations of eGFRcys with risks of 4 clinical outcomes.

RESULTS

Participants had a mean age of 65 years; 54% were women, 41% were Black, and 21% had an eGFRcys<60mL/min/1.73m2. The baseline prevalence of abdominal obesity (waist circumference≥88cm for women or≥102cm for men) was 48% and obesity was 38%. In multivariable adjusted analyses, each 15mL/min/1.73m2 lower eGFRcys was associated with higher HR and 95% CI of mortality in each waist circumference quartile (first quartile, 1.19 [1.15-1.24]; second quartile, 1.22 [1.18-1.26]; third quartile, 1.20 [1.16-1.24]; fourth quartile, 1.19 [1.15-1.23]) as well as within each BMI category (BMI<24.9: 1.21 [1.17-1.25]; BMI 25.0-29.9: 1.21 [1.18-1.25]; BMI 30.0-34.9: 1.20 [1.16-1.25]; BMI≥35: 1.17, [1.12-1.22]). Neither waist circumference nor BMI modified the association of eGFRcys with mortality, kidney failure, incident ASCVD, or incident HF (all Pinteraction>0.05).

LIMITATIONS

Included only Black and White persons in the United States.

CONCLUSION

Obesity did not modify the association of eGFRcys with all-cause mortality, kidney failure, incident ASCVD, or incident HF. Among individuals with obesity, cystatin C may be used to provide eGFR-based risk prognostication for adverse outcomes.

PLAIN-LANGUAGE SUMMARY

Cystatin C is increasingly used in clinical practice to estimate kidney function, and cystatin C-based eGFR (eGFRcys) may be used to determine risk for adverse clinical outcomes. Adiposity may increase serum levels of cystatin C, independent of kidney function. This cohort study investigated whether associations of eGFRcys with adverse kidney and cardiovascular outcomes are modified by measures of obesity, waist circumference, and body mass index. We found that obesity does not modify associations of eGFRcys with 4 clinical outcomes and conclude that among individuals with obesity, cystatin C may be used to provide eGFR-based risk prognostication for adverse outcomes.

Monitoring the interactions between POPG phospholipid bilayer and amyloid-forming protein human cystatin C. Does the bilayer influence the oligomeric state and structure of the protein?

A biological membrane is a structure characteristic for various cells and organelles present in almost all living organisms. Even though, it is one of the most common structures in organisms, where it serves crucial functions, a phospholipid bilayer may also take part in pathological processes leading to severe diseases. Research indicates that biological membranes have a profound impact on the pathological processes of oligomerization of amyloid-forming proteins. These processes are a hallmark of amyloid diseases, a group of pathological states involving, e.g., Parkinson's or Alzheimer's disease. Even though amyloidogenic diseases reap the harvest in modern societies, especially in elderly patients, the mechanisms governing the amyloid deposition are not clearly described. Therefore, the presented study focuses on the description of interactions between a model biological membrane (POPG) and one of amyloid forming proteins - human cystatin C. For the purpose of the study molecular dynamics simulations were applied to confirm interactions between the protein and POPG membrane. Next the NMR techniques were used to verify how the data obtained in solution compared to MD simulations and determine fragments of the protein responsible for interactions with POPG. Finally, circular dichroism was used to monitor the changes in secondary structure of the protein and size exclusion chromatography was used to monitor its oligomerization process. Obtained data indicates that the protein interacts with POPG submerging itself into the bilayer with the AS region. However, the presence of POPG bilayer does not significantly affect the structure or oligomerization process of human cystatin C.

Human cystatin C induces the disaggregation process of selected amyloid beta peptides: a structural and kinetic view

Neurodegenerative diseases, such as Alzheimer's disease (AD) and various types of amyloidosis, are incurable; therefore, understanding the mechanisms of amyloid decomposition is crucial to develop an effective drug against them for future therapies. It has been reported that one out of three people over the age of 85 are suffering from dementia as a comorbidity to AD. Amyloid beta (Aβ), the hallmark of AD, transforms structurally from monomers into β-stranded aggregates (fibrils) via multiple oligomeric states. Astrocytes in the central nervous system secrete the human cystatin C protein (HCC) in response to various proteases and cytokines. The codeposition of Aβ and HCC in the brains of patients with AD led to the hypothesis that cystatin C is implicated in the disease process. In this study, we investigate the intermolecular interactions between different atomic structures of fibrils formed by Aβ peptides and HCC to understand the pathological aggregation of these polypeptides into neurotoxic oligomers and then amyloid plaques. To characterize the interactions between Aβ and HCC, we used a complementary approach based on the combination of small-angle neutron scattering analysis, atomic force microscopy and computational modelling, allowing the exploration of the structures of multicomponent protein complexes. We report here an optimized protocol to study that interaction. The results show a dependency of the sequence length of the Aβ peptide on the ability of the associated HCC to disaggregate it.

Risk due to Elevated Uric Acid Levels in Children With Henoch-Schonlein Purpura

PURPOSE

To compare uric acid levels in children with Henoch-Schonlein purpura (HSP)without nephritis and with renal damage, and at different pathological grades.

METHODS

A total of 451 children were enrolled in this study, including 64 with HSP without nephritis and 387 HSP with kidney damage. Age, gender, uric acid, urea, creatinine and cystatin C levels were reviewed. Pathological findings of those with renal impairment were also reviewed.

RESULTS

Among the HSP children with renal damage, 44 were grade I, 167 were grade II and 176 were grade III. There were significant differences in age, uric acid, urea, creatinine and cystatin C levels between the two groups (p<0.05, all). Correlation analysis showed that uric acid levels in children with HSP without nephritis were positively correlated with urea and creatinine levels (p<0.05). Uric acid levels in HSP children with renal damage was positively correlated with age, urea, creatinine and cystatin C levels (p<0.05, all). Regression analysis found that, without adding any correction factors, there were significant differences in uric acid levels between the two groups; however, after adjusting for pathological grade, there was no longer a significant difference.

CONCLUSIONS

There were significant differences of uric acid levels in children with HSP without nephritis and with renal impairment. Uric acid levels in the renal impairment group were significantly higher than that in the HSP without nephritis group. Uric acid levels were related to only the presence or absence of renal damage, not to the pathological grade.

Association of Kidney Function Measures With Signs of Neurodegeneration and Small Vessel Disease on Brain Magnetic Resonance Imaging: The Atherosclerosis Risk in Communities (ARIC) Study

RATIONALE & OBJECTIVE

Chronic kidney disease (CKD) is a risk factor for cognitive decline, but evidence is limited on its etiology and morphological manifestation in the brain. We evaluated the association of estimated glomerular filtration rate (eGFR) and urinary albumin-creatinine ratio (UACR) with structural brain abnormalities visible on magnetic resonance imaging (MRI). We also assessed whether this association was altered when different filtration markers were used to estimate GFR.

STUDY DESIGN

Cross-sectional study nested in a cohort study.

SETTING & PARTICIPANTS

1,527 participants in the Atherosclerosis Risk in Communities (ARIC) Study.

PREDICTORS

Log(UACR) and eGFR based on cystatin C, creatinine, cystatin C and creatinine in combination, or β2-microglobulin (B2M).

OUTCOMES

Brain volume reduction, infarcts, microhemorrhages, white matter lesions.

ANALYTICAL APPROACH

Multivariable linear and logistic regression models fit separately for each predictor based on a 1-IQR difference in the predictor value.

RESULTS

Each 1-IQR lower eGFR was associated with reduced cortex volume (regression coefficient: -0.07 [95% CI, -0.12 to-0.02]), greater white matter hyperintensity volume (logarithmically transformed; regression coefficient: 0.07 [95% CI, 0.01-0.15]), and lower white matter fractional anisotropy (regression coefficient: -0.08 [95% CI, -0.17 to-0.01]). The results were similar when eGFR was estimated with different equations based on cystatin C, creatinine, a combination of cystatin C and creatinine, or B2M. Higher log(UACR) was similarly associated with these outcomes as well as brain infarcts and microhemorrhages (odds ratios per 1-IQR-fold greater UACR of 1.31 [95% CI, 1.13-1.52] and 1.30 [95% CI, 1.12-1.51], respectively). The degree to which brain volume was lower in regions usually susceptible to Alzheimer disease and LATE (limbic-predominant age-related TDP-43 [Tar DNA binding protein 43] encephalopathy) was similar to that seen in the rest of the cortex.

LIMITATIONS

No inference about longitudinal effects due to cross-sectional design.

CONCLUSIONS

We found eGFR and UACR are associated with structural brain damage across different domains of etiology, and eGFR- and UACR-related brain atrophy is not selective for regions typically affected by Alzheimer disease and LATE. Hence, Alzheimer disease or LATE may not be leading contributors to neurodegeneration associated with CKD.

Expression and role of cystatin C in hyperthermia-induced brain injury in rats

Cystatin C, the full name of cystatin C, is one of the most potent cathepsin inhibitors currently known, which can strongly inhibit cathepsin in lysosomes and regulate the level of intracellular proteolysis. Cystatin C plays a very broad role in the body. High temperature-induced brain injury leads to very serious damage to brain tissue, such as cell inactivation, brain tissue edema, etc. At this time, cystatin C can play a crucial role. Based on the research on the expression and role of cystatin C in high temperature-induced brain injury in rats, this paper draws the following conclusions: high temperature can cause very serious damage to the brain tissue of rats, which can seriously lead to death. Cystatin C has a protective effect on brain cells and cerebral nerves. When the brain is damaged by high temperature, cystatin C can relieve the damage of high temperature to the brain and protect brain tissue. In this paper, a detection method for cystatin C with more outstanding performance is proposed, and compared with the traditional detection method, the detection method in this paper is verified to have more accurate accuracy and excellent stability through comparative experiments. Compared with traditional detection methods, it is more worthwhile to use and is a better detection method.

Effect of antiretroviral therapy on decreasing arterial stiffness, metabolic profile, vascular and systemic inflammatory cytokines in treatment-naïve HIV: A one-year prospective study

INTRODUCTION

Cardiovascular disease is a major cause of death among people living with HIV (PLH). Non-treated PLH show increased levels of inflammation and biomarkers of vascular activation, and arterial stiffness as a prognostic cardiovascular disease risk factor. We investigated the effect of one year of ART on treatment-naïve HIV(+) individuals on arterial stiffness and inflammatory and vascular cytokines.

METHODS

We cross-sectionally compared aortic stiffness via tonometry, inflammatory, and vascular serum cytokines on treatment-naïve (n = 20) and HIV (-) (n = 9) matched by age, sex, metabolic profile, and Framingham score. We subsequently followed young, treatment-naïve individuals after 1-year of ART and compared aortic stiffness, metabolic profile, and inflammatory and vascular serum biomarkers to baseline. Inflammatory biomarkers included: hs-CRP, D-Dimer, SAA, sCD163s, MCP-1, IL-8, IL-18, MRP8/14. Vascular cytokines included: myoglobin, NGAL, MPO, Cystatin C, ICAM-1, VCAM-1, and MMP9.

RESULTS

Treatment-naïve individuals were 34.8 years old, mostly males (95%), and with high smoking prevalence (70%). Baseline T CD4+ was 512±324 cells/mcL. cfPWV was similar between HIV(-) and treatment-naïve (6.8 vs 7.3 m/s; p = 0.16) but significantly decreased after ART (-0.52 m/s; 95% CI -0.87 to -0.16; p0.006). Almost all the determined cytokines were significantly higher compared to controls, except for MCP-1, myoglobin, NGAL, cystatin C, and MMP-9. At follow-up, only total cholesterol and triglycerides increased and all inflammatory cytokines significantly decreased. Regarding vascular cytokines, MPO, ICAM-1, and VCAM-1 showed a reduction. D-Dimer tended to decrease (p = 0.06) and hs-CRP did not show a significant reduction (p = 0.17).

CONCLUSION

One year of ART had a positive effect on reducing inflammatory and vascular cytokines and arterial stiffness.

Mori fructus aqueous extracts attenuate carbon tetrachloride-induced renal injury via the Nrf2 pathway and intestinal flora

Mori fructus aqueous extracts (MFAEs) have been used as a traditional Chinese medicine for thousands of years with the function of strengthening the liver and tonifying the kidney. However, its inner mechanism to alleviative renal injury is unclear. To investigate the attenuation of MFAEs on nephrotoxicity and uncover its potential molecular mechanism, we established a nephrotoxicity model induced by carbon tetrachloride (CCl₄). The mice were randomly divided into control group, CCl₄ model group (10% CCl₄), CCl₄ + low and high MFAEs groups (10% CCl₄ + 100 mg/kg and 200 mg/kg MFAEs). We found that MFAEs decreased the kidney index of mice, restored the pathological changes of renal structure induced by CCl₄, reduced cystatin C, neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule 1 (Kim-1) blood urea nitrogen and creatinine contents in serum, promoted the nuclear transportation of Nrf2 (nuclear factor erythroid derived 2 like 2), elevated the expression of HO-1 (heme oxygenase 1), GPX4 (glutathione peroxidase 4), SLC7A11 (solute carrier family 7 member 11), ZO-1 (zonula occludens-1) and Occludin, suppressed the expression of Keap1 (kelch-like ECH-associated protein 1), HMGB1 (High Mobility Group Protein 1), ACSL4 (acyl-CoA synthetase long chain family member 4) and TXNIP (thioredoxin interacting protein), upregulated the flora of Akkermansia, Anaerotruncus, Clostridium_sensu_stricto, Ihubacter, Alcaligenes, Dysosmobacter, and downregulated the flora of Clostridium_XlVa, Helicobacter, Paramuribaculum. Overlapped with Disbiome database, Clostridium_XlVa, Akkermansia and Anaerotruncus may be the potential genera treated with renal injury. It indicated that MFAEs could ameliorate kidney injury caused by CCl₄ via Nrf2 signaling.

[Clinical Study of miRNAs Derived from Serum Exosomes in Multiple Myeloma]

OBJECTIVE

To investigate the expression level and prognostic value of miR-21, miR-18a, miR-146a, and Let-7b derived from serum exosomes in patients with multiple myeloma (MM).

METHODS

Serum exosomes were extracted from 57 MM patients and 20 healthy persons using ExoQuick exosome precipitation solution kit, and the relative expression level of miR-21, miR-18a, miR-146a, and Let-7b derived from serum exosomes was measured by RT-qPCR. Correlations of the expression levels of all miRNAs mentioned above with routine laboratory parameters were analyzed by Spearman correlation analysis. The relationship between the expression level of miR-21, miR-18a, miR-146a, and Let-7b derived from serum exosomes and overall survival of patients with MM was analyzed using the Kaplan-Meier survival curve.

RESULTS

The expression levels of miR-21, miR-18a, and Let-7b derived from serum exosomes in patients with MM were significantly lower than those in the normal control group (P<0.001), while the expression level of miR-146a between the two groups was not significantly different (P>0.05). The expression level of miR-21 was strongly negatively correlated with serum β₂-microglobulin concentration (r=-0.830), and weakly negatively correlated with serum creatinine, corrected serum calcium, and cystatin C (r=-0.488, -0.282, -0.627). The expression levels of Let-7b and miR-18a were also weakly negatively correlated with the corrected serum calcium, β₂-microglobulin, and cystatin C concentration (r=-0.305, -0.362, -0.461; -0.317, -0.542, -0.434). However, there was no significant correlation between the expression level of miR-146a and routine laboratory parameters in MM patients. The overall survival rate of MM patients with low expression level of miR-21, miR-18a, and Let-7b significantly decreased compared with high expression level group (P<0.05), however, the expression level of miR-146a was not related to the overall survival rate.

CONCLUSION

Aberrant low expression levels of miR-21, miR-18a, and Let-7b derived from serum exosomes exist in patients with MM, which are associated with a worse overall survival rate.

Creatinine-to-cystatin C ratio estimates muscle mass correlating the markers of the patients with severe motor and intellectual disabilities

AIM

The creatinine-to-cystatin C ratio (CCR) has been acknowledged as a potential marker of muscle mass. The purpose of the present study was to evaluate the relationship between CCR and nutritional status in a bioelectrical impedance analysis (BIA) of patients with severe motor and intellectual disabilities (SMID).

METHODS

This study included 39 patients with SMID (17 males, 22 females) over 16 years of age were included retrospectively. CCR was calculated as serum creatinine (mg/dL)/cystatin C (mg/L) × 10. The BIA parameters such as the phase angle (PhA), fat free mass (FFM), appendicular skeletal muscle mass (ASM) and appendicular skeletal muscle mass index (ASMI) values were measured using BIA. Correlation analyses between CCR and the BIA parameters were conducted.

RESULTS

The mean CCR is 4.47 ± 1.34. Significant positive relationships between CCR and FFM, PhA, ASM, ASMI were identified (r = 0.3373, p = 0.0357. r = 0.4273, p = 0.0093. r = 0.5008, p = 0.0012. r = 0.4706, p = 0.0025 and r = 0.4751, p = 0.0022, respectively).

CONCLUSIONS

The study indicated that CCR in the patients with SMID is a useful parameter that allows for the muscle mass to be estimated easily and accurately. This means that evaluating CCR could be used as a simple and important screening tool for PhA, FFM and muscle mass.

Clonal myelopoiesis promotes adverse outcomes in chronic kidney disease

We sought to determine the relationship between age-related clonal hematopoiesis (CH) and chronic kidney disease (CKD). CH, defined as mosaic chromosome abnormalities (mCA) and/or driver mutations was identified in 5449 (2.9%) eligible UK Biobank participants (n = 190,487 median age = 58 years). CH was negatively associated with glomerular filtration rate estimated from cystatin-C (eGFR.cys; β = -0.75, P = 2.37 × 10-4), but not with eGFR estimated from creatinine, and was specifically associated with CKD defined by eGFR.cys < 60 (OR = 1.02, P = 8.44 × 10-8). In participants without prevalent myeloid neoplasms, eGFR.cys was associated with myeloid mCA (n = 148, β = -3.36, P = 0.01) and somatic driver mutations (n = 3241, β = -1.08, P = 6.25 × 10-5) associated with myeloid neoplasia (myeloid CH), specifically mutations in CBL, TET2, JAK2, PPM1D and GNB1 but not DNMT3A or ASXL1. In participants with no history of cardiovascular disease or myeloid neoplasms, myeloid CH increased the risk of adverse outcomes in CKD (HR = 1.6, P = 0.002) compared to those without myeloid CH. Mendelian randomisation analysis provided suggestive evidence for a causal relationship between CH and CKD (P = 0.03). We conclude that CH, and specifically myeloid CH, is associated with CKD defined by eGFR.cys. Myeloid CH promotes adverse outcomes in CKD, highlighting the importance of the interaction between intrinsic and extrinsic factors to define the health risk associated with CH.

Aggregation of Cystatin C Changes Its Inhibitory Functions on Protease Activities and Amyloid β Fibril Formation

Cystatin C (CST3) is an endogenous cysteine protease inhibitor, which is implicated in cerebral amyloid angiopathy (CAA). In CAA, CST3 is found to be aggregated. The purpose of this study is to investigate whether this aggregation could alter the activity of the protein relevant to the molecular pathology of CAA. A system of CST3 protein aggregation was established, and the aggregated protein was characterized. The results showed that CST3 aggregated both at 80 °C without agitation, and at 37 °C with agitation in a time-dependent manner. However, the levels of aggregation were high and appeared earlier at 80 °C. Dot-blot immunoassay for oligomers revealed that CST3 could make oligomeric aggregates at the 37 °C condition. Electron microscopy showed that CST3 could make short fibrillary aggregates at 37 °C. Cathepsin B activity assay demonstrated that aggregated CST3 inhibited the enzyme activity less efficiently at pH 5.5. At 7.4 pH, it lost the inhibitory properties almost completely. In addition, aggregated CST3 did not inhibit Aβ_1-40 fibril formation, rather, it slightly increased it. CST3 immunocytochemistry showed that the protein was positive both in monomeric and aggregated CST3-treated neuronal culture. However, His6 immunocytochemistry revealed that the internalization of exogenous recombinant CST3 by an astrocytoma cell culture was higher when the protein was aggregated compared to its monomeric form. Finally, MTT cell viability assay showed that the aggregated form of CST3 was more toxic than the monomeric form. Thus, our results suggest that aggregation may result in a loss-of-function phenotype of CST3, which is toxic and responsible for cellular degeneration.

A New Panel-Estimated GFR, Including β2-Microglobulin and β-Trace Protein and Not Including Race, Developed in a Diverse Population

RATIONALE AND OBJECTIVE

Glomerular filtration rate (GFR) estimation based on creatinine and cystatin C (eGFRcr-cys) is more accurate than estimated GFR (eGFR) based on creatinine or cystatin C alone (eGFRcr or eGFRcys, respectively), but the inclusion of creatinine in eGFRcr-cys requires specification of a person's race. β2-Microglobulin (B2M) and β-trace protein (BTP) are alternative filtration markers that appear to be less influenced by race than creatinine is.

STUDY DESIGN

Study of diagnostic test accuracy.

SETTING AND PARTICIPANTS

Development in a pooled population of 7 studies with 5,017 participants with and without chronic kidney disease. External validation in a pooled population of 7 other studies with 2,245 participants.

TESTS COMPARED

Panel eGFR using B2M and BTP in addition to cystatin C (3-marker panel) or creatinine and cystatin C (4-marker panel) with and without age and sex or race.

OUTCOMES

GFR measured as the urinary clearance of iothalamate, plasma clearance of iohexol, or plasma clearance of [51Cr]EDTA.

RESULTS

Mean measured GFRs were 58.1 and 83.2 mL/min/1.73 m2, and the proportions of Black participants were 38.6% and 24.0%, in the development and validation populations, respectively. In development, addition of age and sex improved the performance of all equations compared with equations without age and sex, but addition of race did not further improve the performance. In validation, the 4-marker panels were more accurate than the 3-marker panels (P < 0.001). The 3-marker panel without race was more accurate than eGFRcys (percentage of estimates greater than 30% different from measured GFR [1 - P30] of 15.6% vs 17.4%; P = 0.01), and the 4-marker panel without race was as accurate as eGFRcr-cys (1 - P30 of 8.6% vs 9.4%; P = 0.2). Results were generally consistent across subgroups.

LIMITATIONS

No representation of participants with severe comorbid illness and from geographic areas outside of North America and Europe.

CONCLUSIONS

The 4-marker panel eGFR is as accurate as eGFRcr-cys without requiring specification of race. A more accurate race-free eGFR could be an important advance.

The efficacy of biomarkers in the diagnosis of acute kidney injury secondary to liver cirrhosis

ABSTRACT

This study is to investigate the role of neutrophil gelatinase-associated lipocalin (NGAL), cystatin C (CysC) and creatinine in the diagnosis of acute kidney injury (AKI) secondary to liver cirrhosis.A total of 825 patients (including 540 liver cirrhosis patients and 285 healthy controls) were enrolled. Liver cirrhosis patients were further subdivided into AKI secondary to liver cirrhosis group (AKI group, 210 patients) and simple liver cirrhosis group (LC group, 330 patients). Serum NGAL/urine NGAL (sNGAL/uNGAL), and serum creatinine (sCr) levels as well as estimated glomerular filtration rates were measured. The diagnostic performances of these indicators in AKI secondary to liver cirrhosis were evaluated.The levels of sNGAL, uNGAL, CysC and sCr in the AKI group were significantly higher than those of LC and healthy control groups. However, the eGFR and c-aGFR of AKI group were significantly lower. With the progression of AKI (AKI-S1→AKI-S2→AKI-S3), the levels of sNGAL, uNGAL, CysC and sCr increased gradually, while the levels of c-aGFR and eGFR decreased gradually. The sNGAL, uNGAL and CysC were positively correlated with sCr (r = 0.638, 0.635, and 0.650), but negatively correlated with c-aGFR (r = -0.617, -0.606 and -0.655). However, eGFR had a negative correlation with sCr (r = -0.711), but a positive correlation with c-aGFR (r = 0.736). ROC curve analysis showed that the area under the curve for uNGAL was the largest (0.976), followed by sNGAL (0.967). The diagnostic efficacy of uNGAL and sNGAL in AKI group were 0.907 and 0.870, and the risk degrees were OR = 54.524 and 5.115, respectively.NGAL might perform better than sCr and CysC in the diagnosis of AKI secondary to liver cirrhosis, while uNGAL might be a better indicator than sNGAL in AKI diagnosis.

Cold-inducible RNA binding protein promotes breast cancer cell malignancy by regulating Cystatin C levels

Cold-inducible RNA binding protein (CIRBP) is a stress-responsive protein that promotes cancer development and inflammation. Critical to most CIRBP functions is its capacity to bind and posttranscriptionally modulate mRNA. However, a transcriptome-wide analysis of CIRBP mRNA targets in cancer has not yet been performed. Here, we use an ex vivo breast cancer model to identify CIRBP targets and mechanisms. We find that CIRBP transcript levels correlate with breast cancer subtype and are an indicator of luminal A/B prognosis. Accordingly, overexpression of CIRBP in nontumoral MCF-10A cells promotes cell growth and clonogenicity, while depletion of CIRBP from luminal A MCF-7 cells has opposite effects. We use RNA immunoprecipitation followed by high-throughput sequencing (RIP-seq) to identify a set of 204 high confident CIRBP targets in MCF-7 cells. About 10% of these showed complementary changes after CIRBP manipulation in MCF-10A and MCF-7 cells, and were highly interconnected with known breast cancer genes. To test the potential of CIRBP-mediated regulation of these targets in breast cancer development, we focused on Cystatin C (CST3), one of the most highly interconnected genes, encoding a protein that displays tumor suppressive capacities. CST3 depletion restored the effects of CIRBP depletion in MCF-7 cells, indicating that CIRBP functions, at least in part, by down-regulating CST3 levels. Our data provide a resource of CIRBP targets in breast cancer, and identify CST3 as a novel downstream mediator of CIRBP function.

Cystatin C regulates the cytotoxicity of infection-induced endothelial-derived β-amyloid

Infection of rat pulmonary microvascular endothelial cells with the bacterium Pseudomonas aeruginosa induces the production and release of cytotoxic oligomeric tau and beta amyloid (Aβ). Here, we characterized these cytotoxic amyloids. Cytotoxic behavior and oligomeric tau were partially resistant to digestion with proteinase K, but cytotoxicity was abolished by various denaturants including phenol, diethylpyrocarbonate (DEPC), and 1,1,1,3,3,3-hexafluoro-2-isopropanol (HFIP). Ultracentrifugation for 8 h at 150 000 g was required to remove cytotoxic activity from the supernatant. Ultracentrifugation, DEPC treatment, and immunodepletion using antibodies against Aβ also demonstrated that cytoprotective protein(s) are released from endothelial cells during P. aeruginosa infection. Mass spectrometry of endothelial cell culture media following P. aeruginosa infection allowed identification of multiple potential secreted modulators of Aβ, including cystatin C, gelsolin, and ApoJ/clusterin. Immunodepletion, co-immunoprecipitation, and ultracentrifugation determined that the cytoprotective factor released during infection of endothelial cells by P. aeruginosa is cystatin C, which appears to be in a complex with Aβ. Cytoprotective cystatin C may provide a novel therapeutic avenue for protection against the long-term consequences of infection with P. aeruginosa.

Obesity-Induced Increase in Cystatin C Alleviates Tissue Inflammation

We recently demonstrated that removal of one kidney (uninephrectomy [UniNx]) in mice reduced high-fat diet (HFD)-induced adipose tissue inflammation, thereby improving adipose tissue and hepatic insulin sensitivity. Of note, circulating cystatin C (CysC) levels were increased in UniNx compared with sham-operated mice. Importantly, CysC may have anti-inflammatory properties, and circulating CysC levels were reported to positively correlate with obesity in humans and as shown here in HFD-fed mice. However, the causal relationship of such observation remains unclear. HFD feeding of CysC-deficient (CysC knockout [KO]) mice worsened obesity-associated adipose tissue inflammation and dysfunction, as assessed by proinflammatory macrophage accumulation. In addition, mRNA expression of proinflammatory mediators was increased, whereas markers of adipocyte differentiation were decreased. Similar to findings in adipose tissue, expression of proinflammatory cytokines was increased in liver and skeletal muscle of CysC KO mice. In line, HFD-induced hepatic insulin resistance and impairment of glucose tolerance were further aggravated in KO mice. Consistently, chow-fed CysC KO mice were more susceptible to lipopolysaccharide-induced adipose tissue inflammation. In people with obesity, circulating CysC levels correlated negatively with adipose tissue Hif1α as well as IL6 mRNA expression. Moreover, healthy (i.e., insulin-sensitive) subjects with obesity had significantly higher mRNA expression of CysC in white adipose tissue. In conclusion, CysC is upregulated under obesity conditions and thereby counteracts inflammation of peripheral insulin-sensitive tissues and, thus, obesity-associated deterioration of glucose metabolism.

Extracellular Vesicle cystatin c is associated with unstable angina in troponin negative patients with acute chest pain

Background

Despite the use of high-sensitive cardiac troponin there remains a group of high-sensitive cardiac troponin negative patients with unstable angina with a non-neglectable risk for future adverse cardiovascular events, emphasising the need for additional risk stratification. Plasma extracellular vesicles are small bilayer membrane vesicles known for their potential role as biomarker source. Their role in unstable angina remains unexplored. We investigate if extracellular vesicle proteins are associated with unstable angina in patients with chest pain and low high-sensitive cardiac troponin.

Methods

The MINERVA study included patients presenting with acute chest pain but no acute coronary syndrome. We performed an exploratory retrospective case-control analysis among 269 patients. Cases were defined as patients with low high-sensitive cardiac troponin and proven ischemia. Patients without ischemia were selected as controls. Blood samples were fractionated to analyse the EV proteins in three plasma-subfractions: TEX, HDL and LDL. Protein levels were quantified using electrochemiluminescence immunoassay.

Results

Lower levels of (adjusted) EV cystatin c in the TEX subfraction were associated with having unstable angina (OR 0.93 95% CI 0.88–0.99).

Conclusion

In patients with acute chest pain but low high-sensitive cardiac troponin, lower levels of plasma extracellular vesicle cystatin c are associated with having unstable angina. This finding is hypothesis generating only considering the small sample size and needs to be confirmed in larger cohort studies, but still identifies extracellular vesicle proteins as source for additional risk stratification.

The Positive Side of the Alzheimer's Disease Amyloid Cross-Interactions: The Case of the Aβ 1-42 Peptide with Tau, TTR, CysC, and ApoA1

Alzheimer's disease (AD) represents a progressive amyloidogenic disorder whose advancement is widely recognized to be connected to amyloid-β peptides and Tau aggregation. However, several other processes likely contribute to the development of AD and some of them might be related to protein-protein interactions. Amyloid aggregates usually contain not only single type of amyloid protein, but also other type of proteins and this phenomenon can be rationally explained by the process of protein cross-seeding and co-assembly. Amyloid cross-interaction is ubiquitous in amyloid fibril formation and so a better knowledge of the amyloid interactome could help to further understand the mechanisms of amyloid related diseases. In this review, we discuss about the cross-interactions of amyloid-β peptides, and in particular Aβ1-42, with other amyloids, which have been presented either as integrated part of Aβ neurotoxicity process (such as Tau) or conversely with a preventive role in AD pathogenesis by directly binding to Aβ (such as transthyretin, cystatin C and apolipoprotein A1). Particularly, we will focus on all the possible therapeutic strategies aiming to rescue the Aβ toxicity by taking inspiration from these protein-protein interactions.

Neuroprotection mediated by cystatin C-loaded extracellular vesicles

Cystatin C (CysC) is implicated in neuroprotection and repair in the nervous system in response to diverse neurotoxic conditions. In addition to being secreted from cells in a soluble form, CysC is released by cells in association with extracellular vesicles (EVs), including exosomes. We demonstrate that EVs containing CysC protect cultured cells from starvation-induced death. Moreover, while EVs secreted by CysC-deficient cells were not protective, EVs secreted by CysC-deficient cells treated with exogenous human CysC significantly enhanced the survival of the cells. CysC also plays a role in modulating the secretion of EVs, enhancing secretion of EVs by primary cortical neurons and primary cortical smooth muscle cells. Confirming these in vitro findings, higher EV levels were observed in the brain extracellular space of transgenic mice expressing human CysC as compared to littermate controls. Regulation of cell-secreted EV levels and content in the brain is likely to be essential to maintaining normal brain function. We propose that enhanced EV release could rescue the deleterious effects of dysfunction of the endosomal-lysosomal system in neurodegenerative disorders. Moreover, a higher level of CysC-loaded EVs released from cells in the central nervous system has important protective functions, representing a potential therapeutic tool for disorders of the central nervous system.

Hospitalization Risk among Older Adults with Chronic Kidney Disease

INTRODUCTION

Chronic kidney disease (CKD) risk staging is based on estimated glomerular filtration rate (eGFR) and albumin-creatinine ratio (ACR). However, the relationship between all-cause hospitalization risk and the current CKD staging system has not been well studied among older adults, despite a high prevalence of CKD and a high risk of hospitalization in old age.

METHODS

Among 4,766 participants of the Atherosclerosis Risk in Communities study, CKD was staged according to Kidney Disease Improving Global Outcomes (KDIGO) criteria, using creatinine-based eGFR (eGFRcr) and ACR. Incidence rates of all-cause hospitalization associated with each CKD risk group were analyzed using negative binomial regression. Additionally, cause-specific hospitalization risks for cardiovascular, infectious, kidney, and other diseases were estimated. The impacts of using cystatin C-based eGFR (eGFRcys) to estimate the prevalence of CKD and risks of hospitalization were also quantified.

RESULTS

Participants experienced 5,548 hospitalizations and 29% had CKD. Hospitalization rates per 1,000 person-years according to KDIGO risk categories were 208-223 ("low risk"), 288-376 ("moderately increased risk"), 363-548 ("high risk"), and 499-1083 ("very high risk"). The increased risk associated with low eGFR and high ACR persisted in adjusted analyses, examinations of cause-specific hospitalizations, and when CKD was staged by eGFRcys or eGFRcr-cys, a combined equation based on both creatinine and cystatin C. In comparison to eGFRcr, staging by eGFRcys increased the prevalence of CKD to 50%, but hospitalization risks remained similarly high.

DISCUSSION/CONCLUSION

In older adults, decreased eGFR, increased ACR, and KDIGO risk stages based on a combination of these measures, were strong risk factors for hospitalization. These relationships were consistent, regardless of the marker used to estimate GFR, but the use of cystatin C resulted in a substantially higher prevalence of CKD than the use of creatinine. Older adults in the population with very high risk stages of CKD have hospitalization rates exceeding 500 per 1,000 person-years.

Functional characterization of Cystatin C in orange-spotted grouper, Epinephelus coioides

Cystatin C is an endogenous inhibitor of cysteine proteases and widely exist in organisms. Several studies in mammals have showed that Cystatin C plays critical role in the immune defense against microorganisms. It is also well known that some fish Cystatin C have important immune regulation functions in inflammatory responses. However, the function of fish Cystatin C in virus infection as well as its underlying molecular mechanisms remain to be elucidated. In the present study, a Cystatin C gene termed Ec-CysC was identified from orange-spotted grouper, Epinephelus coioides. The full-length of Ec-CysC cDNA was 817 bp with a 387 bp open reading frame (ORF) that encoded a 129-amino acid (aa) protein, including 18-aa signal peptide and 111-aa mature polypeptide. The deduced amino acid of Ec-CysC shared three conserved domains containing Glycine at the N-terminus region, QVVAG motif in the middle and PW motif near the C-terminus region. Transcription analysis of the Ec-CysC gene showed its expression in all twelve examined tissues including liver, spleen, kidney, brain, intestine, heart, skin, muscle, fin, stomach, gill and head kidney. Its expression following stimulation with Singapore grouper iridovirus (SGIV) was further tested in spleen, the relative expression of Ec-CysC was significantly up-regulated at 12 h post-infection. The subcellular localization experiment revealed that Ec-CysC was mainly distributed in the cytoplasm in Grouper Spleen (GS) cells. In vitro, Overexpression of Ec-CysC in GS cells significantly reduced the expression of viral genes, namely, ORF162, ORF049 and ORF072. Meanwhile, we found that overexpression of Ec-CysC resulted in upward trend of expression of inflammatory cytokines TNF-a, IL-1β and IL8 during SGIV infection. Further, SGIV-inducible apoptosis and Caspase-3 activity were also weakened by overexpression Ec-CysC in fathead minnow (FHM) cells. These results indicated that Ec-CysC might have a deeper involvement in fish immune defense, and played important roles in inflammation and apoptosis induced by SGIV.

Stabilized Human Cystatin C Variant L47C/G69C Is a Better Reporter Than the Wild-Type Inhibitor for Characterizing the Thermodynamics of Binding to Cysteine Proteases

Human cystatin C (HCC) binds and inhibits all types of cysteine proteases from the papain family, including cathepsins (a group of enzymes that participate in a variety of physiological processes), which are some of its natural targets. The affinities of diverse proteases for HCC, expressed as equilibrium binding constants (K_b), range from 10⁶ to 10¹⁴ M^-1. Isothermal titration calorimetry (ITC) is one of the most useful techniques to characterize the thermodynamics of molecular associations, making it possible to dissect the binding free energy into its enthalpic and entropic components. This information, together with the structural changes that occur during the different associations, could enable better understanding of the molecular basis of affinity. Notwithstanding the high sensitivity of modern calorimeters, ITC requires protein concentrations in at least the 10-100 μM range to obtain reliable data, and it is known that HCC forms oligomers in this concentration range. We present herein a comparative study of the structural, thermal stability, and oligomerization properties of HCC and its stabilized variant (sHCC) L47C/G69C (which possesses an additional disulfide bridge) as well as their binding thermodynamics to the protease chymopapain, analyzed by ITC. The results show that, because sHCC remains monomeric, it is a better reporter than wild-type HCC to characterize the thermodynamics of binding to cysteine proteases.

Obesity and recovery from acute kidney injury (Ob AKI): a prospective cohort feasibility study

OBJECTIVES

To test the methodology of recruitment, retention and data completeness in a prospective cohort recruited after a hospitalised episode of acute kidney injury (AKI), to inform a future prospective cohort study examining the effect of obesity on AKI outcomes.

DESIGN

Feasibility study.

SETTING

Single centre, multi-site UK tertiary hospital.

PARTICIPANTS

101 participants (67M; 34F) with a median age of 64 (IQR 53-73) years, with and without obesity, recruited within 3 months of a hospitalised episode of AKI.

OUTCOME MEASURES

Feasibility outcomes were recruitment (>15% meeting inclusion criteria recruited), participant retention at 6 and 12 months (≥80%) and completeness of data collection. Exploratory measures included recovery from AKI (regaining >75% of pre-AKI estimated glomerular filtration rate [eGFR]) at 6 months, development or progression of chronic kidney disease (CKD) (kidney function decrease of ≥25% +  rise in CKD category) at 12 months, and associations with poorer kidney outcomes.

RESULTS

41% of eligible patients consented to take part, exceeding the target recruitment uptake rate of 15%. Retention was 86% at 6 months and 78% at 12 months; 10 patients died and three commenced dialysis during the study. Data were 90%-100% complete. Median BMI was 27.9 kg/m2 (range 18.1 kg/m2-54.3 kg/m2). 50% of the cohort had stage 3 AKI and 49% had pre-existing CKD. 46% of the cohort met the AKI recovery definition at 6 months. At 12 months, 20/51 patients developed CKD (39%) and CKD progression occurred in 11/49 patients (22%). Post-AKI interleukin-6 and cystatin-C were associated with 12 months decline in eGFR.

CONCLUSIONS

Feasibility to conduct a long-term observational study addressing AKI outcomes associated with obesity was demonstrated. A fully powered prospective cohort study to examine the relationships between obesity and outcomes of AKI is warranted.

Association of cystatin C- and creatinine-based eGFR with osteoporotic fracture in Japanese postmenopausal women with osteoporosis: sarcopenia as risk for fracture

Coexistence of chronic kidney disease (CKD) is regarded as a risk for osteoporotic fracture particularly in postmenopausal women, not only because of increased parathyroid hormone level but also uremic sarcopenia. We examined the relationships of cystatin C-based glomerular filtration rate (eGFRcys) and creatinine-based GFR (eGFRcr), as well as their ratio with occurrence of osteoporotic fracture in postmenopausal osteoporotic women. This cross-sectional study included 555 postmenopausal women with osteoporosis. eGFRcr and eGFRcys were simultaneously measured, while occurrence of osteoporotic fracture was obtained by a medical chart review. Patients with osteoporotic fractures (n = 211) exhibited significantly lower levels of physical activity, eGFRcr, eGFRcys, and eGFRcys/eGFRcr ratios, while a higher percentage was CKD stage 3 or more, estimated by eGFRcr or eGFRcys (CKDcys), than those without (n = 344). Lower eGFRcys, but not lower eGFRcr, was independently associated with osteoporotic fracture in the entire cohort and that association was retained in CKDcys patients. Of great interest, higher eGFRcr was associated with osteoporotic fracture independent of eGFRcys in CKDcys patients. Furthermore, lower eGFRcys/eGFRcr ratio was independently associated with osteoporotic fracture in both CKDcys patients and the entire cohort. eGFRcys reduction might be associated with osteoporotic fracture in postmenopausal osteoporotic women, indicating the involvement of renal osteopathy in its occurrence. Furthermore, the association of higher, but not lower, eGFRcr with osteoporotic fracture in CKDcys cases might be explained by underestimation of renal dysfunction by eGFRcr resulting from decreased muscle mass and quality in those patients.

Cystatin C in adipose tissue and stimulation of its production by growth hormone and triiodothyronine in 3T3-L1 cells

Cystatin C (CysC) is a marker for estimation of glomerular filtration rate (GFR). CysC levels may depend not only on clearance/GFR but possibly also on changes in production. Our studies on tissue distribution of CysC protein in mice showed that adipose tissue expresses significant amounts of CysC, suggesting that adipocytes could contribute to circulating CysC levels in vivo. As growth hormone (GH) and triiodothyronine (T₃) increase both GFR and CysC (increased in acromegaly and hyperthyroidism) in vivo, we studied whether they could increase CysC production in 3T3-L1 adipocytes in vitro. CysC accumulated in culture media of 3T3-L1 adipocytes in a time-dependent fashion. GH and T₃ both (10 nmol/l) increased accumulation of CysC, to 373 ± 14 and 422 ± 20, respectively, vs 298 ± 10 ng per well over 4 days in controls. Thus, GH and T₃ enhance the production of CysC by adipocytes in vitro.

EVALUATION OF THE ROYAL FREE HOSPITAL CIRRHOSIS GLOMERULAR FILTRATION RATE FORMULA IN HISPANIC PATIENTS WITH CIRRHOSIS: AN EXTERNAL VALIDATION

BACKGROUND AND AIMS

Glomerular filtration rate (GFR) measurement in patients with liver cirrhosis (LC) is the ideal method for adequate evaluation of kidney function. However, it is invasive, costly, and not widely accessible. Moreover, GFR estimation in patients with cirrhosis has been inaccurate. The aim of the present study was to evaluate and validate the recently described Royal Free Hospital (RFH) formula in a Hispanic cohort of patients with LC and compare it with other formulas, including the CKD-EPI cystatin C equation.

METHODS

GFR was measured through the renal clearance of Tc-99m DTPA; it was cross-sectionally evaluated and compared with GFRs that were estimated utilizing the following formulas: RFH, Cockcroft-Gault, 6-variable Modification of Diet in Renal Disease-6, CKD-EPI cystatin C, CKD-EPI Creatinine, and CKD-EPI Cystatin C-Creatinine.

RESULTS

We included 76 patients (53% women). The mean measured GFR in the entire cohort was 64 ml/min/1.73m²; 54% of the patients had a GFR < 60 ml/min/1.73 m² at the time of evaluation. The RFH formula and the CKD-EPI cystatin C formula showed the best performance, with a p30 of 62% and 59%, respectively. All formulas performed poorly when GFR was < 60 ml/min/1.73 m².

CONCLUSIONS

The RFH formula showed a better performance than the other formulas based on serum creatinine in a Hispanic population with LC. There was no difference in performance between the RFH formula and the CKD-EPI cystatin C formula.

Serum angiopoietin-2 concentrations of post-PCI are correlated with the parameters of renal function in patients with coronary artery disease

Patients with coronary artery disease (CAD) frequently have comorbidity of chronic kidney disease (CKD). Their renal function may deteriorate because of the use of contrast agent after percutaneous coronary intervention (PCI). Angiopoietin-2 (Ang-2), which is highly expressed in the site of angiogenesis, plays an important role in both CAD and CKD. This study aimed to investigate the relation of serum Ang-2 concentrations with the renal function after PCI.This study enrolled 57 patients with CAD undergoing PCI. Blood samples for Ang-2 were collected in the first morning after admission and within 24 to 48 h after PCI. The parameters of renal function (serum creatinine, cystatin C and eGFR) were tested on the first day after admission and within 72 h after PCI.Overall, serum Ang-2 levels of post-PCI were significantly lower than those of pre-PCI [median, 1733 (IQR, 1100-2568) vs median, 2523 (IQR, 1702-3640) pg/mL; P < .001]. However, in patients with CKD (eGFR < 60 mL/min/1.73 m), there was no significant difference between serum Ang-2 levels of post-PCI and those of pre-PCI [median, 2851 (IQR, 1720-4286) vs. median, 2492 (IQR, 1434-4994) pg/mL; P = .925]. In addition, serum Ang-2 levels of post-PCI, but not pre-PCI, were significantly correlated with the post-PCI parameters of renal function.Serum Ang-2 concentrations of post-PCI are closely related to renal function in patients with CAD. It may have potential to be the early biomarker of contrast-induced nephropathy in the future.

Hypertonic saline resuscitation protects against kidney injury induced by severe burns in rats

BACKGROUND

Proper fluid resuscitation can relieve visceral damage and improve survival in severely burned patients. This study compared the effectiveness of resuscitation with 400mEq/L hypertonic saline (HS) and sodium lactate Ringer's solution (LR) in rats with kidney injury caused by burn trauma.

METHODS

Rats (Sprague-Dawley) underwent burn injury and were randomized into sham, LR, and HS groups. Samples from the kidney were assayed for water content ratio, histopathology, and oxidative stress (superoxide dismutase (SOD) and malondialdehyde (MDA)). Serum sodium, renal function (creatinine and cystatin (Cys)-C), and inflammatory response (tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and high mobility group protein box (HMGB)-1) were also examined as serum markers.

RESULTS

Hypertonic saline resuscitation reduced the renal water content ratio and improved renal histopathology caused by severe burns. This effect was accompanied by reductions in serum creatinine and Cys-C as well as TNF-α, IL-1β, and HMGB1. Serum sodium concentration and SOD activity were increased, whereas MDA content was decreased in the kidney tissue of the HS group.

CONCLUSIONS

The data indicate that 400mEq/L HS solution reduces hyponatremia and renal edema, inhibits the release of inflammatory mediators, and alleviates oxidative stress injury, thus protecting against kidney injury induced by severe burns.

Combining GFR estimates from cystatin C and creatinine-what is the optimal mix?

BACKGROUND

Combining estimated glomerular filtration rate (eGFR) equations based on creatinine and cystatin C has been shown to improve the accuracy of GFR estimation. This study aims to optimize this strategy for height-independent GFR estimation in children.

METHODS

Retrospective study of 408 inulin clearance tests with simultaneous International Federation of Clinical Chemistry-calibrated measurements of creatinine, cystatin C, and urea in children (mean age 12.5 years, GFR 91.2 ml/min/1.73m²) comparing the arithmetic (mean_arith) and geometric means (mean_geom) of a height-independent creatinine-based (full age spectrum, based on age (FASage)) and a cystatin C-based equation (FAScys), with the complex height-dependent CKiD3 equation incorporating gender, height, cystatin C, creatinine, and urea.

RESULTS

Mean_geom had a P₃₀ accuracy of 89.2% compared to mean_arith 87.7% (p = 0.030) as well as lower bias and %precision error and performed almost as well as CKiD3 (P₃₀ accuracy 90.9%). Modifying the weight of FASage and FAScys when calculating the means showed that an equal contribution was most accurate in most patients. In spina bifida patients, FAScys alone outperformed any combination. Malignancy or nephritis patients had slightly higher accuracy with weighted means favoring cystatin C or creatinine, respectively. Disagreement between FAScys and FASage was inversely correlated with the accuracy of mean_geom. When disagreement exceeded 40%, application of weighted means based on diagnosis improved the performance of eGFR.

CONCLUSIONS

In the absence of height data, the optimal strategy for estimating GFR in children is by using the geometric mean of FASage and FAScys. When there is large disagreement between the two, weighted means based on diagnosis improve accuracy.

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

Cathepsin S (CTSS) activity is elevated in Sjögren's Syndrome (SS) patient tears. Here we tested whether protease inhibition and cystatin C (Cys C) levels are reduced in SS tears, which could lead to enhanced CTSS-driven degradation of tear proteins. CTSS activity against Cys C, LF and sIgA was tested in SS or healthy control tears. Tears from 156 female subjects (33, SS; 33, rheumatoid arthritis; 31, other autoimmune diseases; 35, non-autoimmune dry eye (DE); 24, healthy controls) were analyzed for CTSS activity and Cys C, LF, and sIgA levels. Cys C and LF showed enhanced degradation in SS tears supplemented with recombinant CTSS, but not supplemented healthy control tears. CTSS activity was significantly increased, while Cys C, LF and sIgA levels were significantly decreased, in SS tears compared to other groups. While tear CTSS activity remained the strongest discriminator of SS in autoimmune populations, combining LF and CTSS improved discrimination of SS beyond CTSS in DE patients. Reductions in Cys C and other endogenous proteases may enhance CTSS activity in SS tears. Tear CTSS activity is reconfirmed as a putative biomarker of SS in an independent patient cohort while combined LF and CTSS measurements may distinguish SS from DE patients.

Combination of pediatric and adult formulas yield valid glomerular filtration rate estimates in young adults with a history of pediatric chronic kidney disease

As patients with chronic kidney disease (CKD) transition from pediatric nephrology care to adult care, their kidney function is clinically assessed by estimated glomerular filtration rate (eGFR) using both pediatric and adult equations, which may not be congruent. Here we evaluated commonly used eGFR equations and directly measured iohexol GFR (iGFR) among participants between ages 18 and 26 with a diagnosis of pediatric CKD in the Chronic Kidney Disease in Children (CKiD) cohort. The bedside serum creatinine (SCr)-only equation (CKiDSCr), the SCr-only CKD-EPI (CKD-EPISCr), the cystatin C (Cys)-only CKD-EPI (CKD-EPICys) and the combined SCr and Cys CKD-EPI (CKD-EPISCr-Cys) were compared with a) 279 measured iGFRs obtained from 187 participants and b) 548 eGFRs from the SCr and Cys-based CKiD equation (CKiDSCr-Cys) obtained from 219 participants. Among emerging adults with a median iGFR of 49 ml/min/1.73m2, the CKiDSCr-Cys equation had low bias (+1.5 ml/min/1.73m2) and high correlation (0.94), while CKiDSCr underestimated iGFR and CKiDSCr-Cys (-5.6 and -7.4 ml/min/1.73m2, respectively) and CKD-EPISCr had an overestimation bias (+8.2 and +6.1 ml/min/1.73m2, respectively). However, the CKD-EPICys and CKD-EPISCr-Cys exhibited strong agreement with both iGFR and CKiDSCr-Cys. GFR may also be validly estimated in this population by taking the simple average of CKiDSCr and CKD-EPISCr (average bias +1.3 compared to iGFR and -0.6 compared to CKiDSCr-Cys). Clinicians should be aware that individually the pediatric and adult SCr-based estimates of GFR had large discrepancies among emerging adults with pediatric CKD. Thus, when cystatin C is not available, we recommend the average of pediatric and adult SCr-based eGFR as a valid tool for clinical use.

Diagnostic performance of plasma and urine neutrophil gelatinase-associated lipocalin, cystatin C, and creatinine for acute kidney injury in burn patients: A prospective cohort study

Background

Diagnosing acute kidney injury quickly is imperative since it is known as an independent risk factor for mortality in burn patients. We evaluated the diagnostic power of creatinine, cystatin, serum and urine neutrophil gelatinase-associated lipocalin at different time periods and observed the changes from baseline for each biomarker.

Methods

This was a prospective observation study from January 2015 to February 2016. A total of 84 patients were enrolled consecutively. Serum creatinine, serum cystatin C, and serum and urine neutrophil gelatinase-associated lipocalin were measured at admission, 7^th, 14^th, 21^st, and 28^th days after admission. All samples were collected until acute kidney injury developed.

Results

Acute kidney injury developed in 35 patients. The mean age was 49.6 years with a male predominance. The median urine neutrophil gelatinase-associated lipocalin was the lowest (11.6 ng/dL) at admission, and the highest at 85.5 ng/dL on day 7. Mean creatinine level was the highest (0.88 mg/dL) at admission and the median creatinine level was the lowest (0.56 mg/dL) on the 14^th day. The area under the curve of creatinine levels was the highest with 0.857 during the 1^st week. The area under the curve of urine neutrophil gelatinase-associated lipocalin was the highest with 0.803 during the 5^th week.

Conclusions

Within 1 week of acute kidney injury, creatinine level was the optimal biomarker for diagnosis while urine neutrophil gelatinase-associated lipocalin showed better diagnostic performance following the 4- week period.

Ameliorative effect of ursolic acid on renal fibrosis in adenine-induced chronic kidney disease in rats

Ursolic acid (UA), an ursane-type pentacyclic triterpenoid commonly found in apple peels and holy basil has been shown to possess many beneficial effects. Renal fibrosis is a complication of kidney injury and associated with increased risk of morbidity and mortality. In our previous investigation, a lupane-type pentacyclic triterpenoid, betulinic acid (BA) was found to have protective effect on chronic kidney disease (CKD) and renal fibrosis. This prompted us to explore the therapeutic value of UA, a chemically related compound to BA in CKD. CKD was induced by feeding adenine with the feed at a concentration of 0.75% for 28 days. UA at the dose rate of 30 mg/kg in 0.5% carboxy methyl cellulose (CMC) was administered by oral route, simultaneously with adenine feeding for 28 days. Adenine feeding increased the kidney weight to body weight index, decreased the kidney function due to injury as indicated by increased markers like serum urea, uric acid, creatinine, cystatin C and neutrophil gelatinase-associated lipocalin (NGAL) and initiated the fibrotic response in kidney by increasing the profibrotic proteins viz. transforming growth factor-beta (TGF-β), connective tissue growth factor (CTGF), fibronectin and collagen. However, treatment with UA reversed the damage induced by adenine as shown by reduced kidney injury and fibrosis markers which was further clearly evident in histological picture indicating the suitability of UA for use in CKD.

Adiponectin is not associated with renal function decline in community-dwelling elderly adults

Adiponectin secreted by adipocytes plays an important role in the regulation of glucose and fatty acid metabolism. Contrary to findings in patients with chronic kidney disease (CKD), no prospective data about the association of serum adiponectin with renal function decline in the general population have yet appeared. Our objective was to analyze the relationship of total and high molecular weight (HMW) adiponectin with renal function decline as measured by cystatin C in community-dwelling elderly adults without moderate or severe CKD.In a prospective observational analysis, a total of 216 healthy elderly volunteers with eGFRcys ≥60 mL/min/1.73 m underwent anthropometric and laboratory tests at baseline and at follow-up visits. A subgroup with serum samples collected 5 years apart was further analyzed.There were no differences in either total or HMW adiponectin level between subjects subsequently undergoing rapid renal function decline and subjects with normal physiologic renal function decline (P = .71, P = .81). On univariate linear regression, neither total nor HMW adiponectin were associated with annual renal function decline (β = -0.23; P = .71, β = -0.057; P = .90). Multivariate analysis did not show a significant contribution of either total or HMW adiponectin to annual renal function decline (β = -0.50; P = .46, β = 0.01; P = .98). In the logistic regression analysis, we did not observe any statistically significant association of serum adiponectin levels with rapid renal function decline or incidence of CKD.Contrary to findings in populations with CKD, neither total nor HMW adiponectin had a substantial association with renal function decline in an elderly population with eGFRcys ≥60 mL/min/1.73 m. Our results and conclusions should not be extrapolated to subjects with other characteristics.

Can Serum Cystatin C predict long-term survival in cardiac surgery patients?

Renal dysfunction is a risk factor for morbidity and mortality in cardiac surgery patients. Serum Cystatin C (sCysC) is a well-recognized marker of early renal dysfunction but few reports evaluate its prognostic cardio-vascular role. The aim of the study is to consider the prognostic value of sCysC for cardiovascular mortality. Four hundred twenty-four cardiac-surgery patients (264 men and 160 women) were enrolled. At admission, all patients were tested for renal function and inflammatory status. Patients were subdivided in subgroups according to the values of the following variables: sCysC, serum Creatinine (sCrea), age, high sensitivity-C Reactive Protein, fibrinogen, surgical procedures and Kaplan-Meier cumulative survival curves were plotted. The primary end-point was cardiovascular mortality. In order to evaluate the simultaneous independent impact of all measured variables on survival we fitted a multivariate Cox-Proportional Hazard Model (CPHM). In Kaplan-Meier analysis 124 patients (29.4%) reached the end-point. In multivariate CPHM, the only significant predictors of mortality were sCysC (p<0.00001, risk ratio: 1.529, CI: 1.29-1.80) and age (p=0.039, risk ratio: 1.019, CI: 1.001-1.037). When replacing sCysC with sCrea, the only significant predictor of mortality was sCrea (p=0.0026; risk ratio 1.20; CI: 1.06-1.36). Increased levels of sCysC can be considered a useful biomarker of cardiovascular mortality in cardiac-surgery patients.

Expression of cystatin C in the female reproductive tract and its effect on human sperm capacitation

BACKGROUND

Cystatin C (CST3), a cysteine protease inhibitor in seminal plasma, is expressed in animal uteri. However, its expression in the human female reproductive tract and its effect on human sperm capacitation are unclear.

METHODS

The cellular localization of CST3 was observed using immunohistochemistry. The binding of CST3 to sperm was examined using immunocytochemistry. Sperm motility parameters were analyzed using computer-assisted sperm analysis. Sperm capacitation was evaluated by analyzing cholesterol content, protein tyrosine phosphorylation levels, and the acrosome reaction.

RESULTS

Immunohistochemical staining demonstrated that CST3 is prominently expressed in the female reproductive tract, including the epithelial lining and cervix and endometrium fluids, particularly at times near ovulation. It can bind to human sperm on the post-acrosomal head region and the mid and principal piece of the tail. CST3 enhances sperm motility and inhibits the signal initiating sperm capacitation, i.e., efflux of cholesterol from the sperm plasma membrane and a late sperm capacitation event, i.e., the increase in the sperm protein tyrosine phosphorylation. The suppressive trend on sperm acrosome reaction further supports CST3's ability to inhibit sperm capacitation.

CONCLUSIONS

These findings suggest that cervical CST3 may prevent precocious capacitation and acrosome reaction, thus preserving sperm fertilizing ability before it reaches the fallopian tube. Additionally, CST3 may help sperm enter the upper reproductive tract by enhancing sperm motility.

Differential redox sensitivity of cathepsin B and L holds the key to autophagy-apoptosis interplay after Thioredoxin reductase inhibition in nutritionally stressed SH-SY5Y cells

Reactive oxygen species (ROS) are essential for induction of protective autophagy, however unexpected rise in cellular ROS levels overpowers the cellular defense and therefore promotes the programmed apoptotic cell death. We recently reported that inhibition of thioredoxin reductase (TrxR) in starving SH-SY5Y cells interrupted autophagy flux by induction of lysosomal deficiency and promoted apoptosis. (Free Radic Biol Med. 2016: 101:53-70). Here, we aimed to elucidate the underlying mechanisms during autophagy-apoptosis interplay, and focused on regulation of cathepsin B (CTSB) and L (CTSL), the pro-apoptotic and pro-autophagy cathepsins respectively. Inhibition of TrxR by Auranofin, caused lysosomal membrane permeabilization (LMP) that was associated with a significant upregulation of CTSB activity, despite no significant changes in CTSB protein level. Conversely, a significant rise in CTSL protein levels was observed without any apparent change in CTSL activity. Using thiol-trapping techniques to examine the differential sensitivity of cathepsins to oxidative stress, we discovered that Auranofin-mediated oxidative stress interferes with CTSL processing and thereby interrupts its pro-autophagy function. No evidence of CTSB susceptibility to oxidative stress was observed. Our data suggest that cellular fate in these conditions is mediated by two concurrent systems: while oxidative stress prevents the protective autophagy by inhibition of CTSL processing, concomitantly, apoptosis is induced by increasing lysosomal membrane permeability and leakage of CTSB into cytoplasm. Inhibition of CTSB in these conditions inhibited apoptosis and increased cell viability. To our knowledge this is the first report uncovering the impact of redox environment on autophagy-apoptosis interplay in neuronal cells.

Epithelial proteome profiling suggests the essential role of interferon-inducible proteins in patients with allergic rhinitis

BACKGROUND

Seasonal allergic rhinitis (SAR) caused by intermittent exposure to seasonal pollen causes itching, nasal congestion, and repeated sneezing, with profound effects on quality of life, work productivity, and school performance. Although both the genotype and environmental factors can contribute to the immunologic basis of allergic reactions, the molecular underpinnings associated with the pathogenesis of allergic rhinitis are not entirely clear.

METHODS

To address these questions, nasal epithelial brushings were collected from 29 patients with SAR and 31 control subjects during and after the pollen season. We then implemented an orbitrap-based, bottom-up, label-free quantitative proteomics approach, followed by multivariate analyses to identify differentially abundant (DA) proteins among the 4 sample groups.

RESULTS

We identified a total of 133 DA proteins for which the most significantly overrepresented functional category was found to be interferon 1 signaling. Two proteins, cystatin 1 and myeloblastin, the former of which protects against protease activity of allergens and the latter with a role in epithelial barrier function, were DA in patients with SAR and control subjects, irrespective of season. Moreover, interferon-inducible protein with tetratricopeptide repeats 1, cystatin 1, and interferon-inducible protein with tetratricopeptide repeats 3 were found to be differentially regulated between patients with SAR and control subjects, with inverse abundance dynamics during the transition from fall to spring.

CONCLUSION

We identified type 1 interferon-regulated proteins as biomarkers in patients with SAR, potentially playing an important role in its pathogenesis. Moreover, when compared with patients with SAR, healthy subjects exhibit an antagonistic proteomic response across seasons, which might prove to be a therapeutic target for disease prevention.

Effect of large weight reductions on measured and estimated kidney function

BACKGROUND

When patients experience large weight loss, muscle mass may be affected followed by changes in plasma creatinine (pCr). The MDRD and CKD-EPI equations for estimated GFR (eGFR) include pCr. We hypothesised that a large weight loss reduces muscle mass and pCr causing increase in eGFR (creatinine-based equations), whereas measured GFR (mGFR) and cystatin C-based eGFR would be unaffected if adjusted for body surface area.

METHODS

Prospective, intervention study including 19 patients. All attended a baseline visit before gastric bypass surgery followed by a visit six months post-surgery. mGFR was assessed during four hours plasma 51Cr-EDTA clearance. GFR was estimated by four equations (MDRD, CKD-EPI-pCr, CKD-EPI-cysC and CKD-EPI-pCr-cysC). DXA-scans were performed at baseline and six months post-surgery to measure changes in lean limb mass, as a surrogate for muscle mass.

RESULTS

Patients were (mean ± SD) 40.0 ± 9.3 years, 14 (74%) were female and 5 (26%) had type 2 diabetes, baseline weight was 128 ± 19 kg, body mass index 41 ± 6 kg/m2 and absolute mGFR 122 ± 24 ml/min. Six months post-surgery weight loss was 27 (95% CI: 23; 30) kg, mGFR decreased by 9 (-17; -2) from 122 ± 24 to 113 ± 21 ml/min (p = 0.024), but corrected for current body surface area (BSA) mGFR was unchanged by 2 (-5; 9) ml/min/1.73 m2 (p = 0.52). CKD-EPI-pCr increased by 12 (6; 17) and MDRD by 13 (8; 18) (p < 0.001 for both), while CKD-EPI-cysC was unchanged by 2 (-8; 4) ml/min/1.73 m2 (p = 0.51). Lean limb mass was reduced by 3.5 (-4.4;-2.6; p < 0.001) kg and change in lean limb mass correlated with change in plasma creatinine (R 2 = 0.28, p = 0.032).

CONCLUSIONS

Major weight reductions are associated with a reduction in absolute mGFR, which may reflect resolution of glomerular hyperfiltration, while mGFR adjusted for body surface area was unchanged. Estimates of GFR based on creatinine overestimate renal function likely due to changes in muscle mass, whereas cystatin C based estimates are unaffected.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT02138565 . Date of registration: March 24, 2014.

Cystatin C in aging and in Alzheimer's disease

Under normal conditions, the function of catalytically active proteases is regulated, in part, by their endogenous inhibitors, and any change in the synthesis and/or function of a protease or its endogenous inhibitors may result in inappropriate protease activity. Altered proteolysis as a result of an imbalance between active proteases and their endogenous inhibitors can occur during normal aging, and such changes have also been associated with multiple neuronal diseases, including Amyotrophic Lateral Sclerosis (ALS), rare heritable neurodegenerative disorders, ischemia, some forms of epilepsy, and Alzheimer's disease (AD). One of the most extensively studied endogenous inhibitor is the cysteine-protease inhibitor cystatin C (CysC). Changes in the expression and secretion of CysC in the brain have been described in various neurological disorders and in animal models of neurodegeneration, underscoring a role for CysC in these conditions. In the brain, multiple in vitro and in vivo findings have demonstrated that CysC plays protective roles via pathways that depend upon the inhibition of endosomal-lysosomal pathway cysteine proteases, such as cathepsin B (Cat B), via the induction of cellular autophagy, via the induction of cell proliferation, or via the inhibition of amyloid-β (Aβ) aggregation. We review the data demonstrating the protective roles of CysC under conditions of neuronal challenge and the protective pathways induced by CysC under various conditions. Beyond highlighting the essential role that balanced proteolytic activity plays in supporting normal brain aging, these findings suggest that CysC is a therapeutic candidate that can potentially prevent brain damage and neurodegeneration.

Characteristics of C-terminal, β-amyloid peptide binding fragment of neuroprotective protease inhibitor, cystatin C

Cystatin C originally identified as a cysteine proteases inhibitor has a broad spectrum of biological roles ranging from inhibition of extracellular cysteine protease activities, bone resorption, and modulation of inflammatory responses to stimulation of fibroblasts proliferation. There is an increasing number of evidence to suggest that human cystatin C (hCC) might play a protective role in the pathophysiology of sporadic Alzheimer's disease. In vivo and in vitro results well documented the association of hCC with Aβ and the hCC-induced inhibition of Aβ fibril formation. In our earlier work, using a combination of selective proteolytic methods and MS spectroscopy, C-terminal fragment hCC(101-117) was identified as the Aβ-binding region. The fragment of Aβ peptide responsible for the complex formation with hCC was found in the middle, highly hydrophobic part, Aβ(17-24). Structures and affinities of both Aβ and hCC binding sites were characterized by the enzyme-linked immunosorbent assay-like assay, by surface plasmon resonance, and by nano-ESI-FTICR MS of the hCC-Aβ-binding peptide complexes. In the in vitro inhibition studies, the binding cystatin sequence, hCC(101-117), revealed the highest relative inhibitory effect toward Aβ-fibril formation. Herein, we present further studies on molecular details of the hCC-Aβ complex. With Ala substitution, affinity experiments, and enzyme-linked immunosorbent assay-like assays for the Aβ-binding fragment, hCC(101-117), and its variants, the importance of individual amino acid residues for the protein interaction was evaluated. The results were analyzed using hCC(101-117) nuclear magnetic resonance structural data with molecular dynamics calculations and molecular modeling of the complexes. The results point to conformational requirements and special importance of some amino acid residues for the protein interaction. The obtained results might be helpful for the design of low molecular compounds modulating the biological role of both proteins. Copyright © 2016 John Wiley & Sons, Ltd.

Cystatin C Shifts APP Processing from Amyloid-β Production towards Non-Amyloidgenic Pathway in Brain Endothelial Cells

Amyloid-β (Aβ), the major component of neuritic plaques in Alzheimer's disease (AD), is derived from sequential proteolytic cleavage of amyloid protein precursor (APP) by secretases. In this study, we found that cystatin C (CysC), a natural cysteine protease inhibitor, is able to reduce Aβ40 secretion in human brain microvascular endothelial cells (HBMEC). The CysC-induced Aβ40 reduction was caused by degradation of β-secretase BACE1 through the ubiquitin/proteasome pathway. In contrast, we found that CysC promoted secretion of soluble APPα indicating the activated non-amyloidogenic processing of APP in HBMEC. Further results revealed that α-secretase ADAM10, which was transcriptionally upregulated in response to CysC, was required for the CysC-induced sAPPα secretion. Knockdown of SIRT1 abolished CysC-triggered ADAM10 upregulation and sAPPα production. Taken together, our results demonstrated that exogenously applied CysC can direct amyloidogenic APP processing to non-amyloidgenic pathway in brain endothelial cells, mediated by proteasomal degradation of BACE1 and SIRT1-mediated ADAM10 upregulation. Our study unveils previously unrecognized protective role of CysC in APP processing.

Cystatin C as a predictor factor in patients with renal cell carcinoma treated by everolimus

BACKGROUND

We evaluated the influence of serum cystatin C (CysC) with respect to other glomerular filtration rate (GFR) markers on the treatment effect of everolimus in a phase II study in patients with metastatic renal cell carcinoma (mRCC).

MATERIALS AND METHODS

Outcomes were from the study's primary analysis. GFR was calculated according to CKD-EPI-sCr equation, CKD-EPI-CysC equation and CKD-EPI-sCr-CysC equation, Modification of Diet in Renal Disease (MDRD) equation and Cockcroft-Gault (CG) equation, serum levels of creatinine (sCr) and CysC before the treatment.

RESULTS

We observed in 56 patients analysed patients high correlation (R Spearman from ±0.69 to ±1.00; P < 0.0001) between CysC level and GFR markers: sCr, CKD-EPI-sCr, CKD-EPI-CysC, CKD-EPI-sCr-CysC, MDRD, GFR (CG) before everolimus therapy. We observed that the adverse independent predictors for everolimus therapy were increased CysC level [HR: 2.85 (95 % CI 1.34-6.05), P = 0.0065], histologic grade G1/2 [HR: 3.38 (95 % CI 1.59-7.20), P = 0.0016] and increased LDH level [HR: 5.59 (95 % CI 2.52-12.40), P < 0.0001]. Worse OS was seen in multivariate analysis in patients with increased cystatin C level before treatment [HR: 2.60 (1.03-2.60), P = 0.0428], increased corrected calcium level [HR: 2.78 (95 % CI 1.03-7.54), P = 0.0441] and increased LDH level before treatment [HR: 2.34 (95 % CI 1.11-4.97), P = 0.0262].

CONCLUSION

Increased serum CysC level in contrast to other studied GFR markers had predictive significance in patients with mRCC.

Evidence of Alternative Cystatin C Signal Sequence Cleavage Which Is Influenced by the A25T Polymorphism

Cystatin C (Cys C) is a small, potent, cysteine protease inhibitor. An Ala25Thr (A25T) polymorphism in Cys C has been associated with both macular degeneration and late-onset Alzheimer's disease. Previously, studies have suggested that this polymorphism may compromise the secretion of Cys C. Interestingly, we found that untagged A25T, A25T tagged C-terminally with FLAG, or A25T FLAG followed by green fluorescent protein (GFP), were all secreted as efficiently from immortalized human cells as their wild-type (WT) counterparts (e.g., 112%, 100%, and 88% of WT levels from HEK-293T cells, respectively). Supporting these observations, WT and A25T Cys C variants also showed similar intracellular steady state levels. Furthermore, A25T Cys C did not activate the unfolded protein response and followed the same canonical endoplasmic reticulum (ER)-Golgi trafficking pathway as WT Cys C. WT Cys C has been shown to undergo signal sequence cleavage between residues Gly26 and Ser27. While the A25T polymorphism did not affect Cys C secretion, we hypothesized that it may alter where the Cys C signal sequence is preferentially cleaved. Under normal conditions, WT and A25T Cys C have the same signal sequence cleavage site after Gly26 (referred to as 'site 2' cleavage). However, in particular circumstances when the residues around site 2 are modified (such as by the presence of an N-terminal FLAG tag immediately after Gly26, or by a Gly26Lys (G26K) mutation), A25T has a significantly higher likelihood than WT Cys C of alternative signal sequence cleavage after Ala20 ('site 1') or even earlier in the Cys C sequence. Overall, our results indicate that the A25T polymorphism does not cause a significant reduction in Cys C secretion, but instead predisposes the protein to be cleaved at an alternative signal sequence cleavage site if site 2 is hindered. Additional N-terminal amino acids resulting from alternative signal sequence cleavage may, in turn, affect the protease inhibition function of Cys C.

Human kidney proximal tubule cells are vulnerable to the effects of Rauwolfia serpentina

Rauwolfia serpentina (or Snake root plant) is a botanical dietary supplement marketed in the USA for maintaining blood pressure. Very few studies have addressed the safety of this herb, despite its wide availability to consumers. Its reported pleiotropic effects underscore the necessity for evaluating its safety. We used a human kidney cell line to investigate the possible negative effects of R. serpentina on the renal system in vitro, with a specific focus on the renal proximal tubules. We evaluated cellular and mitochondrial toxicity, along with a variety of other kidney-specific toxicology biomarkers. We found that R. serpentina was capable of producing highly detrimental effects in our in vitro renal cell system. These results suggest more studies are needed to investigate the safety of this dietary supplement in both kidney and other target organ systems.

Development of a Competitive Cystatin C-Specific Bioassay Suitable for Repetitive Measurements

Human cystatin C (hCC), a cysteine protease inhibitor, has been proposed as a diagnostic marker because its serum levels correlate with certain cardiovascular and kidney diseases. All current hCC assays are based on ex vivo detection. Here we describe the generation and evaluation of antibodies that allow the repetitive binding and release of hCC and hCC-fusion proteins, a prerequisite for long-term measurement, which is required for compatibility with implantable biochip devices and for the development of innovative antibody-based assays suitable for continuous in vivo and in vitro monitoring. Recombinant hCC and hCC-fusion proteins were produced in Escherichia coli and HEK293T cells and were used to generate antibodies by hybridoma technology. After screening by indirect and sandwich ELISAs, 12 monoclonal hybridoma cell lines producing hCC-specific monoclonal antibodies were identified. To determine their hCC association and dissociation properties, the antibodies were analysed by surface plasmon resonance spectroscopy, revealing three with the desired fast binding and moderate-to-fast release characteristics. The analysis of binding and dissociation in the presence of hCC and hCC-fusion proteins using fluorescence-based replacement assays showed that mAb CyDI-4 was the most suitable for further analysis. The results showed that repetitive replacement on mAb CyDI-4 was possible and that most of the change in signal intensity occurred after 20-30 min. Furthermore, the suitability of mAb CyDI-4 for serum hCC measurement was confirmed by a fluorescence-based replacement assay using serially-diluted reference serum from the Institute for Reference Materials and Measurements (ERM-DA471/IFCC). Our results suggest that the assay covers the physiological and pathological ranges of hCC.