Cystatins--inhibitors of cysteine proteinases

The Levels of Leptin, Cystatin C, Neuropilin-1 and Tau Protein in Relation to Dietary Habits in Patients with Alzheimer's Disease

Alzheimer's disease (AD) is the most common form of dementia in older people. Its prevalence is expected to increase, and therefore it poses a serious challenge to the healthcare system. The aim of the study was to assess the concentration of leptin, cystatin C, neuropilin-1 and tau protein, as well as the influence of dietary habits on these parameters, in a group of AD patients (n = 110) compared to 60 healthy people (n = 60). It has been shown that AD patients, compared to healthy people, are characterized by significantly higher median concentrations of leptin (9.97 vs. 3.08), cystatin c (1.53 vs. 0.56) and tau protein (8.46 vs. 4.19), but significantly lower median neuropilin-1 (69.94 vs. 167.28). Multiple regression analyses showed that leptin levels could be explained by dietary habits in 27%, cystatin C in 51%, neuropilin-1 in 41% and tau protein in 25% of cases. Modification of eating habits may contribute to improving the values of the discussed parameters.

Identification, expression profiling, and functional characterization of cystatin C from big-belly seahorse (Hippocampus abdominalis)

Cystatins are natural inhibitors of lysosomal cysteine proteases, including cathepsins B, L, H, and S. Cystatin C (CSTC) is a member of the type 2 cystatin family and is an essential biomarker in the prognosis of several diseases. Emerging evidence suggests the immune regulatory roles of CSTC in antigen presentation, the release of different inflammatory mediators, and apoptosis in various pathophysiologies. In this study, the 390-bp cystatin C (HaCSTC) cDNA from big-belly seahorse (Hippocampus abdominalis) was cloned and characterized by screening the pre-established cDNA library. Based on similarities in sequence, HaCSTC is a homolog of the teleost type 2 cystatin family with putative catalytic cystatin domains, signal peptides, and disulfide bonds. HaCSTC transcripts were ubiquitously expressed in all tested big-belly seahorse tissues, with the highest expression in ovaries. Immune challenge with lipopolysaccharides, polyinosinic:polycytidylic acid, Edwardsiella tarda, and Streptococcus iniae caused significant upregulation in HaCSTC transcript levels. Using a pMAL-c5X expression vector, the 14.29-kDa protein of recombinant HaCSTC (rHaCSTC) was expressed in Escherichia coli BL21 (DE3), and its protease inhibitory activity against papain cysteine protease was determined with the aid of a protease substrate. Papain was competitively blocked by rHaCSTC in a dose-dependent manner. In response to viral hemorrhagic septicemia virus (VHSV) infection, HaCSTC overexpression strongly decreased the expression of VHSV transcripts, pro-inflammatory cytokines, and pro-apoptotic genes; while increasing the expression of anti-apoptotic genes in fathead minnow (FHM) cells. Furthermore, HaCSTC overexpression protected VHSV-infected FHM cells against VHSV-induced apoptosis and increased cell viability. Our findings imply the profound role of HaCSTC against pathogen infections by modulating fish immune responses.

Salivary Protein and Electrolyte Profiles during Primary Teeth Eruption: A Cross-Sectional Study

This study aimed to assess the qualitative changes in the saliva during the process of primary teeth eruption. This cross-sectional study was conducted on 147 children from 2 to 48 months, of which 49 were in group A (no erupted primary teeth), 53 were in group B (at least one active erupting primary tooth), and 45 were in group C (eruption of all 20 primary teeth was completed). Salivary proteins were evaluated by sodium dodecyl sulfate electrophoresis with polyacrylamide gel, while the concentrations of salivary sodium, potassium, chloride, and calcium ions were evaluated by ion selective electrodes. The data were analyzed using ANOVA and Bonferroni tests (alpha = 0.05). The concentration of proteins with molecular weights of 20-30 KDa was significantly higher in group A, and it gradually decreased with age. The concentration of proteins with molecular weights of 50-60 KDa in group B was significantly lower than those of groups A and C. The calcium ion concentration in group A was significantly higher than that of the other groups. The concentration of potassium ions was minimal in group C. The proteins and electrolyte profiles of the subjects' saliva changed in the process of primary tooth eruption. The highest concentrations of proteins such as statherin, histatin, P-B peptide, and cystatin and the lowest concentrations of proteins such as amylase were present in group B.

Serum cystatin C and mild cognitive impairment: The mediating role of glucose homeostasis

Background

This study explored the mediating role of glucose homeostasis indicators in the relationship between serum cystatin C and mild cognitive impairment (MCI).

Methods

The present study used a cross-sectional design and included 514 participants aged ≥50 years in Beijing, China. The Mini-Mental State Examination was used to assess cognitive function. Serum cystatin C and a comprehensive set of glucose homeostasis indicators were detected, including fasting blood glucose (FBG), glycosylated albumin percentage (GAP), glycated hemoglobin (HbAlc), insulin, and homeostatic model assessment of insulin resistance (HOMA-IR), and beta cell function (HOMA-β). Generalized linear models were used to investigate the associations among cystatin C, glucose homeostasis indicators, and cognitive function. Mediation analysis was conducted to explore potential mediator variables.

Results

In this study of 514 participants, 76 (14.8%) had MCI. Those with cystatin C levels ≥1.09 mg/L had a 1.98-fold higher risk of MCI than those with levels <1.09 mg/L (95% CI, 1.05–3.69). FBG, GAP, and HbA1c increased the risk of MCI, while HOMA-β decreased the risk. Notably, the associations between MCI risk and cystatin C or glucose homeostasis were only founded in diabetes patients. Serum cystatin C was found to be positively associated with HOMA-β (beta (95% CI): 0.20 [0.06, 0.34]), HOMA-IR (0.23 [0.09, 0.36]), and insulin (0.22 [0.09, 0.34]) levels. Moreover, HOMA-β was identified as playing a negative mediating role (proportion mediated: −16%) in the relationship between cystatin C and MCI.

Conclusion

Elevated levels of cystatin C are associated with an increased risk of MCI. The glucose homeostasis indicator, HOMA-β, plays a negative mediating role in the relationship between cystatin C and MCI risk.

Does cystatin C have an immunomodulatory role in Hashimoto's thyroiditis?

OBJECTIVES

Studies which report cystatin C's (Cys-C) role in immunological disorders are increasing. However, data in the pediatric age group is limited. In this study, we aimed to evaluate the association between serum Cys-C levels and thyroid autoantibodies in children and adolescents diagnosed with euthyroid Hashimoto's thyroiditis.

METHODS

The patient group was included 50 participants aged between 3 and 18 years, and the control group included 50 healthy children matched for age, gender, and body mass index. Patients with hypothyroidism or taking any medication were not included in the study. Fasting glucose, liver enzymes, urea, creatinine, lipid profile, Cys-C, free thyroxine (fT4), free triiodothyronine (fT3), thyroid-stimulating hormone (TSH), thyroid peroxidase antibody (TPOAb), and thyroglobulin antibodies (TGAb) levels were recorded in all subjects.

RESULTS

The mean age of control group was 13.5 ± 2.5 years, and the mean age of Hashimoto thyroiditis (HT) group was 14.2 ± 2.7 years, no statistically significant differences existed (p=0.205). Cys-C values were significantly higher in the HT group than in the control group (p=0.041). When all cases were evaluated, Cys-C levels were statistically positively correlated with fT3, TPOAb, and TGAb values (p<0.001, p=0.029, p=0.013 respectively).

CONCLUSIONS

Based on the results of our study, Cys-C levels in children and adolescents with euthyroid Hashimoto thyroiditis were statistically higher than their healthy peers. In conclusion, it can be said that Cys-C may be a factor in the etiopathogenesis of autoimmune thyroiditis, and even small changes in TSH values affect Cys-C levels.

Detection of urinary cystatin-c in IUGR neonates by immunoblot SDS-PAGE

BACKGROUND

it is known that intrauterine growth retardation (IUGR) represents a risk factor for the deterioration of renal function as it can adversely impact on the number of nephrons developed in the kidney during nephrogenesis. An interesting molecule is the Cystatin-C (cyst-C): it is considered to have the potency to detect both glomerular and proximal renal injury. Recently, using a quantitative EIA cyst-C detection kit, we found increased levels of cyst-C in the urine of neonates with IUGR. Since cyst-C molecules can be present in both monomer and/or polymer forms, the purpose of this study is to investigate in which forms this molecule is present in the urine of IUGR neonates by Immunoblot SDS-PAGE in order to verify if the presence or absence of a particular type of cyst-C conformation can give more information about the renal functioning.

METHODS

urine samples were collected from 64 neonates with IUGR, and 86 healthy controls defined as appropriate for gestational age (AGA). Urinary cyst-C was investigated by the Immunoblot SDS-PAGE.

RESULTS

in all urine samples, SDS-PAGE analysis showed a reactivity of the IgG anti cyst-C with a complex of about 70 kDa. The monomer form at 13 KDa appeared in 78% of IUGR neonates and in 12% of AGA neonates.

CONCLUSIONS

this study revealed the presence of monomer cyst-C in the urine of IUGR neonates, and suggests an insufficient and/or non-compensatory reabsorption by tubular cells. Monomeric cyst-C can be considered an early biochemical marker to identify and to select IUGR neonates who need to be monitored for risk of renal injury.

Cystatin SN is a potent upstream initiator of epithelial-derived type 2 inflammation in chronic rhinosinusitis

BACKGROUND

Cystatin SN (CST1) and cystatin SA (CST2) are cysteine protease inhibitors that protect against allergen, viral, and bacterial proteases. Cystatins are overexpressed in the setting of allergic rhinitis and chronic rhinosinusitis with nasal polyps (CRSwNP); however, their role in promoting type 2 inflammation remains poorly characterized.

OBJECTIVE

The purpose of this study was to use integrated poly-omics and a murine exposure model to explore the link between cystatin overexpression in CRSwNP and type 2 inflammation.

METHODS

In this institutional review board- and institutional animal care and use committee-approved study, we compared tissue, exosome, and mucus CST1 and CST2 between CRSwNP and controls (n = 10 per group) by using matched whole exome sequencing, transcriptomic, proteomic, posttranslational modification, histologic, functional, and bioinformatic analyses. C57/BL6 mice were dosed with 3.9 μg/mL of CST1 or PBS intranasally for 5 to 18 days in the presence or absence of epithelial ABCB1a knockdown. Inflammatory cytokines were quantified by using Quansys multiplex assays or ELISAs.

RESULTS

Of the 1305 proteins quantified, CST1 and CST2 were among the most overexpressed protease inhibitors in tissue, exosome, and mucus samples; they were localized to the epithelial layer. Multiple posttranslational modifications were identified in the polyp tissue. Exosomal CST1 and CST2 were strongly and significantly correlated with eosinophils and Lund-Mackay scores. Murine type 2 cytokine secretion and TH2 cell infiltration increased in a time-dependent manner following CST1 exposure and was abrogated by epithelial knockdown of ABCB1a, a regulator of epithelial cytokine secretion.

CONCLUSION

CST1 is a potent upstream initiator of epithelial-derived type 2 inflammation in CRSwNP. Therapeutic strategies targeting CST activity and its associated posttranslational modifications deserve further interrogation.

Diagnostic circulating biomarkers to detect vision-threatening diabetic retinopathy: Potential screening tool of the future?

With the increasing prevalence of diabetes in developing and developed countries, the socio-economic burden of diabetic retinopathy (DR), the leading complication of diabetes, is growing. Diabetic retinopathy (DR) is currently one of the leading causes of blindness in working-age adults worldwide. Robust methodologies exist to detect and monitor DR; however, these rely on specialist imaging techniques and qualified practitioners. This makes detecting and monitoring DR expensive and time-consuming, which is particularly problematic in developing countries where many patients will be remote and have little contact with specialist medical centres. Diabetic retinopathy (DR) is largely asymptomatic until late in the pathology. Therefore, early identification and stratification of vision-threatening DR (VTDR) is highly desirable and will ameliorate the global impact of this disease. A simple, reliable and more cost-effective test would greatly assist in decreasing the burden of DR around the world. Here, we evaluate and review data on circulating protein biomarkers, which have been verified in the context of DR. We also discuss the challenges and developments necessary to translate these promising data into clinically useful assays, to detect VTDR, and their potential integration into simple point-of-care testing devices.

Ovocystatin Induced Changes in Expression of Alzheimer's Disease Relevant Proteins in APP/PS1 Transgenic Mice

Background: Ovocystatin is marked by structural and biological similarities to human cystatin C, which plays an important role in the course of neurodegenerative diseases. Recently, it has been shown that ovocystatin might prevent aging-related cognitive impairment in rats and reduce memory decline in an APP/PS1 mice model. Thus, this study aimed to assess the effect of ovocystatin on histopathological changes in APP/PS1 mice. Materials and methods: Ovocystatin was administered intraperitoneally for four weeks (40 μg/mouse) to 35-weeks-old transgenic (AD, n = 14) and wild type (NCAR, n = 15) mice (stock B6C3-Tg(APPswe, PSEN1dE9)85Dbo/Mmjax). A histopathological evaluation comprised antibodies directed against β-amyloid (1:400, SIG-39320-1000, Covance) and Tau (1:4000, AHB0042, Invitrogen). Three regions of the hippocampus— the dentate gyrus (DG) and the cornu ammonis (CA1 and CA3)—were analyzed by immunohistochemistry in each animal. All differences are expressed as percentage relative to the control group. Results: The main results showed that the percentage of immunoreactive area of β-amyloid, tau protein deposits in APP/PS1+ovCYS was decreased in DG, CA1, and CA3 regions compared with the APP/PS1 control, respectively (p < 0.05). Conclusions: Ovocystatin caused significant changes in the expression pattern of all investigated proteins in hippocampal tissues both in APP/PS1 and NCAR mice.

Comparative evaluation of cystatin C and neutrophil gelatinase-associated lipocalin in patients with thalassemia major versus thalassemia intermedia

Kidney disorders are long-term complications in thalassemia patients, especially with the high life expectancy of these patients. Proper evaluation of kidney impairment in β-thalassemia patients can be difficult due to higher intake of iron chelators, resulting in renal impairment. Early biomarkers of renal disease are used for the diagnosis of tubular and glomerular abnormalities. The current study was conducted on 88 individuals, 25 healthy people and 63 β-thalassemia patients. Circulating levels of urea, creatinine, cystatin C and neutrophil gelatinase-associated lipocalin were measured in all groups. Compared to healthy control, patients with thalassemia major and intermedia showed a significant increase in both cystatin C and NGAL levels, with no effects on creatinine levels. Furthermore, urea levels were markedly higher in patients with thalassemia major compared to control. As early renal dysfunction markers, cystatin C and NGAL should be routinely evaluated in thalassemia patients major and intermedia.

Multiomic Analyses of Dopaminergic Neurons Isolated from Human Substantia Nigra in Parkinson's Disease: A Descriptive and Exploratory Study

Dopaminergic neurons (DA) of the substantia nigra pars compacta (SNpc) selectively and progressively degenerate in Parkinson’s disease (PD). Until now, molecular analyses of DA in PD have been limited to genomic or transcriptomic approaches, whereas, to the best of our knowledge, no proteomic or combined multiomic study examining the protein profile of these neurons is currently available. In this exploratory study, we used laser capture microdissection to extract regions from DA in 10 human SNpc obtained at autopsy in PD patients and control subjects. Extracted RNA and proteins were identified by RNA sequencing and nanoliquid chromatography–mass spectrometry, respectively, and the differential expression between PD and control group was assessed. Qualitative analyses confirmed that the microdissection protocol preserves the integrity of our samples and offers access to specific molecular pathways. This multiomic analysis highlighted differential expression of 52 genes and 33 proteins, including molecules of interest already known to be dysregulated in PD, such as LRP2, PNMT, CXCR4, MAOA and CBLN1 genes, or the Aldehyde dehydrogenase 1 protein. On the other hand, despite the same samples were used for both analyses, correlation between RNA and protein expression was low, as exemplified by the CST3 gene encoding for the cystatin C protein. This is the first exploratory study analyzing both gene and protein expression of laser-dissected neuronal parts from SNpc in PD. Data are available via ProteomeXchange with identifier PXD024748 and via GEO with identifier GSE 169755.

Extracellular protein components of amyloid plaques and their roles in Alzheimer's disease pathology

Alzheimer's disease (AD) is pathologically defined by the presence of fibrillar amyloid β (Aβ) peptide in extracellular senile plaques and tau filaments in intracellular neurofibrillary tangles. Extensive research has focused on understanding the assembly mechanisms and neurotoxic effects of Aβ during the last decades but still we only have a brief understanding of the disease associated biological processes. This review highlights the many other constituents that, beside Aβ, are accumulated in the plaques, with the focus on extracellular proteins. All living organisms rely on a delicate network of protein functionality. Deposition of significant amounts of certain proteins in insoluble inclusions will unquestionably lead to disturbances in the network, which may contribute to AD and copathology. This paper provide a comprehensive overview of extracellular proteins that have been shown to interact with Aβ and a discussion of their potential roles in AD pathology. Methods that can expand the knowledge about how the proteins are incorporated in plaques are described. Top-down methods to analyze post-mortem tissue and bottom-up approaches with the potential to provide molecular insights on the organization of plaque-like particles are compared. Finally, a network analysis of Aβ-interacting partners with enriched functional and structural key words is presented.

Study of the ultrastructure of Enterococcus faecalis and Streptococcus mutans incubated with salivary antimicrobial peptides

OBJECTIVES

Enterococcus faecalis has been associated with root canal infections, while Streptococcus mutans has a central role in the etiology of dental caries. One of the main reasons of endodontic failure has been associated to the presence of E. faecalis and the formation of biofilms. S. mutans inhabits the oral cavity, specifically the dental plaque, which is a multispecies biofilm formed on the hard surfaces of the tooth. The biofilm formation is the main factor determining the pathogenicity of numerous bacteria. Natural antimicrobial peptides in the saliva protect against pathogenic bacteria and biofilms. The aim of this study was to assess the ultrastructural damage induced by salivary peptides in bacteria involved in biofilms has not been previously studied.

MATERIAL AND METHODS

Enterococcus faecalis and S. mutans incubated with cystatin C, chromogranin A, or histatin 5 were morphologically analyzed and counted. The ultrastructural damage was evaluated by transmission electron microscopy (TEM).

RESULTS

A decrease in bacterial numbers was observed after incubation with cystatin C, chromogranin A, or histatin 5, compared to the control group (P <  0.001). Ultrastructural damage in E. faecalis and S. mutans incubated with salivary peptides was found in the cell wall, plasma membrane with a decreased distance between the bilayers, a granular pattern in the cytoplasm, and pyknotic nucleoids.

CONCLUSIONS

This study demonstrated that salivary peptides exert antibacterial activity and induce morphological damage on E. faecalis and S. mutans. Knowledge on the ultrastructural damage inflicted by salivary antimicrobial peptides on two important bacteria causing dental caries and root canal infections could aid the design of new therapeutic approaches to facilitate the elimination of these bacteria.

Radiotherapy changes the salivary proteome in head and neck cancer patients: evaluation before, during, and after treatment

OBJECTIVES

Salivary glands are affected during radiotherapy in the head and neck region, leading to a reduction in salivary flow and changes its composition. Besides negatively affecting the oral soft tissues, this can also lead to dental impairment. Thus, we evaluated the effect of radiotherapy in the proteomic profile of the saliva in patients with head and neck cancer (HNC).

MATERIALS AND METHODS

HNC patients had their saliva collected before (BRT), during (2-5 weeks; DRT), and after (3-4 months; ART) radiotherapy. Saliva was also collected from healthy volunteers (control; C). Samples were processed for proteomic analysis.

RESULTS

In total, 1055 proteins were identified, among which 46 were common to all groups, while 86, 86, 286, and 395 were exclusively found in C, BRT, DRT, and ART, respectively. Remarkably, alpha-enolase was increased 35-fold DRT compared with BRT, while proline-rich proteins were decreased. ART there was a 16-fold increase in scaffold attachment factor-B1 and a 3-fold decrease in alpha-enolase and several cystatins. When compared with C, salivary proteins of BRT patients showed increases cystatin-C, lysozyme C, histatin-1, and proline-rich proteins CONCLUSION/CLINICAL REVELANCE: Both HNC and radiotherapy remarkably change the salivary protein composition. Altogether, our results, for the first time, suggest investigating alpha-enolase levels in saliva DRT in future studies as a possible biomarker and strategy to predict the efficiency of the treatment. Moreover, our data provide important insights for designing dental products that are more effective for these patients and contribute to a better understanding of the progressive changes in salivary proteins induced by radiotherapy. Graphical abstract.

Serum Cystatin C and Coronavirus Disease 2019: A Potential Inflammatory Biomarker in Predicting Critical Illness and Mortality for Adult Patients

This study aimed at determining the relationship between baseline cystatin C levels and coronavirus disease 2019 (COVID-19) and investigating the potential prognostic value of serum cystatin C in adult patients with COVID-19. 481 patients with COVID-19 were consecutively included in this study from January 2, 2020, and followed up to April 15, 2020. All clinical and laboratory data of COVID-19 patients with definite outcomes were reviewed. For every measure, COVID-19 patients were grouped into quartiles according to the baseline levels of serum cystatin C. The highest cystatin C level was significantly related to more severe inflammatory conditions, worse organ dysfunction, and worse outcomes among patients with COVID-19 (P values < 0.05). In the adjusted logistic regression analyses, the highest cystatin C level and ln-transformed cystatin C levels were independently associated with the risks of developing critically ill COVID-19 and all-cause death either in overall patients or in patients without chronic kidney disease (P values < 0.05). As a potential inflammatory marker, increasing baseline levels of serum cystatin C might independently predict adverse outcomes for COVID-19 patients. Serum cystatin C could be routinely monitored during hospitalization, which showed clinical importance in prognosticating for adult patients with COVID-19.

Structural Characterization of Covalently Stabilized Human Cystatin C Oligomers

Human cystatin C (HCC), a cysteine-protease inhibitor, exists as a folded monomer under physiological conditions but has the ability to self-assemble via domain swapping into multimeric states, including oligomers with a doughnut-like structure. The structure of the monomeric HCC has been solved by X-ray crystallography, and a covalently linked version of HCC (stab-1 HCC) is able to form stable oligomeric species containing 10-12 monomeric subunits. We have performed molecular modeling, and in conjunction with experimental parameters obtained from atomic force microscopy (AFM), transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS) measurements, we observe that the structures are essentially flat, with a height of about 2 nm, and the distance between the outer edge of the ring and the edge of the central cavity is ~5.1 nm. These dimensions correspond to the height and diameter of one stab-1 HCC subunit and we present a dodecamer model for stabilized cystatin C oligomers using molecular dynamics simulations and experimentally measured parameters. Given that oligomeric species in protein aggregation reactions are often transient and very highly heterogeneous, the structural information presented here on these isolated stab-1 HCC oligomers may be useful to further explore the physiological relevance of different structural species of cystatin C in relation to protein misfolding disease.

Transcriptomic profiling of microglia and astrocytes throughout aging

Background

Activation of microglia and astrocytes, a prominent hallmark of both aging and Alzheimer’s disease (AD), has been suggested to contribute to aging and AD progression, but the underlying cellular and molecular mechanisms are largely unknown.

Methods

We performed RNA-seq analyses on microglia and astrocytes freshly isolated from wild-type and APP-PS1 (AD) mouse brains at five time points to elucidate their age-related gene-expression profiles.

Results

Our results showed that from 4 months onward, a set of age-related genes in microglia and astrocytes exhibited consistent upregulation or downregulation (termed “age-up”/“age-down” genes) relative to their expression at the young-adult stage (2 months). And most age-up genes were more highly expressed in AD mice at the same time points. Bioinformatic analyses revealed that the age-up genes in microglia were associated with the inflammatory response, whereas these genes in astrocytes included widely recognized AD risk genes, genes associated with synaptic transmission or elimination, and peptidase-inhibitor genes.

Conclusions

Overall, our RNA-seq data provide a valuable resource for future investigations into the roles of microglia and astrocytes in aging- and amyloid-β-induced AD pathologies.

Cystatin C regulates major histocompatibility complex-II-peptide presentation and extracellular signal-regulated kinase-dependent polarizing cytokine production by bone marrow-derived dendritic cells

Cystatin C is a ubiquitously expressed cysteine protease inhibitor that protects cells from either improper hydrolysis by endogenous proteases or pathogen growth/virulence by exogenous proteases. Although commonly used as a serum biomarker for evaluating renal function, cystatin C is associated with many immunological disorders under various pathophysiological conditions. How cystatin C affects immune cells, especially dendritic cells (DCs), however, is far from clear. In this study, we found that pharmacological treatment with or genetic overexpression of cystatin C in bone marrow-derived DCs (BMDCs) reduced their capacity to stimulate CD4⁺ T-cell proliferation, despite increased antigen uptake. This reduced capacity corresponded with reduced major histocompatibility complex-II presentation owing to diminished levels of the chaperon H2-DM in BMDCs. Instead of promoting proliferation, cystatin C promoted skewing of T cells toward proinflammatory T-helper (Th)1/Th17 differentiation. This was mediated by augmented extracellular signal-regulated kinase 1/2 mitogen-activated protein kinase phosphorylation in BMDCs, leading to secretion of polarizing cytokines, which in turn led to the Th deviation. Collectively, our study explained the cellular and molecular basis of how this protease inhibitor can regulate immune responses, namely by affecting BMDCs and their cytokine pathway. Our results might open up an avenue for the development of therapeutic agents for the treatment of cystatin C-related immunological diseases.

Molecular characterization, expression and functional analysis of cystatin C in Japanese flounder (Paralichthys olivaceus)

Cystatins are natural tight-binding reversible inhibitors of cysteine proteases found in a wide arrange of organisms. Studies have shown that cystatins play important roles under both physiological and pathological conditions in mammals. However, much less is known about fish cystatins. In this study, we described the identification and analysis of the gene encoding cystatin C in Japanese flounder (Paralichthys olivaceus). This gene had a high homology with the sequence of cystatin C in many fish species and had a signal peptide and three conserved functional sites. The results of qRT-PCR showed that the gene was highly expressed in the liver. Lipopolysaccharide, peptidoglycan and polyinosinic-polycytidylic acid all increased its expression after stimulation. Functional analysis showed that the recombinant P. olivaceus cystatin C purified from Escherichia coli had cysteine protease inhibitory activity and could inhibit bacterial growth by binding to bacteria. Meanwhile, rPocystatin C could up-regulate the expression of cytokines tumor necrosis factor α and interleukin 10. These results indicated that cystatin C of P. olivaceus might be considered to have the similar immunomodulatory function to mammalian cystatin.

Combination of Cystatins 9 and C Modulates Serum Biomarkers Associated with Inflammation and Provides Prophylactic as Well as Long-Term Protection against Multidrug-Resistant Klebsiella pneumoniae

We have identified recombinant human cystatins 9 (rCST9) and C (rCSTC) as a combination immunotherapeutic treatment against multidrug-resistant (MDR) New Delhi metallo-β-lactamase-1 (NDM-1)-producing Klebsiella pneumoniae We evaluated the lasting protection of rCST9/rCSTC treatment against MDR NDM-1 K. pneumoniae pneumonia. Results showed that rCST9/rCSTC treatment modulated endogenous serum biomarkers, cystatins 9 and C and amyloid A, associated with poor patient outcomes and provided prophylactic and long-term protection in a murine model of pneumonia.

Proteomics of the acid-soluble fraction of whole and major gland saliva in burning mouth syndrome patients

OBJECTIVE

In the present study the salivary proteome of burning mouth syndrome patients and healthy subjects was characterized by a top-down proteomic approach and compared to highlight possible qualitative and quantitative differences that may give suggestions about the causes of this pathology which are still unknown.

MATERIALS AND METHODS

Resting and stimulated whole saliva, stimulated parotid and submandibular/sublingual saliva samples were collected from burning mouth syndrome patients (n = 16) and age- and gender-matched healthy subjects (n = 14). An equal volume of 0.2% trifluoroacetic acid was added to each sample immediately after collection and the supernatants were analysed by liquid chromatography coupled to electrospray-ionisation mass spectrometry. Proteins and peptides were quantified using a label-free approach measuring the extracted ion current peak areas of the main salivary proteins and peptides.

RESULTS

The quantitation of the main salivary proteins and peptides revealed a higher concentration of cystatin SN in resting saliva of burning mouth syndrome patients with respect to healthy controls and no other conspicuous changes.

CONCLUSIONS

The reported data showed that the salivary protein profile was not affected, in composition and relative abundance, by the burning mouth syndrome, except for the cystatin SN, a protein up-regulated in several pathological conditions, that might be considered potentially indicative of the disease.

Impact of fibrates on circulating cystatin C levels: a systematic review and meta-analysis of clinical trials

AIMS

To assess the effect of fibrates on circulating cystatin C levels.

MATERIAL AND METHODS

Clinical studies evaluating the effect of a fibrate on circulating cystatin C levels were searched in PubMed-Medline, SCOPUS, Web of Science, and Google Scholar databases. A random-effect model and generic inverse variance method were used for quantitative data synthesis, sensitivity analysis conducted using the leave-one-out method, and weighted random-effects meta-regression performed to evaluate potential confounders on cystatin C levels.

RESULTS

This meta-analysis of data from nine published studies (16 treatment arms) involved a total of 2195 subjects. In a single-arm analysis of clinical trials (without control group; eight studies comprising 14 treatment arms), fibrate therapy increased circulating cystatin C concentrations (WMD: 0.07 mg/dL, 95% CI: 0.04, 0.10, p < .001; I² = 82.66%). When the analysis was restricted to randomized controlled trials (four studies comprising six treatment arms), again elevation of circulating cystatin C levels was observed (WMD: 0.06 mg/L, 95% CI: 0.03, 0.09, p < .001; I² = 42.98%). Elevated cystatin C levels were only seen with fenofibrate and not with other fibrates.

CONCLUSIONS

The results suggest that fenofibrate treatment adversely affects cystatin C levels and might partially explain the limited efficacy of fenofibrate in reducing cardiovascular events. Key message Fenofibrate treatment adversely affects cystatin C levels and might partially explain the limited efficacy of fenofibrate in reducing cardiovascular events.

Cystatins 9 and C as a Novel Immunotherapy Treatment That Protects against Multidrug-Resistant New Delhi Metallo-Beta-Lactamase-1-Producing Klebsiella pneumoniae

Multidrug-resistant (MDR) bacterial pneumonia can induce dysregulated pulmonary and systemic inflammation leading to morbidity and mortality. Antibiotics to treat MDR pathogens do not function to modulate the extent and intensity of inflammation and can have serious side effects. Here we evaluate the efficacy of two human cysteine proteinase inhibitors, cystatin 9 (CST9) and cystatin C (CSTC), as a novel immunotherapeutic treatment to combat MDR New Delhi metallo-beta-lactamase-1 (NDM-1)-producing Klebsiella pneumoniae. Our results showed that mice infected intranasally (i.n.) with a 90% lethal dose (LD₉₀) challenge of NDM-1 K. pneumoniae and then treated with the combination of human recombinant CST9 (rCST9) and rCSTC (rCSTs; 50 pg of each i.n. at 1 h postinfection [p.i.] and/or 500 pg of each intraperitoneally [i.p.] at 3 days p.i.) had significantly improved survival compared to that of infected mice alone or infected mice treated with individual rCSTs (P < 0.05). Results showed that both of our optimal rCST treatment regimens modulated pulmonary and systemic proinflammatory cytokine secretion in the serum, lungs, liver, and spleen in infected mice (P < 0.05). Treatment also significantly decreased the bacterial burden (P < 0.05) while preserving lung integrity, with reduced inflammatory cell accumulation compared to that in infected mice. Further, rCST treatment regimens reduced lipid peroxidation and cell apoptosis in the lungs of infected mice. Additionally, in vitro studies showed that rCSTs (50 or 500 pg of each) directly decreased the viability of NDM-1 K. pneumoniae. In conclusion, the data showed that rCST9/rCSTC worked synergistically to modulate host inflammation against MDR NDM-1 K. pneumoniae pneumonia, which significantly improved survival. Therefore, rCST9/rCSTC is a promising therapeutic candidate for the treatment of bacterial pneumonia.

Revealing the Amylase Interactome in Whole Saliva Using Proteomic Approaches

Understanding proteins present in saliva and their function when isolated is not enough to describe their real role in the mouth. Due to protein-protein interactions, structural changes may occur in macromolecules leading to functional modulation or modification. Besides amylase's function in carbohydrate breakdown, amylase can delay proteolytic degradation of protein partners (e.g., histatin 1) when complexed. Due to its biochemical characteristics and high abundance in saliva, amylase probably interacts with several proteins acting as a biological carrier. This study focused on identifying interactions between amylase and other proteins found in whole saliva (WS) using proteomic approaches. Affinity chromatography was used, followed by gel electrophoresis methods, sodium dodecyl sulfate and native, tryptic in-solution and in-gel digestion, and mass spectrometry. We identified 66 proteins that interact with amylase in WS. Characterization of the identified proteins suggests that acidic (pI < 6.8) and low molecular weight (MW < 56 kDa) proteins have preference during amylase complex formation. Most of the identified proteins present biological functions related to host protection. A new protein-amylase network was constructed using the STRING database. Further studies are necessary to investigate individualities of the identified amylase interactors. These observations open avenues for more comprehensive studies on not yet fully characterized biological function of amylase.

Involvement of cystatin C in immunity and apoptosis

As an abundantly expressed cysteine protease inhibitor widely distributed in the organisms, cystatin C is involved in various physiological processes. Due to its relatively small molecular weight and easy detection, cystatin C is commonly used as a measure for glomerular filtration rate. In pathological conditions, however, growing evidences suggest that cystatin C is associated with various immune responses against either exogenous or endogenous antigens, which ultimately result in inflammatory autoimmune diseases or tumor development if not properly controlled. Thus the fluctuation of cystatin C levels might have more clinical implications than a reflection of kidney functions. Here, we summarize the latest development of studies on the pathophysiological functions of cystatin C, with focus on its immune regulatory roles at both cellular and molecular levels including antigen presentation, secretion of cytokines, synthesis of nitric oxide, as well as apoptosis. Finally, we discuss the clinical implications and therapeutic potentials of what this predominantly expressed protease inhibitor can bring to us.

Ultrastructural damage in Streptococcus mutans incubated with saliva and histatin 5

OBJECTIVE

To study the ultrastructural alterations induced in Streptococcus mutans (ATCC 25175) incubated with saliva, saliva plus histatin 5 and histatin 5.

METHODS

S. mutans incubated with saliva histatin 5 or a combination of both were morphologically analyzed and counted. The results were expressed as (CFU)ml^-1. Ultrastructural damage was evaluated by transmission electron microscopy. Ultrastructural localization of histatin 5 was examined using immunogold labeling. Apoptotic cell death was determined by flow cytometry (TUNEL).

RESULTS

A decrease in the bacteria numbers was observed after incubation with saliva, saliva with histatin 5 or histatin 5 compared to the control group (p<0.0001). Ultrastructural damage in S. mutans incubated with saliva was found in the cell wall. Saliva plus histatin 5 induced a cytoplasmic granular pattern and decreased the distance between the plasma membrane bilayers, also found after incubation with histatin 5, together with pyknotic nucleoids. Histatin 5 was localized on the bacterial cell walls, plasma membranes, cytoplasm and nucleoids. Apoptosis was found in the bacteria incubated with saliva (63.9%), saliva plus histatin 5 (71.4%) and histatin 5 (29.3%). Apoptosis in the control bacteria was 0.2%.

CONCLUSIONS

Antibacterial activity against S. mutans and the morphological description of damage induced by saliva and histatin 5 was demonstrated. Pyknotic nucleoids observed in S. mutans exposed to saliva, saliva plus histatin 5 and histatin 5 could be an apoptosis-like death mechanism. The knowledge of the damage generated by histatin 5 and its intracellular localization could favor the design of an ideal peptide as a therapeutic agent.

Salivary proteome and glucose levels are related with sweet taste sensitivity in young adults

Sweet taste plays a critical role in determining food preferences and choices. Similar to what happens for other oral sensations, individuals differ in their sensitivity for sweet taste and these inter-individual differences may be responsible for variations in food acceptance. Despite evidence that saliva plays a role in taste perception, this fluid has been mainly studied in the context of bitterness or astringency. We investigated the possible relationship between sweet taste sensitivity and salivary composition in subjects with different sucrose detection thresholds. Saliva collected from 159 young adults was evaluated for pH, total protein concentration and glucose. One- and bi-dimensional electrophoresis (2-DE) were performed and protein profiles compared between sweet sensitivity groups, with proteins that were differently expressed being identified by MALDI-FTICR-MS. Moreover, Western blotting was performed for salivary carbonic anhydrase VI (CA-VI) and cystatins and salivary amylase enzymatic activity was assessed in order to compare groups. Females with low sensitivity to sweet taste had higher salivary concentrations of glucose compared to those with sensitivity. For protein profiles, some differences were sex-dependent, with higher levels of α-amylase and CA-VI in low-sensitivity individuals and higher levels of cystatins in sensitive ones for both sexes. Body mass index was not observed to affect the association between salivary proteome and taste sensitivity. To our knowledge, these are the first data showing an association between sweet taste and saliva proteome.

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.

Transcriptome Comparison Reveals the Adaptive Evolution of Two Contrasting Ecotypes of Zn/Cd Hyperaccumulator Sedum alfredii Hance

Hyperaccumulating ecotype (HE) and non-hyperaccumulating ecotype (NHE) of Sedum alfredii Hance belong to the same species but exhibit contrasting characteristics regarding hyperaccumulation and hypertolerance to cadmium and zinc. The Illumina Hiseq 2500 platform was employed to sequence HE and NHE to study the genetic evolution of this contrasting trait. Greater than 90 million clean reads were obtained and 118,479/228,051 unigenes of HE/NHE were annotated based on seven existing databases. We identified 149,668/319,830 single nucleotide polymorphisms (SNPs) and 12,691/14,428 simple sequence repeats (SSRs) of HE/NHE. We used a branch-site model to identify 18 divergent orthologous genes and 57 conserved orthologous genes of S. alfredii Hance. The divergent orthologous genes were mainly involved in the transcription and translation processes, protein metabolism process, calcium (Ca²⁺) pathway, stress response process and signal transduction process. To the best of our knowledge, this is the first study to use RNA-seq to compare the genetic evolution of hyperaccumulating and non-hyperaccumulating plants from the same species. In addition, this study made the sole concrete for further studies on molecular markers and divergent orthologous genes to depict the evolution process and formation of the hyperaccumulation and hypertolerance traits in S. alfredii Hance.

Defense-related proteins involved in sugarcane responses to biotic stress

Sugarcane is one of the most important agricultural crops in the world. However, pathogen infection and herbivore attack cause constant losses in yield. Plants respond to pathogen infection by inducing the expression of several protein types, such as glucanases, chitinases, thaumatins, peptidase inhibitors, defensins, catalases and glycoproteins. Proteins induced by pathogenesis are directly or indirectly involved in plant defense, leading to pathogen death or inducing other plant defense responses. Several of these proteins are induced in sugarcane by different pathogens or insects and have antifungal or insecticidal activity. In this review, defense-related proteins in sugarcane are described, with their putative mechanisms of action, pathogen targets and biotechnological perspectives.

Cystatin C Is a Crucial Endogenous Protective Determinant Against Stroke

BACKGROUND AND PURPOSE

Endogenous neuroprotection can be induced by ischemic and nonischemic preconditioning. However, not all subjects that undergo preconditioning exhibit similar favorable outcome. This study is to explore the molecules responsible for this phenomenon and find new therapeutic targets for stroke.

METHODS

Adult male Sprague-Dawley rats were subjected to transient middle cerebral artery occlusion. High-throughput proteomic technique, isobaric tag for relative and absolute quantification, was used to screen differentially expressed proteins in the rats that developed ischemic tolerance from hyperbaric oxygen (HBO) preconditioning. The proteomic results were verified by Western blot and ELISA. Then, short interfering RNA and gene knockout rats were used to further determine the pivotal role of candidate proteins in HBO preconditioning-induced endogenous neuroprotection. Finally, lysosomal permeability was tested to elaborate the mechanism underlying this intrinsic neuroprotective effect.

RESULTS

Nine proteins differentially expressed in the serum of rats, which acquired benefits from HBO preconditioning, were screened and identified. Western blot and ELISA revealed that cystatin C (CysC) and mannose-binding lectin protein C were uniquely changed in rats with smaller infarction after HBO preconditioning and cerebral ischemia. Knockdown and knockout of CysC abolished HBO-induced neuroprotection. Moreover, HBO-induced endogenous CysC elevation preserved lysosomal membrane integrity after stroke in wild-type rats but not in CysC siRNA infusion or CysC^-/- rats. Most importantly, exogenous CysC also induced neuroprotection against ischemic/reperfusion injury.

CONCLUSIONS

CysC is a crucial determinant contributing to endogenous neuroprotection. It is also a novel candidate for stroke treatment through maintaining lysosomal membrane integrity.

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.

Amyloid properties of the leader peptide of variant B cystatin C: implications for Alzheimer and macular degeneration

Variant B (VB) of cystatin C has a mutation in its signal peptide (A25T), which interferes with its processing leading to reduced secretion and partial retention in the vicinity of the mitochondria. There are genetic evidences of the association of VB with Alzheimer's disease (AD) and age-related macular degeneration (AMD). Here, we investigated aggregation and amyloid propensities of unprocessed VB combining computational and in vitro studies. Aggregation predictors revealed the presence of four aggregation-prone regions, with a strong one at the level of the signal peptide, which indeed formed toxic aggregates and mature amyloid fibrils in solution. In light of these results, we propose for the first time the role of the signal peptide in pathogenesis of AD and AMD.

Search for Nodulation and Nodule Development-Related Cystatin Genes in the Genome of Soybean (Glycine max)

Nodulation, nodule development and senescence directly affects nitrogen fixation efficiency, and previous studies have shown that inhibition of some cysteine proteases delay nodule senescence, so their nature inhibitors, cystatin genes, are very important in nodulation, nodule development, and senescence. Although several cystatins are actively transcribed in soybean nodules, their exact roles and functional diversities in legume have not been well explored in genome-wide survey studies. In this report, we performed a genome-wide survey of cystatin family genes to explore their relationship to nodulation and nodule development in soybean and identified 20 cystatin genes that encode peptides with 97-245 amino acid residues, different isoelectric points (pI) and structure characteristics, and various putative plant regulatory elements in 3000 bp putative promoter fragments upstream of the 20 soybean cystatins in response to different abiotic/biotic stresses, hormone signals, and symbiosis signals. The expression profiles of these cystatin genes in soybean symbiosis with rhizobium strain Bradyrhizobium japonicum strain 113-2 revealed that 7 cystatin family genes play different roles in nodulation as well as nodule development and senescence. However, these genes were not root nodule symbiosis (RNS)-specific and did not encode special clade cystatin protein with structures related to nodulation and nodule development. Besides, only two of these soybean cystatins were not upregulated in symbiosis after ABA treatment. The functional analysis showed that a candidate gene Glyma.15G227500 (GmCYS16) was likely to play a positive role in soybean nodulation. Besides, evolutionary relationships analysis divided the cystatin genes from Arabidopsis thaliana, Nicotiana tabacum, rice, barley and four legume plants into three groups. Interestingly, Group A cystatins are special in legume plants, but only include one of the above-mentioned 7 cystatin genes related to nodulation and nodule development. Overall, our results provide useful information or clues for our understanding of the functional diversity of legume cystatin family proteins in soybean nodulation and nodule development and for finding nodule-specific cysteine proteases in soybean.

Innate Humoral Defense Factors

Although innate immunity came into the research spotlight in the late 1990s when its instructive role in the adaptive immune response was recognized, innate humoral defense factors have a much older history. The exocrine secretions of the body contain a plethora of distinct soluble factors (lysozyme, lactoferrin, peroxidases, proline-rich proteins, histatins, etc.) that protect the body from mucosal microbial pathogens. More recent studies have established that the humoral arm of innate immunity contains a heterogeneous group of pattern-recognition molecules (e.g., pentraxins, collectins, and ficolins), which perform diverse host-defense functions, such as agglutination and neutralization, opsonization, control of inflammation, and complement activation and regulation. These pattern-recognition molecules, which act as functional predecessors of antibodies (“ante-antibodies”), and the classic soluble innate defense factors form an integrated system with complementary specificity, action, and tissue distribution, and they are the subject of this chapter.

Cystatin C: a new renal marker and its potential use in small animal medicine

The occurrence of chronic kidney disease is underestimated in both human and veterinary medicine. Glomerular filtration rate (GFR) is considered the gold standard for evaluating kidney function. However, GFR assessment is time-consuming and labor-intensive and therefore not routinely used in practice. The commonly used indirect GFR markers, serum creatinine (sCr) and urea, are not sufficiently sensitive or specific to detect early renal dysfunction. Serum cystatin C (sCysC), a proteinase inhibitor, has most of the properties required for an endogenous GFR marker. In human medicine, numerous studies have evaluated its potential use as a GFR marker in several populations. In veterinary medicine, this marker is gaining interest. The measurement is easy, which makes it an interesting parameter for clinical use. This review summarizes current knowledge about cystatin C (CysC) in humans, dogs, and cats, including its history, assays, relationship with GFR, and biological and clinical variations in both human and veterinary medicine.

A novel Glycine soja cysteine proteinase inhibitor GsCPI14, interacting with the calcium/calmodulin-binding receptor-like kinase GsCBRLK, regulated plant tolerance to alkali stress

It has been well demonstrated that cystatins regulated plant stress tolerance through inhibiting the cysteine proteinase activity under environmental stress. However, there was limited information about the role of cystatins in plant alkali stress response, especially in wild soybean. Here, in this study, we focused on the biological characterization of a novel Glycine soja cystatin protein GsCPI14, which interacted with the calcium/calmodulin-binding receptor-like kinase GsCBRLK and positively regulated plant alkali stress tolerance. The protein-protein interaction between GsCBRLK and GsCPI14 was confirmed by using split-ubiquitin based membrane yeast two-hybrid analysis and bimolecular fluorescence complementation assay. Expression of GsCPI14 was greatly induced by salt, ABA and alkali stress in G. soja, and GsCBRLK overexpression (OX) in Glycine max promoted the stress induction of GmCPI14 expression under stress conditions. Furthermore, we found that GsCPI14-eGFP fusion protein localized in the entire Arabidopsis protoplast and onion epidermal cell, and GsCPI14 showed ubiquitous expression in different tissues of G. soja. In addition, we gave evidence that the GST-GsCPI14 fusion protein inhibited the proteolytic activity of papain in vitro. At last, we demonstrated that OX of GsCPI14 in Arabidopsis promoted the seed germination under alkali stress, as evidenced by higher germination rates. GsCPI14 transgenic Arabidopsis seedlings also displayed better growth performance and physiological index under alkali stress. Taken together, results presented in this study demonstrated that the G. soja cysteine proteinase inhibitor GsCPI14 interacted with the calcium/calmodulin-binding receptor-like kinase GsCBRLK and regulated plant tolerance to alkali stress.

Cystatin C triggers neuronal degeneration in a model of multiple system atrophy

Multiple system atrophy is an intractable neurodegenerative disease caused by α-synuclein (α-syn) accumulation in oligodendrocytes and neurons. With the use of a transgenic mouse model overexpressing human α-syn in oligodendrocytes, we demonstrated that oligodendrocytic α-syn inclusions induce neuronal α-syn accumulation, resulting in progressive neuronal degeneration. The mechanism through which oligodendrocytic α-syn inclusions trigger neuronal α-syn accumulation leading to multiple system atrophy is unknown. In this study, we identified cystatin C, an oligodendrocyte-derived secretory protein that triggers α-syn up-regulation and insoluble α-syn accumulation, in neurons of the mouse central nervous system. Cystatin C was released by mouse oligodendrocytes overexpressing human α-syn, and extracellular cystatin C increased the expression of the endogenous α-syn gene in wild-type mouse neurons. These neurons then accumulate insoluble α-syn and may undergo apoptosis. Cystatin C is a potential pathogenic signal triggering neurodegeneration in multiple system atrophy.

Cystatin SN neutralizes the inhibitory effect of cystatin C on cathepsin B activity

Cystatin SN (CST1) is one of the several salivary cystatins that form tight equimolar complexes with cysteine proteases, such as the cathepsins. High expression of CST1 is correlated with advanced pTNM stage in gastric cancer. However, the functional role of CST1 in tumorigenesis has not been elucidated. In this study, we showed that CST1 was highly expressed in colon tumor tissues, compared with nontumor regions. Increased cell proliferation and invasiveness were observed in HCT116 cell lines stably transfected with CST1 cDNA (HCT116-CST1) but not in CST3-transfected cells. We also demonstrated that CST1-overexpressing cell lines exhibited increased tumor growth as well as metastasis in a xenograft nude mouse model. Interestingly, CST1 interacted with cystatin C (CST3), a potent cathepsin B (CTSB) inhibitor, with a higher affinity than the interaction between CST3 and CTSB in the extracellular space of HCT116 cells. CTSB-mediated cellular invasiveness and proteolytic activities were strongly inhibited by CST3, but in the presence of CST1 CTSB activities recovered significantly. Furthermore, domain mapping of CST1 showed that the disulfide-bonded conformation, or conserved folding, of CST1 is important for its secretion and for the neutralization of CST3 activity. These results suggest that CST1 upregulation might be involved in colorectal tumorigenesis and acts by neutralizing the inhibition of CTSB proteolytic activity by CST3.

Attenuation of early brain injury and learning deficits following experimental subarachnoid hemorrhage secondary to Cystatin C: possible involvement of the autophagy pathway

Cystatin C (CysC) is a cysteine protease inhibitor and previous studies have demonstrated that increasing endogenous CysC expression has therapeutic implications on brain ischemia, Alzheimer's disease, and other neurodegenerative disorders. Our previous reports have demonstrated that the autophagy pathway was activated in the brain after experimental subarachnoid hemorrhage (SAH), and it may play a beneficial role in early brain injury (EBI). This study investigated the effects of exogenous CysC on EBI, cognitive dysfunction, and the autophagy pathway following experimental SAH. All SAH animals were subjected to injections of 0.3 ml fresh arterial, nonheparinized blood into the prechiasmatic cistern in 20 s. As a result, treatment with CysC with low and medial concentrations significantly ameliorated the degree of EBI when compared with vehicle-treated SAH rats. Microtubule-associated protein light chain-3 (LC3), a biomarker of autophagosomes, and beclin-1, a Bcl-2-interacting protein required for autophagy, were significantly increased in the cortex 48 h after SAH and were further up-regulated after CysC therapy. By ultrastructural observation, there was a marked increase in autophagosomes and autolysosomes in neurons of CysC-treated rats. Learning deficits induced by SAH were markedly alleviated after CysC treatment with medial doses. In conclusion, pre-SAH CysC administration may attenuate EBI and neurobehavioral dysfunction in this SAH model, possibly through activating autophagy pathway.

Immunomodulatory and antibacterial effects of cystatin 9 against Francisella tularensis

Cystatin 9 (CST9) is a member of the type 2 cysteine protease inhibitor family, which has been shown to have immunomodulatory effects that restrain inflammation, but its functions against bacterial infections are unknown. Here, we report that purified human recombinant (r)CST9 protects against the deadly bacterium Francisella tularensis (Ft) in vitro and in vivo. Macrophages infected with the Ft human pathogen Schu 4 (S4), then given 50 pg of rCST9 exhibited significantly decreased intracellular bacterial replication and increased killing via preventing the escape of S4 from the phagosome. Further, rCST9 induced autophagy in macrophages via the regulation of the mammalian target of rapamycin (mTOR) signaling pathways. rCST9 promoted the upregulation of macrophage proteins involved in antiinflammation and antiapoptosis, while restraining proinflammatory-associated proteins. Interestingly, the viability and virulence of S4 also was decreased directly by rCST9. In a mouse model of Ft inhalation, rCST9 significantly decreased organ bacterial burden and improved survival, which was not accompanied by excessive cytokine secretion or subsequent immune cell migration. The current report is the first to show the immunomodulatory and antimicrobial functions of rCST9 against Ft. We hypothesize that the attenuation of inflammation by rCST9 may be exploited for therapeutic purposes during infection.