Involvement of cystatin C in oxidative stress-induced apoptosis of cultured rat CNS neurons

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.

Differential Proteome Profiling Analysis under Pesticide Stress by the Use of a Nano-UHPLC-MS/MS Untargeted Proteomic-Based Approach on a 3D-Developed Neurospheroid Model: Identification of Protein Interactions, Prognostic Biomarkers, and Potential Therapeutic Targets in Human IDH Mutant High-Grade Gliomas

High-grade gliomas represent the most common group of infiltrative primary brain tumors in adults associated with high invasiveness, agressivity, and resistance to therapy, which highlights the need to develop potent drugs with novel mechanisms of action. The aim of this study is to reveal changes in proteome profiles under stressful conditions to identify prognostic biomarkers and altered apoptogenic pathways involved in the anticancer action of human isocitrate dehydrogenase (IDH) mutant high-grade gliomas. Our protocol consists first of a 3D in vitro developing neurospheroid model and then treatment by a pesticide mixture at relevant concentrations. Furthermore, we adopted an untargeted proteomic-based approach with high-resolution mass spectrometry for a comparative analysis of the differentially expressed proteins between treated and nontreated spheroids. Our analysis revealed that the majority of altered proteins were key members in glioma pathogenesis, implicated in the cellular metabolism, biological regulation, binding, and catalytic and structural activity and linked to many cascading regulatory pathways. Our finding revealed that grade-IV astrocytomas promote the downstream of the mitogen-activated-protein-kinases/extracellular-signal-regulated kinase (MAPK1/ERK2) pathway involving massive calcium influx. The gonadotrophin-releasing-hormone signaling enhances MAKP activity and may serve as a negative feedback compensating regulator. Thus, our study can pave the way for effective new therapeutic and diagnostic strategies to improve the overall survival.

Changes in Serum Cystatin C Levels and the Associations With Cognitive Function in Alzheimer's Disease Patients

Background and Objective

Cystatin C is indicated to be involved in the pathogenesis of Alzheimer's disease (AD) and cognitive impairment. Our objective is to examine the serum Cystatin C levels, and to clarify the correlations between serum Cystatin C and cognitive performance in Chinese AD patients.

Methods

The serum Cystatin C concentrations in AD patients and age, sex, and body mass index (BMI) matched-healthy controls were measured. The cognitive functions of the AD patients were evaluated by using the Mini-mental State Examination (MMSE) and the Montreal Cognitive Assessment (MoCA). The severity of dementia was determined with clinical dementia rating (CDR).

Results

A total of 463 AD patients and 1,389 matched healthy subjects were included. AD patients had higher serum Cystatin C than healthy controls. Serum cystatin C levels were correlated with MoCA scores in AD patients. In an ordinal logistic regression model, AD patients with higher serum cystatin C levels had increased odds of severe cognitive dysfunction.

Conclusion

Our study suggested that AD patients had higher levels of serum cystatin C than age/sex/BMI-matched normal control subjects. Higher serum cystatin C may be associated with worse cognitive performance, but more studies are required to verify such association.

Sunscreens containing zinc oxide nanoparticles can trigger oxidative stress and toxicity to the marine copepod Tigriopus japonicus

The study, for the first time, evaluated the leaching rate of zinc oxide nanoparticles (nZnO) from human skins which were applied with three commercial sunscreens containing nZnO as an active ingredient. The leaching rate of nZnO varied greatly among the sunscreens, with a range of 8-72% (mean ± SD: 45% ± 33%). We further investigated their toxicities to the marine copepod Tigriopus japonicus. We found that 96-h median lethal concentrations of the three sunscreens to T. japonicus were > 5000, 230.6, and 43.0 mg chemical L^-1, respectively, equivalent to Zn²⁺ concentrations at >82.5, 3.2, and 1.2 mg Zn L^-1, respectively. Exposure to the individual sunscreens at environmentally realistic concentrations for 96 h led to up-regulation of antioxidant genes in T. japonicus, while they triggered the release of reactive oxygen species based on the results of in vivo assays. Evidently, these nZnO-included sunscreens can cause oxidative stress and hence pose risk to marine organisms.

Relationship between sarcopenia and the serum creatinine/cystatin C ratio in Japanese rural community-dwelling older adults

Background:Sarcopenia, the age-related decline in skeletal muscle volume and function, is associated with negative clinical and socioeconomic outcomes in elderly people. Clinical biomarkers to diagnose sarcopenia that can be quantified in a reliable, and cost- effective manner, are needed. We investigated whether the creatinine (Cr) /cystatin C (CysC) ratio is correlated with muscle volume and physical function in Japanese community-dwelling elderly subjects. Methods: The present study included 213 men aged 73.2±6.2 years and 464 women aged 72.4±5.5 years from a rural area in the Hyogo prefecture of Japan. To evaluate whether the Cr/CysC ratio is correlated with sarcopenia criteria in elderly individuals with preserved kidney function, we excluded subjects with estimate glomerular filtration rate (eGFR) <45. Results:The prevalence of sarcopenia diagnosed according to the AWGS criteria was 2.8% in men and 3.4% in women. The Cr/CysC ratio correlated with skeletal mass index (r = 0.49, p <0.0001), skeletal muscle mass (r = 0.53, p <0.0001), grip power (r = 0.59, p <0.0001), knee extension muscle strength (r = 0.49, p <0.0001), normal gait speed (r = 0.18, p <0.0001), and maximal gait speed (r = 0.32, p <0.0001). A negative correlation between the Cr/CysC ratio and, body fat mass (r = -0.20, p <0.0001) and percentage of body fat mass (r = -0.39, p <0.0001) was observed. In a multiple regression analysis, Cr/CysC was also found to be significantly positively correlated with each component of the sarcopenia criteria. Conclusions:Even in elderly individuals with preserved kidney function, the Cr/CysC ratio was positively correlated with muscle volume and physical function and negatively correlated with body fat mass. Therefore, the Cr/CysC ratio might be a useful biomarker to predict sarcopenia. 

Potential skin involvement in ALS: revisiting Charcot's observation - a review of skin abnormalities in ALS

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease affecting motor neurons of the brain and spinal cord, leading to progressive paralysis and death. Interestingly, many skin changes have been reported in ALS patients, but never as yet fully explained. These observations could be due to the common embryonic origin of the skin and neural tissue known as the ectodermal germ layer. Following the first observation in ALS patients' skin by Dr Charcot in the 19th century, in the absence of bedsores unlike other bedridden patients, other morphological and molecular changes have been observed. Thus, the skin could be of interest in the study of ALS and other neurodegenerative diseases. This review summarizes skin changes reported in the literature over the years and discusses about a novel in vitro ALS tissue-engineered skin model, derived from patients, for the study of ALS.

SNPs in Aβ clearance proteins: Lower CSF Aβ1-42 levels and earlier onset of dementia in PD

OBJECTIVE

To evaluate whether genetic variants in β-amyloid (Aβ) clearance proteins are associated with CSF levels of Aβ_1-42 on a biological level and the onset of dementia on a clinical level in Parkinson disease (PD).

METHODS

We analyzed genetic variants known to be involved in Aβ clearance in a PD group comprising 456 patients, 103 of them with dementia. Single nucleotide polymorphisms in the genes APOE, cystatin C (CST), and membrane metalloendopeptidase (MME) were evaluated in relation to demographic variables, clinical phenotypes, and CSF Aβ_1-42 levels using a cross-sectional approach.

RESULTS

Risk variants in the genes APOE and CST were associated with lower CSF Aβ_1-42 levels. Clinically, patients with 2 risk alleles in CST tended to show a shorter interval from age at onset of PD to age at onset of dementia.

CONCLUSIONS

This study suggests that genetic variants associated with Aβ clearance are involved in the pathogenesis of dementia in PD and possibly influence the onset of dementia.

Mansouramycin C kills cancer cells through reactive oxygen species production mediated by opening of mitochondrial permeability transition pore

Cancer is one of the deadliest diseases in the world and the search for novel anticancer agents is urgently required. Marine-derived isoquinolinequinones have exhibited promising anticancer activities. However, the exact mechanisms of cytotoxic activities of these isoquinolinequinones are poorly characterized. In this study, we investigated the anticancer effects and molecular mechanisms of mansouramycin C (Mm C), a cytotoxic isoquinolinequinone isolated from a marine streptomycete. We demonstrated that Mm C preferentially killed cancer cells and the cytotoxic effects were mediated by reactive oxygen species (ROS) generation. Mass spectrometry based proteomic analysis of Mm C-treated A549 cells revealed that many ROS-related proteins were differentially expressed. Proteomic-profiling after Mm C treatment identified oxidative phosphorylation as the most significant changes in pathways. Analysis also revealed extensive defects in mitochondrial structure and function. Furthermore, we disclosed that Mm C-induced ROS generation was caused by opening of mitochondrial permeability transition pore. Notably, Mm C synergized with sorafenib to induce cell death in A549 cells. Hence, we propose that the marine-derived natural compound Mm C is a potent inducer of the mitochondrial permeability transition and a promising anticancer drug candidate. Moreover, molecular mechanisms of Mm C shed new light on the understanding of the cytotoxic mechanisms of marine-derived isoquinolinequiones.

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.

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

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

Coenzyme Q10 benefits symptoms in Gulf War veterans: results of a randomized double-blind study

We sought to assess whether coenzyme Q10 (CoQ10) benefits the chronic multisymptom problems that affect one-quarter to one-third of 1990-1 Gulf War veterans, using a randomized, double-blind, placebo-controlled study. Participants were 46 veterans meeting Kansas and Centers for Disease Control criteria for Gulf War illness. Intervention was PharmaNord (Denmark) CoQ10 100 mg per day (Q100), 300 mg per day (Q300), or an identical-appearing placebo for 3.5 ± 0.5 months. General self-rated health (GSRH), the primary outcome, differed across randomization arms at baseline, and sex significantly predicted GSRH change, compelling adjustment for baseline GSRH and prompting sex-stratified analysis. GSRH showed no significant benefit in the combined-sex sample. Among males (85% of participants), Q100 significantly benefited GSRH versus placebo and versus Q300, providing emphasis on Q100. Physical function (summary performance score, SPS) improved on Q100 versus placebo. A rise in CoQ10 approached significance as a predictor of improvement in GSRH and significantly predicted SPS improvement. Among 20 symptoms each present in half or more of the enrolled veterans, direction-of-difference on Q100 versus placebo was favorable for all except sleep problems; sign test 19:1, p=0.00004) with several symptoms individually significant. Significance for these symptoms despite the small sample underscores large effect sizes, and an apparent relation of key outcomes to CoQ10 change increases prospects for causality. In conclusion, Q100 conferred benefit to physical function and symptoms in veterans with Gulf War illness. Examination in a larger sample is warranted, and findings from this study can inform the conduct of a larger trial.

Power of proteomics in linking oxidative stress and female infertility

Endometriosis, PCOS, and unexplained infertility are currently the most common diseases rendering large numbers of women infertile worldwide. Oxidative stress, due to its deleterious effects on proteins and nucleic acids, is postulated to be the one of the important mechanistic pathways in differential expression of proteins and in these diseases. The emerging field of proteomics has allowed identification of proteins involved in cell cycle, as antioxidants, extracellular matrix (ECM), cytoskeleton, and their linkage to oxidative stress in female infertility related diseases. The aim of this paper is to assess the association of oxidative stress and protein expression in the reproductive microenvironments such as endometrial fluid, peritoneal fluid, and follicular fluid, as well as reproductive tissues and serum. The review also highlights the literature that proposes the use of the fertility related proteins as potential biomarkers for noninvasive and early diagnosis of the aforementioned diseases rather than utilizing the more invasive methods used currently. The review will highlight the power of proteomic profiles identified in infertility related disease conditions and their linkage with underlying oxidative stress. The power of proteomics will be reviewed with regard to eliciting molecular mechanisms for early detection and management of these infertility related conditions.

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.

Protein clearance mechanisms of alpha-synuclein and amyloid-Beta in lewy body disorders

Protein clearance is critical for the maintenance of the integrity of neuronal cells, and there is accumulating evidence that in most-if not all-neurodegenerative disorders, impaired protein clearance fundamentally contributes to functional and structural alterations eventually leading to clinical symptoms. Dysfunction of protein clearance leads to intra- and extraneuronal accumulation of misfolded proteins and aggregates. The pathological hallmark of Lewy body disorders (LBDs) is the abnormal accumulation of misfolded proteins such as alpha-synuclein (Asyn) and amyloid-beta (Abeta) in a specific subset of neurons, which in turn has been related to deficits in protein clearance. In this paper we will highlight common intraneuronal (including autophagy and unfolded protein stress response) and extraneuronal (including interaction of neurons with astrocytes and microglia, phagocytic clearance, autoimmunity, cerebrospinal fluid transport, and transport across the blood-brain barrier) protein clearance mechanisms, which may be altered across the spectrum of LBDs. A better understanding of the pathways underlying protein clearance-in particular of Asyn and Abeta-in LBDs may result in the identification of novel biomarkers for disease onset and progression and of new therapeutic targets.

Cystatin C induces apoptosis and tyrosine hydroxylase gene expression through JNK-dependent pathway in neuronal cells

Cystatin C (CysC), an endogenous cysteine protease inhibitor, has been implicated in the apoptosis and differentiation processes of neuronal cells. In this study, we have investigated the pathway involved in the process. A human neuronal hybridoma cell line (A1 cell) was treated with CysC in both undifferentiated and retinoic acid (RA)-induced differentiated conditions, which decreased overall process length in both conditions. Also, CysC increased apoptotic cell number time-dependently, as revealed by TUNEL assay. Western blot analysis demonstrated that in differentiated A1 cells, CysC treatment decreased Bcl-2 and increased active caspase-9 protein level time-dependently. Immunocytochemistry results revealed that, CysC treatment significantly increased active form of Bax expressing cell number, which co-localized with mitochondria. Mitogen activated protein (MAP) kinase inhibition experiments showed that Bax mRNA induction and Bcl-2 mRNA inhibition by CysC treatment were c-Jun N-terminal kinase (JNK)-dependent. After RA-induced differentiation, choline acetyltransferase (ChAT) and neurofilament (NF) mRNA levels were increased in A1 cells. CysC treatment inhibited NF mRNA level in both undifferentiated and RA-differentiated, and increased TH mRNA in differentiated A1 neurons. Analysis of signal transduction pathway demonstrated that TH gene induction was also JNK-dependent. Thus, our results demonstrated the significance of JNK-dependent pathways on CysC-induced apoptosis and TH gene expression in neuronal cells, which might be an important target in the management of CysC dependent neurodegenerative processes.

Protective mechanisms by cystatin C in neurodegenerative diseases

Neurodegeneration occurs in acute pathological conditions such as stroke, ischemia, and head trauma and in chronic disorders such as Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis. While the cause of neuronal death is different and not always known in these varied conditions, hindrance of cell death would be beneficial in the prevention of, slowing of, or halting disease progression. Enhanced cystatin C (CysC) expression in these conditions caused a debate as to whether CysC up-regulation facilitates neurodegeneration or it is an endogenous neuroprotective attempt to prevent the progression of the pathology. However, recent in vitro and in vivo data have demonstrated that CysC plays protective roles via pathways that are dependent on inhibition of cysteine proteases, such as cathepsin B, or by induction of autophagy, induction of proliferation, and inhibition of amyloid-beta aggregation. Here we review the data demonstrating the protective roles of CysC under conditions of neuronal challenge and the protective pathways induced under various conditions. These data suggest that CysC is a therapeutic candidate that can potentially prevent brain damage and neurodegeneration.

Cystatin C rescues degenerating neurons in a cystatin B-knockout mouse model of progressive myoclonus epilepsy

In vitro studies have shown that cystatin C (CysC) is neuroprotective. Here we demonstrate that CysC is neuroprotective in vivo, in a mouse model of the inherited neurodegenerative disorder, progressive myoclonic epilepsy type 1 (EPM1). Loss-of-function mutations in the cystatin B (CysB) gene, an intracellular cysteine protease inhibitor, lead to this human disease. A CysB-knockout (CysBKO) mouse model develops symptoms that mimic EPM1. CysB deficiency in these mice results in enhanced cathepsin B and D activities, indicating lysosomal dysfunction. We show that expression of CysC is enhanced in the brains of CysBKO mice. Crossbreeding of CysBKO mice with either CysC-overexpressing transgenic mice or CysC-knockout mice demonstrates that clinical symptoms and neuropathologies, including motor coordination disorder, cerebellar atrophy, neuronal loss in the cerebellum and cerebral cortex, and gliosis caused by CysB deficiency, are rescued by CysC overexpression and exacerbated by CysC deficiency. Thus, CysC effectively rescues the CysB loss-of-function mutations, facilitating the reversal of pathophysiological changes and suggesting a novel therapeutic intervention for patients with EPM1 and other neurodegenerative disorders.

Hydrogen peroxide induces lysosomal protease alterations in PC12 cells

Alterations in lysosomal proteases have been implicated in many neurodegenerative diseases. The current study demonstrates a concentration-dependent decrease in PC12 cell viability and transient changes in cystatin C (CYSC), cathepsin B (CATB), cathepsin D (CATD) and caspase-3 following exposure to H2O2. Furthermore, activation of CATD occurred following exposure to H2O2 and cysteine protease suppression, while inhibition of CATD with pepstatin A significantly improved cell viability. Additionally, significant PARP cleavage, suggestive of caspase-3-like activity, was observed following H2O2 exposure, while inhibition of caspase-3 significantly increased cell viability compared to H2O2 administration alone. Collectively, our data suggest that H2O2 induced cell death is regulated at least in part by caspase-3 and CATD. Furthermore, cysteine protease suppression increases CATD expression and activity. These studies provide insight for alternate pathways and potential therapeutic targets of cell death associated with oxidative stress and lysosomal protease alterations.

The role of cystatin C in cerebral amyloid angiopathy and stroke: cell biology and animal models

A variant of the cysteine protease inhibitor, cystatin C, forms amyloid deposited in the cerebral vasculature of patients with hereditary cerebral hemorrhage with amyloidosis, Icelandic type (HCHWA-I), leading to cerebral hemorrhages early in life. However, cystatin C is also implicated in neuronal degenerative diseases in which it does not form the amyloid protein, such as Alzheimer disease (AD). Accumulating data suggest involvement of cystatin C in the pathogenic processes leading to amyloid deposition in cerebral vasculature and most significantly to cerebral hemorrhage in patients with cerebral amyloid angiopathy (CAA). This review focuses on cell culture and animal models used to study the role of cystatin C in these processes.

Regulation of cysteine cathepsin expression by oxidative stress in the retinal pigment epithelium/choroid of the mouse

Cystatin C is the major inhibitor of the cysteine cathepsins. Polymorphisms in the cystatin C gene have recently been associated with the risk of developing Age-related Macular Degeneration (AMD). Oxidative stress is also thought to play a key role in the pathogenesis of AMD. We surveyed the retinal pigment epithelium (RPE) and choroid of the C57BL/6J mouse for the expression of the cysteine cathepsins under normoxic and hyperoxic (75% O(2)) conditions. Microarray analysis of RPE/choroid mRNA revealed the expression of cathepsins B and L, as well as cystatin C under all experimental conditions. The microarray results were confirmed by real-time quantitative polymerase chain reaction (PCR). Localization of the mRNA species for cystatin C and cathepsin B, as well as, localization of protein species for cystatin C, cathepsins B and L were performed to evaluate the tissue distribution of these species. Our results indicate that cystatin C is largely synthesized in the RPE and secreted from the basal side. Cathepsin B is the major cysteine protease in the RPE and choroid. The expression of all mRNAs and proteins was elevated by exposure to oxidative stress.

Enhanced cystatin C and lysosomal protease expression following 6-hydroxydopamine exposure

6-Hydroxydopamine (6-OHDA) is a selective neurotoxin used to induce apoptosis in catecholamine-containing neurons. Although biochemical products and reactive oxygen species (ROS) of 6-OHDA have been well documented, the activation of cellular pathways following exposure are not well understood. Apoptosis in PC12 (Pheochromocytoma) cells was induced by 6-OHDA in a dose (10-150 microM) and time-dependent (24-72 h) manner compared to experimental controls (no treatment). PC 12 cells exposed to 50 microM 6-OHDA demonstrated the involvement of caspase 3 and lysosomal protease alterations. Following 6-OHDA exposure, the caspase 3-like inhibitor Ac-DEVD-CHO significantly decreased 6-OHDA induced cell death. In addition, alterations in expression of the lysosomal cysteine and aspartic proteases, cathepsin B (CB) and cathepsin D (CD) and the endogenous cysteine protease inhibitor cystatin C were observed utilizing immunocytochemical analysis at 24, 48, and 72 h following 6-OHDA exposure. Furthermore, CB and CD and cystatin C immuno-like reactivity was more pronounced in TUNEL positive cells. Moreover, Western blot analysis confirmed a significant increase in protein expression for CB and CD at 72 h and a temporal and concentration dependent increase in cystatin C in response to 6-OHDA. Cells treated with pepstatin A, an inhibitor for CD, showed a significant decrease in cell death, however, CA-074ME, a specific inhibitor for CB, failed to protect cells from 6-OHDA induced cell death. Thus, these results suggest that apoptosis induced by 6-OHDA exposure is mediated in part through caspase 3 activation and lysosomal protease CD.

Alteration of the glutamate and GABA transporters in the hippocampus of the Niemann-Pick disease, type C mouse using proteomic analysis

Niemann-Pick disease type C (NPC) is a fatal autosomal recessive cholesterol disorder characterized by severe progressive neurodegeneration. To unveil the mechanism of neurodegeneration, proteomic and morphological approaches were applied to the hippocampus in NPC -/- mouse. Two-DE was utilized to resolve the hippocampal protein expression profiles of 4- and 8-week-old NPC +/+ and -/- mice. Differentially expressed protein spots were identified by MALDI-TOF MS and database searching. At 4 weeks of age, there was no significant difference in protein profiles between NPC +/+ and -/- mice. However, at the age of 8 weeks, NPC +/+ and -/- mice showed marked difference in protein expressions. Among these, glutamate receptor 2 precursor was identified. The immunohistochemical study on neurotransporters showed that glial GABA transporter (GAT-3) increased in both 4- and 8-week-old NPC -/- mouse and glutamic acid decarboxylase (GAD-6) increased in 8-week-old NPC -/- mouse. Glial glutamate transporter, excitatory amino acids carrier-1 (EAAC1), decreased in 8-week-old NPC -/- mouse. In conclusion, our data may provide insight into the understanding of the basic mechanism through perturbation of protein networks and neurotransporter systems in a single gene knockout model of NPC disease.

Neuronal cell death induced by cystatin C in vivo and in cultured human CNS neurons is inhibited with cathepsin B

Cystatin C, a cysteine protease inhibitor, is implicated in pathogenesis of late-onset Alzheimer's disease and other neurological disorders. Our recent study showed that cystatin C injection into rat hippocampus induced neuronal cell death in granule cell layer of dentate gyrus in vivo. We further confirmed that cystatin C neurotoxicity was inhibited by simultaneous coapplication of cathepsin B, a cysteine protease. In vitro cytotoxicity was also studied in cultures of human CNS neurons, mixed cultures with astrocytes and A1 human hybrid neurons. Cystatin C induced neuronal cell death in a dose-dependent manner, which accompanied increased number of TUNEL (+) cells, up-regulation of active caspase-3 and DNA ladder. The results of the present study indicate that cystatin C participates in the process of apoptotic neuronal cell death in experimental conditions by means of inhibitory activity of cysteine proteases, and that cystatin C might be involved in the pathogenesis in human neurological disorders including Alzheimer's disease.

Cystatin C modulates neurodegeneration and neurogenesis following status epilepticus in mouse

Brain damaging insults cause alterations in neuronal networks that trigger epileptogenesis, and eventually lead to the appearance of spontaneous seizures. The present experiments were designed to study the cellular expression and functions of a cysteine proteinase inhibitor, cystatin C, whose gene expression is previously shown to be upregulated in the rat hippocampus during status epilepticus (SE)-induced epileptogenesis. The present data showed that the expression of cystatin C protein increased in the mouse hippocampus 7 days following SE and localized mainly to astrocytes and microglia. Acute neuronal death in the hippocampus at 24 h after SE was reduced in cystatin C-/- mice. Also, the basal level of neurogenesis in the subgranular layer of dentate gyrus was decreased in cystatin C-/- mice compared to wildtype littermates. Interestingly, migration of newly born neurons within the granule cell layer was attenuated in cystatin C-/- mice. These data demonstrate that cystatin C has a role in neuronal death and neurogenesis during SE-induced network reorganization.

The relation between serum MDA and cystatin C levels in chronic spinal cord injury patients

OBJECTIVES

The assessment of renal function is particularly important in patients with spinal cord injury (SCI). Creatinine (Cr) is known to be unsuitable as a marker of renal function in SCI because of muscle wasting. Although cystatin C (cys-C) is more reliable than Cr, its expression may be affected by oxidative stress accompanying SCI. The aim of the study was to estimate the cys-C levels in SCI patients with normal functioning kidneys. The prooxidant/antioxidant state in plasma of the patients and controls was measured, and any correlations between these parameters and cys-C were determined.

DESIGN AND METHODS

Blood samples from 41 chronic SCI patients and 13 controls were obtained. Serum Cr was assayed by the Cobas Integra 400 autoanalyzer and cys-C by particle-enhanced immunoturbidimetry. Heparinized plasma was used for biochemical determinations of vitamin E, total antioxidant status (TAS) and malondialdehyde (MDA).

RESULTS

Cr, TAS and MDA levels were significantly lower in SCI patients compared to the controls (P = 0.007, P = 0.019, P = 0.000, respectively), whereas no difference was seen in cys-C and vit E concentrations. Body mass indices (BMI) of SCI patients were less than those of the controls (P = 0.03). No correlation existed between cys-C and MDA in SCI patients and controls. Cys-C levels were independent from the body mass indices of subjects.

CONCLUSION

In our study, although BMI and MDA were both affected in SCI patients, cys-C levels were unchanged. Therefore, the measurement of cys-C appeared to be of value for the follow-up of renal function in SCI. The low MDA levels observed in these patients suggest that various adaptation mechanisms may be relevant for subjects undergoing prolonged stress situations.

Oxidative imbalance and cathepsin D changes as peripheral blood biomarkers of Alzheimer disease: A pilot study

Markers of oxidative stress in peripheral blood from patients with Alzheimer disease (AD) were analyzed. Thirty-three AD patients were recruited. Plasma antioxidant power (AOP), plasma Cystatin C as well as Cathepsin D in PBL were evaluated. We found that the AOP levels were significantly decreased in AD patients if compared to healthy donors, while the plasma level of Cystatin C was significantly higher. Importantly, a significantly decreased expression of Cathepsin D in PBL was also observed. These results suggest that oxidative imbalance in the peripheral blood of AD patients could mirror oxidative changes previously described in the central nervous system.

Cystatin C prevents degeneration of rat nigral dopaminergic neurons: in vitro and in vivo studies

Destruction of nigrostriatal dopaminergic (DA) pathway triggers various persistent responses, such as inflammation and increased synthesis of neural growth factors, both in striatum and in substantia nigra. The pathological processes involved in such responses are poorly characterized and could contribute to secondary damage and/or regeneration in the central nervous system (CNS). Cystatin C was previously implicated in the process of neurodegeneration. However, its biological role during neurodegeneration is not understood and remains controversial. The present study identified an increased cystatin C mRNA level in the DA-depleted rat striatum, starting from the second week following a 6-OHDA-induced lesion. Immunohistochemical analysis confirmed the increase in cystatin C protein level in the striatum following DA depletion. Double-labeled fluorescence immunohistochemistry revealed that nigrostriatal neurons, astrocytes, and microglia contributed to the elevated level of cystatin C. Exposure to 6-hydroxydopamine, a DA-specific neurotoxin, resulted in DA neurons loss in the fetal mesencephalic cultures, an effect which could be partially reversed by treatment with cystatin C. Moreover, in vivo DA neurons survival study showed that administration of cystatin C in rats with 6-OHDA-induced lesion partially rescued the nigral DA neurons. The results indicate that the 6-OHDA lesioning induced a relatively slow but sustained up-regulation of cystatin C expression and suggest that the inhibitor may exert a neuroprotective action on DA neurons. The findings raise the possibility that cysteine proteinase inhibitors may be new candidates for neuroprotective treatment of Parkinson's disease. Cystatin C may be useful therapeutically in limiting neuropathy in Parkinson's disease.

Gene deletion of cystatin C aggravates brain damage following focal ischemia but mitigates the neuronal injury after global ischemia in the mouse

Cystatin C is distributed in all human tissues and fluids with a particular abundance in the cerebrospinal fluid. Cystatin C is a strong endogenous inhibitor of lysosomal cysteine proteases, such as cathepsin B, L, H and S, that are involved in various biological processes such as degradation of cellular proteins and regulation of enzymes, as well as in pathological processes. Pharmacological inhibition of cathepsins has been shown to reduce neuronal damage after brain ischemia, suggesting that cystatin C is an endogenous neuroprotectant. Cystatin C has also amyloidogenic properties and is co-localized with beta-amyloid in degenerated neurons in Alzheimer's disease, suggesting a role in neuronal degeneration. To test the hypothesis that endogenous cystatin C is neuroprotective during brain ischemia, global and focal brain ischemia was induced in mice with the cystatin C gene knocked out. Following focal ischemia, larger brain infarcts were found in cystatin C knockout mice, probably due to a reduced inhibition of the cathepsins during ischemia. In contrast, brain damage after global ischemia was diminished in cystatin C knockout mice, suggesting that cystatin C has an aggravating effect on selective neuronal damage after global ischemia.

Identification of up-regulated genes by array analysis in scrapie-infected mouse brains

The major neuropathological features of the transmissible spongiform encephalopathies (TSEs) are well documented, however, the underlying molecular events are poorly defined. We have applied cDNA expression arrays and quantitative RT-PCR to the study of gene expression in the brain, and more specifically in the hippocampus, of the well-characterized ME7/CV mouse model of scrapie. The number of genes showing consistent, scrapie-associated changes in expression was limited, and was primarily restricted to glial-associated genes. Increased expression of genes encoding glial fibrillary acidic protein, vimentin, complement component 1q (alpha and beta polypeptides), cathepsin D, clusterin and cystatin C was evident in the hippocampus from 170 days after inoculation (dpi), with expression increasing thereafter to terminal disease (225-235 dpi). Elevation of gene expression preceded clinical disease by approximately 30 days, and coincided with a 20-day period in the ME7/CV model during which 50% of the CA1 hippocampal neurones are lost. Increased expression of cystatin C, an inhibitor of lysosomal cysteine proteases, is a novel finding in the context of TSE neuropathology and was confirmed by Western analysis and immunocytochemistry.

Cystatin 10, a Novel Chondrocyte-specific Protein, May Promote the Last Steps of the Chondrocyte Differentiation Pathway

This study attempts to characterize cystatin 10 (Cst10), which we recently identified as a novel protein implicated in endochondral ossification. Expression of Cst10 was specific to cartilage, localized in the cytosol of prehypertrophic and hypertrophic chondrocytes of the mouse growth plate. In the mouse chondrogenic cell line ATDC5, Cst10 expression preceded type X collagen expression and increased in synchrony with maturation. When we compared ATDC5 cells transfected with Cst10 cDNA with cells transfected with a mock vector, hypertrophic maturation and mineralization of chondrocytes were promoted by Cst10 gene overexpression in that type X collagen expression was observed earlier, and alizarin red staining was stronger. On the other hand, type II collagen expression and Alcian blue staining, both of which are markers of the early stage of chondrocyte differentiation, were similar in both cells. Overexpression of the Cst10 gene also caused fragmentation of nuclei, the appearance of annexin V, a change in the mitochondrial membrane potential, and activation of caspases. These results strongly suggest that Cst10 may play an important role in the last steps of the chondrocyte differentiation pathway as an inducer of maturation, followed by apoptosis of chondrocytes.

Proteomic analysis of astrocytic secretion in the mouse. Comparison with the cerebrospinal fluid proteome

Astrocytes, the most abundant cell type in the central nervous system, are intimately associated with synapses. They play a pivotal role in neuronal survival and the brain inflammatory response. Some astrocytic functions are mediated by the secretion of polypeptides. Using a proteomic approach, we have identified more than 30 proteins released by cultured astrocytes. These include proteases and protease inhibitors, carrier proteins, and antioxidant proteins. Exposing astrocytes to brefeldin A, which selectively blocks secretory vesicle assembly, suppressed the release of some of these proteins. This indicates that astrocytes secrete these proteins by a classic vesicular mechanism and others by an alternative pathway. Astrocytes isolated from different brain regions secreted a similar pattern of proteins. However, the secretion of some of them, including metalloproteinase inhibitors and apolipoprotein E, was region-specific. In addition, pro-inflammatory treatments modified the profile of astrocytic protein secretion. Finally, more than two thirds of the proteins identified in the astrocyte-conditioned medium were detectable in the mouse cerebrospinal fluid, suggesting that astrocytes contribute to the cerebrospinal fluid protein content. In conclusion, this study provides the first unbiased characterization of the major proteins released by astrocytes, which may play a crucial role in the modulation of neuronal survival and function.

Cystatin C colocalizes with amyloid-beta and coimmunoprecipitates with amyloid-beta precursor protein in sporadic inclusion-body myositis muscles

Cystatin C (CC), an endogenous cysteine protease inhibitor, is accumulated within amyloid-beta (A beta) amyloid deposits in Alzheimer's disease (AD) brain and was proposed to play a role in the AD pathogenesis. Because the chemo-morphologic muscle phenotype of sporadic inclusion-body myositis (s-IBM) has several similarities with the phenotype of AD brain, including abnormal accumulation of A beta deposits, we studied expression and localization of CC in muscle biopsies of 10 s-IBM, and 16 disease- and five normal-control muscle biopsies. Physical interaction of CC with amyloid-beta precursor protein (A beta PP) was studied by a combined immunoprecipitation/immunoblotting technique in the s-IBM muscle biopsies and in A beta PP-overexpressing cultured human muscle fibers. In all s-IBM muscle biopsies, CC-immunoreactivity either colocalized with, or was adjacent to, the A beta-immunoreactive inclusions in 80-90% of the vacuolated muscle fibers, mostly in non-vacuolated regions of their cytoplasm. Ultrastructurally, CC immunoreactivity-colocalized with A beta on 6-10 nm amyloid-like fibrils and floccular material. By immunoblotting, CC expression was strongly increased in IBM muscle as compared to the controls. By immunoprecipitation/immunoblotting experiments, CC coimmunoprecipitated with A beta PP, both in s-IBM muscle and in A beta PP-overexpressing cultured normal human muscle fibers. Our studies (i) demonstrate for the first time that CC physically associates with A beta PP, and (ii) suggest that CC may play a novel role in the s-IBM pathogenesis, possibly by influencing A beta PP processing and A beta deposition.

Upregulation of cystatin C expression in the rat hippocampus during epileptogenesis in the amygdala stimulation model of temporal lobe epilepsy

PURPOSE

Cystatin C is a cysteine proteinase inhibitor with widespread distribution in body fluids and tissues, abundant in the cerebrospinal fluid and in brain tissue. There is an implied role for cystatin C in several neurologic disorders, but the actual function of cystatin C in the brain remains unknown. Moreover, the reports on the distribution of cystatin C in the brain are controversial. We present the data on the distribution of cystatin C in normal brain tissue and during epileptogenesis.

METHODS

Epileptogenesis was triggered by inducing self-sustained status epilepticus (SSSE) with a 20- to 30-min electrical stimulation of the amygdala in rats. Animals were monitored continuously for 2 weeks with video-EEG to ascertain that they were in an epileptogenic phase.

RESULTS

Analysis of double-stained immunopreparations indicated that in normal brain, cystatin C is expressed mainly in microglia. In epileptogenic animals, immunostaining was increased in the microglia as well as in the neuropil at 4 days, 1 week, and 2 weeks after SSSE. Moreover, the density of cystatin C-positive microglia was associated with the severity of neuronal damage in the CA1 subfield of the hippocampus.

CONCLUSIONS

This is the first report linking cystatin C with epileptogenesis and epilepsy. Further studies will explore the potential neuroprotective functions of this protein during epileptogenesis and whether the manipulation of its expression or function will have therapeutic implications.

Apoptosis in skeletal muscle with aging

Sarcopenia may be partly due to a loss in total fiber number by apoptosis. We have investigated age-related alterations in the mitochondria-mediated pathway leading to apoptosis in the gastrocnemius muscle from 6-mo-old and 24-mo-old male Fisher 344 rats. Apoptosis (mono- and oligonucleosome fragmentation) in the gastrocnemius muscle was increased by 50% in the old rats compared with the adult animals. Furthermore, there was a significant correlation between cytosolic cytochrome c and caspase-3 activity, although neither cytochrome c nor caspase-3 activity increased significantly with age. Furthermore, there was a significant correlation between caspase-3 activity and mono- and oligonucleosome fragmentation in the old rats only. Mitochondrial Bcl-2 and Bax were not altered with age. In vitro experiments demonstrated that activation of the caspase cascade in skeletal muscle might be limited by procaspase-9 activation. This is the first study to explore the role of apoptosis in sarcopenia and suggests that subtle changes in apoptosis are involved.

Cystatin C, a cysteine protease inhibitor, is persistently up-regulated in neurons and glia in a rat model for mesial temporal lobe epilepsy

Cystatin C (CSTC), a cysteine protease inhibitor, has been implicated in the processes of neuronal degeneration and repair of the nervous system. Using serial analysis of gene expression (SAGE), we recently identified CSTC as one of the genes that are overexpressed after electrically induced status epilepticus (SE). In the present study, Western blot analysis extended the SAGE results, showing increased CSTC protein in the hippocampus and entorhinal cortex. Immunocytochemistry revealed an increase in CSTC expression in glial cells, which was first apparent 24 h after onset of SE, and persisted for at least 3 months. Double immunolabelling confirmed that both reactive astrocytes, and activated microglia were CSTC immunopositive. Within the hippocampus, up-regulation was also observed in neuronal cells within one day after SE. Up-regulation was still present in hippocampal pyramidal cells and surviving interneurons of chronic epileptic rats (3-8 months post-SE). This study demonstrates that status epilepticus leads to a widespread and persistent up-regulation of CSTC in the hippocampus and entorhinal cortex, which may represent an intrinsic neuroprotective mechanism in the course of epileptogenesis that may counteract progression of the disease.