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

Changes in the Dentate Gyrus Gene Expression Profile Induced by Levetiracetam Treatment in Rats with Mesial Temporal Lobe Epilepsy

Temporal lobe epilepsy (TLE) is one of the most common forms of focal epilepsy. Levetiracetam (LEV) is an antiepileptic drug whose mechanism of action at the genetic level has not been fully described. Therefore, the aim of the present work was to evaluate the relevant gene expression changes in the dentate gyrus (DG) of LEV-treated rats with pilocarpine-induced TLE. Whole-transcriptome microarrays were used to obtain the differential genetic profiles of control (CTRL), epileptic (EPI), and EPI rats treated for one week with LEV (EPI + LEV). Quantitative RT-qPCR was used to evaluate the RNA levels of the genes of interest. According to the results of the EPI vs. CTRL analysis, 685 genes were differentially expressed, 355 of which were underexpressed and 330 of which were overexpressed. According to the analysis of the EPI + LEV vs. EPI groups, 675 genes were differentially expressed, 477 of which were downregulated and 198 of which were upregulated. A total of 94 genes whose expression was altered by epilepsy and modified by LEV were identified. The RT-qPCR confirmed that LEV treatment reversed the increased expression of Hgf mRNA and decreased the expression of the Efcab1, Adam8, Slc24a1, and Serpinb1a genes in the DG. These results indicate that LEV could be involved in nonclassical mechanisms involved in Ca2+ homeostasis and the regulation of the mTOR pathway through Efcab1, Hgf, SLC24a1, Adam8, and Serpinb1a, contributing to reduced hyperexcitability in TLE patients.

NOX4 Deficiency Exacerbates the Impairment of Cystatin C-Dependent Hippocampal Neurogenesis by a Chronic High Fat Diet

Hippocampal neurogenesis is linked with a cognitive process under a normal physiological condition including learning, memory, pattern separation, and cognitive flexibility. Hippocampal neurogenesis is altered by multiple factors such as the systemic metabolic changes. NADPH oxidase 4 (NOX4) has been implicated in the regulation of brain function. While the role of NOX4 plays in the brain, the mechanism by which NOX4 regulates hippocampal neurogenesis under metabolic stress is unclear. In this case, we show that NOX4 deficiency exacerbates the impairment of hippocampal neurogenesis by inhibiting neuronal maturation by a chronic high fat diet (HFD). NOX4 deficiency resulted in less hippocampal neurogenesis by decreasing doublecortin (DCX)-positive neuroblasts, a neuronal differentiation marker, and their branched-dendrites. Notably, NOX4 deficiency exacerbates the impairment of hippocampal neurogenesis by chronic HFD. Moreover, NOX4 deficiency had a significant reduction of Cystatin C levels, which is critical for hippocampal neurogenesis, under chronic HFD as well as normal chow (NC) diet. Furthermore, the reduction of Cystatin C levels was correlated with the impairment of hippocampal neurogenesis in NOX4 deficient and wild-type (WT) mice under chronic HFD. Our results suggest that NOX4 regulates the impairment of Cystatin C-dependent hippocampal neurogenesis under chronic HFD.

Neuroprotection mediated by cystatin C-loaded extracellular vesicles

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

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.

Journey of cystatins from being mere thiol protease inhibitors to at heart of many pathological conditions

Cystatins are thiol proteinase inhibitors (TPI), present ubiquitously in animals, plants and micro-organisms. These are not merely inhibitors rather they are at heart of many pathological conditions ranging from diabetes to renal failure. These are essential for maintenance of protein balance of the cell; once this balance gets disturbed, it may lead to cell death. Thus, cystatins cannot be merely regarded as TPI's as these have been found to play a pivotal role in tumorigenesis and neurodegenerative diseases. Many studies have reported the variation in cystatin level in incidences of different types of cancer; highlighting an important role played by these inhibitors in cancer development and progression. Cystatin C is increasingly replacing creatinine as a biomarker of glomerular filtration rate (GFR) thereby highlighting the importance of this important inhibitor. Some recent studies have also reported the interaction pattern of various anti-cancer drugs with cystatins in a bid to find how these drugs affect this important inhibitors and whether these drugs have any side effect on cystatins. Thus, in this growing disease era it can be said that cystatins are no more just inhibitors blocking the activity of thiol proteases rather they play a pivotal role in variety of pathological conditions.

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.

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

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

Innate Immune Response in Brain, NF-Kappa B Signaling and Cystatins

Recently several reports have demonstrated that innate immune response and inflammation have an important role in major neurodegenerative diseases. The activation of the NF-κB family of transcription factors is a key step in the regulation of pro inflammatory cytokine expression. Microglia and other cell types in the brain can be activated in response to endogenous danger molecules as well as aggregated proteins and brain injury. During the past couple of years several studies reported the role of cystatins in neuroinflammation and neurodegeneration. In the present review, I will summarize and analyze recent findings regarding the role of cystatins in inflammation and NF-κB activation. Type I cystatin stefin B (cystatin B) is an endogenous cysteine cathepsin inhibitor localized in the cytosol, mitochondria and nucleus. Mutations in the gene of stefin B are associated with the neurodegenerative disease known as Unverricht-Lundborg disease and microglial activation plays an important role in the pathogenesis of the disease. Stefin B deficient mice have increased caspase-11 expression and secreted higher amounts of pro-inflammatory cytokines. The increased caspase-11 gene expression, was a consequence of increased NF-κB activation.

Epileptogenesis after traumatic brain injury in Plau-deficient mice

Several components of the urokinase-type plasminogen activator receptor (uPAR)-interactome, including uPAR and its ligand sushi-repeat protein 2, X-linked (SRPX2), are linked to susceptibility to epileptogenesis in animal models and/or humans. Recent evidence indicates that urokinase-type plasminogen activator (uPA), a uPAR ligand with focal proteinase activity in the extracellular matrix, contributes to recovery-enhancing brain plasticity after various epileptogenic insults such as traumatic brain injury (TBI) and status epilepticus. Here, we examined whether deficiency of the uPA-encoding gene Plau augments epileptogenesis after TBI. Traumatic brain injury was induced by controlled cortical impact in the somatosensory cortex of adult male wild-type and Plau-deficient mice. Development of epilepsy and seizure susceptibility were assessed with a 3-week continuous video-electroencephalography monitoring and a pentylenetetrazol test, respectively. Traumatic brain injury-induced cortical or hippocampal pathology did not differ between genotypes. The pentylenetetrazol test revealed increased seizure susceptibility after TBI (p<0.05) in injured mice. Epileptogenesis was not exacerbated, however, in Plau-deficient mice. Taken together, Plau deficiency did not worsen controlled cortical impact-induced brain pathology or epileptogenesis caused by TBI when assessed at chronic timepoints. These data expand previous observations on Plau deficiency in models of status epilepticus and suggest that inhibition of focal extracellular proteinase activity resulting from uPA-uPAR interactions does not modify epileptogenesis after TBI.

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.

Cystatins in immune system

Cystatins comprise a large superfamily of related proteins with diverse biological activities. They were initially characterised as inhibitors of lysosomal cysteine proteases, however, in recent years some alternative functions for cystatins have been proposed. Cystatins possessing inhibitory function are members of three families, family I (stefins), family II (cystatins) and family III (kininogens). Stefin A is often linked to neoplastic changes in epithelium while another family I cystatin, stefin B is supposed to have a specific role in neuredegenerative diseases. Cystatin C, a typical type II cystatin, is expressed in a variety of human tissues and cells. On the other hand, expression of other type II cystatins is more specific. Cystatin F is an endo/lysosome targeted protease inhibitor, selectively expressed in immune cells, suggesting its role in processes related to immune response. Our recent work points on its role in regulation of dendritic cell maturation and in natural killer cells functional inactivation that may enhance tumor survival. Cystatin E/M expression is mainly restricted to the epithelia of the skin which emphasizes its prominent role in cutaneous biology. Here, we review the current knowledge on type I (stefins A and B) and type II cystatins (cystatins C, F and E/M) in pathologies, with particular emphasis on their suppressive vs. promotional function in the tumorigenesis and metastasis. We proposed that an imbalance between cathepsins and cystatins may attenuate immune cell functions and facilitate tumor cell invasion.

Cystatin C in Alzheimer's disease

Changes in expression and secretion levels of cystatin C (CysC) in the brain in various neurological disorders and in animal models of neurodegeneration underscore a role for CysC in these conditions. A polymorphism in the CysC gene (CST3) is linked to increased risk for Alzheimer's disease (AD). AD pathology is characterized by deposition of oligomeric and fibrillar forms of amyloid β (Aβ) in the neuropil and cerebral vessel walls, neurofibrillary tangles composed mainly of hyperphosphorylated tau, and neurodegeneration. The implication of CysC in AD was initially suggested by its co-localization with Aβ in amyloid-laden vascular walls, and in senile plaque cores of amyloid in the brains of patients with AD, Down's syndrome, hereditary cerebral hemorrhage with amyloidosis, Dutch type (HCHWA-D), and cerebral infarction. CysC also co-localizes with Aβ amyloid deposits in the brains of non-demented aged individuals. Multiple lines of research show that CysC plays protective roles in AD. In vitro studies have shown that CysC binds Aβ and inhibits Aβ oligomerization and fibril formation. In vivo results from the brains and plasma of Aβ-depositing transgenic mice confirmed the association of CysC with the soluble, non-pathological form of Aβ and the inhibition of Aβ plaques formation. The association of CysC with Aβ was also found in brain and in cerebrospinal fluid (CSF) from AD patients and non-demented control individuals. Moreover, in vitro results showed that CysC protects neuronal cells from a variety of insults that may cause cell death, including cell death induced by oligomeric and fibrillar Aβ. These data suggest that the reduced levels of CysC manifested in AD contribute to increased neuronal vulnerability and impaired neuronal ability to prevent neurodegeneration. This review elaborates on the neuroprotective roles of CysC in AD and the clinical relevance of this protein as a therapeutic agent.

Dysregulation of macrophage-secreted cathepsin B contributes to HIV-1-linked neuronal apoptosis

Chronic HIV infection leads to the development of cognitive impairments, designated as HIV-associated neurocognitive disorders (HAND). The secretion of soluble neurotoxic factors by HIV-infected macrophages plays a central role in the neuronal dysfunction and cell death associated with HAND. One potentially neurotoxic protein secreted by HIV-1 infected macrophages is cathepsin B. To explore the potential role of cathepsin B in neuronal cell death after HIV infection, we cultured HIV-1_ADA infected human monocyte-derived macrophages (MDM) and assayed them for expression and activity of cathepsin B and its inhibitors, cystatins B and C. The neurotoxic activity of the secreted cathepsin B was determined by incubating cells from the neuronal cell line SK-N-SH with MDM conditioned media (MCM) from HIV-1 infected cultures. We found that HIV-1 infected MDM secreted significantly higher levels of cathepsin B than did uninfected cells. Moreover, the activity of secreted cathepsin B was significantly increased in HIV-infected MDM at the peak of viral production. Incubation of neuronal cells with supernatants from HIV-infected MDM resulted in a significant increase in the numbers of apoptotic neurons, and this increase was reversed by the addition of either the cathepsin B inhibitor CA-074 or a monoclonal antibody to cathepsin B. In situ proximity ligation assays indicated that the increased neurotoxic activity of the cathepsin B secreted by HIV-infected MDM resulted from decreased interactions between the enzyme and its inhibitors, cystatins B and C. Furthermore, preliminary in vivo studies of human post-mortem brain tissue suggested an upregulation of cathepsin B immunoreactivity in the hippocampus and basal ganglia in individuals with HAND. Our results demonstrate that HIV-1 infection upregulates cathepsin B in macrophages, increases cathepsin B activity, and reduces cystatin-cathepsin interactions, contributing to neuronal apoptosis. These findings provide new evidence for the role of cathepsin B in neuronal cell death induced by HIV-infected macrophages.

A systems level, functional genomics analysis of chronic epilepsy

Neither the molecular basis of the pathologic tendency of neuronal circuits to generate spontaneous seizures (epileptogenicity) nor anti-epileptogenic mechanisms that maintain a seizure-free state are well understood. Here, we performed transcriptomic analysis in the intrahippocampal kainate model of temporal lobe epilepsy in rats using both Agilent and Codelink microarray platforms to characterize the epileptic processes. The experimental design allowed subtraction of the confounding effects of the lesion, identification of expression changes associated with epileptogenicity, and genes upregulated by seizures with potential homeostatic anti-epileptogenic effects. Using differential expression analysis, we identified several hundred expression changes in chronic epilepsy, including candidate genes associated with epileptogenicity such as Bdnf and Kcnj13. To analyze these data from a systems perspective, we applied weighted gene co-expression network analysis (WGCNA) to identify groups of co-expressed genes (modules) and their central (hub) genes. One such module contained genes upregulated in the epileptogenic region, including multiple epileptogenicity candidate genes, and was found to be involved the protection of glial cells against oxidative stress, implicating glial oxidative stress in epileptogenicity. Another distinct module corresponded to the effects of chronic seizures and represented changes in neuronal synaptic vesicle trafficking. We found that the network structure and connectivity of one hub gene, Sv2a, showed significant changes between normal and epileptogenic tissue, becoming more highly connected in epileptic brain. Since Sv2a is a target of the antiepileptic levetiracetam, this module may be important in controlling seizure activity. Bioinformatic analysis of this module also revealed a potential mechanism for the observed transcriptional changes via generation of longer alternatively polyadenlyated transcripts through the upregulation of the RNA binding protein HuD. In summary, combining conventional statistical methods and network analysis allowed us to interpret the differentially regulated genes from a systems perspective, yielding new insight into several biological pathways underlying homeostatic anti-epileptogenic effects and epileptogenicity.

Mechanisms of epileptogenesis and potential treatment targets

Prevention of epileptogenesis after brain trauma is an unmet medical challenge. Recent molecular profiling studies have provided an insight into molecular changes that contribute to formation of ictogenic neuronal networks, including genes regulating synaptic or neuronal plasticity, cell death, proliferation, and inflammatory or immune responses. These mechanisms have been targeted to prevent epileptogenesis in animal models. Favourable effects have been obtained using immunosuppressants, antibodies blocking adhesion of leucocytes to endothelial cells, gene therapy driving expression of neurotrophic factors, pharmacological neurostimulation, or even with conventional antiepileptic drugs by administering them before the appearance of genetic epilepsy. Further studies are needed to clarify the optimum time window and aetiological specificity of treatments. Questions related to adverse events also need further consideration. Encouragingly, the recent experimental studies emphasise that the complicated process of epileptogenesis can be favourably modified, and that antiepileptogenesis as a treatment indication might not be an impossible mission.

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.

Proteomics of dense core secretory vesicles reveal distinct protein categories for secretion of neuroeffectors for cell-cell communication

Regulated secretion of neurotransmitters and neurohumoral factors from dense core secretory vesicles provides essential neuroeffectors for cell-cell communication in the nervous and endocrine systems. This study provides comprehensive proteomic characterization of the categories of proteins in chromaffin dense core secretory vesicles that participate in cell-cell communication from the adrenal medulla. Proteomic studies were conducted by nano-HPLC Chip MS/MS tandem mass spectrometry. Results demonstrate that these secretory vesicles contain proteins of distinct functional categories consisting of neuropeptides and neurohumoral factors, protease systems, neurotransmitter enzymes and transporters, receptors, enzymes for biochemical processes, reduction/oxidation regulation, ATPases, protein folding, lipid biochemistry, signal transduction, exocytosis, calcium regulation, as well as structural and cell adhesion proteins. The secretory vesicle proteomic data identified 371 proteins in the soluble fraction and 384 membrane proteins, for a total of 686 distinct secretory vesicle proteins. Notably, these proteomic analyses illustrate the presence of several neurological disease-related proteins in these secretory vesicles, including huntingtin interacting protein, cystatin C, ataxin 7, and prion protein. Overall, these findings demonstrate that multiple protein categories participate in dense core secretory vesicles for production, storage, and secretion of bioactive neuroeffectors for cell-cell communication in health and disease.

Microarray analysis of rat hippocampus exposed to excitotoxicity: reversal Na(+)/Ca(2+) exchanger NCX3 is overexpressed in glial cells

Multiple factors are involved in the glutamate-induced excitotoxicity phenomenon, such as overload of ionotropic and metabotropic receptors, excess Ca(2+) influx, nitric oxide synthase activation, oxidative damage due to increase in free radicals, and release of endogenous polyamine, among others. In order to attempt a more integrated approach to address this issue, we established, by microarray analysis, the hippocampus gene expression profiles under glutamate-induced excitotoxicity conditions. Increased gene expression is mainly related to excitotoxicity (CaMKII, glypican 2, GFAP, NCX3, IL-2, and Gmeb2) or with cell damage response (dynactin and Ecel1). Several genes that augmented their expression are related to glutamatergic system modulation, in particular with NMDA receptor modulation and calcium homeostasis (IL-2, CaMKII, acrosin, Gmeb2, hAChE, Slc83a, and SP1 factor). Conversely, among genes that diminished their expression, we found the Syngap 1, which is downregulated by CaMKII, and the MHC II, which is downregulated by glutamate. Changes observed in gene expression induced by monosodium glutamate (MSG) neonatal treatment in the hippocampus are consistent with the activation of the mechanisms that modulate NMDA receptor function as well as with the implementation of plastic response to cell damage and intracellular calcium homeostasis. Regarding this aspect, we report here that NCX3/Slc8a3, a Na(+)/Ca(2+) membrane exchanger, is highly expressed in astrocytes, both in vitro and in vivo, in response to glutamate-induced excitotoxicity. Hence, the results of this analysis present a broad view of the expression profile elicited by MSG neonatal treatment, and lead us to suggest the possible molecular pathways of action and reaction involved under this experimental model of excitotoxicity.

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.

Extracellular matrix protein SC1/hevin in the hippocampus following pilocarpine-induced status epilepticus

Pilocarpine-induced status epilepticus (SE) mimics many features of temporal lobe epilepsy and is a useful model to study neural changes that result from prolonged seizure activity. In this study, distribution of the anti-adhesive extracellular matrix protein SC1 was examined in the rat hippocampus following SE. Western blotting showed decreased levels of SC1 protein in the week following SE. Immunohistochemistry demonstrated that the decrease in overall SC1 protein levels was reflected by a reduction of SC1 signal in granule cells of the dentate gyrus. Interestingly, levels of SC1 protein in neurons of the seizure-resistant CA2 sector of the hippocampus did not change throughout the seizure time course. However, at 1 day post-SE, a subset of neurons of the hippocampal CA1, CA3, and hilar regions, which are noted for extensive neuronal degeneration after SE, exhibited a transient increase in SC1 signal. Neurons exhibiting enhanced SC1 signal were not detected at 7 days post-SE. The cellular stress response was also examined. A prominent induction of heat-shock protein (Hsp70) and Hsp27 was detected following SE, while levels of constitutively expressed Hsp40, Hsp90, Hsp110, and Hsc70 showed little change at the time points examined. The subset of neurons that demonstrated a transient increase in SC1 colocalized with the cellular stress marker Hsp70, the degeneration marker Fluoro-Jade B, and the neuron activity marker activity-regulated cytoskeleton-associated protein (Arc). Taken together, these findings suggest that SC1 may be a component of the 'matrix response' involved in remodeling events associated with neuronal degeneration following neural injury.

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.

Purification and Characterization of High Molecular Mass and Low Molecular Mass Cystatin from Goat Brain

Cystatin are thiol proteinase inhibitors ubiquitously present in mammalian body and serve various important physiological functions. In the present study two cystatins were isolated from goat brain using alkaline treatment, ammonium sulphate fractionation, gel filtration and ion exchange chromatography. The high molecular mass cystatin of 70.8 kDa was named as HM-GBC (high molecular mass goat brain cystatin) and the low molecular mass cystatin of 12.72 kDa was named as LM-GBC (low molecular mass goat brain cystatin). The molecular mass determined by SDS-PAGE was found to be 70.8 and 12.88 kDa for HM-GBC and LM-GBC, respectively, however with gel filtration the masses were found to be 70.8 and 12.58 kDa. Both the cystatins were found to be stable in broad range of pH and temperature. HM-GBC was found to have 2% carbohydrate content while LM-GBC lacks any carbohydrate content. Both cystatins were found to be devoid of any sulphydryl content. Stoke's radii of 36 and 16 A, and diffusion coefficient of 6.189 x 10(-15) and 1.392 x 10(-14) cm(2)/s were calculated for HM-GBC and LM-GBC. K (i) values with papain were found to be 1.875 x 10(-8) and 3.125 x 10(-8) M for HM-GBC and LM-GBC, respectively. K (+1), K (-1) and half-life calculated along with K (i) values obtained showed that HM-GBC inhibited papain more specifically as compared to LM-GBC. The IC(50) values obtained for HM-GBC and LM-GBC also showed that HM-GBC binds more effectively to papain than LM-GBC. Ultraviolet and fluorescence spectra indicated that upon formation of papain-HM-GBC/LM-GBC complex there is significant conformational change after interaction in one or both the proteins of the complex.

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.

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.

Cystatin C expression is increased in the hippocampus following photothrombotic stroke in rat

Stroke is a major cause of epilepsy, but the molecular mechanisms underlying post-stroke epileptogenesis are unknown. The expression of cystatin C, a cysteine protease inhibitor, is increased in the hippocampus during status epilepticus (SE)-induced epileptogenesis, and regulates both cell death and birth. To test the hypothesis that increased cystatin C expression represents a common molecular alteration induced by epileptogenic brain insults, we investigated the time course, cellular localization, and association of cystatin C expression with neuronal damage during post-stroke epileptogenesis. Stroke was induced with photothrombosis, which leads to epilepsy in approximately 20-30% of rats. Cystatin C expression was increased in the CA1 area of the hippocampus 4 days after photothrombosis, when the diameter of the lesion was the largest. Double-labeling and confocal analysis indicated that cystatin C was expressed in astrocytes and microglia. Unlike after SE, cystatin C expression did not change in the dentate gyrus. Also, increased cystatin C expression was not associated with neurodegeneration, which was demonstrated as an absence of Fluoro Jade B-positive cells in adjacent sections. The present study provides evidence that cystatin C may be involved in cellular alterations that occur after an epileptogenic insult, not only after SE but also after photothrombotic stroke.

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.

Cystatin C expression is associated with granule cell dispersion in epilepsy

Human temporal lobe epilepsy (TLE) is associated with cellular alterations (eg, hilar cell death, neurogenesis, and granule cell dispersion) in the dentate gyrus but their underlying molecular mechanism are not known. We previously demonstrated increased expression of cystatin C, a protease inhibitor linked to both neurodegeneration and neurogenesis, during epileptogenesis in the rat hippocampus. Here, we investigated cystatin C expression in the dentate gyrus in chronic epilepsy and its association with neuronal loss and neurogenesis. In both rats with epilepsy and human patients with TLE, cystatin C expression was increased in glial cells in the molecular layer of the dentate gyrus, being most prominent in cases with granule cell dispersion. In patients with TLE, high cystatin C expression associated with greater numbers of polysialylated neural cell adhesion molecule-positive newborn cells in the molecular layer, although the overall number was decreased, indicating that the newborn cells migrate to abnormal locations in the epileptic dentate gyrus. These data thus demonstrate that cystatin C expression is altered during the chronic phase of epilepsy and suggest that cystatin C plays a role in network reorganization in the epileptic dentate gyrus, especially in granule cell dispersion and guidance of migrating newborn granule cells.

cDNA profiling of epileptogenesis in the rat brain

Symptomatic temporal lobe epilepsy typically develops in three phases: brain insult --> latency period (epileptogenesis) --> recurrent seizures (epilepsy). We hypothesized that remodeling of neuronal circuits underlying epilepsy is associated with altered gene expression during epileptogenesis. Epileptogenesis was induced by electrically triggered status epilepticus (SE) in rats. Animals were continuously monitored with video-EEG, and the hippocampus and temporal lobe were collected either during epileptogenesis (1, 4 and 14 days) or after the first spontaneous seizures (14 days) for cDNA array analysis. Altogether, 282 genes had altered expression, from which 87 were in the hippocampus and 208 in the temporal lobe (overlap in 13). Assessment of hippocampal gene expression during epileptogenesis indicated that 37 genes were altered in the 1-day group, 12 in the 4-day group and 14 in the 14-day epileptogenesis group. There were 42 genes with altered expression in the 14-day epilepsy group. In the temporal lobe, the number of genes with altered expression was 29 in the 1-day group, 155 in the 4-day group, 32 in the 14-day epileptogenesis group and 62 in the 14-day epilepsy group. Products of the altered genes are involved in neuronal plasticity, gliosis, organization of the cytoskeleton or extracellular matrix, cell adhesion, signal transduction, regulation of cell cycle, and metabolism. As most of these genes have not previously been implicated in epileptogenesis or epilepsy, these data open new avenues for understanding the molecular basis of epileptogenesis and provide new targets for rational development of anti-epileptogenic treatments for patients with an elevated risk of epileptogenesis after brain injury.