Simultaneous induction of mitochondrial heat shock protein mRNAs in rat forebrain ischemia

Analysis of spatial and temporal protein expression in the cerebral cortex after ischemia-reperfusion injury

Background and Purpose

Hypoxia, or ischemia, is a common cause of neurological deficits in the elderly. This study elucidated the mechanisms underlying ischemia-induced brain injury that results in neurological sequelae.

Methods

Cerebral ischemia was induced in male Sprague-Dawley rats by transient ligation of the left carotid artery followed by 60 min of hypoxia. A two-dimensional differential proteome analysis was performed using matrix-assisted laser desorption ionization-time-of-flight mass spectrometry to compare changes in protein expression on the lesioned side of the cortex relative to that on the contralateral side at 0, 6, and 24 h after ischemia.

Results

The expressions of the following five proteins were up-regulated in the ipsilateral cortex at 24 h after ischemia-reperfusion injury compared to the contralateral (i.e., control) side: aconitase 2, neurotensin-related peptide, hypothetical protein XP-212759, 60-kDa heat-shock protein, and aldolase A. The expression of one protein, dynamin-1, was up-regulated only at the 6-h time point. The level of 78-kDa glucose-regulated protein precursor on the lesioned side of the cerebral cortex was found to be high initially, but then down-regulated by 24 h after the induction of ischemia-reperfusion injury. The expressions of several metabolic enzymes and translational factors were also perturbed soon after brain ischemia.

Conclusions

These findings provide insights into the mechanisms underlying the neurodegenerative events that occur following cerebral ischemia.

Heat shock proteins: cellular and molecular mechanisms in the central nervous system

Emerging evidence indicates that heat shock proteins (HSPs) are critical regulators in normal neural physiological function as well as in cell stress responses. The functions of HSPs represent an enormous and diverse range of cellular activities, far beyond the originally identified roles in protein folding and chaperoning. HSPs are now understood to be involved in processes such as synaptic transmission, autophagy, ER stress response, protein kinase and cell death signaling. In addition, manipulation of HSPs has robust effects on the fate of cells in neurological injury and disease states. The ongoing exploration of multiple HSP superfamilies has underscored the pluripotent nature of HSPs in the cellular context, and has demanded the recent revamping of the nomenclature referring to these families to reflect a re-organization based on structure and function. In keeping with this re-organization, we first discuss the HSP superfamilies in terms of protein structure, regulation, expression and distribution in the brain. We then explore major cellular functions of HSPs that are relevant to neural physiological states, and from there we discuss known and proposed HSP impacts on major neurological disease states. This review article presents a three-part discussion on the array of HSP families relevant to neuronal tissue, their cellular functions, and the exploration of therapeutic targets of these proteins in the context of neurological diseases.

Identification of proteins regulated by estradiol in focal cerebral ischemic injury--a proteomics approach

Estradiol protects neuronal cells against permanent and focal ischemic brain damage. We identified the proteins that are expressed following estradiol administration during cerebral ischemia in an animal model. Adult female rats were ovariectomized and treated with oil or estradiol prior to middle cerebral artery occlusion (MCAO) to induce cerebral ischemia, and brains were collected 24h after MCAO. Protein analysis was performed on the cerebral cortex using two-dimensional gel electrophoresis. Protein spots with difference in intensity between oil- and estradiol-treated groups were identified by mass spectrometry. Among these proteins, levels of protein phosphatase 2A (PP2A) and astrocytic phosphoprotein PEA-15 were significantly decreased in the oil-treated group in comparison to the estradiol-treated group. Moreover, Western blot analysis demonstrated that estradiol treatment prevents injury-induced decrease of PP2A and PEA-15 levels during both MCAO-induced injury and glutamate exposure in HT22 cells. In contrast, levels of the 60kDa heat shock protein (Hsp 60) were significantly increased in oil-treated animals, while estradiol prevented the injury-induced increase of Hsp 60. The results of this study provide an evidence that estradiol protects neuronal cells against ischemic brain injury through the up- and down-modulation of specific proteins.

Behavioral and quantitative mitochondrial proteome analyses of the effects of simvastatin: implications for models of neural degeneration

The 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor, simvastatin, is used for lowering elevated low-density lipoprotein cholesterol concentrations. This translates into reduced cardiovascular disease-related morbidity and mortality, while the drugs' anti-oxidant and anti-inflammatory properties have earmarked it as a potential treatment strategy against various neurological conditions. Statins have been shown to protect neurons from degeneration in a number of animal models. Although no mechanism completely explains the multiple benefits exerted by statins, emerging evidence suggests that in some degenerative and brain injury models, mitochondrial impairment may play a contributive rate. However, [corrected] evidence lacks to support a directly influencing role for statins on mitochondria-related proteins and motor behavior. Mitochondrial dysfunction may increase oxygen free radical production, which in turn leaves cells susceptible to energy failure, apoptosis and related events [corrected] which could prove fatal. The potential link between simvastatin treatment and mitochondrial function would be supported if key mitochondrial proteins were altered by simvastatin exposure. Using mass spectroscopy (MS), we identified 24 mitochondrial proteins that differed significantly (P < 0.05) in relative abundancy as a result of simvastatin treatment. The identified proteins represented many facets of mitochondrial integrity, with the majority forming part of the electron transport chain machinery, which is necessary for energy production. In a follow-up study, we then addressed whether simvastatin is capable of altering sensorimotor function in a mitochondrial toxin-induced animal model. Rats were pre-treated with simvastatin for 14 days, followed by a single unihemispheric (substantia nigra; SN) injection of rotenone, a mitochondrial complex I (Co-I) inhibitor. Results showed that simvastatin improved motor performance in rotenone-infused rats. The data are consistent with the possibility that alteration of mitochondrial function may contribute to the beneficial effects associated with statin use.

Proteomic approach to studying the cytotoxicity of YC-1 on U937 leukemia cells and antileukemia activity in orthotopic model of leukemia mice

To evaluate the effects of YC-1 on leukemia cell lines, PI incorporation was used to determine cell viability. YC-1 induced a dose- and time-dependent decrease in viability and apoptosis in YC-1-treated U937 cells. YC-1-induced apoptosis is a cyclic guanosine monophosphate (cGMP)-independent pathway. Proteomic analysis showed that the altered proteins include the significant regulation of HSP70, chaperonin, ATP synthase beta chains, and Chain F. Western blotting and immuno-cytochemistry stain showed that YC-1 treatment caused a time-dependent increase in cytosolic Cytochrome c, pro-caspase-9, Apaf-1, and the activation of caspase-9 and -3. Importantly, the in vivo antileukemia effects of YC-1 were evaluated in BALB/c mice inoculated with WEHI-3B orthotopic model. YC-1 enhanced survival rate and prevented the body weight loss in leukemia mice. The enlargement of spleen and lymph nodes were reduced in YC-1 treated than that in leukemia mice. H-E stain of spleen sections revealed that infiltration of immature myeloblastic cells into red pulp was reduced in YC-1-treated group. The apoptotic cells of splenocyte were significantly increased in YC-1 treated than that in leukemia mice by Tdt-mediated deoxyuridine triphosphate nick end labeling (TUNEL) assay. Taken together, we conclude that YC-1 acted against U937 cells in vitro via a mitochondrial-dependent apoptosis pathway, and in orthotopic leukemia model, YC-1 administered antileukemia activity.

A novel inhibitor of advanced glycation and endoplasmic reticulum stress reduces infarct volume in rat focal cerebral ischemia

We have developed a novel, non-toxic inhibitor of advanced glycation and oxidative stress, TM2002, devoid of effect on blood pressure. In transient focal ischemia, TM2002 significantly decreased infarct volume compared with vehicle (79.5+/-18.7 vs. 183.3+/-22.9 mm3, p<0.01). In permanent focal ischemia, TM2002 (2.79, 5.58, and 11.16 mg/kg twice a day) dose-dependently reduced infarct volume (242.1+/-32.3, 201.3+/-15.1, and 171.3+/-15.2 mm3, respectively), and improved neurological deficits. Reduction of infarct volume is demonstrable, provided that TM2002 was administered within 1.5 h after the occlusion. To unravel TM2002's mechanism of action, we examined its in vitro effect on endoplasmic reticulum (ER) stress, using aortic smooth muscle cells isolated from ORP 150(+/-) mice and F9 Herp null mutated cells. Cell death induced by ER stress (tunicamycin or hypoxia) was dose-dependently prevented by TM2002. In vivo immunohistochemical study demonstrated a significant reduction of ORP- and TUNEL-positive apoptotic cells, especially in the penumbra. Inhibition of advanced glycation and oxidative stress was confirmed by a significantly reduced number of cells positive for advanced glycation end products and heme oxygenase-1. TM2002 reduced the levels of protein carbonyl formation in ischemic caudate. The efficacy of TM2002 is equivalent to that of a known neuroprotective agent, NXY-059. In conclusion, TM2002 significantly ameliorates ischemic cerebral damage through reduction of ER stress, advanced glycation, and oxidative stress, independently of blood pressure lowering.

Interferon-gamma-induced expressions of heat shock protein 60 and heat shock protein 10 in C6 astroglioma cells: identification of the signal transducers and activators of transcription 3-binding site in bidirectional promoter

Heat shock protein 60 and heat shock protein 10 are mitochondrial chaperonin proteins. Here, we report that the expressions of heat shock protein 60 and heat shock protein 10 were upregulated in interferon-gamma-treated C6 astroglioma cells, and the 582 bp in the bidirectional promoter of the heat shock protein 60 and heat shock protein 10 genes is responsible for interferon-gamma-induced induction. The induction of heat shock protein 60 and heat shock protein 10 by interferon-gamma was virtually abolished by introducing mutations into the putative signal transducers and activators of transcription 3-response element in the promoter, and the same mutation impaired increment of the signal transducers and activators of transcription 3-binding after interferon-gamma treatment. Moreover, Rac1 GTPase was required for maximal heat shock protein 10 and heat shock protein 60 inductions by interferon-gamma. These results suggest that interferon-gamma-induced upregulations of heat shock protein 60 and heat shock protein 10 in C6 astroglioma cells are mediated by the signal transducers and activators of transcription 3-binding site, localized in the bidirectional promoter.

NO-induced downregulation of HSP10 and HSP60 expression in the postischemic brain

Heat shock protein 60 (HSP60) and HSP10 are mitochondrial chaperonin proteins and are responsible for the folding of newly imported proteins and 13 polypeptides encoded by mitochondrial DNA. The expressions of HSP60 and HSP10 are regulated simultaneously because these genes are localized head to head on chromosome, separated by a bidirectional promoter, which harbors heat shock element (HSE), CHOP, STAT3, and SP1 binding sites. In the present study, we show that the expressions of HSP60 and HSP10 in the brain after middle cerebral artery occlusion (MCAO) are induced significantly. Interestingly, the expressions of HSP60 and HSP10 were further upregulated by the administration of aminoguanidine (AG), an inhibitor of the inducible nitric oxide synthase (iNOS), which is known to reduce ischemic damage in an animal model after MCAO. The results obtained in the present study suggest that HSP10 and HSP60 are induced in the postischemic brain, yet are downregulated by NO generated from 12 hr after MCAO/reperfusion. The downregulation of HSP60 and HSP10 by NO were confirmed in vitro, wherein HSP10 and SHP60 expressions were increased by treatment of LPS and IFN gamma (LPS/INF gamma) in C6 astroglioma cells and further upregulated by NMMA, another iNOS inhibitor. Reporter gene analysis combined with deletion and mutation studies showed that STAT3 binding site in the bidirectional promoter is responsible for LPS/INF gamma-induced upregulation and for downregulation by NO. Our results indicated that NO suppresses HSP60 and HSP10 inductions in the postischemic brain by suppressing STAT3 binding to its recognition site.

Redox regulation of cellular stress response in aging and neurodegenerative disorders: role of vitagenes

Reduced expression and/or activity of antioxidant proteins lead to oxidative stress, accelerated aging and neurodegeneration. However, while excess reactive oxygen species (ROS) are toxic, regulated ROS play an important role in cell signaling. Perturbation of redox status, mutations favoring protein misfolding, altered glyc(osyl)ation, overloading of the product of polyunsaturated fatty acid peroxidation (hydroxynonenals, HNE) or cholesterol oxidation, can disrupt redox homeostasis. Collectively or individually these effects may impose stress and lead to accumulation of unfolded or misfolded proteins in brain cells. Alzheimer's (AD), Parkinson's and Huntington's disease, amyotrophic lateral sclerosis and Friedreich's ataxia are major neurological disorders associated with production of abnormally aggregated proteins and, as such, belong to the so-called "protein conformational diseases". The pathogenic aggregation of proteins in non-native conformation is generally associated with metabolic derangements and excessive production of ROS. The "unfolded protein response" has evolved to prevent accumulation of unfolded or misfolded proteins. Recent discoveries of the mechanisms of cellular stress signaling have led to new insights into the diverse processes that are regulated by cellular stress responses. The brain detects and overcomes oxidative stress by a complex network of "longevity assurance processes" integrated to the expression of genes termed vitagenes. Heat-shock proteins are highly conserved and facilitate correct protein folding. Heme oxygenase-1, an inducible and redox-regulated enzyme, has having an important role in cellular antioxidant defense. An emerging concept is neuroprotection afforded by heme oxygenase by its heme degrading activity and tissue-specific antioxidant effects, due to its products carbon monoxide and biliverdin, which is then reduced by biliverdin reductase in bilirubin. There is increasing interest in dietary compounds that can inhibit, retard or reverse the steps leading to neurodegeneration in AD. Specifically any dietary components that inhibit inappropriate inflammation, AbetaP oligomerization and consequent increased apoptosis are of particular interest, with respect to a chronic inflammatory response, brain injury and beta-amyloid associated pathology. Curcumin and ferulic acid, the first from the curry spice turmeric and the second a major constituent of fruit and vegetables, are candidates in this regard. Not only do these compounds serve as antioxidants but, in addition, they are strong inducers of the heat-shock response. Food supplementation with curcumin and ferulic acid are therefore being considered as a novel nutritional approach to reduce oxidative damage and amyloid pathology in AD. We review here some of the emerging concepts of pathways to neurodegeneration and how these may be overcome by a nutritional approach.

Mitochondrial heat shock protein 60 is increased in cerebrospinal fluid following pediatric traumatic brain injury

Mitochondrial dysfunction occurs after traumatic brain injury (TBI) and contributes significantly to subsequent cell death. Heat shock protein 60 (hsp60) is a predominantly mitochondrial protein with important homeostatic functions. Induction of hsp60 has been demonstrated in cerebral ischemia models, possibly reflecting mitochondrial stress. We measured hsp60 concentration in the cerebrospinal fluid (CSF) of 34 infants and children after severe TBI and of 7 control patients by ELISA. Peak CSF hsp60 concentration was increased in TBI patients versus controls (0.84 ng/ml, range 0-44.59, vs. 0.0 ng/ml, range 0-0.48; p<0.05). Induction of hsp60 occurred early after the injury. Peak hsp60 concentration was independently associated with the severity of injury, defined as the admission Glasgow Coma Scale score. These data suggest that increased hsp60 in CSF might reflect the severity of early mitochondrial stress or damage after TBI.

Expression of chaperonin 60 in the hippocampus of the streptozotocin diabetic rat

Mitochondrial dysfunction and oxidative stress are implicated in the pathological changes observed in the diabetic central nervous system. In this study, using the streptozotocin-induced diabetic rat model we document for the first time the over-expression of a mitochondrial specific stress protein (chaperonin 60) in the CA1/CA3 regions of the diabetic hippocampus in the absence of neurodegeneration. The increase in expression of chaperonin 60 was not observed in the cohort treated with insulin, suggesting that the observed effect was not due to streptozotocin per se but due to the hyperglycaemic state induced by the diabetic state. The expression of chaperonin 60 was also positively correlated with a marker of mitochondrial oxidative stress (manganese superoxide dismutase). We suggest that chaperonin 60 could be an early event marker of mitochondrial dysfunction in the diabetic central nervous system and indeed be neuroprotective in the early stages of hyperglycaemic-induced oxidative stress.

Redox modulation of heat shock protein expression by acetylcarnitine in aging brain: relationship to antioxidant status and mitochondrial function

There is significant evidence to show that aging is characterized by a stochastic accumulation of molecular damage and by a progressive failure of maintenance and repair processes. Protective mechanisms exist in the brain which are controlled by vitagenes and include members of the heat shock system, heme oxygenase-I, and Hsp70 as critical determinants of brain stress tolerance. Given the broad cytoprotective properties of the heat shock response, molecules inducing this defense mechanism appear to be possible candidates for novel cytoprotective strategies. Acetyl-L-carnitine is proposed as a therapeutic agent for several neurodegenerative disorders, and the present study reports that treatment for 4 months of senescent rats with acetyl-L-carnitine induces heme oxygenase-1 as well as Hsp70 and SOD-2. This effect was associated with upregulation of GSH levels, prevention of age-related changes in mitochondrial respiratory chain complex expression, and decrease in protein carbonyls and HNE formation. We hypothesize that maintenance or recovery of the activity of vitagenes may delay the aging process and decrease the risk of age-related diseases. Particularly, modulation of endogenous cellular defense mechanisms via acetyl-L-carnitine may represent an innovative approach to therapeutic intervention in diseases causing tissue damage, such as neurodegeneration.

Induction of heat shock proteins by hyperglycemic cerebral ischemia

Hyperglycemia worsens the neuronal death induced by cerebral ischemia. A previous study demonstrated that diabetic hyperglycemia suppressed the expression of heat shock protein 70 (HSP70) in the liver. The objective of this study is to determine whether hyperglycemia exacerbates ischemic brain damage by suppressing the expression of heat shock proteins (HSPs) in the brain. Both normoglycemic and hyperglycemic rats were subjected to a transient global cerebral ischemia of 15 min and followed by 0.5, 1 and 3 h of reperfusion. The expression of stress-related genes and levels of HSP proteins were determined by DNA microarray, immunocytochemistry and Western blot analyses. The results showed that hyperglycemic ischemia upregulated the expressions of hsp70, hsp90A, hsp90B, heat shock cognate 71 kD protein (hsc70) and mthsp70. Protein levels of HSP70 and HSP60 were enhanced by hyperglycemia compared with normoglycemia. The results suggested that hyperglycemia-exacerbated ischemic brain damage is not mediated by the suppression of the HSPs. The increased levels of HSPs and mthsp70 suggest that the cell and the mitochondrion had strong stress responses to hyperglycemic ischemia.

Acetylcarnitine induces heme oxygenase in rat astrocytes and protects against oxidative stress: involvement of the transcription factor Nrf2

Efficient functioning of maintenance and repair processes seem to be crucial for both survival and physical quality of life. This is accomplished by a complex network of the so-called longevity assurance processes, under control of several genes termed vitagenes. These include members of the heat shock protein system, and there is now evidence that the heat shock response contributes to establishing a cytoprotective state in a wide variety of human conditions, including inflammation, neurodegenerative disorders, and aging. Among the various heat shock proteins, heme oxygenase-1 has received considerable attention; it has been recently demonstrated that heme oxygenase-1 induction, by generating the vasoactive molecule carbon monoxide and the potent antioxidant bilirubin, could represent a protective system potentially active against brain oxidative injury. Acetyl-L-carnitine is proposed as a therapeutic agent for several neurodegenerative disorders. Accordingly, we report here that treatment of astrocytes with acetyl-L-carnitine induces heme oxygenase-1 in a dose- and time-dependent manner and that this effect was associated with up-regulation of heat shock protein 60 as well as high expression of the redox-sensitive transcription factor Nrf2 in the nuclear fraction of treated cells. In addition, we show that addition of acetyl-L-carnitine to astrocytes, prior to proinflammatory lipopolysaccharide- and interferon-gamma-induced nitrosative stress, prevents changes in mitochondrial respiratory chain complex activity, protein nitrosation and antioxidant status induced by inflammatory cytokine insult. Given the broad cytoprotective properties of the heat shock response, molecules inducing this defense mechanism appear to be possible candidates for novel cytoprotective strategies. Particularly, manipulation of endogenous cellular defense mechanisms via acetyl-L-carnitine may represent an innovative approach to therapeutic intervention in diseases causing tissue damage, such as neurodegeneration. We hypothesize that maintenance or recovery of the activity of vitagenes may delay the aging process and decrease the risk of age-related diseases.

DNA microarray analysis of hippocampal gene expression measured twelve hours after hypoxia-ischemia in the mouse

Cell death from cerebral ischemia is a dynamic process. In the minutes to days after an ischemic insult, progressive changes in cellular morphology occur. Associated with these events is the regulation of competing programs of gene expression; some are protective against ischemic insult, and others contribute to delayed cell death. Many genes involved in these processes have been identified, but individually, these findings have provided only limited insight into the systems biology of cerebral ischemia. Attempts to characterize the coordinated expression of large numbers of genes in cerebral ischemia has only recently become possible. Today, DNA microarray technology provides a powerful tool for investigating parallel expression changes for thousands of genes at one time. In this study, adult mice were subjected to 30 minutes of hypoxia-ischemia (HI), and the hippocampus was examined 12 hours later for differential gene expression using a 15K high-density mouse EST array. The genomic response to HI is complex, affecting approximately 7% of the total number of ESTs examined. Assigning differentially expressed ESTs to molecular functional groups revealed that HI affects many pathways including the molecular chaperones, transcription factors, kinases, and calcium ion binding genes. A comprehensive list of regulated genes should prove valuable in advancing our understanding of the pathogenesis of cerebral ischemia.

Ten kilodalton heat shock protein (HSP10) is overexpressed during carcinogenesis of large bowel and uterine exocervix

In the present study, we evaluated the presence and the level of expression of HSP10 in two carcinogenetic models: the 'adenoma-carcinoma sequence' of large bowel and the 'dysplasia-carcinoma sequence' of uterine exocervix. We found HSP10 was overexpressed during the carcinogenesis of both organs. In particular, HSP10 was overexpressed early in large bowel carcinogenesis, while the expression of this protein in exocervical carcinogenesis gradually increased from normal through dysplastic to neoplastic tissues. The quantitative analysis of immunohistochemistry and the Western blotting confirmed these results. Our previous observations showed overexpression of HSP60 in the same carcinogenetic models. This report correlates the overexpression of HSP10 with that of HSP60 during carcinogenesis in vivo. These results could stimulate further studies on the pathogenetic role of these proteins during the carcinogenesis as well as their use as diagnostic and prognostic tools in oncology.

Induction of mitochondrial heat shock protein 60 and 10 mRNAs following transient focal cerebral ischemia in the rat

Heat shock proteins (HSPs) 60 and 10 are stress-inducible mitochondrial matrix proteins that form a chaperonin complex that is important for mitochondrial protein folding and function. The effect of cerebral ischemia on mitochondrial HSPs is unclear. The topographical and chronological patterns of HSP60 and HSP10 messenger ribonucleic acid (mRNA) expression and induction were investigated in the rat focal cerebral ischemia model. Focal cerebral ischemia was produced by transient middle cerebral artery occlusion for 30 or 90 min. Expression of mRNAs was analyzed using reverse transcription-polymerase chain reaction (RT-PCR) and in situ hybridization. RT-PCR analysis showed that both HSP60 and HSP10 mRNA levels increased significantly in the ischemic cortex from 4 to 24 h of reperfusion after 30 min of occlusion. In situ hybridization analysis demonstrated significant induction of both mRNAs in the whole ischemic cortex after 30 min of occlusion and in the dorsomedial border (penumbra) of the ischemic cortex and ipsilateral hippocampus after 90 min of occlusion. Expression patterns and the timing of the induction of both HSP60 and HSP10 mRNAs were identical throughout the experiments. Simultaneous induction of the mRNAs for the mitochondrial chaperonins, HSP60 and HSP10, in various regions in focal cerebral ischemia demonstrates that mitochondrial stress conditions persist concomitantly with cytosolic stress conditions in focal cerebral ischemia.