Biomedical subjects

Ruben Mestril

Publications and source records attributed to Ruben Mestril.

At least 19 recordsLinked to original sources

PubMed2007

Influence of PKC-alpha overexpression on HSP70 and cardioprotection.

Recent research has indicated that the protein kinase C (PKC) isoforms and the heat shock proteins (HSPs) are involved in cardioprotection. We have investigated the possible interaction between these two protein families. We have found that adenoviral-mediated expression of PKC-alpha in neonatal rat ventricular myocytes (NRVM) not only increases the expression of HSP70 but also protects against simulated ischemia-reperfusion. In addition, Western blots of PKC-alpha-infected NRVM indicated that other HSPs are not induced in the same manner as HSP70. In an effort to determine the mechanism of induction of HSP70 by PKC-alpha, we tested a chimeric construct that linked the luciferase reporter gene to the 5'-promoter region of HSP70 in myogenic H9c2 cells. When PKC-alpha was expressed, the 5'-promoter region of the HSP70 responded robustly, indicating that PKC-alpha induction of HSP70 expression is through transcription activation. Electrophoretic mobility shift assay determined that overexpression of PKC-alpha, PKC-delta, or PKC-epsilon did not induce activation of heat shock factor-1 (HSF-1). Therefore, induction of HSP70 by PKC-alpha is independent of heat shock factor-1 activation. We also measured cellular injury by assessing creatine kinase (CK) release from NRVM after simulated ischemia to determine cardioprotection. NRVM infected with the wild-type adenoviral construct AdwtPKC-alpha released 54% less CK than control NRVM. Experiments using small interfering RNA against HSP70 indicate that loss of PKC-alpha-induced HSP70 expression results in increased CK release or a loss of protection. Our results show that there is a close interaction between PKC-alpha and HSP70, independent of heat shock factor-1 activation, and that the protection conferred by PKC-alpha overexpression is mediated by the transcriptionally induced expression of HSP70.

Animals↗

PubMed2006

Differential effects of mitochondrial heat shock protein 60 and related molecular chaperones to prevent intracellular beta-amyloid-induced inhibition of complex IV and limit apoptosis.

Defects in mitochondrial oxidative metabolism, in particular decreased activity of cytochrome c oxidase, have been reported in Alzheimer disease tissue and in cultured cells that overexpress amyloid precursor protein. Mitochondrial dysfunction contributes to neurodegeneration in Alzheimer disease partly through formation of reactive oxygen species and the release of sequestered molecules that initiate programmed cell death pathways. The heat shock proteins (HSP) are cytoprotective against a number of stressors, including accumulations of misfolded proteins and reactive oxygen species. We reported on the property of Hsp70 to protect cultured neurons from cell death caused by intraneuronal beta-amyloid. Here we demonstrate that Hsp60, Hsp70, and Hsp90 both alone and in combination provide differential protection against intracellular beta-amyloid stress through the maintenance of mitochondrial oxidative phosphorylation and functionality of tricarboxylic acid cycle enzymes. Notably, beta-amyloid was found to selectively inhibit complex IV activity, an effect selectively neutralized by Hsp60. The combined effect of HSPs was to reduce the free radical burden, preserve ATP generation, decrease cytochrome c release, and prevent caspase-9 activation, all important mediators of beta-amyloid-induced neuronal dysfunction and death.

Amyloid beta-Peptides↗

PubMed2006

Ca2+/Calmodulin-dependent protein kinase II phosphorylation of ryanodine receptor does affect calcium sparks in mouse ventricular myocytes.

Previous studies in transgenic mice and with isolated ryanodine receptors (RyR) have indicated that Ca2+-calmodulin-dependent protein kinase II (CaMKII) can phosphorylate RyR and activate local diastolic sarcoplasmic reticulum (SR) Ca2+ release events (Ca2+ sparks) and RyR channel opening. Here we use relatively controlled physiological conditions in saponin-permeabilized wild type (WT) and phospholamban knockout (PLB-KO) mouse ventricular myocytes to test whether exogenous preactivated CaMKII or endogenous CaMKII can enhance resting Ca2+ sparks. PLB-KO mice were used to preclude ancillary effects of CaMKII mediated by phospholamban phosphorylation. In both WT and PLB-KO myocytes, Ca2+ spark frequency was increased by both preactivated exogenous CaMKII and endogenous CaMKII. This effect was abolished by CaMKII inhibitor peptides. In contrast, protein kinase A catalytic subunit also enhanced Ca2+ spark frequency in WT, but had no effect in PLB-KO. Both endogenous and exogenous CaMKII increased SR Ca2+ content in WT (presumably via PLB phosphorylation), but not in PLB-KO. Exogenous calmodulin decreased Ca2+ spark frequency in both WT and PLB-KO (K0.5 approximately 100 nmol/L). Endogenous CaMKII (at 500 nmol/L [Ca2+]) phosphorylated RyR as completely in <4 minutes as the maximum achieved by preactivated exogenous CaMKII. After CaMKII activation Ca2+ sparks were longer in duration, and more frequent propagating SR Ca2+ release events were observed. We conclude that CaMKII-dependent phosphorylation of RyR by endogenous associated CaMKII (but not PKA-dependent phosphorylation) increases resting SR Ca2+ release or leak. Moreover, this may explain the enhanced SR diastolic Ca2+ leak and certain triggered arrhythmias seen in heart failure.

Animals↗

PubMed2006

Effect of lifelong overexpression of HSP70 in skeletal muscle on age-related oxidative stress and adaptation after nondamaging contractile activity.

Skeletal muscle aging is characterized by atrophy, a deficit in specific force generation, increased susceptibility to injury, and incomplete recovery after severe injury. The ability of muscles of old mice to produce heat shock proteins (HSPs) in response to stress is severely diminished. Studies in our laboratory using HSP70 overexpressor mice demonstrated that lifelong overexpression of HSP70 in skeletal muscle provided protection against damage and facilitated successful recovery after damage in muscles of old mice. The mechanisms by which HSP70 provides this protection are unclear. Aging is associated with the accumulation of oxidation products, and it has been proposed that this may play a major role in age-related muscle dysfunction. Muscles of old wild-type (WT) mice demonstrated increased lipid peroxidation, decreased glutathione content, increased catalase and superoxide dismutase (SOD) activities, and an inability to activate nuclear factor (NF)-kappaB after contractions in comparison with adult WT mice. In contrast, levels of lipid peroxidation, glutathione content, and the activities of catalase and SOD in muscles of old HSP70 overexpressor mice were similar to adult mice and these muscles also maintained the ability to activate NF-kappaB after contractions. These data provide an explanation for the preservation of muscle function in old HSP70 overexpressor mice.

Actins↗

PubMed2006

Aberrant protein aggregation is essential for a mutant desmin to impair the proteolytic function of the ubiquitin-proteasome system in cardiomyocytes.

Aberrant protein aggregates in cardiomyocytes are frequently observed in many forms of cardiomyopathies and are often associated with impairment of proteolytic function of the ubiquitin-proteasome system (UPS). However, a causal relationship between mutant desmin (MT-des) induced aberrant protein aggregation and UPS impairment has not been established. The present study has tested the causal relationship. In cultured neonatal rat ventricular myocytes, modest overexpression of a human (cardio)myopathy-linked MT-des protein led to formation of desmin-positive aggregates and inhibited UPS proteolytic function in cardiomyocytes in a dose-dependent manner. Prevention or reduction of aberrant protein aggregation by co-expression of a heat shock protein (Hsp), alphaB-crystallin or inducible Hsp70, or by treatment of Congo red prevented and/or significantly attenuated the induction of UPS malfunction by MT-des. These findings prove for the first time that aberrant protein aggregation is not only sufficient but also required for MT-des to impair UPS proteolytic function in cardiomyocytes.

Animals↗

PubMed2006

Dynamic changes in free Ca-calmodulin levels in adult cardiac myocytes.

Despite its multifunctional role in cardiac myocyte function, little is known about dynamic changes in activation state of calmodulin (CaM). Thus, the purpose of this study was to develop a tool to measure Ca bound CaM (Ca-CaM) levels in intact cardiac myocytes. For dynamic measurements of Ca-CaM, we generated an adenoviral vector which expresses a cyan and a yellow fluorescent protein linked by a modified version of the Ca-CaM binding domain of avian smooth muscle myosin light chain kinase. Adult rabbit cardiac myocytes were infected with the Ca-CaM sensing probe or simultaneously infected with viruses containing CaM and the Ca-CaM sensing probe for 24-48 h. Myocytes were then field stimulated (1 Hz) and excited at 440 nm with emitted fluorescence measured at 485 and 535 nm. Changes in [Ca-CaM] are expressed as the ratio of 485 nm/535 nm. Small beat-to-beat changes of [Ca-CaM] were detected, but only when CaM was co-expressed with the sensor. However, upon beta-adrenergic stimulation with isoproterenol, there was an increase in the amplitude of the signals during each beat (parallel to the shortening, which is an indirect measure of [Ca]i) and also a rise in the diastolic [Ca-CaM]. Total [CaM] measured by both competitive ELISA and semi-quantitative Western blots was 5-6 microM in isolated adult ventricular myocytes. Our results indicate that there are dynamic changes in free Ca-CaM levels (a phasic component tracking [Ca]i) as well as system memory that integrates the [Ca]i signals (a tonic component).

Adult↗

PubMed2006

Downregulation of the constitutively expressed Hsc70 in diabetic myocardium is mediated by insulin deficiency.

The 70 kDa heat shock protein family plays important cardiac protective roles against myocardial injuries. Reduced myocardial protection is a common feature of diabetic myocardium. This study was carried out to define the changes in the 70 kDa heat shock protein family in the myocardium in the of streptozotocin-diabetes rats, and to explore the mechanisms through which diabetes alters the abundance of Hsp70/Hsc70 in cardiac muscle. In the diabetic myocardium, the abundance of Hsc70 was significantly reduced. The abundance of Hsp70 was low in cardiac muscle and was not induced in the diabetic myocardium. Unlike Hsp60, Hsp70 and Hsc70 did not augment insulin-like growth factor-I receptor signaling in cardiac muscle cells. In cultured cardiomyocytes, insulin directly increased the abundance of Hsc70, whereas insulin could not modulate Hsp70. Treating diabetic rats with insulin restored myocardial Hsc70 level, but phlorizin treatment failed to restore myocardial Hsc70. These in vivo and in vitro studies showed that downregulation of Hsc70 in diabetic myocardium was secondary to insulin deficiency. Thus, insulin played a major role in maintaining adequate expression of Hsc70 in cardiac muscle.

Adenoviridae↗

PubMed2005

Impairment of the ubiquitin-proteasome system in desminopathy mouse hearts.

Protein misfolding and aberrant aggregation are associated with many severe disorders, such as neural degenerative diseases, desmin-related myopathy (DRM), and congestive heart failure. Intrasarcoplasmic amyloidosis and increased ubiquitinated proteins are observed in human failing hearts. The pathogenic roles of these derangements in the heart remain unknown. The ubiquitin-proteasome system (UPS) plays a central role in intracellular proteolysis and regulates critical cellular processes. In cultured cells, aberrant aggregation by a mutant (MT) or misfolded protein impairs the UPS. However, this has not been demonstrated in intact animals, and it is unclear how the UPS is impaired. Cross-breeding UPS reporter mice with a transgenic mouse model of DRM featured by aberrant protein aggregation in cardiomyocytes, we found that overexpression of MT-desmin but not normal desmin protein impairs UPS proteolytic function in the heart. The primary defect does not appear to be in the ubiquitination or the proteolytic activity of the 20S proteasome, because ubiquitinated proteins and the peptidase activities of 20S proteasomes were significantly increased rather than decreased in the DRM heart. Therefore, the defect resides apparently in the entry of ubiquitinated proteins into the 20S proteasome. Consistent with this notion, key components (Rpt3 and Rpt5) of 19S proteasomes were markedly decreased, while major components of 20S proteasomes were increased. Additional experiments with HEK cells suggest that proteasomal malfunction observed in MT-desmin hearts is not secondary to cardiac malfunction or to disruption of desmin filaments. Thus, UPS impairment may represent an important pathogenic mechanism underlying cardiac disorders with abnormal protein aggregation.

Animals↗

PubMed2005

Overexpression of inducible 70-kDa heat shock protein in mouse attenuates skeletal muscle damage induced by cryolesioning.

Heat shock protein expression is elevated upon exposure to a variety of stresses and limits the extent of stress-induced damage. To investigate the putative role of inducible 70-kDa heat shock protein (HSP70) in skeletal muscle damage and regeneration, soleus and tibialis anterior (TA) muscles from HSP70-overexpressing transgenic mice were subjected to cryolesioning and analyzed after 1, 10, and 21 days. Histological analysis showed that the muscles from both HSP70 and wild-type mice treated with radicicol (a HSP inducer) had decreased necrosis after cryolesioning compared with controls. The decrease in muscle fiber cross-sectional area in both soleus and TA muscles in 10 days postlesioning was attenuated in HSP70 mice compared with wild-type mice. Glutathione peroxidase activity was increased 1 day after cryolesioning in both HSP70 and control mice and remained elevated for up to 21 days. Immunodetection of neuronal cell adhesion molecule (a satellite cell marker) and developmental/neonatal MHC were significantly lower in cryolesioned HSP70-overexpressing mice than in cryolesioned controls. These results suggest that HSP70 protects skeletal muscle against injury and radicicol might be useful as a skeletal muscle protective agent.

Animals↗

PubMed2005

Phosphorylation and binding of AUF1 to the 3'-untranslated region of cardiomyocyte SERCA2a mRNA.

Experimental animals and patients with cardiac hypertrophy and heart failure display abnormally slowed myocardial relaxation, which is associated with downregulation of sarco(endo)plasmic reticulum calcium ATPase 2a (SERCA2a), the cardiomyocyte sarcoplasmic reticulum Ca2+ pump. We previously showed that SERCA2a downregulation can be simulated in cultured neonatal rat ventricular myocytes (NRVM) by treatment with the hypertrophic agonist phorbol myristate acetate (PMA) or by overexpression of the novel protein kinase C (PKC) isoenzymes PKCdelta and PKCepsilon. PKC activation, in turn, decreased SERCA2a promoter activity and destabilized the SERCA2a mRNA. Here we demonstrate by using an RSV beta-galactosidase reporter system that a 609-nt fragment of the SERCA2a mRNA 3'-untranslated region (UTR), containing five adenylate-uridylate (AU)-rich regions, may be responsible for destabilizing the message following PMA treatment. UV cross-linking analysis demonstrated that several proteins found in the NRVM cell extracts bind to the 609-nt fragment. In addition, protein binding was transiently increased in response to PMA stimulation. 3'-UTR mRNA pull-down assays and Western blot analysis indicated that the AU binding protein AUF1 interacted with the SERCA2a 3'-UTR. AUF1 binding activity was predominantly found in the nuclear fraction, and PMA-induced AUF1 binding was associated with increased threonine phosphorylation of AUF1. These data suggest that the phosphorylation, binding, and location of AUF1 affect the posttranscriptional regulation of the SERCA2a message in NRVM.

3' Untranslated Regions↗

PubMed2005

4-Tertiary butyl phenol exposure sensitizes human melanocytes to dendritic cell-mediated killing: relevance to vitiligo.

The trigger initiating an autoimmune response against melanocytes in vitiligo remains unclear. Patients frequently experience stress to the skin prior to depigmentation. 4-tertiary butyl phenol (4-TBP) was used as a model compound to study the effects of stress on melanocytes. Heat shock protein (HSP)70 generated and secreted in response to 4-TBP was quantified. The protective potential of stress proteins generated following 4-TBP exposure was examined. It was studied whether HSP70 favors dendritic cell (DC) effector functions as well. Melanocytes were more sensitive to 4-TBP than fibroblasts, and HSP70 generated in response to 4-TBP exposure was partially released into the medium by immortalized vitiligo melanocyte cell line PIG3V. Stress protein HSP70 in turn induced membrane tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) expression and activation of DC effector functions towards stressed melanocytes. Melanocytes exposed to 4-TBP demonstrated elevated TRAIL death receptor expression. DC effector functions were partially inhibited by blocking antibodies to TRAIL. TRAIL expression and infiltration by CD11c+ cells was abundant in perilesional vitiligo skin. Stressed melanocytes may mediate DC activation through release of HSP70, and DC effector functions appear to play a previously unappreciated role in progressive vitiligo.

Adenoviridae↗

PubMed2004

The use of transgenic mice to study cytoprotection by the stress proteins.

Heat shock or stress proteins (HSPs) have been shown to be able to confer cytoprotection in a diversity of cell types and organisms. We were interested in assessing if HSPs, in particular HSP70, were protective against pathophysiological stresses such as myocardial ischemia. Our approach was to generate a transgenic mouse line that would constitutively express high levels of an inducible rat HSP70 isoform in the heart. The hearts of the transgenic mice were then used in an isolated perfused mouse heart model to assess whether increased expression of HSP70 alone was protective against ischemia-reperfusion injury. Our study showed that there was a significant improvement in contractile recovery, less cellular damage, and a reduction in infarct size in the hearts of transgenic mice as compared to non-transgenic mice following global ischemia in our isolated perfused mouse heart model. Additional studies have since shown that increased expression of HSP70 as well as other stress proteins in transgenic mice protects against different forms of pathological stresses. We present here the methods we used to generate HSP70 transgenic mice and assess their increased tolerance to ischemia-reperfusion injury.

Animals↗

PubMed2004

Interleukin-18 is a pro-hypertrophic cytokine that acts through a phosphatidylinositol 3-kinase-phosphoinositide-dependent kinase-1-Akt-GATA4 signaling pathway in cardiomyocytes.

In patients with congestive heart failure, high serum levels of the proinflammatory cytokine interleukin (IL)-18 were reported. A positive correlation was described between serum IL-18 levels and the disease severity. IL-18 has also been shown to induce atrial natriuretic factor (ANF) gene expression in adult cardiomyocytes. Because re-expression of the fetal gene ANF is mostly associated with hypertrophy, a hallmark of heart failure, we hypothesized that IL-18 induces cardiomyocyte hypertrophy. Treatment of the cardiomyocyte cell line HL-1 with IL-18 induced hypertrophy as characterized by increases in protein synthesis, phosphorylated p70 S6 kinase, and ribosomal S6 protein levels as well as cell surface area. Furthermore, IL-18 induced ANF gene transcription in a time-dependent manner as evidenced by increased ANF secretion and ANF promoter-driven reporter gene activity. Investigation into possible signal transduction pathways mediating IL-18 effects revealed that IL-18 activates phosphoinositide 3-kinase (PI3K), an effect that was blocked by wortmannin and LY-294002. IL-18 induced Akt phosphorylation and stimulated its activity, effects that were abolished by Akt inhibitor or knockdown. IL-18 stimulated GATA4 DNA binding activity and increased transcription of a reporter gene driven by multimerized GATA4-binding DNA elements. Pharmacological inhibition or knockdown studies revealed that IL-18 induced cardiomyocyte hypertrophy and ANF gene transcription via PI3K, PDK1, Akt, and GATA4. Most importantly, IL-18 induced ANF gene transcription and hypertrophy of neonatal rat ventricular myocytes via PI3K-, Akt-, and GATA4-dependent signaling. Together these data provide the first evidence that IL-18 induces cardiomyocyte hypertrophy via PI3K-dependent signaling, defines a mechanism of IL-18-mediated ANF gene transcription, and further supports a role for IL-18 in inflammatory heart diseases including heart failure.

Androstadienes↗

PubMed2004

Radicicol activates heat shock protein expression and cardioprotection in neonatal rat cardiomyocytes.

Heat shock proteins (HSPs) constitute an endogenous cellular defense mechanism against environmental stresses. In the past few years, studies have shown that overexpression of HSPs can protect cardiac myocytes against ischemia-reperfusion injury. In an attempt to increase the HSPs in cardiac tissue, we used the compound radicicol that activates HSP expression by binding to the HSP 90 kDa (HSP90). HSP90 is the main component of the cytosolic molecular chaperone complex, which has been implicated in the regulation of the heat shock factor 1 (HSF1). HSF1 is responsible for the transcriptional activation of the heat shock genes. In the present study, we show that radicicol induces HSP expression in neonatal rat cardiomyocytes, and this increase in HSPs confers cardioprotection to these cardiomyocytes. We also show that radicicol induction of the HSP and cardioprotection is dependent on the inhibition of HSP90 in cardiomyocytes. These results indicate that modulation of the active HSP90 protein level plays an important role in cardioprotection. Therefore, compounds, such as radicicol and its possible derivatives that inhibit the function of HSP90 in the cell may represent potentially useful cardioprotective agents.

Animals↗

PubMed2004

Progressive decrease in chaperone protein levels in a mouse model of Huntington's disease and induction of stress proteins as a therapeutic approach.

The manipulation of chaperone levels has been shown to inhibit aggregation and/or rescue cell death in Saccharomyces cerevisiae, Caenorhabditis elegans, Drosophila melanogaster and cell culture models of Huntington's disease (HD) and other polyglutamine (polyQ) disorders. We show here that a progressive decrease in Hdj1, Hdj2, Hsp70, alphaSGT and betaSGT brain levels likely contributes to disease pathogenesis in the R6/2 mouse model of HD. Despite a predominantly extranuclear location, Hdj1, Hdj2, Hsc70, alphaSGT and betaSGT were found to co-localize with nuclear but not with extranuclear aggregates. Quantification of Hdj1 and alphaSGT mRNA levels showed that these do not change and therefore the decrease in protein levels may be a consequence of their sequestration to aggregates, or an increase in protein turnover, possibly as a consequence of their relocation to the nucleus. We have used genetic and pharmacological approaches to assess the therapeutic potential of chaperone manipulation. Ubiquitous overexpression of Hsp70 in the R6/2 mouse (as a result of crossing to Hsp70 transgenics) delays aggregate formation by 1 week, has no effect on the detergent solubility of aggregates and does not alter the course of the neurological phenotype. We used an organotypic slice culture assay to show that pharmacological induction of the heat shock response might be a more useful approach. Radicicol and geldanamycin could both maintain chaperone induction for at least 3 weeks and alter the detergent soluble properties of polyQ aggregates over this time course.

Animals↗

PubMed2004

Mediators of ischemic preconditioning identified by microarray analysis of rat spinal cord.

Spinal ischemia is a frequent cause of paralysis. Here we explore the biological basis of ischemic preconditioning (IPC), the phenomenon in which a brief period of ischemia can confer protection against subsequent longer and normally injurious ischemia, to identify mediators of endogenous neuroprotection. Using microarrays, we examined gene expression changes induced by brief spinal ischemia using a rat balloon occlusion model. Among the nearly 5000 genes assayed, relatively few showed two-fold changes, and three groups stood out prominently. The first group codes for heat shock protein 70, which is induced selectively and robustly at 30 min after brief ischemia, with increases up to 100-fold. A second group encodes metallothioneins 1 and 2. These mRNAs are increased at 6 and 12 h after ischemia, up to 12-fold. The third group codes for a group of immediate-early genes not previously associated with spinal ischemia: B-cell translocation gene 2 (BTG2), the transcription factors early growth response 1 (egr-1) and nerve growth factor inducible B (NGFI-B), and a mitogen-activated protein kinase phosphatase, ptpn16, an important cell signaling regulator. These mRNAs peak at 30 min and return to baseline or are decreased 6 h after ischemia. Several other potentially protective genes cluster with these induced mRNAs, including small heat shock proteins, and many have not been previously associated with IPC. These results provide both putative mediators of IPC and molecular targets for testing preconditioning therapies.

Animals↗

PubMed2004

Spinal heat shock protein (70) expression: effect of spinal ischemia, hyperthermia (42 degrees C)/hypothermia (27 degrees C), NMDA receptor activation and potassium evoked depolarization on the induction.

The present study shows that anoxic neuronal depolarization or NMDA receptor activation are potent stimuli for inducing spinal neuronal heat shock protein 70 (Hsp70). Spinal hyperthermia, despite its significant glutamate releasing effect, induced only glial Hsp70 upregulation. No significant increase in spinal Hsp70 expression after potassium depolarization was seen. Transient spinal ischemia (6 min) was induced by the inflation of a 2F Fogarty catheter placed into descending thoracic aorta during concurrent hypotension (40 mmHg). To determine the onset of anoxic depolarization extracellular concentration of K+ was measured in the lumbar dorsal horn using a microelectrode. Spinal hyperthermia (42 degrees C) or hypothermia (27 degrees C) was induced using a heat exchanger placed in the paravertebral subcutaneous space overlying Th5-S4 spinal segments. To measure extracellular concentration of glutamate during hyperthermia a loop dialysis catheter was implanted into lumbar intrathecal space. Receptor specific (NMDA, 3 microg) or non-specific (KCl, 10 microl, 1M) neuronal depolarization was induced using previously implanted intrathecal catheters. After ischemia, temperature manipulations or drug injections animals survived for 4 or 24h. Animals were then terminally anesthetized and perfusion fixed for Hsp70 immunohistochemistry. After spinal ischemia or NMDA administration a neuronal Hsp70 expression was seen at 24h. After spinal hyperthermia only glial expression was seen at 4h. Hyperthermia significantly increased CSF glutamate concentration, however, MK-801 (a non-competitive NMDA receptor antagonist) pretreatment failed to block Hsp70 expression. After hypothermia or potassium depolarization only minimal or no Hsp70 expression was seen in glial cells. Exposure of neuronal tissue to a specific stimuli may lead to intervals of increased resistance to subsequent neurotoxic/ischemic insult. The intervening biochemistry of this protection has been attributed to a family of molecules referred to as HSP. In the present study, we demonstrate that short-lasting anoxic depolarization or activation of NMDA receptor are the most potent stimuli for spinal neuronal Hsp70 induction. This effect corresponds with the observed ischemic tolerance state induced by short-lasting preconditioning spinal ischemia.

Amino Acids↗

PubMed2003

Overexpression of HSP70 in mouse skeletal muscle protects against muscle damage and age-related muscle dysfunction.

Ageing is associated with skeletal muscle atrophy, a deficit in force generation, an increased susceptibility to contraction-induced injury, and a permanent force deficit following severe injury. Muscles of young mice adapt rapidly following exercise by an increase in the production of heat shock proteins (HSPs), whereas muscles of old mice show a severely diminished response. We hypothesized that overexpression of HSP70 in muscle throughout life would reduce age-related changes in function. The maximum tetanic force of extensor digitorum longus (EDL) muscles of adult and old wild-type (WT) and HSP70 overexpressor transgenic mice was determined. EDL muscles were subjected to damaging lengthening contractions and the ability to generate force was assessed for up to 28 days following the contractions. Overexpression of HSP70 in muscles of old transgenic mice prevented the specific force deficit observed in muscles of old WT mice. The complete recovery of muscles of old HSP70 transgenic mice by 14 days following the contraction protocol was in contrast to the 44% force deficit, which remained in muscles of old WT mice at 28 days following the protocol. These data indicate that a diminished production of HSP70 in muscles of old mammals has a major effect on age-related functional deficits.

Aging↗