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.     

Hereditary spastic paraplegia

The hereditary spastic paraplegias (HSPs) comprise a large group of inherited neurologic disorders. HSP is classified according to the mode of inheritance, the HSP locus when known, and whether the spastic paraplegia syndrome occurs alone or is accompanied by additional neurologic or systemic abnormalities. Analysis of 11 recently discovered HSP genes provides insight into HSP pathogenesis. Hereditary spastic paraplegia is a clinical diagnosis for which laboratory confirmation is sometimes possible, and careful exclusion of alternate and co-existing disorders is an important element in HSP diagnosis. Treatment for HSP is presently limited to symptomatic reduction of muscle spasticity, reduction in urinary urgency, and strength and gait improvement through physical therapy. Prenatal genetic testing in HSP is possible for some individuals with the increasing availability of HSP gene analysis.     

Hereditary spastic paraplegia

The hereditary spastic paraplegias (HSPs) comprise a large group of inherited neurologic disorders. HSP is classified according to the mode of inheritance, the HSP locus when known, and whether the spastic paraplegia syndrome occurs alone or is accompanied by additional neurologic or systemic abnormalities. Analysis of 11 recently discovered HSP genes provides insight into HSP pathogenesis. Hereditary spastic paraplegia is a clinical diagnosis for which laboratory confirmation is sometimes possible, and careful exclusion of alternate and co-existing disorders is an important element in HSP diagnosis. Treatment for HSP is presently limited to symptomatic reduction of muscle spasticity, reduction in urinary urgency, and strength and gait improvement through physical therapy. Prenatal genetic testing in HSP is possible for some individuals with the increasing availability of HSP gene analysis.     

Neuroprotective preconditioning of rat brain cultures with ethanol: potential transduction by PKC isoforms and focal adhesion kinase upstream of increases in effector heat shock proteins

Preconditioning rat hippocampal-entorhinocortical (HEC) slice or cerebellar cell cultures with moderate concentrations of ethanol (20-30 mm) neuroprotects against pro-inflammatory proteins such as HIV-1 glycoprotein 120 (gp120) or amyloid-β. The neuroprotective mechanism of ethanol is unclear, but it conceivably involves sensors→transducers→effectors, analogous to other preconditioning modalities. We initially found that the preconditioning augmented two likely heat shock protein (HSP) 'effectors', HSP70 and HSP27, and that precluding HSP upregulation abolished neuroprotection. Here we examined whether pro-survival kinases are transducers potentially leading to HSP effectors. In cerebellar cultures, protein kinase C (PKC) activity increased modestly after 2 days of 30 mm ethanol and was significantly induced after 6 days, when neuroprotection against gp120 becomes manifest. After 4 and particularly after 6 days of preconditioning, immunoblots showed highly elevated PKCε levels and moderately increased PKCα and PKCδ, accompanied by increased membrane translocation (activation) of these isoforms. Also, at the latter preconditioning duration, focal adhesion kinase (FAK), an important actin-associated kinase, and its Y397-phosphorylated form (p-FAK) were elevated, along with parallel increases in HSP27, S85p-HSP27 and HSP70. Furthermore, while confirming increased HSP27 and HSP70 in HEC slices ethanol-preconditioned for 6 days, we detected elevations in PKC isoforms, FAK, p-FAK and p-HSP27 in these organotypic cultures. Importantly, PKC inhibition with GF109203X suppressed FAK, HSP70 and HSP27 amplification/activation in ethanol-preconditioned cerebellar cultures, indicating that PKC is an upstream transducer of FAK and the HSP effectors. Neuroprotection associated with increases in HSP27/HSP70 from ethanol preconditioning entails upregulation/activation of PKC isoforms and FAK, the latter kinase implicating actin cytoskeletal prosurvival pathways in brain preconditioning.     

Hereditary spastic paraplegia: genetic heterogeneity and genotype-phenotype correlation

Hereditary spastic paraplegia (HSP) is a group of disorders whose primary symptom is insidiously progressive, lower extremity spasticity and weakness. Neuropathological analysis of "pure" HSP reveals axonal degeneration that is maximal in the terminal portions of the longest descending and ascending tracts (crossed and uncrossed corticospinal tracts to the legs and fasciculus gracilis, respectively). HSP may be transmitted as an X-linked, autosomal recessive, or autosomal dominant trait, each of which is genetically heterogeneous: mutations in different genes cause clinically similar disorders. To date, there are at least three genetic loci for X-linked HSP; at least three genetic loci for autosomal recessive HSP; and at least six genetic loci for autosomal dominant HSP. The genetic basis for three of these twelve forms of HSP have been discovered. One form of autosomal recessive HSP (on chromosome 16) is due to mutations in the paraplegin gene, which encodes a mitochondrial protein homologous to metalloproteases. One form of X-linked HSP is caused by mutations in the proteolipoprotein gene, an intrinsic myelin protein. Mutation in this gene also causes the dysmyelinating disorder, Pelizeaus-Merzbacher disease. X-linked spastic paraplegia can be caused also by mutations in the L1CAM gene. This review summarizes our current understanding of genetic heterogeneity and genotype-phenotype correlation in HSP.     

Glial expression of small heat shock proteins following an excitotoxic lesion in the immature rat brain

Heat shock proteins (HSPs) are chaperones induced under pathological conditions and involved in protein stabilization and cellular protection. In this study, we have evaluated the expression pattern of the glial cell-related HSP27, HSP32, and HSP47 following an excitotoxic lesion in the immature rat brain. Postnatal day 9 rats received an intracortical injection of N-methyl-D-aspartate and tissue was processed immunohistochemically for HSPs and double labeling using astroglial and microglial markers. HSP expression was quantified by image analysis. Excitotoxic damage caused primary cortical degeneration and secondary damage in the corresponding thalamus. In the injured cortex, reactive microglia/macrophages expressed HSP32 from 10 h until 14 days postlesion (PL), showing maximal levels at days 3-5. In parallel, most cortical reactive astrocytes showed expression of HSP47 from 10 h until 14 days PL and a population of them also displayed HSP27 labeling from 1 day PL. In addition, some cortical reactive astrocytes showed a temporary expression of HSP32 at day 1. In general, astroglial HSP expression in the cortex achieved maximal levels at days 3-5 PL. In the damaged thalamus, HSP32 was not significantly induced, but reactive astrocytes expressed HSP47 and some of them also HSP27. Thalamic astroglial HSP induction was transient, peaked at 5 days PL and reached basal levels by day 14. The injury-induced expression of HSP32, HSP27, and HSP47 in glial cells may contribute to glial cell protection and adaptation to damage, therefore playing an important role in the evolution of the glial response and the excitotoxic lesion outcome. HSP32 may provide antioxidant protective mechanisms to microglia/macrophages, whereas HSP47 could contribute to extracellular matrix remodeling and HSP27 may stabilize the astroglial cytoskeleton and participate in astroglial antioxidant mechanisms.     

Hereditary spastic paraplegias

Hereditary spastic paraplegias (HSP) are characterised by symmetric spastic paraplegia, pallhypaesthesia, and urinary dysfunction (uncomplicated HSP). Complicated HSP is present if uncomplicated HSP additionally presents with epilepsy, dementia, cataract, extrapyramidal dysfunction, amyotrophy, polyneuropathy, or ichthyosis. Clinically, HSP are similar but genetically even more heterogeneous. The disease course is slowly progressive and, the earlier the disease onset, the slower the course. Causes of HSP are mutations in 20 different genes, of which eight have been identified so far. A single mutation can cause complicated and uncomplicated HSP. Onset and severity can be quite variable between both groups and within families. Despite molecular genetic advances, diagnosis of HSP still relies on clinical features and the exclusion of various differential diagnoses. Neuropathologically, there is degeneration of corticospinal, posterior column, and spinocerebellar axons. Most likely, degeneration of the longest CNS axons is due to an impaired energy supply of the anterograde and retrograde axonal transport.     

Glucocorticoids regulate the synthesis of HSP27 in rat brain slices

Using mild heat shock of rat brain slices as a model for cellular insult, corticosteroid-mediated regulation of protein synthesis has been investigated. Following a single in vivo injection of rats with corticosterone or the Type II glucocorticoid receptor agonist, RU-28362, synthesis of a 28 kDa protein is elevated in cerebellar slices which are subsequently incubated in vitro at 39°C for 3 h. Immunoblotting of proteins subsequent to separation by two-dimensional gel electrophoresis has identified this glucocorticoid-sensitive protein to be the small molecular weight heat-shock protein, HSP27. Synthesis of the major heat-shock proteins, HSP70 and HSP90, is not glucocorticoid-sensitive. When animals are sacrificed at either 4 h following an aldosterone injection or at 24 h following a corticosterone injection, the synthesis of HSP27 in cerebellar slices is decreased. Treatment of adrenalectomized rats with either corticosterone, RU-28362 or aldosterone produces increased synthesis of HSP27. With duration of heat shock, there is a transient increase in the synthesis of HSP27 after 2 h at 39°C in slices from the cerebral cortex, with a more sustained synthesis of HSP27 in cerebellar slices. In hippocampal slices, HSP27 is rarely present. The upregulated synthesis of HSP27 in the cerebellum following an acute exposure to stress-like elevations in corticosterone titers may contribute to the relative resistance of this brain region to cellular insults.     

Structure, properties, and functions of the human small heat-shock protein HSP22 (HspB8, H11, E2IG1): a critical review

The recently described human HSP22 belongs to the superfamily of small heat-shock proteins containing a conservative alpha-crystallin domain. HSP22 seems to be involved in regulation of cell proliferation, cardiac hypertrophy, apoptosis, and carcinogenesis, and expression of point mutants of HSP22 correlates with development of different neuromuscular diseases. Therefore, an investigation of the structure and properties of HSP22 is desirable for understanding its multiple functions. HSP22 seems to belong to the group of so-called intrinsically disordered proteins and possesses a highly flexible structure. HSP22 tends to form small-molecular-mass oligomers and interacts with biological membranes and many different proteins, among them glycolytic enzymes and different protein kinases. HSP22 possesses chaperonelike activity and prevents aggregation of denatured proteins both in vitro and in vivo. Depending on the cell type and its expression, HSP22 might have either pro- or anti-apoptotic effects. Chaperonelike activity seems to be important for antiapoptotic effects, whereas interaction with and regulation of certain protein kinases might be important for the proapoptotic effects of HSP22. Expression of K141N or K141E mutants of HSP22 correlates with development of distal hereditary motor neuropathy and/or Charcot-Marie-Tooth disease. These mutations destabilize the structure of HSP22, affect its interaction with other small heat-shock proteins, and decrease its chaperonelike activity. HSP22 decreases or prevents aggregation of Huntingtin fragments and amyloid-beta peptide 1-40 of the Dutch type. Thus, HSP22 seems to play an important role in the nervous system, and further investigations are needed to understand the molecular mechanisms of its functioning.     

Paraplegin gene analysis in hereditary spastic paraparesis (HSP) pedigrees in northeast England

OBJECTIVE: To identify the frequency and characterize the phenotype of paraplegin mutations in the hereditary spastic paraparesis (HSP) population in the northeast of England. BACKGROUND: HSP is a disorder that shows both clinical and genetic heterogeneity. To date, 13 loci have been associated with an HSP phenotype, with the causative gene having been identified in four of these. Two autosomal genes have been identified, paraplegin and spastin, and two X-linked genes have been identified, L1CAM (cell adhesion molecule) and proteolipid protein. METHODS: Thirty HSP pedigrees from the northeast of England were analyzed for mutation in each of the 17 exons of the paraplegin gene. RESULTS: A single family with a paraplegin mutation was identified in which the paraplegin mutation co-segregates with an HSP phenotype in an apparent dominant manner. The authors also describe frequent polymorphism in the paraplegin gene in both the HSP and control populations. CONCLUSION: Mutations in the paraplegin gene are not a common cause of HSP in the northeast of England. The phenotype of the paraplegin-related HSP family described had several striking features including amyotrophy, raised creatine kinase, sensorimotor peripheral neuropathy, and oxidative phosphorylation defect on muscle biopsy.     

Overexpression of HSP72 after induction of experimental stroke protects neurons from ischemic damage.

The 72-kD inducible heat shock protein (HSP72) can attenuate cerebral ischemic injury when overexpressed before ischemia onset. Whether HSP72 overexpression is protective when applied after ischemia onset is not known, but would have important clinical implications. Fifty-seven rats underwent middle cerebral artery occlusion for 1 hour. Defective herpes simplex viral (HSV) vectors expressing hsp72 with lacZ as a reporter were delivered 0.5, 2, and 5 hours after ischemia onset into each striatum. Control animals received an identical vector containing only lacZ. Striatal neuron survival at 2 days was improved by 23% and 15% when HSP72 vectors were delayed 0.5 and 2 hours after ischemic onset, respectively ( P < 0.05). However, when delayed by 5 hours, HSP72 overexpression was no longer protective. This is the first demonstration that HSP72 gene transfer even after ischemia onset is neuroprotective. Because expression from these HSV vectors begins 4 to 6 hours after injection, this suggests that the temporal therapeutic window for HSP72 is at least 6 hours after ischemia onset. Future strategies aimed at enhancing HSP72 expression after clinical stroke may be worth pursuing. The authors suggest that in the future HSP72 may be an effective treatment for stroke.     

Different pattern of HSP47 expression in skeletal muscle of patients with neuromuscular diseases

Heat shock protein (HSP) 47, a collagen-specific molecular chaperone, is involved in the processing and secretion of procollagens, and its expression is increased in various fibrotic diseases. However, its involvement in muscle diseases is unknown. In this study, we analyzed HSP47 expression in muscular dystrophies and other muscle diseases. We found an overexpression of HSP47 in fibrous connective tissue and in the adjacent muscle membrane in various muscular dystrophies. However, in Ullrich congenital muscular dystrophy (UCMD), the overexpression of HSP47 was found only in the connective tissue, and not in the muscle membrane. The overexpression of HSP47 was found only in the muscle membrane in the case of active inflammatory myopathy. In particular, HSP47 was strongly expressed in the membrane of regenerating fibers. We found that HSP47 in the muscle membrane locates in the basement membrane with confocal microscopy. Our findings suggest that HSP47 may be involved in the repair or regeneration of muscle fibers in addition to the fibrotic change in the connective tissue.     

Mice overexpressing rat heat shock protein 70 are protected against cerebral infarction

Increased expression of heat shock protein 70 (HSP70) in the brain has been extensively documented in association with a variety of insults, including ischemia, and is suggested to play a role in cell survival and recovery after ischemic injury. To more directly assess the protective role of HSP70 during ischemic brain damage, we used transgenic mice overexpressing the rat HSP70 (HSP70tg mice). In contrast to wild-type (wt) littermates, high levels of HSP70 messenger RNA and protein were detected in brains of HSP70tg mice under normal conditions, and immunohistochemical analysis revealed primarily neuronal expression of HSP70. Heterozygous HSP70tg mice and their wt littermates were subjected to permanent focal cerebral ischemia by intraluminal blockade of the middle cerebral artery. Cerebral infarction after 6 hours of ischemia, as evaluated by Nissl staining, was significantly less in HSP70tg mice compared with wt mice. This reduction in infarction volume in HSP70tg mice was not attributable to an altered cardiovascular anatomy or to initial differences in body temperature or hemodynamic parameters. The HSP70tg mice were still protected against cerebral infarction 24 hours after permanent focal ischemia. The data suggest that HSP70 can markedly protect the brain against ischemic damage and that approaches aimed at inducing HSP70 may lead to new therapeutic interventions in cerebrovascular injuries.     

Hyperthermic pre-conditioning protects retinal neurons from N-methyl-D-aspartate (NMDA)-induced apoptosis in rat

Glutamate-induced excitotoxicity is associated with a selective loss of retinal neurons after retinal ischemia and possibly in glaucoma. Since heat shock protein (HSP) 70 is known to play a protective role against ischemic neuronal injury, which is also linked to excitotoxicity, we studied the expression of inducible (HSP72) and constitutive (HSC70) forms of HSP70 in apoptosis of retinal ganglion cells (RGCs) after intravitreal injection of 8 nmoles N-methyl-D-aspartate (NMDA), a glutamate receptor agonist. Approximately 18 h after NMDA injection, there were increased numbers of TUNEL-positive cells and cells with elevated HSP72 immunoreactivity in the retinal ganglion cell layer (RGCL), but there were no noticeable changes in HSC70 immunoreactivity. These HSPs positive cells were also Thy-1 positive, a marker for RGCs. Hyperthermic pre-conditioning, which is known to induce HSPs, given 6 or 12 h prior to NMDA injection ameliorated neuronal loss in the RGCL as counted 7 days after NMDA injection but pre-conditioning at 18 h prior to NMDA injection did not have any ameliorative effect. Quercetin, an inhibitor of HSP synthesis, abolished the ameliorative effect of hyperthermic pre-conditioning. Pre-conditioning elevated HSP72 but not HSC70 immunoreactivity and reduced the number of TUNEL-positive cells in the RGCL at 18 h. Our results suggest that intravitreal injection of NMDA induces an up-regulation of HSP72 in a time-dependent manner but not HSC70 in RGCs, indicating a stress response of HSP72 in RGCs and other inner retinal neurons after exposure to NMDA. Hyperthermic pre-conditioning given within a therapeutic window is neuroprotective to the retina against NMDA-induced excitotoxicity, likely by inhibiting apoptosis through the modulation of HSP72 expression.     

Induction of 27-kDa heat shock protein following cerebral ischemia in a rat model of ischemic tolerance

Preconditioning the brain with sublethal cerebral ischemia induces tolerance to subsequent lethal periods of ischemia (ischemic tolerance). The purpose of this study is to investigate the role of low-molecular weight stress proteins, 27-kDa heat shock protein (HSP27) and αB crystallin, in ischemic tolerance. We measured the content of these proteins with enzyme immunoassay in the rat hippocampus and cerebral cortex following 6 min of ischemia with and without preconditioning with 3 min of ischemia and 3 days of reperfusion. We also visualized the localization of HSP27 immunohistochemically in comparison with that of HSP70. A 3-min period of ischemia caused a 2.4-fold increase in HSP27 content in the hippocampus after 3 days. Immunohistochemical localization of HSP27 was found in glial cells in all subregions of the hippocampus, whereas HSP70 immunostaining was seen only in CA1 pyramidal neurons. HSP27 content in the hippocampus decreased 2 h after 6 min of ischemia. HSP27 content progressively increased in the unpreconditioned hippocampus after 1 and 3 days, but returned to preischemic levels in the preconditioned hippocampus. HSP27 and HSP70 immunostaining was seen in CA1 pyramidal neurons after 1 day both with and without preconditioning. After 3 and 7 days, an intense HSP27 staining was observed in reactive glial cells in the CA1 without preconditioning, whereas the staining decreased in the preconditioned hippocampus. HSP70 staining was seen only in neurons at these time points. We observed no significant changes in HSP27 content in the cerebral cortex although neurons in the third and fifth layers were immunostained after 1 and 3 days. We observed no alterations in αB crystallin content after ischemia both in the hippocampus and the cortex. The present study demonstrated that cerebral ischemia induces HSP27 expression but not αB crystallin. Both HSP27 and HSP70 induction had a good temporal correlation with the induction of ischemic tolerance. However, different sites of action were suggested because the localization and cell types of HSP27 induction were quite different from those of HSP70 induction. The result suggests that it is unlikely that HSP27 is directly involved in the protection afforded by ischemic preconditioning.     

Changed distribution pattern of the constitutive rather than the inducible HSP70 chaperone in neuromelanin-containing neurones of the Parkinsonian midbrain

Aberrant protein aggregation has been recognized as an important factor in the degeneration of melanized dopaminergic neurones in Parkinson's disease (PD). The constitutive (HSP73) and (heat)-inducible (HSP72) proteins of the heat shock 70 family form a major defence system against pathological protein aggregation. However, the distribution patterns of these chaperones in nigral neuromelanin-laden neurones are largely unknown. The present study determined the distribution of HSP72 and HSP73 in control and Parkinsonian substantia nigra, using immunohistochemistry. In the neuromelanin-laden neurones of controls, HSP72 was nondetectable, whereas HSP73 was weakly expressed in both the cytosol and the nucleus. Surprisingly, in PD subjects, marked nuclear HSP73, but not HSP72 immunoreactivity was observed, while cytosolic immunoreactivity of the two chaperones resembled the labelling pattern observed in controls. Furthermore, HSP73 immunoreactivity was observed in a subset of the Lewy bodies (LBs) detected in the substantia nigra of PD subjects, whereas only few of these LBs were labelled with HSP72. Interestingly, HSP72 and to a lesser extent HSP73 immunoreactivity was much stronger in nonmelanized neurones as compared with melanized neurones in this area. Thus, we conclude that the distribution pattern of HSP73 rather than HSP72 is changed in the nigral neuromelanin-laden neurones of PD subjects as compared with control subjects. The impaired ability of aged, dopaminergic neurones to express high levels of chaperones, may contribute to the preferential vulnerability of the latter cells in PD.     

Exogenous androgen treatment delays the stress response following hamster facial nerve injury

Following injury or stress of any type, cells undergo a stress response, involving the cessation of general protein synthesis and the up-regulation of heat shock proteins (HSP), which have been implicated in promoting cell survival and repair. In a variety of neuronal injury models, including the hamster facial motoneurone (FMN) model, steroid hormones augment regeneration and are neuroprotective. We have previously shown that facial nerve axotomy induces expression of HSP70 (HSP70) and/or up-regulates constitutively expressed HSP70 (HSC70) mRNA in axotomised hamster FMN and that testosterone propionate (TP) treatment reduces this response. These previous studies were unable to differentiate between HSC70 mRNA and HSP70 mRNA. Therefore, an objective of the present study was to determine which HSP (HSC70 or HSP70) was being up-regulated by axotomy and reduced by TP. Axotomy increased HSC70 protein in axotomised and non-axotomised FMN, relative to untreated baseline hamsters. Interestingly, TP transiently delayed the stress-induced up-regulation of HSC70 protein in axotomised FMN compared to axotomised FMN from non-TP treated controls. A potential explanation for this delay may involve the TP-induced liberation of HSP from the androgen receptor, which would provide the injured cell with an immediately available pool of protective HSP. An hypothesis is presented suggesting that this TP-induced delay of stress-induced HSC70 up-regulation might allow for the diversion of cellular energy away from HSP synthesis and towards the synthesis of proteins required for regeneration and survival.     

沙鼠脑缺血耐受的组织学变化及HSP在其中的作用

目的 :观察脑缺血耐受时的组织学变化及 HSP在其中的作用。方法 :通过 HE染色观察脑缺血耐受时的组织学变化 ,并通过免疫组化染色 ,了解 HSP70及 HSP2 7在其中的作用。结果 :一次性 5分钟缺血后 7天海马 CA1区神经元大多坏死 ,若在缺血前给予 2分钟的缺血预处理 ,该区神经元大多保留 ,表现出明显的保护作用。只给一次性 5分钟缺血 ,海马 CA1区神经元无 HSP70染色。若在缺血前给予预处理 ,海马 CA1区神经元可见明显 HSP70染色。而HSP2 7主要在胶质细胞表达 ,海马区的神经元未见其表达。结论 :缺血前给予预处理对以后的缺血有保护作用 ;在缺血耐受过程中 ,HSP70表达出一定的保护作用。     

Activation of p38 MAPK participates in brain ischemic tolerance induced by limb ischemic preconditioning by up-regulating HSP 70

This study investigates whether activation of p38 MAPK by the up-regulation of HSP 70 participates in the induction of brain ischemic tolerance by limb ischemic preconditioning (LIP). Western blot and immunohistochemical assays indicated that p38 MAPK activation occurred earlier than HSP 70 induction in the CA1 region of the hippocampus after LIP. P-p38 MAPK expression was up-regulated at 6 h and reached its peak 12 h after LIP, while HSP 70 expression was not significantly increased until 1 day and peaked 2 days after LIP. Neuropathological evaluation by thionin staining showed that quercetin (4 ml/kg, 50 mg/kg, intraperitoneal injection), an inhibitor of HSP 70, blocked the protective effect of LIP against delayed neuronal death that is normally induced by lethal brain ischemic insult, indicating that HSP 70 participates in the induction of brain ischemic tolerance by LIP. Furthermore, SB 203580, an inhibitor of HSP 70, inhibited HSP 70 activation in the CA1 region of the hippocampus induced by LIP either with or without the presence of subsequent brain ischemic insult. Based on the above results, it can be concluded that activation of p38 MAPK participates in the brain ischemic tolerance induced by LIP at least partly by the up-regulation of HSP 70 expression.     

Neuronal induction of 72-kDa heat shock protein following methamphetamine-induced hyperthermia in the mouse hippocampus

By means of an immunohistochemical technique, we examined the neuronal induction of 72-kDa heat shock protein (HSP72) in response to methamphetamine-induced hyperthermia in the mouse hippocampus. Strong HSP72 immunoreactivity (ir) was found in the neurons of hippocampus proper, particularly in the CA1/2 and medial CA3 subfields, at 10 h after drug injection. By 18 h, those neurons still revealed HSP72-ir, while neurons of the dentate gyrus also appeared positive for HSP72. At this stage, intense HSP72-ir was first detected in non-neuronal cells, i.e. glial and vascular endothelial cells. At 24 h, no apparent HSP72-ir was found in the hippocampal neurons, while only non-neuronal cells still revealed immunoreactivity for HSP72. In addition, no morphological evidence of cell degeneration or loss was noted in the CA1 sector or other hippocampal regions at 5 days after hyperthermic insult. In conclusion, (1) methamphetamine-induced hyperthermia per se is a stressful stimulant causing neuronal induction of HSP72 in the hippocampus neurons, particularly of CA1/2 and medial CA3 sectors, but does not prove fatal to the cells; (2) there is a cell type-specific difference in response to hyperthermic insult by inducing HSP72 and the timing of the induction response in the hippocampal formation; and (3) the animals that underwent drug-induced hyperthermia may be useful as an experimental model for the study of the protective mechanism of heat shock proteins against subsequent harmful stimuli.