Differential expression of heat shock protein HSP27 in human neurons and glial cells in culture

Regional Differences in Heat Shock Protein 25 Expression in Brain and Spinal Cord Astrocytes of Wild-Type and SOD1 G93A Mice

Heterogeneity of glia in different CNS regions may contribute to the selective vulnerability of neuronal populations in neurodegenerative conditions such as amyotrophic lateral sclerosis (ALS). Here, we explored regional variations in the expression of heat shock protein 25 in glia under conditions of acute and chronic stress. Hsp27 (Hsp27; murine orthologue: Hsp25) fulfils a number of cytoprotective functions and may therefore be a possible therapeutic target in ALS. We identified a subpopulation of astrocytes in primary murine mixed glial cultures that expressed Hsp25. Under basal conditions, the proportion of Hsp25-positive astrocytes was twice as high in spinal cord cultures than in cortical cultures. To explore the physiological role of the elevated Hsp25 expression in spinal cord astrocytes, we exposed cortical and spinal cord glia to acute stress, using heat stress and pro-inflammatory stimuli. Surprisingly, we observed no stress-induced increase in Hsp25 expression in either cortical or spinal cord astrocytes. Similarly, exposure to endogenous stress, as modelled in glial cultures from SOD1 G93A-ALS mice, did not increase Hsp25 expression above that observed in astrocytes from wild-type mice. In vivo, Hsp25 expression was greater under conditions of chronic stress present in the spinal cord of SOD1 G93A mice than in wild-type mice, although this increase in expression is likely to be due to the extensive gliosis that occurs in this model. Together, these results show that there are differences in the expression of Hsp25 in astrocytes in different regions of the central nervous system, but Hsp25 expression is not upregulated under acute or chronic stress conditions.

Neuroinflammatory processes are augmented in mice overexpressing human heat-shock protein B1 following ethanol-induced brain injury

Background

Heat-shock protein B1 (HSPB1) is among the most well-known and versatile member of the evolutionarily conserved family of small heat-shock proteins. It has been implicated to serve a neuroprotective role against various neurological disorders via its modulatory activity on inflammation, yet its exact role in neuroinflammation is poorly understood. In order to shed light on the exact mechanism of inflammation modulation by HSPB1, we investigated the effect of HSPB1 on neuroinflammatory processes in an in vivo and in vitro model of acute brain injury.

Methods

In this study, we used a transgenic mouse strain overexpressing the human HSPB1 protein. In the in vivo experiments, 7-day-old transgenic and wild-type mice were treated with ethanol. Apoptotic cells were detected using TUNEL assay. The mRNA and protein levels of cytokines and glial cell markers were examined using RT-PCR and immunohistochemistry in the brain. We also established primary neuronal, astrocyte, and microglial cultures which were subjected to cytokine and ethanol treatments. TNFα and hHSPB1 levels were measured from the supernates by ELISA, and intracellular hHSPB1 expression was analyzed using fluorescent immunohistochemistry.

Results

Following ethanol treatment, the brains of hHSPB1-overexpressing mice showed a significantly higher mRNA level of pro-inflammatory cytokines (Tnf, Il1b), microglia (Cd68, Arg1), and astrocyte (Gfap) markers compared to wild-type brains. Microglial activation, and 1 week later, reactive astrogliosis was higher in certain brain areas of ethanol-treated transgenic mice compared to those of wild-types. Despite the remarkably high expression of pro-apoptotic Tnf, hHSPB1-overexpressing mice did not exhibit higher level of apoptosis. Our data suggest that intracellular hHSPB1, showing the highest level in primary astrocytes, was responsible for the inflammation-regulating effects. Microglia cells were the main source of TNFα in our model. Microglia isolated from hHSPB1-overexpressing mice showed a significantly higher release of TNFα compared to wild-type cells under inflammatory conditions.

Conclusions

Our work provides novel in vivo evidence that hHSPB1 overexpression has a regulating effect on acute neuroinflammation by intensifying the expression of pro-inflammatory cytokines and enhancing glial cell activation, but not increasing neuronal apoptosis. These results suggest that hHSPB1 may play a complex role in the modulation of the ethanol-induced neuroinflammatory response.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-020-02070-2.

Spinal heat shock protein 27 participates in PDGFRβ-mediated morphine tolerance through PI3K/Akt and p38 MAPK signalling pathways

BACKGROUND AND PURPOSE

The development of antinociceptive morphine tolerance is a clinically intractable problem. Earlier work has demonstrated the pivotal roles of PDGF and its receptor PDGFRβ in morphine tolerance. Here, we have investigated the role of spinal heat shock protein 27 (HSP27) in morphine tolerance and its relationship with PDGFRβ activation.

EXPERIMENTAL APPROACH

Rats were treated with morphine for 9 days, and its anti-nociceptive effect against thermal pain was evaluated by a tail-flick latency test. Western blot, real-time PCR, immunofluorescent staining, and various antagonists, agonists, and siRNA lentiviral vectors elucidated the roles of HSP27, PDGFRβ, and related signalling pathways in morphine tolerance.

KEY RESULTS

Chronic morphine administration increased expression and phosphorylation of HSP27 in the spinal cord. Down-regulating HSP27 attenuated the development of morphine tolerance. PDGFRβ antagonism inhibited HSP27 activation and attenuated and reversed morphine tolerance. PDGFRβ induction increased HSP27 expression and activation and partly decreased morphine analgesia. PDGFRβ inhibition reduced Akt and p38 MAPK activity in morphine tolerance. PI3K and p38 inhibitors reversed morphine tolerance and suppressed morphine-induced HSP27 phosphorylation.

CONCLUSION AND IMPLICATIONS

This study demonstrated for the first time that spinal HSP27 participates in PDGFRβ-mediated morphine tolerance via the PI3K/Akt and p38 MAPK signalling pathways. These findings suggest a potential clinical strategy for prolonging the antinociceptive effects of opioids during long-term pain control.

CHIP mutations affect the heat shock response differently in human fibroblasts and iPSC-derived neurons

C-terminus of HSC70-interacting protein (CHIP) encoded by the gene STUB1 is a co-chaperone and E3 ligase that acts as a key regulator of cellular protein homeostasis. Mutations in STUB1 cause autosomal recessive spinocerebellar ataxia type 16 (SCAR16) with widespread neurodegeneration manifesting as spastic-ataxic gait disorder, dementia and epilepsy. CHIP^-/- mice display severe cerebellar atrophy, show high perinatal lethality and impaired heat stress tolerance. To decipher the pathomechanism underlying SCAR16, we investigated the heat shock response (HSR) in primary fibroblasts of three SCAR16 patients. We found impaired HSR induction and recovery compared to healthy controls. HSPA1A/B transcript levels (coding for HSP70) were reduced upon heat shock but HSP70 remained higher upon recovery in patient- compared to control-fibroblasts. As SCAR16 primarily affects the central nervous system we next investigated the HSR in cortical neurons (CNs) derived from induced pluripotent stem cells of SCAR16 patients. We found CNs of patients and controls to be surprisingly resistant to heat stress with high basal levels of HSP70 compared to fibroblasts. Although heat stress resulted in strong transcript level increases of many HSPs, this did not translate into higher HSP70 protein levels upon heat shock, independent of STUB1 mutations. Furthermore, STUB1(-/-) neurons generated by CRISPR/Cas9-mediated genome editing from an isogenic healthy control line showed a similar HSR to patients. Proteomic analysis of CNs showed dysfunctional protein (re)folding and higher basal oxidative stress levels in patients. Our results question the role of impaired HSR in SCAR16 neuropathology and highlight the need for careful selection of proper cell types for modeling human diseases.

Destructive Effect of Intravitreal Heat Shock Protein 27 Application on Retinal Ganglion Cells and Neurofilament

Heat shock protein 27 (HSP27) is commonly involved in cellular stress. Increased levels of HSP27 as well as autoantibodies against this protein were previously detected in glaucoma patients. Moreover, systemic immunization with HSP27 induced glaucoma-like damage in rodents. Now, for the first time, the direct effects of an intravitreal HSP27 application were investigated. For this reason, HSP27 or phosphate buffered saline (PBS, controls) was applied intravitreally in rats (n = 12/group). The intraocular pressure (IOP) as well as the electroretinogram recordings were comparable in HSP27 and control eyes 21 days after the injection. However, significantly fewer retinal ganglion cells (RGCs) and amacrine cells were observed in the HSP27 group via immunohistochemistry and western blot analysis. The number of bipolar cells, on the other hand, was similar in both groups. Interestingly, a stronger neurofilament degeneration was observed in HSP27 optic nerves, while no differences were noted regarding the myelination state. In summary, intravitreal HSP27 injection led to an IOP-independent glaucoma-like damage. A degeneration of RGCs as well as their axons and amacrine cells was noted. This suggests that high levels of extracellular HSP27 could have a direct damaging effect on RGCs.

Heat shock protein B1 is required for the prolactin-induced cytoprotective effects on pancreatic islets

The success of islet transplantation has improved lately. Unfortunately, it is still compromised by cell loss. We have shown that prolactin (PRL) inhibits beta-cell apoptosis and up-regulates the antiapoptotic Heat Shock Protein B1 (HSPB1) in human islets. Since its function in pancreatic islets has not been studied, we explored the role of HSPB1 in PRL-induced beta-cell survival. The significant PRL-induced cytoprotection in control cells was abrogated in HSPB1 silenced cells, overexpression of HSPB1 recovered survival. PRL-mediated inhibition of cytokine-induced caspase activities and cytokine-induced decrease of BCL-2/BAX ratio was significantly reverted in knocked-down cells. Kinetics of HSPB1 and HSF1 expression were studied in primary cultures of murine and human pancreatic islets. These findings are highly relevant for the improvement of clinical islet transplantation success rate since our results demonstrated a key role for HSPB1 pointing it as a promising target for beta-cell cytoprotection through the up-regulation of an endogenous protective pathway.

Melatonin reverses morphine tolerance by inhibiting microglia activation and HSP27 expression

AIMS

Melatonin has been reported to attenuate opioid tolerance. In this study, we explored the possible mechanism of melatonin in diminishing morphine tolerance.

MAIN METHODS

Two intrathecal (i.t.) catheters were implanted in male Wistar rats for drug delivery. One was linked to a mini-osmotic pump for morphine or saline infusion. On the seventh day, 50μg of melatonin or vehicle was injected through the other catheter instantly after discontinuation of morphine or saline infusion; 3h later, 15μg of morphine or saline was injected. The antinociceptive response was then measured using the tail-flick test every 30min for 120min.

KEY FINDINGS

The results showed that chronic morphine infusion elicited antinociceptive tolerance and upregulated heat shock protein 27 (HSP27) expression in the dorsal horn of the rat spinal cord. Melatonin pretreatment partially restored morphine's antinociceptive effect in morphine-tolerant rats and reversed morphine-induced HSP27 upregulation. In addition, chronic morphine infusion induced microglial cell activation and was reversed by melatonin treatment.

SIGNIFICANCE

The present study provides evidence that melatonin, acting via inhibiting morphine-induced neuroinflammation, can be useful as a therapeutic adjuvant for patients under long-term opioid treatment for pain relief.

Cross-talk between human neural stem/progenitor cells and peripheral blood mononuclear cells in an allogeneic co-culture model

Transplantation of human neural stem/progenitor cells (hNSCs) as a regenerative cell replacement therapy holds great promise. However, the underlying mechanisms remain unclear. We, here, focused on the interaction between hNSCs and allogeneic peripheral blood mononuclear cells (PBMCs) in a co-culture model. We found that hNSCs significantly decrease the CD3⁺ and CD8⁺ T cells, reduce the gamma delta T cells and increase the regulatory T cells, along with reduced pro-inflammatory cytokines and increased anti-inflammatory cytokines after co-culture. We also found that PBMCs, in turn, significantly promote the proliferation and differentiation of hNSCs. Our data suggest that hNSCs cross-talk with immune cells.

Mode of action of S-methyl-N, N-diethylthiocarbamate sulfoxide (DETC-MeSO) as a novel therapy for stroke in a rat model

One approach for protecting neurons from excitotoxic damage in stroke is to attenuate receptor activity with specific antagonists. S-Methyl-N, N-diethylthiocarbamate sulfoxide (DETC-MeSO), the active metabolite of disulfiram, has been shown to be a partial antagonist of glutamate receptors and effective in reducing seizure. First, we investigated neuroprotective effect of DETC-MeSO on primary cortical neuronal culture under hypoxia/reoxygenation condition in vitro. Then, DETC-MeSO was administered subcutaneously for 4 and 8 days with the first injection occurring 1 h before or 24 h after reperfusion in the rat middle cerebral artery occlusion stroke model. Rats were subjected to the neuroscore test, and the brain was analyzed for infarct size. Monitoring neurotransmitter release was carried out by microdialysis. Heat shock proteins, key proteins involved in apoptosis and endoplasmic reticulum (ER) stress, were analyzed by immunoblotting. DETC-MeSO greatly reduced both cell death following hypoxia/reoxygenation and brain infarct size. It improved performance on the neuroscore test and attenuated proteolysis of αII-spectrin. The level of pro-apoptotic proteins declined, and anti-apoptotic and HSP27 protein expressions were markedly increased. Levels of the ER stress protein markers p-PERK, p-eIF2α, ATF4, JNK, XBP-1, GADD34, and CHOP significantly declined after DETC-MeSO administration. Microdialysis data showed that DETC-MeSO increased high potassium-induced striatal dopamine release indicating that more neurons were protected and survived under ischemic insult in the presence of DETC-MeSO. We also showed that DETC-MeSO can prevent gliosis. DETC-MeSO elicits neuroprotection through the preservation of ER resulting in reduction of apoptosis by increase of anti-apoptotic proteins and decrease of pro-apoptotic proteins.

Reaction of small heat-shock proteins to different kinds of cellular stress in cultured rat hippocampal neurons

Upregulation of small heat-shock proteins (sHsps) in response to cellular stress is one mechanism to increase cell viability.We previously described that cultured rat hippocampal neurons express five of the 11 family members but only upregulate two of them (HspB1 and HspB5) at the protein level after heat stress. Since neurons have to cope with many other pathological conditions, we investigated in this study the expression of all five expressed sHsps on mRNA and protein level after sublethal sodium arsenite and oxidative and hyperosmotic stress. Under all three conditions, HspB1, HspB5, HspB6, and HspB8 but not HspB11 were consistently upregulated but showed differences in the time course of upregulation. The increase of sHsps always occurred earlier on mRNA level compared with protein levels. We conclude from our data that these four upregulated sHsps (HspB1, HspB5, HspB6, HspB8) act together in different proportions in the protection of neurons from various stress conditions.

Enhanced reclosure of surgically induced spinal open neural tube defects in chick embryos by injecting human bone marrow stem cells into the amniotic cavity

OBJECTIVE

To evaluate the reclosure-promoting capacity of a neural stem cell line (F3) and a human bone marrow stem cell line (B10) injected into the amniotic cavity of spinal open neural tube defects (ONTDs) of chick embryos of Hamburger and Hamilton stage 18 or 19.

METHODS

Fifteen chick embryos that survived the procedure were obtained for each of 4 groups: untreated control, F3-, B10-, and HFF-1 (human foreskin fibroblast)-treated groups. Embryos in the control group underwent ONTD surgery but no cell injection.

RESULTS

Compared with the untreated control and HFF-1 groups, the B10 group showed enhanced reclosure at 3, 5, and 7 days after injection, whereas the F3 group did not. B10 cells were not incorporated into reclosed neural tubes but simply covered ONTDs during the process of reclosure. F3 cells did not cover ONTDs. The cell survival of F3 cells exposed to the chick amniotic fluid in vitro for 48 hours was significantly lower than that of B10 cells.

CONCLUSION

The results confirmed that B10 cells enhance reclosure of ONTDs by covering and protecting neural tissues, not by direct cell incorporation. The lack of reclosure capacity in the F3 group may be related to the poor survival of F3 cells in the amniotic fluid.

Betamethasone therapy in ataxia telangiectasia: unraveling the rationale of this serendipitous observation on the basis of the pathogenesis

Ataxia telangiectasia (A-T) is a rare autosomal recessive disorder characterized by progressive neurological dysfunction. To date, only supportive care aimed to halt the progressive neurodegeneration is available for the treatment. Recently, an improvement of neurological signs during short-term treatment with betamethasone has been reported. To date, the molecular and biochemical mechanisms by which the steroid produces such effects have not yet been elucidated. Therefore, a review of the literature was carried out to define the potential molecular and functional targets of the steroid effects in A-T. Glucocorticoids (GCs) are capable of diffusing into the CNS by crossing the blood-brain barrier (BBB) where they exert effects on the suppression of inflammation or as antioxidant. GCs have been shown to protect post-mitotic neurons from apoptosis. Eventually, GCs may also modulate synaptic plasticity. A better understanding of the mechanisms of action of GCs in the brain is needed, because in A-T during the initial phase of cell loss the neurological impairment may be rescued by interfering in the biochemical pathways. This would open a new window of intervention in this so far incurable disease.

Human neural stem cells overexpressing glial cell line-derived neurotrophic factor in experimental cerebral hemorrhage

Recent studies have reported that glial cell line-derived growth factor (GDNF) has neurotrophic effects on the central nervous system, and the neural stem cells (NSCs) engrafted in animal models of stroke survive and ameliorate the neurological deficits. In this study, a stable human NSC line overexpressing GDNF (F3.GDNF) was transplanted next to the intracerebral hemorrhage (ICH) lesion site and a possible therapeutic effect was investigated. F3.GDNF human NSC line was transplanted into the cortex overlying the striatal ICH lesion. ICH was induced in adult mice by the unilateral injection of bacterial collagenase into the striatum. The animals were evaluated for 8 weeks with rotarod and limb placement tests. Transplanted NSCs were detected by beta-gal immunostaining with double labeling of neurofilament, microtubule associated protein-2, glial fibrillary acidic protein or human nuclear matrix antigen (HuNuMA). F3.GDNF human NSCs produced a four times higher amount of GDNF over parental F3 cells in vitro, induced behavioral improvement in ICH mice after brain transplantation and two- to threefold increase in cell survival of transplanted NSCs at 2 and 8 weeks post-transplantation. In F3.GDNF-grafted ICH brain, a significant increase in the antiapoptotic protein and cell survival signal molecules, and a marked reduction in proapoptotic proteins were found as compared with control group. Brain transplantation of human NSCs overexpressing GDNF in ICH animals provided functional recovery in ICH animals, and survival and differentiation of grafted human NSCs. These results indicate that the F3.GDNF human NSCs should be of a great value as a cellular source for the cellular therapy in animal models of human neurological disorders including ICH.

Potent induction of IFN-alpha and chemokines by autoantibodies in the cerebrospinal fluid of patients with neuropsychiatric lupus

Neuropsychiatric disease in systemic lupus erythematosus (NPSLE) is a poorly understood, but potentially fatal, disease manifestation. A pathogenetic role for autoantibodies is suspected, but the mechanism is unclear. Since immune complexes in SLE can stimulate IFN-alpha and there is strong evidence in humans and in mice that IFN-alpha can cause neuropsychiatric manifestations, we asked whether NPSLE patient serum and/or cerebrospinal fluid (CSF) contain abnormally high IFN-alpha-inducing activity. In a bioassay containing plasmacytoid dendritic cells and a source of Ag, NPSLE CSF induced significantly higher IFN-alpha compared with CSF from patients with multiple sclerosis or other autoimmune disease controls. When normalized for IgG concentration, NPSLE CSF was 800-fold more potent at inducing IFN-alpha compared with paired serum due to inhibitors present in serum. Analysis of Ig-deficient patient serum, depletion of IgG from normal serum, as well as addition of purified IgG to NPSLE CSF and serum in the bioassays revealed that one inhibitor was contained within the IgG fraction itself. In addition to IFN-alpha, immune complexes formed by CSF autoantibodies produced significantly increased levels of IFN-gamma-inducible protein 10 (IP-10/CXCL), IL-8, and MCP-1, all of which have been reported to be elevated in CSF from NPSLE patients. Taken together, these findings are consistent with a two-step model of NPSLE whereby CSF autoantibodies bind to Ags released by neurocytotoxic Abs or other brain cell injury, and the resulting immune complexes stimulate IFN-alpha and proinflammatory cytokines and chemokines.

Production and characterization of immortal human neural stem cell line with multipotent differentiation property

We document the protocols and methods for the production of immortalized cell lines of human neural stem cells from the human fetal central nervous system (CNS) cells by using a retroviral vector encoding v-myc oncogene. One of the human neural stem cell lines (HB1.F3) was found to express nestin and other specific markers for human neural stem cells, giving rise to three fundamental cell types of the CNS: neurons, astrocytes, and oligodendrocytes. After transplantation into the brain of mouse model of stroke, implanted human neural stem cells were observed to migrate extensively from the site of implantation into other anatomical sites and to differentiate into neurons and glial cells.

Pilocarpine-induced status epilepticus in rats involves ischemic and excitotoxic mechanisms

The neuron loss characteristic of hippocampal sclerosis in temporal lobe epilepsy patients is thought to be the result of excitotoxic, rather than ischemic, injury. In this study, we assessed changes in vascular structure, gene expression, and the time course of neuronal degeneration in the cerebral cortex during the acute period after onset of pilocarpine-induced status epilepticus (SE). Immediately after 2 hr SE, the subgranular layers of somatosensory cortex exhibited a reduced vascular perfusion indicative of ischemia, whereas the immediately adjacent supragranular layers exhibited increased perfusion. Subgranular layers exhibited necrotic pathology, whereas the supergranular layers were characterized by a delayed (24 h after SE) degeneration apparently via programmed cell death. These results indicate that both excitotoxic and ischemic injuries occur during pilocarpine-induced SE. Both of these degenerative pathways, as well as the widespread and severe brain damage observed, should be considered when animal model-based data are compared to human pathology.

Brain transplantation of immortalized human neural stem cells promotes functional recovery in mouse intracerebral hemorrhage stroke model

We have generated stable, immortalized cell lines of human NSCs from primary human fetal telencephalon cultures via a retroviral vector encoding v-myc. HB1.F3, one of the human NSC lines, expresses a normal human karyotype of 46, XX, and nestin, a cell type-specific marker for NSCs. F3 has the ability to proliferate continuously and differentiate into cells of neuronal and glial lineage. The HB1.F3 human NSC line was used for cell therapy in a mouse model of intracerebral hemorrhage (ICH) stroke. Experimental ICH was induced in adult mice by intrastriatal administration of bacterial collagenase; 1 week after surgery, the rats were randomly divided into two groups so as to receive intracerebrally either human NSCs labeled with beta-galactosidase (n = 31) or phosphate-buffered saline (PBS) (n = 30). Transplanted NSCs were detected by 5-bromo-4-chloro-3-indolyl-beta-d-galactoside histochemistry or double labeling with beta-galactosidase (beta-gal) and mitogen-activated protein (MAP)2, neurofilaments (both for neurons), or glial fibrillary acidic protein (GFAP) (for astrocytes). Behavior of the animals was evaluated for period up to 8 weeks using modified Rotarod tests and a limb placing test. Transplanted human NSCs were identified in the perihematomal areas and differentiated into neurons (beta-gal/MAP2(+) and beta-gal/NF(+)) or astrocytes (beta-gal/GFAP(+)). The NSC-transplanted group showed markedly improved functional performance on the Rotarod test and limb placing after 2-8 weeks compared with the control PBS group (p < .001). These results indicate that the stable immortalized human NSCs are a valuable source of cells for cell replacement and gene transfer for the treatment of ICH and other human neurological disorders. Disclosure of potential conflicts of interest is found at the end of this article.

Cerebral neurons and glial cell types inducing heat shock protein Hsp70 following heat stress in the rat

In this chapter, the distribution of Hsp70 in brain cell types following whole body hyperthermia is reviewed. The prevalence of Hsp70 expression in oligodendrocytes, microglia, and vascular cells in this type of stress contrasts with scarcity of Hsp70 induction in astrocytes and most neurons of the hyperthermic brain. However, a similarity between hyperthermic- and arsenite-induced brain patterns of Hsp70 expression supports the view that denaturation of specific proteins plays a major role in the selectivity of glial/vascular expression also during hyperthermia in vivo. The mechanism of neuronal Hsp70 non-responsiveness in heat stress despite their ability to use Hsc70 in a partial heat stress response remains to be elucidated.

Phosphorylation of HSP27 and synthesis of 14-3-3ε are parallel responses to hyperosmotic stress in the hippocampus

A stress-responsive, mitogen-activated protein kinase, p38, is activated by phosphorylation in response to adverse environmental insults. In the present study, the effects of hyperosmolarity on p38 activation and protein synthesis in the brain were examined. Hyperosmotic stress of rat brain slices, produced by addition of sorbitol to the incubation buffer, produced prolonged phosphorylation and activation of p38, most prominently in the hippocampus as compared to the cortex or cerebellum. In comparison, the prototypic mitogen-activated protein kinase, extracellular signal-regulated kinase, was transiently phosphorylated and another stress-activated protein kinase, c-Jun NH(2)-terminal kinase, was not phosphorylated above basal levels. Examination of downstream p38 signaling events revealed phosphorylation of the small heat shock protein 27 (HSP27) that was abolished by incubation with SB202190 [4-(4-Fluorophenyl)-2-(4-hydroxyphenyl)-5-(4-pyridyl)1H-imidazole], a p38 inhibitor. Concomitantly, hyperosmolarity diminished total levels of protein synthesis within hippocampal slices, as determined by incorporation of (35)S-labeled methionine/cysteine into protein during tissue incubation. However, synthesis of a 30-kDa protein, identified as 14-3-3epsilon with mass spectrometry, increased in response to hyperosmolarity. The synthesis of 14-3-3epsilon was dose-dependently induced by increasingly hyperosmotic conditions in a p38-independent manner. We conclude from these results that 14-3-3epsilon synthesis and p38-mediated HSP27 phosphorylation in the hippocampus are parallel responses to the hyperosmotic environment.

Brain transplantation of human neural stem cells transduced with tyrosine hydroxylase and GTP cyclohydrolase 1 provides functional improvement in animal models of Parkinson disease

Parkinson disease is a neurodegenerative disease characterized by loss of midbrain dopaminergic neurons resulting in movement disorder. Neural stem cells (NSC) of the CNS have recently aroused a great deal of interest, not only because of their importance in basic research of neural development, but also for their therapeutic potential in neurological disorders. We have recently generated an immortalized human NSC cell line, HB1.F3, via retrovirus-mediated v-myc transfer. This line is capable of self-renewal, is multipotent, and expresses cell specific markers for NSC, ATP-binding cassettes transporter (ABCG2) and nestin. Next, we co-transduced the F3 NSC line with genes encoding tyrosine hydroxylase (TH) and GTP cyclohydrolase 1 (GTPCH1) in order to generate dopamine-producing NSC. The F3.TH.GTPCH human NSC line expresses TH and GTPCH phenotypes as determined by RT-PCR, western blotting and immunocytochemistry, and shows a 800 to 2000-fold increase in production of L-dihydroxyphenyl alanine in HPLC analysis. A marked improvement in amphetamine-induced turning behavior was observed in parkinsonian rats implanted with F3.TH.GTPCH cells, but not in control rats receiving F3 NSC. In the animals showing functional improvement, a large number of TH-positive F3.TH.GTPCH NSC were found at injection sites. These results indicate that human NSC, genetically transduced with TH and GTPCH1 genes, have great potential in clinical utility for cell replacement therapy in patients suffering from Parkinson disease.

ANG II increases 2-deoxyglucose uptake in mouse embryonic stem cells

It is now suggested that all components of the renin-angiotensin system are present in many tissues, including the embryo and may play a major role in embryo development and differentiation. However, little is known regarding whether ANG II regulates glucose transport in mouse embryonic stem (ES) cells. Thus, the effects of ANG II on [3H]-2-deoxyglucose (2-DG) uptake and its related signal pathways were examined in mouse ES cells. ANG II significantly increased cell proliferation and 2-DG uptake in concentration- and time-dependent manner (>18 h, >10(-8) M) and increased mRNA and protein level of GLUT1 by 31+/-7% and 22+/-5% compared to control, respectively. Actinomycin D and cycloheximide completely blocked the effect of ANG II on 2-DG uptake. ANG II-induced increase of 2-DG uptake was blocked by losartan, an ANG II type 1 (AT1) receptor blocker, but not by PD 123319, an ANG II type 2 (AT2) receptor blocker. In addition, ANG II-induced stimulation of 2-DG uptake was attenuated by phospholipase C (PLC) inhibitors, neomycin and U 73122 and ANG II increased inositol phosphates (IPs) formation by 37+/-8% of control. Protein kinase C (PKC) inhibitors, staurosporine, bisindolylmaleimide I, and H-7 also blocked ANG II-induced stimulation of 2-DG uptake. Indeed, ANG II activated a PKC translocation from the cytosolic to membrane fraction, suggesting a role of PKC. A 23187 (Ca2+ ionophore) increased 2-DG uptake and nifedifine (L-type Ca2+ channel blocker) blocked it. In conclusion, ANG II increased 2-DG uptake by PKC activation via AT1 receptor in mouse ES cells.

Microglia in health and disease

Microglia, one of three glial cell types in the central nervous system (CNS), play an important role as resident immunocompetent and phagocytic cells in the CNS in the event of injury and disease. It was del Rio Hortega in 1927 who determined that microglia belong a distinct glial cell type apart from astrocytes and oligodendrocytes, and since 1970s there has been wide recognition that microglia are immune effectors in the CNS that respond to pathological conditions and participate in initiation and progression of neurological disorders including Alzheimer's disease, Parkinson's disease, multiple sclerosis, and acquired immune deficiency syndrome dementia complex by releasing potentially cytotoxic molecules such as proinflammatory cytokines, reactive oxygen intermediates, proteinases and complement proteins. There is also evidence to suggest that microglia are capable of secreting neurotrophic or neuron survival factors upon activation via inflammation or injury. It is thus timely to review current status of knowledge on biology and immunology of microglia, and consider new directions of investigation on microglia in health and disease.

Brain transplantation of genetically engineered human neural stem cells globally corrects brain lesions in the mucopolysaccharidosis type VII mouse

In the present study, we investigated the feasibility of using human neural stem cells (NSCs) in the treatment of diffuse central nervous system (CNS) alterations in a murine model of mucopolysaccharidosis VII (MPS VII), a lysosomal storage disease caused by a genetic defect in the beta-glucuronidase gene. An immortalized NSC line derived from human fetal telencephalon was genetically engineered to overexpress beta-glucuronidase and transplanted into the cerebral ventricles of neonatal MPS VII mouse. Transplanted human NSCs were found to integrate and migrate in the host brain and to produce large amount of beta-glucuronidase. Brain contents of the substrates of beta-glucuronidase were reduced to nearly normal levels, and widespread clearing of lysosomal storage was observed in the MPS VII mouse brain at 25 days posttransplantation. The number of engrafted cells decreased markedly after the transplantation, and it appears that the major cause of the cell death was not the immune response of the host but apoptotic cell death of grafted human NSCs. Results showed that human NSCs would serve as a useful gene transfer vehicle for the treatment of diffuse CNS lesions in human lysosomal storage diseases and are potentially applicable in the treatment of patients suffering from neurological disorders.

High threshold for induction of the stress response in motor neurons is associated with failure to activate HSF1

Heat shock protein 70 (Hsp70) protects cultured motor neurons from the toxic effects of mutations in Cu/Zn-superoxide dismutase (SOD-1), which is responsible for a familial form of the disease, amyotrophic lateral sclerosis (ALS). Here, the endogenous heat shock response of motor neurons was investigated to determine whether a high threshold for activating this protective mechanism contributes to their vulnerability to stresses associated with ALS. When heat shocked, cultured motor neurons failed to express Hsp70 or transactivate a green fluorescent protein reporter gene driven by the Hsp70 promoter, although Hsp70 was induced in glial cells. No increase in Hsp70 occurred in motor neurons after exposure to excitotoxic glutamate or expression of mutant SOD-1 with a glycine--> alanine substitution at residue 93 (G93A), nor was Hsp70 increased in spinal cords of G93A SOD-1 transgenic mice or sporadic or familial ALS patients. In contrast, strong Hsp70 induction occurred in motor neurons with expression of a constitutively active form of heat shock transcription factor (HSF)-1 or when proteasome activity was sufficiently inhibited to induce accumulation of an alternative transcription factor HSF2. These results indicate that the high threshold for induction of the stress response in motor neurons stems from an impaired ability to activate the main heat shock-stress sensor, HSF1.

Changes in heat shock protein 27 phosphorylation and immunocontent in response to preconditioning to oxygen and glucose deprivation in organotypic hippocampal cultures

Organotypic hippocampal cultures have been recently used to study in vitro ischaemic neuronal death. Sub-lethal periods of ischaemia in vivo confer resistance to lethal insults and many studies have demonstrated the involvement of heat shock proteins in this phenomenon. We used organotypic hippocampal cultures to investigate the involvement of heat shock protein (HSP) 27 in preconditioning to oxygen and glucose deprivation. Neuronal damage was assessed using propidium iodide fluorescence; HSP27 phosphorylation and immunocontent were obtained using (32)Pi labelling followed by sodium dodecylsulfate-polyacrylamide gel electrophoresis and immunoblotting. We observed that immunocontent of HSP27 was increased after lethal or sub-lethal treatment, indicating it is a response to metabolic stress. Treatments with 5 or 10 min of oxygen and glucose deprivation (OGD) or 1- microM N-methyl-D-aspartate (NMDA) induced tolerance to 40 min of OGD associated with an increase in HSP27 immunocontent and phosphorylation. These data suggest that, in vitro, phosphorylated HSP27 might be involved in preconditioning, probably acting as a modulator of actin filaments or by the blockage of neurodegenerative processes.

The constitutive and inducible expression of Nurr1, a key regulator of dopaminergic neuronal differentiation, in human neural and non-neural cell lines

Nur-related factor 1 (Nurr1), nerve growth factor-induced gene B (NGFI-B) and neuron-derived orphan receptor-1 (NOR-1) constitute the orphan nuclear receptor subfamily of transcription factors. Previous studies showed that midbrain dopaminergic neuronal precursor cells failed to differentiate in Nurr1-deficient mice. To investigate a role of Nurr1 in human neuronal function, Nurr1 mRNA expression was studied in human neural cell lines by RT-PCR and northern blot analysis. Nurr1, NGFI-B and NOR-1 mRNA were coexpressed in all human neural and nonneural cell lines under the serum-containing culture condition, except for SK-N-SH neuroblastoma, in which Nurr1 mRNA was undetectable. The levels of Nurr1, NGFI-B and NOR-1 mRNA were elevated markedly in NTera2 teratocarcinoma-derived neurons (NTera2-N), a model of differentiated human neurons, following a 1.5 or 3 h-exposure to 1 mM dibutyryl cyclic AMP or 100 nm phorbol 12-myristate 13-acetate. NGFI-B mRNA levels were also elevated in NTera2-N cells by exposure to 100 ng/mL brain-derived neurotrophic factor (BDNF). To identify Nurr1-target genes, the mRNA expression of 27 genes potentially involved in dopaminergic neuronal differentiation and survival, including BDNF, glia-derived neurotrophic factor, their receptors, tyrosine hydroxylase and alpha-synuclein, were studied in HEK293 cells following overexpression of Nurr1. None of these genes examined, however, showed significant changes. These results indicate that Nurr1, NGFI-B and NOR-1 mRNA are expressed constitutively in various human neural and non-neural cell lines under the serum-containing culture condition, and their levels are up-regulated in human neurons by activation of protein kinase A or protein kinase C pathway, although putative coactivators expressed in dopaminergic neuronal precursor cells might be required for efficient transcriptional activation of Nurr1-target genes.

Astrocytes in culture produce anandamide and other acylethanolamides

Anandamide (arachidonylethanolamide) is an endocannabinoid that belongs to the acylethanolamide lipid family. It is produced by neurons in a calcium-dependent manner and acts through cannabinoid CB1 receptors. Other members of the acylethanolamide lipid family are also produced by neurons and act through G-protein-coupled receptors: homo-gamma-linolenylethanolamide (HEA) and docosatetraenylethanolamide (DEA) act through CB1 receptors, palmitylethanolamide (PEA) acts through CB2-like receptors, and oleylethanolamide (OEA) acts through receptors that have not yet been cloned. Although it is clear that anandamide and other acylethanolamides play a major role in neuronal signaling, whether astrocytes also produce these lipids is unknown. We developed a chemical ionization gas chromatography/mass spectrometry method that allows femtomole detection and quantification of anandamide and other acylethanolamides. Using this method, we unambiguously detected and quantified anandamide, HEA, DEA, PEA, and OEA in mouse astrocytes in culture. Stimulation of mouse astrocytes with ionomycin, a calcium ionophore, enhanced the production of anandamide, HEA, and DEA, whereas PEA and OEA levels were unchanged. Endothelin-1, a peptide known to act on astrocytes, enhanced the production of anandamide, without affecting the levels of other acylethanolamides. These results show that astrocytes produce anandamide, HEA, and DEA in a calcium-dependent manner and that anandamide biosynthesis can be selectively stimulated under physiologically relevant conditions. The relative levels of acylethanolamides in astrocytes from rat and human were different from the relative levels of acylethanolamides in mouse astrocytes, indicating that the production of these lipids differs between species. Because astrocytes are known to express CB1 receptors and inactivate endocannabinoids, our finding strongly suggests the existence of a functional endocannabinoid signaling system in these cells.

Effects of global cerebral ischemia and preconditioning on heat shock protein 27 immunocontent and phosphorylation in rat hippocampus

Global cerebral ischemia, with or without preconditioning, leads to an increase in heat shock protein 27 (HSP27) immunocontent and alterations in HSP27 phosphorylation in CA1 and dentate gyrus areas of the hippocampus. We studied different times of reperfusion (1, 4, 7, 14, 21 and 30 days) using 2 min, 10 min or 2+10 min of ischemia. The results showed an increase in HSP27 immunocontent of about 300% after 10 min of ischemia in CA1 and dentate gyrus. CA1, a hippocampal vulnerable area, showed an increase in HSP27 phosphorylation, parallel with immunocontent. In dentate gyrus, a resistant area, the increase in HSP phosphorylation was lower than immunocontent. After preconditioned ischemia (2+10 min), when CA1 neurons are protected to a lethal, 10 min insult, we observed an increase in HSP immunocontent and a decrease in phosphorylation in both regions of the hippocampus, suggesting that, when there is no neuronal death, HSP27 in a vulnerable area responds similarly to the resistant area.When dephosphorylated, HSP27 acts as a chaperone, protecting other proteins from denaturation. As it is markedly expressed in astrocytes, we suggest that HSP27 could be protecting hippocampal astrocytes, which could then be helping neurons to resist to the insult, maintaining tissue normal homeostasis.

Expression of small heat shock proteins and intermediate filaments in the human optic nerve head astrocytes exposed to elevated hydrostatic pressure in vitro

The small heat shock proteins (sHSP), alpha B-crystallin and Hsp27 are chaperone molecules that maintain the integrity of intermediate filament (IF) network and prevent unfolding of cellular proteins induced by stress. In the optic nerve head (ONH) of eyes with glaucoma, reactive astrocytes expressed Hsp27, perhaps in response to stress related to elevated intraocular pressure. In this study, we determined the effect of elevated hydrostatic pressure (HP) in the synthesis, distribution and co-localization of alpha B-crystallin and Hsp27 with IF in cultured ONH astrocytes. Astrocyte monolayers were pressurized to 60 mm Hg (92% air 8% CO(2)) and incubated at 37 degrees C for 6, 24 or 48 hr. Controls were exposed to ambient pressure. Cells were analyzed by immunocytochemistry, Western blot and immunoprecipitation using antibodies to Hsp27, alpha B-crystallin, vimentin or GFAP. Control astrocytes seemed flat, polygonal with short processes. alpha B-crystallin appeared granular in the perinuclear area and filamentous in the cell periphery. Fine granular Hsp27 was distributed throughout the cytoplasm. GFAP and vimentin co-localized with Hsp27 in the cytoplasm. Astrocytes exposed to HP were star-shaped with long processes. Hsp27 was condensed in large granules around the nucleus. GFAP and vimentin co-localized with Hsp27 and alpha B-crystallin in the perinuclear area. Western blot and metabolic labeling detected increased synthesis of Hsp27, GFAP and vimentin but no change in alpha B-crystallin. These results indicated that GFAP and vimentin associate with Hsp27 and alpha B-crystallin in ONH astrocytes. HP affected the integrity of the cytoskeleton consistent with morphological changes. Small HSP may reinforce and maintain IF integrity in response to HP.

Activation of mitogen-activated protein kinase by muscarinic receptors in astroglial cells: role in DNA synthesis and effect of ethanol

Mitogen-activated protein kinase (MAPK) can be phosphorylated by mitogens binding to G-protein-coupled receptors and is considered a major pathway involved in cell proliferation. In this study, we report on the activation of MAPK by muscarinic acetylcholine receptors in astroglial cells, namely the 1321N1 human astrocytoma cell line, primary rat cortical astrocytes, and fetal human astrocytes. Carbachol caused a rapid and transient phorphorylation of MAPK (ERK1/2) in all cell types, with an increase in MAPK activity, without changing the levels of MAPK proteins. Human astrocytoma cells were used to characterize the effect of carbachol on MAPK. Experiments with M2- and M3-receptor subtype-selective antagonists, and with pertussis toxin, indicated that the M3 subtype is responsible for activating MAPK in glial cells. Pretreatment of cells with the protein kinase C (PKC) inhibitor bisindolylmaleimide I, or downregulation of PKC by 24-h treatment with the phorbol ester TPA inhibited carbachol-induced MAPK activation. Additional experiments with PKC alpha- or PKC epsilon-specific compounds indicated that the epsilon isozyme of PKC is primarily involved in MAPK activation by carbachol. Chelation of calcium also inhibited MAPK activation by carbachol. Two MEK (MAPK kinase) inhibitors inhibited carbachol-induced DNA synthesis but only at concentrations that exceeded those sufficient to block carbachol-induced MAPK activation. Ethanol (< or =200 mM) had no effect on MAPK when present alone and did not affect carbachol-induced MAPK activation under various experimental conditions, although it inhibits carbachol-induced DNA synthesis at low concentrations (10-100 mM). These results suggest that activation of MAPK by carbachol may be necessary but not sufficient for its mitogenic effect in astroglial cells, and that does not represent a target for ethanol-induced inhibition of DNA synthesis elicited by muscarinic receptors.

Mutant Cu/Zn-superoxide dismutase proteins have altered solubility and interact with heat shock/stress proteins in models of amyotrophic lateral sclerosis

Mutations in the Cu/Zn-superoxide dismutase (SOD-1) gene are responsible for a familial form of amyotrophic lateral sclerosis. In humans and experimental models, death of motor neurons is preceded by formation of cytoplasmic aggregates containing mutant SOD-1 protein. In our previous studies, heat shock protein 70 (HSP70) prolonged viability of cultured motor neurons expressing mutant human SOD-1 and reduced formation of aggregates. In this paper, we report that mutant SOD-1 proteins have altered solubility in cells relative to wild-type SOD-1 and can form a direct association with HSP70 and other stress proteins. Whereas wild-type human and endogenous mouse SOD-1 were detergent-soluble, a portion of mutant SOD-1 was detergent-insoluble in protein extracts of NIH3T3 transfected with SOD-1 gene constructs, spinal cord cultures established from G93A SOD-1 transgenic mouse embryos, and lumbar spinal cord from adult G93A transgenic mice. A direct association of HSP70, HSP40, and alphaB-crystallin with mutant SOD-1 (G93A or G41S), but not wild-type or endogenous mouse SOD-1, was demonstrated by coimmunoprecipitation. Mutant SOD-1.HSP70 complexes were predominantly in the detergent-insoluble fraction. However, only a small percentage of total cellular mutant SOD-1 was detergent-insoluble, suggesting that mutation-induced alteration of protein conformation may not in itself be sufficient for direct interaction with heat shock proteins.

Dorsal horn lesion resulting from spinal root avulsion leads to the accumulation of stress-responsive proteins

The aim of this study was to demonstrate acute to subacute molecular episodes in the dorsal horn following root avulsion using immunohistochemical methods with the markers for synapses, astrocytes and such stress-responsive molecules as heat shock proteins (Hsps) and p38 MAP kinase (p38). Among them, Hsp27 was accumulated selectively in the injured substantia gelatinosa 24 h after avulsion injury. The localization of Hsp27 in astrocytes within the substantia gelatinosa was confirmed by the double immunofluorescence method using anti-Hsp27 antibody and either anti-synaptophysin antibody or anti-glutamine synthetase antibody and by immunoelectron microscopy for Hsp27. The pattern of Hsp27 expression subsequently changed from glial pattern to punctate pattern by 7 days. Immunoelectron microscopy revealed that the punctate pattern in the subacute stage corresponded to distal parts of the astrocytic processes. Hsp27 immunoreaction was decreased 21 days after root avulsion. In the distal axotomy model, Hsp27 was accumulated later in the ipsilateral dorsal horn in a punctate pattern from 7 days after the axotomy. Phosphorylation of p38 was detected in microglia in the dorsal horn following both avulsion and axotomy. Substance P was slightly decreased in the injured substantia gelatinosa in both the avulsion and axotomy models around 14-21 days. We conclude that Hsp27 is a useful marker for demonstrating dorsal horn lesions following avulsion injury and that avulsion injury may induce Hsp27 in the dorsal horn more rapidly than distal axotomy.

Differential expression of stress proteins in human adult astrocytes in response to cytokines

Various lines of evidence suggest a close relationship between heat shock proteins (hsp) and several autoimmune diseases such as arthritis, diabetes and multiple sclerosis. While enhanced expression of hsp in autoimmune diseases is often regarded as a non-specific bystander effect of the inflammatory process, surprisingly little is known on hsp regulation by inflammatory mediators such as cytokines. In this study cytokine-induced expression of hsp60, hsp27 and alphaB-crystallin was studied in cultures of primary human adult astrocytes at the mRNA as well as at the protein level. We show differential hsp expression patterns in response to pro-inflammatory and immunoregulatory cytokines. Hsp60 expression was found to be enhanced in response to cytokines as diverse as IL-1beta, TNF-alpha, IL-4, IL-6 and IL-10. Upregulation of hsp27, however, was primarily induced by immunoregulatory cytokines like IL-4, IL-6 and TGF-beta whereas alphaB-crystallin expression was found to be enhanced by the pro-inflammatory cytokine TNF-alpha only. None of the cytokines studied was able to enhance expression of all three hsp simultaneously. These results show that in human astrocytes induced expression of hsp27 and alphaB-crystallin is dependent on the presence of a defined set of stimuli, while induced expression of hsp60 is a much less selective event. This highly differential pattern of hsp expression in response to inflammatory mediators known to play an important role in the pathogenesis of autoimmune diseases indicates that hsp responses are specific rather than non-specific bystander responses.

Differential gene expression between human neurons and neuronal progenitor cells in culture: an analysis of arrayed cDNA clones in NTera2 human embryonal carcinoma cell line as a model system

To elucidate the highly complex expression pattern of the genes involved in human neuronal differentiation, differential gene expression between human neurons and neuronal progenitor cells was investigated by analysis of a cDNA expression array in a pluripotent human embryonal carcinoma cell line NTera2 (NT2), a model system of human neuronal differentiation. Among 588 arrayed cDNA clones, 87 genes showed a differential expression pattern between undifferentiated neuronal progenitor cells (NT2-U) and NT2-derived differentiated neurons induced by treatment with retinoic acid (RA) (NT2-N), while 26 genes could not be analyzed due to high background signals. The levels of expression of 76 genes, including those encoding a group of transcription factors, intracellular signal-transducing proteins, cell death-regulatory proteins, and growth factors/cytokines/neurotransmitters and their receptors, were elevated after neuronal differentiation, while the levels of 11 genes, including those coding for cellular proliferation-related proteins, were decreased. Among the differentially expressed genes following induction of neuronal differentiation, significant up-regulation of the growth-associated protein (GAP-43), low-affinity nerve growth factor receptor p75 (LNGFR), and defender against apoptotic cell death (DAD1) mRNAs and substantial down-regulation of the proliferation-associated gene (PAG), fibroblast growth factor receptor-1 (FGFR-1), and cellular RA-binding protein-II (CRABP-II) mRNAs were verified by Northern blot analysis. These results indicate that the analysis of cDNA expression arrays provides a useful approach for screening and identification of a set of distinct genes that undergo highly complex regulation during human neuronal differentiation.

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 degrees 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 degrees 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.

Regulation of protein phosphorylation in astrocyte cultures by external calcium ions: specific effects on the phosphorylation of glial fibrillary acidic protein (GFAP), vimentin and heat shock protein 27 (HSP27)

The effect of external Ca2+ ([Ca2+]e) on the incorporation of [32P] into total protein, cytoskeletal proteins and the heat shock protein HSP27, was studied in primary cultures of astrocytes from the rat hippocampus. Zero [Ca2+]e increased total 32P-incorporation into astrocyte protein and when this was normalized to 100%, incorporation was significantly increased into glial fibrillary acidic protein (GFAP), vimentin (VIM) and HSP27. The difference in total 32P-incorporation between zero [Ca2+]e and 1 mM [Ca2+]e was reversed by incubation of the cells with the protein phosphatase inhibitor okadaic acid in the range 1-10 nM; higher concentrations of okadaic acid (50-100 nM) further increased total 32P-incorporation. In zero [Ca2+]e the non-specific channel blocker Co2+ (1 mM) decreased total 32P-incorporation by approximately 30%. The results were compared with a previous study [S.T. Wofchuk, R. Rodnight, Age-dependent changes in the regulation by external calcium ions of the phosphorylation of glial fibrillary acidic protein in slices of rat hippocampus, Dev. Brain Res. 85 (1995) 181-186] in which it was shown that in immature hippocampal slices zero [Ca2+]e compared with 1 mM [Ca2+]e increased 32P-incorporation into GFAP without changing total incorporation. The difference between the results for total 32P-incorporation obtained in cultured astrocytes and immature brain tissue was found to be related to the concentration of [Ca2+]e in the medium since in slices concentrations of [Ca2+]e higher than 1 mM progressively decreased total incorporation. The difference may reflect a higher Ca2+-permeability of the plasma membrane in cultured astrocytes and/or to the complex structure of the slice tissue. In two-dimensional electrophoresis HSP27, in contrast to GFAP and VIM, was separated into 3 immunodetectable isoforms only two of which were normally phosphorylated. After labelling in the presence of okadaic acid both immunodetectable and phosphorylated HSP27 focussed as a single polypeptide. Phorbol dibutyrate (1 microM) and zero [Ca2+]e stimulated the phosphorylation of both isoforms, but in the case of zero [Ca2+]e the effect on the more acidic isoform was proportionally greater.

Up-regulation of protein chaperones preserves viability of cells expressing toxic Cu/Zn-superoxide dismutase mutants associated with amyotrophic lateral sclerosis

Mutations in the Cu/Zn-superoxide dismutase (SOD-1) gene underlie some familial cases of amyotrophic lateral sclerosis, a neurodegenerative disorder characterized by loss of cortical, brainstem, and spinal motor neurons. We present evidence that SOD-1 mutants alter the activity of molecular chaperones that aid in proper protein folding and targeting of abnormal proteins for degradation. In a cultured cell line (NIH 3T3), resistance to mutant SOD-1 toxicity correlated with increased overall chaperoning activity (measured by the ability of cytosolic extracts to prevent heat denaturation of catalase) as well as with up-regulation of individual chaperones/stress proteins. In transgenic mice expressing human SOD-1 with the G93A mutation, chaperoning activity was decreased in lumbar spinal cord but increased or unchanged in clinically unaffected tissues. Increasing the level of the stress-inducible chaperone 70-kDa heat shock protein by gene transfer reduced formation of mutant SOD-containing proteinaceous aggregates in cultured primary motor neurons expressing G93A SOD-1 and prolonged their survival. We propose that insufficiency of molecular chaperones may be directly involved in loss of motor neurons in this disease.

Cytokine-induced production of macrophage inflammatory protein-1alpha (MIP-1alpha) in cultured human astrocytes

Macrophage inflammatory protein-1alpha (MIP-1alpha) is a member of a superfamily of inflammatory cytokines termed chemokines, and it has been implicated in the pathogenesis of several human diseases with inflammatory components. It has been known that MIP-1alpha plays a role in recruiting and activating mononuclear phagocytes in the central nervous system (CNS), and that astrocytes and microglia are sources of this chemokine. However, details of the regulation of MIP-1alpha production by these glial cells are not known. In the present study, expression of MIP-1alpha was determined in purified cultures of human astrocyte. MIP-1alpha mRNA levels in human astrocyte cell preparations were determined by reverse transcription polymerase chain reaction (RT-PCR) and amount of MIP-1alpha protein secreted into culture supernatants by human astrocytes was assayed by enzyme-linked immunosorbent assay (ELISA). Under the unstimulated conditions, human astrocytes did not express MIP-1alpha message or protein, indicating that human astrocytes do not constitutively carry MIP-1alpha message. Following treatment with interleukin-1beta (IL-1beta), human astrocytes demonstrated increased message and protein expression for MIP-1alpha, while other immune modulators such as interferon-gamma (IFN)-gamma, tumor necrosis factor-alpha (TNF-alpha), granulocyte-macrophage colony-stimulating factor (GM-CSF), lipopolysaccharide, or phorbol ester (a protein kinase C activator) did not induce MIP-1alpha expression in human astrocytes.

Cholinergic agonists increase intracellular Ca2+ in cultured human microglia

Microglia are resident phagocytic cells in the central nervous system (CNS), and can be activated in response to various stimuli including neurotransmitters. Using fura-2 imaging, we investigated the effects of carbachol (CCh), a cholinergic agonist, on [Ca2+]i in cultured human microglia. Treatment of microglia with CCh (100 microM) produced a transient increase in [Ca2+]i, which was atropine-sensitive and was associated with release from intracellular Ca2+ stores. Successive applications of CCh showed a change in the amplitude of the [Ca2+]i signal consistent with desensitization. These results show that human microglia express functional muscarinic receptors and respond to cholinergic agonists. The rapid change of [Ca2+]i in microglia may serve as a second messenger to trigger downstream cascades which contribute to signalling pathways in CNS pathology.

Constitutive and heat-inducible expression of HSP105 in neurons and glial cells in culture

The constitutive and heat-inducible expression of HSP105 was investigated in newborn mouse brain cell cultures by Northern blotting, Western blotting and immunocytochemistry. HSP105 was expressed most abundantly in the brain among the various tissues examined. HSP105 mRNA and protein were both present at substantial levels in brain cell cultures under unstressed conditions and up-regulated greatly during 3-48 h following exposure to heat stress (43 degrees C/20 min). HSP105 was expressed in nearly all neurons, oligodendrocytes, microglia and astrocytes with its location of both cytoplasmic and nuclear regions under unstressed and heat-stressed conditions. HSP105 expression was significantly down-regulated in astrocytes following treatment with IL-beta or TNF-alpha (50 ng/ml for 6 days), both of which are known growth-stimulatory cytokines for astrocytes. These results indicate that HSP105 is constitutive and heat-inducible HSP in neurons and glial cells in which its expression is under the control of both stressful stimuli and growth-regulatory factors.

Cultured skin fibroblasts isolated from mice devoid of the prion protein gene express major heat shock proteins in response to heat stress

Recent evidence has suggested that molecular chaperones participate in the conformational change between the normal cellular prion protein (PrPC) and its scrapie isoform (PrPSc). To study a role of PrPC in the regulation of expression of heat shock proteins (HSPs), a group of molecular chaperones, heat-induced expression of major HSPs (HSP105, HSP90alpha, HSP72, HSC70, HSP60, and HSP25) was investigated in cultured skin fibroblasts isolated from the mice homogeneous for a disrupted PrP gene (PrP-/- mice) by Western blot analysis and immunocytochemistry. Two lines of fibroblasts were established and designated SFK derived from the PrP-/- mice and SFH derived from the PrP+/+ mice, respectively. In both SFK and SFH cells, HSP105, HSP72, and HSP25 were expressed at low levels under unstressed conditions but they were induced markedly following exposure to heat stress (43 degreesC/20 min) at 3-72 h postrecovery. In both cell types, HSC70 and HSP60 were expressed at high levels under unstressed conditions and their levels remained unchanged after heat shock treatment. HSP90alpha was undetectable in both cell types under any conditions examined. The pattern of expression, induction, and subcellular location of HSP105, HSP72, HSC70, HSP60, and HSP25 was not significantly different between SFK and SFH cells under unstressed and heat-stressed conditions. Furthermore, the levels of constitutive expression of HSP105, HSC70, HSP60, and HSP25 were similar between the brain tissues isolated from the PrP-/- and PrP+/+ mice. These results indicate that HSP induction is not affected by either the existence or the absence of PrPC in the cells.

Expression of alphaB-crystallin in glia cells during lesional development in multiple sclerosis

The small heat shock protein alphaB-crystallin was recently identified as a dominant human T-cell antigen in myelin derived from multiple sclerosis (MS) patients. Using immunohistochemical techniques, oligodendrocytes as well as astrocytes in MS lesions were shown to express alphaB-crystallin. In the present study we examined the expression of alphaB-crystallin, human natural killer cell marker (HNK-1; as a marker for immature oligodendrocytes) and heat shock protein 60 (hsp60) in glia cells at different stages of MS lesion development i.e. in early active lesions, late active lesions and inactive lesions. The results demonstrate that already at the earliest stages of lesional development a subpopulation of oligodendrocytes express detectable levels of alphaB-crystallin. In active lesions about 5-10% of all oligodendrocytes were found to express alphaB-crystallin, whereas in inactive lesions the relative number of alphaB-crystallin-expressing oligodendrocytes was approximately tenfold less. For astrocytes the relative number of alphaB-crystallin-expressing cells was 40-50% for all three types of lesions. Also, alphaB-crystallin-expressing oligodendrocytes and astrocytes displayed different patterns of distribution in lesional areas. These data suggest different regulatory pathways for alphaB-crystallin expression in either type of glia cell. No correlation was found between expression patterns of HNK-1 and alphaB-crystallin indicating that the subpopulation of alphaB-crystallin-expressing oligodendrocytes consisted of both mature and immature oligodendrocytes. In addition, no correlation was found between expression of hsp60 and alphaB-crystallin in MS lesions suggesting different regulatory pathways for either hsp.