A protective role of 27-kDa heat shock protein in glucocorticoid-evoked apoptotic cell death of hippocampal progenitor cells

Heat Shock Proteins and their Protective Roles in Stem Cell Biology

Stem cells (SCs) are discovered long back but the idea that SCs possess therapeutic potential came up just a few decades back. In a past decade stem cell therapy is highly emerged and displayed tremendous potential for the treatment of a wide range of diseases and disorders such as blindness and vision impairment, type I diabetes, infertility, HIV, etc. SCs are very susceptible to destruction after transplantation into the host because of the inability to sustain elevated stress conditions inside the damaged tissue/organ. Heat shock proteins (HSPs) are molecular chaperones/stress proteins expressed in response to stress (elevated temperature, harmful chemicals, ischemia, viruses, etc) inside a living cell. HSPs protect the cell from damage by assisting in the proper folding of cellular proteins. This review briefly summarises different types of HSPs, their classification, cellular functions as well as the role of HSPs in regulating SC self-renewal and survival in the transplanted host. Applications of HSP modulated SCs in regenerative medicine and for the treatment of ischemic heart disease, myocardial infarction (MI), osteoarthritis, ischemic stroke, spinocerebellar ataxia type 3 (SCA3), leukemia, hepatic ischemia-reperfusion injury, Graft-versus-host disease (GVHD) and Parkinson's disease (PD) are discussed. In order to provide potential insights in understanding molecular mechanisms related to SCs in vertebrates, correlations between HSPs and SCs in cnidarians and planarians are also reviewed. There is a need to advance research in order to validate the use of HSPs for SC therapy and establish effective treatment strategies.

Glucocorticoids, genes and brain function

The identification of key genes in transcriptomic data constitutes a huge challenge. Our review of microarray reports revealed 88 genes whose transcription is consistently regulated by glucocorticoids (GCs), such as cortisol, corticosterone and dexamethasone, in the brain. Replicable transcriptomic data were combined with biochemical and physiological data to create an integrated view of the effects induced by GCs. The most frequently reported genes were Errfi1 and Ddit4. Their up-regulation was associated with the altered transcription of genes regulating growth factor and mTORC1 signaling (Gab1, Tsc22d3, Dusp1, Ndrg2, Ppp5c and Sesn1) and progression of the cell cycle (Ccnd1, Cdkn1a and Cables1). The GC-induced reprogramming of cell function involves changes in the mRNA level of genes responsible for the regulation of transcription (Klf9, Bcl6, Klf15, Tle3, Cxxc5, Litaf, Tle4, Jun, Sox4, Sox2, Sox9, Irf1, Sall2, Nfkbia and Id1) and the selective degradation of mRNA (Tob2). Other genes are involved in the regulation of metabolism (Gpd1, Aldoc and Pdk4), actin cytoskeleton (Myh2, Nedd9, Mical2, Rhou, Arl4d, Osbpl3, Arhgef3, Sdc4, Rdx, Wipf3, Chst1 and Hepacam), autophagy (Eva1a and Plekhf1), vesicular transport (Rhob, Ehd3, Vps37b and Scamp2), gap junctions (Gjb6), immune response (Tiparp, Mertk, Lyve1 and Il6r), signaling mediated by thyroid hormones (Thra and Sult1a1), calcium (Calm2), adrenaline/noradrenaline (Adcy9 and Adra1d), neuropeptide Y (Npy1r) and histamine (Hdc). GCs also affected genes involved in the synthesis of polyamines (Azin1) and taurine (Cdo1). The actions of GCs are restrained by feedback mechanisms depending on the transcription of Sgk1, Fkbp5 and Nr3c1. A side effect induced by GCs is increased production of reactive oxygen species. Available data show that the brain's response to GCs is part of an emergency mode characterized by inactivation of non-core activities, restrained inflammation, restriction of investments (growth), improved efficiency of energy production and the removal of unnecessary or malfunctioning cellular components to conserve energy and maintain nutrient supply during the stress response.

Neuroprotective effects of intravitreal triamcinolone acetonide and dexamethasone implant in rabbit retinas after pars plana vitrectomy and silicone oil injection

PURPOSE

To investigate potential retinal neuroprotective effects of intravitreal triamcinolone acetonide and dexamethasone implant in rabbits after pars plana vitrectomy and intravitreal silicone oil injection.

METHODS

The right eyes of 84 rabbits, divided into 3 groups of 28 rabbits each, underwent standard 3-port pars plana vitrectomy with silicone oil (SO group), silicone oil and intravitreal dexamethasone implant (SO/DEX group), or silicone oil and triamcinolone acetonide (SO/TA group). The retina from the left eye of each rabbit served as a control. The animals were killed at 4 weeks after surgery. Qualitative and quantitative histopathologic analyses were performed 4 weeks after surgery, and investigation for apoptosis was performed using the Tunel assay.

RESULTS

Intravitreal triamcinolone acetonide and dexamethasone implant were associated with increased retinal neuronal survival, primarily in the outer nuclear layer, inner nuclear layer, and ganglion cell layer. In the SO group, the cell density in eyes that underwent PPV/SO was 31% lower in the outer nuclear layer, 33% lower in the inner nuclear layer, and 45% lower in the ganglion cell layer compared to control eyes (p < 0.05 for all PPV/SO versus control comparisons). Compared to eyes that underwent PPV/SO, the cell density in eyes treated with triamcinolone was 27% higher in the outer nuclear layer, 66% higher in the inner nuclear layer, and 100% higher in the ganglion cell layer (p < 0.05 for all triamcinolone versus PPV/SO comparisons). Compared to eyes that underwent PPV/SO, the cell density in eyes treated with dexamethasone was 46% higher in the outer nuclear layer, 62% higher in the inner nuclear layer, and 77% higher in the ganglion cell layer (p < 0.05 for all dexamethasone versus PPV/SO comparisons). Analyses using the Tunnel assay demonstrated apoptotic bodies in all eyes in the SO group, compared with none of the eyes in the SO/TA and SO/DEX groups. The presence of cell nuclei stained with 49,6-diamidino-2-phenylindole (DAPI) was demonstrated in all groups.

CONCLUSION

In this experimental model of neuroprotection, increased retinal neuronal survival was seen in the steroid-treated groups compared with the controls.

Transduced protein transduction domain linked HSP27 protected LECs against UVB radiation-induced damage

PTD-fusion protein technology was used to transduce heat shock protein 27 (HSP27), an anti-apoptotic protein, into human lens epithelial cells (HLECs) (SRA01/04). The protein transduction domain (PTD) of the 11-amino acid YGRKKRRQRRR was tagged at the N-terminus of HSP27. The fusion protein was purified from bacteria transformed with a pKYB-PTD-HSP27 construct. The HLECs were incubated with PTD-HSP27-FITC and the fluorescence inside HLECs was found by fluorescence microscopic examination. To test the ability of PTD-HSP27 to pass through the corneas, PTD-HSP27-FITC was dropped onto the conjunctival sacs of rabbits; fluorescent labeled PTD-HSP27 was then observed in the rabbit aqueous humor. After being incubated with the PTD-HSP27 protein and irradiated with ultraviolet-B (UVB) light, HLECs was analyzed by flow cytometry, Hoechst 33258 staining and measurement of the potential of the mitochondrial transmembrane. HLECs incubated with PTD-HSP27 had a lower apoptotic rate and a higher mitochondrial membrane potential than the control cells. PTD-HSP27 appears to be sufficient to protect HLECs against UVB-induced apoptosis.

The effect of manganese-induced cytotoxicity on mRNA expressions of HSP27, HSP40, HSP60, HSP70 and HSP90 in chicken spleen lymphocytes in vitro

The purpose of this study was to investigate the effect of manganese (Mn)-induced cytotoxicity on heat shock proteins in chicken spleen lymphocytes. Lymphocytes were cultured in medium in the absence and presence of MnCl2 (2 × 10(-4), 4 × 10(-4), 6 × 10(-4), 8 × 10(-4), 10 × 10(-4), and 12 × 10(-4) mmol/L) for 12, 24, 36, and 48 h in vitro. Then, the mRNA levels of HSP27, HSP40, HSP60, HSP70, and HSP90 were examined by real-time quantitative PCR. The results showed that the mRNA levels of HSP27, HSP40, HSP60, HSP70, and HSP90 in all treatment groups at all time points, except mRNA levels of HSP27 at 48 h, had the same tendency. As manganese concentration increased, the mRNA expression of the heat shock proteins first increased and then decreased. In other words, we demonstrated that the mRNA expression of the heat shock proteins was induced at lower concentrations of manganese and was inhibited at higher concentrations. Mn had a dosage-dependent effect on HSP27, HSP40, HSP60, HSP70, and HSP90 mRNA expression in chicken spleen lymphocytes in vitro.

NonO binds to the CpG island of oct4 promoter and functions as a transcriptional activator of oct4 gene expression

We investigated the relationship between oct4 gene expression patterns and CpG sites methylation profiles during ES cell differentiation into neurons, and identified relevant binding factor. The oct4 gene expression level gradually declined as ES cell differentiation progressed, and the CpG sites in the oct4 proximal enhancer (PE) and promoter regions were methylated in concert with ES cell differentiation. An electro-mobility shift assay (EMSA) showed that putative proteins bind to CpG sites in the oct4 PE/promoter. We purified CpG binding proteins with DNAbinding purification method, and NonO was identified by liquid chromatography-mass spectrometry. EMSA with specific competitors revealed that NonO specifically binds to the conserved CCGGTGAC sequence in the oct4 promoter. Methylation at a specific cytosine residue (CC* GGTGAC) reduced the binding affinity of NonO for the recognition sequence. Chromatin immunoprecipitation analysis confirmed that NonO binds to the unmethylated oct4 promoter. There were no changes in the NonO mRNA and protein levels between ES cells and differentiated cells. The transcriptional role of NonO in oct4 gene expression was evaluated by luciferase assays and knockdown experiments. The luciferase activity significantly increased threefold when the NonO expression vector was cotransfected with the NonO recognition sequence, indicating that NonO has a transcription activator effect on oct4 gene expression. In accordance with this effect, when NonO expression was inhibited by siRNA treatment, oct4 expression was also significantly reduced. In summary, we purified NonO, a novel protein that binds to the CpG island of oct4 promoter, and positively regulates oct4 gene expression in ES cells.

Heat shock protein 27 mediated signaling in viral infection

Heat shock proteins (HSPs) play a critical role in many intracellular processes, including apoptosis and delivery of other proteins to intracellular compartments. Small HSPs have been shown previously to participate in many cellular functions, including IL-8 induction. Human adenovirus infection activates intracellular signaling, involving particularly the c-Src and mitogen-activated protein kinases [Natarajan, K., et al. (2003) J. Immunol. 170, 6234-6243]. HSP27 and MK2 are also phosphorylated, and c-Src, and its downstream targets, p38, ERK1/2, and c-Jun-terminal kinase (JNK), differentially mediate IL-8 and MCP-1 expression. Specifically, activation and translocation of transcription factor NFκB-p65 occurs in a p38-dependent fashion [Rajaiya, J., et al. (2009) Mol. Vision 15, 2879-2889]. Herein, we report a novel role for HSP27 in an association of p38 with NFκB-p65. Immunoprecipitation assays of virus-infected but not mock-infected cells revealed a signaling complex including p38 and NFκB-p65. Transfection with HSP27 short interfering RNA (siRNA) but not scrambled RNA disrupted this association and reduced the level of IL-8 expression. Transfection with HSP27 siRNA also reduced the level of nuclear localization of NFκB-p65 and p38. By use of tagged p38 mutants, we found that amino acids 279-347 of p38 are necessary for the association of p38 with NFκB-p65. These studies strongly suggest that HSP27, p38, and NFκB-p65 form a signalosome in virus-infected cells and influence downstream expression of pro-inflammatory mediators.

Loss of proteostatic control as a substrate for atrial fibrillation: a novel target for upstream therapy by heat shock proteins

Atrial fibrillation (AF) is the most common, sustained clinical tachyarrhythmia associated with significant morbidity and mortality. AF is a persistent condition with progressive structural remodeling of the atrial cardiomyocytes due to the AF itself, resulting in cellular changes commonly observed in aging and in other heart diseases. While rhythm control by electrocardioversion or drug treatment is the treatment of choice in symptomatic AF patients, its efficacy is still limited. Current research is directed at preventing first-onset AF by limiting the development of substrates underlying AF progression and resembles mechanism-based therapy. Upstream therapy refers to the use of non-ion channel anti-arrhythmic drugs that modify the atrial substrate- or target-specific mechanisms of AF, with the ultimate aim to prevent the occurrence (primary prevention) or recurrence of the arrhythmia following (spontaneous) conversion (secondary prevention). Heat shock proteins (HSPs) are molecular chaperones and comprise a large family of proteins involved in the protection against various forms of cellular stress. Their classical function is the conservation of proteostasis via prevention of toxic protein aggregation by binding to (partially) unfolded proteins. Our recent data reveal that HSPs prevent electrical, contractile, and structural remodeling of cardiomyocytes, thus attenuating the AF substrate in cellular, Drosophila melanogaster, and animal experimental models. Furthermore, studies in humans suggest a protective role for HSPs against the progression from paroxysmal AF to persistent AF and in recurrence of AF. In this review, we discuss upregulation of the heat shock response system as a novel target for upstream therapy to prevent derailment of proteostasis and consequently progression and recurrence of AF.

Role of heat shock proteins in stem cell behavior

Stress response is well appreciated to induce the expression of heat shock proteins (Hsps) in the cell. Numerous studies have demonstrated that Hsps function as molecular chaperones in the stabilization of intracellular proteins, repairing damaged proteins, and assisting in protein translocation. Various kinds of stem cells (embryonic stem cells, adult stem cells, or induced pluripotent stem cells) have to maintain their stemness and, under certain circumstances, undergo stress. Therefore, Hsps should have an important influence on stem cells. Actually, numerous studies have indicated that some Hsps physically interact with a number of transcription factors as well as intrinsic and extrinsic signaling pathways. Importantly, alterations in Hsp expression have been demonstrated to affect stem cell behavior including self-renewal, differentiation, sensitivity to environmental stress, and aging. This chapter summarizes recent findings related to (1) the roles of Hsps in maintenance of stem cell dormancy, proliferation, and differentiation; (2) the expression signature of Hsps in embryonic/adult stem cells and differentiated stem cells; (3) the protective roles of Hsps in transplanted stem cells; and (4) the possible roles of Hsps in stem cell aging.

Glucocorticoid regulation of astrocytic fate and function

Glial loss in the hippocampus has been suggested as a factor in the pathogenesis of stress-related brain disorders that are characterized by dysregulated glucocorticoid (GC) secretion. However, little is known about the regulation of astrocytic fate by GC. Here, we show that astrocytes derived from the rat hippocampus undergo growth inhibition and display moderate activation of caspase 3 after exposure to GC. Importantly, the latter event, observed both in situ and in primary astrocytic cultures is not followed by either early- or late-stage apoptosis, as monitored by stage I or stage II DNA fragmentation. Thus, unlike hippocampal granule neurons, astrocytes are resistant to GC-induced apoptosis; this resistance is due to lower production of reactive oxygen species (ROS) and a greater buffering capacity against the cytotoxic actions of ROS. We also show that GC influence hippocampal cell fate by inducing the expression of astrocyte-derived growth factors implicated in the control of neural precursor cell proliferation. Together, our results suggest that GC instigate a hitherto unknown dialog between astrocytes and neural progenitors, adding a new facet to understanding how GC influence the cytoarchitecture of the hippocampus.

Class-C SOX transcription factors control GnRH gene expression via the intronic transcriptional enhancer

GnRH is a pivotal hypothalamic neurohormone governing reproduction and sexual development. Because transcriptional regulation is crucial for the spatial and temporal expression of the GnRH gene, a region approximately 3.0 kb upstream of the mammalian GnRH promoter has been extensive studied. In the present study, we demonstrate a transcription-enhancer located in the first intron (intron A) region of the GnRH gene. This transcriptional enhancer harbors putative sex-determining region Y-related high-mobility-group box (SOX) family transcription factor-binding sites, which are well conserved across many mammalian species. The class-C SOX member proteins (SOX-C) (SOX4 and SOX11) specifically augment this transcriptional activation by binding to these SOX-binding sites. In accordance, SOX11 is highly enriched in immortalized GnRH-producing GT1-1 cells, and suppression of its expression significantly decreases GnRH gene expression as well as GnRH secretion. Chromatin immunoprecipitation shows that endogenous SOX-C factors recognize and bind to the intronic enhancer in GT1-1 cells and the hypothalamus. Accompanying immunohistochemical analysis demonstrates that SOX4 or SOX11 are highly expressed in the majority of hypothalamic GnRH neurons in adult mice. Taken together, these findings demonstrate that SOX-C transcription factors function as important transcriptional regulators of cell type-specific GnRH gene expression by acting on the intronic transcriptional enhancer.

Downregulation of both gene expression and activity of Hsp27 improved maturation of mouse oocyte in vitro

BACKGROUND

Heat shock protein 27 (Hsp27), a member of the small heat shock protein family, is an apoptosis regulator. Our previous proteomic study showed that Hsp27 mainly expressed in human oocyte, and that Hsp27 expression was downregulated in the ovaries derived from women with the polycystic ovary syndrome (PCOS), a well known endocrinal disorder with abnormal apoptotic activity and folliculogenesis. However, the exact effects of Hsp27 downregulation on oocyte development have not yet been clarified.

METHODS

The expression of Hsp27 gene was downregulated in the mouse oocytes cultured in vitro using siRNA adenovirus infection, while the activity of Hsp27 was decreased by microinjection of polyclonal Hsp27 antibody into the cytoplasm of germinal vesicle (GV) oocytes. Oocyte maturation rate was evaluated by morphological observation. Early stage of apoptosis was determined using Annexin-V staining analysis and some critical apoptotic factors and cytokines were also monitored at both mRNA level by real time RT-PCR and protein expression level by immunofluorescence and western blot.

RESULTS

Hsp27 expressed at high level in maturing oocytes. Infection with AdshHsp27, and microinjection of Hsp27 antibody into GV oocytes, resulted in the improved oocyte development and maturation. Germinal vesicle breakdown (GVBD) rates were significantly increased in two AdshHsp27-treated groups (88.7%, 86.0%) and Hsp27 antibody-injected group (77.0%) when compared with control (76.2% in AdGFP, 64.4% in IgG-injected), respectively. In addition, the rates of metaphase II (MII) development in two AdshHsp27-treated groups (73.8%, 76.4%) and Hsp27 antibody-injected group (67.3%) were higher than that in the controls (59.6% in AdGFP, 55.1% in IgG-injected). We also found that the rates of early stage of apoptosis in Hsp27 downregulated groups (46.5% and 45.6%) were higher than that in control group (34.1%) after 8 h of IVM. Similarly, downregulation of Hsp27 caused a significantly enhanced the expression of apoptotic factors (caspase 8, caspase 3) and cytokines (bmp 15 and gdf 9).

CONCLUSIONS

Downregulation of Hsp27 improved the maturation of mouse oocytes, while increased early stage of apoptosis in oocytes by inducing the activation of extrinsic, caspase 8-mediated pathway.

Mechanism of glucocorticoid-induced oxidative stress in rat hippocampal slice cultures

Prolonged stress results in elevation of glucocorticoid (GC) hormones, which can have deleterious effects in the brain. The hippocampus, which has a high concentration of glucocorticoid receptors, is especially vulnerable to increasing levels of GCs. GCs have been suggested to endanger hippocampal neurons by exacerbating the excitotoxic glutamate-calcium-reactive oxygen species (ROS) cascade. In an effort to reveal the mechanisms underlying GC-mediated hippocampal neurotoxicity, we aimed to clarify the molecular pathway of GC-induced ROS increase by using organotypic hippocampal slice cultures. Assays for ROS, using 2',7'-dichlorodihydrofluorescein diacetate fluorescence, showed that treatment of synthetic GC, dexamethasone (DEX) significantly enhanced ROS levels. Time course and dose response analyses indicated that peak amount of ROS was generated at 4 h after treatment with 50 micromol/L DEX. By contrast, other steroid hormones, progesterone and estradiol did not influence ROS production. N-acetyl-L-cysteine completely suppressed ROS produced by DEX. Propidium iodide staining exhibited prominent cell death in the hippocampal layer after 96 h of DEX treatment. RU486, a GC receptor antagonist, almost completely blocked the effect of DEX on ROS production and cell death, indicating that DEX-induced ROS overproduction and hippocampal death are mediated via GC receptors. Real-time reverse transcriptase PCR analysis demonstrated that after DEX treatment the level of glutathione peroxidase mRNA was decreased whereas that of NADPH oxidase mRNA was significantly enhanced. These findings suggest that excess GCs cause hippocampal damage by regulating genes involved in ROS generation.

Mechanisms regulating the susceptibility of hematopoietic malignancies to glucocorticoid-induced apoptosis

Glucocorticoids (GCs) are commonly used in the treatment of hematopoietic malignancies owing to their ability to induce apoptosis of these cancerous cells. Whereas some types of lymphoma and leukemia respond well to this drug, others are resistant. Also, GC-resistance gradually develops upon repeated treatments ultimately leading to refractory relapsed disease. Understanding the mechanisms regulating GC-induced apoptosis is therefore uttermost important for designing novel treatment strategies that overcome GC-resistance. This review discusses updated data describing the complex regulation of the cell's susceptibility to apoptosis triggered by GCs. We address both the genomic and nongenomic effects involved in promoting the apoptotic signals as well as the resistance mechanisms opposing these signals. Eventually we address potential strategies of clinical relevance that sensitize GC-resistant lymphoma and leukemia cells to this drug. The major target is the nongenomic signal transduction machinery where the interplay between protein kinases determines the cell fate. Shifting the balance of the kinome towards a state where Glycogen synthase kinase 3alpha (GSK3alpha) is kept active, favors an apoptotic response. Accumulating data show that it is possible to therapeutically modulate GC-resistance in patients, thereby improving the response to GC therapy.

Proteomic analysis identifies protein targets responsible for depsipeptide sensitivity in tumor cells

Depsipeptide FR901228 (FK228) is a new kind of histone deacetylase inhibitors (HDACi) that induces growth arrest and cell death in a variety of tumor cells. Though its effects on oncogene expression and degradation have been documented, the detailed mechanism of FK228-induced cytotoxicity is still undefined. In this study, a differential proteomic analysis was performed to identify proteins associated with FK228-induced cytotoxicity in human lung cancer cells. Two-dimensional gel electrophoresis (2-DE) revealed a distinct protein profile of H322 cells in response to FK228 treatment, and 45 protein spots with significant alteration were screened. In total, 27 proteins were identified by mass spectrometry and involved in signal transduction, transcriptional regulation, metabolism, cytoskeletal organization, and protein folding, synthesis and degradation, consistent with multiple effects of FK228 on tumor cells. Notably, a novel target protein, thioredoxin reductase (TrxR), was identified, which is downregulated in FK228-sensitive cancer cells, but upregulated in resistant cells. The expression level of TrxR was negatively correlated with ROS accumulation, DNA damage and apoptosis, implicating TrxR in FK228-induced apoptosis and HDACi sensitivity in cancer cells. Thus, proteomic analysis provides new information about target proteins important for FK228-induced cytotoxicity in cancer cells.

Doxorubicin-induced cardiotoxicity: direct correlation of cardiac fibroblast and H9c2 cell survival and aconitase activity with heat shock protein 27

The use of doxorubicin (Dox) and its derivatives as chemotherapeutic drugs to treat patients with cancer causes dilated cardiomyopathy and congestive heart failure due to Dox-induced cardiotoxicity. In this work, using heat shock factor-1 wild-type (HSF-1(+/+)) and HSF-1 knockout (HSF-1(-/-)) mouse fibroblasts and embryonic rat heart-derived cardiac H9c2 cells, we show that the magnitude of protection from Dox-induced toxicity directly correlates with the level of the heat shock protein 27 (HSP27). Western blot analysis of normal and heat-shocked cells showed the maximum expression of HSP27 in heat-shocked cardiac H9c2 cells and no HSP27 in HSF-1(-/-) cells (normal or heat-shocked). Correspondingly, the cell viability, measured [with (3,4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay] after treatment with various concentrations of Dox, was the highest in heat-shocked H9c2 cells and the lowest in HSF-1(-/-) cells. Depleting HSP27 in cardiac H9c2 cells by small interfering (si)RNA also reduced the viability against Dox, confirming that HSP27 does protect cardiac cells against the Dox-induced toxicity. The cells that have lower HSP27 levels such as HSF-1(-/-), were found to be more susceptible for aconitase inactivation. Based on these results we propose a novel mechanism that HSP27 plays an important role in protecting aconitase from Dox-generated O(2)*(-), by increasing SOD activity. Such a protection of aconitase by HSP27 eliminates the catalytic recycling of aconitase released Fe(II) and its deleterious effects in cardiac cells.

Protective effect of heat shock protein 27 using protein transduction domain-mediated delivery on ischemia/reperfusion heart injury

Heat shock protein 27 (HSP27) is an intracellular stress protein with the cytoprotective effect for a variety of noxious stresses. In this study, using a protein delivery system, we demonstrated the potential cytoprotective effect of HSP27 as a therapeutic protein in cardiac cells and ischemia/reperfusion animal model. We constructed a recombinant HSP27 fused to the protein transduction domain (PTD) derived from HIV-1 TAT protein. Purified recombinant TAT-HSP27 protein was efficiently delivered to H9c2 cells, and its transduction showed cytoprotective effect against the hypoxic stress. Moreover, transduction of TAT-HSP27 also attenuated hypoxia-induced apoptosis, which was accompanied by reduced caspase-3 activity. In addition, intraperitoneal injection of TAT-HSP27 into rat resulted in efficient protein transduction in heart tissues, decreased infarcted myocardium (control vs TAT-HSP27, 39.1% vs 29.5%, P<0.05) and preserved heart function (fractional shortening, 15.6% vs 33.4%, P<0.05), as determined at 7 d after I/R. These results suggest that the PTD-mediated delivery of HSP27 protein may represent a potential therapeutic strategy as protein drug for ischemic heart diseases.

Hsp27 regulates Akt activation and polymorphonuclear leukocyte apoptosis by scaffolding MK2 to Akt signal complex

We have shown previously that Akt exists in a signal complex with p38 MAPK, MAPK-activated protein kinase-2 (MK2), and heat shock protein 27 (Hsp27) and MK2 phosphorylates Akt on Ser-473. Additionally, dissociation of Hsp27 from Akt, prior to Akt activation, induced polymorphonuclear leukocyte (PMN) apoptosis. However, the role of Hsp27 in regulating Akt activation was not examined. This study tested the hypothesis that Hsp27 regulates Akt activation and promotes cell survival by scaffolding MK2 to the Akt signal complex. Here we show that loss of Akt/Hsp27 interaction by anti-Hsp27 antibody treatment resulted in loss of Akt/MK2 interaction, loss of Akt-Ser-473 phosphorylation, and induced PMN apoptosis. Transfection of myristoylated Akt (AktCA) in HK-11 cells induced Akt-Ser-473 phosphorylation, activation, and Hsp27-Ser-82 phosphorylation. Cotransfection of AktCA with Hsp27 short interfering RNA, but not scrambled short interfering RNA, silenced Hsp27 expression, without altering Akt expression in HK-11 cells. Silencing Hsp27 expression inhibited Akt/MK2 interaction, inhibited Akt phosphorylation and Akt activation, and induced HK-11 cell death. Deletion mutagenesis studies identified acidic linker region (amino acids 117-128) on Akt as an Hsp27 binding region. Deletion of amino acids 117-128 on Akt resulted in loss of its interaction with Hsp27 and MK2 but not with Hsp90 as demonstrated by immunoprecipitation and glutathione S-transferase pulldown studies. Co-transfection studies demonstrated that constitutively active MK2 (MK2EE) phosphorylated Aktwt (wild type) on Ser-473 but failed to phosphorylate Akt(Delta117-128) mutant in transfixed cells. These studies collectively define a novel role of Hsp27 in regulating Akt activation and cellular apoptosis by mediating interaction between Akt and its upstream activator MK2.

Interactions between methamphetamine and environmental stress: role of oxidative stress, glutamate and mitochondrial dysfunction

AIMS

Methamphetamine is an amphetamine derivative that is abused increasingly world-wide at an alarming rate over the last decade. Pre-clinical and human studies have shown that methamphetamine is neurotoxic to brain dopamine and serotonin. Other lines of study indicate that stress enhances the vulnerability to drug abuse. The purpose of this review is to shed light on the biochemical similarities between methamphetamine and stress in an effort to highlight the possibility that prior exposure to stress may interact with methamphetamine to exacerbate neurotoxicity.

METHODS

A review of the literature on methamphetamine and stress was conducted that focused on the common neurotoxic and biochemical consequences of methamphetamine administration and stress exposure.

RESULTS

Experimental findings of a large number of studies suggest that there are parallels between stress and methamphetamine with regard to their ability to increase glutamate release, produce a metabolic compromise and cause oxidative damage.

CONCLUSION

A combination of methamphetamine administration and stress can act synergistically and/or additively to cause or augment toxicity in brain regions such as striatum and hippocampus.

HSPBAP1 is found extensively in the anterior temporal neocortex of patients with intractable epilepsy

Heat Shock Protein BAP1 (heat shock 27-kDa-associated protein 1, HSPBAP1) inhibits the function of heat shock protein 27, which has a neuroprotective effect during experimentally induced epileptic neuropathology. In our study, fluorescence quantitative polymerase chain reaction, immunohistochemistry, immunofluorescence, western blot were used to test the levels of HSPBAP1 mRNA and protein in surgical samples of the anterior temporal neocortex of patients with intractable epilepsy (IE) and normal controls samples. HSPBAP1 mRNA was abnormally expressed in the anterior temporal neocortex of patients with IE. Moreover, HSPBAP1 was found extensively in the cytoplasm of neurons and glial cells in all epilepsy specimens. Western blot showed a clear immunoreactive band of HSPBAP1 in IE specimens whereas it was absent in control specimens. The expression of HSPBAP1 mRNA and protein in the anterior temporal neocortex from patients with IE may play a role in the development of epileptic seizures in patients with cell loss in this brain region. Additional studies will be required to elucidate the mechanism by which HSPBAP1 affects brain function in IE.

Stressed stem cells: Temperature response in aged mesenchymal stem cells

Mesenchymal stem cells (MSCs) derived from young (6 week) and aged (56 week) Wistar rats were cultured at standard (37 degrees C) and reduced (32 degrees C) temperature and compared for age markers and stress levels. (ROS, NO, TBARS, carbonyls, lipofuscin, SOD, GPx, apoptosis, proteasome activity) and heat shock proteins (HSP27, -60, -70, -90). Aged MSCs display many of the stress markers associated with aging in other cell types, but results vary across marker categories and are temperature dependant. In young MSCs, culturing at reduced temperature had a generally beneficial effect: the anti-apoptotic heat shock proteins HSP 27, HSP70, and HSP90 were up-regulated; pro-apoptotic HSP60 was downregulated; SOD, GPx increased; and levels in ROS, NO, TBARS, carbonyl, and lipofuscin were diminished. Apoptosis was reduced, but also proteasome activity. In contrast, in aged MSCs, culturing at reduced temperature generally produced no 'beneficial' changes in these parameters, and can even have detrimental effects. Implications for tissue engineering and for stem cell gerontology are discussed. The results suggest that a 'hormesis' theory of stress response can be extended to MSCs, but that cooling cultivation temperature stress produces positive effects in young cells only.