Biomedical subjects

Akira Nakai

Publications and source records attributed to Akira Nakai.

At least 19 recordsLinked to original sources

PubMed2006

Genetic evidence for a protective role of heat shock factor 1 against irritant-induced gastric lesions.

Gastric lesions result from an imbalance between aggressive and defensive factors. Indirect lines of evidence suggest that heat shock proteins (HSPs) induced by various aggressive factors provide a major protective mechanism. In this study, we compared gastric ulcerogenic response in wild-type mice and in those lacking heat shock factor 1 (HSF1), a transcription factor for hsp genes. The severity of gastric lesions induced by ethanol or hydrochloric acid was worsened in HSF1-null mice. Immunoblotting, real-time reverse transcription-polymerase chain reaction, immunohistochemical analysis, and terminal deoxynucleotidyl transferase dUTP nick-end labeling assay revealed that the ethanol administration up-regulated gastric mucosal HSPs, in particular HSP70, in an HSF1-dependent manner, and more apoptotic cells were observed in the gastric mucosa of HSF1-null mice than in wild-type mice. In contrast, other parameters governing the gastric ulcerogenic response, including gastric acid secretion, gastric mucosal blood flow, and prostaglandin E(2) levels, were not significantly affected by the absence of the hsf1 gene. Geranylgeranylacetone (GGA), a clinically used antiulcer drug with HSP-inducing activity, suppressed ethanol-induced gastric lesions in wild-type mice but not in heat shock factor 1 (HSF1)-null mice. The results suggest that the aggravation of irritant-induced gastric lesions in HSF1-null mice is due to their inability to up-regulate HSPs, leading to apoptosis. It is also suggested that the HSP-inducing activity of GGA contributes to the drug's antiulcer activity. This study provides direct genetic evidence that HSPs, after their HSF1-dependent up-regulation, confer gastric protection against the irritant-induced lesions.

Animals↗

PubMed2006

The induction mechanism of the molecular chaperone HSP70 in the gastric mucosa by Geranylgeranylacetone (HSP-inducer).

To elucidate the induction mechanism of HSP70 by geranylgeranylacetone (GGA), we investigated GGA specific binding proteins using a GGA-affinity column. Alteration of chaperone activity of HSP70 and binding affinity of HSP70 to heat shock factor-1 (HSF-1) was evaluated in the presence or absence of GGA. The binding domain of HSP70 to GGA was also analyzed. A 70-kDa protein eluted by 10 mM GGA from the GGA-affinity column was identical to constitutively expressed HSP70 on immunoblotting. GGA-binding domain of HSP70 was C-terminal of the protein as peptide-binding domain (HSP70C). The chaperone activity of HSP70 and recombinant HSP70C was suppressed by GGA. Furthermore, dissociation of the HSP70 from HSF-1 was observed in the presence of GGA. GGA preferentially binds to the C-terminal of HSP70 which binds to HSF-1. After dissociation of HSP70, free HSF-1 could acquire the ability to bind to HSE (the promoter region of HSP70) gene.

Animals↗

PubMed2006

Upregulation of heat shock transcription factor 1 plays a critical role in adaptive cardiac hypertrophy.

Exercise-induced cardiac hypertrophy has been reported to have better prognosis than pressure overload-induced cardiac hypertrophy. Cardiac hypertrophy induced by exercise was associated with less cardiac fibrosis and better systolic function, suggesting that the adaptive mechanisms may exist in exercise-induced hypertrophy. Here, we showed a critical role of heat shock transcription factor 1 (HSF1), an important transcription factor for heat shock proteins, in the adaptive mechanism of cardiac hypertrophy. We examined expression of 8800 genes in the heart of exercise-induced hypertrophy model using DNA chip technique and compared with pressure overload-induced hypertrophy. Expression of HSF1 and its target molecule heat shock proteins was significantly upregulated in the heart by exercise but not by chronic pressure overload. Constitutive activation of HSF1 in the heart significantly ameliorated death of cardiomyocytes and cardiac fibrosis and thereby prevented cardiac dysfunction as well as hypertrophy induced by chronic pressure overload. Conversely, decreased activity of HSF1 in the heart promoted cardiac dysfunction in response to exercise, a load that normally leads to adaptive hypertrophy with preserved systolic function. Likewise, cardiac function was significantly impaired from the early phase of pressure overload, when HSF1 activation was inhibited. These results suggest that HSF1 plays a critical role in the transition between adaptive and maladaptive hypertrophy.

Adaptation, Physiological↗

PubMed2006

A novel HSF1-mediated death pathway that is suppressed by heat shock proteins.

Heat shock response is an adoptive response to proteotoxic stress, and a major heat shock transcription factor 1 (HSF1) has been believed to protect cells from cell death by inducing heat shock proteins (Hsps) that assist protein folding and prevent protein denaturation. However, it is revealed recently that HSF1 also promotes cell death of male germ cells. Here, we found a proapoptotic Tdag51 (T-cell death associated gene 51) gene as a direct target gene of HSF1. Heat shock and other stresses induced different levels of Hsps and Tdag51, which depend on cell types. Hsps bound directly to the N-terminal pleckstrin-homology like (PHL) domain of Tdag51, and suppressed death activity of the C-terminal proline/glutamine/histidine-rich domain. Tdag51, but not major Hsps, were induced in male germ cells exposed to high temperatures. Analysis of Tdag51-null testes showed that Tdag51 played substantial roles in promoting heat shock-induced cell death in vivo. These data suggest that cell fate on proteotoxic condition is determined at least by balance between Hsp and Tdag51 levels, which are differently regulated by HSF1.

Animals↗

PubMed2006

HSF1 and constitutively active HSF1 improve vascular endothelial function (heat shock proteins improve vascular endothelial function).

We have been examining the role of heat shock factor 1 (HSF1) in the pleiotropic effects of statins. In parallel studies, we found that statin induces the nuclear translocation of HSF1 and that a decoy oligonucleotide encoding the heat shock element inhibits the statin-induced expression of heat shock protein 70, endothelial nitric oxide synthase (eNOS) and thrombomodulin. Also, in vascular endothelial cells, increases in the expression of human HSF1 corresponded with elevated steady-state levels of eNOS and thrombomodulin and reduced levels of endothelin-1 and plasminogen activator inhibitor-1. We also found that heat shock proteins induced eNOS and thrombomodulin expression and reduced PAI-1 and ET-1 expression. In particular, a combination of HSP70 and HSP90 strongly induced eNOS expression and reduced PAI-1 expression. In the current studies, we generated a constitutively active form of HSF1 and found that it is more effective than the wild-type HSF at inducing thrombomodulin and eNOS expression and decreasing endothelin-1 and plasminogen activator inhibitor-1 expression. These results show that the wild-type and constitutively active forms of HSF1 induce anticoagulation and relaxation factors in vascular endothelial cells and could therefore be used to treat cardiovascular disease.

Aorta↗

PubMed2006

Depletion of hsp90beta induces multiple defects in B cell receptor signaling.

Hsp90 participates in many distinct aspects of cellular functions and accomplishes these roles by interacting with multiple client proteins. To gain insight into the interactions between Hsp90 and its clients, here we have reduced the protein level of Hsp90 in avian cells by gene targeting in an attempt to elicit the otherwise undetectable (because of the vast amount of cellular Hsp90) Hsp90-interacting proteins. Hsp90beta-deficient cells can grow, albeit more slowly than wild-type cells. B cell antigen receptor signaling is multiply impaired in these mutant cells; in particular, the amount of immunoglobulin M heavy chain protein is markedly reduced. Furthermore, serum activation does not promote ERK phosphorylation in Hsp90beta-deficient cells. These multifaceted depressive effects seem to be provoked independently of each other and possibly recapitulate the proteome-wide in vivo functions of Hsp90. Reintroduction of the Hsp90beta gene efficiently restores all of the defects. Unexpectedly, however, introducing the Hsp90alpha gene is also effective in restoration; thus, these defects might be caused by a reduction in the total expression of Hsp90 rather than by loss of Hsp90beta-specific function.

Animals↗

PubMed2005

PDSM, a motif for phosphorylation-dependent SUMO modification.

SUMO (small ubiquitin-like modifier) modification regulates many cellular processes, including transcription. Although sumoylation often occurs on specific lysines within the consensus tetrapeptide PsiKxE, other modifications, such as phosphorylation, may regulate the sumoylation of a substrate. We have discovered PDSM (phosphorylation-dependent sumoylation motif), composed of a SUMO consensus site and an adjacent proline-directed phosphorylation site (PsiKxExxSP). The highly conserved motif regulates phosphorylation-dependent sumoylation of multiple substrates, such as heat-shock factors (HSFs), GATA-1, and myocyte enhancer factor 2. In fact, the majority of the PDSM-containing proteins are transcriptional regulators. Within the HSF family, PDSM is conserved between two functionally distinct members, HSF1 and HSF4b, whose transactivation capacities are repressed through the phosphorylation-dependent sumoylation. As the first recurrent sumoylation determinant beyond the consensus tetrapeptide, the PDSM provides a valuable tool in predicting new SUMO substrates.

Amino Acid Motifs↗

PubMed2005

Simvastatin induces heat shock factor 1 in vascular endothelial cells.

Statins not only reduce serum cholesterol but they also improve vascular endothelial function independent of their lipid-lowering effects. However, except for the mechanism of nitric oxide induction via calveolin, the physiologic basis for the pleiotropic effect of statins remains unknown. In the present study, we investigated the relationship between the effects of statins on vascular endothelial cell function and heat shock proteins. We found that, in vascular endothelial cells, simvastatin increased the steady-state levels of heat shock proteins 90 and 70, and heme oxygenase-1 and caused the nuclear translocation of heat shock factor 1. A decoy oligonucleotide encoding the heat shock element inhibited statin-induced expression of heat shock protein 70, endothelial nitric oxide synthase, and thrombomodulin. This decoy oligonucleotide also inhibited the ability of statin to reduce endothelin-1 and plasminogen activator inhibitor-1 expression. These results indicate that statins improve vascular endothelial function via heat shock factor 1, which may contribute to their ability to improve cardiovascular disease.

Analysis of Variance↗

PubMed2005

Geranylgeranylacetone, a heat shock protein inducer, prevents acoustic injury in the guinea pig.

Geranylgeranylacetone (GGA) used widely as anti-ulcer agent is accepted as an inducer of the heat shock proteins (Hsps) at gastric mucosa, liver, heart, and brain. However, there have been no reports that GGA could induce Hsps in the cochlea leading up to the oto-protection. The purpose of the present study was to investigate whether single oral dose of GGA could induce Hsps at cochlea and oral administration had protective effect to the cochlea against noise trauma. We used Hartley guinea pigs and investigated the expression of Hsp70, 40, and 27 in cochlea by Western blot analysis. To evaluate cochlear function, we assessed thresholds of the auditory brain stem response (ABR). For histological assessment, we observed the sensory epithelium using surface preparation technique. GGA (600 mg/kg) or vehicle was given orally to animals. Western blot analysis showed that the expressions of Hsp 70, 40, and 27 were increased 24-48 h after administration of single dose of GGA, whereas there was less expression in the animals given vehicle. In the animals given GGA once a day for a week before sound exposure (130 dB SPL octave band noise with a center frequency of 4 kHz) for 3 h, their ABR threshold elevations were lowered significantly. In addition, significantly fewer defects were observed on outer hair cells of organ of Corti in the animals treated by GGA than those of the animals without GGA. This result shows that pretreatment by GGA have a potential to prevent cochlea damage against the intense noise.

Animals↗

PubMed2005

Maintenance of olfactory neurogenesis requires HSF1, a major heat shock transcription factor in mice.

Heat shock transcription factors (HSFs) play roles not only in heat shock response but also in development of the reproductive organs, brain, and lens. Here, we analyzed sensory organs and found abnormalities of the olfactory epithelium in adult HSF1-null mice, which is developmentally related to the lens. The olfactory epithelium was normal until postnatal 3 weeks but was not maintained later than 4 weeks in HSF1-null mice. The olfactory epithelium was atrophied with increased cell death of olfactory sensory neurons. Analysis of the epithelium revealed that induction of HSP expression and reduction of LIF expression are lacking in adult HSF1-null mice. We found that DNA binding activity of HSF1 is induced in the olfactory epithelium later than 4 weeks and that HSF1 binds directly to Lif gene and inhibits its expression. HSF4 has opposing effects on LIF expression and olfactory neurogenesis. These data indicate that HSF1 is required for the precise expression of Hsp and cytokine genes that is obligatory for maintenance of olfactory neurogenesis in adult mice and suggest that stress-related processes are involved in its maintenance.

Animals↗

PubMed2005

Active HSF1 significantly suppresses polyglutamine aggregate formation in cellular and mouse models.

Polyglutamine diseases are inherited neurodegenerative diseases characterized by misfolding and aggregation of proteins possessing expanded polyglutamine repeats. As overexpression of some heat shock protein (Hsp) suppresses polyglutamine aggregates and cell death, it is assumed that combined overexpression of Hsps will suppress that more effectively. Here, we examined the impact of active forms of heat shock transcription factor 1 (HSF1), which induces a set of Hsps, on polyglutamine inclusion formation and disease progression. We found that active HSF1 suppressed polyglutamine inclusion formation more significantly than any combination of Hsps in culture cells, possibly by regulating expression of unknown genes, as well as major Hsps. We crossed R6/2 Huntington disease mice with transgenic mice expressing an active HSF1 (HSF1Tg). Analysis of the skeletal muscle revealed that the polyglutamine inclusion formation and its weight loss were improved in R6/2/HSF1Tg mice. Unexpectedly, the life span of R6/2/HSF1Tg mice was significantly improved, although active HSF1 is not expressed in the brain. These results indicated that active HSF1 has a strong inhibitory effect on polyglutamine aggregate formation in vivo and in vitro.

Adenoviridae↗

PubMed2004

HSF4 is required for normal cell growth and differentiation during mouse lens development.

The heat shock transcription factor (HSF) family consists of three members in mammals and regulates expression of heat shock genes via a heat shock element. HSF1 and HSF2 are required for some developmental processes, but it is unclear how they regulate these processes. To elucidate the mechanisms of developmental regulation by HSFs, we generated mice in which the HSF4 gene is mutated. HSF4-null mice had cataract with abnormal lens fiber cells containing inclusion-like structures, probably due to decreased expression of gamma-crystallin, which maintains protein stability. Furthermore, we found increased proliferation and premature differentiation of the mutant lens epithelial cells, which is associated with increased expression of growth factors, FGF-1, FGF-4, and FGF-7. Unexpectedly, HSF1 competed with HSF4 for the expression of FGFs not only in the lens but also in other tissues. These findings reveal the lens-specific role of HSF4, which activates gamma-crystallin genes, and also indicate that HSF1 and HSF4 are involved in regulating expression of growth factor genes, which are essential for cell growth and differentiation.

Animals↗

PubMed2004

Feeding induces expression of heat shock proteins that reduce oxidative stress.

Heat shock proteins (Hsps) are induced in response to various kinds of environmental and physiological stresses. However, it is unclear whether Hsps play roles in protecting cells in the digestive organs against xenobiotic chemicals. Here, we found that feeding induces expression of a set of Hsps specifically in the mouse liver and intestine by activating heat shock transcription factor 1 (HSF1). In the liver, HSF1 is required to suppress toxic effects of electrophiles, which are xenobiotic chemicals causing oxidative stress. We found that overexpression of Hsp27, which elevates cellular glutathione level, promotes survival of culture cells exposed to electrophiles. These results suggest a novel mechanism of cell protection against xenobiotic chemicals in the food.

Animal Feed↗

PubMed2004

Impaired IgG production in mice deficient for heat shock transcription factor 1.

Heat shock factor 1 (HSF1) is a major transactivator of heat shock proteins in response to heat shock, and it is also involved in oogenesis, spermatogenesis, and placental development. However, we do not know the molecular mechanisms controlling developmental processes. In this study, we found that HSF1-null mice exhibited a significant decrease in the T cell-dependent B cell response. When mice were immunized intraperitoneally with sheep red blood cells, the sheep red blood cell-specific IgG production, especially IgG2a production, in HSF1-null mice was about 50% lower than that in wild-type mice at 6 days after the immunization, whereas IgM production was normal. The number of bromodeoxyuridine-incorporated spleen cells in immunized HSF1-null mice was one-third that in immunized wild-type mice, indicating reduced proliferation of the spleen cells. We analyzed levels of cytokines and chemokines in spleen cells and in peritoneal macrophages stimulated with lipopolysaccharide and interferon-gamma and found that expression levels of interleukin-6 and CCL5 were significantly lower in HSF1-null cells than those in wild-type cells. Furthermore, we demonstrated that the IL-6 gene is a direct target gene of HSF1. These results revealed a novel molecular link between HSF1 and a gene related to immune response and inflammation.

Animals↗

PubMed2004

Hsp25, a member of the Hsp30 family, promotes inclusion formation in response to stress.

Protein aggregates are oligomeric complexes of misfolded proteins, and serve as the seeds of inclusion bodies termed aggresomes in the cells. Heat shock proteins (Hsps) prevent misfolding and aggregate formation. Here, we found that only avian Hsp25 dominantly accumulated in the aggresomes induced by proteasome inhibition. Molecular cloning of chicken Hsp25 (cHsp25) revealed that it belongs to the Hsp30 family, which is a subfamily of the alpha-crystallin/small Hsp gene family. Unexpectedly, overexpression of cHsp25 into HeLa cells promoted inclusion formation whereas overexpression of mouse Hsp27 and its chicken homologue did not. These results suggest that cHsp25 acts differently from other small Hsps on protein aggregates.

Amino Acid Sequence↗

PubMed2004

Changes in cyclic nucleotide phosphodiesterase activity and calmodulin concentration in heart muscle of cardiomyopathic hamsters.

Cyclic nucleotides (cAMP and cGMP) phosphodiesterase (PDE) activities and expression are altered in the cardiac muscle of cardiomyopathic heart failure, and PDE inhibitors improve the abnormal muscle condition through changing the cyclic nucleotide concentration. These observations prompted us to investigate the role of calmodulin (CaM) in the regulation of cyclic nucleotide PDE activities, and moreover to study the modulation of the PDE isozymes in heart failure, using cardiac muscles of cardiomyopathic hamster. The CaM concentrations in the heart muscle of the normal control and cardiomyopathic hamsters (each of three to four hamsters) varied with cell fraction and with the age of the animal. The CaM concentrations in the soluble fraction obtained from cardiomyopathic hamster tissue were significantly increased at 25 and 32 weeks of age (2.02 +/- 0.62 microg/mg protein (mean +/- S.E.), and 3.21 +/- 0.95) compared with that obtained from the control (0.60 +/- 0.04) or cardiomyopathic (0.95 +/- 0.12) hamsters at 8 weeks of age. The solubilized PDE isolated from the hamster heart muscle (three or four hamsters in each age) by column chromatography on diethylaminoethyl (DEAE)-cellulose revealed three peaks of activity, which may correspond to the isozymes of PDE classified recently, namely PDE I, II, and III. These three peaks of activity, particularly peak III, seen in the soluble fraction of cardiomyopathic hamster heart declined in proportion to the age of the animal compared with that of the control hamster heart. In the cGMP-PDE assay system, the concentration of CaM inhibitor W-7 required for 50% inhibition (IC(50)) of PDE I, II, and III peak activities was 140, 29, and 46 microM, respectively, suggesting that PDE II is more sensitive to W-7. These results suggest that alteration in these isozyme activities accompanied with changes of CaM concentration may influence the cardiac muscle contractility in cardiomyopathic hamster via changes of cyclic nucleotide concentration.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed2004

Development of casting investment preventing blackening of noble metal alloys part 3. Effect of reducing agent addition on the strength and expansion of the investments.

Different reducing agents (B, Al, Si and Ti) were individually added to two gypsum-bonded investments to prepare investments preventing surface blackening of some noble cast alloys. The effect of different additive contents on green-body and burnout compressive strength, setting and thermal expansion of the investments were evaluated. The strength and expansion of the investments were changed by the additives. The compressive strength of Al-, Si- and Ti-added investments decreased with the increase of additive contents. The burnout strength of B-added investments significantly increased while green-body strength remained unchanged. The setting expansion of the B-added investments increased while those of the Al-, Si- and Ti-added investments decreased with the increase of additive contents. The thermal expansion of the Si- and Ti-added investments decreased, and that of the Al- and B-added investments remained unchanged. Further study is necessary to evaluate the effects of these additives on the accuracy of dental castings.

Aluminum↗

PubMed2004

Study of resin-bonded calcia investment. Part 3: Hardness of titanium castings.

The Vickers hardness of the cross-sectioned area of titanium castings made from an experimental resin-bonded calcia investment and three commercial investments was evaluated. The microstructure and element distribution of the surface zone were analyzed using an EPMA. The results showed that the high hardness of the casting surface could be decreased using the experimental investment. The hardness of the castings made from the experimental investment at a 25-50 microm depth was lower than those from the other investments, and the thickness of the hardened casting surface was 125 microm. Layered structures with fewer layers were formed on the surfaces of the castings made from the experimental investment. The layered structures were influenced by both the investment components and the mold temperature at casting. The less contaminating nature of the experimental investment components and the technology of the room temperature mold contributed to the improved surface properties of the resulting castings.

Calcium Compounds↗