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ABSTRACT: We have previously reported that transforming growth factor-β (TGF-β) stimulates heat shock protein 27 (HSP27) induction via p44/p42 mitogen-activated protein (MAP) kinase, p38 MAP kinase and stress-activated protein kinase/c-Jun N-terminal kinase in osteoblast-like MC3T3-E1 cells, and that the release of vascular endothelial growth factor (VEGF) is induced by TGF-β in these cells. In the present study, we investigated the effect of HSP27 knockdown on the TGF-β-stimulated VEGF release in these cells. Gene silencing using short interfering RNA against HSP27 (HSP27-siRNA) significantly suppressed the TGF-β-induced VEGF release. Immunofluorescence microscopy also revealed that HSP27-siRNA suppressed the TGF-β-stimulated VEGF induction as well as the reduction of HSP27 induction in these cells. However, the mRNA expression of VEGF stimulated by TGF-β was not reduced even in cells transfected with HSP27-siRNA. These results strongly suggest that HSP27 induction is critical for TGF-β-induced VEGF release in osteoblasts.
International Journal of Molecular Medicine 03/2011; 27(3):423-8. · 1.98 Impact Factor
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Yukiko Enomoto,
Seiji Adachi,
Tomoaki Doi,
Hideo Natsume,
Kenji Kato,
Rie Matsushima-Nishiwaki,
Shigeru Akamatsu,
Haruhiko Tokuda,
Shinichi Yoshimura, Takanobu Otsuka,
Shinji Ogura,
Osamu Kozawa,
Toru Iwama
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ABSTRACT: Elevation of cAMP in platelets is recognized to play a suppressive role in platelet functions. We have previously shown that adenosine diphosphate (ADP)-induced phosphorylation of heat shock protein 27 (HSP27) via p38 mitogen-activated protein (MAP) kinase is correlated with platelet-derived growth factor (PDGF)-AB secretion and soluble CD40 ligand (sCD40L) release. In the present study, we investigated the relationship between cAMP and HSP27 phosphorylation in platelet function. 8-Bromoadenosine-3',5'-cyclic monophosphate (8-bromo-cAMP), a plasma membrane-permeable cAMP analogue, or cilostazol, an inhibitor of cAMP phosphodiesterase, markedly attenuated the ADP-induced phosphorylation levels of p38 MAP kinase. In addition, the ADP-induced HSP27 phosphorylation was suppressed by 8-bromo-cAMP or cilostazol. 8-Bromo-cAMP, forskolin and cilostazol remarkably reduced the ADP-stimulated PDGF-AB secretion and sCD40L release. These results strongly suggest that cAMP regulates ADP-stimulated platelet activation due to inhibition of HSP27 phosphorylation via p38 MAP kinase.
International Journal of Molecular Medicine 03/2011; 27(5):695-700. · 1.98 Impact Factor
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ABSTRACT: It is currently recognized that the Wnt signaling pathway regulates bone mass. We have previously reported that the basic fibroblast growth factor (FGF-2) stimulates the synthesis of the vascular endothelial growth factor (VEGF) at least in part via the p44/p42 mitogen-activated protein (MAP) kinase and the stress-activated protein kinase (SAPK)/c-Jun N-terminal kinase (JNK) in osteoblast-like MC3T3-E1 cells. In the present study, we investigated the effect of Wnt3a on FGF-2-stimulated VEGF synthesis in MC3T3-E1 cells. Wnt3a significantly augmented the FGF-2-stimulated VEGF release in a dose-dependent manner in the range between 1 and 30 ng/ml. Lithium chloride and SB216763, inhibitors of glycogen synthase kinase 3β (GSK3β), enhanced the FGF-2-stimulated VEGF release. Wnt3a did not affect the phosphorylation of the p44/p42 MAP kinase, SAPK/JNK, Akt, p38 MAP kinase or the p70 S6 kinase induced by FGF-2. Wnt3a and SB216763 increased the levels of VEGF mRNA expression induced by FGF-2. These results strongly suggest that Wnt3a enhances VEGF synthesis stimulated by FGF-2 via activation of the canonical Wnt/β-catenin pathway in osteoblasts.
International Journal of Molecular Medicine 03/2011; 27(6):859-64. · 1.98 Impact Factor
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Kenji Kato,
Seiji Adachi,
Rie Matsushima-Nishiwaki,
Chiho Minamitani,
Hideo Natsume,
Yasuo Katagiri,
Yoshinobu Hirose,
Jun Mizutani,
Haruhiko Tokuda,
Osamu Kozawa, Takanobu Otsuka
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ABSTRACT: We have previously reported that various stimuli, including sphingosine 1-phosphate, are able to induce heat shock protein (HSP) 27 in osteoblast-like MC3T3-E1 cells. However, the precise role of HSP27 in bone metabolism has not been satisfactory clarified. In this study, we investigated the effect of HSP27 on osteocalcin synthesis induced by bone morphogenetic protein (BMP)-4 or T₃ in these cells. In MC3T3-E1 cells, pretreatment with sphingosine 1-phosphate, sodium arsenite, or heat stress caused the attenuation of osteocalcin synthesis induced by BMP-4 or T₃ with concurrent HSP27 induction. To further investigate the effect of HSP27, we established stable HSP27-transfected cells. The osteocalcin synthesis was significantly reduced in the stable HSP27-transfected MC3T3-E1 cells and normal human osteoblasts compared with empty-vector transfected cells. On the other hand, anisomycin, a p38 MAPK activator, caused the phosphorylation of HSP27 in both sphingosine 1-phosphate-stimulated untransfected MC3T3-E1 cells and HSP27-transfected MC3T3-E1 cells. An immunofluorescence microscopy study showed that the phosphorylated HSP27 induced by anisomycin concentrated perinuclearly in these cells, in which it colocalized with the endoplasmic reticulum. We also established stable mutant-HSP27-transfected cells. Osteocalcin synthesis induced by either BMP-4 or T₃ was markedly suppressed in the nonphosphorylatable HSP27-overexpressing MC3T3-E1 cells compared with the phosphomimic HSP27-overexpressing cells. In contrast, the matrix mineralization was more obvious in nonphosphorylatable HSP27-overexpressing cells than that in phosphomimic HSP27-overexpressing cells. Taken together, these results strongly suggest that unphosphorylated HSP27 has an inhibitory effect on osteocalcin synthesis, but has a stimulatory effect on mineralization, in osteoblasts.
Endocrinology 03/2011; 152(5):1872-82. · 4.46 Impact Factor
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ABSTRACT: It is recognized that catechin possesses beneficial properties for bone metabolism. We previously revealed that triiodothyronine (T₃)-activated p38 mitogen-activated protein (MAP) kinase, but not p44/p42 MAP kinase, is involved in the synthesis of osteocalcin in osteoblast-like MC3T3-E1 cells. In the present study, we investigated the effect of (-)-epigallocatechin gallate (EGCG), the predominant green tea polyphenol, on the synthesis of osteocalcin in MC3T3-E1 cells. EGCG significantly suppressed T₃-stimulated osteocalcin synthesis. The inhibitory effect of EGCG was dose-dependent in the range of 3 to 30 µM. On the other hand, T₃-induced phosphorylation of p38 MAP kinase was not affected by EGCG. EGCG profoundly inhibited T₃-stimulated transcriptional activity. These results strongly suggest that EGCG suppresses T3-stimulated osteocalcin synthesis upstream of the transcriptional level in osteoblast-like MC3T3-E1 cells.
Molecular Medicine Reports 03/2011; 4(2):297-300. · 0.42 Impact Factor
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ABSTRACT: It is recognized that Wnt pathways regulate bone metabolism. We have previously shown that tumor necrosis factor-α (TNF-α) stimulates synthesis of interleukin-6 (IL-6), a potent bone resorptive agent, via p44/p42 mitogen-activated protein (MAP) kinase and phosphatidylinositol 3-kinase (PI3-kinase)/Akt in osteoblast-like MC3T3-E1 cells. In the present study, we investigated the effect of Wnt3a on TNF-α-stimulated IL-6 synthesis in these cells. Wnt3a, which alone did not affect the IL-6 levels, significantly suppressed the TNF-α-stimulated IL-6 release. Lithium Chloride (LiCl), which is an inhibitor of GSK3β, markedly reduced the TNF-α-stimulated IL-6 release, similar to the results with Wnt3a. The suppression by Wnt3a or LiCl was also observed in the intracellular protein levels of IL-6 elicited by TNF-α. Wnt3a failed to affect the TNF-α-induced phosphorylation of p44/p42 MAP kinase, Akt, IκB or NFκB. Either Wnt3a or LiCl failed to reduce, rather increased the IL-6 mRNA expression stimulated by TNF-α. Lactacystin, a proteasome inhibitor, and bafilomycin A1, a lysosomal protease inhibitor, significantly restored the suppressive effect of Wnt3a on TNF-α-stimulated IL-6 release. Taken together, our results strongly suggest that Wnt3a regulates IL-6 release stimulated by TNF-α at post-transcriptional level in osteoblasts.
Molecular and Cellular Endocrinology 01/2011; 331(1):66-72. · 4.19 Impact Factor
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ABSTRACT: AMP-activated protein kinase (AMPK) is recognized as a regulator of energy homeostasis. We have previously reported that basic fibroblast growth factor (FGF-2) stimulates vascular endothelial growth factor (VEGF) release through the activation of p44/p42 mitogen-activated protein (MAP) kinase and stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) in osteoblast-like MC3T3-E1 cells. In the present study, we investigated the involvement of AMPK in FGF-2-stimulated VEGF release in these cells. FGF-2 time-dependently induced the phosphorylation of AMPK α-subunit (Thr-172). Compound C, an AMPK inhibitor, which suppressed the FGF-2-induced phosphorylation of AMPK, significantly inhibited the VEGF release stimulated by FGF-2. The AMPK inhibitor also reduced the mRNA expression of VEGF induced by FGF-2. The FGF-2-induced phosphorylation of both p44/p42 MAP kinase and SAPK/JNK was attenuated by compound C. These results strongly suggest that AMPK positively regulates the FGF-2-stimulated VEGF synthesis via p44/p42 MAP kinase and SAPK/JNK in osteoblasts.
Biochemical and Biophysical Research Communications 09/2010; 400(1):123-7. · 2.48 Impact Factor
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Tomoaki Doi,
Seiji Adachi,
Rie Matsushima-Nishiwaki,
Hisaaki Kato,
Yukiko Enomoto,
Hideo Natsume,
Kenji Kato,
Jun Mizutani, Takanobu Otsuka,
Haruhiko Tokuda,
Shigeru Akamatsu,
Toru Iwama,
Osamu Kozawa,
Shinji Ogura
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ABSTRACT: Although antithrombin-III (AT-III), an anti-coagulant, has been shown to affect human platelet functions, the direct effect of AT-III on platelets is still unknown. We recently reported that the collagen-induced phosphorylation of the heat shock protein 27 (HSP27) via the p44/p42 mitogen-activated protein (MAP) kinase is sufficient for granule secretion and the release of soluble CD40 ligand (sCD40L) from platelets but not platelet aggregation. In the present study, we investigated whether AT-III affects the collagen-induced secretion of the platelet-derived growth factor (PDGF)-AB and sCD40L release. AT-III inhibited collagen-stimulated platelet aggregation. The collagen-induced secretion of PDGF-AB was significantly suppressed by AT-III. AT-III also reduced sCD40L release. AT-III markedly attenuated the collagen-induced phosphorylated levels of p44/p42 MAP kinase. In addition, AT-III suppressed collagen-induced HSP27 phosphorylation. These results strongly suggest that AT-III reduced collagen-stimulated platelet granule secretion due to the inhibition of HSP27 phosphorylation via p44/p42 MAP kinase.
International Journal of Molecular Medicine 09/2010; 26(3):387-92. · 1.98 Impact Factor
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Hisaaki Kato,
Seiji Adachi,
Tomoaki Doi,
Rie Matsushima-Nishiwaki,
Chiho Minamitani,
Shigeru Akamatsu,
Yukiko Enomoto,
Haruhiko Tokuda, Takanobu Otsuka,
Toru Iwama,
Osamu Kozawa,
Shinji Ogura
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ABSTRACT: Collagen plays a crucial role in hemostasis and thrombosis by activating platelets and reportedly induces the phosphorylation of heat shock protein (HSP) 27 in human platelets. However, the exact role of HSP27 phosphorylation in human platelets has not yet been clarified. In the present study, we investigated the mechanism of collagen-induced HSP27 phosphorylation and the role in human platelets. The collagen-effect on the phospholylation of HSP27 was dose-dependent in the range between 0.03 and 1.0 microg/ml. The phosphorylation of p44/p42 mitogen-activated protein kinase (MAPK) was also stimulated by collagen. PD98059, a specific inhibitor of MAPK kinase (MEK1/2), reduced collagen-induced HSP27 phosphorylation as well as p44/p42 MAPK phosphorylation. PD98059 significantly suppressed collagen-induced releases of serotonin (5-HT), platelet-derived growth factor (PDGF)-AB and soluble CD40 ligand (sCD40L) while it had little effect on the platelet aggregation. These results strongly suggest that the collagen-induced phosphorylation of HSP27 via p44/p42 MAPK is sufficient for releases of 5-HT, PDGF-AB and sCD40L from human platelets.
Thrombosis Research 07/2010; 126(1):39-43. · 2.44 Impact Factor
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ABSTRACT: We previously showed that tumor necrosis factor-alpha (TNF-alpha) stimulates synthesis of interleukin-6 (IL-6), a potent bone resorptive agent, via p44/p42 mitogen-activated protein (MAP) kinase and phosphatidylinositol 3-kinase/Akt in osteoblast-like MC3T3-E1 cells. In the present study, we investigated the effect of vasoactive intestinal peptide (VIP) on TNF-alpha-induced IL-6 synthesis in these cells. VIP, which by itself slightly stimulated IL-6 synthesis, synergistically enhanced the TNF-alpha-induced IL-6 synthesis in MC3T3-E1 cells. The synergistic effect of VIP on the TNF-alpha-induced IL-6 synthesis was concentration-dependent in the range between 1 and 70 nM. We previously reported that VIP stimulated cAMP production in MC3T3-E1 cells. Forskolin, a direct activator of adenylyl cyclase, or 8-bromoadenosine-3',5'-cyclic monophosphate (8bromo-cAMP), a plasma membrane-permeable cAMP analogue, markedly enhanced the TNF-alpha-induced IL-6 synthesis as well as VIP. VIP markedly up-regulated the TNF-alpha-induced p44/p42 MAP kinase phosphorylation. The Akt phosphorylation stimulated by TNF-alpha was only slightly affected by VIP. PD98059, a specific inhibitor of MEK1/2, significantly suppressed the enhancement of TNF-alpha-induced IL-6 synthesis by VIP. The synergistic effect of a combination of VIP and TNF-alpha on the phosphorylation of p44/p42 MAP kinase was diminished by H-89, an inhibitor of cAMP-dependent protein kinase. These results strongly suggest that VIP synergistically enhances TNF-alpha-stimulated IL-6 synthesis via up-regulating p44/p42 MAP kinase through the adenylyl cyclase-cAMP system in osteoblasts.
International Journal of Molecular Medicine 05/2010; 25(5):813-7. · 1.98 Impact Factor
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ABSTRACT: Nuclear factor-kappaB (NF-kappaB) is involved in the pathophysiology of rheumatoid arthritis (RA) and is considered to be a feasible molecular target in treating patients. In the RA joint tissues, activation of NF-kappaB is often observed together with high amounts of the proinflammatory cytokines tumor necrosis factor (TNF)alpha and interleukin (IL)-1beta. TNFalpha and IL-1beta are known to stimulate NF-kappaB signaling and are produced as the effect of NF-kappaB signaling, thus forming a vicious cycle leading to a self-perpetuating nature of rheumatoid inflammation and expansion of such inflammatory response to other joints. Because a kinase called IkappaB kinase complex (IKK) is involved in the NF-kappaB activation cascade, we examined the effect of a novel IKK inhibitor, (7-[2-(cyclopropyl-methoxy)-6-hydroxyphenyl]-5-[(3S)-3-piperidinyl]-1,4-dihydro-2H-pyrido[2,3-d][1,3]oxazin-2-one hydrochloride; CHPD), on the production of inflammatory cytokines from rheumatoid synovial fibroblasts (RSF). TNFalpha stimulation induced production of inflammatory cytokines such as IL-6 and IL-8 in RSF, and the extent of IL-6 and IL-8 induction was dramatically reduced by CHPD under noncytotoxic concentrations. Likewise, expression of il-6 and il-8 genes was significantly reduced by CHPD. In addition, chromatin immunoprecipitation assays revealed that the DNA binding of NF-kappaB (p65) to il-8 promoter in RSF was induced after TNFalpha stimulation and that, upon CHPD treatment to RSF for 1 h, the NF-kappaB binding to il-8 promoter was significantly decreased. Here, we have demonstrated that an IKKbeta inhibitor, CHPD, acts as an effective inhibitor for the production of inflammatory cytokines in response to proinflammatory cytokines. These findings indicate that such a IKKbeta inhibitor could be a feasible candidate for an antirheumatic drug.
Journal of Pharmacology and Experimental Therapeutics 04/2010; 333(1):236-43. · 3.83 Impact Factor
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Hideo Natsume,
Haruhiko Tokuda,
Seiji Adachi,
Shinji Takai,
Rie Matsushima-Nishiwaki,
Kenji Kato,
Chiho Minamitani,
Shunpei Niida,
Jun Mizutani,
Osamu Kozawa, Takanobu Otsuka
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ABSTRACT: We previously reported that basic fibroblast growth factor (FGF-2) stimulates the release of vascular endothelial growth factor (VEGF) via p44/p42 mitogen-activated protein (MAP) kinase and stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) in osteoblast-like MC3T3-E1 cells and that FGF-2-activated p38 MAP kinase negatively regulates the VEGF release in osteoblast-like MC3T3-E1 cells. In the present study, we investigated whether Rho-kinase is involved in FGF-2-stimulated VEGF release in MC3T3-E1 cells. FGF-2 induced the phosphorylation of myosin phosphatase targeting subunit (MYPT-1), a substrate of Rho-kinase. Y27632, a specific inhibitor of Rho-kinase, which attenuated the MYPT-1 phosphorylation, significantly enhanced the FGF-2-stimulated VEGF release. Fasudil, another Rho-kinase inhibitor, also amplified the VEGF release. FGF-2 significantly stimulated VEGF accumulation and fasudil enhanced FGF-2-stimulated VEGF accumulation also in whole cell lysates. Neither Y27632 nor fasudil affected the phosphorylation levels of p44/p42 MAP kinase or p38 MAP kinase. Y27632 and fasudil markedly strengthened the FGF-2-induced phosphorylation of SAPK/JNK. Y27632 as well as fasudil enhanced FGF-2-stimulated VEGF release and Y27632 enhanced the FGF-2-induced phosphorylation levels of SAPK/JNK also in human osteoblasts. These results strongly suggest that Rho-kinase negatively regulates FGF-2-stimulated VEGF release in osteoblasts.
Bone 04/2010; 46(4):1068-74. · 4.02 Impact Factor
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ABSTRACT: Gliostatin/thymidine phosphorylase (GLS/TP) is known to have angiogenic and arthritogenic activities. The purpose of this study was to determine the inhibitory effects of FK506 (tacrolimus) on GLS production in rheumatoid arthritis (RA). We investigated the modulation of serum GLS by FK506 therapy and the effect of FK506 on the production of GLS in fibroblast-like synoviocytes (FLSs). Serum samples were collected from 11 RA patients with active disease at baseline and after 12 weeks of FK506 treatment. Serum concentrations of GLS and matrix metalloproteinase (MMP)-3 were measured by ELISA and found to be down-regulated in responders evaluated with a disease activity score. Patient FLSs were cultured and stimulated by tumor necrosis factor (TNF)-α with or without FK506. The expression levels of GLS were determined using reverse transcription-polymerase chain reaction (RT-PCR) and enzyme immunoassay and shown to be significantly increased. GLS levels in TNF-α-stimulated FLSs were reduced by FK506 treatment. Our data show a novel mechanism for the action of physiological concentrations of FK506 in RA that regulates the production of GLS in FLSs.
Rheumatology International 03/2010; 31(7):903-9. · 1.88 Impact Factor
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ABSTRACT: To determine whether aquaporins (AQPs) are expressed in the synovial tissues of patients with OA and RA, and to examine the patterns of expression in patients with and without hydrarthrosis.
AQPs were detected in synovial tissue samples from patients with OA and RA using RT-PCR and immunohistochemistry. Fibroblast-like synoviocytes (FLSs) from patients with OA and RA were cultured and stimulated with TNF-alpha. The expression of AQPs in FLSs was examined using RT-PCR and western blot analyses and the function of aquaglyceroporins was examined by a glycerol uptake assay.
AQP1, -3 and -9 mRNAs were expressed in synovial tissues from patients with OA and RA. AQP1, -3 and -9 proteins were also detected by immunohistochemistry. AQP9 mRNA was expressed more strongly in the synovial tissues of OA patients with hydrarthrosis than those without. AQP9 mRNA and protein expression were strongly induced with TNF-alpha treatment in FLSs, whereas the expression of AQP1 and -3 mRNAs was not induced with TNF-alpha treatment. AQP9 as an aquaglyceroporin was induced by TNF-alpha.
AQP9 mRNA was detected in synovial tissues from OA and RA patients with hydrarthrosis. AQP9 expression was strongly induced in FLSs with TNF-alpha. Although the functions of AQP1, -3 and -9 in synovial tissues remain to be elucidated, it suggested that AQP9 might be related to the pathogenesis of hydrarthrosis and inflammatory synovitis.
Rheumatology (Oxford, England) 02/2010; 49(5):898-906. · 4.24 Impact Factor
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Thermal Medicine 01/2010; 26(1):19-29.
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ABSTRACT: We previously reported that prostaglandin D(2) (PGD(2)) stimulates heat shock protein 27 (HSP27) induction through p44/p42 mitogen-activated protein (MAP) kinase, p38 MAP kinase and stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) in osteoblast-like MC3T3-E1 cells. In addition, we recently showed that PGD(2) activates Rho-kinase, resulting in the regulation of interleukin-6 synthesis via activation of p38 MAP kinase but not p44/p42 MAP kinase in these cells. In the present study, in order to investigate whether Rho-kinase is involved in the PGD(2)-stimulated HSP27 induction in MC3T3-E1 cells, we examined the effects of Rho-kinase inhibitors on HSP27 induction. Y27632 and fasudil, Rho-kinase inhibitors, markedly suppressed the HSP27 induction stimulated by PGD(2) in a dose-dependent manner without affecting levels of HSP70 in the presence of PGD(2). Immunofluorescence microscopy studies also revealed that Y27632 and fasudil markedly suppressed the induction of HSP27. Y27632 and fasudil attenuated the PGD(2)-induced phosphorylation levels of SAPK/JNK. In conclusion, Rho-kinase inhibitors regulate PGD(2)-stimulated HSP27 induction via activation of both SAPK/JNK and p38 MAP kinase in osteoblasts.
Experimental and therapeutic medicine 01/2010; 1(4):579-583.
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ABSTRACT: STUDY DESIGN.: Case report. OBJECTIVE.: To present a rare case of extramedullary-intradural hemangioblastoma in the thoracic spine and to review the literature on this condition. SUMMARY OF BACKGROUND DATA.: Spinal hemangioblastoma is rare, and moreover, there is seldom purely extramedullary-intradural hemangioblastoma of the spinal cord and there are few reports on histopathological features of spinal hemangioblastoma. METHODS.: A 65-year-old Japanese woman presented with gait disturbance and numbness below the trunk that had gradually worsened, and finally she was unable to walk by herself. Physiologic and neurologic examinations at admission revealed severe transverse neurologic defects, with no sign of von Hippel-Lindau's disease. Radiologic methods showed an extramedullary-intradural mass at Th4-5. A diagnosis of extramedullary-intradural spinal tumor was done, total tumorectomy was performed with recapped laminoplasty. RESULTS.: The patient's neurologic condition gradually improved after the operation. The immunohistopathological findings revealed the diagnosis of hemangioblastoma. CONCLUSION.: A rare case of extramedullary-intradural spinal hemangioblastoma was reported. The immunohistopathological findings were helpful for making a final diagnosis.
Spine 12/2009; 34(26):E969-72. · 2.08 Impact Factor
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ABSTRACT: Our previous study demonstrated that tumor necrosis factor-alpha (TNF-alpha) stimulates the synthesis of interleukin-6 (IL-6), a potent bone resorptive agent, via p44/p42 mitogen-activated protein (MAP) kinase and phosphatidylinositol 3-kinase/Akt in osteoblast-like MC3T3-E1 cells. In the present study, we investigated whether p70 S6 kinase is involved in TNF-alpha-stimulated IL-6 synthesis in MC3T3-E1 cells. TNF-alpha time dependently induced the phosphorylation of p70 S6 kinase. Rapamycin, an inhibitor of p70 S6 kinase, which attenuated the phosphorylation of p70 S6 kinase induced by TNF-alpha, significantly amplified the TNF-alpha-stimulated IL-6 synthesis. TNF-alpha-induced phosphorylations of both p44/p42 MAP kinase and Akt were markedly enhanced by rapamycin. The amplification by rapamycin of TNF-alpha-induced IL-6 synthesis was reduced by PD98059, a specific inhibitor of MEK1/2, or Akt inhibitor. Rapamycin enhanced the IL-6 synthesis and the phosphorylation of Akt induced by TNF-alpha also in human osteoblasts. Taken together, these results strongly suggest that p70 S6 kinase limits the TNF-alpha-stimulated IL-6 synthesis at a point upstream from p44/p42 MAP kinase and Akt in osteoblast-like cells.
Molecular and Cellular Endocrinology 10/2009; 315(1-2):195-200. · 4.19 Impact Factor
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Hideo Natsume,
Seiji Adachi,
Shinji Takai,
Haruhiko Tokuda,
Rie Matsushima-Nishiwaki,
Chiho Minamitani,
Junichi Yamauchi,
Kanefusa Kato,
Jun Mizutani,
Osamu Kozawa, Takanobu Otsuka
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ABSTRACT: We previously reported that sphingosine 1-phosphate stimulates the induction of heat shock protein 27 (HSP27) through p38 mitogen-activated protein (MAP) kinase and phosphatidylinositol 3-kinase/Akt in osteoblast-like MC3T3-E1 cells. In the present study, we investigated whether (-)-epigallocatechin gallate (EGCG), the major polyphenol found in green tea, affects the induction of HSP27 in these cells and its mechanism, since it was previously reported that catechin, including EGCG, suppresses bone resorption. EGCG significantly reduced the induction of HSP27 stimulated by sphingosine 1-phosphate in a dose-dependent manner between 10 and 30 microM. Immunofluorescence microscopy studies revealed that sphingosine 1-phosphate certainly stimulated the induction of HSP27 in the cytosol of these cells, and that EGCG clearly suppressed its induction. However, sphingosine 1-phosphate-stimulated phosphorylation of p38 MAP kinase or MAPKAP-2 was not affected by EGCG. By contrast, EGCG markedly suppressed the phosphorylations of both Akt and glycogen synthase kinase-3beta stimulated by sphingosine 1-phosphate. These results strongly suggest that EGCG suppresses the induction of HSP27 stimulated by sphingosine 1-phosphate via attenuation of, not the p38 MAP kinase pathway, but of the phosphatidylinositol 3-kinase/Akt pathway in osteoblasts.
International Journal of Molecular Medicine 09/2009; 24(2):197-203. · 1.98 Impact Factor
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ABSTRACT: We previously reported that sphingosine 1-phosphate induces heat shock protein 27 (HSP 27) via activation of phosphatidylinositol 3-kinase (PI3K)/Akt and p38 mitogen-activated protein (MAP) kinase in osteoblast-like MC3T3-E1 cells. In the present study, we investigated whether Rho-kinase is implicated in sphingosine 1-phosphate-stimulated induction of HSP27 in MC3T3-E1 cells. Sphingosine 1-phosphate time-dependently induced the phosphorylation of myosin phosphatase targeting subunit (MYPT-1), a Rho-kinase substrate. Y27632, a specific Rho-kinase inhibitor, significantly reduced sphingosine 1-phosphate-stimulated HSP27 induction, as well as MYPT-1 phosphorylation. Fasudil, another inhibitor of Rho-kinase, also suppressed sphingosine 1-phosphate-stimulated HSP27 induction. Y27632, as well as fasudil, attenuated sphingosine 1-phosphate-induced phosphorylation of p38 MAP kinase. However, Akt phosphorylation induced by sphingosine 1-phosphate was not affected by either Rho-kinase inhibitor. These results strongly suggest that Rho-kinase regulates sphingosine 1-phosphate-stimulated induction of HSP27 at a point upstream of p38 MAP kinase in osteoblasts.
International Journal of Molecular Medicine 08/2009; 24(1):77-82. · 1.98 Impact Factor
