Daijiro Hatakeyama

Effects of green tea polyphenol on methylation status of RECK gene and cancer cell invasion in oral squamous cell carcinoma cells.

RECK is a novel tumour suppressor gene that negatively regulates matrix metalloproteinases (MMPs) and inhibits tumour invasion, angiogenesis and metastasis. In the present study, we investigated the effects of epigallocatechin-3-gallate (EGCG), a major polyphenol in green tea, on the methylation status of the RECK gene and cancer invasion in oral squamous cell carcinoma cell lines. Our results showed that treatment of oral cancer cells with EGCG partially reversed the hypermethylation status of the RECK gene and significantly enhanced the expression level of RECK mRNA. Inhibition of MMP-2 and MMP-9 levels was also observed in these cells after treatment with EGCG. Interestingly, EGCG significantly suppressed cancer cell-invasive ability by decreasing the number of invasive foci (P<0.0001) as well as invasion depth (P<0.005) in three-dimensional collagen invasion model. Although further investigation is required to assess the extent of contribution of RECK on MMPs to the suppression of invasive behaviour, these results support the conclusion that EGCG plays a key role in suppressing cell invasion through multiple mechanisms, possibly by demethylation effect on MMP inhibitors such as RECK.

Characterization of Dental Pulp Stem Cells of Human Tooth Germs

In previous studies, human dental pulp stem cells (hDPSCs) were mainly isolated from adults. In this present study, we characterized hDPSCs isolated from an earlier developmental stage to evaluate the potential usage of these cells for tissue-regenerative therapy. hDPSCs isolated at the crown-completed stage showed a higher proliferation rate than those isolated at a later stage. When the cells from either group were cultured in medium promoting differentiation toward cells of the osteo/odontoblastic lineage, both became alkaline-phosphatase-positive, produced calcified matrix, and were also capable of forming dentin-like matrix on scaffolds in vivo. However, during long-term passage, these cells underwent a change in morphology and lost their differentiation ability. The results of a DNA array experiment showed that the expression of several genes, such as WNT16, was markedly changed with an increasing number of passages, which might have caused the loss of their characteristics as hDPSCs.

Divergent regulation by p44/p42 MAP kinase and p38 MAP kinase of bone morphogenetic protein‐4‐stimulated osteocalcin synthesis in osteoblasts

In the present study, we investigated whether the mitogen‐activated protein (MAP) kinase superfamily is involved in the bone morphogenetic protein (BMP)‐4‐stimulated synthesis of osteocalcin in osteoblast‐like MC3T3‐E1 cells. BMP‐4 dose‐dependently stimulated osteocalcin synthesis. BMP‐4 markedly induced the phosphorylation of p44/p42 MAP kinase and p38 MAP kinase, while having little effect on SAPK (stress‐activated protein kinase)/JNK (c‐Jun N terminal kinase) phosphorylation. SB203580 and PD169316, specific inhibitors of p38 MAP kinase, significantly reduced the osteocalcin synthesis stimulated by BMP‐4. In contrast, PD98059 and U0126, inhibitors of upstream kinase of p44/p42 MAP kinase, markedly enhanced the BMP‐4‐stimulated osteocalcin synthesis. The BMP‐4‐induced phosphorylation of p44/p42 MAP kinase was suppressed by PD98059, which did not, however, affect the BMP‐4‐induced phosphorylation of p38 MAP kinase. Taken together, our results strongly suggest that p38 MAP kinase takes part in BMP‐4‐stimulated osteocalcin synthesis as a positive regulator in osteoblasts, whereas p44/p42 MAP kinase acts as a negative regulator in the synthesis. J. Cell. Biochem. 84: 583–589, 2002.

Mechanism of simvastatin on induction of heat shock protein in osteoblasts

It has recently been reported that 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) stimulate bone formation. However, the mechanism of stimulation of bone metabolism by statins is not precisely clarified. In this study, we investigated whether simvastatin induces heat shock protein (HSP) 27, HSP70, and HSP90 in osteoblast-like MC3T3-E1 cells. Simvastatin increased the levels of HSP27 while having little effect on the levels of HSP70 or HSP90. The effect of simvastatin on HSP27 accumulation was dose dependent. Cycloheximide reduced the accumulation. Simvastatin induced an increase in the levels of mRNA for HSP27. Actinomycin D suppressed the mRNA levels. Simvastatin induced the phosphorylation of p38 mitogen-activated protein (MAP) kinase among the MAP kinase superfamily. SB203580 and PD169316, inhibitors of p38 MAP kinase, suppressed the HSP27 accumulation by simvastatin while SB202474, a negative control of p38 MAP kinase inhibitor, had no effect. SB203580 reduced the simvastatin-increased mRNA levels for HSP27. Lovastatin, another statin, also induced the HSP27 accumulation and SB203580 suppressed the HSP27 accumulation. These results strongly suggest that statins such as simvastatin do not stimulate the induction of HSP70 and HSP90, but do stimulate the induction of HSP27 in osteoblasts and that p38 MAP kinase plays a role in this induction.

Involvement of MAP kinases in TGF-β-stimulated vascular endothelial growth factor synthesis in osteoblasts

Transforming growth factor-beta (TGF-beta) reportedly induces vascular endothelial growth factor (VEGF) synthesis in osteoblast-like MC3T3-E1 cells. We have recently shown that TGF-beta activates p44/p42 mitogen-activated protein (MAP) kinase and p38 MAP kinase in these cells. In the present study, we investigated the exact mechanism of TGF-beta behind the synthesis of VEGF in MC3T3-E1 cells. PD98059 and U-0126, specific inhibitors of MEK, suppressed the VEGF synthesis induced by TGF-beta. U-0126 inhibited the TGF-beta-induced p44/p42 MAP kinase phosphorylation. SB203580 and PD169316, inhibitors of p38 MAP kinase, reduced the TGF-beta-stimulated VEGF synthesis. SB202474, a negative control for p38 MAP kinase inhibitor, did not affect the VEGF synthesis. A combination with PD98059 and SB203580 almost completely suppressed the TGF-beta-induced VEGF synthesis. Retinoic acid, which alone failed to affect VEGF synthesis, markedly enhanced the VEGF synthesis stimulated by TGF-beta. Retinoic acid enhanced the TGF-beta-increased levels of VEGF mRNA. The amplifications by retinoic acid of TGF-beta-increased VEGF synthesis and levels of VEGF mRNA were reduced by PD98059 or SB203580. The combination of PD98059 and SB203580 almost completely suppressed the enhancement by retinoic acid of VEGF synthesis induced by TGF-beta. Taken together, our results strongly suggest that both p44/p42 MAP kinase and p38 MAP kinase take part in TGF-beta-stimulated VEGF synthesis in osteoblasts, and that retinoic acid upregulates the VEGF synthesis.

HSP20, low-molecular-weight heat shock-related protein, acts extracellularly as a regulator of platelet functions :a novel defense mechanism

We previously showed that a dissociated form of a low-molecular-weight heat shock-related protein 20 (HSP20) but not an aggregated form of HSP20 suppresses platelet aggregation. In the present study, we investigated the behavior of HSP20 in response to endothelial injury and the possible mechanism of HSP20 in platelet functions. The levels of HSP20 in vessel wall after endothelial injury were markedly reduced. This observation was supported by the results of Western blotting analysis and immunohistochemical analysis. Additionally, the plasma levels of HSP20 in cardiomyopathic hamsters were markedly elevated. Centrifugation on sucrose density gradients allowed detection mainly of the dissociated form of plasma HSP20 in these hamsters. Human platelets showed specific binding sites for HSP20. Moreover, HSP20 markedly reduced thrombin-induced phosphoinositide hydrolysis by phospholipase C in human platelets. Taken together, our results strongly suggest that HSP20, which immediately responds to pathological events, acts extracellularly as a regulator of platelet functions.

Endothelin-1 induces vascular endothelial growth factor synthesis in osteoblasts: involvement of p38 mitogen-activated protein kinase.

We previously reported that endothelin-1 (ET-1) stimulates p44/p42 mitogen-activated protein (MAP) kinase and p38 MAP kinase in osteoblast-like MC3T3-E1 cells. In the present study, we investigated the effect of ET-1 on the synthesis of vascular endothelial growth factor (VEGF) in these cells. ET-1 significantly stimulated VEGF secretion time-dependently 18 hours after the stimulation. The stimulatory effect was dose-dependent in the range between 0.1 nM and 0.1 micro;M. BQ123, an antagonist of endothelin(A) (ET(A)) receptor, inhibited the ET-1-induced VEGF secretion. The ET-1-induced VEGF secretion was suppressed by SB203580 and PD169316, inhibitors of p38 MAP kinase, but not PD98059, an inhibitor of the upstream kinase that activates p44/p42 MAP kinase. 12-O-Tetradecanoylphorbol-13-acetate (TPA), a protein kinase C (PKC)-activating phorbol ester, stimulated VEGF secretion. Calphostin C, a specific PKC inhibitor, suppressed the VEGF secretion by ET-1. TPA-induced VEGF secretion was suppressed by SB203580. Taken together, our results strongly suggest that ET-1 stimulates VEGF synthesis via ET(A) receptor in osteoblasts and that p38 MAP kinase is involved at a point downstream from PKC in the VEGF synthesis.

Hypermethylation of the RECK gene predicts poor prognosis in oral squamous cell carcinomas

The RECK gene is a novel tumor suppressor gene that regulates matrix metalloproteinases (MMPs) to inhibit tumor angiogenesis, invasion and metastasis. We investigated the methylation status of the RECK gene in 40 primary oral squamous cell carcinomas (OSCC) and 20 paired adjacent normal mucosa by methylation-specific PCR. Furthermore, we determined the prognostic importance of RECK hypermethylation in OSCC patients. Our findings showed that the RECK gene was methylated in 52.5% (21 of 40) of the primary OSCC. Among the 20 cases with corresponding normal tissues, RECK hypermethylation was detected in both primary tumor (55%, 11 of 20) and adjacent normal mucosa (30%, 6 of 20). Methylation of the RECK gene was not detected in all normal oral mucosa samples of the 12 healthy controls. In univariate analysis, RECK hypermethylation was inversely correlated with recurrence-free survival (p=0.027) and overall survival (p=0.023) of the OSCC patients. Multivariate analysis showed that the methylation status of the RECK gene was the only independent prognostic factor affecting overall survival (p=0.037). The result indicates that hypermethylation of RECK promoter is a common event in human OSCC, occurs concurrently in tumor-adjacent normal mucosa and is correlated with poor prognosis in OSCC patients. Although additional work is needed, hypermethylation of the RECK gene is a promising biomarker in early detection and prognosis for oral cancer patients.

Nuclear factor-κB activates dual inhibition sites in the regulation of tumor necrosis factor-α-induced neutrophil apoptosis

Abstract The objective of this study was to elucidate the role of the nuclear factor-κB (NF-κB) pathway in tumor necrosis factor-α (TNF-α)-induced neutrophil apoptosis. A single treatment with TNF-α produced significant caspase-3 activiation in a time- and concentration-dependent manner, while no significant morphological change in neutrophils was observed. After pretreatment of neutrophils with cycloheximide or actinomycin D, TNF-α produced morphologically typical apoptosis in a time- and concentration-dependent manner. Similarly, following pretreatment of neutrophils with the specific NF-κB inhibitors, pyrrolidine dithiocarbamate or SN50, TNF-α also produced neutrophil apoptosis (assessed morphologically). Caspase-3 activation by TNF-α was significantly enhanced by pretreatment with both cycloheximide and pyrrolidine dithiocarbamate. TNF-α-induced a rapid phosphorylation and degradation of IκB-α in neutrophils. Furthermore, TNF-α increased NF-κB DNA binding, which was abolished by pretreatment with pyrrolidine dithiocarbamate. These results indicate that the NF-κB pathway is crucial for neutrophil survival against TNF-α cell toxicity. Furthermore, it is proposed that NF-κB-induced proteins act on dual inhibitory sites, both upstream and downstream of caspase-3, to protect against apoptosis.

Mechanism of prostaglandin D2-stimulated heat shock protein 27 induction in osteoblasts

We previously showed that prostaglandin D(2) (PGD(2)) stimulates activation of protein kinase C (PKC). We investigated whether PGD(2) stimulates the induction of heat shock protein (HSP) 27 and HSP70 in osteoblast-like MC3T3-E1 cells and the mechanism underlying the induction. PGD(2) increased the levels of HSP27 while having little effect on HSP70 levels. PGD(2) stimulated the accumulation of HSP27 dose dependently in the range between 10 nM and 10 microM. PGD(2) induced an increase in the levels of mRNA for HSP27. The PGD(2)-stimulated accumulation of HSP27 was reduced by staurosporine or calphostin C, inhibitors of PKC. PGD(2) induced the phosphorylation of p44/p42 mitogen-activated protein (MAP) kinase and p38 MAP kinase. The HSP27 accumulation induced by PGD(2) was significantly suppressed by PD98059, an inhibitor of the upstream kinase of p44/p42 MAP kinase, or SB203580, an inhibitor of p38 MAP kinase. Calphostin C suppressed the PGD(2)-induced phosphorylation of p44/p42 MAP kinase and p38 MAP kinase. PD98059 or SB203580 suppressed the PGD(2)-increased levels of mRNA for HSP27. These results strongly suggest that PGD(2) stimulates HSP27 induction through p44/p42 MAP kinase activation and p38 MAP kinase activation in osteoblasts and that PKC acts at a point upstream from both the MAP kinases.