(-)-Epigallocatechin gallate selectively inhibits adenosine diphosphate­stimulated human platelet activation: suppression of heat shock protein 27 phosphorylation via p38 mitogen­activated protein kinase.

(­)­Epigallocatechin gallate (EGCG) is a major component of green tea. It has been demonstrated that EGCG has an antithrombotic effect by inhibiting platelet aggregation. However, the detailed mechanisms underlying the effects of EGCG remain to be elucidated. The present study examined the effects of EGCG on human platelet activation by various stimulators and the exact underlying mechanisms. EGCG suppressed adenosine diphosphate (ADP)­stimulated platelet aggregation dose dependently between 30 and 70 µM. By contrast, EGCG failed to affect platelet aggregation stimulated by collagen, U46619 (a TP agonist) or ristocetin (an activator of GPIb/IX/V). EGCG attenuated the ADP­induced phosphorylation of p38 mitogen­activated protein (MAP) kinase and heat shock protein 27 (HSP27). The ADP­stimulated release of platelet­derived growth factor (PDGF)­AB and the soluble CD40 (sCD40) ligand was inhibited by EGCG. These findings suggest that EGCG selectively inhibits ADP­stimulated human platelet activation and that EGCG reduces the release of PDGF­AB and the sCD40 ligand due to suppressing HSP27 phosphorylation via p38 MAP kinase.

Vitamin D deficiency in elderly women in nursing homes: investigation with consideration of decreased activation function from the kidneys.

OBJECTIVES: To determine the approximate percentage of women in nursing homes who have vitamin D deficiency and to investigate whether, in assessing vitamin D status in elderly women, there are problems with measuring only 25 hydroxy-vitamin D(3) (25(OH)D(3) ) and whether decreased vitamin D activation as a result of poor renal function needs to be considered. DESIGN: Cross-sectional study. SETTING: Forty-eight nursing homes in Japan. PARTICIPANTS: Four hundred three women with a mean age of 86.5 living in nursing homes who had participated in a clinical trial for hip protectors and were not bedridden. MEASUREMENTS: At the start of the trial, in addition to general biochemical data, 25(OH)D(3) , 1,25-dihydroxy-vitamin D(3) (1,25(OH)(2) D(3) ), intact parathyroid hormone (intact PTH), calcium (Ca), phosphorus (P), bone alkaline phosphate (BAP), cross-linked N-telopeptide of type I collagen (NTx), and osteocalcin were measured in participants' blood, and statistical analysis was performed. RESULTS: 25(OH)D(3) , which is thought to reflect vitamin D status in the body, was surveyed and found to have a mean value of 16.7 ng/mL. 25(OH)D(3) was less than 16 ng/mL in 49.1% of all participants. Creatinine clearance (CCr) was less than 30 mL/min in 20.1% of participants. Participants with serum 25(OH)D(3) less than 16 ng/mL and CCr less than 30 mL/min had significantly higher levels of intact PTH and serum NTx. Participants with a CCr less than 30 mL/min had significantly lower levels of 1,25(OH)(2) D(3) . CONCLUSION: Frail elderly adults living in nursing homes with poor renal function had lower 1,25(OH)(2) D(3) and higher intact PTH levels and were thus thought to have poorer vitamin D activating capacity. Supplementation with cholecalciferol may be insufficient in people who have poor renal function.

(-)-Epigallocatechin gallate reduces transforming growth factor beta-stimulated HSP27 induction through the suppression of stress-activated protein kinase/c-Jun N-terminal kinase in osteoblasts.

We previously reported that transforming growth factor-beta (TGF-beta) stimulates heat shock protein 27 (HSP27) induction through p38 mitogen-activated protein (MAP) kinase and extracellular signal-regulated kinase 1/2 (ERK1/2) 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 TGF-beta-stimulated induction of HSP27 in these cells, and its underlying mechanism. EGCG significantly suppressed the HSP27 induction stimulated by TGF-beta in a dose-dependent manner between 10 and 30 microM without affecting the HSP70 levels. TGF-beta with or without EGCG did not affect the advanced oxidation protein products. The TGF-beta-induced phosphorylation of p38 MAP kinase and ERK1/2 was not affected by EGCG. SP600125, a specific inhibitor of stress-activated protein kinase (SAPK)/c-Jun N-terminal kinase (JNK), markedly reduced the HSP27 expression induced by TGF-beta. EGCG significantly suppressed the TGF-beta-induced phosphorylation of SAPK/JNK without affecting the phosphorylation of Smad2. EGCG attenuated the phosphorylation of both MKK4 and TAK1 induced by TGF-beta. These results strongly suggest that EGCG suppresses the TGF-beta-stimulated induction of HSP27 via the attenuation of the SAPK/JNK pathway in osteoblasts, and that this effect is exerted at a point upstream from TAK1.

Adenylyl cyclase-cAMP system inhibits thyroid hormone-stimulated osteocalcin synthesis in osteoblasts.

It is generally recognized that thyroid hormone modulates osteoblast cell function. We have previously shown that triiodothyronine (T(3)) activates p38 mitogen-activated protein (MAP) kinase, resulting in the synthesis of osteocalcin in osteoblast-like MC3T3-E1 cells. In the present study, we investigated the effect of the adenylyl cyclase-cAMP system on thyroid hormone-stimulated osteocalcin synthesis in these cells. Dibutyryl-cAMP (DBcAMP) reduced the osteocalcin synthesis stimulated by T(3). Forskolin and cholera toxin suppressed the osteocalcin synthesis while dideoxyforskolin, a forskolin derivative that does not activate adenylyl cyclase, had little effect on the synthesis. KT5720, a selective inhibitor of protein kinase A, reversed the inhibitory effect of forskolin or DBcAMP. DBcAMP and forskolin markedly reduced the phosphorylation of p38 MAP stimulated by T(3). Pituitary adenylate cyclase-activating polypeptide (PACAP) significantly inhibited the T(3)-stimulated osteocalcin synthesis. These results strongly suggest that the adenylyl cyclase-cAMP system has an inhibitory role in thyroid hormone-stimulated osteocalcin synthesis via suppression of p38 MAP kinase activation in osteoblasts.