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Kainuma S, Otsuka T, Kuroyanagi G, Yamamoto N, Matsushima-Nishiwaki R, Kozawa O, Tokuda H. Possible involvement of AMP-activated protein kinase in PGE 1-induced synthesis of osteoprotegerin in osteoblasts. Exp Ther Med 2016; 11:2042-2048. [PMID: 27168848 DOI: 10.3892/etm.2016.3099] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2015] [Accepted: 01/15/2016] [Indexed: 12/14/2022] Open
Abstract
AMP-activated protein kinase (AMPK) is firmly established as a central regulator of cellular energy homeostasis. We have previously reported that prostaglandin E1 (PGE1) stimulates the synthesis of osteoprotegerin through p38 mitogen-activated protein (MAP) kinase and stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) in osteoblast-like MC3T3-E1 cells. The present study investigated the involvement of AMPK in PGE1-induced osteoprotegerin synthesis in MC3T3-E1 cells. The levels of osteoprotegerin were measured using an enzyme-linked immunosorbent assay, while the phosphorylation of AMPK, acetyl-CoA carboxylase, p38 MAP kinase and SAPK/JNK were analyzed by western blotting. In addition, the mRNA expression levels of osteoprotegerin were determined by a reverse transcription-quantitative polymerase chain reaction. It was revealed that PGE1 significantly induced the phosphorylation of the α and β subunits of AMPK in a time-dependent manner (P<0.05). In addition, acetyl-CoA carboxylase, a direct substrate of AMPK, was significantly phosphorylated by PGE1 (P<0.05). Compound C, an AMPK inhibitor, was revealed to suppress the phosphorylation of acetyl-CoA carboxylase, which significantly reduced the release and mRNA expression levels of PGE1-stimulated osteoprotegerin (P<0.05). However, the PGE1-induced phosphorylation of p38 MAP kinase and SAPK/JNK were not affected by compound C. The results of the present study indicated that AMPK may positively regulate PGE1-stimulated osteoprotegerin synthesis in osteoblasts; thus providing novel insight into the regulatory mechanisms underlying bone metabolism.
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Affiliation(s)
- Shingo Kainuma
- Department of Orthopedic Surgery, Nagoya City University Graduate School of Medical Sciences, Nagoya, Aichi 467-8601, Japan; Department of Pharmacology, Gifu University Graduate School of Medicine, Gifu 501-1194, Japan
| | - Takanobu Otsuka
- Department of Orthopedic Surgery, Nagoya City University Graduate School of Medical Sciences, Nagoya, Aichi 467-8601, Japan
| | - Gen Kuroyanagi
- Department of Orthopedic Surgery, Nagoya City University Graduate School of Medical Sciences, Nagoya, Aichi 467-8601, Japan; Department of Pharmacology, Gifu University Graduate School of Medicine, Gifu 501-1194, Japan
| | - Naohiro Yamamoto
- Department of Orthopedic Surgery, Nagoya City University Graduate School of Medical Sciences, Nagoya, Aichi 467-8601, Japan; Department of Pharmacology, Gifu University Graduate School of Medicine, Gifu 501-1194, Japan
| | | | - Osamu Kozawa
- Department of Pharmacology, Gifu University Graduate School of Medicine, Gifu 501-1194, Japan
| | - Haruhiko Tokuda
- Department of Pharmacology, Gifu University Graduate School of Medicine, Gifu 501-1194, Japan; Department of Clinical Laboratory, National Center for Geriatrics and Gerontology, Obu, Aichi 474-8511, Japan
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Kainuma S, Otsuka T, Kuroyanagi G, Yamamoto N, Matsushima-Nishiwaki R, Kozawa O, Tokuda H. Regulation by AMP-activated protein kinase of PGE2-induced osteoprotegerin synthesis in osteoblasts. Mol Med Rep 2016; 13:3363-9. [PMID: 26935864 DOI: 10.3892/mmr.2016.4900] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2015] [Accepted: 01/28/2016] [Indexed: 11/06/2022] Open
Abstract
Adenosine monophosphate-activated protein kinase (AMPK) is currently recognized to act as a key sensing enzyme in the regulation of cellular energy homeostasis. It has been previously demonstrated that prostaglandin E2 (PGE2) stimulates the synthesis of osteoprotegerin (OPG) through the activation of p38 mitogen-activated protein (MAP) kinase, p44/p42 MAP kinase and stress-activated protein kinase/c‑Jun N‑terminal kinase (SAPK/JNK) in osteoblast‑like MC3T3‑E1 cells. In the present study, it was investigated whether AMPK is implicated in the PGE2‑induced OPG synthesis in MC3T3‑E1 cells. PGE2 was observed to induce the phosphorylation of AMPKα (Thr‑172) and AMPKβ (Ser‑108) in a time‑dependent manner. PGE2 additionally induced the phosphorylation of acetyl‑coenzyme A (CoA) carboxylase, a direct substrate of AMPK. Compound C, an inhibitor of AMPK, which attenuated the phosphorylation of acetyl‑CoA carboxylase, significantly suppressed the PGE2‑stimulated OPG release and the mRNA expression level. Compound C failed to affect the PGE2‑stimulated phosphorylation of p38 MAP kinase or p44/p42 MAP kinase. On the contrary, the phosphorylation of SAPK/JNK was markedly attenuated by compound C. The results of the current study suggest that AMPK acts as a positive regulator in PGE2-stimulated OPG synthesis via SAPK/JNK signaling in osteoblasts.
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Affiliation(s)
- Shingo Kainuma
- Department of Orthopedic Surgery, Nagoya University Graduate School of Medical Sciences, Nagoya, Aichi 467‑8601, Japan
| | - Takanobu Otsuka
- Department of Orthopedic Surgery, Nagoya University Graduate School of Medical Sciences, Nagoya, Aichi 467‑8601, Japan
| | - Gen Kuroyanagi
- Department of Orthopedic Surgery, Nagoya University Graduate School of Medical Sciences, Nagoya, Aichi 467‑8601, Japan
| | - Naohiro Yamamoto
- Department of Orthopedic Surgery, Nagoya University Graduate School of Medical Sciences, Nagoya, Aichi 467‑8601, Japan
| | - Rie Matsushima-Nishiwaki
- Department of Pharmacology, Gifu University Graduate School of Medicine, Gifu, Gifu 501‑1194, Japan
| | - Osamu Kozawa
- Department of Pharmacology, Gifu University Graduate School of Medicine, Gifu, Gifu 501‑1194, Japan
| | - Haruhiko Tokuda
- Department of Pharmacology, Gifu University Graduate School of Medicine, Gifu, Gifu 501‑1194, Japan
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Kainuma S, Tokuda H, Kuroyanagi G, Yamamoto N, Ohguchi R, Fujita K, Matsushima-Nishiwaki R, Kozawa O, Otsuka T. PGD2 stimulates osteoprotegerin synthesis via AMP-activated protein kinase in osteoblasts: Regulation of ERK and SAPK/JNK. Prostaglandins Leukot Essent Fatty Acids 2015; 101:23-9. [PMID: 26365271 DOI: 10.1016/j.plefa.2015.08.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Revised: 08/17/2015] [Accepted: 08/24/2015] [Indexed: 12/25/2022]
Abstract
AMP-activated protein kinase (AMPK), a key enzyme sensing cellular energy metabolism, is currently known to regulate multiple metabolic pathways. Osteoprotegerin plays a pivotal role in the regulation of bone metabolism by inhibiting osteoclast activation. We have previously reported that prostaglandin D2 (PGD2) stimulates the synthesis of osteoprotegerin through the activation of p38 mitogen-activated protein (MAP) kinase, p44/p42 MAP kinase and stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) in osteoblast-like MC3T3-E1 cells. On the basis of these findings, we herein investigated the implication of AMPK in PGD2-stimulated osteoprotegerin synthesis in these cells. PGD2 induced the phosphorylation of AMPKα (Thr-172) and AMPKβ (Ser-108), and the phosphorylation of acetyl-coenzyme A carboxylase, a direct AMPK substrate. Compound C, an AMPK inhibitor, which suppressed the phosphorylation of acetyl-coenzyme A carboxylase, significantly attenuated both the release and the mRNA levels of osteoprotegerin stimulated by PGD2. The PGD2-induced phosphorylation of p44/p42 MAP kinase and SAPK/JNK but not p38 MAP kinase were markedly inhibited by compound C. These results strongly suggest that AMPK regulates the PGD2-stimulated osteoprotegerin synthesis at a point upstream of p44/p42 MAP kinase and SAPK/JNK in osteoblasts.
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Affiliation(s)
- Shingo Kainuma
- Department of Orthopedic Surgery, Nagoya City University Graduate School of Medical Sciences, Nagoya 467-8601, Japan; Department of Pharmacology, Gifu University Graduate School of Medicine, Gifu 501-1194, Japan
| | - Haruhiko Tokuda
- Department of Pharmacology, Gifu University Graduate School of Medicine, Gifu 501-1194, Japan; Department of Clinical Laboratory, National Center for Geriatrics and Gerontology, Obu, Aichi 474-8511, Japan.
| | - Gen Kuroyanagi
- Department of Orthopedic Surgery, Nagoya City University Graduate School of Medical Sciences, Nagoya 467-8601, Japan; Department of Pharmacology, Gifu University Graduate School of Medicine, Gifu 501-1194, Japan
| | - Naohiro Yamamoto
- Department of Orthopedic Surgery, Nagoya City University Graduate School of Medical Sciences, Nagoya 467-8601, Japan; Department of Pharmacology, Gifu University Graduate School of Medicine, Gifu 501-1194, Japan
| | - Reou Ohguchi
- Department of Orthopedic Surgery, Nagoya City University Graduate School of Medical Sciences, Nagoya 467-8601, Japan; Department of Pharmacology, Gifu University Graduate School of Medicine, Gifu 501-1194, Japan
| | - Kazuhiko Fujita
- Department of Orthopedic Surgery, Nagoya City University Graduate School of Medical Sciences, Nagoya 467-8601, Japan; Department of Pharmacology, Gifu University Graduate School of Medicine, Gifu 501-1194, Japan
| | | | - Osamu Kozawa
- Department of Pharmacology, Gifu University Graduate School of Medicine, Gifu 501-1194, Japan
| | - Takanobu Otsuka
- Department of Orthopedic Surgery, Nagoya City University Graduate School of Medical Sciences, Nagoya 467-8601, Japan
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Jang HJ, Tsoyi K, Kim YM, Park EJ, Park SW, Kim HJ, Lee JH, Chang KC. (S)-1-α-naphthylmethyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline (CKD712), promotes wound closure by producing VEGF through HO-1 induction in human dermal fibroblasts and mouse skin. Br J Pharmacol 2013; 168:1485-96. [PMID: 23088309 DOI: 10.1111/bph.12031] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2012] [Revised: 10/01/2012] [Accepted: 10/15/2012] [Indexed: 12/01/2022] Open
Abstract
BACKGROUND AND PURPOSE Given the importance of VEGF and haem oxygenase (HO)-1 in wound healing, the present study tested the hypothesis that CKD712, a synthetic tetrahydroisoquinoline alkaloid, activated VEGF production through the induction of HO-1 in human dermal fibroblasts (HDFs) and in mouse skin to stimulate wound healing. EXPERIMENTAL APPROACH Using HDFs, the effects of CKD712 on the production of VEGF and migration were evaluated. The mechanisms responsible were investigated using various signal inhibitors and small interfering RNA techniques. The ability of CKD712 to promote wound healing was also investigated in full-thickness skin-wounded mice. KEY RESULTS CKD712 treatment of HDFs increased VEGF production and accelerated migration, which was antagonized by anti-VEGF antibodies. Both an AMPK inhibitor (compound C) and a HO-1 activity inhibitor (SnPPIX) but not inhibitors of MAPKs, PI3K and PKC reduced the production of VEGF by CKD712. Interestingly, SnPPIX inhibited HO-1 expression but not p-AMPK, whereas compound C inhibited both p-AMPK and HO-1 induction by CKD712. Moreover, CKD712 decreased HO-1 expression without affecting the expression of p-AMPK by siHO-1 transfection, but it failed to induce HO-1 in siAMPKα1-transfected cells, suggesting that AMPK is involved in HO-1 induction by CKD712 in HDFs. Also, CKD712 shortened the time of wound closure in an SnPPIX-sensitive manner in a full-thickness skin-wounded mouse model. CONCLUSION AND IMPLICATIONS CKD712 accelerated cutaneous wound healing, at least in part, by the production of VEGF through HO-1 induction in HDFs and mouse skin.
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Affiliation(s)
- Hwa Jin Jang
- Department of Pharmacology, School of Medicine Gyeongsang National University, Institute of Health Sciences, Jinju, Korea
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KONDO AKIRA, OTSUKA TAKANOBU, KATO KENJI, MATSUSHIMA-NISHIWAKI RIE, KUROYANAGI GEN, MIZUTANI JUN, TOKUDA HARUHIKO, KOZAWA OSAMU. AMP-activated protein kinase regulates thyroid hormone-stimulated osteocalcin synthesis in osteoblasts. Int J Mol Med 2013; 31:1457-62. [DOI: 10.3892/ijmm.2013.1349] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2013] [Accepted: 03/08/2013] [Indexed: 11/05/2022] Open
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KONDO AKIRA, OTSUKA TAKANOBU, KATO KENJI, NATSUME HIDEO, KUROYANAGI GEN, MIZUTANI JUN, ITO YOSHIKI, MATSUSHIMA-NISHIWAKI RIE, KOZAWA OSAMU, TOKUDA HARUHIKO. AMP-activated protein kinase inhibitor decreases prostaglandin F2α-stimulated interleukin-6 synthesis through p38 MAP kinase in osteoblasts. Int J Mol Med 2012; 30:1487-92. [DOI: 10.3892/ijmm.2012.1159] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2012] [Accepted: 09/25/2012] [Indexed: 11/06/2022] Open
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Lu Z, Wang G, Dunstan CR, Zreiqat H. Short-Term Exposure to Tumor Necrosis Factor-Alpha Enables Human Osteoblasts to Direct Adipose Tissue-Derived Mesenchymal Stem Cells into Osteogenic Differentiation. Stem Cells Dev 2012; 21:2420-9. [DOI: 10.1089/scd.2011.0589] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Affiliation(s)
- ZuFu Lu
- Biomaterials and Tissue Engineering Research Unit, School of AMME, The University of Sydney, Sydney, Australia
| | - Guocheng Wang
- Biomaterials and Tissue Engineering Research Unit, School of AMME, The University of Sydney, Sydney, Australia
| | - Colin R. Dunstan
- Biomaterials and Tissue Engineering Research Unit, School of AMME, The University of Sydney, Sydney, Australia
| | - Hala Zreiqat
- Biomaterials and Tissue Engineering Research Unit, School of AMME, The University of Sydney, Sydney, Australia
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Tokuda H, Kato K, Natsume H, Kondo A, Kuroyanagi G, Matsushima-Nishiwaki R, Ito Y, Otsuka T, Kozawa O. Involvement of AMP-activated protein kinase in thrombin-stimulated interleukin 6 synthesis in osteoblasts. J Mol Endocrinol 2012; 49:47-55. [PMID: 22645249 DOI: 10.1530/jme-11-0165] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
We previously demonstrated that thrombin stimulates synthesis of interleukin 6 (IL6), a potent bone resorptive agent, in part via p44/p42 MAP kinase and p38 MAP kinase but not through stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) among the MAP kinase superfamily in osteoblast-like MC3T3-E1 cells. In this study, we investigated the involvement of AMP-activated protein kinase (AMPK), a regulator of energy metabolism, in thrombin-stimulated IL6 synthesis in MC3T3-E1 cells. The phosphorylation of p44/p42 MAP kinase, p38 MAP kinase, SAPK/JNK, or AMPK was determined by western blot analysis. The release of IL6 was determined by the measurement of IL6 concentration in the conditioned medium using an ELISA kit. The expression of IL6 mRNA was determined by RT-PCR. Thrombin time dependently induced the phosphorylation of AMPK α-subunit (Thr-172). Compound C, an inhibitor of AMPK, dose-dependently suppressed the thrombin-stimulated IL6 release in the range between 0.3 and 10 μM. Compound C reduced thrombin-induced acetyl-CoA carboxylase phosphorylation. The IL6 mRNA expression induced by thrombin was markedly reduced by compound C. Downregulation of AMPK by siRNA suppressed the thrombin-stimulated IL6 release. The thrombin-induced phosphorylation of p44/p42 MAP kinase and p38 MAP kinase was inhibited by compound C, which failed to affect SAPK/JNK phosphorylation. These results strongly suggest that AMPK regulates thrombin-stimulated IL6 synthesis via p44/p42 MAP kinase and p38 MAP kinase in osteoblasts.
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Affiliation(s)
- H Tokuda
- Department of Clinical Laboratory, National Center for Geriatrics and Gerontology, Obu 474-8511, Japan.
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Kato K, Tokuda H, Matsushima-Nishiwaki R, Natsume H, Kondo A, Ito Y, Kozawa O, Otsuka T. AMPK limits IL-1-stimulated IL-6 synthesis in osteoblasts: involvement of IκB/NF-κB pathway. Cell Signal 2012; 24:1706-12. [PMID: 22560875 DOI: 10.1016/j.cellsig.2012.04.012] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2012] [Revised: 04/09/2012] [Accepted: 04/18/2012] [Indexed: 01/20/2023]
Abstract
AMP-activated protein kinase (AMPK) is currently known to act as a key regulator of metabolic homeostasis. Several biosynthetic enzymes for fatty acid or glycogen are recognized as the targets of AMPK. In the present study, we investigated the role of AMPK in the interleukin-1 (IL-1)-stimulated IL-6 synthesis in osteoblast-like MC3T3-E1 cells. IL-1 induced phosphorylation of AMPK-α (Thr-172), which regulates AMPK activities, and acetyl-CoA carboxylase, a direct substrate of AMPK. Compound C, an inhibitor of AMPK, which suppressed the IL-1-induced phosphorylation of acetyl-CoA carboxylase, increased the release and the mRNA level of IL-6 stimulated by IL-1. Transfection of AMPK siRNA-α also amplified the IL-1-stimulated IL-6 release compared to the control cells. On the other hand, IL-1 elicited the phosphorylation of IκB, which caused subsequent decrease of total level of IκB. Wedelolactone, an inhibitor of IκB kinase, which reduced the phosphorylation both of IκB and NF-κB, significantly enhanced the IL-1-stimulated IL-6 synthesis. Compound C remarkably suppressed the IL-1-induced phosphorylation of IκB. These results strongly suggest that AMPK negatively regulates IL-1-stimulated IL-6 synthesis through the IκB/NF-κB pathway in osteoblasts.
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Affiliation(s)
- Kenji Kato
- Department of Orthopedic Surgery, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan
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Vascular endothelial growth factors and receptors are up-regulated during development of apical periodontitis. J Endod 2012; 38:628-35. [PMID: 22515891 DOI: 10.1016/j.joen.2012.01.005] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2011] [Revised: 01/05/2012] [Accepted: 01/08/2012] [Indexed: 11/22/2022]
Abstract
INTRODUCTION Apical periodontitis is a common inflammatory disease caused by persistent root canal infection and is characterized by bone resorption. Vascular endothelial growth factors (VEGFs) and their receptors (VEGFRs) have been described in many pathologic and inflammatory conditions, but their involvement in the development of apical periodontitis has not been thoroughly investigated. The aim of this study was to quantify gene expression and localize VEGF-A, VEGF-C, and VEGF-D and VEGFR-2 and VEGFR-3 in a rat model of apical periodontitis. METHODS Molar pulps were unilaterally exposed to the oral cavity for 10 or 21 days. Jaw sections were used for localization of VEGFs and VEGFRs with immunohistochemistry and identification of cells with double immunofluorescence. Gene expression analysis for VEGF-A, VEGF-C, and VEGFR-3 of periapical tissues was performed with quantitative real-time polymerase chain reaction. RESULTS All investigated factors and receptors were expressed immunohistochemically in blood vessels at the periodontal ligament of control teeth and were up-regulated during lesion development. In apical lesions, macrophages and neutrophils expressed all studied factors and receptors, with macrophages being an important source of VEGF-C and VEGF-D. Osteoclasts expressed VEGFR-2 and VEGFR-3, and the latter was also identified in fibroblast-like cells in the lesions. VEGF-A and VEGFR-3 gene expression was up-regulated at days 10 and 21 (P < .05). CONCLUSIONS The current findings indicate that the VEGF family and receptors are involved in vascular remodeling and immune functions during disease development. The presence of VEGFR-2 and VEGFR-3 on osteoclasts indicates that bone resorbing activity is influenced by VEGFs.
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Mizutani J, Tokuda H, Matsushima-Nishiwaki R, Kato K, Kondo A, Natsume H, Kozawa O, Otsuka T. Involvement of AMP-activated protein kinase in TGF-β-stimulated VEGF synthesis in osteoblasts. Int J Mol Med 2012; 29:550-6. [PMID: 22294055 PMCID: PMC3577364 DOI: 10.3892/ijmm.2012.893] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2011] [Accepted: 12/12/2011] [Indexed: 12/14/2022] Open
Abstract
It is generally recognized that AMP-activated protein kinase (AMPK) acts as a key regulator of energy homeostasis. We have previously shown that transforming growth factor-β (TGF-β) stimulates synthesis of vascular endothelial growth factor (VEGF) via p44/p42 mitogen-activated protein (MAP) kinase, stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) and p38 MAP kinase in osteoblast-like MC3T3-E1 cells. In the present study, we investigated whether AMPK is involved in the TGF-β-stimulated VEGF synthesis in osteoblast-like MC3T3-E1 cells. TGF-β time-dependently induced the phosphorylation of the AMPK α-subunit (Thr172) and the AMPK β-subunit (Ser108). Compound C, an AMPK inhibitor, significantly reduced the TGF-β-stimulated VEGF release. The inhibitory effect of compound C was also observed in normal human osteoblasts (NHOst). Although compound C failed to affect the TGF-β-induced phosphorylation of SAPK/JNK, p38 MAP kinase or Smad2, it markedly suppressed the TGF-β-induced phosphorylation of both MEK1/2 and p44/p42 MAP kinase. In addition, compound C significantly suppressed the VEGF mRNA expression induced by TGF-β. Taken together, our results strongly suggest that AMPK is involved in TGF-β-stimulated VEGF synthesis, and that it functions at a point upstream of MEK1/2.
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Affiliation(s)
- Jun Mizutani
- Department of Orthopedic Surgery, Nagoya City University Graduate School of Medical Sciences, Mizuho-Cho, Mizuho-Ku, Nagoya 467-8601, Japan
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Kato K, Otsuka T, Kondo A, Matsushima-Nishiwaki R, Natsume H, Kozawa O, Tokuda H. AMP-activated protein kinase regulates PDGF-BB-stimulated interleukin-6 synthesis in osteoblasts: involvement of mitogen-activated protein kinases. Life Sci 2011; 90:71-6. [PMID: 22100508 DOI: 10.1016/j.lfs.2011.10.023] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2011] [Revised: 09/26/2011] [Accepted: 10/08/2011] [Indexed: 01/01/2023]
Abstract
AIM We have previously reported that platelet-derived growth factor (PDGF)-BB stimulates synthesis of interleukin-6 (IL-6), a potent bone resorptive agent, in osteoblast-like MC3T3-E1 cells, and that the activation of p44/p42 mitogen-activated protein (MAP) kinase, p38MAP kinase and stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) is implicated in the IL-6 synthesis. In the present study,we investigated the involvement of AMP-activated protein kinase (AMPK), a regulator of energy metabolism, in the PDGF-BB-stimulated IL-6 synthesis in MC3T3-E1 cells. MAIN METHODS The levels of IL-6 were measured by ELISA. The phosphorylation of each protein kinases was analyzed by Western blotting. The mRNA levels of IL-6 were determined by real-time RT-PCR. KEY FINDINGS PDGF-BB time-dependently induced the phosphorylation of AMPK. Compound C, an inhibitor of AMPK, which reduced PDGF-BB-induced acetyl-CoA carboxylase phosphorylation, dose-dependently suppressed the PDGF-BB-stimulated IL-6 release. In addition, the PDGF-BB-stimulated IL-6 release in human osteoblasts was also inhibited by compound C. The mRNA expression of IL-6 induced by PDGF-BB was markedly reduced by compound C. The PDGF-BB-induced phosphorylation of p44/p42 MAP kinase, p38 MAP kinase and SAPK/JNK was inhibited by compound C. SIGNIFICANCE These results strongly suggest that AMPK positively regulates PDGF-BB-stimulated IL-6 synthesis via the MAP kinases in osteoblasts.
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Affiliation(s)
- Kenji Kato
- Department of Orthopedic Surgery, Nagoya City University Graduate School of Medical Sciences, Nagoya 467-8601, Japan
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