Involvement of Ras/extracellular signal-regulated kinase, but not Akt pathway in risedronate-induced apoptosis of U937 cells and its suppression by cytochalasin B

Hirofumi Fujita, Toshihiko Utsumi, Shikibu Muranaka, Tetsuya Ogino, Hiromi Yano, Jitsuo Akiyama, Tatsuji Yasuda, Kozo Utsumi

Research output: Contribution to journalArticle

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Abstract

Although risedronate, a nitrogen containing bisphosphonate (BPs), strongly inhibits bone resorption by enhanced apoptosis of osteoclasts, its mechanism remained unclear. In this study, we investigated the molecular mechanism of risedronate-induced apoptosis of U937 cells, with a focus on extracellular signal-regulated kinase 1/2 (ERK 1/2) and protein kinase B (Akt) pathways, mitochondria-mediated apoptosis, and the effect of disruption of the actin cytoskeleton. Risedronate facilitated the relocation of Ras from membrane to cytosol through inhibited isoprenylation. Accordingly, risedronate suppressed the phosphorylation of ERK 1/2, a downstream survival signaling kinase of Ras, affected the intracellular distribution of Bcl-xL, and induced the mitochondrial membrane depolarization, cytochrome c release, activated caspase cascade and DNA fragmentation. The risedronate-induced apoptosis was effectively suppressed with cyclosporine A plus trifluoperazine, potent inhibitors of mitochondrial membrane permeability transition (MPT). The risedronate-induced apoptosis was independent of Akt, another cAMP-dependent survival signaling kinase. Risedronate facilitated dephosphorylation of Bad at Ser112, an ERK phosphorylation site, but not at Ser136, an Akt phosphorylation site. All of these apoptosis-related changes induced by risedronate were strongly suppressed by cytochalasin B, an inhibitor of actin filament polymerization. These results indicate that risedronate-induced apoptosis in U937 cells involves Ras/ERK, but not Akt signaling pathway, and is dependent on MPT, and that disruption of the actin cytoskeleton inhibits the risedronate-induced apoptosis at its early step.

Original languageEnglish
Pages (from-to)1773-1784
Number of pages12
JournalBiochemical Pharmacology
Volume69
Issue number12
DOIs
Publication statusPublished - Jun 15 2005

Fingerprint

U937 Cells
Cytochalasin B
Extracellular Signal-Regulated MAP Kinases
Apoptosis
Phosphorylation
Actin Cytoskeleton
Membranes
Actins
Mitogen-Activated Protein Kinase 3
Mitogen-Activated Protein Kinase 1
Mitochondrial Membranes
Permeability
Phosphotransferases
Risedronate Sodium
Prenylation
Trifluoperazine
Proto-Oncogene Proteins c-akt
Mitochondria
Relocation
Depolarization

Keywords

  • Apoptosis
  • Bad
  • Bisphosphonate
  • Cytochalasin B
  • ERK1/2
  • Membrane permeability transition

ASJC Scopus subject areas

  • Pharmacology

Cite this

Involvement of Ras/extracellular signal-regulated kinase, but not Akt pathway in risedronate-induced apoptosis of U937 cells and its suppression by cytochalasin B. / Fujita, Hirofumi; Utsumi, Toshihiko; Muranaka, Shikibu; Ogino, Tetsuya; Yano, Hiromi; Akiyama, Jitsuo; Yasuda, Tatsuji; Utsumi, Kozo.

In: Biochemical Pharmacology, Vol. 69, No. 12, 15.06.2005, p. 1773-1784.

Research output: Contribution to journalArticle

Fujita, Hirofumi ; Utsumi, Toshihiko ; Muranaka, Shikibu ; Ogino, Tetsuya ; Yano, Hiromi ; Akiyama, Jitsuo ; Yasuda, Tatsuji ; Utsumi, Kozo. / Involvement of Ras/extracellular signal-regulated kinase, but not Akt pathway in risedronate-induced apoptosis of U937 cells and its suppression by cytochalasin B. In: Biochemical Pharmacology. 2005 ; Vol. 69, No. 12. pp. 1773-1784.
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AU - Fujita, Hirofumi

AU - Utsumi, Toshihiko

AU - Muranaka, Shikibu

AU - Ogino, Tetsuya

AU - Yano, Hiromi

AU - Akiyama, Jitsuo

AU - Yasuda, Tatsuji

AU - Utsumi, Kozo

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AB - Although risedronate, a nitrogen containing bisphosphonate (BPs), strongly inhibits bone resorption by enhanced apoptosis of osteoclasts, its mechanism remained unclear. In this study, we investigated the molecular mechanism of risedronate-induced apoptosis of U937 cells, with a focus on extracellular signal-regulated kinase 1/2 (ERK 1/2) and protein kinase B (Akt) pathways, mitochondria-mediated apoptosis, and the effect of disruption of the actin cytoskeleton. Risedronate facilitated the relocation of Ras from membrane to cytosol through inhibited isoprenylation. Accordingly, risedronate suppressed the phosphorylation of ERK 1/2, a downstream survival signaling kinase of Ras, affected the intracellular distribution of Bcl-xL, and induced the mitochondrial membrane depolarization, cytochrome c release, activated caspase cascade and DNA fragmentation. The risedronate-induced apoptosis was effectively suppressed with cyclosporine A plus trifluoperazine, potent inhibitors of mitochondrial membrane permeability transition (MPT). The risedronate-induced apoptosis was independent of Akt, another cAMP-dependent survival signaling kinase. Risedronate facilitated dephosphorylation of Bad at Ser112, an ERK phosphorylation site, but not at Ser136, an Akt phosphorylation site. All of these apoptosis-related changes induced by risedronate were strongly suppressed by cytochalasin B, an inhibitor of actin filament polymerization. These results indicate that risedronate-induced apoptosis in U937 cells involves Ras/ERK, but not Akt signaling pathway, and is dependent on MPT, and that disruption of the actin cytoskeleton inhibits the risedronate-induced apoptosis at its early step.

KW - Apoptosis

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