HSP90 inhibitors potentiate PGF2α-induced IL-6 synthesis via p38 MAP kinase in osteoblasts.

Kazuhiko Fujita,Tetsu Kawabata,Go Sakai,Naohiro Yamamoto,Osamu Kozawa,Takanobu Otsuka,Gen Kuroyanagi,Rie Matsushima-Nishiwaki,Shingo Kainuma,Haruhiko Tokuda,Dominique Heymann

doi:10.1371/journal.pone.0177878

Kazuhiko Fujita, Tetsu Kawabata + Show 9 more

Open Access

https://doi.org/10.1371/journal.pone.0177878

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Journal: PloS one	Publication Date: May 19, 2017
Citations: 11	License type: CC BY 4.0

Affiliation: Nagoya City University, Gifu University

Abstract

Heat shock protein 90 (HSP90) that is ubiquitously expressed in various tissues, is recognized to be a major molecular chaperone. We have previously reported that prostaglandin F2α (PGF2α), a potent bone remodeling mediator, stimulates the synthesis of interleukin-6 (IL-6) through p44/p42 mitogen-activated protein (MAP) kinase and p38 MAP kinase in osteoblast-like MC3T3-E1 cells, and that Rho-kinase acts at a point upstream of p38 MAP kinase. In the present study, we investigated the involvement of HSP90 in the PGF2α-stimulated IL-6 synthesis and the underlying mechanism in MC3T3-E1 cells. Geldanamycin, an inhibitor of HSP90, significantly amplified both the PGF2α-stimulated IL-6 release and the mRNA expression levels. In addition, other HSP90 inhibitors, 17-allylamino-17demethoxy-geldanamycin (17-AAG) and 17-dimethylamino-ethylamino-17-demethoxy-geldanamycin (17-DMAG) and onalespib, enhanced the PGF2α-stimulated IL-6 release. Geldanamycin, 17-AAG and onalespib markedly strengthened the PGF2α-induced phosphorylation of p38 MAP kinase. Geldanamycin and 17-AAG did not affect the PGF2α-induced phosphorylation of p44/p42 MAP kinase and myosin phosphatase targeting subunit (MYPT-1), a substrate of Rho-kinase, and the protein levels of RhoA and Rho-kinase. In addition, HSP90-siRNA enhanced the PGF2α-induced phosphorylation of p38 MAP kinase. Furthermore, SB203580, an inhibitor of p38 MAP kinase, significantly suppressed the amplification by geldanamycin, 17-AAG or 17-DMAG of the PGF2α-stimulated IL-6 release. Our results strongly suggest that HSP90 negatively regulates the PGF2α-stimulated IL-6 synthesis in osteoblasts, and that the effect of HSP90 is exerted through regulating p38 MAP kinase activation.

Highlights

In order to investigate the involvement of Heat shock protein 90 (HSP90) in the prostaglandin F2α (PGF2α)-induced synthesis of IL-6 in osteoblast-like MC3T3-E1 cells, we first examined the effects of these HSP90 inhibitors on the PGF2α-stimulated IL-6 release
We demonstrated that HSP90 inhibitors including geldanamycin, 17-AAG and 17-DMAG significantly enhanced the PGF2α-stimulated release of IL-6 in osteoblast-like MC3T3-E1 cells
We found that onalespib, another type HSP90 inhibitor [31], amplified the IL-6 release induced by PGF2α in these cells

Summary

Introduction

We show that HSP90 inhibitors enhance the PGF2α-stimulated IL-6 synthesis in these cells, and that the amplifying effect is exerted through up-regulating p38 MAP kinase activation. The cultured cells were pretreated with various doses of geldanamycin, 17-AAG or onalespib for 60 min, and stimulated by 10 μM of PGF2α or vehicle in α-MEM containing 0.3% FBS for the indicated periods.

Results

Conclusion