Metal-Stimulated Interleukin-6 Production Through a Proton-Sensing Receptor, Ovarian Cancer G Protein-Coupled Receptor 1, in Human Bronchial Smooth Muscle Cells: A Response Inhibited by Dexamethasone

Maiko Kadowaki; Koichi Sato; Hisashi Kamio; Makoto Kumagai; Rikishi Sato; Takafumi Nyui; Yukihiro Umeda; Yuko Waseda; Masaki Anzai; Haruka Aoki-Saito; Yasuhiko Koga; Takeshi Hisada; Hideaki Tomura; Fumikazu Okajima; Tamotsu Ishizuka

doi:10.2147/JIR.S326964

Metal-Stimulated Interleukin-6 Production Through a Proton-Sensing Receptor, Ovarian Cancer G Protein-Coupled Receptor 1, in Human Bronchial Smooth Muscle Cells: A Response Inhibited by Dexamethasone

J Inflamm Res. 2021 Dec 18:14:7021-7034. doi: 10.2147/JIR.S326964. eCollection 2021.

Authors

Affiliations

¹ Third Department of Internal Medicine, Faculty of Medical Sciences, University of Fukui, Fukui, 910-1193, Japan.
² Laboratory of Signal Transduction, Institute for Molecular and Cellular Regulation, Gunma University, Maebeshi, 371-8512, Japan.
³ Laboratory of Signal Transduction, Faculty of Pharmaceutical Sciences, Aomori University, Aomori, 030-0943, Japan.
⁴ Department of Respiratory Medicine, Gunma University Graduate School of Medicine, Maebeshi, 371-8511, Japan.
⁵ Gunma University Graduate School of Health Sciences, Maebeshi, 371-8514, Japan.
⁶ Laboratory of Cell Signaling Regulation, Division of Life Science, School of Agriculture, Meiji University, Kawasaki, 214-8571, Japan.

^# Contributed equally.

Abstract

Purpose: Human bronchial smooth muscle cells (BSMCs) contribute to airway obstruction and hyperresponsiveness in patients with bronchial asthma. BSMCs also generate cytokines and matricellular proteins in response to extracellular acidification through the ovarian cancer G protein-coupled receptor 1 (OGR1). Cobalt (Co) and nickel (Ni) are occupational agents, which cause occupational asthma. We examined the effects of Co and Ni on interleukin-6 (IL-6) secretion by human BSMCs because these metals may act as ligands of OGR1.

Methods: Human BSMCs were incubated in Dulbecco's Modified Eagle Medium (DMEM) containing 0.1% bovine serum albumin (BSA) (0.1% BSA-DMEM) for 16 hours and stimulated for the indicated time by exchanging the medium with 0.1% BSA-DMEM containing any of the metals or pH-adjusted 0.1% BSA-DMEM. IL-6 mRNA expression was quantified via reverse transcription polymerase chain reaction (RT-PCR) using the real-time TaqMan technology. IL-6 was measured using an enzyme-linked immunosorbent assay. Dexamethasone (DEX) was added 30 minutes before each stimulation. To knock down the expression of OGR1 in BSMCs, small interfering RNA (siRNA) targeting OGR1 (OGR1-siRNA) was transfected to the cells and non-targeting siRNA (NT-siRNA) was used as a control.

Results: Co and Ni both significantly increased IL-6 secretion in human BSMCs at 300 μM. This significant increase in IL-6 mRNA expression was observed 5 hours after stimulation. BSMCs transfected with OGR1-siRNA produced less IL-6 than BSMCs transfected with NT-siRNA in response to either Co or Ni stimulation. DEX inhibited Co- and Ni-stimulated IL-6 secretion by human BSMCs as well as pH 6.3-stimulated IL-6 secretion in a dose-dependent manner. DEX did not decrease phosphorylation of ERK1/2, p38 MAP kinase, and NF-κB p65 induced by either Co or Ni stimulation.

Conclusion: Co and Ni induce secretion of IL-6 in human BSMCs through activation of OGR1. Co- and Ni-stimulated IL-6 secretion is inhibited by DEX.

Keywords: asthma; cobalt; cytokine; glucocorticoid; nickel; proton.

Grants and funding

This work was supported by a Grant-in-Aid for scientific research from the Japan Society for the Promotion of Science from the Ministry of Education, Culture, Sports, Science, and Technology of Japan, 20K08538 and 21K08174 (M. Kadowaki and T. Ishizuka).