Pulsed Electromagnetic Fields Increased the Anti-Inflammatory Effect of A2A and A3 Adenosine Receptors in Human T/C-28a2 Chondrocytes and hFOB 1.19 Osteoblasts

Fabrizio Vincenzi,Pier Andrea Borea,Stefania Merighi,Martina Targa,Carmen Corciulo,Stefania Setti,Stefania Gessi,Katia Varani,Ruggero Cadossi,Mary B Goldring,David M Ojcius

doi:10.1371/journal.pone.0065561

Abstract

Adenosine receptors (ARs) have an important role in the regulation of inflammation and their activation is involved in the inhibition of pro-inflammatory cytokine release. The effects of pulsed electromagnetic fields (PEMFs) on inflammation have been reported and we have demonstrated that PEMFs increased A2A and A3AR density and functionality in different cell lines. Chondrocytes and osteoblasts are two key cell types in the skeletal system that play important role in cartilage and bone metabolism representing an interesting target to study the effect of PEMFs. The primary aim of the present study was to evaluate if PEMF exposure potentiated the anti-inflammatory effect of A2A and/or A3ARs in T/C-28a2 chondrocytes and hFOB 1.19 osteoblasts. Immunofluorescence, mRNA analysis and saturation binding assays revealed that PEMF exposure up-regulated A2A and A3AR expression. A2A and A3ARs were able to modulate cAMP production and cell proliferation. The activation of A2A and A3ARs resulted in the decrease of some of the most relevant pro-inflammatory cytokine release such as interleukin (IL)-6 and IL-8, following the treatment with IL-1β as an inflammatory stimuli. In human chondrocyte and osteoblast cell lines, the inhibitory effect of A2A and A3AR stimulation on the release of prostaglandin E2 (PGE2), an important lipid inflammatory mediator, was observed. In addition, in T/C-28a2 cells, the activation of A2A or A3ARs elicited an inhibition of vascular endothelial growth factor (VEGF) secretion. In hFOB 1.19 osteoblasts, PEMF exposure determined an increase of osteoprotegerin (OPG) production. The effect of the A2A or A3AR agonists in the examined cells was enhanced in the presence of PEMFs and completely blocked by using well-known selective antagonists. These results demonstrated that PEMF exposure significantly increase the anti-inflammatory effect of A2A or A3ARs suggesting their potential therapeutic use in the therapy of inflammatory bone and joint disorders.

Highlights

Chronic inflammation represent an important factor in the pathophysiology of several joint diseases [1]
A2A and A3AR mRNA levels (Figure 2A) as well as their protein expression (Figure 2B and C) were augmented by pulsed electromagnetic fields (PEMFs) while A1 and A2BARs were not affected by PEMF exposure
Chondrocyte and osteoblast cell proliferation represent an important issue in the cartilage and bone metabolism. For this reason we have evaluated the effect of A2A and A3AR agonists on T/C-28a2 and hFOB 1.19 cell proliferation in the absence or in the presence of PEMF exposure

Summary

Introduction

Chronic inflammation represent an important factor in the pathophysiology of several joint diseases [1]. On the other hand continuous remodeling by bone cells such as osteoblasts and osteoclasts allows the skeleton to grow, adapt and repair itself [5,6]. In healthy adults bone remodeling, an important homeostatic function, is well balanced and abnormalities in this process can result in a variety of skeletal disorders [7]. The number of osteoblasts decreases with age, affecting the balance of formation and resorption in the bone tissue, and potentially leading to osteoporosis [8]. It is well accepted that osteoblasts release the receptor activator of nuclear factor kB (NF-kB) ligand (RANKL) modulating signaling pathways that promote osteoclast differentiation and survival [10]. Osteoblasts produce a protein named osteoprotegerin (OPG) that, preventing the biological effects of RANKL, plays an important osteoprotective role [11]

Objectives

Methods

Results

Conclusion