NMDA receptor activation inhibits the antifibrotic effect of BM-MSCs on bleomycin-induced pulmonary fibrosis.

Xiaohong Li,Feiyan Zhao,Wei Liu,Yanhong Huang,Caixia Hao,Xiaoting Huang,Chen Li,Siyuan Tang,Qingmei Cheng,Jianping Xu,Dandan Feng,Jianzhong Han,Ziqiang Luo,Yiting Tang,Shaojie Yue

doi:10.1152/ajplung.00002.2018

Abstract

Endogenous glutamate (Glu) release and N-methyl-d-aspartate (NMDA) receptor (NMDAR) activation are associated with lung injury in different animal models. However, the underlying mechanism is unclear. Bone marrow-derived mesenchymal stem cells (BM-MSCs), which show potential use for immunomodulation and tissue protection, play a protective role in pulmonary fibrosis (PF) process. Here, we found the increased Glu release from the BM cells of bleomycin (BLM)-induced PF mice in vivo. BLM stimulation also increased the extracellular Glu in BM-MSCs via the antiporter system xc− in vitro. The gene expression of each subunit of NMDAR was detected in BM-MSCs. NMDAR activation inhibited the proliferation, migration, and paracrine function of BM-MSCs in vitro. BM-MSCs were derived from male C57BL/6 mice, transfected with lentiviral vectors carrying the enhanced green fluorescence protein gene, pretreated with NMDA, and transplanted into the female recipient mice that were intratracheally injected with BLM to induce PF. Transplantation of NMDA-pretreated BM-MSCs significantly aggravated PF as compared with that in the normal BM-MSCs transplantation group. The sex determination gene Y chromosome and green fluorescence protein genes of BM-MSCs were detected to observe BM-MSCs homing in the fibrotic lungs. Moreover, NMDAR activation inhibited BM-MSC migration by downregulating the stromal cell-derived factor-1/C-X-C chemokine receptor type 4 signaling axis. NMDAR activation aggravated the transforming growth factor-β1-induced extracellular matrix production in alveolar epithelial cells and fibroblasts through the paracrine effects of BM-MSCs. In summary, these findings suggested that NMDAR activation-mediated Glu excitotoxicity induced by BLM in BM-MSCs abolished the therapeutic effects of normal BM-MSCs transplantation on BLM-induced PF.

Highlights

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, and irreversible lung-restricted disease and the most common outcome of the interstitial lung diseases [33]
The green fluorescence protein (GFP)-labeled Bone marrow-derived mesenchymal stem cells (BM-mesenchymal stem cells (MSCs)) were identified by their typical fibroblast-like appearance (Fig. 1A) and their differentiation potentials into adipocytes, osteoblasts, and chondrocytes as shown by Oil Red O staining (Fig. 1C), Alizarin Red S staining (Fig. 1D), and Alcian Blue staining (Fig. 1E)
We further studied the role of NMDAR activation of bone marrow (BM)-MSCs in Transforming growth factor-␤ (TGF-␤)1-induced epithelial-mesenchymal transition (EMT) and fibroblast activation by the Transwell coculture system

Summary

Introduction

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, and irreversible lung-restricted disease and the most common outcome of the interstitial lung diseases [33]. This disease is characterized by replacement of the normal lung tissues by fibrotic scarring, honeycombing, and abnormal proliferation of myofibroblasts. Alveolar epithelial cell (AEC)-derived fibroblasts are the other components of fibroblastic foci during pulmonary fibrosis (PF). These cells facilitate epithelial-mesenchymal transition (EMT), which involves continuous decrease in epithelial markers, including E-cadherin and keratin, and continuous increase in mesenchymal markers, including N-cadherin, vimentin, and ␣-SMA [24]. Rock et al [50] once suggested in 2011 that EMT is not a source of fibroblasts in mouse fibrotic lungs, the recent literature still mentions that EMT is one of the sources of myofibroblasts [49]

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Conclusion