N-methyl-D-aspartate receptor blockers attenuate bleomycin-induced pulmonary fibrosis by inhibiting endogenous mesenchymal stem cells senescence

A large number of our previous studies showed that endogenous glutamate and N-methyl-D-aspartate receptor (NMDAR) activation may be involved in various types of acute lung injury, airway inflammation, asthma, and pulmonary fibrosis. In animal models, the transplantation of exogenous bone marrow mesenchymal stem cells (BM-MSCs) is the most promising treatment for idiopathic pulmonary fibrosis. However, there are limited reports on the status of endogenous BM-MSCs in the process of bleomycin-induced pulmonary fibrosis in animals.

High concentrations of NMDA can promote senescence of BM-MSCs. NMDAR blockers may inhibit endogenous BM-MSCs aging through the WNT signaling pathway, thereby reducing the effect of bleomycin-induced pulmonary fibrosis.

We constructed a mouse model of bleomycin-induced pulmonary fibrosis. In vitro, the senescence model of BM-MSCs was constructed with hydrogen peroxide and high concentration of N-methyl-D-aspartate (NDMA). The changes in aging-related indexes were detected by senescence associated beta-galactosidase (SA-β-gal) staining, western blot, flow cytometry and real time-PCR. The epithelial-mesenchymal transformation (EMT) changes of mouse lung epithelial cells (MLE-12) co-cultured with senescent BM-MSCs were detected by immunofluorescence and western blotting.

We observed that endogenous BM-MSCs senescence occurs during bleomycin-induced pulmonary fibrosis in mice, and the model group had a higher expression level of the NMDAR subunit than the control group. We observed a significant increase in NMDAR subunit expression in a hydrogen peroxide-induced senescent cell model in vitro. BM-MSCs showed senescence-related phenotype and cell cycle arrest after high concentration of NMDA treatment. At the same time, the expression levels of the classic Wingless and int-1 (Wnt) pathway protein β-cantenin and downstream cyclin D1 also changed. In the co-culture of aged BM-MSCs and MLE-12 cells, EMT can be promoted in MLE-12 cells, and MK-801 can partially antagonize the occurrence of EMT. The NMDAR antagonist can partially prevent the above phenomenon. Conclusions: High concentrations of NMDA can promote senescence of BM-MSCs. NMDAR blockers may inhibit endogenous BM-MSCs aging through the WNT signaling pathway, thereby reducing the effect of bleomycin-induced pulmonary fibrosis.