Reactions of the blood system and stem cells in bleomycin-induced model of lung fibrosis

NMDAR activation attenuates the protective effect of BM-MSCs on bleomycin-induced ALI via the COX-2/PGE2 pathway

N-methyl-d-aspartate (NMDA) receptor (NMDAR) activation mediates glutamate (Glu) toxicity and involves bleomycin (BLM)-induced acute lung injury (ALI). We have reported that bone marrow-derived mesenchymal stem cells (BM-MSCs) are NMDAR-regulated target cells, and NMDAR activation inhibits the protective effect of BM-MSCs on BLM-induced pulmonary fibrosis, but its effect on ALI remains unknown. Here, we found that Glu release was significantly elevated in plasma of mice at d 7 after intratracheally injected with BLM. BM-MSCs were pretreated with NMDA (the selective agonist of NMDAR) and transplanted into the recipient mice after the BLM challenge. BM-MSCs administration significantly alleviated the pathological changes, inflammatory response, myeloperoxidase activity, and malondialdehyde content in the damaged lungs, but NMDA-pretreated BM-MSCs did not ameliorate BLM-induced lung injury in vivo. Moreover, NMDA down-regulated prostaglandin E2 (PGE2) secretion and cyclooxygenase (COX)-2 expression instead of COX-1 expression in BM-MSCs in vitro. We also found that NMDAR1 expression was increased and COX-2 expression was decreased, but COX-1 expression was not changed in primary BM-MSCs of BLM-induced ALI mice. Further, the cultured supernatants of lipopolysaccharide (LPS)-pretreated RAW264.7 macrophages were collected to detect inflammatory factors after co-culture with NMDA-pretreated BM-MSCs. The co-culture experiments showed that NMDA precondition inhibited the anti-inflammatory effect of BM-MSCs on LPS-induced macrophage inflammation, and PGE2 could partially alleviate this inhibition. Our findings suggest that NMDAR activation attenuated the protective effect of BM-MSCs on BLM-induced ALI in vivo. NMDAR activation inhibited COX-2 expression and PGE2 secretion in BM-MSCs and weakened the anti-inflammatory effect of BM-MSCs on LPS-induced macrophage inflammation in vitro. In conclusion, NMDAR activation attenuates the protective effect of BM-MSCs on BLM-induced ALI via the COX-2/PGE2 pathway. Keywords: Acute Lung Injury, BM-MSCs, NMDA receptor, COX-1/2, PGE2.

Excessive activation of NMDA receptor inhibits the protective effect of endogenous bone marrow mesenchymal stem cells on promoting alveolarization in bronchopulmonary dysplasia

We studied the role of bone marrow mesenchymal stem cells (MSCs) in our established model of bronchopulmonary dysplasia (BPD) induced by intrauterine hypoxia in the rat. First, we found that intrauterine hypoxia can reduce the number of MSCs in lungs and bone marrow of rat neonates, whereas the administration of granulocyte colony-stimulating factor or busulfan to either motivate or inhibit bone marrow MSCs to lungs altered lung development. Next, in vivo experiments, we confirmed that intrauterine hypoxia also impaired bone marrow MSC proliferation and decreased cell cycling activity. In vitro, by using the cultured bone marrow MSCs, the proliferation and the cell cycling activity of MSCs were also reduced when N-methyl-d-aspartic acid (NMDA) was used as an NMDA receptor (NMDAR) agonist. When MK-801 or memantine as NMDAR antagonists in vitro or in vivo was used, the reduction of cell cycling activity and proliferation were partially reversed. Furthermore, we found that intrauterine hypoxia could enhance the concentration of glutamate, an amino acid that can activate NMDAR, in the bone marrow of neonates. Finally, we confirmed that the increased concentration of TNF-ɑ in the bone marrow of neonatal rats after intrauterine hypoxia induced the release of glutamate and reduced the cell cycling activity of MSCs, and the latter could be partially reversed by MK-801. In summary, intrauterine hypoxia could decrease the number of bone marrow MSCs that could affect lung development and lung function through excessive activation of NMDAR that is partially caused by TNF-ɑ.

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

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 x_c⁻ 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.

Mesenchymal stem cells in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a major cause of respiratory failure in critically ill patients and common outcome of various lung interstitial diseases. Its mortality remains high, and no effective pharmacotherapy, in addition to artificial ventilation and transplantation, exists. As such, the administration of mesenchymal stem or stromal cells (MSCs) is currently investigated as a new therapeutic method for pulmonary fibrosis. Clinical trials on MSC-based therapy as a potential treatment for lung injury and fibrosis are also performed. MSCs can migrate to injured sites and secrete multiple paracrine factors and then regulate endothelial and epithelial permeability, decrease inflammation, enhance tissue repair, and inhibit bacterial growth. In this review, recent studies on stem cells, particularly MSCs, involved in alleviating lung inflammation and fibrosis and their potential MSC-induced mechanisms, including migration and differentiation, soluble factor and extracellular vesicle secretion, and endogenous regulatory functions, were summarized.

Modulation of bleomycin-induced lung fibrosis by pegylated hyaluronidase and dopamine receptor antagonist in mice

Hyaluronidases are groups of enzymes that degrade hyaluronic acid (HA). To stop enzymatic hydrolysis we modified testicular hyaluronidase (HYAL) by activated polyethylene oxide with the help of electron-beam synthesis. As a result we received pegylated hyaluronidase (pegHYAL). Spiperone is a selective D2 dopamine receptor antagonist. It was demonstrated on the model of a single bleomycin damage of alveolar epithelium that during the inflammatory phase monotherapy by pegHYAL or spiperone reduced the populations of hematopoietic stem /progenitor cells in the lung parenchyma. PegHYAL also reduced the levels of transforming growth factor (TGF)-β, interleukin (IL)-1β, tumor necrosis factor (TNF)-α in the serum and lungs, while spiperone reduced the level of the serum IL-1β. Polytherapy by spiperone and pegHYAL caused the increase of the quantity of hematopoietic stem/ progenitor cells in the lungs. Such an influx of blood cell precursors was observed on the background of considerable fall level of TGF-β and the increase level of TNF-α in the serum and lungs. These results show pegHYAL reduced the bleomycin-induced fibrosis reaction (production and accumulation of collagen) in the lung parenchyma. This effect was observed at a single and repetitive bleomycin damage of alveolar epithelium, the antifibrotic activity of pegHYAL surpassing the activity of testicular HYAL. The antifibrotic effect of pegHYAL is enhanced by an additional instillation of spiperone. Therapy by pegHYAL causes the flow of CD31‒ CD34‒ CD45‒ CD44+ CD73+ CD90+ CD106+-cells into the fibrous lungs. These cells are incapable of differentiating into fibroblast cells. Spiperone instillation separately or together with pegHYAL reduced the MSC-like cells considerably. These data enable us to assume, that pegHYAL is a new and promising instrument both for preventive and therapy of toxic pneumofibrosis. The blockage of D2 dopamine receptors with the following change of hyaluronan matrix can be considered as a new strategy in treatment of pneumofibrosis.

Effect of immobilized hyaluronidase on stem and progenitor cells in pulmonary fibrosis

The effect of immobilized hyaluronidase on stem and progenitor cells of the lungs was studied on the model of partially reversible toxic bleomycin-induced pulmonary fibrosis in C57Bl/6 mice. During the inflammation phase, immobilized hyaluronidase reduced infiltration of alveolar interstitium with hemopoietic stem cells Sca-1(+), c-Kit(+), CD34(-), (CD3, CD45R (B220), Ly6C, Ly6G (Gr1), CD11b (Mac1), TER-119)(-). Improvement of histological parameters of bleomycin lungs during the phase of collagen fiber deposition after the treatment was accompanied by accumulation of mesenchymal multipotent stromal cells (CD31(-), CD34(-), CD45(-), CD44(+), CD73(+), CD90(+), CD106(+)decrease in the population of pan-hemopoietic cells (CD45(+)), accelerated restoration of the content of endothelial cells, and inhibition of clonal activity of fibroblast precursors (CD45(-)).

Anti-inflammatory and antifibrotic effects of a combination of spiperone and immobilized hyaluronidase on partially reversible and irreversible toxic pneumofibrosis

The possibility of boosting antifibrotic activity of testicular hyaluronidase immobilized on polyethylene oxide with spiperone was studied on the bleomycin models of a single (partially reversible pneumofibrosis) and repeated (irreversible pneumofibrosis) injuries to the alveolar epithelium in C57Bl/6 mice. The antifibrotic effect was more pronounced after successive treatment with immobilized hyaluronidase and spiperone than after individual treatment with each of the compounds: no collagen deposition in the parenchyma of bleomycin-damaged lungs was found. The decrease in inflammatory cell (lymphocytes, macrophages, neutrophils, plasma cells) infiltration of the alveoli and alveolar tracts interstitium in mice treated by immobilized hyaluronidase and spiperone did not differ from the anti-inflammatory effect of spiperone monotherapy.

Nonmicrobial-mediated inflammatory airway diseases--an update

In lungs, airways are in constant contact with air, microbes, allergens, and environmental pollutants. The airway epithelium represents the first line of lung defense through different mechanisms, which facilitate clearance of inhaled pathogens and environmental particles while minimizing an inflammatory response. The innate immune system facilitates immediate recognition of both foreign pathogens and tissue damage through toll-like receptor, which acts as a gateway for all intracellular events leading to inflammation. In the absence of microbial stimulus, the immune system is capable of detecting a wide range of insults against the host. This review focuses on various molecular mechanisms involved in pathophysiology of airway inflammation mediated by environmental factors, cellular stress, and pharmacological and clinical agents.