Fibroblast growth factor 10 protects against particulate matter-induced airway inflammatory response through regulating inflammatory signaling and apoptosis

Abstract

Chronic respiratory disorders are some of the most frequent and severe chronic diseases in China. Epidemiological research has shown that particulate matter (PM) is a risk factor and is closely correlated to the progression of numerous respiratory diseases. Fibroblast growth factor 10 (FGF10) is a mesenchymal-epithelial signaling messenger essential for the development and environmental stability of several tissues. Nevertheless, its role in PM-induced airway inflammation remains unclear. The present study aimed to explore the mechanisms underlying the FGF10-related slowing of lung injury and inflammation in vivo and in vitro, as well as the therapeutic potential of these phenomena. Mice were intraperitoneally injected with a vehicle (PBS) or FGF10 (0.5 mg/kg) at one hour before intratracheal treatment with vehicle (PBS) or PM (4 mg/kg) for two consecutive days. Human airway epithelial BEAS-2B cells were exposed to a vehicle (PBS) or FGF10 (10 ng/ml) in vitro at one hour prior to incubation with a vehicle or PM (200 ug/ml) for 24 hours. Then, the impact on inflammatory molecules was investigated. In vivo, it was found that FGF10 diminished the inflammatory cell aggregation and reduced the apoptosis. Interestingly, in the PM group, the level of FGF10 increased in the bronchoalveolar lavage fluid (BALF). However, the pre-treatment with FGF10 markedly impaired the PM-induced increase in IL-6, IL-8, TNF-α and PGE2 levels in BALF and the cell supernatant. In conclusion, the present findings indicate that FGF10 attenuates PM-induced airway inflammation by inhibiting apoptosis and inflammation. This may be exploited for the prevention and management of PM-induced airway inflammation.

Keywords: Airway inflammation; apoptosis; chronic respiratory disorders (CRD); fibroblast growth factor 10 (FGF10); particulate matter.

Figure 1

Schematic diagram of the in vivo experimental design. PM, Particulate matter; FGF10, Fibroblast growth factor.

Figure 2

Effect of PM on airway inflammation in mice. A. Histological changes of lung were detected by H&E staining after PM induction. The inflammatory cells were increased in the airway after PM instillation. The hematoxylin staining (blue) indicates the localization of nuclei, while the eosin staining (red) indicates the localization of the cytoplasm. These images were taken using a BX51 microscope DP71 camera at ×40, ×200, or ×400 magnification. B. The inflammation scores for the two groups. C. The level of FGF10 in the BALF was detected by ELISA. The results are presented as mean ± standard error of the mean (SEM; *P<0.05, **P<0.01, n=6).

Figure 3

FGF10 protects against lung histological and inflammatory after PM induction. A. The histological changes of lungs detected by H&E staining at 48 hours. The animals were randomly assigned into four groups: vehicle group, FGF10 group, PM group, and PM+FGF10 group. The images were taken using a BX51 microscope DP71 camera at ×40, ×200, or ×400 magnification. B. The inflammation scores for the four groups. C. The total protein level in the BALF was detected using a BSA protein assay kit. D-G. The expression of IL-6, IL-8, TNF-α and PGE2 in the BALF was measured by ELISA assay. The results are presented as mean ± standard error of the mean (SEM; **P < 0.01 vs Vehicle group; ##P < 0.01 vs PM group, n=3).

Figure 4

FGF10 protects against PM-induced lung injury, reduces the apoptosis level and increases the cell proliferation in lung tissue. (A) The representative sections of nuclear DNA fragmentation staining using TUNEL in the different groups, and the quantitative analysis of the number of TUNEL-positive airway epithelial cells (B) The IHC of cleaved-caspase 3 and (C) Ki67 of lung tissue sections obtained from the indicated groups, and the quantification of cleave-caspase 3 expression and Ki67 in lung tissue are shown. Scale bar = 100 µm. The results are presented as mean ± standard error of the mean (SEM; **P < 0.01 vs Vehicle group; ##P < 0.01 vs PM group, n=3).

Figure 5

Effects of FGF10 on PM-induced cell migration, and the increase in proinflammatory marker in BEAS-2B cells. Cells treated with FGF10 (10 ng/ml) were used to treat BEAS-2B cells at one hour before stimulation with PM, and subsequently stimulated for 24 hours. A. Cell migration growth was analyzed by scratch assay. B-E. The intracellular concentrations of IL-6, IL-8, TNF-α and PGE2 were measured using ELISA. The results are presented as mean ± standard error of the mean (SEM; **P < 0.01 vs Vehicle group; ##P < 0.01 vs PM group, n=3).

Figure 6

FGF10 reduces PM-induced apoptosis and proapoptotic protein expression, and increases cell proliferation in BEAS-2B cells. Cells were treated with FGF10 (10 ng/ml), were used to treat BEAS-2B cells at one hour before stimulation with PM, and subsequently stimulated for 24 hours. A. The apoptosis of BEAS-2B cells stimulated by PM and FGF10 detected by flow cytometry in the (1) vehicle, (2) FGF10 (10 ng/ml), (3) PM (200 ug/ml) and (4) PM+FGF10 groups. B. The in vitro proliferation assay by CCK-8 demonstrate that FGF10 significantly promoted cellular proliferation in BEAS-2B cells. C. The results of the protein expression of cleaved csapase-3, Bcl-2, Bax and GAPDH as loading control in the four groups, as determined by western blot. The results are presented as mean ± standard error of the mean (SEM; **P < 0.01 vs Vehicle group; #P < 0.05, ##P < 0.01 vs PM group, n=3).