Effects Of Chrysin On Airway Inflammation And Airway Remodeling In Chronic Bronchial Asthma And Its Mechanisms

Part 1 Chrysin inhibits human airway smooth muscle cells proliferation through ERK1/2 pathwayObjective: To explore the effects and mechanisms of chrysin on proliferation and apoptosis of human airway smooth muscle cells(HASMCs).Methods: Cell Counting Kit-8(CCK-8) assay was applied to examin the effect of chrysin on the basal and platelet-derived growth factor-BB(PDGF-BB) –induced proliferation in HASMCs. Flow cytometry was used to detect apoptosis in HASMCs with the treatment of chrysin and PDGF-BB alone or in combination. Western blot was utilized to evaluate the effect of chrysin on PDGF-BB-induced increase in ERK1/2 phosphorylation in HASMCs.Results: Chrysin(20 μM, 40 μM) could significantly inhibit the basal proliferation of HASMCs at 24 h and 48 h in a dose and time dependent way(P < 0.05). PDGF-BB(10 ng/m L) could obviously induce HASMCs proliferation(P < 0.05). Chrysin(10 μM, 20 μM, 40 μM) could remarkably suppress PDGF-BB-induced proliferation in HASMCs at 24 h and 48 h, also in a dose and time dependent way(P < 0.05). Both PDGF-BB(10 ng/m L) and chrysin(20 μM) had no significant effects on HASMCs apoptosis. Chrysin(20 μM) didn’t affect the basal phosphorylation of ERK1/2 in HASMCs, but significantly reduce the PDGF-BB(10 ng/m L)-induced elevation of extracellular signal-regulated kinase1/2(ERK1/2) phosphorylation in HASMCs(P < 0.05).Conclusions: Chrysin could significantly inhibit both basal and PDGF-BB-induced proliferation in HASMCs. The chrysin’s suppression on proliferation in HASMCs induced by PDGF-BB might be mediated by decreasing ERK1/2 phosphorylation.Part 2 Chrysin alleviates airway inflammation and remodeling in a murine model of chronic asthmaObjective: To investigate the effects of chrysin on airway inflammation and remodeling in a murine model of chronic asthma and the mechanism involed.Methods: Forty-eight female BALB/c mice were randomly divided into four groups: the control group, the ovalbumin(OVA) group, the dexamethasone(DEX) group and the chrysin group. On days 0 and 14, mice were sensitized by intraperitoneal injection of OVA. From day 21, mice were challenged with aerosol inhalation of 1 % OVA 30 min/day, 3 days/week for 8 weeks. Mice in the chrysin group were intragastrically administered with chrysin(100 mg/kg) daily for 8 weeks. Mice in the DEX group were intraperitoneally injected(ip) with DEX(2 mg/kg) 30 min before each challenge. Airway responsiveness to acetylcholine chloride(Ach) was measured with a whole-body and invasive plethysmography 24 h after the last OVA challenge. Enzyme-linked immunosorbent assay(ELISA) was used to detect interleukin(IL)-4,IL-13 in bronchoalveolar lavage fluid(BALF) and tatal immunoglobulin E(Ig E) in serum. The lung sections were stained with eitherhematoxylin & eosin(HE) to assess the inflammatory cell infiltration or periodic acid schiff(PAS) to quantify global cell hyperplasia. The expression of α-smooth muscle actin(α-SMA) in lung tissues was evaluated by immunohistochemistry. Western blot was applied to analyze the expressions of Akt, p-Akt, ERK1/2, p-ERK1/2 in lung tissues.Results: There was no significant differences at the baseline of airway resistance(RL) among these four groups. RL in the OVA group was remarkably increased in a dose-dependent way by administration of Ach, while only a slight increase of RL could be detected in the control group. RL generated by the administration of Ach at doses from 3.15mg/m L to 25 mg/m L in the OVA group is much greater than that in the control group(P < 0.05). Treatment with either DEX or chrysin could significantly decrease RL compared with the OVA group(P < 0.05). The numbers of total inflammatory cells, macrophages, eosinophils, lymphocytes and neutrophils in BALF in the OVA group increased obviously compared with the control group(P < 0.05), but these inflammatory cells could be significantly reduced by administrated with DEX or chrysin compared with the OVA group(P < 0.05). IL-4 and IL-13 in BALF and the total Ig E in serum in the OVA group were much higher than those in the control group(P < 0.05). Administrations of both DEX and chrysin could markedly decrease the Th2 cytokines in BALF and serum total Ig E compared with the OVA group(P < 0.05). OVA could significantly induce goblet cell hyperplasia compared with the control group(P < 0.05). Either DEX or chrysin could significantly reduce OVA-induced increase in PAS-positive epithelial cells(P < 0.05). The expression of α-SMA around bronchiole increased significantly in the OVA group compared with that in the control group(P < 0.05), while both DEX and chrysin could obviously decrease OVA-induced expression of α-SMA(P < 0.05). The phosphorylation levels of Akt and ERK1/2 were much higher after OVA intervention compared with the control group(P < 0.05), whereas either DEX or chrysin could remarkably alleviate OVA-mediated phosphorylation of Akt and ERK1/2(P < 0.05).Conclusions: Chrysin could significantly alleviate airway hyperresponsiveness, airway inflammation and remodeling in a murine model of chronic asthma, which might be related to the suppression of phosphorylation of Akt and ERK1/2.