[The role of S100A8/RAGE and Caveolin-1 and the effect of roxithromycin on their expression in a rat model of neutrophilic asthma].

Objective: To explore the role of S100A8, the receptor for advanced glycation endproducts (RAGE) and Caveolin-1 in neutrophilic asthmatic rats, and to further study the intervention of roxithromycin and the possible mechanisms. Methods: Male Brown Norway rats were randomly assigned to a control group, an asthma group and a Roxithromycin group. The asthmatic rat model was established by intraperitoneal injection of ovalbumin (OVA) and Freund's complete adjuvant (FCA) mixture, and aerosol inhalation of OVA. Rats in the Roxithromycin group were given roxithromycin injection 30 mg/kg 30 minutes before each challenge. Rats in the control and the asthma groups were replaced with equal volumes of saline, respectively. Bronchoalveolar lavage fluid (BALF) neutrophil percentage (Neu%) and pathological changes of pulmonary tissue (hematoxylin-eosin, HE staining) were measured to confirm the establishment of asthmatic models. The concentration of inflammatory cytokines and S100A8 were quantified by enzyme-linked immunosorbent assay (ELISA), and the expression of Caveolin-1 and RAGE at protein levels were detected by immunohistochemistry and Western blot. Results: Neu% in BALF of the asthma group was significantly higher than those of the control group, and Neu% in the Roxithromycin group was lower than the asthma group (all P<0.01). Pulmonary histology revealed that there were a large number of inflammatory cells infiltrated in the bronchial and perivascular, pulmonary interstitial and alveolar spaces, and the bronchial wall and smooth muscles were thickened obviously in the asthma group. Rats in the Roxithromycin group showed milder inflammation and airway remodeling change than the asthma group. There was no obvious pathological damage in the control group. The concentration of IL-6 and IL-17 in BALF and serum of rats in the asthma group were significantly higher than those in the control group (P<0.01), and Roxithromycin inhibited the high expression of these cytokines (P<0.05). The expression of S100A8 and RAGE in the asthma group were significantly higher than those in the control group [(20.6±4.4) vs (7.1±2.0) ng/L; (885±118) vs (462±102) ng/L; (14.2±1.7) vs (7.6±1.8) ng/L; (774±166) vs (406±69) ng/L, all P<0.05], and Roxithromycin inhibited the high expression of these proteins [(14.3±3.7) vs (20.6±4.4) ng/L; (650±53) vs (885±118) ng/L; (10.4±1.2) vs (14.2±1.7) ng/L; (560±64) vs (728±72) ng/L] (all P<0.05). Meanwhile, the expression of Caveolin-1 in the asthma group was significantly lower than that in the control group (P<0.01), and Roxithromycin up-regulated its expression (P<0.01). Correlation analysis showed that there was a significantly positive correlation between the expression of S100A8 and RAGE (r=0.706, P<0.01), while there was a significantly negative correlation between the expression of S100A8 and Caveolin-1 (r=-0.775, P<0.01), and between the expression of Caveolin-1 and RAGE (r=-0.919, P<0.01). Conclusion: S100A8 and Caveolin-1 may play an important role in neutrophilic asthma via RAGE, and Roxithromycin may exerts anti-inflammatory effects and inhibition of airway remodeling partly through this signaling pathway.

Eosinophil differentiation in the bone marrow is promoted by protein tyrosine phosphatase SHP2.

SHP2 participates in multiple signaling events by mediating T-cell development and function, and regulates cytokine-dependent granulopoiesis. To explore whether and how SHP2 can regulate bone-marrow eosinophil differentiation, we investigate the contribution of SHP2 in the bone-marrow eosinophil development in allergic mice. Blockade of SHP2 function by SHP2 inhibitor PHPS-1 or conditional shp2 knockdown by adenovirus-inhibited bone-marrow-derived eosinophil differentiation in vitro, with no detectable effects on the apoptosis of eosinophils. Furthermore, SHP2 induced eosinophil differentiation via regulation of the extracellular signal-regulated kinase pathway. Myeloid shp2 conditional knockout mice (LysM(cre)shp2(flox/flox)) failed to induce eosinophilia as well as airway hyper-responsiveness. The SHP2 inhibitor PHPS-1 also alleviated eosinophilic airway inflammation and airway hyper-responsiveness, accompanied by significantly reduced levels of systemic eosinophils and eosinophil lineage-committed progenitors in allergic mice. We demonstrate that inhibition of eosinophil development is SHP2-dependent and SHP2 is sufficient to promote eosinophil formation in vivo. Our data reveal SHP2 as a critical regulator of eosinophil differentiation, and inhibition of SHP2 specifically in myeloid cells alleviates allergic airway inflammation.