[Role of Foxp3/Treg and RORγt/Th17 cell imbalance in rat model of chronic obstructive pulmonary disease].

OBJECTIVE

To observe the changes in forkhead/winged helix transcription factor p3(Foxp3), regulatory T cells (Treg), retinoid-related orphan receptor gamma (RORγt) in rat model of chronic obstructive pulmonary disease (COPD).

METHODS

Twenty Sprague-Dawley (SD) rats were randomly divided into normal control group and COPD model group, with 10 rats in each group. The COPD model was reproduced by smoke inhalation and tracheal instillation of lipopolysaccharide (LPS), and no such treatment was conducted in normal control group. Twenty-eight days after the model reproduction, the pulmonary function was determined, the pathological changes of lung tissue were observed with haematoxylin-eosin (HE) staining, interleukins (IL-6, IL-10) in serum were detected by enzyme-linked immunosorbent assay (ELISA), CD4⁺ CD25⁺ Foxp3⁺ Treg of peripheral blood was determined by flow cytometry, and the expressions of Foxp3, RORγt, IL-17 protein in lung tissue were assayed by Western Blot.

RESULTS

Under light microscope, significal interstitial infiltration of inflammatory cells was found in alveoli and interstitial tissue of the lung, and destruction of alveolar tissue, alveolar wall thinning, and even rupture to fuse into bullae, and bleeding into alveoli in different degress could be observed. Compared with the normal control group, forced vital capacity (FVC), forced expiratory volume in 0.3 second (FEV0.3), FEV0.3/FVC, peak expiratory flow (PEF) in model group were significantly decreased [FVC (mL): 8.04 ± 2.03 vs. 9.97 ± 2.14, FEV0.3 (mL): 6.16 ± 2.23 vs. 8.84 ± 2.12, FEV0.3/FVC: 0.70 ± 0.09 vs. 0.85 ± 0.11, PEF (mL/s): 33.56 ± 4.76 vs. 40.14 ± 5.64, P<0.05 or P<0.01]. Serum IL-6 was obviously increased (ng/L: 93.17 ±20.96 vs. 76.28 ± 13.24, P<0.05), IL-10 was significantly decreased (ng/L: 78.62 ± 15.17 vs. 104.34 ± 19.46, P<0.01), and CD4⁺ CD25⁺ FoxP3(+)Treg was significantly diminished [(2.75 ± 0.83)% vs. (4.16 ± 1.14)%, P<0.01] in model group compared with those in the normal control group. The expression of Foxp3 protein in lung tissue in model group was significantly down-regulated compared with that in the normal control group (gray scale: 0.38 ± 0.15 vs. 0.63 ± 0.11, P<0.01), and RORγt and IL-17 protein expressions were significantly up-regulated [RORγt (gray scale): 0.96 ± 0.23 vs. 0.47 ± 0.11, IL-17 (gray scale): 1.02 ± 0.24 vs. 0.34 ± 0.08, both P<0.01]. Correlation analysis showed that FEV0.3 was positively correlated with Foxp3 (r=0.585, P<0.05), and FEV0.3/FVC was negatively correlated with IL-6 and RORγt (r=-0.655, r=-0.607, both P<0.05). PEF was positively correlated with Treg (r=0.573, P<0.05), and negatively correlated with IL-17 (r=-0.198, P<0.05). IL-6 was negatively correlated with Foxp3(r=-0.603, P<0.05),and positively correlated with RORγt (r=0.588, P<0.05). IL-10 was positively correlated with Treg (r=0.573, P<0.05). Treg was positively correlated with Foxp3 (r=0.607, P<0.05), and negatively correlated with IL-17 (r=-0.569, P<0.05). Foxp3 was negatively correlated with RORγt (r=-0.591, P<0.05). RORγt was positively correlated with IL-17 (r=0.578, P<0.05).

CONCLUSIONS

There is a relationship among decreased pulmonary function, inflammation and imbalance of Foxp3/Treg and RORγt/Th17 in COPD.