[Changes of CD(4)(+)Foxp3(+) regulatory T cells and CD(4)(+)IL-17(+)T cells in cigarette smoke-exposed rats]

To evaluate the changes of CD(4)(+)IL-17(+) T (Th17) and CD(4)(+)Foxp3(+) regulatory T (Treg) cells in peripheral blood and bronchoalveolar lavage fluid (BALF), and therefore to explore the role of Th17 and Treg in cigarette smoke-induced airway inflammation/COPD in rats.

Forty male Wistar rats were randomly divided into 4 groups: a 12 wk smoke-exposure group, a 24 wk smoke-exposure group, a 12 wk control group and a 24 wk control group (n = 10 each). Cells in BALF were collected and analyzed by absolute and differential cell counts. IL-17 and IL-6 levels in serum and BALF were tested by enzyme linked immunosorbent assay (ELISA). The proportion of CD(4)(+)IL-17(+) T and CD(4)(+)Foxp3(+) Treg in peripheral blood and BALF were determined by flow cytometry. The mRNA expressions of IL-17 and Foxp3 were measured by real-time PCR. Comparisons of the data between different groups were performed using one-way ANOVA, and SNK and Games-Howell test were used for comparison between 2 groups.

Levels of IL-17 were remarkable increased in the 12 wk smoke-exposure group and the 24 wk smoke-exposure group in serum [(52.6 ± 1.8) ng/L, (75.4 ± 6.0) ng/L] and BALF [(78.1 ± 5.8) ng/L, (95.0 ± 6.8) ng/L] compared with the 12 wk control group [(40.0 ± 3.2)ng/L, (54.5 ± 4.6) ng/L] and the 24 wk control group [(36.7 ± 3.2) ng/L, (53.9 ± 3.7) ng/L], all P < 0.05. IL-6 in serum was significantly increased in the 24 wk smoke-exposure group [(31.4 ± 2.1) ng/L] compared with the 24 wk control group [(11.5 ± 0.5) ng/L], and it was increased in the 12 wk and the 24 wk smoke-exposure group [(33.3 ± 2.3) ng/L, (44.6 ± 3.0) ng/L] compared with the 12 wk and the 24 wk control group [(15.6 ± 1.8) ng/L, (18.0 ± 1.9) ng/L] in BALF. Ratio of Th17 was higher in the 12 wk and the 24 wk smoke-exposure groups in peripheral blood [(1.81 ± 0.19)%, (3.74 ± 0.55)%] and BALF [(7.84 ± 0.28)%, (8.01 ± 0.39)%] compared with the12 wk [(0.97 ± 0.08)%, (5.64 ± 0.54)%] and the 24 wk control group [(1.08 ± 0.10)%, (5.95 ± 0.48)%]. Ratio of Treg in BALF was higher in the smoke-exposure groups [(8.81 ± 0.49)%, (11.98 ± 0.72)%] compared with the control groups [(4.34 ± 0.28)%, (5.21 ± 0.42)%]. The level of IL-17 mRNA was increased in the 12 wk and the 24 wk smoke-exposure group in peripheral blood (25.7 ± 2.0, 33.9 ± 1.5) and in BALF (22.2 ± 1.8, 34.7 ± 4.2) compared with the 12 wk (11.3 ± 2.6, 11.6 ± 2.4) and the 24 wk (11.1 ± 2.0, 13.5 ± 3.4) control groups. Foxp3 mRNA was increased in the smoke-exposure groups (24.4 ± 2.7, 30.3 ± 2.7) compared with the control groups (12.7 ± 2.7, 14.6 ± 3.8). Th17 in smoke-exposure groups was positively correlated with counts of total cells and macrophages (r = 0.512, 0.543, all P < 0.05).

An elevated expression of Th17 and Treg cells and an increase of inflammatory cytokines were evident in airway inflammation of cigarette smoke-exposed rats, suggesting that Treg was involved in the immunological regulation and Th17 was associated with the persistent inflammation in cigarette smoke-induced airway inflammation in rats.