Effect of cigarette smoke exposure on the percentage of CD(4)(+)CD(25)(+) regulatory T cells and the expression of transcription factor Foxp3 in asthmatic rats

Abstract

To investigate the effect of cigarette smoke exposure on the ratio of CD(4)(+)CD(25)(+) regulatory T cells (Treg) and expression of transcription factor Foxp3 in asthmatic rats. Forty male Wistar rats were randomly divided into 4 groups (n = 10 for each group): a normal saline group, an aerosolized ovalbumin (OVA) exposure group, a cigarette smoke exposure group and a combined OVA and cigarette smoke exposure group. The rats were exposed to air or cigarette smoke and to normal saline or OVA aerosol for 8 weeks respectively. The percentage of CD(4)(+)CD(25)(+) T cells was determined by flow cytometry analysis. The concentration of interleukin-4 (IL-4) and interferon-γ (INF-γ) in peripheral blood and lung homogenates were measured by enzyme-linked immunosorbent assay (ELISA). The protein expression of Foxp3 in the lung was detected by Western blot. (1) The percentage of CD(4)(+)CD(25)(+) T cells in aerosolized OVA group [(6.4 ± 1.0)%] was significantly lower than that in the normal saline group [(9.9 ± 1.0)%] (P < 0.01). The percentage of CD(4)(+)CD(25)(+) T cells [(3.3 ± 0.8)%] in OVA combined cigarette smoke exposure group was remarkably lower than that in the aerosolized OVA exposure group and in the normal saline group(P < 0.01). (2) IL-4 in both plasma and lung [(22.6 ± 4.3) ng/L, (0.8 ± 0.1) ng/L] was significantly increased in the OVA-exposed rats compared with the normal saline group [(11.4 ± 2.9) ng/L, (0.3 ± 0.1) ng/L] (P < 0.01). Further remarkable increase in IL-4 of both plasma and lung was observed in the group exposed to both OVA and cigarette smoke [(34.1 ± 6.1) ng/L, (1.4 ± 0.3) ng/L] compared with the aerosolized OVA exposure group and the normal saline group (P < 0.05). INF-γ of plasma in OVA-exposed group [(59 ± 20) ng/L] was significantly decreased compared with the normal saline group [(151 ± 56) ng/L] (P < 0.01), and a further remarkable decrease in INF-γ of plasma was observed in the group exposed to both OVA and cigarette smoke [(10 ± 3) ng/L] compared with the aerosolized OVA exposure group and the normal saline group (P < 0.05). (3) Protein expression of Foxp3 in the aerosolized OVA group (8.18 ± 0.26) was lower than that in the normal saline group (10.27 ± 0.33, P < 0.01), while the protein expression of Foxp3 in OVA combined cigarette smoke exposure group (6.36 ± 0.38) was lower than that in the normal saline group and the aerosolized OVA exposure group (P < 0.01). The number of CD(4)(+)CD(25)(+) Treg cells and the expression of Foxp3 are likely to be altered by cigarette smoke exposure, which might play an important role in cigarette smoking-induced Th1/Th2 imbalance in asthmatic rats.