[Effects of glucocorticoid on airway mucus secretion in asthma: experiment with asthmatic mouse model]

To study the effects of glucocorticoid on airway mucus secretion in asthma.

Twenty-four BALB/c mice were randomly divided into 3 equal groups: asthma group [ovalbumin (OVA) and aluminum hydroxide were injected intraperitoneally on day 0 and day 14 so as to establish mouse asthma model and aerosol inhalation of OVA PBS was conducted for 30 min on the days 21, 22, and 24], asthma + dexamethasone group (OVA and aluminum hydroxide were injected intraperitoneally on days 0 and 14, aerosol inhalation of OVA PBS was conducted for 30 min on the days 21, 22, and 24, and dexamethasone was injected intraperitoneally 1 hour before the aerosol inhalation), and control group (aerosol inhalation of PBS was conducted instead). Twenty-fours hours after the last exposure the mice were anesthetized deeply and their left lungs were excised to collect the bronchoalveolar lavage fluid (BALF) to calculate the numbers of total cells and eosinophils, then Alcian blue/periodic acid-Schiff staining and immunohistochemistry of the air passage were conducted to measure the expression levels of MUC5AC mRNA and protein and interleukin-4 (IL-4) mRNA.

The numbers of total cells in the BALF of the asthma group were (12.50 +/- 0.14) x 10(9)/L and (1.12 +/- 0.10) x 10(9)/L respectively, both significantly higher than those of the control group, (6.49 +/- 0.05) x 10(9)/L and (0.05 +/- 0.02) x 10(9)/L respectively (both P < 0.01), and were significantly higher than those of the asthma + dexamethasone group, (6.68 +/- 0.03) x 10(9)/L and (0.06 +/- 0.01) x 10(9)/L respectively too (both P < 0.01). The levels of MUC5AC mRNA, MUC5AC protein, and IL-4 mRNA of the asthma group were 0.5341 +/- 0.303, 0.1906 +/- 0.0008, and 0.6265 +/- 0.0932 respectively, all significantly higher than those of the control group (0.1994 +/- 0.0128, 0.1194 +/- 0.0007, and 0.2389 +/- 0.0289 respectively, all P < 0.01), and those of the asthma + dexamethasone group (0.2729 +/- 0.0345, 0.1456 +/- 0.0003, and 0.2424 +/- 0.0260, all P < 0.05). The MUC5AC protein expression and mRNA expression, and IL-4 mRNA expression of the asthma group were 0.1906 +/- 0.0008, 0.5341 +/- 0.0303, and 0.6265 +/- 0.0932 respectively, all significantly higher than those of the control group (0.1194 +/- 0.0007, 0.1994 +/- 0.0128, and 0.2398 +/- 0.0289 respectively, all P < 0.01). The MUC5AC protein expression and mRNA expression, and IL-4 mRNA expression of the asthma + dexamethasone group were 0.1456 +/- 0.0003, 0.2729 +/- 0.0345, and 0.2424 +/- 0.0260 respectively, all significantly lower than those of the asthma group (all P < 0.01). The MUC5AC protein expression and mRNA expression of the asthma + dexamethasone group were still significantly higher than those of the control group (both P < 0.01), however, the IL-4 mRNA expression of the asthma + dexamethasone group was not significantly different from that of the control group (P > 0.05).

Relieving the inflammation, glucocorticoid may play a role in the treatment of excessive mucus production through down-regulating the expression of MUC5AC and of IL-4.