OBJECTIVETo study the expression of signal transducer and activator of transcription 5b (STAT5b) mRNA and interleukin-4 (IL-4) mRNA in blood mononuclearcells in a rat model of asthma and the effect of montelukast (MK) and BCG-polysaccharide and nucleic acid injection (BCG-PSN) on STAT5b mRNA and IL-4 mRNA expression.

METHODSFifty-two male Sprague-Dawley rats (weight:140-200 g) were randomly divided into four groups: asthma, MK treated and BCG-PSN-treated and control groups. Rat model of asthma was prepared by ovalbumin (OVA) sensitization. The rats were sacrificed 24 hrs after the last sensitization. Blood eosinophils (EOS) were counted. Plasma contens of IL-4 and interferon-gamma (IFN-gamma) were measured using ELISA. Expression of STAT5b mRNA and IL-4 mRNA in blood mononuclearcells was detected with SYBR GREEN I fluorescent quantitation PCR method.

RESULTSBlood contents of STAT5b mRNA and IL-4 mRNA in the untreated asthma group were significantly higher than those in the other three groups (<0.01). Blood EOS count and plasma IL-4 contents in the untreated asthma group significantly increased, while plasma IFN-gamma contents significantly decreased compared with the other three groups (<0.01). There were no significant differences in the parameters measured among the MK-treated, the BCG-PSNjtreated and the control groups. STAT5b mRNA expression was positively correlated to IL-4 mRNA expression, IL-4 content and EOS count (r=0.730,0.650, 0.664, respectively; <0.01), but negatively correlated to IFN-gamma content (r=-0.798; <0.01).

CONCLUSIONSSTAT5b mRNA and IL-4 mRNA were strongly expressed in blood mononuclearcells in rats with asthma, and there was a positive correlation between them. MK and BCG-PSN had inhibitory effects on the expression of STAT5b mRNA and IL-4 mRNA, which might be contributed to suppression of airway inflammation in asthma.