Changes in transforming growth factor (TGF)-β and mothers against decapentaplegic homolog (Smad) expression in chronic asthmatic rats induced by ovalbumin and aluminum hydroxide

Abstract

The aim of this study was to investigate the transforming growth factor (TGF)-β 1/mothers against decapentaplegic homolog (Smad) signaling pathway associated with airway reconstruction in chronic asthmatic rats by studying mRNA and protein expression. Twenty-four (24) Sprague-Dawley rats were randomly divided into two groups: a normal control group treated with 0.9% saline and an OVE+ALU group treated with a mixture of 10% ovalbumin and 10% aluminum hydroxide. Hematoxylin-eosin (HE) staining was used to observe the pathomorphological changes, and the locations of TGF-β and Smad 2, 4 and 7 were determined by immunohistochemistry. The mRNA expression of TGF-β and Smad 2, 4 and 7 was determined by real time-polymerase chain reaction (RT-PCR). The protein expression of TGF-β was determined by enzyme-linked immunosorbent assay (ELISA), whereas that of Smad 2, 4 and 7 was determined by western blotting. HE staining revealed that the OVE+ALU group displayed obvious signs of bleeding and expansion of lung alveolar and inflammatory cells. Immunofluorescence showed that TGF-β and Smad 2, 4 and 7 proteins were located in the bronchial wall or alveolar wall. RT-PCR showed that mRNA expression of Smad 2 was significantly higher in the OVE+ALU group than in the control group (P < 0.05) and that mRNA expression of Smad 7 was significantly lower in the OVE+ALU group than in the control group (P < 0.05). There was no significant difference in Smad 4 mRNA expression between the two groups (P > 0.05). Western blotting showed that TGF-β 1 and Smad 2 protein expression was significantly higher in the OVE+ALU group than in the control group (P < 0.05), whereas, in contrast, Smad 4 and 7 protein expression was significantly lower in the OVE+ALU group than in the control group (P < 0.05). The process of chronic asthma rats, TGF-β  and Smad 2, 4 and 7 expressions were changeable, thus the TGF-β/Smad signaling pathway may play a role in chronic asthma.

Keywords: Chronic asthma, Smad 2, 4 and 7, real time-polymerase chain reaction (RT-PCR)

African Journal of Biotechnology Vol. 11(29), pp. 7528-7534, 10 April, 2012