Downregulation of NOX4 improves airway remodeling and inflammation by the TGF-β1-Smad2/3 pathway in asthma.

Asthma is a respiratory inflammatory disease, and nicotinamide adenine dinucleotide phosphate oxidase 4 (NOX4) is involved in the progression of respiratory diseases. However, the role of NOX4 in asthma remains unclear. In the present study, we aimed to explore the effects of NOX4 on airway remodeling and inflammation. NOX4 expression was measured using immunocytochemistry (IHC), western blot, and real-time PCR (qPCR). Lung tissues were stained using the H&E assay. ELISA was used to examine the levels of airway remodeling-related indicators, and qPCR was used to detect airway inflammatory factors. The results indicated that NOX4 is highly expressed in lung tissues, bronchoalveolar lavage fluid (BALF), and serum of OVA-treated mice. Inhibition of NOX4 alleviated OVA-induced airway remodeling and inflammation. Similarly, TGF-β1 was also upregulated in BALF and serum OVA-induced mice. Inhibition of TGF-β1 signaling also improved airway remodeling and inflammation induced by OVA. Moreover, the downregulation of NOX4 inactivated the TGF-β1-Smad2/3 pathway, and TGF-β1 decreased Smad2/3 expression. Moreover, inhibition of the TGF-β1 was enhanced, while TGF-β1 reversed the effects on airway remodeling and inflammation induced by NOX4 inhibition. Taken together, the downregulation of NOX4 improves airway remodeling and inflammation via inactivation of the TGF-β1-Smad2/3 pathway in asthma mice, suggesting that NOX4 may be a therapeutic target for asthma.