High humidity and NO2 co-exposure exacerbates allergic asthma by increasing oxidative stress, inflammatory and TRP protein expressions in lung tissue.

Allergic asthma is a chronic inflammatory airway disease with a high mortality rate and a rapidly increasing prevalence in recent decades that is closely linked to environmental change. Previous research found that high humidity (HH) and the traffic-related air pollutant NO 2 both aggregated allergic asthma. Their combined effect and mechanisms on asthma exacerbation, however, are unknown. Our study aims to toxicologically clarify the role of HH (90%) and NO 2 (5 ppm) on allergic asthma. Ninety male Balb/c mice were randomly assigned to one of six groups (n = 15 in each): saline control, ovalbumin (OVA)-sensitized, OVA + HH, OVA + NO 2 , OVA + HH + NO 2 , and OVA + HH + NO 2 +Capsazepine (CZP). After 38 days of treatment, the airway function, pathological changes in lung tissue, blood inflammatory cells, and oxidative stress and inflammatory biomarkers were comprehensively assessed. Co-exposure to HH and NO 2 exacerbated histopathological changes and airway hyperresponsiveness, increased IgE, oxidative stress markers malonaldehyde (MDA) and allergic asthma-related inflammation markers (IL-1β, TNF-α and IL-17), and upregulated the expressions of the transient receptor potential (TRP) ion channels (TRPA1, TRPV1 and TRPV4). Our findings show that co-exposure to HH and NO 2 disrupted the Th1/Th2 immune balance, promoting allergic airway inflammation and asthma susceptibility, and increasing TRPV1 expression, whereas CZP reduced TRPV1 expression and alleviated allergic asthma symptoms. Thus, therapeutic treatments that target the TRPV1 ion channel have the potential to effectively manage allergic asthma. [Display omitted] • High humidity (HH) and NO 2 induce allergic asthmatic airway inflammation in mice. • HH and NO 2 co-exposure enhances physiological and biochemical indicators of asthma. • Expression of TRPA1, TRPV4 and TRPV1 ion channels is upregulated in asthmatic mice. • TRPV1 ion pathway plays a key role in asthma exacerbation by HH and NO 2 co-exposure. • Capsazepine can significantly reduce the exacerbation of allergic asthma. [ABSTRACT FROM AUTHOR]