In
respiratory diseases, the induction of allergic
asthma is one of the hottest issues of international concern. The adjuvant effect of
air pollutants including nanoparticles (NPs) has be pointed out to facilitate the occurrence and development of allergic
asthma. This work studied the development of allergic
asthma upon exposures of
carbon black nanoparticles (CB NPs, 30-50 nm) and/or high environmental humidity (90% relative humidity). The mechanisms involved were investigated from perspectives of the activation of oxidative stress and transient receptor potential vanilloid 1 (TRPV1) pathways and the alteration in intestinal microbiota. Both high humidity and CB NPs aggravated the airway hyperreactivity, remodeling, and
inflammation in Balb/c mice sensitized by
ovalbumin. The co-exposure of these two risk factors exhibited adjuvant effect on the development of
asthma likely through activating oxidative stress pathway and TRPV1 pathway and then facilitating
type I hypersensitivity. Additionally, exposures of high humidity and/or CB NPs reduced the richness of intestinal microbes, altered microbial community composition, and weakened corresponding biological functions, which may interact with the development of
asthma. The findings will add new toxicological knowledge to the health risk assessment and management of co-exposures of NPs and other risk factors in the environment.