Aryl hydrocarbon receptor (AhR) regulates organic dust and organic dust-associated bacterial extracellular...

Exposure to agricultural organic dust increases the risk of respiratory diseases. Aryl hydrocarbon receptor (AhR), a transcription factor activated by environmental chemicals and endogenous metabolites, regulates immune and inflammatory responses, but its role in organic dust-induced lung inflammation is not known. Our study elucidated mechanisms by which AhR modulates bronchial epithelial cell inflammatory responses induced by poultry farm organic dust extract (DE) and organic dust-associated (OD) bacterial extracellular vesicles (EVs).

The role of AhR in the DE- and OD-bacterial EVs-mediated inflammatory responses in Beas2B bronchial epithelial cells was investigated using siRNA knockdown. AhR expression and nuclear translocation, reactive oxygen species (ROS), and inflammatory mediator (pro-IL-1β, ICAM-1, IL-6, IL-8) levels were evaluated by western immunoblotting, immunostaining, DCFDA labeling, real-time qRT-PCR, and ELISA. The induction of lung inflammatory cytokines by OD-bacterial EVs was assessed by ELISA in AhR knockout mice.

DE and OD-bacterial EVs increased AhR protein expression and nuclear translocation in a time-dependent manner in Beas2B cells. AhR knockdown reduced ROS and NFκB activation but modulated STAT3 differentially, suppressing DE-induced activation while enhancing OD-bacterial EV-induced activation. Nevertheless, AhR knockdown attenuated the induction of inflammatory mediators by DE and OD-bacterial EVs. Inhibition of NOX, XO, NFκB, and STAT3 attenuated AhR increase by DE- and OD-bacterial EVs. Studies in AhR knockout mice demonstrated that AhR regulates lung inflammatory cytokines in a sex-specific manner.

AhR is a critical modulator of organic dust-induced lung inflammation, potentially driven by a positive feedback loop involving ROS and NFκB/STAT3. Targeting the AhR pathway offers a therapeutic strategy for respiratory diseases afflicting agricultural workers.