Overexpression of the Aryl Hydrocarbon Receptor (Ahr) Mediates an Oxidative Stress Response following Injection of Fine Particulate Matter in the Temporal Cortex.

Studies have shown that particulate matter (PM) induces the expression of the aryl hydrocarbon receptor (Ahr) leading to the activation of the oxidative stress response. This study is aimed at characterizing the specific impact of fine PM on the expression profile of the Ahr and oxidative stress response in the primary auditory cortex. PM2.5 (<1.8 μm)-loaded filters were suspended in sterile saline to 102.6-111.82 μg/ml. Next, 10 μl of PM2.5 or an equal volume of saline was administered intracranially into the temporal cortex of two groups of rats (PM2.5 and control; n = 14 per group), respectively. One week after intracranial injection, the temporal cortex was harvested. Transmission electron microscopy was performed to evaluate the distribution of PM2.5 within the temporal cortex. Additionally, the mRNA and protein expression levels of cytochrome P450 1A1 (CYP1A1), CYP1B1, inducible nitric oxide synthase (iNOS), Ahr, and brevican mRNA and protein were measured using quantitative reverse transcription-polymerase chain reaction (qRT-PCR) or western blotting, respectively. Finally, the protein expression levels of the receptor for advanced glycation end products (RAGE) were estimated using enzyme-linked immunosorbent assay (ELISA). PM2.5 was observed in intracellular vesicles within the temporal cortex following intracranial injection. Levels of oxidative stress molecules (i.e., CYP1A1, CYP1B1, and iNOS), Ahr, Brevican, and RAGE were higher in the PM2.5 group compared with the control group. Intracranial administration of PM2.5 led to increased levels of Ahr and markers of an oxidative stress response in the temporal cortex. The oxidative stress response-mediated increases in the levels of brevican and RAGE.