IL-1 and TNF-α regulation of aryl hydrocarbon receptor (AhR) expression in HSY human salivary cells

Recent findings demonstrate that nuclear receptor – aryl hydrocarbon receptor (AhR) may play an important role in the pathogenesis of Sjögren's syndrome (SS) via involvement in Epstein–Barr virus reactivation. In that study a reporter system was used. Therefore, it was decided to define AhR expression in human salivary cell line (HSY) and its functional regulators. The expression and functional regulation of AhR was studied in HSY cells. The cells were incubated with dioxin (TCDD) – AhR model inducer, IL-1 and TNF-α. qRT-PCR was applied to assess the expression of AHR, AHRR (AhR repressor), ARNT (AhR nuclear translocator) as well as AhR dependent genes: CYP1A1 and CYP1B1. Enzymatic activity of CYP1A1 and CYP1B1 was evaluated using luciferin-labelled CYPs substrate. In general, dioxin did not significantly influence the expression of AHR and ARNT, but reduced AHRR level. AhR dependent gene expression, i.e. CYP1A1 and CYP1B1 increased gradually with TCDD incubation time. TNF-α significantly induced AHR along with CYP1A1 and CYP1B1 expression. IL-1β did not affect AHR expression, and had minimal effects on CYP1 mRNA levels. Exposure of HSY cells to TCDD resulted in time-dependent induction of CYP1A1 and CYP1B1 enzymatic activity. This study documents functional expression of AhR in HSY as well as induction of AhR and its dependent genes by TNF-α.