Modulation of Cell Cycle Progression in the Spermatocyte Cell Line [GC-2spd(ts) Cell-Line] by Cigarette Smoke Condensate (CSC) via Arylhydrocarbon Receptor-Nuclear Factor Erythroid 2-Related Factor 2 (Ahr-Nrf2) Pathway1

Prior studies in our laboratory have demonstrated that cigarette smoke condensate (CSC) activates arylhydrocarbon receptor (Ahr) leading to upregulation of several antioxidant enzymes in murine spermatocytes. In this study, we show that exposure of the spermatocyte cell line GC-2spd(ts) to CSC induces an increase in Cyp1a1, demonstrating AHR activation, and simultaneous expression and nuclear translocation of nuclear factor erythroid 2-related factor 2 (NRF2), where it is believed to modulate Ahr expression by a feedback mechanism. Pharmacological inhibition by the AHR-antagonist CH223191 and interference by Ahr- and Nrf2-small interfering RNA followed by quantitative real-time PCR implicate the Ahr-Nrf2 pathway in the modulation of DNA damage and growth suppression genes such as Gadd45a and P21 and oxidative stress-related genes Cyp1a1, Nrf2, and Ahrr. Flow cytometry accompanied with cell proliferation assay indicate the CSC induces accumulation of spermatocytes at the S-G2/M phase of the cell cycle. Thus, the data obtained suggest that CSC contains several AHR-agonists that are capable of altering the growth pattern of spermatocytes in vitro through the Ahr-Nrf2 signaling mechanism.