Transcriptional regulation of Hb‐α and Hb‐β through nuclear factor E2‐related factor‐2 (Nrf2) activation in human vaginal cells: A novel mechanism of cellular adaptability to oxidative stress

Problem Hemoglobin (Hb), a major protein involved in transport of oxygen (O 2 ), is expressed by erythroid lineages. Until recently, it was not known whether non‐erythroid cells express Hb. The objective was to evaluate the expression and functional significance of Hb‐α and Hb‐β in human primary vaginal epithelial cells ( hPVEC s) and decipher downstream signaling. Methods of study RT ‐ PCR , qRT ‐ PCR , flow cytometry, Western blot, immunofluorescence were used to evaluate the expression of Hb‐α, Hb‐β, and nuclear factor E2‐related factor‐2(Nrf2) after hydrogen peroxide (H 2 O 2 ) induction. Electrophoretic mobility shift assay ( EMSA ) and chromatin immunoprecipitation (Ch IP ) assay were used to determine the binding efficiency of Nrf2 on the Hb‐α promoter. Results Stimulation of hPVEC s and human vaginal epithelial cell line, VK 2/E6E7 with H 2 O 2 augmented the expression of Hb‐α, Hb‐β, Nrf2, heme oxygenase‐1 ( HO ‐1), and reactive oxygen species ( ROS ). Treatment of these cells with Nrf2 inhibitor, trigonelline (Trig) inhibited Hb‐α and Hb‐β expressions. Hb‐α and Hb‐β overexpression downregulated H 2 O 2 ‐induced ROS . The presence of Nrf2 binding domain was demonstrated within Hb‐α promoter. Conclusion The results revealed for the first time that Hb‐α and Hb‐β were induced by oxidative stress through the activation of Nrf2. Overexpression of Hb‐α and Hb‐β ameliorated H 2 O 2 ‐induced oxidative stress, indicating one of the possible mechanism(s) to protect hPVECS from oxidative stress.