The oxidative stress-triggered activation of the PKC-Nrf2-G6PD pathway drives Benz(a)pyrene-induced endometrial stromal cell proliferation.

Benzo(a)pyrene (BaP), a ubiquitous environmental pollutant, exerts reproductive toxicity by disrupting endometrial decidualization, yet the underlying mechanisms remain unclear. This study aimed to dissect the molecular cascade linking BaP-induced oxidative stress to abnormal endometrial stromal cell (ESC) proliferation and decidualization injury. Pregnant mice were gavaged with 0.2 mg kg-1·day-1 BaP from gestational Day 1 to 7, and primary ESCs were treated with BaP, H2O2, NAC and different inhibitor/agonist in vitro. BaP exposure reduced embryo implantation sites, induced asymmetric embryo distribution in bilateral uterine horns, and down-regulated decidualization markers (FOXO1, BMP2, HOXA10) in vivo and in vitro. Concurrently, BaP up-regulated proliferation markers (PHH3, PCNA, Ki67) and EdU incorporation in ESCs. Mechanistically, BaP induced uterine oxidative stress by down-regulating antioxidant enzymes (GPx4, CAT, SOD2) and accumulating intracellular ROS. H2O2 recapitulated BaP-induced phenotypes, while NAC reversed these effects. BaP-induced oxidative stress activated the PKCα/KEAP1 pathway, promoting Nrf2 phosphorylation and nuclear translocation. Inhibition of PKCα by PKC-IN-6 alleviated BaP-induced Nrf2 activation. Activated Nrf2 up-regulated transketolase (TKT) and glucose-6-phosphate dehydrogenase (G6PD), key enzymes of the pentose phosphate pathway (PPP), to drive abnormal ESC proliferation. ML385 inhibited Nrf2 to rescued BaP-induced ESC hyperproliferation and decidualization injury, while SFN activated Nrf2 mimicked BaP's toxic effects. Collectively, BaP induces oxidative stress in early pregnancy uteri, sequentially activating the PKCα/KEAP1/Nrf2 pathway and G6PD and TKT, leading to ESC proliferation-differentiation imbalance and decidualization impairment. This study uncovers a novel oxidative stress-mediated mechanism of BaP reproductive toxicity, identifying Nrf2 and PPP enzymes as potential therapeutic targets for pollutant-related pregnancy disorders.