Chlamydia trachomatis Pgp3 protein regulates oxidative stress via activation of the Nrf2/NQO1 signal pathway.

Aim: Chlamydia trachomatis has evolved various strategies to alleviate oxidative stress of host cells to maintain their intracellular survival. However, the exact mechanism of anti-oxidative stress of C. trachomatis is still unclear. The activation of nuclear factor erythroid 2-related factor 2/quinone oxidoreductase (Nrf2/NQO1) signal pathway has been identified as an efficient antioxidant defensive mechanism used by host cells to counteract oxidative stress. Pgp3 is a pivotal virulence factor of C. trachomatis involved in intracellular survival. The aim of this study is to explore the role of Pgp3 on Nrf2/NQO1 signal pathway against oxidative stress.

Main Methods: After HeLa cells were stimulated with Pgp3 protein, Nrf2 location and the inclusion bodies of C. trachomatis were detected by indirect immunofluorescence, western blotting and Oxidative stress assay kits were used to separately determine the protein expression and the content of malondialdehyde (MDA), superoxide dismutase (SOD) and total antioxidant capacity (T-AOC) before and after the interference of Nrf-2 and NQO1.

Key Findings: Pgp3 promoted the nuclear translocation of Nrf2 to increase NQO1 expression and reduced oxidative stress induced by LPS to contribute to the survival of C. trachomatis. Inhibition of Nrf2/NQO1 signal pathway with Nrf2 inhibitor and down-regulation of NQO1 with siRNA-NQO1 suppressed oxidative stress resistance induced by Pgp3.

Significance: Here we found that Pgp3 alleviated oxidative stress to promote the infectivity of C. trachomatis through activation of Nrf2/NQO1 signal pathway, which provided a novel understanding of the effects of Pgp3 in the pathogenesis of C. trachomatis.