[Anti-Chlamydia trachomatis activity and underlying mechanisms of baicalin in vitro]

Objective To examine the inhibitory effect of baicalin on Chlamydia trachomatis (C.trachomatis) activity and its impact on pyroptosis in infected cells in vitro. Methods A cell model of C.trachomatis infection was established. The effects of various concentrations of baicalin on C.trachomatis inclusion bodies and infectious progeny were assessed. Cell viability was measured using the CCK-8 assay to determine the optimal non-cytotoxic concentration of baicalin for subsequent experiments. The time-dependent inhibitory effect of baicalin was analyzed using a drug withdrawal protocol. Cellular morphology was observed under an inverted phase-contrast microscope to detect pyroptotic features. The expression levels of pyroptosis-related proteins NLRP3, pro-caspase-1, cleaved-caspase-1, gasdermin D-N(GSDMD-N), and gasdermin E (GSDME) in C.trachomatis-infected cells were measured by Western blot. Results Baicalin inhibited C.trachomatis growth in a concentration-dependent manner. CCK-8 assays indicated that baicalin, at concentrations as high as 90 μmol/L, had no significant effect on host cell viability (>90%). The anti-chlamydial activity of baicalin was also time-dependent. Inverted microscopy revealed that C.trachomatis-infected cells exhibited characteristic pyroptotic morphology, including cell swelling and bubble-like protrusions, which were markedly attenuated by baicalin treatment. Western blot analysis revealed that baicalin markedly suppressed the protein expression levels of NLRP3, pro-caspase-1, cleaved-caspase-1, GSDMD-N, and GSDME in C.trachomatis-infected cells. Conclusion Baicalin effectively inhibits C.trachomatis growth in vitro. The underlying mechanism may be associated with the modulation of pyroptosis pathways mediated by both the NLRP3/caspase-1/GSDMD axis and GSDME.