Fig. 9: CYP1B1-AS1 and CYP1B1 regulate mitochondrial ROS and inhibit apoptosis.

a–f Flow cytometry analysis of apoptosis during CYP1B1-AS1 (lncCYPB), CYP1B1 (CYPB), dual knockdown (dCYPB), negative control (NC), and C. burnetii-infected (NMII) conditions at 24 h and 48 h p.i. Cells were stained with propidium Iodide (PI) and FITC-Annexin-V, at 24 h and 48 h p.i. to quantify populations of early apoptotic (Annexin-V⁺ PI⁻; Q1), late apoptotic (Annexin-V⁺ PI⁺; Q2), dead (PI⁺; Q3), and non-apoptotic (Annexin-V⁻ PI⁻; Q4) cells. Percentage of (a) early apoptotic, b late apoptotic, c dead cells at 24 h p.i. Percentage of (d) early apoptotic, e late apoptotic, f dead cells at 48 h p.i. For a–f, data represent mean ± SD from three independent experiments (n = 3). Statistical test: one-way ANOVA; *p < 0.05; **p < 0.01; ***p < 0.001; ****p < 0.0001; ns not significant, p ≥ 0.05. Exact p-values are provided in the Source Data file. g Proposed model of CYP1B1-AS1-mediated regulation of CYP1B1 during C. burnetii (Cb) infection. During Cb infection, aryl hydrocarbon receptor (AHR) is activated and translocates into the nucleus, where it transcriptionally induces both CYP1B1-AS1 and CYP1B1 from a shared bidirectional promoter. The activation of CYP1B1-AS1 influences CYP1B1 expression through a cis-regulatory mechanism within the local genome, thereby modulating CYP1B1 transcript levels. This enhances turnover of CYP1B1, a mitochondria-enriched cytochrome P450 enzyme involved in maintaining redox homeostasis. CYP1B1 modulates reactive oxygen species (ROS), suppresses ROS-driven inflammation, and inhibits apoptosis, thereby facilitating an intracellular environment favorable for Cb replication. Schematic was created using BioRender.com.