Benchmark Dose Estimation from Transcriptomics Data for Methylimidazolium Ionic Liquid Hepatotoxicity: Implications for Health Risk Assessment of Green Solvents

Ionic liquids (ILs), traditionally considered environmentally benign solvents, have shown potential toxicity to organisms, raising concerns about their safety. Among them, 1-octyl-3-methylimidazolium (M8OI) has been detected at high concentrations in soils and exhibits hepatotoxic properties. To uncover the molecular mechanisms underlying this toxicity, whole-transcriptome sequencing was performed, coupled with benchmark dose (BMD) modeling, to derive transcriptomic points-of-departure (tPOD) through dose-response analysis. The transcriptomic analysis identified 425, 667, and 567 differentially expressed genes (DEGs) following low (10 μmol/L), medium (50 μmol/L), and high (200 μmol/L) doses of M8OI exposure, respectively. Enrichment analysis revealed significant perturbations in pathways related to cytokine-cytokine receptor interaction and IL-17 signaling. BMD modeling yielded tPOD values of 1.51 μmol/L (median of the 20 most sensitive genes, omicBMD₂₀), 2.98 μmol/L (tenth percentile of all genes, omicBMD_10th), 6.83 μmol/L (mode of the first peak of all gene BMDs, omicBMD_mode), and 5.9 μmol/L for pathway-level analysis. These transcriptomics-derived tPODs were at least 105-fold lower than M8OI's hepatotoxic concentration, as indicated by its EC₅₀ of 723.6 μmol/L in HepG2 cells. Functional analysis of the transcriptomic data identified legionellosis, rheumatoid arthritis, and transcriptional misregulation in cancer as the most sensitive pathways affected by M8OI. These findings highlight the molecular mechanisms driving M8OI-induced hepatotoxicity and underscore the utility of transcriptomics in deriving sensitive and quantitative toxicity thresholds. The results provide critical insights for guideline-driven toxicological evaluations and regulatory decision-making, supporting a more comprehensive assessment of IL safety.