Chloroxylenol induces hematopoietic bias and immune dysregulation in zebrafish associated with MAPK signaling disruption.

Chloroxylenol (PCMX), a widely used phenolic disinfectant, is an emerging aquatic pollutant whose immunotoxicity remains poorly understood. This study employed zebrafish models to evaluate PCMX toxicity across a concentration range (0.25-7.5 mg/L) spanning environmentally detectable levels to higher, toxicologically informative concentrations. Acute exposure caused dose-dependent developmental defects, oxidative stress, and apoptosis in both embryos and adults. Embryonic toxicological assessment revealed a 96-h LC50 of 3.98 mg/L for larvae, with significant hatching reduction at ≥2 mg/L and malformation elevation at ≥0.5 mg/L. PCMX disrupted innate immunity by depleting neutrophils while paradoxically expanding macrophages, RNA-seq revealed 353 dysregulated genes in adult kidney, with KEGG enrichment identifying the MAPK pathway as a central hub. Network toxicology and molecular docking predicted moderate binding of PCMX to MAPK nodes (TGFBR1, GRB2, AKT1; -6.66 to -4.5 kcal/mol), corroborated by qPCR validation of MAPK and hematopoietic regulators (optn, atf3, irak3, prkcba, tgfbr2a, spi1a, c1qb, fosab). We propose that PCMX-induced oxidative stress converges on MAPK disruption, driving immune dysregulation and biased hematopoiesis, though this causal model is inferred from correlative evidence and requires functional validation. Despite the concentration gap, these findings show that PCMX, even at sublethal doses, can disrupt conserved immune and hematopoietic pathways, raising concern for aquatic organisms.