Direct CDK1 engagement underlies carbaryl-induced genotoxic cell cycle arrest
Carbaryl, a widely used carbamate pesticide, has been epidemiologically associated with genotoxic and carcinogenic outcomes in exposed human populations, including elevated cancer risk at several tissue sites and, in some agricultural communities, chronic tubulointerstitial kidney disease of unknown etiology (CKDu). However, the cellular mechanisms underlying these associations, and whether carbaryl acts uniformly across tissues, remain poorly defined. Screening a panel of cell lines of distinct species and lineage, we found that carbaryl elicits pronounced, dose-dependent cytotoxicity and cell cycle arrest selectively in a renal tubular epithelial line (IMCD3) and, to a lesser extent, a cervical epithelial line (HeLa), while a fibroblast line (NIH3T3) was unaffected. In IMCD3 cells, carbaryl induces S- and G2/M-phase arrest through direct binding to DNA and consequent DNA damage, triggers Bcl-2-mediated late apoptosis independently of reactive oxygen species, and drives irreversible mitotic arrest. Molecular dynamics simulations, cellular thermal shift assays, and kinase measurements converge on CDK1 as a direct target of carbaryl: carbaryl destabilises the CDK1 active site and inhibits its catalytic activity, whereas CDK2 is engaged through an opposing, rigidifying mode with no functional consequence. This asymmetry provides a coherent mechanistic basis for the combined S-phase and G2/M arrest observed. Together, these findings establish carbaryl as a genotoxic, cell-cycle-disrupting agent with tissue-selective potency acting directly on CDK1, and provide a cell-based mechanistic framework for interpreting its reported associations with renal and other tissue pathologies in exposed human populations.