Integrated experimental, modeling, and transcriptomic approaches to characterize polyhexamethylene guanidine-induced cytotoxicity in human renal HK-2 cells

Polyhexamethylene-guanidine (PHMG) is a cationic polymer biocide associated with severe pulmonary and renal toxicities. However, the cellular and molecular mechanisms underlying its nephrotoxicity remain poorly understood. This study aimed to quantitatively characterize PHMG-induced cytotoxicity and associated molecular responses in human-renal-proximal-tubular epithelial-cells (HK-2) using in vitro assays, mathematical modeling, and transcriptome-based systems analysis. HK-2 cells were exposed to increasing concentrations of PHMG (0.1–20 μg/mL) for up to 72 h. Cell viability, apoptosis, and reactive-oxygen-species (ROS) generation were quantified. Time- and concentration-dependent toxicity profiles were characterized using a Weibull–Hill quantitative model. Ribonucleic acid sequencing was performed to identify differentially expressed genes and to conduct transcriptomic analyses, followed by construction of a protein–protein interaction (PPI) network. PHMG exposure induced a dose- and time-dependent reduction in cell viability, accompanied by elevated ROS generation and apoptosis. The toxicodynamic model quantitatively characterized the concentration- and time-dependent cytotoxicity profiles with good model fit. Transcriptomic profiling revealed significant downregulation of DNA replication, chromosome segregation, and cell cycle checkpoint pathways, alongside upregulation of oxidoreductase complex, tricarboxylic acid cycle, and adenosine triphosphate synthesis. PPI network analysis identified network hub candidates associated with cell-cycle regulation, oxidative stress responses, and protein homeostasis, whereas representative genes selected for quantitative real-time polymerase chain reaction validation supported transcriptomic findings. Transcriptomic and network analyses further indicated associations with altered cell-cycle regulation, mitochondrial metabolic programs, and protein-homeostasis-related stress responses. This complementary approach combines quantitative characterization of cellular toxicodynamics (TD) with transcriptomic contextualization and supports further exposure-oriented interpretation using physiologically-based toxicokinetic–TD modeling.