A Multi-Route Permeability-Limited Physiologically-Based Kinetic Model for Perfluorooctanoic Acid (PFOA) Exposure of in Male and Female Rats

Paraskevi Papakyriakopoulou, Periklis Tsiros, Vassilis Minadakis, Haralambos Sarimveis Affiliation: School of Chemical Engineering, National Technical University of Athens, 157 80 Athens, Greece A Multi-Route Permeability-Limited Physiologically-Based Kinetic Model for Perfluorooctanoic Acid (PFOA) Exposure of in Male and Female Rats Introduction Perand polyfluoroalkyl substances (PFAS), persistent synthetic chemicals prevalent in industrial and consumer applications. Among them, perfluorooctanoic acid (PFOA) is one of the most studied congeners due to its widespread detection in humans. Notably, it has been detected in up to 99% of individuals in the U.S. population and is linked to various adverse health effects [1]. While ingestion of contaminated food and water is the primary exposure route, inhalation also contributes to human PFOA intake, particularly in occupational settings. In this context, the present study develops a detailed physiologically-based kinetic (PBK) model for rats that offers a mechanistic framework for simulating the absorption, distribution, and excretion of PFOA across various organs and tissues and understanding key processes that affect its internal disposition. Methods The model builds upon and extends previous modelling attempts [2,3], incorporating 16 compartments and using a middleout approach, with parameterization through both in vitro and in vivo data. Specifically, five in vivo studies were employed for parameter calibration The model accounts for various administration routes including intravenous, oral, and inhalation. Passive diffusion, through paracellular and transcellular pathways, and active transport mediated by membrane transporters were included to characterize tissue-specific distribution processes. Different doses (0.041 to 320 mg/kg BW) and both sexes, validated through five independent datasets. Sensitivity analysis identified key influential parameters governing the internal disposition of PFOA. Results ✓ Extensive validation of the PBK model across multiple doses showed excellent predictive accuracy for plasma, tissue, and excreta concentrations with reliable capture of sex-specific biodistribution differences, with predicted concentrations generally falling within a 2– 3 fold error margin compared to observed experimental values. ✓Sex-specific renal factors were critical for accurate predictions. Testing different parameter combinations showed that variation in Oatp1a1 transporter expression alone could explain the faster PFOA elimination in females ✓Based on the in vitro apparent permeability used to parameterise transcellular capillary diffusion, the estimated paracellular pathway dominated the exchange between capillary and interstitial space. Overall, the model highlights the importance of albumin binding, renal reabsorption, as well as paracellular diffusion in shaping male and female rat PFOA dynamics across multiple routes. Figure 1. Schematic representation of the full-body PFOA PBK model in rats. Two compartments were used to represent the blood pool, namely venous blood and arterial blood. Fourteen compartments are vertically aligned, representing various organs/tissues (kidney, liver, stomach, intestine, lung, spleen, heart, brain, muscle, adipose, gonads, skin, upper airways, and rest of body). Figure 2. Schematic representation of a generic organ compartment in the PFOA PBK model. Three subcompartments were used to represent the regional blood (iB), interstitial fluid (iF) and intracellular space (iT). Figure 3. Schematic representation of the detailed kidney compartmentalization employed. Explicit compartment were used for proximal tubule cells (PTCs), loop of Henle cells (LHCs), distal tubule cells (DTCs), collecting duct cells (CDCs) and rest of kidney cells (KTrest). All cells communicated with the corresponding tubule segment through the apical membrane and with the interstitial space through the basal membrane. Transporters were assumed to be expressed only in the proximal tubule cells. Acknowledgements This work has been financially supported by the SCENARIOS project (Grant Agreement 101037509) which has been funded by the European Commission under the Horizon 2020 Programme. References 1. Schlezinger JJ, Hyötyläinen T, Sinioja T, Boston C, Puckett H, Oliver J, Heiger-Bernays W, Webster TF. Perfluorooctanoic acid induces liver and serum dyslipidemia in humanized PPARαmice fed an American diet. Toxicol Appl Pharmacol. 2021 Sep 1;426:115644. doi: 10.1016/j.taap.2021.115644 2. Worley RR, Fisher J. Application of physiologically-based pharmacokinetic modeling to explore the role of kidney transporters in renal reabsorption of perfluorooctanoic acid in the rat. Toxicol Appl Pharmacol. 2015 Dec 15;289(3):42841. doi: 10.1016/j.taap.2015.10.017 3. Cheng W, Ng CA. A Permeability-Limited Physiologically Based Pharmacokinetic (PBPK) Model for Perfluorooctanoic acid (PFOA) in Male Rats. Environ Sci Technol. 2017 Sep 5;51(17):9930-9939. doi: 10.1021/acs.est.7b02602 EUROTOX Congress 2025 n RMSE MAE within 2-fold within 3-fold within 10-fold 395 0.4305 0.3225 55.94 84.81 96.20 P25-24 Figure 4. Predicted versus observed tissue and serum concentrations, as well as excreta masses. The validation dataset included five independent studies in male and female rats, covering intravenous, oral, and inhalation exposures across a wide dose range. Figure 5. Comparison of paracellular and transcellular flux across model organs. Transcellular flux was calculated as the product of capillary surface area and in vitro-derived apparent permeability, while paracellular flux was calculated using an estimated paracellular permeability coefficient and organ-specific capillary gap surface area.