The development of a physiologically-based pharmacokinetic model using the distribution of 2,3,7,8-tetrachlorodibenzo-p-dioxin in the tissues of the eastern oyster (Crassostrea virginica)

Recent Progress on Physiologically Based Pharmacokinetic (PBPK) Model: A Review Based on Bibliometrics

Physiologically based pharmacokinetic/toxicokinetic (PBPK/PBTK) models are designed to elucidate the mechanism of chemical compound action in organisms based on the physiological, biochemical, anatomical, and thermodynamic properties of organisms. After nearly a century of research and practice, good results have been achieved in the fields of medicine, environmental science, and ecology. However, there is currently a lack of a more systematic review of progress in the main research directions of PBPK models, especially a more comprehensive understanding of the application in aquatic environmental research. In this review, a total of 3974 articles related to PBPK models from 1996 to 24 March 2024 were collected. Then, the main research areas of the PBPK model were categorized based on the keyword co-occurrence maps and cluster maps obtained by CiteSpace. The results showed that research related to medicine is the main application area of PBPK. Four major research directions included in the medical field were "drug assessment", "cross-species prediction", "drug-drug interactions", and "pediatrics and pregnancy drug development", in which "drug assessment" accounted for 55% of the total publication volume. In addition, bibliometric analyses indicated a rapid growth trend in the application in the field of environmental research, especially in predicting the residual levels in organisms and revealing the relationship between internal and external exposure. Despite facing the limitation of insufficient species-specific parameters, the PBPK model is still an effective tool for improving the understanding of chemical-biological effectiveness and will provide a theoretical basis for accurately assessing potential risks to ecosystems and human health. The combination with the quantitative structure-activity relationship model, Bayesian method, and machine learning technology are potential solutions to the previous research gaps.

An Arsenic-76 radiotracer to study the routes of assimilation, hemolymph distribution, and tissue inventories in the bioindicator organism Pomacea canaliculata

The aim of this work was to study the absorption, distribution through the hemolymph, and bioaccumulation of arsenic by the freshwater Pomacea canaliculata using a short-lived tracer (⁷⁶As, t_1/2: 1.07 d) with high specific activity. Arsenic travels mainly dissolved in the plasma of the snail's hemolymph. This element is transferred from the hemolymph to the tissues (87%) 4 h after the inoculation of 50 μL of a 0.04 g/L of ⁷⁶As radiotracer solution, being the digestive gland, kidney, and head-foot the main places of arsenical inventories. Snails exhibited a rapid arsenic accumulation response in a wide range of concentrations (from 1 to 1000 μg/L) of the metalloid dissolved in water and in a concentration-dependent manner. Also, snails incorporated As from the digestive system when they received a single safe dose of ~2 μg of ⁷⁶As inoculated in a fish food pellet. The (semi) physiologically based toxicokinetic model developed in this study is based on anatomical and physiological parameters (blood flow, irrigation, tissue volume and other). Together, these findings make P. canaliculata an excellent sentinel organism to evaluate freshwater bodies naturally contaminated with As.

Toxicokinetic models and related tools in environmental risk assessment of chemicals

Environmental risk assessment of chemicals for the protection of ecosystems integrity is a key regulatory and scientific research field which is undergoing constant development in modelling approaches and harmonisation with human risk assessment. This review focuses on state-of-the-art toxicokinetic tools and models that have been applied to terrestrial and aquatic species relevant to environmental risk assessment of chemicals. Both empirical and mechanistic toxicokinetic models are discussed using the results of extensive literature searches together with tools and software for their calibration and an overview of applications in environmental risk assessment. These include simple tools such as one-compartment models, multi-compartment models to physiologically-based toxicokinetic (PBTK) models, mostly available for aquatic species such as fish species and a number of chemical classes including plant protection products, metals, persistent organic pollutants, nanoparticles. Data gaps and further research needs are highlighted.

A physiologically based toxicokinetic and toxicodynamic model links the tissue distribution of benzo[a]pyrene and toxic effects in the scallop Chlamys farreri

A physiologically based toxicokinetic and toxicodynamic (PBTK-TD) model was developed for benzo[a]pyrene (B[a]P) in scallop Chlamys farreri. The PBTK model structure consisted of gill, digestive gland, adductor muscle, hemolymph and other tissues. In TD modeling, aryl hydrocarbon hydroxylase (AHH) activity assay, comet assay, protein carbonyl measurement and lipid peroxidation level determination in digestive gland were used as biomarkers to reflect toxic effects. We integrated B[a]P concentration and biomarkers by using sigmoid Emax model in digestive gland. The PBTK-TD model predicted the B[a]P concentrations within each organ compartment and the toxic effects in digestive gland. The results showed that the predicted and measured data in different organs were in good agreement and comet assay was considered as the best biomarker. This model would serve as a useful tool for pollution monitoring and food security.

Tissue-specific expression of p53 and ras genes in response to the environmental genotoxicant benzo(α)pyrene in marine mussels

Marine mussels can develop hemeic and gonadal neoplasia in the natural environment. Associated with these diseases are the tumor suppressor (TS) p53 and the proto-oncogene ras coded proteins, both of which are highly conserved among molluscs and vertebrates. We report, for the first time, tissue-specific expression analysis of p53 and ras genes in Mytilus edulis by means of quantitative RT-PCR. A tissue-specific response was observed after 6 and 12 days exposure to a sublethal concentration of a model Polycyclic Aromatic Hydrocarbon (PAH), benzo(α)pyrene (B(α)P). This sublethal concentration (56 μg/L) was selected based on an integrated biomarker analysis carried out prior to gene expression analysis, which included a 'clearance rate' assay, histopathological analysis, and DNA strand break measurements. The results indicated that the selected concentration of B(α)P can lead to the induction of DNA strand breaks, tissue damage, and expression of tumor-regulating genes. Both p53 and ras are expressed in a tissue-specific manner, which collaborate with tissue-specific function in response to genotoxic stress. The integrated biological responses in Mytilus edulis strengthen the use of this organism to investigate the fundamental mechanism of development of malignancy in invertebrate which could be translated to other organisms including humans.

A model for estimating the potential biomagnification of chemicals in a generic food web: preliminary development

GOAL, SCOPE AND BACKGROUND

Bioaccumulation and biomagnification of organic pollutants have been increasingly assessed and modeled during the last years. Due to the complexity of these processes and the large variability of food webs, setting generic assessments for these parameters is really difficult. Equilibrium models, based on a compound's lipophylicity, are the main tool in regulatory proposals, such as for identifying Persistent, Bioaccumulative and Toxic Substances (PBTs), although a refinement has been claimed by the scientific community. Toxicokinetic studies offer an alternative for these estimations, where biomagnification is modeled as a succession of bioaccumulation processes, each one regulated by toxicokinetic parameters.

METHODS

A review of kinetic models covering species belonging to different trophic levels and with different ecological behavior has been conducted. The results were employed for setting a conceptual model for estimating the biomagnification potential in a generic food web, which was mathematically implemented through system dynamic models developed under data sheet software. Crystal Ball was then employed for allowing Monte Carlo based probabilistic calculations. Bioaccumulation laboratory assays have been performed to estimate toxicokinetic parameters in mussels (Mytilus edulis) with two PAHs (chrysene and benzo[a]pyrene). The contamination was delivered via food. The exposure period lasted more than one month followed then by a depuration phase. The contaminant content was determined on an individual basis on five replicates.

RESULTS AND DISCUSSION

. The reviewed information suggested the development of a tiered conceptual biomagnification model, starting with a simplified food chain which can be refined to more realistic and complex models in successive levels.

CONCLUSIONS

The mathematical implementation of the conceptual model offers tools for estimating the potential for bioaccumulation and biomagnification of chemicals under very different conditions. The versatility of the model can be used for both comparative estimations and for validating the model.

RECOMMENDATIONS AND PERSPECTIVES

Since bioaccumulation and biomagnification processes are crucial elements for a proper risk assessment of chemicals, their estimation by mathematical models has been widely tested. However, inregulatory assessments, too simplistic models are still being used quite often. The biomagnification model presented in this study should be amore accurate alternative to these models. In comparison to other previously published biomagnification models, the present one covers the time variation of bioaccumulation using just a few toxicokinetic parameters.

Whole-body physiologically based pharmacokinetic models

This review summarizes the most recent developments in and applications of physiologically based pharmacokinetic (PBPK) modeling methodology originating from both the pharmaceutical and environmental toxicology areas. It focuses on works published in the last 5 years, although older seminal papers have also been referenced. After a brief introduction to the field and several essential definitions, the main body of the text is structured to follow the major steps of a typical PBPK modeling exercise. Various applications of the methodology are briefly described. The major future trends and perspectives are outlined. The main conclusion from the review of the available literature is that PBPK modeling, despite its obvious potential and recent incremental developments, has not taken the place it deserves, especially in pharmaceutical and drug development sciences.

The development of an aquatic bivalve model: evaluating the toxic effects on gametogenesis following 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) exposure in the eastern oyster (Crassostrea virginica)

The objective of this study is to develop a gametogenesis protocol to serve as a model for evaluating the toxic effects of chemicals on oogenesis and spermatogenesis in the eastern oyster (Crassostrea virginica). The compound 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) was selected as a "proof of principle" toxicant to examine developmental toxicity in this invertebrate system. The studies were designed to: (1) test the model using 2,3,7,8-TCDD and (2) to use histopathological evaluations to characterize the effects on oocyte and sperm development during stages of gametogenesis. 2,3,7,8-TCDD at 10 pg/g resulted in significant histopathological gonadal lesions by day 14 of gametogenesis in both female and male oysters. These lesions resulted in complete inhibition of gonadogenesis. Studies also showed that a total body dose of 2 and 10 pg/g 2,3,7,8-TCDD caused adverse responses resulting in abnormal gametogenesis in female and male oysters, respectively, such as: (1) incomplete oocyte division, (2) inhibition of oocyte growth and maturation, (3) unsynchronized sperm development, and (4) inhibition of spermatogenesis. The eastern oyster is one of the most responsive invertebrate models tested to date for reproductive effects of chemicals. Therefore, the eastern oyster can be used as a sensitive toxicological model for examining the effects of dioxin-like compounds and other xenobiotics on gametogenesis. The reported studies show that environmentally relevant concentrations of 2,3,7,8-TCDD (2-10 pg/g) have a significant adverse effect on oyster gametogenesis.

Small is useful in endocrine disrupter assessment--four key recommendations for aquatic invertebrate research

As we enter the 21st "biocentury", with issues such as biodiversity and biotechnology growing in public profile, it is important to reflect on the immense ecological, medical and economic importance of invertebrates. Efforts to understand the diverse biology of invertebrates come from many directions, including Nobel Prize winning developmental biology, research to control insects that threaten human health and food supplies, aquaculture opportunities and also within ecotoxicology. In the latter context, this special journal volume highlights the importance of addressing endocrine disruption in aquatic invertebrates, from molecular and cellular biomarkers to population-relevant adverse effects. The contributors to this special volume have provided an excellent assessment of both the fundamental endocrinology and applied ecotoxicology of many aquatic invertebrate groups. On the premise that reproductive success is ultimately the vital population parameter, this chapter gives a personal view of key gaps in knowledge in invertebrate reproductive and developmental endocrinology and ecotoxicology. Based on current knowledge, there are four key issues that need to be prioritised within aquatic ecotoxicology: (1) a wider assessment of the reproductive status of invertebrates in both freshwater and coastal ecosystems; (2) prioritisation of laboratory studies in OECD and other regulatory test organisms, including basic endocrinology and ADME (absorption, distribution, metabolism and excretion) research; (3) development and validation of mechanistic biomarkers that can be used as "signposts" to help prioritise species and chronic test endpoint selection, and help link data from laboratory and field studies; and (4) develop a comparative invertebrate toxicology database utilising the prioritised reference chemicals from the EDIETA workshop, encompassing the diverse modes-of-action pertinent to endocrine disrupter testing in both aquatic arthropod and non-arthropod invertebrates.