Binding Affinity and Mechanism of Six PFAS with Human Serum Albumin: Insights from Multi-Spectroscopy, DFT and Molecular Dynamics Approaches

Integrated computational analysis of molecular mechanisms underlying perfluorooctane sulfonic acid induced thyroid toxicity

Perfluorooctane sulfonic acid (PFOS), a persistent organic pollutant, significantly disrupts thyroid function. This study presented an integrated computational approach, combining network toxicology, molecular docking, and molecular dynamics simulations to systematically elucidate the molecular mechanisms underlying PFOS induced thyroid toxicity. Through integrated analysis of the Comparative Toxicogenomics Database (CTD), GeneCards, and Online Mendelian Inheritance in Man (OMIM) databases, we identified 205 potential thyroid toxicity-related targets. Protein-protein interaction network analysis revealed 34 hub targets, with TP53, JUN, ESR1, AKT1, and CTNNB1 emerging as central nodes in the toxicity network. Functional enrichment analysis demonstrated significant enrichment in the PPAR signaling pathway, fatty acid metabolism, AGE-RAGE pathway, and AMPK pathway, indicating that PFOS influences thyroid function through multiple signaling pathways. Molecular docking studies showed that PFOS forms stable complexes with core target proteins, with binding energies ranging from - 4.9 to -9.7 kcal/mol. Molecular dynamics simulations further validated the structural stability of these complexes, with PFOS-AKT1 and PFOS-TP53 exhibiting the highest conformational stability. This study revealed the multi-target and multi-pathway characteristics of PFOS-induced thyroid toxicity, providing novel insights into its toxicological mechanisms.

Modular Construction of Multivariate Metal-Organic Frameworks for Luminescent Sensing

Metal-organic frameworks (MOFs) have played a pivotal role as rapid and effective luminescent sensing materials. Numerous MOFs with diverse characteristics have been meticulously designed for target analytes. Previous studies have highlighted the factors of spectral characteristics, energy levels, interaction forces, and sensor stabilities for the luminescent sensing performance in response to a specific analyte. This conventional "point-to-point" approach necessitates the matching of sensing materials to a specific analyte. Herein, we develop a modular MOF-based luminescent sensing platform by using a mixed-ligand strategy. A luminescent MOF Eu-FDA with 2,5-furandicarboxylic acid can serve as the foundational platform, with partial replacement by nine distinct hexacyclic isophthalic acids as the modules, respectively, to specifically accommodate different analytes with particular structures and properties. This substitution has been meticulously confirmed through single-crystal X-ray diffraction. Confronted with analytes possessing diverse structural or property characteristics, modular isophthalic acid derivatives can enhance the sensing capability to achieve heightened sensitivity.

Association between exposure to perfluoroalkyl and polyfluoroalkyl substances with estimated glomerular filtration rate: Mediating role of serum albumin

BACKGROUND

Previous studies have demonstrated perfluoroalkyl and polyfluoroalkyl substances (PFAS) impact renal function, with albumin playing dominant role in their transport and accumulation. However, the mediating role of albumin in PFAS-induced renal impairment and the identification of sensitive populations remain uninvestigated.

METHODS

This study included 9328 individuals from NHANES 1999-2018 with data on serum PFAS, creatinine, albumin, and covariates. The estimated glomerular filtration rate (eGFR) was calculated using standardized creatinine. Associations between perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), perfluorohexane sulfonate (PFHxS), and perfluorononanoic acid (PFNA) with eGFR and the risk of decreased renal function (eGFR < 90 vs. eGFR ≥ 90) using linear and logistic regression, weighted quantile sum (WQS) regression, Bayesian kernel machine regression (BKMR), and restricted cubic spline (RCS) analyses. Subgroup analyses identified sensitive populations. Mediation analysis was performed to examine the mediating role of albumin. Comparative toxicology databases identified relevant genes for mechanistic exploration.

RESULTS

Ln-transformed PFOA (β = -1.91, 95 % CI: -2.82 to -1), PFOS (β = -1.48, 95 % CI: -2.19 to -0.78) and PFHxS (β = -0.94, 95 % CI: -1.65 to -0.23) were negatively correlated with eGFR. PFOA (aOR = 1.21, 95 % CI: 1.1-1.32), PFOS (aOR = 1.2, 95 % CI: 1.12-1.29), and PFHxS (aOR = 1.13, 95 % CI: 1.05-1.21) were positively correlated with the risk of decreased renal function. Subgroup analyses indicated that individuals ≤ 45 years, females and other races were more sensitive. Albumin mediated 18.2 %, 16.4 %, 29.8 %, and 18.7 % of the negative effects of PFOA, PFOS, PFHxS, and PFNA on eGFR, respectively. Functional enrichment analysis suggested PFAS impair renal function by affecting lipid metabolism and increasing oxidative stress.

CONCLUSIONS

PFAS exposure is negatively associated with eGFR and positively associated with the risk of decreased renal function, with albumin playing a partial mediating role.

An in vitro and machine learning framework for quantifying serum albumin binding of per- and polyfluoroalkyl substances

Per- and polyfluoroalkyl substances (PFAS) are a diverse class of anthropogenic chemicals; many are persistent, bioaccumulative, and mobile in the environment. Worldwide, PFAS bioaccumulation causes serious adverse health impacts, yet the physiochemical determinants of bioaccumulation and toxicity for most PFAS are not well understood, largely due to experimental data deficiencies. As most PFAS are proteinophilic, protein binding is a critical parameter for predicting PFAS bioaccumulation and toxicity. Among these proteins, human serum albumin (HSA) is the predominant blood transport protein for many PFAS. We previously demonstrated the utility of an in vitro differential scanning fluorimetry assay for determining relative HSA binding affinities for 24 PFAS. Here, we report HSA affinities for 65 structurally diverse PFAS from 20 chemical classes. We leverage these experimental data, and chemical/molecular descriptors of PFAS, to build 7 machine learning classifier algorithms and 9 regression algorithms, and evaluate their performance to identify the best predictive binding models. Evaluation of model accuracy revealed that the top-performing classifier model, logistic regression, had an AUROC (area under the receiver operating characteristic curve) statistic of 0.936. The top-performing regression model, support vector regression, had an R2 of 0.854. These top-performing models were then used to predict HSA-PFAS binding for chemicals in the EPAPFASINV list of 430 PFAS. These developed in vitro and in silico methodologies represent a high-throughput framework for predicting protein-PFAS binding based on empirical data, and generate directly comparable binding data of potential use in predictive modeling of PFAS bioaccumulation and other toxicokinetic endpoints.

Key characteristics of carcinogens meet hallmarks for prevention-cutting the Gordian knot

The complexity of cancer requires a comprehensive approach to understand its diverse manifestations and underlying mechanisms. Initially outlined by Hanahan and Weinberg in 2000 and updated in 2010, the hallmarks of cancer provide a conceptual basis for understanding inherent variability in cancer biology. Recent expansions have further elucidated additional hallmarks, including phenotypic plasticity and senescent cells. The International Agency for Research on Cancer (IARC) has identified the key characteristics of carcinogens (KCCs) to evaluate their carcinogenic potential. We analyzed chemicals of concern for environmental exposure that interact with specific receptors to induce genomic instability, epigenetic alterations, immune suppression, and receptor-mediated effects, thereby contributing to chronic inflammation. Despite their varying degrees of carcinogenicity, these chemicals have similar KCC profiles. Our analysis highlights the pivotal role of receptor binding in activating most other KCCs, underscoring their significance in cancer initiation. Although KCCs are associated with early molecular or cellular events, they do not encompass processes directly linked to full cellular malignancy. Thus, there is a need to integrate clear endpoints that anchor KCCs to the acquisition of a complete malignant phenotype into chemical testing. From the perspective of toxicology and cancer research, an all-encompassing strategy that incorporates both existing and novel KCCs and cancer hallmarks is essential to enable the targeted identification of prevalent carcinogens and facilitate zone-specific prevention strategies. To achieve this goal, collaboration between the KCC and cancer hallmarks communities becomes essential.

Association between per- and polyfluoroalkyl substances exposure and prevalence of chronic obstructive pulmonary disease: The mediating role of serum albumin

BACKGROUND

No study has examined the association between per- and polyfluoroalkyl substances (PFAS) exposure and chronic obstructive pulmonary disease (COPD) risk. This study aims to explore this relationship.

METHODS

This study enrolled 4541 individuals who had available data on PFAS, COPD, and covariates from NHANES 2007-2018. Serum PFAS including perfluorohexane sulfonate (PFHxS), perfluorononanoic acid (PFNA), perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS) were analyzed, because of high detective rates. Considering the skew distribution of PFAS levels, the natural logarithm-transformed PFAS (Ln-PFAS) was used. Logistic regression analysis, restricted cubic spline (RCS), and weighted quantile sum (WQS) regression were performed to explore the single, nonlinear, and mixed effects. A mediating analysis was used to evaluate the mediated effects of albumin.

RESULTS

Individuals with COPD had higher levels of PFHxS, PFNA, PFOA, and PFOS compared to those without COPD. Ln-PFNA (OR males: 1.92, 95 % CI:1.31 to 2.80, P: <0.001; OR females: 1.07, 95 % CI: 0.81 to 1.40, P: 0.636) and ln-PFOA (OR males: 2.17, 95 % CI:1.38 to 3.41, P: <0.001; OR females: 1.49, 95 % CI: 1.08 to 2.05, P: 0.016) were associated with COPD risk especially in males. The interaction between PFNA exposure and sex on COPD risk was significant (P interaction: <0.001). The RCS curve demonstrated the nonlinear relationship between the ln-PFOA (P nonlinear:0.001), ln-PFNA (P nonlinear:0.045), and COPD risk in males. WQS analysis showed mixed PFAS exposure was correlated with COPD risk in males (OR: 1.44, 95 % CI:1.18 to 1.75, P: <0.001). Albumin mediated the relationship between PFOA and COPD (mediated proportion: -17.94 %).

CONCLUSION

This study concludes PFOA and PFNA are linked to a higher COPD risk in males, and serum albumin plays a mediating role in the relationship between PFOA and COPD. Thess findings are beneficial for the prevention of COPD. Further studies are required to explore potential mechanisms.

Quantitative cross-species comparison of serum albumin binding of per- and polyfluoroalkyl substances from five structural classes

Per- and polyfluoroalkyl substances (PFAS) are a class of over 8000 chemicals, many of which are persistent, bioaccumulative, and toxic to humans, livestock, and wildlife. Serum protein binding affinity is instrumental in understanding PFAS toxicity, yet experimental binding data is limited to only a few PFAS congeners. Previously, we demonstrated the usefulness of a high-throughput, in vitro differential scanning fluorimetry assay for determination of relative binding affinities of human serum albumin for 24 PFAS congeners from 6 chemical classes. In the current study, we used this assay to comparatively examine differences in human, bovine, porcine, and rat serum albumin binding of 8 structurally informative PFAS congeners from 5 chemical classes. With the exception of the fluorotelomer alcohol 1H, 1H, 2H, 2H-perfluorooctanol (6:2 FTOH), each PFAS congener bound by human serum albumin was also bound by bovine, porcine, and rat serum albumin. The critical role of the charged functional headgroup in albumin binding was supported by the inability of albumin of each species tested to bind 6:2 FTOH. Significant interspecies differences in serum albumin binding affinities were identified for each of the bound PFAS congeners. Relative to human albumin, perfluoroalkyl carboxylic and sulfonic acids were bound with greater affinity by porcine and rat serum albumin, and the perfluoroalkyl ether acid congener bound with lower affinity to porcine and bovine serum albumin. These comparative affinity data for PFAS binding by serum albumin from human, experimental model, and livestock species reduce critical interspecies uncertainty and improve accuracy of predictive bioaccumulation and toxicity assessments for PFAS.