Analysis of Polycyclic Aromatic Hydrocarbons and Phthalate Esters in Soil and Food Grains from the Balkan Peninsula: Implication on DNA Adduct Formation by Aristolochic Acid I and Balkan Endemic Nephropathy

Combustion-Derived Pollutants Linked with Kidney Disease in Low-Lying Flood-Affected Areas in the Balkans

Tens of thousands of people in southern Europe suffer from Balkan endemic nephropathy (BEN), and four times as many are at risk. Incidental ingestion of aristolochic acids (AAs), stemming from the ubiquitousAristolochia clematitis(birthwort) weed in the region, leads to DNA adduct-induced toxicity in kidney cells, the primary cause of BEN. Numerous cofactors, including toxic organics and metals, have been investigated, but all have shown small contributions to the overall BEN relative to non-BEN village distribution gradients. Here, we reveal that combustion-derived pollutants from wood and coal burning in Serbia also contaminate arable soil and test as plausible causative factors of BEN. Using a GC-MS screening method, biomass-burning-derived furfural and coal-burning-derived medium-chain alkanes were detected in soil samples from BEN endemic areas levels at up to 63-times and 14-times higher, respectively, than in nonendemic areas. Significantly higher amounts were also detected in colocated wheat grains. Coexposure studies with cultured kidney cells showed that these pollutants enhance DNA adduct formation by AA, - the cause of AA nephrotoxicity and carcinogenicity. With the coincidence of birthwort-derived AAs and the widespread practice of biomass and coal burning for household cooking and heating purposes and agricultural burning in rural low-lying flood-affected areas in the Balkans, these results implicate combustion-derived pollutants in promoting the development of BEN.

Development and Application of a Comprehensive Nontargeted Screening Strategy for Aristolochic Acid Analogues

Aristolochic acid analogs (AAAs) are naturally occurring carcinogenic and toxic compounds that pose a safety threat to pharmaceuticals and the environment. It is challenging to screen AAAs due to their lack of characteristic mass spectral fragmentation and their presence of structural diversity. A comprehensive nontargeted screening strategy was proposed by taking into account diverse factors and incorporating various self-developed techniques, and a Python3-based toolkit called AAAs_finder was developed for its implementation. The main procedures consist of virtual structure and ultraviolet and visible (UV) spectra database creation, exact mass and UV spectra-based suspect data extraction, tandem mass spectra (MS/MS) anthropomorphic interpretation, and multicondition retention time (RT) prediction-based candidate structures ranking. To initially assess screening feasibility, eight hypothetical unknown samples were subjected to nontargeted screening using the AAAs_finder toolkit and two other advanced tools. The results showed that the former successfully identified all, while the latter two only managed to identify two and three, respectively, indicating that our strategy was more feasible. After that, the strategy was carefully evaluated for false positives and false negatives, instrument dependence, reproducibility, and sensitivity. After the evaluation, the strategy was successfully applied to the screening of AAAs in real samples, such as herbal medicine, spiked soil, and water. Overall, this study proposed a nontargeted screening strategy and toolkit independent of characteristic mass spectral fragmentation and able to overcome challenges posed by structural diversity for the AAAs screening, which is also valuable for other classes of compounds.

Exogenous IAA application affects the specific characteristics of fluoranthene distribution in Arabidopsis

Indole-3-acetic acid (IAA) is a crucial growth regulator involved in the accumulation of polycyclic aromatic hydrocarbons (PAHs). However, the precise physiological and molecular mechanisms underlying IAA-mediated plant growth and PAH accumulation are not yet fully understood. In this study, two distinct IAA-sensitive genotypes of Arabidopsis thaliana (wild type and Axr5 mutant) were chosen to investigate the mechanisms of fluoranthene (Flu) uptake and accumulation in plant tissues (roots and leaves) through physiological and molecular analyses. The results revealed that the Flu concentration in Axr5 leaves was significantly higher than that in wild-type (WT) leaves. In roots, the Flu content decreased significantly with increasing IAA treatment, while no significant changes were observed with lower IAA treatment. Principal component analysis demonstrated that Flu accumulation in Arabidopsis roots was associated with IAA concentrations, whereas Flu accumulation in leaves was dependent on the genotype. Moreover, Flu accumulation showed a positive correlation with the activity of glutathione S-transferase (GST) and root length and a positive correlation with catalase (CAT) and peroxidase (POD) activity in the leaves. Transcriptome analysis confirmed that the expression of the ethylene-related gene ATERF6 and GST-related genes ATGSTF14 and ATGSTU27 in roots, as well as the POD-related genes AtPRX9 and AtPRX25 and CAT-related gene AtCAT3 in leaves, played a role in Flu accumulation. Furthermore, WRKY transcription factors (TFs) in roots and NAC TFs in leaves were identified as important regulators of Flu accumulation. Understanding the mechanisms of Flu uptake and accumulation in A. thaliana provides valuable insights for regulating PAH accumulation in plants.

Aristolochic acid I exposure triggers ovarian dysfunction by activating NLRP3 inflammasome and affecting mitochondrial homeostasis

Aristolochic acids are widely distributed in the plants of Aristolochiaceae family and Asarum species. Aristolochic acid I (AAI) is the most frequent compound of aristolochic acids, which can accumulate in the soil, and then contaminates crops and water and enters the human body. Research has shown that AAI affects the reproductive system. However, the mechanism of AAI's effects on the ovaries at the tissue level still needs to be clarified. In this research, we found AAI exposure reduced the body and ovarian growth in mice, decreased the ovarian coefficient, prevented follicular development, and increased atretic follicles. Further experiments showed that AAI upregulated nuclear factor-κB and tumor necrosis factor-α expression, activated the NOD-like receptor protein 3 inflammasome, and led to ovarian inflammation and fibrosis. AAI also affected mitochondrial complex function and the balance between mitochondrial fusion and division. Metabolomic results also showed ovarian inflammation and mitochondrial dysfunction due to AAI exposure. These disruptions reduced the oocyte developmental potential by forming abnormal microtubule organizing centers and expressing abnormal BubR1 to destroy spindle assembly. In summary, AAI exposure triggers ovarian inflammation and fibrosis, affecting the oocyte developmental potential.

Effects of Diet on Aristolochic Acid-DNA Adduct Formation: Implications for Balkan Endemic Nephropathy Etiology

Prolonged exposure to aristolochic acids (AAs) through AA-containing herbal medicine or AA-contaminated food is associated with the development of aristolochic acid nephropathy (AAN) and Balkan endemic nephropathy (BEN), both public health risks to which the World Health Organization is calling for global action to remove exposure sources. The AA exposure-induced DNA damage is believed to be related to both the nephrotoxicity and carcinogenicity of AA observed in patients suffering from BEN. While the chemical toxicology of AA is well-studied, we investigated in this study the understated effect of different nutrients, food additives, or health supplements on DNA adduct formation by aristolochic acid I (AA-I). By culturing human embryonic kidney cells in an AAI-containing medium enriched with different nutrients, results showed that cells cultured in fatty acid-, acetic acid-, and amino acid-enriched media produced ALI-dA adducts at significantly higher frequencies than that cultured in the normal medium. ALI-dA adduct formation was most sensitive to amino acids, indicating that amino acid- or protein-rich diets might lead to a higher risk of mutation and even cancer. On the other hand, cells cultured in media supplemented with sodium bicarbonate, GSH, and NAC reduced ALI-dA adduct formation rates, which sheds light on their potential use as risk-mitigating strategies for people at risk of AA exposure. It is anticipated that the results of this study will help to better understand the effect of dietary habits on cancer and BEN development.

Bioaccumulation and DNA Adduct Formation of Aristolactam I: Unmasking a Toxicological Mechanism in the Pathophysiology of Aristolochic Acid Nephropathy

Prolonged exposure to aristolochic acid (AA) through AA-containing herbal medicines or AA-tainted food is putting a large portion of the global population at risk of developing renal fibrosis and tumors of the upper urinary tract. In an effort to better understand the organotropic property of AA, we studied the cytotoxicity, absorption, oxidative-stress inducing potential, and DNA adduct formation capability of aristolactam I (ALI), one of the major urinary metabolites of aristolochic acid I (AAI) in human cells. Despite ALI having a slightly lower cytotoxicity than that of AAI, the analysis revealed, for the first time, that ALI is bioaccumulated 900 times more than that of AAI inside cultured kidney cells. Furthermore, ALI induced a significantly larger glutathione depletion than that of AAI in the exposed cells. Together with the formation of ALI-DNA adduct at a reasonably high abundance, results of this study unmasked a previously disregarded causative role of ALI in the organotropic tumor-targeting property of AA.

Wide occurrence of seven phthalate plasticizers and two typical microplastics in pig feed

Plastics are widely used as packaging and engineering materials in feed processing, which leads to the potential contamination of plasticizers and microplastics (MPs) in animal feeds. In this study, the concentrations of two typical MPs, i.e., polyethylene terephthalate (PET) and polycarbonate (PC), and seven phthalates (PAEs) as well as their corresponding monoester metabolites (mPAEs) in 45 pig feed samples in China were analyzed by mass spectrometers. Among PAEs, dibutyl phthalate (DBP) and bis(2-ethylhexyl) phthalate (DEHP) were detected in all samples, and DEHP showed the highest concentrations of 8.26-2464 μg/kg, which accounted for 65.6% of the total detected PAEs. PET MPs (<MDL-302 μg/kg) were detected in 97.8% of samples. Meanwhile, mPAEs were also detected in feed samples with high detection rates but of much lower concentrations. A significantly positive correlation was observed between DEHP and PET MPs. This indicates that the sources of DEHP and MPs in feeds are homologous, mainly from processing and packaging. Besides, the significantly positive correlations between DBP/DEHP and mBP/mEHP indicated the degradation of PAEs to mPAEs during feed production and transportation. The estimated daily intake (EDI) of PAEs and PET MPs were 2.40-70.3 and 0.800-7.79 μg/kg-bw-day, respectively. The results of this study provided new insight into the first evidence of the co-occurrence and risk of MPs, PAE, and mPAEs in pig feed.

Polyurethane Foam Face Masks as a Dosimeter for Quantifying Personal Exposure to Airborne Volatile and Semi-Volatile Organic Compounds

Airborne volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs) are commonly quantitated by collecting the analytes on solid sorbent tubes or passive air samplers, followed by solvent extraction and instrumental analysis, or by grab bag/canister measurements. We report herein a user-friendly sampling method by breathing through polyurethane foam (PUF) face masks to collect airborne VOCs and SVOCs for chemical analysis. Specifically, dibasic esters, phthalate esters, polycyclic aromatic hydrocarbons, linalool, and nicotine trapped on PUF masks were quantitated by gas chromatography-mass spectrometry analysis as model VOCs and SVOCs. Results showed that the amount of these model VOCs and SVOCs trapped on PUF masks is proportional to the exposure duration. After cross-validation by parallel sampling using XAD-2 packed sorbent tubes, the method was used to quantitate VOCs and SVOCs in a variety of indoor and outdoor environments with varying air concentrations of analytes, temperature, humidity, and wind speed. Because air pollution is considered a major cause of many human diseases and premature deaths and the developed PUF mask sampling method showed high trapping efficiencies for both VOCs and SVOCs, it is believed that the developed sampling method will find wide application in assessing air pollution-associated disease risks with possible extension to more classes of VOCs and SVOCs when coupled with suitable instrumental detection methods.

Aristolochic acid I as an emerging biogenic contaminant involved in chronic kidney diseases: A comprehensive review on exposure pathways, environmental health issues and future challenges

Described in the 1950s, Balkan Endemic Nephropathy (BEN) has been recognized as a chronic kidney disease (CKD) with clinical peculiarities and multiple etiological factors. Environmental contaminants - aromatic compounds, mycotoxins and phytotoxins like aristolochic acids (AAs) - polluting food and drinking water sources, were incriminated in BEN, due to their nephrotoxic and carcinogenic properties. The implication of AAs in BEN etiology is currently a highly debated topic due to the fact that they are found within the Aristolochiaceae plants family, used around the globe as traditional medicine and they were also incriminated in Aristolochic Acid Nephropathy (AAN). Exposure pathways have been investigated, but it is unclear to what extent AAs are acting alone or in synergy with other cofactors (environmental, genetics) in triggering kidney damage. Experimental studies strengthen the hypothesis that AAI, the most studied compound in the AAs class, is a significant environmental contaminant and a most important causative factor of BEN. The aim of this review is to compile information about the natural exposure pathways to AAI, via traditional medicinal plants, soil, crop plants, water, food, air. Data that either supports or contradicts the AAI theory concerning BEN etiology was consolidated and available solutions to reduce human exposure were discussed. Because AAI is a phytotoxin with physicochemical properties that allow its transportation in environmental matrices from different types of areas (endemic, nonendemic), and induce CKDs (BEN, AAN) and urinary cancers through bioaccumulation, this review aims to shed a new light on this compound as a biogenic emerging pollutant.

Fetal exposure of Aristolochic Acid I undermines ovarian reserve by disturbing primordial folliculogenesis

The primordial follicle pool established in early life determines the ovarian reserve in the female reproductive lifespan. Premature exhaustion of primordial follicles contributes to primary ovarian insufficiency (POI), that is dependent by the initial size of the primordial follicle pool and by the rate of its activation and depletion. AAI, a powerful nephrotoxin with carcinogenic potential, is present in the Aristolochiaceae species, which can release AAI into soil as a persistent pollutant. In order to assess the potential risk of Aristolochic Acid I (AAI) exposure on mammalian oogenesis, we uncovered its adverse effect on primordial folliculogenesis in the neonatal mouse ovary and its effect on female fertility in adulthood. Pregnant mice were orally administrated with doses of AAI without hepatic or renal toxicity during late-gestation. Ovaries from offspring of administered female displayed gross aberrations during primordial folliculogenesis. Also, unenclosed oocytes in germ-cell cysts showed increased DNA damage. Furthermore, several key factors, including NANOS3, SOX9, KLF4, that govern early gonad's differentiation were abnormally expressed in the exposed ovary, while the follicle formation was partially restored by knockdown of Nanos3 or sox9. In adulthood, these aberrations evolved into a significant reduction in offspring number and impaired ovarian reserve. Together, our results show that AAI influences primordial folliculogenesis and, importantly, affected female fertility. This study shows that administration of drugs herbs or consumption of vegetables that contain AAs during pregnancy may adversely influence the fertility of offspring.

Synergistic Interaction of Polycyclic Aromatic Hydrocarbons, Phthalate Esters, or Phenol on DNA Adduct Formation by Aristolochic Acid I: Insights into the Etiology of Balkan Endemic Nephropathy

Balkan endemic nephropathy (BEN) is a multifactorial environmental disease, with chronic exposure to aristolochic acids (AAs) through AA-contaminated food being one of the major etiological mechanisms. However, the bulk of previous research has only focused on investigating the possible roles of individual pollutants in disease development and the etiological mechanism of BEN remains controversial. In this study, we investigated the exposure concentration and duration dependence of coexposure to phthalate esters and lignite coal-derived phenol and polycyclic aromatic hydrocarbons (PAHs) on the metabolism and DNA adduct formation of aristolochic acid I (AAI). Results showed that both the metabolic activation and DNA adduct formation of AAI in cultured human kidney cells were affected by their coexposure to the above-mentioned environmental pollutants. Furthermore, our results suggest that chemicals leached from lignite coal likely played a role by triggering AA-activating enzymes to produce more of the promutagenic DNA adducts, thus further elevating the nephrotoxicity and carcinogenicity of AAs and increasing the risk of BEN. It is believed that the results of this study provide a better understanding of the etiological mechanism of BEN and offer insights into methods and policies to lower the risk of this devastating disease.

The reaction laws and toxicity effects of phthalate acid esters (PAEs) ozonation degradation on the troposphere

Low-molecular-weight (LMW) phthalate acid esters (PAEs) tend to enter the atmosphere, flying for several kilometers, so it is easy to endanger human health. This work is the first to use quantum chemistry calculations (Gaussian 16 program) and computational toxicology (ECOSAR, TEST, and Toxtree software) to comprehensively study the ozonolysis mechanism of six LMW PAEs (dimethyl phthalate (DMP), diethyl phthalate (DEP), dipropyl phthalate (DPP), diisopropyl phthalate (DIP), dibutyl phthalate (DBP), and diisobutyl phthalate (DIBP)) in the atmosphere and the toxicity of DMP (take DMP as an example) in the conversion process. The results show that the electron-donating effect of the ortho position of the LMW PAEs has the most obvious influence on the ozonolysis. We summarized the ozonation reaction law of LMW PAEs at the optimal reaction site. At 298 K, the law of initial ozonolysis total rate constant of the LMW PAEs is k_DIP > k_DPP > k_DIBP > k_DMP > k_DEP > k_DBP, and the range is 9.56 × 10^-25 cm³ molecule^-1 s^-1 - 1.47 × 10^-22 cm³ molecule^-1 s^-1. According to the results of toxicity assessment, the toxicity of products is lower than DMP for aquatic organisms after ozonolysis. But those products have mutagenicity, developmental toxicity, non-genotoxicity, carcinogenicity, and corrosiveness to the skin. The proposed ozonolysis mechanism promotes our understanding of the environmental risks of PAEs and provides new ideas for studying the degradation of PAEs in the tropospheric gas phase.