Determination of Aristolochic Acids in Vegetables: Nephrotoxic and Carcinogenic Environmental Pollutants Contaminating a Broad Swath of the Food Supply and Driving Incidence of Balkan Endemic Nephropathy

Aristolochic Acids and Aristoloxazines Are Widespread in the Soil of Aristolochiaceae Herb Cultivation Fields

The cancer risk associated with aristolochic acid (AA) exposure through the consumption of AA-containing herbal medicine has received tremendous attention in the past decades. However, environmental exposure routes from the associated medicinal herb cultivation fields have received little attention. We reveal through liquid chromatography-tandem mass spectrometry analysis of over 400 soil samples collected from three different Aristolochiaceae herb cultivation fields that AAs, which are nephrotoxic and carcinogenic, and aristoloxazines (AXs), a family of recently identified neurotoxic and genotoxic AA analogues, are widespread pollutants in these areas. In particular, aristoloxazine C was detected for the first time in the environment and was found in 318 out of 320 soil samples, at concentrations as high as 2.8 mg/kg, from an Asarum heterotropoides cultivation field. We show that in fact AXs are ecotoxic, inhibiting plant growth and significantly reducing the soil microorganism population. With the extensive cultivation of Aristolochiaceae herbs in order to meet their market demand, we believe our study points to an important environmental hazard that may place food crops and non-AA/AX-producing medicinal herbs at risk of AA/AX contamination. While previous research focused primarily on the health risks associated with exposure to AAs, this study uncovers environmental exposure as a new human exposure pathway that warrants the attention of both the general public and regulatory agencies.

Palmatine reverse aristolochic acid-induced heart failure through activating EGFR pathway via upregulating IKBKB

Aristolochic acid (AA) is renowned for engendering nephrotoxicity and teratogenicity. Previous literature has reported that AA treatment resulted in heart failure (HF) via inflammatory pathways. Yet, its implications in HF remain comparatively uncharted territory, particularly with respect to underlying mechanisms. In our study, the zebrafish model was employed to delineate the cardiotoxicity of AA exposure and the restorative capacity of a phytogenic alkaloid palmatine (PAL). PAL restored morphology and blood supply in AA-damaged hearts by o-dianisidine staining, fluorescence imaging, and Hematoxylin and Eosin staining. Furthermore, PAL attenuated the detrimental effects of AA on ATPase activity, implying myocardial energy metabolism recovery. PAL decreased the co-localization of neutrophils with cardiomyocytes, implying an attenuation of the inflammatory response induced by AA. A combination of network pharmacological analysis and qPCR validation shed light on the therapeutic mechanism of PAL against AA-induced heart failure via upregulation of the epidermal growth factor receptor (EGFR) signaling pathway. Subsequent evaluations using a transcriptological testing, inhibitor model, and molecular docking assay corroborated PAL as an IKBKB enzyme activator. The study underscores the possible exploitation of the EGFR pathway as a potential therapeutic target for PAL against AA-induced HF, thus furthering the continued investigation of the toxicology and advancement of protective pharmaceuticals for AA.

Catalpol from Rehmannia glutinosa Targets Nrf2/NF-κB Signaling Pathway to Improve Renal Anemia and Fibrosis

Rehmannia glutinosa is widely recognized as a prominent medicinal herb employed by practitioners across various generations for the purpose of fortifying kidney yin. Within Rehmannia glutinosa, the compound known as catalpol (CAT) holds significant importance as a bioactive constituent. However, the protective effects of CAT on kidneys, including ameliorative effects on chronic kidney disease - most prominently renal anemia and renal fibrosis - have not been clearly defined. In this study, the kidney injury model of NRK-52E cells and C57BL/6N male mice was prepared by exposure to aristolochic acid I (AA-I), and it was discovered that CAT could ameliorate oxidative stress injury, inflammatory injury, apoptosis, renal anemia, renal fibrosis, and other renal injuries both in vivo and in vitro. Further treatment of NRK-52E cells with Nrf2 inhibitors (ML385) and activators (ML334), as well as NF-κB inhibitors (PDTC), validated CAT's ability to target Nrf2 activation. Furthermore, the expression of phosphorylated NF-κB p65, IL-6, and Cleaved-Caspase3 protein was inhibited. CAT also inhibited NF-κB, and then inhibited the expression of IL-6, p-STAS3, TGF-β1 protein. Therefore, CAT can regulate Nrf2/NF-κB signaling pathway, significantly correct renal anemia and renal fibrosis, and is conducive to the preservation of renal structure and function, thus achieving a protective effect on the kidneys.

Ratiometric luminescent simultaneous sensing of aristolochic acids (I-IV) by a novel metal-organic framework and its nanowire

Aristolochic acids (AAs), which are a group of nitrophenanthrene carboxylic acids formed by Aristolochia plant, have become an increasing serious threat to humans due to their nephrotoxicity and carcinogenicity. Fast and accurate approaches capable of simultaneous sensing of aristolochic acids (I-IV) are vital to avoid intake of such compounds. In this research, the novel ratiometric fluorescence zinc metal-organic framework and its nanowire have been prepared. The two different coordination modes (tetrahedral configuration and twisted triangular bipyramidal configuration) within zinc metal-organic framework lead to the significant double emissions. The ratiometric fluorescence approach based on nanowire provides a broader concentration range (3.00 × 10-7~1.00 × 10-4 M) and lower limit of detection (3.70 × 10-8 M) than that based on zinc metal-organic framework (1.00 × 10-6~1.00 × 10-4 M, 5.91 × 10-7 M). The RSDs of the results are in the range 1.4-3.5% (nanowire). The density functional theory calculations and UV-Vis absorption verify that the sensing mechanism is due to charge transfer and energy transfer. Excellent spiked recoveries for AAs(I-IV) in soil and water support that nanowire is competent to simultaneously detect these targets in real samples, and the proposed approach has potential as a fluorescence sensing platform for the simultaneous detection of AAs (I-IV) in complex systems.

Effects of Heavy Metal Co-Exposure on the formation of DNA Adducts from Aristolochic Acid I: Implications for Balkan Endemic Nephropathy Development

Accumulated evidence has shown that Balkan endemic nephropathy (BEN) is a multifactorial environmental disease, with exposure to aristolochic acids (AA), and the associated DNA adduct formation, as a key causative factor of BEN development. Here, we show that coexposure to arsenic, cadmium, and iron increases the DNA adduct formation of AA in cultured kidney cells, while exhibiting both an exposure concentration and duration dependence. In contrast, coexposure to calcium and copper showed a decreasing DNA adduct formation. Because DNA damage is responsible for both the nephrotoxicity and carcinogenicity of AA, these results shed greater light on the endemic nature of BEN.

Factors influencing the fate of chemical food safety hazards in the terrestrial circular primary food production system-A comprehensive review

Food safety is recognized as a major hurdle in the transition toward circular food production systems due to the potential reintroduction and accumulation of chemical contaminants in these food systems. Effectively managing these hazardous contaminants in a risk-based manner requires quantitative insights into the factors influencing the presence and fate of contaminants in the entire circular food chain. A systematic literature review was performed to gain an up-to-date overview of the known factors and their influence on the transfer and accumulation of contaminants. This review focused on the terrestrial circular primary food production system, including the pathways between waste- or byproduct-based fertilizers, soil, crops, animal feed, and farmed animals. This review revealed an imbalance in research regarding the different pathways: studies on the soil-to-crop pathway were most abundant. The factors identified can be categorized as compound-related (intrinsic) factors, such as hydrophobicity, molecular weight, and chain length, and extrinsic factors, such as soil organic matter and carbon, pH, milk yield of cows, crop age, and biomass. Quantitative data on the influence of the identified factors were limited. Most studies quantified the influence of individual factors, whereas only a few studies quantified the combined effect of multiple factors. By providing a holistic insight into the influential factors and the quantification of their influence on the fate of contaminants, this review contributes to the improvement of food safety management for chemical hazards when transitioning to a circular food system.

Fabrication of a Simple and Efficient HPLC Reduction Column for Online Conversion of Aristolochic Acids to Aristolactams Prior to Sensitive Fluorescence Detection

Aristolochic acids (AAs) are nephrotoxic and carcinogenic nitrophenanthrene carboxylic acids produced naturally by plants from the Aristolochia and Asarum genera, which have been used extensively as herbal medicines. In addition to consuming AA-containing herbal medicinal products, there is emerging evidence that humans are also exposed to AA through the environment. In 2022, the World Health Organization (WHO) called for global action to remove AA exposure sources and to implement preventative measures against the development of AA-associated cancers. Herein, we report the development of a simple and efficient iron powder-packed reduction column that allows online post-column conversion of the nonfluorescing AA to its corresponding strongly fluorescing aristolactam (AL), facilitating the sensitive and selective detection of AA in herbal medicinal products, food grain, arable soil, or groundwater samples by high-performance liquid chromatography with fluorescence detection. Moreover, AL, a group of naturally occurring derivatives of AA that have demonstrated toxicity to cultured bacteria, human cells, and rats, is monitored and quantified simultaneously with AA in one single run without sacrificing sensitivity. In comparison with existing analytical methods for AA measurement, the newly developed method is not only inexpensive and less laborious, but it also offers improved sensitivity. We believe this novel method will find wide application in identifying the presence of AA in food, herbal medicines, and environmental samples, thus assisting in the identification and removal of AA exposure sources.

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.

Occurrence and stability of PCMX in water environments and its removal by municipal wastewater treatment processes

Para-chloro-meta-xylenol (PCMX) is a synthetic antiseptic used extensively to control the spread of germs and viruses, and as a result, enormous amount of PCMX could be discharged to water environments through drainage. To investigate the extent of PCMX contamination, water samples were collected from rivers and coastal waters in Hong Kong, and PCMX concentrations were determined by a newly developed method using liquid chromatography-tandem mass spectrometry combined with stable isotope-dilution. We discovered widespread PCMX pollution in the water environment. Then, we revealed for the first time that PCMX in wastewater is not effectively removed by chemically enhanced primary treatment (CEPT), one of the wastewater treatment processes used in Hong Kong (∼75% of wastewater) and other megacities around the world. This suggests that the CEPT effluent or the primary treatment effluent is an unintended continuous source of pollution for PCMX in water environments. Finally, we found that PCMX was relatively stable in the water environment and could pose a risk to aquatic organisms. These findings underscore the importance of raising public awareness of the environmental consequences from overuse of PCMX-based disinfectants and the need to reevaluate the various wastewater treatment processes in removing PCMX.

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.

Broad-specificity indirect competitive enzyme-linked immunosorbent assay for aristolochic acids: Computer-aided hapten design and molecular mechanism of antibody recognition

Long-term dietary exposure of aristolochic acids (AAs)-contaminated food proved to be one of the main culprits of Endemic Nephropathy, renal failure; and urothelial cancer. The antibodies utilized in immunoassays for AAs suffer from low affinity and failure of recognition to the family of AAs. This study, we prepared a broad-specificity monoclonal antibody (mAb) 5H5 with highly and uniform affinity for AAs by help of computational chemistry fully exposing the AAs common structures of methoxy and hydroxyl groups. The mAb 5H5 exhibited half inhibitory concentrations of AAA, AAB, AAC, AAD were 0.03, 0.06, 0.05, 0.03 ng/mL. To explain the broad-specificity profile of mAb 5H5, molecular docking was performed. Results shown that multiple conformations of AAs can be flexibly oriented in the spacious cavity of single-chain variable fragment antibody (scFv) 5H5 and the specific hydron bonds were formed by ASN62 and GLY64 of scFV 5H5 to the nitro group of AAs which gave an explanation of the high cross-reactivity of mAb 5H5. The ELISA based on the broad-specificity mAb 5H5with detection limits of 0.04-0.11 μg/kg and 0.02-0.06 μg/kg for four AAs in flour and soil samples, respectively. The study provided a promising method for the family of AAs in environmental and food samples.

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.

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.

Aristolochic acid: What urologists should know

To the Editor, Aristolochic acid is one of major causes for upper tract urothelial carcinoma, especially in younger population. While it is mentioned as a cause in guidelines, little is actually known about the toxin by urologists. We are aiming in our letter to provide some direct and clear information to ourselves that would help us to know more about that toxin and how it can adversely affect our patients [...].

Analysis of aristolochic acid I in mouse serum and tissues by using magnetic solid-phase extraction and UHPLC-MS/MS

A method combining magnetic solid-phase extraction (MSPE) and ultra-high-pressure liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) was developed for the analysis of aristolochic acids I (AAI) in mouse serum and tissues. The magnetic covalent organic frameworks (MNP@COF)-based MSPE exhibited high adsorption capacity towards AAI (93.1 mg/g) in optimal conditions. After MSPE extraction, AAI was separated with C18 column using gradient elution and quantified (m/z 342.21 → 298.13) by UHPLC-MS/MS with monitor reaction monitoring (MRM) mode. This MSPE-based UHPLC-MS/MS method was validated with respected to lower limit of quantification (LLOQ), linearity, recovery, precision and accuracy of intra- and inter-day, and matrix effect. Good calibration linearities at the range of 1-500 ng/L for AAI in biological matrices (serum, kidney, and liver) with high correlation coefficient (R²) > 0.9970, and high enrichment factors (mean values from 1038 to 1045) were obtained. This method was highly sensitive to determine AAI with LLOQ within the range of 4.62-5.24 ng/L in extracted serum, kidney, and liver samples. Recoveries at 5, 50, 100 and 300 ng/L in biological samples ranged from 93.2 to 104.0%, and intra- and inter day accuracy and precision (defined as bias and coefficient of variation, respectively) were below ± 15%. The method was successfully applied in the analysis of biological samples collected from mice exposed with AAI with concentrations range of 0.007-0.041 μg/L for consecutive four days. The established method might be applied for the investigation of risk assessment and toxicity induced by long-time use of AAI-containing herbs or dietary supplements.

Involvement of REV-ERBα dysregulation and ferroptosis in aristolochic acid I-induced renal injury

The molecular events underlying aristolochic acid (AA) nephropathy are poorly understood, and specific therapies for treatment of AA nephropathy are still lacking. Here we aimed to investigate a potential role of REV-ERBα and ferroptosis in renal injury induced by aristolochic acid I (AAI), a typical AA. The regulatory effects of REV-ERBα on AAI-induced renal injury were determined using kidney-specific Rev-erbα knockout mice. Ferroptosis was assessed based on measurements of iron, GSH, and GPX4. Targeted antagonism of REV-ERBα to alleviate AAI-induced renal injury and ferroptosis was assessed using the small molecule antagonist SR8278. mRNAs and proteins were quantified by qPCR and Western blotting, respectively. We first showed that REV-ERBα was upregulated and its target BMAL1 was downregulated in the kidney of mice with AAI nephropathy. Upregulation of REV-ERBα protein was confirmed in aristolactam I (ALI, a nephrotoxic metabolite of AAI)-treated mRTECs. We also observed enhanced ferroptosis (known to be regulated by REV-ERBα) in mice with AAI nephropathy and in ALI-treated mRTECs. Kidney-specific knockout of Rev-erbα reduced the sensitivity of mice to AAI-induced ferroptosis and renal injury. Furthermore, knockdown of Rev-erbα by siRNA or SR8278 (a REV-ERBα antagonist) treatment attenuated ALI-induced ferroptosis in mRTECs. Moreover, REV-ERBα antagonism by SR8278 alleviated ferroptosis and renal injury caused by AAI in mice. In conclusion, we identify REV-ERBα as a regulator of AAI-induced renal injury via promoting ferroptosis. Targeting REV-ERBα may represent a promising approach for management of AAI nephropathy.

Aristolochic acid I: an investigation into the role of food crops contamination, as a potential natural exposure pathway

Aristolochic acid I (AAI) is a potent nephrotoxic and carcinogenic compound produced by plants of the Aristolochiaceae family and thoroughly investigated as a main culprit in the etiology of Balkan endemic nephropathy (BEN). So far, the AAI exposure was demonstrated to occur through the consumption of Aristolochia clematitis plants as traditional remedies, and through the contamination of the surrounding environment in endemic areas: soil, food and water contamination. Our study investigated for the first time the level of AAI contamination in 141 soil and vegetable samples from two cultivated gardens in non-endemic areas, A. clematitis being present in only one of the gardens. We developed and validated a simple and sensitive ultra-high-performance liquid chromatography-ion trap mass spectrometry method for qualitative and quantitative AAI analysis. The results confirmed the presence of AAI at nanogram levels in soil and vegetable samples collected from the non-endemic garden, where A. clematitis grows. These findings provide additional evidence that the presence of A. clematitis can cause food crops and soil contamination and unveil the pathway through which AAI could move from A. clematitis to other plant species via a common matrix: the soil. Another issue regarding the presence of AAI, in a non-endemic BEN area from Romania, could underlie a more widespread environmental exposure to AAI and explain certain BEN-like cases in areas where BEN has not been initially described.

Probing the Hidden Role of Mitochondrial DNA Damage and Dysfunction in the Etiology of Aristolochic Acid Nephropathy

Aristolochic acid nephropathy (AAN) is a unique type of progressive renal interstitial fibrotic disease caused by prolonged exposure to aristolochic acids (AAs) through AA-containing herbal medicines or AA-tainted food. Despite decades of research and affecting millions of people around the world, the pathophysiology of AAN remains incompletely understood. In this study, we tested the potential causative role of mitochondrial dysfunction in AAN development. Our findings revealed AA exposure induces an exposure concentration and duration dependent lowering of adenosine triphosphate in both cultured human kidney and liver cells, highlighting an AA exposure effect on mitochondrial energy production in the kidney and liver, which both are highly metabolically active and energy-demanding organs. Analysis with liquid chromatography-tandem mass spectrometry coupled with stable isotope dilution method detected high levels of mutagenic 8-oxo-2'-deoxyguanosine and 7-(deoxyadenosine-N⁶-yl)-aristolactam adduct on mitochondrial DNA isolated from AA-treated cells, unmasking a potentially important causative, but previously unknown role of mitochondrial DNA mutation in the pathophysiology of AAN development.

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

Balkan endemic nephropathy (BEN) is a chronic tubulointerstitial nephropathy affecting residents of rural farming areas in many Balkan countries. Although it is generally believed that BEN is an environmental disease caused by multiple geochemical factors with much attention on aristolochic acids (AAs), its etiology remains controversial. In this study, we tested the hypothesis that environmental contamination and subsequent food contamination by polycyclic aromatic hydrocarbons (PAHs) and phthalate esters are AA toxicity factors and important to BEN development. We identified significantly higher concentrations of phenanthrene, anthracene, diethyl phthalate (DEP), dibutyl phthalate (DBP), and benzyl butyl phthalate (BBP) in both maize and wheat grain samples collected from endemic villages than from nonendemic villages. Other PAHs and phthalate esters were also detected at higher concentrations in the soil samples from endemic villages. Subsequent genotoxicity testing of cultured human kidney cells showed an alarming phenomenon that phenanthrene, DEP, BBP, and DBP can interact synergistically with AAs to form elevated levels of AA-DNA adducts, which are associated with both the nephrotoxicity and carcinogenicity of AAs, further increasing their disease risks. This study provides direct evidence that prolonged coexposure to these environmental contaminants via dietary intake may lead to greater toxicity and accelerated development of BEN.