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The term “aristolochic acid nephropathy” (AAN) is used to include any form of toxic interstitial nephropathy that is caused either by ingestion of plants containing aristolochic acids (AA) as part of traditional phytotherapies (formerly known as “Chinese herbs nephropathy”), or by the environmental contaminants in food (Balkan endemic nephropathy). It is frequently associated with urothelial malignancies. Although products containing AA have been banned in most of countries, AAN cases remain regularly reported all over the world. Moreover, AAN incidence is probably highly underestimated given the presence of AA in traditional herbal remedies worldwide and the weak awareness of the disease. During these two past decades, animal models for AAN have been developed to investigate underlying molecular and cellular mechanisms involved in AAN pathogenesis. Indeed, a more-in-depth understanding of these processes is essential to develop therapeutic strategies aimed to reduce the global and underestimated burden of this disease. In this regard, our purpose was to build a broad overview of what is currently known about AAN. To achieve this goal, we aimed to summarize the latest data available about underlying pathophysiological mechanisms leading to AAN development with a particular emphasis on the imbalance between vasoactive factors as well as a focus on the vascular events often not considered in AAN.

Aristolochic acid (AA) is a plant alkaloid that causes aristolochic acid nephropathy (AAN) and Balkan endemic nephropathy (BEN), unique renal diseases frequently associated with upper urothelial cancer (UUC). This review summarizes the significance of AA-derived DNA adducts in the aetiology of UUC leading to specific A:T to T:A transversion mutations (mutational signature) in AAN/BEN-associated tumours, which are otherwise rare in individuals with UCC not exposed to AA. Therefore, such DNA damage produced by AA-DNA adducts is one rare example of the direct association of exposure and cancer development (UUC) in humans, confirming that the covalent binding of carcinogens to DNA is causally related to tumourigenesis. Although aristolochic acid I (AAI), the major component of the natural plant extract AA, might directly cause interstitial nephropathy, enzymatic activation of AAI to reactive intermediates capable of binding to DNA is a necessary step leading to the formation of AA-DNA adducts and subsequently AA-induced malignant transformation. Therefore, AA-DNA adducts can not only be utilized as biomarkers for the assessment of AA exposure and markers of AA-induced UUC, but also be used for the mechanistic evaluation of its enzymatic activation and detoxification. Differences in AA metabolism might be one of the reasons for an individual’s susceptibility in the multi-step process of AA carcinogenesis and studying associations between activities and/or polymorphisms of the enzymes metabolising AA is an important determinant to identify individuals having a high risk of developing AA-mediated UUC.

Aristolochic acids (AAs) are a family of natural compounds with AA I and AA II being known carcinogens, whose bioactivation causes DNA adducts formation. However, other congeners have rarely been investigated. This study aimed to investigate genotoxicity of AA IVa, which differs from AA I by a hydroxyl group, abundant in Aristolochiaceae plants. AA IVa reacted with 2'-deoxyadenosine (dA) and 2'-deoxyguanosine (dG) to form three dA and five dG adducts as identified by high-resolution mass spectrometry, among which two dA and three dG adducts were detected in reactions of AA IVa with calf thymus DNA (CT DNA). However, no DNA adducts were detected in the kidney, liver, and forestomach of orally dosed mice at 40 mg/kg/day for 2 days, and bone marrow micronucleus assay also yielded negative results. Pharmacokinetic analyses of metabolites in plasma indicated that AA IVa was mainly O-demethylated to produce a metabolite with two hydroxyl groups, probably facilitating its excretion. Meanwhile, no reduced metabolites were detected. The competitive reaction of AA I and AA IVa with CT DNA, with adducts levels varying with pH of reaction revealed that AA IVa was significantly less reactive than AA I, probably by hydroxyl deprotonation of AA IVa, which was explained by theoretical calculations for reaction barriers, energy levels of the molecular orbits, and charges at the reaction sites. In brief, although it could form DNA adducts in vitro, AA IVa was non-genotoxic in vivo, which was attributed to its low reactivity and biotransformation into an easily excreted metabolite rather than bioactivation.

Aristolochic acid analogues (AAAs), naturally existing in herbal Aristolochia and Asarum genera, were once widely used in traditional pharmacopeias because of their anti-inflammatory properties, but lately they were identified as potential nephrotoxins and mutagens. A method for rapid characterization of AAAs in serum was developed using ion mobility spectrometry coupled with mass spectrometry (IMS-MS). Five AAAs, containing four aristolochic acids and one aristolactam, were separated and identified within milliseconds. AAAs were separated in gas phase based on the difference of their ion mobility (K0), and then identified based on their K0 values, m/z, and product ions from MS/MS. Quantitative analysis of AAAs was performed using an internal standard with a satisfactory sensitivity. Limits of detection (signal-to-noise = 3) and quantification (signal-to-noise = 10) were 1–5 ng/mL and 3–8 ng/mL, respectively. The method was validated and successfully applied to the pharmacokinetics study of AAAs in rats, offering a promising way for fast screening and evaluation of AAAs in biological samples.

Endemic (Balkan) nephropathy (EN), a devastating renal disease affecting men and women living in rural areas of Bosnia, Bulgaria, Croatia, Romania, and Serbia, is characterized by its insidious onset, invariable progression to chronic renal failure and a strong association with transitional cell (urothelial) carcinoma of the upper urinary tract. Significant epidemiologic features of EN include its focal occurrence in certain villages and a familial, but not inherited, pattern of disease. Our experiments test the hypothesis that chronic dietary poisoning by aristolochic acid is responsible for EN and its associated urothelial cancer. Using ³²P-postlabeling/PAGE and authentic standards, we identified dA-aristolactam (AL) and dG-AL DNA adducts in the renal cortex of patients with EN but not in patients with other chronic renal diseases. In addition, urothelial cancer tissue was obtained from residents of endemic villages with upper urinary tract malignancies. The AmpliChip p53 microarray was then used to sequence exons 2-11 of the p53 gene where we identified 19 base substitutions. Mutations at A:T pairs accounted for 89% of all p53 mutations, with 78% of these being A:T [rightward arrow] T:A transversions. Our experimental results, namely, that (i) DNA adducts derived from aristolochic acid (AA) are present in renal tissues of patients with documented EN, (ii) these adducts can be detected in transitional cell cancers, and (iii) A:T [rightward arrow] T:A transversions dominate the p53 mutational spectrum in the upper urinary tract malignancies found in this population lead to the conclusion that dietary exposure to AA is a significant risk factor for EN and its attendant transitional cell cancer.

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. Graphical Abstract

Aristolochic acid I (AAI) is a plant alkaloid causing aristolochic acid nephropathy, Balkan endemic nephropathy and their associated urothelial malignancies. AAI is detoxified by cytochrome P450 (CYP)-mediated O-demethylation to 8-hydroxyaristolochic acid I (aristolochic acid Ia, AAIa). We previously investigated the efficiencies of human and rat CYPs in the presence of two other components of the mixed-functions-oxidase system, NADPH:CYP oxidoreductase and cytochrome b5, to oxidize AAI. Human and rat CYP1A are the major enzymes oxidizing AAI. Other CYPs such as CYP2C, 3A4, 2D6, 2E1, and 1B1, also form AAIa, but with much lower efficiency than CYP1A. Based on velocities of AAIa formation by examined CYPs and their expression levels in human and rat livers, here we determined the contributions of individual CYPs to AAI oxidation in these organs. Human CYP1A2 followed by CYP2C9, 3A4 and 1A1 were the major enzymes contributing to AAI oxidation in human liver, while CYP2C and 1A were most important in rat liver. We employed flexible in silico docking methods to explain the differences in AAI oxidation in the liver by human CYP1A1, 1A2, 2C9, and 3A4, the enzymes that all O-demethylate AAI, but with different effectiveness. We found that the binding orientations of the methoxy group of AAI in binding centers of the CYP enzymes and the energies of AAI binding to the CYP active sites dictate the efficiency of AAI oxidation. Our results indicate that utilization of experimental and theoretical methods is an appropriate study design to examine the CYP-catalyzed reaction mechanisms of AAI oxidation and contributions of human hepatic CYPs to this metabolism.

The efficient synthetic routes and evaluates cytotoxic profiles of denitroaristolochic acids II–V (DAA-II–V) were demonstrated in this study. Based on retrosynthetic analysis, a modular synthetic strategy was developed through Suzuki–Miyaura coupling, Wittig reaction, and bismuth triflate-catalyzed intramolecular Friedel–Crafts cyclization to efficiently construct the phenanthrene core. Process optimization significantly improved yields: aryl bromide intermediate A reached 50.8% yield via bromination refinement, while arylboronic ester intermediate B overcame selectivity limitations. Combining Darzens condensation with Wittig reaction enhanced throughput, achieving 88.4% yield in the key cyclization. Structures were confirmed by NMR and mass spectra. CCK-8 cytotoxicity assays in human renal proximal tubular epithelial cells revealed distinct toxicological profiles: DAA-III and DAA-IV exhibited IC50 values of 371 μM and 515 μM, respectively, significantly higher than the nitro-containing prototype AA-I (270 μM), indicating that the absence of nitro group attenuates but does not eliminate toxicity, potentially via altered metabolic activation. DAA-II and DAA-V showed no detectable cytotoxicity within assay limits, suggesting reduced toxicological impact. Structure–activity analysis exhibited that the nitro group is not essential for cytotoxicity, with methoxy substituents exerting limited influence on potency. This challenges the conventional DNA adduct-dependent toxicity paradigm, implying alternative mechanisms like oxidative stress or mitochondrial dysfunction may mediate damage in denitro derivatives. These systematic findings provide new perspectives for AA analog research and a foundation for the rational use and safety assessment of Aristolochiaceae plants.

Consumption of aristolochic acids (AA) from the plant results in the formation of bulky aristolactam-dA (dA-AL) and aristolactam-dG (dG-AL) adducts in cellular DNA ultimately leading to the development of urothelial cancer. Intriguingly, the dA-AL adducts induce A•T→T•A transversions in tumor cells preferentially in CpA*→TpG context. The human mismatch-specific thymine-DNA glycosylase (TDG) protects cells against mutagenesis induced by spontaneous deamination of 5-methylcytosine (5mC) by removing thymine opposite to guanine in a CpG context in the base excision repair (BER) pathway. Nevertheless, challenges for DNA glycosylases to the faithful discrimination between non-damaged and damaged DNA strands do exist, such as mismatched pairs between two canonical bases, which may result due to DNA polymerase errors during replication. Previously, we demonstrated that TDG is prone to aberrant excision of T opposite to damaged adenine in duplex DNA in CpA*/TpG context. In the present work, using reconstitution assays, we investigated whether TDG participates in the aberrant removal of thymine opposite to dA-AL adducts in duplex DNA. We have demonstrated that TDG either does not excise thymine or does so with extremely low efficiency when it is paired with dA-AL or dG-ALII adducts in duplex DNA. At the same time, TDG excises with high efficiency thymine opposite to guanine and hypoxanthine in T•G and T•Hx mispairs. These findings strongly suggest that the human TDG is not involved in the aberrant DNA repair of AA-induced DNA damage.

Aristolochic acids are known for nephrotoxicity, and implicated in multiple cancer types such as hepatocellular carcinomas demonstrated by recent studies. Natural products that are analogues to aristolochic acids have been constantly isolated from organisms; a larger chemical space of these compounds and a wider coverage of biological sources should be determined in consideration of the potential hazard of aristolochic acid analogues and the wide distribution of their biological sources in the nature. Therefore, we carried out an in silico research of naturally occurring aristolochic acid analogues and their biological sources, as a supplement to existing studies. The result shows a chemical space of 238 naturally occurring aristolochic acid analogues that are present in 175 species of biological sources including 44 traditional medicines. With the computational estimation for toxicity and the implication in hazard assessment of a biological source with the presence of aristolochic acid analogues, we propose that additional awareness should be raised to the public for avoidance of toxic species, especially those that are used as herbal medicines and easily accessible.