Co-Exposure to Aristolochic Acids I and II Increases DNA Adduct Formation Responsible for Aristolochic Acid I-Mediated Carcinogenicity in Rats.

František Bárta,Michaela Bebová,Volker M Arlt,Marie Stiborová,Heinz H Schmeiser,Šárka Dušková,Jaroslav Mráz,Petr Hodek,Alena Dedíková

doi:10.3390/ijms221910479

Abstract

The plant extract aristolochic acid (AA), containing aristolochic acids I (AAI) and II (AAII) as major components, causes aristolochic acid nephropathy (AAN) and Balkan endemic nephropathy (BEN), unique renal diseases associated with upper urothelial cancer. Recently (Chemical Research in Toxicology 33(11), 2804–2818, 2020), we showed that the in vivo metabolism of AAI and AAII in Wistar rats is influenced by their co-exposure (i.e., AAI/AAII mixture). Using the same rat model, we investigated how exposure to the AAI/AAII mixture can influence AAI and AAII DNA adduct formation (i.e., AA-mediated genotoxicity). Using 32P-postlabelling, we found that AA-DNA adduct formation was increased in the livers and kidneys of rats treated with AAI/AAII mixture compared to rats treated with AAI or AAII alone. Measuring the activity of enzymes involved in AA metabolism, we showed that enhanced AA-DNA adduct formation might be caused partially by both decreased AAI detoxification as a result of hepatic CYP2C11 inhibition during treatment with AAI/AAII mixture and by hepatic or renal NQO1 induction, the key enzyme predominantly activating AA to DNA adducts. Moreover, our results indicate that AAII might act as an inhibitor of AAI detoxification in vivo. Consequently, higher amounts of AAI might remain in liver and kidney tissues, which can be reductively activated, resulting in enhanced AAI DNA adduct formation. Collectively, these results indicate that AAII present in the plant extract AA enhances the genotoxic properties of AAI (i.e., AAI DNA adduct formation). As patients suffering from AAN and BEN are always exposed to the plant extract (i.e., AAI/AAII mixture), our findings are crucial to better understanding host factors critical for AAN- and BEN-associated urothelial malignancy.

Highlights

It is responsible for two serious renal diseases, aristolochic acid nephropathy (AAN) and Balkan endemic nephropathy (BEN), both of which are associated with the development of upper urothelial cancer [9,10,11,12,13,15,16,17]
While aristolochic acids I (AAI), the major component of the plant extract, has been identified as a crucial factor for the development of upper urothelial cancer (UUC) by inducing specific A:T→T:A transversion mutations in the DNA of patients suffering from AAN and BEN [4,13,38,40,42], the effects of the second major component, AAII, remain to better understood
Considering the fact that patients suffering from AAN or BEN or users of traditional herbal medicine are exposed to the natural mixture, which consists of both

Summary

Introduction

Aristolochic acid (AA) is the natural plant extract of both the Aristolochia and Asarum genera of the family Aristolochiaceae, namely Aristolochia clematitis in particular in Europe [1]. The plant extract consists of structurally related nitrophenanthrene carboxylic acids, with aristolochic acid I (8-methoxy-6-nitro-phenanthro-(3,4-d)-1,3-dioxolo-5-carboxylic acid, AAI) and aristolochic acid II (6-nitro-phenanthro-(3,4-d)-1,3-dioxolo-5-carboxylic acid, AAII) being the major components (Figure 1). There is overwhelming evidence that human exposure to AA leads to chronic renal disease and upper urothelial cancer (UUC), known as aristolochic acid nephropathy (AAN) [8,9,10], which is recognised as a global disease [10,11]. AA is considered to be the cause of another chronic renal disease associated with urothelial malignancy known as Balkan endemic nephropathy (BEN) [12,13,14,15,16,17]

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