New approaches for biomonitoring exposure to the human carcinogen aristolochic acid

Abstract

Aristolochic acids (AA) are found in all Aristolochia herbaceous plants, many of which have been used worldwide for medicinal purposes for centuries. AA are causal agents of the chronic kidney disease entity termed aristolochic acid nephropathy (AAN) and potent upper urinary tract carcinogens in humans. AAN and upper urinary tract cancers are endemic in rural areas of Croatia and other Balkan countries where exposure to AA occurs through the ingestion of home-baked bread contaminated with Aristolochia seeds. In Asia, exposure to AA occurs through usage of traditional Chinese medicinal herbs containing Aristolochia. Despite warnings from regulatory agencies, traditional Chinese herbs containing AA continue to be used world-wide. In this review, we highlight novel approaches to quantify exposure to AA, by analysis of aristolactam (AL) DNA adducts, employing ultraperformance liquid chromatography–electrospray ionization/multistage mass spectrometry (UPLC-ESI/MSn). DNA adducts are a measure of internal exposure to AA and serve as an important end point for cross-species extrapolation of toxicity data and human risk assessment. The level of sensitivity of UPLC-ESI/MSn surpasses the limits of detection of AL-DNA adducts obtained by 32P-postlabeling techniques, the most widely employed methods for detecting putative DNA adducts in humans. AL-DNA adducts can be measured by UPLC-ESI/MS3, not only in fresh frozen renal tissue, but also in formalin-fixed, paraffin-embedded (FFPE) samples, an underutilized biospecimen for assessing chemical exposures, and in exfoliated urinary cells, a non-invasive approach. The frequent detection of AL DNA adducts in renal tissues, combined with the characteristic mutational spectrum induced by AA in TP53 and other genes provides compelling data for a role of AA in upper urothelial tract cancer.

Biomonitoring DNA Adducts of Cooked Meat Carcinogens in Human Prostate by Nano Liquid Chromatography–High Resolution Tandem Mass Spectrometry: Identification of 2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine DNA Adduct

“…The uncertainty in labeling efficiency and the lack of physiochemical structural confirmation puts DNA adduct analysis by 32 P-postlabeling methods into question. 28,29 …”

Human Biomonitoring of DNA Adducts by Ion Trap Multistage Mass Spectrometry

“…However, the need to confirm adduct structure by a higher level of fragmentation of the adducted base or higher resolving power have turned researchers to other mass analyzers such as ion trap (IT) or time-offlight (TOF; Tretyakova et al, 2012). Our laboratory has extensively used IT-MS employing the multi-stage scanning (MS n ) feature to screen for DNA adducts present at trace levels in humans (Goodenough et al, 2007;Gu et al, 2012;Yun et al, 2015).…”

“…This method built the foundation for a series of publications on the measurement of aristolactam DNA adducts in fresh frozen but also in formalin‐fixed paraffin‐embedded (FFPE) renal tissues, and exfoliated urothelial cells. Employing HPLC‐LIT‐MS 3 , dA‐AL‐I was quantified in renal cortex and upper urothelial tumor tissues from nearly 200 patients with upper urothelial cancer from Taiwan, the Balkan endemic regions, and Romania (Yun et al., , , , ).…”

DNA adducts: Formation, biological effects, and new biospecimens for mass spectrometric measurements in humans

“…Our laboratory in conjunction with collaborators at Stony Brook University and Peking University First Hospital, Beijing, China, showed that the DNA adduct of aristolochic acids, dA‐AL‐l, can be measured in DNA of EUC from patients with renal disease and a known history of ingestion of traditional Chinese medicines. The DNA adduct measurements were conducted by UPLC‐ESI‐IT‐MS on EUC specimens collected for 12 or 24 hr . The recovery of DNA ranged between 11 and 33 μg, a level that was sufficient to measure the dA‐AL‐I at levels above LOQ value, three adducts per 10 9 bases, with only two μg of DNA required for assay.…”

“…Recent studies have also shown that DNA obtained from exfoliated oral cells can be used to screen for DNA adducts of carcinogens present in tobacco smoke, cooked meat, and ethanol by MS‐based methods . Thus, current LC/MS instruments have the required sensitivities to screen for many DNA adducts in human biospecimens.…”