Aristolochic acid (AA) is a naturally occurring compound found only in Aristolochia plants. Although Aristolochia
species have long been used for medicinal purposes, their carcinogenic and nephrotoxic properties were
recognized only recently. Significant amounts of AA are present in herbal supplements marketed through the
Internet. And, in China and other Asian countries, where herbal remedies are widely used, 100 million people
are estimated to be at risk of developing aristolochic acid nephropathy (AAN), a devastating and uniformly fatal
disease. Importantly, AA’s unique mutational signature has clearly demonstrated its worldwide association with
upper urothelial tract cancers, bladder cancer, renal cell carcinoma, hepatocellular carcinoma and intrahepatic
cholangiocarcinoma. In this research, we use a multipronged approach to solve a complex global health problem.
Thus, we propose to identify mechanisms of AA-induced carcinogenicity and nephrotoxicity, important causes
of morbidity and mortality worldwide.
Our guiding hypothesis is that genes involved in bioactivation and inactivation of AA, and its transport to
target tissues, act both independently and together to determine individual susceptibility to AA’s toxic effects.
Using an integrated human liver-kidney-on-a-chip, we have recently demonstrated that AA activation occurs
primarily in the liver. Activated, chemically labile AA metabolites bind tightly to serum albumin and subsequently
are transported to the kidney, where they form covalent adducts with proteins and DNA. In Aim 1, we establish
pathways of AA metabolism, monitor the pharmacokinetics of AA, and quantify the distribution of AA metabolites,
aristolactam (AL)-DNA adducts, and AL-protein adducts among the blood, urine, and target tissues of sensitive
and resistant strains of mice. In Aim 2, we extend our human “organs-on-a-chip” studies and apply mass
spectrometric, fluorometric, and plasmon resonance techniques to illuminate the critical role of serum albumin
in protecting and transporting activated species of AA. However, although the genotoxic properties of AA account
for its carcinogenic effects, the molecular mechanisms of its nephrotoxicity are unknown. We hypothesize that
selective binding of AA to proteins in the renal proximal tubule initiates the cytotoxicity underlying AA’s
nephrotoxic effects. Thus, in Aim 3, we use novel proteomic techniques, affinity probes, and monoclonal
antibodies to explore nephrotoxic events, with the goal of identifying the specific renal tubular proteins involved.
Successful completion of this research program will advance significantly our knowledge of mechanisms involved
in the dual toxicities of AA. Also, data obtained in this study may provide a basis for establishing individual
susceptibility to AA, and will facilitate early diagnosis, prevention, and treatment of AA-induced cancers and
chronic renal disease. Given the worldwide exposure to AA, this research has significant implications for global
public health. Additionally, the techniques perfected in the three aims of this project will serve as templates for
investigating other causes of nephrotoxicity and carcinogenicity.
