p53 mutations as fingerprints for aristolochic acid: an environmental carcinogen in endemic (Balkan) nephropathy

IL-22 is secreted by proximal tubule cells and regulates DNA damage response and cell death in acute kidney injury

Acute kidney injury (AKI) affects over 13 million people worldwide annually and is associated with a 4-fold increase in mortality. Our lab and others have shown that DNA damage response (DDR) governs the outcome of AKI in a bimodal manner. Activation of DDR sensor kinases protects against AKI, while hyperactivation of DDR effector proteins, such as p53, induces cell death and worsens AKI. The factors that trigger DDR to switch from pro-repair to pro-cell death remain to be resolved. Here we investigated the role of interleukin 22 (IL-22), an IL-10 family member whose receptor (IL-22RA1) is expressed on proximal tubule cells (PTCs), in DDR activation and AKI. Using cisplatin and aristolochic acid (AA) induced nephropathy as models of DNA damage, we identified PTCs as a novel source of urinary IL-22. Functionally, IL-22 binding IL-22RA1 on PTCs amplified the DDR. Treating primary PTCs with IL-22 alone induced rapid activation of the DDR. The combination of IL-22 and either cisplatin- or AA-induced cell death in primary PTCs, while the same dose of cisplatin or AA alone did not. Global deletion of IL-22 protected against cisplatin- or AA-induced AKI, reduced expression of DDR components, and inhibited PTC cell death. To confirm PTC IL-22 signaling contributed to AKI, we knocked out IL-22RA1 specifically in kidney tubule cells. IL-22RA1ΔTub mice displayed reduced DDR activation, cell death, and kidney injury compared to controls. Thus, targeting IL-22 represents a novel therapeutic approach to prevent the negative consequences of the DDR activation while not interfering with repair of damaged DNA.

IL-22 promotes acute kidney injury through activation of the DNA damage response and cell death in proximal tubule cells

Acute kidney injury (AKI) affects over 13 million people world-wide annually and is associated with a fourfold increase in mortality. Our lab and others have shown that DNA damage response (DDR) governs the outcome of AKI in a bimodal manner. Activation of DDR sensor kinases protects against AKI, while hyperactivation of DDR effector proteins, such as p53, induces to cell death and worsens AKI. The factors that trigger the switch from pro-reparative to pro-cell death DDR remain to be resolved. Here we investigate the role of interleukin 22 (IL-22), an IL-10 family member whose receptor (IL-22RA1) is expressed on proximal tubule cells (PTCs), in DDR activation and AKI. Using cisplatin and aristolochic acid (AA) induced nephropathy as models of DNA damage, we identify PTCs as a novel source of urinary IL-22, making PTCs the only epithelial cells known to secret IL-22, to our knowledge. Functionally, IL-22 binding its receptor (IL-22RA1) on PTCs amplifies the DDR. Treating primary PTCs with IL-22 alone induces rapid activation of the DDR in vitro. The combination of IL-22 + cisplatin or AA treatment on primary PTCs induces cell death, while the same dose of cisplatin or AA alone does not. Global deletion of IL-22 protects against cisplatin or AA induced AKI. IL-22 deletion reduces expression of components of the DDR and inhibits PTC cell death. To confirm PTC IL-22 signaling contributes to AKI, we knocked out IL-22RA1 in renal epithelial cells by crossing IL-22RA1floxed mice with Six2-Cre mice. IL-22RA1 KO reduced DDR activation, cell death, and kidney injury. These data demonstrate that IL-22 promotes DDR activation in PTCs, switching pro-recovery DDR responses to a pro-cell death response and worsening AKI. Targeting IL-22 represents a novel therapeutic approach to prevent the negative consequences of the DDR activation while not interfering with the processes necessary for repair of damaged DNA.

Molecular Characterization of Microrna Interference and Aristolochic Acid Intoxication Found in Upper Tract Urothelial Carcinoma in Patients with Balkan Endemic Nephropathy: A Systematic Review of the Current Literature

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) or by the environmental contaminants in food such as in Balkan endemic nephropathy (BEN). Aristolochic acid (AA) intoxication is strongly associated with the development of upper tract urothelial carcinoma (UTUC); however, the underlying molecular mechanism remains to be defined. MicroRNAs (miRNA) regulate several biological processes, including cell proliferation, differentiation, and metabolism, acting as oncogenes or tumor suppressors. A unique miRNA expression profile suggested that miRNAs could function as regulators in UTUC developmental processes. This review aimed to summarize data available in the literature about underlying molecular mechanisms leading to the expression of miRNAs in AA-UTUC patients with BEN. Strong correlation in AA-UTUC has a distinctive gene alteration pattern, AL-DNA adducts, and a unique tumor protein (TP53) mutational spectrum AAG to TAG (A: T→T: A) transversion in codon 139 (Lys → Stop) of exon 5 activates the p53 tumor suppressor protein. Further, p53 protein is responsible not only for the expression of miRNAs but also acts as a target molecule for miRNAs and plays a crucial function in the AA-UTUC pathogenicity through activation of cyclin-dependent kinase (CyclinD1) and cyclin protein kinase 6(CDK6) to support cell cycle arrest. This study, proposed a molecular mechanism that represented a possible unique relationship between AA intoxication, miRNAs expression, and the progression of UTUC in patients with BEN.

De novo assembly of a chromosome-level reference genome of the ornamental butterfly Sericinus montelus based on nanopore sequencing and Hi-C analysis

Sericinus montelus (Lepidoptera, Papilionidae, Parnassiinae) is a high-value ornamental swallowtail butterfly species widely distributed in Northern and Central China, Japan, Korea, and Russia. The larval stage of this species feeds exclusively on Aristolochia plants. The Aristolochia species is well known for its high levels of aristolochic acids (AAs), which have been found to be carcinogenic for numerous animals. The swallowtail butterfly is among the few that can feed on these toxic host plants. However, the genetic adaptation of S. montelus to confer new abilities for AA tolerance has not yet been well explored, largely due to the limited genomic resources of this species. This study aimed to present a chromosome-level reference genome for S. montelus using the Oxford Nanopore long-read sequencing, Illumina short-read sequencing, and Hi-C technology. The final assembly was composed of 581.44 Mb with an expected genome size of 619.27 Mb. Further, 99.98% of the bases could be anchored onto 30 chromosomes. The N50 of contigs and scaffolds was 5.74 and 19.12 Mb, respectively. Approximately 48.86% of the assembled genome was suggested to be repeat elements, and 13,720 protein-coding genes were predicted in the current assembly. The phylogenetic analysis indicated that S. montelus diverged from the common ancestor of swallowtails about 58.57-80.46 million years ago. Compared with related species, S. montelus showed a significant expansion of P450 gene family members, and positive selections on eloa, heatr1, and aph1a resulted in the AA tolerance for S. montelus larva. The de novo assembly of a high-quality reference genome for S. montelus provided a fundamental genomic tool for future research on evolution, genome genetics, and toxicology of the swallowtail butterflies.

First-line Immune Checkpoint Inhibitor Versus Immune Checkpoint Inhibitor With Chemotherapy for Cisplatin-ineligible Metastatic Urothelial Carcinoma: Evidence From a Real-world, Multicenter Analysis

Immune checkpoint inhibitors (ICIs) are widely used for first-line cisplatin-ineligible patients with metastatic urothelial carcinoma (mUC). However, whether to use ICIs as monotherapy or in combination with chemotherapy is still uncertain. We retrospectively analyzed cisplatin-ineligible patients with mUC who underwent first-line ICI monotherapy or ICI plus chemotherapy at 2 medical centers in Taiwan from 2016 to 2021. We calculated the objective response rate, progression-free survival, and overall survival (OS) using the Kaplan-Meier method and Cox regression model for multivariable analysis. In total, 130 patients were enrolled and categorized into 2 groups: an ICI monotherapy group [immunotherapy (IO), n=101] and an ICI plus noncisplatin chemotherapy group [immunotherapy and chemotherapy (IC), n=29]. The median OS of patients in the IO and IC groups was 19.5 and 9.7 months ( P =0.33). Among patients with high programmed cell death ligand-1-expressing tumors, the median OS was significantly prolonged in the IO group compared with the IC group (not reached vs. 6.3 mo, P =0.02). First-line ICI monotherapy demonstrated robust antitumor activity in cisplatin-ineligible patients with mUC. Combining noncisplatin chemotherapy with ICI did not improve clinical outcomes.

Nephrotoxicity of Herbal Medicine and Its Prevention

Herbal medicine (HM) has been widely used to treat diseases for thousands of years and has greatly contributed to the health of human beings. Many new drugs have been developed from HM, such as artemisinin. However, artemisinin has adverse effects, such as renal toxicity. In 1993, a study conducted in Belgium reported for the first time that the root extracts of Aristolochia obliqua S. M. Hwang led to progressive interstitial renal fibrosis. The nephrotoxicity of HM has attracted worldwide attention. More than 100 kinds of HM induce renal toxicity, including some herbs, animal HMs, and minerals. This paper aimed to summarize the HM compounds that cause nephrotoxicity, the mechanisms underlying the toxicity of these compounds, biomarkers of renal injury, and prevention strategies. These findings provide a basis for follow-up studies on the prevention and treatment of HM nephrotoxicity.

Aristolochic Acid-Induced Genotoxicity and Toxicogenomic Changes in Rodents

Aristolochic acid (AA) is a group of structurally related nitrophenanthrene carboxylic acids found in many plants that are widely used by many cultures as traditional herbal medicines. AA is a causative agent for Chinese herbs nephropathy, a term replaced later by AA nephropathy. Evidence indicates that AA is nephrotoxic, genotoxic, and carcinogenic in humans; and it also induces tumors in the forestomach, kidney, renal pelvis, urinary bladder, and lung of rats and mice. Therefore, plants containing AA have been classified as carcinogenic to humans (Group 1) by the International Agency for Research on Cancer. In our laboratories, we have conducted a series of genotoxicity and toxicogenomic studies in the rats exposed to AA of 0.1–10 mg/kg for 12 weeks. Our results demonstrated that AA treatments induced DNA adducts and mutations in the kidney, liver, and spleen of rats, as well as significant alteration of gene expression in both its target and nontarget tissues. AA treatments altered mutagenesis- or carcinogenesis-related microRNA expression in rat kidney and resulted in significant changes in protein expression profiling. We also applied benchmark dose (BMD) modeling to the 3-month AA-induced genotoxicity data. The obtained BMDL₁₀ (the lower 95% confidence interval of the BMD₁₀ that is a 10% increase over the background level) for AA-induced mutations in the kidney of rats was about 7 μg/kg body weight per day. This review constitutes an overview of our investigations on AA-induced genotoxicity and toxicogenomic changes including gene expression, microRNA expression, and proteomics; and presents updated information focused on AA-induced genotoxicity in rodents.

Systematic Overview of Aristolochic Acids: Nephrotoxicity, Carcinogenicity, and Underlying Mechanisms

Aristolochic acids (AAs) are a group of toxins commonly present in the plants of genus Aristolochia and Asarum, which are spread all over the world. Since the 1990s, AA-induced nephropathy (AAN) and upper tract urothelial carcinoma (UTUC) have been reported in many countries. The underlying mechanisms of AAN and AA-induced UTUC have been extensively investigated. AA-derived DNA adducts are recognized as specific biomarkers of AA exposure, and a mutational signature predominantly characterized by A→T transversions has been detected in AA-induced UTUC tumor tissues. In addition, various enzymes and organic anion transporters are involved in AA-induced adverse reactions. The progressive lesions and mutational events initiated by AAs are irreversible, and no effective therapeutic regimen for AAN and AA-induced UTUC has been established until now. Because of several warnings on the toxic effects of AAs by the US Food and Drug Administration and the regulatory authorities of some other countries, the sale and use of AA-containing products have been banned or restricted in most countries. However, AA-related adverse events still occur, especially in the Asian and Balkan regions. Therefore, the use of AA-containing herbal remedies and the consumption of food contaminated by AAs still carry high risk. More strict precautions should be taken to protect the public from AA exposure.

Cooking methods employing natural anti-oxidant food additives effectively reduced concentration of nephrotoxic and carcinogenic aristolochic acids in contaminated food grains

Emerging evidence suggests that aristolochic acids (AA) produced naturally by a common weed Aristolochia clematitis in the cultivation fields is contaminating the food products in Balkan Peninsula and acting as the etiological agent in the development of Balkan endemic nephropathy. In this study, we investigated the combined use of natural anti-oxidative "food additives" and different cooking methods to find a solution for the widespread contamination of AA in food products. The results indicated that the addition of healthy dietary supplements (such as cysteine, glutathione, ascorbic acid, citric acid and magnesium) during cooking, is a highly efficient method in lowering the concentration of AA in the final food products. Because previous observation indicated one of the toxicological mechanisms by which AA exert its toxicity is to induce oxidative stress in internal organs, it is anticipated that these added anti-oxidants will also help to attenuate the nephrotoxicity of AA.

An Integrated View of Aristolochic Acid Nephropathy: Update of the Literature

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.

Lynch syndrome and exposure to aristolochic acid in upper-tract urothelial carcinoma: its clinical impact?

The purpose of the current review was to describe the clinical risk for Lynch syndrome (LS) after exposure to aristolochic acid (AA) in cases of upper urinary-tract urothelial carcinoma (UTUC). A systematic review of the scientific literature was performed using the Medline database (National Library of Medicine, PubMed) using the following keywords: epidemiology, risk factor, AA, Balkan nephropathy (BNe), LS, hereditary cancer, hereditary non-polyposis colorectal cancer (HNPCC), mismatch repair genes, urothelial carcinomas, upper urinary tract, renal pelvis, ureter, Amsterdam criteria, genetic counselling, mismatch repair genes, genetic instability, microsatellite, and Bethesda guidelines. LS is a specific risk for UTUC, which is the third most frequent cancer (in its tumor spectrum) after colon and uterine lesions. Mutation of the MSH2 gene is the most commonly described cause of UTUC in LS. Diagnosis is based on clinical suspicion and is guided by Bethesda and Amsterdam criteria. It is secondarily confirmed by immunohistochemical analyses of the tumor and a search for gene mutations. The presence of LS in patients with UTUC is a favorable prognosis factor for survival during follow-ups. AA is a specific environmental risk factor for UTUC and tubulo-interstitial nephropathy. It has been involved in the development of nephropathies in link with the Balkan disease and intake of Chinese herbal medicine. More broadly, the use of traditional plant medicines from the genus Aristolochia has created worldwide public-health concerns. UTUCs share common risk factors with other urothelial carcinomas such as tobacco or occupational exposure. However, these tumors have also specific risk factors such as AA exposure and LS that clinicians should be aware of because of their clinical implication in further management and follow-up.

Quantitation of Aristolochic Acids in Corn, Wheat Grain, and Soil Samples Collected in Serbia: Identifying a Novel Exposure Pathway in the Etiology of Balkan Endemic Nephropathy

While to date investigations provided convincing evidence on the role of aristolochic acids (AAs) in the etiology of Balkan endemic nephropathy (BEN) and upper urothelial cancer (UUC), the exposure pathways by which AAs enter human bodies to cause BEN and UUC remain obscure. The goal of this study is to test the hypothesis that environmental pollution by AAs and root uptake of AAs in the polluted soil may be one of the pathways by which AAs enter the human food chain. The hypothesis driving this study was that the decay of Aristolochia clematitis L., a AA-containing herbaceous plant that is found growing widespread in the endemic regions, could release free AAs to the soil, which could be taken up by food crops growing nearby, thereby transferring this potent human nephrotoxin and carcinogen into their edible parts. Using the highly sensitive and selective high-performance liquid chromatography coupled with fluorescence detection method, we identified and quantitated in this study for the first time AAs in corn, wheat grain, and soil samples collected from the endemic village Kutles in Serbia. Our results provide the first direct evidence that food crops and soil in the Balkans are contaminated with AAs. It is possible that the presence of AAs in edible parts of crops originating from the AA-contaminated soil could be one of the major pathways by which humans become exposed to AAs.

Uptake and Accumulation of Nephrotoxic and Carcinogenic Aristolochic Acids in Food Crops Grown in Aristolochia clematitis-Contaminated Soil and Water

Emerging evidence has suggested aristolochic acids (AAs) are linked to the development of Balkan endemic nephropathy (BEN), a chronic renal disease affecting numerous farmers living in the Balkan peninsula. However, the pathway by which AAs enter the human food chain and cause kidney disease remains poorly understood. Using our previously developed analytical method with high sensitivity and selectivity (Chan, W.; Lee, K. C.; Liu, N.; Cai, Z. J. Chromatogr. A 2007, 1164, 113-119), we quantified AAs in lettuce, tomato, and spring onion grown in AA-contaminated soil and culture medium. Our study revealed that AAs were being taken up from the soil and bioaccumulated in food crops in a time- and dose-dependent manner. To the best of our knowledge, this study is the first to identify one of the possible pathways by which AAs enter our food chain to cause chronic food poisoning. Results also demonstrated that AAs were resistant to the microbial activity of the soil/water.

Differential microRNA expression in aristolochic acid-induced upper urothelial tract cancers ex vivo

Aristolochic acid (AA) is a carcinogenic, mutagenic and nephrotoxic compound commonly isolated from members of the plant family of Aristolochiaceae (such as Aristolochia and Asarum) and used in Chinese herbal medicine. Use of AA and AA-containing plants causes chronic kidney disease (CKD) and upper urinary tract carcinoma (UUC); however, the underlying mechanism remains to be defined. miRNAs regulate a number of biological processes, including cell proliferation, differentiation and metabolism. This study explored differentially expressed miRNAs between AA-induced upper urothelial tract cancer (AAN-UUC) and non-AAN-UUC tissues. Patients with AAN-UUC and non-AAN-UUC (n=20/group) were recruited in the present study. Five tissue samples from each group were used for miRNA microarray profiling and the rest of the tissue samples were subjected to reverse transcription-quantitative polymerase chain reaction analysis including seven selected miRNAs for confirmation. A total of 29 miRNAs were differentially expressed between AAN-UUC and non-AAN-UUC tissues (P<0.05). TargenScan and Gene ontology analyses predicted the functions and targeted genes of these differentially expressed miRNAs, i.e. Akt3, FGFR3, PSEN1, VEGFa and AR. Subsequently, expression of the selected differentially expressed miRNAs (Hsa-miR-4795-5p, Hsa-miR-488, Hsa-miR-4784, Hsa-miR-330, Hsa-miR-3916, Hsa-miR-4274 and Hsa-miR-181c) was validated in another set of tissue samples. A total of 29 miRNAs were identified to be differentially expressed between AAN-UUC and non-AAN-UUC tissues and these miRNA target genes in FGFR3 and Akt pathways, which regulate cell growth and tumor progression, respectively.

Aristolochic acids - Induced transcriptomic responses in rat renal proximal tubule cells in vitro

Aristolochic acids (AAs) are the active components of herbal drugs derived from Aristolochia species that have been used for medicinal purposes since antiquity. However, AAs have recently been discovered to be highly nephrotoxic and induced urothelial cancer in humans and malignant tumors in the kidney and urinary tract of rodents. In this study, we exposed rat renal proximal tubule cells in vitro to a sub-cytotoxic level of AAs at three different time points (6 h, 24 h and 72 h). We then analyzed the gene expression profile after the compound exposure. Functional analysis with Ingenuity Pathways Analysis and DAVID tools revealed that at the late time point (72 h) there are many significantly altered genes involved in cancer-related pathways such as p53 signaling. MIAMI-compliant microarray data are deposited in the NCBI GEO database under accession number GSE68687 and can be found at: http://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE68687.

Integrated microRNA, mRNA, and protein expression profiling reveals microRNA regulatory networks in rat kidney treated with a carcinogenic dose of aristolochic acid

Background

Aristolochic Acid (AA), a natural component of Aristolochia plants that is found in a variety of herbal remedies and health supplements, is classified as a Group 1 carcinogen by the International Agency for Research on Cancer. Given that microRNAs (miRNAs) are involved in cancer initiation and progression and their role remains unknown in AA-induced carcinogenesis, we examined genome-wide AA-induced dysregulation of miRNAs as well as the regulation of miRNAs on their target gene expression in rat kidney.

Results

We treated rats with 10 mg/kg AA and vehicle control for 12 weeks and eight kidney samples (4 for the treatment and 4 for the control) were used for examining miRNA and mRNA expression by deep sequencing, and protein expression by proteomics. AA treatment resulted in significant differential expression of miRNAs, mRNAs and proteins as measured by both principal component analysis (PCA) and hierarchical clustering analysis (HCA). Specially, 63 miRNAs (adjusted p value < 0.05 and fold change > 1.5), 6,794 mRNAs (adjusted p value < 0.05 and fold change > 2.0), and 800 proteins (fold change > 2.0) were significantly altered by AA treatment. The expression of 6 selected miRNAs was validated by quantitative real-time PCR analysis. Ingenuity Pathways Analysis (IPA) showed that cancer is the top network and disease associated with those dysregulated miRNAs. To further investigate the influence of miRNAs on kidney mRNA and protein expression, we combined proteomic and transcriptomic data in conjunction with miRNA target selection as confirmed and reported in miRTarBase. In addition to translational repression and transcriptional destabilization, we also found that miRNAs and their target genes were expressed in the same direction at levels of transcription (169) or translation (227). Furthermore, we identified that up-regulation of 13 oncogenic miRNAs was associated with translational activation of 45 out of 54 cancer-related targets.

Conclusions

Our findings suggest that dysregulated miRNA expression plays an important role in AA-induced carcinogenesis in rat kidney, and that the integrated approach of multiple profiling provides a new insight into a post-transcriptional regulation of miRNAs on their target repression and activation in a genome-wide scale.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1516-2) contains supplementary material, which is available to authorized users.

TP53 mutations in human cancer: database reassessment and prospects for the next decade

More than 50% of human tumors carry TP53 gene mutations and in consequence more than 45,000 somatic and germline mutations have been gathered in the UMD TP53 database (http://p53.fr). Analyses of these mutations have been invaluable for bettering our knowledge on the structure-function relationships within the TP53 protein and the high degree of heterogeneity of the various TP53 mutants in human cancer. In this review, we discuss how with the release of the sequences of thousands of tumor genomes issued from high-throughput sequencing, the description of novel TP53 mutants is now reaching a plateau indicating that we are close to the full set of mutants that target the elusive tumor-suppressive activity of this protein. We performed an extensive and thorough analysis of the TP53 mutation database, focusing particularly on specific sets of mutations that were overlooked in the past because of their low frequencies, for example, synonymous mutations, splice mutations, or mutations-targeting residues subject to posttranslational modifications. We also discuss the evolution of the statistical methods used to differentiate TP53 passenger mutations and artifactual data from true mutations, a process vital to the release of an accurate TP53 mutation database that will in turn be an invaluable tool for both clinicians and researchers.

Knockout and humanized mice as suitable tools to identify enzymes metabolizing the human carcinogen aristolochic acid

1. Aristolochic acid I (AAI) is the predominant component in plant extract of Aristolochia genus that is involved in development of aristolochic acid nephropathy, Balkan endemic nephropathy and urothelial cancer. The diseases do not develop in all individuals exposed to AAI and patients exhibit different clinical outcomes. Differences in the activities of enzymes catalyzing the metabolism of AAI might be one of the reasons for this individual susceptibility. 2. Understanding which human enzymes are involved in reductive activation of AAI generating AAI-DNA adducts, and/or its detoxication to the O-demethylated metabolite, aristolochic acid Ia (AAIa), is necessary in the assessment of the susceptibility to this compound. 3. This review summarizes the results of the latest studies utilizing genetically engineered mouse models to identify which human and rodent enzymes catalyze the reductive activation of AAI to AAI-DNA adducts and its oxidative detoxication to AAIa in vivo. 4. The use of hepatic cytochrome P450 (Cyp) reductase null (HRN) mice, in which NADPH:Cyp oxidoreductase (Por) is deleted in hepatocytes, Cyp1a1((-/-)), Cyp1a2((-/-)) single-knockout, Cyp1a1/1a2((-/-)) double-knockout and CYP1A-humanized mice revealed that mouse and human CYP1A1 and 1A2, besides mouse

NAD(P)H

quinone oxidoreductase, were involved in the activation of AAI but CYP1A1 and 1A2 also oxidatively detoxified AAI.

Upper urothelium carcinomas in Croatian endemic area

BACKGROUND/AIMS

Endemic nephropathy (EN) is a chronic tubulointerstitial disease. Strong association between EN and urothelial carcinoma was noted as early as 40-50 ago. The aim of the study was to determine and compare specific mortality and morbidity of renal pelvis and ureter (upper urothelium) carcinoma (UUC) among Croatia as a whole, Brod-Posavina County, and Croatian endemic area.

METHODS

Data on UUC mortality and morbidity were analyzed. Indirect standardization was employed on data comparison by calculating standardized mortality ratio and morbidity ratio.

RESULTS

Our study results showed the specific mortality rate in the endemic area to be 26.3-fold and 7.3-fold the rate recorded in Croatia and Brod-Posavina County, respectively. The mean standardized mortality ratio obtained by indirect standardization yielded an 8-fold and 32-fold risk of death from UUC in the endemic area vs. Brod-Posavina County and Croatia as a whole, respectively. These data revealed the specific morbidity in the Croatian endemic area and Brod-Posavina County to be 13.95-fold and 3.78-fold the morbidity recorded at the national level, respectively. The standardized morbidity ratio also showed the risk of developing UUC in the Croatian endemic area to be 3.75-fold the risk in Brod-Posavina County and 16.4-fold the risk in Croatia.

CONCLUSIONS

These results showed that specific mortality and morbidity as well as standardized morbidity ratio and standardized mortality ratio were higher in Croatian endemic area than in Brod-Posavina County and Croatia.

Genomics Traces Carcinogen Fingerprints

Genome-wide sequencing highlights the distinctive pattern of mutations caused by a plant that contains a potent carcinogen.

Molecular aspects of upper tract urothelial carcinoma

OBJECTIVES

Primary upper tract urothelial carcinoma (UTUC) is a relatively rare tumor with up to 60% of cases being muscle invasive at presentation. In this article we review the molecular biology of UTUC, an understanding of which may help to address some of the dilemmas surrounding the diagnosis and treatment of this disease and ultimately lead to the introduction of personalized treatment plans.

METHODS

The literature search on the molecular aspects of UTUC was performed using the National Library of Medicine database.

RESULTS

UTUC and urothelial carcinomas of the bladder share many common biological pathways. UTUC are more commonly associated with conditions such as Balkan Endemic Nephropathy and Hereditary Non Polyposis Colon Cancer (HNPCC), the molecular basis of which is now being understood. A large number of potential biomarkers have been studied to help identify robust prognostic markers in UTUC.

CONCLUSION

Advances in our understanding of the biology of UTUC is may in the future help to identify novel druggable targets, clinically applicable biomarkers and guide treatment of the rare but lethal condition.

Angiogenesis in upper tract urothelial carcinoma associated with Balkan endemic nephropathy

Upper tract urothelial carcinoma (UTUC) associated with Balkan endemic nephropathy (BEN) is characterized by a number of aberrations in cell-cycle regulation and apoptosis. The aim of this study was to detect angiogenesis-related marker(s) specific for BEN UTUC, and to examine the influence of HIF 1α upon angiogenesis and apoptosis in UTUC. Present investigation included 110 patients with UTUC, 50 from BEN region and 60 control tumors. Altered expression of VEGFR1 was more often present in control UTUC than in BEN tumors (p<0.005). It was associated with high grade, low and high stage, solid growth, and metaplastic change of control UTUC. Microvessel density assessed by CD31 (MVD CD31) was significantly higher in UTUC with lymphovascular invasion (p<0.05), and in BEN tumors with papillary growth (p<0.05). Discriminant analysis indicated that BEN and control tumors do not differ significantly in expression of angiogenesis related markers. The most important discriminant variable that determined control UTUC was expression of VEGFR1 (p=0.002). HIF 1α in UTUC significantly correlated with the low stage, papillary growth and expression of Bcl-2, Caspase-3 index, and MVD CD34 (p<0.001; 0.0005; 0.01; 0.005; 0.01, respectively). HIF-1α may be helpful marker in evaluation of UTUC, especially when combined with angiogenesis and apoptosis.

A reassessment of risk associated with dietary intake of ochratoxin A based on a lifetime exposure model

Mycotoxins, such as ochratoxin A (OTA), can occur from fungal growth on foods. OTA is considered a possible risk factor for adverse renal effects in humans based on renal tumors in male rats. For risk mitigation, Health Canada proposed maximum limits (MLs) for OTA based largely on a comparative risk assessment conducted by Health Canada (Kuiper-Goodman et al., 2010), in which analytical data of OTA in foods were used to determine the possible impact adopting MLs may have on OTA risks. The EU MLs were used for comparison and resultant risk was determined based on age-sex strata groups. These data were reevaluated here to determine comparative risk on a lifetime basis instead of age strata. Also, as there is scientific disagreement over the mechanism of OTA-induced renal tumors, mechanistic data were revisited. On a lifetime basis, risks associated with dietary exposure were found to be negligible, even without MLs, with dietary exposures to OTA three to four orders of magnitude below the pivotal animal LOAEL and the TD(05). Our review of the mechanistic data supported a threshold-based mechanism as the most plausible. In particular, OTA was negative in genotoxicity assays with the highest specificity and levels of DNA adducts were very low and not typical of genotoxic carcinogens. In conclusion, OTA exposures from Canadian foods do not present a significant cancer risk.

Could disappearance of endemic (Balkan) nephropathy be expected in forthcoming decades?

BACKGROUND/AIMS

An epidemiological survey of endemic nephropathy (EN) was performed in endemic Croatian areas and the current prevalence was compared to that reported for the same villages several decades ago.

METHODS

A total of 2,487 adult farmers from 6 endemic villages and 3 non-endemic villages were enrolled. An extensive epidemiological questionnaire, clinical examination and laboratory analyses of blood and urine were performed. According to the modified WHO criteria, participants were classified into diseased, suspected of having EN, and those at risk of developing EN.

RESULTS

The overall prevalence of EN in the Croatian areas was 1.0%, ranging between 0.3 and 2.3% in different villages. Those suspected of having EN amounted to 3.9%. In the endemic villages a decreasing trend in the prevalence of EN was observed comparable to the results obtained in previous surveys. It is interesting to note that no EN patients were recorded in the endemic village of Dubočac.

CONCLUSION

The prevalence of EN in the endemic Croatian areas appears to be decreasing. For the first time, we failed to detect any EN patients in a village that was previously considered endemic, which might indicate that EN is diminishing.

Kinetics of aristolochic acid I after oral administration of Radix Aristolochiae or Guanxinsuhe preparation in canines

ETHNOPHARMACOLOGICAL RELEVANCE

Aristolochic acid I (AAI), a major component derived from Aristolochia species, which have been known for a long time and remain in use today, particularly in Asia and Central America. It has been confirmed to induce a type of so-called aristolochic acid nephropathy (AAN) and involved in the development of Balkan endemic nephropathy (BEN).

AIM OF THE STUDY

To investigate the kinetic of AAI in beagle dogs after single-dose oral administration of Radix Aristolochiae or its preparation, Guanxinsuhe, as well as the effects of compound compatibility in traditional Chinese medicine on the pathologic processes of AAN.

MATERIALS AND METHODS

Beagle dogs were orally administrated Radix Aristolochiae (0.3 g/kg/day), Guanxinsuhe preparation (0.9 g/kg/day) (with an identical dosage of AAI), and empty capsules respectively for 180 days. Canines (n=2) were euthanized on day 90, 180, 210, HPLC was established to determine the AAI level in plasma and the kinetic behaviors of AAI in dogs were elucidated after single dosing. Hematoxylin and eosin (H&E)-staining was applied for histopathologic examination to evaluate the pathological status of kidneys.

RESULTS

Compared to canines with Radix Aristolochiae treatment, the Cmax, AUC, Tmax, and t(1/2β) of AAI in Guanxinsuhe preparation group were elevated, while t(1/2α) of AAI was decreased. The results indicated the co-existing components in Guanxinsuhe preparation could increase the absorption, accelerate the distribution, but delay the absorption and elimination of AAI. After long-term dosing, animals treated with Radix Aristolochiae were found with more severe renal impairment and higher AAI level in plasma.

CONCLUSIONS

It was demonstrated that the compound compatibility in Guanxinsuhe preparation can affect the kinetic process of AAI and attenuate the toxic effect on kidney when the duration of treatment was prolonged.

Herbal bioactivation, molecular targets and the toxicity relevance

There have been increasing reports on the adverse reactions associated with herbal consumption. For many of these adverse reactions, the underlying biochemical mechanisms are unknown, but bioactivation of herbal compounds to generate reactive intermediates have been implicated. This minireview updates our knowledge on metabolic activation of herbal compounds, molecular targets and the toxicity relevance. A number of studies have documented that some herbal compounds can be converted to toxic or even carcinogenic metabolites by Phase I [e.g. cytochrome P450s (CYPs)] and less frequently by Phase II enzymes. For example, aristolochic acids (AAs) in Aristolochia spp, which undergo reduction of the nitro group by hepatic CYP1A1/2 or peroxidases in extrahepatic tissues to generate highly reactive cyclic nitrenium ions. The latter can react with macromolecules (DNA and protein), resulting in activation of H-ras and myc oncogenes and gene mutation in renal cells and finally carcinogenesis of the kidneys. Teucrin A and teuchamaedryn A, two diterpenoids found in germander (Teuchrium chamaedrys) used as an adjuvant to slimming herbal supplements that caused severe hepatotoxicity, are converted by CYP3A4 to reactive epoxide which reacts with proteins such as CYP3A and epoxide hydrolase and inactivate them. Some naturally occurring alkenylbenzenes (e.g. safrole, methyleugenol and estragole) and flavonoids (e.g. quercetin) can undergo bioactivation by sequential 1-hydroxylation and sulfation, resulting in reactive intermediates capable of forming DNA adducts. Extensive pulegone metabolism generated p-cresol that is a glutathione depletory. The hepatotoxicity of kava is possibly due to intracellular glutathione depletion and/or quinone formation. Moreover, several herbal compounds including capsaicin from chili peppers, dially sulfone in garlic, methysticin and dihydromethysticin in kava, oleuropein in olive oil, and resveratrol found in grape seeds are mechanism-based (suicide) inhibitors of various CYPs. Together with advances of proteomics, metabolomics and toxicogenomics, an integrated systems toxicological approach may provide deep insights into mechanistic aspects of herb-induced toxicities, and contribute to bridging the relationships between herbal bioactivation, protein/DNA adduct formation and the toxicological consequences.

Aristolochic acid I induced oxidative DNA damage associated with glutathione depletion and ERK1/2 activation in human cells

Aristolochic acid I (AAI) has been widely found in herbal remedies and linked to the development of nephropathy and urothelial carcinoma in humans. This study elucidated the mechanism of oxidative stress and DNA damage mediated by AAI in human cells. Treatment of human promyelocytic leukemia cells (HL-60) and human renal proximal tubular cells (HK-2) with AAI led to a dose-dependent increase of reactive oxygen species (ROS). AAI also elevated the levels of DNA strand breaks and 8-hydroxy guanosine in HL-60 and HK-2 cells. Antioxidants, including Tiron, N-acetyl-l-cysteine (NAC) and glutathione (GSH), effectively suppressed the AAI-induced ROS and AAI-elicited genotoxicity, indicating that AAI induced the DNA damage through oxidative stress. GSH depletion was also found in AAI-treated cultures and proceeded prior to ROS formation. Exposure of HL-60 cells with AAI activated both ERK1/2 and p38 kinase phosphorylation, while only MEK1/2 inhibitor, U0126, significantly decreased AAI-mediated ROS. Preincubation of cells with thiol-containing compounds (NAC and GSH) inhibited the caspase 3 activity triggered by AAI, but non-thiol Tiron did not show a similar effect. This study demonstrated that AAI treatment results in oxidative stress-related DNA damage through GSH depletion and ERK1/2 activation; AAI-induced apoptosis is associated with GSH loss, but is independent of ROS generation.

Understanding wild-type and mutant p53 activities in human cancer: new landmarks on the way to targeted therapies

Three decades of p53 research have led to many advances in understanding the basic biology of normal and cancer cells. Nonetheless, the detailed functions of p53 in normal cells, and even more so in cancer cells, remain obscure. A major breakthrough is the realization that mutant p53 has a life of its own: it contributes to cancer not only through loss of activity, but also through gain of specific 'mutant functions'. This new focus on mutant p53 is the rationale behind the meeting series dedicated to advances on mutant p53 biology. This review provides an overview of results presented at the Fourth International Workshop on Mutant p53, held in Akko, Israel in March 2009. New roles and functions of p53 relevant for tumor suppressions were presented, including the regulation of microRNAs networks, the modulation of cell-stroma interactions and the induction of senescence. A main focus of the meeting was the rapidly growing body of knowledge on autonomous properties of mutant p53 and on their oncogenic 'gain of function' impact. Importantly, the meeting highlighted that, 30 years after p53 discovery, research on mutant p53 is entering the clinical and translational era. Two major steps forward in this respect are a better understanding of the active mechanism of small drugs targeting mutant p53 in tumor cells and an improved definition of the prognostic and predictive value of mutant p53 in human cancer.

Dietary influences on mutagenesis--where is this field going?

Early studies on dietary mutagenesis were mostly observational, with large numbers of potential dietary mutagens being identified from every conceivable dietary source. These included known dietary carcinogens such as aflatoxin B1 and benzo[a]pyrene, and hitherto unrecognized dietary mutagens, such as the pyrolysis products formed during the heating of proteinaceous materials (heterocyclic amines). The 1993 evaluation of 2-amino-3-methyl-3H-imidazo(4,5-j)quinoline as a probable human carcinogen by the International Agency for Research on Cancer was a landmark, as this was done in the absence of specific human carcinogenicity data, and strongly influenced by mutagenicity test data. In the 21st century, the field has moved from the identification of more and more mutagens, to molecular epidemiologic approaches that not only show a mutagenic effect but also seek to link it to a dietary (or environmental) cause. Effects of diet in stimulating chronic inflammation may lead to reactive species and thereby mutation as a secondary consequence, while dietary deficiencies and nutrient imbalances may be strong sources of mutagenesis. Recognition of the roles of nutrients in cell signaling processes and control of microRNAs suggest major influences on gene expression, in the absence of permanent DNA changes. Genome-wide association studies have highlighted new pathways such as JAK/STAT signaling that profoundly influence genomic instability and responses to dietary mutagens. With improved methodologies for DNA sequencing and epigenetic changes, it is time to apply more sophisticated approaches to recognizing and proving the role of diet as a primary modulator of mutagenesis in humans.

«Suspects» in etiology of endemic nephropathy: aristolochic acid versus mycotoxins

Despite many hypotheses that have been challenged, the etiology of endemic nephropathy (EN) is still unknown. At present, the implications of aristolochic acid (AA) and mycotoxins (ochratoxin A-OTA and citrinin-CIT) are under debate. AA-theory is based on renal pathohistological similarities between Chinese herbs nephropathy (CHN) and EN, findings of AA-DNA adducts in EN and in patients with urinary tract tumors (UTT), as well as the domination of A:T®T:A transversions in the p53 mutational spectrum of UTT patients, which corresponds with findings of such mutations in AA-treated rats. However, exposure pathways of EN residents to AA are unclear. Experimental studies attempting to deduce whether nephrotoxins OTA and CIT appear at higher frequencies or levels (or both) in the food and blood or urine of EN residents support the mycotoxin theory. Also, some molecular studies revealed the presence of OTA-DNA adducts in the renal tissue of EN and UTT patients. In this review, data supporting or arguing against AA and mycotoxin theory are presented and discussed.