Consensus statement on screening, diagnosis, classification and treatment of endemic (Balkan) nephropathy

Assessment of Retinal Microangiopathy in Patients with Balkan Endemic Nephropathy Using Optical Coherence Tomography Angiography-A Pilot Study

Background and Objectives: It is well known that alterations in microvascular structure and function contribute to the development of ocular, renal, and cardiovascular diseases. Accordingly, the presence of fundus vascular changes in patients suffering from chronic kidney disease (CKD) and Balkan endemic nephropathy (BEN) may provide information of prognostic value regarding the progression of renal disease. This study aimed to examine the associations between clinical characteristics and retinal optical coherence tomography angiography (OCTA) parameters in patients with BEN and compare them with those in CKD. Materials and Methods: This pilot study, conducted from March 2021 to April 2022, included 63 patients who were divided into two groups: the first group consisted of 29 patients suffering from BEN, and the second was a control group of 34 patients with CKD. Demographic, laboratory, clinical, and medication data were noted for all the patients included in this study. Each eye underwent OCT angiography, and the results were interpreted in accordance with the practical guide for the interpretation of OCTA findings. Results: Statistically significantly higher levels of total serum protein and triglycerides were recorded in the BEN group than in the CKD group, while the level of HDL cholesterol was lower. Based on the performed urinalysis, statistically significantly higher values of total protein and creatinine were detected in patients with CKD compared to the BEN group. It was demonstrated that the OCTA vascular plexus density of certain parts of the retina was in significant association with systolic and diastolic blood pressure, creatinine clearance, urinary creatinine, total cholesterol, diabetes mellitus type 2, age, body mass index, total serum and urinary protein, sCRP, and diuretic and antihypertensive treatment. Conclusions: In comparison with CKD, BEN leads to more significant disturbances in retinal vasculature density.

Unusual Urothelial Tumors and Refractory Uremia Due to Balkan Endemic Nephropathy: A Case Report

Balkan endemic nephropathy (BEN) is a rare progressive chronic renal disease found in residents living along the Balkan peninsula. We present a 92-year-old female who complained initially of cardio-respiratory symptoms and was found to have an acute hypoxemic respiratory failure with hypervolemia. The patient underwent computed tomography imaging and was found to have bilateral pleural effusions and moderate left-sided renal atrophy with left-sided hydronephrosis. The patient underwent diuresis for fluid overload and was treated with broad-spectrum antibiotics for hospital-acquired pneumonia. Further urological work-up revealed masses in the posterior bladder wall and left ureteropelvic junction. A biopsy of the posterior bladder wall mass confirmed high-grade papillary urothelial carcinoma. A review of the epidemiological history revealed the patient lived in Kosovo/former Yugoslavia for several decades following birth. A review of old records revealed the patient had chronic kidney disease (CKD) that was not fully explained by other causes, such as hypertension or diabetes. Given the epidemiological history, accelerated CKD, and unusual locations of urothelial carcinoma, the patient was diagnosed with BEN. Despite medical management and hemodialysis, the patient's renal function and mental status continued to deteriorate, and the decision was made to proceed with palliative care measures.

GPX3 rs8177412 Polymorphism Modifies Risk of Upper Urothelial Tumors in Patients with Balkan Endemic Nephropathy

Current data suggest that aristolochic acid (AA) exposure is a putative cause of Balkan endemic nephropathy (BEN), a chronic kidney disease strongly associated with upper tract urothelial carcinoma. The cellular metabolism of AA is associated with the production of reactive oxygen species, resulting in oxidative distress. Purpose: Therefore, the aim of this study was to analyze individual, combined and cumulative effect of antioxidant gene polymorphisms (Nrf2 rs6721961, KEAP1 rs1048290, GSTP1AB rs1695, GSTP1CD rs1138272, GPX3 rs8177412 and MDR1 rs1045642), as well as GSTP1ABCD haplotypes with the risk for BEN development and associated urothelial cell carcinoma in 209 BEN patients and 140 controls from endemic areas. Experimental method: Genotyping was performed using polymerase chain reaction (PCR) and PCR with confronting two-pair primers (PCR-CTTP) methods. Results: We found that female patients carrying both variant GPX3 rs8177412 and MDR1 rs1045642 genotypes in combination exhibited significant risk towards BEN (OR 1 = 3.34, 95% CI = 1.16-9.60, p = 0.025; OR 2 = 3.79, 95% CI = 1.27-11.24, p = 0.016). Moreover, significant association was determined between GPX3rs8174412 polymorphism and risk for urothelial carcinoma. Carriers of variant GPX3*TC + CC genotype were at eight-fold increased risk of BEN-associated urothelial tumors development. There was no individual or combined impact on BEN development and BEN-associated tumors among all examined polymorphisms. The haplotype consisting of variant alleles for both polymorphisms G and T was associated with 1.6-fold increased risk although statistically insignificant (OR = 1.64; 95% CI = 0.75-3.58; p = 0.21). Conclusions: Regarding GPX3 rs8177412 polymorphism, the gene variant that confers lower expression is associated with significant increase in upper urothelial carcinoma risk. Therefore, BEN patients carrying variant GPX3 genotype should be more frequently monitored for possible upper tract urothelial carcinoma development.

Aristolochic acid I as an emerging biogenic contaminant involved in chronic kidney diseases: A comprehensive review on exposure pathways, environmental health issues and future challenges

Described in the 1950s, Balkan Endemic Nephropathy (BEN) has been recognized as a chronic kidney disease (CKD) with clinical peculiarities and multiple etiological factors. Environmental contaminants - aromatic compounds, mycotoxins and phytotoxins like aristolochic acids (AAs) - polluting food and drinking water sources, were incriminated in BEN, due to their nephrotoxic and carcinogenic properties. The implication of AAs in BEN etiology is currently a highly debated topic due to the fact that they are found within the Aristolochiaceae plants family, used around the globe as traditional medicine and they were also incriminated in Aristolochic Acid Nephropathy (AAN). Exposure pathways have been investigated, but it is unclear to what extent AAs are acting alone or in synergy with other cofactors (environmental, genetics) in triggering kidney damage. Experimental studies strengthen the hypothesis that AAI, the most studied compound in the AAs class, is a significant environmental contaminant and a most important causative factor of BEN. The aim of this review is to compile information about the natural exposure pathways to AAI, via traditional medicinal plants, soil, crop plants, water, food, air. Data that either supports or contradicts the AAI theory concerning BEN etiology was consolidated and available solutions to reduce human exposure were discussed. Because AAI is a phytotoxin with physicochemical properties that allow its transportation in environmental matrices from different types of areas (endemic, nonendemic), and induce CKDs (BEN, AAN) and urinary cancers through bioaccumulation, this review aims to shed a new light on this compound as a biogenic emerging pollutant.

Molecular profiles and urinary biomarkers of upper tract urothelial carcinomas associated with aristolochic acid exposure

Recurrent upper tract urothelial carcinomas (UTUCs) arise in the context of nephropathy linked to exposure to the herbal carcinogen aristolochic acid (AA). Here we delineated the molecular programs underlying UTUC tumorigenesis in patients from endemic aristolochic acid nephropathy (AAN) regions in Southern Europe. We applied an integrative multiomics analysis of UTUCs, corresponding unaffected tissues and of patient urines. Quantitative microRNA (miRNA) and messenger ribonucleic acid (mRNA) expression profiling, immunohistochemical analysis by tissue microarrays and exome and transcriptome sequencing were performed in UTUC and nontumor tissues. Urinary miRNAs of cases undergoing surgery were profiled before and after tumor resection. Ribonucleic acid (RNA) and protein levels were analyzed using appropriate statistical tests and trend assessment. Dedicated bioinformatic tools were used for analysis of pathways, mutational signatures and result visualization. The results delineate UTUC-specific miRNA:mRNA networks comprising 89 miRNAs associated with 1,862 target mRNAs, involving deregulation of cell cycle, deoxyribonucleic acid (DNA) damage response, DNA repair, bladder cancer, oncogenes, tumor suppressors, chromatin structure regulators and developmental signaling pathways. Key UTUC-specific transcripts were confirmed at the protein level. Exome and transcriptome sequencing of UTUCs revealed AA-specific mutational signature SBS22, with 68% to 76% AA-specific, deleterious mutations propagated at the transcript level, a possible basis for neoantigen formation and immunotherapy targeting. We next identified a signature of UTUC-specific miRNAs consistently more abundant in the patients' urine prior to tumor resection, thereby defining biomarkers of tumor presence. The complex gene regulation programs of AAN-associated UTUC tumors involve regulatory miRNAs prospectively applicable to noninvasive urine-based screening of AAN patients for cancer presence and recurrence.

Risk characterisation of constituents present in jamu to promote its safe use

Safety in use of jamu consumption, as part of traditional medicine from Indonesia, is dependent on the complete and adequate assessment of potential hazards and risks of the botanicals and botanical constituents included. This includes especially hazards and risks related to the presence in jamu of active pharmaceutical ingredients (APIs) as well as of constituents that are genotoxic and carcinogenic. The present review presents an overview of the current state-of-the art on these hazards and risks based on case reports on adulteration, and the actual detection of genotoxic and carcinogenic ingredients of concern in jamu. Based on the overview thus obtained, it appears that drug-adulteration presents important hazards responsible for potential adverse effects, due to overdosing. The potential hazards of exposure to APIs mainly relate to the presence of constituents that may cause liver damage, renal impairment, kidney failure, steroid dependence or genotoxicity and carcinogenicity. For these APIs, a risk characterisation was performed based on comparison of health-based guidance values (HBGVs) and exposure, while for the genotoxic carcinogens the margin of exposure (MOE) approach was used. Results of this risk characterisation should be used by risk managers to impose specification for constituents of health concern to protect consumers. It is concluded that to manage the risks identified and further improve the safety in use of jamu, a collaboration between farmers, manufacturer/producers, academia, government, health professionals, and consumers is indicated.

Microarray analysis of the time-dependent expression profiles of long non-coding RNAs in the progression of vein graft stenotic disease

Long non-coding RNAs (lncRNAs) have been reported to be involved in various biological processes, including cell proliferation and apoptosis. However, the expression profiles of lncRNAs in patients with vein graft restenosis remain unknown. In the present study, the time-dependent expression profiles of genes in vein bypass grafting models were examined by microarray analysis. A total of 2,572 lncRNAs and 1,652 mRNAs were identified to be persistently significantly differentially expressed. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analysis was performed to investigate the functions of these lncRNAs. A total of 360 lncRNAs and 135 protein-coding genes were predicted to be involved in the vascular remodeling process. Co-expression network analysis revealed the association between 194 lncRNAs and seven associated protein-coding genes, including transforming growth factor-β1, Fes, Yes1 associated transcriptional regulator, sphingosine-1-phosphate receptor 1, Src, insulin receptor and melanoma cell adhesion molecule. Moreover, reverse transcription-quantitative PCR results supported those of the microarray data, and overexpression of AF062402, which regulates the transcription of Src, stimulated the proliferation of primary vascular smooth muscle cells. The findings of the present study may facilitate the development of novel therapeutic targets for vein graft restenosis and may help to improve the prognosis of patients following coronary artery bypass grafting.

Aristolochic acid-associated urinary tract cancers: an updated meta-analysis of risk and oncologic outcomes after surgery and systematic review of molecular alterations observed in human studies

BACKGROUND

The risk of primary aristolochic acid (AA)-associated urothelial carcinoma (AA-UC) has been summarized by a 2013-published meta-analysis. Given that additional evidence has been continuously reported by original studies, an updated meta-analysis is needed. Meanwhile, to complete the whole picture, a systematic review of molecular alterations observed in AA-urinary tract cancers (AA-UTC) was also performed.

METHODS

We searched PubMed, Embase and four Chinese databases up to October 2020. Observational studies comparing risk or oncologic outcomes of UTC between patients with and without AA exposure were eligible for systematic review and meta-analysis. Studies investigating molecular alterations in AA-UTC using human tissue samples were eligible for systematic review.

RESULTS

In total, 38 and 20 studies were included in the systematic review and meta-analysis, respectively. Exposure to AA led to an overall increased risks of primary UTC [UC and renal cell carcinoma (RCC)] (OR 6.085, 95% CI 3.045-12.160) and postoperatively recurrent UC (RR 1.831, 95% CI 1.528-2.194). Subgroup analysis of postoperative primary AA-upper tract UC (AA-UTUC) showed increased risks of bladder recurrence (adjusted RR 1.949, 95% CI 1.462-2.597) and contralateral UTUC recurrence (crude RR 3.760, 95% CI 2.225-6.353), worse overall survival (adjusted HR 2.025, 95% CI 1.432-2.865) and worse disease-specific survival (adjusted HR 3.061, 95% CI 1.190-7.872), but no effect on cancer-specific survival (adjusted HR 0.772, 95% CI 0.269-2.215). High mutation load with AA mutational signature presenting largely in the putative driver genes was observed in AA-UTUC. In contrast, AA mutational signature is rarely found in the mutated RCC driver genes and the mutation load in AA-RCC is low. Therefore, AA has different roles in the genesis of UTUC and RCC.

CONCLUSIONS

Implementing effective strategies to completely protect people from exposure to AA is urgently needed. Additionally, more effort should be made in identifying the precise carcinogenic mechanisms of AA to determine the future treatment strategies.

PLAIN LANGUAGE SUMMARY

Risk, recurrence and survival outcomes after surgery and molecular changes possibly involved in the genesis of aristolochic acid-associated urinary tract cancers Background: The association between aristolochic acid (AA) and primary urothelial carcinoma (UC) has been summarized by a 2013-published meta-analysis. Given that additional evidence has been reported in the past 7 years, an updated meta-analysis is needed. Meanwhile, to complete the whole picture, a systematic review of molecular changes possibly involved in AA-mediated urinary tract carcinogenesis was also performed. Methods: We searched PubMed, Embase and four Chinese databases for human studies up to October 2020. Studies comparing the risk of urinary tract cancer (UTC) between patients with and without AA exposure and studies investigating the molecular changes in AA-associated UTC (AA-UTC) using human tissue samples were eligible for inclusion. Thirty-eight studies were finally included. Results: The results showed that exposure to AA was associated with a 6-fold increased risk of primary UTC (UC and renal cell carcinoma, RCC) and a 1.8-fold increased risk of postoperatively recurrent UC. After studies reporting primary AA-upper tract UC (AA-UTUC) were analyzed, a 1.9-fold increased risk of bladder recurrence and a 3.8-fold increased risk of contralateral UTUC recurrence was observed. Additionally, exposure to AA worsened the postoperative survival of patients with UTUC by a 2-fold increased risk of overall death and a 3-fold increased risk of death from other diseases and recurrences. However, there was no effect on death due to cancer. Lastly, AA seemed to play different roles in the etiology of UTUC and RCC based on the observations of different mutation loads and different distributions of AA-induced mutations in AA-UTUC and AA-RCC samples. Conclusions: Implementing effective strategies to completely protect people from exposure to AA is urgently needed. Moreover, more effort should be made in identifying the precise carcinogenic mechanisms of AA-UTC to determine the future treatment strategies.

Aristolochic acid and its effect on different cancers in uro-oncology

PURPOSE OF REVIEW

To acquaint urologists with aristolochic acid nephropathy, an iatrogenic disease that poses a distinct threat to global public health. In China alone, 100 million people may currently be at risk. We illustrate the power of molecular epidemiology in establishing the cause of this disease.

RECENT FINDINGS

Molecular epidemiologic approaches and novel mechanistic information established a causative linkage between exposure to aristolochic acid and urothelial carcinomas of the bladder and upper urinary tract. Noninvasive tests are available that detect urothelial cancers through the genetic analysis of urinary DNA. Combined with cytology, some of these tests can detect 95% of patients at risk of developing bladder and/or upper urothelial tract cancer. Robust biomarkers, including DNA-adduct and mutational signature analysis, unequivocally identify aristolochic acid-induced tumours. The high mutational load associated with aristolochic acid-induced tumours renders them candidates for immune-checkpoint therapy.

SUMMARY

Guided by recent developments that facilitate early detection of urothelial cancers, the morbidity and mortality associated with aristolochic acid-induced bladder and upper tract urothelial carcinomas may be substantially reduced. The molecular epidemiology tools that define aristolochic acid-induced tumours may be applicable to other studies assessing potential environmental carcinogens.

The role of HLA in Balkan endemic nephropathy

Balkan endemic nephropathy (BEN), a progressive chronic tubulointerstitial disease, occurs in the endemic focus of Croatia in a population of about 10,000 inhabitants. One of its most peculiar characteristics is a strong association with upper tract urothelial carcinoma (UTUC). Despite a high number of studies, currently there are insufficient data about the association of BEN and HLA genes. The aim of this study was to investigate the polymorphism of HLA-A, -B, and -DRB1 alleles and haplotypes among BEN patients and to determine whether an association between HLA and BEN exists. In this study, we investigated HLA-A, -B, and -DRB1 alleles and haplotypes in a population of patients with BEN (N = 111) and matched healthy controls (N = 190). All individuals were tested by PCR-SSO and PCR-SSP methods to assess the possible contribution of HLA alleles and haplotypes to the development of/protection from BEN. Our results showed a positive association between the presence of HLA-B*35:02 and DRB1*04:02 alleles and BEN (P = 0.0179 and P = 0.0151, respectively) in contrast to the protective effect of HLA-A*01:01, B*27:05 and B*57:01 alleles (P = 0.0111, P = 0.0330 and P = 0.0318, respectively). Moreover, when BEN patients' HLA haplotypes were compared to controls, two haplotypes were associated with BEN susceptibility among Croatians (HLA-A*02:01~B*08:01~DRB1*03:01 and HLA-A*02:01~B*27:02~DRB1*16:01, P = 0.0064 and P = 0.0023, respectively), while haplotypes HLA-A*02:01~B*27:05~DRB1*01:01 and HLA-A*02:01~B*38:01~DRB1*13:01 each showed a possible protective effect (P = 0.0495). Our results point toward genetic susceptibility to BEN and observed differences in both susceptible/protective HLA profiles indicate the necessity of further studies in order to elucidate the pathogenesis of this disease.

Local and Systemic Oxidative Stress in Balkan Endemic Nephropathy Is Not Associated with Xanthine Oxidase Activity

Balkan endemic nephropathy (BEN) represents a chronic tubulointerstitial nephropathy which is followed by the progression of kidney fibrosis to end-stage kidney failure. The critical involvement of poisons in food (aristolochic acid (AA), ochratoxin, and heavy metals) and selenium deficiency are among nutritive factors which contribute to the pathogenesis of BEN, due to reactive oxygen species (ROS) liberation and/or decreased antioxidative defence system. The aim of the study is to distinguish a possible systemic and local origin of ROS through the measurement of xanthine oxidase (XO) activity in urine and plasma, along with the determination of the oxidative changes in lipids and proteins. The study included 50 patients with BEN and 38 control healthy subjects. We noted increased levels of both thiobarbituric acid-reactive substances (TBARS) and advanced oxidation protein products (AOPPs) in the plasma of patients with BEN, compared to the control group (p < 0.001). The urinary levels of AOPPs were higher in patients with BEN in comparison to the control (p < 0.001). The specific activity of XO was significantly lower in plasma and urine in BEN samples, compared to controls (p < 0.005). Based on these results, we hypothesize that XO might not be considered a direct systemic or local contributor to ROS production in BEN, most probably because of the diminished kidney functional tissue mass and/or AA-induced changes in purine nucleotide conformation. The increased AOPP and TBARS level in both plasma and urine in BEN may predict ROS systemic liberation with toxic local effects.

Genetic and Developmental Factors in Chronic Kidney Disease Hotspots

Chronic kidney disease increasingly is being recognized as an important global public health problem. Interindividual susceptibility to kidney disease is high and likely is dependent on risk modulation through genetics, fetal and early childhood development, environmental circumstances, and comorbidities. Traditionally, the chronic kidney disease burden has been ascribed largely to hypertension and diabetes. Increasingly, evidence is accumulating that nontraditional risk factors may predominate in some regions and populations, contributing to epidemics of kidney disease. Such nontraditional risk factors include environmental exposures, traditional medicines, fetal and maternal factors, infections, kidney stones, and acute kidney injury. Genetic factors may predispose patients to chronic kidney disease in some populations. Chronic kidney disease of unknown origin has its epicenters in Central America and South Asia. Such clustering of CKD may represent either genetic or environmentally driven kidney disease, or combinations of both. Developmental conditions impacting kidney development often are related to poverty and structural factors that persist throughout life. In this article, we explore the possibilities that genetic and developmental factors may be important contributors to the epidemics in these regions and suggest that optimization of factors impacting kidney development hold promise to reduce the risk of kidney disease in future generations.

Geographic distribution and risk of upper urothelial carcinomas in Croatia, 2001-2011

BACKGROUND

Strong associations exist between Balkan endemic nephropathy (BEN) and upper urothelial carcinomas (UUCs). However, the common etiology between the two remains unclear and there are no studies to date that visualize UUC risks in Croatia. In Croatia, 14 villages in the southwestern part of Brod-Posavina County are considered endemic for BEN. The aim of this ecological study is to map cancer risks and describe the case distribution of UUCs in Croatia at the county level during 2001-2011.

METHODS

A total of 608 incident cases from the Croatian National Cancer Registry were identified. Indirect standardization was employed to compute standardized incidence ratios (SIRs).

RESULTS

Counties with SIRs greater than 1 were concentrated around the agricultural region of Slavonia and the coastal region of Dalmatia. However, only Brod-Posavina County and Vukovar-Srijem County had a statistically significant risk of UUC development, where there were 390 and 210% more UUC cases observed than expected, respectively. Only unique to Brod-Posavina County, females were at higher risk (SIR 4.96; 95% CI 3.59-6.34) of developing UUCs than males (SIR 3.03; 95% CI 2.04-4.01) when compared to their Croatian counterparts. Although Brod-Posavina County only made up 3.7% of the total Croatian population (as of 2011), it had the highest frequency of incident UUC cases after the capital City of Zagreb. No elevated cancer risks were noted in the City of Zagreb, even after stratifying by sex.

CONCLUSION

Our findings suggest that Brod-Posavina County had the highest cancer risk for UUCs, especially among females, when compared to Croatia as a whole during 2001-2011. Given that a majority of BEN patients develop associated UUCs, concurrent screening programs for UUCs and BEN should be considered not only in endemic areas of BEN but also the surrounding rural areas and amongst at-risk groups such as those undergoing hemodialysis, who frequently develop UUCs, to help clarify BEN-UUC associations by identifying common risk factors while standardizing disease estimates across endemic regions for BEN.

Association of SOD2 (rs4880) and GPX1 (rs1050450) Gene Polymorphisms with Risk of Balkan Endemic Nephropathy and its Related Tumors

Background: Experimental data show that superoxide dismutase 2 (SOD2) is involved in ochratoxin (OTA)-induced nephrotoxicity, whereas clinical data indicate the role of SOD2 rs4880 or glutathione peroxidase 1 (GPX1) rs1050450 polymorphisms in end-stage renal disease and urothelial carcinoma risk, known to be the major complications of Balkan endemic nephropathy (BEN). Therefore, we hypothesized that SOD2 and GPX1 gene polymorphisms would influence the risk of BEN and its associated tumors. Materials and Methods: The study was conducted in 207 BEN patients and 86 controls from endemic areas. Results: Individuals with both copies of variant SOD2 allele, known for lower mitochondrial antioxidant protection, are at a significantly higher BEN risk (OR = 2.6, p = 0.021). No association was observed between GPX1 gene polymorphism and BEN risk. Combining SOD2 and GPX1 genotypes did not alter the risk of BEN development. Regarding the risk of urothelial tumors in BEN patients, none of the polymorphisms studied was significantly associated with the risk of these tumors. Conclusions: Polymorphism in SOD2 rs4880 gene affects the risk of BEN development. Hence, SOD2 genotyping could, together with a panel of other enzymes, be used as a biomarker of susceptibility in BEN areas.

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.

Increased Glomerular Filtration Rate in Early Stage of Balkan Endemic Nephropathy

Background: A previous study indicated that Balkan endemic nephropathy (BEN) patients in the early stage of the disease had significantly higher creatinine clearance (Ccr) than healthy persons. The aim of the study was to assess whether tubular creatinine secretion affects Ccr in early stages of BEN and to check the applicability of serum creatinine-based glomerular filtration rate (GFR) equations in these patients. Methods: The study involved 21 BEN patients with estimated GFR (eGFR) above 60 mL/min/1.73 m², excluding any conditions that could affect GFR or tubular creatinine secretion, and 15 healthy controls. In all participants Ccr with and without cimetidine and iohexol clearance (mGFR) were measured and eGFR calculated using Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) and Modification of Diet in Renal Disease Study (MDRD) equations. Glomerular hyperfiltration cutoff (GFR-HF) was calculated. Results: There was no significant difference between the groups in Ccr before and after cimetidine or for eGFR, but mGFR was significantly higher in BEN patients than in controls (122.02 ± 28.03 mL/min/1.73 m² vs. 101.15 ± 27.32 mL/min/1.73 m²; p = 0.032). Cimetidine administration reduced Ccr by 10% in both groups. The ratio of Ccr to mGFR was significantly above one in seven BEN patients and five controls and their mGFR values were similar. Seven other patients and eight controls had this ratio equal to one, while values below one were recorded for seven more patients and two controls. mGFR of all these 14 patients was significantly higher than that of healthy controls (129.88 ± 27.52 mL/min/1.73 m² vs. 107.43 ± 19.51 mL/min/1.73 m²; p = 0.009). Mean GFR-HF was significantly higher than mGFR in controls, but these two values were similar in BEN patients. eGFR underestimated mGFR in both BEN patients and controls. Conclusion: The ratio of Ccr to mGFR and mGFR to GFR-HF indicated that elevated mGFR in early stages of BEN could be explained by increased glomerular filtration, but tubular creatinine secretion augmented Ccr in a smaller proportion of patients, who did not differ from healthy subjects.

Critical Appraisal of International Clinical Practice Guidelines in Kidney Transplantation Using the Appraisal of Guidelines for Research and Education II Tool: A Systematic Review

BACKGROUND

Although clinical practice guidelines (CPGs) are used for the development of local protocols in kidney transplantation (Ktx), the quality of their methodology is variable. This systematic review aimed to critically appraise international CPGs in all aspects of Ktx using the Appraisal of Guidelines for Research and Evaluation II tool.

METHODS

Clinical Practice Guidelines in Ktx and donation published between 2010 and 2017 were identified from MEDLINE, Embase, National Guideline Clearinghouse, National Health Service and National Institute for Health and Care Excellence Evidence Searches, and the websites of transplant societies. Using Appraisal of Guidelines for Research and Evaluation II, 3 appraisers assessed the quality of CPGs. Interrater reliability was measured using the intraclass correlation coefficient (ICC).

RESULTS

Searches identified 3168 records, and 115 CPGs were included. The highest scoring Appraisal of Guidelines for Research and Evaluation II domain was "scope and purpose" (80%; range, 30%-100%), followed by "clarity of presentation" (77%; range, 43%-98%), "editorial independence" (52%; range, 0%-94%), "rigor of development" (47%; range 6%-97%) and "stakeholder involvement" (41%; range, 11%-85%). The poorest scoring domain was "applicability" (31%; range, 3%-74%). Most CPGs were recommended for future use either with (63%) or without (18%) modifications. A small number (14%) were not recommended for future use or reviewers (5%) did not agree on recommending the CPG. The overall mean CPG quality score was 4 of 7 (range, 2-7). The mean ICC of 0.74 indicated substantial agreement between reviewers.

CONCLUSIONS

The quality of international CPGs in Ktx was variable, and most CPGs lacked key aspects of methodological robustness and transparency. Improvements in methodology, patient involvement, and strategies for implementation are required.

Arterial Stiffness in Balkan Endemic Nephropathy, an Environmental Form of Aristolochic Acid Nephropathy

Balkan endemic nephropathy (BEN), an environmental form of aristolochic acid nephropathy is characterized with later onset and milder forms of hypertension (HT). Thus, we hypothesized that arterial stiffness progresses slower in BEN patients resulting in lower CV mortality. A total of 186 hemodialysed (HD) patients (90 BEN, 96 non-BEN; 67.3 + 13.0 years) were enrolled and followed-up for 25 months. Brachial blood pressure (BP) and pulse wave velocity (PWV) were determined before mid-week dialysis. BEN patients were older (72.1 ± 37.1 vs. 62.8 ± 15.1; p < 0.001), had shorter duration of HT prior commencement of HD than non-BEN patients (36 vs. 84 months; p < 0.001). There were no differences in BP, but BEN patients were treated with less antihypertensive drugs (p < 0.01). BEN patients had lower PWV values at baseline and at the end of follow-up period despite being chronologically older (p < 0.001). Baseline PWV > 10 m/s was associated with higher risk for CV mortality (aHR 1.8 [1.4, 2.4]). In multivariate analyses BEN was predictor of lower PWV. During the follow-up period significantly less CV deaths were observed in BEN vs. on-BEN patients (12 vs. 31; p = 0.001). CV mortality adjusted for other risk factors was significantly lower in BEN group (aHR 0.2 [0.1, 0.5]). Overall BEN patients had longer mean survival time on HD (22.3 vs. 18.2 months; p < 0.001). Observed slower vascular aging (i.e., lower PWV) in BEN patients compared to other ESRD patients is related to the later onset of HT and milder stages of HT during predialytic clinical course and better control of BP and phosphate during HD.

Differences in Risk Factors and Prevalence of Vascular Calcification between Pre-Dialysis and Hemodialysis Balkan Nephropathy Patients

Aims: The aim of this study was to compare the risk factors and prevalence of vascular calcification (VC) in pre-dialysis and hemodialysis (HD) patients with Balkan endemic nephropathy (BEN) or other kidney diseases (non-BEN). Materials and Methods: The study involved 115 patients, 32 pre-dialysis and 83 HD patients, separated into groups of BEN and non-BEN patients. In addition to interviews, objective examinations and laboratory analyses, VC was assessed using Adragao score. Results: Patients with BEN were significantly older in both groups, while pre-dialysis BEN patients had significantly lower systolic blood pressure, serum cholesterol and phosphorus levels, but higher urinary excretion of phosphorus than non-BEN patients. These differences were lost in HD groups. In pre-dialysis patients, prevalence of VC was lower in BEN than in non-BEN group and mean VC score differed significantly between them (2.8 (1.7) vs. 4.6 (1.8); p = 0.009). No significant difference in VC score was found between BEN and non-BEN patients on HD. Multivariate analysis showed that in pre-dialysis patients VC score >4 was associated with lower iPTH and higher serum cholesterol level, but in the HD group with higher serum triglyceride level and longer HD vintage. Conclusions: Lower prevalence of risk factors for VC in the BEN than non-BEN patients was found in pre-dialysis but not in HD group and this was reflected in the prevalence and severity of VC in the groups. Prevalence of VC and mean VC score were significantly lower in pre-dialysis BEN than in non-BEN patients but not for those on HD.

Upper Urinary Tract Urothelial Cancer in Croatian and Bosnian Endemic Nephropathy Regions

Objectives

Endemic nephropathy (EN) is a chronic tubulointerstitial renal disease associated with increased incidence of upper urinary tract urothelial cancer (UTUC) occurring predominantly in geographically limited areas in villages along big Danube river. Based on results obtained by the research it is confirmed that aristolochic acid is causative agent of endemic nephropathy (EN).

Aim

The aim of this study was to determine characteristics of UTUC in two endemic areas and analyze trends in 5-year period.

Methods

This study included all patients with UTUC with or without synchronous/metachronous urothelial cancer in urinary bladder, from Croatian and Bosnian EN and non-EN regions. We analyzed archival data bases from all patients with UTUC who were admitted and operated in Department for surgery and urology, General Hospital Josip Bencevic Slavonski Brod in the time period between 2005 and 2010. Analyzed groups of patients were divided and compared as EN group (that includes patients from Croatian and Bosnian EN region) and non-EN group (that includes patients from Croatian and Bosnian non-EN region). All surgical specimens were processed according to standardized pathological procedures.

Results

Comparing patients basic characteristics from Croatian and Bosnian EN region there was no significant difference in gender (females were more frequently affected in both EN regions, p=0.99) or age (p=0.43) of patients. We found higher blood levels of urea and creatinine in group of patients from Croatian EN region when compared with group of patients from Bosnian EN region but the difference was not statistically significant (p=0.79 and p=0.44, respectively). In patients from Croatian EN group Hemoglobin levels were significantly lower than levels from Bosnian EN region patients, p=0.0049. In group of patients from Bosnian EN region ureteral tumors were more frequently observed than in Croatian group of patients, when compared with renal pelvis tumors but the difference was not statistically significant (p=0.258).

Conclusion

Our data showed some differences in tumor localization between to investigated, relatively nearly situated, EN regions in Croatia and Bosnia. Statistically significant difference in hemoglobin levels between Croatian and Bosnian EN regions that should be further analyzed to give some reasonable explanation.

Reliability of CKD-EPI predictive equation in estimating chronic kidney disease prevalence in the Croatian endemic nephropathy area

Introduction

Chronic kidney disease (CKD) is a significant public health problem and it is not possible to precisely predict its progression to terminal renal failure. According to current guidelines, CKD stages are classified based on the estimated glomerular filtration rate (eGFR) and albuminuria. Aims of this study were to determine the reliability of predictive equation in estimation of CKD prevalence in Croatian areas with endemic nephropathy (EN), compare the results with non-endemic areas, and to determine if the prevalence of CKD stages 3-5 was increased in subjects with EN.

Materials and methods

A total of 1573 inhabitants of the Croatian Posavina rural area from 6 endemic and 3 non-endemic villages were enrolled. Participants were classified according to the modified criteria of the World Health Organization for EN. Estimated GFR was calculated using Chronic Kidney Disease Epidemiology Collaboration equation (CKD-EPI).

Results

The results showed a very high CKD prevalence in the Croatian rural area (19%). CKD prevalence was significantly higher in EN then in non EN villages with the lowest eGFR value in diseased subgroup.

Conclusions

eGFR correlated significantly with the diagnosis of EN. Kidney function assessment using CKD-EPI predictive equation proved to be a good marker in differentiating the study subgroups, remained as one of the diagnostic criteria for EN.

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.

Balkan endemic nephropathy: an update on its aetiology

Balkan endemic nephropathy (BEN) is a unique, chronic renal disease frequently associated with upper urothelial cancer (UUC). It only affects residents of specific farming villages located along tributaries of the Danube River in Bosnia-Herzegovina, Croatia, Macedonia, Serbia, Bulgaria, and Romania where it is estimated that ~100,000 individuals are at risk of BEN, while ~25,000 have the disease. This review summarises current findings on the aetiology of BEN. Over the last 50 years, several hypotheses on the cause of BEN have been formulated, including mycotoxins, heavy metals, viruses, and trace-element insufficiencies. However, recent molecular epidemiological studies provide a strong case that chronic dietary exposure to aristolochic acid (AA) a principal component of Aristolochia clematitis which grows as a weed in the wheat fields of the endemic regions is the cause of BEN and associated UUC. One of the still enigmatic features of BEN that need to be resolved is why the prevalence of BEN is only 3-7 %. This suggests that individual genetic susceptibilities to AA exist in humans. In fact dietary ingestion of AA along with individual genetic susceptibility provides a scenario that plausibly can explain all the peculiarities of BEN such as geographical distribution and high risk of urothelial cancer. For the countries harbouring BEN implementing public health measures to avoid AA exposure is of the utmost importance because this seems to be the best way to eradicate this once mysterious disease to which the residents of BEN villages have been completely and utterly at mercy for so long.

Biomarkers of oxidative damage and antioxidant enzyme activities in pre-dialysis Balkan endemic nephropathy patients

AIM

To obtain more insight into molecular mechanisms underlying oxidative stress in Balkan endemic nephropathy (BEN), biomarkers of oxidative stress and antioxidant enzyme activities were studied in 38 pre-dialysis BEN patients, 21 healthy BEN family members and 36 healthy subjects from non-endemic areas.

METHODS

Protein thiol groups (P-SH), antioxidant enzyme activities [superoxide dismutase (SOD) and glutathione peroxidase (GPX)], were determined in plasma spectrophotometrically, while malondialdehyde adducts (MDA) by enzyme immunoassay.

RESULTS

BEN patients had significantly lower plasma GPX activity in comparison with values for both control groups (p = 0.016), gradually decreasing with kidney function impairment estimated by glomerular filtration rate (r = 0.53, p = 0.002). GPX activity was inversely correlated with serum urea (r = -0.627, p < 0.001), creatinine (r = -0.53, p < 0.05), urinary excretion of protein and α1-microglobulin (r = -0.44, p = 0.012; r = -0.50, p < 0.007). Significant upregulation of SOD activity was observed in healthy BEN family members (p < 0.05). While the concentration of MDA adducts was similar in all three groups, BEN patients and healthy BEN family members exhibited increased protein damage, based on fewer P-SH groups in comparison with subjects from non-BEN areas (p = 0.085; p = 0.014, respectively).

CONCLUSIONS

Based on our results on increased oxidative protein damage in both pre-dialysis BEN patients and healthy BEN family members, it can be speculated that individuals from BEN areas, in general, are chronically exposed to some prooxidant environmental compounds. Moreover, decrease in plasma GPX activity, as a consequence of impaired kidney function, could further affect oxidative status in BEN patients.

Low-Coverage Exome Sequencing Screen in Formalin-Fixed Paraffin-Embedded Tumors Reveals Evidence of Exposure to Carcinogenic Aristolochic Acid

BACKGROUND

Dietary exposure to cytotoxic and carcinogenic aristolochic acid (AA) causes severe nephropathy typically associated with urologic cancers. Monitoring of AA exposure uses biomarkers such as aristolactam-DNA adducts, detected by mass spectrometry in the kidney cortex, or the somatic A>T transversion pattern characteristic of exposure to AA, as revealed by previous DNA-sequencing studies using fresh-frozen tumors.

METHODS

Here, we report a low-coverage whole-exome sequencing method (LC-WES) optimized for multisample detection of the AA mutational signature, and demonstrate its utility in 17 formalin-fixed paraffin-embedded urothelial tumors obtained from 15 patients with endemic nephropathy, an environmental form of AA nephropathy.

RESULTS

LC-WES identified the AA signature, alongside signatures of age and APOBEC enzyme activity, in 15 samples sequenced at the average per-base coverage of approximately 10×. Analysis at 3 to 9× coverage revealed the signature in 91% of the positive samples. The exome-wide distribution of the predominant A>T transversions exhibited a stochastic pattern, whereas 83 cancer driver genes were enriched for recurrent nonsynonymous A>T mutations. In two patients, pairs of tumors from different parts of the urinary tract, including the bladder, harbored overlapping mutation patterns, suggesting tumor dissemination via cell seeding.

CONCLUSIONS

LC-WES analysis of archived tumor tissues is a reliable method applicable to investigations of both the exposure to AA and its biologic effects in human carcinomas.

IMPACT

By detecting cancers associated with AA exposure in high-risk populations, LC-WES can support future molecular epidemiology studies and provide evidence-base for relevant preventive measures.

Kidney length in healthy members of Balkan endemic nephropathy families

BACKGROUND

Kidney size may differ between healthy members of Balkan endemic nephropathy (BEN) and non-BEN families. The present study was designed to elucidate this, in comparison with values for BEN patients.

METHODS

A total of 71 BEN patients (34 males, 64.4 ± 12.0 years), 74 healthy BEN family members (39 males, 49.1 ± 12.2 years), and 59 non-BEN family members (19 males, 49.2 ± 12.3 years) were involved. We measured the longest craniocaudal length and minimal parenchymal thickness on each kidney of all examined subjects using ultrasound.

RESULTS

No significant difference was found between the kidney length of healthy subjects from BEN (11.0 ± 0.8 cm) and non-BEN families (10.9 ± 0.8 cm), but kidneys were significantly longer than in BEN patients (9.9 ± 1.3 cm). Minimal parenchymal thickness was similar in all three groups. When subjects from each group were divided according to estimated glomerular filtration rate (eGFR), kidney length of the healthy groups was significantly longer than in BEN patients both in stage 1 (p =0.039) and stage 2 (p =0.044) of chronic kidney disease. The parental history of BEN was not associated with kidney dimensions, eGFR, or urinary excretion of albumin and alpha1-microglobulin.

CONCLUSION

Kidneys of BEN patients were significantly shorter than in healthy members of both BEN and non-BEN families, but no difference was found in kidney length and parenchymal thickness between healthy members of BEN and non-BEN families. No significant association was found between parental history of BEN and kidney size and function either in BEN patients or in healthy members from BEN families. Hippokratia 2015; 19 (4): 304-308.

Revealing a Pre-neoplastic Renal Tubular Lesion by p-S6 Protein Immunohistochemistry after Rat Exposure to Aristolochic Acid

Aristolochic acid (AA) has, in the last decade, become widely promoted as the cause of the Balkan endemic nephropathy and associated renal or urothelial tumours, although without substantial focal evidence of the quantitative dietary exposure via bread in specific households in hyperendemic villages. Occasional ethnobotanical use of Aristolochia clematitis might be a source of AA, and Pliocene lignite contamination of well-water is also a putative health risk factor. The aim of this study was two-fold: to verify if extracts of A. clematitis and Pliocene, or AA by itself, could induce the development of renal or urothelial tumours, and to test the utility of the ribosomal protein p-S6 to identify preneoplastic transformation. Rats were given extracts of A. clematitis in drinking water or AA I, by gavage. After seven months, renal morphology was studied using conventional haematoxylin and eosin and immunohistochemistry for ribosomal p-S6 protein. Plant extracts (cumulative AA approximately 1.8 g/kg b.w.) were tolerated and caused no gross pathology or renal histopathological change, with only faint diffuse p-S6 protein (except in the papilla) as in controls. Cumulative AA I (150 mg/kg b.w. given over 3 days) was also tolerated for seven months by all recipients, without gross pathology or kidney tumours. However, p-S6 protein over-expression was consistent particularly within the renal papilla. In one case given AA I, intense p-S6 protein staining of a proximal tubule fragment crucially matched the pre-neoplastic histology in an adjacent kidney section. We briefly discuss these findings, which compound uncertainty concerning the cause of the renal or upper urinary tract tumours of the Balkan endemic nephropathy.

Arsenic-mediated nephrotoxicity

Chronic kidney disease (CKD) is an important global health problem that affects 8-15% of the population according to epidemiological studies done in different countries. Essential to prevention is the knowledge of the environmental factors associated with this disease, and heavy metals such as lead and cadmium are clearly associated with kidney injury and CKD progression. Arsenic is one of the most abundant contaminants in water and soil, and many epidemiological studies have found an association between arsenic and type 2 diabetes mellitus, hypertension and cancer; however, there is a scarcity of epidemiological studies about its association with kidney disease, and the evidence linking urinary arsenic excretion with CKD, higher urinary excretion of low molecular proteins, albuminuria or other markers of renal in injury is still limited, and more studies are necessary to characterize the role of arsenic on renal injury and CKD progression. Global efforts to reduce arsenic exposure remain important and research is also needed to determine whether specific therapies are beneficial in susceptible populations.

Chronic dietary exposure to aristolochic acid and kidney function in native farmers from a Croatian endemic area and Bosnian immigrants

BACKGROUND AND OBJECTIVES

Improvements in agricultural practices in Croatia have reduced exposure to consumption of aristolochic acid-contaminated flour and development of endemic (Balkan) nephropathy. Therefore, it was hypothesized that Bosnian immigrants who settled in an endemic area in Croatia 15-30 years ago would be at lower risk of developing endemic nephropathy because of reduced exposure to aristolochic acid. To test this hypothesis, past and present exposure to aristolochic acid, proximal tubule damage as a hallmark of endemic nephropathy, and prevalence of CKD in Bosnian immigrants were analyzed.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

In this cross-sectional observational study from 2005 to 2010, 2161 farmers were divided into groups: indigenous inhabitants from endemic nephropathy and nonendemic nephropathy villages and Bosnian immigrants; α-1 microglobulin-to-creatinine ratio >31.5 mg/g and eGFR<60 ml/min per 1.73 m(2) were considered to be abnormal.

RESULTS

CKD and proximal tubule damage prevalence was significantly lower in Bosnian immigrants than inhabitants of endemic nephropathy villages (6.9% versus 16.6%; P<0.001; 1.3% versus 7.3%; P=0.003, respectively); 20 years ago, Bosnian immigrants observed fewer Aristolochia clematitis in cultivated fields (41.9% versus 67.8%) and fewer seeds among wheat seeds (6.1% versus 35.6%) and ate more purchased than homemade bread compared with Croatian farmers from endemic nephropathy villages (38.5% versus 14.8%, P<0.001). Both Croatian farmers and Bosnian immigrants observe significantly fewer Aristolochia plants growing in their fields compared with 15-30 years ago. Prior aristolochic acid exposure was associated with proximal tubule damage (odds ratio, 1.64; 95% confidence interval, 1.04 to 2.58; P=0.02), whereas present exposure was not (odds ratio, 1.31; 95% confidence interval, 0.75 to 2.30; P=0.33). Furthermore, immigrant status was an independent negative predictor of proximal tubule damage (odds ratio, 0.40; 95% confidence interval, 0.19 to 0.86; P=0.02).

CONCLUSIONS

Bosnian immigrants and autochthonous Croats residing in endemic areas are exposed significantly less to ingestion of aristolochic acid than in the past. The prevalence of endemic nephropathy and its associated urothelial cancers is predicted to decrease over time.

Is increased susceptibility to Balkan endemic nephropathy in carriers of common GSTA1 (*A/*B) polymorphism linked with the catalytic role of GSTA1 in ochratoxin a biotransformation? Serbian case control study and in silico analysis

Although recent data suggest aristolochic acid as a putative cause of Balkan endemic nephropathy (BEN), evidence also exists in favor of ochratoxin A (OTA) exposure as risk factor for the disease. The potential role of xenobiotic metabolizing enzymes, such as the glutathione transferases (GSTs), in OTA biotransformation is based on OTA glutathione adducts (OTHQ-SG and OTB-SG) in blood and urine of BEN patients. We aimed to analyze the association between common GSTA1, GSTM1, GSTT1, and GSTP1 polymorphisms and BEN susceptibility, and thereafter performed an in silico simulation of particular GST enzymes potentially involved in OTA transformations. GSTA1, GSTM1, GSTT1 and GSTP1 genotypes were determined in 207 BEN patients and 138 non-BEN healthy individuals from endemic regions by polymerase chain reaction (PCR). Molecular modeling in silico was performed for GSTA1 protein. Among the GST polymorphisms tested, only GSTA1 was significantly associated with a higher risk of BEN. Namely, carriers of the GSTA1*B gene variant, associated with lower transcriptional activation, were at a 1.6-fold higher BEN risk than those carrying the homozygous GSTA1*A/*A genotype (OR = 1.6; p = 0.037). In in silico modeling, we found four structures, two OTB-SG and two OTHQ-SG, bound in a GSTA1 monomer. We found that GSTA1 polymorphism was associated with increased risk of BEN, and suggested, according to the in silico simulation, that GSTA1-1 might be involved in catalyzing the formation of OTHQ-SG and OTB-SG conjugates.

Mechanisms of enzyme-catalyzed reduction of two carcinogenic nitro-aromatics, 3-nitrobenzanthrone and aristolochic acid I: Experimental and theoretical approaches

This review summarizes the results found in studies investigating the enzymatic activation of two genotoxic nitro-aromatics, an environmental pollutant and carcinogen 3-nitrobenzanthrone (3-NBA) and a natural plant nephrotoxin and carcinogen aristolochic acid I (AAI), to reactive species forming covalent DNA adducts. Experimental and theoretical approaches determined the reasons why human

NAD(P)H

quinone oxidoreductase (NQO1) and cytochromes P450 (CYP) 1A1 and 1A2 have the potential to reductively activate both nitro-aromatics. The results also contributed to the elucidation of the molecular mechanisms of these reactions. The contribution of conjugation enzymes such as N,O-acetyltransferases (NATs) and sulfotransferases (SULTs) to the activation of 3-NBA and AAI was also examined. The results indicated differences in the abilities of 3-NBA and AAI metabolites to be further activated by these conjugation enzymes. The formation of DNA adducts generated by both carcinogens during their reductive activation by the NOQ1 and CYP1A1/2 enzymes was investigated with pure enzymes, enzymes present in subcellular cytosolic and microsomal fractions, selective inhibitors, and animal models (including knock-out and humanized animals). For the theoretical approaches, flexible in silico docking methods as well as ab initio calculations were employed. The results summarized in this review demonstrate that a combination of experimental and theoretical approaches is a useful tool to study the enzyme-mediated reaction mechanisms of 3-NBA and AAI reduction.

Balkan endemic nephropathy-current status and future perspectives

Balkan endemic nephropathy (BEN), originally described in 1956, is a unique familial, chronic renal disease encountered with a high-prevalence rate in Serbia, Bulgaria, Romania, Croatia and Bosnia and Herzegovina. The most prominent features of the disease are its endemic nature, long-incubation period, familial clustering of the disease and an unusually high incidence of associated upper urothelial cancer (UUC). There are no clear-cut data on BEN incidence and prevalence, since the studies carried out in different endemic areas yielded contradictory information. In spite of intermittent variations, the incidence of new cases has remained stable over time. It has been estimated that almost 100 000 people are at risk of BEN, whereas 25 000 have the disease. The clinical signs and symptoms of BEN are non-specific and often remain unrecognized for years. There are no pathognomonic diagnostic features of BEN, but the set of epidemiological, clinical and biochemical data along with the pattern of pathologic injury in the absence of any other renal diseases are highly suggestive of this entity. Although the aetiology has been extensively studied, fostering the publication of various hypotheses, only one of them has provided conclusive evidence related to the aetiology of BEN. Studies conducted over the past decade have provided particularly strong arguments that BEN and UUC are caused by chronic poisoning with aristolochic acids (AAs). In light of these later studies, one can raise the question whether AAs could be responsible for previously and currently widespread unrecognized global renal disease and UUC.