SGLT2 inhibitor dapagliflozin protects the kidney in a murine model of Balkan nephropathy.

Proximal tubular uptake of aristolochic acid (AA) forms aristolactam (AL)-DNA adducts, which cause a p53/p21-mediated DNA damage response and acute tubular injury. Recurrent AA exposure causes kidney function loss and fibrosis in humans (Balkan endemic nephropathy) and mice and is a model of (acute kidney injury) AKI to chronic kidney disease (CKD) transition. Inhibitors of the proximal tubule sodium-glucose transporter SGLT2 can protect against CKD progression, but their effect on AA-induced kidney injury remains unknown. C57BL/6J mice (15-wk-old) were administered vehicle or AA every 3 days for 3 wk (10 and 3 mg/kg ip in females and males, respectively). Dapagliflozin (dapa, 0.01 g/kg diet) or vehicle was initiated 7 days prior to AA injections. All dapa effects were sex independent, including a robust glycosuria. Dapa lowered urinary kidney-injury molecule 1 (KIM-1) and albumin (both normalized to creatinine) after the last AA injection and kidney mRNA expression of early DNA damage response markers (p53 and p21) 3 wk later at the study end. Dapa also attenuated AA-induced increases in plasma creatinine as well as AA-induced up-regulation of renal pro-senescence, pro-inflammatory and pro-fibrotic genes, and kidney collagen staining. When assessed 1 day after a single AA injection, dapa pretreatment attenuated AL-DNA adduct formation by 10 and 20% in kidney and liver, respectively, associated with reduced p21 expression. Initiating dapa application after the last AA injection also improved kidney outcome but in a less robust manner. In conclusion, the first evidence is presented that pretreatment with an SGLT2 inhibitor can attenuate the AA-induced DNA damage response and subsequent nephropathy.NEW & NOTEWORTHY Recurrent exposure to aristolochic acid (AA) causes kidney function loss and fibrosis in mice and in humans, e.g., in the form of the endemic Balkan nephropathy. Inhibitors of the proximal tubule sodium-glucose transporter SGLT2 can protect against CKD progression, but their effect on AA-induced kidney injury remains unknown. Here we provide the first evidence in a murine model that pretreatment with an SGLT2 inhibitor can attenuate the AA-induced DNA damage response and subsequent nephropathy.

Critical review of renal tubule karyomegaly in non-clinical safety evaluation studies and its significance for human risk assessment.

Scientific databases were searched for terms applicable to karyomegaly in renal tubules of laboratory animals used in preclinical safety evaluation studies, and in humans. Renal tubule karyomegaly was more frequently reported in the rat in response to chemical exposure compared to other laboratory animal species. Renal tubule karyomegaly also occurred in the mouse in response to chemical insult, but much less commonly than in the rat. This nuclear lesion was recorded infrequently for hamster, dog, guinea pig, rabbit, pig, and non-human primate. Most instances of renal karyomegaly reported in humans represented cases of the genetic syndrome, karyomegalic interstitial nephritis, known to be caused by a mutation in the FAN1 gene. Human reports of karyomegaly in the kidney associated with chemical exposure are rare, and linked mainly to chemotherapeutic or antiviral therapies. The rat appears to be highly predisposed to developing karyomegaly as a renal response on exposure to diverse chemical agents, but karyomegaly in the rat is not consistently associated with renal tubule tumor development. Because of this inconsistency, renal tubule karyomegaly is an inaccurate predictor of renal tubule neoplasia, and there is no evidence that karyomegalic cells are involved in tumor development as a form of preneoplasia. A chemically induced karyomegalic response in the rat does not necessarily predict a similar alteration in human kidneys. Because modest nuclear enlargement of kidney tubule cells can occur as physiological or functional responses, it is recommended that the threshold for diagnosing renal tubule karyomegaly in animal studies should be accepted as at least four times normal nuclear size or larger.Abbreviations: BEN: Balkan Endemic Nephropathy; DMN: dimethylnitrosamine; GLP: Good Laboratory Practice; KIN: karyomegalic interstitial nephritis; LAL: lysinoalanine; MeCCNU: 1-(2-chloroethyl)-3-(trans-4-methylcyclohexyl)-1-nitrosourea; NTP: National Toxicology Program; OSOM: outer stripe of outer medulla; OTA: ochratoxin A; RTT: renal tubule tumor.

The Phytoalexin Resveratrol Ameliorates Ochratoxin A Toxicity in Human Embryonic Kidney (HEK293) Cells.

Ochratoxin A (OTA) is a nephrotoxic mycotoxin produced by Aspergillus and Penicillium fungi. It contaminates human and animal food products, and chronic exposure is associated with renal fibrosis in humans (Balkan endemic nephropathy). Resveratrol, a phytoalexin, possesses anti-cancer and antioxidant properties. We investigated the mechanism of cellular oxidative stress induced by OTA, and the effect of resveratrol in human embryonic kidney (HEK293) cells over 24 and 48 h. Cells were exposed to OTA [IC50 = 1.5 µM (24 h) and 9.4 µM (48 h) determined using MTT assay] and 25 µM resveratrol. Glutathione was quantified by luminometry and gene expression of Nrf2 and OGG1 was determined by qPCR. Protein expression of Nrf2, LonP1, SIRT3, and pSIRT1 was assessed by Western blot, DNA damage (comet assay), and intracellular reactive oxygen species (flow cytometry). At 24 h, resveratrol increased mRNA expression of the DNA repair enzyme, OGG1 (P < 0.05), whereas OTA and OTA+resveratrol significantly decreased OGG1 expression (P < 0.05). OGG1 expression increased during 48-h exposure to resveratrol and OTA+resveratrol (P < 0.05). Comet tail lengths doubled in 48-h OTA-treated cells, whereas at both time periods, OTA+resveratrol yielded shorter comet tails (P < 0.0001). During 24- and 48-h exposure, OTA, resveratrol, and OTA+resveratrol significantly decreased mRNA expression of Nrf2 (P < 0.05). Luminometry analysis of GSH revealed an increase by OTA+resveratrol for 24 and 48 h (P < 0.05 and P < 0.001, respectively). Western blot analysis showed decreased Nrf2 protein expression during 24-h exposure, but increased Nrf2 expression during 48 h. LonP1 protein expression increased during 24-h exposure to OTA (P < 0.05) and OTA+resveratrol (P < 0.0011) and during 48-h exposure to resveratrol (P < 0.0005).

Ochratoxin A and human health risk: a review of the evidence.

Ochratoxin A (OTA) is a mycotoxin produced by several fungal species including Aspergillus ochraceus, A. carbonarius, A. niger, and Penicillium verrucosum. OTA causes nephrotoxicity and renal tumors in a variety of animal species; however, human health effects are less well-characterized. Various studies have linked OTA exposure with the human diseases Balkan endemic nephropathy (BEN) and chronic interstitial nephropathy (CIN), as well as other renal diseases. This study reviews the epidemiological literature on OTA exposure and adverse health effects in different populations worldwide, and assesses the potential human health risks of OTA exposure. Epidemiological studies identified in a systematic review were used to calculate unadjusted odds ratios for OTA associated with various health endpoints. With one exception, there appears to be no statistically significant evidence for human health risks associated with OTA exposure. One Egyptian study showed a significantly higher risk of nephritic syndrome in those with very high urinary OTA levels compared with relatively unexposed individuals; however, other potential risk factors were not controlled for in the study. Larger cohort or case-control studies are needed in the future to better establish potential OTA-related human health effects, and further duplicate-diet studies are needed to validate biomarkers of OTA exposure in humans.

Morphology of Balkan endemic nephropathy: current state.

Balkan endemic nephropathy (BEN) is interesting renal disease, because of its unique clinical, epidemiological and morphological characteristics: intensive interstitial fibrosis and tubular atrophy without any inflammation. In the present paper we evaluate the incidence of BEN from the morphological point of view for the last decade. Therefore we analyzed material obtained from autopsies, kidney biopsies and nephrectomy due to upper urothelial cancer (UUC) from the patients which were divided into two groups: those with permanent residence in BEN areas and those from nonendemic areas. At the Institute of Pathology, University of Belgrade for the last 15 years we had only 1 autopsy due to BEN out of 6,825. More than 30 years ago there were over 50 autopsy cases of BEN at the same institute. For the last decade we had only 2 kidney biopsies suspected for BEN out of 2,182, but morphologically not confirmed as BEN. However, previously we had over 40 kidney biopsies diagnosed as early or late stage of BEN. At the Clinical Center of Serbia 180 nephrectomies were performed due to UUC. The incidence of UUC for the last five years in BEN regions has significantly decreased, whereas at the same time in non-BEN regions it has remained on the same level. There was no morphological difference of the renal tissue adjacent to tumor between patients from BEN and non-BEN regions. According to our study based on routine pathological work, we could clearly conclude that BEN today is more clinical and epidemiological than a morphological entity.

Characteristics of upper urothelial carcinoma in an area of Balkan endemic nephropathy in south Serbia. A fifty-year retrospective study.

AIMS AND BACKGROUND: Upper urinary tract transitional cell carcinoma, a relatively rare tumor, is up to 100 times more frequent in regions with Balkan endemic nephropathy. Characteristics of transitional cell carcinoma in the endemic South Morava Region in Serbia in the previous 50 years were evaluated. PATIENTS: We analyzed 477 cases with pathologically confirmed transitional cell carcinoma who underwent surgery from 1957 to 2006: 91 from endemic, 106 from adjacent and 280 from control settlements. Cases in the study came from 10 endemic villages, 46 adjacent villages, 51 control villages and the city of Nis. RESULTS: The increase in number of transitional cell carcinoma from 1957 was followed by a peak between 1967 and 1978 (yearly incidence 21.9 per 100,000) and a slow decrease thereafter to 7.4 (1997-2006). In the control settlements, the increase was steady. Reduced kidney function at surgery was found in 58% of patients from endemic and in 20% from control settlements. Age at surgery has significantly increased from 52.3 and 51.5 (1957-1966) to 70.9 and 66.1 (1997-2006) for endemic and control settlements, respectively. The female sex was predominant in endemic and adjacent settlements and the male sex in control settlements. Transitional cell carcinoma from endemic settlements was of a lower grade in the period from 1957-1986, but in the period from 1987-2006 they were predominantly high grade. Low tumor stage (pTa-pT1) predominated in transitional cell carcinoma from the endemic and adjacent but not the control settlements in the period from 1957 to 1986. However, in the last 20 years, upper urinary tract transitional cell carcinoma stage increased, the highest in the period from 1997 to 2006 in all settlements studied. Conservative surgery was advocated for transitional cell carcinoma in Balkan endemic nephropathy areas up to 1996. Transitional cell carcinoma are now more malignant and more advanced than before, and a less aggressive approach is used only for absolute indications. CONCLUSIONS: An increased number of transitional cell carcinoma in endemic settlements was observed, markedly decreasing in the last decade. An increasing age and a shorter survival were recorded in patients both from Balkan endemic nephropathy and control settlements. Sporadic cases upper urinary tract transitional cell carcinoma in settlements adjacent to endemic settlements were demonstrated.

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.

Upper urothelial carcinoma in Balkan endemic nephropathy and non-endemic regions: a comparative study of pathological features.

Upper urothelial carcinoma (UUC), a rare neoplasm, occurs more frequently in some regions of Balkan countries than in other areas in the world. The aim of this study is to compare phenotypic morphological characteristics of UUC in Balkan endemic nephropathy (BEN) region and control rural and city populations free of BEN, and to determine the characteristic(s) that could discriminate tumors in endemic and non-endemic regions. The authors analyzed biopsies from 88 patients with UUC, 40 patients who live in Balkan endemic (BEN) settlements and 48 control subjects. The histological sections were used to assess morphological variables: histologic grade, pathologic stage (pT), growth pattern, pattern of invasion, lympho-vascular invasion (LVI), presence of necrosis and metaplastic changes (squamous or glandular) within the tumor. Statistically significant differences between the groups were found concerning tumor grade, pattern of invasion, growth pattern and metaplastic changes. High-grade tumors and trabecular/infiltrative patterns of invasion were more frequent in the group of BEN tumors (chi(2)=4.583, p<0.05; chi(2)=8.064, p<0.05). Moreover, solid growth and metaplastic changes are significant in BEN tumor, chi(2)=9.696, p<0.01; chi(2)=9.35, p<0.01, respectively. Discriminant analysis of morphological variables had indicated that BEN and control tumors are significantly different (Wilks' lambda=0.833, chi(2)=15.044 and p<0.05). The best characteristic that differentiated them was growth pattern; i.e., solid growth for BEN tumors and papillary for control tumors.

Molecular markers in upper urothelial carcinoma associated to Balkan endemic nephropathy. Aristolochic acid as the major risk factor of the worldwide disease.

The role of aristolochic acid in the etiology of Balkan endemic nephropathy (BEN) and associated upper urothelial carcinoma (UUC) was recently confirmed. The aim of this study was to determine the marker(s) specific for BEN-associated UUC. A total of 82 patients with UUC (38 from the BEN region and 44 control tumors) were included in the study. The Ki-67 index in BEN tumors correlated with the grade and multifocality (p < 0.05), but in regression analysis, only the grade of BEN tumor. The p53 index was significantly higher in BEN than in control tumors (p < 0.05), as well as the alteration of p53 (p < 0.05). BEN low-stage tumors, tumors without limphovascular invasion (LVI), and tumors of the renal pelvis had a higher p53 index than the control tumors (p < 0.05, 0.01, 0.05, respectively). The Ki-67 index was higher in control tumors with high-stage and solid growth than in BEN UUC (p < 0.050, 0.005). The Ki-67 correlated with the grade, growth, stage, LVI, and multifocality of UUC on the best way, but not with the group. In regression analysis, only multifocality of UUC had predictive influence on Ki-67 activity (p < 0.001). P53 correlated with the grade, growth, and group (p < 0.05). This investigation identifies the p53 pathway as the specific cell cycle marker involved in BEN-associated UUC.

Balkan Endemic Nephropathy and the Causative Role of Aristolochic Acid.

Balkan endemic nephropathy is a chronic tubulointerstitial disease with insidious onset, slowly progressing to end-stage renal disease and frequently associated with urothelial carcinoma of the upper urinary tract (UTUC). It was described in South-East Europe at the Balkan peninsula in rural areas around tributaries of the Danube River. After decades of intensive investigation, the causative factor was identified as the environmental phytotoxin aristolochic acid (AA) contained in Aristolochia clematitis, a common plant growing in wheat fields that was ingested through home-baked bread. AA initially was involved in the outbreak of cases of rapidly progressive renal fibrosis reported in Belgium after intake of root extracts of Aristolochia fangchi imported from China. A high prevalence of UTUC was found in these patients. The common molecular link between Balkan and Belgian nephropathy cases was the detection of aristolactam-DNA adducts in renal tissue and UTUC. These adducts are not only biomarkers of prior exposure to AA, but they also trigger urothelial malignancy by inducing specific mutations (A:T to T:A transversion) in critical genes of carcinogenesis, including the tumor-suppressor TP53. Such mutational signatures are found in other cases worldwide, particularly in Taiwan, highlighting the general public health issue of AA exposure by traditional phytotherapies.

Balkan nephropathy: evolution of our knowledge.

Balkan endemic nephropathy (BEN), originally described in the late 1950s as a chronic tubulointerstitial kidney disease, is identified by its unique epidemiological features. The most remarkable characteristic of BEN is the focal topographical nature that characterizes its occurrence at the global, national, and even household level. BEN affects only certain endemic rural foci along tributaries of the Danube River in the Balkan countries of Bosnia, Bulgaria, Croatia, Romania, and Serbia. The spatial distribution has remained astonishingly unchanged with time because the disease affects the same endemic clusters as 50 years ago. The natural course of the disease is characterized by universal development of end-stage renal disease and the frequent development of upper urinary tract tumors, posing a substantial disease burden to the afflicted areas. The greatest challenge in the study of BEN has been the elucidation of its cause. The unique features of the disease, in particular its endemic nature and the long incubation period required for the disease to develop, have led to the proposal that BEN represents a unique environmental disease. The quest for the responsible environmental factor has been long and diverse, and although no definitive answer has been provided to date, converging lines of evidence support the theory that long-term consumption of food contaminated with aristolochic acid underlies the pathogenesis of BEN. The present review describes the evolution of our knowledge of BEN in relation to the development of the main theories for its pathogenesis.

Contribution to the definition of diagnostic criteria for Balkan endemic nephropathy.

BACKGROUND: Diagnostic criteria for Balkan endemic nephropathy (BEN) have not been precisely established. In the present study the predictive value of variables previously proposed as diagnostic criteria for BEN was examined. METHODS: The study involved 182 patients: 98 patients with BEN, 57 patients with other kidney diseases (20 with glomerulonephritis, 17 with tubulointerstitial diseases and 20 with hypertensive nephrosclerosis) and 27 healthy subjects. The BEN group comprised patients who fulfilled criteria for BEN and suspected BEN, together with patients with proteinuria and at least two tubular abnormalities or one tubular abnormality and a history of urothelial tumour. Demographic, clinical, laboratory and ultrasound variables of examined groups were combined in univariate/multivariate logistic regression analysis. RESULTS: Out of 28 analysed variables only urine alpha1-microglobulin (MG) and kidney length were selected as significant predictors in differentiating BEN from other kidney diseases and healthy controls. Using ROC curves the cutoff values of these variables and proteinuria and kidney volume, variables collinear with them, were found. Moderate sensitivity and specificity characterized all these cutoff values except for proteinuria, which provided high sensitivity and specificity in combination of BEN and healthy persons. The predictive value of different combinations of selected variables was not significantly different from the predictive value of each variable individually. CONCLUSIONS: Proteinuria, urine alpha1-MG, kidney length and volume were selected as significant predictors of BEN. Variables related to kidney failure as well as several tubular disorders (urine specific gravity, FENa and TRP) had an insignificant predictive value and could not be used for differential diagnosis of BEN.

Balkan endemic nephropathy: a still unsolved puzzle.

Balkan endemic nephropathy (BEN) is a chronic tubulointerstitial renal disease, occurring in certain regions in 5 countries of the Balkan peninsula. Its etiology is largely unknown, though several hypotheses have been formulated and are discussed in this review. In several cases, etiological hypotheses (e.g., viral, ochratoxin or trace element involvement) are verified only in local endemic areas and can not be confirmed when tested elsewhere. Only certain families in the endemic areas are affected. An exposure of at least 20 years to the unknown factors in the endemic areas seems to be mandatory for the development of the disease, but a genetic predisposition to this disease also seems to be mandatory. Prominent clinical features are severely shrunken kidneys, a more severe anemia relative to the level of renal function, and a slow progression to end-stage renal failure. An international approach to solving the etiological and pathogenetic enigma of BEN is needed in the coming years. It is also time to reevaluate other chronic, slowly progressive tubulointerstitial nephropathies diagnosed elsewhere in the world and to search for possible etiological similarities with BEN.

Comparison of kidney size between patients with Balkan endemic nephropathy and other kidney diseases.

BACKGROUND: The aim of this study was to assess the relationship between kidney dimensions and creatinine clearance (Ccr) in patients with Balkan endemic nephropathy (BEN), nephrosclerosis (NSc), glomerulonephritis (GN), diabetic nephropathy (DN) and in healthy persons. The main objective was to find out at which stage of BEN the kidneys start to shrink. METHODS: The study involved 84 patients with BEN, 39 with NSc, 56 with GN, 55 with DN, and 52 healthy subjects, allocated to group 1 (n = 28) sex- and age-matched with BEN/NSc patients, or group 2 (n = 24) sex- and age-matched with GN/DN patients. Based on Ccr, patients were classified according to the NKF/DOQI guidelines. RESULTS: The kidney dimensions of BEN patients in all stages of the disease were significantly shorter than those of healthy controls and patients with GN and DN. In stages 3-5, BEN patients had significantly smaller kidneys than patients with NSc. Patients with NSc had smaller kidney dimensions than controls and GN/DN patients but all of these differences were not significant. CONCLUSION: BEN patients had significantly smaller kidneys than sex- and age-matched healthy persons and patients with GN and DN in all stages of the disease and patients with NSc in stages 3-5 of the disease.

Metabolic activation of carcinogenic aristolochic acid, a risk factor for Balkan endemic nephropathy.

Aristolochic acid (AA), a naturally occurring nephrotoxin and carcinogen, is associated with tumor development in patients suffering from Chinese herbs nephropathy (now termed aristolochic acid nephropathy, AAN) and may also be a cause for the development of a similar type of nephropathy, the Balkan endemic nephropathy (BEN). Major DNA adducts [7-(deoxyadenosin-N6-yl)-aristolactam and 7-(deoxyguanosin-N2-yl)aristolactam] formed from AA after reductive metabolic activation were found in renal tissues of patients with both diseases. Understanding which human enzymes are involved in AA activation and/or detoxication is important in the assessment of an individual's susceptibility to this plant carcinogen. This paper reviews major hepatic and renal enzymes responsible for AA-DNA adduct formation in humans. Phase I biotransformation enzymes play a crucial role in the metabolic activation of AA to species forming DNA adducts, while a role of phase II enzymes in this process is questionable. Most of the activation of AA in human hepatic microsomes is mediated by cytochrome P450 (CYP) 1A2 and, to a lower extent, by CYP1A1; NADPH:CYP reductase plays a minor role. In human renal microsomes NADPH:CYP reductase is more effective in AA activation. Prostaglandin H synthase (cyclooxygenase, COX) is another enzyme activating AA in human renal microsomes. Among the cytosolic reductases, NAD(P)H:quinone oxidoreductase (NQO1) is the most efficient in the activation of AA in human liver and kidney. Studies with purified enzymes confirmed the importance of CYPs, NADPH:CYP reductase, COX and NQO1 in the AA activation. The orientation of AA in the active sites of human CYP1A1, -1A2 and NQO1 was predicted from molecular modeling and explains the strong reductive potential of these enzymes for AA detected experimentally. We hypothesized that inter-individual variations in expressions and activities of enzymes activating AA may be one of the causes responsible for the different susceptibilities to this carcinogen reflected in the development of AA-induced nephropathies and associated urothelial cancer.

Increased blood pressure in adult offspring of families with Balkan endemic nephropathy: a prospective study.

BACKGROUND: Previous studies have linked smaller kidney dimensions to increased blood pressure. However, patients with Balkan Endemic Nephropathy (BEN), whose kidneys shrink during the course of the disease, do not manifest increased blood pressure. The authors evaluated the relationship between kidney cortex width, kidney length, and blood pressure in the offspring of BEN patients and controls. METHODS: 102 offspring of BEN patients and 99 control offspring of non-BEN hospital patients in the Vratza District, Bulgaria, were enrolled in a prospective study and examined twice (2003/04 and 2004/05). Kidney dimensions were determined using ultrasound, blood pressure was measured, and medical information was collected. The parental disease of BEN was categorized into three groups: mother, father, or both parents. Repeated measurements were analyzed with mixed regression models. RESULTS: In all participants, a decrease in minimal kidney cortex width of 1 mm was related to an increase in systolic blood pressure of 1.4 mm Hg (p = 0.005). There was no association between kidney length and blood pressure. A maternal history of BEN was associated with an increase in systolic blood pressure of 6.7 mm Hg (p = 0.03); paternal BEN, +3.2 mm Hg (p = 0.35); or both parents affected, +9.9 mm Hg (p = 0.002). There was a similar relation of kidney cortex width and parental history of BEN with pulse pressure; however, no association with diastolic blood pressure was found. CONCLUSION: In BEN and control offspring, a smaller kidney cortex width predisposed to higher blood pressure. Unexpectedly, a maternal history of BEN was associated with average increased systolic blood pressure in offspring.

Renal function, protein excretion and pathology of Balkan endemic nephropathy. I. Renal function.

Renal function studies were performed on 59 patients who had the clinical criteria for Balkan endemic nephropathy (BEN). They were divided into three groups according to DTPA clearance (DTPA). Group 1, 11 individuals, had a mean age of 41.6 years and DTPA greater than 100 ml/min. Group 2, 20 persons, had a mean age of 49 years and DTPA of 60 to 100 ml/min. Group 3 was made up of 28 people with a DTPA less than 60 ml/min and an average age of 50.4 years. No distinguishing specific or characteristic symptoms of BEN were found in any of the three groups. Anemia was not found to be an early indicator when compared to other forms of progressive renal disease. Proteinuria was minimal and intermittent in all three groups. Maximum concentrating ability was significantly reduced only in the third group. These features do not allow the clinical differentiation of BEN from other chronic progress tubulointerstitial nephropathies. The geographic isolation and familial nature of the disease, associated with minimal proteinuria make BEN a unique entity. Kidney size by ultrasound was decreased in all three groups, suggesting that this may be another early and characteristic feature to BEN.

Renal function, protein excretion, and pathology of Balkan endemic nephropathy. II. Protein excretion.

The urinary proteins of 40 patients with Balkan endemic nephropathy from the Tuzla region were examined using ultrathin-layer SDS pore-gradient polyacrylamide gel electrophoresis in combination with silver staining. The typical urinary protein spectrum contained immunoglobulin G, Tamm-Horsfall protein, transferrin, albumin, beta 2-microglobulin (beta 2m), immunoglobulin light chains, retinol-binding protein, and alpha 1-microglobulin (alpha 1m). Densitometric measurements were used to derive glomerular tubular protein ratios (GTPR) and to characterize protein excretion patterns in the 28 patients who excreted more than 150 mg/liter of protein. Results showed that proteinuria of Balkan nephropathy is predominantly tubular, consisting of low-molecular-weight species. The most commonly identified proteins were alpha 1m, light chains, retinol binding protein, and beta 2m. The pattern of proteinuria based on GTPR did not correlate with the underlying histology or the degree of renal failure. These findings, using the ultrathin-layer SDS pore-gradient method of protein separation, more accurately demonstrates the low-molecular-weight proteinuria characteristic for the early stages of BEN.

Renal function, protein excretion, and pathology of Balkan endemic nephropathy. III. Light and electron microscopic studies.

This study was performed to evaluate histomorphological features of BEN in 50 kidney biopsies from patients who met the epidemiologic, clinical and laboratory criteria for BEN. This is the first such study reported in detail. The patients were divided into three groups based on the DTPA clearance values: group 1, greater than 99 ml/min, group 2, 51 to 99 ml/min, and group 3, 29 to 50 ml/min. All patients in all groups had an increase in proteinuria consisting of proteins less than 25,000 daltons. Multifocal interstitial sclerosis spreading from the superficial into the deep cortex was found in 49 (98%), tubular atrophy in 48 (96%), and global glomerular sclerosis with microvascular hyalinosis/sclerosis of sclerotic and atrophic changes were significantly increased when compared to age-related standards. An accelerated aging process may be assumed to occur in BEN. More peculiar additional findings with much lower incidence and extent included multifocal vascular and glomerular capillary changes resembling the chronic form of thrombotic microangiopathy group of diseases. These findings, together with the presence of arteriolar hyalinosis and tubulointerstitial sclerosis seen in patients with cyclosporine nephrotoxicity suggest that the mechanism of toxicity may be similar to BEN. We conclude that the histopathology is predominantly tubulointerstitial sclerosis without infiltrates. The combination of the histology, tubular proteinuria, geographic distribution, familial occurrence, and the remarkable association with papillary transitional cell carcinoma of the renal pelvis and ureters, qualifies BEN as a unique disease.

Renal function, protein excretion, and pathology of Balkan endemic nephropathy. IV. Immunohistology.

Few controversial observations on the deposition of immunoglobulins (Igs) and complement components in kidney biopsies of Balkan endemic nephropathy (BEN) patients have been reported. In the present study, direct or indirect immunofluorescence testing of the deposition of IgA, IgG, IgM, C3, C1q, C4 fibrin/fibrinogen, albumin, B2-microglobulin (beta 2m) and Tamm-Horsfall glycoprotein (THG) on frozen renal tissue sections was performed in 52 BEN patients. Glomerular findings were negative or mostly insignificant, with mild or moderate mesangial deposition of IgM in 16, IgA in 11, IgG in three, C3 in 15, C1q in two, C4 in one and fibrin/fibrinogen in two cases, respectively. The predominance of mesangial IgA deposits in five cases suggested IgA glomerulonephritis (GN) concomitant with BEN. Homogeneous lumpy or granular deposits in small extraglomerular vessels contained IgM in nine, C3 in 45, C1q in three, and C4 in one case. Focal linear or granular C3 was noted along the tubular basement membrane in eight cases. Resorptive droplets in tubular epithelial cells contained Igs and albumin, while complement, fibrin/fibrinogen and THG were found in tubular casts. There was no positive reaction with anti-beta 2m and anti-THG antibodies. According to these results, humoral immune mechanisms would not appear to play a pathogenetic role in BEN. However, immunohistologic examinations are important in recognition of possible concomitant immune complex-mediated GN.