Overview of aristolochic acid nephropathy: an update

Aristolochic acid nephropathy (AAN) is a rapidly progressive renal interstitial fibrosis caused by medical or environmental exposure to aristolochic acid (AA). Since the outbreak of AAN in Belgium was reported nearly 30 years ago, the safety of herbal remedies has drawn considerable attention, and AAN has become a global public health problem. Breakthroughs have been made to better understand the disease, including the toxicity of AAs, the possible mechanisms of AAN, the disease patterns, and the pathological features; however, some critical problems remain unresolved. Because of the insidious onset of the disease, the incidence of AAN and the prevalence of exposure to AAs are unknown and might be largely underestimated. During the past decades, AA-containing herbs have been strictly administrated in many regions and the occurrence of AAN has declined sharply, yet cases of AAN are still sporadically reported. Despite the progress in the understanding of the disease's pathogenesis, there is no effective treatment for delaying or reversing the renal deterioration caused by AAN. Therefore, the risk of exposure to AAs should be taken seriously by public health workers and clinicians. In this review, we updated the latest data on AAN, summarized the advances throughout these years, and put forward some challenges for future research.

Rapid identification and detection of aristolochic acids in the herbal extracts by Raman spectroscopy

Herbs containing aristolochic acids (AAs) have already been proven to be highly carcinogenic and nephrotoxic. In this study, a novel surface-enhanced Raman scattering (SERS) identification method was developed. Ag-APS nanoparticles with a particle size of 3.53 ± 0.92 nm were produced by combining silver nitrate and 3-aminopropylsilatrane. The reaction between the carboxylic acid group of aristolochic acid I (AAI) and amine group of Ag-APS NPs was used to form amide bonds, and thus, concentrate AAI, rendering it easy to detect via SERS and amplified to obtain the best SERS enhancement effect. Detection limit was calculated to be approximately 40 nM. Using the SERS method, AAI was successfully detected in the samples of four Chinese herbal medicines containing AAI. Therefore, this method has a high potential to be applied in the future development of AAI analysis and rapid qualitative and quantitative analysis of AAI in dietary supplements and edible herbs.

Use of Medicinal Plants in Africa: A Case Study From the Democratic Republic of Congo (DRC)

Although medicinal plants are beneficial, they also can be important risk factors for the development of acute and chronic kidney injury, as well toxicity of other solid organs. There are a lack of reports of adverse kidney events and drug interactions resulting from medicinal plants owing to a lack of professional surveillance and specific data on kidney toxicity, especially in low-resource settings. Within the context of increased medicinal plant use and lack of effective regulatory control, safety is a key priority issue. We review the benefits and adverse effects of medicinal plants with particular reference to nephrotoxicity encountered in the Democratic Republic of Congo in sub-Saharan Africa.

Aristolochic acid-associated cancers: a public health risk in need of global action

Aristolochic acids (AAs) are a group of naturally occurring compounds present in many plant species of the Aristolochiaceae family. Exposure to AA is a significant risk factor for severe nephropathy, and urological and hepatobiliary cancers (among others) that are often recurrent and characterized by the prominent mutational fingerprint of AA. However, herbal medicinal products that contain AA continue to be manufactured and marketed worldwide with inadequate regulation, and possible environmental exposure routes receive little attention. As the trade of food and dietary supplements becomes increasingly globalized, we propose that further inaction on curtailing AA exposure will have far-reaching negative effects on the disease trends of AA-associated cancers. Our Review aims to systematically present the historical and current evidence for the mutagenicity and carcinogenicity of AA, and the effect of removing sources of AA exposure on cancer incidence trends. We discuss the persisting challenges of assessing the scale of AA-related carcinogenicity, and the obstacles that must be overcome in curbing AA exposure and preventing associated cancers. Overall, this Review aims to strengthen the case for the implementation of prevention measures against AA's multifaceted, detrimental and potentially fully preventable effects on human cancer development.

Nephrotoxicity induced by natural compounds from herbal medicines - a challenge for clinical application

Herbal medicines (HMs) have long been considered safe and effective without serious toxic and side effects. With the continuous use of HMs, more and more attention has been paid to adverse reactions and toxic events, especially the nephrotoxicity caused by natural compounds in HMs. The composition of HMs is complex and various, especially the mechanism of toxic components has been a difficult and hot topic. This review comprehensively summarizes the kidney toxicity characterization and mechanism of nephrotoxic natural compounds (organic acids, alkaloids, glycosides, terpenoids, phenylpropanoids, flavonoids, anthraquinones, cytotoxic proteins, and minerals) from different sources. Recommendations for the prevention and treatment of HMs-induced kidney injury were provided. In vitro and in vivo models for evaluating nephrotoxicity and the latest biomarkers are also included in this investigation. More broadly, this review may provide theoretical basis for safety evaluation and further comprehensive development and utilization of HMs in the future.

Aristolochic Acid-Induced Nephrotoxicity: Molecular Mechanisms and Potential Protective Approaches

Aristolochic acid (AA) is a generic term that describes a group of structurally related compounds found in the Aristolochiaceae plants family. These plants have been used for decades to treat various diseases. However, the consumption of products derived from plants containing AA has been associated with the development of nephropathy and carcinoma, mainly the upper urothelial carcinoma (UUC). AA has been identified as the causative agent of these pathologies. Several studies on mechanisms of action of AA nephrotoxicity have been conducted, but the comprehensive mechanisms of AA-induced nephrotoxicity and carcinogenesis have not yet fully been elucidated, and therapeutic measures are therefore limited. This review aimed to summarize the molecular mechanisms underlying AA-induced nephrotoxicity with an emphasis on its enzymatic bioactivation, and to discuss some agents and their modes of action to reduce AA nephrotoxicity. By addressing these two aspects, including mechanisms of action of AA nephrotoxicity and protective approaches against the latter, and especially by covering the whole range of these protective agents, this review provides an overview on AA nephrotoxicity. It also reports new knowledge on mechanisms of AA-mediated nephrotoxicity recently published in the literature and provides suggestions for future studies.

Recent advances in upper tract urothelial carcinomas: From bench to clinics

Urothelial carcinoma in the upper tract is rare and often discussed separately. Many established risk factors were identified for the disease, including genetic and external risk factors. Radiographic survey, endoscopic examination and urine cytology remained the most important diagnostic modalities. In localized upper tract urothelial carcinomas, radical nephroureterectomy with bladder cuff excision are the gold standard for large, high-grade and suspected invasive tumors of the renal pelvis and proximal ureter, whereas kidney-sparing surgeries should be considered in patients with low-risk disease. Advances in technology have given endoscopic surgery an important role, not only in diagnosis, but also in treatment. Although platinum-based combination chemotherapy is efficacious in advanced or metastatic disease, current established chemotherapy regimens are toxic and lack a sustained response. Immune checkpoint inhibitors have led to a new era of treatment for advanced or metastatic urothelial carcinomas. The remarkable results achieved thus far show that immunotherapy will likely be the future treatment paradigm. The combination of immune checkpoint inhibitors and other agents is another inspiring avenue to explore that could benefit even more patients. With respect to the high incidence rate and different clinical appearance of upper tract urothelial carcinomas in Taiwan, a possible correlation exists between exposure to certain external risk factors, such as arsenic in drinking water and aristolochic acid in Chinese herbal medicine. As more gene sequencing differences between upper tract urothelial carcinomas and various disease causes are detailed, this has warranted the era of individualized screening and treatment for the disease.

Update of aristolochic acid nephropathy in Korea

BACKGROUND/AIMS

The true incidence of aristolochic acid nephropathy (AAN) is thought to be underestimated because numerous ingredients known or suspected to contain aristolochic acid (AA) are used in traditional medicine in Korea.

METHODS

We collected data on cases of AAN since 1996 via a database in Korea. We evaluated the year of AAN development, route to obtaining AA-containing herbal medicine, gender, reason for taking AA-containing herbal medicine, clinical manifestations, histological findings, phytochemical analysis, and prognosis of patients with AAN.

RESULTS

Data on 16 cases of AAN were collected. Thirteen cases developed AAN before and three cases after the prohibition of AA-containing herbal medicine by the Korea Food and Drug Administration. Patients were prescribed AA-containing herbal medicine from oriental clinics or had purchased it from traditional markets. AAN was distributed in all age groups. Young females were most commonly exposed to AA-containing herbal medicine for slimming purposes and postpartum health promotion, while older adults took AA-containing compounds for the treatment of chronic diseases. The most common symptoms presented at hospitalization were nausea and vomiting, and acute kidney injury was accompanied by Fanconi syndrome in almost half of the patients. Phytochemical analysis of AA in herbal medicine was available in six cases. Progression to end stage renal disease (ESRD) was observed in seven patients (43.8%), and five patients (31.3%) had progressed to ESRD within 6 months of diagnosis.

CONCLUSION

Our report shows that patients were still exposed to AA-containing herbal medicine and that there is a possibility of underdiagnosis of AAN in Korea. A stronger national supervision system of herbal ingredients and remedies in oriental medicine is needed to prevent AAN.

Traditional Medicines and Kidney Disease in Low- and Middle-Income Countries: Opportunities and Challenges

Traditional medicines are a principal form of health care for many populations, particularly in low- and middle-income countries, and they have gained attention as an important means of health care coverage globally. In the context of kidney diseases, the challenges and opportunities presented by traditional medicine practices are among the most important considerations for developing effective and sustainable public health strategies. However, little is known about the practices of traditional medicines in relation to kidney diseases, especially concerning benefits and harms. Kidney diseases may be caused, treated, prevented, improved, or worsened by traditional medicines depending on the setting, the person, and the types, modes, and frequencies of traditional medicine use. Given the profound knowledge gaps, nephrology practitioners and researchers may be uniquely positioned to facilitate more optimal public health strategies through recognition and careful investigation of traditional medicine practices. Effective implementation of such strategies also will require local partnerships, including engaging practitioners and users of traditional medicines. As such, practitioners and researchers investigating kidney diseases may be uniquely positioned to bridge the cultural, social, historical, and biologic differences between biomedicine and traditional medicine, and they have opportunities to lead efforts in developing public health strategies that are sensitive to these differences.

Environmental toxin-induced acute kidney injury

Human beings are exposed to various potentially toxic agents and conditions in their natural and occupational environments. The kidney, due to its concentrating ability and excretory function, is highly vulnerable to the effects of environmental toxins. Identifying the precise cause and mechanisms of environmentally induced renal injury remains a challenge for which various scientific disciplines need to be involved. Investigations in this field are confronted with the apparent infinite types of toxins, their mutual interaction, handling/metabolization by the body, ways of exposure, etc. Although interdisciplinary efforts and persistence are required to identify, mechanistically unravel and tackle environmental toxin-induced pathologies, research eventually pays off in ameliorated working/living conditions and development of preventive/therapeutic strategies. This review was compiled to particularly emphasize the need for a maintained awareness of environmental threats in general and those targeting the kidney. Different mechanisms of renal toxicity are illustrated and discussed, thereby focusing on three types of environmental toxins, namely aristolochic acid, melamine and heavy metals.

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.

Total synthesis of the aristolochic acids, their major metabolites, and related compounds

Plants from the Aristolochia genus have been recommended for the treatment of a variety of human ailments since the time of Hippocrates. However, many species produce the highly toxic aristolochic acids (AAs), which are both nephrotoxic and carcinogenic. For the purposes of extensive biological studies, a versatile approach to the synthesis of the AAs and their major metabolites was devised based primarily on a Suzuki-Miyaura coupling reaction. The key to success lies in the preparation of a common ring-A precursor, namely, the tetrahydropyranyl ether of 2-nitromethyl-3-iodo-4,5-methylendioxybenzyl alcohol (27), which was generated in excellent yield by oxidation of the aldoxime precursor 26. Suzuki-Miyaura coupling of 27 with a variety of benzaldehyde 2-boronates was accompanied by an aldol condensation/elimination reaction to give the desired phenanthrene intermediate directly. Deprotection of the benzyl alcohol followed by two sequential oxidation steps gave the desired phenanthrene nitrocarboxylic acids. This approach was used to synthesize AAs I-IV and several other related compounds, including AA I and AA II bearing an aminopropyloxy group at position-6, which were required for further conversion to fluorescent biological probes. Further successful application of the Suzuki-Miyaura coupling reaction to the synthesis of the N-hydroxyaristolactams of AA I and AA II then allowed the synthesis of the putative, but until now elusive, N-acetoxy- and N-sulfonyloxy-aristolactam metabolites.

Response of Bone Resorption Markers to Aristolochia longa Intake by Algerian Breast Cancer Postmenopausal Women

Aristolochia longa is widely used in traditional medicine in Algeria to treat breast cancer. The aim of the present study was to investigate the response of bone resorption markers to A. longa intake by Algerian breast cancer postmenopausal women. According to the A. longa intake, breast cancer patients were grouped into A. longa group (Al) (n = 54) and non-A. longa group (non-Al) (n = 24). 32 women constituted the control group. Bone resorption markers (from urine) pyridinoline (PYD) and deoxypyridinoline (DPD) were determined by HPLC. Serum and urinary creatinine, uric acid, and urea were measured. 1 g of A. longa intake resulted in significant rise of renal serum markers and a pronounced increase of bone resorption markers. The intake of A. longa roots is detrimental for kidney function and resulted in high bone resorption, maybe due to the reduction in renal function caused by the aristolochic acids contained in the roots.

Aristolochic acid-induced upper tract urothelial carcinoma in Taiwan: clinical characteristics and outcomes

Aristolochic acid (AA), a component of all Aristolochia-based herbal medicines, is a potent nephrotoxin and human carcinogen associated with upper urinary tract urothelial carcinoma (UUC). To investigate the clinical and pathological characteristics of AA-induced UUC, this study included 152 UUC patients, 93 of whom had been exposed to AA based on the presence of aristolactam-DNA adducts in the renal cortex. Gene sequencing was used to identify tumors with A:T-to-T:A transversions in TP53, a mutational signature associated with AA. Cases with both aristolactam-DNA adducts and A:T-to-T:A transversions in TP53 were defined as AA-UUC, whereas patients lacking both of these biomarkers were classified as non-AA-UUC. Cases with either biomarker were classified as possible-AA-UUC. Forty (26%), 60 (40%), and 52 (34%) patients were classified as AA-UUC, possible-AA-UUC and non-AA-UUC, respectively. AA-UUC patients were younger (median ages: 64, 68, 68 years, respectively; p=0.189), predominately female (65%, 42%, 35%, respectively; p=0.011), had more end-stage renal disease (28%, 10%, 12%, respectively; p=0.055), and were infrequent smokers (5%, 22%, 33%, respectively; p=0.07) compared to possible-AA-UUC and non-AA-UUC patients. All 14 patients who developed contralateral UUC had aristolactam-DNA adducts; ten of these also had signature mutations. The contralateral UUC-free survival period was shorter in AA-UUC compared to possible- or non-AA-UUC (p=0.019 and 0.002, respectively), whereas no differences among groups were observed for bladder cancer recurrence. In conclusion, AA-UUC patients tend to be younger and female, and have more advanced renal disease. Notably, AA exposure was associated with an increased risk for developing synchronous bilateral and metachronous contralateral UUC.

Aristolochic acid nephropathy: variation in presentation and prognosis

BACKGROUND

Aristolochic acid nephropathy (AAN) is a worldwide problem and one of the common causes of chronic kidney disease (CKD) in China.

METHODS

Three hundred patients diagnosed as AAN from 1997 to 2006 were enrolled. Medical histories of Chinese herb ingestion, clinical-pathological features and risk factors for renal failure were recorded. Patients were followed up for 2-156 months. Factors involved in the prognosis of AAN were investigated.

RESULTS

The 300 patients with AAN manifested three clinical subtypes, including acute kidney injury (acute AAN) in 13 patients, abrupt tubular dysfunction with normal serum creatinine (Scr) levels in seven cases and chronic tubulointerstitial nephropathy with decreased estimated glomerular filtration rate (eGFR) (chronic AAN) in 280 cases. The acute AAN cases had the highest aristolochic acid (AA)-I intake per day and developed progressive kidney failure during 1-7 years follow-up. The tubular dysfunction AAN patients had the lowest cumulative AA-I intake and were able to keep normal Scr levels during 2-8 years follow-up. The chronic AAN patients took the lowest AA-I dose per day but with the longest period and the highest cumulative dosage and exhibited a very large range of eGFR changing rate (from -21.6 to 5.2, median -3.5 mL/min/year). The cumulative AA-I intake (r = 0.330, P = 0.045) and the time course from the termination of AA medication to the start of follow-up (r = -0.430, P = 0.009) were found to be independent factors correlated with the decrease rate of eGFR in the chronic AAN patients. AA and the metabolites could be detected in a high frequency in patients who had stopped herbal medication for 1 year, which indicates a rather long washout time for these chemicals.

CONCLUSIONS

AAN has variant phenotypes with distinct prognosis, which is determined by the variable AA medications. With better understanding of toxic and environmental causes for kidney injury, there would be a better chance to uncover the causal factors of cases of 'CKD without known causes' which is crucial for improving the disease outcomes.

Pharmacokinetics of p-Aminohippuric Acid and Inulin in Rabbits with Aristolochic Acid Nephropathy

The characteristics of aristolochic acid nephropathy (AAN) are interstitial fibrosis and atrophy of the proximal tubules, but with no change in glomeruli. To investigate the effects of AA on renal functions and the pharmacokinetics (PKs) of p-aminohippuric acid (PAH) and inulin, New Zealand white rabbits were used in this study. The plasma concentrations of PAH and inulin were determined by validated HPLC methods. After a single intravenous administration of 0.5 mg/kg aristolochic acid sodium (AANa), rabbits exhibited mild to moderate nephrotoxicity on the 7th day. Significant tubulointerstitial damage to kidney specimens was found, but there were no remarkable glomerular changes. Clearance rates of PAH and inulin both significantly decreased in AANa-treated rabbits. In addition, there was a significant correlation among the degree of tubulointerstitial changes and PK parameters of PAH after AANa administration, but no correlation was noted with the PKs of inulin. With mild to moderate AAN in rabbits, the renal plasma flow significantly decreased by 55%, and the glomerular filtration rate also significantly decreased by 85%. In conclusion, major renal lesions were found on proximal tubules after AANa administration. The PKs of PAH and inulin significantly changed, and kidney functions, including the RPF and GFR, were reduced.

Acute nephrotoxicity of aristolochic acids in mice

Aristolochic acids (AA), present in Aristolochia plants, are the toxin responsible for Chinese herbs nephropathy (CHN), a rapidly progressive tubulointerstitial nephritis (TIN). To clarify the mechanisms of the development of CHN, we tried to induce TIN in mice using AA. Three strains of inbred mice, BALB/c, C3H/He and C57BL/6, received 2.5 mg kg−1 of AA or AA sodium salt (AANa) daily by intraperitoneal or oral administration, 5 days a week for 2 weeks. Serum and renal tissue were obtained at sacrifice. Twelve-hour urine samples were individually collected in a metabolic cage at one-week intervals. In the AA-injected groups, severe tubular injury, with the appearance of acute tubular necrosis, and rare cell infiltration into the interstitium, were seen in BALB/c mice. C3H/He mice also developed TIN with prominent cell infiltration into the interstitium and interstitial fibrosis. In C57BL/6 mice, only mild and focal tubulointerstitial changes were seen. Serum creatinine and blood urea nitrogen increased in BALB/c and C3H/He mice. Immunofluorescent study revealed no deposition of immune components in kidneys. In the AANa-treated groups, TIN was also seen in all groups, but even more severe tubulointerstitial changes were induced by intraperitoneal injection. Further examination using purified AAI, AAII, AAIVa and aristolactam I (ALI) revealed that AAI induced strong nephrotoxicity in mice, and that AAII resulted in mild nephrotoxicity. However, AAIVa and ALI caused no nephrotoxicity in this experimental system. There are strain differences in mice in their susceptibility to AA nephropathy. AAI exerted the strongest nephrotoxic effect in mice.

Antiplasmodial Activity of Some Medicinal Plants Used in Sudanese Folk-medicine

Ten plants indigenous to Sudan and of common use in Sudanese folk-medicine, were examined in vitro for antimalarial activity against schizonts maturation of Plasmodium falciparum, the major human malaria parasite. All plant samples displayed various antiplasmodial activity. Three plant extracts caused 100% inhibition of the parasite growth at concentrations of plant material Collapse

Key Words

• antiplasmodial activity
• folk-medicine
• medicinal plants

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MESH Headings Collapse

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Affiliation(s)

El-Hadi M. Ahmed Department of Chemistry and Pharmacognosy, Faculty of Pharmacy, University of Gezira, P.O. Box 20 Wad Medani, Sudan
Bakri Y.M. Nour Blue Nile National Institute for Communicable Diseases, University of Gezira, P.O. Box 20 Wad Medani, Sudan
Yousif G. Mohammed Department of Chemistry and Pharmacognosy, Faculty of Pharmacy, University of Gezira, P.O. Box 20 Wad Medani, Sudan
Hassan S. Khalid Medicinal and Aromatic Plants Research Institute, National Council for Research, Khartoum, Sudan.

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Prescription profile of potentially aristolochic acid containing Chinese herbal products: an analysis of National Health Insurance data in Taiwan between 1997 and 2003

Background

Some Chinese herbal products (CHPs) may contain aristolochic acid (AA) or may be adulterated by the herbs suspected of containing AA which is nephrotoxic and carcinogenic. This study aims to identify the risk and the prescription profile of AA-containing CHPs (AA-CHPs) in Taiwan.

Methods

A longitudinal analysis was conducted on a randomly sampled cohort of 200,000 patients using the data from the National Health Insurance (NHI) in Taiwan between 1997 and 2003.

Results

During the 7-year study period, 78,644 patients were prescribed with AA-CHPs; most patients were females, or middle-aged, or both. A total of 526,867 prescriptions were made to use 1,218 licensed AA-CHPs. Over 85% of the AA-exposed patients took less than 60 g of AA-herbs; however, about 7% were exposed to a cumulated dose of over 100 g of Radix et Rhizoma Asari (Xixin), Caulis Akebiae (Mutong) or Fructus Aristolochiae (Madouling). Patients of respiratory and musculoskeletal diseases received most of the AA-CHP prescriptions. The most frequently prescribed AA-CHPs Shujing Huoxie Tang, Chuanqiong Chadiao San and Longdan Xiegan Tang, containing Radix Stephaniae Tetrandrae, Radix et Rhizoma Asari and Caulis Akebiae, respectively.

Conclusion

About one-third of people in Taiwan have been prescribed with AA-CHPs between 1997 and 2003. Although the cumulated doses were not large, further actions should be carried out to ensure the safe use of AA-CHPs.

Aristolochic acid-induced cell cycle G1 arrest in human urothelium SV-HUC-1 cells

Aristolochic acid (AA) has been implicated in urothelial carcinoma in humans. To evaluate the impact of AA on the human urinary tract epithelium cells, a study of SV-HUC-1 cells cultured with mixture of AA (AAM; 41% AA I, 56% AA II) was conducted. Cell viability was assayed in cultures exposed to 0.0125-0.2mM AAM for 1, 3, and 5 days, a concentration-dependent inhibition on the growth of SV-HUC-1 cells was demonstrated. Cell cycle distribution determined by flow cytometry revealed an accumulation of cells in the G0/G1 phase (from 37.6% to 49.2%). Regarding the cell cycle control proteins, the levels of p53, p21 and p27 increased in a concentration-dependent manner. Immunoprecipitation demonstrated a decrease in the formation of cyclin E/cdk2 complex, but not cyclin D1/cdk4 complex, which leads to an increase in the free form of cdk2. Additionally, a decrease in the phospho-Rb correlates with an increase in Rb/E2F-1 complex which prevents the release of E2F transcription factor, thus preventing the transcription of the genes required for cell proliferation. Our results provide evidence that AAM induce cell cycle arrest in SV-HUC-1 cells. Whether this cell cycle block is associated with AA-related human urothelial carcinoma requires further study to clarify.

Cytotoxicity of Phenanthrenes Extracted from Aristolochia contorta in Human Proximal Tubular Epithelial Cell Line

BACKGROUND/AIMS

Aristolochic acid nephropathy, a progressive tubulointerstitial renal disease, is predominantly a result of aristolochic acid I (AA-I) intoxication. However, other unidentified phytotoxins have indeed been postulated as the cause of this unique interstitial nephropathy. The purpose of this study was to investigate the cytotoxicity of other phenanthrene derivatives extracted from Aristolochia contorta in the human proximal tubular epithelial cell line HK-2.

METHODS

After HK-2 cells were incubated with an indicated concentration of test compounds for 24 h, cell viability was assessed by lactate dehydrogenase (LDH) leakage assay (cell membrane damage) in combination with MTT assay (metabolic capability). Cellular morphologic assessments were performed with a phase-contrast inverted microscope and transmission electron microscope.

RESULTS

In all test compounds at 5 microg/ml, AA-I, 7-methoxy-aristololactam IV and aristololactam IVa showed cytotoxic activity in HK-2 cells in both MTT assay and LDH leakage assay (p < 0.01). At high concentration (5-80 microg/ml), these three compounds caused a dose-dependent decrease in MTT reduction and a dose-dependent increase in LDH leakage compared to non-treated cells (p <0.01). In LDH leakage assay, 40 mug/ml 7-methoxy-aristololactam IV induced a 1.58-fold LDH leakage compared to AA-I at the same concentration (p < 0.01). Moreover, the IC50 of these three compounds were 16.675 microg/ml for AA-I, 4.535 microg/ml for 7-methoxy-aristololactam IV, and 30.244 microg/ml for aristololactam IVa in MTT assay. The cellular morphologic assessments suggest interactions with cell membrane and intracellular structures such as lysosome and mitochondria are likely to be involved in cell injury induced by these three compounds.

CONCLUSION

The potency of cytotoxic activity of aristololactam IVa and 7-methoxy-aristololactam IV extracted from A. contorta is similar to or even stronger than that of AA-I.

Determination of aristolochic acid in Chinese herbal medicine by capillary electrophoresis with laser-induced fluorescence detection

We have demonstrated the analysis of aristolochic acids (AAs) that are naturally occurring nephrotoxin and carcinogen by capillary electrophoresis in conjunction with laser-induced fluorescence detection (CE-LIF). Owing to lack of intrinsic fluorescence characteristics of oxidized AAs (OAAs), reduction of the analytes by iron powder in 10.0 mM HCl is required prior to CE analysis. The reduced AAs (RAAs) exhibit fluorescence at 477 nm when excited at 405 nm using a solid-state blue laser. By using 50.0 mM sodium tetraborate (pH 9.0) containing 10.0 mM SDS, the determination of AA-I and AA-II by CE-LIF has been achieved within 12 min. The CE-LIF provides the LODs of 8.2 and 5.4 nM for AA-I and AA-II, respectively. The simple CE-LIF method has been validated by the analysis of 61 Chinese herbal samples. Prior to CE analysis, OAAs were extracted by using 5.0 mL MeOH, and then the extracts were subjected to centrifugation at 3,000 rpm for 5 min. After reduction, extraction, and centrifugation, the supernatants were collected and subjected to CE analysis. Of the 61 samples, 14 samples contain AA-I and AA-II, as well as 10 samples contain either AAI or AAII. The relative standard deviation (RSD) values of the migration times for AA-I and AA-II are less than 2.5% and 2.1% for three consecutive measurements of each sample. The RSD values for the peak heights corresponding to AA-I and AA-II in most samples are about 8.0% and 10.0%, respectively. The result shows that the present CE-LIF approach is sensitive, simple, efficient, and accurate for the determination of AAs in real samples.

Induction of urothelial proliferation in rats by aristolochic acid through cell cycle progression via activation of cyclin D1/cdk4 and cyclin E/cdk2

Aristolochic acid (AA) has been implicated in urothelial carcinoma in humans. However, the mechanism by which AA induces this cancer has not been completely established. To evaluate the effects of AA on the urinary bladder of rats, a histopathological study of three-month intragastric feeding with mixture of AA (41% AA I, 56% AA II) was carried out. A total of 18 experimental rats were divided into three feeding regimens, with six rats in each group (group I, normal basal diet; groups II and III received intragastric 5 mg and 10 mg isolated AA mixture/kg/day for 5 days/week for 12 weeks). Dosage-dependent urothelial proliferation, but not carcinoma, was found in the urothelium of the bladder of the rats administered with AA mixture. Immunoprecipitation showed elevations of cyclin D(1)/cdk4 (increased induction by 1.57- and 1.95-fold in the groups II and III) and/or cyclin E/cdk2 complex (increased induction by 1.46- and 1.62-fold in the groups II and III), which promote the increasing phosphorylation of Rb (increased induction by 1.75- and 2.07-fold in the groups II and III) and result in decrease of the Rb/E2F complex (decreased expression by 0.65- and 0.24-fold in the groups II and III). Our results provide evidence to suggest that exposure to AA results in urothelial proliferation in rats through cell cycle progression via activation of cyclin D(1)/cdk4 and cyclin E/cdk2.

Herbs and the kidney

The use of herbal therapy has increased dramatically in past years and may lead to renal injury or various toxic insults, especially in renal patients. In most countries, herbal products are not regulated as medicines. Herbal poisoning may be secondary to the presence of undisclosed drugs or heavy metals, interaction with the pharmacokinetic profile of concomitantly administered drugs, or association with a misidentified herbal species. Various renal syndromes were reported after the use of medicinal plants, including tubular necrosis, acute interstitial nephritis, Fanconi's syndrome, hypokalemia or hyperkalemia, hypertension, papillary necrosis, chronic interstitial nephritis, nephrolithiasis, urinary retention, and cancer of the urinary tract. It seems critical that caregivers be aware of the potential risk of such often underreported therapy and carefully question their patients about their use of this popular branch of alternative medicine.

Aristolochic acid and 'Chinese herbs nephropathy': a review of the evidence to date

Chinese herbs nephropathy (CHN) is a rapidly progressive interstitial nephropathy reported after the introduction of Chinese herbs in a slimming regimen followed by young Belgian women. It is characterised by early, severe anaemia, mild tubular proteinuria and initially normal arterial blood pressure in half of the patients. Renal histology shows unusual extensive, virtually hypocellular cortical interstitial fibrosis associated with tubular atrophy and global sclerosis of glomeruli decreasing from the outer to the inner cortex. Urothelial malignancy of the upper urinary tract develops subsequently in almost half of the patients. Suspicion that the disease was due to the recent introduction of Chinese herbs in the slimming regimen was reinforced by identification in the slimming pills of the nephrotoxic and carcinogenic aristolochic acid (AA) extracted from species of Aristolochia. This hypothesis was substantiated by the identification of premutagenic AA-DNA adducts in the kidney and ureteric tissues of CHN patients. Finally, induction of the clinical features (interstitial fibrosis and upper urothelial malignancy) typical of CHN in rodents given AA alone removed any doubt on the causal role of this phytotoxin in CHN, now better called aristolochic acid nephropathy (AAN). AAN is not restricted to the Belgian cases. Similar cases have been observed throughout the world, but AA is sometimes incriminated on the basis of the known content of AA in the herbs. The possibility remains that in some individuals in whom AA has not been demonstrated, other phytotoxins might be implicated. Biological and morphological features of AAN are strikingly similar to those reported in another fibrosing interstitial nephropathy of still unknown aetiology, Balkan endemic nephropathy (BEN). Interestingly, AA was incriminated as the cause of BEN many years ago, a hypothesis yet to be fully explored. The intake of AA and the presence of tissular AA-DNA adducts in patients with an unequivocal diagnosis of BEN remains to be demonstrated. The tragic phenomenon of CHN, recognised only 10 years ago, has been at the root of significant research and progress both in nephrology and oncology. It has provided a fascinating opportunity to understand the link between a fibrosing interstitial nephropathy and urothelial carcinoma. It allows the categorisation of interstitial nephritis on the basis of histological findings, of initiating toxic substances and of associated clinical features. Finally, it has led to the withdrawal in several countries of a previously unsuspected carcinogenic and nephrotoxic substance.

Detection of aristolochic acid in Chinese phytomedicines and dietary supplements used as slimming regimens

Over the last 10 years, numerous cases of intoxications, leading for the most part to end-stage renal failure, have been reported after consumption of slimming regimens made of Chinese herbal preparations. These intoxications were associated with species of the Aristolochia genus, such as Aristolochia fangchi (Aristolochiaceae), known to contain very nephrotoxic and carcinogenic metabolites named aristolochic acids. Several commercial dietary supplements, teas and phytomedicines used as slimming regimens were analysed for their aristolochic acid I content. A preliminary detection of this toxic compound was made by thin-layer chromatography. The presence of aristolochic acid I in these preparations was confirmed by a HPLC/UV-DAD/MS analysis. A quantitative determination of aristolochic acid I was also achieved in the incriminated preparations using both UV and MS detection. Out of 42 analysed preparations, four were found to contain aristolochic acid I and two were suspected to contain aristolochic acid derivatives. Immediate removal of these products from the Swiss market was called for.

Risks associated with herbal slimming remedies

The market for non-conventional, natural herbal medicines is growing. This marketing opportunity has been seized upon by some unscrupulous practitioners to sell potentially unsafe 'herbal' products. Several people attended a Chinese herbalist for weight loss advice and were sold 'herbal' preparations that contained fenfluramine, a drug which was withdrawn from sale in the West in 1997 after its use was linked to primary pulmonary hypertension and valvular heart disease. Adulteration of Chinese medicines with Western drugs is becoming an increasing problem, and deaths have been reported from Japan and other Far Eastern countries linked to Chinese slimming aids containing N-nitroso-fenfluramine. There is a need for increased public awareness of such risks associated with the use of unlicensed medicines; a system of registration for medical herbalists is also required to protect both the reputable practitioners and the general public.

Mutagenicity of aristolochic acid in the lambda/lacZ transgenic mouse (MutaMouse)

Aristolochic acid (AA) is found in a plant that causes urothelial carcinomas in patients with Chinese herb nephropathy (CHN). To evaluate the in vivo mutagenicity of AA, we analysed the mutant frequency (MF) in the lacZ and cII gene of 10 organs of the lambda/lacZ transgenic mouse (MutaMouse) after intragastric treatment with AA (15mg/kg per week x 4). Simultaneously, the clastogenicity of AA was evaluated by the peripheral blood micronucleus assay. The nature of the mutations induced by AA was revealed by the sequence analysis of the cII gene, which is also a phenotypically selectable marker in the lambda transgene. MFs in the target organs-forestomach, kidney, and bladder of AA-treated mice were significantly higher than those of control mice (forestomach 33- and 15-fold; kidney 10- and 9-fold; bladder 16- and 31-fold, for the lacZ and cII, respectively). The MFs in non-target organs, except the colon, showed only slight increases. Sequence analysis of cII mutants in target organs revealed that AA induced mainly A:T to T:A transversions whereas G:C to A:T transitions at CpG sites predominated among spontaneous mutations. These results suggested that AA, which is activated by cytochrome P450 and peroxidase to form cyclic nitrenium ions that bind to deoxyadenine, caused the A to T transversions in the target organs of mice.

Progression rate of Chinese herb nephropathy: impact of Aristolochia fangchi ingested dose

BACKGROUND

Renal failure after ingestion of Chinese herbs between 1990 and 1992 was related to the replacement of Stephania tetrandra by Aristolochia fangchi (ST-AF), containing nephrotoxic and carcinogenic aristolochic acids. However, the relationship between ST-AF and renal failure is still a matter of debate. We therefore tested the impact of the ST-AF ingested dose on the progression of renal function deterioration.

METHODS

Analysis of medical charts and prescriptions between 1990 and 1992 was carried out to determine the presence of risk factors for kidney failure and the cumulative dose of pill components. Individual progression rate of renal impairment was studied by the time-course of the inverse of blood creatinine level (1/P(creat)).

RESULTS

Patients were divided into an end-stage renal disease (ESRD) group (n=44) and a chronic renal failure (CRF) group (n=27) according to their P(creat) at the time of this study. The mean number of risk factors (+/-SD) was equally distributed within both groups (1.50+/-0.18 vs 1.59+/-0.17, P=0.74). Patients from the ESRD group ingested significantly higher cumulative doses of ST--AF (192+/-13.1 g vs 138+/- 16.3 g), Magnolia officinalis, (80.1+/-6.3 g vs 59.8+/-11.7 g), diethylpropion (14.7+/-1.4 g vs 10.0+/-1.4 g) and fenfluramine (14.1+/-1.6 g vs 8.7+/-1.3 g). In the ESRD group, some patients who had received steroids had a slower progression to ESRD than the others. In multiple regression analysis, ST-AF emerged as the only significant drug predicting the slope of the progression of renal failure. Moreover, hypothesizing a linear dose-response relationship, the risk of developing ESRD linearly increased with ST-AF doses.

CONCLUSIONS

The relationship between the cumulative ST-AF dose and the renal failure progression rate confirms that regular ingestion of Aristolochia sp. extracts is causally involved in the onset of chronic interstitial nephropathy leading to ESRD.

Aristolochic acid nephropathy in a Chinese patient: time to abandon the term "Chinese herbs nephropathy"?

The causal role of aristolochic acid (AA) in the so-called Chinese herbs nephropathy (CHN) has been conclusively demonstrated only in the Belgian epidemic. We report a biopsy-proven hypocellular interstitial fibrosing nephropathy in a Chinese patient who had ingested a Chinese herbal preparation bought in Shanghai. The identification of AA in the preparation and of AA-DNA adducts in the kidney tissue unequivocally demonstrates, for the first time, the causal role of AA outside the Belgian epidemic. Because the ingested preparation is very popular in China as an over-the-counter product, our observation raises the possibility that many such cases due to AA might be currently unrecognized in China. AA should be banned from herbal preparations worldwide. All cases of the so-called CHN, in which the causal role of AA has been thoroughly documented, should be further identified as aristolochic acid nephropathy (AAN). The term phytotherapy-associated interstitial nephritis (PAIN) might refer to the other cases associated with phytotherapy without identification, as yet, of the causal agent.

Aristolochic acid impedes endocytosis and induces DNA adducts in proximal tubule cells

BACKGROUND

Aristolochic acid (AA), present in Aristolochia plants, appears to be the toxin responsible for Chinese herbs nephropathy (CHN), a rapidly progressive tubulointerstitial nephritis. One of the earliest sign of CHN is the urinary excretion of low-molecular-weight proteins (LMWP), suggesting that AA is toxic to proximal tubules (PT).

METHODS

The effects of AA on PT functions including reabsorption of LMWP were investigated on the well-established opossum kidney (OK) cell line, a model for PT, and compared with those of the classical PT toxin cadmium chloride (CdCl2).

RESULTS

OK cell monolayers internalized albumin and beta2-microglobulin by receptor-mediated endocytosis, both proteins apparently competing for the same receptor, a complex of megalin and cubulin. The process was significantly impaired by 24-hour preincubation with AA (10 or 20 micromol/L) or CdCl2 (15 micromol/L). Furthermore, 24-hour exposure to AA followed by its removal during one to six days led to a persistent inhibition of the uptake of albumin, in contrast to the substantial recovery observed after CdCl2 removal. Neither AA nor CdCl2 affected cell viability, Na+-glucose cotransport or total rate of protein synthesis. AA significantly decreased megalin expression and formed specific DNA adducts in OK cells, similar to those found in kidneys from CHN patients.

CONCLUSIONS

The present data support the involvement of AA in the early PT dysfunction found in CHN; furthermore, they suggest a causal relationship between DNA adduct formation, decreased megalin expression, and inhibition of receptor-mediated endocytosis of LMWP.

Chronic aristolochic acid toxicity in rabbits: a model of Chinese herbs nephropathy?

BACKGROUND

Chinese herbs nephropathy (CHN) is a new type of subacute interstitial nephritis that is attributed to aristolochic acid (AA), which inadvertently has been included in slimming pills. The contribution of other simultaneously prescribed drugs remains disputed. In the present study, the effects of a chronic intake of AA given as a single drug was evaluated through renal histology and function in rabbits.

METHODS

Female New Zealand White rabbits were injected intraperitoneally with either 0.1 mg AA/kg or with saline 5 days a week for 17 to 21 months. Body weight, renal function, and urinary excretion of glucose and low molecular weight proteins were monitored prior to sacrifice at the end of the study period.

RESULTS

All animals given AA developed renal hypocellular interstitial fibrosis, which was classified into three patterns. Fibrosis was confined to medullary rays (MRs) in pattern I (N = 3), extended to the outer cortical labyrinth (OCL) in pattern II (N = 2), and eventually to the inner cortical labyrinth (ICL) in pattern III (N = 6). Fibrosis in MR and OCL was associated with mainly proximal tubular epithelial cell flattening. All treated animals displayed urothelial atypia. Three of them also developed tumors of the urinary tract. No significant pathologic changes were found in control rabbits. AA-treated animals differed from controls by an impaired growth, increased serum creatinine, glucosuria, tubular proteinuria, and anemia.

CONCLUSION

The observed pattern of renal histopathological lesions and disorders of the renal function, as well as urothelial atypia and malignancy, are very reminiscent of CHN. Our observations therefore support a causal role of AA alone in the genesis of this new nephropathy.

Urothelial carcinoma associated with the use of a Chinese herb (Aristolochia fangchi)

BACKGROUND

Chinese-herb nephropathy is a progressive form of renal fibrosis that develops in some patients who take weight-reducing pills containing Chinese herbs. Because of a manufacturing error, one of the herbs in these pills (Stephania tetrandra) was inadvertently replaced by Aristolochia fangchi, which is nephrotoxic and carcinogenic.

METHODS

The diagnosis of a neoplastic lesion in the native urinary tract of a renal-transplant recipient who had Chinese-herb nephropathy prompted us to propose regular cystoscopic examinations and the prophylactic removal of the native kidneys and ureters in all our patients with end-stage Chinese-herb nephropathy who were being treated with either transplantation or dialysis. Surgical specimens were examined histologically and analyzed for the presence of DNA adducts formed by aristolochic acid. All prescriptions written for Chinese-herb weight-reducing compounds during the period of exposure (1990 to 1992) in these patients were obtained, and the cumulative doses were calculated.

RESULTS

Among 39 patients who agreed to undergo prophylactic surgery, there were 18 cases of urothelial carcinoma (prevalence, 46 percent; 95 percent confidence interval, 29 to 62 percent): 17 cases of carcinoma of the ureter, renal pelvis, or both and 1 papillary bladder tumor. Nineteen of the remaining patients had mild-to-moderate urothelial dysplasia, and two had normal urothelium. All tissue samples analyzed contained aristolochic acid-related DNA adducts. The cumulative dose of aristolochia was a significant risk factor for urothelial carcinoma, with total doses of more than 200 g associated with a higher risk of urothelial carcinoma.

CONCLUSIONS

The prevalence of urothelial carcinoma among patients with end-stage Chinese-herb nephropathy (caused by aristolochia species) is a high.

Misuse of herbal remedies: the case of an outbreak of terminal renal failure in Belgium (Chinese herbs nephropathy)

At least 100 cases of extensive interstitial fibrosis of the kidneys were observed in Belgium in women who had followed a weight-loss regimen that included the use of Chinese herbs. The possible relation between the renal disease and these Chinese herbs was investigated. It was shown that the prescribed Chinese herb called Stephania tetrandra was, in fact, inadvertently replaced by another Chinese herb, namely Aristolochia fangchi in the powdered extracts delivered in Belgium and in France. The development of renal disease in about 100 patients exposed to the so-called Stephania tetrandra stresses the need for more stringent control of herbal medicine.

Harmless herbs? A review of the recent literature

Herbal medicines have become a popular form of therapy. They are often perceived as being natural and therefore harmless. This article reviews the recent literature on the adverse effects of herbal remedies. Examples of allergic reactions, toxic reactions, adverse effects related to an herb's desired pharmacological actions, possible mutagenic effects, drug interactions, drug contamination, and mistaken plant identities are provided. Because of underreporting, our present knowledge may well be just the "tip of the iceberg." Little is known about the relative safety of herbal remedies compared to synthetic drug treatments, although for some herbal remedies, the risks may be less than for conventional drugs.