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

Human UDP-glucuronosyltransferase 1As catalyze aristolochic acid D O-glucuronidation to form a lesser nephrotoxic glucuronide

ETHNOPHARMACOLOGICAL RELEVANCE

Aristolochic acids (AAs) are naturally occurring nitro phenanthrene carboxylic acids primarily found in plants of the Aristolochiaceae family. Aristolochic acid D (AAD) is a major constituent in the roots and rhizomes of the Chinese herb Xixin (the roots and rhizomes of Asarum heterotropoides F. Schmidt), which is a key material for preparing a suite of marketed Chinese medicines. Structurally, AAD is nearly identical to the nephrotoxic aristolochic acid I (AAI), with an additional phenolic group at the C-6 site. Although the nephrotoxicity and metabolic pathways of AAI have been well-investigated, the metabolic pathway(s) of AAD in humans and the influence of AAD metabolism on its nephrotoxicity has not been investigated yet.

AIM OF THE STUDY

To identify the major metabolites of AAD in human tissues and to characterize AAD O-glucuronidation kinetics in different enzyme sources, as well as to explore the influence of AAD O-glucuronidation on its nephrotoxicity.

MATERIALS AND METHODS

The O-glucuronide of AAD was biosynthesized and its chemical structure was fully characterized by both 1H-NMR and 13C-NMR. Reaction phenotyping assays, chemical inhibition assays, and enzyme kinetics analyses were conducted to assess the crucial enzymes involved in AAD O-glucuronidation in humans. Docking simulations were performed to mimic the catalytic conformations of AAD in human UDP-glucuronosyltransferases (UGTs), while the predicted binding energies and distances between the deprotonated C-6 phenolic group of AAD and the glucuronyl moiety of UDPGA in each tested human UGT isoenzyme were measured. The mitochondrial membrane potentials (MMP) and reactive oxygen species (ROS) levels in HK-2 cells treated with either AAI, or AAD, or AAD O-glucuronide were tested, to elucidate the impact of O-glucuronidation on the nephrotoxicity of AAD.

RESULTS

AAD could be rapidly metabolized in human liver and intestinal microsomes (HLM and HIM, respectively) to form a mono-glucuronide, which was purified and fully characterized as AAD-6-O-β-D-glucuronide (AADG) by NMR. UGT1A1 was the predominant enzyme responsible for AAD-6-O-glucuronidation, while UGT1A9 contributed to a lesser extent. AAD-6-O-glucuronidation in HLM, HIM, UGT1A1 and UGT1A9 followed Michaelis-Menten kinetics, with the Km values of 4.27 μM, 9.05 μM, 3.87 μM, and 7.00 μM, respectively. Docking simulations suggested that AAD was accessible to the catalytic cavity of UGT1A1 or UGT1A9 and formed catalytic conformations. Further investigations showed that both AAI and AAD could trigger the elevated intracellular ROS levels and induce mitochondrial dysfunction and in HK-2 cells, but AADG was hardly to trigger ROS accumulation and mitochondrial dysfunction.

CONCLUSION

Collectively, UGT1A-catalyzed AAD 6-O-glucuronidation represents a crucial detoxification pathway of this naturally occurring AAI analogs in humans, which is very different from that of AAI.

Comprehensive HRMS Screening and Risk Assessments of Aristolochic Acid Analogues in Asari Radix et Rhizoma and Related Commercial Health Products

Aristolochic acid analogues (AAAs) are well-known toxins. We performed the first comprehensive screening on AAAs in Asari Radix et Rhizoma (underground part of Asarum heterotropoides Schmidt), the only Aristolochiaceae plant widely used in clinical practice. LC-HRMS revealed 70 trace AAAs using polygonal mass defect filtering and precursor ion list strategies, 38 of which were newly discovered in A. heterotropoides. UHPLC-QTrap-MS/MS was then utilized for quantitative/semiquantitative analysis of 26 abundant compounds. Seventeen AAAs were detected from 91 batches of A. heterotropoides and 20 AAAs from 166 consumable products. For 141 Asari-containing proprietary products, aristolactam I and aristolactam II-glucoside exhibited the widest distribution, present in 98% products. AA IVa was the most abundant, detected in 91%. Notably, 60% of the products contained AA I (0.03-0.79 ppm). The safety was assessed using linear extrapolation, permitted daily exposure, cumulative amount, and the margin of exposure. It is recommended that AA I content be limited to 3 ppm.

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 and Simultaneous Quantification of Six Aristolochic Acids and Two Lignans in Asari Radix et Rhizoma Using Ultra-Performance Liquid Chromatography-Triple Quadrupole Tandem Mass Spectrometry

Asari Radix et Rhizoma (AR) is a widely-used Chinese herbal medicine containing multiple active lignans and rare nephrotoxic components-aristolochic acids derivatives (AAs). However, the current quality control method carried out by Chinese Pharmacopoeia has defects in trace AAs detection and insufficient marker ingredients, which is unable to comprehensively evaluate the efficacy and safety of AR. To improve the quality control method of AR, a rapid, sensitive, and reliable chromatographic analytic method based on ultra-high-performance liquid chromatography-triple quadrupole tandem mass spectrometry (UHPLC-QqQ-MS) was established for the simultaneous analysis of multiple AAs and lignans in AR samples. Positive electrospray ionization mode with multiple reaction monitoring (MRM) was applied for the detection of the eight analytes. The method showed available linearity (R ² ≥ 0.991), the limit of quantification (2-5 ng/mL), precision (RSD <8.12%), and accuracy (89.78-112.16%). A total of 6 AAs and 2 lignans were quantified for their content in 15 AR samples. The content of AA-IVa, AA-VIIa, and aristololactam I (AL-I) was much higher than the AA-I controlled by pharmacopoeia. Considering the potential toxicity of AAs, AA-IVa, AA-VIIa, and AL-I should also be controlled in AR. A considerable amount of active sesamin was detected in AR, suggesting that it could be added as a quality marker for the quality control of AR. The newly developed analytical method could be applied for the fast evaluation of toxic AA's content and quality during quality control of AR or preparations containing AR.

The genus Asarum: A review on phytochemistry, ethnopharmacology, toxicology and pharmacokinetics

ETHNOPHARMACOLOGICAL RELEVANCE

In essentially every quadrant of the globe, many species of genus Asarum are used as a common herbal medicine and appear in many formulas or Kampo. Crude drug from several medicinal plants of genus Asarum (MA) known as Asari Radix et Rhizoma (ARR) has been proven to have the functions of dispelling cold, relieving pain, and reducing phlegm according to Traditional Chinese Medicine (TCM) theory for thousands of years.

AIM OF THE STUDY

This article reviews the ethnopharmacology, phytochemistry, pharmacology, toxicology and metabolic kinetics related research of genus Asarum to evaluate its ethnopharmacology use and future opportunities for research.

MATERIALS AND METHODS

Information on relevant studies of the genus Asarum was gathered via the Internet using Baidu Scholar, Web of Science, Elsevier, ResearchGate, ACS, Pudmed and Chinese National Knowledge Infrastructure (CNKI). Additionally, information was also obtained from some local books, PhD, MS's dissertations and Pharmacopeias.

RESULTS

The genus Asarum has played an important role in herbal treatment. At present, more than 277 compounds have been isolated or identified from genus Asarum. Among them, volatile oil and lignans are the major active constituents and important chemotaxonomic markers. Modern pharmacological studies indicated that genus Asarum and its active compounds possess a wide range of pharmacological effects, especially analgesic, anti-inflammatory, neuroprotective, cardiovascular protection, antitussive, immunosuppressive, anti-tumor, and microbicidal activities.

CONCLUSIONS

Based on this review, therapeutic potential of genus Asarum has been demonstrated with the pharmacological effects on inflammation, CNS, respiratory regulation, cardiovascular diseases, cancer and microbial infection. The available literature showed that the major activities of the genus Asarum can be attributed to the active lignans and essential oils. Further in-depth studies on the aspects of the genus for mechanism of actions, metabolism, pharmacokinetics, toxicology, drug interactions, and clinical trials are still limited, thereby intensive research and assessments should be performed.

Treatment of Lupus Nephritis from Iranian Traditional Medicine and Modern Medicine Points of View: A Comparative Study

Objective

Nephritis or kidney inflammation is characterized as one of the most common renal disorders leading to serious damage to the kidneys. Nephritis, especially lupus nephritis (LN), has remained as the main cause of chronic renal failure which needs serious therapeutic approaches such as dialysis and kidney transplant. Heredity, infection, high blood pressure, inflammatory diseases such as lupus erythematosus and inflammatory bowel disease, and drug-related side effects are known as the main causes of the disease. According to Iranian traditional medicine (ITM), infectious diseases and fever are the main reasons of nephritis, which is called “Varam-e-Kolye” (VK).

Results

There are various plant-based remedies recommended by ITM for the treatment of nephritis, as discussed herein, comparing with those available in the modern medicine. There is no definite cure for the treatment of nephritis, and immunosuppressive drugs such as corticosteroids and nonsteroidal anti-inflammatory drugs, antibiotics, diuretics, analgesics, and finally dialysis and kidney transplantation are usually used. Based on the efficacy of medicinal plants, jujube (Ziziphus jujuba), almond (Prunus amygdalus), pumpkin seeds (Cucurbita pepo), purslane (Portulaca oleracea), and fig (Ficus carica) were found to be effective for the treatment of kidney inflammation in ITM.

Conclusion

Considering the fact that there is no efficient strategy for the treatment of nephritis, use of herbal medicine, particularly based on the fruits or nuts that have been safely used for several years can be considered as a versatile supplement along with other therapeutic methods.

Aristolochic acid IVa forms DNA adducts in vitro but is non-genotoxic in vivo

Aristolochic acids (AAs) are a family of natural compounds with AA I and AA II being known carcinogens, whose bioactivation causes DNA adducts formation. However, other congeners have rarely been investigated. This study aimed to investigate genotoxicity of AA IVa, which differs from AA I by a hydroxyl group, abundant in Aristolochiaceae plants. AA IVa reacted with 2'-deoxyadenosine (dA) and 2'-deoxyguanosine (dG) to form three dA and five dG adducts as identified by high-resolution mass spectrometry, among which two dA and three dG adducts were detected in reactions of AA IVa with calf thymus DNA (CT DNA). However, no DNA adducts were detected in the kidney, liver, and forestomach of orally dosed mice at 40 mg/kg/day for 2 days, and bone marrow micronucleus assay also yielded negative results. Pharmacokinetic analyses of metabolites in plasma indicated that AA IVa was mainly O-demethylated to produce a metabolite with two hydroxyl groups, probably facilitating its excretion. Meanwhile, no reduced metabolites were detected. The competitive reaction of AA I and AA IVa with CT DNA, with adducts levels varying with pH of reaction revealed that AA IVa was significantly less reactive than AA I, probably by hydroxyl deprotonation of AA IVa, which was explained by theoretical calculations for reaction barriers, energy levels of the molecular orbits, and charges at the reaction sites. In brief, although it could form DNA adducts in vitro, AA IVa was non-genotoxic in vivo, which was attributed to its low reactivity and biotransformation into an easily excreted metabolite rather than bioactivation.

Nephrotoxicity of Herbal Medicine and Its Prevention

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

Medicinally Used Asarum Species: High-Resolution LC-MS Analysis of Aristolochic Acid Analogs and In vitro Toxicity Screening in HK-2 Cells

Species of Asarum are used in traditional Chinese medicine and, similar to members of the genus Aristolochia, they contain aristolochic acid analogs (AAAs). These compounds are known for their nephrotoxic and carcinogenic effects. So far, the phytochemistry and nephrotoxicity of species of Asarum is not well studied. A high-resolution LC-MS-based metabolomic approach was used to study the phytochemical variation in medicinally used Asarum species. The cytotoxicity of the samples was assessed using human kidney (HK-2) cells. The majority of samples contained potentially nephrotoxic AAAs, including 9-methoxy aristolactam (AL) IV, AL I, and AL IV. These compounds were present in methanol as well as water extracts. AAAs were detected in all parts of the plant. The majority of the extracts were not cytotoxic to HK-2 cells at the doses tested. However, other mechanisms relating to aristolochic acid nephropathy and cancer development, such as DNA adduct formation may occur. The results of this study provide a model for assessing lesser-known plant species for toxicity.

LC-MS- and (1)H NMR-Based Metabolomic Analysis and in Vitro Toxicological Assessment of 43 Aristolochia Species

Species of Aristolochia are used as herbal medicines worldwide. They cause aristolochic acid nephropathy (AAN), a devastating disease associated with kidney failure and renal cancer. Aristolochic acids I and II (1 and 2) are considered to be responsible for these nephrotoxic and carcinogenic effects. A wide range of other aristolochic acid analogues (AAAs) exist, and their implication in AAN may have been overlooked. An LC-MS- and (1)H NMR-based metabolomic analysis was carried out on 43 medicinally used Aristolochia species. The cytotoxicity and genotoxicity of 28 Aristolochia extracts were measured in human kidney (HK-2) cells. Compounds 1 and 2 were found to be the most common AAAs. However, AA IV (3), aristolactam I (4), and aristolactam BI (5) were also widespread. No correlation was found between the amounts of 1 or 2 and extract cytotoxicity against HK-2 cells. The genotoxicity and cytotoxicity of the extracts could be linked to their contents of 5, AA D (8), and AA IIIa (10). These results undermine the assumption that 1 and 2 are exclusively responsible for the toxicity of Aristolochia species. Other analogues are likely to contribute to their toxicity and need to be considered as nephrotoxic agents. These findings facilitate understanding of the nephrotoxic mechanisms of Aristolochia and have significance for the regulation of herbal medicines.

Bioactive compounds from the roots of Asiasarum heterotropoides

A new tetrahydrofuran lignan, (7S,8R,7'S,8'S)-3-methoxy-3',4'-methylenedioxy-7,9'-epoxylignane-4,7',9-triol (1), and 21 known compounds 2–22 were isolated from the roots of Asiasarum heterotropoides by chromatographic separation methods. The structures of all compounds 1–22 were elucidated by spectroscopic analysis including 1D- and 2D-NMR. Fourteen of these compounds (1–3, 7, 10, 12–17, 19, 21, and 22) were isolated from this species in this study for the first time. All of the isolates were evaluated for their anticancer activities using in vitro assays. Among the 22 tested compounds, two (compounds 5 and 7) induced the downregulation of NO production, FOXP3 expression, and HIF-1α transcriptional activity.

Evidence-based toxicity evaluation and scheduling of Chinese herbal medicines

ETHNOPHARMACOLOGICAL RELEVANCE

While there is an increasing number of toxicity report cases and toxicological studies on Chinese herbal medicines, the guidelines for toxicity evaluation and scheduling of Chinese herbal medicines are lacking.

AIM

The aim of this study was to review the current literature on potentially toxic Chinese herbal medicines, and to develop a scheduling platform which will inform an evidence-based regulatory framework for these medicines in the community.

MATERIALS AND METHODS

The Australian and Chinese regulations were used as a starting point to compile a list of potentially toxic herbs. Systematic literature searches of botanical and pharmaceutical Latin name, English and Chinese names and suspected toxic chemicals were conducted on Medline, PubMed and Chinese CNKI databases.

RESULTS

Seventy-four Chinese herbal medicines were identified and five of them were selected for detailed study. Preclinical and clinical data were summarised at six levels. Based on the evaluation criteria, which included risk-benefit analysis, severity of toxic effects and clinical and preclinical data, four regulatory classes were proposed: Prohibited for medicinal usage, which are those with high toxicity and can lead to injury or death, e.g., aristolochia; Restricted for medicinal usage, e.g., aconite, asarum, and ephedra; Required warning label, e.g., coltsfoot; and Over-the-counter herbs for those herbs with a safe toxicity profile.

CONCLUSION

Chinese herbal medicines should be scheduled based on a set of evaluation criteria, to ensure their safe use and to satisfy the need for access to the herbs. The current Chinese and Australian regulation of Chinese herbal medicines should be updated to restrict the access of some potentially toxic herbs to Chinese medicine practitioners who are qualified through registration.

Comparative study of the contents of analogues of aristolochic acid in two kinds of Aristolochiae Fructus by high-performance liquid chromatography

Aristolochiae Fructus ("Madouling") is derived from the fruits of Aristolochia contorta and A. debilis (Aristolochiaceae). These two species contain potentially nephrotoxic constituents, but are officially used in China. Distinction of constituents and toxicity between these two species remains unclear. A high-performance liquid chromatography method was developed and validated for the simultaneous determination of seven analogues of aristolochic acid (aristolochic acids I, II, IIIa, IVa and VIIa), as well as aristololactams I and II in Aristolochiae Fructus. Chromatographic separation was achieved on a Zorbax SB-C(18) column with a gradient mobile phase comprising acetonitrile and 1 % acetic acid-30 mM triethylamine (20:1, v/v) buffer. Analytes were detected with a diode array detector at 250 and 260 nm. The contents of seven constituents in samples (11 batches of A. contorta fruits, 15 batches of A. debilis fruits and 33 commercial samples of Madouling) were determined. The content of aristolochic acid IVa was higher than that of aristolochic acid VIIa in A. contorta fruits, whereas the opposite was true in A. debilis fruits. This feature can be used to distinguish the two species from each other and identify the resource plant of Madouling. Through a morphological method and a newly found principle based on the ratio AA-IVa/AA-VIIa, we found that the 33 commercial samples collected from 12 provinces in China were all derived from the fruits of A. contorta.

Hepatoxicity of major constituents and extractions of Radix Polygoni Multiflori and Radix Polygoni Multiflori Praeparata

ETHNOPHARMACOLOGICAL RELEVANCE

Radix Polygoni Multiflori (RPM) and Radix Polygoni Multiflori Praeparata (RPMP) were traditionally widely used as Chinese herbal medicine. However, liver adverse reactions caused by RPM or RPMP were frequently reported all around the world recent years. The aim of this study was to study the cytotoxicities of RPM, RPMP and their major constituents on human liver cell L-02 simultaneously.

MATERIALS AND METHODS

Multi-assays, including MTT assay, neutral red uptake (NRU) assay, LDH leakage percentage and liver enzyme secretion (AST, ALT and ALP) were used. Cytotoxicities of major chemical constituents of RPM, 2, 3, 5, 4'-tetrahydroxy-stilbene-2-O-β-D-glucoside (TSG), physcion and emodin, were tested. The cytotoxicities of water, 50% ethanol and 95% ethanol extractions of RPM and RPMP were tested. HPLC-DAD analysis was carried to reveal the content change of TSG, physcion and emodin after the processing procedure.

RESULTS

The TD(50) of TSG, physcion and emodin in MTT assay were >10,000 μM, 2853.61 μM and 520.37 μM. In the NRU assay, the TD(50) of TSG, physcion and emodin were much smaller (1401.53 μM, 1140.00 μM, and 3.80 μM). Emodin induced much severe liver enzyme secretion than TSG and physcion. Cell proliferation and LDH leakage rate showed no difference between RPM and RPMP extractions, but ALP, AST and ALT secretions in RPMP extractions were significant lower than that of PMR groups. Water extractions of RPM and RPMP were less toxic than any other solvent in most of the assays. Positive correlation was found between the TSG/emodin ratio and MTT survival rate. The emodin/physcion ratio also showed positive correlation with the LDH leakage percentage.

CONCLUSIONS

In conclusion, Radix Polygonum multiflorum and Radix Polygonum multiflorum Praeparata were not liver injure inducing in our in vitro assays. However, the processing produce of RPM could reduce its effect on both cell proliferation and enzyme secretion of liver cell. Judging from cell proliferation, integrity of cell membrane and enzyme secretion, three major chemical constituents of RPM: TSG, physcion and emodin showed no, moderate and severe cytotoxicity against human liver cell line L-02 respectively. Chemical constituents-cytotoxicity relationship investigation revealed that TSG and physcion probably had attenuating effect to emodin. The attenuating mechanisms were still under investigation.

5–Methoxyaristololactam I, the First Natural 5–Substituted Aristololactam from Asarum ichangense

A new aristololactam, 5-methoxyaristololactam I (1), was isolated from an ethanol extract of the whole plant of Asarum ichangense C. Y. Cheng et C. S. Yang, together with twenty known compounds (2 – 21). The structure of 1 was elucidated by spectroscopic methods. Compounds 11, 13, 17, and 19 were isolated from Aristolochiaceae for the first time. Compounds 2, 14, and 15 are considered as common constituents of the genus Asarum.

Herbal medicines and chronic kidney disease

Alternative and indigenous systems of medicine are popular amongst the poorer sections of society in the developing world. Their use in the developed world has also increased in recent times. The source and composition of these medicines vary in different parts of the world, but herbs and other botanicals are central to these systems. Largely outside the ambit of regulatory control, herbal remedies are prepared by quasi-trained herbalists and not tested for safety. Toxicity can occur when a herb with unknown toxicity is consumed, incorrect identification leads to substitution of an innocuous herb with a toxic one, preparations are contaminated with toxic non-herbal compounds or when a herb potentiates the nephrotoxic effect of a conventional therapy. Renal injury has been reported in association with several herbs. The best-known herb-induced chronic kidney disease (CKD) is aristolochic acid nephropathy. The condition is characterized by progressive interstitial nephritis, with a proportion of patients developing urothelial malignancies. The toxic compound is aristolochic acid (AA); AA-DNA adducts have been identified in the renal and urothelial tissues. Recent evidence suggests that AA also contributes to the development of Balkan endemic nephropathy. The role of herbs has been postulated in the development of CKD in other parts of the developing world, especially amongst the rural population. Public awareness and regulation of use of herbal medicines are required to eradicate this entity from the community.

Activation of p53 promotes renal injury in acute aristolochic acid nephropathy

Ingestion of aristolochic acid (AA) can cause AA nephropathy (AAN), in which excessive death of tubular epithelial cells (TECs) characterize the acute phase. AA forms adducts with DNA, which may lead to TEC apoptosis via p53-mediated signaling. We tested this hypothesis both by studying p53-deficient mice and by blocking p53 in TECs with its inhibitor pifithrin-alpha. AA induced acute AAN in wild-type mice, resulting in massive apoptotic and necrotic TEC death and acute renal failure; p53 deficiency or pharmacologic inhibition attenuated this injury. In vitro, AA induced apoptotic and necrotic death of TEC in a time- and dosage-dependent manner, with apoptosis marked by a 10-fold increase in cleaved caspase-3 and terminal deoxynucleotidyl transferase-mediated digoxigenin-deoxyuridine nick-end labeling-positive/Annexin V-positive propidium iodide-negative TECs (all P < 0.001). AA induced dephosphorylation of STAT3 and the subsequent activation of p53 and TEC apoptosis. In contrast, overexpression of STAT3, p53 inhibition, or p53 knockdown with small interfering RNA all attenuated AA-induced TEC apoptosis. Taken together, these results suggest that AA induces TEC death via apoptosis by dephosphorylation of STAT3 and posttranslational activation of p53, supporting the hypothesis that p53 promotes renal injury in acute AAN.

Potential risks associated with the use of herbal anti-obesity products

The public wants an easy way to control obesity. Herbal anti-obesity products attract users because of their health claims, assumed safety, easy availability and extensive marketing. These products can be very heterogeneous in nature and have unpredictable levels of active ingredients, and unpredictable and potentially harmful effects. They may contain highly toxic herbs (e.g. Aristolochia species), potent herbs not recommended for use in weight control (e.g. Ephedra sinica) and herbal laxatives with potential hepatotoxic and nephrotoxic effects (e.g. anthraquinones). However, the presence of such herbs may not be disclosed on the product label. They may contain adulterants (e.g. drugs, drug analogues and thyroid extracts), including drugs that have been withdrawn from the market (e.g. fenfluramine). For all these reasons, herbal anti-obesity products can cause direct toxicity or adverse interactions with concurrent medications. Physicians and other healthcare professionals need to be aware of the problem. They should warn their patients about the heterogeneous nature of these agents and the potential risks associated with their use. They should report suspected adverse reactions to their national spontaneous reporting system.

Ischemic injury underlies the pathogenesis of aristolochic acid-induced acute kidney injury

Aristolochic acid nephropathy (AAN) is a progressive tubulointerstitial renal disease caused by aristolochic acid intake. To determine the contribution of renal ischemia to the pathogenesis of AAN, we characterized changes in the expression of angiogenic factors and vasoactive substances, and then we evaluated the expression of a marker of hypoxia in an acute AAN rat model. Rats were orally administrated either a decoction of Aristolochiae manshuriensis that contained 20 mg/kg of aristolochic acid-I or an equal volume of distilled water (control group) once daily for 4 days or 7 days. Renal histology and serum creatinine were assessed. Expression of endothelin-1 (ET-1) and hypoxia inducible factor-1 alpha (HIF-1alpha) mRNA within renal cortex were determined by semiquantitative reverse-transcription polymerase chain reaction. Levels of ET-1, nitric oxide (NO), vascular endothelial growth factor (VEGF), and HIF-1alpha in kidneys were determined by radioimmunoassay, Griess method, Western blot, and immunohistochemistry, respectively. Tubular injury scores and ET-1 mRNA expression were increased in the AA-treated rats at both days 4 and 8, whereas serum creatinine level and ET-1 protein expression was increased only at day 4. In contrast, NO production in AA-treated rats was decreased at day 8 compared with the control group. Similarly, VEGF protein expression was reduced in the AA-treated rats at both days 4 and 8. A dramatic increase in nuclear staining for HIF-1alpha was observed mainly in the tubular cells of tubulointerstitial damage area in the AA-treated rats at day 8. The observed increase in HIF-1alpha protein expression, decrease in VEGF protein expression, and imbalance of vasoactive substances after induction of acute kidney injury by AA suggests that ischemic injury contributes to the pathogenesis of AAN.

Selective Toxicity of Aristolochic Acids I and II

Ingestion of herbal remedies containing aristolochic acids (AAs) is associated with the development of a syndrome, designated aristolochic acid nephropathy (AAN), which is characterized by chronic renal failure, tubulointerstitial fibrosis, and urothelial cancer. To distinguish the component(s) of AA responsible for these varied toxic effects, we administered 2.5 mg/kg/day of AA-I or AA-II for 9 days, either i.p. or p.o., to male C3H/He mice. Tissues were then collected and subjected to biochemical and histopathologic examination. Genotoxicity was assessed by determining quantitatively the level of aristolactam-DNA adducts in various tissues using (32)P-postlabeling/polyacrylamide gel electrophoresis and an internal standard. In the primary target tissues, represented by the renal cortex, medulla, and bladder, we found similar levels of DNA adducts derived from AA-I and AA-II. However, in nontarget tissues, the liver, stomach, intestine, and lung, the levels of aristolactam-DNA adducts derived from AA-I were significantly higher than those derived from AA-II. Histopathologic analysis revealed tubular cell necrosis and interstitial fibrosis in the renal cortex of AA-I-treated mice but only minimal changes in the renal cortex of mice treated with AA-II. We conclude that AA-I and AA-II have similar genotoxic and carcinogenic potential, and, although both compounds are cytotoxic, AA-I is solely responsible for the nephrotoxicity associated with AAN.