Differences in p38-STAT3-S100A11 signaling after the administration of aristolochic acid I and IVa may account for the disparity in their nephrotoxicity.

BACKGROUND: The safety of herbs containing aristolochic acids (AAs) has become a widespread concern. Previous reports indicate that AAs are highly nephrotoxic and carcinogenic, although there are more than 170 analogues of aristolochic acid. Not all AAs have the same degree of nephrotoxicity or carcinogenicity. Previous studies have found that aristolochic acid IVa (AA-IVa), the principal component of AAs within members of the Aristolochiaceae family, especially Asarum, a commonly used herb in China, has essentially no significant nephrotoxicity. However, several studies, including ours, have shown that aristolochic acid I (AA-I) is clearly nephrotoxic. PURPOSE: The focus of the study was to elucidate the molecular mechanism responsible for the difference in nephrotoxicity between the AA-I and AA-IVa. STUDY DESIGN/METHOD: Mice were administered with AA-I or AA-IVa for 22 weeks through the oral route, followed by a 50-week recovery time. The kidney tissues of mice were extracted at the end of 22 weeks. Pathological examination and proteomic detection (tandem mass tagging (TMT) and phosphorylated proteomics) were performed on the kidney tissue to investigate the key signaling pathways and targets of AAs-induced renal interstitial fibrosis (RIF). The key signaling pathways and targets were verified by Western blot (WB), siRNA transfection, and luciferase assays. RESULTS: AA-I caused severe nephrotoxicity, high mortality, and extensive RIF. However, the same AA-IVa dosage exhibited almost no nephrotoxicity and does not trigger RIF. The activation of the p38-STAT3-S100A11 signaling pathway and upregulated expression of α smooth muscle actin (α-SMA) and Bcl2-associated agonist of cell death (Bad) proteins could be the molecular mechanism underlying AA-I-induced nephrotoxicity. On the other hand, AA-IVa did not regulate the activation of the p38-STAT3-S100A11 signaling pathway and had relatively little effect on the expression of α-SMA and Bad. Consequently, the difference in the regulation of p38-STAT3-S100A11 pathway, α-SMA, and Bad proteins between AA-I and AA-IVa may be responsible for the divergence in their level of nephrotoxicity. CONCLUSION: This is the first study to reveal the molecular mechanism underlying the difference in nephrotoxicity between AA-I and AA-IVa. Whether STAT3 is activated or not may be the key factor leading to the difference in nephrotoxicity between AA-I and AA-IVa.

Effects of tumor necrosis factor-α inhibition on kidney fibrosis and inflammation in a mouse model of aristolochic acid nephropathy.

Tumor necrosis factor (TNF)-α is a potent mediator of inflammation and is involved in the pathophysiology of chronic kidney disease (CKD). However, the effects of TNF-α inhibition on the progression of kidney fibrosis have not been fully elucidated. We examined the effects of TNF-α inhibition by etanercept (ETN) on kidney inflammation and fibrosis in mice with aristolochic acid (AA) nephropathy as a model of kidney fibrosis. C57BL/6 J mice were administered AA for 4 weeks, followed by a 4-week remodeling period. The mice exhibited kidney fibrosis, functional decline, and albuminuria concomitant with increases in renal mRNA expression of inflammation- and fibrosis-related genes. The 8-week ETN treatment partially but significantly attenuated kidney fibrosis and ameliorated albuminuria without affecting kidney function. These findings were accompanied by significant suppression of interleukin (IL)-1ß, IL-6, and collagen types I and III mRNA expression. Moreover, ETN tended to reduce the AA-induced increase in interstitial TUNEL-positive cells with a significant reduction in Bax mRNA expression. Renal phosphorylated p38 MAPK was significantly upregulated by AA but was normalized by ETN. These findings indicate a substantial role for the TNF-α pathway in the pathogenesis of kidney fibrosis and suggest that TNF-α inhibition could become an adjunct therapeutic strategy for CKD with fibrosis.

Aristolochic Acid Induces Renal Fibrosis and Senescence in Mice.

The kidney is one of the most susceptible organs to age-related impairments. Generally, renal aging is accompanied by renal fibrosis, which is the final common pathway of chronic kidney diseases. Aristolochic acid (AA), a nephrotoxic agent, causes AA nephropathy (AAN), which is characterized by progressive renal fibrosis and functional decline. Although renal fibrosis is associated with renal aging, whether AA induces renal aging remains unclear. The aim of the present study is to investigate the potential use of AAN as a model of renal aging. Here, we examined senescence-related factors in AAN models by chronically administering AA to C57BL/6 mice. Compared with controls, the AA group demonstrated aging kidney phenotypes, such as renal atrophy, renal functional decline, and tubulointerstitial fibrosis. Additionally, AA promoted cellular senescence specifically in the kidneys, and increased renal p16 mRNA expression and senescence-associated ß-galactosidase activity. Furthermore, AA-treated mice exhibited proximal tubular mitochondrial abnormalities, as well as reactive oxygen species accumulation. Klotho, an antiaging gene, was also significantly decreased in the kidneys of AA-treated mice. Collectively, the results of the present study indicate that AA alters senescence-related factors, and that renal fibrosis is closely related to renal aging.

Aristololactam alkaloids from the roots of Dasymaschalon rostratum.

A novel aristololactam alkaloid, dasymalactam A (1), together with nine known analogues (2-10), were isolated from the roots of Dasymaschalon rostratum. Their structures were elucidated by IR, NMR and MS spectrums and comparisons with data reported in the literature. All compounds demonstrated weak cytotoxicity against Hela, MCF-7, A-549, MGC-803, and COLO-205 human cancer cell lines.

Two New Aristolochic Acid Analogues from the Roots of Aristolochia contorta with Significant Cytotoxic Activity.

Twelve compounds, including two new aristolochic acid analogues with a formyloxy moiety (9-10) and 10 known aristolochic acid derivates (1-8 and 11-12), were obtained from the roots of Aristolochiacontorta. Their structures were elucidated using extensive spectroscopic methods. Their cytotoxic activity in human proximal tubular cells HK-2 was evaluated by the MTT method, which has been widely used to assess cell viability. Among these molecules, compounds 3 and 9 were found to be more cytotoxic. Furthermore, molecular modeling was used to evaluate, for the first time, the interactions of compounds 3 and 9 with the target protein organic anionic transporter 1 (OAT1) that plays a key role in mediating aristolochic acid nephropathy. Structure-activity relationships are briefly discussed.

Aristolochia Herbs and Iatrogenic Disease: The Case of Portland's Powders.

Aristolochia herbals have a 2500-year history of medicinal use. We focused this article on Portland's Powders, an 18th-century British gout medicine containing Aristolochia herbs. The powders constitute an 18th-century iteration of an herbal remedy, which was used, with variations, since at least the fifth century BCE. The use of Portland's Powders in Great Britain may appear to be an unusual choice for investigating a public health problem currently widespread in Asia. Yet it exemplifies long-term medicinal use of Aristolochia herbs, reflecting our argument that aristolochic acid nephropathy (AAN) is a historically persistent iatrogenic disease. Moreover, we provide compelling evidence that individuals taking Portland's Powders for gout would have ingested toxic quantities of aristolochic acid, which causes AAN and cancer. Several factors, including long history of use, latency of toxic effects, and lack of effective regulation, perpetuate usage of Aristolochia herbals to the present day.

Aristolochic acid mutational signature defines the low-risk subtype in upper tract urothelial carcinoma.

Rationale: Dietary exposure to aristolochic acids and similar compounds (collectively, AA) is a significant risk factor for nephropathy and subsequent upper tract urothelial carcinoma (UTUC). East Asian populations, who have a high prevalence of UTUC, have an unusual genome-wide AA-induced mutational pattern (COSMIC signature 22). Integrating mutational signature analysis with clinicopathological information may demonstrate great potential for risk ranking this UTUC subtype. Methods: We performed whole-genome sequencing (WGS) on 90 UTUC Chinese patients to extract mutational signatures. Genome sequencing data for urinary cell-free DNA from 26 UTUC patients were utilized to noninvasively identify the mutational signatures. Genome sequencing for primary tumors on 8 out of 26 patients was also performed. Metastasis-free survival (MFS) and cancer-specific survival (CSS) were measured using Kaplan-Meier methods. Results: Data analysis showed that a substantial proportion of patients harbored the AA mutational signature and were associated with AA-containing herbal drug intake, female gender, poor renal function, and multifocality. Field cancerization was found to partially contribute to multifocality. Nevertheless, AA Sig subtype UTUC patients exhibited favorable outcomes of CSS and MFS compared to the No-AA Sig subtype. Additionally, AA Sig subtype patients showed a higher tumor mutation burden, higher numbers of predicted neoantigens, and infiltrating lymphocytes, suggesting the potential for immunotherapy. We also confirmed the AA signature in AA-treated human renal tubular HK-2 cells. Notably, the AA subtype could be ascertained using a clinically applicable sequencing strategy (low coverage) in both primary tumors and urinary cell-free DNA as a basis for therapy selection. Conclusion: The AA mutational signature as a screening tool defines low-risk UTUC with therapeutic relevance. The AA mutational signature, as a molecular prognostic marker using either ureteroscopy and/or urinary cell-free DNA, is especially useful for diagnostic uncertainty when kidney-sparing treatment and/or immune checkpoint inhibitor therapy were considered.

Characterization of cytotoxic effects of aristolochic acids on the vascular endothelium.

Aristolochic acid nephropathy (AAN) is characterized by interstitial fibrosis, proximal tubular atrophy, and hypoxia. A correlation between a reduced peritubular capillary density and the severity of fibrosis has been demonstrated. As calcium, redox and energetic homeostasis are crucial in maintaining endothelial cell function and survival, we aimed to investigate AA-induced disturbances involved in endothelial cell injury. Our results showed a cytotoxic effect of AA on EAhy926 endothelial cells. Exposure of aortic rings to AA impaired vascular relaxation to Acetylcholine (ACh). Increased levels of intracellular reactive oxygen species (ROS) were observed in cells exposed to AA. Pre-treatment with antioxidant N-acetyl cysteine inhibited AA-induced cell death. Superoxide dismutase resulted in restoring ACh-induced relaxation. An increase in intracellular calcium level ([Ca2+]i) was observed on endothelial cells. Calcium chelators BAPTA-AM or APB, a specific inhibitor of IP3R, improved cell viability. Moreover, AA exposure led to reduced AMP-activated protein kinase (AMPK) expression. AICAR, an activator of AMPK, improved the viability of AA-intoxicated cells and inhibited the rise of cytosolic [Ca2+]i levels. This study provides evidence that AA exposure increases ROS generation, disrupts calcium homeostasis and decreases AMPK activity. It also suggests that significant damage observed in endothelial cells may enhance microcirculation defects, worsening hypoxia and tubulointerstitial lesions.

The Impact of p53 on Aristolochic Acid I-Induced Gene Expression In Vivo.

Exposure to aristolochic acid (AA) is linked to kidney disease and urothelial cancer in humans. The major carcinogenic component of the AA plant extract is aristolochic acid I (AAI). The tumour suppressor p53 is frequently mutated in AA-induced tumours. We previously showed that p53 protects from AAI-induced renal proximal tubular injury, but the underlying mechanism(s) involved remain to be further explored. In the present study, we investigated the impact of p53 on AAI-induced gene expression by treating Trp53(+/+), Trp53(+/-), and Trp53(-/-) mice with 3.5 mg/kg body weight (bw) AAI daily for six days. The Clariom™ S Assay microarray was used to elucidate gene expression profiles in mouse kidneys after AAI treatment. Analyses in Qlucore Omics Explorer showed that gene expression in AAI-exposed kidneys is treatment-dependent. However, gene expression profiles did not segregate in a clear-cut manner according to Trp53 genotype, hence further investigations were performed by pathway analysis with MetaCore™. Several pathways were significantly altered to varying degrees for AAI-exposed kidneys. Apoptotic pathways were modulated in Trp53(+/+) kidneys; whereas oncogenic and pro-survival pathways were significantly altered for Trp53(+/-) and Trp53(-/-) kidneys, respectively. Alterations of biological processes by AAI in mouse kidneys could explain the mechanisms by which p53 protects from or p53 loss drives AAI-induced renal injury in vivo.

Aristolochic Acid Affects Upper Tract Urothelial Cancer Behavior through the MAPK Pathway.

The prevalence of upper tract urothelial carcinoma (UTUC) in Taiwan is relatively higher than thatin Western countries. Aristolochic acid (AA), which is widely used in traditional Chinese herbology, is now recognized to be one of the carcinogens for UTUC. Numerous UTUC patients have chronic kidney diseases or end-stage renal diseases; however, little literature hasreported on theoncogenic pathway of AA-related UTUC. The aim of our study was to identify the potential target treatment for AA-related UTUC. Here, we established an AA pre-exposure followed bya 3-methylcholanthrene (MCA) stimulus tumorigenic cell model. We not only demonstrated that AA pre-exposure MCA stimulus tumorigenic cells have more behaviors of cell migration and invasion by enhancing the metalloproteinases (MMP) activity, which is compatible with clinical findings of AA-related UTUC, but we also validated that AA pre-exposure MCA stimulus tumorigeniccells could be activated through the mitogen-activated protein kinases (MAPK) pathway. We further dissected the route of the MAPK pathway and found that the p38 and extracellular signal regulated kinases (ERK) sub-pathways might play essential roles in AA pre-exposure urothelial cancer cell lines. This consequence was also corroborated with a tissue study in AA-exposed patients.

Quantitation of N6-Formyl-lysine Adduct Following Aristolochic Acid Exposure in Cells and Rat Tissues by Liquid Chromatography-Tandem Mass Spectrometry Coupled with Stable Isotope-Dilution Method.

N6-Formyl-lysine (FLys) is an abundant and lasting protein adduct formed when formaldehyde generated by nitrosative/oxidative stress and inflammation reacts with lysine residues. It is believed that the post-translational N6-formylation of lysine is associated with a variety of pathological processes and human diseases. Thus, FLys may serve well as a dosimetric biomarker for exposure to formaldehyde and other oxidative stress-inducing toxicants. However, since current methods for FLys determination are tedious and time-consuming, we developed and validated an aqueous normal phase liquid chromatography-tandem mass spectrometry (LC-MS/MS) coupled with isotope-dilution method for the rigorous quantification of FLys with enhanced sensitivity and selectivity. After validating the accuracy and precision of the method with a synthetic peptide containing FLys, the method was applied to quantitate the concentration-dependent formation of FLys in cells exposed to formaldehyde and Fe2+-EDTA, an OH radical-mediated oxidant. The study reveals formaldehyde and Fe2+-EDTA produced FLys at a frequency of 20.2 and 4.1 per 104 lysine per mM, respectively, after correcting for losses during protein digestion steps. The study was further extended to quantitate the concentration-dependent formation of FLys in aristolochic acid I (AA-I) exposed Escherichia coli cells and rat tissues. This study demonstrates for the first time that AA-I exposure induces time- and dose-dependent formation of FLys in cellular proteins. Furthermore, results show AA-I exposure leads to organotropic N6-formylation of lysine, with elevated levels of FLys detectable in the kidney, which is the one of the tumor targeting organs of AAs. Previous studies have also revealed AA exposure induced renal interstitial fibrosis in both laboratory rodents and humans, by a yet to be determined molecular mechanism. These data shed light on the potential caustative role of N6-formylation in the pathophysiology of AA nephrotoxicity and carcinogenicity.

Inhibition of 4E-BP1 phosphorylation promotes tubular cell escaping from G2/M arrest and ameliorates kidney fibrosis.

Upon occurrence of kidney injury, tubular cells arrested in G2/M stage may promote interstitial fibroblast activation and kidney fibrosis through producing large amounts of pro-fibrotic cytokines. MTORC1 signaling is essential for controlling cell growth, however, the role and mechanisms for mTORC1 in regulating tubular cell cycle progression during kidney fibrosis are not clear. Here we reported that p-S6 abundance was increased at 15 min, reached peak at 1 h and declined from 3 h to 24 h, while the abundance of p-4E-BP1 and p-Histone H3 was increased from 15 min to 24 h in tubular epithelial cells at the similar pattern after serum stimulation. The phosphorylation of 4E-BP1 was prohibited in NRK-52E cells by the transfection of 4E-BP1 plasmid with four phospho-sites mutation (4E-BP1A4). 4E-BP1A4 transfection led to less G2/M cell arrest as well as the production of pro-fibrotic cytokine and extracellular matrix in NRK-52E cells. In addition, aristolochic acid (AA)-induced tubular cell G2/M arrest induced by treatment was also largely attenuated in NRK-52E cells transfected with 4E-BP1A4. In mouse kidneys with UUO nephropathy, p-4E-BP1 abundance was markedly elevated in the mitotic tubular cells. Therefore, these data indicates that suppressing 4E-BP1 phosphorylation may inhibit tubular cell G2/M-arrest and kidney fibrosis.

Worldwide research trends on aristolochic acids (1957-2017): Suggestions for researchers.

Aristolochic acids and their derivatives are components of many traditional medicines that have been used for thousands of years, particularly in Asian countries. To study the trends of research into aristolochic acids and provide suggestions for future study, we performed the following work. In this paper, we performed a bibliometric analysis using CiteSpace and HistCite software. We reviewed the three phases of the development of aristolochic acids by using bibliometrics. In addition, we performed a longitudinal review of published review articles over 60 years: 1,217 articles and 189 review articles on the history of aristolochic acid research published between 1957 and 2017 were analyzed. The performances of relevant countries, institutions, and authors are presented; the evolutionary trends of different categories are revealed; the history of research into aristolochic acids is divided into three phases, each of which has unique characteristics; and a roadmap of the historical overview of aristolochic acid research is finally established. Finally, five pertinent suggestions for future research into aristolochic acid are offered: (1) The study of the antitumor efficacy of aristolochic acids is of value; (2) The immune activity of aristolochic acids should be explored further; (3) Researchers should perform a thorough overview of the discovery of naturally occurring aristolochic acids; (4) More efforts should be directed toward exploring the correlation between aristolochic acid mutational signature and various cancers; (5) Further efforts should be devoted to the research and review work related to analytical chemistry. Our study is expected to benefit researchers in shaping future research directions.

Exposure to aristolochic acid I compromises the maturational competency of porcine oocytes via oxidative stress-induced DNA damage.

Aristolochic acid (AA) is a class of carcinogenic and nephrotoxic nitrophenanthrene carboxylic acids naturally found in Aristolochia plants. These plants have been widely used as herbal medicines and also enter the human food chain as the persistent soil pollutants. It has been known that AA exposure is implicated in multiple cancer types, kidney failure and ovarian dysfunction. However, whether AA exposure would influence the oocyte quality has not yet determined. Here, we document that AAI has the negative effects on the competency of oocyte maturation and fertilization. We show that AAI exposure leads to the oocyte meiotic failure via impairing the meiotic apparatus, displaying a prominently defective spindle assembly, actin dynamics and mitochondrial integrity. AAI exposure also causes the abnormal distribution of cortical granules and ovastacin, which is consistent with the observation that fewer sperm bound to the zona pellucida surrounding the unfertilized AAI-exposed eggs, contributing to the fertilization failure. In addition, AAI exposure induces the increased levels of ROS, DNA damage and early apoptosis in porcine oocytes. Collectively, we demonstrate that AAI exposure perturbs the oocyte meiotic progression and fertilization capacity via disruption of both nuclear maturation and cytoplasmic maturation of oocyte, which might be caused by the excessive oxidative stress-induced DNA damage and apoptosis.

Quantitation of DNA Adducts in Target and Nontarget Organs of Aristolochic Acid I-Exposed Rats: Correlating DNA Adduct Levels with Organotropic Activities.

Chronic exposure to aristolochic acids (AAs) from Aristolochia plants is one of the major causes of nephropathy and cancer of the kidney and forestomach. However, the organotropic activities of AAs remain poorly understood. In this study, using LC-MS/MS coupled with a stable isotope-dilution method, we rigorously quantitated for the first time the organ-specific dosage- and time-dependent formation of DNA-AA adducts in the tumor target and nontarget organs of AA-I-treated rats. The results support the proposal that the DNA adduct level is a major contributor to the observed organotropic activities of AAs.

Aristolochic acid I interferes with the expression of BLCAP tumor suppressor gene in human cells.

Aristolochic acid I (AAI) is a phytocompound that is linked to the progressive renal disease and development of human urothelial carcinoma. The bladder cancer-associated protein (BLCAP) gene exhibits a tumor suppressor function in various tumors, including bladder carcinoma. This study evaluated the effect of AAI on BLCAP expression and its associated mechanism in human cells. Administering AAI to human embryonic kidney cells (HEK293), human proximal tubule epithelial cells (HK-2) and urinary bladder cancer cells (HT-1376) significantly reduced the expression of BLCAP mRNA and protein. AAI also effectively suppressed the luciferase activities driven by BLCAP promoters of various lengths in HEK293 cells. AAI significantly reduced both activator protein 1 (AP-1) and nuclear factor-κB (NF-κB) activities in reporter assays, but further point mutations revealed that Ap-1 and NF-κB binding sites on the BLCAP promoter were not AAI-responsive elements. Application of the DNA methyltransferase inhibitor, 5-aza-2'-deoxycytidine (5-aza-dC), reversed the decline of BLCAP expression that had been induced by AAI. However, AAI exposure did not alter hypermethylation of the BLCAP promoter, determined by methyl-specific polymerase chain reaction (PCR) and bisulfate sequencing. Knocking down BLCAP in HEK293 cell line enhanced the potential for cellular migration, invasion, and proliferation, along with the induction of a capacity for anchorage-independent growth. In conclusion, AAI down-regulated the expression of BLCAP gene and the deficiency in BLCAP expression contributed to the malignant transformation of human cells, implying that BLCAP may have a role in mediating AAI-associated carcinogenesis.

Natural Aristolochia Alkaloid Aristololactam-ß-D-glucoside: Interaction with Biomacromolecules and Correlation to the Biological Perspectives.

BACKGROUND: Natural aristolochia alkaloids have attracted the attention of both chemists and biologists from the stand point of their structural and pharmacological aspects. Many of the compounds isolated in this group are potent tumor inhibitors. These are divided into nitrophenanthrinic acid, phenanthrene lactams and isoquinoline alkaloids. A number of structure-activity studies have been performed on aristolochia alkaloids. Of particular interest is the molecule with the ß-D-glucoside moiety that has similarity to the clinical anticancer agent daunomycin. OBJECTIVE: The anticancer activity of aristololactam-ß-D-glucoside has been thought to be due to its DNA and RNA binding activities among other actions. In this article we focus on the physicochemical property of this alkaloid and the structural and functional aspects of its binding to different nucleic acid and protein structures. METHODS: This review highlights a large number of biophysical studies employing various analytical techniques like absorbance, fluorescence, circular dichroism, thermal melting, viscosity, IR study, isothermal calorimetry and differential scanning calorimetry. RESULT: The detailed binding mechanism in terms of the structural and thermodynamic aspects at the molecular level has been discussed. CONCLUSION: This review enables to assess the high potential of developing aristololactam-ß-Dglucoside and related alkaloids as therapeutic agents.

Marcanine G, a new cytotoxic 1-azaanthraquinone from the stem bark of Goniothalamus marcanii Craib.

The ethanolic extract from the stem bark of Goniothalamus marcanii Craib was shown in preliminary brine shrimp lethality data having good cytotoxic activity. Further bioassay guided isolation was done by means of solvent partition, chromatography and precipitation to provide four isolated compounds: a novel compound 1 with the core structure of 1-azaanthraquinone moiety referred as marcanine G; as well as compounds 2-4 with known aristolactam structures namely, piperolactam C, cepharanone B and taliscanine. These compounds were characterised by spectroscopic techniques. The assessment of cytotoxicity was established on an SRB assay using doxorubicin as a positive control. Marcanine G (1) was considered the most active compound indicating the IC50 values of 14.87 and 15.18 µM against human lung cancer cells (A549) and human breast cancer cells (MCF7), respectively. However, 2 showed mild activity with the IC50 values of 83.72 and 82.32 µM against A549 and MCF7 cells, respectively.

Aristolochic acid and its derivatives as inhibitors of snake venom L-amino acid oxidase.

Snake venom L-amino acid oxidase (LAAO) exerts toxicity by inducing hemorrhage, pneumorrhagia, pulmonary edema, cardiac edema, liver cell necrosis etc. Being well conserved, inhibitors of the enzyme may be synthesized using the template of the substrate, substrate binding site and features of the catalytic site of the enzyme. Previous findings showed that aristolochic acid (AA), a major constituent of Aristolochia indica, inhibits Russell's viper venom LAAO enzyme activity since, AA interacts with DNA and causes genotoxicity, derivatives of this compound were synthesized by replacing the nitro group to reduce toxicity while retaining the inhibitory potency. The interactions of AA and its derivatives with LAAO were followed by inhibition kinetics and surface plasmon resonance. Similar interactions with DNA were followed by absorption spectroscopy and atomic force microscopy. LAAO-induced cytotoxicity was evaluated by generation of reactive oxygen species (ROS), cell viability assays, confocal and epifluorescence microscopy. The hydroxyl (AA-OH) and chloro (AA-Cl) derivatives acted as inhibitors of LAAO but did not interact with DNA. The derivatives significantly reduced LAAO-induced ROS generation and cytotoxicity in human embryonic kidney (HEK 293) and hepatoma (HepG2) cell lines. Confocal images indicated that AA, AA-OH and AA-Cl interfered with the binding of LAAO to the cell membrane. AA-OH and AA-Cl significantly inhibited LAAO activity and reduced LAAO-induced cytotoxicity.

Targeting human telomeric G-quadruplex DNA with antitumour natural alkaloid aristololactam-ß-D-glucoside and its comparison with daunomycin.

Study on anticancer agents that act via stabilization of telomeric G-quadruplex DNA has emerged as novel and exciting field for anticancer drug discovery. The interaction of carbohydrate containing anticancer alkaloid aristololactam-ß-D-glucoside (ADG) with human telomeric G-quadruplex DNA sequence was characterized by different biophysical techniques. The binding parameters were compared with daunomycin (DAN), a well-known chemotherapeutic drug. The Scatchard binding isotherms revealed noncooperative binding for both with the binding affinity values of (1.01 ± 0.05) × 106 and (1.78 ± 0.18) × 106 M-1 for ADG and DAN, respectively. Circular dichroism, ferrocyanide quenching study, anisotropy study, thiazole orange displacement, optical melting, differential scanning calorimetry study, and molecular docking study suggest significant stacking and stabilizing efficiency of ADG with comparison to DAN. The energetics of the interaction for ADG and DAN revealed that both reactions were predominantly entropy driven. Negative heat capacity values were obtained from the temperature dependence of the enthalpy change. The standard molar Gibbs energy change exhibited only marginal alterations with temperature suggesting the occurrence of enthalpy-entropy compensation. These findings indicate that ADG can act as a stabilizer of telomeric G-quadruplex DNA and thereby can be considered as a potential telomerase inhibitor.