Interference with DNA damage repair and translesion synthesis: a possible mechanism for natural products chemoprevention and indirect genotoxicity

Interference with DNA damage repair and translesion synthesis: a possible mechanism for natural products chemoprevention and indirect genotoxicity Amandine Nachtergael, Mélanie Poivre, Pierre Duez. Objectives of the study: Balance between DNA damage and repair appears vital to the cellular machinery, to health and longevity. Given the complexity of DNA lesion tolerance and repair mechanisms and the high number of proteins and cofactors involved, we hypothesize that natural products from food and medicinal plants may interfere in these processes, notably by activating or inhibiting repair. Methods: Original methods were developed to probe the modulation of major mechanisms by natural products: (i) fidelity of translesion synthesis (TLS), a DNA damage tolerance mechanism that relies on specialized DNA polymerases (pols) able to insert a nucleotide opposite a lesion on the template strand (capillary electrophoresis); (ii) kinetics of rejoining strand breaks arising from damage and excision repair (comet assay); (iii) capacity of double-strand breaks repair by non-homologous end-joining (NHEJ), a preponderant mechanism in eukaryotes (on-chips microelectrophoresis); (iv) capacity of base excision repair, the major repair pathway responsible for removal of small DNA lesions (oligonucleotide repair chips). Nuclear extracts were obtained from either plant extracts-pretreated FHs 74 Int cells (treatment at non-lethal concentrations, determined by a MTT cytotoxicity test) or control cells. Common flavonoids were tested for their capacity to interact in these mechanisms. Food plants were treated following their usual processing for human consumption and extracted with ethanol/water 50/50, then evaporated to dryness. Results: All methods were validated and could be applied to the study of modulation by natural products. None of tested flavonoids inhibits repair; quercetin increases non-specific endonuclease activity, apigenin and epicatechin increase the excision of damages; sakuranetin increases non-specific enzymatic activities and decreases or increases specific activities. Plant extracts variously modulate activities. Conclusion: Although some of these protocols represent a simplification of the complexity of the in vivo organization of DNA into chromatin, data obtained so far show that plant extracts are likely to interfere in TLS and repair capacity

Genotoxicity and carcinogenicity of herbal products

In 2012, the World Health Organization (WHO) recorded 14 million new cases of cancer and 8.2 million cancer-related deaths. Remarkably the WHO estimates that 30 % of cancer mortalities are due to lifestyle choices and environmental factors that can and should be avoided. In line with these recommendations, the present chapter discusses the genotoxicity and carcinogenicity of herbal products. Although often perceived as innocuous by the general public, many herbs harbor phytochemicals that are either directly reactive towards DNA or likely to disturb cellular homeostasis, cell cycle and/or genome maintenance mechanisms; this may translate into genotoxicity, carcinogenicity or co-carcinogenicity. Genotoxicity refers to the deleterious effect of a chemical compound or a physical event on the genetic material; such genotoxic events are considered hallmarks of cancer risk. Nevertheless many damages to the genetic material can be efficiently bypassed and/or repaired by the numerous genome maintenance mechanisms of the cell and may not lead to cancer. The long-term safety evaluation is probably better investigated through carcinogenicity which denotes the capacity of a chemical substance or a mixture of chemical substances to induce cancer or increase its incidence. The major mechanisms of carcinogenicity are discussed along with biomarkers and approved regulatory guidelines. The recent development of innovative carcinogenicity testing strategies, especially based on functional genomics, are debated and evaluated for a possible application to the precocious evaluation of herbal products long-term safety. Finally, this chapter draws up from literature the current state of knowledge on proven or suspected carcinogenic herbal products

Assessment of the Cytotoxicity, Mutagenicity, and Genotoxicity of Two Traditional Chinese Herbs: Aristolochia baetica and Magnolia officinalis

peer reviewedHerbal remedies used in traditional medicine often contain several compounds combined in order to potentiate their own intrinsic properties. However, herbs can sometimes cause serious health troubles. In Belgium, patients who developed severe aristolochic acid nephropathy ingested slimming pills containing root extracts of an Aristolochia species, as well as the bark of Magnolia officinalis. The goal of the study was to evaluate, on a human renal cell line, Aristolochia and Magnolia extracts for their cytotoxicity by a resazurin cell viability assay, and their genotoxicity by immunodetection and quantification of the phosphorylated histone γ-H2AX. The present study also sought to assess the mutagenicity of these extracts, employing an OECD recognized test, the Ames test, using four Salmonella typhimurium strains with and without a microsomial fraction. Based on our results, it has been demonstrated that the Aristolochia–Magnolia combination (aqueous extracts) was more genotoxic to human kidney cells, and that this combination (aqueous and methanolic extracts) was more cytotoxic to human kidney cells after 24 and 48 h. Interestingly, it has also been shown that the Aristolochia–Magnolia combination (aqueous extracts) was mutagenic with a TA98 Salmonella typhimurium strain in the presence of a microsomial liver S9 fraction. This mutagenic effect appears to be dose-dependent

In vitro genotoxicity tests point to an unexpected and harmful effect of a Magnolia and Aristolochia association

peer reviewedEthnopharmacological relevance: In the 1990's, a Belgian cohort of more than 100 patients reported cases of Aristolochic Acid Nephropathy (AAN). This progressive renal and interstitial fibrosis, frequently associated with urothelial malignancies, was consecutive to the Chinese-herbs based slimming capsules intake where a plant Stephania tetrandra S. Moore was replaced by a highly genotoxic Aristolochia species. 70% of the Belgian patients evolved into end-stage renal disease, requiring dialysis or renal transplantation. Furthermore the prevalence of upper urinary tract carcinoma was found alarmingly high in these patients. The Aristolochia adulteration was blamed for the intoxication cases and, to the best of our knowledge, the prescription itself has not been further investigated. Aim of the study: This work proposes to evaluate the in vitro cytotoxicity and genotoxicity of Aristolochia and Magnolia traditional aqueous decoctions and their association. Materials and methods: The cytotoxicity of extracts has been assessed by a MTT cell proliferation assay and the genotoxicity by measuring the presence of γ-H2AX, a phosphorylated histone associated with DNA damages. Results: Treating cells for 24h with a mixture 1:1 of Magnolia officinalis and Aristolochia baetica decoctions led to an increase in the production of γ-H2AX. Conclusions: This genotoxic potentiation warrants further studies but may lead to an explanatory factor for the 'Chinese herb nephropathy' cases

Genotoxicity and carcinogenicity of herbal products

In 2012, the World Health Organization (WHO) recorded 14 million new cases of cancer and 8.2 million cancer-related deaths. Remarkably, the WHO estimates that 30 % of cancer mortalities are due to lifestyle choices and environmental factors that can and should be avoided. In line with these recommendations, this chapter discusses the genotoxicity and carcinogenicity of herbal products. Although often perceived as innocuous by the general public, many herbs harbor phytochemicals that are either directly reactive towards DNA or likely to disturb cellular homeostasis, cell cycle, and/or genome maintenance mechanisms; this may translate into genotoxicity, carcinogenicity, or co-carcinogenicity. Genotoxicity refers to the deleterious effect of a chemical compound or a physical event on the genetic material; such genotoxic events are considered hallmarks of cancer risk. Nevertheless, much of the damage to the genetic material can be efficiently bypassed and/or repaired by the numerous genome maintenance mechanisms of the cell and may not lead to cancer. The long-term safety evaluation is probably better investigated through carcinogenicity, which denotes the capacity of a chemical substance or a mixture of chemical substances to induce cancer or increase its incidence. The major mechanisms of carcinogenicity are discussed along with biomarkers and approved regulatory guidelines. The recent development of innovative carcinogenicity testing strategies, especially based on functional genomics, are debated and evaluated for possible application to the precocious evaluation of herbal products’ long-term safety. Finally, this chapter provides some examples of proven or suspected carcinogenic herbal products reported in the current literature.SCOPUS: ch.binfo:eu-repo/semantics/publishe

Assessment of the Cytotoxicity, Mutagenicity, and Genotoxicity of Two Traditional Chinese Herbs: Aristolochia baetica and Magnolia officinalis

Herbal remedies used in traditional medicine often contain several compounds combined in order to potentiate their own intrinsic properties. However, herbs can sometimes cause serious health troubles. In Belgium, patients who developed severe aristolochic acid nephropathy ingested slimming pills containing root extracts of an Aristolochia species, as well as the bark of Magnolia officinalis. The goal of the study was to evaluate, on a human renal cell line, Aristolochia and Magnolia extracts for their cytotoxicity by a resazurin cell viability assay, and their genotoxicity by immunodetection and quantification of the phosphorylated histone γ-H2AX. The present study also sought to assess the mutagenicity of these extracts, employing an OECD recognized test, the Ames test, using four Salmonella typhimurium strains with and without a microsomial fraction. Based on our results, it has been demonstrated that the Aristolochia–Magnolia combination (aqueous extracts) was more genotoxic to human kidney cells, and that this combination (aqueous and methanolic extracts) was more cytotoxic to human kidney cells after 24 and 48 h. Interestingly, it has also been shown that the Aristolochia–Magnolia combination (aqueous extracts) was mutagenic with a TA98 Salmonella typhimurium strain in the presence of a microsomial liver S9 fraction. This mutagenic effect appears to be dose-dependent.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Assessment of the Cytotoxicity, Mutagenicity, and Genotoxicity of Two Traditional Chinese Herbs: <i>Aristolochia baetica</i> and <i>Magnolia officinalis</i>

Herbal remedies used in traditional medicine often contain several compounds combined in order to potentiate their own intrinsic properties. However, herbs can sometimes cause serious health troubles. In Belgium, patients who developed severe aristolochic acid nephropathy ingested slimming pills containing root extracts of an Aristolochia species, as well as the bark of Magnolia officinalis. The goal of the study was to evaluate, on a human renal cell line, Aristolochia and Magnolia extracts for their cytotoxicity by a resazurin cell viability assay, and their genotoxicity by immunodetection and quantification of the phosphorylated histone γ-H2AX. The present study also sought to assess the mutagenicity of these extracts, employing an OECD recognized test, the Ames test, using four Salmonella typhimurium strains with and without a microsomial fraction. Based on our results, it has been demonstrated that the Aristolochia–Magnolia combination (aqueous extracts) was more genotoxic to human kidney cells, and that this combination (aqueous and methanolic extracts) was more cytotoxic to human kidney cells after 24 and 48 h. Interestingly, it has also been shown that the Aristolochia–Magnolia combination (aqueous extracts) was mutagenic with a TA98 Salmonella typhimurium strain in the presence of a microsomial liver S9 fraction. This mutagenic effect appears to be dose-dependent

厚朴及其成分的生物活性和毒性

Traditional Chinese herbal drugs have been used for thousands of years in Chinese pharmacopoeia. The bark of Magnolia officinalis Rehder & E. Wilson, known under the pinyin name “Houpo”, has been traditionally used in Chinese and Japanese medicines for the treatment of anxiety, asthma, depression, gastrointestinal disorders, headache, and more. Moreover, Magnolia bark extract is a major constituent of currently marketed dietary supplements and cosmetic products. Much pharmacological activity has been reported for this herb and its major compounds, notably antioxidant, anti-inflammatory, antibiotic and antispasmodic effects. However, the mechanisms underlying this have not been elucidated and only a very few clinical trials have been published. In vitro and in vivo toxicity studies have also been published and indicate some intriguing features. The present review aims to summarize the literature on M. officinalis bark composition, utilisation, pharmacology, and safety