Unlocking Biological Activity and Metabolomics Insights: Primary Screening of Cyanobacterial Biomass from a Tropical Reservoir.

Cyanobacterial harmful algal blooms can pose risks to ecosystems and human health worldwide due to their capacity to produce natural toxins. The potential dangers associated with numerous metabolites produced by cyanobacteria remain unknown. Only select classes of cyanopeptides have been extensively studied with the aim of yielding substantial evidence regarding their toxicity, resulting in their inclusion in risk management and water quality regulations. Information about exposure concentrations, co-occurrence, and toxic impacts of several cyanopeptides remains largely unexplored. We used liquid chromatography-mass spectrometry (LC-MS)-based metabolomic methods associated with chemometric tools (NP Analyst and Data Fusion-based Discovery), as well as an acute toxicity essay, in an innovative approach to evaluate the association of spectral signatures and biological activity from natural cyanobacterial biomass collected in a eutrophic reservoir in southeastern Brazil. Four classes of cyanopeptides were revealed through metabolomics: microcystins, microginins, aeruginosins, and cyanopeptolins. The bioinformatics tools showed high bioactivity correlation scores for compounds of the cyanopeptolin class (0.54), in addition to microcystins (0.54-0.58). These results emphasize the pressing need for a comprehensive evaluation of the (eco)toxicological risks associated with different cyanopeptides, considering their potential for exposure. Our study also demonstrated that the combined use of LC-MS/MS-based metabolomics and chemometric techniques for ecotoxicological research can offer a time-efficient strategy for mapping compounds with potential toxicological risk. Environ Toxicol Chem 2024;43:2222-2231. © 2024 SETAC.

CarcSeq detection of lorcaserin-induced clonal expansion of Pik3ca H1047R mutants in rat mammary tissue.

Lorcaserin is a 5-hydroxytryptamine 2C (serotonin) receptor agonist and a nongenotoxic rat carcinogen, which induced mammary tumors in male and female rats in a 2-yr bioassay. Female Sprague Dawley rats were treated by gavage daily with 0, 30, or 100 mg/kg lorcaserin, replicating bioassay dosing but for shorter duration, 12 or 24 wk. To characterize exposure and eliminate possible confounding by a potentially genotoxic degradation product, lorcaserin and N-nitroso-lorcaserin were quantified in dosing solutions, terminal plasma, mammary, and liver samples using ultra-high-performance liquid chromatography-electrospray tandem mass spectrometry. N-nitroso-lorcaserin was not detected, supporting lorcaserin classification as nongenotoxic carcinogen. Mammary DNA samples (n = 6/dose/timepoint) were used to synthesize PCR products from gene segments encompassing hotspot cancer driver mutations, namely regions of Apc, Braf, Egfr, Hras, Kras, Nfe2l2, Pik3ca, Setbp1, Stk11, and Tp53. Mutant fractions (MFs) in the amplicons were quantified by CarcSeq, an error-corrected next-generation sequencing approach. Considering all recovered mutants, no significant differences between lorcaserin dose groups were observed. However, significant dose-responsive increases in Pik3ca H1047R mutation were observed at both timepoints (ANOVA, P < 0.05), with greater numbers of mutants and mutants with greater MFs observed at 24 wk as compared with 12 wk. These observations suggest lorcaserin promotes outgrowth of spontaneously occurring Pik3ca H1047R mutant clones leading to mammary carcinogenesis. Importantly, this work reports approaches to analyze clonal expansion and demonstrates CarcSeq detection of the carcinogenic impact (selective Pik3ca H0147R mutant expansion) of a nongenotoxic carcinogen using a treatment duration as short as 3 months.

The First Steps on AOPs' Concepts, Development, and Applications in Teratology.

An Adverse Outcome Pathway (AOP) is an analytical model that describes, through a graphical representation, a linear sequence of biologically connected events at different levels of biological organization, causally leading to an adverse effect on human health or the environment. In general, AOPs are constructed based on five central principles: systematic development and review, chemical-agnostic, modular, networks, and living documents. Furthermore, AOPs have the potential to be used, for example, to investigate certain molecular targets; relate the regulation of specific genes or proteins among AOPs; extrapolate biological processes, pathways, or diseases from one species to another; and even predict adverse effects in particular populations. AOPs also emerge as an alternative to animal experimentation in studies of developmental malformations. It's even possible now to develop a quantitative AOP to predict teratogenic effects for some substances. However, the construction of high-quality AOPs requires standardization in the way these models are developed and reviewed, ensuring an adequate degree of flexibility and guaranteeing efficiency. The development of AOPs should strictly be based on the guidance documents developed by the OECD. Nevertheless, an important step for those developing AOPs is the choice of an apical endpoint or an initiating molecular event in order to initiate the construction of the pathway. Another crucial step is a systematic literature review based on the random combination of the blocks of information. With these two fundamental steps completed, it only remains to follow the guidance documents on Developing and Assessing Adverse Outcome Pathways and AOP Developers' Handbook supplement provided by the OECD to organize and construct an AOP. This modern approach will bring radical changes in the field of toxicity testing, regarding the prediction of apical toxic effects using molecular-level effects.

AOP Report: Glutathione Conjugation Leading to Reproductive Dysfunction via Oxidative Stress.

We propose an adverse outcome pathway (AOP) for reproductive dysfunction via oxidative stress (OS). The AOP was developed based on Organisation for Economic Co-operation and Development (OECD) Guidance Document 184 and on the specific considerations of the OECD users' handbook supplement to the guidance document for developing and assessing AOPs (no. 233). According to the qualitative and quantitative experimental data evaluation, glutathione (GSH) conjugation is the first upstream key event (KE) of this AOP to reproductive dysfunction triggering OS. This event causes depletion of GSH basal levels (KE2 ). Consequently, this drop of free GSH induces an increase of reactive oxygen species (KE3 ) generated by the natural cellular metabolic processes (cellular respiration) of the organism. Increased levels of these reactive species, in turn, induce an increase of lipid peroxidation (KE4 ). This KE consequently leads to a rise in the amount of toxic substances, such as malondialdehyde and hydroxynonenal, which are associated with decreased quality and competence of gamete cell division, consequently impairing fertility (KE5 and adverse outcome). The overall assessment of the general biological plausibility, the empirical support, and the essentiality of KE relationships was considered as high for this AOP. We conclude that GSH conjugation is able to lead to reproductive disorder in fishes and mammals, via OS, but that the amount of stressor needed to trigger the AOP differs between stressors. Environ Toxicol Chem 2023;42:2519-2528. © 2023 SETAC.

The numerical probability of carcinogenicity to humans of some pharmaceutical drugs: Alkylating agents, topoisomerase inhibitors or poisons, and DNA intercalators.

The nonclinical branch of regulatory pharmacology has traditionally relied on the sensitivity and specificity of regulatorily recommended bioassays. Nonetheless, any predictive testing (eg, safety pharmacology) with less than 100% sensitivity or 100% specificity is prone to deliver false positive or negative results (namely, outcomes discordant to the clinical gold standard). It was recently suggested that the statistics-based and regulatory pertinent "predictive values approach" (PVA) might help to reach a more predictive use of preclinical testing data. To resolve the associated probability of carcinogenicity to humans, the PVA was applied to 37 pharmaceuticals bearing inadequate epidemiological evidence of carcinogenicity, but identifiable as unequivocal mutagens. According to current knowledge, a 98.9% (or more) probability of carcinogenicity to humans was reckoned for those 37 genotoxic drugs. Accordingly, these pharmaceutical drugs might be either scientifically or regulatorily regarded as "carcinogenic to humans." In the USA, European Union, or Canada as examples, the great majority of these 37 pharmaceuticals are authorized for medical use in humans. From the results of the present appraisal, the following is suggested (1) for the pharmaceuticals listed in this report, to include significant carcinogenicity warnings in their prescribing information; (2) to conduct pharmacoepidemiology studies or risk-benefit analyses (if warranted), and (3) based on the respective risk-benefit analyses, to re-evaluate the authorization of hydralazine and phenoxybenzamine as antihypertensives, oxcarbazepine as an anticonvulsant, and phenazopyridine as a urinary tract antimicrobial or analgesic. For the four latter drugs (eg, phenoxybenzamine), a 99.5% probability of carcinogenicity to humans was estimated.

Towards a personalized risk assessment for exposure of humans to toxic substances / Em direção a uma avaliação de risco personalizado para exposição de seres humanos a substâncias tóxicas

Abstract Great response variability caused by genetic and/or environmental factors has been observed among organisms exposed to hazardous chemicals. This subject has been a topic of intense discussion in the USA since President Obama announced support for an “era of precision medicine”, which consists in the inclusion of genetic data of patients in the treatment design, imposing a new approach to risk assessment. Personalized evaluation must consider the phenotypic factors of an individual. Among the markers that have been developed to evaluate any alteration in the structure or function of organisms, biomarkers of susceptibility are of great importance because they indicate the natural characteristics of a given organism which make it more sensitive to a specific adverse effect or disease, or more responsive to exposure to a specific chemical/drug. The ‘-omics’ technologies provide an insight into the relationship between chemical effects and molecular mechanisms of action. These technologies are the pillars for a personalized toxicology and precision medicine. Predictive toxicology requires a more comprehensive knowledge on specific individual factors or susceptibilities predisposing to diseases, enabling personalized risk assessment and adequate medical treatment.

Resumo Há uma grande variabilidade nas respostas observadas entre os organismos expostos a uma substância química perigosa. Essa variabilidade é causada por causas genéticas e / ou ambientais. Esse assunto tem sido intensamente discutido, mesmo nos Estados Unidos, desde que o presidente Obama anunciou o apoio a uma “era da medicina de precisão”, a qual consiste na inclusão de dados genéticos do paciente no projeto do tratamento, impondo uma nova abordagem para avaliação de risco. A avaliação personalizada deve considerar fatores fenotípicos de um indivíduo. Entre os biomarcadores que foram desenvolvidos para avaliar qualquer alteração da estrutura ou função do organismo, os biomarcadores de susceptibilidade têm uma grande importância, uma vez que indicam as características naturais de um dado organismo, que o tornam mais sensíveis a um efeito ou doença adversa específica ou em resposta a uma determinada exposição. As tecnologias “ômicas” permitem a compreensão da relação entre os efeitos químicos e dos mecanismos moleculares de ação. Essas tecnologias “ômicas” são os pilares para a toxicologia personalizada e para a medicina de precisão. Toxicologia preditiva exige uma melhor compreensão dos fatores ou susceptibilidades individuais específicas predisponentes a doenças, permitindo uma avaliação de riscos personalizada e um tratamento médico adequado.