Differential expression of genes in C. elegans reveals transcriptional responses to indirect-acting xenobiotic compounds and insensitivity to 2,3,7,8-tetrachlorodibenzodioxin

CYP14 family in Caenorhabditis elegans: Mitochondrial function, detoxification, and lifespan

CYP-14 members of the Caenorhabditis elegans (C. elegans) Cytochrome P450 (CYP) enzyme family, plays important roles in mitochondrial dysfunction, detoxification, lipid metabolism, defense and lifespan regulation. The review identifies CYP-14 members: cyp-14A1, cyp-14A2, cyp-14A3, cyp-14A4, cyp-14A5 and their homology with human CYP families. Despite limited studies on C. elegans cyp-14 members, the findings unraveled their complex crosstalk between mitochondrial stress, detoxification mechanisms, and lifespan regulation, emphasizing the complexity of these interconnected pathways as well as how their regulation depends on environmental cues changes including pH, nutrients, ROS and chemical stressors. The review underscores the translational relevance to human health, shedding light on potential human homologues and their implications in age-related, metabolic and respiratory diseases. Among other genes, cyp-14A2 and cyp-14A4 predominate the mitochondrial function, heat resistance, lipid metabolism, detoxification and lifespan pathways. In conclusion, these insights pave the way for future research, offering promising avenues for therapeutic interventions targeting CYP-14 activity to address age-related diseases and promote healthy aging.

Transgenerational toxicity induced by maternal AFB1 exposure in Caenorhabditis elegans associated with underlying epigenetic regulations

Aflatoxin B1 (AFB1), usually seriously contaminates in grain and oil foods or feed, displayed significant acute and chronic toxic effects in human and animal populations. However, little is known about the transgenerational toxic effects induced by a maternal AFB1 intake at a lower dose on offspring. In our study, only parental wild-type Caenorhabditis elegans was exposed to AFB1 (0-8 μg/ml) and the following three filial generations were grown on AFB1-free NGM. Results showed that the toxic effects of AFB1 on the growth (body length) and reproduction (brood size, generation time and morphology of gonad arm) can be transmitted through generations. Moreover, the levels of MMP and ATP were irreversibly inhibited in the filial generations. By using RNomics and molecular biology techniques, we found that steroid biosynthesis, phagosome, valine/leucine/isoleucine biosynthesis and oxidative phosphorylation (p < 0.05) were the core signaling pathways to exert the transgenerational toxic effects on nematodes. Also, notably increased histone methylation level at H3K36me3 was observed in the first generation. Taken together, our study demonstrated that AFB1 has notable transgenerational toxic effects, which were resulted from the complex regulatory network of various miRNAs, mRNAs and epigenetic modification in C. elegans.

How neurobehavior and brain development in alternative whole-organism models can contribute to prediction of developmental neurotoxicity

Developmental neurotoxicity (DNT) is not routinely evaluated in chemical risk assessment because current test paradigms for DNT require the use of mammalian models which are ethically controversial, expensive, and resource demanding. Consequently, efforts have focused on revolutionizing DNT testing through affordable novel alternative methods for risk assessment. The goal is to develop a DNT in vitro test battery amenable to high-throughput screening (HTS). Currently, the DNT in vitro test battery consists primarily of human cell-based assays because of their immediate relevance to human health. However, such cell-based assays alone are unable to capture the complexity of a developing nervous system. Whole organismal systems that qualify as 3 R (Replace, Reduce and Refine) models are urgently needed to complement cell-based DNT testing. These models can provide the necessary organismal context and be used to explore the impact of chemicals on brain function by linking molecular and/or cellular changes to behavioural readouts. The nematode Caenorhabditis elegans, the planarian Dugesia japonica, and embryos of the zebrafish Danio rerio are all suited to low-cost HTS and each has unique strengths for DNT testing. Here, we review the strengths and the complementarity of these organisms in a novel, integrative context and highlight how they can augment current cell-based assays for more comprehensive and robust DNT screening of chemicals. Considering the limitations of all in vitro test systems, we discuss how a smart combinatory use of these systems will contribute to a better human relevant risk assessment of chemicals that considers the complexity of the developing brain.

A Multiplex Gene Expression Assay for Direct Measurement of RNA Transcripts in Crude Lysates of the Nematode Caenorhabditis elegans Used as a Bioanalytical Tool

Gene expression profiling in Caenorhabditis elegans has been demonstrated to be a potential bioanalytical tool to detect the toxic potency of environmental contaminants. The RNA transcripts of genes responding to toxic exposure can be used as biomarkers for detecting these toxins. For routine application in environmental quality monitoring, an easy-to-use multiplex assay is required to reliably quantify expression levels of these biomarkers. In the present study, a bead-based assay was developed to fingerprint gene expression in C. elegans by quantitating messenger RNAs (mRNAs) of multiple target genes directly from crude nematode lysates, circumventing RNA extraction and purification steps. The assay uses signal amplification rather than target amplification for direct measurement of toxin-induced RNA transcripts. Using a 50-gene panel, the expression changes of four candidate reference genes and 46 target mRNAs for various contaminants and wastewaters were successfully measured, and the expression profiles indicated the type of toxin present. Moreover, the multiplex assay response was in line with previous results obtained with more time-consuming reverse-transcription quantitative polymerase chain reaction and microarray analyses. In addition, the transcriptomic profiles of nematodes exposed to wastewater samples and extracts prepared from tissues of swimming crabs were evaluated. The profiles indicated the presence of organic pollutants. The present study illustrates the successful development of a multiplex fluorescent bead-based approach using nematode C. elegans crude lysates for gene expression profiling of target RNAs. This method can be used to routinely fingerprint the presence of toxic contaminants in environmental samples and to identify the most biologically active fraction of the contaminant mixture in a toxicity identification and evaluation approach. Environ Toxicol Chem 2023;42:130-142. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Determining Toxic Potencies of Water-Soluble Contaminants in Wastewater Influents and Effluent Using Gene Expression Profiling in C. elegans as a Bioanalytical Tool

With chemical analysis, it is impossible to qualify and quantify the toxic potency of especially hydrophilic bioactive contaminants. In this study, we applied the nematode C. elegans as a model organism for detecting the toxic potency of whole influent wastewater samples. Gene expression in the nematode was used as bioanalytical tool to reveal the presence, type and potency of molecular pathways induced by 24-h exposure to wastewater from a hospital (H), nursing home (N), community (C), and influent (I) and treated effluent (E) from a local wastewater treatment plant. Exposure to influent water significantly altered expression of 464 genes, while only two genes were differentially expressed in nematodes treated with effluent. This indicates a significant decrease in bioactive pollutant-load after wastewater treatment. Surface water receiving the effluent did not induce any genes in exposed nematodes. A subset of 209 genes was differentially expressed in all untreated wastewaters, including cytochromes P450 and C-type lectins related to the nematode's xenobiotic metabolism and immune response, respectively. Different subsets of genes responded to particular waste streams making them candidates to fingerprint-specific wastewater sources. This study shows that gene expression profiling in C. elegans can be used for mechanism-based identification of hydrophilic bioactive compounds and fingerprinting of specific wastewaters. More comprehensive than with chemical analysis, it can demonstrate the effective overall removal of bioactive compounds through wastewater treatment. This bioanalytical tool can also be applied in the process of identification of the bioactive compounds via a process of toxicity identification evaluation.

CYP35 family in Caenorhabditis elegans biological processes: fatty acid synthesis, xenobiotic metabolism, and stress responses

With more than 80 cytochrome P450 (CYP) encoding genes found in the nematode Caenorhabditis elegans (C. elegans), the cyp35 genes are one of the important genes involved in many biological processes such as fatty acid synthesis and storage, xenobiotic stress response, dauer and eggshell formation, and xenobiotic metabolism. The C. elegans CYP35 subfamily consisted of A, B, C, and D, which have the closest homolog to human CYP2 family. C. elegans homologs could answer part of the hunt for human disease genes. This review aims to provide an overview of CYP35 in C. elegans and their human homologs, to explore the roles of CYP35 in various C. elegans biological processes, and how the genes of cyp35 upregulation or downregulation are influenced by biological processes, upon exposure to xenobiotics or changes in diet and environment. The C. elegans CYP35 gene expression could be upregulated by heavy metals, pesticides, anti-parasitic and anti-chemotherapeutic agents, polycyclic aromatic hydrocarbons (PAHs), nanoparticles, drugs, and organic chemical compounds. Among the cyp35 genes, cyp-35A2 is involved in most of the C. elegans biological processes regulation. Further venture of cyp35 genes, the closest homolog of CYP2 which is the largest family of human CYPs, may have the power to locate cyps gene targets, discovery of novel therapeutic strategies, and possibly a successful medical regime to combat obesity, cancers, and cyps gene-related diseases.