Multi-generational obesogenic effects of sulfomethoxazole on Caenorhabditis elegans through epigenetic regulation

Intermittent multi-generational reproductive toxicities of 1-alkyl-3-methylimidazolium tetrafluoroborate with essential involvement of lipid metabolism

Ionic liquids (ILs) become emerging environmental pollutants. Especially, alkyl imidazolium ILs commonly showed stimulation in toxicological studies and mechanisms remained to be explored. In the present study, alkyl imidazolium tetrafluoroborate ([amim]BF4), with ethyl ([emim]), hexyl ([hmim]) and octyl ([omim]) as side-chains, were chosen as target ILs. Their toxicities on the reproduction and lifespan of Caenorhabditis elegans were explored with two types (A and B) exposure arrangements to mimic realistic intermittent multi-generational exposure scenarios. In type A scenario, there was an exposure every 4 generations with 12 generations in total, and in type B one, there was an exposure every two generations with 12 generations in total. Result showed that [emim]BF4 caused inhibition on the reproduction in 8 generations in type A exposure but 6 ones in type B exposure. Meanwhile, [hmim]BF4 showed inhibition in one generation and stimulation in 3 generations in type A exposure, but stimulation in 6 generations in type B exposure. Also, [omim]BF4 showed stimulation in one generation in type B exposure. Collectively, the results demonstrated less frequencies of inhibition, or more frequencies of stimulation, in the exposure scenario with more frequent exposures. Further mechanism exploration was performed to measure the lipid storage and metabolism in the aspect of energy supply. Results showed that [emim]BF4, [hmim]BF4 and [omim]BF4 commonly stimulated the triglyceride (TG) levels across generations. They also disturbed the activities of glycerol-3-phosphate acyltransferase (GPAT) and acetyl CoA carboxylase (ACC) in lipogenesis, those of adipose triglyceride lipase (ATGL) and carnitine acyl transferase (CPT) in lipolysis, and also the contents of acetyl-CoA (ACA). Further data analysis indicated the energy allocation among life traits including reproduction, antioxidant responses and hormone regulations.

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.

Obesogenic potentials of environmental artificial sweeteners with disturbances on both lipid metabolism and neural responses

Artificial sweeteners (ASs) entered the environments after application and emissions. Recent studies showed that some ASs had obesogenic risks. However, it remained unclear whether such risks are common and how they provoke such effects. Presently, the effects of 8 widely used ASs on lipid accumulation were measured in Caenorhabditis elegans. Potential mechanisms were explored with feeding and locomotion behavior, lipid metabolism and neural regulation. Results showed that acesulfame (ACE), aspartame (ASP), saccharin sodium (SOD), sucralose (SUC) and cyclamate (CYC) stimulated lipid accumulation at μg/L levels, showing obesogenic potentials. Behavior investigation showed that ACE, ASP, SOD, SUC and CYC biased more feeding in the energy intake aspect against the locomotion in the energy consumption one. Neotame (NEO), saccharin (SAC) and alitame (ALT) reduced the lipid accumulation without significant obesogenic potentials in the present study. However, all 8 ASs commonly disturbed enzymes (e.g., acetyl-CoA carboxylase) in lipogenesis and those (e.g., carnitine palmitoyl transferase) in lipolysis. In addition, ASs disturbed PPARγ (via expressions of nhr-49), TGF-β/DAF-7 (daf-7) and SREBP (sbp-1) pathways. Moreover, they also interfered neurotransmitters including serotonin (5-HT), dopamine (DA) and acetylcholine (ACh), with influences in Gsα (e.g., via expressions of gsα-1, ser-7), glutamate (e.g., mgl-1), and cGMP-dependent signaling pathways (e.g., egl-4). In summary, environmental ASs commonly disturbed neural regulation connecting behavior and lipid metabolism, and 5 out of 8 showed clear obesogenic potentials. ENVIRONMENTAL IMPLICATION: Artificial sweeteners (ASs) are become emerging pollutants after wide application and continuous emission. Recent studies showed that some environmental ASs had obesogenic risks. The present study employed Caenorhabditis elegans to explore the influences of 8 commonly used ASs on lipid metabolisms and also the underlying mechanisms. Five out of 8 ASs stimulated lipid accumulation at μg/L levels, and they biased energy intake against energy consumption. The other three ASs reduced the lipid accumulation. ASs commonly disturbed lipogenesis and lipolysis via PPARγ, TGF-β and SREBP pathways, and also influenced neurotransmitters with Gsα, glutamate and cGMP-dependent signaling pathways.

Metastatic effects of perfluorooctanoic acid (PFOA) on Drosophila melanogaster with metabolic reprogramming and dysrhythmia in a multigenerational exposure scenario

Perfluorooctanoic acid (PFOA) exposure correlated with various cancers and their mortality. Its persistence in the environment made its long-term multigenerational influences of significant concerns. However, it remained unanswered whether its multigenerational exposure could influence metastasis which contributes ~90 % to cancer mortality. In the present study, long-term effects of PFOA were measured in Drosophila melanogaster over 3 consecutive generations. In the morning-eclosed (AM) adult flies, PFOA significantly promoted tumor invasion rates and distances which increased over generations. Regarding metabolic reprogramming, PFOA disturbed the expressions of Glut1 and Pdk1, activities and contents of FASN1 (fatty acid synthase), ACC (acetyl-CoA carboxylase) and SREBP1 (sterol regulatory element binding protein). Regarding antioxidant responses, PFOA exposure generated provoked oxidative stress via H2O2 and stimulated antioxidants including glutathione (GSH), catalase (CAT), melatonin, serotonin and cortisol, with downregulations on PI3K/AKT pathways and upregulations on MAPK ones. The biochemical and molecular effects altered over generations. In the afternoon-eclosed (PM) adult flies, the metastasis of PFOA was more deteriorated than in AM adults. The significant influences of dysrhythmia were also observed in the multigenerational effects of PFOA on the metabolism reprogramming and antioxidant responses. The effects on rhythm-regulating gene expressions and protein levels explained the dysrhythmia and also indicated close interactions among metabolism reprogramming, antioxidant responses and rhythm regulation. ENVIRONMENTAL IMPLICATION: Numerous emerging per- and polyfluoroalkyl substances (PFASs) are being detected. Meanwhile, the toxicities of the emerging PFASs still depend on the progress of legacy PFASs for the continuity of scientific studies. As one legacy PFAS, perfluorooctanoic acid (PFOA) exposure correlated with various cancers and their mortality. Its persistence in the environment made its long-term multigenerational influences of significant concerns. However, it remained unanswered whether its multigenerational exposure could influence metastasis which contributes ~90 % to cancer mortality. The present study performed PFOA exposure for 3 consecutive generations. Results showed that the metastasis by PFOA increased over generations, and it was further deteriorated by dysrhythmia. Further analysis demonstrated the interactive involvement of metabolism reprogramming, antioxidant responses and rhythm regulation. The findings of the present study would highlight considerate points for studying the toxicities of emerging PFASs.

Lipid metabolism analysis providing insights into nonylphenol multi-toxicity mechanism

Nonylphenol (NP), a widely recognized endocrine disruptor, exhibits lipophobic properties that drive its accumulation in adipose tissue, leading to various physiological disruptions. Using Caenorhabditis elegans, this study investigated the effects of NP exposure on lipid homeostasis and physiological indicators. NP exposure increased lipid storage, hindered reproduction and growth, and altered phospholipid composition. Transcriptional analysis revealed NP's promotion of lipogenesis and inhibition of lipolysis. Metabolites related to lipid metabolism like citrate, amino acids, and neurotransmitters, along with lipids, collectively influenced physiological processes. This work elucidates the complex link between lipid metabolism disturbances and NP-induced physiological disruptions, enhancing our understanding of NP's multifaceted toxicity.

Multi- and trans-generational effects of di-n-octyl phthalate on behavior, lifespan and reproduction of Caenorhabditis elegans through neural regulation and lipid metabolism

Di-n-octyl phthalate (DOP) is one important phthalate analog whose toxicities need comprehensive investigation to fully demonstrate phthalates health risks. In the present study, apical effects of DOP on behavior, lifespan and reproduction and the underlying mechanisms were explored in Caenorhabditis elegans for four consecutive generations (F1 to F4) and the trans-generational effects were also measured in the great-grand-children (T4 and T4') of F1 and F4. Multi-generational results showed that DOP caused both stimulation and inhibition on head swing, body bending, reverse, Omega steering, pharyngeal pump and satiety quiescence. The stimulation and inhibition altered over concentrations and across generations, and the alteration was the greatest in reverse locomotion which showed both concentration-dependent hormesis and trans-hormesis. DOP stimulated lifespan and inhibited reproduction, showing trade-off relationships. Significant trans-generational residual effects were found in T4 and T4' where the exposure was completed eliminated. Moreover, both similar and different effects were found in comparisons between F1 and F4, between F1 and T4, between F4 and T4' and also between T4 and T4'. Further analysis showed close connections between effects of DOP on neurotransmitters (including dopamine, acetylcholine, γ-aminobutyric acid and serotonin) and enzymes in lipid metabolism (including lipase, acetyl CoA carboxylase, fatty acid synthetase, carnitine palmitoyl-transferase, glycerol phosphate acyltransferase and acetyl CoA synthetase). Moreover, the close connections were also found between biochemical and apical effects. Notably, the connections were different in multi- and trans-generational effects, which urged further studies to reveal the response strategies underlying the exposure scenarios.

Emerging Metabolic Profiles of Sulfonamide Antibiotics by Cytochromes P450: A Computational-Experimental Synergy Study on Emerging Pollutants

Metabolism, especially by CYP450 enzymes, is the main reason for mediating the toxification and detoxification of xenobiotics in humans, while some uncommon metabolic pathways, especially for emerging pollutants, probably causing idiosyncratic toxicity are easily overlooked. The pollution of sulfonamide antibiotics in aqueous system has attracted increasing public attention. Hydroxylation of the central amine group can trigger a series of metabolic processes of sulfonamide antibiotics in humans; however, this work parallelly reported the coupling and fragmenting initiated by amino H-abstraction of sulfamethoxazole (SMX) catalyzed by human CYP450 enzymes. Elucidation of the emerging metabolic profiles was mapped via a multistep synergy between computations and experiments, involving preliminary DFT computations and in vitro and in vivo assays, profiling adverse effects, and rationalizing the fundamental factors via targeted computations. Especially, the confirmed SMX dimer was shown to potentially act as a metabolism disruptor in humans, while spin aromatic delocalization resulting in the low electron donor ability of amino radicals was revealed as the fundamental factor to enable coupling of sulfonamide antibiotics by CYP450 through the nonconventional nonrebound pathway. This work may further strengthen the synergistic use of computations prior to experiments to avoid wasteful experimental screening efforts in environmental chemistry and toxicology.

Hormone-mediated multi- and trans-generational reproductive toxicities of 1-ethyl-3-methylimidazolium hexafluorophosphate on Caenorhabditis elegans

Ionic liquids (ILs) are emergent pollutants and their reproductive toxicities show hormesis, earning attentions on their environmental risk. Yet, their reproductive effects over generations and the mechanisms were seldom explored. In the present study, the reproductive effects of 1-ethyl-3-methylimidazolium hexafluorophosphate ([C₂mim]PF₆) on Caenorhabditis elegans were measured in 11 continuously exposed generations (F1 to F11) to explore the multi-generational effects, and also in the non-exposed generations of F1 and F11 (i.e., their great-grand-daughters, T4 and T4') to explore the trans-generational effects. In multi-generational reproductive effects, there were concentration-dependent hormetic effects with hazard-benefit alteration between low and high concentrations (e.g., in F3). There were also generation-dependent hormetic effects with hazard-benefit alterations over generations (e.g., between F4 and F5, between F8 and F9, and between F10 and F11). Meanwhile, the results also showed benefit-hazard alteration between F2 and F3, between F6 and F7, and between F9 and F10. Trans-generational effects showed common inhibitions in T4 and T4' at both low and high concentrations. In the biochemical analysis, hormones and hormone-like substances including progesterone (P), estradiol (E2), prostaglandin (PG) and testosterone (T) showed multi- and trans-generational changes with inhibition and stimulation, which contributed to the reproductive outcomes in each generation. Such contribution was also observed in the hormones' precursor cholesterol and the proteins that are essential for reproduction including vitellogenin (Vn) and major sperm protein (MSP). Moreover, the biochemicals showed significant involvement in the connection among generations. Furthermore, the multi- and trans-generational effects of [C₂mim]PF₆ and histidine showed similar modes of actions despite some differences, implying the contribution of their shared imidazole structure.

Nontargeted metabolomic evidence for antagonism between tetracycline and its resistance bacteria underlying their obesogenic effects on Caenorhabditis elegans

Environmental antibiotics raise serious health concerns due to their contribution to the obesity prevalence. Moreover, antibiotics promote antibiotic-resistance bacteria (ARB) which represent another emerging pollutant. However, the interaction between antibiotic and ARB in the obesogenic effects remained unexplored. In the present study, the obesogenic effects of tetracycline antibiotic (TCH) and ARB containing tetA were studied on C. elegans, and E. coli OP50 (OP50) was referred as a normal bacterial food. Results showed that TCH stimulated nematode triglyceride contents, while ARB alone had no significant influences. The combination of TCH and ARB showed less obesogenic effects than TCH alone, showing antagonism. Biochemical assays showed that the combination of TCH and ARB showed similar effects to ARB alone, and had less increases in lipid metabolism enzymes or metabolites than those of TCH or ARB alone, supporting the antagonism. In the nontargeted metabolomic analysis, TCH with ARB showed less significantly changed metabolites (SCMs) in the nematodes than TCH or ARB alone, partially explaining the antagonism. The metabolomic results also pointed out the significant involvement of amino acids, the carboxylic acids and derivatives, and also the benzene and substituted derivatives in the obesogenic effects of TCH and ARB. The findings of the present study provided a direct support for interaction between antibiotics and ARB underlying their health risks.

Sex-dependent obesogenic effect of tetracycline on Drosophila melanogaster deteriorated by dysrhythmia

Antibiotics have been identified as obesogens contributing to the prevalence of obesity. Moreover, their environmental toxicity shows sex dependence, which might also explain the sex-dependent obesity observed. Yet, the direct evidence for such a connection and the underlying mechanisms remain to be explored. In this study, the effects of tetracycline, which is a representative antibiotic found in both environmental and food samples, on Drosophila melanogaster were studied with consideration of both sex and circadian rhythms (represented by the eclosion rhythm). Results showed that in morning-eclosed adults, tetracycline significantly stimulated the body weight of females (AM females) at 0.1, 1.0, 10.0 and 100.0 µg/L, while tetracycline only stimulated the body weight of males (AM males) at 1.0 µg/L. In the afternoon-eclosed adults, tetracycline significantly stimulated the body weight of females (PM females) at 0.1, 1.0 and 100.0 µg/L, while it showed more significant stimulation in males (PM males) at all concentrations. Notably, the stimulation levels were the greatest in PM males among all the adults. The results showed the clear sex dependence of the obesogenic effects, which was diminished by dysrhythmia. Further biochemical assays and clustering analysis suggested that the sex- and rhythm-dependent obesogenic effects resulted from the bias toward lipogenesis against lipolysis. Moreover, they were closely related to the preference for the energy storage forms of lactate and glucose and also to the presence of excessive insulin, with the involvement of glucolipid metabolism. Such relationships indicated potential bridges between the obesogenic effects of pollutants and other diseases, e.g., cancer and diabetes.

Antibiotics disrupt lipid metabolism in zebrafish (Danio rerio) larvae and 3T3-L1 preadipocytes

Antibiotics are emerging environmental contaminants with wide attention due to their high consumption and pseudo-persistence in the environment. They have been shown to induce obesity or obesity-related metabolic diseases in experimental animals, but the underlying toxicological mechanisms remain unclear. Here, the disruptive effects of four commonly used antibiotics, namely doxycycline (DC), enrofloxacin (ENR), florfenicol (FF) and sulfamethazine (SMT) on lipid metabolism were investigated in zebrafish (Danio rerio) larvae and murine preadipocyte cell line. Triglyceride (TG) content was reduced after 1 ng/L DC or ENR exposure but was increased at higher concentrations up to 100 mg/L. FF increased and SMT reduced TG content but did not show any concentration dependence. None of the antibiotics had any significant effect on total cholesterol (TC) content in zebrafish except 100 μg/L SMT. Expression levels of 8 lipid metabolism-related genes were also quantified. SMT was most disruptive by up-regulating six genes, followed by FF which up-regulated four genes and down-regulated one gene, whereas DC and ENR both up-regulated one gene. In 3T3-L1 preadipocytes, ENR, FF, and SMT in general increased TG content, while 100 mg/L FF reduced TG substantially. DC did not show any effect up to 10 mg/L, at which TG increased significantly. FF and SMT increased TC slightly at low concentrations but reduced it at high concentrations, whereas TC, DC and ENR had no effect at any tested concentrations. Gene expression measurement also indicated that SMT was most disruptive, followed by FF, DC, and ENR. Reporter gene assays showed that only SMT inhibited the transcriptional activity of peroxisome proliferator-activated receptor γ (PPARγ). The above experimental results and clustering analysis demonstrate that the four antibiotics exerted disruption on lipid metabolism through different mechanisms, and one of the mechanisms for SMT may be inhibition of PPARγ transcriptional activity.

Continuous and discontinuous multi-generational disturbances of tetrabromobisphenol A on longevity in Caenorhabditis elegans

Tetrabromobisphenol A (TBBPA) is one of the most prevalently used brominated flame retardants. Due to its persistence, it is predominantly found in environmental matrices and has the potential to generate multi-generational toxicity. However, knowledge of its adaptive response or long-term residual effect in multi-generations, and molecular mechanisms remain understudied. In the current study, the model animal nematode Caenorhabditis elegans (C. elegans) was exposed to TBBPA at environmentally realistic concentrations (0.1-1000 μg L^-1) for four consecutive generations (G₀ to G₃). Degenerative age-related multiple endpoints including lifespan, locomotion behaviors, growth, reproduction, oxidative stress-related biochemical responses, cell apoptosis, and stress related gene expressions were assessed in the continuous exposure generations (G₀ and G₃) and the discontinuously exposed generations (T₃ and T'₃). The results showed that changes in degenerative age-related response monitored four generations varied in direction and magnitude depending on the TBBPA concentrations, and the response intensify ranked as G₀ > T'₃/G₃ > T₃. TBBPA at 1 μg L^-1 dosage was detected as the lowest observed effect concentration in multi-biomarkers. The underlying mechanism of aging phenotypes was that reactive oxygen species accumulation led to cell apoptosis regulated by gene ape-1, and confirmed catalase enzyme and superoxide dismutase activity played a crucial role in the detoxification process of TBBPA at the molecular level. This study provided insights into the underlying mechanism of TBBPA-interfered longevity and its environmental multi-generational potential risks.

A review of transgenerational and multigenerational toxicology in the in vivo model animal Caenorhabditis elegans

A large number of pollutants existing in the environment can last for a long time, and their potential toxic effects can transfer from parents to their offspring. Thus, it is necessary to investigate the toxicity of environmental pollutants across multigenerations and the underlying mechanisms in organisms. Due to its short life cycle and sensitivity to environmental exposures, Caenorhabditis elegans is an important animal model for toxicity assessment of environmental pollutants across multigenerations. In this review, we introduced the transgenerational and multigenerational toxicity caused by various environmental pollutants in C. elegans. Moreover, we discussed the underlying mechanisms for the observed transgenerational and multigenerational toxicity of environmental contaminants in C. elegans.

Balances among reproduction, antioxidant responses and lipid metabolism underlying the multi-generational effects of N-butylpyridinium bromide on Caenorhabditis elegans

Ionic liquids (ILs) are difficult to degrade and even accumulate in the environment. Accordingly, their long-term toxicities are particularly important to demonstrate their accurate risk assessment. However, their long-term toxicities over generations and the toxicity mechanisms lacked thorough investigation. Presently, N-butylpyridinium bromide ([bpyr]Br), a representative IL, was chosen to measure its long-term effects on Caenorhabditis elegans for seven consecutive generations at 0.0225 and 22.5 mg/L. Toxicity mechanisms were explored in F1, F3, F5 and F7 by combining both antioxidant responses and lipid metabolism. Results showed that [bpyr]Br at low concentration provoked oscillatory effects on the reproduction over 7 generations, with inhibition in F1 and F7 and stimulation in F2, F4 and F5. At high concentration, [bpyr]Br showed similar multi-generational oscillation with greater inhibition in F1 and greater stimulation in F5. The effects of [bpyr]Br on the antioxidant responses to oxidative stress also showed oscillation over generations. The integrated biomarker response (IBR) values showed that [bpyr]Br at low concentration did not provoke significant influences on the overall antioxidant homeostasis in F1 and F3, but significantly stimulated it in F5 and F7. Meanwhile, [bpyr]Br at high concentration stimulated the antioxidant homeostasis in F1 and F7 with non-significant influences in F3 and F5. The IBR values regarding indicators in lipid metabolism showed that [bpyr]Br significantly and commonly stimulated the overall metabolism without concentration-dependent differences. Further analysis implied that [bpyr]Br provoked different mechanisms underlying the responses at low and high concentrations.

Review of the toxicity and potential molecular mechanisms of parental or successive exposure to environmental pollutants in the model organism Caenorhabditis elegans

Environmental pollutants such as heavy metals, nano/microparticles, and organic compounds have been detected in a wide range of environmental media, causing long-term exposure in various organisms and even humans through breathing, contacting, ingestion, and other routes. Long-term exposure to environmental pollutants in organisms or humans promotes exposure of offspring to parental and environmental pollutants, and subsequently results in multiple biological defects in the offspring. This review dialectically summarizes and discusses the existing studies using Caenorhabditis elegans (C. elegans) as a model organism to explore the multi/transgenerational toxicity and potential underlying molecular mechanisms induced by environmental pollutants following parental or successive exposure patterns. Parental and successive exposure to environmental pollutants induces various biological defects in C. elegans across multiple generations, including multi/transgenerational developmental toxicity, neurotoxicity, reproductive toxicity, and metabolic disturbances, which may be transmitted to progeny through reactive oxygen species-induced damage, epigenetic mechanisms, insulin/insulin-like growth factor-1 signaling pathway. This review aims to arouse researchers' interest in the multi/transgenerational toxicity of pollutants and hopes to explore the possible long-term effects of environmental pollutants on organisms and even humans, as well as to provide constructive suggestions for the safety and management of emerging alternatives.

Reproductive toxicities of ofloxacin and norfloxacin on Caenorhabditis elegans with multi-generational oscillatory effects and trans-generational residual influences

The reproductive toxicities over generations are essential to assess the long-term impacts environmental fluoroquinolone antibiotics (FQs). In the present study, the multi-generational effects of ofloxacin (OFL) and norfloxacin (NOR) on reproduction were studied on Caenorhabditis elegans from 9 successive generations (F1-F9). Results showed that OFL showed no effects in F1, stimulation in F2 to F4, and inhibition F5 to F9. The effects of NOR also showed oscillation between stimulation and inhibition across generations. Further biochemical analysis demonstrated that the reproductive toxicities of OFL and NOR were more closely connected with total cholesterol (TCHO), progesterone (P) and testosterone (T), than major sperm protein (MSP) and vitellogenin (Vn). Moreover, OFL and NOR also showed significant trans-generational reproductive toxicities in T4 and T4', the great-grand-daughter of F1 and F9. Differences between T4 and T4' and between OFL and NOR, indicated influences of multi-generational exposure and urged more exploration on different mechanisms between FQs.

Intermittent multi-generational effects of 1-hexyl-3-methylimidazolium nitrate on Caenorhabditis elegans mediated by lipid metabolism

Ionic liquids (ILs) become environmental pollutants. Their environmental toxicities included inhibitory effects, stimulatory ones and hormesis combining both aspects on various organisms. However, the mechanisms still need systematic investigations. Presently, 1-hexyl-3-methylimidazolium nitrate ([Hmim]NO₃) was chosen as one representative IL. Its effects on lifespan and reproduction were studied on C. elegans with lipid metabolism as the potential mechanism. Two types (A and B) intermittent multi-generational exposure arrangements were set up to mimic realistic ILs exposure scenarios. Type A arrangement had exposure in F1, F5 and F9 with recovery in T2-T4, T6-T8 and T10-T12, and type B arrangement had exposure in F1, F3, F5, F7, F9 and F11 with recovery in T2, T4, T6, T8, T10 and T12. In type A exposure, the effects of [Hmim]NO₃ on reproduction were 1.32-, 1.68-, 1.23-, 0.96-, 1.68-, 1.07-, 1.25-, 1.64-, 1.31-, 1.11-, 0.89- and 1.02-fold of the control in F1, T2-T4, F5, T6-T8, F9, T10-T12, respectively. The results showed oscillation between stimulatory and inhibitory effects. In type B exposure, the effects showed fewer inhibitions and more stimulations across generations. Moreover, the effects on reproduction showed trade-off relationships with lifespan, and the trade-off was more obvious in type B exposure. Further biochemical and gene expression analysis showed that lipid metabolism was closely related with lifespan and reproduction in type A exposure, but it was connected with cholesterol synthesis in type B exposure. The results demonstrated different strategies in the biological responses to the two arrangements of intermittent multi-generational exposure.

Glutamatergic transmission associated with locomotion-related neurotoxicity to lindane over generations in Caenorhabditis elegans

Organochlorine pesticide lindane in the environment and biota results in the potential risks on ecosystem and human health. Lindane can adversely affect the locomotion and nervous system, yet the potential neurotoxicity of lindane over generations remains uncertain. In this study, the neurotoxicity and underlying mechanisms in Caenorhabditis elegans (C. elegans) were investigated after parental (P0) exposure to lindane at environmentally relevant concentrations over generations. Exposure to lindane at concentrations of 10-100 ng/L significantly decreased body bends and head thrashes in P0 generation. Significant decrease of fluorescence labeled different neurotransmitters, and clear morphological changes by exposure to lindane at 10-100 ng/L suggested that lindane could induce the neuronal damage in C. elegans. During the transgenerational process, decreased locomotive behaviors were also observed in F1-F3 generations, and head thrashes returned to normal levels in F4 generation. Moreover, lindane exposure down-regulated the expression of dat-1, dop-1, glr-1 and mod-1genes, while up-regulated unc-30 gene in P0 generation, which recovered to normal levels in F4 generation. Interestingly, eat-4 continued to be regulated from inhibition to stimulation in P0-F4 generations, suggesting that glutamatergic transmission may more contribute to the neurotoxicity of lindane over generations.

Histone H3K4me3 modification is a transgenerational epigenetic signal for lipid metabolism in Caenorhabditis elegans

As a major risk factor to human health, obesity presents a massive burden to people and society. Interestingly, the obese status of parents can cause progeny's lipid accumulation through epigenetic inheritance in multiple species. To date, many questions remain as to how lipid accumulation leads to signals that are transmitted across generations. In this study, we establish a nematode model of C. elegans raised on a high-fat diet (HFD) that leads to measurable lipid accumulation, which can transmit the lipid accumulation signal to their multigenerational progeny. Using this model, we find that transcription factors DAF-16/FOXO and SBP-1/SREBP, nuclear receptors NHR-49 and NHR-80, and delta-9 desaturases (fat-5, fat-6, and fat-7) are required for transgenerational lipid accumulation. Additionally, histone H3K4 trimethylation (H3K4me3) marks lipid metabolism genes and increases their transcription response to multigenerational obesogenic effects. In summary, this study establishes an interaction between a network of lipid metabolic genes and chromatin modifications, which work together to achieve transgenerational epigenetic inheritance of obesogenic effects.

Obesogenic effect of erythromycin on Caenorhabditis elegans through over-eating and lipid metabolism disturbances

Environmental obesogens contributed significantly to the obesity prevalence. Recently, antibiotics joined the list of environmental obesogens, while the underlying mechanisms remained to be explored. In the present study, effects of erythromycin (ERY), one widely used macrolide antibiotic, were measured on C. elegans to investigate the obesogenic mechanism. Results showed that ERY at 0.1 μg/L significantly increased the fat content by 17.4% more than the control and also stimulated triacylglycerol (TAG) levels by 25.7% more than the control. Regarding the obesogenic mechanisms, ERY provoked over-eating by stimulation on the pharyngeal pumping and reduction on the satiety quiescence percentage and duration. Such effects were resulted from stimulation on the neurotransmitters including serotonin (5-HT), dopamine (DA) and acetylcholine (ACh). The nervous responses involved the up-regulation of Gsα (e.g., ser-7, gsa-1, acy-1 and kin-2) signaling pathway and the down-regulation of TGFβ (daf-7) but not via cGMP-dependent regulations (e.g., egl-4). Moreover, ERY stimulated the activities of fatty acid synthase (FAS) and glycerol-3-phosphateacyl transferases (GPAT) that catalyze lipogenesis, while ERY inhibited those of acyl-CoA synthetase (ACS), carnitine palmitoyl transferase (CPT) and acyl-CoA oxidase (ACO) that catalyze lipolysis. The unbalance between lipogenesis and lipolysis resulted in the fat accumulation which was consistent with up-regulation on mgl-1 and mgl-3 which are the down-steam of TGFβ regulation. Such consistence supported the close connection between nervous regulation and lipid metabolism. In addition, ERY also disturbed insulin which connects lipid with glucose in metabolism.

Multi-generational effects of enrofloxacin on lifespan and reproduction of Caenorhabditis elegans with SKN-1-mediated antioxidant responses and lipid metabolism disturbances

Antibiotics are ubiquitous environmental pollutants and they can provoke multi-generational impacts due to their pseudo-persistence. However, their multi-generational effects and potential mechanisms remained poorly studied. Presently, effects of enrofloxacin (ENR) were studied on Caenorhabditis elegans with a continuous exposure over 9 generations (from F1 to F9) at an environmentally realistic level. Regarding reproduction, ENR showed stimulation in F1 (1.18-fold of the control) and F2 (1.08), inhibition in F3 (0.70), stimulation in F4 (1.86), F5 (3.18) and F6 (1.53), inhibition in F7 (0.73) and F8 (0.69) and stimulation again in F9 (1.89). That is to say, ENR provoked multi-generational oscillatory effects on the reproduction. Such oscillation was also observed in effects on lifespan with much less magnitudes than those on reproduction. Biochemical assays were performed in F1, F3, F4 and F9 which represented the oscillation over generations. Results showed more antioxidants (e.g., superoxide dismutase and glutathione), mild oxidative stress (e.g., reactive oxygen species) and less oxidative damage (i.e., protein carbonyl) underlying the generation-dependent stimulation. Moreover, ENR provoked multi-generational oscillation on the enzymes that regulate the lipogenesis (e.g., fatty acid synthase and acetyl-CoA carboxylase) and lipolysis (e.g., acyl-CoA synthetase), with similarities to the effects on the oxidative stress and damage. Further analysis on SKN-1 and its activating PMK-1 and GSK-3 demonstrated their involvement in regulating both antioxidant detoxification and lipid metabolism.

Multi- and trans-generational disturbances of perfluorobutane sulfonate and perfluorohexane sulfonate on lipid metabolism in Caenorhabditis elegans

Short-chained perfluorobutane sulfonate (PFBS, four-carbon) and perfluorohexane sulfonate (PFHxS, six-carbon) are widely employed to substitute long-chained per- and poly-fluoroalkyl substances (PFASs). Recent studies showed the potential persistence of PFBS and PFHxS, and also reported their correlation with obesity. However, the long-term outcome and underlying mechanisms remained poorly understood. Presently, the effects of PFBS and PFHxS were studied on C. elegans with multi- and trans-generational experiments. The multi-generational effects were measured in continuous four generational exposure (i.e., F1 to F4). Results showed that PFBS did not stimulate the fat content in F1 but in F4 with continuous but different disturbances on the lipid metabolism and the insulin and insulin-like (IIS) pathway. PFHxS stimulated the fat content in F1 and F4 with similar disturbances on the lipid metabolism and IIS pathway. The trans-generational results showed that the effects of PFBS and PFHxS on the lipid metabolism and IIS pathway were not totally recovered in the offspring of F1 (i.e., T1-T3) and F4 (i.e., T1'-T3') which were not continuously exposed. PFHxS showed a common pattern to up-regulate daf-7 in both multi- and trans-generational effects. The long-term consequences of the short-chained PFASs substitutes should be concerned and epigenetic regulations should be considered in future mechanism studies.

Multi- and trans-generational effects of N-butylpyridium chloride on reproduction, lifespan, and pro/antioxidant status in Caenorhabditis elegans

Ionic liquids (ILs) became emerging pollutants. Their poor degradation and accumulation in organisms urged studies on the long-term effects and also the underlying mechanisms. Currently, 1-butylpyrinium chloride ([bpyr]Cl) was chosen to represent the pyridine-based ILs. Its multi-generational effects were measured on C. elegans for 14 consecutive generations (F1 to F14), and the trans-generational effects were also measured in the great-grand-children (T3 and T3') of F1 and F14. The multi-generational results from F1 to F14 showed that the effects of [bpyr]Cl on the initial and total reproduction and lifespan showed oscillation between inhibition and stimulation. Notably, hormetic effects on reproduction were observed in F7 to F10. The trans-generational effects in T3 and T3' showed different residual consequences between one generational exposure (F1) and multiple generational exposure (F14). Further biochemical analysis showed that the pro/antioxidant status also showed oscillation between inhibition and stimulation. The oscillation levels were greater in superoxide dismutase (SOD), catalase (CAT) and protein carbonyl content (PC) than those in glutathione peroxidase (GSH-Px), reactive oxygen species (ROS) and hydroxyl radical (OH). The pro/antioxidant status contributed to both multi- and trans-generational effects of [bpyr]Cl. Future studies should pay attentions to the long-term influence of ILs and also epigenetic explanations.

Influences of sex, rhythm and generation on the obesogenic potential of erythromycin to Drosophila melanogaster

Antibiotics are gaining attention due to their roles as emerging pollutants and environmental obesogens, yet several aspects between their environmental exposure and obesogenic influence on organisms remain poorly explored. Here, Drosophila melanogaster were exposed to erythromycin (ERY, 0.1 μg/L) for three consecutive generations (F1 to F3). Body weight, circadian rhythm (represented by eclosion timing) and lipid metabolism were measured. ERY increased the size of lipid droplets in larvae of all three generations. It modestly inhibited body weight in adults that abnormally eclosed in the morning (AM adults) in the F1 and F2 generations, and the inhibition was less in adults that eclosed in the afternoon (PM adults). In contrast, it stimulated body weight in F3 adults. Notably, ERY promoted morning eclosion of females. Combining the effects from F1 to F3, acyl-CoA oxidase (ACO) was commonly increased in AM female and male adults and also in PM female ones, while it was commonly decreased in PM male adults. Glucokinase (GCK) was commonly increased in both sexes of AM adults but decreased in PM male adults across generations. The IIS pathway showed a common up-regulation in the AM adults despite some differences between sexes, but it did not show any shared changes in the PM adults with dysrhythmia. The AMPK pathway was involved across generations without particular shared changes. Collectively, the effects of ERY on the key metabolites and enzymes in glucolipid metabolism and the genetic regulations depended on sex, rhythm and exposure generation.

Reproductive toxicities of 1-ethyl-3-methylimidazolium bromide on Caenorhabditis elegans with oscillation between inhibition and stimulation over generations

Ionic liquids (ILs) become emerging pollutants and their toxicities earn increasing attentions. Yet, their effects were seldom explored on reproduction which connects generations and also effects across generations. In the present study, reproductive effects of 1-ethyl-3-methylimidazolium bromide ([C₂mim]Br), one representative IL, were studied on C. elegans with 11 continuously exposed generations (F1 to F11). At 8.20E-5 g/L, the effects on the initial reproduction showed oscillatory changes between stimulation (in F1, F3, F4, F6 and F10) and inhibition (in F2, F5, F7, F8 and F11). At 8.20E-3 g/L, the effects on the reproduction over generations also showed such oscillation despite of different stimulation or inhibition levels, and even opposite influences in F4 and F11. The effects of [C₂mim]Br on the total reproduction also showed the concentration-dependent oscillation between stimulation and inhibition over generations, though they had less alteration frequencies than those on the initial reproduction. Biochemical and molecular indicators were further measured in F1, F4, F7 and F11 to explore potential mechanisms. Results showed that the effects on spermatocyte protein 8 (SPE8) showed positive correlation with those on reproduction while the influences on major sperm protein (MSP) and sperm transmembrane protein 9 (SPE9) showed negative correlation with SPE8. Moreover, the dysregulation on expressions of acs-2 and akt-1 indicated the involvement of glucolipid metabolism. The changes in expressions of set-2, met-2, set-25 and mes-4 demonstrated that the long-term reproductive impacts of [C₂mim]Br over generations also involved histone methylation at H3K4, H3K9 and H3K36, which also connected with the glucolipid metabolism.

Comprehensive phenotyping and multi-omic profiling in the toxicity assessment of nanopolystyrene with different surface properties

There is a growing concern regarding the toxic effects of terrestrial nanoplastic contaminants. However, an all-encompassing phenotyping- and omics-based strategy for the toxicity assessment of nanoplastics with different surface properties on soil living organisms remains to be established. Herein, we devised a comprehensive phenotyping and multi-omic profiling method to examine the molecular disturbance of nanopolystyrene (PS)-exposed Caenorhabditis elegans. The exposure time was 24 h with either 1 μg/mL or 10 μg/mL of PS. We found that PS considerably affected the reproduction and locomotion, as well as increased the oxidative stress of worms regardless of their surface properties. Nevertheless, each type of PS affected the metabolome and lipidome of the nematodes differently. Uncharged PS (PS-N) triggered significant metabolic disturbances, whereas the metabolic influences from PS-NH₂ and PS-COOH were subtle. The dysregulated transcriptome profiles of PS-N were strongly associated with the metabolic pathways. Besides, the altered expression of several genes associated with autophagy and longevity was observed. Collectively, we demonstrated that comprehensive phenotyping and omics-based profiling establish a practical framework that allows us to gain deeper insights into the maladaptive consequences of PS in nematodes. It can be utilized for the evaluation of other environmental contaminants in the terrestrial ecosystem.

Life stage-dependent toxicities of 1-ethyl-3-methylimidazolium bromide on Caenorhabditis elegans

Ionic liquids (ILs) are considered as extracting solvents in soil remediation. However, they can be pollutants themselves, and their own toxicities are of concerns. Notably, organisms were exposed to pollutants at random life stages in actual environmental exposure scenario, which is different from the set-up of one uniform life stage in usual experiment designs. The influence of life stages on ILs toxicities will provide essential information on their actual environmental risks. In the present study, effects of 1-ethyl-3-methylimidazolium bromide ([C₂mim]Br) were measured on C. elegans with egg exposure and adult exposure. In egg exposure, [C₂mim]Br increased the lifespan, stimulated initial reproduction and inhibited the total reproduction. Biochemical indices including oxidative stress, antioxidant responses and oxidative damage were further measured to explore the toxicity mechanisms. Results showed that [C₂mim]Br significantly stimulated O₂^-· as the oxidative stress and superoxide dismutase (SOD) as the antioxidant defense. In adult exposure, [C₂mim]Br inhibited initial reproduction, total reproduction and lifespan. Biochemical results showed that [C₂mim]Br significantly stimulated H₂O₂ and oxidized glutathione (GSSG). The overall findings demonstrated that [C₂mim]Br caused life stage-dependent toxicities on C. elegans. Future studies are still needed for the detailed mechanisms.

Multigenerational effects of perfluorooctanoic acid on lipid metabolism of Caenorhabditis elegans and its potential mechanism

Per-and polyfluoroalkyl substances (PFASs), especially perfluorooctanoic acid (PFOA), have been showed to induce obesogenic effects which may last over generations. However, the underlying mechanisms are not yet clear. In the present study, wild-type N2 Caenorhabditis elegans and the daf-2 mutant were exposed to PFOA for 4 consecutive generations (F0 to F3) at 1.0 ng/L. Effects on fat content and fat metabolism in the directly exposed F0 to F3 generations, the offspring of F0 (T1 to T3) and also those of F3 (T1' to T3'). Results showed that PFOA significantly stimulated the fat contents in F0 (with the percentage of the control as 184.1%), T1 (189.5%), F1 (167.3%), F2 (238.0%), T2' (193.9%) and T3' (159.4%) while inhibited them in T3 (70%). The changes of fat contents over generations were accompanied with significant changes in enzymes facilitating fatty acid synthesis (e.g., acetyl-CoA carboxylase, fatty acid synthase and desaturase, and glycerol phosphate acyltransferase) and those in fatty acid consumption (e.g., acetyl CoA synthetase, fatty acid transport protein, acyl-CoA oxidase and carnitine palmitoyl transferase). Furthermore, RNA-Seq analysis was performed on F0, F3 and T3 generations. Based on the KEGG analysis of differential genes, PFOA exposure affected lipid metabolism signaling pathways including MAPK, fatty acid degradation, TGF-β signaling pathways. Notably, PFOA exposure provoked significantly different effects in daf-2 nematodes on fat contents, lipid metabolizing enzymes and even different signaling pathways. The overall results demonstrated that the obesogenic effects of PFOA were resulted from a complex combination of various enzymes and pathways with essential involvement of insulin signaling pathway.

Trans-generational effect of neurotoxicity and related stress response in Caenorhabditis elegans exposed to tetrabromobisphenol A

Tetrabromobisphenol A (TBBPA), one of the most common brominated flame retardants, has been associated with immunotoxicity, neurotoxicity, and reproductive toxicity. However, little attention has been focused on understanding the trans-generational effects of TBBPA. The present study used the Caenorhabditis elegans (C. elegans) animal model to evaluate the trans-generational effects of neurotoxicity induced by environmentally relevant concentrations of TBBPA (0, 0.1, 1, 10, 100, and 1000 µg/L). Multiple indicators including physiological effects (body length, brood size, head thrashes, body bends, and crawling trajectory), degree of neuronal damage (dopamine, GABAergic, and glutamatergic neurons), oxidative stress-related biochemical indicators (superoxide dismutase [SOD] activity, catalase [CAT] enzyme, malondialdehyde [MDA] production, and reactive oxygen species [ROS] accumulation), and stress-related gene expressions have been evaluated in the exposed parental C. elegans generation (G₁) and their progeny (G₂) under TBBPA-free conditions. The results showed that TBBPA exposure induced adverse effects on physiological endpoints, among which body bends and head thrashes were the most sensitive ones, detected above 1 µg/L in G₁ and 100 µg/L in G₂ nematodes, respectively. After contaminant exposure, the three neurons revealed damage related to neurobehavioral endpoints, with no hereditary effects in the progeny. The oxidative stress-related biochemical endpoints demonstrated that when the exposure concentrations were above 1 µg/L in maternal worms, impairment can be detected in both generations, but the progeny recovered at low toxicity concentration (1-100 µg/L). The integrated target gene expression profiles were clearly altered in G₁ and G₂ worms at concentrations between 1 and 1000 µg/L, and a more significant difference existed in two generations of nematodes at low levels (1-10 µg/L) of TBBPA. Studing trans-generational neurotoxicity and the underlying mechanism can generate a precise evaluation of the environmental risk of TBBPA.