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

Dynamic impacts of short-term bath administration of enrofloxacin on juvenile black seabream Acanthopagrus schlegelii

Dynamic impacts of short-term enrofloxacin (ENR) exposure on juvenile marine fish are not well understood, and the underlying mechanisms remain unclear. We therefore investigated the accumulation and elimination of ENR in the liver of juvenile black seabream Acanthopagrus schlegelii. Meanwhile, the dynamic alterations of biochemical parameters and liver transcriptomes after short-term bath immersion and withdrawal treatment were explored. The results indicated that the contents of ENR in the liver were significantly increased after bath administration for 24 h, and then quickly declined to very low concentrations along with the decontamination time increasing. Judging from the changes in biochemical indicators and liver transcriptomic alterations, 0.5 and 1 mg/L ENR exposure for 24 h triggered oxidative stress, impairment of immune system, as well as aberrant lipid metabolism via differential molecular pathways. Interestingly, biochemical and transcriptome analysis as well as integrated biomarker response (IBR) values showed that more significant changes appeared in 1 mg/L ENR group at decontamination periods, which indicated that the impact of high dose ENR on juvenile A. schlegelii may persist even after depuration for 7 days. These results revealed that the risk of short-term bath of 1 mg/L ENR should not be overlooked even after depuration period. Therefore, attention should be paid to the dosage control when administering the drug to juvenile A. schlegelii, and the restoration of physiological disturbance may be an important factor in formulating a reasonable treatment plan.

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.

Influence of dietary status on the obesogenic effects of erythromycin antibiotic on Caenorhabditis elegans

As emerging pollutants, antibiotics were widely detected in water bodies and dietary sources. Recently, their obesogenic effects raised serious concerns. So far, it remained unclear whether their obesogenic effects would be influenced by water- and diet-borne exposure routes. In present study, Caenorhabditis elegans, nematodes free-living in air-water interface and feeding on bacteria, were exposed to water- and diet-borne erythromycin antibiotic (ERY). The statuses of the bacterial food, inactivated or alive, were also considered to explore their influences on the effects. Results showed that both water- and diet-borne ERY significantly stimulated body width and triglyceride contents. Moreover, diet-borne ERY's stimulation on the triglyceride levels was greater with alive bacteria than with inactivated bacteria. Biochemical analysis showed that water-borne ERY inhibited the activities of enzymes like adipose triglyceride lipase (ATGL) in fatty acid β-oxidation. Meanwhile, diet-borne ERY inhibited the activities of acyl-CoA synthetase (ACS) and carnitine palmitoyl transferase (CPT) in lipolysis, while it stimulated the activities of fatty acid synthase (FAS) in lipogenesis. Gene expression analysis demonstrated that water-borne ERY with alive bacteria significantly upregulated the expressions of daf-2, daf-16 and nhr-49, without significant influences in other settings. Further investigation demonstrated that ERY interfered with bacterial colonization in the intestine and the permeability of the intestinal barrier. Moreover, ERY decreased total long-chained fatty acids (LCFAs) in bacteria and nematodes, while it decreased total short-chained fatty acids (SCFAs) in bacteria but increased them in nematodes. Collectively, the present study demonstrated the differences between water- and diet-borne ERY's obesogenic effects, and highlighted the involvement of insulin and nhr-49 signaling pathways, SCFAs metabolism and also the interaction between intestinal bacteria and the host.

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.

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.

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.

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.

Metastatic effects of environmental carcinogens mediated by MAPK and UPR pathways with an in vivo Drosophila Model

Metastasis includes tumor invasion and migration and underlies over 90% of cancer mortality. The metastatic effects of environmental carcinogens raised serious health concerns. However, the underlying mechanisms remained poorly studied. In the present study, an in vivo Ras^V12/lgl^-/- model of the fruitfly, Drosophila melanogaster, with an 8-day exposure was employed to explore the metastatic effects of 3,3',4,4',5-pentachlorobiphenyl (PCB126), perfluorooctanoic acid (PFOA) and cadmium chloride (CdCl₂). At 1.0 mg/L, PCB126, PFOA, and CdCl₂ significantly increased tumor invasion rates by 1.32-, 1.33-, and 1.29-fold of the control, respectively. They also decreased the larval body weight and locomotion behavior. Moreover, they commonly disturbed the expression levels of target genes in MAPK and UPR pathways, and their metastatic effects were significantly abolished by the addition of p38 inhibitor (SB203580), JNK inhibitor (SP600125) and IRE1 inhibitor (KIRA6). Notably, the addition of the IRE inhibitor significantly influenced sna/E-cad pathway which is essential in both p38 and JNK regulations. The results demonstrated an essential role of sna/E-cad in connecting the effects of carcinogens on UPR and MAPK regulations and the resultant metastasis.

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.

Hormesis induced by silver iodide, hydrocarbons, microplastics, pesticides, and pharmaceuticals: Implications for agroforestry ecosystems health

Increasing amounts of silver iodide (AgI) in the environment are expected because of the recent massive expansion of weather modification programs. Concurrently, pharmaceuticals, microplastics, hydrocarbons, and pesticides in terrestrial ecosystems continue contaminating forests and agroforests. Our review supports that AgI induces hormesis, a biphasic dose response characterized by often beneficial low-dose responses and toxic high-dose effects, which adds to the evidence for pharmaceuticals, microplastics, hydrocarbons, and pesticides induced hormesis in numerous species. Doses smaller than the no-observed-adverse-effect-level (NOAEL) positively affect defense physiology, growth, biomass, yields, survival, lifespan, and reproduction. They also lead to negative or undesirable outcomes, including stimulation of pathogenic microbes, pest insects, and weeds with enhanced resistance to drugs and potential negative multi- or trans-generational effects. Such sub-NOAEL effects perplex terrestrial ecosystems managements and may compromise combating outbreaks of disease vectors that can threaten not only forest and agroforestry health but also sensitive human subpopulations living in remote forested areas.

Obesity III: Obesogen assays: Limitations, strengths, and new directions

There is increasing evidence of a role for environmental contaminants in disrupting metabolic health in both humans and animals. Despite a growing need for well-understood models for evaluating adipogenic and potential obesogenic contaminants, there has been a reliance on decades-old in vitro models that have not been appropriately managed by cell line providers. There has been a quick rise in available in vitro models in the last ten years, including commercial availability of human mesenchymal stem cell and preadipocyte models; these models require more comprehensive validation but demonstrate real promise in improved translation to human metabolic health. There is also progress in developing three-dimensional and co-culture techniques that allow for the interrogation of a more physiologically relevant state. While diverse rodent models exist for evaluating putative obesogenic and/or adipogenic chemicals in a physiologically relevant context, increasing capabilities have been identified for alternative model organisms such as Drosophila, C. elegans, zebrafish, and medaka in metabolic health testing. These models have several appreciable advantages, including most notably their size, rapid development, large brood sizes, and ease of high-resolution lipid accumulation imaging throughout the organisms. They are anticipated to expand the capabilities of metabolic health research, particularly when coupled with emerging obesogen evaluation techniques as described herein.

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.

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.