Acute exposure to environmentally relevant concentrations of sucralose disrupts embryonic development and leads to an oxidative stress response in Danio rerio

Vertical distribution and risk assessment of pharmaceuticals and other micropollutants in southern North Sea coastal waters

Pharmaceutical compounds are micropollutants of emerging concern, as well as other classes of chemicals such as UV filters and artificial sweeteners. They enter marine environments via wastewater treatment plants, aquaculture runoff, hospital effluents, and shipping activities. While many studies have investigated the presence and distribution of these pollutants in numerous coastal areas, our study is the first to focus on their occurrence, spatial distribution, and vertical distribution in the sea surface microlayer (SML) and the near-surface layer of marine environments. We analyzed 62 pharmaceutical compounds, one UV filter, and six artificial sweeteners from the SML to the corresponding underlying water (0 cm, 20 cm, 50 cm, 100 cm, and 150 cm) at four stations in the southern North Sea. One station is the enclosed Jade Bay, one is the Weser estuary at Bremerhaven, and the other two stations (NS_7 and NS_8) are in the open German Bight. Jade Bay receives pollutants from surrounding wastewater treatment plants, while the Weser estuary receives pollutants from cities like Bremerhaven, which has dense populations and industrial activities. Concentrations of pharmaceutical compounds were higher in the upper water layers (from the SML to 20 cm). Eleven pharmaceutical compounds (caffeine, carbamazepine, gemfibrozil, ibuprofen, metoprolol, salicylic acid, clarithromycin, novobiocin, clindamycin, trimethoprim, and tylosin) were detected in >95 % of our samples. One UV filter (benzophenone-4) was found in 83 % and three artificial sweeteners (acesulfame, saccharin, and sucralose) in 100 % of all our samples. All artificial sweeteners posed high risks to the freshwater invertebrate Daphnia magna. Understanding the spatial and vertical distribution of pharmaceuticals and other micropollutants in marine environments may be essential in assessing their dispersal and detection in other aquatic environments.

Insight into the evolution of microbial communities and resistance genes induced by sucralose in partial nitrification system with triclosan pre-exposure

Sucralose (SUC), an artificial sweetener widely used in food, beverages and pharmaceuticals, is frequently detected in various environmental matrices. Triclosan (TCS) is commonly used as a disinfectant and often co-exists with SUC in sewage environments. This study investigated the effects of SUC (0.1-10 mg/L) on the transmission of intracellular and extracellular antibiotic resistance genes (ARGs) in the partial nitrification systems with and without TCS pre-exposure. The reactors operated for 150 days, and SUC did not affect ammonia oxidation performance, while TCS led to the maintenance of partial nitrification. The types and abundances of extracellular ARGs in sludge and free ARGs in water increased significantly after TCS pre-exposure when faced SUC stress, which might be caused by a decrease in α-Helix/(β-Sheet + Random coil). SUC was more easily to enrich ARGs in partial nitrification systems with TCS pre-exposure, exacerbating the risk of ARGs transmission. The microbial community showed stronger relationships to cope with the direct stress of SUC, and the functional bacteria (Thauera and Nitrosomonas) in TCS pre-exposure system might be potential hosts of ARGs. This study might provide insights for better understanding the fates of SUC in partial nitrification systems and the ecological risks in wastewater containing TCS and SUC. ENVIRONMENTAL IMPLICATION: Sucralose (SUC) is often detected in the environment and considered as an emerging contaminant due to its soaring consumption and environmental persistence. Triclosan (TCS) is an antibacterial agent that often co-exists with SUC in personal care products and sewage environments. During 150 d, two partial nitrification reactors with and without TCS pre-exposure were established to study the effects of SUC on nitrification performance, antibiotic resistance genes (ARGs) and microbial communities. This study showed the refractory nature of SUC, and SUC led to the transmission of extracellular ARGs in partial nitrification system with TCS pre-exposure, exacerbating the risk of ARGs dissemination.

Health impact assessment after Danio rerio long-term exposure to environmentally relevant concentrations of metformin and guanylurea

The antidiabetic drug metformin (MET) and its metabolite guanylurea (GUA) have been frequently and ubiquitously detected in surface water. Consequently, there has been a consistent rise in studying the toxicity of MET and GUA in fish over the past decade. Nonetheless, it is noteworthy that no study has assessed the harmful effects both compounds might trigger on fish blood and organs after chronic exposure. Taking into consideration the data above, our research strived to accomplish two primary objectives: Firstly, to assess the effect of comparable concentrations of MET and GUA (1, 40, 100 μg/L) on the liver, gills, gut, and brain of Danio rerio after six months of flow-through exposure. Secondly, to compare the outcomes to identify which compound prompts more significant oxidative stress and apoptosis in organs and blood parameter alterations. Herein, findings indicate that both compounds induced oxidative damage and increased the expression of genes associated with apoptosis (bax, bcl2, p53, and casp3). Chronic exposure to MET and GUA also generated fluctuations in glucose, creatinine, phosphorus, liver enzymes, red and white blood count, hemoglobin, and hematocrit levels. The observed biochemical changes indicate that MET and GUA are responsible for inducing hepatic damage in fish, whereas hematological alterations suggest that both compounds cause anemia. Considering GUA altered to a more considerable extent the values of all endpoints compared to the control group, it is suggested transformation product GUA is more toxic than MET. Moreover, based on the above evidence, it can be inferred that a six-month exposure to MET and GUA can impair REDOX status and generate apoptosis in fish, adversely affecting their essential organs' functioning.

Cardiotoxic and neurobehavioral effects of sucralose and acesulfame in Daphnia: Toward understanding ecological impacts of artificial sweeteners

Artificial sweeteners are widely used in food and pharmaceuticals, but their stability and persistence raise concerns about their impact on aquatic life. Although standard toxicity tests do not reveal lethal effects, recent studies suggest a potential neurotoxic mode of action. Using environmentally relevant concentrations, we assessed the effects of sucralose and acesulfame, common sugar substitutes, on Daphnia magna focusing on biochemical (acetylcholinesterase activity; AChE), physiological (heart rate), and behavioural (swimming) endpoints. We found dose-dependent increases in AChE and inhibitory effects on heart rate and behaviour for both substances. Moreover, acesulfame induced a biphasic response in AChE activity, inhibiting it at lower concentrations and stimulating at higher ones. For all endpoints, the EC50 values were lower for acesulfame than for sucralose. Additionally, the relationship between acetylcholinesterase and heart rate differed depending on the substance, suggesting possible differences in the mode of action between sucralose and acesulfame. All observed EC50 values were at μg/l levels, i.e., within the levels reported for wastewater, with adverse effects observed at as low as 0.1 μg acesulfame /l. Our findings emphasise the need to re-evaluate risk assessment thresholds for artificial sweeteners and provide evidence for the neurotoxic effects of artificial sweeteners in the environment, informing international regulatory standards.

Influence of sucralose, acesulfame-k, and their mixture on brain's fish: A study of behavior, oxidative damage, and acetylcholinesterase activity in Daniorerio

Sucralose (SUC) and acesulfame-k (ACE-K) are widely used artificial sweeteners worldwide; however, they are frequently detected in aquatic environments due to their low metabolism and inadequate removal during wastewater treatment. The harmful effects of these compounds on hydrobionts have yet to be fully understood, as data on their toxicity is limited and inconclusive. This research aimed to determine the impact of SUC (50, 75, 125 μg/L) and ACE-K (50, 75, 125 μg/L), individually and in combination, on fish's swimming behavior, acetylcholinesterase activity, and oxidative stress response after four months of exposure. Following exposure, adult Danio rerio displayed anxiety-like behavior, as evidenced by increased freezing time and decreased swimming activity. Additionally, analysis of fish brain tissue revealed a disruption of REDOX homeostasis, leading to oxidative stress, which may be responsible for the observed inhibition of AChE activity. The results indicated that ACE-K was more toxic than SUC, and the mixture of both compounds produced a more detrimental effect than when each compound was administered alone. These findings highlight the hazardous impacts of SUC and ACE-K on fish in environmentally relevant concentrations, suggesting that these compounds should be added to the priority pollutant list.

Long-Term Consumption of Sucralose Induces Hepatic Insulin Resistance through an Extracellular Signal-Regulated Kinase 1/2-Dependent Pathway

Sugar substitutes have been recommended to be used for weight and glycemic control. However, numerous studies indicate that consumption of artificial sweeteners exerts adverse effects on glycemic homeostasis. Although sucralose is among the most extensively utilized sweeteners in food products, the effects and detailed mechanisms of sucralose on insulin sensitivity remain ambiguous. In this study, we found that bolus administration of sucralose by oral gavage enhanced insulin secretion to decrease plasma glucose levels in mice. In addition, mice were randomly allocated into three groups, chow diet, high-fat diet (HFD), and HFD supplemented with sucralose (HFSUC), to investigate the effects of long-term consumption of sucralose on glucose homeostasis. In contrast to the effects of sucralose with bolus administration, the supplement of sucralose augmented HFD-induced insulin resistance and glucose intolerance, determined by glucose and insulin tolerance tests. In addition, we found that administration of extracellular signal-regulated kinase (ERK)-1/2 inhibitor reversed the effects of sucralose on glucose intolerance and insulin resistance in mice. Moreover, blockade of taste receptor type 1 member 3 (T1R3) by lactisole or pretreatment of endoplasmic reticulum stress inhibitors diminished sucralose-induced insulin resistance in HepG2 cells. Taken together, sucralose augmented HFD-induced insulin resistance in mice, and interrupted insulin signals through a T1R3-ERK1/2-dependent pathway in the liver.

Polystyrene microplastics mitigate the embryotoxic damage of metformin and guanylurea in Danio rerio

Microplastics (MPs) alone may endanger the health and fitness of aquatic species through different mechanisms. However, the harmful effects of these when mixed with other emerging contaminants require additional research. Herein, we aimed to determine whether a mixture of MPs with metformin (MET) or guanylurea (GUA) might induce embryotoxicity and oxidative stress in Danio rerio. Upon exposure to mixtures, our results showed MPs reduced the mortality rate of MET and GUA in embryos. Moreover, the severity and the rate of malformations were also decreased in all mixtures with MPs. Concerning oxidative stress, our findings indicated MET, GUA, MPs, and the mixtures increased the levels of lipoperoxidation, hydroperoxide content, and protein carbonyl content in D. rerio larvae. However, the oxidative damage induced in all mixtures was lower than that produced by both drugs alone. Thus, it is likely that the accumulation of MPs avoided the entrance of MET and GUA into the embryos. Once the embryo hatched, MPs did only remain accumulated in the yolk sac of larvae and did not translocate to other organs. Our risk assessment analysis confirmed that MPs shrunk the damage produced by MET and GUA. In a nutshell, MPs mitigate the embryotoxic damage of metformin and guanylurea in D. rerio by blocking their entrance.

Maternal Zearalenone Exposure Affects Gut Microbiota and Follicular Development in Suckled Offspring

Zearalenone (ZEN) is a mycotoxin that is widely present in feed and agricultural products. Studies have demonstrated that ZEN, as a type of estrogen analogue, can significantly affect the female reproductive system. Breast milk is the best nutrient for infant growth and development, but it is still unknown whether ZEN influences the fertility of offspring through suckling. In this study, we collected fecal and ovarian tissue from neonatal female offspring, whose mothers were exposed to ZEN for 21 days, and explored the effects of maternal ZEN exposure on intestinal microecology and follicular development in the mouse using 16S rRNA amplicon sequencing technology. Our findings suggested that maternal ZEN exposure significantly diminished ovarian reserve, increased apoptosis of ovarian granulosa cell (GC), and impacted the developmental competence of oocytes in lactating offspring. In addition, the results of 16S rRNA sequencing showed that the abundance of gut microbiota in offspring was significantly changed, including Bacteroidetes, Proteobacteria, and Firmicutes. This leads to alterations of glutathione metabolism and the expression of antioxidant enzymes in ovaries. In summary, our findings supported a potential relationship between gut microbiota and abnormal ovarian development caused by ZEN, which offers novel insights for therapeutic strategies for reproductive disorders induced by ZEN exposure.