Cadmium (Cd) is a major contaminant in natural environments and exerts adverse effects on aquatic biota at low concentrations. Gill is as vital respiratory organ and may cause pollutants to enter fish during gas exchange. Baicalein (BAI), as a kind of flavonoids, possess antioxidant properties through inactivating free radicals. To confirm the potential effects and approaches of BAI addition in maintaining the gill stability, 90 common carps (Cyprinus carpio L.) were selected and randomly divided into water environment exposure group (0.22 mg/L Cd) and/or feed added with 0.10 g/kg BAI for 30 days. The analysis of ion content in serum showed that Cd exposure disturbed ion homeostasis, and BAI could reduce serum Cd concentration. The histopathological results of gills showed that Cd exposure caused gill tissue lesions and structural damage, and BAI feeding effectively alleviated this damage. In addition, BAI could enhance antioxidant activity and activate Nrf2/HO-1 axis, thereby reducing oxidative stress and endoplasmic reticulum (ER) stress. Moreover, BAI lightened cytokine imbalance, inflam-matory response, and necroptosis. Overall, the results indicated that BAI feeding could maintain gill homeostasis against Cd poisoning via the ROS/ER stress signaling. This trial revealed the properties of BAI resistance to metal Cd in aquaculture and partially elucidated its mechanism.

The current global status of freshwater resources and deterioration of water quality in general have led to limitations on the scope of freshwater aquaculture. The development of technology that would enable aquaculture under saline-alkaline conditions would be valuable. Therefore, the exploration is needed to understand the damage mechanism of saline-alkaline water, particularly the impact of alkalinity, on fish and shellfish. In this study, Chinese mitten crabs (Eriocheir sinensis) were subjected to different concentrations of carbonate alkalinity (0.00, 4.38, 8.75, 17.50, and 35.00 mmol/L) for 96 h. The survival rates in the 17.50 and 35.00 mmol/L alkalinity groups showed a significant decrease compared to the control group and the groups exposed to lower carbonate alkalinity concentrations (4.38 and 8.75 mmol/L). The exposure to carbonate alkalinity had a significant inhibitory effect on the ammonia excretion rate and led to an increase of ammonia content in hemolymph. However, in contrast to the low carbonate alkalinity exposure groups (4.38 and 8.75 mmol/L), the high carbonate alkalinity exposure group (35.00 mmol/L) exhibited a significant reduction in the concentrations of ammonia and urea nitrogen in hemolymph. Moreover, high carbonate alkalinity exposure was found to induce oxidative stress, as indicated by increased levels of reactive oxygen species (ROS) and malondialdehyde. Additionally, there were notable alterations observed in the activities of antioxidant enzymes such as superoxide dismutase, catalase, and glutathione. Flow cytometry analysis and ultrastructural observations revealed that exposure to carbonate alkalinity can induce apoptosis. In the 8.75, 17.50, and 35.00 mmol/L alkalinity groups, the activation of p38 and JNK pathways was observed, along with an increase in the Bax/Bcl-2 ratio and the expression of caspase 3. In summary, the findings of this study suggested that exposure to carbonate alkalinity can disrupt ammonia metabolism, leading to apoptosis through the activation of the ROS/MAPK signaling pathway. This ultimately results in a decrease in the survival rate of crabs. These results provide valuable insights into the toxicological effects of high carbonate alkalinity exposure and shed light on the tolerance mechanisms of high carbonate alkalinity exposure in crabs.

Chlorpyrifos (CPF) has caused large-scale pollution worldwide and posed a threat to non-target organisms. Baicalein (BAI) is a flavonoid extract with anti-oxidant and anti-inflammatory activities. The gills are the mucosal immune organ and the first physical barrier of fish. However, it is not clear whether BAI counteracts organophosphorus pesticide CPF exposure-caused gill damage. Therefore, we established the CPF exposure and BAI intervention models by adding 23.2 μg/L CPF in water and/or 0.15 g/kg BAI in feed for 30 days. The results showed that CPF exposure could cause gill histopathology lesions. Moreover, CPF exposure led to endoplasmic reticulum (ER) stress, caused oxidative stress and Nrf2 pathway activation, and triggered NF-κB-mediated inflammation reaction and necroptosis in carp gills. BAI adding effectively relieved the pathological changes, and lighten inflammation and necroptosis involving in the elF2α/ATF4 and ATF6 pathways through binding to GRP78 protein. Moreover, BAI could ease oxidative stress, but did not affect Nrf2 pathway in carp gills under CPF exposure. These results suggested that BAI feeding could alleviate necroptosis and inflammation against chlorpyrifos toxicity through elF2α/ATF4 and ATF6 axis. The results partially explained the poisoning effect of CPF, and showed BAI could be act as an antidote for organophosphorus pesticides.

The high-order three-dimensional (3D) organization of regulatory genomic elements provides a topological basis for gene regulation, but it remains unclear how multiple regulatory elements across the mammalian genome interact within an individual cell. To address this, herein, we developed scNanoHi-C, which applies Nanopore long-read sequencing to explore genome-wide proximal high-order chromatin contacts within individual cells. We show that scNanoHi-C can reliably and effectively profile 3D chromatin structures and distinguish structure subtypes among individual cells. This method could also be used to detect genomic variations, including copy-number variations and structural variations, as well as to scaffold the de novo assembly of single-cell genomes. Notably, our results suggest that extensive high-order chromatin structures exist in active chromatin regions across the genome, and multiway interactions between enhancers and their target promoters were systematically identified within individual cells. Altogether, scNanoHi-C offers new opportunities to investigate high-order 3D genome structures at the single-cell level.

Imidacloprid (IMI), a systemic neonicotinoid insecticide widely used in agriculture, resulting in persistence in aquatic environments that threaten the survival of organisms. Eucalyptol (EUC), a monoterpenoid found in plants, can be applied to medicine, food, and aquaculture. However, the potential protective effects of EUC on cell damage under neonicotinoid pesticide toxicity, and the role of ER stress and its mediated apoptosis and necroptosis in it, remain unclear. Therefore, we treated Ctenopharyngodon idellus kidney (CIK) cells with 20 mg/L IMI and 20 μM EUC for 48 h. The results showed that IMI exposure caused a higher GRP78 levels, activated ATF6, PERK-eIF2α and IRE1-XBP1 pathways, led to the decline of ATPase activities and ATP content, induced the expression of cytokine (TNF-α, IL-1β, IL-6 and INF-γ), triggered BCL2/BAX-mediated apoptosis and RIP1/RIP3/MLKL-dependent necroptosis in the CIK cell line. Surprisingly, EUC had an effect against IMI-induced cytotoxicity, showing that it effectively mitigated the above-mentioned IMI-exposure-induced changes. Taken together, these results suggested that EUC could alleviated IMI-induced cell death and dysimmunity by recovering ER stress/mitochondria imbalance. These results partly explained the mechanism of biological threat on fish under IMI exposure and the potential application value of EUC in aquaculture.

Acetochlor is a high-volume herbicide whose widespread use threatens ecosystems and affects aquaculture. Apoptosis and autophagy are important causes of hepatotoxicity caused by toxicants, which can be mediated by oxidative stress and the inhibition of PPAR/RXR pathway. However, the mechanism of acetochlor on fish hepatocyte damage still needs to be further investigated. Therefore, we treated the Ctenopharyngodon idella hepatic cell line (L8824 cells) with different concentrations (10, 20, and 40 μM) of acetochlor and/or ROS scavenger NAC (1 mM) for 24 h. The results showed that acetochlor decreased the cell viability in a dose-dependent manner. AO/EB staining and flow cytometry verified the increased apoptotic rates. Quantitative analysis of gene expression levels or protein expression levels displayed that the expression levels of Beclin1, P62, LC3B, BAX, and cleaved Casp3 were increased, and the expression of BCL2 was reduced. Besides, we detected the increased ROS contents and decreased PPAR/RXR pathway expressions after acetochlor treatment. The clearance of ROS alleviated the inhibition of the PPAR/RXR pathway and lightened apoptosis and autophagy under acetochlor stress. Overall, these results revealed that acetochlor exposure triggered BCL2/BAX/Casp3-cascaded apoptosis and Beclin1-dependent autophagy through ROS-mediated PPAR/RXR inhibition. The results partially explain the toxicological mechanism of acetochlor and provide targets for the development of its antidote.

Yeast culture (YC), as a member of probiotics family is a natural product produced from yeast fermentation, affects of improving immunity. However, the intestine and liver injury and immunosuppression mechanism caused by SBA in fish are unclear and more functions of YC supplement in the diet need to be developed. Soybean agglutinin (SBA) is an anti-nutritional factor in soybean and leads to growth-inhibitory effect in feeding of the high proportion of soybean meal replacing fish meal (FM). Therefore, one hundred and thirty-five Pseudobagrus ussuriensis (6.5 ± 0.27 g) were randomly selected and divided into three groups (Control, SBA and YC+SBA groups). For the model, fish were fed with 2% YC for 8 weeks and then given intragastric administration of 0.2-mL SBA solution for 20 days. The results showed that SBA damaged the immune and antioxidant capacity, causing an inflammatory reaction, leading to abnormal expression of cytokines in the intestine and liver of Pseudobagrus ussuriensis. YC could effectively attenuate intestinal and liver damage and downregulate the TLR2/MyD88/NF-κB signaling pathway and suppress oxidative stress in Pseudobagrus ussuriensis. Besides, YC had obvious immune advantage, which could improve the immune ability. In summary, these results showed that YC could reduce immunosuppression and intestinal-liver injury by inhibiting the TLR2/MyD88/NF-κB signal pathway and oxidative stress induced by SBA. This study provided some explanations for the problems of fish diet caused by anti-nutritional factors from soybean meal and provided a theoretical basis for the function development of YC in aquaculture.

An 8-week feeding trial was conducted to determine dietary lysine requirement of juvenile Pseudobagrus ussuriensis (initial body weight: 0.60 g). Six isonitrogenous (crude protein, 400 g/kg) and isolipidic (crude lipid, 50 g/kg) diets were formulated to contain graded levels of dietary lysine (12.8, 19.9, 26.5, 34.0, 40.8 and 44.1 g/kg dry diets, respectively). The results indicated that weight gain, specific growth rate, productive protein value and protein efficiency ratio increased, while feed conversion ratio decreased with increasing dietary lysine level up to 34.0 g/kg dry diet and then levelled off. Fish fed diet with 12.8 g/kg lysine had the lowest lysine content (58.6 g/kg dry matter) in muscle, while fish fed diet with 34.0 g/kg lysine had the highest value (61.6 g/kg dry matter; p < .05). Broken-line analysis on the basis of weight gain showed that the optimal dietary lysine requirement for maximum growth of juvenile Pseudobagras ussuriensis is 33.5 g/kg dry diet (82.4 g/kg dietary protein). Quadratic regression analysis of protein efficiency ratio against dietary lysine levels indicated that the optimal dietary lysine requirement of juvenile Pseudobagras ussuriensis is 36.4 g/kg dry diet (89.5 g/kg dietary protein).