Development of Zalfermin, a Long-Acting Proteolytically Stabilized FGF21 Analog.

Here, we describe the development of the FGF21 analog zalfermin (NNC0194-0499, 15), intended for once-weekly sc dosing. Protein engineering was needed to address inherent druggability issues of the natural FGF21 hormone. Thus, deamidation of Asp121 was solved by mutation to glutamine, and oxidation of Met168 was solved by mutation to leucine. N-terminal region degradation by dipeptidyl peptidase IV was prevented by alanine residue elongation. To prevent inactivating metabolism by fibroblast activation protein and carboxypeptidase-like activity in the C-terminal region, and to achieve t1/2 extension (53 h in cynomolgus monkeys), we introduced a C18 fatty diacid at the penultimate position 180. The fatty diacid binds albumin in a reversible manner, such that the free fraction of zalfermin potently activates the FGF-receptor complex and retains receptor selectivity compared with FGF21, providing strong efficacy on body weight loss in diet-induced obese mice. Zalfermin is currently being clinically evaluated for the treatment of metabolic dysfunction-associated steatohepatitis.

Monolithic tunable dual-wavelength laser utilizing erbium-doped lithium niobate on an insulator.

We demonstrate a monolithic tunable dual-wavelength laser fabricated on erbium-doped lithium niobate on an insulator (Er:LNOI). The dual-wavelength laser enables independent tuning with a continuously linear electro-optic (EO)-modulated tuning range of 11.875 GHz at a tuning efficiency of 0.63 pm/V. Tunable microwave generation within 50 GHz with a maximum extinction ratio of 35 dB is experimentally demonstrated by further exploring the charge accumulation effect in LNOI. The monolithic design of this work paves the way for microscale integration of laser devices, presenting significant prospects in photonics research and applications.

Progenitor cell isolation from mouse epididymal adipose tissue and sequencing library construction.

Here, we present a protocol to isolate progenitor cells from mouse epididymal visceral adipose tissue and construct bulk RNA and assay for transposase-accessible chromatin with sequencing (ATAC-seq) libraries. We describe steps for adipose tissue collection, cell isolation, and cell staining and sorting. We then detail procedures for both ATAC-seq and RNA sequencing library construction. This protocol can also be applied to other tissues and cell types directly or with minor modifications. For complete details on the use and execution of this protocol, please refer to Liu et al. (2023).1.

A single-cell atlas of bovine skeletal muscle reveals mechanisms regulating intramuscular adipogenesis and fibrogenesis.

BACKGROUND: Intramuscular fat (IMF) and intramuscular connective tissue (IMC) are often seen in human myopathies and are central to beef quality. The mechanisms regulating their accumulation remain poorly understood. Here, we explored the possibility of using beef cattle as a novel model for mechanistic studies of intramuscular adipogenesis and fibrogenesis. METHODS: Skeletal muscle single-cell RNAseq was performed on three cattle breeds, including Wagyu (high IMF), Brahman (abundant IMC but scarce IMF), and Wagyu/Brahman cross. Sophisticated bioinformatics analyses, including clustering analysis, gene set enrichment analyses, gene regulatory network construction, RNA velocity, pseudotime analysis, and cell-cell communication analysis, were performed to elucidate heterogeneities and differentiation processes of individual cell types and differences between cattle breeds. Experiments were conducted to validate the function and specificity of identified key regulatory and marker genes. Integrated analysis with multiple published human and non-human primate datasets was performed to identify common mechanisms. RESULTS: A total of 32 708 cells and 21 clusters were identified, including fibro/adipogenic progenitor (FAP) and other resident and infiltrating cell types. We identified an endomysial adipogenic FAP subpopulation enriched for COL4A1 and CFD (log2FC = 3.19 and 1.92, respectively; P < 0.0001) and a perimysial fibrogenic FAP subpopulation enriched for COL1A1 and POSTN (log2FC = 1.83 and 0.87, respectively; P < 0.0001), both of which were likely derived from an unspecified subpopulation. Further analysis revealed more progressed adipogenic programming of Wagyu FAPs and more advanced fibrogenic programming of Brahman FAPs. Mechanistically, NAB2 drives CFD expression, which in turn promotes adipogenesis. CFD expression in FAPs of young cattle before the onset of intramuscular adipogenesis was predictive of IMF contents in adulthood (R2  = 0.885, P < 0.01). Similar adipogenic and fibrogenic FAPs were identified in humans and monkeys. In aged humans with metabolic syndrome and progressed Duchenne muscular dystrophy (DMD) patients, increased CFD expression was observed (P < 0.05 and P < 0.0001, respectively), which was positively correlated with adipogenic marker expression, including ADIPOQ (R2  = 0.303, P < 0.01; and R2  = 0.348, P < 0.01, respectively). The specificity of Postn/POSTN as a fibrogenic FAP marker was validated using a lineage-tracing mouse line. POSTN expression was elevated in Brahman FAPs (P < 0.0001) and DMD patients (P < 0.01) but not in aged humans. Strong interactions between vascular cells and FAPs were also identified. CONCLUSIONS: Our study demonstrates the feasibility of beef cattle as a model for studying IMF and IMC. We illustrate the FAP programming during intramuscular adipogenesis and fibrogenesis and reveal the reliability of CFD as a predictor and biomarker of IMF accumulation in cattle and humans.

Photolysis and photo-enhanced toxicity of three novel designed neonicotinoids: Impact of novel modifying groups.

Three novel neonicotinoids (cycloxaprid, flupyradifurone and sulfoxaflor) were designed to reduce the biotoxicity for non-target organisms. These neonicotinoids were photolyzed under light radiation, but it was unclear for the photo-enhanced toxicity and influences of the novel modifying group of the three neonicotinoids. The photolysis and photo-enhanced toxicity experiments were performed for the three neonicotinoids, coupled with quantum chemistry calculation, the mechanisms of photolysis, photo-enhanced toxicity and the influences of novel modifying groups were analyzed. The results showed the photolysis pathways were enriched as compared with previous neonicotinoids due to the composition of modifying groups, singlet oxygen and hydroxyl participated the photolysis of cycloxaprid and flupyradifurone. All tested neonicotinoids exhibited photo-enhanced toxicity to Vibrio fischeri. Due to the difference of photolysis mechanism and toxicity to V. fischeri, the photo-enhanced toxicity curves showed diverse variation when histidine, tert-butanol or dissolved organic matters was in presence of the test solutions. The impact of novel modifying groups over photolysis and photo-enhanced toxicity were analyzed based on the comparison with previous neonicotinoids, theoretically predicted UV-Vis spectra and photo-physical/chemical property descriptors. The data showed the composition of novel modifying group increased the light absorption and photo-chemical activities for the three neonicotinoids.

Photolysis mechanism of eleven insecticides under simulated sunlight irradiation: Kinetics, pathway and QSAR.

Insecticides are widely used in crop protection against insects and frequently detected in aquatic environment. Photolysis kinetics are directly related with exposure assessment and risk assessment. However, the photolysis mechanism of neonicotinoid insecticides with different structures has not been studied and compared systematically in the literature. In this paper, the photolysis rate constants in water were determined for eleven insecticides under irradiation of simulated sunlight. At the same time, the photolysis mechanism and effect of dissolved organic matter (DOM) on their photolysis were studied. The results showed that photolysis rates of eleven insecticides vary in a large range. The photolysis rates of nitro-substituted neonicotinoids and butenolide insecticide are much faster than that of cyanoimino-substituted neonicotinoids and sulfoximine insecticide. The ROS scavenging activity assays reveal that direct photolysis dominates the degradation of seven insecticides and, on the other hand, self-sensitized photolysis dominates four insecticides. The shading-effect from DOM can reduce the direct photolysis rates, on the other hand, ROSs generated by triplet-state DOM (3DOM*) can also accelerate photolysis of insecticides. According to the photolytic products identified from HPLC-MS, these eleven insecticides have different photolysis pathways. Six insecticides are degraded from the removal of nitro group from their parent compounds and four insecticides are degraded through ·OH reaction or singlet oxygen (1O2) reaction. QSAR (quantitative structure-activity relationship) analysis showed that photolysis rate was directly related to the energy gap between the highest occupied molecular orbital to the lowest unfilled molecular orbital (Egap = ELUMO-EHOMO) and dipole moment (δ). These two descriptors reflect the chemical stability and reactivity of insecticides. The pathways developed from identified products and the molecular descriptors of QSAR models can well verify the photolysis mechanisms of eleven insecticides.

Relationship between photolysis mechanism and photo-enhanced toxicity to Vibrio Fischeri for neonicotinoids with cyano-amidine and nitroguanidine structures.

Neonicotinoids are widely used pesticides that contaminate aquatic environments. Although these chemicals can be photolyzed under sunlight radiation, it is unclear for the relationship between photolysis mechanism and toxicity change in aquatic organisms. This study aims to determine the photo-enhanced toxicity of four neonicotinoids with different main structures (acetamiprid, and thiacloprid for cyano-amidine structure, imidacloprid and imidaclothiz for nitroguanidine). To Achieve the goal, photolysis kinetics, effect of dissolved organic matter (DOM) and reactive oxygen species (ROSs) scavengers on photolysis rates, photoproducts, and photo-enhanced toxicity to Vibrio fischeri were investigated for four neonicotinoids. The results showed direct photolysis plays a key role in the photo-degradation of imidacloprid and imidaclothiz (photolysis rate constants are 7.85 × 10-3 and 6.48 × 10-3 min-1, respectively), while the photosensitization process of acetamiprid and thiacloprid was dominated by ·OH reactions and transformation (photolysis rate constants are 1.16 × 10-4 and 1.21 × 10-4 min-1, respectively). All four neonicotinoid insecticides exerted photo-enhanced toxicity to Vibrio fischeri, indicating photolytic product(s) posed greater toxicity than their parent compounds. The addition of DOM and ROS scavengers influenced photo-chemical transformation rates of parent compounds and their intermediates, leading to diverse effects on photolysis rates and photo-enhanced toxicity for the four insecticides as a result of different photo-chemical transformation processes. Based upon the detection of chemical structures of intermediates and Gaussian calculations, we observed different photo-enhanced toxicity mechanisms for the four neonicotinoid insecticides. Molecular docking was used to analyze the toxicity mechanism of parent compounds and photolytic products. A theoretical model was subsequently employed to describe the variability of toxicity response to each of the four neonicotinoids.

CircTCF4 Suppresses Proliferation and Differentiation of Goat Skeletal Muscle Satellite Cells Independent from AGO2 Binding.

The proliferation and differentiation of mammalian skeletal muscle satellite cells (MuSCs) are highly complicated. Apart from the regulatory signaling cascade driven by the protein-coding genes, non-coding RNAs such as microRNAs (miRNA) and circular RNAs (circRNAs) play essential roles in this biological process. However, circRNA functions in MuSCs proliferation and differentiation remain largely to be elucidated. Here, we screened for an exonic circTCF4 based on our previous RNA-Seq data, specifically expressed during the development of the longest dorsal muscle in goats. Subsequently, the circular structure and whole sequence of circTCF4 were verified using Sanger sequencing. Besides, circTCF4 was spatiotemporally expressed in multiple tissues from goats but strikingly enriched in muscles. Furthermore, circTCF4 suppressed MuSCs proliferation and differentiation, independent of AGO2 binding. Finally, we conducted Poly(A) RNA-Seq using cells treated with small interfering RNA targeting circTCF4 and found that circTCF4 would affect multiple signaling pathways, including the insulin signaling pathway and AMPK signaling pathway related to muscle differentiation. Our results provide additional solid evidence for circRNA regulating skeletal muscle formation.

Loss of Acta2 in cardiac fibroblasts does not prevent the myofibroblast differentiation or affect the cardiac repair after myocardial infarction.

In response to myocardial infarction (MI), quiescent cardiac fibroblasts differentiate into myofibroblasts mediating tissue repair. One of the most widely accepted markers of myofibroblast differentiation is the expression of Acta2 which encodes smooth muscle alpha-actin (SMαA) that is assembled into stress fibers. However, the requirement of Acta2/SMαA in the myofibroblast differentiation of cardiac fibroblasts and its role in post-MI cardiac repair remained unknown. To answer these questions, we generated a tamoxifen-inducible cardiac fibroblast-specific Acta2 knockout mouse line. Surprisingly, mice that lacked Acta2 in cardiac fibroblasts had a normal post-MI survival rate. Moreover, Acta2 deletion did not affect the function or histology of infarcted hearts. No difference was detected in the proliferation, migration, or contractility between WT and Acta2-null cardiac myofibroblasts. Acta2-null cardiac myofibroblasts had a normal total filamentous actin level and total actin level. Acta2 deletion caused a significant compensatory increase in the transcription level of non-Acta2 actin isoforms, especially Actg2 and Acta1. Moreover, in myofibroblasts, the transcription levels of cytoplasmic actin isoforms were significantly higher than those of muscle actin isoforms. In addition, we found that myocardin-related transcription factor-A is critical for myofibroblast differentiation but is not required for the compensatory effects of non-Acta2 isoforms. In conclusion, the Acta2 deletion does not prevent the myofibroblast differentiation of cardiac fibroblasts or affect the post-MI cardiac repair, and the increased expression and stress fiber formation of non-SMαA actin isoforms and the functional redundancy between actin isoforms are able to compensate for the loss of Acta2 in cardiac myofibroblasts.

Maternal L-carnitine supplementation promotes brown adipose tissue thermogenesis of newborn goats after cold exposure.

Brown adipose tissue (BAT) is an important component of energy expenditure and necessary to maintain body temperature for newborn mammals. In the previous study, we found that L-carnitine was enriched in BAT and promoted BAT adipogenesis and thermogenesis in goat brown adipocytes. However, whether dietary L-carnitine regulates BAT heat production and energy expenditure in lambs remains unclear. In this study, maternal L-carnitine supplementation elevated the rectal temperature, as well as the expression of UCP1 and mitochondrial DNA content to promote BAT thermogenesis in newborn goats. Moreover, maternal L-carnitine supplementation increased the levels of triglycerides (TG), non-esterified fatty acids (NEFA), and lactate in plasma, as well as the content of lipid droplet and glycogen in BAT of newborn goats. Lipidomic analysis showed that maternal L-carnitine supplementation remodeled the lipid composition of BAT in newborn goats. L-carnitine significantly increased the levels of TG and diglyceride (DG) and decreased the levels of glycerophospholipids and sphingolipids in BAT. Further studies showed that L-carnitine promoted TG and glycogen deposition in brown adipocytes through AMPKα. Our results indicate that maternal L-carnitine supplementation promotes BAT development and thermogenesis in newborn goats and provides new evidence for newborn goats to maintain body temperature in response to cold exposure.

Investigating mitochondria-immune responses in zebrafish, Danio rerio (Hamilton, 1822): A case study with the herbicide dinoseb.

The dinitrophenol herbicide dinoseb is an uncoupler of mitochondrial oxidative phosphorylation (OXPHOS). Studies in fish demonstrate impaired OXPHOS is associated with altered immune system responses and locomotor activity in fish. The objective of this study was to determine the effect of dinoseb on zebrafish (Danio rerio) during early stages of development. We measured oxygen consumption rates of embryos, transcripts related to OXPHOS, growth, and the immune system (cytokines and immune-signaling transcripts), and locomotor activity. We hypothesized that OXPHOS of fish would be impaired in vivo, leading to altered basal immune system expression and locomotor activity. Oxidative respiration assessments in embryos revealed that dinoseb decreased both mean basal respiration and oligomycin-induced ATP-linked respiration. Expression levels of cytochrome c oxidase complex IV, 3-hydroxyacyl-COA dehydrogenase and superoxide dismutase 1 were decreased in larvae following exposure to dinoseb while succinate dehydrogenase complex flavoprotein subunit A, insulin growth factor 1 (igf1) and igf2a mRNA were increased in abundance. Immune-related transcripts chemokine (C-X-C motif) ligand 1 and matrix metallopeptidase 9 (MMP-9) were decreased in expression levels while toll-like receptor 5a and 5b were increased in expression. In addition, a visual motor response test was conducted on both 6 and 7 dpf larvae to determine if dinoseb impaired locomotor activity. Dinoseb decreased locomotor activity in 7 dpf larvae but not 6 dpf. This study improves knowledge of toxicity mechanisms for dinoseb in early stages of fish development and demonstrates that mitochondrial toxicants may disrupt immune signaling in zebrafish.

Preparation, toxicity reduction and radiation therapy application of gold nanorods.

Gold nanorods (GNRs) have a broad application prospect in biomedical fields because of their unique properties and controllable surface modification. The element aurum (Au) with high atomic number (high-Z) render GNRs ideal radiosensitive materials for radiation therapy and computed tomography (CT) imaging. Besides, GNRs have the capability of efficiently converting light energy to heat in the near-infrared (NIR) region for photothermal therapy. Although there are more and more researches on GNRs for radiation therapy, how to improve their biocompatibility and how to efficiently utilize them for radiation therapy should be further studied. This review will focuse on the research progress regarding the preparation and toxicity reduction of GNRs, as well as GNRs-mediated radiation therapy.

Identification of IGF2BP1-related lncRNA-miRNA-mRNA network in goat skeletal muscle satellite cells.

Insulin-like growth factor 2 mRNA-binding protein 1 (IGF2BP1) plays essential roles in the proliferation of skeletal muscle satellite cells (MuSCs). Increasing evidence has shown that IGF2BP1 regulates the expression of noncoding RNAs and mRNAs. However, the related molecular network remains to be fully understood. Therefore, we performed RNA sequencing and analyzed the microRNAs (miRNAs), long noncoding RNAs (lncRNAs), and mRNAs differentially expressed in goat MuSCs treated with IGF2BP1 overexpressing and empty vectors. A total of 36 miRNAs, 59 lncRNAs, and 44 mRNAs were differentially expressed caused by IGF2BP1. Expectedly, they were enriched in muscle development-related Rap1, PI3K-AKT, and FoxO signaling pathways. Finally, we constructed a lncRNA-miRNA-mRNA interaction network containing 30 lncRNAs, 15 miRNAs, and 34 mRNAs, in which several miRNAs, including miR-133a-3p, miR-204-5p, miR-125a-3p, miR-145-3p, and miR-423-5p, relate with cell growth and participate in muscle development. Overall, we constructed an IGF2BP1-related network, which provides new insight into the myogenic proliferation of goat.

Integrated application of metabolomics and RNA-seq reveals thermogenic regulation in goat brown adipose tissues.

Brown adipose tissue (BAT) plays an important role on no shivering thermogenesis during cold exposure to maintain animal body temperature and energy homeostasis. However, knowledge of the cellular transition from white adipose tissue (WAT) to BAT is still limited. In this study, we provided a comprehensive metabolomics and transcriptional signatures of goat BAT and WAT. A total of 157 metabolites were significantly changed, including 81 upregulated and 76 downregulated metabolites. In addition, we identified the citric acid cycle, fatty acid elongation, and degradation pathways as coordinately activated in BAT. Interestingly, five unsaturated fatty acids (Eicosadienoic Acid, C20:2; γ-Linolenic acid, C20:3; Arachidonic Acid, C20:4; Adrenic acid, C22:4; Docosahexaenoic acid, C22:6), Succinate, L-carnitine, and L-palmitoyl-carnitine were found to be abundant in BAT. Furthermore, L-carnitine, an intermediate of fatty acid degradation, is required for goat brown adipocyte differentiation and thermogenesis through activating AMPK pathway. However, L-carnitine decreased lipid accumulation through inducing lipolysis and thermogenesis in white adipocytes. These results revealed that there are the significant alterations in transcriptomic and metabolomic profiles between goat WAT and BAT, which may contribute to better understanding the roles of metabolites in BAT thermogenesis process.

Dynamic Expression Profiles of Circular RNAs during Brown to White Adipose Tissue Transformation in Goats (Capra hircus).

Adipose tissues are mainly divided into brown adipose tissue (BAT) and white adipose tissue (WAT). WAT mainly functions to buffer excess calories, whereas BAT plays a role in the non-shivering thermogenesis to maintain body temperature and energy balance. Moreover, circRNAs play important roles in various biological processes. However, knowledge of the expression profile and function of circRNAs from BAT to WAT remains largely unknown. In this study, a total of 6610 unique circRNAs were identified in the perirenal adipose tissues of 1-day, 30-days, and 1-year goats. Functional annotation revealed that host genes of circRNAs were involved in some BAT-related pathways, such as the thyroid hormone signaling pathway, MAPK signaling pathway, and VEGF signaling pathway. Furthermore, a total of 61 DEcircRNAs were detected across three stages. Additionally, five selected circRNAs were validated by RNase R assay, qPCR, and Sanger sequencing. Finally, the circRNA-miRNA network was constructed between the DEcircRNAs and their miRNA binding sites.

CircRNA-Protein Interactions in Muscle Development and Diseases.

Circular RNA (circRNA) is a kind of novel endogenous noncoding RNA formed through back-splicing of mRNA precursor. The biogenesis, degradation, nucleus-cytoplasm transport, location, and even translation of circRNA are controlled by RNA-binding proteins (RBPs). Therefore, circRNAs and the chaperoned RBPs play critical roles in biological functions that significantly contribute to normal animal development and disease. In this review, we systematically characterize the possible molecular mechanism of circRNA-protein interactions, summarize the latest research on circRNA-protein interactions in muscle development and myocardial disease, and discuss the future application of circRNA in treating muscle diseases. Finally, we provide several valid prediction methods and experimental verification approaches. Our review reveals the significance of circRNAs and their protein chaperones and provides a reference for further study in this field.

Using RNA-Seq to Identify Reference Genes of the Transition from Brown to White Adipose Tissue in Goats.

Brown adipose tissues have unique non-shivering thermogenesis functions, can be found in newborn ruminate animals, and then are gradually replaced by white adipose tissues in adulthood. For the purpose of exploring the intrinsic mechanism underlying the conversion process from brown (BAT) to white adipose tissue (WAT), it is necessary to utilize Quantitative PCR (qPCR) to study gene expression profiling. In this study, we identified reference genes that were consistently expressed during the transformation from goat BAT to WAT using RNA-seq data. Then, twelve genes were evaluated as candidate reference genes for qPCR in goat perirenal adipose tissue using three tools (geNorm, Normfinder, and BestKeeper). In addition, the selected reference genes were used to normalize the gene expression of PGC-1α and GPAT4. It was found that traditional reference genes, such as GAPDH, RPLP0, HPRT1, and PPIA were not suitable for target gene normalization. In contrast, CTNNB, PFDN5, and EIF3M, selected from RNA sequencing data, showed the least variation and were recommended as the best reference genes during the transformation from BAT to WAT.

Recent advances in optical aptasensor technology for amplification strategies in cancer diagnostics.

Aptamers are chemically synthetic single-stranded DNA or RNA molecules selected by molecular evolution. They have been widely used as attractive tools in biosensing and bioimaging because they can bind to a large variety of targets with high sensitivity and high affinity and specificity. As recognition elements, aptamers contribute in particular to cancer diagnostics by recognizing different cancer biomarkers, while they can also facilitate ultrasensitive detection by further employing signal amplification elements. Optical techniques have been widely used for direct and real-time monitoring of cancer-related biomolecules and bioprocesses due to the high sensitivity, quick response, and simple operation, which has greatly benefited cancer diagnostics. In this review, we highlight recent advances in optical platform-based sensing strategies for cancer diagnostics aided by aptamers. Limitations and current challenges are also discussed.

Assessing the toxicity of the benzamide fungicide zoxamide in zebrafish (Danio rerio): Towards an adverse outcome pathway for beta-tubulin inhibitors.

Commercial benzamide fungicides are applied to crops to control damage caused by oomycete fungi and are used as veterinary pharmaceuticals in aquaculture. The mechanism of action of these fungicides is to induce mitotic arrest via binding to beta-tubulin, thus inhibiting tubulin polymerization. However, there are little toxicity data available for benzimidazole fungicides in fish. To address this knowledge gap, we conducted zebrafish embryo toxicity tests to assess deformities, survival, and sub-lethal responses following exposure to zoxamide (0, 0.5, 1.0, 2.5, 5.0 and 10 µM zoxamide). We hypothesized that skeletal deformities would be prevalent in zebrafish due to its mechanism of inhibiting beta-tubulin polymerization. Zoxamide was relatively toxic to zebrafish embryos and larvae, and survival was reduced ∼50 % at 2 days post fertilization (dpf) with 10 µM exposure and over time at 6 dpf, 2.5 µM exposure reduced survival by ∼20 %. Frequency of hatch was also reduced/delayed in zebrafish at 3 dpf with >2.5 µM zoxamide. Pericardial edema, body length shortening, and spine curvature were observed in larvae exposed to >5 µM. Mitochondrial bioenergetics were assessed in ∼30 hpf embryos (24-hour exposure) using an XFe24 Flux Analyzer and regression analysis revealed a negative relationship between basal respiration and zoxamide concentration. Superoxide dismutase 1 and caspase 3 mRNA levels were both decreased in 6 dpf larvae exposed to 2.5 µM zoxamide, but were not changed in expression at 0.5 nor 1 µM zoxamide. Continuous 6-day exposure to zoxamide reduced larval activity at 2.5 µM; conversely a 24-hour exposure (at 5-6 dpf) induced hyperactivity at 5 µM suggesting dose and time dependent effects on fish behavior. Based on sub-lethal endpoints, we conceptualize an adverse outcome pathway for chemicals that inhibit tubulin polymerization.

Investigation into the sub-lethal effects of the triazole fungicide triticonazole in zebrafish (Danio rerio) embryos/larvae.

Global use of azole fungicides is expected to increase over the next several years. Triticonazole is a triazole fungicide that is used for turf protection, residential, and other commercial applications. As such, it can enter local rural and urban water systems via run-off and rain events. Early life stages of aquatic organisms can be susceptible to pesticides that enter the water, but in the case of triticonazole, data on the potential for subacute toxicity are lacking. Here, we determined the effects of triticonazole on development, oxygen consumption rates, and locomotor activity in zebrafish to address this knowledge gap. Wild-type zebrafish (ABTu strain) embryos and larvae were exposed to triticonazole (1-100 µM) in early development for different lengths of time depending on the assay conducted. Triticonazole did not affect survival nor induce significant deformity (pericardial edema, skeletal defects) in zebrafish at doses up to 100 µM. Oxygen consumption rate was measured in embryos after 24 and 48 hour exposure to triticonazole beginning at ∼6 hpf using the XFe flux analyzer. Triticonazole did not affect basal respiration, oligomycin-induced ATP linked respiration, FCCP-induced maximum respiration, proton leak, spare capacity, nor non-mitochondrial respiration at doses up to 100 µM for 24 hours, even for exposure up to 250 µM for 48 hours. To determine whether the fungicide affected larval swimming activity, the visual motor response test was conducted following triticonazole exposure for 6 days. Larval zebrafish exposed to triticonazole showed hypoactivity in the dark following a 100 µM treatment, suggesting that the fungicide can affect the locomotor activity of zebrafish, albeit at relatively high levels. Given the fact that sublethal biological responses were absent at lower environmentally relevant concentrations, we conclude that triticonazole, relative to other triazole fungicides and types of pesticides, exhibits a relatively low risk of toxicity to the early life stages of fish.