Effects of microplastic exposure on the early developmental period and circadian rhythm of zebrafish (Danio rerio): A comparative study of polylactic acid and polyglycolic acid

Polyglycolic acid (PGA) is an emerging biodegradable plastic material. Together with polylactic acid (PLA), PGA is considered a suitable alternative to conventional plastics and has been widely used in biomedical and food packaging industries. However, degradable plastics continue to face the drawbacks of harsh degradation environment and long degradation time, and may harm the environment and the human body. Therefore, our study focused on assessing the effects of degradable microplastics PGA and PLA on the development and neurobehavior of zebrafish. The results showed that PGA and PLA had little effect on 3–10 hpf embryos. However, developmental stunting was observed in a100 mg/L PGA and PLA-exposed group at 24 hpf. In addition, PGA and PLA exposure decreased the survival and hatching rates, increased wakefulness, and reduced sleep in zebrafish. This indicates that PGA and PLA may affect the circadian behavior of zebrafish by affecting the brain–derived neurotrophic factor (BDNF). Therefore, our results suggest that PGA and PLA exposure induces developmental toxicity, reduces voluntary locomotion, induces of anxiety–like behaviors, and impairs sleep/wake behaviors in zebrafish larvae. This also suggests that the potentially toxic effects of degradable plastics cannot be ignored and that the biological effects of PGA require further research

Cardiotoxicity of Zebrafish Induced by 6-Benzylaminopurine Exposure and Its Mechanism

6-BA is a common plant growth regulator, but its safety has not been conclusive. The heart is one of the most important organs of living organisms, and the cardiogenesis process of zebrafish is similar to that of humans. Therefore, based on wild-type and transgenic zebrafish, we explored the development of zebrafish heart under 6-BA exposure and its mechanism. We found that 6-BA affected larval cardiogenesis, inducing defective expression of key genes for cardiac development (myl7, vmhc, and myh6) and AVC differentiation (bmp4, tbx2b, and notch1b), ultimately leading to weakened cardiac function (heart rate, diastolic speed, systolic speed). Acridine orange staining showed that the degree of apoptosis in zebrafish hearts was significantly increased under 6-BA, and the expression of cell-cycle-related genes was also changed. In addition, HPA axis assays revealed abnormally expressed mRNA levels of genes and significantly increased cortisol contents, which was also consistent with the observed anxiety behavior in zebrafish at 3 dpf. Transcriptional abnormalities of pro- and anti-inflammatory factors in immune signaling pathways were also detected in qPCR experiments. Collectively, we found that 6-BA induced cardiotoxicity in zebrafish, which may be related to altered HPA axis activity and the onset of inflammatory responses under 6-BA treatment

Curvature of Buckybowl Corannulene Enhances Its Binding to Proteins

Corannulene, a polycyclic aromatic hydrocarbon, has garnered much attention on account of its promising applications in high-performance electronics. Investigations of its potential biological applications have, however, remained hitherto scarce. In the present contribution, to explain the distinctive interaction of the geodesic corannulene with proteins, the adducts formed by lysozyme (LSZ) and two carbon materials, namely, corannulene:LSZ and perylene:LSZ, were prepared and investigated using a variety of experimental and computational approaches. We find that LSZ binds the two ligands at its active site, forming stable complexes. Interestingly, although corannulene and perylene have very similar structures, standard binding free-energy calculations demonstrate that the former possesses a much greater binding affinity for LSZ compared with the latter, which can be ascribed to its three-dimensional π-bowl curvature and unique charge distribution, enhancing its electrostatic interaction with LSZ. Corannulene is found to be more effective than perylene in inhibiting the protein activity. In addition, corannulene hardly affects the fluorescence of LSZ. The present work indicates that endowed with a curved π-surface and large dipole moment, corannulene is a promising ligand, capable of binding a broad range of proteins through a variety of intermolecular interactions, modulating their biological or catalytic activity, yet not affecting their fluorescent properties

A novel model of demyelination and remyelination in a GFP-transgenic zebrafish

Demyelinating diseases consist of a variety of autoimmune conditions in which the myelin sheath is damaged due to genetic and/or environmental factors. During clinical treatment, some patients undergo partial remyelination, especially during the early disease stages. However, the mechanisms that regulate demyelination remain unclear. The myelin structure, myelin formation and myelin-related gene expression are highly conserved between mammals and zebrafish. Therefore, the zebrafish is an ideal model organism to study myelination. In this study, we generated a transgenic zebrafish Tg(mbp:nfsB-egfp) expressing a fusion protein composed of enhanced green fluorescent protein (EGFP) and NTR from the myelin basic protein (mbp) promoter. Tg(mbp:nfsB-egfp) expressed NTR-EGFP reproducibly and hereditarily in oligodendrocytes along the spinal cord. Treatment of zebrafish larvae Tg(mbp:nfsB-egfp) with metronidazole (Mtz) resulted in the selective ablation of oligodendrocytes and led to demyelination, accompanied by behavioral changes, including decreased total movement distance, velocity, total movement time and fast movement time. After withdrawal of Mtz for a seven day recovery period, the expression of EGFP and MBP protein was observed again which indicates remyelination. Additionally, locomotor capacity was restored. Collectively, Tg(mbp:nfsB-egfp), a heritable and stable transgenic line, provides a novel, powerful tool to study the mechanisms of demyelination and remyelination

Adsorption Behavior of Hydrophobin Proteins on Polydimethylsiloxane Substrates

The design of a bioactive surface with appropriate wettability for effective protein immobilization has attracted much attention. Previous experiments showed that the adsorption of hydrophobic protein HFBI onto a polydimethylsiloxane (PDMS) substrate surface can reverse the inherent hydrophobicity of the surface, hence making it suitable for immobilization of a secondary protein. In this study, atomistic molecular dynamics simulations have been conducted to elucidate the adsorption mechanism of HFBI on the PDMS substrate in an aqueous environment. Nine independent simulations starting from three representative initial orientations of HFBI toward the solid surface were performed, resulting in different adsorption modes. The main secondary structures of the protein in each mode are found to be preserved in the entire course of adsorption due to the four disulfide bonds. The relative binding free energies of the different adsorption modes were calculated, showing that the mode, in which the binding residues of HFBI fully come from its hydrophobic patch, is most energetically favored. In this favorable binding mode, the hydrophilic region of HFBI is fully exposed to water, leading to a high hydrophilicity of the modified PDMS surface, consistent with experiments. Furthermore, a set of residues consisting of Leu12, Leu24, Leu26, Ile27, Ala66, and Leu68 were found to play an important role in the adsorption of HFBI on different hydrophobic substrates, irrespective of the structural features of the substrates

Alcohol exposure leads to unrecoverable cardiovascular defects along with edema and motor function changes in developing zebrafish larvae

Maternal alcohol consumption during pregnancy can cause a series of developmental disorders in the fetus called FAS (fetal alcohol syndrome). In the present study we exposed zebrafish embryos to 1% and 2% alcohol and observed the morphology of heart and blood vessels during and after exposure to investigate motor function alterations, and damage and recovery to the cardiovascular system. The results showed that alcohol exposure could induce heart deformation, slower heart rate, and incomplete blood vessels and pericardium. After stopping exposure, larvae exposed to 1% alcohol could recover only in heart morphology, but larvae in 2% alcohol could not recover either morphology or function of cardiovascular system. The edema-like characteristics in the 2% alcohol group became more conspicuous afterwards, with destruction in the dorsal aorta, coarctation in segmental arteries and a decrease in motor function, implying more serious unrecoverable cardiovascular defects in the 2% group. The damaged blood vessels in the 2% alcohol group resulted in an alteration in permeability and a decrease of blood volume, which were the causes of edema in pathology. These findings contribute towards a better understanding of ethanol-induced cardiovascular abnormalities and co-syndrome in patients with FAS, and warns against excessive maternal alcohol consumption during pregnancy

Fabrication of mesoporous silica-coated CNTs and application in size-selective protein separation

In this study, we report a simple method to coat mesoporous silica onto carbon nanotubes (CNTs) via a two-step procedure. Mesoporous CNTs@SiO(2) composites have been obtained by extracting cetyltrimethylammonium bromide (CTAB) via an ion-exchange procedure after silica-coated carbon nanotubes were synthesized with the aid of the cationic surfactant CTAB. The coating process was explicitly investigated, and a possible formation mechanism of the mesoporous CNTs@SiO(2) was proposed, which reveals that the ratio of CTAB/CNTs plays a critical role in the coating process. Furthermore, the pore size of the as-prepared mesoporous silica could be exactly controlled by using different amounts of the bromide surfactant CTAB. The obtained mesoporous CNTs@SiO(2) composite nanomaterial was evaluated with three typical proteins, cytochrome c (Cyt c), bovine serum albumin (BSA) and lysozyme (Lyz), with different molecular sizes. The adsorption and desorption of binary mixtures of Cyt c and BSA, Cyt c and Lyz, and a ternary mixture of Cyt c, BSA and Lyz showed that the mesoporous CNTs@SiO(2) are effective and highly selective adsorbents for Cyt c. The as-prepared mesoporous CNTs@SiO(2) composites have shown effective performance in size-selective adsorption of biomacromolecules, demonstrating great potential in biomacromolecular separation

Reversal of reserpine-induced depression and cognitive disorder in zebrafish by sertraline and Traditional Chinese Medicine (TCM)

Abstract Background With increased social pressure, individuals face a high risk of depression. Subsequently, depression affects cognitive behaviour and negatively impacts daily life. Fortunately, the Traditional Chinese Medicine Jia Wei Xiao Yao (JWXY) capsule is effective in reducing depression and improving cognitive behaviour. Methods The constituents of JWXY capsule were identified by ultra-performance liquid chromatography and quadrupole time-of-flight mass spectrometry analyses. We analysed behaviours of depression-like zebrafish in the novel tank with an automatic 3D video-tracking system and conducted the colour preference test, as well detected physiological changes after sertraline and JWXY capsule treatments. Results Both sertraline and JWXY capsule rescued the decreased locomotive behaviour and depression phenotype of zebrafish caused by reserpine. JWXY capsule especially improved the inhibited exploratory behaviour caused by reserpine. In addition, with the onset of depressive behaviour, zebrafish exhibited alterations in cognitive behaviour as indicated by colour preference changes. However, compared with sertraline, JWXY capsule was more efficaciously in rescuing this change in the colour preference pattern. Moreover, an increased level of cortisol, increased expression of tyrosine hydroxylase (TH) and decreased monoamine neurotransmitters, including serotonin (5-HT) and noradrenaline, were involved in the depressive behaviours. In addition, sertraline and JWXY capsule rescued the depressive phenotype and cognitive behaviour of zebrafish by altering the levels of endogenous cortisol and monoamine neurotransmitters. Conclusions JWXY capsule was more effectively than sertraline in rescuing reserpine-induced depression and cognitive disorder in zebrafish. Potentially, our study can provide new insights into the clinical treatment of depression and the mechanism of action of JWXY capsule

Exploring the Toxicity of a Bismuth–Asparagine Coordination Polymer on the Early Development of Zebrafish Embryos

Nanoparticles are widely used in nanomedicine, raising concerns about their toxicity. In this study, the toxicity of bismuth–asparagine coordination polymer spheres (BACP-2) was assessed in zebrafish embryos. Injection of 1–4 cell stage embryos with BACP-2 resulted in smaller head size (particularly smaller eye size), shorter body length, and pericardial edemas. The severity and occurrence of the resulting phenotype were concentration-dependent. The expression of genes such as <i>krox20</i>, orthodenticle homeobox 2 (<i>otx2</i>), and cardiac myosin light chain-2 (<i>cmlc2</i>) indicates that the effects of BACP-2 on the head and heart were related to changes in gene expression patterns. A delay in epiboly was observed, and the expression levels of the no tail (<i>ntl</i>) gene indicated that the delay in epiboly resulted both from the effect of BACP-2 on cell migration during epiboly and from slow growth. These findings indicate that BACP-2 exhibits concentration-dependent developmental toxicity, providing insight into the nanotoxicity of bismuth derivatives, which must be rigorously evaluated with respect to toxicity before their application in nanomedicine