Nanoparticles with biomedical applications should be evaluated for their biocompatibility. Rare-earth doped nanoparticles with unique spectral properties are superior in vivo optical probes in comparison with quantum dots and organic dyes, however, studies describing their nano-bio interactions are still limited. Here, we have evaluated the nano-bio interactions of green-synthesized, phase-pure BaF(2) nanoparticles doped with rare-earth (RE(3+) = Ce(3+)/Tb(3+)) ions using larval zebrafish. We found that zebrafish can tolerate a wide concentration range of these nanoparticles, as the maximal lethality was observed at very high concentrations (more than 200 mg L(-1)) upon five days of continuous exposure. At a concentration of 10 mg L(-1), at which Zn(2+), Ti(4+) and Ag(+) nanoparticles are reported to be lethal to developing zebrafish, continuous exposure to our nanoparticles for four days produced no developmental anomalies, craniofacial defects, cardiac toxicity or behavioural abnormalities in the developing zebrafish larvae. We have also found that the doping of rare-earth ions has no major effect on these biomarkers. Interestingly, the function of acetylcholinesterase (AChE) and the cellular metabolic activity of whole zebrafish larvae remained unchanged, even during continuous exposure to these nanoparticles at 150 mg L(-1) for four days; however, severe developmental toxicities were evident at this high concentration. Based on these results, we can conclude that the biocompatibility of rare-earth doped nanoparticles is concentration dependent. Not all biomarkers are sensitive to these nanoparticles. The high concentration-dependent toxicity occurs through a mechanism distinct from changes in the metabolic or AChE activity. The significance of these findings lies in using these nanoparticles for bioimaging applications and biomarker studies, especially for prolonged exposure times.
The widespread use of triclosan in personal care products as an antimicrobial agent is leading to its alarming tissue-bioaccumulation including human brain. However, knowledge of its potential effects on the vertebrate nervous system is still limited. Here, we hypothesized that sublethal triclosan concentrations are potent enough to alter motor neuron structure and function in zebrafish embryos exposed for prolonged duration. In this study, zebrafish embryos were used as vertebrate-animal model. Prolonged exposure (up to 4 days) of 0.6 mg/L (LC50, 96 h) and 0.3 mg/L (
Title: Triclosan alters adult zebrafish behavior and targets acetylcholinesterase activity and expression Pullaguri N, Nema S, Bhargava Y, Bhargava A Ref: Environ Toxicol Pharmacol, 75:103311, 2019 : PubMed
Triclosan is widely used in consumer products as an antimicrobial agent. Epidemiological studies have reported the association of triclosan with adverse birth outcomes. The toxic effects of triclosan on the developing stages of zebrafish are reported, however, its role as behavioral modifier is limited. In the present study, adult zebrafish were exposed to triclosan (0.3 and 0.6 mg/L) for 48 h and the exploratory behavior was analyzed using ZebraTrack. Triclosan exposed group showed significantly reduced locomotion concomitant with increased freezing duration. They also showed erratic movements suggesting that triclosan induced anxiety-like behavior in adult zebrafish. Next, we tested the hypothesis that the anxiety-like behavior is linked to altered acetylcholinesterase activity. We found that the triclosan exposure decreased acetylcholinesterase activity in the brain and skeletal muscle but acetylcholinesterase (ache) gene was significantly down-regulated only in the skeletal muscle of the adult zebrafish exposed to triclosan. In addition, we also observed a down-regulation of myelin basic protein (mbp) gene in the skeletal muscle of adult zebrafish treated with triclosan. Thus, our data indicates that even short exposure of triclosan is potent enough to induce behavioral anomalies in adult zebrafish that appear to involve acetylcholinesterase and other structural proteins especially in the skeletal muscle.
Title: Allosteric nature of P2X receptor activation probed by photoaffinity labelling Bhargava Y, Rettinger J, Mourot A Ref: British Journal of Pharmacology, 167:1301, 2012 : PubMed
BACKGROUND AND PURPOSE: In P2X receptors, agonist binding at the interface between neighbouring subunits is efficiently transduced to ion channel gating. However, the relationship between binding and gating is difficult to study because agonists continuously bind and unbind. Here, we covalently incorporated agonists in the binding pocket of P2X receptors and examined how binding site occupancy affects the ability of the channel to gate. EXPERIMENTAL APPROACH: We used a strategy for tethering agonists to their ATP-binding pocket, while simultaneously probing ion channel gating using electrophysiology. The agonist 2',3'-O-(4-benzoylbenzoyl)-ATP (BzATP), a photoaffinity analogue of ATP, enabled us to trap rat homomeric P2X2 receptor and a P2X2/1 receptor chimera in different agonist-bound states. UV light was used to control the degree of covalent occupancy of the receptors. KEY RESULTS: Irradiation of the P2X2/1 receptor chimera - BzATP complex resulted in a persistent current that lasted even after extensive washout, consistent with photochemical tethering of the agonist BzATP and trapping of the receptors in an open state. Partial labelling with BzATP primed subsequent agonist binding and modulated gating efficiency for both full and partial agonists. CONCLUSIONS AND IMPLICATIONS: Our photolabelling strategy provides new molecular insights into the activation mechanism of the P2X receptor. We show here that priming with full agonist molecules leads to an increase in gating efficiency after subsequent agonist binding.
