Zebrafish Optogenetic & Optopharmacology : the 1st turnkey system
OptoGluNAM4.1, a negative allosteric modulator (NAM) of metabotropic glutamate receptor 4 (mGlu4) contains a reactive group that covalently binds to the receptor and a blue-light-activated, fast-relaxing azobenzene group that allows reversible receptor activity photocontrol in vitro and in vivo. OptoGluNAM4.1 induces light-dependent behavior in zebrafish and reverses the activity of the mGlu4 agonist LSP4-2022 in a mice model of chronic pain, defining a photopharmacological tool to better elucidate the physiological roles of the mGlu4 receptor in the nervous system.
Tacrine is a small organic compound that was discovered to mimic the functions of the neural cell adhesion molecule L1 by promoting the cognate functions of L1 in vitro, such as neuronal survival, neuronal migration, neurite outgrowth, and myelination. Based on studies indicating that L1 enhances functional recovery in different central and peripheral nervous system disease paradigms of rodents, it deemed interesting to investigate the beneficial role of tacrine in the attractive zebrafish animal model, by evaluating functional recovery after spinal cord injury. To this aim, larval and adult zebrafish were exposed to tacrine treatment after spinal cord injury and monitored for locomotor recovery and axonal regrowth. Tacrine promoted the rapid recovery of locomotor activities in both larval and adult zebrafish, enhanced regrowth of severed axons and myelination, and reduced astrogliosis in the spinal cords. Tacrine treatment upregulated the expression of L1.1 (a homolog of the mammalian recognition molecule L1) and enhanced the L1.1-mediated intracellular signaling cascades in the injured spinal cords. These observations lead to the hope that, in combination with other therapeutic approaches, this old drug may become a useful reagent to ameliorate the deficits resulting from acute and chronic injuries of the mammalian nervous system.
Vitamin E (α-tocopherol, VitE) was discovered in 1922 for its role in preventing embryonic mortality. We investigated the underlying mechanisms causing lethality using targeted metabolomics analyses of zebrafish VitE-deficient embryos over five days of development, which coincided with their increased morbidity and mortality. VitE deficiency resulted in peroxidation of docosahexaenoic acid (DHA), depleting DHA-containing phospholipids, especially phosphatidylcholine, which also caused choline depletion. This increased lipid peroxidation also increased NADPH oxidation, which depleted glucose by shunting it to the pentose phosphate pathway. VitE deficiency was associated with mitochondrial dysfunction with concomitant impairment of energy homeostasis. The observed morbidity and mortality outcomes could be attenuated, but not fully reversed, by glucose injection into VitE-deficient embryos at developmental day one. Thus, embryonic VitE deficiency in vertebrates leads to a metabolic reprogramming that adversely affects methyl donor status and cellular energy homeostasis with lethal outcomes.
Journal of Inorganic Materials
A novel noninvasive yet highly efficient neuromodulation method via photoelectric nanocomposites (NCs) was proposed. The NCs were constructed by Au nanoparticles-attached TiO2 nanocrystals. Upon 405 nm light exposure, the photocurrent was enhanced when the pure TiO2 nanocrystals were modified with Au nanoparticles. It is evidenced that effective depolarization of NCs-treated neurons takes place upon 405 nm light illumination, certified by fluorescent dye test on PC12 cells. Furthermore, the NCs could remarkably remit the epilepsy seizures of zebrafishes, indicating that the NCs are potential candidates for curing neurological disorders.
Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by progressive loss of motor neurons. ALS can be modeled in zebrafish (Danio rerio) through the expression of human ALS-causing genes, such as superoxide dismutase 1 (SOD1). Overexpression of mutated human SOD1 protein causes aberrant branching and shortening of spinal motor axons. Despite this, the functional relevance of this axon morphology remains elusive. Our aim was to determine whether this motor axonopathy is correlated with impaired movement in mutant (MT) SOD1-expressing zebrafish. Transgenic zebrafish embryos that express blue fluorescent protein (mTagBFP) in motor neurons were injected with either wild-type (WT) or MT (A4V) human SOD1 messenger ribonucleic acid (mRNA). At 48 hours post-fertilization, larvae movement (distance traveled during behavioral testing) was examined, followed by quantification of motor axon length. Larvae injected with MT SOD1 mRNA had significantly shorter and more aberrantly branched motor axons (p < 0.002) and traveled a significantly shorter distance during behavioral testing (p < 0.001) when compared with WT SOD1 and noninjected larvae. Furthermore, there was a positive correlation between distance traveled and motor axon length (R2 = 0.357, p < 0.001). These data represent the first correlative investigation of motor axonopathies and impaired movement in SOD1-expressing zebrafish, confirming functional relevance and validating movement as a disease phenotype for the testing of disease treatments for ALS.
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The Faseb Journal
Glycosaminoglycans such as chondroitin sulfate (CS) and dermatan sulfate (DS) are long chains of repeating disaccharide units, covalently linked to core proteins to form proteoglycans. Proteoglycans can be cell membrane–bound or are part of the extracellular matrix. They are important in a wide range of biologic processes, including development, synaptic plasticity, and regeneration after injury, as well as modulation of growth factor signaling, cell migration, survival, and proliferation. Synthesis of CS and DS in the Golgi apparatus is mediated by sulfotransferases that modify sugar chains through transfer of sulfate groups to specific positions on the sugar moieties. To clarify the functions of CS and DS during nervous system regeneration, we studied the effect of chondroitin 4-O-sulfotransferase-1/carbohydrate sulfotransferase-11 (C4ST-1/Chst-11) and dermatan 4-O-sulfotransferase-1/Chst-14 (D4ST-1/Chst-14) down-regulation on spinal cord regeneration in larval and adult zebrafish. In our study, knockdown of C4ST1/Chst-11 accelerated regeneration after spinal cord injury in larval and adult zebrafish and knockdown of D4ST1/Chst-14 did not alter regenerative capacity. From these and previous observations, we drew the conclusion that different CS and DS expression patterns can be growth permitting, growth inhibiting, or neutral for regrowing or sprouting axons, depending on the tissue environment of a particular animal species.—Sahu, S., Li, R., Loers, G., Schachner, M. Knockdown of chondroitin-4-sulfotransferase-1, but not of dermatan-4-sulfotransferase-1, accelerates regeneration of zebrafish after spinal cord injury.
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Concluding remarks :
This dissertation aimed to study the role of genetics in prediction and treatment of chronic postsurgical pain. In view of this, we started genetic screening and provided a genome-wide insight into the genetics of CPSP. This initial step identified the first potential risk loci and candidates for follow up studies. Furthermore, we have shown the important role of genetic variations related to dopaminergic neurotransmission in CPSP and preformed first steps in genetic and pharmacological screening in a zebrafish nociception model. With this dissertation a framework is provided for future studies and a combined and focussed clinical /pre-clinical approach aimed to develop personalized medicine in treatment of CPSP.
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