The influence of the zebrafish genetic background on Parkinson's disease-related aspects

Mitochondrial Complex I Reversible S-Nitrosation Improves Bioenergetics and Is Protective in Parkinson's Disease

AIMS

This study was designed to explore the neuroprotective potential of inorganic nitrite as a new therapeutic avenue in Parkinson's disease (PD).

RESULTS

Administration of inorganic nitrite ameliorates neuropathology in phylogenetically distinct animal models of PD. Beneficial effects are not confined to prophylactic treatment and also occur if nitrite is administered when the pathogenic cascade is already active. Mechanistically, the effect is mediated by both complex I S-nitrosation, which under nitrite administration is favored over formation of other forms of oxidation, and down-stream activation of the antioxidant Nrf2 pathway. Nitrite also rescues respiratory reserve capacity and increases proton leakage in LRRK2 PD patients' dermal fibroblasts.

INNOVATION

The study proposes an unprecedented approach based on the administration of the nitrosonium donor nitrite to contrast complex I and redox anomalies in PD. Dysfunctional mitochondrial complex I propagates oxidative stress in PD, and treatments mitigating this defect may, therefore, limit disease progression. Therapeutic complex I targeting has been successfully achieved in ischemia/reperfusion by using nitrosonium donors such as nitrite to reversibly modify its subunits and protect from oxidative damage after reperfusion. This evidence led to the innovative hypothesis that nitrite could exert protective effects also in pathological conditions where complex I dysfunction occurs in normoxia, such as in PD.

CONCLUSIONS

Overall, these results demonstrate that administration of inorganic nitrite improves mitochondrial function in PD, and it, therefore, represents an amenable intervention to hamper disease progression. Antioxid. Redox Signal. 28, 44-61.

Understanding taurine CNS activity using alternative zebrafish models

Taurine is a highly abundant "amino acid" in the brain. Despite the potential neuroactive role of taurine in vertebrates has long been recognized, the underlying molecular mechanisms related to its pleiotropic effects in the brain remain poorly understood. Due to the genetic tractability, rich behavioral repertoire, neurochemical conservation, and small size, the zebrafish (Danio rerio) has emerged as a powerful candidate for neuropsychopharmacology investigation and in vivo drug screening. Here, we summarize the main physiological roles of taurine in mammals, including neuromodulation, osmoregulation, membrane stabilization, and antioxidant action. In this context, we also highlight how zebrafish models of brain disorders may present interesting approaches to assess molecular mechanisms underlying positive effects of taurine in the brain. Finally, we outline recent advances in zebrafish drug screening that significantly improve neuropsychiatric translational researches and small molecule screens.

Complex molecular changes induced by chronic progestogens exposure in roach, Rutilus rutilus

In our previous study, we measured 0.23-13.67ng/L progestogens (progesterone, drospirenone, levonorgestrel) in natural waters in the catchment area of the largest shallow lake of Central Europe, Lake Balaton. Progestogen contaminations act as potent steroids with mixed progestagenic, androgenic and mild estrogenic effects that is why our aim was to investigate the morphological and molecular effects of mixture of progesterone, drospirenone, and levonorgestrel in environmentally relevant (10ng/L) and higher (50 and 500ng/L) exposure concentrations in common roach, Rutilus rutilus. Steroids (e.g. progestogens) and the protein deglycase DJ-1 chaperon molecule aim the same target molecules in cells, therefore, we hypothesized that a relationship may exist between progestogens and DJ-1. Furthermore, our other aim was to follow the changes of signal molecules of different biological function due to progestogen treatment in serum and brain. Adult roaches were exposed to 10, 50 and 500ng/L of mixture of progestogen for 42 days and their somatic indices (brain-somatic, liver-somatic, gonadosomatic and kidney-somatic) were measured. Vitellogenin (VTG) expression (estrogen effect) or inhibition (androgen effect) in fish is a widely used biomarker so we measured its changes in liver by ELISA. To determine the quantity and to map the spatial distribution of DJ-1 chaperon protein the brain and liver tissues were analyzed by ELISA and immunohistochemistry. Furthermore, we also studied molecular alterations: a) in the serum by measuring cholesterol, low-density lipoprotein (LDL), high-density lipoprotein (HDL) and triglyceride concentrations and b) in brain homogenate using a cell stress array kit (26 protein). The somatic index of liver and kidney significantly in all the treated groups, whereas the gonadosomatic index of 500ng/L treated group showed significant decrease compared to control animals. VTG level increased significantly in 500ng/L progestogen treated group. Since the concentration of DJ-1 significantly increased in brain and liver in all progestogen treatment groups, the DJ-1 protein could be able to a more sensitive marker than VTG. Serum LDL and cholesterol levels of exposed fish were significantly decreased. DJ-1 was mediated through the stimulation of the expression of LDL-receptor which facilitates reuptake subsequently. In summary, our observations unfolded new data about molecular alterations induced by the combined action of environmental progestogens. In addition, the DJ-1 chaperon protein as a possible biomarker helped to trace the abiotic chemical environmental contaminations, like progestogens in the freshwater ecosystems.

Oxidative stress and regulation of Pink1 in zebrafish (Danio rerio)

Oxidative stress-mediated neuronal dysfunction is characteristic of several neurodegenerative disorders, including Parkinson's disease (PD). The enzyme tyrosine hydroxylase (TH) catalyzes the formation of L-DOPA, the rate-limiting step in the biosynthesis of dopamine. A lack of dopamine in the striatum is the most characteristic feature of PD, and the cause of the most dominant symptoms. Loss of function mutations in the PTEN-induced putative kinase (PINK1) gene cause autosomal recessive PD. This study explored the basic mechanisms underlying the involvement of pink1 in oxidative stress-mediated PD pathology using zebrafish as a tool. We generated a transgenic line, Tg(pink1:EGFP), and used it to study the effect of oxidative stress (exposure to H2O2) on pink1 expression. GFP expression was enhanced throughout the brain of zebrafish larvae subjected to oxidative stress. In addition to a widespread increase in pink1 mRNA expression, mild oxidative stress induced a clear decline in tyrosine hydroxylase 2 (th2), but not tyrosine hydroxylase 1 (th1) expression, in the brain of wild-type larvae. The drug L-Glutathione Reduced (LGR) has been associated with anti-oxidative and possible neuroprotective properties. Administration of LGR normalized the increased fluorescence intensity indicating pink1 transgene expression and endogenous pink1 mRNA expression in larvae subjected to oxidative stress by H2O2. In the pink1 morpholino oliogonucleotide-injected larvae, the reduction in the expression of th1 and th2 was partially rescued by LGR. The pink1 gene is a sensitive marker of oxidative stress in zebrafish, and LGR effectively normalizes the consequences of mild oxidative stress, suggesting that the neuroprotective effects of pink1 and LGR may be significant and useful in drug development.

Rapid cohort generation and analysis of disease spectrum of large animal model of cone dystrophy

Large animal models are an important resource for the understanding of human disease and for evaluating the applicability of new therapies to human patients. For many diseases, such as cone dystrophy, research effort is hampered by the lack of such models. Lentiviral transgenesis is a methodology broadly applicable to animals from many different species. When conjugated to the expression of a dominant mutant protein, this technology offers an attractive approach to generate new large animal models in a heterogeneous background. We adopted this strategy to mimic the phenotype diversity encounter in humans and generate a cohort of pigs for cone dystrophy by expressing a dominant mutant allele of the guanylate cyclase 2D (GUCY2D) gene. Sixty percent of the piglets were transgenic, with mutant GUCY2D mRNA detected in the retina of all animals tested. Functional impairment of vision was observed among the transgenic pigs at 3 months of age, with a follow-up at 1 year indicating a subsequent slower progression of phenotype. Abnormal retina morphology, notably among the cone photoreceptor cell population, was observed exclusively amongst the transgenic animals. Of particular note, these transgenic animals were characterized by a range in the severity of the phenotype, reflecting the human clinical situation. We demonstrate that a transgenic approach using lentiviral vectors offers a powerful tool for large animal model development. Not only is the efficiency of transgenesis higher than conventional transgenic methodology but this technique also produces a heterogeneous cohort of transgenic animals that mimics the genetic variation encountered in human patients.

Feed and feeding regime affect growth rate and gonadosomatic index of adult zebrafish (Danio rerio)

A 5-week study was conducted to evaluate commercially available Artemia, Ziegler zebrafish diet, and Calamac diet fed in five different feeding regimes on the growth and reproductive development of 7-month-old zebrafish. Zebrafish were fed to satiation three times daily during the normal work week and twice daily during the weekend and holidays. Zebrafish in dietary groups CCC (Calamac three times daily) and CCA (Calamac twice daily, Artemia once daily) had a significantly (p<0.05) greater weight gain and specific growth rate as compared to all other dietary groups. Male zebrafish in dietary group 5 had significantly larger gonadosomatic index (GSI) values than all other groups, while female zebrafish in dietary group CCC had significantly larger GSI values than all other groups. No differences in the fatty acid content of female gonads were detected. Zebrafish fed solely Artemia had the greatest weight loss and lowest GSI values. Preliminary evidence of protein sparing in zebrafish is reported. Collectively, this study sheds more light into the effects of the use of commercially available feeds and feeding regime on the rearing of zebrafish.

Invertebrate models of dystonia

The neurological movement disorder dystonia is an umbrella term for a heterogeneous group of related conditions where at least 20 monogenic forms have been identified. Despite the substantial advances resulting from the identification of these loci, the function of many DYT gene products remains unclear. Comparative genomics using simple animal models to examine the evolutionarily conserved functional relationships with monogenic dystonias represents a rapid route toward a comprehensive understanding of these movement disorders. Current studies using the invertebrate animal models Caenorhabditis elegans and Drosophila melanogaster are uncovering cellular functions and mechanisms associated with mutant forms of the well-conserved gene products corresponding to DYT1, DYT5a, DYT5b, and DYT12 dystonias. Here we review recent findings from the invertebrate literature pertaining to molecular mechanisms of these gene products, torsinA, GTP cyclohydrolase I, tyrosine hydroxylase, and the alpha subunit of Na+/K ATPase, respectively. In each study, the application of powerful genetic tools developed over decades of intensive work with both of these invertebrate systems has led to mechanistic insights into these human disorders. These models are particularly amenable to large-scale genetic screens for modifiers or additional alleles, which are bolstering our understanding of the molecular functions associated with these gene products. Moreover, the use of invertebrate models for the evaluation of DYT genetic loci and their genetic interaction networks has predictive value and can provide a path forward for therapeutic intervention.