Abstract
The laboratory zebrafish (Danio rerio) is now an accepted model in toxicologic research. The zebrafish model fills a niche between in vitro models and mammalian biomedical models. The ...developmental characteristics of the small fish are strategically being used by scientists to study topics ranging from high-throughput toxicity screens to toxicity in multi- and transgenerational studies. High-throughput technology has increased the utility of zebrafish embryonic toxicity assays in screening of chemicals and drugs for toxicity or effect. Additionally, advances in behavioral characterization and experimental methodology allow for observation of recognizable phenotypic changes after xenobiotic exposure. Future directions in zebrafish research are predicted to take advantage of CRISPR-Cas9 genome editing methods in creating models of disease and interrogating mechanisms of action with fluorescent reporters or tagged proteins. Zebrafish can also model developmental origins of health and disease and multi- and transgenerational toxicity. The zebrafish has many advantages as a toxicologic model and new methodologies and areas of study continue to expand the usefulness and application of the zebrafish.
Use of Zebrafish in Drug Discovery Toxicology Cassar, Steven; Adatto, Isaac; Freeman, Jennifer L ...
Chemical research in toxicology,
01/2020, Letnik:
33, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Unpredicted human safety events in clinical trials for new drugs are costly in terms of human health and money. The drug discovery industry attempts to minimize those events with diligent preclinical ...safety testing. Current standard practices are good at preventing toxic compounds from being tested in the clinic; however, false negative preclinical toxicity results are still a reality. Continual improvement must be pursued in the preclinical realm. Higher-quality therapies can be brought forward with more information about potential toxicities and associated mechanisms. The zebrafish model is a bridge between in vitro assays and mammalian in vivo studies. This model is powerful in its breadth of application and tractability for research. In the past two decades, our understanding of disease biology and drug toxicity has grown significantly owing to thousands of studies on this tiny vertebrate. This Review summarizes challenges and strengths of the model, discusses the 3Rs value that it can deliver, highlights translatable and untranslatable biology, and brings together reports from recent studies with zebrafish focusing on new drug discovery toxicology.
The zebrafish (
) is routinely used in biological studies as a vertebrate model system that provides unique strengths allowing applications in studies of neurodevelopmental and neurodegenerative ...diseases. One specific advantage is that the neurotransmitter systems are highly conserved throughout vertebrate evolution, including between zebrafish and humans. Disruption of the dopaminergic signaling pathway is linked to multiple neurological disorders. One of the most common is Parkinson's disease, a neurodegenerative disease associated with the loss of dopaminergic neurons, among other neuropathological characteristics. In this review, the development of the zebrafish's dopaminergic system, focusing on genetic control of the dopaminergic system, is detailed. Second, neurotoxicant models used to study dopaminergic neuronal loss, including 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), the pesticides paraquat and rotenone, and 6-hydroxydopamine (6-OHDA), are described. Next, zebrafish genetic knockdown models of
,
, and
established for investigating mechanisms of Parkinson's disease are discussed. Chemical modulators of the dopaminergic system are also highlighted to showcase the applicability of the zebrafish to identify mechanisms and treatments for neurodegenerative diseases such as Parkinson's disease associated with the dopaminergic system.
The therapeutic success of interventions targeting glucokinase (GK) activation for the treatment of type 2 diabetes has been limited by hypoglycemia, steatohepatitis, and loss of efficacy over time. ...The clinical characteristics of patients with GK-activating mutations or GK regulatory protein (GKRP) loss-of-function mutations suggest that a hepatoselective GK activator (GKA) that does not activate GK in β cells or affect the GK-GKRP interaction may reduce hyperglycemia in patients with type 2 diabetes while limiting hypoglycemia and liver-associated adverse effects. Here, we review the rationale for TTP399, an oral hepatoselective GKA, and its progression from preclinical to clinical development, with an emphasis on the results of a randomized, double-blind, placebo- and active-controlled phase 2 study of TTP399 in patients with type 2 diabetes. In this 6-month study, TTP399 (800 mg/day) was associated with a clinically significant and sustained reduction in glycated hemoglobin, with a placebo-subtracted least squares mean HbA
change from baseline of -0.9% (
< 0.01). Compared to placebo, TTP399 (800 mg/day) also increased high-density lipoprotein cholesterol (3.2 mg/dl;
< 0.05), decreased fasting plasma glucagon (-20 pg/ml;
< 0.05), and decreased weight in patients weighing ≥100 kg (-3.4 kg;
< 0.05). TTP399 did not cause hypoglycemia, had no detrimental effect on plasma lipids or liver enzymes, and did not increase blood pressure, highlighting the importance of tissue selectivity and preservation of physiological regulation when targeting key metabolic regulators such as GK.
Iconic as a novelist and popular cultural figure, Zora Neale Hurston remains underappreciated as an anthropologist. Is it inevitable that Hurston's literary authority should eclipse her ...anthropological authority? If not, what socio-cultural and institutional values and processes shape the different ways we read her work? Jennifer L. Freeman Marshall considers the polar receptions to Hurston's two areas of achievement by examining the critical response to her work across both fields. Drawing on a wide range of readings, Freeman Marshall explores Hurston's popular appeal as iconography, her elevation into the literary canon, her concurrent marginalization in anthropology despite her significant contributions, and her place within constructions of Black feminist literary traditions. Perceptive and original, Ain't I an Anthropologist is an overdue reassessment of Zora Neale Hurston's place in American cultural and intellectual life.
•Studies support developmental origin of Pb-induced adult neurodegenerative disease.•Zebrafish is a powerful model for neurotoxicity and neurodegenerative diseases.•Current research with zebrafish is ...expanding knowledge on Pb neurotoxicity.
Lead (Pb) exposure has long been recognized to cause neurological alterations in both adults and children. While most of the studies in adults are related to higher dose exposure, epidemiological studies indicate cognitive decline and neurobehavioral alterations in children associated with lower dose environmental Pb exposure (a blood Pb level of 10μg/dL and below). Recent animal studies also now report that an early-life Pb exposure results in pathological hallmarks of Alzheimer's disease later in life. While previous studies evaluating higher Pb exposures in adult animal models and higher occupational Pb exposures in humans have suggested a link between higher dose Pb exposure during adulthood and neurodegenerative disease, these newer studies now indicate a link between an early-life Pb exposure and adult neurodegenerative disease. These studies are supporting the “fetal/developmental origin of adult disease” hypothesis and present a new challenge in our understanding of Pb neurotoxicity. There is a need to expand research in this area and additional model systems are needed. The zebrafish presents as a complementary vertebrate model system with numerous strengths including high genetic homology. Several zebrafish genes orthologous to human genes associated with neurodegenerative diseases including Alzheimer's and Parkinson's diseases are identified and this model is starting to be applied in neurodegenerative disease research. Moreover, the zebrafish is being used in developmental Pb neurotoxicity studies to define genetic mechanisms of toxicity and associated neurobehavioral alterations. While these studies are in their infancy, the genetic and functional conservation of genes associated with neurodegenerative diseases and application in developmental Pb neurotoxicity studies supports the potential for this in vivo model to further investigate the link between developmental Pb exposure and adult neurodegenerative disease pathogenesis. In this review, the major factors influencing the pathogenesis of neurodegenerative diseases, Pb neurotoxicity, the developmental origin of adult disease paradigm, and the zebrafish as a model system to investigate the developmental origin of low-dose Pb-induced neurodegenerative diseases is discussed.
Antiretroviral therapy (ART) is a lifesaver for individual patients treated for Human Immunodeficiency Virus (HIV) and Acquired Immune Deficiency Syndrome (AIDS). Maintaining optimal adherence to ...antiretroviral drugs is essential for HIV infection management. This study aimed to understand the factors influencing adherence amongst ART-prescribed patients and care providers in Nepal.
A cross-sectional mixed-methods study surveying 330 ART-prescribed patients and 34 in-depth interviews with three different types of stakeholders: patients, care providers, and key people at policy level. Adherence was assessed through survey self-reporting and during the interviews. A multivariate logistic regression model was used to identify factors associated with adherence, supplemented with a thematic analysis of the interview transcripts.
A total of 282 (85.5%) respondents reported complete adherence, i.e. no missed doses in the four-weeks prior to interview. Major factors influencing adherence were: non-disclosure of HIV status (OR = 17.99, p = 0.014); alcohol use (OR = 12.89, p = <0.001), being female (OR = 6.91, p = 0.001), being illiterate (OR = 4.58, p = 0.015), side-effects (OR = 6.04, p = 0.025), ART started ≤24 months (OR = 3.18, p = 0.009), travel time to hospital >1 hour (OR = 2.84, p = 0.035). Similarly, lack of knowledge and negative perception towards ART medications also significantly affected non-adherence. Transport costs (for repeat prescription), followed by pills running out, not wanting others to notice, side-effects, and being busy were the most common reasons for non-adherence. The interviews also revealed religious or ritual obstacles, stigma and discrimination, ART-associated costs, transport problems, lack of support, and side-effects as contributing to non-adherence.
Improving adherence requires a supportive environment; accessible treatment; clear instructions about regimens; and regimens tailored to individual patients' lifestyles. Healthcare workers should address some of the practical and cultural issues around ART medicine whilst policy-makers should develop appropriate social policy to promote adherence among ART-prescribed patients.
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•LC50s of PFAA decreased with the increase in chain length.•PFOA caused hyperactivity and PFBA hypoactivity.•PFOA, PFHxA, and PFBA exposure caused morphological alterations specific ...to each.•Unique transcriptome profiles were observed for each PFAA.•Transcriptomics at end of embryogenesis predicted adverse human health outcomes.
Perfluoroalkyl substances (PFAS) are a class of synthetic chemicals that are persistent in the environment. Due to adverse health outcomes associated with longer chain PFAS, shorter chain chemicals were used as replacements, but developmental toxicity assessments of the shorter chain chemicals are limited. Toxicity of three perfluoroalkyl acids (PFAAs) perfluorooctanoic acid (PFOA), composed of 8 carbon (C8), perfluorohexanoic acid (PFHxA, C6), and perfluorobutanoic acid (PFBA, C4) was compared in developing zebrafish (Danio rerio). LC50s at 120 h post fertilization (hpf) assessed potency of each PFAA by exposing developing zebrafish (1–120 hpf) to range of concentrations. Zebrafish were then exposed to sublethal concentrations (0.4–4000 ppb, µg/L) throughout embryogenesis (1–72 hpf). Effects of the embryonic exposure on locomotor activities was completed with the visual motor response test at 120 hpf. At 72 hpf, morphological changes (total body length, head length, head width) and transcriptome profiles to compare altered molecular and disease pathways were determined. The LC50 ranking followed trend as expected based on chain length. PFOA caused hyperactivity and PFBA hypoactivity, while PFHxA did not change behavior. PFOA, PFHxA, and PFBA caused morphological and transcriptomic alterations that were unique for each chemical and were concentration-dependent indicating different toxicity mechanisms. Cancer was a top disease for PFOA and FXR/RXR activation was a top canonical pathway for PFBA. Furthermore, comparison of altered biological and molecular pathways in zebrafish exposed to PFOA matched findings reported in prior epidemiological studies and other animal models, supporting the predictive value of the transcriptome approach and for predicting adverse health outcomes associated with PFHxA or PFBA exposure.
Despite advances in exogenous insulin therapy, many patients with type 1 diabetes do not achieve acceptable glycemic control and remain at risk for ketosis and insulin-induced hypoglycemia. We ...conducted a randomized controlled trial to determine whether TTP399, a novel hepatoselective glucokinase activator, improved glycemic control in people with type 1 diabetes without increasing hypoglycemia or ketosis.
SimpliciT1 was a phase 1b/2 adaptive study. Phase 2 activities were conducted in two parts. Part 1 randomly assigned 20 participants using continuous glucose monitors and continuous subcutaneous insulin infusion (CSII). Part 2 randomly assigned 85 participants receiving multiple daily injections of insulin or CSII. In both parts 1 and 2, participants were randomly assigned to 800 mg TTP399 or matched placebo (fully blinded) and treated for 12 weeks. The primary end point was change in HbA
from baseline to week 12.
The difference in change in HbA
from baseline to week 12 between TTP399 and placebo was -0.7% (95% CI -1.3, -0.07) in part 1 and -0.21% (95% CI -0.39, -0.04) in part 2. Despite a greater decrease in HbA
with TTP399, the frequency of severe or symptomatic hypoglycemia decreased by 40% relative to placebo in part 2. In both parts 1 and 2, plasma β-hydroxybutyrate and urinary ketones were lower during treatment with TTP399 than placebo.
TTP399 lowers HbA
and reduces hypoglycemia without increasing the risk of ketosis and should be further evaluated as an adjunctive therapy for the treatment of type 1 diabetes.
Neurotransmission is the basis of neuronal communication and is critical for normal brain development, behavior, learning, and memory. Exposure to drugs and chemicals can alter neurotransmission, ...often through unknown pathways and mechanisms. The zebrafish (
) model system is increasingly being used to study the brain and chemical neurotoxicity. In this review, the major neurotransmitter systems, including glutamate, GABA, dopamine, norepinephrine, serotonin, acetylcholine, histamine, and glutamate are surveyed and pathways of synthesis, transport, metabolism, and action are examined. Differences between human and zebrafish neurochemical pathways are highlighted. We also review techniques for evaluating neurological function, including the measurement of neurotransmitter levels, assessment of gene expression through transcriptomic analysis, and the recording of neurobehavior. Finally examples of chemical toxicity studies evaluating alterations in neurotransmitter systems in the zebrafish model are reviewed.
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