Aldehyde dehydrogenase inhibition as a pathogenic mechanism in Parkinson disease

Parkinson disease (PD) is a neurodegenerative disorder particularly characterized by the loss of dopaminergic neurons in the substantia nigra. Pesticide exposure has been associated with PD occurrence, and we previously reported that the fungicide benomyl interferes with several cellular processes potentially relevant to PD pathogenesis. Here we propose that benomyl, via its bioactivated thiocarbamate sulfoxide metabolite, inhibits aldehyde dehydrogenase (ALDH), leading to accumulation of the reactive dopamine metabolite 3,4-dihydroxyphenylacetaldehyde (DOPAL), preferential degeneration of dopaminergic neurons, and development of PD. This hypothesis is supported by multiple lines of evidence. (i) We previously showed in mice the metabolism of benomyl to S-methyl N-butylthiocarbamate sulfoxide, which inhibits ALDH at nanomolar levels. We report here that benomyl exposure in primary mesencephalic neurons (ii) inhibits ALDH and (iii) alters dopamine homeostasis. It induces selective dopaminergic neuronal damage (iv) in vitro in primary mesencephalic cultures and (v) in vivo in a zebrafish system. (vi) In vitro cell loss was attenuated by reducing DOPAL formation. (vii) In our epidemiology study, higher exposure to benomyl was associated with increased PD risk. This ALDH model for PD etiology may help explain the selective vulnerability of dopaminergic neurons in PD and provide a potential mechanism through which environmental toxicants contribute to PD pathogenesis

Neurotoxicity of the Parkinson’s Disease-Associated Pesticide Ziram is Synuclein Dependent

Parkinson’s disease (PD) is the second most common neurodegenerative disease, affecting seven to ten million people worldwide. Familial forms of PD account for 5-10% of all PD cases suggesting that other factors such as the environment have a role in the development of sporadic cases of PD. Epidemiological studies have indicated that exposure to pesticides increases the risk for PD. Ziram, a dithiocarbamate fungicide commonly used in California, increases the risk of PD for individuals living and working in areas where the pesticide is sprayed. Ziram has previously been found in vitro to cause selective dopaminergic cell toxicity, inhibition of the ubiquitin proteasome system (UPS), and increased α-synuclein (α-syn) levels in primary neuronal cultures. In this dissertation we utilize zebrafish embryos (ZF, Danio rerio) to study ziram in an in vivo system and to determine if ziram’s toxicity is mediated via synuclein.We found that ziram is toxic to ZF at nanomolar concentrations and caused selective loss of dopaminergic (DA) neurons and impaired swimming behavior in ZF. Since ziram increases α-syn concentrations in rat primary neuronal cultures, we investigated the effect of ziram on ZF γ-synuclein 1 (γ1). ZF express 3 synuclein isoforms and ZF γ1 appears to be a functional homologue of α-syn. We found that recombinant ZF γ1 formed fibrils in vitro and overexpression of ZF γ1 in ZF embryos led to the formation of neuronal aggregates and neurotoxicity similarly to α-syn. Importantly, knockdown of ZF γ1 with morpholinos or disruption of oligomers with the molecular tweezer CLR01 protected against ziram’s DA toxicity.Over the course of this dissertation we have demonstrated that ziram is selectively toxic to DA neurons in vivo and that its toxicity is synuclein-dependent. These findings provide potentially important mechanistic implications on how ziram and possibly other environmental toxins can contribute to the pathogenesis of neurodegenerative disorders such as PD

Rutgers University Wind Initiative and Development (RU WIND): Bringing Wind Power to Rutgers

The goal of the RU WIND group is to bring wind energy to Rutgers University to make the university more sustainable.Fall 200

Axon degeneration and PGC-1α-mediated protection in a zebrafish model of α-synuclein toxicity

α-synuclein (aSyn) expression is implicated in neurodegenerative processes, including Parkinson’s disease (PD) and dementia with Lewy bodies (DLB). In animal models of these diseases, axon pathology often precedes cell death, raising the question of whether aSyn has compartment-specific toxic effects that could require early and/or independent therapeutic intervention. The relevance of axonal pathology to degeneration can only be addressed through longitudinal, in vivo monitoring of different neuronal compartments. With current imaging methods, dopaminergic neurons do not readily lend themselves to such a task in any vertebrate system. We therefore expressed human wild-type aSyn in zebrafish peripheral sensory neurons, which project elaborate superficial axons that can be continuously imaged in vivo. Axonal outgrowth was normal in these neurons but, by 2 days post-fertilization (dpf), many aSyn-expressing axons became dystrophic, with focal varicosities or diffuse beading. Approximately 20% of aSyn-expressing cells died by 3 dpf. Time-lapse imaging revealed that focal axonal swelling, but not overt fragmentation, usually preceded cell death. Co-expressing aSyn with a mitochondrial reporter revealed deficits in mitochondrial transport and morphology even when axons appeared overtly normal. The axon-protective protein Wallerian degeneration slow (WldS) delayed axon degeneration but not cell death caused by aSyn. By contrast, the transcriptional coactivator PGC-1α, which has roles in the regulation of mitochondrial biogenesis and reactive-oxygen-species detoxification, abrogated aSyn toxicity in both the axon and the cell body. The rapid onset of axonal pathology in this system, and the relatively moderate degree of cell death, provide a new model for the study of aSyn toxicity and protection. Moreover, the accessibility of peripheral sensory axons will allow effects of aSyn to be studied in different neuronal compartments and might have utility in screening for novel disease-modifying compounds

Neurotoxicity of the Parkinson Disease-Associated Pesticide Ziram Is Synuclein-Dependent in Zebrafish Embryos.

BackgroundExposure to the commonly used dithiocarbamate (DTC) pesticides is associated with an increased risk of developing Parkinson disease (PD), although the mechanisms by which they exert their toxicity are not completely understood.ObjectiveWe studied the mechanisms of ziram's (a DTC fungicide) neurotoxicity in vivo.MethodsZebrafish (ZF) embryos were utilized to determine ziram's effects on behavior, neuronal toxicity, and the role of synuclein in its toxicity.ResultsNanomolar-range concentrations of ziram caused selective loss of dopaminergic (DA) neurons and impaired swimming behavior. Because ziram increases α-synuclein (α-syn) concentrations in rat primary neuronal cultures, we investigated the effect of ziram on ZF γ-synuclein 1 (γ1). ZF express 3 synuclein isoforms, and ZF γ1 appears to be the closest functional homologue to α-syn. We found that recombinant ZF γ1 formed fibrils in vitro, and overexpression of ZF γ1 in ZF embryos led to the formation of neuronal aggregates and neurotoxicity in a manner similar to that of α-syn. Importantly, knockdown of ZF γ1 with morpholinos and disruption of oligomers with the molecular tweezer CLR01 prevented ziram's DA toxicity.ConclusionsThese data show that ziram is selectively toxic to DA neurons in vivo, and this toxicity is synuclein-dependent. These findings have important implications for understanding the mechanisms by which pesticides may cause PD. Citation: Lulla A, Barnhill L, Bitan G, Ivanova MI, Nguyen B, O'Donnell K, Stahl MC, Yamashiro C, Klärner FG, Schrader T, Sagasti A, Bronstein JM. 2016. Neurotoxicity of the Parkinson disease-associated pesticide ziram is synuclein-dependent in zebrafish embryos. Environ Health Perspect 124:1766-1775; http://dx.doi.org/10.1289/EHP141