Abstract
Parkinson's disease is a neurodegenerative disorder characterized by the prominent degeneration of dopaminergic (DA) neurons among other cell types. Here we report a first chemical screen of over 5,000 compounds in zebrafish, aimed at identifying small molecule modulators of DA neuron development or survival. We find that Neriifolin, a member of the cardiac glycoside family of compounds, impairs survival but not differentiation of both zebrafish and mammalian DA neurons. Cardiac glycosides are inhibitors of Na+/K+ ATPase activity and widely used for treating heart disorders. Our data suggest that Neriifolin impairs DA neuronal survival by targeting the neuronal enriched Na+/K+ ATPase α3 subunit (ATP1A3). Modulation of ionic homeostasis, knockdown of p53, or treatment with antioxidants protects DA neurons from Neriifolin-induced death. These results reveal a previously unknown effect of cardiac glycosides on DA neuronal survival and suggest that it is mediated through ATP1A3 inhibition, oxidative stress, and p53. They also elucidate potential approaches for counteracting the neurotoxicity of this valuable class of medications.
Highlights
Since its discovery as a prominent chemical neurotransmitter in the vertebrate nervous system, dopamine (DA) is recognized to have many important physiological functions including the control of movement, cognition, affect, as well as neuroendocrine secretion [1,2]
The ventral forebrain (VFB) DA neurons were the focus of our analysis because of their prominence and similarity to mammalian midbrain DA neurons that degenerate in Parkinson’s disease (PD)
We propose the following model (Fig. 6) to explain Neriifolin-induced DA neuronal death: Inhibition of Na+/K+ ATPase activity by cardiac glycosides causes an ionic imbalance; in particular, increased intracellular Na+ levels aggravate oxidative stress
Summary
Since its discovery as a prominent chemical neurotransmitter in the vertebrate nervous system, dopamine (DA) is recognized to have many important physiological functions including the control of movement, cognition, affect, as well as neuroendocrine secretion [1,2]. Recent studies show that neurodegeneration in PD appears more widespread than only affecting substantia nigral DA neurons, which possibly underlies some of the non-motor symptoms of the disease [3]. DA neurons are detected in the ventral forebrain (posterior tuberculum and hypothalamus), dorsal forebrain (telencephalon), olfactory bulb and retina [6,7] in patterns that closely resemble those found in the adult zebrafish brain [8]. These neurons display adult-like ascending and descending projections shortly after hatching [9,10]. While DA neurons are conspicuously absent from the ventral midbrain, the ventral forebrain DA neurons ascending to the striatum (where ventral midbrain DA neurons in mammals project) are likely the functional counterpart of the mammalian midbrain DA neurons [11,12]
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