Mitochondrial superoxide generation induces a parkinsonian phenotype in zebrafish and huntingtin aggregation in human cells

Brígida R Pinho,Sara D Reis,Richard C Hartley,Michael P Murphy,Jorge M.A Oliveira

doi:10.1016/j.freeradbiomed.2018.10.446

Abstract

Superoxide generation by mitochondria respiratory complexes is a major source of reactive oxygen species (ROS) which are capable of initiating redox signaling and oxidative damage. Current understanding of the role of mitochondrial ROS in health and disease has been limited by the lack of experimental strategies to selectively induce mitochondrial superoxide production. The recently-developed mitochondria-targeted redox cycler MitoParaquat (MitoPQ) overcomes this limitation, and has proven effective in vitro and in Drosophila. Here we present an in vivo study of MitoPQ in the vertebrate zebrafish model in the context of Parkinson's disease (PD), and in a human cell model of Huntington's disease (HD). We show that MitoPQ is 100-fold more potent than non-targeted paraquat in both cells and in zebrafish in vivo. Treatment with MitoPQ induced a parkinsonian phenotype in zebrafish larvae, with decreased sensorimotor reflexes, spontaneous movement and brain tyrosine hydroxylase (TH) levels, without detectable effects on heart rate or atrioventricular coordination. Motor phenotypes and TH levels were partly rescued with antioxidant or monoaminergic potentiation strategies. In a HD cell model, MitoPQ promoted mutant huntingtin aggregation without increasing cell death, contrasting with the complex I inhibitor rotenone that increased death in cells expressing either wild-type or mutant huntingtin. These results show that MitoPQ is a valuable tool for cellular and in vivo studies of the role of mitochondrial superoxide generation in redox biology, and as a trigger or co-stressor to model metabolic and neurodegenerative disease phenotypes.

Highlights

Reactive oxygen species (ROS) were originally characterized as celldamaging by-products of biological reactions
The differential impact of MitoPQ and paraquat upon these neuronal clusters could explain their differential effects upon spontaneous movement. These results show that MitoPQ induces in vivo oxidative damage and a parkinsonian phenotype in zebrafish, the reduced mobility and decreased brain levels of tyrosine hydroxylase that are common features of Parkinson's Disease (PD) [22]
The generation of mitochondrial superoxide plays an important role in reactive oxygen species (ROS) signaling and oxidative damage, but the lack of strategies for its selective generation have limited advancement in this field of research

Summary

Introduction

Reactive oxygen species (ROS) were originally characterized as celldamaging by-products of biological reactions. Superoxide produced by mitochondrial respiratory complexes is a major source of ROS, involved in signaling to other cellular compartments and in oxidative damage [1]. Available strategies to increase mitochondrial superoxide include respiratory complex inhibitors, which disturb the membrane potential and ATP synthesis [30], and non-targeted redox cyclers, which lead to substantial superoxide production outside mitochondria [6], thereby confounding data interpretation. The current understanding of the pathophysiological role of mitochondrial superoxide has been limited by the lack of strategies to selectively increase its generation in cells and in vivo [20]. It was previously shown in vitro that MitoPQ increases mitochondrial superoxide production in cells, and disturbs cardiac function in the isolated perfused mouse heart [41]. MitoPQ was previously tested only in flies

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