Proceedings of The Physiological Society

Mitochondria: Form and function (London, UK) (2017) Proc Physiol Soc 38, PC02

Poster Communications

Drug Development For The Treatment Of Mitochondrial Optic Neuropathies

C. Varricchio1

1. School of Pharmacy and Pharmaceutical Sciences, Cardiff University, Cardiff, United Kingdom.

In recent years, an increasing number of studies have shown evidence of mitochondrial involvement in a variety of neuro-ophthalmologic diseases.1 Unfortunately, to date the treatment of mitochondrial disease is currently limited to symptomatic therapies, and there is no cure or substantial treatment option that guarantees a significant improvement and consequently, thus there is a pressing need to identify novel therapies. An approach that could represent a useful solution to treat these conditions is the identification of small molecules that restore energy production and/or reduce the level of oxidative stress. In the last few years, Idebenone has shown promising evidence of efficacy in limiting vision loss in patients with different mitochondrial dysfunctions.2 Nevertheless, researchers have raised some concerns about idebenone, which can inhibit Complex I, due to a slow dissociation from the binding-site and increase the production of superoxide.3 Furthermore, there is uncertainty around the mechanism of action of Idebenone, recently it was proposed that Idebenone activity lies on its metabolic activation from the NQO1 (NADH-Quinone oxidoreductase-1) enzyme and the reduced form of Idebenone (Idebenol) can act as electron donors for Complex III, thereby bypassing dynsfunctional Complex I to provide cellular energy rescue as well as antioxidant activity.4 In the light of this recent studies, the aim of this project is to investigate novel compounds that, targeting NQO1, show cellular energy rescue as well as antioxidant properties avoid Idebenone side effects. Given the abundance of crystal structure information available for NQO1, an in silico approaches were applied to screen a library of commercial compounds. The selected compounds, were tested in specific in vitro assays, both in cell-free systems and in cells, in order to investigate their mode of action and their ability to enable mitochondrial respiration. In particular, the compounds were analysed to determine if they can act as electron acceptors from NQO1, and/or Complex I, an essential enzymes, which catalyse the first step of the mitochondrial electron transport chain.5 The compounds were then tested in cellular assays using two immortalized cell lines, HepG2 and R28, to determine whether they can maintain cellular energy production by-passing the inhibition of Complex I. This evaluation was made by monitoring the compounds effect on reductive activity, with an MTT assay, and on ATP production, with a lucipherase assay. These initial findings indicate that the compounds identified in this study might be associated with a specific mechanism of action, involving a significant turnover by NQO1 corresponding to a significant increase of ATP production under Complex I impairment conditions Figure1 and Figure2. This evidence makes these compounds a promising starting point for further structure optimization.

Where applicable, experiments conform with Society ethical requirements