Oxidative Stress Induces Mitochondrial Dysfunction in a Subset of Autism Lymphoblastoid Cell Lines in a Well-Matched Case Control Cohort

Shannon Rose,S Jill James,John Slattery,Richard E Frye,Oleksandra Pavliv,Rebecca Wynne,Marie Tippett,Stepan Melnyk,Nuri Gueven

doi:10.1371/journal.pone.0085436

Abstract

There is increasing recognition that mitochondrial dysfunction is associated with the autism spectrum disorders. However, little attention has been given to the etiology of mitochondrial dysfunction or how mitochondrial abnormalities might interact with other physiological disturbances associated with autism, such as oxidative stress. In the current study we used respirometry to examine reserve capacity, a measure of the mitochondrial ability to respond to physiological stress, in lymphoblastoid cell lines (LCLs) derived from children with autistic disorder (AD) as well as age and gender-matched control LCLs. We demonstrate, for the first time, that LCLs derived from children with AD have an abnormal mitochondrial reserve capacity before and after exposure to increasingly higher concentrations of 2,3-dimethoxy-1,4-napthoquinone (DMNQ), an agent that increases intracellular reactive oxygen species (ROS). Specifically, the AD LCLs exhibit a higher reserve capacity at baseline and a sharper depletion of reserve capacity when ROS exposure is increased, as compared to control LCLs. Detailed investigation indicated that reserve capacity abnormalities seen in AD LCLs were the result of higher ATP-linked respiration and maximal respiratory capacity at baseline combined with a marked increase in proton leak respiration as ROS was increased. We further demonstrate that these reserve capacity abnormalities are driven by a subgroup of eight (32%) of 25 AD LCLs. Additional investigation of this subgroup of AD LCLs with reserve capacity abnormalities revealed that it demonstrated a greater reliance on glycolysis and on uncoupling protein 2 to regulate oxidative stress at the inner mitochondria membrane. This study suggests that a significant subgroup of AD children may have alterations in mitochondrial function which could render them more vulnerable to a pro-oxidant microenvironment derived from intrinsic and extrinsic sources of ROS such as immune activation and pro-oxidant environmental toxicants. These findings are consistent with the notion that AD is caused by a combination of genetic and environmental factors.

Highlights

The autism spectrum disorders (ASD) are a heterogeneous group of neurodevelopmental disorders defined by impairments in communication and social interactions along with restrictive and repetitive behaviors [1]
Mitochondrial Function in autistic disorder (AD) lymphoblastoid cell lines (LCLs) with reactive oxygen species (ROS) Challenge ATP-linked respiration was overall higher for AD LCLs as compared to control LCLs [F(1,776) = 79.43, p,0.0001] (Figure 2A)
Proton leak respiration was overall higher in AD LCLs [F(1,776) = 197.08, p,0.0001] (Figure 2B) and significantly increased as DMNQ increased [F(4,96) = 176.89, p,0.0001]

Summary

Introduction

The autism spectrum disorders (ASD) are a heterogeneous group of neurodevelopmental disorders defined by impairments in communication and social interactions along with restrictive and repetitive behaviors [1]. Recent studies have recognized that a broad range of children with ASD have impairments in several basic physiological processes such as energy generation systems [4] and redox homeostasis [5,6,7]. Mitochondrial dysfunction has become increasingly accepted as a major physiological disturbance in ASD [8]. The etiology of mitochondrial dysfunction is not known. Mitochondrial deoxyribonucleic acid (DNA) mutations are commonly found in classical mitochondrial disease (MD), such mutations are found in only 23% of ASD children diagnosed with

Methods

Results

Discussion

Conclusion