Attention deficit-hyperactivity disorder suffers from mitochondrial dysfunction

Background

Pathophysiology of attention-deficit hyperactivity disorder (ADHD) is not known, and therefore the present study investigated mitochondrial defects, if any in cybrids created from patients and control population.

Methods

To investigate mitochondrial pathology in ADHD, cybrids cell lines were created from ADHD probands and controls by fusing their platelets with ρ⁰-cells prepared from SH-SY5Y neuroblastoma cell line. Cellular respiration, oxidative stress, mitochondrial membrane potential and morphology were evaluated employing oxygraph, mitochondria-specific fluorescence staining and evaluation by FACS, and immunocytochemistry. HPLC-electrochemical detection, quantitative RT-PCR and Blue Native PAGE were employed respectively for assays of serotonin, mitochondrial ATPase 6/8 subunits levels and complex V activity.

Results

Significantly low cellular and mitochondrial respiration, ATPase6/8 transcripts levels, mitochondrial complex V activity and loss of mitochondrial membrane potential and elevated oxidative stress were observed in ADHD cybrids. Expression of monoamine oxidizing mitochondrial enzymes, MAO-A and MAO-B levels remained unaffected. Two-fold increase in serotonin level was noted in differentiated cybrid-neurons.

Conclusions

Since cybrids are shown to replicate mitochondrial defects seen in post-mortem brains, these observed defects in ADHD cybrids strongly suggest mitochondrial pathology in this disorder.

General significance

Mitochondrial defects are detected in ADHD cybrids created from patients' platelets, implying bioenergetics crisis in the mitochondria could be a contributory factor for ADHD pathology and/or phenotypes.