Immortalized Parkinson's disease lymphocytes have enhanced mitochondrial respiratory activity

Abstract

In combination with studies of post-mortem Parkinson's disease (PD) brains, pharmacological and genetic models of PD have suggested that two fundamental interacting cellular processes are impaired – proteostasis and mitochondrial respiration. We have re-examined the role of mitochondrial dysfunction in lymphoblasts isolated from individuals with idiopathic PD and an age-matched control group. As previously reported for various PD cell types, the production of reactive oxygen species (ROS) by PD lymphoblasts was significantly elevated. However, this was not due to an impairment of mitochondrial respiration, as is often assumed. Instead, basal mitochondrial respiration and ATP synthesis are dramatically elevated in PD lymphoblasts. The mitochondrial mass, genome copy number and membrane potential were unaltered, but the expression of indicative respiratory complex proteins was also elevated. This explains the increased oxygen consumption rates by each of the respiratory complexes in experimentally uncoupled mitochondria of iPD cells. However, it was not attributable to increased activity of the stress- and energy-sensing protein kinase AMPK, a regulator of mitochondrial biogenesis and activity. The respiratory differences between iPD and control cells were sufficiently dramatic as to provide a potentially sensitive and reliable biomarker of the disease state, unaffected by disease duration (time since diagnosis) or clinical severity. Lymphoblasts from control and PD individuals thus occupy two distinct, quasi-stable steady states; a ‘normal’ and a ‘hyperactive’ state characterized by two different metabolic rates. The apparent stability of the ‘hyperactive’ state in patient-derived lymphoblasts in the face of patient ageing, ongoing disease and mounting disease severity suggests an early, permanent switch to an alternative metabolic steady state. With its associated, elevated ROS production, the ‘hyperactive’ state might not cause pathology to cells that are rapidly turned over, but brain cells might accumulate long-term damage leading ultimately to neurodegeneration and the loss of mitochondrial function observed post-mortem. Whether the ‘hyperactive’ state in lymphoblasts is a biomarker specifically of PD or more generally of neurodegenerative disease remains to be determined.

Misfolded α-synuclein causes hyperactive respiration without functional deficit in live neuroblastoma cells

“…In support of this, numerous studies on mitochondrial respiration in various cell types in small cohorts of ante mortem PD patients have failed to produce conclusive findings (Ambrosi et al, 2014;Barroso et al, 1993;Bravi et al, 1992;Cronin-Furman et al, 2013;Esteves et al, 2010;Martin et al, 1996;Parker and Swerdlow, 1998;Shinde and Pasupathy, 2006;Yoshino et al, 1992). Importantly, recently a larger study examining mitochondrial respiration in immortalized lymphocytes from 30 patients found enhanced respiratory activity with no functional deficit (Annesley et al, 2016). This elevation was found to be independent of age, disease duration or disease severity and hence supports the theory that mitochondria are adaptive in disease.…”

Metabolic Dysfunction in Parkinson’s Disease: Bioenergetics, Redox Homeostasis and Central Carbon Metabolism

“…For example, pathogenic T-cell populations potentiate microglial activation [41, 275]. Importantly, peripheral cells such as lymphocytes and neutrophiles from PD patients observe mitochondrial dysfunction and increased oxidative stress [18, 55, 107, 263, 264, 326], but whether ROS generation from infiltrating cells contributes to PD has not been explored. A disruption in the BBB has also been linked to aging and PD, which might involve dysfunction in both endothelial and astrocytes [45, 117].…”

A novel selective VPAC2 agonist peptide-conjugated chitosan modified selenium nanoparticles with enhanced anti-type 2 diabetes synergy effects

“…Intracellular ROS levels were determined with fluorometric intracellular ROS kit (Sigma-Aldrich) using the method described previously. 31 For SCD (10 nM) treatment, the same doses of SeNPs, SC (210 nM, using the final concentration of SeNPs as the quantitative index), BAY55-9837, Ex-4, DBAYL (10 nM) or the same volume of PBS were used for controls.…”