Mitochondrial and Endoplasmic Reticulum Stress Trigger Triglyceride Accumulation in Models of Parkinson’s Disease Independent of Mutations in MAPT

Abstract

The metabolic basis of Parkinson’s disease pathology is poorly understood. However, the involvement of mitochondrial and endoplasmic reticulum stress in dopamine neurons in disease aetiology is well established. We looked at the effect of rotenone- and tunicamycin-induced mitochondrial and ER stress on the metabolism of wild type and microtubule-associated protein tau mutant dopamine neurons. Dopamine neurons derived from human isolated iPSCs were subjected to mitochondrial and ER stress using RT and TM, respectively. Comprehensive metabolite profiles were generated using a split phase extraction analysed by reversed phase lipidomics whilst the aqueous phase was measured using HILIC metabolomics. Mitochondrial and ER stress were both shown to cause significant dysregulation of metabolism with RT-induced stress producing a larger shift in the metabolic profile of both wild type and MAPT neurons. Detailed analysis showed that accumulation of triglycerides was a significant driver of metabolic dysregulation in response to both stresses in both genotypes. Whilst the consequence is similar, the mechanisms by which triglyceride accumulation occurs in dopamine neurons in response to mitochondrial and ER stress are very different. Thus, improving our understanding of how these mechanisms drive the observed triglyceride accumulation can potentially open up new therapeutic avenues.

Changes in Oxidised Phospholipids in Response to Oxidative Stress in Microtubule-Associated Protein Tau (MAPT) Mutant Dopamine Neurons

“…The data described in this study were previously published by Fernandes et al [15], and a detailed description of the methods including the generation of dopamine neurons and metabolic analysis can be found in this paper. The previous publication focused on the effect of mitochondrial and endoplasmic reticulum stress on global metabolic dysregulation in iPSC-derived dopamine neurons, whilst this study focuses directly on the effect of mutations in the gene encoding of the microtubule-associated protein Tau on the formation of oxidised phospholipids.…”

“…The methods used in this study have been described previously [15,18]. Briefly, 140 µL of methyl tertiary-butyl ether and 40 µL methanol of methanol were added to disrupt cellular membranes, with 30 µL added prior to spinning at 5000× g to achieve phase separation.…”

“…Previous metabolomic approaches to study tauopathy and MAPT mutations took a general view of metabolism rather than focusing on the impact of ROS and formation of oxidised lipid species [15]. Owing to their involvement in a wide range of important biological processes, including neuroinflammation, disruption of the phospholipid membrane integrity and neuronal signalling, it is crucial to understand their contribution to pathology.…”

Novel Metabolomic Approach for Identifying Pathology-Specific Biomarkers in Rare Diseases: A Case Study in Oculopharyngeal Muscular Dystrophy (OPMD)

“…Then, 25 µL of homogenate or 15 µL of plasma was transferred to an Agilent HPLC Vial with a 250 µL glass insert. Samples were then extracted using a modified version of an in-vial dual extraction described previously [ 21 , 22 ]. Briefly, 5 µL of HILIC internal standard (2.5 mM L-valine 13C515N in 80:20 MeOH:H2O), 140 µL of MTBE containing 15 µM of tripentadecanoin and 40 µL of methanol were added to all cell pellets and left to stand for 10 min to disrupt the cell membranes.…”

Medium-Chain Fatty Acids Rescue Motor Function and Neuromuscular Junction Degeneration in a Drosophila Model of Amyotrophic Lateral Sclerosis

“…The anterior and posterior of the larvae were removed, and the body wall muscles were collected for muscle samples. Extraction of metabolites from each tissue was performed using a modified version of a method published previously [41,42]. Briefly, a ball bearing (4 mm steel) was added to the tube containing the sample and 30 µL of methanol.…”