PROPIONIC ACID REMODELS MITOCHONDRIAL METABOLISM IN SH-SY5Y CELLS

Mitochondrial mechanisms are increasingly implicated in complex neurological conditions, including Autism Spectrum Disorder (ASD). Preclinical models of ASD have employed Propionic Acid (PPA) to study the relationship between neuronal metabolism, development and function. PPA has been shown to alter mitochondrial biogenesis, dynamics and quality control in neuronal-like SH-SY5Y cells. However, the molecular mechanisms that drive PPA-induced mitochondrial dysfunction are not fully understood. Here, we aimed to characterize molecular and metabolic features of mitochondrial remodelling under PPA stress in the SH-SY5Y system. Using RT-qPCR, we found that PPA (3 – 10mM) systemically altered the transcriptional regulation of mitochondrial biogenesis, fission and fusion in a time- and dose-dependent manner. Western blots revealed associated disruptions to canonical mitochondrial quality control proteins, suggesting a decrease in mitochondrial content (TOMM20), impaired mitochondria fusion (L-OPA1, MFN2), increased mitochondrial fission (DRP1) and elevated mitophagic flux (LC3II). Time-lapse confocal microscopy demonstrated a dose-dependent upregulation of both fission and fusion events that culminated in impairments to mitochondrial network integrity, connectivity and turnover. Live-cell respirometry revealed subsequent deficits in both oxidative and glycolytic energy production, marked by a decrease in basal, maximal, spare and non-mitochondrial respiratory capacity. Concurrently, respiratory chain electron flow assays demonstrated a distinct shift in TCA cycle flux, driven by a remodelling of substrate utilization associated with PPA metabolism. Together, this work describes a molecular signature of metabolic stress in the SH-SY5Y system, providing novel insights into the mechanisms and manifestations of PPA-induced neurotoxicity.