Differential Susceptibility and Vulnerability of Brain Cells in C57BL/6 Mouse to Mitochondrial Dysfunction Induced by Short-Term Cuprizone Exposure

Abstract

Cuprizone (CPZ) is a chemical chelator toxic to mitochondria of cells. While inducing oligodendrocyte (OL) loss and demyelination, CPZ caused no fatal damage to the other brain cells (neurons, astrocytes, and microglia) in previous studies, suggesting differential susceptibility and vulnerability of brain cells to the CPZ intoxication. To demonstrate this interpretation, C57BL/6 mice were fed rodent chow without or with CPZ (0.2%, w/w) for 7 days. One day later, mitochondrial function of brain cells was assessed by proton magnetic resonance spectroscopy ( 1 H-MRS) and biochemical analysis. Another batch of mice were processed to localize the CPZ-induced damage to mitochondrial DNA, label brain cells, and identify apoptotic cells. Compared to controls, CPZ-exposed mice showed significantly lower levels of N-acetyl-L-aspartate, phosphocreatine, and ATP detected by 1 H-MRS, indicating mitochondrial dysfunction in brain cells. Susceptibility analysis showed an order of OLs, microglia, and astrocytes from high to low, in terms of the proportion of 8-OHdG labeled cells in each type of these cells in corpus callosum. Vulnerability analysis showed the highest proportion of caspase-3 positive cells in labeled OLs in cerebral cortex and hippocampus, where neurons showed no caspase-3 labeling, but the highest proportion of 8-OHdG labeling, indicating a lowest vulnerability but highest susceptibility to CPZ-induced mitochondrial dysfunction. Immature OLs, microglia, and astrocytes showed adaptive changes in proliferation and activation in response to CPZ-exposure. These data for the first time demonstrated the CPZ-induced mitochondria dysfunction in brain cells of living mouse and specified the differential susceptibility and vulnerability of brain cells to the CPZ intoxication.

Oligodendrocyte death and myelin loss in the cuprizone model: an updated overview of the intrinsic and extrinsic causes of cuprizone demyelination

“…ROS also directly induce oligodendrocyte death (e.g., ferroptosis [ 101 ]). Staining the corpus callosum with 8-OhdG reveals that oligodendrocytes contain oxidized nucleotides – an indication of elevated ROS [ 123 ] – after 1 week of cuprizone treatment [ 124 ]. Oligodendrocytes are particularly sensitive to ROS given their heightened storage of Fe 3+ within ferritin.…”

Maternal separation with early weaning impairs neuron-glia integrity: non-invasive evaluation and substructure demonstration

“…These results suggest that brain neurons are more resistant to stress-induced mitochondrial damage relative to OLs. This suggestion has been elegantly tested true in a very recent study of our team, which showed that brain neurons are most sensitive but most resistant to mitochondria oxidative stress whereas mature OLs are sensitive and most vulnerable 57 . Relevantly, patients with Canavan's disease show NAA accumulation along with myelin defect due to the deficiency of ASPA 58 .…”

Cuprizone-Induced Neurotoxicity in Human Neural Cell Lines Is Mediated by a Reversible Mitochondrial Dysfunction: Relevance for Demyelination Models

“…In fact, differential susceptibility of neurons and glia against oxidative or mitochondrial damage in the aged or diseased brains has been the subject of intensive research [ 48 , 49 ]. In a very recent study, Luo et al, (2020) demonstrated a differential vulnerability, in terms of mitochondrial dysfunction, of brain cells of C57BL/6 mice subjected to short-term CPZ intoxication; the more efficient REDOX system of neurons makes them more resistant than OLGs to oxidative stress and mitochondrial damage [ 50 ]. The results show that CPZ alters energetic metabolism but why OLGs are more sensitive to these alterations is still an open question.…”