Incidence of Abcd1 level on the induction of cell death and organelle dysfunctions triggered by very long chain fatty acids and TNF-α on oligodendrocytes and astrocytes

X-linked adrenoleukodystrophy (X-ALD) is characterized by ABCD1 deficiency. This disease is associated with elevated concentrations of very long chain fatty acids (C24:0 and C26:0) in the plasma and tissues of patients. Under its severe form, brain demyelination and inflammation are observed. Therefore, we determined the effects of C24:0 and C26:0 on glial cells:oligodendrocytes, which synthesize myelin, and astrocytes, which participate in immune response. So, 158N murine oligodendrocytes, rat C6 glioma cells, rat primary cultures of neuronal–glial cells, and of oligodendrocytes were treated for various periods of time in the absence or presence of C24:0 and C26:0 used at plasmatic concentrations found in X-ALD patients (1–5 μM) and higher (10, 20, 40 μM). To evaluate the importance of extrinsic and intrinsic factors, the part taken by TNF-α and reduced Abcd1 level was studied. Whatever the cells considered, no effects on cell growth and/or viability were detected at 1–5 μM, more or less pronounced effects were identified at 10 μM, and an induction of cell death with increased permeability to propidium iodide and loss of transmembrane mitochondrial potential was observed at 20–40 μM. On 158N, cell death was characterized by (i) an increased superoxide anion production at the mitochondrial level; (ii) the presence of vacuoles of different sizes and shapes; a destabilization of lysosomal membrane and a cytoplasmic redistribution of lysosomes; (iii) a modulation of Abcd3/PMP70 and Acox-1 protein expression, and a decrease in catalase activity at the peroxisomal level. When TNF-α was combined with C24:0 or C26:0 and used on 158N cells, C6 cells, and on 158N cells after siRNA mediated knockdown of Abcd1, no or slight potentiation was revealed. Thus, on the different cell models used, an induction of cell death with marked cellular dysfunctions at the mitochondrial, lysosomal, and peroxisomal levels were found with C24:0 and C26:0 at 20 μM and higher. However, in our experimental conditions, plasmatic concentrations of these fatty acids were unable to induce cell death, and organelle dysfunctions on oligodendrocytes and astrocytes, and additional intrinsic and environmental factors, such as reduced Abcd1 level and/or TNF-α, were ineffective to potentiate their side effects.

► Effects of C24:0 and C26:0 on various types of oligodendrocytes and astrocytes: cell lines (158N murine oligodendrocytes, rat C6 glioma cells), rat primary cultures of neuronal–glial cells, and rat primary cultures of oligodendrocytes. ► Effects of C24:0 and C26:0 evaluated at physiological concentrations found in the plasma of patients with X-ALD comparatively to higher concentrations previously used on different cell types. ► Effects of C24:0 and C26:0 evaluated at the mitochondrial, lysosomal, and peroxisomal levels. Evaluation of the side effects of C24:0 and C26:0 at the lysosomal and peroxisomal levels were never previously described. ► Incidence of environmental and intrinsic factors, TNF-α and low levels of Abcd1, respectively, on the ability of C24:0 and C26:0 to induce cell death on astrocytes and oligodendrocytes. ► On the different cell models used, an induction of cell death and marked cellular dysfunctions at the mitochondrial, lysosomal, and peroxisomal levels were observed with C24:0 and C26:0 at 20 μM and higher. However, in our experimental conditions, physiological plasmatic concentrations of these fatty acids were unable to induce cell death, and organelle dysfunctions on oligodendrocytes and astrocytes, and additional environmental and intrinsic factors, such as TNF-α and/or low levels of Abcd1, were ineffective to potentiate their side effects.