Toxic effects of X-linked adrenoleukodystrophy-associated, very long chain fatty acids on glial cells and neurons from rat hippocampus in culture

Abstract

Saturated very long chain fatty acids (VLCFAs; > or =C22:0) accumulate in X-linked adrenoleukodystrophy (X-ALD, OMIM 300100), a severe hereditary neurodegenerative disease, due to peroxisomal impairment. Previous studies analysed the development of X-ALD in humans and gene knockout animal models. However, the toxic effect of VLCFA leading to severe symptoms with progressive and multifocal demyelination, adrenal insufficiency and inflammation still remains unclear. To understand the toxic effects of VLCFA in the brain, here we exposed neural cells to VLCFA and analysed the cellular consequences. We found that oligodendrocytes and astrocytes challenged with docosanoic- (C22:0), tetracosanoic- (C24:0) and hexacosanoic acids (C24:0) die within 24 h. VLCFA-induced depolarization of mitochondria in situ and increased intracellular Ca2+ level in all three brain cell types provides indications about the mechanism of toxicity of VLCFA. Interestingly, VLCFAs affect to the largest degree the myelin-producing oligodendrocytes. In isolated mitochondria, VLCFAs exert a detrimental effect by affecting the inner mitochondrial membrane and promoting the permeability transition. In conclusion, we suggest that there is a potent toxic activity of VLCFA due to dramatic cell physiological effects with mitochondrial dysfunction and Ca2+ deregulation. This provides the first evidence for mitochondrial-based cell death mechanisms in neurodegenerative disease with peroxisomal defects and subsequent VLCFA accumulation.

Microglial dysfunction as a key pathological change in adrenomyeloneuropathy

“…Neither human nor mouse AMN spinal cord displays cell death despite accumulation of LPC C26:0 42. For some time, it has been known that excess VLCFA (40 µM and above) affects membrane function and causes toxicity to adrenocortical cells, oligodendrocytes, astrocytes, and neurons 43, 44. For example, excess free VLCFA induces depolarization of mitochondria and deregulation of the intracellular calcium homeostasis,42 and in the brain, this can cause activation and apoptosis of microglia 4.…”

Very long-chain fatty acid accumulation causes lipotoxic response via 5-lipoxygenase in cerebral adrenoleukodystrophy

“…6A ) supports the hypothesis that LTs may contribute to the observed oxidative burden, even in the histologically normal-looking area of the cALD brain. The VLCFA C26:0 has been implicated in reductions of GSH in cultured cells ( 8 ), and it also alters calcium homeostasis and mitochondrial potential in neural cells, including oligodendrocytes ( 6 ). Redox imbalance is supported by the enhanced expression of MnSOD and HSP-70 in the normal-looking area away from the plaque ( Fig.…”

Impact of C24:0 on actin-microtubule interaction in human neuronal SK-N-BE cells: evaluation by FRET confocal spectral imaging microscopy after dual staining with rhodamine-phalloidin and tubulin tracker green

“…In the present study, we characterized the effects of C24:0 on human neuronal SK-N-BE cells. As various cytotoxic effects associated with cell death have been observed in different cell types treated with C24:0 (Kahn et al, 2011;Baarine et al, 2012;Zarrouk et al, 2012;Hein et al, 2008), we wondered whether this fatty acid is able to induce cytoskeleton modifications. Using various flow cytometric, microscopic and biochemical methods, we demonstrated changes in actin and A.…”

“…Increased levels of VLCFAs have also been found in the plasma and red blood cells of patients with AD (Zarrouk, 2013). Notably, in glial and neuronal cells (Hein et al, 2008;Baarine et al, 2012;Zarrouk et al, 2012), it was previously reported that tetracosanoic acid (C24:0) (used at concentrations in the 5-20 μM range) is capable of triggering mitochondrial dysfunctions and oxidative stress associated with a non-apoptotic mode of cell death. These are regarded as important events leading to the development of AD (Kahn et al, 2011;Silva et al, 2012;von Bernhardi et al, 2012).…”

“…We focused on the activity of C24:0 for the following reasons: it is found at higher concentrations than C22:0 and C26:0 in the plasma and tissues of patients with peroxisomopathies (Kemp et al, 2011;Baarine et al, 2012), and it has also been detected at increased levels in the plasma and cortex of patients with AD (Kou et al, 2011;Zarrouk, 2013;Zarrouk et al, 2015). Whereas this fatty acid is known to have pronounced side effects, contributing to cell death of various neural cells (Hein et al, 2008;Baarine et al, 2012;Zarrouk et al, 2012), its effects on the cytoskeleton are still unknown. It was thus considered of interest to establish the precise impact of C24:0, at cytotoxic concentrations, on the organization of microtubules and actin in human neuronal SK-N-BE cells.…”