ABSTRACT
X-linked adrenoleukodystrophy (X-ALD) is a severe neurodegenerative disorder resulting from defective ABCD1 transport protein. ABCD1 mediates peroxisomal uptake of free very-long-chain fatty acids (VLCFA) as well as their CoA-esters. Consequently, VLCFA accumulate in patients' plasma and tissues, which is considered as pathogenic X-ALD triggering factor. Clinical symptoms are mostly manifested in neural tissues and adrenal gland. Here, we investigate astrocytes from wild-type control and a genetic X-ALD mouse model (Abcd1-knockout), exposed to supraphysiological VLCFA (C22:0, C24:0 and C26:0) concentrations. They exhibit multiple impairments of energy metabolism. Furthermore, brain mitochondria from Abcd1(-/-) mice and wild-type control respond similarly to VLCFA with increased ROS generation, impaired oxidative ATP synthesis and diminished Ca(2+) uptake capacity, suggesting that a defective ABCD1 exerts no adaptive pressure on mitochondria. In contrast, astrocytes from Abcd1(-/-) mice respond more sensitively to VLCFA than wild-type control astrocytes. Moreover, long-term application of VLCFA induces high ROS generation, and strong in situ depolarization of mitochondria, and, in Abcd1(-/-) astrocytes, severely diminishes the capability to revert oxidized pyridine nucleotides to NAD(P)H. In addition, observed differences in responses of mitochondria and astrocytes to the hydrocarbon chain length of VLCFA suggest that detrimental VLCFA activities in astrocytes involve defective cellular functions other than mitochondria. In summary, we clearly demonstrate that VLCFA increase the vulnerability of Abcd1(-/-) astrocytes.
Subject(s)
ATP-Binding Cassette Transporters/deficiency , Adrenoleukodystrophy/metabolism , Astrocytes/drug effects , Energy Metabolism/drug effects , Fatty Acids/pharmacology , Mitochondria/drug effects , ATP Binding Cassette Transporter, Subfamily D, Member 1 , ATP-Binding Cassette Transporters/genetics , Adrenoleukodystrophy/genetics , Animals , Animals, Newborn , Apoptosis/drug effects , Astrocytes/metabolism , Calcium/metabolism , Calcium/pharmacokinetics , Cells, Cultured , Fatty Acids/chemistry , Ion Transport/drug effects , Membrane Potential, Mitochondrial/drug effects , Mice, Inbred C57BL , Mice, Knockout , Microscopy, Fluorescence , Mitochondria/metabolism , NADP/metabolism , Oxidative Phosphorylation/drug effects , Reactive Oxygen Species/metabolism , Spectrometry, Fluorescence , Thiobarbituric Acid Reactive Substances/metabolismABSTRACT
The accumulation of the two branched-chain fatty acids phytanic acid and pristanic acid is known to play an important role in several diseases with peroxisomal impairment, like Refsum disease, Zellweger syndrome and α-methylacyl-CoA racemase deficiency. Recent studies elucidated that the toxic activity of phytanic acid and pristanic acid is mediated by multiple mitochondrial dysfunctions, generation of reactive oxygen species and Ca2+ deregulation via the InsP3-Ca2+ signaling pathway in glial cells. However, the exact signaling mechanism through which both fatty acids mediate toxicity is still under debate. Here, we studied the ability of phytanic acid and pristanic acid to activate the free fatty acid receptor GPR40, a G-protein-coupled receptor, which was described to be involved in the Ca2+ signaling of fatty acids. We treated HEK 293 cells expressing the GPR40 receptor with phytanic acid or pristanic acid. This resulted in a significant increase in the intracellular Ca2+ level, similar to the effect seen after treatment with the synthetic GPR40 agonist GW9508. Furthermore, we demonstrate that the GPR40 activation might be due to an interaction of the carboxylate moiety of fatty acids with the receptor. Our findings indicate that the phytanic acid- and pristanic acid-mediated Ca2+ deregulation can involve the activation of GPR40. Therefore, we suppose that activation of GPR40 might be part of the signaling cascade of the toxicity of phytanic and pristanic acids.
Subject(s)
Calcium Signaling/drug effects , Fatty Acids/pharmacology , Intracellular Fluid/drug effects , Phytanic Acid/pharmacology , Receptors, G-Protein-Coupled/metabolism , Refsum Disease/metabolism , Calcium Signaling/physiology , Cell Line, Tumor , Fatty Acids/chemistry , Fatty Acids/metabolism , Fatty Acids, Nonesterified/metabolism , HEK293 Cells , Humans , Inositol 1,4,5-Trisphosphate/physiology , Intracellular Fluid/physiology , Linoleic Acid/chemistry , Linoleic Acid/pharmacology , Lipid Metabolism/drug effects , Lipid Metabolism/physiology , Methylamines/chemistry , Methylamines/pharmacology , Phytanic Acid/chemistry , Propionates/chemistry , Propionates/pharmacology , Receptors, G-Protein-Coupled/physiologyABSTRACT
BACKGROUND: Hydroxy-1-aryl-isochromans (HAIC) are newly emerging natural polyphenolic antioxidants, enriched in extravirgin olive oil, whose antioxidative potency was only scarcely characterized using cell-free systems and cells. METHODS: We characterized the activity of HAIC to inactivate reactive oxygen species (ROS) generated by the xanthine/xanthine oxidase system, mitochondria (rat brain) and neural cells. ROS levels were estimated using ROS-sensitive probes, such as Amplex Red, MitoSOXRED. RESULTS: HAIC (with 2, 3 or 4 hydroxyl substituents) effectively scavenge ROS released from mitochondria. EC50 values estimated with mitochondria and submitochondrial particles were around 20 microM. Moreover, in PC12 and cultured neural primary cells, HAIC buffered cytosolic ROS. Although HAIC permeate biological membranes, HAIC fail to buffer matrix ROS in isolated mitochondria. We show that hydrogen peroxide was effectively abolished by HAIC, whereas the production of superoxide was not affected. CONCLUSION: HAIC exert high antioxidative activity to reduce hydrogen peroxide. The antioxidative activity of HAIC is comparable with that of the stilbene-like, polyphenolic resveratrol, but much higher than that of trolox, N-acetylcysteine or melatonin. GENERAL SIGNIFICANCE: Unlike resveratrol, HAIC do not impair mitochondrial ATP synthesis or Ca2+ retention by mitochondria. Thus, HAIC have the decisive advantage to be potent antioxidants with no detrimental side effects on mitochondrial functions.
Subject(s)
Antioxidants/pharmacology , Flavonoids/pharmacology , Phenols/pharmacology , Plant Oils/chemistry , Animals , Antioxidants/chemistry , Cell-Free System/drug effects , Cell-Free System/metabolism , Cells, Cultured , Drug Evaluation, Preclinical , Flavonoids/adverse effects , Flavonoids/chemistry , Mitochondria/drug effects , Mitochondria/metabolism , Mitochondria/physiology , Models, Biological , Olive Oil , Oxidative Stress/drug effects , PC12 Cells , Phenols/adverse effects , Phenols/chemistry , Plant Oils/pharmacology , Polyphenols , Rats , Reactive Oxygen Species/metabolism , Resveratrol , Stilbenes/chemistry , Stilbenes/pharmacology , Xanthine Oxidase/metabolismABSTRACT
Pristanic acid and phytanic acid are branched-chain fatty acids, which play an important role in diseases with peroxisomal impairment, like Refsum disease (MIM 266500), Zellwegers syndrome and alpha-methylacyl-CoA racemase deficiency (MIM 604489). Several studies revealed that the toxic activity of phytanic acid is mediated by multiple mitochondrial dysfunctions. However, the action of pristanic acid on brain cells is still completely unknown. Here, we exposed astrocytes, oligodendrocytes and neurons in mixed culture to pristanic acid and phytanic acid to analyse cellular consequences. Pristanic acid exerts a strong cytotoxic activity on brain cells, displayed by dramatic Ca2+ deregulation, in situ mitochondrial depolarization and cell death. Interestingly, pristanic acid strongly induced generation of reactive oxygen species (ROS), whereas phytanic acid exerts weaker effects on ROS production. In conclusion, pristanic acid as well as phytanic acid induced a complex array of toxic activities with mitochondrial dysfunction and Ca2+ deregulation.
