Characterization of oxidative stress and mitochondrial dysfunction in X-linked adrenoleukodystrophy

by Maxi Sophia Lüttgens
Doctoral thesis
Date of Examination:2025-12-18
Date of issue:2025-12-02
Advisor:Prof. Dr. Jutta Gärtner
Referee:Prof. Dr. Jutta Gärtner
Referee:PD Dr. Dirk Fitzner
Persistent Address: http://dx.doi.org/10.53846/goediss-11673

 

 

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Abstract

English

X-linked adrenoleukodystrophy (X-ALD) is a peroxisomal disorder with heterogeneous clinical manifestations, ranging from asymptomatic carriers to patients with rapidly progressive cerebral disease. Reliable biomarkers for disease onset and progression remain lacking. Disrupted oxidative homeostasis has been implicated in X-ALD pathophysiology, yet the relationships between oxidative stress, mitochondrial dysfunction, and elevated very long-chain fatty acids (VLCFAs) remain incompletely understood. In this study, primary fibroblasts from X-ALD patients were assessed for reactive oxygen species (ROS) levels, mitochondrial respiration, and NRF2 pathway activation. ROS production was quantified using the 2',7'-dichlorofluorescein diacetate assay, mitochondrial function via Seahorse XFe24 extracellular flux analysis, and stress-induced gene expression by quantitative real-time PCR. Cells were exposed to tert-butyl hydroperoxide (TBHP) and C26:0 as oxidative and metabolic stressors. Patient-derived X-ALD fibroblasts displayed fundamentally reduced mitochondrial function across all 12 cell lines, with variable severity among patients. TBHP exposure elicited a dose-dependent ROS increase, which was significantly more pronounced in X-ALD cells, indicating compromised antioxidant defenses. NRF2 pathway analysis revealed decreased expression of key antioxidant genes, with preliminary differences between CALD and non-CALD lines. Treatment with VLCFAs upregulated antioxidant genes in non-CALD fibroblasts and induced dose-dependent cytotoxicity across all cell lines, with X-ALD cells undergoing apoptosis at lower C26:0 concentrations. C26:0 exposure further impaired mitochondrial respiration and elevated ROS; however, these effects were less pronounced in X-ALD fibroblasts compared to healthy controls, suggesting either enhanced early adaptive responses or premature cell death limiting measurable stress accumulation. These findings highlight oxidative imbalance and mitochondrial dysfunction as central features of X-ALD. Elevated VLCFAs alone do not fully account for oxidative stress, indicating additional factors contribute to disease pathogenesis. Future studies should explore oxidative stress markers as potential biomarkers for disease onset and severity.
Keywords: ROS; oxidative stress; VLCFA; ABCD1; X-ALD; NRF2