ABSTRACT
Very long-chain acyl-CoA dehydrogenase (VLCAD) deficiency is the most common defect of mitochondrial long-chain fatty acid ß-oxidation. Patients present with heterogeneous clinical phenotypes affecting heart, liver and skeletal muscle predominantly. The full pathophysiology of the disease is unclear and patient response to current therapeutic regimens is incomplete. To identify additional cellular alterations and explore more effective therapies, mitochondrial bioenergetics and redox homeostasis were assessed in VLCAD-deficient fibroblasts, and several protective compounds were evaluated. The results revealed cellular and tissue changes, including decreased respiratory chain (RC) function, increased reactive oxygen species (ROS) production and altered mitochondrial function and signaling pathways in a variety of VLCAD-deficient fibroblasts. The mitochondrially enriched electron and free radical scavengers JP4-039 and XJB-5-131 improved RC function and decreased ROS production significantly, suggesting that they are viable candidate compounds to further develop to treat VLCAD-deficient patients.
Subject(s)
Acyl-CoA Dehydrogenase, Long-Chain/deficiency , Antioxidants/pharmacology , Congenital Bone Marrow Failure Syndromes/metabolism , Electron Transport/drug effects , Energy Metabolism/drug effects , Lipid Metabolism, Inborn Errors/metabolism , Mitochondria/drug effects , Mitochondria/metabolism , Mitochondrial Diseases/metabolism , Muscular Diseases/metabolism , Acyl-CoA Dehydrogenase, Long-Chain/metabolism , Adenosine Triphosphate/metabolism , Apoptosis/drug effects , Cell Survival/drug effects , Congenital Bone Marrow Failure Syndromes/etiology , Endoplasmic Reticulum/metabolism , Lipid Metabolism, Inborn Errors/etiology , Membrane Potential, Mitochondrial/drug effects , Mitochondrial Diseases/etiology , Mitochondrial Dynamics/drug effects , Muscular Diseases/etiology , Oxidation-Reduction/drug effects , Oxygen Consumption , Reactive Oxygen Species/metabolism , Signal TransductionABSTRACT
Mitochondrial complex I (CI) deficiency is the most frequent cause of oxidative phosphorylation (OXPHOS) disorders in humans. In order to benchmark the effects of CI deficiency on mitochondrial bioenergetics and dynamics, respiratory chain (RC) and endoplasmic reticulum (ER)-mitochondria communication, and superoxide production, fibroblasts from patients with mutations in the ND6, NDUFV1 or ACAD9 genes were analyzed. Fatty acid metabolism, basal and maximal respiration, mitochondrial membrane potential, and ATP levels were decreased. Changes in proteins involved in mitochondrial dynamics were detected in various combinations in each cell line, while variable changes in RC components were observed. ACAD9 deficient cells exhibited an increase in RC complex subunits and DDIT3, an ER stress marker. The level of proteins involved in ER-mitochondria communication was decreased in ND6 and ACAD9 deficient cells. |ΔΨ| and cell viability were further decreased in all cell lines. These findings suggest that disruption of mitochondrial bioenergetics and dynamics, ER-mitochondria crosstalk, and increased superoxide contribute to the pathophysiology in patients with ACAD9 deficiency. Furthermore, treatment of ACAD9 deficient cells with JP4-039, a novel mitochondria-targeted reactive oxygen species, electron and radical scavenger, decreased superoxide level and increased basal and maximal respiratory rate, identifying a potential therapeutic intervention opportunity in CI deficiency.
Subject(s)
Acyl-CoA Dehydrogenases/genetics , Electron Transport Complex I/deficiency , Fibroblasts/enzymology , Mitochondrial Diseases/genetics , NADH Dehydrogenase/genetics , Reactive Oxygen Species/metabolism , Acyl-CoA Dehydrogenases/deficiency , Adenosine Triphosphate/agonists , Adenosine Triphosphate/biosynthesis , Electron Transport/drug effects , Electron Transport/genetics , Electron Transport Complex I/genetics , Endoplasmic Reticulum/drug effects , Endoplasmic Reticulum/metabolism , Endoplasmic Reticulum/pathology , Fibroblasts/drug effects , Fibroblasts/pathology , Free Radical Scavengers/pharmacology , Gene Expression , Humans , Membrane Potential, Mitochondrial/drug effects , Mitochondria/drug effects , Mitochondria/enzymology , Mitochondria/pathology , Mitochondrial Diseases/enzymology , Mitochondrial Diseases/pathology , NADH Dehydrogenase/deficiency , Nitrogen Oxides/pharmacology , Oxidative Phosphorylation/drug effects , Primary Cell Culture , Reactive Oxygen Species/antagonists & inhibitorsABSTRACT
The high incidence of resistance to DNA-damaging chemotherapeutic drugs and severe side effects of chemotherapy have led to a search for biomarkers able to predict which patients are most likely to respond to therapy. ERCC1-XPF nuclease is required for nucleotide excision repair of helix-distorting DNA damage and the repair of DNA interstrand crosslinks. Thus, it is essential for several pathways of repair of DNA damage by cisplatin and related drugs, which are widely used in the treatment of non-small cell lung carcinoma and other late-stage tumors. Consequently, there is tremendous interest in measuring ERCC1-XPF expression in tumor samples. Many immunohistochemistry studies have been done, but the antibodies for ERCC1-XPF were not rigorously tested for antigen specificity. Herein, we survey a battery of antibodies raised against human ERCC1 or XPF for their specificity using ERCC1-XPF-deficient cells as a negative control. Antibodies were tested for the following applications: immunoblotting, immunoprecipitation from cell extracts, immunofluorescence detection in fixed cells, colocalization of ERCC1-XPF with UV radiation-induced DNA damage in fixed cells, and immunohistochemistry in paraffin-embedded samples. Although several commercially available antibodies are suitable for immunodetection of ERCC1-XPF in some applications, only a select subset is appropriate for detection of this repair complex in fixed specimens. The most commonly used antibody, 8F1, is not suitable for immunodetection in tissue. The results with validated antibodies reveal marked differences in ERCC1-XPF protein levels between samples and cell types.
