1
|
Taheri P, Dave DD, Dash RK, Sharma GP, Clough AV, Jacobs ER, Audi SH. Mitochondrial function in lungs of rats with different susceptibilities to hyperoxia-induced acute lung injury. J Appl Physiol (1985) 2024; 137:233-253. [PMID: 38867668 DOI: 10.1152/japplphysiol.00243.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2024] [Revised: 06/10/2024] [Accepted: 06/11/2024] [Indexed: 06/14/2024] Open
Abstract
Adult rats exposed to hyperoxia (>95% O2) die from respiratory failure in 60-72 h. However, rats preconditioned with >95% O2 for 48 h followed by 24 h in room air acquire tolerance of hyperoxia (H-T), whereas rats preconditioned with 60% O2 for 7 days become more susceptible (H-S). Our objective was to evaluate lung tissue mitochondrial bioenergetics in H-T and H-S rats. Bioenergetics was assessed in mitochondria isolated from lung tissue of H-T, H-S, and control rats. Expressions of complexes involved in oxidative phosphorylation (OxPhos) were measured in lung tissue homogenate. Pulmonary endothelial filtration coefficient (Kf) and tissue mitochondrial membrane potential (Δψm) were evaluated in isolated perfused lungs (IPLs). Results show that ADP-induced state 3 OxPhos capacity (Vmax) decreased in H-S mitochondria but increased in H-T. Δψm repolarization time following ADP-stimulated depolarization increased in H-S mitochondria. Complex I expression decreased in H-T (38%) and H-S (43%) lung homogenate, whereas complex V expression increased (70%) in H-T lung homogenate. Δψm is unchanged in H-S and H-T lungs, but complex II has a larger contribution to Δψm in H-S than H-T lungs. Kf increased in H-S, but not in H-T lungs. For H-T, increased complex V expression and Vmax counter the effect of the decrease in complex I expression on Δψm. A larger complex II contribution to Δψm along with decreased Vmax and increased Kf could make H-S rats more hyperoxia susceptible. Results are clinically relevant since ventilation with ≥60% O2 is often required for extended periods in patients with acute respiratory distress syndrome (ARDS).NEW & NOTEWORTHY We assessed lung tissue mitochondrial bioenergetics in rats with tolerance (H-T) or susceptibility (H-S) to hyperoxia-induced ARDS. Results from studies in isolated mitochondria, tissue homogenate, and isolated perfused lungs show that mitochondrial bioenergetics are differentially altered in H-T and H-S lungs suggesting a potential role for mitochondrial bioenergetics in hyperoxia-induced ARDS. Results are clinically relevant since hyperoxia exposure is a primary therapy for patients with ARDS, and differential sensitivity to hyperoxia surely occurs in humans.
Collapse
Affiliation(s)
- Pardis Taheri
- Department of Biomedical Engineering, Medical College of Wisconsin, Marquette University, Milwaukee, Wisconsin, United States
| | - Devanshi D Dave
- Department of Biomedical Engineering, Medical College of Wisconsin, Marquette University, Milwaukee, Wisconsin, United States
| | - Ranjan K Dash
- Department of Biomedical Engineering, Medical College of Wisconsin, Marquette University, Milwaukee, Wisconsin, United States
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin, United States
| | - Guru P Sharma
- Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, Wisconsin, United States
| | - Anne V Clough
- Department of Biomedical Engineering, Medical College of Wisconsin, Marquette University, Milwaukee, Wisconsin, United States
- Research Service, Clement J. Zablocki V.A. Medical Center, Milwaukee, Wisconsin, United States
- Department of Mathematical and Statistical Sciences, Marquette University, Milwaukee, Wisconsin, United States
| | - Elizabeth R Jacobs
- Research Service, Clement J. Zablocki V.A. Medical Center, Milwaukee, Wisconsin, United States
- Division of Pulmonary and Critical Care Medicine, Medical College of Wisconsin, Milwaukee, Wisconsin, United States
| | - Said H Audi
- Department of Biomedical Engineering, Medical College of Wisconsin, Marquette University, Milwaukee, Wisconsin, United States
- Research Service, Clement J. Zablocki V.A. Medical Center, Milwaukee, Wisconsin, United States
- Division of Pulmonary and Critical Care Medicine, Medical College of Wisconsin, Milwaukee, Wisconsin, United States
| |
Collapse
|
2
|
Gnaiger E. Complex II ambiguities-FADH 2 in the electron transfer system. J Biol Chem 2024; 300:105470. [PMID: 38118236 PMCID: PMC10772739 DOI: 10.1016/j.jbc.2023.105470] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2023] [Revised: 11/01/2023] [Accepted: 11/06/2023] [Indexed: 12/22/2023] Open
Abstract
The prevailing notion that reduced cofactors NADH and FADH2 transfer electrons from the tricarboxylic acid cycle to the mitochondrial electron transfer system creates ambiguities regarding respiratory Complex II (CII). CII is the only membrane-bound enzyme in the tricarboxylic acid cycle and is part of the electron transfer system of the mitochondrial inner membrane feeding electrons into the coenzyme Q-junction. The succinate dehydrogenase subunit SDHA of CII oxidizes succinate and reduces the covalently bound prosthetic group FAD to FADH2 in the canonical forward tricarboxylic acid cycle. However, several graphical representations of the electron transfer system depict FADH2 in the mitochondrial matrix as a substrate to be oxidized by CII. This leads to the false conclusion that FADH2 from the β-oxidation cycle in fatty acid oxidation feeds electrons into CII. In reality, dehydrogenases of fatty acid oxidation channel electrons to the Q-junction but not through CII. The ambiguities surrounding Complex II in the literature and educational resources call for quality control, to secure scientific standards in current communications of bioenergetics, and ultimately support adequate clinical applications. This review aims to raise awareness of the inherent ambiguity crisis, complementing efforts to address the well-acknowledged issues of credibility and reproducibility.
Collapse
|
3
|
Shim D, Han J. Coordination chemistry of mitochondrial copper metalloenzymes: exploring implications for copper dyshomeostasis in cell death. BMB Rep 2023; 56:575-583. [PMID: 37915136 PMCID: PMC10689082] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2023] [Revised: 10/01/2023] [Accepted: 10/16/2023] [Indexed: 11/03/2023] Open
Abstract
Mitochondria, fundamental cellular organelles that govern energy metabolism, hold a pivotal role in cellular vitality. While consuming dioxygen to produce adenosine triphosphate (ATP), the electron transfer process within mitochondria can engender the formation of reactive oxygen species that exert dual roles in endothelial homeostatic signaling and oxidative stress. In the context of the intricate electron transfer process, several metal ions that include copper, iron, zinc, and manganese serve as crucial cofactors in mitochondrial metalloenzymes to mediate the synthesis of ATP and antioxidant defense. In this mini review, we provide a comprehensive understanding of the coordination chemistry of mitochondrial cuproenzymes. In detail, cytochrome c oxidase (CcO) reduces dioxygen to water coupled with proton pumping to generate an electrochemical gradient, while superoxide dismutase 1 (SOD1) functions in detoxifying superoxide into hydrogen peroxide. With an emphasis on the catalytic reactions of the copper metalloenzymes and insights into their ligand environment, we also outline the metalation process of these enzymes throughout the copper trafficking system. The impairment of copper homeostasis can trigger mitochondrial dysfunction, and potentially lead to the development of copper-related disorders. We describe the current knowledge regarding copper-mediated toxicity mechanisms, thereby shedding light on prospective therapeutic strategies for pathologies intertwined with copper dyshomeostasis. [BMB Reports 2023; 56(11): 575-583].
Collapse
Affiliation(s)
- Daeun Shim
- Department of Applied Chemistry, University of Seoul, Seoul 02504, Korea
| | - Jiyeon Han
- Department of Applied Chemistry, University of Seoul, Seoul 02504, Korea
| |
Collapse
|