Alpha-lipoic acid supplementation protects enzymes from damage by nitrosative and oxidative stress.
BACKGROUND
S-nitrosylation of mitochondrial enzymes involved in energy transfer under nitrosative stress may result in ATP deficiency. We investigated whether α-lipoic acid, a powerful antioxidant, could alleviate nitrosative stress by regulating S-nitrosylation, which could result in retaining the mitochondrial enzyme activity.


METHODS
In this study, we have identified the S-nitrosylated forms of subunit 1 of dihydrolipoyllysine succinyltransferase (complex III), and subunit 2 of the α-ketoglutarate dehydrogenase complex by implementing a fluorescence-based differential quantitative proteomics method.


RESULTS
We found that the activities of these two mitochondrial enzymes were partially but reversibly inhibited by S-nitrosylation in cultured endothelial cells, and that their activities were partially restored by supplementation of α-lipoic acid. We show that protein S-nitrosylation affects the activity of mitochondrial enzymes that are central to energy supply, and that α-lipoic acid protects mitochondrial enzymes by altering S-nitrosylation levels.


CONCLUSIONS
Inhibiting protein S-nitrosylation with α-lipoic acid seems to be a protective mechanism against nitrosative stress.


CONCLUSIONS
Identification and characterization of these new protein targets should contribute to expanding the therapeutic power of α-lipoic acid and to a better understanding of the underlying antioxidant mechanisms.
Department of Pathology and Laboratory Medicine, The University of North Carolina at Chapel Hill, Chapel Hill, NC, United States.
Sylvia
S
Hiller
Lineberger Comprehensive Cancer Center, The University of North Carolina at Chapel Hill, Chapel Hill, NC, United States.
Robert
R
DeKroon
Department of Neurosciences, Medical University of South Carolina, Charleston, SC, United States.
Eric D
ED
Hamlett
Department of Pathology and Laboratory Medicine, The University of North Carolina at Chapel Hill, Chapel Hill, NC, United States.
Longquan
L
Xu
Systems Proteomics Center, The University of North Carolina at Chapel Hill, Chapel Hill, NC, United States.
Cristina
C
Osorio
Department of Neurosciences, Medical University of South Carolina, Charleston, SC, United States; Systems Proteomics Center, The University of North Carolina at Chapel Hill, Chapel Hill, NC, United States.
Jennifer
J
Robinette
Proteomic Research Core Unit, NHEERL, U.S. Environmental Protection Agency, Research Triangle Park, NC, United States.
Witold
W
Winnik
Lineberger Comprehensive Cancer Center, The University of North Carolina at Chapel Hill, Chapel Hill, NC, United States.
Stephen
S
Simington
Department of Pathology and Laboratory Medicine, The University of North Carolina at Chapel Hill, Chapel Hill, NC, United States.
Nobuyo
N
Maeda
Texas A&M Health Science Center, College Station, TX, United States. Electronic address: alzate@medicine.tamhsc.edu.
Oscar
O
Alzate
Department of Pathology and Laboratory Medicine, The University of North Carolina at Chapel Hill, Chapel Hill, NC, United States. Electronic address: xyi2000@med.unc.edu.
Xianwen
X
Yi
D000255:Adenosine Triphosphate / Q000096:biosynthesis; D000818:Animals; D002478:Cells, Cultured; D014450:Electron Transport Complex III / Q000378:metabolism*; D007655:Ketoglutarate Dehydrogenase Complex / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism*; D018384:Oxidative Stress; D008063:Thioctic Acid / Q000494:pharmacology*
D009569:Nitric Oxide; D008063:Thioctic Acid; D000255:Adenosine Triphosphate; D007655:Ketoglutarate Dehydrogenase Complex; D014450:Electron Transport Complex III
ATP; Antioxidant; Mitochondria; Nitric oxide (NO); Nitrosative stress (NS); Reactive oxygen species (ROS); S-nitrosylation; α-Lipoic acid