Dysregulation of very long chain acyl-CoA dehydrogenase coupled with lipid peroxidation

Abstract

Idiopathic pulmonary fibrosis (IPF) is a chronic progressive lung disease of unknown etiology. We previously revealed increased oxidative stress and high expression of antioxidant proteins in culture cell lines established from lesional lung tissues with IPF (Kabuyama Y, Oshima K, Kitamura T, Homma M, Yamaki J, Munakata M, Homma Y. Genes Cells 12: 1235-1244, 2007). In this study, we show that IPF cells contain high levels of free cholesterol and its peroxidized form as compared with normal TIG7 lung fibroblasts, suggesting that radical oxygen species (ROS) are generated within specific organelles. To understand the molecular basis underlying the generation of ROS in IPF cells, we performed proteomic analysis of mitochondrial proteins from TIG and IPF cells. This analysis shows that the phosphorylation of Ser586 of very long chain acyl-CoA dehydrogenase (VLCAD) is significantly reduced in IPF cells. Similar results are obtained from immunoblotting with anti-pS586 antibody. Kinase activity toward a peptide containing Ser586 from IPF cells is significantly lower than that from TIG cells. Furthermore, a phosphorylation-negative mutant (S586A) VLCAD shows reduced electron transfer activity and a strong dominant-negative effect on fatty acid beta-oxidation. The ectopic expression of the S586A mutant induced human embryonic kidney (HEK) 293 cells to produce significantly high amounts of oxidized lipids and hydrogen peroxide. HEK293 cells expressing the S586A mutant exhibit a reduction in cell growth and an enhancement in apoptosis. These results suggest a novel regulatory mechanism for homeostatic VLCAD activity, whose dysregulation might be involved in the production of oxidative stress and in the pathogenesis of IPF.

WITHDRAWN: Ginkgolide B reduces hepatic lipid accumulation and ameliorates nonalcoholic fatty liver disease in high-fat diet–induced obese mice

“…Free fatty acids are especially associated with an inflammatory response of epididymal adipose tissue and the liver macrophages, and with adipose tissue and liver insulin resistance [1,33]; in addition, excess free fatty acids are metabolized to release energy or excreted into the feces or urine to reduce organ damage [47]. We found that ginkgolide B enhanced long-chain fatty acid decomposition in the liver by β-oxidation, which increased CPT-1and CD36 expression; however, β-oxidation of fatty acids may also produce lipid oxidative toxicity [48]. Using the fluorescent dye BODIPY 581/591 C11, we found that ginkgolide B significantly reduced lipid peroxidation and the toxic effects of lipid metabolism.…”

A Pneumocyte–Macrophage Paracrine Lipid Axis Drives the Lung toward Fibrosis

“…Although oxidative stress has been a recognized feature of fibrotic lung diseases, our work provides insight into how oxidative injury contributes to the pathogenesis of these disorders (45). We determined that oxidized phospholipids accumulate in the insulted murine lung and that oxPc serves as an important driver of profibrotic macrophages in rodents and humans.…”

Nitric Oxide Regulates Mitochondrial Fatty Acid Metabolism Through Reversible Protein S -Nitrosylation

“…VLCAD is a homodimer consisting of 67 kDa subunits and is embedded in the inner mitochondria membrane 26-28). The enzymatic activity of VLCAD appears to be regulated by protein abundance and phosphorylation of Ser 586 (29). Our data indicate that S-nitrosylation of VLCAD at Cys 238 through eNOS-derived nitric oxide results in reversible activation of enzymatic activity through conformational changes that alter the K M of the enzyme and could substantially influence the in vivo β-oxidation of fatty acids.…”