Phospholipase A2-modified low density lipoprotein induces mitochondrial uncoupling and lowers reactive oxygen species in phagocytes.
Low density lipoprotein modified by secretory phospholipase A(2) (PLA-LDL) protects monocytes against oxidative stress. In this study we investigated possible direct effects of PLA-LDL on mitochondrial membrane potential and reactive oxygen species generation. Mitochondrial membrane potential in human monocytic THP-1 cells or primary human monocytes was monitored by flow cytometry using the fluorescent dye 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolylcarbocyanine iodide or respirometry. Formation of reactive oxygen species was determined by flow cytometric measuring 2',7'-dichlorofluorescin oxidation. Cell death was assessed using Annexin V/propidium iodide staining. We observed that PLA-LDL caused mitochondrial uncoupling in monocyte/macrophage cell lines as well as in primary human monocytes. PLA-LDL-associated non-esterified fatty acids provoked uncoupling. Uncoupling attenuated reactive oxygen species formation induced by hydrogen peroxide, 2,3-dimethoxy-1,4-naphthoquinone or oxidized LDL. Knock-down of uncoupling protein UCP2 affected neither PLA-LDL-induced uncoupling, nor reactive oxygen species generation. Furthermore, we observed that the chemical uncoupler carbonyl cyanide m-chlorophenylhydrazone increased THP-1 cell survival after hydrogen peroxide treatment. Thus, PLA-LDL-induced uncoupling attenuates reactive oxygen species generation, which may contribute to increased monocyte survival in atherosclerotic plaques and support pro-atherogenic effects of LDL modified by PLA(2).
Namgaladze
Dmitry
D
Goethe-University, Faculty of Medicine, Institute of Biochemistry I/ZAFES, Theodor-Stern-Kai 7, Frankfurt, Germany.
Preiss
Stefan
S
Dröse
Stefan
S
Brandt
Ulrich
U
Brüne
Bernhard
B
D002478:Cells, Cultured; D006801:Humans; D008077:Lipoproteins, LDL / Q000378:metabolism*; D053078:Membrane Potential, Mitochondrial / Q000502:physiology*; D010586:Phagocytes / Q000378:metabolism*; D054467:Phospholipases A2 / Q000502:physiology*; D017382:Reactive Oxygen Species / Q000378:metabolism*
D008077:Lipoproteins, LDL; D017382:Reactive Oxygen Species; D054467:Phospholipases A2