title: Genetic ablation and short-duration inhibition of lipoxygenase results in increased macroautophagy.
abstract: 12/15-lipoxygenase (12/15-LOX) is involved in organelle homeostasis by degrading mitochondria in maturing red blood cells and by eliminating excess peroxisomes in liver. Furthermore, 12/15-LOX contributes to diseases by exacerbating oxidative stress-related injury, notably in stroke. Nonetheless, it is unclear what the consequences are of abolishing 12/15-LOX activity. Mice in which the alox15 gene has been ablated do not show an obvious phenotype, and LOX enzyme inhibition is not overtly detrimental. We show here that liver histology is also unremarkable. However, electron microscopy demonstrated that 12/15-LOX knockout surprisingly leads to increased macroautophagy in the liver. Not only macroautophagy but also mitophagy and pexophagy were increased in hepatocytes, which otherwise showed unaltered fine structure and organelle morphology. These findings were substantiated by immunofluorescence showing significantly increased number of LC3 puncta and by Western blotting demonstrating a significant increase for LC3-II protein in both liver and brain homogenates of 12/15-LOX knockout mice. Inhibition of 12/15-LOX activity by treatment with four structurally different inhibitors had similar effects in cultured HepG2 hepatoma cells and SH-SY5Y neuroblastoma cells with significantly increased autophagy discernable already after 2 hours. Hence, our study reveals a link between ablation or inhibition of 12/15-LOX and stimulation of macroautophagy. The enhanced macroautophagy may be related to the known tissue-protective effects of LOX ablation or inhibition under various diseased conditions caused by oxidative stress and ischemia. This could provide an important cleaning mechanism of cells and tissues to prevent accumulation of damaged mitochondria and other cellular components.
authors.affiliation: Department of Integrated OMICS for Biomedical Science, WCU Program of Graduate School, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-749, South Korea.
authors.forename: Insook
authors.initials: I
authors.lastname: Jang
authors.affiliation: Department of Integrated OMICS for Biomedical Science, WCU Program of Graduate School, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-749, South Korea.
authors.forename: Sujin
authors.initials: S
authors.lastname: Park
authors.affiliation: Department of Integrated OMICS for Biomedical Science, WCU Program of Graduate School, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-749, South Korea.
authors.forename: Jin Won
authors.initials: JW
authors.lastname: Cho
authors.affiliation: Neuroprotection Research Laboratory, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA.
authors.forename: Kazim
authors.initials: K
authors.lastname: Yigitkanli
authors.affiliation: Neuroprotection Research Laboratory, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA.
authors.forename: Klaus
authors.initials: K
authors.lastname: van Leyen
authors.affiliation: Department of Integrated OMICS for Biomedical Science, WCU Program of Graduate School, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-749, South Korea. Electronic address: jurgen.roth@bluewin.ch.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Roth
mesh_terms: D000818:Animals; D001092:Arachidonate 12-Lipoxygenase / Q000235:genetics*; D001093:Arachidonate 15-Lipoxygenase / Q000235:genetics*; D001343:Autophagy / Q000187:drug effects* / Q000235:genetics*; D017353:Gene Deletion; D056945:Hep G2 Cells; D006801:Humans; D016859:Lipoxygenase Inhibitors / Q000494:pharmacology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D013997:Time Factors; D014407:Tumor Cells, Cultured; D015854:Up-Regulation / Q000187:drug effects / Q000235:genetics
chemical_list: C475064:12-15-lipoxygenase; D016859:Lipoxygenase Inhibitors; D001092:Arachidonate 12-Lipoxygenase; D001093:Arachidonate 15-Lipoxygenase
keywords: Autophagy; Brain; Lipoxygenase; Lipoxygenase inhibition; Lipoxygenase knockout; Liver; Mitophagy; Oxidative stress