title: Neutral sphingomyelinase inhibition alleviates apoptosis, but not ER stress, in liver ischemia-reperfusion injury.
abstract: Previous studies have revealed the activation of neutral sphingomyelinase (N-SMase)/ceramide pathway in hepatic tissue following warm liver ischemia reperfusion (IR) injury. Excessive ceramide accumulation is known to potentiate apoptotic stimuli and a link between apoptosis and endoplasmic reticulum (ER) stress has been established in hepatic IR injury. Thus, this study determined the role of selective N-SMase inhibition on ER stress and apoptotic markers in a rat model of liver IR injury. Selective N-SMase inhibitor was administered via intraperitoneal injections. Liver IR injury was created by clamping blood vessels supplying the median and left lateral hepatic lobes for 60 min, followed by 60 min reperfusion. Levels of sphingmyelin and ceramide in liver tissue were determined by an optimized multiple reactions monitoring (MRM) method using ultrafast-liquid chromatography (UFLC) coupled with tandem mass spectrometry (MS/MS). Spingomyelin levels were significantly increased in all IR groups compared with controls. Treatment with a specific N-SMase inhibitor significantly decreased all measured ceramides in IR injury. A significant increase was observed in ER stress markers C/EBP-homologous protein (CHOP) and 78 kDa glucose-regulated protein (GRP78) in IR injury, which was not significantly altered by N-SMase inhibition. Inhibition of N-SMase caused a significant reduction in phospho-NF-kB levels, hepatic TUNEL staining, cytosolic cytochrome c, and caspase-3, -8, and -9 activities which were significantly increased in IR injury. Data herein confirm the role of ceramide in increased apoptotic cell death and highlight the protective effect of N-SMase inhibition in down-regulation of apoptotic stimuli responses occurring in hepatic IR injury.
authors.affiliation: a Department of Medical Biochemistry , Akdeniz University Faculty of Medicine , Antalya , Turkey.
authors.forename: Hazal
authors.initials: H
authors.lastname: Tuzcu
authors.affiliation: b Department of Pathology , Akdeniz University Faculty of Medicine , Antalya , Turkey.
authors.forename: Betul
authors.initials: B
authors.lastname: Unal
authors.affiliation: a Department of Medical Biochemistry , Akdeniz University Faculty of Medicine , Antalya , Turkey.
authors.forename: Ebru
authors.initials: E
authors.lastname: Kırac
authors.affiliation: c Department of Histology , Akdeniz University Faculty of Medicine , Antalya , Turkey.
authors.forename: Esma
authors.initials: E
authors.lastname: Konuk
authors.affiliation: a Department of Medical Biochemistry , Akdeniz University Faculty of Medicine , Antalya , Turkey.
authors.forename: Filiz
authors.initials: F
authors.lastname: Ozcan
authors.affiliation: b Department of Pathology , Akdeniz University Faculty of Medicine , Antalya , Turkey.
authors.forename: Gulsum O
authors.initials: GO
authors.lastname: Elpek
authors.affiliation: c Department of Histology , Akdeniz University Faculty of Medicine , Antalya , Turkey.
authors.forename: Necdet
authors.initials: N
authors.lastname: Demir
authors.affiliation: a Department of Medical Biochemistry , Akdeniz University Faculty of Medicine , Antalya , Turkey.
authors.forename: Mutay
authors.initials: M
authors.lastname: Aslan
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D001808:Blood Vessels / Q000187:drug effects / Q000473:pathology; D020169:Caspases / Q000096:biosynthesis; D002518:Ceramides / Q000378:metabolism; D000091342:Endoplasmic Reticulum Chaperone BiP; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000008:administration & dosage*; D006028:Glycosphingolipids / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000096:biosynthesis; D006801:Humans; D008099:Liver / Q000187:drug effects* / Q000293:injuries / Q000473:pathology; D051381:Rats; D015427:Reperfusion Injury / Q000188:drug therapy*; D013108:Sphingomyelin Phosphodiesterase / Q000037:antagonists & inhibitors / Q000235:genetics*; D051742:Transcription Factor CHOP / Q000096:biosynthesis
chemical_list: D002518:Ceramides; C497251:Ddit3 protein, rat; D000091342:Endoplasmic Reticulum Chaperone BiP; D004791:Enzyme Inhibitors; C051684:GRP78 protein, rat; D006028:Glycosphingolipids; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; D051742:Transcription Factor CHOP; D013108:Sphingomyelin Phosphodiesterase; D020169:Caspases
keywords: Liver; ceramide; ischemia–reperfusion injury; neutral sphingomyelinase