title: Defining a role for acid sphingomyelinase in the p38/interleukin-6 pathway.
abstract: Acid sphingomyelinase (ASM) is one of the key enzymes involved in regulating the metabolism of the bioactive sphingolipid ceramide in the sphingolipid salvage pathway, yet defining signaling pathways by which ASM exerts its effects has proven difficult. Previous literature has implicated sphingolipids in the regulation of cytokines such as interleukin-6 (IL-6), but the specific sphingolipid pathways and mechanisms involved in inflammatory signaling need to be further elucidated. In this work, we sought to define the role of ASM in IL-6 production because our previous work showed that a parallel pathway of ceramide metabolism, acid β-glucosidase 1, negatively regulates IL-6. First, silencing ASM with siRNA abrogated IL-6 production in response to the tumor promoter, 4β-phorbol 12-myristate 13-acetate (PMA), in MCF-7 cells, in distinction to acid β-glucosidase 1 and acid ceramidase, suggesting specialization of the pathways. Moreover, treating cells with siRNA to ASM or with the indirect pharmacologic inhibitor desipramine resulted in significant inhibition of TNFα- and PMA-induced IL-6 production in MDA-MB-231 and HeLa cells. Knockdown of ASM was found to significantly inhibit PMA-dependent IL-6 induction at the mRNA level, probably ruling out mechanisms of translation or secretion of IL-6. Further, ASM knockdown or desipramine blunted p38 MAPK activation in response to TNFα, revealing a key role for ASM in activating p38, a signaling pathway known to regulate IL-6 induction. Last, knockdown of ASM dramatically blunted invasion of HeLa and MDA-MB-231 cells through Matrigel. Taken together, these results demonstrate that ASM plays a critical role in p38 signaling and IL-6 synthesis with implications for tumor pathobiology.
authors.affiliation: From the Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, South Carolina 29425.
authors.forename: David M
authors.initials: DM
authors.lastname: Perry
authors.affiliation: the Stony Brook Cancer Center and.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Newcomb
authors.affiliation: the Stony Brook Cancer Center and.
authors.forename: Mohamad
authors.initials: M
authors.lastname: Adada
authors.affiliation: From the Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, South Carolina 29425.
authors.forename: Bill X
authors.initials: BX
authors.lastname: Wu
authors.affiliation: From the Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, South Carolina 29425.
authors.forename: Patrick
authors.initials: P
authors.lastname: Roddy
authors.affiliation: the Tohoku Medical Megabank Organization and Department of Obstetrics and Gynecology, Tohoku University Graduate School of Medicine, Sendai 980-8575, Japan.
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Kitatani
authors.affiliation: the Department of Pharmacology and Toxicology, University of Louisville, Louisville, Kentucky 40202.
authors.forename: Leah
authors.initials: L
authors.lastname: Siskind
authors.affiliation: the Department of Medicine Stony Brook University, Stony Brook, New York 11794, and the Northport Veterans Affairs Hospital, Northport, New York 11768.
authors.forename: Lina M
authors.initials: LM
authors.lastname: Obeid
authors.affiliation: the Stony Brook Cancer Center and yusuf.hannun@sbumed.org.
authors.forename: Yusuf A
authors.initials: YA
authors.lastname: Hannun
mesh_terms: D045744:Cell Line, Tumor; D002478:Cells, Cultured; D003891:Desipramine / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D055785:Gene Knockdown Techniques; D006367:HeLa Cells; D006801:Humans; D015850:Interleukin-6 / Q000235:genetics / Q000378:metabolism*; D061986:MCF-7 Cells; D009361:Neoplasm Invasiveness / Q000235:genetics / Q000503:physiopathology; D009542:Niemann-Pick Diseases / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D015398:Signal Transduction; D013108:Sphingomyelin Phosphodiesterase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
chemical_list: D004791:Enzyme Inhibitors; C508600:IL6 protein, human; D015850:Interleukin-6; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D048051:p38 Mitogen-Activated Protein Kinases; D013108:Sphingomyelin Phosphodiesterase; D013755:Tetradecanoylphorbol Acetate; D003891:Desipramine
keywords: Acid Sphingomyelinase; Cancer Biology; Cell Signaling; Interleukin 6 (IL-6); Sphingolipid; p38 MAPK