title: Sphingosine kinase activity and sphingosine-1 phosphate production in rat pancreatic islets and INS-1 cells: response to cytokines.
abstract: Sphingosine-1 phosphate (S1P) is a bioactive sphingolipid with the potential to mobilize Ca2+, to inhibit apoptosis, and to promote mitogenesis. Sphingosine kinase (SPHK) and S1P were characterized in INS-1 insulinoma cells and isolated rat islets of Langerhans. SPHK activity increased in INS-1 cell homogenates treated with interleukin-1beta (IL-1beta) or tumor necrosis factor-alpha (TNF-alpha), and responses were additive. IL-1beta or TNF-alpha increased islet SPHK activity within 15 min to 1 h; activity remained elevated after 8 h. SPHK2 was the predominant active isoform in INS-1 cells; little or no SPHK1 activity was detected. Cytokines increased endogenous S1P biosynthesis in 32P(i)-prelabeled INS-1 cells, and cycloheximide inhibited the response after 8 h, suggesting that protein synthesis mediated the response. There was no [32P]S1P release from cells. Compared with basal values, IL-1beta and TNF-alpha induced increases in SPHK1a mRNA levels relative to 18S ribosomal RNA in INS-1 cells within 1 h; relative SPHK2 mRNA levels were unchanged after cytokine treatment. IL-1beta, but not TNF-alpha, induced relative SPHK1a mRNA expression levels within 1 h in islets, whereas SPHK2 mRNA levels were unchanged. Thus, IL-1beta and TNF-alpha induced an early and sustained increase in SPHK activity in INS-1 cells and isolated islets, suggesting that S1P plays a role in the pathological response of pancreatic beta-cells to cytokines.
authors.affiliation: Department of Pharmacology and Toxicology, The State University of New York at Buffalo, Buffalo, NY, USA.
authors.forename: Lucy D
authors.initials: LD
authors.lastname: Mastrandrea
authors.forename: Shawn M
authors.initials: SM
authors.lastname: Sessanna
authors.forename: Suzanne G
authors.initials: SG
authors.lastname: Laychock
mesh_terms: D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D045744:Cell Line, Tumor; D016207:Cytokines / Q000494:pharmacology*; D017931:DNA Primers; D007375:Interleukin-1 / Q000494:pharmacology; D007515:Islets of Langerhans / Q000187:drug effects / Q000502:physiology*; D007700:Kinetics; D008246:Lysophospholipids / Q000378:metabolism*; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000378:metabolism*; D013379:Substrate Specificity; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D000099157:Sphingosine Kinase
chemical_list: D016207:Cytokines; D017931:DNA Primers; D007375:Interleukin-1; D008246:Lysophospholipids; D017853:Phosphotransferases (Alcohol Group Acceptor); D012333:RNA, Messenger; D013110:Sphingosine; D014409:Tumor Necrosis Factor-alpha; D000099157:Sphingosine Kinase; C060506:sphingosine 1-phosphate