title: Cytokines and nitric oxide inhibit the enzyme activity of catalase but not its protein or mRNA expression in insulin-producing cells.
abstract: Pancreatic beta-cells have low activities of the antioxidant enzyme catalase. Nitric oxide interacts with the haem group of catalase inhibiting its activity. We have studied the activity of catalase in beta-cells under conditions mimicking prediabetes and in which nitric oxide is generated from cytokine treatment in vitro. We also studied whether there is regulation of catalase enzyme activity by nitric oxide at the protein or gene expression level. RINm5F insulin-producing cells, treated for 24 h with cytokines, showed increased medium nitrite production (17+/-2.2 vs 0.3+/-0.2 pmol/ micro g protein) and significantly decreased cellular catalase activity (42.4+/-4.5%) compared with control cells. A similar reduction was seen in catalase-overexpressing RIN-CAT cells and in rat or human pancreatic islets of Langerhans. Catalase activity was also suppressed by the long-acting nitric oxide donor diethylenetriamine/nitric oxide adduct (Deta-NO) and this inhibition was reversible. The inhibition of catalase activity by cytokines in RINm5F cells was significantly reversed by the addition of the nitric oxide synthase 2 (NOS2) inhibitors nitro monomethylarginine or N-(3-(aminomethyl)benzyl)acetamidine (1400W). Protein expression was found to be unchanged in cytokine- or Deta-NO-treated RINm5F cells, while mRNA expression was marginally increased. We have shown that inhibition of catalase activity by cytokines is nitric oxide dependent and propose that this inhibition may confer increased susceptibility to cytokine- or nitric oxide-induced cell killing.
authors.affiliation: Pharmacy and Biomolecular Sciences, Cockcroft Building, Room 708, University of Brighton, Lewes Road, Brighton BN2 4GJ, UK.
authors.forename: L A
authors.initials: LA
authors.lastname: Sigfrid
authors.forename: J M
authors.initials: JM
authors.lastname: Cunningham
authors.forename: N
authors.initials: N
authors.lastname: Beeharry
authors.forename: S
authors.initials: S
authors.lastname: Lortz
authors.forename: M
authors.initials: M
authors.lastname: Tiedge
authors.forename: S
authors.initials: S
authors.lastname: Lenzen
authors.forename: C
authors.initials: C
authors.lastname: Carlsson
authors.forename: I C
authors.initials: IC
authors.lastname: Green
mesh_terms: D000578:Amidines / Q000494:pharmacology; D000818:Animals; D001596:Benzylamines / Q000494:pharmacology; D002374:Catalase / Q000378:metabolism*; D016923:Cell Death / Q000502:physiology; D016207:Cytokines / Q000494:pharmacology*; D004789:Enzyme Activation / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007328:Insulin / Q000378:metabolism; D007340:Insulinoma / Q000201:enzymology*; D007515:Islets of Langerhans / Q000201:enzymology; D009569:Nitric Oxide / Q000494:pharmacology*; D019001:Nitric Oxide Synthase / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II; D010190:Pancreatic Neoplasms / Q000201:enzymology*; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D014226:Triazenes / Q000494:pharmacology; D014407:Tumor Cells, Cultured
chemical_list: C105351:1-hydroxy-2-oxo-3,3-bis(2-aminoethyl)-1-triazene; D000578:Amidines; D001596:Benzylamines; D016207:Cytokines; D004791:Enzyme Inhibitors; D007328:Insulin; C104820:N-(3-(aminomethyl)benzyl)acetamidine; D012333:RNA, Messenger; D014226:Triazenes; D009569:Nitric Oxide; D002374:Catalase; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II