Interleukin-1beta inhibits ATP-induced protein kinase B activation in renal mesangial cells by two different mechanisms: the involvement of nitric oxide and ceramide.
1 Extracellular nucleotides, like ATP and UTP, have been shown to activate the protein kinase B (PKB) pathway in mesangial cells. In this study we report that the pro-inflammatory cytokine interleukin-1beta (IL-1beta) inhibits ATP-induced PKB activation. 2 Pretreatment of mesangial cells with IL-1beta leads to a time-dependent decrease of ATP-induced PKB phosphorylation. Maximal inhibition is seen after 6 h of pretreatment. Incubating cells with IL-1beta in the presence of the NO synthase inhibitor, N-monomethyl-L-arginine (L-NMMA), reversed the IL-1beta inhibition of PKB activity. A similar decrease in ATP-evoked PKB activation is obtained when cells were pretreated with the nitric oxide (NO) donor, (Z)-1-[2-Aminoethyl)-N-(2-ammonioethyl)amino]diazen-1-ium-1,2-diolate (Deta-NO), but not with the cell-permeable cGMP analogue, 8-bromo-cGMP. 3 The NO- and IL-1beta-mediated delayed inhibition of PKB activity is completely reversed by the phosphatase inhibitor calyculin A, but not by ocadaic acid, suggesting that NO upregulates a protein phosphatase activity, which most probably belongs to the group of protein phosphatases type 1. 4 In addition, IL-1beta also triggers a short-term and transient inhibitory effect on ATP-induced PKB activation which is maximal after 2-5 min of pre-incubation with IL-1beta. This effect occurs independently of NO generation, because no NO synthase is expressed at that time, and consequently, L-NMMA does not reverse the effect. Rather an involvement of the sphingolipid ceramide is likely, since IL-1beta triggers rapid ceramide formation and incubation of cells with the cell-permeable C6-ceramide blocked ATP-induced PKB phosphorylation. 5 In summary, our data show that IL-1beta exerts both short-term and long-term inhibitory effects on ATP-stimulated PKB activation, the short-term effect probably involves ceramide formation, whereas the long-term effect is due to inducible NO synthase induction and subsequent NO formation. These results reveal a further facet in the mechanisms of ceramide- and NO-induced cell death, i.e. by turning off the survival signal elicited by PKB.
Rölz
Waltraud
W
Pharmazentrum Frankfurt, Klinikum der Johann Wolfgang Goethe-Universität, Theodor-Stern-Kai 7, D-60590 Frankfurt am Main, Germany.
Xin
Cuiyan
C
Ren
Shuyu
S
Pfeilschifter
Josef
J
Huwiler
Andrea
A
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D015153:Blotting, Western; D002478:Cells, Cultured; D002518:Ceramides / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D004790:Enzyme Induction; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005920:Glomerular Mesangium / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D007375:Interleukin-1 / Q000378:metabolism* / Q000494:pharmacology; D008387:Marine Toxins; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000096:biosynthesis; D052247:Nitric Oxide Synthase Type II; D019319:Okadaic Acid / Q000494:pharmacology; D010080:Oxazoles / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats
D002518:Ceramides; D004791:Enzyme Inhibitors; D007375:Interleukin-1; D008387:Marine Toxins; D010080:Oxazoles; D011518:Proto-Oncogene Proteins; D019319:Okadaic Acid; D009569:Nitric Oxide; C059041:calyculin A; D000255:Adenosine Triphosphate; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt