Endothelin-1 inhibits TNF alpha-induced iNOS expression in 3T3-F442A adipocytes.
1. Endothelin-1 (ET-1) and tumor necrosis factor alpha (TNFalpha) by their action on adipocytes have been independently linked to the pathogenesis of insulino-resistance. In isolated adipocytes, TNFalpha induces the expression of the inducible nitric oxide synthase (iNOS). The purpose of the present work was, in the 3T3-F442A adipocyte cell line, to characterise TNFalpha-induced iNOS expression and to determine whether or not ET-1 could influence TNFalpha-induced iNOS expression and NO production. 2. In differentiated 3T3-F442A, treatment with TNFalpha (20 ng ml(-1)) induced the expression of a functional iNOS as demonstrated by nitrite assay, Western blot, reverse transcription-polymerase chain reaction and Northern blot analysis. TNFalpha-induced iNOS expression requires nuclear factor kappaB activation, but does not necessitate the activation of the PI-3 kinase/Akt and P38-MAP kinase pathways. 3. ET-1, but not ET-3, inhibited the TNFalpha-induced expression of iNOS protein and mRNA as well as nitrite production. The effects of ET-1 were blocked by a specific ETA (BQ123, pA(2) 7.4) but not by a specific ETB receptor antagonist (BQ788). 3T3-F442A adipocytes express the mRNAs for prepro-ET-1 and the ET-A receptor subtype, but not for the ET-B subtype. 4. The inhibitory effect of ET-1 was not affected by bisindolylmaleimide, SB 203580 or indomethacin, inhibitors of protein kinase C, p38-MAP kinase and cyclooxygenase, respectively, and was not associated with cAMP production. However, the effect of ET-1 was partially reversed by wortmannin, suggesting the involvement of PI3 kinase in the transduction signal of ET-1. 5. Differentiated 3T3-F442A adipocytes did not release ET-1 with or without exposure to TNFalpha, although the mRNA for preproET-1 was detected in both pre- and differentiated adipocytes. 6. Thus, these results confirm that adipocytes are a target for circulating ET-1 and demonstrate that the activation of the ETA receptor subtype can prevent TNFalpha-induced iNOS expression.
Mérial-Kieny
Christelle
C
Département Diabète et Maladies Métaboliques, Institut de Recherche SERVIER, Suresnes 92150, France.
Lonchampt
Michel
M
Cogé
Francis
F
Verwaerde
Patrick
P
Galizzi
Jean-Pierre
JP
Boutin
Jean A
JA
Lafontan
Max
M
Levens
Nigel
N
Galitzky
Jean
J
Félétou
Michel
M
D016475:3T3 Cells; D017667:Adipocytes / Q000187:drug effects / Q000201:enzymology*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D019332:Endothelin-1 / Q000502:physiology*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000502:physiology*; D051379:Mice; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors* / Q000096:biosynthesis* / Q000235:genetics; D052247:Nitric Oxide Synthase Type II; D012333:RNA, Messenger / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D019332:Endothelin-1; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse