Molecular mechanisms by which iron induces nitric oxide synthesis in cultured proximal tubule cells.
Nitric oxide (NO) levels are increased after exposure of cultured proximal tubule cells (PTC) to non-haem iron, potentially contributing to PTC injury in disease states associated with increased iron exposure, including proteinuric renal disease. The mechanisms underlying this observed increase were investigated. After 3 h exposure to 400 microM nitrilotriacetate (NTA)-Fe, inducible nitric oxide synthase (iNOS) mRNA expression was significantly increased, with a corresponding increase in iNOS protein after 12 h. The nuclear binding activity of NFkappaB with 400 microM NTA-Fe was increased, and pyrrolidine dithiocarbamate (PDTC), an antioxidant inhibitor of NFkappaB, prevented both activation of NFkappaB and NO production in response to NTA-Fe. Inhibition of protein tyrosine kinase reduced iNOS mRNA, iNOS protein levels and NO production in response to NTA-Fe. The effect of tyrosine kinase inhibition on NFkappaB activation was variable, with herbimycin but not genistein having an inhibitory effect. Activation of either protein kinase A or C increased iNOS mRNA and protein levels, and NO production in response to NTA-Fe, whereas only the protein kinase C activator phorbol dibutyrate (PDBu) had a stimulatory effect on NFkappaB activation. The protein kinase A activator forskolin did not alter iron-induced activation of NFkappaB. These data suggest that the observed increase in NO production by PTC in response to iron is due to increased transcription of iNOS. The transcriptional regulation of this response is complex and involves NFkappaB, protein tyrosine kinase and the protein kinases A and C.
Chen
L
L
Department of Renal Medicine, The University of Sydney at Westmead Hospital, Westmead, NSW, Australia.
Wang
Y
Y
Kairaitis
L K
LK
Wang
Y
Y
Zhang
B H
BH
Harris
D C
DC
D000818:Animals; D016227:Benzoquinones; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology*; D054746:Cyclic AMP-Dependent Protein Kinase Type II; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D005290:Ferric Compounds / Q000494:pharmacology*; D015971:Gene Expression Regulation, Enzymologic; D019833:Genistein / Q000494:pharmacology*; D007501:Iron / Q000378:metabolism*; D007502:Iron Chelating Agents / Q000378:metabolism; D007687:Kidney Tubules, Proximal / Q000187:drug effects* / Q000378:metabolism; D047029:Lactams, Macrocyclic; D008297:Male; D016328:NF-kappa B / Q000378:metabolism*; D009569:Nitric Oxide / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II; D009571:Nitrilotriacetic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology*; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology*; D011493:Protein Kinase C / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D011759:Pyrrolidines / Q000494:pharmacology*; D011809:Quinones / Q000494:pharmacology*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D017828:Rifabutin / Q000031:analogs & derivatives; D013859:Thiocarbamates / Q000494:pharmacology*
D016227:Benzoquinones; D005290:Ferric Compounds; D007502:Iron Chelating Agents; D047029:Lactams, Macrocyclic; D016328:NF-kappa B; D011759:Pyrrolidines; D011809:Quinones; D012333:RNA, Messenger; D013859:Thiocarbamates; D005576:Colforsin; D017828:Rifabutin; C020972:pyrrolidine dithiocarbamic acid; D009569:Nitric Oxide; D015240:Phorbol 12,13-Dibutyrate; C020754:herbimycin; D019833:Genistein; D007501:Iron; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat; D011505:Protein-Tyrosine Kinases; D054746:Cyclic AMP-Dependent Protein Kinase Type II; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D009571:Nitrilotriacetic Acid; C020326:ferric nitrilotriacetate