Hyperhomocysteinemia activates NF-kappaB and inducible nitric oxide synthase in the kidney.
BACKGROUND
Hyperhomocysteinemia is an independent risk factor for cardiovascular disorders. Injury of multiple organs, including the kidney, was observed in hyperhomocysteinemic individuals. Activation of a transcription factor, namely, nuclear factor kappa B (NF-kappaB), plays an important role in inflammatory response and can exacerbate organ injury. The objective of the present study was to investigate the effect of hyperhomocysteinemia on renal NF-kappaB activation and the consequence of such activation.


METHODS
Hyperhomocysteinemia was induced in Sprague-Dawley rats after 4 weeks of a high-methionine diet. Activation of NF-kappaB was determined by electrophoretic mobility shift assay. Role of inhibitor protein IkappaBalpha was examined by Western immunoblotting analysis.


RESULTS
There was a significant increase in the level of phosphorylated IkappaBalpha protein in kidneys of hyperhomocysteinemic rats. This resulted in a decrease in the IkappaBalpha protein level leading to NF-kappaB activation. As a consequence, the expression of inducible nitric oxide synthase (iNOS) mRNA and protein was significantly elevated in kidneys of hyperhomocysteinemic rats. Increased nitric oxide production (150% of the control) resulted in peroxynitrite formation in these kidneys. Pretreatment of rats with a NF-kappaB inhibitor not only abolished NF-kappaB activation, but also reversed hyperhomocysteinemia-induced iNOS expression in the kidney.


CONCLUSIONS
Hyperhomocysteinemia alone can activate NF-kappaB and hence induce iNOS-mediated nitric oxide production in the kidney leading to increased peroxynitrite formation. This may represent one of the mechanisms for renal dysfunction in hyperhomocysteinemia.
Zhang
Fan
F
Department of Pharmacology, Faculty of Medicine, University of Hong Kong, Hong Kong, China.
Siow
Yaw L
YL
O
Karmin
K
D000818:Animals; D004032:Diet; D020138:Hyperhomocysteinemia / Q000201:enzymology / Q000378:metabolism*; D007668:Kidney / Q000201:enzymology / Q000378:metabolism*; D008297:Male; D008715:Methionine / Q000008:administration & dosage; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II; D011392:Proline / Q000031:analogs & derivatives* / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013859:Thiocarbamates / Q000494:pharmacology; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000096:biosynthesis
D016328:NF-kappa B; D012333:RNA, Messenger; D013859:Thiocarbamates; C066229:prolinedithiocarbamate; C002744:3-nitrotyrosine; D014443:Tyrosine; D011392:Proline; D008715:Methionine; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat