NF-kappaB inhibitors stabilize the mRNA of high-affinity type-2 cationic amino acid transporter in LPS-stimulated rat liver.
BACKGROUND
Induction of inducible nitric oxide synthase (iNOS) results in nitric oxide (NO) overproduction during endotoxemia. Cellular uptake of L-arginine, modulated by the isozymes of type-2 cationic amino acid transporters (CAT), including CAT-2, CAT-2A and CAT-2B, has been reported to be a crucial factor in the regulation of iNOS activity. We sought to elucidate the expression of CAT-2 isozymes and the role of nuclear factor-kappaB (NF-kappaB) in this expression in lipopolysaccharide (LPS)-treated rat liver.


METHODS
Adult male Sprague-Dawley rats were randomly given intravenous (i.v.) injections of normal saline (N/S), LPS, LPS preceded by an NF-kappaB inhibitor (PDTC, dexamethasone or salicylate) or an NF-kappaB inhibitor alone. After injection, rats were sacrificed at different times and enzyme expression and liver injury were examined. Hepatic and systemic NO production were also measured.


RESULTS
CAT-2, CAT-2A and CAT-2B were constitutively expressed in un-stimulated rat liver. LPS stimulation not only significantly increased iNOS mRNA and NO concentrations but also decreased the mRNA concentrations of CAT-2 and CAT-2B, but not CAT-2A, in a time-dependent manner. LPS-induced hepatic and systemic NO overproduction was associated with hepatocellular injury. Pre-treatment with NF-kappaB inhibitors significantly attenuated LPS-induced iNOS induction as well as CAT-2/CAT-2B mRNA destabilization, which was associated with significant inhibition of NO biosynthesis and less liver injury.


CONCLUSIONS
NF-kappaB inhibitors stabilize CAT-2 and CAT-2B mRNA in LPS-stimulated rat liver. The hepatic CAT-2/CAT-2B pathway may be a constitutive part of cytoprotective mechanisms against sepsis.
Yang
C-H
CH
Department of Anesthesiology, Mackay Memorial Hospital, Taipei, Taiwan.
Tsai
P-S
PS
Lee
J-J
JJ
Huang
C-H
CH
Huang
C-J
CJ
D000410:Alanine Transaminase / Q000097:blood; D000818:Animals; D001219:Aspartate Aminotransferases / Q000097:blood; D027202:Cationic Amino Acid Transporter 2 / Q000096:biosynthesis*; D056486:Chemical and Drug Induced Liver Injury / Q000201:enzymology / Q000473:pathology; D006439:Hemodynamics / Q000187:drug effects; D007527:Isoenzymes / Q000096:biosynthesis; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008099:Liver / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D008163:Luminescent Measurements; D008297:Male; D016328:NF-kappa B / Q000037:antagonists & inhibitors*; D019001:Nitric Oxide Synthase / Q000096:biosynthesis; D052247:Nitric Oxide Synthase Type II; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013268:Stimulation, Chemical
D027202:Cationic Amino Acid Transporter 2; D007527:Isoenzymes; D008070:Lipopolysaccharides; D016328:NF-kappa B; D012333:RNA, Messenger; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat; D001219:Aspartate Aminotransferases; D000410:Alanine Transaminase