Norfloxacin reduces aortic NO synthases and proinflammatory cytokine up-regulation in cirrhotic rats: role of Akt signaling.
OBJECTIVE
Arterial vasodilation plays a role in the pathogenesis of the complications of cirrhosis. This vasodilation is caused by the overproduction of arterial nitric oxide (NO). Bacterial translocation may be involved in NO synthase (NOS) up-regulation by activating both endothelial NOS (eNOS) and inducible NOS (iNOS). The prevention of intestinal gram-negative translocation by norfloxacin administration corrects systemic circulatory changes by decreasing NO production in cirrhosis. However, the signaling mechanisms for NO overproduction from bacterial translocation are unknown. In this study, we investigated the signal transduction pathway of bacterial translocation-induced aortic NOS up-regulation in cirrhotic rats.


METHODS
Proinflammatory cytokine levels, Akt and NOS activities, eNOS phosphorylation, and NOS expressions were assessed in aorta from norfloxacin-treated and untreated cirrhotic rats. Norfloxacin was administered to reduce intestinal bacterial translocation.


RESULTS
Aortic eNOS and iNOS protein expressions, Akt activity, and eNOS phosphorylation by Akt at serine 1177 were up-regulated in cirrhotic rats. Norfloxacin administration significantly decreased the incidence of gram-negative translocation and proinflammatory cytokine (tumor necrosis factor-alpha, interferon-gamma, and interleukin-6) levels; norfloxacin also decreased aortic Akt activity, eNOS phosphorylation, and NOS expressions and activities. The decrease in aortic Akt activity and NOS expressions also was obtained after colistin or anti-tumor necrosis factor-alpha antibody administration to cirrhotic rats.


CONCLUSIONS
This study identifies a signaling pathway in which bacterial translocation induces aortic NOS up-regulation and thus NO overproduction in cirrhotic rats. These results strongly suggest that bacterial translocation and proinflammatory cytokines play a role in systemic NO overproduction in cirrhosis by the Akt pathway.
Tazi
Khalid A
KA
Laboratoire d'Hémodynamique Splanchnique et de Biologie Vasculaire, INSERM, Hôpital Beaujon, Clichy, France. ktazi@bichat.inserm.fr
Moreau
Richard
R
Hervé
Philippe
P
Dauvergne
Agnes
A
Cazals-Hatem
Dominique
D
Bert
Frederic
F
Poirel
Odile
O
Rabiller
Anne
A
Lebrec
Didier
D
D000818:Animals; D001011:Aorta / Q000187:drug effects* / Q000201:enzymology / Q000276:immunology; D018988:Bacterial Translocation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005243:Feces / Q000382:microbiology; D008103:Liver Cirrhosis / Q000276:immunology / Q000378:metabolism* / Q000473:pathology; D008297:Male; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; D009643:Norfloxacin / Q000494:pharmacology*; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D000637:Transaminases / Q000097:blood; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects
D004791:Enzyme Inhibitors; D011518:Proto-Oncogene Proteins; D014409:Tumor Necrosis Factor-alpha; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; C496318:Nos2 protein, rat; C496316:Nos3 protein, rat; D000637:Transaminases; C494920:Akt1 protein, rat; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D009643:Norfloxacin