Deleterious effects of silymarin on the expression of genes controlling endothelial nitric oxide synthase activity in carbon tetrachloride-treated rat livers.
OBJECTIVE
Defects in intrahepatic nitric oxide (NO) are attributed to reduced blood flow due to portal hypertension caused by diminished endothelial NO synthase (eNOS) activity. The aim of this study is to identify the therapeutic effects of silymarin on eNOS/NO-related enzymes and hepatic enzymes in carbon tetrachloride (CCl4)-induced cirrhotic rats.


METHODS
CCl4 treated for 12 weeks was discontinued and then administrated with silymarin daily for 4 weeks. Collagen concentrations were determined by measuring hydroxyproline content. Serum was assayed for hepatic enzymes like alanine aminotransferase (ALT), aspartate aminotransferase (AST) and alkaline phosphatase (ALP) activities. NOS activities were measured by oxyhemoglobin oxidation assay, and levels of enzyme expression and phosphorylation were detected by Western-blot analyses.


RESULTS
Silymarin treatment restored the values for collagen content and ALT and ALP activities when compared to the values with spontaneous resolution following discontinuation of CCl4. CCl4 treatment highly increased eNOS expression and NOS activity in livers, but the phosphorylation was markedly decreased. Silymarin decreased significantly eNOS expression and activity. Expression and/or phosphorylation of enzymes activating eNOS were unchanged (Akt and AMPK) or decreased (PKA) by silymarin. Especially, the expression of caveolin-1, an inhibitor of eNOS was unchanged by CCl4, but its phosphorylation was significantly increased. However, silymarin markedly increased caveolin-1 expression but decreased its phosphorylation to expression.


CONCLUSIONS
These results suggest that chronic silymarin treatment can improve cirrhosis-induced liver enzyme activities and fibrosis, but may aggravate the hemodynamic eNOS activity, particularly by decreasing eNOS expression and increasing caveolin-1 expression.
Cho
Yong Kyun
YK
Department of Internal Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul 110-746, Republic of Korea.
Yun
Jung Won
JW
Park
Jung Ho
JH
Kim
Hong Joo
HJ
Park
Dong Il
DI
Sohn
Chong Il
CI
Jeon
Woo Kyu
WK
Kim
Byung Ik
BI
Jin
Wook
W
Kwon
Yong-Hyun
YH
Shin
Mi-Kyung
MK
Yoo
Tae Moo
TM
Kang
Ju-Hee
JH
Park
Chang-Shin
CS
D000818:Animals; D015153:Blotting, Western; D002251:Carbon Tetrachloride; D003094:Collagen / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects*; D008106:Liver Cirrhosis, Experimental / Q000139:chemically induced / Q000201:enzymology / Q000517:prevention & control*; D008111:Liver Function Tests; D008297:Male; D052250:Nitric Oxide Synthase Type III / Q000235:genetics* / Q000378:metabolism; D020011:Protective Agents / Q000008:administration & dosage / Q000627:therapeutic use*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012838:Silymarin / Q000008:administration & dosage / Q000627:therapeutic use*
D020011:Protective Agents; D012838:Silymarin; D003094:Collagen; D002251:Carbon Tetrachloride; D052250:Nitric Oxide Synthase Type III; C496316:Nos3 protein, rat