Research Article
Resveratrol improves intrahepatic endothelial dysfunction and reduces hepatic fibrosis and portal pressure in cirrhotic rats

https://doi.org/10.1016/j.jhep.2012.12.012Get rights and content

Background & Aims

Resveratrol, a polyphenol found in a variety of fruits, exerts a wide range of beneficial effects on the endothelium, regulates multiple vasoactive substances and decreases oxidative stress, factors involved in the pathophysiology of portal hypertension. Our study aimed at evaluating the effects of resveratrol on hepatic and systemic hemodynamics, hepatic endothelial dysfunction, and hepatic fibrosis in CCl4 cirrhotic rats.

Methods

Resveratrol (10 and 20 mg/kg/day) or its vehicle was administered to cirrhotic rats for two weeks and hepatic and systemic hemodynamics were measured. Moreover, we evaluated endothelial function by dose-relaxation curves to acetylcholine, hepatic NO bioavailability and TXA2 production. We also evaluated liver fibrosis by Sirius Red staining of liver sections, collagen-1, NFκB, TGFβ mRNA expression, and desmin and α-smooth muscle actin (α-SMA) protein expression, as a surrogate of hepatic stellate cell activation.

Results

Resveratrol administration significantly decreased portal pressure compared to vehicle (12.1 ± 0.9 vs. 14.3 ± 2.2 mmHg; p <0.05) without significant changes in systemic hemodynamics. Reduction in portal pressure was associated with an improved vasodilatory response to acetylcholine, with decreased TXA2 production, increased endothelial NO, and with a significant reduction in liver fibrosis. The decrease in hepatic fibrosis was associated with a reduced collagen-1, TGFβ, NFκB mRNA expression and desmin and α-SMA protein expression.

Conclusions

Resveratrol administration reduces portal pressure, hepatic stellate cell activation and liver fibrosis, and improves hepatic endothelial dysfunction in cirrhotic rats, suggesting it may be a useful dietary supplement in the treatment of portal hypertension in patients with cirrhosis.

Introduction

In cirrhosis, the initial factor determining the onset of portal hypertension is the increase in intrahepatic vascular resistance. This is not only due to morphological changes resulting from chronic liver inflammation and fibrosis, but also to reversible functional alterations, including an exaggerated response of the porto-hepatic vascular bed to vasoconstrictors and a deficient response to vasodilators [1]. A decreased nitric oxide (NO) availability and an increase in cyclo-oxygenase-1 (COX-1)-derived prostanoids within the liver play a major role in the pathogenesis of these dynamic alterations [2], [3], [4], [5].

Reduced NO availability has been shown to be in part due to an increase scavenging by superoxide (O2-) and different strategies aimed at reducing O2- levels [6], [7], such as superoxide dismutase (SOD) gene transfer, are able to reduce portal pressure in experimental models of cirrhosis in the rat.

Resveratrol (3,5,4′-trihydroxystilbene) is a natural polyphenolic flavonoid found in a large amount of plant species, including grapes and their derivatives, berries and nuts. It has been suggested to have important health benefits attributed to its demonstrated anti-oxidant, anti-neoplastic, anti-inflammatory and anti-platelet aggregation activities [8], [9], [10], [11]. Specifically, in different experimental models, resveratrol improves vascular dysfunction, an effect that is attributed to its ability to reduce oxidative stress, to upregulate endothelial nitric oxide synthase (eNOS) expression and activity, and to inhibit COX-1 activity [12], [13], [14], [15].

Resveratrol has been shown to exert anti-oxidant effects in experimental models of liver injury induced by ischemia/reperfusion and ethanol by inducing the enzymatic activity of SOD and catalase [16], [17], and to attenuate fibrosis development when co-administered with CCl4 to rats [18]. Additionally, resveratrol reduces the hepatotoxicity induced by acetaminophen, ethanol and carbone tetrachloride (CCl4), and prevents liver damage due to ischemia-reperfusion, irradiation, and high-fat diet [19]. Overall, we hypothesized that resveratrol may exert beneficial effects in the pathophysiological mechanisms involved in the development of portal hypertension in cirrhosis.

Therefore, the aim of the present study was to investigate the effects of chronic administration of resveratrol in CCl4-cirrhotic rats with portal hypertension.

Section snippets

Induction of cirrhosis by CCl4 and resveratrol administration

In male Wistar rats (50–75 g), cirrhosis was induced by inhalation of CCl4 three times a week, and phenobarbital (0.3 g/L) was added to the drinking water as previously described [6]. When cirrhotic rats had developed ascites, after approximately 12–15 weeks of CCl4 inhalation, administration of CCl4 and phenobarbital was discontinued. One week later, the animals were randomized to receive resveratrol (10 mg/kg body weight (bw); Sigma, Tres Cantos, Madrid, Spain) or its vehicle

Effect of resveratrol on hepatic and systemic hemodynamics in cirrhotic rats

Cirrhotic rats receiving long-term treatment with resveratrol (10 mg/kg bw/day) had a significantly lower PP than cirrhotic rats treated with vehicle (12.1 ± 0.9 vs. 14.3 ± 2.2 mmHg; p = 0.02), corresponding to a PP reduction of 15%. No significant changes in PBF, SMABF, MAP or HR were observed (Table 1). Intrahepatic vascular resistance was lower in resveratrol-treated rats, although the difference did not reach statistical significance.

Effect of resveratrol on endothelial function in cirrhotic rat livers

To further characterize the effects of resveratrol on liver

Discussion

In cirrhosis, an increase in hepatic vascular resistance to portal blood flow is the primary factor in the development of portal hypertension [3]. Therefore, it is of great interest to develop therapeutic strategies aimed at decreasing portal pressure by reducing hepatic vascular resistance.

Resveratrol is a natural substance with many biological functions; among others, it induces antioxidant enzymes, increases NO bioavailability and inhibits the production of inflammatory factors [33].

The main

Financial support

This study was supported by grants from the Ministerio de Economía y Competitividad (SAF 2010/17043) and from the Instituto de Salud Carlos III (ACI 2009-0938 and FIS PS09/01261), Spain. Jorge Gracia-Sancho has a Ramón y Cajal contract from the Ministerio de Economía y Competitividad. Ciberehd is funded by the Instituto de Salud Carlos III.

Conflict of interest

The authors who have taken part in this study declared that they do not have anything to disclose regarding funding or conflict of interest with respect to this manuscript.

Acknowledgements

Part of this work was carried out at the Esther Koplowitz Centre, Barcelona.

The authors thank Héctor García and Montse Monclús for experienced technical assistance.

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      While this concentration is below the range studied in the present analysis, the direct comparison of serum and local hepatic concentrations may be misleading as the nutritional intake of resveratrol will first yield relatively high local concentrations in liver due to the direct supply via the portal vein, accumulation processes in hepatocytes and enterohepatic cycling [86]. Accordingly, health effects from supplemental resveratrol are consistently observed in models of liver injury, where the stilbenoid accumulates [87,88]. Consecutively, a majority of resveratrol becomes then conjugated with sulphates or glucuronides by hepatic biotransformation yielding a range of secondary metabolites.

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    These authors contributed equally to this work and share first authorship.

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