New therapeutic aspect for carvedilol: Antifibrotic effects of carvedilol in chronic carbon tetrachloride-induced liver damage

https://doi.org/10.1016/j.taap.2012.04.012Get rights and content

Abstract

Portal hypertension is a common complication of chronic liver diseases associated with liver fibrosis and cirrhosis. At present, beta-blockers such as carvedilol remain the medical treatment of choice for protection against variceal bleeding and other complications. Since carvedilol has powerful antioxidant properties we assessed the potential antifibrotic effects of carvedilol and the underlying mechanisms that may add further benefits for its clinical usefulness using a chronic model of carbon tetrachloride (CCl4)-induced hepatotoxicity. Two weeks after CCl4 induction of chronic hepatotoxicity, rats were co-treated with carvedilol (10 mg/kg, orally) daily for 6 weeks. It was found that treatment of animals with carvedilol significantly counteracted the changes in liver function and histopathological lesions induced by CCl4. Also, carvedilol significantly counteracted lipid peroxidation, GSH depletion, and reduction in antioxidant enzyme activities; glutathione-S-transferase and catalase that was induced by CCl4. In addition, carvedilol ameliorated the inflammation induced by CCl4 as indicated by reducing the serum level of acute phase protein marker; alpha-2-macroglobulin and the liver expression of nuclear factor-kappa B (NF-κB). Finally, carvedilol significantly reduced liver fibrosis markers including hydroxyproline, collagen accumulation, and the expression of the hepatic stellate cell (HSC) activation marker; alpha smooth muscle actin. In conclusion, the present study provides evidences for the promising antifibrotic effects of carvedilol that can be explained by amelioration of oxidative stress through mainly, replenishment of GSH, restoration of antioxidant enzyme activities and reduction of lipid peroxides as well as amelioration of inflammation and fibrosis by decreasing collagen accumulation, acute phase protein level, NF-κB expression and finally HSC activation.

Highlights

► Carvedilol is a beta blocker with antioxidant and antifibrotic properties. ► It restores GSH and antioxidant enzyme activities and reduces lipid peroxidation. ► It ameliorates inflammation and nuclear factor kappa-B expression. ► It ameliorates fibrosis by decreasing collagen accumulation and HSC activation.

Introduction

Progressive hepatic fibrosis is the final common pathway for most chronic liver injuries, leading to cirrhosis with risk of liver failure and hepatocellular carcinoma. It is now recognized that fibrosis is a dynamic process, and may be reversible prior to the establishment of advanced architectural changes to the liver (Thompson and Patel, 2010). Oxidative stress through generation of reactive oxygen species (ROS) plays an important role in producing liver damage and initiating hepatic fibrogenesis. Oxidative disruption of lipids, proteins, and DNA induces necrosis and apoptosis of hepatocytes, and amplifies the inflammatory response, resulting in initiation of fibrosis. Additionally, ROS stimulate the production of profibrogenic mediators from Kupffer cells and circulating inflammatory cells (Friedman, 2008).

Liver fibrosis is characterized by an accumulation of extracellular matrix (ECM) proteins secreted by activated hepatic stellate cells (HSCs). Proliferation and differentiation of HSCs into myofibroblast-like cells have been related to the development of liver fibrosis and can be detected by the expression of alpha-smooth muscle actin (ASMA) (Carpino et al., 2004). The accumulation of ECM proteins distorts the hepatic architecture by forming a fibrous scar, and the subsequent development of nodules of regenerating hepatocytes defines cirrhosis. Consequently, cirrhosis produces hepatocellular dysfunction and increased intrahepatic resistance to blood flow, which result in hepatic insufficiency and portal hypertension, respectively (Povero et al., 2010). Portal hypertension is the most common complication of chronic liver disease and develops in the vast majority of patients with cirrhosis. It is characterized by an increase of the portal vein pressure, and leads to development of gastroesophageal varices, ascites, renal dysfunction, as well as hepatic encephalopathy. Over the years, it has become clear that a decrease in portal pressure, not only protective against the risk of variceal bleeding but, is also associated with a lower long-term risk of developing other complications, and with an improved long-term survival. At present, beta-blockers remain the medical treatment of choice for both primary and secondary prophylaxis (Laleman and Nevens, 2006). One of the most important beta-blockers is carvedilol. It was more effective than propranolol in reducing hepatic venous pressure gradient (Tripathi and Hayes, 2010). Carvedilol has been shown to possess both ROS-scavenging and ROS-suppressive effects, and its use is associated with reduction in oxidative stress that is cardinal in the pathogenesis of cardiovascular diseases (Dandona et al., 2007). In the last decade, several studies revealed that carvedilol could attenuate myocardial degeneration and fibrosis (Chua et al., 2008, Nanjo et al., 2006). Furthermore, Ronsein et al. (2005) demonstrated that carvedilol exerted cytoprotective effects against oxidative injury caused by acetaminophen in acute liver toxicity. Moreover, a recent study suggested that carvedilol provided protection against heart, liver, and kidney damage induced by angiotensin II and this protection was independent on its antihypertensive effects (Vialati Mdo et al., 2010).

Although the powerful antioxidant properties of carvedilol have been approved, its effectiveness in ameliorating oxidative stress-induced liver fibrosis has not yet been studied. From the above, we can predict that carvedilol may exert antifibrotic effect in chronic liver injury; hence it could be used as an antifibrotic drug in the future. Accordingly, the present study was designed to investigate the potential antifibrotic effect of carvedilol and the possible underlying mechanisms of this effect in a chronic liver injury model induced by carbon tetrachloride (CCl4).

Section snippets

Drugs and chemicals

Carvedilol was obtained from EPICO (Cairo, Egypt) and given orally at a dose of 10 mg/kg. It has been reported that carvedilol at a dose up to 10 mg/kg for rat could prevent cardiac growth and remodeling without reducing systemic blood pressure (Massart et al., 1999). Carbon tetrachloride (CCl4), reduced glutathione (GSH), Ellman's reagent [5,5-dithio-bis (2-nitrobenzoic acid); DTNB], hydroxyproline standard, and thiobarbituric acid (TBA) were purchased from Sigma Chemical Company (St. Louis, MO,

Hepatotoxicity indices

Individual body weight at the start of the experiment and on the termination day was recorded, and % change was calculated for all groups. It was found that the body weight decreased significantly by 16% and liver weight increased remarkably in CCl4-intoxicated group, which is a typical feature of chronic liver intoxication. On the other hand, treatment of CCl4 intoxicated group with carvedilol markedly improved the weight of rat and liver (data not shown). Biochemical measurement of liver

Discussion

Carvedilol is a nonselective beta-blocker with potent antioxidant and free radical scavenging properties that is used in the treatment of portal hypertension, commonly associated with chronic liver diseases. According to these powerful antioxidant properties of carvedilol, we predicted that carvedilol may exert antifibrotic effect in chronic liver injury; and that will add further clinical usefulness for carvedilol. So, in the present study, we examined the potential antifibrotic effects of

Conflict of interest statement

The authors declare that there are no conflicts of interest.

Acknowledgment

The authors thank Professor Kholoussy A.B. (Department of Pathology, Faculty of Veterinary Medicine, Cairo University, Egypt) for his kind help in pathology.

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