Chemoprevention of Diethylnitrosamine-Initiated and Phenobarbital-Promoted Hepatocarcinogenesis in Rats by Sulfated Polysaccharides and Aqueous Extract of Ulva lactuca

Abstract

Hepatocellular carcinoma (HCC) is one of the common cancers and lethal diseases worldwide. Both oxidative stress and chronic inflammation contribute to the pathogenesis of HCC. Because of limited treatment options and a grave prognosis of HCC, preventive management has been emphasized. The marine macroalgae Ulva lactuca (Ulvaceae) is consumed by humans and livestock because of its nutritional value. Recent studies showed that various extracts of U. lactuca possess antiviral, antiplasmodial, antinephrotoxic, antioxidant, and anti-inflammatory properties. However, very limited information is available on anticancer potential of U. lactuca with no reports on liver cancer chemopreventive efficacy of this marine algae. Accordingly, the present study was initiated to evaluate the possible antihepatocarcinogenic effects and antioxidant mechanisms of action of various U. lactuca extracts against a clinically relevant rodent model of HCC. Initiation of hepatocarcinogenesis was performed in Sprague-Dawley rats by a single injection of dietary carcinogen diethylnitrosamine (DENA, 200 mg/kg, intraperitoneally), followed by promotion with phenobarbital (0.05%) in drinking water. The rats were fed with daily oral dose (50 mg/kg) of polysaccharide sulfate or aqueous extract of U. lactuca for 2, 12, and 24 weeks. At these timepoints, blood samples were taken to measure hepatic injury markers, including alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, γ-glutamyl transferase, and bilirubin. The liver tissue was harvested for measurement of hepatic oxidative indices, including lipid peroxidation, reduced glutathione, nitric oxide, catalase, superoxide dismutase, glutathione reductase, and glutathione S-transferase. Hepatic histopathology, immunohistochemical analysis of cell proliferation and apoptosis by DNA fragmentation assay were performed. Our results clearly indicate that sulfated polysaccharides of U. lactuca exert a marked chemoprevention of DENA-initiated hepatocarcinogenesis through inhibition of abnormal cell proliferation and induction of apoptosis. A modest inhibition rat liver carcinogenesis was observed with the aqueous extract. The sulfated polysaccharides altered serum parameters of hepatic damage and modulated various components of the hepatic enzymatic and nonenzymatic antioxidant defense systems. The sulfated polysaccharides from U. lactuca may have unique properties of providing protection against DENAinduced oxidative stress which could contribute to chemoprevention of experimental hepatocarcinogenesis. U. lactuca sulfated polysaccharides could be developed as chemopreventive and therapeutic drug against human HCC.

Potential Using of Ulvan Polysaccharide from Ulva lactuca as a Prebiotic in Synbiotic Yogurt Production

“…The dried samples were crushed, ground in an electric blender to form a powder, and stored in the refrigerator as recorded by Tran et al [5]. Ulvan polysaccharide was extracted by the modified procedure of Hussein et al [6] using the methods of hot water-extraction and ethanol-precipitation. 100 g of dried Ulva lactuca were extracted three times at 100°C for 2 h with double-distilled water.…”

“…These variations can be referred to the differences in the composition and structure of prepared ulvan polysaccharides; which vary, depending on the algae species and age, geographic location and season of cultivation, and the method of extraction. Particularly, in edible species U. lactuca, the results of published studies confirmed that the structural composition of ulvan polysaccharides is changeable and complex [5][6][7].…”

“…Ulvan is highly charged sulfated polyelectrolytes, mainly consisting of rhamnose, xylose, and uronic acid as the basic monomer sugars, and also containing disaccharide. The ulvans cell-wall polysaccharides represent 38-54% of the dry matter of algal [6]. They are rich in hydroxyl (-OH) groups, which make them hydrophilic and water-soluble; and establish rigid and stiff intra-chain H-bond networks, so they considering good thickeners.…”

A novel chemoprotective effect of tiopronin against diethylnitrosamine‐induced hepatocellular carcinoma in rats: Role of ASK1/P38 MAPK‐P53 signalling cascade

“…In this model, administration of DENA to Wistar rats in the drinking water for 8 weeks was reported as a complete hepatocarcinogen for HCC induction in which DENA can function as both tumour initiator and promoter simultaneously . We employed this particular model due to its ease of applicability over the other routes of administration such as oral gavage or intraperitoneal injection of DENA in which the latter may additionally produce a drug‐ drug interaction with the intraperitoneally injected tiopronin or combining DENA with other drugs as sodium phenobarbital or thioacetamide . However, this model is time consuming as the appearance of recognizable tumour lesions occurs after a long latent period (after at least 16 weeks from the first DENA exposure) that allows for the cancer promotion and progression phases to be completed…”

“…13,30 We employed this particular model due to its ease of applicability over the other routes of administration such as oral gavage 31 or intraperitoneal injection of DENA 32,33 in which the latter may additionally produce a drug-drug interaction with the intraperitoneally injected tiopronin or combining DENA with other drugs as sodium phenobarbital or thioacetamide. [34][35][36] However, this model is time consuming as the appearance of recognizable tumour lesions occurs after a long latent period (after at least 16 weeks from the first DENA exposure) that allows for the cancer promotion and progression phases to be completed. 37 In this study, the induction of HCC was accompanied by a significant decrease in the total body weight and deterioration of the liver functions as well as an elevation of AFP tumour marker in the animals treated with DENA.…”