Modulation of carcinogenic response and antioxidant enzymes of rats administered with 1,2-dimethylhydrazine by Picroliv

Chemopreventive efficacy of gallic acid, an antioxidant and anticarcinogenic polyphenol, against 1,2-dimethyl hydrazine induced rat colon carcinogenesis

Colon cancer is a major cause of morbidity and mortality in developed and developing countries and its etiology is known to be a combination of hereditary, environmental, dietary factors and lack of physical activity. Chemoprevention offers a novel approach to control the incidence of colon cancer. Gallic acid (GA) is a polyphenol widely present in tea and other plants which is popularly used in the traditional medicine of China. The present study was to evaluate the efficacy of GA supplementation on tissue lipid peroxidation and antioxidant defense system in 1,2-dimethyhydrazine (DMH) induced colon carcinogenesis in male Wistar rats. The rats were assorted into six groups, viz., group1 control rats received modified pellet diet; group 2 rats received GA (50 mg/kg body weight) orally along with modified pellet diet; group 3 rats received DMH (20 mg/kg body weight) subcutaneously once a week for the first 15 weeks; groups 4, 5 and 6 rats received GA along with DMH during the initiation, post- initiation stages and the entire period of study respectively. All the rats were sacrificed at the end of 30 weeks and the tissues were evaluated biochemically. We observed decreased lipid peroxidation (LPO) products such as thiobarbituric acid reactive substances (TBARS), lipid hydroperoxides (LOOH) and conjugated dienes (CD) and diminished levels of antioxidants such as superoxide dismutase (SOD), catalase (CAT), reduced glutathione (GSH), glutathione reductase (GR) and glutathione peroxidase (GPx) in the tissues of DMH treated rats, which were elevated significantly on GA supplementation. Moreover, enhanced activity of ascorbic acid and alpha-tocopherol levels were also observed in DMH alone treated rats which were significantly reduced on GA supplementation. Our results suggest that GA could exert a significant chemopreventive effect on DMH induced colon carcinogenesis.

Modification of cysteine residue in p65 subunit of nuclear factor-kappaB (NF-kappaB) by picroliv suppresses NF-kappaB-regulated gene products and potentiates apoptosis

Picroliv, an iridoid glycoside derived from the plant Picrorhiza kurroa, is used traditionally to treat fever, asthma, hepatitis, and other inflammatory conditions. However, the exact mechanism of its therapeutic action is still unknown. Because nuclear factor-kappaB (NF-kappaB) activation plays a major role in inflammation and carcinogenesis, we postulated that picroliv must interfere with this pathway by inhibiting the activation of NF-kappaB-mediated signal cascade. Electrophoretic mobility shift assay showed that pretreatment with picroliv abrogated tumor necrosis factor (TNF)-induced activation of NF-kappaB. The glycoside also inhibited NF-kappaB activated by carcinogenic and inflammatory agents, such as cigarette smoke condensate, phorbol 12-myristate 13-acetate, okadaic acid, hydrogen peroxide, lipopolysaccharide, and epidermal growth factor. When examined for the mechanism of action, we found that picroliv inhibited activation of IkappaBalpha kinase, leading to inhibition of phosphorylation and degradation of IkappaBalpha. It also inhibited phosphorylation and nuclear translocation of p65. Further studies revealed that picroliv directly inhibits the binding of p65 to DNA, which was reversed by the treatment with reducing agents, suggesting a role for a cysteine residue in interaction with picroliv. Mutation of Cys(38) in p65 to serine abolished this effect of picroliv. NF-kappaB inhibition by picroliv leads to suppression of NF-kappaB-regulated proteins, including those linked with cell survival (inhibitor of apoptosis protein 1, Bcl-2, Bcl-xL, survivin, and TNF receptor-associated factor 2), proliferation (cyclin D1 and cyclooxygenase-2), angiogenesis (vascular endothelial growth factor), and invasion (intercellular adhesion molecule-1 and matrix metalloproteinase-9). Suppression of these proteins enhanced apoptosis induced by TNF. Overall, our results show that picroliv inhibits the NF-kappaB activation pathway, which may explain its anti-inflammatory and anticarcinogenic effects.

Hesperetin exerts dose dependent chemopreventive effect against 1,2-dimethyl hydrazine induced rat colon carcinogenesis

Colon cancer is still one of the leading causes of death in USA and is increasing at an alarming rate in Asia. It is one of the major causes of death in industrialized countries, and its etiology is known to be a combination of hereditary, environmental, dietary factors and lack of physical activity. Chemoprevention plays a potential role in colorectal cancer. The present study was performed to evaluate the efficacy of hesperetin supplementation on colonic aberrant crypt foci, lipid peroxidation and antioxidant defense system in 1,2-dimethylhydrazine (DMH) induced colon carcinogenesis in male Wistar rats. The rats were segregated into six groups viz., group 1, control rats received modified pellet diet; group 2 rats received modified pellet diet along with hesperetin (30 mg/kg body weight/day); groups 3-6 administrated DMH (20 mg/kg body weight) subcutaneous injection once a week for the first 4 weeks; in addition groups 4-6 received hesperetin at three different doses of 10, 20 and 30 mg/kg body weight/day for 16 weeks. All the rats were sacrificed at the end of the experimental period of 16 weeks. Increased tumor incidence and increased number aberrant crypt foci (ACF) accompanied by a decrease in the tissue lipid peroxidation, glutathione S-transferase (GST), glutathione peroxidase (GPx), superoxide dismutase (SOD), and catalase (CAT) activities were observed in DMH-treated rats. Administration of hesperetin to DMH treated rats significantly decreased the tumor incidence, the number of aberrant crypt foci with simultaneous enhancement of tissue lipid peroxidation, GST, GPx, SOD, and CAT activities. The results of this study suggest that hesperetin at a dose of 20 mg/kg body weight showed a significant beneficial effect against chemically induced colonic carcinogenesis in rats as compared to the other two doses.

Effect of morin on tissue lipid peroxidation and antioxidant status in 1, 2-dimethylhydrazine induced experimental colon carcinogenesis

Colon cancer is the third most malignant neoplasm in the world and it remains today an important cause of death, especially in western countries. In this study, we have evaluated the chemopreventive efficacy of morin on tissue lipid peroxidation and antioxidant status, which are used as biomarkers in 1,2-dimethylhydrazine-induced colon carcinogenesis in a rat model. Male Wistar rats were divided into four groups and received high fat diet. Group 1 served as control, groups 2 and 4 were given a daily treatment of morin (50 mg/kg body weight) orally, everyday for a total period of 30 weeks. Groups 3 and 4 were given weekly subcutaneous injections of DMH at a dose of 20 mg/kg body weight in the groin for 15 weeks. Animals were sacrificed at the end of 30 weeks. The liver, intestine, colon and caecum from different groups were subjected to histopathological studies, determination of lipid peroxidation and antioxidant status. Our results showed decreased levels of liver enzymic and non-enzymic antioxidants and increased levels of lipid peroxidation (LPO) products such as tissue thiobarbituricacid substances (TBARS), lipid hydroperoxides (LOOH) and conjugated dienes (CD) in DMH treated rats, which were significantly (P < 0.05) reversed on morin supplementation. Moreover, intestinal, colonic and caecal TBARS, LOOH, CD and also the antioxidants superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), glutathione peroxidase (GPx), glutathione reductase (GR) and reduced glutathione (GSH) were significantly diminished in DMH treated rats, which were significantly (P < 0.05) elevated on simultaneous morin supplementation. Moreover, enhanced activity of intestinal, colonic and caecal ascorbic acid and alpha-tocopherol levels were also observed in DMH alone treated rats, which were significantly (P < 0.05) reduced on morin supplementation. These results indicate that morin could exert a significant chemopreventive effect on colon carcinogenesis induced by DMH.

Dose-response efficacy of caraway (Carum carvi L.) on tissue lipid peroxidation and antioxidant profile in rat colon carcinogenesis

Colon cancer is a leading cause of cancer death and its prevention is of great interest throughout the world. This study was conducted to examine the efficacy of different doses of dietary caraway (Carum carvi L.) on tissue lipid peroxidation (LPO) and antioxidant profile in rat colon carcinogenesis. Wistar male rats were divided into 6 groups and were fed a modified pellet diet for the whole of 30 weeks. To induce colon cancer, rats were given a weekly subcutaneous injection of 1,2-dimethylhydrazine (DMH) at a dose of 20 mg kg(-1) (based on body weight) for the first 15 weeks. Caraway was supplemented every day orally at doses of 30, 60 and 90 mg kg(-1) for different groups of rats for the total period of 30 weeks. All rats were sacrificed at the end of 30 weeks, the colons were examined visually for masses and were subsequently evaluated histologically. The results showed diminished levels of intestinal, colonic and caecal LPO products, such as conjugated dienes (CD), lipid hydroperoxides (LOOH) and thiobarbituric acid reactive substances (TBARS) and also the antioxidants superoxide dismutase (SOD), catalase (CAT), reduced glutathione (GSH) and glutathione reductase (GR) in DMH treated rats, which were significantly reversed (P<0.05) on caraway supplementation. Moreover, enhanced activity of intestinal, colonic and caecal glutathione peroxidase (GPx), glutathione S-transferase (GST) and colonic ascorbic acid and alpha-tocopherol levels were observed in carcinogen-treated rats, which were significantly (P<0.05) reduced on caraway supplementation. Thus, our study showed that caraway supplementation at a dose of 60 mg kg(-1) had a modulatory role on tissue LPO, antioxidant profile and prevented DMH-induced histopathological lesions in colon cancer rats.

Chemopreventive effect of trans -resveratrol - a phytoalexin against colonic aberrant crypt foci and cell proliferation in 1,2-dimethylhydrazine induced colon carcinogenesis

Prevention of cancer remains a primary need and new chemopreventive agents must be developed for this purpose. Towards this goal, a chemoprevention study was conducted to evaluate the activity of resveratrol (Res), a phytoalexin, as an inhibitor of colon carcinogenesis. Wistar male rats were divided into six groups, group 1 were control rats, group 2 were control rats that received Res (8 mg/kg body wt p.o. everyday), rats in groups 3-6 were treated weekly with 1,2-dimethylhydrazine (DMH, 20 mg/kg body wt, s.c. x 15 times). In addition, groups 4, 5 and 6 received Res as in group 2. Modifying effects were assessed using aberrant crypt foci (ACF) and the extent of histopathological lesions as end point markers. At the end of 30 weeks, Res markedly reduced tumor incidence, the degree of histological lesions and also the size of tumors significantly (P < 0.05) as compared with the rats treated with unsupplemented DMH. The number of ACF consisting of more than six aberrant crypts per rat was observed in group 6 (6.2 +/- 1.4), group 5 (7.7 +/- 1.0) and group 4 (8.2 +/- 1.4) which were significantly lower than that of group 3 (22.3 +/- 2.4) (P < 0.05). The most pronounced inhibition of ACF development was noted in rats fed Res for the entire period and also during the post-initiation period. Also, Res administration lowered the number of argyrophilic nucleolar organizing region-associated proteins (AgNORs) per nucleus in non-lesional colonic crypts, which reflects the cell proliferation activity. Oxidative imbalance in DMH-treatment was significantly (P < 0.01) modulated on Res supplementation as indicated by optimal concentration of thiobarbituric acid reactive substances (TBARS), superoxide dismutase (SOD), catalase (CAT) and reduced glutathione (GSH). The results of our study suggest Res to be an effective chemopreventive agent, which suppresses DMH-induced colon carcinogenesis at various stages.