INVESTIGATION OF THE ROLE OF TRANS-ANETHOLE IN PAAC INDUCED CARDIAC HYPERTROPHY

Abstract

BACKGROUND Cardiac hypertrophy is initially an. adaptive response to the hemodynamic overload thrown over the heart in which the cardiac insults by hypertension or by myocardial infarction is counterbalance by increasing the numbers of contractile units in left ventricle. But adaptation has its limits and this hypertrophy eventually lead to heart failure. Across the globe cardiac hypertrophy load is 1:500 which translates to 7, 00,000 affected Americans and about 2 million affected patient in India and China. At myocytes level, increased growth of cell as well as its extracellular matrix (ECM), protein synthesis, gene expression programming and sarcomeric addition and derangements are seen in cardiac remodelling. Physiological stress causes volume overload and thus sarcomeres are added in series, which is called as Eccentric or physiological hypertrophy while pathological stimuli leads to lateral expansion of myocytes with sarcomeric growth in parallel direction to ventricle, which is called as pathological hypertrophy. This leads to increase in thickness of left ventricles and thus reduces left ventricle diameter in order to compensate for pressure overload. The ejection fraction and systolic performance of the left ventricles also gets disturbed. Left ventricular hypertrophy (LVH) can be induced chemically or mechanically by surgery. Partial abdominal aortic constriction (PAAC) causes pressure overload in ventricles and thus induce LVH after 4 weeks of constriction. The mechanosensors such as various growth factors, Ang-II, Endothelin-I, integrins and melucin on cell membrane of myocytes receives stress stimuli due to pressure overload and generates reactive oxygen species (ROS) from various sources like NADPH- oxidase, xanthene oxidase, improper mitochondrial metabolism etc. This ROS acts as secondary messengers and transfer signals for hypertrophy to cell nucleus via different intracellular and intercellular pathways like Mitogen activated protein kinase (MAP Kinase)/ Extracellular signal regulated (Erk) pathway, calcineurin-NFAT, phosphatidyl inositol (PI) 3-kinase–Akt/protein. Kinase B. Extracellularly they also activate the receptors on fibroblast and myofibroblast for the growth of various hypertrophic proteins such as fibronectin, N-cadherin, collagen, vimentin and many more. Currently no specific treatment is available for cardiac hypertrophy but Ang-II and ACE inhibitors are given for symptomatic relief. Trans-anethole is a volatile oil obtained from the various dietary sources like Foeniculum vulgare (87.85%), Pimpinella anisum (85-96%), Nigella sativa (38.3%), Illicium verum fruit(89.5%), which are some of the daily consumable plants in Gujarat. Previous studies on trans-anethole have proven its potent antioxidant property. OBJECTIVE The main aim of the study was to evaluate efficacy of trans-anethole in prevention of PAAC surgery induced cardiac hypertrophy and to study mechanism of action of trans-anethole in prevention of cardiac hypertrophy. MATERIAL AND METHODS: Left ventricle cardiac hypertrophy was induced by PAAC surgery, where abdominal aorta of the rat was constricted for 6 weeks. Wistar rats were divided into four groups: Sham control, Sham control treated with trans-anethole (80mg/kg/day/p.o.), PAAC control and PAAC treated with trans-anethole (80mg/kg/day/p.o.) Rats were treated with drug from 0th day to 6 weeks. Surgery was done on 3rd day after the treatment was started. After 6 weeks various parameters such as hemodynamic, hypertrophic, histopathological studies, protein expression analysis by western blot and oxidative parameters in the heart homogenate One-way ANOVA followed by Tuckey post-test using Graph Pad Prism software (version ). The results was considered significant when p<0.05. RESUTS There was the significant. (p<0.05) increase in mean blood pressure and heart rate in PAAC (disease) control animals as compared to sham control animals and treatment with trans-anethole significantly reduced blood pressure and heart rate as compared to PAAC control animals. Significant decrease in rate of pressure development and decay (%dp/dt) was observed in PAAC control animals as compared with sham control animals and significant increase in rate of pressure development and decay in PAAC treated animals as compared with PAAC control animals. Significant (p<0.05) increase in hypertrophic index, left ventricular hypertrophic index, left ventricular thickness, left ventricular weight/right ventricular weight ratio, heart weight/body weight ratio and collagen content of left ventricles of PAAC control animals and significant decrease in all hypertrophic parameters was seen in PAAC treated animals. Significant decrease in Superoxide dismutase (SOD) activity, reduced glutathione (GSH) level, catalase activity and increase in melondialdehyde (MDA) levels were observed in PAAC control. Significant improvement in oxidative stress level was seen with trans-anethole treated group. On the basis of band intensity of the hypertrophic proteins on the western blot was measured using band area on graph, significant increase in expression of hypertrophic proteins such as N- cadherin, Alfa-SMA and fibronectin in PAAC control group and their expression were significantly decreased in PAAC treated group. In PAAC control group myocytes were shapeless and intercalated discs were injured severely and increased vacuolar spaces were visible. In PAAC treated group, histology of cardiac muscle cells was in its proper format in terms of shape and other architecture of the tissue. IHC staining data indicated binding of antibodies with their respective hypertrophic proteins such as N-cadherin, fibronectin and alfa –SMA. These bindings were significantly reduced in PAAC treated group indicating delay in the occurrence of cardiac hypertrophy. CONCLUSION The available data suggests that PAAC could induce cardiac hypertrophy in the rats. Treatment with trans-anethole could reduce the cardiac hypertrophic parameters and improve the systolic performance of the heart. Reduction in the growth of hypertrophic proteins and oxidative stress in left ventricles was seen as a result of chronic treatment with trans-anethole. This may conclude that trans-anethole could delay the duration LVH. The data suggests that trans-anethole possibly acts via antioxidant mechanism in PAAC induced cardiac hypertrophy.