Effects of ethyl-all-cis-5,8,11,14,17-icosapentaenoate (EPA-E), pravastatin and their combination on serum lipids and intimal thickening of cuff-sheathed carotid artery in rabbits

Chemical composition and biological activities of trans-Himalayan alga Spirogyra porticalis (Muell.) Cleve

The freshwater alga Spirogyra porticalis (Muell.) Cleve, a filamentous charophyte, collected from the Indian trans-Himalayan cold desert, was identified on the basis of morpho-anatomical characters. Extracts of this alga were made using solvents of varying polarity viz. n-hexane, acetonitrile, methanol and water. The antioxidant capacities and phenolic profile of the extracts were estimated. The methanol extract showing highest antioxidant capacity and rich phenolic attributes was further investigated and phytochemical profiling was conducted by gas chromatography-mass spectrometry (GC/MS) hyphenated technique. The cytotoxic activity of methanol extract was evaluated on human hepatocellular carcinoma HepG2 and colon carcinoma RKO cell lines. The anti-hypoxic effect of methanol extract of the alga was tested on in vivo animal system to confirm its potential to ameliorate oxidative stress. The antioxidant assays viz. ferric reducing antioxidant power (FRAP), 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS), 1,1-diphenyl-2-picrylhydrazyl (DPPH) and nitric oxide (NO) radical scavenging capacities, β-carotene-linoleic acid bleaching property and lipid peroxidation exhibited analogous results, wherein the algal extracts showed significantly high antioxidant potential. The extracts were also found to possess high content of total proanthocyanidin, flavonoid and polyphenol. GC/MS analysis revealed the presence of thirteen chemotypes in the methanol extract representing different phytochemical groups like fatty acid esters, sterols, unsaturated alcohols, alkynes etc. with substantial phyto-pharmaceutical importance. The methanol extract was observed to possess anticancer activity as revealed from studies on HepG2 and RKO cell lines. In the present study, S. porticalis methanol extract also provided protection from hypoxia-induced oxidative stress and accelerated the onset of adaptative changes in rats during exposure to hypobaric hypoxia. The bioactive phytochemicals present in this trans-Himalayan alga are of enormous interest and can be utilized sustainably for discovery of novel drugs against oxidative stress.

A review of omega-3 ethyl esters for cardiovascular prevention and treatment of increased blood triglyceride levels

The two marine omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), prevalent in fish and fish oils, have been investigated as a strategy towards prophylaxis of atherosclerosis. While the results with fish and fish oils have been not as clear cut, the data generated with the purified ethyl ester forms of these two fatty acids are consistent. Although slight differences in biological activity exist between EPA and DHA, both exert a number of positive actions against atherosclerosis and its complications. EPA and DHA as ethyl esters inhibit platelet aggregability, and reduce serum triglycerides, while leaving other serum lipids essentially unaltered. Glucose metabolism has been studied extensively, and no adverse effects were seen. Pro-atherogenic cytokines are reduced, as are markers of endothelial activation. Endothelial function is improved, vascular occlusion is reduced, and the course of coronary atherosclerosis is mitigated. Heart rate is reduced, and heart rate variability is increased by EPA and DHA. An antiarrhythmic effect can be demonstrated on the supraventricular and the ventricular level. More importantly, two large studies showed reductions in clinical endpoints like sudden cardiac death or major adverse cardiac events. As a consequence, relevant cardiac societies recommend using 1 g/day of EPA and DHA for cardiovascular prevention, after a myocardial infarction and for prevention of sudden cardiac death.

Improving effect of ethyl eicosapentanoate on statin-induced rhabdomyolysis in Eisai hyperbilirubinemic rats

The effect of ethyl eicosapentanoate (EPA-E) on statin-induced rhabdomyolysis was investigated by co-administration of EPA-E and pravastatin (PV), as a typical statin, to Eisai hyperbilirubinemic rats (EHBR). It was confirmed that the plasma PV concentration was not affected by simultaneous administration of EPA-E, and there was no cumulative increase of PV during prolonged co-administration of EPA-E and PV. Muscular degeneration was prominent (incidence 5/5; average grade 3.5 (range 2-4)) in EHBR treated with PV alone at 200 mg/kg/day for 14 days, but co-administration of EPA-E at doses of 100, 300, and 1000 mg/kg/day decreased the average grades to 1.4 (range 0.3-3.0), 0.5 (0.2-1.0), and 0.6 (0.0-1.7), respectively. Creatine phosphokinase (CPK) and myoglobin levels in plasma were well correlated with the grade of skeletal muscle degeneration. Thus, EPA-E appears to reduce the severity of statin-induced rhabdomyolysis.

Eicosapentaenoic acid reduces myocardial injury induced by ischemia and reperfusion in rabbit hearts

Intake of fish oil is known to have cardioprotective effects and reduce cardiovascular mortality. However, it is not widely recognized that eicosapentaenoic acid (EPA), one of the n-3 polyunsaturated fatty acids (PUFAs), exerts beneficial effects against myocardial ischemia/reperfusion injury. The purpose of this study is to investigate whether EPA attenuates the severity of myocardial ischemia/reperfusion injury and which cellular mechanism is involved. Rabbits were treated with or without EPA (600 mg/kg/day) for 2 weeks. Infarct size was measured in open-chest rabbits after 30-minute occlusion of the left anterior descending coronary artery (LAD) and after the subsequent 3-hour reperfusion. In several groups, NG-nitro-L-arginine methyl ester (L-NAME), an inhibitor of nitric oxide (NO) synthase, or charybdotoxin, a blocker of calcium-activated potassium (K(Ca)) channels, was infused intravenously beginning 20 minutes before LAD occlusion and continuing during reperfusion. Infarct size was reduced in the group treated with EPA compared with the control group (7.2 +/- 1.0% vs 24.6 +/- 2.3%; P < 0.01). The occurrence of ventricular arrhythmias in the reperfusion period tended to decrease in the EPA group. Either L-NAME or charybdotoxin partially blunted or completely abolished the infarct size-limiting effect of EPA, respectively. Eicosapentaenoic acid significantly increased the n-3:n-6 ratio of PUFA. Eicosapentaenoic acid reduces myocardial infarct size, mainly via the opening of K(Ca) channel-mediated and partially NO-mediated mechanisms in rabbit hearts.

Changes in aspects such as the collagenous fiber density and foam cell size of atherosclerotic lesions composed of foam cells, smooth muscle cells and fibrous components in rabbits caused by all-cis-5, 8, 11, 14, 17-icosapentaenoic acid

Atherosclerotic plaques composed of foamed macrophages, smooth muscle cells and fibrous components in the twice-injured carotid artery from 1% cholesterol diet (HCD)-fed rabbits were prepared and the effects of all-cis-5, 8, 11, 14, 17-icosapentaenoic acid (EPA) on the histopathological properties of atherosclerotic lesions were examined. During the test period, there was no significant difference between the control and the EPA-treated groups in serum lipid levels. In the control group, atherosclerotic lesions were composed of foamed macrophages, smooth muscle cells and fibrous components. Some of the lesions had a large core of foamed macrophages covered with a thin cap of smooth muscle cells and fibrous components, and were morphologically similar to human vulnerable plaques. The classification of plaques, composing atherosclerotic lesions based on collagenous fiber density and foam cell size indicated that over 70% of plaques in the control group were poor in collagenous fiber, while about 20% of plaques contained only large foam cells. In contrast to the control group, over 70% of plaques in the EPA-treated group were rich in collagenous fiber and only 3% consisted of large foam cells. These results suggest that EPA changes certain aspects of pre-existing atherosclerotic lesions.

Effect of ethyl icosapentaenoate (EPA) on the concentration of tumor necrosis factor (TNF) and interleukin-1 (IL-1) in the carotid artery of cuff-sheathed rabbit models

To evaluate the effect of ethyl icosapentaenoate (EPA) on the metabolism of tumor necrosis factor alpha (TNFalpha) and interleukin-1beta (IL-1beta), the concentrations of these cytokines in the carotids of rabbits sheathed in a cuff were studied. Japanese white rabbits were divided into two groups; the EPA group, in which 600 mg/kg/day EPA was administered forcibly p.o. for 1 week before cuff treatment, and the control group. Carotid artery samples were obtained just before, 3 days and 7 days after cuff treatment, and TNFalpha and IL-1beta were determined separately with the Western blot analysis method. In the control group, there were 43.5 (+/- 3.0) pg/microg protein of TNFalpha and 53.5 (+/- 4.8) pg/microg protein of IL-1beta just before cuff treatment. Compared to the control group, these concentrations of the EPA group were both significantly low. Three days after cuff treatment, TNFalpha of the EPA group was still significantly low, while IL-1beta showed no difference. There was no significant difference between the two groups 7 days after cuff treatment. These findings suggested that EPA could influence TNFalpha and IL-1beta metabolism in the arterial wall even at baseline. Furthermore, EPA suppressed TNFalpha and IL-1beta production in the early phase of intimal thickening, indicating a mechanism inhibiting the activation of smooth muscle cells such as their proliferation and migration, induced by the cuff-sheath method.