Effects and mechanism of turmeric vasorelaxation of the thoracic aorta in hypercholesterolemic rats.
ABSTRACT An extract of Curcuma longa was tested in hypercholesterolemic rats to investigate its potential therapeutic effect on vascular conditions. Four experimental groups were used: normal diet (ND) control group, high cholesterol diet (HCD) group, and HCD subgroups supplemented with turmeric extract at 100 or 300 mg/kg of body weight (HCD100Tur and HCD300Tur groups, respectively). Turmeric extract was fed orally to animals, and dietary treatments lasted for 28 days. Hypercholesterolemia developed in the HCD, HCD100Tur, and HCD300Tur rats. Segments of the thoracic aorta were isolated, and an organ bath experiment was used to assess the vasorelaxation capability among all rats. Rats fed only HCD showed a marked decrease in acetylcholine-induced vasorelaxation compared with ND control rats. The HCD100Tur and HCD300Tur rats showed significant improvement in vasorelaxation compared with HCD rats. When vasorelaxation was induced by high concentrations of sodium nitroprusside, no differences in vasorelaxation were observed among the four groups of rats. A mechanistic study showed that HCD100Tur and HCD300Tur rats had significantly higher levels of the antioxidant enzymes superoxide dismutase and glutathione peroxidase than HCD rats. The transcript levels of heat shock protein 70 (hsp70), bcl2, bax-α, caspase (casp3), and glyceraldehyde 3-phosphate dehydrogenase in aortic tissues indicated that hypercholesterolemia significantly increased the expression of bax-α and casp3 but down-regulated bcl2 expression compared with the control group. Turmeric increased the expression of hsp70 and bcl2 but greatly reduced casp3 expression, indicating that turmeric improves vasorelaxation of the aorta in hypercholesterolemic rats by increasing antioxidant enzyme activities and likely suppressing apoptosis.