Effects of low-density lipoprotein from normal rabbits on hypercholesterolemia and the development of atherosclerosis

Inhibitory effect of co-administration of atorvastatin and endothelin-1 receptor antagonist on the progression of atherosclerosis in rabbit

Atorvastatin, a hydroxymethylglutaryl-CoA reductase inhibitor, and endothelin-1 (ET-1) receptor antagonist have been separately indicated to ameliorate disease progression in atherosclerosis. However, no study has evaluated the effect of their combination on atherosclerosis. The objective of the current study was to evaluate the direct in vivo effects of a combination regimen of atorvastatin and ET-1 receptor antagonist on male New Zealand white rabbit models of atherosclerosis (injury-induced). Thirty-two atherosclerotic rabbits were divided into four experimental groups: (a) injury group - fed high-fat diet; (b) ET-1 receptor antagonist preventive group - fed high-fat diet, but with intragastric administration of the ET-1 receptor antagonist, darusentan; (c) combined preventive group - fed high-fat diet, but with intragastric administration of both darusentan and atorvastatin; and (d) treatment group - fed high-fat diet for the first 8 weeks, followed by normal diet and intragastric administration of both darusentan and atorvastatin up to 16 weeks. A further eight non-atherosclerotic rabbits were fed normal diet and classified as the control group. At the end of 8 and 16 weeks, compared with the injury group, the combined preventive group had significant reduction in both the concentration of serum lipids and inflammatory factors and atherosclerosis formation, indicative of a multifaceted anti-atherosclerotic impact. The relative area of atherosclerotic lesions in the injury group (30.84%) was significantly higher than the control group (4.62%; p < 0.05). The combined preventive group showed a significantly robust effect on lowering serum lipid, inflammatory cytokines, and maintained homeostatic balance of free radicals, and important downstream effectors like ET-1 and matrixmetalloproteinase-9. Our data show that atorvastatin and ET-1 receptor antagonist co-administration may decrease lipid levels, stabilize plaques and relieve vascular inflammation. By reducing the plaque burden, this regimen may minimize the risk of atherosclerotic plaque rupture or arterial occlusion.

Oxidized LDLs but not native LDLs augment Ba2+ currents through L-type Ca2+ channels of the A7r5 smooth muscle-derived cell line

The whole-cell patch-clamp method was used on A7r5 smooth muscle-derived cell line, and Ba2+ currents through Ca2+ channels were recorded. The A7r5 cells showed voltage-dependent, long-lasting Ba2+ currents which were markedly inhibited by nifedipine (10 microM). The magnitude of the maximum Ba2+ current (IBa(max)) was augmented by an application of dbcAMP (1 mM), but not affected by TPA (80 nM). Noradrenaline (NA) at 100 microM caused an increase in the IBa(max) by 19.7% in the presence of phentolamine (10 microM). This effect was cancelled by Rp-cAMPs (10 microM). In the presence of propranolol (10 microM), NA tended to reduce the IBa(max). Application of Ox-LDLs at 100 microg protein/ml caused an increase in the IBa(max) by 15.7%, whereas native LDLs did not change the IBa(max). Rp-cAMPs was ineffective to the Ox-LDL action on the IBa(max). In the presence of Ox-LDLs, NA augmented the IBa(max) by 21.4% in the presence of phentolamine. These results suggest that Ox-LDLs activate L-type Ca2+ channels of A7r5 cells by a mechanism independent of cAMP/PKA signalling.