The possible influence of smoking on the low-density lipoprotein (LDL) and its biological activity was investigated. Plasma LDL was prepared from healthy male smokers and nonsmokers, and oxidized with Cu (II) as prooxidant. Oxidized LDL from smokers generated significantly more lipid peroxidation products, so-called thiobarbituric acid reactive substances (TBARS), when compared to oxidized nonsmoker LDL. Analysis of vitamin E levels in LDL obtained from both smokers and nonsmokers revealed that the vitamin E content of smoker LDL was significantly less than that of nonsmoker LDL. The amounts of cholesteryl esters formed in cultured P388. D.1 macrophages were greater in the presence of smoker LDL than with nonsmoker LDL. The data suggest that some of the proatherogenic effects of smoking may be related to oxidative modification of LDL and alteration of its biological activity.

In cigarette smokers endothelial dysfunction, measured by flow-mediated dilation (FMD), precedes cardiovascular disease (CVD) and can be improved by supplementation with n - 3 polyunsaturated fatty acids (PUFAs). We developed a mouse model of cigarette smoke (CS)-induced endothelial dysfunction that resembles impaired FMD observed in human cigarette smokers and investigated the mechanism by which n - 3 PUFAs mediate vasoprotection. We hypothesized that loss of nitric oxide (NO)-dependent vasodilation in CS-exposed mice would be prevented by dietary n - 3 PUFAs via a decrease in oxidative stress. C57BL/6 mice were fed a chow or n - 3 PUFA diet for 8 weeks and then exposed to mainstream CS or filtered air for 5 days, 2 h/day. Mesenteric arterioles were preconstricted with U46619 and dilated by stepwise increases in pressure (0-40 mmHg), resulting in increases in flow, ± inhibitor of NO production or antioxidant, Tempol. Markers of oxidative stress were measured in lung and heart. CS-exposed mice on a chow diet had impaired FMD, resulting from loss of NO-dependent dilation, compared with air exposed mice. Tempol restored FMD by normalizing NO-dependent dilation and increasing NO-independent dilation. CS-exposed mice on the n - 3 PUFA diet had normal FMD, resulting from a significant increase in NO-independent dilation, compared with CS-exposed mice on a chow diet. Furthermore, n - 3 PUFAs decreased two CS-induced markers of oxidative stress, 8-epiprostaglandin-F2α levels and heme oxygenase-1 mRNA, and significantly attenuated CS-induced cytochrome P4501A1 mRNA expression. These data demonstrate that dietary n - 3 PUFAs can protect against CS-induced vascular dysfunction via multiple mechanisms, including increasing NO-independent vasodilation and decreasing oxidative stress.

Studies of the role of the endothelium in coronary resistance vessels are limited to investigations of endothelium-derived relaxing factor mediated effects using various blocking agents. Endothelium removal as an alternative approach, is restricted to larger epicardial vessels. This study demonstrates the effect of endothelial damage by saponin on coronary resistance vessels remaining intact within the heart. In an isolated perfused guinea pig heart a saponin-containing solution (50 micrograms/ml) was infused over 2 min to damage specifically the endothelium. Increases of coronary flow in response to carbachol, histamine, and serotonin were completely blocked and reversed to decreases. Angiotensin-I-induced vasoconstriction was attenuated, whereas angiotensin-II-induced vasoconstriction remained unchanged. Vasodilatory response to sodium-nitroprusside was not attenuated by saponin-treatment. In contrast inhibition of endothelium derived relaxing factor by gossypol inhibited carbachol-induced vasodilation but did not result in vasoconstriction. Electron microscopic examination ensured that while the endothelium was destroyed by saponin-treatment the vascular smooth muscle was left intact. Our data indicate a regulating influence of the vascular endothelium on coronary resistance vessels which can be totally eliminated by saponin-treatment.

The mechanisms that mediate the cardiovascular protective effects of omega 3 (n-3) polyunsaturated fatty acids (PUFAs) have not been fully elucidated. Cytochrome P450 1A1 efficiently metabolizes n-3 PUFAs to potent vasodilators. Thus, we hypothesized that dietary n-3 PUFAs increase nitric oxide (NO)-dependent blood pressure regulation and vasodilation in a CYP1A1-dependent manner. CYP1A1 wild-type (WT) and knockout (KO) mice were fed an n-3 or n-6 PUFA-enriched diet for 8 weeks and were analyzed for tissue fatty acids and metabolites, NO-dependent blood pressure regulation, NO-dependent vasodilation of acetylcholine (ACh) in mesenteric resistance arterioles, and endothelial NO synthase (eNOS) and phospho-Ser1177-eNOS expression in the aorta. All mice fed the n-3 PUFA diet showed significantly higher levels of n-3 PUFAs and their metabolites, and significantly lower levels of n-6 PUFAs and their metabolites. In addition, KO mice on the n-3 PUFA diet accumulated significantly higher levels of n-3 PUFAs in the aorta and kidney without a parallel increase in the levels of their metabolites. Moreover, KO mice exhibited significantly less NO-dependent regulation of blood pressure on the n-3 PUFA diet and significantly less NO-dependent, ACh-mediated vasodilation in mesenteric arterioles on both diets. Finally, the n-3 PUFA diet significantly increased aortic phospho-Ser1177-eNOS/eNOS ratio in the WT compared with KO mice. These data demonstrate that CYP1A1 contributes to eNOS activation, NO bioavailability, and NO-dependent blood pressure regulation mediated by dietary n-3 PUFAs.