Homeostatic role of Toll-like receptor 4 in the endothelium and heart.

Toll-like receptor 4 (TLR4) is a pattern recognition receptor for lipopolysaccharide from Gram negative bacteria and thus is integral to the innate immune response in mammals. In addition, TLR4 is associated with atherosclerosis in murine models. The current study shows that blood vessels from TLR4(-/-) mice have an intact endothelial layer and comparable expression of nitric oxide synthase 3 protein. However, endothelium-dependent dilation in response to acetylcholine in vessels from TLR4(-/-) mice is greatly reduced. By contrast, endothelium-independent smooth muscle dilation in response to sodium nitroprusside in vessels from TLR4(-/-) mice remains intact. Furthermore, this study shows that hearts from TLR4(-/-) mice display signs of left ventricular dilation. In contrast to results in vessels from TLR4(-/-) mice, endothelium-dependent responses to acetylcholine in vessels from TLR2(-/-) mice remain intact. These observations illustrate a novel role for TLR4 in the homeostatic control of a functional endothelium and, thereby, cardiovascular health.

Plasma F2 isoprostanes: direct evidence of increased free radical damage during acute hyperglycemia in type 2 diabetes.

OBJECTIVES: Acute hyperglycemia in type 2 diabetes increases the generation of plasma 8-epi-prostaglandin F2 (8-epi-PGF2alpha) isoprostane, a sensitive direct marker of in vivo free radical oxidative damage to membrane phospholipids. RESEARCH DESIGN AND METHODS: A total of 21 patients with type 2 diabetes underwent an oral 75-g glucose tolerance test. Plasma 8-epi-PGF2alpha isoprostane concentrations (by gas chromatography [GC]/mass spectrometry [MS]), intralymphocyte reduced-to-oxidized glutathione ratios, and plasma total antioxidant capacity were measured at baseline and 90 min after glucose loading. RESULTS: Plasma 8-epi-PGF2alpha isoprostane concentrations rose significantly (P=0. 010) from 0.241 +/- 0.1 to 0.326 +/- 0.17 ng/l after 90 min. Intracellular oxidative balance and plasma antioxidant capacity did not change in either group. CONCLUSIONS: Plasma concentrations of 8-epi-PGF2alpha isoprostane increase during acute hyperglycemia in type 2 diabetes, providing direct evidence of free radical-mediated oxidative damage and demonstrating a pathway for an association between acute rather than fasting hyperglycemia and macrovascular risk in type 2 diabetes.

Elucidation of the temporal relationship between endothelial-derived NO and EDHF in mesenteric vessels.

Although the endothelium co-generates both nitric oxide (NO) and endothelium-derived hyperpolarizing factor (EDHF), the relative contribution from each vasodilator is not clear. In studies where the endothelium is stimulated acutely, EDHF responses predominate in small arteries. However, the temporal relationship between endothelial-derived NO and EDHF over more prolonged periods is unclear but of major physiological importance. Here we have used a classical pharmacological approach to show that EDHF is released transiently compared with NO. Acetylcholine (3 x 10(-6) mol/l) dilated second- and/or third-order mesenteric arteries for prolonged periods of up to 1 h, an effect that was reversed fully and immediately by the subsequent addition of L-NAME (10(-3) mol/l) but not TRAM-34 (10(-6) mol/l) plus apamin (5 x 10(-7) mol/l). When vessels were pretreated with L-NAME, acetylcholine induced relatively transient dilator responses (declining over approximately 5 min), and vessels were sensitive to TRAM-34 plus apamin. When measured in parallel, the dilator effects of acetylcholine outlasted the smooth muscle hyperpolarization. However, in the presence of L-NAME, vasodilatation and hyperpolarization followed an identical time course. In vessels from NOSIII(-/-) mice, acetylcholine induced small but detectable dilator responses that were transient in duration and blocked by TRAM-34 plus apamin. EDHF responses in these mouse arteries were inhibited by an intracellular calcium blocker, TMB-8, and the phospholipase A(2) inhibitor AACOCF(3), suggesting a role for lipid metabolites. These data show for the first time that EDHF is released transiently, whereas endothelial-derived NO is released in a sustained manner.

Comparison of red wine extract and polyphenol constituents on endothelin-1 synthesis by cultured endothelial cells.

Regular consumption of red wine reduces mortality from coronary heart disease. This observation has been attributed to the anti-thrombotic effects of ethanol and to the antioxidant properties of polyphenolic compounds present in red wine. Here we show that an extract of red wine polyphenols causes a concentration-dependent inhibition of endothelin-1 synthesis in cultured bovine aortic endothelial cells. This action was associated with modifications in phosphotyrosine staining, indicating that the active components of red wine cause specific modifications of tyrosine kinase signalling. Thus inhibition of endothelin-1 synthesis by red wine may reduce the development of atherosclerosis, and hence decrease coronary heart disease.