[Effects of estrogens on the vascular wall: cellular and molecular mechanisms]. / Wirkungen von Ostrogenen auf die Gefässwand: Zelluläre und molekulare Mechanismen.

There is evidence from animal models and in vitro experiments that estrogens exert direct effects on the vascular wall. 17 beta-estradiol mediates vasodilatation and inhibits smooth muscle cell proliferation/migration. Furthermore, it modulates the vascular inflammatory response by inhibiting cytokine activation and expression of cell adhesion molecules. Finally, 17 beta-estradiol inhibits platelet aggregation and adhesion. Thus, vasoprotection by estrogens is mediated via genomic and nongenomic pathways. Estrogens regulate gene expression by interacting with estrogen receptors (ER) and other transcription factors. The possible estrogen actions include nongenomic stimulation of membrane mediators and second messenger systems. The existence of two ER subtypes alpha and beta indicates the potential of different biological estrogen effects. At present, the expression, the relation, and the biological actions of ER alpha and beta in different vascular beds of origin, in female and male as well as in healthy and atherosclerotic blood vessels are not known.

Postmenopausal hormone replacement therapy and the vascular wall: epidemiology and clinical studies.

The clinical relevance of estrogen's multiple acute and more delayed effects on vascular wall structure and function is incompletely understood. This review attempts to reevaluate epidemiological findings and clinical studies concerning the vascular actions of estrogens and gives implications for strategies in postmenopausal hormone replacement therapy (HRT). There is large evidence from observational studies that HRT reduces the risk of cardiovascular mortality and morbidity in postmenopausal women. However, according to the only large randomized, placebo-controlled, secondary prevention Heart and Estrogen/progestin Replacement Study (HERS), women with prevalent cardiovascular disease (CVD) have increased CVD events within the first year after onset of HRT. The net effects of HRT on atherosclerosis, coagulation, fibrinolysis or the inflammatory response are unproven. Randomized trials of intermediate outcomes reveal that HRT has favorable effects on isolated cardiovascular risk factors, e.g. lipoproteins, carbohydrate metabolism and vasodilatation, but the impact of this effects on clinical endpoints is still not clear. The basis of "evidenced based medicine" is currently not sufficient to provide exact recommendation who will benefit from HRT and who might not. Therefore, the decision about hormone use should consider individual benefit-risk profiles.

Postmenopausal hormone replacement therapy and the vascular wall: mechanisms of 17 beta-estradiol's effects on vascular biology.

17 beta-estradiol (E2) protects against atherosclerosis independent of changes in plasma lipoproteins in a variety of animal models, which is explained by direct effects of E2 on the vascular wall. E2 improves vasomotion by modulation of vasoconstrictor and vasodilator systems through endothelium-dependent and endothelium-independent mechanisms. E2 affects the remodeling of the vascular wall by inhibiting smooth muscle cell proliferation and accelerating reendothelialization of injured blood vessels. E2 modulates the vascular inflammatory response by inhibiting cytokine production, cytokine-induced expression of cell adhesion molecules and platelet aggregation/adhesion. This review focuses on the cellular and molecular mechanisms underlying these vasculoprotective actions of E2. E2 can act through nongenomic stimulation of membrane/intracellular mediators and/or the classical genomic pathway of steroid actions, which is dependent on transcription and protein synthesis. The existence of at least two nuclear estrogen receptor (ER) subtypes alpha and beta and a putative membrane ER present the potential of tissue-specific as well as biologically different E2 actions. Nuclear ERs act as ligand-activated transcription factors and can affect gene regulation by interaction with the classical estrogen response element or other nonreceptor transcription factors. The molecular basis of genomic E2 actions by identifying transcription factors and regulatory elements involved in the induction and inhibition of E2 regulated gene expression is only at the beginning of being understood. The impact of E2-mediated increased NO availability on the hemodynamic and antiatherosclerotic actions of E2 is still a debate of controversy.

Peripheral blood mononuclear cells isolated from patients with diabetic nephropathy show increased activation of the oxidative-stress sensitive transcription factor NF-kappaB.

Increased oxidative stress and subsequent activation of the transcription factor NF-kappaB has been linked to the development of late diabetic complications. To determine whether oxidative stress dependent NF-kappaB activation is evident in patients with diabetic nephropathy we used an Electrophoretic Mobility Shift Assay based semiquantitative detection system which enabled us to determine NF-kappaB activation in ex vivo isolated peripheral blood mononuclear cells. We examined 33 patients with diabetes mellitus (Type I and Type II). Patients with diabetic nephropathy showed higher NF-kappaB binding activity in Electrophoretic Mobility Shift Assays and stronger immunohistological staining for activated NF-kappaBp65 than patients without renal complications. NF-kappaB binding activity correlated with the degree of albuminuria (r = 0.316) and with thrombomodulin plasma concentrations (r = 0.33), indicative for albuminuria associated endothelial dysfunction. In a 3 day intervention study in which 600 mg of the antioxidant thioctic acid (alpha-lipoic acid) per day were given to nine patients with diabetic nephropathy oxidative stress in plasma samples was decreased by 48% and NF-kappaB binding activity in ex vivo isolated peripheral blood mononuclear cells by 38%. In conclusion, activation of the transcription factor NF-kappaB in ex vivo isolated peripheral blood mononuclear cells of patients with diabetes mellitus correlates with the degree of diabetic nephropathy. NF-kappaB activation is at least in part dependent on oxidative stress since thioctic acid (alpha-lipoic acid) reduced NF-kappaB binding activity.

Insufficient glycemic control increases nuclear factor-kappa B binding activity in peripheral blood mononuclear cells isolated from patients with type 1 diabetes.

OBJECTIVE: The redox-sensitive transcription factor nuclear factor-kappa B (NF-kappa B) is believed to contribute to late diabetic complications. It is unknown whether NF-kappa B is influenced by glycemic control. RESEARCH DESIGN AND METHODS: To determine whether NF-kappa B is activated in patients with insufficient glycemic control (HbA1c > 10%), we developed a tissue culture-independent electrophoretic mobility shift assay (EMSA)-based semiquantitative detection system that allowed us to determine NF-kappa B activation in ex vivo-isolated peripheral blood mononuclear cells (PBMCs). We included 43 patients with type 1 diabetes in this cross-sectional study. 10 of those received the antioxidant thioctic acid (600 mg/day p.o.) for 2 weeks. RESULTS: Monocytes of patients with HbA1c levels > 10% demonstrated significantly higher NF-kappa B binding activity in an EMSA and a stronger NF-kappa B staining in immunohistochemistry than monocytes of patients with HbA1c levels of 6-8%. The increase in NF-kappa B activation correlated with an increase in plasmatic markers of lipid peroxidation. Treatment with the antioxidant thioctic acid decreased NF-kappa B binding activity. CONCLUSIONS: Hyperglycemia induces activation of the transcription factor NF-kappa B in ex vivo-isolated PBMCs of patients with type 1 diabetes. NF-kappa B activation is at least partially dependent on oxidative stress, since the antioxidant thioctic acid significantly lowered the extent of NF-kappa B binding activity.