Microvascular Effects of Aldosterone and Angiotensin Type 2 Receptors

Pathogenesis of vascular complications in Cushing's syndrome

Chronic exposure to high glucocorticoid levels in Cushing's syndrome (CS) is often associated with alterations in the hemostatic system and the expression of prothrombotic phenotypes. Increased frequency of both atherothrombotic and venous thromboembolic events (VTE) has been reported in patients with CS. In general, cardiovascular complications in these patients cause a five-fold increase in mortality compared to the normal population. Although numerous abnormalities in the hemostatic system have been detected in patients with CS, the underlying mechanisms of the prothrombotic state are not fully elucidated. High levels of factor VIII and von Willebrand factor, with evidence of enhanced thrombin generation and decreased fibrinolytic activity, have been documented in several studies. However, it is not clear to what extent these changes contribute to the shift of hemostatic balance towards the hypercoagulable state and expression of thrombophilic phenotypes. Thrombosis is usually a multicausal disease, and all three components of the so-called Virchow triad, namely 1) vascular abnormalities and endothelial dysfunction, 2) hypercoagulability and 3) stasis, may play a variable role in the pathogenesis of the prothrombotic state in CS patients. Larger studies are needed to establish strategies for prevention of cardiovascular complications in patients with Cushing's syndrome.

Hypertrophic remodeling of subcutaneous small resistance arteries in patients with Cushing's syndrome

OBJECTIVE

Structural alterations of small resistance arteries in essential hypertensive patients (EH) are mostly characterized by inward eutrophic remodeling. However, we observed hypertrophic remodeling in patients with renovascular hypertension, in those with acromegaly, as well as in patients with non-insulin-dependent diabetes mellitus, suggesting a relevant effect of humoral growth factors on vascular structure, even independent from the hemodynamic load. Cortisol may stimulate the renin-angiotensin system and may induce cardiac hypertrophy. However, presently no data are available about small artery structure in patients with Cushing's syndrome.

SUBJECTS

We have investigated the structure of sc small resistance arteries in 12 normotensive subjects (NT), in 12 EH subjects, and in eight patients with Cushing's syndrome (CS). Small arteries from sc fat were dissected and mounted on a micromyograph. The normalized internal diameter, media thickness, media to lumen ratio, and the media cross-sectional area were measured, as well as indices of oxidative stress.

RESULTS

Demographic variables were similar in the three groups, except for clinic blood pressure. The media to lumen ratio was significantly greater in EH and CS, compared with NT; no difference was observed between EH and CS. The media cross-sectional area was significantly greater in CS compared with EH and with NT. An increased vascular oxidative stress was present in CS, as demonstrated by increased levels of superoxide anions, cyclooxygenase-1 and endothelial nitric oxide synthase in the microvessels.

CONCLUSION

Our results suggest the presence of hypertrophic remodeling in sc small resistance arteries of CS, probably as a consequence of growth-promoting properties of circulating cortisol and/or increased vascular oxidative stress.