Corticosteroid-dependent, aldosterone-independent mineralocorticoid-receptor activation in the heart

The hypertension of Cushing's syndrome: controversies in the pathophysiology and focus on cardiovascular complications

Cushing's syndrome is associated with increased mortality, mainly due to cardiovascular complications, which are sustained by the common development of systemic arterial hypertension and metabolic syndrome, which partially persist after the disease remission. Cardiovascular diseases and hypertension associated with endogenous hypercortisolism reveal underexplored peculiarities. The use of exogenous corticosteroids also impacts on hypertension and cardiovascular system, especially after prolonged treatment. The mechanisms involved in the development of hypertension differ, whether glucocorticoid excess is acute or chronic, and the source endogenous or exogenous, introducing inconsistencies among published studies. The pleiotropic effects of glucocorticoids and the overlap of the several regulatory mechanisms controlling blood pressure suggest that a rigorous comparison of in-vivo and in-vitro studies is necessary to draw reliable conclusions. This review, developed during the first ‘Altogether to Beat Cushing's syndrome’ workshop held in Capri in 2012, evaluates the most important peculiarities of hypertension associated with CS, with a particular focus on its pathophysiology. A critical appraisal of most significant animal and human studies is compared with a systematic review of the few available clinical trials. A special attention is dedicated to the description of the clinical features and cardiovascular damage secondary to glucocorticoid excess. On the basis of the consensus reached during the workshop, a pathophysiology-oriented therapeutic algorithm has been developed and it could serve as a first attempt to rationalize the treatment of hypertension in Cushing's syndrome.

Impairment of Arterial Compliance in Cushing's Syndrome

Arterial stiffness may be useful for stratifying cardiovascular risk in individuals suffering from a number of pathologies, such as hypertension, diabetes, obesity, dyslipidaemia and coronary artery disease. Cushing's syndrome is underpinned by a complex metabolic syndrome, which is potentially implicated in the onset of blood vessel alterations and the increase in arterial wall stiffness. The aim of this paper was to perform a review about the most important studies conducted in order to evaluate the arterial distensibility profile of subjects affected by Cushing's syndrome. Increased arterial stiffness may persist even after successful cure of this disease. It is therefore of fundamental importance to identify the presence of early vascular alterations in these patients, in order to commence their treatment and thus attempt to prevent the subsequent onset of adverse cardiovascular events.

Diameters and wall-to-lumen ratio of retinal arterioles in patients with retinal vein occlusion before and after treatment with dexamethasone intravitreal implants

BACKGROUND

To evaluate the diameters and wall-to-lumen ratio (WLR) of retinal arterioles in patients with retinal vein occlusion (RVO) before and after a 0.7 mg dexamethasone (DEX) intravitreal implant and compare it with a matched control group of normal eyes.

METHODS

This was a single-site, multi-investigator, prospective, open-label, observational study in 15 patients with vision loss due to branch or central RVO treated with a single injection of DEX implant. An age-matched control group of 16 normal eyes was recruited. External and internal arteriolar diameters, WLR, and wall thickness were assessed in vivo using scanning-laser Doppler flowmetry. Visual acuity (VA) and central macular thickness (CMT) were evaluated.

RESULTS

Mean internal diameter showed a significant reduction in post-treatment RVO patients compared with pre-treatment RVO patients (56.0±18.0 μm vs. 67.9±16.9 μm, respectively; P=0.02). Mean WLR in pre-treatment RVO patients was 0.47±0.19, showing an increase to 0.63±0.23 3 months after treatment (P=0.037). No significant difference was found in arteriolar external diameter between normotensive, pre-treatment, and post-treatment subjects.

CONCLUSION

Treatment with a DEX implant in RVO patients led to significant improvements in both VA and CMT. These changes were accompanied by reductions in arteriolar lumen diameter, which could contribute to decreased capillary leakage and macular swelling.

[Telomeres, aging and Cushing's syndrome: are they related?]

Cushing's syndrome is due to excess cortisol secretion and is associated to increased mortality and severe morbidity that are not fully reversible despite biochemical control. The syndrome consists of a set of systemic manifestations similar to those found in aging. Chronic stress, which also causes hyperstimulation of the hypothalamic-pituitary-adrenal axis, has been related to accelerated telomere shortening, oxidative damage, and cell aging. Although premature aging in patients with Cushing's syndrome could be related to environmental factors, the possibility that chronic exposure to hypercortisolism causes telomere shortening, and thus premature aging, cannot be ruled out. This review discusses the available evidence supporting a link between Cushing's syndrome and cell aging.

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.

Effects of aldosterone on coronary function

Our understanding of the effects of aldosterone and its mechanisms has increased substantially in recent years, probably because of the importance of the mineralocorticoid receptor (MR) antagonists in several major cardiovascular diseases. Recent clinical studies have confirmed the benefits of MR antagonists in patients with heart failure, left ventricular dysfunction after myocardial infarction, hypertension or diabetic nephropathy. However, it would be a gross oversimplification to conclude that the role of aldosterone is unequivocally negative. Aldosterone is synthesized in the adrenal glands and binds to specific MRs in target epithelial cells. The steroid-receptor complex penetrates the cell nucleus where it modulates gene expression and activates specific aldosterone-induced proteins that control sodium reabsorption. Recent studies have shown that aldosterone also impacts a wide range of non-epithelial tissues such as the heart and blood vessels. Remarkably, aldosterone can also be synthesized in extra-adrenal tissues and it may act in a rapid non-genomic manner.We note the existence of glucocorticoids that exhibit plasma concentrations much higher than those of aldosterone and that are structurally very similar to aldosterone. It is thus possible that glucocorticoids may bind to the aldosterone receptor in some cell types. Diverse experimental models and several strains of transgenic mice have allowed us to better understand the effects of aldosterone on the heart. Specifically, it seems that a slight increase in cardiac aldosterone concentrations induces a decreased coronary reserve in mice by decreasing the BKCa potassium channels associated with coronary smooth muscle cells. Taken together, these experiments indicate that vascular cells are the primary targets of aldosterone in the cardiovascular system. The hormone directly affects NO and EDHF-mediated coronary relaxation. Both mechanisms may contribute to the deleterious cardiovascular effects of MR stimulation.