Introduction: Higher cortisol levels are associated with cardiovascular morbidity and mortality in the elderly, partially resulting from biologic effects of glucocorticoids (GCs) on endothelial cells observed in an experimental setting. These features are replicated in patients with endogenous GC excess (Cushing's syndrome) or with exogenous hypercortisolism due to excessive pharmacological application of GCs. Both groups present also an increased cardiovascular disease event rate. GCs may also adversely influence recovery after myocardial infarction. Recently it was proposed that microRNAs (miRNAs) - small noncoding RNAs functioning as antisense regulators of gene expression by targeting mRNA - may have a central role in regulating endothelial function through multiple mechanisms. Thus, the purpose of this study was to evaluate the effects of chronic GC excess on the expression of selected endothelium-controlling miRNAs expressed in nucleated cells circulating in peripheral blood (PBNCs) of patients with endogenous hypercortisolism either due to corticotrophin-independent or corticotrophin-dependent Cushing's syndrome (CS).
Material and methods: Peripheral blood nuclear cells were collected from 35 healthy subjects and 31 patients with endogenous hypercortisolism as a source of miRNAs. A self-validated individual quantitative RT-PCR study was then performed to evaluate the expression levels of selected miRNAs in PBNCs. Additionally, endothelin-1 (ET-1) expression in peripheral blood was assessed with respect to endothelial dysfunction using Western blotting.
Results: The ET-1 expression levels in CS were higher than in controls, confirming endothelial dysfunction in the CS group. Furthermore, miRNA analysis revealed a significantly decreased intracellular expression of selected endothelium-related miRNAs in patients with endogenous hypercortisolism, including miRNA-17-5p, miRNA-126-3p, and miRNA-126-5p, compared to controls. In contrast, two other angiogenic miRNAs, miRNA-150-5p and miRNA-223-3p, were significantly upregulated compared to controls.
Conclusions: Cardiovascular events related to hypercortisolism remain a challenging problem in medical practice. This study has demonstrated that the chronic excess of GCs in endogenous CS might induce significant dysregulation of selected miRNAs involved in the control of endothelium biology. However, the lack of knowledge about specific miRNA expression postpones the full understanding of the biological roles of such miRNAs in hypercortisolism. Moreover, dysregulated miRNAs seem to be promising targets for further research, especially to search for potential therapies for several GC-induced cardiovascular complications.
Keywords: Cushing’s syndrome; cardiovascular abnormalities; endocrine diseases; microRNA.