miR-10b promotes aortic aneurysm formation and aortic rupture in angiotensin II-induced ApoE-deficient mice.

Abdominal aortic aneurysm (AAA) is associated with increased plasma levels of microRNA (miR) -10b. 5 nmols of miR-10b or miR control was administrated to Apolipoprotein E-deficient mice three days prior implantation of osmotic mini-pumps containing angiotensin II, and for three additional times once a week, which increased expression of miR-10b in plasma. Animals receiving miR-10b had a mortality rate due to aortic rupture of 61% compared to 11% in the miR controls (p < 0.05). Further, miR- 10b resulted in an increased aneurysm formation and growth (p < 0.05), which was accompanied by increased elastin degradation, neutrophil and mast cell markers (p < 0.05). In conclusion, miR-10b is functionally affecting aneurysm development and rupture and not only a marker of AAA. More mechanistic studies are required to better understand miR-10b's role in AAA formation.

Renal neurohormonal regulation in heart failure decompensation.

Decompensation in heart failure occurs when the heart fails to balance venous return with cardiac output, leading to fluid congestion and contributing to mortality. Decompensated heart failure can cause acute kidney injury (AKI), which further increases mortality. Heart failure activates signaling systems that are deleterious to kidneys such as renal sympathetic nerve activity (RSNA), renin-angiotensin-aldosterone system, and vasopressin secretion. All three reduce renal blood flow (RBF) and increase tubular sodium reabsorption, which may increase renal oxygen consumption causing AKI through renal tissue hypoxia. Vasopressin contributes to venous congestion through aquaporin-mediated water retention. Additional water retention may be mediated through vasopressin-induced medullary urea transport and hyaluronan but needs further study. In addition, there are several systems that could protect the kidneys and reduce fluid retention such as natriuretic peptides, prostaglandins, and nitric oxide. However, the effect of natriuretic peptides and nitric oxide are blunted in decompensation, partly due to oxidative stress. This review considers how neurohormonal signaling in heart failure drives fluid retention by the kidneys and thus exacerbates decompensation. It further identifies areas where there is limited data, such as signaling systems 20-HETE, purines, endothelin, the role of renal water retention mechanisms for congestion, and renal hypoxia in AKI during heart failure.