The Effects of Aldosterone and Cytokines IL-1beta, TNF-alpha on the Expression of Angiotensin Converting Enzyme Gene in Vascular Smooth Muscle Cells

Abstract

Background:It has been suggested that all components of the renin-angiotensin-aldosterone system (RAAS) are present in the vascular wall and that the vascular RAAS modulates vascular tone and vascular hypertrophy. One of the catalytic step in the RAAS cascade is the local conversion of angiotensin I to angiotensin II (Ang II) by angiotensin converting enzyme (ACE). One of the major sources of ACE in the vasculature is vascular smooth muscle cells (VSMC). Here, we provide insight into the intrinsic mechanisms by which the components of RAAS regulate gene expression of ACE in cultured smooth muscle cells of the rat and we also investigated the effects of cytokines on ACE mRNA. Methods:RNA was extracted from the primary cultured VSMCs. We analyzed the expression levels of ACE by competitive reverse transcriptionPCR using recombinant RNA as an internal standard. Results:1) ACE mRNA level was increased markedly by aldosterone in a dose-and time-dependent manner, indicating that there exists positive feedback mechanism within RAAS. 2) The induction of ACE mRNA by aldosterone was inhibited by spironolactone. 3) Aldosteronestimulated expression of ACE was also inhibited by Ang II, which shows that Ang II acts as a negative regulator of the expression of ACE in RAAS cascade. 4) Interleukin-1β or TNF-α did not induce ACE mRNA expression. 5) However, mixture of interleukin-1β and TNF-α (CytoMix) significantly increased the expression of ACE. It was also shown that CytoMix increased aldosterone-stimulated ACE mRNA expression in an additative manner. Conclusions:These results indicate that the expression of ACE in smooth muscle