Lipopolysaccharides, but not Angiotensin ll, lnduces Direct Pro-lnflammatory Effects in Cultured Mouse Arteries and Human Endothelial and Vascular Smooth Muscle Cells

Angiotensin II (Ang II) might induce pro-inflammatory effects directly in the vascular wall independently of its haemodynamic effects. The aim of our study was to investigate the putative direct pro-inflammatory and vasomotor effects of Ang II and compare to those of lipopolysaccharides (LPS) in mouse isolated mesenteric resistance-sized arteries (MRA) supported by experiments in cultured human primary endothelial and vascular smooth muscle cells. Results showed that 24-hr organ culture of mouse MRA with 10 nM Ang II had, unlike 100 ng/mL LPS, no effects on IL-6 or MCP-1 secretion, VCAM1 mRNA expression or endothelial function, while Ang II significantly decreased maximal vasomotor responses to phenylephrine. In support, 24-hr organ culture of mouse MRA significantly suppressed Agtr1a mRNA and augmented Tlr4 mRNA along with attenuated vasomotor responses to Ang II. Moreover, contrary to LPS and TNF-α, Ang II and [Sar1]-Ang II had no concentration- or time-dependent effects on IL-6 and MCP-1 secretion in human umbilical vein endothelial cells (HUVEC) and human aortic smooth muscle cells (HASMC). AGTR1 or AGTR2 mRNA expression was undetectable in HUVEC, whereas HASMC expressed only AGTR1 mRNA. In summary, contrary to previous studies and the observed effects of LPS, we could not demonstrate direct vascular pro-inflammatory effects of Ang II ex vivo or in vitro. As indicated by our results, down-regulation or desensitization of AT1 R during culture may explain our findings.