The circumventricular organs (CVO) lack a well-formed blood-brain barrier and produce superoxide (O2•−) in response to angiotensin II and other hypertensive stimuli. This increase in central O2•− has been implicated in regulation of blood pressure. The extracellular superoxide dismutase (SOD3) is highly expressed in cells associated with CVO, and particularly with tanycytes lining this region. To understand the role of SOD3 in the CVO in blood pressure regulation, we performed intracerebroventricular (ICV) injection an adenovirus encoding Cre-recombinase (AdCre, 5×108 particles/ml) in mice with loxP sites flanking the SOD3 coding region (SOD3loxp/loxp mice). An adenovirus encoding red-fluorescent protein (AdRFP) was injected as a control. Deletion of CVO SOD3 increased baseline blood pressure modestly and markedly augmented the hypertensive response to low-dose angiotensin II (140 ng/kg/day), while ICV injection of AdRFP had minimal effects on these parameters. AdCre treated mice exhibited increased sympathetic modulation of heart rate and blood pressure variability, increased vascular superoxide production and T cell activation as characterized by increased circulating CD69+/CD3+ cells. Deletion of CVO SOD3 also markedly increased vascular T cell and leukocyte infiltration caused by angiotensin II. We conclude that SOD3 in the CVO plays a critical role in regulation of blood pressure and its loss promotes T cell activation and vascular inflammation, in part by modulating sympathetic outflow. These findings provide insight into how central signals produce vascular inflammation in response to hypertensive stimuli such as angiotensin II.

Inactivation of the tumor suppressor adenomatous polyposis coli, with the resultant activation of β-catenin, is the initiating event in the development of a majority of colorectal cancers. Krüppel-like factor 5 (KLF5), a proproliferative transcription factor, is highly expressed in the proliferating intestinal crypt epithelial cells. To determine whether KLF5 contributes to intestinal adenoma formation, we examined tumor burdens in ApcMin/+ mice and ApcMin/+/Klf5+/− mice. Compared with ApcMin/+ mice, ApcMin/+/Klf5+/− mice had a 96% reduction in the number of intestinal adenomas. Reduced tumorigenicity in the ApcMin/+/Klf5+/− mice correlated with reduced levels and nuclear localization of β-catenin as well as reduced expression of two β-catenin targets, cyclin D1 and c-Myc. In vitro studies revealed a physical interaction between KLF5 and β-catenin that enhanced the nuclear localization and transcriptional activity of β-catenin. Thus, KLF5 is necessary for the tumor-initiating activity of β-catenin during intestinal adenoma formation in ApcMin/+ mice, and reduced expression of KLF5 offsets the tumor-initiating activity of the ApcMin mutation by reducing the nuclear localization and activity of β-catenin.

Rationale We have previously found that T lymphocytes are essential for development of angiotensin II-induced hypertension however the mechanisms responsible for T cell activation in hypertension remain undefined. Objective To study the roles of the central nervous system and pressure elevation in T cell activation and vascular inflammation caused by angiotensin II. Methods and Results To prevent the central actions of angiotensin II we created anteroventral third cerebral ventricle (AV3V) lesions in mice. The elevation in blood pressure in response to angiotensin II was virtually eliminated by AV3V lesions, as was activation of circulating T cells and the vascular infiltration of leukocytes. In contrast, AV3V lesioning did not prevent the hypertension and T cell activation caused by the peripheral acting agonist norepinephrine. To determine if T cell activation and vascular inflammation are due to central influences or are mediated by blood pressure elevation, we administered hydralazine (250 mg/L) in the drinking water. Hydralazine prevented the hypertension, and abrogated the increase in circulating activated T cells and vascular infiltration of leukocytes caused by angiotensin II. Conclusions We conclude that the central and pressor effects of angiotensin II are critical for T cell activation and development of vascular inflammation. These findings also support a feed forward mechanism in which modest degrees of blood pressure elevation lead to T cell activation, which in turn promotes inflammation and further raises blood pressure, leading to severe hypertension. Brief summary We have previously shown that T cells are important for the development of hypertension and others have shown that CNS lesions such as AV3V disruption prevent hypertension. We examined the relationship between central actions of angiotensin II, T cell activation and hypertension by determining how AV3V lesions affect T cell activation and hypertensive responses to angiotensin II and norepinephrine. Our data are compatible with a scenario in which modest degrees of pressure elevation, mediated either directly by norepinephrine or via central actions of angiotensin II, promote an inflammatory response that leads to severe hypertension. These studies provide new insight into how the central nervous system contributes to systemic inflammation in hypertension.