With prevalence as high as 55% for individuals aged 55 and older in United States, hypertension is a major risk factor contributing to cardiovascular diseases (CVD) and global mortality, hence remaining an increasingly important medical and public health issue. The role of the renin-angiotensin system (RAS) in the maintenance of normal blood pressure (BP) and in the neuro-cardiovascular dysregulation leading to hypertension has been firmly established. Angiotensin (Ang)-II, by means of its type 1 receptor (AT1R), promotes increased sympathetic activity, salt and water reabsorption, vasoconstriction, aldosterone and vasopressin release and inflammation, all contributing to hypertension. Angiotensin Converting Enzyme type 2 (ACE2), one of the latest identified members of this system cleaves Ang-II and produces Ang-(1-7) which plays a compensatory role and opposes the RAS deleterious effects. Beyond establishing ACE2 as a critical player in the prevention of neurogenic hypertension, our group was the first to report that Ang-II mediates ACE2 ubiquitination and degradation via AT1R activation, effects that were prevented by pretreatment with a lysosomal inhibitor. Although confirmed by independent groups, the therapeutic potential of preventing ACE2 ubiquitination and degradation has not been investigated. Our pilot data, show that mutation of the C-terminus of ACE2 prevents the ubiquitination and preserves ACE2 compensatory activity while treatment with an ubiquitination-resistant ACE2 virus blunts the development of Ang-II-mediated hypertension in mice otherwise lacking ACE2. In addition, we show that targeting NEDD4, a major family of E3 ubiquitin ligases, neutralizes the deleterious effects of Ang-II on ACE2 activity, while a pilot proteomics analysis highlighted gender-specific modulation of other E3 ligases and de- ubiquitinases in the hypothalamus of mice undergoing salt-sensitive hypertension. Our preliminary data further highlight that this mechanism is not restricted to AT1R but that bradykinin B1R, activated by the inflammatory response associated to hypertension, are also involved. Thus, the hypothesis of this work is that RAS over- activation and hypertension-associated inflammation exacerbate ACE2 ubiquitination, resulting in enhanced degradation of this enzyme and a loss of its compensatory activity, ultimately reinforcing hypertension. Here, we will target ACE2 ubiquitination using novel viral approaches and unique transgenic models with an emphasis on gender- and cell-specific differences in the central nervous system and the vasculature. Validation of our hypothesis will open the door for new targeting approaches aimed at preserving ACE2 compensatory activity in hypertension and CVD.

Public Health Relevance

The brain renin-angiotensin system (RAS) has major deleterious effects in the development and maintenance of cardiovascular diseases (CVD), particularly in hypertension, which affects 55% of individuals above age 55 in United States. Based on our preliminary results, angiotensin converting enzyme 2 (ACE2) ubiquitination is a new and unexplored mechanism leading to a loss of compensatory activity in hypertension and CVD. Targeting of this mechanism will be investigated both in vitro and in vivo in order to determine the overall benefits on the treatment of hypertension.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Research Project (R01)
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Hypertension and Microcirculation Study Section (HM)
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OH, Youngsuk
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Louisiana State Univ Hsc New Orleans
Schools of Medicine
New Orleans
United States
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