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Novel Variants of Angiotensin Converting Enzyme-2 of Shorter Molecular Size to Target the Kidney Renin Angiotensin System.

ABSTRACT: ACE2 is a monocarboxypeptidase which generates Angiotensin (1-7) from Angiotensin II (1-8). Attempts to target the kidney Renin Angiotensin System using native ACE2 to treat kidney disease are hampered by its large molecular size, 100 kDa, which precludes its glomerular filtration and subsequent tubular uptake. Here, we show that both urine and kidney lysates are capable of digesting native ACE2 into shorter proteins of ~60-75 kDa and then demonstrate that they are enzymatically very active. We then truncated the native ACE2 by design from the C-terminus to generate two short recombinant (r)ACE2 variants (1-605 and 1-619AA). These two truncates have a molecular size of ~70 kDa, as expected from the amino acid sequence and as shown by Western blot. ACE2 enzyme activity, measured using a specific substrate, was higher than that of the native rACE2 (1-740 AA). When infused to mice with genetic ACE2 deficiency, a single i.v. injection of 1-619 resulted in detectable ACE2 activity in urine, whereas infusion of the native ACE2 did not. Moreover, ACE2 activity was recovered in harvested kidneys from ACE2-deficient mice infused with 1-619, but not in controls (23.1 ± 4.3 RFU/µg creatinine/h and 1.96 ± 0.73 RFU/µg protein/hr, respectively). In addition, the kidneys of ACE2-null mice infused with 1-619 studied ex vivo formed more Ang (1-7) from exogenous Ang II than those infused with vehicle (AUC 8555 ± 1933 vs. 3439 ± 753 ng/mL, respectively, p < 0.05) further demonstrating the functional effect of increasing kidney ACE2 activity after the infusion of our short ACE2 1-619 variant. We conclude that our novel short recombinant ACE2 variants undergo glomerular filtration, which is associated with kidney uptake of enzymatically active proteins that can enhance the formation of Ang (1-7) from Ang II. These small ACE2 variants may offer a potentially useful approach to target kidney RAS overactivity to combat kidney injury.

SUBMITTER: Wysocki J

PROVIDER: S-EPMC6995632 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Rationale: Smoking is a major risk factor for the development of cardiovascular and pulmonary diseases. The importance of the renin–angiotensin system in the development of cardiovascular and pulmonary disease is well established. Angiotensin-II, by means of its type 1 receptor (angiotensin type 1 receptor, AT1R), promotes increased sympathetic activity, salt and water reabsorption, vasoconstriction, inflammation, and aldosterone and vasopressin release, contributing to tissue fibrosis, endothelium dysfunction, and hypertension. Angiotensin-converting enzyme 2 cleaves angiotensin-II into the vasodilator peptide, angiotensin-(1–7), hence playing a pivotal role in the angiotensin-converting enzyme 2/angiotensin-(1–7) compensatory axis of the renin–angiotensin system. Angiotensin type 2 receptor (AT2R), another receptor for angiotensin-II, opposes the deleterious effects of AT1R activation, and angiotensin-converting enzyme 2–formed angiotensin-(1–7) has been shown to activate AT2R. Objectives: The goal of the present study was to examine how nicotine, the addictive component of cigarette smoke, alters the homeostasis of the renin–angiotensin system. Methods: Quantitative real-time polymerase chain reaction was performed to examine the expression of the components of the renin–angiotensin system after cigarette smoke exposure or direct nicotine inhalation. Radio telemetry was used for continuous blood pressure recording in conscious, unrestrained mice. Results: Our study showed that cigarette smoke or direct nicotine inhalation inhibits the expression of angiotensin-converting enzyme 2/AT2R in multiple organs and cell types. In the lung, cigarette smoke (6 cigarettes/d, 12 wk) inhibited the expression of both angiotensin-converting enzyme 2 and AT2R. In cardiac fibroblasts, nicotine exposure resulted in near complete suppression of angiotensin-converting enzyme 2 and AT2R. In the brain, nicotine vapor inhalation inhibited angiotensin-converting enzyme 2 expression in the hypothalamus, a region involved in central regulation of cardiopulmonary function. In addition, cultured Neuro2A cells exposed to nicotine showed a dose-dependent reduction of enzymatic activity of angiotensin-converting enzyme 2. Functionally, mice exposed to nicotine vapor (12 h/d, 4 wk) exhibited significantly increased mean arterial blood pressure, which was more pronounced during the night active cycle (mean?±?SE, 124?±?0.6 mm Hg in nicotine vapor–exposed mice vs. 107?±?0.4 mm Hg in air control mice; P <?0.0001). Conclusions: Our findings suggest that, by downregulating the compensatory angiotensin-converting enzyme 2/AT2R elements, nicotine disrupts the homeostasis of the renin–angiotensin system in multiple organs, which is likely an important mechanism leading to the development of cardiovascular and pulmonary disease.

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Novel Variants of Angiotensin Converting Enzyme-2 of Shorter Molecular Size to Target the Kidney Renin Angiotensin System.

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