Objective Inflammation has been proposed as a key component in the development of hypertension and cardiac remodeling associated with different cardiovascular diseases. However, the role of the proinflammatory cytokine interleukin-6 in the chronic stage of hypertension is not well defined. Here, we tested the hypothesis that deletion of interleukin-6 protects against the development of hypertension, cardiac inflammation, fibrosis, remodeling and dysfunction induced by high salt diet and angiotensin II (Ang II). Methods Male C57BL/6J and interleukin-6-knock out (KO) mice were implanted with telemetry devices for blood pressure (BP) measurements, fed a 4% NaCl diet, and infused with either vehicle or Ang II (90 ng/min per mouse subcutaneously) for 8 weeks. We studied BP and cardiac function by echocardiography at baseline, 4 and 8 weeks. Results Myocyte cross-sectional area (MCSA), macrophage infiltration, and myocardial fibrosis were also assessed. BP increased similarly in both strains when treated with Ang II and high salt (Ang II-high salt); however, C57BL/6J mice developed a more severe decrease in left ventricle ejection fraction, fibrosis, and macrophage infiltration compared with interleukin-6-KO mice. No differences between strains were observed in MCSA, capillary density and MCSA to capillary density ratio. Conclusion In conclusion, absence of interleukin -6 did not alter the development of Ang II-high salt-induced hypertension and cardiac hypertrophy, but it prevented the development of cardiac dysfunction, myocardial inflammation, and fibrosis. This indicates that interleukin-6 plays an important role in hypertensive heart damage but not in the development of hypertension.

Purpose of the Review The main goal of this article is to discuss how the development of state-of-the-art technology has made it possible to address fundamental questions related to how the renin-angiotensin system (RAS) operates within the brain from the neurophysiological and molecular perspective. Recent Findings The existence of the brain RAS remains surprisingly controversial. New sensitive in situ hybridization techniques and novel transgenic animals expressing reporter genes have provided pivotal information of the expression of RAS genes within the brain. We discuss studies using genetically engineered animals combined with targeted viral microinjections to study molecular mechanisms implicated in the regulation of the brain RAS. We also discuss novel drugs targeting the brain RAS that have shown promising results in clinical studies and trials. Summary Over the last 50 years, several new physiological roles of the brain RAS have been identified. In the coming years, efforts to incorporate cutting-edge technologies such as optogenetics, chemogenetics, and single-cell RNA sequencing will lead to dramatic advances in our full understanding of how the brain RAS operates at molecular and neurophysiological levels. Keywords Renin. Prorenin receptor. Angiotensin receptor. Biased agonist. Blood pressure. Neurophysiology This article is part of the Topical Collection on Inflammation and Cardiovascular Diseases

Galectin-3 (Gal-3), a member of the β-galactoside lectin family, has an important role in immune regulation. In hypertensive rats and heart failure patients, Gal-3 is considered a marker for an unfavorable prognosis. Nevertheless, the role and mechanism of Gal-3 action in hypertension-induced target organ damage are unknown. We hypothesized that, in angiotensin II (ANG II)-induced hypertension, genetic deletion of Gal-3 prevents left ventricular (LV) adverse remodeling and LV dysfunction by reducing the innate immune responses and myocardial fibrosis. To induce hypertension, male C57BL/6J and Gal-3 knockout (KO) mice were infused with ANG II (3 μg·min·kg sc) for 8 wk. We assessed: 1) systolic blood pressure by plethysmography, 2) LV function and remodeling by echocardiography, 3) myocardial fibrosis by histology, 4) cardiac CD68 macrophage infiltration by histology, 5) ICAM-1 and VCAM-1 expression by Western blotting, 6) plasma cytokines, including interleukin-6 (IL-6), by enzyme-linked immunosorbent assay, and 7) regulatory T (T) cells by flow cytometry as detected by their combined expression of CD4, CD25, and FOXP3. Systolic blood pressure and cardiac hypertrophy increased similarly in both mouse strains when infused with ANG II. However, hypertensive C57BL/6J mice suffered impaired ejection and shortening fractions. In these mice, the extent of myocardial fibrosis and macrophage infiltration was greater in histological sections, and cardiac ICAM-1, as well as plasma IL-6, expression was higher as assessed by Western blotting. However, all these parameters were blunted in Gal-3 KO mice. Hypertensive Gal-3 KO mice also had a higher number of splenic T lymphocytes. In conclusion, in ANG II-induced hypertension, genetic deletion of Gal-3 prevented LV dysfunction without affecting blood pressure or LV hypertrophy. This study indicates that the ANG II effects are, in part, mediated or triggered by Gal-3 together with the related intercellular signaling (ICAM-1 and IL-6), leading to cardiac inflammation and fibrosis.

The anti-inflammatory peptide Ac-SDKP is released from thymosin-␤4 by renal meprin-␣ and prolyl oligopeptidase. Am J Physiol Renal Physiol 310: F1026 -F1034, 2016. First published March 9, 2016 doi:10.1152/ajprenal.00562.2015.-N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) is a natural tetrapeptide with antiinflammatory and antifibrotic properties. Previously, we have shown that prolyl oligopeptidase (POP) is involved in the Ac-SDKP release from thymosin-␤4 (T␤4). However, POP can only hydrolyze peptides shorter than 30 amino acids, and T␤4 is 43 amino acids long. This indicates that before POP hydrolysis takes place, T␤4 is hydrolyzed by another peptidase that releases NH2-terminal intermediate peptide(s) with fewer than 30 amino acids. Our peptidase database search pointed out meprin-␣ metalloprotease as a potential candidate. Therefore, we hypothesized that, prior to POP hydrolysis, T␤4 is hydrolyzed by meprin-␣. In vitro, we found that the incubation of T␤4 with both meprin-␣ and POP released Ac-SDKP, whereas no Ac-SDKP was released when T␤4 was incubated with either meprin-␣ or POP alone. Incubation of T␤4 with rat kidney homogenates significantly released Ac-SDKP, which was blocked by the meprin-␣ inhibitor actinonin. In addition, kidneys from meprin-␣ knockout (KO) mice showed significantly lower basal Ac-SDKP amount, compared with wild-type mice. Kidney homogenates from meprin-␣ KO mice failed to release Ac-SDKP from T␤4. In vivo, we observed that rats treated with the ACE inhibitor captopril increased plasma concentrations of Ac-SDKP, which was inhibited by the coadministration of actinonin (vehicle, 3.1 Ϯ 0.2 nmol/l; captopril, 15.1 Ϯ 0.7 nmol/l; captopril ϩ actinonin, 6.1 Ϯ 0.3 nmol/l; P Ͻ 0.005). Similar results were obtained with urinary Ac-SDKP after actinonin treatment. We conclude that release of Ac-SDKP from T␤4 is mediated by successive hydrolysis involving meprin-␣ and POP.N-acetyl-seryl-aspartyl-lysyl-proline; thymosin-␤4; meprin-␣; prolyl oligopeptidase; angiotensin-converting enzyme THE ANTI-INFLAMMATORY PEPTIDE N-acetyl-seryl-aspartyl-lysylproline (Ac-SDKP) was identified originally in the bone marrow (24). It has also been widely distributed in mammalian organs, plasma, urine, and circulating mononuclear cells (23,39,46). In animal diseases with hypertension, as well as cardiovascular and kidney disease, Ac-SDKP reduces inflammatory cell infiltration and collagen deposition in the heart, kidney, lung, and liver (14,15,33,34,37,44). Ac-SDKP is hydrolyzed by angiotensin-converting enzyme (ACE) and has a short half-life of 4.5 min in the circulation (16). Treatment with ACE inhibitors significantly increased plasma concentration of Ac-SDKP (2), and some of the ACE inhibitors protective effects were reported to be mediated by the increases in Ac-SDKP concentrations (34, 35).Thymosin-␤4 (T␤4) is a major G-actin-sequestering peptide that consists of 43 amino acids. Since it contains the Ac-SDKP sequence in its NH 2 -terminal, T␤4 is considered to be the precursor of 39). Our group has shown p...

Balb/c mice, which are T-helper lymphocyte 2 (Th2) responders, are highly susceptible to infectious and non-infectious heart diseases, whereas C57BL/6 mice (Th1 responders) are not. Angiotensin II (Ang II) is not only a vasopressor but also a pro-inflammatory factor that leads to cardiac hypertrophy, fibrosis and dysfunction. We hypothesized that Ang II exacerbates cardiac damage in Balb/c but not in C57BL/6 mice even though both strains have a similar level of hypertension. Twelve-week-old male C57BL/6J and Balb/c mice received either vehicle or Ang II (1.4mg kg−1 day−1, s.c. via osmotic minipump) for 8 weeks. At baseline, Balb/c mice exhibited the following: (1) a lower heart rate; (2) an enlarged left ventricular chamber; (3) a lower ejection fraction and shortening fraction; and (4) twice the left ventricular collagen deposition of age-matched C57BL/6J mice. Angiotensin II raised systolic blood pressure (to ~150 mmHg) and induced cardiomyocyte hypertrophy in a similar manner in both strains. While C57BL/6J mice developed compensatory concentric hypertrophy and fibrosis in response to Ang II, Balb/c mice demonstrated severe left ventricular chamber dilatation, wall thinning and fibrosis, leading to congestive heart failure as evidenced by dramatically decreased ejection fraction and lung congestion (significant increase in lung weight), which are both characteristic of dilated cardiomyopathy. Our study suggests that the Th phenotype plays an active role in cardiac remodelling and function both in basal conditions and in hypertension. Angiotensin II-induced dilated cardiomyopathy in Balb/c mice is an ideal animalmodel for studying the impact of the adaptive immune system on cardiac remodelling and function and for testing strategies to prevent or treat hypertension-associated heart failure.