DC ENaC-Dependent Inflammasome Activation Contributes to Salt-Sensitive Hypertension.

BACKGROUND: Salt sensitivity of blood pressure is an independent predictor of cardiovascular morbidity and mortality. The exact mechanism by which salt intake increases blood pressure and cardiovascular risk is unknown. We previously found that sodium entry into antigen-presenting cells (APCs) via the amiloride-sensitive epithelial sodium channel EnaC (epithelial sodium channel) leads to the formation of IsoLGs (isolevuglandins) and release of proinflammatory cytokines to activate T cells and modulate salt-sensitive hypertension. In the current study, we hypothesized that ENaC-dependent entry of sodium into APCs activates the NLRP3 (NOD [nucleotide-binding and oligomerization domain]-like receptor family pyrin domain containing 3) inflammasome via IsoLG formation leading to salt-sensitive hypertension. METHODS: We performed RNA sequencing on human monocytes treated with elevated sodium in vitro and Cellular Indexing of Transcriptomes and Epitopes by Sequencing analysis of peripheral blood mononuclear cells from participants rigorously phenotyped for salt sensitivity of blood pressure using an established inpatient protocol. To determine mechanisms, we analyzed inflammasome activation in mouse models of deoxycorticosterone acetate salt-induced hypertension as well as salt-sensitive mice with ENaC inhibition or expression, IsoLG scavenging, and adoptive transfer of wild-type dendritic cells into NLRP3 deficient mice. RESULTS: We found that high levels of salt exposure upregulates the NLRP3 inflammasome, pyroptotic and apoptotic caspases, and IL (interleukin)-1ß transcription in human monocytes. Cellular Indexing of Transcriptomes and Epitopes by Sequencing revealed that components of the NLRP3 inflammasome and activation marker IL-1ß dynamically vary with changes in salt loading/depletion. Mechanistically, we found that sodium-induced activation of the NLRP3 inflammasome is ENaC and IsoLG dependent. NLRP3 deficient mice develop a blunted hypertensive response to elevated sodium, and this is restored by the adoptive transfer of NLRP3 replete APCs. CONCLUSIONS: These findings reveal a mechanistic link between ENaC, inflammation, and salt-sensitive hypertension involving NLRP3 inflammasome activation in APCs. APC activation via the NLRP3 inflammasome can serve as a potential diagnostic biomarker for salt sensitivity of blood pressure.

Genetic ablation of serotonin receptor 2B improves aortic valve hemodynamics of Notch1 heterozygous mice in a high-cholesterol diet model.

Calcific aortic valve disease (CAVD) is a deadly disease that is rising in prevalence due to population aging. While the disease is complex and poorly understood, one well-documented driver of valvulopathy is serotonin agonism. Both serotonin overexpression, as seen with carcinoid tumors and drug-related agonism, such as with Fenfluramine use, are linked with various diseases of the valves. Thus, the objective of this study was to determine if genetic ablation or pharmacological antagonism of the 5-HT2B serotonin receptor (gene: Htr2b) could improve the hemodynamic and histological progression of calcific aortic valve disease. Htr2b mutant mice were crossed with Notch1+/- mice, an established small animal model of CAVD, to determine if genetic ablation affects CAVD progression. To assess the effect of pharmacological inhibition on CAVD progression, Notch1+/- mice were treated with the 5-HT2B receptor antagonist SB204741. Mice were analyzed using echocardiography, histology, immunofluorescence, and real-time quantitative polymerase chain reaction. Htr2b mutant mice showed lower aortic valve peak velocity and mean pressure gradient-classical hemodynamic indicators of aortic valve stenosis-without concurrent left ventricle change. 5-HT2B receptor antagonism, however, did not affect hemodynamic progression. Leaflet thickness, collagen density, and CAVD-associated transcriptional markers were not significantly different in any group. This study reveals that genetic ablation of Htr2b attenuates hemodynamic development of CAVD in the Notch1+/- mice, but pharmacological antagonism may require high doses or long-term treatment to slow progression.

Characterisation of aortic stenosis severity: a retrospective analysis of echocardiography reports in a clinical laboratory.

OBJECTIVE: To evaluate how common echocardiographic metrics of aortic stenosis (AS) influence the proportion of patients who may be categorised as having severe stenosis and therefore considered for valve replacement. METHODS: Retrospective analysis was performed of all echocardiograms with aortic valve area (AVA) ≤1.2 cm2 and peak jet velocity (Vmax) ≥3 m/s from 1 December 2014 through 30 October 2017 at a single academic medical centre. Echocardiographic indices collected include AVA, Vmax, left ventricular ejection fraction, stroke volume and annotated aortic stenosis severity. RESULTS: Among 807 patients with AVA ≤1.2 cm2 and Vmax ≥3 m/s (44.0% female, median age 74 years (IQR: 66-81)), 45.6% had Vmax ≥4 m/s, while 75.8% had AVA ≤1 cm2. 40.0% of patients had concordant indices (Vmax ≥4 m/s and AVA ≤1 cm2), and 35.8% had discordant indices (Vmax <4 m/s and AVA ≤1 cm2) of severe AS. Compared with those with concordant indices, patients with discordant indices were more commonly female (54.0% vs 44.3%, p<0.05) and less commonly characterised as severe (42.6% vs 93.8%, p<0.001). Patients with paradoxical low-flow, low-gradient severe AS by echocardiography were disproportionately female (61.5% vs 41.8%, p<0.001), and their disease was characterised as severe only 49.5% of the time. CONCLUSIONS: Patients with discordant indices, who are disproportionately female, are commonly described in clinical echocardiography reports as having less than severe AS. Given the potential benefit of AVR in patients with AVA ≤1 cm2 regardless of Vmax, this could have important clinical implications.

Macrophages Promote Aortic Valve Cell Calcification and Alter STAT3 Splicing.

OBJECTIVE: Macrophages have been described in calcific aortic valve disease, but it is unclear if they promote or counteract calcification. We aimed to determine how macrophages are involved in calcification using the Notch1+/- model of calcific aortic valve disease. Approach and Results: Macrophages in wild-type and Notch1+/- murine aortic valves were characterized by flow cytometry. Macrophages in Notch1+/- aortic valves had increased expression of MHCII (major histocompatibility complex II). We then used bone marrow transplants to test if differences in Notch1+/- macrophages drive disease. Notch1+/- mice had increased valve thickness, macrophage infiltration, and proinflammatory macrophage maturation regardless of transplanted bone marrow genotype. In vitro approaches confirm that Notch1+/- aortic valve cells promote macrophage invasion as quantified by migration index and proinflammatory phenotypes as quantified by Ly6C and CCR2 positivity independent of macrophage genotype. Finally, we found that macrophage interaction with aortic valve cells promotes osteogenic, but not dystrophic, calcification and decreases abundance of the STAT3ß isoform. CONCLUSIONS: This study reveals that Notch1+/- aortic valve disease involves increased macrophage recruitment and maturation driven by altered aortic valve cell secretion, and that increased macrophage recruitment promotes osteogenic calcification and alters STAT3 splicing. Further investigation of STAT3 and macrophage-driven inflammation as therapeutic targets in calcific aortic valve disease is warranted.

Adaptive immune cells in calcific aortic valve disease.

Calcific aortic valve disease (CAVD) is highly prevalent and has no pharmaceutical treatment. Surgical replacement of the aortic valve has proved effective in advanced disease but is costly, time limited, and in many cases not optimal for elderly patients. This has driven an increasing interest in noninvasive therapies for patients with CAVD. Adaptive immune cell signaling in the aortic valve has shown potential as a target for such a therapy. Up to 15% of cells in the healthy aortic valve are hematopoietic in origin, and these cells, which include macrophages, T lymphocytes, and B lymphocytes, are increased further in calcified specimens. Additionally, cytokine signaling has been shown to play a causative role in aortic valve calcification both in vitro and in vivo. This review summarizes the physiological presence of hematopoietic cells in the valve, innate and adaptive immune cell infiltration in disease states, and the cytokine signaling pathways that play a significant role in CAVD pathophysiology and may prove to be pharmaceutical targets for this disease in the near future.

Celecoxib Is Associated With Dystrophic Calcification and Aortic Valve Stenosis.

Calcific aortic valve disease is a progressive fibrocalcific process that can only be treated with valve replacement. Cadherin-11 has recently been identified as a potential therapeutic target for calcific aortic valve disease. The already approved drug celecoxib, a cyclooxygenase-2 inhibitor, binds cadherin-11, and was investigated as a therapeutic against calcific aortic valve disease. Unexpectedly, celecoxib treatment led to hallmarks of myofibroblast activation and calcific nodule formation in vitro. Retrospective electronic medical record analysis of celecoxib, ibuprofen, and naproxen revealed a unique association of celecoxib use and aortic stenosis.

Experimental and Computational Study of the Gas-Phase Acidities of Acidic Di- and Tripeptides.

Gas-phase acidities (GA or Δ Gacid) of acidic di- and tripeptides are determined for the first time. The peptides studied are composed of inert alanine (A) residues and one X residue of either aspartic acid (D) or glutamic acid (E): AX, XA, AAX, AXA, and XAA. Experimental GAs were measured by the thermokinetic method of deprotonation ion/molecule reactions in a Fourier transform ion cyclotron resonance mass spectrometer. Calculated GAs were obtained by composite correlated molecular orbital theory at the G3(MP2) level for deprotonation of carboxylic acid groups both at the C-terminus and at the side chain. Excellent agreement was found between experimental and calculated GA values. There is a slight preference for peptides with D being more acidic than analogous peptides with E, which agrees with the GAs of the corresponding amino acids. Experiments showed that peptides are more acidic (lower numerical GA values) when the acidic residue is located at the C-terminus (i.e., AX or AAX). The lowest energy form of deprotonated AAE has a unique structure where the longer side chain of E allows the two carboxylates, which are in close proximity, to share the proton. The tripeptides are less acidic (higher GA value) by 3-7 kcal/mol when the acidic residue is in the center. The tripeptides are more acidic (by 2-10 kcal/mol) than dipeptides containing the same acidic residue at the same location.