The Role of Angiotensin II and Cyclic AMP in Alveolar Active Sodium Transport

A 1H NMR spectroscopic metabolomic study of the protective effects of irbesartan in a rat model of chronic mountain sickness

Chronic mountain sickness (CMS) is a significant pathology in most high-altitude regions globally, affecting the cardiopulmonary system and its mechanism is largely unknown. A metabonomic approach using ¹H nuclear magnetic resonance spectroscopy allows for detecting differential metabolites, which provides a global view and mechanisms during CMS development. In this study, we simulated a high-altitude environment to establish a rat model of CMS. Irbesartan was administered to CMS rats at three doses (6.75, 13.5, and 27 mg/kg) once a day for 15 days. HE staining and transmission electron microscopy were used to evaluate the effect of changes on the lung. Based on ¹H NMR spectra obtained from serum samples, partial least squares-discriminant analysis (PLS-DA) and its variant orthogonal PLS-DA (OPLS-DA) models were applied to distinguish the different groups. Histopathological sections showed that the alveolar structure was abnormal, inflammatory infiltration occurred in CMS rats, and CMS induced notable metabolic disorder according to the ¹H NMR result. However, irbesartan reversed the imbalanced metabolites via energy metabolism, amino acid metabolism, and taurine metabolism pathways, and its effect was also confirmed by the general signs and morphology of the lung. The results revealed that irbesartan as an effective therapeutic agent to improve CMS is warranted.

Do Changes in ACE-2 Expression Affect SARS-CoV-2 Virulence and Related Complications: A Closer Look into Membrane-Bound and Soluble Forms

The SARS-CoV-2 virus utilizes angiotensin converting enzyme (ACE-2) for cell entry and infection. This enzyme has important functions in the renin-angiotensin aldosterone system to preserve cardiovascular function. In addition to the heart, it is expressed in many tissues including the lung, intestines, brain, and kidney, however, its functions in these organs are mostly unknown. ACE-2 has membrane-bound and soluble forms. Its expression levels are altered in disease states and by a variety of medications. Currently, it is not clear how altered ACE-2 levels influence ACE-2 virulence and relevant complications. In addition, membrane-bound and soluble forms are thought to have different effects. Most work on this topic in the literature is on the SARS-CoV virus that has a high genetic resemblance to SARS-Co-V-2 and also uses ACE-2 enzyme to enter the cell, but with much lower affinity. More recent studies on SARS-CoV-2 are mainly clinical studies aiming at relating the effect of medications that are thought to influence ACE-2 levels, with COVID-19 outcomes for patients under these medications. This review paper aims to summarize what is known about the relationship between ACE-2 levels and SARS-CoV/SARS-CoV-2 virulence under altered ACE-2 expression states.

Irbesartan ameliorates chronic mountain sickness in a rat model via the cholesterol metabolism: An iTRAQ -based proteomics analysis

OBJECTIVE

To study the effects of irbesartan on pulmonary artery lesions in a rat model with chronic mountain sickness (CMS) and identify the biomarkers involved.

METHODS

In this study, we used a rat model of CMS to evaluate the therapeutic effect of irbesartan by measuring pulmonary artery pressure and evaluating the histopathology of the pulmonary artery. We also used proteomics technology to identify differentially expressed proteins (DEPs) in the serum and performed bioinformatics analysis. Results were then verified by enzyme linked immunosorbent assay (ELISA) and immunohistochemistry (IHC).

RESULTS

Irbesartan treatment induced a significant decrease (P < 0.05) in the pulmonary artery pressure of CMS rats. Histopathological and electron microscope further confirmed that high altitude hypoxia induced changes in the structure of the pulmonary artery tissue and caused ultrastructural lesions. Proteomics analysis identified 40 DEPs; bioinformatics analysis further revealed that the cholesterol metabolism pathway plays a crucial role in the occurrence of CMS. ELISA and IHC verified that several DEPs (Apo-A1, Apo-C1, Apo-E, IGF-1, Profilin1, and Col1a1) represent critical biological markers in pulmonary artery disease caused by CMS.

CONCLUSIONS

Irbesartan significantly improved pulmonary artery damage in a rat model of CMS possibly by impacting on the cholesterol metabolism pathway and by reducing damage to vascular endothelial cells. Irbesartan also inhibited the expression levels of IGF-1, Profilin1 and Col1a1 to relieve pulmonary artery pressure and improve lung function by inhibiting vascular remodeling. Several proteins were identified as potential biomarkers of CMS, including Apo-A1, Apo-C1, Apo-E, IGF-1, Profilin1, and Col1a1.

Identification, localization and expression of NHE isoforms in the alveolar epithelial cells

Na+/H+ exchangers (NHEs), encoded by Solute Carrier 9A (SLC9A) genes in human, are ubiquitous integral membrane ion transporters that mediate the electroneutral exchange of H+ with Na+ or K+. NHEs, found in the kidney and intestine, play a major role in the process of fluid reabsorption together via Na+,K+-ATPase pump and Na+ channels. Nevertheless, the expression pattern of NHE in the lung and its role in alveolar fluid homeostasis has not been addressed. Therefore, we aimed to examine the expression of NHE specific isoforms in alveolar epithelial cells (AECs), and assess their role in congestive heart failure (CHF). Three NHE isoforms were identified in AEC and A549 cell line, at the level of protein and mRNA; NHE1, NHE2 and mainly NHE8, the latter was shown to be localized in the apical membrane of AEC. Treating A549 cells with angiotensin (Ang) II for 3, 5 and 24 hours displayed a significant reduction in NHE8 protein abundance. Moreover, the abundance of NHE8 protein was downregulated in A549 cells that were treated overnight with Ang II. NHE8 abundance in whole lung lysate was increased in rats with 1-week CHF compared to sham operated rats. However, lower abundance of NHE8 was observed in 4-week CHF group. In conclusion, we herein show for the first time, the expression of a novel NHE isoform in AEC, namely NHE8. Notably, Ang II decreased NHE8 protein levels. Moreover, NHE8 was distinctly affected in CHF rats, probably depending on the severity of the heart failure.

Candesartan could ameliorate the COVID-19 cytokine storm

BACKGROUND

Angiotensin receptor blockers (ARBs) reducing inflammation and protecting lung and brain function, could be of therapeutic efficacy in COVID-19 patients.

METHODS

Using GSEA, we compared our previous transcriptome analysis of neurons injured by glutamate and treated with the ARB Candesartan (GSE67036) with transcriptional signatures from SARS-CoV-2 infected primary human bronchial epithelial cells (NHBE) and lung postmortem (GSE147507), PBMC and BALF samples (CRA002390) from COVID-19 patients.

RESULTS

Hundreds of genes upregulated in SARS-CoV-2/COVID-19 transcriptomes were similarly upregulated by glutamate and normalized by Candesartan. Gene Ontology analysis revealed expression profiles with greatest significance and enrichment, including proinflammatory cytokine and chemokine activity, the NF-kappa B complex, alterations in innate and adaptive immunity, with many genes participating in the COVID-19 cytokine storm.

CONCLUSIONS

There are similar injury mechanisms in SARS-CoV-2 infection and neuronal injury, equally reduced by ARB treatment. This supports the hypothesis of a therapeutic role for ARBs, ameliorating the COVID-19 cytokine storm.

Hyperacute graft dysfunction in an orthotopic heart transplant in the presence of non-HLA antibodies

Antibody-mediated rejection (AMR) in heart transplants in the absence of anti-HLA donor-specific antibody (DSA) is not well studied or documented. This case reviews hyperacute fulminant graft dysfunction suspected to be mediated by non-HLA antibodies. After cross clamp removal, the patient developed severe pulmonary edema, profound coagulopathy, and biventricular failure. The patient's presumed AMR, cardiogenic shock, and coagulopathy were treated with extracorporeal membrane oxygenation (ECMO), plasmapheresis, intravenous immunoglobulin (IVIG), multiple blood products, and prothrombin complex concentrate. The recipient was 0% panel-reactive antibody (PRA), ABO, and crossmatch compatible. Intraoperative biopsy sample revealed a thrombotic process suggestive of a coagulation pathway activated by AMR; however, no C4d deposition was detected. Postmortem biopsies also suggested AMR. Retrospective testing of the patient's pretransplant serum revealed strong antiangiotensin II type 1 receptor (AT1R) antibodies and a strongly positive endothelial cell crossmatch. Anti-AT1R antibodies are known to be AT1 receptor agonists and may trigger inflammation and activate the extrinsic coagulation pathway. Given the potential effects of signaling through the AT1R, the patient's preexisting anti-AT1R antibodies and procoagulant therapy may have adversely affected the patient's clinical course.

Altered pulmonary capillary permeability in immunosuppressed guinea pigs infected with Legionella pneumophila serogroup 1

In immunosuppressed hosts, Legionella pneumophila (Lp) infection usually develops into severe pneumonia, which is pathologically characterized by increased vascular permeability and pulmonary edema. At present, mechanisms associated with changes in pulmonary capillary permeability (PCP) and the pathogenesis of pulmonary edema in immunosuppressed hosts with Lp infection are unclear. Therefore, in the present study an animal model of normal and immunosuppressed guinea pigs infected with Lp was established. An isolated perfused lung system was used to investigate the extent of changes in PCP. Pathological and immunofluorescence examinations were performed to explore the mechanism underlying these changes. The results indicated that PCP increased with the highest magnitude in immunosuppressed guinea pigs infected with Lp, with repeated ANOVA indicating synergism between infection and immunosuppression (P=0.0444). Hematoxylin and eosin staining and electron microscopy revealed more severe morphological damages in the lung tissues and pulmonary capillaries of the immunosuppressed animals infected with Lp compared with normal animals infected with Lp. Immunofluorescence analysis showed that immunosuppression reduced the expression of the vascular endothelial cell junction protein VE-cadherin (P=0.027). Following Lp infection, VE-cadherin expression was significantly lower in the immunosuppressed guinea pigs compared with their immunocompetent counterparts (P=0.001). These results suggest that immunosuppression combined with Lp infection induces more significant damage to pulmonary capillaries compared with Lp infection alone, resulting in a significantly increased PCP.

A pilot clinical trial of recombinant human angiotensin-converting enzyme 2 in acute respiratory distress syndrome

Background

Renin-angiotensin system (RAS) signaling and angiotensin-converting enzyme 2 (ACE2) have been implicated in the pathogenesis of acute respiratory distress syndrome (ARDS). We postulated that repleting ACE2 using GSK2586881, a recombinant form of human angiotensin-converting enzyme 2 (rhACE2), could attenuate acute lung injury.

Methods

We conducted a two-part phase II trial comprising an open-label intrapatient dose escalation and a randomized, double-blind, placebo-controlled phase in ten intensive care units in North America. Patients were between the ages of 18 and 80 years, had an American-European Consensus Criteria consensus diagnosis of ARDS, and had been mechanically ventilated for less than 72 h. In part A, open-label GSK2586881 was administered at doses from 0.1 mg/kg to 0.8 mg/kg to assess safety, pharmacokinetics, and pharmacodynamics. Following review of data from part A, a randomized, double-blind, placebo-controlled investigation of twice-daily doses of GSK2586881 (0.4 mg/kg) for 3 days was conducted (part B). Biomarkers, physiological assessments, and clinical endpoints were collected over the dosing period and during follow-up.

Results

Dose escalation in part A was well-tolerated without clinically significant hemodynamic changes. Part B was terminated after 39 of the planned 60 patients following a planned futility analysis. Angiotensin II levels decreased rapidly following infusion of GSK2586881, whereas angiotensin-(1–7) and angiotensin-(1–5) levels increased and remained elevated for 48 h. Surfactant protein D concentrations were increased, whereas there was a trend for a decrease in interleukin-6 concentrations in rhACE2-treated subjects compared with placebo. No significant differences were noted in ratio of partial pressure of arterial oxygen to fraction of inspired oxygen, oxygenation index, or Sequential Organ Failure Assessment score.

Conclusions

GSK2586881 was well-tolerated in patients with ARDS, and the rapid modulation of RAS peptides suggests target engagement, although the study was not powered to detect changes in acute physiology or clinical outcomes.

Trial registration

ClinicalTrials.gov, NCT01597635. Registered on 26 January 2012.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-017-1823-x) contains supplementary material, which is available to authorized users.