Targeting Procalcitonin Protects Vascular Barrier Integrity

Risk Factors Associated with Intensive Care Admission in Children with Severe Acute Respiratory Syndrome Coronavirus 2-Related Multisystem Inflammatory Syndrome (MIS-C) in Latin America: A Multicenter Observational Study of the REKAMLATINA Network

Background: Multisystem inflammatory syndrome in children (MIS-C) associated with coronavirus disease 2019 varies widely in its presentation and severity, with low mortality in high-income countries. In this study in 16 Latin American countries, we sought to characterize patients with MIS-C in the pediatric intensive care unit (PICU) compared with those hospitalized on the general wards and analyze the factors associated with severity, outcomes, and treatment received. Study Design: An observational ambispective cohort study was conducted including children 1 month to 18 years old in 84 hospitals from the REKAMLATINA network from January 2020 to June 2022. Results: A total of 1239 children with MIS-C were included. The median age was 6.5 years (IQR 2.5-10.1). Eighty-four percent (1043/1239) were previously healthy. Forty-eight percent (590/1239) were admitted to the PICU. These patients had more myocardial dysfunction (20% vs 4%; P < 0.01) with no difference in the frequency of coronary abnormalities (P = 0.77) when compared to general ward subjects. Of the children in the PICU, 83.4% (494/589) required vasoactive drugs, and 43.4% (256/589) invasive mechanical ventilation, due to respiratory failure and pneumonia (57% vs 32%; P = 0.01). On multivariate analysis, the factors associated with the need for PICU transfer were age over 6 years (aOR 1.76 95% CI 1.25-2.49), shock (aOR 7.06 95% CI 5.14-9.80), seizures (aOR 2.44 95% CI 1.14-5.36), thrombocytopenia (aOR 2.43 95% CI 1.77-3.34), elevated C-reactive protein (aOR 1.89 95% CI 1.29-2.79), and chest x-ray abnormalities (aOR 2.29 95% CI 1.67-3.13). The overall mortality was 4.8%. Conclusions: Children with MIS-C who have the highest risk of being admitted to a PICU in Latin American countries are those over age six, with shock, seizures, a more robust inflammatory response, and chest x-ray abnormalities. The mortality rate is five times greater when compared with high-income countries, despite a high proportion of patients receiving adequate treatment.

DPP-4 exacerbates LPS-induced endothelial cells inflammation via integrin-α5β1/FAK/AKT signaling

Endothelial dysfunction plays a pivotal role in the pathogenesis of acute lung injury (ALI)/acute respiratory distress syndrome (ARDS). Dipeptidyl peptidase IV (DPP-4), a cell surface glycoprotein, has been implicated in endothelial inflammation and barrier dysfunction. In this study, the role of DPP-4 on lipopolysaccharide (LPS)-induced pulmonary microvascular endothelial cells (HPMECs) dysfunction and the underlying mechanism were investigated by siRNA-mediated knockdown of DPP-4. Our results indicated that LPS (1 μg/ml) challenge resulted in either the production and releasing of DPP-4, as well as the secretion of IL-6 and IL-8 in HPMECs. DPP-4 knockdown inhibited chemokine releasing and monolayer hyper-permeability in LPS challenged HPMECs. When cocultured with human polymorphonuclear neutrophils (PMNs), DPP4 knockdown suppressed LPS-induced neutrophil-endothelial adhesion, PMN chemotaxis and trans-endothelial migration. Western blotting showed that DPP-4 knockdown attenuated LPS-induced activation of TLR4/NF-κB pathway. Immunoprecipitation and liquid chromatography-tandem mass spectrometry revealed that DPP-4 mediated LPS-induced endothelial inflammation by interacting with integrin-α5β1. Moreover, exogenous soluble DPP-4 treatment sufficiently activated integrin-α5β1 downstream FAK/AKT/NF-κB signaling, thereafter inducing ICAM-1 upregulation in HPMECs. Collectively, our results suggest that endothelia synthesis and release DPP-4 under the stress of endotoxin, which interact with integrin-α5β1 complex in an autocrine or paracrine manner to exacerbate endothelial inflammation and enhance endothelial cell permeability. Therefore, blocking DDP-4 could be a potential therapeutic strategy to prevent endothelial dysfunction in ALI/ARDS.

The association between hypoalbuminemia and microcirculation, endothelium, and glycocalyx disorders in children with sepsis

OBJECTIVE

The objective of this study was to evaluate the association between serum albumin levels and microcirculation changes, glycocalyx degradation, and the clinical outcomes of interest.

METHODS

Observational, prospective study in children with sepsis. The primary outcome was the association between hypoalbuminemia and microcirculation disorders, endothelial activation and glycocalyx degradation using a perfused boundary region (PBR) (abnormal >2.0 μm on sublingual video microscopy) or plasma biomarkers (syndecan-1, angiopoietin-2).

RESULTS

A total of 125 patients with sepsis were included. The median age was 2.0 years (IQR 0.5-12.5). Children with hypoalbuminemia had more abnormal microcirculation with a higher PBR (2.16 μm [IQR 2.03-2.47] vs. 1.92 [1.76-2.28]; p = .01) and more 4-6 μm capillaries recruited (60% vs. 40%; p = .04). The low albumin group that had the worst PBR had the most 4-6 μm capillaries recruited (rho 0.29; p < .01), 48% higher Ang-2 (p = .04), worse annexin A5 (p = 0.03) and no syndecan-1 abnormalities (p = .21). Children with hypoalbuminemia and a greater percentage of blood volume in their capillaries needed mechanical ventilation more often (56.3% vs. 43.7%; aOR 2.01 95% CI 1.38-3.10: p < .01).

CONCLUSIONS

In children with sepsis, an association was found between hypoalbuminemia and microcirculation changes, vascular permeability, and greater endothelial glycocalyx degradation.

Procalcitonin and Adrenomedullin in Infectious Diseases

Calcitonin (CT) and adrenomedullin (ADM) are members of the CT family. Procalcitonin (PCT) is a prohormone of CT. Elevations in serum PCT and ADM levels are associated with severe sepsis and coronavirus disease 2019 (COVID-19). PCT enhances sepsis mortality and it binds to the CGRP receptor, which is a heterodimer of CT receptor-like receptor and receptor activity-modifying protein 1. The N-terminal truncated form of PCT, PCT3-116, is produced by the cleavage of PCT by dipeptidyl peptidase 4 (DPP-4) and is the main form of PCT in serum during sepsis, inducing microvascular permeability. Mid-regional pro-adrenomedullin (MR-proADM) is used instead of ADM as a biological indicator because ADM is rapidly degraded, and MR-proADM is released at the same rate as ADM. ADM reduces endothelial permeability and promotes endothelial stability. Endothelial dysfunction is responsible for multiple organ failure in sepsis and COVID-19 patients. Therefore, ADM may be an important molecule for improving the severity associated with sepsis and COVID-19. This review focuses on the current knowledge of PCT and ADM in sepsis and COVID-19.

The dipeptidyl peptidase-4 inhibitor linagliptin ameliorates LPS-induced acute lung injury by maintenance of pulmonary microvascular barrier via activating the Epac1/AKT pathway

Pulmonary microvascular endothelial cells (PMVECs) barrier dysfunction is a main pathophysiological feature of sepsis-related acute lung injury (ALI). This study aimed to investigate whether the dipeptidyl peptidase (DPP)-4 inhibitor linagliptin could protect against LPS-induced PMVECs barrier disruption and its underlying molecular mechanisms. A classical ALI animal model and LPS-treated PMVECs were applied and all were treated with or without linagliptin. Cellular experiments demonstrated that linagliptin could mitigate LPS-induced PMVECs hyperpermeability and intercellular junction (VE-cadherin, β-catenin, and ZO-1) disruption in a dose-dependent manner. Correspondingly, it was observed that linagliptin pretreatment distinctly relieved LPS-induced lung injury, oxidative stress, and pulmonary edema in vivo. Furthermore, we found that the inhibition of oxidative stress by linagliptin may be achieved by reversing impaired mitochondrial function. Mechanistically, linagliptin administration promoted the activation of the Epac1 pathway and its downstream AKT pathway, while inhibition of the Epac1/Akt signaling pathway significantly alleviated the above-mentioned protective effect of linagliptin on the PMVECs barrier. Taken together, these data suggest that linagliptin can effectively reserve PMVECs barrier dysfunction and inhibit oxidative stress to protect against ALI via activating the Epac1/AKT signaling pathway, and thus may become a potential clinical therapeutic strategy for ALI.

ARDS in the Time of Corona: Context and Perspective

For more than 2 years, COVID-19 has been holding the world at awe with new waves of infections, novel mutants, and still limited (albeit improved) means to combat SARS-CoV-2-induced respiratory failure, the most common and fatal presentation of severe COVID-19. In the present perspective, we draw from the successes and—mostly—failures in previous acute respiratory distress syndrome (ARDS) work and the experiences from COVID-19 to define conceptual barriers that have so far hindered therapeutic breakthroughs in this deadly disease, and to open up new avenues of thinking and thus, ultimately of therapy.

Procalcitonin mediates vascular dysfunction in obesity

AIMS

Obesity is accompanied by a chronic low-grade inflammation associated with endothelial dysfunction and vascular complications. Procalcitonin is a marker of inflammation, secreted by adipose tissue and elevated in obese subjects. We here investigated whether visceral or perivascular fat-derived procalcitonin is a target to improve obesity-induced endothelial dysfunction.

MATERIALS AND METHODS

Procalcitonin expression was identified by Western blot. Murine endothelial cells were isolated using CD31-antibody-coated magnetic beads and reactive oxygen species and nitric oxide (NO) determined by H2DCF- or DAF-FM diacetate loading. Endothelium-dependent vasorelaxation was analyzed using pressure myography of murine arterioles. Calcitonin gene-related peptide (CGRP) was used to activate the calcitonin receptor-like receptor (CRLR)/RAMP1 complex and olcegepant or the dipeptidyl-peptidase 4 (DPP4) inhibitor sitagliptin to block procalcitonin signaling or activation.

KEY FINDINGS

In addition to visceral adipose tissue, procalcitonin was present in perivascular and epicardial tissue. In concentrations typical for obesity, procalcitonin doubled reactive oxygen species formation and decreased endothelial nitric oxide production in murine endothelial cells. Intravenous delivery of procalcitonin to mice in obesity-associated concentrations impaired endothelium-dependent vasorelaxation in a CRLR/RAMP1-dependent manner and antagonized CGRP-induced endothelial NO release in vitro. Use of CRLR/RAMP1-receptor antagonist olcegepant counteracted procalcitonin effects on vasodilation, nitric oxide production and reactive oxygen species formation. Similarly, blocking procalcitonin activation by the DPP4 inhibitor sitagliptin antagonized endothelial procalcitonin effects.

SIGNIFICANCE

Procalcitonin, liberated either from visceral or perivascular adipose tissue, contributes to endothelial dysfunction by antagonizing CGRP signaling in obesity. Targeting hyperprocalcitonemia may be a means to preserve endothelial function and reduce comorbidity burden in obese subjects.

Regulation and Dysregulation of Endothelial Permeability during Systemic Inflammation

Systemic inflammation can be triggered by infection, surgery, trauma or burns. During systemic inflammation, an overshooting immune response induces tissue damage resulting in organ dysfunction and mortality. Endothelial cells make up the inner lining of all blood vessels and are critically involved in maintaining organ integrity by regulating tissue perfusion. Permeability of the endothelial monolayer is strictly controlled and highly organ-specific, forming continuous, fenestrated and discontinuous capillaries that orchestrate the extravasation of fluids, proteins and solutes to maintain organ homeostasis. In the physiological state, the endothelial barrier is maintained by the glycocalyx, extracellular matrix and intercellular junctions including adherens and tight junctions. As endothelial cells are constantly sensing and responding to the extracellular environment, their activation by inflammatory stimuli promotes a loss of endothelial barrier function, which has been identified as a hallmark of systemic inflammation, leading to tissue edema formation and hypotension and thus, is a key contributor to lethal outcomes. In this review, we provide a comprehensive summary of the major players, such as the angiopoietin-Tie2 signaling axis, adrenomedullin and vascular endothelial (VE-) cadherin, that substantially contribute to the regulation and dysregulation of endothelial permeability during systemic inflammation and elucidate treatment strategies targeting the preservation of vascular integrity.