Immature monocytes contribute to cardiopulmonary bypass-induced acute lung injury by generating inflammatory descendants

Sulfotransferase homolog 2 receptors blockade on monocyte subsets along with their inflammatory cytokines for septic lung injury

PURPOSE OF THE STUDY

To observe the dynamic changes in monocyte subsets during septic lung injury and to assess the anti-inflammatory role of the sulfotransferase homolog 2 (ST2) receptor.

MATERIALS AND METHODS

Dynamic changes of monocyte subsets from patients with septic lung injury and mice post-cecal ligation and puncture (CLP) were monitored. ST2 receptors on mice monocytes and concentrations of IL-33, IL-1β, IL-12, and IL-27 from peripheral blood or culture supernatant were detected.

RESULTS

CD14lowCD16- (Mo0) and CD14++CD16+ (Mo2) monocyte subsets were significantly expanded in patients with sepsis-related acute respiratory distress syndrome. In sepsis model mice, monocyte counts, particularly of Ly6Cint and CDLy6Cint+hi monocytes, were significantly increased. The mean optical density value of TNF-α after CLP mainly increased after 24 h, whereas that of IL-6 was significantly increased at all time points assessed after CLP. The levels of IL-1β, IL-12, IL-27, and IL-33 increased to variable degrees at 6, 12, 24, and 48h after CLP, and ST2+ monocytes were significantly expanded in sepsis model mice compared to sham-operated mice. ST2 receptor blockade suppressed IL-1β and IL-12 production in cell culture.

CONCLUSIONS

Changes in monocyte subsets expressing the ST2 receptor play an important role in septic lung injury by modulating inflammatory cytokine secretion.

Association between cardiopulmonary bypass time and mortality among patients with acute respiratory distress syndrome after cardiac surgery

BACKGROUND

Cardiopulmonary bypass (CPB) can lead to lung injury and even acute respiratory distress syndrome (ARDS) through triggering systemic inflammatory response. The objective of this study was to investigate the impact of CPB time on clinical outcomes in patients with ARDS after cardiac surgery.

METHODS

Totally, patients with ARDS after cardiac surgery in Beijing Anzhen Hospital from January 2005 to December 2015 were retrospectively included and were further divided into three groups according to the median time of CPB. The primary endpoints were the ICU mortality and in-hospital mortality, and ICU and hospital stay. Restricted cubic spline (RCS), logistic regression, cox regression model, and receiver operating characteristic (ROC) curve were adopted to explore the relationship between CPB time and clinical endpoints.

RESULTS

A total of 54,217 patients underwent cardiac surgery during the above period, of whom 210 patients developed ARDS after surgery and were finally included. The ICU mortality and in-hospital mortality were 21.0% and 41.9% in all ARDS patients after cardiac surgery respectively. Patients with long CPB time (CPB time ≥ 173 min) had longer length of ICU stay (P = 0.011), higher ICU (P < 0.001) mortality and in-hospital(P = 0.002) mortality compared with non-CPB patients (CPB = 0). For each ten minutes increment in CPB time, the hazards of a worse outcome increased by 13.3% for ICU mortality and 9.3% for in-hospital mortality after adjusting for potential factors. ROC curves showed CPB time presented more satisfactory power to predict mortality compared with APCHEII score. The optimal cut-off value of CPB time were 160.5 min for ICU mortality and in-hospital mortality.

CONCLUSIONS

Our findings demonstrated the significant prognostic value of CPB time in patients with ARDS after cardiac surgery. Longer time of CPB was associated with poorer clinical outcomes, and could be served as an indicator to predict short-term mortality in patients with ARDS after cardiac surgery.

Off-pump vs. on-pump bypass surgery grafting in diabetic patients with three-vessel disease: a propensity score matching study

Background

Controversy exists regarding the advantages and risks of off-pump vs. on-pump coronary artery bypass grafting (CABG) for patients with diabetes. We therefore compare the early clinical outcomes of off-pump vs. on-pump procedures for diabetic patients with three-vessel disease.

Materials and methods

We conducted a retrospective analysis of clinical data obtained from 548 diabetic patients with three-vessel coronary artery disease who underwent isolated CABG between January 2016 and June 2020. To adjust the differences of baseline characteristics between the off-pump CABG (OPCAB) and on-pump CABG (ONCAB) groups, propensity score matching (PSM) was used. Following 1:1 matching, we selected 187 pairs of patients for further comparison of outcomes within the first 30 days after surgery.

Results

The preoperative characteristics of the patients between the two groups were clinically comparable after PSM. The OPCAB group exhibited a significantly higher incidence of incomplete revascularization (27.3% vs. 14.4%; P = 0.002) compared with the ONCAB group. No differences were seen in mortality within 30 days between the matched groups (1.1% vs. 3.7%; P = 0.174). Notably, the OPCAB group had a lower risk of respiratory failure or infection (2.1% vs. 7.0%; P = 0.025), less postoperative stroke (1.1% vs. 4.8%; P = 0.032), and reduced postoperative ventilator assistance time (35.8 ± 33.7 vs. 50.9 ± 64.8; P = 0.005).

Conclusion

OPCAB in diabetic patients with three-vessel disease is a safe procedure with reduced early stroke and respiratory complications and similar mortality rate, myocardial infarction, and renal failure requiring dialysis to conventional on-pump revascularization.

Monocyte Adhesion and Transmigration Through Endothelium Following Cardiopulmonary Bypass Shearing is Mediated by IL-8 Signaling

Background

The use of cardiopulmonary bypass (CPB) can induce sterile systemic inflammation that contributes to morbidity and mortality, especially in children. Patients have been found to have increased expression of cytokines and transmigration of leukocytes during and after CPB. Previous work has demonstrated that the supraphysiologic shear stresses present during CPB are sufficient to induce proinflammatory behavior in non-adherent monocytes. The interactions between shear stimulated monocytes and vascular endothelial cells have not been well studied and have important translational implications.

Methods

To test the hypothesis that non-physiological shear stress experienced by monocytes during CPB affects the integrity and function of the endothelial monolayer via IL-8 signaling pathway, we have used an in vitro CPB model to study the interaction between THP-1 monocyte-like cells and human neonatal dermal microvascular endothelial cells (HNDMVECs). THP-1 cells were sheared in polyvinyl chloride (PVC) tubing at 2.1 Pa, twice of physiological shear stress, for 2 hours. Interactions between THP-1 cells and HNDMVECs were characterized after coculture.

Results

We found that sheared THP-1 cells adhered to and transmigrated through the HNDMVEC monolayer more readily than static controls. When co-culturing, sheared THP-1 cells also disrupted in the VE-cadherin and led to reorganization of cytoskeletal F-actin of HNDMVECs. Treating HNDMVECs with IL-8 resulted in upregulation of vascular cell adhesion molecule 1 (VCAM-1) and intercellular adhesion molecule 1 (ICAM-1) while also increasing the adherence of non-sheared THP-1 cells. Preincubating HNDMVECs with Reparixin, an inhibitor of CXCR2/IL-8 receptor inhibited sheared THP-1 cell adhesion to the HNDMVECs.

Conclusions

These results suggested that IL-8 not only increases the endothelium permeability during monocyte migration, but also affects the initial adhesion of monocytes in a CPB setup. This study revealed a novel mechanism of post-CPB inflammation and will contribute to the development of targeted therapeutics to prevent and repair the damage to neonatal patients.

Highlights

Shear stress in a CPB-like environment promoted the adhesion and transmigration of monocytes to and through endothelial monolayer.

Treating endothelial monolayer with sheared monocytes led to disruption of VE-cadherin and reorganization of F-actin.

Interaction between sheared monocytes resulted in a significant increase of IL-8 release.

Inhibiting IL-8 receptor prevented sheared monocyte adhesion, while IL-8 promoted naive monocyte adhesion.

Exosome from BMMSC Attenuates Cardiopulmonary Bypass-Induced Acute Lung Injury Via YAP/β-Catenin Pathway: Downregulation of Pyroptosis

Acute lung injury (ALI) accompanied with systemic inflammatory response is an important complication after cardiopulmonary bypass (CPB). Pyroptosis, which is induced by the secretion of inflammatory factors, has been implicated in ALI. However, recent studies have suggested that bone marrow mesenchymal stem cell-derived exosomes (BMMSC-Exo) can ameliorate ALI, but the mechanism is poorly understood. Therefore, we aim to examine the effects of BMMSC-Exo in CPB-induced ALI, and its underlying mechanism. CPB rat models (male Sprague-Dawley rats) were administered BMMSC-Exo intravenously before induction of ALI. Lung tissue, bronchoalveolar lavage fluid (BALF), and alveolar macrophage (AM) were collected after the treatments for further analysis, and rat AM NR8383 cells were used for in vitro study. HE staining was performed to detect macrophage infiltration. Western blot was used to detect related proteins expression. And ELISA assay was performed to investigate secretion of inflammatory factors. These results showed that BMMSC-Exo treatment ameliorated macrophage infiltration and oxidative stress, and downregulated expression of pyroptosis-related proteins, including NLRP3, cleaved caspase-1, and GSDMD-N, in the lung tissue and AM, as well as decreased the secretion of IL-18 and IL-1β in BALF. Moreover, BMMSC-Exo activated YAP/β-catenin signaling pathway. Overall, these findings of this study indicated that BMMSC-Exo suppressed CPB-induced pyroptosis in ALI by activating YAP/β-catenin axis, which could be a novel strategy for lung protection during CPB.

Immunotherapy strategies and prospects for acute lung injury: Focus on immune cells and cytokines

Acute lung injury/acute respiratory distress syndrome (ALI/ARDS) is a disastrous condition, which can be caused by a wide range of diseases, such as pneumonia, sepsis, traumas, and the most recent, COVID-19. Even though we have gained an improved understanding of acute lung injury/acute respiratory distress syndrome pathogenesis and treatment mechanism, there is still no effective treatment for acute lung injury/acute respiratory distress syndrome, which is partly responsible for the unacceptable mortality rate. In the pathogenesis of acute lung injury, the inflammatory storm is the main pathological feature. More and more evidences show that immune cells and cytokines secreted by immune cells play an irreplaceable role in the pathogenesis of acute lung injury. Therefore, here we mainly reviewed the role of various immune cells in acute lung injury from the perspective of immunotherapy, and elaborated the crosstalk of immune cells and cytokines, aiming to provide novel ideas and targets for the treatment of acute lung injury.

Phenotypic and functional alterations of monocyte subsets with aging

BACKGROUND

It has been widely accepted that monocytes are one of the central mediators contributing to inflammaging. However, it remains unclear whether aged monocytes, similar to aged T cells, have characteristics of hyperactivation and increased expression of co-inhibitory molecules.

METHODS

Peripheral blood mononuclear cells (PBMCs) were isolated from young (21-40 years old), middle-aged (41-60 years old), and older human subjects (> 60 years old). Flow cytometry was used to monitor changes in the expression of surface molecules of monocyte subsets and cytokine-producing capacity.

RESULTS

We observed increased tumor necrosis factor-α: TNF-α and decreased interleukin-6 (IL-6) production in monocytes from older adults compared with young and middle-aged adults. Older adults had a greater percentage of intermediate and non-classical monocyte subsets, along with increased levels of the immune activation markers human leukocyte antigen-DR (HLA-DR), and adhesion molecules cluster of differentiation molecule 11b (CD11b) and L-selectin (CD62L). Furthermore, we observed increased C-C motif chemokine receptor 2 (CCR2) expression on classical monocytes and decreased C-X3-C motif chemokine receptor 1 (CX3CR1) expression on non-classical monocytes in older adult subjects. The expression of co-inhibitory receptors was reduced on monocyte subsets in older adults.

CONCLUSIONS

Circulating monocytes in older adults exhibit increased expression of activation, adhesion, and migration markers, but decreased expression of co-inhibitory molecules.

Lung injury following cardiopulmonary bypass: a clinical update

INTRODUCTION

Cardiopulmonary bypass (CPB) is an integral component of cardiac surgery; however, one of its most critical complications is acute lung injury induced by multiple factors including systemic inflammatory response.

AREAS COVERED

The objective of this review is to investigate the multiple factors that can lead to CPB-induced lung injury. These include contact of blood components with the artificial surface of the CPB circuit, local and systemic inflammatory response syndrome (SIRS), lung ischemia/re-perfusion injury, arrest of ventilation, and circulating endotoxins. We also focus on possible interventions to curtail the negative impact of CPB, such as off-pump surgery, impregnation of the circuit with less biologically active substances, leukocyte depletion filters and ultrafiltration, and pharmacological agents such as steroids and aprotinin.

EXPERT OPINION

Although many aspects of CPB are proposed to contribute to lung injury, its overall role is still not clear. Multiple interventions have been introduced to reduce the risk of pulmonary dysfunction, with many of these interventions having shown promising results, significantly attenuating inflammatory mediators and improving post-operative outcome. However, since lung injury is multifactorial and affected by inextricably linked components, multiple interventions tackling each of them is required.

LONG-TERM EFFECTS OF SHAM SURGERY ON PHAGOCYTE FUNCTIONS IN RATS

Animal models of inflammatory disorders, including those of the nervous system are commonly used to explore the pathophysiological role of immune cell response in disease triggering and course and to develop biotechnology products for therapeutic use. Modeling some of these disorders, particularly neurodegenerative diseases, implies surgical manipulations for the intracerebral introduction of disease-initiating substances (toxins, amyloids etc.). Design of these experiments involves the use of sham-operated animals as a control of non-specific intrinsic side-effects elicited by surgical manipulations per se, including local and systemic inflammation, where phagocytic cells are key participants. Short-term post-surgical immunomodulatory effects are widely reported. However, no study thus far has examined the long term effects of sham-surgery on phagocyte functions. The purpose of this study was to evaluate the effect of sham-surgery, commonly used for modeling neurodegenerative diseases, on phagocyte functions in the far terms after the surgical manipulations. Materials and Methods. Adult male Wistar rats were used in the study. Sham surgery consisted of stereotactic unilateral injection of saline solution into the median forebrain bundle (sham-operated 1, SO1) or directly into the substantia nigra (sham-operated 2, SO2). Before the placebo surgery, animals were anaesthetized using nembutal and ketamine/xylazine correspondingly. Functional characteristics (phagocytic activity, oxidative metabolism, CD80/86 and CD206 expression) of phagocytes (microglia, peritoneal macrophages, circulating monocytes and granulocytes) were examined by flow cytometry. Differential leukocyte count was conducted using hematological analyzer. Results. Phagocytes from animals underwent of different protocols of placebo surgery, demonstrated various patterns of functional changes on day 29 after the manipulations. In animals from SO1 group, we observed signs of residual neuroinflammation (pro-inflammatory shift of microglia functional profile) along with ongoing resolution of systemic inflammation (anti-inflammatory metabolic shift of circulating phagocytes and peritoneal macrophages). In rats from SO2 group, pro-inflammatory polarized activation of peritoneal phagocytes was registered along with anti-inflammatory shift in microglia and circulating phagocytes. Conclusions. Sham surgery influences functions of phagocytic cells of different locations even in the far terms after the manipulations. These effects can be considered as combined long-term consequences of surgical brain injury and the use of anesthetics. Our observations evidences, that sham associated non-specific immunomodulatory effects should always be taken into consideration in animal models of inflammatory central nervous system diseases.

Single-cell transcriptomics highlights immunological dysregulations of monocytes in the pathobiology of COPD

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is a common respiratory disease, whose pathogenetic complexity was strongly associated with aging/smoking and poorly understood.

METHODS

Here we performed single-cell RNA sequencing (scRNA-seq) analysis of 66,610 cells from COPD and age-stratified control lung tissues of donors with different smoking histories to prioritize cell types most perturbed in COPD lungs in aging/smoking dependent or independent manner. By performing an array of advanced bioinformatic analyses, such as gene set enrichment analysis, trajectory analysis, cell-cell interactions analysis, regulatory potential analysis, weighted correlation network analysis, functional interaction analysis, and gene set variation analysis, we integrated cell-type-level alterations into a system-level malfunction and provided a more clarified COPD pathological model containing specific mechanisms by which aging and smoking facilitate COPD development. Finally, we integrated the publicly available scRNA-seq data of 9 individuals, resulting in a total of 110,931 cells, and replicated the analyses to enhance the credibility of our findings.

RESULTS

Our study pointed to enrichment of COPD molecular alteration in monocytes, which further induced a previously unrecognized pro-inflammatory effect on alveolar epithelial cells. In addition, aged monocytes and club cells facilitated COPD development via maintaining an autoimmune airway niche. Unexpectedly, macrophages, whose defect to resolve inflammation was long-recognized in COPD pathogenesis, primarily induced an imbalance of sphingolipids rheostat in a smoking-dependent way. These findings were validated in a meta-analysis including other public single-cell transcriptomic data.

CONCLUSIONS

In sum, our study provided a clarified view of COPD pathogenesis and demonstrated the potential of targeting monocytes in COPD diagnosis and treatment.

COVID-19 in the Perioperative Period of Cardiovascular Surgery: the Brazilian Experience

INTRODUCTION

We investigated the clinical course and outcomes of patients submitted to cardiovascular surgery in Brazil and who had developed symptoms/signs of coronavirus disease 2019 (COVID-19) in the perioperative period.

METHODS

A retrospective multicenter study including 104 patients who were allocated in three groups according to time of positive real time reverse transcriptase-polymerase chain reaction (RT-PCR) for the SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2): group 1, patients who underwent cardiac surgery > 10 days after positive RT-PCR; group 2, patients with a positive RT-PCR within 10 days before or after surgery; group 3, patients who presented positive RT-PCR > 10 days after surgery. The primary outcome was mortality and secondary outcomes were postoperative complications, intensive care unit (ICU) length of stay, and postoperative days of hospitalization.

RESULTS

The three groups were similar with respect to age, the European System of Cardiac Operative Risk Evaluation score, and comorbidities, except hypertension. Postoperative complications and death were significantly higher in groups 2 and 3 than in group 1, and no significant difference between groups 2 and 3 was seen. Group 2 showed a high prevalence of surgery performed as an urgent procedure. Although no significant differences were observed in ICU length of stay, total postoperative hospitalization time was significantly higher in group 3 than in groups 1 and 2.

CONCLUSION

COVID-19 affecting the postoperative period of patients who underwent cardiovascular surgery is associated with a higher rate of morbidity and mortality. Delaying procedures in RT-PCR-positive patients may help reduce risks of perioperative complications and death.

Long-term survivors of murine sepsis are predisposed to enhanced LPS-induced lung injury and proinflammatory immune reprogramming

Millions of people who survive sepsis each year are rehospitalized and die due to late pulmonary complications. To prevent and treat these complications, biomarkers and molecular mediators must be identified. Persistent immune reprogramming in the form of immunoparalysis and impaired host defense is proposed to mediate late pulmonary complications after sepsis, particularly new pulmonary infections. However, immune reprogramming may also involve enhanced/primed responses to secondary stimuli, although their contribution to long-term sepsis complications remains understudied. We hypothesize that enhanced/primed immune responses in the lungs of sepsis survivors are associated with late pulmonary complications. To this end, we developed a murine sepsis model using cecal ligation and puncture (CLP) followed 3 wk later by administration of intranasal lipopolysaccharide to induce inflammatory lung injury. Mice surviving sepsis exhibit enhanced lung injury with increased alveolar permeability, neutrophil recruitment, and enhanced Ly6C^hi monocyte Tnf expression. To determine the mediators of enhanced lung injury, we performed flow cytometry and RNA sequencing of lungs 3 wk after CLP, prior to lipopolysaccharide. Sepsis survivor mice showed expanded Ly6C^hi monocytes populations and increased expression of many inflammatory genes. Of these, S100A8/A9 was also elevated in the circulation of human sepsis survivors for months after sepsis, validating our model and identifying S100A8/A9 as a potential biomarker and therapeutic target for long-term pulmonary complications after sepsis. These data provide new insight into the importance of enhanced/primed immune responses in survivors of sepsis and establish a foundation for additional investigation into the mechanisms mediating this response.

PIM1 inhibition attenuated endotoxin-induced acute lung injury through modulating ELK3/ICAM1 axis on pulmonary microvascular endothelial cells

OBJECTIVE

The dysfunction of pulmonary microvascular endothelial cells (PMVECs) is one of the critical characteristics of acute lung injury/acute respiratory distress syndrome (ALI/ARDS) induced by severe infection. PIM1 is a constitutively active serine/threonine kinase that is involved in multiple biological processes. However, the underlying correlation between PIM1 and PMVECs injury remains unclear. The main purpose of this study was to reveal roles of PIM1 and explore the potential mechanisms during the development of endotoxin-induced ALI induced by intraperitoneal LPS administration.

MATERIALS AND METHODS

PIM1 level in the lung tissues of endotoxin-induced ALI mice or plasma derived from cardiopulmonary bypass (CPB)-induced ALI patients were measured. The protective roles of PIM1 specific inhibitor SMI-4a on endotoxin-induced lung injuries were evaluated through histological, permeability, neutrophil infiltration and survival assessment. The relationship between PIM1 and ELK3/ICAM-1 axis was validated in vivo and vitro. The correlation between plasma PIM1 and indicative vascular endothelium injury biomarkers (PaO2/FiO2 ratio, Ang-II, E-selectin and PAI-1) levels derived from CPB-induced ALI patient were analyzed.

RESULTS

PIM1 expression in the lung tissues was increased in the mice of endotoxin-induced ALI. The PIM1 specific inhibitor SMI-4a administration relieved the severity of endotoxin-induced ALI. More importantly, PIM1 modulates ICAM1 expression through regulating transcription factor ELK3 expression in vitro. Eventually, plasma PIM1 level was positively correlated with Ang-II and PAI-1 levels but negatively correlated with SpO2/FiO2 ratio among CPB induced ALI patients.

CONCLUSION

Our results indicated that PIM1 inhibition carried a protective role against endotoxin-induced ALI by modulating the ELK3/ICAM1 axis on PMVECs. PIM1 may be a potential therapeutic target for endotoxin-induced ALI.

Dexmedetomidine Improves Lung Function by Promoting Inflammation Resolution in Patients Undergoing Totally Thoracoscopic Cardiac Surgery

Objective

Totally thoracoscopic cardiac surgery under cardiopulmonary bypass combined with one-lung ventilation has been identified as the trend in cardiac surgery. The aim of this study was to examine the effects of the selective α ₂ adrenergic receptor agonist dexmedetomidine on the pulmonary function of patients who underwent mitral valve surgery using the totally thoracoscopic technique.

Methods

Fifty-seven patients who underwent thoracoscopic mitral valve surgery between July 2019 and December 2019 were selected. The patients were randomly divided into the control (Con) group (n = 28) and the dexmedetomidine (DEX) group (n = 29) using the random number table method. Arterial blood gas analyses were performed, and the oxygenation (PaO₂/FiO₂) and respiratory indexes (P(A-a)O/PaO₂) were calculated 5 min after tracheal intubation (T1), 2 h after operation (T2), 6 h after operation (T3), and 24 h after operation (T4). Moreover, the serum cytokines interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and intercellular adhesion molecule-1 (ICAM-1) were detected using the enzyme-linked immunosorbent method at all time points. Chest radiography was performed 24 h after surgery. Peripheral blood samples were collected before and after the operation for a complete hemogram. Additionally, the procalcitonin concentration was measured and recorded when the patients were transported to the intensive care unit (ICU). The postoperative extubation time, length of ICU stay, and pulmonary infection rate were also recorded.

Results

Inflammatory reaction after surgery was evident. However, the inflammatory cytokines IL-6, TNF-α, and ICAM-1 in the DEX group were lower than those in the Con group after surgery (T2 to T4; P < 0.05). Neutrophil counts and procalcitonin concentration were higher in the Con group than in the DEX group (P < 0.05). In addition, in the DEX group, pulmonary exudation on chest radiography was lower, and pulmonary function, as shown by an increase in oxidation index and decrease in the respiratory index, improved after surgery (P < 0.05). Moreover, the duration of mechanical ventilation in the Con group was 3.4 h longer than that in the DEX group.

Conclusion

Dexmedetomidine has a protective effect on pulmonary function in patients undergoing mitral valve surgery using a totally video-assisted thoracoscopic technique, which may be related to a reduction in the concentration of inflammatory cytokines in the early perioperative period.

Intermediate monocytes exhibit higher levels of TLR2, TLR4 and CD64 early after congenital heart surgery

INTRODUCTION

Congenital heart surgery with cardiopulmonary bypass (CPB) initiates an immune response which frequently leads to organ dysfunction and a systemic inflammatory response. Complications associated with exacerbated immune responses may severely impact the postoperative recovery. The objective was to describe the characteristics of monocyte subpopulations and neutrophils at the level of pattern recognition receptors (PRR) and the cytokine response after CPB in infants.

METHODS

An observational cohort study was conducted between June 2016 and June 2017 of infants < 2 years of age, electively admitted for surgical correction of acyanotic congenital heart defects using CPB. Fourteen blood samples were collected sequentially and processed immediately during and up to 48 h following cardiac surgery for each patient. Flow cytometry analysis comprised monocytic and granulocytic surface expression of CD14, CD16, CD64, TLR2, TLR4 and Dectin-1 (CLEC7A). Monocyte subpopulations were further defined as classical (CD14⁺⁺/CD16^-), intermediate (CD14⁺⁺/CD16⁺) and nonclassical (CD14⁺/CD16⁺⁺) monocytes. Plasma concentrations of 14 cytokines, including G-CSF, GM-CSF, IL-1β, IL-1RA, IL-4, IL-6, IL-8, IL-10, IL-12p40, IL-12p70, TNF-α, IFN-γ, MIP-1β (CCL4) and TGF-β1, were measured using multiplex immunoassay for seven points in time.

RESULTS

Samples from 21 infants (median age 7.4 months) were analyzed by flow cytometry and from 11 infants, cytokine concentrations were measured. Classical and intermediate monocytes showed first receptor upregulation with an increase in CD64 expression four hours post CPB. CD64-expression on intermediate monocytes almost tripled 48 h post CPB (p < 0.0001). TLR4 was only increased on intermediate monocytes, occurring 12 h post CPB (p = 0.0406) along with elevated TLR2 levels (p = 0.0002). TLR4 expression on intermediate monocytes correlated with vasoactive-inotropic score (r_s = 0.642, p = 0.0017), duration of ventilation (r_s = 0.485, p = 0.0259), highest serum creatinine (r_s = 0.547, p = 0.0102), postsurgical transfusion (total volume per kg bodyweight) (r_s = 0.469, p = 0.0321) and lowest mean arterial pressure (r_s = -0.530, p = 0.0135). Concentrations of IL-10, MIP-1β, IL-8, G-CSF and IL-6 increased one hour post CPB. Methylprednisolone administration in six patients had no significant influence on the studied surface receptors but led to lower IL-8 and higher IL-10 plasma concentrations.

CONCLUSIONS

Congenital heart surgery with CPB induces a systemic inflammatory process including cytokine response and changes in PRR expression. Intermediate monocytes feature specific inflammatory characteristics in the 48 h after pediatric CPB and TLR4 correlates with poorer clinical course, which might provide a potential diagnostic or even therapeutic target.

Myeloid-Derived Suppressor Cells Mediate Immunosuppression After Cardiopulmonary Bypass

OBJECTIVES

Cardiopulmonary bypass is associated with severe immune dysfunctions. Particularly, a cardiopulmonary bypass-related long-lasting immunosuppressive state predisposes patients to a higher risk of postoperative complications, such as persistent bacterial infections. This study was conducted to elucidate mechanisms of post-cardiopulmonary bypass immunosuppression.

DESIGN

In vitro studies with human peripheral blood mononuclear cells.

SETTING

Cardiosurgical ICU, University Research Laboratory.

PATIENTS

Seventy-one patients undergoing cardiac surgery with cardiopulmonary bypass (enrolled May 2017 to August 2018).

INTERVENTIONS

Peripheral blood mononuclear cells before and after cardiopulmonary bypass were analyzed for the expression of immunomodulatory cell markers by real-time quantitative reverse transcription polymerase chain reaction. T cell effector functions were determined by enzyme-linked immunosorbent assay, carboxyfluorescein succinimidyl ester staining, and cytotoxicity assays. Expression of cell surface markers was assessed by flow cytometry. CD15 cells were depleted by microbead separation. Serum arginine was measured by mass spectrometry. Patient peripheral blood mononuclear cells were incubated in different arginine concentrations, and T cell functions were tested.

MEASUREMENTS AND MAIN RESULTS

After cardiopulmonary bypass, peripheral blood mononuclear cells exhibited significantly reduced levels of costimulatory receptors (inducible T-cell costimulator, interleukin 7 receptor), whereas inhibitory receptors (programmed cell death protein 1 and programmed cell death 1 ligand 1) were induced. T cell effector functions (interferon γ secretion, proliferation, and CD8-specific cell lysis) were markedly repressed. In 66 of 71 patients, a not yet described cell population was found, which could be characterized as myeloid-derived suppressor cells. Myeloid-derived suppressor cells are known to impair immune cell functions by expression of the arginine-degrading enzyme arginase-1. Accordingly, we found dramatically increased arginase-1 levels in post-cardiopulmonary bypass peripheral blood mononuclear cells, whereas serum arginine levels were significantly reduced. Depletion of myeloid-derived suppressor cells from post-cardiopulmonary bypass peripheral blood mononuclear cells remarkably improved T cell effector function in vitro. Additionally, in vitro supplementation of arginine enhanced T cell immunocompetence.

CONCLUSIONS

Cardiopulmonary bypass strongly impairs the adaptive immune system by triggering the accumulation of myeloid-derived suppressor cells. These myeloid-derived suppressor cells induce an immunosuppressive T cell phenotype by increasing serum arginine breakdown. Supplementation with L-arginine may be an effective measure to counteract the onset of immunoparalysis in the setting of cardiopulmonary bypass.

Design and synthesis of novel pyrazolo[4,3-d]pyrimidines as potential therapeutic agents for acute lung injury

Four series of total 35 new pyrazolo[4,3-d]pyrimidine compounds were designed, synthesized and evaluated for their inhibitory activity against LPS-induced NO production in RAW264.7 macrophages. Among them, compound 4e was found to be the most potent inhibitor, which decreased the production of cytokines in vitro, such as NO, IL-6 and TNF-α, with IC₅₀ values of 2.64, 4.38 and 5.63 μM, respectively. Further studies showed that compound 4e inhibited cytokines secretion of macrophages through suppressing TLR4/p38 signaling pathway. Additionally, compound 4e showed in vivo anti-inflammatory activity in LPS-induced model of acute lung injury. These data suggested that compound 4e may be a promising lead structure for the treatment of ALI.

The effect of methylprednisolone prophylaxis on inflammatory monocyte subsets and suppressive regulatory T cells of patients undergoing cardiopulmonary bypass

BACKGROUND

Cardiopulmonary bypass (CPB) during open-heart surgery triggers an inflammatory response that can cause significant morbidity and mortality. Human monocytes and regulatory T (Treg) cells are phenotypically and functionally heterogeneous and have been shown to play a significant role in the inflammatory dysfunction triggered by CPB. Glucocorticoids (GCs) have been widely administered for decades in patients undergoing CPB to reduce this inflammatory response. However, it has not been clearly established how routine prophylactic administration of glucocorticoids (GCs) affects monocyte and Treg subsets.

METHODS

Thirty-six patient who underwent heart surgery with CPB were randomly assigned to a methylprednisolone group (MG, N = 18; 500 mg in the CPB priming) and a non-methylprednisolone group (NMG, N = 18). The circulating monocyte and Treg subsets were analyzed by flow cytometry.

RESULTS

The MG and NMG groups had comparable percentages of monocyte subsets and similar expression levels of HLA-DR, CD86, CD64 and toll-like receptor 4 (TLR4). Remarkably, methylprednisolone increased the percentage of CD4+CD25+ Treg cells among CD4+ T cells in patients undergoing CPB, but did not increase the proportion of suppressive Treg cells, either resting or activated, in these patients undergoing CPB.

CONCLUSIONS

Our results showed that prophylactic administration of methylprednisolone neither decreased the percentages and counts of inflammatory monocyte subsets nor did it induce the expansion of suppressive Treg cells in patients undergoing CPB. These results clarified the effects of GCs on cell-mediated immune responses and provided additional evidence in practice.

TRIAL REGISTRATION

Clinicaltrials.gov : NCT01296074. Registered 14 February 2011.

Blood cytokine expression correlates with early multi-organ damage in a mouse model of moderate hypothermia with circulatory arrest using cardiopulmonary bypass

Cardiopulmonary bypass (CPB) with moderate hypothermic cardiac arrest (MHCA) is essential for prolonged complex procedures in cardiac surgery and is associated with postoperative complications. Although cytokine release provoked through MHCA under CPB plays a pivotal role in postoperative organ damage, the pathomechanisms are unclear. Here, we investigated the cytokine release pattern and histological organ damage after MHCA using a recently described mouse CPB model. Eight BALB/c mice underwent 60 minutes of circulatory arrest under CPB, were successively rewarmed and reperfused. Blood cytokine concentrations and liver and kidney function parameters were measured and histological changes to these organs were compared to control animals. Our results showed a marked increase in proinflammatory cytokines and histological changes in the kidney, lung, and liver after CPB. Furthermore, clinical chemistry showed signs of hemolysis and acute kidney injury. These results suggest early onset of solid organ injury which correlates with increased leukocyte infiltration. A better understanding of the interplay between pro-inflammatory cytokine activation and solid organ injury in this model of CBP with MHCA will inform strategies to reduce organ damage during cardiac surgeries in the clinic.

Efficacy of Xuebijing Injection () on Cardiopulmonary Bypass-Associated Pulmonary Injury: A Prospective, Single-center, Randomized, Double Blinded Trial

OBJECTIVE

To evaluate the efficacy of Xuebijing Injection (, XBJ) on the lung injury induced by cardiopulmonary bypass (CPB).

METHODS

Fifty patients undergoing CPB were randomized to either the saline group or XBJ group according to a random number table (25 cases in each group). The patients in the saline group received saline and patients in XBJ group received XBJ at 12 h prior to the operation, at the beginning of the operation, and at 12 h after the second injection. The PaO₂/FiO₂ at extubation 3 days post-operation, duration of ventilation in the intensive care unit (ICU), and lengths of stay in the ICU and hospital were recorded. The levels of inflammatory mediators including interleukin (IL)-1β, IL-8, IL-10, and C-reactive protein (CRP) in bronchoalveolar lavage fluid (BALF) and plasma were measured. The neutrophil count and elastase neutrophil elastase in BALF were also measured. In addition, adverse events were monitored.

RESULTS

The PaO₂/FiO₂ in the XBJ group was higher than that in the saline group from 12 to 72 h post-operation (all P<0.05). The blood levels of IL-1β, IL-8, and CRP in the XBJ group from 12 to 72 h were all significantly lower than those in the saline group (all P<0.05). In contrast, the level of the anti-inflammatory cytokine IL-10 was significantly higher in the XBJ group than in the saline group (P<0.05). In addition, 4 patients presented with atelectasis in the saline group and none in the XBJ group. Ten patients experienced mild acute respiratory distress syndrome (ARDS) during hospitalization, and 5 patients with mild ARDS were in the XBJ group (P<0.05).

CONCLUSION

XBJ shows protective potential against lung injury in patients who undergo CPB surgery, possibly through the downregulation of inflammatory mediators, reduction in neutrophil infiltration, and upregulation of IL-10 (Trial registry: ChiCTR-TRC-14004628).

Protective effect of HTK solution on postoperative pulmonary function in infants with CHD and PAH

Objective: In the present study, we aimed to investigate the effect of pulmonary arterial perfusion (PAP) with Histidine–tryptophan–ketoglutarate (HTK) on lung protection in infants with congenital heart disease (CHD) and pulmonary arterial hypertension (PAH) after cardiopulmonary bypass (CPB).

Methods: Fifty infant patients with CHD and PAH at our hospital from January, 2016 to February, 2017 were randomly divided into control group and HTK group. The levels of interleukin-6 (IL-6), malondialdehyde (MDA), and endothelin-1 (ET-1) in serum were detected using ELISA Kit. Oxygen index (OI) and respiratory index (RI) were calculated at each time point. The time of postoperative mechanical ventilation and ICU stay was counted, and the right lower lung tissues in patients were taken for pathological examination.

Results: Compared with preanesthesia, the levels of IL-6, MDA, and ET-1 in the two groups were significantly increased after CPB, and their levels in HTK group were significantly lower than that in control group. Moreover, OI in control group decreased markedly and RI in control group increased significantly after CPB. Compared with control group, the postoperative mechanical ventilation time, postoperative ICU stay, and total hospital stay in HTK group were markedly short. In addition, inflammatory cells infiltration decreased and pulmonary interstitial showed mild edema in HTK group.

Conclusion: PAP with HTK could effectively reduce CPB-induced lung injury and improve lung function.

Impaired lung repair during neutropenia can be reverted by matrix metalloproteinase-9

BACKGROUND

Neutrophils may cause tissue disruption during migration and by releasing cytotoxic molecules. However, the benefits of neutrophil depletion observed in experimental models of lung injury do not correspond with the poor outcome of neutropenic patients.

METHODS

To clarify the role of neutrophils during repair, mice with ventilator induced lung injury (VILI) were rendered neutropenic after damage, and followed for 48 hours of spontaneous breathing. Lungs were harvested and inflammatory mediators and matrix metalloproteinases measured. Bronchoalveolar lavage fluid (BALF) from ventilated patients with acute respiratory distress syndrome, with or without neutropenia, was collected, the same mediators measured and their effects in an ex vivo model of alveolar repair studied. Finally, neutropenic mice were treated after VILI with exogenous matrix metalloproteinase-9 (MMP-9).

RESULTS

Lungs from neutropenic animals showed delayed repair and displayed higher levels of tumour necrosis factor α, interferon γ and macrophage inflammatory protein 2, and absence of MMP-9. BALF from ventilated neutropenic patients with acute respiratory distress syndrome showed similar results. BALFs from neutropenic patients yielded a delayed closure rate of epithelial wounds ex vivo, which was improved by removal of collagen or addition of exogenous MMP-9. Lastly, treatment of neutropenic mice with exogenous MMP-9 after VILI reduced tissue damage without modifying cytokine concentrations.

CONCLUSION

Release of MMP-9 from neutrophils is required for adequate matrix processing and lung repair.