A neutralizing anti-G-CSFR antibody blocks G-CSF-induced neutrophilia without inducing neutropenia in nonhuman primates

Whole blood transcriptomics reveals granulocyte colony-stimulating factor as a mediator of cardiopulmonary bypass-induced systemic inflammatory response syndrome

Objectives

Systemic inflammatory response syndrome (SIRS) is a frequent complication of cardiopulmonary bypass (CPB). SIRS is associated with significant morbidity and mortality, but its pathogenesis remains incompletely understood, and as a result, biomarkers are lacking and treatment remains expectant and supportive. This study aimed to understand the pathophysiological mechanisms driving SIRS induced by CPB and identify novel therapeutic targets that might reduce systemic inflammation and improve patient outcomes.

Methods

Twenty-one patients undergoing cardiac surgery and CPB were recruited, and blood was sampled before, during and after surgery. SIRS was defined using the American College of Chest Physicians/Society of Critical Care Medicine criteria. We performed immune cell profiling and whole blood transcriptomics and measured individual mediators in plasma/serum to characterise SIRS induced by CPB.

Results

Nineteen patients fulfilled criteria for SIRS, with a mean duration of 2.7 days. Neutrophil numbers rose rapidly with CPB and remained elevated for at least 48 h afterwards. Transcriptional signatures associated with neutrophil activation and degranulation were enriched during CPB. We identified a network of cytokines governing these transcriptional changes, including granulocyte colony-stimulating factor (G-CSF), a regulator of neutrophil production and function.

Conclusions

We identified neutrophils and G-CSF as major regulators of CPB-induced systemic inflammation. Short-term targeting of G-CSF could provide a novel therapeutic strategy to limit neutrophil-mediated inflammation and tissue damage in SIRS induced by CPB.

Granulocyte Colony-Stimulating Factor is a Determinant of Severe Bronchopulmonary Dysplasia and Coincident Retinopathy

Bronchopulmonary dysplasia (BPD), also called chronic lung disease of immaturity, afflicts approximately one third of all extremely premature infants, causing lifelong lung damage. There is no effective treatment other than supportive care. Retinopathy of prematurity (ROP), which impairs vision irreversibly, is common in BPD, suggesting a related pathogenesis. However, specific mechanisms of BPD and ROP are not known. Herein, a neonatal mouse hyperoxic model of coincident BPD and retinopathy was used to screen for candidate mediators, which revealed that granulocyte colony-stimulating factor (G-CSF), also known as colony-stimulating factor 3, was up-regulated significantly in mouse lung lavage fluid and plasma at postnatal day 14 in response to hyperoxia. Preterm infants with more severe BPD had increased plasma G-CSF. G-CSF-deficient neonatal pups showed significantly reduced alveolar simplification, normalized alveolar and airway resistance, and normalized weight gain compared with wild-type pups after hyperoxic lung injury. This was associated with a marked reduction in the intensity, and activation state, of neutrophilic and monocytic inflammation and its attendant oxidative stress response, and protection of lung endothelial cells. G-CSF deficiency also provided partial protection against ROP. The findings in this study implicate G-CSF as a pathogenic mediator of BPD and ROP, and suggest the therapeutic utility of targeting G-CSF biology to treat these conditions.

Neutrophils in autoimmunity: when the hero becomes the villain

Neutrophils were long considered to be a short-lived homogenous cell population, limited to their role as first responders in anti-bacterial and -fungal immunity. While it is true that neutrophils are first to infiltrate the site of infection to eliminate pathogens, growing evidence suggests their functions could extend beyond those of basic innate immune cells. Along with their well-established role in pathogen elimination, utilizing effector functions such as phagocytosis, degranulation, and the deployment of neutrophil extracellular traps (NETs), neutrophils have recently been shown to possess antigen-presenting capabilities. Moreover, the identification of different subtypes of neutrophils points to a multifactorial heterogeneous cell population with great plasticity in which some subsets have enhanced pro-inflammatory characteristics, while others seem to behave as immunosuppressors. Interestingly, the aberrant presence of activated neutrophils with a pro-inflammatory profile in several systemic and organ-specific autoimmune diseases such as systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), systemic sclerosis (SSc), multiple sclerosis (MS), and type 1 diabetes (T1D) could potentially be exploited in novel therapeutic strategies. The full extent of the involvement of neutrophils, and more specifically that of their various subtypes, in the pathophysiology of autoimmune diseases is yet to be elucidated.

Highlights of the ERS Lung Science Conference 2022

This article presents the highlights of the ERS Lung Science Conference 2022, including a session organised by the Early Career Member Committee (ECMC) dedicated to career development https://bit.ly/3tarCXc.

Endotype of Chronic Rhinosinusitis with Nasal Polyps in Morocco

BACKGROUND

With the advent of biotherapies, endotyping of chronic rhinosinusitis with nasal polyps (CRSwNP) is becoming more and more important to optimize therapeutic management. While the majority of CRSwNPs in the United States, Europe, and Japan exhibit type 2 eosinophil-dominant inflammation response, other parts of Asia display mixed patterns including neutrophil-dominant inflammation. Until now, no study has focused on the proportion of inflammation patterns in Morocco or anywhere on the African continent. We aim to fill this gap by studying tissue inflammatory response in our operated patients.

MATERIAL AND METHODS

After searching the database of the pathology department, we retrieved from the archives the stained pathology slides of all our patients who underwent surgery for CRSwNP over 5 years from 2017 to 2021. We counted then the number of eosinophils in the lamina propria at high-power magnification to determine the predominant inflammatory pattern.

RESULTS

A total of 35 reports were collected. We found that eosinophilic inflammation was predominant, accounting for 97% of the cases.

CONCLUSIONS

The CRSwNP endotype in our region would mainly be type 2. However, our results must be confirmed by multicenter studies involving a large number of patients.

Interleukin-6 and granulocyte colony-stimulating factor as predictors of the prognosis of influenza-associated pneumonia

Background

Pneumonia is a common complication of influenza and closely related to mortality in influenza patients. The present study examines cytokines as predictors of the prognosis of influenza-associated pneumonia.

Methods

This study included 101 inpatients with influenza (64 pneumonia and 37 non-pneumonia patients). 48 cytokines were detected in the serum samples of the patients and the clinical characteristics were analyzed. The correlation between them was analyzed to identify predictive biomarkers for the prognosis of influenza-associated pneumonia.

Results

Seventeen patients had poor prognosis and developed pneumonia. Among patients with influenza-associated pneumonia, the levels of 8 cytokines were significantly higher in those who had a poor prognosis: interleukin-6 (IL-6), interferon-γ (IFN-γ), granulocyte colony-stimulating factor (G-CSF), monocyte colony-stimulating factor (M-CSF), monocyte chemoattractant protein-1 (MCP-1), monocyte chemoattractant protein-3, Interleukin-2 receptor subunit alpha and Hepatocyte growth factor. Correlation analysis showed that the IL-6, G-CSF, M-CSF, IFN-γ, and MCP-1 levels had positive correlations with the severity of pneumonia. IL-6 and G-CSF showed a strong and positive correlation with poor prognosis in influenza-associated pneumonia patients. The combined effect of the two cytokines resulted in the largest area (0.926) under the receiver-operating characteristic curve.

Conclusion

The results indicate that the probability of poor prognosis in influenza patients with pneumonia is significantly increased. IL-6, G-CSF, M-CSF, IFN-γ, and MCP-1 levels had a positive correlation with the severity of pneumonia. Importantly, IL-6 and G-CSF were identified as significant predictors of the severity of influenza-associated pneumonia.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-022-07321-6.

Role for Granulocyte Colony-Stimulating Factor in Neutrophilic Extramedullary Myelopoiesis in a Murine Model of Systemic Juvenile Idiopathic Arthritis

OBJECTIVE

Systemic juvenile idiopathic arthritis (JIA) is a systemic inflammatory disease with childhood onset. Systemic JIA is associated with neutrophilia, including immature granulocytes, potentially driven by the growth factor granulocyte-colony stimulating factor (G-CSF). This study was undertaken to investigate the role of G-CSF in the pathology of systemic JIA.

METHODS

Injection of Freund's complete adjuvant (CFA) in BALB/c mice induces mild inflammation and neutrophilia in wild-type (WT) mice and a more pronounced disease, reminiscent to that of JIA patients, in interferon-γ-knockout (IFNγ-KO) mice. Extramedullary myelopoiesis was studied in CFA-immunized mice by single-cell RNA sequencing, and the effect of G-CSF receptor (G-CSFR) blockage on neutrophil development and systemic JIA pathology was evaluated. Additionally, plasma G-CSF levels were measured in patients.

RESULTS

Both in systemic JIA patients and in a corresponding mouse model, plasma G-CSF levels were increased. In the mouse model, we demonstrated that G-CSF is responsible for the observed neutrophilia and extramedullary myelopoiesis and the induction of immature neutrophils and myeloid-derived suppressor-like cells. Administration of a G-CSFR antagonizing antibody blocked the maturation and differentiation of neutrophils in CFA-immunized mice. In IFNγ-KO mice, treatment was associated with almost complete inhibition of arthritis due to reduced neutrophilia and osteoclast formation. Disease symptoms were ameliorated, but slight increases in interleukin-6 (IL-6), tumor necrosis factor, and IL-17 were detected upon G-CSFR inhibition in the IFNγ-KO mice, and were associated with mild increases in weight loss, tail damage, and immature red blood cells.

CONCLUSION

We describe the role of G-CSF in a mouse model of systemic JIA and suggest an important role for G-CSF-induced myelopoiesis and neutrophilia in regulating the development of arthritis.

Characterizing the Neutrophilic Inflammation in Chronic Rhinosinusitis With Nasal Polyps

The mechanisms underlying neutrophilic inflammation in chronic rhinosinusitis with nasal polyps (CRSwNP) remain poorly investigated. This study aimed to examine the factors that contribute to tissue neutrophilia in CRSwNP. The numbers of neutrophils and active caspase-3-positive apoptotic neutrophils in sinonasal tissues were assessed via immunofluorescence staining. The 95th percentile of tissue neutrophil numbers in control subjects was selected as a cut-off to define neutrophil-high (Neu-high) or neutrophil-low (Neu-low) nasal polyps (NPs). The levels of 34 inflammatory mediators in sinonasal tissues were analyzed using Bio-Plex assay. Purified human peripheral blood neutrophils were incubated with nasal tissue homogenates, and the apoptotic neutrophils were assessed via flow cytometry. The cut-off for Neu-high NPs was >10 myeloperoxidase positive cells/high-power field. Compared with Neu-low NPs, Neu-high NPs had higher tissue levels of IL-1β, IL-1Ra, IL-6, IL-8, G-CSF, MCP-1, and MIP-1α, but lower levels of IL-5, IL-13, IgE, and eosinophils. Principal component and multiple correspondence analyses revealed mixed type 1, type 2, and type 3 endotypes for Neu-low NPs, and predominant type 1 and type 3 endotypes for Neu-high NPs. Neu-high NPs had lower percentages of apoptotic neutrophils than Neu-low NPs. The numbers of neutrophils and the percentages of apoptotic neutrophils correlated with G-CSF and IL-6 levels in the NPs. Tissue homogenates from Neu-high NPs, but not those from Neu-low NPs, suppressed neutrophil apoptosis in vitro, which was reversed by anti-G-CSF treatment. Tissue neutrophil numbers were associated with difficult-to-treat disease in patients with CRSwNP after surgery. We propose that G-CSF promotes neutrophilic inflammation by inhibiting neutrophil apoptosis in CRSwNP.

G-CSF - A double edge sword in neutrophil mediated immunity

Neutrophils are vital for the innate immune system's control of pathogens and neutrophil deficiency can render the host susceptible to life-threatening infections. Neutrophil responses must also be tightly regulated because excessive production, recruitment or activation of neutrophils can cause tissue damage in both acute and chronic inflammatory diseases. Granulocyte colony stimulating factor (G-CSF) is a key regulator of neutrophil biology, from production, differentiation, and release of neutrophil precursors in the bone marrow (BM) to modulating the function of mature neutrophils outside of the BM, particularly at sites of inflammation. G-CSF acts by binding to its cognate cell surface receptor on target cells, causing the activation of intracellular signalling pathways mediating the proliferation, differentiation, function, and survival of cells in the neutrophil lineage. Studies in humans and mice demonstrate that G-CSF contributes to protecting the host against infection, but conversely, it can play a deleterious role in inflammatory diseases. As such, neutrophils and the G-CSF pathway may provide novel therapeutic targets. This review will focus on understanding the role G-CSF plays in the balance between effective neutrophil mediated host defence versus neutrophil-mediated inflammation and tissue damage in various inflammatory and infectious diseases.

G-CSFR antagonism reduces neutrophilic inflammation during pneumococcal and influenza respiratory infections without compromising clearance

Excessive neutrophilic inflammation can contribute to the pathogenesis of pneumonia. Whilst anti-inflammatory therapies such as corticosteroids are used to treat excessive inflammation, they do not selectively target neutrophils and may compromise antimicrobial or antiviral defences. In this study, neutrophil trafficking was targeted with a granulocyte-colony stimulating factor receptor monoclonal antibody (G-CSFR mAb) during Streptococcus pneumoniae (serotype 19F) or influenza A virus (IAV, strain HKx31) lung infection in mice. Firstly, we demonstrated that neutrophils are indispensable for the clearance of S. pneumoniae from the airways using an anti-Ly6G monoclonal antibody (1A8 mAb), as the complete inhibition of neutrophil recruitment markedly compromised bacterial clearance. Secondly, we demonstrated that G-CSF transcript lung levels were significantly increased during pneumococcal infection. Prophylactic or therapeutic administration of G-CSFR mAb significantly reduced blood and airway neutrophil numbers by 30–60% without affecting bacterial clearance. Total protein levels in the bronchoalveolar lavage (BAL) fluid (marker for oedema) was also significantly reduced. G-CSF transcript levels were also increased during IAV lung infection. G-CSFR mAb treatment significantly reduced neutrophil trafficking into BAL compartment by 60% and reduced blood neutrophil numbers to control levels in IAV-infected mice. Peak lung viral levels at day 3 were not altered by G-CSFR therapy, however there was a significant reduction in the detection of IAV in the lungs at the day 7 post-infection phase. In summary, G-CSFR signalling contributes to neutrophil trafficking in response to two common respiratory pathogens. Blocking G-CSFR reduced neutrophil trafficking and oedema without compromising clearance of two pathogens that can cause pneumonia.

G-CSF partially mediates bone loss induced by Staphylococcus aureus infection in mice

Bone loss in Staphylococcus aureus (S. aureus) osteomyelitis poses a serious challenge to orthopedic treatment. The present study aimed to elucidate how S. aureus infection in bone might induce bone loss. The C57BL/6 mice were injected with S. aureus (10⁶ CFU/ml, 100 μl) or with the same amount of vehicle (control) via the tail vein. Microcomputed tomography (microCT) analysis showed bone loss progressing from week 1 to week 5 after infection, accompanied by a decreased number of osteocalcin-positive stained osteoblasts and the suppressed mRNA expression of Runx2 and osteocalcin. Transcriptome profiles of GSE30119 were downloaded and analyzed to determine the differences in expression of inflammatory factors between patients with S. aureus infected osteomyelitis and healthy controls, the data showed significantly higher mRNA expression of granulocyte colony-stimulating factor (G-CSF) in the whole blood from patients with S. aureus infection. Enzyme-linked immunosorbent assay (ELISA) analysis confirmed an increased level of G-CSF in the bone marrow and serum from S. aureus infected mice, which might have been due to the increased amount of F4/80⁺ macrophages. Interestingly, G-CSF neutralizing antibody treatment significantly rescued the bone loss after S. aureus infection, as evidenced by its roles in improving BV/TV and preserving osteocalcin- and osterix-positive stained cells. Importantly, we found that G-CSF level was significantly up-regulated in the serum from osteomyelitis patients infected by S. aureus Together, S. aureus infection might suppress the function of osteoblastic cells and induce progressive bone loss by up-regulating the level G-CSF, suggesting a therapeutic potential for G-CSF neutralization in combating bone loss in S. aureus osteomyelitis.