Stability of eosinophilic inflammation in COPD bronchial biopsies

Increased mast cell activation in eosinophilic chronic obstructive pulmonary disease

Objectives

A subset of chronic obstructive pulmonary disease (COPD) patients have increased numbers of airway eosinophils associated with elevated markers of T2 inflammation. This analysis focussed on mast cell counts and mast cell‐related gene expression in COPD patients with higher vs lower eosinophil counts.

Methods

We investigated gene expression of tryptase (TPSAB1), carboxypeptidase A3 (CPA3), chymase (CMA1) and two mast cell specific gene signatures; a bronchial biopsy signature (MC_bb) and an IgE signature (MC_IgE) using sputum cells and bronchial epithelial brushings. Gene expression analysis was conducted by RNA‐sequencing. We also examined bronchial biopsy mast cell numbers by immunohistochemistry.

Results

There was increased expression of TPSAB1, CPA3 and MC_bb in eosinophil^high than in eosinophil^low COPD patients in sputum cells and bronchial epithelial brushings (fold change differences 1.21 and 1.28, respectively, P < 0.01). Mast cell gene expression was associated with markers of T2 and eosinophilic inflammation (IL13, CLCA1, CST1, CCL26, eosinophil counts in sputum and bronchial mucosa; rho = 0.4–0.8; P < 0.05). There was no difference in MC_IgE gene expression between groups. There was no difference in the total number of bronchial biopsy mast cells between groups.

Conclusion

These results demonstrate that eosinophilic inflammation is associated with altered mast cell characteristics in COPD patients, implicating mast cells as a component of T2 inflammation present in a subset of COPD patients.

Blood Eosinophils and Chronic Obstructive Pulmonary Disease: A GOLD Science Committee 2022 Review

COPD is a heterogeneous condition. Some patients benefit from treatment with inhaled corticosteroids (ICS) but this requires a precision medicine approach, based on clinical characteristics (phenotyping) and biological information (endotyping) in order to select patients most likely to benefit. The GOLD 2019 report recommended using exacerbation history combined with blood eosinophil counts (BEC) to identify such patients. Importantly, the relationship between BEC and ICS effects is continuous; no / small effects are observed at lower BEC, with increasing effects at higher BEC. The GOLD 2022 report has added additional evidence and recommendations concerning the use of BEC in COPD in clinical practice. Notably, associations have been demonstrated in COPD patients between higher BEC and increased levels of type-2 inflammation in the lungs. These differences in type-2 inflammation can explain the differential ICS response according to BEC. Additionally, lower BEC are associated with greater presence of proteobacteria, notably haemophilus, and increased bacterial infections and pneumonia risk. These observations support management strategies that use BEC to help identify subgroups with increased ICS response (higher BEC) or increased risk of bacterial infection (lower BEC). Recent studies in younger individuals without COPD have also shown that higher BEC are associated with increased risk of FEV1 decline and the development of COPD. Here we discuss and summarise the GOLD 2022 recommendations concerning the use of BEC as a biomarker that can facilitate a personalised management approach in COPD.

The PDE4 inhibitor tanimilast shows distinct immunomodulatory properties associated with a type 2 endotype and CD141 upregulation

Background

Tanimilast is a novel and selective inhaled inhibitor of phosphodiesterase-4 in advanced clinical development for chronic obstructive pulmonary disease (COPD). Tanimilast is known to exert prominent anti-inflammatory activity when tested in preclinical experimental models as well as in human clinical studies. Recently, we have demonstrated that it also finely tunes, rather than suppressing, the cytokine network secreted by activated dendritic cells (DCs). This study was designed to characterize the effects of tanimilast on T-cell polarizing properties of DCs and to investigate additional functional and phenotypical features induced by tanimilast.

Methods

DCs at day 6 of culture were stimulated with LPS in the presence or absence of tanimilast or the control drug budesonide. After 24 h, DCs were analyzed for the expression of surface markers of maturation and activation by flow cytometry and cocultured with T cells to investigate cell proliferation and activation/polarization. The regulation of type 2-skewing mediators was investigated by real-time PCR in DCs and compared to results obtained in vivo in a randomized placebo-controlled trial on COPD patients treated with tanimilast.

Results

Our results show that both tanimilast and budesonide reduced the production of the immunostimulatory cytokine IFN-γ by CD4⁺ T cells. However, the two drugs acted at different levels since budesonide mainly blocked T cell proliferation, while tanimilast skewed T cells towards a Th2 phenotype without affecting cell proliferation. In addition, only DCs matured in the presence of tanimilast displayed increased CD86/CD80 ratio and CD141 expression, which correlated with Th2 T cell induction and dead cell uptake respectively. These cells also upregulated cAMP-dependent immunosuppressive molecules such as IDO1, TSP1, VEGF-A and Amphiregulin. Notably, the translational value of these data was confirmed by the finding that these same genes were upregulated also in sputum cells of COPD patients treated with tanimilast as add-on to inhaled glucocorticoids and bronchodilators.

Conclusion

Taken together, these findings demonstrate distinct immunomodulatory properties of tanimilast associated with a type 2 endotype and CD141 upregulation in DCs and provide a mechanistic rationale for the administration of tanimilast on top of inhaled corticosteroids.