Objective: This study aims to identify clinically relevant diagnostic biomarkers in chronic obstructive pulmonary disease (COPD) while exploring how immune cell infiltration contributes towards COPD pathogenesis.Methods: The GEO database provided two human COPD gene expression datasets (GSE38974 and GSE76925; n=134) along with the relevant controls (n=49) for differentially expressed gene (DEG) analyses. Candidate biomarkers were identified using the support vector machine recursive feature elimination (SVM-RFE) analysis and the LASSO regression model. The discriminatory ability was determined using the area under the receiver operating characteristic curve (AUC) values. These candidate biomarkers were characterized in the GSE106986 dataset (14 COPD patients and 5 controls) in terms of their respective diagnostic values and expression levels. The CIBERSORT program was used to estimate patterns of tissue infiltration of 22 types of immune cells. Furthermore, the in vivo and in vitro model of COPD was established using cigarette smoke extract (CSE) to validated the bioinformatics results.Results: 80 genes were identified via DEG analysis that were primarily involved in cellular amino acid and metabolic processes, regulation of telomerase activity and phagocytosis, antigen processing and MHC class I-mediated peptide antigen presentation, and other biological processes. LASSO and SVM-RFE were used to further characterize the candidate diagnostic markers for COPD, SLC27A3, and STAU1. SLC27A3 and STAU1 were found to be diagnostic markers of COPD in the metadata cohort (AUC=0.734, AUC=0.745). Their relevance in COPD were validated in the GSE106986 dataset (AUC=0.900 AUC=0.971). Subsequent analysis of immune cell infiltration discovered an association between SLC27A3 and STAU1 with resting NK cells, plasma cells, eosinophils, activated mast cells, memory B cells, CD8+, CD4+, and helper follicular T-cells. The expressions of SLC27A3 and STAU1 were upregulated in COPD models both in vivo and in vitro. Immune infiltration activation was observed in COPD models, accompanied by the enhanced expression of SLC27A3 and STAU1. Whereas, the knockdown of SLC27A3 or STAU1 attenuated the effect of CSE on BEAS-2B cells.Conclusion: STUA1 and SLC27A3 are valuable diagnostic biomarkers of COPD. COPD pathogenesis is heavily influenced by patterns of immune cell infiltration. This study provides a molecular biology insight into COPD occurrence and in exploring new therapeutic means useful in COPD.

Purpose: Pulmonary surfactant proteins A (SP-A) and D (SP-D) are lectins, involved in host defense and regulation of pulmonary inflammatory response. However, studies on the assessment of COPD progress are limited. Patients and Methods: Pulmonary surfactant proteins were obtained from the COPD mouse model induced by cigarette and lipopolysaccharide, and the specimens of peripheral blood and bronchoalveolar lavage (BALF) in COPD populations. H&E staining and RT-PCR were performed to demonstrate the successfully established of the mouse model. The expression of SP-A and SP-D in mice was detected by Western Blot and immunohistochemistry, while the proteins in human samples were measured by ELISA. Pulmonary function test, inflammatory factors (CRP, WBC, NLR, PCT, EOS, PLT), dyspnea index score (mMRC and CAT), length of hospital stay, incidence of complications and ventilator use were collected to assess airway remodeling and progression of COPD. Results: COPD model mice with emphysema and airway wall thickening were more prone to have decreased SP-A, SP-D and increased TNF-α, TGF-β, and NF-kb in lung tissue. In humans, SP-A and SP-D decreased in BALF, but increased in serum. The serum SP-A and SP-D were negatively correlated with FVC, FEV1, FEV1/FVC, and positively correlated with CRP, WBC, NLR, mMRC and CAT scores (P < 0.05, respectively). The lower the SP-A and SP-D in BALF, the worse the lung function and the increased probability of complications and ventilator use. Moreover, the same trend emerged in COPD patients grouped according to GOLD severity grade (Gold 1– 2 group vs Gold 3– 4 group). The worse the patient’s condition, the more pronounced the change. Conclusion: This study suggests that SP-A and SP-D may be related to the progression and prognostic evaluation of COPD in terms of airway remodeling, inflammatory response and clinical symptoms, and emphasizes the necessity of future studies of surfactant protein markers in COPD.

Background: Blood eosinophil levels are a known marker for the effects of therapy in patients with chronic obstructive pulmonary disease (COPD). This study aimed to clarify the cutoff values for blood eosinophils (EOS) to predict exacerbation risk and prognosis of acute exacerbation COPD (AECOPD) and investigate their correlation using inflammatory indicators and clinical characteristics. Methods: In this observational study of 174 patients with AECOPD, we assessed the relationship between EOS and COPD. According to the percentage of blood EOS, patients were grouped into two groups (Group 1: EOS <2%, n=98; Group 2: EOS ≥2%, n=76), and Group 2 was further divided into Group A (2%≤ EOS <4%) and Group B (EOS ≥4%) based on a cutoff value of 4%. Patients received standardized treatment after collection of peripheral blood specimen. Associations of EOS with laboratory indicators before any treatment in hospital and with clinical data were compared. Results: Patients in Group 1 showed significantly severe inflammation, worse pulmonary function, longer length of stay (LOS) (P<0.001), higher mMRC score (P<0.05), higher CAT score (P<0.05), higher rates of mortality (P<0.05), and greater noninvasive mechanical ventilation usage (P<0.05) compared with Group 2. Intriguingly, the CRP, total mMRC and CAT scores of patients in Group A were significantly lower than those in Group B (P<0.001; P<0.01; P<0.05, respectively). Pearson correlation analysis showed that a low percentage blood eosinophil level was negatively associated with higher WBC count (r=–0.155, P<0.05), NLR (r=–0.227, P<0.01) and CRP (r=–0.308, P<0.01). Conclusions: Different cutoff values for percentage blood EOS might be useful biomarkers for predicting the severity of exacerbation and prognosis of inpatients with AECOPD.