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Respiratory MUC5B disproportion is involved in severe community-acquired pneumonia

Abstract

Background

Mucus production is a process involved in the pathogenesis of Community-acquired pneumonia (CAP). The study is to determine Mucin 5B (MUC5B) protein concentration and its proportion in the bronchoalveolar lavage fluid (BALF) of CAP patients and evaluate its value to help assess disease severity.

Methods

A total of 118 patients were enrolled in this cross-sectional study, including 45 with severe CAP (SCAP) and 73 with non-severe CAP (NSCAP). MUC5B concentration in BALF were determined by immunoblotting analysis. Total protein concentration of BALF was detected by Pierce BCA kit. Cytokines IL6, IL10, IFNγ, IL13, and IL17 in BALF were measured using commercial enzyme-linked immunosorbent assay (ELISA). Spearman’s correlation analysis was applied to evaluate the relationships between MUC5B concentration or MUC5B/total protein ratio and the CURB-65 score, as well as cytokines. Logistic regression analysis was used to identify the independent factors associated with severe CAP. Receiver operating characteristic (ROC) curve was used to evaluate the assessment value of MUC5B/total protein ratio and other indexes for CAP severity.

Results

MUC5B concentration in the BALF of NSCAP group was higher than that in SCAP group [NSCAP 13.56 µg/ml (IQR 5.92–25.79) vs. SCAP 8.20 µg/ml (IQR 4.97–14.03), p = 0.011]. The total protein concentration in the BALF of NSCAP group was lower than that in SCAP group [NSCAP 0.38 mg/ml (IQR 0.15–1.10) vs. SCAP 0.68 mg/ml (IQR 0.46–1.69), p = 0.002]. The MUC5B/total protein ratio was remarkably higher in NSCAP group than that in SCAP groups [NSCAP 3.66% (IQR 1.50–5.56%) vs. SCAP 1.38% (IQR 0.73–1.76%), p < 0.001]. MUC5B/total protein ratio was negatively correlated with total protein concentration (rs = − 0.576, p < 0.001), IL6 (rs = − 0.312, p = 0.001), IL10 (rs = − 0.228, p = 0.013), IL13 (rs = − 0.183, p = 0.048), IL17 (rs = − 0.282, p = 0.002) and CURB-65 score (rs = − 0.239, p = 0.009). Logistic regression identified that MUC5B/total protein ratio, IL6 level and CURB-65 score as independent variables related to CAP severity. ROC curve demonstrated best assessment value of MUC5B/total protein ratio for SCAP (AUC 0.803, p < 0.001), with a sensitivity of 88.9% and a specificity of 64.4%.

Conclusions

Respiratory MUC5B disproportion is related to CAP severity. MUC5B/total protein ratio may serve as an assessment marker and a potential therapeutic target for severe CAP.

Peer Review reports

Introduction

Community-acquired pneumonia (CAP) is one of major lethal infectious disease [1] with the incidence reaches 30–50% in adults [2]. Approximately 10% patients with CAP will develop severe CAP (SCAP) and require ICU treatment in which the mortality rate ranges from 19 to 50% [3]. Common symptoms of CAP include fever, cough and increased sputum production [4]. However, severe cases are prone to develop serious complications due to complexity and heterogeneity of variant risk factors [5], such as virulence and serotypes of pathogens, the age, immune state and comorbidities of patients, as well as genetic variants [6]. Given the inadequacy of the condition assessment of SCAP, a profound understanding of SCAP pathogenesis and a sensitive molecular marker are expected to improve patients’ diagnosis and treatment.

One major feature of CAP is mucus production and mucus is mainly composed of mucins [7, 8]. Previous animal experiments have proved that airway secreted mucin MUC5B but not Mucin 5AC (MUC5AC) plays a critical role in immune defense against bacterial infections [9]. MUC5B helps form gel in the airway as a defensive barrier and regulates the rheology of airway mucus [10]. Electron microscopy has shown that multiple MUC5B filaments always appear as strands lining in the airway. It traps and sweeps away pathogens from the lung by working with other types of mucins [11]. Previous studies showed that MUC5B participates in the development of pulmonary diseases, such as pulmonary fibrosis, chronic obstructive pulmonary disease (COPD) and bronchiectasis [12,13,14]. So far, whether MUC5B expression is involved in the development of SCAP has not been studied.

In our study, we compared the MUC5B concentration and its proportion in bronchoalveolar lavage fluid (BALF) of patients with NSCAP and SCAP. We analyzed the correlation between MUC5B expression and CAP severity to determine its value as a marker to help assess disease severity.

Material and methods

Study design

This cross-sectional study recruited patients from three hospitals including Jiangsu Province Hospital, Nanjing Chest Hospital and Qixia Branch of Jiangsu Province Hospital. The consecutive adult CAP patients treated in the respiratory and critical care general ward or intensive care unit (ICU) from Jan 2021 to Aug 2021 were screened for participants. The study was approved by the Institutional Review Board of coordinating center Jiangsu Province Hospital (No. 2021-SR-028). Written informed consent of the bronchoalveolar lavage (BAL) procedure and BALF sample utilization was obtained from each participant or from a relative or main care.

The inclusion criteria were as follows: 1. Men and women aged over 18 years old; 2. Diagnosed of CAP according the ATS guidelines; 3. Untreated or received treatment less than 24 h before admission; 4. Patients underwent BAL as standard of diagnosis [15, 16]; 5. Signed informed consent form. The exclusion criteria were as follows: 1. Patients with active pulmonary tuberculosis; 2. Patients with chronic pulmonary disease including chronic bronchitis, bronchiectasis, asthma, lung cancer, pulmonary embolism or interstitial lung diseases; 3. Patients with malignancy or severe immunosuppression; 4. Patients with pregnancy.

According to the ATS Guidelines [17] for the management of adults with CAP: CAP was diagnosed if the patient presented with at least one newly acquired respiratory symptoms such as cough, sputum and dyspnea setting on at communities, accompanied with fever, abnormal breath sounds and crackles. Each patient underwent a computerized tomography (CT) scan to identify patchy infiltrate shadows, lobar or segmental consolidation shadows, ground glass shadows or interstitial changes.

Severe CAP (SCAP) was defined during 24 h after admission by the criteria in ATS consensus guidelines 2007 [18]. The major criteria are as follows: 1. Patients needing invasive mechanical ventilation; 2. Patients showing septic shock needing vasopressors. The minor criteria included: 1. Respiratory rate ≥ 30 breaths/min; 2. PaO2/FiO2 ratio ≤ 250; 3. Multi-lobar infiltrates; 4. Confusion/disorientation; 5. Uraemia (BUN level ≥ 20 mg/dl); 6. Leucopenia (WBC < 4,000/mm3); 7. Thrombocytopenia (platelet count < 100,000 /mm3); 8. Hypothermia (core temperature < 36 °C); 9. Hypotension requiring aggressive fluid resuscitation. CAP patients presenting at least one major criterion or at least three minor criteria were diagnosed as SCAP.

Baseline clinical parameters of patients were collected from electronic hospital records (EHR). All participants received BAL procedure during 24 h after hospitalization. Through standardized bronchoscopy and performed the protocol of 2012 ATS guideline for BAL [19], the BAL was proceeded using a 120 ml lavage of 0.9% saline [20]. The BAL fluid (BALF) was then collected through a sputum box attaching to the suction canal of the bronchoscope with qualified at least 10% returned rate [21]. The BALF sample was filtered by gauze and immediately frozen at − 80 °C for further experiment. CT scan and blood test were carried out before lavage. Blood indexes included white blood cells count (WBC), leukocyte classification, lactate dehydrogenase (LDH), C-reaction protein (CRP), erythrocyte sedimentation rate (ESR), fibrinogen (Fib), and d-dimer (D-D).

Inflammatory markers in BALF tested by ELISA

Concentration of cytokines including interleukin-6 (IL6), interleukin-10 (IL10), interferon-γ (IFNγ), interleukin-13 (IL13), and interleukin-17 (IL17) in BALF was determined using commercial enzyme-linked immunosorbent assay (ELISA) kits specific for human following protocols (IL6, Cat. #: EHC007; IL10, Cat. #: EHC009; IFNγ, Cat. #: EHC102g; IL13, Cat. #: EHC137; IL17 Cat. #: EHC170; Neobioscience; Shenzhen; China).

MUC5B expression measurement

The BALF was thawed and then centrifuged at 1200r for 10 min at 4 °C. MUC5B in the supernatant was measured by immunoblotting analysis using S&S MINIFOLD® I and has been described in our previous study [22]. The MUC5B standard concentration driving from human saliva ranged from 0.87 to 0.01 (µg/ml). Samples were diluted with dilution buffer (3 M urea) with a ratio of 1:50. Standards and samples were run in duplicate (100 ul per sample). The protein blots binding to PVDF membrane were incubated with MUC5B primary antibodies (Santa Cruz Bio.), then with secondary goat anti-rabbit IgG Biotin conjugate and strep-HRP (Life Technologies). The blots were visualized using an enhanced chemiluminescence system. Immunoreactive dots were quantified using ImageJ software. Total protein concentration in BALF supernatant was determined by Pierce BCA protein assay kit (Cat. #: 23227; Thermo Scientific, Rockford, USA).

Statistical analysis

The current sample size achieved the study objectives with a desired power 0.80. Statistical analyses were performed with SPSS 17.0 (SPSS Inc., Chicago, IL). Continuous variables with normal distribution were presented as mean ± SD. Variables with abnormal distribution were presented as median (Interquartile range, IQR). Categorical variables were displayed as percentages. Student t-test was applied for comparison between normal distributed variables. Mann–Whitney U test was used to compare abnormal distributed variables. The Fisher’s exact test or chi-square test was used to compare categorical variables. Spearman’s correlation coefficients (rs) were measured to evaluate the relationships between MUC5B concentration or MUC5B/Total protein ratio and CURB-65 score, total protein concentration, as well as inflammatory markers in BALF. Binary logistic regression analysis was used to identify independent factors associated with severe CAP. The assessment value of MUC5B/Total protein ratio or other indexes for CAP severity was evaluated using receiver operating characteristic (ROC) curve. All statistics were two-sided, only a p value less than 0.05 was considered statistically significant.

Results

Demographic characteristics and clinical parameters of participants

A total of 118 patients confirmed with CAP were included in the research and divided into NSCAP group (n = 73) and SCAP group (n = 45) (Fig. 1). Demographic characteristics and clinical parameters are described in Table 1. The frequency of difficulty breathing was significantly higher in SCAP group than in NSCAP group (p = 0.001). Other symptoms including cough, sputum and fever showed no significant differences between the two groups. CURB-65 scores were significantly higher in SCAP group than that in NSCAP group (p < 0.001). In laboratory parameters, percentage of neutrophils (NE%), serum levels of LDH, CRP, ESR, plasma level of Fib and D-D were remarkably higher in SCAP patients than those in NSCAP patients (p < 0.05, respectively). Percentage of lymphocytes (LYM%) in SCAP group was lower than that in NSCAP group (p = 0.028).

Fig. 1
figure 1

Study flowchart of patient enrollment. CAP community-acquired pneumonia, NSCAP non-severe CAP, SCAP severe CAP

Table 1 Demographic and clinical characteristics of the subjects enrolled in this study

MUC5B condition and its correlation with related indexes

MUC5B concentration in the BALF of NSCAP group was higher than that in SCAP group [NSCAP 13.56 µg/ml (IQR 5.92–25.79) vs. SCAP 8.20 µg/ml (IQR 4.97–14.03), p = 0.011]. The total protein concentration in the BALF of NSCAP group was lower than that in SCAP group [NSCAP 0.38 mg/ml (IQR 0.15–1.10) vs. SCAP 0.68 mg/ml (IQR 0.46–1.69), p = 0.002]. The MUC5B/total protein ratio was remarkably higher in NSCAP group than that in SCAP groups [NSCAP 3.66% (IQR 1.50–5.56%) vs. SCAP 1.38% (IQR 0.73–1.76%), p < 0.001]. For inflammatory markers in BALF, the levels of IL6, IL13 and IL17 were lower in NSCAP group than those in SCAP group (p < 0.05). The levels of IL10 and IFNγ showed no significant difference between the two groups (Table 2).

Table 2 MUC5B concentration and inflammatory biomarkers in BALF of NSCAP patients and SCAP patients

The correlations among MUC5B level, total protein concentration, MUC5B/total protein ratio and the inflammatory parameters in BALF as well as CURB-65 score were investigated by Spearman’s correlation analysis (Table 3). MUC5B level had positive correlation with total protein concentration (rs = 0.423, p < 0.001) but no correlation with inflammatory cytokines. MUC5B/total protein ratio was negatively correlated with total protein concentration (rs = − 0.576, p < 0.001), IL6 (rs = − 0.312, p = 0.001), IL10 (rs = − 0.228, p = 0.013), IL13 (rs = − 0.183, p = 0.048) and IL17 (rs = − 0.282, p = 0.002). MUC5B level and MUC5B/total protein ratio both had negative correlations with CURB-65 score (rs = − 0.218, p = 0.018 for MUC5B, rs = − 0.239, p = 0.009 for MUC5B/total protein ratio, respectively).

Table 3 Correlation between MUC5B level, total protein concentration, MUC5B/total protein ratio and related indexes

Assessment performance of MUC5B/total protein ration for CAP severity

Though MUC5B concentration and total protein level showed significant differences between NSCAP and SCAP groups, the binary logistic regression analysis revealed that MUC5B concentration and total protein level were not independent factors associated with CAP severity. Logistic regression identified that MUC5B/total protein ratio, IL6 level and CURB-65 score remained as variables significantly related to CAP severity (Table 4).

Table 4 Logistic regression of variable parameters for determining the severity of CAP

ROC analysis was applied to evaluate whether MUC5B/total protein ratio could be used as a sensitive biomarker for CAP severity. Table 5 and Fig. 2 showed MUC5B/total protein ratio (AUC 0.803, p < 0.001) presented a better performance to assess the CAP severity with a sensitivity of 88.9% and a specificity of 64.4% comparing to CURB-65 score (AUC 0.692, p < 0.001) and the cytokine IL6 (AUC = 0.791, p < 0.001). The optimal cut-off point of MUC5B/total protein ratio to distinguish SCAP from NSCAP was 2.117%, with a positive predictive value of 60.6% and a negative predictive value of 90.4%.

Table 5 Areas under the curve of variable parameters for determining the severity of CAP
Fig. 2
figure 2

ROC curve analysis of various parameters for discriminating SCAP from NSCAP

Discussion

In the present study, we showed that the MUC5B concentration and MUC5B/total protein ratio in SCAP group were obviously lower than those in NSCAP group. The MUC5B/total protein ratio was an independent factor associated with CAP severity. We speculate that the disproportion of respiratory MUC5B plays an important role in regulating pulmonary inflammation in severe CAP.

MUC5B is the main expressed mucin in normal human and mouse airway [23, 24]. It plays a constitutive role in mucus barrier which traps and eliminates particulates and pathogens via mucociliary clearance (MCC) [25, 26]. In vivo and vitro experiments showed MUC5B expression could be induced by multiple pathogens, such as Rhinovirus (RV) [27], Mengovirus [28], Pseudomonas aeruginosa (PA) [29], Mycoplasma pneumoniae [30], A. pleuropneumoniae [31] and Pneumocystis [32]. The mechanism mainly involves STAT3-STAT6/EGFR-FOXA2 signaling [29, 30, 33]. Overexpressed MUC5B can bind to pathogens to prevent their attachment to the epithelium and initiate the clearance of airway pathogens [34, 35]. Furthermore, Muc5b defect increases the accumulation of pathogens in mice respiratory tract, which leads to chronic bacterial infection and hardly dissolved inflammation [9, 36]. By contrast, Muc5AC is the other secreted mucin expressed in airway, but it is not required for MCC or for diminishing infections in the airway [9]. It was concluded that MUC5B is the only secreted mucin that regulates airway homeostasis and mucosal immunity in humans [9]. In our observational study, the result showed MUC5B/total protein ratio was significantly related with CAP severity. However, whether lower concentration of MUC5B was involved in the develop of CAP severity was uncertain. We assume that MUC5B disproportion may diminish the barrier function of respiratory tract during CAP pathological process, but the hypothesis needs to be proved by further animal experiments.

Furthermore, we assessed the relationship between MUC5B and inflammatory factors. The results showed that the SCAP patients exhibited an increase in a broad scope of cytokines in BALF, especially IL6, IL13 and IL17. MUC5B/total protein ratio was negatively correlated with levels of IL6, IL10, IL13 and IL17, especially IL6 (p = 0.001) and IL17 (p = 0.002). IL6 is a pro-inflammatory cytokine involved in the pathogenesis of airway inflammatory diseases [37]. It decides CD4 + T cell fate and promotes preferential Th2 differentiation [38, 39]. In vitro study has demonstrated that IL-6 regulates Muc5b expression via the ERK signaling pathway [40]. IL-17 is also a strong pro-inflammatory factor that can induce excess inflammation through cytokine cascade [41]. It has been reported that IL-17 mediates Muc5b expression by the ERK signaling pathway and NF-kB-based transcriptional mechanism [40, 42]. MUC5B disproportion was correlated with high IL6 and IL17, indicating its contribution to lung inflammatory augmentation in severe CAP. We suggest that multiple inflammatory pathways coordinate with MUC5B disproportion regulate CAP pathogenesis.

MUC5B disproportion could also be detected in other pulmonary diseases and smoke exposure. The SPIROMICS data showed that MUC5B concentration in sputum increased with COPD severity [13]. Ever-smokers (current and former smokers) without evidence of COPD also had a higher concentration of MUC5B in sputum than no-smoke controls [43]. Our studies excluded patients with history of COPD. But the percentage of ever-smokers in NSCAP group was slightly higher than the SCAP group. It seems that smoke exposure might be partially accountable to the higher MUC5B level in NSCAP group. But when comparing the MUC5B level between ever-smokers and no-smokers, no significant difference was detected neither in the NSCAP group nor in the SCAP group. We assumed there may be limited impact of smoke exposure on the level of MUC5B. In the future we would like to conduct a randomized controlled trail to clarify this issue. MUC5B disproportion could also be found in other pulmonary diseases. In Non-CF Bronchiectasis (NCFB) study, the ratio of MUC5AC to MUC5B was about 4 times higher in NCFB patients than in healthy controls [14]. In asthma, MUC5B levels decreased or remained the same, while other types of mucin levels were increased significantly [44]. The latest reports showed abnormal MUC5B expression in COVID-19 patients [45]. Further study found MUC5B playing a protective role against COVID-19 [46]. We suggested that regulating MUC5B proportion might be a therapy target for SCAP patients in future. A recent research has proven that restoring Muc5b level can improve lung function and alleviate inflammatory responses in a rodent model [47], but more studies are needed to confirm the role of MUC5B in SCAP development.

Limitations

First, this result was based on a small population sized cross-sectional study. The patients included in the study underwent BAL as standard of diagnosis. It may lead to a selection bias. In the further, we would like to conduct a randomized controlled trial to get results nearer to true circumstance. Second, the possible difference in MUC5B concentration between BALF and spontaneous sputum should be considered. Another issue is that we used immunoblotting to detect the concentration of MUC5B by antibody binding reaction, the accuracy of which might be affected by complex patterns of MUC5B glycosylation. These limitations will be overcome in future studies.

Conclusions

Respiratory MUC5B disproportion is related to CAP severity. MUC5B/total protein ratio is inversely correlated with the levels of inflammatory cytokines and may serve as an assessment marker and a potential therapeutic target for severe CAP.

Availability of data and materials

The datasets used and analysed during the current study are available from the corresponding author on reasonable request.

Abbreviations

CAP:

Community-acquired pneumonia

SCAP:

Severe CAP

NSCAP:

Non-severe CAP

COPD:

Chronic obstructive pulmonary disease

MUC5B:

Mucin 5B

MUC5AC:

Mucin 5AC

BAL:

Bronchoalveolar lavage

BALF:

Bronchoalveolar lavage fluid

ELISA:

Enzyme-linked immunosorbent assay

ROC:

Receiver operating characteristic

AUC:

Area under the curve

ICU:

Intensive care unit

CT:

Computerized tomography

EHR:

Electronic hospital records

CURB-65:

Confusion, urea level, respiratory rate, blood pressure, and age > 65 years

WBC:

White blood cells

NE%:

Percentage of neutrophils

LYM%:

Percentage of lymphocytes

MO%:

Percentage of monocytes

EO%:

Percentage of eosinophilic granulocytes

PLT:

Blood platelets

LDH:

Lactate dehydrogenase

CRP:

C-reaction protein

ESR:

Erythrocyte sedimentation rate

Fib:

Fibrinogen

D-D:

D-dimer

IL6:

Interleukin-6

IL10:

Interleukin-10

IFNγ:

Interferon-γ

IL13:

Interleukin-13

IL17:

Interleukin-17

IQR:

Interquartile range

CI:

Confidence interval

OR:

Odds ratio

rs :

Spearman rho correlation coefficients

References

  1. Welte T, Torres A, Nathwani D. Clinical and economic burden of community-acquired pneumonia among adults in Europe. Thorax. 2012;67(1):71–9.

    CAS  PubMed  Article  Google Scholar 

  2. Weiss AJ, Wier LM, Stocks C, Blanchard J. Overview of emergency department visits in the United States. Statistical Brief #174 (Healthcare Cost and Utilization Project (HCUP) Statistical Briefs [Internet]). 2011.

  3. Woodhead M, Welch CA, Harrison DA, Bellingan G, Ayres JG. Community-acquired pneumonia on the intensive care unit: secondary analysis of 17,869 cases in the ICNARC Case Mix Programme Database. Crit Care. 2006;10(Suppl 2):S1.

    PubMed  PubMed Central  Article  Google Scholar 

  4. Lanks CW, Musani AI, Hsia DW. Community-acquired pneumonia and hospital-acquired pneumonia. Med Clin North Am. 2019;103(3):487–501.

    PubMed  Article  Google Scholar 

  5. Christ-Crain M, Opal SM. Clinical review: the role of biomarkers in the diagnosis and management of community-acquired pneumonia. Crit Care. 2010;14(1):203.

    PubMed  PubMed Central  Article  Google Scholar 

  6. Rautanen A, Mills TC, Gordon AC, Hutton P, Steffens M, Nuamah R, Chiche JD, Parks T, Chapman SJ, Davenport EE, Elliott KS, Bion J, Lichtner P, Meitinger T, Wienker TF, Caulfield MJ, Mein C, Bloos F, Bobek I, Cotogni P, Sramek V, Sarapuu S, Kobilay M, Ranieri VM, Rello J, Sirgo G, Weiss YG, Russwurm S, Schneider EM, Reinhart K, Holloway PA, Knight JC, Garrard CS, Russell JA, Walley KR, Stuber F, Hill AV, Hinds CJ. Genome-wide association study of survival from sepsis due to pneumonia: an observational cohort study. Lancet Respir Med. 2015;3(1):53–60.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  7. Dekker J, Rossen JW, Buller HA, Einerhand AW. The MUC family: an obituary. Trends Biochem Sci. 2002;27(3):126–31.

    CAS  PubMed  Article  Google Scholar 

  8. Rose MC, Voynow JA. Respiratory tract mucin genes and mucin glycoproteins in health and disease. Physiol Rev. 2006;86(1):245–78.

    CAS  PubMed  Article  Google Scholar 

  9. Roy MG, Livraghi-Butrico A, Fletcher AA, McElwee MM, Evans SE, Boerner RM, Alexander SN, Bellinghausen LK, Song AS, Petrova YM, Tuvim MJ, Adachi R, Romo I, Bordt AS, Bowden MG, Sisson JH, Woodruff PG, Thornton DJ, Rousseau K, De la Garza MM, Moghaddam SJ, Karmouty-Quintana H, Blackburn MR, Drouin SM, Davis CW, Terrell KA, Grubb BR, O’Neal WK, Flores SC, Cota-Gomez A, Lozupone CA, Donnelly JM, Watson AM, Hennessy CE, Keith RC, Yang IV, Barthel L, Henson PM, Janssen WJ, Schwartz DA, Boucher RC, Dickey BF, Evans CM. Muc5b is required for airway defence. Nature. 2014;505(7483):412–6.

    CAS  PubMed  Article  Google Scholar 

  10. Sepper R, Prikk K, Metsis M, Sergejeva S, Pugatsjova N, Bragina O, Marran S, Fehniger TE. Mucin5B expression by lung alveolar macrophages is increased in long-term smokers. J Leukoc Biol. 2012;92(2):319–24.

    CAS  PubMed  Article  Google Scholar 

  11. Ostedgaard LS, Moninger TO, McMenimen JD, Sawin NM, Parker CP, Thornell IM, Powers LS, Gansemer ND, Bouzek DC, Cook DP, Meyerholz DK, Abou AM, Stoltz DA, Welsh MJ. Gel-forming mucins form distinct morphologic structures in airways. Proc Natl Acad Sci USA. 2017;114(26):6842–7.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  12. Seibold MA, Wise AL, Speer MC, Steele MP, Brown KK, Loyd JE, Fingerlin TE, Zhang W, Gudmundsson G, Groshong SD, Evans CM, Garantziotis S, Adler KB, Dickey BF, du Bois RM, Yang IV, Herron A, Kervitsky D, Talbert JL, Markin C, Park J, Crews AL, Slifer SH, Auerbach S, Roy MG, Lin J, Hennessy CE, Schwarz MI, Schwartz DA. A common MUC5B promoter polymorphism and pulmonary fibrosis. N Engl J Med. 2011;364(16):1503–12.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  13. Kesimer M, Ford AA, Ceppe A, Radicioni G, Cao R, Davis CW, Doerschuk CM, Alexis NE, Anderson WH, Henderson AG, Barr RG, Bleecker ER, Christenson SA, Cooper CB, Han MK, Hansel NN, Hastie AT, Hoffman EA, Kanner RE, Martinez F, Paine RR, Woodruff PG, O’Neal WK, Boucher RC. Airway mucin concentration as a marker of chronic bronchitis. N Engl J Med. 2017;377(10):911–22.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  14. Ramsey KA, Chen A, Radicioni G, Lourie R, Martin M, Broomfield A, Sheng YH, Hasnain SZ, Radford-Smith G, Simms LA, Burr L, Thornton DJ, Bowler SD, Livengood S, Ceppe A, Knowles MR, Noone PS, Donaldson SH, Hill DB, Ehre C, Button B, Alexis NE, Kesimer M, Boucher RC, McGuckin MA. Airway mucus hyperconcentration in non-cystic fibrosis bronchiectasis. Am J Respir Crit Care Med. 2020;201(6):661–70.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  15. Wu X, Li Y, Zhang M, Li M, Zhang R, Lu X, Gao W, Li Q, Xia Y, Pan P, Li Q. Etiology of severe community-acquired pneumonia in adults based on metagenomic next-generation sequencing: a prospective multicenter study. Infect Dis Ther. 2020;9(4):1003–15.

    PubMed  PubMed Central  Article  Google Scholar 

  16. Metlay JP, Waterer GW, Long AC, Anzueto A, Brozek J, Crothers K, Cooley LA, Dean NC, Fine MJ, Flanders SA, Griffin MR, Metersky ML, Musher DM, Restrepo MI, Whitney CG. Diagnosis and Treatment of Adults with Community-acquired Pneumonia. An official clinical practice guideline of the American Thoracic Society and Infectious Diseases Society of America. Am J Respir Crit Care Med. 2019;200(7):e45–67.

    PubMed  PubMed Central  Article  Google Scholar 

  17. Niederman MS, Bass JJ, Campbell GD, Fein AM, Grossman RF, Mandell LA, Marrie TJ, Sarosi GA, Torres A, Yu VL. Guidelines for the initial management of adults with community-acquired pneumonia: diagnosis, assessment of severity, and initial antimicrobial therapy. American Thoracic Society. Medical Section of the American Lung Association. Am Rev Respir Dis. 1993;148(5):1418–26.

    CAS  PubMed  Article  Google Scholar 

  18. Mandell LA, Wunderink RG, Anzueto A, Bartlett JG, Campbell GD, Dean NC, Dowell SF, File TJ, Musher DM, Niederman MS, Torres A, Whitney CG. Infectious Diseases Society of America/American Thoracic Society consensus guidelines on the management of community-acquired pneumonia in adults. Clin Infect Dis. 2007;44(Suppl 2):S27–72.

    CAS  PubMed  Article  Google Scholar 

  19. Meyer KC, Raghu G, Baughman RP, Brown KK, Costabel U, du Bois RM, Drent M, Haslam PL, Kim DS, Nagai S, Rottoli P, Saltini C, Selman M, Strange C, Wood B. An official American Thoracic Society clinical practice guideline: the clinical utility of bronchoalveolar lavage cellular analysis in interstitial lung disease. Am J Respir Crit Care Med. 2012;185(9):1004–14.

    PubMed  Article  Google Scholar 

  20. Hellyer TP, Morris AC, McAuley DF, Walsh TS, Anderson NH, Singh S, Dark P, Roy AI, Baudouin SV, Wright SE, Perkins GD, Kefala K, Jeffels M, McMullan R, O’Kane CM, Spencer C, Laha S, Robin N, Gossain S, Gould K, Ruchaud-Sparagano MH, Scott J, Browne EM, MacFarlane JG, Wiscombe S, Widdrington JD, Dimmick I, Laurenson IF, Nauwelaers F, Simpson AJ. Diagnostic accuracy of pulmonary host inflammatory mediators in the exclusion of ventilator-acquired pneumonia. Thorax. 2015;70(1):41–7.

    PubMed  Article  Google Scholar 

  21. Sehgal IS, Dhooria S, Choudhary H, Aggarwal AN, Garg M, Chakrabarti A, Agarwal R. Utility of serum and bronchoalveolar lavage fluid galactomannan in diagnosis of chronic pulmonary aspergillosis. J Clin Microbiol. 2019;57(3):e01821-e1918.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  22. Monte AA, Sun H, Rapp-Olsson AM, Mohamed F, Gawarammana I, Buckley NA, Evans CM, Yang IV, Schwartz DA. The plasma concentration of MUC5B is associated with clinical outcomes in paraquat-poisoned patients. Am J Respir Crit Care Med. 2018;197(5):663–5.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  23. Lachowicz-Scroggins ME, Yuan S, Kerr SC, Dunican EM, Yu M, Carrington SD, Fahy JV. Abnormalities in MUC5AC and MUC5B protein in airway mucus in asthma. Am J Respir Crit Care Med. 2016;194(10):1296–9.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  24. Zhu Y, Ehre C, Abdullah LH, Sheehan JK, Roy M, Evans CM, Dickey BF, Davis CW. Munc13-2−/− baseline secretion defect reveals source of oligomeric mucins in mouse airways. J Physiol. 2008;586(7):1977–92.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  25. Fahy JV, Dickey BF. Airway mucus function and dysfunction. N Engl J Med. 2010;363(23):2233–47.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  26. Button B, Cai LH, Ehre C, Kesimer M, Hill DB, Sheehan JK, Boucher RC, Rubinstein M. A periciliary brush promotes the lung health by separating the mucus layer from airway epithelia. Science. 2012;337(6097):937–41.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  27. Inoue D, Yamaya M, Kubo H, Sasaki T, Hosoda M, Numasaki M, Tomioka Y, Yasuda H, Sekizawa K, Nishimura H, Sasaki H. Mechanisms of mucin production by rhinovirus infection in cultured human airway epithelial cells. Respir Physiol Neurobiol. 2006;154(3):484–99.

    CAS  PubMed  Article  Google Scholar 

  28. Rosenthal LA, Szakaly RJ, Amineva SP, Xing Y, Hill MR, Palmenberg AC, Gern JE, Sorkness RL. Lower respiratory tract infection induced by a genetically modified picornavirus in its natural murine host. PLoS ONE. 2012;7(2):e32061.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  29. Hao Y, Kuang Z, Xu Y, Walling BE, Lau GW. Pyocyanin-induced mucin production is associated with redox modification of FOXA2. Respir Res. 2013;14:82.

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  30. Hao Y, Kuang Z, Jing J, Miao J, Mei LY, Lee RJ, Kim S, Choe S, Krause DC, Lau GW. Mycoplasma pneumoniae modulates STAT3-STAT6/EGFR-FOXA2 signaling to induce overexpression of airway mucins. Infect Immun. 2014;82(12):5246–55.

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  31. Kim CH, Oh Y, Han K, Seo HW, Kim D, Kang I, Park C, Jang KY, Kim SH, Chae C. Expression of secreted mucins (MUC2, MUC5AC, MUC5B, and MUC6) and membrane-bound mucin (MUC4) in the lungs of pigs experimentally infected with Actinobacillus pleuropneumoniae. Res Vet Sci. 2012;92(3):486–91.

    CAS  PubMed  Article  Google Scholar 

  32. Mendez A, Rojas DA, Ponce CA, Bustamante R, Beltran CJ, Toledo J, Garcia-Angulo VA, Henriquez M, Vargas SL. Primary infection by Pneumocystis induces Notch-independent Clara cell mucin production in rat distal airways. PLoS ONE. 2019;14(6):e217684.

    Article  CAS  Google Scholar 

  33. Rojas DA, Iturra PA, Mendez A, Ponce CA, Bustamante R, Gallo M, Borquez P, Vargas SL. Increase in secreted airway mucins and partial Muc5b STAT6/FoxA2 regulation during Pneumocystis primary infection. Sci Rep. 2019;9(1):2078.

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  34. Ermund A, Meiss LN, Rodriguez-Pineiro AM, Bahr A, Nilsson HE, Trillo-Muyo S, Ridley C, Thornton DJ, Wine JJ, Hebert H, Klymiuk N, Hansson GC. The normal trachea is cleaned by MUC5B mucin bundles from the submucosal glands coated with the MUC5AC mucin. Biochem Biophys Res Commun. 2017;492(3):331–7.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  35. White MR, Helmerhorst EJ, Ligtenberg A, Karpel M, Tecle T, Siqueira WL, Oppenheim FG, Hartshorn KL. Multiple components contribute to ability of saliva to inhibit influenza viruses. Oral Microbiol Immunol. 2009;24(1):18–24.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  36. Janssen WJ, Stefanski AL, Bochner BS, Evans CM. Control of lung defence by mucins and macrophages: ancient defence mechanisms with modern functions. Eur Respir J. 2016;48(4):1201–14.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  37. Kwak S, Choi YS, Na HG, Bae CH, Song SY, Kim YD. Glyoxal and methylglyoxal as E-cigarette vapor ingredients-induced pro-inflammatory cytokine and mucins expression in human nasal epithelial cells. Am J Rhinol Allergy. 2020;35(2):213–20.

    PubMed  Article  Google Scholar 

  38. Balkrishna A, Solleti SK, Singh H, Verma S, Sharma N, Nain P, Varshney A. Herbal decoction Divya–Swasari–Kwath attenuates airway inflammation and remodeling through Nrf-2 mediated antioxidant lung defence in mouse model of allergic asthma. Phytomedicine. 2020;78:153295.

    CAS  PubMed  Article  Google Scholar 

  39. Dienz O, Rincon M. The effects of IL-6 on CD4 T cell responses. Clin Immunol. 2009;130(1):27–33.

    CAS  PubMed  Article  Google Scholar 

  40. Chen Y, Thai P, Zhao YH, Ho YS, DeSouza MM, Wu R. Stimulation of airway mucin gene expression by interleukin (IL)-17 through IL-6 paracrine/autocrine loop. J Biol Chem. 2003;278(19):17036–43.

    CAS  PubMed  Article  Google Scholar 

  41. Iwakura Y, Ishigame H, Saijo S, Nakae S. Functional specialization of interleukin-17 family members. Immunity. 2011;34(2):149–62.

    CAS  PubMed  Article  Google Scholar 

  42. Fujisawa T, Chang MM, Velichko S, Thai P, Hung LY, Huang F, Phuong N, Chen Y, Wu R. NF-kappaB mediates IL-1beta- and IL-17A-induced MUC5B expression in airway epithelial cells. Am J Respir Cell Mol Biol. 2011;45(2):246–52.

    CAS  PubMed  Article  Google Scholar 

  43. Radicioni G, Ceppe A, Ford AA, Alexis NE, Barr RG, Bleecker ER, Christenson SA, Cooper CB, Han MK, Hansel NN, Hastie AT, Hoffman EA, Kanner RE, Martinez FJ, Ozkan E, Paine R, Woodruff PG, O’Neal WK, Boucher RC, Kesimer M. Airway mucin MUC5AC and MUC5B concentrations and the initiation and progression of chronic obstructive pulmonary disease: an analysis of the SPIROMICS cohort. Lancet Respir Med. 2021;9(11):1241–54.

    CAS  PubMed  Article  Google Scholar 

  44. Welsh KG, Rousseau K, Fisher G, Bonser LR, Bradding P, Brightling CE, Thornton DJ, Gaillard EA. MUC5AC and a glycosylated variant of MUC5B alter mucin composition in children with acute asthma. Chest. 2017;152(4):771–9.

    PubMed  PubMed Central  Article  Google Scholar 

  45. Liu Y, Lv J, Liu J, Li M, Xie J, Lv Q, Deng W, Zhou N, Zhou Y, Song J, Wang P, Qin C, Tong WM, Huang B. Mucus production stimulated by IFN-AhR signaling triggers hypoxia of COVID-19. Cell Res. 2020;30(12):1078–87.

    CAS  PubMed  Article  Google Scholar 

  46. Chatterjee M, van Putten J, Strijbis K. Defensive properties of mucin glycoproteins during respiratory infections-relevance for SARS-CoV-2. MBio. 2020;11(6):e02374-e2420.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  47. Song Y, Wang W, Xie Y, Xiang B, Huang X, Guan W, Zheng J. Carbocisteine inhibits the expression of Muc5b in COPD mouse model. Drug Des Dev Ther. 2019;13:3259–68.

    CAS  Article  Google Scholar 

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Acknowledgements

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Funding

This work was supported by the National Natural Science Foundation of China (82072158), Jiangsu Province’s key provincial talents program (WSN-003).

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LF analysed the data, prepared the original draft. YL and YW recruited the subjects and did the BAL procedure. XZ and YW were responsible for Data collection and validation. HS was responsible for conceptualization, methodology, writing—review and editing. JZ contributed to study supervision and funding acquisition. All authors read and approved the final manuscript.

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Correspondence to Hao Sun or Jinsong Zhang.

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Fan, L., Lu, Y., Wang, Y. et al. Respiratory MUC5B disproportion is involved in severe community-acquired pneumonia. BMC Pulm Med 22, 90 (2022). https://doi.org/10.1186/s12890-022-01870-x

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Keywords

  • Community-acquired pneumonia
  • MUC5B
  • Severity
  • Disproportion