Article Text

Prognostic significance of serum cytokines during acute exacerbation of idiopathic interstitial pneumonias treated with thrombomodulin
  1. Toru Arai1,
  2. Hiroto Matsuoka2,
  3. Masaki Hirose1,
  4. Hiroshi Kida3,4,
  5. Suguru Yamamoto5,
  6. Yoshitaka Ogata6,
  7. Masahide Mori3,
  8. Kazuyoshi Hatsuda1,
  9. Chikatoshi Sugimoto1,
  10. Kazunobu Tachibana1,
  11. Masanori Akira1 and
  12. Yoshikazu Inoue1
  1. 1Clinical Research Center, National Hospital Organization Kinki-Chuo Chest Medical Center, Sakai City, Japan
  2. 2Department of Respiratory Medicine, Osaka Prefectural Hospital Organization Osaka Habikino Medical Center, Habikino City, Japan
  3. 3Department of Respiratory Medicine, National Hospital Organization Osaka Toneyama Medical Center, Toyonaka City, Japan
  4. 4Department of Respiratory Medicine and Clinical Immunology, Osaka University Graduate School of Medicine, Suita City, Japan
  5. 5Department of Respiratory Medicine, National Hospital Organization Osaka Minami Medical Center, Kawachinagano City, Japan
  6. 6Department of Critical Care Medicine, Yao Tokushukai Hospital, Yao City, Japan
  1. Correspondence to Dr Yoshikazu Inoue; giichiyi{at}me.com

Abstract

Background Acute exacerbation (AE) has been reported to herald a poor prognosis in idiopathic pulmonary fibrosis and is now thought to do so in idiopathic interstitial pneumonias (IIPs). However, the pathophysiology of AE-IIPs is not sufficiently understood. In our previously reported SETUP trial, we found better survival in patients with AE-IIPs treated with corticosteroids and thrombomodulin than in those treated with corticosteroids alone. In that study, we collected serum samples to evaluate changes in cytokine levels and retrospectively examined the prognostic significance and pathophysiological role of serum cytokines in patients with AE-IIPs.

Methods This study included 28 patients from the SETUP trial for whom serial serum samples had been prospectively obtained. AE-IIPs were diagnosed using the Japanese Respiratory Society criteria. All patients were treated with intravenous thrombomodulin and corticosteroids from 2014 to 2016. Serum levels of 27 cytokines were measured using Bio-Plex. The high-resolution CT pattern at the time of diagnosis of AE was classified as diffuse or non-diffuse.

Results Univariate analysis revealed that higher serum levels of interleukin (IL)-2, IL-7, IL-9, IL-12, IL13, basic fibroblast growth factor, granulocyte-macrophage colony-stimulating factor, interferon-γ inducible protein-10, platelet-derived growth factor and regulated on activation, normal T cell expressed and secreted (RANTES) at AE were significant predictors of 90-day survival. The HRCT pattern was also a significant clinical predictor of 90-day survival. Multivariate analysis with stepwise selection identified a higher serum RANTES level at AE to be a significant predictor of 90-day survival, including after adjustment for HRCT pattern. Multivariate analysis with stepwise selection suggested that a marked increase in the serum IL-10 level on day 8 could predict 90-day mortality.

Conclusions A higher serum RANTES level at AE the time of diagnosis predicted a good survival outcome, and an elevated serum IL-10 level on day 8 predicted a poor survival outcome.

Trial registration number UMIN000014969.

  • interstitial fibrosis
  • cytokine biology

Data availability statement

No data are available. The data that support the findings of this study have not been made available because this study was approved in 2014 and data sharing was not included in the design of this study.

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This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/.

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Key messages

  • What is the most important cytokine to predict survival of acute exacerbation (AE) in idiopathic interstitial pneumonias (IIPs)?

  • We found that a higher serum regulated on activation, normal T cell expressed and secreted level at the time of diagnosis of AE predicted a good survival outcome, and an elevated serum interleukin-10 level on day 8 predicted a poor outcome.

  • The result might suggest pathophysiological significance of these cytokines and lead to the new treatment of AE-IIPs.

Introduction

Idiopathic pulmonary fibrosis (IPF) is a lung disease of unknown aetiology and has a poor prognosis.1 2 Some patients with IPF experience rapid potentially fatal deterioration1–4 known as acute exacerbation (AE) of IPF (AE-IPF). AE is the most common cause of death in IPF,4 despite affected patients usually being treated with corticosteroids according to the 2011 American Thoracic Society (ATS)/European Respiratory Society (ERS)/Japanese Respiratory Society (JRS)/Latin American Thoracic Association guidelines for diagnosis and management of IPF.1 Therefore, a better understanding of the pathophysiology of AE-IPF is required to improve its management. Furthermore, the prognosis of AE in unclassifiable idiopathic interstitial pneumonias (IIPs) or interstitial lung disease other than IIPs is as poor as that of IPF.5 6

Recombinant human soluble thrombomodulin (rhTM), which contains only the extracellular domain of thrombomodulin, has recently been approved for treatment of disseminated intravascular coagulation (DIC)7 and has been reported to be effective for AE-IPF8 when coupled with conventional corticosteroid therapy. We have previously reported on the efficacy of rhTM in patients with AE-IIPs who participated in our prospective multicentre SETUP trial.9 Thrombomodulin regulates coagulation10 and inhibits inflammation by preventing adhesion of neutrophils to the endothelium, decreasing the expression of adhesion molecules and enhancing the barrier function of endothelium and degradation of high-mobility group box 1.

Although the pathophysiology of AE-IPF is unknown, disordered integrity of epithelial cells, cellular inflammation, cytokines, matrix metalloproteinases, coagulation and fibrinolysis are likely to be involved, and rapid changes in these phenomena are thought to contribute to AE-IPF.4 Collard et al11 found that serum Krebs von den Lungen (KL)-6, interleukin (IL)-6 and thrombomodulin levels were higher in patients with AE-IPF than in those with stable IPF. Moreover, using a small number of lung specimens from patients with AE-IPF or stable IPF, Konishi et al12 found that gene expression of AE-IPF was associated with more severe epithelial injury and proliferation.

Although there have been a few reports on changes in serum levels of several cytokines in patients with AE-IPF,13–15 their importance in the pathophysiology and prognosis of AE-IPF and AE-IIPs has not been examined in sufficient depth. Therefore, in this retrospective study, we evaluated the prognostic and pathophysiological significance of serum cytokine levels in patients with AE-IIPs who had participated in the SETUP trial and from whom serum samples had been collected.

Materials and methods

Subjects

The SETUP trial included 39 patients with a diagnosis of AE-IIPs based on the modified JRS criteria16 who had been prospectively enrolled and treated with rhTM and conventional therapy, including corticosteroids and immunosuppressants, from 2014 to 2016. Patients with severe non-pulmonary disease, life-threatening bleeding, clinically significant infection, known hypersensitivity to rhTM, a cerebrovascular event within the past year or surgery within the previous month were excluded. Pregnancy or the possibility of pregnancy was an additional exclusion criterion. Serum samples had been collected from 28 of the 39 patients at the time of diagnosis of AE-IIPs (on day 1) and from 22 patients on day 8 (online supplemental figure 1). Patient characteristics of 28 patients with serum samples in the present study were similar to the rest of the subjects in SETUP trial (n=11) without serum samples (online supplemental table 1).

The trial was registered with the University Hospital Medical Information Network Center (28 August 2014). All participants in SETUP provided written informed consent.

Methods

Diagnosis of underlying IIPs and AE-IIPs

The underlying IPF was diagnosed based on the ATS/ERS/JRS/Latin American Thoracic Association guidelines for diagnosis and management of IPF.1 The diagnosis of IIPs was based on the ATS/ERS/JRS statement,17 and IIPs that could not be diagnosed as IPF was classified as non-IPF IIPs. Patients with non-IPF IIPs did not undergo surgical lung biopsy and were diagnosed to have unclassifiable IIPs.

AE-IIPs were diagnosed based on the following modified JRS diagnostic criteria for AE-IPF.16 (1) Within 1 month, the following three conditions should be satisfied: (A) progressively worsening dyspnoea; (B) new ground-glass opacities evident on high-resolution CT (HRCT) scans superimposed on background reticular opacity, traction bronchiectasis, traction bronchiolectasis or honeycombing; and (C) a reduction in resting partial pressure of oxygen in arterial blood (PaO2) of >10 Torr compared with previous measurements. (2) Other causes of acute respiratory impairment, such as infection, pneumothorax, cancer, pulmonary embolism and congestive cardiac failure, should be excluded. However, the possibility that some patients had AE triggered by infection4 could not be excluded because bronchoalveolar lavage could not be performed in all cases.

Treatment for AE-IIPs

Details of the treatment of the patients with AE-IIPs in the SETUP trial are provided in online supplemental table 2. Treatment included prednisolone with/without an immunosuppressant after intravenous administration of high-dose methylprednisolone for three consecutive days. Polymyxin B-immobilised fibre column direct hemoperfusion (PMX/DHP) therapy13 15 was administered in one case using the Toraymyxin system (Toray Medical, Tokyo, Japan), which was attached for 4–6 hours at a flow rate of 80 mL/min and repeated once within 48 hours. Nafamostat mesilate (Torii Pharmaceuticals, Tokyo, Japan) was used to reduce the risk of clot formation in the catheter. Anticoagulant and antiplatelet drugs were permitted only to treat comorbidities. Invasive or non-invasive positive pressure ventilation or nasal high flow therapy was introduced to maintain oxygenation in some patients with severe respiratory failure. rhTM was started at a rate of 380 U/kg/day for 6 days, as approved for treatment of DIC,7–9 on the day of AE-IIPs diagnosis.

Evaluation of AE-IIPs

AE-IIPs were evaluated before and at the time of diagnosis of AE as described in our previous report.9 Briefly, the severity of IIPs (stages I–IV, mildest to most severe) in the stable state was evaluated in most cases within 6 months before the time of diagnosis of AE according to the JRS criteria.16 Shortness of breath was evaluated based on the modified Medical Research Council score.18 DIC was diagnosed according to the Japanese Association for Acute Medicine scoring system.19 The fibrin degradation product level was classified as higher (≥10 mg/L) or lower (<10 mg/L). The HRCT pattern at the time of diagnosis of AE-IIPs was classified as peripheral, multifocal or diffuse using the definition proposed by Akira et al3 and subsequently according to whether it was diffuse or non-diffuse. Patients with a PaO2/fraction of inspired oxygen (FiO2) ratio ≤20020 were deemed to have severely impaired oxygenation.

Evaluation of serum biomarkers

Serum KL-6 levels were measured using a commercial ELISA kit (Eizai, Tokyo, Japan). The KL-6 cut-off level was 500 U/mL.9 Cytokine levels in the serum samples (pg/mL) were quantified using the Bio-Plex Suspension Array System with Bio-Plex Pro Human Cytokine Group 27-Plex Panel (Bio-Rad Laboratories, Hercules, California, USA) according to the manufacturer’s instructions.15 This panel was selected because we could simultaneously measure serum levels of chemokines, fibrotic cytokines and angiogenic cytokines, and it was used in our previous study.15 The cytokines measured included IL-1β, IL-1ra, IL-2, IL-4, IL-5, IL-6, IL-7. IL-8, IL-9, IL-10, IL-12 (p70), IL-13, IL-15, IL-17A, eotaxin/CC chemokine ligand (CCL) 11, basic fibroblast growth factor (b-FGF), granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage colony-stimulating factor, interferon (IFN)-γ, IFN-γ inducible protein 10 (IP-10)/CXC chemokine ligand (CXCL) 10, monocyte chemotactic protein-1 (MCP-1)/CCL2, macrophage inflammatory protein (MIP)-1α/CCL3, MIP-1β/CCL4, platelet-derived growth factor (PDGF)-BB, regulated on activation, normal T cell expressed and secreted (RANTES)/CCL5, tumour necrosis factor (TNF)-α and vascular endothelial growth factor (VEGF)-A. The cytokine levels in each patient, out of the range below or above, were defined to the upper range or half of the lower range, respectively. Serum IL-1β, IL-15 and VEGF-A levels at the time of diagnosis of AE were out of range in more than half of all cases (n=26, n=22 and n=19, respectively). These three cytokines were excluded from further examination.

Statistical analysis

Continuous and categorical data are presented as the median (IQR) or the number (percentage) and were compared between the rhTM and control arms using the Wilcoxon rank-sum test and Fisher’s exact test, respectively. Logistic regression analysis was performed to predict 90-day survival using clinical parameters, serum cytokine levels at the time of diagnosis of AE and the increase in serum cytokine levels on day 8. All statistical analyses were performed using JMP software V.11 (SAS Institute). All p values are two sided. A p value <0.05 was considered statistically significant.

Results

Patient characteristics

The 28 patients with AE-IIPs comprised eight with IPF and 20 with non-IPF IIPs. Clinical parameters before and at the time of diagnosis of AE were similar between those with AE-IPF and those with AE-non-IPF. The 90-day survival rate was similar between these two groups (table 1). Underlying IIPs were treated with antifibrotic drugs (n=5; nintedanib for one case and pirfenidone for four cases) and prednisolone (n=9) before the time of diagnosis of AE (table 1). Univariate logistic regression analysis revealed that use of antifibrotic drugs in a stable state, a diffuse HRCT pattern and higher serum KL-6 and lactate dehydrogenase levels at the time of diagnosis of AE were significant clinical predictors of 90-day mortality (table 2). Use of antifibrotic drugs in a stable state and a diffuse HRCT pattern at the time of diagnosis of AE were significant predictors in multivariate analysis. Use of antifibrotic drugs at stable state was significantly associated with introduction of long-term oxygen therapy (p=0.0047) and disease severity stage IV (p=0.0047) before the diagnosis of AE (online supplemental table 3).

Table 1

Patient characteristics in this study*

Table 2

Prognostic significance of clinical parameters in patients with AE-IIPs determined by logistic regression analysis

There was no significant difference in serum cytokine levels between the AE-IPF and AE-non-IPF groups (online supplemental table 4).

Survival and cytokines at the time of diagnosis of AE

Serum cytokine levels were compared between patients who were alive at 90 days and those who were not. Serum IL-2, IL-7, IL-9, IL-13, GM-CSF, IP-10, PDGF-BB and RANTES/CCL5 levels were higher in survivors than in non-survivors (table 3). Univariate logistic regression analysis revealed higher IL-2, IL-7, IL-9, IL-12, IL13, b-FGF, GM-CSF, IP-10, PDGF-BB and RANTES/CCL5 levels to be significant predictors of 90-day survival (table 4). Multivariate logistic analysis with stepwise selection revealed that IL-7 and RANTES/CCL5 should be included in the model; multivariate analysis using these two parameters identified RANTES/CCL5 to be a significant predictor of 90-survival (table 4). RANTES/CCL5 was a significant predictor after adjustment for HRCT pattern at the time of diagnosis of AE and antifibrotic drug use before AE (table 4). RANTES/CCL5 was a significant predictor of 90-day survival in AE-IIPs without use of antifibrotic drugs before AE (p=0.010, data not shown).

Table 3

Serum cytokines at the time of diagnosis of AE-IIPs: comparison between 90-day survivors and non-survivors*

Table 4

Prognostic significance of serum cytokines for AE-IIPs determined by logistic regression analysis for 90-day mortality

RANTES/CCL5 level and clinical parameters

The serum RANTES/CCL5 level was not significantly associated with any clinical parameter suggesting severe underlying IIPs in a stable state or during AE, including use of long-term oxygen therapy in a stable state and the PaO2/FiO2 and HRCT pattern at the time of diagnosis of AE. There was a significant correlation between the serum RANTES/CCL5 level and administration of antifibrotic drugs before AE (online supplemental table 5); however, only five patients were treated with these agents (table 1).

Cytokine levels from days 1–8

By day 8, there was a significant increase in serum IL-4, IL-13, eotaxin and b-FGF levels and a significant decrease in serum IL1-ra, IL-9, IL-10, IFN-γ, IP-10, MIP-1β, RANTES/CCL5 and TNF-α levels (online supplemental table 6).

Survival and increased cytokines on day 8

The increase in serum IL-2, IL-5, IL-7, IL-9, IL-10, G-CSF, IFN-γ and MCP-1 levels on day 8 was significantly smaller in survivors than in non-survivors at 90 days (table 5). The median increase in the levels of these cytokines except for IL-2 was less than zero, suggesting a decrease on day 8 in 90-day survivors. Univariate logistic regression analysis revealed that an increase in IL-7, IL-10, G-CSF, IFN-γ and MCP-1 levels suggested mortality at 90 days, and multivariate analysis with stepwise selection suggested that an increase in IL-10 on day 8 could predict 90-day mortality (table 6).

Table 5

Increase in serum cytokines in patients with AE-IIPs who were alive at 90 days and those who were not*

Table 6

Prognostic significance of an increase in serum cytokine levels at day 8 from baseline levels for AE-IIPs: logistic regression analysis of 90-day mortality

Increased serum IL-10 and clinical parameters

There was no association between an increased IL-10 level on day 8 and any other clinical parameter at the time of diagnosis of AE or in a stable state (online supplemental table 7).

Discussion

We have examined the levels of multiple cytokines in serum samples that were prospectively collected from patients with AE-IIPs enrolled in the SETUP trial.9 This type of evaluation is rare. We found that a higher serum RANTES/CCL5 level at the time of diagnosis of AE-IIPs suggested a good prognosis after treatment with corticosteroids and thrombomodulin. Furthermore, a greater increase in serum IL-10 at 1 week after the time of diagnosis of AE was a significant predictor of a poor prognosis.

RANTES/CCL5 is reportedly a chemotactic factor for lymphocytes, eosinophils, monocytes and mast cells and is produced by lymphocytes, fibroblasts, platelets, endothelial cells and epithelial cells.21 RANTES/CCL5 has been found to be elevated in the bronchoalveolar lavage fluid of patients with nonspecific interstitial pneumonia22 and in those with IPF.23 Pierce et al24 showed that RANTES/CCL5 works with CCL21 to affect pulmonary fibrosis. RANTES/CCL5 is reported to increase inflammation and fibrosis in the presence of renal or hepatic disease.25 Hence, the good prognosis suggested by a higher RANTES/CCL5 level at the time of diagnosis of AE in our study indicates that it has an important pathophysiological role in AE-IIPs.

We also found that serum IL-7, IL-9, IL-13, GM-CSF, IP-10, PDGF-BB and RANTES/CCL5 levels were significantly higher in survivors than in non-survivors. PDGF26 and IL-1327 are profibrotic cytokines, similar to RANTES/CCL5,21–25 while IL-7,28 29 GM-CSF30 and IP-10/CXCL1031 are antifibrotic cytokines. Whether IL-9 is profibrotic32 or antifibrotic33 is controversial; however, IL-9 is associated with regulation of pulmonary fibrosis. The results of our study suggest that an early increase in fibrosis-associated profibrotic and antifibrotic cytokines might affect the prognosis of AE-IIPs.

The pathophysiology of AE-IIPs is not yet fully clarified; however, it is thought to involve acute epithelial injury superimposed on chronic progressive interstitial lung disease. If the epithelial cells regenerate rapidly, the intact alveolar epithelial cell layer can suppress proliferation of fibroblasts and pulmonary fibrosis may be inhibited.26 34 35 Although overgrowth of fibroblasts and overproduction of collagen are not favourable for pulmonary fibrosis, keratinocyte growth factor secreted by fibroblasts helps recovery from injury-stimulated proliferation of alveolar epithelial cells.36 Hence, rapid recruitment of fibroblasts at the site of injury by fibrosis-related cytokines and increased production of keratinocyte growth factor might lead to rapid repair of alveolar epithelial cells. Rapid reduction in fibrosis-related cytokine levels and proliferating fibroblasts might be necessary to prevent development of fibrosis.

The pathophysiology of AE-IPF has some similarity to that of the COVID-19 caused by SARS-CoV-2.37 The virus infects the epithelium of the upper and lower airways via ACE 2 receptors, and diffuse alveolar damage occurs after extensive apoptosis of alveolar epithelial cells. Recently, Sugiyama et al37 reported a low CCL17 level at the time of diagnosis of SARS-CoV-2 infection to be a significant predictor of severe COVID-19. CCL17 is reported to be a profibrotic cytokine in mice with bleomycin-induced lung injury38 and to be elevated in bronchioalveolar lavage fluid from patients with IPF.39 The disadvantage of lower levels of profibrotic cytokines in early lung injury might be similar between COVID-19 infection and AE-IPF or AE-IIPs.

Fibrocytes are circulating cells with fibroblast-like properties that are involved in both normal tissue wound repair and fibrosis. Fibrocytes secrete a variety of cytokines to augment fibrotic lesions by activating resident fibroblasts.40 Fibrocytes are an important source of fibroblasts and myofibroblasts. In one study, circulating fibrocytes indicated a poor prognosis in IPF,41 with circulating fibrocyte counts in the blood of patients with AE-IPF found to be elevated by up to 10-fold in comparison with the values in stable IPF.

Human fibrocytes express several chemokine receptors, including CCR2, CCR5, CCR7 and CXCR4.42 RANTES/CCL5 is known to induce migration of circulating fibrocytes in patients with severe asthma43 and might be associated with pulmonary fibrosis. Although this hypothesis supports the notion that RANTES/CCL5 worsens pulmonary fibrosis, Tai et al44 demonstrated in a mouse model that intravenous infusion of fibrocytes ameliorated lipopolysaccharide-induced acute lung injury by decreasing inflammatory cytokine and chemokine levels and reducing accumulation of neutrophils in the lung. Early recruitment of an appropriate number of fibrocytes might lead to normal repair instead of pulmonary fibrosis; this hypothesis is consistent with our finding that higher levels of serum RANTES/CCL5 at the time of diagnosis of AE are associated with a good prognosis in patients with AE-IIPs.

IL-7 inhibits production of transforming growth factor (TGF)-β and fibroblast signalling.28 Moreover, IL-7 and TGF-β play counter-regulatory roles in synthesis of collagen by fibroblasts in pulmonary fibrosis.29 We have shown that a higher IL-7 level at the time of diagnosis of AE can predict a good prognosis and that the IL-7 level was significantly lower on day 8 than at the time of diagnosis. We have previously reported that an increase in IL-7 24–48 hours after the start of PMX/DHP therapy predicts a good survival outcome.15 These results may seem inconsistent; however, the exact time course of the serum IL-7 level from the time of diagnosis of AE-IIPs (day 1) to day 8 is not known, and the peak level may be on day 3.

In this study, we demonstrated that a greater increase in serum IL-10 1 week after the time of diagnosis of AE was a significant predictor of a poor prognosis. IL-10 is a well-known anti-inflammatory cytokine that inhibits production of proinflammatory cytokines and chemokines by monocytes and macrophages.45 The profibrotic role of IL-10 is controversial. Silica-induced pulmonary fibrosis was markedly less severe in IL-10 deficient mice than in wild-type mice because of a reduction in lung levels of TGF-β, which is a potent inducer of pulmonary fibrosis.45 However, transient expression of IL-10 by gene transfer for less than 1 week reduced the severity of bleomycin-induced pulmonary fibrosis by reducing production and activation of TGF-β in bronchioalveolar lavage fluid when compared with mice that underwent control gene transfer.46 47 These inconsistent reports concerning the effect of IL-10 on fibrosis might reflect a difference in duration of IL-10 expression.

Long-term, lung-specific overexpression of IL-10 in mature mice for 1 and 3 months resulted in infiltration of mononuclear cells into the lung and increased expression of MCP-1/CCL2 mRNA48; moreover, pulmonary fibrosis in IL-10 transgenic mice was found to be inhibited by anti-MCP1/CCL2 antibody.48 Induction of MCP-1/CCL2 by long-term elevation of serum IL-10 in transgenic mice may be consistent with the significant predictive value of ΔMCP-1 with regard to 90-day survival noted in our present study. Association between persistent elevation of IL-10 and pulmonary fibrosis in the transgenic mice48 might explain our finding of a poor prognosis in patients with a marked increase in serum IL-10 levels by day 8. This hypothesis is consistent with the poor survival documented in patients with interstitial lung disease associated with clinically amyopathic dermatomyositis who are antimelanoma differentiation-associated gene 5 antibody positive and show an increase in serum IL-10 during their clinical course.49

The results of this study could alter the treatment strategy for AE-IIPs. Nintedanib50 is known to suppress the effects of profibrotic cytokines, including VEGF,51 b-FGF52 and PDGF.25 The ability of nintedanib to inhibit AE of IPF was demonstrated in the INPULSYS trial50; however, there was no improvement in survival after the time of diagnosis of AE in nintedanib-treated cases.53 If our findings are correct, use of nintedanib soon after the time of diagnosis of AE might result in a poor survival outcome in patients with AE-IIPs. Higher serum levels of profibrotic cytokines, including b-FGF and PDGF, at the time of diagnosis of AE were significantly good prognostic factors in our patients with AE-IIPs. Hence, administration of nintedanib for more than 7 days after the time of diagnosis of AE rather than early administration might confer a survival advantage in AE-IPF. In addition, we have shown AE-IIPs with use of antifibrotic drugs before AE showed worse survival than those without their use (table 2 and online supplemental table 3). This can be explained by difference in severity of patients of IIPs before AE with or without use of antifibrotic drugs in our study (online supplemental table 3); however, cessation of antifibrotic drugs temporally during the 7 days after the AE diagnosis might be better to improve prognosis of AE-IIPs from our hypothesis. How to use antifibrotic drugs for AE-IPF patients is important problem to be solved by future studies.

Effects of thrombomodulin on cytokine production have not been clarified sufficiently; however, they have been investigated for other diseases except for AE-IIPs. Kudo et al54 reported IL-10 and TGF-β in the lung homogenate of lipopolysaccharide induced acute respiratory distress syndrome (ARDS) model mice treated by rhTM was significantly elevated 24 hours after the onset of ARDS as compared with control mice without rhTM treatment. Temporal elevation of these two cytokines might help recovery from the epithelial injury and inflammation at AE as we have shown from our data. In addition, rhTM might inhibit endothelial cell injury and help reduction of RANTES/CCL5 as shown in patients treated with haematopoietic stem cell transplantaion.55 56 When and how long to administer rhTM might be important to improve the prognosis of AE-IIP.

This study has several limitations. First, the numbers of patients with AE-IPF and AE-non-IPF were too small to draw definitive conclusion. We cannot divide subjects into original and validation cohorts. We cannot separately analyse AE-IPF and AE-non-IPF to reduce bias, either. Second, serum samples were obtained from patients with AE-IIPs treated with rhTM and corticosteroids of SETUP trial; however, serum samples could not be obtained from all the subjects of the trial. Third, a randomised controlled trial of rhTM could not clarify its efficacy in AE-IPF,57 and we cannot recommend it as a treatment for AE-IPF or AE-IIPs based on the present evidence. Therefore, our present findings need to be confirmed in a study of patients with AE-IIPs who are treated with corticosteroids only. Fourth, the levels of several cytokines could not be measured simultaneously using the Bio-Plex system. Fifth, PMX/DHP therapy is known to reduce various serum cytokine levels13 and might have affected the serum cytokine profile on day 8; however, only one case was treated with the therapy.

Conclusions

An elevated serum RANTES/CCL5 level at the time of diagnosis of AE predicted a good survival outcome in patients with AE-IIPs and a marked increase in serum IL-10 on day 8 predicted a poor survival outcome. Therefore, early elevation of serum RANTES/CCL5 and a rapid reduction of IL-10 could predict 90-day survival in patients with AE-IIPs treated with corticosteroids and rhTM.

Data availability statement

No data are available. The data that support the findings of this study have not been made available because this study was approved in 2014 and data sharing was not included in the design of this study.

Ethics statements

Ethics approval

This study was approved by the Institutional Review Board of the Kinki-Chuo Chest Medical Center (KCCMC; approval number: 447, 24 February 2014), as well as the review boards of the other institutions. Written informed consent was obtained from all participants in the rhTM arm.

Acknowledgments

We are grateful to Ms Homma T, Ms Hirakawa C and Ms Matsui Y for their secretarial work and to Ms Imai Y for the data management work. We would like to thank Editage (www.editage.com) for English language editing.

References

Supplementary materials

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Footnotes

  • Contributors TA contributed to study conception and design, radiological findings, data analysis and interpretation and manuscript preparation. TA had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. HM, SY, YO, CS, KT and HK contributed to study conception and design, data acquisition, data analysis and interpretation and manuscript preparation. YI and MM contributed to study conception and design, data analysis and interpretation and manuscript preparation. MH and KH contributed to data acquisition, data analysis and interpretation and manuscript preparation. MA contributed to the radiological findings and manuscript preparation. All authors approved the final version of the manuscript.

  • Funding This study was partially supported by a JSPS KAKENHI Grant Number JP17K09636 awarded to TA, YI and MH, a National Hospital Organization {H28-NHO (Kokyu)-2} grant awarded to TA and YI, and AMED grants (DLD/14526278 and PAP/14526182) awarded to YI and to YI and TA, respectively.

  • Competing interests HM, MH, HK, SY, YO, MM, KH, CS, KT and MA have no competing interests. YI is an advisor to Boehringer Ingelheim, Shionogi and Asahi Kasei. TA has received lecture fees from Boehringer Ingelheim and Shionogi for activities not connected with the submitted work.

  • Patient and public involvement statement This research was done without patient involvement. Patients were not invited to comment on the study design and were not consulted to develop patient relevant outcomes or interpret the results. Patients were not invited to contribute to the writing or editing of this document for readability or accuracy.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.

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