Treatment with imatinib results in reduced IL-4-producing T cells, but increased CD4+ T cells in the broncho-alveolar lavage of patients with systemic sclerosis
Highlights
► IL-4+ T cells are reduced in lungs of scleroderma patients treated with imatinib. ► Lung IL-4+ T cells correlate with ground glass opacity in scleroderma patients. ► IL-4+ T cells in lung correlate with inflammatory and wounding response proteins. ► IL-4–CD4+ T cells, ICAM3 and PECAM1 increase in BAL after imatinib treatment. ► T cell subsets substantially differ between different lobes of lung in scleroderma.
Introduction
Uncontrolled tissue repair or fibrosis is a common end-result of tissue injury, including inflammation. Chronic inflammation and fibrosis are hallmarks of systemic sclerosis (SSc, scleroderma) that involves multiple organs. SSc-associated interstitial lung disease (SSc-ILD) is a major cause of morbidity and mortality, but its pathogenesis is poorly understood. Studies in patients with SSc-ILD and animal models suggest a role for T cells that produce type-2 cytokines such as IL-4 [1], [2]. It is unclear whether any of the treatments currently used in patients with SSc modulate the production of these cytokines.
Currently, no treatment reverses fibrosis and no drug has been approved by the Food and Drug Administration for SSc. However, lack of worsening of lung fibrosis in SSc-ILD patients treated with cyclophosphamide [3] provides hope that fibrosis might be amenable to therapy. Imatinib, a tyrosine kinase inhibitor approved for the treatment of leukemia and gastrointestinal tumors [4], inhibits tyrosine kinase activity of c-abl, c-kit and c-fms [5]. Interestingly, c-abl deficiency attenuates the induction of extracellular matrix proteins by transforming growth factor β (TGFβ), a pro-fibrotic cytokine [6]. Imatinib also blocks the tyrosine kinase activity of platelet-derived growth factor (PDGF) receptor that is implicated in fibrosis [7]. Thus, imatinib may target two pro-fibrotic pathways activated in SSc. Indeed, several case reports in patients with SSc, nephrogenic systemic fibrosis, and graft-versus-host-disease report regression of fibrosis following imatinib treatment [[8], [9], [10]].
Thus we and others have evaluated the effect of imatinib in SSc-ILD in a phase I/IIa one-year open-label trial [11], [12]. Treatment with imatinib led to an estimated improvement of forced vital capacity (FVC) % of 1.74% and modified Rodnan skin score (MRSS) of 3.9 units [11]. To assess the impact of T cell alterations in relation to disease and imatinib treatment, we correlated T cell subsets with proteins in BAL and disease parameters including high-resolution computerized tomography (HRCT) findings and pulmonary function tests (PFT). We report that IL-4+ T cells in BAL that correlate with baseline HRCT findings of SSc-ILD decrease significantly post-imatinib. However, CD4+ T cells increased in all except one patient who had worsening of SSc-ILD post-imatinib.
Section snippets
Patients
Patients are participants in a single center, open-label study of imatinib for treatment of active SSc-ILD with disease duration ≤ 7 years, FVC < 85% predicted and ≥ 50% predicted, dyspnea on exertion, and presence of ground glass opacity (GGO) on HRCT (Table I). The study “Pilot Study to Examine the Use of Imatinib (Gleevec) for the Treatment of Active Alveolitis in Systemic Sclerosis” was approved by the University of California at Los Angeles Institutional Review Board and informed consent was
Results
Demographic and clinical characteristics of SSc patients enrolled in this study are described in Table I. HRCT scans of lung were performed at baseline and scored for GGO, fibrosis, and honeycombing (Fig. S1). BAL samples were collected from the right middle lobe (RML) and right lower lobe (RLL) and pooled for analysis in the first two patients. However, their HRCT scores were substantially different between RML and RLL. Hence, in subsequent patients we analyzed the RML and RLL samples
Discussion
Many reports have described T cell subsets in relation to lung function in patients with SSc [1], [24], [25]. A few studies have also investigated T cells in relation to lung pathology as defined by histology or HRCT findings of SSc-ILD [26]. In this article, we extend these observations and report a relation between T cell subsets at the affected site (BAL) and HRCT-defined GGO and fibrotic lesions of SSc-ILD. CD4+ T cells and CD4+/CD4− IL-4+ T cells showed a stronger correlation with GGO than
Conflict of interest statement
The authors declare that there are no conflicts of interest.
Author contributions
AAD performed all experiments, analyzed data and wrote the manuscript; DK and DEF contributed to clinical trial, data analysis, and manuscript editing; AF quantitated HRCT scans; PM performed statistical analysis; RS and RS performed bronchoscopies and collected BAL samples; RRS supervised all aspects of this study.
Acknowledgements
This work was supported in part by NIH NIAMS U01AR55057-01S1 (AAD/DEF), NIAID R01AI80778 (RRS), NIAMS R01AR56465 (RRS), NIAMS K23 AR053858-04 (DK), and Cure Scleroderma Foundation. We thank Dr. Pallavi Gangalum for technical assistance.
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