Fungal cell wall agents and bacterial lipopolysaccharide in organic dust as possible risk factors for pulmonary sarcoidosis.

Sanja Stopinšek,Barbara Salobir,Alojz Ihan,Saša Simčič,Marjeta Terčelj

doi:10.1186/s12995-016-0135-4

Abstract

BackgroundComposition of organic dust is very complex, involving particles of microbial, animal and plant origin. Several environmental exposure studies associate microbial cell wall agents in organic dust with various respiratory symptoms and diseases. The aim of the present study was to investigate the in vitro effects of the co-exposure of fungal cell wall agents (FCWAs) and bacterial lipopolysaccharide (LPS) on inflammatory immune responses of peripheral blood mononuclear cells (PBMCs) from patients with pulmonary sarcoidosis.MethodsPBMCs from 22 patients with pulmonary sarcoidosis and 20 healthy subjects were isolated and stimulated in vitro with FCWAs (soluble and particulate (1 → 3)-β-D-glucan, zymosan and chitosan) and/or LPS. Subsequently, cytokines were measured by ELISA and the mRNA expression of dectin-1, toll-like receptor 2 (TLR2), TLR4 and mannose receptor (MR) was analysed by real-time RT-PCR.ResultsPatients with sarcoidosis had a significantly higher secretion of inflammatory cytokines tumour necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), IL-10 and IL-12 (1.7-fold, 2.0-fold, 2.2-fold, and 2.8-fold, respectively; all p < 0.05) after in vitro co-stimulation of PBMCs with FCWAs and LPS. We showed that PBMCs from patients with sarcoidosis had a higher baseline mRNA expression of dectin-1, TLR2, TLR4 and MR (6-fold, 11-fold, 18-fold, and 4-fold, respectively). Furthermore, we found a reduced expression of dectin-1, TLR2 and TLR4 after stimulation with FCWAs and/or LPS, although the reduction was significantly weaker in patients than in healthy subjects.ConclusionsIn conclusion, co-stimulation with FCWAs and LPS of PBMC from patients with sarcoidosis caused a weaker reduction of dectin-1, TLR2, TLR4 receptors expression, which could increase the sensitivity of PBMCs, leading to excessive inflammatory cytokine responses and result in the development or progression of pulmonary sarcoidosis.

Highlights

Composition of organic dust is very complex, involving particles of microbial, animal and plant origin
In vitro inflammatory cytokine response to fungal cell wall agents (FCWAs) and LPS by peripheral blood mononuclear cells (PBMCs) from patients with sarcoidosis After co-stimulation of PBMCs with FCWAs and LPS, the production of Tumour necrosis factor-alpha (TNF-α), IL-6, IL-10 and IL-12 was significantly higher in patients with sarcoidosis, compared to healthy subjects (1.7-fold, 2.0-fold, 2.2-fold, and 2.8-fold, respectively; all p < 0.05) (Fig. 1)
PBMCs mRNA expression of dectin-1, toll-like receptor 2 (TLR2), TLR4, and mannose receptor (MR) at baseline and after in vitro stimulation with FCWAs and/ or LPS in patients with sarcoidosis As shown in Fig. 2, baseline dectin-1, TLR2, TLR4 and MR mRNA expression in PBMCs was higher in patients with sarcoidosis than in healthy subjects (6-fold, 11-fold, 18-fold, and 4-fold, respectively)

Summary

Introduction

Composition of organic dust is very complex, involving particles of microbial, animal and plant origin. Several environmental exposure studies associate microbial cell wall agents in organic dust with various respiratory symptoms and diseases. Several environmental exposure studies at workplaces or at homes associate microbial cell wall agents in organic dust with various respiratory symptoms and diseases, the immunopathological events involved in these diseases are very complex and not well understood. Terčelj et al proposed a hypothesis that microbial cell wall agents, agents from moulds, even in the absence of clinical infections can cause a late hypersensitivity reaction leading to granulomas [2]. In support of this hypothesis, several epidemiological studies describe the association between sarcoidosis and living in a damp and mouldy. In clinical studies in which sarcoidosis was treated with antifungals, greater clinical improvement was reported compared with corticosteroid treatment [9, 10]

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