PAR-2, IL-4R, TGF-β and TNF-α in bronchoalveolar lavage distinguishes extrinsic allergic alveolitis from sarcoidosis

Abstract

Sarcoidosis (SARC) and extrinsic allergic alveolitis (EAA) share certain markers, making a differential diagnosis difficult even with histopathological investigation. In lung tissue, proteinase-activated receptor-2 (PAR-2) is primarily investigated with regard to epithelial and inflammatory perspectives. Varying levels of certain chemokines can be a useful tool for distinguishing EAA and SARC. Thus, in the present study, differences in the levels of transforming growth factor (TGF)-β1, tumor necrosis factor (TNF)-α, interleukin-4 receptor (IL-4R) and PAR-2 in bronchoalveolar lavage fluid (BALF) were compared, using an ELISA method, between 14 patients with EAA and six patients with SARC. Statistically significant higher levels of IL-4R, PAR-2 and the PAR-2/TGF-β1 and PAR-2/TNF-α ratios were observed in EAA patients as compared with SARC patients. Furthermore, the ratios of TNF-α/total protein, TGF-β1/PAR-2 and TNF-α/PAR-2 were significantly lower in EAA patients than in SARC patients. The results indicated a higher detection of PAR-2 in EAA samples in association with TNF-α and TGF-β levels. As EAA and PAR-2 in parallel belong to the Th2-mediated pathway, the results significantly indicated an association between this receptor and etiology. In addition, the results indicated that SARC is predominantly a granulomatous inflammatory disease, thus, higher levels of TNF-α are observed. Therefore, the detection of PAR-2 and investigated chemokines in BALF may serve as a useful tool in the differential diagnosis between EAA and SARC.

Keywords: extrinsic allergic alveolitis; interleukin-4 receptor; proteinase-activated receptor-2; sarcoidosis; transforming growth factor-β; tumor necrosis factor-α.

Figure 1

(A) Histopathological image of an epithelioid granuloma of sarcoid type in the transbronchial biopsy specimen of the peribronchial lung parenchyma, compatible with a diagnosis of pulmonary SARC (HE; magnification, ×200). (B) Epithelioid granuloma of sarcoid type formation in the mediastinal lymphatic node in an EBUS-TBNA specimen, compatible with lymphatic node involvement by SARC (HE; magnification, ×400). SARC, sarcoidosis; HE, hematoxylin and eosin; EBUS-TBNA, endobronchial ultrasound-guided transbronchial needle aspiration.

Figure 2

Schematic conformational status (A) prior to and (B) following PAR-2 activation. Following the specific proteolytic cleavage of the receptor, the new N-terminal is presented to the transmembrane domains as the tethered ligand. Receptor activation leads to various intracellular responses (6). The figure was composed using Servier Powerpoint image bank: www.servier.com. PAR-2, proteinase-activated receptor-2.

Figure 3

Statistically significant higher levels (P<0.05) of (A) IL-4R (1182.7 vs. 302.7 pg/ml; P=0.046), (B) PAR-2 (2009.4 vs. 329.5 pg/ml; P=0.018), (C) PAR-2/TGF-β1 ratio (9.29 vs. 1.61; P=0.026) and (D) PAR-2/TNF-α ratio (1.5 vs. 0.26; P=0.042) were identified in EAA patients as compared with SARC patients. (E) The ratio of TNF-α/total protein was significantly lower in EAA patients than in SARC patients (10.64 vs. 18.24; P=0.032). IL-4R, interleukin-4 receptor; PAR-2, proteinase-activated receptor-2; TGF, transforming growth factor; TNF, tumor necrosis factor; EAA, extrinsic allergic alveolitis; SARC, sarcoidosis

Figure 4

(A) TGF-β1/PAR-2 ratio derived from individual results using the ELISA method. The ratio (0.217 vs. 0.791; P=0.0000923) was significantly lower in EAA cases and the statistically significant difference complied with a FDR-adjusted critical level of 0.004. (B) TNF-α/PAR-2 ratio derived from individual results using the ELISA method. The ratio (1.26 vs. 5.45; P=0.0000503) was significantly lower in cases of EAA and the statistically significant difference complied with a FDR-adjusted critical level of 0.004. TGF, transforming growth factor; PAR-2, proteinase-activated receptor-2; EAA, extrinsic allergic alveolitis; FDR, false discovery rate; TNF, tumor necrosis factor.