Reduced expression of peroxisome proliferator-activated receptor alpha in BAL and blood T cells of non-löfgren's sarcoidosis patients

Abstract

Background: Sarcoidosis is a granulomatous disease affecting in particular the lungs. The peroxisome proliferator-activated receptors (PPARs) play important regulatory roles in inflammation. The aim of this study was to gain more insight about the expression of all three PPARs (α, β/δ and γ) in sarcoidosis.

Methods: Bronchoalveolar lavage (BAL) cells and peripheral blood cells were obtained from healthy controls (HC) and sarcoidosis patients with Löfgren's syndrome (LS) and without Löfgren's syndrome (non-LS). PPARs mRNA expression was analyzed in total BAL cells and in FACS (Fluorescence-activated cell sorting) sorted alveolar macrophages (AM) and CD4(+) T cells respectively by comparative RT-PCR. PPARs protein expression was analyzed in AM, and in BAL and blood CD4(+) and CD8(+) T cells by flow cytometry.

Results: In BAL CD4(+) T cells, we noticed a significantly lower PPARα mRNA expression in sarcoidosis patients compared with HC. In non-LS patients, a significantly lower PPARα protein expression in BAL CD4(+) T cells was detected as compared with LS patients. In peripheral blood CD4(+) T cells, non-LS patients had a significantly lower expression of PPARα and PPARγ compared with LS patients.

Conclusion: The lower protein expression of PPARα and PPARγ could contribute to the persistent T-cell driven inflammation noted especially in non-resolving sarcoidosis, common in non-LS patients.

Keywords: Alveolar macrophages; BAL and blood CD4+- and CD8+ T lymphocytes; Bronchoalveolar lavage (BAL); Flow cytometry; Peroxisome proliferator-activated receptors α; RT-PCR; Sarcoidosis; β/δ and γ.

Figure 1

The relative mRNA expression in total BAL cells of (a) PPARα, (b) PPARβ/δ and (c) PPARγ of HC (n = 6), patients with sarcoidosis (n = 16) and patients subgroups (LS = 7, non-LS = 9) are shown. The boxes show median (25th-75th percentiles) values and the whiskers show minimum and maximum values. Each symbol represents an individual patient.

Figure 2

The relative mRNA expression FACS-sorted BAL CD4 ⁺ T cells of (a) PPARα, (b) PPARβ/δ and (c) PPARγ of HC (n = 12), patients with sarcoidosis (n = 17) and patients subgroups (LS = 7, non-LS = 10) are shown. The boxes show median (25th-75th percentiles) values and the whiskers show minimum and maximum values. Each symbol represents an individual patient.

Figure 3

The relative mRNA expression in FACS-sorted BAL macrophages of (a) PPARα, (b) PPARβ/δ and (c) PPARγ of HC (n = 11), patients with sarcoidosis (n = 21) and patients subgroups (LS = 12, non-LS = 9) are shown. The boxes show median (25th-75th percentiles) values and the whiskers show minimum and maximum values. Each symbol represents an individual patient.

Figure 4

Representative histogram overlay (a) -in a patient with LS syndrome- of PPARα expression in BAL CD4 ⁺ T cells and the gating plots on CD4 ⁺ T cells (b). Black histogram is the isotype control; light gray histogram is the anti-PPARα. The x-axis of each histograms represents fluorescence intensity of the isotype and PPARα on a logarithmic scale, and the y-axis represents the total number of events. The values of the medians using the x-axis channels are presented in the table.

Figure 5

Flow cytometric analysis of PPARs expression in BAL CD4 ⁺ T cells. (a) PPARα. (b) PPARβ/δ. (c) PPARγ. HC: (n = 6); LS patients (n = 4); non-LS patients (n = 5). MFI: median fluorescence intensity. The boxes show median (25th-75th percentiles) values and the whiskers show minimum and maximum values. Each symbol represents an individual patient.

Figure 6

Flow cytometric analysis of PPARs expression in peripheral blood CD4 ⁺ T cells. (a) PPARα. (b) PPARβ/δ. (c) PPARγ. HC (n = 6); LS patients (n = 4); non-LS patients (n = 4). MFI: median fluorescence intensity. The boxes show median (25th-75th percentiles) values and the whiskers show minimum and maximum values. Each symbol represents an individual patient.

Figure 7

Representative histogram overlay (a) of PPARα expression in alveolar macrophages and the gating of alveolar macrophages in a FSC-SCC dot (b). Black histogram is the isotype control; light gray histogram is the anti-PPARα. The x-axis of each histograms represents fluorescence intensity of the isotype and PPARα on a logarithmic scale, and the y-axis represents the total number of events. The values of the medians using the x-axis channels are presented in the table.

Figure 8

Flow cytometric analysis of PPARs expression in alveolar macrophages. (a) PPARα. (b) PPARβ/δ. (c) PPARγ. HC (n = 6); LS patients (n = 4); non-LS patients (n = 5). MFI: median fluorescence intensity. The boxes show median (25th-75th percentiles) values and the whiskers show minimum and maximum values. Each symbol represents an individual patient.