Post-treatment with propofol inhibits inflammatory response in LPS-induced alveolar type II epithelial cells

Abstract

Over-inflammation and severe lung injury are major causes of morbidity and mortality in patients with coronavirus disease 2019 (COVID-19). With the COVID-19 pandemic, an increasing number of patients with preexisting lung injury and inflammation are undergoing surgery or artificial ventilation under sedation in intensive care units, where 2,6-diisopropylphenol (propofol) is a commonly used drug for sedation. The aim of the present study was to investigate whether post-inflammation treatment with propofol protects epithelial type II cells against inflammation in an in vitro model of inflammation. The A549 cell line, characterised as epithelial type II cells, were exposed to lipopolysaccharide (LPS) for 2 h and subsequently treated with different concentrations of propofol (0, 10, 25 or 50 µM) for 3 h. Western blot and reverse transcription-quantitative PCR analyses were used to detect the protein and mRNA expression levels, respectively, of CD14 and Toll-like receptor 4 (TLR4). Immunofluorescence staining was used to detect the in situ CD14 and TLR4 expression in epithelial type II cells. Tumor necrosis factor (TNF)-α production was also examined using ELISA. LPS significantly increased the expression of CD14 and TLR4, as well as the secretion of TNF-α. Post-treatment with 25 and 50 µM propofol of the LPS-treated cells significantly decreased CD14 and TLR4 expression, as well as TNF-α secretion, compared with the cells treated with LPS only, indicating that post-treatment with propofol alleviated inflammation and this effect was dose-dependent. The present study suggested that treatment with propofol after LPS administration has a protective effect on epithelial type II cells.

Keywords: CD14; Toll-like receptor 4; epithelial type II cell; lipopolysaccharides; propofol.

Figure 1

Post-treatment with propofol inhibits LPS-induced expression of CD14 and TLR4. (A) Western blot analysis indicated that LPS upregulated CD14 and TLR4 expression and post-treatment with propofol downregulated CD14 and TLR4 expression in A549 cells. (B) RT-qPCR suggested that the mRNA expression levels of CD14 increased in the A549 cell line when treated with LPS. The mRNA expression levels of CD14 decreased significantly in A549 cells treated with 25 or 50 µM propofol vs. those in the control LPS group. (C) RT-qPCR indicated that the TLR4 mRNA expression levels increased in LPS-treated A549 cells. TLR4 expression decreased significantly in the A549 cells treated with 25 and 50 µM propofol vs. that in the control LPS group. Data are derived from three independent experiments. ^*P<0.05 vs. control group; ^#P<0.05 vs. LPS group. LPS, lipopolysaccharide; TLR4, Toll-like receptor 4; RT-qPCR, reverse transcription-quantitative PCR.

Figure 2

Post-treatment with propofol suppresses LPS-induced CD14 and TLR4 expression. Fluorescent microscope images displaying CD14 (green) and TLR4 (red) expression. Nuclei were stained with DAPI (blue). An increase in CD14 and TLR4 expression was observed in the LPS group. Post-treatment with propofol (10, 25 and 50 µM) suppressed CD14 and TLR4 expression (scale bars, 30 µM). Data are derived from three independent experiments. ^*P<0.05 vs. control group; ^#P<0.05 vs. LPS group. TLR4, Toll-like receptor 4; LPS, lipopolysaccharide.

Figure 3

Post-treatment with propofol inhibits the LPS-induced expression of TNF-α. ELISA indicated that the concentration of TNF-α was significantly increased in LPS-treated A549 cells. The concentration of TNF-α was significantly decreased in the A549 cells treated with 25 and 50 µM propofol vs. the control LPS group. Data are derived from six independent experiments. ^*P<0.05 vs. control group; ^#P<0.05 vs. LPS group. LPS, lipopolysaccharide; TNF-α, tumor necrosis factor α.