Role of Nrf2 signaling pathway in endoplasmic reticulum stress response during lipopolysaccharide-induced acute lung injury in mice

Abstract

Objective To evaluate the role of nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway in endoplasmic reticulum stress response during lipopolysaccharide (LPS)-induced acute lung injury (ALI) in mice. Methods Forty clean-grade healthy male C57BL/6 mice, aged 6-8 weeks, weighing 22-26 g, were divided into 4 groups (n=10 each) using a random number table method: control group (group C), group ALI, salubrinal group (group S) and salubrinal plus brusatol group (group S+ B). Animals were intratracheally instilled with 5 mg/kg of LPS diluted in normal saline to establish the model of ALI.Animals were intratracheally instilled with 100 μl of normal saline in group C. Mice in group S were intraperitoneally injected with endoplasmic reticulum stress response inhibitor 1 mg/kg salubrinal at 1 and 24 h after LPS instillation.Mice of group S+ B were intraperitoneally injected with brusatol 2 mg/kg once every other day for 10 days prior to LPS instillation, and the other treatments were similar to those previously described in group S. Mice were sacrificed at 48 h after LPS administration, and lungs were removed for microscopic examination of the pathological changes of lung tissues which were scored and for determination of contents of IL-17A, tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6) in lung tissues (by enzyme-linked immunosorbent assay) and expression of Nrf2, CCAAT/enhancer-binding protein homologous protein (CHOP) and caspase-12 in lung tissues (by Western blot). Lung water content was calculated. Results Compared with group C, the lung water content and contents of IL-17A, TNF-α and IL-6 were significantly increased, the expression of CHOP and caspase-12 in cytoplasma was up-regulated, and the expression of Nrf2 in nuclei was down-regulated in ALI and S+ B groups, and the lung water content and contents of IL-17A, TNF-α and IL-6 were significantly increased, the expression of Nrf2 in nuclei and CHOP in cytoplasma was up-regulated, and the expression of caspase-12 was down-regulated in group S (P<0.05). Compared with group ALI, the lung water content and contents of IL-17A, TNF-α and IL-6 were significantly decreased, the expression of CHOP and caspase-12 in cytoplasma was down-regulated, the expression of Nrf2 in nuclei was up-regulated (P<0.05), and the pathological changes were significantly attenuated in group S. Compared with group S, the lung water content and contents of IL-17A, TNF-α and IL-6 were significantly increased, the expression of CHOP and caspase-12 in cytoplasma was up-regulated, the expression of Nrf2 in nuclei was down-regulated (P<0.05), and the pathological changes of lung tissues were accentuated in group S+ B. Conclusion Nrf2 signaling pathway is involved in the process of endoplasmic reticulum stress response during LPS-induced ALI in mice. Key words: NF-E2-related factor 2; Endotoxins; Acute lung injury; Endoplasmic reticulum stress