Honokiol alleviates LPS-induced acute lung injury by inhibiting NLRP3 inflammasome-mediated pyroptosis via Nrf2 activation in vitro and in vivo

Yuhan Liu,Luorui Shang,Jinxiao Li,Fangyuan Zhou,Jiabin Zhou,Yingying Luo,Shenglan Yang

doi:10.1186/s13020-021-00541-z

Abstract

BackgroundHonokiol (HKL) has been reported to ameliorate lipopolysaccharide (LPS)-induced acute lung injury (ALI). However, its potential mechanism of its protective effects remains unclear. In this study, the protective mechanism of HKL on LPS-induced ALI was explored in vivo and in vitro.MethodsIn vivo, the SD rats were intratracheally instilled with LPS (5 mg/kg) to establish an acute lung injury model and then treated with HKL (1.25/2.5/5 mg/kg) or ML385 (30 mg/kg) intraperitoneally. In vitro, the human bronchial epithelial cell line (BEAS-2B) was stimulated with LPS and ATP to induce pyroptosis and treated with HKL (12.5/25/50 μM). Small interfering RNA (siRNA) technique was used to knockdown Nrf2 in BEAS-2B cells. The protein and mRNA expression levels of Nrf2, HO-1, NLRP3, ASC, CASP1, and GSDMD in cells and lung tissues were detected by western blot and real time-PCR. The expression levels of interleukin (IL)-1β, IL-18, MPO, MDA, and SOD in bronchoalveolar lavage fluid (BALF) and supernatant were determined by ELISA. The degree of pathological injury of lung tissue was evaluated by H&E staining.ResultsThe results showed that HKL could alleviate oxidative stress and inflammatory responses by regulating the levels of MPO, MDA, SOD, IL-1β, IL-18 in supernatant. And it could also inhibit the expression levels of NLRP3, ASC, CASP1, GSDMD via activation of Nrf2 in BEAS-2B cells. Further studies revealed that HKL could attenuate the pathological injury in LPS-induced ALI rats, and the molecular mechanism was consistent with the results in vitro.ConclusionsOur study demonstrated that HKL could alleviate LPS-induced ALI by reducing the oxidative stress and inhibiting NLRP3 inflammasome-mediated pyroptosis, which was partly dependent on the Nrf2 activation.Graphical

Highlights

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are mainly responsible for hypoxic respiratory failure in adults with high morbidity and mortality during hospitalization [1]
To assess the cytotoxicity of HKL in Human bronchial epithelial cell line (BEAS-2B) cells, the cells were treated with HKL (6.25, 12.5, 25, 50, 100 μM) for 24 or 48 h, cell viability was detected by Cell Counting Kit-8 (CCK8) assay
Honokiol inhibits NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome‐mediated pyroptosis in LPS and ATP‐ stimulated BEAS‐2B cells To explore the effect of HKL on pyroptosis, the BEAS-2B cells were treated with LPS and ATP, and the level of pyroptosis was determined by calculating the ratio of Propidium iodide (PI)-positive cells and the level of Lactate dehydrogenase (LDH) released from the cell supernatant

Summary

Introduction

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are mainly responsible for hypoxic respiratory failure in adults with high morbidity and mortality during hospitalization [1]. Increasing evidence depicts that airway epithelial cells are involved in the pathogenesis of ALI/ARDS. As the first line of lung defense against lung injury, airway epithelial cells can produce the epithelial-associated inflammatory factors and participate in promoting oxidative stress, local response, and tissue damage [3, 4]. Airway epithelial cells are the potential therapeutic targets for preventing and treating ALI/ARDS. Recent evidence suggests that NLRP3 inflammasome-mediated pyroptosis in macrophages aggravates lung inflammation in LPS-induced ALI [8]. The role of pyroptosis in airway epithelial cells for the LPS-induced ALI remains unclear. Honokiol (HKL) has been reported to ameliorate lipopolysaccharide (LPS)-induced acute lung injury (ALI). The protective mechanism of HKL on LPS-induced ALI was explored in vivo and in vitro

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