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Published on: March 21, 2021
Isoalantolactone Attenuates LPS-Induced Acute Lung Injury, an Effect Associated with Suppressed MAPK/STAT3 Activation
Chia-Yang Li1,2,3, Chung-Wei Liu4, Hsin-Han Tseng1
1Graduate Institute of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung 80708, Taiwan.
Background:
Acute lung injury (ALI) is characterized by a high mortality rates and acute inflammation that compromises the epithelial and endothelial barriers of the respiratory system. Isoalantolactone (IsoA) is a natural compound derived from Inula helenium that has been shown to exhibit anti-inflammatory activity. However, its ability to preserve epithelial barrier integrity or modulate mitogen-activated protein kinase/signal transducer and activator of transcription 3 (MAPK/STAT3) signaling and epithelial-mesenchymal transition (EMT) has not been evaluated in ALI.
Methods:
Human bronchial epithelial cells (HBEC3-KT and BEAS-2B) were stimulated with lipopolysaccharide (LPS) with or without IsoA to assess cytotoxicity and cytokine release. In vivo, female C57BL/6 mice were pretreated with IsoA (10-20 mg/kg, intraperitoneally) or vehicle 1 h before LPS challenge (1 mg/kg, intratracheally). At 4 h, lung tissues and bronchoalveolar lavage fluid (BALF) were collected for histopathology and to measure total protein, cellular composition, and cytokine levels (tumor necrosis factor-α [TNF-α], interleukin-6 [IL-6], monocyte chemoattractant protein-1 [MCP-1]); leukocyte subsets were quantified by multicolor flow cytometry. Lung homogenates were analyzed using Western blot for phosphorylated/total extracellular signal-regulated kinase 1/2 (ERK1/2), c-Jun N-terminal kinase 1/2 (JNK1/2), p38 MAPKs, STAT3, and EMT markers (E-cadherin, N-cadherin, snail).
Results:
In LPS-stimulated HBEC3-KT and BEAS-2B cells, IsoA significantly reduced IL-6 secretion. In the murine model of LPS-induced ALI, IsoA administration alleviated lung tissue damage, decreased inflammatory cell infiltration, and reduced IL-6 and TNF-α concentration in BALF and serum. Mechanistically, IsoA attenuated the phosphorylation of ERK, JNK, and p38 MAPKs and suppressed STAT3 activation in lung tissues. Furthermore, IsoA attenuated EMT, as evidenced by decreased N-cadherin and snail expressions and restored E-cadherin expression.
Conclusions:
IsoA alleviates LPS-induced ALI by reducing MAPK/STAT3 activation and EMT-associated epithelial injury. These findings suggest that IsoA may be a promising candidate for the targeted modulation of inflammatory lung injury, and that further preclinical and translational studies are justified.
