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Ghrelin protects alveolar macrophages against lipopolysaccharide-induced apoptosis through growth hormone secretagogue receptor 1a-dependent c-Jun N-terminal kinase and Wnt/ß-catenin signaling and suppresses lung inflammation.

Authors: Li, Bin  Zeng, Mian  He, Wanmei  Huang, Xubin  Luo, Liang  Zhang, Hongwu  Deng, David Y B 
Citation: Li B, etal., Endocrinology. 2015 Jan;156(1):203-17. doi: 10.1210/en.2014-1539.
Pubmed: (View Article at PubMed) PMID:25337654
DOI: Full-text: DOI:10.1210/en.2014-1539

Alveolar macrophages (AMs) undergo increased apoptosis during sepsis-induced acute respiratory distress syndrome (ARDS). Ghrelin exhibits an antiapoptotic effect in several cell types and protects against sepsis-induced ARDS in rats; however, the molecular mechanisms underlying this antiapoptotic effect remain poorly understood. In this study, we first examined the antiapoptotic effect of ghrelin on lipopolysaccharide (LPS)-stimulated AMs in vitro. In AMs, GH secretagogue receptor-1a (GHSR-1a), the ghrelin receptor, was expressed, and treatment of AMs with ghrelin markedly reduced LPS-induced apoptosis, mitochondrial transmembrane potential decrease, and cytochrome c release. These effects of ghrelin were mediated by GHSR-1a because a GHSR-1a-targeting small interfering RNA abolished the antiapoptotic action of ghrelin. LPS treatment activated the c-Jun N-terminal kinase (JNK) signaling pathway but inhibited the Wnt/ß-catenin pathway. Interestingly, combined LPS-ghrelin treatment reduced JNK activation and increased Wnt/ß-catenin activation. Furthermore, like ghrelin treatment, the addition of the JNK inhibitor SP600125 or the glycogen synthase kinase-3ß inhibitor SB216763 rescued AMs from apoptosis. We also demonstrated that ghrelin altered the balance of Bcl-2-family proteins and inhibited caspase-3 activity. Next, we investigated whether ghrelin protected against septic ARDS in vivo. Sepsis was induced in male rats by performing cecal ligation and puncture; administration of ghrelin reduced sepsis-induced AMs apoptosis, pulmonary injury, protein concentrations in the bronchoalveolar lavage fluid, the lung neutrophil infiltration, and wet to dry weight ratio. However, administration of a specific ghrelin-receptor antagonist, [D-Lys-3]-GH-releasing peptide-6, abolished the beneficial effects of ghrelin. Collectively our results suggest that ghrelin exerts an antiapoptotic effect on AMs at least partly by inhibiting JNK and activating the Wnt/ß-catenin pathway and thereby helps alleviate septic ARDS in rats.

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CRRD Object Information
CRRD ID: 12907499
Created: 2017-06-06
Species: All species
Last Modified: 2017-06-06
Status: ACTIVE



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RGD is funded by grant HL64541 from the National Heart, Lung, and Blood Institute on behalf of the NIH.