Lipoxin A4 receptor agonist BML-111 induces autophagy in alveolar macrophages and protects from acute lung injury by activating MAPK signaling.

BACKGROUND: Acute lung injury (ALI) is a life-threatening lung disease where alveolar macrophages (AMs) play a central role both in the early phase to initiate inflammatory responses and in the late phase to promote tissue repair. In this study, we examined whether BML-111, a lipoxin A4 receptor agonist, could alter the phenotypes of AM and thus present prophylactic benefits for ALI. METHODS: In vitro, isolated AMs were treated with lipopolysaccharide (LPS) to induce ALI. In response to BML-111 pre-treatment, apoptosis and autophagy of AMs were examined by flow cytometry, and by measuring biomarkers for each process. The potential involvement of MAPK1 and mTOR signaling pathway was analyzed. In vivo, an LPS-induced septic ALI model was established in rats and the preventative significance of BML-111 was assessed. On the cellular and molecular levels, the pro-inflammatory cytokines TNF-α and IL-6 from bronchoalveolar lavage were measured by ELISA, and the autophagy in AMs examined using Western blot. RESULTS: BML-111 inhibited apoptosis and induced autophagy of AMs in response to ALI inducer, LPS. The enhancement of autophagy was mediated through the suppression of MAPK1 and MAPK8 signaling, but independent of mTOR signaling. In vivo, BML-111 pre-treatment significantly alleviated LPS-induced ALI, which was associated with the reduction of apoptosis, the dampened production of pro-inflammatory cytokines in the lung tissue, as well as the increase of autophagy of AMs. CONCLUSIONS: This study reveals the prophylactic significance of BML-111 in ALI and the underlying mechanism: by targeting the MAPK signaling but not mTOR pathway, BML-111 stimulates autophagy in AMs, attenuates the LPS-induced cell apoptosis, and promotes the resolution of ALI.

Genome-wide analysis of long noncoding RNA expression profiles in patients with non-alcoholic fatty liver disease.

Non-alcoholic fatty liver disease (NAFLD) is a common liver disorder poising burgeoning health problem to humans. Recent studies have shown that long non-coding RNA (lncRNA) plays critical roles in a myriad of biological processes and human diseases. Since the roles of lncRNA in NAFLD remain unknown, they were investigated in the study. Microarray expression profiling of mRNAs and lncRNAs was conducted using RNA extracted from patients with and without NAFLD. One thousand seven hundred thirty-five lncRNAs and 1485 mRNA were found differentially expressed in NAFLD samples compared with those in control samples. Among them 535 and 1,200 lncRNAs were upregulated and downregulated in NAFLD, respectively; 760 and 725 mRNAs were upregulated and downregulated in NAFLD, respectively. Moreover, seven lncRNAs and seven mRNAs that were highly up- or downregulated in NAFLD samples were validated by quantitative real-time polymer chain reactions. Kyoto Encyclopedia of Genes and Genomes pathway analysis and Gene Ontology analysis for the differentially expressed mRNAs showed that these RNAs are involved in various metabolic processes, cellular components, and molecular functions. Our findings indicate that the expression profiles of lncRNAs have changed in NAFLD as compared with normal liver, and the identified regulated RNAs may provide novel insight into the molecular mechanisms underlying the disease and potential novel diagnostic or therapeutic targets for NAFLD.

miR-21 regulates triglyceride and cholesterol metabolism in non-alcoholic fatty liver disease by targeting HMGCR.

Non-alcoholic fatty liver disease (NAFLD) has emerged as a public health issue with a prevalence of 15-30% in Western populations and 6-25% in Asian populations. Certain studies have revealed the alteration of microRNA (miRNA or miR) profiles in NAFLD and it has been suggested that miR-21 is associated with NAFLD. In the present study, we measured the serum levels of miR-21 in patients with NAFLD and also performed in vitro experiments using a cellular model of NAFLD to further investigate the effects of miR-21 on triglyceride and cholesterol metabolism. Furthermore, a novel target through which miR-21 exerts its effects on NAFLD was identified. The results revealed that the serum levels of miR-21 were lower in patients with NAFLD compared with the healthy controls. In addition, 3-hydroxy-3-methylglutaryl-co-enzyme A reductase (HMGCR) expression was increased in the serum of patients with NAFLD both at the mRNA and protein level. To mimic the NAFLD condition in vitro, HepG2 cells were treated with palmitic acid (PA) and oleic acid (OA). Consistent with the results obtained in the in vivo experiments, the expression levels of miR-21 were decreased and those of HMGCR were increased in the in vitro model of NAFLD. Luciferase reporter assay revealed that HMGCR was a direct target of miR-21 and that miR-21 exerted an effect on both HMGCR transcript degradation and protein translation. Furthermore, the results from the in vitro experiments revealed that miR-21 decreased the levels of triglycerides (TG), free cholesterol (FC) and total cholesterol (TC) in the PA/OA-treated HepG2 cells and that this effect was attenuated by HMGCR overexpression. Taken together, to the best of our knowledge, the present study is the first to report that miR-21 regulates triglyceride and cholesterol metabolism in an in vitro model of NAFLD, and that this effect is achieved by the inhibition of HMGCR expression. We speculate that miR-21 may be a useful biomarker for the diagnosis and treatment of NAFLD.