Lipoxin A4 Ameliorates Lipopolysaccharide-lnduced A549 Cell Injury through Upregulation of N-myc Downstream-Regulated Gene-1

Background： Lipoxin A4 （LXA4） can alleviate lipopolysaccharide （LPS）-induced acute lung injury （ALl） and acute respiratory distress syndrome through promoting epithelial sodium channel （ENaC） expression in lung epithelial cells. However, how LXA4 promote ENaC expression is still largely elusive. The present study aimed to explore genes and signaling pathway involved in regulating ENaC expression induced by LXA4. Methods： A549 cells were incubated with LPS and LXA4, or in combination, and analyzed by quantitative real-time polymerase chain reaction （qRT-PCR） of ENaC-α/γ. Candidate genes affected by LXA4 were explored by transcriptome sequencing ofA549 cells. The critical candidate gene was validated by qRT-PCR and Western blot analysis ofA549 cells treated with LPS and LXA4 at different concentrations and time intervals. LXA4 receptor （ALX） inhibitor BOC-2 was used to test induction of candidate gene by LXA4. Candidate gene siRNA was adopted to analyze its influence on A549 viability and ENaC-α expression. Phosphoinositide 3-kinase （PI3K） inhibitor LY294002 was utilized to probe whether the PI3K signaling pathway was involved in LXA4 induction of candidate gene expression. Results： The A549 cell models of ALl were constrticted and subjected to transcriptome sequencing. Among candidate genes, N-myc downstream- regulated gent- 1 （NDRG 1 ） was validated by real-time-PCR and Western blot. NDRG 1 mRNA was elevated in a dose-dependent manner of LXA4, whereas BOC-2 antagonized NDRG 1 expression induced by LXA4. NDRG I siRNA suppressed viability of LPS-treated A549 cells （treatment vs. control, 0.605± 0.063 vs. 0.878 ± 0.083, P = 0.040） and ENaC-α expression （treatment vs. control, 0.458 ± 0.038 vs. 0.711 ± 0.035, P = 0.008）. LY294002 inhibited NDRG 1 （treatment vs. control, 0.459 ± 0.023 vs. 0.726 ± 0.020, P 0.001 ） and ENaC-α （treatment vs. control, 0.236 ± 0.021 vs. 0.814 ±0.025, P 〈 0.001 ） expressions and serum- and glucocorticoid-inducible kinase I phosphorylation （treatment vs. control, 0.442± 0.024 vs. 1.046 ± 0.082, P = 0.002）, indicating the PI3K signaling pathway was involved in regulating NDRG 1 expression induced by LXA4. Conclusion： Our research uncovered a critical role of NDRG1 in LXA4 alleviation of LPS-induced A549 cell injury through mediating PI3K signaling to restore ENaC expression.

NDRG1 promotes endothelial dysfunction and hypoxia-induced pulmonary hypertension by targeting TAF15

Background:Pulmonary hypertension(PH)represents a threatening pathophysiologic state that can be induced by chronic hypoxia and is characterized by extensive vascular remodeling.However,the mechanism underlying hypoxia-induced vascular remodeling is not fully elucidated.Methods and Results:By using quantitative polymerase chain reactions,western blotting,and immunohistochemistry,we demon-strate that the expression of N-myc downstream regulated gene-1(NDRG1)is markedly increased in hypoxia-stimulated endothelial cells in a time-dependent manner as well as in human and rat endothelium lesions.To determine the role of NDRG1 in endothelial dysfunction,we performed loss-of-function studies using NDRG1 short hairpin RNAs and NDRG1 over-expression plasmids.In vitro,silencing NDRG1 attenuated proliferation,migration,and tube formation of human pulmonary artery endothelial cells(HPAECs)un-der hypoxia,while NDRG1 over-expression promoted these behaviors of HPAECs.Mechanistically,NDRG1 can directly interact with TATA-box binding protein associated factor 15(TAF15)and promote its nuclear localization.Knockdown of TAF15 abrogated the effect of NDRG1 on the proliferation,migration and tube formation capacity of HPAECs.Bioinformatics studies found that TAF15 was involved in regulating PI3K-Akt,p53,and hypoxia-inducible factor 1(HIF-1)signaling pathways,which have been proved to be PH-related pathways.In addition,vascular remodeling and right ventricular hypertrophy induced by hypoxia were markedly alleviated in NDRG1 knock-down rats compared with their wild-type littermates.Conclusions:Taken together,our results indicate that hypoxia-induced upregulation of NDRG1 contributes to endothelial dysfunction through targeting TAF15,which ultimately contributes to the development of hypoxia-induced PH.