Depression of lncRNA MINCR antagonizes LPS-evoked acute injury and inflammatory response via miR-146b-5p and the TRAF6-NFkB signaling

(2021) 27:124 Gao and Zhang Mol Med https://doi.org/10.1186/s10020-021-00367-3 RESEARCH ARTICLE Molecular Medicine Open Access Depression of lncRNA MINCR antagonizes LPS‑evoked acute injury and inflammatory response via miR‑146b‑5p and the TRAF6‑NFkB signaling Wei Gao1 and Ying Zhang2* Abstract Background: Inflammation plays an important role in the development of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). The long non-coding RNA (lncRNA) MINCR is closely related to inflammation injury. This study was performed to explore the protective effects and mechanisms of MINCR in lipopolysaccharide (LPS)induced lung injury and inflammation. Methods: The expression levels of MINCR and miR-146b-5p in lung tissue status were detected by using quantitative real-time polymerase chain reaction (qRT-PCR), hematoxylin and eosin staining, immunohistochemical staining, and terminal deoxynucleotidyl transferase dUTP nick end labeling assay. Enzyme-linked immunosorbent assay and Western blotting analysis were used to detect the expression of inflammatory factors such as tumor necrosis factor (TNF)-α, interleukin (IL)-6, and IL-10 in lung tissue. The relationship between MINCR, miR-146b-5p, and TRAF6 was explored using bioinformatics analysis and luciferase assay. Results: The expression levels of MINCR were increased in a mouse model of LPS-induced ALI and small airway epithelial cells (SAECs). shMINCR resulted in increased cell viability and decreased apoptosis, which protected against LPS-induced cell damage. shMINCR can inhibit the formation of neutrophil extracellular traps, neutrophil numbers, myeloperoxidase activity, and the production of inflammatory cytokines IL-6, IL-1β, and TNF-α induced by LPS. The silencing of miR-146b-5p reversed the effects of MINCR on LPS-induced lung damage. Sh-MINCR decreased the expression levels of TRAF6 and p-P65 in LPS-induced SAECs and lung tissues. Co-transfection of sh-MINCR with miR146b-5p inhibitor reversed the effect of sh-MINCR on the expression of TRAF6 and p-P65. Conclusions: MINCR may induce alveolar epithelial cell injury and inflammation and aggravate the progression of ALI/ARDS through miR-146b-5p and TRAF6/NF-κB pathways, which would provide a promising target for the treatment of ALI/ARDS. Keywords: MINCR, miR-146b-5p, TRAF6/NF-κB, LPS, ALI/ARDS *Correspondence: 2 Department of Respiratory, The Second Hospital of Shandong University, No.247 Beiyuan Avenue, Jinan 250033, Shandong, People’s Republic of China Full list of author information is available at the end of the article Background Acute lung injury (ALI) is a disease that is widely distributed worldwide. It is an acute progressive insufficiency or respiratory failure caused by various internal and external factors of the lung, with a mortality rate of up to 40% (Tao et al. 2019). The common pathological manifestations of © The Author(s) 2021. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. Gao and Zhang Mol Med (2021) 27:124 ALI are damage to alveolar epithelial cells, an increase in pulmonary capillary permeability, thickening of the alveolar wall, and the release of inflammatory factors in the alveoli cavity (Ochroch et al. 2019). With reduced lung volume, reduced lung compliance can develop into acute respiratory distress syndrome (ARDS) in later stages (Cao et al. 2018). The pathogenesis of ARDS is affected by coagulation and fibrinolysis. The function of the human coagulation system is enhanced, whereas the fibrinolysis system is inhibited, leading to a large area of thrombosis and a large amount of fibrin deposition, resulting in vascular blockage and microcirculation structure damage (Bender et al. 2020). The lipopolysaccharide (LPS)induced lung injury model has been widely used in studies on lung injury (Zhu et al. 2013). There are no specific response methods for ALI. Currently, auxiliary ventilation and drug therapy are the main clinical response methods (Chiumello et al. 2019). Therefore, it is important to elucidate the regulatory mechanisms and signaling pathways involved in the pathological process of ALI to provide targeted drugs for clinical treatment. At present, the pathogenesis of ALI is considered to be an inflammatory response of the body. Infection is a common risk factor for ALI, and LPS is the main endotoxin (Cheung et al. 2018). Long non-coding RNAs (lncRNAs) play key roles in regulating inflammatory immune genes (Wu et al. 2018). These can act as regulatory factors and exert their functions by interacting with proteins, RNAs, and DNA to regulate their expression at transcriptional and post-transcriptional levels (Liu et al. 2009). Several studies have investigated the regulation of lncRNAs on epigenetics and gene transcription and their involvement in disease occurrence and development, particularly in Alzheimer’s disease, cancer, and other diseases (Wang et al. 2017; Xie et al. 2019). lncRNAs also play roles in controlling the balance of inflammatory responses (Fava et al. 2017). For example, lncRNA CASC2 reduces apoptosis of pulmonary epithelial cells and improves ALI by regulating the miR-144-3p/AQP1 axis (Li et al. 2018a). A better understanding of lncRNAs will provide new ideas for exploring the nature of sepsis and regulating the uncontrolled inflammatory cascade in sepsis. The lncRNA MINCR is a newly identified lncRNA that is abnormally expressed in many diseases (Hu et al. 2018). For example, the expression levels of MINCR are significantly increased in primary liver cancer tissues (Lyu et al. 2019). However, the functions and mechanisms of MINCR in ALI have not yet been studied. MicroRNAs (miRNAs) are involved in many important pathophysiological processes. In recent years, studies have explored their regulation in tumors, inflammation, and other aspects in molecular biology, cell biology, and clinical medicine (Emma et al. 2020). miRNAs are widely Page 2 of 14 involved in the immune regulation of systemic inflammatory response syndrome and ALI (Iacona et al. 2018). In the process of the systemic inflammatory response, miRNAs regulate the expression of various inflammatory genes and transcription factors, the proli (...truncated)