Long noncoding RNA Mirt2 prohibits lipopolysaccharide-evoked HK-2 cell injury via modulation of microRNA-126

The impact and role of identified long noncoding RNAs in nonalcoholic fatty liver disease: A narrative review

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is the most common liver disease worldwide, but its mechanism and pathophysiology remain unclear. Long noncoding RNAs (lncRNAs) may exert a vital influence on regulating various biological functions in NAFLD.

METHODS

The databases such as Google Scholar, PubMed, and Medline were searched using the following keywords: nonalcoholic fatty liver disease, nonalcoholic fatty liver disease, NAFLD, nonalcoholic steatohepatitis, nonalcoholic steatohepatitis, NASH, long noncoding RNAs, and lncRNAs. Considering the titles and abstracts, unrelated studies were excluded. The authors evaluated the full texts of the remaining studies.

RESULTS

We summarized the current knowledge of lncRNAs and the main signaling pathways of lncRNAs involved in NAFLD explored in recent years. As a heterogeneous group of noncoding RNAs (ncRNAs), lncRNAs play crucial roles in biological processes underlying the pathophysiology of NAFLD. The mechanisms, particularly those associated with the regulation of the expression and activities of lncRNAs, play important roles in NAFLD.

CONCLUSION

A better comprehension of the mechanism controlled by lncRNAs in NAFLD is necessary for the identification of novel therapeutic targets for drug development and improved, noninvasive methods for diagnosis.

The myocardial infarction-associated transcript 2 inhibits lipid accumulation and promotes cholesterol efflux in oxidized low-density lipoprotein-induced THP-1-derived macrophages via inhibiting mitogen-activated protein kinase signaling and activating the nuclear factor erythroid-related factor 2 signaling pathway

Dysregulated lipid metabolism of macrophages contributes to thrombosis and antiphospholipid syndrome (APS). The long non-coding RNAs (lncRNA) myocardial infarction-associated transcript 2 (Mirt2) has been reported to inhibit inflammation and lipid accumulation; therefore, this study intended to clarify whether Mirt2 served a role in lipid metabolism. THP-1-derived macrophages with or without Mirt2-knockdown or overexpression, were exposed to oxidized low-density lipoprotein (ox-LDL), then cell migration, lipid accumulation, cholesterol efflux and inflammation were assessed using wound healing, oil red staining, commercial kits and western blot assays. Besides, ML385 was used to treat THP-1-derived macrophages to inhibit nuclear factor erythroid-related factor 2 (NRF2) expression. The expression of proteins involved in the above processes were measured by western blot. Results demonstrated that phorbol 12-myristate 13-acetate (PMA) significantly increased Mirt2 expression in THP-1 cells. Mirt2-knockdown enhanced ox-LDL-induced macrophage migration, lipid accumulation, inflammation, and inhibited cholesterol efflux. By contrast, Mirt2 overexpression displayed the opposite effects. Furthermore, Mirt2-knockdown inhibited NRF2 signaling and enhanced mitogen-activated protein kinase (MAPK) signaling, while Mirt2 overexpression displayed the opposite effects. Finally, the NRF2 inhibitor ML385 significantly reversed the above effects of Mirt2. In summary, Mirt2 served an important role in regulating lipid metabolism in macrophages via inhibiting MAPK signaling and activating the NRF2 signaling pathway.

lncRNA Mirt2 upregulates miR-1246 through methylation to suppress LPS-induced lung cell apoptosis

INTRODUCTION

Long noncoding RNA Mirt2 has been proven to be a suppressor of lipopolysaccharide (LPS) (a key player in sepsis)-induced inflammation responses. Therefore, Mirt2 may also participate in sepsis. This study was carried out to analyze the interactions between Mirt2 and microRNA-1246 (miR-1246) in sepsis, with a specific focus on sepsis-induced acute lung injury (sepsis-ALI).

METHODS

Forty sepsis patients (sepsis group; 23 males and 17 females; 40-65 years, 48.6 ± 6.3 years), 40 sepsis patients with acute lung injury (sepsis-ALI group, 23 males and 17 females; 40-65 years, 48.7 ± 6.4 years), and 40 healthy controls (control group, 23 males and 17 females; 40-65 years, 48.6 ± 6.1 years) were included. Mirt2 and miR-1246 expression in plasma samples from these patients were determined by a reverse transcription-quantitative polymerase chain reaction (PCR). Overexpression of Mirt2 and miR-1246 was achieved in human bronchial epithelial cells (HBEpCs) to explore the interaction between them. The effects of Mirt2 overexpression on miR-1246 methylation were analyzed by methylation-specific PCR. Cell apoptosis analysis was performed to analyze the role of Mirt2 and miR-1246 in the apoptosis of HBEpCs.

RESULTS

Mirt2 expression was downregulated in sepsis and was further downregulated in patients with sepsis-ALI. Mirt2 and miR-1246 found to be positively correlated. Downregulation of Mirt2 and miR-1246 was observed in HBEpCs with LPS treatment. In HBEpCs, Mirt2 overexpression increased miR-1246 expression but decreased its gene methylation. Cell apoptosis analysis showed that Mirt2 and miR-1246 negatively regulated the apoptosis of HBEpCs induced by LPS. In addition, miR-1246 inhibition reduced the inhibitory effects of Mirt2 overexpression on cell apoptosis.

CONCLUSIONS

Mirt2 may upregulate miR-1246 through methylation to suppress lung cell apoptosis.

Long noncoding RNAs: A potential target in sepsis-induced cellular disorder

Sepsis, an inflammation-related clinical syndrome, is characterized by disrupted immune homeostasis accompanied by infection and multiple organ dysfunction as determined by the Sequential Organ Failure Assessment (SOFA). Substantial evidence has recently suggested that lncRNAs orchestrate various biological processes in diseases, and lncRNAs play special roles in the diagnosis and management of sepsis. To date, very few reviews have provided clear and comprehensive clues to demonstrate the roles of lncRNAs in the pathogenesis of sepsis. Based on previously published studies, in this review, we summarize the different functions of lncRNAs in sepsis-induced cellular disorders and sepsis-induced organ failure to show the potential roles of lncRNAs in the diagnosis and management of sepsis. We further depict the function of some lncRNAs known to be pivotal regulators in the pathogenesis of sepsis to discuss the underlying molecular events. Additionally, we list and discuss several hotspots in research on lncRNAs, which may be conducive to future lncRNA-targeted therapeutic approaches for sepsis treatment.