Long Non-coding RNA XIST Impedes LPS-induced AC16 Cell Inflammation and Apoptosis through Down-regulating miR-370-3p and Regulating PI3K/AKT/mTOR Pathways
Authors: Qiu Min , Xiao Jun , Long Mingzhi , Zhou Shushu , Guo Shouyu , Xu Shaohua , Jiang Hai 
Published: February 2023

Background/Purpose:
Myocarditis is a severe disorder characterized by the inflammation of the heart's muscular walls, thereby leading to sudden death in young adults. Long non-coding RNA X-inactive specific transcripts (LncRNA XIST) are a class of transcripts having a length ˃ 200 nts with the absence of protein-coding abilities. They exert their function of apoptosis in various cancers and inflammatory diseases.

background:
Myocarditis is a severe disorder characterized by the inflammation of the heart muscular walls leading to the sudden death in young adults. Long non-coding RNA X-inacitve specific transcript (LncRNA XIST) are a class of transcripts having length ˃ 200 nts with absence of protein coding abilities. They exerts its function in apoptosis in various cancers and inflammation diseases.

Objective:
The current work intended to investigate the impact and mechanism of XIST on inflammation induced by LPS in AC16 cells.

objective:
The current work intended to investigate the impact and mechanism of XIST in in the inflammation induced by LPS in AC16 cells.

Methods:
An in vitro inflammatory injury model was established by stimulating AC16 cells with LPS. CCK-8 was used to test AC16 cell viability and FCM to detect apoptosis. The Elisa assay was used to measure the level of IL-8, IL-1β, and TNF-α. The RT-qPCR was used to detect XIST, miR-370-3p, Bax, and Bcl-2 in LPS-stimulated AC16 cells. The Elisa assay was performed to assess the phosphorylation of PI3K, AKT and mTOR in AC16 cells.

method:
An in vitro inflammatory injury model was established by stimulating AC16 cells with LPS. CCK-8 assay was employed to examine the AC16 cell viability while the cell apoptosis was detected by FCM assay. The level of IL-8, IL-1β, and TNF-α were assessed using Elisa assay. The expression of XIST, miR-370-3p and the mRNA expressions of Bax and Bcl-2 in AC16 cells stimulated with LPS were detected using RT-qPCR. Elisa assay was performed to assess the phosphorylation of PI3K, AKT and mTOR in AC16 cells.

Results:
Our findings showed LPS exposure to significantly reduce AC16 cell viability while increasing inflammation and apoptosis. Also, XIST expression was reduced in AC16 cells stimulated with LPS. Overexpression of XIST in AC16 cells increased cell survival, inhibited apoptosis, and increased the expressions of Bcl-2, Bax, and inflammatory modulators (IL-8, TNF-α, and IL-1β). Inhibiting XIST in AC16 cells produced opposite outcomes. MiR-370-3p mimics inhibited XIST's effect on inflammation, viability, and apoptosis. Moreover, XIST inhibited the phosphorylation levels of mTOR, AKT, and PI3K in LPS-injured AC16 cells.

result:
Our results indicated that exposure of LPS significantly decreased the AC16 cell viability while increased the inflammation and apoptosis in AC16 cells. Also, XIST expression was reduced in AC16 cells stimulated with LPS. Overexpression of XIST mitigated the injury induced by LPS in AC16 cells, proved by enhancing the cell viability, inhibiting apoptosis rate and levels of Bcl-2 and Bax and inflammatory modulators (IL-8, TNF-α, and IL-1β) in LPS-stimulated AC16 cells. Besides, opposite results were observed by the inhibition of XIST in AC16 cells. Furthermore, XIST negatively regulated miR-370-3p expression and the impact of XIST overexpression on the inflammation, viability and apoptosis was blocked by miR-370-3p mimic. Moreover, XIST inhibited the phosphorylation level of mTOR, AKT, and PI3K in LPS-injured AC16 cells.

Conclusion:
The data elucidate lncRNA XIST to exert its anti-inflammatory and anti-apoptotic effects on AC16 cells stimulated by LPS via down-regulating miR-370-3p and inhibiting PI3K/AKT/mTOR pathways. These findings suggest a novel treatment strategy for myocarditis.

other:
Not applicable