circ_VMA21 protects WI-38 cells against LPS-induced apoptotic and inflammatory injury by acting on the miR-409-3p/KLF4 axis

Abstract

Highlights1. circ_VMA21 ameliorates LPS-induced WI-38 cellular apoptosis and inflammation 2. circ_VMA21 targets miR-409-3p and KLF4 is a target of miR-409-3p 3. circ_VMA21 promotes the expression of KLF4 via sponging miR-409-3p Abstract. Pneumonia is a common inflammatory lung disease. Circular RNA (circRNA) vacuolar ATPase assembly factor (circ_VMA21) has been reported to mitigate the inflammatory injury in WI-38 cells. This study was to investigate the functional mechanism of circ_VMA21. Cell model was established by lipopolysaccharide (LPS) treatment in WI-38 cells. Cell cycle and apoptosis were analyzed by flow cytometry. Cell proliferation was assessed by colony formation and MTT assays. The expression quantification of circ_VMA21, microRNA-409-3p (miR-409-3p) and Kruppel-like transcription factor 4 (KLF4) was performed by qRT-PCR method. The expression of relative protein was detected by Western blot. Inflammatory response was evaluated by ELISA. The target binding was validated by dual-luciferase reporter assay. Cellular analysis indicated that LPS repressed cell cycle and proliferation but induced apoptosis. circ_VMA21 was downregulated in pneumonia samples and LPS-treated WI-38 cells. Functionally, circ_VMA21 assuaged the LPS-induced apoptotic and inflammatory damages. In addition, circ_VMA21 directly targeted miR-409-3p and its function was dependent on the sponge effect on miR-409-3p. Also, KLF4 was a target of miR-409-3p and miR-409-3p inhibitor attenuated LPS-induced cell injury by upregulating KLF4. Moreover, KLF4 was upregulated by circ_VMA21/miR-409-3p axis. These findings suggested that circ_VMA21 relieved the LPS-induced apoptotic and inflammatory injury by the regulation of miR-409-3p/KLF4 axis.

Sinomenine attenuates lipopolysaccharide‐induced inflammation and apoptosis of WI‐38 cells by reducing glutathione S‐transferase M1 expression

“…However, a previous study showed that apoptotic processes and inflammation inhibit each other (Wallach & Kovalenko, 2014), which contradicts our results. Actually, many previous reports demonstrated simultaneous apoptosis and inflammation following LPS treatment in WI‐38 cells (Li, Li, et al, 2021; Li, Xie, & Zhang, 2021; Ma et al, 2021; Wang, Zhang, & Chen, 2021; Wang, Zhang, Zhao, & Dai, 2021; Zhang, Dong, et al, 2020; Zhang, Xiang, et al, 2020; Zhou et al, 2019). The contradictory results may be due to the different cell lines used.…”

“…Similarly, our study found that sinomenine blunted the inflammation in WI‐38 cells challenged by LPS, indicating its anti‐inflammatory role in WI‐38 cells. Lung cell apoptosis is also an important property in LPS‐induced pediatric pneumonia model (He et al, 2021; Wang, Zhang, & Chen, 2021; Wang, Zhang, Zhao, & Dai, 2021; Yang et al, 2021). Consistent to these reports, this research also found the increased apoptosis in LPS‐challenged WI‐38 cells.…”

Circular RNA circ_0099188 contributes to lipopolysaccharide (LPS)-induced HPAEpiC cell injury by targeting the miR-1236-3p/HMGB3 axis

“…As a matter of fact, circRNAs have aroused growing attention for the development of the ideal candidate biomarkers, based on their salient features, containing stability, conservation, abundance, and tissues and stage specificity (17,36). Lately, several circRNAs are being found to be frequently abnormally expressed in the pathological processes of pneumonia (37)(38)(39). Notably, LPS performs as a powerful proinflammatory molecule (40,41).…”

Circ_0035292 knockdown alleviates lipopolysaccharide (LPS)‐induced WI‐38 cell apoptosis and inflammatory injury

“…For example, circ‐UQCRC2 absence alleviated lipopolysaccharide (LPS)‐triggered 16HBE cell inflammation in IP via MYD88 expression 10 . Circ_VMA21 receded LPS‐initiated Wistsar Institute (WI)‐38 cell injury via enhancing KLF4 through sponging miR‐409‐3p 11 . Moreover, circ_0035292 (circTMOD3) interference was able to relieve LPS‐caused cell injury via miR‐146b‐3p/CXCR1 pathway 12 .…”

“… 10 Circ_VMA21 receded LPS‐initiated Wistsar Institute (WI)‐38 cell injury via enhancing KLF4 through sponging miR‐409‐3p. 11 Moreover, circ_0035292 (circTMOD3) interference was able to relieve LPS‐caused cell injury via miR‐146b‐3p/CXCR1 pathway. 12 Even so, circ_0035292‐mediated potential regulatory mechanisms in IP are largely elusive.…”