CircSmox knockdown alleviates PC12 cell apoptosis and inflammation in spinal cord injury by miR‐340‐5p/Smurf1 axis

Abstract

Background Spinal cord injury (SCI) is a traumatic central nervous system disorder that leads to irreversible neurological dysfunction. Emerging evidence has shown that differentially expressed circular RNAs (circRNAs) after SCI is closely associated with the pathophysiological process. Herein, the potential function of circRNA spermine oxidase (circSmox) in functional recovery after SCI was investigated. Methods Differentiated PC12 cells stimulated with lipopolysaccharide (LPS) were employed as an in vitro model for neurotoxicity research. Levels of genes and proteins were detected by quantitative real‐time PCR and Western blot analysis. Cell viability and apoptosis were determined by CCK‐8 assay and flow cytometry. Western blot analysis was used to detect the protein level of apoptosis‐related markers. The levels of interleukin (IL)‐1β, IL‐6, IL‐8, and tumor necrosis factor (TNF)‐α. Dual‐luciferase reporter, RIP, and pull‐down assays were used to confirm the target relationship between miR‐340‐5p and circSmox or Smurf1 (SMAD Specific E3 Ubiquitin Protein Ligase 1). Results LPS elevated the levels of circSmox and Smurf1, but decreased the levels of miR‐340‐5p in PC12 cells in a dose‐dependent manner. Functionally, circSmox silencing alleviated LPS‐induced apoptosis and inflammation in PC12 cells in vitro. Mechanistically, circSmox directly sponged miR‐340‐5p, which targeted Smurf1. Rescue experiments showed that miR‐340‐5p inhibition attenuated the neuroprotective effect of circSmox siRNA in PC12 cells. Moreover, miR‐340‐5p suppressed LPS‐triggered neurotoxicity in PC12 cells, which was reversed by Smurf1 overexpression. Conclusion CircSmox enhances LPS‐induced apoptosis and inflammation via miR‐340‐5p/Smurf1 axis, providing an exciting view of the potential involvement of circSmox in SCI pathogenesis.

Unveiling the hidden players: noncoding RNAs orchestrating polyamine metabolism in disease

“…To gain a deeper understanding of circSMOX, future analysis will be required to investigate its specific role, the mechanisms governing its expression, and the effects of circSMOX on its linear counterpart and PA metabolism. A recent study by Han and colleagues demonstrated that circSMOX plays a functional role in PC12 cell response to LPS stimulation [ 157 ]. Indeed, the authors demonstrated that the circRNA expression increases after stimulation and that circSMOX interacts with the miR‐340‐5p, functioning as a miRNA sponge.…”

The roles of circular RNAs in nerve injury and repair

“…Additionally, circ0000962 is down-regulated after SCI, and its overexpression can reduce the inflammatory response through the miR-302b-3p-mediated PI3K/Akt/NF-κB signaling ( He et al, 2020 ). CircSmox expression was also increased after SCI, and its knockdown alleviates LPS-induced neuroinflammation and apoptosis in PC12 cells via the miR-12-340p/Smurf5 axis, exerting a neuroprotective effect ( Han et al, 2023 ). Furthermore, circRNA_014301 is associated with neuroinflammation and its silencing has been shown to attenuate apoptosis and inflammation in PC12 cells ( Xie et al, 2021 ).…”

Down-regulated miR-10a protects against spinal cord injury by up-regulating SIRT1

“…The literature indicates the involvement of miRNAs in different biological mechanisms, such as cell apoptosis, growth, and differentiation (7)(8)(9). Traumatic SCI-induced alterations in the expression of various miRNAs have been identi ed in adult rats, for instance, miR-21 (10), miR-125b (11), and miR-340-5p (12). Furthermore, miR-10a has been linked with different neurological diseases, for instance, Alzheimer's disease (13,14), Parkinson's disease (14), and ischemic stroke (15), suggesting its potential involvement in neurodegenerative processes.…”