CircSOD2: Disruption of intestinal mucosal barrier function in ulcerative colitis by regulating the miR-378g/Snail1 axis

BACKGROUND AND AIM

Circular RNA (circRNA) has been found to mediate ulcerative colitis (UC) progression by regulating intestinal mucosal barrier function. However, the role of circSOD2 in UC process and its underlying molecular mechanism still need to be further elucidated.

METHODS

Lipopolysaccharide (LPS)-induced Caco2 cells were used to mimic UC cell models. CircSOD2, miR-378g, and Snail1 levels were determined by quantitative real-time PCR. Cell viability was detected using MTT assay, and inflammatory cytokine levels were measured using ELISA. The intestinal mucosal barrier function was evaluated by testing transepithelial electrical resistance and fluorescein isothiocyanate (FITC)-dextran permeability. Snail1 and tight junction-related markers (Zo-1 and Claudin2) protein levels were examined using western blot. The interaction between miR-378g and circSOD2 or Snail1 was confirmed by dual-luciferase reporter assay. Dextran sulfate sodium (DSS) was used to induce UC rat models in vivo.

RESULTS

CircSOD2 was overexpressed in UC patients, and its knockdown significantly increased cell viability, transepithelial electrical resistance, and tight junction-related protein expression, while reduced inflammation cytokine levels and the permeability of FITC-dextran in LPS-induced Caco2 cells. In terms of mechanism, circSOD2 sponged miR-378g to positively regulate Snail1 expression. MiR-378g inhibitor reversed the effect of circSOD2 knockdown on intestinal mucosal barrier injury and Snail1 expression in LPS-induced Caco2 cells. In DSS-induced UC rat models, circSOD2 knockdown also could repair the intestinal mucosal barrier injury through regulating miR-378g/Snail1 axis.

CONCLUSION

CircSOD2 could destroy intestinal mucosal barrier function in LPS-induced Caco2 cells and DSS-induced UC rats by miR-378g/Snail1 axis.

CircSOD2 polarizes macrophages towards the M1 phenotype to alleviate cisplatin resistance in gastric cancer cells by targeting the miR-1296/STAT1 axis

Cisplatin is the first-line drug for gastric cancer (GC). Cisplatin resistance is the most important cause of poor prognosis for GC. Increasing evidence has identified the important role of macrophage polarization in chemoresistance. CircRNAs are newly discovered non-coding RNAs, characterized by covalently closed loops with high stability. Previous studies have reported a significant difference between circRNA profiles expressed in classically activated M1 macrophages, and those expressed in alternatively activated M2 macrophages. However, the underlying mechanism behind the regulation of GC cisplatin resistance by macrophages remains unclear. In our study, we observed the aberrant high expression of circSOD2 in M1 macrophages derived from THP-1. These expression patterns were confirmed in macrophages from patients with GC. Detection of the M1 and M2 markers confirmed that overexpression of circSOD2 enhances M1 polarization. The viability of cisplatin-treated GC cells was significantly reduced in the presence of macrophages overexpressing circSOD2, and cisplatin-induced apoptosis increased dramatically. In vivo experiments showed that macrophages expressing circSOD2 enhanced the effect of cisplatin. Moreover, we demonstrated that circSOD2 acts as a microRNA sponge for miR-1296 and regulates the expression of its target gene STAT1 (signal transducer and activator of transcription 1). CircSOD2 exerts its function through the miR-1296/STAT1 axis. Inhibition of circSOD2/miR-1296/STAT1 may therefore reduce M1 polarization. Overexpression of circSOD2 promotes the polarization of M1 macrophages and enhances the effect of cisplatin in GC. CircSOD2 is a novel positive regulator of M1 macrophages and may serve as a potential target for GC chemotherapy.

Knockdown of circSOD2 ameliorates osteoarthritis progression via the miR-224-5p/PRDX3 axis

BACKGROUND

Although the implications of circular RNAs (circRNAs) with the progression of diverse pathological conditions have been reported, the circRNA players in osteoarthritis (OA) are barely studied.

METHODS

In this study, twenty-five OA patients who received arthroplasty were recruited for cartilage tissue collection. Public circRNA microarray data from Gene Expression Omnibus was retrieved for circRNA identification. An in vitro cell model of OA-related damages was constructed by treating human chondrocytes (CHON-001 cell line) with IL-1β, and circSOD2 siRNA was used to silence circSOD2 expression to study its functional role in apoptosis, inflammatory responses, and extracellular matrix (ECM) degradation. Besides, we investigated the functional interactions among circSOD2, miR-224-5p, and peroxiredoxin 3 (PRDX3) by luciferase reporter assay, RNA-immunoprecipitation assay, and quantitative reverse transcription polymerase chain reaction.

RESULTS

Our findings revealed the overexpression of circSOD2 in the OA cartilage and cell samples, and circSOD2 knockdown alleviated ECM degradation, inflammation, and apoptosis in CHON-001 cell model. In addition, our findings suggested the regulatory function of circSOD2 knockdown on miR-224-5p expression, while miR-224-5p was capable of downregulating PRDX3 expression. The co-transfection of miR-224-5p inhibitor or pcDNA-PRDX3 could prevent the effect of circSOD2 knockdown.

CONCLUSION

Hence, our results demonstrated that knockdown of circSOD2 may serve as an intervention strategy to alleviate OA progression through modulating miR-224-5p/PRDX3 signaling axis.