RESUMO
ObjectiveTo investigate the regulatory effect of circular RNA circ_0120051 on the fibrotic phenotype of cardiac fibroblasts and the potential mechanism involved. MethodsThe expression of circ_0120051 and its host gene of solute carrier family 8 member A1（SLC8A1） mRNA in the myocardium of healthy organ donors （n=24） and heart failure （HF） patients （n=21） were assessed by real-time quantitative polymerase chain reaction （RT-qPCR） assay. RNA stability of circ_0120051 was identified by RNase R exonuclease digestion assay. The cytoplasmic and nuclear distribution of circ_0120051 in human cardiomyocyte AC16 was detected by RT-qPCR assay. The expression of fibrosis-related genes in mouse cardiac fibroblasts （mCFs） with adenovirus-mediated overexpression of circ_0120051 was detected by RT-qPCR and Western blot assay， respectively. The effect of overexpression of circ_0120051 on the migration activity of mCFs was evaluated by wound-healing assay. RNA co-immunoprecipitation （RIP） was conducted to detect the interaction between circ_0120051 and miR-144-3p. The binding site of miR-144-3p in the 3'-UTR of isocitrate dehydrogenase 2 （Idh2） mRNA was identified by the dual luciferase reporter gene assay. ResultsCirc_0120051 was significantly up-regulated in the myocardium of HF patients， while the mRNA expression of its host gene SLC8A1 was not changed. Circ_0120051 was mainly located in the cytoplasm of human AC16 cells. Results of RNase R exonuclease digestion revealed that circ_0120051 possesses the characteristic stability of circular RNA compared to the linear SLC8A1 mRNA. Overexpression of circ_0120051 could inhibit the expression of fibrosis-related gene in mCFs and mCFs migration. RIP assay confirmed the specific interaction between circ_0120051 and miR-144-3p. Transfection of miR-144-3p mimic could efficiently promote the expression of fibrosis-related genes in mCFs and reverse the inhibitory effect of circ_0120051 on the fibrotic phenotype of mCFs. Results of the dual luciferase reporter gene assay confirmed the interaction between miR-144-3p and the 3'-UTR of Idh2. Transfection of miR-144-3p transcriptionally inhibited Idh2 expression， and overexpression of circ_0120051 enhanced IDH2 expression in mCFs. MiR-144-3p mimic and Idh2 small interfering RNA （siRNA） could consistently reverse the inhibitory effects of circ_0120051 on fibrosis-related genes expression in mCFs and mCFs migration. ConclusionsCirc_0120051 inhibits the fibrotic phenotype of cardiac fibroblasts via sponging miR-144-3p to enhance the target gene of IDH2 expression.
RESUMO
ObjectiveTo investigate the effect of circSLC8A1_005 on the fibrotic phenotype of cardiac fibroblasts and the potential mechanism involved. MethodsThe effect of adenovirus-mediated overexpression of circSLC8A1_005 on the expression of fibrosis-related genes， collagen type I alpha 1 chain （Col1a1）， collagen type Ⅲ alpha 1 chain （Col3a1） and smooth muscle actin alpha 2 （Acta2）， in mouse cardiac fibroblasts （mCFs） were detected. The proliferation and migration activities of mCFs were detected by EdU and wound-healing assay， respectively. Dual luciferase reporter gene assay was performed to detect the activity of potential internal ribozyme entry site （IRES） in circSLC8A1_005. CircSLC8A1_005-translated protein， SLC8A1-605aa， and its intracellular distribution was identified by Western blot assay. The effect of SLC8A1-605aa protein on transcription activity of Sod2 gene was detected by the dual luciferase reporter gene assay. RNA binding protein immunoprecipitation （RIP） was utilized to verify the interaction between SLC8A1-605aa and superoxide dismutase 2 （Sod2） mRNA. Actinomycin D treatment was used to detect the effect of SLC8A1-605aa on Sod2 mRNA stability in mCFs. ResultsAn efficient adenovirus-mediated overexpression of circSLC8A1_005 was achieved in mCFs. The enforced expression of circSLC8A1_005 suppressed proliferation and migration of mCFs， and inhibited the expression of fibrosis-related genes in mCFs. The dual luciferase reporter gene assay revealed the activities of 2 IRES in circSLC8A1_005. Results of Western blot assay showed that circSLC8A1_005 could translate protein SLC8A1-605aa with the prospected molecular weight of 70 ku， which is predominantly distributed in the nucleus. Overexpression of the circSLC8A1_005 and SLC8A1-605aa could consistently inhibit the fibrotic phenotype of mCFs. SLC8A1-605aa could up-regulate superoxide dismutase 2 （Sod2） expression， but not at the transcriptional level. RIP assay indicated that SLC8A1-605aa could specifically interact with Sod2 mRNA， and the results of actinomycin D assay showed that SLC8A1-605aa could enhance the stability of Sod2 mRNA in mCFs. ConclusionCircSLC8A1_005 inhibits the fibrotic phenotype of cardiac fibroblasts via translating SLC8A1-605aa protein， and SLC8A1-605aa may be a potential target for the treatment of myocardial fibrosis.