ABSTRACT
Objective To investigate the effects of a microRNA family member , let-7e, on mono-cytic cell line THP-1 with regard to cell apoptosis and cytokine secretion and to analyze the possible mecha -nism.Methods THP-1 cells were transfected with mimic negative control (cy3) and observed with immu-nofluorescence microscopy for the evaluation of transfection rate .The expression of let-7e in THP-1 cells re-spectively transfected with let-7e mimic, mimic negative control, let-7e inhibitor and inhibitor negative con-trol were detected by qRT-PCR.MTT assay and flow cytometry analysis were used to detect the activities and apoptosis of transfected THP-1 cells.Western blot assay was performed to measure the expression of the genes encoding interferon alpha-inducible protein 6( IFI6 ) , enhancer of zeste homolog 2 (EZH 2 ) and caspase -3 that were target genes of let-7e predicted by bioinformatics analysis .THP-1 cells were transfected with let-7e mimic and mimic negative control for 48 h and then stimulated with LPS for 2 h for further detec-tion.The supernatants of cell culture were collected for the detection of secreted cytokines by Human Cyto -kine Array.Results The monocytic THP-1 cells were transfected with mimic negative control with a trans-fection efficiency of about 75%.There were 8.551±0.365, 83.893±15.941, 38.858±2.743 and 0.594± 0.174, 2.427±1.229, 3.053±0.207 fold increases in let-7e expression after the transient transfection of THP-1 cells with let-7e mimic and let-7e inhibitor for 12 h, 24 h and 48 h, respectively.The transfection of let-7e mimic into THP-1 cells enhanced the cell activities and inhibited the apoptosis of the transfected cells . Bioinformatics analysis showed that let-7e bound to the genes encoding EZH 2, IFI6 and caspase-3 with the mirSVR scores of -0.1608,-0.5693 and-0.9423, suggesting them as the predicted target genes of let-7e. The expressions of IFI6, EZH2 and caspase-3 in let-7e mimic transfected THP-1 cells were decreased as in-dicated by Western blot assay .The results of Human Cytokine Array showed that the expression of LPS-in-duced cytokines including CD154, G-CSF, CD54, IL-13, IL-1RA and IL-23 were inhibited in let-7e mimic transfected THP-1 cells. Con clusion Let-7e had an anti-apoptosis effect on monocytic THP-1 cells and in-fluenced the secretion of LPS-induced cytokines in THP-1 cells.Let-7e might regulate the biological function of THP-1 cells through inhibiting the expression of target genes encoding caspase -3, IFI6 and EZH2.
ABSTRACT
Objective To study the effects of a miRNA family member,let-7e,on the LPS-induced expression of TNF-α in primary monocytes and the possible mechanism.Methods Peripheral blood mononuclear cells (PBMCs) were isolated form human blood sample by using density gradient centrifugation for further isolation of primary monocytes.Flow cytometry analysis was used to measure the purity of isolated primary monocytes.The efficiencies of transfection were evaluated by qRT-PCR and immunofluorescence assay after transfecting the primary monocytes with let-7e mimic or miRNA mimic negative control (NC) for 24 h,36 h and 48 h.To screen out the optimal stimulation time,ELISA was performed to detect the concentrations of TNF-α in the supernatants of cell culture after stimulating the primary monocytes with 1 mg/L of LPS for 0 h,1 h,3 h,6 h and 12 h,respectively.ELISA and qRT-PCR were used to measure the expression of TNF-α in the transfected cells with the interference of LPS.Western blot assay was used to detect the level of enhancer of zeste homolog 2 (EZH2) in let-7e mimic-transfected primary monocytes and the levels of NF-κB p65,ADP-ribosylation factor GTPase-activating protein 1 (ARFGAP1) and Arfaptin2 in the siEZH2-transfected monocytes.Results More than 70％ of the isolated cells were CD14+ cells.The miRNA mimics could transfect the primary monocytes effectively and the transfection rate was about 70％.High levels of let7e were detected in let-7e mimic-transfected primary monocytes 24 hours after the transfection.High levels of TNF-α were observed in the primary monocytes after stimulated with LPS for 12 h,which was considered as the optimal LPS stimulation time.Results of the ELISA indicated that let-7e mimic significantly inhibited the LPS-induced expression of TNF-α in primary monocytes at both mRNA and protein levels.Western blot assay showed that the levels of EZH2 in the let-7e mimic transfected primary monocytes were significantly lower than that in mimic NC transfected primary monocytes.Silenced expression of EZH2 significantly inhibited the expression of NF-κB p65 in nucleus as well as the expression of ARFGAP1 and Arfaptin2.Conclusion let-7e mimic significantly inhibited the LPS-induced expression of TNF-α in primary monocytes.It is possible that Let-7e regulates the expression of NF-κB p65,ARFGAP1 and Arfaptin2 by targeting EZH2 directly to inhibit the expression of TNF-α.