Cell culture
Established THP-1 human macrophages (Wang et al. 2016) were purchased from Institute of Cell Research, Chinese Academy of Sciences (Shanghai, China). THP-1 macrophages were cultured in RPMI-1640 containing 10% fetal bovine serum (from Gibco; Thermo Fisher Scientific, Inc.) and 100 U/ml penicillin. We treated THP-1 cells with 100 ng/ml phorbol 12-myristate 13-acetate (PMA, AdipoGen, USA) for 24 h to generate M0 macrophages (M0) (Chanput et al. 2013). 100 ug/ml lipopolysaccharide (LPS) was treated with THP-1 cells (1–1.5 × 108) for 48 h to induced M1 macrophages. PF (MedCham Express) was dissolved in dimethyl sulfoxide (DMSO). Cells were treated with various concentrations of PF (0,1, 10, 100, 500, 1000, 2000 and 3000 ug/ml) for 48 h, and appropriate controls were treated with DMSO at the same concentrations. The cells were placed in a cell incubator containing 5 % CO2 at 37 °C for cultivation.
Cell viability assays
Cell viability was measured by using a Cell Counting Kit-8 (CCK-8, Dojindo, Japan) according to the manufacturer’s instructions. Briefly, cells were seeded at a density of 0.3 × 104 cells/well in 96-well plates, and incubated in 1640 medium overnight. Then, CCK-8 solution (10 ul) and 90 ul 1640 medium (serum free) was added to each well for 2 h and optical density was measured at 450 nm. The proliferation of cells was detected at 12 h, 24 h, 36 and 24 h.
Quantitative real‐time (RT-PCR)
For RT-PCR analysis, total RNA was isolated by using the TRIzol reagent (Takara Bio, Inc), and reverse transcription was performed using the PrimeScript RT reagent kit (Takara Bio, Inc) according to manufacturer’s instructions. The primers used in this study were shown as follow: GAPDH (forward sequence (F): 5′–GAAGGTGAAGGTCGGAGTC–3′ and reverse sequence (R): 5′–GAAGATGGTGATGGGATTTC–3′), IL-6 (F: 5′–ATGAACTCCTTCTCCACAAGC–3′ and R: 5–CTACATTTGCCGAAGAGCCCTCAGGCTGGACTG–3′), TNF-α (F:5′–ATGAGCACTGAAAGCATGATC–3′ and R:5′–TCACAGGGCAATGATCCCAAAGTAGACCTGCCC–3′), IL-1β (F: 5′–ATGATGGCTTATTACAGTGGCAA–3′ and R: 5′–GTCGGAGATTCGTAGCTGGA–3′), miR-124 (5′–GCGAGGATCTGTGAATGCCAAA–3′) and U6 (CD201-1045, Provided by Tiangen Biotech). GAPDH and U6 were used as negative control. The gene expression analysis was performed by quantitative real-time PCR (StepOne Plus; Applied Biosystems, USA) with standard SYBR-Green PCR kits (Takara Bio, Inc). Reactions were conducted by an initial incubation at 95 °C for 2 min, followed by 40 cycles of 95 °C for 15 s and 60 °C for 30 s. The relative expression of each target gene normalized to GAPDH was calculated using the 2−ΔΔct method.
Western blot
We lysed the cells using a protein extraction reagent (Beyotime, Jiangsu, China) in the presence of protease and phosphatase inhibitor cocktail tablets. We measured protein concentration using a BCA Protein Assay Kit (Beyotime, Jiangsu, China). Soluble lysates containing about 50 µg proteins per sample were resolved with sodium dodecyl sulfate–polyacrylamide gel electrophoresis and transferred to a polyvinylidene fluoride membrane (Merck Millipore). After blocking using 10 % fat-free milk, membranes were incubated with primary antibodies against IL-6 (1:100, CST), TNF-α (1:100,CST), IL-1β (ab234437, abacam) and β-actin (1:100, CST) overnight at 4 °C overnight and secondary antibodies (1:1000) at room temperature for 1 h. After several washes, the immunoblot was detected with enhanced chemi-luminescence (Pierce Biotechnology) according to the manufacturer’s instructions.
Apoptosis assay
After drug treatment for 48 h, cells were harvested and washed twice with PBS and resuspended in binding buffer, then the cells were double-stained with Annexin V-Phycoerythrin (PE) and 7-aminoactinomycin (7-AAD) (BD Biosciences) for 15 min at room temperature in the dark. Subsequently, cells were analyzed by flow cytometry using Calibur (BD Biosciences) within 1 h.
2.6 Cell transfection
miRNA-124 mimic and inhibitor were purchased from GenePharma (Shanghai, China). The miRNA-124 mimic and miRNA-124 inhibitor were designed according to the sequence: 5′–GCGAGGATCTGTGAATGCCAAA–3′. Inhibitor-Negative Control (inhibitor-NC) and mimic-NC were provided by GenePharma (Shanghai, China). Cells were transfected with 25–50 nM of the indicated miRNA-124 mimic, mimic-NC, miRNA-124 inhibitor and inhibitor-NC using Lipofectamine 200 reagent (GenePharma, Shanghai, China).
ELISA
The Human TNF alpha ELISA Kit (ab181421, abacam), Human IL-6 ELISA Kit (ab178013, abacam) and Human IL-1 beta ELISA Kit (ab214025, abacam) were used to detected the expression of TNF-α, IL-6 and IL-1β in the cell lysate and cell supernatant of THP-1 cells. Each experiment was repeated at least three times.
Bioinformatics prediction
The 2D and 3D structure of PF was provided by PubChem (https://pubchem.ncbi.nlm.nih.gov/). The potential mechanism involved in PF was predicted via the Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform (TCMSP) (https://tcmspw.com/tcmsp.php). The potential miRNA targets of LPS-binding protein were predicted via the miRwalk (http://mirwalk.umm.uni-heidelberg.de/), Targetscan (http://www.targetscan.org/mamm_31/) and miRDB (http://mirdb.org/) database.
Statistical analysis
The SPSS version 21.0 software was used for data analyses. Statistical significance was confirmed using a Student’s t test. Statistically significant differences were defined as p < 0.05.