1.1 Animals
180 clean healthy SD rats, weighing 200-250g, were supplied by the Experimental Animal Center of Guangxi Food and Drug Inspection Institute. The experimental operation was carried out in the experimental operation room of the First Affiliated Hospital of Guangxi University of Traditional Chinese Medicine. All rats were classified at random into 9 groups, each with 20 rats: blank group, LPS (Sigma, USA) control group, LPS + NF-κB blocker (PDTC) group, LPS + p38MAPK blocker (SB203580) group, LPS + PDTC + SB203580 group, LPS + rhubarb lingxian (Jiangyin Tianjiang Pharmaceutical Co, Ltd. China) group, LPS+ PDTC+ rhubarb lingxian group, LPS + SB203580 + rhubarb lingxian group, and LPS + PDTC + SB203580 + rhubarb lingxian group.
1.2 Method
1.2.1 Bile duct cell isolation and culture
After anesthetizing the rats and removing most of the liver tissue, a complete bile duct tree for the separation of bile duct cells was obtained under a microscope. Free bile duct tree was grinded and bile duct cells were digested by adding 2.5 g / L pancreatin, 2 × 104 U / L Dnase I collagen digestion enzyme and 2 × 105 U / L Dnase IV collagen digestion enzyme. Then the cells were separated and purified with immunomagnetic beads and cultured in 1 × 10^5 /ml cells in flasks. After 6 days of culture, fluorescence microscopy was used to identify the concentration of bile duct epithelial cells. The fixing of cultured cells in methanol at -20 ° C for 20 min and washing with phosphate buffered saline twice (2 min / time) were conducted. Rabbit anti-mouse CK 19 (5 μg / ml, Santa Cruze, USA) was added to incubate overnight at 4 ° C. Alexa Flourr®594 donkey anti-rabbit IgG second antibody (1: 1000, Introvigen, USA) was add to incubate at 37 ° C for 30 min on the next day. Finally, DAPI staining (1 μg / ml) was used to investigate whether the purity of isolated rat bile duct epithelial cells was reached to 95% under a fluorescence microscope. Meanwhile, trypan blue staining exclusion method was used to determine the activity of epithelial cells. After staining, the survival rate of these cells was found to be above 90%. The cell densities were adjusted to 1 × 10^5 cells / ml. The cells were inoculated into a 50 ml plastic culture bottle coated with type I rat tail collagen in 37℃, 5% CO2 incubator.
1.2.2 Survival rate
Applying CCK-8 colorimetric method, cell viability was determined. Cells were cultured in 96-well plates in 5% CO2, 37˚C incubator overnight wherein the density was adjusted to 5 × 10^3 cells / well, and then stimulated with or without LPS (650, 1250, 2500, 5000 and 10000 ng / ml), rhubarb lingxian (0.5, 0.75, 1.0, 1.25 and 1.5 mg / ml), PDTC (2.5, 5, 10, 20 and 40 µmol / l), SB203580 (2.5, 5, 10, 20 and 40 µmol / l) for 24 h. Finally, incubations were completed for 1 hour at 37˚C after adding 10 μl CCK-8 into each well, and then the measurement of absorbance was achieved at 450 nm.
1.2.3 RT-PCR
The extraction of total RNA was conducted utilizing the Trizol method. The concentration was measured on an ultra-micro UV photometer to determine the RNA quality. The DNA purity with an OD260/OD280 ratio of 1.8–2.0 can meet the needs of subsequent RT-qPCR. After removing genomic DNA, first-strand cDNA was produced according to (Promega, USA) protocol. Resulting cDNA was amplified in a 20 µL reaction mixture with the use of SYBR Green PCR Master Mix (Roche, USA), as well as 7500 Real-Time PCR System (Applied Biosystem). Primer 5.0 software was used to design primers for each gene and GAPDH (Table 1). Fold changes in expression were calculated with the use of 2–ΔΔCT method. GAPDH was utilized as reference gene for standardization. The mRNA expression levels were tested with 3 replicate wells, and the final results were averaged.
Table 1
The primer of target genes and GAPDH.
Genes
|
Primers
|
Myd88 Forward
|
CTAGCCTTGTTAGACCGTGA
|
Myd88 Reverse
|
GTCTGTGGGACACTGCTCT
|
TRAF6 Forward
|
GCCCATGCCGTATGAAGAGA
|
TRAF6 Reverse
|
ACTGAATGTGCAGGGGACTG
|
TAK1 Forward
|
CGCCATCGCAGGTCCTTAAC
|
TAK1 Reverse
|
GGCTGCATGCTGTGCAGGTA
|
IKKa Forward
|
AAGTTCGGTTTAGTAGCC
|
IKKa Reverse
|
CTTCCTTTAGCCCAGATA
|
NF-κB Forward
|
GAAGCAACAGCTCACGGAGGA
|
NF-κB Reverse
|
TGTTCTGGAAGTTGAGGAAGGCC
|
β-actin Forward
|
CACGATGGAGGGGCCGGACTCATC
|
β-actin Reverse
|
TAAAGACCTCTATGCCAACACAGT
|
1.2.4 Western blot
The bile duct epithelial cells were pretreated with 1 mg / ml rhubarb lingxian, PDTC and SB203580 for 2 hours in 36 well culture plates (5 × 10^5 cells / ml), and then stimulated with 500 ng / ml LPS for 12h. The protein extraction kit was utilized to isolate the total protein, whereas the BCA protein detection kit to determine protein concentration. An equal amount of protein (25 µg) were added, separated with 30% sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and then transferred onto polyvinylidene difluoride membranes (PVDF), which was sealed at room temperature with 5% nonfat milk for 1 hour, and subsequently incubated with mouse anti-β actin mAb (Zhongshan, China), NF-κB p65 (CST, USA), p38MAPK (CST, USA) and TLR4 (Proteintech, USA) antibody. The detection strip of the electrochemiluminescence kit. Image J v1.8.0 software, along with GraphPad Prism v.6 software was served for protein-level analysis.
1.2.5 Detection of inflammatory cytokines
The cells on a 36-well culture plate (5 × 10^5 cells / ml) were pretreated with 1 mg / ml rhubarb lingxian formula, PDTC and SB203580 for 2 hours according to grouping requirements, and then treated with LPS (500 ng / ml) for 12 hours. The collected cellular supernatant was adopted to detect serum TNF-α (Cusabio, China), IL-6 (Cusabio, China) and IL-8 (Cusabio, China) levels by ELISA kit.
1.3 Statistical analysis
All data were displayed as mean ± standard deviation (X ± S) and tested for normality homogeneity of variance prior to analysis. If the data showed in compliance with the test, the LSD method was used for comparison between groups; if not, the Dunnett's T3 method was used. The rank sum test is used if the variable doesn’t obey normal distribution. P < 0.05 represents harboring statistical significances.