- Mice, virus and drugs
Male ICR mice at 6-8 weeks of age, were purchased from Beijing Vital River Laboratory Animal Technology Company (Beijing, China). The mice were randomly divided into 6 groups: control group, model group, prophylactic group, therapeutic group, sham group and ribavirin group. Mice were monitored for survival, weight loss, and clinical signs of illness (e.g., inactivity, ruffled fur, hunched posture, poor appetite, rapid shallow breathing and audible crackling) for 14 days. The influenza A/PR/8/H1N1 virus was kindly gifted by professor Yu Hao from the Department of Immunology and Microbiology, Beijing University of Chinese Medicine (Beijing, China). The LD50 was determined in mice after serial dilution of the stock. We challenged ICR mice with 5 LD50 A/PR8 (25 mL). Infection was established by intranasal inoculation in mice after anesthetized by isoflurane. Ribavirin was purchased from Biokin Pharmaceutical (Sichuan, China). The ribavirin group was given ribavirin (100mg/kg), once a day for 7 days. All experimental procedures were conducted according to the National Institute of Health Guide for the Care and Use of Laboratory Animals, and approved by the Animal Care Committee of Beijing University of Chinese Medicine.
- Gua Sha treatment on experimental mice
Mice were anesthetized by 5% isoflurane and maintained at 1.5-2%. In the prophylactic and therapeutic groups, Gua Sha was performed on the side of the mouse's back by using a buffalo-horn Gua Sha plate, after the hair was shaved with a clipper a day prior to the experiment. The shaved skin area was wiped with 70% ethanol and left to dry. Then, scrape the back 100-150 times/min from neck to tail in a unidirectional manner, with an angle of about 90° between the Gua Sha plate and the mouse's back. The force of scrape was based on the appearance of red spots or freckles. Meanwhile, the sham group was scraping at the same frequency and force in the left thigh of the mouse.
- Pathological analysis
At the end of experiment, the whole lungs of the mice were removed, washed in phosphate buffer and fixed in 10% formaldehyde at room temperature. Then lung tissues were dehydrated in graded concentration of ethanol, embedded in paraffin and sliced. Tissue sections of 4 μm thickness were stained with hematoxylin-eosin (HE). Then two experienced pathologists blinded with mice group observed sections of lung tissue under a light microscope and scored the lung injury through the method as described by Mikawa [18]: (a) alveolar congestion, (b) hemorrhage, (c) neutrophil infiltration in the alveolar and vascular wall, and (d) alveolar wall thickening/the formation of the hyaline membrane. Each of the above items was graded into five levels: 0=no damage, 1=slight damage, 2=moderate damage, 3= severe damage, and 4=extremely severe damage. The sum of the four items was the final score with a maximum of 16.
- Immunohistochemistry
Immunohistochemistry (IHC) method was adopted to detect the expression of MMP-9 in the paraffin sections of mouse lung tissue. After being sliced, dewaxed, and hydrated, sections were placed in 3% H2O2 to incubate for 10 min, then rinsed 5 min three times with phosphate-buffered saline (PBS). Then they were incubated with 0.01 M citrate buffer for 15 min in 95℃ water and flushed 5 min three times with PBS. For primary antibody incubation, anti-mouse MMP-9 antibody (from BioLegend, Inc., San Diego, CA) was diluted at 1:1000 with PBS and added into sections at 4℃ overnight. Horseradish Peroxidase(HPR)-labeled secondary antibody (from Zsbio Commerce Store, Beijing, China) was incubated at 37℃ for 20 min. Peroxidase activity was detected by using 3,3-diaminobenzidine tetrachloride (DAB; Beijing solarbio science﹠technology co., ltd., Beijing, China). Sections were counterstained by using hematoxylin and then observed under microscope. Ten visual fields were randomly selected for each group, and their integral optical density (OD) was measured by use of Image Pro software, and then semiquantitative analysis was conducted by means of statistical software.
- Cell isolation from lung tissues
After sacrificing on day 6, lung tissues from mice were aseptically collected. To isolate single cell suspension from lung tissues, lungs were minced and digested with 1 mg/ml type IV collagenase (Worthington) and 50 μg/ml DNase I (Roche) for 45min at 37°C on a rotator. Then digested tissues liquid were filtered through 70-μm cell strainers and enriched with 40% Percoll gradient after red blood cells were lysed. Single-cell suspensions from lungs were used for subsequent flow cytometry staining.
- Flow cytometry analysis
For intracellular cytokine staining, cells were stimulated with Cell Stimulation Cocktail (eBioscience) and incubated for 5 hours at 37°C. Cells were preincubated with anti-mouse CD16/32 (BioLegend) to block Fc receptors and washed before further staining. Then cells were stained with FITC conjugated anti-CD4 (BioLegend) and PercPCy5.5 conjugated anti-CD25 (BioLegend), following by fixing and permeabilizing with BD Cytofix/Cytoperm buffer. At last, cells were stained with PE conjugated IL-17A (BioLegend). For measurement of transcription factors, cells were fixed and permeabilized with the Foxp3/Transcription Factor Staining Buffer Set (eBioscience) according to the manufacturer's instructions and stained with antibodies APC-FoxP3 (BioLegend). Cells were detected by CantoⅡ (BD, Biosciences) and analyzed by FlowJo software.
- Statistical analysis
The SPSS16.0 Software was used to complete the statistical analysis. Student’s t-test was used to compare continuous variables between two groups, and ANOVA was used to compare continuous variables across multiple groups. Mantel-Cox test was used for Survival data. A p-value less than 0.05 was considered statistically significant.