Mouse models of SAH and drugs administration
C57BL/6 mice (male, 22-25g) were purchased from Vital River Laboratory Animal Technology (Beijing, China). The procedures involved in mice were conformed to the guidelines of the National Institutes of Health on the care and use of laboratory animals and approved by the Institutional Animal Care and Use Committee of Shandong First Medical University.
SAH model was constructed via endovascular perforation as the previous study[29]. Briefly, After the mice were anesthetized, the nylon suture was passed through the external carotid artery to the bifurcation of the anterior and middle artery and ultimately punctured to cause blood to flow into the subarachnoid space.
Mice were injected with 30 mg/kg capsazepine (CPZ) subcutaneously or 10mg/kg capsaicin (CAP) intraperitoneally post-modeling to inhibit or active TRPV1[27, 30], respectively. MCC950 (40 mg/kg) were intraperitoneally injected post-modeling and 12h later[9]. The drugs above were all purchased from MedChemExpress.
Magnetic-activated cell sorting (MACS) and qPCR analysis
Ipsilateral hemispheres were harvested at 24h post-SAH, dissociated mechanically using a glass homogenizer, and filtered into a 70-μm strainer to obtain a single-cell suspension. The single-cell suspension was isolated with 30% Percoll solutions, incubated with CD11b microbeads (Miltenyi Biotec, Germany, 130-126-725), and then divided into CD11b positive and negative cells.
Total mRNA of tissues and cells was extracted using TRIzol™ Reagent (Life Technologies, USA), used to synthesize cDNA using Evo M-MLV Reverse Transcriptase (Takara, Japan, RR420A), and then performed the qPCR analysis using SYBR Premix Ex Taq™ Kit (Takara, Japan, RR036A) according to manufacturer’s protocol. The primers were listed in Supplementary Table 1.
Brain water content
The ipsilateral hemisphere was harvested 24h after SAH and weighed to obtain the wet weight, followed immediately by drying at 105℃ for 3 days and then obtaining the dry weight. The brain water content was calculated as the wet weight minus the dry weight and then divided by the wet weight.
Neurobehavioral assessment
Neurobehavioral assessment containing modified Garcia and beam balance test was performed 24h post-SAH to evaluate neurological function[31]. Modified Garcia and beam balance scores ranged from 3 to 18 and 0 to 4 respectively, with higher scores indicating better neurological function.
Histological staining analysis
Mice were anesthetized and perfused sufficiently with 4% paraformaldehyde (PFA) at 24h after SAH to harvest the brain tissues. The brain tissues were fixed in 4% PFA for 24h, dehydrated in 30% sucrose solution, embedded in OCT compound, and then sliced into 10μm coronal sections for immunofluorescence and Nissl staining analysis.
For immunofluorescence staining analysis, mice brain sections were blocked and permeabilized with 5% bovine serum containing 0.3% Triton-X100 for 1h at room temperature and incubated with primary antibodies overnight at 4°C followed by 1 hour incubation at room temperature with the corresponding secondary antibody. The primary antibodies included anti-Iba-1 (Abcam, Cambridge, UK, ab-5076), anti-TRPV1(Abcam, Cambridge, UK, ab203103), and anti-CD16/CD32 antibody (Biolegend, USA, 101329).
For Nissl staining, mice brain sections were stained with 0.5% cresyl violet for 0.5h at room temperature and dehydrated with ethanol absolute[32]. The images were analyzed using Image J (NIH).
Western blot
Proteins of tissues and cells were extracted using RIPA lysis buffer(Beyotime, Shanghai, China, P0013B), separated by SDS-PAGE, transferred into PVDF membrane, blocked with 5% non-fat powdered milk, incubated with primary antibodies overnight at 4°C followed by 1 hour incubation at room temperature with the corresponding secondary antibody. Then, the PVDF membrane was visualized using the ECL Plus chemiluminescence reagent kit. The primary antibodies included anti-β-actin (Proteintech, Hubei, China, 60008-1-Ig), anti-ZO-1 (Santa Cruz, TX, USA, sc-33725), anti-claudin-5 (Santa Cruz, TX, USA, sc-28670), anti-occludin (Santa Cruz, TX, USA, sc-133256), anti-NLRP3(Abcam, Cambridge, UK, ab210491), anti-ASC (Santa Cruz, TX, USA, sc-271054), anti-caspase-1 p20 (Santa Cruz, TX, USA,sc-22165). The protein expression was quantified using Image J (NIH).
ELISA
The total protein content of tissues and cell culture supernatants was determined via BCA assay (Beyotime, China). The expression level of IL-1β was detected using ELISA kit (Boster, Wuhan, China, EK0394) according to the manufacturer’s protocol.
In vitro SAH model
Murine BV2 cells were stimulated by 200μM hemin (Sigma-Aldrich, MO, USA, H9039) to establish the SAH model in vitro. Meanwhile, BV2 cells were treated with 10μM CAP[33] and BAPTA-AM[27] to investigate the mechanism of the TRPV1-activated NLRP3 inflammasome.
Calcium concentration detection
Calcium concentration was detected as previously reported[34]. Briefly, BV2 cells were incubated with 4μM Fura-2/AM (YEASEN, Shanghai, China, 40702ES50) for 30min, and captured the fluorescence intensities when excited at 340 and 380 nm and emitted at 510nm. The calcium concentration was calculated as followed: the fluorescence intensities at 340nm/ the fluorescence intensities at 380nm.
Statistical Analysis
The data were analyzed by SPSS 22.0 and GraphPad Prism 8.0 to test whether met the normal distribution and variance homogeneity by Shapiro-Wilk and Levene methods, respectively. When met, data were analyzed by Student’s t-test (two groups) or one-way analysis of variance (ANOVA) with Tukey’s post hoc contrasts (more than three groups); otherwise, data were analyzed by Mann–Whitney nonparametric test (two groups) and Kruskal-Wallis test with post hoc contrast by the Dunn-Bonferroni test (more than three groups).