Experimental animals and group details
The experimental scheme and implementation procedure have been approved by the Experimental Animal Ethics Committee of Guilin Medical University(GLMC-IACUC-2021014). Thirty-two healthy adult SPF male SD rats purchased from Hunan Shrek Jingda Experimental Animal Co., Ltd. (SCXK (Hunan) 2019-0004) were 8–10 weeks old and weighed 240-260g. Raised in the Animal Experimental Center of Guilin Medical University: room temperature 22–25 ℃, relative humidity 35–60%, alternate light cycle for 12 hours, free diet. After a week of adaptive feeding, It is divided into four groups by the method of random number table(n = 8): Sham operation group (Sham group),AOLT group (I/R group), AOLT + ferroptosis inhibitor Ferrostain-1 group (I/R + Fer-1 group), AOLT + iron chelator deferoxamine(DFO) group (I/R + DFO group). In Sham group, only laparotomy was performed and the abdomen was closed after the corresponding blood vessels were dissociated;AOLT model was established in the other three groups, In I/R + Fer-1 group, 5 mg/kg of Ferrostain-1 (batch number: HY-100579,MCE Company) was injected intraperitoneally 30 min before operation and dissolved with DMSO 2ml༛In I/R + DFO group, DFO (batch number: HY-B0988,MCE) 100mg/kg was injected intraperitoneally 1 hour before operation and 12 hours after operation.
The rats were euthanized before the liver samples were taken out. Necessary measures were used to minimize the animals suffering during the experiment.
Model establishment
Establishment of AOLT model in rats[8].Rats were fasted for 12 hours before surgery and drank water freely, and were prohibited for 2 hours before surgery. Rats were injected intraperitoneally with 3% sodium pentobarbital (0.2ml/100g) for anesthesia maintenance before surgery, and 0.005% fentanyl (0.16ml/100g) was injected intraperitoneally to relieve pain, After the supine position was taken and fixed, the femoral artery was punctured under skin incision, and the transducer was connected to continuously monitor the arterial blood pressure and observe the respiration of the rats. The abdomen depilates and prepares the skin, carries on the disinfection with the iodophor, spreads the aseptic hole towel, cuts along the abdominal midline. After laparotomy, the left triangular ligament and hepatic falciform ligament were dissociated, and the inferior hepatic vena cava (IHVC) and superior hepatic vena cava (SHVC) were carefully and bluntly separated, so that they were fully exposed. The hepatoduodenal ligament was cut open to separate the proper hepatic artery and hepatic portal vein (PV). IHVC, PV and proper hepatic artery were blocked with non-invasive hemostatic clamp. Above the blocking site of PV, 1ml of saline containing 30U heparin was punctured and infused with scalp needle, Make the blood in the liver enter the systemic circulation through SHVC, then block the SHVC with a hemostatic clamp, start the anhepatic phase and time, continuously infuse 4 ℃ normal saline through PV, cut a small opening above the blocking site of IHVC as an outflow channel, and discharge the fluid circulating in the liver, the perfusion time is 30 ± 1min. After perfusion, the liver gradually changed from dark red to khaki. After perfusion, the outflow tract in IHVC and the puncture hole in PV were sutured with 8 − 0 non-invasive vascular suture, The proper hepatic artery, PV, IHVC and SHVC were opened successively, and the vascular reflow was made to restore the liver color to bright red. After the operation, Rinse the abdominal cavity with 36℃ normal saline and carefully sutured layer by layer(Fig. 1).
Specimen collection
24 hours after the end of ALOT in the rat, the rat was anesthetized again and the abdominal cavity was opened, and 2ml of inferior vena cava blood was taken and placed into a BD tube. Use a high-speed centrifuge to prepare serum samples, and store the prepared serum samples in a refrigerator at-80℃ for later use. After successful collection of blood from the inferior vena cava, 50ml of heparinized physiological saline at 4°C was slowly injected into the left ventricle of the rat, and a small opening was cut in the right atrial appendage to serve as the outflow tract. By fully perfusing heparinized physiological saline at 4°C, residual blood in each organ was washed as thoroughly as possible, and then the liver tissue of the rat was taken out and stored in a refrigerator at-80 ° C for later use.
Details of testing indicators
The pathological changes of the liver of rats in each group were observed under high magnification
Partial rat liver tissue was fixed with 4% paraformaldehyde solution for over 24 hours. After embedding the liver tissue specimen in paraffin, the liver tissue specimen was sectioned (with a thickness of 5µm) using a microtome and gradually stained with H&E. The pathological changes of liver tissue sections were observed under a high power light microscope (EVOS M5000, Thermo Fisher Scientific, USA) (×200). The operation was carried out by two pathology professionals from the Department of Pathology of the Affiliated Hospital of Guilin Medical University.
Detection of serum ALT and AST levels in rats
The serum was thawed and the levels of AST and ALT in serum of mice were detected by AST and ALT detection kits respectively, according to the instructions of the kit.
Determination of serum IL-6 levels in rats
IL-6 ELISA KIT (item number: SEKR-0005, Beijing Solebo Biotechnology Co., Ltd.) was used to detect the level of inflammatory cytokines (serum IL-6) in rat serum.
Analysis of MDA content in liver tissue and serum
The maximum absorption peak is at 532 nm, and the peroxide product MDA combines with TBA and forms a red product. Use an instrument to measure the OD value of the sample, and then calculate the MDA content.The degree of lipid oxidation can be assessed by determining the MDA concentration. In short, 0.1 g of rat liver tissue was collected, homogenate was prepared, and centrifuged at 8000g at 4°C for 10 minutes. The supernatant was collected and placed on crushed ice for testing. After centrifuging the anticoagulated blood, the upper serum was collected, and the MDA content in liver tissue and serum was measured using a lipid diamine peroxide content detection kit (Catalog No.: BC0025, Beijing Solarbio Science & Technology Co., Ltd.).
Determination of SOD activity
Superoxide dismutase(SOD) is the main enzyme of antioxidation in the body, which can protect the cells from oxidative damage by scavenging ·O2–. Strictly follow the SOD activity test kit (item number: BC0170, Beijing Solebao Biotechnology Co., Ltd.) for testing.
Determination of Fe2+ content in liver tissue
0.1 g of liver tissue and 1 ml of extract were mixed and homogenized in an ice bath. Centrifuge at 4000g for 10 minutes at 4°C and collect the supernatant. The Fe2+ content in the supernatant of liver tissue samples was detected using a tissue iron content detection kit (Beijing Solarbio Science & Technology Co., Ltd., catalog number: BC4355).
GPX4 activity in liver tissue
0.1 g of rat liver tissue stored at-80 ° C was completely ground using a fully automatic rapid sample grinder, and 1ml of extract was added to make tissue homogenate. After centrifugation, collect the supernatant and store it at low temperature for later use. Strictly follow the instructions of the GPX4 detection kit(Catalog No.:K003083P Beijing Solarbio Science & Technology Co., Ltd.)to detect the GPX4 content in liver tissue. Then, the OD value of the sample was obtained at a wavelength of 450 nm, and the results were analyzed to calculate the GPX4 content.
The GSH content in liver tissue
(1) 0.1g of frozen liver tissue was weighed and fully ground using an automatic sample rapid grinder (Shanghai Jingxin, China), and 1ml of extract was added to prepare liver tissue homogenate. The samples were then centrifuged at 8000g for 10 minutes at 4℃; the supernatant was taken and stored at 4°C for subsequent analysis.
(2) Anticoagulated blood was centrifuged at 600g at 4°C for 10 minutes. The upper plasma was transferred to another PE tube and centrifuged at 8000g for 10 minutes at 4°C. The supernatant was transferred to a new tube and stored at 4°C. GSH content in liver tissue and serum was detected using reduced GSH content detection kit(catalog no.: BC1175, Beijing Solarbio Science & Technology Co., Ltd.).
Statistical analysis
Establish a database and use SPSS26.0 for statistical analysis. Data conforming to a normal distribution are expressed as mean and standard deviation(‾x ± s). Repeated measures analysis of variance was used to compare differences between groups, and then t-tests were used to compare differences between the two groups. P < 0.05 was considered statistically significant.