ABSTRACT
Objective:To investigate the function of gasdermin D (GSDMD) in intestinal damage of mice with severe acute pancreatitis (SAP).Methods:The healthy C57BL/6 mice were divided into four groups randomly, including normal saline (NS) group, small interfering RNA (siRNA)-NS group, SAP model group and siRNA-SAP group, with 6 mice in each group. The SAP mouse model was reproduced by intraperitoneal injection of caerulein 50 μg/kg combined with lipopolysaccharide (LPS) 10 mg/kg; the NS group was given the same amount of NS; in the siRNA-SAP group and siRNA-NS group, siRNA 50 mg/kg was injected through the tail vein three times before modeling or injection of NS. The blood of mice eyeball in each group was taken 12 hours after modeling, and serum interleukins (IL-1β, IL-18) levels were detected by enzyme linked immunosorbent assay (ELISA). The mice were sacrificed to observe the general changes in abdominal cavity, the pancreas and ileum tissues were taken to observe the pathological changes under a light microscope. The expression of long-chain non-coding RNA uc.173 (lnc uc.173) was detected by reverse transcription-polymerase chain reaction (RT-PCR). Immunohistochemical method was used to detect the expression of tight junction proteins zonula occluden-1 (ZO-1) and Occludin in intestinal mucosal epithelial cells. Western blotting was used to detect the GSDMD protein expression level in the intestinal tissue.Results:The serum levels of IL-1β and IL-18 in the SAP model group were significantly higher than those in the NS group and the siRNA-NS group [IL-1β (ng/L): 146.66±1.40 vs. 44.48±5.76, 81.49±10.75, IL-18 (ng/L): 950.47±177.09 vs. 115.43±16.40, 84.84±21.90, all P < 0.05]; and the levels of IL-1β and IL-18 in the siRNA-SAP group were significantly lower than those in the SAP model group [IL-1β (ng/L): 116.26±15.54 vs. 146.66±1.40, IL-18 (ng/L): 689.96±126.08 vs. 950.47±177.09, both P < 0.05]. General observation showed that there were no obvious abnormalities in the abdominal cavity of the mice in the NS and siRNA-NS groups; the mice in the SAP model group and the siRNA-SAP group had different degrees of edema and congestion in the intestine; compared with the SAP model group, the abnormalities in the siRNA-SAP group was significantly reduced. Under light microscope, there were no obvious changes in the pancreas and intestinal mucosa in the NS group and the siRNA-NS group; the pancreatic tissue of the SAP model group and the siRNA-SAP group had different degrees of edema, inflammatory cell infiltration, and lobular structure damage, and the intestinal mucosa was damaged to a certain degree, and the villi were broken to varying degrees, but the damage in the siRNA-SAP group was lighter. The results of RT-PCR showed that the expression of lnc uc.173 in the intestinal tissues of the model SAP group was significantly lower than that of the NS group and the siRNA-NS group (2 -ΔΔCt: 0.26±0.12 vs. 1.01±0.37, 0.67±0.32, both P < 0.05), while the expression of lnc uc.173 in the siRNA-SAP group was significantly higher than that in the SAP model group (2 -ΔΔCt: 0.60±0.39 vs. 0.26±0.12, P < 0.05). Immunohistochemistry showed that ZO-1 and Occludin proteins in the NS group were distributed along the epithelial cells of the intestinal mucosa, showing a strong expression; ZO-1 and Occludin expressions were significantly reduced in the SAP model group and siRNA-SAP group, but the expressions in the siRNA-SAP group was higher than that in the SAP model group. Western blotting showed that the expression level of GSDMD protein in the intestinal tissues of the SAP model group was significantly higher than that of the NS group and the siRNA-NS group [GSDMD protein (GSDMD-N/β-actin): 1.99±0.46 vs. 1, 1.00±0.78, both P < 0.05]. Compared with the SAP model group, the expression of GSDMD protein in the siRNA-SAP group was significantly decreased [GSDMD protein (GSDMD-N/β-actin): 1.42±0.42 vs. 1.99±0.46, P < 0.05]. Conclusions:The systemic inflammatory response and intestinal mucosal barrier damage of SAP mice may be related to the increase of GSDMD expression in intestinal tissues. GSDMD mediates cell pyrolysis to promote the release of inflammatory factors, cause intestinal injury, and down-regulate the expression of intestinal epithelial cell tight junction proteins such as ZO-1 and Occludin, resulting in intestinal mucosal damage.
ABSTRACT
Objective:To investigate the effects of poly (ADP-ribose) polymerase-1(PARP-1) in intestinal mucosal barrier injury in rat model with severe acute pancreatitis (SAP).Methods:Twenty healthy male Wistar rats were divided into four groups ( n=5 each group) using a random table method: control, SAP, 3-aminobenzamide (3-AB), and 3-AB control groups. The SAP model was induced by intraperitoneal injection of cerulean with lipopolysaccharide. At 30 min, the rats were treated with the PARP-1 inhibitor, 3-AB, or normal saline,separately. After 12 h, all rats were sacrificed to harvest pancreas tissues, intestines tissues, and blood from the hearts for index detection. Serum amylase (AMY) and interleukin (IL)-6 levels were measured using an automatic biochemical instrument and enzyme-linked immunosorbent assay (ELISA), respectively.The protein expression of PARP-1 and nuclear factor (NF-κB) were measured using Western blot and that of occludin was measured using an immunohistochemical test. One-way analysis of variance was used for comparison of multiple groups of variables. Non-parametric tests of rank conversion were used when variances were not uniform. A P <0.05 was considered statistically significant. Results:Compared to the control group, the following indexes in the SAP group were significantly increased: ascites (with serious hemorrhage and necrosis in the pancreas and disordered intestinal villi),serum AMY and IL-6 levels, and the expression of PARP-1 and NF-κB. However, Occludin expression was significantly decreased. There was no significant difference between 3-AB group and 3-AB control group. Compared to the SAP group, the severity of SAP and pancreatitis-associated intestinal injury was significantly attenuated with the administration of 3-AB. Serum AMY and IL-6 levels were significantly decreased (serum AMY: 1 879.25 ± 736.6 U/L vs 5 569.33 ± 1993.48 U/L; IL-6: 77.98 ± 20.65 pg/mL vs 209.14 ± 79.08 pg/mL, both P<0.05), but the expression of PARP-1 and NF-κB were significantly increased (PARP-1: 1.44 ± 0.09 vs 1.49 ± 0.13; NF-κB: 0.63 ± 0.09 vs 0.96±0.08, both P<0.05). Similarly, Occludin expression was significantly decreased (6.7±1.5 vs 3.2±1.1, P<0.05). Conclusions:Inhibition of PARP-1 has protective effects on SAP associated intestinal mucosal barrier damage. The mechanism may be related to the inhibition of NF-κB signaling pathway and increase intestinal mucosal Occludin protein expression.