[Role and mechanism of SIRT1 in regulating Nrf2/HO-1 signaling pathway in septic liver injury].

OBJECTIVE: To investigate the role and mechanism of silent information regulator 1 (SIRT1) in regulating nuclear factor E2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) signaling pathway in oxidative stress and inflammatory response to sepsis-induced liver injury. METHODS: A total of 24 male Sprague-Dawley (SD) rats were randomly divided into sham operation (Sham) group, cecal ligation and puncture (CLP) group, SIRT1 agonist SRT1720 pretreatment (CLP+SRT1720) group and SIRT1 inhibitor EX527 pretreatment (CLP+EX527) group, with 6 rats in each group. Two hours before operation, SRT1720 (10 mg/kg) or EX527 (10 mg/kg) were intraperitoneally injected into the CLP+SRT1720 group and CLP+EX527 group, respectively. Blood was collected from the abdominal aorta at 24 hours after modeling and the rats were sacrificed for liver tissue. The serum levels of interleukins (IL-6, IL-1ß) and tumor necrosis factor-α (TNF-α) were detected by enzyme-linked immunosorbent assay (ELISA). The serum levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were detected by microplate method. Hematoxylin-eosin (HE) staining was used to observe the pathological injury of rats in each group. The levels of malondialdehyde (MDA), 8-hydroxydeoxyguanosine (8-OHdG), glutathione (GSH) and superoxide dismutase (SOD) in liver tissue were detected by corresponding kits. The mRNA and protein expressions of SIRT1, Nrf2 and HO-1 in liver tissues were detected by real-time quantitative polymerase chain reaction (RT-qPCR) and Western blotting. RESULTS: Compared with the Sham group, the serum levels of IL-6, IL-1ß, TNF-α, ALT and AST in the CLP group were significantly increased; histopathological results showed that liver cords were disordered, hepatocytes were swollen and necrotic, and a large number of inflammatory cells infiltrated; the contents of MDA and 8-OHdG in liver tissue increased, while the contents of GSH and SOD decreased; and the mRNA and protein expressions of SIRT1, Nrf2 and HO-1 in liver tissues were significantly decreased. These results suggest that sepsis rats have liver dysfunction, and the levels of SIRT1, Nrf2, HO-1 and antioxidant protein in liver tissues were decreased, while the levels of oxidative stress and inflammation were increased. Compared with the CLP group, the levels of inflammatory factors and oxidative stress were significantly decreased in the CLP+SRT1720 group, the mRNA and protein expressions of SIRT1, Nrf2 and HO-1 were significantly increased [IL-6 (ng/L): 34.59±4.21 vs. 61.84±3.78, IL-1ß (ng/L): 41.37±2.70 vs. 72.06±3.14, TNF-α (ng/L): 76.43±5.23 vs. 130.85±5.30, ALT (U/L): 30.71±3.63 vs. 64.23±4.59, AST (U/L): 94.57±6.08 vs. 145.15±6.86, MDA (µmol/g): 6.11±0.28 vs. 9.23±0.29, 8-OHdG (ng/L): 117.43±10.38 vs. 242.37±11.71, GSH (µmol/g): 11.93±0.88 vs. 7.66±0.47, SOD (kU/g): 121.58±5.05 vs. 83.57±4.84, SIRT1 mRNA (2-ΔΔCt): 1.20±0.13 vs. 0.46±0.02, Nrf2 mRNA (2-ΔΔCt): 1.21±0.12 vs. 0.58±0.03, HO-1 mRNA (2-ΔΔCt): 1.71±0.06 vs. 0.48±0.07, SIRT1 protein (SIRT1/ß-actin): 0.89±0.04 vs. 0.58±0.03, Nrf2 protein (Nrf2/ß-actin): 0.87±0.08 vs. 0.51±0.09, HO-1 protein (HO-1/ß-actin): 0.93±0.14 vs. 0.54±0.12, all P < 0.05], these results indicated that SIRT1 agonist SRT1720 pretreatment could improve liver injury in sepsis rats. However, pretreatment with SIRT1 inhibitor EX527 showed the opposite effect [IL-6 (ng/L): 81.05±6.47 vs. 61.84±3.78, IL-1ß (ng/L): 93.89±5.83 vs. 72.06±3.14, TNF-α (ng/L): 177.67±5.12 vs. 130.85±5.30, ALT (U/L): 89.33±9.52 vs. 64.23±4.59, AST (U/L): 179.59±6.44 vs. 145.15±6.86, MDA (µmol/g): 11.39±0.51 vs. 9.23±0.29, 8-OHdG (ng/L): 328.83±11.26 vs. 242.37±11.71, GSH (µmol/g): 5.07±0.34 vs. 7.66±0.47, SOD (kU/g): 59.37±4.28 vs. 83.57±4.84, SIRT1 mRNA (2-ΔΔCt): 0.34±0.03 vs. 0.46±0.02, Nrf2 mRNA (2-ΔΔCt): 0.46±0.04 vs. 0.58±0.03, HO-1 mRNA (2-ΔΔCt): 0.21±0.03 vs. 0.48±0.07, SIRT1 protein (SIRT1/ß-actin): 0.47±0.04 vs. 0.58±0.03, Nrf2 protein (Nrf2/ß-actin): 0.32±0.07 vs. 0.51±0.09, HO-1 protein (HO-1/ß-actin): 0.19±0.09 vs. 0.54±0.12, all P < 0.05]. CONCLUSIONS: SIRT1 can inhibit the release of proinflammatory factors and alleviate the oxidative damage of hepatocytes by activating Nrf2/HO-1 signaling pathway, thus playing a protective role against CLP-induced liver injury.

[Predictive value of six critical illness scores for 28-day death risk in comprehensive and specialized intensive care unit patients based on MIMIC-IV database].

OBJECTIVE: To explore the basic characteristics of various types of intensive care unit (ICU) patients and the predictive value of six common disease severity scores in critically ill patients on the first day on the 28-day death risk. METHODS: The general information, disease severity scores [acute physiology score III (APS III), Oxford acute disease severity (OASIS) score, Logistic organ dysfunction score (LODS), simplified acute physiology score II (SAPS II), systemic inflammatory response syndrome (SIRS) score and sequential organ failure assessment (SOFA) score], prognosis and other indicators of critically ill patients admitted from 2008 to 2019 were extracted from Medical Information Mart for Intensive Care-IV 2.0 (MIMIC-IV 2.0). The receiver operator characteristic curve (ROC curve) of six critical illness scores for 28-day death risk of patients in various ICU, and the area under the ROC curve (AUC) was calculated, the optimal Youden index was used to determine the cut-off value, and the AUC of various ICU was verified by Delong method. RESULTS: A total of 53 150 critically ill patients were enrolled, with medical ICU (MICU) accounted for the most (19.25%, n = 10 233), followed by cardiac vascular ICU (CVICU) with 17.78%(n = 9 450), and neurological ICU (NICU) accounted for the least (6.25%, n = 3 320). The patients in coronary care unit (CCU) were the oldest [years old: 71.79 (60.27, 82.33)]. The length of ICU stay in NICU was the longest [days: 2.84 (1.51, 5.49)] and accounted for the highest proportion of total length of hospital stay [63.51% (34.61%, 97.07%)]. The patients in comprehensive ICU had the shortest length of ICU stay [days: 1.75 (0.99, 3.05)]. The patients in CVICU had the lowest proportion of length of ICU stay to total length of hospital stay [27.69% (18.68%, 45.18%)]. The six scores within the first day of ICU admission in NICU patients were lower than those in the other ICU, while APS III, LODS, OASIS, and SOFA scores in MICU patients were higher than those in the other ICU. SAP II and SIRS scores were both the highest in CVICU, respectively. In terms of prognosis, MICU patients had the highest 28-day mortality (14.14%, 1 447/10 233), while CVICU patients had the lowest (2.88%, 272/9 450). ROC curve analysis of the predictive value of each score on the 28-day death risk of various ICU patients showed that, the predictive value of APS III, LODS, and SAPS II in comprehensive ICU were higher [AUC and 95% confidence interval (95%CI) were 0.84 (0.83-0.85), 0.82 (0.81-0.84), and 0.83 (0.82-0.84), respectively]. The predictive value of OASIS, LODS, and SAPS II in surgical ICU (SICU) were higher [AUC and 95%CI were 0.80 (0.79-0.82), 0.79 (0.78-0.81), and 0.79 (0.77-0.80), respectively]. The predictive value of APS III and SAPS II in MICU were higher [AUC and 95%CI were 0.84 (0.82-0.85) and 0.82 (0.81-0.83), respectively]. The predictive value of APS III and SAPS II in CCU were higher [AUC and 95%CI were 0.86 (0.85-0.88) and 0.85 (0.83-0.86), respectively]. The predictive value of LODS and SAPS II in trauma ICU (TICU) were higher [AUC and 95%CI were 0.83 (0.82-0.83) and 0.83 (0.82-0.84), respectively]. The predictive value of OASIS and SAPS II in NICU were higher [AUC and 95%CI were 0.83 (0.80-0.85) and 0.81 (0.78-0.83), respectively]. The predictive value of APS III, LODS, and SAPS II in CVICU were higher [AUC and 95%CI were 0.84 (0.83-0.85), 0.81 (0.80-0.82), and 0.78 (0.77-0.78), respectively]. CONCLUSIONS: For the patients in comprehensive ICU, MICU, CCU, and CVICU, APS III or SAPS II can be applied for predicting 28-day death risk. For the patients in SICU and NICU, OASIS or SAPS II can be applied to predict 28-day death risk. For the patients in TICU, SAPS II or LODS can be applied for predicting 28-day death risk. For CVICU patients, APS III or LODS can be applied to predict 28-day death risk.

[Activation of NOD-like receptor protein 3 inflammasome mediates inflammatory response and apoptosis in septic intestinal injury model].

OBJECTIVE: To investigate the expression of NOD-like receptor protein 3 (NLRP3) inflammasome in intestinal injury models with different severity of sepsis and the inflammatory response and apoptosis mediated by NLRP3 inflammasome. METHODS: Human colorectal adenocarcinoma cells (Caco-2) were cultured in vitro. The logarithmic growth phase cells were divided into blank control group (normal culture in complete medium) and lipopolysaccharide (LPS) 1, 2 and 4 mg/L groups (complete medium containing 1, 2 and 4 mg/L LPS, respectively). The supernatant were collected at 6, 12 and 24 hours, and the levels of tumor necrosis factor-α (TNF-α), interleukins (IL-6, IL-1ß, IL-18) were detected by enzyme linked immunosorbent assay (ELISA). The apoptotic level of cells was detected by flow cytometry. The cells were harvested, and the real-time fluorescence quantitative reverse transcription-polymerase chain reaction (RT-qPCR) was used to detect the mRNA expressions of NLRP3 and silent information regulator 1 (SIRT1). Western blotting was used to detect the protein expressions of NLRP3, SIRT1, caspase-1 and apoptosis-associated speck-like protein (ASC). RESULTS: ELISA results showed that the levels of IL-6, TNF-α, IL-1ß, and IL-18 in cell supernatant of LPS groups increased in a dose-dependent and time-dependent manner as compared with the blank control group during the same intervention period. The increase was most significant in LPS 4 mg/L group at 24 hours [IL-6 (ng/L): 3.55±0.06 vs. 0.67±0.09, TNF-α (ng/L): 15.37±0.19 vs. 5.04±0.14, IL-1ß (ng/L): 2.26±0.10 vs. 0.56±0.09, IL-18 (ng/L): 433.92±22.55 vs. 93.55±21.13, all P < 0.05]. The results of the apoptotic test showed that, compared with the blank control group, the apoptotic rate of LPS groups increased in a dose-dependent and time-dependent manner, and the apoptotic rate of LPS 4 mg/L group increased most significantly at 24 hours [(14.83±3.73)% vs. (5.87±1.17)%, P < 0.05]. RT-qPCR results showed that the expression level of NLRP3 mRNA was increased, while the expression level of SIRT1 mRNA was decreased with the increase of LPS intervention dose and the prolonging of intervention time. At 24 hours, there were significant differences between LPS 4 mg/L group and blank control group [NLRP3 mRNA (2-ΔΔCt): 8.20±2.82 vs. 1.00±0.36, SIRT1 mRNA (2-ΔΔCt): 0.58±0.01 vs. 1.03±0.06, both P < 0.05]. Western blotting showed that compared with the blank control group, the protein expression levels of NLRP3, caspase-1 and ASC in LPS groups were significantly increased, while the protein expression levels of SIRT1 were significantly decreased. During each intervention period, with the increase of LPS dose, the expressions of NLRP3, caspase-1 and ASC protein increased gradually, while the expression of SIRT1 protein decreased gradually. At 24 hours, the difference between the LPS 4 mg/L group and the blank control group was significant [NLRP3 protein (NLRP3/ß-actin): 1.48±0.03 vs. 0.90±0.12, caspase-1 protein (caspase-1/ß-actin): 1.18±0.11 vs. 0.72±0.09, ASC protein (ASC/ß-actin) : 1.09±0.01 vs. 0.82±0.03, SIRT1 protein (SIRT1/ß-actin): 0.48±0.03 vs. 0.76±0.05, all P < 0.05]. CONCLUSIONS: In vitro, in the sepsis induced intestinal inflammation model, with the increase of LPS intervention dose and the prolongation of intervention time, intestinal inflammatory response and cell apoptosis showed an increasing trend, which may be related to the up-regulation of NLRP3 inflammasome and its downstream products ASC and caspase-1, and to the down-regulation of SIRT1 expression.

[Effects of resveratrol-mediated inhibition of NOD-like receptor protein 3 inflammasomevia activating silent information regulator 1 on the injury of intestinal mucosal barrier function after sepsis].

OBJECTIVE: To explore whether resveratrol (RSV) could activate silent information regulator 1 (SIRT1) to regulate the activation of NOD-like receptor protein 3 (NLRP3) inflammasome in sepsis induced intestinal injury model, and then reduce intestinal inflammation and cell apoptosis, so as to play a protective role in intestinal barrier function. METHODS: (1) In vitro experiment: human Colorectal adenocarcinoma cells (Caco-2) were cultured, which were divided into normal group (normal culture on complete medium for 48 hours), lipopolysaccharide (LPS) group (normal culture on complete medium for 24 hours, then LPS containing 2 mg/L complete medium intervention for 6 hours), RSV low, medium and high concentration groups and SIRT1 inhibitor (EX-527) group (complete medium normal culture for 24 hours, LPS containing 2 mg/L complete medium intervention for 6 hours, followed by RSV 10, 20, 40 µmol/L or EX-527 10 µmol/L intervention for 6 hours, respectively). The levels of tumor necrosis factor-α (TNF-α) and interleukins (IL-6, IL-18, IL-1ß) in the cell supernatant were determined by enzyme linked immunosorbent assay (ELISA). The apoptosis level of the cells was detected by flow cytometry. Western blotting was used to detect the protein levels of NLRP3, SIRT1, caspase-1 and apoptosis-related point-like protein (ASC). (2) In vivo experiment: according to random number table method, 24 male Wistar rats were divided into sham operation group (Sham group), cecal ligation and perforation (CLP) 6 hours group (CLP 6 h group), CLP 24 h group and RSV intervention group [RSV (20 mg/kg) was intraperitoneally injected 6 hours and 12 hours after CLP], with 6 rats in each group. The levels of NLRP3, caspase-1 and ASC in the intestine of rats were detected by immunohistochemistry. RESULTS: (1) Compared with the normal group, the levels of inflammatory factors in the cell supernatant of the LPS group were increased and the expression of SIRT1 protein was decreased, while the protein expressions of NLRP3, caspase-1 and ASC were increased. Compared with LPS group, different concentrations of RSV reduced the level of inflammatory factors, increased the activity of SIRT1, inhibited the expression of NLRP3 inflammasome and its downstream products caspase-1 and ASC, and the effect of high concentration of RSV (40 µmol/L) was the most significant [TNF-α (ng/L): 8.77±0.43 vs. 12.66±0.81, IL-6 (ng/L): 1.35±0.20 vs. 1.93±0.09, IL-1ß (ng/L): 1.05±0.04 vs. 1.31±0.07, IL-18 (ng/L): 519.50±11.16 vs. 622.70±30.69, SIRT1/ß-actin: 0.80±0.05 vs. 0.58±0.02, caspase-1/ß-actin: 0.55±0.06 vs. 0.78±0.06, ASC/ß-actin: 0.78±0.08 vs. 1.04±0.15, all P < 0.05], while SIRT1 inhibitor EX-527 had the opposite effects. There was no significant difference in the apoptosis rate among normal group, LPS group, and low, medium and high concentration RSV groups, as well as EX-527 group [(7.03±0.57)%, (9.67±0.55)%, (9.57±0.70)%, (9.30±2.15)%, (9.87±0.97)%, (9.07±0.93)%, F = 2.590, P = 0.082]. (2) Immunohistochemical results showed that compared with the Sham group, the expressions of NLRP3 inflammasomes and downstream products caspase-1 and ASC in the intestinal epithelial cells in CLP 6 h group, CLP 24 h group and RSV intervention group were significantly increased. The percentage of ASC-positive area in intestinal epithelium of RSV intervention group was significantly lower than that of CLP 6 h group [(15.22±2.73)% vs. (19.88±2.67)%, P < 0.05], and the expressions of NLRP3 and caspase-1 were significantly lower than those of CLP 24 h group [(9.31±1.37)% vs. (13.19±1.92)%, (19.57±3.92)% vs. (27.28±6.33)%, both P < 0.05]. CONCLUSIONS: After sepsis, high concentration of RSV could inhibit the activation of NLRP3 inflammasome by activating SIRT1, thereby reduce the expression of caspase-1 and ASC, and inhibit the secretion of inflammatory factors to reduce the inflammatory response.

[Ulinastatin protects intestinal mucosal barrier by inhibiting the activation of intestinal NLRP3 inflammasomes in septic rats].

OBJECTIVE: To explore the damage of the intestinal mucosal barrier of septic rats by the activation of NOD-like receptor family, pyrin domain-containing 3 (NLRP3) inflammasomes and the role of Ulinastatin (UTI) on the expression of intestinal nuclear factor-κB (NF-κB)/NLRP3 inflammasome signaling pathway in septic rats. METHODS: According to the random number table method, 64 male Wistar rats were divided into sham operation group (Sham group), cecal ligation and puncture (CLP) group, UTI treatment group (100 kU/kg UTI was intraperitoneally injected 1, 6, 12 and 18 hours after CLP), and UTI pretreatment group (100 kU/kg UTI was given 1 hour before CLP), with 16 rats in each group. The survival of rats was observed after 24 hours, and the blood was collected from abdominal aorta at 24 hours after modeling, then rats were killed and their ileum tissues were taken. Hematoxylin-eosin (HE) staining was used to observe histopathological changes and Chiu score. The levels of tumor necrosis factor-α (TNF-α), interleukin-1ß (IL-1ß) and intestinal fatty acid binding protein (I-FABP) in serum were detected by enzyme linked immunosorbent assay (ELISA). The protein expression of NF-κB p65 in intestinal tissue was detected by Western blotting. The expression of intestinal tight junction proteins Claudin-1, Occludin and the inflammasome NLRP3, apoptosis-associated speck-like protein containing CARD (ASC) and caspase-1 were detected by immunohistochemistry. RESULTS: Compared with Sham group, the 24-hour survival rate of CLP group was significantly reduced. Histopathological results showed that the CLP group had severe edema of mucosa and submucosal stroma with obvious infiltration of inflammatory cells and disordered villi arrangement. Some glands were incomplete, and the villus structure was severely damaged. The Chiu score was significantly increased. The levels of TNF-α, IL-1ß, I-FABP in serum and the protein expression of NF-κB p65 in intestinal tissue were significantly increased. The positive expressions of NLRP3, caspase-1 and ASC were also significantly increased. However, the positive expression of tight junction protein in small intestine tissue such as Occludin and Claudin-1 were significantly reduced. It suggested that when sepsis occurs, small intestinal mucosal barrier dysfunction happens, and mucosal permeability increases, while tight junction protein expression decreases, NLRP3 inflammasome and its upstream molecule NF-κB p65 were activated. After UTI treatment and UTI pretreatment intervention, although there was no significant difference in 24-hour survival compared with CLP group (62.5%, 68.8% vs. 43.8%, both P > 0.05), the intestinal tissue damage of septic rats was significantly improved. Specifically: Chiu score and the levels of TNF-α, IL-1ß, I-FABP in serum were significantly decreased [Chiu score: 3.37±0.25, 3.23±0.16 vs. 4.08±0.13, TNF-α (ng/L): 147.62±20.74, 140.71±24.81 vs. 222.82±16.84, IL-1ß (ng/L): 80.64±5.68, 78.11±4.75 vs. 133.73±3.92, I-FABP (µg/L): 38.29±3.60, 35.88±4.52 vs. 59.81±4.66, all P < 0.05]; the protein expression of NF-κB p65 was significantly decreased (NF-κB p65/ß-actin: 0.65±0.10, 0.69±0.11 vs. 0.99±0.10, both P < 0.05), the positive expressions of Claudin-1 and Occludin in the small intestine tissue were increased [Claudin-1 positive expression area: (19.43±3.08)%, (23.99±6.27)% vs. (7.77±2.03)%; Occludin positive expression area: (19.58±4.75)%, (23.28±3.68)% vs. (11.69±4.30)%, all P < 0.05], while the positive expressions of NLRP3, caspase-1, ASC were decreased [NLRP3 positive expression area: (7.80±3.14)%, (6.86±2.63)% vs. (14.44±3.68)%; caspase-1 positive expression area: (10.62±3.52)%, (9.49±3.09)% vs. (26.69±8.05)%; ASC positive expression area: (9.95±2.81)%, (10.53±3.61)% vs. (24.16±5.48)%, all P < 0.05]. However, there was no significant difference in the improvement effect between UTI treatment group and UTI pretreatment group. CONCLUSIONS: Intestinal barrier dysfunction in sepsis may be related to the activation of NLRP3 inflammasomes in the intestinal mucosa. The protective effect of UTI in the intestinal mucosa may be related to inhibiting the activation of NLRP3 inflammasomes in the intestinal mucosa, but UTI pretreatment has no obvious advantage compared with UTI treatment.