ABSTRACT
Objective:To investigate whether silence information regulator 1 (SIRT1) could regulate nuclear factor E2-related factor 2/heme oxygenase 1 (Nrf2/HO-1) signaling pathway and its role in acute lung injury (ALI) in sepsis rats.Methods:Twenty-four male Sprague-Dawley (SD) rats were randomly divided into sham operation group (Sham group), cecal ligation and puncture (CLP) induced sepsis group (CLP group), sepsis+SIRT1 specific agonist group (CLP+SRT1720 group,10 mg/kg SRT1720 was intraperitoneally injected 2 hours before CLP), sepsis+SIRT1 specific inhibitor group (CLP+EX527 group, 10 mg/kg EX527 was intraperitoneally injected 2 hours before CLP), with 6 rats in each group. The rats were killed 24 hours after modeling and their lung tissues were taken for pathological score (Smith score), superoxide dismutase (SOD), glutathione (GSH), malondialdehyde (MDA), 8-hydroxydeoxyguanosine (8-OHdG), tumor necrosis factor-α (TNF-α), interleukins (IL-6, IL-1β), and SIRT1, Nrf2 and HO-1 mRNA and protein expression were detected.Results:The lung tissue of the CLP group mice was severely damaged, the alveolar interval was widened and a large number of inflammatory cells infiltrated, and there was visible pulmonary capillary hyperemia. The Smith score, the levels of TNF-α, IL-6, IL-1β, MDA and 8-OHdG were significantly increased, the levels of SOD, GSH, SIRT1, Nrf2 and HO-1 were significantly decreased in CLP group. After using SIRT1 specific agonist, the lung injury in CLP+SRT1720 group was significantly alleviated compared with that in CLP group, Smith score and lung tissue TNF-α, IL-6, and IL-1β levels were significantly decreased [Smith score: 2.83±0.75 vs. 5.67±0.52, TNF-α (ng/L): 36.78±5.36 vs. 66.99±5.44, IL-6 (ng/L): 23.97±3.76 vs. 45.70±4.16, IL-1β (ng/L): 16.76±1.39 vs. 39.64±2.59, all P < 0.05], SOD activity and GSH content increased [SOD (kU/g): 115.88±3.31 vs. 101.65±1.09, GSH (μmol/g): 8.42±0.81 vs. 5.74±0.46, both P < 0.05], MDA and 8-OHdG contents decreased [MDA (μmol/g): 5.24±0.33 vs. 9.86±0.66, 8-OHdG (ng/L): 405.76±8.54 vs. 647.12±10.64, both P < 0.05], the mRNA and protein expressions of SIRT1, Nrf2 and HO-1 were increased [SIRT1 mRNA (2 -ΔΔCT): 1.49±0.15 vs. 0.64±0.03, Nrf2 mRNA (2 -ΔΔCT): 1.19±0.08 vs. 0.84±0.02, HO-1 mRNA (2 -ΔΔCT): 1.80±0.41 vs. 0.64±0.11, SIRT1 protein (SIRT1/β-actin): 1.03±0.06 vs. 0.52±0.05, Nrf2 protein (Nrf2/β-actin): 1.14±0.10 vs. 0.63±0.05, HO-1 protein (HO-1/β-actin): 1.01±0.11 vs. 0.73±0.03, all P < 0.05]. The lung injury in CLP+EX527 group was more severe than that in CLP group, Smith score and lung tissue TNF-α, IL-6, IL-1β levels were significantly increased [Smith score: 8.00±0.89 vs. 5.67±0.52, TNF-α (ng/L): 87.15±4.23 vs. 66.99±5.44, IL-6 (ng/L): 66.79±2.93 vs. 45.70±4.16, IL-1β (ng/L): 58.99±2.12 vs. 39.64±2.59, all P < 0.05], SOD activity and GSH content decreased [SOD (kU/g): 72.84±3.85 vs. 101.65±1.09, GSH (μmol/g): 3.30±0.67 vs. 5.74±0.46, both P < 0.05], the contents of MDA and 8-OHdG were increased [MDA (μmol/g): 14.14±0.70 vs. 9.86±0.66, 8-OHdG (ng/L): 927.66±11.47 vs. 647.12±10.64, both P < 0.05], the mRNA and protein expressions of SIRT1, Nrf2 and HO-1 were decreased [SIRT1 mRNA (2 -ΔΔCT): 0.40±0.07 vs. 0.64±0.03, Nrf2 mRNA (2 -ΔΔCT): 0.48±0.07 vs. 0.84±0.02, HO-1 mRNA (2 -ΔΔCT): 0.27±0.14 vs. 0.64±0.11, SIRT1 protein (SIRT1/β-actin): 0.20±0.05 vs. 0.52±0.05, Nrf2 protein (Nrf2/β-actin): 0.45±0.01 vs. 0.63±0.05, HO-1 protein (HO-1/β-actin): 0.36±0.08 vs. 0.73±0.03, all P < 0.05]. Conclusions:In the rat model of ALI induced by sepsis, SIRT1 can regulate the activation of Nrf2/HO-1 signaling pathway, upregulate the expression of downstream antioxidant enzymes, reduce oxidative stress injury, and then alleviate the ALI induced by sepsis in rats.
ABSTRACT
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-1β) 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-1β, 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-1β (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/β-actin): 0.89±0.04 vs. 0.58±0.03, Nrf2 protein (Nrf2/β-actin): 0.87±0.08 vs. 0.51±0.09, HO-1 protein (HO-1/β-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-1β (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/β-actin): 0.47±0.04 vs. 0.58±0.03, Nrf2 protein (Nrf2/β-actin): 0.32±0.07 vs. 0.51±0.09, HO-1 protein (HO-1/β-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.