Role Of ROS/Nrf2 Signaling Pathway In Desflurane-preconditioning Reducing Lipopolysaccharide-induced Acute Cerebral Inflammation In Rats

Objective: To investigate the role of reactive oxygen species(ROS)/nuclear factor erythroid 2-related factor 2(Nrf2)signaling pathway in desflurane-preconditioning reducing lipopolysaccharide(LPS)-induced acute cerebral inflammation in rats.Methods : One hundred sisty-eight healthy male clean SD rats were randomly divided into 4 groups(n=42 each): control group(group C),acute cerebral inflammation group(group L),desflurane preconditioning plus acute cerebral inflammation group(group DL),and N-acetylcysteine plus desflurane preconditioning plus acute cerebral inflammation group(group N+DL).Rats were intravenously injected LPS(1 mg/kg)to establish the model of acute cerebral inflammation in L,DL and N+DL groups.In group C,rats were intravenously injected saline solution of the same dose.In group DL,rats were pretreated with 1hour desflurane exposure at a dose of 8.2% for 5 consecutive days,and were intravenously injected LPS at 24 h after the fifth inhalation.In group N+DL,30 min before each preconditioning,rats were intraperitoneally injected N-acetylcysteine(150 mg/kg),and the other treatments were similar to those previous described in group DL.At 18 h before LPS injection,the hippocampus was isolated for the content of ROS,the activity of antioxidant enzyme by enzyme-linked immunosorbent assay and the expression of kelch-like ECH-associated protein 1(Keap1)and Nrf2 by Western blot.The brain was removed for determination the expression of Nrf2 in neuroglias in the cerebral cortex and the CA1 region of the hippocampus by immunofluorescence double staining.Rats were selected for performing Morris water maze test at 6,12 and 24 h after injection of LPS.The escape latency,space exploration time spent at the target platform quadrant,and frequency of crossing the target platform were recorded.After the end of the Morris water maze test,the hippocampus was isolated for the expression of NOD-like receptor family pyrin domain containing 3(NLRP3),apoptosis-associated speck-like protein(ASC)and Caspase-1 by Western blot and the content of IL-18 and IL-1β by enzyme-linked immunosorbent assay.The brain was removed for assessment of the number of normal neurons and the number of activated neuroglias in the cerebral cortex and the CA1 region of the hippocampus at 24 h after injection of LPS by Nissl staining and immunofluorescence staining.Results : Compared with group C,the content of ROS,the activity of antioxidant enzyme including SOD,CAT and GSH-Px,the expression of Keap1 and the expression of Nrf2 in neuroglias were no significant change before injection of LPS in group L(P>0.05),the escape latency was significantly prolonged,the space exploration time spent at the target platform quadrant was shortened,the frequency of crossing the target platform was decreased,the expression of NLRP3,ASC and Caspase-1 was significantly up-regulated,the content of IL-18 and IL-1β were significantly increased,the number of normal neurons was reduced,the number of activated neuroglias was increased after injection of LPS in group L(P<0.05).Compared with group L,the content of ROS was significantly increased,the activity of antioxidant enzyme including SOD,CAT and GSH-Px were significantly increased,the expression of Nrf2 in neuroglias significantly up-regulated,the expression of Keap1 significantly down-regulated before injection of LPS in group DL(P<0.05),the escape latency was significantly shortened,the space exploration time spent at the target platform quadrant was prolonged,the frequency of crossing the target platform was increased,the expression of NLRP3,ASC and Caspase-1 was down-regulated,the content of IL-18 and IL-1β were significantly decreased,the number of normal neurons was reduced,the number of activated neuroglias was increased after injection of LPS in DL groups(P<0.05).Compared with group DL,the content of ROS was significantly decreased,the activity of antioxidant enzyme including SOD,CAT and GSH-Px were significantly decreased,the expression of Nrf2 in neuroglias significantly down-regulated,the expression of Keap1 significantly up-regulated before injection of LPS in group N+DL(P<0.05),the escape latency was significantly prolonged,the space exploration time spent at the target platform quadrant was shortened,the frequency of crossing the target platform was decreased,the expression of NLRP3,ASC and Caspase-1 was significantly up-regulated,the content of IL-18 and IL-1β were significantly increased,the number of normal neurons was reduced,the number of activated neuroglias was increased after injection of LPS in group N+DL(P<0.05).Conclusion: Desflurane preconditioning reduces LPS-induced acute cerebral inflammation probably through ROS/Nrf2 signaling pathway to enhance antioxidant stress and inhibit the production of NLRP3 inflammasome.