Objective:To evaluate the role of miR-146a in hippocampal inflammatory responses in postoperative cognitive dysfunction (POCD) in mice.Methods:One hundred and sixty clean-grade male C57BL/6 mice, aged 12-16 weeks, weighing 22-28 g, were divided into 5 groups ( n=32 each) using a random number table method: control group (group C), group POCD, miR-146a agomir group (group Ag), miR-146a antagomir group (group At) and negative control group (group NC). The mice were subjected to an intramedullary fixation for tibial fracture under 1.5% isoflurane anesthesia to establish POCD model.At 2 days before operation, miR-146a agomir 0.5 nmol (0.1 nmol/μl) was injected into bilateral hippocampi in group Ag, miR-146a antagomir 2.5 nmol (0.5 nmol/μl) was injected in group At, miR-146a negative control solution 2.5 nmol (0.5 nmol/μl) was given in group NC, and the animals in group C did not receive any treatment.At 1 day before operation and at 1, 3 and 7 days after operation, open-field test was performed to evaluate spontaneous motor activity, and contextual fear conditioning test was performed to evaluate cognitive ability 15 min later.At 1 and 3 days after operation, the animals were sacrificed and hippocampi was removed for determination of expression of CD11b (a marker for activation of microglia) in hippocampal CA1 region by immunofluorescence staining.At 6, 12 and 24 h after operation, the expression of miR-146a was detected by quantitative real-time polymerase chain reaction, the expression of interleukin-1 receptor-associated kinase 1 (IRAK1), tumor necrosis factor receptor-associated factor 6 (TRAF6), nuclear factor kappa B p65 (NF-κB p65) and tumor necrosis factor-alpha (TNF-α) was determined by Western blot and interleukin-1beta (IL-1β) and IL-6 contents were determined by enzyme-linked immunosorbent assay. Results:There was no significant difference in the total exploring distance in the open-field test or percentage of freezing time in tone-fear conditioning test at each time point among the five groups( P>0.05). Compared with group C, the percentage of freezing time in the contextual fear conditioning test was significantly decreased at 1, 3 and 7 days after operation, the expression of CD11b at 1 and 3 days after surgery and expression of miR-146a, IRAK1, TRAF6, NF-κB p65 and TNF-α were up-regulated and the contents of IL-1 β and IL-6 were increased at 6, 12 and 24 h after operation in group POCD ( P<0.05). Compared with group NC, the percentage of freezing time in the contextual fear conditioning test was significantly increased at 1, 3 and 7 days after operation, and the expression of CD11b was down-regulated at 1 and 3 days after surgery, and the expression of miR-146a, IRAK1, TRAF6, NF-κB p65 and TNF-α was up-regulated and IL-1β and IL-6 contents were decreased at 6, 12 and 24 h after operation in group Ag, and the percentage of freezing time in the contextual fear conditioning test was decreased at 1, 3 and 7 days after operation, the expression of CD11b at 1 and 3 days after surgery was up-regulated, the expression of miR-146a was down-regulated and IRAK1, TRAF6, NF-κB p65 expression was up-regulated at 6, 12 and 24 h after operation, TNF-α expression was up-regulated and IL-1β and IL-6 contents were increased at 12 and 24 h after operation in group At ( P<0.05). Conclusion:miR-146a is involved in the process of hippocampal inflammatory responses, and the mechanism may be related to the inhibition of IRAK1-TRAF6-NF-κB signaling pathway in mice.

Objective To investigate the changes of miR-146a expression in serum,hippocam-pus and prefrontal cortex in postoperative cognitive dysfunction (POCD) mice.Methods Fifty healthy male C57BL/6 mice,aged 12-14 weeks,weighing 25-30 g,were randomly divided into two groups (n =25 each)using a random number table:control group (group C)and anesthesia plus sur-gery group (group AS).Mice in group AS underwent open tibial fracture of the left hind paw with in-tramedullary fixation in aseptic conditions under general anesthesia with 2.1% isoflurne.Ten mice in each group received the fear conditioning test (FCT)on the 1,3 and 7 days after anesthesia/surgery. The rest of mice were sacrificed 24 h before (baseline),and 6,12,24,48 h after anesthesia/surgery, and then the serum,prefrontal cortex and hippocampus were collected or removed for detection of the expression of miR-146a using quantitative reverse transcription polymerase chain reaction (qRT-PCR).Results Compared with group C,the percentage of freezing time in contextual FCT was sig-nificantly decreased (P <0.05)in group AS,while no significant change in freezing time percentage was found in tone-cued FCT.In serum,compared with group C,miR-146a expression at 6,12,24, 48 h after anesthesia/surgery was significantly up-regulated in group AS (P < 0.05 );and in group AS,the expression of miR-146a was significantly decreased 6,24,48 h as compared to that at 12 h after anesthesia/surgery (P <0.05).In hippocampus,compared with group C,miR-146a expression at 6,12,24,48 h after surgery was significantly up-regulated in group AS (P <0.05);and in group AS,the expression of miR-146a at 6,48 h after surgery was significantly decreased as compared to that at 12 h after anesthesia/surgery (P <0.05).In prefrontal cortex,compared with group C,miR-146a expression at 24,48 h after surgery was significantly up-regulated in group AS (P <0.05);and in group AS,the expression of miR-146a was significantly increased at 48 h as compared to that at 24 h after anesthesia/surgery (P <0.05).Conclusion The expression of miR-146a in serum,hippocam-pus and prefrontal cortex in POCD mice was up-regulated,and changes of miR-146a expression may be related to the development of POCD.

Objective To evaluate the effect of exogenous miR-181b on postoperative cognitive dysfunction ( POCD) in mice. Methods A total of 108 clean-grade healthy male C57BL∕6 mice, weighing 25-30 g, were divided into 4 groups ( n=27 each) using a random number table method: control group ( group C) , POCD group, miR-181b agonist agomir group ( group Ag) , and agomir negative control group ( group AC) . POCD was induced by open tibial fracture in 2. 1％ isoflurane-anesthetized mice. A total vol-ume of miR-181b agomir 4μl ( 0. 25 nmol∕μl) was injected into bilateral hippocampi at 2 days before estab-lishing the model in group Ag. Agomir negative control solution 4μl was given at 2 days before establishing the model in group AC. Eighteen mice were selected at days 1, 3 and 7 after surgery, and contextual fear conditioning test was performed to assess cognitive function. Nine mice in each group were sacrificed at 6, 12 and 24 h after surgery ( 3 mice at each time point) , and the hippocampus was isolated for determination of miR-181b expression ( by quantitative real-time polymerase chain reaction) and interleukin-1β ( IL-1β) and tumor necrosis factor-α ( TNF-α) contents ( by enzyme-linked immunosorbent assay) . Results Com-pared with group C, the percentage of time spent freezing in the contextual fear conditioning test was signifi-cantly decreased at 1, 3 and 7 days after surgery, and the expression of miR-181b was down-regulated and the contents of IL-1β and TNF-α were increased at 6, 12 and 24 h after surgery in POCD and AC groups( P<0. 05) . Compared with POCD and AC groups, the percentage of time spent freezing in the contextual fear conditioning test was significantly increased 1, 3 and 7 days after surgery, and the expression of miR-181b was up-regulated and the contents of IL-1βand TNF-αwere decreased at 6, 12 and 24 h after surgery in group Ag ( P<0. 05). Conclusion Exogenous miR-181b can mitigate POCD, and the mechanism may be related to inhibiting inflammatory responses in the hippocampus of mice.