Effect of long-term intake of ω-3 polyunsaturated fatty acids on activation of hippocampal microglia in a mouse model of POCD / 中华麻醉学杂志

ABSTRACT

Objective:To evaluate the effect of long-term intake of ω-3 polyunsaturated fatty acids (ω-3 PUFAs) on the activation of hippocampal microglia in a mouse model of postoperative cognitive dysfunction (POCD).Methods:Ninety-six clean-grade healthy male C57BL/6 mice, aged 8 weeks, weighing 18-24 g, were stratified according to body weight and divided into 4 groups ( n=24 each) by a random number table method: control diet group (group C), ω-3 PUFAs group (group ω), control diet plus POCD group (group C+ P) and ω-3 PUFAs plus POCD group (group ω+ P). Mice were fed a special ω-3 PUFAs diet (DHA 0.14 g/100 g, EPA 0.03 g/100 g) for 12 weeks in group ω and group ω+ P, while mice were fed with a control diet for 12 weeks in group C and group C+ P.Tibial fracture procedures were performed under isoflurane anesthesia to develop the POCD model after 12 weeks of feeding.The fear conditioning test and Y maze test were performed on 1st and 3rd days after developing the model.The mice were sacrificed after behavioral tests, and the hippocampal tissues were removed for determination of the contents of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) (by gas chromatography-mass spectroscopy), density of Iba-1 positive microglia (by immunofluorescence staining), and expression of mature brain-derived neurotrophic factor (mBDNF) and precursor brain-derived neurotrophic factor (pro-BDNF) (by Western blot), and contents of interleukin-1beta (IL-1β) and interleukin-6 (IL-6) (by enzyme-linked immunosorbent assay). Results:Compared with group C, the contents of DHA and EPA were significantly increased, the percentage of freezing time in the contextual test was increased, mBDNF/pro-BDNF ratio was increased ( P<0.05), no significant change was found in the rotation accuracy in Y maze test, density of Iba-1 positive microglia and contents of IL-1β and IL-6 in hippocampus ( P>0.05) in group ω ( P<0.05), and no significant change was found in the contents of DHA and EPA ( P>0.05), the percentage of freezing time in the contextual test and accuracy of rotation in Y maze test were decreased on 1st and 3rd days after operation, the density of Iba-1 positive microglia and contents of IL-1β and IL-6 were increased, and mBDNF/pro-BDNF ratio was decreased in group C+ P ( P<0.05). Compared with group C+ P, the contents of DHA and EPA were significantly increased, the percentage of freezing time in the contextual test and accuracy of rotation in Y maze test were increased on 1st and 3rd days after operation, the density of Iba-1 positive microglia and contents of IL-1β and IL-6 were decreased, and mBDNF/pro-BDNF ratio was increased in group ω+ P ( P<0.05). Conclusions:Long-term intake of ω-3 PUFAs can improve cognitive function in a mouse model of POCD, and the mechanism may be related to inhibition of activation of hippocampal microglia, reduction of inflammatory responses, and thus increasing the mBDNF/Pro-BDNF ratio.