ABSTRACT
Objective:
To evaluate the relationship between the mechanism underlying
electroacupuncture-induced reduction of
postoperative cognitive dysfunction and microglial
nuclear factor kappa B (NF-κB)/
NOD-like receptor protein 3 (NLRP3) signaling pathway in
aged mice.
Methods:
Sixty SPF healthy
male C57BL/6
mice,
aged 18 months, weighing 27-30 g, were allocated into 4 groups ( n=15 each) using a random number table
method:
control group (C group), operation group (O group), operation plus sham
electroacupuncture group (O+ SE group) and operation plus
electroacupuncture group (O+ Egroup). In O+ E group, the
mice received
electrical stimulation at the Baihui and Shenting
acupoints for a duration of 30 min. The
electroacupuncture entailed the utilization of a continuous
wave with a frequency of 10 Hz, an intensity of 1 mA, and a daily application for 5 consecutive days. The
mice in Y group underwent the same
procedure as O+ E group, except that no
electrical stimulation was administered.
Laparotomy was performed on the
mice following a 3%
isoflurane anesthesia in O, O+ SE, and O+ E groups. The
open field test was conducted in the morning of 6th day after
surgery to assess the spontaneous activity and
anxiety-like
behavior. The
novel object recognition test was subsequently performed in the afternoon of 6th day after
surgery. The
fear conditioning test was performed on 7th day postoperatively. The
mice were sacrificed under deep
anesthesia at the end of behavioral testing, and the hippocampal
tissue was extracted for
determination of the expression of phosphorylated NF-κB p65 (p-NF-κB p65), NLRP3,
postsynaptic density protein-95 (PSD-95), and
synaptic vesicle protein (SYN) (by
Western blot) and the co-
staining area of NLRP3 and ionized
calcium-binding adapter molecule 1 (Iba1, a specific marker for
microglia) (by
immunofluorescence staining) and for measurement of the dendritic length and
dendritic spine density of
neurons in the
hippocampal CA1 region (using Golgi
staining).
Results:
No statistically significant differences were observed in terms of
movement speed, distance traveled, and
time of center stay during the
open field test among the four groups ( P>0.05). Compared to C group, the percentage of novel object exploration and discrimination index were significantly decreased, the
freezing time was prolonged, the expression of p-NF-κB p65 and NLRP3 in the hippocampal
tissue was up-regulated, the co-
staining area of NLRP3 and Iba1 was increased, the expression of PSD-95 and SYN was down-regulated, and the dendritic length and
dendritic spine density of hippocampal
neurons were decreased in O, O+ SE and O+ E groups ( P<0.05). Compared to O group, the percentage of novel object exploration and discrimination index were significantly increased, the
freezing time was shortened, the expression of p-NF-κB p65 and NLRP3 in the hippocampal
tissue was down-regulated, the co-
staining area of NLRP3 and Iba1 was decreased, the expression of PSD-95 and SYN was up-regulated, and the dendritic length and
dendritic spine density of hippocampal
neurons were increased in O+ E group ( P<0.05), and no significant change was found in each parameter in O+ SE group ( P>0.05). Compared to O+ SE group, the percentage of novel object exploration and discrimination index were significantly increased, the
freezing time was shortened, the expression of p-NF-κB p65 and NLRP3 in the hippocampal
tissue was down-regulated, the co-
staining area of NLRP3 and Iba1 was decreased, the expression of PSD-95 and SYN was up-regulated, and the dendritic length and
dendritic spine density of hippocampal
neurons were increased in O+ E group ( P<0.05).
Conclusions:
The mechanism by which
electroacupuncture attenuates
postoperative cognitive dysfunction is associated with inhibition of activation of NF-κB/NLRP3 signaling pathway in
microglial cells and improvement in
synaptic plasticity in
aged mice.
