Preoperative Sleep Disturbance Exaggerates Surgery-Induced Neuroinflammation and Neuronal Damage in Aged Mice

Abstract

Postoperative cognitive dysfunction (POCD) is defined as new cognitive impairment (memory impairment and impaired performance) after surgery, especially in aged patients. Sleep disturbance is a common phenomenon before surgery that has been increasingly thought to affect patient recovery. However, little is known about the functional impact of preoperative sleep disturbance on POCD. Here, we showed that tibial fracture surgery induced cognitive deficit and production of proinflammatory cytokines interleukin-6 (IL-6) and IL-1β, along with microglia and astrocyte activation, neuronal damage, and blood-brain barrier (BBB) disruption. Preoperative sleep disturbance enhanced the surgery-induced neuroinflammation, neuronal damage, BBB disruption, and memory impairment 24 h after surgery. Taken together, these results demonstrated that preoperative sleep disturbance aggravated postoperative cognitive function in aged mice and the mechanism may be related to central nervous system (CNS) inflammation and neuronal damage.

Figures

Figure 1

Study design. (a) Experiment 1: the training phase of the trace fear conditioning test was performed 1 day before surgery; afterwards, all mice were divided into four groups. Sleep disturbance lasted for 8 h before tibia fracture surgery. All mice underwent the trace fear conditioning and Y maze tests 24 h after surgery, after which the hippocampus was collected. (b) Experiment 2: after the behavioural tests, intravenous injection of EB was performed and the hippocampus was collected to detect EB extravasation.

Figure 2

Preoperative sleep disturbance enhanced postoperative cognitive impairment in aged mice. (a) The freezing time in the contextual fear response task. (b) The number of learning trials in the Y maze test. The data are presented as the mean ± sem (n = 12). ∗∗P < 0.01 vs. the Con group; #P < 0.05 and ##P < 0.01 vs. the Sur group.

Figure 3

Preoperative sleep disturbance promoted the surgery-induced increase of IL-6 and IL-1β levels in the hippocampus. (a) Levels of IL-6 in the hippocampus as detected by ELISA. (b) Levels of IL-1β in the hippocampus as detected by ELISA. The data are presented as the mean ± sem (n = 6). ∗∗P < 0.01 vs. the Con group; #P < 0.05 and ##P < 0.01 vs. the Sur group.

Figure 4

Preoperative sleep disturbance enhanced microglial activation in the hippocampus induced by the tibial surgery. (a) Representative immunohistochemistry images of microglia (red arrows) in areas CA1 and CA3 of the hippocampus based on staining with an anti-Iba1 antibody. Scale bar: 100 μm. (b) Quantification of Iba1-positive cells in areas CA1 and CA3 of the hippocampus. (c) Expression levels of Iba1 protein in the hippocampus. The data are presented as the mean ± sem (n = 4). ∗P < 0.05 and ∗∗P < 0.01 vs. the Con group; #P < 0.05 and ##P < 0.01 vs. the Sur group.

Figure 5

Preoperative sleep disturbance accelerated surgery-induced astrocyte activation in the hippocampus. (a) Representative images of activated astrocytes in areas CA1 and CA3 of the hippocampus based on staining with an anti-GFAP antibody. Scale bar: 100 μm. (b) Quantification of GFAP-positive cell areas CA1 and CA3 of the hippocampus. (c) Expression levels of GFAP protein. The data are presented as the mean ± sem (n = 4). ∗P < 0.05 and ∗∗P < 0.01 vs. the Con group; #P < 0.05 and ##P < 0.01 vs. the Sur group.

Figure 6

Preoperative sleep disturbance augmented surgery-induced neuronal activation and apoptosis in the hippocampus. (a, b) Representative immunohistochemistry images of neuronal damage based on staining with anti-c-fos and anti-caspsase-3 antibody in areas CA1 and CA3 of the hippocampus. Scale bar: 100 μm. (c, d) Quantification of c-fos-positive and caspsase-3-positive cells in areas CA1 and CA3 of the hippocampus. The data are presented as the mean ± sem (n = 4). ∗P < 0.05 and ∗∗P < 0.01 vs. the Con group; #P < 0.05 and ##P < 0.01 vs. the Sur group.

Figure 7

Preoperative sleep disturbance augmented operation-induced blood-brain barrier disruption. (a) EB content and the protein levels of albumin in the hippocampus. (b) Expression levels of occludin and claudin-5 protein in the hippocampus. (c) Expression levels of MMP-2 and MMP-9 protein in the hippocampus. The data are presented as the mean ± sem (n = 4). ∗P < 0.05 and ∗∗P < 0.01 vs. the Con group; #P < 0.05 and ##P < 0.01 vs. the Sur group.