Young plasma reverses anesthesia and surgery-induced cognitive impairment in aged rats by modulating hippocampal synaptic plasticity

Abstract

We investigated the protective effect of young plasma on anesthesia- and surgery-induced cognitive impairment and the potential underlying mechanism using bioinformatics, functional enrichment analysis, gene set enrichment analysis, Golgi-Cox staining, dendritic spine analysis, immunofluorescence assay, western blot analysis, and transmission electron microscopy. Furthermore, we performed behavioral assessments using the open field test, the novel object recognition test, and the Morris water maze test. We identified 1969 differentially expressed genes induced by young plasma treatment, including 800 upregulated genes and 1169 downregulated genes, highlighting several enriched biological processes (signal release from synapse, postsynaptic density and neuron to neuron synapse). Anesthesia- and surgery-induced cognitive impairment in aged rats was comparatively less severe following young plasma preinfusion. In addition, the decreased levels of synapse-related and tyrosine kinase B/extracellular signal-regulated protein kinase/cyclic adenosine monophosphate response element-binding protein (TrkB/ERK/CREB) signaling pathway-related proteins, dendritic and spine deficits, and ultrastructural changes were ameliorated in aged mice following young plasma preinfusion. Together, these findings suggest that young plasma reverses anesthesia- and surgery-induced cognitive impairment in aged rats and that the mechanism is associated with the activation of the TrkB/ERK/CREB signaling pathway and improvement in hippocampal synaptic plasticity.

Keywords: TrkB/ERK/CREB signaling pathway; aged; cognitive impairment; synaptic plasticity; young plasma.

FIGURE 1

Experimental flow chart of the study (Drawn by Figdraw platform, ID:UYRPS4e4ff). Rats were treated with a young plasma injection for 24 days, comprising eight pre-infusions, and were subjected to anesthesia and tibial fracture surgery 24 h after the final pre-infusion. After the open field test, novel object recognition test, and Morris water maze test, the rats were sacrificed for a series of tests.

FIGURE 2

Results of bioinformatics analysis. (A) Principal component analysis diagram. (B) Differential gene volcano map. (C) Heatmap of differential gene cluster analysis. (D) GO enrichment analysis pathways. (E) Interaction network diagram of Top100 DEGs.

FIGURE 3

Anesthesia and surgery had no effect on the spontaneous activity of the aged rats. (A) Traveling trajectory in the open field. (B) Total distance traveled. (C) Mean traveling speed. (D) Central area residence time. (E) Traveling distance in the center of the open field.

FIGURE 4

Young plasma alleviated anesthesia- and surgery-induced postoperative cognitive dysfunction (POCD) in aged rats. (A) Schematic of the novel object recognition test (NORT). (B) Exploration time to the familiar object. (C) Exploration time to the familiar and novel objects during the novel object recognition phase. (D) Recognition index. (E) Swimming trajectory. (F) Escape latency. (G) Times of crossing the platform. (H) Total times spent in the target quadrant. (I) Average swimming speed. Data are shown as means ± standard deviations. *p < 0.05 compared with group C, **p < 0.05 compared with group POCD (n = 30 per group).

FIGURE 5

Young plasma alleviated dendritic and spine deficits in the hippocampus of postoperative cognitive dysfunction (POCD) rats. (A) Representative hippocampal Golgi-Cox staining images showing dendritic arborization in hippocampal CA1 pyramidal neurons and an intersection diagram of dendritic arborization and concentric circles in hippocampal slices. Scale bar: 400 μm and 50 μm for enlarged inserts. (B) Quantification of the dendritic length of hippocampal CA1 pyramidal neurons. (C) The number of dendrites in hippocampal CA1 pyramidal neurons. (D) Spine density of dendrites in hippocampal CA1 pyramidal neurons. (E) Quantitative analysis of the number of intersections of dendrites in hippocampal CA1 pyramidal neurons. Data are shown as means ± standard deviations. *p < 0.05 compared with group C, **p < 0.05 compared with group POCD (n = 8 per group).

FIGURE 6

Young plasma improved the ultrastructure of hippocampal synapses. (A) Representative images of hippocampal synapses under transmission electron microscope (TEM). The yellow arrows indicate synapse. Scale bar: 1 μm. (B) Representative images of single synapse. The position between two gray arrows indicate synaptic gap width. Scale bar: 500 nm. (C) Quantitative statistics of synaptic density in different groups. (D) Quantitative analysis of synaptic gap width. Data are shown as mean ± SD. *P < 0.05 compared with group C, **P < 0.05 compared with group POCD (n = 8 per group).

FIGURE 7

Young plasma increased the synapse-associated protein expression in postoperative cognitive dysfunction (POCD) rats. The expression of synapse-associated proteins including (A) PSD-95, (B) SYP, (C) GAP-43 and (D) synapsin-I. (E) Representative immunostaining showing the colocalization of Neun (green), synapsin-I (red), and DAPI (blue) in the hippocampus of CA1. Scale bar: 200 μm. (F) Bar graph summarizing the fluorescence intensity of synapsin-I in the hippocampal CA1. Data are shown as means ± standard deviations. *p < 0.05 compared with group C, **p < 0.05 compared with group POCD (n = 7 per group).

FIGURE 8

Young plasma activated the tyrosine kinase B/extracellular signal-regulated protein kinase/cyclic adenosine monophosphate response element-binding protein (TrkB/ERK/CREB) signaling pathway to exert a neuroprotective effect in postoperative cognitive dysfunction (POCD) rats. The expression of proteins related to the TrkB/ERK/CREB signaling pathway including phosphorylated TrkB/TrkB (A), phosphorylated ERK/ERK (B), and phosphorylated CREB (pCREB)/CREB (C). (D) Representative immunostaining showing the colocalization of Neun (green), p-CREB (red), and DAPI (blue) in the CA1 of the hippocampus. Scale bar: 200 μm. (E) Bar graph summarizing the fluorescence intensity of p-CREB in the hippocampal CA1. Data are shown as means ± standard deviations. *p < 0.05 compared with group C, **p < 0.05 compared with group POCD (n = 7 per group).

FIGURE 9

Schematic diagram of the neuroprotective effect of young plasma (Drawn by Figdraw platform, ID:WARIWa686f). Young plasma improves synaptic plasticity by activating TrkB/ERK/CREB signaling pathway, thereby inhibiting cognitive impairment caused by surgery and anesthesia.