Propofol exerted the neuroprotective effects by regulating renin-angiotensin system and mitochondria-associated endoplasmic reticulum membrane in the postoperative cognitive dysfunction

Fig. 1. Schematic diagram of the experimental protocol. The study was divided into two parts. A The in vivo study to establish a rat model of postoperative cognitive dysfunction (POCD). Aged Sprague-Dawley (SD) rats (n = 6/group) underwent Morris Water Maze (MWM) training for 4 days (Pre-op Day 5 − 1) to establish a behavioral baseline, with a probe trial on Day − 1. On Day 0, splenectomy was performed under different anesthetics to induce POCD. Postoperative cognitive function was evaluated by MWM probe trials on Days 1, 3, 5, and 7. At the endpoint (Day 7), rats were euthanized for hippocampal tissue collection. Downstream analyses on hippocampal tissue included Long-Term Potentiation (LTP) recording, Renin-Angiotensin System (RAS) component ELISAs, and mitochondrial Reactive Oxygen Species (ROS) & ATP assays. B The in vitro mechanistic exploration. In Step 1, primary hippocampal neurons were isolated from P0 rat pups for cell culture. In Step 2, cultured neurons were treated with pharmacological agents such as Angiotensin II (Ang II), propofol, or siRNAs for 6 h. Downstream analyses on treated neurons included apoptosis assay (flow cytometry), Western blotting, mitochondria-associated…

Fig. 2. Propofol mitigated cognitive deficits and long-term potentiation impairments associated with postoperative cognitive dysfunction in aged rats. A Results of Morris water maze escape latency in various groups of rats. B Number of times rats crossed the platform in each group. C Time percentage in target quadrant in each group. D The escape latent distance in each group. E Quantification of long-term potentiation elicited in the CA1 region of the hippocampus. Data in (A-D) are presented as mean ± SD (n=6 per group). Statistical analysis was performed using two-way repeated-measures ANOVA followed by Bonferroni's post hoc test. The horizontal bracket above each graph denotes a significant main effect of time (***p < 0.001), indicating that performance improved significantly across all groups over the 7-day training period. The vertical significance markers represent the comparison between the Propofol group and the Control group at Day 1 (left) and Day 7 (right). ns: not significant; **p< 0.01, ***p < 0.001 vs. Control group. Data in (E) are presented as mean ± SD (n=6 per group). Statistical significance was determined by one-way ANOVA followed by Bonferroni's post hoc test. *p <…

Fig. 3. The effects of different anesthetic drugs on the renin-angiotensin system in aged rats with postoperative cognitive dysfunction. Enzyme-linked immunosorbent assay was used to detect the levels of angiotensin II. A, angiotensin IV (B) and angiotensin (1-7) (C), and the activity of angiotensin-converting enzyme (D) and angiotensin-converting enzyme 2 (E) in the hippocampal tissues. F The renin-angiotensin system-related proteins were detected by western blotting. All data are presented as mean ± SD, with significance levels indicated as * p < 0.05, ** p < 0.01,***p < 0.001

Fig. 4. Propofol, candesartan and perindopril inhibited angiotensin II-induced neuronal injury. A Representative images of cultured neurons identified by MAP2 (microtubule-associated protein 2) staining (red fluorescence indicates MAP2-positive neuronal processes; blue fluorescence indicates DAPI-stained cell nuclei; scale bar = 100 μm. B Excitatory postsynaptic current amplitude of neurons in each group. C Neurons in each group were observed under a microscope. D Neuronal apoptosis in each group. All data are presented as mean ± SD, with significance levels indicated as * p < 0.05, ** p < 0.01,***p < 0.001

Fig. 5. Propofol, candesartan and perindopril inhibited angiotensin II-induced changes in the renin-angiotensin system. Enzyme-linked immunosorbent assay was used to detect the activity of angiotensin-converting enzyme (A) and angiotensin-converting enzyme 2 (B) in the hippocampal neurons. C Western blotting was used to detect the levels of synaptophysin, postsynaptic density protein 95, angiotensin type 1 receptor and angiotensin type 2 receptor. All data are presented as mean ± SD, with significance levels indicated as * p< 0.05, ** p < 0.01, ***p < 0.001

Fig. 6. Propofol reversed angiotensin II-induced inhibition of mitochondria-associated endoplasmic reticulum membrane formation. A Transmission electron microscopy was used to observe mitochondria-associated endoplasmic reticulum membranes. B Western blotting was used to detect the levels of mitochondria-associated endoplasmic reticulum membrane-related proteins, glucose-regulated protein 75, inositol 1,4,5-trisphosphate receptor type 3 and voltage-dependent anion channel 1. Mitochondrial calcium uptake (C), mitochondrial reactive oxygen species (D) and mitochondrial adenosine triphosphate (E) in each group. All data are presented as mean ± SD, with significance levels indicated as * p < 0.05, ** p < 0.01, ***p < 0.001

Fig. 7. Propofol and glucose-regulated protein 75 small interfering RNA regulated angiotensin II-induced neuronal injury. A Neurons in each group were observed under a microscope. B Excitatory postsynaptic current amplitude of neurons in each group. C Neuronal apoptosis in each group. All data are presented as mean ± SD, with significance levels indicated as * p < 0.05, ** p < 0.01,***p < 0.001