Whole-transcriptome sequencing identifies neuroinflammation, metabolism and blood-brain barrier related processes in the hippocampus of aged mice during perioperative period

Intermittent fasting alleviates postoperative cognitive dysfunction by reducing neuroinflammation in aged mice

Elderly individuals undergoing surgical procedures are often confronted with the peril of experiencing postoperative cognitive dysfunction (POCD). Prior research has demonstrated the exacerbating effect of sevoflurane anesthesia on neuroinflammation, which can further deteriorate the condition of POCD in elderly patients. Intermittent fasting (IF) restricts food consumption to a specific time window and has been demonstrated to ameliorate cognitive dysfunction induced by neuropathic inflammation. We subjected 18-month-old male mice to 16hours of fasting and 8hours of unrestricted eating over a 24-hour period for 0, 1, 2, and 4 weeks, followed by abdominal exploration under sevoflurane anesthesia. In this study, we aim to explore the potential impact of IF on postoperative cognitive function in aged mice undergoing sevoflurane surgery through the preoperative implementation of IF measures. The findings indicate two weeks of IF leads to a significant enhancement of learning and memory capabilities in mice following surgery. The cognitive performance, as determined by the novel object recognition and Morris water maze tests, as well as the synaptic plasticity, as measured by in vivo electrophysiological recordings, has demonstrated marked improvements. Furthermore, the administration of IF markedly enhances the expression of synaptic-associated proteins in hippocampal neurons, concomitant with a decreasing expression of pro-inflammatory factors and a reduced density of microglial cells within the hippocampal brain region. To summarize, the results of this study indicate that IF may mitigate inflammation in the hippocampal area of the brain. Furthermore, IF appears to provide a safeguard against cognitive impairment and synaptic plasticity impairment brought on by sevoflurane anesthesia.

The cGAS/STING signaling pathway is involved in sevoflurane induced neuronal necroptosis via regulating microglia M1 polarization

OBJECTIVE

The specific mechanisms of sevoflurane-induced neurotoxicity are still undetermined. The aim of the current study was to investigate the role of the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) signaling pathway in sevoflurane-induced neuronal necroptosis.

METHODS

BV2 microglial cells were divided into a control group and a 4% sevoflurane exposure group. Western blotting was used to detect expression of the M1 polarization marker inducible nitric oxide synthase (iNOS). RNA was collected for RNA sequencing analysis. After STING knockdown in microglia, western blotting was performed to examine expression of the pro-inflammatory markers CD16 and CD32. The tumor necrosis factor-α (TNF-α) level in media was detected using an enzyme-linked immunosorbent assay. BV2 microglia conditioned media was collected to incubate HT22 neuronal cells, and their cell activity was measured using a CCK8 assay. Calcium was observed by fluorescence. Western blotting was performed to evaluate receptor-interacting protein kinase 1 (RIPK1), RIPK3, and mixed lineage kinase domain-like (MLKL) expression. Neuronal necroptosis rate were detected using flow cytometry.

RESULTS

Sevoflurane exposure promoted microglial M1 polarization. The cGAS/STING pathway was screened and identified by RNA sequencing analysis of sevoflurane-exposed microglia and the control group. Compared with the control group, STING knockdown in microglia rescued the amoeboid morphology, inhibited TNF-α release, and significantly decreased iNOS, CD16, and CD32 expression. Moreover, calcium ions and necroptosis within neurons were decreased, and RIPK1, RIPK3, and p-MLKL expression was markedly decreased in microglia media culture with STING knockdown.

CONCLUSION

These results suggest that sevoflurane can regulate microglial M1 polarization by activating the cGAS/STING signaling pathway and increasing immune factor release, thus accelerating the neuronal necroptosis induced by calcium overload.

Kapβ2 Inhibits Perioperative Neurocognitive Disorders in Rats with Mild Cognitive Impairment by Reversing the Nuclear-Cytoplasmic Mislocalization of hnRNPA2/B1

Harmful stimuli trigger mutations lead to uncontrolled accumulation of hnRNPA2/B1 in the cytoplasm, exacerbating neuronal damage. Kapβ2 mediates the bidirectional transport of most substances between the cytoplasm and the nucleus. Kapβ2 guides hnRNPA2/B1 back into the nucleus and restores its function, alleviating related protein toxicity. Here, we aim to explore the involvement of Kapβ2 in neurodegeneration in rats with MCI following sevoflurane anesthesia and surgery. Firstly, novel object recognition test and Barnes maze were conducted to assess behavioral performances, and we found Kapβ2 positively regulated the recovery of memory and cognitive function. In vivo electrophysiological experiments revealed that the hippocampal theta rhythm energy distribution was disrupted, coherence was reduced, and long-term potentiation was attenuated in MCI rats. LTP was greatly improved with positive modulation of Kapβ2. Next, functional MRI and BOLD imaging will be employed to examine the AFLL and FC values of dynamic connectivity between the cortex and hippocampus of the brain. The findings show that regulating Kapβ2 in the hippocampus region enhances functional activity and connections between brain regions in MCI rats. WB results showed that increasing Kapβ2 expression improved the expression and recovery of cognitive-related proteins in the hippocampus of MCI rats. Finally, WB and immunofluorescence were used to examine the changes in hnRNPA2/B1 expression in the nucleus and cytoplasm after overexpression of Kapβ2, and it was found that nucleocytoplasmic mis location was alleviated. Overall, these data show that Kapβ2 reverses the nucleoplasmic misalignment of hnRNPA2/B1, which slows neurodegeneration towards dementia in MCI after sevoflurane anesthesia and surgery. Our findings may lead to new approaches for perioperative neuroprotection of MCI patients.

A nomogram for predicting the risk of cancer-related cognitive impairment in breast cancer patients based on a scientific symptom model

Cancer-related cognitive impairment is a significant clinical challenge observed in patients with breast cancer, manifesting during or after treatment. This impairment leads to deteriorations in memory, processing speed, attention, and executive functioning, which profoundly impact patients' occupational performance, daily living activities, and overall quality of life. Grounded in the Symptom Science Model 2.0, this study investigates the contributing factors to Cancer-related cognitive impairment in breast cancer patients and develops a predictive nomogram for this demographic. Employing both univariate and multivariate logistic regression analyses, this investigation delineates the predictive factors influencing outcomes in breast cancer patients. A nomogram was constructed leveraging these identified predictive factors, accompanied by internal validation through bootstrap resampling methodology (1000 bootstrap samples). The efficacy of the predictive model was assessed by employing the Hosmer-Lemeshow goodness-of-fit test and calibration curves. The prevalence of cognitive impairment in breast cancer patients was identified to be 45.83%.Multivariate logistic regression analysis identified the independent predictors of Cancer-related cognitive impairment in breast cancer patients as place of residence, educational level, chemotherapy, benefit finding, post-traumatic growth, anxiety, fear of cancer progression, and fasting blood glucose levels. these factors were integrated into the nomogram. The Hosmer-Lemeshow goodness-of-fit test demonstrated that the prediction model was appropriately calibrated (χ2 = 11.520, P = 0.174). Furthermore, the model exhibited an area under the curve of 0.955 (95% CI 0.939 to 0.971) and a sensitivity of 0.906, evidencing its robust discriminative capacity and accuracy. Utilizing the Symptom Science Model 2.0 as a framework, this study comprehensively examines the multifaceted factors influencing Cancer-related cognitive impairment in breast cancer patients, spanning five critical domains: complex symptoms, phenotypic characterization, biobehavioral factors, social determinants of health, and patient-centered experiences. A predictive nomogram model was established, demonstrating satisfactory predictive accuracy and capability. This model is capable of identifying breast cancer patients with cognitive impairments with high precision. The findings furnish empirical evidence in support of the early detection, diagnosis, and intervention strategies for high-risk breast cancer patients afflicted with Cancer-related cognitive impairment.

Middle aged CAMKII-Cre:Cbsfl/fl mice: a new model for studying perioperative neurocognitive disorders

Postoperative complications, such as perioperative neurocognitive disorders (PND), have become a major issue affecting surgical outcomes. However, the mechanism of PND remains unclear, and stable animal models of middle-aged PND are lacking. S-adenosylmethionine (SAM), a cystathionine beta-synthase (CBS) allosteric activator, can reduce the level of plasma homocysteine and prevent the occurrence of PND. However, the time and resource-intensive process of constructing models of PND in elderly animals have limited progress in PND research and innovative therapy development. The present study aimed to construct a stable PND model in middle-aged CAMKII-Cre:Cbsfl/fl mice whose Cbs was specifically knocked out in CAMKII positive neurons. Behavioral tests showed that these middle-aged mice displayed cognitive deficits which were aggravated by exploratory laparotomy under isoflurane anesthesia. Compared with typical PND mice which were 18-month-old, these middle-aged mice showed similar cognitive deficits after undergoing exploratory laparotomy under isoflurane anesthesia. Though there was no significant difference in the number of neurons in either the hippocampus or the cortex, a significant increase in numbers of microglia and astrocytes in the hippocampus was observed. These indicate that middle-aged CAMKII-Cre:Cbsfl/fl mice can be used as a new PND model for mechanistic studies and therapy development for PND.

Dysregulation of iron homeostasis and ferroptosis in sevoflurane and isoflurane associated perioperative neurocognitive disorders

In recent years, sevoflurane and isoflurane are the most popular anesthetics in general anesthesia for their safe, rapid onset, and well tolerant. Nevertheless, many studies reported their neurotoxicity among pediatric and aged populations. This effect is usually manifested as cognitive impairment such as perioperative neurocognitive disorders. The wide application of sevoflurane and isoflurane during general anesthesia makes their safety a major health concern. Evidence indicates that iron dyshomeostasis and ferroptosis may establish a role in neurotoxicity of sevoflurane and isoflurane. However, the mechanisms of sevoflurane- and isoflurane-induced neuronal injury were not fully understood, which poses a barrier to the treatment of its neurotoxicity. We, therefore, reviewed the current knowledge on mechanisms of iron dyshomeostasis and ferroptosis and aimed to promote a better understanding of their roles in sevoflurane- and isoflurane-induced neurotoxicity.

LXA4 attenuates perioperative neurocognitive disorders by suppressing neuroinflammation and oxidative stress

Perioperative neurocognitive disorder (PND) is a common complication that increases morbidity and mortality in elderly patients undergoing surgery. Abnormal microglia activation causes neuroinflammation and contributes to the development of PND. Growing evidence shows that lipoxin A4 (LXA4), a lipid mediator, possesses potent anti-inflammatory activities. In this study, we investigated whether LXA4 exerted a protective effect against surgery-induced neurocognitive deficits and explored the underlying mechanisms. Mice were subjected to laparotomy under sevoflurane anesthesia to establish an animal model of PND. LXA4 (15 μg/kg/d, ip) was administered three days prior surgery. We showed that LXA4 significantly alleviated surgery-induced cognitive impairments, attenuated neuroinflammation and microglial activation in hippocampus. In BV2 microglial cells treated with LPS (100 ng/mL), pre-application of LXA4 (100 nΜ) significantly inhibited M1 polarization and promoted M2 polarization, and decreased the levels of pro-inflammatory cytokines (IL-1β, TNF-α, IL-6) and increased the levels of anti-inflammatory cytokine (IL-10). LXA4 also mitigated LPS-regulated expression of HO-1, NOX2, and SOD1, elevated SOD activity, and attenuated ROS production. Furthermore, we revealed that LXA4 increased the expression of SIRT1 and decreased the protein level of acetylated NF-κB p65. SIRT1 inhibitor EX-527 abolished the anti-inflammatory and antioxidant response effects of LXA4 in BV2 microglial cells. Hence, LXA4 is a potential therapeutic agent for surgery-induced neuroinflammation, oxidative stress, and cognitive deficit, and the effect of LXA4 is probably mediated by the activation of the SIRT1/NF-κB signaling pathway in microglia.

CRTC1 is a potential target to delay aging-induced cognitive deficit by protecting the integrity of the blood-brain barrier via inhibiting inflammation

Aging can cause attenuation in the functioning of multiple organs, and blood-brain barrier (BBB) breakdown could promote the occurrence of disorders of the central nervous system during aging. Since inflammation is considered to be an important factor underlying BBB injury during aging, vascular endothelial cell senescence serves as a critical pathological basis for the destruction of BBB integrity. In the current review, we have first introduced the concepts related to aging-induced cognitive deficit and BBB integrity damage. Thereafter, we reviewed the potential relationship between disruption of BBB integrity and cognition deficit and the role of inflammation, vascular endothelial cell senescence, and BBB injury. We have also briefly introduced the function of CREB-regulated transcription co-activator 1 (CRTC1) in cognition and aging-induced CRTC1 changes as well as the critical roles of CRTC1/cyclooxygenase-2 (COX-2) in regulating inflammation, endothelial cell senescence, and BBB injury. Finally, the underlying mechanisms have been summarized and we propose that CRTC1 could be a promising target to delay aging-induced cognitive deficit by protecting the integrity of BBB through promoting inhibition of inflammation-mediated endothelial cell senescence.

Neuroprotective effects of different doses of Maresin1 pretreatment in aged rats after anesthesia/surgery

OBJECTIVE

The study is to investigate the neuroprotective effect of different doses of Maresin1 pretreatment in aged rats after anesthesia/surgery and the related mechanisms.

METHODS

Aged male rats were randomly divided into a control group, an anesthesia/surgery group, and low, medium, and high-dose Maresin1 pretreatment groups, and the hippocampus was taken for study. The Morris water maze was performed to detect the cognitive ability of rats. Western blot and immunofluorescence were used to detect the expression of glial fibrillary acidic protein (GFAP) and central nervous system-specific protein (S100β). The ultrastructure of astrocytes was observed by a transmission electron microscope. Quantitative real-time PCR was used to detect the relative expression of IL-1β, IL-6, and TNF-α mRNA.

RESULTS

Compared with the control group, the cognition of rats in the anesthesia/surgery group was significantly reduced. The expression of astrocyte markers (GFAP and S100β) in the hippocampus of rats in the anesthesia/surgery group was increased. The levels of hippocampal inflammatory cytokines (TNF-α, IL-1β, and IL-6) were also higher in the anesthesia/surgery group than in the control group. After pretreatment with different doses of Maresin1, the cognitive impairment of rats was alleviated to varying degrees. Maresin1 pretreatment decreased the expression of astrocyte markers and inflammatory factors in the hippocampus of rats after anesthesia/surgery, and improve the microstructures of activated astrocytes, especially in the medium-dose group.

CONCLUSION

Pretreatment with Maresin1 (especially at medium-dose) showed neuroprotective effects in aged rats after anesthesia/surgery, which may be related to the inhibition of astrocyte activation.

Sepsis-like Energy Deficit Is Not Sufficient to Induce Early Muscle Fiber Atrophy and Mitochondrial Dysfunction in a Murine Sepsis Model

Sepsis-induced myopathy is characterized by muscle fiber atrophy, mitochondrial dysfunction, and worsened outcomes. Whether whole-body energy deficit participates in the early alteration of skeletal muscle metabolism has never been investigated. Three groups were studied: “Sepsis” mice, fed ad libitum with a spontaneous decrease in caloric intake (n = 17), and “Sham” mice fed ad libitum (Sham fed (SF), n = 13) or subjected to pair-feeding (Sham pair fed (SPF), n = 12). Sepsis was induced by the intraperitoneal injection of cecal slurry in resuscitated C57BL6/J mice. The feeding of the SPF mice was restricted according to the food intake of the Sepsis mice. Energy balance was evaluated by indirect calorimetry over 24 h. The tibialis anterior cross-sectional area (TA CSA), mitochondrial function (high-resolution respirometry), and mitochondrial quality control pathways (RTqPCR and Western blot) were assessed 24 h after sepsis induction. The energy balance was positive in the SF group and negative in both the SPF and Sepsis groups. The TA CSA did not differ between the SF and SPF groups, but was reduced by 17% in the Sepsis group compared with the SPF group (p < 0.05). The complex-I-linked respiration in permeabilized soleus fibers was higher in the SPF group than the SF group (p < 0.05) and lower in the Sepsis group than the SPF group (p < 0.01). Pgc1α protein expression increased 3.9-fold in the SPF mice compared with the SF mice (p < 0.05) and remained unchanged in the Sepsis mice compared with the SPF mice; the Pgc1α mRNA expression decreased in the Sepsis compared with the SPF mice (p < 0.05). Thus, the sepsis-like energy deficit did not explain the early sepsis-induced muscle fiber atrophy and mitochondrial dysfunction, but led to specific metabolic adaptations not observed in sepsis.

Construction and analysis of circular RNA-associated competing endogenous RNA network in the hippocampus of aged mice for the occurrence of postoperative cognitive dysfunction

Circular RNAs are highly stable single-stranded circular RNAs and enriched in the brain. Previous studies showed that circRNAs, as part of competing endogenous RNAs (ceRNAs) network, play an important role in neurodegenerative and psychiatric diseases. However, the mechanism of circRNA-related ceRNA networks in postoperative cognitive dysfunction (POCD) has not been elucidated yet. POCD usually occurs in elderly patients and is characterized by hippocampal dysfunction. Here, aged C57BL/6 mice were subjected to exploratory laparotomy under sevoflurane anesthesia, and this POCD model was verified by Morris water maze test. Whole-transcriptome sequencing was performed on the hippocampus of control group (Con) and surgery group. One hundred and seventy-seven DEcircRNAs, 221 DEmiRNAs and 2,052 DEmRNAs were identified between two groups. A ceRNA network was established with 92 DEcircRNAs having binding sites with 76 DEmiRNAs and 549 target DEmRNAs. In functional enrichment analysis, a pathological pattern of POCD was highlighted in the ceRNA network: Abnormal metabolic process in neural cells, including oxygen metabolism, could promote apoptosis and then affect the synaptic function, which may undermine the neural plasticity and eventually lead to changes in cognitive function and other behavioral patterns. In conclusion, this specific ceRNA network of circRNAs–miRNAs–mRNAs has provided novel insights into the regulatory mechanisms of POCD and revealed potential therapeutic gene targets.

Research progress on perioperative blood-brain barrier damage and its potential mechanism

The blood-brain barrier (BBB) is an important barrier separating the central nervous system from the periphery. The composition includes endothelial cells, pericytes, astrocytes, synapses and tight junction proteins. During the perioperative period, anesthesia and surgical operations are also a kind of stress to the body, which may be accompanied by blood-brain barrier damage and brain metabolism dysfunction. Perioperative blood-brain barrier destruction is closely associated with cognitive impairment and may increase the risk of postoperative mortality, which is not conducive to enhanced recovery after surgery. However, the potential pathophysiological process and specific mechanism of blood-brain barrier damage during the perioperative period have not been fully elucidated. Changes in blood-brain barrier permeability, inflammation and neuroinflammation, oxidative stress, ferroptosis, and intestinal dysbiosis may be involved in blood-brain barrier damage. We aim to review the research progress of perioperative blood-brain barrier damage and its potential adverse effects and potential molecular mechanisms, and provide ideas for the study of homeostasis maintenance of brain function and precision anesthesia.

Mdivi-1 improves postoperative neurocognitive disorders in aged rats undergoing splenectomy by inhibiting dynamin-related protein-1

Background

The regulatory role of mitochondria in the inflammatory response of the nervous system postoperatively remains unclear. This study explored the relationship between mitochondria and postoperative neurocognitive dysfunction (PNCD) by regulating mitochondrial function in aged rats undergoing splenectomy.

Methods

A total of 120 aged rats were randomly divided into five groups (n=24) as follows: Control group (not subjected to any form of treatment), Sham group (subjected only to sham-splenectomized operation after anesthesia), Splenectomy group (only underwent splenectomy after anesthesia), Synonyms Mitochondrial division inhibitor 1 (Mdivi-1) group [treated with Mdivi-1, a dynamin-relatedprotein 1 (Drp1) inhibitor], and Dimethyl Sulfoxide (DMSO) group (treated with DMSO, a solvent). Inflammatory markers, namely interleukin-1β (IL-1β) and tumor necrosis factor α (TNF-α), were measured in the plasma and brains of the rats. Cognitive function was assessed using the Morris water maze test.

Results

During the perioperative period, the physiological parameters did not differ among the five groups (P>0.05). The results of the Morris water maze experiments showed that the memory of the rats was significantly impaired after splenectomy, which was alleviated by Mdivi-1 administration (P=0.04). Postoperatively, the proinflammatory cytokine levels in the serum and hippocampus tissue were upregulated, while Mdivi-1 administration reduced this increase. The electron microscopy and hematoxylin-eosin (HE) staining results indicated that the structure of neurons and mitochondria was minimally impaired in the Mdivi-1 group.

Conclusions

Aged rats that underwent splenectomy exhibited significant postoperative cognitive impairments. The selective inhibitor of Drp1, Mdivi-1, exerted protective effects against PNCD by ameliorating mitochondrial dysfunction and reducing the inflammatory response.