Inhibition of the integrated stress response reverses oxidative stress damage-induced postoperative cognitive dysfunction

miR-206-3p Targets Brain-Derived Neurotrophic Factor and Affects Postoperative Cognitive Function in Aged Mice

Postoperative cognitive dysfunction (POCD) occurs after surgery and severely impairs patients' quality of life. Finding POCD-associated variables can aid in its diagnosis and prognostication. POCD is associated with noncoding RNAs, such as microRNAs (miRNAs), involved in metabolic function, immune response alteration, and cognitive ability impairment; however, the underlying mechanisms remain unclear. The aim of this study was to investigate hub miRNAs (i.e., miRNAs that have an important regulatory role in diseases) regulating postoperative cognitive function and the associated mechanisms. Hub miRNAs were identified by bioinformatics, and their expression in mouse hippocampus tissues was determined using real-time quantitative polymerase chain reaction. Hub miRNAs were overexpressed or knocked down in cell and animal models to test their effects on neuroinflammation and postoperative cognitive function. Six differentially expressed hub miRNAs were identified. miR-206-3p was the only broadly conserved miRNA, and it was used in follow-up studies and animal experiments. Its inhibitors reduced the release of proinflammatory cytokines in BV-2 microglia by regulating its target gene, brain-derived neurotrophic factor (BDNF), and the downstream signaling pathways. miR-206-3p inhibition suppressed microglial activation in the hippocampi of mice and improved learning and cognitive decline. Therefore, miR-206-3p significantly affects POCD, implying its potential as a therapeutic target.

iMPAQT reveals that adequate mitohormesis from TFAM overexpression leads to life extension in mice

Mitochondrial transcription factor A, TFAM, is essential for mitochondrial function. We examined the effects of overexpressing the TFAM gene in mice. Two types of transgenic mice were created: TFAM heterozygous (TFAM Tg) and homozygous (TFAM Tg/Tg) mice. TFAM Tg/Tg mice were smaller and leaner notably with longer lifespans. In skeletal muscle, TFAM overexpression changed gene and protein expression in mitochondrial respiratory chain complexes, with down-regulation in complexes 1, 3, and 4 and up-regulation in complexes 2 and 5. The iMPAQT analysis combined with metabolomics was able to clearly separate the metabolomic features of the three types of mice, with increased degradation of fatty acids and branched-chain amino acids and decreased glycolysis in homozygotes. Consistent with these observations, comprehensive gene expression analysis revealed signs of mitochondrial stress, with elevation of genes associated with the integrated and mitochondrial stress responses, including Atf4, Fgf21, and Gdf15. These found that mitohormesis develops and metabolic shifts in skeletal muscle occur as an adaptive strategy.

HIF1A overexpression caused by etomidate activates PGK1-induced oxidative stress in postoperative cognitive dysfunction

Etomidate (ETO), a hypnotic agent used for anesthesia induction, has been shown to induce long-lasting cognitive deficits. In the present study, we investigated whether ETO could activate the HIF1A/PGK1 pathway to antagonize oxidative damage in mice with postoperative cognitive dysfunction (POCD). A mouse model of ETO-mediated POCD was established, and pathological changes, apoptosis, and inflammatory factors in mouse hippocampal tissues were analyzed by HE staining, TUNEL assay, and ELISA. ETO was revealed to cause cognitive dysfunction in mice. Integrated database mining was conducted to screen out transcription factors that are both related to ETO and POCD. Hypoxia-inducible factor 1-alpha (HIF1A) was overexpressed in mice with POCD, and downregulation of HIF1A alleviated cognitive dysfunction in mice. HIF1A downregulation inhibited the transcription of phosphoglycerate kinase 1 (PGK1). Overexpression of PGK1 abated the alleviating effects of HIF1A knockdown on oxidative stress in mice with POCD. In addition, HIF1A activation of PGK1 induced oxidative stress and apoptosis in HT-22 cells while inhibiting cell viability. Taken together, we demonstrated that HIF1A activation of PGK1 induced oxidative stress in ETO-mediated POCD.

Impaired synaptic plasticity and decreased glutamatergic neuron excitability induced by SIRT1/BDNF downregulation in the hippocampal CA1 region are involved in postoperative cognitive dysfunction

BACKGROUND

Postoperative cognitive dysfunction (POCD) is a common complication after anesthesia/surgery, especially among elderly patients, and poses a significant threat to their postoperative quality of life and overall well-being. While it is widely accepted that elderly patients may experience POCD following anesthesia/surgery, the exact mechanism behind this phenomenon remains unclear. Several studies have indicated that the interaction between silent mating type information regulation 2 homologue 1 (SIRT1) and brain-derived neurotrophic factor (BDNF) is crucial in controlling cognitive function and is strongly linked to neurodegenerative disorders. Hence, this research aims to explore how SIRT1/BDNF impacts cognitive decline caused by anesthesia/surgery in aged mice.

METHODS

Open field test (OFT) was used to determine whether anesthesia/surgery affected the motor ability of mice, while the postoperative cognitive function of 18 months old mice was evaluated with Novel object recognition test (NORT), Object location test (OLT) and Fear condition test (FC). The expressions of SIRT1 and other molecules were analyzed by western blot and immunofluorescence staining. The hippocampal synaptic plasticity was detected by Golgi staining and Long-term potentiation (LTP). The effects of SIRT1 and BDNF overexpression as well as chemogenetic activation of glutamatergic neurons in hippocampal CA1 region of 18 months old vesicular glutamate transporter 1 (VGLUT1) mice on POCD were further investigated.

RESULTS

The research results revealed that older mice exhibited cognitive impairment following intramedullary fixation of tibial fracture. Additionally, a notable decrease in the expression of SIRT1/BDNF and neuronal excitability in hippocampal CA1 glutamatergic neurons was observed. By increasing levels of SIRT1/BDNF or enhancing glutamatergic neuron excitability in the CA1 region, it was possible to effectively mitigate synaptic plasticity impairment and ameliorate postoperative cognitive dysfunction.

CONCLUSIONS

The decline in SIRT1/BDNF levels leading to changes in synaptic plasticity and neuronal excitability in older mice could be a significant factor contributing to cognitive impairment after anesthesia/surgery.

Latest advances and clinical application prospects of resveratrol therapy for neurocognitive disorders

Neurocognitive disorders, such as Alzheimer's disease, vascular dementia, and postoperative cognitive dysfunction, are non-psychiatric brain syndromes in which a significant decline in cognitive function causes great trauma to the mental status of the patient. The lack of effective treatments for neurocognitive disorders imposes a considerable burden on society, including a substantial economic impact. Over the past few decades, the identification of resveratrol, a natural plant compound, has provided researchers with an opportunity to formulate novel strategies for the treatment of neurocognitive disorders. This is because resveratrol effectively protects the brain of those with neurocognitive disorders by targeting some mechanisms such as inflammation and oxidative stress. This article reviews the status of recent research investigating the use of resveratrol for the treatment of different neurocognitive disorders. By examining the possible mechanisms of action of resveratrol and the shared mechanisms of different neurocognitive disorders, treatments for neurocognitive disorders may be further clarified.

Endoplasmic reticulum stress exacerbates microplastics-induced toxicity in animal cells

Human and animal exposure to microplastics (MPs) contained in food is inevitable because of their widespread existence in the environment. Nevertheless, MPs toxicity studies in ruminants often lack attention. Here, we assessed the cytotoxicity of polystyrene microplastics (PS MPs) on goat mammary epithelial cells (GMECs). Compared to controls, PS MPs treatment significantly reduced cell viability, altered cell morphology and disrupted organelle integrity. Detection of membrane potential and reactive oxygen species (ROS) suggested that PS MPs induced mitochondrial dysfunction and oxidative stress. Further transcriptome analysis also confirmed alterations in these pathways. In addition, several genes related to endoplasmic reticulum (ER) homeostasis were significantly regulated in the transcriptional profile. Subsequent experiments confirmed that PS MPs induce ER stress via the PERK/eIF2α/CHOP pathway, accompanied by intracellular Ca2+ overload. Meanwhile, downstream activation of the Bax/Bcl-2 pathway and caspase cascade released apoptotic signals, which led to apoptosis in GMECs. Interestingly, the addition of PERK inhibitor (ISRIB) attenuated PS MPs-induced ER stress and apoptosis, which suggests that ER stress may exacerbate PS MPs-induced cytotoxicity. This work reveals the impact of MPs on mammalian cytotoxicity, enriches the mechanisms for the toxicity of MPs, and provides insight for further assessment of the risk of MPs in food.

Smad7 in the hippocampus contributes to memory impairment in aged mice after anesthesia and surgery

BACKGROUND

Postoperative cognitive dysfunction (POCD) is a common neurological complication following anesthesia and surgery. Increasing evidence has demonstrated that neuroinflammation caused by systemic inflammatory responses during the perioperative period is a key factor in the occurrence of POCD. In addition, SMAD family member 7 (Smad7) has been confirmed to play vital roles in the pathogenesis and treatment of inflammatory diseases, such as inflammatory bowel disease. However, whether Smad7 participates in the regulatory process of neuroinflammation and apoptosis in the development of POCD is still unknown.

METHODS

In this study, a POCD mouse model was constructed by unilateral nephrectomy under anesthesia, and cognitive function was assessed using the fear conditioning test and open field test. The expression of Smad7 at the mRNA and protein levels in the hippocampus 3 days after surgery was examined by qRT-PCR, western blot and immunofluorescence assays. Furthermore, to identify whether the elevation of Smad7 in the hippocampus after unilateral nephrectomy contributes to cognitive impairment, the expression of Smad7 in the hippocampal CA1 region was downregulated by crossing Smad7fl/fl conditional mutant mice and CaMKIIα-Cre line T29-1 transgenic mice or stereotaxic injection of shRNA-Smad7. Inflammation and apoptosis in the hippocampus were assessed by measuring the mRNA levels of typical inflammatory cytokines, including TNF-α, IL-1β, IL-6, CCL2, CXCL1, and CXCL2, and the protein levels of apoptotic proteins, including Bax and Bcl2. In addition, apoptosis in the hippocampus postoperation was investigated by a terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining assay. Finally, western blotting was used to explore how Smad7 mediates inflammation and apoptosis postoperation.

RESULTS

The results unequivocally revealed that elevated Smad7 in the hippocampal CA1 region significantly inhibited TGF-β signal transduction by blocking Smad2/3 phosphorylation, which enhanced neuroinflammation and apoptosis in the hippocampus and further led to learning and memory impairment after surgery.

CONCLUSIONS

Our results revealed that Smad7 contributes to cognitive impairment after surgery by enhancing neuroinflammation and apoptosis in the hippocampus and might serve as a promising therapeutic target for the treatment of memory impairment after anesthesia surgery.

Caffeic Acid Phenethyl Ester Suppresses Oxidative Stress and Regulates M1/M2 Microglia Polarization via Sirt6/Nrf2 Pathway to Mitigate Cognitive Impairment in Aged Mice following Anesthesia and Surgery

Postoperative cognitive dysfunction (POCD) is a severe neurological complication after anesthesia and surgery. However, there is still a lack of effective clinical pharmacotherapy due to its unclear pathogenesis. Caffeic acid phenethyl ester (CAPE), which is obtained from honeybee propolis and medicinal plants, shows powerful antioxidant, anti-inflammatory, and immunomodulating properties. In this study, we aimed to evaluate whether CAPE mitigated cognitive impairment following anesthesia and surgery and its potential underlying mechanisms in aged mice. Here, isoflurane anesthesia and tibial fracture surgery were used as the POCD model, and H2O2-induced BV2 cells were established as the microglial oxidative stress model. We revealed that CAPE pretreatment suppressed oxidative stress and promoted the switch of microglia from the M1 to the M2 type in the hippocampus, thereby ameliorating cognitive impairment caused by anesthesia and surgery. Further investigation indicated that CAPE pretreatment upregulated hippocampal Sirt6/Nrf2 expression after anesthesia and surgery. Moreover, mechanistic studies in BV2 cells demonstrated that the potent effects of CAPE pretreatment on reducing ROS generation and promoting protective polarization were attenuated by a specific Sirt6 inhibitor, OSS_128167. In summary, our findings opened a promising avenue for POCD prevention through CAPE pretreatment that enhanced the Sirt6/Nrf2 pathway to suppress oxidative stress as well as favor microglia protective polarization.