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.

Development of a rapid visual detection technology for BmNPV based on CRISPR/Cas13a system.

Pathogenic microorganism of silkworm are important factors that threaten the high-quality development of sericulture. Among them, Bombyx mori nucleopolyhedrovirus (BmNPV) caused diseases often lead to frequent outbreaks and high mortality, resulting in huge losses to sericultural industry. Current molecular detection methods for BmNPV require expensive equipment and sikilled technical personnel. As a result, the most commonly detection method for silkworm egg production enterprises involves observing the presence of polyhedra under a microscope. However, this method has low accuracy and sensitivity. There is an urgent need to develop a new detection technology with high sensitivity, high specificity, and applicability for silkworm farms, silkworm egg production enterprises and quarantine departments. In this study, we successfully established the CRISPR/Cas13a BmNPV visualized detection technology by combining Recombinase Polymerase Amplification (RPA) technology and CRISPR/Cas13a system. This technology is based on microplate lateral, flow test strips and portable fluorescence detector. The detection sensitivity can reach up to 1 copies/µL for positive standard plasmid and 1 fg/µL for BmNPV genome in 30-45 min, demonstrating high sensitivity. By detecting silkworm tissues infected with different pathogens, we determined that CRISPR/Cas13a detection technology has good specificity. In summary, the newly established nucleic acid detection technology for BmNPV is characterized by high sensitivity, high specificity, low cost and convenience for visualization. It can be applied in field detection and silkworm egg quality monitory system.

Lnc557 promotes Bombyx mori nucleopolyhedrovirus replication by interacting with BmELAVL1 to enhance its stability and expression.

Bombyx mori nucleopolyhedrovirus (BmNPV) is a major pathogen that threatens the growth and sustainability of the sericultural industry. Currently, accumulated studies showed that long non-coding RNAs (lncRNAs) play important roles in the genesis and progression of various viruses and host-pathogens interactions. However, the functions and regulatory mechanisms of lncRNAs in insect-virus interaction are still limited. In this study, transcriptome sequencing and ribosome profiling sequencing (Ribo-seq) were performed in the BmNPV-infected midgut and control tissue, and a total of 9 differentially expressed (DE) lncRNAs and 27 small ORFs (sORFs) with micropeptide coding potential were identified. Among them, lncRNA XR_001139971.3 (lnc557) is verified to be significantly up-regulated upon BmNPV infection and may have the potential to encode a small peptide (ORF-674). The subcellular localization experiment showed that lnc557 was expressed in the cytoplasm. Overexpression of lnc557 promotes BmNPV replication and vice versa. By combining RNA pull-down, mass spectrometry, protein truncation and RNA immunoprecipitation (RIP) assays, we confirmed that lnc557 can bind to the RRM-5 domain of BmELAVL1 protein. Subsequently, we found that lnc557 could promote the expression of BmELAVL1 by enhancing the stability of BmELAVL1. Further, enhancing the expression of BmELAVL1 can promote the proliferation of BmNPV, while knockdown shows the opposite effect. Our data suggest that lnc557-mediated BmELAVL1 expression enhancement could play a positive role in BmNPV replication, which will provide a new insight into the molecular mechanism of interaction between Bombyx mori and virus.

Role of the circRNA_34414/miR-6960a-5p/SIRT3 axis in postoperative delirium via CA1 Vglut1+ neurons in older mice.

AIMS: Postoperative delirium (POD) is a common neurological complication in elderly patients after anesthesia/surgery. The main purpose of this study is to explore the effect of circRNA-targeted miRNA regulating SIRT3 on mitochondrial function through ceRNA mechanism under the surgical model of tibial fracture and to further explore the potential mechanism of postoperative delirium mediated by circRNA, so as to provide new ideas for clinical diagnosis and prevention of POD. METHODS: The surgical model of tibial fracture under sevoflurane anesthesia caused acute delirium-like behavior in elderly mice. We observed that the decrease of SIRT3 and mitochondrial dysfunction was related to POD, and miRNA and circRNA (circRNA_34414) related to SIRT3 were further studied. Through luciferase and RAP, we observed that circRNA_34414, as a miRNA sponge, was involved in the regulation of SIRT3 expression. RESULTS: Postoperative delirium in elderly mice showed decreased expression of hippocampal circRNA_34414, increased expression of miR-6960-5p, decreased expression of SIRT3, and impaired mitochondrial membrane potential. Overexpression of circRNA_34414, or knockdown of miR-6960-5p, or overexpression of SIRT3 in hippocampal CA1 glutamatergic neurons significantly upregulated hippocampal SIRT3 expression, increased mitochondrial membrane potential levels, and significantly ameliorated postoperative delirium in aged mice; CircRNA_34414 ameliorates postoperative delirium in mice, possibly by targeting miR-6960-5p to upregulate SIRT3. CONCLUSIONS: CircRNA_34414 is involved in the improvement of postoperative delirium induced by anesthesia/surgery by upregulating SIRT3 via sponging miR-6960-5p.

CRISPR/Cas13a-mediated visual detection: A rapid and robust method for early detection of Nosema bombycis in silkworms.

The sericulture industry faces a significant threat from the Pebrine disease of silkworms, caused by Nosema bombycis. Nonetheless, the current microscopic diagnostic methods can be time-consuming, labor-intensive, and lacking sensitivity and accuracy. Therefore, it is crucial to develop a novel detection approach that is efficient, highly sensitive, and low-cost. In this regard, the CRISPR/Cas system has the potential to be a fast, accurate, and highly specific method of detection. Herein, using a microplate reader, a portable fluorescence detection device, and test strips as signal output tools respectively, we have efficiently developed three rapid and facile visual detection methods for N. bombycis using a CRISPR/Cas13a system with conjugation of Recombinase polymerase amplification (RPA). We evaluated the sensitivity of this combined technology by comparing it with the positive plasmid standard and the genome standard of N. bombycis. Remarkably, the sensitivity of the CRISPR/Cas13a system for N. bombycis positive plasmid standard based on the microplate reader, portable fluorescence detection device, and test strips was 1 copy/µL, 10 copies/µL, and 1 copy/µL, respectively, while for the N. bombycis genome standards, the detection sensitivity was 10 fg/µL, 10 fg/µL, and 1 fg/µL, respectively. In addition, extensive evaluations have demonstrated that the established technology can accurately detect N. bombycis without cross-reactivity with other pathogens, ensuring a specificity rate of 100%. In brief, this study will provide a practical, efficient, and affordable method for early and rapid detection of N. bombycis in various settings.

BLA-involved circuits in neuropsychiatric disorders.

The basolateral amygdala (BLA) is the subregion of the amygdala located in the medial of the temporal lobe, which is connected with a wide range of brain regions to achieve diverse functions. Recently, an increasing number of studies have focused on the participation of the BLA in many neuropsychiatric disorders from the neural circuit perspective, aided by the rapid development of viral tracing methods and increasingly specific neural modulation technologies. However, how to translate this circuit-level preclinical intervention into clinical treatment using noninvasive or minor invasive manipulations to benefit patients struggling with neuropsychiatric disorders is still an inevitable question to be considered. In this review, we summarized the role of BLA-involved circuits in neuropsychiatric disorders including Alzheimer's disease, perioperative neurocognitive disorders, schizophrenia, anxiety disorders, depressive disorders, posttraumatic stress disorders, autism spectrum disorders, and pain-associative affective states and cognitive dysfunctions. Additionally, we provide insights into future directions and challenges for clinical translation.

GLT-1 downregulation in hippocampal astrocytes induced by type 2 diabetes contributes to postoperative cognitive dysfunction in adult mice.

AIMS: Type 2 diabetes mellitus (T2DM) is related to an increased risk of postoperative cognitive dysfunction (POCD), which may be caused by neuronal hyperexcitability. Astrocyte glutamate transporter 1 (GLT-1) plays a crucial role in regulating neuron excitability. We investigated if T2DM would magnify the increased neuronal excitability induced by anesthesia/surgery (A/S) and lead to POCD in young adult mice, and if so, determined whether these effects were associated with GLT-1 expression. METHODS: T2DM model was induced by high fat diet (HFD) and injecting STZ. Then, we evaluated the spatial learning and memory of T2DM mice after A/S with the novel object recognition test (NORT) and object location test (OLT). Western blotting and immunofluorescence were used to analyze the expression levels of GLT-1 and neuronal excitability. Oxidative stress reaction and neuronal apoptosis were detected with SOD2 expression, MMP level, and Tunel staining. Hippocampal functional synaptic plasticity was assessed with long-term potentiation (LTP). In the intervention study, we overexpressed hippocampal astrocyte GLT-1 in GFAP-Cre mice. Besides, AAV-Camkllα-hM4Di-mCherry was injected to inhibit neuronal hyperexcitability in CA1 region. RESULTS: Our study found T2DM but not A/S reduced GLT-1 expression in hippocampal astrocytes. Interestingly, GLT-1 deficiency alone couldn't lead to cognitive decline, but the downregulation of GLT-1 in T2DM mice obviously enhanced increased hippocampal glutamatergic neuron excitability induced by A/S. The hyperexcitability caused neuronal apoptosis and cognitive impairment. Overexpression of GLT-1 rescued postoperative cognitive dysfunction, glutamatergic neuron hyperexcitability, oxidative stress reaction, and apoptosis in hippocampus. Moreover, chemogenetic inhibition of hippocampal glutamatergic neurons reduced oxidative stress and apoptosis and alleviated postoperative cognitive dysfunction. CONCLUSIONS: These findings suggest that the adult mice with type 2 diabetes are at an increased risk of developing POCD, perhaps due to the downregulation of GLT-1 in hippocampal astrocytes, which enhances increased glutamatergic neuron excitability induced by A/S and leads to oxidative stress reaction, and neuronal apoptosis.

Regulating the activity of GABAergic neurons in the ventral pallidum alters the general anesthesia effect of propofol.

The full mechanism of action of propofol, a commonly administered intravenous anesthetic drug in clinical practice, remains elusive. The focus of this study was the role of GABAergic neurons which are the main neuron group in the ventral pallidum (VP) closely associated with anesthetic effects in propofol anesthesia. The activity of VP GABAergic neurons following propofol anesthesia in Vgat-Cre mice was observed via detecting c-Fos immunoreactivity by immunofluorescence and western blotting. Subsequently, chemogenetic techniques were employed in Vgat-Cre mice to regulate the activity of VP GABAergic neurons. The role of VP GABAergic neurons in generating the effects of general anesthesia induced by intravenous propofol was further explored through behavioral tests of the righting reflex. The results revealed that c-Fos expression in VP GABAergic neurons in Vgat-Cre mice dramatically decreased after propofol injection. Further studies demonstrated that chemogenetic activation of VP GABAergic neurons during propofol anesthesia shortened the duration of anesthesia and promoted wakefulness. Conversely, the inhibition of VP GABAergic neurons extended the duration of anesthesia and facilitated the effects of anesthesia. The results obtained in this study suggested that regulating the activity of GABAergic neurons in the ventral pallidum altered the effect of propofol on general anesthesia.

GABAergic Neurons in the Nucleus Accumbens are Involved in the General Anesthesia Effect of Propofol.

The mechanism underlying the hypnosis effect of propofol is still not fully understood. In essence, the nucleus accumbens (NAc) is crucial for regulating wakefulness and may be directly engaged in the principle of general anesthesia. However, the role of NAc in the process of propofol-induced anesthesia is still unknown. We used immunofluorescence, western blotting, and patch-clamp to access the activities of NAc GABAergic neurons during propofol anesthesia, and then we utilized chemogenetic and optogenetic methods to explore the role of NAc GABAergic neurons in regulating propofol-induced general anesthesia states. Moreover, we also conducted behavioral tests to analyze anesthetic induction and emergence. We found out that c-Fos expression was considerably dropped in NAc GABAergic neurons after propofol injection. Meanwhile, patch-clamp recording of brain slices showed that firing frequency induced by step currents in NAc GABAergic neurons significantly decreased after propofol perfusion. Notably, chemically selective stimulation of NAc GABAergic neurons during propofol anesthesia lowered propofol sensitivity, prolonged the induction of propofol anesthesia, and facilitated recovery; the inhibition of NAc GABAergic neurons exerted opposite effects. Furthermore, optogenetic activation of NAc GABAergic neurons promoted emergence whereas the result of optogenetic inhibition was the opposite. Our results demonstrate that NAc GABAergic neurons modulate propofol anesthesia induction and emergence.

The Role of Epigenetic Modifications in Neurotoxicity Induced by Neonatal General Anesthesia.

It has been widely demonstrated by numerous preclinical studies and clinical trials that the neonates receiving repeated or long-time general anesthesia (GA) could develop prolonged cognitive dysfunction. However, the definite mechanism remains largely unknown. Epigenetics, which is defined as heritable alterations in gene expression that are not a result of alteration of DNA sequence, includes DNA methylation, histone post-translational modifications, non-coding RNAs (ncRNAs), and RNA methylation. In recent years, the role of epigenetic modifications in neonatal GA-induced neurotoxicity has been widely explored and reported. In this review, we discuss and conclude the epigenetic mechanisms involving in the process of neonatal anesthesia-induced cognitive dysfunction. Also, we analyze the wide prospects of epigenetics in this field and its possibility to work as treatment target.

Neonatal Exposure to Propofol Interferes with the Proliferation and Differentiation of Hippocampal Neural Stem Cells and the Neurocognitive Function of Rats in Adulthood via the Akt/p27 Signaling Pathway.

Objective: Neonatal exposure to propofol has been reported to cause neurotoxicity and neurocognitive decline in adulthood; however, the underlying mechanism has not been established. Methods: SD rats were exposed to propofol on postnatal day 7 (PND-7). Double-immunofluorescence staining was used to assess neurogenesis in the hippocampal dentate gyrus (DG). The expression of p-Akt and p27 were measured by western blotting. The Morris water maze, novel object recognition test, and object location test were used to evaluate neurocognitive function 2-month-old rats. Results: Phosphorylation of Akt was inhibited, while p27 expression was enhanced after neonatal exposure to propofol. Propofol also inhibited proliferation of neural stem cells (NSCs) and decreased differentiation to neurons and astroglia. Moreover, the neurocognitive function in 2-month-old rats was weakened. Of significance, intra-hippocampal injection of the Akt activator, SC79, attenuated the inhibition of p-AKT and increase of p27 expression. SC79 also rescued the propofol-induced inhibition of NSC proliferation and differentiation. The propofol-induced neurocognition deficit was also partially reversed by SC79. Conclusion: Taken together, these results suggest that neurogenesis is hindered by neonatal propofol exposure. Specifically, neonatal propofol exposure was shown to suppress the proliferation and differentiation of NSCs by inhibiting Akt/p27 signaling pathway.