Maf1 mitigates sevoflurane-induced microglial inflammatory damage and attenuates microglia-mediated neurotoxicity in HT-22 cells by activating the AMPK/Nrf2 signaling

Astragalin-functionalized ultrasmall nanoparticles modulate the complement pathway to inhibit microglial synaptic phagocytosis for reducing anesthetic neurotoxicity

Synaptic impairment is identified as a primary pathology in sevoflurane-induced neurotoxicity, contributing to neurobehavioral and neurodevelopmental deficits. Synaptic loss in neurons occurs through microglia-mediated synaptic phagocytosis via the complement pathway. Astragalin, a natural flavonoid compound, exhibits diverse bioactivities, such as anti-tumor, anti-complement, and anti-inflammatory effects. Herein, astragalin-functionalized Cu 2-x Se nanoparticles (CSPA NPs) can effectively inhibit the complement pathway, mitigating microglia-mediated synaptic phagocytosis and promoting synaptic restoration to repair sevoflurane-induced neurotoxicity. They efficiently target and reduce microglial activation and phagocytosis. By downregulating sortilin, CSPA NPs increase progranulin expression, promoting TFEB cytoplasmic translocation to decrease lysosomal activity and microglial phagocytosis. Furthermore, CSPA NPs decrease complement C1q and C3 levels, inhibiting microglial synaptic engulfment and ameliorating cognition dysfunction in sevoflurane-treated mice. This study illustrates that CSPA NPs inhibit microglial synaptic elimination via the complement pathway, alleviating sevoflurane-induced neurotoxicity and providing insights into treating complement pathway-related diseases.

Suppression of mPFC-Amygdala Circuit Mitigates Sevoflurane-Induced Cognitive Deficits in Aged Mice

BACKGROUND

Perioperative neurocognitive disorders (PND) are common and costly complications in elderly surgical patients, yet the involvement of specific neural circuits in their etiology remains poorly understood. We hypothesized that neural projections from the medial prefrontal cortex (mPFC) to the amygdala contribute to PND pathogenesis.

METHODS

Using chemogenetic approaches, we selectively suppressed or excited the mPFC and its projections to the amygdala in a murine model exposed to sevoflurane. We assessed cognitive deficits, synaptic plasticity (AMPA receptor activity, long-term potentiation [LTP]), mitochondrial stress, neuroinflammatory markers, and neuronal apoptosis in the amygdala. Additional interventions included pharmacological suppression of AMPA receptors, glutamate biosynthesis, and mitochondrial stress within the amygdala.

RESULTS

Sevoflurane exposure activated the mPFC-amygdala circuit. Chemogenetic suppression of the mPFC attenuated sevoflurane-induced cognitive deficits, AMPA receptor hyperexcitation, mitochondrial dysfunction, neuroinflammation, and neuronal apoptosis in the amygdala. Retrograde inhibition of mPFC projections to the amygdala alleviated cognitive impairments, whereas retrograde excitation exacerbated them. Suppressing AMPA receptors, glutamate synthesis, or mitochondrial stress in the amygdala similarly reduced cognitive deficits and pathological alterations. Notably, mPFC suppression rescued sevoflurane-induced LTP impairment in the amygdala.

CONCLUSIONS

These findings demonstrate that sevoflurane activates the mPFC-amygdala circuit, driving PND-associated cognitive deficits and neuropathological changes. Targeting this circuit or downstream mechanisms (AMPA signaling, mitochondrial stress) may mitigate sevoflurane-induced PND. This study provides empirical evidence implicating specific neural circuitry in anesthetic-related neurocognitive dysfunction.

The role of sevoflurane exposure on systemic inflammation and neuroinflammation: a systematic review and meta-analysis of in vivo and in vitro studies

Neuroinflammation induced by anaesthetics may negatively affect neurocognitive functions after surgery in humans. This systematic review and meta-analysis aimed to evaluate the impact of sevoflurane exposure on systemic inflammation and neuroinflammation and to assess alterations in behavioural/cognitive functions in experimental rodent models not exposed to surgery nor to other inflammatory stimuli. Databases were searched for in vivo and/or in vitro studies examining inflammation after sevoflurane exposure compared to control conditions. Inflammatory biomarkers, including interleukin (IL)-6, IL-1β, and tumor necrosis factor alfa (TNFα), at the peak time of production (primary outcomes) were investigated. The secondary outcome was to evaluate the presence of alterations in behavioural/cognitive tests. Subgroup analyses on young and adult rodents were performed for in vivo studies. Thirty-five in vivo and in vitro studies were selected. Results from meta-analyses demonstrated significant increases in the secretion peak of all inflammatory markers in vivo models. Significantly higher plasma peaks of IL-6 (SMD: 7.97, 95 % CI: 4.76-11.17), IL-1β (SMD: 5.71, 95 % CI: 1.88-9.55) and TNFα (SMD: 6.64, 95 % CI: 3.73-9.56) were found only in adult rodents exposed to sevoflurane. Similar findings were observed in brain tissue homogenates. Rodents exposed to sevoflurane exhibited significant alterations in behavioural/cognitive tests and significance persisted only in adult rodents. Sevoflurane exposure may trigger systemic inflammation and neuroinflammation in experimental rodent models with marked effects in adult rodents. Alterations in behavioural/cognitive tests suggest a potential role of sevoflurane in the development of postoperative cognitive disorders in the elderly, independently of surgery. Further research is needed in humans.

Transcriptome and proteome changes triggered by overexpression of the transcriptional regulator Maf1 in the human pathogen Leishmania major

Maf1, originally described as a repressor of RNA polymerase III (RNAP III) transcription in yeast, participates in multiple functions across eukaryotes. However, the knowledge about Maf1 in protozoan parasites is scarce. To initiate the study of Maf1 in Leishmania major, we generated a cell line that overexpresses this protein. Overexpression of Maf1 led to a significant reduction in the abundance of tRNAs, 5S rRNA, and U4 snRNA, demonstrating that Maf1 regulates RNAP III activity in L. major. To further explore the roles played by Maf1 in this microorganism, global transcriptomic and proteomic changes due to Maf1 overexpression were determined using RNA-sequencing and label-free quantitative mass spectrometry. Compared to wild-type cells, differential expression was observed for 1082 transcripts (615 down-regulated and 467 up-regulated) and 205 proteins (132 down-regulated and 73 up-regulated) in the overexpressing cells. A correlation of 44% was found between transcriptomic and proteomic results. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses revealed that the differentially expressed genes and proteins are mainly involved in transcription, cell cycle regulation, lipid metabolism and transport, ribosomal biogenesis, carbohydrate metabolism, autophagy, and cytoskeleton modification. Thus, our results suggest the involvement of Maf1 in the regulation of all these processes in L. major, as reported in other species, indicating that the functions performed by Maf1 were established early in eukaryotic evolution. Notably, our data also suggest the participation of L. major Maf1 in mRNA post-transcriptional control, a role that, to the best of our knowledge, has not been described in other organisms.

MANF Alleviates Sevoflurane-Induced Cognitive Impairment in Neonatal Mice by Modulating Microglial Activation and Polarization

The precise mechanism underlying sevoflurane-induced neurotoxicity and cognitive impairment remains largely unknown. Mesencephalic astrocyte-derived neurotrophic factor (MANF) is a neuroprotective factor that has shown promise in various neurological disorders. However, its impact on sevoflurane-induced alterations has not been investigated. Thus, the objective of this study was to examine the effect of MANF in mitigating sevoflurane-induced neurotoxicity in young mice. Anesthesia with 3% sevoflurane 2 h daily was administered to young mice on postnatal day (P) 3, 6 and 9. We also constructed mono-macrophage-specific MANF knockout (MKO) mice in the mechanistic studies. Finally, the recombinant human MANF (rhMANF, 20 μg) protein was intraperitoneally administrated to neonatal mice before the sevoflurane anesthesia and the cognitive function, levels of pro-inflammatory cytokine and synapse-associated protein PSD95, the status of neural apoptosis, microglia activation and oxidative stress in hippocampus of the mice were investigated. The sevoflurane anesthesia increased the expression of endogenous MANF in the hippocampus, especially in microglia. MKO upregulated the expression of tumor necrosis factor-α (TNF-α), accelerated the neural apoptosis and the activation of microglia in hippocampus in young mice. MANF reversed the sevoflurane-induced cognitive impairment and inhibited the upregulation of TNF-α, the neural apoptosis and the reduction of the postsynaptic density protein-95 (PSD95) induced by sevoflurane anesthesia. Also, pretreatment with MANF alleviated the sevoflurane-induced activation of microglia and oxidative stress. Our current results demonstrated that MANF ameliorated neurotoxicity induced by the sevoflurane anesthesia in young mice, and such protective effect was associated with inhibition of microglia activation and neuroinflammation.

Research progress on molecular mechanisms of general anesthetic-induced neurotoxicity and cognitive impairment in the developing brain

General anesthetics-induced neurotoxicity and cognitive impairment in developing brains have become one of the current research hotspots in the medical science community. The underlying mechanisms are complex and involve various related molecular signaling pathways, cell mediators, autophagy, and other pathological processes. However, few drugs can be directly used to treat neurotoxicity and cognitive impairment caused by general anesthetics in clinical practice. This article reviews the molecular mechanism of general anesthesia-induced neurotoxicity and cognitive impairment in the neonatal brain after surgery in the hope of providing critical references for the treatments of clinical diseases.

AMPK and NRF2: Interactive players in the same team for cellular homeostasis?

NRF2 (Nuclear factor E2 p45-related factor 2) is a stress responsive transcription factor lending cells resilience against oxidative, xenobiotic, and also nutrient or proteotoxic insults. AMPK (AMP-activated kinase), considered as prime regulator of cellular energy homeostasis, not only tunes metabolism to provide the cell at any time with sufficient ATP or building blocks, but also controls redox balance and inflammation. Due to observed overlapping cellular responses upon AMPK or NRF2 activation and common stressors impinging on both AMPK and NRF2 signaling, it is plausible to assume that AMPK and NRF2 signaling may interdepend and cooperate to readjust cellular homeostasis. After a short introduction of the two players this narrative review paints the current picture on how AMPK and NRF2 signaling might interact on the molecular level, and highlights their possible crosstalk in selected examples of pathophysiology or bioactivity of drugs and phytochemicals.