Electroacupuncture pretreatment preserves telomerase reverse transcriptase function and alleviates postoperative cognitive dysfunction by suppressing oxidative stress and neuroinflammation in aged mice

Unraveling the role and mechanism of mitochondria in postoperative cognitive dysfunction: a narrative review

Postoperative cognitive dysfunction (POCD) is a frequent neurological complication encountered during the perioperative period with unclear mechanisms and no effective treatments. Recent research into the pathogenesis of POCD has primarily focused on neuroinflammation, oxidative stress, changes in neural synaptic plasticity and neurotransmitter imbalances. Given the high-energy metabolism of neurons and their critical dependency on mitochondria, mitochondrial dysfunction directly affects neuronal function. Additionally, as the primary organelles generating reactive oxygen species, mitochondria are closely linked to the pathological processes of neuroinflammation. Surgery and anesthesia can induce mitochondrial dysfunction, increase mitochondrial oxidative stress, and disrupt mitochondrial quality-control mechanisms via various pathways, hence serving as key initiators of the POCD pathological process. We conducted a review on the role and potential mechanisms of mitochondria in postoperative cognitive dysfunction by consulting relevant literature from the PubMed and EMBASE databases spanning the past 25 years. Our findings indicate that surgery and anesthesia can inhibit mitochondrial respiration, thereby reducing ATP production, decreasing mitochondrial membrane potential, promoting mitochondrial fission, inducing mitochondrial calcium buffering abnormalities and iron accumulation, inhibiting mitophagy, and increasing mitochondrial oxidative stress. Mitochondrial dysfunction and damage can ultimately lead to impaired neuronal function, abnormal synaptic transmission, impaired synthesis and release of neurotransmitters, and even neuronal death, resulting in cognitive dysfunction. Targeted mitochondrial therapies have shown positive outcomes, holding promise as a novel treatment for POCD.

Keap1-independent GSK-3β/Nrf2 signaling mediates electroacupuncture inhibition of oxidative stress to induce cerebral ischemia-reperfusion tolerance

PURPOSE

Cerebral ischemia-reperfusion (CIR) injury is a devastating consequence of stroke characterized by oxidative stress-induced neuronal damage. Electroacupuncture (EA) has emerged as a potential therapeutic intervention for ischemic stroke, but its underlying mechanisms remain incompletely understood. This study aimed to elucidate whether EA exerts anti-oxidative stress effects against CIR injury by modulating the GSK-3β/Nrf2 pathway.

METHODS

CIR mouse models were established using the suture-occluded method and underwent EA pretreatment. Cognitive and neurologic function, cerebral infarct volume, and neuronal damage were assessed in mice. Oxidative stress levels and the expression of components of the GSK-3β/Nrf2 pathway in the cerebral cortex were measured. The regulatory effect of GSK-3β on Nrf2 and its role in electroacupuncture to alleviate oxygen-glucose deprivation/reoxygenation (OGD/R)-induced neuronal injury were investigated by modulating GSK-3β expression in HT22 hippocampal neuronal cells and electroacupuncture serum intervention. Ultimately, Nrf2 knockout mice, GSK-3β knockout mice, and wild-type mice treated with TBHQ (an Nrf2 activator) were utilized for further validation.

RESULTS

EA pretreatment improved cognitive impairment and neuronal damage induced by CIR injury. Mechanistically, EA inhibited oxidative stress in the cerebral cortex, manifested by reduced levels of reactive oxygen species and malondialdehyde, along with increased superoxide dismutase activity. Furthermore, EA upregulated the expression of Nrf2 and its downstream antioxidant enzymes HO-1 and NQO1, while Keap1 expression remained unaffected. In vitro, GSK-3β overexpression inhibited the protective effects of EA serum on OGD/R-induced neuronal damage. In vivo, knockout of either Nrf2 or Gsk-3β genes abolished the neuroprotective effects of EA, and TBHQ exerted effects similar to EA, confirming the significant role of GSK-3β/Nrf2 in mediating EA antioxidative effects.

CONCLUSION

EA exerts antioxidative stress effects against CIR injury by activating the GSK-3β/Nrf2 signaling pathway, independent of Keap1 regulation.

Postoperative Electroacupuncture Boosts Cognitive Function Recovery after Laparotomy in Mice

Postoperative cognitive dysfunction (POCD) is a common complication that affects memory, executive function, and processing speed postoperatively. The pathogenesis of POCD is linked to excessive neuroinflammation and pre-existing Alzheimer's disease (AD) pathology. Previous studies have shown that acupuncture improves cognition in the early phase of POCD. However, POCD can last for longer periods (up to weeks and years). The long-term effects of acupuncture are unknown. In this study, we hypothesized that electroacupuncture (EA) could reduce inflammation and cognitive dysfunction induced by laparotomy over a longer period. We characterized the effects of postoperative EA on cognitive changes and investigated the underlying molecular mechanisms in mice. Laparotomy was performed in 3-month-old mice followed by daily EA treatment for 2 weeks. Our data indicated that laparotomy induced prolonged impairment in memory and executive functions, which were mitigated by postoperative EA. EA also reduced tau phosphorylation and suppressed the activation of tau-related kinases and glia, with effects comparable to ibuprofen. These findings demonstrate the beneficial effects of EA in a mouse model of POCD, suggesting that EA's ability to suppress neuroinflammation may contribute to its protective effects. In conclusion, EA may be a viable non-pharmacological intervention for managing POCD in different phases of the medical condition.

Updated insights into the NLRP3 inflammasome in postoperative cognitive dysfunction: emerging mechanisms and treatments

Postoperative cognitive dysfunction (POCD) poses a significant threat to patients undergoing anesthesia and surgery, particularly elderly patients. It is characterized by diminished cognitive functions post surgery, such as impaired memory and decreased concentration. The potential risk factors for POCD include age, surgical trauma, anesthetic type, and overall health condition; however, the precise mechanisms underlying POCD remain elusive. Recent studies suggest that neuroinflammation might be a primary pathogenic factor. NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) inflammasomes are implicated in exacerbating POCD by promoting the release of inflammatory factors and proteins that initiate pyroptosis, further influencing the disease process. The regulation of NLRP3 inflammasome activity, including its activation and degradation, is tightly controlled through multiple pathways and mechanisms. In addition, autophagy, a protective mechanism, regulates the NLRP3 inflammasome to control the progression of POCD. This review reviews recent findings on the role of the NLRP3 inflammasome in POCD pathogenesis and discusses therapeutic strategies aimed at reducing NLRP3 sources, inhibiting cellular pyroptosis, and enhancing autophagy.

Electroacupuncture Ameliorates Neuronal Damage and Neurological Deficits after Cerebral Ischemia-Reperfusion Injury via Restoring Telomerase Reverse Transcriptase

The purpose of this study is to identify the therapeutic effect of electroacupuncture (EA) on cerebral ischemia-reperfusion (I/R) injury, and to clarify the regulatory mechanism related to telomerase reverse transcriptase (TERT)-mediated telomerase activity. A Middle cerebral artery occlusion/reperfusion (MCAO/R) animal model was constructed and rats were treated by EA invention at the Baihui (GV20) and Fengchi (GB20) acupoints. Neurological deficits were assessed via rotarod test and Morris water maze test. 2,3,5-Triphenyltertrazolium chloride (TTC) staining was performed to evaluate infarct volume. Histological changes were observed under H&E staining and Nissl staining. TERT expression was examined using qRT-PCR and western blot. Telomerase activity was assessed with TRAP method. Neuron apoptosis and senescence were assessed by TUNEL and immunofluorescence assays. Inflammatory cytokines and oxidative stress-indicators were examined using commercial kits. EA intervention at both GV20 and GB20 acupoints reduced infarct volumes (2.48 ± 1.89 vs. 29.56 ± 2.55), elevated the telomerase activity (0.84 ± 0.08 vs. 0.34 ± 0.09), and upregulated the levels of total TERT protein (0.61 ± 0.09 vs. 0.21 ± 0.05) and mitochondrial TERT (Mito-TERT; 0.54 ± 0.03 vs. 0.27 ± 0.03) in hippocampus tissues of MCAO/R rats. EA intervention attenuated motor dysfunction (112.00 ± 6.69 vs. 30.02 ± 2.60) and improved spatial learning (23.87 ± 1.90 vs. 16.23 ± 1.45) and memory ability (8.38 ± 1.06 vs. 4.13 ± 1.13) of rats with cerebral I/R injury. In addition, EA intervention significantly attenuated histopathological changes of injured neurons, mitigated neuron apoptosis (32.27 ± 5.52 vs. 65.83 ± 4.31) and senescence in MCAO/R rats, as well as inhibited excessive production of inflammatory cytokines and attenuated oxidative stress. However, the above therapeutic efficiency of EA intervention in MCAO/R rats was partly eliminated by TERT knockdown. EA intervention at GB20 and GV20 acupoints exerted a protective role in cerebral I/R injury partly through restoring TERT function, implying the clinical potential of EA treatment in the treatment of ischemic stroke.

Effects of electroacupuncture on postoperative cognitive dysfunction and its underlying mechanisms: a literature review of rodent studies

With the aging of the population, the health of the elderly has become increasingly important. Postoperative cognitive dysfunction (POCD) is a common neurological complication in elderly patients following general anesthesia or surgery. It is characterized by cognitive decline that may persist for weeks, months, or even longer. Electroacupuncture (EA), a novel therapy that combines physical nerve stimulation with acupuncture treatment from traditional Chinese medicine, holds potential as a therapeutic intervention for preventing and treating POCD, particularly in elderly patients. Although the beneficial effects of EA on POCD have been explored in preclinical and clinical studies, the reliability of EA is limited by methodological shortcomings, and the underlying mechanisms remain largely unexplored. Therefore, we have synthesized existing evidence and proposed potential biological mechanisms underlying the effects of EA on neuroinflammation, oxidative stress, autophagy, the microbiota-gut-brain axis, and epigenetic modification. This review summarizes recent advances in EA and POCD, provides a theoretical foundation, explores potential molecular mechanisms for the prevention and treatment of POCD, and offers a basis for conducting relevant clinical trials.

Electroacupuncture pretreatment preserves telomerase reverse transcriptase function and alleviates postoperative cognitive dysfunction by suppressing oxidative stress and neuroinflammation in aged mice

BACKGROUND

Elderly patients often exhibit postoperative cognitive dysfunction (POCD), a postsurgical decline in memory and executive function. Oxidative stress and neuroinflammation, both pathological characteristics of the aged brain, contribute to this decline. This study posits that electroacupuncture (EA) stimulation, an effective antioxidant and anti-inflammatory modality, may enhance telomerase reverse transcriptase (TERT) function, the catalytic subunit of telomerase known for its protective properties against cellular senescence and oxidative damage, to alleviate POCD in aged mice.

METHODS

The animal POCD model was created by subjecting aged mice to abdominal surgery, followed by EA pretreatment at the Baihui acupoint (GV20). Postoperative cognitive function was gauged using the Morris water maze (MWM) test. Hippocampal TERT mRNA levels and telomerase activity were determined through qPCR and a Telomerase PCR ELISA kit, respectively. Oxidative stress was assessed through superoxide dismutase (SOD), reactive oxygen species (ROS), and malondialdehyde (MDA) levels. Iba-1 immunostaining determined the quantity of hippocampal microglia. Additionally, western blotting assessed TERT, autophagy markers, and proinflammatory cytokines at the protein level.

RESULTS

Abdominal surgery in aged mice significantly decreased telomerase activity and TERT mRNA and protein levels, but increased oxidative stress and neuroinflammation and decreased autophagy in the hippocampus. EA-pretreated mice demonstrated improved postoperative cognitive performance, enhanced telomerase activity, increased TERT protein expression, improved TERT mitochondrial localization, and reduced oxidative damage, autophagy dysfunction, and neuroinflammation. The neuroprotective benefits of EA pretreatment were diminished following TERT knockdown.

CONCLUSIONS

Our findings underscore the significance of TERT function preservation in alleviating surgery-induced oxidative stress and neuroinflammation in aged mice. A novel neuroprotective mechanism of EA stimulation is highlighted, whereby modulation of TERT and telomerase activity reduces oxidative damage and neuroinflammation. Consequently, maintaining TERT function via EA treatment could serve as an effective strategy for managing POCD in elderly patients.