The effect of propofol on hypoxia- and TNF-α-mediated BDNF/TrkB pathway dysregulation in primary rat hippocampal neurons

Research progress of propofol in alleviating cerebral ischemia/reperfusion injury

Ischemic stroke is a leading cause of adult disability and death worldwide. The primary treatment for cerebral ischemia patients is to restore blood supply to the ischemic region as quickly as possible. However, in most cases, more severe tissue damage occurs, which is known as cerebral ischemia/reperfusion (I/R) injury. The pathological mechanisms of brain I/R injury include mitochondrial dysfunction, oxidative stress, excitotoxicity, calcium overload, neuroinflammation, programmed cell death and others. Propofol (2,6-diisopropylphenol), a short-acting intravenous anesthetic, possesses not only sedative and hypnotic effects but also immunomodulatory and neuroprotective effects. Numerous studies have reported the protective properties of propofol during brain I/R injury. In this review, we summarize the potential protective mechanisms of propofol to provide insights for its better clinical application in alleviating cerebral I/R injury.

Propofol and salvianolic acid A synergistically attenuated cardiac ischemia-reperfusion injury in diabetic mice via modulating the CD36/AMPK pathway

Background

Prevention of diabetic heart myocardial ischemia-reperfusion (IR) injury (MIRI) is challenging. Propofol attenuates MIRI through its reactive oxygen species scavenging property at high doses, while its use at high doses causes hemodynamic instability. Salvianolic acid A (SAA) is a potent antioxidant that confers protection against MIRI. Both propofol and SAA affect metabolic profiles through regulating Adenosine 5'-monophosphate-activated protein kinase (AMPK). The aim of this study was to investigate the protective effects and underlying mechanisms of low doses of propofol combined with SAA against diabetic MIRI.

Methods

Diabetes was induced in mice by a high-fat diet followed by streptozotocin injection, and MIRI was induced by coronary artery occlusion and reperfusion. Mice were treated with propofol at 46 mg/kg/h without or with SAA at 10 mg/kg/h during IR. Cardiac origin H9c2 cells were exposed to high glucose (HG) and palmitic acid (PAL) for 24 h in the absence or presence of cluster of differentiation 36 (CD36) overexpression or AMPK gene knockdown, followed by hypoxia/reoxygenation (HR) for 6 and 12 h.

Results

Diabetes-exacerbated MIRI is evidenced as significant increases in post-ischemic infarction with reductions in phosphorylated (p)-AMPK and increases in CD36 and ferroptosis. Propofol moderately yet significantly attenuated all the abovementioned changes, while propofol plus SAA conferred superior protection against MIRI to that of propofol. In vitro, exposure of H9c2 cells under HG and PAL decreased cell viability and increased oxidative stress that was concomitant with increased levels of ferroptosis and a significant increase in CD36, while p-AMPK was significantly reduced. Co-administration of low concentrations of propofol and SAA at 12.5 μM in H9c2 cells significantly reduced oxidative stress, ferroptosis and CD36 expression, while increasing p-AMPK compared to the effects of propofol at 25 μM. Moreover, either CD36 overexpression or AMPK silence significantly exacerbated HR-induced cellular injuries and ferroptosis, and canceled propofol- and SAA-mediated protection. Notably, p-AMPK expression was downregulated after CD36 overexpression, while AMPK knockdown did not affect CD36 expression.

Conclusions

Combinational usage of propofol and SAA confers superior cellular protective effects to the use of high-dose propofol alone, and it does so through inhibiting HR-induced CD36 overexpression to upregulate p-AMPK.

Influence of short-term hypoxic exposure on spatial learning and memory function and brain-derived neurotrophic factor in rats-A practical implication to human's lost way

The present study aimed to investigate the effects of a short period of normobaric hypoxic exposure on spatial learning and memory, and brain-derived neurotrophic factor (BDNF) levels in the rat hippocampus. Hypoxic conditions were set at 12.5% O2. We compared all variables between normoxic trials (Norm), after 24 h (Hypo-24 h), and after 72 h of hypoxic exposure (Hypo-72 h). Spatial learning and memory were evaluated by using a water-finding task in an open field. Time to find water drinking fountains was significantly extended in Hypo 24 h (36.2 ± 21.9 s) compared to those in Norm (17.9 ± 12.8 s; P < 0.05), whereas no statistical differences between Norm and Hypo-72 h (22.7 ± 12.3 s). Moreover, hippocampal BDNF level in Hypo-24 h was significantly lower compared to Norm (189.4 ± 28.4 vs. 224.9 ± 47.7 ng/g wet tissue, P < 0.05), whereas no statistically differences in those between Norm and Hypo-72 h (228.1 ± 39.8 ng/g wet tissue). No significant differences in the changes in corticosterone and adrenocorticotropic hormone levels were observed across the three conditions. When data from Hypo-24 h and Hypo-72 h of hypoxia were pooled, there was a marginal negative relationship between the time to find drinking fountains and BDNF (P < 0.1), and was a significant negative relationship between the locomotor activities and BDNF (P < 0.05). These results suggest that acute hypoxic exposure (24 h) may impair spatial learning and memory; however, it recovered after 72 h of hypoxic exposure. These changes in spatial learning and memory may be associated with changes in the hippocampal BDNF levels in rats.

[Brain-derived neurotrophic factor in the acute and early recovery period of ischemic stroke: the role of nocturnal hypoxemia]

OBJECTIVE

To study the relationship between brain-derived neurotrophic factor (BDNF) and the severity of nocturnal hypoxemia in patients in the acute and early recovery period of ischemic stroke (IS).

MATERIAL AND METHODS

We enrolled 44 patients (27 men, 17 women), aged 18-85 years, in the acute phase of IS. At 3-month follow-up, 35 people were examined (21 men and 14 women). In the acute period, in addition to routine diagnostic procedures, respiratory monitoring was carried out, and the serum level of BDNF was measured by enzyme-linked immunosorbent assay. BDNF level was also evaluated at 3-month follow-up visit. Neurological status and its dynamics in the acute period of stroke were assessed as part of the clinical routine according to the National Institutes of Health Stroke Scale (NIHSS) at admission and discharge.

RESULTS

We found a direct correlation between the duration of hypoxemia with SpO2 less than 90% (r=0.327, p=0.035) and less than 85% (r=0.461, p=0.003) and BDNF level in the acute phase of IS. BDNF level in the acute period of IS was negatively correlated with the minimum saturation value (r=-0.328, p=0.034). There was a direct relationship between BDNF level in the early recovery period and the duration of hypoxemia with SpO2 less than 85% (r=-0.389, p=0.028). A regression model showed that BDNF level was associated with the minimum SpO2 level. No significant associations were found with indicators of sleep-disordered breathing severity, such as the apnea-hypopnea index and the oxygen desaturation index.

CONCLUSION

The severity of nocturnal hypoxemia is associated with the increase in BDNF levels both in the acute and recovery periods of IS, regardless of the presence of concomitant breathing disorders during sleep.

lncRNA TUSC7 sponges miR-10a-5p and inhibits BDNF/ERK pathway to suppress glioma cell proliferation and migration

OBJECTIVE

Gliomas as primary cerebral malignancies frequently occurring in adults have relatively high morbidity and mortality. The underlying role of long non-coding ribonucleic acids (lncRNAs) in malignancies has attracted much attention, among which tumor suppressor candidate 7 (TUSC7) is a novel tumor suppressor gene whose regulatory mechanism in human cerebral gliomas remains inconclusive.

METHODS AND RESULTS

In this study, bioinformatics analysis indicated that TUSC7 could specifically bind to microRNA (miR)-10a-5p, and according to quantitative polymerase chain reaction (q-PCR), miR-10a-5p was up-regulated in human glioma cells and negatively correlated with TUSC7 expression. Dual-luciferase reporter gene assay showed the ability of TUSC7 to bind to miR-10a-5p, and overexpression of TUSC7 notably inhibited miR-10a-5p expression, restrained human glioma cell proliferation and migration, and regulated cell cycle and cyclin expression via the brain-derived neurotrophic factor/extracellular signal-regulated kinase (BDNF/ERK) pathway. The inhibitory effect of TUSC7 on miR-10a-5p was also verified by designing miR-10a-5p overexpression and knockdown panels for wound healing, Transwell and Western blotting assays.

CONCLUSIONS

TUSC7 suppresses human glioma cell proliferation and migration by negatively modulating miR-10a-5p and inhibiting the BDNF/ERK pathway, thus acting as a tumor suppressor gene in human gliomas.

Tau protein plays a role in the mechanism of cognitive disorders induced by anesthetic drugs

Cognitive disorders are mental health disorders that can affect cognitive ability. Surgery and anesthesia have been proposed to increase the incidence of cognitive dysfunction, including declines in memory, learning, attention and executive function. Tau protein is a microtubule-associated protein located in the axons of neurons and is important for microtubule assembly and stability; its biological function is mainly regulated by phosphorylation. Phosphorylated tau protein has been associated with cognitive dysfunction mediated by disrupting the stability of the microtubule structure. There is an increasing consensus that anesthetic drugs can cause cognitive impairment. Herein, we reviewed the latest literature and compared the relationship between tau protein and cognitive impairment caused by different anesthetics. Our results substantiated that tau protein phosphorylation is essential in cognitive dysfunction caused by anesthetic drugs, and the possible mechanism can be summarized as "anesthetic drugs-kinase/phosphatase-p-Tau-cognitive impairment".

The Mechanism of TNF-α-Mediated Accumulation of Phosphorylated Tau Protein and Its Modulation by Propofol in Primary Mouse Hippocampal Neurons: Role of Mitophagy, NLRP3, and p62/Keap1/Nrf2 Pathway

Background

Neuroinflammation-induced phosphorylated Tau (p-Tau) deposition in central nervous system contributes to neurodegenerative disorders. Propofol possesses neuroprotective properties. We investigated its impacts on tumor necrosis factor-α (TNF-α)-mediated p-Tau deposition in neurons.

Methods

Mouse hippocampal neurons were exposed to propofol followed by TNF-α. Cell viability, p-Tau, mitophagy, reactive oxygen species (ROS), NOD-like receptor protein 3 (NLRP3), antioxidant enzymes, and p62/Keap1/Nrf2 pathway were investigated.

Results

TNF-α promoted p-Tau accumulation in a concentration- and time-dependent manner. TNF-α (20 ng/mL, 4 h) inhibited mitophagy while increased ROS accumulation and NLRP3 activation. It also induced glycogen synthase kinase-3β (GSK3β) while inhibited protein phosphatase 2A (PP2A) phosphorylation. All these effects were attenuated by 25 μM propofol. In addition, TNF-α-induced p-Tau accumulation was attenuated by ROS scavenger, NLRP3 inhibitor, GSK3β inhibitor, or PP2A activator. Besides, compared with control neurons, 100 μM propofol decreased p-Tau accumulation. It also decreased ROS and NLRP3 activation, modulated GSK3β/PP2A phosphorylation, leaving mitophagy unchanged. Further, 100 μM propofol induced p62 expression, reduced Keap1 expression, triggered the nuclear translocation of Nrf2, and upregulated superoxide dismutase (SOD) and heme oxygenase-1 (HO-1) expression, which was abolished by p62 knockdown, Keap1 overexpression, or Nrf2 inhibitor. Consistently, the inhibitory effect of 100 μM propofol on ROS and p-Tau accumulation was mitigated by p62 knockdown, Keap1 overexpression, or Nrf2 inhibitor.

Conclusions

In hippocampal neurons, TNF-α inhibited mitophagy, caused oxidative stress and NLRP3 activation, leading to GSK3β/PP2A-dependent Tau phosphorylation. Propofol may reduce p-Tau accumulation by reversing mitophagy and oxidative stress-related events. Besides, propofol may reduce p-Tau accumulation by modulating SOD and HO-1 expression through p62/Keap1/Nrf2 pathway.