Clonidine Protects Against Neurotoxicity Induced by Sevoflurane Through NF-κB Signaling Inhibition and Proinflammatory Cytokine Release in Rats

Dexmedetomidine and Clonidine Attenuate Sevoflurane-Induced Tau Phosphorylation and Cognitive Impairment in Young Mice via α-2 Adrenergic Receptor

BACKGROUND

Anesthetic sevoflurane induces tau phosphorylation and cognitive impairment in young mice. The underlying mechanism and the targeted interventions remain largely unexplored. We hypothesized that dexmedetomidine and clonidine attenuated sevoflurane-induced tau phosphorylation and cognitive impairment by acting on α-2 adrenergic receptor.

METHODS

Six-day-old mice received anesthesia with 3% sevoflurane 2 hours daily on postnatal days 6, 9, and 12. Alpha-2 adrenergic receptor agonist dexmedetomidine and clonidine were used to treat the mice with and without the α-2 adrenergic receptor antagonist yohimbine. Mouse hippocampi were harvested and subjected to western blot analysis. The New Object Recognition Test and Morris Water Maze were used to measure cognitive function. We analyzed the primary outcomes by using 2- and 1-way analysis of variance (ANOVA) and Mann-Whitney U test to determine the effects of sevoflurane on the amounts of phosphorylated tau, postsynaptic density-95, and cognitive function in young mice after the treatments with dexmedetomidine, clonidine, and yohimbine.

RESULTS

Both dexmedetomidine and clonidine attenuated the sevoflurane-induced increase in phosphorylated tau amount (94 ± 16.3% [dexmedetomidine plus sevoflurane] versus 240 ± 67.8% [vehicle plus sevoflurane], P < .001; 125 ± 13.5% [clonidine plus sevoflurane] versus 355 ± 57.6% [vehicle plus sevoflurane], P < .001; mean ± standard deviation), sevoflurane-induced reduction in postsynaptic density-95 (82 ± 6.6% [dexmedetomidine plus sevoflurane] versus 31 ± 12.4% [vehicle plus sevoflurane], P < .001; 95 ± 6.4% [clonidine plus sevoflurane] versus 62 ± 18.4% [vehicle plus sevoflurane], P < .001), and cognitive impairment in the young mice. Interestingly, yohimbine reversed the effects of dexmedetomidine and clonidine on attenuating the sevoflurane-induced changes in phosphorylated tau, postsynaptic density-95, and cognitive function.

CONCLUSIONS

Dexmedetomidine and clonidine could inhibit the sevoflurane-induced tau phosphorylation and cognitive impairment via activation of α-2 adrenergic receptor. More studies are needed to confirm the results and to determine the clinical relevance of these findings.

The Effects of Hesperidin on Neuronal Apoptosis and Cognitive Impairment in the Sevoflurane Anesthetized Rat are Mediated Through the PI3/Akt/PTEN and Nuclear Factor-κB (NF-κB) Signaling Pathways

Background

Hesperidin (HPD) is a bioflavonoid found in citrus fruits. This study aimed to investigate the effects of HPD on cerebral morphology and cognitive behavior in sevoflurane anesthetized neonatal rats and the molecular mechanisms involved.

Material/Methods

Sixty neonatal Sprague–Dawley rats were divided into five groups, including the untreated control group, and the sevoflurane anesthesia groups untreated and treated with 25 mg/kg/day of HPD (HPD25), 50 mg/kg/day of HPD (HPD50), and 100 mg/kg/day of HPD (HPD100). The rat model was created by the administration of sevoflurane on the sixth postnatal day (P6) and for a further three days. Neonatal rats pre-treated with HPD for 19 days were given sevoflurane 30 minutes beforehand (P3 to P21). Rat hippocampal tissue specimens were investigated using the TUNEL assay for apoptosis. Hippocampal tissue homogenates underwent Western blot for the quantification of markers of neuroinflammation and oxidative stress. The neonatal rats were also investigated for behavior, learning, and memory.

Results

HPD significantly reduced sevoflurane-induced neuronal apoptosis and protein expression of cleaved caspase-3, BAD, BAX, NF-κB, TNF-α, IL-6, and IL-1β (p<0.05). HPD significantly increased the expression of Bcl-xL and Bcl-2 (p<0.05), and activated the PI3/Akt pathway. Learning and memory were significantly improved following HPD treatment (p<0.05). HPD treatment modulated the PI3/Akt/PTEN and NF-κB signaling pathways, and reduced oxidative stress (p<0.05).

Conclusions

In the sevoflurane anesthetized neonatal rat model, treatment with HPD reduced neuronal degeneration, hippocampal inflammation, and improvised memory, learning, and cognitive responses by modulating the PI3/Akt/PTEN and NF-κB signaling pathways.

Compound Porcine Cerebroside and Ganglioside Injection (CPCGI) Attenuates Sevoflurane-Induced Nerve Cell Injury by Regulating the Phosphorylation of p38 MAP Kinase (p38MAPK)/Nuclear Factor kappa B (NF-κB) Pathway

Background

Compound porcine cerebroside and ganglioside injection (CPCGI) has been widely applied in clinical practice in China to treat functional confusion caused by brain diseases. Sevoflurane, a frequently-used inhalational anesthetic, was discovered to have neurotoxicity that can cause neurological damage in patients. The present study was performed to investigate the protective effect of CPCGI on sevoflurane-induced nerve damage and to reveal the neuroprotective mechanisms of CPCGI.

Material/Methods

Firstly, the hippocampal neurons were separated from Sprague-Dawley embryonic rats, and were stimulated by 3% sevoflurane for different times (0, 2, 4, and 6 h). Then, cell viability and cell apoptosis were assessed by thiazolyl blue tetrazolium bromide (MTT) and flow cytometry (FCM), respectively. Western blot analysis was used to determine the apoptosis-related protein expression levels.

Results

The results demonstrated that 3% sevoflurane significantly inhibited cell viability but induced cell apoptosis in neurons in a time-dependent manner. Treatment with 3% sevoflurane also promoted the Bax [B cell leukemia/lymphoma 2 (Bcl2)-associated X protein] and cleaved caspase3 protein expressions, and suppressed Bcl-2 and pro-caspase3 expressions in hippocampal neurons. In addition, phosphorylated (p)-p38 and p-p65 expression and the ratio of p-p38/p38 and p-p65/p65 were upregulated in a time-dependent manner after 3% sevoflurane treatment. Further analysis indicated that all the effects of 3% sevoflurane on hippocampal neurons were reversed by CPCGI pre-treatment.

Conclusions

We demonstrated the neuroprotective role of CPCGI in sevoflurane-stimulated neuronal cell damage via regulation of the MAPK/NF-κB signaling pathway.