Impact of repeated sevoflurane anesthesia on hippocampal dendritic spine development in neonatal mice and the mechanism of microtubule polyglutamylation mediated by TTLL6
10.3760/cma.j.cn371468-20241017-00489
- VernacularTitle:多次七氟烷麻醉对幼鼠海马区树突棘发育的影响及TTLL6介导的微管多聚谷氨酰化机制
- Author:
Yang YU
1
;
Yue ZHAO
1
;
Jingyu FENG
1
;
Yue YANG
1
;
Yanan LI
1
;
Jiafeng YU
1
;
Yonghao YU
1
Author Information
1. 天津医科大学总医院麻醉科（天津市麻醉学研究所），天津 300052
- Publication Type:Journal Article
- Keywords:
Sevoflurane;
Cognitive impairment;
Dendritic spine development;
Microtubule protein;
Polyglutamylated microtubules protein;
Microtubule cleaving protein;
Mo
- From:
Chinese Journal of Behavioral Medicine and Brain Science
2025;34(3):193-200
- CountryChina
- Language:Chinese
-
Abstract:
Objective:To evaluate the role of tubulin tyrosin ligase like-6 (TTLL6)-mediated microtubule polyglutamylation and Spastin(a microtubule cleaving protein)-induced excessive microtubule cleavage in the developmental impairment of dendritic spines in neonatal mice following repeated sevoflurane anesthesia, by utilizing TTLL6 conditional knockout mice.Methods:Fifty SPF female TTLL6 brain tissue-specific knockout (TTLL6 CKO: Camk2-Cre + ; TTLL6 f/f) and fifty control (TTLL6 CON: TTLL6 f/f) mice with C57BL/6J background, aged 6 days old were selected.TTLL6 CKO mice were divided into TTLL6 CON control group and TTLL6 CON sevoflurane group, and TTLL6 CKO mice were divided into TTLL6 CKO control group and TTLL6 CKO sevoflurane group, with 25 mice in each group by random block method.Mice in the sevoflurane groups were exposed to 3% sevoflurane with 60% O 2 for 2 hours daily on postnatal days 6, 8, and 10.The mice in control groups received only 60% O 2 under the same condition.The polyGlu-Tubulin and postsynaptic density 95(PSD95) protein expression were detected using Western blot. The expressions of TTLL6, Spastin, and α-Tubulin were assessed via immunofluorescence.Golgi staining and electron microscopy were employed to observe the density of hippocampal dendritic spines and synaptic conditions. The Morris water maze test was used to evaluate spatial memory capabilities. Statistical analysis was performed using GraphPad Prism 8.0 software. Results:(1) Behavioral results showed significant time and group interactions among the four groups in terms of latency to find the platform ( F=8.22, P<0.001).Mice in the TTLL6 CON sevoflurane group had a significantly longer escape latency on days 3-7 compared with the TTLL6 CON control group (all P<0.05), while there was no significant difference between the TTLL6 CKO sevoflurane group and the TTLL6 CKO control group (all P>0.05). The number of platform crossings differed significantly among the four groups ( H=11.95, P=0.007).The TTLL6 CON sevoflurane group had significantly fewer crossing times than the TTLL6 CON control group ( P<0.05), but no significant difference was observed between the TTLL6 CKO sevoflurane group and the TTLL6 CKO control group ( P>0.05). (2) Golgi staining and electron microscopy results revealed significant differences in dendritic spine density and synapse number among the four groups( F=29.00, 41.94, both P<0.001). The dendritic spine density ((5.83±0.40)/10 μm) and the number of synapses ((3.67±0.58)/10 μm) in the TTLL6 CON sevoflurane group were both significantly lower than those in the TTLL6 CON control group ((12.87±1.70)/10 μm, (9.33±0.57)/10 μm)(both P<0.05). In contrast, there was no statistically significant difference between the TTLL6 CKO sevoflurane group and TTLL6 CKO control group (both P>0.05). (3) Immunofluorescence results showed significant differences in the percentage of TTLL6 and Spastin and α-Tubulin co-expressed positive cells in the CA3 region of the hippocampus among the four groups of mice ( F=215.20, 26.08, both P<0.001). The percentage of TTLL6 and Spastin and α-Tubulin co-expressed positive cells in the TTLL6 CON sevoflurane group ((16.75±1.81) %, (47.98±8.42) %) were significantly higher than those in the TTLL6 CON control group ((2.44±0.58) %, (20.07±4.54) %)(both P<0.05), while there was no statistically significant difference between the TTLL6 CKO sevoflurane group and TTLL6 CKO control group ( P>0.05). (4) Western blot results indicated significant differences in the expression of polyGlu-Tubulin and PSD95 proteins in the hippocampal tissue among the four groups of mice ( F=19.66, 8.57, both P<0.001). The TTLL6 CON sevoflurane group had higher polyGlu-Tubulin expression (0.86±0.19) and lower PSD95 expression (0.61±0.13) compared to the TTLL6 CON control group (0.51±0.11, 1.01±0.07) (both P<0.05).However, there was no significant difference between the TTLL6 CKO sevoflurane group and the TTLL6 CKO control group ( P>0.05). Conclusion:The mechanism underlying long-term cognitive impairment in developing brain of neonatal mice caused by repeated sevoflurane anesthesia may relate to the upregulation of TTLL6-induced microtubule polyglutamylation and accelerated Spastin-mediated microtubule severing, which ultimately leads to abnormal dendritic spine development.
