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Isoflurane Damages the Developing Brain of Mice and Induces Subsequent Learning and Memory Deficits through FASL-FAS Signaling.

Yi X, Cai Y, Li W - Biomed Res Int (2015)

Bottom Line: MWM showed isoflurane treatment of wild type mice significantly prolonged escape latency and reduced platform crossing times compared with gene-knockout isoflurane-treated groups.Conclusion.Isoflurane induces apoptosis in developing hippocampi of wild type mice but not in FAS- and FASL-knockout mice and damages brain development through FASL-FAS signaling.

View Article: PubMed Central - PubMed

Affiliation: Department of Anesthesiology, The Eye, Ear, Nose and Throat Hospital, Fudan University, Shanghai 200031, China.

ABSTRACT
Background. Isoflurane disrupts brain development of neonatal mice, but its mechanism is unclear. We explored whether isoflurane damaged developing hippocampi through FASL-FAS signaling pathway, which is a well-known pathway of apoptosis. Method. Wild type and FAS- or FASL-gene-knockout mice aged 7 days were exposed to either isoflurane or pure oxygen. We used western blotting to study expressions of caspase-3, FAS (CD95), and FAS ligand (FASL or CD95L) proteins, TUNEL staining to count apoptotic cells in hippocampus, and Morris water maze (MWM) to evaluate learning and memory. Result. Isoflurane increased expression of FAS and FASL proteins in wild type mice. Compared to isoflurane-treated FAS- and FASL-knockout mice, isoflurane-treated wild type mice had higher expression of caspase-3 and more TUNEL-positive hippocampal cells. Expression of caspase-3 in wild isoflurane group, wild control group, FAS/FASL-gene-knockout control group, and FAS/FASL-gene-knockout isoflurane group showed FAS or FASL gene knockout might attenuate increase of caspase-3 caused by isoflurane. MWM showed isoflurane treatment of wild type mice significantly prolonged escape latency and reduced platform crossing times compared with gene-knockout isoflurane-treated groups. Conclusion. Isoflurane induces apoptosis in developing hippocampi of wild type mice but not in FAS- and FASL-knockout mice and damages brain development through FASL-FAS signaling.

No MeSH data available.


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(a) Western blot showed the caspase-3 expression of the four groups. FAS-knockout mice had comparable baseline caspase-3 levels with wild type control mice. Treating FAS-knockout mice with isoflurane did not increase caspase-3 levels (n = 5). Wild isoflurane mice showed the highest expression of caspase-3. (b) Quantification of the western blot for caspase-3 levels showed that isoflurane anesthesia caused an increase in caspase-3 level in hippocampus of wild mice compared with FAS-knockout mice plus oxygen group (∗P = 0.023). FAS knockout reduced the level of caspase-3 caused by isoflurane (#P = 0.017). At last, there was an interaction between FAS knockout and isoflurane anesthesia in that FAS knockout mitigated the isoflurane-induced increase in caspase-3 levels in the hippocampus of neonatal mice (&P = 0.011). No differences in caspase-3 expression were found among wild type control mice, FAS-knockout control mice, and FAS-knockout isoflurane mice. (c) FASL-knockout mice had comparable baseline caspase-3 levels with wild type control mice. Treating FASL-knockout mice with isoflurane did not increase caspase-3 levels (n = 5). Wild isoflurane mice showed the highest expression of caspase-3. (d) Quantification of the western blot for caspase-3 levels showed that isoflurane anesthesia caused an increase in caspase-3 level in hippocampus of wild mice compared with FASL-knockout mice plus oxygen group (∗P = 0.02). FASL knockout reduced the level of caspase-3 caused by isoflurane (#P = 0.03). At last, there was an interaction between FASL knockout and isoflurane anesthesia in that FASL knockout mitigated the isoflurane-induced increase in caspase-3 levels in the hippocampus of neonatal mice (&&P = 0.001). No differences in caspase-3 expression were found among wild type control mice, FASL-knockout control mice, and FASL-knockout isoflurane mice. Error bars represent the standard deviation (SD) of four independent experiments; P < 0.05.
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fig3: (a) Western blot showed the caspase-3 expression of the four groups. FAS-knockout mice had comparable baseline caspase-3 levels with wild type control mice. Treating FAS-knockout mice with isoflurane did not increase caspase-3 levels (n = 5). Wild isoflurane mice showed the highest expression of caspase-3. (b) Quantification of the western blot for caspase-3 levels showed that isoflurane anesthesia caused an increase in caspase-3 level in hippocampus of wild mice compared with FAS-knockout mice plus oxygen group (∗P = 0.023). FAS knockout reduced the level of caspase-3 caused by isoflurane (#P = 0.017). At last, there was an interaction between FAS knockout and isoflurane anesthesia in that FAS knockout mitigated the isoflurane-induced increase in caspase-3 levels in the hippocampus of neonatal mice (&P = 0.011). No differences in caspase-3 expression were found among wild type control mice, FAS-knockout control mice, and FAS-knockout isoflurane mice. (c) FASL-knockout mice had comparable baseline caspase-3 levels with wild type control mice. Treating FASL-knockout mice with isoflurane did not increase caspase-3 levels (n = 5). Wild isoflurane mice showed the highest expression of caspase-3. (d) Quantification of the western blot for caspase-3 levels showed that isoflurane anesthesia caused an increase in caspase-3 level in hippocampus of wild mice compared with FASL-knockout mice plus oxygen group (∗P = 0.02). FASL knockout reduced the level of caspase-3 caused by isoflurane (#P = 0.03). At last, there was an interaction between FASL knockout and isoflurane anesthesia in that FASL knockout mitigated the isoflurane-induced increase in caspase-3 levels in the hippocampus of neonatal mice (&&P = 0.001). No differences in caspase-3 expression were found among wild type control mice, FASL-knockout control mice, and FASL-knockout isoflurane mice. Error bars represent the standard deviation (SD) of four independent experiments; P < 0.05.

Mentions: The homozygous FAS- and FASL-knockout mice (B6.MRL-Faslpr and B6Smn.C3-Faslgld, resp.) are mice that have a nonfunctional mutation in the FAS gene and FASL gene, respectively [18, 19]. The expression levels of caspase-3 protein in the hippocampus of FAS-knockout mice treated with pure oxygen or isoflurane were both comparable to wild type control mice. However, the expression of caspase-3 in wild type mice treated with isoflurane was clearly increased compared with FAS-knockout mice treated with pure oxygen or isoflurane, P < 0.05. The result of two-way ANOVA suggested that loss of FAS attenuates the increase of caspase-3 induced by isoflurane (Figures 3(a) and 3(b)).


Isoflurane Damages the Developing Brain of Mice and Induces Subsequent Learning and Memory Deficits through FASL-FAS Signaling.

Yi X, Cai Y, Li W - Biomed Res Int (2015)

(a) Western blot showed the caspase-3 expression of the four groups. FAS-knockout mice had comparable baseline caspase-3 levels with wild type control mice. Treating FAS-knockout mice with isoflurane did not increase caspase-3 levels (n = 5). Wild isoflurane mice showed the highest expression of caspase-3. (b) Quantification of the western blot for caspase-3 levels showed that isoflurane anesthesia caused an increase in caspase-3 level in hippocampus of wild mice compared with FAS-knockout mice plus oxygen group (∗P = 0.023). FAS knockout reduced the level of caspase-3 caused by isoflurane (#P = 0.017). At last, there was an interaction between FAS knockout and isoflurane anesthesia in that FAS knockout mitigated the isoflurane-induced increase in caspase-3 levels in the hippocampus of neonatal mice (&P = 0.011). No differences in caspase-3 expression were found among wild type control mice, FAS-knockout control mice, and FAS-knockout isoflurane mice. (c) FASL-knockout mice had comparable baseline caspase-3 levels with wild type control mice. Treating FASL-knockout mice with isoflurane did not increase caspase-3 levels (n = 5). Wild isoflurane mice showed the highest expression of caspase-3. (d) Quantification of the western blot for caspase-3 levels showed that isoflurane anesthesia caused an increase in caspase-3 level in hippocampus of wild mice compared with FASL-knockout mice plus oxygen group (∗P = 0.02). FASL knockout reduced the level of caspase-3 caused by isoflurane (#P = 0.03). At last, there was an interaction between FASL knockout and isoflurane anesthesia in that FASL knockout mitigated the isoflurane-induced increase in caspase-3 levels in the hippocampus of neonatal mice (&&P = 0.001). No differences in caspase-3 expression were found among wild type control mice, FASL-knockout control mice, and FASL-knockout isoflurane mice. Error bars represent the standard deviation (SD) of four independent experiments; P < 0.05.
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fig3: (a) Western blot showed the caspase-3 expression of the four groups. FAS-knockout mice had comparable baseline caspase-3 levels with wild type control mice. Treating FAS-knockout mice with isoflurane did not increase caspase-3 levels (n = 5). Wild isoflurane mice showed the highest expression of caspase-3. (b) Quantification of the western blot for caspase-3 levels showed that isoflurane anesthesia caused an increase in caspase-3 level in hippocampus of wild mice compared with FAS-knockout mice plus oxygen group (∗P = 0.023). FAS knockout reduced the level of caspase-3 caused by isoflurane (#P = 0.017). At last, there was an interaction between FAS knockout and isoflurane anesthesia in that FAS knockout mitigated the isoflurane-induced increase in caspase-3 levels in the hippocampus of neonatal mice (&P = 0.011). No differences in caspase-3 expression were found among wild type control mice, FAS-knockout control mice, and FAS-knockout isoflurane mice. (c) FASL-knockout mice had comparable baseline caspase-3 levels with wild type control mice. Treating FASL-knockout mice with isoflurane did not increase caspase-3 levels (n = 5). Wild isoflurane mice showed the highest expression of caspase-3. (d) Quantification of the western blot for caspase-3 levels showed that isoflurane anesthesia caused an increase in caspase-3 level in hippocampus of wild mice compared with FASL-knockout mice plus oxygen group (∗P = 0.02). FASL knockout reduced the level of caspase-3 caused by isoflurane (#P = 0.03). At last, there was an interaction between FASL knockout and isoflurane anesthesia in that FASL knockout mitigated the isoflurane-induced increase in caspase-3 levels in the hippocampus of neonatal mice (&&P = 0.001). No differences in caspase-3 expression were found among wild type control mice, FASL-knockout control mice, and FASL-knockout isoflurane mice. Error bars represent the standard deviation (SD) of four independent experiments; P < 0.05.
Mentions: The homozygous FAS- and FASL-knockout mice (B6.MRL-Faslpr and B6Smn.C3-Faslgld, resp.) are mice that have a nonfunctional mutation in the FAS gene and FASL gene, respectively [18, 19]. The expression levels of caspase-3 protein in the hippocampus of FAS-knockout mice treated with pure oxygen or isoflurane were both comparable to wild type control mice. However, the expression of caspase-3 in wild type mice treated with isoflurane was clearly increased compared with FAS-knockout mice treated with pure oxygen or isoflurane, P < 0.05. The result of two-way ANOVA suggested that loss of FAS attenuates the increase of caspase-3 induced by isoflurane (Figures 3(a) and 3(b)).

Bottom Line: MWM showed isoflurane treatment of wild type mice significantly prolonged escape latency and reduced platform crossing times compared with gene-knockout isoflurane-treated groups.Conclusion.Isoflurane induces apoptosis in developing hippocampi of wild type mice but not in FAS- and FASL-knockout mice and damages brain development through FASL-FAS signaling.

View Article: PubMed Central - PubMed

Affiliation: Department of Anesthesiology, The Eye, Ear, Nose and Throat Hospital, Fudan University, Shanghai 200031, China.

ABSTRACT
Background. Isoflurane disrupts brain development of neonatal mice, but its mechanism is unclear. We explored whether isoflurane damaged developing hippocampi through FASL-FAS signaling pathway, which is a well-known pathway of apoptosis. Method. Wild type and FAS- or FASL-gene-knockout mice aged 7 days were exposed to either isoflurane or pure oxygen. We used western blotting to study expressions of caspase-3, FAS (CD95), and FAS ligand (FASL or CD95L) proteins, TUNEL staining to count apoptotic cells in hippocampus, and Morris water maze (MWM) to evaluate learning and memory. Result. Isoflurane increased expression of FAS and FASL proteins in wild type mice. Compared to isoflurane-treated FAS- and FASL-knockout mice, isoflurane-treated wild type mice had higher expression of caspase-3 and more TUNEL-positive hippocampal cells. Expression of caspase-3 in wild isoflurane group, wild control group, FAS/FASL-gene-knockout control group, and FAS/FASL-gene-knockout isoflurane group showed FAS or FASL gene knockout might attenuate increase of caspase-3 caused by isoflurane. MWM showed isoflurane treatment of wild type mice significantly prolonged escape latency and reduced platform crossing times compared with gene-knockout isoflurane-treated groups. Conclusion. Isoflurane induces apoptosis in developing hippocampi of wild type mice but not in FAS- and FASL-knockout mice and damages brain development through FASL-FAS signaling.

No MeSH data available.


Related in: MedlinePlus