Quetiapine Ameliorates Schizophrenia-Like Behaviors and Protects Myelin Integrity in Cuprizone Intoxicated Mice: The Involvement of Notch Signaling Pathway

Abstract

Background: White matter disturbances and myelin impairment are key features of schizophrenia. The antipsychotic drug quetiapine can promote the maturation of oligodendrocytes, but the molecular mechanisms remain largely unknown.

Methods: The schizophrenia-like behaviors, degrees of demyelination, and levels of Notch signaling molecules in forebrains of adult male C57BL/6 mice were examined after fed with cuprizone (0.2% wt/wt) in the presence or absence of 10mg/kg/d quetiapine for 6 weeks. These parameters were also observed after the transcranial injection of Notch signaling inhibitor MW167 (1mM) daily during the last week of the treatment period.

Results: Quetiapine ameliorated the schizophrenia-like behaviors and decreased expression of myelin basic protein and inhibition of Notch signaling molecules, such as Notch1, Hes1, and Hes5, in the forebrain that induced by cuprizone. These beneficial effects of quetiapine were abolished by MW167.

Conclusions: The antipsychotic and myelin protective effects of quetiapine are mediated by Notch signaling in a mouse model of cuprizone-induced demyelination associated with schizophrenia-like behaviors. The Notch pathway might therefore be a novel target for the development of antipsychotic drugs.

Keywords: Notch; myelination; quetiapine; schizophrenia.

Figure 1.

Schematic diagram detailing the time course of cuprizone, quetiapine, and MW167 treatment. (A) The timeline for experiment 1. All animals were subjected to 1 week of adaptation, and then animals were treated with drugs (eg, cuprizone and/or quetiapine) as indicated for 6 weeks, and subjected to 1 week of behavioral analysis before sacrifice. (B) The timeline for experiment 2. This experiment was carried out as in (A), except that mice from all groups went through lateral ventricular catheterization surgery for intracranial delivery of MW167 or vehicle 5 weeks into the 6-week drug treatment. Mice in the control + MW167 and cuprizone + quetiapine + MW167 group were treated with 2 μL of 1mM MW167 daily during the final week of the drug treatment period. At the end of the experiments described in (A) and (B), animals were sacrificed to assess molecular differences among all groups.

Figure 2.

Behavioral effects of cuprizone and quetiapine treatment. (A) The cuprizone-treated mice had an inferior prepulse inhibition (PPI), which was reversed by quetiapine treatment (main effect of treatment, F _{3, 92}=3.835, P=.013). (B-C) The cuprizone-treated mice spent less time (F _{3, 20}=4.886, P<.05), travelled a shorter distance (F _{3, 18}=4.212, P<.05) in the central area of the open field test, and exhibited anxiety-like behaviors, which were ameliorated by quetiapine cotreatment. (D) In the Y-maze test, cuprizone-treated mice showed impaired spatial working memory and spatial cognitive ability, which was rescued by quetiapine administration (F _{3, 25}=3.114, P<.05). (E-F) In the 3-chamber test, mice in the cuprizone group showed reduced social interactions and weaker social memory. Mice in the cuprizone + quetiapine group performed better than those treated with cuprizone alone. #P<.05 compared with the control group or the CPZ + Que group; *P<.05, **P<.01, ⁺ P<.05, ⁺⁺ P<.01, compared with the empty wire cup or Stranger 1.

Figure 3.

Quetiapine protected the forebrain from demyelination. (A) MBP immunofluorescent in the ventral lateral part of the caudoputamen (CPu) and cerebral cortex (CTX) of mice in each group (n=6). (B-C) Histogram represents the quantitative analysis of the integral optical density (IOD) of MBP level in CPu (F _{3, 20} = 33.79, P<.01) and CTX (F _{3, 20}=5.978, P<.01). (D) Western-blot assays demonstrated reduced expression of MBP in the forebrain of cuprizone-treated mice was restored by quetiapine cotreatment (F _{3, 20}=7.084, P<.01). Scale bar A=500 μm. *P<.05, **P<.01.

Figure 4.

Examination of the expression of molecules in the Notch signaling pathway in the forebrain of mice for all treatment groups (n=6 for each group). (A-B) RT-PCR showed no change of Notch2 (F _{3, 25}=0.323, P=.809), and Notch4 levels (F _{3, 18} = 0.708, P=.56) in each group. (C-E) RT-PCR results demonstrated that Notch1, Hes1, and Hes5 were upregulated by quetiapine and downregulated by cuprizone. Notch1 (C) (F _{3, 24} = 8.335, P<.01), Hes1 (D) (F _{3, 22} = 8.637, P<.01), and Hes5 (E) (F _{3, 24} = 4.478, P<.05) all increased in the cuprizone/quetiapine cotreatment group. (F-H) Western-blot analysis showed decreased expressions of Hes1 (F _3,22=7.498, P<.01), and Hes5 (F _{3, 22}=10.335, P<.01) in CPZ group and were upregulated after quetiapine co-administration. *P<.05, **P<.01.

Figure 5.

The antipsychotic effects of quetiapine were inhibited by MW167. (A) MW167 could affect the prepulse inhibition (PPI) and block the increased PPI induced by quetiapine. (B-C) The open field test revealed the anti-anxiety effects of quetiapine were blocked by MW167. (D) The Y-maze test showed quetiapine rescue of working memory deficits was blocked by MW167 injection. (E-F) In the 3-chamber test, mice in the cuprizone (CPZ) group and the CPZ + quetiapine (Que) + MW167 group showed reduced social interactions and weaker social memory. Mice in the cuprizone + quetiapine group performed better than those treated with cuprizone or cuprizone plus MW167. *P<.05, **P<.01; ⁺ P<.05, compared with the empty wire-cup or Stranger 1; # P<.05 compared with CPZ + Que group.

Figure 6.

The pro-myelinating effects of quetiapine require Notch signaling activation. Microphotographs (A) and histograms (B-C) represent the expression and quantitative analysis of the integral optical density (IOD) of MBP level. Cuprizone induced significant demyelination in the cerebral cortex (CTX) and ventral lateral caudoputamen (CPu), which was reversed by quetiapine coadministration. Intra-ventricular administration of MW167 reduced the myelin-protective effect of quetiapine. (B) Western-blot assays illustrating reduced expression levels of MBP induced by cuprizone in the mouse forebrain. MBP was upregulated by quetiapine cotreatment and this effect was blocked by MW167. Scale bar A=500 μm. #P<.05 compared with CPZ + Que group.

Figure 7.

Examination of the expression of molecules in the Notch signaling pathway in the forebrain of mice after MW167 and quetiapine treatment. (A-C) RT-PCR showed that the elevated mRNA levels of Notch1, Hes1, and Hes5of quetiapine were inhibited by MW167. (D-H) Western-blot analysis showed the rescue expressions of Hes1 and Hes5 in the quetiapine-treated group were blocked by MW167. **P<.01, #P<.05 compared with CPZ + Que group.