Demonstration of an action pathway in mouse platelets leading to prolongation of bleeding time by fluoxetine.

Fluoxetine is one of SSRIs commonly used as first-line antidepressants. It also induces adverse effects, including bleeding events. This study clarified the bleeding effect of fluoxetine and explored the action cascade of this drug leading to a longer bleeding time. A total of 48 male adult mice were evenly distributed into four groups and given fluoxetine in saline at 0, 4, 8, or 16 mg/kg, for 14 days. On day 15, tail bleeding time of 6 mice/group was measured, and their blood samples were collected for analyses of relevant platelet functions. The remained mice were allowed to survive for another 14 days without fluoxetine, and subjected to the same analyses on day 29. A significant effect of fluoxetine was reveled on bleeding time (F (3,20) = 16.842, P < 0.01) and intraplatelet serotonin (F (3,20) = 90.967, P < 0.01). Moreover, fluoxetine effectively inhibited platelet aggregation (F(3, 20) = 30.247, P < 0.01), decreased amount of GPIbα (F(3, 20) = 23.855, P < 0.01), suppressed GPIIb/IIIa activation (F(3, 20) = 89.441, P < 0.01), and lowered P-selectin (F(3, 20) = 7.960, P < 0.01) on platelet surface. Negative correlations existed between bleeding time and the aforementioned four indices, whereas correlations between intraplatelet serotonin and the same indices were positive. All changes returned to same levels as Control group after fluoxetine withdrawal. These data suggest an action pathway of fluoxetine starting at binding to serotonin transporter, followed by decreased intraplatelet serotonin, increased GPIbα shedding, suppressed GPIIb/IIIa activation, and inhibited α-granule release, and concluding with prolonged bleeding time in mice.

The Long-Term Effects of Adolescent Social Defeat Stress on Oligodendrocyte Lineage Cells and Neuroinflammatory Mediators in Mice.

OBJECTIVE: Adverse childhood and adolescent experiences are associated with the emergences of psychopathology later in life and have negative consequences on white matter integrity. However, this adversity-induced white matter impairment remains not fully investigated. METHODS: Adolescent Balb/c mice were subjected to intermittent social defeat stress once a day during postnatal days 25 to 40. Then, the subjects were allowed to recover for three weeks before sacrifice. At the end, oligodendrocyte (OL) lineage cells, cell proliferation, and microglia activation, as well as myelin basic protein (MBP) levels in frontal cortex and hippocampus were evaluated. The levels of interleukin (IL)-1ß and IL-6 in the brain regions were assessed. RESULTS: MBP protein level in frontal cortex, but not in the hippocampus of defeated mice, decreased significantly compared to controls. The numeral densities of mature OLs, oligodendrocyte progenitor cells, and proliferating cells in medial prefrontal cortex were comparable between the defeated mice and controls. The defeated mice, however, showed significantly higher IL-1ß level, although IL-6 level and numeral density of microglia in frontal cortex did not change relative to controls. CONCLUSION: These results indicate that effects of intermittent social defeat stress on the white matter integrity and OL lineage cells in mouse brain are region- and developmental stage-specific. Upregulated IL-1ß may contribute to this negative consequence though the underlying mechanism remains to be investigated.

Exome Sequencing Identifies TENM4 as a Novel Candidate Gene for Schizophrenia in the SCZD2 Locus at 11q14-21.

Schizophrenia is a complex psychiatric disorder with high genetic heterogeneity, however, the contribution of rare mutations to the disease etiology remains to be further elucidated. We herein performed exome sequencing in a Han Chinese schizophrenia family and identified a missense mutation (c.6724C>T, p.R2242C) in the teneurin transmembrane protein 4 (TENM4) gene in the SCZD2 locus, a region previously linked to schizophrenia at 11q14-21. The mutation was confirmed to co-segregate with the schizophrenia phenotype in the family. Subsequent investigation of TENM4 exons 31, 32, and 33 adjacent to the p.R2242C mutation revealed two additional missense mutations in 120 sporadic schizophrenic patients. Residues mutated in these mutations, which are predicted to be deleterious to protein function, were highly conserved among vertebrates. These rare mutations were not detected in 1000 Genomes, NHLBI Exome Sequencing Project databases, or our in-house 1136 non-schizophrenic control exomes. Analysis of RNA-Seq data showed that TENM4 is expressed in the brain with high abundance and specificity. In line with the important role of TENM4 in central nervous system development, our findings suggested that increased rare variants in TENM4 could be associated with schizophrenia, and thus TENM4 could be a novel candidate gene for schizophrenia in the SCZD2 locus.

Changes in proinflammatory cytokines and white matter in chronically stressed rats.

Although the pathogenesis of depression, an incapacitating psychiatric ailment, remains largely unknown, previous human and animal studies have suggested that both proinflammatory cytokines and altered oligodendrocytes play important roles in the condition. This study examined these two factors in the brains of rats following unpredictable chronic mild stress for 4 weeks, with the hypothesis that chronic stress may affect oligodendrocytes and elevate proinflammatory cytokines in the brain. After suffering unpredictable stressors for 4 weeks, the rats showed depression-like behaviors, including decreased locomotion in the open field, increased immobility time in the forced swim test, and decreased sucrose consumption and less sucrose preference when compared with controls. Immunohistochemical staining of brain sections showed higher immunoreactivity of proinflammatory cytokines in certain brain regions of stressed rats compared with controls; lower immunoreactivity of myelin basic protein and fewer mature oligodendrocytes were seen in the prefrontal cortex, but no demyelination was detected. These results are interpreted and discussed in the context of recent findings from human and animal studies.

Behavioral and neurobiological studies on the male progeny of maternal rats exposed to chronic unpredictable stress before pregnancy.

Studies have shown that maternal chronic stress or depression is linked to an increased risk for affective disorders in progeny. However, the impact of maternal chronic stress before pregnancy on their progeny in animal models has not been well studied. We investigated the behaviors and the neurobiology in 60-day-old male progeny of maternal rats exposed to a 21-day chronic unpredictable stress (CUS) before pregnancy, with male progeny of unstressed maternal rats as the control. Sucrose consumption test showed that both sucrose intake and sucrose consumption percentage of the CUS progeny were lower than those of the control progeny (P<0.05). The number of times crossing the removed hidden platform in the CUS progeny was significantly fewer than that in the control progeny in Morris water maze test (P<0.05). The level of 5-hydroxytryptamine (5-HT) in the hypothalamus was reduced but the level of norepinephrine (NE) in the hippocampus was increased in CUS progeny when compared to the control (P<0.05). Western blotting showed that the relative level of phosphorylated CREB (P-CREB) in the CUS progeny was lower than that in the control progeny (P<0.05). There were significant positive correlations between sucrose consumption percentage and the level of 5-HT in hypothalamus P<0.05) or the level of P-CREB in hippocampus (P<0.05). In conclusion, depression or stressful events before pregnancy was also associated with high risk of depression in progeny, and the down-regulation of P-CREB in the hippocampus might be one of the mechanisms underlying depression in the CUS progeny.

[Transmission disequilibrium analysis of 1137-1140 Del GTGA frameshift mutation within the KCNN3 gene and schizophrenia based on family trios].

OBJECTIVE: To investigate the relationship between 1137-1140 Del GTGA in exon 1 at KCNN3 gene and schizophrenia. METHODS: The study included 289 subjects (affected 107; unaffected 182) from 95 schizophrenic trios. All subjects were collected from Han Chinese in south China and genotyped for 1137-1140 Del GTGA in KCNN3 using PCR and restriction endonuclease Dde I. All the affected patients met the CCMD-II-R criteria for schizophrenia. The haplotype-based haplotype relative risk(HHRR) and transmission/disequilibrium test(TDT) analyses were done in 95 schizophrenic trios. RESULTS: Comparative analysis on the distribution of alleles between the affected and unaffected parents(87 family trios) showed no significant difference(X(2)=0.253, P> 0.05). HHRR showed that KCNN3 gene alleles transmitted to the patients were not different from that of the non-transmitted parental alleles(X(2)=0.042, P> 0.05). TDT revealed that A(2) alleles were not preferentially transmitted to schizophrenic patients(X(2)=3.000, P=0.0833). CONCLUSION: In this study a lower frequency for 1137-1140 Del homozygote of KCNN3 gene was observed, and the HHRR and TDT analyses suggested that the 1137-1140 Del alleles of KCNN3 gene be unlikely to confer susceptibility to schizophrenia.