Increased ratio of calcineurin immunoreactive neurons in the caudate nucleus of patients with schizophrenia

Ultrastructural disturbances in microglia-neuron interactions in the head of the caudate nucleus in schizophrenia

Previously we found altered microglia-neuron interactions in the prefrontal cortex in schizophrenia. We hypothesized that microglia-neuron interactions may be dysregulated in the caudate nucleus in schizophrenia. A postmortem ultrastructural morphometric study was performed to investigate satellite microglia (SatMg) and adjacent neurons in the head of the caudate nucleus in 21 cases of schizophrenia and 20 healthy controls. We found increased microglial density in young schizophrenia patients compared to elderly controls. Volume density (Vv) and the number (N) of mitochondria were lower and total area of vacuoles of endoplasmic reticulum was higher in SatMg in the schizophrenia group compared to controls. The mitochondrial decline has progressed with age and illness duration. Areas of neuronal somata, nucleus, mitochondria and vacuoles of endoplasmic reticulum were significantly higher in schizophrenia compared to controls. These neuronal parameters were positively correlated with area and Vv of vacuoles of endoplasmic reticulum in SatMg in the schizophrenia group but not in the control group. Besides, area of mitochondria in neurons was negatively correlated with N of mitochondria in SatMg. Vv of lipofuscin granules in neurons was higher in elderly patients compared to young patients and was positively correlated with age, illness duration and Vv of lipofuscin granules in SatMg in the schizophrenia group. The disturbances of SatMg-neuronal interactions may be related to the endoplasmic reticulum stress, alterations and deficit of mitochondria in SatMg due to chronic stress, activation and priming of SatMg followed by neurotoxicity. SatMg may participate in neuronal aging in schizophrenia.

Effects of long-term antipsychotic medication on brain instability in first-episode schizophrenia patients: a resting-state fMRI study

Early initiation of antipsychotic treatment plays a crucial role in the management of first-episode schizophrenia (FES) patients, significantly improving their prognosis. However, limited attention has been given to the long-term effects of antipsychotic drug therapy on FES patients. In this research, we examined the changes in abnormal brain regions among FES patients undergoing long-term treatment using a dynamic perspective. A total of 98 participants were included in the data analysis, comprising 48 FES patients, 50 healthy controls, 22 patients completed a follow-up period of more than 6 months with qualified data. We processed resting-state fMRI data to calculate coefficient of variation of fractional amplitude of low-frequency fluctuations (CVfALFF), which reflects the brain regional activity stability. Data analysis was performed at baseline and after long-term treatment. We observed that compared with HCs, patients at baseline showed an elevated CVfALFF in the supramarginal gyrus (SMG), parahippocampal gyrus (PHG), caudate, orbital part of inferior frontal gyrus (IOG), insula, and inferior frontal gyrus (IFG). After long-term treatment, the instability in SMG, PHG, caudate, IOG, insula and inferior IFG have ameliorated. Additionally, there was a positive correlation between the decrease in dfALFF in the SMG and the reduction in the SANS total score following long-term treatment. In conclusion, FES patients exhibit unstable regional activity in widespread brain regions at baseline, which can be ameliorated with long-term treatment. Moreover, the extent of amelioration in SMG instability is associated with the amelioration of negative symptoms.

Hippocampal volume and hippocampal neuron density, number and size in schizophrenia: a systematic review and meta-analysis of postmortem studies

Reduced hippocampal volume is a consistent finding in neuroimaging studies of individuals with schizophrenia. While these studies have the advantage of large-sample sizes, they are unable to quantify the cellular basis of structural or functional changes. In contrast, postmortem studies are well suited to explore subfield and cellular alterations, but low sample sizes and subject heterogeneity impede establishment of statistically significant differences. Here we use a meta-analytic approach to synthesize the extant literature of hippocampal subfield volume and cellular composition in schizophrenia patients and healthy control subjects. Following pre-registration (PROSPERO CRD42019138280), PubMed, Web of Science, and PsycINFO were searched using the term: (schizophrenia OR schizoaffective) AND (post-mortem OR postmortem) AND hippocampus. Subjects were adult men and women with schizophrenia or schizoaffective disorder or non-psychiatric control subjects, and key outcomes, stratified by hippocampal hemisphere and subfield, were volume, neuron number, neuron density, and neuron size. A random effects meta-analysis was performed. Thirty-two studies were included (413 patients, 415 controls). In patients, volume and neuron number were significantly reduced in multiple hippocampal subfields in left, but not right hippocampus, whereas neuron density was not significantly different in any hippocampal subfield. Neuron size, averaged bilaterally, was also significantly reduced in all calculated subfields. Heterogeneity was minimal to moderate, with rare evidence of publication bias. Meta-regression of age and illness duration did not explain heterogeneity of total hippocampal volume effect sizes. These results extend neuroimaging findings of smaller hippocampal volume in schizophrenia patients and further our understanding of regional and cellular neuropathology in schizophrenia.

Reduced density of oligodendrocytes and oligodendrocyte clusters in the caudate nucleus in major psychiatric illnesses

Functional dysconnectivity in schizophrenia and affective disorders may be associated with myelin and oligodendrocyte abnormalities. Altered network integration involving the caudate nucleus (CN) and metabolic abnormalities in fronto-striatal-thalamic white matter tracts have been reported in schizophrenia and impaired patterns of cortico-caudate functional connectivity have been found in both bipolar disorder (BPD) and schizophrenia compared to healthy controls. Postmortem studies have found ultrastructural dystrophy and degeneration of oligodendrocytes and dysmyelination in the CN in schizophrenia and BPD. We aimed to test the hypothesis that oligodendrocyte density may be reduced in the CN in major psychiatric disorders and may thereby form the cellular basis for the functional dysconnectivity observed in these disorders. Optical disector was used to estimate the numerical density (Nv) of oligodendrocytes and oligodendrocyte clusters (OLC) in the CN of cases with schizophrenia, BPD and major depressive disorder (MDD) and in normal controls (15 cases per group). A significant reduction in the Nv of oligodendrocytes was found in schizophrenia and BPD as compared to the control group (p < 0.05), and the Nv of OLC was significantly lowered in schizophrenia and BPD compared to controls (p < 0.05). There were no significant differences between MDD and control groups. The Nv of OLC was significantly decreased in the left hemisphere in schizophrenia as compared to the left hemisphere of the control group (-52%, p < 0.01). The data indicates that a decreased density of oligodendrocytes and OLC could contribute to the altered functional connectivity of the CN in subjects with severe mental illnesses.

Differential protein expression of DARPP-32 versus Calcineurin in the prefrontal cortex and nucleus accumbens in schizophrenia and bipolar disorder

Dopamine- and cAMP-regulated phosphoprotein of molecular weight 32 kDa (DARPP-32) integrates dopaminergic signaling into that of several other neurotransmitters. Calcineurin (CaN), located downstream of dopaminergic pathways, inactivates DARPP-32 by dephosphorylation. Despite several studies have examined their expression levels of gene and protein in postmortem patients’ brains, they rendered inconsistent results. In this study, protein expression levels of DARPP-32 and CaN were measured by enzyme-linked immunosorbent assay (ELISA) in the prefrontal cortex (PFC), and nucleus accumbens (NAc) of 49 postmortem samples from subjects with schizophrenia, bipolar disorder, and normal controls. We also examined the association between this expression and genetic variants of 8 dopaminergic system-associated molecules for 55 SNPs in the same postmortem samples. In the PFC of patients with schizophrenia, levels of DARPP-32 were significantly decreased, while those of CaN tended to increase. In the NAc, both of DARPP-32 and CaN showed no significant alternations in patients with schizophrenia or bipolar disorder. Further analysis of the correlation of DARPP-32 and CaN expressions, we found that positive correlations in controls and schizophrenia in PFC, and schizophrenia in NAc. In PFC, the expression ratio of DARPP-32/CaN were significantly lower in schizophrenia than controls. We also found that several of the aforementioned SNPs may predict protein expression, one of which was confirmed in a second independent sample set. This differential expression of DARPP-32 and CaN may reflect potential molecular mechanisms underlying the pathogenesis of schizophrenia and bipolar disorder, or differences between these two major psychiatric diseases.

Schizophrenia alters intra-network functional connectivity in the caudate for detecting speech under informational speech masking conditions

BACKGROUND

Speech recognition under noisy "cocktail-party" environments involves multiple perceptual/cognitive processes, including target detection, selective attention, irrelevant signal inhibition, sensory/working memory, and speech production. Compared to health listeners, people with schizophrenia are more vulnerable to masking stimuli and perform worse in speech recognition under speech-on-speech masking conditions. Although the schizophrenia-related speech-recognition impairment under "cocktail-party" conditions is associated with deficits of various perceptual/cognitive processes, it is crucial to know whether the brain substrates critically underlying speech detection against informational speech masking are impaired in people with schizophrenia.

METHODS

Using functional magnetic resonance imaging (fMRI), this study investigated differences between people with schizophrenia (n = 19, mean age = 33 ± 10 years) and their matched healthy controls (n = 15, mean age = 30 ± 9 years) in intra-network functional connectivity (FC) specifically associated with target-speech detection under speech-on-speech-masking conditions.

RESULTS

The target-speech detection performance under the speech-on-speech-masking condition in participants with schizophrenia was significantly worse than that in matched healthy participants (healthy controls). Moreover, in healthy controls, but not participants with schizophrenia, the strength of intra-network FC within the bilateral caudate was positively correlated with the speech-detection performance under the speech-masking conditions. Compared to controls, patients showed altered spatial activity pattern and decreased intra-network FC in the caudate.

CONCLUSIONS

In people with schizophrenia, the declined speech-detection performance under speech-on-speech masking conditions is associated with reduced intra-caudate functional connectivity, which normally contributes to detecting target speech against speech masking via its functions of suppressing masking-speech signals.

Transcriptome sequencing implicates dorsal striatum-specific gene network, immune response and energy metabolism pathways in bipolar disorder

Bipolar disorder (BD) is a highly heritable and heterogeneous mental illness whose manifestations often include impulsive and risk-taking behavior. This particular phenotype suggests that abnormal striatal function could be involved in BD etiology, yet most transcriptomic studies of this disorder have concentrated on cortical brain regions. We believe we report the first transcriptome sequencing of the postmortem human dorsal striatum comparing bipolar (18) and control (17) subjects. Fourteen genes were detected as differentially expressed at a 5% false discovery rate, including a few immune response genes such as NLRC5, S100A12, LILRA4 and FCGBP, as well as an assortment of non-protein coding genes. Functional pathway analysis found an enrichment of upregulated genes across many immune/inflammation pathways and an enrichment of downregulated genes among oxidative phosphorylation pathways. Co-expression network analysis revealed 20 modules of highly interconnected genes; two of the modules were significantly enriched for BD susceptibility single-nucleotide polymorphisms deriving from a large genome-wide association study data set. Remarkably, the module with the highest genetic association signal for BD, which contained many genes from signaling pathways, was also enriched in markers characteristic of gene expression in dorsal striatum medium spiny neurons-unlike most other modules, which showed no such regional and neuronal specificity. These findings draw a link between BD etiology at the gene level and a specific brain region, and highlight striatal signaling pathways as potential targets for the development of novel treatments to manage BD.

Prominent increased calcineurin immunoreactivity in the superior temporal gyrus in schizophrenia: A postmortem study

Many neuroimaging studies have demonstrated structural changes in the superior temporal gyrus (STG) in patients with schizophrenia. Several postmortem studies have reported on the pathogenesis of schizophrenia, but few reports have investigated alterations in molecules in the STG. In addition, several studies have suggested that calcineurin (CaN) inadequacy may be a risk factor for schizophrenia, but no reports about CaN expression in the STG in schizophrenia have been published. We compared the density of CaN-immunoreactive (CaN-IR) neurons in the STG from 11 patients with schizophrenia with that of 11 sex- and age-matched controls. We used immunohistochemical analysis with rabbit polyclonal antibodies against human CaN. In the STG, the density of CaN-IR neurons in layers II - VI in the group with schizophrenia was significantly higher than that in the control group. Our results confirmed pathological changes in the STG in patients with schizophrenia, suggesting that alterations in the CaN pathway play a role in the pathogenesis of schizophrenia.

Role of NMDA Receptor-Mediated Glutamatergic Signaling in Chronic and Acute Neuropathologies

N-Methyl-D-aspartate receptors (NMDARs) have two opposing roles in the brain. On the one hand, NMDARs control critical events in the formation and development of synaptic organization and synaptic plasticity. On the other hand, the overactivation of NMDARs can promote neuronal death in neuropathological conditions. Ca(2+) influx acts as a primary modulator after NMDAR channel activation. An imbalance in Ca(2+) homeostasis is associated with several neurological diseases including schizophrenia, Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis. These chronic conditions have a lengthy progression depending on internal and external factors. External factors such as acute episodes of brain damage are associated with an earlier onset of several of these chronic mental conditions. Here, we will review some of the current evidence of how traumatic brain injury can hasten the onset of several neurological conditions, focusing on the role of NMDAR distribution and the functional consequences in calcium homeostasis associated with synaptic dysfunction and neuronal death present in this group of chronic diseases.

Decreased calcineurin immunoreactivity in the postmortem brain of a patient with schizophrenia who had been prescribed the calcineurin inhibitor, tacrolimus, for leukemia

BACKGROUND

The calcineurin (CaN) inhibitor, tacrolimus, is widely used in patients undergoing allogeneic organ transplantation and in those with certain allergic diseases. Recently, several reports have suggested that CaN is also associated with schizophrenia. However, little data are currently available on the direct effect of tacrolimus on the human brain.

CASE

A 23-year-old Japanese female experienced severe delusion of persecution, delusional mood, suspiciousness, aggression, and excitement. She visited our hospital and was diagnosed with schizophrenia. When she was 27 years old, she had severe general fatigue, persistent fever, systemic joint pain, gingival bleeding, and breathlessness and was diagnosed with acute myelomonocytic leukemia. Later she underwent bone marrow transplantation (BMT), she was administered methotrexate and cyclosporin A to prevent graft versus host disease (GVHD). Three weeks after BMT, she showed initial symptoms of GVHD and was prescribed tacrolimus instead of cyclosporin A. Seven months after BMT at the age of 31 years, she died of progression of GVHD. Pathological anatomy was examined after her death, including immunohistochemical analysis of her brain using anti-CaN antibodies. For comparison, we used our previous data from both a schizophrenia group and a healthy control group. No significant differences were observed in the percentage of CaN-immunoreactive neurons among the schizophrenia group, healthy control group, and the tacrolimus case (all P>0.5, analysis of covariance). Compared with the healthy control group and schizophrenia group, the percentages of CaN-immunoreactive neurons in layers III-VI of the BA46 and the putamen tended to be lower in the tacrolimus case.

CONCLUSION

Tacrolimus may decrease CaN immunoreactivity in some regions of the human brain. Thus, tacrolimus may introduce side effects such as cognitive dysfunction and extrapyramidal symptoms. In addition, we also found that the effect of tacrolimus on CaN immunore-activity in human brain was stronger than the effect of schizophrenia.

Elevated postmortem striatal t-DARPP expression in schizophrenia and associations with DRD2/ANKK1 polymorphism

BACKGROUND

Dopamine- and cAMP-regulated phosphoprotein of molecular weight 32 kDa (DARPP-32) and calcineurin (CaN) have been implicated in the pathogenesis of schizophrenia because they function as molecular integrators of dopamine and glutamate signaling. DARPP-32 and CaN are mainly expressed in the caudate nucleus and putamen; however, a few postmortem brain studies have focused on DARPP-32 expression in striatum from patients with schizophrenia.

METHODS

We used immunoblotting techniques and postmortem tissue samples from patients with schizophrenia and from normal control individuals to examine the expression of two major DARPP-32 isoforms, full-length (FL-DARPP) and truncated (t-DARPP), and of CaN in the striatum. We also assessed whether there was any significant correlation between the expression levels of either protein and the A1 allele of Taq1A genotype in the dopamine D2 receptor (DRD2) gene/ankyrin-repeat containing kinase 1 (ANKK1) gene.

RESULTS

We found that the mean t-DARPP expression level in the caudate was higher in patients with schizophrenia than in control individuals (P<0.05) and the A1 allele of Taq1A genotype in DRD2/ANKK1 was significantly associated with elevated expression of t-DARPP in the caudate. Also, the A1 allele was significantly correlated with the total score of antemortem psychiatric symptoms.

CONCLUSION

These results may reflect potential molecular mechanisms important to the pathogenesis of schizophrenia.

Synaptic proteins in the postmortem anterior cingulate cortex in schizophrenia: relationship to treatment and treatment response

The anterior cingulate cortex (ACC) is one of several brain regions that are abnormal in schizophrenia (SZ). Here we compared markers of synapse and mitochondrial function using western blots of postmortem ACC in: 1) normal controls (NCs, n=13) vs subjects with SZ (n=25); NC, treatment-resistant SZ, and treatment-responsive SZ; and 3) NC and SZ treated with typical or atypical antipsychotic drugs (APDs). Protein levels of synaptophysin, mitofusin-2, vGLUT1, and calcineurin did not differ between the NC and SZ group as a whole, or the NCs vs the SZ group divided by treatment response or type of APDs. In several cases, the levels of vGLUT1 were minuscule or absent. The proportion of NCs lacking vGLUT1 was significantly less than that of the SZ groups. There were several positive correlations across all subjects between: 1) synaptophysin and vGLUT1; 2) synaptophysin and calcineurin; 3) synaptophysin and mitofusin; and 4) calcineurin and mitofusin. Synaptophysin and calcineurin were positively correlated in responders, and this correlation was significantly stronger than that in treatment-resistant SZ subjects or in NCs. Synaptophysin and calcineurin were positively correlated in SZ patients on atypical APDs; this correlation was significantly stronger than that in SZ patients on typical APDs or in NCs. Mitofusin-2 and calcineurin were positively correlated in SZ patients on atypical APDs and in NCs; this correlation was stronger in SZ patients on atypical rather than typical APDs or in NCs. The correlation between these proteins, which have roles in synaptic vesicle cycling, glutamate transmission, mitochondrial fusion, and calcium buffering, is complex and was differentially regulated among the groups.