Reduced microglial immunoreactivity for endogenous NMDA receptor agonist quinolinic acid in the hippocampus of schizophrenia patients.

Postmortem and positron emission tomography studies have indicated the pathophysiological involvement of microglial cells in schizophrenia. We hypothesized that the microglial production of quinolinic acid (QUIN), an endogenous N-methyl-d-aspartate receptor (NMDAR) agonist, may be linked to the previously described glutamatergic deficits in the hippocampus of schizophrenia patients. We performed a semi-quantitative assessment of QUIN-immunoreactive microglial cells in schizophrenia patients and matched controls in the CA1, CA2/3, and dentate gyrus (DG) area of the posterior hippocampal formation. Complementary immunostaining of the commonly used microglial surface marker HLA-DR was performed in adjacent histological sections. Fewer QUIN-immunoreactive microglial cells were observed in the CA1 hippocampal subregion of schizophrenia patients compared to controls (left p=0.028, right p=0.018). No significant diagnosis-dependent changes were observed in the CA2/3 and DG regions. These results were controlled for potential confounds by age, duration of disease, autolysis time, psychotropic medication, and hippocampal volume. No diagnosis-related differences were observed for the overall density of microglial cells (HLA-DR expression). Our findings suggest that reduced microglial QUIN content in the hippocampal CA1 region is associated with schizophrenia. We hypothesize that this association may contribute to impaired glutamatergic neurotransmission in the hippocampus of schizophrenia patients.

Volumetric analysis of the hypothalamus, amygdala and hippocampus in non-suicidal and suicidal mood disorder patients--a post-mortem study.

In recent years, the hypothalamus, amygdala and hippocampus have attracted increased interest with regard to the effects of stress on neurobiological systems in individuals with depression and suicidal behaviour. A large body of evidence indicates that these subcortical regions are involved in the pathogenetic mechanisms of mood disorders and suicide. The current neuroimaging techniques inadequately resolve the structural components of small and complex brain structures. In previous studies, our group was able to demonstrate a structural and neuronal pathology in mood disorders. However, the impact of suicide remains unclear. In the current study we used volumetric measurements of serial postmortem sections with combined Nissl-myelin staining to investigate the hypothalamus, amygdala and hippocampus in suicide victims with mood disorders (n = 11), non-suicidal mood disorder patients (n = 9) and control subjects (n = 23). Comparisons between the groups by using an ANCOVA showed a significant overall difference for the hypothalamus (p = 0.001) with reduced volumes in non-suicidal patients compared to suicide victims (p = 0.018) and controls (p = 0.006). To our surprise, the volumes between the suicide victims and controls did not differ significantly. For the amygdala and hippocampus no volume changes between the groups could be detected (all p values were n. s.). In conclusion our data suggest a structural hypothalamic pathology in non-suicidal mood disorder patients. The detected differences between suicidal and non-suicidal patients suggest that suicidal performances might be related to the degree of structural deficits.

Reduced density of hypothalamic VGF-immunoreactive neurons in schizophrenia: a potential link to impaired growth factor signaling and energy homeostasis.

Protein expression of VGF (nonacronymic) is induced by nerve/brain-derived growth factor, neurotrophin 3, and insulin. VGF is synthesized by neurons in the paraventricular (PVN) and supraoptic (SON) nuclei of the hypothalamus. After enzymatic processing, smaller VGF-derived peptides are secreted into the cerebrospinal fluid (CSF) or blood. These peptides play important roles by improving synaptic plasticity, neurogenesis, and energy homeostasis, which are impaired in schizophrenia. Based on previous observations of neuroendocrine and hypothalamic deficits in schizophrenia and to determine whether increased levels of the VGF fragment 23-62 in CSF, which have been described in a recent study, were related to changes in hypothalamic VGF expression, an immunohistochemical study was performed in 20 patients with schizophrenia and 19 matched control subjects. N- (D-20) and C-terminal (R-15) VGF antibodies yielded similar results and immunolabeled a vast majority of PVN and SON neurons. Additionally, D20-VGF immunohistochemistry revealed immunostained fibers in the pituitary stalk and neurohypophysis that ended at vessel walls, suggesting axonal transport and VGF secretion. The cell density of D20-VGF-immunoreactive neurons was reduced in the left PVN (P = 0.002) and SON (P = 0.008) of patients with schizophrenia. This study provides the first evidence for diminished hypothalamic VGF levels in schizophrenia, which might suggest increased protein secretion. Our finding was particularly significant in subjects without metabolic syndrome (patients with a body mass index ≤28.7 kg/m(2)). In conclusion, apart from beneficial effects on synaptic plasticity and neurogenesis, VGF may be linked to schizophrenia-related alterations in energy homeostasis.

Dopamine-glutamate abnormalities in the frontal cortex associated with the catechol-O-methyltransferase (COMT) in schizophrenia.

Catechol-O-methyltransferase (COMT) plays an important role in brain catecholamine metabolism. Several studies point to the involvement of COMT in schizophrenia. We applied COMT immunohistochemistry to paraffin-embedded brain sections and assessed the cell density of COMT expressing glial cells and COMT expressing neurons in the gray matter of the frontal cortex of patients with schizophrenia compared with control subjects. We found a significantly increased cell density of COMT expressing glial cells (p=0.003), but an unchanged cell density of COMT expressing neurons (p=0.778) in the gray matter of the frontal cortex of patients with schizophrenia compared with control subjects. Our study demonstrates that schizophrenia might involve increased COMT expression in glial cells in the frontal cortex, which might be associated with a neuronal-glial abnormality and a disturbed dopamine-glutamate interaction.

The volumes of the fornix in schizophrenia and affective disorders: a post-mortem study.

Structural and functional pathology of limbic structures including the hippocampus are frequently replicated in schizophrenia. Although the fornix is the main afferent system of the hippocampus to the septal nuclei and the hypothalamus (especially the mammillary bodies), relatively few studies have investigated structural changes of the fornix in schizophrenia. We measured the volume of the fornix in post-mortem brains in 19 patients with schizophrenia, 9 patients with bipolar disorder, 7 patients with unipolar depression, and 14 control subjects by planimetry of serial sections. The volumes, the mean cross-sectional areas, and the anterior to posterior distances of the fornix did not differ among patients with schizophrenia, bipolar disorder, unipolar depression, and control subjects. No lateralization existed between the right and the left fornices in among patients in the diagnostic groups and the control subjects. The fornix does not show morphometrical abnormalities in patients with schizophrenia, bipolar disorder and unipolar depression compared with control subjects, which might indicate that the fornix is not a primary focus of structural changes in these diseases.