Henrik Dobrowolny

Evidence for structural abnormalities of the human habenular complex in affective disorders but not in schizophrenia

BACKGROUND The habenular complex is composed of important relay nuclei linking the limbic forebrain to the midbrain and brain stem nuclei. Based on clinical observations, experiments with animals and theoretical considerations, it has been speculated that this brain area might be involved in psychiatric diseases (i.e. schizophrenia and depression). However, evidence in favour of this hypothesis is still lacking because the human habenular complex has rarely been studied with regard to mental illness. METHOD We examined habenular volumes in post-mortem brains of 17 schizophrenia patients, 14 patients with depression (six patients with major depression and eight patients with bipolar depression) and 13 matched controls. We further determined the neuronal density, cell number and cell area of the medial habenular nuclei of the same cohorts using a counting box and a computer-assisted instrument. RESULTS Significantly reduced habenular volumes of the medial and lateral habenula were estimated in depressive patients in comparison to normal controls and schizophrenia patients. We also found a reduction in neuronal cell number and cell area in depressive patients for the right side compared to controls and schizophrenia patients. No such changes were seen in schizophrenia. CONCLUSIONS Our anatomical data argue against prominent structural alterations of the habenular nuclei in schizophrenia but demonstrate robust alterations in depressive patients. We are currently applying immunohistochemical markers to better characterize neuronal subpopulations of this brain region in schizophrenia and depression.

Immunohistochemical evidence for impaired neuregulin-1 signaling in the prefrontal cortex in schizophrenia and in unipolar depression.

Abstract:  In the central nervous system (CNS), neuregulin‐1 (NRG‐1) proteins function in neuronal migration, differentiation, and survival of oligodendrocytes. The NRG‐1 gene codes for at least 15 different isoforms, which may be classified on the basis of their molecular structure. At least two different haplotypes of the NRG‐1 gene may be associated with schizophrenia. An abnormal expression pattern of NRG‐1 mRNA was found in the prefrontal cortex of schizophrenic patients in comparison to controls. We here show that the NRG‐1α isoform is significantly reduced in white matter of the prefrontal cortex in schizophrenia but not in affective disorder. In the prefrontal gray matter, the density of NRG‐1α expressing neurons was reduced in individuals with schizophrenia and in unipolar patients. We studied brains of 22 schizophrenics, 12 patients with affective disorders (7 unipolar and 5 bipolar), and 22 matched controls. NRG‐1α immunoreactive material was detected with a polyclonal antiserum against the synthetic peptide from α‐type EGF‐like domain of human NRG. The demonstrated decreased number of NRG‐1 immunoreactive neurons in the brains of schizophrenics and patients with unipolar depression points to an important role of this NRG‐1α splice variant in neuropsychiatric disorders. Reduced NRG‐1α protein concentrations were found in brains of schizophrenics after Western blot analysis. The diminished expression of NRG‐1α strongly supports an early neurodevelopmental component to schizophrenia.

Glial cells as key players in schizophrenia pathology: recent insights and concepts of therapy

The past decade has witnessed an explosion of knowledge on the impact of glia for the neurobiological foundation of schizophrenia. A plethora of studies have shown structural and functional abnormalities in all three types of glial cells. There is convincing evidence of reduced numbers of oligodendrocytes, impaired cell maturation and altered gene expression of myelin/oligodendrocyte-related genes that may in part explain white matter abnormalities and disturbed inter- and intra-hemispheric connectivity, which are characteristic signs of schizophrenia. Earlier reports of astrogliosis could not be confirmed by later studies, although the expression of a variety of astrocyte-related genes is abnormal in psychosis. Since astrocytes play a key role in the synaptic metabolism of glutamate, GABA, monoamines and purines, astrocyte dysfunction may contribute to certain aspects of disturbed neurotransmission in schizophrenia. Finally, increased densities of microglial cells and aberrant expression of microglia-related surface markers in schizophrenia suggest that immunological/inflammatory factors are of considerable relevance for the pathophysiology of psychosis. This review describes current evidence for the multifaceted role of glial cells in schizophrenia and discusses efforts to develop glia-directed therapies for the treatment of the disease.

Localization of neuregulin-1α (heregulin-α) and one of its receptors, ErbB-4 tyrosine kinase, in developing and adult human brain

Abstract Using immunohistochemistry, Western blot analysis, and RT-polymerase chain reaction, we studied the distribution of neuregulin-1 splice variant α (NRG-1α) and one of its putative receptors, ErbB-4 tyrosine kinase, in human brain. In the pre- and perinatal human brain immunoreactivity was confined to numerous neurons, with the highest cell density found in cortical gray matter, hypothalamus and cerebellum. In the adult brain, single cortical gray and white matter neurons showed NRG-1α immunoreactivity. Occasionally, immunoreactive oligodendrocytes were observed. NRG-1α-expressing neurons were also found in the hypothalamus, hippocampus, basal ganglia and brain stem. Application of two antibodies recognizing α and β isoforms revealed a different distribution pattern in that many cortical and hippocampal pyramidal neurons were labeled. ErbB-4 immunoreactivity was expressed in both neurons and oligodendrocytes. Our data show that NRG-1α expression is lower in the adult human brain than in the developing brain, and, therefore, support a role for NRG-1α in brain development.

Effects of risperidone treatment in adolescence on hippocampal neurogenesis, parvalbumin expression, and vascularization following prenatal immune activation in rats

Maternal infection in pregnancy is an environmental risk factor for the development of schizophrenia and related disorders in the offspring, and this association is recapitulated in animal models using gestational infection or immune stimulation. We have recently shown that behavioral abnormalities and altered hippocampal morphology emerging in adult offspring of dams treated with the viral mimic polyriboinosinic-polyribocytidilic acid (poly I:C) are prevented by treatment with the atypical antipsychotic drug risperidone (RIS) in adolescence. Here we used a battery of cellular markers and Nissl stain to morphometrically analyze different hippocampal cell populations in the offspring of poly I:C and saline-treated mothers that received saline or RIS in adolescence, at different time points of postnatal development. We report that impaired neurogenesis, disturbed micro-vascularization and loss of parvalbumin-expressing hippocampal interneurons, are found in the offspring of poly I:C-treated dams. Most, but not all, of these neuropathological changes are not present in poly I:C offspring that had been treated with RIS. These effects may be part of the complex processes underlying the capacity of RIS treatment in adolescence to prevent structural and behavioral abnormalities deficits in the poly I:C offspring.

Strongly reduced number of parvalbumin-immunoreactive projection neurons in the mammillary bodies in schizophrenia: further evidence for limbic neuropathology.

Abstract:  The mammillary bodies (MB) are important relay nuclei within limbic and extralimbic connections. They are known to play important roles in memory formation and are affected in alcoholism and vitamin B1 deficiency. Their strategic position linking temporo‐limbic to cortico‐thalamic brain structures make the MB a candidate brain structure for alterations in schizophrenia. We studied 15 postmortem brains of schizophrenics and 15 matched control brains. Brain sections were stained either with Heidenhain‐Woelcke, glutamic acid decarboxylase (GAD), calretinin, or parvalbumin. We determined the volumes of the MB and performed cell countings using stereological principles and a computerized image analysis system. The volumes of MB do not differ between schizophrenics and controls. However, in schizophrenia the number of neurons as well as the resulting neuronal densities was significantly reduced on both sides (on left side by 38.9%, on right side by 22%). No changes were seen in the number of GAD‐expressing or calretinin‐containing neurons, whereas the number of parvalbumin‐immunoreactive MB neurons was reduced by more than 50% in schizophrenia. This cell loss (as a result of developmental malformation and/or neurodegeneration) points to a prominent involvement of the MB in the pathomorphology of schizophrenia. Parvalbumin‐immunoreactive GABAergic interneurons have been reported to be diminished in schizophrenia. However, in the MB parvalbumin labels a subpopulation of glutamate/aspartate‐containing neurons projecting mainly to the anterior thalamus. Thus, our data provide new evidence for impaired limbic circuits in schizophrenia.

S100B-immunopositive astrocytes and oligodendrocytes in the hippocampus are differentially afflicted in unipolar and bipolar depression: A postmortem study

BACKGROUND Previous studies have suggested that affective disorders are characterized by glial pathology. In this context, it has been hypothesized that elevated S100B serum and cerebrospinal fluid levels may represent a suitable surrogate marker. However, brain studies on the cellular distribution pattern of S100B in depressed patients are lacking so far. Such analyses are crucial, since S100B has been detected in various other cell types, even outside the central nervous system. METHODS Therefore, we performed a first postmortem analysis on this topic in the hippocampus--which is of major importance for emotional and cognitive aspects of affective disorders. S100B-immunopositive astrocytes and oligodendrocytes were evaluated in the alveus and the CA1 pyramidal layer of patients with major depressive disorder (MDD) or bipolar I disorder (BD) compared to controls. RESULTS As revealed by the optical disector cell-counting method, the numerical density of S100B-immunopositive astrocytes was bilaterally decreased in the CA1 pyramidal layer of MDD and BD patients compared to controls, whereas only the bipolar group showed a decreased density of S100B-immunopositive oligodendrocytes in the left alveus. These results were not confounded by gender, age, duration of disease, medication dosage, or autolysis time. CONCLUSIONS Confirming the idea of previous S100B serum and cerebrospinal fluid studies, our data suggest that S100B-immunopositive glia is dysregulated in the brains of depressed patients. These findings are in accordance with animal experiments in rodents showing a reduced astrocytic S100B-immunoreactivity in the hippocampus after pharmacological serotonin depletion (modeling depression).

Nitric oxide and schizophrenia: present knowledge and emerging concepts of therapy.

Schizophrenia is a devastating, chronic brain disorder afflicting about 1 percent of the population. The etiology, neuropathology, and pathophysiology of schizophrenia remain elusive. Intense research has been conducted in order to identify specific biological markers of schizophrenia. The gas nitric oxide (NO) is an important signaling molecule involved in many cellular events that take place in the cardiovascular, immune and nervous systems of animals. This present review aims to show that NO and its metabolites play eminent roles in schizophrenia and have a significant influence on our understanding of the development, progression and, possibly, treatment of the disease. Special emphasis is given to aspects of genetic linkage between NO generating and modulating proteins and schizophrenia, and the impact of NO metabolism on processes known to be disturbed in this neuropsychiatric disorder (i. e., nerve cell migration, formation and maintenance of synapses, N-methyl-D-aspartic acid receptor mediated neurotransmission, adult hippocampal neurogenesis, membrane pathology and cognitive abilities). Although certain alterations of brain NO metabolism are not unique to, or indicative of, schizophrenia, their modulation might be a promising therapeutic option for the future.

Suicide and depression in the quantitative analysis of glutamic acid decarboxylase-Immunoreactive neuropil.

BACKGROUND Alterations of GABAergic neurotransmission are assumed to play a crucial role in the pathophysiology of mood disorders. Glutamic acid decarboxylase (GAD) is the key enzyme of GABA synthesis. METHODS Immunohistochemical staining of GAD 65/67 was performed in the orbitofrontal, anterior cingulate and dorsolateral prefrontal cortex (DLC), the entorhinal cortex (EC), the hippocampal formation, and the medial dorsal and lateral dorsal thalamic nuclei, with consecutive determination of GAD-immunoreactive (-ir) neuropil relative density. The study was performed on paraffin-embedded brains from 21 depressed patients (14 of whom had committed suicide) and 18 matched controls. The data were tested using Kruskal-Wallis, Mann-Whitney (U) and Spearman statistical procedures. RESULTS As shown by post-hoc U-tests, an increase in the relative density of GAD-ir neuropil was present in the hippocampal formation, specific for suicidal patients. The EC was the only area where non-suicidal patients also revealed an increase compared with controls. On the contrary, the DLC was the only area where a significant decrease existed, specific for non-suicidal patients. Numerous negative correlations were found between the investigated parameter and psychotropic medication. LIMITATIONS A major limitation of this study is the relatively small case number. A further limitation is given by the lack of data on drug exposure across the whole life span. The possible impact of unipolar-bipolar dichotomy of mood disorders on the obtained results should also be considered. CONCLUSION The study, revealing predominantly an increased relative density of GAD-ir neuropil, suggests the diathesis of GABAergic system specific for depressed suicidal patients.

ADAM (a disintegrin and metalloprotease) 12 is expressed in rat and human brain and localized to oligodendrocytes

ADAM12 is a member of the large family of multidomain metalloprotease‐disintegrins which possess cell‐binding and metalloprotease properties. Typically, ADAM12 is expressed in mesenchymal cells, developing and regenerating heart and skeletal muscle, bone as well as in certain tumours. This report shows by means of reverse transcriptase‐polymerase chain reaction (RT‐PCR) and immunohistochemistry that the protease ADAM12 is detectable in human and rat brain tissue as well as in cultured cells derived from rat brain. With the exception of a very few immunopositive pyramidal neurons in the developing rat brain, the cellular localization of ADAM12 was exclusively confined to oligodendroglial cells. Thus, ADAM12 may be regarded a new suitable marker for this cell type.