Initial studies of embryonic transplants of human hippocampus and cerebral cortex derived from schizophrenic women

Morphogenetic theory of mental and cognitive disorders: the role of neurotrophic and guidance molecules

Mental illness and cognitive disorders represent a serious problem for the modern society. Many studies indicate that mental disorders are polygenic and that impaired brain development may lay the ground for their manifestation. Neural tissue development is a complex and multistage process that involves a large number of distant and contact molecules. In this review, we have considered the key steps of brain morphogenesis, and the major molecule families involved in these process. The review provides many indications of the important contribution of the brain development process and correct functioning of certain genes to human mental health. To our knowledge, this comprehensive review is one of the first in this field. We suppose that this review may be useful to novice researchers and clinicians wishing to navigate the field.

Lymphocytes as a neural probe: potential for studying psychiatric disorders

There is an increasing body evidence pointing to a close integration between the central nervous system (CNS) and immunological functions with lymphocytes playing therein a central role. The authors provide arguments to consider blood lymphocytes as a convenient probe of--an albeit--limited number of cellular functions, including gene expression. The use of brain biopsies of living patients is unrealistic for biochemical investigation, therefore lymphocytes may be a convenient and accessible alternative. Numerous studies showed similarities between receptor expression and mechanisms of transduction processes of cells in the nervous system (e.g. neurons and glia) and lymphocytes. In several neuropsychiatric disorders, alteration of metabolism and cellular functions in the CNS, as well as disturbances in the main neurotransmitter and hormonal systems are concomitant with altered function and metabolism of blood lymphocytes. We summarize relevant investigations on depression, stress, Alzheimer's disease (AD) and schizophrenia. New techniques such as cDNA microarray gene expression and proteomics may give clues to define molecular abnormalities in psychiatric disorders and could eventually reveal information for diagnostic and treatment purposes. Taken together, these considerations suggest that lymphocyte could reflect the metabolism of brain cells, and may be exploited as a neural and possible genetic probe in studies of psychiatric disorders.

Neurotrophic factors and CNS disorders: findings in rodent models of depression and schizophrenia

Nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) are proteins involved in neuronal survival and plasticity of dopaminergic, cholinergic and serotonergic neurons in the central nervous system (CNS). Loss of neurons in specific brain regions has been found in depression and schizophrenia, and this chapter summarizes the findings of altered neurotrophins in animal models of those two disorders under baseline condition and following antidepressive and antipsychotic treatments. In a model of depression (Flinders sensitive line/Flinders resistant line; FSL/FRL rats), increased NGF and BDNF concentrations were found in frontal cortex of female, and in occipital cortex of male 'depressed' FSL compared to FRL control rats. Using the same model, the effects of electroconvulsive stimuli (ECS) and chronic lithium treatment on brain NGF, BDNF and glial cell line-derived neurotrophic factors were investigated. ECS and lithium altered the brain concentrations of neurotrophic factors in the hippocampus, frontal cortex, occipital cortex and striatum. ECS mimic the effects of electroconvulsive therapy (ECT) that is an effective treatment for depression and also schizophrenia. Since NGF and BDNF may also be changed in the CNS of animal models of schizophrenia, we investigated whether treatment with antipsychotic drugs (haloperidol, risperidone, and olanzapine) affects the constitutive levels of NGF and BDNF in the CNS. Both typical and atypical antipsychotic drugs altered the regional brain levels of NGF and BDNF. Other studies also demonstrated that these drugs differentially altered neurotrophin mRNAs. Overall, these studies indicate that alteration of brain level of NGF and BDNF could constitute part of the biochemical alterations induced by antipsychotic drugs.

Stress and nerve growth factor: findings in animal models and humans

Stress is elicited by environmental, social or pathological conditions occurring during the life of animals and humans that determine changes in the nervous, endocrine and immune systems. In the present review, we present data supporting the hypothesis that stress-related events both in animal models and humans are characterized by modifications of endogenous nerve growth factor (NGF) synthesis and/or utilization. Stress inducing alteration in NGF synthesis and/or utilization appears to be more severe during neurogenesis and in early postnatal life. However, NGF endogenously released during stress may promote remodeling of damaged tissues following acute and/or chronic stressful events.

Prenatal exposure to methylazoxymethanol acetate in the rat alters neurotrophin levels and behavior: considerations for neurodevelopmental diseases

We did a single injection of methylazoxymethanol acetate (MAM) in pregnant rats on gestational day (GD) 11 or 12 to investigate the long-lasting effects of early entorhinal cortex (EC) and hippocampus maldevelopment on behavior, brain nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) levels, and the neurotrophin receptor p75 and choline acetyltransferase (ChAT) immunoreactivity. Adult animals treated with MAM had compromised EC development and showed changes in locomotion and displacement activities. In addition, rats treated on GD 12 had increased concentration of NGF and BDNF in the EC and hippocampus if compared to control rats. Prenatal MAM administration did not affect significantly p75 and ChAT distribution in the EC and septum. Results are discussed in reference to the neurodevelopmental hypothesis of psychiatric disorders.

Data and hypotheses on the role of nerve growth factor and other neurotrophins in psychiatric disorders

Nerve growth factor (NGF) was discovered and characterized for its role on the growth, differentiation and maintenance of specific neurons of the peripheral nervous system. Subsequent studies revealed that NGF is synthesized and released within the central nervous system and exerts a trophic and functional role on basal forebrain cholinergic neurons; it is involved in a protective role following brain insults induced by an epileptic status, seizure, as well as surgical and chemical lesions.More recently our collaborative studies provided evidence that NGF is implicated in neurobehavioral response including cerebral alterations associated with psychiatric disorders. In this brief review, ongoing and emerging data are presented and discussed.

Brain-derived neurotrophic factor and tyrosine kinase receptor TrkB in rat brain are significantly altered after haloperidol and risperidone administration

The antipsychotics haloperidol and risperidone are widely used in the therapy of schizophrenia. The former drug mainly acts on the dopamine (DA) D(2) receptor whereas risperidone binds to both DA and serotonin (5HT) receptors, particularly in the neurons of striatal and limbic structures. Recent evidence suggests that neurotrophins might also be involved in antipsychotic action in the central nervous system (CNS). We have previously reported that haloperidol and risperidone significantly affect brain nerve growth factor (NGF) level suggesting that these drugs influence the turnover of endogenous growth factors. Brain-derived neurotrophic factor (BDNF) supports survival and differentiation of developing and mature brain DA neurons. We hypothesized that treatments with haloperidol or risperidone will affect synthesis/release of brain BDNF and tested this hypothesis by measuring BDNF and TrkB in rat brain regions after a 29-day-treatment with haloperidol or risperidone added to chow. Drug treatments had no effects on weight of brain regions. Chronic administration of these drugs, however, altered BDNF synthesis or release and expression of TrkB-immunoreactivity within the brain. Both haloperidol and risperidone significantly decreased BDNF concentrations in frontal cortex, occipital cortex and hippocampus and decreased or increased TrkB receptors in selected brain structures. Because BDNF can act on a variety of CNS neurons, it is reasonable to hypothesize that alteration of brain level of this neurotrophin could constitute one of the mechanisms of action of antipsychotic drugs. These observations also support the possibility that neurotrophic factors play a role in altered brain function in schizophrenic disorders.

Studies in animal models and humans suggesting a role of nerve growth factor in schizophrenia-like disorders

Neurotrophic factors, such as nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF), are known to play a crucial role in growth, differentiation and function in a variety of brain neurons during development and in adult life. We have recently shown that environmental changes, aggressive behavior and anxiety-like responses alter both circulating and brain basal NGF levels. In the present review, we present data obtained using animal models which suggest that neurotrophic factors, particularly NGF and BDNF, might be implicated in mechanism(s) leading to a condition associated with schizophrenic-like behaviors. The hypothesis that neurotrophins of the NGF family can be implicated in some maldevelopmental aspects of schizophrenia is supported by findings indicating that the constitutive levels of NGF and BDNF are affected in schizophrenic patients.

Is schizophrenia a lifetime disorder of brain plasticity, growth and aging?

Chronic schizophrenia is characterized by change in the normal brain cortical structure, asymmetric reduction, and ventricular enlargement. The debate continues as to whether these anomalies occur early in development or represent an active progressive process continuing after the onset of psychosis. The case is made in the present manuscript for a continuing aberrant lifetime brain process. It is proposed that the underlying basis for the neuropathology of schizophrenia resides in the periodic activation of a defective gene or genes that determine the rate of cerebral growth. This process causes subtle cortical maldevelopment prenatally and through early childhood, is activated again during adolescent pruning of neurons, and again during the gradual aging process in the brain throughout adulthood. The case for a progressive active brain process in schizophrenia is thus presented.

Cultured skin fibroblasts as a cell model for investigating schizophrenia

Cultured skin fibroblasts, among other non-neuronal cells (e.g. platelets, lymphocytes, red blood cells), provide an advantageous system for investigating dynamic molecular regulatory processes underlying abnormal cell growth, metabolism, and receptor-mediated signal transduction, without the confounding effects of disease state and its treatment in a variety of brain disorders, including schizophrenia, and are useful for studies of systemic biochemical defects with predominant consequences for brain function. These cells are also useful for studying aspects of neurotransmitter functions because the cells express enzymes involved in their metabolism, as well as their receptors with complete machinery for signal transduction. These processes also function predictably with receptors that are transfected in fibroblasts. This review will focus on the use of cultured skin of which have also been studied in post-mortem brains. These mechanisms might involve DNA processing and mitogenesis, cell-cell adhesion molecules, actions of growth factors, oxidative damage, and membrane phospholipid derived second messengers. This review will further discuss the implications of these processes to clinical and structural brain abnormalities. An understanding of these biochemical processes might help establish therapeutic implications and identify the risk for illness through experimental strategies such as epidemiology, family pedigree and high risk populations. Finally, despite some methodological limitations, skin fibroblasts are relatively easy to grow and maintain as primary cultures or as immortalized cell lines for long periods of time for use in investigating newly identified biochemical abnormalities.

Oxidative injury and potential use of antioxidants in schizophrenia

There is increasing evidence that oxidative injury contributes to pathophysiology of schizophrenia, indicated by the increased lipid peroxidation products in plasma and CSF, and altered levels of both enzymatic and non-enzymatic antioxidants in chronic and drug-naive first-episode schizophrenic patients. The increased plasma lipid peroxidation is also supported by concomitant lower levels of esterified polyunsaturated essential fatty acids of red blood cell plasma membrane phospholipids. Because membrane phospholipids play a critical role in neuronal signal transduction, oxidative damage of these lipids may contribute to the proposed altered neurotransmitter receptor-mediated signal transduction and thereby alter information processing in schizophrenia. Adjunctive treatment with antioxidants (e.g. vitamins E and C, beta-carotene and quinones) at the initial stages of illness may prevent further oxidative injury and thereby ameliorate and prevent further possible deterioration of associated neurological and behavioral deficits in schizophrenia.

Free radical pathology and antioxidant defense in schizophrenia: a review

There is increasing evidence that free radical-mediated CNS neuronal dysfunction is involved in the pathophysiology of schizophrenia. Free radicals (oxyradicals, such as superoxide, hydroxyl ions, and nitric oxide) cause cell injury when they are generated in excess or the antioxidant defense is impaired. Both of these processes seem to be affected in schizophrenia. Evidence of excessive oxyradical generation is premised on the assumption that there is increased catecholamine turnover, though there is little direct evidence to support such a view, which is further accentuated by neuroleptic treatment. However, antioxidant enzymes (superoxide dismutase, SOD; glutathione peroxidase, GSHPx; and catalase, CAT) which are constitutively expressed in all tissues, are found to be altered in erythrocytes of schizophrenic patients. Also, possible oxyradical-mediated injury to CNS is suggested by increased lipid peroxidation products in cerebrospinal fluid and plasma, and reduced membrane polyunsaturated fatty acids (PUFAs) in the brain and RBC plasma membranes. The brain is more vulnerable to oxyradical-mediated injury,because its membranes are preferentially enriched in oxyradical sensitive PUFAs, and damaged adult neurons cannot be replaced. In addition to their pathological role, oxyradicals have critical physiological functions in neuronal development, differentiation, and signal transduction, all of which may be altered in some cases of schizophrenia. It may be possible to define cellular injury processes, investigate underlying dynamic regulatory molecular processes, and find ways to prevent these injury processes using peripheral cell models, e.g., red blood cells, lymphocytes and cultured skin fibroblasts. Information on the clinical implications of these processes are valuable for developing new and innovative therapeutic strategies for schizophrenia.

Human fetal cortical tissue fragments survive grafting following one week storage at +4 degrees C

Grafting of human fetal tissue fragments has been used successfully in experimental and clinical trials. The development of techniques to store human fetal tissue fragments for longer time periods would allow to establish temporary tissue banks. We dissected several human cortical tissue fragments from one fetus and tested different storage conditions (cooling, freezing, culturing). After storage, the tissue fragments were transplanted into cavities in the cortex of host rats and the volume of the surviving grafts calculated. We report that human cortical tissue fragments grafted immediately after dissection (control group) or grafted after storage for 3 h in cryopreservation medium at room temperature survived grafting and resulted in graft sizes of 102 +/- 26 mm3 and 242 +/- 210 mm3, respectively, however, statistically not different. When the human cortical tissue fragments were slowly frozen and stored for 1 wk and/or when the fragments were cultured for 1 week in culture medium using a roller tube technique, grafts did not survive under our conditions. However, when the human cortical tissue fragments were stored for 1 week at +4 degrees C in cryopreservation medium, the graft size (48 +/- 24 mm3) was reduced but statistically not different from the control group. We conclude that human cortical tissue fragments can be stored at +4 degrees C for at least 1 wk without major loss of ability to survive grafting.

Decreased adhesiveness and altered cellular distribution of fibronectin in fibroblasts from schizophrenic patients

Relative to those from normal subjects, cultured skin fibroblasts from schizophrenic patients have been found to show abnormal growth characteristics and morphology. This study compared skin fibroblasts from 10 drug-free schizophrenic patients and 10 normal control subjects on cell adhesiveness to the substratum. Relative to fibroblasts from normal controls, those from patients showed significantly decreased cell adhesiveness, with no overlap in distribution between the groups. Since fibronectin, a major cell surface molecule, is known to be involved in the fibroblast adhesion to substratum, its extracellular and intracellular distribution was determined by immunocytochemical analysis. Both extracellular and intracellular levels of fibronectin were significantly lower, and the distribution was altered in fibroblasts from the patients.