Peptidomic analysis of the anterior temporal lobe and corpus callosum from schizophrenia patients.

Schizophrenia is a complex disorder hypothesized to develop from a combination of genetic, neurodevelopmental, and environmental factors. Molecules that are directly involved in the pathogenesis of schizophrenia and may serve as biomarker candidates can be identified with "omics" approaches such as proteomics and peptidomics. In this context, we performed a peptidomic study in schizophrenia postmortem brains, to our knowledge the first such study in schizophrenia patients. We investigated the anterior temporal lobe (ATL) and corpus callosum (CC) by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) and a label-free ion quantification technique based on data-dependent acquisition (DDA). Results indicated alterations in a specific intracellular neurogranin peptide in both the ATL and CC and a decrease of PepH, a fragment of histone H2B type 1-H intracellular peptide, in the ATL. PepH was tested in serum-deprived Neuro2A cells and showed a protective effect against cell death. Cells were also challenged with lipopolysaccharide (LPS), and PepH was able to prevent the endotoxic effects of LPS. Our data suggest that specific intracellular peptides are altered in schizophrenia patients. The potential biological activity of PepH supports intracellular peptides as novel targets in the study not only of schizophrenia but also of other neuropsychiatric diseases. BIOLOGICAL SIGNIFICANCE: Psychiatric disorders are considerably more difficult to diagnose in their early stages. Usually, by the time the diagnosis is clear and clinical treatment can be started, the disorder is already established and thus of greater severity. Consequently, the scientific community has been searching for biomarker candidates that can aid the early detection of such disorders and for novel therapeutics to improve treatment or at least delay disease progression. Moreover, key molecules involved in the establishment of psychiatric diseases may help the understanding of their pathogenesis and thus drive the development of more effective treatments. The present work screened peptides that might be possible novel targets to control cell machinery in schizophrenia and identified an intracellular peptide with potential cytoprotective activity. To our knowledge, this is the first peptidomic study in schizophrenia patients.

BDNF receptor blockade hinders the beneficial effects of exercise in a rat model of Parkinson's disease.

Physical exercise is known to produce beneficial effects to the nervous system. In most cases, brain-derived neurotrophic factor (BDNF) is involved in such effects. However, little is known on the role of BDNF in exercise-related effects on Parkinson's disease (PD). The aim of this study was to investigate the effects of intermittent treadmill exercise-induced behavioral and histological/neurochemical changes in a rat model of unilateral PD induced by striatal injection of 6-hydroxydopamine (6-OHDA), and the role of BDNF in the exercise effects. Adult male Wistar rats were divided into two main groups: (1) injection of K252a (a blocker of BDNF receptors), and (2) without BDNF receptor blockade. These groups were then subdivided into four groups: control (CLT), sedentary (SED, non-exercised with induction of PD), exercised 3×/week during four weeks before and four weeks after the induction of PD (EXB+EXA), and exercised 3×/week during four weeks after the induction of PD (EXA). One month after 6-OHDA injections, the animals were subjected to rotational behavioral test induced by apomorphine and the brains were collected for immunohistochemistry and immunoblotting assays, in which we measured BDNF and tyrosine hydroxylase (TH) in the substantia nigra pars compacta (SNc) and the striatum (caudate-putamen, CPu). Our results showed a significant reduction of rotational asymmetry induced by apomorphine in the exercised parkinsonian rats. BDNF decreased in the SNc of the SED group, and exercise was able to revert that effect. Exercised groups exhibited reduced damage to the dopaminergic system, detected as a decreased drop of TH levels in SNc and CPu. On the other hand, BDNF blockade was capable of substantially reducing TH expression postlesion, implying enhanced dopaminergic cell loss. Our data revealed that physical exercise is capable of reducing the damage induced by 6-OHDA, and that BDNF receptors are involved in that effect.

Unconventional neurotransmitters, neurodegeneration and neuroprotection.

Neurotransmitters are also involved in functions other than conventional signal transfer between nerve cells, such as development, plasticity, neurodegeneration, and neuroprotection. For example, there is a considerable amount of data indicating developmental roles for the glutamatergic, cholinergic, dopaminergic, GABA-ergic, and ATP/adenosine systems. In this review, we discuss the existing literature on these 'new' functions of neurotransmitters in relation to some unconventional neurotransmitters, such as the endocannabinoids and nitric oxide. Data indicating both transcriptional and post-transcriptional modulation of endocannabinoid and nitrinergic systems after neural lesions are discussed in relation to the non-conventional roles of these neurotransmitters. Knowledge of the roles of neurotransmitters in brain functions other than information transfer is critical for a more complete understanding of the functional organization of the brain and to provide more opportunities for the development of therapeutical tools aimed at minimizing neuronal death.

Unconventional neurotransmitters, neurodegeneration and neuroprotection

Neurotransmitters are also involved in functions other than conventional signal transfer between nerve cells, such as development, plasticity, neurodegeneration, and neuroprotection. For example, there is a considerable amount of data indicating developmental roles for the glutamatergic, cholinergic, dopaminergic, GABA-ergic, and ATP/adenosine systems. In this review, we discuss the existing literature on these "new" functions of neurotransmitters in relation to some unconventional neurotransmitters, such as the endocannabinoids and nitric oxide. Data indicating both transcriptional and post-transcriptional modulation of endocannabinoid and nitrinergic systems after neural lesions are discussed in relation to the non-conventional roles of these neurotransmitters. Knowledge of the roles of neurotransmitters in brain functions other than information transfer is critical for a more complete understanding of the functional organization of the brain and to provide more opportunities for the development of therapeutical tools aimed at minimizing neuronal death.

Expression of alpha-synuclein is increased in the hippocampus of rats with high levels of innate anxiety.

A genomic region neighboring the alpha-synuclein gene, on rat chromosome 4, has been associated with anxiety- and alcohol-related behaviors in different rat strains. In this study, we have investigated potential molecular and physiological links between alpha-synuclein and the behavioral differences observed between Lewis (LEW) and Spontaneously Hypertensive (SHR) inbred rats, a genetic model of anxiety. As expected, LEW rats appeared more fearful than SHR rats in three anxiety models: open field, elevated plus maze and light/dark box. Moreover, LEW rats displayed a higher preference for alcohol and consumed higher quantities of alcohol than SHR rats. alpha-Synuclein mRNA and protein concentrations were higher in the hippocampus, but not the hypothalamus of LEW rats. This result inversely correlated with differences in dopamine turnover in the hippocampus of LEW and SHR rats, supporting the hypothesis that alpha-synuclein is important in the downregulation of dopamine neurotransmission. A novel single nucleotide polymorphism was identified in the 3'-untranslated region (3'-UTR) of the alpha-synuclein cDNA between these two rat strains. Plasmid constructs based on the LEW 3'-UTR sequence displayed increased expression of a reporter gene in transiently transfected PC12 cells, in accordance with in-vivo findings, suggesting that this nucleotide exchange might participate in the differential expression of alpha-synuclein between LEW and SHR rats. These results are consistent with a novel role for alpha-synuclein in modulating rat anxiety-like behaviors, possibly through dopaminergic mechanisms. Since the behavioral and genetic differences between these two strains are the product of independent evolutionary histories, the possibility that polymorphisms in the alpha-synuclein gene may be associated with vulnerability to anxiety-related disorders in humans requires further investigation.

Frequent occurrence of nicotinic acetylcholine receptors in GABAergic neurons of the chick visual system.

Double-labeling immunohistochemical methods were used to investigate the occurrence of the alpha8 and alpha5 nicotinic receptor subunits in presumptive GABAergic neurons of the chick nervous system. Nicotinic receptor immunoreactivity was often found in cells exhibiting GABA-like immunoreactivity, especially in the visual system. The alpha8 subunit appeared to be present in presumptive GABAergic cells of the ventral lateral geniculate nucleus, nucleus of the basal optic root of the accessory optic system, and the optic tectum, among several other structures. The alpha5 subunit was also found in GABA-positive neurons, as observed in the lentiform nucleus of the mesencephalon and other pretectal nuclei. The numbers of alpha8- and alpha5-positive neurons that were also GABA-positive represented high percentages of the total number of neurons containing nicotinic receptor labeling in several brain areas, which indicates that most of the alpha8 and alpha5 nicotinic receptor subunits are present in GABAergic cells. Taken together with data from other studies, our results indicate an important role of the nicotinic acetylcholine receptors in the functional organization of GABAergic circuits in the visual system.

Frequent occurrence of nicotinic acetylcholine receptors in GABAergic neurons of the chick visual system

Double-labeling immunohistochemical methods were used to investigate the occurrence of the alpha8 and alpha5 nicotinic receptor subunits in presumptive GABAergic neurons of the chick nervous system. Nicotinic receptor immunoreactivity was often found in cells exhibiting GABA-like immunoreactivity, especially in the visual system. The alpha8 subunit appeared to be present in presumptive GABAergic cells of the ventral lateral geniculate nucleus, nucleus of the basal optic root of the accessory optic system, and the optic tectum, among several other structures. The alpha5 subunit was also found in GABA-positive neurons, as observed in the lentiform nucleus of the mesencephalon and other pretectal nuclei. The numbers of alpha8- and alpha5-positive neurons that were also GABA-positive represented high percentages of the total number of neurons containing nicotinic receptor labeling in several brain areas, which indicates that most of the alpha8 and alpha5 nicotinic receptor subunits are present in GABAergic cells. Taken together with data from other studies, our results indicate an important role of the nicotinic acetylcholine receptors in the functional organization of GABAergic circuits in the visual system

Differential localization of acetylcholinesterase in relation to pre- and postsynaptic nicotinic receptors in the chick brain.

Immunofluorescence and confocal microscopy were combined to study the distribution of acetylcholinesterase in relation to the localization of the beta2 subunit of the nicotinic acetylcholine receptors in the chick brain. In several areas where the beta2 subunit is recognizably part of presynaptic receptors, the localization of acetylcholinesterase appeared not to overlap the localization of beta2. On the other hand, acetylcholinesterase and the beta2 subunit exhibited a strictly matching localization in areas where postsynaptic nicotinic receptors are known to be present. These data may represent a morphological substrate for possible differential actions of acetylcholinesterase at presynaptic and postsynaptic nicotinic sites.

Expression of cholinergic system molecules during development of the chick nervous system.

There are suggestions of the participation of nicotinic acetylcholine receptors (nAChRs), the acetylcholine degradation enzyme, acetylcholinesterase (AChE), and the acetylcholine synthesizing enzyme, choline acetyltransferase (ChAT), in the development of the nervous system. In this study, we aimed at comparing the development of some subunits of the nAChRs, AChE, and ChAT in the chick nervous system by standard immunohistochemical methods. The expression of all molecules investigated here appeared very early in ganglia (embryonic day 3.5-4), persisting into posthatching, except for ChAT, which is not detected after hatching in ganglia. A differential development was observed for nAChR subunits, with these receptors appearing around embryonic day 6 in some sites. The time-course of development of different nAChR subunits revealed several instances of transient expression (such as in the cerebellum), increasing expression (such as in the nucleus spiriformis lateralis), and diminishing expression into posthatching stages (such as in the oculomotor and throclear nuclei). Expression of AChE and ChAT also starts around embryonic day 6 in some structures and follows mainly increasing time-courses in the chick brain. The results of this study reveal a developmentally regulated expression of cholinergic system-related molecules in the chick nervous system and characterize differential time-courses of expression for nAChR subunits, AChE, and ChAT during development.

Effects of cholinergic deafferentation upon the expression of the alpha2 subunit of the nicotinic acetylcholine receptors in the chick lateral spiriform nucleus.

Lesion, immunohistochemical, and immunoblotting methods were used to evaluate the effects of cholinergic deafferentation upon the expression of the alpha2 subunit of the nicotinic acetylcholine receptors in the lateral spiriform nucleus (SpL) of the chick brain. The expression of the alpha2 subunit in the SpL showed biphasic changes after lesion of its cholinergic source (nucleus semilunaris), with an increase after 2 days postlesion and a decrease after 3-7 days. Our results could represent a correlate of the phenomena of nicotinic receptor up- and down-regulation, induced by removal of the cholinergic input.

A comparative non-radioactive in situ hybridization and immunohistochemical study of the distribution of alpha7 and alpha8 subunits of the nicotinic acetylcholine receptors in visual areas of the chick brain.

The distribution of mRNA transcripts corresponding to the alpha7 and alpha8 subunits of the nicotinic acetylcholine receptors (nAChRs) was studied in selected structures of the chick visual system with non-radioactive in situ hybridization and immunohistochemical techniques. The results indicated that the alpha7 and alpha8 nAChR transcripts are widely distributed in the brain, exhibiting differential expression in some structures but also some degree of co-localization. The pattern of localization of alpha7 and alpha8 nAChR transcripts was highly correlated with immunohistochemical data, with very few instances of possible mismatches between the distribution of mRNAs and their corresponding proteins.

Distribution of the alfa2, alfa3, and alfa5 nicotinic acetylcholine receptor subunits in the chick brain

Nicotinic acetylcholine receptors (nAChRs) are ionotropic receptors comprised of alpha and beta subunits. These receptors are widely distributed in the central nervous system, and previous studies have revealed specific patterns of localization for some nAChR subunits in the vertebrate brain. In the present study we used immunohistochemical methods and monoclonal antibodies to localize the alpha2, alpha3, and alpha5 nAChR subunits in the chick mesencephalon and diencephalon. We observed a differential distribution of these three subunits in the chick brain, and showed that the somata and neuropil of many central structures contain the alpha5 nAChR subunit. The alpha2 and alpha3 subunits, on the other hand, exhibited a more restricted distribution than alpha5 and other subunits previously studied, namely alpha7, alpha8 and beta2. The patterns of distribution of the different nAChR subunits suggest that neurons in many brain structures may contain several subtypes of nAChRs and that in a few regions one particular subtype may determine the cholinergic nicotinic responses.

Distribution of the alpha 2, alpha 3, and alpha 5 nicotinic acetylcholine receptor subunits in the chick brain.

Nicotinic acetylcholine receptors (nAChRs) are ionotropic receptors comprised of alpha and beta subunits. These receptors are widely distributed in the central nervous system, and previous studies have revealed specific patterns of localization for some nAChR subunits in the vertebrate brain. In the present study we used immunohistochemical methods and monoclonal antibodies to localize the alpha 2, alpha 3, alpha 5 nAChR subunits in the chick mesencephalon and diencephalon. We observed a differential distribution of these three subunits in the chick brain, and showed that the somata and neuropil of many central structures contain the alpha 5 nAChR subunit. The alpha 2 and alpha 3 subunits, on the other hand, exhibited a more restricted distribution than alpha 5 and other subunits previously studies, namely alpha 7, alpha 8 and beta 2. The patterns of distribution of the different nAChR subunits suggest that neurons in many brain structures may contain several subtypes of nAChRs and that in a few regions one particular subtype may determine the cholinergic nicotinic responses.

Presumptive presynaptic nicotinic acetylcholine receptors in the chick tectum: effects of lesions of the lateral spiriform nucleus.

There are indications that nicotinic acetylcholine receptor subunits in the superficial layers of the chick tectum (Cajal's layers 1-7) may be transported from the retina. However, nicotinic receptor subunits are detectable by immunohistochemistry in all layers of the optic tectum. In this study, we performed unilateral electrolytic lesions of the lateral spiriform nucleus, which projects to the deep layers of the tectum and contains high amounts of nicotinic receptors in its perikarya. Following lesions of the lateral spiriform nucleus, both the alpha 5 and the beta 2 subunits were markedly depleted in the neuropil of the deep layers of the ipsilateral optic tectum (layers 8-13). No changes were observed in somata that contain either subunit. The present results suggest that most of the nicotinic acetylcholine receptor subunits in the chick optic tectum occur in axonal systems and could then constitute presynaptic receptors.

Effects of retinal lesions upon the distribution of nicotinic acetylcholine receptor subunits in the chick visual system.

Immunohistochemistry was used in this study to evaluate the effects of retinal lesions upon the distribution of neuronal nicotinic acetylcholine receptor subunits in the chick visual system. Following unilateral retinal lesions, the neuropil staining with an antibody against the beta 2 receptor subunit, a major component of alpha-bungarotoxin-insensitive nicotinic receptors, was dramatically reduced or completely eliminated in all of the contralateral retinorecipient structures. On the other hand, neuropil staining with antibodies against two alpha-bungarotoxin-sensitive receptor subunits, alpha 7 and alpha 8, was only slightly affected after retinal lesions. Decreased neuropil staining for alpha 7-like immunoreactivity was only observed in the nucleus of the basal optic root and layers 2-4 and 7 of the optic tectum. For alpha 8-like immunoreactivity, slight reduction of neuropil staining could be observed in the ventral geniculate complex, griseum tecti, nucleus lateralis anterior, nucleus lentiformis mesencephali, layers 4 and 7 of the tectum, and nucleus suprachiasmaticus. Taken together with previous data on the localization of nicotinic receptors in the retina, the present results indicate that the beta 2 subunit is transported from retinal ganglion cells to their central targets, whereas the alpha 7 and alpha 8 subunit immunoreactivity appears to have a central origin. The source of these immunoreactivities could be, at least in part, the stained perikarya that were observed to contain alpha 7 and alpha 8 subunits in all retinorecipient areas. In agreement with this hypothesis, the beta 2 subunit of the nicotinic acetylcholine receptors was not frequently found in perikarya of the same areas.