Reduced Neuropeptide Y Concentrations in Suicide Brain

Neuropeptide Y (NPY) was measured in postmortem brain tissue from victims of suicide and from individuals dying a sudden natural or accidental death (controls). Concentrations of NPY-immunoreactivity were measured by radioimmunoassay in frontal cortex (BA 10), temporal cortex (BA 22), caudate nucleus, and cerebellum. Concentrations of NPY-immunoreactivity were significantly lower in postmortem frontal cortex (-14%) and caudate nucleus (-27%) from suicide victims compared with age-matched controls. A subgroup of suicides with evidence of a history of depression revealed more robust reductions in concentrations of NPY-immunoreactivity in frontal cortex and caudate nucleus, as did four individuals who died from natural causes and also were described as having a possible history of depression. Concentrations of NPY-immunoreactivity in temporal cortex and cerebellum from victims of suicide or from the subgroup of subjects with a possible history of depression were not significantly different from those of age-matched controls. We suggest there is a deficit in the brain NPY system leading to region-specific reductions in peptide concentrations in subjects who have a history of depression.     

Enhanced Rate of Expression and Biosynthesis of Neuropeptide Y After Kainic Acid-Induced Seizures

Recent studies have shown marked increases in brain content of neuropeptide Y (NPY) after seizures induced by intraperitoneal injection of kainic acid and after pentylenetetrazole kindling in the rat. We have now investigated possible changes in the rate of biosynthesis of NPY after kainic acid treatment, by using pulse-labeling of the peptide and by determining prepro-NPY mRNA concentrations. For pulse labeling experiments, [3H]tyrosine was injected into the frontal cortex, and the incorporation of the amino acid into NPY was determined after purifying the peptide by gel filtration chromatography, antibody affinity chromatography, and reversed-phase HPLC. At 2 and 30 days after kainic acid treatment, the rate of tyrosine incorporation was enhanced by approximately 380% in the cortex. In addition, concentrations of pre-pro-NPY mRNA were determined in four different brain areas by hybridization of Northern blots with a complementary 32P-labeled RNA probe 2, 10, 30, and 60 days after kainic acid treatment. Marked increases were observed in the frontal cortex (by up to 350% of controls), in the dorsal hippocampus (by 750%), and in the amygdala/pyriform cortex (by 280%) at all intervals investigated. In the striatum only a small, transient increase was observed. The data demonstrate increased expression of prepro-NPY mRNA and an enhanced rate of in vivo synthesis of NPY as a result of seizures induced by the neurotoxin kainic acid.     

Epigenomic profiling reveals DNA-methylation changes associated with major psychosis

Epigenetic misregulation is consistent with various non-Mendelian features of schizophrenia and bipolar disorder. To date, however, few studies have investigated the role of DNA methylation in major psychosis, and none have taken a genome-wide epigenomic approach. In this study we used CpG-island microarrays to identify DNA-methylation changes in the frontal cortex and germline associated with schizophrenia and bipolar disorder. In the frontal cortex we find evidence for psychosis-associated DNA-methylation differences in numerous loci, including several involved in glutamatergic and GABAergic neurotransmission, brain development, and other processes functionally linked to disease etiology. DNA-methylation changes in a significant proportion of these loci correspond to reported changes of steady-state mRNA level associated with psychosis. Gene-ontology analysis highlighted epigenetic disruption to loci involved in mitochondrial function, brain development, and stress response. Methylome network analysis uncovered decreased epigenetic modularity in both the brain and the germline of affected individuals, suggesting that systemic epigenetic dysfunction may be associated with major psychosis. We also report evidence for a strong correlation between DNA methylation in the MEK1 gene promoter region and lifetime antipsychotic use in schizophrenia patients. Finally, we observe that frontal-cortex DNA methylation in the BDNF gene is correlated with genotype at a nearby nonsynonymous SNP that has been previously associated with major psychosis. Our data are consistent with the epigenetic theory of major psychosis and suggest that DNA-methylation changes are important to the etiology of schizophrenia and bipolar disorder.     

Decreased expression of Sprouty2 in the dorsolateral prefrontal cortex in schizophrenia and bipolar disorder: a correlation with BDNF expression

Background

Current theories on the pathophysiology of schizophrenia suggest altered brain plasticity such as decreased neural proliferation and migration, delayed myelination, and abnormal synaptic modeling, in the brain of subjects with schizophrenia. Though functional alterations in BDNF, which plays important role in neuroplasticity, are implicated in many abnormalities found in schizophrenia, the regulatory mechanism(s) involved in the abnormal signaling of BDNF in schizophrenia is not clear. The present study investigated whether Sprouty2, a regulator of growth factor signaling, is abnormally expressed in schizophrenia, and is associated with the changes in BDNF mRNA in this disorder. The potential effect of antipsychotic drugs on Sprouty2 expression was tested in adult rats.

Methods and Findings

Sprouty2 and BDNF gene expression were analyzed in dorsolateral prefrontal cortex samples from the Stanley Array Collection. Quantitative real-time PCR analysis of RNA in 100 individuals (35 with schizophrenia, 31 with bipolar disorder, and 34 psychiatrically normal controls) showed significantly decreased expression of Sprouty2 and BDNF in both schizophrenia and bipolar disorder. Moreover, a significant correlation between these two genes existed in control, schizophrenia and bipolar subjects. Long-term treatment with antipsychotic drugs, haloperidol and olanzapine, showed differential effects on both Sprouty2 and BDNF mRNA and protein levels in the frontal cortex of rats.

Conclusion

These findings demonstrating decreased expression of Sprouty2 associated with changes in BDNF, suggest the possibility that these decreases are secondary to treatment rather than to factors that are significant in the disease process of either schizophrenia and/or bipolar disorder. Further exploration of Sprouty2-related signal transduction pathways may be helpful to design novel treatment strategies for these disorders.     

Phosphodiesterases PDE2A and PDE10A both change mRNA expression in the human brain with age,but only PDE2A changes in a region-specific manner with psychiatric disease

Many studies implicate altered cyclic nucleotide signaling in the pathophysiology of major depressive disorder (MDD), bipolar disorder (BPD), and schizophrenia (SCZ). As such, we explored how phosphodiesterases 2A (PDE2A) and 10A (PDE10A)—enzymes that break down cyclic nucleotides—may be altered in brains of these patients. Using autoradiographic in situ hybridization on postmortem brain tissue from the Stanley Foundation Neuropathology Consortium, we measured expression of PDE2 and PDE10 mRNA in multiple brain regions implicated in psychiatric pathophysiology, including cingulate cortex, orbital frontal cortex (OFC), superior temporal gyrus, hippocampus, parahippocampal cortex, amygdala, and the striatum. We also assessed how PDE2A and PDE10A expression changes in these brain regions across development using the Allen Institute for Brain Science Brainspan database. Compared to controls, patients with SCZ, MDD and BPD all showed reduced PDE2A mRNA in the amygdala. In contrast, PDE2A expression changes in frontal cortical regions were only significant in patients with SCZ, while those in caudal entorhinal cortex, hippocampus, and the striatum were most pronounced in patients with BPD. PDE10A expression was only detected in striatum and did not differ by disease group; however, all groups showed significantly less PDE10A mRNA expression in ventral versus dorsal striatum. Across development, PDE2A mRNA increased in these brain regions; whereas, PDE10A mRNA expression decreased in all regions except striatum. Thus, PDE2A mRNA expression changes in both a disorder- and brain region-specific manner, potentially implicating PDE2A as a novel diagnostic and/or patient-selection biomarker or therapeutic target.     

Decrease of hypothalamic neuropeptide Y gene expression by vanadyl sulfate in streptozotocin-induced diabetic rats.

In an attempt to elucidate the effect of vanadium compounds on the gene expression of neuropeptide Y (NPY), vanadyl sulfate (VOSO4) was orally administrated at the dose of 1 mg/kg body weight into streptozotocin-induced diabetic rats (STZ-diabetic rats) three times daily for 1 week. We found a marked lowering of plasma glucose with a significant decrease of food and water intake in these STZ-diabetic rats treated with VOSO4, although the weight gain was unaffected. The increase of hypothalamic NPY, both the mRNA level and peptide concentration, in STZ-diabetic rats was also reduced by this oral treatment of VOSO4. However, similar treatment of VOSO4 in normal rats failed to modify the feeding behavior and hypothalamic NPY gene expression. These data suggest that decrease of hypothalamic NPY gene expression by VOSO4 is related to the recovery of hyperphagia in diabetic rats lacking insulin.     

Opposite regulation of hypothalamic orexin and neuropeptide Y receptors and peptide expressions in obese Zucker rats

Many hyothalamic neuropeptides are involved in the regulation of food intake and body weight. The orexins (OX) which are synthesized in the lateral hypothalamus are among the most recently characterized whereas neuropeptide Y (NPY) belongs to a group of "older" peptides extensively studied for their effects on feeding behavior. Both stimulate food ingestion in rodents. In this experiment, we measured the expressions of these peptides as well as of their receptors (OX1-R and OX2-R, Y1 and Y5) in the hypothalamus of obese hyperphagic and lean Zucker rats by real-time RT-PCR using the TaqMan apparatus. NPY mRNA expression in the obese rats was significantly increased by a factor of 10 (P < 0.002) whereas expressions of the Y1 and Y5 receptors were decreased by 25% (P < 0.01) and 50% (P < 0.002), respectively. Their prepro-orexin mRNA expression was more than twofold decreased (P < 0.01) and expressions of their OX receptors 1 and 2 mRNA were five- and fourfold increased (P < 0.05), respectively. An inverse phenomenon was therefore noted between the two peptides: for NPY, increased levels and downregulation of receptors; and for OX, diminished levels with upregulation of receptors. The reasons for these changes might be linked to the absence of leptin signaling as similar profiles are found in the ob/ob mice. For orexins at least, other factors such as hyperglycemia might be involved. Based on anatomical considerations, a direct effect of NPY or of other brain peptides such as CRH cannot be excluded. We conclude that the diminution in the OX tone might participate in a counterregulatory system necessary to limit the noxious effects of NPY on food intake and body weight.     

Chronic Administration of Mood Stabilizers Upregulates BDNF and Bcl-2 Expression Levels in Rat Frontal Cortex

Brain-derived neurotrophic factor (BDNF) and B-cell lymphoma-2 (Bcl-2) proteins are neuroprotective factors involved in neuronal signaling, survival and plasticity. Both can be regulated by cyclic AMP response element binding (CREB) protein. Decreased levels of BDNF and Bcl-2 are implicated in the pathogenesis of bipolar disorder. The present study investigated whether chronically administered mood stabilizers would increase BDNF and/or Bcl-2 levels in rat brain. Real time RT-PCR, sandwich ELISA and Western blotting were used to measure BDNF and Bcl-2 mRNA and protein levels in the frontal cortex of rats chronically administered carbamazepine (CBZ) or lamotrigine (LTG) to produce plasma concentrations therapeutically relevant to bipolar disorder. Chronic CBZ and LTG significantly increased BDNF and Bcl-2 mRNA and protein levels in the frontal cortex. A common mechanism of action of mood stabilizers in the treatment of bipolar disorder may involve neuroprotection mediated by upregulation of brain BDNF and Bcl-2 expression.     

Gray matter deficits in bipolar disorder are associated with genetic variability at interleukin‐1 beta gene (2q13)

Twin, family and recent molecular studies support the hypothesis of genetic overlapping between schizophrenia and bipolar disorder. Brain structural features shared by both psychiatric disorders might be the phenotypic expression of a common genetic risk background. Interleukin‐1 (IL‐1) cluster (chromosome 2q13) genetic variability, previously associated with an increased risk both for schizophrenia and for bipolar disorder, has been also associated with gray matter (GM) deficits, ventricular enlargement and hypoactivity of prefrontal cortex in schizophrenia. The aim of the present study was to analyze the influence of IL‐1 cluster on brain morphology in bipolar disorder. Genetic variability at IL‐1B and IL‐1RN genes was analyzed in 20 DSM‐IV ( Diagnostic and Statistical Manual of Mental Disorders ‐Fourth Edition) bipolar patients. Magnetic resonance imaging (MRI) measurements were obtained for whole‐brain GM and white matter, dorsolateral prefrontal cortex (DLPFC), superior temporal gyrus, hippocampus and lateral ventricles. MRI data were corrected for age and cranial size using regression parameters from a group of 45 healthy subjects. A ?511C/T polymorphism (rs16944) of IL‐1B gene was associated with whole‐brain GM deficits (P = 0.031) and left DLPFCGM deficits (P = 0.047) in bipolar disorder patients. These findings support the hypothesis of IL‐1 cluster variability as a shared genetic risk factor contributing to GM deficits both in bipolar disorder and in schizophrenia. Independent replication in larger samples would be of interest to confirm these results.     

Regulation of food intake by neuropeptide Y in goldfish

In mammals, neuropeptide Y (NPY) is a potent orexigenic factor. In the present study, third brain ventricle (intracerebroventricular) injection of goldfish NPY (gNPY) caused a dose-dependent increase in food intake in goldfish, and intracerebroventricular administration of NPY Y1-receptor antagonist BIBP-3226 decreased food intake; the actions of gNPY were blocked by simultaneous injection of BIBP-3226. Goldfish maintained on a daily scheduled feeding regimen display an increase in NPY mRNA levels in the telencephalon-preoptic area and hypothalamus shortly before feeding; however, a decrease occured in optic tectum-thalamus. In both fed and unfed fish, brain NPY mRNA levels decreased after scheduled feeding. Restriction in daily food ration intake for 1 wk or food deprivation for 72 h resulted in increased brain NPY mRNA levels. Results from these studies demonstrate that NPY is a physiological brain signal involved in feeding behavior in goldfish, mediating its effects, at least in part, through Y1-like receptors in the brain.     

Decreased neuropeptide Y (NPY) expression in the infundibular nucleus of patients with nonthyroidal illness

In patients with a variety of illnesses, serum concentrations of T3 decrease without giving rise to elevated serum levels of TSH, a phenomenon known as the sick euthyroid syndrome or nonthyroidal illness (NTI). Our previous studies in postmortem brain material showed decreased thyrotropin-releasing hormone (TRH) messenger RNA (mRNA) in the paraventricular nucleus (PVN) of patients with NTI, suggesting a role for TRH cells in the persistence of low TSH levels in NTI.In the present study, we hypothesized that changes in neuropeptide Y (NPY) input from the infundibular nucleus (IFN) to TRH cells in the PVN might be a determinant of decreased TRH expression in NTI. We investigated the hypothalamus of nine patients whose endocrine status had been assessed in a serum sample taken less than 24h before death and we examined NPY expression in the IFN by means of immunocytochemistry and mRNA in situ hybridization using an image analysis system. There was a negative correlation (r = -0.88; p = 0.01) between serum leptin concentrations and total NPY mRNA in the IFN. The total amount of NPY immunoreactivity in the IFN correlated with total NPY mRNA (r = 0.69; p = 0.04). In contrast to the situation in food-deprived rodents, total NPY immunoreactivity in the IFN showed a positive correlation with total TRH mRNA in the PVN (r = 0.77; p = 0.02). The results suggest a role for decreased NPY input from the IFN in the resetting of thyroid hormone feedback on hypothalamic TRH cells in NTI.     

Sex differences in neuropeptide distribution in the rat brain

We have investigated possible sex differences in the regional concentrations of neuropeptides in the rat brain. Immunoreactive neurotensin (NT), neurokinin A (NKA), galanin (GAL), calcitonin gene-related peptide (CGRP), substance P (SP) and neuropeptide Y (NPY) were measured by radioimmunoassay in frontal cortex, occipital cortex, hippocampus, striatum, hypothalamus and pituitary in male and female pre- and postpubertal rats. Sex differences were found for NPY (p < 0.001), NT (p < 0.01) and GAL (p < 0.05), in particular in hippocampus, striatum, hypothalamus and pituitary, but not for CGRP, SP and NKA. Results from analysis of neuropeptides in one sex may not be entirely applicable to the other.     

Expression of NPY Y1 and Y5 receptors in the hypothalamic paraventricular nucleus of aged Fischer 344 rats

Many mammals, nearing the end of life, spontaneously decrease their food intake and body weight, a stage we refer to as senescence. The spontaneous decrease in food intake and body weight is associated with attenuated responses to intracerebroventricular injections of neuropeptide Y (NPY) compared with old presenescent or with young adult rats. In the present study, we tested the hypothesis that this blunted responsiveness involves the number and expression of hypothalamic paraventricular nucleus (PVN) Y(1) and/or Y(5) NPY receptors, both of which are thought to mediate NPY-induced food intake. We found no significant difference in mRNA levels, via quantitative PCR, for Y(1) and Y(5) receptors in the PVN of senescent vs. presenescent rats. In contrast, immunohistochemistry indicated that the number of PVN neurons staining for Y(1) receptor protein was greater in presenescent compared with senescent rats. We conclude that a decreased expression and number of Y(1) or Y(5) receptors in the PVN cannot explain the attenuated responsiveness of the senescent rats to exogenous NPY.     

Leptin receptor long-form splice-variant protein expression in neuron cell bodies of the brain and co-localization with neuropeptide Y mRNA in the arcuate nucleus.

Reduced leptin (Ob protein) signaling is proposed to be a stimulus for the activation of neuropeptide Y (NPY) gene activity and increased expression of mRNA for the long form of the leptin receptor (Ob-Rb) in the hypothalamic arcuate nucleus. To determine if Ob-Rb protein is expressed in arcuate nucleus NPY neurons, we developed an affinity-purified polyclonal antibody against amino acids 956-1102 of human Ob-Rb. This antibody specifically recognizes the cytoplasmic tail of Ob-Rb and does not react with shorter leptin-receptor variants. Western immunoblots of Ob-Rb-transfected COS cells showed a single 150-kD band, and immunofluorescence revealed intense perinuclear staining in the cytoplasm. A 150-kD band was also present in Western immunoblots of hypothalamus. Immunocytochemical staining of brain slices revealed immunoreactive Ob-Rb protein concentrated in many neuronal cell bodies in the same regions of the forebrain that also express Ob-Rb mRNA. In the hypothalamus, Ob-Rb-positive cell bodies were abundant in the arcuate nucleus and ventromedial nucleus, with lesser numbers in the dorsomedial nucleus and paraventricular nucleus. Immunostaining was also detected in cell bodies of pyramidal cell neurons of the pyriform cortex and cerebral cortex, in neurons of the thalamus, and on the surface of ependymal cells lining the third ventricle. The choroid plexus, which expresses the short Ob-Ra form, was negative. Combined immunocytochemistry for Ob-Rb protein and fluorescence in situ hybridization for NPY mRNA identified arcuate nucleus neurons containing both NPY mRNA and Ob-Rb protein. The present finding of Ob-Rb protein in neurons that express NPY mRNA supports the hypothesis that arcuate nucleus NPY neurons are direct targets of leptin and play an important role in regulation of food intake and body weight.