Éva Keller

Estrogen Receptor Gene Expression in Relation to Neuropsychiatric Disorders

Abstract: Compelling evidence now exists for estrogens involvement in the regulation of mood and cognitive functions. Serum estrogen levels have been shown to play an important role in the expression of psychiatric disorders such as depression and schizophrenia. We have characterized the distribution of the estrogen receptors, ERα and ERβ, in the human brain and showed a preferential limbic‐related expression pattern for these transcripts. The ERα mRNA dominates in the amygdala and hypothalamus, suggesting estrogen modulation of autonomic and neuroendocrine as well as emotional functions. In contrast, the hippocampal formation, entorhinal cortex, and thalamus appear to be ERβ‐dominant areas, suggesting a role for ERβ in cognition, non‐emotional memory, and motor functions. The role of estradiol can also be examined in regard to its relationship to other neurotransmitter systems known to be linked to specific psychiatric disorders. Estradiol has been shown to regulate the serotonin (5‐HT) system, which has been strongly implicated in affective disorders. We have studied a genetic animal model of depression, and found altered 5‐HT receptor mRNA levels in discrete brain regions; many of the abnormalities are reversed by estradiol treatment, especially for the 5‐HT2A receptor subtype. The norepinephrine (NE) system is, similar to serotonin, a target for antidepressant drugs, and projects to mesocorticolimbic structures implicated in mood disorders. We have recently observed that NE neurons in the human locus coeruleus (LC) express moderate levels of both ER transcripts. The possibility of estrogens regulating LC function has been documented in animal studies. Results from our preliminary experiments have revealed that the ERβ mRNA is decreased in persons committing suicide, a cause of death that is highly linked to affective disorder. Follow‐up studies are currently under way with a much larger population to validate these results. Overall, the discrete anatomical organization of the ER mRNAs in the human brain provide evidence as to the specific neuronal populations in which the actions of ERs could modulate mood and thus underlie the neuropathology of psychiatric disorders such as depression.

The human forebrain has discrete estrogen receptor α messenger RNA expression : High levels in the amygdaloid complex

Estrogen is considered to play an important role in neuropsychiatric disorders and the estrogen receptors mediate the action of the hormone. In the present study, the messenger RNA expression pattern of the estrogen receptor alpha subtype was identified in the post mortem human brain. High stringent in situ hybridization histochemistry was performed using a riboprobe specific for the estrogen receptor alpha subtype. The human brain was mainly characterized by abundant estrogen receptor alpha messenger RNA expression in the amygdala and hypothalamus, but labeling (lower) was also found in the extended sublenticular amygdala, cerebral cortex, and hippocampus. In the amygdala, the estrogen receptor alpha messenger RNA was preferentially expressed in medially-localized nuclei suggesting that estrogen regulates distinct human amygdala-mediated functions. The Cynomologous monkey brain was also examined in the present study and a similar distribution of the estrogen receptor alpha messenger RNA signal was observed in the human and monkey brain. However, the primate expression pattern differed in part from the known distribution in the rat. The current results show that estrogen receptor alpha messenger RNA is expressed in discrete areas of the human brain not only related to neuroendocrine function, but also emotion, memory, and cognition, which is consistent with the hypothesized involvement of estrogen in schizophrenia, affective disorders, and Alzheimers disease.

Preferential limbic expression of the cannabinoid receptor mRNA in the human fetal brain

The cannabinoid receptor one (CB1) is responsible for the effects of cannabis on motor and cognitive function in the CNS. There is to date very limited information about the CB1 gene expression in the human brain, in particular during fetal development. In the present study, in situ hybridization experiments were used to examine the microscopic and macroscopic organization of the CB1 mRNA expression in normal human fetal (approximately 20 weeks of development) and adult brains. The fetal brain showed a distinct heterogeneous pattern of the CB1 mRNA expression which was low to moderate in many brain areas. The most striking feature of the fetal brain was the intense expression in the hippocampal CA region and basal nuclear group of the amygdaloid complex. Many of the same brain areas that showed positive expression of the CB1 mRNA in the fetal brain also expressed the gene in the adult brain. However, aside from an intense expression in the hippocampus which resembled that in fetal brain, the adult brain showed very high expression throughout the cerebral cortex, caudate nucleus, putamen and cerebellar cortex. These results document a different pattern of the anatomical organization of the CB1 mRNA expression in the mid-gestation fetal and adult human brain. Overall, the high CB1 mRNA expression in the fetal hippocampus and amygdala indicates that these limbic structures might be most vulnerable to prenatal cannabis exposure.

Activated MAO-B in the brain of Alzheimer patients, demonstrated by [11C]-L-deprenyl using whole hemisphere autoradiography

In the human brain the monoaminooxidase-B enzyme or MAO-B is highly abundant in astrocytes. As astrocyte activity and, consequently, the activity of the MAO-B enzyme, is up-regulated in neuroinflammatory processes, radiolabelled analogues of deprenyl may serve as an imaging biomarker in neuroinflammation and neurodegeneration, including Alzheimers disease. In the present study [(11)C]-L-deprenyl, the PET radioligand version of L-deprenyl or selegiline®, a selective irreversible MAO-B inhibitor was used in whole hemisphere autoradiographic experiments in human brain sections in order to test the radioligands binding to the MAO-B enzyme in human brain tissue, with an eye on exploring the radioligands applicability as a molecular imaging biomarker in human PET studies, with special regard to diagnostic detection of reactive astrogliosis. Whole hemisphere brain sections obtained from Alzheimer patients and from age matched control subjects were examined. In control brains the binding of [(11)C]-L-deprenyl was the highest in the hippocampus, in the basal ganglia, the thalamus, the substantia nigra, the corpus geniculatum laterale, the nucleus accumbens and the periventricular grey matter. In Alzheimer brains significantly higher binding was observed in the temporal lobes and the white matter. Furthermore, in the Alzheimer brains in the hippocampus, temporal lobe and white matter the binding negatively correlated with Braak stages. The highest binding was observed in Braak I-II, whereas it decreased with increasing Braak grades. The increased regional binding in Alzheimer brains coincided with the presence of an increased number of activated astrocytes, as demonstrated by correlative immunohistochemical studies with GFAP in adjacent brain slices. Deprenyl itself as well as the MAO-B antagonist rasagiline did effectively block the binding of the radioligand, whereas the MAO-A antagonist pirlindole did not affect it. Compounds with high affinity for the PBR system did not block the radioligand binding either, providing evidence for the specificity of [(11)C]-L-deprenyl for the MAO-B enzyme. In conclusion, the present observations indicate that [(11)C]-L-deprenyl may be a promising and selective imaging biomarker of increased MAO-B activity in the human brain and can therefore serve as a prospective PET tracer targeting neuroinflammation and neurodegeneration.

Mu opioid receptor A118G polymorphism in association with striatal opioid neuropeptide gene expression in heroin abusers.

μ Opioid receptors are critical for heroin dependence, and A118G SNP of the μ opioid receptor gene (OPRM1) has been linked with heroin abuse. In our population of European Caucasians (n = 118), ≈90% of 118G allelic carriers were heroin users. Postmortem brain analyses showed the OPRM1 genotype associated with transcription, translation, and processing of the human striatal opioid neuropeptide system. Whereas down-regulation of preproenkephalin and preprodynorphin genes was evident in all heroin users, the effects were exaggerated in 118G subjects and were most prominent for preproenkephalin in the nucleus accumbens shell. Reduced opioid neuropeptide transcription was accompanied by increased dynorphin and enkephalin peptide concentrations exclusively in 118G heroin subjects, suggesting that the peptide processing is associated with the OPRM1 genotype. Abnormal gene expression related to peptide convertase and ubiquitin/proteosome regulation was also evident in heroin users. Taken together, alterations in opioid neuropeptide systems might underlie enhanced opiate abuse vulnerability apparent in 118G individuals.

The human brain has distinct regional expression patterns of estrogen receptor α mRNA isoforms derived from alternative promoters

Abstract: The human estrogen receptor (ER) α gene is transcribed from multiple promoters, generating mRNA isoforms with unique 5′ ends in the untranslated region. In the present study, alternative promoters were shown to regulate the ERα gene expression in different neuronal populations of the human brain. By using in situ hybridization histochemistry, the A and B promoters, but not the C promoter, in the ERα gene were found to be active in the human forebrain. The mRNA isoform transcribed from the A promoter was expressed in low levels in most of the brain areas where ERα mRNA was present. In contrast, the B promoter mRNA isoform was more restricted, localized predominantly in high‐expressing ERα mRNA regions. The gross anatomical distribution of the different mRNA isoforms analyzed with RT‐PCR generally supported the results obtained by the in situ hybridization. Estrogen is known to modulate many different brain functions, such as neuroendocrine events associated with reproduction, mood, and cognition, likely to be mediated by different neuronal populations. Thus, the current findings of alternative ERα promoter expression in distinct neuronal populations suggest that multiple promoter usage is a possible mechanism to achieve differentiated regulation of the ERα expression, dependent on the cell phenotype and consequently the functions mediated by the specific neuron.

Opioid neuropeptide genotypes in relation to heroin abuse: Dopamine tone contributes to reversed mesolimbic proenkephalin expression

Striatal enkephalin and dynorphin opioid systems mediate reward and negative affect, respectively, relevant to addiction disorders. We examined polymorphisms of proenkephalin (PENK) and prodynorphin (PDYN) genes in relation to heroin abuse and gene expression in the human striatum and the relevance of genetic dopaminergic tone, critical for drug reward and striatal function. Heroin abuse was significantly associated with PENK polymorphic 3′ UTR dinucleotide (CA) repeats; 79% of subjects homozygous for the 79-bp allele were heroin abusers. Such individuals tended to express higher PENK mRNA than the 81-bp homozygotes, but PENK levels within the nucleus accumbens (NAc) shell were most strongly correlated to catecholamine-O-methyltransferase (COMT) genotype. Control Met/Met individuals expressed lower PENK mRNA than Val carriers, a pattern reversed in heroin users. Up-regulation of NAc PENK in Met/Met heroin abusers was accompanied by impaired tyrosine hydroxylase (TH) mRNA expression in mesolimbic dopamine neurons. In contrast to PENK, no association was detected between PDYN genotype (68-bp repeat element containing one to four copies of AP-1 binding sites in the promoter region) and heroin abuse, although there was a clear functional association with striatal PDYN mRNA expression: an increased number of inducible repeats (three and four) correlated with higher PDYN levels than adult or fetal subjects with noninducible (one and two) alleles. Moreover, PDYN expression was not related to COMT genotype. Altogether, the data suggest that dysfunction of the opioid reward system is significantly linked to opiate abuse vulnerability and that heroin use alters the apparent influence of heritable dopamine tone on mesolimbic PENK and TH function.

Preprotachykinin-A mRNA expression in the human and monkey brain: An in situ hybridization study

The mRNA expression for preprotachykinin‐A (PPT‐A) was studied throughout the human and cynomolgus monkey brain to assess the neuroanatomical expression pattern of the PPT‐A gene in primates. In situ hybridization showed that the PPT‐A mRNA is expressed highly in specific regions of the postmortem human brain, including the striatum, islands of Calleja, hypothalamus (posterior, premammillary, medial mammillary, and ventromedial nuclei), superior and inferior colliculi, periaqueductal gray, and oculomotor nuclear complex. PPT‐A mRNA‐expressing neurons also were present in the paranigralis (ventral tegmental area) and were scattered in the bed nucleus stria terminalis throughout the sublenticular substantia innominata region, including the diagonal band of Broca and the nucleus basalis of Meynert. In the hippocampus, high PPT‐A mRNA expression was localized predominantly to the polymorphic layer of the dentate gyrus; no labeled cells were present in the granular layer. Positively labeled cells also were found scattered in the CA regions as well as in the amygdaloid complex. Neocortical expression of PPT‐A mRNA was localized mainly to the deep laminae (layers V/VI), except for the striate cortex (labeling was seen also in superficial layers). The subiculum, thalamus, globus pallidus, ventral pallidum, substantia nigra pars compacta, red nucleus, pontine nuclei, and cerebellum were characterized by very weak to undetectable expression of PPT‐A mRNA. An expression pattern was evident in the monkey forebrain similar to that observed in the human, except for the absence of PPT mRNA‐expressing cells in the medial mammillary nucleus despite intense expression in supramammillary, lateral mammillary, and premammillary nuclei. Overall, more similarities than differences are apparent between primate species in the expression pattern of the PPT‐A gene. J. Comp. Neurol. 411;56–72, 1999.

Dysregulated postsynaptic density and endocytic zone in the amygdala of human heroin and cocaine abusers.

BACKGROUND Glutamatergic transmission in the amygdala is hypothesized as an important mediator of stimulus-reward associations contributing to drug-seeking behavior and relapse. Insight is, however, lacking regarding the amygdala glutamatergic system in human drug abusers. METHODS We examined glutamate receptors and scaffolding proteins associated with the postsynaptic density in the human postmortem amygdala. Messenger RNA or protein levels were studied in a population of multidrug (seven heroin, eight cocaine, seven heroin/cocaine, and seven controls) or predominant heroin (29 heroin and 15 controls) subjects. RESULTS The amygdala of drug abusers was characterized by a striking positive correlation (r > .8) between α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid glutamate receptor subunit 1 (GluA1) and postsynaptic density protein-95 (PSD-95) mRNA levels, which was not evident in control subjects. Structural equation multigroup analysis of protein correlations also identified the relationship between GluA1 and PSD-95 protein levels as the distinguishing feature of abusers. In line with the GluA1-PSD-95 implications of enhanced synaptic plasticity, Homer 1b/c protein expression was increased in both heroin and cocaine users as was its binding partner, dynamin-3. Furthermore, there was a positive relationship between Homer 1b/c and dynamin-3 in drug abusers that reflected an increase in the direct physical coupling between the proteins. A noted age-related decline of Homer 1b/c-dynamin-3 interactions, as well as GluA1 levels, was blunted in abusers. CONCLUSIONS Impairment of key components of the amygdala postsynaptic density and coupling to the endocytic zone, critical for the regulation of glutamate receptor cycling, may underlie heightened synaptic plasticity in human drug abusers.

Evaluation of meteorological factors on sudden cardiovascular death

Climatic and seasonal triggering factors have received an increasing attention among risk factors of sudden cardiac death. The relationship between cold weather conditions and ischemic heart disease death is well established. In this study, there were 7450 (4967 males, 2483 females) cardiovascular death cases medico-legally autopsied between 1995 and 2004. In most of the cases (76%) cardiac death occurred at the scene, and 17% had acute ischemic heart disease. In order to examine the relationship between daily maximum, minimum and mean temperature, air humidity, air pressure, wind speed, global radiation and the daily numbers of death cases, statistical analysis were accomplished using correlation coefficients, and Box-Whisker-plot diagrams. A significant negative correlation was detected between daily mean temperature and cardiovascular mortality. A remarkable seasonal variation was found. Cold and dry weather may be an important risk factor in bringing on the onset of sudden cardiac death.