Protective role of neuronal and lymphoid cannabinoid CB2 receptors in neuropathic pain.

Cannabinoid CB2 receptor (CB2) agonists are potential analgesics void of psychotropic effects. Peripheral immune cells, neurons and glia express CB2; however, the involvement of CB2 from these cells in neuropathic pain remains unresolved. We explored spontaneous neuropathic pain through on-demand self-administration of the selective CB2 agonist JWH133 in wild-type and knockout mice lacking CB2 in neurons, monocytes or constitutively. Operant self-administration reflected drug-taking to alleviate spontaneous pain, nociceptive and affective manifestations. While constitutive deletion of CB2 disrupted JWH133-taking behavior, this behavior was not modified in monocyte-specific CB2 knockouts and was increased in mice defective in neuronal CB2 knockouts suggestive of increased spontaneous pain. Interestingly, CB2-positive lymphocytes infiltrated the injured nerve and possible CB2transfer from immune cells to neurons was found. Lymphocyte CB2depletion also exacerbated JWH133 self-administration and inhibited antinociception. This work identifies a simultaneous activity of neuronal and lymphoid CB2that protects against spontaneous and evoked neuropathic pain.

Identification of the mitochondrial MSRB2 as a binding partner of LG72.

Genetic studies have linked the evolutionary novel, anthropoid primate-specific gene locus G72/G30 in the etiology of schizophrenia and other psychiatric disorders. However, the function of the protein encoded by this locus, LG72, is currently controversially discussed. Some studies have suggested that LG72 binds to and regulates the activity of the peroxisomal enzyme D-amino-acid-oxidase, while others proposed an alternative role of this protein due to its mitochondrial location in vitro. Studies with transgenic mice expressing LG72 further suggested that high levels of LG72 lead to an impairment of mitochondrial functions with a concomitant increase in reactive oxygen species production. In the present study, we now performed extensive interaction analyses and identified the mitochondrial methionine-R-sulfoxide reductase B2 (MSRB2) as a specific interaction partner of LG72. MSRB2 belongs to the MSR protein family and functions in mitochondrial oxidative stress defense. Based on our results, we propose that LG72 is involved in the regulation of mitochondrial oxidative stress.

Analysis of quantitative trait loci in mice suggests a role of Enoph1 in stress reactivity.

Significant progress in elucidating the genetic etiology of anxiety and depression has been made during the last decade through a combination of human and animal studies. In this study, we aimed to discover genetic loci linked with anxiety as well as depression in order to reveal new candidate genes. Therefore, we initially tested the behavioral sensitivity of 543 F2 animals derived from an intercross of C57BL/6J and C3H/HeJ mice in paradigms for anxiety and depression. Next, all animals were genotyped with 269 microsatellite markers with a mean distance of 5.56 cM. Finally, a Quantitative Trait Loci (QTL) analysis was carried out, followed by selection of candidate genes. The QTL analysis revealed several new QTL on chromosome 5 with a common core interval of 19 Mb. We further narrowed this interval by comparative genomics to a region of 15 Mb. A database search and gene prioritization revealed Enoph1 as the most significant candidate gene on the prioritization list for anxiety and also for depression fulfilling our selection criteria. The Enoph1 gene, which is involved in polyamine biosynthesis, is differently expressed in parental strains, which have different brain spermidine levels and show distinct anxiety and depression-related phenotype. Our result suggests a significant role in polyamines in anxiety and depression-related behaviors.

Involvement of the primate specific gene G72 in schizophrenia: From genetic studies to pathomechanisms.

Schizophrenia is a human mental disorder that affects an individual's thoughts, perception, affect and behavior, which is caused by a complex interaction of genetic and environmental factors. Genetic studies have implicated the evolutionary novel, anthropoid primate-specific gene locus G72/G30 in the etiology of schizophrenia and other psychiatric disorders. This gene encodes the protein LG72, which has been discussed as a modulator of the peroxisomal enzyme d-amino-acid-oxidase (DAO), or, alternatively as a mitochondrial protein. Recently, G72 transgenic (G72Tg) mice were generated that express the protein throughout the brain. These mice show several behavioral deficits that are related to schizophrenia. Further, G72Tg mice have a reduced activity of mitochondrial complex I, with a concomitantly increased production of reactive oxygen species, as well as deficits in short-term plasticity. Results from these studies demonstrate that expression of the human G72/G30 gene locus in mice produces behavioral phenotypes that are relevant to schizophrenia. They implicate LG72-induced mitochondrial and synaptic defects as a possible pathomechanism of this disease.

CC chemokine receptor 4 is required for experimental autoimmune encephalomyelitis by regulating GM-CSF and IL-23 production in dendritic cells.

Dendritic cells (DCs) are pivotal for the development of experimental autoimmune encephalomyelitis (EAE). However, the mechanisms by which they control disease remain to be determined. This study demonstrates that expression of CC chemokine receptor 4 (CCR4) by DCs is required for EAE induction. CCR4(-/-) mice presented enhanced resistance to EAE associated with a reduction in IL-23 and GM-CSF expression in the CNS. Restoring CCR4 on myeloid cells in bone marrow chimeras or intracerebral microinjection of CCR4-competent DCs, but not macrophages, restored EAE in CCR4(-/-) mice, indicating that CCR4(+) DCs are cellular mediators of EAE development. Mechanistically, CCR4(-/-) DCs were less efficient in GM-CSF and IL-23 production and also T(H)-17 maintenance. Intraspinal IL-23 reconstitution restored EAE in CCR4(-/-) mice, whereas intracerebral inoculation using IL-23(-/-) DCs or GM-CSF(-/-) DCs failed to induce disease. Thus, CCR4-dependent GM-CSF production in DCs required for IL-23 release in these cells is a major component in the development of EAE. Our study identified a unique role for CCR4 in regulating DC function in EAE, harboring therapeutic potential for the treatment of CNS autoimmunity by targeting CCR4 on this specific cell type.

Early onset of aging-like changes is restricted to cognitive abilities and skin structure in Cnr1⁻/⁻ mice.

Genetic deletion of the cannabinoid 1 (CB1) receptor leads to an early onset of learning and memory impairment. In the present study we asked whether the lack of CB1 receptors accelerates aging in general or is selective for cognitive functions. We therefore compared the onset and dynamics of age-dependent changes in social memory, locomotor activity, hearing ability, and in the histopathology of peripheral organs between wild-type and Cnr1 knockout (Cnr1(-/-)) mice. We observed deficits in social memory already in 3-month-old Cnr1(-/-) mice. In contrast, wild-type animals showed such deficits at the age of 6 months. Sensory and motor functions were similar between the genotypes. Thus, hearing loss for higher frequencies and the development of hypomotility showed a similar age-dependent course. In the periphery we detected an early onset of aging-like histological changes in the skin, but not in other organs. We conclude that the lack of CB1 receptor does not induce accelerated aging in general, but induces changes in cognitive function and in skin structure that resemble those associated with aging.

N-acetyl cysteine treatment rescues cognitive deficits induced by mitochondrial dysfunction in G72/G30 transgenic mice.

Genetic studies have implicated the evolutionary novel, anthropoid primate-specific gene locus G72/G30 in psychiatric diseases. This gene encodes the protein LG72 that has been discussed to function as a putative activator of the peroxisomal enzyme D-amino-acid-oxidase (DAO) and as a mitochondrial protein. We recently generated 'humanized' bacterial artificial chromosome transgenic mice (G72Tg) expressing G72 transcripts in cells throughout the brain. These mice exhibit several behavioral phenotypes related to psychiatric diseases. Here we show that G72Tg mice have a reduced activity of mitochondrial complex I, with a concomitantly increased production of reactive oxygen species. Affected neurons display deficits in short-term plasticity and an impaired capability to sustain synaptic activity. These deficits lead to an impairment in spatial memory, which can be rescued by pharmacological treatment with the glutathione precursor N-acetyl cysteine. Our results implicate LG72-induced mitochondrial and synaptic defects as a possible pathomechanism of psychiatric disorders.

Modulation of alcohol and nicotine responses through the endogenous opioid system.

It has been estimated that more than 80% of alcoholics are also nicotine dependent and that, vice versa, the rate of alcoholism is substantially increased by a factor of 4-10 in the nicotine-dependent population. However, the cause for this very high degree of comorbidity is still largely unknown. At the molecular and cellular level, both drugs have very different mechanisms of action. Nicotine specifically activates ligand-gated ion channels in the brain, which are normally gated by acetylcholine, while alcohol interacts with various neurotransmitter receptors. Despite this diversity, both drugs seem to engage the endogenous opioid system as a modulator of some of its pharmacological effect. An acute exposure to nicotine or alcohol leads to a release of opioid peptides in specific brain regions, thus resulting in an activation of their corresponding receptors. If the brain is exposed repeatedly or chronically to these drugs, adaptive changes in the level and expression of opioid peptides and receptors occur. These adaptive changes are thought to contribute to the homeostatic or allostatic adaptations of the brain, which have been associated with drug dependence. This review summarizes pharmacological and genetic studies in animal models and in humans that have addressed the role of specific opioid peptides and receptors in various stages of the addiction process.

Quantitative trait loci contributing to physiological and behavioural ethanol responses after acute and chronic treatment.

The aim of the present study was the identification of gene loci that contribute to the development and manifestation of behaviours related to acute and chronic alcohol exposure, as well as to alcohol withdrawal. For this purpose, we performed a serial behavioural phenotyping of 534 animals from the second filial (F2) generation of a C57BL/6J and C3H/HeJ mice intercross in paradigms with relevance to alcohol dependence. First, ethanol-induced hypothermia was determined in ethanol-naive animals. The mice then received an ethanol solution for several weeks as their only fluid source. Ethanol tolerance, locomotor activity and anxiety-related behaviours were evaluated. The ethanol was next withdrawn and the withdrawal severity was assessed. The ethanol-experienced animals were finally analysed in a two-bottle choice paradigm to determine ethanol preference and stress-induced changes in ethanol preference. The genotypes of these mice were subsequently assessed by microsatellite marker mapping. We genotyped 264 markers with an average marker distance of 5.56 cM, which represents a high-density whole genome coverage. Quantitative trait loci (QTL) were subsequently identified using univariate analysis performed with the R/qtl tool, which is an extensible, interactive environment for mapping QTL in experimental crosses. We found QTL that have already been published, thus validating the serial phenotyping protocol, and identified several novel loci. Our analysis demonstrates that the various responses to ethanol are regulated by independent groups of genes.

Effects of the cannabinoid receptor agonist WIN 55,212-2 on operant behavior and locomotor activity in rats.

Cannabinoids influence the motivational state of a subject and affect motor behavior. In the present study, we examined the acute effects of the cannabinoid (CB) receptor agonist WIN 55,212-2 (WIN) in three different doses (0.6, 1.2 and 1.8 mg/kg) on the performance of rats in a progressive ratio operant behavior task and on locomotor activity. WIN dose-dependently reduced the break point and the total number of lever-presses under a progressive ratio schedule. A food preference test revealed a preference for freely available casein pellets over lab chow in all treatment groups, indicating no WIN-effects on primary motivation. There was a significant reduction in the amount of casein pellets consumed by animals treated with 1.8 mg/kg WIN. Locomotor activity in the open field was increased by 0.6 mg/kg, but not by higher doses of WIN. These data show that administration of the synthetic cannabinoid receptor agonist WIN leads to dose-dependent alterations of the performance in an operant behavior task and of motor behavior. We confirm previous findings of dose-dependent motor stimulating and inhibiting effects of cannabinoids, and show an impairment of a complex operant behavior at higher doses of WIN.

Recovery of semantic word processing in global aphasia: a functional MRI study.

One important issue concerning the recovery of higher cognitive functions-such as word comprehension in aphasia-is to what extent impairments can be compensated for by intact parts of the network of areas normally involved in a closely related function ("redundancy recovery"). In a previous functional MRI investigation, we were able to show that left hemispheric redundancy recovery within a distributed system of related lexical-semantic functions was the most probable basis of recovery of comprehension from transcortical sensory aphasia. The question remained, however, whether redundancy recovery may play a more general role in the recovery of comprehension after large left hemispheric lesions and severe aphasia. We had the possibility, using the same fMRI paradigm, to study seven cases with left middle cerebral artery (MCA) infarction and partial recovery of comprehension > or =6 months after presentation with global aphasia on acute assessment. Lateralization of activation did not differ significantly between patients and controls. The most consistent regions of activation included the left extrasylvian posterior temporal and the right posterior parietal cortex. Recovery of language comprehension was associated predominantly with activations in regions, which were also activated in several normal subjects. We suggest that a redundancy recovery mechanism within multiple representations of closely related functions was more important than take-over of function by previously unrelated areas (vicariation) as the basis of recovery of word comprehension in our patients in spite of extensive left hemispheric damage. We conclude that redundancy within the lexical-semantic system seems to make an important contribution to recovery of comprehension even in severe aphasia.

Recovery of semantic word processing in transcortical sensory aphasia: a functional magnetic resonance imaging study.

In a previous functional magnetic resonance imaging (fMRI) study with normal subjects, we demonstrated regions related to conceptual-semantic word processing around the first frontal sulcus (BA 9) and the posterior parietal lobe (BA 7/40) in agreement with several previous reports. We had the possibility, using the same fMRI paradigm, to study two consecutive cases with left middle cerebral artery (MCA) infarction (RC and HP) and lesions affecting either solely the pre-frontal (HP) or both the pre-frontal and posterior parietal part of the network activated in normal subjects (RC). Both patients showed transcortical sensory aphasia (TSA) on acute assessment. This contradicts classical disconnection accounts of the syndrome stating intact conceptual representations in TSA. Their recovery of language comprehension was associated with activation of a left hemispheric network. Mainly activations of left perilesional pre-frontal regions (RC), left Wernicke's area (RC and HP) or the left posterior middle and inferior temporal cortex (HP) were demonstrated in the TSA patients. The latter findings suggest that in our cases of TSA functional take-over has occurred in regions with related functions ('redundancy recovery') rather than in previously unrelated areas ('vicarious functioning'). Our data support distributed models of conceptual-semantic word processing and multiple left hemispheric representations of closely related functions.