Low intensity exercise attenuates disease progression and stimulates cell proliferation in the spinal cord of a mouse model with progressive motor neuronopathy.

Physical exercise has been shown to stimulate neurogenesis, increase resistance to brain trauma and disease, improve learning and increase levels of growth factors. We show that low intensity exercise has profound effects on the phenotype of a mouse mutant with progressive motor neuronopathy. These animals normally die at 47 days of age due to motoneuron loss and muscle atrophy. When mice undergo low intensity exercise, their lifespan increased by 74%, they exhibited a decreased loss of motoneurons, improved muscle integrity and a twofold increase in proliferating cells in the spinal cord. The molecular mechanism of neuroprotection may be related to insulin-like-growth factor 1 (IGF-1) since injections of antibodies to IGF-1 abrogated the effects of exercise on the increased life-span. Thus IGF-1 may act as a possible "exercise-induced" neuroprotective factor.

Neurofilament proteins and cAMP pathway in brains of mu-, delta- or kappa-opioid receptor gene knock-out mice: effects of chronic morphine administration.

Opiate addiction is associated with abnormalities of neurofilament (NF) proteins and upregulation of cAMP signaling in the brain, which may modulate neuronal plasticity. This study investigated, using gene-targeted mice lacking mu-, delta- or kappa-opioid receptors, the role of these receptors in modulating the basal activity and the chronic effects of morphine on both intracellular targets. In WT mice, chronic treatment (5 days) with morphine (20-100 mg/kg) resulted in decreases in the immunodensity of neurofilament (NF)-L in the cerebral cortex (14-23%). In contrast, chronic morphine did not decrease NF-L in cortices of mu-, delta-, and kappa-KO mice, suggesting the involvement of the three types of opioid receptors in this effect of morphine. Also, the marked increase in phosphorylated NF-H induced by chronic morphine in WT mice (two-fold) was abolished in mu -KO mice. In cortex and/or striatum of mu-, delta- and kappa-KO mice, the basal immunodensities of Galphai1/2 proteins, the catalytic isoform (Calpha) of protein kinase A (PKA) and the total content of cAMP response element-binding protein (CREB, the nuclear target of PKA) were not different from those of WT mice. In contrast, phosphorylated CREB (the active form of this transcription factor) was reduced in cortex and/or striatum (23-26%) of mu- and delta-KO mice, but not in kappa-KO animals. These results suggest that the endogenous opioid tone acting on mu-/delta-receptors tonically stimulate CREB activation in the brain. In cortex and/or striatum of WT mice, chronic morphine did not induce upregulation of the main components of the cAMP signaling pathway. In contrast, chronic morphine treatment in mu-KO mice, but not in delta- or kappa-KO, resulted in a paradoxical upregulation of Galphai1/2 (12-19%), PKA (19-21%,) and phosphorylated CREB (21-73%), but not total CREB, in cortex and/or striatum. The induction of heterologous receptor adaptations in mu-KO mice may explain this paradoxical effect of morphine.

Acute and chronic effects of morphine and naloxone on the phosphorylation of neurofilament-H proteins in the rat brain.

Increased amounts of phosphorylated neurofilaments (pNF-H and pNF-M) are found in postmortem brains of opioid addicts. Because of the potential relevance of aberrant pNF in opioid addiction (alterations of neuronal cytoskeleton and associated functions), the effects of opiate drugs on pNF-H were investigated in rat brain. Acute morphine (30 mg/kg, 2 h) induced a marked increase in the immunodensity of pNF-H in the cerebral cortex (93%). Chronic morphine (10-100 mg/kg for 5 days) followed by opiate withdrawal resulted in a time-dependent decline in pNF-H (induction of tolerance). Thus, 2 h after the last dose of morphine, the abundance of pNF-H was still increased (27%), which was followed (6-24 h) by down-regulation of pNF-H (5% increase at 6 h; 5% decrease at 12 h, and 29% decrease at 24 h). The acute (10 mg/kg for 2 h) and chronic (2 x 10 mg/kg for 14 days) treatments with naloxone, an opioid receptor antagonist, did not alter pNF-H in the cerebral cortex, suggesting that the opioid receptors (probably the mu-type) modulating the phosphorylation state of NF-H are not tonically activated by endogenous opioids. The results indicate that morphine addiction is associated with an aberrant hyperphophorylation of NF-H in the rat brain.

FADD adaptor and PEA-15/ERK1/2 partners in major depression and schizophrenia postmortem brains: basal contents and effects of psychotropic treatments.

Enhanced brain apoptosis (neurons and glia) may be involved in major depression (MD) and schizophrenia (SZ), mainly through the activation of the intrinsic (mitochondrial) apoptotic pathway. In the extrinsic death pathway, pro-apoptotic Fas-associated death domain (FADD) adaptor and its non-apoptotic p-Ser194 FADD form have critical roles interacting with other death regulators such as phosphoprotein enriched in astrocytes of 15 kDa (PEA-15) and extracellular signal-regulated kinase (ERK). The basal status of FADD (protein and messenger RNA (mRNA)) and the effects of psychotropic drugs (detected in blood/urine samples) were first assessed in postmortem prefrontal cortex of MD and SZ subjects (including a non-MD/SZ suicide group). In MD, p-FADD, but not total FADD (and mRNA), was increased (26%, n=24; all MD subjects) as well as p-FADD/FADD ratio (a pro-survival marker) in antidepressant-free MD subjects (50%, n=10). In contrast, cortical FADD (and mRNA), p-FADD, and p-FADD/FADD were not altered in SZ brains (n=21) regardless of antipsychotic medications (except enhanced mRNA in treated subjects). Similar negative results were quantified in the non-MD/SZ suicide group. In MD, the regulation of multifunctional PEA-15 (i.e., p-Ser116 PEA-15 blocks pro-apoptotic FADD and PEA-15 prevents pro-survival ERK action) and the modulation of p-ERK1/2 were also investigated. Cortical p-PEA-15 was not changed whereas PEA-15 was increased mainly in antidepressant-treated subjects (16-20%). Interestingly, cortical p-ERK1/2/ERK1/2 ratio was reduced (33%) in antidepressant-free when compared to antidepressant-treated MD subjects. The neurochemical adaptations of brain FADD (increased p-FADD and pro-survival p-FADD/FADD ratio), as well as its interaction with PEA-15, could play a major role to counteract the known activation of the mitochondrial apoptotic pathway in MD.

Behavioral, neurochemical and morphological changes induced by the overexpression of munc18-1a in brain of mice: relevance to schizophrenia.

Overexpression of the mammalian homolog of the unc-18 gene (munc18-1) has been described in the brain of subjects with schizophrenia. Munc18-1 protein is involved in membrane fusion processes, exocytosis and neurotransmitter release. A transgenic mouse strain that overexpresses the protein isoform munc18-1a in the brain was characterized. This animal displays several schizophrenia-related behaviors, supersensitivity to hallucinogenic drugs and deficits in prepulse inhibition that reverse after antipsychotic treatment. Relevant brain areas (that is, cortex and striatum) exhibit reduced expression of dopamine D(1) receptors and dopamine transporters together with enhanced amphetamine-induced in vivo dopamine release. Magnetic resonance imaging demonstrates decreased gray matter volume in the transgenic animal. In conclusion, the mouse overexpressing brain munc18-1a represents a new valid animal model that resembles functional and structural abnormalities in patients with schizophrenia. The animal could provide valuable insights into phenotypic aspects of this psychiatric disorder.

Gene expression patterns in brain cortex of three different animal models of depression.

Animal models represent a very useful tool for the study of depressive-like behavior and for the evaluation of the therapeutic efficacy of antidepressants. Nevertheless, gene expression patterns of these different animal models and whether genes classically associated with human major depression are present in these genetic profiles remain unknown. Gene expression was evaluated in three animal models of depression: acute treatment with reserpine, olfactory bulbectomy and chronic treatment with corticosterone. Gene expression analysis was carried out using the Affymetrix GeneChip technology. The results were evaluated using the GeneChip Operating software (Gcos 1.3) and analyzed with the GeneSpring GX v7.3 bioinformatics software (Agilent) and dChip 2005 software. Expression changes were validated with quantitative real-time polymerase chain reaction (RT-PCR) assays. Many transcripts were differentially expressed in the cortex of depressed-like animals in each model. Gene ontology analysis showed that significant gene changes were clustered primarily into functional neurochemical pathways associated with apoptosis and neuronal differentiation. When expression profiles were compared among the three models, the number of transcripts differentially expressed decreased and only two transcripts (complement component 3 and fatty acid-binding protein 7) were differentially expressed in common. Both genes were validated with RT-PCR. Moreover, five (Htr2a, Ntrk3, Crhr1, Ntrk2 and Crh) of the genes classically related to human major depression were differentially expressed in at least one of these models. The different animal models of depression share relevant characteristics although gene expression patterns are different among them. Moreover, some of the classical genes related to human major depression are differentially expressed in these models.

Long-term regulation of signalling components of adenylyl cyclase and mitogen-activated protein kinase in the pre-frontal cortex of human opiate addicts.

Opiate addiction involves the development of chronic adaptive changes in micro -opioid receptors and associated pathways (e.g. cAMP signalling) which lead to neuronal plasticity in the brain. This study assessed the status of cAMP and mitogen-activated protein kinase (MAPK) pathways in brains (pre-frontal cortex) of chronic opiate addicts. In these subjects (n = 24), the immunodensities of adenylyl cyclase-I, PKA Calpha, total and phosphorylated CREB were not different from those in sex-, age- and PMD-matched controls. Moreover, the ratio pCREB/tCREB was similar in opiate addicts (0.74) and controls (0.76), further indicating that opiate addiction in humans is not associated with an upregulation of several key components of cAMP signalling in the pre-frontal cortex. In contrast, the components of MAPK cascade (Ras/c-Raf-1/MEK/ERK) were decreased in the same brains. Notably, pronounced downregulations of phosphorylated MEK (85%) and ERK1/2 (pERK1: 81%; pERK2: 80%) were quantitated in brains of opiate addicts. Chronic morphine treatment in rats (10-100 mg/kg for 5 days) was also associated with decreases of pERK1/2 (59-68%) in the cortex. In SH-SY5Y cells, morphine also stimulated the activity of pERK1/2 (2.5-fold) and the MEK inhibitor PD98059 blocked this effect (90%). The abnormalities of MAPK signalling might have important consequences in the long term development of various forms of neural plasticity associated with opiate addiction in humans.

Regulation of nonphosphorylated and phosphorylated forms of neurofilament proteins in the prefrontal cortex of human opioid addicts.

The neurofilament (NF) proteins (NF-H, NF-M, and NF-L for high, medium, and low molecular weights) play a crucial role in the organization of neuronal shape and function. In a preliminary study, the abundance of total NF-L was shown to be decreased in brains of opioid addicts. Because of the potential relevance of NF abnormalities in opioid addiction, we quantitated nonphosphorylated and phosphorylated NF in postmortem brains from 12 well-defined opioid abusers who had died of an opiate overdose (heroin or methadone). Levels of NF were assessed by immunoblotting techniques using phospho-independent and phospho-dependent antibodies, and the relative (% changes in immunoreactivity) and absolute (changes in ng NF/microg total protein) amounts of NF were calculated. Decreased levels of nonphosphorylated NF-H (42-32%), NF-M (14-9%) and NF-L (30-29%) were found in the prefrontal cortex of opioid addicts compared with sex, age, and postmortem delay-matched controls. In contrast, increased levels of phosphorylated NF-H (58-41%) and NF-M (56-28%) were found in the same brains of opioid addicts. The ratio of phosphorylated to nonphosphorylated NF-H in opioid addicts (3.4) was greater than that in control subjects (1.6). In the same brains of opioid addicts, the levels of protein phosphatase of the type 2A were found unchanged, which indicated that the hyperphosphorylation of NF-H is not the result of a reduced dephosphorylation process. The immunodensities of GFAP (the specific glial cytoskeletol protein), alpha-internexin (a neuronal filament related to NF-L) and synaptophysin (a synapse-specific protein) were found unchanged, suggesting a lack of gross changes in glial reaction, other intermediate filaments of the neuronal cytoskeletol, and synaptic density in the prefrontal cortex of opioid addicts. These marked reductions in total NF proteins and the aberrant hyperphosphorylation of NF-H in brains of opioid addicts may play a significant role in the cellular mechanisms of opioid addiction.