Monoamine oxidase-A physically interacts with presenilin-1(M146V) in the mouse cortex

The concentration of presenilin-1 (PS-1) protein at the mitochondrial-associated aspect of the endoplasmic reticulum supports the potential for a mitochondrial influence of PS-1. Given that carriers of certain Alzheimer's disease (AD)-related PS-1 variants are predisposed to clinical depression and that depression has been historically associated with the mitochondrial enzyme, monoamine oxidase-A (MAO-A), we investigated cortical MAO-A function in the AD-related PS-1(M146V) knock-in mouse. The MAO-A system was clearly altered in the PS-1(M146V) mouse as revealed by (a) a mismatch between MAO-A protein expression and MAO-A activity; (b) changes in MAO-A-mediated monoaminergic neurotransmitter metabolism; (c) changes in non-cognitive behavior following treatment with the irreversible MAO-A inhibitor clorgyline; and (d) an increase in the potency of clorgyline in these same mice. We next investigated whether PS-1(M146V) could be influencing MAO-A directly. We observed (a) an enhanced MAO-A activity in necropsied PS-1(M146V) mouse cortical extracts incubated with DAPT (a PS-1 substrate-competitor); (b) the proximity of PS-1 with MAO-A and mitochondrial markers in cortical sections and in primary cortical neurons; (c) the co-segregation and co-immunoprecipitation of PS-1 and MAO-A within the mitochondrial fraction; and (d) the co-immunoprecipitation of overexpressed PS-1(M146V) and MAO-A proteins from N2a lysates. The PS-1(ΔEx9) and PS-1(D257A) variants, known to have low substrate-binding capacity, co-immunoprecipitated weakly with MAO-A. These combined data support a physical interaction between PS-1 and MAO-A that could influence MAO-A activity and contribute to the monoaminergic disruptions common to disorders as seemingly diverse as depression and AD.

Serine 209 resides within a putative p38(MAPK) consensus motif and regulates monoamine oxidase-A activity

The p38 mitogen-activated protein kinase (MAPK) cascade as well as the enzyme monoamine oxidase-A (MAO-A) have both been associated with oxidative stress. We observed that the specific inhibition of the p38(MAPK) protein [using either a chemical inhibitor or a dominant-negative p38(MAPK) clone] selectively induces MAO-A activity and MAO-A-sensitive toxicity in several neuronal cell lines, including primary cortical neurons. Over-expression of a constitutively active p38(MAPK) results in the phosphorylation of the MAO-A protein and inhibition of MAO-A activity. The MAO-A(Ser209Glu) phosphomimic - bearing a targeted substitution within a putative p38(MAPK) consensus motif - is neither active nor neurotoxic. In contrast, the MAO-A(Ser209Ala) variant (mimics dephosphorylation) does not associate with p38(MAPK), and is both very active and very toxic. Substitution of the homologous serine in the MAO-B isoform, i.e. Ser200, with either Glu or Ala does not affect the catalytic activity of the corresponding over-expressed proteins. These combined in vitro data strongly suggest a direct p38(MAPK)-dependent inhibition of MAO-A function. Based on published observations, this endogenous means of selectively regulating MAO-A function could provide for an adaptive response to oxidative stress associated with disorders as diverse as depression, reperfusion/ischemia, and the early stages of Alzheimer's disease.

Percutaneous vertebroplasty and kyphoplasty for painful vertebral body fractures in cancer patients

OBJECT

The current North American experience with minimally invasive vertebro- and kyphoplasty is largely limited to the treatment of benign osteoporotic compression fractures. The objective of this study was to assess the safety and efficacy of these procedures for painful vertebral body (VB) fractures in cancer patients.

METHODS

The authors reviewed a consecutive group of cancer patients (21 with myeloma and 35 with other primary malignancies) undergoing vertebro- and kyphoplasty at their institution. Ninety-seven (65 vertebro- and 32 kyphoplasty) procedures were performed in 56 patients during 58 treatment sessions. The mean patient age was 62 years (+/- 13 years [standard deviation]) and the median duration of symptoms was 3.2 months. All patients suffered intractable spinal pain secondary to VB fractures. Patients noted marked or complete pain relief after 49 procedures (84%), and no change after five procedures (9%); early postoperative Visual Analog Scale (VAS) pain scores were unavailable in four patients (7%). No patient was worse after treatment. Reductions in VAS pain scores remained significant up to 1 year (p = 0.02, Wilcoxon signed-rank test). Analgesic consumption was reduced at 1 month (p = 0.03, Wilcoxon signed-rank test). Median follow-up length was 4.5 months (range 1 day-19.7 months). Asymptomatic cement leakage occurred during vertebroplasty at six (9.2%) of 65 levels; no cement extravasation was seen during kyphoplasty. There were no deaths or complications related to the procedures. The mean percentage of restored VB height by kyphoplasty was 42 +/- 21%.

CONCLUSIONS

Percutaneous vertebro- and kyphoplasty provided significant pain relief in a high percentage of patients, and this appeared durable over time. The absence of cement leakage-related complications may reflect the use of 1) high-viscosity cement; 2) kyphoplasty in selected cases; and 3) relatively small volume injection. Precise indications for these techniques are evolving; however, they are safe and feasible in well-selected patients with refractory spinal pain due to myeloma bone disease or metastases.

Expression of brain-derived neurotrophic factor mRNA in rat hippocampus after treatment with antipsychotic drugs

Typical and atypical antipsychotic drugs, though both effective, act on different neurotransmitter receptors and are dissimilar in some clinical effects and side effects. The typical antipsychotic drug haloperidol has been shown to cause a decrease in the expression of brain-derived neurotrophic factor (BDNF), which plays an important role in neuronal cell survival, differentiation, and neuronal connectivity. However, it is still unknown whether atypical antipsychotic drugs similarly regulate BDNF expression. We examined the effects of chronic (28 days) administration of typical and atypical antipsychotic drugs on BDNF mRNA expression in the rat hippocampus using in situ hybridization. Quantitative analysis revealed that the typical antipsychotic drug haloperidol (1 mg/kg) down-regulated BDNF mRNA expression in both CA1 (P < 0.05) and dentate gyrus (P < 0.01) regions compared with vehicle control. In contrast, the atypical antipsychotic agents clozapine (10 mg/kg) and olanzapine (2.7 mg/kg) up-regulated BDNF mRNA expression in CA1, CA3, and dentate gyrus regions of the rat hippocampus compared with their respective controls (P < 0.01). These findings demonstrate that the typical and atypical antipsychotic drugs differentially regulate BDNF mRNA expression in rat hippocampus.

Brain-derived neurotrophic factor (BDNF) mRNA in rats with neonatal ibotenic acid lesions of the ventral hippocampus

Increasing evidence suggests that schizophrenia is a neurodevelopmental disorder with a progressive course characterized by worsening of symptoms and morphological alterations within the brain. This suggests that a neurodegenerative component may exist in schizophrenia. The role of brain-derived neurotrophic factor (BDNF) in neurodevelopment, cell viability and synaptic plasticity led to the investigation of BDNF as a potential candidate molecule in the pathophysiology of schizophrenia. BDNF mRNA was examined by in situ hybridization in the prefrontal cortex and hippocampus of animals with neonatal ibotenic acid lesions of the ventral hippocampus, a putative neurodevelopmental animal model of schizophrenia. Results demonstrate that animals with neonatal ibotenic acid lesions of the ventral hippocampus have reduced basal levels of BDNF mRNA. It is possible that alterations in this trophic factor render animals more susceptible to neurodegenerative insults.

Differential regulation of hippocampal BDNF mRNA by typical and atypical antipsychotic administration

Apart from their differential propensities to block dopamine D2 and serotonin 5-HT2 receptors, the molecular mechanisms underlying the clinical efficacy of typical and atypical antipsychotics in schizophrenia are largely unknown. Given recent interest in the effects of antipsychotics on neurotrophic and other growth related factors, the effects of antipsychotics on brain-derived neurotrophic factor (BDNF), a neurotrophin crucial to the structural integrity of adult neurons, were investigated in male Wistar rats. Chronic (19 day) but not acute (45 min) antipsychotic administration significantly altered levels of hippocampal BDNF mRNA. In addition, whereas chronic treatment with the strong D2 receptor-blocker haloperidol significantly downregulated hippocampal BDNF mRNA, the selective 5-HT2 receptor-blocker ritanserin significantly upregulated CA1 hippocampal BDNF mRNA in comparison to controls. Since high doses of risperidone and clozapine produce potent inhibition of both 5-HT2 and D2 receptors, while lower doses produce significantly greater 5-HT2 vs. D2 receptor blockade, a dose-response study was employed to determine whether low doses of these atypical antipsychotics would also upregulate hippocampal BDNF mRNA in the absence of significant D2 receptor blockade. Whereas chronic haloperidol and high-dose risperidone significantly downregulated hippocampal BDNF mRNA, intermediate and lower doses of risperidone and clozapine were, unlike ritanserin, without effect when compared to controls. Thus, although the long-term downregulation of hippocampal BDNF mRNA may underlie the different clinical profiles of certain antipsychotics, this effect seems to be associated with antipsychotic doses that not only cause significant D2 receptor inhibition, but are usually associated with side effects rather than therapeutic efficacies.

Quetiapine attenuates the immobilization stress-induced decrease of brain-derived neurotrophic factor expression in rat hippocampus

Quetiapine is a new atypical antipsychotic drug widely used in the treatment of schizophrenia and other psychotic disorders. This study examined the influence of quetiapine on the decrease of brain-derived neurotrophic factor (BDNF) expression, induced by chronic immobilization stress, in the hippocampus of the rat. Pretreatment with 10 mg/kg of quetiapine markedly attenuated the stress-induced decrease in levels of BDNF protein, as determined by Western blot analyses, and the reduction of BDNF immunoreactivity, in hippocampal pyramidal and dentate granular neurons. These results suggest that the chronic administration of quetiapine could be neuroprotective to hippocampal neurons in schizophrenia and this effect may be related to its antipsychotic effect in patients with schizophrenia.

Kindling of claustrum and insular cortex: comparison to perirhinal cortex in the rat

The perirhinal cortex has recently been implicated in the kindling of limbic generalized seizures. The following experiments in rats tested the selectivity of the perirhinal cortex's epileptogenic properties by comparing its kindling profile with those of the adjacent insular cortex, posterior (dorsolateral) claustrum and amygdala. The first experiment examined the kindling and EEG profiles, and found that both the claustrum and insular cortex demonstrated rapid epileptogenic properties similar to the perirhinal cortex, including very rapid kindling rates and short latencies to convulsion. Furthermore, electrical stimulation of all three structures led to a two-phase progression through stage-5 seizures which had characteristics of both neocortical and amygdaloid kindling. In a second experiment rats were suspended in a harness to allow for more detailed documentation of both forelimb and hindlimb convulsions. With this procedure we were able to detect subtle yet unique differences in convulsion characteristics from each of the kindled sites and stage-5 seizure phases. Some of these convulsive parameters were correlated with changes in FosB/DeltaFosB protein and BDNF mRNA expression measured two hours after the last convulsion. Overall, it appears that the perirhinal cortex is not unique in its property of rapid epileptogenesis. Moreover, the posterior claustrum exhibited the fastest kindling and most vigorous patterns of clonus, suggesting that it may be even more intimately associated with the motor substrates responsible for limbic seizure generalization than is the perirhinal cortex.

Antidepressants upregulate messenger RNA levels of the neuroprotective enzyme superoxide dismutase (SOD1)

OBJECTIVE

To investigate the effect of amitriptyline, bupropion, doxepin or venlafaxine on the gene expression of the neuroprotective enzyme superoxide dismutase (SOD1) in a catecholamine cell in vitro model.

DESIGN

Molecular study of a cultured cell line.

INTERVENTIONS

Rat pheochromocytoma (PC12) cells were incubated in 1 and 10 mumol/L of various antidepressant medications for 24 or 48 hours.

OUTCOME MEASURES

Northern blot analysis.

RESULTS

Amitriptyline up-regulated SOD1 messenger RNA in a time- and dose-dependent manner. The greatest up-regulation was following incubation with 10 mumol/L amitriptyline for 48 hours. The addition of bupropion, doxepin or venlafaxine to PC12 cell cultures also up-regulated SOD1 mRNA.

CONCLUSIONS

These findings suggest that some antidepressants have the ability to positively regulate neuroprotective genes.

Region-specific induction of deltaFosB by repeated administration of typical versus atypical antipsychotic drugs

Whereas acute administration of many types of stimuli induces c-Fos and related proteins in brain, recent work has shown that chronic perturbations cause the region-specific accumulation of novel Fos-like proteins of 35-37 kD. These proteins, termed chronic FRAs (Fos-related antigens), have recently been shown to be isoforms of DeltaFosB, which accumulate in brain due to their enhanced stability. In the present study, we sought to extend earlier findings that documented the effects of acute administration of antipsychotic drugs (APDs) on induction of Fos-like proteins by investigating the ability of typical and aytpical APDs, after chronic administration, to induce these DeltaFosB isoforms in several brain regions implicated in the clinical actions of these agents. By Western blotting we found that chronic administration of the typical APD, haloperidol, dramatically induces DeltaFosB in caudate-putamen (CP), a brain region associated with the extrapyramidal side effects of this drug. A smaller induction was seen in the nucleus accumbens (NAc) and prefrontal cortex (PFC), brain regions associated with the antipsychotic effects of the drug. In contrast, chronic administration of the prototype atypical APD clozapine failed to significantly increase levels of DeltaFosB in any of the three brain regions, and even tended to reduce DeltaFosB levels in the NAc. Two putative atypical APDs, risperidone and olanzapine, produced small but still significant increases in the levels of DeltaFosB in CP, but not NAc or PFC. Studies with selective receptor antagonists suggested that induction of DeltaFosB in CP and NAc is most dependent on antagonism of D2-D3 dopamine receptors, with antagonism of D1-like receptors most involved in the PFC. Immunohistochemical analysis confirmed the greater induction of DeltaFosB in CP by typical versus atypical APDs, with no significant induction seen in PFC with either class of APD. Together, these findings demonstrate that repeated administration of APDs results in the induction of long-lasting Fos-like transcription factors that could mediate some of the persistent and region-specific changes in brain function associated with chronic drug exposure. Synapse 33:118-128, 1999.

Differential effects of olanzapine on the gene expression of superoxide dismutase and the low affinity nerve growth factor receptor

Neuroanatomical studies of schizophrenia suggest that progressive neuropathological changes (such as neuronal atrophy and/or cell death) occur over the lifetime course of the disease. Early intervention with atypical neuroleptics has been shown to prevent progression of at least some symptoms, although the mechanisms by which neuroleptics may do this remain unknown. In this study, PC12 cells were used to determine the effects of the new atypical antipsychotic olanzapine on the gene expression of superoxide dismutase (SOD1) and the low affinity nerve growth factor receptor (p75). The results show that olanzapine increases SOD1 at concentrations of 10 and 100 microM after 48 hr of incubation in PC12 cultures. The treatment decreases p75 gene expression at concentrations 100 microM after 48 hr of incubation. Since both the upregulation of SOD1 mRNA and the antisense blockade of p75 mRNA have been associated with reduced cell death, our results suggest that olanzapine has neuroprotective potential and thus may be useful in preventing further neurodegeneration accompanying schizophrenia.