Hooriyah S. Rizavi

Reduced activation and expression of ERK1/2 MAP kinase in the post-mortem brain of depressed suicide subjects.

The extracellular regulated kinases (ERK) 1 and ERK2 are members of mitogen‐activated protein (MAP) kinase family that play an important role in transducing extracellular signals to the nucleus and have been implicated in a broad spectrum of biological responses. To test the hypothesis that MAP kinases may be involved in depression, we examined the activation of p44/42 MAP kinase and expression of ERK1 and ERK2 in the post‐mortem brain tissue obtained from non‐psychiatric control subjects (n = 11) and age‐ and the post‐mortem interval‐matched depressed suicide subjects (n = 11). We observed that p44/42 MAP kinase activity was significantly decreased in the prefrontal cortical areas (Brodmanns areas 8, 9 and 10) and the hippocampus of depressed suicide subjects without any change in the cerebellum. This decrease was associated with a decrease in mRNA and protein levels of ERK1 and ERK2. In addition, the expression of MAP kinase phosphatase (MKP)2, a ‘dual function’ ERK1/2 phosphatase, was increased in the prefrontal cortex and hippocampus. These studies suggest that p44/42 MAP kinases are less activated in the post‐mortem brain of depressed suicide subjects and this may be because of reduced expression of ERK1/2 and increased expression of MKP2. Given the role of MAP kinases in various physiological functions and gene expression, alterations in p44/42 MAP kinase activation and expression of ERK1/2 may contribute significantly to the pathophysiology of depressive disorders.

MicroRNA Expression Is Down-Regulated and Reorganized in Prefrontal Cortex of Depressed Suicide Subjects

Background Recent studies suggest that alterations in expression of genes, including those which regulate neural and structural plasticity, may be crucial in the pathogenesis of depression. MicroRNAs (miRNAs) are newly discovered regulators of gene expression that have recently been implicated in a variety of human diseases, including neuropsychiatric diseases. Methodology/Principal Findings The present study was undertaken to examine whether the miRNA network is altered in the brain of depressed suicide subjects. Expression of miRNAs was measured in prefrontal cortex (Brodmann Area 9) of antidepressant-free depressed suicide (n = 18) and well-matched non-psychiatric control subjects (n = 17) using multiplex RT-PCR plates. We found that overall miRNA expression was significantly and globally down-regulated in prefrontal cortex of depressed suicide subjects. Using individual tests of statistical significance, 21 miRNAs were significantly decreased at p = 0.05 or better. Many of the down-regulated miRNAs were encoded at nearby chromosomal loci, shared motifs within the 5′-seeds, and shared putative mRNA targets, several of which have been implicated in depression. In addition, a set of 29 miRNAs, whose expression was not pairwise correlated in the normal controls, showed a high degree of co-regulation across individuals in the depressed suicide group. Conclusions/Significance The findings show widespread changes in miRNA expression that are likely to participate in pathogenesis of major depression and/or suicide. Further studies are needed to identify whether the miRNA changes lead to altered expression of prefrontal cortex mRNAs, either directly (by acting as miRNA targets) or indirectly (e.g., by affecting transcription factors).

Antidepressants reverse corticosterone-mediated decrease in brain-derived neurotrophic factor expression: Differential regulation of specific exons by antidepressants and corticosterone

Earlier studies have implicated brain-derived neurotrophic factor in stress and in the mechanism of action of antidepressants. It has been shown that antidepressants upregulate, whereas corticosterone downregulates, brain-derived neurotrophic factor expression in rat brain. Whether various classes of antidepressants reverse corticosterone-mediated downregulation of brain-derived neurotrophic factor is unclear. Also not known is how antidepressants or corticosterone regulates brain-derived neurotrophic factor expression. To clarify this, we examined the effects of various classes of antidepressants and corticosterone, alone and in combination, on the mRNA expression of total brain-derived neurotrophic factor and of individual brain-derived neurotrophic factor exons, in rat brain. Normal or corticosterone pellet-implanted (100 mg, 21 days) rats were injected with different classes of antidepressants, fluoxetine, desipramine, or phenelzine, intraperitoneally for 21 days and killed 2 h after the last injection. mRNA expression of total brain-derived neurotrophic factor and of exons I-IV was measured in frontal cortex and hippocampus. Given to normal rats, fluoxetine increased total brain-derived neurotrophic factor mRNA only in hippocampus, whereas desipramine or phenelzine increased brain-derived neurotrophic factor mRNA in both frontal cortex and hippocampus. When specific exons were examined, desipramine increased expression of exons I and III in both brain areas, whereas phenelzine increased exon I in both frontal cortex and hippocampus but exon IV only in hippocampus. On the other hand, fluoxetine increased only exon II in hippocampus. Corticosterone treatment of normal rats decreased expression of total brain-derived neurotrophic factor mRNA in both brain areas, specifically decreasing exons II and IV. Treatment with desipramine or phenelzine of corticosterone pellet-implanted rats reversed the corticosterone-induced decrease in total brain-derived neurotrophic factor expression in both brain areas; however, fluoxetine reversed the decrease only partially in hippocampus. Interestingly, antidepressant treatment of corticosterone pellet-implanted rats increased only those specific exons that are increased during treatment of normal rats with each particular antidepressant. We found that although corticosterone and antidepressants both modulate brain-derived neurotrophic factor expression, and antidepressants reverse the corticosterone-induced brain-derived neurotrophic factor decrease, antidepressants and corticosterone differ in how they regulate the expression of brain-derived neurotrophic factor exon(s).

Proinflammatory cytokines in the prefrontal cortex of teenage suicide victims

Teenage suicide is a major public health concern, but its neurobiology is not well understood. Proinflammatory cytokines play an important role in stress and in the pathophysiology of depression-two major risk factors for suicide. Cytokines are increased in the serum of patients with depression and suicidal behavior; however, it is not clear if similar abnormality in cytokines occurs in brains of suicide victims. We therefore measured the gene and protein expression levels of proinflammatory cytokines interleukin (IL)-1β, IL-6, and tissue necrosis factor (TNF)-α in the prefrontal cortex (PFC) of 24 teenage suicide victims and 24 matched normal control subjects. Our results show that the mRNA and protein expression levels of IL-1β, IL-6, and TNF-α were significantly increased in Brodmann area 10 (BA-10) of suicide victims compared with normal control subjects. These results suggest an important role for IL-1β, IL-6, and TNF-α in the pathophysiology of suicidal behavior and that proinflammatory cytokines may be an appropriate target for developing therapeutic agents.

Brain-derived neurotrophic factor and tyrosine kinase B receptor signalling in post-mortem brain of teenage suicide victims

Teenage suicide is a major public health concern, but its neurobiology is not very well understood. Stress and major mental disorders are major risk factors for suicidal behaviour, and it has been shown that brain-derived neurotrophic factor (BDNF) and its receptor tyrosine kinase B (TrkB) are not only regulated by stress but are also altered in these illnesses. We therefore examined if BDNF/TrkB signalling is altered in the post-mortem brain of teenage suicide victims. Protein and mRNA expression of BDNF and of TrkB receptors were determined in the prefrontal cortex (PFC), Brodmanns Area 9 (BA 9), and hippocampus obtained from 29 teenage suicide victims and 25 matched normal control subjects. Protein expression was determined using the Western blot technique; mRNA levels by a quantitative RT-PCR technique. The protein expression of BDNF was significantly decreased in the PFC of teenage suicide victims compared with normal control subjects, whereas no change was observed in the hippocampus. Protein expression of TrkB full-length receptors was significantly decreased in both PFC and hippocampus of teenage suicide victims without any significant changes in the truncated form of TrkB receptors. mRNA expression of both BDNF and TrkB was significantly decreased in the PFC and hippocampus of teenage suicide victims compared with normal control subjects. These studies indicate a down-regulation of both BDNF and its receptor TrkB in the PFC and hippocampus of teenage suicide victims, which suggests that stress and altered BDNF may represent a major vulnerability factor in teenage suicidal behaviour.

Suicide Brain Is Associated with Decreased Expression of Neurotrophins

BACKGROUND Neurotrophins mediate diverse biological responses, including maintenance and growth of neurons and synaptic plasticity in adult brain. This study examined whether suicide brain is associated with changes in the expression of neurotrophins. METHODS Messenger ribonucleic acid (mRNA) levels of nerve growth factor (NGF), neurotrophin (NT)-3, NT-4/5, and of cyclophilin and neuron-specific enolase (NSE) were measured by quantitative reverse transcriptase polymerase chain reaction, whereas protein levels of neurotrophins were determined by enzyme-linked immunosorbent assay, in prefrontal cortex (PFC) and hippocampus from 28 suicide victims and 21 control subjects. RESULTS In hippocampus of suicide subjects compared with control subjects mRNA levels of NGF (p < .001), NT-3 (p < .001), and NT-4/5 (p < .001) were decreased, whether or not they were expressed as a ratio to cyclophilin or NSE. This was accompanied by a decrease in their respective protein levels (NGF [p < .001], NT-3 [p < .001], and NT-4/5 [p < .001]). In PFC, however, mRNA (p = .001) and protein (p < .001) levels of NT-4/5 and only protein level of NGF (p < .001) were decreased; NT-3 levels were unchanged. CONCLUSIONS Given the role of neurotrophins in synaptic plasticity and maintenance of adult neurons, our findings of altered expression of neurotrophins in postmortem brain of suicide victims suggest that these molecules might play a vital role in the pathophysiology of suicide.

ERK MAP kinase signaling in post-mortem brain of suicide subjects: differential regulation of upstream Raf kinases Raf-1 and B-Raf

The Raf kinases Raf-1 and B-Raf are upstream activators of the extracellular signal-regulated kinase (ERK)-signaling pathway and therefore participates in many physiological functions in brain, including neuronal survival and synaptic plasticity. Previously, we observed that activation of ERK-1/2, the downstream component of ERK signaling, is significantly reduced in post-mortem brain of suicide victims. The present study was undertaken to further examine whether suicide brain is also associated with abnormalities in upstream molecules in ERK signaling. The study was performed in prefrontal cortex (PFC) and hippocampus obtained from 28 suicide victims and 21 normal controls. mRNA levels of Raf-1, B-Raf, and cyclophilin were measured by quantitative RT-PCR. Protein levels of Raf-1 and B-Raf were determined by Western blot, whereas their catalytic activities were determined by immunoprecipitation and enzymatic assays. It was observed that the catalytic activity of B-Raf was significantly reduced in PFC and hippocampus of suicide subjects. This decrease was associated with a decrease in its protein, but not mRNA, level. On the other hand, catalytic activity, and mRNA and protein levels, of Raf-1 were not altered in post-mortem brain of suicide subjects. The observed changes were not related to confounding variables; however, Raf-1 showed a negative correlation with age. Also, the changes in B-Raf were present in all suicide subjects, irrespective of psychiatric diagnosis. Our results of selective reduction in catalytic activity and expression of B-Raf but not Raf-1 suggest that B-Raf may be playing an important role in altered ERK signaling in brain of suicide subjects, and thus in the pathophysiology of suicide.

Expression of microRNAs and Other Small RNAs in Prefrontal Cortex in Schizophrenia, Bipolar Disorder and Depressed Subjects

Because of the role played by miRNAs in post-transcriptional regulation of an array of genes, their impact in neuropsychiatric disease pathophysiology has increasingly been evident. In the present study, we assessed microRNA expression in prefrontal cortex (Brodmann area 10) of a well-characterized cohort of major depressed, bipolar, and schizophrenia subjects (obtained from Stanley Neuropathology Consortium; n = 15 in each group), using high throughput RT-PCR plates. Discrete miRNA alterations were observed in all disorders, as well as in suicide subjects (pooled across diagnostic categories) compared to all non-suicide subjects. The changes in the schizophrenia group were partially similar to those in the bipolar group, but distinct from changes in depression and suicide. Intriguingly, those miRNAs which were down-regulated in the schizophrenia group tended to be synaptically enriched, whereas up-regulated miRNAs tended not to be. To follow this up, we purified synaptosomes from pooled samples of the schizophrenia vs. control groups and subjected them to Illumina deep sequencing. There was a significant loss of small RNA expression in schizophrenia synaptosomes only for certain sequence lengths within the miRNA range. Moreover, 73 miRNAs were significantly down-regulated whereas only one was up-regulated. Strikingly, across all expressed miRNAs in synaptosomes, there was a significant inverse correlation between the fold-change of a given miRNA seen in schizophrenia and its synaptic enrichment ratio observed in controls. Thus, synaptic miRNAs tended to be down-regulated in schizophrenia, and the more highly synaptically enriched miRNAs tended to show greater down-regulation. These findings point to some deficit in miRNA biogenesis, transport, processing or turnover in schizophrenia that is selective for the synaptic compartment. A novel class of ncRNA-derived small RNAs, shown to be strongly induced during an early phase of learning in mouse, is also expressed in man, and at least one representative (SNORD85) was strongly down-regulated in schizophrenia synaptosomes.

Brain-derived neurotrophic factor gene and protein expression in pediatric and adult depressed subjects

BACKGROUND Brain-derived neurotrophic factor (BDNF) is a member of a neurotrophin family and is involved in many physiological functions, including cell proliferation, migration, and differentiation, and neuron survival in the human nervous system. Abnormalities of BDNF have been implicated in the pathophysiology of depression based on observations that antidepressant drugs cause increases in the levels of BDNF in rat brains and its abnormalities have appeared in the serum of depressed patients and in postmortem brains of suicide victims. METHODS We examined the gene expression of BDNF in the lymphocytes and protein expression in the platelets of adult and pediatric depressed patients during a drug-free period. We determined BDNF gene expression using a quantitative RT-PCR method and protein expression using the ELISA method. RESULTS We observed that the gene expression of BDNF was significantly decreased in the lymphocytes of adult and pediatric depressed patients compared with normal control subjects. Similarly, the protein expression of BDNF was significantly decreased in the platelets of adult and pediatric depressed patients compared with normal control subjects. CONCLUSIONS To our knowledge, this is the first study that reports a decrease in BDNF gene expression in the peripheral cells of depressed patients. Because of the bidirectional movement of BDNF between the periphery and the CNS, the reduced gene expression in the lymphocytes and the protein expression in the platelets may be an index of similar abnormalities in the brain and could be a target for antidepressant drugs.

Protein kinase a in postmortem brain of depressed suicide victims: Altered expression of specific regulatory and catalytic subunits

BACKGROUND We recently reported reduced [3H]cyclic adenosine monophosphate binding and catalytic activity of protein kinase A in prefrontal cortex of depressed suicide victims. Here we examined the molecular basis of these alterations and whether these findings can be replicated in another cohort. METHODS Prefrontal cortex from depressed suicide victims and nonpsychiatric controls were obtained from the Lenhossek Human Brain Program, Budapest and the Maryland Brain Collection Program. [3H]cyclic adenosine monophosphate binding and protein kinase A activity were determined by radioligand binding and enzymatic assay, respectively. Expression of catalytic and regulatory subunits was determined by quantitative reverse transcription polymerase chain reaction and Western blot, respectively. RESULTS [3H]cyclic adenosine monophosphate binding and total and endogenous protein kinase A activity were significantly decreased in membrane and cytosol fractions of prefrontal cortex of depressed suicide victims from the Budapest cohort, with a similar magnitude (33%-40% reduction) as reported for the Maryland cohort. In both cohorts, selective reduction (36%-41%) in mRNA and protein expression of the regulatory RIIbeta and the catalytic Cbeta was observed. CONCLUSIONS Our results suggest abnormalities in [3H]cyclic adenosine monophosphate binding and catalytic activity kinase A in brain of depressed suicide victims, which could be due to reduced expression of RIIbeta and Cbeta. These abnormalities in PKA may be critical in the pathophysiology of depression.