Jun-Feng Wang

Increased temporal cortex CREB concentrations and antidepressant treatment in major depression

There was no correlation between temporal cortex CREB concentration and age (r =0·046, p=0·73) or postmortem interval (r = 0·039, p=0·77). In the MDD group, higher temporal cortex CREB concentrations were found in patients treated with antidepressants at the time of death (figure) than in untreated patients (p=0·01). Furthermore, MDD patients not on antidepressants at the time of death had lower CREB concentrations than controls (p=0·02), whereas treated patients did not differ from the control group (p=0·17). There were no differences in the occipital cortex, which suggests that the effects of antidepressants may be regional. There were no differences in CREB concentrations between patients with bipolar disorder or schizophrenia and controls or between treated and untreated patients with bipolar disorder and schizophrenia, which suggests that this drug effect may be specific to MDD. Downstream changes in the cAMP pathway may occur in patients with MDD and antidepressant treatment may be associated with a return to normal temporal cortex of CREB in patients with MDD. The cAMP pathway might ultimately be one of many intracellular pathways contributing to the pathophysiology of depression and its

Role of glutathione in neuroprotective effects of mood stabilizing drugs lithium and valproate

Mood stabilizing drugs lithium and valproate are the most commonly used treatments for bipolar disorder. Previous studies in our laboratory indicate that chronic treatment with lithium and valproate inhibits oxidative damage in primary cultured rat cerebral cortical cells. Glutathione, as the major antioxidant in the brain, plays a key role in defending against oxidative damage. The purpose of this study was to determine the role of glutathione in the neuroprotective effects of lithium and valproate against oxidative damage. We found that chronic treatment with lithium and valproate inhibited reactive oxygen metabolite H(2)O(2)-induced cell death in primary cultured rat cerebral cortical cells, while buthionine sulfoximine, an inhibitor of glutathione rate-limiting synthesis enzyme glutamate-cysteine ligase, reduced the neuroprotective effect of lithium and valproate against H(2)O(2)-induced cell death. Further, we found that chronic treatment with lithium and valproate increased glutathione levels in primary cultured rat cerebral cortical cells and that the effects of lithium and valproate on glutathione levels were dose-dependent in human neuroblastoma SH-SY5Y cells. Chronic treatment with lithium and valproate also increased the expression of glutamate-cysteine ligase in both rat cerebral cortical cells and SH-SY5Y cells. In addition, chronic treatment with other mood stabilizing drugs lamotrigine and carbamazepine, but not antidepressants desipramine and fluoxetine, increased both glutathione levels and the expression of glutamate-cysteine ligase in SH-SY5Y cells. These results suggest that glutathione plays an important role in the neuroprotective effects of lithium and valproate, and that glutathione may be a common target for mood stabilizing drugs.

G protein-coupled cyclic AMP signaling in postmortem brain of subjects with mood disorders : Effects of diagnosis, suicide, and treatment at the time of death

Abstract : Components of cyclic AMP (cAMP) signaling were examined in postmortem cerebral cortex of a well characterized group of patients with mood disorders and nonpsychiatric control subjects. We measured G protein levels, adenylyl cyclase (AC) activity, and CREB levels in cerebral cortex of the subjects with respect to diagnosis, treatment, and suicide. There was no effect of diagnosis on any measure, except for a trend toward decreased stimulated AC activity in subjects with mood disorders relative to control subjects. We also detected a significant effect of suicide on temporal cortex CREB levels in subjects that died as a result of suicide relative to those that did not, which was more evident in patients with major depressive disorder. Bipolar disorder (BD) subjects treated with anticonvulsants at the time of death had decreased temporal cortex CREB levels relative to those not receiving anticonvulsants. Furthermore, we found a trend toward decreased occipital cortex GαS (short) levels in BD subjects treated with lithium. These results support the hypothesis of altered cAMP signaling in mood disorders and raise the possibility that factors other than diagnosis, such as treatment and suicide, may be relevant to cell‐signaling abnormalities reported in the literature.

Oxidative damage to RNA but not DNA in the hippocampus of patients with major mental illness.

BACKGROUNDnOxidative damage in the central nervous system is increasingly recognized as an important pathological process in many diseases. Previously, our laboratory found that oxidative damage to lipids and proteins was increased in postmortem brain tissue from patients with bipolar disorder and schizophrenia. In the current study, we analyzed oxidative damage to nucleic acids in the CA1, CA3 and dentate gyrus regions of postmortem hippocampus tissue from patients with bipolar disorder, schizophrenia and major depression.nnnMETHODSnWe examined oxidative damage to nucleic acids by performing immunohistochemistry with a monoclonal antibody that recognizes both 8-hydroxy-guanosine in RNA and 8-hydroxy-2-deoxyguanosine in DNA.nnnRESULTSnWe found that the amount of oxidative damage to nucleic acids was elevated in the CA1, CA3 and dentate gyrus regions of the hippocampus among patients with bipolar disorder, schizophrenia and major depressive disorder. This damage was predominantly in the cytoplasm, suggesting that the damage was primarily to RNA. Compared with oxidative damage in control samples, the magnitude of damage was high in patients with schizophrenia, modest in patients with bipolar disorder and lower in patients with major depression.nnnLIMITATIONSnThe interpretation of our results is limited by a number of factors, including the retrospective review of patient history, the relatively small sample size and the inclusion of patients who had substance abuse and were undergoing various drug treatments at the time of death.nnnCONCLUSIONnOur results suggest that oxidative damage to RNA, rather than to DNA, occurs in vulnerable neurons of the brain in patients with major mental illness and may contribute to the pathology of these disorders. The magnitude of RNA oxidative damage may be associated with the severity of mental illness.

Gene expression differences in bipolar disorder revealed by cDNA array analysis of post-mortem frontal cortex.

Previous studies have implicated a number of biochemical pathways in the etiology of bipolar disorder (BD). However, the precise abnormalities underlying this disorder remain to be established. To investigate novel factors that may be important in the pathophysiology of BD, we utilized cDNA expression arrays to examine differences in expression of up to 1200 genes known to be involved in potentially relevant biochemical processes. This investigation was undertaken in post‐mortem samples of frontal cortex tissue from patients with BD and matched controls, obtained (nu2003=u200310/group) from the Stanley Foundation Neuropathology Consortium. Results include significant (greater than 35% change in signal intensity) differences between BD and controls in a number of genes (nu2003=u200324). Selected targets were analyzed by RT‐PCR, which confirmed a decrease in transforming growth factor‐beta1 (TGF‐β1), and an increase in both caspase‐8 precursor (casp‐8) and transducer of erbB2 (Tob) expression in BD. We further observed a significant decrease of TGF‐β1 mRNA levels in BD by RT‐PCR in individual post‐mortem samples. Given the neuroprotective role attributed to this inhibitory cytokine, our results suggest that the down‐regulation of TGF‐β1 may lead to various neurotoxic insults potentially involved in the etiology of certain mood disorders.

Effects of restraint stress on the expression of proteins involved in synaptic vesicle exocytosis in the hippocampus.

Chronic restraint stress has been associated with induction of morphological changes in the hippocampus. Postsynaptically, these changes include decreased length and branching of apical dendrites from CA3 pyramidal neurons, while presynaptically, depletion and clustering of synaptic vesicles have been observed. However, the molecular correlates of these changes remain poorly defined; while some studies have identified changes in the levels of some presynaptic proteins, none have assessed the coordinate expression of components of the membrane fusion complex, including synaptobrevin, syntaxin, and synaptosomal-associated protein 25 kDa, and their major regulatory molecules synaptotagmin, synaptophysin, and synapsin. Therefore, we undertook to assess the immunoreactivity of these proteins in hippocampal slices obtained from rats subjected to either acute (one 6 h session) or chronic (21 days at 6 h per day) of restraint stress. Specifically, we observed a significant increase in synaptobrevin immunoreactivity in the inner molecular layer of the dentate gyrus (54.2%; P=0.005), the stratum radiatum in the CA1 subfield (55.5%; P=0.007), and a region including the stratum lucidum and the proximal portion of the stratum radiatum in the CA3 subfield (52.7%; P=0.002); we also observed a trend toward increased synaptophysin levels in the stratum lucidum/radiatum of the CA3 subfield (8.0%; P=0.051) following chronic, but not acute, restraint stress. In that synaptobrevin has been associated with replenishment of the readily-releasable pool of synaptic vesicles and the efficiency of neurotransmitter release, the present results suggest that stress-induced changes in synaptobrevin may at least in part underlie the previously observed changes in synaptic and neuronal morphology.

Regulation of GAP-43 expression by chronic desipramine treatment in rat cultured hippocampal cells

BACKGROUNDnThe importance of molecular and cellular changes in hippocampus in major depression and in the mechanism of action of antidepressants has become increasingly clear. Identification of novel targets for antidepressants in hippocampus is important to understanding their therapeutic effects.nnnMETHODSnWe used cDNA microarray to measure the expression patterns of multiple genes in primary cultured rat hippocampal cells. In situ hybridization and Northern and immunoblotting analysis were used to determine brain regional distribution and mRNA and protein levels of target genes.nnnRESULTSnAfter comparing hybridized signals between control and desipramine treated groups, we found that chronic treatment with desipramine increased the expression of six genes and decreased the expression of two genes. One of the upregulated genes is growth associated protein GAP-43. In situ hybridization revealed that desipramine increased GAP-43 gene expression in dentate gyrus but not other brain regions. Northern and immunoblotting analysis revealed that desipramine increased GAP-43 mRNA and protein levels. GAP-43 expression is also increased by another antidepressant, tranylcypromine, but not by lithium or haloperidol.nnnCONCLUSIONSnBecause GAP-43 regulates growth of axons and modulates the formation of new connections, our findings suggest that desipramine may have an effect on neuronal plasticity in the central nervous system.

Amygdala cyclic adenosine monophosphate response element binding protein phosphorylation in patients with mood disorders: effects of diagnosis, suicide, and drug treatment.

BACKGROUNDnSignal transduction abnormalities have been identified in patients with bipolar (BD) and major depressive (MDD) disorders and are targets for lithium and antidepressant drugs. A key downstream target for signal transduction pathways is the transcription factor cyclic adenosine monophosphate (cAMP) response element binding protein (CREB). Therefore, we measured the levels of phosphorylated CREB (pCREB) in the amygdala, a region critical to emotional processing and important in the pathophysiology of both BD and MDD.nnnMETHODSnHuman postmortem amygdala sections were generously provided by the Stanley Foundation Neuropathology Consortium. Samples consisted of subjects with MDD, BD, schizophrenia (SCZ), and nonpsychiatric-nonneurologic comparison subjects (n = 15 per group). Levels of pCREB were measured by immunohistochemistry, relative to total cell number.nnnRESULTSnThere were no differences between diagnostic groups--control subjects and subjects with BD, MDD, or SCZ--but increased numbers of pCREB stained cells were found in several amygdalar nuclei in subjects who had died by suicide. In contrast, patients treated with lithium at the time of death had significantly lower pCREB levels in the same region.nnnCONCLUSIONSnThese results suggest that CREB activity may be an important factor in the neurobiology of suicide and the well-documented antisuicidal effect of lithium.

Identification of lithium-regulated genes in cultured lymphoblasts of lithium responsive subjects with bipolar disorder.

Lithium, a common drug for the treatment of bipolar disorder (BD), requires chronic administration to prevent recurrences of the illness. The necessity for long-term treatment suggests that changes in genes expression are involved in the mechanism of its action. We studied effects of lithium on gene expression in lymphoblasts from BD patients, all excellent responders to lithium prophylaxis. Gene expression was analyzed using cDNA arrays that included a total of 2400 cDNAs. We found that chronic lithium treatment at a therapeutically relevant concentration decreased the expression of seven genes in lymphoblasts from lithium responders. Five of these candidate lithium-regulated genes, including alpha1B-adrenoceptor (α1B-AR), acetylcholine receptor protein alpha chain precursor (ACHR), cAMP-dependent 3′,5′-cyclic phosphodiesterase 4D (PDE4D), substance-P receptor (SPR), and ras-related protein RAB7, were verified by Northern blotting analysis in lithium responders. None of these genes were regulated by lithium in healthy control subjects. When we compared the expression of these five genes between bipolar subjects and healthy control subjects at baseline, prior to lithium administration, we found that α1B-AR gene expression was higher in bipolar subjects than in healthy control subjects. Our findings indicate that α1B-AR may play an important role in the mechanism of action of lithium treatment.

Increased hippocampal supragranular Timm staining in subjects with bipolar disorder.

Biochemical and structural abnormalities have been reported in hippocampus of subjects with mood disorders. This study examined the organization of mossy fibers in anterior hippocampus of subjects obtained from the Stanley Neuropathology Consortium. Frozen postmortem hippocampal sections from subjects with major depression, bipolar disorder, schizophrenia and non-psychiatric controls were stained using the Neo-Timm procedure, which selectively stains mossy fibers. Increased Timm staining in the supragranular layer was found in subjects with bipolar disorder relative to control subjects. These results are suggestive of neuronal sprouting in hippocampus of subjects with bipolar disorder. There were no significant associations between supragranular Timm staining and suicide, length of illness or drug treatment at the time of death.