Extracellular CIRP Activates the IL-6Rα/STAT3/Cdk5 Pathway in Neurons.

Extracellular cold-inducible RNA-binding protein (eCIRP) stimulates microglial inflammation causing neuronal damage during ischemic stroke and is a critical mediator of alcohol-induced cognitive impairment. However, the precise role of eCIRP in mediating neuroinflammation remains unknown. In this study, we report that eCIRP activates neurotoxic cyclin-dependent kinase-5 (Cdk5)/p25 through the induction of IL-6Rα/STAT3 pathway in neurons. Amyloid ß (Aß)-mediated neuronal stress, which is associated with Alzheimer's disease, increased the levels of eCIRP released from BV2 microglial cells. The released eCIRP levels from BV2 cells increased 3.2-fold upon stimulation with conditioned medium from Neuro-2a (N2a) cells containing Aß compared to control N2a supernatant in a time-dependent manner. Stimulation of N2a cells and primary neurons with eCIRP upregulated the neuronal Cdk5 activator p25 expression in a dose- and time-dependent manner. eCIRP directly induced neuronal STAT3 phosphorylation and p25 increase via its novel receptor IL-6Rα. Next, we showed using surface plasmon resonance that eCIRP-derived peptide C23 inhibited the binding of eCIRP to IL-6Rα at 25 µM, with a 40-fold increase in equilibrium dissociation constant (Kd) value (from 8.08 × 10-8 M to 3.43 × 10-6 M), and completely abrogated the binding at 50 µM. Finally, C23 reversed the eCIRP-induced increase in neuronal STAT3 phosphorylation and p25 levels. In conclusion, the current study demonstrates that the upregulation of neuronal IL-6Rα/STAT3/Cdk5 pathway is a key mechanism of eCIRP's role in neuroinflammation and that C23 as a potent inhibitor of this pathway has translational potential in neurodegenerative pathologies controlled by eCIRP.

CDK5 Participates in Amyloid-ß Production by Regulating PPARγ Phosphorylation in Primary Rat Hippocampal Neurons.

Cyclin-dependent kinase 5 (CDK5) in adipose tissue mediates peroxisome proliferator-activated receptor γ (PPARγ) phosphorylation at Ser273 to inhibit its activity, causing PPARγ target gene expression changes. Among these, insulin-degrading enzyme (IDE) degrades amyloid-ß peptide (Aß), the core pathological product of Alzheimer's disease (AD), whereas ß-amyloid cleavage enzyme 1 (BACE1) hydrolyzes amyloid-ß protein precursor (AßPP). Therefore, we speculated that CDK5 activity in the brain might participate in Aß production, thereby functioning as a key molecule in AD pathogenesis. To confirm this hypothesis, we transduced primary rat hippocampal neurons using CDK5-expressing lentiviral vectors. CDK5 overexpression increased PPARγ Ser273 phosphorylation, decreased IDE expression, increased BACE1 and AßPP expression, increased Aß levels, and induced neuronal apoptosis. The CDK5 inhibitor roscovitine effectively reversed these CDK5 overexpression-mediated effects. Moreover, silencing of the Cdk5 gene via CDK5 shRNA-expressing lentiviral vectors in primary hippocampal neurons did not exert any protective effect against normal neuronal apoptosis, nor were significant effects observed on Aß levels, PPARγ phosphorylation, or PPARγ target gene expression in the cells. However, Cdk5 gene silencing exhibited a neuroprotective effect in the Aß-induced AD neuron model by effectively inhibiting the Aß-induced neuronal apoptosis, PPARγ phosphorylation, PPARγ expression downregulation, and PPARγ target gene expression changes, and reducing Aß levels. In conclusion, this study demonstrated that CDK5 played an important role in the pathogenesis of AD. Specifically, CDK5 participated in Aß production by regulating PPARγ phosphorylation. Targeted therapy against CDK5 could effectively reduce and reverse the neurotoxic effects of Aß and may represent a novel approach for AD treatment.

Crosstalk between Cdk5/p35 and ERK1/2 signalling mediates spinal astrocyte activity via the PPARγ pathway in a rat model of chronic constriction injury.

The specific mechanisms underlying cyclin-dependent kinase 5 (Cdk5)-mediated neuropathic pain at the spinal cord level remain elusive. The aim of the present study was to explore the role of crosstalk between Cdk5/p35 and extracellular signal-regulated kinase 1/2 (ERK1/2) signalling in mediating spinal astrocyte activity via the PPARγ pathway in a rat model of chronic constriction injury (CCI). Here, we quantified pain behaviour after CCI; detected the localization of p35, Cdk5, phosphorylated ERK1/2 (pERK1/2), phosphorylated peroxisome proliferator-activated receptor γ (pPPARγ), neuronal nuclei (a neuronal marker), glial fibrillary acidic protein (GFAP, an activated astrocyte marker) and ionized calcium binding adaptor molecule 1 (a microglial marker) in the dorsal horn using immunofluorescence; measured the protein levels of Cdk5, p35, pERK1/2, pPPARγ and GFAP using western blot analysis; and gauged the enzyme activity of Cdk5/p35 kinase using a Cdk5/p35 kinase activity assay kit. Tumour necrosis factor-α, interleukin (IL)-1ß and IL-6 levels were measured using enzyme-linked immunosorbent assay (ELISA). Ligation of the right sciatic nerve induced mechanical allodynia; thermal hyperalgesia; and the time-dependent upregulation of p35, pERK1/2 and GFAP and downregulation of pPPARγ. p35 colocalized with Cdk5, pERK1/2, pPPARγ, neurons and astrocytes but not microglia. Meanwhile, intrathecal injection of the Cdk5 inhibitor roscovitine, the mitogen-activated ERK kinase (MEK) inhibitor U0126 and the PPARγ agonist pioglitazone prevented or reversed behavioural allodynia, increased pPPARγ expression, inhibited astrocyte activation and alleviated proinflammatory cytokine (tumour necrosis factor-α, IL-1ß, and IL-6) release from activated astrocytes. Furthermore, crosstalk between the Cdk5/p35 and ERK1/2 pathways was observed with CCI. Blockade of either Cdk5/p35 or ERK1/2 inhibited Cdk5 activity. These findings indicate that spinal crosstalk between the Cdk5/p35 and ERK1/2 pathways mediates astrocyte activity via the PPARγ pathway in CCI rats and that targeting this crosstalk could be an effective strategy to attenuate CCI and astrocyte-derived neuroinflammation.

MicroRNA-505-5p functions as a tumor suppressor by targeting cyclin-dependent kinase 5 in cervical cancer.

MicroRNAs (miRs) are considered to be tumor suppressors or oncogenes as they regulate cell proliferation, migration, invasion, and differentiation. Recently, microRNA-505 (miR-505) has been reported as being involved in the progression of several human cancers. In the present study, we aim to investigate the expression rate and functional role of miR-505-5p in cervical cancer (CC) to determine its significance regarding the disease's development.The expression of miR-505-5p and cyclin-dependent kinase 5 (CDK5) in specimens of patients with CC and CC cell lines was examined by quantitative real-time PCR (qRT-PCR) and Western Blot. The relationship between miR-505-5p and CDK5 was verified by luciferase reporter assay. Cell counting kit-8 (CCK-8) assay, Scratch wound healing assay and transwell assay were used to detect the roles of miR-505-5p and CDK5 in CC cell functions. Western Blot was utilized to explore the epithelial-mesenchymal transition (EMT) markers.The result showed that in CC tissues and CC cell lines miR-505-5p was down-regulated while CDK5 level was up-regulated. MiR-505-5p was closely correlated with the metastasis-associated clinicopathological features. Overexpression of miR-505-5p inhibited cell viability, cell metastasis and EMT in CC cells. CDK5 was confirmed as a direct target of miR-505-5p and inverse relationship between them was also observed. Overexpression of CDK5 reduces the inhibitory effects of miR-505-5p in CC.Taken together, these results determine that miR-505-5p is a tumor suppressor miRNA which regulates tumor cell proliferation, migration, and invasion via binding to the functional target CDK5 and demonstrates its potential for future use in the treatment of CC.

ARNTL hypermethylation promotes tumorigenesis and inhibits cisplatin sensitivity by activating CDK5 transcription in nasopharyngeal carcinoma.

BACKGROUND: Increasing evidence support an important role for DNA methylation in nasopharyngeal carcinoma (NPC). Here, we explored the role of circadian clock gene Aryl Hydrocarbon Receptor Nuclear Translocator-Like (ARNTL) methylation in NPC. METHODS: We employed bisulfite pyrosequencing to determine the epigenetic change of ARNTL in NPC cell lines and tissues. ARNTL mRNA and protein expression in cell lines and tissues were detected by real-time PCR and western blotting. Then, we constructed cell lines overexpressing ARNTL and knocked down ARNTL to explore its function and effect on chemotherapy sensitivity of NPC cell lines to cisplatin in vitro and vivo. Finally, we investigated the potential molecular mechanism of ARNTL by gene set enrichment analysis (GSEA), dual Luciferase reporter assay and chromatin immunoprecipitation assay. RESULTS: ARNTL was hypermethylated, and its mRNA and protein were significantly down-regulated in NPC cell lines and tissues. When treated by 5-aza-2'-deoxycytidine, mRNA expression was up-regulated. Overexpression of ARNTL could suppress NPC cells proliferation in vitro and vivo while silencing of ARNTL using shRNA achieved opposite results. GSEA assay found that ARNTL was associated with cell cycle and ectopic ARNTL overexpression could induce G2-M phase arrest. Then, we identified and validated cyclin-dependent kinase 5 (CDK5) as the targeting gene of ARNTL by dual Luciferase reporter assay and chromatin immunoprecipitation assay. When transiently infected ARNTL-overexpression cells with PENTER-vector or PENTER-CDK5 plasmids, the later could reverse the suppressive effects of ARNTL on NPC cell proliferation. Moreover, ARNTL significantly enhanced sensitivity to cisplatin in NPC cells. CONCLUSIONS: ARNTL suppresses NPC cell proliferation and enhances sensitivity to cisplatin by targeting CDK5. ARNTL may represent a novel therapeutic target for NPC.

Sex-Specific Regulation of Fear Memory by Targeted Epigenetic Editing of Cdk5.

BACKGROUND: Sex differences in the expression and prevalence of trauma- and stress-related disorders have led to a growing interest in the sex-specific molecular and epigenetic mechanisms underlying these diseases. Cyclin-dependent kinase 5 (CDK5) is known to underlie both fear memory and stress behavior in male mice. Given our recent finding that targeted histone acetylation of Cdk5 regulates stress responsivity in male mice, we hypothesized that such a mechanism may be functionally relevant in female mice as well. METHODS: We applied epigenetic editing of Cdk5 in the hippocampus and examined the regulation of fear memory retrieval in male and female mice. Viral expression of zinc finger proteins targeting histone acetylation to the Cdk5 promoter was paired with a quantification of learning and memory of contextual fear conditioning, expression of CDK5, and enrichment of histone modifications of the Cdk5 gene. RESULTS: We found that male mice exhibit stronger long-term memory retrieval than do female mice, and this finding was associated with male-specific epigenetic activation of hippocampal Cdk5 expression. Sex differences in behavior and epigenetic regulation of Cdk5 occurred after long-term, but not short-term, fear memory retrieval. Finally, targeted histone acetylation of hippocampal Cdk5 promoter attenuated fear memory retrieval and increased tau phosphorylation in female but not male mice. CONCLUSIONS: Epigenetic editing uncovered a female-specific role of Cdk5 activation in attenuating fear memory retrieval. This finding may be attributed to CDK5 mediated hyperphosphorylation of tau only in the female hippocampus. Sex-specific epigenetic regulation of Cdk5 may reflect differences in the effect of CDK5 on downstream target proteins that regulate memory.

Hyperactive Innate Immunity Causes Degeneration of Dopamine Neurons upon Altering Activity of Cdk5.

Innate immunity is central to the pathophysiology of neurodegenerative disorders, but it remains unclear why immunity is altered in the disease state and whether changes in immunity are a cause or a consequence of neuronal dysfunction. Here, we identify a molecular pathway that links innate immunity to age-dependent loss of dopaminergic neurons in Drosophila. We find, first, that altering the expression of the activating subunit of the Cdk5 protein kinase (Cdk5α) causes severe disruption of autophagy. Second, this disruption of autophagy is both necessary and sufficient to cause the hyperactivation of innate immunity, particularly expression of anti-microbial peptides. Finally, it is the upregulation of immunity that induces the age-dependent death of dopaminergic neurons. Given the dysregulation of Cdk5 and innate immunity in human neurodegeneration and the conserved role of the kinase in the regulation of autophagy, this sequence is likely to have direct application to the chain of events in human neurodegenerative disease.

Role of Post-Transcriptional Control of Calpain by miR-124-3p in the Development of Alzheimer's Disease.

Alzheimer's disease (AD) is a neurodegenerative disease prevalent in aged people, clinically characterized by progressive memory loss, behavioral and learning dysfunction, and cognitive deficits. The pathogenesis of AD is hallmarked by formation of amyloid-ß peptide aggregates (Aß) and intraneuronal neurofibrillary tangles (NFTs), which are induced by hyperphosphorylation of amyloid-ß protein precursor and tau protein, respectively. The hyperphosphorylation is controlled by cyclin-dependent kinase-5 (CDK5), the aberrant activation of which is mediated by calpain (CAPN)-induced cleavage of p35 into p25. However, the regulation of CAPN in AD remains largely unknown. Here, we studied the post-transcriptional control of CAPN1 by microRNAs (miRNAs) in the setting of AD. We found that miR-124-3p, previously reported as a miRNA that was downregulated in AD, was a CAPN1-targeting miRNA that functionally inhibited the protein translation of CAPN1 in a human neural cell line, HCN-2. In vitro, transfection with miR-124-3p reduced the levels of CAPN1 protein, the cleavage of p35 into p25, and cell apoptosis dose-dependently in HCN-2 cells. Moreover, a significant inverse correlation was detected between the levels of miR-124-3p and CAPN1 in AD specimens. Furthermore, intracranial injection of adeno-associated virus expressing miR-124-3p into APP/PS1-AD mice significantly reduced Aß deposition and significantly improved the AD-mouse behavior in the social recognition test and plus-maze discriminative avoidance task. Together, our data suggest that post-transcriptional control of calpain by miR-124-3p plays an essential role in the development of AD.

EphA4 promotes cell proliferation and cell adhesion-mediated drug resistance via the AKT pathway in multiple myeloma.

Eph receptor A4 (EphA4), a member of the erythropoietin-producing hepatocellular (Eph) family, has been reported to upregulate in several tumors. However, the role of EphA4 in multiple myeloma has not been clarified yet. In this study, we found that EphA4 promoted proliferation of multiple myeloma cells via the regulation of cell cycle. Besides, EphA4 was closely related to cell adhesion of multiple myeloma cells and promoted cell adhesion-mediated drug resistance by enhancing the phosphorylation levels of Akt (p-AKT) expression in multiple myeloma. More interestingly, we discovered that EphA4 can interact with cyclin-dependent kinase 5 (CDK5) and regulate its expression in multiple myeloma. CDK5 has been reported to be overexpressed in multiple myeloma which mediated bortezomib resistance and also participated in AKT pathway. And we have also proved the fact. So, we supposed that EphA4 interacted with CDK5 and promoted its expression which in turn enhanced p-AKT expression and promoted cell adhesion-mediated drug resistance in multiple myeloma. Therefore, this study clarifies the molecular mechanism of cell adhesion-mediated drug resistance and may be useful in identifying potential target for treatment of multiple myeloma.

Synapsin III acts downstream of semaphorin 3A/CDK5 signaling to regulate radial migration and orientation of pyramidal neurons in vivo.

Synapsin III (SynIII) is a phosphoprotein that is highly expressed at early stages of neuronal development. Whereas in vitro evidence suggests a role for SynIII in neuronal differentiation, in vivo evidence is lacking. Here, we demonstrate that in vivo downregulation of SynIII expression affects neuronal migration and orientation. By contrast, SynIII overexpression affects neuronal migration, but not orientation. We identify a cyclin-dependent kinase-5 (CDK5) phosphorylation site on SynIII and use phosphomutant rescue experiments to demonstrate its role in SynIII function. Finally, we show that SynIII phosphorylation at the CDK5 site is induced by activation of the semaphorin-3A (Sema3A) pathway, which is implicated in migration and orientation of cortical pyramidal neurons (PNs) and is known to activate CDK5. Thus, fine-tuning of SynIII expression and phosphorylation by CDK5 activation through Sema3A activity is essential for proper neuronal migration and orientation.

AC1MMYR2 impairs high dose paclitaxel-induced tumor metastasis by targeting miR-21/CDK5 axis.

Paclitaxel (taxol) is a widely used chemo-drug for many solid tumors, while continual taxol treatment is revealed to stimulate tumor dissemination. We previously found that a small molecule inhibitor of miR-21, termed AC1MMYR2, had the potential to impair tumorigenesis and metastasis. The aim of this study was to investigate whether combining AC1MMYR2 with taxol could be explored as a means to limit tumor metastasis. Here we showed that abnormal activation of miR-21/CDK5 axis was associated with breast cancer lymph node metastasis, which was also contribute to high dose taxol-induced invasion and epithelial mesenchymal transition (EMT) in both breast cancer cell line MDA-MB-231 and glioblastoma cell line U87VIII. AC1MMYR2 attenuated CDK5 activity by functional targeting CDK5RAP1, CDK5 activator p39 and target p-FAK(ser732). A series of in vitro assays indicated that treatment of AC1MMYR2 combined with taxol suppressed tumor migration and invasion ability in both MDA-MB-231 and U87VIII cell. More importantly, combination therapy impaired high-dose taxol induced invadopodia, and EMT markers including ß-catenin, E-cadherin and vimentin. Strikingly, a significant reduction of lung metastasis in mice was observed in the AC1MMYR2 plus taxol treatment. Taken together, our work demonstrated that AC1MMYR2 appeared to be a promising strategy in combating taxol induced cancer metastasis by targeting miR-21/CDK5 axis, which highlighted the potential for development of therapeutic modalities for better clinic taxol application.

Targeting cyclin dependent kinase 5 in hepatocellular carcinoma--A novel therapeutic approach.

BACKGROUND & AIMS: For a long time cyclin dependent kinase 5 (Cdk5) was thought to be exclusively important in neuronal cells. However, increasing evidence recently suggests a function of Cdk5 in cancer progression. In this study, we examined the role of Cdk5 and its therapeutic accessibility in hepatocellular carcinoma (HCC), a highly chemoresistant cancer with poor prognosis and paramount clinical importance in order to develop novel targeted therapies for systemic treatment. METHODS: Expression and activity of Cdk5 was analyzed in a human HCC tissue microarray, human patient samples and HCC cell lines. To characterize Cdk5 functions and signaling pathways in HCC, we applied genetic downregulation and pharmacologic inhibition in various approaches including cell based assays and mouse xenograft models. RESULTS: Expression and activity of Cdk5 was increased in human HCC tissues as compared to normal liver tissues. Functional ablation of Cdk5 significantly decreased HCC cell proliferation and clonogenic survival. Moreover, genetic and pharmacological inhibition of Cdk5 showed in vivo efficacy in HCC xenograft mouse models. Investigating the mechanisms behind these functional effects revealed that Cdk5 is most active in the nucleus of cells in G2/M phase. Cdk5 regulates DNA damage response by phosphorylating ataxia telangiectasia mutated (ATM) kinase and thereby influencing its downstream cascade. Consequently, combination of Cdk5 inhibition with DNA-damage-inducing chemotherapeutics synergistically inhibited HCC tumor progression in vitro and in vivo. CONCLUSIONS: In summary, we introduce Cdk5 as a novel drugable target for HCC treatment and suggest the combination of Cdk5 inhibition and DNA damaging agents as a novel therapeutic approach.

Cyclin-dependent kinase 5 decreases in gastric cancer and its nuclear accumulation suppresses gastric tumorigenesis.

PURPOSE: As a cyclin-independent atypical CDK, the role of CDK5 in regulating cell proliferation in gastric cancer remains unknown. EXPERIMENTAL DESIGN: Expression of CDK5 in gastric tumor and paired adjacent noncancerous tissues from 437 patients was measured by Western blotting, immunohistochemistry, and real-time PCR. The subcellular translocation of CDK5 was monitored during gastric cancer cell proliferation. The role of nuclear CDK5 in gastric cancer tumorigenic proliferation and ex vivo xenografts was explored. Furthermore, by screening for compounds in the PubChem database that disrupt CDK5 association with its nuclear export facilitator, we identified a small molecular (NS-0011) that inhibits gastric cancer cell growth. RESULTS: CDK5 level was significantly decreased in the majority of gastric tumor tissues, and the reduction of CDK5 correlated with the severity of gastric cancer based on tumor and lymph node metastasis and patient 5-year fatality rate. Nuclear localization of CDK5 was found to be significantly decreased in tumor tissues and gastric cancer cell lines, whereas exogenously expression of nucleus-targeted CDK5 inhibited the proliferation and xenograft implantation of gastric cancer cells. Treatment with the small molecule NS-0011, which increases CDK5 accumulation in the nucleus, suppressed both cancer cell proliferation and xenograft tumorigenesis. CONCLUSIONS: Our results suggest that low CDK5 expression is associated with poor overall survival in patients with gastric cancer, and nuclear accumulation of CDK5 inhibits the proliferation and tumorigenicity of human gastric cancer cells.

c-Met signalling is required for efficient postnatal thymic regeneration and repair.

We have reported that in vivo administration of the hybrid cytokine rIL-7/HGFß or rIL-7/HGFα, which contains interleukin-7 (IL-7) and the ß- or α-chain of hepatocyte growth factor (HGF), significantly enhances thymopoiesis in mice after bone marrow transplantation. We have shown that the HGF receptor, c-Met, is involved in the effect of the hybrid cytokines. To address the role of c-Met signalling in thymocyte development and recovery, we generated conditional knockout (cKO) mice in which c-Met was specifically deleted in T cells by crossing c-Met(ft/ft) mice with CD4-Cre transgenic mice. We show here that although the number of total thymocytes and thymocyte subsets in young c-Met cKO mice is comparable to age-matched control (Ctrl) mice, the cKO mice were more susceptible to sub-lethal irradiation and dexamethasone treatment. This was demonstrated by low recovery in thymic cellularity in c-Met cKO mice after insult. Furthermore, the number of total thymocytes and thymocyte subsets was markedly reduced in 6- to 12-month-old cKO mice compared with age-matched Ctrl mice, and the thymic architecture of 12-month-old cKO mice was similar to that of 20-month-old wild-type mice. In addition, c-Met deficiency reduced cell survival and the expression of Bcl-xL in double-positive thymocytes, and decreased cell proliferation and the expression of cyclin E and cyclin-dependent kinase 5 in single-positive thymocytes. Our data indicate that c-Met signalling plays an important role in thymic regeneration after thymic insult. In addition, T-cell-specific inactivation of c-Met accelerates age-related thymic involution.

Effects of sevoflurane on the expression of tau protein mRNA and Ser396/404 site in the hippocampus of developing rat brain.

BACKGROUND: General anesthesia induces a transient hyperphosphorylation of tau protein that is associated with neurotoxicity in neonatal rats, but the mechanism remains unknown. The current study sought to investigate the effects of sevoflurane on the levels of tau phosphorylation at phosphor-Ser396/404 and total tau mRNA in the hippocampus of neonatal rats. MATERIALS AND METHODS: Thirty-six 7-day-old rats were randomly exposed for 6 h to either 3% sevoflurane (S) or air (NC) as a placebo. They were sacrificed at 1, 7 and 14 days after the anesthesia, respectively, and thus assigned to S1d , S7d , S14d , NC1d , NC7d , and NC14d groups (n = 6). Their brain tissues were harvested and then subjected to histopathologic, Western blot and real-time polymerase chain reaction analysis. RESULTS: Microtubule cytoskeletons were arranged in neat parallel rows in rats exposed only to air, whereas the microtubules were arranged in a disorderly and intermittent (nonparallel) fashion in rats exposed to sevoflurane. The levels of tau mRNA in the S1d and S7d groups were significantly higher than those in the NC1d and NC7d groups. There was no significant difference in the levels of tau mRNA between the S14d and NC14d groups. The levels of tau protein at Ser404 in the S1d , S7d, and S14d groups were significantly higher than those in NC1d , NC7d, and NC14d groups. The levels of tau protein at Ser396 in the S1d , and S7d groups were significantly higher than those in the NC1d , and NC7d groups, while there was no significant difference in the levels of tau protein at Ser396 between the S14d group and the NC14d group, respectively. CONCLUSION: In rat hippocampus, sevoflurane was associated with microtubular disarray as well as increased levels of tau mRNA and excessive phosphorylation of tau protein at Ser396 and Ser404. This implicates that sevoflurane may induce neurotoxicity.

Cyclin-dependent kinase-5 and p35/p25 activators in schizophrenia and major depression prefrontal cortex: basal contents and effects of psychotropic medications.

Cyclin-dependent kinase-5 (CDK5) and p35/p25 activators, interacting with the exocytotic machinery (e.g. munc18-1 and syntaxin-1A), play critical roles in neurosecretion. The basal status of CDK5/p35/p25 and the effect of psychotropic drugs (detected in blood/urine samples) were investigated in post-mortem prefrontal cortex (PFC)/Brodmann's area 9 of schizophrenia (SZ) and major depression (MD) subjects. In SZ (all subjects, n = 24), CDK5 and p35, but not p25, were reduced (-28 to -58%) compared to controls. In SZ antipsychotic-free (n = 12), activator p35 was decreased (-52%). In SZ antipsychotic-treated (n = 12), marked reductions of CDK5 (-47%), p35 (-76%) and p25 (-36%) were quantified. In MD (n = 13), including antidepressant-free/treated subgroups, CDK5, p35 and p25 were unaltered. In SZ (n = 24), CDK5, p35 or p25 correlated with munc18-1a, but not with syntaxin-1A. The results demonstrate reduced p35 basal content and down-regulation of CDK5/p35/p25 by antipsychotics in SZ. The suggested CDK5/munc18-1a functional interaction may lead to dysregulated neurosecretion in SZ PFC.

Chronic atomoxetine treatment during adolescence decreases impulsive choice, but not impulsive action, in adult rats and alters markers of synaptic plasticity in the orbitofrontal cortex.

RATIONALE: Impulsivity is a key symptom of attention-deficit hyperactivity disorder (ADHD). The use of the norepinephrine reuptake inhibitor, atomoxetine, to treat ADHD suggests that the activity of the norepinephrine transporter (NET) may be important in regulating impulsive behavior. Many ADHD patients receive chronic drug treatment during adolescence, a time when frontal brain regions important for impulse control are undergoing extensive development. OBJECTIVES: The current study aimed to determine the effects of chronic atomoxetine treatment during adolescence in rats on two distinct forms of impulsivity in adulthood and whether any behavioral changes were accompanied by alterations in mRNA or protein levels within the frontal cortices. METHODS: Rats received daily injections of saline or atomoxetine (1 mg/kg) during adolescence (postnatal days 40-54). Two weeks later, animals were trained to perform either the delay-discounting test or the five-choice serial reaction time task (5CSRT). RESULTS: Adolescent atomoxetine treatment caused a stable decrease in selection of small immediate rewards over larger delayed rewards (impulsive choice) in adulthood, but did not affect premature responding (impulsive action) in the 5CSRT. Chronic atomoxetine treatment also altered the ability of acute atomoxetine to modulate aspects of impulsivity, but did not change the response to d-amphetamine. Ex vivo analysis of brain tissue indicated that chronic atomoxetine decreased phosphorylation of CREB and ERK in the orbitofrontal cortex and decreased mRNA for BDNF and cdk5. CONCLUSIONS: These data suggest that repeated administration of atomoxetine in adolescence can lead to stable decreases in impulsive choice during adulthood, potentially via modulating development of the orbitofrontal cortex.

Direct effects of HIV-1 Tat on excitability and survival of primary dorsal root ganglion neurons: possible contribution to HIV-1-associated pain.

The vast majority of people living with human immunodeficiency virus type 1 (HIV-1) have pain syndrome, which has a significant impact on their quality of life. The underlying causes of HIV-1-associated pain are not likely attributable to direct viral infection of the nervous system due to the lack of evidence of neuronal infection by HIV-1. However, HIV-1 proteins are possibly involved as they have been implicated in neuronal damage and death. The current study assesses the direct effects of HIV-1 Tat, one of potent neurotoxic viral proteins released from HIV-1-infected cells, on the excitability and survival of rat primary dorsal root ganglion (DRG) neurons. We demonstrated that HIV-1 Tat triggered rapid and sustained enhancement of the excitability of small-diameter rat primary DRG neurons, which was accompanied by marked reductions in the rheobase and resting membrane potential (RMP), and an increase in the resistance at threshold (R(Th)). Such Tat-induced DRG hyperexcitability may be a consequence of the inhibition of cyclin-dependent kinase 5 (Cdk5) activity. Tat rapidly inhibited Cdk5 kinase activity and mRNA production, and roscovitine, a well-known Cdk5 inhibitor, induced a very similar pattern of DRG hyperexcitability. Indeed, pre-application of Tat prevented roscovitine from having additional effects on the RMP and action potentials (APs) of DRGs. However, Tat-mediated actions on the rheobase and R(Th) were accelerated by roscovitine. These results suggest that Tat-mediated changes in DRG excitability are partly facilitated by Cdk5 inhibition. In addition, Cdk5 is most abundant in DRG neurons and participates in the regulation of pain signaling. We also demonstrated that HIV-1 Tat markedly induced apoptosis of primary DRG neurons after exposure for longer than 48 h. Together, this work indicates that HIV-1 proteins are capable of producing pain signaling through direct actions on excitability and survival of sensory neurons.

Heterogeneity of genetic associations of CDKAL1 and HHEX with susceptibility of type 2 diabetes mellitus by gender.

We examined the genetic associations of previously identified sequence variants with type 2 diabetes mellitus (T2DM) and its potentially genetic heterogeneity by gender in a large-scale cohort. A total of 613 T2DM patients and 8221 control subjects from the Korea Association REsource (KARE) cohort were included in the analysis of genetic association of T2DM with 33 nucleotide polymorphic markers identified by previous studies. The association analysis was further conducted with data partitioned by gender. The association analysis resulted in five nucleotide sequence variants associated with the susceptibility of T2DM after Bonferonni correction (P < 0.0015). One was located near the gene of hematopoietically expressed homeobox (HHEX), and the others were all in the gene of cyclin-dependent kinase 5 regulatory subunit-associated protein 1-like 1 (CDKAL1). Further analysis revealed that the sequence variant (rs5015480) near HHEX and two SNPs (rs7756992 and rs9465871) in CDKAL1 were associated with the susceptibility of T2DM in females (P<0.005), but not in males (P>0.005). We suggested heterogeneous genetic associations of the T2DM susceptibility with the CDKAL1 and HHEX genes by gender.

Expression of CDK5/p35 in resected patients with non-small cell lung cancer: relation to prognosis.

Overall outcome of those patients with non-small cell lung cancer (NSCLC) remains poor. Recently, several studies demonstrated that cyclin-dependent kinase-5 (CDK5) activity with its specific activator protein p35 was important for spontaneous metastasis in various types of carcinomas. Our objective was to explore the expression of CDK5 and its prognostic indicator in patients with NSCLC. Immunofluorescent staining was used to detect the expression of CDK5/p35 in the lung tissue of 95 patients with NSCLC and 20 patients with benign pulmonary disease. The correlation between the expression of CDK5/p35 and clinicopathologic features of patients with NSCLC was investigated. The 5-year overall survival of patients with tumors expressing different levels of CDK5/p35 was evaluated by the Kaplan-Meier method. Positive expressions of CDK5/p35 were detected in the tumor cells in 66 samples (69.5%) of the 95 patients with NSCLC. Although no remarkable correlation between CDK5/p35 expression and age at the time of surgery, gender, and histopathologic type, there were significant differences between CDK5/p35 expression and degree of differentiation, pathological stage and lymph node metastasis in patients with NSCLC. In addition, we demonstrated that median survival for patients with and without CDK5/p35 expression was 24 and 58 months, respectively, and 5-year overall survival rate 25.8 and 48.3%, respectively (P<0.05). Patients with lung cancer with a positive CDK5/p35 expression had a poorer prognosis than those with a negative CDK5/p35 expression. Based on our results, CDK5/p35 may represent a biomarker for prognosis in patients with NSCLC.