The Effects of Self-Care Intervention Programs for Elderly with Mild Cognitive Impairment.

This study examined the effects of a self-care intervention program on self-efficacy, dementia-preventive behavior, cognitive function, depression, and quality of life in elderly with mild cognitive impairment. The study employed a quasi-experimental study design using a nonequivalent control group pre-post. Data were analyzed using the chi-square test, independent t-test, and repeated-measures ANOVA. The results of the study showed that the program reduced dementia risk and strengthened self-care ability in older adults with MCI.

Anti-photoaging effect of aaptamine in UVB-irradiated human dermal fibroblasts and epidermal keratinocytes.

Chronic exposure to ultraviolet (UV) irradiation causes sunburn, inflammatory responses, skin cancer, and photoaging. Photoaging, in particular, generates reactive oxygen species (ROS) that stimulate mitogen-activated protein kinase (MAPK) signaling and transcription factors. UV irradiation also activates matrix metalloproteinases (MMPs) expression and inactivates collagen synthesis. Aaptamine, a marine alkaloid isolated from the marine sponge, has been reported to have antitumor, antimicrobial, antiviral, and antioxidant activities. However, the photo-protective effects of aaptamine have not been elucidated. In this study, our data demonstrated that aaptamine deactivated UVB-induced MAPK and activator protein-1 signaling by suppressing ROS, resulting in attenuating the expression of MMPs in UVB-irradiated human dermal fibroblasts. Aaptamine also decreased proinflammatory cytokines such as cyclooxygenase-2, tumor necrosis factor-α, interleukin-1ß, and nuclear factor-kappa B subunits in UVB-irradiated human keratinocytes. In conclusion, we suggest that aaptamine represents a novel and effective strategy for treatment and prevention of photoaging.

5,7-Dimethoxyflavone, an activator of PPARα/γ, inhibits UVB-induced MMP expression in human skin fibroblast cells.

Peroxisome proliferator-activated receptors (PPARs), which are members of the nuclear hormone receptor superfamily, are a family of ligand-activated transcription factors that consist of three isotypes (PPAR α, δ and γ). PPAR activity was previously thought to be limited to lipid metabolism and glucose homeostasis; however, intensive studies of PPARα/γ in recent years have revealed their importance in age-related inflammation and photoaging as regulators of cytokines, matrix metalloproteinases (MMPs) and nuclear factor-kappa B (NF-κB). We evaluated the ability of the PPARα/γ activator 5,7-dimethoxyflavone (5,7-DMF) to inhibit ultraviolet B (UVB)-induced MMP expression in Hs68 human skin fibroblasts. Hs68 cells were treated with 5,7-DMF and then exposed to UVB irradiation. MMP expression, production and activity were determined by reverse transcription-polymerase chain reaction, enzyme-linked immunosorbent assay and gelatin zymography. PPARα/γ expression, catalase expression, and mitogen-activated protein kinase (MAPK), activator protein-1 (AP-1) and NF-κB signalling were evaluated by Western blot analysis. PPARα/γ activity was assessed with the GAL4/PPARα/γ transactivation assay. We found that 5,7-DMF strongly decreased MMP expression, production and activity. In addition, 5,7-DMF significantly increased PPARα/γ activation and catalase expression, thereby downregulating UVB-induced reactive oxygen species (ROS) production, ROS-induced MAPK signalling and downstream transcription factors. Finally, 5,7-DMF reduced IκBα phosphorylation, blocked NF-κB p65 nuclear translocation, strongly suppressed proinflammatory cytokines such as interleukin-6 (IL-6) and IL-8. 5,7-DMF prevents UVB-induced MMP expression by suppressing UVB-induced oxidative stress and age-related inflammation via NF-κB and MAPK/AP-1 pathways. Our findings suggest the usefulness of 5,7-DMF for preventing and treating skin photoaging.

Effects of macelignan isolated from Myristica fragrans (Nutmeg) on expression of matrix metalloproteinase-1 and type I procollagen in UVB-irradiated human skin fibroblasts.

Exposure to ultraviolet (UV) light causes premature skin aging that is associated with upregulated matrix metalloproteinases (MMPs) and decreased collagen synthesis. Macelignan, a natural lignan compound isolated from Myristica fragrans HOUTT. (nutmeg), has been reported to possess antioxidant and antiinflammatory activities. This study assessed the effects of macelignan on photoaging and investigated its mechanisms of action in UV-irradiated human skin fibroblasts (Hs68) by reverse transcription-polymerase chain reaction, Western blot analysis, 2',7'-dichlorofluorescein diacetate assay, and enzyme-linked immunosorbent assay. Our results show that macelignan attenuated UV-induced MMP-1 expression by suppressing phosphorylation of mitogen-activated protein kinases (MAPKs) induced by reactive oxygen species. Macelignan also increased type I procollagen expression and secretion through transforming growth factor ß (TGF-ß)/Smad signaling. These findings indicate that macelignan regulates the expression of MMP-1 and type I procollagen in UV-irradiated human skin fibroblasts by modulating MAPK and TGF-ß/Smad signaling, suggesting its potential as an efficacious antiphotoaging agent.

Boesenbergia pandurata attenuates diet-induced obesity by activating AMP-activated protein kinase and regulating lipid metabolism.

Obesity, a chronic metabolic disorder, is characterized by enlarged fat mass and dysregulation of lipid metabolism. The medicinal plant, Boesenbergia pandurata (Roxb.) Schltr., has been reported to possess anti-oxidative and anti-inflammatory properties; however, its anti-obesity activity is unexplored. The present study was conducted to determine whether B. pandurata extract (BPE), prepared from its rhizome parts, attenuated high-fat diet (HFD)-induced obesity in C57BL/6J mice. The molecular mechanism was investigated in 3T3-L1 adipocytes and HepG2 human hepatoma cells. BPE treatment decreased triglyceride accumulation in both 3T3-L1 adipocytes and HepG2 hepatocytes by activating AMP-activated protein kinase (AMPK) signaling and regulating the expression of lipid metabolism-related proteins. In the animal model, oral administration of BPE (200 mg/kg/day for 8 weeks) significantly reduced HFD-induced body weight gain without altering the amount of food intake. In addition, elevated serum levels of total cholesterol, low-density lipoprotein cholesterol, and triglycerides were suppressed by BPE administration. Fat pad masses were reduced in BPE-treated mice, as evidenced by reduced adipocyte size. Furthermore, BPE protected against the development of nonalcoholic fatty liver by decreasing hepatic triglyceride accumulation. BPE also activated AMPK signaling and altered the expression of lipid metabolism-related proteins in white adipose tissue and liver. Taken together, these findings indicate that BPE attenuates HFD-induced obesity by activating AMPK and regulating lipid metabolism, suggesting a potent anti-obesity agent.

HIF-1alpha controls keratinocyte proliferation by up-regulating p21(WAF1/Cip1).

The cyclin-dependent kinase inhibitor p21(WAF1/Cip1) plays a central role in a spatial and temporal balance of epidermal keratinocyte proliferation and growth arrest. However, what controls p21 expression in keratinocytes remains uncertain. Hypoxia-inducible factor 1alpha (HIF-1alpha) does not only express a variety of genes essential for hypoxic adaptation, but also up-regulates p21 so as to slow down cell cycle under hypoxic conditions. In the present study, we examined the role of HIF-1alpha in p21-mediated growth arrest of keratinocyte. Keratinocyte proliferation was arrested in the G1 phase at a high cell density. p21 was also up-regulated in a cell density-dependent manner and was found to be highly expressed in epidermal keratinocytes of normal human skins. In addition, in the same specimens and cells, we noted robust HIF-1alpha expression. HIF-1alpha siRNAs inhibited p21 expression and released the G1 arrest. In vivo, moreover, the intradermal injection of HIF-1alpha siRNA attenuated p21 expression in rat epidermis and induced skin hyperplasia. Mechanistically, we propose that the production of mitochondrial reactive oxygen species and the activation of the MEK/ERK pathway are involved in the HIF-1alpha stabilization in keratinocytes. These results imply that HIF-1alpha functions as an up-stream player in the p21-mediated growth arrest of keratinocytes.

A novel mode of action of YC-1 in HIF inhibition: stimulation of FIH-dependent p300 dissociation from HIF-1{alpha}.

Hypoxia-inducible factor (HIF)-1 plays a key role in tumor promotion by inducing approximately 60 genes required for tumor adaptation to hypoxia; thus, it is viewed as a target for cancer therapy. For this reason, YC-1, which down-regulates HIF-1alpha and HIF-2alpha at the post-translational level, is being developed as a novel anticancer drug. We here found that YC-1 acts in a novel manner to inhibit HIF-1. In the Gal4 reporter system, which is not degraded by YC-1, YC-1 was found to significantly inactivate the COOH-terminal transactivation domain (CAD) of HIF-1alpha, whereas it failed to inactivate CAD(N803A) mutant. In coimmunoprecipitation assays, YC-1 stimulated factor inhibiting HIF (FIH) binding to CAD even in hypoxia, whereas it failed to increase the cellular levels of hydroxylated Asn803 of CAD. It was also found that YC-1 prevented p300 recruitment by CAD in mammalian two-hybrid and coimmunoprecipitation assays. The involvement of FIH in YC-1-induced CAD inactivation was confirmed in EPO-enhancer and Gal4 reporter systems using FIH small interfering RNA and dimethyloxalylglycine FIH inhibitor. Indeed, FIH inhibition rescued HIF target gene expressions repressed by YC-1. In cancer cell lines other than Hep3B, YC-1 inhibits HIF-1alpha via the FIH-dependent CAD inactivation as well as via the protein down-regulation. Given these results, we suggest that the functional inactivation of HIF-alpha contributes to the YC-1-induced deregulation of hypoxia-induced genes.

CCAAT box is required for the induction of human thrombospondin-1 gene by trichostatin A.

Histone deacetylase (HDAC) inhibitors have been reported to inhibit angiogenesis as well as tumor growth. Thrombospondin-1 (TSP1) has been recognized as a potent inhibitor of angiogenesis. Such an action of TSP1 may account for the effect of HDAC inhibitors. In the present study, we investigated the molecular mechanism by which trichostatin A, a HDAC inhibitor, induces the expression of TSP1 gene. Trichostatin A increased both mRNA and protein levels of TSP1 in HeLa cells. Promoter and actinomycin D chase assays showed that trichostatin A-induced TSP1 expression was regulated at the transcriptional level without changing mRNA stability. CCAAT box on the TSP1 promoter was found to primarily mediate the trichostatin A response by deletion and mutation analyses of the TSP1 promoter. Electrophoretic mobility shift assay indicated that CCAAT-binding factor (CBF) was specifically bound to the CCAAT box of TSP1 promoter. Moreover, chromatin immunoprecipitation assay showed that trichostatin A increased the binding of acetylated form of histone H3 to the CCAAT box region of TSP1 promoter. Taken together, these results strongly suggest that trichostatin A activates the transcription of TSP1 gene through the binding of transcription factor CBF to CCAAT box and the enhanced histone acetylation. Thus, the present study provides the clue that the inhibition of angiogenesis by trichostatin A is accomplished through the upregulation of TSP1, the anti-angiogenic factor.

Exendin-4 induction of Egr-1 expression in INS-1 beta-cells: interaction of SRF, not YY1, with SRE site of rat Egr-1 promoter.

Glucagon-like peptide-1 (GLP-1) induces several immediate early response genes such as c-fos, c-jun, and early growth response-1 (Egr-1), which are involved in cell proliferation and differentiation. We recently reported that exendin-4 (EX-4), a potent GLP-1 agonist, upregulated Egr-1 expression via phosphorylation of CREB, a transcription factor in INS-1 beta-cells. This study was designed to investigate the role of another transcription factors, serum response factor (SRF) and Yin Yang-1 (YY1), in EX-4-induced Egr-1 expression. EX-4 significantly increased Egr-1 mRNA and subsequently its protein level. EX-4-induced Egr-1 expression was inhibited by pretreatment with a PKA inhibitor, H-89, and an MEK inhibitor, PD 98059. The siRNA-mediated inhibition of PKA and ERK1 resulted in significant reduction of EX-4-induced Egr-1 expression. Promoter analyses showed that SRE clusters were essential for Egr-1 transcription, and YY1 overexpression did not affect Egr-1 promoter activity. EMSA results demonstrated that EX-4-induced transient increase in DNA-protein complex on SRE site, and that both SRF and phospho-SRF were bound to this site. Treatment of either YY1 consensus oligonucleotide or YY1 antibody did not effect the change of density or migration of the DNA-protein complex. Collectively, EX-4-induced Egr-1 expression is largely dependent on cAMP-mediated extracellular signal-regulated kinase activation, and EX-4 induces Egr-1 transcription via the interaction of SRF and phospho-SRF to SRE sites.

Curcumin attenuates cytochrome P450 induction in response to 2,3,7,8-tetrachlorodibenzo-p-dioxin by ROS-dependently degrading AhR and ARNT.

TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) is a highly toxic environmental contaminant. When exposed to TCDD, mammalian cells undergo malignant transformation via abnormal intracellular signaling cascades, and the robust inductions of cytochrome P450 (CYP) enzymes are considered to mediate carcinogenesis by producing genotoxic metabolites. We here examined whether curcumin has preventive activity against TCDD-induced CYP production and cell transformation. Initially, the cellular levels of cytochrome P450 (CYP) 1A1 and 1B1 were examined, because these are known to generate estrogen metabolites that mediate genotoxic stress. Curcumin inhibited CYP1A1 and 1B1 induction by TCDD at the mRNA and protein levels. Notably, the nuclear levels of arylhydrocarbon receptor (AhR) and AhR nuclear translocator (ARNT) were decreased by curcumin, but those in the cytoplasm were not. It was also found that oxidative stress mediated the curcumin-induced degradations of AhR and ARNT. Furthermore, in vitro transformation assays showed that in normal human embryonic kidney cells and normal prostate cells curcumin prevents the anchorage-independent growth induced by TCDD. In conclusion, curcumin attenuates AhR/ARNT-mediated CYP induction by dioxin and presumably this mode-of-action may be responsible for the curcumin prevention of malignant transformation. The findings of this study should be found helpful in the design stage of pharmacodynamic studies for developing curcumin as a chemopreventive or anticancer agent.

Contribution of HIF-1alpha or HIF-2alpha to erythropoietin expression: in vivo evidence based on chromatin immunoprecipitation.

Circulating erythropoietin (EPO) is mainly produced by the kidneys and mediates erythrogenesis in bone marrow and nonhematopoietic cell survival. EPO is also produced in other tissues where it functions as a paracrine. Moreover, the hypoxic induction of EPO is known to be mediated by HIF-1alpha and HIF-2alpha, but it remains obscure as to which of these two mediators mainly contributes to EPO expression. Thus, we designed in vivo experiments to evaluate the contributions made by HIF-1alpha and HIF-2alpha to EPO expression. In mice exposed to mild whole body hypoxia, HIF-1alpha and HIF-2alpha were both induced in all tissues examined. However, EPO mRNA was expressed in kidney and brain, but not in liver and lung. Likewise, chromatin immunoprecipitation (CHIP) analyses demonstrated that HIF-1alpha or HIF-2alpha binding to the EPO gene increased under hypoxic conditions only in kidney and brain. A comparison of CHIP data and EPO mRNA levels suggested that, during mild hypoxia, renal EPO transcription is induced equally by HIF-1alpha and HIF-2alpha, but that brain EPO is mainly induced during hypoxia by HIF-2alpha. Thus, HIF-1alpha and HIF-2alpha appear to contribute to EPO expression tissue specifically.

YC-1 induces S cell cycle arrest and apoptosis by activating checkpoint kinases.

Hypoxia-inducible factor-1alpha (HIF-1alpha) seems central to tumor growth and progression because it up-regulates genes essential for angiogenesis and the hypoxic adaptation of cancer cells, which is why HIF-1alpha inhibition is viewed as a cancer therapy strategy. Paradoxically, HIF-1alpha also leads to cell cycle arrest or the apoptosis of cancer cells. Thus, the possibility cannot be ruled out that HIF-1alpha inhibitors unlock cell cycle arrest under hypoxic conditions and prevent cell death, which would limit the anticancer effect of HIF-1alpha inhibitors. Previously, we reported on the development of YC-1 as an anticancer agent that inhibits HIF-1alpha. In the present study, we evaluated the effects of YC-1 on hypoxia-induced cell cycle arrest and cell death. It was found that YC-1 does not reverse the antiproliferative effect of hypoxia, but rather that it induces S-phase arrest and apoptosis at therapeutic concentrations that inhibit HIF-1alpha and tumor growth; however, YC-1 did not stimulate cyclic guanosine 3',5'-monophosphate production in this concentration range. It was also found that YC-1 activates the checkpoint kinase-mediated intra-S-phase checkpoint, independently of ataxia-telangiectasia mutated kinase or ataxia-telangiectasia mutated and Rad3-related kinase. These results imply that YC-1 does not promote the regrowth of hypoxic tumors because of its cell cycle arrest effect. Furthermore, YC-1 may induce the combined anticancer effects of HIF-1alpha inhibition and cell growth inhibition.

NOX4 as an oxygen sensor to regulate TASK-1 activity.

When oxygen sensing cells are excited by hypoxia, background K+ currents are inhibited. TASK-1, which is commonly expressed in oxygen sensing cells and makes a background K+ current, is inactivated by hypoxia. Thus TASK-1 is a candidate molecule responsible for hypoxic excitation. However, TASK-1 per se cannot sense oxygen and may require a regulatory protein that can. In the present study, we propose that the NADPH oxidase NOX4 functions as an oxygen-sensing partner and that it modulates the oxygen sensitivity of TASK-1. Confocal imaging revealed the co-localization of TASK-1 and NOX4 in the plasma membrane. In HEK293 cells expressing NOX4 endogenously, the activity of expressed TASK-1 was moderately inhibited by hypoxia, and this oxygen response was significantly augmented by NOX4. Moreover, the oxygen sensitivity of TASK-1 was abolished by NOX4 siRNA and NADPH oxidase inhibitors. These results suggest a novel function for NOX4 in the oxygen-dependent regulation of TASK-1 activity.

Transmodulation between phospholipase D and c-Src enhances cell proliferation.

Phospholipase D (PLD) has been implicated in the signal transduction pathways initiated by several mitogenic protein tyrosine kinases. We demonstrate for the first time that most notably PLD2 and to a lesser extent the PLD1 isoform are tyrosine phosphorylated by c-Src tyrosine kinase via direct association. Moreover, epidermal growth factor induced tyrosine phosphorylation of PLD2 and its interaction with c-Src in A431 cells. Interaction between these proteins is via the pleckstrin homology domain of PLD2 and the catalytic domain of c-Src. Coexpression of PLD1 or PLD2 with c-Src synergistically enhances cellular proliferation compared with expression of either molecule. While PLD activity as a lipid-hydrolyzing enzyme is not affected by c-Src, wild-type PLDs but not catalytically inactive PLD mutants significantly increase c-Src kinase activity, up-regulating c-Src-mediated paxillin phosphorylation and extracellular signal-regulated kinase activity. These results demonstrate the critical role of PLD catalytic activity in the stimulation of Src signaling. In conclusion, we provide the first evidence that c-Src acts as a kinase of PLD and PLD acts as an activator of c-Src. This transmodulation between c-Src and PLD may contribute to the promotion of cellular proliferation via amplification of mitogenic signaling pathways.

Open channel block of Kv1.3 by rosiglitazone and troglitazone: Kv1.3 as the pharmacological target for rosiglitazone.

The effects of rosiglitazone and troglitazone were examined on cloned Kv1.3 channels stably expressed in Chinese hamster ovary cells using the whole-cell configuration of the patch-clamp technique. Rosiglitazone decreased the Kv1.3 currents and accelerated the decay rate of current inactivation in a concentration-dependent manner with an IC(50) of 18.6 microM. These effects were reversible after washout of the drug. Troglitazone caused the block of Kv1.3 with a similar pattern but was five times more potent than rosiglitazone with an IC(50) of 3.5 microM. The block of Kv1.3 by rosiglitazone and troglitazone was voltage-dependent at a membrane potential coinciding with the activation of the channels. Both drugs decreased the tail current amplitude and slowed the deactivation process of Kv1.3, resulting in a tail crossover phenomenon. These results indicate that rosiglitazone and troglitazone block the open state of Kv1.3 channels, suggesting that it is an important pharmacological target for rosiglitazone as a potent blocker of Kv1.3 channels.

Differential responses of two degradation domains of HIF-1alpha to hypoxia and iron deficiency.

HIF-1alpha is a transcription factor involved in the cellular adaptation to either hypoxia or iron deficiency. In the presence of oxygen and iron, proline residues in two degradation domains are modified by HIF-1-prolyl hydroxylases (PHDs), resulting in ubiquitination and degradation of HIF-1alpha. Since both molecular oxygen and iron are elements required for this hydroxylation process, HIF-1alpha might be unmodified and stable in conditions lacking oxygen or iron. If so, two degradation domains may respond to hypoxia and iron-depletion in the same way. In this study, however, we found two degradation domains to differentially regulate the stability of HIF-1alpha. The C-terminal domain responded to both hypoxia and iron-depletion, but the N-terminal domain to only iron-depletion. The deletion or point-mutation of the C-terminal domain blunted the hypoxic induction of HIF-1alpha. However, PHD-silencing siRNAs revealed that two degradation domains were not regulated by different types of PHDs. Both domains were regulated mainly by PHD2. The further mutational analysis demonstrated that the ARD1-acetylated motif near the C-terminal degradation domain (CDD) modulates the oxygen-dependent regulation of HIF-1alpha. The oxygen-dependent HIF-1alpha regulation requiring both proline hydroxylation and lysine acetylation may be more complicated than the iron-dependent regulation requiring only proline hydroxylation.

Spatial profile of back-propagating action potential-evoked Ca2+ transients in basal dendrites.

Calcium influx in basal dendrites evoked by back-propagating action potentials is important for understanding the input-specific modulation of synaptic transmission. Calcium transients evoked by back-propagating action potentials were measured for the basal dendrites of layer II/III pyramidal neurons in visual cortex slices. In contrast to apical dendrites, the peak calcium transients evoked by a single somatic action potential increased with distance from the soma. The peak calcium transients evoked by bursts of back-propagating action potentials (three or five pulses, 20 Hz) were greater than those evoked by a single back-propagating action potential. These different spatial profiles for calcium transients triggered by back-propagating action potentials between apical and basal dendrites suggest that the segregated inputs from brain areas might be modulated in different ways, according to their synaptic location.

Desensitization of somatostatin-induced inhibition of low extracellular magnesium concentration-induced calcium spikes in cultured rat hippocampal neurons.

Neuronal excitability is inhibited by somatostatin, which might play important roles in seizure and neuroprotection. The possibility of whether the effect of somatostatin on neurotransmission is susceptible to desensitization was investigated. We tested the effects of prolonged exposure to somatostatin on 0.1 mM extracellular Mg(2+) concentration ([Mg(2+)](o))-induced intracellular free Ca(2+) concentration ([Ca(2+)](i)) spikes in cultured rat hippocampal neurons using fura-2-based microfluorimetry. Reducing [Mg(2+)](o) to 0.1 mM elicited repetitive [Ca(2+)](i) spikes. These [Ca(2+)](i) spikes were inhibited by exposure to somatostatin-14. The inhibitory effects of somatostatin were blocked by pretreatment with pertussis toxin (PTX, 100 ng/ml) for 18-24 h. Prolonged exposure to somatostatin induced a desensitization of the somatostatin-induced inhibition of [Ca(2+)](i) spikes in a concentration-dependent manner. The somatostatin-induced desensitization was retarded by the nonspecific protein kinase C (PKC) inhibitor staurosporin (100 nM) or chronic treatment with phorbol dibutyrate (1 microM) for 24 h, but not by the protein kinase A inhibitor KT5720. The desensitization was significantly retarded by the novel PKCepsilon translocation inhibitor peptide (1 microM). In addition, suramin (3 microM), an inhibitor of G-protein-coupled receptor kinase 2 (GRK2), caused a reduction in the desensitization. After tetrodotoxin (TTX, 1 microM) completely blocked the low [Mg(2+)](o)-induced [Ca(2+)](i) spikes, glutamate-induced [Ca(2+)](i) transients were slightly inhibited by somatostatin and the inhibition was desensitized by prolonged exposure to somatostatin. These results indicate that the prolonged activation of somatostatin receptors induces the desensitization of somatostatin-induced inhibition on low [Mg(2+)](o)-induced [Ca(2+)](i) spikes through the activation of GRK2 and partly a novel PKCepsilon in cultured rat hippocampal neurons.

Serotonin inhibits the induction of NMDA receptor-dependent long-term potentiation in the rat primary visual cortex.

An increase in serotonin [5-hydroxytryptamine (5-HT)] levels in the rat visual cortex is correlated with the developmental decrease in long-term potentiation (LTP), and 5-HT may play an important role in the closure of the critical period by regulating LTP. The effect of 5-HT on the induction of N-methyl-D-aspartate receptor (NMDAR)-dependent and metabotropic glutamate receptor (mGluR)-dependent LTP in visual cortex slices from young rats was investigated. The field potential in layer II/III was recorded by stimulating the underlying layer IV. NMDAR-dependent LTP was induced in slices from 3-week-old rats by theta-burst stimulation (TBS) but not in slices from 5-week-old rats. However, LTP was induced in 5-HT-depleted slices from 5-week-old rats by incubation with para-chloroamphetamine (10 microM, 2 h), a 5-HT-depleting agent. The reinstated LTP in 5-HT-depleted slices was inhibited by the application of D-aminopentanoate, an NMDAR antagonist (50 microM) and 5-HT (10 and 30 microM). In contrast, the induction of mGluR-dependent LTP by weak TBS in disinhibited slices with picrotoxin (1 microM) in the bath was not affected by 5-HT application. The coapplication of 5-HT1A and 5-HT2 receptor agonists inhibited the induction of NMDAR-dependent LTP in 5-HT-depleted slices. 5-HT levels in the visual cortex increased with age. Based on these findings, we conclude that NMDAR-dependent LTP is specifically inhibited by coactivation of 5-HT1A and 5-HT2 receptors with the increase in 5-HT levels in the rat visual cortex at the end of the critical period.

Early expression of myocardial HIF-1alpha in response to mechanical stresses: regulation by stretch-activated channels and the phosphatidylinositol 3-kinase signaling pathway.

Vascular endothelial growth factor (VEGF) expression is upregulated by hypoxia-inducible factor-1 (HIF-1) in ischemic tissues and growing tumors. Normally, HIF-1 activity depends on the amount of HIF-1alpha subunit, which is tightly regulated by the oxygen tension. In the myocardium, VEGF expression has been shown to be induced under nonhypoxic conditions by mechanical stresses. However, the cellular mechanism of stress-mediated VEGF induction remains unclear. Therefore, we examined the possible involvement of HIF-1 in stress-mediated VEGF induction in rat hearts. In this study, we increased the left ventricular wall tension using 3 different methods, namely by inducing regional ischemia, by expanding an intraventricular balloon, and by producing hemodynamic overload using an aortocaval shunt. In all cases, HIF-1alpha accumulated in the nuclei of cardiac myocytes in the early phase, and this was followed by VEGF induction. Phosphatidylinositol 3-kinase (PI3K)-dependent Akt phosphorylation was found to be activated by mechanical stress and completely blocked by wortmannin (a PI3K inhibitor). Moreover, the stress-mediated induction of HIF-1alpha and VEGF was suppressed by gadolinium (a stretch-activated channel inhibitor), wortmannin, and rapamycin (a FRAP inhibitor). Our results suggest that HIF-1alpha plays an important role in the induction of VEGF in nonischemic and mechanically stressed myocardium, and that this is regulated by stretch-activated channels and the PI3K/Akt/FRAP pathway. Moreover, this signaling pathway, which induces HIF-1alpha, seems to play an important role in the adaptation of the myocardium to stresses. The full text of this article is available at http://www.circresaha.org.