Calcitonin gene-related peptide protects rats from cerebral ischemia/reperfusion injury via a mechanism of action in the MAPK pathway

The aim of the present study was to investigate the protective function and underlying mechanism of calcitonin gene-related peptide (CGRP) on cerebral ischemia/reperfusion damage in rats. Adult male Wistar rats were selected for the establishment of an ischemia/reperfusion injury model through the application of a middle cerebral artery occlusion. Animals were randomly divided into 6 groups of 24 animals. Drugs were administered according to the design of each group; animals were administered CGRP, CGRP8-37, PD98059 and SB20358. The neurobehavioral scores of the rat cerebral ischemia model in each group were calculated. The infarction range of the rat brain tissues was observed by 2,3,5-triphenyltetrazolium chloride staining. The expression levels of three proteins, phosphorylated c-Jun N-terminal kinase (JNK)/JNK, phosphorylated extracellular signal-regulated protein kinase (ERK)/ERK and p-p38/p38, in the mitogen-activated protein kinase (MAPK) pathway in the brain tissues was detected by western blotting. The results showed that CGRP could improve the neurobehavioral function of the ischemic rats and reduce the infarction range. Western blotting results confirmed that the function of the CGRP was mediated mainly through the reduction of the JNK and p38 phosphorylation and the promotion of ERK phosphorylation. Therefore, the present study confirmed that an increase in the exogenous CRGP could effectively improve ischemia/reperfusion injury of the brain tissue. The mechanisms of action were achieved through a reduction in JNK and p38 phosphorylation and an increase in ERL phosphorylation in the MAPK pathway. These mechanisms were interdependent.

Substitution at rt269 in Hepatitis B Virus Polymerase Is a Compensatory Mutation Associated with Multi-Drug Resistance

The emergence of compensatory mutations in the polymerase gene of drug resistant hepatitis B virus (HBV) is associated with treatment failure. We previously identified a multi-drug resistant HBV mutant, which displayed resistance towards lamivudine (LMV), clevudine (CLV), and entecavir (ETV), along with a strong replication capacity. The aim of this study was to identify the previously unknown compensatory mutations, and to determine the clinical relevance of this mutation during antiviral therapy. In vitro mutagenesis, drug susceptibility assay, and molecular modeling studies were performed. The rtL269I substitution conferred 2- to 7-fold higher replication capacity in the wild-type (WT) or YMDD mutation backbone, regardless of drug treatment. The rtL269I substitution alone did not confer resistance to LMV, ETV, adefovir (ADV), or tenofovir (TDF). However, upon combination with YMDD mutation, the replication capacity under LMV or ETV treatment was enhanced by several folds. Molecular modeling studies suggested that the rtL269I substitution affects template binding, which may eventually lead to the enhanced activity of rtI269-HBV polymerase in both WT virus and YMDD mutant. The clinical relevance of the rtL269I substitution was validated by its emergence in association with YMDD mutation in chronic hepatitis B (CHB) patients with sub-optimal response or treatment failure to LMV or CLV. Our study suggests that substitution at rt269 in HBV polymerase is associated with multi-drug resistance, which may serve as a novel compensatory mutation for replication-defective multi-drug resistant HBV.

Valproic Acid Regulates α-Synuclein Expression through JNK Pathway in Rat Primary Astrocytes

Although the role of α-synuclein aggregation on Parkinson's disease is relatively well known, the physiological role and the regulatory mechanism governing the expression of α-synuclein are unclear yet. We recently reported that α-synuclein is expressed and secreted from cultured astrocytes. In this study, we investigated the effect of valproic acid (VPA), which has been suggested to provide neuroprotection by increasing α-synuclein in neuron, on α-synuclein expression in rat primary astrocytes. VPA concentrationdependently increased the protein expression level of α-synuclein in cultured rat primary astrocytes with concomitant increase in mRNA expression level. Likewise, the level of secreted α-synuclein was also increased by VPA. VPA increased the phosphorylation of Erk1/2 and JNK and pretreatment of a JNK inhibitor SP600125 prevented the VPA-induced increase in α-synuclein. Whether the increased α-synuclein in astrocytes is involved in the reported neuroprotective effects of VPA awaits further investigation.

Oroxylin A Induces BDNF Expression on Cortical Neurons through Adenosine A2A Receptor Stimulation: A Possible Role in Neuroprotection

Oroxylin A is a flavone isolated from a medicinal herb reported to be effective in reducing the inflammatory and oxidative stresses. It also modulates the production of brain derived neurotrophic factor (BDNF) in cortical neurons by the transactivation of cAMP response element-binding protein (CREB). As a neurotrophin, BDNF plays roles in neuronal development, differentiation, synaptogenesis, and neural protection from the harmful stimuli. Adenosine A2A receptor colocalized with BDNF in brain and the functional interaction between A2A receptor stimulation and BDNF action has been suggested. In this study, we investigated the possibility that oroxylin A modulates BDNF production in cortical neuron through the regulation of A2A receptor system. As ex-pected, CGS21680 (A2A receptor agonist) induced BDNF expression and release, however, an antagonist, ZM241385, prevented oroxylin A-induced increase in BDNF production. Oroxylin A activated the PI3K-Akt-GSK-3β signaling pathway, which is inhibited by ZM241385 and the blockade of the signaling pathway abolished the increase in BDNF production. The physiological roles of oroxylin A-induced BDNF production were demonstrated by the increased neurite extension as well as synapse formation from neurons. Overall, oroxylin A might regulate BDNF production in cortical neuron through A2A receptor stimulation, which promotes cellular survival, synapse formation and neurite extension.

Transcriptional Upregulation of Plasminogen Activator Inhibitor-1 in Rat Primary Astrocytes by a Proteasomal Inhibitor MG132

Plasminogen activator inhibitor-1 (PAI-1) is a member of serine protease inhibitor family, which regulates the activity of tissue plasminogen activator (tPA). In CNS, tPA/PAI-1 activity is involved in the regulation of a variety of cellular processes such as neuronal development, synaptic plasticity and cell survival. To gain a more insights into the regulatory mechanism modulating tPA/PAI-1 activity in brain, we investigated the effects of proteasome inhibitors on tPA/PAI-1 expression and activity in rat primary astrocytes, the major cell type expressing both tPA and PAI-1. We found that submicromolar concentration of MG132, a cell permeable peptide-aldehyde inhibitor of ubiquitin proteasome pathway selectively upregulates PAI-1 expression. Upregulation of PAI-1 mRNA as well as increased PAI-1 promoter reporter activity suggested that MG132 transcriptionally increased PAI-1 expression. The induction of PAI-1 downregulated tPA activity in rat primary astrocytes. Another proteasome inhibitor lactacystin similarly increased the expression of PAI-1 in rat primary astrocytes. MG132 activated MAPK pathways as well as PI3K/Akt pathways. Inhibitors of these signaling pathways reduced MG132-mediated upregulation of PAI-1 in varying degrees and most prominent effects were observed with SB203580, a p38 MAPK pathway inhibitor. The regulation of tPA/PAI-1 activity by proteasome inhibitor in rat primary astrocytes may underlie the observed CNS effects of MG132 such as neuroprotection.

Hepatitis B virus inhibits liver regeneration via epigenetic regulation of urokinase-type plasminogen activator

Liver regeneration after liver damage caused by toxins and pathogens is critical for liver homeostasis. Retardation of liver proliferation was reported in hepatitis B virus (HBV) X protein (HBx)-transgenic mice. However, the underlying mechanism of the HBx-mediated disturbance of liver regeneration is unknown. We investigated the molecular mechanism of the inhibition of liver regeneration using liver cell lines and a mouse model. The mouse model of acute HBV infection was established by hydrodynamic injection of viral DNA. Liver regeneration after partial hepatectomy was significantly inhibited in the HBV DNA-treated mice. Mechanism studies have revealed that the expression of urokinase-type plasminogen activator (uPA), which regulates the activation of hepatocyte growth factor (HGF), was significantly decreased in the liver tissues of HBV or HBx-expressing mice. The down-regulation of uPA was further confirmed using liver cell lines transiently or stably transfected with HBx and the HBV genome. HBx suppressed uPA expression through the epigenetic regulation of the uPA promoter in mouse liver tissues and human liver cell lines. Expression of HBx strongly induced hypermethylation of the uPA promoter by recruiting DNA methyltransferase (DNMT) 3A2.

CONCLUSION

Taken together, these results suggest that infection of HBV impairs liver regeneration through the epigenetic dysregulation of liver regeneration signals by HBx.

Synergistic activation of lipopolysaccharide-stimulated glial cells by propofol

Despite the extensive use of propofol in general anesthetic procedures, the effects of propofol on glial cell were not completely understood. In lipopolysaccharide (LPS)-stimulated rat primary astrocytes and BV2 microglial cell lines, co-treatment of propofol synergistically induced inflammatory activation as evidenced by the increased production of NO, ROS and expression of iNOS, MMP-9 and several cytokines. Propofol augmented the activation of JNK and p38 MAPKs induced by LPS and the synergistic activation of glial cells by propofol was prevented by pretreatment of JNK and p38 inhibitors. When we treated BV2 cell culture supernatants treated with LPS plus propofol on cultured rat primary neuron, it induced a significant neuronal cell death. The results suggest that the repeated use of propofol in immunologically challenged situation may induce glial activation in brain.

RPS3a over-expressed in HBV-associated hepatocellular carcinoma enhances the HBx-induced NF-κB signaling via its novel chaperoning function

Hepatitis B virus (HBV) infection is one of the major causes of hepatocellular carcinoma (HCC) development. Hepatitis B virus X protein (HBx) is known to play a key role in the development of hepatocellular carcinoma (HCC). Several cellular proteins have been reported to be over-expressed in HBV-associated HCC tissues, but their role in the HBV-mediated oncogenesis remains largely unknown. Here, we explored the effect of the over-expressed cellular protein, a ribosomal protein S3a (RPS3a), on the HBx-induced NF-κB signaling as a critical step for HCC development. The enhancement of HBx-induced NF-κB signaling by RPS3a was investigated by its ability to translocate NF-κB (p65) into the nucleus and the knock-down analysis of RPS3a. Notably, further study revealed that the enhancement of NF-κB by RPS3a is mediated by its novel chaperoning activity toward physiological HBx. The over-expression of RPS3a significantly increased the solubility of highly aggregation-prone HBx. This chaperoning function of RPS3a for HBx is closely correlated with the enhanced NF-κB activity by RPS3a. In addition, the mutational study of RPS3a showed that its N-terminal domain (1–50 amino acids) is important for the chaperoning function and interaction with HBx. The results suggest that RPS3a, via extra-ribosomal chaperoning function for HBx, contributes to virally induced oncogenesis by enhancing HBx-induced NF-κB signaling pathway.

Cellular stress-induced up-regulation of FMRP promotes cell survival by modulating PI3K-Akt phosphorylation cascades

Background

Fragile X syndrome (FXS), the most commonly inherited mental retardation and single gene cause of autistic spectrum disorder, occurs when the Fmr1 gene is mutated. The product of Fmr1, fragile X linked mental retardation protein (FMRP) is widely expressed in HeLa cells, however the roles of FMRP within HeLa cells were not elucidated, yet. Interacting with a diverse range of mRNAs related to cellular survival regulatory signals, understanding the functions of FMRP in cellular context would provide better insights into the role of this interesting protein in FXS. Using HeLa cells treated with etoposide as a model, we tried to determine whether FMRP could play a role in cell survival.

Methods

Apoptotic cell death was induced by etoposide treatment on Hela cells. After we transiently modulated FMRP expression (silencing or enhancing) by using molecular biotechnological methods such as small hairpin RNA virus-induced knock down and overexpression using transfection with FMRP expression vectors, cellular viability was measured using propidium iodide staining, TUNEL staining, and FACS analysis along with the level of activation of PI3K-Akt pathway by Western blot. Expression level of FMRP and apoptotic regulator BcL-xL was analyzed by Western blot, RT-PCR and immunocytochemistry.

Results

An increased FMRP expression was measured in etoposide-treated HeLa cells, which was induced by PI3K-Akt activation. Without FMRP expression, cellular defence mechanism via PI3K-Akt-Bcl-xL was weakened and resulted in an augmented cell death by etoposide. In addition, FMRP over-expression lead to the activation of PI3K-Akt signalling pathway as well as increased FMRP and BcL-xL expression, which culminates with the increased cell survival in etoposide-treated HeLa cells.

Conclusions

Taken together, these results suggest that FMRP expression is an essential part of cellular survival mechanisms through the modulation of PI3K, Akt, and Bcl-xL signal pathways.

Inhibition of GSK-3beta mediates expression of MMP-9 through ERK1/2 activation and translocation of NF-kappaB in rat primary astrocyte

Glycogen synthase kinase (GSK)-3beta and extracellular signal-regulated kinase (ERK) regulate several cellular signaling pathways in common, including embryonic development, cell differentiation and apoptosis. In this study, we investigated whether GSK-3beta inhibition is involved in ERK activation, which affects the activation of NF-kappaB and induction of MMP-9 in cultured rat primary astrocytes. Here, we found that GSK-3beta inhibition using GSK-3beta inhibitor TDZD-8 increased the phosphorylation of GSK-3beta at Ser9 site as well as the phosphorylation of ERK1/2 and Akt at Ser473 site. In this condition, GSK-3beta inhibition increased MMP-9 but not MMP-2 activity in a concentration-dependent manner. In RT-PCR analysis, MMP-9 mRNA level was increased by GSK-3beta inhibition in a concentration-dependent manner. MMP-9 promoter reporter activity was similarly increased by GSK-3beta inhibition. Pretreatment of U-0126 (MEK1/2 inhibitor) completely abolished the GSK-3beta inhibition-induced phosphorylation of ERK1/2. U-0126 prevented GSK-3beta inhibition-mediated induction of MMP-9 reporter activity as well as the MMP-9 gene expression. The transcriptional activity of NF-kappaB was significantly increased by GSK-3beta inhibition, which was determined by nuclear translocation of NF-kappaB. Inhibition of ERK1/2 activity by U-0126 also completely blocked the nuclear translocation of NF-kappaB. Transfection of dominant negative plasmid (S9A) of GSK-3beta significantly decreased phosphorylation of ERK, MMP-9 expression and nuclear translocation of NF-kappaB by GSK-3beta inhibition as compared to wild type GSK-3beta. These data suggest that GSK-3beta inhibition mediates ERK1/2 activation followed by NF-kappaB activation, which directly regulates the induction of MMP-9 in rat primary astrocytes.

Identification and characterization of four novel peptide motifs that recognize distinct regions of the transcription factor CP2

Although ubiquitously expressed, the transcriptional factor CP2 also exhibits some tissue- or stage-specific activation toward certain genes such as globin in red blood cells and interleukin-4 in T helper cells. Because this specificity may be achieved by interaction with other proteins, we screened a peptide display library and identified four consensus motifs in numerous CP2-binding peptides: HXPR, PHL, ASR and PXHXH. Protein-database searching revealed that RE-1 silencing factor (REST), Yin-Yang1 (YY1) and five other proteins have one or two of these CP2-binding motifs. Glutathione S-transferase pull-down and coimmunoprecipitation assays showed that two HXPR motif-containing proteins REST and YY1 indeed were able to bind CP2. Importantly, this binding to CP2 was almost abolished when a double amino acid substitution was made on the HXPR sequence of REST and YY1 proteins. The suppressing effect of YY1 on CP2's transcriptional activity was lost by this point mutation on the HXPR sequence of YY1 and reduced by an HXPR-containing peptide, further supporting the interaction between CP2 and YY1 via the HXPR sequence. Mapping the sites on CP2 for interaction with the four distinct CP2-binding motifs revealed at least three different regions on CP2. This suggests that CP2 recognizes several distinct binding motifs by virtue of employing different regions, thus being able to interact with and regulate many cellular partners.

Synthesis andin vitro cytotoxicity of 1,3-dioxoindan-2-carboxylic acid arylamides

A series of 1,3-dioxoindan-2-carboxylic acid arylamides were synthesized and evaluated for in vitro cytotoxicity against four human cancer cell lines (HOP62, SK-OV-3, MD-MB-468 and T-47D). The most active was compound 3e (1.2 microM against SK-OV-3 cell line) bearing a 4-methyl substituent.

Transcription factor CP2 is involved in activating mBMP4 in mouse mesenchymal stem cells

CP2 is a member of a family of transcription factors that regulate genes involved in events from early development to terminal differentiation. In an effort to understand how it selects its target genes we carried out a database search, and located several CP2 binding motifs in the promoter region of bone morphogenetic protein-4 (BMP4). BMP4 is a key regulator of cell fate and body patterning throughout development. For the CP2 binding motifs in BMP4 promoter region to be relevant in vivo, CP2 and BMP4 should be expressed together. We found that CP2b and CP2c, two potent transcriptional activators, are expressed in a manner similar to BMP4 during osteoblast differentiation of C3H10T1/2 cells. In in vitro assays, the CP2 proteins bound to two CP2 binding motifs (-715 to -676 and -147 to -118) in the BMP4 promoter, and luciferase reporter assays indicated that this binding was essential for transcription of BMP4 during osteoblast differentiation. Taken together, our data indicate that CP2b and CP2c play important roles during bone development by activating BMP4 transcription.

Synthesis and in vitro evaluation of 7-dialkylaminomethylbenzo[ g ]quinoxaline-5,10-diones

A series of benzo[g]quinoxaline-5,10-dione derivatives carrying a 7-dialkylaminomethyl substituent was synthesized and their in vitro cytotoxic activities were evaluated against four human cancer cell lines (HCT-15, SK-OV-3, MD-MB-468 and T-47D). The most active compound 9d showed cytotoxic activity comparable to that of doxorubicin against HCT-15 cancer cell line.

Synthesis and in vitro evaluation of 1,8-diazaanthraquinones bearing 3-dialkylaminomethyl or 3-(N-alkyl- or N-aryl)carbamoyloxymethyl substituent

A series of 1,8-diazaanthraquinone derivatives carrying a 3-dialkylaminomethyl or a 3-(N-alkyl or aryl)carbamoyloxymethyl substituent was synthesised and their in vitro cytotoxic activities were evaluated against eight human cancer cell lines (HOP62, SK-OV-3, HCT-15, SF295, MCF7, SNU-354, KB-3-1 and KB-V-1). A number of compounds including 8c, 8d and 11c showed cytotoxic activity comparable to that of doxorubicin against all human cancer cell lines tested. The compounds 8c and 8d were 2-100 times more potent than doxorubicin against HCT-15, MCF7 and SNU-354 cancer cell lines. Furthermore, these compounds retained considerable cytotoxic activity against the doxorubicin-resistant cell line KB-V-1, implying their therapeutic potential to treat doxorubicin-resistant tumours. These compounds inhibited topoisomerase II-mediated DNA relaxation in vitro, suggesting that this inhibitory effect be attributable to their cytotoxicity.

Design and synthesis of isoindoloquinoline derivatives as potential antitumor agents

A series of isoindoloquinoline derivatives was synthesized and evaluated in vitro cytotoxicity against four human cancer cell lines (HCT15, SK-OV-3, MDA-MB-468 and T-47D).

Synthesis and in vitro cytotoxicity of 4-alkyl- or 4-arylaminosubstituted cyclopenta[c]quinoline derivatives

Twelve 4-substituted cyclopenta[c]quinoline derivatives were synthesized and evaluated in vitro cytotoxicity against four human cancer cell lines (HOP62, SK-OV-3, MD-MB-468 and T-47D). The compounds 6c and 6e bearing p-anisidine and pyrrolidine side chain were more active than the others.

Overexpression of Akt inhibits NGF-induced growth arrest and neuronal differentiation of PC12 cells

To investigate the role of Akt in nerve growth factor (NGF)-induced neuronal differentiation, PC12 cells ectopically expressing wild-type or dominant-inhibitory forms of Akt were analyzed. NGF-induced neurite outgrowth was greatly accelerated in cells expressing dominant-inhibitory Akt, compared to parental PC12 cells, but was almost completely blocked in cells expressing wild-type Akt. Since neuronal differentiation requires an arrest of cell growth, several aspects of cell growth of the different cell lines were compared. Cells expressing wild-type Akt were not susceptible to the growth-arresting effect of NGF, whereas parental PC12 cells and notably cells expressing mutant Akt were so affected. Accompanying this, the expressions of CDKs and p21(WAF1) were down- and up-regulated, respectively, in both parental PC12 cells and cells expressing mutant Akt. When treated with some growth arrest-inducing agents such as sodium nitroprusside, forskolin and butyrolactone I, cells expressing wild-type Akt regained their responsiveness to the effects of NGF on differentiation. In summary, our results indicate that Akt overrides the growth-arresting effect of NGF and thereby, negatively regulates neuronal differentiation.

Synthesis and in vitro cytotoxicity of 2-alkylaminosubstituted quinoline derivatives

Eight 2-alkylaminosubstituted 5,8-dimethoxy-4-methylquinolines and nine 2-alkylaminosubstituted or 2,6-disubstituted 4-methylquinoline-5,8-diones were synthesized and evaluated in vitro cytotoxicity against four human cancer cell lines (HOP62, SK-OV-3, HCT15 and SF295).

Heat shock-induced, caspase-3-independent rapid breakdown of Akt and consequent alteration of its total phosphorylation/activity level

The immediate effect of a 15-min heat shock was examined on the level and the activity of Akt. Following heat shock, the Akt level decreased by 15-70% in a temperature-dependent and phosphorylation status-independent manner. This decrease of Akt level was not prevented by caspase inhibitors. At 48 degrees C, the extent of the breakdown was so immense that the total phosphorylation/activity level of Akt was not increased over the control level, implying that the total cellular activity of Akt governed by the level and the molar activity does not necessarily undergo the ensuing change.

Experience with continuous infusion of recombinant activated factor VII in the Asia-Pacific region

There is increasing interest in continuous infusion of recombinant activated factor VII (rFVIIa) as a convenient and safe alternative to intermittent bolus therapy. In the Australian patients reported in this paper, cost savings of up to 25% in the first 12 h of treatment with continuous infusion of rFVIIa have been achieved safely, suggesting that substantial overall savings are possible. However, in the Thai patient reported, a dose reduction of 35% in the first 12 h was associated with poor haemostatic control, suggesting that a dose reduction of >25% may be inadvisable. The indications for treatment in the five Australian patients were: retroperitoneal haemorrhage (n = 3); right forearm compartment syndrome (n = 1); wrist haemarthrosis and median nerve compression (n = 2); sublingual haematoma (n = 1); and cerebral (mid-brain) haemorrhage (n = 1). Treatment was effective in four out of five patients (six bleeding episodes) and there was one treatment failure where treatment had been substantially delayed. The Thai patient was treated as part of a prospective, uncontrolled, observational study of 34 bleeding episodes in 22 patients in the Asia-Pacific region. Treatment was judged ineffective after 24 h, but full haemostatic control was subsequently achieved with intermittent rFVIIa therapy.

Regulatory mechanism of polarized membrane transport by glucocorticoid in renal proximal tubule cells: involvement of [Ca2+]i

We examined the effect of glucocorticoids on brush border membrane transporters and, furthermore, the involvement of Ca2+ in its action in the primary cultured rabbit renal proximal tubule cells (PTCs). Dexamethasone (DEX, 10(-9) M) decreased Pi uptake by 17%; whereas DEX affected neither alpha-methyl-glucopyranoside (alpha-MG) uptake nor Na+ uptake. The DEX-induced inhibition of Pi uptake was due to a decrease of V(max). In contrast, other steroid hormones such as progesterone, testosterone, and 17beta-estradiol (10(-9) M) did not induce inhibition of Pi uptake. In order to examine the involvement of Ca2+ in DEX-induced inhibition of Pi uptake, PTCs were treated with A 23187 (10(-6) M, Ca2+ ionophore). A 23187 also inhibited Pi uptake, mimicking DEX action in Pi uptake. Treatments with W-7 (10(-4) M, calmodulin dependent kinase inhibitor), KN-62 (10(-6) M, Ca2+/calmodulin-dependent protein kinase II inhibitor), and BAPTA/AM (10(-6) M) or TMB-8 (10(-4) M) (intracellular Ca2+ mobilization blockers) blocked the DEX-induced inhibition of Pi uptake. However, nifedifine, methoxyverapamil (10(-6) M, L-type Ca2+ channel blockers), and EGTA (1 mM, extracellular Ca2+ chelator) did not block it. In conclusion, DEX inhibited Pi uptake via, in part, Ca2+/calmodulin pathway mediated by intracellular Ca2+ mobilization in the PTCs.

Synthesis and in vitro cytotoxicity of 1-azaanthraquinone-3-carboxamides

Five 1-azaanthraquinone-3-carboxamides were synthesized and evaluated in vitro cytotoxicity against four human cancer cell lines. The most active compound, 7b, exhibited cytotoxic activity comparable to doxorubicin.

Psammaplin A, a natural bromotyrosine derivative from a sponge, possesses the antibacterial activity against methicillin-resistant Staphylococcus aureus and the DNA gyrase-inhibitory activity

Psammaplin A, a natural bromotyrosine derivative from an associated form of two sponges (Poecillastra sp. and Jaspis sp.) was found to possess the antimicrobial effect on the Gram-positive bacteria, especially on methicillin-resistant Staphylococcus aureus (MRSA). The minimal inhibitory concentration of psammaplin A against twenty one MRSAs ranged from 0.781 to 6.25 microg/ml, while that of ciprofloxacin was 0.391-3.125 microg/ml. Psammaplin A could not bind to penicillin binding protein, but inhibited the DNA synthesis and the DNA gyrase activity with the respective 50% (DNA synthesis) and 100% (DNA gyrase) inhibitory concentration 2.83 and 100 microg/ml. These results indicate that psammaplin A has a considerable antibacterial activity, although restricted to a somewhat narrow range of bacteria, probably by inhibiting DNA gyrase.

Synthesis and in vitro cytotoxicity of 3-substituted-1,8-diazaanthraquinones produced by Lewis-acid catalyzed hetero Diels-Alder reaction

A hetero Diels-Alder reaction of quinoline-5,8-dione with 1-(N,N-dimethylamino)-3-methyl-1-aza-1,3-butadiene proceeded to give 3-methyl-1,8-diazaanthraquinone (100% regioselectivity) in the presence of Lewis-acid catalyst (ZnCl2 or ZnBr2). Subsequent functionalizations of the benzylic methyl group resulted in the 1,8-diazaanthraquinone analogues as potential antitumor agents. The most active compound, 8, exhibited in vitro cytotoxic activity comparable to that of doxorubicin.

The protein kinase encoded by the Akt proto-oncogene is a target of the PDGF-activated phosphatidylinositol 3-kinase

The serine/threonine protein kinase encoded by the Akt proto-oncogene is catalytically inactive in serum-starved primary and immortalized fibroblasts. Here we show that Akt and the Akt-related kinase AKT2 are activated by PDGF. The activation was rapid and specific, and it was abrogated by mutations in the Akt Pleckstrin homology (PH) domain. The Akt activation was also shown to depend on PDGFR beta tyrosines Y740 and Y751, which bind phosphatidylinositol 3-kinase (PI 3-kinase) upon phosphorylation. Moreover, Akt activation was blocked by the PI 3-kinase-specific inhibitor wortmannin and the dominant inhibitory N17Ras. Conversely, Akt activity was induced following the addition of phosphatidylinositol-3-phosphate to Akt immunoprecipitates from serum-starved cells in vitro. These results identify Akt as a novel target of PI 3-kinase and suggest that the Akt PH domain may be a mediator of PI 3-kinase signaling.

AH/PH domain-mediated interaction between Akt molecules and its potential role in Akt regulation

The cytoplasmic serine-threonine protein kinase coded for by the c-akt proto-oncogene features a protein kinase C-like catalytic domain and a unique NH2-terminal domain (AH domain). The AH domain is a member of a domain superfamily whose prototype was observed in pleckstrin (pleckstrin homology, or PH, domain). In this communication, we present evidence that the AH/PH domain is a domain of protein-protein interaction which mediates the formation of Akt protein complexes. The interaction between c-akt AH/PH domains is highly specific, as determined by the failure of this domain to bind AKT2. The AH/PH domain-mediated interactions depend on the integrity of the entire domain. Akt molecules with deletions of the NH2-terminal portion (amino acids 11 to 60) and AH/PH constructs with deletions of the C-terminal portion of this domain (amino acids 107 to 147) fail to interact with c-akt. To determine the significance of these findings, we carried out in vitro kinase assays using Akt immunoprecipitates from serum-starved and serum-starved, platelet-derived growth factor-stimulated NIH 3T3 cells. Addition of maltose-binding protein-AH/PH fusion recombinant protein, which is expected to bind Akt, to the immunoprecipitates from serum-starved cells induced the activation of the Akt kinase.

Influence of intact and partially hydrolysed guar gum on iron utilization in rats fed on iron-deficient diets

Effects of partially hydrolysed guar gum (PHGG) or intact guar gum (GG) on iron utilization in rats fed on several iron-deficient diets were examined. Hemoglobin, serum iron and iron storage in liver of rats fed on iron-deficient diets as a control group (without PHGG and GG) significantly decreased, while those of the test group fed together with PHGG or GG were unchanged. In an iron balance test for 3 days, administration of PHGG or GG caused an increase in iron absorption. The results suggested that PHGG or its metabolites increase the bioavailability of dietary iron in deficiency.

Comparison of heterotrimeric protein phosphatase 2A containing different B subunits

Protein phosphatase 2A (PP2A) is composed of structural (A), catalytic (C), and regulatory subunits (B). Immunological analyses identified B alpha/PR55 alpha as the major regulatory subunit of brain PP2A while a unique B' subunit was associated with the cardiac enzyme. Recombinant PP2A heterotrimers were purified from insect cells infected with baculoviruses expressing A and C, in combination with viruses expressing B alpha/PR55 alpha, B beta/PR55 beta, or SV40 small tumor antigen (st). Phosphatase activities of rAC-B alpha and rAC-B beta were similar to those for brain AC-B alpha, while rAC-st was 50-80% less active. Heparin had no effect on rAC-st myosin light chain phosphatase activity, while the B subunit-containing forms were stimulated 2-3-fold. Protamine caused a 3-4-fold increase in AC-B alpha and rAC-st activities and a marked activation of rAC-B beta (6-fold) and AC-B' (10.5-fold). When histone H1 was used as substrate, all of the heterotrimers were stimulated approximately 4-fold by heparin. The activity of AC-B' and rAC-B beta were increased 2-fold by Mn2+, while a 6-fold stimulation was observed with rAC-st. Chemical cross-linking of AC-B alpha and AC-B beta generated 200-kDa complexes, while AC-st was present as a 150-kDa complex. These results demonstrate that different regulatory proteins affect enzyme activity and the response to agents that modify PP2A activity in vitro. Different PP2A heterotrimers are likely to have distinct functions in vivo, and changes in subunit composition will have an important impact on signal transduction pathways.

p-Chlorophenylalanine damages pancreatic acinar cell of the chicken

1. Birds were injected intraperitoneally with DL-p-chlorophenylalanine (p-CP), which is an inhibitor of phenylalanine hydroxylase, or saline one day before the experiment. The weight and cell size of pancreas increased by the p-CP treatment. 2. The application of acetylcholine (5.50 x 10(-9) to 5.50 x 10(-5) M) caused a dose dependent increase in amylase release from the superfused segment of pancreas, although the response significantly decreased in the pancreatic segment treated with p-CP, compared with the control.

Medium-chain triacylglycerols enhance release of cholecystokinin in chicks

Whether medium-chain triacylglycerols (MCT) affect the plasma concentration of cholecystokinin (CCK) and crop-emptying rate in chicks was investigated after 0, 30, 60, 90, 120 or 180 min of diet intubation. Triacylglycerol sources used were corn oil [containing long-chain triacylglycerols (LCT)], glyceryl tricaprate and glyceryl tricaprylate at a level of 200 g/kg diet. Plasma CCK concentration was significantly enhanced in chicks given the two MCT treatments, but not in those given the LCT treatment, after 30 min feeding relative to the initial level. At all time points, chicks fed the diet containing LCT had significantly lower plasma CCK concentrations than those fed MCT, and chicks fed glyceryl tricaprate had higher concentrations than those fed glyceryl tricaprylate. Dietary MCT sources significantly delayed diet passage from the crop compared with dietary LCT. These results indicate that MCT are more potent stimulators of CCK secretion in chicks than LCT.

Influence of dietary protein concentrations or of duodenal amino acid infusion on cholecystokinin release in goats

1. Whether dietary protein levels or duodenal infusion of amino acids alters the release of cholecystokinin (CCK) in blood plasma of goats was investigated in three experiments. The CCK determination was done by radioimmunoassay with specific CCK-8 antibody. The male adult Shiba goat, a miniature Japanese native goat, was used. 2. In Experiment 1, four goats were offered a diet containing 4.94 g crude protein (CP)/kg BW0.75 for the first 7 days. They were then given a diet containing 5.86 g CP/kg BW0.75 for 7 days and thereafter 6.79 g CP/kg BW0.75 for the following 7 days. On the last day of each experimental period, blood samples were taken from the jugular vein at zero (before feeding), 30, 60, 120, 240 or 360 min after the feeding of the diet. Plasma CCK levels were not affected by dietary protein levels and time after feeding. 3. Influence of phenylalanine or tryptophan (2 mmol/20 ml) infusion into the duodenum was investigated by a 3 x 3 latin square in Experiment 2. Plasma CCK level was determined at 15 min intervals for 1 hr. Both phenylalanine and tryptophan gradually enhanced plasma CCK concentrations with time after infusion. 4. Branched-chain amino acids such as leucine and isoleucine were supplemented intraduodenally in Experiment 3 as in Experiment 2. No significant change in plasma CCK levels was observed.

Influence of dietary sorbose on lipogenesis in gold thioglucose-injected obese mice

1. The influence of dietary sorbose on food intake and fatty acid synthesis of the liver and epididymal white adipose tissue (EWAT) was investigated in gold thioglucose (GTG)-injected obese mice from 12 to 14 weeks of age. 2. Sorbose was supplemented to a semi-purified diet at a level of 200 g/kg diet at the expense of sucrose. 3. On the last day of the experiment, fatty acids synthesis in the liver and EWAT was measured using an i.p. injection [1-14C]sodium acetate. 4. The decreases in body weight and food intake by dietary sorbose in GTG-injected obese mice were greater than those in control mice. 5. Lipid content and fatty acid synthesis in the liver and EWAT of control mice were not influenced by dietary sorbose. 6. In GTG-injected obese mice, the reduction of food intake by dietary sorbose suppressed fatty acid synthesis and lipid deposition in both liver and EWAT.

Energy utilisation in germ-free and conventional chicks fed diets containing sorbose

1. In experiment 1, growing conventional (CV) chicks were fed on diets containing graded amounts (0, 100, 200 and 300 g/kg diet) of sorbose from 4 to 14 d. Protein, fat and energy deposition were determined after carcase analysis. The values for growth, food efficiency, metabolisable energy (ME) and fat and energy depositions declined as the dietary sorbose content increased. 2. In experiment 2, the performances of germ-free (GF) and CV chicks fed on diets with (100 g sorbose/kg diet) or without sorbose were investigated. On both diets, body weight gain, food consumption and protein accumulation in GF chicks were significantly higher than those in CV birds. No significant differences were observed between the dietary treatment except for ME values, which were significantly lower for the sorbose diet. 3. It is suggested that dietary sorbose decreased energy utilisation, and that the microbial contribution to the utilisation of dietary sorbose was negligible in the chicken.

Control of protein phosphatase 2A by simian virus 40 small-t antigen

Soluble, monomeric simian virus 40 (SV40) small-t antigen (small-t) was purified from bacteria and assayed for its ability to form complexes with protein phosphatase 2A (PP2A) and to modify its catalytic activity. Different forms of purified PP2A, composed of combinations of regulatory subunits (A and B) with a common catalytic subunit (C), were used. The forms used included free A and C subunits and AC and ABC complexes. Small-t associated with both the free A subunit and the AC form of PP2A, resulting in a shift in mobility during nondenaturing polyacrylamide gel electrophoresis. Small-t did not interact with the free C subunit or the ABC form. These data demonstrate that the primary interaction is between small-t and the A subunit and that the B subunit of PP2A blocks interaction of small-t with the AC form. The effect of small-t on phosphatase activity was determined by using several exogenous substrates, including myosin light chains phosphorylated by myosin light-chain kinase, myelin basic protein phosphorylated by microtubule-associated protein 2 kinase/ERK1, and histone H1 phosphorylated by protein kinase C. With the exception of histone H1, small-t inhibited the dephosphorylation of these substrates by the AC complex. With histone H1, a small stimulation of dephosphorylation by AC was observed. Small-t had no effect on the activities of free C or the ABC complex. A maximum of 50 to 75% inhibition was obtained, with half-maximal inhibition occurring at 10 to 20 nM small-t. The specific activity of the small-t/AC complex was similar to that of the ABC form of PP2A with myosin light chains or histone H1 as the substrate. These results suggested that small-t and the B subunit have similar qualitative and quantitative effects on PP2A enzyme activity. These data show that SV40 small-antigen binds to purified PP2A in vitro, through interaction with the A subunit, and that this interaction inhibits enzyme activity.

Effect of short chain fatty acids on the performance and intestinal weight in germ-free and conventional chicks

1. In experiment 1, the performance and tissue weights of germ-free (GF) and conventional (CV) chicks fed on diets containing 25.4 g acetic acid/kg diet (AD) or 25.4 g kaolin/kg diet (KD) were investigated. Body weight gain in GF chicks was significantly higher on the AD, but significantly lower on the KD compared with their CV counterparts. The values for food efficiency, protein retention and energy retention followed a similar pattern to that of the body weight gain. 2. The weights of all sections of the intestine except the colon were significantly greater in CV chicks. In CV but not in GF birds the jejunum and ileum were heavier from birds fed on the AD than from those on the KD diet. 3. In experiment 2, the influence of butyric acid administration on the weight of some organs in chicks was investigated. The weight of duodenum, jejunum and ileum was significantly increased by intraperitoneal administration of butyric acid (2 ml of 100 mM solution/d) for 4 d, but no significant effect was observed by oral administration. 4. It might be suggested that short chain fatty acids such as acetic and butyric acids formed by bacterial action in the crop and subsequently absorbed are at least partly responsible for the heavier gut weight in CV birds.

Enhanced release of cholecystokinin in chickens fed diets high in phenylalanine or tyrosine

1. Whether the ingestion of excess phenylalanine (Phe) or tyrosine (Tyr) in diets alters the release of cholecystokinin (CCK) into the blood was investigated in chickens. A single meal of control, Phe excess, or Tyr excess diets was given through a stomach tube, followed by the CCK determination with specific CCK-8 antibody. 2. Plasma CCK level increased significantly at 30 min after feeding the diets: about 2.5 times the basal level in the control group and about 3 times the basal level in both of the experimental groups. 3. The Phe excess diet significantly delayed crop emptying rates compared to the control diet, while the Tyr diet on the contrary enhanced the emptying rate. 4. Enhanced plasma CCK levels and delayed crop emptying by Phe excess diet are suggested to be associated with depressed food intake.

Enhanced release of cholecystokinin by soya-bean trypsin inhibitor in chickens

Whether ingestion of soya-bean trypsin inhibitor (SBTI) alters the release of cholecystokinin (CCK) was investigated in chickens. A meal of an adequate diet supplemented with SBTI (0, 100, or 1000 mg/kg) was given through a stomach tube, followed by CCK determination with specific CCK-8 antibody. The plasma CCK level increased from a basal level (control diet) of 9.6 +/- 0.6 to 13.4 +/- 0.6 and 18.1 +/- 0.8 fmol/ml plasma at 90 min after feeding the diet supplemented with 100 and 1000 mg SBTI, respectively. Since the SBTI supplementation did not affect crop emptying rates significantly, it was concluded that SBTI by itself enhanced CCK release into circulation in a dose-dependent fashion.

Effect of alanine-producing bacteria on the growth of chicks

The effects of alanine-producing bacteria administered orally on the growth of chicks was investigated. The chicks were given diets containing adequate amounts of only the essential amino acids as sources of nitrogen: a basal diet (BD); a BD plus 40 g of urea per kilogram of diet (UD); a UD with bacteria named AR-8-3; a UD with bacteria named AB-605; and a BD plus 59.4 g and plus 118.7 g of L-alanine per kg of diet, respectively, from Day 8 to Day 15. The growth of chicks fed diets containing urea or alanine was significantly faster than that of the BD controls; no significant difference in growth was detected among the groups given the UD and bacteria. Since viable bacteria could not be detected from the intestinal content or from excreta for both groups given the bacteria, the establishment and achievement of alanine-producing activity by the bacteria in the gastrointestinal tract were considered doubtful. The supplement with 59.4 g of alanine per kg of diet improved the growth rate, but the higher inclusion (118.7 g of alanine per kg of diet) resulted in no further improvement.

Effect of phenylalanine on pancreatic amylase secretion in chicks (Gallus domesticus)

1. Effect of phenylalanine (Phe) on pancreatic amylase secretion in growing chicks was investigated in four experiments. 2. In Experiment 1, birds were injected through a wing vein with 0.25 ml Phe at 0, 0.1, 0.5, 2.5 and 12.5 mM in physiological saline. No significant difference was observed in amylase secretion among treatments. 3. Effect of various concentrations of Phe with cholecystokinin (CCK, 0.31 Crick unit) on amylase secretion was investigated in Experiment 2. Amylase secretion increased with time, although no significant effect was detected in Phe treatment. 4. Efficacy of Phe and tyrosine (Tyr) injection with CCK on amylase secretion was compared. There was no significant difference between Phe and Tyr treatments. 5. Birds were injected intraperitoneally with dl-p-chlorophenylalanine (p-CP), which is an inhibitor of phenylalanine hydroxylase, or saline 1 day before the collection of pancreatic amylase in Experiment 4. Both chicks showed increased amylase secretion with CCK (0.31 Crick unit), whereas the response was at a drastically reduced rate in chicks with the p-CP treatment.

Responses of the pancreatic digestive enzyme secretion to various combinations of amino acids and cholecystokinin in chicks (Gallus domesticus)

1. Effect of amino acid administration on pancreatic secretion of digestive enzymes, amylase, trypsinogen and chymotrypsinogen was studied after wing vein injection of an amino acid (AAs) mixture (Thr, Lys, Phe, Leu, Ile, Glu, Val, His, and Met) or combinations of selected amino acids, i.e. Thr + Phe + Ile, Thr + Phe, Thr + Ile or Phe + Ile, in the presence of cholecystokinin (CCK) in chicks. 2. Time course changes of enzyme output were similar in all treatment groups having a peak within 10-30 min, except for Phe + Ile that resulted in delayed induction of the enzyme release as shown by significant increases in the last 20 min compared with those in the rest. 3. When increases in enzyme outputs for the first 30 min were compared, it was shown that the three enzyme responses brought about by the administration of the AAs mixture was almost entirely accounted for by the combined injection of Thr + Phe. 4. Neither Thr + Ile nor Phe + Ile was as effective as Thr + Phe in inducing the output of these pancreatic enzymes. 5. The present results suggest that Thr and Phe may have a specific regulatory role in the secretion of pancreatic digestive enzymes in chicks when administered simultaneously.

Enhanced release of cholecystokinin by dietary amino acids in chicks (Gallus domesticus)

1. The effect of dietary amino acids and protein on cholecystokinin (CCK) release into plasma was investigated in chicks by feeding a meal through a stomach tube, followed by the CCK determination with specific CCK-8 antibody. 2. The results showed that both isolated soya protein and an amino acid mixture simulating the amino acid composition of the soya protein increased the release of CCK, though to a lesser extent with a delayed response in the former, when added to a protein-free diet. 3. Among amino acids added singly to the protein-free diet, phenylalanine was more efficient than arginine and valine, exerting a response almost identical to the complete amino acid mixture.

Responses of the pancreatic digestive enzyme secretion to amino acids, glucose and cholecystokinin in chicks

1. Pancreatic secretion of digestive enzymes, amylase, trypsinogen and chymotrypsinogen, was studied in response to the wing vein injection of digestive end products, various single amino acids and glucose, with or without cholecystokinin (CCK) in chicks. 2. Among amino acids administered, only phenylalanine significantly (P less than 0.05) increased trypsinogen and chymotrypsinogen secretions, while other amino acids did not. 3. Simultaneous injection of single amino acids with CCK increased digestive enzyme secretion to various extents depending on the kind of amino acids whereas the injection of glucose with CCK did not affect when compared with that of CCK alone. 4. By varying doses, a synergetic action of CCK plus amino acid on the secretion of pancreatic digestive enzymes was observed at 0.5 mM for valine and 5 mM for arginine.

Molecular cloning and sequence analysis of the catalytic subunit of bovine type 2A protein phosphatase

We have isolated a cDNA clone corresponding to the Mr 38,000 catalytic subunit of bovine type 2A protein phosphatase. The cDNA was isolated from a bovine adrenal gland cDNA library through the use of oligonucleotide probes whose sequences were based on partial amino acid sequence obtained from cyanogen bromide fragments of the purified cardiac enzyme. The entire 1724-base-pair cDNA has been sequenced and found to contain an open reading frame coding for a protein of 325 amino acids having a calculated molecular weight of 37,320. The deduced amino acid sequence contains the experimentally determined sequences of five different cyanogen bromide peptides. Transfection of COS-m6 cells with the cloned cDNA resulted in transient expression of a protein that could be detected by immunoblot analysis with a monoclonal antibody directed against the purified cardiac protein phosphatase. The expressed protein had the same apparent molecular weight as the purified enzyme when analyzed by NaDodSO4/polyacrylamide gel electrophoresis, suggesting that this clone contains the entire coding region of the phosphatase mRNA. The cloned cDNA hybridizes to a mRNA of 2.0 kilobases in bovine heart and adrenal gland. Under conditions of reduced stringency, the cDNA also hybridizes to a mRNA species of 1.2 kilobases in cardiac tissue.