Time-dependent Manner In Response Research Articles

The real catecholamine content of secretory vesicles in the CNS revealed by electrochemical cytometry

Resolution of synaptic vesicle neurotransmitter content has mostly been limited to the study of stimulated release in cultured cell systems, and it has been controversial as to whether synaptic vesicle transmitter levels are saturated in vivo. We use electrochemical cytometry to count dopamine molecules in individual synaptic vesicles in populations directly sampled from brain tissue. Vesicles from the striatum yield an average of 33,000 dopamine molecules per vesicle, an amount considerably greater than typically measured during quantal release at cultured neurons. Vesicular content was markedly increased by L-DOPA or decreased by reserpine in a time-dependent manner in response to in vivo administration of drugs known to alter dopamine release. We investigated the effects of the psychostimulant amphetamine on vesicle content, finding that vesicular transmitter is rapidly depleted by 50% following in vivo administration, supporting the “weak base hypothesis” that amphetamine reduces synaptic vesicle transmitter and quantal size.

Induction of autophagy by amino acid starvation in fish cells.

Autophagy is well established as a starvation-induced process in yeast and mammalian cells and tissues. To elucidate the cellular mechanisms induced by starvation in fish, we characterized the induction of autophagy in cultured zebrafish cells under starvation conditions. As an autophagic marker protein, the microtubule-associated protein 1-light chain 3B protein (MAP1-LC3B) was cloned from the fish cells, and its expression and localization were characterized. In zebrafish embryonic (ZE) cells, posttranslational modifications produced two distinct forms of MAP1-LC3B, i.e., a cytosolic form and a membrane-bound form (types I and II, respectively). Immunofluorescence microscopy revealed fluorescently labeled autophagosomes in cells stably transfected with a green fluorescent protein (GFP)–MAP1-LC3B fusion protein and showed that this protein accumulated in punctate dots in a time-dependent manner in response to amino acid starvation. Starvation also induced the degradation of long-lived proteins. Treatment with 3-methyladenine and wortmannin, two class-III inhibitors of phosphoinositide 3-kinase (PI3K), repressed autophagy under starvation conditions, indicating that the PI3K class-III pathway regulates starvation-induced autophagy in fish.

Maternal protein restriction regulates IGF2 system in placental labyrinth

This study was to test the hypothesis that altered IGF2 system in the placental labyrinth zone (LZ) impairs feto-placental growth in response to maternal protein restriction. Rats were fed a 20% protein diet and an isocaloric 6 % protein diet (LP) from day 1 to days 14, 18, or 21 of pregnancy. The effects of diet, gender of placenta and fetus, and day of pregnancy on placental weight, fetal weight, and expression of the IGF2 axis in the placental LZ and amino acids in maternal plasma were analyzed. Growth restriction occurred in both female and male fetuses by LP, coincident with impaired LZ growth and efficiency. The expression of Igf2, Igf2P0, Igf1r, Igf2r, Insr, Igfbp1, and Igfbp2 in placental LZ were affected by diet, gender and/or day of pregnancy. Concentrations of total essential amino acids and total nonessential amino acids were reduced and increased, respectively, in maternal plasma of LP-fed rats. These results indicate that adaptation of the IGF2 system in rat LZ occurs in a sex- and time-dependent manner in response to maternal protein restriction; however, these adaptations cannot prevent the growth restriction of both male and female fetuses during late pregnancy.

Maternal protein restriction regulates IGF2 system in placental labyrinth.

This study was to test the hypothesis that altered IGF2 system in the placental labyrinth zone (LZ) impairs feto-placental growth in response to maternal protein restriction. Rats were fed a 20% protein diet and an isocaloric 6 % protein diet (LP) from day 1 to days 14, 18, or 21 of pregnancy. The effects of diet, gender of placenta and fetus, and day of pregnancy on placental weight, fetal weight, and expression of the IGF2 axis in the placental LZ and amino acids in maternal plasma were analyzed. Growth restriction occurred in both female and male fetuses by LP, coincident with impaired LZ growth and efficiency. The expression of Igf2, Igf2P0, Igf1r, Igf2r, Insr, Igfbp1, and Igfbp2 in placental LZ were affected by diet, gender and/or day of pregnancy. Concentrations of total essential amino acids and total nonessential amino acids were reduced and increased, respectively, in maternal plasma of LP-fed rats. These results indicate that adaptation of the IGF2 system in rat LZ occurs in a sex- and time-dependent manner in response to maternal protein restriction; however, these adaptations cannot prevent the growth restriction of both male and female fetuses during late pregnancy.

Abstract A18: Inflaming breast cancer development: Expression of aromatase is increased by TNFα via the early growth response genes

Abstract Introduction: Breast cancer remains the leading cause of cancer-related death in Western women. In postmenopausal cases, up to 70% of tumors are classed as estrogen receptor positive (ER+), dependent on estrogen for continued growth and proliferative advantage. Adjuvant antiestrogen therapies are considered the cornerstone approach to the treatment of such tumors, and as such research is ongoing to maximize the effectiveness of drug treatments. The major source of estrogens for growth of ER+ breast cancers is local conversion of androgen precursors by the enzyme P450 aromatase. Inflammatory factors such as tumor necrosis factor-α (TNFα) stimulate transcription of the CYP19A1 gene that encodes aromatase, via its adipose-specific promoter I.4 (PI.4). The pathways by which this is achieved are not fully understood. Increased concentrations of TNFα are frequently detected within the stromal and epithelial compartments of an ER+ breast tumor microenvironment, contributing to a more invasive tumor fed by the increases in local estrogen production which are, in part, being driven by this critical cytokine. This study aims to identify the mechanisms underlying TNFα-dependent aromatase induction in the context of estrogen-dependent breast cancer. Methods: A custom gene array was performed to assess mRNA changes in primary human breast adipose fibroblasts (BAFs) that had been treated for 1 hr with 5ng/ml TNFα. This data was validated by qRT-PCR. Luciferase reporter assays were performed in C0S7 cells and EMSA assays were carried out using γP-32 detection. Results: A custom array showed that mRNA expression of the early growth response gene Egr1 was increased in BAFs that had been treated for 1 hr with TNFα. The family of early growth response genes Egr1, Egr2, Egr3 and Egr4 were all found to be significantly upregulated in a time-dependent manner in response to TNFα treatment, as validated by qRT-PCR. This occurs via induction of the NFkB pathway, as Egr mRNA induction was reduced in a dose-dependent manner upon pathway inhibition with the IKK-inhibiting compound BAY-11-7082. Egr2, Egr3 and Egr4 were able to induce Pl.4-driven luciferase reporter activity, with Egr2 proving to be the most potent activator. Serial 5′ deletion analysis of the 1 kb PI.4 promoter region revealed that the Egr2-induced promoter activity was mediated by a 41 bp sequence at the 3′ end, a region that did not contain any putative Egr binding sites. EMSA confirmed that there was no binding of any of the four Egr transcription factors to the 41 bp region. Mutagenesis of the 41 bp fragment is being carried out to narrow down the specific region of interest, and novel transcription factor binding sites will be confirmed with further luciferase assays and EMSA. Conclusion: We have elucidated a novel pathway by which TNFα is able to induce aromatase expression and thus estrogen biosynthesis in the breast via induction of the NFkB pathway and early growth response genes. Understanding TNFα signalling and the transcription factors it activates to turn on PI.4 CYP19A1 expression in BAFs is vital to the understanding of breast cancer pathology. These insights may help in the development of diagnostic tools or novel therapeutics in order to tackle the growing instances of this disease. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the Second AACR International Conference on Frontiers in Basic Cancer Research; 2011 Sep 14-18; San Francisco, CA. Philadelphia (PA): AACR; Cancer Res 2011;71(18 Suppl):Abstract nr A18.

TFF3 mediated induction of VEGF via hypoxia in human gastric cancer SGC-7901 cells

Increasing evidence indicates that in gastric epithelial cells, induction of TFF3 by hypoxia is mediated by HIF-1. Since VEGF is one of the most important angiogenic factors on cancer progression, we have started to investigate the possible link among HIF-1α, VEGF, and TFF3 in gastric cancer cells. We induced the hypoxic condition in SGC-7901cells using hypoxia-mimetic agent of CoCI2. SGC7901 cells were transfected with pcPUR+U6 plasmid carrying RNAi targeted to human TFF3 and selected puromycin-resistant pools to establish the stable knockdown of TFF3 cells. Our results showed the induction of HIF-1a via hypoxia and consequences of increased expressions of the TFF3 and VEGF in gastric cancer SGC-7901 cells. Overexpression of TFF3 upregulated the mRNA expressions of VEGF and HIF-1a induced by hypoxia, and stable knockdown of TFF3 impaired the mRNA upregulations of VEGF and HIF-1a induced by hypoxia. Furthermore, knockdown of TFF3 reduced the VEGF protein secretion: as VEGF secretion was increased time dependent manner in response to the hypoxia induction in TFF3-WT cells; however, VEGF production was significantly decreased in TFF3-KD cells (621±89 vs. 264±73 at 6h and 969±97 vs. 508±69 at 12h, P<0.05). Our data demonstrated the TFF3 mediated regulation of VEGF expression induced by hypoxia, and implicated that TFF3 might be applied as a potential anti-angiogenic target for treatment of gastric cancer.

β1,4-galactosyltransferase-I in synovial tissue of collagen-induced rat model of rheumatoid arthritis

β1,4-galactosyltransferase-I (β1,4-GalT-I), which is one of the best-studied glycosyltransferases, plays a key role in the synthesis of selectin ligands such as sialyl Lewis (sLe(x)) and sulfated sLe(x). Previous studies showed that inflammatory responses of β1,4-GalT-I-deficient mice were impaired because of the defect in selectin-ligand biosynthesis. However, the expression of β1,4-GalT-I and its biological function in rheumatoid arthritis (RA) remain to be elucidated. The mRNA and protein expression of β1,4-GalT-I increased in synovial tissue of the RA group compared with the Normal group at 10d and 15d after collagen-induced. Double staining indicated β1,4-GalT-I overlapped with macrophage-like synoviocytes (MLSs), fibroblast-like synoviocytes (FLSs), neutrophils and tumor necrosis factor-α (TNF-α). Moreover, β1,4-GalT-I mRNA in FLSs in vitro was affected in a dose- and time-dependent manner in response to TNF-α stimulation. ELISA revealed that expression of TNF-α was attenuated in FLSs in vitro treated with β1,4-GalT-I-Ab. We therefore suggest that β1,4-GalT-I may play an important role in the inflammation process of RA synovial tissue, which would provide the foundation for further researching into the concrete mechanism of β1,4-GalT-I in RA.

Tamoxifen-induced apoptosis of rat C6 glioma cells via PI3K/Akt, JNK and ERK activation

To elucidate the mechanism of TAM treatment on gliomas, we hypothesised that PI3K/Akt and MAPK signaling pathway may play important roles on TAM-induced apoptosis in C6 glioma cells. Our results demonstrated that TAM induced apoptosis of C6 glioma cells in a dose-dependent manner. The activation of AKT significantly decreased in a time-dependent manner in response to TAM treatment, JNK was transiently activated, and subsequently decreased activation and kept stable level, whereas ERK evidenced sustained activations in response to the drug treatment. The inhibition of PI3K/Akt and JNK both accelerated and enhanced TAM-induced apoptosis and ERK inhibition apparently exerted negative effect on apoptosis. We also observed that PI3K/Akt had intimate association with JNK and ERK activation in TAM-induced apoptosis. These findings may provide strategies for the molecularly targeted therapy in malignant gliomas.

Dietary fat decreases intestinal levels of the anorectic lipids through a fat sensor

This study was undertaken to investigate the link between dietary fat content and intestinal levels of anorectic N-acylethanolamines (NAEs), including oleoylethanolamide (OEA), palmitoylethanolamide (PEA), and linoleoylethanolamide (LEA). Male rats were fed high-fat diets (HFDs) with variable percentages of fat [20-45% of total energy (E%)] for 1-7 d; afterward, the jejunums were isolated, and jejunal NAE levels were measured by liquid-chromatography mass spectrometry. Enzyme activities and mRNA expression levels were measured for two synthesizing enzymes, N-acylphosphatidylethanolamine-specific phospholipase D (NAPE-PLD) and glycerophosphodiesterase (GDE1), and one degrading enzyme, fatty acid amide hydrolase (FAAH). We found a dose-response relation between the quantity/percentage of dietary fat, irrespective of the energy density, and the reduction of intestinal levels of OEA, PEA, and LEA. The reductions were present after 1 d of 45E% HFD. LEA, the major NAE species, was shown to have an anorectic potency slightly less than that of OEA but higher than PEA. Regulation at the enzyme level seems not to explain the changes in NAE levels. The results suggest the presence of a fat sensor, mediating the reduced intestinal NAE levels. The intestinal NAE levels are reduced in a dose- and time-dependent manner in response to dietary fat intake, and this may contribute to the well-known hyperphagic effect of HFDs.

Ovaprim abrogates expression of GnRH receptor- II in the Indian catfish

Hormone-induced breeding of fish has been effectively achieved with ovaprim, a salmon GnRH analog, in several teleost fish but not quite successfully in the Indian catfish. In order to analyze the rationale behind ovaprim ineffectiveness in this species, we investigated the effect of ovaprim injection on the GnRH receptors of the ovary and other extra-pituitary organs, since GnRH receptors are known to be over-expressed during spawning. RT-PCR analysis revealed that the GnRH receptor-II is present not only in the ovary, but also in the testis, liver and heart tissues of the catfish. However, the expression of the receptor declined in a time-dependent manner in response to ovaprim injection in all the above tissues. Concomitant changes were observed in the histology of the ovary, which indicated a decrease in the number of the immature ovarian follicles, thus elucidating the rationale behind partial success of ovaprim-induced spawning in the Indian catfish, as compared to other teleosts.

Hypoxia-induced Bcl-2 expression in endothelial cells via p38 MAPK pathway

Angiogenesis and apoptosis are reciprocal processes in endothelial cells. Bcl-2, an anti-apoptotic protein, has been found to have angiogenic activities. The purpose of this study was to determine the role of Bcl-2 in hypoxia-induced angiogenesis in endothelial cells and to investigate the underlying mechanisms. Human aortic endothelial cells (HAECs) were exposed to hypoxia followed by reoxygenation. Myocardial ischemia and reperfusion mouse model was used and Bcl-2 expression was assessed. Bcl-2 expression increased in a time-dependent manner in response to hypoxia from 2 to 72 h. Peak expression occurred at 12 h (3- to 4-fold, p < 0.05). p38 inhibitor (SB203580) blocked hypoxia-induced Bcl-2 expression, whereas PKC, ERK1/2 and PI3K inhibitors did not. Knockdown of Bcl-2 resulted in decreased HAECs’ proliferation and migration. Over-expression of Bcl-2 increased HAECs’ tubule formation, whereas knockdown of Bcl-2 inhibited this process. In this model of myocardial ischemia and reperfusion, Bcl-2 expression was increased and was associated with increased p38 MAPK activation. Our results showed that hypoxia induces Bcl-2 expression in HAECs via p38 MAPK pathway.

Abstract C203: Inhibition of TTK activates the p53 pathway

Abstract Background: TTK, also known as Mps1, is a dual-specificity kinase that is essential for the proper amphitelic attachment of chromosomes to the mitotic spindle during mitosis and for preventing anaphase progression until the chromosomes are properly attached. Given the role of TTK in genome integrity, we evaluated the effect of MPI-0479605, a potent and selective inhibitor of TTK, on the p53 pathway. Materials and Methods: For image analysis, cells were fixed and stained with Hoechst dye and anti-β-tubulin and anti-pericentrin antibodies. Images were taken on a BD Pathway high content imaging system. For cell cycle analysis, cells were fixed, stained with propidium iodide and analyzed by FACS. For Western blot analysis, cell lysates were run on SDS-polyacrylamide gels and proteins were transferred to PVDF membrane. Membranes were probed with the indicated antibodies. Results: Inhibition of TTK induced severe defects in chromosome segregation, as shown by the presence of lagging chromosomes and/or anaphase bridges during mitosis and the formation of micronuclei at interphase. Anaphase bridges may result in DNA double-strand breaks. Cell cycle analysis showed that a subpopulation of treated cells exhibited a tetraploid phenotype. Because either DNA damage or tetraploidy may induce the p53 pathway, we examined whether p53 was induced by treatment with MPI-0479605. Expression of p53 was induced in a dose- and time-dependent manner in response to MPI-0479605, with maximal levels occurring between 24 and 48 hours of treatment. Induction of p53 correlated with an increase in p21 expression and a decrease in survivin protein levels, indicating that p53 is transcriptionally active. Using phosphospecific antibodies, we determined that p53 is phosphorylated on Ser15 in response to MPI-0479605 treatment but not Thr18, Ser20, Ser37 or Ser46. Phosphorylation of γH2AX at Ser139, which is a marker for the presence of double-strand DNA breaks, was induced by treatment with MPI-0479605 in a time-dependent manner similar to p53 induction. Phosphorylation of p53 on Ser15 and H2AX on Ser139 can be mediated by the DNA damage checkpoint protein ATM. ATM also phosphorylates Chk2 on Thr68 and induces its activity, but, treatment with MPI-0479605 did not induce an increase in Chk2 Thr68 phosphorylation. Conclusions: Treatment of cells with the small molecule TTK inhibitor, MPI-0479605, activates p53. This may be due to chromosome segregation defects, which cause subsequent DNA double strand breaks and/or tetraploidy. In response to TTK inhibition, we observe an increase in H2AX phosphorylation, followed by the phosphorylation (Ser15) and activation of p53. Given that inhibition of TTK induces an apoptotic cell death, activation of p53 may be one mechanism by which the apoptotic pathway is induced in response to MPI-0479605. Citation Information: Mol Cancer Ther 2009;8(12 Suppl):C203.

Metabolic profiles of sunflower genotypes with contrasting response to Sclerotinia sclerotiorum infection

We report a comprehensive primary metabolite profiling of sunflower ( Helianthus annuus) genotypes displaying contrasting behavior to Sclerotinia sclerotiorum infection. Applying a GC–MS-based metabolite profiling approach, we were able to identify differential patterns involving a total of 63 metabolites including major and minor sugars and sugar alcohols, organic acids, amino acids, fatty acids and few soluble secondary metabolites in the sunflower capitulum, the main target organ of pathogen attack. Metabolic changes and disease incidence of the two contrasting genotypes were determined throughout the main infection period (R5.2–R6). Both point-by-point and non-parametric statistical analyses showed metabolic differences between genotypes as well as interaction effects between genotype and time after inoculation. Network correlation analyses suggested that these metabolic changes were synchronized in a time-dependent manner in response to the pathogen. Concerted differential metabolic changes were detected to a higher extent in the susceptible, rather than the resistant genotype, thereby allowing differentiation of modules composed by intermediates of the same pathway which are highly interconnected in the susceptible line but not in the resistant one. Evaluation of these data also demonstrated a genotype specific regulation of distinct metabolic pathways, suggesting the importance of detection of metabolic patterns rather than specific metabolite changes when looking for metabolic markers differentially responding to pathogen infection. In summary, the GC–MS strategy developed in this study was suitable for detection of differences in carbon primary metabolism in sunflower capitulum, a tissue which is the main entry point for this and other pathogens which cause great detrimental impact on crop yield.

Invasion of Endothelial Cells by Tissue-invasive M3 Type Group A Streptococci Requires Src Kinase and Activation of Rac1 by a Phosphatidylinositol 3-Kinase-independent Mechanism

Streptococcus pyogenes can cause invasive diseases in humans, such as sepsis or necrotizing fasciitis. Among the various M serotypes of group A streptococci (GAS), M3 GAS lacks the major epithelial invasins SfbI/PrtF1 and M1 protein but has a high potential to cause invasive disease. We examined the uptake of M3 GAS into human endothelial cells and identified host signaling factors required to initiate streptococcal uptake. Bacterial uptake is accompanied by local F-actin accumulation and formation of membrane protrusions at the entry site. We found that Src kinases and Rac1 but not phosphatidylinositol 3-kinases (PI3Ks) are essential to mediate S. pyogenes internalization. Pharmacological inhibition of Src activity reduced bacterial uptake and abolished the formation of membrane protrusions and actin accumulation in the vicinity of adherent streptococci. We found that Src kinases are activated in a time-dependent manner in response to M3 GAS. We also demonstrated that PI3K is dispensable for internalization of M3 streptococci and the formation of F-actin accumulations at the entry site. Furthermore, Rac1 was activated in infected cells and accumulated with F-actin in a PI3K-independent manner at bacterial entry sites. Genetic interference with Rac1 function inhibited streptococcal internalization, demonstrating an essential role of Rac1 for the uptake process of streptococci into endothelial cells. In addition, we demonstrated for the first time accumulation of the actin nucleation complex Arp2/3 at the entry port of invading M3 streptococci.

Claspin is involved in S-phase checkpoint induced by benzo(a)pyrene in 16HBE cells

Environmental carcinogen benzo(a)pyrene (BaP) can damage DNA by forming bulky adducts that are degraded further to DNA strand breaks, thus contributing to induce DNA damage checkpoint response. Claspin is a critical checkpoint protein in response to multiple forms of genotoxic stress including UV, IR and hydroxyurea (HU). In the present study we have investigated the role of human Claspin in the DNA damage checkpoint elicited by BaP in 16HBE cells. We observed that Claspin levels are increased in a time-dependent manner in response to S-phase arrest induced by BaP. In addition, the levels of phosphorylation of Chk1 on S345 were increased, but the levels of Cdc25A were decreased after treatment with BaP. Inhibition of Claspin expression (siRNA) attenuated the effect of BaP on S-phase arrest and abrogated the activation of Chk1 and degradation of Cdc25A in response to BaP. Taken together, these data imply that Claspin plays an important role in S-phase checkpoint induced by BaP, and it participates in the activation of Chk1 and Cdc25A in this checkpoint pathway.

LIM Kinase regulation of cofilin activity mediates PDGF‐induced VSMC migration

Platelet derived growth factor (PDGF) is a pro‐migratory factor released in response to vascular injury. Vascular smooth muscle cells (VSMCs) mediate this response and contribute significantly to neointimal formation, thus delineating the molecular mechanisms of VSMC migration is critical to understanding the vascular repair process. Signaling cascades activated by PDGF ultimately converge upon the actin cytoskeleton which is a key regulator of migration. Recent studies report that cofilin, which upon activation depolymerizes actin and it's phosphatase Slingshot (SSH) are essential to PDGF‐induced VSMC migration. In addition to SSH, cofilin activity is also regulated by LIM‐kinase, which attenuates its activity. Thus, in these studies we examined the role of LIMK in PDGF‐induced VSMC migration. Immunoblotting with phosphospecific antibodies confirmed that LIMK activity was increased in a time dependent manner in response to PDGF. Transfection of VSMCs cells with LIMK siRNA attenuated PDGF induced migration by 70% vs. control VSMCs. The knockdown of LIMK expression by siRNA also decreased basal phosphorylation of cofilin and potentiated the cofilin response to PDGF‐induced activation. As PDGF‐induced LIMK regulation appears to mediate VSMC migration, these studies show the importance of further examining the SSH/LIMK balance in mediating cytoskeletal events associated with cofilin activity.

Elevated β1,4-galactosyltransferase-I induced by the intraspinal injection of lipopolysaccharide

Beta1,4-galactosyltransferase-I (beta1,4-GalT-I) is one of the best studied glycosyltransferases. Previous studies demonstrated that beta1,4-GalT-I was a major galactosyltransferase responsible for selectin-ligand biosynthesis and that inflammatory responses of beta1,4-GalT-I deficient mice were impaired. In this study, we investigate the expression of beta1,4-GalT-I in lipopolysaccharide (LPS)-induced neuroinflammatory processes. The results of this study demonstrated that beta1,4-GalT-I was strongly induced by intraspinal administration of LPS. More than 90% galactose-containing glycans and beta1,4-GalT-I were expressed in immune cells. The ELISA assay shows focal injection LPS also induces TNF-alpha alteration. Double staining indicated beta1,4-GalT-I overlapped with TNF-alpha. Moreover, RT-PCR for beta1,4-GalT-I mRNA showed that beta1,4-GalT-I mRNA in microglia in vitro was affected in a dose- and time dependent manner in response to LPS or TNF-alpha stimulation. All these results indicated that the increase of beta1,4-GalT-I might attribute to the effect of TNF-alpha excreting during inflammation. E-selectin, which ligand was modified by beta1,4-GalT-I, was correlated with galactose-containing glycans following injecting LPS into spinal cord. We therefore suggest that beta1,4-GalT-I may play an important role in regulating immune cell migration into the inflammatory site.

159 Thrombin Stimulates Interleukin-8 Production in Human Macrophages Through a JNK and NFκB Pathway

Wound healing is a complex biological event orchestrated by various resident and infiltrating cell types spanning multiple stages. Thrombin, a multifunctional serine protease released upon wounding, stimulates fibroblasts and macrophages at the sites of wounds to express, chemokines, such as interleukin-8 (IL-8). We have used cellular and molecular approaches to investigate the mechanisms involved in thrombin induces IL-8 expression in human macrophages. Western blot analysis and RT-PCR show that thrombin stimulates IL-8 in a rapid and dose-dependent manner. Various inhibitors for signal transduction proteins were used to delineate the pathways involved. We found that, at nanomolar concentrations, inhibitors for both c-Jun N-terminal Kinase (JNK) and NFɻB strongly inhibited the thrombin-induced production of IL-8 suggesting that they are major regulators of this stimulation. JNK was shown to be phorsphorylated in a time-dependent manner in response to thrombin treatment confirming its involvement. In order to identify the mediator of JNK and the thrombin receptor, we use affinity pull down and found that Rho GTPase was activated by thrombin suggesting that Rho may be the mediator of JNK activation. In addition, we found that PKC is a negative regulator of thrombin-induced IL-8 expression. Our study broadens the horizon of how IL-8 is regulated in wound healing and may help develop pharmaceutical methods to manipulate this process in pathological conditions.

Regulation of Telomeric Repeat Binding Factor 1 Binding to Telomeres by Casein Kinase 2-mediated Phosphorylation

Telomere maintenance is essential for continued cell proliferation and chromosome stability. Telomeres are maintained by telomerase and a collection of associated proteins. The telomeric protein telomeric repeat binding factor 1 (TRF1) negatively regulates telomere length by inhibiting access of telomerase at telomere termini. Here we report that TRF1 interacts with the beta subunit of casein kinase 2 (CK2) and serves as a substrate for CK2. CK2-mediated phosphorylation is required for the efficient telomere binding of TRF1 in vitro and in vivo. Inhibition of CK2 by the CK2 inhibitor 5,6-dichloro-1-beta-d-ribofuranosylbenzimidazole decreased the ability of TRF1 to bind telomeric DNA. The resulting telomere-unbound form of TRF1 was then ubiquitinated and degraded by the proteasome. Partial knockdown of CK2 by small interfering RNA resulted in removal of TRF1 from telomeres and subsequent degradation of TRF1. Mapping of the CK2 target site identified threonine 122 as a substrate in TRF1. A threonine to alanine change at this position led to a diminished DNA binding due to reduced dimerization of TRF1. In addition, phosphorylation of threonine 122 seemed critical for TRF1-mediated telomere length control. Our findings suggest that CK2-mediated phosphorylation of TRF1 plays an important role in modulating telomere length homeostasis by determining the levels of TRF1 at telomeres.

PPAR-γ expression in animals subjected to volume overload and chronic Urotensin II administration

Activation of PPAR-gamma through the administration of glitazones has shown promise in preserving function following cardiac injury, although recent evidence has suggested their use may be contraindicated in the case of severe heart failure. This study tested the hypothesis that PPAR-gamma expression increases in a time dependent manner in response to chronic volume overload (VO) induced heart failure. Additionally, we attempted to determine what effect 4 week administration of Urotensin II (UTII) may have on PPAR-gamma expression. VO induced heart failure was produced in Sprague-Dawley rats (n=32) by aorta-caval fistula. Animals were sacrificed at 1, 4, and 14 weeks following shunt creation. In a separate set of experiments, animals were administered 300 pmol/kg/h of UTII for 4 weeks, subjected to 4 weeks of volume overload, or given UTII+VO. Densitometric analysis of left ventricular (LV) protein demonstrated PPAR-gamma expression was significantly ((*)p<0.05) upregulated at 4 and 14 weeks (31.5% and 37%, respectively) post-fistula formation compared to control values. PPAR-gamma activation was decreased in the 4 and 14 week (39.16% and 42.4%, respectively), but not in the 1-week animals, and these changes did not correlate with NF-kappaB activity. Animals given UTII either with or without VO demonstrated increased expression of PPAR-gamma as did animals subjected to 4 week VO alone. Animals given UTII either with or without VO had decreased activity vs. control. These data suggest PPAR-gamma may play a role in the progression of heart failure, however, the exact nature has yet to be determined.