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Biomedical subjects

K Brand

Publications and source records attributed to K Brand.

At least 37 records · Page 2Linked to original sources
PubMed2000

Adhesion of monocyte very late antigen-4 to endothelial vascular cell adhesion molecule-1 induces interleukin-1beta-dependent expression of interleukin-6 in endothelial cells.

In atheroma, T cell-derived interferon-gamma (INF-gamma) stimulates endothelial cells and facilitates recruitment of monocytes. We investigated potential mechanisms by which these interactions could contribute to local and systemic inflammatory responses. Specifically, we analyzed the expression of interleukin (IL)-1beta and IL-6 in both cell types after coculture, the relevant adhesion molecules in this interaction, and transcriptional control by NF-kappaB. We studied coculture of purified peripheral blood monocytes with human umbilical vein endothelial cells (HUVECs), which were stimulated with INF-gamma (10(6) U/L) to model the activated endothelium of atherosclerotic lesions. Coculture of monocytes with activated HUVECs resulted in release of IL-1beta (40. 6+/-3 pg/24 h, P=0.002) and IL-6 (46.6+/-7 ng/24 h, P=0.0015). Electrophoretic mobility gel shift assay and Northern blotting in each cell type separately revealed NF-kappaB activation in both cell types, IL-1beta mRNA expression predominantly in monocytes, and IL-6 mRNA expression predominantly in HUVECs. The endothelial IL-6 release was IL-1-dependent, because it was suppressed by IL-1 receptor antagonist. Experiments with blocking antibodies demonstrated that binding of monocyte very late antigen-4 (VLA-4) to endothelial vascular cell adhesion molecule-1 (VCAM-1) was necessary for the induction of IL-1beta in monocytes. Binding of monocyte VLA-4 to endothelial VCAM-1 induces NF-kappaB activation in both cell types with expression and release of IL-1beta by monocytes, which in turn stimulates endothelial release of IL-6. The beta(1)-integrin-mediated expression of IL-1beta and IL-6 could contribute to local and systemic inflammatory reactions in atherosclerosis.

Cell Membrane↗
PubMed1999

Differential effects of lipopolysaccharide and tumor necrosis factor on monocytic IkappaB kinase signalsome activation and IkappaB proteolysis.

The inflammatory mediators lipopolysaccharide (LPS) and tumor necrosis factor (TNF) are potent activators of NF-kappaB. This study compared the effect of these stimuli on endogenous IkappaB kinase (IKK) signalsome activation and IkappaB phosphorylation/proteolysis in human monocytic cells and investigated the role of the signalsome proteins IKK-alpha, IKK-beta, NF-kappaB-inducing kinase (NIK), IKK-gamma (NF-kappaB essential modulator), and IKK complex-associated protein. Kinase assays showed that TNF elicited a rapid but short-lived induction of IKK activity with a 3-fold greater effect on IKK-alpha than on IKK-beta, peaking at 5 min. In contrast, LPS predominantly stimulated IKK-beta activity, which slowly increased, peaking at 30 min. A second peak was observed at a later time point following LPS stimulation, which consisted of both IKK-alpha and -beta activity. The endogenous levels of the signalsome components were unaffected by stimulation. Furthermore, our studies showed association of the IKK-alpha/beta heterodimer with NIK, IkappaB-alpha and -epsilon in unstimulated cells. Exposure to LPS or TNF led to differential patterns of IkappaB-alpha and IkappaB-epsilon disappearance from and reassembly with the signalsome, whereas IKK-alpha, IKK-beta, and NIK remained complex-associated. NIK cannot phosphorylate IkappaB-alpha directly, but it appears to be a functionally important subunit, because mutated NIK inhibited stimulus-induced kappaB-dependent transcription more effectively than mutated IKK-alpha or -beta. Overexpression of IKK complex-associated protein inhibited stimulus-mediated transcription, whereas NF-kappaB essential modulator enhanced it. The understanding of LPS- and TNF-induced signaling may allow the development of specific strategies to treat sepsis-associated disease.

Enzyme Activation↗
PubMed1999

Involvement of nuclear factor-kappaB in a murine model for the acute form of autoimmune-like toxic oil syndrome.

The toxic oil syndrome (TOS) represents an exogenously induced autoimmune disease with acute or chronic symptoms similar to systemic lupus erythematosus or scleroderma. When genetically different mouse strains were exposed to oleic acid anilide (OAA), it was possible to mimic the different syndrome manifestations. The aim of the present study was to examine the role of NF-kappaB/Rel transcription factors in the development of the severe acute wasting disease observed in A/J mice. Within a week of OAA exposure, the A/J, but not B10.S strain, displayed weight loss, cachexia, apathy, reduced activity, and breathing difficulties. In affected A/J mice we observed a marked increase in NF-kappaB activation (p50/p65 dimers) both in splenic T cells and peritoneal macrophages as well as in tissue from aorta and gut. Incubation of splenocytes with OAA in vitro induced a dose-dependent removal of IkappaB-alpha, accompanied by NF-kappaB activation, whereas Sp-1 binding was not affected. Furthermore, we demonstrated the increased expression of the two NF-kappaB target genes IL-6 and IL-1beta in OAA-exposed mice and a transient OAA-induced accumulation of TNFalpha in vitro. This is the first report which implicates NF-kappaB/Rel in acute forms of chemically induced autoimmune-like disease and may serve as a paradigm for the involvement of this transcriptional system in acute processes associated with autoimmunity, suggesting possible avenues of therapeutic intervention.

Acute Disease↗
PubMed1999

4-Hydroxynonenal prevents NF-kappaB activation and tumor necrosis factor expression by inhibiting IkappaB phosphorylation and subsequent proteolysis.

Extensively oxidized low density lipoprotein (ox-LDL), a modulator of atherogenesis, down-regulates the lipopolysaccharide (LPS)-induced activation of transcription factor NF-kappaB. We investigated whether 4-hydroxynonenal (HNE), a prominent aldehyde component of ox-LDL, represents one of the inhibitory substances. NF-kappaB activation by stimuli such as LPS, interleukin (IL)-1beta, and phorbol ester, but not tumor necrosis factor (TNF), was reversibly inhibited by HNE in a dose-dependent manner in human monocytic cells, whereas AP-1 binding was unaffected. Using similar HNE concentrations, LPS-induced kappaB- and TNF or IL-8 promoter-dependent transcription was prevented. Furthermore, pretreatment with HNE suppressed TNF production but not lactate dehydrogenase levels. Under these conditions the binding of LPS to monocytic cells was not significantly affected. However, induced proteolysis of the inhibitory proteins IkappaB-alpha, IkappaB-beta, and, at a later time point, IkappaB-epsilon was prevented. This is not due to inhibition of the proteasome, the major proteolytic activities of which remain unaffected, but rather to a specific prevention of the activation-dependent phosphorylation of IkappaB-alpha. This is the first report which demonstrates that HNE specifically inhibits the NF-kappaB/Rel system. Down-modulation of NF-kappaB-regulated gene expression may contribute at certain stages of atherosclerosis to low levels of chronic inflammation and may also be involved in other inflammatory/degenerative diseases.

Aldehydes↗
PubMed1999

Relationships between aggressive behavior in cognitively impaired nursing home residents and use of restraints, psychoactive drugs, and secured units.

This study examined relationships between aggressive behavior in cognitively impaired nursing home residents and physical restraints, psychoactive drugs, and placement on a secured unit. Data were obtained from 116 residents who were consistently aggressive as measured by the Ryden Aggression Scale 2. Subjects averaged 9.5 aggressive behaviors per day. Forty-seven percent of subjects were restrained, and 62% were regularly receiving psychoactive drugs. Use of restraints, antipsychotics, and placement on a secured unit were all significantly related to increased physical aggression scores. Four variables accounted for 23% of the variance in physical aggression scores: location on a secured unit, not receiving an antidepressant, being restrained, and number of psychotropic and/or anxiolytic medications administered. Significantly lower physical aggression scores were noted for subjects receiving antidepressants.

Aged↗
PubMed1999

Induction of apoptosis and G2/M arrest by infection with replication-deficient adenovirus at high multiplicity of infection.

Replication-deficient adenoviruses are among the most widely used vectors in gene therapy and are also becoming increasingly popular as analytical tools in basic research. However, significant toxicity of these vectors in vivo has been reported. Here, we show that in an in vitro setting, first generation adenoviruses lead to growth retardation, prolongation of the G2/M phase and induction of apoptosis if applied at a high multiplicity of infection (MOI). These findings were obtained in p53-deficient hepatocytes, derived from knock-out mice (A2 cells) and in several tumor cell lines containing wild-type (wt) or mutant p53. Apoptosis induction was correlated with increased levels of p53 and bax proteins and it was stronger in cells containing wt p53 as compared with cells lacking functional p53. Apoptosis was highly dependent on the MOI used with marked effects starting at an MOI twice as high as needed for 100% gene transfer. Expression of the adenoviral E4 ORF6 gene as well as adenoviral replication were detected in all cell lines infected with first generation adenovirus. Apoptosis could be considerably reduced but not abrogated by UV inactivation of adenovirus, which indicates proapoptotic effects caused by the infection event as well as by residual adenoviral gene expression or adenoviral replication. First generation adenoviruses apparently display proapoptotic activity if used at higher MOIs, which may be of relevance when these vectors are used as analytical or gene therapeutic tools.

Adenoviridae↗
PubMed1999

Tissue factor expression of human monocytes is suppressed by lysophosphatidylcholine.

The expression of tissue factor (TF), the principal initiator of coagulation, is increased during inflammation and atherosclerosis. Both conditions are promoted by lysophosphatidylcholine (lysoPC). We observed in the present study that lysoPC (1 to 10 micromol/L) dose-dependently reduced TF activity in human monocytes, as elicited by lipopolysaccharide (LPS). Lysophosphatidylethanolamine (lysoPE) and other lysophospholipids did not affect LPS-induced TF activity of human monocytes. TF antigen expression as elicited by LPS was also lowered by lysoPC. Phospholipid analyses indicated a selective increase in the lysoPC content of the monocytes after preincubation with the lysophospholipid. LysoPC inhibited the TF activity of Mono Mac-6 cells to a similar extent as in the monocytes. LPS binding to plasma membrane receptors and internalization of LPS into monocytes were not affected by lysoPC. In contrast, LPS-mediated nuclear binding of nuclear factor-kappaB/Rel to a TF-specific kappaB site was inhibited by lysoPC. Induction of TF mRNA expression by LPS tended to be partially reduced by the lysophospholipid. Preincubation with lysoPC increased monocytic cAMP levels. Inhibition of adenylyl cyclase by pretreatment with 2'-deoxy-3'-adenosine monophosphate partially reversed the inhibition of TF activity promoted by lysoPC. In conclusion, lysoPC markedly decreases LPS-mediated TF expression of human monocytes, the effect probably being mediated by both transcriptional and posttranscriptional mechanisms. LysoPC may thus attenuate activation of coagulation during inflammation and atherosclerosis.

Adenylyl Cyclase Inhibitors↗
PubMed1998

Activated platelets induce monocyte chemotactic protein-1 secretion and surface expression of intercellular adhesion molecule-1 on endothelial cells.

BACKGROUND: Platelet/endothelium interaction plays an important role in the pathophysiology of inflammation and atherosclerosis. The role of platelets for monocyte chemotactic protein-1 (MCP-1) secretion and surface expression of intercellular adhesion molecule-1 (ICAM-1) on endothelial cells has been assessed. METHODS AND RESULTS: Monolayers of human umbilical vein endothelial cells were incubated with nonstimulated or ADP-activated platelets for 6 hours, and secretion of MCP-1 and surface expression of ICAM-1 were determined by ELISA and flow cytometry, respectively. In the presence of ADP-activated platelets, both MCP-1 secretion and ICAM-1 surface expression were significantly increased compared with nonstimulated platelets (P<0.02). Activation of the transcription factor nuclear factor-kappaB (NF-kappaB) determined by electrophoretic mobility shift assay and kappaB-dependent transcriptional activity was enhanced in the presence of activated platelets. In addition, ADP-activated platelets induced MCP-1 and ICAM-1 promoter-dependent transcription. Liposomal transfection of a double-stranded kappaB phosphorothioate oligonucleotide, but not of the mutated form, inhibited MCP-1 secretion and surface expression of ICAM-1 on activated endothelium (P<0.05). CONCLUSIONS: The present study indicates that activated platelets modulate chemotactic (MCP-1) and adhesive (ICAM-1) properties of endothelial cells via an NF-kappaB-dependent mechanism. Platelet-induced activation of the NF-kappaB system might contribute to early inflammatory events in atherogenesis.

Arteriosclerosis↗
PubMed1998

Effect of proteasome inhibitors on monocytic IkappaB-alpha and -beta depletion, NF-kappaB activation, and cytokine production.

We investigated the effect of proteasome inhibitors on the lipopolysaccharide (LPS)-induced expression of several monocytic cytokines, which may be dependent on the transcription factor, nuclear factor-kappaB (NF-kappaB). Exposure of human monocytic THP-1 cells to ALLN and Mu873 prevented the LPS-induced degradation of IkappaB-alpha and -beta, as did the more potent proteasome inhibitor, PSI, whereas several calpain inhibitors were ineffective. This was accompanied by the inhibition of nuclear NF-kappaB binding activity and NF-kappaB transcriptional activation. At the mRNA level, the inhibitors blocked the expression of tumor necrosis factor (TNF) and interleukin-1beta (IL-1beta), whereas IL-8 remained unaffected by ALLN and was only partially reduced by the highest dose of PSI. The latter effect appears to be due to an increase in IL-8 mRNA stability in the presence of proteasome inhibitors. Furthermore, the production of TNF was efficiently suppressed by ALLN and PSI, less by Mu873, and not at all by calpain inhibitors. In primary human blood monocytes ALLN also prevented the LPS-induced degradation of IkappaB-alpha and -beta, efficiently blocked the production of TNF and, to a lesser extent, IL-1beta, whereas that of IL-8 was not inhibited. The expression of NF-kappaB-dependent monocytic cytokines may be selectively controlled by the proteasome, offering a potential therapeutic target in inflammatory disease.

Cell Line↗
PubMed1998

Nuclear factor kappaB is activated in macrophages and epithelial cells of inflamed intestinal mucosa.

BACKGROUND & AIMS: Transcription factors of the nuclear factor kappaB (NF-kappaB) family play an important role in the regulation of genes involved in inflammation. In inflammatory bowel diseases, proinflammatory cytokines known to be regulated by NF-kappaB are involved. The aim of this study was to investigate the role of NF-kappaB activation during mucosal inflammation in situ. METHODS: A monoclonal antibody, alpha-p65mAb, was applied for immunofluorescence and immunohistochemical analysis that recognizes activated NF-kappaB. Electrophoretic mobility shift assay was used to directly demonstrate the presence of active DNA-binding NF-kappaB. RESULTS: Using the alpha-p65mAb antibody, activated NF-kappaB could be found in biopsy specimens from inflamed mucosa but was almost absent in uninflamed mucosa. The number of cells showing NF-kappaB activation correlated with the degree of mucosal inflammation but was not significantly different between inflamed mucosa from patients with Crohn's disease, ulcerative colitis, and nonspecific colitis or diverticulitis. NF-kappaB activation was localized in macrophages and in epithelial cells as identified by double-labeling techniques. Electrophoretic mobility shift assay with isolated lamina propria mononuclear cells and epithelial cells confirmed these results. CONCLUSIONS: This study shows for the first time the activation of NF-kappaB during human mucosal inflammation in situ. In addition to macrophages, epithelial cells contained activated NF-kappaB, indicating an involvement in the inflammatory process.

Adult↗
PubMed1998

Tumor cell-specific transgene expression prevents liver toxicity of the adeno-HSVtk/GCV approach.

Treatment of colorectal liver metastases with the HSVtk/GCV approach and adenoviral vectors is highly toxic. We present a nontoxic alternative using the cell type-specific CEA promoter instead of the widely used hCMV immediate-early promoter to drive tk gene expression in the context of a recombinant adenovirus. Analysis of CEA promoter-dependent tk gene expression showed significant activity of this promoter in several human and rat tumor-derived cell lines but not in rat primary hepatocytes and in mouse liver, whereas the CMV promoter was highly active in all cell types and tissues investigated. CEA promoter-dependent tk gene expression was sufficient to kill 100% of cancer cells in vitro, even if less than 10% were infected by the adenoviral vector, indicating a significant bystander effect. Moreover, treatment of subcutaneous tumors in SCID mice with Ad.CEA-tk led to a several-fold reduction of tumor growth, and tail vein injection of a high dose of Ad.CEA-tk caused no side-effects in the liver. The CMV promoter was more potent than the CEA promoter in mediating GCV sensitivity to cancer cells in vitro and in vivo, but even a 20-fold reduction of the dose of Ad.CMV-tk did not prevent its liver cell toxicity after systemic application to mice and still resulted in the death of all animals within 4 days after the start of GCV treatment. These results indicate that restriction of tk gene expression to tumor cells in the liver prevents systemic toxicity. Moreover, the CEA promoter is a safe and efficient tool for tumor cell-specific expression of suicide genes in the liver.

Adenoviridae↗
PubMed1997

Glucose regulates the promoter activity of aldolase A and pyruvate kinase M2 via dephosphorylation of Sp1.

Proliferating cells and tumour cells maintain a high glycolytic rate even under aerobic conditions. FTO2B cells, a rat hepatoma cell line, show high activities of glycolytic enzymes. Within a culture period of 48 h the cell number increases 5-fold. Replacement of glucose by pyruvate in the culture medium lowers glycolytic enzyme activity and prevents proliferation. Transfection assays revealed that glucose deprivation dramatically decreases the transcriptional activities of the Sp1-dependent aldolase and pyruvate kinase promoters leading to reduced reporter gene expression. Sp1 binding activity is also inhibited by ocadaic acid, an inhibitor of protein phosphatase 1. Western blot analyses with nuclear extracts from FTO2B cells cultured in the presence or absence of glucose revealed differences in the phosphorylation state of Sp1. From these results we conclude that glucose increases the amount of the dephosphorylated form of Sp1 which has a higher DNA binding activity. As a consequence gene expression of the glycolytic enzymes is increased which is a prerequisite for cell proliferation.

Animals↗
PubMed1997

[p16 and p53 genes transferred with the help of adenovirus to induce apoptic tumor cell death].

Based on studies of the cell cycle in tissue cultures of cancer cell lines and cells from normal tissue interference in the regulatory network of pRB/cdk4/cyclin D1/p16 in combination with the tumour suppressor gene p53 was investigated. It was shown that overexpression of p53 and p16, but not p53 on its own, induced apoptotic cell death only in tumour cells. Gene transfer of the same two genes to tumours transplanted subcutaneously in mice also caused fast regression of some of the tumours.

Adenoviruses, Human↗
PubMed1997

Induction of cytokine expression in leukocytes by binding of thrombin-stimulated platelets.

BACKGROUND: Activated platelets tether and activate myeloid leukocytes. To investigate the potential relevance of this mechanism in acute myocardial infarction (AMI), we examined cytokine induction by leukocyte-platelet adhesion and the occurrence of leukocyte-platelet conjugates in patients with AMI. METHODS AND RESULTS: We obtained peripheral venous blood samples in 20 patients with AMI before and daily for 5 days after direct percutaneous transluminal coronary angioplasty (PTCA) and in 20 patients undergoing elective PTCA. Throughout the study period, CD41 immunofluorescence of leukocytes (flow cytometry) revealed increased leukocyte-platelet adhesion in patients with AMI compared with control patients (mean +/- SE of fluorescence [channels] before PTCA: 77 +/- 16 versus 35 +/- 9; P = .003). In vitro, thrombin-stimulated fixed platelets bound to neutrophils and monocytes. Within 2 hours, this resulted in increased mRNA for interleukin (IL),1 beta, IL-8, and monocyte chemoattractant protein (MCP)-1 in unfractionated leukocytes. After 4 hours, IL-1 beta and IL-8 concentration of the cell-free supernatant had increased by 268 +/- 36% and 210 +/- 7%, respectively, and cellular MCP-1 content had increased by 170 +/- 8%. Addition of activated platelets to adherent monocytes had a similar effect and was associated with nuclear factor-kappa B activation. Inhibition of binding by anti-P selectin antibodies reduced the effect of activated platelets on cytokine production. CONCLUSIONS: In patients with AMI, leukocyte-platelet adhesion is increased. Binding of activated platelets induces IL-1 beta, IL-8, and MCP-1 in leukocytes. Our findings suggest that leukocyte-platelet adhesion contributes to the regulation of inflammatory responses in AMI.

Adult↗
PubMed1997

Role of the stimulatory proteins Sp1 and Sp3 in the regulation of transcription of the rat pyruvate kinase M gene.

Site-directed mutagenesis of cis-regulatory elements in the 5' flanking region of the rat pyruvate kinase M gene revealed that two out of the three GC boxes (-133/-124 and -48/-39) are involved in the stimulation of a core promoter (-35/+46). These two regions were also protected in DNaseI footprinting assays. Sp1 and Sp3 were identified as binding proteins to all three GC boxes by supershift experiments. Cotransfections in Drosophila SL2 cells revealed a strong stimulatory function of Sp1 and a synergistic effect of Sp3 to Sp1 in the activation of the pyruvate kinase M promoter. No inhibitory effect of Sp3 was detected. These data indicate that binding of Sp1 at two GC boxes is required for full promoter activity of the pyruvate kinase M gene and thus contributes to the observed cell-cycle-dependent expression of this enzyme in proliferating rat thymocytes.

Animals↗
PubMed1997

Redox-regulated expression of glycolytic enzymes in resting and proliferating rat thymocytes.

Resting rat thymocytes partially degrade glucose aerobically to CO2 and H2O and produce reactive peroxide anions. In contrast proliferating cells, due to enhanced induction of glycolytic enzymes, degrade glucose almost completely to lactate thus minimizing the production of reactive oxygen species. In this paper we show that under conditions of oxidative stress the induction of the glycolytic enzymes in cultured rat thymocytes is markedly reduced. Furthermore, transfection assays with a rat hepatoma cell line and Drosophila Schneider cells revealed that reactive oxygen intermediates dramatically decrease the transcriptional activities of the Sp1-dependent aldolase A and pyruvate kinase M2 promoters leading to reduced reporter gene expression. These results indicate that cellular redox changes can regulate gene expression by reversible oxidative inactivation of Sp1 binding.

Animals↗
PubMed1997

Aerobic glycolysis by proliferating cells: protection against oxidative stress at the expense of energy yield.

Primary cultures of mitogen-activated rat thymocytes were used to study energy metabolism, gene expression of glycolytic enzymes, and production of reactive oxygen species during cell cycle progression. During transition from the resting to the proliferating state a 7- to 10-fold increase of glycolytic enzyme induction occurs which enables the cells to meet the enhanced energy demand by increased aerobic glycolysis. Cellular redox changes have been found to regulate gene expression of glycolytic enzymes by reversible oxidative inactivation of Sp1-binding to the cognate DNA-binding sites in the promoter region. In contrast to nonproliferating cells, production of phorbol 12-myristate 13-acetate (PMA)-primed reactive oxygen species (ROS) in proliferating rat thymocytes and HL-60 cells is nearly abolished. Pyruvate, a product of aerobic glycolysis, is an effective scavenger of ROS, which could be shown to be generated mainly at the site of complex III of the mitochondrial respiratory chain. Aerobic glycolysis by proliferating cells is discussed as a means to minimize oxidative stress during the phases of the cell cycle when maximally enhanced biosynthesis and cell division do occur.

Aerobiosis↗