Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P43026 (lipopolysaccharide)
 62,215 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The dose-response inhibition of the splenic plaque-forming cell (PFC) response and serum IgM units to the antigen, trinitrophenyl-lipopolysaccharide, was determined for several polychlorinated biphenyl (PCB) mixtures and congeners in female B3C3F1 mice. The ED50 values for Aroclor 1260-, 1254-, 1248-, and 1242-induced immunotoxicity varied by less than twofold from 355 to 699 mg/kg. The range of ED50 values for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), 3,3',4,4'-tetrachlorobiphenyl, 3,3',4,4',5-pentaCB, 3,3',4,4',5,5'-hexaCB, 2,3,3',4,4'-pentaCB, 2,3',4,4',5-pentaCB, 2,3,3',4,4',5-hexaCB, 2,3,3',4,4',5,5'-heptaCB, 2,2',3,3',4,4',5-heptaCB, and 2,2',3,4,4',5,5'-heptaCB were 4.6 to 4.9, 134 to 245, 4.7 to 7.0, 6.9 to 11.1, 88,000 to 121,000, 122,000 to 132,000, 99,000 to 157,000, 89,000 to 129,000, 117,000 to 240,000, and 132,000 to 238,000 micrograms/kg, respectively. The immunotoxicity-derived toxic equivalency factors (TEFs) for these congeners could be calculated from the ED50 (TCDD)/ED50 (congener) ratios and the TEF values were within the range of those previously determined for other aryl hydrocarbon receptor-mediated responses. Based on the known concentrations of these congeners in the PCB mixtures, TCDD or toxic equivalents (TEQs) in the mixture were calculated [i.e., TEQ = sigma (PCBcongener x TEF)] using the immunotoxicity-derived TEFs (plaque-forming cells/10(6) viable cells). TEQ values for Aroclors 1260, 1254, 1248, and 1242 were 16.0, 54.4, 260.4, and 197 ppm, respectively. Based on the ED50 value for the immunosuppressive activity of TCDD (4.8 micrograms/kg), the calculated ED50 values for immune suppression by Aroclors 1260, 1254, 1248, and 1242 were 300, 88, 18, and 24 mg/kg, respectively. The ED50 (observed)/ED50 (calculated) ratios were 1.2, 5.9, 21, and 22.0 for Aroclors 1260, 1254, 1248 and 1242, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:Immunosuppressive activity of polychlorinated biphenyl mixtures and congeners: nonadditive (antagonistic) interactions. 758 23

The immune system has been identified as a sensitive target for the toxic effects produced by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Furthermore, the B cell has been identified as a sensitive cellular target of TCDD by previous cell-type fractionation studies from this laboratory. The mechanism responsible for the immunotoxic effects produced by TCDD is unclear; however, many of the biological effects of TCDD are thought to be mediated by the aryl hydrocarbon receptor (AhR). Here, we describe two B cell lines that differ considerably in their expression of the AhR and in their sensitivity to TCDD. Our results demonstrated a marked expression of the AhR protein in the CH12.LX B cell line but not in the BCL-1 B cell line. Transcripts for the AhR were not detected by reverse transcriptase-polymerase chain reaction in the BCL-1 cells. The AhR nuclear translocator (ARNT) protein was highly expressed in both cell lines. In addition, the AhR and ARNT are functional in CH12.LX cells as demonstrated by TCDD-induced CYP1A1 induction. TCDD did not induce CYP1A1 in BCL-1 cells. Furthermore, TCDD treatment resulted in suppression of lipopolysaccharide (LPS)-induced IgM secretion in CH12.LX cells. Conversely, TCDD-induced inhibition of IgM secretion was not demonstrated in LPS-stimulated BCL-1 cells, implicating a role for the AhR in the inhibition of B cell effector function. LPS-induced differentiation of the CH12.LX cells also resulted in a marked induction of Ahr expression which was not induced in LPS-stimulated BCL-1 cells. These studies have implicated the AhR as a critical factor in TCDD-induced inhibition of IgM secretion and have demonstrated an induction of AhR gene and protein expression after B cell activation.
 ...
PMID:Aryl hydrocarbon receptor-dependent suppression by 2,3,7, 8-tetrachlorodibenzo-p-dioxin of IgM secretion in activated B cells. 954 51

Halogenated aromatic hydrocarbons (HAHs) are ubiquitous environment contaminants that produce many of their toxic effects by binding to the aryl hydrocarbon receptor (AhR). However, several investigations have demonstrated that certain polychlorinated biphenyl (PCB) congeners, principally di-ortho-chlorinated PCB congeners, or mixtures containing multiple di-ortho-chlorinated PCBs, inhibit AhR-mediated responses induced by other toxic HAHs. Most relevant to the present study are past reports demonstrating antagonism by these uniquely acting PCB congeners on AhR agonist-mediated inhibition of humoral immune responses. The mechanism responsible for antagonism of AhR agonists by certain PCBs is presently unknown. The present study evaluated the antagonist activity of several di-ortho-substituted PCB congeners [PCB47 (2,2',4,4'), PCB52 (2,2',5,5'), PCB128 (2,2',3,3',4,4'), and PCB153 (2,2',4,4',5,5')] when present in combination with AhR agonists [TCDD (2,3,7,8,-tetrachlorodibenzo-p-dioxin), PCB126 (3,3',4,4',5), and PCB77 (3,3',4,4')] on CYP1A1 induction and inhibition of lipopolysaccharide (LPS)-induced immunoglobulin production in the CH12.LX B cell line. In contrast to non-ortho-substituted PCB (PCB77), which showed additive effects on CYP1A1 induction in combination with TCDD, all of the di-ortho-substituted PCBs examined produced antagonism. Di-ortho-substituted PCB (PCB52) also antagonized TCDD- or PCB126- mediated inhibition of IgM secretion and immunoglobulin heavy chain mRNA expression in the LPS-activated B cells. In addition, PCB52 inhibited TCDD-induced AhR DNA binding to a dioxin-responsive element. Collectively, these results suggest that the mechanism responsible for antagonism by di-ortho-substituted PCB congeners of AhR agonist-mediated CYP1A1 induction and inhibition of antibody responses in B cells occurs through interference with agonist activation of the cytosolic AhR complex.
 ...
PMID:Antagonism of aryl hydrocarbon receptor-dependent induction of CYP1A1 and inhibition of IgM expression by di-ortho-substituted polychlorinated biphenyls. 1262 80

Polychlorinated biphenyls (PCBs) are persistent environmental contaminants, and their ubiquitous nature has prompted studies of their potential health hazards. As a result of their lipophilic nature, PCBs accumulate in breast milk and subsequently affect the health of offspring of exposed individuals. Biological effects of PCBs in animals have mostly been attributed to coplanar congeners, although effects of ortho congeners also have been demonstrated. To investigate the relationship of immunotoxicity and chlorine substitution pattern, the effects of PCB congeners and mixtures of ortho and non-ortho-substituted constituents of Aroclor 1242 on splenocytes from C57B1/6 mice were examined. The immunotoxic endpoints investigated included splenocyte viability, lipopolysaccharide (LPS)-induced splenocyte proliferation, and LPS-induced antibody secretion. Congeners with multiple ortho chlorines preferentially inhibited splenocyte proliferation as compared with non- or mono-ortho-substituted congeners. However, mixtures of non- and mono-ortho-substituted congeners and multi-ortho-substituted congeners inhibited LPS-induced splenocyte proliferation and antibody secretion at similar concentrations. Exposure of splenocytes to these mixtures did not activate the aryl hydrocarbon receptor (AhR) signal transduction pathway. These results suggest individual multi-ortho-substituted congeners preferentially inhibit LPS-induced splenocyte proliferation, while congeners not exhibiting an effect individually may have additive effects in a mixture to produce an immunotoxic response through an AhR-independent pathway.
 ...
PMID:Inhibition of LPS-induced splenocyte proliferation by ortho-substituted polychlorinated biphenyl congeners. 1276 1

Several studies have shown that exposure to bacterial lipopolysaccharide (LPS) can either prevent or inhibit asthma in humans and laboratory rodents. Much emphasis has been placed on the role of cytokines and chemokines in the establishment and maintenance of allergic airway disease. Therefore, it is of interest to study the role of LPS in affecting airway pathology and lung cytokine and chemokine responses in the maintenance phase of asthma. Increasing doses of LPS were administered into the airways of mice presensitized with cockroach allergen (CRAg), then allergic airway disease parameters were assessed after CRAg challenge. Airway hyperresponsiveness after antigen challenge decreased at the highest dose of LPS tested, which was accompanied by a decrease in airway and lung eosinophils. However, a dramatic increase in lung inflammation because of neutrophil influx was observed. Measurement of cytokines in lungs of LPS-treated, CRAg-sensitized mice indicated that interleukin (IL)-12 levels were increased by LPS treatment in a dose-dependent manner, as were levels of several inflammatory chemokines. In contrast, levels of IL-4, IL-13, IL-5, and IL-10 were reduced in whole lung homogenates only of high-dose LPS-treated mice. Intranasal administration of neutralizing anti-IL-12 at the time of high-dose LPS challenge reduced lung IL-12, interferon-gamma, CXCL9, and CXCL10 but did not affect levels of the other chemokines or Th2-type cytokines, and did not restore AHR. These findings suggest that the amelioration of airway hyperresponsiveness observed in LPS-treated, CRAg-sensitized mice is coincident with an immune deviation of the lung inflammatory response, independent of IL-12.
 ...
PMID:Interleukin-12-independent down-modulation of cockroach antigen-induced asthma in mice by intranasal exposure to bacterial lipopolysaccharide. 1457 95

Transcriptional regulation of the Ig heavy chain gene involves several regulatory elements, including the 3'alpha enhancer, which is composed of four distinct regulatory domains. DNA binding sites for several transcription factors, including B cell-specific activator protein, nuclear factor for immunoglobulin kappa chain in B cells, and octamer have been identified within the 3'alpha enhancer domains and are believed to be important in regulating 3'alpha enhancer activity. We have identified an additional DNA binding motif, the dioxin-responsive element (DRE), which can contribute to 3'alpha enhancer regulation. 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), a known disrupter of B cell differentiation (i.e., decreased plasma cell formation, inhibition of micro heavy chain expression, and suppression of IgM secretion), induces binding of the aryl hydrocarbon receptor (AhR) nuclear complex to DREs. TCDD also induces AhR binding to the hypersensitive (hs)4 domain of the 3'alpha enhancer. Interestingly, TCDD enhances LPS-induced activation of the hs4 domain but profoundly inhibits LPS-induced activation of the complete 3'alpha enhancer. Furthermore, site-directed mutational analysis demonstrated that a DRE and kappaB element in the hs4 domain is modulated by TCDD in lipopolysaccharide-activated B cells. We propose that the AhR is a novel transcriptional regulator of the 3'alpha enhancer, which can mediate, at least in part, the effects of TCDD on the 3'alpha enhancer and its domains, putatively contributing to a marked suppression of IgM production.
 ...
PMID:2,3,7,8-tetrachlorodibenzo-p-dioxin, an exogenous modulator of the 3'alpha immunoglobulin heavy chain enhancer in the CH12.LX mouse cell line. 1471 3

The hepatic cytochrome P-450 (CYP) enzyme system provides a major aspect of liver function, yet alterations of CYP in sepsis remain largely unknown. Although we have recently shown that CYP1A2, one of the major isoforms of CYP in rats, is downregulated in sepsis, the underlying mechanism and possible therapeutic approaches warrant further investigation. The aim of this study was to determine whether Kupffer cells (KCs) play any role in suppressing CYP1A2 in the hepatocytes (HCs) and if so, how to modulate CYP1A2 expression in sepsis. To study this, primary KCs and HCs were cultured separately or together with or without transwells. Cells and supernatant samples were collected after various stimulations. Additionally, polymicrobial sepsis was induced in rats by cecal ligation and puncture (CLP) with or without curcumin pretreatment. Liver samples were harvested 20 h post-CLP. The results show that lipopolysaccharide (LPS) did not suppress CYP1A2 in HC or HC/KC coculture with transwells. However, LPS downregulated CYP1A2, aryl hydrocarbon receptor (AhR, a nuclear receptor) and AhR nuclear translocator (Arnt) in coculture without transwells. Anti-TNF-alpha and anti-IL-1beta antibodies attenuated this downregulation. Moreover, elevated hepatic levels of TNF-alpha and IL-1beta post-CLP were decreased by curcumin pre-treatment. This reduction was associated with increased expression of AhR and CYP1A2. These results indicate that KCs-derived proinflammatory cytokines may play an important role in downregulating CYP1A2 in sepsis. The reduction of AhR/Arnt may be the underlying mechanism for such downregulation. Inhibition of proinflammatory cytokines by curcumin may provide a novel approach to modulate the hepatic CYP function in sepsis.
 ...
PMID:Suppression of hepatocyte CYP1A2 expression by Kupffer cells via AhR pathway: the central role of proinflammatory cytokines. 1682 Sep 44

We previously demonstrated that tumor necrosis factor alpha (TNF-alpha) and lipopolysaccharide (LPS) downregulate aryl hydrocarbon receptor (AhR)-regulated genes, such as cytochrome P450 1a1 (Cyp1a1) and NADPH: quinone oxidoreductase 1 (Nqo1) gene expression, yet the mechanisms involved remain unknown. The correlation between the inflammation-mediated suppression of AhR-regulated genes and the TNF-alpha or LPS-induced nitric oxide (NO) production especially in murine hepatoma Hepa 1c1c7 cells has been questioned; therefore we investigated whether NO is involved in the modulation of Cyp1a1 and Nqo1 by TNF-alpha or LPS in Hepa 1c1c7 cells. A significant dose-dependent increase in the inducible nitric oxide synthase (NOS2) expression and NO production were observed by various concentrations of TNF-alpha (1, 5, and 10 ng/mL) and LPS (1 and 5 microg/mL) which was completely inhibited by a NOS2 inhibitor, L-N6-(1-iminoethyl) lysine (L-NIL) (1 mM). Furthermore, TNF-alpha and LPS significantly induced NOS2 expression. Both TNF-alpha and LPS repressed the beta-naphthoflavone (betaNF)-mediated induction of Cyp1a1 and Nqo1 at mRNA and activity levels. The downregulation of Cyp1a1, but not Nqo1, was significantly prevented by L-NIL. However, proxynitrite decomposer, iron tetrakis (N-methyl-4'-pyridyl) porphyrinato (FeTMPyP) (5 microM) did not affect TNF-alpha- and LPS-mediated downregulation of Cyp1a1 and Nqo1 at mRNA and activity levels. These results show that NO, but not peroxynitrite, may be involved in TNF-alpha- and LPS-mediated downregulation of Cyp1a1 without affecting the downregulation of Nqo1.
 ...
PMID:Role of nitric oxide in downregulation of cytochrome P450 1a1 and NADPH: Quinone oxidoreductase 1 by tumor necrosis factor-alpha and lipopolysaccharide. 1758 58

Diclofenac (DCLF) is a nonsteroidal anti-inflammatory drug that is associated with idiosyncratic adverse drug reactions in humans. Previous studies revealed a crucial role for intestine-derived bacteria and/or lipopolysaccharide (LPS) in DCLF-induced hepatotoxicity. We further explored this mechanism by conducting gene expression analysis of livers from rats treated with a hepatotoxic dose of DCLF (100 mg/kg) with or without oral antibiotic pretreatment. Genes for which expression was altered by DCLF were divided into two groups: genes with expression altered by antibiotic treatment and those unaffected by antibiotics. The former group of genes represented the ones for which DCLF-induced alterations in expression depended on intestinal bacteria. The expression of the latter group of genes was probably changed by direct effect of DCLF rather than by intestinal bacteria. Functional analysis of genes in the former group revealed LPS-related signaling, further suggesting a role for bacterial endotoxin in the liver injury. Functional analysis of genes in the latter group revealed changes in signaling pathways related to inflammation, hypoxia, oxidative stress, the aryl hydrocarbon receptor, and peroxisome proliferator-activated receptor alpha. Neutrophil depletion failed to protect from DCLF-induced hepatotoxicity, suggesting that intestinal bacteria contribute to liver injury in a neutrophil-independent manner. Hypoxia occurred in the livers of rats treated with DCLF, and hypoxia in vitro rendered hepatocytes sensitive to DCLF-induced cytotoxicity. These results support the hypothesis that intestinal bacteria are required for DCLF-induced hepatotoxicity and suggest that hypoxia plays an important role in the pathogenesis.
 ...
PMID:Gene expression profiles in livers from diclofenac-treated rats reveal intestinal bacteria-dependent and -independent pathways associated with liver injury. 1880 49

The 90 kDa heat shock proteins (Hsp90), which are integrally involved in cell signaling, proliferation, and survival, are ubiquitously expressed in cells. Many proteins in tumor cells are dependent upon the Hsp90 protein folding machinery for their stability, refolding, and maturation. Inhibition of Hsp90 uniquely targets client proteins associated with all six hallmarks of cancer. Thus, Hsp90 has emerged as a promising target for the treatment of cancer. Hsp90 exists as a homodimer, which contains three domains. The N-terminal domain contains an ATP-binding site that binds the natural products geldanamycin and radicicol. The middle domain is highly charged and has high affinity for co-chaperones and client proteins. Initial studies by Csermely and co-workers suggested a second ATP-binding site in the C-terminus of Hsp90. This C-terminal nucleotide binding pocket has been shown to not only bind ATP, but cisplatin, novobiocin, epilgallocatechin-3-gallate (EGCG) and taxol. The coumarin antibiotics novobiocin, clorobiocin, and coumermycin A1 were isolated from several streptomyces strains and exhibit potent activity against Gram-positive bacteria. These compounds bind type II topoisomerases, including DNA gyrase, and inhibit the enzyme-catalyzed hydrolysis of ATP. As a result, novobiocin analogues have garnered the attention of numerous researchers as an attractive agent for the treatment of bacterial infection. Novobiocin was reported to bind weakly to the newly discovered Hsp90 C-terminal ATP binding site ( approximately 700 M in SkBr3 cells) and induce degradation of Hsp90 client proteins. Structural modification of this compound has led to an increase of 1000-fold in activity in anti-proliferative assays. Recent studies of structure-activity relationship (SAR) by Renoir and co-workers highlighted the crucial role of the C-4 and/or C-7 positions of the coumarin and removal of the noviose moiety, which appeared to be essential for degradation of Hsp90 client proteins. Unlike the N-terminal ATP binding site, there is no reported co-crystal structure of Hsp90 C-terminus bound to any inhibitor. The Hsp90 C-terminal domain, however, is known to contain a conserved pentapeptide sequence (MEEVD) which is recognized by co-chaperones. Cisplatin is a platinum-containing chemotherapeutic used to treat various types of cancers, including testicular, ovarian, bladder, and small cell lung cancer. Most notably, cisplatin coordinates to DNA bases, resulting in cross-linked DNA, which prohibits rapidly dividing cells from duplicating DNA for mitosis. Itoh and co-workers reported that cisplatin decreases the chaperone activity of Hsp90. This group applied bovine brain cytosol to a cisplatin affinity column, eluted with cisplatin and detected Hsp90 in the eluent. Subsequent experiments indicated that cisplatin exhibits high affinity for Hsp90. Moreover Csermely and co-workers determined that the cisplatin binding site is located proximal to the C-terminal ATP binding site. EGCG is one of the active ingredients found in green tea. EGCG is known to inhibit the activity of many Hsp90-dependent client proteins, including telomerase, several kinases, and the aryl hydrocarbon receptor (AhR). Recently Gasiewicz and co-workers reported that EGCG manifests its antagonistic activity against AhR through binding Hsp90. Similar to novobiocin, EGCG was shown to bind the C-terminus of Hsp90. Unlike previously identified N-terminal Hsp90 inhibitors, EGCG does not appear to prevent Hsp90 from forming multiprotein complexes. Studies are currently underway to determine whether EGCG competes with novobiocin or cisplatin binding. Taxol, a well-known drug for the treatment of cancer, is responsible for the stabilization of microtubules and the inhibition of mitosis. Previous studies have shown that taxol induces the activation of kinases and transcription factors, and mimics the effect of bacterial lipopolysaccharide (LPS), an attribute unrelated to its tubulin-binding properties. Rosen and co-workers prepared a biotinylated taxol derivative and performed affinity chromatography experiments with lysates from both mouse brain and macrophage cell lines. These studies led to identification of two chaperones, Hsp70 and Hsp90, by mass spectrometry. In contrast to typical Hsp90-binding drugs, taxol exhibits a stimulatory response. Recently it was reported that the geldanamycin derivative 17-AAG behaves synergistically with taxol-induced apoptosis. This review describes the different C-terminal inhibitors of Hsp90, with specific emphasis on structure-activity relationship studies of novobiocin and their effects on anti-proliferative activity.
 ...
PMID:Novobiocin and additional inhibitors of the Hsp90 C-terminal nucleotide-binding pocket. 1899 31


1 2 3 4 5 6 Next >>