| 1. |
- Kamp-Nielsen, Christian, et al.
(författare)
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The leukotriene receptor CysLT1 and 5-lipoxygenase are upregulated in colon cancer.
- 2003
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Ingår i: Advances in Prostaglandin, Leukotriene, and other Bioactive Lipid Research. - Boston, MA : Springer US. - 0065-2598. - 9780306477638 ; 525, s. 201-204
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Bokkapitel (refereegranskat)abstract
- The metabolites of arachidonic acid are well connected to pathological situations such as inflammation, cancer and asthmA. Sheng et al. [7] found that COX-2 is upregulated in colon cancer tissue and tumor cell lines indicating that COX-2 is involved in colon cancer. This is supported by studies showing that patients treated with nonsteroidal anti-inflammatory drugs, inhibitors of COX-2, exhibit a lower frequency of colon cancer [8]. When the non-transformed intestinal epithelial cell line, Int 407 was stimulated with LTD4 or LTB4 we observed an accumulation of COX-2 in membrane fractions as well as an increased production of prostaglandin E2 [5]. Treatment of these cells with the COX-2 inhibitor NS-398 caused apoptosis and this effect could be prevented by LTD4 [5] or LTB4 [4]. Similar results were obtained when cell viability with LTD4 or LTB4 in the presence or absence of NS-398 was assayed [4,5]. The results demonstrate that these leukotrienes can suppress the NS-398 induced apoptosis in intestinal cells.
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| 2. |
- Massoumi, Ramin, et al.
(författare)
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Leukotriene D(4) affects localisation of vinculin in intestinal epithelial cells via distinct tyrosine kinase and protein kinase C controlled events
- 2001
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Ingår i: Journal of Cell Science. - 0021-9533. ; 114:10, s. 1925-1934
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Tidskriftsartikel (refereegranskat)abstract
- Local inflammatory reactions affect the integrity of intestinal epithelial cells, such as E-cadherin-mediated cell-cell interactions. To elucidate this event, we investigated the effects of an inflammatory mediator, leukotriene D(4 )(LTD(4)), on the phosphorylation status and properties of vinculin, a multi-binding protein known to interact with both the E-cadherin-catenin complex and the cytoskeleton. Treatment of an intestinal epithelial cell line with LTD(4 )induced rapid tyrosine phosphorylation of vinculin, which was blocked by the Src family tyrosine kinase inhibitor PP1. Simultaneously, LTD(4) caused an increased association between vinculin and actin, and that association was decreased by PP1. LTD(4) also induced dissociation of vinculin from alpha-catenin without affecting the catenin complex itself. This dissociation was not blocked by PP1 but was mimicked by the protein kinase C (PKC) activator 12-O-tetradecanoylphorbol 13-acetate (TPA). Also, the PKC inhibitor GF109203X abolished both the LTD(4)- and the TPA-induced dissociation of vinculin from alpha-catenin. Furthermore, LTD(4) caused a colocalisation of vinculin with PKC-alpha in focal adhesions. This accumulation of vinculin was blocked by transfection with a dominant negative inhibitor of PKC (PKC regulatory domain) and also by preincubation with either GF109203X or PP1. Thus, various LTD(4)-induced phosphorylations of vinculin affect the release of this protein from catenin complexes and its association with actin, two events that are necessary for accumulation of vinculin in focal adhesions. Functionally this LTD(4)-induced redistribution of vinculin was accompanied by a PKC-dependent upregulation of active beta1 integrins on the cell surface and an enhanced beta1 integrin-dependent adhesion of the cells to collagen IV.
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| 3. |
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| 4. |
- Massoumi, Ramin, et al.
(författare)
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Leukotriene D-4 induces stress-fibre formation in intestinal epithelial cells via activation of RhoA and PKC delta
- 2002
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Ingår i: Journal of Cell Science. - 0021-9533. ; 115:17, s. 3509-3515
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Tidskriftsartikel (refereegranskat)abstract
- The intestinal epithelial barrier, which is regulated by the actin cytoskeleton, exhibits permeability changes during inflammation. Here we show that activation of the CysLT(1) receptor by the inflammatory mediator leukotriene D-4 (LTD4) causes a rapid increase in stress-fibre formation in intestinal epithelial cells. This effect was mimicked by cytotoxic necrotising factor-1 (CNF-1)-induced activation of RhoA, overexpression of constitutively active RhoA (L63-RhoA) and phorbol-ester-induced activation of protein kinase C (PKC). In accordance, inhibition of RhoA, by C3 exoenzyme or by dominant-negative RhoA (N19-RhoA), as well as GF109203X-induced inhibition of PKC, suppressed the LTD4-induced stress-fibre formation. Introduction of the dominant-negative regulatory domain of PKCdelta, but not the corresponding structures from PKCalpha, betaII or epsilon, blocked the LTD4-induced stress-fibre formation. Evaluating the relationship between PKCdelta and RhoA in LTD4-induced stress-fibre formation, we found that C3 exoenzyme inhibited the rapid LTD4-elicited translocation of PKCdelta to the plasma membrane. Furthermore, CNF-1-induced stress-fibre formation was blocked by GF109203X and by overexpression of the regulatory domain of PKC-delta, whereas PKC-induced stress-fibre production was not affected by N19-RhoA. We conclude that PKC-delta is located downstream of RhoA and that active RhoA and PKCdelta are both necessary for LTD4-induced stress-fibre formation.
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| 5. |
- Massoumi, Ramin
(författare)
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Regulation of the cytoskeleton and the adhesiveness of intestinal epithelial cells by leukotriene D4
- 2002
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Leukotrienes belong to a family of biologically active conjugated trienes that are formed from arachidonic acid via the 5-lipoxygenase pathway and are important mediators of inflammatory reactions. The CysLT1 receptor that specifically serves as receptor for leukotriene D4 (LTD4) has been identified as a G-protein coupled receptor. Cell-cell and cell-matrix complexes of epithelial cells are interconnected through cytoskeletal filaments and proteins, and they influence the activities and outcome of various cellular processes. This thesis is focused primarily on the effect that LTD4 has on reorganisation of the actin cytoskeleton and on cell-cell and cell-matrix adhesion properties. We found that LTD4 caused dramatic changes in the actin cytoskeleton in intestinal epithelial cells, and an important factor in this context was the impact of this leukotriene on the actin-binding protein vinculin, which included inducing translocation of vinculin from a cell-cell to a cell-matrix complex. In general, cell adhesion favours cell survival signalling, and integrins are the main receptors responsible for mediating the attachment of different types of cells to matrix proteins. We have unequivocally established that direct signalling occurs between the LTD4 receptor and the collagen integrins in two different cell lines respectively derived from human colon carcinoma and intestinal epithelial cells. Increased adhesion of the cancer cells depended on activation of cyclooxygenase-2, an enzyme that is involved in progression of colon cancers, whereas adhesion of the intestinal epithelial cells was augmented by LTD4-induced translocation of protein kinase C to areas where integrins bind to matrix proteins (focal adhesions). In conclusion, inflammatory mediators such as LTD4 can affect cell survival through their impact on specific integrins.
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| 6. |
- Thodeti, Charles Kumar, et al.
(författare)
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Leukotriene D4 induces association of active RhoA with phospholipase C-gamma1 in intestinal epithelial cells.
- 2002
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Ingår i: Biochemical Journal. - 0264-6021. ; 365:Pt 1, s. 157-163
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Tidskriftsartikel (refereegranskat)abstract
- It has been previously suggested that leukotriene-induced Ca2+ signalling is mediated through a Rho-dependent process, but neither direct activation of Rho nor a mechanism underlying such signalling has been reported. Accordingly, we used the Rhotekin binding assay to assess RhoA activation in intestinal epithelial cells and observed that RhoA was activated by leukotriene D4 (LTD4). We also found that, within 15 s, activation of RhoA by LTD4 led to an increased association of RhoA with G-protein betagamma (Gbetagamma) and phospholipase C-gamma1 (PLC-gamma1) in the plasma membrane, as evidenced by the results of co-immunoprecipitation, glutathione S-transferase (GST) pulldown assays, and confocal microscopy. Amounts of RhoA increased in both Gbeta and PLC-gamma1 immunoprecipitates within 15 s of LTD4 treatment. An interaction between RhoA, Gbetagamma and PLC-gamma1 is supported by our finding that a GST fusion protein of constitutively active RhoA (GST-RhoAV14) precipitated Gbetagamma and PLC-gamma1 from cell lysates in an agonist-dependent manner. Such an association is also substantiated by our confocal immunofluorescence results, which revealed that LTD4 induction increased co-localization of constitutively active RhoA and PLC-gamma1 to the plasma membrane of cells transfected with enhanced green fluorescent protein L63RhoA. Furthermore, microinjection of neutralizing RhoA antibodies, but not control antibodies, significantly reduced LTD4-induced Ca2+ mobilization. Our results are the first to demonstrate a LTD4-induced activation of RhoA and more importantly its association with PLC-gamma1, which are essential for the PLC-gamma1-mediated calcium mobilization.
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