Leukotrienes induce cell-survival signaling in intestinal epithelial cells.
OBJECTIVE
Inflammatory bowel conditions, particularly ulcerative colitis, are associated with an increased incidence of neoplastic transformation. High levels of proinflammatory leukotrienes (LTs) and up-regulated expression of cyclooxygenase (COX)-2 are characteristic of inflammation. Moreover, COX-2 has been implicated in cell survival and early colon carcinogenesis. Other aspects of interest for intestinal cell viability are the levels of beta-catenin and the antiapoptotic protein Bcl-2. We investigated the possibility that LTs participate in the regulation of these survival factors.


METHODS
We used the human intestinal epithelial cell line Int 407 and the rat intestinal epithelial cell line IEC-6. Immunoblotting was applied to ascertain protein expression and distribution, and enzyme immunoassay methodology was used to measure prostaglandin E(2) (PGE(2)) production. Apoptotic ability was assessed by trypan blue exclusion, Hoechst staining, DNA fragmentation, and a caspase-3 activity assay.


RESULTS
LTD(4) and LTB(4), but not LTC(4), caused a time- and dose-dependent increase in expression and/or membrane accumulation of COX-2, beta-catenin, and Bcl-2, as well as PGE(2) production. Apoptosis assays showed that the effects of LTs on these transformation-associated proteins correlated well with the ability of these LTs to reduce programmed cell death.


CONCLUSIONS
The results suggest that inflammatory conditions are associated with the expression and distribution of proteins that are characteristic of transformed cells; such conditions may involve a signaling mechanism comprising an altered rate of apoptosis.
Ohd
J F
JF
Division of Experimental Pathology, Department of Laboratory Medicine, Lund University, University Hospital Malmö, Malmö, Sweden.
Wikström
K
K
Sjölander
A
A
D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology*; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; D003598:Cytoskeletal Proteins / Q000378:metabolism; D015232:Dinoprostone / Q000378:metabolism; D006801:Humans; D007413:Intestinal Mucosa / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D007527:Isoenzymes / Q000378:metabolism; D007700:Kinetics; D007975:Leukotriene B4 / Q000494:pharmacology; D017997:Leukotriene C4 / Q000494:pharmacology; D017998:Leukotriene D4 / Q000494:pharmacology; D015289:Leukotrienes / Q000494:pharmacology*; D008565:Membrane Proteins; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction / Q000502:physiology*; D015534:Trans-Activators; D051176:beta Catenin
C495270:CTNNB1 protein, human; C495268:Ctnnb1 protein, rat; D003598:Cytoskeletal Proteins; D007527:Isoenzymes; D015289:Leukotrienes; D008565:Membrane Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D015534:Trans-Activators; D051176:beta Catenin; D007975:Leukotriene B4; D017997:Leukotriene C4; D017998:Leukotriene D4; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; C496511:PTGS1 protein, human; C496540:PTGS2 protein, human; D011451:Prostaglandin-Endoperoxide Synthases; C496513:Ptgs1 protein, rat; C505407:CASP3 protein, human; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases; D015232:Dinoprostone