RESUMEN

Etiology of colorectal cancer (CRC) is related, at least in part, with nutritional profile and epidemiological data indicating a key role of dietary fat on CRC pathogenesis. Moreover, inflammation and eicosanoids produced from arachidonic acid might have a pivotal role in CRC development. However, the effect of specific fatty acids (FAs) on intestinal epithelial cell growth is not completely studied now. By this reason, the aim of this work is to unravel the effect of different saturated and unsaturated long-chain fatty acids (LCFA) and some LCFA metabolites on CRC cell line growth and their possible mechanisms of action. Our results demonstrated that oleic acid is a potent mitogenic factor to Caco-2 cells, at least in part, through 10-hydroxy-8-octadecenoic synthesized by lipoxigenase pathway, whereas polyunsaturated FAs such as eicosapentaenoic (EPA) acid has a dual behavior effect depending on its concentration. A high concentration, EPA induced apoptosis through intrinsic pathway, whereas at low concentration induced cell proliferation that could be related to the synthesis of eicosanoids such as prostaglandin E3 and 12-hydroxyeicosapentaenoic acid and the subsequent induction of mitogenic cell signaling pathways (ERK 1/2, CREB, p38α). Thus, this study contributes to understand the complicated relationship between fat ingest and CRC.

RESUMEN

Leukotriene D4 (LTD4) is a pro-inflammatory mediator formed from arachidonic acid through the action of 5-lipoxygenase (5-LOX). Its biological effects are mediated by at least two G-coupled plasmatic cysteinyl LT receptors (CysLT1-2R). It has been reported an upregulation of the 5-LOX pathway in tumor tissue unlike in normal colon mucosa. Colon tumors generally have an increased expression of CysLT1R and colon cancer patients with high expression levels of CysLT1R have poor prognosis. We previously observed that the cyclooxygenase pathway is involved in the control of intestinal epithelial cancer cell growth through PGE2 production. The aim of this study was therefore to assess the effect of LTD4 binding with CysLT1R on Caco-2 cell growth. We note a number of key findings from this research. We observed that at a concentration similar to that found under inflammatory conditions, LTD4 was able to induce Caco-2 cell proliferation and DNA synthesis. Moreover, with the use of a specific receptor antagonist this study has demonstrated that the effect of LTD4 is a result of its interaction with CystLT1R. We also note the possible participation of the PLC-IP3-Ca(2+)/DAG-PKC signaling pathways in cytosolic PLA2 and [(3)H]AA release induced by LTD4-CystLT1R interaction. Finally, we found that the resulting activation of the AA cascade and the production of PGE2 eicosanoid could be related to the activation of cell signaling pathways such as ERK and CREB. These findings will help facilitate our understanding of how inflammatory mediators can affect the survival and dissemination of intestinal carcinoma cells.

RESUMEN

Cyclooxygenases (COXs) and lipoxygenases (LOXs) are important enzymes that metabolize arachidonic and linoleic acids. Various metabolites generated by the arachidonic acid cascade regulate cell proliferation, apoptosis, differentiation, and senescence. Hydroxyoctadecadienoic acids (HODEs) are synthesized from linoleic acid, giving two enantiomeric forms for each metabolite. The aim was to investigate the effect of 13-HODE enantiomers on nondifferentiated Caco-2 cell growth/apoptosis. Our results indicate that 13(S)-HODE decreases cell growth and DNA synthesis of nondifferentiated Caco-2 cells cultured with 10% fetal bovine serum (FBS). Moreover, 13(S)-HODE showed an apoptotic effect that was reduced in the presence of a specific peroxisome proliferator-activated receptor-γ (PPARγ) antagonist. In addition, we observed that 13(S)-HODE but not 13(R)-HODE is a ligand to PPARγ, confirming the implication of this nuclear receptor in 13(S)-HODE actions. In contrast, 13(R)-HODE increases cell growth and DNA synthesis in the absence of FBS. 13(R)-HODE interaction with BLT receptors activates ERK and CREB signaling pathways, as well as PGE2 synthesis. These results suggest that the proliferative effect of 13(R)-HODE could be due, at least in part, to COX pathway activation. Thus both enantiomers use different receptors and have contrary effects. We also found these differential effects of 9-HODE enantiomers on cell growth/apoptosis. Therefore, the balance between (R)-HODEs and (S)-HODEs in the intestinal epithelium could be important to its cell growth/apoptosis homeostasis.

Asunto(s)

RESUMEN

Increasingly evidence indicates that enzymes, receptors and metabolites of the arachidonic acid (AA) cascade play a role in intestinal epithelial cell proliferation and colorectal tumorigenesis. However, the information available does not provide a complete picture and contains a number of discrepancies. For this reason it might be appropriate a thorough study into the impacts of the AA cascade on intestinal epithelial cell growth. Our data show that non-differentiated Caco-2 cells cultured with 10% fetal bovine serum (FBS) synthesize appreciable amounts of prostaglandin E2 (PGE2), leukotriene B4 (LTB4) and 5-, 12 and 15-hydroxyeicosatetraenoic acid (HETE) but not LTD4, 20-HETE and epoxyeicosatrienoic acids. We also found that inhibitors of PGE2, LTB4 and 5-, 12-, 15-HETE synthesis as well as receptor antagonists of PGE2 and LTB4 blocked Caco-2 cell growth and DNA synthesis induced by 10% FBS without cytotoxic or apoptotic activity. Interestingly, PGE2, LTB4 and 5-, 12- and 15-HETE at concentrations reached in 10% FBS Caco-2 cultures (1-10nM) were able to induce Caco-2 cell growth and DNA synthesis. This was due to the interaction of PGE2 with EP1 and EP4 receptors and LTB4 and HETEs with BLT1 and BLT2 receptors. Moreover, we provide evidence that PGE2 stimulates several cell signaling pathways such as ERK, P38α, CREB and GSKß/ß-catenin involved in the regulation of Caco-2 growth. Finally, we provide evidence that the mitogenic effects of LTB4 and HETEs can be dependent, at least in part, on PGE2 synthesis.

Asunto(s)