N-3 and N-6 fatty acid regulation of restitution in the IEC-6 model of intestinal wound healing

The effects of specific fatty acids on cellular function in relation to the prevention and treatment of disease are active areas of research. Much remains to be learned about the process of epithelial restitution. The effects of (n-3), (n-6) and trans fatty acids on IEC-6 cultures and restitution of wounded IEC-6 monolayers were investigated. The modulation of epithelial restitution was examined by razor blade wounding confluent IEC-6 monolayers grown in media supplemented with various fatty acids. Eicosapentaenoic [20:5(n-3)], docosapentaenoic, [22:5(n-3)], alpha-linolenic [18:3(n-3)], linoleic [18:2(n-6)], gamma-linolenic [18:3(n-6)] and arachidonic [20:4(n-6)] acids all significantly enhanced cellular migration in the IEC-6 model of wound healing. Inhibition of eicosanoid synthesis by indomethacin reduced the stimulation of restitution by n-6 but not n-3 fatty acids. Subsequent studies were undertaken to determine the mechanistic pathway(s) involved in this fatty acid modulation of restitution. The effect of inhibiting phospholipase A2 and eicosanoid synthesis pathways on fatty acid stimulation of cellular migration in confluent, wounded IEC-6 monolayers was determined. The production of prostaglandin E2, transforming growth factor beta1 and extracellular matrix protein expression (laminin and fibronectin) was also determined in this model. Inhibition of phospholipase A2 attenuated the effect of fatty acid stimulation of restitution in both n-3 and n-6 supplemented cultures. The lipoxygenase inhibitor, nordihydorguaretic acid (2mumol/L) had no effect on stimulation of migration by fatty acids. The cyclooxygenase inhibitor piroxicam (5mumol/L) and cyclooxygenase2 specific inhibitors dexamethasone (2mumol/L) and NS-398 (10mumol/L) all attenuated the fatty acid stimulation of migration by n-6 fatty acids but had no effect on n-3 stimulated restitution. Prostaglandin E2 production in n-6 supplemented cultures was elevated compared to control and n-3 supplemented cultures. Piroxicam and NS-398 reduced the production of prostaglandin E2 but levels remained several times greater than control. Latent transforming growth factor beta1 production in n-3 supplemented cultures was significantly elevated. N-6 fatty acid modulation of restitution appears to be mediated through the production of eicosanoid products. However, prostaglandin E2 does not appear to be the sole prostanoid involved. N-3 supplementation elevates the production of latent transforming growth factor beta1 and may be responsible for n-3 mediated stimulation of restitution.