N-3 and n-6 fatty acids stimulate restitution by independent mechanisms in the IEC-6 model of intestinal wound healing

We have shown that intestinal epithelial restitution is stimulated by n-3 and n-6 fatty acids. The current studies were undertaken to elucidate the mechanistic pathway(s) involved in this fatty acid modulation of restitution. Inhibition of phospholipase A2 and eicosanoid synthesis and its effect on fatty acid stimulation of cellular migration in confluent, wounded IEC-6 monolayers was examined. The production of prostaglandin E2 and transforming growth factor β1 were also measured in fatty acid supplemented cultures. 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 (2 μmol/L), had no effect on stimulation of migration by fatty acids. The cyclooxygenase inhibitor piroxicam (5 μmol/L) and cyclooxygenase-2 specific inhibitors dexamethasone (2 μmol/L) and NS-398 (10 μmol/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 significantly greater than in control and n-3 supplemented cultures and was partially inhibited by dexamethasone and NS-398. Latent transforming growth factor β1 production in n-3 supplemented cultures was significantly higher than baseline and n-6 supplemented cultures. Docosapentaenoic acid supplementation significantly enhanced the restitution process and NS-398 treatment had no effect on this stimulation of cellular migration. The liberation of fatty acid from the sn-2 position of phospholipid appears to be necessary for both n-3 and n-6 fatty acid stimulation of restitution. 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 β1 and may be responsible for n-3 mediated stimulation of restitution. These results further emphasize that n-3 and n-6 fatty acids convey their effects through unique pathways.