Research Article Novel Biphasic Role of Resolvin D1 on Expression of

which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Fibroblasts, far frombeing merely bystander cells, are known to play a specific role in inflammation resolution after an acute injury. As the endogenous “braking signal, ” resolvins possess potent anti-inflammatory and proresolution actions. We demonstrated that the expression of COX-2 protein was significantly peaked initially at 6 hours but then also at 48 hours after LPS stimulation in lung fibroblasts. PGE 2 levels also peaked at 6 hours, and PGD 2 levels were increased and peaked at 48 hours. However, no significant change in the protein expression of COX-1 was observed after treatment with LPS in lung fibroblasts. Exogenous resolvin D1 inhibited the first peak of COX-2 expression as well as the production of PGE 2 induced by LPS. In contrast, exogenous resolvin D1 increased the second peak of COX-2 expression as well as the production of PGD 2 induced by LPS. In addition, resolvin D1 inhibited COX-2 expression at 6 hours, which was partly through PI3K/AKT and ERK2 signalling pathways. 1