MP010
DOCOSAHEXAENOIC ACID ATTENUATION OF TUMOR PROMOTER-INDUCED UROKINASE-TYPE PLASMINOGEN ACTIVATOR RECEPTOR IS MEDIATED BY HEME OXYGENASE-1 IN HUMAN ENDOTHELIAL CELLS Free

Introduction and Aims: The overexpression of urokinase-type plasminogen activator receptor (uPAR) is associated with inflammation and virtually all human cancers. Despite the fact that docosahexaenoic acid (DHA) has been reported to possess anti-inflammatory and anti-tumor properties, the negative regulation of uPAR by DHA cells is still undefined.

Methods: Here, we investigated the effect of DHA on 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced uPAR expression and the underlying molecular mechanisms of this expression in human endothelial ECV304 cells.

Results: TPA time-dependently induced uPAR expression, and DHA dose-dependently inhibited uPAR. TPA activated reactive oxygen species (ROS), protein kinase C (PKC), Akt, c-jun NH₂-terminal kinase (JNK), extracellular signal-regulated kinase (Erk), and p38 mitogen-activated protein kinase (p38 MAPK) and induced DNA binding of activator protein-1(AP-1) and nuclear factor-κB (NF-κB). Specific inhibitors of ROS (NAC), NADPH oxidase (DPI), PKC (GF109203X), PKCδ (Rottlerin), JNK1/2(SP600125), Erk1/2 (PD98059), NF-κB (BAY11-7082), and AP-1 (curcumin) inhibited TPA-induced uPAR expression. Further, NAC, DPI, and rottlerin suppressed activation of JNK1/2 and Erk1/2. Deletions and site-directed mutagenesis confirmed the role of AP-1 and NF-κB in TPA-induced uPAR expression. Application of DHA suppressed TPA-induced ROS generation, translocation of PKCδ, activation of the JNK1/2 and Erk1/2 signaling pathways, and subsequent AP-1 and NF-κB transactivation. Moreover, DHA induced heme oxygenase-1 (HO-1) and knockdown of HO-1 prevented the inhibition of uPAR expression by DHA. Induction of HO-1 by ferric protoporphyrin IX (FePP) inhibited TPA-induced uPAR expression. Additionally, carbon monoxide, an HO-1 end product, attenuated TPA-induced uPAR and related signaling.

Conclusions: In conclusion, these observations suggest a novel role for HO-1 induced by DHA in reducing uPAR expression and cell invasion by inhibition of ROS, PKCδ, Erk1/2, and JNK1/2, and the reduction of AP-1 and NF-κB activation. The induction of HO-1 is partially involved in the inhibition of TPA-induced uPAR by DHA in human endothelial ECV304 cells.