15-deoxy-Δ(12,14)-PGJ(2) promotes inflammation and apoptosis in cardiomyocytes via the DP2/MAPK/TNFα axis

BACKGROUND: Prostaglandins (PGs), lipid autacoids derived from arachidonic acid, play a pivotal role during inflammation. PGD(2) synthase is abundantly expressed in heart tissue and PGD(2) has recently been found to induce cardiomyocyte apoptosis. PGD(2) is an unstable prostanoid metabolite; therefore the objective of the present study was to elucidate whether its final dehydration product, 15-deoxy-Δ(12,14)-PGJ(2) (15d-PGJ(2), present at high levels in ischemic myocardium) might cause cardiomyocyte damage. METHODS AND RESULTS: Using specific (ant)agonists we show that 15d-PGJ(2) induced formation of intracellular reactive oxygen species (ROS) and phosphorylation of p38 and p42/44 MAPKs via the PGD(2) receptor DP2 (but not DP1 or PPARγ) in the murine atrial cardiomyocyte HL-1 cell line. Activation of the DP2-ROS-MAPK axis by 15d-PGJ(2) enhanced transcription and translation of TNFα and induced apoptosis in HL-1 cardiomyocytes. Silencing of TNFα significantly attenuated the extrinsic (caspase-8) and intrinsic apoptotic pathways (bax and caspase-9), caspase-3 activation and downstream PARP cleavage and γH2AX activation. The apoptotic machinery was unaffected by intracellular calcium, transcription factor NF-κB and its downstream target p53. Of note, 9,10-dihydro-15d-PGJ(2) (lacking the electrophilic carbon atom in the cyclopentenone ring) did not activate cellular responses. Selected experiments performed in primary murine cardiomyocytes confirmed data obtained in HL-1 cells namely that the intrinsic and extrinsic apoptotic cascades are activated via DP2/MAPK/TNFα signaling. CONCLUSIONS: We conclude that the reactive α,β-unsaturated carbonyl group of 15d-PGJ(2) is responsible for the pronounced upregulation of TNFα promoting cardiomyocyte apoptosis. We propose that inhibition of DP2 receptors could provide a possibility to modulate 15d-PGJ(2)-induced myocardial injury.