15-deoxy-Δ12,14-PGJ2 promotes inflammation and apoptosis in cardiomyocytes via the DP2/MAPK/TNFα axis

Abstract

BackgroundProstaglandins (PGs), lipid autacoids derived from arachidonic acid, play a pivotal role during inflammation. PGD2 synthase is abundantly expressed in heart tissue and PGD2 has recently been found to induce cardiomyocyte apoptosis. PGD2 is an unstable prostanoid metabolite; therefore the objective of the present study was to elucidate whether its final dehydration product, 15-deoxy-Δ12,14-PGJ2 (15d-PGJ2, present at high levels in ischemic myocardium) might cause cardiomyocyte damage.Methods and resultsUsing specific (ant)agonists we show that 15d-PGJ2 induced formation of intracellular reactive oxygen species (ROS) and phosphorylation of p38 and p42/44 MAPKs via the PGD2 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-PGJ2 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-PGJ2 (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.ConclusionsWe conclude that the reactive α,β-unsaturated carbonyl group of 15d-PGJ2 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-PGJ2-induced myocardial injury.

Response to letter by Tsikas et al. 15-deoxy-Δ12,14-PGJ2: An interesting but unapproachable pharmacological target?

“…We read with great interest the article by Koyani et al reporting that 15-deoxy-Δ 12,14 -prostaglandin (PG) J 2 (15d-PGJ 2 ) promotes apoptosis and inflammation in cardiomyocytes [1]. Although there is no question that 15d-PGJ 2 and relatives including Δ 12 -PGJ 3 have multiple biological activities [2][3][4][5][6][7][8][9], the most important question is still [10] whether 15d-PGJ 2 is formed in vivo at sufficiently high concentrations or can be applied pharmacologically or nutritionally at such doses that are likely to provide 15d-PGJ 2 concentrations high enough to exert biologic activity.…”

“…These values correspond to 15d-PGJ 2 concentrations of 0.4 and 0.7 nM, respectively. Thus, in the study by Koyani et al [1] and in studies from other groups [3][4][5][6][7][8], 15d-PGJ 2 was used in the majority of their experiments at a concentration of 15 μM, which is at least three orders of magnitude higher than expectable tissue 15d-PGJ 2 concentrations. Lower, more pathophysiologically relevant but still too high concentrations (e.g., 50 nM) were used only in very few experiments [1].…”

“…Many biological effects of 15d-PGJ 2 including apoptosis in cardiomyocytes are attributed to the intracellular production of reactive oxygen species (ROS) which are frequently measured by the DCF fluorescence assay [1]. Yet, the ROS studies by Koyani et al [1] were performed at the very high 15d-PGJ 2 concentration of 15 μM, which renders the oxidative effects of 15d-PGJ 2 at least partially nonpathophysiologically relevant.…”

“…Thus, in the study by Koyani et al [1] and in studies from other groups [3-8], 15d-PGJ 2 was used in the majority of their experiments at a concentration of 15 μM, which is at least three orders of magnitude higher than expectable tissue 15d-PGJ 2 concentrations. Lower, more pathophysiologically relevant but still too high concentrations (e.g., 50 nM) were used only in very few experiments [1].Many biological effects of 15d-PGJ 2 including apoptosis in cardiomyocytes are attributed to the intracellular production of reactive oxygen species (ROS) which are frequently measured by the DCF fluorescence assay [1]. Yet, the ROS studies by Koyani et al…”

Atrial Fibrillation Promotion in a Rat Model of Rheumatoid Arthritis

“…Saba et al25 found that cardiac‐specific overexpression of TNF‐α could cause atrial contractile dysfunction, fibrosis, and arrhythmias in a mouse model. Moreover, a recent study has revealed that enhanced expression of TNF‐α in the murine atrial cardiomyocyte HL‐1 cell line promoted cardiomyocyte apoptosis by activating CASP‐3 26. IL‐6 has also been shown to be an important regulator of cardiac interstitial fibrosis.…”