PAR1‐dependent COX‐2/PGE₂ production contributes to cell proliferation via EP₂ receptors in primary human cardiomyocytes

Abstract

BACKGROUND AND PURPOSEDifferent protease-activated receptors (PARs) activated by thrombin are involved in cardiovascular disease, via up-regulation of inflammatory proteins including COX-2. However, the mechanisms underlying thrombin-regulated COX-2 expression in human cardiomyocytes remain unclear. EXPERIMENTAL APPROACHHuman cardiomyocytes were used in the study. Thrombin-induced COX-2 protein and mRNA expression, and signalling pathways were determined by Western blot, real-time PCR and COX-2 promoter luciferase reporter assays, and pharmacological inhibitors or siRNAs. PGE2 generation and cell proliferation were also determined. KEY RESULTSThrombin-induced COX-2 protein and mRNA expression, promoter activity and PGE2 release was attenuated by the PAR1 antagonist (SCH79797) or the inhibitors of proteinase activity (PPACK), MEK1/2 (U0126), p38 MAPK (SB202190) or JNK1/2 (SP600125), and transfection with small interfering RNA (siRNA) of PAR1, p38, p42 or JNK2. These results suggested that PAR1-dependent MAPKs participate in thrombin-induced COX-2 expression in human cardiomyocytes. Moreover, thrombin stimulated phosphorylation of MAPKs, which was attenuated by PPACK and SCH79797. Furthermore, thrombin-induced COX-2 expression was blocked by the inhibitors of AP-1 (tanshinone IIA) and NF-κB (helenalin). Moreover, thrombin-stimulated phosphorylation of c-Jun/AP-1 and p65/NF-κB was attenuated by tanshinone IIA and helenalin, respectively, suggesting that thrombin induces COX-2 expression via PAR1/MAPKs/AP-1 or the NF-κB pathway. Functionally, thrombin increased human cardiomyocyte proliferation through the COX-2/PGE2 system linking to EP2 receptors, as determined by proliferating cell nuclear antigen and cyclin D1 expression. CONCLUSIONS AND IMPLICATIONSThese findings demonstrate that MAPKs-mediated activation of AP-1/NF-κB pathways is, at least in part, required for COX-2/PGE2/EP2-triggered cell proliferation in human cardiomyocytes. AbbreviationsANF, atrial natriuretic factor; PAR, protease-activated receptor; PCNA, proliferating cell nuclear antigen BJP British Journal of Pharmacology

Cardiac injury modulates critical components of prostaglandin E2 signaling during zebrafish heart regeneration

“…In other model systems, PGE 2 has been shown to directly promote the proliferation of multiple cell types, including skeletal muscle stem cells 28 and primary human CMs 15 . However, a large body of work also supports a role for PGE 2 in governing the recruitment, retention, and pro-regenerative polarization of neutrophils, macrophages, and T cells 17,18,53 .…”

“…Among the principal signaling molecules released during acute inflammation are the prostaglandins. Notably, Prostaglandin E 2 (PGE 2 ) has been shown to promote tissue regeneration by directly stimulating the proliferation of target cells 15,16 , as well as indirectly, by governing the recruitment and polarization of immune cells [17][18][19] . PGE 2 is synthesized through the sequential catalytic activity of cyclooxygenase (COX) enzymes, prostaglandin-endoperoxide synthase −1 and −2 (colloquially termed COX1 and −2), followed by the terminal synthase Prostaglandin E synthases (PTGES).…”

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“…The elevation of these protective cardiokines reduces the apoptosis of cardiomyocytes in the infarct area and improves the survival of mice after MI. The advancing effect of PGE 2 on cardiomyocyte replenishment may also be related to the function of PGE 2 in promoting proliferation of adult stem cells [60, 61]. Administration of PGE 2 to human mesenchymal stem cells maintains proliferation and self-renewal of these cells via the EP2 receptor which then enhances the production and autocrine effect of PGE 2 itself [61].…”

“…Administration of PGE 2 to human mesenchymal stem cells maintains proliferation and self-renewal of these cells via the EP2 receptor which then enhances the production and autocrine effect of PGE 2 itself [61]. Moreover, human cardiomyocytes stimulated with thrombin triggers the production of PGE 2 , which in turn promotes cardiomyocyte proliferation via EP2 receptors [60]. Whether PGE 2 exerts the same proliferative effects on CPCs in the ischemic hearts requires further investigation.…”

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