Abstract
In the regions of tissue injuries and inflammatory diseases, sphingosine 1-phosphate (S1P), a proinflammatory mediator, is increased. S1P may induce the upregulation of cyclooxygenase-2 (COX-2)/prostaglandin E2 (PGE2) system in various types of cells to exacerbate heart inflammation. However, the detailed molecular mechanisms by which S1P induces COX-2 expression in human cardiac fibroblasts (HCFs) remain unknown. HCFs were incubated with S1P and analyzed by Western blotting, real time-Polymerase chain reaction (RT-PCR), and immunofluorescent staining. Our results indicated that S1P activated S1PR1/3-dependent transcriptional activity to induce COX-2 expression and PGE2 production. S1P recruited and activated PTX-sensitive Gi or -insensitive Gq protein-coupled S1PR and then stimulated PKCα-dependent phosphorylation of p42/p44 MAPK, p38 MAPK, and JNK1/2, leading to activating transcription factor NF-κB. Moreover, S1P-activated NF-κB was translocated into the nucleus and bound to its corresponding binding sites on COX-2 promoters determined by chromatin immunoprecipitation (ChIP) and promoter-reporter assays, thereby turning on COX-2 gene transcription associated with PGE2 production in HCFs. These results concluded that in HCFs, activation of NF-κB by PKCα-mediated MAPK cascades was essential for S1P-induced up-regulation of the COX-2/PGE2 system. Understanding the mechanisms of COX-2 expression and PGE2 production regulated by the S1P/S1PRs system on cardiac fibroblasts may provide rationally therapeutic interventions for heart injury or inflammatory diseases.
Highlights
Sphingosine 1-phosphate (S1P) has been characterized as a potent bioactive sphingolipid molecule that regulates a wide range of physiological and pathological functions, including inflammation, angiogenesis, endothelial barrier function, lymphocyte egress, apoptosis, and proliferation (Proia and Hla, 2015; Pyne et al, 2016; Vogt and Stark, 2017)
Several proinflammatory mediators have been shown to play critical roles in inflammation due to the upregulation of NF-κB-dependent genes such as COX-2 (Barnes and Karin, 1997; Hsieh et al, 2008), the detail mechanisms by which S1P induced COX-2 expression and prostaglandin E2 (PGE2) release were investigated in human cardiac fibroblasts (HCFs) by using pharmacological inhibitors and gene silencing approaches. These findings indicated that S1Pinduced COX-2 expression is mediated through transcription and translation, which are via coupling to both Gi and Gq protein S1PR1/3, activation of PKCα-dependent p42/p44 mitogen-activated protein kinases (MAPKs), p38 MAPK, JNK1/2, and NF-κB signaling pathways, leading to PGE2 production in HCFs
There was a significant increase within 4 h and reached a maximum at 8 h, which was attenuated by pretreatment with a COX-2 activity inhibitor NS-398 (10 μM), indicating that S1P induced a COX-2-dependent PGE2 generation in HCFs
Summary
Sphingosine 1-phosphate (S1P) has been characterized as a potent bioactive sphingolipid molecule that regulates a wide range of physiological and pathological functions, including inflammation, angiogenesis, endothelial barrier function, lymphocyte egress, apoptosis, and proliferation (Proia and Hla, 2015; Pyne et al, 2016; Vogt and Stark, 2017). Cardiac fibroblasts are one of main cellular constituents of the heart and play numerous roles in cardiac functions including proliferation, migration, secretion of growth factors and cytokines, and inflammation (Porter and Turner, 2009). S1P may play an important role in regulation of cardiovascular functions and can be a therapeutically target in inflammatory heart disorders
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
