Ceramide Kinase Mediates Cytokine- and Calcium Ionophore-induced Arachidonic Acid Release

Abstract

Despite the importance of prostaglandins, little is known about the regulation of prostanoid synthesis proximal to the activation of cytosolic phospholipase A 2 , the initial rate-limiting step. In this study, ceramide-1-phosphate (C-1-P) was shown to be a specific and potent inducer of arachidonic acid (AA) and prostanoid synthesis in cells. This study also demonstrates that two well established activators of AA release and prostanoid synthesis, the cytokine, interleukin-1␤ (IL-1␤), and the calcium ionophore, A23187, induce an increase in C-1-P levels within the relevant time-frame of AA release. Furthermore, the enzyme responsible for the production of C-1-P in mammalian cells, ceramide kinase, was activated in response to IL-1␤ and A23187. RNA interference targeted to ceramide kinase specifically down-regulated ceramide kinase mRNA and activity with a concomitant decrease of AA release in response to IL-1␤ and A23187. Down-regulation of ceramide kinase had no effect on AA release induced by exogenous C-1-P. Collectively, these results indicate that ceramide kinase, via the formation of C-1-P, is an upstream modulator of phospholipase A 2 activation. This study identifies previously unknown roles for ceramide kinase and its product, C-1-P, in AA release and production of eicosanoids and provides clues for potential new targets to block inflammatory responses.

JNK and Ceramide Kinase Govern the Biogenesis of Lipid Droplets through Activation of Group IVA Phospholipase A2

“…This suggests that Cer-1-P does not solely promote association of the enzyme with membranes. Our data fully support a formerly proposed mechanism (32,40) whereby Cer-1-P activates the JNK cascade, either directly or after the inhibition of protein phosphatases 1 and 2A. This mechanism is in keeping with our observation that okadaic acid induces LD biogenesis in a JNK-and cPLA 2 ␣-dependent fashion.…”

Distinct receptor-mediated activities in macrophages for natural ceramide-1-phosphate (C1P) and for phospho-ceramide analogue-1 (PCERA-1)

“…However, recent studies by Chalfant's group suggested that C1P is the actual regulator of AA and prostaglandin (PG) production (Pettus et al, 2003). The importance of CERK, and its product C1P, in cell signaling was highlighted by using specific siRNA to down-regulate its activity in A549 lung adenocarcinoma cells.…”

“…This treatment inhibited AA release and PGE 2 production in response to a calcium ionophore and to interleukin 1 (IL-1 (Chalfant and Spiegel, 2005;Pettus et al, 2003). Of relevance, C1P was shown to be generated by the actions of either a calcium ionophore or IL-1 on A549 lung adenocarcinoma cells (Pettus et al, 2003), and M-CSF on bone A c c e p t e d M a n u s c r i p t 4 marrow-derived macrophages (BMDM) (Gangoiti et al, 2008b). A crucial discovery was the direct implication of C1P in the inflammatory response.…”

Ceramide‐1‐phosphate promotes cell survival through activation of the phosphatidylinositol 3‐kinase/protein kinase B pathway

“…In these experiments, an aqueous dispersion of C1P was prepared by sonication, and the optimal concentration of C1P was 30 lM. When C1P is dissolved in a mixture of 49:1 methanol/dodecane or ethanol/ dodecane, dispersion is improved and effects on cell proliferation in fibroblasts or arachidonic acid release in A549 cells have been reported at concentrations as low as 2.5 lM [3,6,7]. In the present work, we found that although 2.5 lM C1P was effective in promoting macrophage survival when added in methanol/dodecane, the solvent mixture alone caused an increase of about 18% on macrophage survival, and therefore it was decided not to use methanol/ dodecane in subsequent experiments.…”

“…Ceramide-1-phosphate (C1P) is emerging as a new bioactive molecule [1] capable of regulating vital pathophysiological functions including cell proliferation [2,3], apoptosis [4], phagocytosis [5], and inflammation [6,7]. Although the existence of C1P and its metabolizing enzymes, ceramide kinase and C1P phosphatase, in mammalian tissues have been known for over a decade [8][9][10], current understanding of the metabolic and signaling pathways that are affected by this bioactive sphingolipid is incomplete.…”