No abstract

(C1P) is implicated in inflammatory responses and was recently shown to promote cell migration. However, the mechanisms involved in these actions are poorly described. Using J774A.1 macrophages, we have now discovered a new biological activity of C1P: stimulation of monocyte chemoattractant protein-1 (MCP-1) release. This novel effect of C1P was pertussis toxin (PTX) sensitive, suggesting the intervention of Gi protein-coupled receptors. Treatment of the macrophages with C1P caused activation of the phosphatidylinositol 3-kinase (PI3K)/Akt, mitogen-activated protein kinase kinase (MEK)/extracellularly regulated kinases (ERK), and p38 pathways. Inhibition of these kinases using selective inhibitors or specific siRNA blocked the stimulation of MCP-1 release by C1P. C1P stimulated nuclear factor-B activity, and blockade of this transcription factor also resulted in complete inhibition of MCP-1 release. Also, C1P stimulated MCP-1 release and cell migration in human THP-1 monocytes and 3T3-L1 preadipocytes. A key observation was that sequestration of MCP-1 with a neutralizing antibody or treatment with MCP-1 siRNA abolished C1P-stimulated cell migration. Also, inhibition of the pathways involved in C1P-stimulated MCP-1 release completely blocked the stimulation of cell migration by C1P. It can be concluded that C1P promotes MCP-1 release in different cell types and that this chemokine is a major mediator of C1P-stimulated cell migration. The PI3K/Akt, MEK/ ERK, and p38 pathways are important downstream effectors in this action.ceramide 1-phosphate; monocyte chemoattractant protein-1 release; macrophage migration; sphingosine 1-phosphate REGULATION OF CELL MIGRATION is a complex process involving hundreds of molecules. It is necessary for tissue homeostasis and is crucial for regulation of vital biological processes including embryogenesis, organogenesis, or regeneration (reviewed in Refs. 38, 48). Also, cell migration is fundamental to inflammatory responses (1, 49), but inadequate migratory signals may induce the migration of the wrong cell type to the wrong place, which may have severe effects in the organism. Some examples include autoimmune syndromes, angiogenesis, or the process of metastasis. Although cell migration is a subject of intense investigation, the mechanisms involved in controlling cell movements are incompletely understood. In this connection, growing evidence suggests that some sphingolipids are key metabolites for controlling chemotaxis (52). Our group recently reported that ceramide 1-phosphate (C1P), a sphingolipid metabolite that is present in serum or plasma (25), and which we found to regulate cell growth and survival (15,17,18,20,22), is a chemoattractant molecule for macrophages (23). This finding is particularly relevant when considering that macrophages play critical roles in chronic and acute inflammation and that these cells facilitate cancer cell migration (21, 46). In addition, Barth et al. (4) recently showed that ceramide kinase, the enzyme responsible for the phosphorylation of ce...

No abstract

No abstract

No abstract

No abstract

Sphingolipids are major constituents of biological membranes of eukaryotic cells. Many studies have shown that sphingomyelin (SM) is a major phospholipid in cell bilayers and is mainly localized to the plasma membrane of cells, where it serves both as a building block for cell architecture and as a precursor of bioactive sphingolipids. In particular, upregulation of (C-type) sphingomyelinases will produce ceramide, which regulates many physiological functions including apoptosis, senescence, or cell differentiation. Interestingly, the venom of some arthropodes including spiders of the genus Loxosceles, or the toxins of some bacteria such as Corynebacterium tuberculosis, or Vibrio damsela possess high levels of D-type sphingomyelinase (SMase D). This enzyme catalyzes the hydrolysis of SM to yield ceramide 1-phosphate (C1P), which promotes cell growth and survival and is a potent pro-inflammatory agent in different cell types. In particular, C1P stimulates cytosolic phospholipase A2 leading to arachidonic acid release and the subsequent formation of eicosanoids, actions that are all associated to the promotion of inflammation. In addition, C1P potently stimulates macrophage migration, which has also been associated to inflammatory responses. Interestingly, this action required the interaction of C1P with a specific plasma membrane receptor, whereas accumulation of intracellular C1P failed to stimulate chemotaxis. The C1P receptor is coupled to Gi proteins and activates of the PI3K/Akt and MEK/ERK1-2 pathways upon ligation with C1P. The proposed review will address novel aspects on the control of inflammatory responses by C1P and will highlight the molecular mechanisms whereby C1P exerts these actions.

No abstract