Anales RANF

S2-02 CROSSROAD BETWEEN BIOACTIVE LIPIDS AND PURINERGIC SIGNALLING IN MACROPHAGES Lisardo Boscá, Marta Paz-García, Sergio Sánchez-García, Francisco J. de Castro and Rafael I. Jaén. Instituto de Investigaciones Biomédicas Alberto Sols (CSIC-UAM). Madrid (Spain) Receptors for purine and pyrimidine nucleotides (P2) are involved in many pathophysiological processes, including short-term purinergic signaling such as immune responses, neurotransmission, neuromodulation, neurosecretion, inflammation, platelet aggregation and vasodilatation; and long-term purinergic signaling of cell proliferation, differentiation, motility, death in development and regeneration. Under inflammatory conditions or in early stages of many diseases characterized by the occurrence of associated inflammatory processes, chemical mediators of lipidic nature accumulate at sites of tissue damage. One of these molecules is PGE2 that activates specific G-protein coupled membrane receptors (EP receptors). Four different receptors, EP1-EP4, can be distinguished pharmacologically; however, in addition to EP-mediated effects PGs may exert other EP-independent actions. In addition to PGs, P2 nucleotide agonists are released during the course of inflammatory responses and activate immune cells, such as monocytes, macrophages and lymphocytes. These extracellular nucleotides exert several effects on immune cells and are involved in cytoskeleton reorganization, cell migration, phagocytosis or exocytosis. Therefore, extracellular nucleotides acting on specific P2 receptors are important modulators of inflammation. This regulation coexists with the temporal framework of pro-inflammatory and pro-resolution mediator lipids released by immune cells, including macrophages. Since inflammatory cells release large amounts of prostaglandins (PGs), such as PGE2 due to COX-2 expression, we have investigated the impact of these bioactive lipids on the EP-dependent and independent receptors. Interestingly, in alternatively activated (anti-inflammatory) macrophages PGE2 selectively impairs P2Y but not P2X7 Ca2+-mobilization. This effect is absent in LPS-activated cells and is specific for PGE2 as it cannot be obtained when cells are treated with other PGs, such as those with cyclopentenone structure that are chemically more reactive than the classic PGs. The inhibition of P2Y responses by PGE2 involves the activation of new protein kinase C isoforms (PKCε) and/or PKD. Selective inhibitors of these PKCs or expression of dominant negative forms of PKD impairs the inhibitory effect of PGE2 on P2Y signaling. There are several examples of cross-regulation between the purinergic system and inflammatory molecules. In macrophages, it has been described that UTP potentiates PGE2 release, which is involved in the enhancement of inducible nitric oxide synthase (NOS2) induction by LPS. In platelets, a cross-desensitization between ADP and thromboxane receptor signaling has been reported, and there is mounting evidence supporting that these interactions play important roles in several inflammatory and degenerative disorders, such as multiple sclerosis, amyotrophic lateral sclerosis or Alzheimer´s disease. In these pathologies, extracellular ATP exerts pro-inflammatory actions provoking cytokine release and PGs production. Therefore, the inhibition of P2Y signaling by PGE2 has an impact on the cell migration elicited by P2Y-agonists in resting and alternatively activated macrophages, which provides new clues to understand the resolution phase of inflammation, when accumulation of PGE2, anti-inflammatory and pro-resolving mediators occurs. In this presentation, we will provide data supporting a role for PGE2 in resting and pro-resolution macrophages.