Further diversity among EP receptors is generated in both the EP1 and EP3 receptors by alternatively spliced C-terminal variants, as discussed elsewhere. The EP2 receptor can downregulate antigen-mediated mast cell responses through Gas-dependent production of cAMP, whereas the EP3 receptor can up-regulate antigen-mediated mast cell responses through enhanced calcium-dependent signaling. It has been suggested that differences in EP2 and EP3 receptor expression in mast cells could dictate the upregulation or downregulation of antigen-mediated responses by PGE2. Thus, the distribution and relative expression of these four receptor subtypes provide a flexible system describing the GDC-0879 905281-76-7 ability of PGE2 to evoke pleiotropic, sometimes opposing, tissue and cell actions. Notably, the beneficial in vivo effects of PGE2 in murine models of allergic asthma might be mediated through EP2 receptors in airway mast cells. This study aimed to evaluate how PGE2 modulates the response to mannitol through prostanoid receptors as a model of exerciseinduced asthma in human mast cells, and to clarify the related signaling events. This study aimed to evaluate the protective effect of PGE2 on mannitol-induced mast cell activation as a model of EIB in Asthma, where mannitol was used as a hyperosmolar stimulus. The use of a hypertonic agent stems from the theory that EIB is caused by increased osmolarity of the surface of the airways through the release of proinflammatory mediators. Previous in vitro work on HLMCs showed that hyperosmolar stimulation induced histamine release, suggesting that hyperosmolar mediated release was a mechanism by which exercise-induced hyperventilation might induce asthma. Our results show that mannitol induces mast cell signaling events that are possibly involved in the inflammatory response observed in asthma. At early stages, mannitol increased degranulation in a calcium dependent manner before IL-8 and TNF alfa production occurred. Mannitol triggered the activation of PI3K and MAPK cascades, which enhanced ERK1/2, p38 and JNK phosphorylation. The MAPK pathway activates transcription factors such as AP-1 that in turn regulate cytokine and metalloprotease production. Additionally ERK1/2 phosphorylates cytoplasmic phospholipase A2, which is involved in the production of the eicosanoid precursor arachidonic acid. Interestingly, previous studies reported ERK phosphorylation in airway smooth muscle cells that cause increased production of both IL-1b and granulocyte-macrophage colony-stimulating factor, which are involved in the contractile response and remodeling of the airways in asthma. The role of JNK in asthma is related to extracellular matrix deposition, with its activation causing the release of growth factors such as transforming growth factor beta, which may explain the phenotype transition from fibroblasts to myofibroblasts in the lung. Moreover, p38 regulates the antigen-triggered migration of mast cells and mediates the production of IL-8. PGE2 is a highly pluripotent prostanoid displaying a wide range of effects, including smooth muscle relaxation and contraction, and both pro-inflammatory and anti-inflammatory properties. These opposing effects are possible due to the presence of at least four subclasses of EP receptors. It has been reported that CD34+ derived mast cells express the PGE2 receptors EP2, EP3, and EP4. Our data shows that the LAD2 cell line has a similar PGE2 receptor pattern. The aim of the study was to evaluate how PGE2 modulates. For that reason we used antagonist of the receptor instead of direct agonist of them.