Previously we have described increased expression of both
Previously, we have described increased expression of both cytokine and chemokine mRNA (e.g. MCP-5 and fractalkine) in the left ventricle of male EP4-KO mice with dilated cardiomyopathy . Takayama et al.  have shown that PGE2 potently inhibits cytokine/chemokine secretion (MCP-1, interleukin 8, macrophage inflammatory protein, and CxCL10) in human macrophages. Thus, inhibition of chemokine or cytokine release may be a significant mechanism to explain how treatment with AAV9-EP4 reduces macrophage infiltration. Treatment with AAV9-EP4 also significantly prevented increases in TNFα mRNA after MI. TNFα is a major cytokine implicated in heart failure and increases in TNFα have been correlated with the severity of cardiac disease although anti-TNFα therapies have met with little clinical success [32,33]. In addition to alterations in TNFα, our results also show that overexpression of EP4 affects other chemokines/cytokines. Using a mouse cytokine/chemokine array we detected a significant reduction in MCP-1 protein levels in the left ventricle and increases in IL-10, an anti-inflammatory cytokine, after treatment of MI hearts with AAV9-EP4. Unfortunately, protein levels of these cytokines/chemokines were below the limits of detection in isolated mouse cardiomyocytes treated with AAV9-EP4 or control virus, even after stimulation with LPS. Thus, we cannot be certain if overexpression of EP4 affects production of these factors from cardiomyocytes or if it has paracrine effects. However, our data shows that reduction of pro-inflammatory cytokines/chemokines may be one mechanism by which over-expression of the EP4 prevents the deleterious effects of MI.
Introduction Asthma is characterized by airway eosinophilia, goblet cell hyperplasia with mucus hypersecretion, and airway hyperresponsiveness . In particular, mucus hypersecretion is related to small airway obstruction and mortality in severe Paroxetine HCl . MUC5AC, the principal gel-forming mucin in airway, is primarily expressed in goblet cells and asthmatic patients produce MUC5AC-rich mucus , . The T2 cytokine, IL-13, drives primary airway cells towards a goblet cell phenotype , . Prostaglandin E2 (PGE2) is a cyclooxygenase metabolite of arachidonic acid and has pleiotropic effects on airway structure and function. The most abundant sources of PGE2 are epithelial cells, fibroblasts, and macrophages . PGE2 concentration is increased in sputum from subjects with asthma . PGE2 acts through four distinct E-type prostanoid receptors that are expressed in the airway, EP1- 4 , . Among these four G protein-coupled receptors, EP2 and EP4 receptor activation produces bronchodilation and anti-inflammatory effects in human and rodent airway smooth muscle cells and macrophages , , . In contrast, EP3 receptor activation contributes to cough by activating airway sensory nerves . The EP2/EP4 receptor dual agonist, misoprostol can increase MUC5AC protein production in cultured human airway epithelial cells . PGE2 is produced by secretory phospholipases A2 (sPLA2) initiating the cyclooxygenase pathway, and stimulates mucus secretion , . We have shown that sPLA2 are secreted from the ciliated cells and can dramatically induced mucus secretion from IL-13 transformed goblet cells . We hypothesized that PGE2 would stimulate cultured airway cells towards goblet cell metaplasia via specific EP receptor activation and that mucin production by EP receptor activation would be enhanced in goblet cells.
Materials and methods
Discussion The EP4 receptor is a G protein-coupled receptor, activating adenyl cyclase to convert ATP into the second messenger cAMP , . Increased cAMP activates protein kinase A and MAPK pathways. CREB is subsequently activated by these upstream pathways and mediates mucin secretion stimulated by PGE2 and prostaglandin F2α , . We found that CREB phosphorylation by EP4 receptor activation was greater in goblet-enriched cells. An increase in phosphorylated CREB is reported in airway biopsy specimens from subjects with asthma and is associated with asthma severity . Although the effect of IL-13 on secreted MUC5AC plateaued at 5 ng/mL, increased EP4 receptor expression and CREB phosphorylation, which is independent of the IL-13 activated JAK/STAT6 pathway may further increase MUC5AC in goblet-enriched cells .