The vascular endothelium interfacing between the blood and vessel wall has the vital functions of regulating tissue fluid balance and supplying the essential nutrients needed for the survival of the organism. It is known that loss of this function results in tissue inflammation, the hallmark of inflammatory diseases such as the Acute Respiratory Distress Syndrome. Dynamic interaction between adherens junctions and cell-matrix attachments plays a primary role in regulating endothelial permeability. However, counter-adhesive forces generated by actinomysin molecular motors activated upon inflammatory mediators such as thrombin, bradykinin, histamine, VEGF, and others upon binding to their receptors, disrupt the organization of adherens junctions and cell-matrix complexes, thereby opening the junctional barrier. An increase in cytosolic Ca2+ has been established as the initial pivotal signal that precedes endothelial cell shape change and opening of adherens junctions resulting in barrier dysfunction. Following cell stimulation with inflammatory mediators, an increase in cytosolic Ca2+ concentration is apparent. There is an initial transient peak as the result of Ca2+ release from endoplasmic reticulum (ER) stores, which is followed by more sustained response secondary to Ca2+ entry via plasmalemma channels. Ca2+ entry refills ER stores and sustains Ca2+ signaling. Proteins of the transient receptor channel (TRPC) family are non-selective cation channels present in endothelial cells that increase intracellular Ca2+, and play an important role in regulating actin-myosin motor activity and endothelial barrier function. Human pulmonary endothelial cells highly expressed TRPC1 and TRPC6, whereas TRPC3, TRPC4, and TRPC7 are expressed only weakly. TRPC1, TRPC4, and TRPC5 are activated by depletion of ER stores, and are therefore called store-operated channels (SOCs), whereas TRPC3 and TRPC6 are activated independently of store depletion, and are referred to as receptor-operated channels (ROC). SOCs and ROCs provide the primary structures by which Ca2+ enters endothelial cells. Both SOC and ROC have been shown to induced actin-myosin induced endothelial cell contraction and thereby endothelial permeability. In contrast to Ca2+, an increase in the concentration of cAMP is known to stengthen endothelial barrier function such that it prevents increased permeability in response to known permeability-increasing mediators in endothelial cells and intact microvessels. Evidence indicates that increased levels of cAMP can be endothelial barrier protective through the cAMP-dependent kinase, PKA as well as modulation of adherens junctions and cell-matrix attachemnets. Cyclic AMP response element binding (CREB) protein is a nuclear transcriptional factor that regulates several cellular functions such as inflammation, cell proliferation, differentiation, adaptation and survival. We have shown that CREB plays a pivotal role in regulating endothelial barrier function by restricting endothelial contraction through regulating the expression of p190RhoGAP. These findings indicate that TRPC and cAMP-mediated signaling mechanisms must intersect with each other to regulate endothelial permeability. My objectives in this presentation will be to discuss the data from genetic, physiological, cellular, and morphological studies whether TRPC- and cAMP-mediated signaling intersects and how this intersection plays a role in regulating endothelial barrier function.