Signal transduction pathways in enhanced microvascular permeability

We have been investigating the molecular mechanisms underlying pathophysiol ogical regulation of microvascular permeability on isolated venules and cul tured venular endothelial monolayers. Physiological approaches have been em ployed in combination with molecular analyses to probe the signal transduct ion pathways leading to enhanced microvascular permeability. A newly develo ped technique of protein transfection into cells and intact microvessels en ables the correlation of functional reactions and signaling events at the m olecular level in a direct and specific fashion. The results indicate that inflammatory mediators increase microvascular permeability via intracellula r signaling pathways involving the activation of phospholipase C, cytosolic calcium, protein kinase C, nitric oxide synthase, guanylate cyclase, and p rotein kinase G. in response to the signaling stimulation, complex biochemi cal and conformational reactions occur at the endothelial structural protei ns Specifically, myosin light-chain activation-mediated myosin light-chain phosphorylation carl result in cell contraction. VE-cadherin and beta -cate nin phosphorylation may induce dissociation of the junctional proteins and their connection to the cytoskeleton, leading to a loose or opened intercel lular junction. Focal adhesion phosphorylation and redistribution further p rovide an anchorage support for the conformational changes in the cells and at the cell junction. The three processes may act in concert to facilitate the flux of fluid and macromolecules across the microvascular endothelium.