The intrinsic signaling aspects of the coagulation cascade have emerged as major contributors and regulators of systemic inflammation and sepsis. Our experiments uncovered an unexpected thrombin-protease activated receptor (PAR) 1 signaling pathway on dendritic cells (DCs) that is responsible for exacerbated systemic inflammatory response syndromes leading to sepsis lethality. Thrombin-activated PAR1 uniquely couples to sphingosine 1 phosphate (S1P) receptor 3 (S1P3) to promote DC-dependent inflammation and to induce endothelial dysfunction and vascular leakage. Paradoxically, PAR1 signaling by endogenous or therapeutically administered activated protein C (aPC) is sepsis protective. Our data indicate that therapeutic action of aPC targets both DC-dependent inflammation and vascular leakage, excluding that the """"""""PAR1 paradox"""""""" can simply be reduced to cell type specific signaling effects. We propose to test the overall hypothesis that coupling of PAR1 to S1P receptor subtypes and regulatory co-receptors are the key determinants for the observed protease signaling specificity of PAR activation in vivo. The experiments in the upcoming two years will advance these concepts by focusing on the role of PAR1 signaling in DCs and endothelial cells.
Aim 1 is to define the specific cell populations that are the target for thrombin and aPC signaling to regulate innate immune function in severe sepsis. These experiments advance our understanding of the innate immune cells that are controlled by the intrinsic signaling of the coagulation cascade and lay the foundation for testing new concepts of pharmacological modulation of the pro-inflammatory PAR1-S1P3 signaling pathway of DCs.
In Aim 2, we use genetic and pharmacological perturbations of the intravascular coagulant balance to further characterize the dual role of PAR1 as a barrier disruptive and barrier protective receptor in sepsis. These experiments expand our knowledge of how co-receptors of PAR1 signaling contribute to the regulation of vascular barrier function and set the stage for further testing of new therapeutic strategies that improve vascular dysfunction in inflammatory disorders and sepsis. 3.
The studies proposed in this grant evaluate central signaling axes of coagulation proteases that operate both on immune and vascular cells. We will test optimal points for therapeutic intervention in coagulation protease signaling mechanisms in order to improve outcomes of therapy in severe systemic inflammatory response syndromes and sepsis.
| von Drygalski, Annette; Furlan-Freguia, Christian; Ruf, Wolfram et al. (2013) Organ-specific protection against lipopolysaccharide-induced vascular leak is dependent on the endothelial protein C receptor. Arterioscler Thromb Vasc Biol 33:769-76 |
| von Drygalski, Annette; Furlan-Freguia, Christian; Mosnier, Laurent O et al. (2012) Infrared fluorescence for vascular barrier breach in vivo--a novel method for quantitation of albumin efflux. Thromb Haemost 108:981-91 |
