POST-ENDOCYTOTIC INFLAMMATORY SIGNALING AFTER TRAUMA

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Traumatic injury involving shock, tissue injury, fracture and transfusion, releases circulating factors (such as TNFalpha, IL-1 and IPS) that promote systemic hyper-inflammation. These agents immediately activate signaling receptors on circulating leukocytes, endothelium and vascular cells, thereby priming or altering these cell-types, and their subsequent responses. The initial phase of signaling by ligand activated receptor from the plasma membrane surface, is mediated by second messengers, ion-fluxes, and protein phosphorylation occurring within minutes. Activated receptors recruit adaptor proteins often coordinated with change in Ca++ and local membrane composition. A series of assembly events forms clustered signaling complexes that build-up multi-domain protein scaffolds which simultaneously conduct endocytosis and activate kinase modules such as MAPKs and IKK. These modules cause many sustained changes to the transcriptome, thereby affecting all subsequent cellular responses for hours or days, including cell-cycling or apoptosis. In leukocytes, MAPK modules regulate pro-inflammatory actions: superoxide secretion, and degranulation in neutrophils, synthesis and release of cytokines and chemokines. In vascular endothelial and smooth muscle cells, NF-kB and AP-1 upregulate expression of leuko-adhesive proteins, promoting inflammation and leak. Cell biologists have known that that clathrin-mediated endocytosis (CME) can be blocked by hypertonicity and primary amines block (by affecting endosome assembly or disrupting its maturation). In several transformed cells, interfering with CME prevents MAPK or NF-kB signaling by bioactive mediators (such as catechols, lipids and TNFalpha). However, it is unclear how the different stages of CME processing regulates kinase signaling by internalized receptors in mammalian, especially human, cells. Further, would the results in primary cells reflect inflammatory signaling in animal models? Remarkably, advances in resuscitation suggest that hypertonicity has additional advantages for preventing pro-inflammatory priming. Separately, some primary amines and microtubule effectors appear promising for inflammation control. In this proposal we assess whether suppressing endocytosis affects postendocytotic signaling for a permuted list of culpable agents and cells. If so, could the mechanisms suggest improvements or alternatives?