Date of Award

5-7-2019

Document Type

Thesis

Degree Name

Doctor of Philosophy (PhD)

First Advisor

Ping Wang, MD

Second Advisor

Weng-Lang Yang, PhD

Abstract

Hemorrhagic shock (HS) is a clinical condition characterized by a global ischemic injury, which extends into reperfusion and is associated with the activation of inflammatory pathways and oxidative stress. During ischemia various intracellular components are released into the circulation, including cell free (cf) DNA and extracellular cold inducible RNA-binding protein (eCIRP) which have been implicated in increasing the intracellular levels of DNA, exacerbating inflammation and contributing to tissue damage. This dissertation focuses on the role in HS of the stimulator of interferon genes (STING), an endoplasmic reticulum membrane protein that is activated by cytosolic DNA and induce the production of type I interferons (IFNs), which have been shown to modulate the immune response after binding to its receptor, IFNAR1. We hypothesized that the STING signaling by enhancing the inflammatory response via type I IFNs, played a major detrimental role in HS. In order to study this, we subjected mice to a severe animal models of HS-injury. Animals treated with anti IFNAR1 antibody, were protected against HS-induced tissue injury, inflammation, and apoptosis. We then exposed STING knockout (-/-) mice to HS, and demonstrate the detrimental role of STING in promoting the production of type I IFNs and contributing to the excessive inflammation response and oxidative stress that exacerbates the tissue damage and mortality after HS. Additionally, we treated mice with DNase I which degrades cfDNA, and revealed to be protective against HS. These findings support the targeting of cfDNA with DNase to inhibit the activation of the STING signaling as a prophylactic immunomodulatory adjunct treatment of HS. This was further validated in MEF cells from WT and STING-/-after being exposed to serum from HS mice, where we elucidate the direct effect between the cfDNA-released after HS and the production of type I IFNs mediated by STING. Finally, we identified a novel mechanism mediated by eCIRP to activate the STING signaling pathway and promote the production of type IFN by stimulating peritoneal macrophage from WT, TLR4-/-, MyD88-/-, TRIF-/- and STING-/- with rmCIRP. Thus, these studies highlight the importance of the STING signaling in the production of type I IFNs in HS and its detrimental role contributing to the excessive inflammatory response and tissue damage, with implications for potential adjunct therapies that could decrease the morbidity and mortality associated with HS.

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