The establishment of non-resolving inflammation underlies the pathogenesis of chronic inflammatory diseases in humans. Super low dose (SLD) endotoxin has been associated with exacerbating inflammation and the pathogenesis of chronic inflammatory diseases. However, the underlying molecular mechanisms are not well studied. In this study, I tested the hypothesis that SLD endotoxin may potentiate non-resolving innate immune cell inflammation through disrupting cellular endoplasmic reticulum (ER) homeostasis. We chose to study the dynamics of ER homeostasis in macrophages stimulated with SLD endotoxin. In naïve cells, ER stressor such as tunicamycin (TM) not only will induce cellular stress and inflammation through JNK and NFkβ activation, but also will cause subsequent compensatory homeostasis through inducing homeostatic molecules such as XBP1 and GRP78/BiP. We observed that cells challenged with SLD endotoxin have significantly reduced expression of homeostatic molecules XBP1 and BiP. Mechanistically, we observed that SLD-LPS increases phosphorylated HCK expression in TM treated cells. Phosphorylated HCK activation resulted in the phosphorylation of Golgi protein GRASP, leading to unstacking of Golgi cisterna and overall dysfunction of the Golgi apparatus. Dysfunctional Golgi apparatus and its effect on protein transport and secretion, may account for decreased levels of Site 2 Protease, reduced generation of ATF6 and its transcriptional target BiP. Taken together, our study reveal that super low dose endotoxin exacerbates low grade inflammation through increasing phosphorylation of HCK, inducing Golgi dysfunction, and decreasing BiP /homeostatic protein expression in innate immune cells. / Ph. D. / Non-resolving inflammation is a common factor shared in in many chronic inflammatory diseases such as atherosclerosis and diabetes mellitus type 2. Low levels of endotoxin have been shown to increase inflammation as well as further increase disease development. However, how such low levels of endotoxin is able to produce this effect is not well understood. This research focuses on how low levels of endotoxin can increase inflammation by decreasing the ability of the cell to restore homeostasis. It was found that a super low dose (SLD) endotoxin decreased activation of the unfolded protein response pathway (UPR). The UPR pathway is a prominent signaling pathway utilized by the cell to restore homeostasis and is activated following an accumulation of unfolded proteins in the endoplasmic reticulum of the cell. The disruption of this pathway by SLD endotoxin resulted in increased inflammatory signaling and decreased cellular homeostasis.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/86360 |
| Date | 20 June 2017 |
| Creators | Lyle, Chimera |
| Contributors | Biological Sciences, Li, Liwu, Bevan, David R., Lawrence, Christopher B., Yuan, Lijuan |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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