Abstract 1609 Comparing Gene Expression in the Liver of Wild-Type vs. TLR4 -/- Mice

Endotoxemia, the presence of lipopolysaccharide (LPS) endotoxin in the bloodstream occurs primarily in septic shock patients. Sepsis consistently remains one of the most lethal conditions in the United States, with about half of cases caused by infections from Gram-negative bacteria. LPS is a Gram-negative bacterial membrane-anchored molecule that causes the activation of Toll-like receptor 4 (TLR4). Upon activation of the TLR4 signaling pathway during a Gram-negative bacterial infection, the immune system initiates excessive inflammation to over-protect itself causing pathogenic symptoms. TLR4 deficient (TLR4-/-) C57BL6 mice are used to model the immune refractory period following septic shock and compared to wild-type (WT) mice. In the serum of WT and TLR4-/- mice, 51 proteins shared between both experimental groups were previously found to be dysregulated over the course of endotoxemia. We hypothesize that these proteins characterize TLR4-independent immune activation by LPS. To test our hypothesis, we conducted quantitative polymerase chain reaction (qPCR) using a murine model of endotoxemia in three biological replicates to investigate the regulation of genes: Dmtn, MDH1, Adsl, Coro1a, and Fga, all of which code for proteins in the previously identified 51 shared dysregulated genes. In WT mice, over the course of endotoxemia, we observed a downregulation in genes involved in T-cell function (Coro1a), and cellular replication and metabolism (Adsl and MDH1). Changes in MDH1 transcript levels have a more distinct downregulation. The TLR4-/- mice are found to maintain transcript levels of these genes over the course of endotoxemia. Fga, a gene involved in coagulation was seen to be increasingly upregulated over time in WT, with a similar initial upregulation in TLR4-/- mice followed by a stabilization to baseline transcript levels as the disease course continued. Future directions will focus on manipulating the signaling pathway to modify endotoxemia outcomes thereby providing insights into targeted treatments for immunosuppressed septic shock patients. This research was funded by the Faculty Development & Research Committee Grant awarded to Dr. Erin Harberts and partially funded by the USM LSAMP program, supported by NSF LSAMP Award # 2207374.