Combination of mouse prion protein with detoxified lipopolysaccharide triggers colon genes related to inflammatory, antibacterial, and apoptotic responses.

Previously we observed that bacterial lipopolysaccharide (LPS) was able to instantly convert recombinant murine prion protein (moPrP) from an alpha-helical to a beta-sheet enriched state. The objectives of this study were to evaluate the effects of a single in vitro administration of recombinant moPrP alone or combined with detoxified lipopolysaccharide (D-LPS) on innate immunity and antibacterial gene expression in the colon of male FVB/N mice, under an Ussing chamber system. Results showed that moPrP alone affected the expression of genes related to both toll-like receptor (TLR)- and nod-like receptor (NLR)-signaling as well as pro- and anti-inflammatory responses. moPrP induced a strong antibacterial response with Slpi mRNA over expression (> 9-fold). Combination of moPrP with D-LPS on the mucosal side of the colon induced genes associated with TLR-signaling, apoptosis, and a very strong antibacterial response (> 35-fold Slpi expression). Administration of moPrP on the mucosal side and D-LPS on the serosal side triggered expression of 12 genes related to TLR signaling, apoptosis, and antibacterial responses, as illustrated by overexpression of Slpi by >30-fold. The over expression of Slpi mRNA was further reaffirmed by ELISA and when moPrP was added to the mucosal side and D-LPS on the serosal side, an increased Slpi protein was observed. Application of combined moPrP and D-LPS on the mucosal side significantly increased the Slpi protein. Results of this study demonstrated that moPrP alone or combined with D-LPS affected the expression of various genes related to inflammation, antibacterial, and apoptotic responses.

Recombinant mouse prion protein alone or in combination with lipopolysaccharide alters expression of innate immunity genes in the colon of mice.

The objectives of this study were to test whether recombinant mouse (mo)PrP alone or in combination with LPS or under simulated endotoxemia would affect expression of genes related to host inflammatory and antimicrobial responses. To test our hypotheses colon tissues were collected from 16 male mice (FVB/N strain) and mounted in an Ussing chamber. Application of moPrP to the mucosal side of the colon affected genes related to TLR- and NLR- signaling and antimicrobial responses. When LPS was added on the mucosal side of the colon, genes related to TLR, Nlrp3 inflammasome, and iron transport proteins were over-expressed. Addition of LPS to the serosal side of the colon up-regulated genes related to TLR- and NLR-signaling, Nlrp3 inflammasome, and a chemokine. Treatment with both moPrP and LPS to the mucosal side of the colon upregulated genes associated with TLR, downstream signal transduction (DST), inflammatory response, attraction of dendritic cells to the site of inflammation, and the JNK-apoptosis pathway. Administration of moPrP to the mucosal side and LPS to the serosal side of the colon affected genes related to TLR- and NLR-signaling, DST, apoptosis, inflammatory response, cytokines, chemokines, and antimicrobial peptides. Overall this study suggests a potential role for moPrP as an endogenous 'danger signal' associated with activation of colon genes related to innate immunity and antibacterial responses.