Treatment with the TLR4-interacting SPA4 peptide controls accumulation of damage-associated molecular patterns in lung tissues of mice infected with Pseudomonas aeruginosa 2654

Abstract Description Activation of Toll-like receptor 4 (TLR4) and release of damage-associated molecular patterns (DAMPs) are hallmarks of infection and inflammation. Based on our published results that the SPA4 peptide (amino acids: GDFRYSDGTPVNYTNWYRGE) modulates TLR4-signaling against Pseudomonas aeruginosa, we studied the expression of TLR4 and DAMPs. Mice (C57BL6) were intratracheally challenged with 1 x 107 live P. aeruginosa PAO1 and treated with 50 μg SPA4 peptide or vehicle at 1 h post-challenge. The lungs were harvested during necropsy of mice after 5 h. Total protein amounts and TLR4 expression were analyzed in lung homogenates using biochemical and immunoblotting methods, respectively. Levels of DAMPs were measured by immunoassay. The results (6-10 mice per group) were analyzed using t-test or ANOVA. The expression of TLR4 and DAMPs was significantly increased in P. aeruginosa-infected, vehicle-treated mice compared to those in unchallenged, untreated mice. While increased TLR4 expression was not affected, the levels of DAMPs were reduced in SPA4 peptide-treated (High Mobility Group Box1, HMGB1 11.8 μg, fibronectin 17.9 μg, fibrinogen 8.7 μg, hyaluronan 34.2 μg, per g lung weight, p < 0.005) versus vehicle-treated mice (HMGB1 15.9 μg, fibronectin 22.3 μg, fibrinogen 13.2 μg, hyaluronan 53.6 μg, per g lung weight) against P. aeruginosa. These findings suggest that the modulation of TLR4-signaling by SPA4 peptide can control the tissue accumulation of DAMPs against infectious stimuli. Funding Sources Supported by NIH P20GM103648 Project #3; NIH R01HL136325 Topic Categories Innate Immune Responses and Host Defense: Molecular Mechanisms (INM)