SPA4 peptide attenuates the accumulation of selected damage-associated molecules and pulmonary cellularity during acute Pseudomonas aeruginosa infection in mice

Activation of Toll-like receptor 4 (TLR4) and accumulation of damage-associated molecular patterns (DAMPs) are hallmarks of infection and inflammation. The SPA4 peptide (amino acid sequence: GDFRYSDGTPVNYTNWYRGE) modulates TLR4-dependent host defense against Pseudomonas aeruginosa . In this study, we investigated the expression of TLR4, major DAMPs, and cellularity in the lungs of P. aeruginosa -infected mice treated with SPA4 peptide or vehicle. The expression of TLR4 and levels of DAMPs were analyzed by immunoblotting and enzyme-linked immunosorbent assay, respectively. Cellularity was determined in hematoxylin and eosin-stained lung tissue sections by microscopy. Our results demonstrated that the expression of TLR4 and DAMPs, as well as tissue cellularity, were increased in the lungs of infected mice. While P. aeruginosa -induced TLR4 expression was not affected, the levels of DAMPs were reduced in mice therapeutically treated with SPA4 peptide (fibrinogen: 8,730 ng; fibronectin: 17,925 ng; High Mobility Group Box-1 [HMGB-1]: 11,758 ng; and hyaluronan: 34,157 ng per g lung weight) compared with vehicle-treated mice (fibrinogen: 13,178 ng; fibronectin: 22,348 ng; HMGB-1: 15,896 ng; and hyaluronan: 53,644 ng per g lung weight). Correspondingly, reduced cellularity was noted in the lungs of SPA4 peptide-treated mice. These results advance our understanding of the SPA4 peptide activity against infectious stimuli.