The innate immune system is comprised of many components that function coordinately to prevent bacterial
sepsis. However, thermal injury suppresses many of these factors, and the opportunistic pathogen Pseudomonas aeruginosa takes advantage of this condition, making it one of the leading causes of morbidity and mortality in the setting of thermal injury. P. aeruginosa is extremely efficient at colonizing
burn wounds, spreading systemically, and causing
sepsis, which often results in a systemic inflammatory response,
multiple-organ failure, and death. The pathogenicity of P. aeruginosa is due to the arsenal of
virulence factors produced by the pathogen and the immunocompromised state of the host.
Syndecan 1 is a major
heparan sulfate proteoglycan present on many host cells involved in thermal injury.
Syndecan 1 anchored to the cell surface can be cleaved in a process termed ectodomain shedding.
Syndecan 1 shedding results in the release of intact, soluble
proteoglycan ectodomains that have diverse roles in innate immunity. Here we show for the first time that thermal injury results in shedding of
syndecan 1 from host tissue. Our data show that
syndecan 1 null mice are significantly less susceptible to P. aeruginosa
infection than their wild-type counterparts, as demonstrated by (i) significantly lower mortality; (ii) absence of systemic spread of P. aeruginosa; and (iii) significant reductions in some proinflammatory
cytokines. These results suggest that shed
syndecan 1 plays an important role in the pathogenesis of P. aeruginosa
infection of thermal injury and that
syndecan 1-neutralizing agents may be effective supplements to current P. aeruginosa treatments.