137 Expression of Cathelicidin (LL-37) in Thermal Injury

Abstract

Sepsis remains a common and serious complication of major burn injury and currently accounts for over 54% of deaths in burn patients. Burns have been associated with high levels of circulating proinflammatory cytokines and immunosuppression which promotes systemic inflammatory response syndrome (SIRS) and sepsis, for which no effective treatment is currently available. Defensins and cathelicidins, a family of cationic naturally occurring antimicrobial peptides, are considered important components of the innate immune system as they play a major role in the body’s defense by inhibiting several bacteria, fungi and enveloped viruses. Our prior studies using RT-PCR and fluorescence deconvolution microscopy suggest decreased expression of human β defensin 2 (HBD2) in burn wounds. In this study we have characterized cathelicidin (LL-37) protein levels using in representative skin samples of deep partial and full thickness burns and in unburned skin. Our results show that in unburned skin, the majority of LL-37 was located in the malphigian layer and was concentrated on the stratum corneum as well as colocalized with sweat ducts. In burned skin, in which the epidermis was destroyed, this pattern of LL-37 was absent. The surviving dermal and subcutaneous layers revealed LL-37 presence in very high concentrations colocalized with sweat duct epithelia. The result of these studies will contribute to an understanding of the role of antimicrobial peptides in the pathophysiology of burn injury, associated immunosuppression, and sepsis.