053 Nitric Oxide Metabolites in Wound Fluid of Adults with Pressure Ulcers on V.A.C.® Therapy

Abstract

Introduction: Compelling evidence suggests that nitric oxide (NO•) plays an important role in wound healing. Not only does it possess cytotoxic properties, but also regulatory functions on various cells involved in inflammation and proliferation. In wounds, inducible NO synthase (iNOS) catalyzes arginine to citrulline and NO•, whereas arginase converts arginine to ornithine and urea. Ornithine is an essential substrate for the synthesis of polyamines, which are important in cellular proliferation and repair. A model for regulation of wound healing proposes the importance of a strict reciprocal control of these enzymes in wounds. Human studies using impaired wound healing models, however, are lacking in this area. Thus, the purpose of this study was to investigate arginine metabolism in wound fluids of patients with pressure ulcers on Vacuum Assisted Closure (V.A.C.®) therapy. Methods: Wound fluid extracts from 11 patients with stage III or IV pressure ulcer were analyzed for cytokines and metabolites of arginine. Sample age ranged from 31–92 years. Wound fluid was collected prior to V.A.C.® application and post-V.A.C.® within 24 hours, 3 days, and 7 days. Subjects served as their own control in this quasi-experimental repeated measures design. Spectrophotometric quantification of nitrates and nitrites using the Griess diazotization reaction method was performed. Tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β) concentrations were measured by enzyme-linked immunosorbent assay. Levels of arginine, citrulline, ornithine, and proline were analyzed by high performance liquid chromatography. Results: There was no significant differences between pre- and post-V.A.C.® concentrations of NO•, citrulline, ornithine, and proline. However, there was a statistically significant decrease in arginine levels measured at baseline and day'3 of V.A.C.® treatment. Also, NO• measured at 24 hours of V.A.C.® placement decreased significantly at day 7 of therapy. Furthermore, post-V.A.C.® levels of TNF-α decreased significantly from baseline. A less cytotoxic environment is created, thus indicating a healing wound following 1 week of V.A.C.® therapy. Discussion: Arginine and its metabolites are detectable in wound fluids from patients with pressure ulcers. To our knowledge, the metabolism of arginine has not been described in human subjects with pressure ulcers on V.A.C.® therapy. The determination of NO• in these wound environments provides baseline information on the mechanisms involved in aberrant wound healing.