Antibacterial photosensitization through activation of coproporphyrinogen oxidase.

Gram-positive bacteria cause the majority of skin and soft tissue infections (SSTIs), resulting in the most common reason for clinic visits in the United States. Recently, it was discovered that Gram-positive pathogens use a unique heme biosynthesis pathway, which implicates this pathway as a target for development of antibacterial therapies. We report here the identification of a small-molecule activator of coproporphyrinogen oxidase (CgoX) from Gram-positive bacteria, an enzyme essential for heme biosynthesis. Activation of CgoX induces accumulation of coproporphyrin III and leads to photosensitization of Gram-positive pathogens. In combination with light, CgoX activation reduces bacterial burden in murine models of SSTI. Thus, small-molecule activation of CgoX represents an effective strategy for the development of light-based antimicrobial therapies.

Optically mediated nerve stimulation: Identification of injury thresholds.

BACKGROUND AND OBJECTIVE: Transient optical nerve stimulation is a promising new non-contact, spatially precise, artifact-free neural excitation technique useful in research and clinical settings. This study evaluates safety of this pulsed infrared laser technique by histopathologic examination of stimulated peripheral nerves. STUDY DESIGN/MATERIALS AND METHODS: Exposed rat sciatic nerves were functionally stimulated with the pulsed Holmium:YAG laser, previously validated as an effective tool for optical stimulation. Nerves were removed immediately and up to 2 weeks after stimulation and assessed histologically for thermal damage. Laser parameters studied include upper limits for radiant exposure, repetition rate, and duration of stimulation. RESULTS: Radiant exposures with <1% probability of thermal tissue damage (0.66-0.70 J/cm(2)) are significantly greater than radiant exposures required for reliable stimulation (0.34-0.48 J/cm(2)). The upper limit for safe laser stimulation repetition rate occurs near 5 Hz. Maximum duration for constant low repetition rate stimulation (2 Hz) is approximately 4 minutes with adequate tissue hydration. CONCLUSION: Results confirm that optical stimulation has the potential to become a powerful non-contact clinical and research tool for brief nerve stimulation with low risk of nerve thermal damage.

Systemic nf-kappaB activation in a transgenic mouse model of acute pancreatitis.

BACKGROUND: Transcription factor NF-kappaB has been implicated in numerous human inflammatory diseases. Acute pancreatitis can result in remote tissue injury, but the involved mechanisms are unknown. This study evaluates the role of systemic NF-kappaB activation in the pathogenesis of lung inflammation in a transgenic pancreatitis model. MATERIALS AND METHODS: Using transgenic mice expressing photinus luciferase controlled by an NF-kappaB-dependent promoter, luciferase activity was measured in pancreas, liver, and lung tissues as a surrogate marker of NF-kappaB activity. Luciferase activity was measured by in vivo bioluminescence and correlated to an in vitro luciferase assay of organ homogenates. Following measurement of luciferase activity in uninjured animals, these animals were fed a choline-deficient, ethionine supplemented diet for 48 h to induce pancreatitis, and luciferase activity was then measured at 48, 60, 72, and 96 h. Lung inflammation was determined by total nucleated cell counts in bronchoalveolar lavage (BAL) fluid. RESULTS: Bioluminescence detected increased luciferase activity over the upper abdominal region at 48 and 60 h (P < 0.05), and over the thorax at 60 and 72 h (P < 0.05). Luciferase assays showed significantly increased luciferase activity in both liver and lung tissue at 48 (liver = P < 0.005, lung = P < 0.05) and 60 h (liver = P < 0.05, lung = P < 0.05) compared to activity in uninjured controls. Total nucleated cell counts in BAL fluid were significantly increased at 72 h (P < 0.05) compared with controls. CONCLUSION: In this model, NF-kappaB binding activity is increased in the liver and lung. These data suggest that the liver modulates pancreatitis-induced systemic inflammatory response syndrome (SIRS) and suggest strategies to reduce multisystem injury.