Prophylactic uses of integrin CD18-βA peptide in a murine polymicrobial peritonitis model

Figure 1 CD18-βA peptide protects mice against cecal ligation and puncture (CLP)-induced lethality and inflammatory responses. A: Mice were injected with either sterile saline or CD18-βA peptide intraperitoneally at 12 h intervals beginning 2 h after CLP (as indicated by arrows), and were monitored continually over 48 h. There was statistically significant improvement in survival of septic shock mice that received CD18-βA injection (P < 0.01), compared to those that received saline. n = 8 for each experimental groups; B: Measurement of endotoxin activity and tumor necrosis factor (TNF)-α and interleukin (IL)-6 levels in blood circulation. Injection of CD18-βA peptide achieved significant reductions in endotoxin activity at 24 h, and reductions in TNF-α and IL-6 at 12 and 24 h after CLP. 12 h, n = 5 and 24 h, n = 6 for each experimental group. ^aP < 0.05, ^bP < 0.01 vs saline group (one-way ANOVA). Error bars represent mean ± SD.

Figure 2 CD18-βA peptide inhibits CD45+ leukocyte infiltration into lung and liver in CLP-induced mice. A: CD45+ leukocyte content in lung and liver after CLP was visualized by immunohistochemistry. Images are representative of n = 6 for each experimental group. Scale bar, 80 μmol/L; B: Real-time polymerase chain reaction (PCR) analysis of CD3 mRNA level in lungs and liver, normalized to β-actin, at 12 and 24 h after CLP. Significant reductions in CD3 mRNA contents were observed in lungs and liver of septic mice that have been treated with CD18-βA peptide. ^aP < 0.05 vs saline group (one-way ANOVA); C: Pulmonary expression of adhesion molecules was studied using immunohistochemistry and real-time PCR. Lung sections were stained with VCAM and E-selectin antibody, and images are representative of n = 6 for each experimental group. Scale bars, 80 μm. Real-time PCR was employed to study mRNA expression of ICAM-1, VCAM, and E-selectin in lungs. Significant reductions in adhesion molecule mRNA contents were observed in lungs of septic mice that were treated with CD18-βA peptide. ^bP < 0.01, ^dP < 0.001 vs saline group (one-way ANOVA). For all real-time PCR study, n = 6 for each experimental group at 12 and 24 h. Error bars represent mean ± SD.

Figure 3 A predicted model of the amphipathic helix sequence at CD18-βA that binds bacterial endotoxin. Shown is the polypeptide sequence of the CD18-βA domain of leukocyte β2 integrin, and the two LPS-binding sites are colored green and red. CD18-βA peptide is derived from the red binding site. The underlined portion of CD18-βA peptide demonstrates a feature of the amphipathic helix, as revealed by the helical wheel diagram.