Cathelicidin Family of Antibacterial Peptides CAP18 and CAP11 Inhibit the Expression of TNF-α by Blocking the Binding of LPS to CD14+ Cells

Abstract

Mammalian myeloid and epithelial cells express several kinds of antibacterial peptides (α-/β-defensins and cathelicidins) that contribute to the innate host defense by killing invading micro-organisms. In this study we evaluated the LPS-neutralizing activities of cathelicidin peptides human CAP18 (cationic antibacterial proteins of 18 kDa) and guinea pig CAP11 using the CD14+ murine macrophage cell line RAW264.7 and the murine endotoxin shock model. Flow cytometric analysis revealed that CAP18 and CAP11 inhibited the binding of FITC-conjugated LPS to RAW264.7 cells. Likewise, Northern and Western blot analyses indicated that CAP18 and CAP11 suppressed LPS-induced TNF-α mRNA and protein expression by RAW264.7 cells. Interestingly, CAP18 and CAP11 possessed LPS-binding activities, and they strongly suppressed the interaction of LPS with LPS binding protein that mediates the transport of LPS to CD14 to facilitate the activation of CD14+ cells by LPS. Moreover, when CAP18 and CAP11 were preincubated with RAW264.7 cells, they bound to the cell surface CD14 and inhibited the binding of FITC-LPS to the cells. Furthermore, in the murine endotoxin shock model, CAP18 or CAP11 administration inhibited the binding of LPS to CD14+ cells (peritoneal macrophages) and suppressed LPS-induced TNF-α expression by these cells. Together these observations indicate that cathelicidin peptides CAP18 and CAP11 probably exert protective actions against endotoxin shock by blocking the binding of LPS to CD14+ cells, thereby suppressing the production of cytokines by these cells via their potent binding activities for LPS and CD14.

Effects of human cathelicidin antimicrobial peptide LL‐37 on lipopolysaccharide‐induced nitric oxide release from rat aorta in vitro

“…However, this tendency was not statistically significant. The concentrations of LL-37 required to inhibit the effects of LPS in our study were similar to those found by Turner et al and Nagaoka et al in non-vascular models (13,16). In contrast to the results from the contraction experiments with phenylephrine in which LL-37 did not affect the vascular response to IL-1b, LL-37 at the highest concentration used reduced the IL-1b-induced NO production.…”

“…The present results suggest that the naturally occurring peptide binds LPS. An alternative explanation for our findings could be the binding of LL-37 to the cell-surface-bound LPS receptor, CD14, thereby inhibiting the LPSinduced activation of NO synthesis as demonstrated in RAW 264.7 cells (16). However, the expression of CD14 in vascular tissue seems to be absent or very low (26,27).…”

Inhibition of Lipopolysaccharide Activity by a Bacterial Cyclic Lipopeptide Surfactin

“…Ninety-six-well microtiter plates (Immulon 2H; Dynex Technologies, Ashford, U.K.) were coated with lipid A, and the interaction of the immobilized-lipid A with LBP was measured as described previously [19,20]. Briefly, lipid A at 5 mg/well in 20 ml of ethanol was placed in the ninetysix-well microtiter plates, and the solvent was evaporated in ambient air.…”

Cathelicidins in inflammation and tissue repair: Potential therapeutic applications for gastrointestinal disorders

“…The chemotactic activity of human and mouse cathelicidins are mediated by the engagement of the peptides with the formyl peptide receptor-like 1 (FPRL1), a G protein-coupled, seven-transmembrane cell receptor found on macrophages, neutrophils, and subsets of lymphocytes [8,15] . Moreover, these peptides participate in inflammation by activating mast cells to release histamine through calcium mobilization [14,16] . LL-37 also induces secretion of interleukin (IL)-8 in airway epithelial cells, leading to increased infiltration of neutrophils and amplification of inflammatory signal.…”