Beta-endorphin and lipopolysaccharide interactions with human neutrophils.

The binding of the Escherichia coli peptide, N-formyl methionyl leucyl phenylalanine (FMLP), to human neutrophils was found to be reduced by E coli lipopolysaccharide (LPS). This reduction is reversed by human β-endorphin 1-31. β-Endorphin (BE) also increased the binding of FMLP in the absence of LPS. Structural analogs of BE, namely BE 1-27 and N-acetyl BE 1-31, were equal to BE in potency. BE 6-31, however, was less potent than BE. These effects may be mediated by a neutrophil binding site for BE, which was found to have a K(D) of 4.1 × 10(7) and 315,930 sites per cell. These findings provide an explanation for the authors' previous observation that BE enhances the chemotaxis of neutrophils toward FMLP. Furthermore, these data suggest that there may be a role for BE in the modulation of neutrophilic function in the septic state.