Additive effects of orexin B and vasoactive intestinal polypeptide on LL-37-mediated antimicrobial activities

The present study examined the bactericidal effects of orexin B (ORXB) and vasoactive intestinal peptide (VIP) alone or combined with cationic antimicrobial peptides, such as LL-37, on Escherichia coli, Pseudomonas aeruginosa, Streptococcus mutans and Staphylococcus aureus. The bactericidal effect of ORXB or VIP alone was detected in low NaCl concentration, but attenuated in physiological NaCl concentration (150 mM). However, such attenuated bactericidal activities of ORXB and VIP in 150 mM NaCl were regained by adding LL-37. Therefore, our results indicate that VIP and ORXB appear to mediate bactericidal effects in concert with LL-37 in the physiological context of mucosal tissue.