Immunomodulatory and anti-inflammatory activity in vitro and in vivo of a novel antimicrobial candidate.

The synthetic antimicrobial peptide SET-M33 has strongactivity against bacterial infections caused by Gram-negativebacteria. It is currently in preclinical development as a new drugto treat lung infections caused by Gram-negative bacteria. Herewe report its strong anti-inflammatory activity in terms ofreduced expression of a number of cytokines, enzymes, and sig-nal transduction factors involved in inflammation triggered byLPSfromPseudomonas aeruginosa,Klebsiella pneumoniae,andEscherichia coli. Sixteen cytokines and other major agentsinvolved in inflammation were analyzed in macrophages andbronchial cells after stimulation with LPS and incubation withSET-M33. The bronchial cells were obtained from a cystic fibro-sis patient. A number of these proteins showed up to 100%reduction in expression as measured by RT-PCR, Western blot-ting, or Luminex technology. LPS neutralization was also dem-onstratedin vivoby challenging bronchoalveolar lavage of SET-M33-treated mice with LPS, which led to a sharp reduction inTNF-with respect to non-SET-M33-treated animals. We alsodescribe a strong activity of SET-M33 in stimulating cell migra-tion of keratinocytes in wound healing experimentsin vitro,demonstrating a powerful immunomodulatory action generallycharacteristic of molecules taking part in innate immunity.