The presence of antibacterial and opioid peptides in human plasma during coronary artery bypass surgery

Antibacterial peptides, found in both invertebrates and vertebrates, repres ent a potential innate defense mechanism against microbial infections. Howe ver, it is unknown whether this process occurs in humans during surgery. We looked for evidence of release of antibacterial peptides during coronary a rtery bypass grafting (CABG). We used immunological techniques and antibact erial assays combined with high-performance gel-permeation chromatography, reverse-phase HPLC, N-terminal sequencing and comparison with synthetic sta ndards to characterize the peptide B/enkelytin. We show the presence of ani onic antibacterial peptide, the peptide B/enkelytin which correspond to the C-terminal part of proenkephalin A, from the plasma of patients undergoing CABG. Our studies show that peptide B/enkelytin is initially present at lo w levels in plasma and is then released in increased amounts just after ski n incision. Antibacterial assays confirmed that the peptides specifically t arget gram-positive bacteria. We also demonstrate that peptide B/enkelytin is metabolized in vivo to the opioid peptides methionine-enkephalin-Arg-Phe and methionine-enkephalin, peptides that we show have granulocyte chemotac tic activity. These findings suggest that in humans, surgical incision lead s to the release of antibacterial peptides, Furthermore, these antibacteria l peptides can be metabolized into compounds that have immune-activating pr operties, (C) 2000 Elsevier Science B.V. All rights reserved.