title: Expression and secretion of cathelicidin antimicrobial peptides in murine mammary glands and human milk.
abstract: Mammalian milk possesses inherent antimicrobial properties that have been attributed to several diverse molecules. Recently, antimicrobial peptides that belong to the cathelicidin gene family have been found to be important to the mammalian immune response. This antimicrobial is expressed in several tissues and increased in neonatal skin, possibly to compensate for an immature adaptive immune response. We hypothesized that the mammary gland could produce and secrete cathelicidin onto the epithelial surface and into milk. Human cathelicidin hCAP18/LL-37 mRNA was detected in human milk cells by PCR. Quantitative real-time PCR demonstrated an increase in relative expression levels at 30 and 60 d after parturition. Immunohistochemistry of mouse breast tissue identified the murine cathelicidin-related antimicrobial peptide in lobuloacinar and ductules. Western blot analysis of human milk showed that LL-37 was secreted and present in the mature peptide form. The antimicrobial activity of LL-37 against Staphylococcus aureus, group A Streptococcus, and enteroinvasive Escherichia coli O29 in the human milk ionic environment was confirmed by solution colony-forming assay using synthetic peptide. These results indicate that cathelicidin is secreted in mammary gland and human milk, has antimicrobial activity against both Gram-positive and Gram-negative bacteria, and can contribute to the anti-infectious properties of milk.
authors.affiliation: Division of Dermatology, University of California, San Diego, and VA San Diego Healthcare System, 3350 La Jolla Village Drive, San Diego, CA 92161, USA.
authors.forename: Masamoto
authors.initials: M
authors.lastname: Murakami
authors.forename: Robert A
authors.initials: RA
authors.lastname: Dorschner
authors.forename: Lauren J
authors.initials: LJ
authors.lastname: Stern
authors.forename: Kenneth H
authors.initials: KH
authors.lastname: Lin
authors.forename: Richard L
authors.initials: RL
authors.lastname: Gallo
mesh_terms: D000328:Adult; D000818:Animals; D000890:Anti-Infective Agents / Q000494:pharmacology; D023181:Antimicrobial Cationic Peptides / Q000096:biosynthesis* / Q000378:metabolism*; D015153:Blotting, Western; D004926:Escherichia coli / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D008321:Mammary Glands, Animal / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008895:Milk, Human / Q000378:metabolism*; D012313:RNA / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013211:Staphylococcus aureus / Q000378:metabolism; D013291:Streptococcus / Q000378:metabolism; D013997:Time Factors; D014018:Tissue Distribution; D023083:beta-Defensins / Q000096:biosynthesis; D054804:Cathelicidins
chemical_list: D000890:Anti-Infective Agents; D023181:Antimicrobial Cationic Peptides; C406407:DEFB1 protein, human; D012333:RNA, Messenger; D023083:beta-Defensins; D012313:RNA; D054804:Cathelicidins