Regulation of antimicrobial peptide gene expression by nutrients and by-products of microbial metabolism.
BACKGROUND
Antimicrobial peptides (AMPs) are synthesized and secreted by immune and epithelial cells that are constantly exposed to environmental microbes. AMPs are essential for barrier defense, and deficiencies lead to increased susceptibility to infection. In addition to their ability to disrupt the integrity of bacterial, viral and fungal membranes, AMPs bind lipopolysaccharides, act as chemoattractants for immune cells and bind to cellular receptors and modulate the expression of cytokines and chemokines. These additional biological activities may explain the role of AMPs in inflammatory diseases and cancer. Modulating the endogenous expression of AMPs offers potential therapeutic treatments for infection and disease.


METHODS
The present review examines the published data from both in vitro and in vivo studies reporting the effects of nutrients and by-products of microbial metabolism on the expression of antimicrobial peptide genes in order to highlight an emerging appreciation for the role of dietary compounds in modulating the innate immune response.


RESULTS
Vitamins A and D, dietary histone deacetylases and by-products of intestinal microbial metabolism (butyrate and secondary bile acids) have been found to regulate the expression of AMPs in humans. Vitamin D deficiency correlates with increased susceptibility to infection, and supplementation studies indicate an improvement in defense against infection. Animal and human clinical studies with butyrate indicate that increasing expression of AMPs in the colon protects against infection.


CONCLUSIONS
These findings suggest that diet and/or consumption of nutritional supplements may be used to improve and/or modulate immune function. In addition, by-products of gut microbe metabolism could be important for communicating with intestinal epithelial and immune cells, thus affecting the expression of AMPs. This interaction may help establish a mucosal barrier to prevent invasion of the intestinal epithelium by either mutualistic or pathogenic microorganisms.
Department of Biochemistry and Biophysics, Linus Pauling Institute, Oregon State University, 307 Linus Pauling Science Center, Corvallis, OR 97331, USA.
Yan
Y
Campbell
Mary L
ML
Fantacone
Adrian F
AF
Gombart
D000818:Animals; D023181:Antimicrobial Cationic Peptides; D001419:Bacteria / Q000378:metabolism*; D001647:Bile Acids and Salts / Q000378:metabolism; D002087:Butyrates / Q000378:metabolism; D054804:Cathelicidins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D023082:Defensins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D004352:Drug Resistance, Microbial / Q000187:drug effects; D004847:Epithelial Cells / Q000187:drug effects / Q000276:immunology / Q000382:microbiology; D005786:Gene Expression Regulation; D006655:Histone Deacetylases / Q000494:pharmacology; D006801:Humans; D007113:Immunity, Innate; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000382:microbiology; D017879:Isothiocyanates; D008070:Lipopolysaccharides / Q000378:metabolism; D013454:Sulfoxides; D013861:Thiocyanates / Q000378:metabolism; D014801:Vitamin A / Q000494:pharmacology; D014807:Vitamin D / Q000494:pharmacology; D014808:Vitamin D Deficiency / Q000503:physiopathology; D014815:Vitamins / Q000494:pharmacology
D023181:Antimicrobial Cationic Peptides; D001647:Bile Acids and Salts; D002087:Butyrates; D054804:Cathelicidins; D023082:Defensins; D017879:Isothiocyanates; D008070:Lipopolysaccharides; D013454:Sulfoxides; D013861:Thiocyanates; D014815:Vitamins; D014801:Vitamin A; D014807:Vitamin D; D006655:Histone Deacetylases; C016766:sulforaphane