Reduction of disulphide bonds unmasks potent antimicrobial activity of human β-defensin 1.
Human epithelia are permanently challenged by bacteria and fungi, including commensal and pathogenic microbiota. In the gut, the fraction of strict anaerobes increases from proximal to distal, reaching 99% of bacterial species in the colon. At colonic mucosa, oxygen partial pressure is below 25% of airborne oxygen content, moreover microbial metabolism causes reduction to a low redox potential of -200 mV to -300 mV in the colon. Defensins, characterized by three intramolecular disulphide-bridges, are key effector molecules of innate immunity that protect the host from infectious microbes and shape the composition of microbiota at mucosal surfaces. Human β-defensin 1 (hBD-1) is one of the most prominent peptides of its class but despite ubiquitous expression by all human epithelia, comparison with other defensins suggested only minor antibiotic killing activity. Whereas much is known about the activity of antimicrobial peptides in aerobic environments, data about reducing environments are limited. Herein we show that after reduction of disulphide-bridges hBD-1 becomes a potent antimicrobial peptide against the opportunistic pathogenic fungus Candida albicans and against anaerobic, Gram-positive commensals of Bifidobacterium and Lactobacillus species. Reduced hBD-1 differs structurally from oxidized hBD-1 and free cysteines in the carboxy terminus seem important for the bactericidal effect. In vitro, the thioredoxin (TRX) system is able to reduce hBD-1 and TRX co-localizes with reduced hBD-1 in human epithelia. Hence our study indicates that reduced hBD-1 shields the healthy epithelium against colonisation by commensal bacteria and opportunistic fungi. Accordingly, an intimate interplay between redox-regulation and innate immune defence seems crucial for an effective barrier protecting human epithelia.
Dr. Margarete Fischer-Bosch-Institute of Clinical Pharmacology, 70376 Stuttgart, Germany.
Bjoern O
BO
Schroeder
Zhihong
Z
Wu
Sabine
S
Nuding
Sandra
S
Groscurth
Moritz
M
Marcinowski
Julia
J
Beisner
Johannes
J
Buchner
Martin
M
Schaller
Eduard F
EF
Stange
Jan
J
Wehkamp
D000595:Amino Acid Sequence; D000890:Anti-Infective Agents / Q000737:chemistry / Q000276:immunology / Q000378:metabolism* / Q000494:pharmacology*; D001644:Bifidobacterium / Q000187:drug effects / Q000276:immunology; D055162:Biocatalysis; D002176:Candida albicans / Q000187:drug effects / Q000276:immunology; D003106:Colon / Q000276:immunology / Q000378:metabolism / Q000382:microbiology; D004220:Disulfides / Q000737:chemistry / Q000378:metabolism*; D004229:Dithiothreitol / Q000494:pharmacology; D006801:Humans; D007113:Immunity, Innate; D007413:Intestinal Mucosa / Q000276:immunology / Q000378:metabolism / Q000382:microbiology; D007778:Lactobacillus / Q000187:drug effects / Q000276:immunology; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction / Q000187:drug effects; D010100:Oxygen / Q000378:metabolism; D010313:Partial Pressure; D011487:Protein Conformation / Q000187:drug effects; D013879:Thioredoxins / Q000378:metabolism; D023083:beta-Defensins / Q000737:chemistry / Q000276:immunology / Q000378:metabolism* / Q000494:pharmacology*
D000890:Anti-Infective Agents; D004220:Disulfides; D023083:beta-Defensins; D013879:Thioredoxins; D010100:Oxygen; D004229:Dithiothreitol
Proc Natl Acad Sci U S A. 1998 Dec 8;95(25):14961-6
9843998
Peptides. 2003 Apr;24(4):523-30
12860195
Proc Natl Acad Sci U S A. 2010 May 11;107(19):8772-7
20421464
Microbes Infect. 2009 Mar;11(3):384-93
19397883
Antimicrob Agents Chemother. 2010 Jun;54(6):2312-22
20308372
Methods Mol Biol. 2010;618:15-30
20094855
J Endotoxin Res. 2007;13(6):317-38
18182460
Nature. 2002 Jan 24;415(6870):389-95
11807545
Nat Rev Immunol. 2009 May;9(5):313-23
19343057
Eur J Biochem. 2000 Oct;267(20):6102-9
11012661
J Clin Microbiol. 2003 Jan;41(1):90-6
12517831
Nat Rev Immunol. 2004 Jun;4(6):478-85
15173836
Gastroenterology. 2006 Oct;131(4):1110-21
17030181
Annu Rev Biochem. 1985;54:237-71
3896121
Methods Enzymol. 1984;107:295-300
6390091
Nat Rev Microbiol. 2006 Jul;4(7):529-36
16778838
Curr Opin Immunol. 1994 Aug;6(4):584-9
7946046
Science. 2001 Feb 2;291(5505):881-4
11157169
Eur J Immunol. 2005 Feb;35(2):408-17
15627982
Scand J Gastroenterol. 2008 Mar;43(3):299-307
18938660
J Microbiol Methods. 2006 May;65(2):335-45
16182394
FEBS Lett. 1995 Jul 17;368(2):331-5
7628632
Biopolymers. 2008;90(1):1-7
18041067
J Immunol Methods. 1991 Mar 21;137(2):167-73
1901580
Contrib Microbiol. 2003;10:106-48
12530324
Drugs. 2010 May 7;70(7):841-58
20426496
Genes Immun. 2010 Jan;11(1):45-54
19829306
J Dent Res. 2010 Jun;89(6):631-6
20371866
Nat Rev Immunol. 2009 Sep;9(9):609-17
19704417