- Article
- Open Access
- Published:
Proteolytic Degradation of reduced Human Beta Defensin 1 generates a Novel Antibiotic Octapeptide
Abstract
Microbial
resistance against clinical used antibiotics is on the rise.
Accordingly, there is a high demand for new innovative antimicrobial
strategies. The host-defense peptide human beta-defensin 1 (hBD-1) is
produced continuously by epithelial cells and exhibits compelling
antimicrobial activity after reduction of its disulphide bridges. Here
we report that proteolysis of reduced hBD-1 by gastrointestinal
proteases as well as human duodenal secretions produces an eight-amino
acid carboxy-terminal fragment. The generated octapeptide retains
antibiotic activity, yet with distinct characteristics differing from
the full-length peptide. We modified the octapeptide by stabilizing its
termini and by using non-natural D-amino acids. The native and modified
peptide variants showed antibiotic activity against pathogenic as well
as antibiotic-resistant microorganisms, including E. coli, P. aeruginosa and C. albicans. Moreover, in an in vitro C. albicans infection model the tested peptides demonstrated effective amelioration of C. albicans
infection without showing cytotoxity on human cells. In summary,
protease degradation of hBD-1 provides a yet unknown mechanism to
broaden antimicrobial host defense, which could be used to develop
defensin-derived therapeutic applications.
Introduction
Antimicrobial
peptides (AMPs) are evolutionary ancient peptide antibiotics produced
by all multicellular organisms. They are part of the primary defense
against microbial infections and exhibit antimicrobial activity against
bacteria, fungi and some enveloped viruses1,2.
Humans produce different classes of AMPs, one of them are the
defensins. These secreted peptides are characterized by their small size
(3 to 5 kDa), cationic net charge and six conserved cysteine residues,
which are connected via three disulphide bridges1,3,4.
Human beta-defensin 1 (hBD-1) was the first beta-defensin identified in
humans and is produced by epithelia, monocytes, plasmacyoid dendritic
cells and platelets5,6,7,8.
In contrast to inducible beta-defensins 2 and 3, hBD-1 is produced
constitutively and its expression can be regulated by peroxisome
proliferator-activated receptor gamma (PPARγ) and hypoxia-inducible
factor alpha (HIF1-α)6,9,10.
We could recently show that antimicrobial activity of hBD-1 is strongly
increased after reduction of its three disulphide bridges independent
of bacterial Gram-status11,12. Activation of the peptide could be executed by a reducing environment or enzymatically by the oxido-reductase thioredoxin11,13.
Due to their ancient evolutionary origin and the strong demand for novel antimicrobial strategies, AMPs have been considered as potential antibiotic drug candidates. Mainly because they target “Achilles heels” of microorganisms, only few resistance mechanisms have been evolved over long time14,15. Still, large-scale chemical synthesis of defensins containing three native disulphide-bridges has been a challenge and rendered the production expensive.
Accordingly, the production of smaller, but yet antibiotic, fragments of defensins without disulphide bridges is a promising option. We have shown previously that reduced hBD-1 can be degraded by the intestinal protease trypsin16.
Here, we evaluate a carboxy-terminal fragment of hBD-1 that is generated after proteolytic digestion by intestinal proteases. We investigate its antimicrobial activity and its potential to be exploited as a possible candidate for future antibiotic drug development.
Betadefensiiniä erittyy neutrofiileistä ja se tehoaa S. aureusta ja hemofilus influenzaeta vastaan.
Neutrofiilien ( granulosyytit) normaalius ja normaalimäärä verenkuvassa on olennaista. Esim. radioaktiivisuus vaikuttaa neutrofiilien määrään vähentävästi, mikä romahduttaa luonollsita vastustuskykyä. neutrofiilejä pitää olla valmiina veressä aina, ne kuuluvat luonnollieen puolustukseen ja defensiinit ovat yksi niiden aseista.
Due to their ancient evolutionary origin and the strong demand for novel antimicrobial strategies, AMPs have been considered as potential antibiotic drug candidates. Mainly because they target “Achilles heels” of microorganisms, only few resistance mechanisms have been evolved over long time14,15. Still, large-scale chemical synthesis of defensins containing three native disulphide-bridges has been a challenge and rendered the production expensive.
Accordingly, the production of smaller, but yet antibiotic, fragments of defensins without disulphide bridges is a promising option. We have shown previously that reduced hBD-1 can be degraded by the intestinal protease trypsin16.
Here, we evaluate a carboxy-terminal fragment of hBD-1 that is generated after proteolytic digestion by intestinal proteases. We investigate its antimicrobial activity and its potential to be exploited as a possible candidate for future antibiotic drug development.
- Beta-defensiini1: HBD1, DEFB1 (8p23.1)https://www.ncbi.nlm.nih.gov/gene/1672
Betadefensiiniä erittyy neutrofiileistä ja se tehoaa S. aureusta ja hemofilus influenzaeta vastaan.
Neutrofiilien ( granulosyytit) normaalius ja normaalimäärä verenkuvassa on olennaista. Esim. radioaktiivisuus vaikuttaa neutrofiilien määrään vähentävästi, mikä romahduttaa luonollsita vastustuskykyä. neutrofiilejä pitää olla valmiina veressä aina, ne kuuluvat luonnollieen puolustukseen ja defensiinit ovat yksi niiden aseista.
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