Expression of Antimicrobial Peptides in Cutaneous Infections after Skin Surgery

M.R. Kesting; M. Stoeckelhuber; F. Hölzle; T. Mücke; K. Neumann; K. Woermann; F. Jacobsen; L. Steinstraesser; K.-D. Wolff; D.J. Loeffelbein; N.H. Rohleder

Disclosures

The British Journal of Dermatology. 2010;163(1):121-127. 

In This Article

Abstract and Introduction

Abstract

Background Increasing numbers of antibiotics have lost efficiency because of bacterial resistance. The consequences can be severe when surgical wounds become infected during postoperative care. Natural peptide antibiotics, the so-called host defence peptides (HDPs), have been investigated since the 1990s in a search for alternative treatment strategies. HDPs build up a protection shield against pathological microorganisms, especially in human epithelium. The use of HDPs is currently being discussed as a new antimicrobial therapeutic strategy. Accordingly, a profound knowledge of the quantitative relationships of the effectors is essential.
Objectives To evaluate differences in HDP expression between postoperatively inflamed and healthy epithelium.
Methods Expression profiles of the genes encoding HDP human β-defensin (hBD)-1 (DEFB1, previously known as HBD-1), hBD-2 (DEFB4A, previously known as HBD-2), hBD-3 (DEFB103A, previously known as HBD-3) and psoriasin (S100A7) were assessed in samples of surgical wound healing disorders (n = 27) and healthy epithelium (n = 16) by using real-time polymerase chain reaction. Immunohistochemical staining was performed in the same samples.
Results A significant overexpression of DEFB4A (P < 0·001), DEFB103A (P = 0·001) and S100A7 (P < 0·001) was found in cutaneous surgical site infections. Immunohistochemistry revealed intensely elevated protein levels of psoriasin in infected wounds, and differences in distribution with respect to the epithelial layers.
Conclusions The study demonstrates upregulated mRNA expression and protein levels of HDPs in postoperatively inflamed epithelium. The results may be a starting point for novel pharmacological treatments.

Introduction

Attempts to improve the treatment of infected cutaneous wounds after skin surgery have not been completely satisfactory. Emerging rates of bacterial resistance to conventional antibiotics have led to an increase in the proportion of wound infections with Gram-positive bacteria.[1,2] Therefore, the search for alternative therapeutic options has become a top priority.[3]

As a promising approach for the reduction of bacterial pathogens in wounds, the innate immune system has aroused new scientific interest. A group of peptide molecules has been found to play a major role as cutaneous antimicrobial and immunomodulating agents, the so-called host defence peptides (HDPs) or antimicrobial peptides (AMPs).[4] They show broad activity against bacteria, viruses and fungi.[5,6] A subgroup of HDPs, the human β-defensins (hBDs), have been described as a major class of effector molecules of the innate immune system, and their involvement in wound healing has been subject to numerous studies.[7] After epidermal injury, the AMPs can suppress microbial growth within hours, or for prolonged phases in the case of ongoing infection.[8] Defensins possess the capability to permeabilize the membranes of their target cells,[9] presumably by their ability to form ion-permeable channels in lipid bilayer membranes.[10]

In skin, hBD-1 is produced by keratinocytes, by various skin glands and by CD4+/CD8+ T cells. hBD-1 shows activity against Gram-positive and -negative bacteria. hBD-2 is produced by keratinocytes and glandular cells, mast cells and CD4+/CD8+ T cells. hBD-2 exhibits activity against Gram-positive and -negative bacteria and against fungi. hBD-3 is produced in keratinocytes, monocytes and CD4+ T cells and is effective against Gram-positive and -negative bacteria and against fungi.[5,7,11–13] Psoriasin (S100A7), another interesting HDP, is produced in keratinocytes and exhibits activity against Gram-positive and -negative bacteria;[5,7,14] it was originally identified as being upregulated in skin lesions of patients with psoriasis.[15] Similar to the defensins, psoriasin disrupts bacterial membranes by permeabilization and has also recently been found to act as a chemoattractant for leucocytes.[16,17]

The usefulness of the antimicrobial capacities of the HDPs in possible new therapeutic strategies has been investigated.[18] HDP derivates and combinations of conventional antibiotics with HDPs have been tested in vitro, but, although increased bactericidal activity has been found in some studies, an accompanying increase in cytotoxity has been observed.[7,19] As a consequence, the development of synthetic HDPs with less cytotoxity has been initiated,[20] but suitable substances are not yet available for clinical use. In order to achieve comprehensive knowledge of HDPs with respect to their regulation and quantitative relationships, further research at both the gene expression and protein levels is necessary. The development of new anti-infectious therapeutic strategies on the basis of such findings might also lead to advancements in the management of postoperative cutaneous inflammation. However, to date, no quantitative data comparing differences in the expression of hBDs and psoriasin between surgical wound healing disorders and healthy epithelium are available.

We have investigated the expression levels of the above named HDPs in samples of these two groups by means of real-time reverse transcription–polymerase chain reaction (RT-PCR). The respective protein products were examined by immunohistochemistry.

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