UV-B radiation induces the expression of antimicrobial peptides in human keratinocytes in vitro and in vivo.
BACKGROUND
Suppression of the adaptive immune system by UV radiation plays an important role in photocarcinogenesis. Exacerbation of skin infections has been proposed as a further consequence of UV-induced immunosuppression. Clinically bacterial infections are not a problem. For defense against bacteria, the innate immune response including the release of antimicrobial peptides is much more relevant than the adaptive immune response. Keratinocytes have the capacity to release antimicrobial peptides.


OBJECTIVE
We asked whether UV radiation induces antimicrobial peptides in vitro and in vivo.


METHODS
Antimicrobial peptide expression by normal human keratinocytes was measured by real-time PCR and fluorescence-activated cell sorting analysis. Biopsies taken from human volunteers and skin explants were studied with immunohistochemistry.


RESULTS
Real-time PCR of normal human keratinocytes revealed a dose-dependent increase of human beta-defensin-2, -3, ribonuclease 7, and psoriasin (S100A7) after UV radiation. This was confirmed at the protein level by intracellular fluorescence-activated cell sorting and in vitro immunofluorescence analysis. Immunohistochemistry of biopsies taken from healthy volunteers exposed to different UV radiation doses revealed enhanced epidermal expression of antimicrobial peptides after UV exposure. This was also confirmed by exposing human skin explants to UV radiation.


CONCLUSIONS
UV radiation exerts diverse effects on the immune system, suppressing the adaptive but inducing the innate immune response. This may explain why T-cell-mediated immune reactions are suppressed on UV exposure but not host defense reactions against bacterial attacks.
Gläser
Regine
R
Department of Dermatology and Allergology, University Kiel, Kiel, Germany.
Navid
Fatemeh
F
Schuller
Winfried
W
Jantschitsch
Christian
C
Harder
Jürgen
J
Schröder
Jens M
JM
Schwarz
Agatha
A
Schwarz
Thomas
T