Injury enhances TLR2 function and antimicrobial peptide expression through a vitamin D–dependent mechanism
Jürgen Schauber, … , Robert L. Modlin, Richard L. Gallo
Jürgen Schauber, … , Robert L. Modlin, Richard L. Gallo
Published March 1, 2007
Citation Information: J Clin Invest. 2007;117(3):803-811. https://doi.org/10.1172/JCI30142.
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Research Article Dermatology

Injury enhances TLR2 function and antimicrobial peptide expression through a vitamin D–dependent mechanism

Abstract

An essential element of the innate immune response to injury is the capacity to recognize microbial invasion and stimulate production of antimicrobial peptides. We investigated how this process is controlled in the epidermis. Keratinocytes surrounding a wound increased expression of the genes coding for the microbial pattern recognition receptors CD14 and TLR2, complementing an increase in cathelicidin antimicrobial peptide expression. These genes were induced by 1,25(OH)2 vitamin D3 (1,25D3; its active form), suggesting a role for vitamin D3 in this process. How 1,25D3 could participate in the injury response was explained by findings that the levels of CYP27B1, which converts 25OH vitamin D3 (25D3) to active 1,25D3, were increased in wounds and induced in keratinocytes in response to TGF-β1. Blocking the vitamin D receptor, inhibiting CYP27B1, or limiting 25D3 availability prevented TGF-β1 from inducing cathelicidin, CD14, or TLR2 in human keratinocytes, while CYP27B1-deficient mice failed to increase CD14 expression following wounding. The functional consequence of these observations was confirmed by demonstrating that 1,25D3 enabled keratinocytes to recognize microbial components through TLR2 and respond by cathelicidin production. Thus, we demonstrate what we believe to be a previously unexpected role for vitamin D3 in innate immunity, enabling keratinocytes to recognize and respond to microbes and to protect wounds against infection.

Authors

Jürgen Schauber, Robert A. Dorschner, Alvin B. Coda, Amanda S. Büchau, Philip T. Liu, David Kiken, Yolanda R. Helfrich, Sewon Kang, Hashem Z. Elalieh, Andreas Steinmeyer, Ulrich Zügel, Daniel D. Bikle, Robert L. Modlin, Richard L. Gallo

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Figure 2

The effect of 1,25D3 on the expression of TLRs in cultured keratinocytes.

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The effect of 1,25D3 on the expression of TLRs in cultured keratinocytes...
(A) Expression of TLR2 and CD14 mRNA was increased by 1,25D3 (100 nM) in cultured keratinocyte monolayers after 24 hours. (B) Expression of TLR2 and CD14 protein was increased by 1,25D3 (100 nM) in monolayer keratinocyte extracts evaluated by Western blot and quantified by image density analysis. (C) Keratinocytes grown in differentiated epidermal constructs stimulated with 1,25D3 (100 nM) also showed an increase in CD14 and TLR2 transcript abundance. Data are mean ± SD of a representative experiment performed in triplicate. *P < 0.05, **P < 0.01, Student’s t test. (D) Skin from healthy volunteers (n = 7) was treated with 1,25D3 (1.0 mM applied once). Controls are contralateral skin treated with vehicle. After 4 days, punch biopsies from both sites were obtained, and skin sections were stained for TLR2 expression. Staining intensity — graded according to the intensity of immunoreactivity (0, no expression; 3, strong expression) — increased in patients treated with topical 1,25D3, as determined by an investigator blinded to treatment group. Sections from 1 representative study participant are displayed. *P < 0.05, Mann-Whitney test.