PPARγ mediates innate immunity by regulating the 1α,25-dihydroxyvitamin D3 induced hBD-3 and cathelicidin in human keratinocytes

J Dermatol Sci. 2010 Dec;60(3):179-86. doi: 10.1016/j.jdermsci.2010.09.008. Epub 2010 Oct 23.

Abstract

Background: Production of antimicrobial peptides (AMPs) is the primary mechanism by which skin innate immunity protects against infection. Hormonally active vitamin D3 (1α,25-dihydroxyvitamin D3; 1,25D₃) is a vital regulator of skin innate immunity, and has been shown to increase the expression and function of AMPs.

Objective: PPARγ is a ligand-activated nuclear receptor and plays a role in keratinocyte differentiation and cutaneous homeostasis. In this study, we investigate whether 1,25D₃-activated PPARγ signaling regulates AMP expression in keratinocytes.

Methods: Subconfluent keratinocytes were treated with 1,25D₃ for the indicated times. The mRNA and protein levels of AMPs were detected by RT-PCR and Western blot, and the DNA binding activation of PPARγ, VDRE and AP-1 was investigated by EMSA. To examine the role of PPARγ, the recombinant adenovirus carrying a dominant-negative form of PPARγ (dn-PPARγ) was constructed and transfected into keratinocytes.

Results: We show here that 1,25D₃ significantly enhances hBD-3 and cathelicidin expression in keratinocytes. Expression of dn-PPARγ did not affect binding to the vitamin D-responsive element (VDRE), which is crucial for cathelicidin induction by VD3; however, it did decrease 1,25D₃ induction of both hBD-3 and cathelicidin. Inhibition of the p38, ERK, and JNK signaling pathways blocked hBD-3 expression, whereas only p38 inhibition suppressed cathelicidin induction. dn-PPARγ had no effect on ERK and JNK activity, but inhibited p38 phosphorylation and suppressed 1,25D₃-induced AP-1 activation via effects on Fra1 and c-Fos proteins.

Conclusions: In conclusion, PPARγ regulates the 1,25D₃-induced hBD-3 and cathelicidin expression in keratinocytes through the regulation of AP-1 and p38 activity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antimicrobial Cationic Peptides / biosynthesis*
  • Antimicrobial Cationic Peptides / genetics
  • Antimicrobial Cationic Peptides / immunology
  • Base Sequence
  • Calcitriol / pharmacology
  • Cells, Cultured
  • DNA Primers / genetics
  • Humans
  • Immunity, Innate* / drug effects
  • Keratinocytes / drug effects
  • Keratinocytes / immunology*
  • Keratinocytes / metabolism*
  • MAP Kinase Signaling System / immunology
  • PPAR gamma / antagonists & inhibitors
  • PPAR gamma / genetics
  • PPAR gamma / immunology*
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Signal Transduction / drug effects
  • Signal Transduction / immunology
  • Transcription Factor AP-1 / metabolism
  • beta-Defensins / biosynthesis*
  • beta-Defensins / genetics
  • beta-Defensins / immunology
  • p38 Mitogen-Activated Protein Kinases / metabolism

Substances

  • Antimicrobial Cationic Peptides
  • DEFB103A protein, human
  • DNA Primers
  • PPAR gamma
  • RNA, Messenger
  • Transcription Factor AP-1
  • beta-Defensins
  • ropocamptide
  • p38 Mitogen-Activated Protein Kinases
  • Calcitriol