Localization and gene expression of human beta-defensin 9 at the human ocular surface epithelium.
OBJECTIVE
Antimicrobial peptides (AMPs) are multifunctional host defense molecules. Human beta-defensin 9 (HBD9) has previously been shown to be downregulated during ocular surface (OS) infection or inflammation. Here, the authors aimed to study localization of HBD9 protein in different OS regions and to determine the role of Toll-like receptors (TLRs), nucleotide oligomerization domain (NOD)-like receptors, and proinflammatory cytokines in HBD9 expression.


METHODS
Immunolocalization of HBD9 protein was carried out on the normal human OS regions (cornea, limbus, and conjunctiva). Quantitative PCR analysis of HBD9 mRNA was performed in SV40-transformed human corneal epithelial cells (hCECs) treated for different durations with synthetic pathogen-associated molecular patterns (PAMPs) and recombinant cytokines.


RESULTS
HBD9 protein was constitutively expressed on OS epithelia. Corneal and limbal epithelia and corneal stroma demonstrated modest levels of HBD9, whereas conjunctival epithelium demonstrated high levels of HBD9 protein. TLR02, TLR03, TLR04, and TLR05 were shown to modulate HBD9 mRNA in hCECs. Similarly, NOD2 and IL-1beta were also shown to alter HBD9 in a time-dependent manner. In response to infection-related PAMPs and inflammatory cytokines, an initial increase in HBD9 mRNA levels was observed, followed by a significant downregulation.


CONCLUSIONS
This is the first demonstration of HBD9 protein expression at different OS regions. The authors also determined the role of various innate immune receptors in HBD9 mRNA modulation. Further understanding of the signaling mechanisms involved in the initial response of HBD9 to infection or inflammation is likely to indicate future therapeutic directions with this AMP.
Mohammed
Imran
I
Larry A. Donoso Laboratory for Eye Research, Division of Ophthalmology and Visual Sciences, The University of Nottingham, Queens Medical Centre, University Hospital, Nottingham, United Kingdom.
Suleman
Hanif
H
Otri
Ahmad M
AM
Kulkarni
Bina B
BB
Chen
Peng
P
Hopkinson
Andrew
A
Dua
Harminder S
HS
D002461:Cell Line, Transformed; D003228:Conjunctiva / Q000166:cytology / Q000502:physiology; D015536:Down-Regulation / Q000502:physiology; D004847:Epithelial Cells / Q000166:cytology / Q000502:physiology*; D019573:Epithelium, Corneal / Q000166:cytology / Q000502:physiology*; D015870:Gene Expression / Q000187:drug effects / Q000502:physiology; D006801:Humans; D053583:Interleukin-1beta / Q000378:metabolism / Q000494:pharmacology; D016850:Limbus Corneae / Q000166:cytology / Q000502:physiology; D053474:Nod1 Signaling Adaptor Protein / Q000378:metabolism / Q000494:pharmacology; D053473:Nod2 Signaling Adaptor Protein / Q000378:metabolism / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D051193:Toll-Like Receptors / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism / Q000494:pharmacology; D023083:beta-Defensins / Q000235:genetics*
C526629:DEFB-109 peptide, human; D053583:Interleukin-1beta; C119067:NOD1 protein, human; C429018:NOD2 protein, human; D053474:Nod1 Signaling Adaptor Protein; D053473:Nod2 Signaling Adaptor Protein; D012333:RNA, Messenger; D051193:Toll-Like Receptors; D014409:Tumor Necrosis Factor-alpha; D023083:beta-Defensins