Skip to main content

Research Repository

Advanced Search

In vitro studies on the antimicrobial peptide human beta-defensin 9 (HBD9): signalling pathways and pathogen-related response (an American Ophthalmological Society thesis)

Dua, Harminder S.; Otri, Ahmad Muneer; Hopkinson, Andrew; Mohammed, Imran

Authors

HARMINDER DUA harminder.dua@nottingham.ac.uk
Professor of Ophthalmology and Visual Sciences

Ahmad Muneer Otri

Andrew Hopkinson



Abstract

Purpose: Human β-defensins (HBDs) are an important part of the innate immune host defense at the ocular surface. Unlike other defensins, expression of HBD9 at the ocular surface is reduced during microbial infection, but activation of toll-like receptor 2 (TLR2) in corneal epithelial cells has been shown to up-regulate HBD9. Our purpose was to test the hypothesis that TLR2 has a key role in the signalling pathway(s) involved in the overexpression or underexpression of HBD9, and accordingly, different pathogens would induce a different expression pattern of HBD9. Methods: The in vitro RNAi silencing method and response to dexamethasone were used to determine key molecules involved in signalling pathways of HBD9 in immortalized human corneal epithelial cells. The techniques included cell culture with exposure to specific transcription factor inhibitors and bacteria, RNA extraction and cDNA synthesis, quantitative real-time polymerase chain reaction, and immunohistology. Results: This study demonstrates that TLR2 induces HBD9 mRNA and protein expression in a time-and dose-dependent manner. Transforming growth factor-β–activated kinase 1 (TAK1) plays a central role in HBD9 induction by TLR2, and transcription factors c-JUN and activating transcription factor 2 are also involved. Dexamethasone reduces TLR2-mediated up-regulation of HBD9 mRNA and protein levels in mitogen-activated protein kinase phosphatase 1 (MKP1)-dependent and c-JUN-independent manner. HBD9 expression differs with gram-negative and gram-positive bacteria. Conclusions: TLR2-mediated MKPs and nuclear factor-κB signalling pathways are involved in HBD9 expression. TAK-1 is a key molecule. These molecules can be potentially targeted to modulate HBD9 expression. Differential expression of HBD9 with different bacteria could be related to differences in pathogen-associated molecular patterns of these organisms.

Journal Article Type Article
Publication Date Jul 15, 2014
Journal Transactions of the American Ophthalmological Society
Peer Reviewed Peer Reviewed
Volume 112
Pages 50-73
APA6 Citation Dua, H. S., Otri, A. M., Hopkinson, A., & Mohammed, I. (2014). In vitro studies on the antimicrobial peptide human beta-defensin 9 (HBD9): signalling pathways and pathogen-related response (an American Ophthalmological Society thesis). Transactions of the American Ophthalmological Society, 112, 50-73
Publisher URL https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4311673/
;