Dry eye modulates the expression of toll-like receptors on the ocular surface

Abstract

We aimed to determine if toll-like receptor (TLR) expression is modulated in response to dry eye-associated conditions and in Dry Eye Syndrome (DES).Primary human corneal epithelial cells (HCEC), a SV40 HCEC cell line or a normal human conjunctival epithelial cell line (IOBA-NHC) were cultured under hyperosmolar stress (HOS) (400-500 mOsm/kg) or with DES associated cytokines (IL-1α/β, TNFα or TGFβ) at concentrations ranging from 1-1000 ng/ml for up to 24 hrs. Epithelial cells were harvested from a human cornea organ culture model following 24 hrs of desiccation. Conjunctival impression cytology samples were harvested from subjects with DES and age and gender-matched normal subjects. TLR4, TLR5 or TLR9 mRNA or protein was examined by quantitative RT-PCR, western blotting or flow cytometry. TLR functionality was evaluated in terms of addition of TLR agonists and quantitation of secreted inflammatory cytokines by the use of ELISA and Luminex assays. In SV40 HCEC, HOS significantly increased TLR4 by 8.18 fold, decreased TLR9 by 0.58 fold, but had no effect on TLR5 mRNA expression. TLR4 and TLR9 protein were decreased by 67.7% and 72% respectively. TLR4 mRNA was also significantly up-regulated by up to 9.70 and 3.36 fold in primary HCEC and IOBA-NHC respectively. DES associated cytokines had no effect on TLR4, 5 and 9 expression. In response to desiccation, TLR4 and TLR5 mRNA were significantly up-regulated by 4.81 and 2.51 fold respectively, while TLR9 mRNA was down-regulated by 0.86 fold in HCEC. A similar trend for TLR4 and TLR9 protein was observed. TLR9 mRNA was significantly down-regulated by almost 59.5% in DES subjects. In conclusion, changes in TLR expression occur in dry eye and could have an important role in ocular surface susceptibility to inflammation and infection.

Modulation of Inflammation-Related Genes in the Cornea of a Mouse Model of Dry Eye upon Treatment with Cyclosporine Eye Drops

“…This positive ρ correlation suggests that TLR4 can be implicated in corneal epithelium alteration severity 50 (S100A8 and S100A9, identified endogenous TLR4 protein ligands, were demonstrated to be associated with DED severity 27 ), inflammation, 51 and the healing process. 52 In the present study, we found that DED did not significantly increase TLR4 gene expression in the cornea, but treatments Table 3.…”

High-Mobility Group Box 1 in Dry Eye Inflammation

“… 59 , 60 In addition to RAGE, 19 HMGB1 binds to TLR2, 61 TLR4, 51 , 61 , 62 and TLR9. 63 We have previously demonstrated that HCEC secrete inflammatory cytokines and chemokines when stimulated by TLR agonists 17 , 64 and have shown TLR upregulation in the cornea, conjunctiva, and lacrimal gland in EDE mice. 18 We have also reported an increase in TLR4 expression in DED subjects.…”

“… 10 , 16 Importantly for the context of DED, TLRs are expressed at the ocular surface and have been implicated in dry eye-related inflammation. 17 , 18 Therefore, TLR activation by DAMPs may perpetuate ocular surface proinflammatory responses leading to chronic inflammation.…”

Clinical impact of inflammation in dry eye disease: proceedings of the ODISSEY group meeting

“…; Redfern et al. ). There is also an increase in expression and activation of enzymes involved in the innate immunity (e.g.…”

“…human leucocyte antigen [HLA]-DR, CD40, CD40 ligand, toll-like receptor 4 and 5 and C-C chemokine receptor 5) and adhesion receptors (e.g. intercellular adhesion molecule [ICAM]-1), facilitating inflammatory mediators' recruitment and migration from the ocular surface (Calonge et al 2010;Redfern et al 2015). There is also an increase in expression and activation of enzymes involved in the innate immunity (e.g.…”