C-Jun NH2 Terminal Kinase (JNK) Has a Critical Role in Toll Like Receptor 2 (TLR2)-Induced CXC Chemokine Production by Corneal Epithelial Cells, and in S. Aureus / TLR2 Mediated Corneal Inflammation

Abstract

Purpose:: The activation of Toll Like receptors (TLR) by microbial products results in corneal inflammation. This study determined the role of Mitogen Activated Protein Kinases (MAPK) in TLR2 mediated keratitis.

Methods:: Human Corneal epithelial (HEC) cells were stimulated with UV-killed S aureus or the TLR2 ligand Pam3Cys in the presence of specific MAPK inhibitors. The effect on MAPK, NF-ΚB activation and cytokine production was detected by Western blot and ELISA. The role of MAPK in corneal inflammation was determined using a mouse model of TLR2/ S. aureus keratitis in which corneal inflammation was measured by neutrophil infiltration to the corneal stroma and the development of corneal haze.

Results:: S. aureus or Pam3Cys exposure leads to activation of JNK, p38MAPK, ERK and NF-ΚB pathway by increased phosphorylation of IKBα. Specific inhibition of JNK by SP600125 significantly reduced IKBα phosphorylation compared with inhibition of ERK or p38 MAPK by specific inhibitors. SP600125 also reduced production of CXCL1, CXCL5 and IL-8/CXCL8 when cells were stimulated with S. aureus. Corneal inflammation induced by Pam3Cys or UV inactivated S. aureus was significantly inhibited in SP600125 treated C57BL/6 mice and in JNK1^-/- mice with respect to neutrophil infiltration and corneal haze.

Conclusions:: These findings provide evidence that JNK has a critical role in TLR2 - induced CXC chemokine production by corneal epithelial cells and in S aureus / TLR2 mediated corneal inflammation.

Keywords: keratitis • bacterial disease • signal transduction