C-Jun NH2 terminal kinase (JNK) is an essential mediator of Toll-like receptor 2-induced corneal inflammation

Abstract

TLRs play an important role in the host inflammatory response to bacteria and bacterial products by activating a cascade of intracellular events leading to production of proinflammatory and chemotactic cytokines. To determine the role of MAPKs in TLR-induced corneal inflammation, we stimulated human corneal epithelial (HCE) cells with TLR2 ligands, tripalmitoyl-S-glyceroCys-(Lys)4 (Pam3Cys) or inactivated Staphylococcus aureus, and examined the time course of expression of MAPKs and the effect of MAPK inhibition on IkBα degradation and CXC chemokine production. We found that S. aureus and Pam3Cys stimulate phosphorylation of JNK, p38 MAPK, and ERK within 4 h and that blockade of JNK, but not p38 or ERK phosphorylation, had an inhibitory effect on IkBα degradation and CXC chemokine production. To determine if JNK is also important in TLR2-induced corneal inflammation in vivo, we examined JNK1 −/− mice and pharmacological inhibitors in a murine model of TLR2-induced corneal inflammation which is characterized by neutrophil recruitment to the corneal stroma and development of corneal haze. We found that corneal inflammation was significantly impaired in JNK1 −/− mice compared with control mice, and in mice treated with the JNK inhibitor compared with vehicle control. Taken together with results from HCE cells, these findings demonstrate that JNK has an essential role in TLR2-induced corneal inflammation.

Toll-like Receptor 2 (TLR2), Transforming Growth Factor-β, Hyaluronan (HA), and Receptor for HA-mediated Motility (RHAMM) Are Required for Surfactant Protein A-stimulated Macrophage Chemotaxis

“…Indeed, JNK Ϫ/Ϫ mice had decreased responses to S. aureus-stimulated inflammation. Our results differ somewhat from those of Adhikary et al (40) in that both JNK and ERK were required for the expression of TGF␤. These differences are possibly due to cell type specificity in responses.…”

“…These include activation of NFB, JNK, ERK, and p38 (63). Adhikary et al (40) studied TLR2-specific signaling pathways and showed that Pam3Cys stimulation of corneal epithelial cells resulted in phosphorylation of JNK, ERK, and p38 but that only blockade of JNK had an inhibitory effect on activation of NFB. Indeed, JNK Ϫ/Ϫ mice had decreased responses to S. aureus-stimulated inflammation.…”

“…MAPKs play an important role for TLR2-induced inflammation (40,41). We therefore examined if MAPK signaling was also important in TLR2-stimulated macrophage chemotaxis.…”

Interferon-γ-induced MD-2 Protein Expression and Lipopolysaccharide (LPS) Responsiveness in Corneal Epithelial Cells Is Mediated by Janus Tyrosine Kinase-2 Activation and Direct Binding of STAT1 Protein to the MD-2 Promoter

“…After Passage 1, antibiotics were omitted from the culture medium, and cells were harvested with 0.25% trypsin and transferred to a 50-cm 2 flask. The medium was changed every 4 days, and cells from passages 2-5 were used for experiments when cells were 70% confluent (21).…”

“…As mouse primary corneal epithelial cells are difficult to culture and cell lines are not available, we examined the effect of IFN-␥ on MD-2 mRNA and protein expression in primary human corneal epithelial (HCE) cells in an SV40-transfected HCE cell line (HCEC) (9,21,26) and in a telomerase immortalized HCE cell line (HCET) (20).…”