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Abstract: Thrombomodulin (TM) is a single-transmembrane glycoprotein receptor for thrombin, which is best known as a cofactor for thrombin-mediated activation of anticoagulant protein C. C-type lectin-like domain (CTLD) of TM has distinct coagulation/fibrinolysis-independent anti-inflammatory properties. Here we found anti-inflammatory effects of a novel peptide (GC31) from CTLD of TM in endotoxin-induced uveitis, which was characterized by a reduction of leukocyte counts, protein concentration, tumor necrosis factor (TNF)-α and monocyte chemoattractant protein (MCP)-1 levels in aqueous humor. Through in vitro experiments, we further found that GC31 suppressed TNF-α and interleukin (IL)-6 expressions in lipopolysaccharide (LPS)-stimulated macrophage-like RAW264.7 cells and interrupted LPS-induced nuclear factor-κB (NF-κB) activation. These data indicate a beneficial role of peptide GC31 in preventing intraocular inflammatory response, especially uveitis. [Copyright &y& Elsevier]

In keratitis, keratocytes play a vital role by releasing inflammatory cytokines and expressing intercellular cell adhesion molecule-1(ICAM-1). GC31 is a peptide derived from thrombomodulin, an endogenous protein with potential anti-inflammation properties. We evaluated the protective effect of GC31 in LPS- or poly(I:C)-induced corneal fibroblasts. Cultured keratocytes were treated with either LPS or poly(I:C); The mRNA and protein expressions of IL-6, IL-8, MCP-1, and IFN-γ were determined by real-time RT-PCR and ELISA. The expression level of ICAM-1 was estimated by real-time RT-PCR, immunofluorescence, and western blot. The underlying pathways were investigated by detecting NF-κB p65 translocation and phosphorylation of IκBα, p65, p38, JNK, and ERK. The MTS assay was used to measure cell viability of keratocytes after GC31 incubation. The elevation of IL-6, IL-8, MCP-1, and IFN-γ expression induced by LPS or poly(I:C) was significantly inhibited by GC31 in a dose-dependent manner at both mRNA and protein levels. GC31 also reduced the expression of ICAM-1 in keratocytes after LPS or poly(I:C) stimulation. LPS or poly(I:C) induced p65 translocation and phosphorylation of IκBα, p65, p38, and JNK were suppressed by GC31.GC31 is not only an effective inhibitor of LPS-induced inflammatory response, but it also inhibits poly(I:C)-induced release of inflammatory cytokines and ICAM-1 expression by blocking the NF-κB and MAPK (p38 and JNK) pathways. This suggested that GC31 may exert a protective effect in attenuating corneal inflammation by suppressing the immune response of the fibroblasts. [ABSTRACT FROM AUTHOR]

Keratitis is a worldwide sight-threatening disease. Current drugs generate various adverse effects. Large molecules hardly penetrate ocular tissues. Small peptides derived from endogenous protein display certain advantages. Previously we indentified a novel peptide (PAPep) from human pancreatitis-associated protein (PAP), a protein with protective effect against inflammatory diseases. To further examine the effect of PAPep on inflammatory disease and expand its scope of potential clinical application, especially in keratitis, we tested the effect of PAPep on various aspects of lipopolysaccharide (LPS)—induced corneal inflammation in vivo and in vitro. Dexamethasone (DXM) was used as a drug control. Our results suggested that PAPep suppressed the clinical manifestation, histological disorder and inflammatory cells infiltration and reduced the release of interleukin (IL)-6, IL-8 and monocyte chemotactic protein (MCP)-1 in the cornea. Moreover, PAPep inhibited LPS-induced mRNA and protein expression of the three cytokines in the corneal fibroblasts, prevented translocation of NF–κB and interrupted the phosphorylation of IKKα/β/IκBα/NF–κB. Our study demonstrates that PAPep could effectively attenuate LPS-induced keratitis, more likely by virtue of inhibiting the activation of the IKKα/β/IκBα/NF–κB pathway. PAPep may be considered to be a promising and safe drug for therapeutic application for ocular inflammation. [ABSTRACT FROM AUTHOR]