The expression of intercellular adhesion molecule-1 induced by CD40-CD40L ligand signaling in orbital fibroblasts in patients with Graves' ophthalmopathy.

PURPOSE

The aim of the present study was to examine the effect of CD40 ligand (CD40L) on intercellular adhesion molecule-1 (ICAM-1) production and involvement of mitogen-activated protein kinases (MAPKs) and nuclear factor-kappaB (NF-kappaB) signaling pathways by CD40-CD40L ligand in orbital fibroblasts (OFs) in patients with Graves' ophthalmopathy (GO).

METHODS

OFs were stimulated with soluble CD40L, and conditioned media and lysed cells were subjected to Western blot and real-time quantitative polymerase chain reaction analyses. Inhibitors specific to various signal transduction pathways were used to determine the signal pathways involved.

RESULTS

ICAM-1 protein and mRNA in OFs of GO groups were upregulated by CD40L compared with those in normal OFs. Treatment of OFs with CD40L increased ICAM-1 mRNA levels in a dose- and time-dependent manner. CD40L induced the phosphorylation of p38 MAPK, extracellular-regulated kinase1/2 (ERK1/2), c-Jun NH2-terminal kinase (JNK), and IkappaB and the activation of NF-kappaB. Inhibition of the ERK1/2, p38, JNK, and NF-kappaB pathways blocked CD40L-induced ICAM-1 secretion. Furthermore, the activation of NF-kappaB was significantly affected by ERK1/2 and JNK inhibitors, but not by p38. OF ICAM-1 expression was predominantly p38 MAPK and NF-kappaB dependent. ERK1/2 and JNK were implicated in the NF-kappaB pathway. Analyses of ICAM-1 mRNA synthesis revealed that CD40L-induced ICAM-1 expression was mediated by multiple factors.

CONCLUSIONS

CD40L can potently induce ICAM-1 expression in OF cells through multiple signal pathways. The p38 MAPKs and NF-kappaB pathways may play an important permissive role in CD40L-induced ICAM-1 expression in OFs.