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

Abstract

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.