Toll-like receptor 2–mediated NF-κB inflammatory responses in dry eye associated with cGVHD

PURPOSE Dry eye syndrome is one of the most common pathological manifestations in patients with chronic graft-versus-host disease (cGVHD). When dry eye occurs in association with cGVHD, the local inflammation is secondary to the systemic onset of inflammation. Toll-like receptor 2 (TLR2) signaling is thought to be essential for the inflammatory response and for immune disorders. The aim of this study was to explore whether the TLR2-mediated nuclear factor-kappa B (NF-κB) signaling pathway contributes to the inflammatory process of dry eye associated with cGVHD. METHODS Twenty patients with dry eye related to cGVHD and 20 controls were enrolled in this study. The patients with dry eye associated with cGVHD were diagnosed based on the clinical presentation and related ocular surface examinations such as Schirmer's test and fluorescein staining. In addition, dry eye symptom scoring (National Institutes of Health consensus criteria) and Ocular Surface Disease Index (OSDI) scoring were also evaluated in all patients. Peripheral blood was collected from the patients and the controls for subsequent experiments. mRNA levels of TLR2 and its downstream molecules, NF-κB and tumor necrosis factor (TNF)-α, were measured by quantitative Real-Time PCR (qRT-PCR). The protein level of TNF-α was detected by Enzyme-linked Immuno Sorbent Assay (ELISA). RESULTS TLR2 mRNA in the peripheral blood from patients with dry eye related to cGVHD increased significantly compared with the controls. NF-κB, the downstream target of TLR2, also showed a marked elevation. The mRNA and protein levels of TNF-α were significantly upregulated in these patients. Importantly, the TLR2 level was strongly correlated with the OSDI and the Schirmer's test (r=0.565, p=0.010<0.05; r=0.564, p=0.016<0.05) in dry eye related to cGVHD compared with the controls. CONCLUSIONS The TLR2-mediated NF-κB signaling pathway is activated in dry eye associated with cGVHD and contributes to the inflammatory state, which may predict the onset and progression of dry eye associated with cGVHD.