Aim: To observe whether the TIR-domain-containing adaptor inducing interferon-β (TRIF) is activated in THP-1 cells treated with β₂ GPI/anti-β₂ GPI complex and investigate the roles of TRIF-dependent signaling pathway of Toll-like receptor 4 (TLR4) in antiphospholipid syndrome (APS).
Methods: The total RNA was extracted and the protein lysates were collected from THP-1 cells stimulated with β₂ GPI/anti-β₂ GPI complex. And the level of TRIF mRNA in THP-1 cells was detected by Real-time PCR (RT-PCR), TRIF protein expression was investigated by western blotting, respectively. Furthermore, whether TLR4 inhibitor, TAK-242, could interrupt the expression of TRIF as well as some inflammatory cytokines such as IL-6, IL-8 and TNF-α in THP-1 cells stimulated with β₂ GPI/anti-β₂ GPI complex was also investigated.
Results: Both mRNA and protein levels of TRIF could be significantly increased in THP-1 cells with treatment of β₂ GPI/anti-β₂ GPI complex (100 mg/L). The expression of TRIF was shown in a manner of time-dependence, with the maximal levels at 1 hour (mRNA) and 2 hour (protein) stimulation respectively. The β₂ GPI/anti-β₂ GPI complex-induced TRIF and inflammatory cytokines including IL-6, IL-8 and TNF-α expression in THP-1 cells could be inhibited by TAK-242 (5 μmol/L).
Conclusion: TRIF-dependent signaling pathway of Toll-like receptor 4 is involved in the activation of THP-1 cells induced by β₂ GPI/anti-β₂GPI complex, suggesting that TRIF may play an important role in the pathogenesis of antiphospholipid syndrome.