Abstract
PurposeTo explore whether IRAK1 and IRAK4 are involved in the pathogenesis of Vogt-Koyanagi-Harada (VKH) disease.MethodsThirty-nine VKH patients and thirty-two healthy controls were included in this study. The mRNA levels of IRAK1 and IRAK4 from active VKH patients, inactive VKH patients, and normal controls in peripheral blood mononuclear cells (PBMCs) were detected using real-time quantitative PCR. CD4+T cells were purified from PBMCs obtained from active VKH patients and normal controls. The effect of IRAK1/4 inhibition on CD4+T cell proliferation following stimulation with IL-18 or IL-1β was measured using a modified MTT assay. CD4+T cell expression of IFN-γ and IL-17 were detected by flow cytometry (FCM) and enzyme-linked immunosorbent assay (ELISA). The effect of IRAK1/4 inhibition on NF-κB, STAT1, and STAT3 activation was detected by FCM.ResultsThe mRNA levels of IRAK1 and IRAK4 were both significantly increased in active VKH patients compared to inactive VKH patients and healthy controls. No difference in the IRAK1 or IRAK4 mRNA level could be detected between inactive patients and healthy controls. After incubation with IRAK1/4 inhibitor, the proliferation of CD4+T cells was inhibited both in the active VKH patients and in the healthy controls. IRAK1/4 inhibition was also associated with a decreased expression of IFN-γ and IL-17. Phosphorylation of NF-κB, STAT1, and STAT3 in CD4+T from healthy controls was significantly decreased after inhibition of IRAK1/4.ConclusionsHigh mRNA levels of IRAK1 and IRAK4 correlated with VKH disease activity. IRAK1 and IRAK4 play a role in the activation and proliferation of CD4+T cells and the higher expression observed in VKH may contribute to the pathogenesis of this blinding condition.
Highlights
Interleukin-1 receptor-associated kinases (IRAKs) are a unique family of death domain containing protein kinases that play a key role in the signaling cascades of two receptor families, toll-like receptors (TLRs) and interleukin-1 receptors (IL-1Rs)
IRAK1 and IRAK4 mRNA level from peripheral blood mononuclear cells (PBMCs) is increased in active VKH patients
The mRNA level of IRAK1 and IRAK4 in PBMCs was determined by real-time PCR
Summary
Interleukin-1 receptor-associated kinases (IRAKs) are a unique family of death domain containing protein kinases that play a key role in the signaling cascades of two receptor families, toll-like receptors (TLRs) and interleukin-1 receptors (IL-1Rs). IRAKs are categorized as serine/threonine protein kinases and all contain a kinase-like domain, only IRAK1 and IRAK4 exhibit kinase activity [1,2,3]. It has been reported that mice deficient for IRAK4 are severely impaired in their cellular responses to IL-1, IL-18, and most TLR ligands, sharing an overlapping phenotype with IRAK4-deficient human patients [7]. IRAK4-deficient mice display broad susceptibility to viral and bacterial infections, IRAK4-deficient human patients exhibit a narrow infectious phenotype, limited primarily to pyogenic bacterial infections at an early age [8,9]. IRAK1-deficient mice were impaired in their ability to develop experimental autoimmune encephalomyelitis (EAE) [12]
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