The Role Of IL-27and AhR In The Pathogenesis Of Vogt-koyanagi-harada Syndrome And Behcet’s Disease

BackgroundUveitis usually refers to the inflammation that occurres in uveal, retina andretinal vascular. It more occures in young adults, intractable, andirreversible and permanent blindness as its damage to the retina. VKH isan autoimmune disease characterized by uveitis, meningeal irritation,vitiligo and hearing damage. Behcet’s disease is characterized by Behcet’sdisease (BD) is an autoinflammatory disease characterized by ocular,mucosal, skin and neurological lesions. VKH syndrome and Behcet’sdisease are the most common and the highest rate that lead to blindness ofuveitis entities. However, the pathogenesis of the above two kind ofuveitis are unclear and it is currently recognized as an autoimmunedisorder was involved in the pathogenesis of the two diseases. Previousresearches have reported that there was an imbalance of the fucntion andnumber between Th17and Treg cell was involved in the development ofthe two diseases.IL-27is mainly secreted by the antigen presenting cells, recent studieshave shown that IL-27has immunosuppressive properties and can suppress experimental autoimmune encephalomyelitis (EAE) andexperimental autoimmune uveitis(EAU) by inhibiting the development orexpansion of Th17cells and by inducing T regulatory (Tr1) cells. However,IL-27role in human autoimmune disease is not clear. Recently, It has beenreported that aryl hydrocarbon receptor(AhR) participated thedevelopment of autoimmune disease and inflammation. ITE, a kind ofAhR ligands, could inhibit the development of EAE by inhibiting Th17cell immune response. And AhR knockout macrophage could secrete moreinflammatory cytokines. But the role of AhR in the human autoimmunedisease is not still clear.Based on the above background, the main subject included thefollowing two experiments:(1)To investigate the expression of IL-27andAhR in uveitis patiens with VKH syndrome or Behcet’s disease, so that wecan determine whether it was involved in the development and progressionof both two diseases.(2) Further to explore the role and mechanism bywhich IL-27and AhR activation participate in these two diseases. Throughthese studies to elucidate the pathogenesis of these diseases, and toprovide new strategies and new targets for prevention and treatment ofthese diseases. PartⅠ The role of IL-27in the pathogenesis ofVogt-Koyanagi-Harada diseasePurposeAlthough VKH disease is considered to be autoimmune disease, itsexact pathogenesis remains unclear. IL-27has emerged as an importantregulator of proinflammatory T cell responses in animal models. Weinvestigated the pathophysiological role of IL-27inVogt-Koyanagi-Harada (VKH) disease.MethodsIL-27P28and EBI3mRNA expression in peripheral blood mononuclearcells (PBMCs) frome VKH patients and normal controls were assayed byRT-PCR. Cytokines in the serum and supernatants of PBMCs, na ve CD4+T cells and DC-T cocultures were assayed by ELISA. The frequencies ofIL-17–producing CD4+T cells were evaluated by flow cytometry.ResultsThe active VKH patients showed a decreased IL-27P28mRNAexpression in PBMCs and lower IL-27expression in the serum andsupernatants of PBMCs, but a higher Th17cells in PBMCs. EBI3mRNAexpression was not different among the groups tested. Stimulation ofna ve CD4+T cells under Th17polarizing conditions showed a higherTh17cell differentiation in active VKH patients. IL-27significantly inhibited Th17cell differentiation. IL-27-treated DCs showed a significantinhibition on Th17differentiation. There was a significant defect in theTr1cell induction as measured by IL-10in active VKH patients.Treatment with corticosteroids and cyclosporine A (CsA) resolved theintraocular inflammation in association with an upregulation of IL-27anda downregulation of IL-17. In vitro experiments showed thatcorticosteroids, but not CsA, significantly upregulated the expression ofIL-27.ConclusionsThe present study suggests that decreased IL-27expression may resultin a higher Th17in active VKH patients, which may promote theautoimmune response observed in these patients. Manipulation of IL-27may offer a novel target for treatment of this disease.PartⅡ The role of aryl hydrocarbon receptor in thepathogenesis of Behcet’s diseasePurposeThe aryl hydrocarbon receptor (AhR) is emerging as an importantcontrol element of immune and inflammatory responses. AhR exerts itsrole via interaction with various ligands, such as6-formylindolo[3,2-b]carbazole (FICZ), and2-(1′Hindole-3′ -carbonyl)-thiazole-4-carboxylic acid methyl ester (ITE). We investigatedthe role of AhR activation in Behcet’s disease, which is a typicalrepresentative of an autoinflammatory disease and studied theimmunological pathways involved.MethodsAhR expression in peripheral blood mononuclear cells (PBMCs) wasevaluated using RT-PCR. The effect of FICZ and ITE on PBMCs, CD4+Tcells and DCs was detected by ELISA and flow cytometry. Flowcytometry and RT-PCR were performed to study the mechanisms involvedin the effect of FICZ and ITE on CD4+T cells. Human monocyte-derivedDCs were generated from monocytes stimulated with GM-CSF and IL-4.Cytokine production by DCs stimulated with or without AhR ligands andCD4+T cells that were cocultured with DCs was detected by ELISA. Thefrequency of Th1and Th17cells and the surface markers of FICZ orITE-treated DCs were determined by flow cytometry.ResultsAhR expression was significantly decreased in Behcet’s disease.Both FICZ and ITE inhibited Th1and Th17polarization, and inducedIL-22production. FICZ and ITE caused a decreased expression of keytranscription factors of Th1and Th17cells and increased STAT3andSTAT5phosphorylation. we showed that AhR activation by FICZ and ITEdownregulated the expression of co-stimulatory molecules including HLA-DR, CD80and CD86, while it had no effect on the expression ofCD83and CD40on DCs derived from BD patients and normal controls.LPS-treated DCs from active BD patients showed a higher level of IL-1β,IL-6, IL-23and TNF-α production. FICZ or ITE significantly inhibitedthe production of IL-1β, IL-6, IL-23and TNF-α, but induced IL-10production by DCs derived from active BD patients and normal controls.FICZ or ITE-treated DCs significantly inhibited the Th17and Th1cellresponse.ConclusionsThe present study suggests that a decreased AhR expression isassociated with disease activity in Behcet’s disease. Lower AhRactivation may result in an enhanced Th1and Th17immune response.AhR activation may offer a possible novel therapeutic approach for BDand other autoinflammatory disorders.