Aim: To determine the relationship of ER stress and IL-10 signalling pathway in type 1 diabetic patients (T1D), first degree relatives (FDR) and healthy controls (HC).
Background: Autoimmune diseases, including T1D, result from disordered immune tolerance. We have previously shown that an endoplasmic reticulum (ER) stress signature predicted poor outcome in recent-onset T1D patients, and in a proportion of at-risk FDR. IL-10 is a cytokine with pleiotropic effects in immunoregulation and inflammation. Binding of IL-10 to its receptor (IL-10R) leads to phosphorylation of Signal Transducer and Activator of Transcription (STAT)3. IL-10 has been shown to block ER stress in gut epithelium and to prevent protein misfolding in goblet cells in a STAT3 dependent manner.
Method: We compared monocyte and T cell constitutive total (T)-and phospho (P)-STAT3 and its response to in-vitro IL-10 or IL-6 stimulation in 30 T1D, 35 FDR and 11 HC. IL-10 receptor with or without Tunicamycin treatment was detected in peripheral blood monocytes and T cells by flow cytometry. Expression of ER stress genes GRP78 and DDIT3 and IL-10Ra, b were quantified by RT-PCR from peripheral blood mononuclear cells relative to HPRT.
Results: IL-10 but not IL-6 induced or basal p-STAT3 was significantly reduced in monocytes and T cells of T1D and FDR compared to HC. Correlated to IL-10 induced p-STAT3, IL-10R expression in monocytes and T cell was markedly reduced, while there was no difference in IL-10Ra, B gene expression. GRP78 and DDIT3 were higher in T1D patients than HC and were inversely correlated to IL-10R or IL-10 induced P-STAT3. Reduction in IL-10R expression in CD3+ T cells was noticed after exposure to ER stress inducing agent Tunicamycin in T1D and FDR but not HC.
Conclusion: These results suggest that ER stress in T1D and FDR could act in a negative feedback loop reducing IL-10R expression and subsequently IL-10-induced P-STAT3 which further impairs the ability of the T cells to regulate ER stres.