Factors Associated with Higher Pro-Inflammatory Tumor Necrosis Factor-α Levels in Young Women with Type 1 Diabetes

Dermal fibroblasts cultured from donors with type 2 diabetes mellitus retain an epigenetic memory associated with poor wound healing responses

The prevalence of Type 2 diabetes mellitus (T2DM) is escalating globally. Patients suffer from multiple complications including the development of chronic wounds that can lead to amputation. These wounds are characterised by an inflammatory environment including elevated tumour necrosis factor alpha (TNF-α). Dermal fibroblasts (DF) are critical for effective wound healing, so we sought to establish whether there were any differences in DF cultured from T2DM donors or those without diabetes (ND-DF). ND- and T2DM-DF when cultured similarly in vitro secreted comparable concentrations of TNF-α. Functionally, pre-treatment with TNF-α reduced the proliferation of ND-DF and transiently altered ND-DF morphology; however, T2DM-DF were resistant to these TNF-α induced changes. In contrast, TNF-α inhibited ND- and T2DM-DF migration and matrix metalloprotease expression to the same degree, although T2DM-DF expressed significantly higher levels of tissue inhibitor of metalloproteases (TIMP)-2. Finally, TNF-α significantly increased the secretion of pro-inflammatory cytokines (including CCL2, CXCL1 and SERPINE1) in ND-DF, whilst this effect in T2DM-DF was blunted, presumably due to the tendency to higher baseline pro-inflammatory cytokine expression observed in this cell type. Collectively, these data demonstrate that T2DM-DF exhibit a selective loss of responsiveness to TNF-α, particularly regarding proliferative and secretory functions. This highlights important phenotypic changes in T2DM-DF that may explain the susceptibility to chronic wounds in these patients.

Dominant TNFα and impaired IL-2 cytokine profiles of CD4+ T cells from children with type-1 diabetes

Aberrantly activated CD4⁺ T memory cells play a central role in the development of type-1-diabetes. Interleukin-7 promotes generation of autoimmune memory T cells and increased Interleukin-7 availability is associated with type-1-diabetes susceptibility. T-cell-mediated immune pathology at onset of type-1-diabetes is well defined, but characteristics of long-term symptomatic disease stages remain largely elusive. In the present study, memory CD4⁺ T-cell activation and cytokine expression as well as sensitivity to Interleukin-7 in vitro were compared between patients with type-1-diabetes at clinical onset (n=25), long-term symptomatic disease (median duration 4.5 years, n=19) and matched healthy controls (n=21). T-cell responses of type-1-diabetes patients were characterized by higher frequencies of cytokine and activation marker expressing CD4⁺ memory T cells as compared to healthy controls. Notably, correction for individual cytokine expression levels revealed qualitative differences of cytokine profiles characterized by significantly increased TNFα and decreased IL-2-expressing T-cell proportions in long-term type-1-diabetes patients. IL-7-mediated T-cell co-stimulation induced quantitative and qualitative cytokine expression differences highly similar to type-1-diabetes-specific profiles. In addition, CD4⁺ memory T cells from children with long-term type-1-diabetes were more sensitive to in vitro IL-7 co-stimulation. Global transcriptome analysis revealed IL-7 induced expression differences of CD4⁺ T cells, including increased IL-2R expression and effects on subsequent T-cell receptor activation. We conclude that long-term symptomatic type-1-diabetes patients differed in memory T-cell cytokine profiles and Interleukin-7 co-stimulation. Regulation of IL-2 expression and sensitivity are affected with possible consequences for disease course and severity at long-term type-1-diabetes stages.