Fibronectin receptor defects in NOD mouse leucocytes: possible consequences for type 1 diabetes

Sphingosine-1-Phosphate Receptor 1 Is Involved in Non-Obese Diabetic Mouse Thymocyte Migration Disorders

NOD (non-obese diabetic) mice spontaneously develop type 1 diabetes following T cell-dependent destruction of pancreatic β cells. Several alterations are observed in the NOD thymus, including the presence of giant perivascular spaces (PVS) filled with single-positive (SP) CD4⁺ and CD8⁺ T cells that accumulate in the organ. These cells have a decreased expression of membrane CD49e (the α5 integrin chain of the fibronectin receptor VLA-5 (very late antigen-5). Herein, we observed lower sphingosine-1-phosphate receptor 1 (S1P1) expression in NOD mouse thymocytes when compared with controls, mainly in the mature SP CD4⁺CD62L^hi and CD8⁺CD62L^hi subpopulations bearing the CD49e^− phenotype. In contrast, differences in S1P1 expression were not observed in mature CD49e⁺ thymocytes. Functionally, NOD CD49e^− thymocytes had reduced S1P-driven migratory response, whereas CD49e⁺ cells were more responsive to S1P. We further noticed a decreased expression of the sphingosine-1-phosphate lyase (SGPL1) in NOD SP thymocytes, which can lead to a higher sphingosine-1-phosphate (S1P) expression around PVS and S1P1 internalization. In summary, our results indicate that the modulation of S1P1 expression and S1P/S1P1 interactions in NOD mouse thymocytes are part of the T-cell migratory disorder observed during the pathogenesis of type 1 diabetes.

Adhesive substrates modulate the activation and stimulatory capacity of non-obese diabetic mouse-derived dendritic cells

It is known that adsorbed adhesive proteins on implanted biomaterials modulate inflammatory responses; however, modulation of dendritic cell (DC) responses upon interaction with adhesive proteins has only begun to be characterized. DCs are specialized antigen-presenting cells that modulate both innate and adaptive immune responses. Previously we have shown that the activation and stimulatory capacity of DCs derived from C57BL6/j mice is differentially modulated by adhesive substrates. Here we extend our investigation of adhesive substrate modulation of DC responses to consider the case where the DCs had maturational defects associated with diabetes. Understanding the adhesive responses of DCs in diabetics is potentially important for immunotherapy and tissue engineering applications. In this work we use the non-obese diabetic (NOD) mouse, an established animal model for type 1 diabetes, to generate DCs (NOD-DCs). We demonstrate that NOD-DCs cultured on different adhesive substrates (collagen, fibrinogen, fibronectin, laminin, vitronectin, albumin and serum) respond with substrate-dependent modulation of the surface expression of the stimulatory molecule MHC-II and the co-stimulatory molecules CD80 and CD86 and production of the cytokines IL-12p40 and IL-10. Furthermore, the capacity of NOD-DCs to stimulate CD4(+) T-cell proliferation and cytokine production (IL-4 and IFN-γ) showed substrate-dependent modulation. Specifically, NOD-DCs cultured on vitronectin induced the highest IL-12p40 production, whereas collagen induced the highest IL-10 production. Dendritic cells cultured on collagen, fibrinogen and serum-coated substrates stimulated the highest CD4(+) T-cell proliferation. It was further determined that DCs cultured on vitronectin induced the highest percent population of IL-4-producing T-cells and DCs cultured on a fibronectin-coated substrate induced the highest expression of IFN-γ in T-cells. Pearson's correlation analysis revealed high correlations between T-cell proliferation and DC expression level of CD80 and T-cell production of IL-4 and DC production of IL-10. This demonstration of substrate-based control of NOD-DC activatory and stimulatory capacity, distinct from non-diabetic B6-DC responses, establishes the field of adhesive modulation of immune cell responses and informs the rational design of biomaterials for patients with type 1 diabetes.

Thymic microenvironmental alterations in experimentally induced diabetes

Little is known about the immunologic consequences from endocrine changes observed in diabetes. Since a preserved thymic microenvironment is of critical importance for the T cell development and maturation, we have examined the thymus from alloxan-diabetic mice. An intense thymic atrophy accompanied by changes in histological pattern and in thymocyte subpopulations were observed in diabetic mice. Laminin and fibronectin, which are closely associated with thymocytes maturation, were evaluated, but, only laminin presented an altered distribution and density in thymuses from diabetes group. the expression of fibronectin and laminin receptors was found to be decreased in diabetic mice. There was also intense decrease in the expression of two important chemokines for thymus, CCL25 and CXCL12, and in the CCR9 (CCL25 receptor), but the expression of CXCR4 (CXCL12 receptor) did not drop on cells. However, no significant difference was observed in the in vitro thymocytes migratory capacity from diabetic mice. The results show significant alterations in thymus microenvironment in diabetes and offer insights for studies involving endocrine influences on lymphatic organs and T cell maturation.

Fibronectin-alpha4beta1 integrin interactions regulate metalloproteinase-9 expression in steatotic liver ischemia and reperfusion injury

Ischemia/reperfusion injury is a major cause of the highly dysfunctional rate observed in marginal steatotic orthotopic liver transplantation. In this study, we document that the interactions between fibronectin, a key extracellular matrix protein, and its integrin receptor alpha4beta1, expressed on leukocytes, specifically up-regulated the expression and activation of metalloproteinase-9 (MMP-9, gelatinase B) in a well-established steatotic rat liver model of ex vivo ice-cold ischemia followed by isotransplantation. The presence of the active form of MMP-9 was accompanied by massive intragraft leukocyte infiltration, high levels of proinflammatory cytokines, such as interleukin-1beta and tumor necrosis factor-alpha, and impaired liver function. Interestingly, MMP-9 activity in steatotic liver grafts was, to a certain extent, independent of the expression of its natural inhibitor, the tissue inhibitor of metalloproteinases-1. Moreover, the blockade of fibronectin-alpha4beta1-integrin interactions inhibited the expression/activation of MMP-9 in steatotic orthotopic liver transplantations without significantly affecting the expression of metalloproteinase-2 (MMP-2, gelatinase A). Finally, we identified T lymphocytes and monocytes/macrophages as major sources of MMP-9 in steatotic liver grafts. Hence, these findings reveal a novel aspect of the function of fibronectin-alpha4beta1 integrin interactions that holds significance for the successful use of marginal steatotic livers in transplantation.