Curative and β cell regenerative effects of α1-antitrypsin treatment in autoimmune diabetic NOD mice

Abstract

Invasive insulitis is a destructive T cell-dependent autoimmune process directed against insulin-producing ␤ cells that is central to the pathogenesis of type 1 diabetes mellitus (T1DM) in humans and the clinically relevant nonobese diabetic (NOD) mouse model. Few therapies have succeeded in restoring long-term, drug-free euglycemia and immune tolerance to ␤ cells in overtly diabetic NOD mice, and none have demonstrably enabled enlargement of the functional ␤ cell mass. Recent studies have emphasized the impact of inflammatory cytokines on the commitment of antigen-activated T cells to various effector or regulatory T cell phenotypes and insulin resistance and defective insulin signaling. Hence, we tested the hypothesis that inflammatory mechanisms trigger insulitis, insulin resistance, faulty insulin signaling, and the loss of immune tolerance to islets. We demonstrate that treatment with ␣1-antitrypsin (AAT), an agent that dampens inflammation, does not directly inhibit T cell activation, ablates invasive insulitis, and restores euglycemia, immune tolerance to ␤ cells, normal insulin signaling, and insulin responsiveness in NOD mice with recent-onset T1DM through favorable changes in the inflammation milieu. Indeed, the functional mass of ␤ cells expands in AAT-treated diabetic NOD mice.autoimmunity ͉ type 1 diabetes ͉ inflammation A destructive T cell-dependent autoimmune process directed against insulin-producing ␤ cells causes type 1 diabetes mellitus (T1DM) in humans and the nonobese diabetic (NOD) mouse model (1, 2). Although many therapeutic interventions, including viral-mediated gene transfer of human ␣1-antitrypsin (AAT) (3), can prevent T1DM or resolve the T cell-rich, ␤ cell-invasive insulitis lesion in prediabetic hosts, surprisingly few therapies have succeeded in restoring long-term drug-free euglycemia and immune tolerance to ␤ cells in overtly diabetic NOD mice (4-8). Although each of these successful therapies directly targets T cells, each bears an element that may dampen proinflammatory responses or their consequences upon target tissues.Inflammatory cytokines direct the commitment of antigenactivated CD4 ϩ T cells to specific effector or Foxp3ϩ regulatory phenotypes (9-11). In addition, islets are sensitive to proinflammatory cytokines (12-15). Adverse inflammation in muscle and fat causes faulty insulin signaling and insulin resistance (16) in type 2 diabetes mellitus (13) and, as recently shown, T1DM (7,17). Hence, we have tested the hypothesis that treatment with AAT, an acutephase reactant with known antiinflammatory and antiapoptotic effects (18-21) including effects on islets (21,22), is effective in NOD mice with overt new-onset T1DM. In short, we are probing the hypothesis that inflammatory mechanisms trigger T1DM. Results AAT Does Not Inhibit T Cell Activation.Purified carboxyfluorescein diacetate succinmidyl ester (CFSE)-labeled C57BL/6 mouse T cells were stimulated with plate-bound anti-CD3 plus soluble anti-CD28 mAbs. AAT did not impair T cell proliferation or acquisition of an ...

Alpha 1-antitrypsin reduces inflammation and enhances mouse pancreatic islet transplant survival

“…In short, the promise of islet cell transplantation in the clinic cannot be realized in the absence of engraftment of healthy and resilient islets. We hypothesized correctly that administration of AAT, an acute phase reactant that serves to quench adverse inflammation (16) and promote islet cytoprotection (10,15,16) would protect autologous islet transplants from destruction and thereby help create and preserve a euglycemic state. The beneficial effects of AAT were readily detectable at the molecular as well as functional levels.…”

Alpha-1-antitrypsin in cell and organ transplantation

“…Anti‐apoptotic effects, inhibition of injurious innate immune responses and other anti‐inflammatory effects, as well as increases in Tregs all likely contribute to beneficial effects of AAT in animal models. They may also contribute to observations that AAT has beneficial effects against autoimmune diabetes in “nonobese diabetic” (NOD) mice, as well as in type 1 diabetes in humans 12, 28…”

“…7 In both murine and human studies, AAT was reported to modulate donor‐derived dendritic cells and to increase CD4+, CD25+ FoxP3+ Tregs 6. These results suggest that a major net effect of AAT in transplantation may be to shift an inflammatory, sensitizing environment to an anti‐inflammatory, tolerance‐inducing environment 28. Initiation of these changes by AAT in the early posttransplant period could decrease the risk of delayed graft function and also promote long‐term graft acceptance.…”

“…Many effects of AAT may involve inhibition of proteases produced by 1 cell that act on adjacent cells and/or inhibition of protease‐activated receptors. Together with intracellular effects, these membrane effects likely contribute to a net decrease in cytokines that favor sensitization, such as IL‐1, TNFα, IL‐6, and IL‐32, while promoting tolerance by preserving transforming growth factor‐β and increasing IL‐10 and IL‐1 receptor antagonist 4, 6, 7, 24, 25, 26, 27, 28. These effects likely contribute to the induction of regulatory T cells (Tregs) that promote allograft survival 6, 7, 9, 25, 26, 27, 28.…”

Identification of the immunodominant cytotoxic T-cell epitope of human -1 antitrypsin

“…Moreover, the hAAT protein itself may have tolerogenic immune properties, since it has recently been shown to induce tolerance to insulin-producing b cells in non-obese diabetic mice and to protect transplanted islet allografts from rejection through the induction of regulatory T cells. 6,7 These observations underscore the need to analyze the ensuing CTL response to hAAT and its modulation by gene transfer vectors, especially since AAV encoding hAAT is currently being pursued in human clinical trials. 8 In this study, we report identification of an immunodominant cytotoxic T lymphocyte epitope of hAAT restricted by H2-D b in C57BL/6 mice that allows us to further characterize the adaptive immune responses after hAAT gene transfer.…”