Alpha-1 Antitrypsin (AAT) Promotes Islets Graft Survival by Modulating Macrophage Activation

Abstract

Infiltrating macrophages can induce inflammation by secretion of proinflammatory cytokines and contribute to islet graft loss shortly after islet transplantation. In this study, we tested the mechanistic effects of AAT in mitigating macrophage mediated inflammation in an intrahepatic islet transplantation model in which human islets (2500 islet equivalent numbers) were transplanted into NOD-SCID mice that had been rendered diabetic (blood glucose >350mg/dl) by streptozotocin treatment. AAT (Prolastin-C, Grifols) was given to recipients intraperitoneally at 4 mg/mouse, every two days for 14 days, beginning before transplantation. In those recipients receiving AAT (n=29), 69.0% reached normoglycemia, compared to 35.7% in controls (n=28, p=0.002, logrank test) at 30 days post transplantation. Compared to mice treated with vehicle, AAT-treated mice had lower serum levels of interleukin 1 β (IL-1β), interferon- γ (IFN-γ) and interleukin 6 (IL-6), at day 1 post transplantation. To explore potential cell target(s) of AAT action, we analyzed activation of macrophages infiltrated into the liver after transplantation. Fewer M1 macrophages were observed in AAT-treated mice than in controls. To measure the effects of AAT on macrophage activation, we added AAT to Raw264.7 cells stimulated with IFN-γ in vitro. Expressions of M1 markers (iNOS, CD11c, TNFα, and IL-6) were dramatically decreased in AAT-treated cells compared to vehicle-treated controls. Co-culture of IFN-γ activated macrophages with islets led to islet cell apoptosis. Addition of AAT in the co-culture system reduced macrophage activation and protected islet cells from apoptosis. In summary, AAT treatment significantly enhances human islet graft survival and function after transplantation into the liver of NOD-SCID mice, in part by suppression of macrophage activation and pro-inflammatory cytokine production. Disclosure W. Gou: None. J. Wang: None. D. Kim: None. L. Song: None. C. Strange: Research Support; Self; Grifols, CSL Behring, Shire. Consultant; Self; Shire. Stock/Shareholder; Self; Abeona. Consultant; Self; CSL Behring. Research Support; Self; Adverum. Consultant; Self; Adverum. Research Support; Self; MatRx. D. Adams: None. K. Morgan: None. H. Wang: None.