1681-P: Alpha-1 Antitrypsin Suppresses Macrophage Activation Post Islet Transplantation

Abstract

Macrophage activation contributes to islet graft loss after transplantation by secretion of proinflammatory cytokines. We showed in previous studies that treatment with alpha-1 antitrypsin (AAT) improved human islet survival after transplantation into the livers of streptozotocin-induced diabetic NOD-SCID mice. To further understand the cellular targets of AAT, we isolated macrophages from control or AAT-treated recipients at day 1 post transplantation (PT) and compared their mRNA profile using RNAseq analysis. 344 genes were changed in AAT-treated recipients compared to controls. Clusters of the inflammatory response, chemokine activity and cytokine and cytokine receptor Gene Otology categories and pathways were significantly affected by AAT-treatment. In vitro, AAT suppressed IFN-γ-induced Raw267.4 cell activation via suppression of STAT1 phosphorylation and iNOS production. This was translated in vitro when human islets were co-transplanted with IFN-γ-treated Raw cells, in the presence or absence of AAT, into diabetic NOD-SCID mice in which macrophages were depleted by liposome. At day 21, all macrophage-depleted diabetic recipients receiving islets alone achieved normoglycemia (n=6). In contrast, only 55.6% (n=9, p=0.001) receiving islets and IFN-γ-treated Raw cells achieved normoglycemia, compared to 90% receiving AAT-treated IFN-γ Raw cells (n=10, p=0.003), suggesting AAT improved islet graft survival via suppressing macrophage activation. The effect of AAT was further confirmed in a major mismatch allogeneic islet transplantation model (Balb/c, H-2b to C57BL/6 H-2d mice) in which macrophage activation contributed to primary nonfunction (PNF) of the transplanted islets. In this model, PNF occurred in 16.7% of AAT-treated recipients (n=6) but in 40% of controls (n=5) when 400 islets were transplanted. In summary, this study further identified that AAT contributed to islet graft survival after transplantation by suppressing macrophage activation. Disclosure W. Gou: None. C. Strange: None. H. Wang: None. Funding National Institutes of Health (DK105183, DK120394, DK118529)