Pepper, A. R. | bioRxiv Science

bioRxiv2023

Long-term survival and induction of operational tolerance to murine islet allografts through the co-transplantation of cyclosporine A eluting microparticles

One strategy to prevent islet rejection, is to create a favorable immune-protective local environment at the transplant site. Herein, we utilize localized cyclosporine A (CsA) delivery to islet grafts via poly(lactic-co-glycolic acid) (PLGA) microparticles to attenuate allograft rejection. CsA microparticles alone significantly delayed islet allograft rejection compared to islets alone (p<0.05). Over 50% (6/11) of recipients receiving CsA microparticles and short-term cytotoxic T lymphocyte-associated antigen 4-Ig (CTLA4-Ig) therapy displayed prolonged allograft survival for 214 days, compared to 25% (2/8) receiving CTLA4-Ig alone (p>0.05). CsA microparticles + CTLA4-Ig islet allografts exhibited reduced T-cell (CD4+ and CD8+ cells) and macrophage (CD68+ cells) infiltration compared to islets alone. We observed reduced mRNA expression of proinflammatory cytokines (IL-6, IL-10, INF-{gamma} & TNF-; p<0.05) and chemokines (CCL2, CCL5, CCL22, and CXCL10; p<0.05) in CsA microparticles + CTLA4-Ig allografts compared to islets alone. Long-term islet allografts contained insulin+ and intra-graft FoxP3+ T regulatory cells. Rapid rejection of third-party skin grafts (C3H) in islet allograft recipients suggested that CsA microparticles + CTLA4-Ig therapy induced donor specific operational tolerance. This study demonstrates that localized CsA drug delivery plus short-course systemic immunosuppression promotes an immune protective transplant niche for allogeneic islets. Article HighlightsO_LISystemic immunosuppression limits patient inclusion for beta cell replacement therapies C_LIO_LILocalized islet graft immunosuppression may reduce drug toxicity and improve graft survival C_LIO_LICyclosporine eluting microparticles + CTLA4-Ig therapy induced donor specific operational tolerance C_LIO_LIGraft localized drug delivery can create an immune protective transplant niche C_LI

immunology↗

bioRxiv2022

Redox sensing by SENP1 augments insulin secretion early after high-fat feeding in mice

Pancreatic {beta}-cells respond to metabolic stress by upregulating insulin secretion, however the underlying mechanisms remain unclear. In {beta}-cells from overweight humans without diabetes, and mice fed a high-fat diet for 2 days, insulin exocytosis and secretion are enhanced without increased Ca2+ influx. {beta}-cell RNA-seq suggests altered metabolic pathways early following HFD, where we find increased basal oxygen consumption, proton leak, but a more reduced cytosolic redox state. Increased {beta}-cell exocytosis after 2-day HFD is dependent on this reduced intracellular redox and requires the sentrin-specific SUMO-protease-1 (SENP1). Mice with either pancreas- or {beta}-cell-specific SENP1 deletion fail to up-regulate exocytosis and become rapidly glucose intolerant after 2-day HFD. Mechanistically, redox-sensing by SENP1 requires a thiol group at C535 which together with Zn+-binding suppresses basal protease activity and unrestrained {beta}-cell exocytosis and increases SENP1 sensitivity to regulation by redox signals.

cell biology↗