Purpose: To identify isletokines released by exosomes from human islets that have been exposed to hypoxic or inflammatory conditions and define stress signaling pathways that can be targeted to suppress their expression and improve islet graft survival during transplantation.

Methods: Human islets were subjected to hypoxic and inflammatory conditions. Exosomes were recovered and isolated from the medium and characterized by TEM and surface marker expression. Luminex multiplex assays were performed to identify isletokines recovered from islet exosomes. Western blot analysis was performed to identify activation of signaling components in islets exposed to hypoxia and cytokines. The phytochemical Withaferin A (WA) was used to block isletokine induction in islets, and effects of WA on stress-signaling components in islets were defined.

Results: Human islets exposed to hypoxia and proinflammatory cytokines showed activation of mTOR/AKT/GSK3β and NF-κB stress signaling pathways resulting in release of exosomes containing IL-6, IL-8, MCP-1, and CXCL10. Exosomal isletokines were suppressed by pretreatment with WA. Suppression of isletokines by WA correlated with inhibition of AKT and mTOR signaling, but was independent of GSK3β activation. WA also blocked induction of canonical NF-κB RelA/p65 signaling indicating its requirement for exosomal isletokine expression.

Conclusion: The study identifies exosomal isletokines produced by stressed islets that are known to induce islet inflammation upon transplantation. These findings indicate that AKT-mTOR and NF-κB stress-induced signaling can be targeted to suppress exosomal expression of isletokines to prevent early innate immune destruction of islets during transplantation to improve transplant outcomes.

CITATION INFORMATION: Saravanan P., Yoshimatsu G., Bhattacharjee R., Chang C., Darden C., Naziruddin B., Lawrence M. Identification of Exosomal Isletokines Released by Pancreatic Islets in Response to Inflammatory Stress Am J Transplant. 2017;17 (suppl 3).

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