Type 1 diabetes (T1D) results from loss of both immune tolerance and functional β-cells. Administration of harmine (H) plus exendin-4 (E) markedly induces human β-cell expansion. Anti-CD3 antibody treatment reduces C-peptide loss in T1D patients. Here, we tested whether combination therapy with anti-CD3 antibody and H+E enhances T1D remission in non-obese diabetic (NOD) mice. First, we tested whether H+E protects human β-cells against inflammation and ER stress. We found that H+E, but not the drugs alone, significantly reduced both thapsigargin- and cytokine-induced human β-cell apoptosis. Single-cell RNAseq of human islets treated with cytokines and H+E showed reduced IL1β and IFNγ signaling in β-cells. Apoptosis genes such as CYLD and RIPK1 were downregulated and prosurvival genes such as HIF1A and VEGFA were upregulated in β-cells of H+E-treated islets. Next, treatment of early-onset diabetic NOD mice with H+E (daily ip) for 8 weeks improved glucose homeostasis but failed to induce long-lasting immune tolerance and T1D remission. Therefore, we next treated early-onset diabetic NOD mice with low-dose anti-CD3 antibody daily for 3 days (40µg/day) followed by 8 weeks treatment with H+E or vehicle (V) (Alzet pumps) . Treatment with anti-CD3 and H+E eliminated hyperglycemia in 100% of the mice vs. only 20% remission in anti-CD3 and V-treated mice. CD3+ T cell numbers were significantly and similarly reduced (∼50%) in mice treated with H+E or V. Preliminary results indicate that activated T cells in pancreatic lymph nodes (PLNs) and islet insulitis were significantly reduced, and T regulatory cells in spleen and PLNs were increased in H+E-treated mice. TUNEL+ β-cells were decreased and Ki67+ β-cells were increased in the pancreas of H+E-treated mice. Collectively, these results indicate that combination therapy with low-dose anti-CD3 antibody and H+E enhances T1D remission in diabetic NOD mice by increasing β-cell viability and favoring immune tolerance.

Disclosure

G.Lu: None. R.Kang: None. Y.Li: None. P.Wang: None. C.Rosselot: None. R.J.Devita: None. A.F.Stewart: None. A.Garcia-ocana: Consultant; Sun Pharmaceutical Industries Ltd.

Funding

NIH DK105015

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