Circulating platelet-neutrophil aggregates characterize the development of type 1 diabetes in humans and NOD mice

Sarah Popp ,Mahalakshmi A Sarma,Emanuele Bosi,Manuela Battaglia,Federica Vecchio,Anna Giovenzana,Karen J Brown,Alessandra Petrelli,Debra J Brown,Jessica Garrett,Charmaine J Simeonovic,Helen E Thomas,Elizabeth E Gardiner,Rikako Wakamatsu,Riho Fukuda,Lucy A Coupland,Christopher R Parish,Beng H Chong,Yuma Takeda,Antony Lafferty ,Yuhko Suzuki

doi:10.1172/jci.insight.153993

Abstract

Platelet-neutrophil aggregates (PNAs) facilitate neutrophil activation and migration and could underpin the recruitment of neutrophils to the pancreas during type 1 diabetes (T1D) pathogenesis. PNAs, measured by flow cytometry, were significantly elevated in the circulation of autoantibody-positive (Aab+) children and new-onset T1D children, as well as in pre-T1D (at 4 weeks and 10–12 weeks) and T1D-onset NOD mice, compared with relevant controls, and PNAs were characterized by activated P-selectin+ platelets. PNAs were similarly increased in pre-T1D and T1D-onset NOD isolated islets/insulitis, and immunofluorescence staining revealed increased islet-associated neutrophil extracellular trap (NET) products (myeloperoxidase [MPO] and citrullinated histones [CitH3]) in NOD pancreata. In vitro, cell-free histones and NETs induced islet cell damage, which was prevented by the small polyanionic drug methyl cellobiose sulfate (mCBS) that binds to histones and neutralizes their pathological effects. Elevated circulating PNAs could, therefore, act as an innate immune and pathogenic biomarker of T1D autoimmunity. Platelet hyperreactivity within PNAs appears to represent a previously unrecognized hematological abnormality that precedes T1D onset. In summary, PNAs could contribute to the pathogenesis of T1D and potentially function as a pre-T1D diagnostic.

Highlights

Type 1 diabetes (T1D) is an autoimmune disease that selectively destroys the insulin-producing β cells within the islets of Langerhans in the pancreas [1,2,3]
We discovered that Platelet-neutrophil aggregates (PNAs) in the peripheral blood of NOD mice increase during T1D development
Mean PNA levels spiked at 4 weeks and 10–12 weeks of age, as well as at T1D-onset, and correlated with histological evidence of increased inflammation (4 weeks) and a higher frequency of host pancreatic islets demonstrating leukocyte invasion — i.e., destructive insulitis at 10–12 weeks and at T1D onset

Summary

Introduction

Type 1 diabetes (T1D) is an autoimmune disease that selectively destroys the insulin-producing β cells within the islets of Langerhans in the pancreas [1,2,3]. T lymphocytes have been identified in human insulitis lesions, strongly suggesting a role for T cell–mediated autoimmune damage of β cells [6, 7]. T cells from T1D donors have displayed considerable heterogeneity in response to conventional β cell antigens in vitro, with some donors being identified as nonresponders [9]. Such findings raise the possibility that other leukocyte populations may actively contribute to β cell destruction

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Results

Conclusion