Inflammatory Cell Infiltration Into Islets Without PD-L1 Expression Is Associated With the Development of Immune Checkpoint Inhibitor-Related Type 1 Diabetes in Genetically Susceptible Patients

Beta cell extracellular vesicle PD-L1 as a novel regulator of CD8+ T cell activity and biomarker during the evolution of type 1 diabetes

AIMS/HYPOTHESIS

Surviving beta cells in type 1 diabetes respond to inflammation by upregulating programmed death-ligand 1 (PD-L1) to engage immune cell programmed death protein 1 (PD-1) and limit destruction by self-reactive immune cells. Extracellular vesicles (EVs) and their cargo can serve as biomarkers of beta cell health and contribute to islet intercellular communication. We hypothesised that the inflammatory milieu of type 1 diabetes increases PD-L1 in beta cell EV cargo and that EV PD-L1 may protect beta cells against immune-mediated cell death.

METHODS

Beta cell lines and human islets were treated with proinflammatory cytokines to model the proinflammatory type 1 diabetes microenvironment. EVs were isolated using ultracentrifugation or size exclusion chromatography and analysed via immunoblot, flow cytometry and ELISA. EV PD-L1 binding to PD-1 was assessed using a competitive binding assay and in vitro functional assays testing the ability of EV PD-L1 to inhibit NOD CD8+ T cells. Plasma EV and soluble PD-L1 were assayed in the plasma of islet autoantibody-positive (Ab+) individuals or individuals with recent-onset type 1 diabetes and compared with levels in non-diabetic control individuals.

RESULTS

PD-L1 protein co-localised with tetraspanin-associated proteins intracellularly and was detected on the surface of beta cell EVs. Treatment with IFN-α or IFN-γ for 24 h induced a twofold increase in EV PD-L1 cargo without a corresponding increase in the number of EVs. IFN exposure predominantly increased PD-L1 expression on the surface of beta cell EVs and beta cell EV PD-L1 showed a dose-dependent capacity to bind PD-1. Functional experiments demonstrated specific effects of beta cell EV PD-L1 to suppress proliferation and cytotoxicity of murine CD8+ T cells. Plasma EV PD-L1 levels were increased in Ab+individuals, particularly in those positive for a single autoantibody. Additionally, in Ab+ individuals or those who had type 1 diabetes, but not in control individuals, plasma EV PD-L1 positively correlated with circulating C-peptide, suggesting that higher EV PD-L1 could be protective for residual beta cell function.

CONCLUSIONS/INTERPRETATION

IFN exposure increases PD-L1 on the beta cell EV surface. Beta cell EV PD-L1 binds PD1 and inhibits CD8+ T cell proliferation and cytotoxicity. Circulating EV PD-L1 is higher in Ab+ individuals than in control individuals. Circulating EV PD-L1 levels correlate with residual C-peptide at different stages in type 1 diabetes progression. These findings suggest that EV PD-L1 could contribute to heterogeneity in type 1 diabetes progression and residual beta cell function and raise the possibility that EV PD-L1 could be exploited as a means to inhibit immune-mediated beta cell death.

Beta cell extracellular vesicle PD-L1 as a novel regulator of CD8+ T cell activity and biomarker during the evolution of Type 1 Diabetes

Aims/hypothesis

Surviving beta cells in type 1 diabetes respond to inflammation by upregulating programmed death-ligand 1 (PD-L1) to engage immune cell programmed death-1 (PD-1) and limit destruction by self-reactive immune cells. Extracellular vesicles (EVs) and their cargo can serve as biomarkers of beta cell health and contribute to islet intercellular communication. We hypothesized that the inflammatory milieu of type 1 diabetes increases PD-L1 in beta cell EV cargo and that EV PD-L1 may protect beta cells against immune-mediated cell death.

Methods

Beta cell lines and human islets were treated with proinflammatory cytokines to model the proinflammatory type 1 diabetes microenvironment. EVs were isolated using ultracentrifugation or size exclusion chromatography and analysed via immunoblot, flow cytometry, and ELISA. EV PD-L1: PD-1 binding was assessed using a competitive binding assay and in vitro functional assays testing the ability of EV PD-L1 to inhibit NOD CD8 T cells. Plasma EV and soluble PD-L1 were assayed in plasma of individuals with islet autoantibody positivity (Ab+) or recent-onset type 1 diabetes and compared to non-diabetic controls.

Results

PD-L1 protein colocalized with tetraspanin-associated proteins intracellularly and was detected on the surface of beta cell EVs. 24-h IFN-α or IFN-γ treatment induced a two-fold increase in EV PD-L1 cargo without a corresponding increase in number of EVs. IFN exposure predominantly increased PD-L1 expression on the surface of beta cell EVs and beta cell EV PD-L1 showed a dose-dependent capacity to bind PD-1. Functional experiments demonstrated specific effects of beta cell EV PD-L1 to suppress proliferation and cytotoxicity of murine CD8 T cells. Plasma EV PD-L1 levels were increased in islet Ab+ individuals, particularly in those with single Ab+, Additionally, in from individuals with either Ab+ or type 1 diabetes, but not in controls, plasma EV PD-L1 positively correlated with circulating C-peptide, suggesting that higher EV-PD-L1 could be protective for residual beta cell function.

Conclusions/interpretation

IFN exposure increases PD-L1 on the beta cell EV surface. Beta cell EV PD-L1 binds PD1 and inhibits CD8 T cell proliferation and cytotoxicity. Circulating EV PD-L1 is higher in islet autoantibody positive patients compared to controls. Circulating EV PD-L1 levels correlate with residual C-peptide at different stages in type 1 diabetes progression. These findings suggest that EV PD-L1 could contribute to heterogeneity in type 1 diabetes progression and residual beta cell function and raise the possibility that EV PD-L1 could be exploited as a means to inhibit immune-mediated beta cell death.

Immune checkpoint inhibitor-related type 1 diabetes mellitus which develops long after treatment discontinuation: a case report and review of literature

Immune checkpoint inhibitor (ICI)-related type 1 diabetes is an immune-related adverse event (irAE), occurring in slightly less than 1% of patients undergoing ICI therapy. Most cases develop during ICI treatment, with occurrences long after discontinuation being extremely rare. A 76-year-old woman, with no history of glucose tolerance issues, was diagnosed with lung adenocarcinoma with pleural invasion and underwent chemotherapy, including atezolizumab, an anti-programmed death-ligand 1 antibody. This treatment was discontinued due to disease progression, although she continued with other chemotherapy regimens. Approximately 5.5 months (166 days) after her last atezolizumab dose, she developed diabetic ketoacidosis, fulfilling the diagnostic criteria for fulminant type 1 diabetes. Anti-glutamic acid decarboxylase antibodies were positive. The patient carried susceptibility human leukocyte antigen (HLA) haplotypes, which are associated with type 1 diabetes. To date, including our patient, only nine cases of ICI-related type 1 diabetes developed after ICI discontinuation have been precisely reported. Eight cases originated from East Asia, with six exhibiting fulminant type 1 diabetes, and seven tested negative for islet-related autoantibodies. The reported cases were independent of ICI types, cycle number, or HLA haplotypes. Median time from the last ICI administration to diabetes onset was 4 months (range: 2-7 months). Although reports of cases occurring after ICI discontinuation are currently limited, their frequency may increase with the wider use of ICIs and improved survival rates of patients post-treatment. Therefore, it is crucial to remain vigilant for the development of ICI-related type 1 diabetes, not only during ICI administration, but also long after discontinuation.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13340-024-00719-4.

Inhibition of the eukaryotic initiation factor-2α kinase PERK decreases risk of autoimmune diabetes in mice

Preventing the onset of autoimmune type 1 diabetes (T1D) is feasible through pharmacological interventions that target molecular stress-responsive mechanisms. Cellular stresses, such as nutrient deficiency, viral infection, or unfolded proteins, trigger the integrated stress response (ISR), which curtails protein synthesis by phosphorylating eukaryotic translation initiation factor-2α (eIF2α). In T1D, maladaptive unfolded protein response (UPR) in insulin-producing β cells renders these cells susceptible to autoimmunity. We found that inhibition of the eIF2α kinase PKR-like ER kinase (PERK), a common component of the UPR and ISR, reversed the mRNA translation block in stressed human islets and delayed the onset of diabetes, reduced islet inflammation, and preserved β cell mass in T1D-susceptible mice. Single-cell RNA-Seq of islets from PERK-inhibited mice showed reductions in the UPR and PERK signaling pathways and alterations in antigen-processing and presentation pathways in β cells. Spatial proteomics of islets from these mice showed an increase in the immune checkpoint protein programmed death-ligand 1 (PD-L1) in β cells. Golgi membrane protein 1, whose levels increased following PERK inhibition in human islets and EndoC-βH1 human β cells, interacted with and stabilized PD-L1. Collectively, our studies show that PERK activity enhances β cell immunogenicity and that inhibition of PERK may offer a strategy for preventing or delaying the development of T1D.

Inhibition of the Eukaryotic Initiation Factor-2-α Kinase PERK Decreases Risk of Autoimmune Diabetes in Mice

Preventing the onset of autoimmune type 1 diabetes (T1D) is feasible through pharmacological interventions that target molecular stress-responsive mechanisms. Cellular stresses, such as nutrient deficiency, viral infection, or unfolded proteins, trigger the integrated stress response (ISR), which curtails protein synthesis by phosphorylating eIF2α. In T1D, maladaptive unfolded protein response (UPR) in insulin-producing β cells renders these cells susceptible to autoimmunity. We show that inhibition of the eIF2α kinase PERK, a common component of the UPR and ISR, reverses the mRNA translation block in stressed human islets and delays the onset of diabetes, reduces islet inflammation, and preserves β cell mass in T1D-susceptible mice. Single-cell RNA sequencing of islets from PERK-inhibited mice shows reductions in the UPR and PERK signaling pathways and alterations in antigen processing and presentation pathways in β cells. Spatial proteomics of islets from these mice shows an increase in the immune checkpoint protein PD-L1 in β cells. Golgi membrane protein 1, whose levels increase following PERK inhibition in human islets and EndoC-βH1 human β cells, interacts with and stabilizes PD-L1. Collectively, our studies show that PERK activity enhances β cell immunogenicity, and inhibition of PERK may offer a strategy to prevent or delay the development of T1D.

Reaching the Diagnosis of Checkpoint Inhibitor-Induced Diabetes Mellitus in Different Clinical Scenarios: A Real-World Application of Updated Diagnostic Criteria

BACKGROUND

Checkpoint inhibitor (CPI)-associated diabetes mellitus (CPI-DM) is a rare immune-related adverse event (irAE) that presents with variable clinical manifestations. Data about its pathogenesis have not yet been adequately studied.

METHODS

Applying the recently updated diagnostic criteria from the American Diabetes Association, we retrospectively reviewed the medical records of all CPI-treated patients referred to our endocrinological unit for managing their endocrine irAEs and analyzed the incidence of CPI-DM, its clinical characteristics, and its management.

RESULTS

Among the 326 CPI-treated patients with endocrine irAEs, 4 patients met the updated criteria for the diagnosis of CPI-DM, representing 1.22% of all endocrine irAEs in our cohort. These four patients presented with distinct clinical scenarios regarding the irAE onset, the underlying malignancy, the administered CPI regimen, and the type of circulating autoantibodies.

CONCLUSION

The variable presentation of CPI-DM and the non-standard sensitivity of the presence of the type 1 DM traditional autoantibodies highlight the need for distinct guidelines and increased awareness of its diagnosis and management.

Immune-related adverse events after immune check point inhibitors: Understanding the intersection with autoimmunity

Immune checkpoint inhibitor therapies act through blockade of inhibitory molecules involved in the regulation of T cells, thus releasing tumor specific T cells to destroy their tumor targets. However, immune checkpoint inhibitors (ICI) can also lead to a breach in self-tolerance resulting in immune-related adverse events (irAEs) that include tissue-specific autoimmunity. This review addresses the question of whether the mechanisms that drive ICI-induced irAEs are shared or distinct with those driving spontaneous autoimmunity, focusing on ICI-induced diabetes, ICI-induced arthritis, and ICI-induced thyroiditis due to the wealth of knowledge about the development of autoimmunity in type 1 diabetes, rheumatoid arthritis, and Hashimoto's thyroiditis. It reviews current knowledge about role of genetics and autoantibodies in the development of ICI-induced irAEs and presents new studies utilizing single-cell omics approaches to identify T-cell signatures associated with ICI-induced irAEs. Collectively, these studies indicate that there are similarities and differences between ICI-induced irAEs and autoimmune disease and that studying them in parallel will provide important insight into the mechanisms critical for maintaining immune tolerance.