Type 1 Diabetes Prone NOD Mice Have Diminished Cxcr1 mRNA Expression in Polymorphonuclear Neutrophils and CD4+ T Lymphocytes

Type 1 diabetes mellitus: Roles of neutrophils in the pathogenesis

Circulating neutrophil counts are reduced both in healthy autoantibody-positive individuals and in patients with type 1 diabetes, which may be related on cell-specific autoimmunity. This paper was written to give an update on roles of neutrophils in the pathogenesis of type 1 diabetes mellitus. Different research search engines like PubMed Central, Scopus, Web of Science, Researchgate, Google Scholar etc were utilised for writing this paper. A drop in blood neutrophil counts in type 1 diabetes may be caused by decreased neutrophil generation and maturation, tissue maintenance, consumption, or peripheral damage. Neutrophil count variations between studies may be explained by results from various stages of diabetes or by ethnic groups. Neutrophils can induce type 1 diabetes by colonizing pancreatic islets and interacting with other immune cells, according to exciting findings that shed new light on their role in the pathogenesis of the disease. Knowing more about the function of neutrophils in the pathogenesis of type 1 diabetes will help in early diagnosis, treatment, and even prevention of the disease.

Human CXCR1 knock-in mice infer functional expression of a murine ortholog

Targeting CXCR1 and CXCR2 chemokine receptors to block neutrophil migration to sites of inflammation is a promising therapeutic approach for various inflammatory and autoimmune diseases. However, assessing the translational potential of such therapies using mouse models is challenging due to the unclear expression of CXCR1 at the protein level. Although CXCR2 has been well characterized in both mice and humans, the protein-level expression of CXCR1 in mice (mCXCR1) remains controversial. To address this issue, we generated a novel human CXCR1 knock-in (hCXCR1 KI) mouse model in which the transgene is under the control of the native mouse promoter and regulatory elements. Using an anti-human CXCR1 monoclonal antibody (anti-hCXCR1 monoclonal antibody), we found that hCXCR1 was highly expressed on neutrophils in the hCXCR1 KI mice, comparable to levels observed in human neutrophils. This successful expression of hCXCR1 in this mouse model suggests that functional mCXCR1 likely exists. To investigate the functional role of CXCR1, we investigated how antagonizing this receptor using anti-hCXCR1 monoclonal antibody in the arthritis model would affect disease outcomes. Antibody treatment significantly alleviated all signs of joint inflammation. In summary, our newly generated hCXCR1 KI transgenic mice provide a valuable tool to investigate the therapeutic efficacy of small molecules or monoclonal antibodies that antagonize this receptor in neutrophil-mediated pathologies.

CXCR1 drives the pathogenesis of EAE and ARDS via boosting dendritic cells-dependent inflammation

Chemokines secreted by dendritic cells (DCs) play a key role in the regulation of inflammation and autoimmunity through chemokine receptors. However, the role of chemokine receptor CXCR1 in inflammation-inducing experimental autoimmune encephalomyelitis (EAE) and acute respiratory distress syndrome (ARDS) remains largely enigmatic. Here we reported that compared with healthy controls, the level of CXCR1 was aberrantly increased in multiple sclerosis (MS) patients. Knockout of CXCR1 not only ameliorated disease severity in EAE mice but also suppressed the secretion of inflammatory factors (IL-6/IL-12p70) production. We observed the same results in EAE mice with DCs-specific deletion of CXCR1 and antibody neutralization of the ligand CXCL5. Mechanically, we demonstrated a positive feedback loop composed of CXCL5/CXCR1/HIF-1α direct regulating of IL-6/IL-12p70 production in DCs. Meanwhile, we found CXCR1 deficiency in DCs limited IL-6/IL-12p70 production and lung injury in LPS-induced ARDS, a disease model caused by inflammation. Overall, our study reveals CXCR1 governs DCs-mediated inflammation and autoimmune disorders and its potential as a therapeutic target for related diseases.

Vitamin D supplementation induces CatG-mediated CD4+ T cell inactivation and restores pancreatic β-cell function in mice with type 1 diabetes

Type 1 diabetes (T1D) is a chronic autoimmune disease accompanied by the immune-mediated destruction of pancreatic β-cells. In this study, we aimed to explore the regulatory effects of vitamin D (VD) supplementation on pancreatic β-cell function by altering the expression of bioinformatically identified cathepsin G (CatG) in T1D mice. A T1D mouse model was established in nonobese diabetic (NOD) mice, and their islets were isolated and purified. Pancreatic mononuclear cells (MNCs) were collected, from which CD4⁺ T cells were isolated. The levels of interleukin (IL)-2, IL-10, tumor necrosis factor-α (TNF-α), and interferon-γ (IFN-γ) in the supernatant of mouse pancreatic tissue homogenate were assessed using ELISA. Immunohistochemistry and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labelin (TUNEL) staining were conducted to evaluate the effects of VD supplementation on pancreatic tissues of T1D mice. The pancreatic β-cell line MIN6 was used for in vitro substantiation of findings in vivo. VD supplementation reduced glucose levels and improved glucose tolerance in T1D mice. Furthermore, VD supplementation improved pancreatic β-cell function and suppressed immunological and inflammatory reactions in the T1D mice. We documented overexpression of CatG in diabetes tissue samples, and then showed that VD supplementation normalized the islet immune microenvironment through downregulating CatG expression in T1D mice. Experiments in vitro subsequently demonstrated that VD supplementation impeded CD4⁺ T activation by downregulating CatG expression and thereby enhanced pancreatic β-cell function. Results of the present study elucidated that VD supplementation can downregulate the expression of CatG and inhibit CD4⁺ T cell activation, thereby improving β-cell function in T1D.NEW & NOTEWORTHY We report that vitamin D (VD) supplementation downregulates CatG expression and inhibits CD4⁺ T cell activation, thereby improving β-cell function in type 1 diabetes (T1D). This study deepens our understanding of the pathogenesis of T1D and clarifies molecular events underlying the alleviatory effect of VD for immunotherapy against T1D.

Dysregulation of Components of the Inflammasome Machinery After Bariatric Surgery: Novel Targets for a Chronic Disease

BACKGROUND

Obesity is a metabolic chronic disease with important associated morbidities and mortality. Bariatric surgery is the most effective treatment for maintaining long-term weight loss in severe obesity and, consequently, for decreasing obesity-related complications, including chronic inflammation.

AIM

To explore changes in components of the inflammasome machinery after bariatric surgery and their relation with clinical/biochemical parameters at baseline and 6 months after bariatric surgery.

PATIENTS AND METHODS

Twenty-two patients with morbid-obesity that underwent bariatric surgery (sleeve gastrectomy and Roux-en-Y gastric bypass) were included. Epidemiological/clinical/anthropometric/biochemical evaluation was performed at baseline and 6 months after bariatric surgery. Inflammasome components and inflammatory-associated factors [nucleotide-binding oligomerization domain-like receptors (NLRs), inflammasome activation components, cytokines and inflammation/apoptosis-related components, and cell-cycle and DNA-damage regulators) were evaluated in peripheral blood mononuclear cells (PBMCs) at baseline and 6 months after bariatric surgery. Clinical molecular correlations/associations were analyzed. Functional parameters (lipid accumulation/viability/apoptosis) were analyzed in response to specific inflammasome components silencing in liver HepG2 cells).

RESULTS

A profound dysregulation of inflammasome components after bariatric surgery was found, especially in NLRs and cell-cycle and DNA damage regulators. Several components were associated with baseline metabolic comorbidities including type 2 diabetes (C-C motif chemokine ligand 2/C-X-C motif chemokine receptor 1/sirtuin 1), hypertension (absent in melanoma 2/ASC/purinergic receptor P2X 7), and dyslipidemia [C-X-C motif chemokine ligand 3 (CXCL3)/NLR family pyrin domain containing (NLRP) 7) and displayed changes in their molecular profile 6 months after bariatric surgery. The gene expression fingerprint of certain factors NLR family CARD domain containing 4 (NLRC4)/NLRP12/CXCL3)/C-C motif chemokine ligand 8/toll-like receptor 4) accurately differentiated pre- and postoperative PBMCs. Most changes were independent of the performed surgical technique. Silencing of NLRC4/NLRP12 resulted in altered lipid accumulation, apoptosis rate, and cell viability in HepG2 cells.

CONCLUSION

Bariatric surgery induces a profound alteration in the gene expression pattern of components of the inflammasome machinery in PBMCs. Expression and changes of certain inflammasome components are associated to baseline metabolic comorbidities, including type 2 diabetes, and may be related to the improvement and reversion of some obesity-related comorbidities after bariatric surgery.

Glucagon Reduces Neutrophil Migration and Increases Susceptibility to Sepsis in Diabetic Mice

Sepsis is one of the most common comorbidities observed in diabetic patients, associated with a deficient innate immune response. Recently, we have shown that glucagon possesses anti-inflammatory properties. In this study, we investigated if hyperglucagonemia triggered by diabetes might reduce the migration of neutrophils, increasing sepsis susceptibility. 21 days after diabetes induction by intravenous injection of alloxan, we induced moderate sepsis in Swiss-Webster mice through cecum ligation and puncture (CLP). The glucagon receptor (GcgR) antagonist des-his1-[Glu9]-glucagon amide was injected intraperitoneally 24h and 1h before CLP. We also tested the effect of glucagon on CXCL1/KC-induced neutrophil migration to the peritoneal cavity in mice. Neutrophil chemotaxis in vitro was tested using transwell plates, and the expression of total PKA and phospho-PKA was evaluated by western blot. GcgR antagonist restored neutrophil migration, reduced CFU numbers in the peritoneal cavity and improved survival rate of diabetic mice after CLP procedure, however, the treatment did no alter hyperglycemia, CXCL1/KC plasma levels and blood neutrophilia. In addition, glucagon inhibited CXCL1/KC-induced neutrophil migration to the peritoneal cavity of non-diabetic mice. Glucagon also decreased the chemotaxis of neutrophils triggered by CXCL1/KC, PAF, or fMLP in vitro. The inhibitory action of glucagon occurred in parallel with the reduction of CXCL1/KC-induced actin polymerization in neutrophils in vitro, but not CD11a and CD11b translocation to cell surface. The suppressor effect of glucagon on CXCL1/KC-induced neutrophil chemotaxis in vitro was reversed by pre-treatment with GcgR antagonist and adenylyl cyclase or PKA inhibitors. Glucagon also increased PKA phosphorylation directly in neutrophils in vitro. Furthermore, glucagon impaired zymosan-A-induced ROS production by neutrophils in vitro. Human neutrophil chemotaxis and adherence to endothelial cells in vitro were inhibited by glucagon treatment. According to our results, this inhibition was independent of CD11a and CD11b translocation to neutrophil surface or neutrophil release of CXCL8/IL-8. Altogether, our results suggest that glucagon may be involved in the reduction of neutrophil migration and increased susceptibility to sepsis in diabetic mice. This work collaborates with better understanding of the increased susceptibility and worsening of sepsis in diabetics, which can contribute to the development of new effective therapeutic strategies for diabetic septic patients.

Differences in Interleukin-8 Plasma Levels between Diabetic Patients and Healthy Individuals Independently on Their Periodontal Status

Chronic periodontitis (CP) and diabetes mellitus (DM) involve several aspects of immune functions, including neutrophil activity and cytokine biology. Considering the critical function of chemokine interleukin-8 (IL-8) in the inflammatory process, the aims of this study were to determine: (i) IL-8 plasma levels; (ii) IL-8 (-251A/T, rs4073) and its receptor 2 (CXCR2, +1208C/T, rs1126579) polymorphisms, and (iii) the presence of the selected periodontal bacteria in types 1 and 2 DM patients (T1DM and T2DM) and systemically healthy controls (HC) with known periodontal status. This case⁻control study comprises of 153 unrelated individuals: 36/44 patients suffering from T1DM+CP/T2DM+CP and 32/41 from HC+CP/non-periodontitis HC. Both the clinical and biochemical parameters were monitored. The genotypes were determined using qPCR, IL-8 plasma levels were measured using an ELISA kit. Subgingival bacterial colonization was analyzed with a DNA microarray detection kit. The IL-8 plasma levels differed significantly between non-periodontitis HC and T1DM+CP/T2DM+CP patients (P < 0.01). Even in HC+CP, IL-8 concentrations were significantly lower than in T1DM+CP/T2DM+CP patients (P ≤ 0.05). No significant associations between the IL-8 plasma levels and the studied IL-8 and CXCR2 polymorphisms or the occurrence of selected periodontal bacteria (P > 0.05) were found. CP does not influence the circulating IL-8 levels. Patients with T1DM+CP/T2DM+CP had higher circulating IL-8 levels than HC+CP/non-periodontitis HC.

Roles of DNA repair enzyme OGG1 in innate immunity and its significance for lung cancer

Cytokines are pivotal mediators of the immune response, and their coordinated expression protects host tissue from excessive damage and oxidant stress. Nevertheless, the development of lung pathology, including asthma, chronic obstructive pulmonary disease, and ozone-induced lung injury, is associated with oxidant stress; as evidence, there is a significant increase in levels of the modified guanine base 7,8-dihydro-8-oxoguanine (8-oxoG) in the genome. 8-OxoG is primarily recognized by 8-oxoguanine glycosylase 1 (OGG1), which catalyzes the first step in the DNA base excision repair pathway. However, oxidant stress in the cell transiently halts enzymatic activity of substrate-bound OGG1. The stalled OGG1 facilitates DNA binding of transactivators, including NF-κB, to their cognate sites to enable expression of cytokines and chemokines, with ensuing recruitments of inflammatory cells. Hence, defective OGG1 will modulate the coordination between innate and adaptive immunity through excessive oxidant stress and cytokine dysregulation. Both oxidant stress and cytokine dysregulation constitute key elements of oncogenesis by KRAS, which is mechanistically coupled to OGG1. Thus, analysis of the mechanism by which OGG1 modulates gene expression helps discern between beneficial and detrimental effects of oxidant stress, exposes a missing functional link as a marker, and yields a novel target for lung cancer.

Proteomic profiling of human islets collected from frozen pancreata using laser capture microdissection

The etiology of Type 1 Diabetes (T1D) remains elusive. Enzymatically isolated and cultured (EIC) islets cannot fully reflect the natural protein composition and disease process of in vivo islets, because of the stress from isolation procedures. In order to study islet protein composition in conditions close to the natural environment, we performed proteomic analysis of EIC islets, and laser capture microdissected (LCM) human islets and acinar tissue from fresh-frozen pancreas sections of three cadaveric donors. 1104 and 706 proteins were identified from 6 islets equivalents (IEQ) of LCM islets and acinar tissue, respectively. The proteomic profiles of LCM islets were reproducible within and among cadaveric donors. The endocrine hormones were only detected in LCM islets, whereas catalytic enzymes were significantly enriched in acinar tissue. Furthermore, high overlap (984 proteins) and similar function distribution were found between LCM and EIC islets proteomes, except that EIC islets had more acinar contaminants and stress-related signal transducer activity proteins. The comparison among LCM islets, LCM acinar tissue and EIC islets proteomes indicates that LCM combined with proteomic methods enables accurate and unbiased profiling of islet proteome from frozen pancreata. This paves the way for proteomic studies on human islets during the progression of T1D.

SIGNIFICANCE

The etiological agent triggering autoimmunity against beta cells in Type 1 diabetes (T1D) remains obscure. The in vitro models available (enzymatically isolated and cultured islets, EIC islets) do not accurately reflect what happens in vivo due to lack of the natural environment where islets exist and the preparation-induced changes in cell physiology. The importance of this study is that we investigated the feasibility of laser capture microdissection (LCM) for the isolation of intact islets from frozen cadaveric pancreatic tissue sections. We compared the protein profile of LCM islets (9 replicates from 3 cadaveric donors) with that of both LCM acinar tissues (6 replicates from the same 3 cadaveric donor as LCM islets) and EIC islets (at least 4 replicates for each sample with the same islets equivalents) by using proteomics techniques with advanced instrumentation, nanoLC-Q Exactive HF Orbitrap mass spectrometry (nano LC-MS/MS). The results demonstrate that the LCM method is reliable in isolating islets with an intact environment. LCM-based islet proteomics is a feasible approach to obtain good proteome coverage for assessing the pathology of T1D using cadaveric pancreatic samples, even from very small sample amounts. Future applications of this LCM-based proteomic method may help us understand the pathogenesis of T1D and identify potential biomarkers for T1D diagnosis at an early stage.

Neutrophils in type 1 diabetes

Type 1 diabetes is an autoimmune disease that afflicts millions of people worldwide. It occurs as the consequence of destruction of insulin-producing pancreatic β-cells triggered by genetic and environmental factors. The initiation and progression of the disease involves a complicated interaction between β-cells and immune cells of both innate and adaptive systems. Immune cells, such as T cells, macrophages and dendritic cells, have been well documented to play crucial roles in type 1 diabetes pathogenesis. However, the particular actions of neutrophils, which are the most plentiful immune cell type and the first immune cells responding to inflammation, in the etiology of this disease might indeed be unfairly ignored. Progress over the past decades shows that neutrophils might have essential effects on the onset and perpetuation of type 1 diabetes. Neutrophil-derived cytotoxic substances, including degranulation products, cytokines, reactive oxygen species and extracellular traps that are released during the process of neutrophil maturation or activation, could cause destruction to islet cells. In addition, these cells can initiate diabetogenic T cell response and promote type 1 diabetes development through cell-cell interactions with other immune and non-immune cells. Furthermore, relevant antineutrophil therapies have been shown to delay and dampen the progression of insulitis and autoimmune diabetes. Here, we discuss the relationship between neutrophils and autoimmune type 1 diabetes from the aforementioned aspects to better understand the roles of these cells in the initiation and development of type 1 diabetes.