Cytokine and Nitric Oxide-Dependent Gene Regulation in Islet Endocrine and Nonendocrine Cells

Single Cell RNAseq Analysis of Cytokine-Treated Human Islets: Association of Cellular Stress with Impaired Cytokine Responsiveness

Pancreatic β-cells are essential for survival, being the only cell type capable of insulin secretion. While they are believed to be vulnerable to damage by inflammatory cytokines such as interleukin-1 beta (IL-1β) and interferon-gamma, we have recently identified physiological roles for cytokine signaling in rodent β-cells that include the stimulation of antiviral and antimicrobial gene expression and the inhibition of viral replication. In this study, we examine cytokine-stimulated changes in gene expression in human islets using single-cell RNA sequencing. Surprisingly, the global responses of human islets to cytokine exposure were remarkably blunted compared to our previous observations in the mouse. The small population of human islet cells that were cytokine responsive exhibited increased expression of IL-1β-stimulated antiviral guanylate-binding proteins, just like in the mouse. Most human islet cells were not responsive to cytokines, and this lack of responsiveness was associated with high expression of genes encoding ribosomal proteins. We further correlated the expression levels of RPL5 with stress response genes, and when expressed at high levels, RPL5 is predictive of failure to respond to cytokines in all endocrine cells. We postulate that donor causes of death and isolation methodologies may contribute to stress of the islet preparation. Our findings indicate that activation of stress responses in human islets limits cytokine-stimulated gene expression, and we urge caution in the evaluation of studies that have examined cytokine-stimulated gene expression in human islets without evaluation of stress-related gene expression.

β-Cell-selective regulation of gene expression by nitric oxide

Nitric oxide is produced at low micromolar levels following the induction of inducible nitric oxide synthase (iNOS) and is responsible for mediating the inhibitory actions of cytokines on glucose-stimulated insulin secretion by islets of Langerhans. It is through the inhibition of mitochondrial oxidative metabolism, specifically aconitase and complex 4 of the electron transport chain, that nitric oxide inhibits insulin secretion. Nitric oxide also attenuates protein synthesis, induces DNA damage, activates DNA repair pathways, and stimulates stress responses (unfolded protein and heat shock) in β-cells. In this report, the time- and concentration-dependent effects of nitric oxide on the expression of six genes known to participate in the response of β-cells to this free radical were examined. The genes included Gadd45α (DNA repair), Puma (apoptosis), Hmox1 (antioxidant defense), Hsp70 (heat shock), Chop (UPR), and Ppargc1α (mitochondrial biogenesis). We show that nitric oxide stimulates β-cell gene expression in a narrow concentration range of ∼0.5-1 µM or levels corresponding to iNOS-derived nitric oxide. At concentrations greater than 1 µM, nitric oxide fails to stimulate gene expression in β-cells, and this is associated with the inhibition of mitochondrial oxidative metabolism. This narrow concentration range of responses is β-cell selective, as the actions of nitric oxide in non-β-cells (α-cells, mouse embryonic fibroblasts, and macrophages) are concentration dependent. Our findings suggest that β-cells respond to a narrow concentration range of nitric oxide that is consistent with the levels produced following iNOS induction, and that these concentration-dependent actions are selective for insulin-containing cells.

Zinc-chelating BET bromodomain inhibitors equally target islet endocrine cell types

Inhibition of the bromodomain and extraterminal domain (BET) protein family is a potential strategy to prevent and treat diabetes; however, the clinical use of BET bromodomain inhibitors (BETis) is associated with adverse effects. Here, we explore a strategy for targeting BETis to β cells by exploiting the high-zinc (Zn2+) concentration in β cells relative to other cell types. We report the synthesis of a novel, Zn2+-chelating derivative of the pan-BETi (+)-JQ1, (+)-JQ1-DPA, in which (+)-JQ1 was conjugated to dipicolyl amine (DPA). As controls, we synthesized (+)-JQ1-DBA, a non-Zn2+-chelating derivative, and (-)-JQ1-DPA, an inactive enantiomer that chelates Zn2+. Molecular modeling and biophysical assays showed that (+)-JQ1-DPA and (+)-JQ1-DBA retain potent binding to BET bromodomains in vitro. Cellular assays demonstrated (+)-JQ1-DPA attenuated NF-ĸB target gene expression in β cells stimulated with the proinflammatory cytokine interleukin 1β. To assess β-cell selectivity, we isolated islets from a mouse model that expresses green fluorescent protein in insulin-positive β cells and mTomato in insulin-negative cells (non-β cells). Surprisingly, Zn2+ chelation did not confer β-cell selectivity as (+)-JQ1-DPA was equally effective in both β and α cells; however, (+)-JQ1-DPA was less effective in macrophages, a nonendocrine islet cell type. Intriguingly, the non-Zn2+-chelating derivative (+)-JQ1-DBA displayed the opposite selectivity, with greater effect in macrophages compared with (+)-JQ1-DPA, suggesting potential as a macrophage-targeting molecule. These findings suggest that Zn2+-chelating small molecules confer endocrine cell selectivity rather than β-cell selectivity in pancreatic islets and provide valuable insights and techniques to assess Zn2+ chelation as an approach to selectively target small molecules to pancreatic β cells.NEW & NOTEWORTHY Inhibition of BET bromodomains is a novel potential strategy to prevent and treat diabetes mellitus. However, BET inhibitors have negative side effects. We synthesized a BET inhibitor expected to exploit the high zinc concentration in β cells to accumulate in β cells. We show our inhibitor targeted pancreatic endocrine cells; however, it was less effective in immune cells. A control inhibitor showed the opposite effect. These findings help us understand how to target specific cells in diabetes treatment.

Silver and gold nanoparticles as a novel approach to fight Sarcoptic mange in rabbits

Various kinds of pets have been known to contract the ectoparasite Sarcoptes scabiei. Current acaricides are becoming less effective because of the resistance developed by the mite besides their adverse effects on the general activity and reproductive performance of domestic pets. For this reason, the present study aims to discover a novel and safe approach using silver and gold nanoparticles to fight Sarcoptic mange in rabbits as well as to explain their mechanism of action. 15 pet rabbits with clinical signs of Sarcoptic mange that were confirmed by the microscopic examination were used in our study. All rabbits used in this study were assessed positive for the presence of different developing stages of S. scabiei. Three groups of rabbits (n = 5) were used as follows: group (1) didn't receive any treatment, and group (2 and 3) was treated with either AgNPs or GNPs, respectively. Both nanoparticles were applied daily on the affected skin areas via a dressing and injected subcutaneously once a week for 2 weeks at a dose of 0.5 mg/kg bwt. Our results revealed that all rabbits were severely infested and took a mean score = 3. The skin lesions in rabbits that didn't receive any treatments progressed extensively and took a mean score = of 4. On the other hand, all nanoparticle-treated groups displayed marked improvement in the skin lesion and took an average score of 0-1. All NPs treated groups showed remarkable improvement in the microscopic pictures along with mild iNOS, TNF-α, and Cox-2 expression. Both nanoparticles could downregulate the m-RNA levels of IL-6 and IFγ and upregulate IL-10 and TGF-1β genes to promote skin healing. Dressing rabbits with both NPs didn't affect either liver and kidney biomarkers or serum Ig levels indicating their safety. Our residual analysis detected AgNPs in the liver of rabbits but did not detect any residues of GNPs in such organs. We recommend using GNPs as an alternative acaricide to fight rabbit mange.

A Supportive Role of Mesenchymal Stem Cells on Insulin-Producing Langerhans Islets with a Specific Emphasis on The Secretome

Type 1 Diabetes (T1D) is a chronic autoimmune disease characterized by a gradual destruction of insulin-producing β-cells in the endocrine pancreas due to innate and specific immune responses, leading to impaired glucose homeostasis. T1D patients usually require regular insulin injections after meals to maintain normal serum glucose levels. In severe cases, pancreas or Langerhans islet transplantation can assist in reaching a sufficient β-mass to normalize glucose homeostasis. The latter procedure is limited because of low donor availability, high islet loss, and immune rejection. There is still a need to develop new technologies to improve islet survival and implantation and to keep the islets functional. Mesenchymal stem cells (MSCs) are multipotent non-hematopoietic progenitor cells with high plasticity that can support human pancreatic islet function both in vitro and in vivo and islet co-transplantation with MSCs is more effective than islet transplantation alone in attenuating diabetes progression. The beneficial effect of MSCs on islet function is due to a combined effect on angiogenesis, suppression of immune responses, and secretion of growth factors essential for islet survival and function. In this review, various aspects of MSCs related to islet function and diabetes are described.

Mechanistic Insights into Immune-Microbiota Interactions and Preventive Role of Probiotics Against Autoimmune Diabetes Mellitus

Recent studies on genetically susceptible individuals and animal models revealed the potential role of the intestinal microbiota in the pathogenesis of type 1 diabetes (T1D) through complex interactions with the immune system. T1D incidence has been increasing exponentially with modern lifestyle altering normal microbiota composition, causing dysbiosis characterized by an imbalance in the gut microbial community. Dysbiosis has been suggested to be a potential contributing factor in T1D. Moreover, several studies have shown the potential role of probiotics in regulating T1D through various mechanisms. Current T1D therapies target curative measures; however, preventive therapeutics are yet to be proven. This review highlights immune microbiota interaction and the immense role of probiotics and postbiotics as important immunological interventions for reducing the risk of T1D.

β-Conglutins' Unique Mobile Arm Is a Key Structural Domain Involved in Molecular Nutraceutical Properties of Narrow-Leafed Lupin (Lupinus angustifolius L.)

Narrow-leafed lupin (NLL; Lupinus angustifolius L.) has multiple nutraceutical properties that may result from unique structural features of β-conglutin proteins, such as the mobile arm at the N-terminal, a structural domain rich in α-helices. A similar domain has not been found in other vicilin proteins of legume species. We used affinity chromatography to purify recombinant complete and truncated (without the mobile arm domain, tβ5 and tβ7) forms of NLL β5 and β7 conglutin proteins. We then used biochemical and molecular biology techniques in ex vivo and in vitro systems to evaluate their anti-inflammatory activity and antioxidant capacity. The complete β5 and β7 conglutin proteins decreased pro-inflammatory mediator levels (e.g., nitric oxide), mRNA expression levels (iNOS, TNFα, IL-1β), and the protein levels of pro-inflammatory cytokine TNF-α, interleukins (IL-1β, IL-2, IL-6, IL-8, IL-12, IL-17, IL-27), and other mediators (INFγ, MOP, S-TNF-R1/-R2, and TWEAK), and exerted a regulatory oxidative balance effect in cells as demonstrated in glutathione, catalase, and superoxide dismutase assays. The truncated tβ5 and tβ7 conglutin proteins did not have these molecular effects. These results suggest that β5 and β7 conglutins have potential as functional food components due to their anti-inflammatory and oxidative cell state regulatory properties, and that the mobile arm of NLL β-conglutin proteins is a key domain in the development of nutraceutical properties, making NLL β5 and β7 excellent innovative candidates as functional foods.

Impact of Chemical Endocrine Disruptors and Hormone Modulators on the Endocrine System

There is growing concern regarding the health and safety issues of endocrine-disrupting chemicals (EDCs). Long-term exposure to EDCs has alarming adverse health effects through both hormone-direct and hormone-indirect pathways. Non-chemical agents, including physical agents such as artificial light, radiation, temperature, and stress exposure, are currently poorly investigated, even though they can seriously affect the endocrine system, by modulation of hormonal action. Several mechanisms have been suggested to explain the interference of EDCs with hormonal activity. However, difficulty in quantifying the exposure, low standardization of studies, and the presence of confounding factors do not allow the establishment of a causal relationship between endocrine disorders and exposure to specific toxic agents. In this review, we focus on recent findings on the effects of EDCs and hormone system modulators on the endocrine system, including the thyroid, parathyroid glands, adrenal steroidogenesis, beta-cell function, and male and female reproductive function.