IL-1beta caused pancreatic beta-cells apoptosis is mediated in part by endoplasmic reticulum stress via the induction of endoplasmic reticulum Ca2+ release through the c-Jun N-terminal kinase pathway

Pancreatic β-Cell Identity Change through the Lens of Single-Cell Omics Research

The main hallmark in the development of both type 1 and type 2 diabetes is a decline in functional β-cell mass. This decline is predominantly attributed to β-cell death, although recent findings suggest that the loss of β-cell identity may also contribute to β-cell dysfunction. This phenomenon is characterized by a reduced expression of key markers associated with β-cell identity. This review delves into the insights gained from single-cell omics research specifically focused on β-cell identity. It highlights how single-cell omics based studies have uncovered an unexpected level of heterogeneity among β-cells and have facilitated the identification of distinct β-cell subpopulations through the discovery of cell surface markers, transcriptional regulators, the upregulation of stress-related genes, and alterations in chromatin activity. Furthermore, specific subsets of β-cells have been identified in diabetes, such as displaying an immature, dedifferentiated gene signature, expressing significantly lower insulin mRNA levels, and expressing increased β-cell precursor markers. Additionally, single-cell omics has increased insight into the detrimental effects of diabetes-associated conditions, including endoplasmic reticulum stress, oxidative stress, and inflammation, on β-cell identity. Lastly, this review outlines the factors that may influence the identification of β-cell subpopulations when designing and performing a single-cell omics experiment.

Role of signal transduction pathways in IL-1β-induced apoptosis: Pathological and therapeutic aspects

BACKGROUND

Interleukin-1β (IL-1β) is a pro-inflammatory cytokine mainly produced by monocytes and macrophages with a wide range of biological effects. Evidence has shown that IL-1β plays a vital role in the process of apoptosis; however, the specific mechanisms, by which IL-1β induces apoptosis, vary due to different cellular and experimental conditions. Therefore, this present reviewstudy aimed to systematically review the association between the molecular mechanisms of IL-1β-induced apoptosis in pathological processes and the role of signaling pathways. This article also sought to briefly investigate the potential of signaling pathway-targeted therapy in the prevention and treatment of disease.

METHODS

This is a literature review article. The present discourse aim is first to scrutinize and assess the available literature on IL-1β and apoptosis. The relevant studies using the keywords of "IL-1β-induced apoptosis" and "signaling pathways" were searched in the databases of PubMed, Scopus, Google Scholar, and Web of Science. Gathered relevant material, and extracted information was then assessed.

RESULTS

IL-1β can induce apoptosis in various types of cells under different external stimuli via the mitochondrial pathway, death receptor pathway and endoplasmic reticulum pathway, and that the different pathways are often interconnected. The NF-kB signaling pathway, p38MAPK, and JNK signaling pathways mainly play a proapoptotic part, and the ERK1/2 pathway has a bidirectional role in regulating apoptosis, while activation of the PI3K-Akt signaling pathway can inhibit apoptosis.

CONCLUSION

This review indicates that IL-1β-induced apoptosis plays an important role in pathogenesis and development of pathology of many inflammatory diseases. Elucidating the role of the signaling pathways will aid the development of targeted therapeutic treatments.

Integrated analysis of endoplasmic reticulum stress regulators' expression identifies distinct subtypes of autism spectrum disorder

Endoplasmic reticulum (ER) stress has been demonstrated to play important roles in a variety of human diseases. However, their relevance to autism spectrum disorder (ASD) remains largely unknown. Herein, we aimed to investigate the expression patterns and potential roles of the ER stress regulators in ASD. The ASD expression profiles GSE111176 and GSE77103 were compiled from the Gene Expression Omnibus (GEO) database. ER stress score determined by the single sample gene set enrichment analysis (ssGSEA) was significantly higher in ASD patients. Differential analysis revealed that there were 37 ER stress regulators dysregulated in ASD. Based on their expression profile, the random forest and artificial neuron network techniques were applied to build a classifier that can effectively distinguish ASD from control samples among independent datasets. Weighted gene co-expression network analysis (WGCNA) screened out the turquoise module with 774 genes was closely related to the ER stress score. Through the overlapping results of the turquoise module and differential expression ER stress genes, hub regulators were gathered. The TF/miRNA-hub gene interaction networks were created. Furthermore, the consensus clustering algorithm was performed to cluster the ASD patients, and there were two ASD subclusters. Each subcluster has unique expression profiles, biological functions, and immunological characteristics. In ASD subcluster 1, the FAS pathway was more enriched, while subcluster 2 had a higher level of plasma cell infiltration as well as the BCR signaling pathway and interleukin receptor reaction reactivity. Finally, the Connectivity map (CMap) database was used to find prospective compounds that target various ASD subclusters. A total of 136 compounds were significantly enriched. In addition to some specific drugs which can effectively reverse the differential gene expression of each subcluster, we found that the PKC inhibitor BRD-K09991945 that targets Glycogen synthase kinase 3β (GSK3B) might have a therapeutic effect on both ASD subtypes that worth of the experimental validation. Our finding proved that ER stress plays a crucial role in the diversity and complexity of ASD, which may inform both mechanistic and therapeutic assessments of the disorder.

Could very low-calorie ketogenic diets turn off low grade inflammation in obesity? Emerging evidence

Obesity is an emerging non-communicable disease associated with chronic low-grade inflammation and oxidative stress, compounded by the development of many obesity-related diseases, such as cardiovascular disease, type 2 diabetes mellitus, and a range of cancers. Originally developed for the treatment of epilepsy in drug non-responder children, the ketogenic diet (KD) is being increasingly used in the treatment of many diseases, including obesity and obesity-related conditions. The KD is a dietary pattern characterized by high fat intake, moderate to low protein consumption, and very low carbohydrate intake (<50 g) that has proved to be an effective and weight-loss tool. In addition, it also appears to be a dietary intervention capable of improving the inflammatory state and oxidative stress in individuals with obesity by means of several mechanisms. The main activity of the KD has been linked to improving mitochondrial function and decreasing oxidative stress. β-hydroxybutyrate, the most studied ketone body, has been shown to reduce the production of reactive oxygen species, improving mitochondrial respiration. In addition, KDs exert anti-inflammatory activity through several mechanisms, e.g., by inhibiting activation of the nuclear factor kappa-light-chain-enhancer of activated B cells, and the inflammatory nucleotide-binding, leucine-rich-containing family, pyrin domain-containing-3, and inhibiting histone deacetylases. Given the rising interest in the topic, this review looks at the underlying anti-inflammatory and antioxidant mechanisms of KDs and their possible recruitment in the treatment of obesity and obesity-related disorders.

β-Cell Death in Diabetes: Past Discoveries, Present Understanding, and Potential Future Advances

β-cell death is regarded as a major event driving loss of insulin secretion and hyperglycemia in both type 1 and type 2 diabetes mellitus. In this review, we explore past, present, and potential future advances in our understanding of the mechanisms that promote β-cell death in diabetes, with a focus on the primary literature. We first review discoveries of insulin insufficiency, β-cell loss, and β-cell death in human diabetes. We discuss findings in humans and mouse models of diabetes related to autoimmune-associated β-cell loss and the roles of autoreactive T cells, B cells, and the β cell itself in this process. We review discoveries of the molecular mechanisms that underlie β-cell death-inducing stimuli, including proinflammatory cytokines, islet amyloid formation, ER stress, oxidative stress, glucotoxicity, and lipotoxicity. Finally, we explore recent perspectives on β-cell death in diabetes, including: (1) the role of the β cell in its own demise, (2) methods and terminology for identifying diverse mechanisms of β-cell death, and (3) whether non-canonical forms of β-cell death, such as regulated necrosis, contribute to islet inflammation and β-cell loss in diabetes. We believe new perspectives on the mechanisms of β-cell death in diabetes will provide a better understanding of this pathological process and may lead to new therapeutic strategies to protect β cells in the setting of diabetes.

Chronic tissue inflammation and metabolic disease

In this review, Lee and Olefsky discuss the characteristics of chronic inflammation in the major metabolic tissues and how obesity triggers these events, including a focus on the role of adipose tissue hypoxia and macrophage-derived exosomes.

Obesity is the most common cause of insulin resistance, and the current obesity epidemic is driving a parallel rise in the incidence of T2DM. It is now widely recognized that chronic, subacute tissue inflammation is a major etiologic component of the pathogenesis of insulin resistance and metabolic dysfunction in obesity. Here, we summarize recent advances in our understanding of immunometabolism. We discuss the characteristics of chronic inflammation in the major metabolic tissues and how obesity triggers these events, including a focus on the role of adipose tissue hypoxia and macrophage-derived exosomes. Last, we also review current and potential new therapeutic strategies based on immunomodulation.

Redox Homeostasis in Pancreatic β-Cells: From Development to Failure

Redox status is a key determinant in the fate of β-cell. These cells are not primarily detoxifying and thus do not possess extensive antioxidant defense machinery. However, they show a wide range of redox regulating proteins, such as peroxiredoxins, thioredoxins or thioredoxin reductases, etc., being functionally compartmentalized within the cells. They keep fragile redox homeostasis and serve as messengers and amplifiers of redox signaling. β-cells require proper redox signaling already in cell ontogenesis during the development of mature β-cells from their progenitors. We bring details about redox-regulated signaling pathways and transcription factors being essential for proper differentiation and maturation of functional β-cells and their proliferation and insulin expression/maturation. We briefly highlight the targets of redox signaling in the insulin secretory pathway and focus more on possible targets of extracellular redox signaling through secreted thioredoxin1 and thioredoxin reductase1. Tuned redox homeostasis can switch upon chronic pathological insults towards the dysfunction of β-cells and to glucose intolerance. These are characteristics of type 2 diabetes, which is often linked to chronic nutritional overload being nowadays a pandemic feature of lifestyle. Overcharged β-cell metabolism causes pressure on proteostasis in the endoplasmic reticulum, mainly due to increased demand on insulin synthesis, which establishes unfolded protein response and insulin misfolding along with excessive hydrogen peroxide production. This together with redox dysbalance in cytoplasm and mitochondria due to enhanced nutritional pressure impact β-cell redox homeostasis and establish prooxidative metabolism. This can further affect β-cell communication in pancreatic islets through gap junctions. In parallel, peripheral tissues losing insulin sensitivity and overall impairment of glucose tolerance and gut microbiota establish local proinflammatory signaling and later systemic metainflammation, i.e., low chronic inflammation prooxidative properties, which target β-cells leading to their dedifferentiation, dysfunction and eventually cell death.

Crosstalk between Macrophages and Pancreatic β-Cells in Islet Development, Homeostasis and Disease

Macrophages are highly heterogeneous and plastic immune cells with peculiar characteristics dependent on their origin and microenvironment. Following pathogen infection or damage, circulating monocytes can be recruited in different tissues where they differentiate into macrophages. Stimuli present in the surrounding milieu induce the polarisation of macrophages towards a pro-inflammatory or anti-inflammatory profile, mediating inflammatory or homeostatic responses, respectively. However, macrophages can also derive from embryonic hematopoietic precursors and reside in specific tissues, actively participating in the development and the homeostasis in physiological conditions. Pancreatic islet resident macrophages are present from the prenatal stages onwards and show specific surface markers and functions. They localise in close proximity to β-cells, being exquisite sensors of their secretory ability and viability. Over the years, the crucial role of macrophages in β-cell differentiation and homeostasis has been highlighted. In addition, macrophages are emerging as central players in the initiation of autoimmune insulitis in type 1 diabetes and in the low-grade chronic inflammation characteristic of obesity and type 2 diabetes pathogenesis. The present work reviews the current knowledge in the field, with a particular focus on the mechanisms of communication between β-cells and macrophages that have been described so far.

Human islet amyloid polypeptide (hIAPP) - a curse in type II diabetes mellitus: insights from structure and toxicity studies

The human islet amyloid polypeptide (hIAPP) or amylin, a neuroendocrine peptide hormone, is known to misfold and form amyloidogenic aggregates that have been observed in the pancreas of 90% subjects with Type 2 Diabetes Mellitus (T2DM). Under normal physiological conditions, hIAPP is co-stored and co-secreted with insulin; however, under chronic hyperglycemic conditions associated with T2DM, the overexpression of hIAPP occurs that has been associated with the formation of amyloid deposits; as well as the death and dysfunction of pancreatic β-islets in T2DM. Hitherto, various biophysical and structural studies have shown that during this process of aggregation, the peptide conformation changes from random structure to helix, then to β-sheet, subsequently to cross β-sheets, which finally form left-handed helical aggregates. The intermediates, formed during this process, have been shown to induce higher cytotoxicity in the β-cells by inducing cell membrane disruption, endoplasmic reticulum stress, mitochondrial dysfunction, oxidative stress, islet inflammation, and DNA damage. As a result, several research groups have attempted to target both hIAPP aggregation phenomenon and the destabilization of preformed fibrils as a therapeutic intervention for T2DM management. In this review, we have summarized structural aspects of various forms of hIAPP viz. monomer, oligomers, proto-filaments, and fibrils of hIAPP. Subsequently, cellular toxicity caused by toxic conformations of hIAPP has been elaborated upon. Finally, the need for performing structural and toxicity studies in vivo to fill in the gap between the structural and cellular aspects has been discussed.

Lactogens Reduce Endoplasmic Reticulum Stress-Induced Rodent and Human β-Cell Death and Diabetes Incidence in Akita Mice

Diabetes occurs due to a loss of functional β-cells, resulting from β-cell death and dysfunction. Lactogens protect rodent and human β-cells in vitro and in vivo against triggers of β-cell cytotoxicity relevant to diabetes, many of which converge onto a common pathway of endoplasmic reticulum (ER) stress. However, whether lactogens modulate the ER stress pathway is unknown. This study examines whether lactogens can protect β-cells against ER stress and mitigate diabetes incidence in Akita (Ak) mice, a rodent model of ER stress-induced diabetes, akin to neonatal diabetes in humans. We show that lactogens protect INS-1 cells, primary rodent and human β-cells in vitro against two distinct ER stressors, tunicamycin and thapsigargin, through activation of the JAK2/STAT5 pathway. Lactogens mitigate expression of proapoptotic molecules in the ER stress pathway that are induced by chronic ER stress in INS-1 cells and rodent islets. Transgenic expression of placental lactogen in β-cells of Ak mice drastically reduces the severe hyperglycemia, diabetes incidence, hypoinsulinemia, β-cell death, and loss of β-cell mass observed in Ak littermates. These are the first studies in any cell type demonstrating that lactogens modulate the ER stress pathway, causing enhanced β-cell survival and reduced diabetes incidence in the face of chronic ER stress.

Advances in the development of gene therapy, noncoding RNA, and exosome-based treatments for tendinopathy

Tendinopathy is a common musculoskeletal disorder characterized by chronic low-grade inflammation and tissue degeneration. Tendons have poor innate healing ability and there is currently no cure for tendinopathy. Studies elucidating mechanisms underlying the pathogenesis of tendinopathy and mechanisms mediating the genesis of tendons during development have provided novel targets and strategies to enhance tendon healing and repair. This review summarizes the current understanding and treatments for tendinopathy. The review also highlights recent advances in gene therapy, the potential of noncoding RNAs, such as microRNAs, and exosomes, which are nanometer-sized extracellular vesicles secreted from cells, for the treatment of tendinopathy.

Chemical chaperones improve the functional recovery of stunned myocardium by attenuating the endoplasmic reticulum stress

AIM

Myocardial ischaemia/reperfusion (I/R) produces structural and functional alterations depending on the duration of ischaemia. Brief ischaemia followed by reperfusion causes reversible contractile dysfunction (stunned heart) but long-lasting ischaemia followed by reperfusion can result in irreversible injury with cell death. Events during I/R can alter endoplasmic reticulum (ER) function leading to the accumulation of unfolded/misfolded proteins. The resulting ER stress induces activation of several signal transduction pathways, known as unfolded protein response (UPR). Experimental evidence shows that UPR contributes to cell death in irreversible I/R injury; however, there is still uncertainty for its occurrence in the stunned myocardium. This study investigated the ER stress response and its functional impact on the post-ischaemic cardiac performance of the stunned heart.

METHODS

Perfused rat hearts were subjected to 20 minutes of ischaemia followed by 30 minutes of reperfusion. UPR markers were evaluated by qRT-PCR and western blot. Post-ischaemic mechanical recovery was measured in absence and presence of two chemical chaperones: tauroursodeoxycholic acid (TUDCA) and 4-phenylbutyric acid (4-PBA).

RESULTS

Analysis of mRNA and protein levels of various ER stress effectors demonstrated that different UPR signalling cascades, involving both pro-survival and pro-apoptotic pathways, are activated. Inhibition of the UPR with chemical chaperones improved the post-ischaemic recovery of cardiac mechanical function without affecting the I/R-induced increase in oxidative stress.

CONCLUSION

Our results suggest that prevention of ER stress by chemical chaperones could be a therapeutic tool to limit deterioration of the contractile function in clinical settings in which the phenomenon of myocardial stunning is present.

Air pollution-associated changes in biomarkers of diabetes risk

Supplemental Digital Content is available in the text.

Background:

Ambient particulate matter (PM) and nitrogen oxide (NO_x) air pollution may be diabetogenic.

Objective:

To examine longitudinal associations of short- and longer-term mean PM ≤10 μm (PM₁₀), PM ≤2.5 μm (PM_2.5), and NO_x concentrations with five biomarkers of diabetes risk.

Methods:

We studied a stratified, random minority oversample of nondiabetic Women’s Health Initiative clinical trials participants with biomarkers and geocoded participant address-specific mean air pollution concentrations available at repeated visits (years = 1993–2004; n = 3,915; mean age = 62.7 years; 84% white). We log-transformed the biomarkers, then used multi-level, mixed-effects, longitudinal models weighted for sampling design/attrition and adjusted for sociodemographic, clinical, and meteorological covariates to estimate their associations with air pollutants.

Results:

Biomarkers exhibited null to suggestively negative associations with short- and longer-term PM₁₀ and NO_x concentrations, e.g., −3.1% (−6.1%, 0.1%), lower homeostatic model assessment of insulin resistance per 10 μg/m³ increase in 12-month PM₁₀. A statistically significant interaction by impaired fasting glucose (IFG) at baseline in this analysis indicated potentially adverse effects only among women with versus without IFG, i.e., 1.4% (−3.5%, 6.5%) versus −4.6% (−7.9%, −1.1%), P_interaction < 0.05. In contrast, longer-term PM_2.5 concentrations were largely but not statistically significantly associated with higher biomarkers.

Conclusions:

Low-level short-term PM₁₀ and NO_x concentrations may have negligible adverse effects on biomarkers of diabetes risk. Although longer-term mean PM_2.5 concentrations showed primarily null associations with these biomarkers, results suggestively indicated that PM_2.5 exposure over the range of concentrations experienced in the United States may adversely affect biomarkers of diabetes risk at the population level, as may longer-term mean PM₁₀ concentrations among women with IFG.

Cadmium exposure induces pancreatic β-cell death via a Ca2+-triggered JNK/CHOP-related apoptotic signaling pathway

Cadmium (Cd) is known to be ranked the 7^th hazardous substance in the Substance Priority List by Agency for Toxic Substances and Disease Registry. The experimental and epidemiological data have suggested that Cd is linked to the development of diabetes mellitus (DM). The molecular mechanism of Cd on the pancreatic β-cell cytotoxicity still remains unclear. Evidence has pointed toward that Ca²⁺ is an important regulator of toxic insult-induced β-cell cytotoxicity. The role of Ca²⁺ in the Cd-induced β-cell cytotoxicity is still unknown. In this study, we found that Cd exposure significantly inhibited insulin secretion and cell viability in the pancreatic β-cell-derived RIN-m5F cells. Cd exposure induced apoptotic events, including the increased populations of apoptotic cells and sub-G1 hypodiploid cells, and caspase-3/-7/-9 and poly (ADP-ribose) polymerase (PARP) activation, which largely depended on the activation of c-Jun N-terminal kinase (JNK) and C/EBP homologous protein (CHOP). Transfection with siRNAs for JNK and CHOP or pretreatment with specific pharmacological inhibitor of JNK (SP600125) in β-cells effectively prevented the Cd-induced insulin secretion dysfunction and apoptosis. JNK-specific siRNA dramatically suppressed Cd-induced JNK phosphorylation and CHOP protein expression, but JNK phosphorylation could not be inhibited by CHOP-specific siRNA. Furthermore, Cd exposure significantly increased the intracellular calcium ([Ca²⁺]_i) levels. Buffering the Ca²⁺ response with BAPTA/AM effectively abrogated the Cd-induced [Ca²⁺]_i elevation, insulin secretion dysfunction, apoptosis, and protein expression of JNK phosphorylation and CHOP activation. Taken together, these findings demonstrated that Cd exposure exerts β-cell death via a [Ca²⁺]_i-dependent JNK activation-activated downstream CHOP-related apoptotic signaling pathway.

Hydrogen inhalation protects hypoxic-ischemic brain damage by attenuating inflammation and apoptosis in neonatal rats

Hypoxic–ischemic brain damage (HIBD) is one of the leading causes of brain injury in infant with high risk of mortality and disability; therefore, it is important to explore more feasible and effective treatment strategies. Here, we assessed the neuroprotective effects of different hydrogen inhalation times for the treatment of HIBD. We induced hypoxia–ischemia in Sprague–Dawley rats (postnatal day 7, both sexes), followed by treatment with hydrogen inhalation for 30, 60, or 90 min. Morphological brain injury was assessed by Nissl and TUNEL staining. Acute inflammation was evaluated by examining the expression of interleukin-1β (IL-1β) and NF-κB p65, as well as Iba-1 immunofluorescence in the brain. Neural apoptosis was evaluated by examining the expression of P-JNK and p53 as well as NeuN immunofluorescence. Neurobehavioral function of rats was evaluated by Morris water maze test at 36 days after surgery. The results showed that hypoxia–ischemia injury induced the inflammatory response of microglia; however, these changes were inhibited by hydrogen inhalation. The inhibitory effects became more apparent as the treatment duration increased ( P < 0.05). Furthermore, hypoxia–ischemia induced neuronal damage and increased the expression of the apoptotic factors, P-JNK, and p53, which were attenuated by hydrogen inhalation ( P < 0.05). Hypoxia–ischemia caused long-term spatial memory deficits during brain maturation, which were ameliorated by hydrogen inhalation ( P < 0.01). In conclusion, hypoxia–ischemia induced severe long-term damage to the brain, which could be alleviated by hydrogen inhalation in a time-dependent manner.

Impact statement

Oxidative stress is known to be involved in the main pathological progression of neonatal hypoxic–ischemic brain damage (HIBD). Hydrogen (H2) is an antioxidant that can be used to treat HIBD; however, the mechanism by which hydrogen may be used as a promising treatment for neonates with HIBD is not very clear. This study demonstrated that inhaled H2 is neuroprotective against HIBD in SpragueDawley rats by inhibiting the brain’s inflammatory response and neuronal apoptosis or damage and protecting against spatial memory decline. Further, this study showed that inhaled H2 has potential as a therapeutic approach for HIBD. This is relevant to clinical treatment protocols when hypoxia–ischemia is suspected in neonates.

Glucose-Induced β-Cell Dysfunction In Vivo: Evidence for a Causal Role of C-jun N-terminal Kinase Pathway

Prolonged elevation of glucose can adversely affect β-cell function. Oxidative stress, which has been implicated in glucose-induced β-cell dysfunction, can activate c-jun N-terminal kinase (JNK). However, whether JNK is causal in glucose-induced β-cell dysfunction in vivo is unclear. Therefore, we aimed at investigating the causal role of JNK activation in in vivo models of glucose-induced β-cell dysfunction. Glucose-induced β-cell dysfunction was investigated in the presence or absence of JNK inhibition. JNK inhibition was achieved using either (i) the JNK-specific inhibitor SP600125 or (ii) JNK-1-null mice. (i) Rats or mice were infused intravenously with saline or glucose with or without SP600125. (ii) JNK-1 null mice and their littermate wild-type controls were infused intravenously with saline or glucose. Following the glucose infusion periods in rats and mice, β-cell function was assessed in isolated islets or in vivo using hyperglycemic clamps. Forty-eight-hour hyperglycemia at ~20 mM in rats or 96-hour hyperglycemia at ~13 mM in mice impaired β-cell function in isolated islets and in vivo. Inhibition of JNK using either SP600125 or JNK-1-null mice prevented glucose-induced β-cell dysfunction in isolated islets and in vivo. Islets of JNK-1-null mice exposed to hyperglycemia in vivo showed an increase in Pdx-1 and insulin 2 mRNA, whereas islets of wild-type mice did not. Together, these data show that JNK pathway is involved in glucose-induced β-cell dysfunction in vivo and is thus a potential therapeutic target for type 2 diabetes.

Abnormal Glucose Metabolism in Rheumatoid Arthritis

The incidence of abnormal glucose metabolism in patients with rheumatoid arthritis was considerably higher than the general population. The persistent systemic inflammatory state in rheumatoid arthritis might be associated with the glucose metabolism dysfunction. In this context, insulin resistance, islet β cell apoptosis, inflammatory cytokines, and other aspects which were linked with abnormal glucose metabolism in rheumatoid arthritis were reviewed. This review will be helpful in understanding the abnormal glucose metabolism mechanism in patients with rheumatoid arthritis and might be conducive to finding an effective treatment.

Transient inflammatory response mediated by interleukin-1β is required for proper regeneration in zebrafish fin fold

Cellular responses to injury are crucial for complete tissue regeneration, but their underlying processes remain incompletely elucidated. We have previously reported that myeloid-defective zebrafish mutants display apoptosis of regenerative cells during fin fold regeneration. Here, we found that the apoptosis phenotype is induced by prolonged expression of interleukin 1 beta (il1b). Myeloid cells are considered to be the principal source of Il1b, but we show that epithelial cells express il1b in response to tissue injury and initiate the inflammatory response, and that its resolution by macrophages is necessary for survival of regenerative cells. We further show that Il1b plays an essential role in normal fin fold regeneration by regulating expression of regeneration-induced genes. Our study reveals that proper levels of Il1b signaling and tissue inflammation, which are tuned by macrophages, play a crucial role in tissue regeneration.

DOI:http://dx.doi.org/10.7554/eLife.22716.001

Animals and other multicellular organisms all have at least some ability to regenerate lost or wounded tissues. Zebrafish are particularly good at this to the extent that they can replace damaged or lost body parts with exact replicas of the originals. In 2015, a team of researchers found that some mutant zebrafish that lack blood cells including immune cells are unable to regenerate lost tissues. This is because the cells that are primed to regenerate die instead, but it was not clear why this happens.

Many immune cells have roles in fighting infection and in responding to tissue damage.When a tissue is damaged, the area often becomes inflamed as white blood cells called macrophages flock to the damaged area to protect it from infection and remove damaged cells.

Hasegawa et al. – who include several researchers involved in the 2015 study – used genetic approaches to investigate the role of inflammation in tissue regeneration in zebrafish. The experiments show that several genes involved in inflammation – including one called interleukin 1b – were active over longer periods of time in the mutant fish compared with normal zebrafish. The gene produces a signal protein and this prolonged activity causes the primed regenerative cells to die. However, the cells can survive if interleukin 1b activity is quickly suppressed by macrophages. The experiments also show that, in order for tissues to regenerate properly, interleukin 1b needs to be active for only a short period of time.

The findings reveal that some inflammation is needed for tissues to regenerate, but that a more severe inflammatory response can block the process. A future challenge will be to identify the signals that macrophages produce to suppress inflammation to allow tissues to regenerate. These anti-inflammatory signals may have the potential to be used as drugs to cure chronic inflammatory diseases and boost tissue regeneration potential in humans.

DOI:http://dx.doi.org/10.7554/eLife.22716.002

Environmental Factors Contribute to β Cell Endoplasmic Reticulum Stress and Neo-Antigen Formation in Type 1 Diabetes

Type 1 diabetes (T1D) is an autoimmune disease in which immune-mediated targeting and destruction of insulin-producing pancreatic islet β cells leads to chronic hyperglycemia. There are many β cell proteins that are targeted by autoreactive T cells in their native state. However, recent studies have demonstrated that many β cell proteins are recognized as neo-antigens following posttranslational modification (PTM). Although modified neo-antigens are well-established targets of pathology in other autoimmune diseases, the effects of neo-antigens in T1D progression and the mechanisms by which they are generated are not well understood. We have demonstrated that PTM occurs during endoplasmic reticulum (ER) stress, a process to which β cells are uniquely susceptible due to the high rate of insulin production in response to dynamic glucose sensing. In the context of genetic susceptibility to autoimmunity, presentation of these modified neo-antigens may activate autoreactive T cells and cause pathology. However, inherent β cell ER stress and protein PTM do not cause T1D in every genetically susceptible individual, suggesting the contribution of additional factors. Indeed, many environmental factors, such as viral infection, chemicals, or inflammatory cytokines, are associated with T1D onset, but the mechanisms by which these factors lead to disease onset remain unknown. Since these environmental factors also cause ER stress, exposure to these factors may enhance production of neo-antigens, therefore boosting β cell recognition by autoreactive T cells and exacerbating T1D pathogenesis. Therefore, the combined effects of physiological ER stress and the stress that is induced by environmental factors may lead to breaks in peripheral tolerance, contribute to antigen spread, and hasten disease onset. This Hypothesis and Theory article summarizes what is currently known about ER stress and protein PTM in autoimmune diseases including T1D and proposes a role for environmental factors in breaking immune tolerance to β cell antigens through neo-antigen formation.

Antiseptic effect of sea cucumber (Holothuria atra) against multi-organ failure induced by sepsis: Molecular and histopathological study

Sepsis is a systemic inflammatory response to infection and severe sepsis patients can develop acute lung and liver injury. The aim of the present study was to evaluate the efficacy of Holothuria atra methanolic body wall extract (HaE), as an antioxidant and anti-inflammatory agent against induced sepsis in a cecal ligation and puncture (CLP) rat model. In total, 30 males albino rats were divided into three groups (n=10 each) as follows: Sham (Sh), which was used as negative control; sepsis (Se), which was used as a positive control and was subjected to CLP surgery; and Ho, which was subjected to CLP and fed with 200 mg/kg (body weight) of HaE, once daily for 7 days. Subsequently, the expression of various genes was detected by polymerase chain reaction, while liver and lung tissues were examined by immunohistochemistry. The expression of Caspase-3 was significantly reduced in liver and lung tissues in the Ho group, while the expression levels of Gsta2, Cat and Sod1 genes were slightly reduced in the Ho group, when compared with the Se group. In addition, expression levels of tumor necrosis factor, interferon-γ, liver interleukin (IL)1b and lung IL1a were reduced in the Ho group compared with the Se group. Furthermore, histopathological changes were observed in liver tissues of the Se group, including congestion of hepatoportal blood vessel and focal hepatic necrosis, while lung tissues showed marked edema, hemorrhage and alveolar septal thickening. The Ho group showed apparent normal hepatic parenchyma and slight interstitial pneumonia. Immunohistochemical staining of caspase-3 in liver and lung tissues showed no expression in the Sh group, strong expression in the Se group and moderate expression in the Ho group. In conclusion, HaE demonstrated beneficial effect against induced sepsis, which may be attributed to its antioxidant and antiapoptotic activities.

Inherent ER stress in pancreatic islet β cells causes self-recognition by autoreactive T cells in type 1 diabetes

Type 1 diabetes (T1D) is an autoimmune disease characterized by pancreatic β cell destruction induced by islet reactive T cells that have escaped central tolerance. Many physiological and environmental triggers associated with T1D result in β cell endoplasmic reticulum (ER) stress and dysfunction, increasing the potential for abnormal post-translational modification (PTM) of proteins. We hypothesized that β cell ER stress induced by environmental and physiological conditions generates abnormally-modified proteins for the T1D autoimmune response. To test this hypothesis we exposed the murine CD4(+) diabetogenic BDC2.5 T cell clone to murine islets in which ER stress had been induced chemically (Thapsigargin). The BDC2.5 T cell IFNγ response to these cells was significantly increased compared to non-treated islets. This β cell ER stress increased activity of the calcium (Ca(2+))-dependent PTM enzyme tissue transglutaminase 2 (Tgase2), which was necessary for full stress-dependent immunogenicity. Indeed, BDC2.5 T cells responded more strongly to their antigen after its modification by Tgase2. Finally, exposure of non-antigenic murine insulinomas to chemical ER stress in vitro or physiological ER stress in vivo caused increased ER stress and Tgase2 activity, culminating in higher BDC2.5 responses. Thus, β cell ER stress induced by chemical and physiological triggers leads to β cell immunogenicity through Ca(2+)-dependent PTM. These findings elucidate a mechanism of how β cell proteins are modified and become immunogenic, and reveal a novel opportunity for preventing β cell recognition by autoreactive T cells.

An initial phase of JNK activation inhibits cell death early in the endoplasmic reticulum stress response

Accumulation of unfolded proteins in the endoplasmic reticulum (ER) activates the unfolded protein response (UPR). In mammalian cells, UPR signals generated by several ER-membrane-resident proteins, including the bifunctional protein kinase endoribonuclease IRE1α, control cell survival and the decision to execute apoptosis. Processing of XBP1 mRNA by the RNase domain of IRE1α promotes survival of ER stress, whereas activation of the mitogen-activated protein kinase JNK family by IRE1α late in the ER stress response promotes apoptosis. Here, we show that activation of JNK in the ER stress response precedes activation of XBP1. This activation of JNK is dependent on IRE1α and TRAF2 and coincides with JNK-dependent induction of expression of several antiapoptotic genes, including cIap1 (also known as Birc2), cIap2 (also known as Birc3), Xiap and Birc6 ER-stressed Jnk1(-/-) Jnk2(-/-) (Mapk8(-/-) Mapk9(-/-)) mouse embryonic fibroblasts (MEFs) display more pronounced mitochondrial permeability transition and increased caspase 3/7 activity compared to wild-type MEFs. Caspase 3/7 activity is also elevated in ER-stressed cIap1(-/-) cIap2(-/-) and Xiap(-/-) MEFs. These observations suggest that JNK-dependent transcriptional induction of several inhibitors of apoptosis contributes to inhibiting apoptosis early in the ER stress response.

Cytokines and Pancreatic β-Cell Apoptosis

The discovery 30 years ago that inflammatory cytokines cause a concentration, activity, and time-dependent bimodal response in pancreatic β-cell function and viability has been a game-changer in the fields of research directed at understanding inflammatory regulation of β-cell function and survival and the causes of β-cell failure and destruction in diabetes. Having until then been confined to the use of pathophysiologically irrelevant β-cell toxic chemicals as a model of β-cell death, researchers could now mimic endocrine and paracrine effects of the cytokine response in vitro by titrating concentrations in the low to the high picomolar-femtomolar range and vary exposure time for up to 14-16h to reproduce the acute regulatory effects of systemic inflammation on β-cell secretory responses, with a shift to inhibition at high picomolar concentrations or more than 16h of exposure to illustrate adverse effects of local, chronic islet inflammation. Since then, numerous studies have clarified how these bimodal responses depend on discrete signaling pathways. Most interest has been devoted to the proapoptotic response dependent upon mainly nuclear factor κ B and mitogen-activated protein kinase activation, leading to gene expressional changes, endoplasmic reticulum stress, and triggering of mitochondrial dysfunction. Preclinical studies have shown preventive effects of cytokine antagonism in animal models of diabetes, and clinical trials demonstrating proof of concept are emerging. The full clinical potential of anticytokine therapies has yet to be shown by testing the incremental effects of appropriate dosing, timing, and combinations of treatments. Due to the considerable translational importance of enhancing the precision, specificity, and safety of antiinflammatory treatments of diabetes, we review here the cellular, preclinical, and clinical evidence of which of the death pathways recently proposed in the Nomenclature Committee on Cell Death 2012 Recommendations are activated by inflammatory cytokines in the pancreatic β-cell to guide the identification of antidiabetic targets. Although there are still scarce human data, the cellular and preclinical studies point to the caspase-dependent intrinsic apoptosis pathway as the prime effector of inflammatory β-cell apoptosis.

Molybdenum induces pancreatic β-cell dysfunction and apoptosis via interdependent of JNK and AMPK activation-regulated mitochondria-dependent and ER stress-triggered pathways

Molybdenum (Mo), a well-known toxic environmental and industrial pollutant, causes adverse health effects and diseases in humans and has received attention as a potential risk factor for DM. However, the roles of Mo in the mechanisms of the toxicological effects in pancreatic β-cells are mostly unclear. In this study, the results revealed dysfunction of insulin secretion and apoptosis in the pancreatic β-cell-derived RIN-m5F cells and the isolated mouse islets in response to Mo. These effects were accompanied by a mitochondria-dependent apoptotic signals including a decreased in the MMP, an increase in cytochrome c release, and the activation of caspase cascades and PARP. In addition, ER stress was triggered as indicated by several key molecules of the UPR. Furthermore, exposure to Mo induced the activation of ERK1/2, JNK, AMPKα, and GSK3-α/β. Pretreatment with specific pharmacological inhibitors (in RIN-m5F cells and isolated mouse islets) of JNK (SP600125) and AMPK (Compound C) or transfection with si-RNAs (in RIN-m5F cells) specific to JNK and AMPKα effectively prevented the Mo-induced apoptosis and related signals, but inhibitors of ERK1/2 and GSK3-α/β (PD98059 and LiCl, respectively) did not reverse the Mo-induced effects. Additionally, both the inhibitors and specific si-RNAs could suppress the Mo-induced phosphorylation of JNK and AMPKα each other. Taken together, these results suggest that Mo exerts its cytotoxicity on pancreatic β-cells by inducing dysfunction and apoptosis via interdependent JNK and AMPK activation downstream-regulated mitochondrial-dependent and ER stress-triggered apoptosis pathways.

T cell epitopes and post-translationally modified epitopes in type 1 diabetes

Type 1 diabetes (T1D) is an autoimmune disease in which progressive loss of self-tolerance, evidenced by accumulation of auto-antibodies and auto-reactive T cells that recognize diverse self-proteins, leads to immune-mediated destruction of pancreatic beta cells and loss of insulin secretion. In this review, we discuss antigens and epitopes in T1D and the role that post-translational modifications play in circumventing tolerance mechanisms and increasing antigenic diversity. Emerging data suggest that, analogous to other autoimmune diseases such as rheumatoid arthritis and celiac disease, enzymatically modified epitopes are preferentially recognized in T1D. Modifying enzymes such as peptidyl deiminases and tissue transglutaminase are activated in response to beta cell stress, providing a mechanistic link between post-translational modification and interactions with the environment. Although studies of such responses in the at-risk population have been limited, current data suggests that breakdown in tolerance through post-translational modification represents an important checkpoint in the development of T1D.

β cell ER stress and the implications for immunogenicity in type 1 diabetes

Type 1 diabetes (T1D) is a chronic autoimmune disease characterized by hyperglycemia due to progressive immune-mediated destruction of insulin-producing pancreatic islet β cells. Although many elegant studies have identified β cell autoantigens that are targeted by the autoimmune response, the mechanisms by which these autoantigens are generated remain poorly understood. Normal β cell physiology includes a high demand for insulin production and secretion in response to dynamic glucose sensing. This secretory function predisposes β cells to significantly higher levels of endoplasmic reticulum (ER) stress compared to nonsecretory cells. In addition, many environmental triggers associated with T1D onset further augment this inherent ER stress in β cells. ER stress may increase abnormal post-translational modification (PTM) of endogenous β cell proteins. Indeed, in other autoimmune disorders such as celiac disease, systemic lupus erythematosus, multiple sclerosis, and rheumatoid arthritis, abnormally modified neo-antigens are presented by antigen presenting cells (APCs) in draining lymph nodes. In the context of genetic susceptibility to autoimmunity, presentation of neo-antigens activates auto-reactive T cells and pathology ensues. Therefore, the ER stress induced by normal β cell secretory physiology and environmental triggers may be sufficient to generate neo-antigens for the autoimmune response in T1D. This review summarizes what is currently known about ER stress and protein PTM in target organs of other autoimmune disease models, as well as the data supporting a role for ER stress-induced neo-antigen formation in β cells in T1D.

Evidence of contribution of iPLA2β-mediated events during islet β-cell apoptosis due to proinflammatory cytokines suggests a role for iPLA2β in T1D development

Type 1 diabetes (T1D) results from autoimmune destruction of islet β-cells, but the underlying mechanisms that contribute to this process are incompletely understood, especially the role of lipid signals generated by β-cells. Proinflammatory cytokines induce ER stress in β-cells and we previously found that the Ca(2+)-independent phospholipase A2β (iPLA2β) participates in ER stress-induced β-cell apoptosis. In view of reports of elevated iPLA2β in T1D, we examined if iPLA2β participates in cytokine-mediated islet β-cell apoptosis. We find that the proinflammatory cytokine combination IL-1β+IFNγ, induces: a) ER stress, mSREBP-1, and iPLA2β, b) lysophosphatidylcholine (LPC) generation, c) neutral sphingomyelinase-2 (NSMase2), d) ceramide accumulation, e) mitochondrial membrane decompensation, f) caspase-3 activation, and g) β-cell apoptosis. The presence of a sterol regulatory element in the iPLA2β gene raises the possibility that activation of SREBP-1 after proinflammatory cytokine exposure contributes to iPLA2β induction. The IL-1β+IFNγ-induced outcomes (b-g) are all inhibited by iPLA2β inactivation, suggesting that iPLA2β-derived lipid signals contribute to consequential islet β-cell death. Consistent with this possibility, ER stress and β-cell apoptosis induced by proinflammatory cytokines are exacerbated in islets from RIP-iPLA2β-Tg mice and blunted in islets from iPLA2β-KO mice. These observations suggest that iPLA2β-mediated events participate in amplifying β-cell apoptosis due to proinflammatory cytokines and also that iPLA2β activation may have a reciprocal impact on ER stress development. They raise the possibility that iPLA2β inhibition, leading to ameliorations in ER stress, apoptosis, and immune responses resulting from LPC-stimulated immune cell chemotaxis, may be beneficial in preserving β-cell mass and delaying/preventing T1D evolution.

JNK1 protects against glucolipotoxicity-mediated beta-cell apoptosis

Pancreatic β-cell dysfunction is central to type 2 diabetes pathogenesis. Prolonged elevated levels of circulating free-fatty acids and hyperglycemia, also termed glucolipotoxicity, mediate β-cell dysfunction and apoptosis associated with increased c-Jun N-terminal Kinase (JNK) activity. Endoplasmic reticulum (ER) and oxidative stress are elicited by palmitate and high glucose concentrations further potentiating JNK activity. Our aim was to determine the role of the JNK subtypes JNK1, JNK2 and JNK3 in palmitate and high glucose-induced β-cell apoptosis. We established insulin-producing INS1 cell lines stably expressing JNK subtype specific shRNAs to understand the differential roles of the individual JNK isoforms. JNK activity was increased after 3 h of palmitate and high glucose exposure associated with increased expression of ER and mitochondrial stress markers. JNK1 shRNA expressing INS1 cells showed increased apoptosis and cleaved caspase 9 and 3 compared to non-sense shRNA expressing control INS1 cells when exposed to palmitate and high glucose associated with increased CHOP expression, ROS formation and Puma mRNA expression. JNK2 shRNA expressing INS1 cells did not affect palmitate and high glucose induced apoptosis or ER stress markers, but increased Puma mRNA expression compared to non-sense shRNA expressing INS1 cells. Finally, JNK3 shRNA expressing INS1 cells did not induce apoptosis compared to non-sense shRNA expressing INS1 cells when exposed to palmitate and high glucose but showed increased caspase 9 and 3 cleavage associated with increased DP5 and Puma mRNA expression. These data suggest that JNK1 protects against palmitate and high glucose-induced β-cell apoptosis associated with reduced ER and mitochondrial stress.

N-terminal hydrophobic amino acids of activating transcription factor 5 (ATF5) protein confer interleukin 1β (IL-1β)-induced stabilization

Activating transcription factor 5 (ATF5) is a stress-response transcription factor that responds to amino acid limitation and exposure to cadmium chloride (CdCl2) and sodium arsenite (NaAsO2). The N-terminal amino acids contribute to the destabilization of the ATF5 protein in steady-state conditions and serve as a stabilization domain in the stress response after CdCl2 or NaAsO2 exposure. In this study, we show that interleukin 1β (IL-1β), a proinflammatory cytokine, increases the expression of ATF5 protein in HepG2 hepatoma cells in part by stabilizing the ATF5 protein. The N-terminal domain rich in hydrophobic amino acids that is predicted to form a hydrophobic network was responsible for destabilization in steady-state conditions and served as an IL-1β response domain. Furthermore, IL-1β increased the translational efficiency of ATF5 mRNA via the 5' UTRα and phosphorylation of the eukaryotic translation initiation factor 2α (eIF2α). ATF5 knockdown in HepG2 cells up-regulated the IL-1β-induced expression of the serum amyloid A 1 (SAA1) and SAA2 genes. Our results show that the N-terminal hydrophobic amino acids play an important role in the regulation of ATF5 protein expression in IL-1β-mediated immune response and that ATF5 is a negative regulator for IL-1β-induced expression of SAA1 and SAA2 in HepG2 cells.

ER Stress and β-Cell Pathogenesis of Type 1 and Type 2 Diabetes and Islet Transplantation

Endoplasmic reticulum (ER) stress affects the pathogenesis of diabetes. ER stress plays important roles, both in type 1 and type 2 diabetes, because pancreatic β-cells possess highly developed ER for insulin secretion. This review summarizes the relationship between ER stress and the pathogenesis of type 1 and type 2 diabetes. In addition, the association between islet transplantation and ER stress is discussed.

Luminal Ca2+ depletion during the unfolded protein response in Xenopus oocytes: cause and consequence

The endoplasmic reticulum (ER) is a Ca(2+) storing organelle that plays a critical role in the synthesis, folding and post-translational modifications of many proteins. The ER enters into a condition of stress when the load of newly synthesized proteins exceeds its folding and processing capacity. This activates a signal transduction pathway called the unfolded protein response (UPR) that attempts to restore homeostasis. The precise role of ER Ca(2+) in the initiation of the UPR has not been defined. Specifically, it has not been established whether ER Ca(2+) dysregulation is a cause or consequence of ER stress. Here, we report that partial depletion of ER Ca(2+) stores induces a significant induction of the UPR, and leads to the retention of a normally secreted protein Carboxypeptidase Y. Moreover, inhibition of protein glycosylation by tunicamycin rapidly induced an ER Ca(2+) leak into the cytosol. However, blockade of the translocon with emetine inhibited the tunicamycin-induced Ca(2+) release. Furthermore, emetine treatment blocked elF2α phosphorylation and reduced expression of the chaperone BiP. These findings suggest that Ca(2+) may be both a cause and a consequence of ER protein misfolding. Thus, it appears that ER Ca(2+) leak is a significant co-factor for the initiation of the UPR.

The role of reactive oxygen species and proinflammatory cytokines in type 1 diabetes pathogenesis

Type 1 diabetes (T1D) is a T cell–mediated autoimmune disease characterized by the destruction of insulin-secreting pancreatic β cells. In humans with T1D and in nonobese diabetic (NOD) mice (a murine model for human T1D), autoreactive T cells cause β-cell destruction, as transfer or deletion of these cells induces or prevents disease, respectively. CD4⁺ and CD8⁺ T cells use distinct effector mechanisms and act at different stages throughout T1D to fuel pancreatic β-cell destruction and disease pathogenesis. While these adaptive immune cells employ distinct mechanisms for β-cell destruction, one central means for enhancing their autoreactivity is by the secretion of proinflammatory cytokines, such as IFN-γ, TNF-α, and IL-1. In addition to their production by diabetogenic T cells, proinflammatory cytokines are induced by reactive oxygen species (ROS) via redox-dependent signaling pathways. Highly reactive molecules, proinflammatory cytokines are produced upon lymphocyte infiltration into pancreatic islets and induce disease pathogenicity by directly killing β cells, which characteristically possess low levels of antioxidant defense enzymes. In addition to β-cell destruction, proinflammatory cytokines are necessary for efficient adaptive immune maturation, and in the context of T1D they exacerbate autoimmunity by intensifying adaptive immune responses. The first half of this review discusses the mechanisms by which autoreactive T cells induce T1D pathogenesis and the importance of ROS for efficient adaptive immune activation, which, in the context of T1D, exacerbates autoimmunity. The second half provides a comprehensive and detailed analysis of (1) the mechanisms by which cytokines such as IL-1 and IFN-γ influence islet insulin secretion and apoptosis and (2) the key free radicals and transcription factors that control these processes.

Inhibition of GPR40 protects MIN6 β cells from palmitate-induced ER stress and apoptosis

Chronic exposure to elevated concentration of free fatty acids (FFA) has been verified to induce endoplasmic reticulum (ER) stress, which leads to pancreatic β-cell apoptosis. As one of the medium and long chain FFA receptors, GPR40 is highly expressed in pancreatic β cells, mediates both acute and chronic effects of FFA on β-cell function, but the role of GPR40 in FFA-induced β-cell apoptosis remains unclear. In this study, we investigated the possible effects of GPR40 in palmitate-induced MIN6 β-cell apoptosis, and found that DC260126, a novel small molecular antagonist of GPR40, could protect MIN6 β cells from palmitate-induced ER stress and apoptosis. Similar results were observed in GPR40-deficient MIN6 cells, indicating that palmitate-induced β-cell apoptosis is at least partially dependent on ER stress pathway via GRP40.

Exercise Training Reduces Inflammatory Mediators in the Intestinal Tract of Healthy Older Adult Mice

Le vieillissement s’allie à une augmentation d’inflammation intestinale et le risque élevé de maladies chroniques, y compris les maladies inflammatoires de l’intestin et le cancer du côlon; nombreuses études épidémiologiques indiquent que l’exercice régulier réduit les risques. Cette étude a examiné les effets à long terme de l’exercice volontaire sur les médiateurs inflammatoires dans les intestins des souris âgées et en bonne santé C57BL/6 (âgées de 15–16 mois). On a désigné les animaux soit à quatre mois de roue d’exercice à souris (RES ; n – 20), soit à une groupe de contrôle « sédentaire » (NRL ; n = 20). Les lymphocytes intestinaux ont été récoltés et analysés pour la présence de (1) pro-inflammatoire (TNF-a, IL-1β) et de cytokines pléotropes (IL-6), et (2) de pro-(caspase-3/-7) et d’anti-(Bcl-2) protéines apoptotiques. L’efficacité d’exercise a été confirmée par l’activité des enzymes dans les muscles squelettiques ; l’évidence de stress a été confirmée par un plasma 8-iso-PGF2α et la corticostérone. Les RES souris ont réalisés une incidence inférieure de TNF-α, de la caspase-7, et de 8-isoprostanes (p < .05) par rapport aux contrôles sédentaires, ce qui suggère que l’exercice à long terme peut « protéger » l’intestin en réduisant la manifestation de cytokines inflammatoires et du protéine apoptotique.

The role of endoplasmic reticulum stress in autoimmune-mediated beta-cell destruction in type 1 diabetes

Unlike type 2 diabetes which is caused by the loss of insulin sensitivity, type 1 diabetes (T1D) is manifested by the absolute deficiency of insulin secretion due to the loss of β mass by autoimmune response against β-cell self-antigens. Although significant advancement has been made in understanding the pathoetiology for type 1 diabetes, the exact mechanisms underlying autoimmune-mediated β-cell destruction, however, are yet to be fully addressed. Accumulated evidence demonstrates that endoplasmic reticulum (ER) stress plays an essential role in autoimmune-mediated β-cell destruction. There is also evidence supporting that ER stress regulates the functionality of immune cells relevant to autoimmune progression during T1D development. In this paper, we intend to address the role of ER stress in autoimmune-mediated β-cell destruction during the course of type 1 diabetes. The potential implication of ER stress in modulating autoimmune response will be also discussed. We will further dissect the possible pathways implicated in the induction of ER stress and summarize the potential mechanisms underlying ER stress for mediation of β-cell destruction. A better understanding of the role for ER stress in T1D pathoetiology would have great potential aimed at developing effective therapeutic approaches for the prevention/intervention of this devastating disorder.

Nifedipine protects INS-1 β-cell from high glucose-induced ER stress and apoptosis

Sustained high concentration of glucose has been verified toxic to β-cells. Glucose augments Ca²⁺-stimulated insulin release in pancreatic β-cells, but chronic high concentration of glucose could induce a sustained level of Ca²⁺ in β-cells, which leads to cell apoptosis. However, the mechanism of high glucose-induced β-cell apoptosis remains unclear. In this study, we use a calcium channel blocker, nifedipine, to investigate whether the inhibition of intracellular Ca²⁺ concentration could protect β-cells from chronic high glucose-induced apoptosis. It was found that in a concentration of 33.3 mM, chronic stimulation of glucose could induce INS-1 β-cells apoptosis at least through the endoplasmic reticulum stress pathway and 10 μM nifedipine inhibited Ca²⁺ release to protect β-cells from high glucose-induced endoplasmic reticulum stress and apoptosis. These results indicated that inhibition of Ca²⁺ over-accumulation might provide benefit to attenuate islet β-cell decompensation in a high glucose environment.

Mechanisms of control of the free Ca2+ concentration in the endoplasmic reticulum of mouse pancreatic β-cells: interplay with cell metabolism and [Ca2+]c and role of SERCA2b and SERCA3

OBJECTIVE

Sarco-endoplasmic reticulum Ca(2+)-ATPase 2b (SERCA2b) and SERCA3 pump Ca(2+) in the endoplasmic reticulum (ER) of pancreatic β-cells. We studied their role in the control of the free ER Ca(2+) concentration ([Ca(2+)](ER)) and the role of SERCA3 in the control of insulin secretion and ER stress.

RESEARCH DESIGN AND METHODS

β-Cell [Ca(2+)](ER) of SERCA3(+/+) and SERCA3(-/-) mice was monitored with an adenovirus encoding the low Ca(2+)-affinity sensor D4 addressed to the ER (D4ER) under the control of the insulin promoter. Free cytosolic Ca(2+) concentration ([Ca(2+)](c)) and [Ca(2+)](ER) were simultaneously recorded. Insulin secretion and mRNA levels of ER stress genes were studied.

RESULTS

Glucose elicited synchronized [Ca(2+)](ER) and [Ca(2+)](c) oscillations. [Ca(2+)](ER) oscillations were smaller in SERCA3(-/-) than in SERCA3(+/+) β-cells. Stimulating cell metabolism with various [glucose] in the presence of diazoxide induced a similar dose-dependent [Ca(2+)](ER) rise in SERCA3(+/+) and SERCA3(-/-) β-cells. In a Ca(2+)-free medium, glucose moderately raised [Ca(2+)](ER) from a highly buffered cytosolic Ca(2+) pool. Increasing [Ca(2+)](c) with high [K] elicited a [Ca(2+)](ER) rise that was larger but more transient in SERCA3(+/+) than SERCA3(-/-) β-cells because of the activation of a Ca(2+) release from the ER in SERCA3(+/+) β-cells. Glucose-induced insulin release was larger in SERCA3(-/-) than SERCA3(+/+) islets. SERCA3 ablation did not induce ER stress.

CONCLUSIONS

[Ca(2+)](c) and [Ca(2+)](ER) oscillate in phase in response to glucose. Upon [Ca(2+)](c) increase, Ca(2+) is taken up by SERCA2b and SERCA3. Strong Ca(2+) influx triggers a Ca(2+) release from the ER that depends on SERCA3. SERCA3 deficiency neither impairs Ca(2+) uptake by the ER upon cell metabolism acceleration and insulin release nor induces ER stress.

The central role of calcium in the effects of cytokines on beta-cell function: implications for type 1 and type 2 diabetes

The appropriate regulation of intracellular calcium is a requirement for proper cell function and survival. This review focuses on the effects of proinflammatory cytokines on calcium regulation in the insulin-producing pancreatic beta-cell and how normal stimulus-secretion coupling, organelle function, and overall beta-cell viability are impacted. Proinflammatory cytokines are increasingly thought to contribute to beta-cell dysfunction not only in type 1 diabetes (T1D), but also in the progression of type 2 diabetes (T2D). Cytokine-induced disruptions in calcium handling result in reduced insulin release in response to glucose stimulation. Cytokines can alter intracellular calcium levels by depleting calcium from the endoplasmic reticulum (ER) and by increasing calcium influx from the extracellular space. Depleting ER calcium leads to protein misfolding and activation of the ER stress response. Disrupting intracellular calcium may also affect organelles, including the mitochondria and the nucleus. As a chronic condition, cytokine-induced calcium disruptions may lead to beta-cell death in T1D and T2D, although possible protective effects are also discussed. Calcium is thus central to both normal and pathological cell processes. Because the tight regulation of intracellular calcium is crucial to homeostasis, measuring the dynamics of calcium may serve as a good indicator of overall beta-cell function.

Deletion of protein kinase Cδ in mice modulates stability of inflammatory genes and protects against cytokine-stimulated beta cell death in vitro and in vivo

AIMS/HYPOTHESIS

Proinflammatory cytokines contribute to beta cell destruction in type 1 diabetes, but the mechanisms are incompletely understood. The aim of the current study was to address the role of the protein kinase C (PKC) isoform PKCδ, a diverse regulator of cell death, in cytokine-stimulated apoptosis in primary beta cells.

METHODS

Islets isolated from wild-type or Prkcd(-/-) mice were treated with IL-1β, TNF-α and IFNγ and assayed for apoptosis, nitric oxide (NO) generation and insulin secretion. Activation of signalling pathways, apoptosis and endoplasmic reticulum (ER) stress were determined by immunoblotting. Stabilisation of mRNA transcripts was measured by RT-PCR following transcriptional arrest. Mice were injected with multiple low doses of streptozotocin (MLD-STZ) and fasting blood glucose monitored.

RESULTS

Deletion of Prkcd inhibited apoptosis and NO generation in islets stimulated ex vivo with cytokines. It also delayed the onset of hyperglycaemia in MLD-STZ-treated mice. Activation of ERK, p38, JNK, AKT1, the ER stress markers DDIT3 and phospho-EIF2α and the intrinsic apoptotic markers BCL2 and MCL1 was not different between genotypes. However, deletion of Prkcd destabilised mRNA transcripts for Nos2, and for multiple components of the toll-like receptor 2 (TLR2) signalling complex, which resulted in disrupted TLR2 signalling.

CONCLUSIONS/INTERPRETATION

Loss of PKCδ partially protects against hyperglycaemia in the MLD-STZ model in vivo, and against cytokine-mediated apoptosis in vitro. This is accompanied by reduced NO generation and destabilisation of Nos2 and components of the TLR2 signalling pathway. The results highlight a mechanism for regulating proinflammatory gene expression in beta cells independently of transcription.

Evidence that low-grade systemic inflammation can induce islet dysfunction as measured by impaired calcium handling

In obesity and the early stages of type 2 diabetes (T2D), proinflammatory cytokines are mildly elevated in the systemic circulation. This low-grade systemic inflammation exposes pancreatic islets to these circulating cytokines at much lower levels than seen within the islet during insulitis. These low-dose effects have not been well described. We examined mouse islets treated overnight with a low-dose cytokine combination commonly associated with inflammation (TNF-alpha, IL-1 beta, and IFN-gamma). We then examined islet function primarily using intracellular calcium ([Ca(2+)](i)), a key component of insulin secretion and cytokine signaling. Cytokine-treated islets demonstrated several features that suggested dysfunction including excess [Ca(2+)](i) in low physiological glucose (3mM), reduced responses to glucose stimulation, and disrupted [Ca(2+)](i) oscillations. Interestingly, islets taken from young db/db mice showed similar disruptions in [Ca(2+)](i) dynamics as cytokine-treated islets. Additional studies of control islets showed that the cytokine-induced elevation in basal [Ca(2+)](i) was due to both greater calcium influx through L-type-calcium-channels and reduced endoplasmic reticulum (ER) calcium storage. Many of these cytokine-induced disruptions could be reproduced by SERCA blockade. Our data suggest that chronic low-grade inflammation produces circulating cytokine levels that are sufficient to induce beta-cell dysfunction and may play a contributing role in beta-cell failure in early T2D.

Endoplasmic reticulum stress-induced apoptosis in the development of diabetes: is there a role for adipose tissue and liver?

Diabetes mellitus (DM) is a multifactorial chronic metabolic disease characterized by hyperglycaemia. Several different mechanisms have been implicated in the development of the disease, including endoplasmic reticulum (ER) stress. ER stress is increasingly acknowledged as an important mechanism in the development of DM, not only for β-cell loss but also for insulin resistance. Accumulating evidence suggests that ER stress-induced apoptosis may be an important mode of β-cell loss and therefore important in the development of diabetes. Recent data also suggest a role of ER stress-induced apoptosis in liver and adipose tissue in relation to diabetes, but more extensive studies on human adipocyte and hepatocyte (patho)physiology and ER stress are needed to identify the exact interactions between environmental signals, ER stress and apoptosis in these organs.

Cytokines in the Progression of Pancreatic β-Cell Dysfunction

The dysfunction of pancreatic β-cell and the reduction in β-cell mass are the decisive events in the progression of type 2 diabetes. There is increasing evidence that cytokines play important roles in the procedure of β-cell failure. Cytokines, such as IL-1β, IFN-γ, TNF-α, leptin, resistin, adiponectin, and visfatin, have been shown to diversely regulate pancreatic β-cell function. Recently, islet-derived cytokine PANcreatic DERived factor (PANDER or FAM3B) has also been demonstrated to be a regulator of islet β-cell function. The change in cytokine profile in islet and plasma is associated with pancreatic β-cell dysfunction and apoptosis. In this paper, we summarize and discuss the recent studies on the effects of certain important cytokines on pancreatic β-cell function. The imbalance in deleterious and protective cytokines plays pivotal roles in the development and progression of pancreatic β-cell dysfunction under insulin-resistant conditions.

Implications of endoplasmic reticulum stress, the unfolded protein response and apoptosis for molecular cancer therapy. Part I: targeting p53, Mdm2, GADD153/CHOP, GRP78/BiP and heat shock proteins

BACKGROUND

In eukaryotes, endoplasmic reticulum stress (ERS) and the unfolded protein response (UPR) are coordinately regulated to maintain steady-state levels and activities of various cellular proteins to ensure cell survival.

OBJECTIVE

This review (Part I of II) focuses on specific ERS and UPR signalling regulators, their expression in the cancer phenotype and apoptosis, and proposes how their implication in these processes can be rationalised into proteasome inhibition, apoptosis induction and the development of more efficacious targeted molecular cancer therapies.

METHOD

In this review, we contextualise many ERS and UPR client proteins that are deregulated or mutated in cancers and show links between ERS and the UPR, their implication in oncogenic transformation, tumour progression and escape from immune surveillance, apoptosis inhibition, angiogenesis, metastasis, acquired drug resistance and poor cancer prognosis.

CONCLUSION

Evasion of programmed cell death or apoptosis is a hallmark of cancer that enables tumour cells to proliferate uncontrollably. Successful eradication of cancer cells through targeting ERS- and UPR-associated proteins to induce apoptosis is currently being pursued as a central tenet of anticancer drug discovery.