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Signaling between pancreatic ? cells and macrophages via S100 calcium-binding protein A8 exacerbates ?-cell apoptosis and islet inflammation.

ABSTRACT: Chronic low-grade inflammation in the pancreatic islets is observed in individuals with type 2 diabetes, and macrophage levels are elevated in the islets of these individuals. However, the molecular mechanisms underlying the interactions between the pancreatic ? cells and macrophages and their involvement in inflammation are not fully understood. Here, we investigated the role of S100 calcium-binding protein A8 (S100A8), a member of the damage-associated molecular pattern molecules (DAMPs), in ?-cell inflammation. Co-cultivation of pancreatic islets with unstimulated peritoneal macrophages in the presence of palmitate (to induce lipotoxicity) and high glucose (to induce glucotoxicity) synergistically increased the expression and release of islet-produced S100A8 in a Toll-like receptor 4 (TLR4)-independent manner. Consistently, a significant increase in the expression of the S100a8 gene was observed in the islets of diabetic db/db mice. Furthermore, the islet-derived S100A8 induced TLR4-mediated inflammatory cytokine production by migrating macrophages. When human islet cells were co-cultured with U937 human monocyte cells, the palmitate treatment up-regulated S100A8 expression. This S100A8-mediated interaction between islets and macrophages evoked ?-cell apoptosis, which was ameliorated by TLR4 inhibition in the macrophages or S100A8 neutralization in the pancreatic islets. Of note, both glucotoxicity and lipotoxicity triggered S100A8 secretion from the pancreatic islets, which in turn promoted macrophage infiltration of the islets. Taken together, a positive feedback loop between islet-derived S100A8 and macrophages drives ?-cell apoptosis and pancreatic islet inflammation. We conclude that developing therapeutic approaches to inhibit S100A8 may serve to prevent ?-cell loss in patients with diabetes.

SUBMITTER: Inoue H

PROVIDER: S-EPMC5912464 | biostudies-literature | 2018 Apr

REPOSITORIES: biostudies-literature

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Signaling between pancreatic β cells and macrophages via S100 calcium-binding protein A8 exacerbates β-cell apoptosis and islet inflammation.

Inoue Hideaki H Shirakawa Jun J Togashi Yu Y Tajima Kazuki K Okuyama Tomoko T Kyohara Mayu M Tanaka Yui Y Orime Kazuki K Saisho Yoshifumi Y Yamada Taketo T Shibue Kimitaka K Kulkarni Rohit N RN Terauchi Yasuo Y

The Journal of biological chemistry 20180301 16

Chronic low-grade inflammation in the pancreatic islets is observed in individuals with type 2 diabetes, and macrophage levels are elevated in the islets of these individuals. However, the molecular mechanisms underlying the interactions between the pancreatic β cells and macrophages and their involvement in inflammation are not fully understood. Here, we investigated the role of S100 calcium-binding protein A8 (S100A8), a member of the damage-associated molecular pattern molecules (DAMPs), in β ...[more]

PMID: 29496993

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Project description:To shed light on the early processes of immune response to peripheral nerve injury, we first used genome-wide transcriptional profiling and bioinformatics (Ingenuity, NextBio) pathway analyses of the proximal (P; regenerating) and distal (D; degenerating) nerve stumps at day 1 in the sciatic nerve axotomy model in rats. We identified a number of specific immunomodulatory genes and pathways that were regulated shortly post-injury in both the P and D segments, including all members of the interleukin (IL), chemokine, tumor necrosis factor (TNF), matrix metalloproteinase (MMP), toll-like receptor (TLR), tissue inhibitor of metalloproteinase (TIMP), ion channel and myosin families. Immunomodulatory calcium-binding S100A8 and S100A9 were the top up-regulated genes in both the D and P segments. In cultured Schwann cells stimulated with the purified S100A8/A9 heterodimer we recorded a high level of similarity of the activated genes and pathways with that of the injured nerve, especially in the activation of the chemokine and cytokine gene networks that support agranulocyte and granulocyte chemotaxis, adhesion, transmigration and rolling signaling pathways. We also confirmed activation of multiple cell death related gene networks supporting TNFR1, natural killer cell receptor and death receptor apoptosis signaling in the D stump, and the gluconeogenesis/glycolysis and cytoskeletal motility signaling in the P stump, corroborated by activation of ERK, PI3K and JNK kinase pathways. As compared to the D segment, multiple additional pathways were more efficiently upregulated in the P stump, including the IL-6 and -17, MMP-9, calcium, activated agranulocyte, leukocyte rolling and glutathione-mediated detoxification signaling pathways. These data suggest that shortly after nerve injury, upregulation of S100A8/A9 is responsible for the expression and release of chemokines and cytokines by Schwann cells, necessary to generate the initial chemotactic gradient and guide the hematogenous immune cells into the injury site. Gene expression profiling of total RNAs extracted from injured and non-injured rat sciatic nerves, and primary rat Schwann cells stimulated with S100A8/A9 proteins

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Signaling between pancreatic ? cells and macrophages via S100 calcium-binding protein A8 exacerbates ?-cell apoptosis and islet inflammation.

Publications

Signaling between pancreatic β cells and macrophages via S100 calcium-binding protein A8 exacerbates β-cell apoptosis and islet inflammation.

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