Dataset Information

Syntaxin 4 Expression in Pancreatic ?-Cells Promotes Islet Function and Protects Functional ?-Cell Mass.

ABSTRACT: Syntaxin 4 (Stx4) enrichment in human and mouse islet grafts improves the success of transplants in reversing streptozotocin (STZ)-induced diabetes in mice, although the underlying molecular mechanisms remain elusive. Toward a further understanding of this, human islets and inducible transgenic mice that selectively overexpress Stx4 in islet ?-cells (?TG-Stx4) were challenged with proinflammatory stressors in vitro and in vivo. Remarkably, ?TG-Stx4 mice resisted the loss of ?-cell mass and the glucose intolerance that multiple low doses of STZ induce. Under standard conditions, glucose tolerance was enhanced and mice maintained normal fasting glycemia and insulinemia. Conversely, Stx4 heterozygous knockout mice succumbed rapidly to STZ-induced glucose intolerance compared with their wild-type littermates. Human islet ?-cells overexpressing Stx4 exhibited enhanced insulin secretory capability; resilience against proinflammatory cytokine-induced apoptosis; and reduced expression of the CXCL9, CXCL10, and CXCL11 genes coordinate with decreased activation/nuclear localization of nuclear factor-?B. Finding ways to boost Stx4 expression presents a novel potential therapeutic avenue for promoting islet function and preserving ?-cell mass.

SUBMITTER: Oh E

PROVIDER: S-EPMC6245223 | biostudies-literature | 2018 Dec

REPOSITORIES: biostudies-literature

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Syntaxin 4 Expression in Pancreatic β-Cells Promotes Islet Function and Protects Functional β-Cell Mass.

Oh Eunjin E Ahn Miwon M Afelik Solomon S Becker Thomas C TC Roep Bart O BO Roep Bart O BO Thurmond Debbie C DC

Diabetes 20181010 12

Syntaxin 4 (Stx4) enrichment in human and mouse islet grafts improves the success of transplants in reversing streptozotocin (STZ)-induced diabetes in mice, although the underlying molecular mechanisms remain elusive. Toward a further understanding of this, human islets and inducible transgenic mice that selectively overexpress Stx4 in islet β-cells (βTG-Stx4) were challenged with proinflammatory stressors in vitro and in vivo. Remarkably, βTG-Stx4 mice resisted the loss of β-cell mass and the g ...[more]

PMID: 30305365

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Project description:The goal of this study was to determine whether recombinant Islet NeoGenesis Associated Protein (rINGAP) and its active core, a pentadecapeptide INGAP104-118 (Ingap-p), protect β cells against cytokine-induced death. INGAP has been shown to induce islet neogenesis in diabetic animals, to stimulate β-cell proliferation and differentiation, and to improve islet survival and function. Importantly, Ingap-p has shown promising results in clinical trials for diabetes (phase I/II). However, the full potential of INGAP and its mechanisms of action remain poorly understood. Using rat insulinoma cells RINm5F and INS-1 treated with interleukin-1β (IL-1β) and interferon-gamma (IFN-γ), we demonstrate here that both rINGAP and Ingap-p inhibit apoptosis, Caspase-3 activation, inducible nitric oxide synthase (iNOS) expression and nitric oxide (NO) production, and explore the related signaling pathways. As expected, IL-1β induced nuclear factor kappa B (NF-κB), p38, and JNK signaling, whereas interferon-gamma (IFN-γ) activated the JAK2/STAT1 pathway and potentiated the IL-1β effects. Both rINGAP and Ingap-p decreased phosphorylation of IKKα/β, IkBα, and p65, although p65 nuclear translocation was not inhibited. rINGAP, used for further analysis, also inhibited STAT3, p38, and JNK activation. Interestingly, all inhibitory effects of rINGAP were observed for the cytokine cocktail, not IL-1β alone, and were roughly equal to reversing the potentiating effects of INFγ. Furthermore, rINGAP had no effect on IL-1β/NF-κB-induced gene expression (e.g., Ccl2, Sod2) but downregulated several IFNγ-stimulated (Irf1, Socs1, Socs3) or IFNγ-potentiated (Nos2) genes. This, however, was observed again only for the cytokine cocktail, not IFNγ alone, and rINGAP did not inhibit the IFNγ-induced JAK2/STAT1 activation. Together, these intriguing results suggest that INGAP does not target either IL-1β or IFNγ individually but rather inhibits the signaling crosstalk between the two, the exact mechanism of which remains to be investigated. In summary, our study characterizes the anti-inflammatory effects of INGAP, both protein and peptide, and suggests a new therapeutic utility for INGAP in the treatment of diabetes.

Dataset Information

Syntaxin 4 Expression in Pancreatic ?-Cells Promotes Islet Function and Protects Functional ?-Cell Mass.

Publications

Syntaxin 4 Expression in Pancreatic β-Cells Promotes Islet Function and Protects Functional β-Cell Mass.

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