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DOC2b enrichment mitigates proinflammatory cytokine-induced CXCL10 expression by attenuating IKKβ and STAT-1
Introduction:
Type 1 diabetic human islet β-cells are deficient in double C 2 like domain beta (DOC2b) protein. Further, DOC2b protects against cytokine-induced pancreatic islet β-cell stress and apoptosis. However, the mechanisms underpinning the protective effects of DOC2b remain unknown.
Methods:
Biochemical studies, qPCR, proteomics, and immuno-confocal microscopy were conducted to determine the underlying protective mechanisms of DOC2b in β-cells. DOC2b- enriched or-depleted primary islets (human and mouse) and β-cell lines challenged with or without proinflammatory cytokines, global DOC2b heterozygous knockout mice subjected to multiple-low-dose-streptozotocin (MLD-STZ), were used for these studies.
Results:
A significant elevation of stress-induced CXCL10 mRNA was observed in DOC2b- depleted β-cells and primary mouse islets. Further, DOC2b enrichment markedly attenuated cytokine-induced CXCL10 levels in primary non-diabetic human islets and β-cells. DOC2b enrichment also reduced total-NF-κB p65 protein levels in human islets challenged with T1D mimicking proinflammatory cytokines. IKKβ, NF-κB p65, and STAT-1 are capable of associating with DOC2b in cytokine-challenged β-cells. DOC2b enrichment in cytokine-stressed human islets and β-cells corresponded with a significant reduction in activated and total IKKβ protein levels. Total IκBβ protein was increased in DOC2b-enriched human islets subjected to acute cytokine challenge. Cytokine-induced activated and total STAT-1 protein and mRNA levels were markedly reduced in DOC2b-enriched human islets. Intriguingly, DOC2b also prevents ER-stress-IKKβ and STAT-1 crosstalk in the rat INS1-832/13 β-cell line.
Conclusion:
The mechanisms underpinning the protective effects of DOC2b involve attenuation of IKKβ-NF-κB p65 and STAT-1 signaling, and reduced CXCL10 expression.
Insights
Double C 2 like domain beta (DOC2b) protein deficiency in type 1 diabetes impairs islet beta-cells. DOC2b protects these cells by reducing inflammation and stress via IKKβ-NF-κB p65 and STAT-1 pathways.
Area of Science:
- Cell Biology
- Endocrinology
- Immunology
Background:
- Type 1 diabetes is characterized by a deficiency of double C 2 like domain beta (DOC2b) protein in human islet beta-cells.
- DOC2b plays a crucial role in protecting pancreatic islet beta-cells from cytokine-induced stress and apoptosis.
Purpose of the Study:
- To elucidate the underlying protective mechanisms of DOC2b in beta-cells.
- To investigate the role of DOC2b in modulating inflammatory signaling pathways relevant to type 1 diabetes.
Main Methods:
- Utilized biochemical assays, qPCR, proteomics, and immuno-confocal microscopy.
- Employed DOC2b-enriched/depleted primary islets (human and mouse) and beta-cell lines challenged with cytokines.
- Studied global DOC2b heterozygous knockout mice subjected to multiple low-dose streptozotocin (MLD-STZ).
Main Results:
- DOC2b depletion elevated stress-induced CXCL10 mRNA in beta-cells and islets.
- DOC2b enrichment attenuated cytokine-induced CXCL10, reduced NF-κB p65, IKKβ, and STAT-1 activation.
- DOC2b prevented ER-stress-IKKβ and STAT-1 crosstalk in a beta-cell line.
Conclusions:
- DOC2b's protective effects stem from attenuating IKKβ-NF-κB p65 and STAT-1 signaling.
- Reduced CXCL10 expression is a key outcome of DOC2b's protective action.
- DOC2b is a critical factor in maintaining beta-cell health and function in the context of type 1 diabetes.
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