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Zhang X, Zhang D, Huo L, Zhou X, Zhang J, Li M, Su D, Sun P, Chen F, Liang X. Upregulation of α-ENaC induces pancreatic β-cell dysfunction, ER stress, and SIRT2 degradation. J Biomed Res 2024; 38:241-255. [PMID: 38769731 PMCID: PMC11144933 DOI: 10.7555/jbr.37.20230128] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2023] [Revised: 11/05/2023] [Accepted: 11/11/2023] [Indexed: 05/22/2024] Open
Abstract
Islet beta cells (β-cells) produce insulin in response to high blood glucose levels, which is essential for preserving glucose homeostasis. Voltage-gated ion channels in β-cells, including Na +, K +, and Ca 2+ channels, aid in the release of insulin. The epithelial sodium channel alpha subunit (α-ENaC), a voltage-independent sodium ion channel, is also expressed in human pancreatic endocrine cells. However, there is no reported study on the function of ENaC in the β-cells. In the current study, we found that α-ENaC was expressed in human pancreatic glandule and pancreatic islet β-cells. In the pancreas of db/db mice and high-fat diet-induced mice, and in mouse islet β-cells (MIN6 cells) treated with palmitate, α-ENaC expression was increased. When α-ENaC was overexpressed in MIN6 cells, insulin content and glucose-induced insulin secretion were significantly reduced. On the other hand, palmitate injured islet β-cells and suppressed insulin synthesis and secretion, but increased α-ENaC expression in MIN6 cells. However, α-ENaC knockout ( Scnn1a -/-) in MIN6 cells attenuated β-cell disorder induced by palmitate. Furthermore, α-ENaC regulated the ubiquitylation and degradation of sirtuin 2 in β-cells. α-ENaC also modulated β-cell function in correlation with the inositol-requiring enzyme 1 alpha/X-box binding protein 1 (IRE1α/XBP1) and protein kinase RNA-like endoplasmic reticulum kinase/C/EBP homologous protein (PERK/CHOP) endoplasmic reticulum stress pathways. These results suggest that α-ENaC may play a novel role in insulin synthesis and secretion in the β-cells, and the upregulation of α-ENaC promotes islet β-cell dysfunction. In conclusion, α-ENaC may be a key regulator involved in islet β-cell damage and a potential therapeutic target for type 2 diabetes mellitus.
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Affiliation(s)
- Xue Zhang
- Department of Pathophysiology, Nanjing Medical University, Nanjing, Jiangsu 211166, China
- Department of Pathology, Nanjing Drum Tower Hospital, the Affiliated Hospital of Nanjing University Medical School, Nanjing, Jiangsu 210009, China
| | - Dan Zhang
- Department of Pathophysiology, Nanjing Medical University, Nanjing, Jiangsu 211166, China
- Department of Pathology, Nanjing Drum Tower Hospital, the Affiliated Hospital of Nanjing University Medical School, Nanjing, Jiangsu 210009, China
| | - Lei Huo
- Department of Pathophysiology, Nanjing Medical University, Nanjing, Jiangsu 211166, China
| | - Xin Zhou
- Department of Pathophysiology, Nanjing Medical University, Nanjing, Jiangsu 211166, China
| | - Jia Zhang
- Key Laboratory of Human Functional Genomics of Jiangsu Province, Department of Biochemistry and Molecular Biology, Nanjing Medical University, Nanjing, Jiangsu 211166, China
| | - Min Li
- Department of Pathology, Nanjing Medical University, Nanjing, Jiangsu 211166, China
| | - Dongming Su
- Department of Pathology, Nanjing Medical University, Nanjing, Jiangsu 211166, China
| | - Peng Sun
- Key Laboratory of Human Functional Genomics of Jiangsu Province, Department of Biochemistry and Molecular Biology, Nanjing Medical University, Nanjing, Jiangsu 211166, China
| | - Fang Chen
- Key Laboratory of Human Functional Genomics of Jiangsu Province, Department of Biochemistry and Molecular Biology, Nanjing Medical University, Nanjing, Jiangsu 211166, China
| | - Xiubin Liang
- Department of Pathophysiology, Nanjing Medical University, Nanjing, Jiangsu 211166, China
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Nylander O, Sjöblom M, Sedin J, Dahlgren D. Effects of α2-adrenoceptor stimulation on luminal alkalinisation and net fluid flux in rat duodenum. PLoS One 2022; 17:e0273208. [PMID: 36006975 PMCID: PMC9409570 DOI: 10.1371/journal.pone.0273208] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Accepted: 08/03/2022] [Indexed: 12/03/2022] Open
Abstract
The sympathetic nervous system is highly involved in the regulation of gastrointestinal functions such as luminal alkalinisation and fluid absorption. However, the exact mechanisms are not clear. This study aimed to delineate how α2-adrenergic receptor stimulation reduces duodenal luminal alkalinisation and induces net fluid absorption. This was tested by perfusing the duodenum of anesthetized rats with isotonic solutions devoid of Cl- and/or Na+, in the absence and presence of the α2-adrenoceptor agonist clonidine. The clonidine was also studied in rats treated with dimethylamiloride (a Na+/H+ exchange inhibitor), vasoactive intestinal peptide, and the nicotinic receptor antagonist hexamethonium. Clonidine reduced luminal alkalinisation and induced net fluid absorption. The Cl--free solution decreased luminal alkalinisation and abolished net fluid absorption, but did not prevent clonidine from doing so. Both the Na+-free solution and luminal dimethylamiloride increased luminal alkalinisation and abolished net fluid absorption, effects counteracted by clonidine. The NaCl-free solution (D-mannitol) did not affect luminal alkalinisation, but reduced net fluid absorption. Clonidine reduced luminal alkalinisation and induced net fluid absorption in rats perfused luminally with mannitol. However, clonidine did not affect the vasoactive intestinal peptide-induced increase in luminal alkalinisation or fluid secretion. Pre-treatment with hexamethonium abolished the effects of clonidine on luminal alkalinisation and net fluid flux. In summary, our in vivo experiments showed that clonidine-induced reduction in luminal alkalinisation and induction of net fluid absorption was unrelated to luminal Na+ and Cl-, or to apical Na+/H+ or Cl-/HCO3- exchangers. Instead, clonidine seems to exert its effects via suppression of nicotinic receptor-activated acetylcholine secretomotor neurons.
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Affiliation(s)
- Olof Nylander
- Division of Physiology, Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Markus Sjöblom
- Division of Physiology, Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - John Sedin
- Division of Physiology, Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - David Dahlgren
- Division of Physiology, Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
- * E-mail:
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