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Kongthitilerd P, Thilavech T, Marnpae M, Rong W, Yao S, Adisakwattana S, Cheng H, Suantawee T. Cyanidin-3-rutinoside stimulated insulin secretion through activation of L-type voltage-dependent Ca 2+ channels and the PLC-IP 3 pathway in pancreatic β-cells. Biomed Pharmacother 2021; 146:112494. [PMID: 34891116 DOI: 10.1016/j.biopha.2021.112494] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2021] [Revised: 11/21/2021] [Accepted: 11/30/2021] [Indexed: 02/08/2023] Open
Abstract
Cyanidin-3-rutinoside (C3R) is an anthocyanin with anti-diabetic properties found in red-purple fruits. However, the molecular mechanisms of C3R on Ca2+-dependent insulin secretion remains unknown. This study aimed to identify C3R's mechanisms of action in pancreatic β-cells. Rat INS-1 cells were used to elucidate the effects of C3R on insulin secretion, intracellular Ca2+ signaling, and gene expression. The results showed that C3R at 60, 100, and 300 µM concentrations significantly increased insulin secretion via intracellular Ca2+ signaling. The exposure of cells with C3R concentrations up to 100 μM did not affect cell viability. Pretreatment of cells with nimodipine (voltage-dependent Ca2+ channel (VDCC) blocker), U73122 (PLC inhibitor), and 2-APB (IP3 receptor blocker) inhibited the intracellular Ca2+ signals by C3R. Interestingly, C3R increased intracellular Ca2+ signals and insulin secretion after depletion of endoplasmic reticulum Ca2+ stores by thapsigargin. However, insulin secretion was abolished under extracellular Ca2+-free conditions. Moreover, C3R upregulated mRNA expression for Glut2 and Kir6.2 genes. These findings indicate that C3R stimulated insulin secretion by promoting Ca2+ influx via VDCCs and activating the PLC-IP3 pathway. C3R also upregulates the expression of genes necessary for glucose-induced insulin secretion. This is the first study describing the molecular mechanisms by which C3R stimulates Ca2+-dependent insulin secretion from pancreatic β-cells. These findings contribute to our understanding on how anthocyanins improve hyperglycemia in diabetic patients.
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Affiliation(s)
- Phutthida Kongthitilerd
- Interdisciplinary Program of Biomedical Sciences, Graduate School, Chulalongkorn University, Bangkok 10330, Thailand.
| | - Thavaree Thilavech
- Department of Food Chemistry, Faculty of Pharmacy, Mahidol University, Bangkok 10440, Thailand.
| | - Marisa Marnpae
- The Halal Science Center, Chulalongkorn University, Bangkok 10330, Thailand; Phytochemical and Functional Food Research Unit for Clinical Nutrition, Department of Nutrition and Dietetics, Faculty of Allied Health Sciences, Chulalongkorn University, Bangkok 10330, Thailand.
| | - Weiqiong Rong
- Department of Comparative Biomedical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803, USA.
| | - Shaomian Yao
- Department of Comparative Biomedical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803, USA.
| | - Sirichai Adisakwattana
- Phytochemical and Functional Food Research Unit for Clinical Nutrition, Department of Nutrition and Dietetics, Faculty of Allied Health Sciences, Chulalongkorn University, Bangkok 10330, Thailand.
| | - Henrique Cheng
- Department of Comparative Biomedical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803, USA.
| | - Tanyawan Suantawee
- Phytochemical and Functional Food Research Unit for Clinical Nutrition, Department of Nutrition and Dietetics, Faculty of Allied Health Sciences, Chulalongkorn University, Bangkok 10330, Thailand.
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Wang CC, Kuo JR, Wang SJ. Fingolimod inhibits glutamate release through activation of S1P1 receptors and the G protein βγ subunit-dependent pathway in rat cerebrocortical nerve terminals. Neuropharmacology 2021; 185:108451. [PMID: 33428887 DOI: 10.1016/j.neuropharm.2021.108451] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2020] [Revised: 12/30/2020] [Accepted: 01/03/2021] [Indexed: 01/28/2023]
Abstract
Fingolimod, a sphingosine-1-phosphate (S1P) receptor modulator approved for treating multiple sclerosis, is reported to prevent excitotoxic insult. Because excessive glutamate release is a major cause of neuronal damage in various neurological disorders, the effect of fingolimod on glutamate release in rat cerebrocortical nerve terminals (synaptosomes) was investigated in the current study. Fingolimod decreased 4-aminopyridine (4-AP)-stimulated glutamate release and calcium concentration elevation. Fingolimod-mediated inhibition of 4-AP-induced glutamate release was dependent on extracellular calcium, persisted in the presence of the glutamate transporter inhibitor DL-TBOA or intracellular Ca2+-releasing inhibitors dantrolene and CGP37157, and was prevented by blocking vesicular transporters or N- and P/Q-type channels. Western blot and immunocytochemical analysis revealed the presence of S1P1 receptor proteins in presynaptic terminals. Fingolimod-mediated inhibition of 4-AP-induced glutamate release was also abolished by the sphingosine kinase inhibitor DMS, selective S1P1 receptor antagonist W146, Gi/o protein inhibitor pertussis toxin, and G protein βγ subunit inhibitor gallein; however, it was unaffected by the adenylyl cyclase inhibitor SQ22536, protein kinase A inhibitor H89, and phospholipase C inhibitor U73122. These data indicate that fingolimod decreases glutamate release from rat cerebrocortical synaptosomes by suppressing N- and P/Q-type Ca2+ channel activity; additionally, the activation of presynaptic S1P1 receptors and the G protein βγ subunit participates in achieving the effect.
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Affiliation(s)
- Che Chuan Wang
- Department of Neurology, Chi Mei Medical Center, Tainan, Taiwan; Biotechnology, Southern Taiwan University of Science and Technology, Tainan, Taiwan
| | - Jinn Rung Kuo
- Department of Neurology, Chi Mei Medical Center, Tainan, Taiwan; Biotechnology, Southern Taiwan University of Science and Technology, Tainan, Taiwan
| | - Su Jane Wang
- School of Medicine, Fu Jen Catholic University, No.510, Zhongzheng Rd, Xinzhuang Dist, New Taipei City, 24205, Taiwan; Graduate Institute of Biomedical and Pharmaceutical Science, Fu Jen Catholic University, No.510, Zhongzheng Rd, Xinzhuang Dist, New Taipei City, 24205, Taiwan; Research Center for Chinese Herbal Medicine, College of Human Ecology, Chang Gung University of Science and Technology, Taoyuan City, Taiwan.
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Abstract
Background Insulin is stored within large dense-core granules in pancreatic beta (β)-cells and is released by Ca2+-triggered exocytosis with increasing blood glucose levels. Polarized and targeted secretion of insulin from β-cells in pancreatic islets into the vasculature has been proposed; however, the mechanisms related to cellular and molecular localization remain largely unknown. Within nerve terminals, the Ca2+-dependent release of a polarized transmitter is limited to the active zone, a highly specialized area of the presynaptic membrane. Several active zone-specific proteins have been characterized; among them, the CAST/ELKS protein family members have the ability to form large protein complexes with other active zone proteins to control the structure and function of the active zone for tight regulation of neurotransmitter release. Notably, ELKS but not CAST is also expressed in β-cells, implying that ELKS may be involved in polarized insulin secretion from β-cells. Scope of review This review provides an overview of the current findings regarding the role(s) of ELKS and other active zone proteins in β-cells and focuses on the molecular mechanism underlying ELKS regulation within polarized insulin secretion from islets. Major conclusions ELKS localizes at the vascular-facing plasma membrane of β-cells in mouse pancreatic islets. ELKS forms a potent insulin secretion complex with L-type voltage-dependent Ca2+ channels on the vascular-facing plasma membrane of β-cells, enabling polarized Ca2+ influx and first-phase insulin secretion from islets. This model provides novel insights into the functional polarity observed during insulin secretion from β-cells within islets at the molecular level. This active zone-like region formed by ELKS at the vascular side of the plasma membrane is essential for coordinating physiological insulin secretion and may be disrupted in diabetes.
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Affiliation(s)
- Mica Ohara-Imaizumi
- Department of Cellular Biochemistry, Kyorin University School of Medicine, Tokyo 181-8611, Japan.
| | - Kyota Aoyagi
- Department of Cellular Biochemistry, Kyorin University School of Medicine, Tokyo 181-8611, Japan
| | - Toshihisa Ohtsuka
- Department of Biochemistry, Graduate School of Medicine, University of Yamanashi, Yamanashi 409-3898, Japan
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Sawatani T, Kaneko YK, Ishikawa T. Dual effect of reduced type I diacylglycerol kinase activity on insulin secretion from MIN6 β-cells. J Pharmacol Sci 2019; 140:178-186. [PMID: 31279581 DOI: 10.1016/j.jphs.2019.06.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2019] [Revised: 05/03/2019] [Accepted: 06/11/2019] [Indexed: 02/07/2023] Open
Abstract
The role of type I diacylglycerol kinases (DGKs) in the regulation of insulin secretion was investigated in MIN6 β-cells. In intracellular Ca2+ concentration ([Ca2+]i) measurement experiments, 1 μM R59949, a type I DGK inhibitor, and 10 μM DiC8, a diacylglycerol (DAG) analog, amplified 22.2 mM glucose-induced [Ca2+]i oscillations in a protein kinase C (PKC)-dependent manner, whereas 10 μM R59949 and 100 μM DiC8 decreased [Ca2+]i independent of PKC. High concentrations of R59949 and DiC8 attenuated voltage-dependent Ca2+ channel currents. According to these results, 22.2 mM glucose-stimulated insulin secretion (GSIS) was potentiated by 1 μM R59949 but suppressed by 10 μM of the same. The DGKα inhibitor R59022 showed a similar dual effect. Conversely, DiC8 at 10 and 100 μM potentiated GSIS, although 100 μM DiC8 decreased [Ca2+]i. These results suggest that DAG accumulated through declined type I DGK activity shows a dual effect on insulin secretion depending on the degree of accumulation; a mild DAG accumulation induces a PKC-dependent stimulatory effect on insulin secretion, whereas an excessive DAG accumulation suppresses it in a PKC-independent manner, possibly via attenuation of VDCC activity.
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Affiliation(s)
- Toshiaki Sawatani
- Department of Pharmacology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka City, Shizuoka, 422-8526, Japan
| | - Yukiko K Kaneko
- Department of Pharmacology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka City, Shizuoka, 422-8526, Japan.
| | - Tomohisa Ishikawa
- Department of Pharmacology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka City, Shizuoka, 422-8526, Japan
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Abstract
The six subtypes of voltage-dependent Ca(2+) channels (VDCCs) mediate a wide range of physiological responses. N-type VDCCs (NCCs) were originally identified as a high voltage-activated Ca(2+) channel selectively blocked by omega-conotoxin (ω-CTX)-GVIA. Predominantly localized in the nervous system, NCCs are key regulators of neurotransmitter release. Both pharmacological blockade with ω-CTX-GVIA and, more recently, mice lacking CNCNA1B, encoding the α1B subunit of NCC, have been used to assess the physiological and pathophysiological functions of NCCs, revealing in part their significant roles in sympathetic nerve activation and nociceptive transmission. The evidence now available indicates that NCCs are a potentially useful therapeutic target for the treatment of several pathological conditions. Efforts are therefore being made to develop effective NCC blockers, including both synthetic ω-CTX-GVIA derivatives and small-molecule inhibitors. Cilnidipine, for example, is a dihydropyridine L-type VDCC blocking agent that also possesses significant NCC blocking ability. As over-activation of the sympathetic nervous system appears to contribute to the pathological processes underlying cardiovascular, renal and metabolic diseases, NCC blockade could be a useful approach to treating these ailments. In this review article, we provide an overview of what is currently known about the physiological and pathophysiological activities of NCCs and the potentially beneficial effects of NCC blockade in several disease conditions, in particular cardiovascular diseases.
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Affiliation(s)
- Koichiro Kuwahara
- Department of Cardiovascular Medicine, Kyoto University Graduate School of Medicine, Kyoto 606-8507, Japan.
| | - Takeshi Kimura
- Department of Cardiovascular Medicine, Kyoto University Graduate School of Medicine, Kyoto 606-8507, Japan
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