1
|
Portales-Castillo I, Jalal A, Kendall PL, Parks D. Normal Levels of Ionized Calcium Despite Persistent Increase in Total Calcium in a Patient With IgA Paraproteinemia. JCEM CASE REPORTS 2024; 2:luad163. [PMID: 38143927 PMCID: PMC10742367 DOI: 10.1210/jcemcr/luad163] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Indexed: 12/26/2023]
Abstract
Approximately half of the calcium in the blood circulates in the ionized, free form; which is critical for cellular function. As a result, its levels are tightly regulated by homeostatic mechanisms dependent on hormones such as PTH, vitamin D, and fibroblast growth factor-23. The other half of the total calcium is in a complex with anions, predominantly albumin. Clinically, the levels of albumin are known to influence the relationship of total calcium to free calcium. However, the relevance of changes in other serum proteins on calcium homeostasis is less appreciated. We present the case of a 70-year-old woman who was followed over 5 years with persistently elevated total calcium levels but with normal ionized calcium levels. Her evaluation was notable for IgA paraprotein, which paralleled her history of elevated total serum calcium. Extensive clinical investigations did not reveal hyperparathyroidism or cancer-mediated hypercalcemia. Additional in vitro analyses comparing the plasma containing the IgA paraprotein against a healthy control revealed that a high-molecular-weight IgA paraprotein in the patient has increased capacity to reduce the amount of free calcium in solution, thus providing a direct mechanistic explanation for the clinical findings.
Collapse
Affiliation(s)
- Ignacio Portales-Castillo
- Department of Medicine, Division of Nephrology, Washington University in St.Louis, St. Louis, MO 63110, USA
| | - Abdullah Jalal
- Department of Medicine, Division of Nephrology, Washington University in St.Louis, St. Louis, MO 63110, USA
| | - Peggy L Kendall
- Department of Medicine, Division of Allergy and Immunology, Washington University in St.Louis, St. Louis, MO 63110, USA
| | - Deborah Parks
- Department of Medicine, Division of Rheumatology, Washington University in St.Louis, St. Louis, MO 63110, USA
| |
Collapse
|
2
|
Wuchu F, Ma X, Que Y, Chen J, Ruan YC. Biphasic regulation of CFTR expression by ENaC in epithelial cells: The involvement of Ca2+-modulated cAMP production. Front Cell Dev Biol 2022; 10:781762. [PMID: 36111343 PMCID: PMC9469783 DOI: 10.3389/fcell.2022.781762] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2021] [Accepted: 07/07/2022] [Indexed: 11/17/2022] Open
Abstract
The regulatory interaction between two typical epithelial ion channels, cystic fibrosis transmembrane conductance regulator (CFTR) and the epithelial sodium channel (ENaC), for epithelial homeostasis has been noted, although the underlying mechanisms remain unclear. Here, we report that in a human endometrial epithelial cell line (ISK), shRNA-based stable knockdown of ENaC produced a biphasic effect: a low (∼23%) degree of ENaC knockdown resulted in significant increases in CFTR mRNA and protein levels, CFTR-mediated Cl− transport activity as well as intracellular cAMP concentration, while a higher degree (∼50%) of ENaC knockdown did not further increase but restored CFTR expression and cAMP levels. The basal intracellular Ca2+ level of ISK cells was lowered by ENaC knockdown or inhibition in a degree-dependent manner. BAPTA-AM, an intracellular Ca2+ chelator that lowers free Ca2+ concentration, elevated cAMP level and CFTR mRNA expression at a low (5 µM) but not a high (50 µM) dose, mimicking the biphasic effect of ENaC knockdown. Moreover, KH-7, a selective inhibitor of soluble adenylyl cyclase (sAC), abolished the CFTR upregulation induced by low-degree ENaC knockdown or Ca2+ chelation, suggesting the involvement of sAC-driven cAMP production in the positive regulation. A luciferase reporter to indicate CFTR transcription revealed that all tested degrees of ENaC knockdown/inhibition stimulated CFTR transcription in ISK cells, suggesting that the negative regulation on CFTR expression by the high-degree ENaC deficiency might occur at post-transcription stages. Additionally, similar biphasic effect of ENaC knockdown on CFTR expression was observed in a human bronchial epithelial cell line. Taken together, these results have revealed a previously unidentified biphasic regulatory role of ENaC in tuning CFTR expression involving Ca2+-modulated cAMP production, which may provide an efficient mechanism for dynamics and plasticity of the epithelial tissues in various physiological or pathological contexts.
Collapse
Affiliation(s)
- Fulei Wuchu
- Department of Biomedical Engineering, Faculty of Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong SAR, China
| | - Xiyang Ma
- Department of Biomedical Engineering, Faculty of Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong SAR, China
| | - Yanting Que
- Department of Biomedical Engineering, Faculty of Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong SAR, China
| | - Junjiang Chen
- Department of Biomedical Engineering, Faculty of Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong SAR, China
- Department of Physiology, Jinan University, Guangzhou, China
| | - Ye Chun Ruan
- Department of Biomedical Engineering, Faculty of Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong SAR, China
- Shenzhen Research Institute, Hong Kong Polytechnic University, Shenzhen, China
- *Correspondence: Ye Chun Ruan,
| |
Collapse
|
3
|
Du X, Zhai J, Li X, Zhang Y, Li N, Xie X. Hydrogel-Based Optical Ion Sensors: Principles and Challenges for Point-of-Care Testing and Environmental Monitoring. ACS Sens 2021; 6:1990-2001. [PMID: 34044533 DOI: 10.1021/acssensors.1c00756] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Hydrogel is a unique family of biocompatible materials with growing applications in chemical and biological sensors. During the past few decades, various hydrogel-based optical ion sensors have been developed aiming at point-of-care testing and environmental monitoring. In this Perspective, we provide an overview of the research field including topics such as photonic crystals, DNAzyme cross-linked hydrogels, ionophore-based ion sensing hydrogels, and fluoroionophore-based optodes. As the different sensing principles are summarized, each strategy offers its advantages and limitations. In a nutshell, developing optical ion sensing hydrogels is still in the early stage with many opportunities lying ahead, especially with challenges in selectivity, assay time, detection limit, and usability.
Collapse
Affiliation(s)
- Xinfeng Du
- Department of Chemistry, Southern University of Science and Technology, Shenzhen, 518055, China
| | - Jingying Zhai
- Academy for Advanced Interdisciplinary Studies, Southern University of Science and Technology, Shenzhen, 518055, China
| | - Xiaoang Li
- Department of Chemistry, Southern University of Science and Technology, Shenzhen, 518055, China
| | - Yupu Zhang
- Department of Chemistry, Southern University of Science and Technology, Shenzhen, 518055, China
| | - Niping Li
- Department of Chemistry, Southern University of Science and Technology, Shenzhen, 518055, China
| | - Xiaojiang Xie
- Department of Chemistry, Southern University of Science and Technology, Shenzhen, 518055, China
| |
Collapse
|
4
|
Daria VR, Castañares ML, Bachor HA. Spatio-temporal parameters for optical probing of neuronal activity. Biophys Rev 2021; 13:13-33. [PMID: 33747244 PMCID: PMC7930150 DOI: 10.1007/s12551-021-00780-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2020] [Accepted: 01/01/2021] [Indexed: 12/28/2022] Open
Abstract
The challenge to understand the complex neuronal circuit functions in the mammalian brain has brought about a revolution in light-based neurotechnologies and optogenetic tools. However, while recent seminal works have shown excellent insights on the processing of basic functions such as sensory perception, memory, and navigation, understanding more complex brain functions is still unattainable with current technologies. We are just scratching the surface, both literally and figuratively. Yet, the path towards fully understanding the brain is not totally uncertain. Recent rapid technological advancements have allowed us to analyze the processing of signals within dendritic arborizations of single neurons and within neuronal circuits. Understanding the circuit dynamics in the brain requires a good appreciation of the spatial and temporal properties of neuronal activity. Here, we assess the spatio-temporal parameters of neuronal responses and match them with suitable light-based neurotechnologies as well as photochemical and optogenetic tools. We focus on the spatial range that includes dendrites and certain brain regions (e.g., cortex and hippocampus) that constitute neuronal circuits. We also review some temporal characteristics of some proteins and ion channels responsible for certain neuronal functions. With the aid of the photochemical and optogenetic markers, we can use light to visualize the circuit dynamics of a functioning brain. The challenge to understand how the brain works continue to excite scientists as research questions begin to link macroscopic and microscopic units of brain circuits.
Collapse
Affiliation(s)
- Vincent R. Daria
- Research School of Physics, The Australian National University, Canberra, Australia
- John Curtin School of Medical Research, The Australian National University, Canberra, Australia
| | | | - Hans-A. Bachor
- Research School of Physics, The Australian National University, Canberra, Australia
| |
Collapse
|
5
|
Ekici Eİ, Güney M, Nazıroğlu M. Protective effect of cabergoline on mitochondrial oxidative stress-induced apoptosis is mediated by modulations of TRPM2 in neutrophils of patients with endometriosis. J Bioenerg Biomembr 2020; 52:131-142. [PMID: 32227254 DOI: 10.1007/s10863-020-09830-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Accepted: 03/20/2020] [Indexed: 12/30/2022]
Abstract
Calcium ion (Ca2+) signaling in endometriosis (ENDO) is associated with increased neutrophil activation and oxidative stress. A Ca2+ signaling modulator and antioxidant actions of cabergoline (CBG) in some cells were recently reported. TRPM2 cation channel is activated by reactive oxygen species (ROS). Antioxidant action of CGB via inhibition of ROS may modulate the channel. We aimed to investigate the effect of CBG on TRPM2 inhibition in serum and neutrophils of patients with ENDO. The serum and neutrophil samples were grouped into healthy samples (no treatment), ENDO and ENDO + CBG treated groups (n = 10 in each). In some experiments, the neutrophils were also incubated with TRPM2 (ACA) and PARP-1 (PJ34) blockers. The values of intracellular ROS, Ca2+ concentration, mitochondrial membrane depolarization, lipid peroxidation, apoptosis, and caspase - 3, caspase - 9, PARP-1 and TRPM2 expressions were high in the neutrophils of patients with ENDO, although antioxidant levels (reduced glutathione, glutathione peroxidase, vitamin A, and vitamin E) were low in the neutrophils and serum from these patients. However, markers for apoptosis, oxidative stress, and mitochondrial dysfunction were reduced with CBG, ACA and PJ34 treatments, although the antioxidant levels were increased in the serum and neutrophils following treatment with CBG. Taken together, our current results suggest that CBG are useful antagonists against apoptosis and mitochondrial oxidative stress via inhibition of TRPM2 in neutrophils of patients with ENDO.
Collapse
Affiliation(s)
- Elif İlknur Ekici
- Department of Obstetrics and Gynecology, Faculty of Medicine, Suleyman Demirel University, Isparta, Turkey
| | - Mehmet Güney
- Department of Obstetrics and Gynecology, Faculty of Medicine, Suleyman Demirel University, Isparta, Turkey
| | - Mustafa Nazıroğlu
- Department of Biophysics, Faculty of Medicine, Suleyman Demirel University, Isparta, Turkey. .,Drug Discovery Unit, BSN Health, Analysis and Innovation Ltd. Inc. Teknokent, Isparta, Turkey. .,Neuroscience Research Center, Suleyman Demirel University, TR-32260, Isparta, Turkey.
| |
Collapse
|
6
|
TRPM7 mediates kidney injury, endothelial hyperpermeability and mortality during endotoxemia. J Transl Med 2020; 100:234-249. [PMID: 31444399 DOI: 10.1038/s41374-019-0304-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Revised: 06/24/2019] [Accepted: 07/19/2019] [Indexed: 12/17/2022] Open
Abstract
Sepsis is the main cause of mortality in patients admitted to intensive care units. During sepsis, endothelial permeability is severely augmented, contributing to renal dysfunction and patient mortality. Ca2+ influx and the subsequent increase in intracellular [Ca2+]i in endothelial cells (ECs) are key steps in the establishment of endothelial hyperpermeability. Transient receptor potential melastatin 7 (TRPM7) ion channels are permeable to Ca2+ and are expressed in a broad range of cell types and tissues, including ECs and kidneys. However, the role of TRPM7 on endothelial hyperpermeability during sepsis has remained elusive. Therefore, we investigated the participation of TRPM7 in renal vascular hyperpermeability, renal dysfunction, and enhanced mortality induced by endotoxemia. Our results showed that endotoxin increases endothelial hyperpermeability and Ca2+ overload through the TLR4/NOX-2/ROS/NF-κB pathway. Moreover, endotoxin exposure was shown to downregulate the expression of VE-cadherin, compromising monolayer integrity and enhancing vascular hyperpermeability. Notably, endotoxin-induced endothelial hyperpermeability was substantially inhibited by pharmacological inhibition and specific suppression of TRPM7 expression. The endotoxin was shown to upregulate the expression of TRPM7 via the TLR4/NOX-2/ROS/NF-κB pathway and induce a TRPM7-dependent EC Ca2+ overload. Remarkably, in vivo experiments performed in endotoxemic animals showed that pharmacological inhibition and specific suppression of TRPM7 expression inhibits renal vascular hyperpermeability, prevents kidney dysfunction, and improves survival in endotoxemic animals. Therefore, our results showed that TRPM7 mediates endotoxemia-induced endothelial hyperpermeability, renal dysfunction, and enhanced mortality, revealing a novel molecular target for treating renal vascular hyperpermeability and kidney dysfunction during endotoxemia, sepsis, and other inflammatory diseases.
Collapse
|
7
|
Qian N, Ichimura A, Takei D, Sakaguchi R, Kitani A, Nagaoka R, Tomizawa M, Miyazaki Y, Miyachi H, Numata T, Kakizawa S, Nishi M, Mori Y, Takeshima H. TRPM7 channels mediate spontaneous Ca 2+ fluctuations in growth plate chondrocytes that promote bone development. Sci Signal 2019; 12:12/576/eaaw4847. [PMID: 30967513 DOI: 10.1126/scisignal.aaw4847] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
During endochondral ossification of long bones, the proliferation and differentiation of chondrocytes cause them to be arranged into layered structures constituting the epiphyseal growth plate, where they secrete the cartilage matrix that is subsequently converted into trabecular bone. Ca2+ signaling has been implicated in chondrogenesis in vitro. Through fluorometric imaging of bone slices from embryonic mice, we demonstrated that live growth plate chondrocytes generated small, cell-autonomous Ca2+ fluctuations that were associated with weak and intermittent Ca2+ influx. Several genes encoding Ca2+-permeable channels were expressed in growth plate chondrocytes, but only pharmacological inhibitors of transient receptor potential cation channel subfamily M member 7 (TRPM7) reduced the spontaneous Ca2+ fluctuations. The TRPM7-mediated Ca2+ influx was likely activated downstream of basal phospholipase C activity and was potentiated upon cell hyperpolarization induced by big-conductance Ca2+-dependent K+ channels. Bones from embryos in which Trpm7 was conditionally knocked out during ex vivo culture exhibited reduced outgrowth and displayed histological abnormalities accompanied by insufficient autophosphorylation of Ca2+/calmodulin-dependent protein kinase II (CaMKII) in the growth plate. The link between TRPM7-mediated Ca2+ fluctuations and CaMKII-dependent chondrogenesis was further supported by experiments with chondrocyte-specific Trpm7 knockout mice. Thus, growth plate chondrocytes generate spontaneous, TRPM7-mediated Ca2+ fluctuations that promote self-maturation and bone development.
Collapse
Affiliation(s)
- Nianchao Qian
- Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 615-8501, Japan
| | - Atsuhiko Ichimura
- Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 615-8501, Japan.,Keihanshin Consortium for Fostering the Next Generation of Global Leaders in Research (K-CONNEX), Kyoto University, Kyoto 606-8501, Japan
| | - Daisuke Takei
- Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 615-8501, Japan
| | - Reiko Sakaguchi
- Institute for Integrated Cell-Material Sciences, Kyoto University, Kyoto 615-8510, Japan
| | - Akihiro Kitani
- Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 615-8501, Japan
| | - Ryohei Nagaoka
- Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 615-8501, Japan
| | - Masato Tomizawa
- Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 615-8501, Japan
| | - Yuu Miyazaki
- Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 615-8501, Japan
| | - Hitoshi Miyachi
- Reproductive Engineering Team, Institute for Frontier Life and Medical Sciences, Kyoto University, Kyoto 606-8507, Japan
| | - Tomohiro Numata
- Graduate School of Medical Sciences, Fukuoka University, Fukuoka 814-0180, Japan.,Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan
| | - Sho Kakizawa
- Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 615-8501, Japan
| | - Miyuki Nishi
- Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 615-8501, Japan.,Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan
| | - Yasuo Mori
- Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan
| | - Hiroshi Takeshima
- Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 615-8501, Japan.
| |
Collapse
|
8
|
Retana Moreira L, Rodríguez Serrano F, Osuna A. Extracellular vesicles of Trypanosoma cruzi tissue-culture cell-derived trypomastigotes: Induction of physiological changes in non-parasitized culture cells. PLoS Negl Trop Dis 2019; 13:e0007163. [PMID: 30789912 PMCID: PMC6383987 DOI: 10.1371/journal.pntd.0007163] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2018] [Accepted: 01/16/2019] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND Trypanosoma cruzi is the obligate intracellular parasite that causes Chagas disease. The pathogenesis of this disease is a multifactorial complex process that involves a large number of molecules and particles, including the extracellular vesicles. The presence of EVs of T. cruzi was first described in 1979 and, since then, research regarding these particles has been increasing. Some of the functions described for these EVs include the increase in heart parasitism and the immunomodulation and evasion of the host immune response. Also, EVs may be involved in parasite adhesion to host cells and host cell invasion. METHODOLOGY/PRINCIPAL FINDINGS EVs (exosomes) of the Pan4 strain of T. cruzi were isolated by differential centrifugation, and measured and quantified by TEM, NTA and DLS. The effect of EVs in increasing the parasitization of Vero cells was evaluated and the ED50 was calculated. Changes in cell permeability induced by EVs were evaluated in Vero and HL-1 cardiomyocyte cells using cell viability techniques such as trypan blue and MTT assays, and by confocal microscopy. The intracellular mobilization of Ca2+ and the disruption of the actin cytoskeleton induced by EVs over Vero cells were followed-up in time using confocal microscopy. To evaluate the effect of EVs over the cell cycle, cell cycle analyses using flow cytometry and Western blotting of the phosphorylated and non-phosphorylated protein of Retinoblastoma were performed. CONCLUSION/SIGNIFICANCE The incubation of cells with EVs of trypomastigotes of the Pan4 strain of T. cruzi induce a number of changes in the host cells that include a change in cell permeability and higher intracellular levels of Ca2+ that can alter the dynamics of the actin cytoskeleton and arrest the cell cycle at G0/G1 prior to the DNA synthesis necessary to complete mitosis. These changes aid the invasion of host cells and augment the percentage of cell parasitization.
Collapse
Affiliation(s)
- Lissette Retana Moreira
- Instituto de Biotecnología, Grupo de Bioquímica y Parasitología Molecular, Departamento de Parasitología, Universidad de Granada, Granada, Spain
| | | | - Antonio Osuna
- Instituto de Biotecnología, Grupo de Bioquímica y Parasitología Molecular, Departamento de Parasitología, Universidad de Granada, Granada, Spain
- * E-mail:
| |
Collapse
|
9
|
Tsuji G, Hattori T, Kato M, Hakamata W, Inoue H, Naito M, Kurihara M, Demizu Y, Shoda T. Design and synthesis of cell-permeable fluorescent nitrilotriacetic acid derivatives. Bioorg Med Chem 2018; 26:5494-5498. [PMID: 30293794 DOI: 10.1016/j.bmc.2018.09.028] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Revised: 09/20/2018] [Accepted: 09/22/2018] [Indexed: 11/26/2022]
Abstract
Fluorescence labeling of the target molecules using a small molecule-based probe is superior than a method using genetically expressed green fluorescence protein (GFP) in terms of convenience in its preparation and functionalization. Fluorophore-nitrilotriacetic acid (NTA) conjugates with several ester protecting groups were synthesized and evaluated for their cell membrane permeability by fluorescence microscopy analysis. One of the derivatives, acetoxymethyl (AM)-protected NTA conjugate is hydrolyzed, resulting in intracellular accumulation, thus providing localized fluorescence intensity in cells. This modification is expected as an effective method for converting a non-cell membrane permeable NTA-BODIPY conjugates to a cell membrane permeable derivatives.
Collapse
Affiliation(s)
- Genichiro Tsuji
- National Institute of Health Sciences, 3-25-26 Tonomachi, Kawasaki-ku, Kawasaki-shi, Kanagawa 210-9501, Japan.
| | - Takayuki Hattori
- National Institute of Health Sciences, 3-25-26 Tonomachi, Kawasaki-ku, Kawasaki-shi, Kanagawa 210-9501, Japan
| | - Masashi Kato
- National Institute of Health Sciences, 3-25-26 Tonomachi, Kawasaki-ku, Kawasaki-shi, Kanagawa 210-9501, Japan; School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo 192-0392, Japan
| | - Wataru Hakamata
- Department of Chemistry and Life Science, College of Bioresource Sciences, Nihon University, 1866 Kameino, Fujisawa, Kanagawa 252-0880, Japan
| | - Hideshi Inoue
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo 192-0392, Japan
| | - Mikihiko Naito
- National Institute of Health Sciences, 3-25-26 Tonomachi, Kawasaki-ku, Kawasaki-shi, Kanagawa 210-9501, Japan
| | - Masaaki Kurihara
- National Institute of Health Sciences, 3-25-26 Tonomachi, Kawasaki-ku, Kawasaki-shi, Kanagawa 210-9501, Japan
| | - Yosuke Demizu
- National Institute of Health Sciences, 3-25-26 Tonomachi, Kawasaki-ku, Kawasaki-shi, Kanagawa 210-9501, Japan
| | - Takuji Shoda
- National Institute of Health Sciences, 3-25-26 Tonomachi, Kawasaki-ku, Kawasaki-shi, Kanagawa 210-9501, Japan.
| |
Collapse
|
10
|
Chen W, Ennes HS, McRoberts JA, Marvizón JC. Mechanisms of μ-opioid receptor inhibition of NMDA receptor-induced substance P release in the rat spinal cord. Neuropharmacology 2017; 128:255-268. [PMID: 29042318 DOI: 10.1016/j.neuropharm.2017.10.014] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2017] [Revised: 09/21/2017] [Accepted: 10/11/2017] [Indexed: 01/17/2023]
Abstract
The interaction between NMDA receptors and μ-opioid receptors in primary afferent terminals was studied by using NMDA to induce substance P release, measured as neurokinin 1 receptor internalization. In rat spinal cord slices, the μ-opioid receptor agonists morphine, DAMGO and endomorphin-2 inhibited NMDA-induced substance P release, whereas the antagonist CTAP right-shifted the concentration response of DAMGO. In vivo, substance P release induced by intrathecal NMDA after priming with BDNF was inhibited by DAMGO. ω-Conotoxins MVIIC and GVIA inhibited about half of the NMDA-induced substance P release, showing that it was partially mediated by the opening of voltage-gated calcium (Cav) channels. In contrast, DAMGO or ω-conotoxins did not inhibit capsaicin-induced substance P release. In cultured DRG neurons, DAMGO but not ω-conotoxin inhibited NMDA-induced increases in intracellular calcium, indicating that μ-opioid receptors can inhibit NMDA receptor function by mechanisms other than inactivation of Cav channels. Moreover, DAMGO decreased the ω-conotoxin-insensitive component of the substance P release. Potent inhibition by ifenprodil showed that these NMDA receptors have the NR2B subunit. Activators of adenylyl cyclase and protein kinase A (PKA) induced substance P release and this was decreased by the NMDA receptor blocker MK-801 and by DAMGO. Conversely, inhibitors of adenylyl cyclase and PKA, but not of protein kinase C, decreased NMDA-induced substance P release. Hence, these NMDA receptors are positively modulated by the adenylyl cyclase-PKA pathway, which is inhibited by μ-opioid receptors. In conclusion, μ-opioid receptors inhibit NMDA receptor-induced substance P release through Cav channel inactivation and adenylyl cyclase inhibition.
Collapse
Affiliation(s)
- Wenling Chen
- Veteran Affairs Greater Los Angeles Healthcare System, 11310 Wilshire Blvd., Building 115, Los Angeles, CA 90073, USA; Vatche and Tamar Manoukian Division of Digestive Diseases, 900 Veterans Ave., Warren Hall Building, Department of Medicine, David Geffen School of Medicine at the University of California Los Angeles, Los Angeles, CA 90095, USA.
| | - Helena S Ennes
- Vatche and Tamar Manoukian Division of Digestive Diseases, 900 Veterans Ave., Warren Hall Building, Department of Medicine, David Geffen School of Medicine at the University of California Los Angeles, Los Angeles, CA 90095, USA.
| | - James A McRoberts
- Vatche and Tamar Manoukian Division of Digestive Diseases, 900 Veterans Ave., Warren Hall Building, Department of Medicine, David Geffen School of Medicine at the University of California Los Angeles, Los Angeles, CA 90095, USA.
| | - Juan Carlos Marvizón
- Veteran Affairs Greater Los Angeles Healthcare System, 11310 Wilshire Blvd., Building 115, Los Angeles, CA 90073, USA; Vatche and Tamar Manoukian Division of Digestive Diseases, 900 Veterans Ave., Warren Hall Building, Department of Medicine, David Geffen School of Medicine at the University of California Los Angeles, Los Angeles, CA 90095, USA.
| |
Collapse
|
11
|
Cell viability modulation through changes of Ca2+-dependent signalling pathways. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2016; 121:45-53. [DOI: 10.1016/j.pbiomolbio.2016.01.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Revised: 01/01/2016] [Accepted: 01/05/2016] [Indexed: 11/22/2022]
|
12
|
Lisak D, Schacht T, Gawlitza A, Albrecht P, Aktas O, Koop B, Gliem M, Hofstetter HH, Zanger K, Bultynck G, Parys JB, De Smedt H, Kindler T, Adams-Quack P, Hahn M, Waisman A, Reed JC, Hövelmeyer N, Methner A. BAX inhibitor-1 is a Ca(2+) channel critically important for immune cell function and survival. Cell Death Differ 2015; 23:358-68. [PMID: 26470731 DOI: 10.1038/cdd.2015.115] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2014] [Revised: 07/20/2015] [Accepted: 07/21/2015] [Indexed: 01/03/2023] Open
Abstract
The endoplasmic reticulum (ER) serves as the major intracellular Ca(2+) store and has a role in the synthesis and folding of proteins. BAX (BCL2-associated X protein) inhibitor-1 (BI-1) is a Ca(2+) leak channel also implicated in the response against protein misfolding, thereby connecting the Ca(2+) store and protein-folding functions of the ER. We found that BI-1-deficient mice suffer from leukopenia and erythrocytosis, have an increased number of splenic marginal zone B cells and higher abundance and nuclear translocation of NF-κB (nuclear factor-κ light-chain enhancer of activated B cells) proteins, correlating with increased cytosolic and ER Ca(2+) levels. When put into culture, purified knockout T cells and even more so B cells die spontaneously. This is preceded by increased activity of the mitochondrial initiator caspase-9 and correlated with a significant surge in mitochondrial Ca(2+) levels, suggesting an exhausted mitochondrial Ca(2+) buffer capacity as the underlying cause for cell death in vitro. In vivo, T-cell-dependent experimental autoimmune encephalomyelitis and B-cell-dependent antibody production are attenuated, corroborating the ex vivo results. These results suggest that BI-1 has a major role in the functioning of the adaptive immune system by regulating intracellular Ca(2+) homeostasis in lymphocytes.
Collapse
Affiliation(s)
- D Lisak
- Focus Program Translational Neuroscience (FTN), Rhine Main Neuroscience Network (rmn) and Department of Neurology, University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - T Schacht
- Focus Program Translational Neuroscience (FTN), Rhine Main Neuroscience Network (rmn) and Department of Neurology, University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - A Gawlitza
- Focus Program Translational Neuroscience (FTN), Rhine Main Neuroscience Network (rmn) and Department of Neurology, University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - P Albrecht
- Heinrich Heine Universität Düsseldorf, Department of Neurology, Düsseldorf, Germany
| | - O Aktas
- Heinrich Heine Universität Düsseldorf, Department of Neurology, Düsseldorf, Germany
| | - B Koop
- Heinrich Heine Universität Düsseldorf, Department of Neurology, Düsseldorf, Germany
| | - M Gliem
- Heinrich Heine Universität Düsseldorf, Department of Neurology, Düsseldorf, Germany
| | - H H Hofstetter
- Heinrich Heine Universität Düsseldorf, Department of Neurology, Düsseldorf, Germany
| | - K Zanger
- Center for Anatomy and Brain Research, Düsseldorf, Germany
| | - G Bultynck
- Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine, KU Leuven, Belgium
| | - J B Parys
- Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine, KU Leuven, Belgium
| | - H De Smedt
- Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine, KU Leuven, Belgium
| | - T Kindler
- III Medical Clinic, University Medical Center of the Johannes Gutenberg-University of Mainz, Mainz, Germany
| | - P Adams-Quack
- Institute for Molecular Medicine, University Medical Center of the Johannes Gutenberg-University of Mainz, Mainz, Germany
| | - M Hahn
- Institute for Molecular Medicine, University Medical Center of the Johannes Gutenberg-University of Mainz, Mainz, Germany
| | - A Waisman
- Institute for Molecular Medicine, University Medical Center of the Johannes Gutenberg-University of Mainz, Mainz, Germany
| | - J C Reed
- Sanford Burnham Institute, La Jolla, CA, USA
| | - N Hövelmeyer
- Institute for Molecular Medicine, University Medical Center of the Johannes Gutenberg-University of Mainz, Mainz, Germany
| | - A Methner
- Focus Program Translational Neuroscience (FTN), Rhine Main Neuroscience Network (rmn) and Department of Neurology, University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
| |
Collapse
|
13
|
Rivera CM, Kwon HJ, Hashmi A, Yu G, Zhao J, Gao J, Xu J, Xue W, Dimitrov AG. Towards a dynamic clamp for neurochemical modalities. SENSORS 2015; 15:10465-80. [PMID: 25946635 PMCID: PMC4481920 DOI: 10.3390/s150510465] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/08/2015] [Revised: 04/27/2015] [Accepted: 04/29/2015] [Indexed: 01/08/2023]
Abstract
The classic dynamic clamp technique uses a real-time electrical interface between living cells and neural simulations in order to investigate hypotheses about neural function and structure. One of the acknowledged drawbacks of that technique is the limited control of the cells' chemical microenvironment. In this manuscript, we use a novel combination of nanosensor and microfluidic technology and microfluidic and neural simulations to add sensing and control of chemical concentrations to the dynamic clamp technique. Specifically, we use a microfluidic lab-on-a-chip to generate distinct chemical concentration gradients (ions or neuromodulators), to register the concentrations with embedded nanosensors and use the processed signals as an input to simulations of a neural cell. The ultimate goal of this project is to close the loop and provide sensor signals to the microfluidic lab-on-a-chip to mimic the interaction of the simulated cell with other cells in its chemical environment.
Collapse
Affiliation(s)
- Catalina Maria Rivera
- Departments of Mathematics, Washington State University Vancouver, Vancouver, WA 98686, USA.
- Department of Physics, Emory University, Atlanta, GA 30332, USA.
| | - Hyuck-Jin Kwon
- Department of Electrical and Computer Engineering, McMaster University, Hamilton, ON L8S4L8, Canada.
| | - Ali Hashmi
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA.
| | - Gan Yu
- Departments of Mechanical Engineering, Washington State University Vancouver, Vancouver, WA 98686, USA.
| | - Jiheng Zhao
- Departments of Mechanical Engineering, Washington State University Vancouver, Vancouver, WA 98686, USA.
| | - Jianlong Gao
- Departments of Mechanical Engineering, Washington State University Vancouver, Vancouver, WA 98686, USA.
| | - Jie Xu
- Department of Mechanical and Industrial Engineering, University of Illinois at Chicago, Chicago, IL 60607, USA.
| | - Wei Xue
- Department of Mechanical Engineering, Rowan University, Glassboro, NJ 08028, USA.
| | - Alexander G Dimitrov
- Departments of Mathematics, Washington State University Vancouver, Vancouver, WA 98686, USA.
| |
Collapse
|
14
|
Assinger A, Volf I, Schmid D. A novel, rapid method to quantify intraplatelet calcium dynamics by ratiometric flow cytometry. PLoS One 2015; 10:e0122527. [PMID: 25849642 PMCID: PMC4388375 DOI: 10.1371/journal.pone.0122527] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2014] [Accepted: 02/18/2015] [Indexed: 11/19/2022] Open
Abstract
Cytosolic free calcium ions represent important second-messengers in platelets. Therefore, quantitative measurement of intraplatelet calcium provides a popular and very sensitive tool to evaluate platelet activation and reactivity. Current protocols for determination of intracellular calcium concentrations in platelets have a number of limitations. Cuvette-based methods do not allow measurement of calcium flux in complex systems, such as whole blood, and therefore require isolation steps that potentially interfere with platelet activation. Flow cytometry has the potential to overcome this limitation, but to date the application of calibrated, quantitative readout of calcium kinetics has only been described for Indo-1. As excitation of Indo-1 requires a laser in the ultraviolet range, such measurements cannot be performed with a standard flow cytometer. Here, we describe a novel, rapid calibration method for ratiometric calcium measurement in platelets using both Ar+-laser excited fluorescence dyes Fluo-4 and Fura Red. We provide appropriate equations that allow rapid quantification of intraplatelet calcium fluxes by measurement of only two standardisation buffers. We demonstrate that this method allows quantitative calcium measurement in platelet rich plasma as well as in whole blood. Further, we show that this method prevents artefacts due to platelet aggregate formation and is therefore an ideal tool to determine basal and agonist induced calcium kinetics.
Collapse
Affiliation(s)
- Alice Assinger
- Institute of Physiology, Centre for Physiology and Pharmacology, Medical University of Vienna, Austria
| | - Ivo Volf
- Institute of Physiology, Centre for Physiology and Pharmacology, Medical University of Vienna, Austria
| | - Diethart Schmid
- Institute of Physiology, Centre for Physiology and Pharmacology, Medical University of Vienna, Austria
- * E-mail:
| |
Collapse
|
15
|
Posey AD, Kawalekar OU, June CH. Measurement of intracellular ions by flow cytometry. ACTA ACUST UNITED AC 2015; 72:9.8.1-9.8.21. [PMID: 25827486 DOI: 10.1002/0471142956.cy0908s72] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Using flow cytometry, single-cell measurements of calcium can be made on isolated populations identified by one or more phenotypic characteristics. Most earlier techniques for measuring cellular activation parameters determined the mean value for a population of cells, which did not permit optimal resolution of the responses. The flow cytometer is particularly useful for this purpose because it can measure ion concentrations in large numbers of single cells and thereby allows ion concentration to be correlated with other parameters such as immunophenotype and cell cycle stage. A limitation of flow cytometry, however, is that it does not permit resolution of certain complex kinetic responses such as cellular oscillatory responses. This unit describes the preparation of cells, including labeling with antibodies and with calcium probes, and discusses the principles of data analysis and interpretation.
Collapse
Affiliation(s)
- Avery D Posey
- Abramson Family Cancer Research Institute, and the Department of Pathology and Laboratory Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania
| | - Omkar U Kawalekar
- Abramson Family Cancer Research Institute, and the Department of Pathology and Laboratory Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania
| | - Carl H June
- Abramson Family Cancer Research Institute, and the Department of Pathology and Laboratory Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania
| |
Collapse
|
16
|
Vocke K, Dauner K, Hahn A, Ulbrich A, Broecker J, Keller S, Frings S, Möhrlen F. Calmodulin-dependent activation and inactivation of anoctamin calcium-gated chloride channels. ACTA ACUST UNITED AC 2014; 142:381-404. [PMID: 24081981 PMCID: PMC3787769 DOI: 10.1085/jgp.201311015] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Calcium-dependent chloride channels serve critical functions in diverse biological systems. Driven by cellular calcium signals, the channels codetermine excitatory processes and promote solute transport. The anoctamin (ANO) family of membrane proteins encodes three calcium-activated chloride channels, named ANO 1 (also TMEM16A), ANO 2 (also TMEM16B), and ANO 6 (also TMEM16F). Here we examined how ANO 1 and ANO 2 interact with Ca2+/calmodulin using nonstationary current analysis during channel activation. We identified a putative calmodulin-binding domain in the N-terminal region of the channel proteins that is involved in channel activation. Binding studies with peptides indicated that this domain, a regulatory calmodulin-binding motif (RCBM), provides two distinct modes of interaction with Ca2+/calmodulin, one at submicromolar Ca2+ concentrations and one in the micromolar Ca2+ range. Functional, structural, and pharmacological data support the concept that calmodulin serves as a calcium sensor that is stably associated with the RCBM domain and regulates the activation of ANO 1 and ANO 2 channels. Moreover, the predominant splice variant of ANO 2 in the brain exhibits Ca2+/calmodulin-dependent inactivation, a loss of channel activity within 30 s. This property may curtail ANO 2 activity during persistent Ca2+ signals in neurons. Mutagenesis data indicated that the RCBM domain is also involved in ANO 2 inactivation, and that inactivation is suppressed in the retinal ANO 2 splice variant. These results advance the understanding of Ca2+ regulation in anoctamin Cl− channels and its significance for the physiological function that anoctamin channels subserve in neurons and other cell types.
Collapse
Affiliation(s)
- Kerstin Vocke
- Department of Molecular Physiology, Centre for Organismal Studies, Heidelberg University, 69120 Heidelberg, Germany
| | | | | | | | | | | | | | | |
Collapse
|
17
|
Abstract
Ca(2+) indicator dyes by necessity are Ca(2+) chelators, because it is the binding of Ca(2+) to dye molecules that induces the change in fluorescence on which the Ca(2+) signal is based. As chelators, once introduced into a cell, they contribute to cellular Ca(2+) buffering. It has been a question of much debate to what extent this added Ca(2+) buffer (exogenous Ca(2+) buffer) changes Ca(2+) homeostasis and the signals of interest. I discuss this problem here, emphasizing the distinction between the influence of the dyes on amplitudes (which may be not so severe) and on the dynamics of Ca(2+) signals (which may be drastic). Once the Ca(2+)-buffering action of dyes relative to intrinsic Ca(2+) buffers is understood for a given preparation, Ca(2+) dyes can be used as very versatile tools for studying both Ca(2+) concentrations and Ca(2+) fluxes. I describe in detail some of my own experiences in calibrating the indicator dye Fura-2. These refer exclusively to experiments in which the dye is loaded into the cell via a patch pipette because acetoxymethyl ester loading introduces problems that very often prohibit precise quantitative conclusions.
Collapse
|
18
|
|
19
|
Abstract
Calcium acts as a prominent second messenger in virtually every cell type and modulates a plethora of cell functions. Thus, Ca(2+) microfluorimetry became a valuable tool to assess information about mechanisms involved in the regulation of the intracellular calcium level in research on living tissues. Here we offer insight into distinct approaches to detect changes in calcium levels specifically in Müller cells, the principal macroglial cells of the retina.
Collapse
|
20
|
Abstract
There is a vast array of dyes currently available for measurement of cytosolic calcium. These encompass single and dual excitation and single and dual emission probes. The choice of particular probe depends on the experimental question and the type of equipment to be used. It is therefore extremely difficult to define a universal approach that will suit all potential investigators. Preparations under investigation are loaded with the selected organic indicator dye by incubation with ester derivatives, by micropipet injection or reverse permeabilization. Indicators can also be targeted to a range of intracellular organelles. Calibration of a fluorescent signal into Ca(2+) concentration is in theory relatively simple but the investigator needs to take great care in this process. This chapter describes the theory of these processes and some of the pitfalls users should be aware of. Precise experimental details can be found in the subsequent chapters of this volume.
Collapse
Affiliation(s)
- Alec W M Simpson
- Department of Cell and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, UK.
| |
Collapse
|
21
|
Lee WT, Lin MH, Lee EJ, Hung YC, Tai SH, Chen HY, Chen TY, Wu TS. Magnolol reduces glutamate-induced neuronal excitotoxicity and protects against permanent focal cerebral ischemia up to 4 hours. PLoS One 2012; 7:e39952. [PMID: 22808077 PMCID: PMC3392264 DOI: 10.1371/journal.pone.0039952] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2012] [Accepted: 05/29/2012] [Indexed: 12/05/2022] Open
Abstract
Neuroprotective efficacy of magnolol, 5,5′-dially-2,2′-dihydroxydiphenyl, was investigated in a model of stroke and cultured neurons exposed to glutamate-induced excitotoxicity. Rats were subjected to permanent middle cerebral artery occlusion (pMCAO). Magnolol or vehicle was administered intraperitoneally, at 1 hr pre-insult or 1–6 hrs post-insult. Brain infarction was measured upon sacrifice. Relative to controls, animals pre-treated with magnolol (50–200 mg/kg) had significant infarct volume reductions by 30.9–37.8% and improved neurobehavioral outcomes (P<0.05, respectively). Delayed treatment with magnolol (100 mg/kg) also protected against ischemic brain damage and improved neurobehavioral scores, even when administered up to 4 hrs post-insult (P<0.05, respectively). Additionally, magnolol (0.1 µM) effectively attenuated the rises of intracellular Ca2+ levels, [Ca2+](i), in cultured neurons exposed to glutamate. Consequently, magnolol (0.1–1 µM) significantly attenuated glutamate-induced cytotoxicity and cell swelling (P<0.05). Thus, magnolol offers neuroprotection against permanent focal cerebral ischemia with a therapeutic window of 4 hrs. This neuroprotection may be, partly, mediated by its ability to limit the glutamate-induced excitotoxicity.
Collapse
Affiliation(s)
- Wei-Ting Lee
- Neurophysiology Laboratory, Neurosurgical Service, Departments of Surgery, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, Tainan, Taiwan
- Institute of Biotechnology, National Cheng Kung University, Tainan, Taiwan
| | - Miao-Hui Lin
- Department of Early Childhood Education, National University of Tainan, Tainan, Taiwan
| | - E-Jian Lee
- Neurophysiology Laboratory, Neurosurgical Service, Departments of Surgery, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, Tainan, Taiwan
- * E-mail:
| | - Yu-Chang Hung
- Neurophysiology Laboratory, Neurosurgical Service, Departments of Surgery, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Shih-Huang Tai
- Neurophysiology Laboratory, Neurosurgical Service, Departments of Surgery, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Hung-Yi Chen
- Institute of Pharmacy, China Medical University, Taichung, Taiwan
| | - Tsung-Ying Chen
- Department of Anesthesiology, Buddhist Tzu-Chi University and Buddhist Tzu Chi General Hospital, Hualien, Taiwan
| | - Tian-Shung Wu
- Institute of Chemistry, National Cheng Kung University, Tainan, Taiwan
| |
Collapse
|
22
|
Than A, Tee WT, Chen P. Apelin secretion and expression of apelin receptors in 3T3-L1 adipocytes are differentially regulated by angiotensin type 1 and type 2 receptors. Mol Cell Endocrinol 2012; 351:296-305. [PMID: 22249006 DOI: 10.1016/j.mce.2012.01.005] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/03/2011] [Revised: 12/27/2011] [Accepted: 01/04/2012] [Indexed: 12/28/2022]
Abstract
Adipocytes play pivotal roles in regulating metabolism through secretion of a variety of adipokines, which in turn is regulated by other metabolic factors (e.g., insulin). Understanding the regulations of adipokine secretion is important because adipokines are implicated with metabolic disorders, such as, obesity and diabetes mellitus. Here, we investigated the regulatory roles of angiotensin II (AngII) on the secretion of apelin in 3T3-L1 adipocytes, and distinct signaling pathways mediated by AngII receptor type 1 (AT₁) and type 2 (AT₂) were revealed. It was found that activation of AT₁ receptors stimulates apelin secretion in Ca²⁺, protein kinase C, and MAPK kinase dependent ways while activation of AT₂ receptors inhibits apelin secretion through cAMP and cGMP dependent pathways. Furthermore, we demonstrate that the expression of apelin receptor (APJ) is also similarly regulated by AT₁ and AT₂ receptors. Finally, a detailed AngII signaling map is proposed.
Collapse
Affiliation(s)
- Aung Than
- Division of Bioengineering, Nanyang Technological University, 70 Nanyang Drive, Singapore 637457, Singapore
| | | | | |
Collapse
|
23
|
Abstract
It has been known for more than 60 years, and suspected for over 100, that alveolar hypoxia causes pulmonary vasoconstriction by means of mechanisms local to the lung. For the last 20 years, it has been clear that the essential sensor, transduction, and effector mechanisms responsible for hypoxic pulmonary vasoconstriction (HPV) reside in the pulmonary arterial smooth muscle cell. The main focus of this review is the cellular and molecular work performed to clarify these intrinsic mechanisms and to determine how they are facilitated and inhibited by the extrinsic influences of other cells. Because the interaction of intrinsic and extrinsic mechanisms is likely to shape expression of HPV in vivo, we relate results obtained in cells to HPV in more intact preparations, such as intact and isolated lungs and isolated pulmonary vessels. Finally, we evaluate evidence regarding the contribution of HPV to the physiological and pathophysiological processes involved in the transition from fetal to neonatal life, pulmonary gas exchange, high-altitude pulmonary edema, and pulmonary hypertension. Although understanding of HPV has advanced significantly, major areas of ignorance and uncertainty await resolution.
Collapse
Affiliation(s)
- J T Sylvester
- Division of Pulmonary & Critical Care Medicine, Department of Medicine, The Johns Hopkins University School ofMedicine, Baltimore, Maryland, USA.
| | | | | | | |
Collapse
|
24
|
Kim B, Takeuchi A, Koga O, Hikida M, Matsuoka S. Pivotal role of mitochondrial Na⁺₋Ca²⁺ exchange in antigen receptor mediated Ca²⁺ signalling in DT40 and A20 B lymphocytes. J Physiol 2011; 590:459-74. [PMID: 22155933 DOI: 10.1113/jphysiol.2011.222927] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Cytoplasmic Ca(2+) concentration ([Ca(2+)](i)) increases upon activation of antigen-receptor in lymphocytes. Mitochondria have been suggested to regulate the [Ca(2+)](i) response, but the molecular mechanisms and the roles are poorly understood. To clarify them, we carried out a combination study of mathematical simulations and knockout or knockdown of NCLX, a gene candidate for the mitochondrial Na(+)-Ca(2+) exchanger (NCX(mit)), in B lymphocytes. A mathematical model of Ca(2+) dynamics in B lymphocytes demonstrated that NCX(mit) inhibition reduces basal Ca(2+) content of endoplasmic reticulum (ER) and suppresses B-cell antigen receptor (BCR)-mediated [Ca(2+)](i) rise. The predictions were validated in DT40 B lymphocytes of heterozygous NCLX knockout (NCLX(+/-)). In NCLX(+/-) cells, mitochondrial Ca(2+) efflux via NCX(mit) was strongly decelerated, suggesting NCLX is a gene responsible for NCX(mit) in B lymphocytes. Consistent with the predictions, ER Ca(2+) content declined and [Ca(2+)](i) hardly rose upon BCR activation in NCLX(+/-) cells. ER Ca(2+) uptake was reduced to ∼58% of the wild-type (WT), while it was comparable to WT when mitochondrial respiration was disturbed. Essentially the same results were obtained by a pharmacological inhibition or knockdown of NCLX by siRNA in A20 B lymphocytes. Unexpectedly, ER Ca(2+) leak was augmented and co-localization of mitochondria with ER was lower in NCLX(+/-) and NCLX silenced cells. Taken together, we concluded that NCLX is a key Ca(2+) provider to ER, and that NCLX-mediated Ca(2+) recycling between mitochondria and ER is pivotal in B cell responses to antigen.
Collapse
Affiliation(s)
- Bongju Kim
- Center for Innovation in Immunoregulative Technology and Therapeutics, Kyoto University, Yoshida-konoe, Sakyo-ku, Kyoto 606-8501, Japan
| | | | | | | | | |
Collapse
|
25
|
Read ND, Allan WTG, Knight H, Knight MR, Malhó R, Russell A, Shacklock PS, Trewavas AJ. Imaging and measurement of cytosolic free calcium in plant and fungal cells. J Microsc 2011. [DOI: 10.1111/j.1365-2818.1992.tb01507.x] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
26
|
Ungerer N, Mücke N, Broecker J, Keller S, Frings S, Möhrlen F. Distinct binding properties distinguish LQ-type calmodulin-binding domains in cyclic nucleotide-gated channels. Biochemistry 2011; 50:3221-8. [PMID: 21413724 DOI: 10.1021/bi200115m] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Cyclic nucleotide-gated (CNG) channels operate as transduction channels in photoreceptors and olfactory receptor neurons. Direct binding of cGMP or cAMP opens these channels which conduct a mixture of monovalent cations and Ca(2+). Upon activation, CNG channels generate intracellular Ca(2+) signals that play pivotal roles in the transduction cascades of the visual and olfactory systems. Channel activity is controlled by negative feedback mechanisms that involve Ca(2+)-calmodulin, for which all CNG channels possess binding sites. Here we compare the binding properties of the two LQ-type calmodulin binding sites, both of which are thought to be involved in channel regulation. They reside on the isoforms CNGB1 and CNGA4. The CNGB1 subunit is present in rod photoreceptors and olfactory receptor neurons. The CNGA4 subunit is only expressed in olfactory receptor neurons, and there are conflicting results as to its role in calmodulin-mediated feedback inhibition. We examined the interaction of Ca(2+)-calmodulin with two recombinant proteins that encompass either of the two LQ sites. Comparing binding properties, we found that the LQ site of CNGB1 binds Ca(2+)-calmodulin at 10-fold lower Ca(2+) levels than the LQ site of CNGA4. Our data provide biochemical evidence against a contribution of CNGA4 to feedback inhibition. In accordance with previous work on photoreceptor CNG channels, our results indicate that feedback control is the exclusive role of the B-subunits in photoreceptors and olfactory receptor neurons.
Collapse
Affiliation(s)
- Nicole Ungerer
- Department of Molecular Physiology, University of Heidelberg, 69120 Heidelberg, Germany
| | | | | | | | | | | |
Collapse
|
27
|
Mori N, Kawabata F, Matsumura S, Hosokawa H, Kobayashi S, Inoue K, Fushiki T. Intragastric administration of allyl isothiocyanate increases carbohydrate oxidation via TRPV1 but not TRPA1 in mice. Am J Physiol Regul Integr Comp Physiol 2011; 300:R1494-505. [PMID: 21430076 DOI: 10.1152/ajpregu.00645.2009] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The transient receptor potential (TRP) channel family is composed of a wide variety of cation-permeable channels activated polymodally by various stimuli and is implicated in a variety of cellular functions. Recent investigations have revealed that activation of TRP channels is involved not only in nociception and thermosensation but also in thermoregulation and energy metabolism. We investigated the effect of intragastric administration of TRP channel agonists on changes in energy substrate utilization of mice. Intragastric administration of allyl isothiocyanate (AITC; a typical TRPA1 agonist) markedly increased carbohydrate oxidation but did not affect oxygen consumption. To examine whether TRP channels mediate this increase in carbohydrate oxidation, we used TRPA1 and TRPV1 knockout (KO) mice. Intragastric administration of AITC increased carbohydrate oxidation in TRPA1 KO mice but not in TRPV1 KO mice. Furthermore, AITC dose-dependently increased intracellular calcium ion concentration in cells expressing TRPV1. These findings suggest that AITC might activate TRPV1 and that AITC increased carbohydrate oxidation via TRPV1.
Collapse
Affiliation(s)
- Noriyuki Mori
- Laboratory of Nutrition Chemistry, Division of Food Science and Biotechnology, Graduate School of Agriculture, Kyoto University, Yoshidahonmachi, Japan
| | | | | | | | | | | | | |
Collapse
|
28
|
|
29
|
Gokina NI, Kuzina OY, Vance AM. Augmented EDHF signaling in rat uteroplacental vasculature during late pregnancy. Am J Physiol Heart Circ Physiol 2010; 299:H1642-52. [PMID: 20817830 DOI: 10.1152/ajpheart.00227.2010] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
A successful pregnancy outcome relies on extensive maternal cardiovascular adaptation, including enhanced uteroplacental vasodilator mechanisms. The objective of the present study was to determine the contribution of the endothelium-derived hyperpolarizing factor (EDHF) signaling in pregnancy-enhanced uterine vasodilation, to define the role of Ca(2+)-activated K(+) channels in mediating EDHF effects, and to explore the impact of endothelial Ca(2+) signaling in pregnancy-specific upregulation of EDHF. Fura 2-based measurements of smooth muscle cell (SMC) and endothelial cell cytosolic Ca(2+) concentration ([Ca(2+)](i)) were performed simultaneously with measurements of the diameter of uterine radial arteries from nonpregnant (NP) and late pregnant (LP) rats. Changes in SMC membrane potential of pressurized arteries from LP rats were assessed using glass microelectrodes. After blockade of nitric oxide and prostacyclin production, a cumulative application of ACh induced rapid and effective dilatation of uterine vessels from both NP and LP rats. This vasodilation was associated with SMC hyperpolarization and SMC [Ca(2+)](i) reduction and was abolished by a high-K(+) solution, demonstrating that N(G)-nitro-L-arginine (L-NNA)- and indomethacin-resistant responses are attributable to EDHF. Pregnancy significantly potentiates EDHF-mediated vasodilation in part due to enhanced endothelial Ca(2+) signaling. L-NNA- and indomethacin-resistant responses were insensitive to iberiotoxin but abolished by a combined treatment with apamin and charybdotoxin, supporting the key role of small- and intermediate-conductance K(+) channels in mediating EDHF signaling in the maternal uterine resistance vasculature.
Collapse
Affiliation(s)
- N I Gokina
- Dept. of Obstetrics, Gynecology, and Reproductive Sciences, College of Medicine, The Univ. of Vermont, Burlington, VT 05405, USA.
| | | | | |
Collapse
|
30
|
Waldeck C, Vocke K, Ungerer N, Frings S, Möhrlen F. Activation and desensitization of the olfactory cAMP-gated transduction channel: identification of functional modules. ACTA ACUST UNITED AC 2009; 134:397-408. [PMID: 19822638 PMCID: PMC2768803 DOI: 10.1085/jgp.200910296] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Olfactory receptor neurons respond to odor stimulation with a receptor potential that results from the successive activation of cyclic AMP (cAMP)-gated, Ca2+-permeable channels and Ca2+-activated chloride channels. The cAMP-gated channels open at micromolar concentrations of their ligand and are subject to a Ca2+-dependent feedback inhibition by calmodulin. Attempts to understand the operation of these channels have been hampered by the fact that the channel protein is composed of three different subunits, CNGA2, CNGA4, and CNGB1b. Here, we explore the individual role that each subunit plays in the gating process. Using site-directed mutagenesis and patch clamp analysis, we identify three functional modules that govern channel operation: a module that opens the channel, a module that stabilizes the open state at low cAMP concentrations, and a module that mediates rapid Ca2+-dependent feedback inhibition. Each subunit could be assigned to one of these functions that, together, define the gating logic of the olfactory transduction channel.
Collapse
Affiliation(s)
- Clemens Waldeck
- Department of Molecular Physiology, University of Heidelberg, 69120 Heidelberg, Germany
| | | | | | | | | |
Collapse
|
31
|
HE H, LEI L, LI J, SHI Z. Synthesis, Characterization and Biological Activities of a New Fluorescent Indicator for the Intracellular Calcium Ions. CHINESE J CHEM 2009. [DOI: 10.1002/cjoc.200990196] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
|
32
|
June CH, Abe R, Rabinovitch PS. Measurement of intracellular calcium ions by flow cytometry. ACTA ACUST UNITED AC 2008; Chapter 9:Unit 9.8. [PMID: 18770760 DOI: 10.1002/0471142956.cy0908s02] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Using flow cytometry, single-cell measurements of calcium can be made on isolated populations identified by one or more phenotypic characteristics. This unit describes the preparation of cells, including labeling with antibodies and with calcium probes, and discusses the principles of data analysis and interpretation.
Collapse
Affiliation(s)
- C H June
- Naval Medical Research Institute, Bethesda, Maryland, USA
| | | | | |
Collapse
|
33
|
Sawada Y, Hosokawa H, Matsumura K, Kobayashi S. Activation of transient receptor potential ankyrin 1 by hydrogen peroxide. Eur J Neurosci 2008; 27:1131-42. [PMID: 18364033 DOI: 10.1111/j.1460-9568.2008.06093.x] [Citation(s) in RCA: 181] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Hydrogen peroxide (H(2)O(2)), which is contained in industrial products, is also generated within cells. H(2)O(2) causes pain but it has not been elucidated how it activates sensory neurons in the pain pathway. Here we show that transient receptor potential ankyrin 1 (TRPA1), expressed by sensory neurons in the pain pathway, is a receptor for H(2)O(2). H(2)O(2) activated mouse TRPA1 to induce Ca(2+) influx and elicit non-selective cation currents. These effects of H(2)O(2) were mimicked by both reactive oxygen species and reactive nitrogen species. Cysteine-reducing agents suppressed H(2)O(2)-induced TRPA1 activation, whereas cysteine-oxidizing agents activated TRPA1. H(2)O(2) caused Ca(2+) influx in a subset of dorsal root ganglia neurons, which responded to allyl isothiocyanate, a TRPA1 ligand. These results suggest that TRPA1 might be involved in the sensation of pain caused by H(2)O(2).
Collapse
Affiliation(s)
- Yosuke Sawada
- Division of Biological Information, Department of Intelligence Science and Technology, Graduate School of Informatics, Kyoto University, Yoshidahonmachi, Kyoto 606-8501, Japan
| | | | | | | |
Collapse
|
34
|
Bengtson CP, Dick O, Bading H. A quantitative method to assess extrasynaptic NMDA receptor function in the protective effect of synaptic activity against neurotoxicity. BMC Neurosci 2008; 9:11. [PMID: 18218077 PMCID: PMC2267199 DOI: 10.1186/1471-2202-9-11] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2007] [Accepted: 01/24/2008] [Indexed: 11/18/2022] Open
Abstract
Background Extrasynaptic NMDA receptors couple to a CREB shut-off pathway and cause cell death, whereas synaptic NMDA receptors and nuclear calcium signaling promote CREB-mediated transcription and neuronal survival. The distribution of NMDA receptors (synaptic versus extrasynaptic) may be an important parameter that determines the susceptibility of neurons to toxic insults. Changes in receptor surface expression towards more extrasynaptic NMDA receptors may lead to neurodegeneration, whereas a reduction of extrasynaptic NMDA receptors may render neurons more resistant to death. A quantitative assessment of extrasynaptic NMDA receptors in individual neurons is needed in order to investigate the role of NMDA receptor distribution in neuronal survival and death. Results Here we refined and verified a protocol previously used to isolate the effects of extrasynaptic NMDA receptors using the NMDA receptor open channel blocker, MK-801. Using this method we investigated the possibility that the known neuroprotective shield built up in hippocampal neurons after a period of action potential bursting and stimulation of synaptic NMDA receptors is due to signal-induced trafficking of extrasynaptic NMDA receptors or a reduction in extrasynaptic NMDA receptor function. We found that extrasynaptic NMDA receptor-mediated calcium responses and whole cell currents recorded under voltage clamp were surprisingly invariable and did not change even after prolonged (16 to 24 hours) periods of bursting and synaptic NMDA receptor activation. Averaging a large number of calcium imaging traces yielded a small (6%) reduction of extrasynaptic NMDA receptor-mediated responses in hippocampal neurons that were pretreated with prolonged bursting. Conclusion The slight reduction in extrasynaptic NMDA receptor function following action potential bursting and synaptic NMDA receptor stimulation could contribute to but is unlikely to fully account for activity-dependent neuroprotection. Other factors, in particular calcium signaling to the nucleus and the induction of survival promoting genes are more likely to mediate acquired neuroprotection.
Collapse
Affiliation(s)
- C Peter Bengtson
- Department of Neurobiology, Interdisciplinary Centre for Neurosciences (IZN), University of Heidelberg, 69120 Heidelberg, Germany.
| | | | | |
Collapse
|
35
|
Shintani-Ishida K, Uemura K, Yoshida KI. Hemichannels in cardiomyocytes open transiently during ischemia and contribute to reperfusion injury following brief ischemia. Am J Physiol Heart Circ Physiol 2007; 293:H1714-20. [PMID: 17557925 DOI: 10.1152/ajpheart.00022.2007] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The aim of this study was to investigate changes in hemichannel activity during in vitro simulated ischemia [oxygen-glucose deprivation (OGD)] and the contribution of hemichannels to ischemia-reperfusion injury in rat neonatal cardiomyocytes. Dye uptake assays showed that hemichannels opened as OGD progressed, peaking after 1 h, and then closed, returning to the pre-OGD state after 2 h of OGD. The increase in dye uptake after 1 h of OGD was inhibited by hemichannel blockers (lanthanum chloride and a connexin 43 mimetic peptide, Gap26). During OGD, intracellular Ca2+ concentration ([Ca2+]i) began to increase after 1 h and reached several micromolar after 2 h. After 1 h of OGD, Gap26 inhibited the increases in hemichannel activity and [Ca2+]i. In contrast, dantrolene [an endo(sarco)plasmic reticulum Ca2+ release inhibitor] suppressed the increase in [Ca2+]i, but not in hemichannel activity. After 2 h of OGD, the combined administration of 2′,4′-dichlorobenzamil and dantrolene reduced [Ca2+]i to <1 μM and increased hemichannel activity to the level attained after 1 h of OGD. Simulated ischemia-reperfusion, induced by 1 h of OGD followed by 2 h of recovery, reduced cell viability to 54% of the control level. The addition of Gap26 to OGD medium improved viability to 80% of the control level. In conclusion, this study demonstrated that 1) hemichannels open transiently during OGD, 2) closure of hemichannels, but not their opening, is regulated by an increase in [Ca2+]i during OGD, and 3) open hemichannels contribute to cell injury during recovery from OGD.
Collapse
Affiliation(s)
- Kaori Shintani-Ishida
- Department of Forensic Medicine, Graduate School of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
| | | | | |
Collapse
|
36
|
Roberts VHJ, Waters LH, Powell T. Purinergic receptor expression and activation in first trimester and term human placenta. Placenta 2006; 28:339-47. [PMID: 16764923 DOI: 10.1016/j.placenta.2006.04.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/20/2006] [Revised: 04/20/2006] [Accepted: 04/24/2006] [Indexed: 11/25/2022]
Abstract
Intracellular calcium concentration ([Ca(2+)](i)) is an important signalling molecule in the human placenta and regulation of [Ca(2+)](i) must be tightly controlled to ensure normal cell function and in order to meet the changing demand for calcium with increased fetal growth over gestation. Little is known about the receptors and mechanisms involved in intracellular calcium signalling in the human placenta but in isolated cytotrophoblast cells members of the P2 purinergic receptor family have been shown to mediate an ATP-stimulated rise in [Ca(2+)](i). In this study we examined activation and expression of several of the purinergic receptor subtypes in human placental villous fragments at two stages of gestation, first trimester and term. We demonstrate mRNA and protein expression of the P2X(4), P2X(7) and P2Y(2) subtypes but found no evidence of P2Y(4) protein in the placenta. Using fluorescent calcium imaging we demonstrate that 300 microM ATP, 450 microM UTP and 300 microM BzATP significantly elevate [Ca(2+)](i) in villous fragments with a significant increase in agonist-induced response seen in the term compared to the first trimester fragments (ATP, P<0.0001; UTP, P=0.018; BzATP, P=0.015). The roles of the purinergic receptors within the human placenta are not known but it seems likely for this study that calcium handling through these receptors is altered with advancing gestation. This may be due to the need to meet increased fetal Ca(2+) requirements due to growth or as a secondary function to alterations in placental [Ca(2+)](i) signalling.
Collapse
Affiliation(s)
- V H J Roberts
- Division of Human Development, St Mary's Hospital, University of Manchester, Manchester M13 0JH, UK.
| | | | | |
Collapse
|
37
|
Paydar MJ, Pousti A, Farsam H, Amanlou M, Mehr SE, Dehpour AR. Effects of diltiazem or verapamil on calcium uptake and release from chicken skeletal muscle sarcoplasmic reticulum. Can J Physiol Pharmacol 2006; 83:967-75. [PMID: 16391705 DOI: 10.1139/y05-062] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The purpose of this study was to determine the effects of 2 Ca2+ channel blockers, verapamil and diltiazem, on calcium loading (active Ca2+ uptake) and the following Ca2+ release induced by silver ion (Ag+) and Ca2+ from the membrane of heavy sarcoplasmic reticulum (SR) of chicken skeletal muscle. A fluorescent probe technique was employed to determine the calcium movement through the SR. Pretreatment of the medium with diltiazem and verapamil resulted in a significant decrease in the active Ca2+ uptake, with IC50 of about 290 micromol/L for verapamil and 260 micromol/L for diltiazem. Inhibition of Ca2+ uptake was not due to the development of a substantial drug-dependent leak of Ca2+ from the SR. It might, in part, have been mediated by a direct inhibitory effect of these drugs on the Ca2+ ATPase activity of the SR Ca2+ pump. We confirmed that Ca2+ channel blockers, administered after SR Ca2+ loading and before induction of Ca2+ release, caused a dose-dependent inhibition of both Ca2+- and Ag+-induced Ca2+ release rate. Moreover, if Ca2+ channel blockers were administered prior to SR Ca2+ loading, in spite of Ca2+ uptake inhibition the same reduction in Ca2+- and Ag+-induced Ca2+ release rate was seen. We showed that the inhibition of Ag+-induced Ca2+ release by L-channel blockers is more sensitive than Ca2+-induced Ca2+ release inhibition, so the IC50 for Ag+- and Ca2+-induced Ca2+ release was about 100 and 310 micromol/L for verapamil and 79 and 330 micromol/L for diltiazem, respectively. Our results support the evidence that Ca2+ channel blockers affect muscle microsome of chicken skeletal muscle by 2 independent mechanisms: first, reduction of Ca2+ uptake rate and Ca2+-ATPase activity inhibition, and second, inhibition of both Ag+- and Ca2+-induced Ca2+ release by Ca2+ release channels. These findings confirm the direct effect of Ca2+ channel blockers on calcium release channels. Our results suggest that even if the SR is incompletely preloaded with Ca2+ because of inhibition of Ca2+ uptake by verapamil and diltiazem, no impairment in Ca2+ release occurs.
Collapse
Affiliation(s)
- Mehrak Javadi Paydar
- Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Iran
| | | | | | | | | | | |
Collapse
|
38
|
Matsunaga H, Ueda H. Evidence for serum-deprivation-induced co-release of FGF-1 and S100A13 from astrocytes. Neurochem Int 2006; 49:294-303. [PMID: 16519964 DOI: 10.1016/j.neuint.2006.01.017] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2005] [Revised: 01/16/2006] [Accepted: 01/16/2006] [Indexed: 11/23/2022]
Abstract
Since fibroblast growth factor (FGF)-1 lacks conventional amino-terminal signal peptide essential for endoplasmic reticulum (ER)-Golgi pathway, the mode of release of this polypeptide remains to be fully understood. We attempted to characterize the non-classical (non-vesicular) mode of FGF-1 release in the analyses using immunocytochemistry and immunoblot of conditioned medium (CM) from astrocytes. FGF-1 was completely released from astrocytes upon serum-deprivation stress in a Brefeldin A-insensitive manner. In the immunoprecipitation study using anti-FGF-1 IgG, S100A13 was identified to be the major protein co-eluted with FGF-1. The interaction between GST-FGF-1 and Strep-tag II-S100A13 was found to be Ca(2+)-sensitive, and to require the C-terminal 11 amino acid peptide sequence of S100A13. The overexpression of Delta88-98 mutant of S100A13 selectively inhibited the serum-deprivation stress-induced release of FGF-1, but not the release of S100A13 mutant from C6 glioma cells. However, amlexanox, anti-allergic drug whose target is S100A13, completely inhibited the stress-induced release of FGF-1 as well as S100A13. The stress-induced release of both proteins was also abolished by BAPTA-AM, an intracellular Ca(2+) chelating agent. The serum-deprivation caused Ca(2+) spikes in omega-conotoxin GVIA and thapsigargin-sensitive manner. All these results suggest that S100A13 is a cargo molecule for the serum-deprivation stress-induced non-classical release of FGF-1, and that its driving force of protein-protein interaction and release is possibly mediated by Ca(2+)-induced Ca(2+) release (CICR) coupled to N-type Ca(2+) channel activity.
Collapse
Affiliation(s)
- Hayato Matsunaga
- Division of Molecular Pharmacology and Neuroscience, Nagasaki University Graduate School of Biomedical Sciences, 1-14 Bunkyo-machi, Nagasaki 852-8521, Japan
| | | |
Collapse
|
39
|
Ishii H, Shibuya K, Ohta Y, Mukai H, Uchino S, Takata N, Rose JA, Kawato S. Enhancement of nitric oxide production by association of nitric oxide synthase with N-methyl-D-aspartate receptors via postsynaptic density 95 in genetically engineered Chinese hamster ovary cells: real-time fluorescence imaging using nitric oxide sensitive dye. J Neurochem 2006; 96:1531-9. [PMID: 16464237 DOI: 10.1111/j.1471-4159.2006.03656.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The current quantitative study demonstrates that the recruitment of neuronal nitric oxide synthase (nNOS) beneath N-methyl-D-aspartate (NMDA) receptors, via postsynaptic density 95 (PSD-95) proteins significantly enhances nitric oxide (NO) production. Real-time single-cell fluorescence imaging was applied to measure both NO production and Ca(2+) influx in Chinese hamster ovary (CHO) cells expressing recombinant NMDA receptors (NMDA-R), nNOS, and PSD-95. We examined the relationship between the rate of NO production and Ca(2+) influx via NMDA receptors using the NO-reactive fluorescent dye, diaminofluorescein-FM (DAF-FM) and the Ca(2+)-sensitive yellow cameleon 3.1 (YC3.1), conjugated with PSD-95 (PSD-95-YC3.1). The presence of PSD-95 enhanced the rate of NO production by 2.3-fold upon stimulation with 100 microm NMDA in CHO1(+) cells (expressing NMDA-R, nNOS and PSD-95) when compared with CHO1(-) cells (expressing NMDA-R and nNOS lacking PSD-95). The presence of nNOS inhibitor or NMDA-R blocker almost completely suppressed this NMDA-stimulated NO production. The Ca(2+) concentration beneath the NMDA-R, [Ca(2+)](NR), was determined to be 5.4 microm by stimulating CHO2 cells (expressing NMDA-R and PSD-95-YC3.1) with 100 microm NMDA. By completely permealizing CHO1 cells with ionomycin, a general relationship curve of the rate of NO production versus the Ca(2+) concentration around nNOS, [Ca(2+)](NOS), was obtained over the wide range of [Ca(2+)](NOS). This sigmoidal curve had an EC(50) of approximately 1.2 microm of [Ca(2+)](NOS), implying that [Ca(2+)](NR) = 5.4 microm can activate nNOS effectively.
Collapse
Affiliation(s)
- Hirotaka Ishii
- Department of Biophysics and Life Sciences, Graduate School of Arts and Sciences, University of Tokyo at Komaba, Tokyo, Japan
| | | | | | | | | | | | | | | |
Collapse
|
40
|
Mora R, Maldonado A, Valverde B, Gutiérrez JM. Calcium plays a key role in the effects induced by a snake venom Lys49 phospholipase A2 homologue on a lymphoblastoid cell line. Toxicon 2006; 47:75-86. [PMID: 16303159 DOI: 10.1016/j.toxicon.2005.10.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2005] [Revised: 10/07/2005] [Accepted: 10/08/2005] [Indexed: 10/25/2022]
Abstract
A catalytically-inactive Lys49 phospholipase A2 homologue from the venom of the snake Bothrops asper induces diverse effects (necrosis, apoptosis and proliferation) in a lymphoblastoid cell line, depending on the toxin concentration. The increments in cytosolic Ca2+ levels induced by this toxin in this cell line were assessed. At high toxin concentration (100 microg/mL) the toxin induces drastic disruption of the plasma membrane, associated with a prominent Ca2+ influx and necrosis. Previous incubation of the cells with the chelating agent EGTA or with ruthenium red, an inhibitor of the uniporter mitochondrial Ca2+ transport, greatly reduced necrosis. At a toxin concentration of 12.5 microg/mL, apoptosis is the predominant response, being associated with lower increments in cytosolic Ca2+. This effect was inhibited by preincubation with ruthenium red and the cytosolic Ca2+ chelator BAPTA-AM. The proliferative response, which occurs at a low toxin concentration (0.5 microg/mL), is associated with a small and oscillatory increment in cytosolic Ca2+. It was inhibited by EGTA, ruthenium red and BAPTA-AM, by inhibitors of the endoplasmic reticulum Ca2+ -ATPase (SERCA) and by blockade of the ryanodine receptor. It is concluded that necrosis and apoptosis induced by this toxin are associated with increments in cytosolic Ca2+ levels following plasma membrane perturbation, together with the involvement of mitochondria. The cellular proliferative response depends on a limited Ca2+ influx through the plasma membrane, being associated with a concerted functional unit constituted by SERCA, the ryanodine receptor and mitochondria, which regulate the observed oscillations in cytosolic Ca2+ concentration.
Collapse
Affiliation(s)
- Rodrigo Mora
- Departamento de Microbiología e Inmunología, Facultad de Microbiología, Universidad de Costa Rica, San José, Costa Rica
| | | | | | | |
Collapse
|
41
|
Kondo RP, Dederko DA, Teutsch C, Chrast J, Catalucci D, Chien KR, Giles WR. Comparison of contraction and calcium handling between right and left ventricular myocytes from adult mouse heart: a role for repolarization waveform. J Physiol 2005; 571:131-46. [PMID: 16357014 PMCID: PMC1805641 DOI: 10.1113/jphysiol.2005.101428] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
In the mammalian heart, the right ventricle (RV) has a distinct structural and electrophysiological profile compared to the left ventricle (LV). However, the possibility that myocytes from the RV and LV have different contractile properties has not been established. In this study, sarcomere shortening, [Ca2+]i transients and Ca2+ and K+ currents in unloaded myocytes isolated from the RV, LV epicardium (LVepi) and LV endocardium (LVendo) of adult mice were evaluated. Maximum sarcomere shortening elicited by field stimulation was graded in the order: LVendo > LVepi > RV. Systolic [Ca2+]i was higher in LVendo myocytes than in RV myocytes. Voltage-clamp experiments in which action potential (AP) waveforms from RV and LVendo were used as the command signal, demonstrated that total Ca2+ influx and myocyte shortening were larger in response to the LVendo AP, independent of myocyte subtypes. Evaluation of possible regional differences in myocyte Ca2+ handling was based on: (i) the current-voltage relation of the Ca2+ current; (ii) sarcoplasmic reticulum Ca2+ uptake; and (iii) mRNA expression of important components of the Ca2+ handling system. None of these were significantly different between RV and LVendo. In contrast, the Ca2+-independent K+ current, which modulates AP repolarization, was significantly different between RV, LVepi and LVendo. These results suggest that these differences in K+ currents can alter AP duration and modulate the [Ca2+]i transient and corresponding contraction. In summary, these findings provide an initial description of regional differences in excitation-contraction coupling in the adult mouse heart [corrected]
Collapse
Affiliation(s)
- Richard P Kondo
- Department of Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0412, USA
| | | | | | | | | | | | | |
Collapse
|
42
|
Plank DM, Sussman MA. Impaired intracellular Ca2+ dynamics in live cardiomyocytes revealed by rapid line scan confocal microscopy. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2005; 11:235-43. [PMID: 16060976 DOI: 10.1017/s1431927605050488] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2004] [Accepted: 12/21/2004] [Indexed: 05/03/2023]
Abstract
Altered intracellular Ca2+ dynamics are characteristically observed in cardiomyocytes from failing hearts. Studies of Ca2+ handling in myocytes predominantly use Fluo-3 AM, a visible light excitable Ca2+ chelating fluorescent dye in conjunction with rapid line-scanning confocal microscopy. However, Fluo-3 AM does not allow for traditional ratiometric determination of intracellular Ca2+ concentration and has required the use of mathematic correction factors with values obtained from separate procedures to convert Fluo-3 AM fluorescence to appropriate Ca2+ concentrations. This study describes methodology to directly measure intracellular Ca2+ levels using inactivated, Fluo-3-AM-loaded cardiomyocytes equilibrated with Ca2+ concentration standards. Titration of Ca2+ concentration exhibits a linear relationship to increasing Fluo-3 AM fluorescence intensity. Images obtained from individual myocyte confocal scans were recorded, average pixel intensity values were calculated, and a plot is generated relating the average pixel intensity to known Ca2+ concentrations. These standard plots can be used to convert transient Ca2+ fluorescence obtained with experimental cells to Ca2+ concentrations by linear regression analysis. Standards are determined on the same microscope used for acquisition of unknown Ca2+ concentrations, simplifying data interpretation and assuring accuracy of conversion values. This procedure eliminates additional equipment, ratiometric imaging, and mathematic correction factors and should be useful to investigators requiring a straightforward method for measuring Ca2+ concentrations in live cells using Ca2+-chelating dyes exhibiting variable fluorescence intensity.
Collapse
Affiliation(s)
- David M Plank
- SDSU Heart Institute, Department of Biology, San Diego State University, San Diego, CA 92182, USA
| | | |
Collapse
|
43
|
Plank DM, Sussman MA. Intracellular Ca2+ measurements in live cells by rapid line scan confocal microscopy: simplified calibration methodology. ACTA ACUST UNITED AC 2005; 25:123-33. [PMID: 15801157 DOI: 10.1007/s11022-004-2043-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Altered intracellular Ca2+ dynamics are characteristically observed in cardiomyocytes from failing hearts. Studies of Ca2+ handling in myocytes predominantly use Fluo-3 AM, a visible light excitable Ca2+ chelating fluorescent dye in conjunction with rapid line-scanning confocal microscopy. However, Fluo-3 AM does not allow for traditional ratiometric determination of intracellular Ca2+ concentration and has required use of mathematic correction factors with values obtained from separate procedures to convert Fluo-3 AM fluorescence to appropriate CA2+ concentrations. This study describes methodology to directly measure intracellular Ca2+ levels using inactivated, Fluo-3 AM loaded cardiomyocytes equilibrated with Ca2+ concentration standards. Titration of Ca2+ concentration exhibits a linear relationship to increasing Fluo-3 AM fluorescence intensity. Images obtained from individual myocyte confocal scans were recorded, average pixel intensity values were calculated, and a plot is generated relating the average pixel intensity to known Ca2+ concentrations. These standard plots can be used to convert transient Ca2+ fluorescence obtained with experimental cells to Ca2+ concentrations by linear regression analysis. Standards are determined on the same microscope used for acquisition of unknown Ca2+ concentrations, simplifying data interpretaton and assuring accuracy of conversion values. This procedure eliminates additional equipment, ratiometric imaging, and mathematic correction factors and should be used to investigators requiring a straightforward method for measuring Ca2+ concentrations in live cells using Ca2+-chelating dyes exhibiting variable fluorescence intensity.
Collapse
Affiliation(s)
- David M Plank
- SDSU Heart Institute, San Diego State University, Department of Biology, San Diego, CA 92182, USA
| | | |
Collapse
|
44
|
Kucherenko YV, Weiss E, Bernhardt I. Effect of the ionic strength and prostaglandin E2 on the free Ca2+ concentration and the Ca2+ influx in human red blood cells. Bioelectrochemistry 2005; 62:127-33. [PMID: 15039015 DOI: 10.1016/j.bioelechem.2003.09.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2003] [Revised: 08/30/2003] [Accepted: 09/12/2003] [Indexed: 11/25/2022]
Abstract
Human red blood cells (RBCs) were loaded with the Ca(2+)-sensitive fluorescent dye fura-2 to investigate the effects of media ionic strength and prostaglandin E2 (PGE2) on the intracellular free Ca2+ concentration ([Ca2+]i). [Ca2+]i of intact RBCs in a Ca(2+)-containing physiological (high) ionic strength (HIS) solution was 75.1 +/- 8.3 nM after 5 min incubation, increasing to 114.9 +/- 9.6 nM after 1 h. In Ca(2+)-containing low ionic strength (LIS) solutions, [Ca2+]i was significantly lower than in the Ca(2+)-containing HIS solution (p = 0.041 or 0.0385 for LIS solutions containing 200 or 250 mM sucrose, respectively), but, as in HIS solution, an increase of [Ca2+]i was seen after 1 h. In Ca(2+)-free (0 Ca2+ plus 15 microM EGTA) media, [Ca2+]i decreased (ranging from 15 to 21 nM), but were not significantly different in HIS or LIS, and did not change following 1 h incubation. The effect of the ionic strength and PGE2 on passive Ca2+ influx was investigated on ATP-depleted RBCs. Ca2+ influx was faster during the initial 10 min in comparison with the subsequent time period (10-45 min), both in HIS and LIS media, decreasing from 20.3 +/- 1.9 to 12.9 +/- 1.3 micromol/(lcells x h) in HIS, and from 36.7 +/- 5.3 to 8.6 +/- 1.2 micromol/(lcells x h) in LIS. Prostaglandin E2 (PGE2; 10(-7)-10(-11) M), dissolved in deionised water or in ethanol, did not affect [Ca2+]i in either normal or in ATP-depleted RBCs suspended in Ca(2+)-containing HIS medium. Finally, the addition of carbachol (100 microM) did not affect [Ca2+]i. The present findings suggest that stimulation of the Ca(2+)-activated K+ channel by PGE2, reported in [J. Biol. Chem. 271 (1996) 18651], cannot be mediated via increased [Ca2+]i.
Collapse
Affiliation(s)
- Yuliya V Kucherenko
- Institute for Problems of Cryobiology and Cryomedicine of the National Academy of Sciences of Ukraine, Pereyaslavskaya str. 23, 61015 Kharkov, Ukraine
| | | | | |
Collapse
|
45
|
June CH, Moore JS. Measurement of intracellular ions by flow cytometry. CURRENT PROTOCOLS IN IMMUNOLOGY 2004; Chapter 5:5.5.1-5.5.20. [PMID: 18432929 DOI: 10.1002/0471142735.im0505s64] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The recent development of a number of new fluorescent probes makes it possible to measure the concentrations of various intracellular free ions in single living cells. Among these ions are calcium, magnesium, sodium, potassium, and hydrogen (pH). This unit describes flow cytometric protocols using the dyes Indo-1 AM, Fluo-3, and Fura Red AM to measure intracellular calcium concentration. Support protocols detail the use of calcium buffers to calibrate a flow cytometric calcium assay, and methods to facilitate dye loading; an alternate protocol describes the use of a spectrofluorimeter to measure intracellular calcium for those investigators without access to a flow cytometer.
Collapse
Affiliation(s)
- Carl H June
- University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania
| | - Jonni S Moore
- University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania
| |
Collapse
|
46
|
Wokosin DL, Loughrey CM, Smith GL. Characterization of a range of fura dyes with two-photon excitation. Biophys J 2004; 86:1726-38. [PMID: 14990500 PMCID: PMC1304008 DOI: 10.1016/s0006-3495(04)74241-1] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Two-photon excitation (TPE) spectra of Fura-2, -4F, -6F, -FF, and Furaptra were characterized using a tunable (750-850 nM) ultra-short pulse laser. Two-photon fluorescence of these dyes was studied in free solution and in the cytosol of isolated rabbit ventricular cardiomyocytes. The TPE spectra of the Ca(2+)-free and Ca(2+)-bound forms of the dyes were measured in free solution and expressed in terms of the two-photon fluorescence cross section (Goppert-Meyer units). The Fura dyes displayed the same Ca(2+)-free TPE spectrum in the intracellular volume of permeabilized and intact cardiomyocytes. Fluorescence measurements over a range of laser powers confirmed the TPE of both Ca(2+)-free and Ca(2+)-bound forms of the dyes. Single-wavelength excitation at 810 nM was used to determine the effective dissociation constants (K(eff)) and dynamic ranges (R(f)) of Fura-2, -4F, -6F, -FF, and Furaptra dyes (K(eff) = 181 +/- 52 nM, 1.16 +/- 0.016 micro M, 5.18 +/- 0.3 micro M, 19.2 +/- 1 micro M, and 58.5 +/- 2 micro M; and R(f) = 22.4 +/- 3.8, 12.2 +/- 0.34, 6.3 +/- 0.17, 16.1 +/- 2.8, and 25.4 +/- 4, respectively). Single-wavelength excitation of intracellular Fura-4F resolved diastolic and peak [Ca(2+)] in isolated stimulated cardiomyocytes after calibration of the intracellular signal using reversible exposure to low (100 micro M) extracellular [Ca(2+)]. Furthermore, TPE of Fura-4F allowed continuous, long-term (5-10 min) Ca(2+) imaging in ventricular cardiomyocytes using laser-scanning microscopy without significant cellular photodamage or photobleaching of the dye.
Collapse
Affiliation(s)
- D L Wokosin
- Centre for Biophotonics, Strathclyde University, Glasgow, United Kingdom
| | | | | |
Collapse
|
47
|
Rebrik TI, Korenbrot JI. In intact mammalian photoreceptors, Ca2+-dependent modulation of cGMP-gated ion channels is detectable in cones but not in rods. ACTA ACUST UNITED AC 2004; 123:63-75. [PMID: 14699078 PMCID: PMC2217411 DOI: 10.1085/jgp.200308952] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Abstract
In the mammalian retina, cone photoreceptors efficiently adapt to changing background light intensity and, therefore, are able to signal small differences in luminance between objects and backgrounds, even when the absolute intensity of the background changes over five to six orders of magnitude. Mammalian rod photoreceptors, in contrast, adapt very little and only at intensities that nearly saturate the amplitude of their photoresponse. In search of a molecular explanation for this observation we assessed Ca2+-dependent modulation of ligand sensitivity in cyclic GMP–gated (CNG) ion channels of intact mammalian rods and cones. Solitary photoreceptors were isolated by gentle proteolysis of ground squirrel retina. Rods and cones were distinguished by whether or not their outer segments bind PNA lectin. We measured membrane currents under voltage-clamp in photoreceptors loaded with Diazo-2, a caged Ca2+ chelator, and fixed concentrations of 8Br-cGMP. At 600 nM free cytoplasmic Ca2+ the midpoint of the cone CNG channels sensitivity to 8BrcGMP, 8BrcGMPK1/2, is ∼2.3 μM. The ligand sensitivity is less in rod than in cone channels. Instantly decreasing cytoplasmic Ca2+ to <30 nM activates a large inward membrane current in cones, but not in rods. Current activation arises from a Ca2+ -dependent modulation of cone CNG channels, presumably because of an increase in their affinity to the cyclic nucleotide. The time course of current activation is temperature dependent; it is well described by a single exponential process of ∼480 ms time constant at 20–21°C and 138 ms at 32°C. The absence of detectable Ca2+-dependent CNG current modulation in intact rods, in view of the known channel modulation by calmodulin in-vitro, affirms the modulation in intact rods may only occur at low Ca2+ concentrations, those expected at intensities that nearly saturate the rod photoresponse. The correspondence between Ca2+ dependence of CNG modulation and the ability to light adapt suggest these events are correlated in photoreceptors.
Collapse
Affiliation(s)
- Tatiana I Rebrik
- Department of Physiology, School of Medicine, University of California at San Francisco, San Francisco, CA 94143, USA
| | | |
Collapse
|
48
|
Chen T, Willoughby KA, Ellis EF. Group I metabotropic receptor antagonism blocks depletion of calcium stores and reduces potentiated capacitative calcium entry in strain-injured neurons and astrocytes. J Neurotrauma 2004; 21:271-81. [PMID: 15115602 DOI: 10.1089/089771504322972068] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Antagonism of the group I metabotropic receptor subtype 1 (mGluR1) with (RS)-1-aminoindan-1,5-dicarboxylic acid (AIDA) has been shown to reduce deficits after in vivo or in vitro traumatic brain injury. We have previously demonstrated that AIDA prevents elevation of astrocyte IP3 subsequent to injury-induced activation of mGluRs and phospholipase C. Since IP3 can cause release of intracellular Ca2+ stores we tested the hypothesis that pre- or post-injury treatment with AIDA can affect (1) the depletion of Ca2+ stores which occurs soon after strain injury of cultured neurons and astrocytes and (2) the delayed potentiation of capacitative calcium entry in strain-injured neurons. Astrocyte or neuronal plus glial cultures were grown on Silastic membranes that were subjected to a 50-msec pulse of compressed gas, which caused membrane displacement and biaxial strain (stretch) injury of the adhering cells. Cells were treated 10 min before or immediately after injury with 100 microM AIDA and the intracellular free Ca2+ ([Ca2+]i) response to thapsigargin, which inhibits the ability of the stores to sequester Ca2+, was measured at 15 min or 3 h after injury. AIDA pre- or post-injury treatment prevented the depletion of intracellular calcium stores at 15 min post-injury in astrocytes and neurons and reduced the potentiated neuronal capacitative calcium influx 3 h after injury. Since Ca2+ and Ca2+ stores influence many factors, including neuronal excitability, plasticity, protein synthesis, and neuronal-glial interactions, prevention of Ca2+ store depletion and subsequent exaggerated capacitative calcium entry may be an important subcellular mechanism by which antagonism of mGluR1 receptors exert an injury-reducing effect. More globally, the results further emphasize the importance of altered signaling and calcium regulatory mechanisms in the immediate and delayed sequelae of traumatic brain injury.
Collapse
Affiliation(s)
- Tao Chen
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA 23298-0613, USA
| | | | | |
Collapse
|
49
|
Samain E, Pili-Floury S, Bouillier H, Clichet A, Safar M, Dagher G, Marty J, Renaud JF. EFFECT OF PROPOFOL ON VASOCONSTRICTION AND CALCIUM MOBILIZATION INDUCED BY ANGIOTENSIN II DIFFERS IN AORTAS FROM NORMOTENSIVE AND HYPERTENSIVE RATS. Clin Exp Pharmacol Physiol 2004; 31:163-8. [PMID: 15008959 DOI: 10.1111/j.1440-1681.2004.03968.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
1. Angiotensin (Ang) II is a potent vasopressor agent, involved in the short-term control of arterial blood pressure during anaesthesia. The aim of the present study was to test the hypothesis that propofol, a widely used intravenous anaesthetic agent, could alter the arterial response to AngII and to evaluate its effect in genetic hypertension. 2. We studied the effect of increasing concentrations of propofol (5.6 x 10-7 to 5.6 x 10-4 mol/L) on aortic ring maximal isometric tension elicited by AngII and on AngII-induced Ca2+ mobilization in aortic smooth muscle cells from Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR). 3. Maximal tension developed by aortic rings from WKY rats was greater than that developed by rings from SHR. In both WKY rats and SHR, propofol at concentrations from 5.6 x 10-6 mol/L decreased maximal tension induced by AngII in a concentration-dependent manner. The magnitude of inhibition was higher in SHR than in WKY rats, whereas pD2 values were not different. In addition, Ca2+ mobilization induced by AngII was inhibited by propofol in a concentration-dependent manner, with the same magnitude and pD2 values. 4. These results suggest that the arterial response to AngII may be altered during propofol anaesthesia, particularly in hypertension.
Collapse
Affiliation(s)
- Emmanuel Samain
- Department of Medical Research, CNRS UMR 8078, Marie Lannelongue Hospital, University of Paris XI, Le Plessis-Robinson, France.
| | | | | | | | | | | | | | | |
Collapse
|
50
|
Sabirsh A, Pettersson A, Boketoft A, Kotarsky K, Owman C. Differential inhibition of receptor activation by two mouse monoclonal antibodies specific for the human leukotriene B4 receptor, BLT1. Int Immunopharmacol 2003; 3:1829-39. [PMID: 14636832 DOI: 10.1016/j.intimp.2003.08.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The inflammatory mediator leukotriene B(4) (LTB(4)) binds to and activates a G-protein-coupled receptor named BLT(1). We have previously produced two monoclonal antibodies, named 7B1 and 14F11, that bind specifically to this receptor. Using a HeLa cell line expressing human BLT(1), we find that both antibodies inhibit LTB(4)-induced calcium release, and activation of a MAP-kinase-sensitive luciferase reporter system. The normal chemotactic movement of polymorphonuclear cells towards higher LTB(4) concentrations was also strongly inhibited by both antibodies. Neither antibody was found to activate BLT(1), and experiments using cyclic peptide fragments of the BLT(1) n-terminal and extracellular loops showed that these antibodies bind only to complex epitopes in the tertiary, membrane bound, conformation of the receptor protein. In ligand binding experiments, 7B1 was found to be a competitive antagonist, while 14F11 was a noncompetitive antagonist that inhibited receptor activation, but not agonist (LTB(4)) binding. 14F11 will be a useful tool for studying the mechanisms of receptor activation.
Collapse
Affiliation(s)
- A Sabirsh
- Molecular Neurobiology, Lund University, BMC A12 Tornavägen 10, 224 81 Lund, Sweden.
| | | | | | | | | |
Collapse
|