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Qian C, Wang Q, Qiao Y, Xu Z, Zhang L, Xiao H, Lin Z, Wu M, Xia W, Yang H, Bai J, Geng D. Arachidonic acid in aging: New roles for old players. J Adv Res 2024:S2090-1232(24)00180-2. [PMID: 38710468 DOI: 10.1016/j.jare.2024.05.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2024] [Revised: 04/26/2024] [Accepted: 05/03/2024] [Indexed: 05/08/2024] Open
Abstract
BACKGROUND Arachidonic acid (AA), one of the most ubiquitous polyunsaturated fatty acids (PUFAs), provides fluidity to mammalian cell membranes. It is derived from linoleic acid (LA) and can be transformed into various bioactive metabolites, including prostaglandins (PGs), thromboxanes (TXs), lipoxins (LXs), hydroxy-eicosatetraenoic acids (HETEs), leukotrienes (LTs), and epoxyeicosatrienoic acids (EETs), by different pathways. All these processes are involved in AA metabolism. Currently, in the context of an increasingly visible aging world population, several scholars have revealed the essential role of AA metabolism in osteoporosis, chronic obstructive pulmonary disease, and many other aging diseases. AIM OF REVIEW Although there are some reviews describing the role of AA in some specific diseases, there seems to be no or little information on the role of AA metabolism in aging tissues or organs. This review scrutinizes and highlights the role of AA metabolism in aging and provides a new idea for strategies for treating aging-related diseases. KEY SCIENTIFIC CONCEPTS OF REVIEW As a member of lipid metabolism, AA metabolism regulates the important lipids that interfere with the aging in several ways. We present a comprehensivereviewofthe role ofAA metabolism in aging, with the aim of relieving the extreme suffering of families and the heavy economic burden on society caused by age-related diseases. We also collected and summarized data on anti-aging therapies associated with AA metabolism, with the expectation of identifying a novel and efficient way to protect against aging.
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Affiliation(s)
- Chen Qian
- Department of Orthopedics, The First Affiliated Hospital of Soochow University, 188 Shizi Street, Suzhou, Jiangsu 215006, PR China
| | - Qing Wang
- Department of Orthopedics, The First Affiliated Hospital of Soochow University, 188 Shizi Street, Suzhou, Jiangsu 215006, PR China
| | - Yusen Qiao
- Department of Orthopedics, The First Affiliated Hospital of Soochow University, 188 Shizi Street, Suzhou, Jiangsu 215006, PR China
| | - Ze Xu
- Department of Orthopedics, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, 17 Lujiang Road, Hefei, Anhui 230031, PR China
| | - Linlin Zhang
- Department of Orthopedics, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, 17 Lujiang Road, Hefei, Anhui 230031, PR China
| | - Haixiang Xiao
- Department of Orthopedics, The First Affiliated Hospital of Soochow University, 188 Shizi Street, Suzhou, Jiangsu 215006, PR China
| | - Zhixiang Lin
- Department of Orthopedics, The First Affiliated Hospital of Soochow University, 188 Shizi Street, Suzhou, Jiangsu 215006, PR China
| | - Mingzhou Wu
- Department of Orthopedics, The First Affiliated Hospital of Soochow University, 188 Shizi Street, Suzhou, Jiangsu 215006, PR China
| | - Wenyu Xia
- Department of Orthopedics, The First Affiliated Hospital of Soochow University, 188 Shizi Street, Suzhou, Jiangsu 215006, PR China
| | - Huilin Yang
- Department of Orthopedics, The First Affiliated Hospital of Soochow University, 188 Shizi Street, Suzhou, Jiangsu 215006, PR China.
| | - Jiaxiang Bai
- Department of Orthopedics, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, 17 Lujiang Road, Hefei, Anhui 230031, PR China.
| | - Dechun Geng
- Department of Orthopedics, The First Affiliated Hospital of Soochow University, 188 Shizi Street, Suzhou, Jiangsu 215006, PR China.
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Burkhardt LM, Bucher CH, Löffler J, Rinne C, Duda GN, Geissler S, Schulz TJ, Schmidt-Bleek K. The benefits of adipocyte metabolism in bone health and regeneration. Front Cell Dev Biol 2023; 11:1104709. [PMID: 36895792 PMCID: PMC9988968 DOI: 10.3389/fcell.2023.1104709] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2022] [Accepted: 02/06/2023] [Indexed: 02/25/2023] Open
Abstract
Patients suffering from musculoskeletal diseases must cope with a diminished quality of life and an increased burden on medical expenses. The interaction of immune cells and mesenchymal stromal cells during bone regeneration is one of the key requirements for the restoration of skeletal integrity. While stromal cells of the osteo-chondral lineage support bone regeneration, an excessive accumulation of cells of the adipogenic lineage is thought to promote low-grade inflammation and impair bone regeneration. Increasing evidence indicates that pro-inflammatory signaling from adipocytes is responsible for various chronic musculoskeletal diseases. This review aims to summarize the features of bone marrow adipocytes by phenotype, function, secretory features, metabolic properties and their impact on bone formation. In detail, the master regulator of adipogenesis and prominent diabetes drug target, peroxisome proliferator-activated receptor γ (PPARG), will be debated as a potential therapeutic approach to enhance bone regeneration. We will explore the possibilities of using clinically established PPARG agonists, the thiazolidinediones (TZDs), as a treatment strategy to guide the induction of a pro-regenerative, metabolically active bone marrow adipose tissue. The impact of this PPARG induced bone marrow adipose tissue type on providing the necessary metabolites to sustain osteogenic-as well as beneficial immune cells during bone fracture healing will be highlighted.
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Affiliation(s)
- Lisa-Marie Burkhardt
- Julius Wolff Institute, Berlin Institute of Health (BIH) Charité, Berlin, Germany.,BIH Center for Regenerative Therapies (BCRT), Charité-Universitätsmedizin, Berlin, Germany
| | - Christian H Bucher
- Julius Wolff Institute, Berlin Institute of Health (BIH) Charité, Berlin, Germany.,BIH Center for Regenerative Therapies (BCRT), Charité-Universitätsmedizin, Berlin, Germany
| | - Julia Löffler
- Julius Wolff Institute, Berlin Institute of Health (BIH) Charité, Berlin, Germany.,BIH Center for Regenerative Therapies (BCRT), Charité-Universitätsmedizin, Berlin, Germany
| | - Charlotte Rinne
- Department of Adipocyte Development and Nutrition, German Institute of Human Nutrition, Potsdam-Rehbrücke, Nuthetal, Germany
| | - Georg N Duda
- Julius Wolff Institute, Berlin Institute of Health (BIH) Charité, Berlin, Germany.,BIH Center for Regenerative Therapies (BCRT), Charité-Universitätsmedizin, Berlin, Germany
| | - Sven Geissler
- Julius Wolff Institute, Berlin Institute of Health (BIH) Charité, Berlin, Germany.,BIH Center for Regenerative Therapies (BCRT), Charité-Universitätsmedizin, Berlin, Germany
| | - Tim J Schulz
- Department of Adipocyte Development and Nutrition, German Institute of Human Nutrition, Potsdam-Rehbrücke, Nuthetal, Germany.,German Center for Diabetes Research (DZD), München-Neuherberg, Germany.,University of Potsdam, Institute of Nutritional Science, Nuthetal, Germany
| | - Katharina Schmidt-Bleek
- Julius Wolff Institute, Berlin Institute of Health (BIH) Charité, Berlin, Germany.,BIH Center for Regenerative Therapies (BCRT), Charité-Universitätsmedizin, Berlin, Germany
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Ahmed ASI, Sheng MHC, Lau KHW, Wilson SM, Wongworawat MD, Tang X, Ghahramanpouri M, Nehme A, Xu Y, Abdipour A, Zhang XB, Wasnik S, Baylink DJ. Calcium released by osteoclastic resorption stimulates autocrine/paracrine activities in local osteogenic cells to promote coupled bone formation. Am J Physiol Cell Physiol 2022; 322:C977-C990. [PMID: 35385325 PMCID: PMC9109806 DOI: 10.1152/ajpcell.00413.2021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A major cause of osteoporosis is impaired coupled bone formation. Mechanistically, both osteoclast-derived and bone-derived growth factors have been previously implicated. We hypothesize that the release of bone calcium during osteoclastic bone resorption is essential for coupled bone formation. Osteoclastic resorption increases interstitial fluid calcium locally from the normal 1.8 mM up to 5 mM. MC3T3-E1 osteoprogenitors, cultured in a 3.6 mM calcium medium, demonstrated that calcium signaling stimulated osteogenic cell proliferation, differentiation, and migration. Calcium channel knockdown studies implicated calcium channels, Cav1.2, store-operated calcium entry (SOCE), and calcium-sensing receptor (CaSR) in regulating bone cell anabolic activities. MC3T3-E1 cultured in a 3.6 mM calcium medium expressed increased gene expression of Wnt signaling and growth factors platelet-derived growth factor (PDGF), vascular endothelial growth factor (VEGF), and bone morphogenic protein-2 (BMP 2). Our coupling model of bone formation, the Receptor activator of nuclear factor-kappa-Β ligand (RANKL) treated mouse calvaria, confirmed the role of calcium signaling in coupled bone formation by exhibiting increased gene expression for osterix and osteocalcin. Critically, dual immunocytochemistry showed that RANKL treatment increased osterix positive cells and increased fluorescence intensity of Cav1.2 and CaSR protein expression per osterix positive cell. The data established that calcium released by osteoclasts contributed to the regulation of coupled bone formation. CRISPR/Cas-9 knockout of Cav1.2 in osteoprogenitors cultured in basal calcium medium caused a >80% decrease in the expression of downstream osteogenic genes, emphasizing the large magnitude of the effect of calcium signaling. Thus, calcium signaling is a major regulator of coupled bone formation.
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Affiliation(s)
- Abu Shufian Ishtiaq Ahmed
- Department of Medicine, Division of Regenerative Medicine, Loma Linda University, Loma Linda, California, United States.,The Lawrence D. Longo, MD Center for Perinatal Biology, Department of Basic Sciences, Loma Linda University School of Medicine, Loma Linda, CA, United States
| | - Matilda H C Sheng
- Department of Medicine, Division of Regenerative Medicine, Loma Linda University, Loma Linda, California, United States.,Musculoskeletal Disease Center, Jerry L. Pettis Memorial Veterans Affairs Medical Center, Loma Linda, California, United States
| | - Kin-Hing William Lau
- Musculoskeletal Disease Center, Jerry L. Pettis Memorial Veterans Affairs Medical Center, Loma Linda, California, United States
| | - Sean M Wilson
- The Lawrence D. Longo, MD Center for Perinatal Biology, Department of Basic Sciences, Loma Linda University School of Medicine, Loma Linda, CA, United States
| | - M Daniel Wongworawat
- Department of Orthopaedic Surgery, Loma Linda University, Loma Linda, California, United States
| | - Xiaolei Tang
- Department of Veterinary Biomedical Sciences, College of Veterinary Medicine, Long Island University, Brookville, NY, United States
| | - Mahdis Ghahramanpouri
- Department of Medicine, Division of Regenerative Medicine, Loma Linda University, Loma Linda, California, United States
| | - Antoine Nehme
- Department of Medicine, Division of Regenerative Medicine, Loma Linda University, Loma Linda, California, United States
| | - Yi Xu
- Department of Medicine, Division of Regenerative Medicine, Loma Linda University, Loma Linda, California, United States.,Division of Hematology and Oncology, Department of Medicine, Loma Linda University and Loma Linda University Cancer Center, Loma Linda, CA, United States
| | - Amir Abdipour
- Division of Nephrology, Department of Medicine, Loma Linda University, Loma Linda, CA, United States
| | - Xiao-Bing Zhang
- Department of Neurosurgery, Loma Linda University, Loma Linda, California, United States
| | - Samiksha Wasnik
- Department of Medicine, Division of Regenerative Medicine, Loma Linda University, Loma Linda, California, United States
| | - David J Baylink
- Department of Medicine, Division of Regenerative Medicine, Loma Linda University, Loma Linda, California, United States
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4
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Riquelme MA, Gu S, Hua R, Jiang JX. Mechanotransduction via the coordinated actions of integrins, PI3K signaling and Connexin hemichannels. Bone Res 2021; 9:8. [PMID: 33531460 PMCID: PMC7854719 DOI: 10.1038/s41413-020-00126-w] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2020] [Revised: 09/25/2020] [Accepted: 10/14/2020] [Indexed: 12/11/2022] Open
Abstract
Mechanical loading opens connexin 43 (Cx43) hemichannels (HCs), leading to the release of bone anabolic molecules, such as prostaglandins, from mechanosensitive osteocytes, which is essential for bone formation and remodeling. However, the mechanotransduction mechanism that activates HCs remains elusive. Here, we report a unique pathway by which mechanical signals are effectively transferred between integrin molecules located in different regions of the cell, resulting in HC activation. Both integrin α5 and αV were activated upon mechanical stimulation via either fluid dropping or flow shear stress (FSS). Inhibition of integrin αV activation or ablation of integrin α5 prevented HC opening on the cell body when dendrites were mechanically stimulated, suggesting mechanical transmission from the dendritic integrin αV to α5 in the cell body during HC activation. In addition, HC function was compromised in vivo, as determined by utilizing an antibody blocking αV activation and α5-deficient osteocyte-specific knockout mice. Furthermore, inhibition of integrin αV activation, but not that of α5, attenuated activation of the phosphoinositide 3-kinase (PI3K)-protein kinase B (AKT) signaling pathway upon mechanical loading, and the inhibition of PI3K/AKT activation blocked integrin α5 activation and HC opening. Moreover, HC opening was blocked only by an anti-integrin αV antibody at low but not high FSS levels, suggesting that dendritic αV is a more sensitive mechanosensor than α5 for activating HCs. Together, these results reveal a new molecular mechanism of mechanotransduction involving the coordinated actions of integrins and PI3K/AKT in osteocytic dendritic processes and cell bodies that leads to HC opening and the release of key bone anabolic factors.
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Affiliation(s)
- Manuel A Riquelme
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, TX, 78229-3900, USA
| | - Sumin Gu
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, TX, 78229-3900, USA
| | - Rui Hua
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, TX, 78229-3900, USA
| | - Jean X Jiang
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, TX, 78229-3900, USA.
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5
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Abstract
Osteoporosis is a global health problem that leads to an increased incidence of fragility fracture. Recent dietary patterns of Western populations include higher than recommended intakes of n-6 (ω-6) polyunsaturated fatty acids (PUFAs) relative to n-3 (ω-3) PUFAs that may result in a chronic state of sterile whole body inflammation. Findings from human bone cell culture experiments have revealed both benefits and detriments to bone-related outcomes depending on the quantity and source of PUFAs. Findings from observational and randomized controlled trials suggest that higher fatty fish intake is strongly linked with reduced risk of fragility fracture. Moreover, human studies largely support a greater intake of total PUFAs, total n-6 (ω-6) fatty acid, and total n-3 (ω-3) fatty acid for higher bone mineral density and reduced risk of fragility fracture. Less consistent evidence has been observed when investigating the role of long chain n-3 (ω-3) PUFAs or the ratio of n-6 (ω-6) PUFAs to n-3 (ω-3) PUFAs. Aspects to consider when interpreting the current literature involve participant characteristics, study duration, diet assessment tools, and the primary outcome measure.
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Affiliation(s)
- Amanda B Longo
- Center for Bone and Muscle Health, and Department of Kinesiology, Faculty of Applied Health Sciences, Brock University, St. Catharines, Canada
| | - Wendy E Ward
- Center for Bone and Muscle Health, and Department of Kinesiology, Faculty of Applied Health Sciences, Brock University, St. Catharines, Canada
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6
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Xu H, Gu S, Riquelme MA, Burra S, Callaway D, Cheng H, Guda T, Schmitz J, Fajardo RJ, Werner SL, Zhao H, Shang P, Johnson ML, Bonewald LF, Jiang JX. Connexin 43 channels are essential for normal bone structure and osteocyte viability. J Bone Miner Res 2015; 30:436-48. [PMID: 25270829 PMCID: PMC4333056 DOI: 10.1002/jbmr.2374] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/27/2014] [Revised: 08/28/2014] [Accepted: 10/01/2014] [Indexed: 11/10/2022]
Abstract
Connexin (Cx) 43 serves important roles in bone function and development. Targeted deletion of Cx43 in osteoblasts or osteocytes leads to increased osteocyte apoptosis, osteoclast recruitment, and reduced biomechanical properties. Cx43 forms both gap junction channels and hemichannels, which mediate the communication between adjacent cells or between cell and extracellular environments, respectively. Two transgenic mouse models driven by a DMP1 promoter with the overexpression of dominant negative Cx43 mutants were generated to dissect the functional contribution of Cx43 gap junction channels and hemichannels in osteocytes. The R76W mutant blocks the gap junction channel, but not the hemichannel function, and the Δ130-136 mutant inhibits activity of both types of channels. Δ130-136 mice showed a significant increase in bone mineral density compared to wild-type (WT) and R76W mice. Micro-computed tomography (µCT) analyses revealed a significant increase in total tissue and bone area in midshaft cortical bone of Δ130-136 mice. The bone marrow cavity was expanded, whereas the cortical thickness was increased and associated with increased bone formation along the periosteal area. However, there is no significant alteration in the structure of trabecular bone. Histologic sections of the midshaft showed increased apoptotic osteocytes in Δ130-136, but not in WT and R76W, mice which correlated with altered biomechanical and estimated bone material properties. Osteoclasts were increased along the endocortical surface in both transgenic mice with a greater effect in Δ130-136 mice that likely contributed to the increased marrow cavity. Interestingly, the overall expression of serum bone formation and resorption markers were higher in R76W mice. These findings suggest that osteocytic Cx43 channels play distinctive roles in the bone; hemichannels play a dominant role in regulating osteocyte survival, endocortical bone resorption, and periosteal apposition, and gap junction communication is involved in the process of bone remodeling.
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Affiliation(s)
- Huiyun Xu
- School of Life Sciences, Northwestern Polytechnical University, Xian, China
- Department of Biochemistry, University of Texas Health Science Center at San Antonio, Texas
| | - Sumin Gu
- Department of Biochemistry, University of Texas Health Science Center at San Antonio, Texas
| | - Manuel A. Riquelme
- Department of Biochemistry, University of Texas Health Science Center at San Antonio, Texas
| | - Sirisha Burra
- Department of Biochemistry, University of Texas Health Science Center at San Antonio, Texas
| | - Danielle Callaway
- Department of Biochemistry, University of Texas Health Science Center at San Antonio, Texas
| | - Hongyun Cheng
- Department of Biochemistry, University of Texas Health Science Center at San Antonio, Texas
| | - Teja Guda
- Department of Biomedical Engineering, University of Texas at San Antonio, Texas
| | - James Schmitz
- Department of Orthopedics, University of Texas Health Science Center at San Antonio, Texas
| | - Roberto J. Fajardo
- Department of Orthopedics, University of Texas Health Science Center at San Antonio, Texas
| | - Sherry L. Werner
- Department of Pathology, University of Texas Health Science Center at San Antonio, Texas
| | - Hong Zhao
- Department of Oral Biology, School of Dentistry, University of Missouri, Kansas City, MO
| | - Peng Shang
- School of Life Sciences, Northwestern Polytechnical University, Xian, China
| | - Mark L. Johnson
- Department of Oral Biology, School of Dentistry, University of Missouri, Kansas City, MO
| | - Lynda F. Bonewald
- Department of Oral Biology, School of Dentistry, University of Missouri, Kansas City, MO
| | - Jean X. Jiang
- Department of Biochemistry, University of Texas Health Science Center at San Antonio, Texas
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Zhang J, Zhang HY, Zhang M, Qiu ZY, Wu YP, Callaway DA, Jiang JX, Lu L, Jing L, Yang T, Wang MQ. Connexin43 hemichannels mediate small molecule exchange between chondrocytes and matrix in biomechanically-stimulated temporomandibular joint cartilage. Osteoarthritis Cartilage 2014; 22:822-30. [PMID: 24704497 PMCID: PMC4706739 DOI: 10.1016/j.joca.2014.03.017] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/25/2013] [Revised: 03/14/2014] [Accepted: 03/22/2014] [Indexed: 02/02/2023]
Abstract
OBJECTIVE Connexin (Cx) 43 hemichannels play a role in mechanotransduction. This study was undertaken in order to determine if Cx43 hemichannels were activated in rat temporomandibular joint (TMJ) chondrocytes under mechanical stimulation. METHODS Sprague-Dawley rats were stimulated dental-mechanically. Cx43 expression in rat TMJ cartilage was determined with immunohistochemistry and real-time PCR, and Cx43 hemichannel opening was evaluated by the extra- and intracellular levels of prostaglandin E2 (PGE2). Both primary rat chondrocytes and ATDC5 cells were treated with fluid flow shear stress (FFSS) to induce hemichannel opening. The Cx43 expression level was then determined by real-time PCR or Western blotting, and the extent of Cx43 hemichannel opening was evaluated by measuring both PGE2 release and cellular dye uptake. RESULTS Cx43 expression and intra- and extracellular PGE2 levels were increased in mechanically-stimulated rat TMJ cartilage compared to the unstimulated control. The FFSS treatment increased Cx43 expression and induced Cx43 hemichannel opening in primary rat chondrocytes and ATDC5 cells indicated by enhanced PGE2 release and dye uptake. Furthermore, the Cx43 hemichannel opening could be blocked by the addition of 18β-glycyrrhetinic acid, a Cx channel inhibitor, Cx43-targeting siRNA, or by withdrawal of FFSS stimulation. The migration of cytosolic Cx43 protein to the plasma membrane in ATDC5 cells was still significant after 8 h post 2-h FFSS treatment, and the Cx43 protein level was still high at 48 h, which returned to control levels at 72 h after treatment. CONCLUSION Cx43 hemichannels are activated and mediate small molecule exchange between TMJ chondrocytes and matrix under mechanical stimulation.
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Affiliation(s)
- J Zhang
- State Key Laboratory of Military Stomatology, Department of Oral Anatomy and Physiology, School of Stomatology, Fourth Military Medical University, 145 Changlexi Road, Xi'an, 710032, China
| | - H Y Zhang
- State Key Laboratory of Military Stomatology, Department of Oral Anatomy and Physiology, School of Stomatology, Fourth Military Medical University, 145 Changlexi Road, Xi'an, 710032, China
| | - M Zhang
- State Key Laboratory of Military Stomatology, Department of Oral Anatomy and Physiology, School of Stomatology, Fourth Military Medical University, 145 Changlexi Road, Xi'an, 710032, China
| | - Z Y Qiu
- College of Life Science, Shaanxi Normal University, Xi'an, 710062, China
| | - Y P Wu
- Institute of Orthopaedics, Xijing Hospital, Fourth Military Medical University, 15 Changlexi Road, Xi'an, 710032, China
| | - D A Callaway
- Department of Biochemistry, University of Texas Health Science Center, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA
| | - J X Jiang
- Department of Biochemistry, University of Texas Health Science Center, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA
| | - L Lu
- State Key Laboratory of Military Stomatology, Department of Oral Anatomy and Physiology, School of Stomatology, Fourth Military Medical University, 145 Changlexi Road, Xi'an, 710032, China
| | - L Jing
- State Key Laboratory of Military Stomatology, Department of Oral Anatomy and Physiology, School of Stomatology, Fourth Military Medical University, 145 Changlexi Road, Xi'an, 710032, China
| | - T Yang
- State Key Laboratory of Military Stomatology, Department of Oral Anatomy and Physiology, School of Stomatology, Fourth Military Medical University, 145 Changlexi Road, Xi'an, 710032, China
| | - M Q Wang
- State Key Laboratory of Military Stomatology, Department of Oral Anatomy and Physiology, School of Stomatology, Fourth Military Medical University, 145 Changlexi Road, Xi'an, 710032, China.
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8
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Madanayake TW, Fidler TP, Fresquez TM, Bajaj N, Rowland AM. Cytochrome P450 2S1 depletion enhances cell proliferation and migration in bronchial epithelial cells, in part, through modulation of prostaglandin E(2) synthesis. Drug Metab Dispos 2012; 40:2119-25. [PMID: 22863683 DOI: 10.1124/dmd.112.046466] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Cytochromes P450 (P450s) contribute to the metabolic activation and inactivation of various endogenous substrates. Despite years of research, the physiological role of CYP2S1 remains unknown. CYP2S1 has demonstrated NADPH P450-reductase-independent metabolism of cyclooxygenase (COX)-derived prostaglandins [e.g., prostaglandin G(2) (PGG(2))] at nanomolar concentrations. Arachidonic acid is converted to prostaglandin precursors [PGG(2) and prostaglandin H(2) (PGH(2))] through COX. These precursors are used to synthesize numerous prostanoids, including PGE(2). Prostaglandin E(2) (PGE(2)) promotes cell proliferation and cell migration and inhibits apoptosis. CYP2S1 metabolism of PGG(2) presumably sequesters PGG(2) and PGH(2), making them unavailable for synthesis of prostanoids such as PGE(2). Whether CYP2S1 contributes to prostaglandin metabolism and influences cell physiological remains to be determined. The purpose of this study was to evaluate the physiological role of CYP2S1, if any, in human bronchial epithelial cells [SV40-derived bronchial epithelial cell line (BEAS-2B)]. To do this, we used small interfering RNA to deplete CYP2S1 mRNA and protein by approximately 75% and evaluated the impact of CYP2S1 depletion on cell proliferation and migration. CYP2S1 depletion enhanced both cell proliferation and migration in BEAS-2B cells. Consistent with the proposed role of CYP2S1 in PGE(2) synthesis, the reduction in CYP2S1 expression doubled intracellular PGE(2) levels. Pharmacological administration of PGE(2) enhanced cell proliferation in BEAS-2B cells but failed to promote migration. Our data reveal an important role for CYP2S1 in the regulation of cell proliferation and migration, occurring in part through modulation of prostaglandin synthesis.
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Affiliation(s)
- T W Madanayake
- Department of Chemistry and Biochemistry, New Mexico State University, Las Cruces, NM 88003, USA
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9
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Prostaglandin promotion of osteocyte gap junction function through transcriptional regulation of connexin 43 by glycogen synthase kinase 3/beta-catenin signaling. Mol Cell Biol 2010; 30:206-19. [PMID: 19841066 DOI: 10.1128/mcb.01844-08] [Citation(s) in RCA: 109] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Gap junction intercellular communication in osteocytes plays an important role in bone remodeling in response to mechanical loading; however, the responsible molecular mechanisms remain largely unknown. Here, we show that phosphoinositide-3 kinase (PI3K)/Akt signaling activated by fluid flow shear stress and prostaglandin E(2) (PGE(2)) had a stimulatory effect on both connexin 43 (Cx43) mRNA and protein expression. PGE(2) inactivated glycogen synthase kinase 3 (GSK-3) and promoted nuclear localization and accumulation of beta-catenin. Knockdown of beta-catenin expression resulted in a reduction in Cx43 protein. Furthermore, the chromatin immunoprecipitation (ChIP) assay demonstrated an association of beta-catenin with the Cx43 promoter, suggesting that beta-catenin could regulate Cx43 expression at the level of gene transcription. We have previously reported that PGE(2) activates cyclic AMP (cAMP)-protein kinase A (PKA) signaling and increases Cx43 and gap junctions. Interestingly, the activation of PI3K/Akt appeared to be independent of the activation of PKA, whereas both PI3K/Akt and PKA signaling inactivated GSK-3 and increased beta-catenin translocation. Together, these results suggest that shear stress, through PGE(2) release, activates both PI3K/Akt and cAMP-PKA signaling, which converge through the inactivation of GSK-3, leading to the increase in nuclear accumulation of beta-catenin. beta-Catenin binds to the Cx43 promoter, stimulating Cx43 expression and functional gap junctions between osteocytes.
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10
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Liu J, Someren E, Mentink A, Licht R, Dechering K, van Blitterswijk C, de Boer J. The effect of PKC activation and inhibition on osteogenic differentiation of human mesenchymal stem cells. J Tissue Eng Regen Med 2009; 4:329-39. [DOI: 10.1002/term.242] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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11
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Xu Z, Choudhary S, Okada Y, Voznesensky O, Alander C, Raisz L, Pilbeam C. Cyclooxygenase-2 gene disruption promotes proliferation of murine calvarial osteoblasts in vitro. Bone 2007; 41:68-76. [PMID: 17467356 PMCID: PMC1993538 DOI: 10.1016/j.bone.2007.03.009] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/26/2006] [Revised: 02/21/2007] [Accepted: 03/12/2007] [Indexed: 12/31/2022]
Abstract
Cyclooxygenase-2 (COX-2) is highly expressed in osteoblasts, and COX-2 produced prostaglandins (PGs) can increase osteoblastic differentiation in vitro. The goal of this study was to examine effects of COX-2 expression on calvarial osteoblastic proliferation and apoptosis. Primary osteoblasts (POBs) were cultured from calvariae of COX-2 wild-type (WT) and knockout (KO) mice. POB proliferation was evaluated by (3)H-thymidine incorporation and analysis of cell replication and cell cycle distribution by flow cytometry. POB apoptosis was evaluated by annexin and PI staining on flow cytometry. As expected, PGE(2) production and alkaline phosphatase (ALP) activity were increased in WT cultures compared to KO cultures. In contrast, cell numbers were decreased in WT compared to KO cells by day 4 of culture. Proliferation, measured on days 3-7 of culture, was 2-fold greater in KO than in WT POBs and associated with decreased Go/G1 and increased S cell cycle distribution. There was no significant effect of COX-2 genotype on apoptosis under basal culture conditions on day 5 of culture. Cell growth was decreased in KO POBs by the addition of PGE(2) or a protein kinase A agonist and increased in WT POBs by the addition of NS398, a selective COX-2 inhibitor. In contrast, differentiation and cell growth in marrow stromal cell (MSC) cultures, evaluated by ALP and crystal violet staining respectively, were increased in MSCs from WT mice compared to MSCs from KO mice, and exogenous PGE(2) increased cell growth in KO MSC cultures. We conclude that PGs secondary to COX-2 expression decrease osteoblastic proliferation in cultured calvarial cells but increase growth of osteoblastic precursors in MSC cultures.
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Affiliation(s)
- Zheng Xu
- Department of Medicine, University of Connecticut Health Center, Farmington, CT 06030
| | - Shilpa Choudhary
- Department of Medicine, University of Connecticut Health Center, Farmington, CT 06030
| | - Yosuke Okada
- First department of Internal Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu 807-8555 Japan
| | - Olga Voznesensky
- Department of Medicine, University of Connecticut Health Center, Farmington, CT 06030
| | - Cynthia Alander
- Department of Medicine, University of Connecticut Health Center, Farmington, CT 06030
| | - Lawrence Raisz
- Department of Medicine, University of Connecticut Health Center, Farmington, CT 06030
| | - Carol Pilbeam
- Department of Medicine, University of Connecticut Health Center, Farmington, CT 06030
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12
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Soldati L, Terranegra A, Baggio B, Biasion R, Arcidiacono T, Priante G, Cusi D, Vezzoli G. Arachidonic acid influences intracellular calcium handling in human osteoblasts. Prostaglandins Leukot Essent Fatty Acids 2006; 75:91-6. [PMID: 16870415 DOI: 10.1016/j.plefa.2006.05.015] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/19/2005] [Revised: 05/03/2006] [Accepted: 05/29/2006] [Indexed: 10/24/2022]
Abstract
The effect of arachidonic acid (AA) on intracellular Ca(2+) concentration ([Ca(2+)]i) in human osteoblasts MG63 was studied. AA caused a concentration-dependent increase in [Ca(2+)]i, mainly due to inward Ca(2+) transport from extracellular environment. Moreover, AA in Ca(2+) -free medium produced a small, transient increase of [Ca(2+)]i, indicating that AA may also trigger Ca(2+) release from intracellular stores. Because the [Ca(2+)]i response to AA was inhibited by the cyclooxygenase (COX) inhibitor indomethacin, we tested the effect of prostaglandins (PGs), products of COX pathway. PGs E1 and E2 caused an increase in [Ca(2+)]i, which, however, was far lower than that obtained with AA. The [Ca(2+)]i response to AA was not inhibited by nifedipine, suggesting that AA did not activate a voltage-dependent Ca(2+) channel. Our results indicate that AA could modulate [Ca(2+)]i in MG63 human osteoblasts, where it may influence Ca(2+) transport across both plasma and endoplasmic membranes. Furthermore, they suggest that osteoblast activity may be modulated by AA.
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Affiliation(s)
- Laura Soldati
- Department of Sciences and Biomedical Technologies, University of Milan, Via Fratelli Cervi 93, 20090, Segrate (Mi), Italy.
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13
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Cherian PP, Siller-Jackson AJ, Gu S, Wang X, Bonewald LF, Sprague E, Jiang JX. Mechanical strain opens connexin 43 hemichannels in osteocytes: a novel mechanism for the release of prostaglandin. Mol Biol Cell 2005; 16:3100-6. [PMID: 15843434 PMCID: PMC1165395 DOI: 10.1091/mbc.e04-10-0912] [Citation(s) in RCA: 372] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Mechanosensing bone osteocytes express large amounts of connexin (Cx)43, the component of gap junctions; yet, gap junctions are only active at the small tips of their dendritic processes, suggesting another function for Cx43. Both primary osteocytes and the osteocyte-like MLO-Y4 cells respond to fluid flow shear stress by releasing intracellular prostaglandin E2 (PGE2). Cells plated at lower densities release more PGE2 than cells plated at higher densities. This response was significantly reduced by antisense to Cx43 and by the gap junction and hemichannel inhibitors 18 beta-glycyrrhetinic acid and carbenoxolone, even in cells without physical contact, suggesting the involvement of Cx43-hemichannels. Inhibitors of other channels, such as the purinergic receptor P2X7 and the prostaglandin transporter PGT, had no effect on PGE2 release. Cell surface biotinylation analysis showed that surface expression of Cx43 was increased by shear stress. Together, these results suggest fluid flow shear stress induces the translocation of Cx43 to the membrane surface and that unapposed hemichannels formed by Cx43 serve as a novel portal for the release of PGE2 in response to mechanical strain.
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Affiliation(s)
- Priscilla P Cherian
- Department of Biochemistry, University of Texas Health Science Center, San Antonio, TX 78229-3900, USA
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14
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Kaspar D, Hedrich CM, Schmidt C, Liedert A, Claes LE, Ignatius AA. Diclofenac hemmt die Proliferation und Matrixbildung osteoblast�rer Zellen. Unfallchirurg 2005; 108:18, 20-4. [PMID: 16149169 DOI: 10.1007/s00113-004-0858-z] [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: 10/26/2022]
Abstract
Cell culture studies have shown that NSAID may influence osteogenic activities of osteoblast cultures. However, these studies did not consider long-term effects on differentiating cells. The influence of Voltaren with the non-steroidal agent diclofenac on proliferation and gene expression of the osteoblast-like cell line SaOS-2 was investigated 2, 9, and 16 days after incubation. Two days after 24 h of incubation, 50 microg/ml diclofenac reduced the proliferation and collagen type I expression while 9 and 16 days later no effect was found on either of the parameters. In contrast, 50 microg/ml NSAID has no effect on alkaline phosphatase expression 2 days after incubation while 9 and 16 days later expression had been reduced. Lower concentrations (1.56 and 0.19 microg/ml) had no effects on the studied parameters. BrdU and MTT test showed that 50 microg/ml diclofenac reduced proliferative and metabolic activity. Lower concentrations (< or =25 microg/ml) had a lower or no influence. The findings indicate that the NSAID impairment depends on cellular differentiation stage and is not confined to the time during or immediately after NSAID incubation. According to these results in vitro testing of drugs should be performed over a longer time period to detect possible long-term impacts.
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Affiliation(s)
- D Kaspar
- Institut für Unfallchirurgische Forschung und Biomechanik, Universitätsklinikum, Ulm.
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15
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Cherian PP, Cheng B, Gu S, Sprague E, Bonewald LF, Jiang JX. Effects of mechanical strain on the function of Gap junctions in osteocytes are mediated through the prostaglandin EP2 receptor. J Biol Chem 2003; 278:43146-56. [PMID: 12939279 DOI: 10.1074/jbc.m302993200] [Citation(s) in RCA: 166] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Osteocytes embedded in the matrix of bone are thought to be mechanosensory cells that translate mechanical strain into biochemical signals that regulate bone modeling and remodeling. We have shown previously that fluid flow shear stress dramatically induces prostaglandin release and COX-2 mRNA expression in osteocyte-like MLO-Y4 cells, and that prostaglandin E2 (PGE2) released by these cells functions in an autocrine manner to regulate gap junction function and connexin 43 (Cx43) expression. Here we show that fluid flow regulates gap junctions through the PGE2 receptor EP2 activation of cAMP-dependent protein kinase A (PKA) signaling. The expression of the EP2 receptor, but not the subtypes EP1,EP3, and EP4, increased in response to fluid flow. Application of PGE2 or conditioned medium from fluid flow-treated cells to non-stressed MLO-Y4 cells increased expression of the EP2 receptor. The EP2 receptor antagonist, AH6809, suppressed the stimulatory effects of PGE2 and fluid flow-conditioned medium on the expression of the EP2 receptor, on Cx43 protein expression, and on gap junction-mediated intercellular coupling. In contrast, the EP2 receptor agonist butaprost, not the E1/E3 receptor agonist sulprostone, stimulated the expression of Cx43 and gap junction function. Fluid flow conditioned medium and PGE2 stimulated cAMP production and PKA activity suggesting that PGE2 released by mechanically stimulated cells is responsible for the activation of cAMP and PKA. The adenylate cyclase activators, forskolin and 8-bromo-cAMP, enhanced intercellular connectivity, the number of functional gap junctions, and Cx43 protein expression, whereas the PKA inhibitor, H89, inhibited the stimulatory effect of PGE2 on gap junctions. These studies suggest that the EP2 receptor mediates the effects of autocrine PGE2 on the osteocyte gap junction in response to fluid flow-induced shear stress. These data support the hypothesis that the EP2 receptor, cAMP, and PKA are critical components of the signaling cascade between mechanical strain and gap junction-mediated communication between osteocytes.
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MESH Headings
- Adenylyl Cyclases/metabolism
- Animals
- Blotting, Western
- Cell Line
- Cells, Cultured
- Connexin 43/metabolism
- Culture Media, Conditioned/metabolism
- Culture Media, Conditioned/pharmacology
- Cyclic AMP/metabolism
- Cyclic AMP-Dependent Protein Kinases/metabolism
- Cyclooxygenase 2
- Dinoprostone/metabolism
- Gap Junctions
- Isoenzymes/metabolism
- Isoquinolines/pharmacology
- Models, Biological
- Osteocytes/metabolism
- Prostaglandin Antagonists/pharmacology
- Prostaglandin-Endoperoxide Synthases/metabolism
- Prostaglandins/metabolism
- RNA, Messenger/metabolism
- Rats
- Receptors, Prostaglandin E/metabolism
- Receptors, Prostaglandin E/physiology
- Receptors, Prostaglandin E, EP2 Subtype
- Reverse Transcriptase Polymerase Chain Reaction
- Signal Transduction
- Stress, Mechanical
- Sulfonamides
- Time Factors
- Xanthones/pharmacology
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Affiliation(s)
- Priscilla P Cherian
- Department of Biochemistry and Radiology, University of Texas Health Science Center, San Antonio, Texas 78229-3900, USA
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16
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Salter DM, Wallace WH, Robb JE, Caldwell H, Wright MO. Human bone cell hyperpolarization response to cyclical mechanical strain is mediated by an interleukin-1beta autocrine/paracrine loop. J Bone Miner Res 2000; 15:1746-55. [PMID: 10976994 DOI: 10.1359/jbmr.2000.15.9.1746] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Mechanical stimuli imparted by stretch, pressure, tension, fluid flow, and shear stress result in a variety of biochemical responses important in bone (re)modeling. The molecules involved in the recognition and transduction of mechanical stimuli that lead to modulation of bone cell function are not yet fully characterized. Cyclical pressure-induced strain (PIS) induces a rapid change in membrane potential of human bone cells (HBC) because of opening of membrane ion channels. This response is mediated via integrins and requires tyrosine kinase activity and an intact actin cytoskeleton. We have used this electrophysiological response to further study the signaling events occurring early after mechanical stimulation of HBC. Stimulation of HBC at 0.33 Hz PIS, but not 0.104 Hz PIS, results in the production of a transferable factor that induces membrane hyperpolarization of unstimulated HBC. The production of this factor is inhibited by antibodies to beta1-integrin. Interleukin-1beta (IL-1beta and prostaglandin E2 (PGE2) were identified as candidate molecules for the transferable factor as both were shown to induce HBC hyperpolarization by opening of small conductance calcium-activated potassium channels, the means by which 0.33 Hz PIS causes HBC hyperpolarization. Antibodies to IL-1beta, but not other cytokines studied, inhibit the hyperpolarization response of HBC to 0.33 Hz PIS. Comparison of the signaling pathways required for 0.33 Hz PIS and IL-1beta-induced membrane hyperpolarization shows that both involve the phospholipase C/inositol triphosphate pathway, protein kinase C (PKC), and prostaglandin synthesis. Unlike 0.33 Hz PIS-induced membrane hyperpolarization, IL-1beta-induced hyperpolarization does not require tyrosine kinase activity or an intact actin cytoskeleton. These studies suggest that 0.33 Hz PIS of HBC induces a rapid, integrin-mediated, release of IL-1beta with a subsequent autocrine/paracrine loop resulting in membrane hyperpolarization. IL-1beta production in response to mechanical stimuli is potentially of importance in regulation of bone (re)modeling.
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Affiliation(s)
- D M Salter
- Department of Pathology, Edinburgh University Medical School, United Kingdom
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17
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Dumont AS, Verma S, Dumont RJ, Hurlbert RJ. Nonsteroidal anti-inflammatory drugs and bone metabolism in spinal fusion surgery: a pharmacological quandary. J Pharmacol Toxicol Methods 2000; 43:31-9. [PMID: 11091128 DOI: 10.1016/s1056-8719(00)00077-0] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The use of nonsteroidal anti-inflammatory drugs (NSAIDs) is ubiquitous in contemporary medical practice and these agents are efficacious in a number of clinical contexts. In particular, NSAIDs have proven to be highly effective adjuncts in the amelioration of postoperative pain in the subset of patients undergoing spinal surgery requiring fusion. NSAIDs act through inhibition of cyclooxygenase enzymes and therefore diminish prostaglandin production. However, prostaglandins are intimately involved in the modulation of bone metabolism and the balance of data, from both clinical and laboratory contexts, indicate that prostaglandins preferentially favor bone anabolism. Most recently, limited emerging evidence suggests that NSAID administration in patients undergoing spinal fusion surgery may increase nonunion rates, which in turn, has important ramifications to the patient, their family and the entire medical system. Hence, disparate views have evolved regarding the use of NSAIDs in postoperative pain control in patients undergoing spinal surgery requiring fusion. NSAIDs have proven efficacy in the management of postoperative pain in these patients, however, this must be weighed against the risk of nonunion and its associated consequences. In this review, the role of prostaglandins in bone metabolism, the pharmacology of NSAIDs and the modulation of bone metabolism by NSAIDs are discussed. Additionally, the current evidence examining the use of NSAIDs in spinal surgery is presented. As rates of spinal surgery continue to rise, it is imperative that the apparent pharmacological quandary surrounding the administration of NSAIDs in patients undergoing spinal surgery requiring fusion be addressed, both to guide present clinical practice and to outline further directions for investigation.
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Affiliation(s)
- A S Dumont
- Department of Neurological Surgery, University of Virginia, Charlottesville, VA, USA.
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18
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Van Den Brink GR, Bloemers SM, Van Den Blink B, Tertoolen LG, Van Deventer SJ, Peppelenbosch MP. Study of calcium signaling in non-excitable cells. Microsc Res Tech 1999; 46:418-33. [PMID: 10504218 DOI: 10.1002/(sici)1097-0029(19990915)46:6<418::aid-jemt9>3.0.co;2-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The fundamental importance of calcium signaling in the control of cellular physiology is widely recognized. A dramatic illustration of this is the fact that a Medline search for review articles containing the word "calcium" in the title reveals 4,629 hits, whereas the whole body of calcium signaling literature (approximately 2 x 10(6) pages) is more than enough to fill a decent-sized library. Most of this literature deals with calcium signaling in excitable cells types (mainly neurons and muscle cells), but non-excitable cell types are capable of calcium signaling as well. Although calcium fluxes in the latter cell types have attracted much less interest, the literature involved is still vast. Nevertheless, in this review article we hope to contribute some valuable insights to the field. First we shall discuss the experimental techniques available to the researcher interested in calcium signaling in non-excitable cell types with special attention to patch clamp electrophysiology. Subsequently, we shall review some of the results obtained with these techniques by focussing on the calcium-regulating mechanisms in non-excitable cells and discussing the importance of these mechanisms for physiology.
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Affiliation(s)
- G R Van Den Brink
- Laboratory for Experimental Internal Medicine, Academic Medical Center, NL-1105 AZ Amsterdam, The Netherlands
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19
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Bhattacharya M, Peri K, Ribeiro-da-Silva A, Almazan G, Shichi H, Hou X, Varma DR, Chemtob S. Localization of functional prostaglandin E2 receptors EP3 and EP4 in the nuclear envelope. J Biol Chem 1999; 274:15719-24. [PMID: 10336471 DOI: 10.1074/jbc.274.22.15719] [Citation(s) in RCA: 175] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The effects of prostaglandin E2 are thought to be mediated via G protein-coupled plasma membrane receptors, termed EP. However recent data implied that prostanoids may also act intracellularly. We investigated if the ubiquitous EP3 and the EP4 receptors are localized in nuclear membranes. Radioligand binding studies on isolated nuclear membrane fractions of neonatal porcine brain and adult rat liver revealed the presence of EP3 and EP4. A perinuclear localization of EP3alpha and EP4 receptors was visualized by indirect immunocytofluorescence and confocal microscopy in porcine cerebral microvascular endothelial cells and in transfected HEK 293 cells that stably overexpress these receptors. Immunoelectron microscopy clearly revealed EP3alpha and EP4 receptors localization in the nuclear envelope of endothelial cells; this is the first demonstration of the nuclear localization of these receptors. Data also reveal that nuclear EP receptors are functional as they affect transcription of genes such as inducible nitric-oxide synthase and intranuclear calcium transients; this appears to involve pertussis toxin-sensitive G proteins. These results define a possible molecular mechanism of action of nuclear EP3 receptors.
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Affiliation(s)
- M Bhattacharya
- Department of Pharmacology & Therapeutics, McGill University, Montreal, PQ, Canada, H3G 1Y6
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