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Moorthy A, Venugopal DC, Shyamsundar V, Madhavan Y, Ravindran S, Kuppuloganathan M, Krishnamurthy A, Sankarapandian S, Ganapathy V, Ramshankar V. Identification of EGFR as a Biomarker in Saliva and Buccal Cells from Oral Submucous Fibrosis Patients—A Baseline Study. Diagnostics (Basel) 2022; 12:diagnostics12081935. [PMID: 36010285 PMCID: PMC9406318 DOI: 10.3390/diagnostics12081935] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2022] [Revised: 08/01/2022] [Accepted: 08/03/2022] [Indexed: 11/30/2022] Open
Abstract
Oral Submucous Fibrosis (OSMF) is a chronic debilitating disease more frequently encountered in the South-East Asian population. This disease represents a public health priority as it is grouped within oral potentially malignant disorders, with malignant transformation rates of around 7–19%. Hence, early identification of high-risk OSMF patients is of the utmost importance to prevent malignant transformation. Among various biomarkers, EGFR overexpression has an unfavorable clinical outcome, poor prognosis, and low survival rates in Oral Squamous Cell Carcinoma (OSCC). The current study aimed to evaluate the expression of EGFR in saliva and exfoliated buccal cells of OSMF. Immunoexpression of EGFR was observed in healthy controls (n = 11), OSCC (n = 106), and OPMD with dysplasia (n = 56), which showed significant expression with increasing grades of dysplasia and OSCC. EGFR expression was evaluated in saliva and exfoliated buccal cells of healthy controls (n = 15), OSMF (n = 24), and OSCC (n = 10) patients using ELISA, which revealed significant expression in OSMF and OSCC. Validation studies were also performed using real-time PCR (RT-PCR) to compare gene expression in healthy controls (n = 9), OSMF (n = 9), and OSCC (n = 25), which showed significant 18-fold upregulation in OSCC and three-fold upregulation in OSMF when compared to healthy controls. Hence, saliva and exfoliated buccal cells could be considered as potential non-invasive diagnostic samples for the evaluation of high-risk patients of OSMF using EGFR as a biomarker.
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Affiliation(s)
- Abirami Moorthy
- Department of Oral Medicine and Radiology, Sri Ramachandra Institute of Higher Education and Research (DU), Porur, Chennai 600116, India
| | - Divyambika Catakapatri Venugopal
- Department of Oral Medicine and Radiology, Sri Ramachandra Institute of Higher Education and Research (DU), Porur, Chennai 600116, India
- Correspondence: (D.C.V.); (V.R.)
| | - Vidyarani Shyamsundar
- Centre for Oral Cancer Prevention and Research, Sree Balaji Dental College and Hospital, Pallikaranai, Chennai 600100, India
| | - Yasasve Madhavan
- Department of Oral Medicine and Radiology, Sri Ramachandra Institute of Higher Education and Research (DU), Porur, Chennai 600116, India
| | - Soundharya Ravindran
- Department of Preventive Oncology (Research), Cancer Institute (WIA), Adyar, Chennai 600020, India
| | | | - Arvind Krishnamurthy
- Department of Surgical Oncology, Cancer Institute (WIA), Adyar, Chennai 600020, India
| | | | - Vani Ganapathy
- Department of Biochemistry, University of Madras, Chennai 600025, India
| | - Vijayalakshmi Ramshankar
- Department of Preventive Oncology (Research), Cancer Institute (WIA), Adyar, Chennai 600020, India
- Correspondence: (D.C.V.); (V.R.)
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Ganapathy V, Bailey E, Mortimer K, Lou Y, Yuan J, Mulder K, Topuria I, Cerf S, Elder K, Booth J, Bruinsma B, Globe D. 56: Real-world clinical effectiveness of elexacaftor/tezacaftor/ivacaftor and ivacaftor in people with CF: Interim results from the HELIO study. J Cyst Fibros 2021. [DOI: 10.1016/s1569-1993(21)01481-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Srinivasan B, Chitharanjan A, Kailasam V, Lavu V, Ganapathy V. Evaluation of leptin concentration in Gingival Crevicular Fluid (GCF) during orthodontic tooth movement and its correlation to the rate of tooth movement. J Orthod Sci 2019; 8:6. [PMID: 31161129 PMCID: PMC6540779 DOI: 10.4103/jos.jos_58_18] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
OBJECTIVES: Leptin, a polypeptide which is related to body fat regulation, is also found to have a role in the inflammatory reaction. The aim of this study is to assess the concentration of leptin in Gingival Crevicular Fluid (GCF) during orthodontic force application and to correlate its concentration to rate of tooth movement. METHODS: Twenty orthodontic patients (10 males and 10 females) were selected for the study. Leptin concentration was measured at T0, before force application; T1, one hour after force application; T2, one day after force application; T3, one week after force application; T4, one month after force application. GCF was collected using filter paper strips from the distal aspect of gingival sulcus of the right maxillary canine distalized by an active lace-backs of tooth movement was measured on dental casts, before and one month after force application. One-way ANOVA with Bonferroni correction and Pearson's correlation test were used to analyze the data. RESULTS: The mean GCF leptin concentration increased from T0 to T1, rose to a peak at T2, then declined to a minimum value at T3 and then increased to a value at T4, closer to the base line value (T0), and it was statistically significant (P < 0.05). There was positive correlation of the overall mean leptin concentration to rate of tooth movement (correlation coefficient = 0.634). CONCLUSION: There was a biphasic change in GCF leptin concentration during one cycle of orthodontic force application. There was a positive correlation between the GCF leptin concentration and rate of tooth movement.
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Affiliation(s)
- Bhadrinath Srinivasan
- Department of Orthodontics, Faculty of Dental Sciences, Sri Ramachandra Medical College and Research Institute, Porur, Chennai, Tamil Nadu, India
| | - Arun Chitharanjan
- Department of Orthodontics, Faculty of Dental Sciences, Sri Ramachandra Medical College and Research Institute, Porur, Chennai, Tamil Nadu, India
| | - Vignesh Kailasam
- Department of Orthodontics, Faculty of Dental Sciences, Sri Ramachandra Medical College and Research Institute, Porur, Chennai, Tamil Nadu, India
| | - Vamsi Lavu
- Department of Periodontics, Faculty of Dental Sciences, Sri Ramachandra Medical College and Research Institute, Porur, Chennai, Tamil Nadu, India
| | - Vani Ganapathy
- Department of Biochemistry, Madras University, Chennai, Tamil Nadu, India
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Coothankandaswamy V, Cao S, Xu Y, Prasad PD, Singh PK, Reynolds CP, Yang S, Ogura J, Ganapathy V, Bhutia YD. Amino acid transporter SLC6A14 is a novel and effective drug target for pancreatic cancer. Br J Pharmacol 2016; 173:3292-3306. [PMID: 27747870 PMCID: PMC5738662 DOI: 10.1111/bph.13616] [Citation(s) in RCA: 82] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2016] [Revised: 08/16/2016] [Accepted: 08/17/2016] [Indexed: 01/04/2023] Open
Abstract
BACKGROUND AND PURPOSE Pancreatic cancer is a solid tumour that is often fatal. Hence, there is an urgent need to identify new drug targets for this disease. Highly proliferating cancer cells have an increased demand for nutrients and, therefore, need to up-regulate selective amino acid transporters. Here, we investigated which amino acid transporters are up-regulated in pancreatic cancer and whether any of these transporters has potential as a drug target for this fatal disease. EXPERIMENTAL APPROACH The expression of amino acid transporters in pancreatic cancer was analysed using publicly available microarray datasets, and the findings with the transporter SLC6A14 were validated by mRNA and protein analysis. The potential of SLC6A14 as a drug target was evaluated using a pharmacological blocker in vitro and in vivo. KEY RESULTS SLC6A14 was up-regulated several fold in patient-derived xenografts, primary tumour tissues and pancreatic cancer cells lines compared to normal pancreatic tissue or normal pancreatic epithelial cells. The magnitude of the up-regulation of SLC6A14 was the highest among the amino acid transporters examined. A pharmacological blocker of SLC6A14, α-methyltryptophan, induced amino acid starvation in pancreatic cancer cells and reduced the growth and proliferation of these cells, both in vitro and in vivo. CONCLUSION AND IMPLICATIONS The salient features of this study are that SLC6A14 is markedly up-regulated in pancreatic cancer and that pharmacological blockade of this transporter interferes with amino acid nutrition and reduces growth and proliferation of pancreatic cancer cells. These findings identify SLC6A14 as a novel druggable target for pancreatic cancer.
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Affiliation(s)
- V Coothankandaswamy
- Department of Biochemistry and Molecular BiologyAugusta UniversityAugustaGA30912USA
| | - S Cao
- Department of Biochemistry and Molecular BiologyUniversity of GeorgiaAthensGAUSA
| | - Y Xu
- Department of Biochemistry and Molecular BiologyUniversity of GeorgiaAthensGAUSA
| | - P D Prasad
- Department of Biochemistry and Molecular BiologyAugusta UniversityAugustaGA30912USA
| | - P K Singh
- Eppley Institute for Research in Cancer and Allied DiseasesUniversity of Nebraska Medical CenterOmahaNEUSA
| | - C P Reynolds
- Department of Cell Biology and Biochemistry and Cancer CenterTexas Tech University Health Sciences CenterLubbockTX30912USA
| | - S Yang
- Department of Cell Biology and Biochemistry and Cancer CenterTexas Tech University Health Sciences CenterLubbockTX30912USA
| | - J Ogura
- Department of Cell Biology and Biochemistry and Cancer CenterTexas Tech University Health Sciences CenterLubbockTX30912USA
| | - V Ganapathy
- Department of Cell Biology and Biochemistry and Cancer CenterTexas Tech University Health Sciences CenterLubbockTX30912USA
| | - Y D Bhutia
- Department of Cell Biology and Biochemistry and Cancer CenterTexas Tech University Health Sciences CenterLubbockTX30912USA
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Sivaprakasam S, Gurav A, Paschall AV, Coe GL, Chaudhary K, Cai Y, Kolhe R, Martin P, Browning D, Huang L, Shi H, Sifuentes H, Vijay-Kumar M, Thompson SA, Munn DH, Mellor A, McGaha TL, Shiao P, Cutler CW, Liu K, Ganapathy V, Li H, Singh N. An essential role of Ffar2 (Gpr43) in dietary fibre-mediated promotion of healthy composition of gut microbiota and suppression of intestinal carcinogenesis. Oncogenesis 2016; 5:e238. [PMID: 27348268 PMCID: PMC4945739 DOI: 10.1038/oncsis.2016.38] [Citation(s) in RCA: 94] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2016] [Revised: 04/12/2016] [Accepted: 04/18/2016] [Indexed: 12/19/2022] Open
Abstract
Composition of the gut microbiota has profound effects on intestinal carcinogenesis. Diet and host genetics play critical roles in shaping the composition of gut microbiota. Whether diet and host genes interact with each other to bring specific changes in gut microbiota that affect intestinal carcinogenesis is unknown. Ability of dietary fibre to specifically increase beneficial gut microbiota at the expense of pathogenic bacteria in vivo via unknown mechanism is an important process that suppresses intestinal inflammation and carcinogenesis. Free fatty acid receptor 2 (FFAR2 or GPR43) is a receptor for short-chain fatty acids (acetate, propionate and butyrate), metabolites of dietary fibre fermentation by gut microbiota. Here, we show FFAR2 is down modulated in human colon cancers than matched adjacent healthy tissue. Consistent with this, Ffar2(-/-) mice are hypersusceptible to development of intestinal carcinogenesis. Dietary fibre suppressed colon carcinogenesis in an Ffar2-dependent manner. Ffar2 played an essential role in dietary fibre-mediated promotion of beneficial gut microbiota, Bifidobacterium species (spp) and suppression of Helicobacter hepaticus and Prevotellaceae. Moreover, numbers of Bifidobacterium is reduced, whereas those of Prevotellaceae are increased in human colon cancers than matched adjacent normal tissue. Administration of Bifidobacterium mitigated intestinal inflammation and carcinogenesis in Ffar2(-/-) mice. Taken together, these findings suggest that interplay between dietary fibre and Ffar2 play a key role in promoting healthy composition of gut microbiota that stimulates intestinal health.
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Affiliation(s)
- S Sivaprakasam
- Department of Biochemistry and Molecular Biology, Georgia Regents University, Augusta, GA, USA
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences, Lubbock, TX, USA
| | - A Gurav
- Department of Biochemistry and Molecular Biology, Georgia Regents University, Augusta, GA, USA
| | - A V Paschall
- Department of Biochemistry and Molecular Biology, Georgia Regents University, Augusta, GA, USA
| | - G L Coe
- Department of Biochemistry and Molecular Biology, Georgia Regents University, Augusta, GA, USA
| | - K Chaudhary
- Cancer Research Center, Georgia Regents University, Augusta, GA, USA
| | - Y Cai
- Department of Biochemistry and Molecular Biology, Georgia Regents University, Augusta, GA, USA
| | - R Kolhe
- Department of Pathology, Georgia Regents University, Augusta, GA, USA
| | - P Martin
- Department of Biochemistry and Molecular Biology, Georgia Regents University, Augusta, GA, USA
| | - D Browning
- Department of Biochemistry and Molecular Biology, Georgia Regents University, Augusta, GA, USA
| | - L Huang
- Cancer Research Center, Georgia Regents University, Augusta, GA, USA
| | - H Shi
- Department of Biochemistry and Molecular Biology, Georgia Regents University, Augusta, GA, USA
- Cancer Research Center, Georgia Regents University, Augusta, GA, USA
| | - H Sifuentes
- Department of Medicine, Georgia Regents University, Augusta, GA, USA
| | - M Vijay-Kumar
- Departments of Nutritional Sciences & Medicine, Pennsylvania State University, Medical Center, Hershey, PA, USA
| | - S A Thompson
- Department of Medicine, Georgia Regents University, Augusta, GA, USA
| | - D H Munn
- Cancer Research Center, Georgia Regents University, Augusta, GA, USA
- Department of Pediatrics, Georgia Regents University, Augusta, GA, USA
| | - A Mellor
- Institute of Cellular Medicine, Newcastle University, Newcastle-upon-Tyne, UK
| | - T L McGaha
- Department of Immunology, University of Toronto, Toronto, ON, Canada
| | - P Shiao
- College of Nursing, Georgia Regents University, Augusta, GA, USA
| | - C W Cutler
- Department of Periodontics, Georgia Regents University, Augusta, GA, USA
| | - K Liu
- Department of Biochemistry and Molecular Biology, Georgia Regents University, Augusta, GA, USA
| | - V Ganapathy
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences, Lubbock, TX, USA
| | - H Li
- Department of Biochemistry and Molecular Biology, Georgia Regents University, Augusta, GA, USA
| | - N Singh
- Department of Biochemistry and Molecular Biology, Georgia Regents University, Augusta, GA, USA
- Cancer Research Center, Georgia Regents University, Augusta, GA, USA
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Miyamoto Y, Ganapathy V, Leibach FH. Role of dipeptidylpeptidase IV in renal handling of peptides. Contrib Nephrol 2015; 68:1-5. [PMID: 3233987 DOI: 10.1159/000416483] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Affiliation(s)
- Y Miyamoto
- Department of Cell and Molecular Biology, Medical College of Georgia, Augusta
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Takhar S, Manning M, Eason A, Dix M, Periyasamy-Thandavan S, Padi R, Bieberich E, Hill W, Browning D, Ganapathy V, Thangaraju M, Schoenlein PV. Abstract B50: MEK inhibitors mount a two-pronged attack to kill estrogen receptor positive (ER+) breast cancer cells undergoing hormonal therapy: Attenuated autophagy and induction of apoptosis. Mol Cancer Res 2014. [DOI: 10.1158/1557-3125.rasonc14-b50] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Abstract
In a recent study, we identified the dephosphorylated form of BimEL as a key death effector of antiestrogen treatment of ER+ breast cancer cells and further showed that MEK1/MAPK1/2 blockade was required to produce high levels of dephosphorylated BimEL, particularly under conditions of insulin like growth factor 1 (IGF1) stimulation (Periyasamy-Thandavan et al., Breast Cancer Res. 14, 2012). Studies by others have identified MEK1/MAPK1/2 activation as essential to autophagy, a catabolic process induced by multiple stresses including ROS, ceramide accumulation, and nutrient deprivation. Autophagy induction results in autophagosome formation, trafficking of damaged proteins and mitochondria to the autophagosomes, and ultimately fusion with the lysosomes resulting in autolysosome formation. The autolysosome and its contents are degraded by the hydrolytic enzymes of the lysosome. Of particular interest to antiestrogen treatment of breast cancer, we and others have shown that pro-survival autophagy facilitates the emergence of antiestrogen resistant breast cancer cells. Thus, we are keenly interested in how MEK1/MAPK1/2 signaling affects pro-survival autophagy and if MEK blockade would be an effective approach toward blocking pro-survival autophagy in ER+ breast cancer cells undergoing hormonal treatment. In this study, we hypothesized that the requirement of MEK1/MAPK1/2 for pro-survival autophagy is due, in part, to its role in blocking the intracellular accumulation of dephosphorylated BimEL. To test this hypothesis, we modulated the expression of dephosphorylated BimEL with either a BimEL cDNA expression vector, siRNA targeting of BimEL, or MEK1 blockade with the small molecule inhibitor U0126 and determined the levels of the autophagic flux in ER+ breast cancer cells undergoing antiestrogen treatment. The determination of autophagic flux was made by comparing the levels of two proteins involved in autophagy -the LC3 /Atg8 and p62 (SQSTM1) proteins- in cell populations undergoing the different treatments in the presence or absence of chloroquine (CQ). The lipidated form of LC3, designated LC3II, is typically increased in cells undergoing autophagy, facilitates the formation of the mature autophagosomal membranes, and is subsequently degraded in the autolysosome. The p62 protein is required for the delivery of ubiquitinated protein complexes to the autophagosome and is degraded along with the ubiquitinated complex of proteins. CQ is a lysosomotrophic agent routinely used in autophagic flux assays because it blocks the turnover of autolysosomes with accumulation of LC3 II and p62, allowing the total levels of LC3II and p62 to be ascertained under all treatment conditions. These studies showed that siRNA targeting of BimEL increased basal and tamoxifen-induced autophagy in ER+ MCF-7 breast cancer cells. In contrast, the overexpression of dephosphorylated BimEL led to an increase in LC3 II and p62 levels due to a significant attenuation of autophagic flux (approximately 50%) in antiestrogen-treated cell populations. Current studies are focused on the mechanism of BimEL-mediated blockade of pro-survival autophagy, with the long term goal of optimizing this “downstream effector” function of MEK1/MAPK1/2 blockade in ER+ breast cancer cells for improved therapeutic outcome.
Citation Format: S. Takhar, M. Manning, A. Eason, M. Dix, S. Periyasamy-Thandavan, R. Padi, E. Bieberich, W. Hill, D. Browning, V. Ganapathy, M. Thangaraju, P. V. Schoenlein. MEK inhibitors mount a two-pronged attack to kill estrogen receptor positive (ER+) breast cancer cells undergoing hormonal therapy: Attenuated autophagy and induction of apoptosis. [abstract]. In: Proceedings of the AACR Special Conference on RAS Oncogenes: From Biology to Therapy; Feb 24-27, 2014; Lake Buena Vista, FL. Philadelphia (PA): AACR; Mol Cancer Res 2014;12(12 Suppl):Abstract nr B50. doi: 10.1158/1557-3125.RASONC14-B50
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Affiliation(s)
- S. Takhar
- GRU Cancer Center, Georgia Regents University, Augusta, GA
| | - M. Manning
- GRU Cancer Center, Georgia Regents University, Augusta, GA
| | - A. Eason
- GRU Cancer Center, Georgia Regents University, Augusta, GA
| | - M. Dix
- GRU Cancer Center, Georgia Regents University, Augusta, GA
| | | | - R. Padi
- GRU Cancer Center, Georgia Regents University, Augusta, GA
| | - E. Bieberich
- GRU Cancer Center, Georgia Regents University, Augusta, GA
| | - W. Hill
- GRU Cancer Center, Georgia Regents University, Augusta, GA
| | - D. Browning
- GRU Cancer Center, Georgia Regents University, Augusta, GA
| | - V. Ganapathy
- GRU Cancer Center, Georgia Regents University, Augusta, GA
| | - M. Thangaraju
- GRU Cancer Center, Georgia Regents University, Augusta, GA
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Alexander SPH, Benson HE, Faccenda E, Pawson AJ, Sharman JL, McGrath JC, Catterall WA, Spedding M, Peters JA, Harmar AJ, Abul-Hasn N, Anderson CM, Anderson CMH, Araiksinen MS, Arita M, Arthofer E, Barker EL, Barratt C, Barnes NM, Bathgate R, Beart PM, Belelli D, Bennett AJ, Birdsall NJM, Boison D, Bonner TI, Brailsford L, Bröer S, Brown P, Calo G, Carter WG, Catterall WA, Chan SLF, Chao MV, Chiang N, Christopoulos A, Chun JJ, Cidlowski J, Clapham DE, Cockcroft S, Connor MA, Cox HM, Cuthbert A, Dautzenberg FM, Davenport AP, Dawson PA, Dent G, Dijksterhuis JP, Dollery CT, Dolphin AC, Donowitz M, Dubocovich ML, Eiden L, Eidne K, Evans BA, Fabbro D, Fahlke C, Farndale R, Fitzgerald GA, Fong TM, Fowler CJ, Fry JR, Funk CD, Futerman AH, Ganapathy V, Gaisnier B, Gershengorn MA, Goldin A, Goldman ID, Gundlach AL, Hagenbuch B, Hales TG, Hammond JR, Hamon M, Hancox JC, Hauger RL, Hay DL, Hobbs AJ, Hollenberg MD, Holliday ND, Hoyer D, Hynes NA, Inui KI, Ishii S, Jacobson KA, Jarvis GE, Jarvis MF, Jensen R, Jones CE, Jones RL, Kaibuchi K, Kanai Y, Kennedy C, Kerr ID, Khan AA, Klienz MJ, Kukkonen JP, Lapoint JY, Leurs R, Lingueglia E, Lippiat J, Lolait SJ, Lummis SCR, Lynch JW, MacEwan D, Maguire JJ, Marshall IL, May JM, McArdle CA, McGrath JC, Michel MC, Millar NS, Miller LJ, Mitolo V, Monk PN, Moore PK, Moorhouse AJ, Mouillac B, Murphy PM, Neubig RR, Neumaier J, Niesler B, Obaidat A, Offermanns S, Ohlstein E, Panaro MA, Parsons S, Pwrtwee RG, Petersen J, Pin JP, Poyner DR, Prigent S, Prossnitz ER, Pyne NJ, Pyne S, Quigley JG, Ramachandran R, Richelson EL, Roberts RE, Roskoski R, Ross RA, Roth M, Rudnick G, Ryan RM, Said SI, Schild L, Sanger GJ, Scholich K, Schousboe A, Schulte G, Schulz S, Serhan CN, Sexton PM, Sibley DR, Siegel JM, Singh G, Sitsapesan R, Smart TG, Smith DM, Soga T, Stahl A, Stewart G, Stoddart LA, Summers RJ, Thorens B, Thwaites DT, Toll L, Traynor JR, Usdin TB, Vandenberg RJ, Villalon C, Vore M, Waldman SA, Ward DT, Willars GB, Wonnacott SJ, Wright E, Ye RD, Yonezawa A, Zimmermann M. The Concise Guide to PHARMACOLOGY 2013/14: overview. Br J Pharmacol 2014; 170:1449-58. [PMID: 24528237 DOI: 10.1111/bph.12444] [Citation(s) in RCA: 146] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The Concise Guide to PHARMACOLOGY 2013/14 provides concise overviews of the key properties of over 2000 human drug targets with their pharmacology, plus links to an open access knowledgebase of drug targets and their ligands (www.guidetopharmacology.org), which provides more detailed views of target and ligand properties from the IUPHAR database. The full contents can be found at http://onlinelibrary.wiley.com/doi/10.1111/bph.12444/full. This compilation of the major pharmacological targets is divided into seven areas of focus: G protein-coupled receptors, ligand-gated ion channels, ion channels, catalytic receptors, nuclear hormone receptors, transporters and enzymes. These are presented with nomenclature guidance and summary information on the best available pharmacological tools, alongside key references and suggestions for further reading. A new landscape format has easy to use tables comparing related targets. It is a condensed version of material contemporary to late 2013, which is presented in greater detail and constantly updated on the website www.guidetopharmacology.org, superseding data presented in previous Guides to Receptors & Channels. It is produced in conjunction with NC-IUPHAR and provides the official IUPHAR classification and nomenclature for human drug targets, where appropriate. It consolidates information previously curated and displayed separately in IUPHAR-DB and GRAC and provides a permanent, citable, point-in-time record that will survive database updates.
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Affiliation(s)
- Stephen P H Alexander
- School of Life Sciences, University of Nottingham Medical School, Nottingham, NG7 2UH, UK
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Wissel J, Ganapathy V, Ma Y, Ward A, Borg J, Ertzgaard P, Fulford-Smith A, Gillard P. OnabotulinumtoxinA improves spasticity related pain in post-stroke patients: Findings from a randomized controlled trial. Ann Phys Rehabil Med 2014. [DOI: 10.1016/j.rehab.2014.03.158] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Sonne SR, Bhalla VK, Barman SA, White RE, Zhu S, Newman TM, Prasad PD, Smith SB, Offermanns S, Ganapathy V. Hyperhomocysteinemia is detrimental to pregnancy in mice and is associated with preterm birth. Biochim Biophys Acta Mol Basis Dis 2013; 1832:1149-58. [PMID: 23579073 DOI: 10.1016/j.bbadis.2013.04.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2013] [Revised: 03/28/2013] [Accepted: 04/01/2013] [Indexed: 11/28/2022]
Abstract
Elevated levels of homocysteine produce detrimental effects in humans but its role in preterm birth is not known. Here we used a mouse model of hyperhomocysteinemia to examine the relevance of homocysteine to preterm birth. The mouse carries a heterozygous deletion of cystathionine β-synthase (Cbs(+/-)). Gestational period was monitored in wild type and Cbs(+/-) female mice. Mouse uterine and placental tissues, human primary trophoblast cells, and human myometrial and placental cell lines were used to determine the influence of homocysteine on expression of specific genes in vitro. The activity of BKCa channel in the myometrial cell line was monitored using the patch-clamp technique. We found that hyperhomocysteinemia had detrimental effects on pregnancy and induced preterm birth in mice. Homocysteine increased the expression of oxytocin receptor and Cox-2 as well as PGE2 production in uterus and placenta, and initiated premature uterine contraction. A Cox-2 inhibitor reversed these effects. Gpr109a, a receptor for niacin, induced Cox-2 in uterus. Homocysteine upregulated GPR109A and suppressed BKCa channel activity in human myometrial cells. Deletion of Gpr109a in Cbs(+/-) mice reversed premature birth. We conclude that hyperhomocysteinemia causes preterm birth in mice through upregulation of the Gpr109a/Cox-2/PGE2 axis and that pharmacological blockade of Gpr109a may have potential in prevention of preterm birth.
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Affiliation(s)
- S R Sonne
- Department of Biochemistry and Molecular Biology, Georgia Regents University, Augusta, GA 30912, USA.
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12
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Pazhanivel T, Devarajan VP, Bharathi G, Senthil K, Ganapathy V, Yong K, Nataraj D. Systematic investigation of the structure and photophysical properties of CdSe, CdSe/ZnS QDs and their hybrid with β-carotene. RSC Adv 2013. [DOI: 10.1039/c3ra41482e] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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13
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Bhalla V, Sonne S, Ganapathy V. Reversal of Premature Delivery Via Cox-2 Inhibition and GPR109A Deletion in Cystathionine-b-Synthase (CBS) Deficient Mice. J Surg Res 2012. [DOI: 10.1016/j.jss.2011.11.385] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
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14
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Babu E, Ramachandran S, CoothanKandaswamy V, Elangovan S, Prasad PD, Ganapathy V, Thangaraju M. Role of SLC5A8, a plasma membrane transporter and a tumor suppressor, in the antitumor activity of dichloroacetate. Oncogene 2011; 30:4026-37. [PMID: 21499304 PMCID: PMC3140604 DOI: 10.1038/onc.2011.113] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
There has been growing interest among the public and scientists in dichloroacetate as a potential anticancer drug. Credible evidence exists for the antitumor activity of this compound, but high concentrations are needed for significant therapeutic effect. Unfortunately, these high concentrations produce detrimental side effects involving nervous system, thereby precluding its use for cancer treatment. The mechanistic basis of the compound’s antitumor activity is its ability to activate pyruvate dehydrogenase complex through inhibition of pyruvate dehydrogenase kinase. Since the compound inhibits the kinase at micromolar concentrations, it is not known why therapeutically prohibitive high doses are needed for suppression of tumor growth. We hypothesized that lack of effective mechanisms for the entry of dichloroacetate into tumor cells may underlie this phenomenon. Here we show that SLC5A8 transports dichloroacetate very effectively with high affinity. This transporter is expressed in normal cells, but the expression is silenced in tumor cells via epigenetic mechanisms. The lack of the transporter makes tumor cells resistant to the antitumor activity of dichloroacetate. However, if the transporter is expressed in tumor cells ectopically, the cells become sensitive to the drug at low concentrations. This is evident in breast cancer cells, colon cancer cells, and prostate cancer cells. Normal cells, which constitutively express the transporter, are however not affected by the compound, indicating the tumor cell-selective therapeutic activity. The mechanism of the antitumor activity of the compound is still its ability to inhibit pyruvate dehydrogenase kinase and force mitochondrial oxidation of pyruvate. Since the silencing of SLC5A8 in tumors involves DNA methylation and its expression can be induced by treatment with DNA methylation inhibitors, our findings suggest that combining dichloroacetate with a DNA methylation inhibitor would offer a means to reduce the doses of dichloroacetate to avoid detrimental effects associated with high doses but without compromising antitumor activity.
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Affiliation(s)
- E Babu
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Georgia Health Sciences University, Augusta, GA 30912, USA
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15
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Anthonysamy A, Lee Y, Karunagaran B, Ganapathy V, Rhee SW, Karthikeyan S, Kim KS, Ko MJ, Park NG, Ju MJ, Kim JK. Molecular design and synthesis of ruthenium(ii) sensitizers for highly efficient dye-sensitized solar cells. ACTA ACUST UNITED AC 2011. [DOI: 10.1039/c1jm11760b] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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16
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Kommareddi PK, Nair TS, Thang LV, Galano MM, Babu E, Ganapathy V, Kanazawa T, McHugh JB, Carey TE. Isoforms, expression, glycosylation, and tissue distribution of CTL2/SLC44A2. Protein J 2010; 29:417-26. [PMID: 20665236 DOI: 10.1007/s10930-010-9268-y] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Antibodies to the solute carrier protein, CTL2/SLC44A2, cause hearing loss in animals, are frequently found in autoimmune hearing loss patients, and are implicated in transfusion-related acute lung injury. We cloned a novel CTL2/SLC44A2 isoform (CTL2 P1) from inner ear and identified an alternate upstream promoter and exon 1a encoding a protein of 704 amino acids which differs in the first 10-12 amino acids from the known exon 1b isoform (CTL2 P2; 706 amino acids). The expression of these CTL2/SLC44A2 isoforms, their posttranslational modifications in tissues and their localization in HEK293 cells expressing rHuCTL2/SLC44A2 were assessed. P1 and P2 isoforms with differing glycosylation are variably expressed in cochlea, tongue, heart, colon, lung, kidney, liver and spleen suggesting tissue specific differences that may influence function in each tissue. Because antibodies to CTL2/SLC44A2 have serious pathologic consequences, it is important to understand its distribution and modifications. Heterologous expression in X. laevis oocytes shows that while human CTL2-P1 does not transport choline, human CTL2-P2 exhibits detectable choline transport activity.
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Affiliation(s)
- P K Kommareddi
- Kresge Hearing Research Institute, Department of Otolaryngology/Head and Neck Surgery, The University of Michigan, 1150 West Medical Center Drive, Room 5311 Medical Science I, Ann Arbor, MI 48109-5516, USA
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17
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Kwon IK, Wang R, Thangaraju M, Shuang H, Liu K, Dashwood R, Dulin N, Ganapathy V, Browning DD. PKG inhibits TCF signaling in colon cancer cells by blocking beta-catenin expression and activating FOXO4. Oncogene 2010; 29:3423-34. [PMID: 20348951 DOI: 10.1038/onc.2010.91] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Activation of cGMP-dependent protein kinase (PKG) has anti-tumor effects in colon cancer cells but the mechanisms are not fully understood. This study has examined the regulation of beta-catenin/TCF signaling, as this pathway has been highlighted as central to the anti-tumor effects of PKG. We show that PKG activation in SW620 cells results in reduced beta-catenin expression and a dramatic inhibition of TCF-dependent transcription. PKG did not affect protein stability, nor did it increase phosphorylation of the amino-terminal Ser33/37/Thr41 residues that are known to target beta-catenin for degradation. However, we found that PKG potently inhibited transcription from a luciferase reporter driven by the human CTNNB1 promoter, and this corresponded to reduced beta-catenin mRNA levels. Although PKG was able to inhibit transcription from both the CTNNB1 and TCF reporters, the effect on protein levels was less consistent. Ectopic PKG had a marginal effect on beta-catenin protein levels in SW480 and HCT116 but was able to inhibit TCF-reporter activity by over 80%. Investigation of alternative mechanisms revealed that cJun-N-terminal kinase (JNK) activation was required for the PKG-dependent regulation of TCF activity. PKG activation caused beta-catenin to bind to FOXO4 in colon cancer cells, and this required JNK. Activation of PKG was also found to increase the nuclear content of FOXO4 and increase the expression of the FOXO target genes MnSOD and catalase. FOXO4 activation was required for the inhibition of TCF activity as FOXO4-specific short-interfering RNA completely blocked the inhibitory effect of PKG. These data illustrate a dual-inhibitory effect of PKG on TCF activity in colon cancer cells that involves reduced expression of beta-catenin at the transcriptional level, and also beta-catenin sequestration by FOXO4 activation.
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Affiliation(s)
- I-K Kwon
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, GA, USA
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18
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Deuther-Conrad W, Patt JT, Lockman PR, Allen DD, Patt M, Schildan A, Ganapathy V, Steinbach J, Sabri O, Brust P. Norchloro-fluoro-homoepibatidine (NCFHEB) - a promising radioligand for neuroimaging nicotinic acetylcholine receptors with PET. Eur Neuropsychopharmacol 2008; 18:222-9. [PMID: 17728108 DOI: 10.1016/j.euroneuro.2007.07.002] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/20/2007] [Revised: 06/27/2007] [Accepted: 07/05/2007] [Indexed: 11/15/2022]
Abstract
Cholinergic neurotransmission depends on the integrity of nicotinic acetylcholine receptors (nAChRs), and impairment of both is characteristic for various neurodegenerative diseases. Visualization of specific receptor subtypes by positron emission tomography (PET) has potential to assist with diagnosis of such neurodegenerative diseases and with design of suitable therapeutic approaches. The goal of our study was to evaluate in vivo the potential of (18)F-labelled (+)- and (-)-norchloro-fluoro-homoepibatidine ([(18)F]NCFHEB) in comparison to 2-[(18)F]F-A-85380 as PET tracers. In the brains of NMRI mice, highest levels of radioactivity were detected at 20 min post-injection of (+)-[(18)F]NCFHEB, (-)-[(18)F]NCFHEB, and 2-F-[(18)F]-A-85380 (7.45, 5.60, and 3.2% ID/g tissue, respectively). No marked pharmacological adverse effects were observed at 25 mug NCFHEB/kg. Uptake studies in RBE4 cells and in situ perfusion studies suggest an interaction of epibatidine and NCFHEB with the carrier-mediated choline transport at the blood-brain barrier. The data indicate that (+)- and (-)-[(18)F]NCFHEB have potential for further development as PET tracers.
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Affiliation(s)
- W Deuther-Conrad
- Institute of Interdisciplinary Isotope Research, Permoserstrasse 15, 04318 Leipzig, Germany.
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19
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Gopal E, Umapathy NS, Martin PM, Ananth S, Gnana-Prakasam JP, Becker H, Wagner CA, Ganapathy V, Prasad PD. Cloning and functional characterization of human SMCT2 (SLC5A12) and expression pattern of the transporter in kidney. Biochim Biophys Acta 2007; 1768:2690-7. [PMID: 17692818 PMCID: PMC2703486 DOI: 10.1016/j.bbamem.2007.06.031] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2007] [Revised: 06/07/2007] [Accepted: 06/21/2007] [Indexed: 11/21/2022]
Abstract
Recently, we cloned two Na(+)-coupled lactate transporters from mouse kidney, a high-affinity transporter (SMCT1 or slc5a8) and a low-affinity transporter (SMCT2 or slc5a12). Here we report on the cloning and functional characterization of human SMCT2 (SLC5A12) and compare the immunolocalization patterns of slc5a12 and slc5a8 in mouse kidney. The human SMCT2 cDNA codes for a protein consisting of 618 amino acids. When expressed in mammalian cells or Xenopus oocytes, human SMCT2 mediates Na(+) -coupled transport of lactate, pyruvate and nicotinate. The affinities of the transporter for these substrates are lower than those reported for human SMCT1. Several non-steroidal anti-inflammatory drugs inhibit human SMCT2-mediated nicotinate transport, suggesting that NSAIDs interact with the transporter as they do with human SMCT1. Immunofluorescence microscopy of mouse kidney sections with an antibody specific for SMCT2 shows that the transporter is expressed predominantly in the cortex. Similar studies with an anti-SMCT1 antibody demonstrate that SMCT1 is also expressed mostly in the cortex. Dual-labeling of SMCT1 and SMCT2 with 4F2hc (CD98), a marker for basolateral membrane of proximal tubular cells in the S1 and S2 segments of the nephron, shows that both SMCT1 and SMCT2 are expressed in the apical membrane of the tubular cells. These studies also show that while SMCT2 is broadly expressed along the entire length of the proximal tubule (S1/S2/S3 segments), the expression of SMCT1 is mostly limited to the S3 segment. These studies suggest that the low-affinity transporter SMCT2 initiates lactate absorption in the early parts of the proximal tubule followed by the participation of the high-affinity transporter SMCT1 in the latter parts of the proximal tubule.
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Affiliation(s)
- E. Gopal
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, Georgia, 30912, U.S.A
| | - N. S. Umapathy
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, Georgia, 30912, U.S.A
| | - P. M. Martin
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, Georgia, 30912, U.S.A
| | - S. Ananth
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, Georgia, 30912, U.S.A
| | - J. P. Gnana-Prakasam
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, Georgia, 30912, U.S.A
| | - H. Becker
- Institute of Physiology and Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland
| | - C. A. Wagner
- Institute of Physiology and Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland
| | - V. Ganapathy
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, Georgia, 30912, U.S.A
| | - P. D. Prasad
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, Georgia, 30912, U.S.A
- Corresponding author: Dr. Puttur D. Prasad, Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, GA 30912-2100, U.S.A. Phone: 706-721-1761, Fax: 706-721-3891, E-mail:
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20
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Baisden B, Sonne S, Joshi RM, Ganapathy V, Shekhawat PS. Antenatal dexamethasone treatment leads to changes in gene expression in a murine late placenta. Placenta 2007; 28:1082-90. [PMID: 17559929 PMCID: PMC2040329 DOI: 10.1016/j.placenta.2007.04.002] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/05/2007] [Revised: 03/30/2007] [Accepted: 04/06/2007] [Indexed: 11/29/2022]
Abstract
Antenatal steroids like dexamethasone (DEX) are used to augment fetal lung maturity and there is a major concern that they impair fetal growth. If delivery is delayed after using antenatal DEX, placental function and hence fetal growth may be compromised even further. To investigate the effects of DEX on placental function, we treated 9 pregnant C57/BL6 mice with DEX and 9 pregnant mice were injected with saline to serve as controls. Placental gene expression was studied using microarrays in 3 pairs and other 6 pairs were used to confirm microarray results by semi-quantitative RT-PCR, real-time PCR, in situ hybridization, western blot analysis and Oligo ApopTaq assay. DEX-treated placentas were hydropic, friable, pale, and weighed less (80.0+/-15.1mg compared to 85.6.8+/-7.6mg, p=0.05) (n=62 placentas). Fetal weight was significantly reduced after DEX use (940+/-32mg compared to 1162+/-79mg, p=0.001) (n=62 fetuses). There was >99% similarity within and between the three gene chip data sets. DEX led to down-regulation of 1212 genes and up-regulation of 1382 genes. RT-PCR studies showed that DEX caused a decrease in expression of genes involved in cell division such as cyclins A2, B1, D2, cdk 2, cdk 4 and M-phase protein kinase along with growth-promoting genes such as EGF-R, BMP4 and IGFBP3. Oligo ApopTaq assay and western blot studies showed that DEX-treatment increased apoptosis of trophoblast cells. DEX-treatment led to up-regulation of aquaporin 5 and tryptophan hydroxylase genes as confirmed by real-time PCR, and in situ hybridization studies. Thus antenatal DEX treatment led to a reduction in placental and fetal weight, and this effect was associated with a decreased expression of several growth-promoting genes and increased apoptosis of trophoblast cells.
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Affiliation(s)
- B Baisden
- Department of Pediatrics, Medical College of Georgia, Augusta, GA 30912, USA
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21
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Abstract
We describe a premature infant with early cystic lung lesions and sepsis due to prenatally acquired Capnocytophaga infection. Early cystic lesions have not been described previously as a characteristic of this infection.
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Affiliation(s)
- A A Howlett
- Department of Pediatrics, Dalhousie University, Halifax, Nova Scotia, Canada.
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Dun Y, Mysona B, Itagaki S, Martin-Studdard A, Ganapathy V, Smith S. Functional and molecular analysis of D-serine transport in retinal Müller cells. Exp Eye Res 2006; 84:191-9. [PMID: 17094966 PMCID: PMC3773703 DOI: 10.1016/j.exer.2006.09.015] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2006] [Revised: 09/21/2006] [Accepted: 09/22/2006] [Indexed: 12/31/2022]
Abstract
D-serine, an endogenous co-agonist of NMDA receptors in vertebrate retina, may modulate glutamate sensitivity of retinal neurons. This study determined at the functional and molecular level the transport process responsible for D-serine in retinal Müller cells. RT-PCR and immunoblotting showed that serine racemase (SR), the synthesizing enzyme for D-serine, is expressed in the rMC-1 Müller cell line and primary cultures of mouse Müller cells (1 degrees MCs). The relative contributions of different amino acid transport systems to d-serine uptake were determined based on differential substrate specificities and ion dependencies. D-serine uptake was obligatorily dependent on Na+, eliminating Na+-independent transporters (asc-1 and system L) for D-serine in Müller cells. The Na+:substrate stoichiometry for the transport process was 1:1. D-serine transport was inhibited by alanine, serine, cysteine, glutamine, and asparagine, but not anionic amino acids or cationic amino acids, suggesting that D-serine transport in Müller cells occurs via ASCT2 rather than ASCT1 or ATB0,+. The expression of mRNAs specific for ASCT1, ASCT2, and ATB0,+ was analyzed by RT-PCR confirming the expression of ASCT2 (and ASCT1) mRNA, but not ATB0,+, in Müller cells. Immunoblotting detected ASCT2 in neural retina and in 1 degrees MCs; immunohistochemistry confirmed these data in retinal sections and in cultures of 1 degrees MCs. The efflux of D-serine via ASCT2 by ASCT2 substrates was demonstrable using the Xenopus laevis oocyte heterologous expression system. These data provide the first molecular evidence for SR and ASCT2 expression in a Müller cell line and in 1 degrees MCs and suggest that D-serine, synthesized in Müller cells by SR, is effluxed via ASCT2 to regulate NMDA receptors in adjacent neurons.
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Affiliation(s)
- Y. Dun
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta, GA
| | - B. Mysona
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta, GA
| | - S. Itagaki
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, GA
| | - A. Martin-Studdard
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta, GA
| | - V. Ganapathy
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, GA
| | - S.B. Smith
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta, GA
- Department of Ophthalmology, Medical College of Georgia, Augusta, GA
- Please send correspondence to: Sylvia B. Smith, Ph.D., Department of Cellular Biology and Anatomy, Medical College of Georgia, 1459 Laney-Walker Blvd., CB 2820, Augusta, GA 30912-2000, 706-721-7392 (phone), 706-721-6839 (fax),
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Devipriya S, Ganapathy V, Shyamaladevi CS. Suppression of tumor growth and invasion in 9,10 dimethyl benz(a) anthracene induced mammary carcinoma by the plant bioflavonoid quercetin. Chem Biol Interact 2006; 162:106-13. [PMID: 16846595 DOI: 10.1016/j.cbi.2006.04.002] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2005] [Revised: 03/31/2006] [Accepted: 04/03/2006] [Indexed: 11/26/2022]
Abstract
Administration of quercetin, a common polyphenolic component of many vascular and edible plants including vegetables, fruits and tea significantly reduced the tumor volume in rats induced for mammary carcinoma using dimethyl benz (a) anthracene (DMBA). Dose response was assessed, by treating the animals with different doses (15-45 mg/kgbw) of quercetin and 25 mg/kgbw was taken as effective dose. Quercetin was administered as an intra tumoral injection once a week for 4 weeks. Serum levels of carcino embryonic antigen (CEA), a potent marker for tumor growth and invasion was significantly decreased on quercetin treatment. Quercetin caused a significant decrease in the activities of acid phosphatase and Cathepsin D in serum of experimental animals. Activities of lysosomal enzymes- (beta-D galactosidase, beta-D glucuronidase, beta-D glucosidase and sialidase), in serum and tissue were significantly altered in DMBA animals compared to control animals. However, quercetin treatment caused no significant change in lysosomal enzyme activities in tissues, whereas the activities were significantly lowered in serum. Partial purification of tissue type plasminogen activator (t-PA) from the tumor and kidney showed increased activity in the DMBA induced animals. Serum urokinase, -like plasminogen activator (u-PA) was also increased in animals with tumor, indicating tumor invasion. Administration of quercetin caused a significant decrease of both t-PA and u-PA. In conclusion, the present study suggests the possible role of quercetin in primary and invasive mammary tumor treatment. The above observations in vivo warrant further studies, due to the easy availability, common occurrence and low toxicity of this dietary bioflavonoid.
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Abstract
ATB(0,+) is a unique amino acid transporter because of its broad substrate specificity and concentrative ability. This transporter recognizes neutral as well as cationic amino acids. It is energized by Na(+) and Cl(-) gradients and membrane potential. Many of the amino acids and amino acid derivatives that are substrates for ATB(0,+) serve as therapeutic agents (e.g., D-serine, carnitine, and nitric oxide synthase inhibitors). Recent studies have shown that the potential of ATB(0,+) as a drug delivery system may be greater than previously envisaged. ATB(0,+) can transport antiviral drugs such as acyclovir and ganciclovir when they are covalently coupled to the side chain of anionic amino acids. Chemical modification of the carboxyl groups in the side chain of aspartate and glutamate with drugs converts these anionic amino acids into neutral amino acid derivatives. Therefore, the modified drugs are recognized by ATB(0,+). Interestingly, even when acyclovir and ganciclovir are coupled as esters with alpha-carboxyl group of neutral amino acids, the modified drugs are transported via ATB(0,+). Similarly, the hydroxyl group in the side chains of serine and threonine can also be used to covalently couple drugs for delivery into cells via ATB(0,+). This increases the potential for designing a wide variety of amino acid-based prodrugs that can utilize ATB(0,+) as drug delivery system. Furthermore, the transporter is expressed in the colon, lung, and eye, the tissues easily amenable for drug delivery. These findings argue strongly in support of ATB(0,+) as a potential delivery system for a wide variety of drugs and prodrugs.
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Affiliation(s)
- M E Ganapathy
- Department of Medicine, Medical College of Georgia, Augusta, GA 30912, USA.
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25
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Miyauchi S, Srinivas SR, Fei YJ, Gopal E, Umapathy NS, Wang H, Conway SJ, Ganapathy V, Prasad PD. Functional characteristics of NaS2, a placenta-specific Na+-coupled transporter for sulfate and oxyanions of the micronutrients selenium and chromium. Placenta 2005; 27:550-9. [PMID: 16129486 DOI: 10.1016/j.placenta.2005.05.004] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/25/2005] [Revised: 05/06/2005] [Accepted: 05/10/2005] [Indexed: 11/29/2022]
Abstract
NaS2 is a Na+-coupled transporter for sulfate that belongs to the SLC13 gene family. This transporter was originally cloned from high endothelial venule endothelial cells, but nothing is known about the functional characteristics of this transporter except that it transports sulfate in a Na+-coupled manner. Northern blot analysis indicates that NaS2 is expressed most robustly in placenta. In the present study, we cloned NaS2 from rat placenta and characterized its transport function in detail using the Xenopus laevis oocyte expression system. Rat NaS2 consists of 629 amino acids and is highly similar to human NaS2. In situ hybridization studies with mouse placental sections show that NaS2 transcripts are expressed primarily in trophoblasts of the labyrinth zone. The expression of the transporter is confirmed in primary cultures of trophoblasts isolated from human placenta. When expressed in X. laevis oocytes, rat NaS2 mediates Na+-coupled transport of sulfate. The transport of sulfate is inhibited by oxyanions of selenium, chromium, arsenic, molybdenum, and phosphorous, suggesting that the transporter may mediate the transport of these oxyanions in addition to sulfate. The Kt for sulfate is 153+/-30 microM and the Na+:sulfate stoichiometry is 3:1. The transport process is electrogenic as evidenced from the inhibition of the uptake process by K+-induced depolarization. We conclude that NaS2 is a placenta-specific Na+-coupled, electrogenic, transporter for sulfate expressed in trophoblasts and that it is also responsible for the transport of oxyanions of the micronutrients selenium and chromium.
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Affiliation(s)
- S Miyauchi
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, GA 30912, USA
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Ganapathy V, Shyamala Devi CS. Effect of histone H1 on the cytosolic calcium levels in human breast cancer MCF 7 cells. Life Sci 2005; 76:2631-41. [PMID: 15769486 DOI: 10.1016/j.lfs.2005.01.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2004] [Accepted: 01/03/2005] [Indexed: 11/20/2022]
Abstract
In human breast cancer MCF 7 cells, the effect of exogenous histone H1 on intracellular calcium ([Ca2+]i) levels was measured using Fura 2AM. The dose and time dependent assessment revealed significant cell killing effect of histone H1 on MCF 7 cells. Histone H1 induced a sustained concentration dependent increase in [Ca2+]i levels in the presence of calcium in the medium, but the increase was reduced in the absence of extra cellular calcium. The effect of histone H1 on intracellular calcium flux measured using 45Ca radiolabel revealed significant inhibition of calcium uptake in endoplasmic reticulum, whereas the rate of uptake was unaltered in the mitochondria. The activities of phospholipase A2 showed a significant transient increase at 1 minute which by the end of 5 minutes decreased, whereas the activities of phospholipase C which showed a transient increase at the end of 1 minute, was maintained at basal levels in histone H1 treated cells compared to control cells. These findings suggest that histone H1 increases [Ca2+]i in MCF 7 cells by stimulating both extra cellular calcium influx and intracellular calcium release at higher concentrations exhibiting cytotoxic effect.
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Affiliation(s)
- Vani Ganapathy
- Department of Biochemistry, University of Madras, Guindy campus, Chennai-600 025, India
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Abstract
SLC5A8 is a candidate tumour suppressor gene that is silenced in colon cancer, gastric cancer and possibly other cancers in humans. This gene codes for a transporter belonging to the Na+/glucose co-transporter gene family (SLC5). The cancer-associated silencing of the gene involves hypermethylation of CpG islands present in exon 1 of the gene. SLC5A8 is expressed in colon, ileum, kidney and thyroid gland. The protein coded by the gene mediates the Na+-coupled and electrogenic transport of a variety of monocarboxylates, including short-chain fatty acids, lactate and nicotinate. It may also transport iodide. The normal physiological function of this transporter in the intestinal tract and kidney is likely to facilitate the active absorption of short-chain fatty acids, lactate and nicotinate. One of the short-chain fatty acids that serves as a substrate for SLC5A8 is butyrate. This fatty acid is an inhibitor of histone deacetylases and is known to induce apoptosis in a variety of tumours including colonic tumour. Since butyrate is produced in the colonic lumen at high concentrations by bacterial fermentation of dietary fibre, we speculate that the ability of SLC5A8 to mediate the entry of this short-chain fatty acid into colonic epithelial cells underlies the potential tumour suppressor function of this transporter.
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Affiliation(s)
- V Ganapathy
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, GA 30912, USA.
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Alteheld B, Evans ME, Gu LH, Ganapathy V, Leibach FH, Jones DP, Ziegler TR. Alanylglutamine dipeptide and growth hormone maintain PepT1-mediated transport in oxidatively stressed Caco-2 cells. J Nutr 2005; 135:19-26. [PMID: 15623827 DOI: 10.1093/jn/135.1.19] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Reactive oxygen species (ROS) produced by gut mucosal cells during conditions such as inflammatory bowel disease (IBD) may impair mucosal repair and nutrient transport/absorptive function. Absorption of di- and tripeptides in the small intestine and colon is mediated by the H(+)-dependent transporter PepT1, but effects of oxidative stress on di- and tripeptide transport are unknown. We assessed whether exposure to hydrogen peroxide (H(2)O(2)) influences dipeptide transport in human colonic epithelial (Caco-2) cells. Uptake of [(14)C]glycylsarcosine (Gly-Sar) was used to evaluate PepT1-mediated dipeptide transport. Exposure to 1-5 mmol/L H(2)O(2) for 24 h caused a dose-dependent decrease in Gly-Sar transport, which was associated with decreased PepT1 transport velocity (V(max)). Treatment with alanylglutamine (Ala-Gln) or growth hormone (GH) did not alter Caco-2 Gly-Sar transport in the absence of H(2)O(2). However, both Ala-Gln and GH prevented the decrease in dipeptide transport observed with 1 mmol/L H(2)O(2) treatment. Ala-Gln, but not GH, maintained cellular glutathione and prevented the decrease in PepT1 protein expression. Thus, these agents should be further investigated as potential therapies to improve absorption of small peptides in disorders associated with oxidative injury to the gut mucosa.
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Affiliation(s)
- B Alteheld
- Department of Nutrition Science, University of Bonn, Germany
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Gupta N, Miyauchi S, Martindale R, Moore-Martin P, Podolsky R, Ganapathy V. Mitoxantrone Resistance protein (MXR) is down-regulated in colorectal cancer. J Surg Res 2004. [DOI: 10.1016/j.jss.2004.07.107] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Baird FE, Beattie KJ, Hyde AR, Ganapathy V, Rennie MJ, Taylor PM. Bidirectional substrate fluxes through the system N (SNAT5) glutamine transporter may determine net glutamine flux in rat liver. J Physiol 2004; 559:367-81. [PMID: 15218073 PMCID: PMC1665133 DOI: 10.1113/jphysiol.2003.060293] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
System N (SNAT3 and SNAT5) amino acid transporters are key mediators of glutamine transport across the plasma membrane of mammalian cell types, including hepatocytes and astrocytes. We demonstrate that SNAT5 shows simultaneous bidirectional glutamine fluxes when overexpressed in Xenopus oocytes. Influx and efflux are both apparently Na+ dependent but, since they are not directly coupled, the carrier is capable of mediating net amino acid movement across the cell membrane. The apparent Km values for glutamine influx and efflux are similar (approximately 1 mm) and the transporter behaviour is consistent with a kinetic model in which re-orientation of the carrier from outside- to inside-facing conformations (either empty or substrate loaded) is the limiting step in the transport cycle. In perfused rat liver, the observed relationship between influent (portal) glutamine concentration and net hepatic glutamine flux may be described by a simple kinetic model, assuming the balance between influx and efflux through System N determines net flux, where under physiological conditions efflux is generally saturated owing to high intracellular glutamine concentration. SNAT5 shows a more periportal mRNA distribution than SNAT3 in rat liver, indicating that SNAT5 may have particular importance for modulation of net hepatic glutamine flux.
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Affiliation(s)
- F E Baird
- Division of Molecular Physiology, School of Life Sciences, University of Dundee, Dundee DD1 5EH, UK
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31
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Prasad P, Leibach F, Mahesh V, Ganapathy V. Human placenta as a target organ for cocaine action: Interaction of cocaine with the placental serotonin transporter. Int J Gynaecol Obstet 2004. [DOI: 10.1016/0020-7292(94)90591-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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32
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Gupta N, Miyauchi S, Ganapathy V, Podolsky R, Tuszynski GP, Albo D. Angiocidin, a novel thrombospondin-1 receptor, and matrix metalloproteinase-9 are up-regulated in colon cancer. Ann Surg Oncol 2004. [DOI: 10.1007/bf02524145] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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33
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Gupta N, Miyauchi S, Martindale R, Herdman A, Hu H, Podolsky R, Mager S, Ganapathy V. Upregulation of the arginine transporter Atb(0,+) in colorectal cancer. J Surg Res 2003. [DOI: 10.1016/j.jss.2003.08.218] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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34
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Rausch JL, Johnson ME, Corley KM, Hobby HM, Shendarkar N, Fei Y, Ganapathy V, Leibach FH. Depressed patients have higher body temperature: 5-HT transporter long promoter region effects. Neuropsychobiology 2003; 47:120-7. [PMID: 12759553 DOI: 10.1159/000070579] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
BACKGROUND Depression has been associated with a decrease in intracellular serotonin (5-HT) reuptake through its transporter, SERT. The 5-HT transporter long promoter region (5-HTTLPR) deletion in the SERT gene has also been associated with a decrease in 5-HT reuptake. Conversely, increases in extracellular 5-HT have been associated with increased temperature. It has not been established, however, whether body temperature in depressed patients is different from controls. Here, we hypothesized that temperature would be increased in depressed patients as well as in those with the 5-HTTLPR deletion. METHODS A strict oral temperature protocol employed single, cross-sectional, naturalistic time-of-day temperature measures in 125 subjects (46 normal controls, 79 outpatients with major depression). Controls and depressed patients were free of psychotropic medication and classified by the Structured Clinical Interview for Psychiatric Diagnoses. Eighty-one of the subjects (68 depressed, 13 normal) were additionally genotyped for 5-HTTLPR polymorphisms. RESULTS Depressed patients had a significantly higher uncorrected body temperature (mean +/- SD 98.38 +/- 0.61 degrees F) than controls (mean +/- SD 98.13 +/- 0.59 degrees F; F = 4.8, p = 0.03). An age (F = 14.09, p < 0.001) and time-of-day (11.4, p = 0.001) correction revealed a more robust (F = 14.02, p < 0.001) difference between depressed patients (mean +/- SD 98.44 +/- 0.55 degrees F) and controls (mean +/- SD 98.02 +/- 0.56 degrees F). When normalized for age and circadian differences between subjects, random, outpatient oral temperatures had a sensitivity of 63% and a specificity of 76% in identifying the depressed subjects from the controls. Independent of depression, subjects with the 5-HTTLPR deletion (short SERT allele) were warmer (mean +/- SD 98.33 +/- 0.65 degrees F) than those lacking the short allele on either chromosome (mean +/- SD 97.91 +/- 0.69 degrees F; F = 7.0, p = 0.01). However, the genotype did not explain the temperature differences between controls and depressed patients. CONCLUSION This is the first demonstration of an increased daytime body temperature in cases with major depression. Subjects with a corrected temperature above 98.3 degrees F were 2.6-fold more likely to be depressed. The results may strengthen the hypothesis of an inflammatory component of depression. In addition, the findings suggest a potential link between genetic differences in 5-HT transport and body temperature.
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Affiliation(s)
- J L Rausch
- Department of Psychiatry and Health Behavior, Veterans Administration, The Medical College of Georgia, Augusta, GA 30912, USA.
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35
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Nelson DM, Smith SD, Furesz TC, Sadovsky Y, Ganapathy V, Parvin CA, Smith CH. Hypoxia reduces expression and function of system A amino acid transporters in cultured term human trophoblasts. Am J Physiol Cell Physiol 2003; 284:C310-5. [PMID: 12388062 DOI: 10.1152/ajpcell.00253.2002] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We tested the hypothesis that hypoxia diminishes the expression and transport of neutral amino acids by system A in full-term human trophoblasts. Cytotrophoblasts from normal human placentas were cultured in standard conditions of 20% O(2) or in 1% and 3% O(2) for 24 h before assay. Neutral amino acid transport for systems A, ASC, and L was assayed at 24 and 72 h by the cluster-tray technique. Hypoxia during the initial 24 h of culture reduced system A transport by 82% in 1% O(2) and by 37% in 3% O(2) (P < 0.01) compared with standard conditions. Hypoxia during the latter 24 h of the 72 h in culture reduced system A transport by 55% in 1% O(2) and by 20% in 3% O(2) (P < 0.05) compared with standard conditions at 72 h. Hypoxia (1% O(2)) also reduced total amino acid transport by 40% in the more differentiated syncytiotrophoblasts present at 72 h. Northern analysis of trophoblasts in standard conditions showed that subtypes of human amino acid transporter A (hATA1 and hATA2) were each expressed in cytotrophoblasts and syncytiotrophoblasts. Hypoxia decreased expression of hATA1 and hATA2 in both trophoblast phenotypes. We conclude that hypoxia downregulates system A transporter expression and activity in cultured human trophoblasts.
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Affiliation(s)
- D M Nelson
- Department of Obstetrics and Gynecology, Washington University School of Medicine, St. Louis, Missouri 63110-1094, USA.
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Abstract
Multiple kinase pathways determine serotonin transporter (SERT) regulation. We hypothesized a decrease in kinase expression with chronic selective serotonin reuptake inhibitor (SSRI) administration necessary to regulate extracellular serotonin. We studied whole brain kinase mRNA expression on Affymetrix gene chips in rats treated with placebo 3 and 21 days, fluoxetine 3 and 21 days, and citalopram 21 days. Protein kinase C (PKC)-delta, PKC-gamma, stress-activated protein kinase, cAMP-dependent protein kinase beta isoform, Janus protein kinase, and phosphofructokinase M were all down regulated chronically with citalopram and fluoxetine, but not with acute fluoxetine. The results are consistent with homeostasis of SERT function through a decrease in PK expression.
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Affiliation(s)
- J L Rausch
- Veterans Administration, Medical College of Georgia, Augusta, GA 30912, USA.
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Kennedy DJ, Leibach FH, Ganapathy V, Thwaites DT. Optimal absorptive transport of the dipeptide glycylsarcosine is dependent on functional Na+/H+ exchange activity. Pflugers Arch 2002; 445:139-46. [PMID: 12397398 DOI: 10.1007/s00424-002-0910-1] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2002] [Accepted: 07/05/2002] [Indexed: 10/27/2022]
Abstract
Optimal nutrient absorption across the intestinal epithelium is dependent on the co-ordinated activity of a number of membrane transporters. Di/tripeptide transport across the luminal membrane of the intestinal enterocyte is mediated by the H(+)-coupled di/tripeptide transporter hPepT1. hPepT1 function is dependent on the existence of a pH gradient (maintained, in part, by the action of the Na(+)/H(+) exchanger NHE3) across the apical membrane of the small intestinal epithelium. The physiological problem addressed here was to determine how two transporters (hPepT1 and NHE3), involved in nutrient absorption and pH(i) homeostasis, function co-operatively to maximise dipeptide absorption when both operate sub-optimally at typical mucosal surface pH values (pH 6.1-6.8). Functional hPepT1 activity in human intestinal epithelial (Caco-2) cell monolayers was determined by measurement of apical uptake and apical-to-basolateral transport of the dipeptide glycylsarcosine. The dependence of hPepT1 on NHE3 activity was measured (either after Na(+) removal or addition of the NHE3-selective inhibitor S1611) using both Caco-2 cell monolayers and hPepT1-expressing Xenopus laevis oocytes. Apical glycylsarcosine uptake in Caco-2 cell monolayers was modulated by apical pH, extracellular Na(+), incubation time and S1611. Uptake in hPepT1-expressing oocytes was independent of Na(+) or S1611. We conclude that functional NHE3 activity is required to allow optimal absorption of dipeptides across the human intestinal epithelium.
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Affiliation(s)
- D J Kennedy
- Department of Physiological Sciences, Medical School, University of Newcastle-upon-Tyne, Newcastle-upon-Tyne NE2 4HH, UK
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38
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Bridges CC, Ola MS, Prasad PD, El-Sherbeny A, Ganapathy V, Smith SB. Regulation of taurine transporter expression by NO in cultured human retinal pigment epithelial cells. Am J Physiol Cell Physiol 2001; 281:C1825-36. [PMID: 11698241 PMCID: PMC4637984 DOI: 10.1152/ajpcell.2001.281.6.c1825] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Taurine is actively transported at the retinal pigment epithelial (RPE) apical membrane in an Na(+)- and Cl(-)-dependent manner. Diabetes may alter the function of the taurine transporter. Because nitric oxide (NO) is a molecule implicated in the pathogenesis of diabetes, we asked whether NO would alter the activity of the taurine transporter in cultured ARPE-19 cells. The activity of the transporter was stimulated in the presence of the NO donor 3-morpholinosydnonimine. The stimulatory effects of 3-morpholinosydnonimine were not observed during the initial 16-h treatment; however, stimulation of taurine uptake was elevated dramatically above control values with 20- and 24-h treatments. Kinetic analysis revealed that the stimulation was associated with an increase in the maximal velocity of the transporter with no significant change in the substrate affinity. The NO-induced increase in taurine uptake was inhibited by actinomycin D and cycloheximide. RT-PCR analysis and nuclear run-on assays provided evidence for upregulation of the transporter gene. This study provides the first evidence of an increase in taurine transporter gene expression in human RPE cells cultured under conditions of elevated levels of NO.
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Affiliation(s)
- C C Bridges
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta, Georgia 30912, USA
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39
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Nakanishi T, Kekuda R, Fei YJ, Hatanaka T, Sugawara M, Martindale RG, Leibach FH, Prasad PD, Ganapathy V. Cloning and functional characterization of a new subtype of the amino acid transport system N. Am J Physiol Cell Physiol 2001; 281:C1757-68. [PMID: 11698233 DOI: 10.1152/ajpcell.2001.281.6.c1757] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have cloned a new subtype of the amino acid transport system N2 (SN2 or second subtype of system N) from rat brain. Rat SN2 consists of 471 amino acids and belongs to the recently identified glutamine transporter gene family that consists of system N and system A. Rat SN2 exhibits 63% identity with rat SN1. It also shows considerable sequence identity (50-56%) with the members of the amino acid transporter A subfamily. In the rat, SN2 mRNA is most abundant in the liver but is detectable in the brain, lung, stomach, kidney, testis, and spleen. When expressed in Xenopus laevis oocytes and in mammalian cells, rat SN2 mediates Na(+)-dependent transport of several neutral amino acids, including glycine, asparagine, alanine, serine, glutamine, and histidine. The transport process is electrogenic, Li(+) tolerant, and pH sensitive. The transport mechanism involves the influx of Na(+) and amino acids coupled to the efflux of H(+), resulting in intracellular alkalization. Proline, alpha-(methylamino)isobutyric acid, and anionic and cationic amino acids are not recognized by rat SN2.
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Affiliation(s)
- T Nakanishi
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, Georgia 30912, USA
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Hatanaka T, Huang W, Martindale RG, Ganapathy V. Differential influence of cAMP on the expression of the three subtypes (ATA1, ATA2, and ATA3) of the amino acid transport system A. FEBS Lett 2001; 505:317-20. [PMID: 11566196 DOI: 10.1016/s0014-5793(01)02848-4] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Treatment of HepG2 cells with forskolin led to 60-100% stimulation of system A activity, measured as the Na+-dependent uptake of alpha-(methylamino)isobutyric acid. The stimulation was reproducible with cholera toxin and dibutyryl cAMP, and inhibitable by H7, a non-specific protein kinase inhibitor. The stimulatory effect was eliminated by cycloheximide and actinomycin D. The forskolin effect was associated with an increase in the maximal velocity of the transport system, with no change in substrate affinity. These cells express three different subtypes of system A (ATA1, ATA2, and ATA3). Treatment with forskolin increased the steady-state levels of ATA1 and ATA2 mRNAs, but decreased that of ATA3 mRNA.
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Affiliation(s)
- T Hatanaka
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, GA 30912, USA
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Avissar NE, Ryan CK, Ganapathy V, Sax HC. Na(+)-dependent neutral amino acid transporter ATB(0) is a rabbit epithelial cell brush-border protein. Am J Physiol Cell Physiol 2001; 281:C963-71. [PMID: 11502573 DOI: 10.1152/ajpcell.2001.281.3.c963] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
System B(0) activity accounts for the majority of intestinal and kidney luminal neutral amino acid absorption. An amino acid transport system, called ATB(0) (also known as ASCT2), with functional characteristics similar to those of system B(0), has been recently cloned. We generated polyclonal antibodies to human and rabbit ATB(0) COOH-terminal peptides and used Western blot analysis to detect ATB(0) protein in rabbit tissues, rabbit ileal brush-border membrane vesicles (BBMV), and HeLa cells transfected with plasmids containing ATB(0) cDNAs. Immunohistochemistry was used to localize ATB(0) in rabbit kidney and intestine. In Western blots of rabbit tissues, ATB(0) was a broad smear of 78- to 85-kDa proteins. In transfected HeLa cells, ATB(0) appeared as a smear consisting of 57- to 65-kDa proteins. The highest expression was found in the kidney. ATB(0) was enriched in rabbit ileal BBMV and in HeLa cells transfected with ATB(0) cDNAs. In the kidney and in the intestine, ATB(0) was confined to the brush-border membrane (BBM) of the proximal tubular cell and of the enterocyte, respectively. Tissue and intracellular distribution of ATB(0) protein parallels that of system B(0) activity. ATB(0) protein could be the transporter responsible for system B(0) in the BBM of epithelial cells.
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Affiliation(s)
- N E Avissar
- Department of Surgery, University of Rochester Medical Center, Rochester, New York 14642, USA.
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42
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Abstract
Vitamin C [ascorbic acid (AA)] is an important antioxidant present in m M amounts in the aqueous humor. Recently, two specific transporters for vitamin C (SVCT1, SVCT2) have been cloned in the rat and the human. The aim of the present study was to characterize vitamin C transport in an immortalized human lens epithelial cell line (HLE-B3). AA uptake was linear for 120 min in experiments conducted with 14C AA + 40 microM unlabelled AA. Uptake was measured at varying AA concentrations (0.04-1 m M) in Na+-containing and Na+-free buffers for 30 min at 37 degrees C. Effect of potential inhibitors of AA transport was also examined. Presence (or absence) of SVCT1 and SVCT2 was studied by RT-PCR of HLE-B3 poly (A)+ RNA using gene specific primers. Uptake studies revealed that AA uptake was highly Na+-dependent and exhibited saturation. Na+-dependent 14C-AA uptake was strongly inhibited (85-90%) by 10 m M unlabelled AA. Incubation of HLE-B3 cells with cAMP (0.1 m M), cytocholasin B (0.1 m M) and phorbol dibutyrate (1 microM) resulted in partial inhibition (36-51%) of AA uptake. Under similar conditions, D -glucose (10 m M) and staurosporine (0.1 microM) had no effect. RT-PCR showed the presence of SVCT2 while SVCT1 could not be amplified. Exposure to the chemical oxidant tert-butylhydroperoxide (TBH) up-regulated SVCT2 gene expression in HLE-B3 cells. Our data suggest that Na+-dependent transport of AA in normal lens epithelium is most likely mediated by SVCT2 rather than by SVCT1. This transport system may be subject to regulation by oxidant stress and by various second messenger signals.
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Affiliation(s)
- R Kannan
- USC Keck School of Medicine, Los Angeles, CA 90033, USA.
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43
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Seth P, Ganapathy ME, Conway SJ, Bridges CD, Smith SB, Casellas P, Ganapathy V. Expression pattern of the type 1 sigma receptor in the brain and identity of critical anionic amino acid residues in the ligand-binding domain of the receptor. Biochim Biophys Acta 2001; 1540:59-67. [PMID: 11476895 DOI: 10.1016/s0167-4889(01)00117-3] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The type 1 sigma receptor (sigmaR1) has been shown to participate in a variety of functions in the central nervous system. To identify the specific regions of the brain that are involved in sigmaR1 function, we analyzed the expression pattern of the receptor mRNA in the mouse brain by in situ hybridization. SigmaR1 mRNA was detectable primarily in the cerebral cortex, hippocampus, and Purkinje cells of cerebellum. To identify the critical anionic amino acid residues in the ligand-binding domain of sigmaR1, we employed two different approaches: chemical modification of anionic amino acid residues and site-directed mutagenesis. Chemical modification of anionic amino acids in sigmaR1 with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide reduced the ligand-binding activity markedly. Since it is known that a splice variant of this receptor which lacks exon 3 does not have the ability to bind sigma ligands, the ligand-binding domain with its critical anionic amino acid residues is likely to be present in or around the region coded by exon 3. Therefore, each of the anionic amino acids in this region was mutated individually and the influence of each mutation on ligand binding was assessed. These studies have identified two anionic amino acids, D126 and E172, that are obligatory for ligand binding. Even though the ligand-binding function was abolished by these two mutations, the expression of these mutants was normal at the protein level. These results show that sigmaR1 is expressed at high levels in specific areas of the brain that are involved in memory, emotion and motor functions. The results also provide important information on the chemical nature of the ligand-binding site of sigmaR1 that may be of use in the design of sigmaR1-specific ligands with potential for modulation of sigmaR1-related brain functions.
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Affiliation(s)
- P Seth
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta 30912, USA
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44
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Moore P, El-sherbeny A, Roon P, Schoenlein PV, Ganapathy V, Smith SB. Apoptotic cell death in the mouse retinal ganglion cell layer is induced in vivo by the excitatory amino acid homocysteine. Exp Eye Res 2001; 73:45-57. [PMID: 11428862 DOI: 10.1006/exer.2001.1009] [Citation(s) in RCA: 104] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Homocysteine, an excitatory amino acid and a homolog of cysteine, induces neuronal cell death in brain via stimulation of N-methyl-D-aspartate (NMDA) receptors. It also selectively activates NMDA receptors of retinal ganglion cells, but it is not known if high levels of homocysteine are toxic to these cells. The purpose of this study was to determine whether increased levels of homocysteine caused death of neurons in the ganglion cell layer; if so whether this death occurred via an apoptotic mechanism and to determine the consequences of simultaneous elevation of homocysteine and glutamate, a known retinal excitotoxin, on the viability of neurons of the ganglion cell layer. C57BL/6 mice were injected intravitreally with either homocysteine or glutamate/homocysteine combined (final concentrations: 25, 75, and 200 microM); injection of glutamate (25 and 200 microM) served as a positive control. Eyes were harvested and cryosections prepared 5-6 days post-injection. Systematic morphometric analysis of retinas of mice injected with homocysteine indicated that the total number of cells in the ganglion cell layer decreased by about 23% following exposure to 200 microM homocysteine. To determine whether the neurons of the ganglion cell layer were dying by apoptosis, the TUNEL method was used and was confirmed by immunohistochemical studies of caspase-3, known to be expressed at high levels during retinal ganglion cell apoptosis. Microscopic analysis revealed significantly more TUNEL-positive cells in the ganglion cell layer in homocysteine-injected eyes than in contralateral PBS-injected eyes. Retinas injected with 75 and 200 microM homocysteine displayed significantly more TUNEL-positive neurons in the ganglion cell layer (2 and 2.9, respectively) than PBS-injected retinas (0.25). In eyes injected simultaneously with homocysteine/glutamate, the number of apoptotic cells in the ganglion cell layer almost doubled that for homocysteine or glutamate injections alone. Immunohistochemical analysis of activated caspase-3 revealed numerous positively labelled neurons in the ganglion cell layer in homocysteine and homocysteine/glutamate-injected eyes, but not in PBS-injected eyes. Quantification of this data revealed a significantly greater number of caspase-3-positive neurons in the ganglion cell layer of retinas injected with 75 and 200 microM homocysteine (2.9 and 4.4, respectively) than for PBS-injected retinas (0.5). This confirms that death of neurons in the ganglion cell layer is occurring by apoptosis. The present study provides the first evidence that homocysteine is toxic to neurons of the ganglion cell layer. In addition, it provides evidence that these retinal neurons are dying by apoptosis and it demonstrates for the first time that excitotoxic damage to neurons of the ganglion cell layer is potentiated by simultaneous elevation of homocysteine and glutamate. These findings are relevant to retinal ganglion cell death characteristic of diabetic retinopathy, which is thought to be mediated by overstimulation of the NMDA receptor.
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Affiliation(s)
- P Moore
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta, GA 30912-2000, U.S.A
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45
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Ramanathan S, Pooyan S, Stein S, Prasad PD, Wang J, Leibowitz MJ, Ganapathy V, Sinko PJ. Targeting the sodium-dependent multivitamin transporter (SMVT) for improving the oral absorption properties of a retro-inverso Tat nonapeptide. Pharm Res 2001; 18:950-6. [PMID: 11496954 DOI: 10.1023/a:1010932126662] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
PURPOSE To investigate the potential for delivering large peptides orally by altering their absorptive transport pathways and improving intestinal permeability. The absorptive transport of retro-inverso (R.I.-) K-Tat9 and R.I.-K(biotin)-Tat9, novel peptidic inhibitors of the Tat protein of HIV-1, and their interactions with human SMVT (hSMVT), a high affinity, low capacity transporter, were investigated using Caco-2 and transfected CHO cells. METHODS Following synthesis on a PAL resin using Fmoc chemistry, the transport of R.I.-K-Tat9 (0.01-25 microM) and R.I.-K(biotin)-Tat9 (0.1-25 microM) was evaluated across Caco-2 cells. The transport and kinetics of biotin, biocytin and desthiobiotin (positive controls for SMVT) were also determined. Uptake of R.I.-K-Tat9 and R.I.K(biotin)-Tat9 (both 0.1-10 microM) was determined in CHO/hSMVT and CHO/pSPORT (control) cells. RESULTS The absorptive transport of R.I.-K-Tat9 was passive, low (Pm approximately 1 x 10(-6) cm/sec) and not concentration dependent. R.I.K(biotin)-Tat9 permeability was 3.2-fold higher than R.I.-K-Tat9 demonstrating active (Ea = 9.1 kcal/mole), concentration dependent and saturable transport (Km = 3.3 microM). R.I.-K(biotin)-Tat9 uptake in CHO/hSMVT cells (Km = 1.0 microM) was - 500-fold greater than R.I.-K-Tat9 (at 10 microM). R.I.-K(biotin)-Tat9 transport in Caco-2 and CHO/hSMVT cells was significantly inhibited by known substrates of SMVT including biotin, biocytin, and desthiobiotin. Passive uptake of R.I.-K(biotin)-Tat9 was significantly greater than R.I.-K-Tat9 uptake in CHO/pSPORT cells. CONCLUSIONS These results demonstrate that the structural modification of R.I.-K-Tat9 to R.I.-K(biotin)-Tat9 altered its intestinal transport pathway resulting in a significant improvement in its absorptive permeability by enhancing nonspecific passive and carrier-mediated uptake by means of SMVT. The specific interactions between R.I.-K(biotin)-Tat9 and SMVT suggest that targeting approaches utilizing transporters such as SMVT may substantially improve the oral delivery of large peptides.
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Affiliation(s)
- S Ramanathan
- College of Pharmacy, Rutgers, The State University of new Jersey, Piscataway 08854, USA
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Friedrich A, George RL, Bridges CC, Prasad PD, Ganapathy V. Transport of choline and its relationship to the expression of the organic cation transporters in a rat brain microvessel endothelial cell line (RBE4). Biochim Biophys Acta 2001; 1512:299-307. [PMID: 11406107 DOI: 10.1016/s0005-2736(01)00333-9] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The present study was undertaken to elucidate the functional characteristics of choline uptake and deduce the relationship between choline uptake and the expression of organic cation transporters in the rat brain microvessel endothelial cell line RBE4. Confluent RBE4 cells were found to express a high affinity choline uptake system. The system is Na(+)-independent and shows a Michaelis-Menten constant of approx. 20 microM for choline. The choline analogue hemicholinium-3 inhibits choline uptake in these cells with an inhibition constant of approx. 50 microM. The uptake system is also susceptible for inhibition by various organic cations, including 1-methyl-4-phenylpyridinium, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, clonidine, procainamide, and tetramethylammonium. The prototypical organic cation tetraethylammonium shows very little affinity for the choline uptake system in these cells. The inhibition of choline uptake by hemicholinium-3 is competitive. Northern analysis and RT-PCR show that these cells do not express the organic cation transporters OCT2 and OCT3. These cells do express, however, low levels of OCT1, but the functional characteristics of choline uptake in these cells are very different from the known properties of choline uptake via OCT1. The Na(+)-coupled high affinity choline transporter CHT1 is not expressed in these cells as evidenced by RT-PCR. This corroborates the Na(+)-independent nature of choline uptake in these cells. It is concluded that RBE4 cells express an organic cation transporter that is responsible for choline uptake in these cells and that this transporter is not identical to any of the organic cation transporters thus far identified at the molecular level in mammalian cells.
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Affiliation(s)
- A Friedrich
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta 30912, USA
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Ling R, Bridges CC, Sugawara M, Fujita T, Leibach FH, Prasad PD, Ganapathy V. Involvement of transporter recruitment as well as gene expression in the substrate-induced adaptive regulation of amino acid transport system A. Biochim Biophys Acta 2001; 1512:15-21. [PMID: 11334620 DOI: 10.1016/s0005-2736(01)00310-8] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
We investigated the molecular mechanism involved in the adaptive regulation of the amino acid transport system A, a process in which amino acid starvation induces the transport activity. These studies were done with rat C6 glioma cells. System A activity in these cells is mediated exclusively by the system A subtype, amino acid transporter A2 (ATA2). The other two known system A subtypes, ATA1 and ATA3, are not expressed in these cells. Exposure of these cells to an amino acid-free medium induces system A activity. This process consists of an acute phase and a chronic phase. Laser-scanning confocal microscopic immunolocalization of ATA2 reveals that the acute phase is associated with recruitment of preformed ATA2 from an intracellular pool to the plasma membrane. In contrast, the chronic phase is associated with an induction of ata2 gene expression as evidenced from the increase in the steady-state levels of ATA2 mRNA, restoration of the intracellular pool of ATA2 protein, and blockade of the induction by cycloheximide and actinomycin D. The increase in system A activity induced by amino acid starvation is blocked specifically by system A substrates, including the non-metabolizable alpha-(methylamino)isobutyric acid.
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Affiliation(s)
- R Ling
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, GA 30912, USA
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Bröer A, Friedrich B, Wagner CA, Fillon S, Ganapathy V, Lang F, Bröer S. Association of 4F2hc with light chains LAT1, LAT2 or y+LAT2 requires different domains. Biochem J 2001; 355:725-31. [PMID: 11311135 PMCID: PMC1221788 DOI: 10.1042/bj3550725] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Heterodimeric amino acid transporters are comprised of a type-II membrane protein named the heavy chain (4F2hc or rBAT) that may associate with a number of different polytopic membrane proteins, called light chains. It is thought that the heavy chain is mainly involved in the trafficking of the complex to the plasma membrane, whereas the transport process itself is catalysed by the light chain. The 4F2 heavy chain (4F2hc) associates with at least six different light chains to induce distinct amino acid-transport activites. To test if the light chains are specifically recognized and to identify domains involved in the recognition of light chains, C-terminally truncated mutants of 4F2hc were constructed and co-expressed with the light chains LAT1, LAT2 and y(+)LAT2. The truncated isoform T1, comprised of only 133 amino acids that form the cytosolic N-terminus and the transmembrane helix, displayed only a slight reduction in its ability to promote LAT1 expression at the membrane surface compared with the 529 amino acid wild-type 4F2hc protein. Co-expression of increasingly larger 4F2hc mutants caused a delayed translocation of LAT1. In contrast to the weak effects of 4F2hc truncations on LAT1 expression, surface expression of LAT2 and y(+)LAT2 was almost completely lost with all truncated heavy chains. Co-expression of LAT1 together with the other light chains did not result in displacement of LAT2 and y(+)LAT2. The results suggest that extracellular domains of the heavy chain are responsible mainly for recognition of light chains other than LAT1 and that the extracellular domain ensures proper translocation to the plasma membrane.
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Affiliation(s)
- A Bröer
- Division of Biochemistry & Molecular Biology, Faculty of Science, Australian National University, Canberra, ACT 0200, Australia
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Hatanaka T, Nakanishi T, Huang W, Leibach FH, Prasad PD, Ganapathy V, Ganapathy ME. Na+ - and Cl- -coupled active transport of nitric oxide synthase inhibitors via amino acid transport system B(0,+). J Clin Invest 2001; 107:1035-43. [PMID: 11306607 PMCID: PMC199559 DOI: 10.1172/jci12060] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Nitric oxide synthase (NOS) inhibitors have therapeutic potential in the management of numerous conditions in which NO overproduction plays a critical role. Identification of transport systems in the intestine that can mediate the uptake of NOS inhibitors is important to assess the oral bioavailability and therapeutic efficacy of these potential drugs. Here, we have cloned the Na+ - and Cl- -coupled amino acid transport system B(0,+) (ATB(0,+)) from the mouse colon and investigated its ability to transport NOS inhibitors. When expressed in mammalian cells, ATB(0,+) can transport a variety of zwitterionic and cationic amino acids in a Na+ - and Cl- -coupled manner. Each of the NOS inhibitors tested compete with glycine for uptake through this transport system. Furthermore, using a tritiated analog of the NOS inhibitor N(G)-nitro-L-arginine, we showed that Na+ - and Cl- -coupled transport occurs via ATB(0,+). We then studied transport of a wide variety of NOS inhibitors in Xenopus laevis oocytes expressing the cloned ATB(0,+) and found that ATB(0,+) can transport a broad range of zwitterionic or cationic NOS inhibitors. These data represent the first identification of an ion gradient-driven transport system for NOS inhibitors in the intestinal tract.
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Affiliation(s)
- T Hatanaka
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, GA 30912, USA
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Nakanishi T, Hatanaka T, Huang W, Prasad PD, Leibach FH, Ganapathy ME, Ganapathy V. Na+- and Cl--coupled active transport of carnitine by the amino acid transporter ATB(0,+) from mouse colon expressed in HRPE cells and Xenopus oocytes. J Physiol 2001; 532:297-304. [PMID: 11306651 PMCID: PMC2278546 DOI: 10.1111/j.1469-7793.2001.0297f.x] [Citation(s) in RCA: 133] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
1. ATB(0,+) is an amino acid transporter energized by transmembrane gradients of Na+ and Cl(-) and membrane potential. We cloned this transporter from mouse colon and expressed the clone functionally in mammalian (human retinal pigment epithelial, HRPE) cells and Xenopus laevis oocytes to investigate the interaction of carnitine and its acyl esters with the transporter. 2. When expressed in mammalian cells, the cloned ATB(0,+) was able to transport carnitine, propionylcarnitine and acetylcarnitine. The transport process was Na(+) and Cl(-) dependent and inhibitable by the amino acid substrates of the transporter. The Michaelis constant for carnitine was 0.83 +/- 0.08 mM and the Hill coefficient for Na(+) activation was 1.6 +/- 0.1. 3. When expressed in Xenopus laevis oocytes, the cloned ATB(0,+) was able to induce inward currents in the presence of carnitine and propionylcarnitine under voltage-clamped conditions. There was no detectable current in the presence of acetylcarnitine. Carnitine-induced currents were obligatorily dependent on the presence of Na(+) and Cl(-). The currents were saturable with carnitine and the Michaelis constant was 1.8 +/- 0.4 mM. The analysis of Na(+)- and Cl(-)-activation kinetics revealed that 2 Na(+) and 1 Cl(-) were involved in the transport of carnitine via the transporter. 4. These studies describe the identification of a novel function for the amino acid transporter ATB(0,+). Since this transporter is expressed in the intestinal tract, lung and mammary gland, it is likely to play a significant role in the handling of carnitine in these tissues. 5. A Na(+)-dependent transport system for carnitine has already been described. This transporter, known as OCTN2 (novel organic cation transporter 2), is expressed in most tissues and transports carnitine with high affinity. It is energized, however, only by a Na(+) gradient and membrane potential. In contrast, ATB(0,+) is a low-affinity transporter for carnitine, but exhibits much higher concentrative capacity than OCTN2 because of its energization by transmembrane gradients of Na(+) and Cl(-) as well as by membrane potential.
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Affiliation(s)
- T Nakanishi
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, GA 30912, USA
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