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Limón LK, Shi K, Dao A, Rugloski J, Tompkins KJ, Aihara H, Gordon WR, Evans RL. The crystal structure of the human smacovirus 1 Rep domain. Acta Crystallogr F Struct Biol Commun 2023; 79:295-300. [PMID: 38051309 PMCID: PMC10833120 DOI: 10.1107/s2053230x23009536] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2023] [Accepted: 10/31/2023] [Indexed: 12/07/2023] Open
Abstract
Replication initiator proteins (Reps) from the HUH endonuclease family process specific single-stranded DNA sequences to initiate rolling-circle replication in viruses. Here, the first crystal structure of the apo state of a Rep domain from the smacovirus family is reported. The structure of the human smacovirus 1 Rep domain was obtained at 1.33 Å resolution and represents an expansion of the HUH endonuclease superfamily, allowing greater diversity in bioconjugation-tag applications.
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Affiliation(s)
- Lidia K. Limón
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
| | - Ke Shi
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
| | - Amy Dao
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
| | - Jacob Rugloski
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
| | - Kassidy J. Tompkins
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
| | - Hideki Aihara
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
| | - Wendy R. Gordon
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
| | - Robert L. Evans
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
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2
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Casadevall G, Pierce C, Guan B, Iglesias-Fernandez J, Lim HY, Greenberg LR, Walsh ME, Shi K, Gordon W, Aihara H, Evans RL, Kazlauskas R, Osuna S. Designing Efficient Enzymes: Eight Predicted Mutations Convert a Hydroxynitrile Lyase into an Efficient Esterase. bioRxiv 2023:2023.08.23.554512. [PMID: 37662272 PMCID: PMC10473745 DOI: 10.1101/2023.08.23.554512] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/05/2023]
Abstract
Hydroxynitrile lyase from rubber tree (HbHNL) shares 45% identical amino acid residues with the homologous esterase from tobacco, SABP2, but the two enzymes catalyze different reactions. The x-ray structures reveal a serine-histidine-aspartate catalytic triad in both enzymes along with several differing amino acid residues within the active site. Previous exchange of three amino acid residues in the active site of HbHNL with the corresponding amino acid residue in SABP2 (T11G-E79H-K236M) created variant HNL3, which showed low esterase activity toward p-nitrophenyl acetate. Further structure comparison reveals additional differences surrounding the active site. HbHNL contains an improperly positioned oxyanion hole residue and differing solvation of the catalytic aspartate. We hypothesized that correcting these structural differences would impart good esterase activity on the corresponding HbHNL variant. To predict the amino acid substitutions needed to correct the structure, we calculated shortest path maps for both HbHNL and SABP2, which reveal correlated movements of amino acids in the two enzymes. Replacing four amino acid residues (C81L-N104T-V106F-G176S) whose movements are connected to the movements of the catalytic residues yielded variant HNL7TV (stabilizing substitution H103V was also added), which showed an esterase catalytic efficiency comparable to that of SABP2. The x-ray structure of an intermediate variant, HNL6V, showed an altered solvation of the catalytic aspartate and a partially corrected oxyanion hole. This dramatic increase in catalytic efficiency demonstrates the ability of shortest path maps to predict which residues outside the active site contribute to catalytic activity.
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Affiliation(s)
- Guillem Casadevall
- Institut de Química Computacional i Catálisi and Departament de Química, Universitat de Girona, Carrer Maria Aurèlia Capmany 69, 17003 Girona, Spain
| | - Colin Pierce
- Biotechnology Institute and Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, 1479 Gortner Avenue, Saint Paul, MN 55108 USA
| | - Bo Guan
- Biotechnology Institute and Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, 1479 Gortner Avenue, Saint Paul, MN 55108 USA
| | - Javier Iglesias-Fernandez
- Institut de Química Computacional i Catálisi and Departament de Química, Universitat de Girona, Carrer Maria Aurèlia Capmany 69, 17003 Girona, Spain
| | - Huey-Yee Lim
- Biotechnology Institute and Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, 1479 Gortner Avenue, Saint Paul, MN 55108 USA
| | - Lauren R Greenberg
- Biotechnology Institute and Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, 1479 Gortner Avenue, Saint Paul, MN 55108 USA
| | - Meghan E Walsh
- Biotechnology Institute and Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, 1479 Gortner Avenue, Saint Paul, MN 55108 USA
| | - Ke Shi
- Biotechnology Institute and Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, 1479 Gortner Avenue, Saint Paul, MN 55108 USA
| | - Wendy Gordon
- Biotechnology Institute and Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, 1479 Gortner Avenue, Saint Paul, MN 55108 USA
| | - Hideki Aihara
- Biotechnology Institute and Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, 1479 Gortner Avenue, Saint Paul, MN 55108 USA
| | - Robert L Evans
- Biotechnology Institute and Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, 1479 Gortner Avenue, Saint Paul, MN 55108 USA
| | - Romas Kazlauskas
- Biotechnology Institute and Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, 1479 Gortner Avenue, Saint Paul, MN 55108 USA
| | - Sílvia Osuna
- Institut de Química Computacional i Catálisi and Departament de Química, Universitat de Girona, Carrer Maria Aurèlia Capmany 69, 17003 Girona, Spain
- ICREA, Barcelona, Spain
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3
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Smiley AT, Tompkins KJ, Pawlak MR, Krueger AJ, Evans RL, Shi K, Aihara H, Gordon WR. Watson-Crick Base-Pairing Requirements for ssDNA Recognition and Processing in Replication-Initiating HUH Endonucleases. mBio 2023; 14:e0258722. [PMID: 36541758 PMCID: PMC9973303 DOI: 10.1128/mbio.02587-22] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2022] [Accepted: 12/05/2022] [Indexed: 12/24/2022] Open
Abstract
Replication-initiating HUH endonucleases (Reps) are sequence-specific nucleases that cleave and rejoin single-stranded DNA (ssDNA) during rolling-circle replication. These functions are mediated by covalent linkage of the Rep to its substrate post cleavage. Here, we describe the structures of the endonuclease domain from the Muscovy duck circovirus Rep in complex with its cognate ssDNA 10-mer with and without manganese in the active site. Structural and functional analyses demonstrate that divalent cations play both catalytic and structural roles in Reps by polarizing and positioning their substrate. Further structural comparisons highlight the importance of an intramolecular substrate Watson-Crick (WC) base pairing between the -4 and +1 positions. Subsequent kinetic and functional analyses demonstrate a functional dependency on WC base pairing between these positions regardless of the pair's identity (i.e., A·T, T·A, G·C, or C·G), highlighting a structural specificity for substrate interaction. Finally, considering how well WC swaps were tolerated in vitro, we sought to determine to what extent the canonical -4T·+1A pairing is conserved in circular Rep-encoding single-stranded DNA viruses and found evidence of noncanonical pairings in a minority of these genomes. Altogether, our data suggest that substrate intramolecular WC base pairing is a universal requirement for separation and reunion of ssDNA in Reps. IMPORTANCE Circular Rep-encoding single-stranded DNA (CRESS-DNA) viruses are a ubiquitous group of viruses that infect organisms across all domains of life. These viruses negatively impact both agriculture and human health. All members of this viral family employ a multifunctional nuclease (Rep) to initiate replication. Reps are structurally similar throughout this family, making them targets of interest for viral inhibition strategies. Here, we investigate the functional dependencies of the Rep protein from Muscovy duck circovirus for ssDNA interaction. We demonstrate that this Rep requires an intramolecular Watson-Crick base pairing for origin of replication (Ori) recognition and interaction. We show that noncognate base pair swaps are well tolerated, highlighting a local structural specificity over sequence specificity. Bioinformatic analysis found that the vast majority of CRESS-DNA Oris form base pairs in conserved positions, suggesting this pairing is a universal requirement for replication initiation in the CRESS-DNA virus family.
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Affiliation(s)
- Adam T. Smiley
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, Minnesota, USA
| | - Kassidy J. Tompkins
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, Minnesota, USA
| | - Matthew R. Pawlak
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, Minnesota, USA
| | - August J. Krueger
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, Minnesota, USA
| | - Robert L. Evans
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, Minnesota, USA
| | - Ke Shi
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, Minnesota, USA
| | - Hideki Aihara
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, Minnesota, USA
| | - Wendy R. Gordon
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, Minnesota, USA
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Tompkins KJ, Houtti M, Litzau LA, Aird EJ, Everett BA, Nelson AT, Pornschloegl L, Limón-Swanson LK, Evans RL, Evans K, Shi K, Aihara H, Gordon WR. Molecular underpinnings of ssDNA specificity by Rep HUH-endonucleases and implications for HUH-tag multiplexing and engineering. Nucleic Acids Res 2021; 49:1046-1064. [PMID: 33410911 PMCID: PMC7826260 DOI: 10.1093/nar/gkaa1248] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2020] [Revised: 12/08/2020] [Accepted: 12/14/2020] [Indexed: 12/11/2022] Open
Abstract
Replication initiator proteins (Reps) from the HUH-endonuclease superfamily process specific single-stranded DNA (ssDNA) sequences to initiate rolling circle/hairpin replication in viruses, such as crop ravaging geminiviruses and human disease causing parvoviruses. In biotechnology contexts, Reps are the basis for HUH-tag bioconjugation and a critical adeno-associated virus genome integration tool. We solved the first co-crystal structures of Reps complexed to ssDNA, revealing a key motif for conferring sequence specificity and for anchoring a bent DNA architecture. In combination, we developed a deep sequencing cleavage assay, termed HUH-seq, to interrogate subtleties in Rep specificity and demonstrate how differences can be exploited for multiplexed HUH-tagging. Together, our insights allowed engineering of only four amino acids in a Rep chimera to predictably alter sequence specificity. These results have important implications for modulating viral infections, developing Rep-based genomic integration tools, and enabling massively parallel HUH-tag barcoding and bioconjugation applications.
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Affiliation(s)
- Kassidy J Tompkins
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota Twin Cities, Minneapolis, MN 55455, USA
| | - Mo Houtti
- Department of Computer Science and Engineering, University of Minnesota Twin Cities, Minneapolis, MN 55455, USA
| | - Lauren A Litzau
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota Twin Cities, Minneapolis, MN 55455, USA
| | - Eric J Aird
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota Twin Cities, Minneapolis, MN 55455, USA
| | - Blake A Everett
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota Twin Cities, Minneapolis, MN 55455, USA
| | - Andrew T Nelson
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota Twin Cities, Minneapolis, MN 55455, USA
| | - Leland Pornschloegl
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota Twin Cities, Minneapolis, MN 55455, USA
| | - Lidia K Limón-Swanson
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota Twin Cities, Minneapolis, MN 55455, USA
| | - Robert L Evans
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota Twin Cities, Minneapolis, MN 55455, USA
| | - Karen Evans
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota Twin Cities, Minneapolis, MN 55455, USA
| | - Ke Shi
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota Twin Cities, Minneapolis, MN 55455, USA
| | - Hideki Aihara
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota Twin Cities, Minneapolis, MN 55455, USA
| | - Wendy R Gordon
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota Twin Cities, Minneapolis, MN 55455, USA
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5
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Evans RL, Bates S, Marriott RE, Arnold DS. The impact of different hair-removal behaviours on the biophysical and biochemical characteristics of female axillary skin. Int J Cosmet Sci 2020; 42:436-443. [PMID: 32638392 PMCID: PMC7984395 DOI: 10.1111/ics.12648] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [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] [Received: 05/12/2020] [Revised: 06/24/2020] [Accepted: 07/02/2020] [Indexed: 11/28/2022]
Abstract
Objective The impact of hair removal on the biophysical and biochemical characteristics of human axillary skin is not fully understood. This study investigated the effect of different hair‐removal techniques on biophysical parameters and the concentrations of key inflammatory biomarkers in the axillae of female Thai subjects. Axillary hair was removed by shaving, plucking or waxing. Methods Following a 2‐week washout phase without hair removal, subjects underwent visual assessment for erythema and skin dryness in one (randomized) axilla, then, hair was removed from the axilla by shaving, plucking or waxing according to each subject’s established habit. Erythema and dryness were assessed again 30 min after hair removal, and buffer scrubs collected from depilated and non‐depilated axillae and analysed for inflammatory cytokines; after a further 48 h, erythema, dryness and post‐inflammatory hyperpigmentation (PIHP) were assessed in the depilated axilla. Biophysical assessments (skin hydration, barrier integrity, elasticity and roughness) were made in depilated and non‐depilated axillae. Results All three hair‐removal techniques induced an increase in axillary erythema and skin dryness. Shaving was associated with significantly less erythema (P < 0.01), but significantly greater skin dryness (P < 0.05) versus the other techniques 30 min after hair removal. There were no between‐technique differences in PIHP or biophysical parameters. Interleukins IL‐1α and IL‐1RA concentrations increased, and IL‐8 concentration decreased following hair removal by each technique. Conclusion This is the first study to identify the principal cytokines associated with the inflammatory process triggered by axillary hair removal. A single hair‐removal treatment did not appear to induce PIHP or further biophysical changes to the skin.
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Affiliation(s)
- R L Evans
- Unilever Research & Development, Port Sunlight Laboratory, Quarry Road East, Bebington, Wirral, Merseyside, CH63 3JW, UK
| | - S Bates
- Unilever Research & Development, Port Sunlight Laboratory, Quarry Road East, Bebington, Wirral, Merseyside, CH63 3JW, UK
| | - R E Marriott
- Unilever Research & Development, Port Sunlight Laboratory, Quarry Road East, Bebington, Wirral, Merseyside, CH63 3JW, UK
| | - D S Arnold
- Unilever Research & Development, Port Sunlight Laboratory, Quarry Road East, Bebington, Wirral, Merseyside, CH63 3JW, UK
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6
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Jones BJ, Evans RL, Mylrea NJ, Chaudhury D, Luo C, Guan B, Pierce CT, Gordon WR, Wilmot CM, Kazlauskas RJ. Larger active site in an ancestral hydroxynitrile lyase increases catalytically promiscuous esterase activity. PLoS One 2020; 15:e0235341. [PMID: 32603354 PMCID: PMC7326234 DOI: 10.1371/journal.pone.0235341] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Accepted: 06/14/2020] [Indexed: 12/02/2022] Open
Abstract
Hydroxynitrile lyases (HNL's) belonging to the α/β-hydrolase-fold superfamily evolved from esterases approximately 100 million years ago. Reconstruction of an ancestral hydroxynitrile lyase in the α/β-hydrolase fold superfamily yielded a catalytically active hydroxynitrile lyase, HNL1. Several properties of HNL1 differ from the modern HNL from rubber tree (HbHNL). HNL1 favors larger substrates as compared to HbHNL, is two-fold more catalytically promiscuous for ester hydrolysis (p-nitrophenyl acetate) as compared to mandelonitrile cleavage, and resists irreversible heat inactivation to 35 °C higher than for HbHNL. We hypothesized that the x-ray crystal structure of HNL1 may reveal the molecular basis for the differences in these properties. The x-ray crystal structure solved to 1.96-Å resolution shows the expected α/β-hydrolase fold, but a 60% larger active site as compared to HbHNL. This larger active site echoes its evolution from esterases since related esterase SABP2 from tobacco also has a 38% larger active site than HbHNL. The larger active site in HNL1 likely accounts for its ability to accept larger hydroxynitrile substrates. Site-directed mutagenesis of HbHNL to expand the active site increased its promiscuous esterase activity 50-fold, consistent with the larger active site in HNL1 being the primary cause of its promiscuous esterase activity. Urea-induced unfolding of HNL1 indicates that it unfolds less completely than HbHNL (m-value = 0.63 for HNL1 vs 0.93 kcal/mol·M for HbHNL), which may account for the ability of HNL1 to better resist irreversible inactivation upon heating. The structure of HNL1 shows changes in hydrogen bond networks that may stabilize regions of the folded structure.
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Affiliation(s)
- Bryan J. Jones
- Department of Biochemistry, Molecular Biology and Biophysics and The Biotechnology Institute, University of Minnesota, Saint Paul, Minnesota, United States of America
| | - Robert L. Evans
- Department of Biochemistry, Molecular Biology and Biophysics and The Biotechnology Institute, University of Minnesota, Saint Paul, Minnesota, United States of America
| | - Nathan J. Mylrea
- Department of Biochemistry, Molecular Biology and Biophysics and The Biotechnology Institute, University of Minnesota, Saint Paul, Minnesota, United States of America
| | - Debayan Chaudhury
- Department of Biochemistry, Molecular Biology and Biophysics and The Biotechnology Institute, University of Minnesota, Saint Paul, Minnesota, United States of America
| | - Christine Luo
- Department of Biochemistry, Molecular Biology and Biophysics and The Biotechnology Institute, University of Minnesota, Saint Paul, Minnesota, United States of America
| | - Bo Guan
- Department of Biochemistry, Molecular Biology and Biophysics and The Biotechnology Institute, University of Minnesota, Saint Paul, Minnesota, United States of America
| | - Colin T. Pierce
- Department of Biochemistry, Molecular Biology and Biophysics and The Biotechnology Institute, University of Minnesota, Saint Paul, Minnesota, United States of America
| | - Wendy R. Gordon
- Department of Biochemistry, Molecular Biology and Biophysics and The Biotechnology Institute, University of Minnesota, Saint Paul, Minnesota, United States of America
| | - Carrie M. Wilmot
- Department of Biochemistry, Molecular Biology and Biophysics and The Biotechnology Institute, University of Minnesota, Saint Paul, Minnesota, United States of America
| | - Romas J. Kazlauskas
- Department of Biochemistry, Molecular Biology and Biophysics and The Biotechnology Institute, University of Minnesota, Saint Paul, Minnesota, United States of America
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7
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Jones BJ, Evans RL, Mylrea NJ, Chaudhury D, Luo C, Guan B, Pierce CT, Gordon WR, Wilmot CM, Kazlauskas RJ. Larger active site in an ancestral hydroxynitrile lyase increases catalytically promiscuous esterase activity.. [DOI: 10.1101/2020.04.06.027797] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/19/2023]
Abstract
AbstractHydroxynitrile lyases (HNL’s) belonging to the α/β-hydrolase-fold superfamily evolved from esterases approximately 100 million years ago. Reconstruction of an ancestral hydroxynitrile lyase in the α/β-hydrolase fold superfamily yielded a catalytically active hydroxynitrile lyase, HNL1. Several properties of HNL1 differ from the modern HNL from rubber tree (HbHNL). HNL1 favors larger substrates as compared to HbHNL, is two-fold more catalytically promiscuous for ester hydrolysis (p-nitrophenyl acetate) as compared to mandelonitrile cleavage, and resists irreversible heat inactivation to 35 °C higher than for HbHNL. We hypothesized that the x-ray crystal structure of HNL1 may reveal the molecular basis for the differences in these properties. The x-ray crystal structure solved to 1.96-Å resolution shows the expected α/β-hydrolase fold, but a 60% larger active site as compared to HbHNL. This larger active site echoes its evolution from esterases since related esterase SABP2 from tobacco also has a 38% larger active site than HbHNL. The larger active site in HNL1 likely accounts for its ability to accept larger hydroxynitrile substrates. Site-directed mutagenesis of HbHNL to expand the active site increased its promiscuous esterase activity 50-fold, consistent with the larger active site in HNL1 being the primary cause of its promiscuous esterase activity. Urea-induced unfolding of HNL1 indicates that it unfolds less completely than HbHNL (m-value = 0.63 for HNL1 vs 0.93 kcal/ mol·M for HbHNL), which may account for the ability of HNL1 to better resist irreversible inactivation upon heating. The structure of HNL1 shows changes in hydrogen bond networks that may stabilize regions of the folded structure.
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8
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Culp DJ, Zhang Z, Evans RL. VIP and muscarinic synergistic mucin secretion by salivary mucous cells is mediated by enhanced PKC activity via VIP-induced release of an intracellular Ca 2+ pool. Pflugers Arch 2020; 472:385-403. [PMID: 31932898 DOI: 10.1007/s00424-020-02348-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2019] [Revised: 12/09/2019] [Accepted: 01/06/2020] [Indexed: 12/12/2022]
Abstract
Mucin secretion by salivary mucous glands is mediated predominantly by parasympathetic acetylcholine activation of cholinergic muscarinic receptors via increased intracellular free calcium ([Ca2+]i) and activation of conventional protein kinase C isozymes (cPKC). However, the parasympathetic co-neurotransmitter, vasoactive intestinal peptide (VIP), also initiates secretion, but to a lesser extent. In the present study, cross talk between VIP- and muscarinic-induced mucin secretion was investigated using isolated rat sublingual tubuloacini. VIP-induced secretion is mediated by cAMP-activated protein kinase A (PKA), independently of increased [Ca2+]i. Synergistic secretion between VIP and the muscarinic agonist, carbachol, was demonstrated but only with submaximal carbachol. Carbachol has no effect on cAMP ± VIP. Instead, PKA activated by VIP releases Ca2+ from an intracellular pool maintained by the sarco/endoplasmic reticulum Ca2+-ATPase pump. Calcium release was independent of phospholipase C activity. The resultant sustained [Ca2+]i increase is additive to submaximal, but not maximal carbachol-induced [Ca2+]i. Synergistic mucin secretion was mimicked by VIP plus either phorbol 12-myristate 13-acetate or 0.01 μM thapsigargin, and blocked by the PKC inhibitor, Gö6976. VIP-induced Ca2+ release also promoted store-operated Ca2+ entry. Synergism is therefore driven by VIP-mediated [Ca2+]i augmenting cPKC activity to enhance muscarinic mucin secretion. Additional data suggest ryanodine receptors control VIP/PKA-mediated Ca2+ release from a Ca2+ pool also responsive to maximal carbachol. A working model of muscarinic and VIP control of mucous cell exocrine secretion is presented. Results are discussed in relation to synergistic mechanisms in other secretory cells, and the physiological and therapeutic significance of VIP/muscarinic synergism controlling salivary mucous cell exocrine secretion.
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Affiliation(s)
- David J Culp
- Center for Oral Biology, University of Rochester Medical Center, 601 Elmwood Ave, Rochester, NY, 14642, USA. .,Department of Oral Biology, UF College of Dentistry, P.O. Box 100424, Gainesville, FL, 32610-3003, USA.
| | - Z Zhang
- Center for Oral Biology, University of Rochester Medical Center, 601 Elmwood Ave, Rochester, NY, 14642, USA
| | - R L Evans
- Center for Oral Biology, University of Rochester Medical Center, 601 Elmwood Ave, Rochester, NY, 14642, USA.,Unilever Research & Development, Port Sunlight Laboratory, Quarry Road East, Bebington, Wirral, CH63 3JW, UK
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Koehn EM, Latham JA, Armand T, Evans RL, Tu X, Wilmot CM, Iavarone AT, Klinman JP. Discovery of Hydroxylase Activity for PqqB Provides a Missing Link in the Pyrroloquinoline Quinone Biosynthetic Pathway. J Am Chem Soc 2019; 141:4398-4405. [PMID: 30811189 DOI: 10.1021/jacs.8b13453] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Understanding the biosynthesis of cofactors is fundamental to the life sciences, yet to date a few important pathways remain unresolved. One example is the redox cofactor pyrroloquinoline quinone (PQQ), which is critical for C1 metabolism in many microorganisms, a disproportionate number of which are opportunistic human pathogens. While the initial and final steps of PQQ biosynthesis, involving PqqD/E and PqqC, have been elucidated, the precise nature and order of the remaining transformations in the pathway are unknown. Here we show evidence that the remaining essential biosynthetic enzyme PqqB is an iron-dependent hydroxylase catalyzing oxygen-insertion reactions that are proposed to produce the quinone moiety of the mature PQQ cofactor. The demonstrated reactions of PqqB are unprecedented within the metallo β-lactamase protein family and expand the catalytic repertoire of nonheme iron hydroxylases. These new findings also generate a nearly complete description of the PQQ biosynthetic pathway.
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Affiliation(s)
- Eric M Koehn
- Department of Chemistry and California Institute for Quantitative Biosciences , University of California-Berkeley , Berkeley , California 94720-3220 , United States
| | - John A Latham
- Department of Chemistry and California Institute for Quantitative Biosciences , University of California-Berkeley , Berkeley , California 94720-3220 , United States
| | - Tara Armand
- Department of Chemistry and California Institute for Quantitative Biosciences , University of California-Berkeley , Berkeley , California 94720-3220 , United States
| | - Robert L Evans
- Department of Biochemistry, Molecular Biology, and Biophysics and The Biotechnology Institute , University of Minnesota , St. Paul , Minnesota 55108 , United States
| | - Xiongying Tu
- Department of Biochemistry, Molecular Biology, and Biophysics and The Biotechnology Institute , University of Minnesota , St. Paul , Minnesota 55108 , United States
| | - Carrie M Wilmot
- Department of Biochemistry, Molecular Biology, and Biophysics and The Biotechnology Institute , University of Minnesota , St. Paul , Minnesota 55108 , United States
| | - Anthony T Iavarone
- Department of Chemistry and California Institute for Quantitative Biosciences , University of California-Berkeley , Berkeley , California 94720-3220 , United States
| | - Judith P Klinman
- Department of Chemistry and California Institute for Quantitative Biosciences , University of California-Berkeley , Berkeley , California 94720-3220 , United States.,Department of Molecular and Cell Biology , University of California-Berkeley , Berkeley , California 94720-3220 , United States
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10
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Tu X, Latham JA, Klema VJ, Evans RL, Li C, Klinman JP, Wilmot CM. Crystal structures reveal metal-binding plasticity at the metallo-β-lactamase active site of PqqB from Pseudomonas putida. J Biol Inorg Chem 2017; 22:1089-1097. [PMID: 28825148 DOI: 10.1007/s00775-017-1486-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2017] [Accepted: 08/16/2017] [Indexed: 02/02/2023]
Abstract
PqqB is an enzyme involved in the biosynthesis of pyrroloquinoline quinone and a distal member of the metallo-β-lactamase (MBL) superfamily. PqqB lacks two residues in the conserved signature motif HxHxDH that makes up the key metal-chelating elements that can bind up to two metal ions at the active site of MBLs and other members of its superfamily. Here, we report crystal structures of PqqB bound to Mn2+, Mg2+, Cu2+, and Zn2+. These structures demonstrate that PqqB can still bind metal ions at the canonical MBL active site. The fact that PqqB can adapt its side chains to chelate a wide spectrum of metal ions with different coordination features on a uniform main chain scaffold demonstrates its metal-binding plasticity. This plasticity may provide insights into the structural basis of promiscuous activities found in ensembles of metal complexes within this superfamily. Furthermore, PqqB belongs to a small subclass of MBLs that contain an additional CxCxxC motif that binds a structural Zn2+. Our data support a key role for this motif in dimerization.
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Affiliation(s)
- Xiongying Tu
- Department of Biochemistry, Molecular Biology, and Biophysics, and The Biotechnology Institute, University of Minnesota, St Paul, MN, 55108, USA
| | - John A Latham
- Departments of Chemistry, and Molecular and Cellular Biology, University of California, Berkeley, CA, 94720, USA
- Department of Chemistry and Biochemistry, University of Denver, Denver, CO, 80208, USA
| | - Valerie J Klema
- Department of Biochemistry, Molecular Biology, and Biophysics, and The Biotechnology Institute, University of Minnesota, St Paul, MN, 55108, USA
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX, 77555, USA
| | - Robert L Evans
- Department of Biochemistry, Molecular Biology, and Biophysics, and The Biotechnology Institute, University of Minnesota, St Paul, MN, 55108, USA
| | - Chao Li
- Department of Biochemistry, Molecular Biology, and Biophysics, and The Biotechnology Institute, University of Minnesota, St Paul, MN, 55108, USA
| | - Judith P Klinman
- Departments of Chemistry, and Molecular and Cellular Biology, University of California, Berkeley, CA, 94720, USA
| | - Carrie M Wilmot
- Department of Biochemistry, Molecular Biology, and Biophysics, and The Biotechnology Institute, University of Minnesota, St Paul, MN, 55108, USA.
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11
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Evans RL, Latham JA, Xia Y, Klinman JP, Wilmot CM. Nuclear Magnetic Resonance Structure and Binding Studies of PqqD, a Chaperone Required in the Biosynthesis of the Bacterial Dehydrogenase Cofactor Pyrroloquinoline Quinone. Biochemistry 2017; 56:2735-2746. [PMID: 28481092 DOI: 10.1021/acs.biochem.7b00247] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Biosynthesis of the ribosomally synthesized and post-translationally modified peptide (RiPP), pyrroloquinoline quinone (PQQ), is initiated when the precursor peptide, PqqA, is recognized and bound by the RiPP precursor peptide recognition element (RRE), PqqD, for presentation to the first enzyme in the pathway, PqqE. Unlike other RiPP-producing, postribosomal peptide synthesis (PRPS) pathways in which the RRE is a component domain of the first enzyme, PqqD is predominantly a separate scaffolding protein that forms a ternary complex with the precursor peptide and first tailoring enzyme. As PqqD is a stable, independent RRE, this makes the PQQ pathway an ideal PRPS model system for probing RRE interactions using nuclear magnetic resonance (NMR). Herein, we present both the solution NMR structure of Methylobacterium extorquens PqqD and results of 1H-15N HSQC binding experiments that identify the PqqD residues involved in binding the precursor peptide, PqqA, and the enzyme, PqqE. The reported structural model for an independent RRE, along with the mapped binding surfaces, will inform future efforts both to understand and to manipulate PRPS pathways.
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Affiliation(s)
- Robert L Evans
- Department of Biochemistry, Molecular Biology, and Biophysics and Biotechnology Institute, University of Minnesota, Twin Cities , St. Paul, Minnesota 55108, United States
| | - John A Latham
- Department of Chemistry and Department of Molecular and Cell Biology, University of California, Berkeley , Berkeley, California 94720, United States
| | - Youlin Xia
- Minnesota NMR Center, University of Minnesota, Twin Cities , Minneapolis, Minnesota 55455, United States
| | - Judith P Klinman
- Department of Chemistry and Department of Molecular and Cell Biology, University of California, Berkeley , Berkeley, California 94720, United States
| | - Carrie M Wilmot
- Department of Biochemistry, Molecular Biology, and Biophysics and Biotechnology Institute, University of Minnesota, Twin Cities , St. Paul, Minnesota 55108, United States
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12
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Evans RL, Latham JA, Klinman JP, Wilmot CM, Xia Y. (1)H, (13)C, and (15)N resonance assignments and secondary structure information for Methylobacterium extorquens PqqD and the complex of PqqD with PqqA. Biomol NMR Assign 2016; 10:385-389. [PMID: 27638737 PMCID: PMC5224828 DOI: 10.1007/s12104-016-9705-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2016] [Accepted: 08/31/2016] [Indexed: 06/06/2023]
Abstract
The ribosomally synthesized and post-translationally modified peptide (RiPP), pyrroloquinoline quinone (PQQ), is a dehydrogenase cofactor synthesized by, but not exclusively used by, certain prokaryotes. RiPPs represent a rapidly expanding and diverse class of natural products-many of which have therapeutic potential-and the biosynthetic pathways for these are gaining attention. Five gene products from the pqq operon (PqqA, PqqB, PqqC, PqqD, and PqqE) are essential for PQQ biosynthesis. The substrate is the peptide PqqA, which is presented to the radical SAM enzyme PqqE by the small protein PqqD. PqqA is unstructured in solution, and only binds to PqqE when in complex with PqqD. PqqD is a member of a growing family of RiPP chaperone proteins (or domains in most cases) that present their associated peptide substrates to the initial RiPP biosynthesis enzymes. An X-ray crystal structure exists for dimeric Xanthomonas campestris PqqD (PDB ID: 3G2B), but PqqD is now known to act as a monomer under physiological conditions. In this study, the PqqD truncation from naturally fused Methylobacterium extorquens (Mex) PqqCD was overexpressed in Escherichia coli and MexPqqA was chemically synthesized. Solution NMR (1)H-,(15)N-HSQC chemical shift studies have identified the PqqD residues involved in binding PqqA, and (1)H, (13)C, and (15)N peak assignments for PqqD alone and for PqqD bound to PqqA are reported herein.
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Affiliation(s)
- Robert L Evans
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Twin Cities, Saint Paul, MN, 55108, USA
| | - John A Latham
- Department of Chemistry, University of California, Berkeley, Berkeley, CA, 94720, USA
- Department of Chemistry and Biochemistry, University of Denver, Denver, CO, 80208, USA
| | - Judith P Klinman
- Department of Chemistry, University of California, Berkeley, Berkeley, CA, 94720, USA
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, 94720, USA
| | - Carrie M Wilmot
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Twin Cities, Saint Paul, MN, 55108, USA.
| | - Youlin Xia
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Twin Cities, Saint Paul, MN, 55108, USA
- Minnesota NMR Center, University of Minnesota, Twin Cities, Minneapolis, MN, 55455, USA
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13
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Abstract
Fluid and exocrine secretion of mucins by salivary mucous glands is regulated predominantly by parasympathetic activation of muscarinic receptors. A direct role for subsequent putative signaling steps, phospholipase C (PLC), increased intracellular calcium ([Ca(2+)](i)), and isoforms of protein kinase C (PKC) in mediating muscarinic exocrine secretion has not been elucidated, and these are potential therapeutic targets to enhance mucin secretion in hyposalivary patients. We found that muscarinic-induced mucin secretion by rat sublingual tubulo-acini was dependent upon PLC activation and the subsequent increase in [Ca(2+)](i), and further identified a transient PKC-independent component of secretion dependent upon Ca(2+) release from intracellular stores, whereas sustained secretion required entry of extracellular Ca(2+). Interactions among carbachol, PKC inhibitors, phorbol 12-myristate 13-acetate, and thapsigargin to modulate [Ca(2+)](i) implicated conventional PKC isoforms in mediating sustained secretion. With increasing times during carbachol perfusion of glands, in situ, PKC-α redistributed across glandular membrane compartments and underwent a rapid and persistent accumulation near the luminal borders of mucous cells. PKC-β1 displayed transient localization near luminal borders, whereas the novel PKCs, PKC-δ or PKC-ε, displayed little or no redistribution in mucous cells. Collective results implicate synergistic interactions between diacylglycerol (DAG) and increasing [Ca(2+)](i) levels to activate cPKCs in mediating sustained muscarinic-induced secretion.
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Affiliation(s)
- D J Culp
- University of Rochester Medical Center, Center for Oral Biology, Rochester, NY 14642, USA.
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Cohen D, Person M, Wang P, Gable CW, Hutchinson D, Marksamer A, Dugan B, Kooi H, Groen K, Lizarralde D, Evans RL, Day-Lewis FD, Lane JW. Origin and extent of fresh paleowaters on the Atlantic continental shelf, USA. Ground Water 2010; 48:143-158. [PMID: 19754848 DOI: 10.1111/j.1745-6584.2009.00627.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
While the existence of relatively fresh groundwater sequestered within permeable, porous sediments beneath the Atlantic continental shelf of North and South America has been known for some time, these waters have never been assessed as a potential resource. This fresh water was likely emplaced during Pleistocene sea-level low stands when the shelf was exposed to meteoric recharge and by elevated recharge in areas overrun by the Laurentide ice sheet at high latitudes. To test this hypothesis, we present results from a high-resolution paleohydrologic model of groundwater flow, heat and solute transport, ice sheet loading, and sea level fluctuations for the continental shelf from New Jersey to Maine over the last 2 million years. Our analysis suggests that the presence of fresh to brackish water within shallow Miocene sands more than 100 km offshore of New Jersey was facilitated by discharge of submarine springs along Baltimore and Hudson Canyons where these shallow aquifers crop out. Recharge rates four times modern levels were computed for portions of New England's continental shelf that were overrun by the Laurentide ice sheet during the last glacial maximum. We estimate the volume of emplaced Pleistocene continental shelf fresh water (less than 1 ppt) to be 1300 km(3) in New England. We also present estimates of continental shelf fresh water resources for the U.S. Atlantic eastern seaboard (10(4) km(3)) and passive margins globally (3 x 10(5) km(3)). The simulation results support the hypothesis that offshore fresh water is a potentially valuable, albeit nonrenewable resource for coastal megacities faced with growing water shortages.
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Affiliation(s)
- Denis Cohen
- Department of Geological & Atmospheric Sciences, Iowa State University, Ames, IA 50011, USA
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15
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Abstract
It is well established that the evaporation of sweat from the human body surface is the main mechanism by which heat balance is maintained following a rise in body core temperature. Since the introduction of the first brand name antiperspirant in the United States during the early 1900s, antiperspirant products designed to control underarm wetness have grown to represent one of the largest cosmetic categories in most global markets. However, although axillary sweating only constitutes less than 1% of whole body sweat rate, consumers, particularly in hot countries, have begun to articulate the concern that antiperspirants may interfere with the body's natural cooling process. To investigate this, we undertook carefully designed experiments that measured the effects of axillary antiperspirant application on whole body sweat rate and body core temperature, following a regimen of exercise-induced heat stress in a hot environment in human volunteers. Our data show clearly that although antiperspirant prevents sweat production in the axillary area, this does not impact the ability of the body to thermoregulate following a rise in body core temperature. Thus, recent consumer questioning over this aspect of antiperspirant use appears to be unwarranted.
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Affiliation(s)
- J S Burry
- Unilever Research & Development, Port Sunlight Laboratory, Bebington, Wirral, UK.
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Steele RG, Hutabarat S, Evans RL, Ackroyd CE, Newman JH. Survivorship of the St Georg Sled medial unicompartmental knee replacement beyond ten years. ACTA ACUST UNITED AC 2006; 88:1164-8. [PMID: 16943465 DOI: 10.1302/0301-620x.88b9.18044] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.1] [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: 11/05/2022]
Abstract
There have been several reports of good survivorship and excellent function at ten years with fixed-bearing unicompartmental knee replacement. However, little is known about survival beyond ten years. From the Bristol database of over 4000 knee replacements, we identified 203 St Georg Sled unicompartmental knee replacements (174 patients) which had already survived ten years. The mean age of the patients at surgery was 67.1 years (35.7 to 85) with 67 (38.5%) being under 65 years at the time of surgery. They were reviewed at a mean of 14.8 years (10 to 29.4) from surgery to determine survivorship and function. There were 99 knees followed up for 15 years, 21 for 20 years and four for 25 years. The remainder failed, were withdrawn, or the patient had died. In 58 patients (69 knees) the implant was in situ at the time of death. Revision was undertaken in 16 knees (7.9%) at a mean of 13 years (10.2 to 21.6) after operation. In seven knees (3.4%) this was for progression of arthritis, in three (1.5%) for wear of polyethylene, in four (2%) for tibial loosening, in two (1%) for fracture of the femoral component and in two (1%) for infection. Two knees (1%) were revised for more than one reason. The mean Bristol knee score of the surviving knees fell from 86 (34 to 100) to 79 (42 to 100) during the second decade. Survivorship to 20 years was 85.9% (95% CI 82.9% to 88.9%) and at 25 years was 80% (95% CI 70.2% to 89.8%). Satisfactory survival of a fixed-bearing unicompartmental knee replacement can be achieved into the second decade and beyond.
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Affiliation(s)
- R G Steele
- The Winford Unit, Avon Orthopaedic Centre Southmead Hospital, Westbury on Trym, Bristol BS10 5NB, UK.
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Sehat KR, Evans RL, Newman JH. Hidden blood loss following hip and knee arthroplasty. Correct management of blood loss should take hidden loss into account. ACTA ACUST UNITED AC 2004. [PMID: 15174554 DOI: 10.1302/0301-620x.86b4.14508] [Citation(s) in RCA: 319] [Impact Index Per Article: 16.0] [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
Following total hip arthroplasty (THA) and total knee arthroplasty (TKR) only the 'visible' measured blood loss is usually known. This underestimates the 'true' total loss, as some loss is 'hidden'. Correct management of blood loss should take hidden loss into account. We studied 101 THAs and 101 TKAs (with re-infusion of drained blood). Following THA, the mean total loss was 1510 ml and the hidden loss 471 ml (26%). Following TKA, the mean total loss was 1498 ml. The hidden loss was 765 ml (49%). Obesity made no difference with either operation. THA involves a small hidden loss, the total loss being 1.3 times that measured. However, following TKA, there may be substantial hidden blood loss due to bleeding into the tissues and residual blood in the joint. The true total loss can be determined by doubling the measured loss.
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Affiliation(s)
- K R Sehat
- Southmead Hospital, Bristol, England, UK
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18
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Sehat KR, Evans RL, Newman JH. Hidden blood loss following hip and knee arthroplasty. Correct management of blood loss should take hidden loss into account. J Bone Joint Surg Br 2004; 86:561-5. [PMID: 15174554] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 04/29/2023]
Abstract
Following total hip arthroplasty (THA) and total knee arthroplasty (TKR) only the 'visible' measured blood loss is usually known. This underestimates the 'true' total loss, as some loss is 'hidden'. Correct management of blood loss should take hidden loss into account. We studied 101 THAs and 101 TKAs (with re-infusion of drained blood). Following THA, the mean total loss was 1510 ml and the hidden loss 471 ml (26%). Following TKA, the mean total loss was 1498 ml. The hidden loss was 765 ml (49%). Obesity made no difference with either operation. THA involves a small hidden loss, the total loss being 1.3 times that measured. However, following TKA, there may be substantial hidden blood loss due to bleeding into the tissues and residual blood in the joint. The true total loss can be determined by doubling the measured loss.
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Affiliation(s)
- K R Sehat
- Southmead Hospital, Bristol, England, UK
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19
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Kjellstrand CM, Evans RL, Petersen RJ, Shideman JR, Hartitzsch BV, Buselmeier TJ. The “unphysiology” of dialysis: A major cause of dialysis side effects? Hemodial Int 2004; 8:24-9. [DOI: 10.1111/j.1492-7535.2004.00083.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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20
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Ashraf T, Newman JH, Evans RL, Ackroyd CE. Lateral unicompartmental knee replacement survivorship and clinical experience over 21 years. J Bone Joint Surg Br 2002; 84:1126-30. [PMID: 12463656 DOI: 10.1302/0301-620x.84b8.13447] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
We describe 88 knees (79 patients) with lateral unicompartmental osteoarthritis which had been treated by the St Georg Sled prosthesis. At a mean follow-up of nine years (2 to 21) 15 knees had revision surgery, nine for progression of arthritis, six for loosening, four for breakage of a component and four for more than one reason. Six patients complained of moderate or severe pain at the final follow-up. Only five knees were lost to follow-up in the 21-year period. We performed survivorship analysis on the group using revision for any cause as the endpoint. At ten years the cumulative survival rate was 83%, and at 15 years, when ten knees were still at risk, it was 74%. Based on our clinical results and survival rate the St Georg Sled may be considered to be a suitable unicompartmental replacement for isolated lateral compartment osteoarthritis.
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Affiliation(s)
- T Ashraf
- Bristol Knee Group, Winford Unit, Avon Orthopaedic Centre, Southmead Hospital, Bristol, England, UK
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22
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Curley RM, Evans RL, Kaylor J, Pogash RM, Chinchilli VM. Development and deployment of an internet-based data management system for use by the Asthma Clinical Research Network. Control Clin Trials 2001; 22:135S-55S. [PMID: 11728620 DOI: 10.1016/s0197-2456(01)00174-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Data management system development for the first Asthma Clinical Research Network (ACRN) study began at the data coordinating center (DCC) in May 1995 with the requirement for delivery of a production system by November 1995. Special methods had to be used to establish an internet local area network (LAN), place clinical client systems, and achieve an accelerated software development cycle. The development of a fully integrated data management system prior to the start of the study was not possible. Therefore an early analysis focused on identifying discrete groupings of data management functions that would allow development of distinct database modules to provide specific functionality such as subject randomization, subject registration, and data entry. The modules were categorized as either being associated with clinical centers or the DCC so that the clinical center modules could be developed and delivered to meet the start date of the study. In the second phase of development during the relatively slow patient-enrollment period, the DCC functional modules were delivered discretely over time. While at the time this development model was a necessity due to limited DCC resources, it continues to be used today as it permits the DCC to implement studies more rapidly and efficiently for the ACRN. This paper describes the methodologies used to develop an internet-based LAN, establish clinical center client systems, establish DCC client and server operations, and develop a data management system. It describes the circumstances that contributed to the development of these systems and the special methodologies developed. The technical aspects of the data management system and LAN are presented as well as a description of the requirements and constraints analysis used to develop the hardware and software systems.
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Affiliation(s)
- R M Curley
- Department of Health Evaluation Sciences, College of Medicine, Pennsylvania State University, Hershey, PA, USA
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24
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Hess HM, Curley RM, Chinchilli VM, Cherniack RM, Evans RL. Modem remote support of pulmonary-function testing and quality control systems. Control Clin Trials 2001; 22:156S-67S. [PMID: 11728621 DOI: 10.1016/s0197-2456(01)00169-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
The data coordinating center (DCC) of the Asthma Clinical Research Network (ACRN) is responsible for the support of 11 pulmonary-function testing systems and two quality control systems. Pulmonary-function data from these systems are used as outcome indicators in studies conducted by the ACRN. Each of these systems is composed of a spirometer, a personal computer for data acquisition from the spirometer, a modem, and a printer. These systems are located at six clinical centers nationwide. An analysis conducted at the beginning of the first ACRN protocol identified the following requirements: (1) standard pulmonary-function testing, (2) standard methacholine-challenge testing, (3) the ability to handle simultaneous multiple protocols as well as have data from non-ACRN subjects, (4) the ability to separate data from different protocols as well as separate ACRN and non-ACRN data, (5) the ability to transmit data from the remote clinical centers to the DCC, (6) the ability to ensure quality data and to report on those results, and (7) the ability to provide remote support.
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Affiliation(s)
- H M Hess
- Department of Health Evaluation Sciences, College of Medicine, Pennsylvania State University, Hershey, PA 17033, USA
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Abstract
PURPOSE Prior rehabilitation outcome studies have had many weaknesses. but they gradually observe a lack of long-term benefits from inpatient care alone. The goal of this study was to measure the additive effect of outpatient, subacute rehabilitation (compared with usual outpatient primary medical care) for adults diagnosed with a disabling disorder in four major diagnostic groups (nervous, circulatory, musculoskeletal and injury). METHOD A randomized clinical trial was conducted to determine the effects of outpatient, subacute rehabilitative care on: (1) physical function; (2) health; (3) well being; (4) family function; and (5) social support. Patients hospitalized for the first time with a disabling condition (n = 180) were provided inpatient rehabilitation and then were randomly assigned to either outpatient, subacute rehabilitation at home (n = 90) or to usual outpatient follow-up (n = 90) in which only primary care medical services were provided. To compare the two groups, univariate analyses of covariance were conducted for the outcome variables. RESULTS The major finding of this study was that of no significant effect of the intervention on any outcome variable. CONCLUSIONS Based on current study results, we conclude that any long term additive benefit of outpatient, subacute rehabilitation may not be detectable across disability categories and may require closer evaluation in studies with a more homogeneous population than in the current study. Providing complex follow-up case management services to all clients is apparently not beneficial and might better be provided using selection criteria based on need. Future studies should determine if services are more effective when provided to those with the most unmet rehabilitative needs. Further outpatient, subacute care rehabilitation studies should address the specific needs of the patients and be adapted individually to those needs.
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Affiliation(s)
- R L Evans
- School of Social Work, University of Washington, Seattle, USA.
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Bronfort G, Evans RL, Kubic P, Filkin P. Chronic pediatric asthma and chiropractic spinal manipulation: a prospective clinical series and randomized clinical pilot study. J Manipulative Physiol Ther 2001; 24:369-77. [PMID: 11514813 DOI: 10.1067/mmt.2001.116417] [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] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
OBJECTIVES The first objective was to determine if chiropractic spinal manipulative therapy (SMT) in addition to optimal medical management resulted in clinically important changes in asthma-related outcomes in children. The second objective was to assess the feasibility of conducting a full-scale, randomized clinical trial in terms of recruitment, evaluation, treatment, and ability to deliver a sham SMT procedure. STUDY DESIGN Prospective clinical case series combined with an observer-blinded, pilot randomized clinical trial with a 1-year follow-up period. SETTING Primary contact, college outpatient clinic, and a pediatric hospital. PATIENTS A total of 36 patients aged 6 to 17 years with mild and moderate persistent asthma were admitted to the study. OUTCOME MEASURES Pulmonary function tests; patient- and parent- or guardian-rated asthma-specific quality of life, asthma severity, and improvement; am and pm peak expiratory flow rates; and diary-based day and nighttime symptoms. INTERVENTIONS Twenty chiropractic treatment sessions were scheduled during the 3-month intervention phase. Patients were randomly assigned to receive either active SMT or sham SMT in addition to their standardized ongoing medical management. RESULTS It is possible to blind the participants to the nature of the SMT intervention, and a full-scale trial with the described design is feasible to conduct. At the end of the 12-week intervention phase, objective lung function tests and patient-rated day and nighttime symptoms based on diary recordings showed little or no change. Of the patient-rated measures, a reduction of approximately 20% in beta(2) bronchodilator use was seen (P =.10). The quality of life scores improved by 10% to 28% (P <.01), with the activity scale showing the most change. Asthma severity ratings showed a reduction of 39% (P <.001), and there was an overall improvement rating corresponding to 50% to 75%. The pulmonologist-rated improvement was small. Similarly, the improvements in parent- or guardian-rated outcomes were mostly small and not statistically significant. The changes in patient-rated severity and the improvement rating remained unchanged at 12-month posttreatment follow-up as assessed by a brief postal questionnaire. CONCLUSION After 3 months of combining chiropractic SMT with optimal medical management for pediatric asthma, the children rated their quality of life substantially higher and their asthma severity substantially lower. These improvements were maintained at the 1-year follow-up assessment. There were no important changes in lung function or hyperresponsiveness at any time. The observed improvements are unlikely as a result of the specific effects of chiropractic SMT alone, but other aspects of the clinical encounter that should not be dismissed readily. Further research is needed to assess which components of the chiropractic encounter are responsible for important improvements in patient-oriented outcomes so that they may be incorporated into the care of all patients with asthma.
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Affiliation(s)
- G Bronfort
- Wolfe-Harris Center for Clinical Studies, Northwestern Health Sciences University, Bloomington, MN 55431, USA
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27
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Park K, Evans RL, Watson GE, Nehrke K, Richardson L, Bell SM, Schultheis PJ, Hand AR, Shull GE, Melvin JE. Defective fluid secretion and NaCl absorption in the parotid glands of Na+/H+ exchanger-deficient mice. J Biol Chem 2001; 276:27042-50. [PMID: 11358967 DOI: 10.1074/jbc.m102901200] [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] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Multiple Na(+)/H(+) exchangers (NHEs) are expressed in salivary gland cells; however, their functions in the secretion of saliva by acinar cells and the subsequent modification of the ionic composition of this fluid by the ducts are unclear. Mice with targeted disruptions of the Nhe1, Nhe2, and Nhe3 genes were used to study the in vivo functions of these exchangers in parotid glands. Immunohistochemistry indicated that NHE1 was localized to the basolateral and NHE2 to apical membranes of both acinar and duct cells, whereas NHE3 was restricted to the apical region of duct cells. Na(+)/H(+) exchange was reduced more than 95% in acinar cells and greater than 80% in duct cells of NHE1-deficient mice (Nhe1(-/-)). Salivation in response to pilocarpine stimulation was reduced significantly in both Nhe1(-/-) and Nhe2(-/-) mice, particularly during prolonged stimulation, whereas the loss of NHE3 had no effect on secretion. Expression of Na(+)/K(+)/2Cl(-) cotransporter mRNA increased dramatically in Nhe1(-/-) parotid glands but not in those of Nhe2(-/-) or Nhe3(-/-) mice, suggesting that compensation occurs for the loss of NHE1. The sodium content, chloride activity and osmolality of saliva in Nhe2(-/-) or Nhe3(-/-) mice were comparable with those of wild-type mice. In contrast, Nhe1(-/-) mice displayed impaired NaCl absorption. These results suggest that in parotid duct cells apical NHE2 and NHE3 do not play a major role in Na(+) absorption. These results also demonstrate that basolateral NHE1 and apical NHE2 modulate saliva secretion in vivo, especially during sustained stimulation when secretion depends less on Na(+)/K(+)/2Cl(-) cotransporter activity.
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Affiliation(s)
- K Park
- Center for Oral Biology, Rochester Institute of Biomedical Sciences, and the Eastman Department of Dentistry, University of Rochester Medical Center, Rochester, New York 14642, USA
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Abstract
Thousands of genetically modified mice have been developed since the first reports of stable expression of recombinant DNA in this species nearly 20 years ago. This mammalian model system has revolutionized the study of whole-animal, organ, and cell physiology. Transgenic and gene-targeted mice have been widely used to characterize salivary-gland-specific expression and to identify genes associated with tumorigenesis. Moreover, several of these mouse lines have proved to be useful models of salivary gland disease related to impaired immunology, i.e., Sjögren's syndrome, and disease states associated with pathogens. Despite the availability of genetically modified mice, few investigators have taken advantage of this resource to better their understanding of salivary gland function as it relates to the production of saliva. In this article, we describe the methods used to generate transgenic and gene-targeted mice and provide an overview of the advantages of and potential difficulties with these models. Finally, using these mouse models, we discuss the advances made in our understanding of the salivary gland secretion process.
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Affiliation(s)
- J E Melvin
- Center for Oral Biology, University of Rochester School of Medicine and Dentistry, Aab Institute of Biomedical Sciences, NY 14642, USA.
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Bronfort G, Evans RL, Anderson AV, Schellhas KP, Garvey TA, Marks RA, Bittell S. Nonoperative treatments for sciatica: a pilot study for a randomized clinical trial. J Manipulative Physiol Ther 2000; 23:536-44. [PMID: 11050610 DOI: 10.1067/mmt.2000.109678] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [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
OBJECTIVES To assess the feasibility of patient recruitment, the ability of patients and clinicians to comply with study protocols, and the use of data collection instruments to collect cost-effectiveness data, and to obtain variability estimates for sample-size calculations for a full-scale trial. STUDY DESIGN Prospective, observer-blinded, pilot randomized clinical trial. SETTING Primary contact chiropractic and medical clinics. PATIENTS Ages 20 to 65 years, with low back-related radiating leg pain (sciatica). OUTCOME MEASURES Self-report questionnaires were administered at baseline and 3 and 12 weeks after randomization. The measures included leg and back pain severity, frequency and bothersomeness of symptoms, leg/back disability, medication use, global improvement, satisfaction, and health care utilization. INTERVENTIONS Medical care, chiropractic care, and epidural steroid injections. RESULTS A total of 706 persons were screened by phone to determine initial eligibility. Of these, over 90% of those persons contacted did not meet the entrance criteria. The most common reason for disqualification was that the duration of the complaint was longer than 3 months. Twenty patients were randomized into the study. All 3 groups showed substantial improvements in the main patient-rated outcomes at the end of the 12-week intervention phase. For leg pain, back pain, frequency and bothersomeness of leg symptoms, and Roland-Morris disability score, the percent improvement varied from 50% to 84%, and the corresponding effect sizes ranged from 0.8 to 2.2. Bothersomeness of leg symptoms was the most responsive outcome associated with the largest magnitude of effect size. All within-group changes from baseline were statistically significant (P <.01). No between-group comparisons were planned or performed because of the insufficient sample size and high risk of committing type I and type II errors. CONCLUSIONS Pilot studies such as these are important for the determination of the feasibility of conducting costly, larger scale trials. Recruitment for a full-scale study of sciatica of 2 to 12 weeks duration is not feasible, given the methods used in this pilot study. Our results do indicate, however, that there are substantial numbers of patients with sciatica more chronic in nature who would be interested in participating in a similar study. In addition, collaboration with a local health maintenance organization would likely facilitate clinician referrals and optimize the recruitment process. Patient and provider compliance was high in the pilot study, which indicates that most study protocols are feasible. Additionally, we were able to collect complete outcomes data, including those regarding health care use. A suggested modification by investigators and outside consultants has resulted in the replacement of the medication group with a minimal intervention control group (ie, self-care advice). As a result, a second pilot study of patients with sciatica of more than 4 weeks duration has been planned before a full-scale trial is attempted.
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Affiliation(s)
- G Bronfort
- Wolfe-Harris Center for Clinical Studies, Northwestern Health Sciences University, Bloomington, MN 55431, USA.
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Evans RL, Park K, Turner RJ, Watson GE, Nguyen HV, Dennett MR, Hand AR, Flagella M, Shull GE, Melvin JE. Severe impairment of salivation in Na+/K+/2Cl- cotransporter (NKCC1)-deficient mice. J Biol Chem 2000; 275:26720-6. [PMID: 10831596 DOI: 10.1074/jbc.m003753200] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The salivary fluid secretory mechanism is thought to require Na(+)/K(+)/2Cl(-) cotransporter-mediated Cl(-) uptake. To directly test this possibility we studied the in vivo and in vitro functioning of acinar cells from the parotid glands of mice with targeted disruption of Na(+)/K(+)/2Cl(-) cotransporter isoform 1 (Nkcc1), the gene encoding the salivary Na(+)/K(+)/2Cl(-) cotransporter. In wild-type mice NKCC1 was localized to the basolateral membranes of parotid acinar cells, whereas expression was not detected in duct cells. The lack of functional NKCC1 resulted in a dramatic reduction (>60%) in the volume of saliva secreted in response to a muscarinic agonist, the primary in situ salivation signal. Consistent with defective Cl(-) uptake, a loss of bumetanide-sensitive Cl(-) influx was observed in parotid acinar cells from mice lacking NKCC1. Cl(-)/ HCO(3)(-) exchanger activity was increased in parotid acinar cells isolated from knockout mice suggesting that the residual saliva secreted by mice lacking NKCC1 is associated with anion exchanger-dependent Cl(-) uptake. Indeed, expression of the Cl(-)/ HCO(3)(-) exchanger AE2 was enhanced suggesting that this transporter compensates for the loss of functional Na(+)/K(+)/2Cl(-) cotransporter. Furthermore, the ability of the parotid gland to conserve NaCl was abolished in NKCC1-deficient mice. This deficit was not associated with changes in the morphology of the ducts, but transcript levels for the alpha-, beta-, and gamma-subunits of the epithelial Na(+) channel were reduced. These data directly demonstrate that NKCC1 is the major Cl(-) uptake mechanism across the basolateral membrane of acinar cells and is critical for driving saliva secretion in vivo.
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Affiliation(s)
- R L Evans
- Center for Oral Biology, Aab Institute of Biomedical Sciences and the Eastman Department of Dentistry, University of Rochester Medical Center, Rochester, New York 14642, USA.
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Affiliation(s)
- K Park
- Center for Oral Biology, Aab Institute of Biomedical Research, University of Rochester Medical Center, New York 14642, USA.
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Pope AR, Rodell DE, Evans RL. Program review of community residential care. Psychol Rep 2000; 86:21-4. [PMID: 10778244 DOI: 10.2466/pr0.2000.86.1.21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [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: 11/15/2022]
Abstract
This article provides an overview of the Department of Veterans Affairs Community Residential Care Program and summarizes key literature about programs developed in the United States. Descriptive data for 1995 and 1996 are provided to assist program planners in comparing and contrasting client characteristics and services. The authors conclude that, in addition to being cost effective, the residential care program strengthens relationships between the health care facility and the community it serves.
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Affiliation(s)
- A R Pope
- Pope & Associates, Chicago, Illinois, USA
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Ananthaswamy HN, Ouhtit A, Evans RL, Gorny A, Khaskina P, Sands AT, Conti CJ. Persistence of p53 mutations and resistance of keratinocytes to apoptosis are associated with the increased susceptibility of mice lacking the XPC gene to UV carcinogenesis. Oncogene 1999; 18:7395-8. [PMID: 10602497 DOI: 10.1038/sj.onc.1203147] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [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: 01/10/2023]
Abstract
Like xeroderma pigmentosum (XP) patients, transgenic mice lacking nucleotide excision repair (NER) genes such as XPA and XPC are extremely susceptible to ultraviolet (UV)-induced skin cancer. Because the p53 gene is an important target for UV carcinogenesis and because the p53 protein modulates NER, we investigated the consequences of NER deficiency on UV-induced p53 mutations in XPC-/- mouse skin tumors. Thirty-eight (76%) of 50 UV-induced XPC-/- skin tumor analysed displayed C-->T or CC-->TT transitions at dipyrimidine sites on the untranscribed strand of the p53 gene. A major hot spot for p53 mutation occurred at codon 270, which is also a hot spot in UV-induced skin tumors from NER-proficient C3H and SKH-hr 1 mice. Interestingly, codon 270 mutations were induced in both XPC-/- and +/+ mouse skin after 1 week of UV irradiation, but the mutations persisted only in XPC-/- mouse skin after 3 - 4 weeks of chronic UV. The persistence of UV-induced p53 mutations in XPC-/- mouse skin was associated with decreased apoptosis and increased proliferation of keratinocytes, suggesting that these events may contribute to the accelerated development of UV-induced skin tumors in XPC-/- mice.
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Affiliation(s)
- H N Ananthaswamy
- Department of Immunology, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Blvd., Houston, Texas, TX 77030, USA
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34
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Evans RL, Tarits P, Chave AD, White A, Heinson G, Filloux JH, Toh H, Seama N, Utada H, Booker JR, Unsworth MJ. Asymmetric Electrical Structure in the Mantle Beneath the East Pacific Rise at 17 degrees S. Science 1999; 286:752-756. [PMID: 10531056 DOI: 10.1126/science.286.5440.752] [Citation(s) in RCA: 109] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The magnetotelluric component of the Mantle Electromagnetic and Tomography (MELT) Experiment measured the electrical resistivity structure of the mantle beneath the fast-spreading southern East Pacific Rise (EPR). The data reveal an asymmetric resistivity structure, with lower resistivity to the west of the ridge. The uppermost 100 kilometers of mantle immediately to the east of the ridge is consistent with a dry olivine resistivity structure indicating a mantle depleted of melt and volatiles. Mantle resistivities to the west of the ridge are consistent with a low-melt fraction (about 1 to 2 percent interconnected melt) distributed over a broad region and extending to depths of about 150 kilometers. The asymmetry in resistivity structure may be the result of asymmetric spreading rates and a westward migration of the ridge axis and suggests distinct styles of melt formation and delivery in the mantle beneath the two plates.
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Affiliation(s)
- RL Evans
- Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA. UMR CNRS 6538, Universite Bretagne Occidentale, Brest, France. Flinders University, Adelaide, South Australia 5042, Australia. Scripps Institution of Oceanography, La Jolla, CA 92093, USA. Toyama University, Toyama 930-8555, Japan. Chiba University, Chiba, Japan. Earthquake Research Institute, University of Tokyo, Tokyo 113, Japan. Geophysics Program AK-50, University of Washington, Seattle, WA 98195, USA
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35
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Evans RL, Bell SM, Schultheis PJ, Shull GE, Melvin JE. Targeted disruption of the Nhe1 gene prevents muscarinic agonist-induced up-regulation of Na(+)/H(+) exchange in mouse parotid acinar cells. J Biol Chem 1999; 274:29025-30. [PMID: 10506152 DOI: 10.1074/jbc.274.41.29025] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.3] [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: 11/06/2022] Open
Abstract
The onset of salivary gland fluid secretion in response to muscarinic stimulation is accompanied by up-regulation of Na(+)/H(+) exchanger (NHE) activity. Although multiple NHE isoforms (NHE1, NHE2, and NHE3) have been identified in salivary glands, little is known about their specific function(s) in resting and secreting acinar cells. Mice with targeted disruptions of the Nhe1, Nhe2, and Nhe3 genes were used to investigate the contribution of these proteins to the stimulation-induced up-regulation of NHE activity in mouse parotid acinar cells. The lack of NHE1, but not NHE2 or NHE3, prevented intracellular pH recovery from an acid load in resting acinar cells, in acini stimulated to secrete with the muscarinic agonist carbachol, and in acini shrunken by hypertonic addition of sucrose. In HCO(3)(-)-containing solution, the rate of intracellular pH recovery from a muscarinic agonist-stimulated acid load was significantly inhibited in acinar cells from mice lacking NHE1, but not in cells from NHE2- or NHE3-deficient mice. These data demonstrate that NHE1 is the major regulator of intracellular pH in both resting and muscarinic agonist-stimulated acinar cells and suggest that up-regulation of NHE1 activity has an important role in modulating saliva production in vivo.
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Affiliation(s)
- R L Evans
- Center for Oral Biology, Rochester Institute of Biomedical Sciences, University of Rochester Medical Center, Rochester, New York 14642, USA
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Sawyer CE, Evans RL, Boline PD, Branson R, Spicer A. A feasibility study of chiropractic spinal manipulation versus sham spinal manipulation for chronic otitis media with effusion in children. J Manipulative Physiol Ther 1999; 22:292-8. [PMID: 10395431 DOI: 10.1016/s0161-4754(99)70061-8] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [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: 10/25/2022]
Abstract
BACKGROUND Pediatric otitis media with effusion is a common and costly condition. Although chiropractors have anecdotally claimed success in treating otitis media, there is little research to support their claims. OBJECTIVE A pilot study was undertaken for the purpose of assessing the feasibility of conducting a full-scale randomized clinical trial investigating the efficacy of chiropractic spinal manipulative therapy (SMT) for children with chronic otitis media with effusion. METHODS This study was a prospective, parallel-group, observer-blinded, randomized feasibility study. Twenty-two patients, ages 6 months to 6 years, received either active chiropractic SMT or placebo chiropractic SMT. Otoscopy and tympanometry were used to create a middle ear status profile, and daily diaries were collected. RESULTS Five newspaper advertisements over 6 months generated 105 responses. Twenty patients subsequently qualified and were randomized into the study. Collection of tympanometric and otoscopic data proved to be challenging. Compliance with the treatment and evaluation protocols and daily diaries was excellent. There were no reports of serious side effects as a result of either the active or placebo chiropractic treatments. CONCLUSION Recruitment for a randomized controlled trial is feasible and could be enhanced by medical collaboration. Patients and parents are able and willing to participate in a study comparing active SMT and placebo SMT. Parents were extremely compliant with the daily diaries, suggesting that similar quality-of-life and functional status measures can be successfully used in a larger trial. We found the objective outcomes assessment involving tympanometry and otoscopy extremely challenging and should be performed by experienced examiners in future studies.
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Affiliation(s)
- C E Sawyer
- Academic Affairs, Northwestern College of Chiropractic, Bloomington, Minnesota 55431, USA
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Abstract
Recent reports characterizing the physiological properties of normal human labial acini are reviewed with particular emphasis on mechanisms related to fluid secretion. In contrast to the salivary glands of several experimental animals, human labial acinar cells do not appear to have a1-adrenergic receptors, substance P peptidergic receptors, or significant levels of Cl-/HCO3- exchange. Nor do they appear to secrete HCO3- in response to Ca2+ mobilizing stimuli. The data presently available indicates that fluid secretion by these glands is mainly under muscarinic control and is due to acinar Cl- secretion driven by a basolateral Na+ -K+ -2Cl- cotansporter.
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Affiliation(s)
- R J Turner
- Gene Therapy and Therapeutics Branch, National Institute of Dental Research, National Institutes of Health, Bethesda, MD 20892, USA.
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38
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Evans RL. Perceived functional health of disabled elderly persons in a follow-up program for primary care. Psychol Rep 1999; 84:553-7. [PMID: 10335067 DOI: 10.2466/pr0.1999.84.2.553] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [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: 11/15/2022]
Abstract
180 disabled elderly persons were followed in a home care program after acute care rehabilitation in order to correlate subjective and objective ratings of medical, physical, and social functioning. To assess the benefits of case management services, 95 test patients receiving such care at home were compared with 85 controls who did not receive services. Both groups reported gains in functional health and their reports were verified with objective measures. There was no difference, however, between the groups in outcome. Our findings indicated that self-assessments correlate highly with measures of functional health. Procedures for self-ratings should be developed as important complements to objective functional health measures.
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Bell SM, Schreiner CM, Schultheis PJ, Miller ML, Evans RL, Vorhees CV, Shull GE, Scott WJ. Targeted disruption of the murine Nhe1 locus induces ataxia, growth retardation, and seizures. Am J Physiol 1999; 276:C788-95. [PMID: 10199808 DOI: 10.1152/ajpcell.1999.276.4.c788] [Citation(s) in RCA: 170] [Impact Index Per Article: 6.8] [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
In most cells, the ubiquitously expressed Na+/H+ exchanger isoform 1 (NHE1) is thought to be a primary regulator of pH homeostasis, cell volume regulation, and the proliferative response to growth factor stimulation. To study the function of NHE1 during embryogenesis when these cellular processes are very active, we targeted the Nhe1 gene by replacing the sequence encoding transmembrane domains 6 and 7 with the neomycin resistance gene. NHE activity assays on isolated acinar cells indicated that the targeted allele is functionally null. Although the absence of NHE1 is compatible with embryogenesis, Nhe1 homozygous mutants (-/-) exhibit a decreased rate of postnatal growth that is first evident at 2 wk of age. At this time, Nhe1 -/- animals also begin to exhibit ataxia and epileptic-like seizures. Approximately 67% of the -/- mutants die before weaning. Postmortem examinations frequently revealed an accumulation of a waxy particulate material inside the ears, around the eyes and chin, and on the ventral surface of the paws. Histological analysis of adult tissues revealed a thickening of the lamina propria and a slightly atrophic glandular mucosa in the stomach.
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Affiliation(s)
- S M Bell
- Division of Developmental Biology, Children's Hospital Research Foundation, Cincinnati 45229, Ohio.
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O'Connell AC, Redman RS, Evans RL, Ambudkar IS. Radiation-induced progressive decrease in fluid secretion in rat submandibular glands is related to decreased acinar volume and not impaired calcium signaling. Radiat Res 1999; 151:150-8. [PMID: 9952299] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
Abstract
The mechanism(s) of radiation-induced salivary gland dysfunction is poorly understood. In the present study, we have assessed the secretory function (muscarinic agonist-stimulated saliva flow, intracellular calcium mobilization, Na+/K+/2Cl- cotransport activity) in rat submandibular glands 12 months postirradiation (single dose, 10 Gy). The morphological status of glands from control and irradiated rats was also determined. Pilocarpine-stimulated salivary flow was decreased by 67% at 12 months (but not at 3 months) after irradiation. This was associated with a 47% decrease in the wet weight of the irradiated glands. Histological and morphometric analysis demonstrated that acinar cells were smaller and occupied relatively less volume and convoluted granular tubules were smaller but occupied the same relative volume, while intercalated and striated ducts maintained their size but occupied a greater relative volume in submandibular glands from irradiated compared to control animals. In addition, no inflammation or fibrosis was observed in the irradiated tissues. Carbachol- or thapsigargin-stimulated mobilization of Ca2+ was similar in dispersed submandibular gland cells from control and irradiated animals. Further, [Ca2+]i imaging of individual ducts and acini from control and irradiated groups showed, for the first time, that mobilization of Ca2+ in either cell type was not altered by the radiation treatment. The carbachol-stimulated, bumetanide-sensitive component of the Na+/K+/ 2Cl- cotransport activity was also similar in submandibular gland cells from control and irradiated animals. These data demonstrate that a single dose of gamma radiation induces a progressive loss of submandibular gland tissue and function. This loss of salivary flow is not due to chronic inflammation or fibrosis of the gland or an alteration in the neurotransmitter signaling mechanism in the acinar or ductal cells. The radiation-induced decrease in fluid secretion appears to be related to a change in either the water-handling capacity of the acini or the number of acinar cells in the gland.
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Affiliation(s)
- A C O'Connell
- Gene Therapy and Therapeutics Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland 20892, USA
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Thompson AM, Cavert HM, Lifson N, Evans RL. Regional tissue uptake of deuterium oxide in perfused organs: rat liver, dog heart and gastrocnemius. ACTA ACUST UNITED AC 1998; 197:897-902. [PMID: 13838057 DOI: 10.1152/ajplegacy.1959.197.4.897] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Abstract
PURPOSE The goal of this clinical trial was to examine the long-term impact of rehabilitative care on the health status of patients diagnosed with a disabling disorder. METHOD Study patients consisted of first-time hospitalizations from diagnostic groups commonly admitted for inpatient rehabilitation, including nervous, circulatory, and musculoskeletal disorders or injury. Patients were randomly assigned to inpatient rehabilitation (n = 43) or to outpatient follow-up (n = 42) in which the usual medical services were provided but no scheduled rehabilitative therapies were offered. Specific objectives of the study were to determine the effects of impatient rehabilitation on: (1) functional ability, (2) health and mental health status, (3) personal adjustment, and (4) family function. Cost and use of health-care resources were descriptively assessed. RESULTS Analysis of covariance found no significant treatment effects, either at 6 months or at 1 year, for any of the variables under study. In addition, there were no differences between groups in their use of nursing homes, length of hospital stay, mortality, or in the number of hospital readmissions or clinic visits during the first year after hospital discharge. Use of rehabilitation services and cost of care was significantly higher than outpatient services. The findings were consistent with previous studies for most outcomes, with the major exception being functional improvements. Contrary to earlier studies, rehabilitation was not found to effectively produce lasting functional outcomes. However, study conditions may not have fully corresponded to those of previous studies, and further research is needed. The patient sample was representative of a full inpatient service and therefore more heterogeneous than samples reported in prior studies, but the small sample size (due to reductions in the number of admitted patients to the rehabilitation unit during the course of the study) precluded subgroup analysis of diagnostic groupings. CONCLUSION The findings suggest that hospital-based rehabilitative care does not have lasting benefits, and that alternative care or supportive follow-up by a subacute-care facility may be needed to assist patients in maintaining functional gains and health benefits.
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Affiliation(s)
- R L Evans
- VA Puget Sound Health Care System (122), Seattle, WA 98108, USA
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Evans RL, Turner RJ. New insights into the upregulation and function of the salivary Na+-K+-2Cl- cotransporter. Eur J Morphol 1998; 36 Suppl:142-6. [PMID: 9825910] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Abstract
In many exocrine epithelia, the Na+-K+-2Cl- cotransporter is the main provider of cellular chloride entry during transepithelial salt and water secretion. Because of its accessibility and hormonal responsiveness, the salivary gland has recently emerged as a convenient preparation in which to study the regulation and characteristics of this transport protein. In this review, we summarize recent findings from our laboratory which demonstrate that muscarinic, alpha1-adrenergic and peptidergic stimulation of rat parotid acinar cells induce a dramatic (up to twenty-fold) upregulation of Na+-K+-2Cl- cotransporter activity. Our results indicate that this effect is dependent on the rise in intracellular calcium concentration ([Ca2+]i) that accompanies stimulation, and is not a consequence of the KCl loss and the concomitant cell shrinkage associated with fluid secretion. In addition, we show that the effect of muscarinic stimulation on the cotransporter can be blocked by inhibitors of phospholipase A2, by a general inhibitor of arachidonic acid metabolism, and by specific inhibitors of the cytochrome P450 pathway. These data argue strongly for the involvement of a product of the cytochrome P450 pathway of arachidonic acid metabolism in upregulation of the salivary Na+-K+-2Cl- cotransporter.
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Affiliation(s)
- R L Evans
- Membrane Biology Section, Gene Therapy and Therapeutics Branch, National Institute of Dental Research, National Institutes of Health, Bethesda, MD 20892, USA.
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Zhang Z, Evans RL, Culp DJ. In vitro studies of the regulation of mucous gland secretion. Eur J Morphol 1998; 36 Suppl:219-21. [PMID: 9825926] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Abstract
Our laboratory is concerned with elucidation of mechanisms regulating the exocrine secretion of mucin glycoproteins by mucous cells of salivary mucous glands. As a model system for our studies we use short-term cultures of acinar structures isolated from rat sublingual glands. Recent results are discussed from an on-going study of cross-talk between the two primary signaling pathways regulating exocrine secretion from isolated sublingual acini: the muscarinic cholinergic and vasoactive intestinal peptide (VIP) pathways. The combination of muscarinic agonist (carbachol) and VIP elicits a secretion equivalent to about 150% of the additive sum of the secretory responses to each agonist alone. This synergistic secretory response is only observed at submaximal concentrations of carbachol. VIP thus serves to decrease the EC50 for carbachol nearly three-fold. Results are thus far consistent with the hypothesis that a sustained rise in the intracellular concentration of calcium ions induced by VIP accounts for synergistic secretion and the heightened sensitivity to carbachol.
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Affiliation(s)
- Z Zhang
- Dept. Dental Research, Univ. of Rochester Medical Center, NY 14642, USA
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Abstract
The secretory Na(+)-K(+)-2Cl- cotransporter in salivary acinar cells is responsible for driving the transepithelial Cl- fluxes that give rise to fluid secretion. We demonstrate that the application of the muscarinic agonist carbachol to rat parotid acini results in an intracellular acid load that can be blocked by bumetanide, a specific inhibitor of the cotransporter. One component of this bumetanide-sensitive acid load is ouabain-sensitive while a second is dependent on the presence of sub-millimolar concentrations of NH4+ in our media. Our data indicate that this latter effect arises from NH4+ entry on the cotransporter operating in a Na(+)-NH4(+)-2Cl- cotransport mode and that at physiological NH4+ levels in the rat (approximately 0.1 mM), 10-15% of the acinar Cl- entry occurs via this route. We suggest that Na(+)-NH4(+)-2Cl- cotransport may also play a significant physiological role in other cell types and that this mode of operation of the secretory Na(+)-K(+)-2Cl- cotransporter could account for the currently unexplained presence of this protein in a number of tissues.
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Affiliation(s)
- R L Evans
- Membrane Biology Section, National Institute of Dental Research, National Institutes of Health, Bethesda, Maryland 20892, USA
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46
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Ananthaswamy HN, Fourtanier A, Evans RL, Tison S, Medaisko C, Ullrich SE, Kripke ML. p53 Mutations in hairless SKH-hr1 mouse skin tumors induced by a solar simulator. Photochem Photobiol 1998; 67:227-32. [PMID: 9487800 DOI: 10.1562/0031-8655(1998)067<0227:mihshm>2.3.co;2] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.8] [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: 02/06/2023]
Abstract
In this study, we investigated whether the spectrum of p53 mutations in skin tumors induced in hairless SKH-hr1 mice by a solar simulator (290-400 nm) are similar to those found in skin tumors induced in C3H mice by UV radiation from unfiltered (250-400 nm) and Kodacel-filtered (290-400 nm) FS40 sunlamps. Analysis of tumor DNA for p53 mutations revealed that 14 of 16 (87.5%) SkH-hr1 skin tumors induced by the solar simulator contained mutations. Single C-->T transitions at dipyrimidine sequences located on the nontranscribed DNA strand were the most predominant type of p53 mutation. Remarkably, 52% of all p53 mutations in solar simulator-induced SKH-hr1 skin tumors occurred at codon 270, which is also a hotspot in C3H skin tumors induced by unfiltered and Kodacel-filtered FS40 sunlamps. However, T-->G transversions, which are hallmarks of UVA-induced mutations, were not detected in any of the solar simulator-induced skin tumors analyzed. These results demonstrate that the p53 mutation spectra seen in solar simulator-induced SKH-hr1 skin tumors are similar to those present in -unfiltered and Kodacel-filtered FS40 sunlamp-induced C3H skin tumors. In addition, our data indicate that the UVA present in solar simulator radiation does not play a role in the induction of p53 mutations that contribute to skin cancer development.
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Affiliation(s)
- H N Ananthaswamy
- Department of Immunology, University of Texas M. D. Anderson Cancer Center, Houston 77030, USA.
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47
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Rodriguez JA, Evans RL, Daiger SP, Northrup H. Molecular analysis of the human vitamin D binding protein (group specific component, Gc) in tuberous sclerosis complex (TSC). J Med Genet 1997; 34:509-11. [PMID: 9192275 PMCID: PMC1050978 DOI: 10.1136/jmg.34.6.509] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [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: 02/04/2023]
Abstract
Group specific component (Gc) is an abundant plasma protein whose functional role is not clearly established. Gc protein is synthesised in the liver and is known to bind vitamin D, vitamin D metabolites, and G actin; Gc protein is also implicated in macrophage activation. Several polymorphic electrophoretic variants of Gc protein are found in all human populations; the most common alleles are Gc-1f, Gc-1s, and Gc-2. In previous studies, Gc allele frequencies, determined using isoelectric focusing or immunofixation or both, were significantly different in patients with tuberous sclerosis complex (TSC) from matched controls, with an excess of Gc-2 in patients. Linkage association between Gc and TSC is unlikely since the Gc locus maps to chromosome 4q12, whereas the two common forms of TSC map to 9q34 and 16p13.1, respectively. However, a direct cause and effect relationship between Gc protein and TSC symptoms is possible. To investigate further the relationship between the Gc locus and TSC, two Gc restriction site polymorphisms, HaeIII and StyI, were typed in 43 unrelated white subjects with TSC. The frequencies of the restriction site polymorphisms in the TSC patients did not differ from those in control populations. Therefore a direct association between Gc type and TSC is unlikely. The previously reported association was either spurious or the result of typing errors in plasma from subjects with underlying abnormalities in plasma proteins.
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Affiliation(s)
- J A Rodriguez
- Department of Pediatrics, University of Texas Medical School-Houston 77030, USA
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48
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Ananthaswamy HN, Loughlin SM, Cox P, Evans RL, Ullrich SE, Kripke ML. Sunlight and skin cancer: inhibition of p53 mutations in UV-irradiated mouse skin by sunscreens. Nat Med 1997; 3:510-4. [PMID: 9142118 DOI: 10.1038/nm0597-510] [Citation(s) in RCA: 166] [Impact Index Per Article: 6.1] [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: 02/04/2023]
Abstract
UV-induced mutations in the p53 tumor suppressor gene play an essential role in skin cancer development. We report here that such mutations can be detected in UV-irradiated mouse skin months before the gross appearance of skin tumors. Application of SPF-15 sunscreens to mouse skin before each UV irradiation nearly abolished the frequency of p53 mutations. These results indicate that p53 mutation is an early event in UV skin carcinogenesis and that inhibition of this event may serve as an early end point for assessing protective measures against skin cancer development.
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Affiliation(s)
- H N Ananthaswamy
- Department of Immunology, University of Texas M.D. Anderson Cancer Center, Houston 77030, USA
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49
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Ferri C, Evans RL, Paulais M, Tanimura A, Turner RJ. Evidence that up-regulation of the parotid Na(+)-K(+)-2Cl- cotransporter by hypertonic shrinkage is not duplicated by isotonic shrinkage. Mol Cell Biochem 1997; 169:21-5. [PMID: 9089627 DOI: 10.1023/a:1006878324913] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [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: 02/04/2023]
Abstract
The application of Ca2+ mobilizing secretagogues to rat parotid acini results in a significant decrease in cell volume (15-30%) due to isotonic salt loss. It is often assumed that the effects of such an isotonic volume decrease can be mimicked by anisotonic cell shrinkage. We demonstrate that the Na(+)-K(+)-2Cl- cotransporter in these cells is up-regulated by Ca2+ mobilizing secretagogues as well as by cell shrinkage in hypertonic media. However, we find that although the protein kinase inhibitors staurosporine (0.3 microM) and K252a (0.6 microM) significantly blunt the latter up-regulation, they are without effect on the former. These observations suggest that hypertonic and isotonic shrinkage do not result in the activation of the same intracellular signalling pathways, and indicate that anisotonic volume perturbations may not provide good experimental models of physiologic isotonic volume changes.
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Affiliation(s)
- C Ferri
- Clinical Investigations and Patient Care Branch, National Institute of Dental Research, National Institutes of Health, Bethesda MD 20892, USA
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50
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Abstract
1. The effects of fluid secretory stimuli on the Na(+)-K(+)-2Cl- cotransporter in rat parotid acini were investigated. Cotransporter activity was measured using NH4+ as a K+ surrogate and following cotransporter-mediated NH4+ fluxes by monitoring intracellular pH. 2. A dramatic upregulation (15- to 20-fold) of acinar Na(+)-K(+)-2Cl- cotransporter activity was induced by muscarinic, alpha 1-adrenergic and peptidergic stimuli. A half-maximal effect of the muscarinic agonist carbachol was observed at approximately 0.5 microM. 3. Our results indicate that the rise in intracellular calcium concentration ([Ca2+]i) which accompanies these stimuli is both a necessary and a sufficient condition for this effect; but it is not a consequence of the KCl loss and concomitant isotonic shrinkage caused by increased [Ca2+]i as it persists when these effects are prevented. 4. The effect of muscarinic stimulation on the cotransporter can, however, be blocked by inhibitors of phospholipase A2 (4-bromophenacylbromide and manoalide), by a general inhibitor of arachidonic acid metabolism (5,8,11,14-eicosatetraynoic acid) and by specific inhibitors of the cytochrome P450 pathway (methoxsalen and ketoconazole). 5. These latter results argue strongly for the involvement of a product of the cytochrome P450 pathway of arachidonic acid metabolism in upregulation of the salivary Na(+)-K(+)-2Cl- cotransporter. 6. Owing to the complexity of the arachidonic acid cascade a wide variety of agents could potentially interfere with this upregulation of the cotransporter, and thereby result in decreased salivary fluid production. We suggest that such an effect could underlie the dry mouth (xerostomia) that occurs as an unexplained side-effect of many commonly prescribed medications.
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Affiliation(s)
- R L Evans
- Clinical Investigations and Patient Care Branch, National Institute of Dental Research, National Institutes of Health, Bethesda, MD 20892-1190, USA
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