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1.
Cureus ; 16(3): e56516, 2024 Mar.
Article in English | MEDLINE | ID: mdl-38646327

ABSTRACT

INTRODUCTION: Therapeutic plasma exchange (TPE) is used to manage various life-threatening illnesses. It is widely performed by nephrologists, intensivists, pathologists, or experts in transfusion medicine worldwide. However, the costs of TPE sessions are exceedingly high, and they have a huge impact on patients' financial burden. Herein, we investigated the outcomes of the reuse of plasma filters in TPE on several occasions. METHODS: This is a retrospective analysis of patients receiving TPE from January 1, 2020, to April 30, 2023, in the Department of Nephrology. A formulation of 4.5% peracetic acid and 24% hydrogen peroxide acid with RO water dilution was used for reprocessing. Clinical outcomes, risks, and cost-benefit were evaluated and compared between the plasma filter reuse group (GP-1) and the no-reuse group (GP-2). RESULTS: A total of 70 patients were included in this study. 200 and 112 TPE sessions were performed in GP-1 and GP-2, respectively. The most common indication for TPE in both groups was neurological. The clinical efficacy of TPE was similar in both groups. There was no difference in the clotting of the plasma filter, any allergic reaction, infection, or bleeding in the group. However, there was a significant difference in levels of fibrinogen (p=0.03) pre and post-procedure in both groups. The incidence of hypotension was found to be higher in GP-1 (26%) compared to GP-2 (15.6%), p = 0.05. The cost of overall treatment was 38% less in GP-1. CONCLUSION: The reuse of plasma filters is a safe and effective method for cost minimization in patients requiring TPE. This method can be effectively utilized in resource-poor settings without any increased risk of adverse effects.

2.
Curr Opin Oncol ; 35(2): 115-124, 2023 03 01.
Article in English | MEDLINE | ID: mdl-36721896

ABSTRACT

PURPOSE OF REVIEW: The increasing global incidence of cancer demands innovative cancer detection modalities. The current population-based early cancer detection approaches focus on several major types of cancers (breast, prostate, cervical, lung and colon) at their early stages, however, they generally do not target high-risk individuals at precancerous stages. RECENT FINDINGS: Some cancers, such as pancreatic cancer, are challenging to detect in their early stages. Therefore, there is a pressing need for improved, accessible, noninvasive, and cost-effective early detection methods. Harnessing cell-free-based biomarker-driven strategies paves a new era of precision diagnosis for multicancer early detection. The majority of these tests are in the early stages and expensive, but these approaches are expected to become cost sensitive in the near future. SUMMARY: This review provides an overview of early cancer detection strategies, highlighting the methods, challenges, and issues to be addressed to revolutionize and improve global early cancer detection.


Subject(s)
Pancreatic Neoplasms , Precision Medicine , Male , Humans , Medical Oncology , Early Detection of Cancer
4.
Open Biol ; 10(9): 200029, 2020 09.
Article in English | MEDLINE | ID: mdl-32873153

ABSTRACT

Tailless is a committed transcriptional repressor and principal regulator of the brain and eye development in Drosophila. Rpd3, the histone deacetylase, is an established repressor that interacts with co-repressors like Sin3a, Prospero, Brakeless and Atrophin. This study aims at deciphering the role of Rpd3 in embryonic segmentation and larval brain development in Drosophila. It delineates the mechanism of Tailless regulation by Rpd3, along with its interacting partners. There was a significant reduction in Tailless in Rpd3 heteroallelic mutant embryos, substantiating that Rpd3 is indispensable for the normal Tailless expression. The expression of the primary readout, Tailless was correlative to the expression of the neural cell adhesion molecule homologue, Fascilin2 (Fas2). Rpd3 also aids in the proper development of the mushroom body. Both Tailless and Fas2 expression are reported to be antagonistic to the epidermal growth factor receptor (EGFR) expression. The decrease in Tailless and Fas2 expression highlights that EGFR is upregulated in the larval mutants, hindering brain development. This study outlines the axis comprising Rpd3, dEGFR, Tailless and Fas2, which interact to fine-tune the early segmentation and larval brain development. Therefore, Rpd3 along with Tailless has immense significance in early embryogenesis and development of the larval brain.


Subject(s)
Brain/metabolism , Drosophila Proteins/genetics , Drosophila Proteins/metabolism , Drosophila/metabolism , Gene Expression Regulation, Developmental , Histone Deacetylase 1/metabolism , Repressor Proteins/genetics , Animals , Base Sequence , Binding Sites , Biomarkers , Brain/embryology , Drosophila/embryology , Embryonic Development/genetics , Fluorescent Antibody Technique , Histone Deacetylase 1/genetics , Loss of Function Mutation , Protein Binding , Repressor Proteins/metabolism
5.
Environ Sci Pollut Res Int ; 27(8): 7795-7811, 2020 Mar.
Article in English | MEDLINE | ID: mdl-31889285

ABSTRACT

The present work describes synthesis, detailed characterization, and application of bare and surfactant-modified titania nanomaterials (NMs) for various wastewater treatment applications as individual cases like cadmium (Cd) removal, methylene blue (MB) dye degradation, and treatment of real textile and dyeing industry effluent. These NMs are used as adsorbents and photocatalysts in an indegenously developed end-to-end treatment process and a photocatalytic reactor for treatment of textile wastewater. The used NMs are suitably filtered and recovered for reuse; however, still this work focusses on the extent of potential risk and environmental safety of these engineered NMs towards seed germination and plant growth, in the event they escape wastewater treatment plants and reach out to natural water bodies and soil systems, accumulate over a period of time, and comes in contact with plant species. For synthesis, sol-gel method was utilized; cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) were used as cationic and anionic surfactants, respectively, to act as particle growth templates and improve surface morphology. Detailed characterization involved XRD (X-ray diffraction), FTIR (Fourier-transform Infrared Spectroscopy), SEM (Scanning Electron Microscopy), TEM (Transmission Electron Microscopy), EDX (Energy Dispersive X-ray analysis), and BET (Brunauer-Emmett-Teller) surface area analysis. Improved morphology and surface properties, from irregular shape in Bare TiO2 to spherical shape in surfactant-modified titania, led to enhanced Cd removal and MB dye degradation efficiency. Bare TiO2 was used for complete treatment of textile wastewater, which took 5 h in achieving water quality, which is safe for discharge and reuse as per norms of Central Pollution Control Board (CPCB), Govt. of India. Phytotoxicity studies of these NMs at a wide concentration range (0-1000 mg L-1) were undertaken towards Vigna radiata, and 500 mg L-1 concentration was found to be optimally safe for seed germination and plant growth.


Subject(s)
Cadmium/analysis , Surface-Active Agents/chemistry , Titanium/chemistry , Vigna , Cadmium/chemistry , Germination , India , Seeds , Textiles
6.
Sleep Med ; 35: 49-61, 2017 Jul.
Article in English | MEDLINE | ID: mdl-28619182

ABSTRACT

The human body persists in its rhythm as per its initial time zone, and transition always occur according to solar movements around the earth over 24 h. While traveling across different latitudes and longitudes, at the pace exceeding the earth's movement, the changes in the external cues exceed the level of toleration of the body's biological clock. This poses an alteration in our physiological activities of sleep-wake pattern, mental alertness, organ movement, and eating habits, causing them to temporarily lose the track of time. This is further re-synchronized with the physiological cues of the destination over time. The mechanism of resetting of the clocks with varying time zones and cues occur in organisms from bacteria to humans. It is the result of the evolution of different pathways and molecular mechanisms over the time. There has been evolution of numerous comprehensive mechanisms using various research tools to get a deeper insight into the rapid turnover of molecular mechanisms in various species. This review reports insights into the evolution of the circadian mechanism and its evolutionary shift which is vital and plays a major role in assisting different organisms to adapt in different zones and controls their internal biological clocks with changing external cues.


Subject(s)
Biological Evolution , Circadian Rhythm , Animals , Bacteria , Circadian Rhythm/physiology , Circadian Rhythm/radiation effects , Humans , Plants
7.
Sci Rep ; 5: 14747, 2015 Oct 07.
Article in English | MEDLINE | ID: mdl-26442596

ABSTRACT

Apoptosis or programmed cell death is critical for embryogenesis and tissue homeostasis. Uncontrolled apoptosis leads to different human disorders including immunodeficiency, autoimmune disorder and cancer. Several small molecules that control apoptosis have been identified. Here, we have shown the functional role of triazole derivative (DCPTN-PT) that acts as a potent HDAC inhibitor and mis-express proto onco microRNA (miRNA) bantam. To further understanding the mechanism of action of the molecule in apoptotic pathway, a series of experiments were also performed in Drosophila, a well known model organism in which the nature of human apoptosis is very analogous. DCPTN-PT mis processes bantam microRNA and alters its down regulatory target hid function and cleavage of Caspase-3 which in turn influence components of the mitochondrial apoptotic pathway in Drosophila. However regulatory microRNAs in other pro-apoptotic genes are not altered. Simultaneously, treatment of same molecule also affects the mitochondrial regulatory pathway in human tumour cell lines suggesting its conservative nature between fly and human. It is reasonable to propose that triazole derivative (DCPTN-PT) controls bantam oncomiRNA and increases hid induced apoptosis and is also able to influence mitochondrial apoptotic pathway.


Subject(s)
Apoptosis/drug effects , Drosophila Proteins/metabolism , Drosophila melanogaster/genetics , Histone Deacetylase Inhibitors/pharmacology , MicroRNAs/genetics , Neuropeptides/metabolism , Proto-Oncogene Proteins/genetics , Signal Transduction/drug effects , Animals , Drosophila Proteins/genetics , Drosophila melanogaster/growth & development , Drosophila melanogaster/metabolism , Histone Deacetylase Inhibitors/chemistry , Humans , Neuropeptides/genetics
8.
Front Plant Sci ; 6: 537, 2015.
Article in English | MEDLINE | ID: mdl-26284080

ABSTRACT

Halophytes are plants which naturally survive in saline environment. They account for ∼1% of the total flora of the world. They include both dicots and monocots and are distributed mainly in arid, semi-arid inlands and saline wet lands along the tropical and sub-tropical coasts. Salinity tolerance in halophytes depends on a set of ecological and physiological characteristics that allow them to grow and flourish in high saline conditions. The ability of halophytes to tolerate high salt is determined by the effective coordination between various physiological processes, metabolic pathways and protein or gene networks responsible for delivering salinity tolerance. The salinity responsive proteins belong to diverse functional classes such as photosynthesis, redox homeostasis; stress/defense, carbohydrate and energy metabolism, protein metabolism, signal transduction and membrane transport. The important metabolites which are involved in salt tolerance of halophytes are proline and proline analog (4-hydroxy-N-methyl proline), glycine betaine, pinitol, myo-inositol, mannitol, sorbitol, O-methylmucoinositol, and polyamines. In halophytes, the synthesis of specific proteins and osmotically active metabolites control ion and water flux and support scavenging of oxygen radicals under salt stress condition. The present review summarizes the salt tolerance mechanisms of halophytes by elucidating the recent studies that have focused on proteomic, metabolomic, and ionomic aspects of various halophytes in response to salinity. By integrating the information from halophytes and its comparison with glycophytes could give an overview of salt tolerance mechanisms in halophytes, thus laying down the pavement for development of salt tolerant crop plants through genetic modification and effective breeding strategies.

9.
Neural Plast ; 2012: 405926, 2012.
Article in English | MEDLINE | ID: mdl-22830051

ABSTRACT

Cessation of one-week oral administration of the benzodiazepine flurazepam (FZP) to rats results in withdrawal anxiety after 1 day of withdrawal. FZP withdrawal is correlated with synaptic incorporation of homomeric GluA1-containing α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptors (AMPARs) in the proximal stratum radiatum of CA1 neurons. After 2 days of withdrawal, Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) phosphorylates GluA1 subunits at Ser(831), increasing channel conductance. Secondary to AMPAR potentiation, GluN2B-containing N-methyl-D-aspartate receptors (NMDARs), known binding partners of CaMKII, are selectively removed from the postsynaptic density (PSD). While activation of synaptic CaMKII is known to involve translocation to the PSD, CaMKII bound to NMDARs may be removed from the PSD. To distinguish these possibilities, the current studies used postembedding immunogold electron microscopy to investigate alterations in CaMKII signaling at CA1 stratum radiatum synapses after 2 days of FZP withdrawal. These studies revealed decreased total, but not autophosphorylated (Thr(286)) CaMKIIα expression in CA1 PSDs. The removal of CaMKII-GluN2B complexes from the PSD during drug withdrawal may serve as a homeostatic mechanism to limit AMPAR-mediated CA1 neuron hyperexcitability and benzodiazepine withdrawal anxiety.


Subject(s)
Calcium-Calmodulin-Dependent Protein Kinase Type 2/physiology , Flurazepam/adverse effects , Glutamates/physiology , Hippocampus/physiology , Hypnotics and Sedatives/adverse effects , Signal Transduction/physiology , Substance Withdrawal Syndrome/physiopathology , Synapses/physiology , Animals , CA1 Region, Hippocampal/physiology , Dendritic Spines/physiology , Excitatory Postsynaptic Potentials/drug effects , Homeostasis/physiology , Immunohistochemistry , Male , Microscopy, Electron , Phosphorylation , Presynaptic Terminals/physiology , Rats , Rats, Sprague-Dawley , Receptors, N-Methyl-D-Aspartate/physiology , Threonine/metabolism , Tissue Embedding
10.
J Comp Neurol ; 518(21): 4311-28, 2010 Nov 01.
Article in English | MEDLINE | ID: mdl-20853509

ABSTRACT

Benzodiazepine withdrawal-anxiety is associated with enhanced α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor (AMPAR)-mediated glutamatergic transmission in rat hippocampal CA1 synapses due to enhanced synaptic insertion and phosphorylation of GluA1 homomers. Interestingly, attenuation of withdrawal-anxiety is associated with a reduction in N-methyl-D-aspartate receptor (NMDAR)-mediated currents and subunit expression, secondary to AMPA receptor potentiation. Therefore, in this study ultrastructural evidence for possible reductions in NMDAR GluN1, GluN2A, and GluN2B subunits was sought at CA1 stratum radiatum synapses in proximal dendrites using postembedding immunogold labeling of tissues from rats withdrawn for 2 days from 1-week daily oral administration of the benzodiazepine, flurazepam (FZP). GluN1-immunogold density and the percentage of immunopositive synapses were significantly decreased in tissues from FZP-withdrawn rats. Similar decreases were observed for GluN2B subunits; however, the relative lateral distribution of GluN2B-immunolabeling within the postsynaptic density did not change after BZ withdrawal. In contrast to the GluN2B subunit, the percentage of synapses labeled with the GluN2A subunit antibody and the density of immunogold labeling for this subunit was unchanged. The spatial localization of immunogold particles associated with each NMDAR subunit was consistent with a predominantly postsynaptic localization. The data therefore provide direct evidence for reduced synaptic GluN1/GluN2B receptors and preservation of GluN1/GluN2A receptors in the CA1 stratum radiatum region during BZ withdrawal. Based on collective findings in this benzodiazepine withdrawal-anxiety model, we propose a functional model illustrating the changes in glutamate receptor populations at excitatory synapses during benzodiazepine withdrawal.


Subject(s)
Benzodiazepines/adverse effects , Hippocampus , Immunohistochemistry , Protein Subunits/metabolism , Receptors, N-Methyl-D-Aspartate/metabolism , Substance Withdrawal Syndrome/metabolism , Synapses , Animals , Benzodiazepines/administration & dosage , Hippocampus/metabolism , Hippocampus/ultrastructure , Male , Rats , Rats, Sprague-Dawley , Synapses/metabolism , Synapses/ultrastructure
11.
J Neurophysiol ; 103(6): 3311-9, 2010 Jun.
Article in English | MEDLINE | ID: mdl-20393063

ABSTRACT

The Kv1.3 voltage-dependent potassium channel is expressed at high levels in mitral cells of the olfactory bulb (OB). Deletion of the Kv1.3 potassium channel gene (Kv1.3-/-) in mice lowers the threshold for detection of odors, increases the ability to discriminate between odors, and alters the firing pattern of mitral cells. We have now found that loss of Kv1.3 produces a compensatory increase in Na(+)-activated K(+) currents (K(Na)) in mitral cells. Levels of the K(Na) channel subunit Slack-B determined by Western blotting are substantially increased in the OB from Kv1.3-/- animals compared with those of wildtype animals. In voltage-clamp recordings of OB slices, elevation of intracellular sodium from 0 to 60 mM increased mean outward currents by 15% in mitral cells from wildtype animals and by 40% in cells from Kv1.3-/- animals. In Kv1.3-/- cells, K(Na) current could even be detected with 0 mM Na(+) internal solutions, provided extracellular Na(+) was present, and this current could be abolished by TTX and ZD7288, blockers of Na(+) influx through voltage-dependent Na(+) channels and H-channels, respectively. The role of enhanced expression of Slack subunits in the increase of K(Na) current in Kv1.3-/- cells was also confirmed using an RNA interference (RNA(i)) approach to suppress Slack expression in primary cultures of olfactory neurons. In Kv1.3-/- neurons, treatment with Slack-specific RNA(i) inhibited approximately 75% of the net outward current, whereas in wildtype cells, the same treatment suppressed only about 25% of the total current. Scrambled and mismatched RNA(i) oligonucleotides failed to suppress currents. Our findings raise the possibility that the olfactory phenotype of Kv1.3-/- animals results in part from an enhancement of K(Na) currents.


Subject(s)
Gene Expression Regulation/genetics , Kv1.3 Potassium Channel/deficiency , Neurons/physiology , Olfactory Bulb/cytology , Potassium Channels/metabolism , Animals , Animals, Newborn , Biophysics/methods , Cardiovascular Agents/pharmacology , Cells, Cultured , Electric Stimulation/methods , In Vitro Techniques , Membrane Potentials/genetics , Membrane Potentials/physiology , Mice , Mice, Inbred C57BL , Mice, Knockout , Nerve Tissue Proteins , Patch-Clamp Techniques/methods , Potassium Channels/genetics , Potassium Channels, Sodium-Activated , Pyrimidines/pharmacology , RNA Interference/physiology , Sodium Channel Blockers/pharmacology , Tetrodotoxin/pharmacology , Transfection/methods
12.
Biochem Soc Trans ; 37(Pt 6): 1394-8, 2009 Dec.
Article in English | MEDLINE | ID: mdl-19909283

ABSTRACT

Long-term BZ (benzodiazepine) anxiolytic therapy increases the risk of physical dependence manifested as withdrawal anxiety. BZ-induced potentiation of GABA(A)R (gamma-aminobutyric acid type-A receptor) function by 1-week oral administration of FZP (flurazepam) bi-directionally modulates excitatory glutamatergic synaptic transmission in hippocampal CA1 neurons during drug withdrawal. Previous electrophysiological studies on acutely isolated and intact CA1 neurons, as well as immunofluorescence and post-embedding immunogold electron microscopy studies, suggest increased synaptic insertion of GluR (glutamate receptor) 2-lacking AMPARs (alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptors) in 2-day FZP-withdrawn rats. Preliminary studies indicated a similar increase in GluR1, then phospho-Ser(831)-GluR1, as well as CaMKIIalpha (Ca(2+)/calmodulin-dependent protein kinase IIalpha), but not phospho-Thr(286)-CaMKII levels at the same time point. In our studies, whole-cell recordings in hippocampal slices revealed that AMPAR mEPSC [miniature EPSC (excitatory postsynaptic current)] amplitude was increased in 1-day FZP-withdrawn rats followed by an increase in estimated single-channel conductance in 2-day-FZP-withdrawn rats. Enhanced conductance was no longer observed in slices pre-incubated for 2 h in the CaMKII inhibitor KN-93, but not the inactive analogue KN-92. To evaluate whether CaMKII-mediated AMPA potentiation could occlude LTP (long-term potentiation), LTP was induced by TBS (theta burst stimulation) and recorded using whole-cell and extracellular techniques. LTP was induced in both groups, but only maintained for <15 min in 2-day FZP-withdrawn rats. LTP was fully restored after 7-day withdrawal. Despite the lack of LTP maintenance, impairment of object recognition, place and context was not observed in 2-day-FZP-withdrawn rats. Since L-VGCC (L-type voltage-gated calcium channel) current density was doubled on drug withdrawal and up to 2 days, Ca(2+) entry through L-VGCCs and perhaps subsequently through Ca(2+)-permeable AMPARs are proposed to be responsible for enhanced CaMKIIalpha levels and AMPAR potentiation. Mechanisms associated with several different models of activity-dependent plasticity may underlie BZ physical dependence.


Subject(s)
Behavior, Animal/physiology , Glutamic Acid/metabolism , Hippocampus/metabolism , Neuronal Plasticity/physiology , Receptors, GABA-A/metabolism , Allosteric Regulation , Animals , Behavior, Animal/drug effects , Benzodiazepines/metabolism , Benzodiazepines/pharmacology , Calcium-Calmodulin-Dependent Protein Kinase Type 2/metabolism , Hippocampus/drug effects , Memory/physiology , Neuronal Plasticity/drug effects , Rats , Receptors, AMPA/metabolism , Receptors, Glutamate/metabolism
13.
J Comp Neurol ; 511(6): 832-46, 2008 Dec 20.
Article in English | MEDLINE | ID: mdl-18924138

ABSTRACT

Prolonged benzodiazepine treatment leads to tolerance and increases the risk of dependence. Flurazepam (FZP) withdrawal is associated with increased anxiety correlated with increased alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-type glutamate receptor (AMPAR)-mediated synaptic function and AMPAR binding in CA1 pyramidal neurons. Enhanced AMPAR synaptic strength is also associated with a shift toward inward rectification of synaptic currents and increased expression of GluR1, but not GluR2, subunits, suggesting augmented membrane incorporation of GluR1-containing, GluR2-lacking AMPARs. To test this hypothesis, the postsynaptic incorporation of GluR1 and GluR2 subunits in CA1 neurons after FZP withdrawal was examined by postembedding immunogold quantitative electron microscopy. The percentage of GluR1 positively labeled stratum radiatum (SR) synapses was significantly increased in FZP-withdrawn rats (88.2% +/- 2.2%) compared with controls (74.4% +/- 1.9%). In addition, GluR1 immunogold density was significantly increased by 30% in SR synapses in CA1 neurons from FZP-withdrawn rats compared with control rats (FZP: 14.1 +/- 0.3 gold particles/mum; CON: 10.8 +/- 0.4 gold particles/mum). In contrast, GluR2 immunogold density was not significantly different between groups. Taken together with recent functional data from our laboratory, the current study suggests that the enhanced glutamatergic strength at CA1 neuron synapses during benzodiazepine withdrawal is mediated by increased incorporation of GluR1-containing AMPARs. Mechanisms underlying synaptic plasticity in this model of drug dependence are therefore fundamentally similar to those that operate during activity-dependent plasticity.


Subject(s)
Benzodiazepines/pharmacology , Hippocampus/drug effects , Receptors, AMPA/drug effects , Substance Withdrawal Syndrome/metabolism , Substance-Related Disorders/metabolism , Synapses/drug effects , Animals , Disease Models, Animal , Glutamic Acid/metabolism , Hippocampus/metabolism , Male , Microscopy, Immunoelectron , Neuronal Plasticity/drug effects , Neuronal Plasticity/physiology , Rats , Rats, Sprague-Dawley , Receptors, AMPA/metabolism , Substance Withdrawal Syndrome/physiopathology , Substance-Related Disorders/physiopathology , Synapses/metabolism , Synaptic Transmission/drug effects , Synaptic Transmission/physiology , Up-Regulation/drug effects , Up-Regulation/physiology
14.
J Pharmacol Exp Ther ; 314(1): 320-8, 2005 Jul.
Article in English | MEDLINE | ID: mdl-15814570

ABSTRACT

Previously, we reported that the GABA(A) receptor antagonist picrotoxin also antagonizes serotonin (5-HT)3 receptors and that its effects are subunit-dependent. Here, we sought to identify amino acids involved in picrotoxin inhibition of 5-HT3 receptors. Mutation of serine to alanine at the transmembrane domain 2 (TM2) 2' position did not affect picrotoxin (PTX) sensitivity in murine 5-HT3A receptors. However, mutation of the 6' TM2 threonine to phenylalanine dramatically reduced PTX sensitivity. Mutation of 6' asparagine to threonine in the 5-HT3B subunit enhanced PTX sensitivity in heteromeric 5-HT3A/3B receptors. Introduction of serine (native to the human 3B subunit) at the 6' position also increased PTX sensitivity, suggesting a species-specific effect. Mutation of the 7' leucine to threonine in 5-HT3A receptors increased PTX sensitivity roughly 10-fold, comparable with that observed in GABA(A) receptors, and also conferred distinct gating kinetics. The equivalent mutation in the 3B subunit (i.e., 7' valine to threonine) had no impact on PTX sensitivity in 5-HT3A/3B receptors. Interestingly, [3H]ethynylbicycloorthobenzoate ([3H]EBOB), a high-affinity ligand to the convulsant site in GABA(A) receptors, did not exhibit specific binding in 5-HT3A receptors. The structurally related compound, tert-butylbicyclophosphorothionate (TBPS), which potently inhibits GABA(A) receptors, did not inhibit 5-HT3 currents. Our results indicate that the TM2 6' residue is a common determinant of PTX inhibition of both 5-HT3 and GABA(A) receptors and demonstrate a role of the 7' residue in PTX inhibition. However, lack of effects of EBOB and TBPS in 5-HT3A receptors suggests that the functional domains in the two receptors are not equivalent and underscores the complexity of PTX modulation of LGICs.


Subject(s)
Picrotoxin/pharmacology , Receptors, Serotonin, 5-HT3/drug effects , Serotonin Antagonists , Animals , Bridged Bicyclo Compounds, Heterocyclic/pharmacology , Convulsants/pharmacology , DNA, Complementary/biosynthesis , Dose-Response Relationship, Drug , Electrophysiology , Gene Expression Regulation , Humans , Ion Channel Gating/drug effects , Mice , Molecular Sequence Data , Mutagenesis, Site-Directed , Receptors, GABA-A/drug effects , Receptors, Serotonin, 5-HT3/chemistry , Receptors, Serotonin, 5-HT3/genetics , Species Specificity , Structure-Activity Relationship , Threonine/chemistry
15.
Brain Res Mol Brain Res ; 119(2): 207-12, 2003 Nov 26.
Article in English | MEDLINE | ID: mdl-14625088

ABSTRACT

There are currently no known agents that display selectivity between homomeric 5-hydroxytryptamine type 3A (5-HT3A) and heteromeric 5-HT3A/3B receptors. In the present study, we show that the CNS convulsant picrotoxin selectively interacts with 5-HT3A receptors. In whole-cell patch clamp recordings, the inhibitory effect of PTX was reduced 100-fold in heteromeric mouse 5-HT3A/3B receptors, compared to homomeric 5-HT3A receptors. Picrotoxin should prove to be a useful probe for determining the presence of homomeric vs. heteromeric 5-HT3 receptors in both native tissue and recombinant receptor preparations.


Subject(s)
GABA Antagonists/pharmacology , Picrotoxin/pharmacology , Serotonin 5-HT3 Receptor Antagonists , Animals , Cell Line , Dose-Response Relationship, Drug , Down-Regulation/drug effects , Down-Regulation/genetics , Drug Tolerance/genetics , Humans , Ion Channel Gating/drug effects , Ion Channel Gating/genetics , Ligands , Mice , Protein Subunits/antagonists & inhibitors , Protein Subunits/genetics , Protein Subunits/metabolism , Receptors, Serotonin, 5-HT3/genetics , Receptors, Serotonin, 5-HT3/metabolism , Serotonin/metabolism , Serotonin/pharmacology , Synaptic Transmission/drug effects , Synaptic Transmission/genetics
16.
J Biol Chem ; 277(11): 9112-7, 2002 Mar 15.
Article in English | MEDLINE | ID: mdl-11744711

ABSTRACT

The central nervous system convulsant picrotoxin (PTX) inhibits GABA(A) and glutamate-gated Cl(minus sign) channels in a use-facilitated fashion, whereas PTX inhibition of glycine and GABA(C) receptors displays little or no use-facilitated block. We have identified a residue in the extracellular aspect of the second transmembrane domain that converted picrotoxin inhibition of glycine alpha1 receptors from non-use-facilitated to use-facilitated. In wild type alpha1 receptors, PTX inhibited glycine-gated Cl(minus sign) current in a competitive manner and had equivalent effects on peak and steady-state currents, confirming a lack of use-facilitated block. Mutation of the second transmembrane domain 15'-serine to glutamine (alpha1(S15'Q) receptors) converted the mechanism of PTX blockade from competitive to non-competitive. However, more notable was the fact that in alpha1(S15'Q) receptors, PTX had insignificant effects on peak current amplitude and dramatically enhanced current decay kinetics. Similar results were found in alpha1(S15'N) receptors. The reciprocal mutation in the beta2 subunit of alpha1beta2 GABA(A) receptors (alpha1beta2(N15'S) receptors) decreased the magnitude of use-facilitated PTX inhibition. Our results implicate a specific amino acid at the extracellular aspect of the ion channel in determining use-facilitated characteristics of picrotoxin blockade. Moreover, the data are consistent with the suggestion that picrotoxin may interact with two domains in ligand-gated anion channels.


Subject(s)
GABA Antagonists/pharmacology , Membrane Proteins/chemistry , Picrotoxin/pharmacology , Receptors, Glycine/antagonists & inhibitors , Receptors, Glycine/chemistry , Binding Sites , Binding, Competitive , GABA-A Receptor Antagonists , Humans , Mutagenesis, Site-Directed , Structure-Activity Relationship
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