1
|
Zhang F, Chen F, Zhong M, Shen R, Zhao Z, Wei H, Zhang B, Fang J. Imaging of Carbonic Anhydrase Level in Epilepsy with an Environment-Sensitive Fluorescent Probe. Anal Chem 2023; 95:14833-14841. [PMID: 37747928 DOI: 10.1021/acs.analchem.3c01368] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/27/2023]
Abstract
Carbonic anhydrases (CAs) participate in various physiological and pathological activities by catalyzing the interconversion between carbon dioxide and bicarbonate ions. Under normal circumstances, they guarantee that the relevant biological reactions in our body occur within an appropriate time scale. Abnormal expression or activity alteration of CAs is closely related to the pathogenesis of diverse diseases. This work reports an inhibitor-directed fluorescent probe FMRs-CA for the detection of CAs. Excellent selectivity, favorable biocompatibility, and desirable blood-brain barrier (BBB) penetration endow the probe with the ability to image the fluctuation of CAs in cells and mice. We achieved in situ visualization of the increased CAs in hypoxic cells with this probe. Additionally, probe FMRs-CA was mainly enriched within the liver and gradually metabolized by the liver. With the help of FMRs-CA, the increase of CAs in epileptic mouse brains was revealed first from the perspective of imaging, providing the mechanism connection between abnormal CA expressions and epilepsy.
Collapse
Affiliation(s)
- Fang Zhang
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, China
| | - Fan Chen
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, China
| | - Miao Zhong
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, China
| | - Ruipeng Shen
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, China
| | - Zhengjia Zhao
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, China
| | - Haopai Wei
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, China
| | - Baoxin Zhang
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, China
| | - Jianguo Fang
- School of Chemistry and Chemical Engineering, Nanjing University of Science & Technology, Nanjing, Jiangsu 210094, China
| |
Collapse
|
2
|
Carbonic Anhydrase Inhibitors and Epilepsy: State of the Art and Future Perspectives. Molecules 2021; 26:molecules26216380. [PMID: 34770789 PMCID: PMC8588504 DOI: 10.3390/molecules26216380] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Revised: 10/20/2021] [Accepted: 10/20/2021] [Indexed: 11/16/2022] Open
Abstract
Carbonic anhydrases (CAs) are a group of ubiquitously expressed metalloenzymes that catalyze the reversible hydration/dehydration of CO2/HCO3. Thus, they are involved in those physiological and pathological processes in which cellular pH buffering plays a relevant role. The inhibition of CAs has pharmacologic applications for several diseases. In addition to the well-known employment of CA inhibitors (CAIs) as diuretics and antiglaucoma drugs, it has recently been demonstrated that CAIs could be considered as valid therapeutic agents against obesity, cancer, kidney dysfunction, migraine, Alzheimer's disease and epilepsy. Epilepsy is a chronic brain disorder that dramatically affects people of all ages. It is characterized by spontaneous recurrent seizures that are related to a rapid change in ionic composition, including an increase in intracellular potassium concentration and pH shifts. It has been reported that CAs II, VII and XIV are implicated in epilepsy. In this context, selective CAIs towards the mentioned isoforms (CAs II, VII and XIV) have been proposed and actually exploited as anticonvulsants agents in the treatment of epilepsy. Here, we describe the research achievements published on CAIs, focusing on those clinically used as anticonvulsants. In particular, we examine the new CAIs currently under development that might represent novel therapeutic options for the treatment of epilepsy.
Collapse
|
3
|
Ozsoy HZ. Anticonvulsant Effects of Carbonic Anhydrase Inhibitors: The Enigmatic Link Between Carbonic Anhydrases and Electrical Activity of the Brain. Neurochem Res 2021; 46:2783-2799. [PMID: 34226984 DOI: 10.1007/s11064-021-03390-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2021] [Revised: 06/08/2021] [Accepted: 06/25/2021] [Indexed: 10/20/2022]
Abstract
Acetazolamide (ACZ), a sulfonamide carbonic anhydrase (CA) inhibitor, was first introduced into medical use as a diuretic in the1950s. Shortly after its introduction, its antiglaucoma and anticonvulsant properties came to light. Subsequently, studies of ACZ have explored a plethora of neurophysiological functions of CAs in the CNS. In addition, topiramate (TPM) and zonisamide (ZNS), which were developed as antiepileptic drugs (AEDs) in the1990s, were found to have the ability to inhibit CAs. How CA inhibition prevents seizures is elusive. CA expression and activity are extensively detected in neurons, the choroid plexus, oligodendrocytes and astrocytes. TPM and ZNS appear to produce multimodal actions in the CNS as well as CA inhibition unlike ACZ. Nonetheless, CA inhibitors share some common denominators. They do not only affect the fine equilibrium among CO2, H+ and HCO3- in the extraneuronal and intraneuronal milieu, but also modulate the activity of ligand gated ion channels at the neuronal level such as GABA-A signaling through inhibiting CA-replenished HCO3- efflux. In addition, there are studies reporting their ability to alter Ca2+ kinetics through modulation of ligand gated Ca2+ channels, voltage gated Ca2+ channels (VGCC) or Ca2+-induced Ca2+ release channels (CICRC). The present study will review the involvement of CAs in the formation of epileptogenesis, and likely mechanisms by which CA inhibitors suppress the electrical activity of the brain. The common properties of CA inhibitors provide some clues for a possible link among metabolism, CAs, Ca2+ and GABA signaling.
Collapse
|
4
|
Sona Khan M, Trenet W, Xing N, Sibley B, Abbas M, al-Rashida M, Rauf K, Mandyam CD. A Novel Sulfonamide, 4-FS, Reduces Ethanol Drinking and Physical Withdrawal Associated With Ethanol Dependence. Int J Mol Sci 2020; 21:E4411. [PMID: 32575871 PMCID: PMC7352747 DOI: 10.3390/ijms21124411] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2020] [Revised: 06/13/2020] [Accepted: 06/17/2020] [Indexed: 01/11/2023] Open
Abstract
Carbonic anhydrase (CA) is abundant in glial cells in the brain and CA type II isoform (CA II) activity in the hippocampus plays an important role in buffering extracellular pH transients produced by neural activity. Chronic ethanol exposure results in respiratory and metabolic acidosis, producing shifts in extracellular pH in the brain and body. These neurophysiological changes by ethanol are hypothesized to contribute to the continued drinking behavior and physical withdrawal behavior in subjects consuming ethanol chronically. We explored whether chronic ethanol self-administration (ethanol drinking, 10% v/v; ED) without or under the influence of chronic intermittent ethanol vapor (CIE-ED) experience alters the expression of CA II in the hippocampus. Postmortem hippocampal tissue analyses demonstrated that CA II levels were enhanced in the hilus region of the hippocampus in ED and CIE-ED rats. We used a novel molecule-4-fluoro-N-(4-sulfamoylphenyl) benzenesulfonamide (4-FS)-a selective CA II inhibitor, to determine whether CA II plays a role in ethanol self-administration in ED and CIE-ED rats and physical withdrawal behavior in CIE-ED rats. 4-FS (20 mg/kg, i.p.) reduced ethanol self-administration in ED rats and physical withdrawal behavior in CIE-ED rats. Postmortem hippocampal tissue analyses demonstrated that 4-FS reduced CA II expression in ED and CIE-ED rats to control levels. In parallel, 4-FS enhanced GABAA receptor expression, reduced ratio of glutamatergic GluN2A/2B receptors and enhanced the expression of Fos, a marker of neuronal activation in the ventral hippocampus in ED rats. These findings suggest that 4-FS enhanced GABAergic transmission and increased activity of neurons of inhibitory phenotypes. Taken together, these findings support the role of CA II in assisting with negative affective behaviors associated with moderate to severe alcohol use disorders (AUD) and that CA II inhibitors are a potential therapeutic target to reduce continued drinking and somatic withdrawal symptoms associated with moderate to severe AUD.
Collapse
Affiliation(s)
- Muhammad Sona Khan
- Abbottabad Campus, COMSATS University Islamabad, Abbottabad, Khyber Pakhtunkhawa 22060, Pakistan;
- VA San Diego Healthcare System, San Diego, CA 92161, USA; (W.T.); (N.X.); (B.S.)
- Department of Anesthesiology, University of California San Diego, San Diego, CA 92161, USA
| | - Wulfran Trenet
- VA San Diego Healthcare System, San Diego, CA 92161, USA; (W.T.); (N.X.); (B.S.)
| | - Nancy Xing
- VA San Diego Healthcare System, San Diego, CA 92161, USA; (W.T.); (N.X.); (B.S.)
| | - Britta Sibley
- VA San Diego Healthcare System, San Diego, CA 92161, USA; (W.T.); (N.X.); (B.S.)
| | - Muzaffar Abbas
- Department of Pharmacy, Capital University of Science & Technology, Islamabad 44000, Pakistan;
| | - Mariya al-Rashida
- Department of Chemistry, Forman Christian College, A Chartered University, Ferozepur Road, Lahore 54600, Pakistan;
| | - Khalid Rauf
- Abbottabad Campus, COMSATS University Islamabad, Abbottabad, Khyber Pakhtunkhawa 22060, Pakistan;
| | - Chitra D. Mandyam
- VA San Diego Healthcare System, San Diego, CA 92161, USA; (W.T.); (N.X.); (B.S.)
- Department of Anesthesiology, University of California San Diego, San Diego, CA 92161, USA
| |
Collapse
|
5
|
Mishra CB, Kumari S, Angeli A, Bua S, Tiwari M, Supuran CT. Discovery of Benzenesulfonamide Derivatives as Carbonic Anhydrase Inhibitors with Effective Anticonvulsant Action: Design, Synthesis, and Pharmacological Evaluation. J Med Chem 2018; 61:3151-3165. [PMID: 29566486 DOI: 10.1021/acs.jmedchem.8b00208] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Two series of novel benzenesulfonamide derivatives were synthesized and evaluated for their human carbonic anhydrase (CA, EC 4.2.1.1) inhibitory activity against four isoforms, hCA I, hCA II, hCA VII, and hCA IX. It was found that compounds of both series showed low to medium nanomolar inhibitory potential against all isoforms. Some of these derivatives displayed selective inhibition against the epileptogenesis related isoforms hCA II and VII, within the nanomolar range. These potent hCA II and VII inhibitors were evaluated as anticonvulsant agents against MES and sc-PTZ induced convulsions. These sulfonamides effectively abolished induced seizures in both models. Furthermore, time dependent seizure protection capability of the most potent compound was also evaluated. A long duration of action was displayed, with efficacy up to 6 h after drug administration. The compound appeared as an orally active anticonvulsant agent without showing neurotoxicity in a rotarod test, a nontoxic chemical profile being observed in subacute toxicity study.
Collapse
Affiliation(s)
- Chandra Bhushan Mishra
- Bio-Organic Chemistry Laboratory, Dr. B. R. Ambedkar Center for Biomedical Research , University of Delhi , 110007 Delhi , India
| | - Shikha Kumari
- Bio-Organic Chemistry Laboratory, Dr. B. R. Ambedkar Center for Biomedical Research , University of Delhi , 110007 Delhi , India
| | - Andrea Angeli
- Dipartimento Neurofarba, Sezione di Scienze Farmaceutiche e Nutraceutiche , Università degli Studi di Firenze , 50019 Florence , Italy
| | - Silvia Bua
- Dipartimento Neurofarba, Sezione di Scienze Farmaceutiche e Nutraceutiche , Università degli Studi di Firenze , 50019 Florence , Italy
| | - Manisha Tiwari
- Bio-Organic Chemistry Laboratory, Dr. B. R. Ambedkar Center for Biomedical Research , University of Delhi , 110007 Delhi , India
| | - Claudiu T Supuran
- Dipartimento Neurofarba, Sezione di Scienze Farmaceutiche e Nutraceutiche , Università degli Studi di Firenze , 50019 Florence , Italy
| |
Collapse
|
6
|
Stridh MH, Alt MD, Wittmann S, Heidtmann H, Aggarwal M, Riederer B, Seidler U, Wennemuth G, McKenna R, Deitmer JW, Becker HM. Lactate flux in astrocytes is enhanced by a non-catalytic action of carbonic anhydrase II. J Physiol 2012; 590:2333-51. [PMID: 22451434 DOI: 10.1113/jphysiol.2011.220152] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Rapid exchange of metabolites between different cell types is crucial for energy homeostasis of the brain. Besides glucose, lactate is a major metabolite in the brain and is primarily produced in astrocytes. In the present study, we report that carbonic anhydrase 2 (CAII) enhances both influx and efflux of lactate in mouse cerebellar astrocytes. The augmentation of lactate transport is independent of the enzyme's catalytic activity, but requires direct binding of CAII to the C-terminal of the monocarboxylate transporter MCT1, one of the major lactate/proton cotransporters in astrocytes and most tissues. By employing its intramolecular proton shuttle, CAII, bound to MCT1, can act as a ‘proton collecting antenna' for the transporter, suppressing the formation of proton microdomains at the transporter-pore and thereby enhancing lactate flux. By this mechanism CAII could enhance transfer of lactate between astrocytes and neurons and thus provide the neurons with an increased supply of energy substrate.
Collapse
Affiliation(s)
- Malin H Stridh
- Division of General Zoology, Department of Biology, University of Kaiserslautern, PO Box 3049, D-67653 Kaiserslautern, Germany
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
7
|
Nonenzymatic augmentation of lactate transport via monocarboxylate transporter isoform 4 by carbonic anhydrase II. J Membr Biol 2010; 234:125-35. [PMID: 20300744 DOI: 10.1007/s00232-010-9240-y] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2009] [Accepted: 02/26/2010] [Indexed: 12/21/2022]
Abstract
Monocarboxylate transporters (MCTs) are carriers of high-energy metabolites like lactate and pyruvate, and different MCT isoforms are expressed in a wide range of cells and tissues. Transport activity of MCT isoform 1 (MCT1), heterologously expressed in Xenopus oocytes, has previously been shown to be supported by carbonic anhydrase II (CAII) in a noncatalytic manner. In the present study, we investigated possible interactions of CAII with MCT4, expressed in Xenopus oocytes. MCT4 transport activity is enhanced both by injected and by coexpressed CAII, similar to MCT1, with the highest augmentation at low extracellular pH and low lactate concentrations. CAII-induced augmentation in MCT4 transport activity is independent from the enzyme's catalytic function, as shown by application of the CA inhibitor ethoxyzolamide and by coexpression of MCT4 with the catalytically inactive mutant CAII-V143Y.
Collapse
|
8
|
Makani S, Chesler M. Rapid rise of extracellular pH evoked by neural activity is generated by the plasma membrane calcium ATPase. J Neurophysiol 2009; 103:667-76. [PMID: 19939954 DOI: 10.1152/jn.00948.2009] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In hippocampus, synchronous activation of CA1 pyramidal neurons causes a rapid, extracellular, population alkaline transient (PAT). It has been suggested that the plasma membrane Ca(2+)-ATPase (PMCA) is the source of this alkalinization, because it exchanges cytosolic Ca(2+) for external H(+). Evidence supporting this hypothesis, however, has thus far been inconclusive. We addressed this long-standing problem by measuring surface alkaline transients (SATs) from voltage-clamped CA1 pyramidal neurons in juvenile mouse hippocampal slices, using concentric (high-speed, low-noise) pH microelectrodes placed against the somata. In saline containing benzolamide (a poorly permeant carbonic anhydrase blocker), a 2-s step from -60 to 0 mV caused a mean SAT of 0.02 unit pH. Addition of 5 mM HEPES to the artificial cerebrospinal fluid diminished the SAT by 91%. Nifedipine reduced the SAT by 53%. Removal of Ca(2+) from the saline abolished the SAT, and addition of BAPTA to the patch pipette reduced it by 79%. The inclusion of carboxyeosin (a PMCA inhibitor) in the pipette abolished the SAT, whether it was induced by a depolarizing step, or by simulated, repetitive, antidromic firing. The peak amplitude of the "antidromic" SAT of a single cell averaged 11% of the PAT elicited by comparable real antidromic activation of the CA1 neuronal population. Caloxin 2A1, an extracellular PMCA peptide inhibitor, blocked both the SAT and PAT by 42%. These results provide the first direct evidence that the PMCA can explain the extracellular alkaline shift elicited by synchronous firing.
Collapse
Affiliation(s)
- Sachin Makani
- Department of Physiology and Neuroscience, New York University Langone Medical Center, New York, New York 10016, USA
| | | |
Collapse
|
9
|
Obara M, Szeliga M, Albrecht J. Regulation of pH in the mammalian central nervous system under normal and pathological conditions: facts and hypotheses. Neurochem Int 2007; 52:905-19. [PMID: 18061308 DOI: 10.1016/j.neuint.2007.10.015] [Citation(s) in RCA: 115] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2007] [Revised: 10/17/2007] [Accepted: 10/22/2007] [Indexed: 11/27/2022]
Abstract
The maintenance of pH homeostasis in the CNS is of key importance for proper execution and regulation of neurotransmission, and deviations from this homeostasis are a crucial factor in the mechanism underlying a spectrum of pathological conditions. The first few sections of the review are devoted to the brain operating under normal conditions. The article commences with an overview of how extrinsic factors modelling the brain at work: neurotransmitters, depolarising stimuli (potassium and voltage changes) and cyclic nucleotides as major signal transducing vehicles affect pH in the CNS. Further, consequences of pH alterations on the major aspects of CNS function and metabolism are outlined. Next, the major cellular events involved in the transport, sequestration, metabolic production and buffering of protons that are common to all the mammalian cells, including the CNS cells. Since CNS function reflects tight interaction between astrocytes and neurons, the pH regulatory events pertinent to either cell type are discussed: overwhelming evidence implicates astrocytes as a key player in pH homeostasis in the brain. The different classes of membrane proteins involved in proton shuttling are listed and their mechanisms of action are given. These include: the Na+/H+ exchanger, different classes of bicarbonate transporters acting in a sodium-dependent- or -independent mode, monocarboxylic acid transporters and the vacuolar-type proton ATPase. A separate section is devoted to carbonic anhydrase, which is represented by multiple isoenzymes capable of pH buffering both in the cell interior and in the extracellular space. Next, impairment of pH regulation and compensatory responses occurring in brain affected by different pathologies: hypoxia/ischemia, epilepsy, hyperammonemic encephalopathies, cerebral tumours and HIV will be described. The review is limited to facts and plausible hypotheses pertaining to phenomena directly involved in pH regulation: changes in pH that accompany metabolic stress but have no distinct implications for the pH regulatory mechanisms are not dealt with. In most cases, the vast body of knowledge derived from in vitro studies remains to be verified in in vivo settings.
Collapse
Affiliation(s)
- Marta Obara
- Department of Neurotoxicology, Medical Research Centre, Polish Academy of Sciences, 5 Pawińskiego Street, 02-106 Warsaw, Poland
| | | | | |
Collapse
|
10
|
Ogilvie JM, Ohlemiller KK, Shah GN, Ulmasov B, Becker TA, Waheed A, Hennig AK, Lukasiewicz PD, Sly WS. Carbonic anhydrase XIV deficiency produces a functional defect in the retinal light response. Proc Natl Acad Sci U S A 2007; 104:8514-9. [PMID: 17485676 PMCID: PMC1895981 DOI: 10.1073/pnas.0702899104] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2007] [Indexed: 11/18/2022] Open
Abstract
Members of the carbonic anhydrase (CA) family play an important role in the regulation of pH, CO(2), ion, and water transport. CA IV and CA XIV are membrane-bound isozymes expressed in the eye. CA IV immunostaining is limited to the choriocapillaris overlying the retina, whereas CA XIV is expressed within the retina in Müller glial cells and retinal pigment epithelium. Here, we have characterized the physiological and morphological phenotype of the CA IV-null, CA XIV-null, and CA IV/CA XIV-double-null mouse retinas. Flash electroretinograms performed at 2, 7, and 10 months of age showed that the rod/cone a-wave, b-wave, and cone b-wave were significantly reduced (26-45%) in the CA XIV-null mice compared with wild-type littermates. Reductions in the dark-adapted response were not progressive between 2 and 10 months, and no differences in retinal morphology were observed between wild-type and CA XIV-null mice. Müller cells and rod bipolar cells had a normal appearance. Retinas of CA IV-null mice showed no functional or morphological differences compared with normal littermates. However, CA IV/CA XIV double mutants showed a greater deficit in light response than the CA XIV-null retina. Our results indicate that CA XIV, which regulates extracellular pH and pCO(2), plays an important part in producing a normal retinal light response. A larger functional deficit in the CA IV/CA XIV double mutants suggests that CA IV can also contribute to pH regulation, at least in the absence of CA XIV.
Collapse
Affiliation(s)
| | - Kevin K. Ohlemiller
- Otolaryngology, Washington University School of Medicine, St. Louis, MO 63110
| | - Gul N. Shah
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO 63104; and
| | - Barbara Ulmasov
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO 63104; and
| | - Timothy A. Becker
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO 63104; and
| | - Abdul Waheed
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO 63104; and
| | | | | | - William S. Sly
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO 63104; and
| |
Collapse
|
11
|
Fedirko N, Svichar N, Chesler M. Fabrication and use of high-speed, concentric h+- and Ca2+-selective microelectrodes suitable for in vitro extracellular recording. J Neurophysiol 2006; 96:919-24. [PMID: 16672303 DOI: 10.1152/jn.00258.2006] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Ion-selective microelectrodes (ISMs) have been used extensively in neurophysiological studies. ISMs selective for H(+) and Ca(2+) are notable for their sensitivity and selectivity, but suffer from a slow response time, and susceptibility to noise because of the high electrical resistance of the respective ion exchange cocktails. These drawbacks can be overcome by using a "coaxial" or "concentric" inner micropipette to shunt the bulk of the ion exchanger resistance. This approach was used decades ago to record extracellular [Ca(2+)] transients in cat cortex, but has not been subsequently used. Here, we describe a method for the rapid fabrication of concentric pH- and Ca(2+)-selective microelectrodes useful for extracellular studies in brain slices or other work in vitro. Construction was simplified compared with previous implementations, by using commercially available, thin-walled borosilicate glass, drawing an outer barrel with a rapid taper (similar to a patch pipette), and by use of a quick and reliable silanization procedure. Using a piezoelectric stepper to effect a rapid solution change, the response time constants of the concentric pH and Ca(2+)-electrodes were 14.9 +/- 1.3 and 5.3 +/- 0.90 ms, respectively. Use of these concentric ISMs is demonstrated in rat hippocampal slices. Activity-dependent, extracellular pH, and [Ca(2+)] transients are shown to arise two- to threefold faster, and attain amplitudes two- to fourfold greater, when recorded by concentric versus conventional ISMs. The advantage of concentric ISMs for studies of ion transport and ion diffusion is discussed.
Collapse
Affiliation(s)
- Nataliya Fedirko
- Dept. of Neurosurgery, NYU School of Medicine, New York, NY 10016, USA
| | | | | |
Collapse
|
12
|
Shah GN, Ulmasov B, Waheed A, Becker T, Makani S, Svichar N, Chesler M, Sly WS. Carbonic anhydrase IV and XIV knockout mice: roles of the respective carbonic anhydrases in buffering the extracellular space in brain. Proc Natl Acad Sci U S A 2005; 102:16771-6. [PMID: 16260723 PMCID: PMC1283849 DOI: 10.1073/pnas.0508449102] [Citation(s) in RCA: 97] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Previous studies have implicated extracellular carbonic anhydrases (CAs) in buffering the alkaline pH shifts that accompany neuronal activity in the rat and mouse hippocampus. CAs IV and XIV both have been proposed to mediate this extracellular buffering. To examine the relative importance of these two isozymes in this and other physiological functions attributed to extracellular CAs, we produced CA IV and CA XIV knockout (KO) mice by targeted mutagenesis and the doubly deficient CA IV/XIV KO mice by intercrossing the individual null mice. Although CA IV and CA XIV null mice both are viable, the CA IV nulls are produced in smaller numbers than predicted, indicating either fetal or postnatal losses, which preferentially affect females. CA IV/XIV double KO mice are also produced in fewer numbers than predicted and are smaller than WT mice, and many females die prematurely before and after weaning. Electrophysiological studies on hippocampal slices on these KO mice showed that either CA can mediate buffering after synaptic transmission in hippocampal slices in the absence of the other, but that eliminating both is nearly as effective as the CA inhibitor, benzolamide, in blocking the buffering seen in the WT mice. Thus, both CA IV and CA XIV contribute to extracellular buffering in the central nervous system, although CA IV appears to be more important in the hippocampus. These individual and double KO mice should be valuable tools in clarifying the relative contributions of each CA to other physiological functions where extracellular CAs have been implicated.
Collapse
Affiliation(s)
- Gul N Shah
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO 63104, USA
| | | | | | | | | | | | | | | |
Collapse
|
13
|
Skoff RP, Bessert DA, Cerghet M, Franklin MJ, Rout UK, Nave KA, Carlock L, Ghandour MS, Armant DR. The myelin proteolipid protein gene modulates apoptosis in neural and non-neural tissues. Cell Death Differ 2005; 11:1247-57. [PMID: 15375385 DOI: 10.1038/sj.cdd.4401498] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Mutations of the myelin proteolipid protein gene (Plp) are associated with excessive programmed cell death (PCD) of oligodendrocytes. We show for the first time that PLP is a molecule ubiquitously expressed in non-neural tissues during normal development, and that the level of native PLP modulates the level of PCD. We analyze three non-neural tissues, and show that native PLP is expressed in trophoblasts, spermatogonia, and cells of interdigital webbing. The non-neural cells that express high levels of native PLP also undergo PCD. The level of PLP expression modulates the level of PCD because mice that overexpress native PLP have increased PCD and mice deficient in PLP have decreased PCD. We show that overexpression of native PLP causes a dramatic acidification of extracellular fluid that, in turn, causes increased PCD. These studies show that the level of native PLP modulates the amount of PCD during normal development via a pH-dependent mechanism.
Collapse
Affiliation(s)
- R P Skoff
- Department of Anatomy and Cell Biology, Wayne State University School of Medicine, Detroit, MI 48201, USA.
| | | | | | | | | | | | | | | | | |
Collapse
|
14
|
Putnam RW, Filosa JA, Ritucci NA. Cellular mechanisms involved in CO(2) and acid signaling in chemosensitive neurons. Am J Physiol Cell Physiol 2004; 287:C1493-526. [PMID: 15525685 DOI: 10.1152/ajpcell.00282.2004] [Citation(s) in RCA: 221] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
An increase in CO(2)/H(+) is a major stimulus for increased ventilation and is sensed by specialized brain stem neurons called central chemosensitive neurons. These neurons appear to be spread among numerous brain stem regions, and neurons from different regions have different levels of chemosensitivity. Early studies implicated changes of pH as playing a role in chemosensitive signaling, most likely by inhibiting a K(+) channel, depolarizing chemosensitive neurons, and thereby increasing their firing rate. Considerable progress has been made over the past decade in understanding the cellular mechanisms of chemosensitive signaling using reduced preparations. Recent evidence has pointed to an important role of changes of intracellular pH in the response of central chemosensitive neurons to increased CO(2)/H(+) levels. The signaling mechanisms for chemosensitivity may also involve changes of extracellular pH, intracellular Ca(2+), gap junctions, oxidative stress, glial cells, bicarbonate, CO(2), and neurotransmitters. The normal target for these signals is generally believed to be a K(+) channel, although it is likely that many K(+) channels as well as Ca(2+) channels are involved as targets of chemosensitive signals. The results of studies of cellular signaling in central chemosensitive neurons are compared with results in other CO(2)- and/or H(+)-sensitive cells, including peripheral chemoreceptors (carotid body glomus cells), invertebrate central chemoreceptors, avian intrapulmonary chemoreceptors, acid-sensitive taste receptor cells on the tongue, and pain-sensitive nociceptors. A multiple factors model is proposed for central chemosensitive neurons in which multiple signals that affect multiple ion channel targets result in the final neuronal response to changes in CO(2)/H(+).
Collapse
Affiliation(s)
- Robert W Putnam
- Department of Anatomy and Physiology, Wright State University School of Medicine, 3640 Colonel Glenn Highway, Dayton, OH 45435, USA.
| | | | | |
Collapse
|
15
|
Whittington DA, Grubb JH, Waheed A, Shah GN, Sly WS, Christianson DW. Expression, Assay, and Structure of the Extracellular Domain of Murine Carbonic Anhydrase XIV. J Biol Chem 2004; 279:7223-8. [PMID: 14660577 DOI: 10.1074/jbc.m310809200] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Carbonic anhydrase (CA) XIV is the most recently identified mammalian carbonic anhydrase isozyme, and its presence has been demonstrated in a number of tissues. Full-length CA XIV is a transmembrane protein composed of an extracellular catalytic domain, a single transmembrane helix, and a short intracellular polypeptide segment. The amino acid sequence identity of human CA XIV relative to the other membrane-associated isozymes (CA IV, CA IX, and CA XII) is 34-46%. We report here the expression and purification of both the full-length enzyme and a truncated, secretory form of murine CA XIV. Both forms of this isozyme are highly active, and both show an abrogation of activity in the presence of 0.2% SDS, in contrast to the behavior of murine CA IV. We also report the crystal structure of the extracellular domain of murine CA XIV at 2.8 A resolution and of an enzyme-acetazolamide complex at 2.9 A resolution. The structure shows a monomeric glycoprotein with a topology similar to that of other mammalian CA isozymes. Based on the x-ray crystallographic results, we compare and contrast known structures of membrane-associated CA isozymes to rationalize the structural elements responsible for the SDS resistance of CA IV and to discuss prospects for the design of selective inhibitors of membrane-associated CA isozymes.
Collapse
Affiliation(s)
- Douglas A Whittington
- Roy and Diana Vagelos Laboratories, Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | | | | | | | | | | |
Collapse
|
16
|
Abstract
The regulation of pH is a vital homeostatic function shared by all tissues. Mechanisms that govern H+ in the intracellular and extracellular fluid are especially important in the brain, because electrical activity can elicit rapid pH changes in both compartments. These acid-base transients may in turn influence neural activity by affecting a variety of ion channels. The mechanisms responsible for the regulation of intracellular pH in brain are similar to those of other tissues and are comprised principally of forms of Na+/H+ exchange, Na+-driven Cl-/HCO3- exchange, Na+-HCO3- cotransport, and passive Cl-/HCO3- exchange. Differences in the expression or efficacy of these mechanisms have been noted among the functionally and morphologically diverse neurons and glial cells that have been studied. Molecular identification of transporter isoforms has revealed heterogeneity among brain regions and cell types. Neural activity gives rise to an assortment of extracellular and intracellular pH shifts that originate from a variety of mechanisms. Intracellular pH shifts in neurons and glia have been linked to Ca2+ transport, activation of acid extrusion systems, and the accumulation of metabolic products. Extracellular pH shifts can occur within milliseconds of neural activity, arise from an assortment of mechanisms, and are governed by the activity of extracellular carbonic anhydrase. The functional significance of these compartmental, activity-dependent pH shifts is discussed.
Collapse
Affiliation(s)
- Mitchell Chesler
- Department of Physiology & Neuroscience, New York University School of Medicine, New York, NY 10016, USA.
| |
Collapse
|
17
|
Spitzer KW, Skolnick RL, Peercy BE, Keener JP, Vaughan-Jones RD. Facilitation of intracellular H(+) ion mobility by CO(2)/HCO(3)(-) in rabbit ventricular myocytes is regulated by carbonic anhydrase. J Physiol 2002; 541:159-67. [PMID: 12015427 PMCID: PMC2290312 DOI: 10.1113/jphysiol.2001.013268] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2001] [Accepted: 02/08/2002] [Indexed: 12/27/2022] Open
Abstract
Intracellular H(+) mobility was estimated in the rabbit isolated ventricular myocyte by diffusing HCl into the cell from a patch pipette, while imaging pH(i) confocally using intracellular ratiometric SNARF fluorescence. The delay for acid diffusion between two downstream regions approximately 40 microm apart was reduced from approximately 25 s to approximately 6 s by replacing Hepes buffer in the extracellular superfusate with a 5 % CO(2)/HCO(3)(-) buffer system (at constant pH(o) of 7.40). Thus CO(2)/HCO(3)(-) (carbonic) buffer facilitates apparent H(+)(i) mobility. The delay with carbonic buffer was increased again by adding acetazolamide (ATZ), a membrane permeant carbonic anhydrase (CA) inhibitor. Thus facilitation of apparent H(+)(i) mobility by CO(2)/HCO(3)(-) relies on the activity of intracellular CA. By using a mathematical model of diffusion, the apparent intracellular H(+) equivalent diffusion coefficient (D(H)(app)) in CO(2)/HCO(3)(-)-buffered conditions was estimated to be 21.9 x 10(-7) cm(2) s(-1), 5.8 times faster than in the absence of carbonic buffer. Facilitation of H(+)(i) mobility is discussed in terms of an intracellular carbonic buffer shuttle, catalysed by intracellular CA. Turnover of this shuttle is postulated to be faster than that of the intrinsic buffer shuttle. By regulating the carbonic shuttle, CA regulates effective H(+)(i) mobility which, in turn, regulates the spatiotemporal uniformity of pH(i). This is postulated to be a major function of CA in heart.
Collapse
Affiliation(s)
- K W Spitzer
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT, USA.
| | | | | | | | | |
Collapse
|
18
|
Leniger T, Wiemann M, Bingmann D, Widman G, Hufnagel A, Bonnet U. Carbonic anhydrase inhibitor sulthiame reduces intracellular pH and epileptiform activity of hippocampal CA3 neurons. Epilepsia 2002; 43:469-74. [PMID: 12027906 DOI: 10.1046/j.1528-1157.2002.32601.x] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
PURPOSE Sulthiame is a carbonic anhydrase (CA) inhibitor with an anticonvulsant effect in the treatment of benign and symptomatic focal epilepsy in children. The aim of the study was to elucidate the mode of action of sulthiame with respect to possible changes of intracellular pH (pHi) that might develop along with sulthiame's anticonvulsant properties. METHODS The effects of sulthiame (a) on pHi of 2',7-bis(2-carboxyethyl)-5(6)-carboxyfluorescein-acetoxymetyl ester (BCECF-AM) loaded CA3 neurones as well as (b) on epileptiform activity (induced by 50 microM 4-aminopyridine) were compared with those of the CA inhibitors acetazolamide and benzolamide. RESULTS In the majority of neurons, sulthiame (1.0-1.5 mM; n = 8) as well as the membrane permeant acetazolamide (0.5-1.0 mM; n = 6) reversibly decreased pHi by 0.18 +/- 0.05 (SD) and 0.17 +/- 0.10 (SD) pH units, respectively, within 10 min. The poor membrane permeant benzolamide (1.0-2.0 mM) had no influence on pHi (n = 8). Sulthiame (1.0-2.5 mM) and acetazolamide (1.0-2.0 mM) reversibly reduced the frequency of action potentials and epileptiform bursts after 10-15 min (n = 9, n = 7), whereas benzolamide (1.0-2.0 mM) had no effect (n = 6). CONCLUSIONS The results suggest that sulthiame acts as a membrane-permeant CA inhibitor whose beneficial effect on epileptiform activity results at least in part from a modest intracellular acidosis of central neurons.
Collapse
Affiliation(s)
- Tobias Leniger
- Department of Neurology, University of Essen, Essen, Germany.
| | | | | | | | | | | |
Collapse
|
19
|
Putnam RW. Intracellular pH regulation of neurons in chemosensitive and nonchemosensitive areas of brain slices. RESPIRATION PHYSIOLOGY 2001; 129:37-56. [PMID: 11738645 DOI: 10.1016/s0034-5687(01)00281-x] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The role of changes of intracellular pH (pH(i)) as the proximal signal in central chemosensitive neurons has been studied. pH(i) recovery from acidification is mediated by Na(+)/H(+) exchange in all medullary neurons and pH(i) recovery from alkalinization is mediated by Cl(-)/HCO(3)(-) exchange in most medullary neurons. These exchangers are more sensitive to inhibition by changes in extracellular pH (pH(o)) in neurons from chemosensitive regions compared to those from nonchemosensitive regions. Thus, neurons from chemosensitive regions exhibit a maintained intracellular acidification in response to hypercapnic acidosis but they show pH(i) recovery in response to isohydric hypercapnia. A similar pattern of pH(i) response is seen in other CO(2)/H(+)-responsive cells, including glomus cells, sour taste receptor cells, and chemosensitive neurons from snails, suggesting that a maintained fall of pH(i) is a common feature of the proximal signal in all CO(2)/H(+)-sensitive cells. To further evaluate the potential role of pH(i) changes as proximal signals for chemosensitive neurons, studies must be done to: determine why a lack of pH(i) recovery from hypercapnic acidosis is seen in some nonchemosensitive neurons; establish a correlation between hypercapnia-induced changes of pH(i) and membrane potential (V(m)); compare the hypercapnia-induced pH(i) changes seen in neuronal cell bodies with those in dendritic processes; understand why the V(m) response to hypercapnia of many chemosensitive neurons is washed out when using whole cell patch pipettes; and employ knock out mice to investigate the role of certain proteins in the CO(2)/H(+) response of chemosensitive neurons.
Collapse
Affiliation(s)
- R W Putnam
- Department of Physiology and Biophysics, Wright State University School of Medicine, 3640 Colonel Glenn Highway, Dayton, OH 45435, USA.
| |
Collapse
|
20
|
Loring JF, Wen X, Lee JM, Seilhamer J, Somogyi R. A gene expression profile of Alzheimer's disease. DNA Cell Biol 2001; 20:683-95. [PMID: 11788046 DOI: 10.1089/10445490152717541] [Citation(s) in RCA: 226] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Postmortem analysis of brains of patients with Alzheimer's disease (AD) has led to diverse theories about the causes of the pathology, suggesting that this complex disease involves multiple physiological changes. In an effort to better understand the variety and integration of these changes, we generated a gene expression profile for AD brain. Comparing affected and unaffected brain regions in nine controls and six AD cases, we showed that 118 of the 7050 sequences on a broadly representative cDNA microarray were differentially expressed in the amygdala and cingulate cortex, two regions affected early in the disease. The identity of these genes suggests the most prominent upregulated physiological correlates of pathology involve chronic inflammation, cell adhesion, cell proliferation, and protein synthesis (31 upregulated genes). Conversely, downregulated correlates of pathology involve signal transduction, energy metabolism, stress response, synaptic vesicle synthesis and function, calcium binding, and cytoskeleton (87 downregulated genes). The results support several separate theories of the causes of AD pathology, as well as add to the list of genes associated with AD. In addition, approximately 10 genes of unknown function were found to correlate with the pathology.
Collapse
Affiliation(s)
- J F Loring
- Department of Life Sciences, Incyte Genomics, Inc., Palo Alto, California 94304, USA.
| | | | | | | | | |
Collapse
|
21
|
Abstract
We tested the hypothesis that extracellular membrane-bound carbonic anhydrase (CA) type IV is responsible for the regulation of interstitial pH (pH(o)) transients in brain. Rat hippocampal slices were incubated in phosphatidylinositol-specific phospholipase C (PI-PLC), which cleaves the link of CA IV to the external face of plasma membranes. Then evoked alkaline pH(o) shifts were studied in a recording chamber, using pH microelectrodes. Incubation fluid was saved for later analysis. The ability to buffer a rapid alkaline load was reduced markedly in PI-PLC-treated tissue as compared with adjacent, paired control slices. The effect of benzolamide (a poorly permeant CA inhibitor) on evoked pH(o) shifts was diminished greatly in the PI-PLC-treated tissue, consistent with the washout of interstitial CA. Treatment of the incubation fluid with SDS abolished nearly all of the CA activity in fluid from controls, whereas an SDS-insensitive component remained in the fluid from PI-PLC-treated slices. These data suggested that CA type II (which is blocked by SDS) leaked from injured glial cells in both slice preparations, whereas CA type IV (which is insensitive to SDS) was liberated selectively into the fluid from PI-PLC-treated tissue. Western blot analysis was consistent with this interpretation, demonstrating a predominance of CA IV in the incubation fluid from PI-PLC-treated tissue and variable amounts of CA II in fluid from PI-PLC-treated and control slices. These results demonstrate that interstitial CA activity brain is attributable principally to membrane-bound CA IV.
Collapse
|
22
|
Parkkila S, Parkkila AK, Rajaniemi H, Shah GN, Grubb JH, Waheed A, Sly WS. Expression of membrane-associated carbonic anhydrase XIV on neurons and axons in mouse and human brain. Proc Natl Acad Sci U S A 2001; 98:1918-23. [PMID: 11172051 PMCID: PMC29357 DOI: 10.1073/pnas.98.4.1918] [Citation(s) in RCA: 98] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Although long suspected from histochemical evidence for carbonic anhydrase (CA) activity on neurons and observations that CA inhibitors enhance the extracellular alkaline shifts associated with synaptic transmission, an extracellular CA in brain had not been identified. A candidate for this CA was suggested by the recent discovery of membrane CA (CA XIV) whose mRNA is expressed in mouse and human brain and in several other tissues. For immunolocalization of CA XIV in mouse and human brain, we developed two antibodies, one against a secretory form of enzymatically active recombinant mouse CA XIV, and one against a synthetic peptide corresponding to the 24 C-terminal amino acids in the human enzyme. Immunostaining for CA XIV was found on neuronal membranes and axons in both mouse and human brain. The highest expression was seen on large neuronal bodies and axons in the anterolateral part of pons and medulla oblongata. Other CA XIV-positive sites included the hippocampus, corpus callosum, cerebellar white matter and peduncles, pyramidal tract, and choroid plexus. Mouse brain also showed a positive reaction in the molecular layer of the cerebral cortex and granular cellular layer of the cerebellum. These observations make CA XIV a likely candidate for the extracellular CA postulated to have an important role in modulating excitatory synaptic transmission in brain.
Collapse
Affiliation(s)
- S Parkkila
- Department of Anatomy and Cell Biology, University of Oulu, 90014 Oulu, Finland
| | | | | | | | | | | | | |
Collapse
|