Carbonic Anhydrase Inhibitory Activity Research Articles

Exploring QSAR for the Inhibitory Activity of a Large Set of Aromatic/Heterocyclic Sulfonamides toward Four Different Isoenzymes of Carbonic Anhydrase

AbstractThe Carbonic Anhydrase (CA) inhibitory activities of a large number of sulfonamide derivatives toward CA isoenzyme types I, II, IV, and IX were collected and then subjected to QSAR analyses. The dataset used consisted of 343 sulfonamide derivatives with 200 calculated descriptors. For each type of isoenzyme, a separate QSAR model was obtained using multiple linear regression analysis with stepwise selection of variables. The generalization, stability, and predictivity of the models were evaluated by leave‐many‐out cross‐validation, using an external test set and chance correlation. All the obtained models represented high statistical quality and prediction ability with q2 and $\rm{ R_{\rm{P}}^{\rm{2}} }$ greater than 0.80. The relative errors of prediction were lower than 5%. By the developed models, the ligand–receptor interactions involved in the binding of sulfonamides to different CA isoenzymes were discussed. For all types of isoenzymes, the topological indices represented significant impacts on the ligand–enzyme interactions. It was found that, for CAI, the acid–base properties play a significant role whereas for CAII the coulombic interactions are controlling factors. In addition, number of thiol functional groups exhibited significant negative effect on the binding of sulfonamides to CAII. For CAIV, the hydrogen bonding interactions were detected as a major factor. Finally, for the binding of sulfonamides to CAIX, the lipophilicity, and acid–base properties were selected as highly influential parameters.

Design, synthesis, and docking studies of new 1,3,4-thiadiazole-2-thione derivatives with carbonic anhydrase inhibitory activity

A new series of 1,3,4-thiadiazole-2-thione derivatives have been prepared and assayed for the inhibition of three physiologically relevant carbonic anhydrase (CA, EC 4.2.1.1) isozymes, the cytosolic human isozymes I and II, and the transmembrane, tumor-associated hCA IX. Against hCA I the investigated thiones, showed inhibition constants in the range of 2.55–222 μM, against hCA II in the range of 2.0–433 μM, and against hCA IX in the range of 1.25–148 μM. Compound 5c, 4-(4,5-dihydro-5-thioxo-1,3,4-thiadiazol-2-yl)-1-(5-nitro-2-oxoindolin-3-ylidene)semicarbazide showed interesting inhibition of the tumor-associated hCA IX with K I value of 1.25 μM, being the first non-sulfonamide type inhibitor of such activity. This result is rather important taking into consideration the known antitumor activity of thiones. In addition, docking of the tested compounds into CA II active site was performed in order to predict the affinity and orientation of these compounds at the isozyme active site. The results showed similar orientation of the target compounds at CA II active site compared with reported sulfonamide type CAIs with the thione group acting as a zinc-binding moiety.

Malarial Parasite Carbonic Anhydrase and Its Inhibitors

Plasmodium falciparum is responsible for the majority of life-threatening cases of human malaria. The global emergence of drug-resistant malarial parasites necessitates identification and characterization of novel drug targets. At present, carbonic anhydrase (CA) genes are identified in limited numbers of protozoa and helminthes parasites, however, they are demonstrated in at least 4 Plasmodium species. The CA gene of P. falciparum encodes an alpha-carbonic anhydrase enzyme possessing catalytic properties distinct of that of the human host enzymes. A small library of aromatic sulfonamides, most of which were Schiff's bases derived from sulfanilamide/homosulfanilamide/4-aminoethylbenzenesulfonamide and substituted-aromatic aldehydes, or ureido-substituted sulfonamides are good inhibitors of P. falciparum enzyme. The 4-(3,4-dichlorophenylureido-ethyl)-benzenesulfonamide is the most effective antimalarial activity against growth of P. falciparum in vitro. The nature of the groups substituting the aromatic-ureido- or aromatic-azomethine fragment of the molecule and the length of the parent sulfonamide (i.e., from sulfanilamide to 4-aminoethylbenzenesulfonamide) from which the Schiff's base obtained, are the critical parameters for the CA inhibitory activities of these aromatic sulfonamide derivatives, both against the malarial as well as human enzymes. Thus, the sulfonamide CA inhibitors may have the potential for the development of novel antimalarial drugs.

A DFT-based quantum theoretic QSAR study of aromatic and heterocyclic sulfonamides as carbonic anhydrase inhibitors against isozyme, CA-II

In this study, DFT/B3LYP level of theory with the 6-31G (d) basis set, was used to calculate a set of molecular descriptors of 30 sulfonamide compounds with carbonic anhydrase inhibitory activity. Quantitative structure–activity relationship (QSAR) models of the biological activity ( K i) of 30 inhibitors of carbonic anhydrase (CA-II) were established using some of the following calculated quantum mechanical descriptors, dipole moment ( μ), average polarizability ( P), ionization potential ( I), electron affinity ( A), LUMO energy ( ɛ LUMO), HOMO energy ( ɛ HOMO), total energy at 0 K (Te), entropy at 298 K ( S), electronegativity ( χ), hardness ( η), electrophilicity ( ω), and differences between HOMO and LUMO energies ( ɛ H − ɛ L). The QSAR models obtained by employing multiple linear regression techniques are aimed at correlating the structures to their reported experimental inhibitory activity values, K i. Among the models presented in this study, statistically the most significant one is a four-parameter linear equation with correlation coefficient, R 2 values of ca. 0.847 and the cross-validated correlation coefficient, R values of ca. 0.775. This study also reconstructed the obtained models using AM1-based calculated descriptors to demonstrate the superiority of DFT over AM1 for quantum calculations of mechanical descriptors. The results are discussed in the light of the main factors that influence the inhibitory activity of carbonic anhydrase (CA-II) isozyme.

A DFT-Based QSARs Study of Acetazolamide/Sulfanilamide Derivatives with Carbonic Anhydrase (CA-II) Isozyme Inhibitory Activity

This study presents Quantitative Structure Activity Relationships (QSAR) studyon a pool of 18 bio-active sulfonamide compounds which includes five acetazolamidederivatives, eight sulfanilamide derivatives and five clinically used sulfonamides moleculesas drugs namely acetazolamide, methazolamide, dichlorophenamide, ethoxolamide anddorzolamide. For all the compounds, initial geometry optimizations were carried out with amolecular mechanics (MM) method using the MM force fields. The lowest energyconformations of the compounds obtained by the MM method were further optimized by theDensity Functional Theory (DFT) method by employing Becke’s three-parameter hybridfunctional (B3LYP) and 6-31G (d) basis set. Molecular descriptors, dipole moment,electronegativity, total energy at 0 K, entropy at 298 K, HOMO and LUMO energiesobtained from DFT calculations provide valuable information and have a significant role inthe assessment of carbonic anhydrase (CA-II) inhibitory activity of the compounds. By usingthe multiple linear regression technique several QSAR models have been drown up with thehelp these calculated descriptors and carbonic anhydrase (CA-II) inhibitory data of themolecules. Among the obtained QSAR models presented in the study, statistically the mostsignificant one is a five parameters linear equation with the squared correlation coefficient R2 values of ca. 0.94 and the squared cross-validated correlation coefficient R2CV values of ca. 0.85. The results were discussed in the light of the main factors that influence theinhibitory activity of the carbonic anhydrase (CA-II) isozyme.

Topiramate Associated Bilateral Acute Angle Closure Glaucoma And Myopia

Topiramate, an oral sulphamate medication, is primarily licensed for treating epilepsy, though it is increasingly being used for treating migraine1. Studies have also established its role in treating cocaine addiction2. Topiramate is thought to potentiate the activity of GABA ( -aminobutyric acid) neurotransmitter by blocking the glutamate receptors3. It also has a weak carbonic anhydrase inhibitory activity. We describe a case of acute myopia and angle closure glaucoma secondary to topiramate, used for the treatment of migraine.

Application of graph theory: Models for prediction of carbonic anhydrase inhibitory activity of sulfonamides

The relationship of Wiener’s index–a distance-based topological descriptor, Zagreb group parameter – M1, an adjacency-based topological descriptor and eccentric connectivity index–an adjacency-cum-distance based topological descriptor with the carbonic anhydrase (CA) isozyme-II inhibitory activity of sulfonamides has been investigated. A training set comprising of 34 analogues of substituted sulfonamides was selected for the present investigations. The values of the Wiener’s index, Zagreb group parameter, and eccentric connectivity index for each of 34 analogues comprising the data set were computed. Resulting data was analyzed and suitable models were developed after identification of active ranges. Subsequently, a biological activity was assigned to each analogue involved in the data set using these models, which was then compared with the reported CA isozyme-II inhibitory activity. Accuracy of prediction was found to vary from a minimum of 82% for model based on Wiener’s index to a maximum of 88% for the model based on Zagreb group parameter. Moreover, highly active range of the proposed models also exhibited appreciable inhibitory activity against CA isozyme-I and CA isozyme-IV.

Chlorthalidone

Modern diuretic therapy evolved from 2 seemingly unrelated events in the 1930s: the development of sulfanilamide, the first truly effective antibacterial agent, and the description of the enzyme carbonic anhydrase. Sulfanilamide was observed to increase sodium (Na+)/potassium and water excretion by inhibition of carbonic anhydrase activity. Recognition of this action proved the impetus for synthesis of compounds, such as acetazolamide, that could more specifically inhibit carbonic anhydrase; however, acetazolamide was a short-acting compound, and diuretics with greater potency and/or duration of action were quickly sought. Chlorothiazide was the first of these new-generation diuretics, and its introduction in 1957 set the modern era of diuretic therapy in motion. Shortly thereafter several loop diuretics and a host of thiazide-type diuretics found their way to the marketplace as the result of active development programs. As diuretics began to proliferate in numbers, loop diuretics were promptly distinguished from thiazide-type diuretics on the basis of potency and were quickly slotted as the more important diuretic class for volume overload states. Thiazide-type diuretics were early on seen as agents with greater effectiveness in reducing blood pressure (BP), but with a lesser ability to impact volume overload states. In the early days of thiazide-type diuretic use there was little effort expended to seriously distinguish one from the other in their BP-lowering effect even if there were major intraclass pharmacokinetic differences. Inexorably, the term “class effect” crept in to describe the actions of thiazide-type diuretics, applied both to BP reduction and ultimately outcomes. Much of the recent debate on diuretic class effect has centered on the similarities and differences between chlorthalidone …

N-[2-(Aminosulfonyl)-5,6-dihydro-6-methyl-7,7-dioxo-4H-thieno[2,3-b]thiopyran-4-yl]acetamide

The title compound, C10H14N2O5S3, has been synthesized as a key inter­mediate in the synthesis of topically active carbonic anhydrase inhibitor MK-0507. N—H⋯O hydrogen bonds are responsible for the formation of centrosymmetric dimers and zigzag mol­ecular chains. The inter­molecular non-bonded S⋯O separation in the crystal structure is 3.415 (2) A, indicating a strong inter­molecular inter­action between the amino­sulfonyl and S-dioxide groups.

Mechanisms behind Pb-induced disruption of Na+and Cl−balance in rainbow trout (Oncorhynchus mykiss)

The mechanism of Pb-induced disruption of Na(+) and Cl(-) balance was investigated in the freshwater rainbow trout (Oncorhynchus mykiss). Na(+) and Cl(-) influx rates were reduced immediately in the presence of 2.40 +/- 0.24 and 1.25 +/- 0.14 muM Pb, with a small increase in efflux rates occurring after 24-h exposure. Waterborne Pb caused a significant decrease in the maximal rate of Na(+) influx without a change in transporter affinity, suggesting a noncompetitive disruption of Na(+) uptake by Pb. Phenamil and bafilomycin markedly reduced Na(+) influx rate but did not affect Pb accumulation at the gill. Time-course analysis in rainbow trout exposed to 0, 0.48, 2.4, and 4.8 microM Pb revealed time- and concentration-dependent branchial Pb accumulation. Na(+)-K(+)-ATPase activity was significantly reduced, with 4.8 microM exposure resulting in immediate enzyme inhibition and 0.48 and 2.4 microM exposures inhibiting activity by 24 h. Reduced activity was weakly correlated with gill Pb accumulation after 3- and 8-h exposures; this relationship strengthened by 24 h. Reduced Na(+) uptake was correlated with gill Pb burden after exposures of 3, 8, and 24 h. Immediate inhibition of branchial carbonic anhydrase activity occurred after 3-h exposure to 0.82 +/- 0.05 or 4.30 +/- 0.05 microM Pb and continued for up to 24 h. We conclude that Pb-induced disruption of Na(+) and Cl(-) homeostasis is in part a result of rapid inhibition of carbonic anhydrase activity and of binding of Pb with Na(+)-K(+)-ATPase, causing noncompetitive inhibition of Na(+) and Cl(-) influx.

Predicting carbonic anhydrase inhibitory activity of sulfonamides: computational approach using topological descriptors

The relationship of Wiener's index—a distance-based topological descriptor, Zagreb group parameter— M 1, an adjacency-based topological descriptor and eccentric connectivity index—an adjacency-cum-distance-based topological descriptor with the carbonic anhydrase inhibitory activity of sulfonamides has been investigated. A training set comprising of 34 analogues of substituted sulfonamides was selected for the present investigations. The values of the Wiener's index, Zagreb group parameter and eccentric connectivity index for each of 34 analogues comprising the data set were computed. Resulting data was analyzed and suitable models developed after identification of active ranges. Subsequently, a biological activity was assigned to each analogue involved in the data set using these models, which was then compared with the reported carbonic anhydrase inhibitory activity. Accuracy of prediction was found to vary from a minimum of 85% for model based on Wiener's index to a maximum of 91% for the model based on Zagreb group parameter.

Impact of Topiramate on Serum Bicarbonate Concentrations in Adults

Topiramate is an antiepileptic medication with multiple pharmacologic effects, including inhibition of carbonic anhydrase activity. It is associated with metabolic acidosis in both children and adults. To evaluate the incidence and magnitude of the effect of topiramate on serum bicarbonate concentrations in an adult population. This was a retrospective cohort study. Data were evaluated to assess the relationship between serum bicarbonate concentrations before and during topiramate therapy. Fifty-four patients (40 females) with a mean age of 47.6 years (range 19-89) were included in the study. Mean +/- SD serum bicarbonate concentrations before and during topiramate therapy were 26.8 +/- 2.9 mEq/L (range 21-36) and 21.7 +/- 3.6 mEq/L (range 13-29), respectively, with a mean difference of 5.1 (95% CI 3.7 to 6.5; p < 0.001). Twenty-six patients (48%) had low serum bicarbonate concentrations while on topiramate, with a mean concentration of 18.8 mEq/L (range 13-21). Topiramate was associated with metabolic acidosis in 48% of the patients studied, which did not result in clinically significant problems.

Novel use of chemical shift in NMR as molecular descriptor: a first report on modeling carbonic anhydrase inhibitory activity and related parameters

A novel use of NMR chemical shift of the SO 2NH 2 protons (in dioxane as solvent) as a molecular descriptor is described for modeling the inhibition constant for benzene sulfonamides against the zinc enzyme carbonic anhydrase (CA, EC 4.2.1.1). The methodology is extended to model diuretic activity and lipophilicity of benzene sulfonamide derivatives. The regression analysis of the data has shown that the NMR chemical shift is incapable of modeling lipophilicity. However, it is quite useful for modeling the diuretic activity of these derivatives. The results are compared with those obtained using distance-based topological indices: Wiener (W)-, Szeged (Sz)-, and PI (Padmakar-Ivan) indices.

Topological modeling of lipophilicity, diuretic activity, and carbonic inhibition activity of benzene sulfonamides: a molecular connectivity approach

A large series of distance-based topological indices has been used for modeling lipophilicity, diuretic activity, and carbonic anhydrase inhibition activity of a library of simple substituted benzene sulfonamides. The results have shown that the topological approach used is quite useful for modeling carbonic anhydrase inhibition and the use of molecular connectivity is the best for this purpose. Excellent results are obtained in multiparametric regressions. The results are critically discussed on the basis of statistical parameters.

Colonic epithelial functional phenotype varies with type and phase of experimental colitis

Background & Aims : Colonic crypt elongation occurs during both chronic colitis and in the recovery phase of acute colitis. The impact of these alterations on epithelial cell functions is not fully defined. Methods: DNA microarray analysis of freshly isolated colonic epithelial cells (CECs) from acute and chronic colitis was performed, and the results were confirmed by reverse transcription polymerase chain reaction. Localization of the selected molecules was examined by immunohistochemistry using newly generated antibodies. The function of selected molecules detected in this study was examined by administering the specific inhibitors in dextran sodium sulfate (DSS) colitis. Results: Several detoxification-associated molecules, which contribute to prevent inflammation by regulating physiological balance under normal conditions, were markedly down-regulated, and anti-inflammatory molecules, which are not normally expressed, were up-regulated in the CEC under the chronic colitis. Among the detoxification-associated molecules, carbonic anhydrase IV was specifically down-regulated in CEC of Th2- but not Th1-mediated colitis. Functionally, inhibition of carbonic anhydrase activity led to the enhancement of recovery from DSS-induced acute colitis by directly stimulating CEC proliferation. Increased expression of regeneration-associated molecules such as regenerating gene-IIIγ was detectable in the CEC of acute and chronic colitis but not in the recovery phase of colitis. The expression of this molecule was restricted in surface epithelium and upper crypts but not lower crypts. Conclusions: These studies suggest that functional alterations, which result in either the exacerbation or the suppression of colitis, coexist in the CEC during chronic colitis. CEC functions are likely to be differentially regulated in the context of the stage and mechanism of colitis.

Modelling of carbonic anhydrase inhibitory activity of sulfonamides using molecular negentropy

The present paper deals with the modelling of carbonic anhydrase inhibitory activity of sulfonamides using molecular negentropy ( N). Excellent results are obtained in multiple regression analysis upon introduction of indicator parameters. The results are critically discussed on the basis of statistical data obtained from regression analysis.

Chloride increases adrenergic receptor–mediated platelet and vascular responses

Background We postulated that increasing intracellular chloride concentration ([Cl −] i) in human platelets would potentiate α 2 adrenergic receptor (A2AR)—mediated platelet aggregation, and that vascular reactivity would also be increased by raising [Cl −] i in blood vessels. We further hypothesized that ligands binding to the A2AR would increase [Cl −] i by stimulating carbonic anhydrase-dependent chloride/bicarbonate exchange. Because diuretics are potent inhibitors of carbonic anhydrase, we speculated that these agents inhibit platelet aggregation and vascular contractility through inhibition of chloride influx by decreasing carbonic anhydrase activity, and subsequently, chloride/bicarbonate exchange. The aim of this study was to test these hypotheses. Methods: Platelet aggregation was measured by determining changes in optical density of platelet-rich plasma. Contractile responses to A2AR agonists were recorded in isolated vascular smooth muscle. The substances [Cl −] i and intracellular pH (pH i) were measured using microfluorometric methods. Carbonic anhydrase activity and chloride/bicarbonate exchange were determined by an in vitro assay based on the Stewart cycle. Results Increasing [Cl −] i potentiated platelet aggregation and vascular contractility, and epinephrine raised [Cl −] i by stimulating carbonic anhydrase-dependent chloride/bicarbonate exchange. Furthermore, diuretic-dependent inhibition of carbonic anhydrase activity decreased chloride/bicarbonate exchange. Conclusions: Our data support the concept that diuretics inhibit carbonic anhydrase activity and chloride/bicarbonate exchange in platelets and vascular smooth muscle. The ensuing reduction in [Cl −] i that is induced by diuretics in these tissues could play a role in reducing the effect of catecholamines on precipitating thrombotic stroke or myocardial infarction.

The Absorption of Phosphate Ions from the Ovine Reticulorumen

The reticulorumen is now recognised to be an important site of net absorption of phosphate ions from ruminal fluid containing phosphate concentrations appropriate to those found in normal farming practice. These rates of absorption were measured in vivo from solutions placed in the washed reticulorumen, isolated in situ, in conscious, trained sheep. Reducing the ruminal sodium concentration led to reduced absorption of phosphate, suggestive that phosphate and sodium fluxes across the apical wall of the ruminal epithelial cell are linked, as they are in the kidney. Increased absorption of short chain fatty acids led to enhanced absorption of phosphate ions. Conversely, inhibition of carbonic anhydrase activity, by the addition of 1mM acetazolamide to the ruminal fluid, led to a reduction in phosphate absorption. An increase in the acidity of the ruminal fluid also increased the absorption of phosphate, as did an increase in the ruminal Ca2+ concentration over the range 1–4mmol per litre. It is suggested that these effects can be accounted for by a Na+/H+ antiporter coupled with a phosphate/proton symporter in the apical membrane of the ruminal epithelial cell.

Crystal structure of human carbonic anhydrase II complexed with an anti-convulsant sugar sulphamate.

The fructose-based sugar sulphamate RWJ-37497, a potent analogue of the widely used anti-epileptic drug topiramate, possesses anti-convulsant and carbonic anhydrase-inhibitory activities. We have studied the binding interactions of RWJ-37497 in the active site of human carbonic anhydrase II by X-ray crystallography. The atomic positions of the enzyme inhibitor complex were refined at a resolution of 2.1 A (1 A=0.1 nm) to the final crystallographic R and R(free) values of 0.18 and 0.23, respectively. The inhibitor co-ordinates to the active-site zinc ion through its oxygen atom and the ionized nitrogen atom of the sulphamate group by replacing the metal-bound water molecules, although the sulphamoyl oxygen atom provides a rather lengthy co-ordination. The 4,5-cyclic sulphate group is positioned in a hydrophobic pocket of the active site, making contacts with the residues Phe-131, Leu-198, Pro-201 and Pro-202. Since the ligand was found to be intact, concerns about RWJ-37947 irreversibly alkylating the enzyme through its 4,5-cyclic sulphate group were dispelled.

Crystal structure of human carbonic anhydrase II complexed with ananti-convulsant sugar sulphamate

The fructose-based sugar sulphamate RWJ-37497, a potent analogue of the widely used anti-epileptic drug topiramate, possesses anti-convulsant and carbonic anhydrase-inhibitory activities. We have studied the binding interactions of RWJ-37497 in the active site of human carbonic anhydrase II by X-ray crystallography. The atomic positions of the enzyme inhibitor complex were refined at a resolution of 2.1 Å (1 Å = 0.1 nm) to the final crystallographic R and Rfree values of 0.18 and 0.23, respectively. The inhibitor co-ordinates to the active-site zinc ion through its oxygen atom and the ionized nitrogen atom of the sulphamate group by replacing the metal-bound water molecules, although the sulphamoyl oxygen atom provides a rather lengthyco-ordination. The 4,5-cyclic sulphate group is positioned in a hydrophobic pocket of the active site, making contacts with the residues Phe-131, Leu-198, Pro-201 and Pro-202. Since the ligand was found to be intact, concerns about RWJ-37947 irreversibly alkylating the enzyme through its 4,5-cyclic sulphate group were dispelled.