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Current
Pharmaceutical Design
ISSN: 1381-6128
Current Pharmaceutical Design
Volume 14, Number 7, 2008
Contents
Carbonic Anhydrases as Drug Targets
Executive Editor: Claudiu T. Supuran
Editorial Pp. 601-602
Carbonic Anhydrases – An Overview
Pp. 603-614
C.T. Supuran
[Abstract]
Design of Zinc Binding Functions for Carbonic
Anhydrase Inhibitors Pp. 615-621
J-Y. Winum, A. Scozzafava, J-L. Montero and C.T. Supuran
[Abstract]
The α
and β
Classes Carbonic Anhydrases from Helicobacter pylori as
Novel Drug Targets Pp. 622-630
I. Nishimori, S. Onishi, H. Takeuchi and C.T. Supuran
[Abstract]
The Alpha-Carbonic Anhydrase from the Malaria Parasite
and its Inhibition Pp. 631-640
J. Krungkrai and C.T. Supuran
[Abstract]
Diuretics: From Classical Carbonic Anhydrase Inhibitors
to Novel Applications of the Sulfonamides Pp. 641-648
C.T. Supuran
[Abstract]
The Development of Topically Acting Carbonic
Anhydrase Inhibitors as Antiglaucoma Agents Pp. 649-654
F. Mincione, A. Scozzafava and C.T. Supuran
[Abstract]
Are Carbonic Anhydrase Inhibitors Suitable for Obtaining
Antiobesity Drugs ? Pp. 655-660
G. De Simone, A. Di Fiore and C.T. Supuran
[Abstract]
Anticonvulsant Sulfonamides/Sulfamates/Sulfamides
with Carbonic Anhydrase Inhibitory Activity: Drug Design and
Mechanism of Action Pp. 661-671
A. Thiry, J-M. Dogné, C.T. Supuran and B. Masereel
[Abstract]
Recent Advances in Research on the Most Novel
Carbonic Anhydrases, CA XIII and XV Pp. 672-678
M. Hilvo, A. Innocenti, S.M. Monti, G. De Simone, C.T.
Supuran and S. Parkkila
[Abstract]
Carbonic Anhydrase Inhibition: Insight into Non-COX-2
Pharmacological Effect of some Coxibs Pp. 679-684
J-M. Dogné, A. Thiry and C.T. Supuran
[Abstract]
Cancer-Associated Carbonic Anhydrases and Their Inhibition
Pp. 685-698
S. Pastorekova, M. Zatovicova and J. Pastorek
[Abstract]
Fluorescence- and Spin-Labeled Carbonic Anhydrase
Inhibitors Pp. 699-707
A. Cecchi and C.T. Supuran
[Abstract]
Carbonic Anhydrase Activation and the Drug Design
Pp. 708-715
C. Temperini, A. Scozzafava and C.T. Supuran
[Abstract]
The β
and γ
Classes of Carbonic Anhydrase Pp. 716-721
S.A. Zimmerman and J.G. Ferry
[Abstract]
Abstracts
[Back to top]
Editorial: Carbonic Anhydrases as Drug Targets
Carbonic anhydrases (CAs), the metalloenzymes that
catalyze the conversion between carbon dioxide and bicarbonate,
continue to be surprising targets, as many exciting new discoveries
related to them emerge constantly. This is indeed unprecedented
as these are quite “old” enzymes, which were discovered
in 1933, and thoroughly investigated since then as drug targets.
Furthermore, their inhibitors are in clinical use since the
50s. However, in the last years, a host of interesting reports
were made regarding the catalytic/inhibition mechanism as
well as isolation/characterization of new isozymes belonging
to this family, as well as of CAs of non-vertebrate origin.
The first paper [1] in this issue of the Journal dedicated
to these enzymes and their inhibitors, represents an overview
of CAs as drug targets. In fact, among the 16 isoforms known
up to now in mammals, 12 catalytically active ones seem to
be appropriate for designing inhibitors with various therapeutic
applications (only CA III seems to remain an orphan target).
In addition, many carbonic anhydrases isolated from other
organisms were recently shown to be possible targets for the
drug design, such as the α-CAs
from Plasmodium falciparum and Helicobacter pylori,
the β-CAs
from Mycobacterium tuberculosis, Candida albicans, Cryptococcus
neoformans, etc. Work is in progress in many laboratories
for developing specific inhibitors targeting these enzymes,
that would lead to conceptually novel therapies. An exhaustive
review regarding the design of such inhibitors possessing
different metal-binding functions than the classical sulfonamide
one is then presented by Winum et al. [2]. The last
years saw many relevant developments in this field with the
report of several interesting classes of such derivatives,
among which the sulfamates, sulfamides, substituted sulfonamides/sulfamides,
etc., as well as a detailed X-ray crystallo- graphic dscription
of their interactions with various pharmacologically relevant
isoforms.
The next contribution deals with the carbonic anhydrases belonging
to the α-
and β-classes
recently cloned and characterized from the widespread pathogen
Helicobacter pylori, producing a wide range of diseases.
In the last years, Nishimori’s group [3] demonstrated
that both these enzymes are druggable targets. Furthermore,
in one of their papers it has been demonstrated for the first
time that a non-α-CA,
i.e., just the beta-CA from H. pylori, can be a druggable
target. At the same level of importance is the report of Krungkrai
et al. [4] regarding the presence of several α-CAs
in the protozoa causing malaria, belonging to the genus Plasmodium.
In several seminal papers, this group reported the cloning,
characterization and inhibition studies of one of these enzymes,
showing it to be a druggable target. The paper in this issue
is just an excellent review of this work, potentially leading
to novel antimalarial drugs.
A reinvestigation of the sulfonamide diuretics belonging to
the thiadiazine and high-ceiling diuretic type provided interesting
clues regarding possible new applications of sulfonamide CAIs.
Indeed, most of these drugs were discovered in a period when
only isoform CA II was well-known. Retesting these compounds
on all the mammalian isozymes, Supuran’s group [5] showed
that many of these clinically used sulfonamide diuretics act
as nanomolar inhibitors against many pharmacologically relevant
“new” CA isoforms.
Historically, in addition to their well-known role for the
development of diuretics, the CA inhibitors were mainly used
as antiglaucoma agents. The review by Mincione et al. [6]
in this issue presents up-to-date data regarding the ophthalmologic
use of systemically- and topically-acting CA inhibitors, as
well as some drug design studies reported ultimately, which
substantially extended the current knowledge in obtaining
water-soluble such derivatives, potentially useful not only
in the treatment of glaucoma but also for the management of
macular degeneration.
In the last years, there are also encouraging reports linking
CA inhibitors to novel antiobesity therapies, field reviewed
in a nice paper by De Simone et al. [7]. In fact
two mitochondrial CA isoforms, CA VA and CA VB are involved
in lipogenesis and their inhibition leads to diminished fatty
acid biosynthesis. De Simone’s group resolved the X-ray
crystallographic structures of many important, clinically
used inhibitors with various isozymes, and performed modelling
studies regarding their binding to targets which have not
been crystallized yet (such as the human CA VA/VB or the human
CA IX). Such data are extremely useful for the drug design
of inhibitors with various applications, not only as antiobesity
agents, but also as antitumor or antiglaucoma drugs.
CA inhibitors were also used as antiepileptic drugs, but with
less fortune. Indeed, the classical derivatives, acetazolamide
and methazolamide, showed reduced utility in the treatment
of seizure, as presented thoroughly in the review of Thiry
et al., [8] regarding the anticonvulsants belonging
to this class of pharmacological agents. However, the last
years saw the discovery of many CA isoforms present in the
brain and a somehow better understanding of their role in
this organ. Furthermore, some newer antiepileptics, such as
topiramate and zonisamide also show substantial CA inhibitory
activity, although it is unclear to what extent this activity
is essential for their anticonvulsant effects, since these
drugs possess a complex mechanism of action.
Hilvo et al. [9] present then a very interesting
review regarding the characterization and inhibition studies
of the last CA isozymes reported in vertebrates, i.e., CA
XIII, and XV. Indeed, Parkkila’s group made seminal
contributions in this field during the last decades, and their
discovery of two of these isoforms (CA XIII and XV) is just
another example of excellency in CA research. Much is to be
understood yet regarding the physiological roles of some of
these “late” isoforms and the consequences of
their inhbition or activation.
Interesting links emerged ultimately also between some CA
inhibitors and inhibitors of cyclooxygenase 2 (COX-2), reviewed
in the excellent paper by Dogné et al. [10].
Indeed, two of the clinically used COX-2 inhibitors, celecoxib
and valdecoxib, are also potent inhibitors of many physiologically
relevant CA isoforms. Thus, potentially important applications
for these dual enzyme inhibitors may be envisaged, although
the COX-2 class of pharmacological agents underwent a drastic
loss of importance after the recent withdrawal of Rofecoxib
(Vioxx) from clinical use.
Probably the most unexpected applications of the CA inhibitors
are those regarding the diagnosis and treatment of tumors.
This very important and dynamic research field is reviewed
in the excellent papers of Pastorekova et al. [11]
(the discoverer of the first tumor-associated CA isozyme),
CA IX and Cecchi et al. [12]. In several seminal
papers from Pastorekova’s group, it has recently been
demonstrated that CA IX (and probably also CA XII, the other
tumor-associated isozyme) is overexpressed in hypoxic tumors
being involved in tumor acidification processes which lead
to metastatic spread and non-responsiveness to chemotherapeutic
agents/radiation treatment. Furthermore, the same group demonstrated
that sulfonamide CA IX-selective inhibitors may revert these
processes, opening the way to conceptually novel anticancer
therapies and diagnostic tools based on CA IX inhibitors.
Ferry’s group reported the first γ-CA
some years ago, which constituted a revolutionary proof regarding
the ubiquity and important roles of these ancient enzymes
all over the phylogenetic tree of living organisms. Indeed,
this enzyme (Cam) was discovered in a methanogenic archaeon.
Subsequently, the same group investigated a very interesting
and relatively simple, monomeric β-CA
(Cab) from another archaeon. All these fascinating discoveries
as well as the first inhibition studies of these non-α-CAs
are extensively reviewed in a nice paper by Zimmerman et
al. [14] in this issue. Indeed, as mentioned briefly
above, CAs are abundant in the genome of many prokaryotes,
but research in this field is still in its infancy. The important
contribution of Zimmerman et al. sheds some new light in this
novel field.
Temperini et al. [13] then presents an update review
on the CA activators, a field much less investigated than
the inhibitor one. In the last years the biochemical mechanisms
of CA activation started to be understood at molecular level
due to the detailed kinetic and X-ray crystallographic work
from the Florence school of CA research. Temperini presents
the state-of-the art view in this new and very dynamic field,
which may lead to important pharmacologic applications of
the activators as anti-Alzheimer’s disease agents or
for the memory therapy.
Over the last 20 years I was personally involved with many
of these projects, and several others related to CA inhibitors
or activators. This is indeed rewarding, since I remember
colleagues prognosticating that this was a dead field already
in the early 90s. These excellent review articles in this
issue of Curr. Pharm. Des. represent the proof (if
that was necessary) that this was not the case. The data presented
throughout these papers clearly show that CAs and their inhibitors
and activators may play an essential role in the development
of new therapeutic approaches against a multitude of disorders
in addition to the classical ones for which such agents were
and are still used clinically. Furthermore, some drug design
studies of CA inhibitors may represent useful paradigms for
developing agents against more complicated targets [15].
I am particularly grateful to the Editor-in-Chief and the
staff from Bentham for inviting me to prepare this issue of
the journal dedicated to CA inhibitors, and to all the scientists
who dedicated much time and energy to produce these nice articles
which will be helpful to all the members of the scientific
community working in the drug design field.
References:
[1] Supuran CT. Carbonic Anhydrases – An Overview.
Curr Pharm Des 2008; 14(7): 603-614.
[2] Winum J-Y, Scozzafava A, Montero J-L, Supuran CT. Design
of Zinc Binding Functions for Carbonic Anhydrase Inhibitors.
Curr Pharm Des 2008; 14(7): 615-621.
[3] Nishimori I, Onishi S, Takeuchi H, Supuran CT. The α
and β
Classes Carbonic Anhydrases from Helicobacter pylori
as Novel Drug Targets. Curr Pharm Des 2008; 14(7): 622-630.
[4] Krungkrai J, Supuran CT.The Alpha-Carbonic Anhydrase from
the Malaria Parasite and Its Inhibition. Curr Pharm Des 2008;
14(7): 631-640.
[5] Supuran CT. Diuretics: From Classical Carbonic Anhydrase
Inhibitors to Novel Applications of the Sulfonamides. Curr
Pharm Des 2008; 14(7): 641-648.
[6] Mincione F, Scozzafava A, Supuran CT. The Development
of Topically Acting Carbonic Anhydrase Inhibitors as Antiglaucoma
Agents. Curr Pharm Des 2008; 14(7): 649-654.
[7] De Simone G, Di Fiore A, Supuran CT. Are Carbonic Anhydrase
Inhibitors Suitable for Obtaining Antiobesity Drugs ? Curr
Pharm Des 2008; 14(7): 655-660.
[8] Thiry A, Dogné J-M, Supuran CT, Masereel B. Anticonvulsant
Sulfonamides/Sulfamates/Sulfamides with Carbonic Anhydrase
Inhibitory Activity: Drug Design and Mechanism of Action.
Curr Pharm Des 2008; 14(7): 661-671.
[9] Hilvo M, Innocenti A, Monti SM, De Simone G, Supuran CT,
Parkkila S. Recent Advances in Research on the Most Novel
Carbonic Anhydrases, CA XIII and XV. Curr Pharm Des 2008;
14(7): 672-678.
[10] Dogné J-M, Thiry A, Supuran CT. Carbonic Anhydrase
Inhibition: Insight into Non-COX-2 Pharmacological Effect
of some Coxibs. Curr Pharm Des 2008; 14(7): 679-684.
[11] Pastorekova S, Zatovicova M, Pastorek J. Cancer-Associated
Carbonic Anhydrases and their Inhibition. Curr Pharm Des 2008;
14(7): 685.698.
[12] Cecchi A, Supuran CT. Fluorescence- and Spin-Labeled
Carbonic Anhydrase Inhibitors. Curr Pharm Des 2008; 14(7):
699-707.
[13] Temperini C, Scozzafava A, Supuran CT. Carbonic Anhydrase
Activation and the Drug Design. Curr Pharm Des 2008; 14(7):
708-715.
[14] Zimmerman SA, Ferry JG. The β
and γ
Classes of Carbonic Anhydrase. Curr Pharm Des 2008; 14(7):
716-721.
[15] Supuran CT. Carbonic anhydrases: novel therapeutic applications
for inhibitors and activators. Nature Reviews Drug Discovery
2008; 7: 168-181.
Claudiu T. Supuran
Università degli Studi di Firenze
Laboratorio di Chimica Bioinorganica
Rm. 188, Via della Lastruccia 3
I-50019 Sesto Fiorentino (Firenze)
Italy
E-mail: claudiu.supuran@unifi.it
[Back to top]
Carbonic Anhydrases – An Overview
C.T. Supuran
Carbonic anhydrases (CAs, EC 4.2.1.1) are widespread
metalloenzymes all over the phylogenetic tree, with at least
4 distinct gene families encoding for them. At least 16 different
α-
CA isoforms were isolated in mammals, where these enzymes
play crucial physiological roles. Representatives of the β
- δ-CA
family are highly abundant in plants, diatoms, eubacteria
and archaea. These enzymes are efficient catalysts for the
reversible hydration of carbon dioxide to bicarbonate, but
at least the α
-CAs possess a high versatility, being able to catalyze different
other hydrolytic processes The catalytic mechanism of the
α-CAs
is understood in detail: the active site consists of a Zn(II)
ion co-ordinated by three histidine residues and a water molecule/hydroxide
ion. The latter is the active species, acting as a potent
nucleophile. For β-
and γ-CAs,
the zinc hydroxide mechanism is valid too, although at least
some β-class
enzymes do not have water directly coordinated to the metal
ion. CAs are inhibited by two classes of compounds: the metal
complexing anions and the sulfonamides and their isosteres
(sulfamates, sulfamides etc.) possessing the general formula
RXSO2NH2
(R = aryl; hetaryl; perhaloalkyl; X = nothing, O or NH). At
least 25 clinically used drugs/agents in clinical development
show applications as diuretics and antiglaucoma drugs, anticonvulsants,
with some compounds being developed as anticancer agents/diagnostic
tools for tumors, antiobesity agents, and antimicrobials/antifungals
(inhibitors targeting CAs from pathogenic organisms such as
Helicobacter pylori, Mycobacterium tuberculosis,
Plasmodium falciparum, Candida albicans, etc). Several
important physiological and physio-pathological functions
are played by CA isozymes present in organisms all over the
phylogenetic tree, related to respiration and transport of
CO2/bicarbonate between metabolizing
tissues and the lungs, pH and CO2
homeostasis, electrolyte secretion in a variety of tissues/organs,
biosynthetic reactions, such as the gluconeogenesis and ureagenesis
among others (in animals), CO2
fixation (in plants and algae), etc. The presence of these
ubiquitous enzymes in so many tissues and in so different
isoforms, represents an attractive goal for the design of
inhibitors or activators with biomedical applications.
[Back to top]
Design of Zinc Binding Functions for Carbonic Anhydrase Inhibitors
J-Y. Winum, A. Scozzafava, J-L. Montero and C.T. Supuran
Zinc ion plays a crucial role in the protein’s
functions and is linked to a variety of physiological processes.
It constitutes an essential component of numerous enzymes
especially carbonic anhydrase (CAs, EC 4.2.1.1), a pharmaceutically-important
metalloprotein which catalyses efficiently the reversible
hydration of carbon dioxide to bicarbonate with discharge
of a proton. The potential therapeutic applications of selective
carbonic anhydrase inhibitors has become an important challenge
over the last few years, as some isoforms of this enzyme on
the 16 described in higher vertebrates have been found to
be involved in important pathologies such as cancer, obesity
and ophthalmologic diseases.
Coordination of the inhibitor with the zinc ion present in
the active site is an important determinant which has to be
taken into consideration for the design of isozyme-specific
and organ-selective inhibitors. Besides the well known sulfonamide
function, others zinc binding groups have been described constituting
a new platform for the development of novel pharmacological
agents. In this review, recent studies on the discovery of
new zinc binding function will be discussed.
[Back to top]
The α
and β
Classes Carbonic Anhydrases from Helicobacter pylori as
Novel Drug Targets
I. Nishimori, S. Onishi, H. Takeuchi and C.T. Supuran
Helicobacter pylori (H. pylori) successfully resides
in the human stomach in highly acidic conditions, causing
a variety of gas-stroduodenal lesions, including gastric ulcer,
gastric cancer and MALT lymphoma. For acid acclimation of
H. pylori, two types of enzymes, urease and carbonic
anhydrase (CA), play a central role. They cooperatively function
to maintain neutral pH in the bacterial cytoplasm and periplasm.
The genome project of H. pylori identified two different
classes of CA with different subcellular localization: a periplasmic
α-class
CA (hpαCA)
and a cytoplasmic β-class
CA (hpβCA).
These two CAs are catalytically efficient with almost identical
activity to that of the human isoform CA I for the CO2
hydration reaction, and highly inhibited by many sulfonamides/sulfamates,
including acetazolamide, ethoxzolamide, topiramate and sulpiride,
all clinically used drugs. Furthermore, certain CA inhibitors,
such as acetazolamide and methazolamide, were shown to inhibit
the bacterial growth in vitro. Since the efficacy
of eradication therapies currently employed has been decreasing
due to drug resistance and side effects of the commonly used
drugs, the dual inhibition of α-
and/or β-CAs
of H. pylori could be applied as an alternative therapy
in patients with H. pylori infection or for the prevention
of gastroduodenal diseases provoked by this widespread pathogen.
[Back to top]
The Alpha-Carbonic Anhydrase from the Malaria Parasite and
its Inhibition
J. Krungkrai and C.T. Supuran
Plasmodium falciparum is the protozoan parasite responsible
for the majority of life-threatening cases of human malaria,
causing more than one million deaths a year. The global emergence
of drug-resistant malarial parasites necessitates identification
and characterization of novel drug targets. At present, α-carbonic
anhydrase (CA) genes are identified in limited numbers of
parasites in both protozoa and helminthes, however, the malarial
genes are found in four species of Plasmodium. The CA gene
of P. falciparum encodes an α-carbonic
anhydrase enzyme possessing catalytic properties distinct
of that of the human host CA I and II isozymes. P. falciparum
native and recombinant enzymes have been prepared. A library
of aromatic sulfonamides, most of which were Schiff’s
bases derived from sulfanilamide/homosulfanilamide/4aminoethylbenzenesulfonamide
and substituted-aromatic aldehydes, or ureido-substituted
sulfonamides are very good inhibitors for P. falciparum enzyme
with Ki values in the range
of 80 nM–0.50 μM.
The 4-(3,4-dichlorophenylureido-ethyl)-benzenesulfonamide
is the most effective antimalarial activity against growth
of P. falciparum in vitro with an IC50
of 2 μM.
The structure 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 enzyme inhibitory activities of these aromatic
sulfonamide derivatives, both against the malarial as well
as human enzymes. This review provides further support that
the CA may have essential roles in the parasite metabolism.
Thus, the aromatic sulfonamide CA inhibitors may have potential
for development of novel antimalarial drugs.
[Back to top]
Diuretics: From Classical Carbonic Anhydrase Inhibitors to
Novel Applications of the Sulfonamides
C.T. Supuran
The widely clinically used benzothiadiazines and high
ceiling diuretics, such as hydrochlorothiazide, hydroflumethiazide,
quinethazone, metolazone, chlorthalidone, indapamide, furosemide
and bumetanide, contain SO2NH2
moieties acting as an effective zinc-binding function in carbonic
anhydrases (CAs, EC 4.2.1.1) inhibitors. These drugs were
launched in a period when only isoform CA II was known and
considered physiologically/pharmacologically relevant. Although
acting as moderate-weak inhibitors of CA II, all these drugs
considerably inhibit other CA isozymes known nowadays to be
involved in critical physiologic processes, among the 16 CAs
present in vertebrates. Some low nanomolar (or even subnanomolar)
inhibitors against such isoforms were recently detected, such
as metholazone against CA VII, XII and XIII, chlorthalidone
against CA VB, VII, IX, XII and XIII, indapamide against CA
VII, IX, XII and XIII, furosemide against CA I, II and XIV,
and bumethanide against CA IX and XII. The X-ray crystal structure
of the CA II – indapamide adduct was also reported recently,
revealing interesting aspects useful for the drug design of
CA inhibitors. It has also been proposed that the recently
observed beneficial effect of indapamide for the treatment
of patients with hypertension and type 2 diabetes might be
due to its potent inhibition of CA isoforms present in kidneys
and blood vessels, which would thus explain both the blood
pressure lowering effects as well as organ-protective activity
of the drug. Thus, these old drugs may be useful as leads
for new applications.
[Back to top]
The Development of Topically Acting Carbonic Anhydrase Inhibitors
as Antiglaucoma Agents
F. Mincione, A. Scozzafava and C.T. Supuran
Inhibition of carbonic anhydrase (CA, EC 4.2.1.1) isoforms
present in the eyes (CA I, II, IV and XII), with sulfonamides
such as acetazolamide, methazolamide, ethoxzolamide and dichlorophenamide,
is still widely used for the systemic treatment of glaucoma.
The mechanism of action of these drugs consists in inhibition
of CA isozymes present in ciliary processes of the eye, with
the consequent reduction of bicarbonate and aqueous humour
secretion, and of elevated intraocular pressure (IOP) characteristic
of this disease. As isoforms CA II/IV/XII are present in many
other tissues/organs, generally, systemic CAIs possess undesired
side effects such as numbness and tingling of extremities;
metallic taste; depression; fatigue; malaise; weight loss;
decreased libido; gastrointestinal irritation; metabolic acidosis;
renal calculi and transient myopia. For avoiding these side
effects, recently, topically effective CAIs have been developed
in the last 10 years, with two drugs available clinically:
dorzolamide and brinzolamide. Both these drugs are applied
topically as water solutions/suspensions, alone or in combination
with other agents (β-blockers,
prostaglandin derivatives, etc) and produce a consistent and
prolonged reduction of IOP. Furthermore, recent reports show
both the systemically as well as topically acting sulfonamide
CAIs to be effective in the treatment of macular edema, macular
degeneration disease, or diabetic retinopathy, for which pharmacological
treatment is unavailable up to now. Much research is in act
in the search of more effective topically acting CAIs, free
of the inconveniences and side effects of the presently available
drugs. For achieving this goal, two recently reported strategy,
the tail approach and its variant, the sugar-tail approach,
were extensively applied for the synthesis of large numbers
of derivatives possessing desired physico-chemical properties.
Many such new sulfonamides showed promising antiglaucoma activity
in animal models of the disease.
[Back to top]
Are Carbonic Anhydrase Inhibitors Suitable for Obtaining Antiobesity
Drugs ?
G. De Simone, A. Di Fiore and C.T. Supuran
Obesity is widespread disease both in the developed and
developing world, which currently affects over 300 million
individuals worldwide and is associated with premature mortality
and chronic morbidity. Although diet, physical activity and
behavioral modifications should theoretically help in controlling
this condition, very often these strategies are insufficient
to normalize the multiple risks associated with this condition.
Thus, pharmacological interventions for the treatment of this
disease are essential. Paradoxically, the currently available
drugs for the treatment of obesity are very few, their mechanism
of action is hardly understood and their side effects are
generally quite serious. Therefore, novel effective anti-obesity
drugs possessing different mechanisms of action are needed.
In this review we describe in detail a possible new approach
for the treatment and prophylaxis of this disease based on
the inhibition of Carbonic Anhydrases (CAs, EC 4..2.1.1),
enzymes involved in several steps of de novo lipogenesis.
In particular, we summarize here a series of kinetic and structural
studies recently reported on Topiramate (TPM)
and Zonisamide (ZNS), two antiepileptic drugs
showing strong CA inhibitory properties, that were shown to
induce persistent weight loss in obese patients. On the basis
of the reviewed studies we suggest that the use of TPM
and ZNS as lead molecules for the design
of CA inhibitors targeting isozymes involved in lipogenesis
could represent the beginning of a very promising approach
for the treatment of obesity.
[Back to top]
Anticonvulsant Sulfonamides/Sulfamates/Sulfamides with Carbonic
Anhydrase Inhibitory Activity: Drug Design and Mechanism of
Action
A. Thiry, J-M. Dogné, C.T. Supuran and B. Masereel
The marketed antiepileptic drugs can not solve entirely
the problem of seizure in patients suffering from refractory
epilepsies. Therefore, new anticonvulsant compounds structurally
and pharmacologically different of the currently prescribed
drugs are needed. Carbonic anhydrase (CA) inhibitors are known
to act as anticonvulsant since several decades while the link
between CA and seizure is not straightforward. However, the
recent discovery that several CA isozymes are expressed in
brain and the better knowledge of their physiological/pathological
role, lead to the emergence of new CA inhibitors with anticonvulsant
effect including: analogues of acetazolamide, analogues of
topiramate, aromatic or heterocyclic sulfonamides incorporating
valproyl or adamantyl moieties. Different strategies are developed
for the design of new more selective CA inhibitors with anticonvulsant
properties.
[Back to top]
Recent Advances in Research on the Most Novel Carbonic Anhydrases,
CA XIII and XV
M. Hilvo, A. Innocenti, S.M. Monti, G. De Simone, C.T.
Supuran and S. Parkkila
The carbonic anhydrase (CA) enzyme family consists of
thirteen active isozymes in mammals. The most recently characterized
members of this family are cytosolic CA XIII and membrane-bound
CA XV. This article describes recent advances in the CA family,
especially CA XIII and XV. We have also included catalytic
activity data on human CA XIII and mouse CA XV. Additionally,
the inhibition constants of acetazolamide toward these isozymes
were determined to be kCat=
1.5 × 105 s-1,
kCat KM
= 1.1 × 107 M-1s-1
and KI = 16 nM for human
CA XIII and kCat = 4.7 ×
105 s-1,
kCat /KM
= 3.3 × 107 M-1
s-1 and KI
= 72 nM for mouse CA XV. Although the activity of CA XIII
is the second lowest reported thus far for any of the human
CAs, it may have a role in maintaining the acid-base balance
in the kidney and the gastrointestinal and reproductive tracts.
CA XV is an exceptional enzyme, as it seems to be active in
numerous species, such as rodents, birds and fish, but is
absent from humans and chimpanzees. Mouse CA XV is a moderately
active enzyme, suggesting that it may play a physiological
role at least in the kidney. It is likely that other isozymes
have substituted for this protein in humans. In addition to
the novel data on CA XIII and XV, we present the catalytic
activities as well as inhibition constants of acetazolamide
for all mammalian CA isozymes in this review.
[Back to top]
Carbonic Anhydrase Inhibition: Insight into Non-COX-2 Pharmacological
Effect of some Coxibs
J-M. Dogné, A. Thiry and C.T. Supuran
Nonsteroidal anti-inflammatory drugs (NSAIDs) represent
the most commonly used medications for the treatment of pain
and inflammation, but numerous well-described adverse drug
reactions (ADRs) limit their use. These drugs act via
the inhibition of cyclooxygenase (COX) enzyme of which at
least two isoforms were described: COX-1 which plays important
roles in homeostatic processes such as thrombogenesis and
homeostasis of the gastrointestinal tract and kidneys and
COX-2 expressed in pathological conditions such as inflammation
or cancer proliferation. Selective COX-2 inhibitors or “coxibs”
were initially developed as a therapeutic strategy to avoid
not only the gastrointestinal but also the renal and cardiovascular
side effects of non specific NSAIDs. However, this class of
drug did not fulfill all their promises. Indeed, numerous
unexpected side effects have limited their use and some of
them have been withdrawn or suspended from the market for
different safety reasons including cardiovascular, hepatic
and skin adverse reactions. For instance, cardiovascular warnings
have been applied to the whole class of coxibs and more recently
for all classical NSAIDs as well. However, differences in
the chemical structures should be taken into consideration
in order to discriminate between coxibs and the development
of some ADRs of which renal events and hypertension. The aim
of this paper is to focus on the differences in chemical structures
of all marketed COX-2 inhibitors and their unexpected effects
on carbonic anhydrase in order to provide non-COX-2 mechanistic
insights into some of the differences observed between coxibs.
[Back to top]
Cancer-Associated Carbonic Anhydrases and Their Inhibition
S. Pastorekova, M. Zatovicova and J. Pastorek
Cells of the growing tumor tissue are exposed to physiological
stresses connected with insufficient delivery of oxygen (hypoxia)
and accumulation of acidic products of the glycolytic metabolism
(acidosis). Adaptation to these microenvironmental stresses
involves remodeling of the cellular expression program mediated
by hypoxia-inducible factor (HIF), which activates broad array
of genes functionally involved in angiogenesis, anaerobic
glycolysis, de-adhesion, invasion etc. This leads to increased
aggressiveness of tumors, metastatic spread and poor response
to therapy. Genes coding for transmembrane carbonic anhydrase
(CA) isoforms IX and XII are induced in response to low oxygen
as a part of the hypoxic transcriptome. Moreover, CA IX is
a direct target of HIF and serves as a surrogate marker of
hypoxia and prognostic indicator. Its expression is strongly
linked to different types of tumors with the HIF pathway activated
due to genetic defect or physiological hypoxia. CA IX (and
possibly also CA XII) is participates in pH regulation, which
is important for survival of hypoxic cells. Both enzymes are
therefore promising therapeutic molecules targetable by inhibitors
of CA activity. Some of these sulfonamide compounds and their
derivatives are capable to block CA-mediated pH regulation
in hypoxia. This review summarizes research data related to
distribution, regulation and functional aspects of CA IX and
CA XII, and describes emerging possibilities for clinical
exploitation of CA inhibitors as imaging tools and anticancer
drugs.
[Back to top]
Fluorescence- and Spin-Labeled Carbonic Anhydrase Inhibitors
A. Cecchi and C.T. Supuran
Carbonic anhydrase IX (hCA IX) is a membrane-associated
glycoprotein that is observed in many tumor tissues and is
strongly overexpressed by hypoxia conditions. Hypoxia is a
clinically important tumor parameter and this enzyme can play
an important role as a potential marker of hypoxic
tumor and as a therapeutic target too. In the last
years, Carbonic Anhydrase IX Inhibitors which possess fluorescent
probe were largely used for visualize hypoxic tumor cell lines
and for understanding the biological roles of hCA IX in acidification
of the external matrix. Here we resume the developement pathways
of such compounds from the design to the final biological
evaluation. Furthermore, spin-labeled CAIs were included to
have a complete overview of the potenciality of this enzyme
as marker of hypoxic tumors
[Back to top]
Carbonic Anhydrase Activation and the Drug Design
C. Temperini, A. Scozzafava and C.T. Supuran
The activation mechanism of Carbonic Anhydrase was recently
explained using kinetic, spectroscopic and X-ray techniques.
It has been demonstrated that the activators molecules (CAAs)
bind at the entrance of the enzyme active-site facilitating
the rate-determining step of CA catalitic cycle. Drug design
studies have been performed in order to obtain strong CAAs
belonging to several chemical classes: amino acids, azoles,
amine and their derivatives, etc.
Structure-activity correlations of different activators are
discussed for the most studied Carbonic Anhydrase isozymes:
isoform I and II.
The physiological relevance of CA activation and the possible
application of CAAs in Alzheimer’s desease and for other
memory therapies are also treated.
[Back to top]
The β
and γ
Classes of Carbonic Anhydrase
S.A. Zimmerman and J.G. Ferry
There are currently five (α,β,γ,δ,ζ)
classes of carbonic anhydrases (CA’s) of which the α-class
from mammalian sources has been studied to a much greater
extent compared to the other four classes. Yet, CA’s
other than the β-class
are widely distributed in Nature and play important roles
in human health, the global carbon cycle, and industrial applications.
In aerobic prokaryotes, β-class
CA’s are implicated in maintaining internal pH and CO2/
bicarbonate balances required for biosynthetic reactions.
In anaerobic prokaryotes, β-class
CA’s are implicated in the transport of CO2
and bicarbonate across the cytoplasmic membrane that regulates
pH and facilitates acquisition of substrates and product removal
required for growth. In phototrophic organisms, β-class
CA’s are particularly important for transport and concentration
of CO2 and bicarbonate for
photosynthesis. The δ-
and ζ-classes
are proposed to function in marine diatoms to concentrate
CO2 for photosynthesis. Physiological
roles for the γ-class
are not as well documented; however, the active site architecture
and catalytic mechanism is well understood as are patterns
of inhibition by sulfonamides and anions.
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