Accumulation, Characterization and Reactivity of Chiral Ammonium-Carboxonium Dications in Superacid

The accumulation of chiral ammonium-oxocarbenium dications in superacid is evidenced by low-temperature NMR spectroscopy, X-ray diffraction analysis and confirmed by DFT calculations. Its potential for the diastereoselective remote hydrofunctionalization of non-activated alkene is also explored.

A Multitarget Approach against Neuroinflammation: Alkyl Substituted Coumarins as Inhibitors of Enzymes Involved in Neurodegeneration

Neurodegenerative disorders (NDs) include a large range of diseases characterized by neural dysfunction with a multifactorial etiology. The most common NDs are Alzheimer's disease and Parkinson's disease, in which cholinergic and dopaminergic systems are impaired, respectively. Despite different brain regions being affected, oxidative stress and inflammation were found to be common triggers in the pathogenesis and progression of both diseases. By taking advantage of a multi-target approach, in this work we explored alkyl substituted coumarins as neuroprotective agents, capable to reduce oxidative stress and inflammation by inhibiting enzymes involved in neurodegeneration, among which are Carbonic Anhydrases (CAs), Monoamine Oxidases (MAOs), and Cholinesterases (ChEs). The compounds were synthesized and profiled against the three targeted enzymes. The binding mode of the most promising compounds (7 and 9) within MAO-A and -B was analyzed through molecular modeling studies, providing and explanation for the different selectivities observed for the MAO isoforms. In vitro biological studies using LPS-stimulated rat astrocytes showed that some compounds were able to counteract the oxidative stress-induced neuroinflammation and hamper interleukin-6 secretion, confirming the success of this multitarget approach.

Design and synthesis of 6-arylpyridine-tethered sulfonamides as novel selective inhibitors of carbonic anhydrase IX with promising antitumor features toward the human colorectal cancer

Hypoxia, a characteristic feature of solid tumors, develops as a result of excessive cell proliferation and rapid tumor growth exceeding the oxygen supply, and can result in angiogenesis activation, increased invasiveness, aggressiveness, and metastasis, leading to improved tumor survival and suppression of anticancer drug therapeutic impact. SLC-0111, a ureido benzenesulfonamide, is a selective human carbonic anhydrase (hCA) IX inhibitor in clinical trials for the treatment of hypoxic malignancies. Herein, we describe the design and synthesis of novel 6-arylpyridines 8a-l and 9a-d as structural analogues of SLC-0111, in the aim of exploring new selective inhibitors for the cancer-associated hCA IX isoform. The para-fluorophenyl tail in SLC-0111 was replaced by the privileged 6-arylpyridine motif. Moreover, both ortho- and meta-sulfonamide regioisomers, as well as an ethylene extended analogous were developed. All 6-arylpyridine-based SLC-0111 analogues were screened in vitro for their inhibitory potential against a panel of hCAs (hCA I, II, IV and IX isoforms) using stopped-flow CO₂ hydrase assay. In addition, the anticancer activity was firstly explored against a panel of 57 cancer cell lines at the USA NCI-Developmental Therapeutic Program. Compound 8g emerged as the best anti-proliferative candidate with mean GI% value equals 44. Accordingly, a cell viability assay (MTS) for 8g was applied on colorectal HCT-116 and HT-29 cancer cell lines as well as on the healthy HUVEC cells. Thereafter, Annexin V-FITC apoptosis detection, cell cycle, TUNEL, and qRT-PCR, colony formation, and wound healing assays were applied to gain mechanistic insights and to understand the behavior of colorectal cancer cells upon the treatment of compound 8g. Also, a molecular docking analysis was conducted to provide in silico insights into the reported hCA IX inhibitory activity and selectivity.

Uncovering Novel Capsaicin Inhibitory Activity towards Human Carbonic Anhydrase Isoforms IX and XII by Combining In Silico and In Vitro Studies

Hot pepper (Capsicum annuum) represents one of the most widespread functional foods of the Mediterranean diet, and is associated with a reduced risk of developing cardiovascular disease, cancer, and mental disorders. In particular, its bioactive spicy molecules, named Capsaicinoids, exhibit polypharmacological properties. Among them, Capsaicin (trans-8-methyl-N-vanillyl-6-nonenamide) is the most studied and reported in variegated scientific contributions for its beneficial effects, often linked to mechanisms of action unrelated to the activation of Transient Receptor Potential Vanilloid 1 (TRPV1). In this study, we present the application of in silico methods to Capsaicin for evaluating its inhibitory activity against the tumor-associated human (h) expressed CA IX and XII. In vitro assays confirmed Capsaicin inhibitory activity towards the most relevant tumor-related hCA isoforms. In particular, the hCAs IX and XII showed an experimental K_I value of 0.28 μM and 0.064 μM, respectively. Then, an A549 model of non-small cell lung cancer, typically characterized by an elevated expression of hCA IX and XII, was employed to test the inhibitory effects of Capsaicin in vitro under both normoxic and hypoxic conditions. Finally, the migration assay revealed that Capsaicin [10 µM] inhibits cells from moving in the A549 cells model.

Escinosome thermosensitive gel optimizes efficacy of CAI-CORM in a rat model of rheumatoid arthritis

Rheumatoid arthritis is among the most common disabling diseases associated with chronic inflammation. The efficacy of the current therapeutic strategies is limited; therefore, new pharmacological agents and formulation approaches are urgently needed. In this work, we developed a thermosensitive gel incorporating escinosomes, innovative nanovesicles made of escin, stabilized with 10% of tween 20 and loaded with a Carbonic Anhydrase Inhibitor (CAI) bearing a Carbon Monoxide Releasing Moiety (CORM) (i.e., CAI-CORM 1), previously synthesized by some of the authors as a new potent pain-relieving agent. The light scattering analysis of the developed formulation showed optimal physical parameters, while the chromatographic analysis allowed the quantification of the encapsulation efficiency (90.1 ± 5.91 and 91.6 ± 8.46 for CAI-CORM 1 and escin, respectively). The thermosensitive gel, formulated using 23% w/v of poloxamer 407, had a sol-gel transition time of 40 s and good syringeability. Its stability in simulated synovial fluid (SSF) was morphologically evaluated by electron microscopy. Nanovesicles were physically stable in contact with the medium for two weeks, maintaining their original dimensions and spherical shape. The viscosity increased by about 30- to 100-fold with the temperature change from 25 °C to 37 °C. The gel erosion in SSF occurred within 9 h (88.2 ± 0.743%), and the drug's passive diffusion from escinosomes lasted 72 h, allowing a potential sustained therapeutic effect. The efficacy of a single intra-articular injection of the gel containing escinosomes loaded with CAI-CORM 1 (3 mg/mL; 30 μL, CAI-CORM 1 formulation) and the gel containing unloaded escinosomes (30 μL, blank formulation) was evaluated in a rat model of Complete Freund's Adjuvant (CFA)-induced rheumatoid arthritis. CAI-CORM 1 formulation was assessed to counteract mechanical hyperalgesia, spontaneous pain, and motor impairments on days 7 and 14 after treatment. The histological evaluation of the joints stressed the improvement of several morphological parameters in CFA + CAI-CORM 1 formulation-treated rats. In conclusion, the hybrid molecule CAI-CORM 1 formulated in escinosome-based thermosensitive gel could represent a new valid approach for managing rheumatoid arthritis.

Novel Insights on CAI-CORM Hybrids: Evaluation of the CO Releasing Properties and Pain-Relieving Activity of Differently Substituted Coumarins for the Treatment of Rheumatoid Arthritis

Pain control is among the most important healthcare services in patients affected by rheumatoid arthritis (RA), but the current therapeutic options (i.e., disease-modifying anti-rheumatic drugs) are limited by the risk of the side effects. In this context, we proposed an innovative approach based on the hybridization between carbonic anhydrase inhibitors (CAIs) and CO releasing molecules (CORMs). The resulting CAI-CORM hybrids were revealed to possess strong anti-inflammatory effects in in vitro models of diseases and to relieve ache symptoms in an in vivo RA rat model. In this work, we have deepened the study of these promising hybrids, designing a library of coumarin-based compounds, also including internal dicobalt hexacarbonyl systems. The results obtained from the CO releasing study, the CA inhibitory activity, and the in vivo pain-relief efficacy evaluation in the RA rat model confirmed the success of this strategy, allowing us to consider CAI-CORM hybrids promising anti-nociceptive agents against arthritis.

New 1H-indole-2,3-dione 3-thiosemicarbazones with 3-sulfamoylphenyl moiety as selective carbonic anhydrase inhibitors

1-Methyl/ethyl/benzyl-5-(un)substituted 1H-indole-2,3-diones (2, 3, and 4) were synthesized by reaction of 5-(un)substituted 1H-indole-2,3-diones (1) with methyl iodide, ethyl chloride, and benzyl bromide. (3-Sulfamoylphenyl)isothiocyanate (6) was obtained by the treatment of 3-aminobenzenesulfonamide (5) with thiophosgene. Compound 6 was reacted with hydrazine to yield 4-(3-sulfamoylphenyl)thiosemicarbazide (7). Novel 1-(un)substituted/methyl/ethyl/benzyl-5-(un)substituted 1H-indole-2,3-dione 3-[4-(3-sulfamoylphenyl)thiosemicarbazone] derivatives (8-11) were prepared by condensation of 7 and 1-4. The structures of the synthesized compounds were confirmed by elemental analysis and spectral data. Inhibition of the widely distributed cytosolic off-targets human carbonic anhydrases (hCAs) I and II, and two tumor-associated membrane-bound isoforms (hCAs IX and XII), by 8-11 was investigated. The hCA II inhibitory effects of all tested compounds were in the subnanomolar to low nanomolar levels (K_i  = 0.32-83.3 nM), and generally high selectivity for hCA II isoenzyme over hCA I, IX, and XII isoenzymes was observed. The strongest inhibitors of hCA II, 1-benzyl-5-(trifluoromethoxy)-substituted 11c (K_i  = 0.32 nM) and 1-ethyl-5-chloro-substituted 10e (K_i  = 0.35 nM), were docked within the enzyme active site. Molecular modeling studies with the most effective hCA IX and XII inhibitors were also carried out.

An innovative spectroscopic approach for qualitative and quantitative evaluation of Mb-CO from myoglobin carbonylation reaction through chemometrics methods

In this work, an innovative approach using K-means and multivariate curve resolution-purity based algorithm (MCR-Purity) for the evaluation and quantification of carboxymyoglobin (Mb-CO) formation from Deoxy-Myoglobin (Deoxy-Mb) was presented. Through a multilevel multifactor experimental design, samples with different concentrations of Mb-CO were created. The UV-Vis spectra of these samples were submitted to K-means analysis, finding 3 clusters. The mean spectra of the clusters were extracted and it was possible to detect 2 totally differentiable groups through peaks 423 and 434 nm, which are wavelengths related to the Mb-CO and Deoxy-Mb components, respectively. The spectral data were subjected to MCR-Purity analysis. The MCR-Purity result successfully described the analyzed reaction, explaining more than 99.9% of the variance (R²) with a LOF of 1.43%. Then, a predictive model of MbCO was created through the linear relationship between MCR-Purity contributions and known concentrations of MbCO. The performance parameters of the created predictive model were R²CV = 0.98, RMSECV = 0.58 and RPDcv = 7.8 for the training set, and R²P = 0.98, RMSEP = 0.7 and RPDp = 6.8 for the test set. Thus, the predictive model presented an excellent performance considering that the Mb-CO variation is comprised between 0 and 21 µM. Therefore, these results demonstrate that the application of the proposed strategy to the analysis of spectral data presenting overlapping bands is feasible and robust.

A Novel Class of Dual-Acting DCH-CORMs Counteracts Oxidative Stress-Induced Inflammation in Human Primary Tenocytes

Carbon monoxide (CO) can prevent cell and tissue damage by restoring redox homeostasis and counteracting inflammation. CO-releasing molecules (CORMs) can release a controlled amount of CO to cells and are emerging as a safer therapeutic alternative to delivery of CO in vivo. Sustained oxidative stress and inflammation can cause chronic pain and disability in tendon-related diseases, whose therapeutic management is still a challenge. In this light, we developed three small subsets of 1,5-diarylpyrrole and pyrazole dicobalt(0)hexacarbonyl (DCH)-CORMs to assess their potential use in musculoskeletal diseases. A myoglobin-based spectrophotometric assay showed that these CORMs act as slow and efficient CO-releasers. Five selected compounds were then tested on human primary-derived tenocytes before and after hydrogen peroxide stimulation to assess their efficacy in restoring cell redox homeostasis and counteracting inflammation in terms of PGE₂ secretion. The obtained results showed an improvement in tendon homeostasis and a cytoprotective effect, reflecting their activity as CO-releasers, and a reduction of PGE₂ secretion. As these compounds contain structural fragments of COX-2 selective inhibitors, we hypothesized that such a composite mechanism of action results from the combination of CO-release and COX-2 inhibition and that these compounds might have a potential role as dual-acting therapeutic agents in tendon-derived diseases.

Tetrahydroquinazole-based secondary sulphonamides as carbonic anhydrase inhibitors: synthesis, biological evaluation against isoforms I, II, IV, and IX, and computational studies

A library of variously decorated N-phenyl secondary sulphonamides featuring the bicyclic tetrahydroquinazole scaffold was synthesised and biologically evaluated for their inhibitory activity against human carbonic anhydrase (hCA) I, II, IV, and IX. Of note, several compounds were identified showing submicromolar potency and excellent selectivity for the tumour-related hCA IX isoform. Structure-activity relationship data attained for various substitutions were rationalised by molecular modelling studies in terms of both inhibitory activity and selectivity.

Mechanisms of the Antiproliferative and Antitumor Activity of Novel Telomerase-Carbonic Anhydrase Dual-Hybrid Inhibitors

Human (h) telomerase (TL; EC 2.7.7.49) plays a key role in sustaining cancer cells by means of elongating telomeric repeats at the 3' ends of chromosomes. Since TL-inhibitor (TI) stand-alone cancer therapy has been proven to be remarkably challenging, a polypharmacological approach represents a valid alternative. Here we consider a series of compounds able to inhibit both hTL and the tumor-associated carbonic anhydrases (CAs; EC 4.2.1.1) IX and XII. Compounds 7 and 9 suppressed hTL activity in both cell lysates and human colon cancer cell lines, and prolonged incubation with either 7 or 9 resulted in telomere shortening, cell cycle arrest, replicative senescence, and apoptosis. Enzyme kinetics showed that 7 and 9 are mixed-type inhibitors of the binding of DNA primers and deoxynucleoside triphosphate (dNTP) to the TL catalytic subunit hTERT, which is in agreement with docking experiments. Compound 9 showed antitumor activity in Colo-205 mouse xenografts and suppressed telomerase activity by telomere reduction.

Zeta-carbonic anhydrases show CS2 hydrolase activity: A new metabolic carbon acquisition pathway in diatoms?

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CDCA1 is a carbonic anhydrase that can utilize Zn(II) or Cd(II) as catalytic metal.

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CDCA1 has been the first enzyme to show an efficient utilization of Cd(II) ions in Nature.

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By using a multidisciplinary approach, we discovered that CS₂ is a substrate for this enzyme.

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CDCA1 is the unique enzyme, known so far, able to use both CS₂ and CO₂ as substrates.

CDCA1 is a very peculiar member of the Carbonic Anhydrase (CA) family. It has been the first enzyme to show an efficient utilization of Cd(II) ions in Nature and a unique adaptation capability to live on the surface ocean. Indeed, in this environment, which is extremely depleted in essential metal ions, CDCA1 can utilize Zn(II) or Cd(II) as catalytic metal to support the metabolic needs of fast growing diatoms. In this paper we demonstrate a further catalytic versatility of this enzyme by using a combination of X-ray crystallography, molecular dynamics simulations and enzymatic experiments. First we identified the CO₂ binding site and the way in which this substrate travels from the environment to the enzyme active site. Then, starting from the observation of a structural similarity with the substrate entry route of CS₂ hydrolase from Acidanius A1-3, we hypothesized and demonstrated that also CS₂ is a substrate for CDCA1. This finding is new and unexpected since until now only few CS₂ hydrolases have been characterized, and none of them is reported to have any CO₂ hydratase action. The physiological implications of this supplementary catalytic activity still remain to be unveiled. We suggest here that it could represent another ability of diatoms expressing CDCA1 to adapt to the external environment. Indeed, the ability of this enzyme to convert CS₂ could represent an alternative source of carbon acquisition for diatoms, in addition to CO₂.

Modulating the Efficacy of Carbonic Anhydrase Inhibitors through Fluorine Substitution

The insertion of fluorine atoms and/or fluoroalkyl groups can lead to many beneficial effects in biologically active molecules, such as enhanced metabolic stability, bioavailability, lipophilicity, and membrane permeability, as well as a strengthening of protein-ligand binding interactions. However, this "magic effect" of fluorine atom(s) insertion can often be meaningless. Taking advantage of the wide range of data coming from the quest for carbonic anhydrase (CA) fluorinated inhibitors, this Minireview attempts to give "general guidelines" on how to wisely insert fluorine atom(s) within an inhibitor moiety to precisely enhance or disrupt ligand-protein interactions, depending on the target location of the fluorine substitution in the ligand. Multiple approaches such as ITC, kinetic and inhibition studies, X-ray crystallography, and NMR spectroscopy are useful in dissecting single binding contributions to the overall observed effect. The exploitation of innovative directions made in the field of protein and ligand-based fluorine NMR screening is also discussed to avoid misconduct and finely tune the exploitation of selective fluorine atom insertion in the future.

High BRAF variant allele frequencies are associated with distinct pathological features and responsiveness to target therapy in melanoma patients

Background

BRAF mutant melanoma patients are commonly treated with anti-BRAF therapeutic strategies. However, many factors, including the percentage of BRAF-mutated cells, may contribute to the great variability in patient outcomes.

Patients and methods

The BRAF variant allele frequency (VAF; defined as the percentage of mutated alleles) of primary and secondary melanoma lesions, obtained from 327 patients with different disease stages, was assessed by pyrosequencing. The BRAF mutation rate and VAF were then correlated with melanoma pathological features and patients’ clinical characteristics. Kaplan–Meier curves were used to study the correlations between BRAF VAF, overall survival (OS), and progression-free survival (PFS) in a subset of 62 patients treated by anti-BRAF/anti-MEK therapy after metastatic progression.

Results

A highly heterogeneous BRAF VAF was identified (3%-90%). Besides being correlated with age, a higher BRAF VAF level was related to moderate lymphocytic infiltration (P = 0.017), to melanoma thickness according to Clark levels, (level V versus III, P = 0.004; level V versus IV, P = 0.04), to lymph node metastases rather than cutaneous (P = 0.04) or visceral (P = 0.03) secondary lesions. In particular, a BRAF VAF >25% was significantly associated with a favorable outcome in patients treated with the combination of anti-BRAF/anti-MEK drug (OS P = 0.04; PFS P = 0.019), retaining a significant value as an independent factor for the OS and the PFS in the multivariate analysis (P = 0.014 and P = 0.003, respectively).

Conclusion

These results definitively support the role of the BRAF VAF as a potential prognostic and predictive biomarker in melanoma patients in the context of BRAF inhibition.

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In melanoma the response to anti-BRAF targeted therapies is heterogeneous and influenced by several features.

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The role of the BRAF VAF as provider of sensitivity to target therapies is debated.

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We found that high BRAF VAFs are associated with patient age, melanoma thickness, non-brisk TILs and lymph node metastases.

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We proved the independent prognostic value of high BRAF VAFs in melanoma patients treated with targeted therapies.

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The quantitative evaluation of BRAF mutations allows stratifying melanoma patients to the BRAF/MEK targeted treatment.

Toxicity evaluation of sulfamides and coumarins that efficiently inhibit human carbonic anhydrases

Here, we report a toxicity study, conducted on zebrafish larvae, of a series of coumarin and sulfamide compounds that were previously reported as inhibitors of human (h) metalloenzymes, carbonic anhydrases (CAs, EC 4.2.1.1). Due to the high relevance of hCA inhibitors as theragnostic agents, it is of pivotal importance to address safety issues that may arise from the initial in vivo toxicological assessment using zebrafish, a relevant model for biomedical research. None of the reported compounds showed adverse phenotypic effects or tissue damage on developing zebrafish larvae after 5 days of exposure. Our study suggests that the coumarin and sulfamide derivatives considered here are safe and suitable for further development and testing.

Bioorganometallic derivatives of 4-hydrazino-benzenesulphonamide as carbonic anhydrase inhibitors: synthesis, characterisation and biological evaluation

A series of bio-organometallic-hydrazones of the general formula [{(η5-C5H4)-C(R)=N-N(H)-C6H4-4-SO2NH2}]MLn(MLn = Re(CO)3, Mn(CO)3, FeCp; R=H, CH3) were prepared by reaction of formyl/acetyl organometallic precursors with 4-hydrazino-benzenesulphonamide. All compounds were characterized by conventional spectroscopic techniques (infra-red, 1H and 13C NMR, mass spectrometry and elemental analysis). Biological evaluation as carbonic anhydrase (CA, EC 4.2.1.1) inhibitors agents was carried out using four human/h) isoforms, hCA I, II, IX and XII. The cytosolic isoforms hCA I and II were effectively inhibited by almost all derivatives with inhibition constants of 1.7-22.4 nM. Similar effects were observed for the tumour-associated transmembrane isoform hCA XII (KIs of 1.9-24.4 nM). hCA IX was less sensitive to inhibition with these compounds. The presence of bio-organometallic or metallo-carbonyl moieties in the molecules of these CAIs makes them amenable for interesting pharmacologic applications, for example for compounds with CO donating properties.

In Silico-Guided Identification of New Potent Inhibitors of Carbonic Anhydrases Expressed in Vibrio cholerae

Carbonic anhydrases from Vibrio cholerae (VchCAs) play a significant role in bacterial pathophysiological processes. Therefore, their inhibition leads to a reduction of gene expression virulence and bacterial growth impairment. Herein, we report the first ligand-based pharmacophore model as a computational tool to study selective inhibitors of the β-class of VchCA. By a virtual screening on a collection of sulfonamides, we retrieved 9 compounds that were synthesized and evaluated for their inhibitory effects against VchCAβ as well as α- and γ-classes of VchCAs and selectivity over human ubiquitous isoforms hCA I and II. Notably, all tested compounds were active inhibitors of VchCAs. The N-(4-sulfamoylbenzyl)-[1,1'-biphenyl]-4-carboxamide (20e) stood out as the most exciting inhibitor toward the β-class (K _i = 95.6 nM), also showing a low affinity against the tested human isoforms. By applying docking procedures, we described the binding mode of the inhibitor 20e within the catalytic cavity of the modeled open conformation of VchCAβ.

Azidothymidine "Clicked" into 1,2,3-Triazoles: First Report on Carbonic Anhydrase-Telomerase Dual-Hybrid Inhibitors

Cancer cells rely on the enzyme telomerase (EC 2.7.7.49) to promote cellular immortality. Telomerase inhibitors (i.e., azidothymidine) can represent promising antitumor agents, although showing high toxicity when administered alone. Better outcomes were observed within a multipharmacological approach instead. In this context, we exploited the validated antitumor targets carbonic anhydrases (CAs; EC 4.2.1.1) IX and XII to attain the first proof of concept on CA–telomerase dual-hybrid inhibitors. Compounds 1b, 7b, 8b, and 11b showed good in vitro inhibition potency against the CAs IX and XII, with K_I values in the low nanomolar range, and strong antitelomerase activity in PC-3 and HT-29 cells (IC₅₀ values ranging from 5.2 to 9.1 μM). High-resolution X-ray crystallography on selected derivatives in the adduct with hCA II as a model study allowed to determine their binding modes and thus to set the structural determinants necessary for further development of compounds selectively targeting the tumoral cells.

A class of carbonic anhydrase IX/XII - selective carboxylate inhibitors

A small series of 2,4-dioxothiazolidinyl acetic acids was prepared from thiourea, chloroacetic acid, aromatic aldehydes, and ethyl-2-bromoacetate. They were assayed for the inhibition of four physiologically relevant carbonic anhydrase (CA, EC 4.2.1.1) isoforms of human (h) origin, the cytosolic hCA I and II, and the transmembrane hCA IX and XII, involved among others in tumorigenesis (hCA IX and XII) and glaucoma (hCA II and XII). The two cytosolic isoforms were not inhibited by these carboxylates, which were also rather ineffective as hCA IX inhibitors. On the other hand, they showed submicromolar hCA XII inhibition, with K_Is in the range of 0.30–0.93 µM, making them highly CA XII-selective inhibitors.

New thiopyrimidine-benzenesulfonamide conjugates as selective carbonic anhydrase II inhibitors: synthesis, in vitro biological evaluation, and molecular docking studies

In the present work, a new series of thiopyrimidine-benzenesulfonamide conjugates was designed, synthesized and tested as carbonic anhydrase (CA, EC 4.2.1.1) inhibitors. Our design strategy was based on the molecular hybridization of the benzenesulfonamide moiety as a zinc binding group (ZBG), an alkylated thiopyrimidine moiety as a spacer and (un)substituted phenyl moieties with various electronic and hydrophobic environments as a tail. The designed and synthesized compounds were evaluated against four human (h) CA isoforms hCA I, hCA II, hCA IX and hCA XII. Series 6 showed promising activity and selectivity toward the cytosolic isoforms hCA I and hCA II versus the membrane bound isoforms hCA IX and hCA XII. Compounds 6e and 6f showed Ki of 0.04 µM against hCA II with a selectivity of 15.8- to 980-fold towards hCA II over hCA I, hCA IX, hCA XII isoforms. Molecular docking in the hCA II active site attributed the promising inhibitory activity of series 6 to the interaction of their sulfonamide moiety with the active site Zn2+ ion as well as its hydrogen bonding with the key amino acids Thr199 and Thr200. Through hydrophobic interaction, the benzenesulfonamide and the thiopyrimidine moieties interact with the hydrophobic side chains of the amino acids Val121/Leu198 and Ile91/Phe131, respectively. These results indicated that the designed and synthesized series is an interesting scaffold that can be further optimized for the development of selective antiglaucoma drugs.

Rho-kinase inhibitors in the management of glaucoma

Introduction: Glaucoma is a group of progressive optic neuropathies in which elevated intraocular pressure (IOP) as a consequence of an increased aqueous humor (AH) outflow resistance, is the main and only clinically modifiable risk factor for its development and progression. Relaxing Trabecular meshwork (TM) tissue, Rho-Kinase (ROCK) inhibitors directly decrease resistance in the conventional AH outflow, thus resulting in a significant IOP-lowering effect. Areas covered: The progress made in the field of ROCK inhibitors for glaucoma treatment will be discussed, referring to the recent patent literature published mainly in the last 3 years. Development and last studies conducted on the recently approved ripasudil and netarsudil will be described, along with newly reported combinations with other antiglaucoma agents. New molecular entities as ROCK inhibitors will be reported as well as new biological approaches to affect the Rho/ROCK pathway. Expert opinion: With three drugs currently available on the market belonging to this class, ROCK inhibitors have been definitely validated as therapeutic agents for glaucoma treatment. The literature of the last 3 years confirmed the success of the soft-drug and bis-functional approaches in the design of ROCK inhibitors. However, few completely new molecular scaffolds have been reported.

Synthesis and Evaluation of Carbonic Anhydrase Inhibitors with Carbon Monoxide Releasing Properties for the Management of Rheumatoid Arthritis

Carbon monoxide (CO) is a gas endogenously produced in humans, reported to exhibit anti-inflammatory and cytoprotective effects at low concentration. In this context, CO releasing molecules (CORMs) are attracting enormous interest. Herein, we report a series of small-molecule hybrids consisting of a carbonic anhydrase (CA; EC 4.2.1.1) inhibitor linked to a CORM tail section (CAI-CORMs). All compounds were screened in vitro for their inhibition activity against the human (h) CA I, II, IV, IX, and XII isoforms. On selected CAI-CORM hybrids, the CO releasing properties were evaluated, along with their pain-relieving effect, in a model of rheumatoid arthritis. One CAI-CORM hybrid (5b) induced a higher pain-relieving effect compared to the one exerted by the single administration of CAI (5a) and CORM (15b) fragments, shedding light on the possibility to enhance the pain relief effect of CA inhibitors inserting a CO releasing moiety on the same molecular scaffold.

New sulfonamides containing organometallic-acylhydrazones: synthesis, characterisation and biological evaluation as inhibitors of human carbonic anhydrases

A series of organometallic acylhydrazones was prepared, incorporating Re(CO)₃, Mn(CO)₃ and ferrocenyl moieties, which were subsequently reacted with amino-sulfonamides in order to obtain carbonic anhydrase (CA, EC 4.2.1.1) inhibitors possessing organometallic moieties in their molecules. The new derivatives were investigated as inhibitors of four human (h) CA isoforms with pharmaceutical applications, such as the cytosolic hCA I, II and VII and the mitochondrial hCA VA. An interesting inhibitory profile against these isoforms was obtained, with some of these metal complexes acting as subnanomolar or low nanomolar inhibitors. They were also thoroughly characterised from the chemical point of view, making them of interest for further developments in the field of metal complexes of sulfonamides with CA inhibitory action.

Novel approaches for designing drugs that interfere with pH regulation

INTRODUCTION

In all living species, pH regulation is a tightly controlled process, with a plethora of proteins involved in its regulation. These include sodium-proton exchangers, carbonic anhydrases, anion exchangers, bicarbonate transporters/cotransporters, H⁺-ATPases, and monocarboxylate transporters. All of them play crucial roles in acid-base balancing, both in eukaryotic as well as in prokaryotic organisms, making them interesting drug targets for the management of pathological events (in)directly involved in pH regulation. Areas covered: Interfering with pH regulation for the treatment of tumors and microbial infections is the main focus of this review, with particular attention paid to inhibitors targeting the above-mentioned proteins. The latest advances in each field id reviewed. Expert opinion: Interfering with the pH regulation of tumor cells is a validated approach to tackle primary tumors and metastases growth. Carbonic anhydrases are the most investigated proteins of those aforementioned, with several inhibitors in clinical development. Recent advances in the characterization of proteins involved in pH homeostasis of various pathogens evidenced their crucial role in the survival and virulence of bacterial, fungal, and protozoan microorganisms. Some encouraging results shed light on the possibility to target such proteins for obtaining new anti-infectives, overcoming the extensive drug resistance problems of clinically used drugs.

Carbonic Anhydrase Inhibitors of Different Structures Dilate Pre-Contracted Porcine Retinal Arteries

Carbonic anhydrase inhibitors (CAIs), such as dorzolamide (DZA), are used as anti-glaucoma drugs to lower intraocular pressure, but it has been found that some of these drugs act as vasodilators of retinal arteries. The exact mechanism behind the vasodilatory effect is not yet clear. Here we have addressed the issue by using small vessel myography to examine the effect of CAIs of the sulfonamide and coumarin type on the wall tension in isolated segments of porcine retinal arteries. Vessels were pre-contracted by the prostaglandin analog U-46619, and CAIs with varying affinity for five different carbonic anhydrase (CA) isoenzymes found in human tissue tested. We found that all compounds tested cause a vasodilation of pre-contracted retinal arteries, but with varying efficacy, as indicated by the calculated mean EC50 of each compound, ranging from 4.12 µM to 0.86 mM. All compounds had a lower mean EC50 compared to DZA. The dilation induced by benzolamide (BZA) and DZA was additive, suggesting that they may act on separate mechanisms. No clear pattern in efficacy and affinity for CA isoenzymes could be discerned from the results, although Compound 5, with a low affinity for all isoenzymes except the human (h) CA isoform IV, had the greatest potency, with the lowest EC50 and inducing the most rapid and profound dilation of the vessels. The results suggest that more than one isozyme of CA is involved in mediating its role in controlling vascular tone in retinal arteries, with a probable crucial role played by the membrane-bound isoform CA IV.

Inhibition of α-, β-, γ-, and δ-carbonic anhydrases from bacteria and diatoms with N'-aryl-N-hydroxy-ureas

The inhibition of α-, β-, γ-, and δ-class carbonic anhydrases (CAs, EC 4.2.1.1) from bacteria (Vibrio cholerae and Porphyromonas gingivalis) and diatoms (Thalassiosira weissflogii) with a panel of N'-aryl-N-hydroxy-ureas is reported. The α-/β-CAs from V. cholerae (VchCAα and VchCAβ) were effectively inhibited by some of these derivatives, with KIs in the range of 97.5 nM - 7.26 µM and 52.5 nM - 1.81 µM, respectively, whereas the γ-class enzyme VchCAγ was less sensitive to inhibition (KIs of 4.75 - 8.87 µM). The β-CA from the pathogenic bacterium Porphyromonas gingivalis (PgiCAβ) was not inhibited by these compounds (KIs > 10 µM) whereas the corresponding γ-class enzyme (PgiCAγ) was effectively inhibited (KIs of 59.8 nM - 6.42 µM). The δ-CA from the diatom Thalassiosira weissflogii (TweCAδ) showed effective inhibition with these derivatives (KIs of 33.3 nM - 8.74 µM). As most of these N-hydroxyureas are also ineffective as inhibitors of the human (h) widespread isoforms hCA I and II (KIs > 10 µM), this class of derivatives may lead to the development of CA inhibitors selective for bacterial/diatom enzymes over their human counterparts and thus to anti-infectives or agents with environmental applications.

SLC-0111 enaminone analogs, 3/4-(3-aryl-3-oxopropenyl) aminobenzenesulfonamides, as novel selective subnanomolar inhibitors of the tumor-associated carbonic anhydrase isoform IX

SLC-0111, an ureido substituted benzenesulfonamide, is a selective carbonic anhydrase (CA, EC 4.2.1.1) IX inhibitor that is currently in Phase I/II clinical trials for the treatment of advanced hypoxic tumors complicated with metastases. Herein we report the synthesis of two series of 3/4-(3-aryl-3-oxopropenyl) aminobenzenesulfonamides 5a-i and 6a-j as SLC-0111 enaminone congeners. The prepared enaminones were in vitro investigated as inhibitors of the metalloenzyme carbonic anhydrase (CA, EC 4.2.1.1) isoforms hCA I, II, IV and IX, using a stopped-flow CO₂ hydrase assay. All these isoforms were inhibited by the enaminones reported here in variable degrees. The target tumor-associated isoform hCA IX was undeniably the most affected one (K_Is: 0.21-7.1 nM), with 6- to 21-fold enhanced activity than SLC-0111 (K_I = 45 nM). All the prepared enaminones displayed interesting selectivity towards hCA IX over hCA I (SI: 32 - >35714), hCA II (SI: 2 - 1689) and hCA IV (SI: 11 - >45454). Of particular interest, bioisosteric replacement of phenyl tail with the bulkier 2-naphthyl tail, sulfonamide 6h, achieved the higher II/IX selectivity herein reported with SI of 1689.

Synthesis and carbonic anhydrase inhibitory properties of novel 4-(2-aminoethyl)benzenesulfonamide-dipeptide conjugates

Thirty novel sulfonamide derivatives incorporating dipeptide were synthesized by facile acylation through benzotriazole mediated reactions and their structures were identified by ¹H NMR, ¹³C NMR, MS and FT-IR spectroscopic techniques and elemental analysis. The carbonic anhydrase (CA, EC 4.2.1.1) inhibitory activity of the new compounds was assessed against four human (h) isoforms, hCA I, hCA II, hCA IV and hCA XII. Most of the synthesized compounds showed excellent in vitro carbonic anhydrase inhibitory properties comparable to those of the clinically used drug acetazolamide (AAZ). The new unprotected dipeptide-sulfonamide conjugates showed very effective inhibitory activity, in the low nanomolar range against II and XII, being less effective as hCA I and IV inhibitors. Four of the thirty compounds also showed strong inhibitory activity against hCA XII compared to AAZ.

1,2,4-Trisubstituted imidazolinones with dual carbonic anhydrase and p38 mitogen-activated protein kinase inhibitory activity

Various 1,2,4 trisubstituted imidazolin-5-one derivatives were synthesized and evaluated for their inhibitory activity against p38 mitogen-activated protein kinase (p38MAPK) and carbonic anhydrase (CA) enzymes aiming to explore potential dual inhibitors. Results revealed that compounds 3c, 3g, 3h, 4a, 6c and 6d were the most effective derivatives against p38αMAPK (IC₅₀ = 0.14, 0.14, 0.056, 0.14, 0.13 and 0.14 μM, respectively) compared to sorafenib (IC₅₀ = 1.58 μM) as standard drug. On the other hand, compound 4a revealed the best inhibitory activity against all the tested carbonic anhydrase isoforms CA I, II, IV and IX with K_i values of 95.0, 0.83, 6.90 and 12.4 nM, respectively compared to acetazolamide with K_i values 250, 12.1, 74 and 12.8 nM, respectively. Therefore, compound 4a can be considered as a potent dual p38αMAPK/CA inhibitor.

Synthesis of novel benzenesulfamide derivatives with inhibitory activity against human cytosolic carbonic anhydrase I and II and Vibrio cholerae α- and β-class enzymes

The synthesis of a new series of sulfamides incorporating ortho-, meta, and para-benzenesulfamide moieties is reported, which were investigated for the inhibition of two human (h) isoforms of the zinc enzyme carbonic anhydrase (CA, EC 4.2.1.1), hCA I and II, and two Vibrio cholerae enzymes, belonging to the α- and β-CA classes (VchCAα, VchCAβ). The compounds were prepared by using the “tail approach”, aiming to overcome the scarcity of selective inhibition profiles associated to CA inhibitors belonging to the zinc binders. The built structure–activity relationship showed that the incorporation of benzhydryl piperazine tails on a phenyl sulfamide scaffold determines rather good efficacies against hCA I and VchCAα, with several compounds showing K_Is < 100 nM. The activity was lower against hCA II and VchCAβ, probably due to the fact that the incorporated tails are quite bulky. The obtained evidences allow us to continue the investigations of different tails/zinc binding groups, with the purpose to increase the effectiveness/selectivity of such inhibitors against bacterial CAs from pathogens, affording thus potential new anti-infectives.

4-Substituted Benzenesulfonamides Incorporating Bi/Tricyclic Moieties Act as Potent and Isoform-Selective Carbonic Anhydrase II/IX Inhibitors

As a part of our efforts to expand chemical diversity in the carbonic anhydrases inhibitors (CAIs), three small series of polyheterocyclic compounds (4-6) featuring the primary benzenesulfonamide moiety linked to bi/tricyclic scaffolds were investigated. Highly effective inhibitors against the target tumor-associated hCA IX (low nanomolar/subnanomolar potency levels) showing significant functional selectivity profile toward hCA I, II, and IV isozymes were identified. Molecular docking studies clarified the reasons behind the activity and selectivity of the new compounds.

[Changes in the electrocardiogram in the elderly patient. The limits between normality and pathology]

Normal electrocardiographic criteria in the elderly are not well defined. The prevalence of electrocardiographic abnormalities is three times higher in subjects over 85 years than in subjects 65-69 years old. With aging the heart rate does not vary during rest and sinus rhythm is prevalent, although sinus pauses, overall at night, are frequently seen. First degree atrio-ventricular block is present in 8.1%-19% of the elderly. 11% of subjects over 70 years suffer from left anterior hemiblock. 4.3% of subjects over 65 years and 7% of those over 85 present a right bundle branch block. 1.7% of subjects older than 65 years and 9% of those older than 85 are affected by a left bundle branch block. Atrial ectopic contractions are present in 8.8% of subjects over 60 years and in all older subjects. Atrial fibrillation is more common as age increases, being found in 2% of under 75s, in 5% of all subjects over this age, in 14% over 85 years and in 27% of patients hospitalized or institutionalized aged over 90 years. The prevalence of ventricular ectopic contractions varies from 76% in studies performed with baseline electrocardiogram to 96% in studies performed with portable monitoring electrocardiogram. Major ST-T wave alterations are present in 6.3%-13% of the elderly. In 340 patients over 80 years, hospitalized for diseases, other than cardiovascular, we found atrial fibrillation in 27.9% of subjects, ectopic beats in 26.2%, first degree atrioventricular block in 8.5%, right bundle branch block in 11.2%, left bundle branch block in 5.9%, left anterior hemiblock in 8.2%, ST-T wave alterations in 23.8% of the population.