The Human Carbonic Anhydrase II in Platelets: An Underestimated Field of Its Activity

Changes in the Proteome of Platelets from Patients with Critical Progression of COVID-19

Platelets, the smallest cells in human blood, known for their role in primary hemostasis, are also able to interact with pathogens and play a crucial role in the immune response. In severe coronavirus disease 2019 (COVID-19) cases, platelets become overactivated, resulting in the release of granules, exacerbating inflammation and contributing to the cytokine storm. This study aims to further elucidate the role of platelets in COVID-19 progression and to identify predictive biomarkers for disease outcomes. A comparative proteome analysis of highly purified platelets from critically diseased COVID-19 patients with different outcomes (survivors and non-survivors) and age- and sex-matched controls was performed. Platelets from critically diseased COVID-19 patients exhibited significant changes in the levels of proteins associated with protein folding. In addition, a number of proteins with isomerase activity were found to be more highly abundant in patient samples, apparently exerting an influence on platelet activity via the non-genomic properties of the glucocorticoid receptor (GR) and the nuclear factor κ-light-chain-enhancer of activated B cells (NFκB). Moreover, carbonic anhydrase 1 (CA-1) was found to be a candidate biomarker in platelets, showing a significant increase in COVID-19 patients.

Thiazides in chronic kidney disease: "back to the future"

The thiazide class diuretics are first-line agents for managing hypertension either as monotherapy or as a fixed-dose combination with other antihypertensive drugs. However, despite the extensive experience with these drugs for >60 years, there is general reluctance to use these agents in patients with advanced chronic kidney disease (CKD) because of concerns about their efficacy and safety as kidney function declines. In this issue of Clinical Kidney Journal, Minutolo et al. performed an updated review of the pharmacological properties, efficacy and side effects and randomized controlled trials that tested these drugs in patients with CKD.

Identification of New Carbonic Anhydrase VII Inhibitors by Structure-Based Virtual Screening

Human carbonic anhydrase VII (hCA VII) constitutes a promising molecular target for the treatment of epileptic seizures and other central nervous system disorders due to its almost exclusive expression in neurons. Achieving isoform selectivity is one of the main challenges for the discovery of new hCA inhibitors, since nonspecific inhibition may lead to tolerance and side effects. In the present work, we report the development of a molecular docking protocol based on AutoDock4_Zn for the search of new hCA VII inhibitors by virtual screening. The docking protocol was applied to the screening of two sets of compounds: a ZINC15 subset of sulfur-containing structures and an in-house library consisting of synthetic and commercial candidates (including approved drugs). Five compounds were selected from the first screening campaign and three from the second one, and they were tested in vitro against the enzyme. Among the eight selected structures, four showed K_i values in the low nanomolar range. These confirmed hits include three approved drugs: meloxicam, piroxicam, and nitrofurantoin, which also showed good selectivity for hCA VII versus hCA II.

Circadian miR-218-5p targets gene CA2 to regulate uterine carbonic anhydrase activity during egg shell calcification

MicroRNAs (miRNAs) are involved in regulating the circadian clock. In our previous work, miR-218-5p was found to be a circadian miRNA in the chicken uterus, but its role in the eggshell formation process was not clear. In the present study, we found that the expression levels of miR-218-5p and two 2 predicted target genes carbonic anhydrase 2 (CA2) and neuronal PAS domain protein 2 (NPAS2) were oscillated in the chicken uterus. The results of dual-luciferase reporter gene assays in the present study demonstrated that miR-218-5p directly targeted the 3’ untranslated regions of CA2 and NPAS2. miR-218-5p showed an opposite expression profile to CA2 within a 24 h cycle in the chicken uterus. Moreover, over-expression of miR-218-5p reduced the mRNA and protein expression of CA2, while miR-218-5p knockdown increased CA2 mRNA and protein expression. Overexpression of CA2 also significantly increased the activity of carbonic anhydrase Ⅱ (P < 0.05), whereas knockdown of CA2 decreased the activity of carbonic anhydrase Ⅱ. miR-218-5p influenced carbonic anhydrase activity via regulating the expression of CA2. These results demonstrated that clock-controlled miR-218-5p regulates carbonic anhydrase activity in the chicken uterus by targeting CA2 during eggshell formation.

Natural disaster stress during pregnancy is linked to reprogramming of the placenta transcriptome in relation to anxiety and stress hormones in young offspring

Prenatal stress can lead to long-term adverse effects that increase the risk of anxiety and other emotional disorders in offspring. The in utero underpinnings contributing to such phenotypes remain unknown. We profiled the transcriptome of placental specimens from women who lived through Hurricane Sandy during pregnancy compared to those pregnant during non-Sandy conditions. Following birth, longitudinal assessments were conducted in their offspring during childhood (~3-4 years old) to measure steroid hormones (in hair) and behavioral and emotional problems. This revealed a significant link between prenatal Sandy stress (PNSS) and child HPA dysfunction, evident by altered cortisol, dehydroepiandrosterone (DHEA), and cortisol:DHEA levels. In addition, PNSS was associated with significantly increased anxiety and aggression. These findings coincided with significant reorganization of the placental transcriptome via vascular, immune, and endocrine gene pathways. Interestingly, many of the most prominently altered genes were known to be uniquely expressed in syncytiotrophoblast (STB)-subtype of placental cells and harbored glucocorticoid response elements in promoter regions. Finally, several vascular development- and immune-related placental gene sets were found to mediate the relationship between PNSS and childhood phenotypes. Overall, these findings suggest that natural disaster-related stress during pregnancy reprograms the placental molecular signature, potentially driving long-lasting changes in stress regulation and emotional health. Further examination of placental mechanisms may elucidate the environment's contribution to subsequent risk for anxiety disorders later in life.

Nitrous anhydrase activity of carbonic anhydrase II: cysteine is required for nitric oxide (NO) dependent phosphorylation of VASP in human platelets

The carbonic anhydrase (CA) family does not only catalyse the reversible hydration of CO₂ to bicarbonate, but it also possesses esterase and phosphatase activity. Recently, bovine CA II and human CA II have been reported to convert inorganic nitrite (O=N-O⁻) to nitric oxide (NO) and nitrous anhydride (N₂O₃). Given the ability of NO to mediate vasodilation and inhibit platelet aggregation, this CA II activity would represent a bioactivation of nitrite. There are contradictory reports in the literature and the physiological role of CA II nitrite bioactivation is still disputed. Here, we provide new experimental data in support of the nitrous anhydrase activity of CA II and the key role L-cysteine in the bioactivation of nitrite by CA II. Using washed human platelets and by measuring VASP phosphorylation we provide evidence that exogenous nitrite (10 µM) is bioactivated to NO in a manner strongly depending on L-cysteine (100 and 200 µM). The process is not inhibitable by acetazolamide, a potent CA inhibitor. The contradictory results of recently published studies in this area are thoroughly discussed.

Monosubstituted Coumarins Inhibit Epinephrine-Induced Platelet Aggregation Antiplatelet Effect of Monosubstituted Coumarins

Aim

The aim of this study was to evaluate the in vitro effect of coumarin and 15 monosubstituted  derivatives on  the inhibition  of human platelet  aggregation  induced by various  pro-aggregatory agonists, particularly by epinephrine.

Background

The emergence of residual platelet reactivity during the use of conventional antiplatelet agents (acetylsalicylic acid and clopidogrel) is one of the main causes of double therapy´s therapeutic failure. Platelet adrenoceptors participate in residual platelet reactivity. Therefore, it is necessary to develop new antiplatelet agents that inhibit epinephrine-induced platelet aggregation as a new therapeutic strategy. Information on the antiplatelet activity of coumarins in inhibiting epinephrine-induced aggregation is limited.

Objective

The objective of this study was to establish the structure-activity relationship (SAR) of coumarin derivatives with hydroxy, methoxy, and acetoxy groups in different positions of the coumarin nucleus to identify the most active molecules. Moreover, this study aimed to use in silico studies to suggest potential drug targets to which the molecules bind to produce antiplatelet effects.

Methods

The platelet aggregation was performed using a Lumi-aggregometer; the inhibitory activity of 16 compounds were evaluated by inducing the aggregation of human platelets (250 × 10³/μl) with epinephrine (10 µM), collagen (2 µg/ml) or ADP (10 µM). The aggregation of control platelets was considered 100% of the response for each pro-aggregatory agonist.

Results

Eleven molecules inhibited epinephrine-induced aggregation, with 3-acetoxycoumarin and 7-methoxycoumarin being the most active. Only coumarin inhibited collagen-induced platelet aggregation, but no molecule showed activity when using ADP as an inducer.

Conclusions

In silico studies suggest that most active molecules might have antagonistic interactions in the α₂ and β₂ adrenoceptors. The antiplatelet actions of these coumarins have the potential to reduce residual platelet reactivity and thus contribute to the development of future treatments for patients who do not respond adequately to conventional agents.

Clear cell injury associated with reduced expression of carbonic anhydrase II in eccrine glands consistently occurs in patients with acquired idiopathic generalized anhidrosis

Acquired idiopathic generalized anhidrosis (AIGA) is characterized by anhidrosis/hypohidrosis without other autonomic and neurological dysfunctions. It has been believed that AIGA patients usually present no significant morphological alterations in the secretory portion of eccrine glands consisting of clear, dark and myoepithelial cells. However, we have recently revealed morphological damage of eccrine glands in AIGA patients by immunohistochemistry. Moreover, inhibitory side-effects against carbonic anhydrase II (CA II) by the antiepileptic reagent topiramate have been reported to cause heat intolerance mimicking AIGA. To determine the precise morphological changes and CA II expression in eccrine glands of AIGA patients, electron microscopic observation and immunohistochemistry were applied to skin of both anhidrotic (non-sweating) and normohidrotic (sweating-preserved) sites, taken from each patient clinically diagnosed with AIGA. We found consistent clear cell injury in eccrine glands in anhidrotic skin samples of AIGA patients. Electron micrographs demonstrated edematous, swollen and destructive damage in clear cells of eccrine glands from non-sweating areas of almost all AIGA patients. Immunohistochemically, clear cells showed reduced CA II expression that was heterogeneously distributed in non-sweating skin. Some areas showed almost complete loss of CA II expression in spite of preserved dark cells, and others showed mild or moderate loss of it. Selective destruction of clear cells resulting in heterogenous atrophy in AIGA patients may be important to elucidate its etiology.

Oxygen-18 and Carbon-13 isotopes in eCO2and erythrocytes carbonic anhydrase activity of Finnish prediabetic population

Complex human physiological processes create the stable isotopic composition of exhaled carbon dioxide (eCO2), measurable with noninvasive breath tests. Recently, isotope-selective breath tests utilizing natural fluctuation in 18O/16O isotope ratio in eCO2 have been proposed for screening prediabetic (PD) individuals. It has been suggested that 18O/16O fractionation patterns reflect shifts in the activity of carbonic anhydrase (CA), an enzyme involved in the metabolic changes in the PD state. To evaluate the applicability of the breath sampling method in Finnish PD individuals, breath delta values (BDVs, ‰) of 18O/16O (δ18O) were monitored for 120 min in real-time with a high-precision optical isotope ratio spectrometer, both in the fasting state and during a 2-hour oral glucose tolerance test (2h OGTT) with non-labelled glucose. In addition, the BDV of 13C/12C (δ13C) was measured, and total erythrocyte CA activity was determined. δ18O and CA did not demonstrate any statistically significant differences between PD and non-diabetic control (NDC) participants. Instead, δ13C was significantly lower in PD patients in comparison to NDCs in the fasting state and at time points 90 and 120 min of the 2h OGTT, thus indicating slightly better potential in identifying Finnish PD individuals. However, overlapping values were measured in PD participants and NDCs, and therefore, δ13C cannot be applied as a sole measure in screening prediabetes at an individual level. Thus, because the combination of environmental and lifestyle factors and anthropometric parameters has a greater effect on glucose metabolism and CA activity in comparison to the PD state, 18O/16O and 13C/12C fractionations or CA activity did not prove to be reliable biomarkers for impaired glucose tolerance in Finnish subjects. This study was conducted under the clinicaltrials.gov ID NCT03156478.

Quinazolinones as Competitive Inhibitors of Carbonic Anhydrase-II (Human and Bovine): Synthesis, in-vitro, in-silico, Selectivity, and Kinetics Studies

Carbonic anhydrase-II (CA-II) is associated with glaucoma, malignant brain tumors, and renal, gastric, and pancreatic carcinomas and is mainly involved in the regulation of the bicarbonate concentration in the eyes. CA-II inhibitors can be used to reduce the intraocular pressure usually associated with glaucoma. In search of potent CA-II inhibitors, a series of quinazolinones derivatives (4a-p) were synthesized and characterized by IR and NMR spectroscopy. The inhibitory potential of all the compounds was evaluated against bovine carbonic anhydrase-II (bCA-II) and human carbonic anhydrase-II (hCA-II), and compounds displayed moderate to significant inhibition with IC50 values of 8.9-67.3 and 14.0-59.6 μM, respectively. A preliminary structure-activity relationship suggested that the presence of a nitro group on the phenyl ring at R position contributes significantly to the overall activity. Kinetics studies of the most active inhibitor, 4d, against both bCA-II and hCA-II were performed to investigate the mode of inhibition and to determine the inhibition constants (Ki). According to the kinetics results, 4d is a competitive inhibitor of bCA-II and hCA-II with Ki values of 13.0 ± 0.013 and 14.25 ± 0.017 μM, respectively. However, the selectivity index reflects that the compounds 4g and 4o are more selective for hCA-II. The binding mode of these compounds within the active sites of bCA-II and hCA-II was investigated by structure-based molecular docking. The docking results are in complete agreement with the experimental findings.

Qualitative Phytochemical Fingerprint and Network Pharmacology Investigation of Achyranthes aspera Linn. Extracts

Achyranthes aspera Linn. (Amaranthaceae), commonly known as the Prickly Chaff flower, is used as herbal medicine in the Ivorian's culture, Africa. Nonetheless, there is currently a paucity of scientific information on A. aspera from the Ivory Coast. Herein, the antioxidant activity of A. aspera extracts (methanol, dichloromethane, ethyl acetate and infusion) as well as the enzymatic inhibitory potentials towards key enzymes in human diseases, namely Alzheimer's disease, (cholinesterases: AchE and BChE), type 2 diabetes (α-glucosidase and α-amylase) and hyperpigmentation (tyrosinase) were assessed. The total phenolic (TPC) and flavonoid (TFC) content was determined using colorimetric methods and the individual compounds were characterized using ultra-high performance liquid chromatography coupled with hybrid quadrupole-Orbitrap high resolution mass spectrometry (UHPLC-HRMS). Furthermore, a network pharmacology analysis was conducted to predict putative targets of identified phenolic compounds. The highest TPC was observed in the infused extract (28.86 ± 0.12 mg GAE/g), while the dichloromethane extract (38.48 ± 1.48 mg RE/g) showed the highest level of TFC. UHPLC-HRMS analysis has revealed an abundance of fatty acids, flavonoids, phenols and acylquinic acids. Among tested extracts, the infused extract displayed the highest free radical quenching, reducing and metal-chelating ability. The extracts (except infusion) were effective as enzyme inhibitors against AChE, while only methanolic and infused extracts showed noteworthy anti-BChE effects. The methanolic extract showed a remarkable antityrosinase effect (56.24 ± 5.05 mg KAE/g), as well. Modest to moderate inhibitory activity was observed against α-amylase (all extracts) and α-glucosidase (only dichloromethane extract). Finally, the network pharmacology analysis suggested the carbonic anhydrase II enzyme as a putative target for explaining, at least in part, the traditional use of A. aspera preparations as diuretic and blood clotting agent. Data amassed herein tend to validate the use of A. aspera in traditional medicine, as well as act as a stepping stone for further studies in the quest for novel phytopharmaceuticals. In this context, it is desirable that this study will contribute to the validation of the traditional uses of this plant in the African herbal medicine, and to the valorization of the whole chain production of A. aspera, as a local and sustainable botanical resource.

Aspirin: A Suicide Inhibitor of Carbonic Anhydrase II

Carbonic anhydrase II (CAII) is a metalloenzyme that catalyzes the reversible hydration/dehydration of CO₂/HCO₃⁻. In addition, CAII is attributed to other catalytic reactions, including esterase activity. Aspirin (acetyl-salicylic acid), an everyday over-the-counter drug, has both ester and carboxylic acid moieties. Recently, compounds with a carboxylic acid group have been shown to inhibit CAII. Hence, we hypothesized that Aspirin could act as a substrate for esterase activity, and the product salicylic acid (SA), an inhibitor of CAII. Here, we present the crystal structure of CAII in complex with SA, a product of CAII crystals pre-soaked with Aspirin, to 1.35Å resolution. In addition, we provide kinetic data to support the observation that CAII converts Aspirin to its deacetylated form, SA. This data may also explain the short half-life of Aspirin, with CAII so abundant in blood, and that Aspirin could act as a suicide inhibitor of CAII.

Study of glycation process of human carbonic anhydrase II as well as investigation concerning inhibitory influence of 3-beta-hydroxybutyrate on it

Glycation is a non-enzymatic reaction between carbonyl groups in sugar and free amino groups in proteins. This reaction leads to changes in structure and functions of proteins in which the advanced glycation end products (AGEs) are the final outcome and cause many complications in diabetic patients. We herein examined the effect of fasting on the glycation process of human Carbonic anhydrase II under physiological conditions (37 °C and pH 7.4) employing various techniques, including Ultraviolet-visible spectroscopy, fluorescence spectroscopy and CD Spectroscopy. We found an increased 3-beta-hydroxybutyrate upon fasting. We studied various samples of control carbonic anhydrase (without glucose and 3-beta-hydroxybutyrate), carbonic anhydrase with glucose, carbonic anhydrase treated with 3-beta-hydroxybutyrate (BHB) and carbonic anhydrase along with glucose and 3-beta-hydroxybutyrate. The samples were incubated for 35 days under physiological conditions. Our results indicated that 3-beta-hydroxybutyrate inhibited the glycation process, decreased glucose binding to the protein, prevented the formation of AGEs, and modified the enzyme activity. Our findings would open new windows toward the enzymatic procedure which would have profound implication in understanding the diabetes mechanisms.

Mechanism of Action of Non-Synonymous Single Nucleotide Variations Associated with α-Carbonic Anhydrase II Deficiency

Human carbonic anhydrase II (CA-II) is a Zinc (Zn 2 + ) metalloenzyme responsible for maintenance of acid-base balance within the body through the reversible hydration of CO 2 to produce protons (H + ) and bicarbonate (BCT). Due to its importance, alterations to the amino acid sequence of the protein as a result of single nucleotide variations (nsSNVs) have detrimental effects on homeostasis. Six pathogenic CA-II nsSNVs, K18E, K18Q, H107Y, P236H, P236R and N252D were identified, and variant protein models calculated using homology modeling. The effect of each nsSNV was analyzed using motif analysis, molecular dynamics (MD) simulations, principal component (PCA) and dynamic residue network (DRN) analysis. Motif analysis identified 11 functionally important motifs in CA-II. RMSD data indicated subtle SNV effects, while PCA analysis revealed that the presence of BCT results in greater conformational sampling and free energy in proteins. DRN analysis showed variant allosteric effects, and the average betweenness centrality (BC) calculations identified Glu117 as the most important residue for communication in CA-II. The presence of BCT was associated with a reduction to Glu117 usage in all variants, suggesting implications for Zn 2 + dissociation from the CA-II active site. In addition, reductions to Glu117 usage are associated with increases in the usage of the primary and secondary Zn 2 + ligands; His94, His96, His119 and Asn243 highlighting potential compensatory mechanisms to maintain Zn 2 + within the active site. Compared to traditional MD simulation investigation, DRN analysis provided greater insights into SNV mechanism of action, indicating its importance for the study of missense mutation effects in proteins and, in broader terms, precision medicine related research.

Carbonic Anhydrases in Photosynthesizing Cells of C3 Higher Plants

The review presents data on the location, nature, properties, number, and expression of carbonic anhydrase genes in the photosynthesizing cells of C3 plants. The available data about the presence of carbonic anhydrases in plasma membrane, cytoplasm, mitochondria, chloroplast stroma and thylakoids are scrutinized. Special attention was paid to the presence of carbonic anhydrase activities in the different parts of thylakoids, and on collation of sources of these activities with enzymes encoded by the established genes of carbonic anhydrases. The data are presented to show that the consistent incorporation of carbonic anhydrases belonging to different families of these enzymes forms a coherent system of CO₂ molecules transport from air to chloroplasts in photosynthesizing cells, where they are included in organic molecules in the carboxylation reaction. It is discussed that the manifestation of the activity of a certain carbonic anhydrase depends on environmental conditions and the stage of ontogenesis.

Medicinal chemistry of metal chelating fragments in metalloenzyme active sites: A perspective

Numerous metal-containing enzymes (metalloenzymes) have been considered as drug targets related to diseases such as cancers, diabetes, anemia, AIDS, malaria, bacterial infection, fibrosis, and neurodegenerative diseases. Inhibitors of the metalloenzymes have been developed independently, most of which are mimics of substrates of the corresponding enzymes. However, little attention has been paid to the interactions between inhibitors and active site metal ions. This review is focused on different metal binding fragments and their chelating properties in the metal-containing active binding pockets of metalloenzymes. We have enumerated over one hundred of inhibitors targeting various metalloenzymes and identified over ten kinds of fragments with different binding patterns. Furthermore, we have investigated the inhibitors that are undergoing clinical evaluation in order to help looking for more potential scaffolds bearing metal binding fragments. This review will provide deep insights for the rational design of novel inhibitors targeting the metal-containing binding sites of specific proteins.