Potential Novel Role of Membrane-Associated Carbonic Anhydrases in the Kidney

Acetazolamide and human carbonic anhydrases: retrospect, review and discussion of an intimate relationship

Acetazolamide (AZM) is a strong pharmacological sulphonamide-type (R-SO2-NH2, pKa 7.2) inhibitor of the activity of several carbonic anhydrase (CA) isoforms, notably of renal CA II (Ki, 12 nM) and CA IV (Ki, 74 nM). AZM is clinically used for about eighty years in various diseases including epilepsy and glaucoma. Pharmacological AZM increases temporarily the urinary excretion of bicarbonate (HCO3-) and sodium ions (Na+) and sustainably the urinary pH. AZM is excreted almost unchanged over several hours at high rates in the urine. Closely parallel concentrations of circulating and excretory AZM are observed upon administration of therapeutical doses of AZM. In a proof-of-principle study, we investigated the effects of the ingestion of a 250-mg AZM-containing tablet by a healthy volunteer on the urinary excretion of organic and inorganic substances over 5 h (range, 0, 0.5, 1, 1.5, 2, 3, 4, 5 h). Measured analytes included: AZM, amino acids and their metabolites such as guanidinoacetate, i.e. the precursor of creatine, of asymmetrically (ADMA) and symmetrically (SDMA) dimethylated arginine, nitrite (O = N-O-, pKa 3.4) and nitrate (O2N-O-, pKa -1.37), the major metabolites of nitric oxide (NO), the C-H acidic malondialdehyde (MDA; (CHO)2CH2, pKa 4.5), and creatinine for correction of analytes excretion. All analytes were measured by validated isotopologues using gas chromatography-mass spectrometry (GC-MS) methods. AZM excretion in the urine reached its maximum value after 2 h and was fairly stable for the next 3 h. Time series analysis by the ARIMA method was performed. AZM ingestion increased temporarily the urinary excretion of the amino acids Leu + Ile, nitrite and nitrate, decreased temporarily the urinary excretion of other amino acids. AZM decreased sustainably the urinary excretion of MDA, a biomarker of oxidative stress (i.e. lipid peroxidation). Whether this decrease is due to inhibition of the excretion of MDA or attenuation of oxidative stress by AZM is unknown. The acute and chronic effects of AZM on the urinary excretion of electrolytes and physiological substances reported in the literature are discussed in depth in the light of its extraordinary pharmacokinetics and pharmacodynamics. Tolerance development/drug resistance to AZM in chronic use and potential mechanisms are also addressed.

Unraveling Protein-Metabolite Interactions in Precision Nutrition: A Case Study of Blueberry-Derived Metabolites Using Advanced Computational Methods

Metabolomics, the study of small-molecule metabolites within biological systems, has become a potent instrument for understanding cellular processes. Despite its profound insights into health, disease, and drug development, identifying the protein partners for metabolites, especially dietary phytochemicals, remains challenging. In the present study, we introduced an innovative in silico, structure-based target prediction approach to efficiently predict protein targets for metabolites. We analyzed 27 blood serum metabolites from nutrition intervention studies' blueberry-rich diets, known for their health benefits, yet with elusive mechanisms of action. Our findings reveal that blueberry-derived metabolites predominantly interact with Carbonic Anhydrase (CA) family proteins, which are crucial in acid-base regulation, respiration, fluid balance, bone metabolism, neurotransmission, and specific aspects of cellular metabolism. Molecular docking showed that these metabolites bind to a common pocket on CA proteins, with binding energies ranging from -5.0 kcal/mol to -9.0 kcal/mol. Further molecular dynamics (MD) simulations confirmed the stable binding of metabolites near the Zn binding site, consistent with known compound interactions. These results highlight the potential health benefits of blueberry metabolites through interaction with CA proteins.

Synthesis and Enzymatic Evaluation of a Small Library of Substituted Phenylsulfonamido-Alkyl Sulfamates towards Carbonic Anhydrase II

A small library of 79 substituted phenylsulfonamidoalkyl sulfamates, 1b-79b, was synthesized starting from arylsulfonyl chlorides and amino alcohols with different numbers of methylene groups between the hydroxyl and amino moieties yielding intermediates 1a-79a, followed by the reaction of the latter with sulfamoyl chloride. All compounds were screened for their inhibitory activity on bovine carbonic anhydrase II. Compounds 1a-79a showed no inhibition of the enzyme, in contrast to sulfamates 1b-79b. Thus, the inhibitory potential of compounds 1b-79b towards this enzyme depends on the substituent and the substitution pattern of the phenyl group as well as the length of the spacer. Bulkier substituents in the para position proved to be better for inhibiting CAII than compounds with the same substituent in the meta or ortho position. For many substitution patterns, compounds with shorter spacer lengths were superior to those with long chain spacers. Compounds with shorter spacer lengths performed better than those with longer chain spacers for a variety of substitution patterns. The most active compound held inhibition constant as low as Ki = 0.67 μM (for 49b) and a tert-butyl substituent in para position and acted as a competitive inhibitor of the enzyme.

Network pharmacology combined with molecular docking and dynamics to assess the synergism of esculetin and phloretin against acute kidney injury-diabetes comorbidity

Acute kidney injury (AKI) is a global health concern with high incidence and mortality, where diabetes further worsens the condition. The available treatment options are not uniformly effective against the complex pathogenesis of AKI-diabetes comorbidity. Hence, combination therapies based on the multicomponent, multitarget approach can tackle more than one pathomechanism and can aid in AKI-diabetes comorbidity management. This study aimed to investigate the therapeutic potential of esculetin and phloretin combination against AKI-diabetes comorbidity by network pharmacology followed by validation by molecular docking and dynamics. The curative targets for diabetes, AKI, esculetin, and phloretin were obtained from DisGeNET, GeneCards, SwissTargetPrediction database. Further, the protein-protein interaction of the potential targets of esculetin and phloretin against AKI-diabetes comorbidity was investigated using the STRING database. Gene ontology and pathway enrichment analysis were performed with the help of the DAVID and KEGG databases, followed by network construction and analysis via Cytoscape. Molecular docking and dynamic simulations were performed to validate the targets of esculetin and phloretin against AKI-diabetes comorbidity. We obtained 6341 targets for AKI-diabetes comorbidity. Further, a total of 54 and 44 targets of esculetin and phloretin against AKI-diabetes comorbidity were retrieved. The top 10 targets for esculetin selected based on the degree value were AKR1B1, DAO, ESR1, PLK1, CA3, CA2, CCNE1, PRKN, HDAC2, and MAOA. Similarly, phloretin's 10 key targets were ACHE, CDK1, MAPK14, APP, CDK5R1, CCNE1, MAOA, MAOB, HDAC6, and PRKN. These targets were enriched in 58 pathways involved in the pathophysiology of AKI-diabetes comorbidity. Further, esculetin and phloretin showed an excellent binding affinity for these critical targets. The findings of this study suggest that esculetin and phloretin combination as a multicomponent multitarget therapy has the potential to prevent AKI-diabetes comorbidity.

A simple yet multifaceted 90 years old, evergreen enzyme: Carbonic anhydrase, its inhibition and activation

Advances in the carbonic anhydrase (CA, EC 4.2.1.1) research over the last three decades are presented, with an emphasis on the deciphering of the activation mechanism, the development of isoform-selective inhibitors/ activators by the tail approach and their applications in the management of obesity, hypoxic tumors, neurological conditions, and as antiinfectives.