Safety of carbonic anhydrase inhibitors

From X-ray crystallographic structure to intrinsic thermodynamics of protein-ligand binding using carbonic anhydrase isozymes as a model system

Carbonic anhydrase (CA) was among the first proteins whose X-ray crystal structure was solved to atomic resolution. CA proteins have essentially the same fold and similar active centers that differ in only several amino acids. Primary sulfonamides are well defined, strong and specific binders of CA. However, minor variations in chemical structure can significantly alter their binding properties. Over 1000 sulfonamides have been designed, synthesized and evaluated to understand the correlations between the structure and thermodynamics of their binding to the human CA isozyme family. Compound binding was determined by several binding assays: fluorescence-based thermal shift assay, stopped-flow enzyme activity inhibition assay, isothermal titration calorimetry and competition assay for enzyme expressed on cancer cell surfaces. All assays have advantages and limitations but are necessary for deeper characterization of these protein-ligand interactions. Here, the concept and importance of intrinsic binding thermodynamics is emphasized and the role of structure-thermodynamics correlations for the novel inhibitors of CA IX is discussed - an isozyme that is overexpressed in solid hypoxic tumors, and thus these inhibitors may serve as anticancer drugs. The abundant structural and thermodynamic data are assembled into the Protein-Ligand Binding Database to understand general protein-ligand recognition principles that could be used in drug discovery.

Mass Balance and Metabolite Profile after Single and Multiple Oral Doses of Pritelivir in Healthy Subjects

Pritelivir is a helicase-primase inhibitor active against HSV. Two human mass balance trials (a multiple-dose trial and a single-dose trial) were performed to characterize the absorption, distribution, metabolism, and excretion of 100 mg oral pritelivir combined with a single microdose of 14C-pritelivir. Blood, urine, and feces samples were collected up to 26 days postdose. The plasma half-life of pritelivir was 63-67 hours. Overall, 92% and 66% of the administered dose was recovered in the multiple and single dose trials, respectively. The low recovery after the single dose (66%) was most likely related to the formulation used. The major metabolic pathway was amide hydrolysis leading to amino thiazole sulfonamide (ATS) and pyridinyl phenyl acetic acid (PPA). In plasma, pritelivir, ATS, PPA, and PPA-acyl glucuronide accounted for 40.6%, 9.4%, 5.1%, and 0.2% of total radioactivity. More than 90% of drug-related material was eliminated 624 hours postdose. The majority was excreted in urine (75% and 77%), followed by feces (16% and 23%). The main components in urine were PPA-acyl glucuronide (and its isomers), ATS, and its N-demethylated isomers. Only minor metabolites were observed in feces. In conclusion, the major metabolic pathways of pritelivir have been identified with the primary excretion route being renal.

Design, synthesis, and biological investigation of selective human carbonic anhydrase II, IX, and XII inhibitors using 7-aryl/heteroaryl triazolopyrimidines bearing a sulfanilamide scaffold

A novel library of human carbonic anhydrase (hCA) inhibitors based on the 2-sulfanilamido[1,2,4]triazolo[1,5-a]pyrimidine skeleton modified at its 7-position was prepared by an efficient convergent procedure. These derivatives were evaluated in vitro for their inhibition properties against a representative panel of hCA isoforms (hCA I, II, IV, IX, and XII). The target tumour-associated isoforms hCA IX and XII were potently inhibited with KIs in the low nanomolar range of 5-96 nM and 4-72 nM, respectively. Compounds 1d, 1j, 1v, and 1x were the most potent hCA IX inhibitors with KIs of 5.1, 8.6, 4.7, and 5.1 nM, respectively. Along with derivatives 1d and 1j, compounds 1r and 1ab potently inhibited hCA XII isoform with KIs in a single-digit nanomolar range of 8.8, 5.4, 4.3, and 9.0 nM, respectively. Compounds 1e, 1m, and 1p exhibited the best selectivity against hCA IX and hCA XII isoforms over off-target hCA II, with selectivity indexes ranging from 5 to 14.

Arterial Blood Gases and Acid-Base Regulation

Disorders of acid-base status are common in the critically ill and prompt recognition is central to clinical decision making. The bicarbonate/carbon dioxide buffer system plays a pivotal role in maintaining acid-base homeostasis, and measurements of pH, PCO2, and HCO3 - are routinely used in the estimation of metabolic and respiratory disturbance severity. Hypoventilation and hyperventilation cause primary respiratory acidosis and primary respiratory alkalosis, respectively. Metabolic acidosis and metabolic alkalosis have numerous origins, that include alterations in acid or base intake, body fluid losses, abnormalities of intermediary metabolism, and renal, hepatic, and gastrointestinal dysfunction. The concept of the anion gap is used to categorize metabolic acidoses, and urine chloride excretion helps define metabolic alkaloses. Both the lungs and kidneys employ compensatory mechanisms to minimize changes in pH caused by various physiologic and disease disturbances. Treatment of acid-base disorders should focus primarily on correcting the underlying cause and the hemodynamic and electrolyte derangements that ensue. Specific therapies under certain conditions include renal replacement therapy, mechanical ventilation, respiratory stimulants or depressants, and inhibition of specific enzymes in intermediary metabolism disorders.

Synthesis and Characterization of Novel 1,3-Diaryltriazene-Substituted Sulfaguanidine Derivatives as Selective Carbonic Anhydrase Inhibitors: Biological Evaluation, in Silico ADME/T and Molecular Docking Study

Sulfonamide compounds known as human carbonic anhydrase (hCA) inhibitors are used in the treatment of many diseases such as epilepsy, antibacterial, glaucoma, various diseases. 1,3-diaryl-substituted triazenes and sulfaguanidine are used for therapeutic purposes in many drug structures. Based on these two groups, the synthesis of new compounds is important. In the present study, the novel 1,3-diaryltriazene-substituted sulfaguanidine derivatives (SG1-13) were synthesized and fully characterized by spectroscopic and analytic methods. Inhibitory effect of these compounds on the hCA I and hCA II was screened as in vitro. All the series of synthesized compounds have been identified as potential hCA isoenzymes inhibitory with KI values in the range of 6.44±0.74-86.85±7.01 nM for hCA I and with KI values in the range of 8.16±0.40-77.29±9.56 nM for hCA II. Moreover, the new series of compounds showed a more effective inhibition effect than the acetazolamide used as a reference. The possible binding positions of the compounds with a binding affinity to the hCA I and hCA II was demonstrated by in silico studies. In conclusion, compounds with varying degrees of affinity for hCA isoenzymes have been designed and as selective hCA inhibitors. These compounds may be potential alternative agents that can be used to treat or prevent diseases associated with glaucoma and hCA inhibition.

UIAA Medical Commission Recommendations for Mountaineers, Hillwalkers, Trekkers, and Rock and Ice Climbers with Diabetes

Hillebrandt, David, Anil Gurtoo, Thomas Kupper, Paul Richards, Volker Schöffl, Pankaj Shah, Rianne van der Spek, Nikki Wallis, and Jim Milledge. UIAA Medical Commission recommendations for mountaineers, hillwalkers, trekkers, and rock and ice climbers with diabetes. High Alt Med Biol. 24: 110-126.-The object of this advice article is not only to give the diabetic mountaineer general guidance but also to inform his or her medical team of practical aspects of care that may not be standard for nonmountaineers. The guidelines are produced in seven sections. The first is an introduction to the guidelines, and the second is an introduction to this medical problem and is designed to be read and understood by diabetic patients and their companions. The third section is for use in an emergency in mountains. The fourth is for rock, ice, and competition climbers operating in a less remote environment. These initial sections are deliberately written in simple language. The fifth and sixth sections are written for clinicians and those with skills to read more technical information, and the seventh looks at modern technology and its pros and cons in diabetes management in a remote area. Sections One and Two could be laminated and carried when in the mountains, giving practical advice.

Acetazolamide for Bipolar Disorders: A Scoping Review

Acetazolamide, a carbonic anhydrase inhibitor, is used to treat a variety of ailments. It has been highlighted for its potential to benefit people with bipolar disorders, for whom there are clear current unmet treatment needs. This scoping review sought to synthesise all available evidence related to the potential effects of acetazolamide on symptoms related to bipolar disorder, acceptability and tolerability, and intervention characteristics (e.g., dose and duration). Following publication of the review protocol, the Pubmed, Embase, and PsycInfo databases were searched (all dated to 31 August 2022). A systematic approach was undertaken to identify eligible articles and extract relevant data from these. Five studies were included, assessing a total of 50 patients treated with acetazolamide. Most patients were from two open-label trials, while the others were case reports. Approximately one third of patients were experiencing psychosis or mania before treatment initiation, and one third had refractory depression. Forty-four percent of patients were estimated to achieve a response (not seemingly affected by the baseline episode type, acetazolamide dose, or duration), while a further 22% appeared to experience minimal benefits from the intervention. Acetazolamide was generally reported to be tolerated well and acceptable for up to 2 years, although reporting for acceptability and tolerability was suboptimal. The reviewed evidence is extremely limited in size and methodology (e.g., no randomised studies, blinding, or standardised outcome assessment). We posit that the current findings are sufficiently encouraging to recommend substantive clinical trials, but we emphasise that at present, the evidence is exceedingly preliminary, and there remains evident uncertainty as to whether acetazolamide could be a viable treatment for bipolar disorders.

Curcumin Attenuates Hydrocephalus via Activation of E2F Transcription Factor 4

BACKGROUND

Recent studies have shown that curcumin can reduce the symptoms of hydrocephalus. However, the underlying mechanisms remain unclear. Our previous studies demonstrated that E2F transcription factor 4 (E2F4) protein plays an important role in hydrocephalus; hence, we hypothesized that E2F4 may involve in curcumin mediated anti-hydrocephalus benefits.

METHODS

E2F4 expression and functions in different human tissues and cell lines were determined and analyzed using the all RNA-seq and ChIP-seq sample and signature search database and ChIP-atlas database. Hydrocephalus mouse model was established through stereotactic injection of shE2F4 into frontal cortex. Mice were treated with curcumin, and then hydrocephalus severity, the expression of E2F4, and downstream targets were analyzed.

RESULTS

E2F4 was highly expressed in the nervous system, which was downregulated in the bran of hydrocephalus patients. Knockdown E2F4 in mice could mimic the phenotype of human hydrocephalus. Upon curcumin administration, E2F4 expression level was increased, and the hydrocephalus severity score was significantly decreased in mouse model. Mechanistically, curcumin attenuated hydrocephalus through activating E2F4 signaling pathway.

CONCLUSION

Curcumin suppresses hydrocephalus progression via activation of E2F4, which could be a target for hydrocephalus treatment.

Serious Adverse Events of Oral and Topical Carbonic Anhydrase Inhibitors

IMPORTANCE

Some ophthalmologists may be reluctant to prescribe oral carbonic anhydrase inhibitors, given the potential for life-threatening systemic adverse reactions.

OBJECTIVE

To conduct a population-based analysis of the safety of oral or topical carbonic anhydrase inhibitors in clinical care.

DESIGN, SETTING, AND PARTICIPANTS

This matched longitudinal cohort study took place in Ontario, Canada. Consecutive patients older than 65 years who were prescribed an oral or topical carbonic anhydrase inhibitor in Ontario, Canada, between January 1, 1995, and January 1, 2020, were identified. Patients were matched 1-to-1 based on age, sex, and diabetes status. Time zero was defined as the date of the first identified prescription for the medication, and the primary analysis focused on the first 120 days of follow-up.

MAIN OUTCOMES AND MEASURES

The primary end point was a severe complicated adverse event of either Stevens-Johnson syndrome, toxic epidermal necrolysis, or aplastic anemia.

RESULTS

Overall, 128 942 matched patients initiated an oral or topical carbonic anhydrase inhibitor during the 25-year study period. The mean (SD) age was 75 (6.6) years, 71 958 (55.8%) were women, and 25 058 (19.4%) had a diagnosis of diabetes. The oral and topical carbonic anhydrase inhibitor groups had similar baseline demographics. Patients prescribed an oral carbonic anhydrase inhibitor had an absolute risk of a severe complicated adverse event of 2.90 per 1000 patients, whereas patients prescribed a topical carbonic anhydrase inhibitor had an absolute risk of 2.08 per 1000 patients. This difference was equivalent to a risk ratio of 1.40, with a number needed to harm of 1 in 1220 patients (95% CI, 1.12-1.74; P = .003). This generally low risk was replicated in multivariable regression controlling for confounding factors. Additional risk factors for a severe complicated adverse event included patients with more comorbidities and those with more frequent clinic contacts.

CONCLUSIONS AND RELEVANCE

The risk of a serious adverse reaction following prescription of an oral or topical carbonic anhydrase inhibitor was low and similar between agents. Given the low risk of severe adverse reactions, this population-level analysis supports reconsidering the reluctance toward prescribing an oral carbonic anhydrase inhibitor.

Elucidating the combined effect of intermittent hypoxia training and acetazolamide on hypoxia induced hematological and physiological changes

As the number of people travelling to altitude increases, the risk of life threatening medical emergencies also increases. It is important that we have effective strategies to minimize the risk of altitude illness. In this study, an attempt was made to investigate the combined effect of non-pharmacological (Intermittent hypoxia training; IHT) and pharmacological (acetazolamide; ACZ) intervention as a prophylactic strategy in order to minimize the risk of high altitude hypoxic related problems using rats as an animal model. Male Sprague Dawley rats were subjected to IHT for 4 h consecutively for 5 days at 12% FiO₂ under normobaric conditions with and without oral ACZ administration at 25 mg/kg body weight. Validation of the intervention was performed by exposing the rats to extreme hypoxia (EH) at 8% FiO₂ to further assess the effect of IHT and ACZ on hypoxic acclimatization. The principal findings of this study is that the combined effect of IHT and ACZ improves the arterial oxygenation by alterations in hemodynamics and in blood gasometry, thereby resulting into an increase in the oxygen carrying capacity of the blood with increase in SpO₂ (peripheral oxygen saturation). The present study showed that the combined effect of IHT with ACZ could be refined as a prophylactic measure for better outcomes during altitude ascent and rapid altitude acclimatization rather than IHT or ACZ alone.

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Combination of IHT with ACZ attenuates the inhibitory effect of respiratory alkalosis.

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It also minimizes pathological changes in hematology and blood gas.

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The strategy improved the oxygen carrying capacity of the blood by increasing SpO₂.

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Thus, it leads to ventilatory Acclimatization.

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The combined treatment could be refined as a prophylactic measure for altitude maladies.

Staphylococcus aureus Genomes Harbor Only MpsAB-Like Bicarbonate Transporter but Not Carbonic Anhydrase as Dissolved Inorganic Carbon Supply System

In recent years, it became apparent that not only autotrophic but also most other bacteria require CO₂ or bicarbonate for growth. Two systems are available for the acquisition of dissolved inorganic carbon supply (DICS): the cytoplasmic localized carbonic anhydrase (CA) and the more recently described bicarbonate transporter MpsAB (membrane potential generating system). In the pathogenic species Staphylococcus aureus, there are contradictions in the literature regarding the presence of a CA or MpsAB. Here, we address these contradictions in detail. We could demonstrate by careful BLASTp analyses with 259 finished and 4,590 unfinished S. aureus genomes that S. aureus does not contain CA and that the bicarbonate transporter MpsAB is the only DICS system in this species. This finding is further supported by two further pieces of evidence: (i) mpsAB deletion mutants in four different S. aureus strains failed to grow under atmospheric air, which should not be the case if they possess CAs, since we have previously shown that both CA and MpsAB can substitute for each other, and (ii) S. aureus is completely resistant to CA inhibitors, whereas Staphylococcus carnosus, which has been shown to have only CA, was inhibited by ethoxyzolamide (EZA). Taken together, we demonstrate beyond doubt that the species S. aureus possesses only the bicarbonate transporter MpsAB as its sole DICS system.

IMPORTANCE The discrepancies in the current literature and even in NCBI database, which listed some protein sequences annotated as Staphylococcus aureus carbonic anhydrase (CA), are misleading. One of the existing problems in publicly available sequence databases is the presence of incorrectly annotated genes, especially if they originated from unfinished genomes. Here, we demonstrate that some of these unfinished genomes are of poor quality and should be interpreted with caution. In the present study, we aimed to address these discrepancies and correct the current literature about S. aureus CA, considering the medical relevance of S. aureus. If left unchecked, these misleading studies and wrongly annotated genes might lead to a continual propagation of wrong annotation and, consequently, wrong interpretations and wasted time. In addition, we also show that bicarbonate transporter MpsAB-harboring bacteria are resistant to CA inhibitor, suggesting that pathogens possessing both MpsAB and CA are not treatable with CA inhibitors.

Evaluation of an oral sodium bicarbonate protocol for high-dose methotrexate urine alkalinization

PURPOSE

Intravenous (IV) sodium bicarbonate is considered standard therapy for high-dose methotrexate (HDMTX) urine alkalinization. Due to a national IV sodium bicarbonate shortage, an oral (PO) sodium bicarbonate protocol was implemented by Alberta Health Services (AHS) for HDMTX urine alkalinization. This study aims to evaluate the efficacy and safety of the PO sodium bicarbonate protocol compared to IV sodium bicarbonate for HDMTX urine alkalinization.

METHODS

A retrospective chart review of adult patients who received HDMTX (> 500 mg/m²) with sodium bicarbonate for urine alkalinization at 4 hospitals in Alberta was conducted. Patients who received IV sodium bicarbonate between January and June 2017 and PO sodium bicarbonate between July and December 2017 were compared for the primary outcome of time to methotrexate clearance.

RESULTS

A total of 84 and 78 HDMTX cycles were included in the IV and PO cohorts, respectively. No difference in time to methotrexate clearance was seen between the IV and PO cohorts, 91.6 (± 35.4) hours and 95.2 (± 44) hours respectively; p = 0.5. The proportion of HDMTX cycles that experienced a > 25% increase in serum creatinine was not statistically significant, IV protocol 12% and PO protocol 5%; p = 0.13. Nausea and emesis occurred more frequently in the PO cohort than the IV cohort, though rarely resulted in refused doses or change to alternate sodium bicarbonate formulations.

CONCLUSIONS

The results of this study indicate that the AHS PO sodium bicarbonate protocol was no different in time to methotrexate clearance or rates of increased serum creatinine when compared to IV sodium bicarbonate.

Side effects of acetazolamide: a systematic review and meta-analysis assessing overall risk and dose dependence

Introduction

Acetazolamide (AZM) is used for various conditions (eg, altitude sickness, sleep apnoea, glaucoma), but therapy is often limited by its side effect profile. Our objective was to estimate the risk of commonly reported side effects based on meta-analyses. We hypothesised that these risks are dose-dependent.

Methods

We queried MEDLINE/EMBASE (Medical Literature Analysis and Retrieval System Online/Excerpta Medica dataBASE) up until 04/10/2019, including any randomised placebo-controlled trial in which adults received oral AZM versus placebo reporting side effects. Eligibility assessment was performed by two independent reviewers. Data were abstracted by one reviewer who verified key entries at a second time point. For side effects reported by >3 studies a pooled effect estimate was calculated, and heterogeneity assessed via I²; for outcomes reported by >5 studies effect modification by total daily dose (EMbyTDD; <400 mg/d, 400–600 mg/d, >600 mg/d) was assessed via meta-regression. For pre-specified, primary outcomes (paraesthesias, taste disturbances, polyuria and fatigue) additional subgroup analyses were performed using demographics, intervention details, laboratory changes and risk of bias.

Results

We included 42 studies in the meta-analyses (N_subjects=1274/1211 in AZM/placebo groups). AZM increased the risk of all primary outcomes (p<0.01, I² ≤16% and low-to-moderate quality of evidence for all)—the numbers needed to harm (95% CI; n_Studies) for each were: paraesthesias 2.3 (95% CI 2 to 2.7; n=39), dysgeusia 18 (95% CI 10 to 38, n=22), polyuria 17 (95% CI 9 to 49; n=22), fatigue 11 (95% CI 6 to 24; n=14). The risk for paraesthesias (beta=1.8 (95% CI 1.1 to 2.9); P_EMbyTDD=0.01) and dysgeusia (beta=3.1 (95% CI 1.2 to 8.2); P_EMbyTDD=0.02) increased with higher AZM doses; the risk of fatigue also increased with higher dose but non-significantly (beta=2.6 (95% CI 0.7 to 9.4); P_EMbyTDD=0.14).

Discussion

This comprehensive meta-analysis of low-to-moderate quality evidence defines risk of common AZM side effects and corroborates dose dependence of some side effects. These results may inform clinical decision making and support efforts to establish the lowest effective dose of AZM for various conditions.

Prevalence of common mental disorders and associated factors among adults with Glaucoma attending University of Gondar comprehensive specialized hospital tertiary eye care and training center, Northwest, Ethiopia 2020

PURPOSE

This study aimed to assess the prevalence of common mental disorders and associated factors among adults with glaucoma at Gondar university comprehensive specialized hospital tertiary eye care and training center. Glaucoma predisposes patients to common mental problems and leads to wasteful, costly and inefficient use of medical services and complications of the diagnoses. So, determining the level and factors associated with common mental disorders among glaucoma patient would help to improve and integrate comprehensive ophthalmic services which address common mental disorder in a follow-up visit.

METHODS

An institution-based cross-sectional study was conducted on 495 glaucoma patients selected by using systematic random sampling. Data were collected through face-to-face interview and chart review. Self-reported questionnaire (SRQ-20) was used to assess the presence of common mental disorders. Binary logistic regression analysis was done to identify factors associated with common mental disorders. Variables with P<0.05 were considered as factors significantly associated with common mental disorders.

RESULT

Four hundred sixty-eight patients were included in this study with a response rate of 94.54%. The mean age of the participant was 58 ± 14.11 years. The prevalence of common mental disorders was found to be 29.5% (95% CI 25.4-33.3). Female sex (AOR = 3.79, 95% CI: 1.66-8.62) (p-value = 0.001), average monthly income of less than 1200 birr (AOR = 6.05 95% CI: 2.26-16.22) (p-value = 0.001), poor level of social support (AOR = 17.39 95% CI: 7.79-38.82) (p-value = 0.001), moderate and high risk of alcohol use (AOR = 10.42 95%CI: 2.74-39.54) (p-value = 0.001), presence of chronic medical illness (AOR = 3.85 95% CI: 2.07-7.16) (p-value = 0.001), receiving both drug and surgical treatment (AOR = 2.50, 95%CI: 1.30-4.83) (p-value = 0.006) and presence of systemic carbonic anhydrase inhibitors use (AOR = 3.16, 95%CI: 1.65-6.06) (p-value = 0.001) were significantly associated with increased level of common mental disorders.

CONCLUSION

Significant numbers of glaucoma patients have CMD and found significantly associated with socio-economic, ocular and systemic clinical factors. Therefore, the integration of psychosocial care into the current treatment of patients with glaucoma would have a significant advantage to help these patients.

Subtherapeutic Acetazolamide Doses as a Noninvasive Method for Assessing Medication Adherence

Adherence monitoring is a vital component of clinical efficacy trials, as the regularity of medication consumption affects both efficacy and adverse effect profiles. Pill-counts do not confirm consumption, and invasive plasma assessments can only assist post hoc assessments. We previously reported on the pharmacokinetics of a potential adherence marker to noninvasively monitor dosage consumption during a trial without breaking a blind. We reported that consumption cessation of subtherapeutic 15 mg acetazolamide (ACZ) doses showed a predictable urinary excretion decay that was quantifiable for an extended period. The current study describes the clinical implementation of 15 mg ACZ doses as an adherence marker excipient in distinct cohorts taking ACZ for different "adherence" durations. We confirm that ACZ output did not change (accumulate) during 18-20 days of adherence, and developed and assessed urinary cutoffs as nonadherence indicators. We demonstrate that whereas an absolute concentration cutoff (989 ng/mL) lacked sensitivity, a creatinine normalized equivalent (1,376 ng/mg ACZ) was highly accurate at detecting nonadherence. We also demonstrate that during nonadherent phases of three trials, creatinine-normalized urinary ACZ elimination was reproducible within and across trials with low variability. Excretion was first order, with a decay half-life averaging ~ 2.0 days. Further, excretion remained quantifiable for 14 days, providing a long period during which the date of last consumption might be determined. We conclude that inclusion of 15 mg ACZ as a dosage form adherence marker excipient, provides a reliable and sensitive mechanism to confirm medication consumption and detect nonadherence during clinical efficacy trials.

Primary Open-angle Glaucoma and Increased Risk of Chronic Kidney Disease

PRECIS

The association between primary open-angle glaucoma (POAG) and subsequent development of chronic kidney disease (CKD) was investigated using a nationwide, population-based, retrospective cohort in South Korea. POAG increases the risk of subsequent CKD development.

PURPOSE

The purpose of this study was to investigate the risk of subsequent CKD development in patients with POAG.

METHODS

In this nationwide, population-based longitudinal cohort, 1,025,340 beneficiaries in the 2002-2013 Korean National Health Insurance database were included. We identified patients with incident POAG and evaluated the risk of subsequent CKD development using diagnostic codes from the database after 2-year wash-out periods. We applied time-varying covariate Cox regression analyses to determine the effect of POAG on the development of CKD: Model 1 included only POAG as a time-varying covariate; Model 2 included Model 1 and demographic information; and Model 3 included Model 2, comorbidity, comedication, and the Charlson Comorbidity Index score.

RESULTS

The fixed cohort included 478,303 eligible subjects, and of these subjects, 1749 suffered incident POAG, and 3157 developed CKD. POAG was associated with an increased risk of CKD development [hazard ratio (HR)=7.63; 95% confidence interval (CI), 5.89-9.87] in Model 1; HR=3.54 (95% CI, 2.73-4.58) in Model 2; and HR=2.90 (95% CI, 2.24-3.76) in Model 3].

CONCLUSION

POAG increased the risk of subsequent CKD in the general population, suggesting that POAG and CKD might share a common pathogenic mechanism.

A Novel Sulfonamide, 4-FS, Reduces Ethanol Drinking and Physical Withdrawal Associated With Ethanol Dependence

Carbonic anhydrase (CA) is abundant in glial cells in the brain and CA type II isoform (CA II) activity in the hippocampus plays an important role in buffering extracellular pH transients produced by neural activity. Chronic ethanol exposure results in respiratory and metabolic acidosis, producing shifts in extracellular pH in the brain and body. These neurophysiological changes by ethanol are hypothesized to contribute to the continued drinking behavior and physical withdrawal behavior in subjects consuming ethanol chronically. We explored whether chronic ethanol self-administration (ethanol drinking, 10% v/v; ED) without or under the influence of chronic intermittent ethanol vapor (CIE-ED) experience alters the expression of CA II in the hippocampus. Postmortem hippocampal tissue analyses demonstrated that CA II levels were enhanced in the hilus region of the hippocampus in ED and CIE-ED rats. We used a novel molecule-4-fluoro-N-(4-sulfamoylphenyl) benzenesulfonamide (4-FS)-a selective CA II inhibitor, to determine whether CA II plays a role in ethanol self-administration in ED and CIE-ED rats and physical withdrawal behavior in CIE-ED rats. 4-FS (20 mg/kg, i.p.) reduced ethanol self-administration in ED rats and physical withdrawal behavior in CIE-ED rats. Postmortem hippocampal tissue analyses demonstrated that 4-FS reduced CA II expression in ED and CIE-ED rats to control levels. In parallel, 4-FS enhanced GABAA receptor expression, reduced ratio of glutamatergic GluN2A/2B receptors and enhanced the expression of Fos, a marker of neuronal activation in the ventral hippocampus in ED rats. These findings suggest that 4-FS enhanced GABAergic transmission and increased activity of neurons of inhibitory phenotypes. Taken together, these findings support the role of CA II in assisting with negative affective behaviors associated with moderate to severe alcohol use disorders (AUD) and that CA II inhibitors are a potential therapeutic target to reduce continued drinking and somatic withdrawal symptoms associated with moderate to severe AUD.

Incidence of Mild Cognitive Impairment with Ascending Altitude

Background: This study aimed to longitudinally quantify the prevalence of mild cognitive impairment (MCI) in individual trekkers at three different ascending altitudes (Site 1: ∼3500 m, Site 2: ∼4400 m, and Site 3: ∼5100 m). We correlated these findings with the presence of acute mountain sickness (AMS). Materials and Methods: We performed serial assays using the environmental quick mild cognitive impairment (eQMCI) score on 103 English-speaking 18- to 65-year-old volunteers trekking to Everest Base Camp in Nepal during spring 2016. We defined MCI as a score less than 67 (lower scores indicating more cognitive impairment). Additional data collected included the Lake Louise Score, demographics, and other possible confounders. Results: eQMCI scores significantly decreased with ascent from Site 1 to 2 (a score of 78.95 [SD = 7.96] to 74.67 [SD = 8.8] [Site 1-2 p = 0.04]), but then increased on ascent to Site 3 to 83.68 (SD = 8.67) (Site 1-3 p = <0.0001, Site 2-3 p = <0.0001). However, subjects who fulfilled eQMCI criteria for MCI increased despite the overall improvement in score: 6.8% (N = 7) at Site 1, 18.7% (N = 14) at Site 2, and 3.3% (N = 2) at Site 3. Incidence of AMS at Sites 1, 2, and 3 was 22.3% (N = 23), 21.3% (N = 16), and 48.3% (N = 29), respectively. Of those with MCI, 1.94% met criteria for AMS at Site 1 (p = 0.0017), 2.67% at Site 2 (p = 0.6949), and 3.33% at Site 3 (p = <0.0001). Conclusions: There is a significant incidence of MCI at high altitude, even in those without subjective findings of AMS. Interestingly, subjects with a decline in cognitive function show an increasing trend for developing AMS at higher altitude. Future research on the clinical impact of MCI on a subject's health, judgment, and performance remains to be elucidated.

Glaucoma in pregnancy: an update

PURPOSE OF REVIEW

Glaucoma management during pregnancy is a complex challenge, which requires balancing the clinical disease of the mother with the potential risks of therapy to the developing child. Because systematic studies are lacking in the pregnant population, this review aims to collect the array of available data from observational studies and case reports to provide the reader with guidance and context for the safety of glaucoma interventions during pregnancy.

RECENT FINDINGS

Surgical glaucoma is a rapidly expanding field with many new technologies and procedures. We review the surgical options for the gravid patient with reference to traditional procedures like trabeculectomy and tube-shunts, and newer MIGS procedures. When indicated, orphan trabeculectomy, or with collagen matrix implant may be a viable solution for severe glaucoma during pregnancy. Newer MIGS procedures such as the gelatin stent may also provide minimally invasive options for pregnant patients. Two new medications, Vyzulta and Rhopressa, were recently released in 2018 and have limited data to support their safety for use during pregnancy.

SUMMARY

The careful consideration of fetal health in the management of glaucoma during pregnancy is best done as a part of a multidisciplinary team including obstetrics and neonatology. When medication is necessary, steps to minimize systemic absorption should be employed. Surgical management should not be excluded for pregnant patients and may be considered before medical management in some cases to prevent fetal exposures and maternal harm.

Carbonic Anhydrase Inhibitors suppress platelet procoagulant responses and in vivo thrombosis

Carbonic anhydrase (CA) inhibitors have a long history of safe clinical use as mild diuretics, in the treatment of glaucoma and for altitude sickness prevention. In this study, we aimed to determine if CA inhibition may be an alternative approach to control thrombosis. We utilized a high-resolution dynamic imaging approach to provide mechanistic evidence that CA inhibitors may be potent anti-procoagulant agents in vitro and effective anti-thrombotics in vivo. Acetazolamide and methazolamide, while sparing platelet secretion, attenuated intracellular chloride ion entry and suppressed the procoagulant response of activated platelets in vitro and thrombosis in vivo. The chemically similar N-methyl acetazolamide, which lacks CA inhibitory activity, did not affect platelet procoagulant response in vitro. Outputs from rotational thromboelastometry did not reflect changes in procoagulant activity and reveal the need for a suitable clinical test for procoagulant activity. Drugs specifically targeting procoagulant remodeling of activated platelets, by blockade of carbonic anhydrases, may provide a new way to control platelet-driven thrombosis without blocking essential platelet secretion responses.

Anti-Helicobacter pylori activity of ethoxzolamide

Ethoxzolamide (EZA), acetazolamide, and methazolamide are clinically used sulphonamide drugs designed to treat non-bacteria-related illnesses (e.g. glaucoma), but they also show antimicrobial activity against the gastric pathogen Helicobacter pylori. EZA showed the highest activity, and was effective against clinical isolates resistant to metronidazole, clarithromycin, and/or amoxicillin, suggesting that EZA kills H. pylori via mechanisms different from that of these antibiotics. The frequency of single-step spontaneous resistance acquisition by H. pylori was less than 5 × 10-9, showing that resistance to EZA does not develop easily. Resistance was associated with mutations in three genes, including the one that encodes undecaprenyl pyrophosphate synthase, a known target of sulphonamides. The data indicate that EZA impacts multiple targets in killing H. pylori. Our findings suggest that developing the approved anti-glaucoma drug EZA into a more effective anti-H. pylori agent may offer a faster and cost-effective route towards new antimicrobials with a novel mechanism of action.

Synthesis, biological evaluation and in silico modelling studies of 1,3,5-trisubstituted pyrazoles carrying benzenesulfonamide as potential anticancer agents and selective cancer-associated hCA IX isoenzyme inhibitors

Inhibition of carbonic anhydrases (CAs, EC 4.2.1.1) has clinical importance for the treatment of several diseases. They participate in crucial regulatory mechanisms for balancing intracellular and extracellular pH of the cells. Among CA isoforms, selective inhibition of hCA IX has been linked to decreasing of cell growth for both primary tumors and metastases. The discovery of novel CA inhibitors as anticancer drug candidates is a current topic in medicinal chemistry. 1,3,5-Trisubstituted pyrazoles carrying benzenesulfonamide were evaluated against physiologically abundant cytosolic hCA I and hCA II and trans-membrane, tumor-associated hCA IX isoforms by a stopped-flow CO2 hydrase method. Their in vitro cytotoxicities were screened against human oral squamous cell carcinoma (OSCC) cell lines (HSC-2) and human mesenchymal normal oral cells (HGF) via 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT) test. Compounds 6, 8, 9, 11, and 12 showed low nanomolar hCA II inhibitory potency with Ki < 10 nM, whereas compounds 9 and 12 displayed Ki < 10 nM against hCA IX isoenzyme when compared with reference Acetazolamide (AZA). Compound 9, 4-(3-(hydrazinecarbonyl)-5-(4-nitrophenyl)-1H-pyrazol-1-yl)benzenesulfonamide, can be considered as the most selective hCA IX inhibitor over off-target cytosolic isoenzymes hCA I and hCA II with the lowest Ki value of 2.3 nM and selectivity ratios of 3217 (hCA I/hCA IX) and 3.9 (hCA II/hCA IX). Isoform selectivity profiles were also discussed using in silico modelling. Cytotoxicity results pointed out that compounds 5 (CC50 = 37.7 μM) and 11 (CC50 = 58.1 μM) can be considered as lead cytotoxic compounds since they were more cytotoxic than 5-Fluorouracil (5-FU) and Methotrexate (MTX).

Does Aerobic Respiration Produce Carbon Dioxide or Hydrogen Ion and Bicarbonate?

Maintenance of intracellular pH is critical for clinical homeostasis. The metabolism of glucose, fatty acids, and amino acids yielding the generation of adenosine triphosphate in the mitochondria is accompanied by the production of acid in the Krebs cycle. Both the nature of this acidosis and the mechanism of its disposal have been argued by two investigators with a long-abiding interest in acid-base physiology. They offer different interpretations and views of the molecular mechanism of this intracellular pH regulation during normal metabolism. Dr. John Severinghaus has posited that hydrogen ion and bicarbonate are the direct end products in the Krebs cycle. In the late 1960s, he showed in brain and brain homogenate experiments that acetazolamide, a carbonic anhydrase inhibitor, reduces intracellular pH. This led him to conclude that hydrogen ion and bicarbonate are the end products, and the role of intracellular carbonic anhydrase is to rapidly generate diffusible carbon dioxide to minimize acidosis. Dr. Erik Swenson posits that carbon dioxide is a direct end product in the Krebs cycle, a more widely accepted view, and that acetazolamide prevents rapid intracellular bicarbonate formation, which can then codiffuse with carbon dioxide to the cell surface and there be reconverted for exit from the cell. Loss of this "facilitated diffusion of carbon dioxide" leads to intracellular acidosis as the still appreciable uncatalyzed rate of carbon dioxide hydration generates more protons. This review summarizes the available evidence and determines that resolution of this question will require more sophisticated measurements of intracellular pH with faster temporal resolution.

Open-Label, Dose-Escalation, Phase 1 Study of Safety and Single and Multiple-Dose Pharmacokinetics of Dichlorphenamide in Healthy Volunteers

Single‐and multiple‐dose pharmacokinetics and safety were investigated in this phase 1 study of dichlorphenamide, a carbonic anhydrase inhibitor approved in the United States for treatment of primary periodic paralysis. Dichlorphenamide was administered to 6 cohorts (n = 6 each) of healthy adults. Cohorts A through E received single doses of 25–400 mg followed by 50–800 mg/day in divided doses for 10 total doses. Cohort F (safety analysis only) received up to 28 titrated doses from 100–800 mg/day. Plasma for pharmacokinetics sampling was obtained predose and up to 48 hours postdose. Twenty‐five of 36 enrolled subjects completed. Median time to maximum plasma concentration ranged from 1.5–3 hours, and mean half‐life from 32–68 hours. Mean area under the concentration‐time curve from time 0 to tau (length of the dosing interval estimated using the trapezoidal method) and maximum observed plasma concentration increased dose‐proportionally after multiple doses. The incidence and severity of adverse events (AEs) were dose‐related, with at least one mild AE reported among 17%, 17%, and 67% of patients in cohorts A, B, and C, respectively; and at least one mild‐to‐moderate AE among 100% of subjects in cohorts D, E, and F. One serious AE of rash was reported in cohort F. Eleven subjects discontinued; 10 due to AEs at 400 or 800 mg/day (cohorts E and F), including 100% of cohort F. Hypokalemia contributed to 5 of 6 discontinuations in cohort F (all 800 mg/day).

Metabolic acidosis and anaemia associated with dorzolamide in a patient with impaired renal function

Topical carbonic anhydrase inhibitors (CAI), used for treatment of glaucoma, are generally regarded as safe and unconnected with systemic side effects. We report an unusual case of fatigue, metabolic acidosis, and normocytic anaemia associated with ocular administration of the CAI, dorzolamide, in a patient with impaired renal function. In chronic kidney disease, where CAI elimination may be decreased, and patients prone to develop metabolic acidosis, systemic absorption of ocular administered CAI could lead to rare, but potentially serious adverse reaction, that are a consequence of inhibition of extraocular carbonic anhydrase isoenzymes.

Findings of Cognitive Impairment at High Altitude: Relationships to Acetazolamide Use and Acute Mountain Sickness

Phillips, Lara, Buddha Basnyat, Yuchiao Chang, Erik R. Swenson, and N. Stuart Harris. Findings of cognitive impairment at high altitude: relationships to acetazolamide use and acute mountain sickness. High Alt Med Biol. 18:121-127, 2017.

OBJECTIVE

Acute mountain sickness (AMS) is defined by patient-reported symptoms using the Lake Louise Score (LLS), which provides limited insight into any possible underlying central nervous system (CNS) dysfunction. Some evidence suggests AMS might coexist with altered neural functioning. Cognitive impairment (CI) may go undetected unless a sensitive test is applied. Our hypothesis was that a standardized test for mild CI would provide an objective measure of CNS dysfunction, which may correlate with the symptoms of AMS and so provide a potential new tool to better characterize altitude-related CNS dysfunction. We compared a cognitive screening tool with the LLS to see if it correlated with CNS dysfunction.

METHODS

Adult native English-speaking subjects visiting Himalayan Rescue Association aid stations in Nepal at 3520 m (11,548 ft) and 4550 m (14,927 ft) were recruited. Subjects were administered the LLS and a slightly modified version of the environmental Quick mild cognitive impairment screen (eQmci). Medication use for altitude illness was recorded. Scores were compared using the Spearman's correlation coefficient. Data also included medication use.

RESULTS

Seventy-nine subjects were enrolled. A cut-off of three or greater was used for the LLS to diagnose AMS and 67 or less for the eQmci to diagnose CI. There were 22 (28%) subjects who met criteria for AMS and 17 (22%) subjects who met criteria for CI. There was a weak correlation (r² = 0.06, p = 0.04) between eQmci score and LLS. In matched subjects with identical LLS, recent acetazolamide use was associated with significantly more CI.

CONCLUSION

Field assessment of CI using a rapid standardized tool demonstrated that a substantial number of subjects were found to have mild CI following rapid ascent to 3520-4550 m (11,548-14,927 ft). The weak correlation between the LLS and eQmci suggests that AMS does not result in CI. Use of acetazolamide appears to be associated with CI at all levels of AMS severity.

Drug Use and Misuse in the Mountains: A UIAA MedCom Consensus Guide for Medical Professionals

Donegani, Enrico, Peter Paal, Thomas Küpper, Urs Hefti, Buddha Basnyat, Anna Carceller, Pierre Bouzat, Rianne van der Spek, and David Hillebrandt. Drug use and misuse in the mountains: a UIAA MedCom consensus guide for medical professionals. High Alt Med Biol. 17:157-184, 2016.-Aims: The aim of this review is to inform mountaineers about drugs commonly used in mountains. For many years, drugs have been used to enhance performance in mountaineering. It is the UIAA (International Climbing and Mountaineering Federation-Union International des Associations d'Alpinisme) Medcom's duty to protect mountaineers from possible harm caused by uninformed drug use. The UIAA Medcom assessed relevant articles in scientific literature and peer-reviewed studies, trials, observational studies, and case series to provide information for physicians on drugs commonly used in the mountain environment. Recommendations were graded according to criteria set by the American College of Chest Physicians.

RESULTS

Prophylactic, therapeutic, and recreational uses of drugs relevant to mountaineering are presented with an assessment of their risks and benefits.

CONCLUSIONS

If using drugs not regulated by the World Anti-Doping Agency (WADA), individuals have to determine their own personal standards for enjoyment, challenge, acceptable risk, and ethics. No system of drug testing could ever, or should ever, be policed for recreational climbers. Sponsored climbers or those who climb for status need to carefully consider both the medical and ethical implications if using drugs to aid performance. In some countries (e.g., Switzerland and Germany), administrative systems for mountaineering or medication control dictate a specific stance, but for most recreational mountaineers, any rules would be unenforceable and have to be a personal decision, but should take into account the current best evidence for risk, benefit, and sporting ethics.

A Pharmacokinetic Study Examining Acetazolamide as a Novel Adherence Marker for Clinical Trials

RATIONALE

Accurate assessment of medication adherence is critical for determination of medication efficacy in clinical trials, but most current methods have significant limitations. This study tests a subtherapeutic (microdose) of acetazolamide as a medication ingestion marker because acetazolamide is rapidly absorbed and excreted without metabolism in urine and can be noninvasively sampled.

METHODS

In a double-blind, placebo-controlled, residential study, 10 volunteers received 15 mg oral acetazolamide for 4 consecutive days. Acetazolamide pharmacokinetics were assessed on day 3, and its pharmacokinetic and pharmacodynamic interactions with a model medication (30 mg oxycodone) were examined on day 4. The rate of acetazolamide elimination into urine was followed for several days after dosing cessation.

RESULTS

Erythrocyte sequestration (half-life = 50.2 ± 18.5 h, mean ± SD, n = 6), resulted in the acetazolamide microdose exhibiting a substantially longer plasma half-life (24.5 ± 5.6 hours, n = 10) than previously reported for therapeutic doses (3-6 hours). After cessation of dosing, the rate of urinary elimination decreased significantly (F3,23 = 247: P < 0.05, n = 6) in a predictable manner with low intersubject variability and a half-life of 16.1 ± 3.8 h (n = 10). For each of 4 consecutive mornings after dosing cessation, the rates of urinary acetazolamide elimination remained quantifiable.There was no overall effect of acetazolamide on the pharmacodynamics, Cmax, Tmax, or elimination half-life of the model medication tested. Acetazolamide may have modestly increased overall oxycodone exposure (20%, P < 0.05) compared with one of the 2 days when oxycodone was given alone, but there were no observed effects of acetazolamide on oxycodone pharmacodynamic responses.

CONCLUSIONS

Coformulation of a once-daily trial medication with an acetazolamide microdose may allow estimation of the last time of medication consumption for up to 96 hours postdose. Inclusion of acetazolamide may therefore provide an inexpensive new method to improve estimates of medication adherence in clinical trials.

Cloning, expression, purification and characterization of human mitochondrial carbonic anhydrase VA

Carbonic anhydrase VA (CAVA) is a mitochondrial enzyme that catalyzes the reversible hydration of CO₂ to produce HCO₃^- and proton. CAV is primarily involved in several biosynthetic processes such as ureagenesis, gluconeogenesis and lipogenesis by providing bicarbonate ion. Here, we report a new strategy for cloning, expression and purification for CAVA in the bacterial system followed by its biophysical characterization. The cDNA of CAVA, a 801 nucleotide long that encodes a 267-amino acid polypeptide of molecular mass of 30-kDa (excluding signal peptide), was sub-cloned in the expression vector pET21c and transformed into Escherichia coli strain BL21 (DE3) for expression. The recombinant protein was purified in two steps by Ni-NTA and DEAE weak anion-exchange chromatography under native condition from the supernatant, while inclusion bodies (IBs) were used to get protein under the denatured condition with a relatively high yield. CAVA was purified under denatured conditions in a single step using Ni-NTA chromatography. SDS-PAGE showed a band of 30-kDa, which was further confirmed as CAVA by Western blot and MALDI-TOF/MS. We further performed enzyme activity to ensure that both forms of purified proteins are enzymatically active. Measurements of secondary structure of the native, denatured and renatured proteins were carried out using circular dichroism. The purified protein can be further used for structural and biochemical studies.

Single-eye trial of a topical carbonic anhydrase inhibitor versus intravitreal bevacizumab for the treatment of taxane drug-induced cystoid macula oedema

Taxanes are a class of microtubule stabilising agents used to treat a wide range of malignancies. Taxane drug-induced cystoid macula oedema (TDICMO) is a known but rare complication of therapy. First reported with Docetaxel in 2003 and Paclitaxel in 2007, there are currently less than 20 cases of TDICMO in the literature. Although most cases resolve following taxane cessation, several authors have tried using carbonic anhydrase inhibitors or intravitreal bevacizumab to accelerate resolution or when taxane therapy cannot be discontinued. We report the first published case of TDICMO treated with a single-eye trial of topical dorzolamide versus intravitreal bevacizumab.

Drug interaction considerations in the therapeutic use of carbonic anhydrase inhibitors

INTRODUCTION

Carbonic anhydrase inhibitors (CAIs) of the sulfonamide and sulfamate type are clinically used drugs as diuretics, antiglaucoma, antiepileptic, antiobesity and anti-high altitude disease agents. Anticancer agents based on CAIs are also in clinical development for the management of hypoxic, metastatic tumors. Acetazolamide, methazolamide, dichlorophenamide, dorzolamide and brinzolamide are mainly used as antiglaucoma drugs, sulthiame, topiramate and zonisamide as antiepileptic/antiobesity agents, celecoxib and polmacoxib are dual carbonic anhydrase/cycloxygenase inhibitors. Girentuximab, a monoclonal antibody and SLC-0111, a sulfonamide inhibitor, are in clinical trials as anticancer agents.

AREAS COVERED

The drug interactions with many classes of pharmacological agents are reviewed. Some of these drugs, such as acetazolamide, topiramate and celecoxib show a large number of interactions with non-steroidal anti-inflammatory drugs (NSAIDs), diuretics, antiepileptics, immunosupressants, anticholinesterase drugs, β-blockers, anesthetics, oral contraceptives, anticancer agents, antifungals, anti-mycobacterials, lithium, metformin and clopidogrel.

EXPERT OPINION

The multiple drug interactions in which CAIs are involved should be carefully considered when such drugs are used in combination with the drug classes mentioned above, as the risks of developing toxicity and serious side effects if the dosages are not adjusted are high. There are also synergistic effects between CAIs and some NSAIDs, anticancer agents and benzodiazepines for the management of cystoid macular edema, some tumor types and neuropathic pain, respectively.

Acetazolamide for the treatment of idiopathic intracranial hypertension

Idiopathic intracranial hypertension (IIH) is characterized by an increase of intracranial pressure in the absence of neurologic tumors. The sulfonamide carbonic anhydrase (CA, EC 4.2.1.1) inhibitor (CAI) acetazolamide (AAZ), a compound developed in the 1950s as a diuretic drug and presently used as an antiglaucoma, antiepileptic and diuretic agent, is effective in the treatment of IIH. AAZ is a low nanomolar inhibitor of CA isoforms involved in cerebrospinal fluid (CSF) secretion. Inhibition of brain/choroid plexus CA II, IV, VA and XII leads to a decreased CSF fluid secretion and control of the intracranial pressure. Although many sulfonamide/sulfamate CAIs are in clinical use for decades, apparently only AAZ is being currently used clinically for IIH. We speculate that more lipophilic CAIs such as methazolamide, zonisamide or topiramate should lead to a more effective control of increased intracranial pressure, thus having the opportunity to become useful in the management of IIH.

New insights into carbonic anhydrase inhibition, vasodilation, and treatment of hypertensive-related diseases

Carbonic anhydrase (CA) and its inhibitors are relevant to many physiological processes and diseases. The enzyme is differentially expressed throughout the body, in concentration and subcellular location, and as 13 catalytically active isoforms. Blood vessels contain small amounts of CA, but the enzyme's role in vascular physiology and blood pressure regulation is uncertain. However, considerable recent evidence points to vasodilation by CA inhibitors. CA inhibition in vascular smooth muscle, endothelium, heart, blood cells, and nervous system could all contribute. It is equally plausible that other targets besides CA for all known CA inhibitors may account for their vascular effects. I will review this knowledge and important remaining gaps relating to treatment of hypertensive-related diseases with potent sulfonamide inhibitors, such as acetazolamide; but also the possibility that CA inhibition by thiazides and loop diuretics, although generally weaker, may have antihypertensive effects beyond their inhibition of renal sodium transporters.

Inhibitory effects of nitrite on the reactions of bovine carbonic anhydrase II with CO2 and bicarbonate consistent with zinc-bound nitrite

Carbonic anhydrase (CA) is a zinc enzyme that catalyzes hydration of carbon dioxide (CO2) and dehydration of bicarbonate in red blood cells, thus facilitating CO2 transport and excretion. Bovine CA II may also react with nitrite to generate nitric oxide, although nitrite is a known inhibitor of the CO2 hydration reaction. To address the potential in vivo interference of these reactions and the nature of nitrite binding to the enzyme, we here investigate the inhibitory effect of 10-30 mM nitrite on Michaelis-Menten kinetics of CO2 hydration and bicarbonate dehydration by stopped-flow spectroscopy. Our data show that nitrite significantly affects the apparent dissociation constant KM for CO2 (11 mM) and bicarbonate (221 mM), and the turnover number kcat for the CO2 hydration (1.467 × 10(6) s(-1)) but not for the bicarbonate dehydration (7.927 × 10(5) s(-1)). These effects demonstrate mixed and competitive inhibition for the reaction with CO2 and bicarbonate, respectively, and are consistent with nitrite binding to the active site zinc. The high apparent dissociation constant found here for CO2, bicarbonate and nitrite (16-120 mM) are all overall consistent with published data and reveal a large capacity of free enzyme available for binding each of the three substrates at their in vivo levels, with little or no significant interference among reactions. The low affinity of the enzyme for nitrite suggests that the in vivo interaction between red blood cell CA II and nitrite requires compartmentalization at the anion exchanger protein of the red cell membrane to be physiologically relevant.

Fluorinated pyrrolidines and piperidines incorporating tertiary benzenesulfonamide moieties are selective carbonic anhydrase II inhibitors

A series of substituted pyrrolidines and piperidines were synthesized using superacid HF/SbF5 chemistry. Investigated as inhibitors of several human carbonic anhydrase (hCA, EC 4.2.1.1) isoforms, i.e. the cytosolic hCA I and II as well as the tumor-associated transmembrane isoforms hCA IX and XII, these compounds showed a never yet reported selectivity toward the human carbonic anhydrase hCA II. In the tertiary benzenesulfonamide family, this class of inhibitors points out a new mechanism of action for human carbonic anhydrase II inhibition.

Discovery and characterization of novel selective inhibitors of carbonic anhydrase IX

Human carbonic anhydrase IX (CA IX) is highly expressed in tumor tissues, and its selective inhibition provides a potential target for the treatment of numerous cancers. Development of potent, highly selective inhibitors against this target remains an unmet need in anticancer therapeutics. A series of fluorinated benzenesulfonamides with substituents on the benzene ring was designed and synthesized. Several of these exhibited a highly potent and selective inhibition profile against CA IX. Three fluorine atoms significantly increased the affinity by withdrawing electrons and lowering the pKa of the benzenesulfonamide group. The bulky ortho substituents, such as cyclooctyl or even cyclododecyl groups, fit into the hydrophobic pocket in the active site of CA IX but not CA II, as shown by the compound's co-crystal structure with chimeric CA IX. The strongest inhibitor of recombinant human CA IX's catalytic domain in human cells achieved an affinity of 50 pM. However, the high affinity diminished the selectivity. The most selective compound for CA IX exhibited 10 nM affinity. The compound that showed the best balance between affinity and selectivity bound with 1 nM affinity. The inhibitors described in this work provide the basis for novel anticancer therapeutics targeting CA IX.

Exploring QSARs of some benzenesulfonamides incorporating cyanoacrylamide moieties as a carbonic anhydrase inhibitors (specifically against tumor-associated isoforms IX and XII)

Benzenesulfonamides incorporating cyanoacrylamide moieties with activity against tumour-associated human (h) isoforms hCA IX and XII (which are validated antitumor targets) were investigated for their quantitative structural activity relationships (QSAR). Multiple linear regression analysis was used to develop model relationships between molecular descriptors and inhibition constants (Ki). The molecular geometry optimization were performed on all molecules at DFT-B3LYP/6-311++G(d,p) level. Over 1250 molecular descriptors were calculated using Gaussian 09, Hyperchem and EDRAGON programs. Multiple linear regression equations have been developed and validated using leave-one-out cross-validated technique. The derived QSAR models are found to be statistically significant and show good predictive ability.