Academic literature on the topic 'Cerebral ischemia, adenosine, carbonic anhydrase'

Ischemic stroke is a leading cause of death and disability worldwide. The only pharmacological treatment available to date for cerebral ischemia is tissue plasminogen activator (t-PA) and the search for successful therapeutic strategies still remains a major challenge. The loss of cerebral blood flow leads to reduced oxygen and glucose supply and a subsequent switch to the glycolytic pathway, which leads to tissue acidification. Carbonic anhydrase (CA, EC 4.2.1.1) is the enzyme responsible for converting carbon dioxide into a protons and bicarbonate, thus contributing to pH regulation and metabolism, with many CA isoforms present in the brain. Recently, numerous studies have shed light on several classes of carbonic anhydrase inhibitor (CAI) as possible new pharmacological agents for the management of brain ischemia. In the present review we summarized pharmacological, preclinical and clinical findings regarding the role of CAIs in strokes and we discuss their potential protective mechanisms.

Abstract Inhibition of carbonic anhydrase (CA, EC 4.2.1.1) was clinically exploited for decades, as most modern diuretics were obtained considering as lead molecule acetazolamide, the prototypical CA inhibitor (CAI). The discovery and characterization of multiple human CA (hCA) isoforms, 15 of which being known today, led to new applications of their inhibitors. They include widely clinically used antiglaucoma, antiepileptic and antiobesity agents, antitumor drugs in clinical development, as well as drugs for the management of acute mountain sickness and idiopathic intracranial hypertension (IIH). Emerging roles of several CA isoforms in areas not generally connected to these enzymes were recently documented, such as in neuropathic pain, cerebral ischemia, rheumatoid arthritis, oxidative stress and Alzheimer’s disease. Proof-of-concept studies thus emerged by using isoform-selective inhibitors, which may lead to new clinical applications in such areas. Relevant preclinical models are available for these pathologies due to the availability of isoform-selective CAIs for all human isoforms, belonging to novel classes of compounds, such as coumarins, sulfocoumarins, dithiocarbamates, benzoxaboroles, apart the classical sulfonamide inhibitors. The inhibition of CAs from pathogenic bacteria, fungi, protozoans or nematodes started recently to be considered for obtaining anti-infectives with a new mechanism of action.

A series of benzenesulfonamides incorporating pyrazole- and pyridazinecarboxamides decorated with several bulky moieties has been obtained by original procedures. The new derivatives were investigated for the inhibition of four physiologically crucial human carbonic anhydrase (hCA, EC 4.2.2.1.1) isoforms, hCA I and II (cytosolic enzymes) as well as hCA IX and XII (transmembrane, tumor-associated isoforms). Examples of isoform-selective inhibitors were obtained for all four enzymes investigated here, and a computational approach was employed for explaining the observed selectivity, which may be useful in drug design approaches for obtaining inhibitors with pharmacological applications useful as antiglaucoma, diuretic, antitumor or anti-cerebral ischemia drugs.

Acetazolamide, a carbonic anhydrase inhibitor, has proved to be useful in the assessment of “vasodilatory capacity” in cerebrovascular disease. To obtain further information on the nature of interictal low-flow regions in migraine, we reinvestigated 20 asymptomatic patients suffering from migraine with aura ( n = 15) or without aura ( n = 5) and who had either minor ( n = 12) or marked ( n = 8) regional hypoperfusion when examined in a previous 99mTc-HMPAO SPECT investigation. These patients received acetazolamide IV prior to tracer application. In 14/20 cases regional hypoperfusion resolved. Three patients with migraine with aura had less pronounced regional hypoperfusion compared to baseline. No change in baseline hypoperfusion was detectable in three older patients. No further decreases in flow were measured. In contrast to patients with cerebrovascular ischemia, in whom acetazolamide usually enhances low-flow regions, vasodilatory capacity appears intact in most migraine patients with interictal regional hypoperfusion. Thus, the “acetazolamide test” might be useful in the differential diagnosis of migraine with aura from transient cerebrovascular ischemia.

A bicarbonate-stimulated adenylyl cyclase (AC) activity was found in ocular ciliary processes, which secrete the aqueous humor of the eye. Other fluid-transporting tissues also showed HCO3(-)-stimulated AC activity. Relative to basal, the response to 10 mM NaHCO3 was greatest in the particulate fraction of bovine ciliary processes, followed by bovine corneal endothelium, bovine choroid plexus, and rat kidney (medulla and cortex). However, no activity was detectable in bovine retina, cerebral cortex, or cerebellum. The activity in ciliary processes was present only in the particulate fraction, was supported by Mg2+ or Mn2+, was independent of GTP, and was additive to the stimulatory G protein-dependent AC response (via beta-adrenergic receptor stimulation). The activation of AC was dose dependent up to 100 mM bicarbonate with a 50% effective concentration of 2-3 mM. The HCO3- response was unaffected by 1 mM methazolamide, a carbonic anhydrase inhibitor, but HSO3- was a partially selective inhibitor compared with its effect on forskolin-stimulated AC activities. The presence of membrane-bound bicarbonate-sensitive AC in fluid-transporting tissues suggests an autoregulatory mechanism for intracellular HCO3- concentration acting via adenosine 3',5'-cyclic monophosphate in the control of membrane ion transporters.

Цель исследования - изучение возможности потенцирования нейропротекторного эффекта гиперкапнической гипоксии при помощи комбинации с фармакологическими активаторами основных механизмов, увеличивающих толерантность головного мозга к ишемии/гипоксии. Методика. Исследования проводились на 140 крысах-самцах Wistar, которые подвергались курсам респираторных воздействий гиперкапнической гипоксии (PO2 - 90 мм рт. ст.; PCO2 - 50 мм рт. ст.) в течении 5 сут по 30 мин ежедневно. После завершения курса тренировок крысам вводили фармакологические препараты (активатор аденозиновых рецепторов, блокатор карбоангидразы, активатор опиоидных рецепторов, блокатор ангиотензин-превращающего фермента) и через 24 ч производилась билатеральная окклюзия общих сонных артерий, а через 72 ч производился подсчет поврежденных/уцелевших клеток в СА1 регионе гиппокампа. Результаты. Морфологическая оценка выживаемости нейронов показала, что применение эналаприла усиливало нейропротекторный эффект гиперкапнической гипоксии, применение АТФ и даларгина не показало значимого прироста эффективности, а блокатор карбоангидразы ацетазоламид полностью устранял нейропротекторный эффект респираторных тренировок. Заключение. Выраженным потенцирующим эффектом на нейропротекцию, обусловленную респираторными тренировками с гиперкапнической гипоксией, обладает ее комбинация с ингибитором АПФ (эналаприлом). Aim. We studied the possibility of potentiating the neuroprotective effect of hypercapnic hypoxia using a combination with pharmacological activators of major mechanisms that increase the brain tolerance to ischemia/hypoxia. Methods. Studies were carried out on 140 male Wistar rats conditioned with respiratory hypercapnic hypoxia (PO2 - 90 mm Hg; PCO2 - 50 mm Hg) for 5 days, 30 min daily. After this exposure, the rats were injected with a drug (adenosine receptor activator (ATP), carbonic anhydrase blocker (acetazolamide), opioid receptor activator (dalargin), angiotensin converting enzyme (ACE) blocker (enalapril). 24 hrs later, the common carotid arteries were occluded bilaterally. 72 hrs after drug injection, the damaged/surviving cells in the CA1 region of the hippocampus were counted. Results. Morphological evaluation of neuronal survival showed that enalapril enhanced the neuroprotective effect of hypercapnic hypoxia. ATP and dalargin did not significantly increase this effect, and acetazolamide completely eliminated this neuroprotective effect. Conclusion. Thus, the neuroprotective effect of hypercapnic hypoxia conditioning was potentiated by its combination with an ACE inhibitor.

: Ischemia reperfusion injury is responsible for impaired graft functioning in organ transplants, cerebral dysfunction, ischemic heart diseases, systemic inflammatory response syndrome, gastrointestinal dysfunction, and multiple organ dysfunction syndromes. Intracellular pH is critical for cell survival in ischemia reperfusion injury. Sodium hydrogen exchanger I and carbonic anhydrase II are critical in regulation of intracellular pH. Inhibition of sodium hydrogen exchanger I and carbonic anhydrase II during reprfusion is found to ameliorate ischemia reperfusion injury separately. An attempt is made to synthesize dual inhibitors of sodium hydrogen exchanger and carbonic anhydrase to have better potential drug molecule in ischemia reperfusion injury treatment. The hydroxybenzotriazole is considered as a central pharmacophore for this dual activity and 12 derivatives are synthesized. All derivatives are tested for sodium hydrogen exchanger I and carbonic anhydrase II inhibitory activity. The tosylate derivative (12) is found to be the most potent derivative with IC50 158.7± 8.4 µM for carbonic anhydrase II and 31.07 ± 1.06 µM for sodium hydrogen exchanger I. Although the potency is less than standard drugs but this is the first report of dual inhibitor of carbonic anhydrase II and sodium hydrogen exchanger.

Background: Neurological disorders are composed of several diseases that affect the central and peripheral nervous system; among these are neurodegenerative diseases, which lead to neuronal death. Many of these diseases have treatment for the disease and symptoms, leading patients to use several drugs that cause side effects. Introduction: The search for new treatments has led to the investigation of multi-target drugs. Method: This review aimed to investigate in the literature the multi-target effect in neurological disorders through an in silico approach. Studies were reviewed on the diseases such as epilepsy, Alzheimer's disease, Amyotrophic Lateral Sclerosis (ALS), Huntington's disease, cerebral ischemia, and Parkinson's disease. Result: As a result, the study emphasize the relevance of research by computational techniques such as quantitative structure-activity relationship (QSAR) prediction models, pharmacokinetic prediction models, molecular docking, and molecular dynamics, besides presenting possible drug candidates with multi-target activity. Conclusion: It was possible to identify several targets with pharmacological activities. Some of these targets had diseases in common such as carbonic anhydrase, acetylcholinesterase, NMDA, and MAO being relevant for possible multi-target approaches.

Cerebral ischemia is a multifactorial pathology characterized by different events evolving in time. The acute injury, characterized by a massive increase of extracellular glutamate levels, is followed by activation of resident immune cells and production or activation of inflammation mediators. Although after ischemia precocious activation of immune cells may be neuroprotective and supportive for regeneration, protracted neuroinflammation is now recognized as the predominant mechanism of secondary brain injury progression. In this thesis, I investigated on the putative protective effects of the agonists at adenosine A2B receptor subtype and of the carbonic anhydrase inhibitors in a rat model of focal ischemia. Demyelination occurs in a variety of pathophysiological conditions of the Central Nervous System (CNS). The most serious demyelination occurs in multiple sclerosis but also following cerebral ischemia. Remyelination does occur but is limited especially in chronic disease stages. Therefore, strategies aimed at promoting remyelination, represent an attractive additional therapy in demyelinating pathologies. The remyelination process is mediated by oligodendrocyte progenitor cells (OPCs), a population of cycling cells which persists in the adult CNS, where they can differentiate into mature myelinating oligodendrocytes (OLs). Oligodendrocytes at all maturational stages, express each of the different adenosine receptor subtypes (A1R, A2AR, A2BR and A3R). A number of pathways have been identified that may contribute to ameliorate/impaired remyelination among them, the adenosinergic signaling and sphingosine kinase/sphingosine 1-phosphate signaling axis (SphK/S1P). Therefore, a first aim of my work was to investigate the role of A2BR and of SphK/S1P signaling in modulating cell proliferation and maturation in cultured OPCs and the presence of a possible cross-talk between S1P/SphK and A2BR signaling. We used two A2BR agonists: BAY60-6583 (BAY) and the newly synthesized drug P453, the S1P analog Fingolimod-phosphate (FTY720-P) and the inhibitors of SphK VPC96047 and VPC96091. In cultured OPCs, phosphorylation of the SphK1 (a SphK subtype), that is a hallmark of the activation state of the enzyme, was enhanced after 10 min treatment with BAY (10 µM). Chronic application (7 days) of BAY (1-10 µM) or of P453 (50-100 nM) in cultured medium reduced OPC differentiation, as indicated by the decrease of the two genes target MAG (myelin-associated glycoprotein) and Mbp3 (myelin basic protein 3), typically expressed by mature oligodendrocytes. FTY720-P (1 µM), mimicked the effect of 10 µM BAY on OPC maturation. On the contrary, VPC96047 (500 nM), a pan-SphK inhibitor, and VPC96091 (500 nM) a selective SphK1 inhibitor, increased MAG and Mbp3 levels. These effects were abolished in the presence of 10 µM BAY. After 48 hours A2BR silencing by RNA interference (RNAi), about 50% of the A2BR was downregulated. A2B downregulation increased OPC differentiation (as demonstrated by the CNPase increase). These data are support that A2BR inhibits OPC maturation. Moreover, cells transfected with A2B-siRNA showed a striking increase in S1P lyase levels, the enzyme responsible for of S1P catabolism. Our results demonstrated that the adenosine A2BR inhibit OPC differentiation in cultured OPCs. Moreover, the A2BR agonist BAY increases the expression of phosphorylated SphK1, indicating an interaction between SphK1 and A2BR activation. To date this is the first characterization of the role of adenosine A2BR in oligodendrocyte maturation and of a cross-talk between A2BR and SphK/S1P signaling axis in inhibiting OPC maturation. Extracellular adenosine concentration dramatically increases during cerebral ischemia and a protective role is recognized to adenosine by acting on A1 receptors. However, the use of adenosine A1 agonists is hampered by peripheral and central side effects. Few studies are present in literature on the role of A2B receptors in brain ischemia. A2B receptors are present on endothelial cells, neurons and astrocytes 24 hours after transient middle cerebral artery occlusion (tMCAo) in the rat. Data in the literature indicate that A2BR agonist BAY protect from endothelial leakage and blood brain barrier permeability 24 hours after focal ischemia To date there are no evidences in literature on the protective effects of A2B receptor agonists at more distant times from ischemia when a defined neuroinflammation develops. A further aim of my thesis was to investigate, in the model of focal transient cerebral ischemia (tMCAo) in the rat, the putative protective effects of the A2B receptor agonist, BAY 7 days after ischemia, when a clear inflammatory response has developed. Treatment with BAY, chronically administered (0.1 mg/kg i.p. for 7 days), improves the neurological deficit evaluated 1 and 5 and up to 7 days after tMCAo (p<0.0005-0.02). Seven days after ischemia, BAY has significantly reduced the infarct volume in cortex (p<0.001) and in striatum (p<0.05), has reconstituted the cortical and striatal cytoarchitecture and has reduced glial cell proliferation that was induced by the ischemic insult. BAY has significantly reverted the increase in number of damaged neurons (stained with the specific marker for neurons, NeuN+). Furthermore, BAY has reverted the strong pattern of microglia activation and reduced the loss of astrocyte. Seven days after ischemia, plasma inflammatory marker of brain damage TNF-α, is definitely increased while the levels of IL10 regulatory cytokine with anti-inflammatory action is decreased. Interestingly, BAY has reverted these modifications. Moreover, two days after ischemia, BAY has reduced granulocytes (evaluated as HIS-48+ cells) infiltration into brain ischemic areas. Our results demonstrated a protective effect of the chronic treatment of the A2BR agonist BAY 7 days after focal ischemia. The protective effects of BAY can be attributed to the stimulation of A2BR located both on central neural cells and on blood cells where A2BR are known to reduce activation and cytokine production thus attenuating neuroinflammation that develops days after ischemia. The evidence that hypoxic microenvironments elicit the expression of specific isoforms of carbonic anhydrase (CA), in particular CAIX and CAXII, through the hypoxia inducible factor, has allowed to hypothesize a possible CA relevance in ischemia. Recently it has been demonstrated that carbonic anhydrase inhibitors (CAIs), sulfonamide and coumarin, were able to improve neurological functionalities after cerebral ischemic insult. Preliminary data obtained in our laboratory in a model of in vitro ischemia demonstrated that two CAIs, acetazolamide and AN11-740 were able to prevent the appearance of anoxic depolarization (AD), a phenomenon strictly related to cell damage and death, 30 minutes after oxygen and glucose deprivation (OGD) condition in hippocampal slices. Based on this preliminary result, the aim of third study in my thesis was to investigate the putative protective effect of two CAIs, acetazolamide and AN11-740 in the in vivo model of permanent cerebral ischemia (pMCAo) in the rat. Sub-chronic treatment with acetazolamide and AN11-740 at the dose 4.4 mg/kg i.p. and 1.0 mg/kg i.p. significantly reduced the neurological deficit (p<0.0010.0001) and the infarct volume in cortex and striatum (p<0.001) 24 hours after ischemia. Treatment with the two CAIs, significantly reverted the decrease in the number of neurons (stained with the specific marker for neurons, NeuN+) induced by pMCAo. Twenty-four hours after focal ischemia, plasma inflammatory markers of brain damage TNF-α, is definitely increased while the levels of IL10 is decreased. The sub-chronic treatment with both carbonic anhydrase inhibitors, acetazolamide and AN11-740, didn’t modify significantly neither TNF-α or IL-10 plasma levels. Our results demonstrated a protective role of CA inhibitors at an early time (i.e. 24 hours) after in vivo ischemia. Likely protective effect of CAIs are attributable to a early direct effect of reduction of excitotoxicity in the first hours after brain ischemia.