Pure Adenosine Research Articles

Anti-Aging and Lightening Effects of Au-Decorated Zeolite-Based Biocompatible Nanocomposites in Epidermal Delivery Systems.

The main challenges in developing zeolites as cosmetic drug delivery systems are their cytotoxicities and the formation of drug-loading pore structures. In this study, Au-decorated zeolite nanocomposites were synthesized as an epidermal delivery system. Thus, 50 nm-sized Au nanoparticles were successfully deposited on zeolite 13X (super cage (α) and sodalite (β) cage structures) using the Turkevich method. Various cosmetic drugs, such as niacinamide, sulforaphane, and adenosine, were loaded under in vitro and in vivo observations. The Au-decorated zeolite nanocomposites exhibited effective cosmetic drug-loading efficiencies of 3.5 to 22.5 wt% under various conditions. For in vitro cytotoxic observations, B16F10 cells were treated with various cosmetic drugs. Niacinamide, sulforaphane, and adenosine-loaded Au-decorated zeolite nanocomposites exhibited clear cell viability of over 80%. Wrinkle improvement and a reduction in melanin content on the skin surface were observed in vivo. The adenosine delivery system exhibited an enhanced wrinkle improvement of 203% compared to 0.04 wt% of the pure adenosine system. The niacinamide- and sulforaphane-loaded Au-decorated zeolite nanocomposites decreased the skin surface melanin content by 123% and 222%, respectively, compared to 2 and 0.01 wt% of pure niacinamide and sulforaphane systems, respectively. As a result, Au-decorated zeolite nanocomposites show great potential as cosmetic drug epidermal delivery systems for both anti-aging and lightening effects.

Effect of purine nucleosides on growth performance, gut morphology, digestive enzymes, serum profile and immune response in broiler chickens

ABSTRACT1. This study was conducted to evaluate the effects of purine nucleosides on performance, gut morphology, intestinal enzymes and immunity functions in broiler chickens from 0 to 21 d of age.2. A total of 360 1-d-old male chickens (Cobb 500) were randomly assigned to 4 treatments with 6 replications. Experimental diets consisted of a control without any additives and diets containing 0.1% pure adenosine, 0.1% pure guanosine and 0.1% equal aliquots of pure adenosine and guanosine. Two birds per cage (12 birds per treatment) were killed on d 11 and 21 in order to obtain serum samples for lipid profile, jejunal samples for morphology and mucosal immunity, digestive enzymes for epithelial maturation, and bursa and spleen samples for relative weight of immune organs to live body weight.3. Birds receiving adenosine in their diets showed a significant increase in body weight and average daily gain and a significantly lower feed conversion ratio compared to the control birds. Villus height and width in jejunal samples also increased significantly in birds supplemented with adenosine. Although maltase was not affected by the experimental diets, adenosine increased alkaline phosphatase and aminopeptidase. Adenosine and its combination with guanosine boosted mucosal immunity as a result of increased IgA production. While there was no significant difference among treatments regarding the relative weight of the spleen, adenosine increased the relative weight of the bursa of Fabricius. Present results also showed that adding guanosine to broiler diets had no significant effects on growth, gut morphology, enzymes activity and immunological indices.4. In conclusion, the improvement in growth performance, gut morphology and immunity in birds receiving adenosine demonstrated that pure adenosine could be a beneficial feed additive for the poultry industry, while guanosine showed no significant improvement.

Adenosine dry powder inhalation for bronchial challenge testing, part 1: Inhaler and formulation development and in vitro performance testing

Dry powder administration of adenosine by use of an effective inhaler may be an interesting alternative to nebulisation of adenosine 5′-monophosphate in bronchial challenge testing, because of a shorter administration time and more consistent delivered fine particle dose over the entire dose range. In this study, we tested various powder formulations and classifier based dispersion principles and investigated the in vitro performance of the most promising formulation/classifier combination in a new test inhaler system. Spray-dried formulations of either pure adenosine (100%) or adenosine and lactose as diluent (1% and 10% adenosine) were prepared to cover the entire expected dose range for adenosine (0.01–20mg). All three powders, in all 12 suggested doses, dispersed well with the newly developed test inhaler with a multiple air jet classifier disperser, into aerosols with an average volume median diameter of 3.1μm (3.0–3.3μm). For eleven out of 12 dose steps, the fine particle fractions<5μm as percent of the loaded dose varied within the range of 67–80% (mean: 74%). The new test concept allows for more consistent aerosol delivery over the entire dose range with narrower size distributions than nebulisation and thus may improve adenosine administration in bronchial challenge testing.

Transferring Protection: Adenosine as the Lone Ranger?

Coronary effluent from a heart undergoing brief periods of ischemia and reperfusion that leads to the cytoprotection of ischemic preconditioning decreases injury when administered before ischemia to a second heart; the “transfer of cardioprotection” phenomena [1]. In the current issue of Cardiovascular Drugs and Therapy, Dr. Leung and colleagues replicate the “transfer of cardioprotection” in an isolated rabbit heart model [2]. The authors hypothesize that increased adenosine content in coronary effluent from the first ischemic preconditioned heart is the key mediator of the protection transferred to the second heart. Four lines of evidence support their hypothesis: (1) the content of adenosine in collected coronary effluent from preconditioned hearts is dramatically increased; (2) the phenomena of “transfer protection” is blocked by a non-selective adenosine receptor inhibitor; (3) direct addition of adenosine into coronary effluent from nonpreconditioned hearts provides a similar reduction in infarct size compared to coronary effluent from the preconditioned hearts; (4) mitochondrial function is improved in hearts treated by coronary effluent from preconditioned hearts. They conclude that the “transfer of protection” is mediated by an increased adenosine content in coronary effluent through preservation of mitochondrial integrity. Activation of adenosine receptors provides solid cardioprotection in experimental hearts following ischemiareperfusion [2–4]. Adenosine treatment also tended to improve outcome in a meta-analysis of clinical trials [5], though outcomes did not reach statistical significance [5], mirroring the failure to demonstrate benefit in the largest single trial [6]. Ischemic damage to mitochondria is a key mechanism of cardiac injury during reperfusion [7]. Protection of mitochondria during ischemia decreases cardiac injury during the subsequent reperfusion [8]. In Dr. Leung’s study, perfusion of collected coronary effluent from preconditioned hearts before ischemia improved the mitochondrial function in the recipient heart, supporting the notion that “transfer cardioprotection” is mediated by mitigating mitochondrial damage during ischemia-reperfusion. Although addition of adenosine into control coronary effluent reduces the infarct size to a similar extent as treatment by coronary effluent from preconditioned hearts, there are different effects on mitochondrial function between these two treatments. Ischemic preconditioning protects mitochondria through inhibition of mitochondrial permeability transition pore (MPTP) [9]. The MPTP is also inhibited in hearts treated by ischemic postconditioning [10, 11]. In the current study, mitochondrial respiration and the integrity of outer mitochondrial membrane are significantly improved in coronary effluent treated hearts. However, pure adenosine treatment improved outer membrane integrity but did not protect the electron transport chain. The adenosine treatment results in a better coupled mitochondrial respiration through an unclear mechanism. These results suggest that adenosine is not the sole substance that induces the transferred protection. Other molecular entities, especially small peptides, may contribute to this protection [12]. The preliminary proteomic study is an exciting step to further clarify the molecular targets in this Q. Chen : E. J. Lesnefsky Department of Medicine (Division of Cardiology, Pauley Heart Center), Virginia Commonwealth University, Richmond, VA 23298, USA

Benefit of nicorandil using an immunologic murine model of experimental colitis

AbstractInflammatory bowel disease (IBD) is a chronic inflammatory condition with an unknown etiology. Nicorandil, a potassium channel opener, has been used for many years for the treatment of angina. Recently, it has been shown that nicorandil possesses some novel traits such as anti-apoptotic, gastroprotective, free radical scavenging, and anti-inflammatory properties. Therefore, we set out to examine the possible beneficial effect of nicorandil in a rat model of IBD. Colitis was induced by rectal administration of 2,4,6-trintrobenzene sulphonic acid (TNBS) into rats. Groups of animals used in this study were sham, control, and exposure to dexamethasone, nicorandil, glibenclamid (a pure adenosine triphosphate sensitive potassium channel (KATP) blocker), or nicorandil plus glibenclamid. Drugs were administered by gavage and animals were sacrificed after 7 days. Biochemical markers, including TNF-α and IL-1β, ferric reducing/antioxidant power (FRAP), myeloperoxidase (MPO) activity and thiobarbitoric acid-reactive substance (TBARS), were measured in the homogenate of colonic tissue. Results indicate that nicorandil significantly reduces macroscopic and histological damage induced by TNBS. Nicorandil diminishes MPO activity and levels of TBARS, TNF-∢, and IL-1β in damaged colonic tissue with a concomitant increase in FRAP value (P&lt;0.01). These effects were not reversed by coadministration of glibenclamide. In conclusion, nicorandil is able to ameliorate experimental IBD with a dose in which it does not show any anti-hypertensive effect, and the mechanism of which is partially or totally independent from KATP channels. It is hypothesized that nitric oxide donation and free-radical scavenging properties of nicorandil upregulate endothelial nitric oxide synthase may be responsible for this phenomenon. These findings suggest that nicorandil can be useful in treatment of IBD, although further investigations are needed to elucidate the mechanisms involved.

Antagonism of adenosine receptors by caffeine and caffeine metabolites in equine forebrain tissues.

To determine the presence of adenosine receptor subtypes A1 and A2a in equine forebrain tissues and to characterize the interactions of caffeine and its metabolites with adenosine receptors in the CNS of horses. Brain tissue specimens obtained during necropsy from 5 adult male research horses. Membrane-enriched homogenates from cerebral cortex and striatum were evaluated by radioligand binding assays with the A1-selective ligand [3H]DPCPX and the A2a-selective ligand [3H]ZM241385. Functional responses to adenosine receptor agonists and antagonists were determined by a nucleotide exchange assay using [35S]-guanosine 5'-(gamma-thio) triphosphate ([35S]GTPgammaS). Saturable high affinity [3H]DPCPX binding (A1) sites were detected in cerebral cortex and striatum, whereas high-affinity [3H]ZM241385 binding (A2a) sites were detected only in striatum. Caffeine and related methylxanthines had similar binding affinities at A1 and A2a sites with rank orders of drug binding affinities (theophylline > paraxanthine > or = caffeine >> theobromine) similar to other species. [35S]GTPgammaS exchange revealed that caffeine and its metabolites act as pure adenosine receptor antagonists at concentrations that correspond to A1 and A2a receptor binding affinities. Results of our study affirm the presence of guanine nucleotide binding protein linked adenosine receptors (ie, high-affinity A1 and A2a adenosine receptors) in equine forebrain tissues and reveal the antagonistic actions by caffeine and several biologically active caffeine metabolites. Antagonism of adenosine actions in the equine CNS by these stimulants may be responsible for some central actions of methylxanthine drugs, including motor stimulation and enhanced racing performance.

Adenosine, AMP, and protein phosphatase activity in sandfly saliva.

As they probe the skin for blood, sand flies inject saliva that prevents hemostasis. Sand fly saliva also promotes leishmaniasis by suppressing immunologic functions of macrophages. Saliva of Phlebotomus papatasi, the vector of Old World cutaneous leishmaniasis, contains adenosine and AMP. We show that Ph. papatasi saliva as well as pure adenosine down-regulate the expression of the inducible nitric oxide (NO) synthase gene in activated macrophages. In addition Ph. papatasi, but not Lutzomyia longipalpis, saliva inhibits the production of NO. Taken together, these data suggest that salivary adenosine is responsible for the down-regulation of NO synthesis. Saliva of both genera Phlebotomus and Lutzomyia contains significant levels of endogenous protein phosphatase-1/2A-like activity that is heat labile, inhibitable by okadaic acid and calyculine a, and does not require divalent cations.

Intervention with spinal NMDA, adenosine, and NO systems for pain modulation.

Understanding of the complex pharmacology of the spinal cord may lead to rational advances in pain treatment. It appears that a number of specific neurochemical mechanisms exist, by which spinally administered receptor selective agents may modify nociceptive transmission. Spinal administration of pure competitive N-methyl-D-aspartate (NMDA) antagonists affects only hyperpathic pain components, i.e. with signs of central sensitization, and most probably has a very limited role in postoperative pain treatment. On the other hand, it is well established that the non-competitive NMDA-antagonist ketamine gives good postoperative analgesia, probably by cerebral mechanisms also affecting other sensory modalities. Pure adenosine A1-receptor agonism at the spinal level mainly affects sensory allodynia to vibration, and is probably no alternative for postoperative pain treatment. In contrast, i.v. infusions of the non-selective A1/A2-receptor agonist adenosine given during a surgical procedure seem to decrease postoperative pain and requirements for postoperative analgesia. This apparent contradiction must be analysed further. Several drugs commonly used to treat postoperative pain, such as opioids, NSAIDs, ketamine and paracetamol, are linked to nitric oxide (NO) in their mechanism of action. The biosynthesis of NO in the central nervous system (CNS) is tonically involved in the nociceptive processing.

Effects of Calaguala and an active principle, adenosine, on platelet activating factor.

Calaguala, an extract from the fern Polypodium decumanum, has been used to treat psoriasis and related immunological disorders. In an effort to explain Calaguala's medicinal effects the inhibitory activity of the extract in two platelet activating factor (PAF) related models has been investigated. In the first model, PAF was used to induce release of the proteolytic enzyme elastase in human neutrophils. Calaguala inhibited this effect with an IC50 of 0.1 mg/ml. The known PAF antagonist ginkgolide BN 52021 was used as a positive control and had an IC50 of 0.034 mg/ml. In the second model the inhibition of biosynthesis of PAF in neutrophils using lyso-PAF and labeled acetyl-CoA was studied. Also in this assay Calaguala showed a dose-dependent activity, the IC50 being 0.2 mg/ml. Since recent findings have indicated that PAF might be involved in the pathogenesis of psoriasis, it is possible that the activity shown by Calaguala in these PAF assays may contribute to the clinical efficacy of the extract. The PAF induced exocytosis assay was further used to guide the fractionation of the crude extract. From the acetone supernatant the nucleoside adenosine was isolated as an active principle. Pure adenosine dose-dependently inhibited the exocytosis induced by PAF (IC50 = 0.024 micrograms/ml) but was inactive in the biosynthesis assay. Adenosine is most probably one of the bioactive compounds of Calaguala responsible for its therapeutic properties.

Methylxanthines inhibit glucose transport in rat adipocytes by two independent mechanisms

In summary, this study characterized the biphasic inhibition of fat cell glucose transport by the lipolytic agents caffeine and theophylline. Like the lipolytic drug forskolin, both methylxanthines produced an immediate inhibition of glucose transport that was not seen with 8-phenyltheophylline, a pure adenosine receptor antagonist. The immediate inhibition was therefore not mediated by the adenosine receptor antagonism but seems to be due to a direct interaction with the hexose transporter. This conclusion is supported by the immediate onset of the inhibition and additionally by the interference of theophylline and caffeine with the binding of cytochalasin B, a ligand of the glucose transporter that binds to an intracellular site of the transporter molecule. In addition, a second, delayed inhibitory effect of theophylline and caffeine on glucose transport was observed. This portion shared many aspects of the inhibitory effect of lipolytic hormones. It developed over a period of about 5 min and was antagonized by the simultaneous addition of the antilipolytic hormone PGE2. This component of transport inhibition could be attributed to the antagonistic effect of methylxanthines at the fat cell A1-adenosine receptor since it was also seen with 8-phenyltheophylline. This conclusion is further supported by data showing that the removal of endogenous adenosine with adenosine deaminase resulted in a comparable 25-30% inhibition of insulin-stimulated glucose transport. In addition, the time course of glucose transport inhibition by the subsequent addition of adenosine deaminase is similar to that of the delayed portion of the inhibition seen with theophylline and caffeine. Both treatments produced their maximal inhibition after 5 min. In conclusion, the methylxanthines theophylline and caffeine inhibit glucose transport by a combination of two different modes of action. The immediate major component is mediated via a direct interaction with the hexose transporter whereas the delayed component involves adenosine receptor antagonism and thereby the interaction with G-proteins.

Mechanism of the Antiplatelet Action of Dipyridamole in Whole Blood: Modulation of Adenosine Concentration and Activity

Dipyridamole inhibits platelet aggregation in whole blood at lower concentrations than in plasma. The blood cells responsible for increased effectiveness in blood are the erythrocytes. Using the impedance aggregometer we have carried out a series of pharmacological studies in vitro to elucidate the mechanism of action of dipyridamole in whole blood. Adenosine deaminase, an enzyme breaking down adenosine, reverses the inhibitory action of dipyridamole. Two different adenosine receptor antagonists, 5'-deoxy-5'-methylthioadenosine and theophylline, also partially neutralize the activity of dipyridamole in blood. Enprofylline, a phosphodiesterase inhibitor with almost no adenosine receptor antagonistic properties, potentiates the inhibition of platelet aggregation by dipyridamole. An inhibitory effect similar to that of dipyridamole can be obtained combining a pure adenosine uptake inhibitor (RE 102 BS) with a pure phosphodiesterase inhibitor (MX-MB 82 or enprofylline). Mixing the blood during preincubation with dipyridamole increases the degree of inhibition. Lowering the haematocrit slightly reduces the effectiveness. Although we did not carry out direct measurements of adenosine levels, the results of our pharmacological studies clearly show that dipyridamole inhibits platelet aggregation in whole blood by blocking the reuptake of adenosine formed from precursors released by red blood cells following microtrauma. Its slight phosphodiesterase inhibitory action potentiates the effects of adenosine on platelets.