The role of adenosine A1 receptor agonist in adenosine augmentation therapy for patients with refractory epilepsy in Sturge-Weber syndrome: An in vitro electrophysiological study.

PURPOSES: This study was to further explore the adenosine dysfunction in refractory epilepsy in Sturge-Weber Syndrome (SWS), to evaluate the neuronal-level effect of the A1 receptor (A1R) agonist on both excitatory pyramidal neurons and inhibitory interneurons, to discuss the possibility of adenosine augmentation therapy (AAT) using A1R agonist for treating refractory epilepsy in SWS. MATERIALS AND METHODS: The intrinsic excitatory properties of pyramidal cells (PCs) and fast-spiking (FS) interneurons from human brain tissues with SWS cases and malformations of cortical development (MCD) cases were compared using electrophysiology. With application of either A1R agonist or antagonist, the neuronal-level effect of A1R agonist was evaluated in vitro in PCs and FS interneurons from SWS cases and MCD cases. RESULTS: No significant difference of passive excitatory properties of PCs and FS interneurons was found between SWS cases and MCD cases. In terms of the neuronal-level effect of A1R agonist, with 22.88 ±â€¯1.12% percentage of decreased frequency, FS interneurons showed relatively highest sensitivity of A1R agonist application, compared with PCs from SWS cases and FS interneurons and PCs from MCD cases. CONCLUSION: Our results supported the potential of AATs using A1R agonist to be a novel therapy for reducing life burden from patients with refractory epilepsy in SWS, with application to epileptic generation region but not propagation region.

Inhibition of adenosine A1 receptors abolished the nutritional ketosis-evoked delay in the onset of isoflurane-induced anesthesia in Wistar Albino Glaxo Rijswijk rats.

BACKGROUND: It has been demonstrated that administration of exogenous ketone supplement ketone salt (KS) and ketone ester (KE) increased blood ketone level and delayed the onset of isoflurane-induced anesthesia in different rodent models, such as Wistar Albino Glaxo Rijswijk (WAG/Rij) rats. The modulatory effect of adenosinergic system may have a role in the ketone supplementation-evoked effects on isoflurane-generated anesthesia. Thus, we investigated whether adenosine receptor antagonists can modulate the effect of exogenous ketone supplements on the onset of akinesia induced by isoflurane. METHODS: To investigate the effect of exogenous ketone supplements on anesthetic induction we used ketone supplement KE, KS, KEKS (1:1 mix of KE and KS), KSMCT and KEMCT (1:1 mix of KS and KE with medium chain triglyceride/MCT oil, respectively) in WAG/Rij rats. Animals were fed with standard diet (SD), which was supplemented by oral gavage of different ketone supplements (2.5 g/kg/day) for 1 week. After 7 days, isoflurane (3%) was administered for 5 min and the time until onset of isoflurane-induced anesthesia (time until immobility; light phase of anesthesia: loss of consciousness without movement) was measured. Changes in levels of blood ß-hydroxybutyrate (ßHB), blood glucose and body weight of animals were also recorded. To investigate the putative effects of adenosine receptors on ketone supplements-evoked influence on isoflurane-induced anesthesia we used a specific adenosine A1 receptor antagonist DPCPX (intraperitoneally/i.p. 0.2 mg/kg) and a selective adenosine A2A receptor antagonist SCH 58261 (i.p. 0.5 mg/kg) alone as well as in combination with KEKS. RESULTS: Significant increases were demonstrated in both blood ßHB levels and the number of seconds required before isoflurane-induced anesthesia (immobility) after the final treatment by all exogenous ketone supplements. Moreover, this effect of exogenous ketone supplements positively correlated with blood ßHB levels. It was also demonstrated that DPCPX completely abolished the effect of KEKS on isoflurane-induced anesthesia (time until immobility), but not SCH 58261. CONCLUSIONS: These findings strengthen our previous suggestion that exogenous ketone supplements may modulate the isoflurane-induced onset of anesthesia (immobility), likely through A1Rs.

The influence of selective A1 and A2A receptor antagonists on the antidepressant-like activity of moclobemide, venlafaxine and bupropion in mice.

OBJECTIVE: The main goal of our study was to investigate whether a selective antagonism of the adenosine A1 or A2A receptors is able to enhance the antidepressant activity of commonly prescribed drugs. MATERIALS AND METHODS: All experiments were carried out on male Albino Swiss mice. The forced swim test and the tail suspension test were used to evaluate the antidepressant-like potential. Drug concentrations in animals' serum and brains were measured by high-performance liquid chromatography. KEY FINDINGS: The antidepressant potential of moclobemide (1.5 mg/kg), venlafaxine (1 mg/kg) and bupropion (10 mg/kg) was enhanced by a co-administration with 3,7-dimethyl-1-propargylxanthine (DMPX; an antagonist of adenosine A2A receptors; 3 mg/kg) or 8-cyclopentyl-1,3-dipropylxanthine (an antagonist of adenosine A1 receptors; 1 mg/kg). However, significant interactions between the tested substances were detected only in the experiments with DMPX. The nature of the observed interplays is rather pharmacodynamic than pharmacokinetic, because neither serum nor brain concentrations of the used drugs were significantly increased. CONCLUSIONS: Blockage of the adenosine receptors (particularly the A2A subtypes) could be considered in future as a novel, promising part of the combined antidepressant therapy. However, further studies on this subject are needed.

Individual differences in the energizing effects of caffeine on effort-based decision-making tests in rats.

Motivated behavior is characterized by activation and high work output. Nucleus accumbens (Nacb) modulates behavioral activation and effort-based decision-making. Caffeine is widely consumed because of its energizing properties. This methylxanthine is a non-selective adenosine A1/A2A receptor antagonist. Adenosine receptors are highly concentrated in Nacb. Adenosine agonists injected into Nacb, shift preference towards low effort alternatives. The present studies characterized effort-related effects of caffeine in a concurrent progressive ratio (PROG)/free reinforcer choice procedure that requires high levels of work output, and generates great variability among different animals. Male Sprague-Dawley rats received an acute dose of caffeine (2.5-20.0 mg/kg, IP) and 30 min later were tested in operant boxes. One group was food-restricted and had to lever pressed for high carbohydrate pellets, another group was non-food-restricted and lever pressed for a high sucrose solution. Caffeine (2.5 and 5.0 mg/kg) increased lever pressing in food-restricted animals that were already high responders. However, in non-restricted animals, caffeine (5.0 and 10.0 mg/kg) increased work output only among low responders. In fact, caffeine (10.0 and 20.0 mg/kg) in non-restricted animals, reduced lever pressing among high responders in the PROG task, and also in a different group of animals lever pressing in an easy task (fixed ratio 7 schedule) that uniformly generates high levels of responding. Caffeine did not modify sucrose preference or consumption under free access conditions. Thus, when animals do not have a homeostatic need, caffeine can help those not very intrinsically motivated to work harder for a more palatable reward. However, caffeine can disrupt performance of animals intrinsically motivated to work hard for a better reward.

Restoring auditory cortex plasticity in adult mice by restricting thalamic adenosine signaling.

Circuits in the auditory cortex are highly susceptible to acoustic influences during an early postnatal critical period. The auditory cortex selectively expands neural representations of enriched acoustic stimuli, a process important for human language acquisition. Adults lack this plasticity. Here we show in the murine auditory cortex that juvenile plasticity can be reestablished in adulthood if acoustic stimuli are paired with disruption of ecto-5'-nucleotidase-dependent adenosine production or A1-adenosine receptor signaling in the auditory thalamus. This plasticity occurs at the level of cortical maps and individual neurons in the auditory cortex of awake adult mice and is associated with long-term improvement of tone-discrimination abilities. We conclude that, in adult mice, disrupting adenosine signaling in the thalamus rejuvenates plasticity in the auditory cortex and improves auditory perception.

Risk-based evaluation of efficacy of rolofylline in patients hospitalized with acute heart failure - Post-hoc analysis of the PROTECT trial.

BACKGROUND: The selective adenosine A1 receptor antagonist rolofylline showed a neutral overall result on clinical outcomes in the PROTECT trial. However, we hypothesized that response to rolofylline treatment could be influenced by underlying clinical risk. METHODS: We performed a post-hoc analysis of the PROTECT trial - a large, double-blind, randomized, placebo-controlled trial that enrolled 2033 patients. Baseline risk of 180-day all-cause mortality was estimated using a previously published 8-item model. Evaluation of efficacy of rolofylline across subpopulations defined based on estimated risk of mortality was performed using subpopulation treatment effect pattern plot (STEPP) analysis. Findings were validated in an independent cohort of acute heart failure patients. RESULTS: Median estimated risk of mortality was 13.0%, IQR [8.0%-23.0%] and was comparable between the rolofylline and placebo arms. In low to intermediate risk subgroups of patients, rolofylline was associated with a higher rate of 180-day all-cause mortality (11.9% in the rolofylline versus 8.4% in the placebo arms, p=0.050). In the high risk subgroup of patients, particularly those with estimated risk of mortality between 20% and 30%, 180-day all-cause mortality rate was markedly lower in the rolofylline arm (18.4% in the rolofylline versus 34.0% in the placebo arms, p=0.003). The trend towards potential harm with rolofylline treatment in the low to intermediate risk subpopulations and significant benefit in high risk patients was also observed in the validation cohort. CONCLUSION: Our findings suggest that selective adenosine A1 receptor antagonism could be harmful in low risk acute heart failure patients, while it might significantly benefit higher risk patients.

Positive allosteric modulation of A1 adenosine receptors as a novel and promising therapeutic strategy for anxiety.

Activation of A1 adenosine receptors (ARs) has been associated with anxiolytic-like effects in different behavioral tests, but development of A1AR agonists for therapeutic use has been hampered, most likely due to the presence of side effects. With the aim to identify a safer approach for the treatment of anxiety, we investigated, in mice, the anxiolytic-like properties of a novel A1AR positive allosteric modulator, TRR469. Acute administration of TRR469 (0.3-3 mg/kg) resulted in robust anxiolytic-like effects in the elevated plus maze, the dark/light box, the open field and the marble burying tests. The magnitude of the anxiolytic action of TRR469 was comparable to that obtained with benzodiazepine diazepam (1 mg/kg). The use of the A1AR antagonist DPCPX (3 mg/kg) suggested that the effects of TRR469 were mediated by this receptor subtype. In contrast to diazepam, the novel positive allosteric modulator did not potentiate the sedative effect of ethanol (3.5 g/kg) evaluated by the loss of righting reflex. While diazepam produced motor coordination impairment in the rotarod test, this effect being enhanced by the presence of ethanol (1.5 g/kg), TRR469 did not elicit locomotor disturbances either when administered alone or in the presence of ethanol. In vitro, TRR469 was able to increase the number of A1AR recognizable by the agonist radioligand [3H]-CCPA in mouse brain regions involved in emotional processes. TRR469 markedly increased the affinity of the agonist CCPA, suggesting the capability, in vivo, to increase the affinity of endogenous adenosine. Taken together, these findings indicate that the positive allosteric modulation of A1AR may represent a promising approach for the treatment of anxiety-related disorders.

Modulation of dopamine-mediated facilitation at the neuromuscular junction of Wistar rats: A role for adenosine A1/A2A receptors and P2 purinoceptors.

This study aims to understand how dopamine and the neuromodulators, adenosine and adenosine triphosphate (ATP) modulate neuromuscular transmission. Adenosine and ATP are well-recognized for their regulatory effects on dopamine in the central nervous system. However, if similar interactions occur at the neuromuscular junction is unknown. We hypothesize that the activation of adenosine A1/A2A and/or P2 purinoceptors may influence the action of dopamine on neuromuscular transmission. Using the rat phrenic nerve hemi-diaphragm, we assessed the influence of dopamine, adenosine and ATP on the height of nerve-evoked muscle twitches. We investigated how the selective blockade of adenosine A1 receptors (2.5nM DPCPX), adenosine A2A receptors (50nM CSC) and P2 purinoceptors (100µM suramin) modified the effects of dopamine. Dopamine alone increased indirect muscle contractions while adenosine and ATP either enhanced or depressed nerve-evoked muscle twitches in a concentration-dependent manner. The facilitatory effects of 256µM dopamine were significantly reduced to 29.62±2.79% or 53.69±5.45% in the presence of DPCPX or CSC, respectively, relative to 70.03±1.57% with dopamine alone. Alternatively, the action of 256µM dopamine was potentiated from 70.03±1.57, in the absence of suramin, to 86.83±4.36%, in the presence of suramin. It can be concluded that the activation of adenosine A1 and A2A receptors and P2 purinoceptors potentially play a central role in the regulation of dopamine effects at the neuromuscular junction. Clinically this study offers new insights for the indirect manipulation of neuromuscular transmission for the treatment of disorders characterized by motor dysfunction.

Adenosine A1 Receptor Protects Against Cisplatin Ototoxicity by Suppressing the NOX3/STAT1 Inflammatory Pathway in the Cochlea.

Cisplatin is a commonly used antineoplastic agent that produces ototoxicity that is mediated in part by increasing levels of reactive oxygen species (ROS) via the NOX3 NADPH oxidase pathway in the cochlea. Recent studies implicate ROS generation in mediating inflammatory and apoptotic processes and hearing loss by activating signal transducer and activator of transcription (STAT1). In this study, we show that the adenosine A1 receptor (A1AR) protects against cisplatin ototoxicity by suppressing an inflammatory response initiated by ROS generation via NOX3 NADPH oxidase, leading to inhibition of STAT1. Trans-tympanic administration of the A1AR agonist R-phenylisopropyladenosine (R-PIA) inhibited cisplatin-induced ototoxicity, as measured by auditory brainstem responses and scanning electron microscopy in male Wistar rats. This was associated with reduced NOX3 expression, STAT1 activation, tumor necrosis factor-α (TNF-α) levels, and apoptosis in the cochlea. In vitro studies in UB/OC-1 cells, an organ of Corti immortalized cell line, showed that R-PIA reduced cisplatin-induced phosphorylation of STAT1 Ser(727) (but not Tyr(701)) and STAT1 luciferase activity by suppressing the ERK1/2, p38, and JNK mitogen-activated protein kinase (MAPK) pathways.R-PIA also decreased the expression of STAT1 target genes, such as TNF-α, inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) and reduced cisplatin-mediated apoptosis. These data suggest that the A1AR provides otoprotection by suppressing NOX3 and inflammation in the cochlea and could serve as an ideal target for otoprotective drug therapy. SIGNIFICANCE STATEMENT: Cisplatin is a widely used chemotherapeutic agent for the treatment of solid tumors. Its use results in significant and permanent hearing loss, for which no US Food and Drug Administration-approved treatment is currently available. In this study, we targeted the cochlear adenosine A1 receptor (A1AR) by trans-tympanic injections of the agonist R-phenylisopropyladenosine (R-PIA) and showed that it reduced cisplatin-induced inflammation and apoptosis in the rat cochlea and preserved hearing. The mechanism of protection involves suppression of the NOX3 NADPH oxidase enzyme, a major target of cisplatin-induced reactive oxygen species (ROS) generation in the cochlea. ROS initiates an inflammatory and apoptotic cascade in the cochlea by activating STAT1 transcription factor, which is attenuated byR-PIA. Therefore, trans-tympanic delivery of A1AR agonists could effectively treat cisplatin ototoxicity.

Transporter Protein-Coupled DPCPX Nanoconjugates Induce Diaphragmatic Recovery after SCI by Blocking Adenosine A1 Receptors.

Respiratory complications in patients with spinal cord injury (SCI) are common and have a negative impact on the quality of patients' lives. Systemic administration of drugs that improve respiratory function often cause deleterious side effects. The present study examines the applicability of a novel nanotechnology-based drug delivery system, which induces recovery of diaphragm function after SCI in the adult rat model. We developed a protein-coupled nanoconjugate to selectively deliver by transsynaptic transport small therapeutic amounts of an A1 adenosine receptor antagonist to the respiratory centers. A single administration of the nanoconjugate restored 75% of the respiratory drive at 0.1% of the systemic therapeutic drug dose. The reduction of the systemic dose may obviate the side effects. The recovery lasted for 4 weeks (the longest period studied). These findings have translational implications for patients with respiratory dysfunction after SCI. SIGNIFICANCE STATEMENT: The leading causes of death in humans following SCI are respiratory complications secondary to paralysis of respiratory muscles. Systemic administration of methylxantines improves respiratory function but also leads to the development of deleterious side effects due to actions of the drug on nonrespiratory sites. The importance of the present study lies in the novel drug delivery approach that uses nanotechnology to selectively deliver recovery-inducing drugs to the respiratory centers exclusively. This strategy allows for a reduction in the therapeutic drug dose, which may reduce harmful side effects and markedly improve the quality of life for SCI patients.

Dual A1/A2B Receptor Blockade Improves Cardiac and Renal Outcomes in a Rat Model of Heart Failure with Preserved Ejection Fraction.

Heart failure with preserved ejection fraction (HFpEF) is prevalent and often accompanied by metabolic syndrome. Current treatment options are limited. Here, we test the hypothesis that combined A1/A2B adenosine receptor blockade is beneficial in obese ZSF1 rats, an animal model of HFpEF with metabolic syndrome. The combined A1/A2B receptor antagonist 3-[4-(2,6-dioxo-1,3-dipropyl-7H-purin-8-yl)-1-bicyclo[2.2.2]octanyl]propanoic acid (BG9928) was administered orally (10 mg/kg/day) to obese ZSF1 rats (n = 10) for 24 weeks (from 20 to 44 weeks of age). Untreated ZSF1 rats (n = 9) served as controls. After 24 weeks of administration, BG9928 significantly lowered plasma triglycerides (in mg/dl: control group, 4351 ± 550; BG9928 group, 2900 ± 551) without adversely affecting plasma cholesterol or activating renin release. BG9928 significantly decreased 24-hour urinary glucose excretion (in mg/kg/day: control group, 823 ± 179; BG9928 group, 196 ± 80) and improved oral glucose tolerance, polydipsia, and polyuria. BG9928 significantly augmented left ventricular diastolic function in association with a reduction in cardiac vasculitis and cardiac necrosis. BG9928 significantly reduced 24-hour urinary protein excretion (in mg/kg/day: control group, 1702 ± 263; BG9928 group, 1076 ± 238), and this was associated with a reduction in focal segmental glomerulosclerosis, tubular atrophy, tubular dilation, and deposition of proteinaceous material in the tubules. These findings show that, in a model of HFpEF with metabolic syndrome, A1/A2B receptor inhibition improves hyperlipidemia, exerts antidiabetic actions, reduces HFpEF, improves cardiac histopathology, and affords renal protection. We conclude that chronic administration of combined A1/A2B receptor antagonists could be beneficial in patients with HFpEF, in particular those with comorbidities such as obesity, diabetes, and dyslipidemias.

Duración del tratamiento antiagregante plaquetario combinado doble tras la implantación de stents farmacoactivos: el jurado continúa reunido / Duration of dual antiplatelet therapy after drug-eluting stents implantation: the jury is still out

No disponible

Terapia antiplaquetaria doble de 6 o de 12 meses tras implante de stents farmacoactivos de nueva generación: análisis emparejado de los registros ESTROFA-DAPT y ESTROFA-2 / Dual antiplatelet therapy for 6 months vs 12 months after new-generation drug-eluting stent implantation: matched analysis of ESTROFA-DAPT and ESTROFA-2

Introducción y objetivos: El periodo de uso recomendado del tratamiento antiagregante plaquetario combinado doble tras implante de stents farmacoactivos va de los 6 a los 12 meses o más. Ensayos recientes indican que es seguro utilizar un tratamiento antiagregante plaquetario combinado doble durante 6 meses, si bien ciertas limitaciones de estos estudios hacen que sea escasa la aplicabilidad de esta estrategia de tratamiento antiagregante plaquetario combinado doble de menor duración en la práctica clínica real. Métodos: Se puso en marcha un registro con la inscripción de pacientes consecutivos a los que se había implantado stent farmacoactivo de nueva generación seguido de una prescripción de 6 meses de tratamiento antiagregante plaquetario combinado doble. Se realizó una igualación por puntuación de propensión con una cohorte histórica de pacientes tratados con stentsfarmacoactivos de segunda generación que recibieron luego 12 meses de tratamiento antiagregante plaquetario combinado doble del registro ESTROFA-2. El tamaño muestral se calculó para el criterio de no inferioridad y el objetivo principal fue la combinación de muerte cardiaca, infarto de miocardio, revascularización o hemorragia mayor a los 12 meses. Resultados: Se incluyó en el análisis a 1.286 pacientes de cada grupo, que no presentaban diferencias significativas en sus características basales. Se produjeron episodios del objetivo principal en el 5,0 y el 6,6% de los pacientes en los grupos de 6 y de 12 meses respectivamente (p = 0,001 para no inferioridad). La incidencia de trombosis del stent definitiva o probable fue del 0,5 y el 0,7% en los grupos de tratamiento de 6 y 12 meses respectivamente (p = 0,4). Los episodios de hemorragia mayor fueron menos en el grupo de 6 meses que en el de 12 (el 0,8 y el 1,4%; p = 0,2). Conclusiones: En pacientes seleccionados de este amplio estudio multicéntrico, la seguridad y la eficacia de 6 meses de tratamiento antiagregante plaquetario combinado doble después del implante de stents farmacoactivos de nueva generación fueron no inferiores a las observadas con 12 meses de tratamiento antiagregante plaquetario combinado doble (AU)

Introduction and objectives: The recommendation for dual antiplatelet therapy following drug-eluting stent implantation ranges from 6 months to 12 months or beyond. Recent trials have suggested the safety of a 6-month dual antiplatelet therapy regimen, yet certain caveats to these studies limit the applicability of this shorter duration dual antiplatelet therapy strategy in real world settings. Methods: A registry was constructed with consecutive recruitment of patients undergoing new-generation drug-eluting stent implantation and prescribed 6 months of dual antiplatelet therapy. Propensity score matching was undertaken with a historical cohort of patients treated with second-generation drug-eluting stents who received 12 months of dual antiplatelet therapy from the ESTROFA-2 registry. The sample size was calculated using a noninferiority basis and the primary endpoint was the combination of cardiac death, myocardial infarction, revascularization, or major bleeding at 12 months. Results: The analysis included 1286 patients in each group, with no significant differences in baseline characteristics. The primary endpoint occurred in 5.0% and 6.6% in the 6-month and 12-month groups, respectively (P = .001 for noninferiority). The incidence of definite or probable stent thrombosis was 0.5% and 0.7% in the 6-month and 12-month groups, respectively (P = .4). Major bleeding events were lower in the 6-month group than in the 12-month group (0.8% vs 1.4%; P = .2) Conclusions: In selected patients in this large multicenter study, the safety and efficacy of a 6-month dual antiplatelet therapy regimen after implantation of new-generation drug-eluting stents appeared to be noninferior to those of a 12-month dual antiplatelet therapy regimen (AU)

Chronic treatment with DCPCX, an adenosine A(1) antagonist, worsens long-term memory.

Alzheimer's disease is characterized by progressive cognitive disturbances and neurotransmitter dysfunction. Previous studies targeting the adrenergic A1 pathway suggest that this plays a role in cognitive impairment in Alzheimer's disease. Previous studies have reported that acute treatment with A1 antagonists appears to improve behavioral deficits in rodent models of memory and behavioral impairment. In this study, we addressed whether the chronic administration of 8-cyclopentyl-1,3-dipropylxanthine, a potent and selective adenosine A1 antagonist, could reverse the memory deficits found in aged APPswe/PS1dE9 mice. Chronic treatment did not improve memory in the APPswe/PS1dE9 mouse model and resulted in reduced exploratory behavior, suggestive of reduced anxiety, and a worsening of long-term memory in nontransgenic mice. These results have important implications for understanding the mechanisms of A1 receptor modulation as a target in Alzheimer's disease therapy.

Simultaneous pharmacokinetic model for rolofylline and both M1-trans and M1-cis metabolites.

Rolofylline is a potent, selective adenosine A1 receptor antagonist that was under development for the treatment of patients with acute congestive heart failure and renal impairment. Rolofylline is metabolized primarily to the pharmacologically active M1-trans and M1-cis metabolites (metabolites) by cytochrome P450 (CYP) 3A4. The aim of this investigation was to provide a pharmacokinetic (PK) model for rolofylline and metabolites following intravenous administration to healthy volunteers. Data included for this investigation came from a randomized, double-blind, dose-escalation trial in four groups of healthy volunteers (N=36) where single doses of rolofylline, spanning 1 to 60 mg ,were infused over 1-2 h. The rolofylline and metabolite data were analyzed simultaneously using NONMEM. The simultaneous PK model comprised, in part, a two-compartment linear PK model for rolofylline, with estimates of clearance and volume of distribution at steady-state of 24.4 L/h and 239 L, respectively. In addition, the final PK model contained provisions for both conversion of rolofylline to metabolites and stereochemical conversion of M1-trans to M1-cis. Accordingly, the final model captured known aspects of rolofylline metabolism and was capable of simultaneously describing the PK of rolofylline and metabolites in healthy volunteers.

Evidence for constitutively-active adenosine receptors at mammalian motor nerve endings.

A study was made to determine if constitutively active adenosine receptors are present at mouse motor nerve endings. In preparations blocked by low Ca(2+)/high Mg(2+) solution, 8-cyclopentyl-1,3,dipropylxanthine (CPX, 10-100 nM), which has been reported to be both an A(1) adenosine receptor antagonist and inverse agonist, produced a dose-dependent increase in the number of acetylcholine quanta released by a nerve impulse. Adenosine deaminase, which degrades ambient adenosine into its inactive congener, inosine, failed to alter the response to 100 nM CPX. 8-Cyclopentyltheophylline (CPT, 3 µM), a competitive inhibitor at A(1) adenosine receptors, prevented the increase in acetylcholine release produced by CPX. At normal levels of acetylcholine release, neither adenosine deaminase nor CPX affected acetylcholine release at low frequencies of nerve stimulation in (+)-tubocurarine blocked preparations. The results suggest that a proportion of the acetylcholine release process is controlled by constitutively active adenosine receptors at murine motor nerve endings, providing the first evidence for constitutive activity of G-protein-coupled receptors that modulate the function of mammalian nerve endings.

Coadministration of cannabinoid CB1-receptor and adenosine A1-receptor antagonists improves the acquisition of spatial memory in mice: participation of glutamatergic neurotransmission.

The aim of this study was to characterize the interaction of adenosine A1-receptor and cannabinoid CB1-receptor antagonists in the water maze and object-location tasks, and to evaluate the participation of glutamatergic neurotransmission in the hippocampus in the learning enhancement induced by the coadministration of both antagonists. Our results show that coadministration of ineffective doses of DPCPX (8-cyclopentyl-1,3-dipropylxanthine) (an A1-receptor antagonist) and AM251 (N-(piperidin-1-yl)-5-(4-iodophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide) (a CB1-receptor antagonist) in different proportions enhanced the acquisition of spatial learning. N-methyl-D-aspartate receptor blockade disrupted the effects of the selected drug combination [AM251 0.25 mg/kg intraperitoneally (i.p.)+DPCPX 0.30 mg/kg i.p.] either in the water maze or in the object-location task. Moreover, this drug combination induced a significant ex-vivo enhancement in glutamate release into hippocampal slices. In addition, the blockade of N-methyl-D-aspartate receptors with MK-801 (0.25 µg/site) infused into the hippocampal CA1 area reversed the effects of coadministration, as evaluated in the object-location task. In conclusion, this is the first study to show that A1-receptor and CB1-receptor antagonists might interact on hippocampal neurons to enhance spatial memory in mice.

The safety of an adenosine A(1)-receptor antagonist, rolofylline, in patients with acute heart failure and renal impairment: findings from PROTECT.

BACKGROUND: Adenosine exerts actions in multiple organ systems, and adenosine receptors are a therapeutic target in many development programmes. OBJECTIVE: The aim of this analysis was to evaluate the safety of rolofylline, an adenosine A(1)-receptor antagonist, in patients with acute heart failure. METHODS: The effect of rolofylline was investigated in patients hospitalized for acute heart failure with impaired renal function. Intravenous rolofylline 30 mg or placebo was infused over 4 hours daily for up to 3 days. Adverse events (AEs) and serious AEs (SAEs) were recorded from baseline through 7 and 14 days, respectively, and clinical events were adjudicated through 60 days. RESULTS: Of 2033 patients enrolled, 2002 received study drug randomized 2 : 1 to rolofylline or placebo. Rolofylline and placebo were associated with a similar risk of pre-specified groups of AEs or SAEs, other than selected neurological events. Investigator-reported seizures occurred in 11 (0.8%) rolofylline-treated patients and zero patients receiving placebo (p = 0.02). Stroke occurred in 21 (1.6%) patients assigned to rolofylline compared with 3 (0.5%) placebo-treated patients through 60 days with a greater risk for stroke in the rolofylline group (hazard ratio 3.49; 95% CI 1.04, 11.71; p = 0.043). There was no temporal relation to rolofylline administration and no specific stroke subtype or clinical characteristics that predicted stroke in the rolofylline group. CONCLUSIONS: Rolofylline treatment was associated with an increased seizure rate, an anticipated complication of A(1)-receptor antagonists. An unanticipated, disproportionate increase in strokes in the rolofylline-treated patients emerged, although no clear temporal relation, aetiology, stroke subtype or interacting factor suggestive of a causal mechanism was identified. Further research into stroke as a potential complication of adenosine-modulating therapies is required. Additionally, this study underscores the value of longer follow-up durations for AEs, even for agents with short treatment periods, such as in acute heart failure.

Rationale, design, and results from RENO-DEFEND 1: a randomized, dose-finding study of the selective A1 adenosine antagonist SLV320 in patients hospitalized with acute heart failure.

BACKGROUND: Baseline renal impairment as well as worsening renal function during hospitalization is associated with worse short- and long-term outcomes in patients hospitalized for acute heart failure (AHF). We hypothesized that selective A1 adenosine receptor blockade would induce natriuresis while preserving renal function in AHF patients with renal dysfunction. METHODS: A phase II, randomized, double-blind, placebo-controlled, parallel group, multicenter study to evaluate the efficacy and safety of 2.5, 7.5, 15, and 30 mg/d SLV320 (1 hour intravenous infusions of 1.25, 3.75, 7.5, and 15 mg SLV320, every 12 hours for 3 days [a total of 6 doses] in addition to standard therapy) in subjects hospitalized with AHF and renal impairment who meet all inclusion/exclusion criteria. The study planned to enroll 450 subjects, with 90 subjects allocated equally to each treatment arm. RESULTS: The study was terminated early. The decision, which was unrelated to the study conduct or results, with a total of 46 subjects randomized. Of those randomized, 6:8:8:8 and 6 patients, respectively, completed the study in each of the dosing subgroups, with placebo as the fifth group. For the 1.25-mg study group, the mean age was 73 years; mean (SD) systolic blood pressure (SBP), 128.5 (16.2); heart rate, 80.8 (25.0); brain natriuretic peptide, 969.7 (571.28); creatinine (µmol/L), 149.7 (41.0); cystatin C, 1.468 (0.2777); estimated glomerular filtration rate, 33.8 (7.913); and blood urea nitrogen, 12.1 (2.9), with roughly similar values in each treatment arm. No seizures were reported during the study. Eight patients died during the study, none of whom were associated with the study drug per an independent, blinded, data safety monitoring board. CONCLUSION: Because of the limited number of subjects and variability observed in the results, no definite conclusions can be made regarding the efficacy and safety of SLV320.