[Activation of the adenosine A2A receptor at the acute stage of moderate traumatic brain injury enhances the neuroprotective effects of oxaloacetate].

The purpose of the present study was to investigate the effect of glutamate scavenger oxaloacetate (OA) combined with CGS21680, an adenosine A2A receptor (A2AR) agonist, on acute traumatic brain injury (TBI), and to elucidate the underlying mechanisms. C57BL/6J mice were subjected to moderate-level TBI by controlled cortical impact, and then were treated with OA, CGS21680, or OA combined with CGS21680 at acute stage of TBI. At 24 h post TBI, neurological severity score, brain water content, glutamate concentration in cerebrospinal fluid (CSF), mRNA and protein levels of IL-1ß and TNF-α, mRNA level and activity of glutamate oxaloacetate aminotransferase (GOT), and ATP level of brain tissue were detected. The results showed that neurological deficit, brain water content, glutamate concentration in CSF, and the inflammatory cytokine IL-1ß and TNF-α production were exacerbated in CGS21680 treated mice. Administrating OA suppressed the rise of both glutamate concentration in CSF and brain water content, and elevated the ATP level of cerebral tissue. More interestingly, neurological deficit, brain edema, glutamate concentration, IL-1ß and TNF-α levels were ameliorated significantly in mice treated with OA combined with CGS21680. The combined treatment exhibited better therapeutic effects than single OA treatment. We also observed that GOT activity was enhanced in single CGS21680 treatment group, and both the GOT mRNA level and GOT activity were up-regulated in early-stage combined treatment group. These results suggest that A2AR can improve the efficiency of GOT and potentiate the ability of OA to metabolize glutamate. This may be the mechanism that A2AR activation in combination group augmented the neuroprotective effect of OA rather than aggravated the brain damages. Taken together, the present study provides a new insight for the clinical treatment of TBI with A2AR agonists and OA.

Adenosine A2A receptor agonist polydeoxyribonucleotide ameliorates short-term memory impairment by suppressing cerebral ischemia-induced inflammation via MAPK pathway.

Cerebral ischemia causes tissue death owing to occlusion of the cerebral blood vessels, and cerebral ischemia activates mitogen-activated protein kinase (MAPK) and induces secretion of pro-inflammatory cytokines. Adenosine A2A receptor agonist, polydeoxyribonucleotide (PDRN), suppresses the secretion of pro-inflammatory cytokines and exhibits anti-inflammatory effect. In the current study, the therapeutic effect of PDRN on cerebral ischemia was evaluated using gerbils. For the induction of cerebral ischemia, the common carotid arteries were exposed, and then aneurysm clips were used to occlude the common carotid arteries bilaterally for 7 minutes. In the PDRN-treated groups, the gerbils were injected intraperitoneally with 0.3 mL of saline containing 8 mg/kg PDRN, per a day for 7 days following cerebral ischemia induction. In order to confirm the participation of the adenosine A2A receptor in the effects mediated by PDRN, 8 mg/kg 7-dimethyl-1-propargylxanthine (DMPX), adenosine A2A receptor antagonist, was treated with PDRN. In the current study, induction of ischemia enhanced the levels of pro-inflammatory cytokines and increased phosphorylation of MAPK signaling factors in the hippocampus and basolateral amygdala. However, treatment with PDRN ameliorated short-term memory impairment by suppressing the production of pro-inflammatory cytokines and inactivation of MAPK signaling factors in cerebral ischemia. Furthermore, PDRN treatment enhanced the concentration of cyclic adenosine-3,5'-monophosphate (cAMP) as well as phosphorylation of cAMP response element-binding protein (p-CREB). Co-treatment of DMPX and PDRN attenuated the therapeutic effect of PDRN on cerebral ischemia. Based on these findings, PDRN may be developed as the primary treatment in cerebral ischemia.

Allosteric Interactions between Adenosine A2A and Dopamine D2 Receptors in Heteromeric Complexes: Biochemical and Pharmacological Characteristics, and Opportunities for PET Imaging.

Adenosine and dopamine interact antagonistically in living mammals. These interactions are mediated via adenosine A2A and dopamine D2 receptors (R). Stimulation of A2AR inhibits and blockade of A2AR enhances D2R-mediated locomotor activation and goal-directed behavior in rodents. In striatal membrane preparations, adenosine decreases both the affinity and the signal transduction of D2R via its interaction with A2AR. Reciprocal A2AR/D2R interactions occur mainly in striatopallidal GABAergic medium spiny neurons (MSNs) of the indirect pathway that are involved in motor control, and in striatal astrocytes. In the nucleus accumbens, they also take place in MSNs involved in reward-related behavior. A2AR and D2R co-aggregate, co-internalize, and co-desensitize. They are at very close distance in biomembranes and form heteromers. Antagonistic interactions between adenosine and dopamine are (at least partially) caused by allosteric receptor-receptor interactions within A2AR/D2R heteromeric complexes. Such interactions may be exploited in novel strategies for the treatment of Parkinson's disease, schizophrenia, substance abuse, and perhaps also attention deficit-hyperactivity disorder. Little is known about shifting A2AR/D2R heteromer/homodimer equilibria in the brain. Positron emission tomography with suitable ligands may provide in vivo information about receptor crosstalk in the living organism. Some experimental approaches, and strategies for the design of novel imaging agents (e.g., heterobivalent ligands) are proposed in this review.

5-N-ethyl Carboxamidoadenosine Stimulates Adenosine-2b Receptor-Mediated Mitogen-Activated Protein Kinase Pathway to Improve Brain Mitochondrial Function in Amyloid Beta-Induced Cognitive Deficit Mice.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder with loss in memory as one of the cardinal features. 5-N-ethyl carboxamidoadenosine (NECA), an agonist of adenosine-2b receptor, exerts neuroprotective activity against several experimental conditions. Further, NECA activates mitogen-activated protein kinase (MAPK) and also attenuates mitochondrial toxicity in mammalian tissues other than brain. Moreover, there is no report on the role of A2b/MAPK-mediated signaling pathway in Aß-induced mitochondrial toxicity in the brain of the experimental animals. Therefore, the present study evaluated the neuroprotective activity of NECA with or without MAPK inhibitor against Aß-induced cognitive deficit and mitochondrial toxicity in the experimental rodents. Further, the effect of NECA with or without MAPK inhibitor was evaluated on Aß-induced mitochondrial toxicity in the memory-sensitive mice brain regions. Intracerebroventricular (ICV) injection of Aß 1-42 was injected to healthy male mice through Hamilton syringe via polyethylene tube to induce AD-like behavioral manifestations. NECA attenuated Aß-induced cognitive impairments in the rodents. In addition, NECA ameliorated Aß-induced Aß accumulation and cholinergic dysfunction in the selected memory-sensitive mouse HIP, PFC, and AMY. Further, NECA significantly attenuated Aß-induced mitochondrial toxicity in terms of decrease in the mitochondrial function, integrity, and bioenergetics in the brain regions of these animals. However, MAPKI diminished the therapeutic effects of NECA on behavioral, biochemical, and molecular observations in AD-like animals. Therefore, it can be speculated that NECA exhibits neuroprotective activity perhaps through MAPK activation in AD-like rodents. Moreover, A2b-mediated MAPK activation could be a promising target in the management of AD.

Harnessing adenosine A2A receptors as a strategy for suppressing the lung inflammation and thrombotic complications of COVID-19: Potential of pentoxifylline and dipyridamole.

Counterproductive lung inflammation and dysregulated thrombosis contribute importantly to the lethality of advanced COVID-19. Adenosine A2A receptors (A2AR), expressed by a wide range of immune cells, as well as endothelial cells and platelets, exert cAMP-mediated anti-inflammatory and anti-thrombotic effects that potentially could be highly protective in this regard. The venerable drug pentoxifylline (PTX) exerts both anti-inflammatory and antithrombotic effects that reflect its ability to boost the responsiveness of A2AR to extracellular adenosine. The platelet-stabilizing drug dipyridamole (DIP) blocks intracellular uptake of extracellularly-generated adenosine, thereby up-regulating A2AR signaling in a way that should be functionally complementary to the impact of PTX in that regard. Moreover, DIP has recently been reported to slow the cellular replication of SARS-CoV-2 in clinically feasible concentrations. Both PTX and DIP are reasonably safe, well-tolerated, widely available, and inexpensive drugs. When COVID-19 patients can be treated within several days of symptom onset, using PTX + DIP in conjunction with hydroxychloroquine (HCQ) and an antibiotic - azithromycin (AZM) or doxycycline - might be warranted. HCQ and AZM can suppress SARS-CoV-2 proliferation in vitro and may slow the cell-to-cell spread of the virus; a large case series evaluating this combination in early-stage patients reported an impressively low mortality rate. However, whereas HCQ and AZM can promote QT interval lengthening and may be contraindicated in more advanced COVID-19 entailing cardiac damage, doxycycline has no such effect and exerts a potentially beneficial anti-inflammatory action. In contrast to HCQ, we propose that the combination of PTX + DIP can be used in both early and advanced stages of COVID-19. Concurrent use of certain nutraceuticals - yeast beta-glucan, zinc, vitamin D, spirulina, phase 2 inducers, N-acetylcysteine, glucosamine, quercetin, and magnesium - might also improve therapeutic outcomes in COVID-19.

Inhibition of A2B Adenosine Receptor Attenuates Intestinal Injury in a Rat Model of Necrotizing Enterocolitis.

Necrotizing enterocolitis (NEC) is a lethal gastrointestinal tract disease that occurs in premature infants. Adenosine receptor A2B (A2BR) regulates the inflammation cytokine secretion and immune cell infiltration in the colonic pathophysiology conditions. In the present study, we aim to determine the roles of A2BR in the development of NEC. A NEC rat model was established and treated with A2BR agonist-BAY60-6583 or A2BR antagonist-PSB1115. Animals in the control group were free from any interventions. Our results showed that the inhibition of A2BR PSB1115 improved intestinal injury and inflammation in newborn NEC rats. The expression levels of caspase-3 and the ratio of apoptotic cells were upregulated in NEC rats, and these indices were downregulated after treating with PSB1115 but further upregulated by BAY60-6583. Meanwhile, a similar trend was also witnessed in the changes of MPO activities and proinflammatory cytokines including IL-6, IFN-γ, and TNF-α. However, the anti-inflammatory cytokine IL-10 in the NECP group was significantly higher than that in the NEC and NECB groups (p < 0.05, respectively). Moreover, the expression of Ki67 was significantly increased in the NECP group as compared with those of the NEC and the NECB groups (p < 0.05, respectively). Collectively, our study suggested that the inhibition of A2BR attenuates NEC in the neonatal rat, at least partially through the modulation of inflammation and the induction of epithelial cell proliferation.

Adenosine A2A receptor agonist (regadenoson) in human lung transplantation.

BACKGROUND: Currently, there are no clinically approved treatments for ischemia-reperfusion injury after lung transplantation. Pre-clinical animal models have demonstrated a promising efficacy of adenosine 2A receptor (A2AR) agonists as a treatment option for reducing ischemia-reperfusion injury. The purpose of this human study, is to conduct a Phase I clinical trial for evaluating the safety of continuous infusion of an A2AR agonist in lung transplant recipients. METHODS: An adaptive, two-stage continual reassessment trial was designed to evaluate the safety of regadenoson (A2AR agonist) in the setting of lung transplantation. Continuous infusion of regadenoson was administered to lung transplant recipients that was started at the time of skin incision. Adverse events and dose-limiting toxicities, as pre-determined by a study team and assessed by a clinical team and an independent safety monitor, were the primary end-points for safety in this trial. RESULTS: Between January 2018 and March 2019, 14 recipients were enrolled in the trial. Of these, 10 received the maximum infused dose of 1.44 µg/kg/min for 12 hours. No dose-limiting toxicities were observed. The steady-state plasma regadenoson levels sampled before the reperfusion of the first lung were 0.98 ± 0.46 ng/ml. There were no mortalities within 30 days. CONCLUSIONS: Regadenoson, an A2AR agonist, can be safely infused in the setting of lung transplantation with no dose-limiting toxicities or drug-related mortality. Although not powered for the evaluation of secondary end-points, the results of this trial and the outcome of pre-clinical studies warrant further investigation with a Phase II randomized controlled trial.

Adenosine A2A receptor (A2AR) stimulation enhances mitochondrial metabolism and mitigates reactive oxygen species-mediated mitochondrial injury.

In OA chondrocytes, there is diminished mitochondrial production of ATP and diminished extracellular adenosine resulting in diminished adenosine A2A receptor (A2AR) stimulation and altered chondrocyte homeostasis which contributes to the pathogenesis of OA. We tested the hypothesis that A2AR stimulation maintains or enhances mitochondrial function in chondrocytes. The effect of A2AR signaling on mitochondrial health and function was determined in primary murine chondrocytes, a human chondrocytic cell line (T/C-28a2), primary human chondrocytes, and a murine model of OA by transmission electron microscopy analysis, mitochondrial stress testing, confocal live imaging for mitochondrial inner membrane polarity, and immunohistochemistry. In primary murine chondrocytes from A2AR-/- null mice, which develop spontaneous OA by 16 weeks, there is mitochondrial swelling, dysfunction, and reduced mitochondrial content with increased reactive oxygen species (ROS) burden and diminished mitophagy, as compared to chondrocytes from WT animals. IL-1-stimulated T/C-28a2 cells treated with an A2AR agonist had reduced ROS burden with increased mitochondrial dynamic stability and function, findings which were recapitulated in primary human chondrocytes. In an obesity-induced OA mouse model, there was a marked increase in mitochondrial oxidized material which was markedly improved after intraarticular injections of liposomal A2AR agonist. These results are consistent with the hypothesis that A2AR ligation is mitoprotective in OA.

Caffeine and adenosine A2A receptors rescue neuronal development in vitro of frontal cortical neurons in a rat model of attention deficit and hyperactivity disorder.

Although some studies have supported the effects of caffeine for treatment of Attention deficit and hyperactivity disorder (ADHD), there were no evidences about its effects at the neuronal level. In this study, we sought to find morphological alterations during in vitro development of frontal cortical neurons from Spontaneoulsy hypertensive rats (SHR, an ADHD rat model) and Wistar-Kyoto rats (WKY, control strain). Further, we investigated the effects of caffeine and adenosine A1 and A2A receptors (A1R and A2AR) signaling. Cultured cortical neurons from WKY and SHR were analyzed by immunostaining of microtubule-associated protein 2 (MAP-2) and tau protein after treatment with either caffeine, or A1R and A2AR agonists or antagonists. Besides, the involvement of PI3K and not PKA signaling was also assessed. Neurons from ADHD model displayed less neurite branching, shorter maximal neurite length and decreased axonal outgrowth. While caffeine recovered neurite branching and elongation from ADHD neurons via both PKA and PI3K signaling, A2AR agonist (CGS 21680) promoted more neurite branching via PKA signaling. The selective A2AR antagonist (SCH 58261) was efficient in recovering axonal outgrowth from ADHD neurons through PI3K and not PKA signaling. For the first time, frontal cortical neurons were isolated from ADHD model and they presented disturbances in the differentiation and outgrowth. By showing that caffeine and A2AR may act at neuronal level rescuing ADHD neurons outgrowth, our findings strengthen the potential of caffeine and A2AR receptors as an adjuvant for ADHD treatment.

Regadenoson myocardial perfusion scintigraphy for the evaluation of coronary artery disease in patients with lung disease: A series of five cases.

Coronary artery disease (CAD) is a leading cause of death and morbidity globally. Myocardial perfusion scintigraphy (MPS) is commonly used for the diagnosis of CAD, necessitating hyperaemia achieved either by physical exertion or by pharmacological stress, most commonly through use of a coronary arteriolar dilator. This is challenging in patients with respiratory conditions because exercise may be submaximal and adenosine is contraindicated because of the risk of bronchoconstriction. Regadenoson is the only selective adenosine A2A receptor agonist approved as a vasodilator in MPS. The risk of bronchospasm with regadenoson has been investigated in large, randomised trials; however, patients with the most severe respiratory conditions were not included. In this case series, we present the use of regadenoson MPS in five patients with moderate-to-severe lung conditions, including patients requiring lung volume reduction surgery and lung transplant. In all cases, regadenoson MPS provided valuable information for risk assessment and treatment optimisation. Although dyspnoea occurred in all patients, regadenoson was well tolerated without serious adverse events or bronchospasm; in no case was intervention required to treat dyspnoea.

Adenosine 2A Receptor Activation Attenuates Ischemia Reperfusion Injury During Extracorporeal Cardiopulmonary Resuscitation.

OBJECTIVE: We tested the hypothesis that systemic administration of an A2AR agonist will reduce multiorgan IRI in a porcine model of ECPR. SUMMARY BACKGROUND DATA: Advances in ECPR have decreased mortality after cardiac arrest; however, subsequent IRI contributes to late multisystem organ failure. Attenuation of IRI has been reported with the use of an A2AR agonist. METHODS: Adult swine underwent 20 minutes of circulatory arrest, induced by ventricular fibrillation, followed by 6 hours of reperfusion with ECPR. Animals were randomized to vehicle control, low-dose A2AR agonist, or high-dose A2AR agonist. A perfusion specialist using a goal-directed resuscitation protocol managed all the animals during the reperfusion period. Hourly blood, urine, and tissue samples were collected. Biochemical and microarray analyses were performed to identify differential inflammatory markers and gene expression between groups. RESULTS: Both the treatment groups demonstrated significantly higher percent reduction from peak lactate after reperfusion compared with vehicle controls. Control animals required significantly more fluid, epinephrine, and higher final pump flow while having lower urine output than both the treatment groups. The treatment groups had lower urine NGAL, an early marker of kidney injury (P = 0.01), lower plasma aspartate aminotransferase, and reduced rate of troponin rise (P = 0.01). Pro-inflammatory cytokines were lower while anti-inflammatory cytokines were significantly higher in the treatment groups. CONCLUSIONS: Using a novel and clinically relevant porcine model of circulatory arrest and ECPR, we demonstrated that a selective A2AR agonist significantly attenuated systemic IRI and warrants clinical investigation.

The A2A receptor agonist CGS 21680 has beneficial and adverse effects on disease development in a humanised mouse model of graft-versus-host disease.

Allogeneic hematopoietic stem cell transplantation (HSCT) is a curative method for blood cancers and other blood disorders, but is limited by the development of graft-versus-host disease (GVHD). GVHD results in inflammatory damage to the host liver, gastrointestinal tract and skin, resulting in high rates of morbidity and mortality in HSCT recipients. Activation of the A2A receptor has been previously demonstrated to reduce disease in allogeneic mouse models of GVHD. This study aimed to investigate the effect of A2A activation on disease development in a humanised mouse model of GVHD. Immunodeficient non-obese diabetic-severe combined immunodeficiency-interleukin (IL)-2 receptor γnull (NSG) mice injected with human (h) peripheral blood mononuclear cells (hPBMCs), were treated with either the A2A agonist CGS 21680 or control vehicle. Contrary to the beneficial effect of A2A activation in allogeneic mouse models, CGS 21680 increased weight loss, and failed to reduce the clinical score or increase survival in this humanised mouse model of GVHD. Moreover, CGS 21680 reduced T regulatory cells and increased serum human IL-6 concentrations. Conversely, CGS 21680 reduced serum human tumour necrosis factor (TNF)-α concentrations and leukocyte infiltration into the liver, indicating that A2A activation can, in part, reduce molecular and histological GVHD in this model. Notably, CGS 21680 also prevented healthy weight gain in NSG mice not engrafted with hPBMCs suggesting that this compound may be suppressing appetite or metabolism. Therefore, the potential benefits of A2A activation in reducing GVHD in HSCT recipients may be limited and confounded by adverse impacts on weight, decreased T regulatory cell frequency and increased IL-6 production.

Reduction of repetitive behavior by co-administration of adenosine receptor agonists in C58 mice.

Repetitive behaviors are diagnostic for autism spectrum disorder (ASD) and commonly observed in other neurodevelopmental disorders. Currently, there are no effective pharmacological treatments for repetitive behavior in these clinical conditions. This is due to the lack of information about the specific neural circuitry that mediates the development and expression of repetitive behavior. Our previous work in mouse models has linked repetitive behavior to decreased activation of the subthalamic nucleus, a brain region in the indirect and hyperdirect pathways in the basal ganglia circuitry. The present experiments were designed to further test our hypothesis that pharmacological activation of the indirect pathway would reduce repetitive behavior. We used a combination of adenosine A1 and A2A receptor agonists that have been shown to alter the firing frequency of dorsal striatal neurons within the indirect pathway of the basal ganglia. This drug combination markedly and selectively reduced repetitive behavior in both male and female C58 mice over a six-hour period, an effect that required both A1 and A2A agonists as neither alone reduced repetitive behavior. The adenosine A1 and A2A receptor agonist combination also significantly increased the number of Fos transcripts and Fos positive cells in dorsal striatum. Fos induction was found in both direct and indirect pathway neurons suggesting that the drug combination restored the balance of activation across these complementary basal ganglia pathways. The adenosine A1 and A2A receptor agonist combination also maintained its effectiveness in reducing repetitive behavior over a 7-day period. These findings point to novel potential therapeutic targets for development of drug therapies for repetitive behavior in clinical disorders.

Therapeutic potential of A2 adenosine receptor pharmacological regulators in the treatment of cardiovascular diseases, recent progress, and prospective.

Adenosine and its analogs are of particular interest as potential therapeutic agents for treatment of cardiovascular diseases (CVDs). A2 adenosine receptor subtypes (A2a and A2b) are extensively expressed in cardiovascular system, and modulation of these receptors using A2 adenosine receptor agonists or antagonists regulates heart rate, blood pressure, heart rate variability, and cardiovascular toxicity during both normoxia and hypoxia conditions. Regulation of A2 adenosine receptor signaling via specific and novel pharmacological regulators is a potentially novel therapeutic approach for a better understanding and hence a better management of CVDs. This review summarizes the role of pharmacological A2 adenosine receptor regulators in the pathogenesis of CVDs.

Feasibility, safety and effectiveness in measuring microvascular resistance with regadenoson.

AIMThe study aims to test whether simultaneous measurement of fractional flow reserve (FFR), coronary flow reserve (CFR) and index of microcirculatory resistance (IMR) is feasible, safe and effective during regadenoson-induced hyperemia.METHODS AND RESULTSFFR, CFR and IMR were measured simultaneously during regadenoson (Rapiscan 400 µg) -induced hyperemia in 50 patients with stable coronary artery disease with a SYNTAX score of <22. Simultaneous measurement of FFR, CFR and IMR was technically feasible in all cases (50/50). No side effects occurred and even patients fulfilling classical contraindications for the use of adenosine (10/50) could be included. Regadenoson-induced hyperemia remained stable after maximal pressure drop for more than 35 sec as measured by systemic aortic and distal coronary pressure. There was a significant drop in transit mean time from baseline to hyperemia of more than 50% (1.0 ± 0.6 s vs. 0.4 ± 0.2 s, p <  0.01). Patients' mean IMR value was 23.4, and IMR values above 75th percentile significantly correlated with metformin demanding diabetes mellitus with OR 21.76 and nicotine abuse with OR 10.28.CONCLUSIONA single intravenous regadenoson bolus via peripheral line increases coronary blood flow without harmful systemic side effects enabling interventionists to simultaneously assess FFR, CFR and IMR in patients with stable coronary artery disease.

Reduction in Blood Glutamate Levels Combined With the Genetic Inactivation of A2AR Significantly Alleviate Traumatic Brain Injury-Induced Acute Lung Injury.

Traumatic brain injury-induced acute lung injury (TBI-ALI) is a serious complication of traumatic brain injury (TBI). Our previous clinical study found that high levels of blood glutamate after TBI were closely related to the occurrence and severity of TBI-ALI, while it remains unknown whether a high concentration of blood glutamate directly causes or aggravates TBI-ALI. We found that inhibition of the adenosine A2A receptor (A2AR) after brain injury alleviated the TBI-ALI; however, it is unknown whether lowering blood glutamate levels in combination with inhibiting the A2AR would lead to better effects. Using mouse models of moderate and severe TBI, we found that intravenous administration of L-glutamate greatly increased the lung water content, lung-body index, level of inflammatory markers in bronchoalveolar lavage fluid and acute lung injury score and significantly decreased the PaO2/FiO2 ratio. Moreover, the incidence of TBI-ALI and the mortality rate were significantly increased, and the combined administration of A2AR activator and exogenous glutamate further exacerbated the above damaging effects. Conversely, lowering the blood glutamate level through peritoneal dialysis or intravenous administration of oxaloacetate notably improved the above parameters, and a further improvement was seen with concurrent A2AR genetic inactivation. These data suggest that A2AR activation aggravates the damaging effect of high blood glutamate concentrations on the lung and that combined treatment targeting both A2AR and blood glutamate may be an effective way to prevent and treat TBI-ALI.

Infarct-Sparing Effect of Adenosine A2B Receptor Agonist Is Primarily Due to Its Action on Splenic Leukocytes Via a PI3K/Akt/IL-10 Pathway.

BACKGROUND: Adenosine A2B receptor (A2BAR) agonist reduces myocardial reperfusion injury by acting on inflammatory cells. Recently, a cardiosplenic axis was shown to mediate the myocardial postischemic reperfusion injury. This study aimed to explore whether the infarct-squaring effect of A2BAR agonist was primarily due to its action on splenic leukocytes. METHODS: C57BL6 (wild type [WT]) mice underwent 40 min of left coronary artery occlusion followed by 60 min of reperfusion. A2BAR knockout (KO) and interleukin (IL)-10KO mice served as donors for splenic leukocytes. Acute splenectomy was performed 30 min before ischemia. The acute splenic leukocyte adoptive transfer was performed by injecting 5 × 106 live splenic leukocytes into splenectomized mice. BAY 60-6583, an A2BAR agonist, was injected by i.v. 15 min before ischemia. The infarct size (IS) was determined using 2,3,5-triphenyltetrazolium chloride and Phthalo blue staining. The expression of p-Akt and IL-10 was estimated by Western blotting. Immunofluorescence staining assessed the localization of IL-10 expression. RESULTS: BAY 60-6583 reduced the myocardial IS in intact mice but failed to reduce the same in splenectomized mice, which had a smaller IS than intact mice. BAY 60-6583 reduced the IS in splenectomized mice with the acute transfer of WT splenic leukocytes; however, it did not protect the heart of splenectomized mice with the acute transfer of A2BRKO splenic leukocytes. Furthermore, BAY 60-6583 increased the levels of p-Akt and IL-10 in the WT spleen. Moreover, it did not exert any protective effect in IL-10KO mice. CONCLUSIONS: A2BAR activation before ischemia stimulated the IL-10 production in splenic leukocytes via a PI3K/Akt pathway, thereby exerting anti-inflammatory effects that limited the myocardial reperfusion injury.

Image-guided chemotherapy with specifically tuned blood brain barrier permeability in glioma margins.

Blood-brain barrier (BBB) disruption is frequently observed in the glioma region. However, the tumor uptake of drugs is still too low to meet the threshold of therapeutic purpose. Method: A tumor vasculature-targeted nanoagonist was developed. Glioma targeting specificity of the nanoagonist was evaluated by in vivo optical imaging. BBB permeability at the glioma margin was quantitatively measured by dynamic contrast enhanced magnetic resonance imaging (DCE-MRI). Single-photon emission computed tomography imaging/computed tomography (SPECT/CT) quantitatively determined the glioma uptake of the radiolabeled model drug. T2-weighted MRI monitored the tumor volume. Results: Immunostaining studies demonstrated that the BBB remained partially intact in the invasive margin of patients' gliomas regardless of their malignancies. DCE-MRI showed that vascular permeability in the glioma margin reached its maximum at 45 min post nanoagonist administration. In vivo optical imaging indicated the high glioma targeting specificity of the nanoagonist. SPECT/CT showed the significantly enhanced glioma uptake of the model drug after pre-treatment with the nanoagonist. Image-guided paclitaxel injection after nanoagonist-mediated BBB modulation more efficiently attenuated tumor growth and extended survival than in animal models treated with paclitaxel or temozolomide alone. Conclusion: Thus, image-guided drug delivery following BBB permeability modulation holds promise to enhance the efficacy of chemotherapeutics to glioma.

Synergistic interaction between a PDE5 inhibitor (sildenafil) and a new adenosine A2A receptor agonist (LASSBio-1359) improves pulmonary hypertension in rats.

INTRODUCTION: Pulmonary hypertension (PH) is characterized by enhanced pulmonary vascular resistance, which causes right ventricle (RV) pressure overload and results in right sided heart failure and death. This work investigated the effectiveness of a combined therapy with PDE5 inhibitor (PDE5i) and a new adenosine A2A receptor (A2AR) agonist in mitigating monocrotaline (MCT) induced PH in rats. METHODS: An in vitro isobolographic analysis was performed to identify possible synergistic relaxation effect between sildenafil and LASSBio 1359 in rat pulmonary arteries (PAs). In the in vivo experiments, PH was induced in male Wistar rats by a single intraperitoneal injection of 60 mg/kg MCT. Rats were divided into the following groups: control (saline injection only), MCT + vehicle, MCT + sildenafil, MCT + LASSBio 1359 and MCT + combination of sildenafil and LASSBio 1359. Fourteen days after the MCT injection, rats were treated daily with oral administration of the regimen therapies or vehicle for 14 days. Cardiopulmonary system function and structure were evaluated by echocardiography. RV systolic pressure and PA endothelial function were measured. RESULTS: Isobolographic analysis showed a synergistic interaction between sildenafil and LASSBio 1359 in rat PAs. Combined therapy with sildenafil and LASSBio 1359 but not monotreatment with low dosages of either sildenafil or LASSBio 1359 ameliorated all of PH related abnormalities in cardiopulmonary function and structure in MCT challenged rats. CONCLUSIONS: The combination of sildenafil and LASSBio 1359 has a synergistic interaction, suggesting that combined use of these pharmacological targets may be an alternative to improve quality of life and outcomes for PH patients.