A genetic variation in the adenosine A2A receptor gene contributes to variability in oscillatory alpha power in wake and sleep EEG and A1 adenosine receptor availability in the human brain

The EEG alpha rhythm (∼ 8-13 Hz) is one of the most salient human brain activity rhythms, modulated by the level of attention and vigilance and related to cerebral energy metabolism. Spectral power in the alpha range in wakefulness and sleep strongly varies among individuals based on genetic predisposition. Knowledge about the underlying genes is scarce, yet small studies indicated that the variant rs5751876 of the gene encoding A2A adenosine receptors (ADORA2A) may contribute to the inter-individual variation. The neuromodulator adenosine is directly linked to energy metabolism as product of adenosine tri-phosphate breakdown and acts as a sleep promoting molecule by activating A1 and A2A adenosine receptors. We performed sleep and positron emission tomography studies in 59 healthy carriers of different rs5751876 alleles, and quantified EEG oscillatory alpha power in wakefulness and sleep, as well as A1 adenosine receptor availability with 18F-CPFPX. Oscillatory alpha power was higher in homozygous C-allele carriers (n = 27, 11 females) compared to heterozygous and homozygous carriers of the T-allele (n(C/T) = 23, n(T/T) = 5, 13 females) (F(18,37) = 2.35, p = 0.014, Wilk's Λ = 0.487). Furthermore, a modulatory effect of ADORA2A genotype on A1 adenosine receptor binding potential was found across all considered brain regions (F(18,40) = 2.62, p = 0.006, Wilk's Λ = 0.459), which remained significant for circumscribed occipital region of calcarine fissures after correction for multiple comparisons. In female participants, a correlation between individual differences in oscillatory alpha power and A1 receptor availability was observed. In conclusion, we confirmed that a genetic variant of ADORA2A affects individual alpha power, while a direct modulatory effect via A1 adenosine receptors in females is suggested.

The association between Adenosine A2A receptor gene polymorphisms and attention deficit hyperactivity disorder in Korean children

Attention deficit hyperactivity disorder (ADHD) is a common and heritable neurodevelopmental disorder. Particularly, ADHD is known to be related to the dopaminergic system. ADHD symptoms can appear when the dopamine binding affinity diminishes due to dopamine receptor abnormalities, such as the dopamine D₂ receptor (D₂R). This receptor interacts with the adenosine A_2A receptor (A_2AR). The A_2AR acts as an antagonist of D₂R, that is, the increased binding of adenosine with A_2AR inhibits the D₂R activity. Furthermore, it is found that the single nucleotide polymorphisms of the adenosine A_2A receptor gene (ADORA2A) revealed a significant relationship with ADHD in various populations. Therefore, we examined the genetic relationship between ADORA2A polymorphisms (rs2297838, rs5751876, and rs4822492) and Korean ADHD children. A case-control study was performed for 150 cases and 322 controls. Genotyping of ADORA2A polymorphisms was conducted by PCR-RFLP. The results demonstrated that the rs5751876 TC genotype was associated with children with ADHD (p = 0.018). The rs2298383 CC genotype was significantly associated with children with ADHD/HI (p = 0.026). However, when Bonferroni correction was used, the significance vanished (p_adjusted = 0.054 and p_adjusted = 0.078, respectively). Haplotype analysis showed that TTC, TCC, and CTG demonstrated a significant difference between ADHD/C children and control groups (p_adjusted = 0.006, p_adjusted = 0.011, and p_adjusted = 0.028, respectively). In conclusion, we propose a possible association between ADORA2A polymorphisms with Korean children having ADHD.

Can the Brazilian Caffeine Expectancy Questionnaires Differentiate the CYP1A2 and ADORA2A Gene Polymorphisms?-An Exploratory Study with Brazilian Athletes

This study investigated the ability of the Brazilian Caffeine Expectancy Questionnaire (CaffEQ-BR), full and brief versions, to differentiate genetic profiles regarding the polymorphisms of the CYP1A2 (rs 762551) and ADORA2A (rs 5751876) genes in a cohort of Brazilian athletes. One-hundred and fifty participants were genotyped for CYP1A2 and ADORA2A. After the recruitment and selection phase, 71 (90% male and 10% female, regular caffeine consumers) completed the CaffEQ-BR questionnaires and a self-report online questionnaire concerning sociodemographic data, general health status, and frequency of caffeine consumption. The order of completion of the CaffEQ-BR questionnaires was counterbalanced. The concordance between the full and brief versions of the CaffEQ-BR was analyzed using the intraclass correlation coefficient (ICC). To determine the discriminatory capacity of the questionnaires for genotype, the receiver operating characteristic (ROC) curve was applied for sensitivity and specificity (significance level of 5%). Mean caffeine intake was 244 ± 161 mg·day−1. The frequency of AA genotypes for CYP1A2 was 47.9% (n = 34) and 52.1% (n = 37) for C-allele carriers (AC and CC). The frequencies of TT genotypes for ADORA2A were 22.7% (n = 15) and 77.3% (n = 51) for C-allele carriers (TC and CC). All CaffEQ-BR factors, for the full and brief versions, were ICCs > 0.75, except for factor 6 (anxiety/negative effects; ICC = 0.60), and presented ROC curve values from 0.464 to 0.624 and 0.443 to 0.575 for CYP1A2 and ADORA2A. Overall, the CaffEQ-BR (full and brief versions) did not show discriminatory capacity for CYP1A2 and ADORA2A gene polymorphisms. In conclusion, the CaffEQ-BR was not able to differentiate genotypes for the CYP1A2 or ADORA2A genes in this group of Brazilian athletes.

The Influence of ADORA2A on Levodopa-Induced Dyskinesia

BACKGROUND

Dopamine deficiency causes Parkinson's disease (PD), and on treatment, levodopa is the gold standard. Various drug-metabolizing enzymes and drug receptors are believed to be involved in prompting dyskinesias due to the extended usage of levodopa. Shreds of evidence in genomic studies have presented that ADORA2A receptor antagonism has beneficial outcomes to avoid these drug-induced side effects.

OBJECTIVE

The aim of this study was to study the polymorphisms of rs2298383, rs35060421, and rs5751876 in the ADORA2A in patients diagnosed as PD and describe their possible relationships with levodopa-induced dyskinesias (LID).

METHODS

One-hundred and seventy-two patients were recruited and separated as the study and the control group. DNA was achieved from peripheral venous blood, high resolution melting analysis, and reverse-transcriptase PCR was performed.

RESULTS

The allele differences among the groups were not statistically significant. Although it was not statistically significant, the rs35060421 allele was observed to repeat more frequently. However, we did not find an association between such polymorphisms of ADORA2A and LID.

CONCLUSIONS

Although this result showed that a higher sample number might produce different results as possible, current results in the Turkish sample indicated that these alleles of ADORA2A might not be related to LID in patients.

Novel Big Data-Driven Machine Learning Models for Drug Discovery Application

Most contemporary drug discovery projects start with a ‘hit discovery’ phase where small chemicals are identified that have the capacity to interact, in a chemical sense, with a protein target involved in a given disease. To assist and accelerate this initial drug discovery process, ’virtual docking calculations’ are routinely performed, where computational models of proteins and computational models of small chemicals are evaluated for their capacities to bind together. In cutting-edge, contemporary implementations of this process, several conformations of protein targets are independently assayed in parallel ‘ensemble docking’ calculations. Some of these protein conformations, a minority of them, will be capable of binding many chemicals, while other protein conformations, the majority of them, will not be able to do so. This fact that only some of the conformations accessible to a protein will be ’selected’ by chemicals is known as ’conformational selection’ process in biology. This work describes a machine learning approach to characterize and identify the properties of protein conformations that will be selected (i.e., bind to) chemicals, and classified as potential binding drug candidates, unlike the remaining non-binding drug candidate protein conformations. This work also addresses the class imbalance problem through advanced machine learning techniques that maximize the prediction rate of potential protein molecular conformations for the test case proteins ADORA2A (Adenosine A2a Receptor) and OPRK1 (Opioid Receptor Kappa 1), and subsequently reduces the failure rates and hastens the drug discovery process.

ATP and cancer immunosurveillance

While intracellular adenosine triphosphate (ATP) occupies a key position in the bioenergetic metabolism of all the cellular compartments that form the tumor microenvironment (TME), extracellular ATP operates as a potent signal transducer. The net effects of purinergic signaling on the biology of the TME depend not only on the specific receptors and cell types involved, but also on the activation status of cis- and trans-regulatory circuitries. As an additional layer of complexity, extracellular ATP is rapidly catabolized by ectonucleotidases, culminating in the accumulation of metabolites that mediate distinct biological effects. Here, we discuss the molecular and cellular mechanisms through which ATP and its degradation products influence cancer immunosurveillance, with a focus on therapeutically targetable circuitries.

ADORA2A rs5760423 and CYP1A2 rs762551 Polymorphisms as Risk Factors for Parkinson's Disease

Background: Parkinson’s disease (PD) is the second commonest neurodegenerative disease. The genetic basis of PD is indisputable. Both ADORA2A rs5760423 and CYP1A2 rs762551 have been linked to PD, to some extent, but the exact role of those polymorphisms in PD remains controversial. Objective: We assessed the role of ADORA2A rs5760423 and CYP1A2 rs762551 on PD risk. Methods: We genotyped 358 patients with PD and 358 healthy controls for ADORA2A rs5760423 and CYP1A2 rs762551. We also merged and meta-analyzed our data with data from previous studies, regarding these two polymorphisms and PD. Results: No significant association with PD was revealed (p > 0.05), for either ADORA2A rs5760423 or CYP1A2 rs762551, in any of the examined genetic model of inheritance. In addition, results from meta-analyses yield negative results. Conclusions: Based on our analyses, it appears rather unlikely that ADORA2A rs5760423 or CYP1A2 rs762551 is among the major risk factors for PD, at least in Greek patients with PD.

Methylation-mediated down-regulation of microRNA-497-195 cluster confers osteogenic differentiation in ossification of the posterior longitudinal ligament of the spine via ADORA2A

Aberrant expression of microRNAs (miRNAs) has been associated with spinal ossification of the posterior longitudinal ligament (OPLL). Our initial bioinformatic analysis identified differentially expressed ADORA2A in OPLL and its regulatory miRNAs miR-497 and miR-195. Hence, this study was conducted to clarify the functional relevance of miR-497-195 cluster in OPLL, which may implicate in Adenosine A2A (ADORA2A). PLL tissues were collected from OPLL and non-OPLL patients, followed by quantification of miR-497, miR-195 and ADORA2A expression. The expression of miR-497, miR-195 and/or ADORA2A was altered in posterior longitudinal ligament (PLL) cells, which then were stimulated with cyclic mechanical stress (CMS). We validated that ADORA2A was expressed highly, while miR-497 and miR-195 were down-regulated in PLL tissues of OPLL patients. miR-195 and miR-497 expression in CMS-treated PLL cells was restored by a demethylation reagent 5-aza-2'-deoxycytidine (AZA). Moreover, expression of miR-195 and miR-497 was decreased by promoting promoter CpG island methylation. ADORA2A was verified as the target of miR-195 and miR-497. Overexpression of miR-195 and miR-497 diminished expression of osteogenic factors in PLL cells by inactivating the cAMP/PKA signaling pathway via down-regulation of ADORA2A. Collectively, miR-497-195 cluster augments osteogenic differentiation of PLL cells by inhibiting ADORA2A-dependent cAMP/PKA signaling pathway.

Caffeine and Exercise Performance: Possible Directions for Definitive Findings

Caffeine is one of the most studied supplements in the world. Studies correlate its use to increased exercise performance in endurance activities, as well as its possible ergogenic effects for both intermittent and strength activities. Recent findings show that caffeine may increase or decrease exercise performance. These antagonist responses may occur even when using the same dosage and for individuals with the same characteristics, making it challenging to explain caffeine's impact and applicability. This review article provides an analytic look at studies involving the use of caffeine for human physical performance, and addresses factors that could influence the ergogenic effects of caffeine on different proposed activities. These factors subdivide into caffeine effects, daily habits, physiological factors, and genetic factors. Each variable has been focused on by discussions to research related to caffeine. A better understanding and control of these variables should be considered in future research into personalized nutritional strategies.

Genetic Polymorphism of ADORA2A Is Associated With the Risk of Epilepsy and Predisposition to Neurologic Comorbidity in Chinese Southern Children

Epilepsy, a common disorder of the brain, exhibits a high morbidity rate in children. Childhood epilepsy (CE) is frequently comorbid with neurologic and developmental disorders, sharing underlying genetic factors. This study aimed to investigate the impact of ADORA2A, BDNF, and NTRK2 gene polymorphisms on the risk of childhood epilepsy and their associations with predisposition to epileptic comorbidities. A total of 444 children were enrolled in this study, and three single nucleotide polymorphisms, including ADORA2A rs2298383, BDNF rs6265, and NTRK2 rs1778929, were genotyped. The frequency distribution of genotypes was compared not only between CE patients and healthy children but also between CE patients with and without comorbidities. The results indicated that the carriers of ADORA2A rs2298383 TT genotype tended to have a lower risk of epilepsy (OR = 0.48, 95% CI = 0.30–0.76), while the CT genotype was related to a higher risk (OR = 1.56, 95% CI = 1.06–2.27). The ADORA2A rs2298383 CC genotype predisposed CE patients to comorbid neurologic disorders (OR = 2.76, 95% CI = 1.31–5.80). Genetic variations in BDNF rs6265 and NTRK2 rs1778929 had no significant association with CE and its comorbidities. Fourteen ADORA2A target genes related to epilepsy were identified by the protein–protein interaction analysis, which were mainly involved in the biological processes of “negative regulation of neuron death” and “purine nucleoside biosynthetic process” through the gene functional enrichment analysis. Our study revealed that the genetic polymorphism of ADORA2A rs2298383 was associated with CE risk and predisposition to neurologic comorbidity in children with epilepsy, and the involved mechanism might be related to the regulation of neuron death and purine nucleoside biosynthesis.

Adenosine-producing regulatory B cells in head and neck cancer

Background

Multiple mechanisms of immunosuppression have been identified in the tumor microenvironment including regulatory B cells (B_reg). Recently, we have shown that B_reg suppress T cell function by production of adenosine (ADO). However, the autocrine effect of ADO on B cells and the role of B_reg in head and neck cancer remains unclear.

Methods

Blood (n = 42) and tumor tissue (n = 39) of head and neck cancer patients and healthy donors (n = 60) were analyzed by FACS. The effect of ADO on phenotype, intracellular signaling pathways, Ca²⁺ influx and ADO production was analyzed in B_reg and effector B cells (B_eff) by FACS, luminescence and mass spectrometry. The blockage of the ADO receptor A_2A was analyzed in a murine head and neck cancer model.

Results

ADO-producing B_reg were found in tumor tissue and peripheral blood. ADO inhibited the intracellular Bruton’s tyrosine kinase (BTK) and Ca²⁺ influx only in B_eff. The inhibition of BTK by ibrutinib mimicked the effect of ADO, and ibrutinib reduced the production of ADO by downregulation of CD39 in vitro. The inhibition of ADO receptor A_2A significantly reduced tumor mass and increased B cell infiltration, in vivo.

Conclusion

Our data demonstrate the presence of a novel ADO-producing B_reg population within the tumor microenvironment in mice and humans. A new model is proposed on how ADO-producing B_reg can influence the function of B_eff cells in healthy donors and cancer patients. Thus, the modulation of the ADO pathway in B cells may serve as a therapeutic approach for cancer patients.

Electronic supplementary material

The online version of this article (10.1007/s00262-020-02535-6) contains supplementary material, which is available to authorized users.

The Impact of Genetic Variations in ADORA2A in the Association between Caffeine Consumption and Sleep

ADORA2A has been shown to be responsible for the wakefulness-promoting effect of caffeine and the 1976T>C genotype (SNP rs5751876, formerly 1083T>C) to contribute to individual sensitivity to caffeine effects on sleep. We investigate the association between six single nucleotide polymorphisms (SNP) from ADORA2A and self-reported sleep characteristics and caffeine consumption in 1023 active workers of European ancestry aged 18-60 years. Three groups of caffeine consumers were delineated: low (0-50 mg/day, less than one expresso per day), moderate (51-300 mg/day), and high (>300 mg/day). We found that at caffeine levels higher than 300 mg/day, total sleep time (TST) decreased (F = 13.9, p < 0.01), with an increase of insomnia (ORa [95%CI] = 1.5 [1.1-1.9]) and sleep complaints (ORa [95%CI] = 1.9 [1.1-3.3]), whatever the ADORA2A polymorphism. Odds ratios were adjusted (ORa) for sex, age, and tobacco. However, in low caffeine consumers, lower TST was observed in the T allele compared to homozygote rs5751876 and rs3761422 C carriers. Conversely, higher TST was observed in rs2298383 T allele compared to C and in rs4822492G allele compared to the homozygote C (p < 0.05). These 4 SNPs are in strong linkage disequilibrium. Haplotype analysis confirmed the influence of multiple ADORA2a SNPs on TST. In addition, the rs2298383 T and rs4822492 G alleles were associated with higher risk of sleep complaints (Ora = 1.9 [1.2-3.1] and Ora = 1.5 [1.1-2.1]) and insomnia (Ora = 1.5 [1.3-2.5] and Ora = 1.9 [1.3-3.2). The rs5751876 T allele was associated with a decreased risk of sleep complaints (Ora = 0.7 [0.3-0.9]) and insomnia (Ora = 0.5 [0.3-0.9]). Our results identified ADORA2A polymorphism influences in the less-than-300-mg-per-day caffeine consumers. This opens perspectives on the diagnosis and pharmacology of sleep complaints and caffeine chronic consumption.

Adenosine 2A receptor inhibition protects phrenic motor neurons from cell death induced by protein synthesis inhibition

Respiratory motor neuron survival is critical for maintenance of adequate ventilation and airway clearance, preventing dependence to mechanical ventilation and respiratory tract infections. Phrenic motor neurons are highly vulnerable in rodent models of motor neuron disease versus accessory inspiratory motor pools (e.g. intercostals, scalenus). Thus, strategies that promote phrenic motor neuron survival when faced with disease and/or toxic insults are needed to help preserve breathing ability, airway defense and ventilator independence. Adenosine 2A receptors (A2A) are emerging as a potential target to promote neuroprotection, although their activation can have both beneficial and pathogenic effects. Since the role of A2A receptors in the phrenic motor neuron survival/death is not known, we tested the hypothesis that A2A receptor antagonism promotes phrenic motor neuron survival and preserves diaphragm function when faced with toxic, neurodegenerative insults that lead to phrenic motor neuron death. We utilized a novel neurotoxic model of respiratory motor neuron death recently developed in our laboratory: intrapleural injections of cholera toxin B subunit (CtB) conjugated to the ribosomal toxin, saporin (CtB-Saporin). We demonstrate that intrapleural CtB-Saporin causes: 1) profound phrenic motor neuron death (~5% survival); 2) ~7-fold increase in phrenic motor neuron A2A receptor expression prior to cell death; and 3) diaphragm muscle paralysis (inactive in most rats; ~7% residual diaphragm EMG amplitude during room air breathing). The A2A receptor antagonist istradefylline given after CtB-Saporin: 1) reduced phrenic motor neuron death (~20% survival) and 2) preserved diaphragm EMG activity (~46%). Thus, A2A receptors contribute to neurotoxic phrenic motor neuron death, an effect mitigated by A2A receptor antagonism.

Association between ADORA2A gene polymorphisms and schizophrenia in the North Chinese Han population

BACKGROUND

A large number of studies have shown a close relationship between ADORA2A and the pathological mechanism of schizophrenia. However, to our knowledge, there has been no studies examining the association between the ADORA2A gene and schizophrenia in Chinese Han population.

PURPOSE

The objective of this study was to examine the relationship between adenosine A2A receptor (ADORA2A) single nucleotide polymorphisms and schizophrenia in the North Chinese Han population.

PATIENTS AND METHODS

We detected ADORA2A single nucleotide polymorphisms (SNPs) using polymerase chain reaction-restriction fragment length polymorphism analyses and summarized our results using SPSS statistical software and Haploview in schizophrenia case group (n=398) and healthy control group (n=535).

RESULTS

The frequency of the CC homozygote genotype of SNP rs2298383T/C were significantly higher in the case than the control group (p=0.005, OR=1.712, 95% CI=1.172-2.502). After linkage disequilibrium analysis, SNPs rs5996696A/C and rs2298383T/C displayed strong linkage disequilibrium. We found that the frequencies of haplotypes TA (χ²=6.268, p=0.0123) and CA (χ²=7.012, p=0.0081) were significantly higher in the case group than in the control group.

CONCLUSION

In conclusion, SNPs in the ADORA2A gene may be associated with schizophrenia in the northern Chinese Han population.

Adenosine A2A receptor gene polymorphisms (ADORA2A) are associated with maximal concentric contraction pain

Objectives

To test associations of adenosine A2A receptor gene (ADORA2A) polymorphisms with maximal concentric contraction pain, caffeine-induced perceptual changes, and responses to mild eccentric injury.

Design

Targeted candidate gene association study.

Methods

ADORA2A (rs5751876) was genotyped in 26 adults. Pain of a maximal elbow flexor contraction was assessed. Participants performed 18 eccentric actions of the elbow flexors. Arm volume was measured before and 24- and 48-h post-injury. At 24- and 48-h post-injury, caffeine or placebo capsules were given using a randomized cross-over design and effort and pain were assessed.

Results

Maximal concentric contraction pain was higher for the CC compared to the CT/TT group (effect size d = 0.89) and lower for the TT compared to the CT/CC group (d = 0.62). There were moderate sized differences between CC and TT/CT groups for post-injury exertion and arm volume 24-h post injury.

Conclusions

ADORA2A polymorphisms are moderately associated with muscle pain during maximal contractions in uninjured muscle.

The Role of Genetics in Moderating the Inter-Individual Differences in the Ergogenicity of Caffeine

Caffeine use is widespread among athletes following its removal from the World Anti-Doping Agency banned list, with approximately 75% of competitive athletes using caffeine. While literature supports that caffeine has a small positive ergogenic effect for most forms of sports and exercise, there exists a significant amount of inter-individual difference in the response to caffeine ingestion and the subsequent effect on exercise performance. In this narrative review, we discuss some of the potential mechanisms and focus on the role that genetics has in these differences. CYP1A2 and ADORA2A are two of the genes which are thought to have the largest impact on the ergogenicity of caffeine. CYP1A2 is responsible for the majority of the metabolism of caffeine, and ADORA2A has been linked to caffeine-induced anxiety. The effects of CYP1A2 and ADORA2A genes on responses to caffeine will be discussed in detail and an overview of the current literature will be presented. The role of these two genes may explain a large portion of the inter-individual variance reported by studies following caffeine ingestion. Elucidating the extent to which these genes moderate responses to caffeine during exercise will ensure caffeine supplementation programs can be tailored to individual athletes in order to maximize the potential ergogenic effect.

PD-L2 amplification and durable disease stabilization in patient with urothelial carcinoma receiving pembrolizumab

We report the immunological profile of a patient with upper-tract urothelial carcinoma experiencing stable disease on pembrolizumab for 20 months. The tumor exhibited extensive infiltration by CD8⁺ cytotoxic T lymphocytes, low-to-moderate mutational burden, no PD-L1 staining by commercially available immunohistochemical assays, but amplification of CD274 (coding for PD-L1) and/or PDCD1LG2 (encoding PD-L2) by fluorescence in situ hybridization. RNA-seq revealed multiple biomarkers of an ongoing immune response and compensatory immune evasion, including moderate PD-L1 levels coupled with robust PD-L2 expression. Pending validation in additional patients, these findings suggest that PD-L2 expression levels may constitute a biomarker of response to immune checkpoint blockade in urothelial carcinoma.

Detailed analysis of adenosine A2a receptor (ADORA2A) and CD73 (5'-nucleotidase, ecto, NT5E) methylation and gene expression in head and neck squamous cell carcinoma patients

Background: The adenosine A2a receptor (A2aR) and the adenosine synthesizing enzyme CD73 have recently evolved as a novel immunotherapeutic target. However, little is known about epigenetic modification of the encoding genes ADORA2A and NT5E. Methods: In the present study, we evaluated methylation at 23 loci of ADORA2A and 17 loci of NT5E with regard to transcriptional activity, human papilloma virus (HPV) status, immune cell infiltration, and outcome in a cohort of 279 head and neck squamous carcinoma (HNSCC) patients obtained from The Cancer Genome Atlas (TCGA). Methylation and mRNA expression were generated by the Infinium HumanMethylation450 BeadChip and Illumina HiSeq 2000 RNA Sequencing Version 2 analysis (Illumina, Inc., San Diego, CA, USA). HPV status was assessed by RNA-Seq data analysis of the viral genes E6 and E7. Results: Thirteen out of 23 ADORA2A loci and 15/17 NT5E loci were significantly correlated with mRNA levels (p < 0.05). Inverse correlations were predominately found in promoter regions, while positive correlations were more profound at intragenic loci. ADORA2A hypermethylation was significantly associated with poor overall survival (OS, p ≤ 0.030), whereas NT5E hypomethylation was associated with decreased OS in HPV-positive tumors (p ≤ 0.024) and increased OS in HPV-negative HNSCC (p ≤ 0.029). Further, we found significant correlations between methylation and immune cell infiltrates. Conclusion: Our data might point towards a significant role of the A2aR/CD73 axis during cancer progression in HNSCC.

Phrenic motor neuron adenosine 2A receptors elicit phrenic motor facilitation

KEY POINTS

Although adenosine 2A (A2A ) receptor activation triggers specific cell signalling cascades, the ensuing physiological outcomes depend on the specific cell type expressing these receptors. Cervical spinal adenosine 2A (A2A ) receptor activation elicits a prolonged facilitation in phrenic nerve activity, which was nearly abolished following intrapleural A2A receptor siRNA injections. A2A receptor siRNA injections selectively knocked down A2A receptors in cholera toxin B-subunit-identified phrenic motor neurons, sparing cervical non-phrenic motor neurons. Collectively, our results support the hypothesis that phrenic motor neurons express the A2A receptors relevant to A2A receptor-induced phrenic motor facilitation. Upregulation of A2A receptor expression in the phrenic motor neurons per se may potentially be a useful approach to increase phrenic motor neuron excitability in conditions such as spinal cord injury.

ABSTRACT

Cervical spinal adenosine 2A (A2A ) receptor activation elicits a prolonged increase in phrenic nerve activity, an effect known as phrenic motor facilitation (pMF). The specific cervical spinal cells expressing the relevant A2A receptors for pMF are unknown. This is an important question since the physiological outcome of A2A receptor activation is highly cell type specific. Thus, we tested the hypothesis that the relevant A2A receptors for pMF are expressed in phrenic motor neurons per se versus non-phrenic neurons of the cervical spinal cord. A2A receptor immunostaining significantly colocalized with NeuN-positive neurons (89 ± 2%). Intrapleural siRNA injections were used to selectively knock down A2A receptors in cholera toxin B-subunit-labelled phrenic motor neurons. A2A receptor knock-down was verified by a ∼45% decrease in A2A receptor immunoreactivity within phrenic motor neurons versus non-targeting siRNAs (siNT; P < 0.05). There was no evidence for knock-down in cervical non-phrenic motor neurons. In rats that were anaesthetized, subjected to neuromuscular blockade and ventilated, pMF induced by cervical (C3-4) intrathecal injections of the A2A receptor agonist CGS21680 was greatly attenuated in siA2A (21%) versus siNT treated rats (147%; P < 0.01). There were no significant effects of siA2A on phrenic burst frequency. Collectively, our results support the hypothesis that phrenic motor neurons express the A2A receptors relevant to A2A receptor-induced pMF.

Targeted neurogenesis pathway-based gene analysis identifies ADORA2A associated with hippocampal volume in mild cognitive impairment and Alzheimer's disease

Alzheimer's disease (AD) patients display hippocampal atrophy, memory impairment, and cognitive decline. New neurons are generated throughout adulthood in 2 regions of the brain implicated in AD, the dentate gyrus of the hippocampus and the subventricular zone of the olfactory bulb. Disruption of this process contributes to neurodegenerative diseases including AD, and many of the molecular players in AD are also modulators of adult neurogenesis. However, the genetic mechanisms underlying adult neurogenesis in AD have been underexplored. To address this gap, we performed a gene-based association analysis in cognitively normal and impaired participants using neurogenesis pathway-related candidate genes curated from existing databases, literature mining, and large-scale genome-wide association study findings. A gene-based association analysis identified adenosine A2a receptor (ADORA2A) as significantly associated with hippocampal volume and the association between rs9608282 within ADORA2A and hippocampal volume was replicated in the meta-analysis after multiple comparison adjustments (p = 7.88 × 10-6). The minor allele of rs9608282 in ADORA2A is associated with larger hippocampal volumes and better memory.

Influence of ADORA2A gene polymorphism on leukoencephalopathy risk in MTX-treated pediatric patients affected by hematological malignancies

BACKGROUND

Methotrexate (MTX) can lead to neurotoxicity and asymptomatic leukoencephalopathy. However, the mechanism of MTX-related leukoencephalopathy is obscure. MTX and its metabolites inhibit 5-aminoimidazole-4-carboxamide ribonucleotide formiltransferase (ATIC) and promote adenosine release. Recently, it has been reported that adenosine and its receptor are related to certain central nervous system diseases. We investigated whether adenosine pathway gene polymorphisms and clinical factors were related to MTX-related leukoencephalopathy in pediatric patients affected by hematological malignancies.

PROCEDURE

Fifty-six Japanese childhood acute lymphoblastic leukemia or lymphoma patients were investigated. Patients were evaluated by magnetic resonance imaging of the brain before maintenance therapy or stem cell transplantation. Gene polymorphisms within the adenosine pathway (ATIC, adenosine A2A receptor [ADORA2A]) and the MTX pathway (methylenetetrahydrofolate reductase [MTHFR] and ABCB1) were genotyped using TaqMan assays. Clinical data were collected by accessing the medical records. MTX-related leukoencephalopathy was evaluated by a pediatric neurologist.

RESULTS

Twenty-one (37%) of 56 patients developed MTX-related leukoencephalopathy. Four of 21 patients developed clinical neurotoxicity. The minor allele CC genotype of rs2298383 (ADORA2A) was associated with MTX-related leukoencephalopathy (P = 0.010, odds ratio = 5.81, 95% confidence interval 1.50-22.50). High cumulative dose of systemic MTX was associated with MTX-related leukoencephalopathy after adjusting for sex, ADORA2A polymorphism, and prolonged high MTX concentration (P = 0.042, odds ratio = 1.18, 95% confidence interval 1.01-1.37).

CONCLUSIONS

ADORA2A rs2298383 and high cumulative dose of systemic MTX administration were significantly associated with MTX-related leukoencephalopathy. Our results indicate that pharmacological intervention within the adenosine pathway may be both a treatment and preventative option for MTX-related leukoencephalopathy.

Differential Expression of Adenosine P1 Receptor ADORA1 and ADORA2A Associated with Glioma Development and Tumor-Associated Epilepsy

Level of adenosine, an endogenous astrocyte-based neuromodulator, is primarily regulated by adenosine P1 receptors. This study assessed expression of adenosine P1 receptors, ADORA1 (adenosine A1 receptor) and ADORA2A (adenosine A2a receptor) and their association with glioma development and epilepsy in glioma patients. Expression of ADORA1/ADORA2A was assessed immunohistochemically in 65 surgically removed glioma tissue and 21 peri-tumor tissues and 8 cases of normal brain tissues obtained from hematoma patients with cerebral trauma. Immunofluorescence, Western blot, and qRT-PCR were also used to verify immunohistochemical data. Adenosine P1 receptor ADORA1 and ADORA2A proteins were localized in the cell membrane and cytoplasm and ADORA1/ADORA2A immunoreactivity was significantly stronger in glioma and peri-tumor tissues that contained infiltrating tumor cells than in normal brain tissues (p < 0.05). The World Health Organization (WHO) grade III gliomas expressed even higher level of ADORA1 and ADORA2A. Western blot and qRT-PCR confirmed immunohistochemical data. Moreover, higher levels of ADORA1 and ADORA2A expression occurred in high-grade gliomas, in which incidence of epilepsy were lower (p < 0.05). In contrast, a lower level of ADORA1/ADORA2A expression was found in peri-tumor tissues with tumor cell presence from patients with epilepsy compared to patients without epilepsy (p < 0.05). The data from the current study indicates that dysregulation in ADORA1/ADORA2A expression was associated with glioma development, whereas low level of ADORA1/ADORA2A expression could increase susceptibility of tumor-associated epilepsy.

The RS685012 Polymorphism of ACCN2, the Human Ortholog of Murine Acid-Sensing Ion Channel (ASIC1) Gene, is Highly Represented in Patients with Panic Disorder

Panic disorder (PD) is a disabling anxiety disorder that is characterized by unexpected, recurrent panic attacks, associated with fear of dying and worrying about possible future attacks or other behavioral changes as a consequence of the attacks. The acid-sensing ion channels (ASICs) are a family of proton-sensing channels expressed throughout the nervous system. Their activity is linked to a variety of behaviors including fear, anxiety, pain, depression, learning, and memory. The human analog of ASIC1a is the amiloride-sensitive cation channel 2 (ACCN2). Adenosine A2A receptors are suggested to play an important role in different brain circuits and pathways involved in anxiety reactions. In this work we aimed to evaluate the distribution of ACCN2 rs685012 and ADORA2A rs2298383 polymorphisms in PD patients compared with healthy subjects. We found no association between ADORA2A polymorphism and PD. Instead, the C mutated allele for ACCN2 rs685012 polymorphism was significantly more frequent in patients than in controls. On the contrary, the TT homozygous wild-type genotype and also the ACCN2 TT/ADORA2A CT diplotype were significantly more represented in controls. These results are suggestive for a role of ACCN2 rs685012 polymorphism in PD development in Caucasian people.

Categorical complexities of Plasmodium falciparum malaria in individuals is associated with genetic variations in ADORA2A and GRK5 genes

In the erythrocytes, malaria parasite entry and infection is mediated through complex membrane sorting and signaling processes. We investigated the effects of single-locus and multilocus interactions to test the hypothesis that the members of the GPCR family genes, adenosine A2a receptor (ADORA2A) and G-protein coupled receptor kinase5 (GRK5), may contribute to the pathogenesis of malaria caused by Plasmodium falciparum (Pf) independently or through complex interactions. In a case-control study of adults, individuals affected by Pf malaria (complicated n=168; uncomplicated n=282) and healthy controls (n=450) were tested for their association to four known SNPs in GRK5 (rs2230345, rs2275036, rs4752307 and rs11198918) and two in ADORA2A (rs9624472 and rs5751876) genes with malaria susceptibility, using techniques of polymerase chain reaction-restriction fragment length polymorphisms and direct DNA sequencing. Single-locus analysis showed significant association of 2 SNPs; rs5751876 (OR=3.2(2.0-5.2); p=0.0006) of ADORA2A and rs2230345 (OR=0.3(0.2-0.5); p=0.0006) of GRK5 with malaria. The mean of the serum creatinine levels were significantly higher in patients with variant GG (p=0.006) of rs9624472 in ADORA2A gene compared to AA and AG genotypes in complicated Pf malaria cases, with the G allele also showing increased risk for malaria (OR=1.3(1.1-1.6); p=0.017). Analyses of predicted haplotypes of the two ADORA2A and the four GRK5 SNPs have identified the haplotypes that conferred risk as well as resistance to malaria with statistical significance. Molecular docking analysis of evolutionary rs2230345 SNP indicated a stable activity of GRK5 for the mutant allele compared to the wild type. Further, generalized multifactor dimensionality reduction to test the contribution of individual effects of the six polymorphisms and higher-order interactions to risk of symptoms/clinical complications of malaria suggested a best six-locus model showing statistical significance. The study provides evidence for the role of ADORA2A and GRK5 that might influence the etiology of malaria infection.

Is there a role for ADORA2A polymorphisms in levodopa-induced dyskinesia in Parkinson's disease patients?

AIM

Levodopa is first line treatment of Parkinson's disease (PD). However, its use is associated with the presence of motor fluctuations and dyskinesias. In recent years, adenosine A2A receptor (A2AR) is rising as a therapeutic target for PD. The aim of the present study was to investigate whether ADORA2A is associated with levodopa adverse effects.

PATIENTS & METHODS

Two hundred and eight PD patients on levodopa therapy were investigated. rs2298383 and rs3761422 at the ADORA2A gene were genotyped by allelic discrimination assays.

RESULTS

A trend for association was observed for both polymorphism and diplotypes with dyskinesia.

CONCLUSION

The present results should be considered as positive preliminary evidence. Further studies are needed to determine the association between ADORA2A and dyskinesia. Original submitted 3 December 2014; Revision submitted 13 February 2015.

Increased striatal adenosine A2A receptor levels is an early event in Parkinson's disease-related pathology and it is potentially regulated by miR-34b

Adenosine A2A receptor (A2AR) is a G-protein coupled receptor that stimulates adenylyl cyclase activity. In the brain, A2ARs are found highly enriched in striatal GABAergic medium spiny neurons, related to the control of voluntary movement. Pharmacological modulation of A2ARs is particularly useful in Parkinson's disease (PD) due to their property of antagonizing dopamine D2 receptor activity. Increases in A2AR levels have been described in PD patients showing an important loss of dopaminergic denervation markers, but no data have been reported about A2AR levels in incidental PD brains. In the present report, we show that increased A2ARs protein levels were also detected in the putamen of incidental PD cases (Braak PD stages 1-2) with respect to age-matched controls. By contrast, A2ARs mRNA levels remained unchanged, suggesting that posttranslational mechanisms could be involved in the regulation of A2ARs. It has been described how miR-34b/c downregulation is an early event in PD cases. We found that miR-34b levels are also significantly reduced in the putamen of incidental PD cases and along disease progression. Given that 3'UTR of A2AR contains a predicted target site for miR-34b, the potential role of this miRNA in protein A2AR levels was assessed. In vitro studies revealed that endogenous A2AR protein levels increased when miR-34b function was blocked using a specific anti-miR-34b. Moreover, using a luciferase reporter assay with point mutations in a miR-34b predicted binding site within the 3'UTR region of A2AR mRNA abolished the effect of the miRNA using a miR-34b mimic. In addition, we showed a reduced percentage of DNA methylation in the 5'UTR region of ADORA2A in advanced PD cases. Overall, these findings reveal that increased A2AR protein levels occur in asymptomatic PD patients and provide new insights into the molecular mechanisms underlying A2AR expression levels along the progression of this neurodegenerative disease.

Reduced striatal adenosine A2A receptor levels define a molecular subgroup in schizophrenia

Schizophrenia (SZ) is a mental disorder of unknown origin. Some scientific evidence seems to indicate that SZ is not a single disease entity, since there are patient groups with clear symptomatic, course and biomarker differences. SZ is characterized by a hyperdopaminergic state related to high dopamine D2 receptor activity. It has also been proposed that there is a hypoadenosynergic state. Adenosine is a nucleoside widely distributed in the organism with neuromodulative and neuroprotective activity in the central nervous system. In the brain, the most abundant adenosine receptors are A1R and A2AR. In the present report, we characterize the presence of both receptors in human postmortem putamens of patients suffering SZ with real time TaqMan PCR, western blotting and radioligand binding assay. We show that A1R levels remain unchanged with respect to age-matched controls, whereas nearly fifty percent of patients have reduced A2AR, at the transcriptional and translational levels. Moreover, we describe how DNA methylation plays a role in the pathological A2AR levels with the bisulfite-sequencing technique. In fact, an increase in 5-methylcytosine percentage in the 5' UTR region of ADORA2A was found in those SZ patients with reduced A2AR levels. Interestingly, there was a relationship between the A2A/β-actin ratio and motor disturbances as assessed with some items of the PANSS, AIMS and SAS scales. Therefore, there may be a subgroup of SZ patients with reduced striatal A2AR levels accompanied by an altered motor phenotype.

Computer-aided identification of novel protein targets of bisphenol A

The xenoestrogen bisphenol A (2,2-bis-(p-hydroxyphenyl)-2-propane, BPA) is a known endocrine-disrupting chemical used in the fabrication of plastics, resins and flame retardants, that can be found throughout the environment and in numerous every day products. Human exposure to this chemical is extensive and generally occurs via oral route because it leaches from the food and beverage containers that contain it. Although most of the effects related to BPA exposure have been linked to the activation of the estrogen receptor (ER), the mechanisms of the interaction of BPA with protein targets different from ER are still unknown. Therefore, the objective of this work was to use a bioinformatics approach to identify possible new targets for BPA. Docking studies were performed between the optimized structure of BPA and 271 proteins related to different biochemical processes, as selected by text-mining. Refinement docking experiments and conformational analyses were carried out using LigandScout 3.0 for the proteins selected through the affinity ranking (lower than -8.0kcal/mol). Several proteins including ERR gamma (-9.9kcal/mol), and dual specificity protein kinases CLK-4 (-9.5kcal/mol), CLK-1 (-9.1kcal/mol) and CLK-2 (-9.0kcal/mol) presented great in silico binding affinities for BPA. The interactions between those proteins and BPA were mostly hydrophobic with the presence of some hydrogen bonds formed by leucine and asparagine residues. Therefore, this study suggests that this endocrine disruptor may have other targets different from the ER.

Role of hepatic resident and infiltrating macrophages in liver repair after acute injury

Treatment of liver disease, caused by hepatotoxins, viral infections, alcohol ingestion, or autoimmune conditions, remains challenging and costly. The liver has a powerful capacity to repair and regenerate, thus a thorough understanding of this tightly orchestrated process will undoubtedly improve clinical means of restoring liver function after injury. Using a murine model of acute liver injury caused by overdose of acetaminophen (APAP), our studies demonstrated that the combined absence of liver resident macrophages (Kupffer cells, KCs), and infiltrating macrophages (IMs) resulted in a marked delay in liver repair, even though the initiation and extent of peak liver injury was not impacted. This delay was not due to impaired hepatocyte proliferation but rather prolonged vascular leakage, which is caused by APAP-induced liver sinusoidal endothelial cell (LSEC) injury. We also found that KCs and IMs express an array of angiogenic factors and induce LSEC proliferation and migration. Our mechanistic studies suggest that hypoxia-inducible factor (HIF) may be involved in regulating the angiogenic effect of hepatic macrophages (Macs), as we found that APAP challenge resulted in hypoxia and stabilization of HIF in the liver and hepatic Macs. Together, these data indicate an important role for hepatic Macs in liver blood vessel repair, thereby contributing to tissue recovery from acute injury.

Reduced neurobehavioral impairment from sleep deprivation in older adults: contribution of adenosinergic mechanisms

A night without sleep is followed by enhanced sleepiness, increased low-frequency activity in the waking EEG, and reduced vigilant attention. The magnitude of these changes is highly variable among healthy individuals. Findings in young men of low and high subjective caffeine sensitivity suggest that adenosinergic mechanisms contribute to inter-individual differences in sleep deprivation-induced changes in EEG theta activity, as well as optimal performance on the psychomotor vigilance task (PVT). In comparison to young subjects, healthy adults of older age typically feel less sleepy after sleep deprivation, and show fewer response lapses, and faster reaction times on the PVT, especially in the morning after the night without sleep. We hypothesized that age-related changes in adenosine signal transmission underlie reduced vulnerability to sleep deprivation in older individuals. To test this hypothesis, the combined effects of prolonged wakefulness and the adenosine receptor antagonist, caffeine, on an antero-posterior power gradient in EEG theta activity and PVT performance were analyzed in healthy older and caffeine-insensitive and -sensitive young men. The results show that age-related differences in sleep loss-induced changes in brain rhythmic activity and neurobehavioral functions are mirrored in young individuals of low and high sensitivity to the stimulant effects of caffeine. Moreover, the effects of sleep deprivation and caffeine on regional theta power and vigilant attention are inversely correlated across older and young age groups. Genetic variants of the adenosine A_2A receptor gene contribute to individual differences in neurobehavioral performance in rested and sleep deprived state, and modulate the actions of caffeine in wakefulness and sleep. Based upon this evidence, we propose that age-related differences in A_2A receptor-mediated signal transduction could be involved in age-related changes in the vulnerability to acute sleep deprivation.