Search

Schizophrenia is a neuropsychiatric illness characterized by altered neurotransmission, in which adenosine, a modulator of glutamate and dopamine, plays a critical role that is relatively unexplored in the human brain. In the present study, postmortem human brain tissue from the anterior cingulate cortex (ACC) of individuals with schizophrenia (n = 20) and sex- and age-matched control subjects without psychiatric illness (n = 20) was obtained from the Bronx–Mount Sinai NIH Brain and Tissue Repository. Enriched populations of ACC pyramidal neurons were isolated using laser microdissection (LMD). The mRNA expression levels of six key adenosine pathway components—adenosine kinase (ADK), equilibrative nucleoside transporters 1 and 2 (ENT1 and ENT2), ectonucleoside triphosphate diphosphohydrolases 1 and 3 (ENTPD1 and ENTPD3), and ecto-5′-nucleotidase (NT5E)—were quantified using real-time PCR (qPCR) in neurons from these individuals. No significant mRNA expression differences were observed between the schizophrenia and control groups (p > 0.05). However, a significant sex difference was found in ADK mRNA expression, with higher levels in male compared with female subjects (Mann–Whitney U = 86; p < 0.05), a finding significantly driven by disease (t(17) = 3.289; p < 0.05). Correlation analyses also demonstrated significant associations (n = 12) between the expression of several adenosine pathway components (p < 0.05). In our dementia severity analysis, ENTPD1 mRNA expression was significantly higher in males in the "mild" clinical dementia rating (CDR) bin compared with males in the "none" CDR bin (F(2, 13) = 5.212; p < 0.05). Lastly, antipsychotic analysis revealed no significant impact on the expression of adenosine pathway components between medicated and non-medicated schizophrenia subjects (p > 0.05). The observed sex-specific variations and inter-component correlations highlight the value of investigating sex differences in disease and contribute to the molecular basis of schizophrenia's pathology. [ABSTRACT FROM AUTHOR]

Background and Purpose: Adenosine receptor activation induces delayed, sustained cardioprotection against ischaemia–reperfusion (IR) injury (24–72 h), but the mechanisms underlying extended cardioprotection duration remain unresolved. We hypothesized that a positive feedback loop involving adenosine receptor‐induced proteasomal degradation of adenosine kinase (ADK) and decreased myocardial adenosine metabolism extends the duration of cardioprotection. Experimental Approach: Mice were administered an ADK inhibitor, ABT‐702, to induce endogenous adenosine signalling. Cardiac ADK protein and mRNA levels were analysed 24–120 h later. Theophylline or bortezomib was administered 24 h after ABT‐702 to examine the late roles of adenosine receptors or proteasomal activity, respectively, in ADK expression and cardioprotection at 72 h. Coronary flow and IR tolerance were analysed by Langendorff technique. The potential for continuous adenosinergic cardioprotection was examined using heterozygous, cardiac‐specific ADK KO (cADK+/−) mice. Cardiac ADK expression was also examined after A1 or A3 receptor agonist, phenylephrine, lipopolysaccharide or sildenafil administration. Key results: ABT‐702 treatment decreased ADK protein content and provided cardioprotection from 24 to 72 h. ADK mRNA upregulation restored ADK protein after 96–120 h. Adenosine receptor or proteasome inhibition at 24 h reversed ABT‐702‐induced ADK protein deficit and cardioprotection at 72 h. cADK+/− hearts exhibited continuous cardioprotection. Diverse preconditioning agents also diminished cardiac ADK protein expression. Conclusion and Implications: A positive feedback loop driven by adenosine receptor‐induced ADK degradation and renewed adenosine signalling extends the duration of cardioprotection by ABT‐702 and possibly other preconditioning agents. The therapeutic potential of continuous adenosinergic cardioprotection is demonstrated in cADK+/− hearts. [ABSTRACT FROM AUTHOR]

Background: Ginsenoside Rg1 (Rg1) is one of the main active components in Chinese medicines, Panax ginseng and Panax notoginseng. Research has shown that Rg1 has a protective effect on the cardiovascular system, including anti-myocardial ischemia-reperfusion injury, anti-apoptosis, and promotion of myocardial angiogenesis, suggesting it a potential cardiovascular agent. However, the protective mechanism involved is still not fully understood. Methods: Based on network pharmacology, ligand-based protein docking, proteomics, Western blot, protein recombination and spectroscopic analysis (UV–Vis and fluorescence spectra) techniques, potential targets and pathways for Rg1 against myocardial ischemia (MI) were screened and explored. Results: An important target set containing 19 proteins was constructed. Two target proteins with more favorable binding activity for Rg1 against MI were further identified by molecular docking, including mitogen-activated protein kinase 1 (MAPK1) and adenosine kinase (ADK). Meanwhile, Rg1 intervention on H9c2 cells injured by H2O2 showed an inhibitory oxidative phosphorylation (OXPHOS) pathway. The inhibition of Rg1 on MAPK1 and OXPHOS pathway was confirmed by Western blot assay. By protein recombination and spectroscopic analysis, the binding reaction between ADK and Rg1 was also evaluated. Conclusion: Rg1 can effectively alleviate cardiomyocytes oxidative stress injury via targeting MAPK1 and ADK, and inhibiting oxidative phosphorylation (OXPHOS) pathway. The present study provides scientific basis for the clinical application of the natural active ingredient, Rg1, and also gives rise to a methodological reference to the searching of action targets and pathways of other natural active ingredients.

Acute liver injury (ALI) is a common life-threatening condition with a high mortality rate due to liver disease-related death. However, current therapeutic interventions for ALI remain ineffective, and the development of effective novel therapies is urgently needed. Liver samples from patients with drug-induced ALI were collected to detect adenosine kinase (ADK) expression. Male C57BL/6 J mice, hepatocyte-specific ADK knockout (ADKHKO) mice, and their controls (ADKf/f) were exposed to acetaminophen (APAP) and other treatments to investigate the mechanisms of APAP-related ALI. ADK expression was significantly decreased in APAP-injured livers. Hepatocyte-specific ADK deficiency exacerbated APAP-induced ALI, while a gain-of-function approach delivering AAV-ADK, markedly alleviated APAP-induced ALI, as indicated by changes in alanine aminotransferases (ALT) levels, aspartate aminotransferase (AST) levels, neutrophil infiltration and hepatocyte death. This study showed that ADK played a critical role in ALI by activating autophagy through two signaling pathways, the adenosine monophosphate-activated protein kinase (AMPK)-mTOR pathway and the adenosine receptor A1 (ADORA1)-Akt-mTOR pathway. Furthermore, we found that metformin upregulated ADK expression in hepatocytes and protected against APAP-induced ALI. These results demonstrate that ADK is critical in protecting against APAP-induced ALI and that developing therapeutics targeting ADK-adenosine-ADORA1 is a new approach for ALI treatment. Metformin is a potential candidate for preventing ALI by upregulating ADK. [ABSTRACT FROM AUTHOR]

Aims Abdominal aortic aneurysm (AAA) is a common, serious vascular disease with no effective pharmacological treatment. The nucleoside adenosine plays an important role in modulating vascular homeostasis, which prompted us to determine whether adenosine kinase (ADK), an adenosine metabolizing enzyme, modulates AAA formation via control of the intracellular adenosine level, and to investigate the underlying mechanisms. Methods and results We used a combination of genetic and pharmacological approaches in murine models of AAA induced by calcium chloride (CaCl2) application or angiotensin II (Ang II) infusion to study the role of ADK in the development of AAA. In vitro functional assays were performed by knocking down ADK with adenovirus-short hairpin RNA in human vascular smooth muscle cells (VSMCs), and the molecular mechanisms underlying ADK function were investigated using RNA-sequencing, isotope tracing, and chromatin immunoprecipitation quantitative polymerase chain reaction (ChIP-qPCR). The heterozygous deficiency of ADK protected mice from CaCl2- and Ang II-induced AAA formation. Moreover, specific knockout of ADK in VSMCs prevented Ang II-induced AAA formation, as evidenced by reduced aortic extracellular elastin fragmentation, neovascularization, and aortic inflammation. Mechanistically, ADK knockdown in VSMCs markedly suppressed the expression of inflammatory genes associated with AAA formation, and these effects were independent of adenosine receptors. The metabolic flux and ChIP-qPCR results showed that ADK knockdown in VSMCs decreased S-adenosylmethionine (SAM)-dependent transmethylation, thereby reducing H3K4me3 binding to the promoter regions of the genes that are associated with inflammation, angiogenesis, and extracellular elastin fragmentation. Furthermore, the ADK inhibitor ABT702 protected mice from CaCl2-induced aortic inflammation, extracellular elastin fragmentation, and AAA formation. Conclusion Our findings reveal a novel role for ADK inhibition in attenuating AAA via epigenetic modulation of key inflammatory genes linked to AAA pathogenesis. [ABSTRACT FROM AUTHOR]

Aim: To investigate the effects of adenosine kinase (ADK), a key enzyme in determining intracellular adenosine levels, on β cells, and their underlying mechanism. Methods: Genetic animal models and transgenic immortalized cells were applied to study the effect of ADK on islet beta‐cell proliferation and function. The beta‐cell mass and response to glucose were measured in vivo using mice with beta‐cell‐specific ADK overexpression, and in vitro using ADK‐overexpressed immortalized beta‐cell. Results: The expression of ADK in human islets at high abundance, especially in β cells, was decreased during the process of β‐cell proliferation. Additionally, a transgenic mouse model (ADKtg/tg /Mip‐Cre) was generated wherein the mouse Insulin1 gene promoter specifically overexpressed ADK in pancreatic β cells. The ADKtg/tg /Mip‐Cre model exhibited impaired glucose tolerance, decreased fasting plasma insulin, loss of β‐cell mass, and inhibited β‐cell proliferation. Proteomic analysis revealed that ADK overexpression inhibited the expression of several proteins that promote cell proliferation and insulin secretion. Upregulating ADK in the β‐cell line inhibited the expression of β‐cell related regulatory molecules, including FoxO1, Appl1, Pxn, Pdx‐1, Creb and Slc16a3. Subsequent in vitro experiments indicated that the inhibition of β‐cell proliferation and the decreased expression of Pdx‐1, Creb and Slc16a3 were rescued by DNA methyltransferase 3A (DNMT3A) knockdown in β cells. Conclusion: In this study, we found that the overexpression of ADK decreased the expression of several genes that regulate β cells, resulting in the inhibition of β‐cell proliferation and dysfunction by upregulating the expression of DNMT3A. [ABSTRACT FROM AUTHOR]

Adenosine kinase (ADK) controls adenosine levels. Abnormal concentration of adenosine lead to multiple disorders in humans. In this study, the effect of non-synonymous single nucleotide polymorphisms (nsSNPs) in human Adk was evaluated on the structure and function of long and short ADK isoforms (ADK-L and ADK-S) using computational tools. Of the 244 coding nsSNPs retrived in Adk, 66 amino acid changes were deleterious by at least five tools: SIFT, PhD-SNP, SNPs&GO, SuSPect, SNAP2, FATHMM, and PolyPhen-2. I-Mutant 2.0 and MUpro showed that among them, 26 substitutions had a strong destabilizing effect on both ADK isoforms. The conserved region and secondary structure of ADK isoforms were predicted by the ConSurf and NetSurfP-3.0 servers, respectively. The HOPE server displayed that 11 nsSNPs, due to the change in amino acid properties, had adverse effects on ADK isoforms. Docking analysis showed that L151 and F218 in ADK-L and their corresponding residues in ADK-S are located in the ligand-binding site and their mutations changed the cavity structure or ligand binding affinity. In conclusion, this study, by using computational methods, identified 11 harmful nsSNPs in human Adk. These predictive results facilitate the association of these nsSNPs with disease susceptibility in population studies. [ABSTRACT FROM AUTHOR]

Schizophrenia is a neuropsychiatric illness characterized by altered neurotransmission, in which adenosine, a modulator of glutamate and dopamine, plays a critical role that is relatively unexplored in the human brain. In the present study, postmortem human brain tissue from the anterior cingulate cortex (ACC) of individuals with schizophrenia (n = 20) and sex- and age-matched control subjects without psychiatric illness (n = 20) was obtained from the Bronx–Mount Sinai NIH Brain and Tissue Repository. Enriched populations of ACC pyramidal neurons were isolated using laser microdissection (LMD). The mRNA expression levels of six key adenosine pathway components—adenosine kinase (ADK), equilibrative nucleoside transporters 1 and 2 (ENT1 and ENT2), ectonucleoside triphosphate diphosphohydrolases 1 and 3 (ENTPD1 and ENTPD3), and ecto-5′-nucleotidase (NT5E)—were quantified using real-time PCR (qPCR) in neurons from these individuals. No significant mRNA expression differences were observed between the schizophrenia and control groups (p > 0.05). However, a significant sex difference was found in ADK mRNA expression, with higher levels in male compared with female subjects (Mann–Whitney U = 86; p < 0.05), a finding significantly driven by disease (t(17) = 3.289; p < 0.05). Correlation analyses also demonstrated significant associations (n = 12) between the expression of several adenosine pathway components (p < 0.05). In our dementia severity analysis, ENTPD1 mRNA expression was significantly higher in males in the “mild” clinical dementia rating (CDR) bin compared with males in the “none” CDR bin (F(2, 13) = 5.212; p < 0.05). Lastly, antipsychotic analysis revealed no significant impact on the expression of adenosine pathway components between medicated and non-medicated schizophrenia subjects (p > 0.05). The observed sex-specific variations and inter-component correlations highlight the value of investigating sex differences in disease and contribute to the molecular basis of schizophrenia’s pathology.

The level of mRNA of the long (L) and short (S) isoforms of adenosine kinase (ADK) was analyzed in patients with colorectal cancer (CRC). ADK is required to convert adenosine (ADO) to AMP. It was shown that tumor and normal colon tissues (n=13) do not differ in the level of ADK-S and ADK-L mRNA. At the same time, the level of ADK-S mRNA (tumor: p=0.0214, normal: p=0.005) in the colon tissue was lower than in the blood of CRC patients (n=20), and the level of ADK-L mRNA (tumor: p=0.007, normal: p=0.024), on the contrary, was higher. A negative correlation was found between the level of ADK-S mRNA and the level of A2aR mRNA in both tumor and normal tissues (p=0.018 and p=0.0014, respectively). In the tumor tissue, a positive correlation was shown between ADK-L and CD73 mRNA levels (p=0.017). The obtained data indicate the association ADK with the expression of CD39/CD73/A2aR in CRC patients. In this regard, the effect of recombinant ADK on the expression of CD39 and CD73 ectonucleotidase by T cells in vitro was analyzed. In a culture of peripheral blood mononuclear cells isolated from the blood of 5 healthy donors, ADK did not abolish the inhibitory effect on the expression of CD39 and CD73 by CD8+T cells in the presence of a high concentration of ATP (a source for ADO). Effects on CD39+CD4+, CD73+CD4+T cells and CD39+ Treg cells were also not found. [ABSTRACT FROM AUTHOR]

Aims: Deep brain stimulation (DBS) of the anterior nucleus of the thalamus, is an effective therapy for patients with drug‐resistant epilepsy, yet, its mechanism of action remains elusive. Adenosine kinase (ADK), a key negative regulator of adenosine, is a potential modulator of epileptogenesis. DBS has been shown to increase adenosine levels, which may suppress seizures via A1 receptors (A1Rs). We investigated whether DBS could halt disease progression and the potential involvement of adenosine mechanisms. Methods: Control group, SE (status epilepticus) group, SE‐DBS group, and SE‐sham‐DBS group were included in this study. One week after a pilocarpine‐induced status epilepticus, rats in the SE‐DBS group were treated with DBS for 4 weeks. The rats were monitored by video‐EEG. ADK and A1Rs were tested with histochemistry and western blot, respectively. Results: Compared with the SE group and SE‐sham‐DBS group, DBS could reduce the frequency of spontaneous recurrent seizures (SRS) and the number of interictal epileptic discharges. The DPCPX, an A1R antagonist, reversed the effect of DBS on interictal epileptic discharges. In addition, DBS inhibited the overexpression of ADK and the downregulation of A1Rs. Conclusion: The findings indicate that DBS can reduce SRS in epileptic rats via inhibition of ADK and activation of A1Rs. A1Rs might be a potential target of DBS for the treatment of epilepsy. [ABSTRACT FROM AUTHOR]

Aims: Mesial temporal lobe epilepsy without hippocampal sclerosis (no‐HS MTLE) refers to those MTLE patients who have neither magnetic resonance imaging (MRI) lesions nor definite pathological evidence of hippocampal sclerosis. They usually have resistance to antiepileptic drugs, difficulties in precise seizure location and poor surgical outcomes. Adenosine is a neuroprotective neuromodulator that acts as a seizure terminator in the brain. The role of adenosine in no‐HS MTLE is still unclear. Further research to explore the aetiology and pathogenesis of no‐HS MTLE may help to find new therapeutic targets. Methods: In surgically resected hippocampal specimens, we examined the maladaptive changes of the adenosine system of patients with no‐HS MTLE. In order to better understand the dysregulation of the adenosine pathway in no‐HS MTLE, we developed a rat model based on the induction of focal cortical lesions through a prenatal freeze injury. Results: We first examined the adenosine system in no‐HS MTLE patients who lack hippocampal neuronal loss and found ectopic expression of the astrocytic adenosine metabolising enzyme adenosine kinase (ADK) in hippocampal pyramidal neurons, as well as downregulation of neuronal A1 receptors (A1Rs) in the hippocampus. In the no‐HS MTLE model rats, the transition of ADK from neuronal expression to an adult pattern of glial expression in the hippocampus was significantly delayed. Conclusions: Ectopic expression of neuronal ADK might be a pathological hallmark of no‐HS MTLE. Maladaptive changes in adenosine metabolism might be a novel target for therapeutic intervention in no‐HS MTLE. [ABSTRACT FROM AUTHOR]

Focal cortical dysplasia (FCD), a common malformation of cortical development, is frequently associated with pharmacoresistant epilepsy in both children and adults. Adenosine is an inhibitory modulator of brain activity and a prospective anti-seizure agent with potential for clinical translation. Our previous results demonstrated that the major adenosine-metabolizing enzyme adenosine kinase (ADK) was upregulated in balloon cells (BCs) within FCD type IIB lesions, suggesting that dysfunction of the adenosine system is implicated in the pathophysiology of FCD. In our current study, we therefore performed a comprehensive analysis of adenosine signaling in surgically resected cortical specimens from patients with FCD type I and type II via immunohistochemistry and immunoblot analysis. Adenosine enzyme signaling was assessed by quantifying the levels of the key enzymes of adenosine metabolism, i.e., ADK, adenosine deaminase (ADA), and ecto-5'-nucleotidase (CD73). Adenosine receptor signaling was assessed by quantifying the levels of adenosine A2A receptor (A2AR) and putative downstream mediators of adenosine, namely, glutamate transporter-1 (GLT-1) and mammalian target of rapamycin (mTOR). Within lesions in FCD specimens, we found that the adenosine-metabolizing enzymes ADK and ADA, as well as the adenosine-producing enzyme CD73, were upregulated. We also observed an increase in A2AR density, as well as a decrease in GLT-1 levels and an increase in mTOR levels, in FCD specimens compared with control tissue. These results suggest that dysregulation of the adenosine system is a common pathologic feature of both FCD type I and type II. The adenosine system might therefore be a therapeutic target for the treatment of epilepsy associated with FCD. [ABSTRACT FROM AUTHOR]

Astrocytes play a dual role in the brain. On the one hand, they are active signaling partners of neurons and can for instance control synaptic transmission and its plasticity. On the other hand, they fulfill various homeostatic functions such as clearance of glutamate and K+ released from neurons. The latter is for instance important for limiting neuronal excitability. Therefore, an impairment or failure of glutamate and K+ clearance will lead to increased neuronal excitability, which could trigger or aggravate brain diseases such as epilepsy, in which neuronal hyperexcitability plays a role. Experimental data indicate that astrocytes could have such a causal role in epilepsy, but the role of astrocytes as initiators of epilepsy and the relevant mechanisms are under debate. In this overview, we will discuss the potential mechanisms with focus on K+ clearance, glutamate uptake and homoeostasis and related mechanisms, and the evidence for their causative role in epilepsy. [ABSTRACT FROM AUTHOR]

Pro-inflammatory and reparative macrophages are crucial in clearing necrotic myocardium and promoting cardiac repair after myocardial infarction (MI), respectively. Extracellular adenosine has been demonstrated to modulate macrophage polarization through adenosine receptors. However, the role of intracellular adenosine in macrophage polarization has not been explored and adenosine kinase (ADK) is a major enzyme regulating intracellular adenosine levels. Here, we aimed to elucidate the role of ADK in macrophage polarization and its subsequent impact on MI. We demonstrated that ADK was upregulated in bone marrow-derived macrophages (BMDMs) after IL-4 treatment and was highly expressed in the infarct area at day 7 post-MI, especially in macrophages. Compared with wild-type mice, myeloid-specific Adk knockout mice showed increased infarct size, limited myofibroblast differentiation, reduced collagen deposition and more severe cardiac dysfunction after MI, which was related to impaired reparative macrophage phenotype in MI tissue. We found that ADK deletion or inhibition significantly decreased the expression of reparative genes, such as Arg1, Ym1, Fizz1, and Cd206 in BMDMs after IL-4 treatment. The increased intracellular adenosine due to Adk deletion inhibited transmethylation reactions and decreased the trimethylation of H3K4 in BMDMs after IL-4 treatment. Mechanistically, we demonstrated that Adk deletion suppressed reparative macrophage phenotype through decreased IRF4 expression, which resulted from reduced levels of H3K4me3 on the Irf4 promotor. Together, our study reveals that ADK exerts a protective effect against MI by promoting reparative macrophage polarization through epigenetic mechanisms. Schematic illustration of the mechanism by which myeloid Adk deficiency impairs cardiac repair by inhibiting reparative macrophage polarization through the H3K4me3-IRF4 pathway. A. ADK wild type (WT) B. ADK knockout (KO). SAM: S-adenosyl methionine; SAH: S-adenosyl homocysteine; Ado: adenosine; Hcy: homocysteine; AMP: adenosine monophosphate; SAHH: S-adenosyl homocysteine hydrolysis; IRF4: interferon regulatory factor 4; -CH3 and Me: methyl group; H3K4: histone 3 lysine 4. [Display omitted] • ADK expression was upregulated in reparative macrophages in the infarct area. • Myeloid Adk deficiency exacerbated cardiac dysfunction after MI. • Myeloid Adk deficiency reduced myofibroblast formation and collagen I deposition. • ADK deletion suppressed reparative macrophage phenotype in MI tissue and BMDMs. • ADK mediated reparative macrophage polarization via H3K4me3-IRF4 pathway. [ABSTRACT FROM AUTHOR]

Schistosomiasis is one of the most important human helminthiases worldwide. Praziquantel is the current treatment, and no vaccine is available until the present. Thus, the presented study aimed to evaluate the immunization effects with recombinant Schistosoma mansoni enzymes: Adenosine Kinase (AK) and Hypoxanthine-Guanine Phosphoribosyltransferase (HGPRT), as well as a MIX of the two enzymes. Female Balb/c mice were immunized in three doses, and 15 days after the last immunization, animals were infected with S. mansoni. Our results showed that the group MIX presented a reduction in the eggs in feces by 30.74% and 29%, respectively, in the adult worms. The groups AK, HGPRT and MIX could produce IgG1 antibodies, and the groups AK and MIX produced IgE antibodies anti-enzymes and anti-S. mansoni total proteins. The groups AK, HGPRT and MIX induced a reduction in the eosinophils in the peritoneal cavity. Besides, the group AK showed a decrease in the number of hepatic granulomas (41.81%) and the eggs present in the liver (42.30%). Therefore, it suggests that immunization with these enzymes can contribute to schistosomiasis control, as well as help to modulate experimental infection inducing a reduction of physiopathology in the disease. [ABSTRACT FROM AUTHOR]

Traumatic brain injury (TBI) presents a significant public health challenge, necessitating innovative interventions for effective treatment. Recent studies have challenged conventional perspectives on neurogenesis, unveiling endogenous repair mechanisms within the adult brain following injury. However, the intricate mechanisms governing post-TBI neurogenesis remain unclear. The microenvironment of an injured brain, characterized by astrogliosis, neuroinflammation, and excessive cell death, significantly influences the fate of newly generated neurons. Adenosine kinase (ADK), the key metabolic regulator of adenosine, emerges as a crucial factor in brain development and cell proliferation after TBI. This study investigates the hypothesis that targeting ADK could enhance brain repair, promote neuronal survival, and facilitate differentiation. In a TBI model induced by controlled cortical impact, C57BL/6 male mice received intraperitoneal injections of the small molecule ADK inhibitor 5-iodotubercidin (ITU) for three days following TBI. To trace the fate of TBI-associated proliferative cells, animals received intraperitoneal injections of BrdU for seven days, beginning immediately after TBI. Our results show that ADK inhibition by ITU improved brain repair 14 days after injury as evidenced by a diminished injury size. Additionally, the number of mature neurons generated after TBI was increased in ITU-treated mice. Remarkably, the TBI-associated pathological events including astrogliosis, neuroinflammation, and cell death were arrested in ITU-treated mice. Finally, ADK inhibition modulated cell death by regulating the PERK signaling pathway. Together, these findings demonstrate a novel therapeutic approach to target multiple pathological mechanisms involved in TBI. This research contributes valuable insights into the intricate molecular mechanisms underlying neurogenesis and gliosis after TBT. [Display omitted] • ADK inhibition promotes brain repair and enhances neuronal survival after TBI. • ITU suppresses TBI-induced gliosis and neuroinflammation. • Adenosine augmentation serves as a therapeutic strategy to halt TBI-induced cell death through the PERK pathway. [ABSTRACT FROM AUTHOR]

Molecular motors are thought to generate force and directional motion via nonequilibrium switching between energy surfaces. Because all enzymes can undergo such switching, we hypothesized that the ability to generate rotary motion and torque is not unique to highly adapted biological motor proteins but is instead a common feature of enzymes. We used molecular dynamics simulations to compute energy surfaces for hundreds of torsions in three enzymes-adenosine kinase, protein kinase A, and HIV-1 protease-and used these energy surfaces within a kinetic model that accounts for intersurface switching and intrasurface probability flows. When substrate is out of equilibrium with product, we find computed torsion rotation rates up ∼140 cycles s-1, with stall torques up to ∼2 kcal mol-1 cycle-1, and power outputs up to ∼50 kcal mol-1 s-1. We argue that these enzymes are instances of a general phenomenon of directional probability flows on asymmetric energy surfaces for systems out of equilibrium. Thus, we conjecture that cyclic probability fluxes, corresponding to rotations of torsions and higher-order collective variables, exist in any chiral molecule driven between states in a nonequilibrium manner; we call this the "Asymmetry-Directionality" conjecture. This is expected to apply as well to synthetic chiral molecules switched in a nonequilibrium manner between energy surfaces by light, redox chemistry, or catalysis.

Adenosine kinase (ADK) deficiency is a rare inborn error of methionine and adenosine metabolism. So far, a total of 27 patients with ADK deficiency have been reported. Here, we describe the first Polish patient diagnosed with ADK deficiency, aiming to highlight the clinical presentation of disease, emphasize diagnostic difficulties, and report the long-term follow-up. Six-month-old patient presented with cholestatic liver disease, macrocytic anemia, developmental delay, generalized hypotonia, delayed brain myelination, and elevated levels of serum methionine. A decrease of mitochondrial respiratory chain complex II and III activity were found in the postnuclear supernatants obtained from skeletal muscle biopsy. The patient underwent living-donor liver transplantation (LTx) at 14 months of age. Ten-year follow-up after LTx revealed a preserved good liver function, persistent regenerative macrocytic anemia, progressive neurological disease but disappearance of brain MR changes, short stature, and cortisol deficiency. Whole exome sequencing revealed the patient to be affected with two novel ADK variants, which pathogenicity was confirmed biochemically by demonstration of elevated concentration of S-adenosylhomocysteine.

Emerging evidence implicates the sphingosine-1-phosphate receptor subtype 1 (S1PR1) in the development of neuropathic pain. Continued investigation of the signaling pathways downstream of S1PR1 are needed to support development of S1PR1 antagonists. In rodents, intrathecal (i.th.) injection of SEW2871, a selective S1PR1 agonist, activates the nod-like receptor family, pyrin domain containing 3 inflammasome, increases interleukin-1β (IL-1β) and causes behavioral hypersensitivity. I.th. injection of a IL-1β receptor antagonist blocks SEW2871-induced hypersensitivity, suggesting that IL-1β contributes to S1PR1's actions. Interestingly, previous studies have suggested that IL-1β increases the expression/activity of adenosine kinase (ADK), a key regulator of adenosine signaling at its receptors (ARs). Increased ADK expression reduces adenosine signaling whereas inhibiting ADK restores the action of adenosine. Here, we show that SEW287-induced behavioral hypersensitivity is associated with increased expression of ADK in astrocytes of the dorsal horn of the spinal cord. Moreover, the ADK inhibitor, ABT702, blocks SEW2871-induced hypersensitivity. These findings link ADK activation to S1PR1. If SEW2871-induced pain is mediated by IL-1β, which in turn activates ADK and leads to mechano-allodynia, then blocking ADK should attenuate IL-1β effects. In support of this idea, recombinant rat (rrIL-1β)-induced allodynia was blocked by at least 90% with ABT702, functionally linking ADK to IL-1β. Moreover, the selective A3AR antagonist, MRS1523, prevents the ability of ABT702 to block SEW2871 and IL-1β-induced allodynia, implicating A3AR signaling in the beneficial effects exerted by ABT702. Our findings provide novel mechanistic insight into how S1PR1 signaling in the spinal cord produces hypersensitivity through IL1-β and ADK activation. [ABSTRACT FROM AUTHOR]

Abstract Adenosine triphosphate (ATP) acts as a crucial energy currency in vivo, and it is a widely used energy and/or phosphate donor for enzyme-catalyzed reactions in vitro. In this study, we established an in vitro multi-enzyme cascade system for ATP production. Using adenosine and inorganic polyphosphate (polyP) as key substrates, we combined adenosine kinase and two functionally distinct polyphosphate kinases (PPKs) in a one-pot reaction to achieve chain-like ATP regeneration and production. Several sources of PPK were screened and characterized, and two suitable PPKs were selected to achieve high rates of ATP production. Among these, Sulfurovum lithotrophicum PPK (SlPPK) exhibited excellent activity over a wide pH range (pH 4.0–9.0) and synthesized ATP from ADP using short-chain polyP. Furthermore, it had a half-life > 155.6 h at 45 °C. After optimizing the reaction conditions, we finally carried out the coupling-catalyzed reaction with different initial adenosine concentrations of 10, 20, and 30 mM. The highest yields of ATP were 76.0, 70.5, and 61.3%, respectively. Graphical Abstract

Some oral squamous cell carcinomas (OSCCs) originate from preexisting oral potentially malignant disorders (OPMDs). Oral leukoplakia (OLK) is the most common and typical OPMD in the clinic, so treatment for it is essential to reduce OSCC incidence. Local chemotherapy is an option other than surgery considering the superficial site of OLK. However, there are no standardized drugs applied to OLK, and traditionally used chemotherapeutic drugs revealed limited efficacy for lack of adhesion. Hence, there is a growing demand to prepare new agents that combine mucoadhesion with an anti-OLK effect. Here, an isoguanosine–tannic acid (isoG-TA) supramolecular hydrogel via dynamic borate esters was successfully fabricated based on isoG and TA. Previously reported guanosine-TA (G-TA) hydrogel was also explored for an anti-OLK effect. Both gels not only exhibited ideal adhesive properties but also integrated anti-OLK activities in one system. In vitro cell viability indicated that isoG and TA inhibited the proliferation of dysplastic oral keratinocytes (DOKs). The in vivo OLK model evidence revealed that both gels showed potential to prevent OLK canceration. In addition, the probable anti-DOK mechanisms of isoG and TA were investigated. The results indicated that isoG could bind to adenosine kinase (ADK) and then affected the mammalian target of rapamycin (mTOR) pathway to inhibit DOK proliferation. TA could significantly and continuously reduce reactive oxygen species (ROS) in DOKs through its antioxidant effect. ROS plays an important role in the progression of cell cycle. We proved that the low level of ROS may inhibit DOK proliferation by inducing G0/G1 arrest in the cell cycle. Altogether, this study innovatively fabricated an isoG-TA hydrogel with ideal adhesion, and both isoG and TA showed in vitro inhibition of DOKs. Moreover, both isoG-TA and G-TA hydrogels possessed potential in delaying the malignant transformation of OLK, and the G-TA hydrogel showed a better statistical effect, providing an effective strategy for controlling OLK. [ABSTRACT FROM AUTHOR]

Adenosinergic activities are suggested to participate in SUDEP pathophysiology; this study aimed to evaluate the adenosine hypothesis of SUDEP and specifically the role of adenosine A2A receptor (A2AR) in the development of a SUDEP mouse model with relevant clinical features. Using a combined paradigm of intrahippocampal and intraperitoneal administration of kainic acid (KA), we developed a boosted-KA model of SUDEP in genetically modified adenosine kinase (ADK) knockdown (Adk+/-) mice, which has reduced ADK in the brain. Seizure activity was monitored using video-EEG methods, and in vivo recording of local field potential (LFP) was used to evaluate neuronal activity within the nucleus tractus solitarius (NTS). Our boosted-KA model of SUDEP was characterized by a delayed, postictal sudden death in epileptic mice. We demonstrated a higher incidence of SUDEP in Adk+/- mice (34.8%) vs. WTs (8.0%), and the ADK inhibitor, 5-Iodotubercidin, further increased SUDEP in Adk+/- mice (46.7%). We revealed that the NTS level of ADK was significantly increased in epileptic WTs, but not in epileptic Adk+/- mutants, while the A2AR level in NTS was increased in epileptic (WT and Adk+/-) mice vs. non-epileptic controls. The A2AR antagonist, SCH58261, significantly reduced SUDEP events in Adk+/- mice. LFP data showed that SCH58261 partially restored KA injection-induced suppression of gamma oscillation in the NTS of epileptic WT mice, whereas SCH58261 increased theta and beta oscillations in Adk+/- mutants after KA injection, albeit with no change in gamma oscillations. These LFP findings suggest that SCH58261 and KA induced changes in local neuronal activities in the NTS of epileptic mice. We revealed a crucial role for NTS A2AR in SUDEP pathophysiology suggesting A2AR as a potential therapeutic target for SUDEP risk prevention. [ABSTRACT FROM AUTHOR]

Methylation is an important mechanism contributing to cancer pathology. Methylation of tumor suppressor genes and oncogenes has been closely associated with tumor occurrence and development. New insights regarding the potential role of the adenosine receptor-independent pathway in the epigenetic modulation of DNA methylation offer the possibility of new interventional strategies for cancer therapy. Targeting DNA methylation of cancer-related genes is a promising therapeutic strategy; drugs like 5-Aza-2′-deoxycytidine (5-AZA-CdR, decitabine) effectively reverse DNA methylation and cancer cell growth. However, current anti-methylation (or methylation modifiers) are associated with severe side effects; thus, there is an urgent need for safer and more specific inhibitors of DNA methylation (or DNA methylation modifiers). The adenosine signaling pathway is reported to be involved in cancer pathology and participates in the development of tumors by altering DNA methylation. Most recently, an adenosine metabolic clearance enzyme, adenosine kinase (ADK), has been shown to influence methylation on tumor suppressor genes and tumor development and progression. This review article focuses on recent updates on ADK and its two isoforms, and its actions in adenosine receptor-independent pathways, including methylation modification and epigenetic changes in cancer pathology. [ABSTRACT FROM AUTHOR]

The molecular mechanisms underlying vascular inflammation and associated inflammatory vascular diseases are not well defined. Here we show that endothelial intracellular adenosine and its key regulator adenosine kinase (ADK) play important roles in vascular inflammation. Pro-inflammatory stimuli lead to endothelial inflammation by increasing endothelial ADK expression, reducing the level of intracellular adenosine in endothelial cells, and activating the transmethylation pathway through increasing the association of ADK with S-adenosylhomocysteine (SAH) hydrolase (SAHH). Increasing intracellular adenosine by genetic ADK knockdown or exogenous adenosine reduces activation of the transmethylation pathway and attenuates the endothelial inflammatory response. In addition, loss of endothelial ADK in mice leads to reduced atherosclerosis and affords protection against ischemia/reperfusion injury of the cerebral cortex. Taken together, these results demonstrate that intracellular adenosine, which is controlled by the key molecular regulator ADK, influences endothelial inflammation and vascular inflammatory diseases.The molecular mechanisms underlying vascular inflammation are unclear. Here the authors show that pro-inflammatory stimuli lead to endothelial inflammation by increasing adenosine kinase expression, and that its knockdown in endothelial cells inhibits atherosclerosis and cerebral ischemic injury in mice.

The nucleoside adenosine is a potent regulator of vascular homeostasis, but it remains unclear how expression or function of the adenosine-metabolizing enzyme adenosine kinase (ADK) and the intracellular adenosine levels influence angiogenesis. We show here that hypoxia lowered the expression of ADK and increased the levels of intracellular adenosine in human endothelial cells. Knockdown (KD) of ADK elevated intracellular adenosine, promoted proliferation, migration, and angiogenic sprouting in human endothelial cells. Additionally, mice deficient in endothelial ADK displayed increased angiogenesis as evidenced by the rapid development of the retinal and hindbrain vasculature, increased healing of skin wounds, and prompt recovery of arterial blood flow in the ischemic hindlimb. Mechanistically, hypomethylation of the promoters of a series of pro-angiogenic genes, especially for VEGFR2 in ADK KD cells, was demonstrated by the Infinium methylation assay. Methylation-specific PCR, bisulfite sequencing, and methylated DNA immunoprecipitation further confirmed hypomethylation in the promoter region of VEGFR2 in ADK-deficient endothelial cells. Accordingly, loss or inactivation of ADK increased VEGFR2 expression and signaling in endothelial cells. Based on these findings, we propose that ADK downregulation-induced elevation of intracellular adenosine levels in endothelial cells in the setting of hypoxia is one of the crucial intrinsic mechanisms that promote angiogenesis.

[This corrects the article on p. 42 in vol. 9, PMID: 27375429.].

Methylation is an important mechanism contributing to cancer pathology. Methylation of tumor suppressor genes and oncogenes has been closely associated with tumor occurrence and development. New insights regarding the potential role of the adenosine receptor-independent pathway in the epigenetic modulation of DNA methylation offer the possibility of new interventional strategies for cancer therapy. Targeting DNA methylation of cancer-related genes is a promising therapeutic strategy; drugs like 5-Aza-2′-deoxycytidine (5-AZA-CdR, decitabine) effectively reverse DNA methylation and cancer cell growth. However, current anti-methylation (or methylation modifiers) are associated with severe side effects; thus, there is an urgent need for safer and more specific inhibitors of DNA methylation (or DNA methylation modifiers). The adenosine signaling pathway is reported to be involved in cancer pathology and participates in the development of tumors by altering DNA methylation. Most recently, an adenosine metabolic clearance enzyme, adenosine kinase (ADK), has been shown to influence methylation on tumor suppressor genes and tumor development and progression. This review article focuses on recent updates on ADK and its two isoforms, and its actions in adenosine receptor-independent pathways, including methylation modification and epigenetic changes in cancer pathology.

Adenosinergic activities are suggested to participate in SUDEP pathophysiology; this study aimed to evaluate the adenosine hypothesis of SUDEP and specifically the role of adenosine A2A receptor (A2AR) in the development of a SUDEP mouse model with relevant clinical features. Using a combined paradigm of intrahippocampal and intraperitoneal administration of kainic acid (KA), we developed a boosted-KA model of SUDEP in genetically modified adenosine kinase (ADK) knockdown (Adk+/-) mice, which has reduced ADK in the brain. Seizure activity was monitored using video-EEG methods, and in vivo recording of local field potential (LFP) was used to evaluate neuronal activity within the nucleus tractus solitarius (NTS). Our boosted-KA model of SUDEP was characterized by a delayed, postictal sudden death in epileptic mice. We demonstrated a higher incidence of SUDEP in Adk+/- mice (34.8%) vs. WTs (8.0%), and the ADK inhibitor, 5-Iodotubercidin, further increased SUDEP in Adk+/- mice (46.7%). We revealed that the NTS level of ADK was significantly increased in epileptic WTs, but not in epileptic Adk+/- mutants, while the A2AR level in NTS was increased in epileptic (WT and Adk+/-) mice vs. non-epileptic controls. The A2AR antagonist, SCH58261, significantly reduced SUDEP events in Adk+/- mice. LFP data showed that SCH58261 partially restored KA injection-induced suppression of gamma oscillation in the NTS of epileptic WT mice, whereas SCH58261 increased theta and beta oscillations in Adk+/- mutants after KA injection, albeit with no change in gamma oscillations. These LFP findings suggest that SCH58261 and KA induced changes in local neuronal activities in the NTS of epileptic mice. We revealed a crucial role for NTS A2AR in SUDEP pathophysiology suggesting A2AR as a potential therapeutic target for SUDEP risk prevention.

Clinical radiation therapy for the treatment of CNS cancers leads to unintended and debilitating impairments in cognition. Radiation-induced cognitive dysfunction is long lasting; however, the underlying molecular and cellular mechanisms are still not well established. Since ionizing radiation causes microglial and astroglial activation, we hypothesized that maladaptive changes in astrocyte function might be implicated in radiation-induced cognitive dysfunction. Among other gliotransmitters, astrocytes control the availability of adenosine, an endogenous neuroprotectant and modulator of cognition, via metabolic clearance through adenosine kinase (ADK). Adult rats exposed to cranial irradiation (10 Gy) showed significant declines in performance of hippocampal-dependent cognitive function tasks [novel place recognition, novel object recognition (NOR), and contextual fear conditioning (FC)] 1 month after exposure to ionizing radiation using a clinically relevant regimen. Irradiated rats spent less time exploring a novel place or object. Cranial irradiation also led to reduction in freezing behavior compared to controls in the FC task. Importantly, immunohistochemical analyses of irradiated brains showed significant elevation of ADK immunoreactivity in the hippocampus that was related to astrogliosis and increased expression of glial fibrillary acidic protein (GFAP). Conversely, rats treated with the ADK inhibitor 5-iodotubercidin (5-ITU, 3.1 mg/kg, i.p., for 6 days) prior to cranial irradiation showed significantly improved behavioral performance in all cognitive tasks 1 month post exposure. Treatment with 5-ITU attenuated radiation-induced astrogliosis and elevated ADK immunoreactivity in the hippocampus. These results confirm an astrocyte-mediated mechanism where preservation of extracellular adenosine can exert neuroprotection against radiation-induced pathology. These innovative findings link radiation-induced changes in cognition and CNS functionality to altered purine metabolism and astrogliosis, thereby linking the importance of adenosine homeostasis in the brain to radiation injury.

Background: Inflammatory disorder and acinar cell death contribute to the initiation and progression of severe acute pancreatitis (SAP). Adenosine kinase (ADK) has potential effects on both inflammation and cell death. However, the role of ADK in SAP remains to be explored.Methods: To establish an experimental SAP model, male C57BL/6 mice were intraperitoneally injected with cerulein (50 μg/kg, seven doses at hourly intervals) and LPS (10 mg/kg, at the last cerulein injection). For ADK inhibition, ABT702 (1.5 mg/kg) was intraperitoneally injected 1 h before cerulein treatment. The pancreas and serum were collected and analyzed to determine the severity of pancreatic injury and explore the potential pathophysiological mechanisms. Pancreatic acinar cells (AR42J) were used to explore the in vitro effects of ADK inhibition on cerulein–induced inflammation and necroptotic cell death.Results: ADK inhibition notably attenuated the severity of SAP, as indicated by the decreased serum amylase (7,416.76 ± 1,457.76 vs. 4,581.89 ± 1,175.04 U/L) and lipase (46.51 ± 11.50 vs. 32.94 ± 11.46 U/L) levels and fewer pancreatic histopathological alterations (histological scores: 6.433 ± 0.60 vs. 3.77 ± 0.70). MOMA-2 and CD11b staining confirmed that ADK inhibition prevented the infiltration of neutrophils and macrophages. The phosphorylation of nuclear factor-κB (NF-κB) was also reduced by ADK inhibition. ADK inhibition markedly limited the necrotic area of the pancreas and prevented the activation of the necroptotic signaling pathway. Endoplasmic reticulum (ER) stress was activated in the pancreas using the SAP model and cerulein–treated AR42J cells whereas ADK inhibition reversed the activation of ER stress both in vivo and in vitro. Moreover, the alleviating effects of ADK inhibition on ER stress, inflammation, and cell necroptosis were eliminated by the adenosine A2A receptor antagonist.Conclusion: ADK inhibition reduced inflammation and necroptotic acinar cell death in SAP via the adenosine A2A receptor/ER stress pathway, suggesting that ADK might be a potential therapeutic target for SAP.

Schistosomiasis is one of the most important human helminthiases worldwide. Praziquantel is the current treatment, and no vaccine is available until the present. Thus, the presented study aimed to evaluate the immunization effects with recombinant Schistosoma mansoni enzymes: Adenosine Kinase (AK) and Hypoxanthine-Guanine Phosphoribosyltransferase (HGPRT), as well as a MIX of the two enzymes. Female Balb/c mice were immunized in three doses, and 15 days after the last immunization, animals were infected with S. mansoni. Our results showed that the group MIX presented a reduction in the eggs in feces by 30.74% and 29%, respectively, in the adult worms. The groups AK, HGPRT and MIX could produce IgG1 antibodies, and the groups AK and MIX produced IgE antibodies anti-enzymes and anti-S. mansoni total proteins. The groups AK, HGPRT and MIX induced a reduction in the eosinophils in the peritoneal cavity. Besides, the group AK showed a decrease in the number of hepatic granulomas (41.81%) and the eggs present in the liver (42.30%). Therefore, it suggests that immunization with these enzymes can contribute to schistosomiasis control, as well as help to modulate experimental infection inducing a reduction of physiopathology in the disease.

Background: Ginsenoside Rg 1 (Rg 1 ) is one of the main active components in Chinese medicines, Panax ginseng and Panax notoginseng . Research has shown that Rg 1 has a protective effect on the cardiovascular system, including anti-myocardial ischemia-reperfusion injury, anti-apoptosis, and promotion of myocardial angiogenesis, suggesting it a potential cardiovascular agent. However, the protective mechanism involved is still not fully understood., Methods: Based on network pharmacology, ligand-based protein docking, proteomics, Western blot, protein recombination and spectroscopic analysis (UV-Vis and fluorescence spectra) techniques, potential targets and pathways for Rg 1 against myocardial ischemia (MI) were screened and explored., Results: An important target set containing 19 proteins was constructed. Two target proteins with more favorable binding activity for Rg 1 against MI were further identified by molecular docking, including mitogen-activated protein kinase 1 (MAPK1) and adenosine kinase (ADK). Meanwhile, Rg 1 intervention on H9c2 cells injured by H 2 O 2 showed an inhibitory oxidative phosphorylation (OXPHOS) pathway. The inhibition of Rg 1 on MAPK1 and OXPHOS pathway was confirmed by Western blot assay. By protein recombination and spectroscopic analysis, the binding reaction between ADK and Rg 1 was also evaluated., Conclusion: Rg 1 can effectively alleviate cardiomyocytes oxidative stress injury via targeting MAPK1 and ADK, and inhibiting oxidative phosphorylation (OXPHOS) pathway. The present study provides scientific basis for the clinical application of the natural active ingredient, Rg 1 , and also gives rise to a methodological reference to the searching of action targets and pathways of other natural active ingredients., Competing Interests: The authors declare no conflict of interest., (© 2024 The Korean Society of Ginseng. Publishing services by Elsevier B.V.)

Adenosine triphosphate (ATP) acts as a crucial energy currency in vivo, and it is a widely used energy and/or phosphate donor for enzyme-catalyzed reactions in vitro. In this study, we established an in vitro multi-enzyme cascade system for ATP production. Using adenosine and inorganic polyphosphate (polyP) as key substrates, we combined adenosine kinase and two functionally distinct polyphosphate kinases (PPKs) in a one-pot reaction to achieve chain-like ATP regeneration and production. Several sources of PPK were screened and characterized, and two suitable PPKs were selected to achieve high rates of ATP production. Among these, Sulfurovum lithotrophicum PPK (SlPPK) exhibited excellent activity over a wide pH range (pH 4.0–9.0) and synthesized ATP from ADP using short-chain polyP. Furthermore, it had a half-life > 155.6 h at 45 °C. After optimizing the reaction conditions, we finally carried out the coupling-catalyzed reaction with different initial adenosine concentrations of 10, 20, and 30 mM. The highest yields of ATP were 76.0, 70.5, and 61.3%, respectively. [ABSTRACT FROM AUTHOR]

Adenosine is an inhibitory modulator of neuronal excitability. Neuronal activity results in increased adenosine release, thereby constraining excessive excitation. The exceptionally high neuronal activity of a seizure results in a surge in extracellular adenosine to concentrations many-fold higher than would be observed under normal conditions. In this review, we discuss the multifarious effects of adenosine signaling in the context of epilepsy, with emphasis on sudden unexpected death in epilepsy (SUDEP). We describe and categorize the beneficial, detrimental, and potentially deadly aspects of adenosine signaling. The good or beneficial characteristics of adenosine signaling in the context of seizures include: (1) its direct effect on seizure termination and the prevention of status epilepticus; (2) the vasodilatory effect of adenosine, potentially counteracting postictal vasoconstriction; (3) its neuroprotective effects under hypoxic conditions; and (4) its disease modifying antiepileptogenic effect. The bad or detrimental effects of adenosine signaling include: (1) its capacity to suppress breathing and contribute to peri-ictal respiratory dysfunction; (2) its contribution to postictal generalized EEG suppression (PGES); (3) the prolonged increase in extracellular adenosine following spreading depolarization waves may contribute to postictal neuronal dysfunction; (4) the excitatory effects of A2A receptor activation is thought to exacerbate seizures in some instances; and (5) its potential contributions to sleep alterations in epilepsy. Finally, the adverse effects of adenosine signaling may potentiate a deadly outcome in the form of SUDEP by suppressing breathing and arousal in the postictal period. Evidence from animal models suggests that excessive postictal adenosine signaling contributes to the pathophysiology of SUDEP. The goal of this review is to discuss the beneficial, harmful, and potentially deadly roles that adenosine plays in the context of epilepsy and to identify crucial gaps in knowledge where further investigation is necessary. By better understanding adenosine dynamics, we may gain insights into the treatment of epilepsy and the prevention of SUDEP.

• Exogenous adenosine inhibits proliferation of astrocytes but not of glioblastoma cells. • Combined adenosine and homocysteine inhibits glioblastoma cell proliferation. • Adenosine alone did not induce cell death in astrocytes or in glioblastoma cells. • Blocking adenosine kinase inhibits cell proliferation in astrocytes and glioblastoma. Glioblastoma (GBM) is the most common brain primary tumour. Hypoxic regions in GBM are associated to tumour growth. Adenosine accumulates in hypoxic regions and can affect cell proliferation and survival. However, how proliferating GBM cells respond/adapt to increased adenosine levels compared to human astrocytes (HA) is not clarified and was addressed in the present work. GBM cell lines and HA were treated for 3 days with test drugs. Thirty Adenosine (30 µM) caused a 43% ± 5% (P < 0.05) reduction of cell proliferation/viability in HA, through an adenosine receptor-independent mechanism, but had no effect in GBM cell lines U87MG, U373MG and SNB19. Contrastingly, inhibition of adenosine phosphorylation (using the adenosine kinase (ADK) inhibitor 5-iodotubercidin (ITU) (25 µM)), produced a strong and similar decrease on cell proliferation in both HA and GBM cells. The effect of adenosine on HA proliferation/viability was potentiated by 100 µM-homocysteine. Combined application of 30 µM-adenosine and 100 µM-homocysteine reduced the cell proliferation/viability in all three GBM cell lines, but this reduction was much lower than that observed in HA. Adenosine alone did not induce cell death, assessed by lactate dehydrogenase (LDH) release, both in HA and GBM cells, but potentiated the cytotoxic effect of homocysteine in HA and in U87MG and U373MG cells. Results show a strong attenuation of adenosine anti-proliferative effect in GBM cells compared to HA, probably resulting from increased adenosine elimination by ADK, suggesting a proliferative-prone adaptation of tumour cells to increased adenosine levels. [ABSTRACT FROM AUTHOR]

Adenosine is an inhibitory modulator of neuronal excitability. Neuronal activity results in increased adenosine release, thereby constraining excessive excitation. The exceptionally high neuronal activity of a seizure results in a surge in extracellular adenosine to concentrations many-fold higher than would be observed under normal conditions. In this review, we discuss the multifarious effects of adenosine signaling in the context of epilepsy, with emphasis on sudden unexpected death in epilepsy (SUDEP). We describe and categorize the beneficial, detrimental, and potentially deadly aspects of adenosine signaling. The good or beneficial characteristics of adenosine signaling in the context of seizures include: (1) its direct effect on seizure termination and the prevention of status epilepticus; (2) the vasodilatory effect of adenosine, potentially counteracting postictal vasoconstriction; (3) its neuroprotective effects under hypoxic conditions; and (4) its disease modifying antiepileptogenic effect. The bad or detrimental effects of adenosine signaling include: (1) its capacity to suppress breathing and contribute to peri-ictal respiratory dysfunction; (2) its contribution to postictal generalized EEG suppression (PGES); (3) the prolonged increase in extracellular adenosine following spreading depolarization waves may contribute to postictal neuronal dysfunction; (4) the excitatory effects of A2A receptor activation is thought to exacerbate seizures in some instances; and (5) its potential contributions to sleep alterations in epilepsy. Finally, the adverse effects of adenosine signaling may potentiate a deadly outcome in the form of SUDEP by suppressing breathing and arousal in the postictal period. Evidence from animal models suggests that excessive postictal adenosine signaling contributes to the pathophysiology of SUDEP. The goal of this review is to discuss the beneficial, harmful, and potentially deadly roles that adenosine plays in the context of epilepsy and to identify crucial gaps in knowledge where further investigation is necessary. By better understanding adenosine dynamics, we may gain insights into the treatment of epilepsy and the prevention of SUDEP. [ABSTRACT FROM AUTHOR]

Adenosine, acting both through G-protein coupled adenosine receptors and intracellularly, plays a complex role in multiple physiological and pathophysiological processes by modulating neuronal plasticity, astrocytic activity, learning and memory, motor function, feeding, control of sleep and aging. Adenosine is involved in stroke, epilepsy and neurodegenerative pathologies. Extracellular concentration of adenosine in the brain is tightly regulated. Adenosine may be generated intracellularly in the central nervous system from degradation of AMP or from the hydrolysis of S-adenosyl homocysteine, and then exit via bi-directional nucleoside transporters, or extracellularly by the metabolism of released nucleotides. Inactivation of extracellular adenosine occurs by transport into neurons or neighboring cells, followed by either phosphorylation to AMP by adenosine kinase or deamination to inosine by adenosine deaminase. Modulation of the nucleoside transporters or of the enzymatic activities involved in the metabolism of adenosine, by affecting the levels of this nucleoside and the activity of adenosine receptors, could have a role in the onset or the development of central nervous system disorders, and can also be target of drugs for their treatment. In this review, we focus on the contribution of 5′-nucleotidases, adenosine kinase, adenosine deaminase, AMP deaminase, AMP-activated protein kinase and nucleoside transporters in epilepsy, cognition, and neurodegenerative diseases with a particular attention on amyotrophic lateral sclerosis and Huntington’s disease. We include several examples of the involvement of components of the adenosine metabolism in learning and of the possible use of modulators of enzymes involved in adenosine metabolism or nucleoside transporters in the amelioration of cognition deficits.

Increased adenosine helps limit infarct size in ischaemia/reperfusion‐injured hearts. In cardiomyocytes, 90% of adenosine is catalysed by adenosine kinase (ADK) and ADK inhibition leads to higher concentrations of both intracellular adenosine and extracellular adenosine. However, the role of ADK inhibition in myocardial ischaemia/reperfusion (I/R) injury remains less obvious. We explored the role of ADK inhibition in myocardial I/R injury using mouse left anterior ligation model. To inhibit ADK, the inhibitor ABT‐702 was intraperitoneally injected or AAV9 (adeno‐associated virus)—ADK—shRNA was introduced via tail vein injection. H9c2 cells were exposed to hypoxia/reoxygenation (H/R) to elucidate the underlying mechanisms. ADK was transiently increased after myocardial I/R injury. Pharmacological or genetic ADK inhibition reduced infarct size, improved cardiac function and prevented cell apoptosis and necroptosis in I/R‐injured mouse hearts. In vitro, ADK inhibition also prevented cell apoptosis and cell necroptosis in H/R‐treated H9c2 cells. Cleaved caspase‐9, cleaved caspase‐8, cleaved caspase‐3, MLKL and the phosphorylation of MLKL and CaMKII were decreased by ADK inhibition in reperfusion‐injured cardiomyocytes. X‐linked inhibitor of apoptosis protein (XIAP), which is phosphorylated and stabilized via the adenosine receptors A2B and A1/Akt pathways, should play a central role in the effects of ADK inhibition on cell apoptosis and necroptosis. These data suggest that ADK plays an important role in myocardial I/R injury by regulating cell apoptosis and necroptosis. [ABSTRACT FROM AUTHOR]

Although aspirin is a well-established antiplatelet agent, the mechanisms of aspirin resistance remain poorly understood. Metabolomics allows for measurement of hundreds of small molecules in biological samples, enabling detailed mapping of pathways involved in drug response. We defined the metabolic signature of aspirin exposure in subjects from the Heredity and Phenotype Intervention Heart Study. Many metabolites, including known aspirin catabolites, changed on exposure to aspirin, and pathway enrichment analysis identified purine metabolism as significantly affected by drug exposure. Furthermore, purines were associated with aspirin response, and poor responders had higher postaspirin adenosine and inosine levels than did good responders (n = 76; both P < 4 × 10(-3)). Using our established "pharmacometabolomics-informed pharmacogenomics" approach, we identified genetic variants in adenosine kinase associated with aspirin response. Combining metabolomics and genomics allowed for more comprehensive interrogation of mechanisms of variation in aspirin response--an important step toward personalized treatment approaches for cardiovascular disease.

Aims Adenosine receptors and extracellular adenosine have been demonstrated to modulate vascular smooth muscle cell (VSMC) proliferation and neointima formation. Adenosine kinase (ADK) is a major enzyme regulating intracellular adenosine levels but is function in VSMC remains unclear. Here, we investigated the role of ADK in vascular injury-induced smooth muscle proliferation and delineated the mechanisms underlying its action. Methods and results We found that ADK expression was higher in the neointima of injured vessels and in platelet-derived growth factor-treated VSMCs. Genetic and pharmacological inhibition of ADK was enough to attenuate arterial injury-induced neointima formation due to inhibition of VSMC proliferation. Mechanistically, using infinium methylation assays and bisulfite sequencing, we showed that ADK metabolized the intracellular adenosine and potentiated the transmethylation pathway, then induced the aberrant DNA hypermethylation. Pharmacological inhibition of aberrant DNA hypermethylation increased KLF4 expression and suppressed VSMC proliferation as well as the neointima formation. Importantly, in human femoral arteries, we observed increased ADK expression and DNA hypermethylation as well as decreased KLF4 expression in neointimal VSMCs of stenotic vessels suggesting that our findings in mice are relevant for human disease and may hold translational significance. Conclusion Our study unravels a novel mechanism by which ADK promotes VSMC proliferation via inducing aberrant DNA hypermethylation, thereby down-regulating KLF4 expression and promoting neointima formation. These findings advance the possibility of targeting ADK as an epigenetic modulator to combat vascular injury. [ABSTRACT FROM AUTHOR]

The outbreak of the novel coronavirus disease 2019 (COVID-19) caused by Severe Acute Respiratory Syndrome CoronaVirus-2 (SARS-CoV-2) requires urgent clinical interventions. Crucial clinical needs are: 1) prevention of infection and spread of the virus within lung epithelia and between people, 2) attenuation of excessive lung injury in Advanced Respiratory Distress Syndrome, which develops during the end stage of the disease, and 3) prevention of thrombosis associated with SARS-CoV-2 infection. Adenosine and the key adenosine regulators adenosine deaminase (ADA), adenosine kinase (ADK), and equilibrative nucleoside transporter 1 may play a role in COVID-19 pathogenesis. Here, we highlight 1) the non-enzymatic role of ADA by which it might out-compete the virus (SARS-CoV-2) for binding to the CD26 receptor, 2) the enzymatic roles of ADK and ADA to increase adenosine levels and ameliorate Advanced Respiratory Distress Syndrome, and 3) inhibition of adenosine transporters to reduce platelet activation, thrombosis and improve COVID-19 outcomes. Depending on the stage of exposure to and infection by SARS-CoV-2, enhancing adenosine levels by targeting key adenosine regulators such as ADA, ADK and equilibrative nucleoside transporter 1 might find therapeutic use against COVID-19 and warrants further investigation.