Search Results (18)

Parkinson’s disease (PD) represents a growing challenge to global health, as it involves millions of people. The high grade of disability is due to the loss of dopaminergic neuron activity, and levodopa is the gold-standard therapy used to restore dopamine in the dopamine-denervated regions. Another therapeutic approach is the use of A_2A adenosine receptor antagonists and, among them, istradefylline is the only one currently approved for therapy in association with levodopa. In this work, we synthesized A_2A adenosine receptor antagonists represented by 9-ethyl-2,8-disubstituted adenine derivatives, which were tested at human adenosine receptors in binding and functional assays. These compounds showed A_2A adenosine receptor-binding affinities in the low nanomolar range and 1, 4, and 5 exhibited good potency in the functional assays. Hence, they were evaluated in in vivo rat models of PD, where they were demonstrated to revert haloperidol-induced catalepsy and potentiate levodopa-induced contralateral rotations in 6-hydroxydopamine-lesioned rats. The most potent derivative, 4, was then evaluated in the tacrine model, where it reduced the tremulous jaw movements, therefore demonstrating an action on parkinsonian tremor. These data revealed 8-ethoxy-2-phenethoxy-9-ethyladenine (4) as an A_2A adenosine receptor antagonist endowed with antiparkinsonian effects and as a good candidate to treat the disease. Full article

Neonatal calves’ diarrhea, which can be severe enough to cause death, has a significant impact on the global cattle industry. In this study, alfalfa polysaccharides and seaweed polysaccharides were found to significantly improve the diarrhea condition in neonatal calves. To explore the underlying mechanisms, further microbiomic and metabolomic analyses were conducted. This study investigated the impact of alfalfa polysaccharides and seaweed polysaccharides on growth performance, serum metabolites, gut microbiota, and metabolomics in neonatal Holstein calves. A total of 24 newborn calves were randomly assigned to three groups, with 8 calves per treatment group. The control (CON) group was fed a basal diet, the alfalfa polysaccharide (AP) group received a basal diet supplemented with alfalfa polysaccharides (4 g/calf/day), and the seaweed polysaccharide group (SP) received a basal diet supplemented with seaweed polysaccharides (4 g/calf/day). These polysaccharides were plant extracts. Compared to the CON group, the results indicated that SP significantly enhanced the body weight, height, chest circumference, and average daily gain of Holstein calves (p < 0.05), while also reducing the diarrhea rate and improving manure scoring (p < 0.05). Compared to the CON, AP also reduced the diarrhea rate (p < 0.05). In terms of serum biochemistry, supplementation with AP and SP increased serum alkaline phosphatase (ALP) and insulin-like growth factor 1 (IGF-1) levels compared to the CON group (p < 0.05). Both AP and SP elevated serum catalase (CAT) and Total Antioxidant Capacity (T-AOC) levels, indicating enhanced antioxidant status (p < 0.05). Regarding immune responses, supplementation with AP and SP significantly increased serum complement component 3 (C3) and immunoglobulin M (IgM) levels, while significantly reducing pro-inflammatory cytokines interleukin-18 (IL-18), tumor necrosis factor alpha (TNF-α), and interferon-gamma (IFN-γ) compared to the CON group (p < 0.05). Microbiota analysis revealed that AP modulated the abundance of Firmicutes, while SP influenced the abundance of Prevotella and Succiniclasticum. AP and SP differentially influenced intestinal metabolites compared to the CON group, leading to enrichment in pathways related to immunity, antibacterial, and anti-inflammatory functions. These pathways included the biosynthesis of alkaloids from ornithine, lysine, and nicotinic acid, glucocorticoid and mineralocorticoid receptor canothersis/antagonists, secondary metabolite biosynthesis, and alkaloid biosynthesis from histidine and purine, thus alleviating intestinal inflammation. Therefore, by supplementing with AP and SP, the diarrhea rate in calves was reduced, and the immune function of Holstein calves was enhanced, while simultaneously promoting a higher relative abundance of beneficial gut bacteria and suppressing the relative abundance of pathogenic bacteria. Additionally, gut pathways associated with immune response and inflammation were modulated by AP and SP. This study provided valuable insights and theoretical underpinnings for the use of AP and SP in preventing diarrhea in neonatal calves. Full article

Purine nucleosides (adenosine) and nucleotides such as adenosine mono/di/triphosphate (AMP/ADP/ATP) may produce complex cardiovascular responses. For example, adenosine-5′-(β-thio)-diphosphate (ADPβS; a stable synthetic analogue of ADP) can induce vasodilatation/vasodepressor responses by endothelium-dependent and independent mechanisms involving purinergic P2Y receptors; however, the specific subtypes participating in these responses remain unknown. Therefore, this study investigated the receptor subtypes mediating the blood pressure changes induced by intravenous bolus of ADPβS in male Wistar rats in the absence and presence of central mechanisms with the antagonists MRS2500 (P2Y₁), PSB0739 (P2Y₁₂), and MRS2211 (P2Y₁₃). For this purpose, 120 rats were divided into 60 anaesthetised rats and 60 pithed rats, and further subdivided into four groups (n = 30 each), namely: (a) anaesthetised rats, (b) anaesthetised rats with bilateral vagotomy, (c) pithed rats, and (d) pithed rats continuously infused (intravenously) with methoxamine (an α₁-adrenergic agonist that restores systemic vascular tone). We observed, in all four groups, that the immediate decreases in diastolic blood pressure produced by ADPβS were exclusively mediated by peripheral activation of P2Y₁ receptors. Nevertheless, the subsequent increases in systolic blood pressure elicited by ADPβS in pithed rats infused with methoxamine probably involved peripheral activation of P2Y₁, P2Y₁₂, and P2Y₁₃ receptors. Full article

Bladder urothelium and suburothelium/lamina propria (LP) have prominent sensory and transducer functions with the active participation of afferent neurons and urothelium-derived purine mediators such as adenosine 5’-triphosphate (ATP), adenosine 5’-diphosphate (ADP), and adenosine (ADO). Effective concentrations of purines at receptor targets depend significantly on the extracellular degradation of ATP by ectonucleotidases (ENTDs). We recently reported the regulated release of soluble ENTDs (s-ENTDs) in the LP and the consequent degradation of ATP to ADP, AMP, and ADO. Afferent neurons in the LP can be activated by urothelial ATP and release peptides and other transmitters that can alter the activity of cells in their vicinity. Using a murine decentralized ex vivo detrusor-free bladder model, 1,N⁶-etheno-ATP (eATP) as substrate, and sensitive HPLC-FLD methodologies, we found that exogenous neuropeptides calcitonin gene-related peptide (CGRP), substance P (Sub P), neurokinin A (NKA), and pituitary adenylate cyclase-activating polypeptide [PACAP (1-38)] all increased the degradation of eATP by s-ENTDs that were released in the LP spontaneously and/or during bladder filling. Using antagonists of neuropeptide receptors, we observed that endogenous NKA did not modify the ATP hydrolysis by s-ENTDs, whereas endogenous Sub P increased both the constitutive and distention-induced release of s-ENTDs. In contrast, endogenous CGRP and PACAP (1-38) increased the distention-induced, but not the spontaneous, release of s-ENTDs. The present study puts forward the novel idea that interactions between peptidergic and purinergic signaling mechanisms in the LP have an impact on bladder excitability and functions by regulating the effective concentrations of adenine purines at effector cells in the LP. Full article

Toll-like receptor 7 (TLR7) is a class of pattern recognition receptors (PRRs) recognizing the pathogen-associated elements and damage and as such is a major player in the innate immune system. TLR7 triggers the release of pro-inflammatory cytokines or type-I interferons (IFN), which is essential for immunoregulation. Increasing reports also highlight that the abnormal activation of endosomal TLR7 is implicated in various immune-related diseases, carcinogenesis as well as the proliferation of human immunodeficiency virus (HIV). Hence, the design and development of potent and selective TLR7 antagonists based on small molecules or oligonucleotides may offer new tools for the prevention and management of such diseases. In this review, we offer an updated overview of the main structural features and therapeutic potential of small-molecule antagonists of TLR7. Various heterocyclic scaffolds targeting TLR7 binding sites are presented: pyrazoloquinoxaline, quinazoline, purine, imidazopyridine, pyridone, benzanilide, pyrazolopyrimidine/pyridine, benzoxazole, indazole, indole, and quinoline. Additionally, their structure-activity relationships (SAR) studies associated with biological activities and protein binding modes are introduced. Full article

Autoimmunity and cancer rates have both been on the rise in Western civilization prompting many to investigate the link between the two entities. This review will investigate the complex interactions between the activation and deactivation of the immune system and the development of malignancy. Additional focus will be placed on the main classes of immune inhibitor therapy utilized in transplant patients and in autoimmune disease including TNF-alpha, Calcineurin, mTOR, purine synthesis antagonists and IMPDH inhibitors. Full article

Glioblastoma is the most commonly malignant and aggressive brain tumor, with a high mortality rate. The role of the purine nucleotide adenosine and its interaction with its four subtypes receptors coupled to the different G proteins, A1, A2A, A2B, and A3, and its different physiological functions in different systems and organs, depending on the active receptor subtype, has been studied for years. Recently, several works have defined extracellular adenosine as a tumoral protector because of its accumulation in the tumor microenvironment. Its presence is due to both the interaction with the A2A receptor subtype and the increase in CD39 and CD73 gene expression induced by the hypoxic state. This fact has fueled preclinical and clinical research into the development of efficacious molecules acting on the adenosine pathway and blocking its accumulation. Given the success of anti-cancer immunotherapy, the new strategy is to develop selective A2A receptor antagonists that could competitively inhibit binding to its endogenous ligand, making them reliable candidates for the therapeutic management of brain tumors. Here, we focused on the efficacy of adenosine receptor antagonists and their enhancement in anti-cancer immunotherapy. Full article

The A_2A adenosine receptor (A_2AAR) is one of the four subtypes activated by nucleoside adenosine, and the molecules able to selectively counteract its action are attractive tools for neurodegenerative disorders. In order to find novel A_2AAR ligands, two series of compounds based on purine and triazolotriazine scaffolds were synthesized and tested at ARs. Compound 13 was also tested in an in vitro model of neuroinflammation. Some compounds were found to possess high affinity for A_2AAR, and it was observed that compound 13 exerted anti-inflammatory properties in microglial cells. Molecular modeling studies results were in good agreement with the binding affinity data and underlined that triazolotriazine and purine scaffolds are interchangeable only when 5- and 2-positions of the triazolotriazine moiety (corresponding to the purine 2- and 8-positions) are substituted. Full article

Caffeine has been reported to induce anti-tumor immunity for attenuating breast cancer by blocking the adenosine 2A receptor. Molecular modeling showed that theacrine, a purine alkaloid structurally similar to caffeine, might be an antagonist of the adenosine 2A receptor equivalent to or more effective than caffeine. Theacrine was further demonstrated to be an effective antagonist of the adenosine 2A receptor as its concurrent supplementation significantly reduced the elevation of AMPK phosphorylation level in MCF-7 human breast cells induced by CGS21680, an agonist of adenosine 2A receptors. In an animal model, the development of mammary carcinoma induced by 7,12-Dimethylbenz[a]anthracene in Sprague–Dawley rats could be attenuated by daily supplement of theacrine of 50 or 100 mg/kg body weight. Both expression levels of cleaved-caspase-3/pro-caspase-3 and granzyme B in tumor tissues were significantly elevated when theacrine was supplemented, indicating the induction of programmed cell death in tumor cells might be involved in the attenuation of mammary carcinoma. Similar to the caffeine, significant elevation of interferon-γ and tumor necrosis factor-α was observed in the serum and tumor tissues of rats after the theacrine supplement of 50 mg/kg body weight. Taken together, theacrine is an effective antagonist of adenosine 2A receptors and possesses great potential to be used to attenuate breast cancer. Full article

The colored grain of wheat (Triticum aestivum L.) contains a large number of polyphenolic compounds that are biologically active ingredients. The purpose of this work was a comparative metabolomic study of extracts from anthocyaninless (control), blue, and deep purple (referred to here as black) grains of seven genetically related wheat lines developed for the grain anthocyanin pigmentation trait. To identify target analytes in ethanol extracts, high-performance liquid chromatography was used in combination with Bruker Daltonics ion trap mass spectrometry. The results showed the presence of 125 biologically active compounds of a phenolic (85) and nonphenolic (40) nature in the grains of T. aestivum (seven lines). Among them, a number of phenolic compounds affiliated with anthocyanins, coumarins, dihydrochalcones, flavan-3-ols, flavanone, flavones, flavonols, hydroxybenzoic acids, hydroxycinnamic acids, isoflavone, lignans, other phenolic acids, stilbenes, and nonphenolic compounds affiliated with alkaloids, carboxylic acids, carotenoids, diterpenoids, essential amino acids, triterpenoids, sterols, nonessential amino acids, phytohormones, purines, and thromboxane receptor antagonists were found in T. aestivum grains for the first time. A comparative analysis of the diversity of the compounds revealed that the lines do not differ from each other in the proportion of phenolic (53.3% to 70.3% of the total number of identified compounds) and nonphenolic compounds (46.7% to 29.7%), but diversity of the compounds was significantly lower in grains of the control line. Even though the lines are genetically closely related and possess similar chemical profiles, some line-specific individual compounds were identified that constitute unique chemical fingerprints and allow to distinguish each line from the six others. Finally, the influence of the genotype on the chemical profiles of the wheat grains is discussed. Full article

The Smoothened (SMO) receptor is the most druggable target in the Hedgehog (HH) pathway for anticancer compounds. However, SMO antagonists such as vismodegib rapidly develop drug resistance. In this study, new SMO antagonists having the versatile purine ring as a scaffold were designed, synthesised, and biologically tested to provide an insight to their mechanism of action. Compound 4s was the most active and the best inhibitor of cell growth and selectively cytotoxic to cancer cells. 4s induced cell cycle arrest, apoptosis, a reduction in colony formation and downregulation of PTCH and GLI1 expression. BODIPY-cyclopamine displacement assays confirmed 4s is a SMO antagonist. In vivo, 4s strongly inhibited tumour relapse and metastasis of melanoma cells in mice. In vitro, 4s was more efficient than vismodegib to induce apoptosis in human cancer cells and that might be attributed to its dual ability to function as a SMO antagonist and apoptosis inducer. Full article

Ischemic stroke is the main cause of death/disability, posing a great menace to human health. Though efforts to search for therapeutic drugs are ongoing, few of them have succeeded. Adenosine A₁ receptor (A1R) activation could ameliorate ischemic injury, representing a very tempting target for stroke treatment. Tetrahydroxy stilbene glycoside (TSG), a potent antioxidant from the well-known Chinese herb Polygonum multiflorum Thunb., has been reported to have notable neuroprotective activities but the underlying mechanisms are elusive. This study investigated the mechanism of TSG focusing on A1R. TSG markedly decreased mortality, neurological deficit score, cerebral infarct size and brain water content of MCAO rats, and ameliorated the disorders in purine metabolism, energy metabolism and antioxidative defense system. TSG helped the survival of SH-SY5Y cells in OGD/R by alleviating oxidative stress and glutamate release, and by maintaining calcium homeostasis. TSG effects were abolished by A1R antagonist DPCPX. Docking and binding assays confirmed the binding of TSG with A1R. In addition, TSG upregulated the A1R level lowered by MCAO and OGD/R. The downstream signals of A1R activation, ERK1/2, HIF-1α and NF-κB contributed to the neuroprotection of TSG. Moreover, void of “well-known” cardiovascular side effects of classical A1R agonists, TSG showcased its great potential for stroke treatment. Full article

Huntington’s disease (HD) is a multi-system disorder that is caused by expanded CAG repeats within the exon-1 of the huntingtin (HTT) gene that translate to the polyglutamine stretch in the HTT protein. HTT interacts with the proteins involved in gene transcription, endocytosis, and metabolism. HTT may also directly or indirectly affect purine metabolism and signaling. We aimed to review existing data and discuss the modulation of the purinergic system as a new therapeutic target in HD. Impaired intracellular nucleotide metabolism in the HD affected system (CNS, skeletal muscle and heart) may lead to extracellular accumulation of purine metabolites, its unusual catabolism, and modulation of purinergic signaling. The mechanisms of observed changes might be different in affected systems. Based on collected findings, compounds leading to purine and ATP pool reconstruction as well as purinergic receptor activity modulators, i.e., P2X7 receptor antagonists, may be applied for HD treatment. Full article

Pharmacometabolomics is a useful tool to identify biomarkers that can assess and predict response after drug administration. The primary purpose of pharmacometabolomics is to better understand the mechanisms and pathways of a drug by searching endogenous metabolites that have significantly changed after drug administration. DA-9701, a prokinetic agent, consists of Pharbitis seed and Corydalis tube extract and it is known to improve the gastrointestinal motility. Although the overall mechanism of action of DA-9701 remains unclear, its active ingredients, corydaline and chlorogenic acid, act as a 5-HT3 and D2 receptor antagonist and 5-HT4 receptor agonist. To determine the significant metabolites after the administration of DA-9701, a qualitative analysis was carried out using ultra-high performance liquid chromatography coupled with orbitrap mass spectrometer followed by a multivariate analysis. Seven candidates were selected and a statistical analysis of fold change was performed over time. Our study concluded that all the seven selected metabolites were commonly involved in lipid metabolism and purine metabolism. Full article

Guanosine, a guanine-based purine nucleoside, has been described as a neuromodulator that exerts neuroprotective effects in animal and cellular ischemia models. However, guanosine’s exact mechanism of action and molecular targets have not yet been identified. Here, we aimed to elucidate a role of adenosine receptors (ARs) in mediating guanosine effects. We investigated the neuroprotective effects of guanosine in hippocampal slices from A_2AR-deficient mice (A_2AR^−/−) subjected to oxygen/glucose deprivation (OGD). Next, we assessed guanosine binding at ARs taking advantage of a fluorescent-selective A_2AR antagonist (MRS7396) which could engage in a bioluminescence resonance energy transfer (BRET) process with NanoLuc-tagged A_2AR. Next, we evaluated functional AR activation by determining cAMP and calcium accumulation. Finally, we assessed the impact of A₁R and A_2AR co-expression in guanosine-mediated impedance responses in living cells. Guanosine prevented the reduction of cellular viability and increased reactive oxygen species generation induced by OGD in hippocampal slices from wild-type, but not from A_2AR^−/− mice. Notably, while guanosine was not able to modify MRS7396 binding to A_2AR-expressing cells, a partial blockade was observed in cells co-expressing A₁R and A_2AR. The relevance of the A₁R and A_2AR interaction in guanosine effects was further substantiated by means of functional assays (i.e., cAMP and calcium determinations), since guanosine only blocked A_2AR agonist-mediated effects in doubly expressing A₁R and A_2AR cells. Interestingly, while guanosine did not affect A₁R/A_2AR heteromer formation, it reduced A_2AR agonist-mediated cell impedance responses. Our results indicate that guanosine-induced effects may require both A₁R and A_2AR co-expression, thus identifying a molecular substrate that may allow fine tuning of guanosine-mediated responses. Full article