Levels Of Guanosine Research Articles

Changes in Purines Concentration in the Cerebrospinal Fluid of Pregnant Women Experiencing Pain During Active Labor.

Labor pain has been reported as a severe pain and can be considered as a model of acute visceral pain. It is well known that extracellular purines have an important role in pain signaling in the central nervous system. This study analyzes the relationship between extracellular purines and pain perception during active labor. A prospective observational study was performed. Cerebrospinal fluid (CSF) levels of the purines and their metabolites were compared between women at term pregnancy with labor pain (n = 49) and without labor pain (Caesarian section; n = 47). Control groups (healthy men and women without chronic or acute pain-n = 40 and 32, respectively) were also investigated. The CSF levels of adenosine were significantly lower in the labor pain group (P = 0.026) and negatively correlated with pain intensity measured by a visual analogue scale (r = -0.48, P = 0.0005). Interestingly, CSF levels of uric acid were significantly higher in healthy men as compared to women. Additionally, pregnant women showed increased CSF levels of ADP, GDP, adenosine and guanosine and reduced CSF levels of AMP, GTP, and uric acid as compared to non-pregnant women (P < 0.05). These findings suggest that purines, in special the nucleoside adenosine, are associated with pregnancy and labor pain.

Longitudinal Metabolomics Profiling of Parkinson's Disease-Related α-Synuclein A53T Transgenic Mice.

Metabolic homeostasis is critical for all biological processes in the brain. The metabolites are considered the best indicators of cell states and their rapid fluxes are extremely sensitive to cellular changes. While there are a few studies on the metabolomics of Parkinson’s disease, it lacks longitudinal studies of the brain metabolic pathways affected by aging and the disease. Using ultra-high performance liquid chromatography and tandem mass spectroscopy (UPLC/MS), we generated the metabolomics profiling data from the brains of young and aged male PD-related α-synuclein A53T transgenic mice as well as the age- and gender-matched non-transgenic (nTg) controls. Principal component and unsupervised hierarchical clustering analyses identified distinctive metabolites influenced by aging and the A53T mutation. The following metabolite set enrichment classification revealed the alanine metabolism, redox and acetyl-CoA biosynthesis pathways were substantially disturbed in the aged mouse brains regardless of the genotypes, suggesting that aging plays a more prominent role in the alterations of brain metabolism. Further examination showed that the interaction effect of aging and genotype only disturbed the guanosine levels. The young A53T mice exhibited lower levels of guanosine compared to the age-matched nTg controls. The guanosine levels remained constant between the young and aged nTg mice, whereas the aged A53T mice showed substantially increased guanosine levels compared to the young mutant ones. In light of the neuroprotective function of guanosine, our findings suggest that the increase of guanosine metabolism in aged A53T mice likely represents a protective mechanism against neurodegeneration, while monitoring guanosine levels could be applicable to the early diagnosis of the disease.

Decreased levels of guanosine 3', 5'-monophosphate (cGMP) in cerebrospinal fluid (CSF) are associated with cognitive decline and amyloid pathology in Alzheimer's disease.

Levels of the cyclic nucleotides guanosine 3', 5'-monophosphate (cGMP) or adenosine 3', 5'-monophosphate (cAMP) that play important roles in memory processes are not characterized in Alzheimer's disease (AD). The aim of this study was to analyse the levels of these nucleotides in cerebrospinal fluid (CSF) samples from patients diagnosed with clinical and prodromal stages of AD and study the expression level of the enzymes that hydrolyzed them [phosphodiesterases (PDEs)] in the brain of AD patients vs. For cGMP and cAMP CSF analysis, the cohort (n = 79) included cognitively normal participants (subjective cognitive impairment), individuals with stable mild cognitive impairment or AD converters (sMCI and cMCI), and mild AD patients. A high throughput liquid chromatography-tandem mass spectrometry method was used. Interactions between CSF cGMP or cAMP with mini-mental state examination (MMSE) score, CSF Aβ(1-42) and CSF p-tau were analysed. For PDE4, 5, 9 and 10 expression analysis, brains of AD patients vs. controls (n = 7 and n = 8) were used. cGMP, and not cAMP levels, were significantly lower in the CSF of patients diagnosed with mild AD when compared with nondemented controls. CSF levels of cGMP showed a significant association with MMSE-diagnosed clinical dementia and with CSF biomarker Aβ42 in AD patients. Significant increase in PDE5 expression was detected in temporal cortex of AD patients compared with that of age-matched healthy control subjects. No changes in the expression of others PDEs were detected. These results support the potential involvement of cGMP in the pathological and clinical development of AD. The cGMP reduction in early stages of AD might participate in the aggravation of amyloid pathology and cognitive decline.

Effects of Biotin Supplementation in the Diet on Adipose Tissue cGMP Concentrations, AMPK Activation, Lipolysis, and Serum-Free Fatty Acid Levels.

Several studies have shown that pharmacological concentrations of biotin decrease hyperlipidemia. The molecular mechanisms by which pharmacological concentrations of biotin modify lipid metabolism are largely unknown. Adipose tissue plays a central role in lipid homeostasis. In the present study, we analyzed the effects of biotin supplementation in adipose tissue on signaling pathways and critical proteins that regulate lipid metabolism, as well as on lipolysis. In addition, we assessed serum fatty acid concentrations. Male BALB/cAnN Hsd mice were fed a control or a biotin-supplemented diet (control: 1.76 mg biotin/kg; supplemented: 97.7 mg biotin/kg diet) over 8 weeks postweaning. Compared with the control group, biotin-supplemented mice showed an increase in the levels of adipose guanosine 3',5'-cyclic monophosphate (cGMP) (control: 30.3±3.27 pmol/g wet tissue; supplemented: 49.5±3.44 pmol/g wet tissue) and of phosphorylated forms of adenosine 5'-monophosphate-activated protein kinase (AMPK; 65.2%±1.06%), acetyl-coenzyme A (CoA), carboxylase-1 (196%±68%), and acetyl-CoA carboxylase-2 (78.1%±18%). Serum fatty acid concentrations were decreased (control: 1.12±0.04 mM; supplemented: 0.91±0.03 mM), and no change in lipolysis was found (control: 0.29±0.05 μmol/mL; supplemented: 0.33±0.08 μmol/mL). In conclusion, 8 weeks of dietary biotin supplementation increased adipose tissue cGMP content and protein expression of the active form of AMPK and of the inactive forms of acetyl-CoA carboxylase-1 and acetyl-CoA carboxylase-2. Serum fatty acid levels fell, and no change in lipolysis was observed. These findings provide insight into the effects of biotin supplementation on adipose tissue and support its use in the treatment of dyslipidemia.

Stimulators of soluble guanylate cyclase (sGC) inhibit experimental skin fibrosis of different aetiologies

ObjectivesStimulators of the soluble guanylate cyclase (sGC) have recently been shown to inhibit transforming growth factor-β signalling. Here, we aimed to demonstrate that riociguat, the drug candidate for clinical trials...

Nitric Oxide Pathway and Proliferation of Neural Progenitors in the Neonatal Rat

Several lines of evidence demonstrate that inhaled nitric oxide (iNO) not only acts locally on the pulmonary vasculature but also has remote effects on the mature and developing brain under basal or pathological conditions by modulating cerebral blood flow and microvascularization, white matter maturation, inflammation, and subsequent brain repair. Previously, consistent studies demonstrated that increased levels of guanosine 3′,5′ cyclic monophosphate (cGMP), the main effector of biological effect induced by nitric oxide (NO), significantly augment proliferation and neuronal differentiation of adult neural progenitor cells (NPCs). In the present study, we ask the question whether iNO could promote the proliferation of NPCs in the uninjured developing brain. We first reported that iNO exposure at a concentration of 20 ppm during the first 7 days of life was associated with a significant but transient elevation of brain cGMP concentration 2 h after the onset of iNO exposure and a subsequent increase in myelin content of the developing white matter at postnatal day (P) 10. Using BrDu labelling and colabelling with specific cell-type markers we found that iNO exposure of rat pups results in an increased NPC proliferation in several layers of the subventricular zone (SVZ) at both early (30 h) and late (P7) time points. These proliferating NPCs were found to be sustainably viable and subsequently differentiated into oligodendroglial cells in the developing white matter and cortex. We also found that NG2 immunoreactivity around vessel walls, labeling pericyte cells, was increased in NO-exposed rat pups in the periventricular SVZ. In conclusion, iNO appears to act on oligodendrocyte progenitor cells, leading to increased density of mature oligodendrocytes and myelin content in the immature rat brain.

Purine Metabolism in Patients with Major Depression: a Follow-up Study.

Introduction Purine metabolism may be affected in major depressive disorder (MDD). Increased enzymatic activity of the purine cycle has been observed in MDD. In MDD patients, purine metabolite levels also react to sertraline treatment. Objectives To compare serum purine metabolites between: 1) MDD patients and non-depressed controls; and 2) remitted and non-remitted MDD patients. Aims To clarify the role of purine metabolism in MDD during active illness and recovery. Methods The sample comprised 99 MDD patients (DSM-IV, SCID interview) and 318 non-depressed controls (Beck Depression Inventory scores Results The participants’ likelihood of belonging to the MDD group increased 1.1-fold for each 1-unit decrease in serum inosine, 3.2-fold for each 1-unit decrease in guanosine levels and 2.2-fold for each 1-unit increase in xanthine levels. The remitted and non-remitted groups displayed no significant metabolite differences, but the remitted group showed a non-significant shift of values towards the values of the non-depressed group. Conclusions Increased degradation of purines and accumulation of xanthine may characterise MDD. Alterations in purine metabolism appear to only partially change during recovery. Nevertheless, recovery-related changes require further investigation in larger samples.

Association of N-Terminal Pro–Brain Natriuretic Peptide, Matrix –Metalloprotinase-9, and 8-Oxo-2 Deoxy Guanosine with the Incidence of Essential Hypertension

Background and Objectives: Oxidative stress and inflammation are cooperative events involved in essential hypertension diseases. This study was as a step for elucidating the contribution of N-terminal pro-brain natriuretic peptide, matrix-metalloprotinase-9 and 8-oxo2-deoxyguanosine with the essential hypertension incidence, development, and progression. Aims: The objective was to determine the serum studied parameters levels in essential hypertensive and normotensive subjects, and to assess the association between these biomarkers with the essential hypertension, and to investigate the effect of other confounding factors like stages, age, and gender and finally find the correlation between all studied parameters. Methods: This study was designed to examine the associations between the focused parameters with the essential hypertension on 50 patients of both genders, as well as an equal numbers of matched age–gender healthy adults were also enrolled in this study as a control group. The hypothesis suggesting that oxidative stress and inflammatory processes influence the risk of adverse clinical outcomes are worth investigating. These parameters were analyzed using enzyme linked immunosorbent assay. Statistical analyses were performed with SPSS version 18. Results: Patients with essential hypertension exhibited significantly higher serum focused parameters levels as compared with the control group. The mean serum N-terminal pro–brain natriuretic peptide levels in patients and control groups were 304.33 ± 204.19, 76.52±20.98 pg/ml respectively. The mean serum matrix–metalloprotinase-9 level in patients and control groups were 2.36±1.1, 1.4±0.8 respectively. The mean serum 8-oxo-2-deoxy guanosine level in patients and control groups were 170.40±41.95, 84.11±34.07 (mg/ml) respectively. Conclusions: Data suggested an association between these circulating biomarkers with the incidence, development, and progression of essential hypertension. No effect of age and gender present on serum levels of focused biomarkers in both groups. These focused parameters seem to be a simple, non-invasive tools and independent parameters for early detection, assessing disease severity, and involved in the etiology of disease. Data indicated an alteration in the oxidative status and inflammatory processes in patients with essential hypertension. Accordingly, this work was undertaken to assess contribution of the oxidative stress and inflammatory process as a risk factors. In addition, these parameters are regarded as markers with prognostic significance and as potential therapeutic targets. These biomarkers are tools that might aid the physicians in diagnosis and subsequent risk stratification, guiding selection of therapy, secondary prevention, and serving as a target for therapy.

Genotype-Specific Differences in the Tumor Metabolite Profile of Pheochromocytoma and Paraganglioma Using Untargeted and Targeted Metabolomics

Pheochromocytomas and paragangliomas (PGLs) are neuroendocrine tumors of sympathetic or parasympathetic paraganglia. Nearly 40% of PGLs are caused by germline mutations. The present study investigated the effect of genetic alterations on metabolic networks in PGLs. Homogenates of 32 sporadic PGLs and 48 PGLs from patients with mutations in SDHB, SDHD, SDHAF-2, VHL, RET, and NF-1 were subjected to proton ((1)H) nuclear magnetic resonance (NMR) spectroscopy at 500 MHz for untargeted and HPLC tandem mass spectrometry for targeted metabolite profiling. (1)H NMR spectroscopy identified 28 metabolites in PGLs of which 12 showed genotype-specific differences. Part of these results published earlier reported low complex II activity (P < .0001) and low ATP/ADP/AMP content (P < .001) in SDH-related PGLs compared with sporadics and PGLs of other genotypes. Extending these results, low levels of N-acetylaspartic acid (NAA; P < .05) in SDH tumors and creatine (P < .05) in VHL tumors were observed compared with sporadics and other genotypes. Positive correlation was observed between NAA and ATP/ADP/AMP content (P < .001) and NAA and complex II activity (P < .0001) of PGLs. Targeted purine analysis in PGLs showed low adenine in cluster 1 compared with cluster 2 tumors (SDH P < .0001; VHL P < .05) whereas lower levels (P < .05) of guanosine and hypoxanthine were observed in RET tumors compared with SDH tumors. Principal component analysis (PCA) of metabolites could distinguish PGLs of different genotypes. The present study gives a comprehensive picture of alterations in energy metabolism in SDH- and VHL-related PGLs and establishes the interrelationship of energy metabolism and amino acid and purine metabolism in PGLs.

Disease-Modifying Effect of Adiponectin in Model of α-Synucleinopathies.

ObjectiveGrowing evidence suggests that neurodegenerative diseases are associated with metabolic disorders, but the mechanisms are still unclear. Better comprehension of this issue might provide a new strategy for treatment of neurodegenerative diseases. We investigated possible roles of adiponectin (APN), the antidiabetes protein, in the pathogenesis of α-synucleinopathies.MethodsUsing biochemical and histological methods, we investigated autopsy brain of α-synucleinopathies including Parkinson's disease (PD) and dementia with Lewy bodies (DLB), and analyzed the effects of APN in cellular and in mouse models of α-synucleinopathies.ResultsWe observed that APN is localized in Lewy bodies derived from α-synucleinopathies, such as Parkinson's disease and dementia with Lewy bodies. In neuronal cells expressing α-synuclein (αS), aggregation of αS was suppressed by treatment with recombinant APN in an AdipoRI-AMP kinase pathway-dependent manner. Concomitantly, phosphorylation and release of αS were significantly decreased by APN, suggesting that APN may be antineurodegenerative. In transgenic mice expressing αS, both histopathology and movement disorder were significantly improved by intranasal treatment with globular APN when the treatment was initiated in the early stage of the disease. In a mouse model, reduced levels of guanosine and inosine monophosphates, both of which are potential stimulators of aggregation of αS, might partly contribute to suppression of aggregation of αS by APN.InterpretationTaken together, APN may suppress neurodegeneration through modification of the metabolic pathway, and could possess a therapeutic potential against α-synucleinopathies.

Guanosine regulates adenosine levels in the kidney.

In cell culture, extracellular guanosine increases extracellular adenosine by attenuating the disposition of extracellular adenosine (American Journal of Physiology – Cell Physiology 304: C406–C421, 2013). The goal of this investigation was to determine whether this “guanosine–adenosine mechanism” is operative in an intact organ. Twenty‐seven isolated, perfused mouse kidneys were subjected to metabolic poisons (iodoacetate plus 2,4‐dinitrophenol) to cause energy depletion and thereby stimulate renal adenosine production. Adenosine levels in the renal venous perfusate increased from a baseline of 36 ± 8 to 499 ± 96, 258 ± 50, and 71 ± 13 nmol/L at 15, 30, and 60 min, respectively, after administering metabolic poisons (% of basal; 1366 ± 229, 715 ± 128, and 206 ± 33, respectively). Changes in renal venous levels of guanosine closely mirrored the time course of changes in adenosine: baseline of 15 ± 2 to 157 ± 13, 121 ± 8, and 50 ± 5 nmol/L at 15, 30, and 60 min, respectively (% of basal; 1132 ± 104, 871 ± 59, and 400 ± 51, respectively). Freeze‐clamp experiments in 12 kidneys confirmed that metabolic poisons increased kidney tissue levels of adenosine and guanosine. In eight additional kidneys, we examined the ability of guanosine to reduce the renal clearance of exogenous adenosine; and these experiments revealed that guanosine significantly decreased the renal extraction of adenosine. Because guanosine is metabolized by purine nucleoside phosphorylase (PNPase), in another set of 16 kidneys we examined the effects of 8‐aminoguanine (PNPase inhibitor) on renal venous levels of adenosine and inosine (adenosine metabolite). Kidneys treated with 8‐aminoguanine showed a more robust increase in both adenosine and inosine in response to metabolic poisons. We conclude that in the intact kidney, guanosine regulates adenosine levels.

Diagnosis of immunodeficiency caused by a purine nucleoside phosphorylase defect by using tandem mass spectrometry on dried blood spots

Purine nucleoside phosphorylase (PNP) deficiency is a rare form of autosomal recessive combined primary immunodeficiency caused by a enzyme defect leading to the accumulation of inosine, 2'-deoxy-inosine (dIno), guanosine, and 2'-deoxy-guanosine (dGuo) in all cells, especially lymphocytes. Treatments are available and curative for PNP deficiency, but their efficacy depends on the early approach. PNP-combined immunodeficiency complies with the criteria for inclusion in a newborn screening program. This study evaluate whether mass spectrometry can identify metabolite abnormalities in dried blood spots (DBSs) from affected patients, with the final goal of individuating the disease at birth during routine newborn screening. DBS samples from 9 patients with genetically confirmed PNP-combined immunodeficiency, 10,000 DBS samples from healthy newborns, and 240 DBSs from healthy donors of different age ranges were examined. Inosine, dIno, guanosine, and dGuo were tested by using tandem mass spectrometry (TMS). T-cell receptor excision circle (TREC) and kappa-deleting recombination excision circle (KREC) levels were evaluated by using quantitative RT-PCR only for the 2 patients (patients 8 and 9) whose neonatal DBSs were available. Mean levels of guanosine, inosine, dGuo, and dIno were 4.4, 133.3, 3.6, and 3.8 μmol/L, respectively, in affected patients. No indeterminate or false-positive results were found. In patient 8 TREC levels were borderline and KREC levels were abnormal; in patient 9 TRECs were undetectable, whereas KREC levels were normal. TMS is a valid method for diagnosis of PNP deficiency on DBSs of affected patients at a negligible cost. TMS identifies newborns with PNP deficiency, whereas TREC or KREC measurement alone can fail.

Tempol prevents genotoxicity induced by vorinostat: role of oxidative DNA damage

Vorinostat is a member of histone deacetylase inhibitors, which represents a new class of anticancer agents for the treatment of solid and hematological malignancies. Studies have shown that these drugs induce DNA damage in blood lymphocytes, which is proposed to be due to the generation of oxidative lesions. The increase in DNA damage is sometimes associated with risk of developing secondary cancer. Thus, finding a treatment that limits DNA damage caused by anticancer drugs would be beneficial. Tempol is a potent antioxidant that was shown to prevent DNA damage induced by radiation. In this study, we aimed to investigate the harmful effects of vorinostat on DNA damage, and the possible protective effects of tempol against this damage. For that, the spontaneous frequency of sister chromatid exchanges (SCEs), chromosomal aberrations (CAs), and 8-hydroxy-2-deoxy guanosine (8-OHdG) levels were measured in cultured human lymphocytes treated with vorinostat and/or tempol. The results showed that vorinostat significantly increases the frequency of SCEs, CAs and 8-OHdG levels in human lymphocytes as compared to control. These increases were normalized by the treatment of cells with tempol. In conclusion, vorinostat is genotoxic to lymphocytes, and this toxicity is reduced by tempol. Such results could set the stage for future studies investigating the possible usefulness of antioxidants co-treatment in preventing the genotoxicity of vorinostat when used as anticancer in human.

Dueling nucleosides: cross-regulation of extracellular adenosine by guanosine. Focus on “Extracellular guanosine regulates extracellular adenosine levels”

<i>Dueling nucleosides: cross-regulation of extracellular adenosine by guanosine</i>. Focus on “Extracellular guanosine regulates extracellular adenosine levels”

Extracellular guanosine regulates extracellular adenosine levels

The aim of this investigation was to test the hypothesis that extracellular guanosine regulates extracellular adenosine levels. Rat preglomerular vascular smooth muscle cells were incubated with adenosine, guanosine, or both. Guanosine (30 μmol/l) per se had little effect on extracellular adenosine levels. Extracellular adenosine levels 1 h after addition of adenosine (3 μmol/l) were 0.125 ± 0.020 μmol/l, indicating rapid disposition of extracellular adenosine. Extracellular adenosine levels 1 h after addition of adenosine (3 μmol/l) plus guanosine (30 μmol/l) were 1.173 ± 0.061 μmol/l, indicating slow disposition of extracellular adenosine. Cell injury increased extracellular levels of endogenous adenosine and guanosine, and the effects of cell injury on endogenous extracellular adenosine were modulated by altering the levels of endogenous extracellular guanosine with exogenous purine nucleoside phosphorylase (converts guanosine to guanine) or 8-aminoguanosine (inhibits purine nucleoside phosphorylase). Extracellular guanosine also slowed the disposition of extracellular adenosine in rat preglomerular vascular endothelial cells, mesangial cells, cardiac fibroblasts, and kidney epithelial cells and in human aortic and coronary artery vascular smooth muscle cells and coronary artery endothelial cells. The effects of guanosine on adenosine levels were not mimicked or attenuated by 5-iodotubericidin (adenosine kinase inhibitor), erythro-9-(2-hydroxy-3-nonyl)-adenine (adenosine deaminase inhibitor), 5-aminoimidazole-4-carboxamide (guanine deaminase inhibitor), aristeromycin (S-adenosylhomocysteine hydrolase inhibitor), low sodium (inhibits concentrative nucleoside transporters), S-(4-nitrobenzyl)-6-thioinosine [inhibits equilibrative nucleoside transporter (ENT) type 1], zidovudine (inhibits ENT type 2), or acadesine (known modulator of adenosine levels). Guanosine also increases extracellular inosine, uridine, thymidine, and cytidine, yet decreases extracellular uric acid. In conclusion, extracellular guanosine regulates extracellular adenosine levels.

Ginsenoside Rb1 relieves glucose fluctuation-induced oxidative stress and apoptosis in Schwann cells.

Cultured Schwann cells were treated with 5.6 mM and 50 mM glucose alternating every 8 hours to simulate intermittent high glucose. The present study analyzed the neuroprotective effects of 1, 10 and 100 μM ginsenoside Rb1 on oxidative damage and apoptosis in Schwann cells induced by intermittent high glucose. Flow cytometry demonstrated that ginsenoside Rb1 reduced intermittent high glucose-mediated reactive oxygen species production. Enzyme linked immunosorbent assay showed that 8-hydroxy-2-deoxy guanosine levels in Schwann cells decreased following ginsenoside Rb1 treatment. Quantitative real-time reverse transcription-PCR and western blot assay results revealed that ginsenoside Rb1 inhibited intermittent high glucose-upregulated Bax expression, but antagonized intermittent high glucose-downregulated Bcl-2 expression in Schwann cells. These effects were most pronounced with 100 μM ginsenoside Rb1. These results indicate that ginsenoside Rb1 inhibits intermittent high glucose-induced oxidative stress and apoptosis in Schwann cells.

Isosorbide-5-mononitrate and endothelial function: a wolf in sheep's clothing

This editorial refers to ‘Chronic therapy with isosorbide-5-mononitrate causes endothelial dysfunction, oxidative stress, and a marked increase in vascular endothelin-1 expression’[†][1], by M. Oelze et al. , on page 3206 In 1846, Ascanio Sobrero first synthesized nitroglycerin and observed that a small quantity of the oily substance placed on the tongue caused a severe headache. In its pure form—without an inert carrier such as lactose—nitroglycerin is explosive. It was therefore used by Alfred Nobel to manufacture dynamite. It took until the end of the 1860s before the antianginal effect of nitroglycerin was discovered. What had happened? Two findings were crucial: first, workers suffering from angina pectoris at the weekend were free of pain during the week; secondly, some workers described severe headaches on Mondays, but felt relief of pain at the end of the week and were absolutely free of pain at the weekends. Those observations were attributed to the vasodilatory properties of nitroglycerin. More than 100 years later, the mechanisms of action were discovered. The molecule nitric oxide (NO) is produced by nitroglycerin in smooth muscle cells. NO activates guanylyl cyclase, increasing intracellular levels of cyclic guanosine 3',5'-monophosphate (cyclic GMP), leading to vasodilation. This was the basis for further studies revealing that mammalian cells produce NO, culminating in awarding the Nobel Prize in Medicine and Physiology to Furchgott, Ignarro, and Murad for ‘their discoveries concerning nitric oxide as a signalling molecule in the cardiovascular system’ in 1998. As well-established drugs, organic nitrates still belong to the … [1]: #fn-2

Abstract 524: Extracellular Guanosine Regulates Extracellular Adenosine Levels

Extracellular adenosine modulates cardiovascular and renal function. While measuring extracellular purines in biological samples, we observed a correlation between levels of adenosine and guanosine. This observation led us to test the hypothesis that extracellular guanosine regulates extracellular adenosine levels in the cardiovascular and renal systems. Rat preglomerular vascular smooth muscle cells in culture were incubated with adenosine and/or guanosine. In the absence of added adenosine, exogenous guanosine (30 μmol/L) had little effect on extracellular adenosine levels, indicating that extracellular guanosine does not trigger the release or production of adenosine. Without added guanosine and 1 hour after adding 3 μmol/L of exogenous adenosine, extracellular adenosine levels were only 0.125 ± 0.020 μmol/L, indicating rapid disposition of extracellular adenosine by a monolayer of cells. In contrast, extracellular adenosine levels 1 hour after adding 3 μmol/L of adenosine plus guanosine (30 μmol/L) were 1.173 ± 0.061 μmol/L (9-fold higher; p&lt;0.0001), indicating slow disposition of extracellular adenosine in the presence of extracellular guanosine. Extracellular guanosine impeded the disposition of extracellular adenosine not only in preglomerular vascular smooth muscle cells, but also in rat preglomerular vascular endothelial cells, mesangial cells, cardiac fibroblasts and kidney epithelial cells, as well as in human aortic vascular smooth muscle cells, coronary artery vascular smooth muscle cells and coronary artery endothelial cells. In rats, infusions of guanosine per se had little effect on cardiovascular/renal variables, yet markedly enhanced the effects of co-infusions of adenosine. For example, in control rats, adenosine (0.3 μmol/kg/min) only modestly decreased mean arterial blood pressure (from 114 ± 4 to 100 ± 4 mm Hg). In contrast, in guanosine-treated rats (10 μmol/kg/min), adenosine profoundly decreased blood pressure (from 109 ± 4 to 79 ± 3 mm Hg; p&lt;0.0001 vs non-guanosine treated group). Conclusion: Extracellular guanosine powerfully regulates extracellular adenosine levels by altering adenosine disposition and this occurs in many, perhaps most, cell types in the cardiovascular system and kidneys.

Associations between Purine Metabolites and Clinical Symptoms in Schizophrenia

BackgroundThe antioxidant defense system, which is known to be dysregulated in schizophrenia, is closely linked to the dynamics of purine pathway. Thus, alterations in the homeostatic balance in the purine pathway may be involved in the pathophysiology of schizophrenia.Methodology/Principal FindingsBreakdown products in purine pathway were measured using high-pressure liquid chromatography coupled with a coulometric multi-electrode array system for 25 first-episode neuroleptic-naïve patients with schizophrenia at baseline and at 4-weeks following initiation of treatment with antipsychotic medication. Associations between these metabolites and clinical and neurological symptoms were examined at both time points. The ratio of uric acid and guanine measured at baseline predicted clinical improvement following four weeks of treatment with antipsychotic medication. Baseline levels of purine metabolites also predicted clinical and neurological symtpoms recorded at baseline; level of guanosine was associated with degree of clinical thought disturbance, and the ratio of xanthosine to guanosine at baseline predicted degree of impairment in the repetition and sequencing of actions.Conclusions/SignificanceFindings suggest an association between optimal levels of purine byproducts and dynamics in clinical symptoms and adjustment, as well as in the integrity of sensory and motor processing. Taken together, alterations in purine catabolism may have clinical relevance in schizophrenia pathology.

ChemInform Abstract: Large Scale H.E.L.P. Synthesis of Oligodeoxynucleotides by the Hydroxybenzotriazole Phosphotriester Approach.

Abstract The hydroxybenzotriazole phosphotriester approach has been successfully applied to the PEG-supported synthesis ( HELP ) of oligodeoxynucleotides. Main advantages over the MSNT-based HELP procedure are the elimination of side-reactions at the guanosine level and the use of the 1ess expensive protected nucleosides as starting materials.