Kegg Pathway: Purine metabolism

J Cereb Blood Flow Metab. 2009 Nov 18;
Kusano Y, Echeverry G, Miekisiak G, Kulik TB, Aronhime SN, Chen JF, Winn HR

The mechanisms responsible for vascular autoregulation in the brain during changes in mean arterial blood pressure are ambiguous. Potentially, adenosine, a Purine nucleoside and potent vasodilator, may be involved as earlier studies have documented an increase in brain adenosine concentrations with cerebral ischemia and hypotension. Consequently, we tested the hypothesis that adenosine is involved in vasodilatation during hypotension within the autoregulatory range (>50 mm Hg) by exposing adenosine 2a receptor (A2aR) knockout and wild type (WT) mice to short (2 to 5 mins) periods of hypotension. We found that autoregulation was significantly (P<0.05) impaired by 29% in A2a knockout mice as compared with WT animals. Furthermore, the A2R antagonist (A2a>A2b:10-85>1), ZM-241385, in a dose (1, 5, 10 mg/kg, intraperitoneally)-related manner, attenuated autoregulation in WT mice. In knockout mice treated with ZM-2413585 (5 and 10 mg/kg), autoregulation was further impaired indicating that A2b receptors also participated in cerebral vasodilatation. Treatment with dipyridamole (1.0 mg/kg) that increases extracellular concentrations of adenosine improved autoregulation in the A2aR knockout mice. We would conclude that adenosine through both A2a and A2b receptors is involved in physiologic vascular regulation during hypotension even within the autoregulatory range.Journal of Cerebral Blood Flow & metabolism advance online publication, 18 November 2009; doi:10.1038/jcbfm.2009.244.

Infect Genet Evol. 2009 Nov 10;
Simo G, Queiroz R, Herder S, Cuny G, Hoheisel J

Trypanosoma brucei subspecies undergo establishment and maturation in tsetse flies mid-gut and salivary glands respectively. Successful establishment of trypanosomes in tsetse mid-gut as well as their migration to saliva gland depends on the ability of these parasites to adapt rapidly to new environmental conditions and to negotiate the physical barriers. To identify subspecies specific genes which are differentially regulated during the establishment of Trypanosoma brucei subspecies in tsetse flies mid gut, a comparative genomic analysis between different Trypanosoma brucei subspecies was performed using microarrays containing about 23 040 Trypanosoma brucei shotgun fragments. The whole genome analyses of RNA expression profiles revealed about 274 significantly differentially expressed genes between Trypanosoma brucei subspecies. About 7% of the differentially regulated clones did not match to any Trypanosoma brucei predicted genes. Most of the differentially regulated transcripts are involved in transport across cell membrane and also in the Purines metabolism. The genes selectively up regulated in Trypanosoma brucei gambiense and Trypanosoma brucei rhodesiense (human infective Trypanosoma brucei) like snoRNA and HSP70 are expressed in response to stress. The high failure rate in the process of establishment and maturation of Trypanosoma brucei gambiense during cyclical transmission in tsetse flies may result from the incapacity of this parasite to regulate its growth due to the expression of a variety of chaperones or heat shock proteins. Genes selectively up regulated in Trypanosoma brucei brucei like NT8.1 nucleoside/nucleobase transporters and S-adenosylmethionine synthetase may favor the establishment of this subspecies in tsetse mid gut. These genes appear as potential targets for investigations on the development of vaccine blocking the transmission of trypanosomes in tsetse flies.

Acta Trop. 2009 Nov 6;
Urbina JA

A critical review of the development of specific chemotherapeutic approaches for the management of American Trypanosomiasis or Chagas disease is presented, including controversies on the pathogenesis of the disease, the initial efforts that led to the development of currently available drugs (nifurtimox and benznidazole), limitations of these therapies and novel approaches for the development of anti-Trypanosoma cruzi drugs, based on our growing understanding of the biology of this parasite. Among the later, the most promising approaches are ergosterol biosynthesis inhibitors such as posaconazole and ravuconazole, poised to enter clinical trials for chronic Chagas disease in the short term; inhibitors of cruzipain, the main cysteine protease of T. cruzi, essential for its survival and proliferation in vitro and in vivo; bisphosphonates, metabolic stable pyrophosphate analogs that have trypanocidal activity through the inhibition of the parasite's farnesyl-pyrophosphate synthase or hexokinase; inhibitors of trypanothione synthesis and redox metabolism and inhibitors of hypoxanthine-guanine phosphoribosyl- transferase, an essential enzyme for Purine salvage in T. cruzi and related organisms. Finally, the economic and political challenges faced by development of drugs for the treatment of neglected tropical diseases, which afflict almost exclusively poor populations in developing countries, are analyzed and recent potential solutions for this conundrum are discussed.

Med Mycol. 2009 Nov; 47(7): 734-44
Zambuzzi-Carvalho PF, Cruz AH, Santos-Silva LK, Goes AM, Soares CM, Pereira M

In the present study, we examined the characteristics of cDNA, the regulation of the gene expression of Paracoccidioides brasiliensis MLS (Pbmls), and the enzymatic activity of the protein P. brasiliensis MLS (PbMLS) from the P. brasiliensis Pb01 isolate. Pbmls cDNA contains 1617 bp, encoding a protein of 539 amino acids with a predicted molecular mass of 60 kDa. The protein presents the MLSs family signature, the catalytic residues essential for enzymatic activity and the peroxisomal/glyoxysomal targeting signal PTS1. The high level of Pbmls transcript observed in the presence of two-carbon (2C) sources suggests that in P. brasiliensis, the primary regulation of carbon flux into the glyoxylate cycle (GC) was at the level of the Pbmls transcript. The gene expression, protein level, and enzymatic activity of Pbmls were highly induced by oxalurate in the presence of glucose and by proline in the presence of acetate. In the presence of glucose, the gene expression, protein level, and enzymatic activity of Pbmls were mildly stimulated by proline. Our results suggested that PbMLS condenses acetyl-CoA from both 2C sources (GC) and nitrogen sources (from proline and Purine metabolism) to produce malate. The regulation of Pbmls by carbon and nitrogen sources was reinforced by the presence of regulatory motifs CREA and UIS found in the promoter region of the gene.

Food Chem Toxicol. 2009 Oct 29;
Abdalla FH, Bellé LP, De Bona KS, Bitencourt PE, Pigatto AS, Moretto MB

Adenosine deaminase (ADA) is involved in Purine metabolism and plays a significant role in the immune system. The focus of this investigation was to examine the effects of low concentrations of organic mercury on ADA activity in human leukocytes and to investigate the relationship between these effects and cell death. We have examined the protective potential effects of Allium sativum extract (GaE) against Methylmercury (MeHg)-induced cytotoxic effects on human leucocytes under in vitro conditions. MeHg (0.05-10muM) significantly decreased leukocyte viability (58.97% for MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide) and 51.67% for Alamar Blue (AB) and this decrease was positively correlated to the MeHg-induced inhibition of ADA activity. N-acetylcysteine (NAC) and GaE prevented both the MeHg-induced cytotoxic effects on leukocytes according to MTT and AB assays and the effects on the ADA activity. The present results suggest that the protective effects of GaE against MeHg-induced leukocyte damage is related to the removal of oxidant species generated in the presence of MeHg due to the antioxidant efficacy of garlic constituents. It is important to point out that the intense presence of ADA in Leukocyte suspension (LS) highlights the relevant effects in the immune system and in vitro cytotoxicity of MeHg exposure.

Nat Rev Drug Discov. 2009 Nov; 8(11): 838-9
Harrison C

Hum Gene Ther. 2008 Nov; 19(11): 1249-60
Hojman P, Gissel H, Andre FM, Cournil-Henrionnet C, Eriksen J, Gehl J, Mir LM

Gene transfer by electroporation is gaining momentum now that high-level, long-term expression of transgenes is being obtained. Several different pulse regimens are efficient, yet little information is available about the physiological muscular response to gene electrotransfer. This paper provides a comprehensive evaluation of the physiological and molecular effects on host tissue after DNA electrotransfer. We have tested several pulse regimens with special emphasis on the pulse combination of a short (100 microsec) high-voltage (HV) pulse followed by a long low-voltage (LV) pulse used for DNA electrotransfer, comparing it with 8 HV pulses designed to ensure extensive permeabilization of the muscle membrane. Using both mouse and rat skeletal muscle tissue, we investigated cell permeabilization by the 51Cr-labeled EDTA assay, lactate dehydrogenase release, Na+ and Ca2+ influx, K+ efflux, ATP release, and water content, as well as muscle function both in vivo and ex vivo, Hsp70 induction, and histology. In all these assays, the HVLV pulse combination gave rise to minimal disturbance of cell function, in all cases significantly different from results when using 8 HV pulses. The evaluated parameters were normalized after 1 week. The addition of DNA caused significantly more transmembrane exchange, and this may be due to entrance of the DNA through the membrane. In conclusion, this study comprehensively documents the immediate effects of DNA electrotransfer and shows that only slight cell disturbances occur with the HVLV pulses used for gene transfer. This is highly important, as minimal perturbation of cell physiology is essential for efficient transgene expression.

Hum Mol Genet. 2009 Oct 27;
van der Harst P, Bakker SJ, de Boer RA, Wolffenbuttel BH, Johnson T, Caulfield MJ, Navis G

Uric acid is the final catabolic product of Purine metabolism and elevated levels are associated with diabetes and cardiovascular disease. A recent meta-analysis of genome-wide association studies totalling 28,141 participants identified 5 novel loci associated with serum uric acid levels. In our population based cohort of 7,795 subjects we replicated 4 of these 5 loci; PDZK1 (rs12129861 P=1.07x10(-3)), GCKR (rs780094 P=4.83x10(-4)), SLC16A9 (rs742132 P=0.047), and SLC22A11 (rs17300741 P=6.13x10(-3)), but not LRRC16A (rs742132 P=0.645). Serum uric acid concentration is a complex trait, closely associated to renal uric acid handling (fractional uric acid excretion; P< 1 x 10(-300)), renal function (serum creatinine; P< 1 x 10(-300)), and the metabolic syndrome (including fasting insulin; P=2.48x10(-232), insulin resistance; P=2.51x10(-258), waist circumference; P< 1 x 10(-300)), and systolic blood pressure (P=1.93 x 10(-219)). Together these factors explain 67% of the variance in uric acid levels. Therefore, we sought to determine the potential contribution of these factors to the association of these novel loci with uric acid levels, by including them as additional explanatory variables in our analyses, and by considering them as alternative response variables. The association with the GCKR locus is attenuated by serum triglycerides and fractional uric acid excretion. We also observed the GCKR locus to be associated with total cholesterol (P= 7.52x10(-6)), triglycerides (P=2.65x10(-9)), fasting glucose (P=0.011), fractional uric acid excretion (P=3.36 x10(-5)), and high-sensitive CRP (P=1.18x10(-3)) also after adjusting for serum UA levels. We argue that GCKR locus affects serum UA levels through a factor that also affects triglycerides.

J Acquir Immune Defic Syndr. 2009 Nov 1; 52(3): 431-2
Calcagno A, Bonora S, Tettoni MC, D'Avolio A, Perri GD, Lanzafame M, Penco G

Arzneimittelforschung. 2009; 59(9): 476-81
Weissenfeld J, Lüngen M, Stock S, Drabik A, Gerber A

On the basis of the rebate contracts between individual statutory health insurance funds and pharmaceutical enterprises, the generic substitution of prescribed medications is economically attractive and is advocated for statutory health insurees in Germany. In addition to the drugs whose substitution can be considered to be uncritical, rebate contracts also include controversial substances such as the bronchodilator theophylline (CAS 58-55-9), which has a narrow therapeutic range and should only be substituted under certain conditions. The objective of this article was to check the safety of the substitution of theophylline by means of a comparative evaluation of bioequivalence studies carried out on theophylline slow-release preparations. A systematic literature search was carried out in the MEDLINE database. The search terms used were combinations of the following key words: theophylline, generics, bioequivalence, substitution, brand and non-brand. In addition, a manual search was performed in the reference lists of the relevant articles. Only articles that were published between January 1, 1988 and August 30, 2008 were to be included. Five studies conformed to the inclusion and exclusion criteria. Two of the studies came to the conclusion that the preparations analysed were bioequivalent. In the remaining three studies there was no bioequivalence found between the preparations and the reference product. Because of the heterogeneity of study outcomes no metanalysis could be performed. On the basis of the studies analysed the conclusion can be drawn that a theophylline slow-release preparation should only be substituted under close monitoring by a physician because of the many factors which can adversely affect serum levels, such as the narrow therapeutic range of the active ingredient, the patient's metabolisation rate or the different galenics of the preparations. Nevertheless, the question remains as to whether the costs saved by the rebate contracts would not be significantly outweighed.

Am J Med. 2009 Nov; 122(11): 1054.e7-1054.e14
Reichlin T, Potocki M, Breidthardt T, Noveanu M, Hartwiger S, Burri E, Klima T, Stelzig C, Laule K, Mebazaa A, Christ M, Mueller C

BACKGROUND: Uric acid was shown to predict outcome in patients with stable chronic heart failure. Its impact in patients admitted in the Emergency Department with acute dyspnea, however, remains unknown. METHODS: We prospectively investigated the diagnostic and prognostic value of uric acid in 743 unselected patients presenting to the Emergency Department with acute dyspnea. RESULTS: Uric acid at admission was higher in patients with acute decompensated heart failure (51% of the cohort) as compared with patients with noncardiac causes of dyspnea (median, 447 micromol/L vs 340 micromol/L, P <.001). The area under the receiver operating characteristic curve for the accuracy to detect acute decompensated heart failure was inferior for uric acid (0.70) than for B-type natriuretic peptide (area under the receiver operating characteristic curve 0.91, P <.001). Patients in the highest uric acid tertile more often required admission to the hospital (92% vs 74% in the first tertile, P <.001) and had higher in-hospital mortality (13% vs 4% in the first tertile, P <.001). Cumulative 24-month mortality rates were 28% in the first, 31% in the second, and 50% in the third tertile (P <.001). After adjustment in multivariable Cox proportional hazard analysis, uric acid predicted 24-month mortality independently of B-type natriuretic peptide (P=.003). CONCLUSIONS: Our study first shows that uric acid, measured at Emergency Department admission or hospital discharge, is a powerful predictor of long-term outcome in dyspneic patients.

Circ Res. 2009 Oct 23; 105(9): 830-41
Lu Z, Scott I, Webster BR, Sack MN

There is emerging recognition of a novel fuel and redox sensing regulatory program that controls cellular adaptation via nonhistone protein lysine residue acetyl posttranslation modifications. This program functions in tissues with high energy demand and oxidative capacity and is highly enriched in the heart. Deacetylation is regulated by NAD(+)-dependent activation of the sirtuin family of proteins, whereas acetyltransferase modifications are controlled by less clearly delineated acetyltransferases. Subcellular localization specific protein targets of lysine-acetyl modification have been identified in the nucleus, cytoplasm, and mitochondria. Despite distinct subcellular localizations, these modifications appear, in large part, to modify mitochondrial properties including respiration, energy production, apoptosis, and antioxidant defenses. These mitochondrial regulatory programs are important in cardiovascular biology, although how protein acetyl modifications effects cardiovascular pathophysiology has not been extensively explored. This review will introduce the role of nonhistone protein lysine residue acetyl modifications, discuss their regulation and biochemistry and present the direct and indirect data implicating their involvement in the heart and vasculature.

Lakartidningen. 2009 Sep 16-22; 106(38): 2374-5
Lindh J

Dtsch Med Wochenschr. 2009 Oct; 134(44): 2228
Henes J, Horger M, Kanz L, Kötter I

HISTORY AND ADMISSION FINDINGS: A 56-year-old woman presented with progressive dyspnea and polyneuropathia. Medical history revealed a bronchial asthma and hypertension. She was in a reduced general condition and had to be admitted to the intensive care unit for mechanical ventilation the same day. INVESTIGATIONS: The computed tomography of the chest revealed distinct pulmonary infiltrates. Laboratory findings showed significantly elevated inflammatory markers as well as an eosinophilia in the differential blood count and the bronchial lavage. Diagnostics for infections were all negative as were antinuclear and anti-neutrophil cytoplasmatic antibodies (ANCAs). DIAGNOSIS, TREATMENT AND COURSE: An ANCA negative Churg Strauss Syndrome (CSS) was diagnosed in accordance with extravascular and blood eosinophilia, pulmonary infiltrates and the neurological symptoms. Aggressive therapy with high dose glucocorticosteroids and cyclophosphamide (CYC) pulses was initiated. The patient improved rapidly and was extubated 6 days after the initiation of treatment. After 6 cycles of CYC with 750 mg/m2 and a maintenance treatment with azathioprine and 5mg prednisolone the patient is still in complete remission 2,5 years after the diagnosis. CONCLUSION: The CSS belongs to the ANCA-associated vasculitides. The patient described here presented with all the characteristic organ involvements of CSS and a fulminate worsening. The fast diagnosis and aggressive therapy which was started only hours after admission to the intensive care unit induced a long lasting remission.

Am J Epidemiol. 2009 Nov 15; 170(10): 1207-21
Taioli E, Garza MA, Ahn YO, Bishop DT, Bost J, Budai B, Chen K, Gemignani F, Keku T, Lima CS, Le Marchand L, Matsuo K, Moreno V, Plaschke J, Pufulete M, Thomas SB, Toffoli G, Wolf CR, Moore CG, Little J

Worldwide, over 1 million cases of colorectal cancer (CRC) were reported in 2002, with a 50% mortality rate, making CRC the second most common cancer in adults. Certain racial/ethnic populations continue to experience a disproportionate burden of CRC. A common polymorphism in the 5,10-methylenetetrahydrofolate reductase (MTHFR) gene has been associated with a lower risk of CRC. The authors performed both a meta-analysis (29 studies; 11,936 cases, 18,714 controls) and a pooled analysis (14 studies; 5,068 cases, 7,876 controls) of the C677T MTHFR polymorphism and CRC, with stratification by racial/ethnic population and behavioral risk factors. There were few studies on different racial/ethnic populations. The overall meta-analysis odds ratio for CRC for persons with the TT genotype was 0.83 (95% confidence interval (CI): 0.77, 0.90). An inverse association was observed in whites (odds ratio = 0.83, 95% CI: 0.74, 0.94) and Asians (odds ratio = 0.80, 95% CI: 0.67, 0.96) but not in Latinos or blacks. Similar results were observed for Asians, Latinos, and blacks in the pooled analysis. The inverse association between the MTHFR 677TT polymorphism and CRC was not significantly modified by smoking status or body mass index; however, it was present in regular alcohol users only. The MTHFR 677TT polymorphism seems to be associated with a reduced risk of CRC, but this may not hold true for all populations.

metabolism. 2009 Oct 19;
Ka T, Inokuchi T, Tamada D, Suda M, Tsutsumi Z, Okuda C, Yamamoto A, Takahashi S, Moriwaki Y, Yamamoto T

To investigate whether the concentration of uridine in plasma is related to the urinary excretion of urea, 45 healthy male subjects with normouricemia and normal blood pressure were studied after providing informed consent. Immediately after collection of 24-hour urine, blood samples were drawn after an overnight fast except for water. The contents of ingested foods during the 24-hour urine collection period were described by the subjects and analyzed by a dietician. Simple regression analysis showed that plasma uridine was correlated with the urinary excretions of urea (R = 0.41, P < .01), uric acid (R = 0.36, P < .05), and uridine (R = 0.30, P < .05), as well as uric acid clearance (R = 0.35, P < .05) and Purine intake (R = 0.30, P < .05). In contrast, multiple regression analysis showed a positive relationship only between plasma uridine and urinary excretion of urea. These results suggest that an increase in de novo pyrimidine synthesis leads to an increased concentration of uridine in plasma via nitrogen catabolism in healthy subjects with normouricemia and normal blood pressure.

Ann N Y Acad Sci. 2009 Oct; 1177: 89-100
Evans AM, Hardie DG, Peers C, Wyatt CN, Viollet B, Kumar P, Dallas ML, Ross F, Ikematsu N, Jordan HL, Barr BL, Rafferty JN, Ogunbayo O

Vital homeostatic mechanisms monitor O2 supply and adjust respiratory and circulatory function to meet demand. The pulmonary arteries and carotid bodies are key systems in this respect. Hypoxic pulmonary vasoconstriction (HPV) aids ventilation-perfusion matching in the lung by diverting blood flow from areas with an O2 deficit to those rich in O2, while a fall in arterial pO2 increases sensory afferent discharge from the carotid body to elicit corrective changes in breathing patterns. We discuss here the new concept that hypoxia, by inhibiting oxidative phosphorylation, activates AMP-activated protein kinase (AMPK) leading to consequent phosphorylation of target proteins, such as ion channels, which initiate pulmonary artery constriction and carotid body activation. Consistent with this view, AMPK knockout mice exhibit an impaired ventilatory response to hypoxia. Thus, AMPK may be sufficient and necessary for hypoxia-response coupling and may regulate O2 and thereby energy (ATP) supply at the whole body as well as the cellular level.

Ann N Y Acad Sci. 2009 Oct; 1177: 66-73
Weinberg F, Chandel NS

Historically, it has been assumed that glycolytic metabolism, not mitochondrial metabolism, is essential for tumor cell proliferation. However, most tumor cells have functional mitochondria, and recent studies suggest that the citric acid cycle (TCA) cycle intermediates are precursors for synthesis of nucleotides, lipids, and amino acids. Here we review the accumulating evidence that mitochondrial metabolism plays an essential role in tumor cell proliferation.

Anesth Analg. 2009 Nov; 109(5): 1486-92
Assad AR, Delou JM, Fonseca LM, Villela NR, Nascimento JH, Verçosa N, Lopes AG, Capella MA

BACKGROUND: Propofol (2,6-diisopropylphenol) has been shown to protect several organs, including the kidneys, from ischemia-reperfusion (I-R)-induced injury. Although propofol affects adenosine triphosphate-sensitive potassium (K(ATP)) channels in nonrenal tissues, it is still not clear by which mechanisms propofol protects renal cells from such damage. In this study, we investigated whether propofol induces renal preconditioning through renal K(ATP) channels. METHODS: A reversible ATP depletion (antimycin A) followed by restoration of substrate supply in LLC-PK1 cells was used as an in vitro model of renal I-R. Cell viability was assessed by dimethylthiazol-diphenyltetrazol bromide and trypan blue dye exclusion test assays. Apoptosis was evaluated by annexin V-fluorescein isothiocyanate staining by flow cytometry and immunofluorescence. Propofol treatments were initiated at various time intervals: 1 or 24 h before ischemia, only during ischemia, or only during reperfusion. To evaluate the mechanisms of propofol protection, specific K(ATP) channel inhibitors or activators were used in some experiments during propofol pretreatment. RESULTS: Propofol attenuated I-R injury on LLC-PK1 cells when present either 1 or 24 h before initiated I-R, and also during the recovery period, but not when added only during ischemia. Propofol pretreatment significantly protected LLC-PK1 from I-R-induced apoptosis. The protective effect of propofol was prevented by glibenclamide (a sarcolemmal ATP-dependent K(+) channel blocker) and decreased by 5-hydroxidecanoic acid (a mitochondrial ATP-dependent K(+) channel blocker), but it was not modified by diazoxide (a selective opener of ATP-sensitive K(+) channel). CONCLUSION: Propofol protected cells against apoptosis induced by I-R. This protection was probably due to a preconditioning effect of propofol and was, at least in part, mediated by K(ATP) channels.

Biochemistry. 2009 Nov 17; 48(45): 10679-81
Aregger R, Klostermeier D

DEAD box helicases unwind RNA duplexes at the expense of ATP hydrolysis. Recently, unwinding has been demonstrated in the absence of ATP hydrolysis. Herein, we show that ADP.BeF(x) supports RNA unwinding by YxiN, a DEAD box helicase that specifically recognizes a hairpin in 23S rRNA. ADP.AlF(x) and ADP.MgF(x) do not promote RNA unwinding, but all ATP analogues induce a closed conformation of the helicase core as required for RNA unwinding. Our results show that the interdomain cleft in the helicase core closes upon ATP binding at the beginning of the cycle. Reopening occurs after ATP hydrolysis, most likely coupled to phosphate release.