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Neurobiology of Disease Feb 2010A limited amount of functional recovery commonly occurs in the weeks and months after stroke, and a number of studies show that such recovery is associated with changes... (Review)
Review
A limited amount of functional recovery commonly occurs in the weeks and months after stroke, and a number of studies show that such recovery is associated with changes in the brain's functional organization. Measures that augment this reorganization in a safe and effective way may therefore help improve outcome in stroke patients. Here we review some of the evidence for functional and anatomical reorganization under normal physiological conditions, along with strategies that augment these processes and improve outcome after brain injury in animal models. These strategies include counteracting inhibitors of axon growth associated with myelin, activating neurons' intrinsic growth state, enhancing physiological activity, and having behavioral therapy. These approaches represent a marked departure from the recent focus on neuroprotection and may provide a more effective way to improve outcome after stroke.
Topics: Animals; Behavior Therapy; Brain; Disease Models, Animal; Growth Cones; Growth Inhibitors; Humans; Inosine; Nerve Growth Factors; Neuronal Plasticity; Recovery of Function; Stroke
PubMed: 19931616
DOI: 10.1016/j.nbd.2009.11.009 -
Pharmaceutical Biology Dec 2021The uric acid metabolism pathway is more similar in primates and humans than in rodents. However, there are no reports of using primates to establish animal models of...
CONTEXT
The uric acid metabolism pathway is more similar in primates and humans than in rodents. However, there are no reports of using primates to establish animal models of hyperuricaemia (HUA).
OBJECTIVES
To establish an animal model highly related to HUA in humans.
MATERIALS AND METHODS
Inosine (75, 100 and 200 mg/kg) was intraperitoneally administered to adult male rhesus monkeys ( = 5/group). Blood samples were collected over 8 h, and serum uric acid (SUA) level was determined using commercial assay kits. XO and PNP expression in the liver and URAT1, OAT4 and ABCG2 expression in the kidneys were examined by qPCR and Western blotting to assess the effects of inosine on purine and uric acid metabolism. The validity of the acute HUA model was assessed using ulodesine, allopurinol and febuxostat.
RESULTS
Inosine (200 mg/kg) effectively increased the SUA level in rhesus monkeys from 51.77 ± 14.48 at 0 h to 178.32 ± 14.47 μmol/L within 30 min and to peak levels (201.41 ± 42.73 μmol/L) at 1 h. PNP mRNA level was increased, whereas XO mRNA and protein levels in the liver were decreased by the inosine group compared with those in the control group. No changes in mRNA and protein levels of the renal uric acid transporter were observed. Ulodesine, allopurinol and febuxostat eliminated the inosine-induced elevation in SUA in tested monkeys.
CONCLUSIONS
An acute HUA animal model with high reproducibility was induced; it can be applied to evaluate new anti-HUA drugs and explore the disease pathogenesis.
Topics: Acute Disease; Allopurinol; Animals; Disease Models, Animal; Dose-Response Relationship, Drug; Febuxostat; Hyperuricemia; Imino Furanoses; Inosine; Macaca mulatta; Male; Pyrimidinones; Reproducibility of Results; Uric Acid
PubMed: 33715593
DOI: 10.1080/13880209.2020.1871373 -
Biosensors Jan 2021Hypoxanthine (hpx) is an important molecule for both biochemistry research and biomedical applications. It is involved in several biological processes associated to...
Hypoxanthine (hpx) is an important molecule for both biochemistry research and biomedical applications. It is involved in several biological processes associated to energy and purine metabolism and has been proposed as a biomarker for a variety of disease states. Consequently, the discovery and development of systems suitable for the detection of hypoxanthine is pretty appealing in this research field. Thus, we have obtained a stable diruthenium (III) compound in its dehydrated and hydrated forms with formula [{Ru(µ-Cl)(µ-hpx)}Cl] () and [{Ru(µ-Cl)(µ-hpx)}Cl]·2HO (), respectively. This purine-based diruthenium(III) system was prepared from two very different starting materials, namely, inosine and azathioprine, the latter being an immunosuppressive drug. Remarkably, it was observed that an unusual azathioprine hydrolysis occurs in the presence of ruthenium, thus generating hypoxanthine instead of the expected 6-mercaptopurine antimetabolite, so that the hpx molecule is linked to two ruthenium(III) ions. and were characterized through IR, SEM, powder and single-crystal X-ray Diffraction and Cyclic Voltammetry (CV). The electrochemical studies allowed us to detect the hpx molecule when coordinated to ruthenium in the reported compound. The grade of sensitivity, repeatability and stability reached by this diruthenium system make it potentially useful and could provide a first step to develop new sensor devices suitable to detect hypoxanthine.
Topics: Azathioprine; Hydrolysis; Hypoxanthine; Immunosuppressive Agents; Inosine; Limit of Detection; Microscopy, Electron, Scanning; Models, Molecular; Molecular Conformation; Purines; Ruthenium; X-Ray Diffraction
PubMed: 33440852
DOI: 10.3390/bios11010019 -
ACS Chemical Biology Feb 2024A-to-I editing catalyzed by adenosine deaminase acting on RNAs impacts numerous physiological and biochemical processes that are essential for cellular functions and is...
A-to-I editing catalyzed by adenosine deaminase acting on RNAs impacts numerous physiological and biochemical processes that are essential for cellular functions and is a big contributor to the infectivity of certain RNA viruses. The outcome of this deamination leads to changes in the eukaryotic transcriptome functionally resembling A-G transitions since inosine preferentially pairs with cytosine. Moreover, hyper-editing or multiple A to G transitions in clusters were detected in measles virus. Inosine modifications either directly on viral RNA or on cellular RNA can have antiviral or pro-viral repercussions. While many of the significant roles of inosine in cellular RNAs are well understood, the effects of hyper-editing of A to I on viral polymerase activity during RNA replication remain elusive. Moreover, biological strategies such as molecular cloning and RNA-seq for transcriptomic interrogation rely on RT-polymerase chain reaction with little to no emphasis placed on the first step, reverse transcription, which may reshape the sequencing results when hypermodification is present. In this study, we systematically explore the influence of inosine modification, varying the number and position of inosines, on decoding outcomes using three different reverse transcriptases (RTs) followed by standard Sanger sequencing. We find that inosine alone or in clusters can differentially affect the RT activity. To gain structural insights into the accommodation of inosine in the polymerase site of HIV-1 reverse transcriptase (HIV-1-RT) and how this structural context affects the base pairing rules for inosine, we performed molecular dynamics simulations of the HIV-1-RT. The simulations highlight the importance of the protein-nucleotide interaction as a critical factor in deciphering the base pairing behavior of inosine clusters. This effort sets the groundwork for decrypting the physiological significance of inosine and linking the fidelity of reverse transcriptase and the possible diverse transcription outcomes of cellular RNAs and/or viral RNAs where hyper-edited inosines are present in the transcripts.
Topics: Base Pairing; Reverse Transcription; RNA, Viral; Inosine; Adenosine Deaminase
PubMed: 38252964
DOI: 10.1021/acschembio.3c00555 -
PloS One 2020Inosine is ubiquitous and essential in many biological processes, including RNA-editing. In addition, oxidative stress on RNA has been a topic of increasing interest...
Inosine is ubiquitous and essential in many biological processes, including RNA-editing. In addition, oxidative stress on RNA has been a topic of increasing interest due, in part, to its potential role in the development/progression of disease. In this work we probed the ability of three reverse transcriptases (RTs) to catalyze the synthesis of cDNA in the presence of RNA templates containing inosine (I), 8-oxo-7,8-dihydroinosine (8oxo-I), guanosine (G), or 8-oxo-7,8-dihydroguanosine (8-oxoG), and explored the impact that these purine derivatives have as a function of position. To this end, we used 29-mers of RNA (as template) containing the modifications at position-18 and reverse transcribed DNA using 17-mers, 18-mers, or 19-mers (as primers). Generally reactivity of the viral RTs, AMV / HIV / MMLV, towards cDNA synthesis was similar for templates containing G or I as well as for those with 8-oxoG or 8-oxoI. Notable differences are: 1) the use of 18-mers of DNA (to explore cDNA synthesis past the lesion/modification) led to inhibition of DNA elongation in cases where a G:dA wobble pair was present, while the presence of I, 8-oxoI, or 8-oxoG led to full synthesis of the corresponding cDNA, with the latter two displaying a more efficient process; 2) HIV RT is more sensitive to modified base pairs in the vicinity of cDNA synthesis; and 3) the presence of a modification two positions away from transcription initiation has an adverse impact on the overall process. Steady-state kinetics were established using AMV RT to determine substrate specificities towards canonical dNTPs (N = G, C, T, A). Overall we found evidence that RNA templates containing inosine are likely to incorporate dC > dT > > dA, where reactivity in the presence of dA was found to be pH dependent (process abolished at pH 7.3); and that the absence of the C2-exocyclic amine, as displayed with templates containing 8-oxoI, leads to increased selectivity towards incorporation of dA over dC. The data will be useful in assessing the impact that the presence of inosine and/or oxidatively generated lesions have on viral processes and adds to previous reports where I codes exclusively like G. Similar results were obtained upon comparison of AMV and MMLV RTs.
Topics: Animals; Avian Myeloblastosis Virus; Base Sequence; DNA, Complementary; Guanosine; HIV Reverse Transcriptase; Humans; In Vitro Techniques; Inosine; Kinetics; Mice; Moloney murine leukemia virus; RNA, Viral; RNA-Directed DNA Polymerase; Templates, Genetic
PubMed: 32857764
DOI: 10.1371/journal.pone.0235102 -
Nature Neuroscience Nov 2013Adenosine-to-inosine (A-to-I) RNA editing, in which genomically encoded adenosine is changed to inosine in RNA, is catalyzed by adenosine deaminase acting on RNA (ADAR).... (Review)
Review
Adenosine-to-inosine (A-to-I) RNA editing, in which genomically encoded adenosine is changed to inosine in RNA, is catalyzed by adenosine deaminase acting on RNA (ADAR). This fine-tuning mechanism is critical during normal development and diseases, particularly in relation to brain functions. A-to-I RNA editing has also been hypothesized to be a driving force in human brain evolution. A large number of RNA editing sites have recently been identified, mostly as a result of the development of deep sequencing and bioinformatic analyses. Deciphering the functional consequences of RNA editing events is challenging, but emerging genome engineering approaches may expedite new discoveries. To understand how RNA editing is dynamically regulated, it is imperative to construct a spatiotemporal atlas at the species, tissue and cell levels. Future studies will need to identify the cis and trans regulatory factors that drive the selectivity and frequency of RNA editing. We anticipate that recent technological advancements will aid researchers in acquiring a much deeper understanding of the functions and regulation of RNA editing.
Topics: Adenosine; Animals; Brain; Computational Biology; Genomics; Humans; Inosine; Mutation; Nervous System Diseases; RNA; RNA Editing
PubMed: 24165678
DOI: 10.1038/nn.3539 -
Current Opinion in Genetics &... Feb 2018Adenosine-to-inosine (A-to-I) RNA editing is the most common type of post-transcriptional nucleotide modification in humans, which is catalyzed in ADAR enzymes. Recent... (Review)
Review
Adenosine-to-inosine (A-to-I) RNA editing is the most common type of post-transcriptional nucleotide modification in humans, which is catalyzed in ADAR enzymes. Recent genomic studies have revealed thousands of altered RNA editing events in various cancer tissues, leading to diverse functional consequences. A critical role of individual A-to-I RNA editing events in cancer has been reported. Here, we review the current state of our knowledge on key A-to-I RNA editing events in coding and non-coding regions for their roles in cancer development and discuss their potential clinical utility. A better understanding of A-to-I RNA editing and its oncogenic mechanisms may facilitate the development of novel cancer therapeutic strategies.
Topics: Adenosine; Inosine; MicroRNAs; Neoplasms; RNA Editing
PubMed: 29127844
DOI: 10.1016/j.gde.2017.10.009 -
The Plant Cell Jan 2023In nucleotide metabolism, nucleoside kinases recycle nucleosides into nucleotides-a process called nucleoside salvage. Nucleoside kinases for adenosine, uridine, and...
In nucleotide metabolism, nucleoside kinases recycle nucleosides into nucleotides-a process called nucleoside salvage. Nucleoside kinases for adenosine, uridine, and cytidine have been characterized from many organisms, but kinases for inosine and guanosine salvage are not yet known in eukaryotes and only a few such enzymes have been described from bacteria. Here we identified Arabidopsis thaliana PLASTID NUCLEOSIDE KINASE 1 (PNK1), an enzyme highly conserved in plants and green algae belonging to the Phosphofructokinase B family. We demonstrate that PNK1 from A. thaliana is located in plastids and catalyzes the phosphorylation of inosine, 5-aminoimidazole-4-carboxamide-1-β-d-ribose (AICA ribonucleoside), and uridine but not guanosine in vitro, and is involved in inosine salvage in vivo. PNK1 mutation leads to increased flux into purine nucleotide catabolism and, especially in the context of defective uridine degradation, to over-accumulation of uridine and UTP as well as growth depression. The data suggest that PNK1 is involved in feedback regulation of purine nucleotide biosynthesis and possibly also pyrimidine nucleotide biosynthesis. We additionally report that cold stress leads to accumulation of purine nucleotides, probably by inducing nucleotide biosynthesis, but that this adjustment of nucleotide homeostasis to environmental conditions is not controlled by PNK1.
Topics: Inosine; Nucleosides; Nucleotides; Purine Nucleotides; Uridine
PubMed: 36342213
DOI: 10.1093/plcell/koac320 -
Communications Biology Jun 2021Adenosine-to-inosine (A-to-I) RNA editing, catalyzed by ADAR enzymes, is an essential post-transcriptional modification. Although hundreds of thousands of RNA editing...
Adenosine-to-inosine (A-to-I) RNA editing, catalyzed by ADAR enzymes, is an essential post-transcriptional modification. Although hundreds of thousands of RNA editing sites have been reported in mammals, brain-wide analysis of the RNA editing in the mammalian brain remains rare. Here, a genome-wide RNA-editing investigation is performed in 119 samples, representing 30 anatomically defined subregions in the pig brain. We identify a total of 682,037 A-to-I RNA editing sites of which 97% are not identified before. Within the pig brain, cerebellum and olfactory bulb are regions with most edited transcripts. The editing level of sites residing in protein-coding regions are similar across brain regions, whereas region-distinct editing is observed in repetitive sequences. Highly edited conserved recoding events in pig and human brain are found in neurotransmitter receptors, demonstrating the evolutionary importance of RNA editing in neurotransmission functions. Although potential data biases caused by age, sex or health status are not considered, this study provides a rich resource to better understand the evolutionary importance of post-transcriptional RNA editing.
Topics: Adenosine; Animals; Brain; Female; Gene Expression Regulation; Inosine; Male; RNA Editing; Swine
PubMed: 34112917
DOI: 10.1038/s42003-021-02238-3 -
Proceedings of the National Academy of... Dec 2018The emergence of primordial RNA-based life would have required the abiotic synthesis of nucleotides, and their participation in nonenzymatic RNA replication. Although...
The emergence of primordial RNA-based life would have required the abiotic synthesis of nucleotides, and their participation in nonenzymatic RNA replication. Although considerable progress has been made toward potentially prebiotic syntheses of the pyrimidine nucleotides (C and U) and their 2-thio variants, efficient routes to the canonical purine nucleotides (A and G) remain elusive. Reported syntheses are low yielding and generate a large number of undesired side products. Recently, a potentially prebiotic pathway to 8-oxo-adenosine and 8-oxo-inosine has been demonstrated, raising the question of the suitability of the 8-oxo-purines as substrates for prebiotic RNA replication. Here we show that the 8-oxo-purine nucleotides are poor substrates for nonenzymatic RNA primer extension, both as activated monomers and when present in the template strand; their presence at the end of a primer also strongly reduces the rate and fidelity of primer extension. To provide a proper comparison with 8-oxo-inosine, we also examined primer extension reactions with inosine, and found that inosine exhibits surprisingly rapid and accurate nonenzymatic RNA copying. We propose that inosine, which can be derived from adenosine by deamination, could have acted as a surrogate for G in the earliest stages of the emergence of life.
Topics: Inosine; Models, Molecular; Nucleic Acid Conformation; Nucleotides; Origin of Life; Purine Nucleotides; Purines; RNA
PubMed: 30509978
DOI: 10.1073/pnas.1814367115