Adenosine N1-oxide Research Articles

Update on monkeypox virus infection: Focusing current treatment and prevention approaches.

While the world is still facing the global pandemic COVID-19, another zoonosis monkeypox (Mpox) has emerged posing a great threat to society. Insight into the pathogenesis, symptoms, and management strategies will aid in the development of potent therapeutics for the treatment of monkeypox virus infection. To get insight into the current treatment and prevention strategies will aid in effectively coping with the disease. For obtaining information regarding the ongoing treatment and prevention strategies and the drugs under pipeline, we referred to Google Scholar, Pub Med, Pub Chem, and WHO official site. There are a few drugs that came out to be effective for the treatment of Mpox. Tecovirimat acts by inhibiting viral replication and viral wrapping. Another drug is cidofovir, which hinders the activity of viral DNA polymerase but has the drawback of nephrotoxicity. To overcome this, a conjugate of cidofovir is being used-known as brincidofovir-which has a similar mechanism as cidofovir but lesser toxicity. Ribavirin acts via inhibiting inosine monophosphate dehydrogenase (IMPDPH) thus disrupting viral translation. It also interferes with helicase activity. Tiazofurin, Adenosine N1 oxide, and HPMPA have shown efficacy in in-vitro studies by inhibiting IMPDH, DNA polymerase, and viral mRNA translation respectively. In-silico studies have proven the effect of nilotinib, simeprevir, and dihydroergotamine for Mpox treatment. They have shown binding affinity for proteins required for the growth and release of MPXV. Vaccines have also been employed for the prevention of Mpox, which includes JYNNEOS, ACAM2000, and VIGIV. This review highlights the pathogenesis of the virus, disease manifestations, drugs, and vaccines that are being used and those under pipeline for the treatment and prevention of Mpox.

Effects of adenosine N1-Oxide and pioglitazone on inflammatory and antioxidant state in sepsis caused by experimental cecal puncture in rat.

Sepsis is an acute condition caused by the systemic inflammatory response syndrome to an infection. There are very few drugs that could improve the severe conditions in patients with sepsis. Hence, it is important to consider different treatment options. In this survey, we studied the effect of adenosine N1-oxide (ANO) and pioglitazone on rats with cecal ligation and perforation (CLP). They were randomly divided to four groups (n = 10) including Group A: as control group receiving normal saline, Group B: the rats with CLP as surgical control group, Group C: the rats receiving ANO, and Group D: the rats receiving pioglitazone. Interleukin (IL) -6, IL-1β, tumor necrosis factor alpha (TNF-α), nitric-oxide (NO) in serum blood and superoxide dismutase (SOD), catalase (CAT) malondialdehyde, (MDA) and myeloperoxidase (MPO) in liver and spleen homogenates were measured. The amount of antioxidant enzymes in the spleen and liver, and finally cell viability and rats' survival were investigated. The measurement of blood serum nitric-oxide and survival of all groups of rats were also performed. The results indicated that both drugs could cause a decrease in IL-1β, IL-6, TNF-α and NO in rat blood serum and MDA and MPO in the liver and spleen homogenates, however, a significant increase in SOD and CAT in the liver and spleen homogenates in rats that received ANO and pioglitazone was observed compared to rats with CLP group. Cell viability and rats' survival were significantly improved in rats that received ANO and pioglitazone compared to rats with CLP group. Adenosine N1-oxide showed stronger and more effective effects.

Effects of Adenosine N1-Oxide and Pioglitazone on Inflammatory and Antioxidant State in Sepsis Caused by Experimental Cecal Puncture in Rat

Effects of Adenosine N1-Oxide and Pioglitazone on Inflammatory and Antioxidant State in Sepsis Caused by Experimental Cecal Puncture in Rat

Adenosine N1-Oxide Exerts Anti-inflammatory Effects through the PI3K/Akt/GSK-3β Signaling Pathway and Promotes Osteogenic and Adipocyte Differentiation.

Previously, we reported that adenosine N1-oxide (ANO), which is found in royal jelly, inhibited the secretion of inflammatory mediators by activated macrophages and reduced lethality in lipopolysaccharide (LPS)-induced endotoxin shock. Here, we examined the regulatory mechanisms of ANO on the release of pro-inflammatory cytokines, with a focus on the signaling pathways activated by toll-like receptor (TLR)4 in response to LPS. ANO inhibited both tumor necrosis factor (TNF)-α and interleukin (IL)-6 secretion from LPS-stimulated RAW264.7 cells without affecting cell proliferation. In this response, phosphorylation of mitogen-activated protein kinase (MAPK) family members (extracellular signal-regulated kinase (ERK)1/2, p38 and SAPK/c-Jun N-terminal kinase (JNK)) and nuclear factor-κB (NF-κB) p65 was not affected by treatment with ANO. In contrast, phosphorylation of Akt (Ser473) and its downstream molecule glycogen synthase kinase-3β (GSK-3β) (Ser9) was up-regulated by ANO, suggesting that ANO stimulated GSK-3β phosphorylation via phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway. The phosphorylation of GSK-3β on Ser9 has been shown to negatively regulate the LPS-induced inflammatory response. Activation of PI3K/Akt signaling pathway has also been implicated in differentiation of mesenchymal stem cells into osteoblasts and adipocytes. As expected, ANO induced alkaline phosphatase activity and promoted calcium deposition in a mouse pre-osteoblastic MC3T3-E1 cell line. The ANO-induced differentiation into osteoblasts was abrogated by coincubation with Wortmannin. Furthermore, ANO promoted insulin/dexamethasone-induced differentiation of mouse 3T3-L1 preadipocytes into adipocytes at much lower concentrations than adenosine. The protective roles of PI3K/Akt/GSK-3β signaling pathway in inflammatory disorders have been well documented. Our data suggest that ANO may serve as a potential candidate for the treatment of inflammatory disorders. Promotion of osteogenic and adipocyte differentiation further suggests its application for regenerative medicine.

Orf virus inhibits interferon stimulated gene expression and modulates the JAK/STAT signalling pathway

Interferons (IFNs) play a critical role as a first line of defence against viral infection. Activation of the Janus kinase/signal transducer and activation of transcription (JAK/STAT) pathway by IFNs leads to the production of IFN stimulated genes (ISGs) that block viral replication. The Parapoxvirus, Orf virus (ORFV) induces acute pustular skin lesions of sheep and goats and is transmissible to man. The virus replicates in keratinocytes that are the immune sentinels of skin. We investigated whether or not ORFV could block the expression of ISGs. The human gene GBP1 is stimulated exclusively by type II IFN while MxA is stimulated exclusively in response to type I IFNs. We found that GBP1 and MxA were strongly inhibited in ORFV infected HeLa cells stimulated with IFN-γ or IFN-α respectively. Furthermore we showed that ORFV inhibition of ISG expression was not affected by cells pretreated with adenosine N1-oxide (ANO), a molecule that inhibits poxvirus mRNA translation. This suggested that new viral gene synthesis was not required and that a virion structural protein was involved. We next investigated whether ORFV infection affected STAT1 phosphorylation in IFN-γ or IFN-α treated HeLa cells. We found that ORFV reduced the levels of phosphorylated STAT1 in a dose-dependent manner and was specific for Tyr701 but not Ser727. Treatment of cells with sodium vanadate suggested that a tyrosine phosphatase was responsible for dephosphorylating STAT1-p. ORFV encodes a factor, ORFV057, with homology to the vaccinia virus structural protein VH1 that impairs the JAK/STAT pathway by dephosphorylating STAT1. Our findings show that ORFV has the capability to block ISG expression and modulate the JAK/STAT signalling pathway.

Anti-inflammatory effects of adenosine N1-oxide

BackgroundAdenosine is a potent endogenous anti-inflammatory and immunoregulatory molecule. Despite its promise, adenosine’s extremely short half-life in blood limits its clinical application. Here, we examined adenosine N1-oxide (ANO), which is found in royal jelly. ANO is an oxidized product of adenosine at the N1 position of the adenine base moiety. We found that it is refractory to adenosine deaminase-mediated conversion to inosine. We further examined the anti-inflammatory activities of ANO in vitro and in vivo.MethodsThe effect of ANO on pro-inflammatory cytokine secretion was examined in mouse peritoneal macrophages and the human monocytic cell line THP-1, and compared with that of adenosine, synthetic adenosine receptor (AR)-selective agonists and dipotassium glycyrrhizate (GK2). The anti-inflammatory activity of ANO in vivo was examined in an LPS-induced endotoxin shock model in mice.ResultsANO inhibited secretion of inflammatory mediators at much lower concentrations than adenosine and GK2 when used with peritoneal macrophages and THP-1 cells that were stimulated by LPS plus IFN-γ. The potent anti-inflammatory activity of ANO could not be solely accounted for by its refractoriness to adenosine deaminase. ANO was superior to the synthetic A1 AR-selective agonist, 2-chloro-N6-cyclopentyladenosine (CCPA), A2A AR-selective agonist, 2-[p-(2-carboxyethyl)phenethylamino]-5’-N-ethylcarboxamideadenosine hydrochloride (CGS21680), and A3 AR-selective agonist, N6-(3-iodobenzyl)adenosine-5’-N-methyluronamide (IB-MECA), in suppressing the secretion of a broad spectrum of pro-inflammatory cytokines by peritoneal macrophages. The capacities of ANO to inhibit pro-inflammatory cytokine production by THP-1 cells were comparable with those of CCPA and IB-MECA. Reflecting its potent anti-inflammatory effects in vitro, intravenous administration of ANO significantly reduced lethality of LPS-induced endotoxin shock. A significant increase in survival rate was also observed by oral administration of ANO. Mechanistic analysis suggested that the up-regulation of the anti-inflammatory transcription factor c-Fos was, at least in part, involved in the ANO-induced suppression of pro-inflammatory cytokine secretion.ConclusionsOur data suggest that ANO, a naturally occurring molecule that is structurally close to adenosine but is functionally more potent, presents potential strategies for the treatment of inflammatory disorders.

Vaccinia virus infection attenuates innate immune responses and antigen presentation by epidermal dendritic cells.

Langerhans cells (LCs) are antigen-presenting cells in the skin that play sentinel roles in host immune defense by secreting proinflammatory molecules and activating T cells. Here we studied the interaction of vaccinia virus with XS52 cells, a murine epidermis-derived dendritic cell line that serves as a surrogate model for LCs. We found that vaccinia virus productively infects XS52 cells, yet this infection displays an atypical response to anti-poxvirus agents. Whereas adenosine N1-oxide blocked virus production and viral protein synthesis during a synchronous infection, cytosine arabinoside had no effect at concentrations sufficient to prevent virus replication in BSC40 monkey kidney cells. Vaccinia virus infection of XS52 cells not only failed to elicit the production of various cytokines, including tumor necrosis factor alpha (TNF-alpha), interleukin-1beta (IL-1beta), IL-6, IL-10, IL-12 p40, alpha interferon (IFN-alpha), and IFN-gamma, it actively inhibited the production of proinflammatory cytokines TNF-alpha and IL-6 by XS52 cells in response to exogenous lipopolysaccharide (LPS) or poly(I:C). Infection with a vaccinia virus mutant lacking the E3L gene resulted in TNF-alpha secretion in the absence of applied stimuli. Infection of XS52 cells or BSC40 cells with the DeltaE3L virus, but not wild-type vaccinia virus, triggered proteolytic decay of IkappaBalpha. These results suggest a novel role for the E3L protein as an antagonist of the NF-kappaB signaling pathway. DeltaE3L-infected XS52 cells secreted higher levels of TNF-alpha and IL-6 in response to LPS and poly(I:C) than did cells infected with the wild-type virus. XS52 cells were productively infected by a vaccinia virus mutant lacking the K1L gene. DeltaK1L-infected cells secreted higher levels of TNF-alpha and IL-6 in response to LPS than wild-type virus-infected cells. Vaccinia virus infection of primary LCs harvested from mouse epidermis was nonpermissive, although a viral reporter protein was expressed in the infected LCs. Vaccinia virus infection of primary LCs strongly inhibited their capacity for antigen-specific activation of T cells. Our results highlight suppression of the skin immune response as a feature of orthopoxvirus infection.

Adenosine N1-Oxide Analogues as Inhibitors of Orthopox Virus Replication

Several new types of adenosineN1-oxide (ANO) derivatives includingN1-alkoxy andN6-alkyl as well as the analogues with a trihydroxycyclopentane ring in place of the ribose residue were synthesized and their antiviral properties were evaluated in Vero and LLC-MK2 cell cultures infected with vaccinia, mousepox, monkeypox, cowpox, and different isolates of smallpox viruses. The antiviral activity of ANO and its derivatives significantly depended on the virus type and cell cultures. Mousepox and monkeypox viruses were the most sensitive to these compounds, while vaccinia and cowpox viruses were inhibited at the concentrations 1-1.5 orders of magnitude higher. The toxicity of the synthesized compounds was much lower than that of ANO. Modifications of the ANON6-position did not offer any advantages over the parent compound. The synthesizedN1-oxide derivatives of noraristeromycin retained the activity comparable with noraristeromycin and displayed a decreased toxicity. No direct correlation between antiviral activity and stability of the compounds was found.

Potential antiviral therapeutics for smallpox, monkeypox and other orthopoxvirus infections

We assessed the activities of 24 different antiviral compounds against smallpox (two strains of variola major and one of variola minor), monkeypox, vaccinia and cowpox viruses by a neutral red uptake assay. To establish assay parameters, we examined viral replication and its inhibition at various times postinfection and at several multiplicities of infection. Drugs were selected to target a range of functions involved in viral replication. Eight compounds (cidofovir, cyclic HPMPC (cHPMPC), HPMPA, ribavirin, tiazofurin, carbocyclic 3-deazaadenosine, 3-deazaneplanocin A and DFBA (1-(2,4-difluorobenzyloxy)adenosine perchlorate)—a derivative of adenosine N1-oxide) inhibited the replication of all three variola strains and the other orthopoxviruses at drug concentrations within a pharmacologically achievable range. Two others (methisazone and bis-POM-PMEA) showed a lesser degree of antiviral effect, while the remainder were inactive. To examine possible naturally occurring drug resistance among a large number of variola isolates obtained from different geographical regions and at different times, we examined the sensitivity of 35 different strains of variola as well as other orthopoxviruses to a subset of three of the most active compounds: cidofovir, cHPMPC, and ribavirin. Preliminary data indicate that nearly all isolates appear to have similar drug sensitivities. These findings are currently being verified and expanded.

Re-design of Rhodobacter sphaeroides Dimethyl Sulfoxide Reductase: ENHANCEMENT OF ADENOSINEN1-OXIDE REDUCTASE ACTIVITY

The periplasmic DMSO reductase from Rhodobacter sphaeroides f. sp. denitrificans has been expressed in Escherichia coli BL21(DE3) cells in its mature form and with the R. sphaeroides or E. coli N-terminal signal sequence. Whereas the R. sphaeroides signal sequence prevents formation of active enzyme, addition of a 6x His-tag at the N terminus of the mature peptide maximizes production of active enzyme and allows for affinity purification. The recombinant protein contains 1.7-1.9 guanines and greater than 0.7 molybdenum atoms per molecule and has a DMSO reductase activity of 3.4-3.7 units/nmol molybdenum, compared with 3.7 units/nmol molybdenum for enzyme purified from R. sphaeroides. The recombinant enzyme differs from the native enzyme in its color and spectrum but is indistinguishable from the native protein after redox cycling with reduced methyl viologen and Me2SO. Substitution of Cys for the molybdenum-ligating Ser-147 produced a protein with DMSO reductase activity of 1.4-1.5 units/nmol molybdenum. The mutant protein differs from wild type in its color and absorption spectrum in both the oxidized and reduced states. This substitution leads to losses of 61-99% of activity toward five substrates, but the adenosine N1-oxide reductase activity increases by over 400%.

Polyclonal antibodies to adenine N1-oxide: characterization and use for the measurement of DNA damage.

Adenine N1-oxide is a DNA lesion whose formation involves the specific oxidation of the adenine base by hydrogen peroxide under nonradical conditions. The damage may be measured using a HPLC/32P-postlabeling method, which however cannot be used for routine analysis. We propose herein as an alternative an immunological assay which allows a rapid evaluation of the level of adenine N1-oxide in DNA exposed to oxidative stress. Two polyclonal antibodies were raised using two different strategies for the coupling of the hapten to the protein. The first approach is based on the universal method of Erlanger and Beiser, whereas the preparation of the second antigen involves the conjugation of a morpholino derivative of adenosine N1-oxide to the carrier protein. The affinity and the specificity of those antibodies were determined by competitive enzyme-linked immunosorbent assay. The antibody obtained by the traditional method shows some cross-reactivity with normal nucleotides, whereas for the other antiserum, the selectivity was found to be higher. Therefore, this polyclonal antibody was used to quantify the level of adenine N1-oxide in calf thymus DNA oxidized either by m-chloroperbenzoic acid or by hydrogen peroxide. The detection limit of the assay is four residues of adenine N1-oxide per 10(6) normal bases. The level of adenine N1-oxide in nonmodified DNA was lower than the detection limit of the assay, whereas in mCPB- and H2O2-modified DNA, it could be up to 14 and 0.7 adenine N1-oxide residues per 10(4) normal bases, respectively.

Synthesis and Antiviral Evaluation of Analogs of Adenosine-N 1-Oxide and 1-(Benzyloxy)Adenosine

The activity of a series of compounds related to adenosine-N 1-oxide (1) and 1-(benzyloxy)adenosine (42) against vaccinia virus has been determined both in vitro and in a vaccinia mouse tailpox model. Significant activities have been found both in vitro and in vivo for a number of the synthetic compounds.

Adenosine N1-oxide inhibits vaccinia virus replication by blocking translation of viral early mRNAs.

Adenosine N1-oxide (ANO) is a potent and highly selective inhibitor of vaccinia virus replication. We examined the impact of ANO on vaccinia virus macromolecular synthesis during synchronous infection of BSC40 cells. Viral DNA replication and viral late protein synthesis were blocked completely by ANO, effects that were attributable to a defect in the expression of viral early genes. Vaccinia virus early proteins were not synthesized in the presence of ANO, even though vaccinia virus early mRNAs were produced. Cellular protein synthesis was unaffected by ANO, and virus infection in the presence of the drug did not elicit the normal shutoff of host protein synthesis. Adenosine N1-oxide triphosphate (ANO-TP), the predominant metabolite of the drug in vivo, could substitute for ATP in RNA synthesis by purified vaccinia virus RNA polymerase. ANO-TP could support early transcription by purified virions if dATP was provided as an energy source. ANO-TP did not inhibit early transcription in the presence of ATP. These findings suggest a novel antiviral mechanism whereby incorporation of a modified nucleotide into viral mRNAs might selectively block viral gene expression at the level of translation. We believe that ANO merits consideration as an antipoxvirus drug for topical treatment of molluscum contagiosum in humans.

5-Aminoimidazole-4-carboxamide ribotide transformylase-IMP cyclohydrolase from human CCRF-CEM leukemia cells: purification, pH dependence, and inhibitors.

The bifunctional enzyme 5-aminoimidazole-4-carboxamide ribotide (AICAR) transformylase-IMP cyclohydrolase has been purified 780-fold to apparent homogeneity from human CCRF-CEM leukemia cells, completed with chromatography on Affi-Gel Blue followed by AICAR-Sepharose 4B. Using a sensitive radioassay, IMP cyclohydrolase has a Ks value for 5-formamidoimidazole-4-carboxamide ribotide (FAICAR) at pH 7.4 of 0.87 +/- 0.11 microM. The following purine nucleotide derivatives were potent competitive inhibitors of IMP cyclohydrolase: 2-mercaptoinosine 5'-monophosphate (Ki = 0.094 +/- 0.024 microM), xanthosine 5'-monophosphate (Ki = 0.12 +/- 0.01 microM), 2-fluoroadenine arabinoside 5'-monophosphate (Ki = 0.16 +/- 0.02 microM), 6-mercaptopurine riboside 5'-monophosphate (Ki = 0.20 +/- 0.02 microM), adenosine N1-oxide 5'-monophosphate (Ki = 0.28 +/- 0.03 microM), and N6-(carboxymethyl)adenosine 5'-monophosphate (Ki = 1.7 +/- 0.42 microM). The pH dependencies of Vmax and Vmax/Ks values for IMP cyclohydrolase are consistent with a single ionizable amino acid residue (pKa = 7.57 +/- 0.09) of the enzyme which must be unprotonated for catalysis to occur and a residue (pKa = 7.57 +/- 0.14) which must be unprotonated for FAICAR to bind. The pKa values of 5.81 +/- 0.03 and 9.41 +/- 0.04 determined for FAICAR indicate that ionization of the substrate does not contribute significantly to the pH effects observed. Chemical modification of IMP cyclohydrolase provides evidence for arginine and cysteine residues at the active site, and roles for these residues in the mechanism of catalysis are proposed.

Hydroxylating activity of a water-soluble manganese porphyrin associated with potassium hydrogen persulfate: Formation of 8-hydroxyadenosine-5′-mono-phosphate from AMP.

The association of potassium monopersulfate, KHSO 5, with a water-soluble manganese porphyrin complex has been recently reported as being a very efficient system for the oxidative cleavage of DNA (Fouquet et al., J. Chem. Soc., Chem. Commun., 1987, 1169); similar results are observed with RNA. As puzzle piece of the mechanism of this oxidative degradation of nucleic acids, we report in the present communication the identification of 8-hydroxyadenosine-5′-monophosphate as oxidation product of adenosine-5′-monophosphate (AMP) by KHSO 5/[Mn(Mepy) 4P](OAc) 5. In the absence of manganese catalyst, the only detectable compound is the adenosine-N 1-oxide- 5′-monophosphate.

Occurrence of S-adenosylhomocysteine hydrolase in prokaryote cells. Characterization of the enzyme from Alcaligenes faecalis and role of the enzyme in the activated methyl cycle.

The occurrence of S-adenosylhomocysteine hydrolase (EC 3.3.1.1) was found in a variety of prokaryotes. These prokaryotes did not exhibit any activities of S-adenosylhomocysteine nucleosidase (EC 3.2.2.9) and S-ribosyl-homocysteine hydrolase (EC 3.3.1.3), which had been the generally accepted prokaryote enzymes for the regeneration of free homocysteine from S-adenosylhomocysteine in the activated methyl cycle. In these prokaryotes S-adenosylhomocysteine hydrolase was suggested to be the only enzyme functioning for the regeneration of free homocysteine by enzymological and immunochemical studies. S-Adenosylhomocysteine hydrolase was purified and crystallized from cells of a prokaryote, Alcaligenes faecalis. The purified enzyme was found to be homogeneous on ultracentrifugation and gel electrophoresis. Its relative molecular mass is approximately 280 000 and it is composed of six identical subunits with a Mr of approximately 48 000. The NH2-terminal and COOH-terminal amino acids are lysine and tyrosine respectively. The enzyme contains 6 mol NAD/mol. Some nucleosides, such as formycin A, nebularine, adenosine N1-oxide and so on, are able to substitute for adenosine yielding the corresponding S-nucleosidylhomocysteine congeners. Modification of the 5'-hydroxymethyl group in adenosine leads to the most potent inhibition of the thioether formation of homocysteine with adenosine. The enzyme from A. faecalis has some immunological similarities to other prokaryote S-adenosylhomocysteine hydrolases, but is different from the enzymes of animal sources.

Adenosine analogues as substrates and inhibitors of S-adenosylhomocysteine hydrolase.

In the reaction adenosine + L-homocysteine = S-adenosyl-L-homocysteine, catalyzed by S-adenosylhomo-cysteine hydrolase from beef liver (EC 3.3.1.1), 11 nucleosides are able to substitute for adenosine to generate their corresponding S-nucleosidylhomocysteine congeners: 3-deaza-adenosine, 2-aza-3-deazaadenosine, nebularine (purine ribonucleoside), formycin, N6-methyladenosine, 8-azaadenosine, adenosine N1-oxide, pyrazomycin, 8-aminoadenosine, inosine, and the carbocyclic analogue of adenosine [(+/-)-aristeromycin]. S-Adenosylhomocysteine hydrolase from lupin seeds is able to utilize all of these nucleosides except inosine to synthesize analogues of S-adenosylhomocysteine. There is no correlation between the ability of these nucleotides to function as substrates and their inhibitory potencies, except in the case of 3-deazaadenosine. The carbocyclic analogue of adenosine is the most potent inhibitor of S-adenosylhomocysteine hydrolase with a Ki of 5 X 10(-9) M. When incubated with 3T3-L1 fibroblasts, the carbocyclic analogue of adenosine caused a 20-fold increase in the cellular concentration of S-adenosyl-homocysteine. The cellular generation of S-2-aza-3-deaza-adenosylhomocysteine was observed when 3T3-L1 fibroblasts were incubated with 2-aza-3-deazaadenosine.

Structure activity relations for inhibition of neurotransmission in rat vas deferens by adenosine

Adenosine inhibits the isometric contractions of the rat vas deferens in response to field stimulation in vitro by presynaptic inhibition of transmitter release. In the present study the structure activity relations for the inhibition of neurotramsmission in the rat vas deferens by adenosine were examined. Adenosine and adenosine-N 1-oxide were the most potent inhibitors studied. 6-Methylaminopurine riboside, 6-hydroxylaminopurine riboside, 5′-deoxyadenosine and 5′-nitroadenosine were slightly less potent inhibitors. The common structural requirements for activity include a primary or secondary amine function at C 6 of the purine ring with little tolerance for major steric changes or substitutions on the sugar moiety. None of the analogues studied prevented the presynaptic inhibitory action of adenosine.

Synthesis of 6-thioguanine and 2,6-diaminopurine nucleosides and nucleotides from adenine counterparts via a facile rearrangement in the base portion (Nucleosides and nucleotides. XIX.

A method of conversion of an adenine moiety to 6-thioguanine (and guanine) and 2, 6-diaminopurine moiety in the nucleoside and nucleotide levels were presented. The action of cyanogen bromide with adenosine N1-oxide afforded an 1, 2, 4-oxadiazolo (3, 2-f)-purine riboside (2a), which was in a pH dependent equilibrium with N6-cyanoadenosine N1-oxide (3a). Methylation followed by alkaline treatment of 3a resulted in a rearrangement leading to give 2-amino-N6-methoxyadenosine (5a). Catalytic hydrogenation of 5a gave 2, 6-diaminopurine riboside (6a). Sulfhydrolysis of 5a gave 6-thioguanosine (7a). By a similar reaction sequence 2'-deoxyadenosine was converted to 2'-deoxy-6-thioguanosine (7b) and 2, 6-diaminopurine 2'-deoxyriboside, respectively. Starting from the N1-oxides of adenosine 5'-phosphate (AMP), 2'-deoxyadenosine 5'-phosphate (dAMP) and 9-β-D-arabinofuranosyladenine 5'-phosphate (araAMP), the corresponding 6-thioguanine nucleotides were likewise prepared.

Participation of N1-oxide derivatives of adenine nucleotides in the phosphotransferase activity of liver mitochondria.

The modified adenine nucleotides ATP-NO, ADP-NO, and AMP-NO were tested as potential substrates and/or inhibitors of mitochondrial phosphotransferases. ADP-NO is not recognized by the translocase system located in the inner mitochondrial membrane; however, it is rapidly phosphorylated to ATP-NO in the outer compartment of mitochondria, by way of the nucleosidediphosphate kinase (EC 2.7.4.6) reaction, provided there is sufficient ATP in the mitochondria. AMP-NO is not phosphorylated by liver mitochondria to the corresponding nucleoside diphosphate; it cannot serve as substrate for adenylate kinase (EC 2.7.4.3). ATP-NO and ADP-NO, however, are substrates of this enzyme. The apparent equilibrium constant for the reaction, ADP-NO + ADP right harpoon over left harpoon ATP-NO + AMP, of 0.908 at pH 7.4 and 5 mM Mg(2+) is significantly higher than that of the reaction with natural nucleotides. Although adenosine N(1)-oxide is easily phosphorylated to AMP-NO by adenosine kinase [Schnebli et al. (1967) J. Biol. Chem. 242, 1997-2004], the formation of corresponding nucleoside triphosphate in vivo seems also to be limited by adenylate kinase; adenosine N(1)-oxide cannot replace adenosine in restoring the normal ATP level in ethionine-treated rats.