Determination of rat cerebrospinal fluid concentrations of adenosine, inosine, hypoxanthine, xanthine and uric acid by high performance liquid chromatography

Isocratic reverse-phase high performance liquid chromatography techniques were developed to resolve and quantitate the purine nucleosides adenosine (Ado) and inosine (Ino) and their metabolites hypoxanthine (Hyp), xanthine (Xan), and uric acid (UA) in the cerebrospinal fluid of the rat. The moving phase composition for resolving hypoxanthine, xanthine and uric acid was a 0.22 M, pH 5.8 phosphate buffer. The moving phase composition for resolving adenosine and inosine was a 0.22 M, pH 6.8 phosphate buffer, 7% methanol (v/v) and 2.5 mM tetrabutylammonium phosphate. The observed cerebrospinal fluid concentrations in the rat were: Ado = 35 +/- 9 nM (s.e.m.), Ino = 359 +/- 85 nM, Hyp = 243 +/- 77 nM, Xan = 1340 +/- 423 nM and UA = 6130 +/- 678 nM.     

Identification of a purine (P2) receptor linked to ion transport in a cultured renal (MDCK) epithelium.

1 Exogenous adenosine triphosphate (ATP) stimulates the short circuit current (SCC) in a cultured renal-derived epithelium (MDCK). Half-maximal stimulation is achieved at 1.91 X 10(-5) M ATP. 2 It is suggested that ATP interacts with a P2 purine receptor upon the basis of (a) agonist potency (ATP greater than adenosine diphosphate much greater than adenosine monophosphate, adenosine; ATP greater than uridine triphosphate greater than inosine triphosphate much greater than cytosine triphosphate, guanosine triphosphate); (b) the inhibition of the ATP response by quinidine (1 X 10(-3) M) but not by theophylline (1 X 10(-3) M). 3 Indomethacin (1 X 10(-5) M) inhibits the response of the cultured epithelium to ATP. 4 Prostaglandin E1 (PGE1) stimulates SCC but potentiates the effect of ATP on SCC. The divalent cationic ionophore A23187 (1 X 10(-6) M) transiently stimulates SCC itself and abolishes ATP-induced stimulation of the SCC.     

丁基苯酞对全脑缺血大鼠的纹状体细胞外液嘌呤类代谢物含量的影响

采用大鼠4动脉阻断的全脑缺血模型,用推挽式微灌流方法,用HPLC-UV检测缺血及重灌期纹状体灌流液中腺苷(Ade)、肌苷(Ino)、次黄嘌呤(Hyp)和黄嘌呤(Xan)的含量。结果表明,ip丁基苯酞20或40mg·kg^-1均能显著降低大鼠全脑缺血纹状体细胞外液Ade,Ino,Hyp和Xan的升高。但对假手术组动物则无影响。Hyp和Xan是产生氧自由基的底物。丁基苯酞这一抑制作用提示它对缺血性神经元的损伤有保护作用。     

Effects of antibiotic antitumor drugs on nucleotide levels in cultured tumor cells: an exploratory method to distinguish the mechanisms of antitumor drug action based on targeted metabolomics

Nucleotide pools in mammalian cells change due to the influence of antitumor drugs, which may help in evaluating the drug effect and understanding the mechanism of drug action. In this study, an ion-pair RP-HPLC method was used for a simple, sensitive and simultaneous determination of the levels of 12 nucleotides in mammalian cells treated with antibiotic antitumor drugs (daunorubicin, epirubicin and dactinomycin D). Through the use of this targeted metabolomics approach to find potential biomarkers, UTP and ATP were verified to be the most appropriate biomarkers. Moreover, a holistic statistical approach was put forward to develop a model which could distinguish 4 categories of drugs with different mechanisms of action. This model can be further validated by evaluating drugs with different mechanisms of action. This targeted metabolomics study may provide a novel approach to predict the mechanism of action of antitumor drugs.Abbreviations: ADP, adenosine diphosphate; AMP, adenosine monophosphate; ANOVA, analysis of variance; ATP, adenosine triphosphate; AUC, area under the curve; CDP, cytidine diphosphate; CTP, cytidine triphosphate; dATP, deoxyadenosine triphosphate; dCDP, deoxycytidine diphosphate; dCTP, deoxycytidine triphosphate; dGMP, deoxyribonucleic monophosphate; dGTP, deoxyguanosine triphosphate; DMEM, Dulbecco׳s modified eagle׳s cell culture media; DMSO, dimethyl sulfoxide; DNA, deoxyribonucleic acid; dUDP, deoxyuridine diphpsphate; dUTP, deoxyuridine triphosphate; EC, energy charge; EDTA, ethylene diamine tetra-acetic acid; FCS, fetal calf serum; GDP, guanosine diphosphate; GMP, guanosine monophosphate; GTP, guanosine triphosphate; HEPES, 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid; MTT, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide; PBS, phosphate buffered saline; PCA, principal component analysis; RNA, ribonucleic acid; ROC, receiver operating characteristic; RPMI-1640, Roswell Park Memorial Institute-1640; TBAHS, tetrabutylammonium hydrogen sulfate; TCA, trichloroacetic acid; UDP, uridine diphosphate; UTP, uridine triphosphateKEY WORDS: Nucleotides, Targeted metabolomics analysis, Tumor cells, Potential biomarkers, Mechanisms of antitumor drug action, Antibiotic anticancer drugs, Principal component analysis, Ion-pair HPLC     

Inhibition of inosinic acid dehydrogenase by 8-substituted purine nucleotides

A series of 8-substituted derivatives of adenosine monophosphate (AMP) and inosine monophosphate (IMP) were synthesized and examined for their ability to inhibit Escherichia coli IMP dehydrogenase. All compounds studied were competitive inhibitors in IMP-dependent competition studies and lacked substrate activity. In oxidized nicotinamide adenine dinucleotide dependent studies, 8-(p-NO2PhCH2S)-IMP was noncompetitive and 8-(p-NO2PhCH2S)-AMP showed mixed inhibition. Multiple regression analysis showed that for the series of 8-(para-substituted-benzylthio)-AMPs and -IMPs, the electron-withdrawing ability of the para substituent on the benzylthio moiety correlated best with log Ki of the analogues.     

Studies on chemical protectors against radiation. XXVIII. Protective effect of nucleic acid constitutional compounds on radiation damages induced by X-irradiation

The effects of various nucleic acid constitutional compounds, base, nucleoside and nucleotide on lethality and skin injury induced by soft X-irradiation were studied. The survival effect was determined by use of survival days after irradiation of lethal dose of 70 kVp, 2100R and the protective effect on skin injury was determined by use of degrees on skin injury after 30 kVp, 1100R soft X-irradiation. As a result of these studies, the survival effect was observed by single injection of inosine at 120, 60 and 5 min before irradiation and three times injection after irradiation. And the other nucleic acid constitutional compounds had no effect on survival. Protective effect of skin injury was observed by single injection of adenosine, guanosine, inosine, 5'-adenosine monophosphate (5'-AMP), 5'-guanosine monophosphate (5'-GMP) and 5'-inosine monophosphate (5'-IMP) before irradiation. Protective effect of skin injury by three time injection before irradiation were revealed in adenosine, inosine, 5'-AMP and 5'-IMP. For the investigation of superoxide anions and hydroxyl radicals scavenge activities, the relationship between radical scavenge activities and protective effect of radiation by using various nucleosides was not observed.     

Ribavirin, tiazofurin, and selenazofurin: mononucleotides and nicotinamide adenine dinucleotide analogues. Synthesis, structure, and interactions with IMP dehydrogenase

A series of dinucleotides, analogous to nicotinamide adenine dinucleotide but containing the five-membered base nucleosides tiazofurin (1a), selenazofurin (1b), ribavirin (2), and AICAR (3) in place of nicotinamide ribonucleoside, were prepared in greater than 50% yield by reacting the corresponding nucleotide imidazolidates (6a-d) with adenosine 5'-monophosphate (AMP). The symmetric dinucleotides of tiazofurin (TTD, 8e) and selenazofurin (SSD, 8f) were also prepared by a similar methodology. These dinucleotides were characterized by 1H NMR and fast atom bombardment MS and were evaluated for their inhibitory potency against a partially purified preparation of tumoral inosine monophosphate dehydrogenase (IMPD) from P388 cells. The order of potency found was SAD (8b) greater than TAD (8a) much greater than SSD (8f) congruent to TTD (8e) congruent to RAD (8c) much much greater than ZAD (8d). On kinetic analysis none of the dinucleotides produced competitive inhibition of IMPD with NAD as a variable substrate. In addition to their superior IMPD inhibitory activity, SAD and TAD appear to be the only dinucleotides, besides NAD, that are formed naturally by the NAD pyrophosphorylase from P388 lymphoblasts.     

Evidence for a mitochondrial impact of trimetazidine during cold ischemia and reperfusion

In organ transplantation, ischemia-reperfusion injury (IRI) has been implicated in delayed graft function (DGF) as well as in short- and long-term complications. Using an autotransplant pig kidney model, changes in renal function and morphology were determined after different periods of cold ischemia in kidneys preserved in the University of Wisconsin solution (UW), high-Na(+) version of UW (HEH) or Celsior (CEL) a newly developed high-Na(+) solution, with or without trimetazidine (TMZ). Kidney function was better preserved in CEL, UW and particularly HEH in combination with TMZ, particularly after 48 and 72 h. Mitochondria integrity was improved in TMZ-preserved groups. This study indicates that TMZ is efficiently protective against IRI even after prolonged preservation and in different preservation solutions.     

Aberrant cyclization affords a C-6 modified cyclic adenosine 5'-diphosphoribose analogue with biological activity in Jurkat T cells

Two nicotinamide adenine dinucleotide (NAD(+)) analogues modified at the 6 position of the purine ring were synthesized, and their substrate properties toward Aplysia californica ADP-ribosyl cyclase were investigated. 6-N-Methyl NAD(+) (6-N-methyl nicotinamide adenosine 5'-dinucleotide 10) hydrolyzes to give the linear 6-N-methyl ADPR (adenosine 5'-diphosphoribose, 11), whereas 6-thio NHD(+) (nicotinamide 6-mercaptopurine 5'-dinucleotide, 17) generates a cyclic dinucleotide. Surprisingly, NMR correlation spectra confirm this compound to be the N1 cyclic product 6-thio N1-cIDPR (6-thio cyclic inosine 5'-diphosphoribose, 3), although the corresponding 6-oxo analogue is well-known to cyclize at N7. In Jurkat T cells, unlike the parent cyclic inosine 5'-diphosphoribose N1-cIDPR 2, 6-thio N1-cIDPR antagonizes both cADPR- and N1-cIDPR-induced Ca(2+) release but possesses weak agonist activity at higher concentration. 3 is thus identified as the first C-6 modified cADPR (cyclic adenosine 5'-diphosphoribose) analogue antagonist; it represents the first example of a fluorescent N1-cyclized cADPR analogue and is a new pharmacological tool for intervention in the cADPR pathway of cellular signaling.     

The influence of calcium antagonists on the adenine nucleotide metabolism in the guinea-pig working heart during ischaemia and reperfusion

Summary With the aim of gaining more insight into the metabolism of adenine nucleotides in working normoxic guinea-pigs and in hearts subjected to 45 min of global ischaemia and subsequent reperfusion for 25 min, we evaluated the effect of nifedipine, verapamil, diltiazem, bepridil, CERM 11956, lidoflazine, mioflazine and dipyridamole on the adenine nucleotide catabolite levels in these hearts. The drugs were applied at the concentrations that reduced the aortic dP/dt of normoxic working hearts by 10% (EC₁₀) and 30% (EC₃₀).In globally ischaemic hearts there was a large accumulation of adenine nucleotide catabolites. Inosine proved to be the major catabolite. The drugs, with the exception of bepridil, CERM 11956 and dipyridamole (3 mol/l), decreased the accumulation of catabolites. In hearts treated with mioflazine and dipyridamole the amount of adenosine increased. A deficit in the balance between adenine nucleotides and catabolites indicated that in globally ischaemic hearts there was a large accumulation of inosine monophosphate. Indeed, a substantial amount of inosine monophosphate was determined in untreated hearts, and hearts treated with nifedipine (EC₃₀) and mioflazine (EC₁₀). During the first 5 min of reperfusion a large quantity of catabolites, mainly inosine, was washed out. During 20 min of subsequent reperfusion in untreated hearts and in nifedipine and mioflazine-treated hearts the efflux of catabolites returned to normoxic values. Similar to the effect in ischaemic hearts, in early perfusate from lidoflazine, mioflazine and dipyridamoletreated hearts the adenosine/inosine ratio was increased. An incomplete balance of adenine nucleotides and catabolites, as well as the presence of a considerable quantity of inosine monophosphate in mioflazine-treated hearts, suggests that adenosine suppresses the breakdown of inosine monophosphate upon reperfusion.A reduced efflux of catabolites and the presence of a considerable amount of inosine monophosphate in lidoflazine, mioflazine and dipyridamole-treated hearts does not lead to an increased synthesis of adenine nucleotides during 25 min of reperfusion. Calcium antagonists without nucleoside transport inhibitory activity exert only limited influence on the adenine nucleotide catabolism in globally ischaemic and reperfused guineapig hearts. The ineffectiveness of all drugs to enhance the adenine nucleotide levels in reperfused hearts seems to results from the incapacity of the adenine nucleotide metabolism to convert inosine monophosphate, nucleosides and hypoxanthine into adenine nucleotides. Send offprint requests to J. G. Hugtenburg at the above address     

Effects of trimetazidine on tissue damage in kidney after hindlimb ischemia-reperfusion.

The objective of this study was to investigate the effects of trimetazidine (TMZ) on tissue damage in kidney after hindlimb ischemia-reperfusion (I/R), by assessing blood biochemical assay and histopathological analysis. Adult male Wistar rats were divided into two groups. TMZ 10 mg kg(-1)day(-1) was administrated twice a day for 10 days to the treatment group (group T, n=10). Sham group was given only 5% gum arabic (group S, n=10). On 11th day of treatment, 8h I/R period was performed on right hindlimb of the rats. At the end of reperfusion period, a 5 ml blood withdrawn from ascending aorta for biochemical assays and their right kidneys were harvested for histopathological examination. Superoxide dismutase, Na(+)-K(+) ATPase, and reduced glutathione levels were significantly increased in group T (P<0.001). On the other hand, myeloperoxidase and malondialdehyde levels were significantly less in group T than group S (P<0.001). Kidneys from the sham-operated group displayed intense leukocytic infiltration in histopathological examination.These overall results strongly suggested that TMZ contributes renal protection from hindlimb I/R injury by decreasing systemic oxidative stress.     

Inhibition of utilization of hypoxanthine and guanine in cells treated with the carbocyclic analog of adenosine. Phosphates of carbocyclic nucleoside analogs as inhibitors of hypoxanthine (guanine) phosphoribosyltransferase

In cell cultures treated with the carbocyclic analog of adenosine (C-Ado, (+/-)-aristeromycin), the utilization of hypoxanthine and guanine has been observed to be blocked. In an attempt to define the mechanism of this inhibition, we have reexamined the metabolism of C-Ado and its effects on the metabolism of guanine and hypoxanthine. In cultures of L1210 cells, C-Ado at a concentration of 25 microM inhibited the utilization of hypoxanthine and guanine for nucleotide synthesis by more than 90% but produced little or no inhibition of the utilization of these bases in cultures of L1210/MeMPR cells which lack adenosine kinase and cannot phosphorylate C-Ado. In cultures of mammalian cells (L1210, HEp-2, and colon-26 cells), C-Ado was converted to the triphosphate (as previously observed) and also to the triphosphate of the carbocyclic analog of guanosine. The presence of coformycin in the medium at a concentration sufficient to inhibit AMP deaminase almost completely prevented the formation of carbocyclic GTP; thus, the deamination of C-Ado monophosphate is essential for the formation of phosphates of carbocyclic guanosine. Since hypoxanthine (guanine) phosphoribosyltransferase is known to be subject to end product inhibition, it was considered likely that phosphates of carbocyclic guanosine or carbocyclic inosine, present in C-Ado-treated cells, were responsible for inhibition of utilization of hypoxanthine and guanine. The 5'-phosphates of the carbocyclic analogs of inosine and guanosine were synthesized and found to be effective inhibitors of the phosphoribosyltransferase. Carbocyclic GMP was a better inhibitor than carbocyclic IMP and was also superior to GMP and IMP; the concentration of C-GMP that produced a 50% inhibition of GMP formation was approximately 1 microM. It is probable that the presence of phosphates of carbocyclic guanosine accounts for the inhibition of utilization of hypoxanthine and guanine in C-Ado-treated cells.     

RP-HPLC同时测定暗紫贝母中10个核苷及碱基类成分的含量

目的:建立RP-HPLC-DAD同时测定暗紫贝母药材中5个核苷类活性成分(尿苷、鸟苷、胸苷、腺苷、肌苷)及5个游离的碱基(腺嘌呤、胸腺嘧啶、鸟嘌呤、尿嘧啶、胞嘧啶)含量的方法。方法:采用Agilent Zorbax Bonus-RP C18色谱柱(4.6 mm×250 mm,5μm);流动相为甲醇和水,梯度洗脱,流速1 mL·min-1;检测波长260 nm;柱温30℃。结果:胞嘧啶、尿苷、鸟苷、胸苷、腺苷、腺嘌呤、肌苷、胸腺嘧啶、鸟嘌呤、尿嘧啶的质量浓度分别在1.78～56.80 mg·L-1、1.84～59.00 mg·L-1、1.58～50.60 mg·L-1、1.73～55.30 mg·L-1、1.78～57.10 mg·L-1、1.63～52.10 mg·L-1、1.79～57.20 mg·L-1、1.80～57.70 mg·L-1、1.63～52.30 mg·L-1、1.63～52.30 mg·L-1范围内与峰面积呈良好线性关系,平均回收率为97.7%～103.2%,RSD≤2.2%。结论:建立了RP-HPLC-DAD同时测定暗紫贝母药材中10个核苷及碱基类成分含量的方法,该方法简单,重复性好,准确可靠;暗紫贝母药材中鸟苷、尿苷、胸苷、腺苷含量较高;青海久治、大通产暗紫贝母药材中核苷含量均高于四川松潘;青海2个产地比较,大通产暗紫贝母药材中核苷含量又明显高于久治。     

Evidence that adenosine triphosphate or a related nucleotide is the transmitter substance released by non-adrenergic inhibitory nerves in the gut

1. Stimulation of the vagal non-adrenergic inhibitory innervation caused the release of adenosine and inosine into vascular perfusates from the stomachs of guinea-pigs and toads.2. Stimulation of portions of Auerbach's plexus isolated from turkey gizzard caused the release of adenosine triphosphate (ATP), adenosine diphosphate (ADP) and adenosine monophosphate (AMP).3. ATP, added to solutions perfused through the toad stomach vasculature, was broken down to adenosine, inosine and adenine.4. Of a series of purine and pyrimidine derivatives tested for inhibitory activity on the guinea-pig isolated taenia coli, ATP and ADP were the most potent.5. ATP caused inhibition of twelve other gut preparations previously shown to contain non-adrenergic inhibitory nerves. The inhibitory action of ATP was not prevented by tetrodotoxin.6. Quinidine antagonized relaxations of the guinea-pig taenia coli caused by catecholamines or adrenergic nerve stimulation. Higher concentrations of quinidine antagonized relaxations caused by ATP or non-adrenergic inhibitory nerve stimulation.7. When tachyphylaxis to ATP had been produced in the rabbit ileum, there was a consistent depression of the responses to non-adrenergic inhibitory nerve stimulation but not of responses to adrenergic nerve stimulation.8. It is suggested that ATP or a related nucleotide is the transmitter substance released by the non-adrenergic inhibitory innervation of the gut.     

曲美他嗪对大鼠心肌缺血-再灌注损伤的保护作用

目的探讨曲美他嗪(TMZ)对缺血-再灌注(I-R)后大鼠心肌细胞凋亡的保护作用。方法 SD大鼠随机分为假手术组(A组)I、-R组(B组)、低浓度TMZ(1 ml/100 g)组(C组)和高浓度TMZ(3 ml/100 g)组(D组),每组6只。制备大鼠心肌I-R模型,采用流式细胞仪(FCM)、原位末端标记(TUNEL)技术、免疫组化检测心肌组织细胞凋亡情况,并观察细胞形态变化。结果 B组细胞凋亡指数、TUNEL阳性细胞数、Bcl-2、Bax较A组增高[(0.2416±0.0263)vs.(0.0469±0.0136),(3.213±0.14)vs.(0.44±0.133),(2.057±0.187)vs.(0.47±0.082),(4.257±0.135)vs.(0.52±0.058)(P<0.05)],而C、D组细胞凋亡指数、TUNEL阳性细胞数、Bax明显下降(P<0.05),D组减低更明显。结论 TMZ可抑制心肌I-R损伤中的细胞凋亡。     

Biased activity of soluble guanylyl cyclase: the Janus face of thymoquinone

The natural compound thymoquinone, extracted from Nigella sativa (black cumin), is widely used in humans for its anti-oxidative properties. Thymoquinone is known for its acute endothelium-independent vasodilator effects in isolated rat aortae and pulmonary arteries, depending in part on activation of adenosine triphosphate-sensitive potassium channels and inhibition of voltage-dependent calcium channels. The compound also improves endothelial dysfunction in mesenteric arteries of ageing rodents and in aortae of rabbits treated with pyrogallol, by inhibiting oxidative stress. Serendipitously, thymoquinone was found to augment contractions in isolated arteries with endothelium of both rats and pigs. The endothelium-dependent augmentation it causes counterintuitively depends on biased activation of soluble guanylyl cyclase (sGC) producing inosine 3ʹ,5ʹ-cyclic monophosphate (cyclic IMP) rather than guanosine 3ʹ,5ʹ-cyclic monophosphate. This phenomenon shows a striking mechanistic similarity to the hypoxic augmentation previously observed in porcine coronary arteries. The cyclic IMP preferentially produced under thymoquinone exposure causes an increased contractility of arterial smooth muscle by interfering with calcium homeostasis. This brief review summarizes the vascular pharmacology of thymoquinone, focussing in particular on how the compound causes endothelium-dependent contractions by biasing the activity of sGC.     

川芎嗪联用维生素C对实验性缺血-再灌注损伤肝脏能量代谢的影响

目的:探讨川芎嗪(LGT)、维生素C(VitC)联合使用对肝缺血-再灌注损伤(HIRI)时肝细胞能量代谢的影响及其机制。方法:实验兔40只,随机分为肝缺血-再灌注组(A组)和肝缺血-再灌注+ LGT治疗组(B组)、肝缺血-再灌注+VitC治疗组(C组)和肝缺血-再灌注+LGT+VitC治疗组(D组)。在再灌注45min时,分别检测肝组织内三磷酸腺苷(ATP)、二磷酸腺苷(ADP)、一磷酸腺苷(AMP)含量、总腺苷酸量(TAN)、能荷(EC)、丙二醛(MDA)含量、超氧化物歧化酶(SOD)活性及一氧化氮代谢产物(NO_2~-/NO_3~-)水平。结果:与A组比较,D组肝组织内ATP、TAN、EC、NO_2~-/NO_3~-含量及SOD活性均明显增高(P＜0．05,P＜0．01),MDA含量显著减少(P＜0．01)。结论:LGT联用VitC可通过降低体内氧自由基水平、提高一氯化氮水平,而改善缺血-再灌注损伤肝脏的能量代谢。     

Thiazole-4-carboxamide adenine dinucleotide (TAD). Analogues stable to phosphodiesterase hydrolysis

Thiazole-4-carboxamide adenine dinucleotide (TAD), the active metabolite of the oncolytic C-nucleoside tiazofurin (TR), is susceptible to phosphodiesteratic breakdown by a unique phosphodiesterase present at high levels in TR-resistant tumors. Since accumulation of TAD, as regulated by its synthetic and degradative enzymes, appears to be an important determinant for sensitivity to the drug, a series of hydrolytically resistant phosphonate analogues of TAD were synthesized with the intent of producing more stable compounds with an ability to inhibit IMP dehydrogenase equivalent to TAD itself. Isosteric phosphonic acid analogues of TR and adenosine nucleotides were coupled with activated forms of AMP and TR monophosphate to give dinucleotides 2 and 4. Coupling of protected adenosine 5'-(alpha, beta-methylene)diphosphate with isopropylidene-TR in the presence of DCC afforded compound 3 after deprotection. These compounds are more resistant than TAD toward hydrolysis and still retain potent activity against IMP dehydrogenase in vitro. beta-Methylene-TAD (3), the most stable of the TAD phosphonate analogues, produced a depletion of guanine nucleotide pools in an experimentally induced TR-resistant P388 tumor variant that was superior to that obtained with TR in the corresponding sensitive line.     

Attenuation of renal ischemia-reperfusion injury by trimetazidine: evidence of an in vivo antioxidant effect

Renal ischemia-reperfusion injury constitutes the most common pathogenic factor for acute renal failure and is the main contributor to renal dysfunction in allograft recipients and revascularization surgeries. Many studies have demonstrated that reactive oxygen species play an important role in ischemic acute renal failure. The aim of the present study was to investigate the effects of the synthetic antiischemic agent trimetazidine in a rat model of renal ischemia-reperfusion injury. Renal ischemia-reperfusion was induced by clamping the unilateral renal artery for 45 min followed by 24 h of reperfusion. Trimetazidine (2.5 mg/kg i.p.) was administered 24 and 12 h prior to renal artery occlusion and the same dose was given intravenously 1 h before inducing ischemia. Tissue lipid peroxidation was measured as thiobarbituric acid reacting substances (TBARS) in kidney homogenates. Renal function was assessed by estimating serum creatinine, blood urea nitrogen (BUN), creatinine and urea clearance. Renal morphological alterations were assessed by histopathological examination of hematoxylin-eosin stained sections of the kidneys. Ischemia-reperfusion produced elevated levels of TBARS and deteriorated the renal function as assessed by increased serum creatinine, BUN and decreased creatinine and urea clearance compared with sham operated rats. The ischemic kidneys of rats showed severe hyaline casts, epithelial swelling, proteinaceous debris, tubular necrosis, medullary congestion and hemorrhage. Trimetazidine markedly reduced elevated levels of TBARS and significantly attenuated renal dysfunction and morphological changes in rats subjected to renal ischemia-reperfusion. These results clearly demonstrate the in vivo antioxidant effect and the therapeutic potential of trimetazidine, an anti-ischemic agent, in attenuating renal ischemia-reperfusion injury.     

The chemistry of nicotinamide adenine dinucleotide (NAD) analogues containing C-nucleosides related to nicotinamide riboside

Oncolytic C-nucleosides, tiazofurin (2-beta-D-ribofuranosylthiazole-4-carboxamide) and benzamide riboside (3-beta-D-ribofuranosylbenzamide) are converted in cell into active metabolites thiazole-4-carboxamide- and benzamide adenine dinucleotide, TAD and BAD, respectively. TAD and BAD as NAD analogues were found to bind at the nicotinamide adenine dinucleotide (cofactor NAD) site of inosine monophosphate dehydrogenase (IMPDH), an important target in cancer treatment. The synthesis and evaluation of anticancer activity of a number of C-nucleosides related to tiazofurin and nicotinamide riboside then followed and are reviewed herein. Interestingly, pyridine C-nucleosides (such as C-nicotinamide riboside) are not metabolized into the corresponding NAD analogues in cell. Their conversion by chemical methods is described. As dinucleotides these compounds show inhibition of IMPDH in low micromolar level. Also, the synthesis of BAD in metabolically stable bis(phosphonate) form is discussed indicating the usefulness of such preformed inhibitors in drug development. Among tiazofurin analogues, Franchetti and Grifantini found, that the replacement of the sulfur by oxygen (as in oxazafurin) but not the removal of nitrogen (tiophenfurin) of the thiazole ring resulted in inactive compounds. The anti cancer activity of their synthetic dinucleotide analogues indicate that inactive compounds are not only poorly metabolized in cell but also are weak inhibitors of IMPDH as dinucleotides.