A multi-omics investigation of the lung injury induced by PM2.5 at environmental levels via the lung-gut axis.

Long-term exposure to fine particulate matter (PM2.5) posed injury for gastrointestinal and respiratory systems, ascribing with the lung-gut axis. However, the cross-talk mechanisms remain unclear. Here, we attempted to establish the response networks of lung-gut axis in mice exposed to PM2.5 at environmental levels. Male Balb/c mice were exposed to PM2.5 (dose of 0.1, 0.5, and 1.0 mg/kg) collected from Chengdu, China for 10 weeks, through intratracheally instillation, and examined the effect of PM2.5 on lung functions of mice. The changes of lung and gut microbiota and metabolic profiles of mice in different groups were determined. Furthermore, the results of multi-omics were conjointly analyzed to elucidate the primary microbes and the associated metabolites in lung and gut responsible for PM2.5 exposure. Accordingly, the cross-talk network and key pathways between lung-gut axis were established. The results indicated that exposed to PM2.5 0.1 mg/kg induced obvious inflammations in mice lung, while emphysema was observed at 1.0 mg/kg. The levels of metabolites guanosine, hypoxanthine, and hepoxilin B3 increased in the lung might contribute to lung inflammations in exposure groups. For microbiotas in lung, PM2.5 exposure significantly declined the proportions of Halomonas and Lactobacillus. Meanwhile, the metabolites in gut including L-tryptophan, serotonin, and spermidine were up-regulated in exposure groups, which were linked to the decreasing of Oscillospira and Helicobacter in gut. Via lung-gut axis, the activations of pathways including Tryptophan metabolism, ABC transporters, Serotonergic synapse, and Linoleic acid metabolism contributed to the cross-talk between lung and gut tissues of mice mediated by PM2.5. In summary, the microbes including Lactobacillus, Oscillospira, and Parabacteroides, and metabolites including hepoxilin B3, guanosine, hypoxanthine, L-tryptophan, and spermidine were the main drivers. In this lung-gut axis study, we elucidated some pro- and pre-biotics in lung and gut microenvironments contributed to the adverse effects on lung functions induced by PM2.5 exposure.

L-arginine metabolism inhibits arthritis and inflammatory bone loss.

OBJECTIVES: To investigate the effect of the L-arginine metabolism on arthritis and inflammation-mediated bone loss. METHODS: L-arginine was applied to three arthritis models (collagen-induced arthritis, serum-induced arthritis and human TNF transgenic mice). Inflammation was assessed clinically and histologically, while bone changes were quantified by µCT and histomorphometry. In vitro, effects of L-arginine on osteoclast differentiation were analysed by RNA-seq and mass spectrometry (MS). Seahorse, Single Cell ENergetIc metabolism by profilIng Translation inHibition and transmission electron microscopy were used for detecting metabolic changes in osteoclasts. Moreover, arginine-associated metabolites were measured in the serum of rheumatoid arthritis (RA) and pre-RA patients. RESULTS: L-arginine inhibited arthritis and bone loss in all three models and directly blocked TNFα-induced murine and human osteoclastogenesis. RNA-seq and MS analyses indicated that L-arginine switched glycolysis to oxidative phosphorylation in inflammatory osteoclasts leading to increased ATP production, purine metabolism and elevated inosine and hypoxanthine levels. Adenosine deaminase inhibitors blocking inosine and hypoxanthine production abolished the inhibition of L-arginine on osteoclastogenesis in vitro and in vivo. Altered arginine levels were also found in RA and pre-RA patients. CONCLUSION: Our study demonstrated that L-arginine ameliorates arthritis and bone erosion through metabolic reprogramming and perturbation of purine metabolism in osteoclasts.

Targeting NAD+ metabolism of hepatocellular carcinoma cells by lenvatinib promotes M2 macrophages reverse polarization, suppressing the HCC progression.

BACKGROUND: Lowered nicotinamide adenine dinucleotide (NAD+) levels in tumor cells drive tumor hyperprogression during immunotherapy, and its restoration activates immune cells. However, the effect of lenvatinib, a first-line treatment for unresectable hepatocellular carcinoma (HCC), on NAD+ metabolism in HCC cells, and the metabolite crosstalk between HCC and immune cells after targeting NAD+ metabolism of HCC cells remain unelucidated. METHODS: Liquid chromatography-tandem mass spectrometry (LC-MS/MS) and ultra-high-performance liquid chromatography multiple reaction monitoring-mass spectrometry (UHPLC-MRM-MS) were used to detect and validate differential metabolites. RNA sequencing was used to explore mRNA expression in macrophages and HCC cells. HCC mouse models were used to validate the effects of lenvatinib on immune cells and NAD+ metabolism. The macrophage properties were elucidated using cell proliferation, apoptosis, and co-culture assays. In silico structural analysis and interaction assays were used to determine whether lenvatinib targets tet methylcytosine dioxygenase 2 (TET2). Flow cytometry was performed to assess changes in immune cells. RESULTS: Lenvatinib targeted TET2 to synthesize and increase NAD+ levels, thereby inhibiting decomposition in HCC cells. NAD+ salvage increased lenvatinib-induced apoptosis of HCC cells. Lenvatinib also induced CD8+ T cells and M1 macrophages infiltration in vivo. And lenvatinib suppressed niacinamide, 5-Hydroxy-L-tryptophan and quinoline secretion of HCC cells, and increased hypoxanthine secretion, which contributed to proliferation, migration and polarization function of macrophages. Consequently, lenvatinib targeted NAD+ metabolism and elevated HCC-derived hypoxanthine to enhance the macrophages polarization from M2 to M1. Glycosaminoglycan binding disorder and positive regulation of cytosolic calcium ion concentration were characteristic features of the reverse polarization. CONCLUSIONS: Targeting HCC cells NAD+ metabolism by lenvatinib-TET2 pathway drives metabolite crosstalk, leading to M2 macrophages reverse polarization, thereby suppressing HCC progression. Collectively, these novel insights highlight the role of lenvatinib or its combination therapies as promising therapeutic alternatives for HCC patients with low NAD+ levels or high TET2 levels.

Polydatin protects against gouty nephropathy by inhibiting renal tubular cell pyroptosis.

OBJECTIVE: To investigate the protective effect and mechanism of polydatin (PD) against gouty nephropathy (GN) in mice. METHODS: Twenty-four mice were randomly divided into three groups: the control group (no treatment), the GN group (300 mg/kg hypoxanthine + 150 mg/kg potassium oxonate), and the GN + PD group (300 mg/kg hypoxanthine + 150 mg/kg potassium oxonate + 50 mg/kg PD). Histological changes in the kidneys and the levels of uric acid (UA), blood urea nitrogen (BUN), and serum creatinine (SCr) in the sera were measured. In addition, the expression of gasdermin D (GSDMD) protein in renal tubular epithelial cells, and the expression of NOD-like receptor protein 3 (NLRP3), GSDMD, and caspase-1 proteins in the kidney tissues were determined by immunohistochemistry, immunofluorescence, and Western blot. RESULTS: In vitro, PD inhibited the expression of NLRP3, caspase-1, and GSDMD and protected the renal tubular epithelial cells from pyroptosis. In vivo, PD treatment significantly ameliorated the pathological changes in kidney tissue, and reversed the decrease of serum UA and BUN in GN model mice. The expression of NLRP3, GSDMD, and caspase-1 proteins was also decreased in the PD-treated GN mice. CONCLUSION: The results suggest that PD has a protective effect on mice with GN, which may be related to the downregulation of NLRP3, GSDMD, and caspase-1 proteins and the inhibition of renal tubular epithelial cells pyroptosis.

Anserine beneficial effects in hyperuricemic rats by inhibiting XOD, regulating uric acid transporter and repairing hepatorenal injury.

This study aims to investigate the anti-hyperuricemia effect and mechanism of anserine in hyperuricemic rats. Hyperuricemic rats were induced with a combination of 750 mg per kg bw d potassium oxazinate (PO) and 200 mg per kg bw d hypoxanthine for a week, and the rats were separately orally administered anserine (20, 40, 80 mg kg-1) and allopurinol (10 mg kg-1) for three weeks. The results show that the content of serum uric acid (SUA) decreased by approximately 40% and 60% after the intervention of anserine and allopurinol, respectively. The activity of superoxide dismutase (SOD) was increased and the levels of malondialdehyde (MDA), alkaline phosphatase (ALP) and alanine aminotransferase (ALT) were significantly decreased in the anserine groups. After the administration of anserine, the contents of blood urea nitrogen (BUN) and creatinine (Cr) were reduced in the kidney, and the levels of the proinflammatory cytokines IL-1ß, IL-6ß, TNF-α and TGF-ß and inflammatory cell infiltration were reduced in both the liver and kidney. Moreover, the gene expressions of xanthine oxidase (XOD), renal urate transporter 1 (URAT1) and glucose transporter type 9 (GLUT9) were downregulated by anserine administration, and the gene expressions of ATP-binding cassette transporter G2 (ABCG2), organic anion transporter 1 (OAT1) and organic anion transporter 3 (OAT3) were upregulated at the same time. These findings suggest that hepatorenal injury was repaired by anserine, which further regulated the expression of hepatic XOD and renal URAT1, GLUT9, ABCG2, OAT1 and OAT3 to relieve hyperuricemia in rats.

Helicobacter pylori Xanthine-Guanine-Hypoxanthine Phosphoribosyltransferase-A Putative Target for Drug Discovery against Gastrointestinal Tract Infections.

Helicobacter pylori (Hp) is a human pathogen that lives in the gastric mucosa of approximately 50% of the world's population causing gastritis, peptic ulcers, and gastric cancer. An increase in resistance to current drugs has sparked the search for new Hp drug targets and therapeutics. One target is the disruption of nucleic acid production, which can be achieved by impeding the synthesis of 6-oxopurine nucleoside monophosphates, the precursors of DNA and RNA. These metabolites are synthesized by Hp xanthine-guanine-hypoxanthine phosphoribosyltransferase (XGHPRT). Here, nucleoside phosphonates have been evaluated, which inhibit the activity of this enzyme with Ki values as low as 200 nM. The prodrugs of these compounds arrest the growth of Hp at a concentration of 50 µM in cell-based assays. The kinetic properties of HpXGHPRT have been determined together with its X-ray crystal structure in the absence and presence of 9-[(N-3-phosphonopropyl)-aminomethyl-9-deazahypoxanthine, providing a basis for new antibiotic development.

Metabolismo do glicogênio muscular durante o exercício físico: mecanismos de regulação / Muscle glycogen metabolism during exercise: mechanism of regulation

Uma série de estudos tem sido realizada para compreensão do metabolismo de glicogênio muscular durante o exercício. Estudos clássicos apontaram uma associação entre as reservas iniciais de glicogênio muscular e o tempo de sustentação do esforço. O glicogênio muscular diminui de forma semi-logarítmica em função do tempo, mas a concentração desse substrato não chega a zero, o que sugere a participação de outros mecanismos de fadiga na interrupção do exercício prolongado. Nesse tipo de atividade, a depleção de glicogênio, primeiro, ocorre nas fibras de contração lenta, seguida pela depleção nas de contração rápida. A diminuição na taxa de utilização de glicogênio muscular está sincronicamente ligada ao aumento no metabolismo de gordura, mas o mecanismo fisiológico é pouco compreendido. Estudos recentes sugerem que uma diminuição da insulina durante o exercício limitaria o transporte de glicose pela membrana plasmática, causando um aumento no consumo de ácidos graxos. Alguns estudos têm demonstrado, também, que a própria estrutura do glicogênio muscular pode controlar a entrada de ácidos graxos livres na célula, via proteína quinase. Fisicamente, a molécula de glicogênio se apresenta de duas formas, uma com estrutura molecular menor (aproximadamente, 4,10(5) Da, Proglicogênio) e outra maior (aproximadamente, 10(7) Da, Macroglicogênio). Aparentemente, a forma Proglicogênio é metabolicamente mais ativa no exercício e a Macroglicogênio mais suscetível a aumentar com dietas de supercompensação. Maior concentração de hipoxantinas e amônia no exercício com depleção de glicogênio muscular também foi relatada, mas estudos com melhor controle da intensidade do esforço podem ajudar a elucidar essa questão.

A large number of studies have been conducted to understand muscle glycogen metabolism during exercise. Classical studies demonstrated a relationship between the pre-exercise muscle glycogen content and duration of exercise. Muscle glycogen declines in a semilogarithmic manner in function of time, but glycogen concentration does not reach zero, which suggests that other fatigue mechanisms participate in the interruption of prolonged exercise. In this type of activity, glycogen depletion occurs first in slow twitch fibers followed by fast twitch fibers. The decrease in the rate of muscle glycogen utilization is synchronized with an increased rate of fat uptake, but the physiological mechanism is not well understood. Recent studies suggest that the decline of insulin during exercise could be a limiting factor of glucose transport through the plasma membrane, which increases the uptake of fatty acids. Others studies have also demonstrated that the structure of muscle glycogen itself can regulate the cellular uptake of free fatty acids via protein kinase. Physically, the glycogen molecule has two forms, one with a smaller molecular structure (approximately 4.10(5) Da, proglycogen) and another one with a larger molecular structure (approximately 10(7) Da, macroglycogen). Apparently, the proglycogen form is more metabolically active during exercise and the macroglycogen form is more susceptible to increase with supercompensation diets. Higher concentrations of hypoxanthines and ammonia during exercise with muscle glycogen depletion have been reported, but studies that control exercise intensity better are necessary to help shed light on this issue.

Intestinal ischemic preconditioning: less xanthine accumulation relates with less apoptosis.

Ischemic preconditioning has shown to reduce apoptosis in the intestinal mucosa during ischemia/reperfusion. This study evaluated if the decrease of apoptotic events found during preconditioning could be related with a reduction of the substrate (i.e., xanthine/hypoxanthine) available for xanthine oxidase (XO). Animals were randomly assigned to the following study groups: C, control; I/R, ischemia/reperfusion; P+I/R, ischemic preconditioning; P+I/R+H/X, ischemic preconditioning plus hypoxanthine/xanthine, and P+I/R+H/X+Allo, ischemic preconditioning plus hypoxanthine/xanthine plus allopurinol. Caspase-3 activity, DNA fragmentation and TUNEL staining increased in the I/R group compared to control. Ischemic preconditioning (P+I/R group) was able to reverse these apoptotic variables to a level similar to that of control rats. The addition of hypoxanthine/xanthine to rats subjected to ischemic preconditioning (P+I/R+H/X group) showed the highest apoptotic activity; however, further addition of allopurinol (P+I/R+H/X+Allo group) decreased significantly apoptotic activity and events. In conclusion, intestinal ischemic preconditioning is able to reduce apoptosis during the following sustained ischemia/reperfusion event because of a reduced accumulation of xanthine/hypoxanthine nucleotide.

The prebiotic synthesis of modified purines and their potential role in the RNA world.

Modified purines are found in all organisms in the tRNA, rRNA, and even DNA, raising the possibility of an early role for these compounds in the evolution of life. These include N6-methyladenine, 1-methyladenine, N6,N6-dimethyladenine, 1-methylhypoxanthine, 1-methylguanine, and N2-methylguanine. We find that these bases as well as a number of nonbiological modified purines can be synthesized from adenine and guanine by the simple reaction of an amine or an amino group with adenine and guanine under the concentrated conditions of the drying-lagoon or drying-beach model of prebiotic synthesis with yields as high as 50%. These compounds are therefore as prebiotic as adenine and guanine and could have played an important role in the RNA world by providing additional functional groups in ribozymes, especially for the construction of hydrophobic binding pockets.

N2-amination of guanine to 2-hydrazinohypoxanthine, a novel in vivo nucleic acid modification produced by the hepatocarcinogen 2-nitropropane.

2-Nitropropane, an industrial chemical and a hepatocarcinogen in rats, induces aryl sulfotransferase-mediated liver DNA and RNA base modifications [Sodum, R. S., Sohn, O. S., Nie, G., and Fiala, E. S. (1994) Chem. Res. Toxicol. 7, 344-351]. Two of these modifications were previously identified as 8-aminoguanine and 8-oxoguanine. We now report that the base moiety of the so far unidentified third nucleic acid modification, namely RX1 in RNA and DX1 in DNA, is 2-hydrazinohypoxanthine (N2-aminoguanine). 2-Hydrazinoinosine and 2-hydrazinodeoxyinosine, synthesized by adapting published procedures, cochromatographed with RX1 and DX1 of liver RNA and DNA, respectively, from 2-nitropropane-treated rats. 2-Hydrazinoinosine and 2-hydrazinodeoxyinosine are unstable in solution like the in vivo products RX1 and DX1. At neutral pH, hypoxanthine nucleoside is the major product of decomposition, while at pH 10 or above, xanthine nucleoside is also formed. RX1 and DX1 could be generated in the anaerobic reactions of hydroxylamine-O-sulfonic acid, an intermediate in the proposed activation pathway of 2-nitropropane, with guanine nucleosides. These results provide further evidence for the activation of 2-nitropropane and other carcinogenic secondary nitroalkanes to a reactive species capable of aminating nucleic acids and proteins.

Relation between left ventricular function and oxidative stress in patients undergoing bypass surgery.

OBJECTIVE: To determine whether preoperative left ventricular ejection fraction (LVEF) is related to the degree of myocardial oxidative stress during bypass surgery in man. DESIGN: Observational study. SETTING: Tertiary care centre. PATIENTS AND INTERVENTIONS: 31 patients (LVEF range was 20% to 68%) undergoing elective coronary bypass surgery with blood cardioplegic reperfusion were studied. Arterial and coronary sinus blood was collected before aortic cross clamping (T0) and at 0 (T1), 15 (T2), and 30 (T3) minutes after unclamping. Transmural left ventricular biopsies were also obtained from 15 patients at T0 and at T1. MAIN OUTCOME MEASURES: Glutathione and adenine nucleotides were measured in myocardial biopsies, while coronary sinus-artery differences for glutathione, nucleotides, and products of lipid peroxidation were calculated from blood specimens. Creatine kinase (myocardial band; CK-MB) was measured in plasma at four and 12 hours after operation. RESULTS: Myocardial glutathione and adenine nucleotides were correlated (p < 0.02) with preoperative LVEF both at T0 (r = 0.909 and 0.672) and T1 (r = 0.603 and 0.605). Oxidised glutathione released from the heart during reperfusion was inversely correlated with LVEF (r = -0.448, -0.466, and -0461 at T1, T2, and T3, p < 0.01), while reduced glutathione (r = 0.519 and 0.640 at T1 and T2) and glutathione redox ratio (r = 0.647, 0.714, 0.645, and 0.702 at T0, T1, T2, and T3) showed a direct correlation (p < 0.01). Lipid peroxidation at T1 was negatively related to LVEF (r = -0.492). CK-MB was also negatively related to LVEF (r = -0.440 at 4 h and -0.462 at 12 h). CONCLUSIONS: The capacity to counterbalance oxidative burst following ischaemia and reperfusion appears to be related to the functional ability of the heart.

Adenosine formation in contracting primary rat skeletal muscle cells and endothelial cells in culture.

1. The present study examined the capacity for adenosine formation, uptake and metabolism in contracting primary rat muscle cells and in microvascular endothelial cells in culture. 2. Strong and moderate electrical simulation of skeletal muscle cells led to a significantly greater increase in the extracellular adenosine concentration (421 +/- 91 and 235 +/- 30 nmol (g protein)-1, respectively; P < 0.05) compared with non-stimulated muscle cells (161 +/- 20 nmol (g protein)-1). The ATP concentration was lower (18%; P < 0.05) in the intensely contracted, but not in the moderately contracted muscle cells. 3. Addition of microvascular endothelial cells to the cultured skeletal muscle cells enhanced the contraction-induced accumulation of extracellular adenosine (P < 0.05), whereas endothelial cells in culture alone did not cause extracellular accumulation of adenosine. 4. Skeletal muscle cells were found to have ecto-forms of several enzymes involved in nucleotide metabolism, including ATPases capable of converting extracellular ATP to ADP and AMP. 5. Adenosine added to the cell medium was taken up by muscle cells and incorporated into the adenine nucleotide pool so that after 30 min of incubation, over 95% of the adenosine label was present in ATP, ADP and AMP. A similar extent of incorporation of adenosine into the nucleotide pool was evident in the endothelial cells. 6. The present data suggest that contracting muscle cells induce an elevation in the extracellular adenosine concentration. Addition of endothelial cells to muscle cells enhances the contraction-induced formation of adenosine. Adenosine taken up by muscle and endothelial cells from the extracellular space is not likely to be used for storage in intracellular pools, but may serve to regulate muscle extracellular adenosine levels.

Hypoxanthine enters human vascular endothelial cells (ECV 304) via the nitrobenzylthioinosine-insensitive equilibrative nucleoside transporter.

The transport properties of the nucleobase hypoxanthine were examined in the human umbilical vein endothelial cell line ECV 304. Initial rates of hypoxanthine influx were independent of extracellular cations: replacement of Na+ with Li+, Rb+, N-methyl-D-glucamine or choline had no significant effect on hypoxanthine uptake by ECV 304 cells. Kinetic analysis demonstrated the presence of a single saturable system for the transport of hypoxanthine in ECV 304 cells with an apparent K(m) of 320 +/- 10 microM and a Vmax of 5.6 +/- 0.9 pmol/10(6) cells per s. Hypoxanthine uptake was inhibited by the nucleosides adenosine, uridine and thymidine (apparent Ki 41 +/- 6, 240 +/- 27 and 59 +/- 8 microM respectively) and the nucleoside transport inhibitors nitrobenzylthioinosine (NBMPR), dilazep and dipyridamole (apparent Ki 2.5 +/- 0.3, 11 +/- 3 and 0.16 +/- 0.006 microM respectively), whereas the nucleobases adenine, guanine and thymine had little effect (50% inhibition at > 1 mM). ECV 304 cells were also shown to transport adenosine via both the NBMPR-sensitive and -insensitive nucleoside carriers. Hypoxanthine specifically inhibited adenosine transport via the NBMPR-insensitive system in a competitive manner (apparent Ki 290 +/- 14 microM). These results indicate that hypoxanthine entry into ECV 304 endothelial cells is mediated by the NBMPR-insensitive nucleoside carrier present in these cells.

Hypoxanthine: a low molecular weight factor essential for growth of erythrocytic Plasmodium falciparum in a serum-free medium.

A low molecular weight factor in a basal medium essential for erythrocytic Plasmodium falciparum development in a serum-free medium using a cell growth-promoting factor derived from adult bovine serum was detected. The factor was hypoxanthine. The optimal hypoxanthine concentration for parasite growth was between 15 and 120 microM. The contribution of hypoxanthine to increased parasite growth was clearly evident in cultures on day 4. Among various low molecular weight supplements tested, adenine, adenosine, AMP, ATP, cyclic AMP, guanine, guanosine, inosine, inosine monophosphate, xanthine, NAD, NADH, NADP, NADPH and deoxyguanosine triphosphate showed a similar effect to that of hypoxanthine in the serum-free culture system. On the other hand, the addition of uric acid, FAD, thymidine, uridine, orotic acid, deoxythymidine triphosphate, deoxycytidine triphosphate, deoxyadenosine triphosphate, ribose-1-phosphate, or ethanolamine was not beneficial to the parasite growth. The results presented here will not only be of practical value, but will provide important information about the developmental requirements of the parasite.

Delay of adenosine triphosphate depletion and hypoxanthine formation in rabbit lung after death.

BACKGROUND: If lungs could be retrieved for transplantation from non-heart-beating cadavers, the shortage of donors might be significantly alleviated. METHODS: Adenosine triphosphate (ATP) and hypoxanthine levels were measured postmortem in rabbit lungs comparing deflation (group 1), ventilation with room air (group 2), inflation with room air (group 3), ventilation with oxygen (group 4), ventilation with cooled air (group 5), deflation plus cadaver cooling (group 6), and cooling by pulmonary arterial flush (group 7). RESULTS: The level of ATP dropped to 25.9% and HYP increased elevenfold at 30 minutes in group 1 but remained constant during 24 hours in group 7. The ATP catabolism beyond 2 hours postmortem appeared less in group 2 compared with group 3 (3.58 +/- 1.24 versus 0.39 +/- 0.08 mumol/g dry weight for ATP and 3.03 +/- 0.49 versus 7.64 +/- 0.94 mumol/g dry weight for hypoxanthine at 24 hours, respectively; p < 0.05). Cadaver cooling significantly slowed ATP catabolism. Changes in ATP level were similar in groups 2, 4, and 5. CONCLUSIONS: These data suggest that in the non-heart-beating cadaver (1) cooling, ventilation, and inflation can delay ATP catabolism; (2) postmortem ventilation but not inflation for more than 2 hours will inhibit further ATP breakdown; (3) ventilation with either oxygen or cooled air is not more beneficial than room air ventilation; and (4) cold flush more than cadaver cooling will prevent ATP depletion.

[The effect of an alpha-tocopherol analog, MDL 73404, on myocardial bioenergetics]. / Vplyv analógu alfatokoferolu MDL 73,404 na bioenergetiku myokardu.

The authors investigated the effect of the synthetic analogue of MDL 73,404 alpha-tocopherol on bioenergetic processes of the cardiac muscle in a control group of rats. After a 10-day application of the presented preparation they analyzed the following parameters of energetic metabolism: ATP, ADP, AMP and inorganic phosphorus. Beside these, the authors investigate the levels of main indicators of the purine metabolism (xanthine, hypoxanthine, inosine and uric acid) in the myocardium. Under the influence of the given analogue of alpha-tocopherol a significant increase in ATP, ADP and hypoxanthine took place in the myocardium. Also the total concentration of adenine nucleotide and relative ATP/ADP ratio increased in the cardiac muscle. On the basis of the gained results the authors came to a conclusion that the synthetic analogue of alpha-tocopherol MDL 73,404 has a favourable effect on the bioenergetic conditions in the myocardium. MDL 73,404 has a favourable cardioprotective effect on the cardiac muscle assumedly by means of stabilization of mitochondrial membranes on the myocardium with a subsequent impact on cellular ATP concentration.

Vincristine resistant HL-60 cells show cross-resistance to hypoxanthine-xanthine oxidase.

This is the first observation that active an oxygen-producing system showed cross-resistance to vincristine (VCR) resistant cells or other anticancer agent-resistant cells. The extent of cross-resistance against oxygen radicals and anticancer agents in wild type and VCR resistant human promyelocytic leukemia cell line, HL-60 and HL-60/VCR, is compared. Superoxide was generated by reaction with hypoxanthine(HX)-xanthine oxidase(XO). HL-60/VCR was 81-fold resistant to VCR, 11.8-fold resistant to adriamycin, and 8.5-fold resistant to the XO concentration required for 50% growth inhibition compared with HL-60. Because oxygen radicals injure the cell membrane, the results indicate an increased resistance to membrane damage by oxygen radicals in drug resistant cells.

Attenuated purine production during subsequent ischemia in preconditioned rabbit myocardium is unrelated to the mechanism of protection.

Preconditioned hearts release less purines during ischemia than virgin hearts. This study tested whether this reduced purine production is related to the mechanism of protection by ischemic preconditioning. Coronary effluent from isolated rabbit hearts was collected and purine (adenosine + inosine + hypoxanthine) levels were measured. All hearts underwent two cycles of 5 min global ischemia, each followed by 10 min reperfusion. In the first minute of reflow after the first ischemic period untreated hearts released 155 +/- 14 nmol purines per g wet weight, but only 104 +/- 16 nmol/g following the second bout of ischemia (P < 0.05). Thus, preconditioned hearts released less purines during ischemia. When 8-(p-sulfophenyl)theophylline (100 microM), which prevents the infarct size-limiting effect of ischemic preconditioning by blocking adenosine receptors was present in the perfusate, the pattern of purine release was not altered (151 +/- 13 nmol/g during the first minute after the first 5-min ischemic episode dropping to 117 +/- 6 nmol/g after the second ischemic period P < 0.05). Furthermore, pharmacological preconditioning with 5 min exposure of the heart to either adenosine (10 microM) or phenylephrine (0.1 microM) 15 min prior to the first ischemia did not affect purine release during early reperfusion after either the first (144 +/- 16 nmol/g and 153 +/- 12 nmol/g, respectively) or second (84 +/- 12 nmol/g and 111 +/- 9 nmol/g, respectively) bout of ischemia. Since the attenuated purine release was apparently unaffected by the presence or absence of a protected state, we conclude that this pattern is unrelated to the mechanism by which preconditioning protects the heart.

Enhanced acquisition of purine nucleosides and nucleobases by purine-starved Crithidia luciliae.

The effects of purine starvation on the ability of the trypanosomatid Crithidia luciliae to accumulate purines were determined. Kinetic studies showed that the uptake of the nucleoside adenosine by purine-starved organisms was approximately 7-fold faster than by nutrient-replete cells. Further, these studies demonstrated that purine-starved organisms accumulated the nucleobases hypoxanthine and adenine at a rate > 100-fold faster than organisms cultivated under replete conditions. Activities of several intracellular purine-salvage enzymes were measured in organisms from both culture conditions. Of those measured, the activities of adenine deaminase and hypoxanthine phosphoribosyltransferase were elevated approximately 4-fold and approximately 11-fold, respectively, in purine-starved organisms. Competitive substrate specificity studies suggested that these elevated enzyme activities were not responsible for the increased rates of uptake by purine-starved cells. The results are consistent with the induction of novel surface membrane purine transporters expressed in response to purine starvation. These studies using C. luciliae may provide insights into the mechanisms of trypanosomatid adaptation to altered environments encountered during the course of the life cycle.