Determination of selected pyrimidines, purines and their metabolites in serum and urine by reversed-phase ion-pair chromatography

Characterization of purinergic signaling in tumor-infiltrating lymphocytes from lower- and high-grade gliomas

Malignant gliomas are highly heterogeneous glia-derived tumors that present an aggressive and invasive nature, with a dismal prognosis. The multi-dimensional interactions between glioma cells and other tumor microenvironment (TME) non-tumoral components constitute a challenge to finding successful treatment strategies. Several molecules, such as extracellular purines, participate in signaling events and support the immunosuppressive TME of glioma patients. The purinergic signaling and the ectoenzymes network involved in the metabolism of these extracellular nucleotides are still unexplored in the glioma TME, especially in lower-grade gliomas (LGG). Also, differences between IDH-mutant (IDH-Mut) versus wild-type (IDH-WT) gliomas are still unknown in this context. For the first time, to our knowledge, this study characterizes the TME of LGG, high-grade gliomas (HGG) IDH-Mut, and HGG IDH-WT patients regarding purinergic ectoenzymes and P1 receptors, focusing on tumor-infiltrating lymphocytes. Here, we show that ectoenzymes from both canonical and non-canonical pathways are increased in the TME when compared to the peripheral blood. We hypothesize this enhancement supports extracellular adenosine generation, hence increasing TME immunosuppression.

Lymphocytes from B-acute lymphoblastic leukemia patients present differential regulation of the adenosinergic axis depending on risk stratification

PURPOSE

Although risk-stratified chemotherapy regimens improve B-cell acute lymphoblastic leukemia (B-ALL) clinical outcome, relapse occurs in a significant number of cases. The identification of new therapeutic targets as well as prognostic and diagnostic biomarkers can improve B-ALL patients' clinical outcomes. Purinergic signaling is an important pathway in cancer progression, however the expression of ectonucleotidases and their impact on immune cells in B-ALL lacks exploration. We aimed to analyze the expression of ectonucleotidases in B-ALL patients' lymphocyte subpopulations.

METHODS

Peripheral blood samples from 15 patients diagnosed with B-ALL were analyzed. Flow cytometry was used to analyze cellularity, expression level of CD38, CD39, and CD73, and frequency of [Formula: see text], and [Formula: see text] in lymphocyte subpopulations. Plasma was used for cytokines (by CBA kit) and adenine nucleosides/nucleotides detection (by HPLC).

RESULTS

Comparing B-ALL patients to health donors, we observed an increase of CD4 + and CD8 + T-cells. In addition, a decrease in CD38 expression in B and Treg subpopulations and an increase in CD39⁺ CD73⁺  frequency in Breg and CD8+ T-cells. Analyzing cytokines and adenine nucleosides/nucleotides, we found a decrease in TNF, IL-1β, and ADO concentrations, together with an increase in AMP in B-ALL patients' plasma.

CONCLUSION

As immunomodulators, the expression of ectonucleotidases might be associated with activation states, as well as the abundance of different cellular subsets. We observed a pro-tumor immunity expression profile in B-ALL patients at diagnosis, being associated with cell exhaustion and immune evasion in B-ALL.

Dysfunctional purinergic signaling correlates with disease severity in COVID-19 patients

Ectonucleotidases modulate inflammatory responses by balancing extracellular ATP and adenosine (ADO) and might be involved in COVID-19 immunopathogenesis. Here, we explored the contribution of extracellular nucleotide metabolism to COVID-19 severity in mild and severe cases of the disease. We verified that the gene expression of ectonucleotidases is reduced in the whole blood of patients with COVID-19 and is negatively correlated to levels of CRP, an inflammatory marker of disease severity. In line with these findings, COVID-19 patients present higher ATP levels in plasma and reduced levels of ADO when compared to healthy controls. Cell type-specific analysis revealed higher frequencies of CD39+ T cells in severely ill patients, while CD4+ and CD8+ expressing CD73 are reduced in this same group. The frequency of B cells CD39+CD73+ is also decreased during acute COVID-19. Interestingly, B cells from COVID-19 patients showed a reduced capacity to hydrolyze ATP into ADP and ADO. Furthermore, impaired expression of ADO receptors and a compromised activation of its signaling pathway is observed in COVID-19 patients. The presence of ADO in vitro, however, suppressed inflammatory responses triggered in patients’ cells. In summary, our findings support the idea that alterations in the metabolism of extracellular purines contribute to immune dysregulation during COVID-19, possibly favoring disease severity, and suggest that ADO may be a therapeutic approach for the disease.

Gallic acid modulates purine metabolism and oxidative stress induced by ethanol exposure in zebrafish brain

Gallic acid (GA) is a secondary metabolite found in plants. It has the ability to cross the blood-brain barrier and, through scavenging properties, has a protective effect in a brain insult model. Alcohol metabolism generates reactive oxygen species (ROS); thus, alcohol abuse has a deleterious effect on the brain. The zebrafish is a vertebrate often used for screening toxic substances and in acute ethanol exposure models. The aim of this study was to evaluate whether GA pretreatment (24 h) prevents the changes induced by acute ethanol exposure (1 h) in the purinergic signaling pathway in the zebrafish brain via degradation of extracellular nucleotides and oxidative stress. The nucleotide cascade promoted by the nucleoside triphosphate diphosphohydrolase (NTPDase) and 5'-nucleotidase was assessed by quantifying nucleotide metabolism. The effect of GA alone at 5 and 10 mg L^-1 did not change the nucleotide levels. Pretreatment with 10 mg L^-1 GA prevented an ethanol-induced increase in ATP and ADP levels. No significant difference was found between the AMP levels of the two pretreatment groups. Pretreatment with 10 mg L^-1 GA prevented ethanol-enhanced lipid peroxidation and dichlorodihydrofluorescein (DCFH) levels. The higher GA concentration was also shown to positively modulate against ethanol-induced effects on superoxide dismutase (SOD), but not on catalase (CAT). This study demonstrated that GA prevents the inhibitory effect of ethanol on NTPDase activity and oxidative stress parameters, thus consequently modulating nucleotide levels that may contribute to the possible protective effects induced by alcohol and purinergic signaling.

Hesperidin mitigates inflammation and modulates ectoenzymes activity and some cellular processes in complete Freund's adjuvant-induced arthritic rats

OBJECTIVES

This study was aimed at assessing the anti-arthritic effects of hesperidin on the inflammatory markers in serum/plasma, ectoenzymes activity in platelet, reactive oxygen species (ROS), apoptosis and cell cycle in bone marrow cells of a rat model of arthritis.

METHODS

Fifty-six adult female Wistar rats (245-274 g) were grouped into eight of seven rats each: control rats given normal saline or 40 mg/kg of hesperidin or 80 mg/kg of hesperidin, 0.2 mg/kg of dexamethasone, arthritic rats given normal saline, or 40 mg/kg of hesperidin or 80 mg/kg of hesperidin, and 0.2 mg/kg of dexamethasone. Myeloperoxidase and nitrate plus nitrite levels were evaluated in the plasma and serum, respectively. The ecto-nucleoside triphosphate diphosphohydrolases, ecto-5'-nucleotidase and ecto-adenosine deaminase activities were assessed in platelets. Subsequently, the cells of the bone marrow were obtained, and the assays for ROS, apoptosis and cell cycle were evaluated using flow cytometry.

KEY FINDINGS

The results showed that hesperidin mitigated inflammation, modulated adenosine nucleotides and nucleoside hydrolysing enzymes and levels, minimized ROS intracellularly, attenuated apoptotic process and activated cell cycle arrest in arthritic rat.

CONCLUSION

This study suggests that hesperidin could be a natural and promising anti-inflammatory compound for the management of arthritis.

Post-weaning social isolation impairs purinergic signaling in rat brain

Early life stressors, such as social isolation (SI), can disrupt brain development contributing to behavioral and neurochemical alterations in adulthood. Purinergic receptors and ectonucleotidases are key regulators of brain development in embryonic and postnatal periods, and they are involved in several psychiatric disorders, including schizophrenia. The extracellular ATP drives purinergic signaling by activating P2X and P2Y receptors and it is hydrolyzed by ectonucleotidases in adenosine, which activates P1 receptors. The purpose of this study was to investigate if SI, a rodent model used to replicate abnormal behavior relevant to schizophrenia, impacts purinergic signaling. Male Wistar rats were reared from weaning in group-housed or SI conditions for 8 weeks. SI rats exhibited impairment in prepulse inhibition and social interaction. SI presented increased ADP levels in cerebrospinal fluid and ADP hydrolysis in the hippocampus and striatum synaptosomes. Purinergic receptor expressions were upregulated in the prefrontal cortex and downregulated in the hippocampus and striatum. A_2A receptors were differentially expressed in SI prefrontal cortex and the striatum, suggesting distinct roles in these brain structures. SI also presented decreased ADP, adenosine, and guanosine levels in the cerebrospinal fluid in response to D-amphetamine. Like patients with schizophrenia, uric acid levels were prominently increased in SI rats after D-amphetamine challenge. We suggest that the SI-induced deficits in prepulse inhibition might be related to the SI-induced changes in purinergic signaling. We provide new evidence that purinergic signaling is markedly affected in a rat model relevant to schizophrenia, pointing out the importance of purinergic system in psychiatry conditions.

New insights into cytotoxic mechanisms of bozepinib against glioblastoma

Glioblastoma (GBM) is the most frequent and aggressive brain tumor in adults and the current treatments only have a modest effect on patient survival. Recent studies show that bozepinib (BZP), a purine derivative, has potential applications in cancer treatment. The aim of this study was to evaluate the effect of BZP against GBM cells, specially concerning the purinergic system. Thus, GBM cells (C6 and U138 cell lines) were treated with BZP and cell viability, cell cycle, and annexin/PI assays, and active caspase-3 measurements were carried out. Besides, the effect of BZP over the purinergic system was also evaluated in silico and in vitro. Finally, we evaluate the action of BZP against important markers related to cancer progression, such as Akt, NF-κB, and CD133. We demonstrate here that BZP reduces GBM cell viability (IC₅₀ = 5.7 ± 0.3 µM and 12.7 ± 1.5 µM, in C6 and U138 cells, respectively), inducing cell death through caspase-dependent apoptosis, autophagosome formation, activation of NF-κB, without any change in cell cycle progression or on the Akt pathway. Also, BZP modulates the purinergic system, inducing an increase in CD39 enzyme expression and activity, while inhibiting CD73 activity and adenosine formation, without altering CD73 enzyme expression. Curiously, one cycle of treatment resulted in enrichment of GBM cells expressing NF-κB and CD133⁺, suggesting resistant cells selection. However, after another treatment round, the resistant cells were eliminated. Altogether, BZP presented in vitro anti-glioma activity, encouraging further in vivo studies in order to better understand its mechanism of action.

Acute moderate-intensity aerobic exercise promotes purinergic and inflammatory responses in sedentary, overweight and physically active subjects

NEW FINDING

What is the central question of this study? How does moderate-intensity aerobic exercise affect the behaviour of purinergic enzymes in sedentary, overweight and physically active subjects? What is the relationship between purinergic and inflammatory responses triggered by exercise? What is the main finding and its importance? Moderate-intensity aerobic exercise modifies the activity of purinergic enzymes and the levels of nucleotides and nucleosides. These results are similar in subjects with different biological characteristics. 5'-Nucleotidase activity and adenosine levels are associated with inflammatory responses. This study suggests that a purinergic pathway is related to the inflammatory responses triggered by exercise.

ABSTRACT

Purinergic signalling is a mechanism of extracellular communication that modulates events related to exercise, such as inflammation and coagulation. Herein, we evaluated the effects of acute moderate-intensity exercise on the activities of purinergic enzymes and plasma levels of adenine nucleotides in individuals with distinct metabolic characteristics. We analysed the relationship between purinergic parameters, inflammatory responses and cardiometabolic markers. Twenty-four healthy males were assigned to three groups: normal weight sedentary (n = 8), overweight sedentary (n = 8) and normal weight physically active (n = 8). The volunteers performed an acute session of moderate-intensity aerobic exercise on a treadmill at 70% of V ̇ O 2 peak ; blood samples were drawn at baseline, immediately post-exercise and at 1 h post-exercise. Immediately post-exercise, all subjects showed increases in ATP, ADP, AMP and p-nitrophenyl thymidine 5'-monophosphate hydrolysis, while AMP hydrolysis remained increased at 1 h after exercise. High-performance liquid chromatography analysis demonstrated lower levels of ATP and ADP at post- and 1 h post-exercise in all groups. Conversely, adenosine and inosine levels increased at post-exercise, but only adenosine remained augmented at 1 h after exercise in all groups. With regard to inflammatory responses, the exercise protocol increased tumour necrosis factor α (TNF-α) and interleukin 8 (IL-8) concentrations in all subjects, but only TNF-α remained elevated at 1 h after exercise. Significant correlations were found between the activity of 5'-nucleotidase, adenosine levels, V ̇ O 2 peak , triglyceride, TNF-α and IL-8 levels. Our findings suggest a purinergic signalling pathway that participates, at least partially, in the inflammatory responses triggered by acute moderate-intensity exercise. The response of soluble nucleotidases to acute moderate exercise appears to be similar between subjects of different biological profiles.

Biochemical analysis of ectonucleotidases on primary rat vascular smooth muscle cells and in silico investigation of their role in vascular diseases

Vascular smooth muscle cells (VSMCs) exhibit a high degree of plasticity when they undergo the progression from a normal to a disease condition, which makes them a potential target for evaluating early markers and for the development of new therapies. Purinergic signalling plays a key role in vascular tonus control, ATP being an inductor of vasoconstriction, whereas adenosine mediates a vasodilation effect antagonising the ATP actions. The control of extracellular ATP and adenosine levels is done by ectonucleotidases, which represent a potential target to be evaluated in the progression of cardiovascular diseases. In this study, we analysed the basal activity and expression of the ectonucleotidases in aortic rat VSMCs, and we further performed in silico analysis to determine the expression of those enzymes in conditions that mimicked vascular diseases. Cultured in vitro VSMCs showed a prominent expression of Entpd1 followed by Entpd2 and Nt5e (CD73) and very low levels of Entpd3. Slightly faster AMP hydrolysis was observed when compared to ATP and ADP nucleotides. In silico analysis showed that the ectonucleotidases were modulated after induction of conditions that can lead to vascular diseases such as, hypertensive and hypotensive mice models (Nt5e); exposition to high-fat (Entpd1 and Entpd2) or high-phosphate (Nt5e) diet; mechanical stretch (Entpd1, Entpd2 and Nt5e); and myocardial infarction (Entpd1). Our data show that VSMCs are able to efficiently metabolise the extracellular nucleotides generating adenosine. The modulation of Entpd1, Entdp2 and Nt5e in vascular diseases suggests these ectoenzymes as potential targets or markers to be investigated in future studies.

Inosine prevents hyperlocomotion in a ketamine-induced model of mania in rats

Bipolar Disorder is a disorder characterized by alternating episodes of depression, mania or hypomania, or even mixed episodes. The treatment consists on the use of mood stabilizers, which imply serious adverse effects. Therefore, it is necessary to identify new therapeutic targets to prevent or avoid new episodes. Evidence shows that individuals in manic episodes present a purinergic system dysfunction. In this scenario, inosine is a purine nucleoside known to act as an agonist of A₁ and A_2A adenosine receptors. Thus, we aimed to elucidate the preventive effect of inosine on locomotor activity, changes in purine levels, and adenosine receptors density in a ketamine-induced model of mania in rats. Inosine pretreatment (25 mg/kg, oral route) prevented the hyperlocomotion induced by ketamine (25 mg/kg, intraperitoneal route) in the open-field test; however, there was no difference in hippocampal density of A₁ and A_2A receptors, where ketamine, as well as inosine, were not able to promote changes in immunocontent of the adenosine receptors. Likewise, no effects of inosine pretreatments or ketamine treatment were observed for purine and metabolic residue levels evaluated. In this sense, we suggest further investigation of signaling pathways involving purinergic receptors, using pharmacological strategies to better elucidate the action mechanisms of inosine on bipolar disorder. Despite the limitations, inosine administration could be a promising candidate for bipolar disorder treatment, especially by attenuating maniac phase symptoms, once it was able to prevent the hyperlocomotion induced by ketamine in rats.

Characterization and antiproliferative activity of glioma-derived extracellular vesicles

Aim: To characterize a method to isolate glioma-derived extracellular vesicles (GEVs) and understand their role in immune system modulation and glioma progression. Materials & methods: GEVs were isolated by differential centrifugation from C6 cell supernatant and characterized by size and expression of CD9, HSP70, CD39 and CD73. The glioma model was performed by injecting C6 glioma cells into the right striatum of Wistar rats in the following groups: controls (C6 cells alone), coinjection (C6 cells + GEVs) and GEVs by intranasal administration followed by immune cells, tumor size and cells proliferation analyses. Results: GEVs presented uniform size (175 nm), expressed CD9, HSP70, CD39, CD73 and produced adenosine. In vivo, we observed a reduction in tumor size, in cell proliferation (Ki-67) and in a regulatory cell marker (FoxP3). Conclusion: GEVs, administered before or at tumor challenge, have antiproliferative properties and reduce regulatory cells in the glioma microenvironment.

Acute Liver Failure Induces Glial Reactivity, Oxidative Stress and Impairs Brain Energy Metabolism in Rats

Acute liver failure (ALF) implies a severe and rapid liver dysfunction that leads to impaired liver metabolism and hepatic encephalopathy (HE). Recent studies have suggested that several brain alterations such as astrocytic dysfunction and energy metabolism impairment may synergistically interact, playing a role in the development of HE. The purpose of the present study is to investigate early alterations in redox status, energy metabolism and astrocytic reactivity of rats submitted to ALF. Adult male Wistar rats were submitted either to subtotal hepatectomy (92% of liver mass) or sham operation to induce ALF. Twenty-four hours after the surgery, animals with ALF presented higher plasmatic levels of ammonia, lactate, ALT and AST and lower levels of glucose than the animals in the sham group. Animals with ALF presented several astrocytic morphological alterations indicating astrocytic reactivity. The ALF group also presented higher mitochondrial oxygen consumption, higher enzymatic activity and higher ATP levels in the brain (frontoparietal cortex). Moreover, ALF induced an increase in glutamate oxidation concomitant with a decrease in glucose and lactate oxidation. The increase in brain energy metabolism caused by astrocytic reactivity resulted in augmented levels of reactive oxygen species (ROS) and Poly [ADP-ribose] polymerase 1 (PARP1) and a decreased activity of the enzymes superoxide dismutase and glutathione peroxidase (GSH-Px). These findings suggest that in the early stages of ALF the brain presents a hypermetabolic state, oxidative stress and astrocytic reactivity, which could be in part sustained by an increase in mitochondrial oxidation of glutamate.

P2X7 Purinergic Receptor Is Involved in the Pathophysiology of Mania: a Preclinical Study

The pathophysiology of bipolar disorder remains incompletely elucidated. The purinergic receptor, P2X7 (P2X7R), plays a central role in neuroinflammation, the establishment, and maintenance of microglial activation and neuronal damage/death, all characteristics of bipolar disorder pathology. The present study aims to explore the participation of the P2X7R in a preclinical pharmacological model of mania. We analyzed the modulatory effects of the P2X7R antagonist, brilliant blue, on behavior, monoamines, gene expression, serum purine levels, and cell typing in a pharmacological model of mania induced by D-amphetamine (AMPH) in mice. Our results corroborate an association between the P2X7 receptor and the preclinical animal model of mania, as demonstrated by the decreased responsiveness to AMPH in animals with pharmacologically blocked P2X7R. This study further suggests a possible dopaminergic mechanism for the action of P2X7 receptor antagonism. Additionally, we observed increased peripheral levels of adenosine, a neuroprotective molecule, and increased central expression of Entpd3 and Entpd1 leading to the hydrolysis of ATP, a danger signal, possibly as an attempt to compensate for the damage induced by AMPH. Lastly, P2X7R antagonism in the AMPH model was found to potentially modulate astrogliosis. Our results support the hypothesis that P2X7R plays a vital role in the pathophysiology of mania, possibly by modulating the dopaminergic pathway and astrogliosis, as reflected in the behavioral changes observed. Taken together, this study suggests that a purinergic system imbalance is associated with the AMPH-induced preclinical animal model of mania. P2X7R may represent a promising molecular therapeutic target for bipolar disorder.

Effect of quercetin on E-NTPDase/E-ADA activities and cytokine secretion of complete Freund adjuvant-induced arthritic rats

The effect of quercetin was assessed in rats induced with complete Freund adjuvant (CFA). Arthritis scores, paw oedema, latency, activities of myeloperoxidase (MPO), ectonucleoside triphosphate diphosphohydrolase (E-NTPDase), and ectoadenosine deaminase (E-ADA) in lymphocytes were determined. Furthermore, nucleotide and nucleoside levels as well as the secretion of pro- and anti-inflammatory cytokines were evaluated. Animals were treated with saline and quercetin in doses of 5, 25, and 50 mg/kg for 45 days. The result revealed that quercetin (50 mg/kg) reduced arthritis score and paw oedema, and increased the latency in the thermal hyperalgesia test. Histopathological analysis showed that all the doses of quercetin reduced infiltration of inflammatory cells. MPO activity was increased in the arthritis group; however, quercetin reduced this activity. E-NTPDase activity was increased in lymphocytes of arthritis rats, and treatment with quercetin reversed this increase. However, E-ADA activity was reduced in the arthritis group, and treatment with quercetin modulated the activity of this enzyme in arthritis rat groups. Serum adenosine levels were increased in arthritis, and the levels were lowered with quercetin treatment. Quercetin treatment in arthritis groups decreased the elevated levels of cytokines in the arthritis control group. Thus, quercetin demonstrated an anti-inflammatory effect, and this flavonoid may be a promising natural compound for the treatment of arthritis. SIGNIFICANCE OF THE STUDY: Quercetin may represent a potential therapeutic compound in the treatment of rheumatoid arthritis. Findings from this study indicate that quercetin suppresses swelling and attenuates the underlying inflammatory responses. This is the first report where quercetin was shown to modulate the immune response to arthritis via attenuation of the purinergic system (E-NTPDase and E-ADA activities) and the levels of IFN-gamma and IL-4. Thus, this work is relevant to basic research and may be translated into clinical practice.

Lipotoxicity-associated inflammation is prevented by guarana (Paullinia cupana) in a model of hyperlipidemia

Hyperlipidemia causes lipotoxicity which prompts an inflammatory response linked to the development of cardiovascular diseases. Natural compounds have been receiving special attention for its potential to treat diseases, inexpensiveness, and safety. Guarana (Paullinia cupana) has demonstrated notable anti-inflammatory and antioxidant effects, which may prevent chronic diseases caused by changes in lipid profile. Thus, this study aims to evaluate the effect of guarana powder (Paullinia cupana) in the purine metabolism and inflammatory profile in lymphocytes and serum of rats with Poloxamer-407-induced hyperlipidemia. Pretreatment with guarana 12.5, 25, and 50 mg/kg/day or caffeine (0.2 mg/kg/day) by gavage was applied to adult male Wistar rats for a period of 30 days. As a comparative standard, we used simvastatin (0.04 mg/kg) post-induction. Hyperlipidemia was acutely induced with intraperitoneally injection of Poloxamer-407 (500 mg/kg). Guarana powder and caffeine increased the activity of the E-NTPDase (ecto-apyrase), and all pretreatments decreased the E-ADA (ecto-adenosine deaminase) activity, reducing the inflammatory process caused by lipotoxicity. In hyperlipidemic rats, ATP levels were increased while adenosine levels were decreased, guarana and caffeine reverted these changes. Guarana powder, caffeine, and simvastatin also prevented the increase in INF-γ and potentiated the increase in IL-4 levels, promoting an anti-inflammatory profile. Guarana promoted a more robust effect than caffeine. Our results show that guarana powder and caffeine have an anti-inflammatory as seen by the shift from a proinflammatory to an anti-inflammatory profile. The effects of guarana were more pronounced, suggesting that guarana powder may be used as a complementary therapy to improve the lipotoxicity-associated inflammation.

Activity and expression of E-NTPDase is altered in peripheral lymphocytes of systemic lupus erythematosus patients

BACKGROUND

Systemic lupus erythematosus (SLE) is an inflammatory autoimmune disease, where there is irreversible breakdown of immunological self-tolerance. Extracellular adenosine triphosphate (ATP) and adenosine are signaling molecules that play an important part in the immune response. During inflammation and the immune response, a group of enzymes control these molecules, including ectonucleoside triphosphate diphosphohydrolase (E-NTPDase), E-5'-nucleotidase, and ecto-adenosine deaminase (E-ADA). We determined the activity and expression of E-NTPDase, the expression of E-5'-nucleotidase, the activity of E-ADA in lymphocytes and serum of SLE patients.

METHODS

This study involved 35 patients with SLE and 30 healthy subjects as a control group. E-NTPDase activity and expression were increased in lymphocytes from SLE patients (31% and 37% for activity and expression, respectively) compared with the control group.

RESULTS

An approximately 42% increase in E-ADA activity in lymphocytes was observed in SLE patients compared with the control group, in serum the ADA activity was decreased by 57% in SLE patients. Expression of E-5'-nucleotidase was not changed in SLE patients.

CONCLUSIONS

E-NTPDase and E-ADA perform key functions in the modulation of the immune and inflammatory response in SLE.

Hypothyroidism and hyperthyroidism change ectoenzyme activity in rat platelets

The purinergic system has an important role in the regulation of vascular functions. The interference of thyroid hormones in this system and in cardiovascular events has been studied in recent years. However, the mechanisms involved in vascular, purinergic, and oxidative changes in thyroid disorders are not completely understood. Therefore, the present study aimed to assess purinergic enzyme activity in platelets from rats with hypothyroidism and hyperthyroidism induced, respectively, by continuous exposure to methimazole (MMI) at 20 mg/100 mL or L-thyroxine at 1.2 mg/100 mL in drinking water for 1 month. Results showed that rats exposed to L-thyroxine had a significant decrease in NTPDase activity, wherein ATP hydrolysis was 53% lower and ADP hydrolysis was 40% lower. Moreover, ecto-5'-nucleotidase activity was decreased in both groups, by 39% in the hypothyroidism group and by 52% in the hyperthyroidism group. On the other hand, adenosine deaminase (ADA) activity was increased in hyperthyroidism (75%), and nucleotide pyrophosphatase/phosphodiesterase (NPP) activity was increased in animals with hypothyroidism (127%) and those with hyperthyroidism (128%). Our findings suggest that changes in purinergic enzyme and purine levels could contribute to the undesirable effects of thyroid disturbances. Moreover, oxidative stress and, in particular, a high level of ROS production, showed a causal relation with changes in ectonucleotidase activity and nucleotide and nucleoside levels.

Nucleotide and nucleoside involvement in immunomodulation in experimental Chagas disease

The aim of this study was to evaluate whether Trypanosma cruzi infections cause alterations in the levels of seric purines, which could contribute to host immunomodulation. Twelve mice were divided into two groups identified as control (uninfected) and infected (T. cruzi) groups. The influence of the disease on seric purine levels was verified on day 20 post-infection (PI) by HPLC. Infected mice had circulating trypomastigotes during the experiment, as well as amastigote forms in the heart associated with inflammatory infiltrates. Increases on adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine (ADO), inosine (INO), and uric acid (URIC) levels were observed in the infected animals, while the adenosine monophosphate (AMP) and xanthine (XAN) levels were reduced compared with mice of the control group, indicating a possible impairment on the purinergic system, and consequently, on the immune system during the clinical course of the disease. In summary, the T. cruzi infection alters the seric purine levels, and consequently, modulates the immune system.

Antacids' side effect hyperuricaemia could be alleviated by long-term aerobic exercise via accelerating ATP turnover rate

Hyperuricemia is the term for an abnormally high serum uric acid level. Many factors contribute to hyperuricemia, however no definite correlation between proton pump inhibitors (PPIs) and hyperuricemia has been reported before. Physical exercise also decreases serum uric acid levels. However, the detailed biochemical-regulatory mechanisms remain unknown. Here we found that adenylate deaminase activities are much higher in hyperuricemia patients than in the healthy people. Therefore, the patients have higher levels of adenosine metabolites hypoxanthine and uric acid. Acid-inhibitory drugs (antacids) significantly increased serum uric acid level and may lead to gout in the hyperuricemia patient. Long-term aerobic exercise significantly increased serum phosphorus and decreased serum ATP and its metabolites, and therefore decreased serum uric acid. Antacids slow down the ATP turnover rate and result in serum uric acid elevation subsequently. While the long-term aerobic exercise decreases serum uric acid levels by accelerating ATP turnover rate. The results imply that long-term aerobic exercise may be a useful strategy to prevent and treat hyperuricaemia.

Diphenyl diselenide modulates nucleotidases, reducing inflammatory responses in the liver of Toxoplasma gondii-infected mice

The aim of this study was to verify the effect of diphenyl diselenide (PhSe)2 on hepatic nucleotidases and on the concentration of purines in mice infected by Toxoplasma gondii. The animals were divided into four groups: Group A (uninfected), Group B (uninfected and treated with (PhSe)2), Group C (infected), and Group D (infected and treated with (PhSe)2). The inoculation (groups C and D) was performed with 50 cysts of T. gondii (ME-49 strain). Mice from groups B and D were treated with 5 μmol kg-1 of (PhSe)2. Liver tissue from infected mice showed less severe inflammation, elevated ATP/ADO ratio, elevated NTPDase, 5'nucleotidase, and ADA activities compared to the uninfected group (Group A; P < 0.05). However, infected and treated mice showed decreased ATP levels and elevated ADO levels, as well as higher NTPDase and 5'nucleotidase activities and decreased ADA activity in the hepatic tissue compared to the infected group (P < 0.05). Moreover, the (PhSe)2 treatment of infected mice reduced the hepatic inflammation and showed an immunomodulatory effect on ectonucleotidases of hepatic lymphocytes, which it returned to basal levels. Therefore, chronic infection by T. gondii induces hepatic inflammation in mice, and it is possible that purine levels and nucleotidase activities in hepatic tissue are related to the pathogenesis of the infection in this tissue. The treatment with (PhSe)2 was able to reverse the hepatic inflammation in mice chronically infected, possibly due to the modulation of purinergic enzymes that produce an anti-inflammatory profile through the purinergic system in the liver tissue.

Pretreatment with quercetin prevents changes in lymphocytes E-NTPDase/E-ADA activities and cytokines secretion in hyperlipidemic rats

Hyperlipidemia (HL) is a condition associated with endothelial dysfunction and inflammatory disorders. Purinergic system ectoenzymes play an important role in modulating the inflammatory and immune response. This study investigated whether the preventive treatment with quercetin is able to prevent changes caused by hyperlipidemia in the purinergic system, through the activities of E-NTPDase and E-ADA in lymphocytes, and quantify the nucleotides and nucleoside, and the secretion of anti- and proinflammatory cytokines. Animals were divided into saline/control, saline/quercetin 5 mg/kg, saline/quercetin 25 mg/kg, saline/quercetin 50 mg/kg, saline/simvastatin (0.04 mg/kg), hyperlipidemia, hyperlipidemia/quercetin 5 mg/kg, hyperlipidemia/quercetin 25 mg/kg, hyperlipidemia/quercetin 50 mg/kg, and hyperlipidemia/simvastatin. Animals were pretreated with quercetin for 30 days and hyperlipidemia was subsequently induced by intraperitoneal administration of 500 mg/kg of poloxamer-407. Simvastatin was administered after the induction of hyperlipidemia. Lymphocytes were isolated and E-NTPDase and E-ADA activities were determined. Serum was separated for the cytokines and nucleotide/nucleoside quantification. E-NTPDase and E-ADA activities were increased in lymphocytes from hyperlipidemic rats and pretreatment with quercetin was able to prevent the increase in the activities of these enzymes caused by hyperlipidemia. Hyperlipidemic rats when receiving pretreatment with quercetin and treatment with simvastatin showed decreased levels of ATP and ADP when compared to the untreated hyperlipidemic group. The IFN-γ and IL-4 cytokines were increased in the hyperlipidemic group when compared with control group, and decreased when hyperlipidemic rats received the pretreatment with quercetin. However, pretreatment with quercetin was able to prevent the alterations caused by hyperlipidemia probably by regulating the inflammatory process. We can suggest that the quercetin is a promising compound to be used as an adjuvant in the treatment of hyperlipidemia.

Post-thyroidectomy hypothyroidism increases the expression and activity of ectonucleotidases in platelets: Possible involvement of reactive oxygen species

Signaling mediated by purines is a widespread mechanism of cell-cell communication related to vasomotor responses and the control of platelet function in the vascular system. However, little is known about the involvement of this signaling as well as the role of reactive oxygen species (ROS) in the development of hypothyroidism. Therefore, the present study investigates changes in the purinergic system, including enzyme activities and expression in platelets, and oxidative profiles in patients with post-thyroidectomy hypothyroidism. The nucleoside triphosphate diphosphohydrolase 1 (NTPDase/CD39) expression in patients increased by 40%, and the adenosine triphosphate (ATP) or adenosine diphosphate (ADP) hydrolyzing activity increased by 82% and 70%, respectively. The activities of ecto-5´-nucleotidase and adenosine deaminase (ADA) also significantly enhanced (39% and 52%, respectively), which correlates with a 45% decrease in adenosine concentration. Furthermore, these patients demonstrated an increased production of ROS (42%), thiobarbituric acid reactive substances (TBARS) (115%), carbonyl protein (30%) and a decreased glutathione S-transferase (GST) activity (20%). This study demonstrates that hypothyroidism interferes with adenine nucleoside and nucleotide hydrolysis and this is correlated with oxidative stress, which might be responsible for the increase in ADA activity. This increase causes rapid adenosine deamination, which can generate a decrease in their concentration in the systemic circulation, which can be associated with the development of vascular complications.

Sepsis induced by cecal ligation and perforation (CLP) alters nucleotidase activities in platelets of rats

Sepsis is a potentially lethal condition, and it is associated with platelet alterations. The present study sought to investigate the activity of ecto-nucleoside triphosphate diphosphohydrolase (E-NTPDase), E-5'-nucleotidase, and ecto-adenosine deaminase (E-ADA) in the platelets of rats that were induced with sepsis. Male Wistar rats were divided into three groups of ten animals each: a negative control group (normal; NC); a group that underwent surgical procedures (sham); and a group that underwent cecal ligation and perforation (CLP). The induction of sepsis was confirmed by bacteremia, and the causative pathogen identified was Escherichia coli. Hematological parameters showed leukocytosis and thrombocytopenia in animals in the septic group. The results also revealed that there were significant (p < 0.05) increases in adenosine triphosphate (ATP) and adenosine monophosphate (AMP) hydrolyses, and in the deamination of adenosine in the CLP group compared to the sham and control groups. Conversely, ADP hydrolysis was significantly decreased (p < 0.05) in the CLP group compared to the sham and control groups. Purine levels were analyzed by high-performance liquid chromatography (HPLC) in serum samples from control, sham, and CLP groups. Increased concentrations of ATP, adenosine, and inosine were found in the CLP group compared to the sham and control groups. Conversely, the concentrations of ADP and AMP in the CPL group were not significantly altered. We suggest that alterations in hematological parameters, nucleotide hydrolysis in platelets, and nucleotide concentrations in serum samples of rats with induced sepsis may be related to thromboembolic events.

Methionine and/or Methionine Sulfoxide Alter Ectoenzymes Activities in Lymphocytes and Inflammatory Parameters in Serum from Young Rats: Acute and Chronic Effects

In this study we investigated the effect of acute and chronic treatment with Met and/or methionine sulfoxide (MetO) on ectonucleotidases and cholinesterases activities from lymphocytes and purine derivatives compounds, C-protein reactive, interleukin-10, interleukin-6, and tumor necrosis factor-α levels in serum of young rats. Adenosine triphosphate hydrolysis was decreased in lymphocytes 1 h after treatment by MetO and Met + MetO. However, adenosine triphosphate and adenosine diphosphate hydrolysis in lymphocytes was increased in the groups MetO and Met + MetO and adenosine deaminase activity was increased in MetO 3 h after the treatment. Acetylcholinesterase activity was increased in lymphocytes after 3 h and 21 days of treatment by MetO and Met + MetO, while serum butyrycholinesterase activity was decreased after 1 h and 21 days of treatment in the same groups. In chronic treatment, interleukin-6 and tumor necrosis factor-α level were increased, while that interleukin-10 level was decreased by Met, MetO, and Met + MetO when compared to control group. C-protein reactive level was increased by MetO and Met + MetO. Adenosine triphosphate and adenosine monophosphate levels were reduced in all amino acids treated groups, while adenosine diphosphate and hypoxanthine were enhanced by MetO and Met + MetO. Adenosine and xanthine were reduced in the MetO group, whereas inosine levels were decreased in the MetO and Met + MetO groups. These findings help to understand the inflammatory alterations observed in hypermethioninemia.

Cellular Migration Ability Is Modulated by Extracellular Purines in Ovarian Carcinoma SKOV-3 Cells

Extracellular nucleotides and nucleosides have emerged as important elements regulating tissue homeostasis. Acting through specific receptors, have the ability to control gene expression patterns to direct cellular fate. We observed that SKOV-3 cells express the ectonucleotidases: ectonucleotide pyrophosphatase 1 (ENPP1), ecto-5'-nucleotidase (NT5E), and liver alkaline phosphatase (ALPL). Strikingly, in pulse and chase experiments supplemented with ATP, SKOV-3 cells exhibited low catabolic efficiency in the conversion of ADP into AMP, but they were efficient in converting AMP into adenosine. Since these cells release ATP, we proposed that the conversion of ADP into AMP is a regulatory node associated with the migratory ability and the mesenchymal characteristics shown by SKOV-3 cells under basal conditions. The landscape of gene expression profiles of SKOV-3 cell cultures treated with apyrase or adenosine demonstrated similarities (e.g., decrease FGF16 transcript) and differences (e.g., the negative regulation of Wnt 2, and 10B by adenosine). Thus, in SKOV-3 we analyzed the migratory ability and the expression of epithelium to mesenchymal transition (EMT) markers in response to apyrase. Apyrase-treatment favored the epithelial-like phenotype, as revealed by the re-location of E-cadherin to the cell to cell junctions. Pharmacological approaches strongly suggested that the effect of Apyrase involved the accumulation of extracellular adenosine; this notion was strengthened when the incubation of the SKOV-3 cell with α,β-methylene ADP (CD73 inhibitor) or adenosine deaminase was sufficient to abolish the effect of apyrase on cell migration. Overall, adenosine signaling is a fine tune mechanism in the control of cell phenotype in cancer. J. Cell. Biochem. 118: 4468-4478, 2017. © 2017 Wiley Periodicals, Inc.

Manganese(II) Chloride Alters Nucleotide and Nucleoside Catabolism in Zebrafish (Danio rerio) Adult Brain

ATP and adenosine, the main signaling molecules of purinergic system, are involved in toxicological effects induced by metals. The manganese (Mn) exposure induces several cellular changes, which could interfere with signaling pathways, such as the purinergic system. In this study, we evaluated the effects of exposure to manganese(II) chloride (MnCl₂) during 96 h on nucleoside triphosphate diphosphohydrolase (NTPDase), ecto-5'-nucleotidase, and adenosine deaminase (ADA) activities, followed by analyzing the gene expression patterns of NTPDases (entpd1, entpd2a.1, entpd2a.2, entpd2-like, entpd3) and ADA (ADA ₁ , ADA _2.1 , ADA _2.2 , ADAasi, ADAL) families in zebrafish brain. In addition, the brain metabolism of nucleotides and nucleosides was evaluated after MnCl₂ exposure. The results showed that MnCl₂ exposure during 96 h inhibited the NTPDase (1.0 and 1.5 mM) and ecto-ADA (0.5, 1.0, and 1.5 mM) activities, further decreasing ADA2.1 expression at all MnCl₂ concentrations analyzed. Purine metabolism was also altered by the action of MnCl₂. An increased amount of ADP appeared at all MnCl₂ concentrations analyzed; however, AMP and adenosine levels are decreased at the concentrations of 1.0 and 1.5 mM MnCl₂, whereas decreased inosine (INO) levels were observed at all concentrations tested. The findings of this study demonstrated that MnCl₂ may inhibit NTPDase and ecto-ADA activities, consequently modulating nucleotide and nucleoside levels, which may contribute for the toxicological effects induced by this metal.

Increased oxidative stress alters nucleosides metabolite levels in sickle cell anemia

OBJECTIVES

This study was conducted to assess the markers of oxidative stress, myeloperoxidase (MPO), acetylcholinesterase (AChE) and xanthine oxidase (XO) activities as well as the levels of nucleotide metabolites in sickle cell anemia (SCA) patients.

METHODS

Fifteen SCA treated patients and 30 health subjects (control group) were selected. The markers of oxidative stress (levels of reactive oxygen species (ROS), plasma proteins, carbonyl content, lipid peroxidation (TBARS), total thiols (T-SH), glutathione and catalase activity), MPO, AChE and XO activities as well as the levels of nucleotide metabolites were measured in SCA patients.

RESULTS

ROS, thiobarbituric acid-reactive substances (TBARS) and T-SH levels as well as the activities of catalase and MPO were significantly increased while glutathione level was reduced in SCA patients. Furthermore, a significant (P < 0.001) increase in hypoxanthine level was demonstrated in SCA patients. However, the serum levels for xanthine (P < 0.01) and uric acid (P < 0.001) were decreased in SCA patients. A significant (P < 0.001) decrease in XO activity was detected in SCA patients.

DISCUSSION

The altered parameters in SCA patients suggest that the generation and impairment of oxidative stress in this disease as well as antioxidant markers are contributory factors towards cellular redox homeostasis and alteration of purine metabolites.

Peripheral adenosine levels in euthymic patients with bipolar disorder

Recent evidence points to the involvement of the purinergic signaling in the pathophysiology of bipolar disorder. The aim of this study was to assess the serum levels of adenosine and to evaluate its relation to functioning in 24 euthymic patients with bipolar disorder type I and in 25 matched healthy controls. Subjects were evaluated using the functioning assessment short test. Serum purine levels were measured by high pressure liquid chromatography. Our results show a decrease in serum adenosine levels in bipolar disorder patients compared with controls (t= -4.8, df= 43.96, p<0.001). Moreover, a significant negative correlation was found between patient adenosine levels and depression scale scores (r= -0.642, p= 0.001). Higher functional impairment was linked to lower levels of adenosine in patients (rho= -0.551, p= 0.008). Taken together, our results provide evidence for a purinergic imbalance in bipolar disorder, specifically an adenosinergic dysfunction. Our results also indicate a relation between adenosine levels and the functional impairment caused by the disorder, which could demonstrate a potential relation of adenosine levels in worsening of symptoms.

Altered extracellular ATP, ADP, and AMP hydrolysis in blood serum of sedentary individuals after an acute, aerobic, moderate exercise session

Nucleotidases participate in the regulation of physiological and pathological events, such as inflammation and coagulation. Exercise promotes distinct adaptations, and can influence purinergic signaling. In the present study, we investigated soluble nucleotidase activities in the blood serum of sedentary young male adults at pre- and post-acute moderate aerobic exercise. In addition, we evaluated how this kind of exercise could influence adenine nucleotide concentrations in the blood serum. Sedentary individuals were submitted to moderate aerobic exercise on a treadmill; blood samples were collected pre- and post-exercise, and serum was separated for analysis. Results showed increases in ATP, ADP, and AMP hydrolysis post-exercise, compared to pre-exercise values. The ecto-nucleotide pyrophosphatase/phosphodiesterase was also evaluated, showing an increased activity post-exercise, compared to pre-exercise. Purine levels were analyzed by HPLC in the blood serum, pre- and post-exercise. Decreased levels of ATP and ADP were found post-exercise, in contrast with pre-exercise values. Conversely, post-exercise levels of adenosine and inosine increased compared to pre-exercise levels. Our results indicate an influence of acute exercise on ATP metabolism, modifying enzymatic behavior to promote a protective biological environment.

Analysis of Extracellular Nucleotide Metabolism in Adult Zebrafish After Embryological Exposure to Valproic Acid

Autism is a neurodevelopmental disorder characterized by symptoms related to stereotyped movements, deficits in social interaction, impaired communication, anxiety, hyperactivity, and the presence of restricted interests. Evidence indicates an important role of extracellular ATP and adenosine as signaling molecules in autism. ATP hydrolysis by ectonucleotidases is an important source of adenosine, and adenosine deaminase (ADA) contributes to the control of the nucleoside concentrations. Considering zebrafish is an animal model that may contribute towards to understanding the mechanisms that underlie social behavior, we investigated the purinergic signaling in a model of embryological exposure to valproic acid (VPA) that induces social interaction deficit in adult zebrafish. We demonstrated embryological exposure to VPA did not change ATP and ADP hydrolysis in zebrafish at 120 dpf, and the cytosolic (soluble) ADA activity was not altered. However, we observed an increase of AMP hydrolysis (12.5 %) whereas the ecto-ADA activity was decreased (19.2 %) in adult zebrafish submitted to embryological exposure to VPA. Quantitative reverse transcription PCR (RT-PCR) analysis showed changes on ntpd8, ADA 2.1, and A2a1 mRNA transcript levels. Brain ATP metabolism showed a rapid catabolism of ATP and ADP, whereas the extracellular metabolism of AMP and adenosine (ADO) occurred slowly. We demonstrated that embryological exposure to VPA altered biochemical and molecular parameters related to purinergic system in adult zebrafish. These findings indicate that the enzyme activities involved in the control of ATP and adenosine levels may be involved in the pathophysiological mechanisms of diseases related to the impairment of social interaction, such as autism.

Methotrexate up-regulates ecto-5'-nucleotidase/CD73 and reduces the frequency of T lymphocytes in the glioblastoma microenvironment

Glioblastoma multiforme (GBM) is a deadly cancer characterized by a pro-tumoral immune response. T-regulatory (Treg) lymphocytes suppress effector immune cells through cytokine secretion and the adenosinergic system. Ecto-5'-nucleotidase/CD73 plays a crucial role in Treg-mediated immunosuppression in the GBM microenvironment (GME). Methotrexate (MTX) is an immunosuppressive drug that can increase the extracellular concentration of adenosine. In this manuscript, C6 GBM cells were treated with 1.0 μM MTX, and ecto-5'-nucleotidase/CD73 expression and extracellular AMP metabolism were analyzed in vitro. For in vivo studies, rats with implanted GBM were treated for 10 days with MTX-loaded lipid-core nanocapsules (MTX-LNCs, 1 mg/kg/day). The activity of ectonucleotidase and the expression of NTPDase1/CD39 and ecto-5'-nucleotidase/CD73 were measured. The frequencies of T lymphocytes (CD3(+)CD4(+), CD3(+)CD8(+), and CD4(+)CD25(high)CD39(+)) were quantified. In vitro, treatment with MTX increased CD73 expression and activity in C6 cells, which is in agreement with higher levels of extracellular adenosine. In vivo, MTX-LNC treatment increased CD39 expression on CD3(+)CD8(+) lymphocytes. In addition, MTX-LNC treatment up-regulated CD73 expression in tissue isolated from GBM, a finding that is in agreement with the higher activity of this enzyme. More specifically, the treatment increased CD73 expression on CD3(+)CD4(+) and CD3(+)CD8(+) lymphocytes. Treatment with MTX-LNCs decreased the frequencies of T-cytotoxic, T-helper, and Treg lymphocytes in the GME. Although more studies are necessary to better understand the complex cross-talk mediated by supra-physiological concentrations of adenosine in the GME, these studies demonstrate that MTX treatment increases CD73 enzyme expression and AMP hydrolysis, leading to an increase in adenosine production and immunosuppressive capability.

Involvement of purinergic system in the release of cytokines by macrophages exposed to glioma-conditioned medium

Macrophages are involved in cancer progression. M1 macrophages have an antitumor effect, whereas M2 phenotype are associated with tumor growth. The progression of gliomas involves the participation of an inflammatory microenvironment. Adenosine triphosphate (ATP) can act as pro-inflammatory signal, whereas adenosine has opposite properties. The biological effects of extracellular nucleotides/nucleosides mediated by purinergic receptors are controlled by ectonucleotidases. In the present work, we evaluated whether glioma-conditioned medium (GL-CM) modulates macrophage differentiation and the participation of ATP and adenosine in the release of pro-and anti-inflammatory cytokines by these cells. The results show that macrophages exposed to GL-CM were modulated to an M2-like phenotype. HPLC analysis of GL-CM demonstrated the presence of significant amounts of ATP and its metabolites. Macrophages exposed to GL-CM presented decreased ATP and AMP hydrolysis and increased IL-10 and MCP-1 secretion, effects that were diminished by P1 or P2 antagonists. GL-CM did not alter the release of IL-6 by macrophages, although treatment with ATP promoted an increase in the release of IL-6, which was prevented by a P2X7 antagonist. In summary, we found that A2A and P2X7 activation is necessary for IL-10, MCP-1, and IL-6 release by macrophages exposed to GL-CM, which, in turn, modulates the macrophages to M2-phenotype. The present study establishes a relationship between M2-like polarization, cytokine release and purinergic receptor activation in macrophages exposed to GL-CM. Therefore, the data presented herein contributes to advancing in the field of cancer-related inflammation and point specific purinergic receptors as targets for modulation of the phenotype of glioma-associated macrophages.

Effect of Uncaria tomentosa extract on purinergic enzyme activities in lymphocytes of rats submitted to experimental adjuvant arthritis model

BACKGROUND

Considering that adjuvant arthritis is an experimental model of arthritis widely used for preclinical testing of numerous anti-arthritic agents, which were taken by a large number of patients worldwide, it is of great interest to investigate the therapeutic action of compounds with anti-inflammatory properties, such as Uncaria tomentosa extract. Moreover, there are no studies demonstrating the effect of U. tomentosa on the metabolism of adenine nucleotides published so far. Thus, the purpose of the present study is to investigate the effects of U. tomentosa extract on E-NTPDase and E-ADA activities in lymphocytes of Complete Freund's Adjuvant (CFA) arthritis induced rats.

METHODS

To evaluate the effect of U. tomentosa extract on the activity of E-NTPDase and ADA in lymphocytes, the rats were submitted to an experimental adjuvant arthritis model. Peripheral lymphocytes were isolated and E-NTPDase and E-ADA activities were determined. Data were analyzed by a one- or two-way ANOVA. Post hoc analyses were carried out by the Student-Newman-Keuls (SNK) Multiple Comparison Test.

RESULTS

E-NTPDase activity was increased in arthritic untreated. Arthritic rats which received U. tomentosa extract, presented similar results to the control group. However, results obtained for adenosine hydrolysis by E-ADA were not altered in arthritic rats. U. tomentosa extract did not alter E-NTPDase and E-ADA activity in healthy animals.

CONCLUSIONS

The present investigation supports the hypothesis that the increased E-NTPDase activity verified in arthritic rats might be an attempt to maintain basal levels of ATP and ADP in the extracellular medium, since the arthritis induction causes tissue damage and, consequently, large amounts of ATP are released into this milieu. Also, it highlights the possibility to use U. tomentosa extract as an adjuvant to treat arthritis.

Unpredictable Chronic Stress Alters Adenosine Metabolism in Zebrafish Brain

Stress is considered a risk factor for several human disorders. Despite the broad knowledge of stress responses in mammals, data on the relationship between unpredictable chronic stress (UCS) and its effects on purinergic signaling are limited. ATP hydrolysis by ectonucleotidases is an important source of adenosine, and adenosine deaminase (ADA) contributes to the control of the nucleoside concentrations. Considering that some stress models could affect signaling systems, the objective of this study was to investigate whether UCS alters ectonucleotidase and ADA pathway in zebrafish brain. Additionally, we analyzed ATP metabolism as well as ada1, ada2.1, ada2.2, adaL, and adaasi gene expression in zebrafish brain. Our results have demonstrated that UCS did not alter ectonucleotidase and soluble ADA activities. However, ecto-ADA activity was significantly decreased (26.8%) in brain membranes of animals exposed to UCS when compared to the control group. Quantitative reverse transcription PCR (RT-PCR) analysis did not show significant changes on ADA gene expression after the UCS exposure. The brain ATP metabolism showed a marked increase in adenosine levels (ADO) in animals exposed to UCS. These data suggest an increase on extracellular adenosine levels in zebrafish brain. Since this nucleoside has neuromodulatory and anxiolytic effects, changes in adenosine levels could play a role in counteracting the stress, which could be related to a compensatory mechanism in order to restore the homeostasis.

Influence of infection by Toxoplasma gondii on purine levels and E-ADA activity in the brain of mice experimentally infected mice

The aim of this study was to assess the purine levels and E-ADA activity in the brain of mice (BALB/c) experimentally infected with Toxoplasma gondii. In experiment I (n=24) the mice were infected with RH strain of T. gondii, while in experiment II (n=36) they were infected with strain ME-49 of T. gondii. Our results showed that, for RH strain (acute phase), an increase in both periods in the levels of ATP, ADP, AMP, adenosine, hypoxanthine, xanthine (only on day 6 PI) and uric acid (only on day 6 PI). By the other hand, the RH strain led, on days 4 and 6 PI, to a reduction in the concentration of inosine. ME-49, a cystogenic strain, showed some differences in acute and chronic phase, since on day 6 PI the levels of ATP and ADP were increased, while on day 30 these same nucleotides were reduced. On day 60 PI, ME-49 induced a reduction in the levels of ATP, ADP, AMP, adenosine, inosine and xanthine, while uric acid was increased. A decrease of E-ADA activity was observed in brain on days 4 and 6 PI (RH), and 30 PI (ME-49); however on day 60 PI E-ADA activity was increased for infection by ME-49 strain. Therefore, it was possible to conclude that infection with T. gondii changes the purine levels and the activity of E-ADA in brain, which may be associated with neurological signs commonly observed in this disease.

Changes in purine levels associated with cellular brain injury in gerbils experimentally infected with Neospora caninum

The present study was carried out in order to assess the possible alterations in purine levels of brain, associated neuronal lesions in gerbils experimentally infected with Neospora caninum. For that, gerbils (Meriones unguiculatus) were inoculated with Nc-1 strain of N. caninum, composing two different experiments: Experiment I (EI) and experiment II (EII), where purine levels were measured along with the histopathologic study, on days 7 (EI), 15 and 30 (EII), post-infection (PI). As a result, it was possible to observe that the purine levels (ATP, ADP, AMP, adenosine, inosine and xanthine) in brain in EI are significantly reduced (p < 0.05), while in EII we faced a different pattern, since in the majority the purine levels were significantly increased (p < 0.05) on days 15 (ATP, AMP, adenosine, hypoxanthine and xanthine) and 30 PI (ATP, ADP, AMP, adenosine, and uric acid). Results of brain histopathology did not show histological lesion in animals of EI; however, in gerbils of EII it was possible to verify that the alterations (lesions) were more pronounced in gerbils evaluated on day 30 PI when compared to day 15 PI. Therefore, it was possible to conclude that the purine levels in brain were altered in both experiments, concomitant with the histopathological injuries observed in EII.

Experimental infection by Haemonchus contortus in lambs: influence of disease on purine levels in serum

The aim of this study was to evaluate the purine levels of lambs experimentally infected with Haemonchus contortus. A total of 12 healthy lambs were divided into two groups, composed of 6 animals each: Group A represented the healthy animals (uninfected), while in Group B the animals were infected with 15 000 larvae of H. contortus. Blood was drawn on days 15, 45 and 75 post-infection (PI) in order to perform the purine analysis (ATP, ADP, AMP, adenosine, inosine, hypoxanthine, xanthine and uric acid) by high pressure liquid chromatography (HPLC) in serum. On day 15 PI a significant (P<0·05) increase in the levels of ATP and inosine was observed in the infected animals, unlike the levels of ADP, adenosine, xanthine and uric acid which were reduced. On day 45 PI a significant (P<0·05) increase in the ATP and xanthine levels in infected animals was observed, contrasting with reduced levels of ADP and uric acid. Finally, on day 75 PI an increase occurred in the levels of ATP, adenosine and hypoxanthine in infected lambs, concomitant with a reduction in the levels of ADP and uric acid (P<0·05). These changes in purine levels may influence the inflammatory process and the pathological events.

Alterations in the cholinesterase and adenosine deaminase activities and inflammation biomarker levels in patients with multiple sclerosis

Multiple sclerosis (MS) is one of the main chronic inflammatory diseases of the CNS that cause functional disability in young adults. It has unknown etiology characterized by the infiltration of lymphocytes and macrophages into the brain. The aim of this study was to evaluate the acetylcholinesterase (AChE) activity in lymphocytes and whole blood, as well as butyrylcholinesterase (BChE) and adenosine deaminase (ADA) activities in serum. We also checked the levels of nucleotides, nucleosides, biomarkers of inflammation such as cytokines (interleukin (IL)-1, IL-6, interferon (IFN)-γ, tumor necrosis factor-alpha (TNF-α) and IL-10) and C-reactive protein (CRP) in serum from 29 patients with the relapsing-remitting form of MS (RRMS) and 29 healthy subjects as the control group. Results showed that AChE in lymphocytes and whole blood as well as BChE, and ADA activities in serum were significantly increased in RRMS patients when compared to the control group (P<0.05). In addition, we observed a decrease in ATP levels and a significant increase in the levels of ADP, AMP, adenosine and inosine in serum from RRMS patients in relation to the healthy subjects (P<0.05). Results also demonstrated an increase in the IFN-γ, TNF-α, IL-1, IL-6 and CRP (P<0.05) and a significant decrease in the IL-10 (P<0.0001) in RRMS patients when compared to control. Our results suggest that alterations in the biomarkers of inflammation and hydrolysis of nucleotides and nucleosides may contribute to the understanding of the neurological dysfunction of RRMS patients.

E-ADA activity in lymphocytes of an experimental model of pythiosis treated with immunotherapy

Pythiosis is a life-threatening disease caused by the oomycete Pythium insidiosum. Some authors have suggested the involvement of a Th2-like immune response in the infected host, which leads to extensive tissue damage. The switch from a Th2 to a Th1 response pattern is one hypothesis to explain the curative properties of immunotherapy. Taking into account the importance of immunotherapy for pythiosis treatment and the contribution of adenine nucleotides in the immunoregulation of the host, we evaluated the ecto-adenosine deaminase (E-ADA; EC 3·5.4·4) activity in lymphocytes from rabbits inoculated with P. insidiosum. Rabbits were inoculated with 1 milliliter of zoospores subcutaneously injected into the lateral thorax; after developing lesions, the rabbits received eight doses of immunotherapy. E-ADA activity was measured in lymphocytes and the adenine nucleotides and adenosine levels were quantitatively determined in serum. Rabbits with characteristic lesions of pythiosis showed a decreased E-ADA activity (82·36%), a decreased adenosine triphosphate concentration (54·04%) and a higher adenosine concentration (2·51 fold), when compared with controls, after 28 days of inoculation. However, after the immunotherapy, the rabbits showed an increase in the E-ADA activity when compared with control (78·62%), contributing for the change in the immune response. Our results reinforce the hypothesis that the change from a Th2 to a Th1 immune response with the participation of the purinergic system could be responsible for the curative properties of immunotherapy.

E-NTPDase and E-ADA activities are altered in lymphocytes of patients with indeterminate form of Chagas' disease

Trypanosoma cruzi infection triggers a chronic inflammatory process in human host and purinergic system ecto-enzymes play an important role in modulating the inflammatory and immune responses. In this study, it was investigated ecto-nucleoside triphosphate diphosphohydrolase (E-NTPDase; EC 3.6.1.5; CD39) and ecto-adenosine deaminase (E-ADA; EC 3.5.4.4) activities in lymphocytes from patients with indeterminate form of Chagas' disease (IFCD). Twenty-five IFCD patients and 25 healthy subjects (control group) were selected. The peripheral lymphocytes were isolated and E-NTPDase and E-ADA activities were determined. Adenine nucleotides and adenosine levels were determined in serum by HPLC and the E-NTPDase1 expression in lymphocytes by Western blot analysis. E-NTPDase (ATP and ADP as substrates) and E-ADA (adenosine as substrate) activities were decreased in lymphocytes from IFCD patients (P<0.05 and P<0.01, respectively), while the E-NTPDase1 expression presented no changes in these patients. Serum ATP levels showed to be decreased (P<0.05) and both AMP (P<0.01) and adenosine (P<0.001) levels were increased in the IFCD group. The enzymatic alterations observed are in agreement with the immune response against T. cruzi infection in IFCD patients, since the decreased extracellular ATP and the increased adenosine levels trigger a Th2 anti-inflammatory response, which it is associated to adaptation of host to parasite, preventing clinical progress of disease.

Endotoxin-induced effects on nucleotide catabolism in mouse kidney

Extracellular adenosine 5'-triphosphate (ATP) acts as a proinflammatory mediator. Adenosine, the final product of ATP breakdown, is an anti-inflammatory compound, acting mainly on adenosine A(2A) receptors. Considering that the kidney is an organ strongly affected during systemic inflammatory responses and that ectonucleotidases are responsible for the control of extracellular nucleotide and nucleoside levels, we examined the endotoxin-induced effects on ectonucleotidases in kidney membranes of mice, and whether CGS-21680 hydrochloride (3-[4-[2-[[6-amino-9-[(2R,3R,4S,5S)-5-(ethylcarbamoyl)-3,4-dihydroxy-oxolan-2-yl]purin-2-yl]amino]ethyl]phenyl]propanoic acid), a selective adenosine A(2A) receptor agonist, antagonizes the lipopolysaccharide (LPS)-induced effects on nucleotide catabolism in kidney. Animals were injected intraperitoneally with 12 mg/kg LPS and/or 0.5mg/kg CGS-21680 or saline. Nucleotidase activities were determined in kidney membrane preparations and ATP metabolism was measured by high performance liquid chromatography (HPLC) assay. Analysis of ectonucleotidase expression was carried out by semi-quantitative semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR). Exposure to endotoxemia promoted an increase in ATP and p-Nitrophenyl thymidine 5'-monophosphate (p-Nph-5'-TMP) hydrolysis, and a decrease in adenosine 5'-monophosphate (AMP) hydrolysis. CGS-21680 treatment failed to reverse these changes. HPLC analysis indicated a decrease in extracellular ATP and adenosine levels in groups treated with LPS and LPS plus CGS-21680. The expression pattern of ectonucleotidases revealed an increase in Entpd3, Enpp2, and Enpp3 mRNA levels after LPS injection. These findings indicate that nucleotide and nucleoside availability in mouse kidney is altered at different stages of endotoxemia, in order to protect the integrity of this organ when exposed to systemic inflammation.

Nucleoside triphosphate diphosphohydrolases role in the pathophysiology of cognitive impairment induced by seizure in early age

Studies have shown that seizures in young animals lead to later cognitive deficits. There is evidence that long-term potentiation (LTP) and long-term depression (LTD) might contribute to the neural basis for learning and memory mechanism and might be modulated by ATP and/or its dephosphorylated product adenosine produced by a cascade of cell-surface transmembrane enzymes, such as E-NTPDases (ecto-nucleoside triphosphate diphosphohydrolases) and ecto-5'-nucleotidase. Thus, we have investigated if hippocampal ecto-nucleotidase activities are altered at different time periods after one episode of seizure induced by kainic acid (KA) in 7 days old rats. We also have evaluated if 90 day-old rats previously submitted to seizure induced by KA at 7 days of age presented cognitive impairment in Y-maze behavior task. Our results have shown memory impairment of adult rats (Postnatal day 90) previously submitted to one single seizure episode in neonatal period (Postnatal day 7), which is accompanied by an increased ATP hydrolysis in hippocampal synaptosomes. The metabolism of ATP evaluated by HPLC confirmed that ATP hydrolysis was faster in adult rats treated with KA in neonatal period than in controls. Surprisingly, the mRNA and protein levels as seen by PCR and Western blot, respectively, were not altered by the KA administration in early age. Since we have found an augmented hydrolysis of ATP and this nucleotide seems to be important to LTP induction, we could assume that impairment of memory and learning observed in adult rats which have experienced a convulsive episode in postnatal period may be a consequence of the increased ATP hydrolysis. These findings correlate the purinergic signaling to the cognitive deficits induced by neonatal seizures and contribute to a better understanding about the mechanisms of seizure-induced memory dysfunction.

L-NAME-treatment alters ectonucleotidase activities in kidney membranes of rats

AIMS

To investigate the effect of N(omega)-Nitro-L-arginine methyl ester (l-NAME) treatment, known to induce a sustained elevation of blood pressure, on ectonucleotidase activities in kidney membranes of rats.

MAIN METHODS

L-NAME (30 mg/kg/day) was administered to Wistar rats for 14 days in the drinking water. Enzyme activities were determined colorimetrically and their gene expression patterns were analyzed by semi-quantitative RT-PCR. The metabolism of ATP and the accumulation of adenosine were evaluated by HPLC in kidney membranes from control and hypertensive rats. PKC phosphorylation state was investigated by Western blot.

KEY FINDINGS

We observed an increase in systolic blood pressure from 115+/-12 mmHg (control group) to 152+/-18 mmHg (l-NAME-treated group). Furthermore, the hydrolysis of ATP, ADP, AMP, and p-Nph-5'TMP was also increased (17%, 35%, 27%, 20%, respectively) as was the gene expression of NTPDase2, NTPDase3 and NPP3 in kidneys of hypertensive animals. Phospho-PKC was increased in hypertensive rats.

SIGNIFICANCE

The general increase in ATP hydrolysis and in ecto-5'-nucleotidase activity suggests a rise in renal adenosine levels and in renal autoregulatory responses in order to protect the kidney against the threat presented by hypertension.