Blockade of CD73 delays glioblastoma growth by modulating the immune environment.

Immunotherapy as an approach for cancer treatment is clinically promising. CD73, which is the enzyme that produces extracellular adenosine, favors cancer progression and protects the tumor from immune surveillance. While CD73 has recently been demonstrated to be a potential target for glioma treatment, its role in regulating the inflammatory tumor microenvironment has not yet been investigated. Thus, this study explores the immunotherapeutic value of the CD73 blockade in glioblastoma. The immuno-therapeutic value of the CD73 blockade was evaluated in vivo in immunocompetent pre-clinical glioblastoma model. As such, glioblastoma-bearing rats were nasally treated for 15 days with a siRNA CD73-loaded cationic-nanoemulsion (NE-siRNA CD73R). Apoptosis was determined by flow cytometry using Annexin-V staining and cell proliferation was analyzed by Ki67 expression by immunohistochemistry. The frequencies of the CD4+, CD8+, and CD4+CD25highCD39+ (Treg) T lymphocytes; CD11b+CD45high macrophages; CD11b+CD45low-microglia; and CD206+-M2-like phenotypes, along with expression levels of CD39 and CD73 in tumor and tumor-associated immune cells, were determined using flow cytometry, while inflammatory markers associated with tumor progression were evaluated using RT-qPCR. The CD73 blockade by NE-siRNA CD73 was found to induce tumor cell apoptosis. Meanwhile, the population of Tregs, microglia, and macrophages was significantly reduced in the tumor microenvironment, though IL-6, CCL17, and CCL22 increased. The treatment selectively decreased CD73 expression in the GB cells as well as in the tumor-associated-macrophages/microglia. This study indicates that CD73 knockdown using a nanotechnological approach to perform nasal delivery of siRNA-CD73 to CNS can potentially regulate the glioblastoma immune microenvironment and delay tumor growth by inducing apoptosis.

ATPergic signaling disruption in human sepsis as a potential source of biomarkers for clinical use.

Sepsis is a life-threatening organ dysfunction caused by a dysregulated inflammatory response to infection. To date, there is no specific treatment established for sepsis. In the extracellular compartment, purines such as adenosine triphosphate (ATP) and adenosine play essential roles in the immune/inflammatory responses during sepsis and septic shock. The balance of extracellular levels among ATP and adenosine is intimately involved in the signals related to immune stimulation/immunosuppression balance. Specialized enzymes, including CD39, CD73, and adenosine deaminase (ADA), are responsible to metabolize ATP to adenosine which will further sensitize the P2 and P1 purinoceptors, respectively. Disruption of the purinergic pathway had been described in the sepsis pathophysiology. Although purinergic signaling has been suggested as a potential target for sepsis treatment, the majority of data available were obtained using pre-clinical approaches. We hypothesized that, as a reflection of deregulation on purinergic signaling, septic patients exhibit differential measurements of serum, neutrophils and monocytes purinergic pathway markers when compared to two types of controls (healthy and ward). It was observed that ATP and ADP serum levels were increased in septic patients, as well as the A2a mRNA expression in neutrophils and monocytes. Both ATPase/ADPase activities were increased during sepsis. Serum ATP and ADP levels, and both ATPase and ADPase activities were associated with the diagnosis of sepsis, representing potential biomarkers candidates. In conclusion, our results advance the translation of purinergic signaling from pre-clinical models into the clinical setting opening opportunities for so much needed new strategies for sepsis and septic shock diagnostics and treatment.

TLR4 expression and functionality are downregulated in glioblastoma cells and in tumor-associated macrophages: A new mechanism of immune evasion?

Glioblastoma (GB) is the most common and aggressive form of primary brain tumor, in which the presence of an inflammatory environment, composed mainly by tumor-associated macrophages (TAMs), is related to its progression and development of chemoresistance. Toll-Like Receptors (TLRs) are key components of the innate immune system and their expression in both tumor and immune-associated cells may impact the cell communication in the tumor microenvironment (TME), further modeling cancer growth and response to therapy. Here, we investigated the participation of TLR4-mediated signaling as a mechanism of induced-immune escape in GB. Initially, bioinformatics analysis of public datasets revealed that TLR4 expression is lower in GB tumors when compared to astrocytomas (AST), and in a subset of TAMs. Further, we confirmed that TLR4 expression is downregulated in chemoresistant GB, as well as in macrophages co-cultured with GB cells. Additionally, TLR4 function is impaired in those cells even following stimulation with LPS, an agonist of TLR4. Finally, experiments performed in a cohort of clinical primary and metastatic brain tumors indicated that the immunostaining of TLR4 and CD45 are inversely proportional, and confirmed the low TLR4 expression in GBs. Interestingly, the cytoplasmic/nuclear pattern of TLR4 staining in cancer tissues suggests additional roles of this receptor in carcinogenesis. Overall, our data suggest the downregulation of TLR4 expression and activity as a strategy for GB-associated immune escape. Additional studies are necessary to better understand TLR4 signaling in TME in order to improve the benefits of immunotherapy based on TLR signaling.

CD73 as a target to improve temozolomide chemotherapy effect in glioblastoma preclinical model.

Glioblastoma is the most devastating primary brain tumor and effective therapies are not available. Treatment is based on surgery followed by radio and chemotherapy with temozolomide (TMZ), but TMZ increases patient survival only by 2 months. CD73, an enzyme responsible for adenosine production, emerges as a target for glioblastoma treatment. Indeed, adenosine causes tumor-promoting actions and CD73 inhibition increases sensitivity to TMZ in vitro. Here, a cationic nanoemulsion to nasal delivery of siRNA CD73 (NE-siRNA CD73) aiming glioblastoma treatment was employed alone or in combination with TMZ. In vitro, two glioblastoma cell lines (C6 and U138MG) with a chemo-resistant profile were used. Treatment alone with NE-siRNA CD73 reduced C6 and U138MG glioma cell viability by 70% and 25%, respectively. On the other hand, when NE-siRNA + TMZ combined treatment was employed, a reduction of 85% and 33% of cell viability was observed. Notably, treatment with NE-siRNA CD73 of glioma-bearing Wistar rats reduced tumor size by 80%, 60% more than the standard chemotherapy with TMZ, but no synergistic or additive effect was observed in vivo. Additionally, NE-siRNA CD73, TMZ or combined therapy decreased adenosine levels in liquor confirming the importance of this nucleoside on in vivo GB growth. Finally, no hemolytic potential was observed. These results suggest that nasal administration of NE-siRNA CD73 exhibits higher antiglioma effect when compared to TMZ. However, no synergistic or additive in vivo was promoted by the therapeutic regimen employed in this study.

Nasal Administration of Cationic Nanoemulsions as CD73-siRNA Delivery System for Glioblastoma Treatment: a New Therapeutical Approach.

Glioblastoma is the most devastating primary brain tumor. Effective therapies are not available, mainly due to high tumor heterogeneity, chemoresistance, and the difficulties imposed by blood-brain barrier. CD73, an enzyme responsible for adenosine (ADO) production, is overexpressed in cancer cells and emerges as a target for glioblastoma treatment. Indeed, ADO causes a variety of tumor-promoting actions, particularly by inducing tumor immune escape, whereas CD73 inhibition impairs tumor progression. Here, a cationic nanoemulsion to deliver CD73siRNA (NE-siRNA CD73R) via nasal route aiming glioblastoma treatment was developed. NE-siRNA CD73R was uptaken by glioma cells in culture, resulting in a parallel 60-80% decrease in AMPase activity and 30-50% in cell viability. Upon nasal delivery, NE-siRNA CD73R was detected in rat brain and serum. Notably, treatment with CD73siRNA complexes of glioma-bearing Wistar rats reduced tumor growth by 60%. Additionally, NE-siRNA CD73R treatment decreased 95% ADO levels in liquor and tumor CD73 expression, confirming in vivo CD73 silencing. Finally, no toxicity was observed in either primary astrocytes or rats with this cationic nanoemulsion. These results suggest that nasal administration of cationic NE as CD73 siRNA delivery system represents a novel potential treatment for glioblastoma. Graphical Abstract Glioblastoma is the most common and devastating form of primary brain tumor. CD73, a protein involved in cell-cell adhesion and migration processes and also responsible for extracellular adenosine (ADO) production, is overexpressed by glioma cells and emerges as an important target for glioma treatment. Indeed, ADO participates in tumor immune escape, cell proliferation, and angiogenesis, and CD73 inhibition impairs those processes. Here, a cationic nanoemulsion to deliver CD73 siRNA (NE-siRNA CD73R) via nasal route aiming glioblastoma treatment was developed. NE-siRNA CD73R knockdown in vitro and in vivo CD73. Upon nasal delivery of NE-siRNA CD73R, the treatment markedly reduced tumor volume by 60% in a rat preclinical glioblastoma model. The treatment was well tolerated, and did not induce kidney, liver, lung, olfactory, bone marrow, or behavior alterations. These results indicate that the nasal administration of NE as a CD73 siRNA delivery system offered an efficient means of gene knockdown and may represent a potential alternative for glioblastoma treatment.

CD73 Downregulation Decreases In Vitro and In Vivo Glioblastoma Growth.

Glioblastoma is the worst and most common primary brain tumor. Here, we demonstrated the role of CD73, an enzyme responsible for adenosine (ADO) production, in glioblastoma progression. ADO increased glioma cell viability via A1 receptor sensitization. CD73 downregulation decreased glioma cell migration and invasion by reducing metalloproteinase-2 and vimentin expression and reduced cell proliferation by 40%, which was related to necrosis and sub-G1 phase blockage of cell cycle. Those effects also involved the stimulation of Akt/NF-kB pathways. Additionally, CD73 knockdown or enzyme inhibition potentiated temozolomide cytotoxic effect on glioma cells by decreasing the IC50 value and sensitizing cells to a non-cytotoxic drug concentration. CD73 inhibition also decreased in vivo rat glioblastoma progression. Delivery of siRNA-CD73 or APCP reduced tumor size by 45 and 40%, respectively, when compared with control. This effect was followed by a parallel 95% reduction of ADO levels in cerebrospinal fluid, indicating the role of extracellular ADO in in vivo glioma growth. Treatment did not induce systemic damage or mortality. Altogether, we conclude that CD73 is an interesting target for glioblastoma treatment and its inhibition may provide new opportunities to improve the treatment of brain tumors. Graphical Abstract ᅟ.

NTPDase and 5' ecto-nucleotidase expression profiles and the pattern of extracellular ATP metabolism in the Walker 256 tumor.

In this study, we evaluated the NTPDases and ecto-5'-nucleotidase (CD73) expression profiles and the pattern of adenine nucleotide hydrolysis in rats submitted to the Walker 256 tumor model, 6, 10 and 15 days after the subcutaneous inoculation. Using RT-PCR analysis, we identified mRNA for all of the members of the ecto-nucleoside triphosphate diphosphohydrolase family investigated and a 5'-nucleotidase. By quantitative real-time PCR, Entpd1 (Cd39) and Entpd2 (Cd39L1) and CD73 were identified as the dominant genes expressed by the Walker 256 tumor, at all times studied. Extracellular adenine nucleotide hydrolysis by the Walker 256 tumor was estimated by HPLC analysis. Rapid hydrolysis of extracellular ATP by the tumor cells was observed, leading to the formation of adenosine and inosine in cells obtained from solid tumors at 6 and 10 days after inoculation. Cells obtained from solid tumors at 15 days of growth presented high levels of AMP and presented adenosine as a final product after 90 min of incubation. Results demonstrate that the presence of NTPDases and 5'-nucleotidase enzymes in Walker 256 tumor cells may be important for regulation of the extracellular adenine nucleotides/adenine nucleoside ratio, therefore leading to tumor growth.

Nucleoside triphosphate diphosphohydrolase-2 (NTPDase2/CD39L1) is the dominant ectonucleotidase expressed by rat astrocytes.

Inflammatory and degenerative pathophysiological processes within the CNS are important causes of human disease. Astrocytes appear to modulate these reactions and are a major source of inflammatory mediators, e.g. extracellular adenine nucleotides, in nervous tissues. Actions following extracellular nucleotides binding to type 2 purinergic receptors are regulated by ectonucleotidases, including members of the CD39/ecto-nucleoside triphosphate diphosphohydrolase family. The ectonucleotidases of astrocytes expressed by rat brain rapidly convert extracellular ATP to ADP, ultimately to AMP. RT-PCR, immunocytochemistry as well as Western blotting analysis demonstrated expression of multiple ecto-nucleoside triphosphate diphosphohydrolase family members at both the mRNA and protein level. By quantitative real-time PCR, we identified Entpd2 (CD39L1) as the dominant Entpd gene expressed by rat hippocampal, cortical and cerebellar astrocytes. These data in combination with the elevated ecto-ATPase activity observed in these brain regions, suggest that NTPDase2, an ecto-enzyme that preferentially hydrolyzes ATP, is the major ecto-nucleoside triphosphate diphosphohydrolase expressed by rat astrocytes. NTPDase2 may modulate inflammatory reactions within the CNS and could represent a useful therapeutic target in human disease.

Identification of valid endogenous control genes for determining gene expression in C6 glioma cell line treated with conditioned medium from adipose-derived stem cell.

INTRODUCTION: There is growing evidence that mesenchymal stem cells (MSCs) can be important players in the tumor microenvironment. They can affect the glioma progression through the modulation of different genes. This modulation can be evaluated through a very useful model, treating the tumor cells with MSC-conditioned medium. However, for an accurate and reliable gene expression analysis, normalization of gene expression data against reference genes is a prerequisite. METHODS: We performed a systematic review in an attempt to find a reference gene to use when analyzing gene expression in C6 glioma cells lines. Considering that we were not able to find a reference gene originated by an appropriate validation, in this study we evaluated candidate genes to be used as reference gene in C6 cells under different treatments with adipose-derived stem cells conditioned medium (CM-ADSCs). ß-actin (ACTB); glyceraldehyde-3-phosphate dehydrogenase (GAPDH); hypoxanthine-guanine phosphoribosyltransferase I (HPRT-1); TATA box binding protein (TBP) and beta-2-microglobulin (B2M) were evaluated by real-time reverse transcription PCR (RT-qPCR). The mean Cq, the maximum fold change (MFC) and NormFinder software were used for reference gene evaluation and selection. RESULTS: The GAPDH and ACTB genes have been the most widely used reference genes to normalize among the different investigated genes in our review, however, controversially these genes underwent a substantial variability among the genes evaluated in the present work. Individually, TBP gene was more stable when compared with other genes analyzed and the combination of TBP and HPRT-1 was even more stable. CONCLUSION: These results evidence the importance of appropriate validation of reference genes before performing qPCR experiments. Besides, our data will contribute with researchers that work analyzing the role of ADSCs in glioma microenvironment through gene expression.

Effect of protein-modifying reagents on ecto-apyrase from rat brain.

We have tested several chemical modifiers to investigate which amino acid residues, present in the primary structure of the ecto-apyrase, could be involved in catalysis. Synaptosomes from cerebral cortex of rats were prepared and the ATP diphosphohydrolase activity was assayed in absence or the presence of the modifiers. Percentages of residual activity for ATPase and ADPase obtained when the following reagents were tested, are respectively: phenylglyoxal (an arginine group modifier) 17 and 30%; Woodward's reagent (a carboxylic group modifier) 33 and 23%; Koshland's reagent (a tryptophan group modifier) 10 and 12%; maleic anhidride (an amino group modifier) 11 and 25% and carbodiimide reagent (a carboxylic group modifier) 56 and 72%. Otherwise, PMSF, a seryl protein modifier and DTNB, a SH-group modifier did not affect either ATPase or ADPase activity. Inhibitions observed after treatment with phenylglyoxal and Woodward's reagent were significantly prevented when the synaptosomal fraction was preincubated with ATP and ADP, indicating that the arginine and the side chain of glutamate or aspartate (carboxyl groups) participate in the structure of the active site. This interpretation was confirmed by using GTP and GDP, two other apyrase substrates. Phenylglyoxal and Woodward's reagent also inhibited the GTPase and GDPase activities and this inhibition was prevented by preincubation with these substrates.

Studies on the anchorage of ATP diphosphohydrolase in synaptic plasma membranes from rat brain.

ATP diphosphohydrolases are described as ecto-enzymes in several tissues. In the present study, synaptic plasma membrane (SPM) was exposed to a series of agents used to distinguish between peripheral (hydrophilic), G-PI-anchored and transmembrane-polypeptide-anchored membrane proteins. These procedures included: (a) nondetergent extraction, (b) Triton X-114 phase partitioning, (c) phosphatidylinositol-specific phospholipase C (PI-PLC) extraction and (d) protease incubation. In cases (a), (c) and (d) the SPM was incubated with different agents and the ATPase-ADPase activities and the protein concentration was determined in the original sample, in the pellet and in the supernatant obtained after 100,000 g centrifugation. In procedure (b), the SPM was solubilized in 1% triton X-114 and submitted to phase separation onto a sucrose cushion. The aqueous and detergent rich phases obtained by this treatment were assayed for ATPase-ADPase activities and protein determination. The results obtained suggest an intrinsic behaviour for ATP diphosphohydrolase since none of the nondetergent treatments was efficient in removing the enzyme from SPM. Moreover, ATPase and ADPase activities were recovered predominantly (> 50%) in the detergent-rich phase obtained by Triton X-114 partitioning. The enzyme was not released by PI-PLC or proteases. These results indicate that the enzyme is not a GPI-anchored protein, but is probably deeply anchored on the plasma membrane in agreement with the amino acid sequence of the enzyme recently published.

Thyroid hormone upregulates ecto-5'-nucleotidase/CD73 in C6 rat glioma cells.

Thyroid hormones have profound effects on the central nervous system, such as proliferation, secretion of growth factors and gene expression regulation. Ecto-NTPDases and ecto-5'-nucleotidase can control the extracellular ATP/adenosine levels, which have been described as proliferation factors. Here, we investigated the influence of T(3) on the enzyme cascade which catalyzes interconversion of purine nucleotides in rat C6 glioma cells. Exposure of C6 cells to T(3) caused a dose dependent increase of 30% in the AMP hydrolysis up to 0.25 nM, which was suppressed by actinomycin. No significant alteration was observed on ATP/ADP hydrolysis and T(4) at higher concentrations (10-1000 nM) promoted an increase in AMP hydrolysis that was not dose dependent. T(3) treatment also increased the expression of CD73 mRNA. Besides the importance of the ecto-5'-NT in the cell proliferation and differentiation, its overexpression can enhance extracellular adenosine levels, which could also be an important proliferation signal.

Ethanolic extract of Casearia sylvestris Sw exhibits in vitro antioxidant and antimicrobial activities and in vivo hypolipidemic effect in rats / Extrato etanólico de Casearia sylvestris Sw apresenta atividade antioxidante e antimicrobiana in vitro e efeito hipolipemiante em ratos

ABSTRACT: The Casearia sylvestris Sw (Flacourtiaceae) is a shrub that occurs in forests of Southern Brazil; its leaves are widely used in folk medicine as a depurative, analgesic, anti-inflammatory and antiulcerogenic agent. The objective of this study was to perform the phytochemical description and to evaluate the pharmacological activities (antimicrobial, antifungal, antioxidant and toxicity) of the ethanolic extract (EE) of C. sylvestris Sw. In addition, we also evaluated the effect of the EE of C. sylvestris Sw on the glucose levels and lipid profile in blood serum of rats submitted to a model of streptozotocin-induced diabetes. Material and Methods: In vitro assay: the detection of chemical groups was done through chemical reactions with the development of color or precipitate and by chromatographic profile; the antioxidant activity was measured by the method of reduction of DPPH free radical (2,2-diphenyl-1-picrylhydrazyl); the Minimum Inhibitory Concentration was evaluated by the broth microdilution method, and the Minimum Bactericide Concentration and the Minimum Fungicide Concentration were performed in Petri dishes; the cytotoxic activity was measured by the Artemia salina test. In vivo assay: diabetic and non-diabetic rats were treated with EE of C. sylvestris Sw (300 mg/kg) for 45 days, and the glycaemia and lipid profile were analyzed. Results: The EE showed a Lethal Dose50 of 724.76 μg.mL-1 and important antioxidant, fungicide and fungistatic activities. The EE showed better antimicrobial activity regarding the microorganisms Staphylococcus aureus, Escherichia coli and Salmonella setubal. Conclusion: The EE of C. sylvestris Sw produces a significant decrease in triglycerides, total cholesterol and VLDL levels without any significant alteration in the glycaemia. The EE of C. sylvestris Sw presents antioxidant and antimicrobial activities and it exhibits a potent hypolipidemic effect.

RESUMO: Casearia sylvestris Sw (Flacourtiaceae) é uma planta comumente encontrada em florestas do sul do Brasil; suas folhas são amplamente utilizadas na medicina popular como depurativa, analgésica, anti-inflamatória e anti ulcerogênica. O objetivo deste estudo foi apresentar uma descrição fitoquímica e da atividade farmacológica (antimicrobiana, antifúngica, antioxidante e toxicidade) do extrato etanólico (EE) da C. Sylvestris Sw. Adicionalmente, procurou-se avaliar o efeito do EE da C. Sylvestris Sw sobre os níveis séricos de glicose e perfil lipídico de ratos submetidos a um modelo de diabetes induzida por estreptozotocina. A detecção de grupos químicos foi realizada por reações químicas de coloração ou precipitação, e também por cromatografia; a atividade antioxidante foi mensurada pelo método de redução do DPPH (2,2-difenil-1-picril-hidrazil); a concentração mínima inibitória foi realizada pela técnica de micro-diluição, e concentração mínima bactericida e concentração mínima fungicida foram realizadas em placa de Petri; enquanto a atividade citotóxica foi conduzida pelo teste da Artemia salina. Nos ensaios in vivo, ratos diabéticos e não-diabéticos foram tratado com EE da C. Sylvestris Sw (300mg/kg) por 45 dias, e os níveis glicêmico e perfil lipídico foram medidos. A dose Letal50 do EE foi de 724.76 μg.mL-1; mostrando importante atividades antioxidante, fungicida e fungistática e melhor atividade antimicrobiana contra Staphylococcus aureus, Escherichia coli e Salmonella setubal. O EE da C. Sylvestris Sw promoveu diminuição significativa nos níveis de triglicerídeos, colesterol total e VLDL; porém sem efeito significativo nos níveis glicêmicos. O EE da C. Sylvestris Sw, além de apresentar atividade antioxidante e antimicrobiana; possui também potente efeito hipolipidêmico.

Identification of brain ecto-apyrase as a phosphoprotein.

Ecto-apyrase is a transmembrane glycoprotein that hydrolyzes extracellular nucleoside tri- or diphosphates. Apyrase activity is affected by several physiological and pathological conditions indicating the existence of regulatory mechanisms. Considering that apyrase presents consensus phosphorylation sites, we studied the phosphorylation of this enzyme. We found an overlay of the immunoblotting and phosphorylated bands in three different preparations from rat brain: (a) hippocampal slices, (b) synaptic plasma membrane fragments and (c) cultured astrocytes. In addition, two-dimensional electrophoresis separations with human astrocytoma cells were done to identify unequivocally the coincidence between the immunodetected and phosphorylated protein. These observations indicate that apyrase can be detected as a phosphoprotein, with obvious implications in the regulation of this enzyme.