Interplay between mTOR and Purine Metabolism Enzymes and Its Relevant Role in Cancer.

Tumor cells reprogram their metabolism to meet the increased demand for nucleotides and other molecules necessary for growth and proliferation. In fact, cancer cells are characterized by an increased "de novo" synthesis of purine nucleotides. Therefore, it is not surprising that specific enzymes of purine metabolism are the targets of drugs as antineoplastic agents, and a better knowledge of the mechanisms underlying their regulation would be of great help in finding new therapeutic approaches. The mammalian target of the rapamycin (mTOR) signaling pathway, which is often activated in cancer cells, promotes anabolic processes and is a major regulator of cell growth and division. Among the numerous effects exerted by mTOR, noteworthy is its empowerment of the "de novo" synthesis of nucleotides, accomplished by supporting the formation of purinosomes, and by increasing the availability of necessary precursors, such as one-carbon formyl group, bicarbonate and 5-phosphoribosyl-1-pyrophosphate. In this review, we highlight the connection between purine and mitochondrial metabolism, and the bidirectional relation between mTOR signaling and purine synthesis pathways.

Effects of Nutraceuticals on Cisplatin-Induced Cytotoxicity in HEI-OC1 Cells.

Cisplatin is a chemotherapeutic drug for the treatment of several solid tumors, whose use is limited by its nephrotoxicity, neurotoxicity, ototoxicity, and development of resistance. The toxicity is caused by DNA cross-linking, increase in reactive oxygen species and/or depletion of cell antioxidant defenses. The aim of the work was to study the effect of antioxidant compounds (Lisosan G, Taurisolo®) or hydrogen sulfide (H2S)-releasing compounds (erucin) in the auditory HEI-OC1 cell line treated with cisplatin. Cell viability was determined using the MTT assay. Caspase and sphingomyelinase activities were measured by fluorometric and colorimetric methods, respectively. Expression of transcription factors, apoptosis hallmarks and genes codifying for antioxidant response proteins were measured by Western blot and/or RT-qPCR. Lisosan G, Taurisolo® and erucin did not show protective effects. Sodium hydrosulfide (NaHS), a donor of H2S, increased the viability of cisplatin-treated cells and the transcription of heme oxygenase 1, superoxide dismutase 2, NAD(P)H quinone dehydrogenase type 1 and the catalytic subunit of glutamate-cysteine ligase and decreased reactive oxygen species (ROS), the Bax/Bcl2 ratio, caspase-3, caspase-8 and acid sphingomyelinase activity. Therefore, NaHS might counteract the cytotoxic effect of cisplatin by increasing the antioxidant response and by reducing ROS levels and caspase and acid sphingomyelinase activity.

Effectiveness and safety of tildrakizumab for the treatment of psoriasis in real-world settings at 24 weeks: A retrospective, observational, multicentre study by the Spanish Psoriasis Group.

BACKGROUND: Tildrakizumab is a humanized, IgG1/κ antibody that interacts with the p19 subunit of interleukin 23. It is approved for the treatment of moderate-to-severe plaque psoriasis. Real-world evidence on the effectiveness and safety of tildrakizumab is limited. OBJECTIVES: To assess the effectiveness and safety of tildrakizumab at 24 weeks in patients with moderate-to-severe plaque psoriasis in routine clinical practice. METHODS: Retrospective, observational, multicentre study including adult patients with moderate-to-severe plaque psoriasis treated with tildrakizumab under real-life conditions. Patient data were extracted from anonymized electronic medical records. Statistical analysis was performed using SPSS22. RESULTS: A total of 190 patients were included. About 53.9% were men with a mean age of 51.45 (SD 3.9) and a mean BMI of 29.13 (SD 6.21). About 79.8% (132 out of 190) of patients had previously received biological therapy (BT) and 17.3% (33 out of 191) had psoriatic arthritis. Baseline PASI was 10.7 (SD 6.53). Up to 109 patients reached Week 24 and at this point mean baseline PASI decreased to 1.7 (SD 4.8), representing an 88.79% mean PASI reduction. At 6 months, 87.1% and 40.3% of the treated patients achieved PASI ≤3 and ≤1, respectively. At Week 24 mean BSA decreased from 13.2 (SD 10.07) to 1.6 (SD 4.40) and mean DLQI went from 12.5 (SD 7.12) to 1.2 (SD 3.27). Multivariate analysis showed no differences when effectiveness was correlated with gender, obesity, psoriatic arthritis or prior exposure to BT. The rate of adverse events (AE) was 5.9% (11 out of 190), where infections were the most frequent AE (4 out of 11). One patient suffered a haemorrhagic ictus and one patient died due to causes unrelated to the study. CONCLUSION: Tildrakizumab was effective and safe in a large cohort of patients with moderate-to-severe plaque psoriasis treated in a routine clinical setting.

Inborn Errors of Purine Salvage and Catabolism.

Cellular purine nucleotides derive mainly from de novo synthesis or nucleic acid turnover and, only marginally, from dietary intake. They are subjected to catabolism, eventually forming uric acid in humans, while bases and nucleosides may be converted back to nucleotides through the salvage pathways. Inborn errors of the purine salvage pathway and catabolism have been described by several researchers and are usually referred to as rare diseases. Since purine compounds play a fundamental role, it is not surprising that their dysmetabolism is accompanied by devastating symptoms. Nevertheless, some of these manifestations are unexpected and, so far, have no explanation or therapy. Herein, we describe several known inborn errors of purine metabolism, highlighting their unexplained pathological aspects. Our intent is to offer new points of view on this topic and suggest diagnostic tools that may possibly indicate to clinicians that the inborn errors of purine metabolism may not be very rare diseases after all.

The Good, the Bad and the New about Uric Acid in Cancer.

Uric acid is the final product of purine catabolism in man and apes. The serum concentration of uric acid is sex-, age- and diet-dependent and is maintained close to its maximal solubility, indicating that it plays some important role. Indeed, it has been demonstrated that, at physiological concentrations, uric acid is a powerful antioxidant, while at high intracellular concentrations, it is a pro-oxidant molecule. In this review, we describe the possible causes of uric acid accumulation or depletion and some of the metabolic and regulatory pathways it may impact. Particular attention has been given to fructose, which, because of the complex correlation between carbohydrate and nucleotide metabolism, causes uric acid accumulation. We also present recent results on the positive and negative effects played by uric acid in cancer and some new findings and hypotheses about the implication of this metabolite in a variety of signaling pathways, which can play a role in the pathogenesis of diseases such as metabolic syndrome, diabetes, and inflammation, thus favoring the development of cancer. The loss of uricase in Homo sapiens and great apes, although exposing these species to the potentially adverse effects of uric acid, appears to be associated with evolutionary advantages.

Sphingomyelin in Human Breast Milk might be Essential for the Hippocampus Maturation.

BACKGROUND: It has been established that sphingomyelin present human breast milk is useful for the brain maturation and cognitive development. At 10 days of breastfeeding the sphingomyelin content is double that present in cow's milk and its content is independent of the maternal diet. The aim of the study was to analyze the content of sphingomyelin in breast milk at 3 months of breastfeeding and to consider the effect of this molecule on synaptic function and nerve conduction through the probable expansion of myelinated axons. METHODS: Therefore, to begin to define and assess this, we performed sphingolipidomic analysis in human breast milk. Then, we cultured embryonic hippocampal cells (HN9.10) in the presence of sphingomyelin at a concentration from 0.6% to 31% of human milk, estimated by considering its bioavailability and its passage into the interstitial fluid. To highlight the effect of sphingomyelin in the cells, cell viability and morphology were evaluated. Analyses of neutral sphingomyelinase gene and protein expression was performed. The entry of sphingomyelin into the cell was studied in immunofluorescence; the expression of heavy neurofilament (NF200) was tested with immunocytochemical technique. RESULTS: We demonstrated that sphingomyelin is able to enter cell nucleus and overexpress the sphingomyelin phosphodiesterase 4 (SMPD4) gene encoding for neutral sphingomyelinase (nSMase), an enzyme useful for its own metabolism. Later, cells displayed changes of the soma and the appearance of neurites supported by NF200 overexpression. CONCLUSIONS: We speculated that the sphingomyelin present in human breast milk is useful in part to regulate nuclear activity and in part to form myelin sheet to facilitate nerve cell maturation. As brain development occurs at 0-3 years, these data open a new avenue of potential intervention to integrate the infant formulas with SM to obtain a product similar to the maternal milk.

Skeletal Muscle and COVID-19: The Potential Involvement of Bioactive Sphingolipids.

SARS-CoV-2 virus infection is the cause of the coronavirus disease 2019 (COVID-19), which is still spreading over the world. The manifestation of this disease can range from mild to severe and can be limited in time (weeks) or persist for months in about 30-50% of patients. COVID-19 is considered a multiple organ dysfunction syndrome and the musculoskeletal system manifestations are beginning to be considered of absolute importance in both COVID-19 patients and in patients recovering from the SARS-CoV-2 infection. Musculoskeletal manifestations of COVID-19 and other coronavirus infections include loss of muscle mass, muscle weakness, fatigue or myalgia, and muscle injury. The molecular mechanisms by which SARS-CoV-2 can cause damage to skeletal muscle (SkM) cells are not yet well understood. Sphingolipids (SLs) represent an important class of eukaryotic lipids with structural functions as well as bioactive molecules able to modulate crucial processes, including inflammation and viral infection. In the last two decades, several reports have highlighted the role of SLs in modulating SkM cell differentiation, regeneration, aging, response to insulin, and contraction. This review summarizes the consequences of SARS-CoV-2 infection on SkM and the potential involvement of SLs in the tissue responses to virus infection. In particular, we highlight the role of sphingosine 1-phosphate signaling in order to aid the prediction of novel targets for preventing and/or treating acute and long-term musculoskeletal manifestations of virus infection in COVID-19.

Encapsulation of Alpha-Lipoic Acid in Functional Hybrid Liposomes: Promising Tool for the Reduction of Cisplatin-Induced Ototoxicity.

In this study, in order to address the drawback of cisplatin (CDDP)-induced ototoxicity, we propose a straightforward strategy based on the delivery of a sulfur-based antioxidant, such as lipoic acid (LA), to HEI-OC1 cells. To this aim, hybrid liposomes (LA@PCGC) with a spherical shape and a mean diameter of 25 nm were obtained by direct sonication of LA, phosphatidylcholine and a gelatin-curcumin conjugate in a physiological buffer. LA@PCGC were found to be stable over time, were quickly (i.e., by 1 h) taken up by HEI-OC1 cells, and guaranteed strong retention of the bioactive molecule, since LA release was less than 20%, even after 100 h. Cell viability studies showed the efficiency of LA@PCGC for stabilizing the protective activity of LA. Curcumin residues within the functional liposomes were indeed able to maintain the biological activity of LA, significantly improving (up to 2.19-fold) the viability of HEI-OC1 cells treated with 5 µM CDDP. Finally, LA@PCGC was incorporated within an alginate-based injectable hydrogel carrier to create a formulation with physical chemical features suitable for potential ear applications.

Brain and gut microbiota disorders in the psychopathology of anorexia nervosa.

Studies of pathophysiological mechanisms involved in eating disorders (EDs) have intensified over the past several years, revealing their unprecedented and unanticipated complexity. Results from many articles highlight critical aspects in each member of ED family. Notably, anorexia nervosa (AN) is a disorder due to undefined etiology, frequently associated with symptoms of depression, anxiety, obsessive-compulsiveness, accompanied by endocrine alterations, altered immune response, increased inflammation, and dysbiosis of the gut microbiota. Hence, an advanced knowledge of how and why a multisystem involvement exists is of paramount importance to understand the pathogenetic mechanisms of AN. In this review, we describe the change in the brain structure/function focusing on hypothalamic endocrine disorders and the disequilibrium of gut microbiota in AN that might be responsible for the psychopathological complication.

Vitamin D3 Enriches Ceramide Content in Exosomes Released by Embryonic Hippocampal Cells.

The release of exosomes can lead to cell-cell communication. Nutrients such as vitamin D3 and sphingolipids have important roles in many cellular functions, including proliferation, differentiation, senescence, and cancer. However, the specific composition of sphingolipids in exosomes and their changes induced by vitamin D3 treatment have not been elucidated. Here, we initially observed neutral sphingomyelinase and vitamin D receptors in exosomes released from HN9.10 embryonic hippocampal cells. Using ultrafast liquid chromatography tandem mass spectrometry, we showed that exosomes are rich in sphingomyelin species compared to whole cells. To interrogate the possible functions of vitamin D3, we established the optimal conditions of cell treatment and we analyzed exosome composition. Vitamin D3 was identified as responsible for the vitamin D receptor loss, for the increase in neutral sphingomyelinase content and sphingomyelin changes. As a consequence, the generation of ceramide upon vitamin D3 treatment was evident. Incubation of the cells with neutral sphingomyelinase, or the same concentration of ceramide produced in exosomes was necessary and sufficient to stimulate embryonic hippocampal cell differentiation, as vitamin D3. This is the first time that exosome ceramide is interrogated for mediate the effect of vitamin D3 in inducing cell differentiation.

Cytosolic 5'-Nucleotidase II Silencing in Lung Tumor Cells Regulates Metabolism through Activation of the p53/AMPK Signaling Pathway.

Cytosolic 5'-nucleotidase II (cN-II) is an allosteric catabolic enzyme that hydrolyzes IMP, GMP, and AMP. The enzyme can assume at least two different structures, being the more active conformation stabilized by ATP and the less active by inorganic phosphate. Therefore, the variation in ATP concentration can control both structure and activity of cN-II. In this paper, using a capillary electrophoresis technique, we demonstrated that a partial silencing of cN-II in a pulmonary carcinoma cell line (NCI-H292) is accompanied by a decrease in adenylate pool, without affecting the energy charge. We also found that cN-II silencing decreased proliferation and increased oxidative metabolism, as indicated by the decreased production of lactate. These effects, as demonstrated by Western blotting, appear to be mediated by both p53 and AMP-activated protein kinase, as most of them are prevented by pifithrin-α, a known p53 inhibitor. These results are in line with our previous observations of a shift towards a more oxidative and less proliferative phenotype of tumoral cells with a low expression of cN-II, thus supporting the search for specific inhibitors of this enzyme as a therapeutic tool for the treatment of tumors.

Risk factors for hospitalization and mortality due to dengue fever in a Mexican population: a retrospective cohort study.

OBJECTIVES: Identify risk factors associated with increased hospital admission and mortality due to dengue fever (DF), and estimate the risk magnitude associated with each individual variable. METHODS: Records of patients diagnosed with dengue were obtained from the Mexican National Epidemiological Surveillance System. Descriptive statistics were performed in all variables. Demographic characteristics and comorbidities were compared between patients based on type of care and mortality. Multivariable analysis was done with a logistic regression model, using two different outcomes: hospitalization and mortality. RESULTS: A total of 24,495 patients were included in the analysis, with a DF case fatality rate of 0.58%. Patients younger than 10 and older than 60, were found to have a greater risk of both hospitalization and mortality due to DF. Comorbidities associated with a higher risk for hospital admission include cirrhosis, CKD, immunosuppression, diabetes, and hypertension. For mortality, CKD, diabetes, and hypertension were identified as risk factors, along with pregnancy. CONCLUSION: Identification of risk factors associated with increased hospitalization and mortality due to DF can help categorize patients that require close monitoring and inpatient care. Early identification of warning signs and patients at increased risk is key to avoiding delay of supportive care.

Metabolic Aspects of Adenosine Functions in the Brain.

Adenosine, acting both through G-protein coupled adenosine receptors and intracellularly, plays a complex role in multiple physiological and pathophysiological processes by modulating neuronal plasticity, astrocytic activity, learning and memory, motor function, feeding, control of sleep and aging. Adenosine is involved in stroke, epilepsy and neurodegenerative pathologies. Extracellular concentration of adenosine in the brain is tightly regulated. Adenosine may be generated intracellularly in the central nervous system from degradation of AMP or from the hydrolysis of S-adenosyl homocysteine, and then exit via bi-directional nucleoside transporters, or extracellularly by the metabolism of released nucleotides. Inactivation of extracellular adenosine occurs by transport into neurons or neighboring cells, followed by either phosphorylation to AMP by adenosine kinase or deamination to inosine by adenosine deaminase. Modulation of the nucleoside transporters or of the enzymatic activities involved in the metabolism of adenosine, by affecting the levels of this nucleoside and the activity of adenosine receptors, could have a role in the onset or the development of central nervous system disorders, and can also be target of drugs for their treatment. In this review, we focus on the contribution of 5'-nucleotidases, adenosine kinase, adenosine deaminase, AMP deaminase, AMP-activated protein kinase and nucleoside transporters in epilepsy, cognition, and neurodegenerative diseases with a particular attention on amyotrophic lateral sclerosis and Huntington's disease. We include several examples of the involvement of components of the adenosine metabolism in learning and of the possible use of modulators of enzymes involved in adenosine metabolism or nucleoside transporters in the amelioration of cognition deficits.

Protopine/Gemcitabine Combination Induces Cytotoxic or Cytoprotective Effects in Cell Type-Specific and Dose-Dependent Manner on Human Cancer and Normal Cells.

The natural alkaloid protopine (PRO) exhibits pharmacological properties including anticancer activity. We investigated the effects of PRO, alone and in combination with the chemotherapeutic gemcitabine (GEM), on human tumor cell lines and non-tumor human dermal fibroblasts (HDFs). We found that treatments with different PRO/GEM combinations were cytotoxic or cytoprotective, depending on concentration and cell type. PRO/GEM decreased viability in pancreatic cancer MIA PaCa-2 and PANC-1 cells, while it rescued the GEM-induced viability decline in HDFs and in tumor MCF-7 cells. Moreover, PRO/GEM decreased G1, S and G2/M phases, concomitantly with an increase of subG1 phase in MIA PaCa-2 and PANC-1 cells. Differently, PRO/GEM restored the normal progression of the cell cycle, altered by GEM, and decreased cell death in HDFs. PRO alone increased mitochondrial reactive oxygen species (ROS) in MIA PaCa-2, PANC-1 cells and HDFs, while PRO/GEM increased both intracellular and mitochondrial ROS in the three cell lines. These results indicate that specific combinations of PRO/GEM may be used to induce cytotoxic effects in pancreatic tumor MIA PaCa-2 and PANC-1 cells, but have cytoprotective or no effects in HDFs.

Cytosolic 5'-Nucleotidase II Is a Sensor of Energy Charge and Oxidative Stress: A Possible Function as Metabolic Regulator.

Cytosolic 5'-nucleotidase II (NT5C2) is a highly regulated enzyme involved in the maintenance of intracellular purine and the pyrimidine compound pool. It dephosphorylates mainly IMP and GMP but is also active on AMP. This enzyme is highly expressed in tumors, and its activity correlates with a high rate of proliferation. In this paper, we show that the recombinant purified NT5C2, in the presence of a physiological concentration of the inhibitor inorganic phosphate, is very sensitive to changes in the adenylate energy charge, especially from 0.4 to 0.9. The enzyme appears to be very sensitive to pro-oxidant conditions; in this regard, the possible involvement of a disulphide bridge (C175-C547) was investigated by using a C547A mutant NT5C2. Two cultured cell models were used to further assess the sensitivity of the enzyme to oxidative stress conditions. NT5C2, differently from other enzyme activities, was inactivated and not rescued by dithiothreitol in a astrocytoma cell line (ADF) incubated with hydrogen peroxide. The incubation of a human lung carcinoma cell line (A549) with 2-deoxyglucose lowered the cell energy charge and impaired the interaction of NT5C2 with the ice protease-activating factor (IPAF), a protein involved in innate immunity and inflammation.

Cholesterol and Sphingolipid Enriched Lipid Rafts as Therapeutic Targets in Cancer.

Lipid rafts are critical cell membrane lipid platforms enriched in sphingolipid and cholesterol content involved in diverse cellular processes. They have been proposed to influence membrane properties and to accommodate receptors within themselves by facilitating their interaction with ligands. Over the past decade, technical advances have improved our understanding of lipid rafts as bioactive structures. In this review, we will cover the more recent findings about cholesterol, sphingolipids and lipid rafts located in cellular and nuclear membranes in cancer. Collectively, the data provide insights on the role of lipid rafts as biomolecular targets in cancer with good perspectives for the development of innovative therapeutic strategies.

U-shaped-aggressiveness of SARS-CoV-2: Period between initial symptoms and clinical progression to COVID-19 suspicion. A population-based cohort study.

BACKGROUND: Early identification of different COVID-19 clinical presentations may depict distinct pathophysiological mechanisms and guide management strategies. OBJECTIVE: To determine the aggressiveness of SARS-CoV-2 using symptom progression in COVID-19 patients. DESIGN: Historic cohort study of Mexican patients. Data from January-April 2020 were provided by the Health Ministry. SETTING: Population-based. Patients registered in the Epidemiologic Surveillance System in Mexico. PARTICIPANTS: Subjects who sought medical attention for clinical suspicion of COVID-19. All patients were subjected to RT-PCR testing for SARS-CoV-2. MEASUREMENTS: We measured the Period between initial symptoms and clinical progression to COVID-19 suspicion (PISYCS) and compared it to the primary outcomes (mortality and pneumonia). RESULTS: 65,500 patients were included. Reported fatalities and pneumonia were 2176 (3.32%), and 11568 (17.66%), respectively. According to the PISYCS, patients were distributed as follows: 14.89% in <24 hours, 43.25% between 1-3 days, 31.87% between 4-7 days and 9.97% >7 days. The distribution for mortality and pneumonia was 5.2% and 22.5% in <24 hours, 2.5% and 14% between 1-3 days, 3.6% and 19.5% between 4-7 days, 4.1% and 20.6% >7 days, respectively (p<0.001). Adjusted-risk of mortality was (OR [95% CI], p-value): <24 hours = 1.75 [1.55-1.98], p<0.001; 1-3 days = 1 (reference value); 4-7 days = 1.53 [1.37-1.70], p<0.001; >7 days = 1.67 [1.44-1.94], p<0.001. For pneumonia: <24 hours = 1.49 [1.39-1.58], p<0.001; 1-3 days = 1; 4-7 days = 1.48 [1.41-1.56], p<0.001; >7 days = 1.57 [1.46-1.69], p<0.001. LIMITATIONS: Using a database fed by large numbers of people carries the risk of data inaccuracy. However, this imprecision is expected to be random and data are consistent with previous studies. CONCLUSION: The PISYCS shows a U-shaped SARS-CoV-2 aggressiveness pattern. Further studies are needed to corroborate the time-related pathophysiology behind these findings.

SARS-CoV-2 Infection: A Role for S1P/S1P Receptor Signaling in the Nervous System?

The recent coronavirus disease (COVID-19) is still spreading worldwide. The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), the virus responsible for COVID-19, binds to its receptor angiotensin-converting enzyme 2 (ACE2), and replicates within the cells of the nasal cavity, then spreads along the airway tracts, causing mild clinical manifestations, and, in a majority of patients, a persisting loss of smell. In some individuals, SARS-CoV-2 reaches and infects several organs, including the lung, leading to severe pulmonary disease. SARS-CoV-2 induces neurological symptoms, likely contributing to morbidity and mortality through unknown mechanisms. Sphingosine 1-phosphate (S1P) is a bioactive sphingolipid with pleiotropic properties and functions in many tissues, including the nervous system. S1P regulates neurogenesis and inflammation and it is implicated in multiple sclerosis (MS). Notably, Fingolimod (FTY720), a modulator of S1P receptors, has been approved for the treatment of MS and is being tested for COVID-19. Here, we discuss the putative role of S1P on viral infection and in the modulation of inflammation and survival in the stem cell niche of the olfactory epithelium. This could help to design therapeutic strategies based on S1P-mediated signaling to limit or overcome the host-virus interaction, virus propagation and the pathogenesis and complications involving the nervous system.