Toxicological effects of hydroxychloroquine sulfate and chloroquine diphosphate substances on the early-life stages of fish in the COVID-19 pandemic context.

Hydroxychloroquine sulfate (HCQ) and chloroquine diphosphate (CQ) have been used at increased rates to treat COVID-19 but can constitute a potential environmental risk. The objective was to evaluate the toxicity of sublethal concentrations of HCQ and CQ in zebrafish embryos/larvae. The 50% lethal concentrations (LC50) of HCQ and CQ at 96 h post-fertilization (hpf) were calculated by testing various concentrations on 2,160 embryos. The LC50 obtained were 560 and 800 µM for HCQ and CQ, respectively. Next, the embryotoxicity assay was performed, where 1,200 embryos were subjected to sublethal concentrations of HCQ and CQ. The hatching and heart rates were recorded. After euthanasia, photomicrographs of all larvae were taken to measure the total length, pericardial and yolk sac areas. The embryos exposed to sublethal concentrations of HCQ and CQ showed delayed hatching at 72 hpf, as well as an increase in the heart rate, larger pericardial and yolk sac areas, and body malformations at 96 hpf. The findings show that HCQ and CQ are toxic to fish in the early development phases. Understanding the mechanisms of toxicity will help extrapolate the effects of 4-aminoquinoline derivatives when they reach the aquatic environment in the context of the COVID-19 pandemic.

Cytotoxic effect of carbohydrate derivatives of digitoxigenin involves modulation of plasma membrane Ca2+ -ATPase.

Cardiac glycosides, such as digoxin and digitoxin, are compounds that interact with Na+ /K+ -ATPase to induce anti-neoplastic effects; however, these cardiac glycosides have narrow therapeutic index. Thus, semi-synthetic analogs of digitoxin with modifications in the sugar moiety has been shown to be an interesting approach to obtain more selective and more effective analogs than the parent natural product. Therefore, the aim of this study was to assess the cytotoxic potential of novel digitoxigenin derivatives, digitoxigenin-α-L-rhamno-pyranoside (1) and digitoxigenin-α-L-amiceto-pyranoside (2), in cervical carcinoma cells (HeLa) and human diploid lung fibroblasts (Wi-26-VA4). In addition, we studied the anticancer mechanisms of action of these compounds by comparing its cytotoxic effects with the potential to modulate the activity of three P-type ATPases; Na+ /K+ -ATPase, sarco/endoplasmic reticulum Ca2+ -ATPase (SERCA), and plasma membrane Ca2+ -ATPase (PMCA). Briefly, the results showed that compounds 1 and 2 were more cytotoxic and selectivity for HeLa tumor cells than the nontumor cells Wi-26-VA4. While the anticancer cytotoxicity in HeLa cells involves the modulation of Na+ /K+ -ATPase, PMCA and SERCA, the modulation of these P-type ATPases was completely absent in Wi-26-VA4 cells, which suggest the importance of their role in the cytotoxic effect of compounds 1 and 2 in HeLa cells. Furthermore, the compound 2 inhibited directly erythrocyte ghosts PMCA and both compounds were more cytotoxic than digitoxin in HeLa cells. These results provide a better understanding of the mode of action of the synthetic cardiac glycosides and highlights 1 and 2 as potential anticancer agents.

Implications of Synthetic Modifications of the Cardiotonic Steroid Lactone Ring on Cytotoxicity.

Na,K-ATPase (NKA) and cardiotonic steroids (CTS) have shown potent cytotoxic and anticancer effects. Here, we have synthesized a series of CTS digoxin derivatives (γ-benzylidene) with substitutions in the lactone ring and evaluated the cytotoxicity caused by digoxin derivatives in tumor and non-tumor cells lines, as well as their effects on NKA. The cytotoxicity assay was determined in HeLa, A549, and WI-26 VA4 after they were treated for 48 h with increased concentrations of CTS. The effects of CTS on NKA activity and immunoblotting of α1 and ß1 isoforms were evaluated at IC50 concentrations in A549 cell membrane. NKA activity from mouse brain cortex was also measured. The majority of CTS exhibited low cytotoxicity in tumor and non-tumor cells, presenting IC50 values at micromolar concentrations, while digoxin showed cytotoxicity at nanomolar concentrations. BD-15 presented the lowest IC50 value (8 µM) in A549 and reduced its NKA activity in 28%. In contrast, BD-7 was the compound that most inhibited NKA (56% inhibition) and presented high IC50 value for A549. In mouse cortex, only BD-15 modulated the enzyme activity in a concentration-dependent inhibition curve. These results demonstrate that the cytotoxicity of these compounds is not related to NKA inhibition. The substitutions in the lactone ring of digoxin led to an increase in the cytotoxic concentration in tumor cells, which may not be interesting for cancer, but it has the advantage of increasing the therapeutic margin of these molecules when compared to classic CTS, and can be used safely in research for other diseases.

The γ-Benzylidene Digoxin Derivative BD-15 Increases the α3-Na, K-ATPase Activity in Rat Hippocampus and Prefrontal Cortex and no Change on Heart.

Our study aimed to investigate the effects of the new cardiotonic steroid BD-15 (γ-benzylidene derivatives) in the behavioral parameters, oxidative stress and the Na, K-ATPase activity in the hippocampus, prefrontal cortex and heart from rats to verify the safety and possible utilization in brain disorders. For this study, groups of male Wistar rats were used after intraperitoneal injection of 20, 100 and 200 µg/Kg with BD-15. The groups were treated for three consecutive days and the control group received 0.9% saline. BD-15 did not alter behavior of rats treated with different doses. An increase in the specific α2,3-Na, K-ATPase activity was observed for all doses of BD-15 tested in the hippocampus. However, in the prefrontal cortex, only the dose of 100 µg/Kg increased the activity of all Na, K-ATPase isoforms. BD-15 did not cause alteration in the lipid peroxidation levels in the hippocampus, but in the prefrontal cortex, a decrease of lipid peroxidation (~ 25%) was observed. In the hippocampus, GSH levels increased with all doses tested, while in the prefrontal cortex no changes were found. Subsequently, when the effect of BD-15 on cardiac tissue was analyzed, no changes were observed in the tested parameters. BD-15 at a dosage of 100 µg/Kg proved to be promising because it is considered therapeutic for brain disorders, since it increases the activity of the α3-Na, K-ATPase in the hippocampus and prefrontal cortex, as well as decreasing the oxidative stress in these brain regions. In addition, this drug did not cause changes in the tissues of the heart and kidneys, preferentially demonstrating specificity for the brain.

Antagonistic anticancer effect of paclitaxel and digoxin combination.

Despite the growing interest in the antitumor effect of cardiotonic steroids, combination treatments with well-established chemotherapy drugs like paclitaxel have been rarely investigated. Moreover, paclitaxel has been suggested as a Na+ /K+ -ATPase inhibitor. Here we investigated the effect of paclitaxel and digoxin alone or in combination on the viability of human lung (A549) and cervical cancer (HeLa) cell lines and the inhibitory effect of paclitaxel on several mammalian Na+ /K+ -ATPases. Although the viability of both tumor cell lines was concentration-dependently affected by digoxin treatment after 48 hours (A549 IC50 = 31 nM and HeLa IC50 = 151 nM), a partial effect was observed for paclitaxel, with a maximal inhibitory effect of 45% at 1000 nM with A549 and around 70% with HeLa cells (IC50 = 1 nM). Although the two drugs were cytotoxic, their combined effect in HeLa cells was revealed to be antagonistic, as estimated by the combination index. No direct inhibitory effect of paclitaxel was detected in human, pig, rat, and mouse Na+ /K+ -ATPase enzymes, but high concentrations of paclitaxel decreased the Na+ /K+ -ATPase activity in HeLa cells after 48 hours without affecting protein expression. Our findings demonstrate that, under our conditions, paclitaxel and digoxin cotreatment produce antagonistic cytotoxic effects in HeLa cells, and the mechanism of action of paclitaxel does not involve a direct inhibition of Na+ /K+ -ATPase. More studies shall be designed to evaluate the consequences of the interaction of cardiotonic steroids and chemotherapy drugs.

Ouabain attenuates oxidative stress and modulates lipid composition in hippocampus of rats in lipopolysaccharide-induced hypocampal neuroinflammation in rats.

Our study aimed to analyze the effect of ouabain (OUA) administration on lipopolysaccharide (LPS)-induced changes in hippocampus of rats. Oxidative parameters were analyzed in Wistar rats after intraperitoneal injection of OUA (1.8 µg/kg), LPS (200 µg/kg), or OUA plus LPS or saline. To reach our goal, activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX), in addition to levels of reduced glutathione (GSH), protein carbonyl (PCO) and lipid peroxidation (LPO) were evaluated. We also analyzed the membrane lipid profile and some important lipids for the nervous system, such as phosphatidylethanolamine (PE), phosphatidylcholine (PC), phosphatidylinositol (PI), phosphatidic acid and sphingomyelin. The group that received only LPS showed increased oxidative stress, as evidenced by an increase in LPO (about twice), PCO (about three times) levels, and CAT activity (80%). Conversely, administration of LPS decreased GSH levels (55%), and GPx activity (30%), besides a reduction in the amount of PI (60%) and PC (45%). By other side, OUA alone increased the amount of PI (45%), PE (85%), and PC (70%). All harmful effects recorded were attenuated by OUA, suggesting a protective effect against LPS-induced oxidative stress. The relevance of our results extends beyond changes in oxidative parameters induced by LPS, because nanomolar doses of OUA may be useful in neurodegenerative models. Other studies on other cardenolides and substances related issues, as well as the development of new molecules derived from OUA, could also be useful in general oxidative and/or cellular stress, a condition favoring the appearance of neuronal pathologies.

Evaluation of the effect of cafeteria diet on the kidney Na,K-ATPase activity, and oxidative stress.

In this study, renal tissue, subdivided into the cortex and medulla of Wistar rats subjected to a cafeteria diet (CAF) for 24 days or to normal diet, was used to analyze whether the renal enzyme Na,K-ATPase activity was modified by CAF diet, as well as to analyze the α1 subunit of renal Na,K-ATPase expression levels. The lipid profile of the renal plasma membrane and oxidative stress were verified. In the Na,K-ATPase activity evaluation, no alteration was found, but a significant decrease of 30% in the cortex was detected in the α1 subunit expression of the enzyme. There was a 24% decrease in phospholipids in the cortex of rats submitted to CAF, a 17% increase in cholesterol levels in the cortex, and a 23% decrease in the medulla. Lipid peroxidation was significantly increased in the groups submitted to CAF, both in the cortical region, 29%, and in the medulla, 35%. Also, a reduction of 45% in the glutathione levels was observed in the cortex and medulla with CAF. CAF showed a nearly two-fold increase in glutathione peroxidase (GPX) activity in relation to the control group in the cortex and a 59% increase in the GPx activity in the medulla. In conclusion, although the diet was administered for a short period of time, important results were found, especially those related to the lipid profile and oxidative stress, which may directly affect renal function.

Assays with recombinant soluble isoforms of DC-SIGN, a dengue virus ligand, show variation in their ability to bind to mannose residues.

The DC-SIGN glycoprotein is responsible for the initial adhesion of dengue virus (DENV) to immune cells by the carbohydrate recognition domain (CRD). There are thirteen soluble and membrane-bound DC-SIGN isoforms, but the role of soluble isoforms in the DENV internalization process is not known. Five isoforms with an altered or absent CRD were identified, and three different soluble isoforms were used to confirm the interactions with mannose residues. The results show the loss of binding ability of one soluble isoform and binding ability of two of them. All of them will be used to verify their role in the DENV internalization process.

Reduced CD8+ T cells infiltration can be associated to a malignant transformation in potentially malignant oral epithelial lesions.

OBJECTIVE: The aim of this study was to evaluate the immunohistochemical expressions of PD1, CD4+, and CD8+ in premalignant lesions (OPML) that were transformed into oral squamous cell carcinoma OSCC (OPML-OSCC), in OSCC and also in premalignant lesions that were not transformed into OSCC (OPML-NOSSC). MATERIALS AND METHODS: Retrospective analyses were performed in order to verify the demographic characteristics of the patients. CD4, CD8, and PD1 IMH studies were carried out on OPML and OSCC samples from 11 patients with OPML-OSCC and OPML, together with samples from 14 patients with OPML-NOSCC. The differences between OPML-OSCC and OPML-NOSCC were analyzed. RESULTS: Non-homogenous leukoplakia, together with the related oral subsite, and the lack of an exposure to tobacco, were all associated with malignant transformations. There were no statistical differences in the PD1 expression and the CD4+ cells in OPML-OSCC and OPML-NOSCC. A significant increment in the CD8+ cells was noted in the OPML that evolved into carcinomas when compared with OPML-NOSCC (p = 0.05), whereas there were higher CD8+ cells levels in the carcinomas when compared with the OPML that evolved into carcinomas (p = 0.027). CONCLUSIONS: CD8+ cells infiltrate more in OPML-NOSCC than in OPML-OSCC. Carcinoma is more infiltrated by CD8+ cells than its associated OPML. CLINICAL RELEVANCE: Understanding immunological factors associated with malignant transformation of oral premalignant lesions can open a new way to treat this disease.

Ouabain attenuates the oxidative stress induced by lipopolysaccharides in the cerebellum of rats.

Our study aimed to analyze the effect of ouabain administration on lipopolysaccharide (LPS)-induced changes in oxidative parameters, membrane lipid composition, and the activities of some important enzymes of the nervous system. The content of phospholipids, cholesterol, and gangliosides were analyzed in Wistar rats after intraperitoneal injection of ouabain (1.8 µg/kg), LPS (200 µg/kg), or saline. Oxidative parameters were also evaluated, including the activities of superoxide dismutase, catalase and glutathione peroxidase, the levels of glutathione and lipid peroxidation, as well as Na,K-ATPase activity and the level of glutamate transporter EAAT4. Administration of LPS resulted in increased oxidative stress, as evidenced by an increase in lipid peroxidation levels, glutathione peroxidase activity, decreased catalase activity and reduced glutathione levels. All changes recorded were attenuated by pretreatment with ouabain. Administration of ouabain plus LPS enhanced the total ganglioside content and EAAT4 levels, but failed to alter the Na,K-ATPase activity. Our data suggest a neuroprotective effect of ouabain against LPS-induced oxidative stress by promoting membrane lipid remodeling and increasing the expression of glutamate transporter EAAT4. Our results emphasize that the observed oxidative stress is not correlated with Na,K-ATPase, but with a possible ouabain-mediated effect on cellular signaling. The relevance of our results extends beyond LPS-induced changes in oxidative parameters, as nanomolar doses of ouabain might prove useful in neurodegenerative models. Further study of other cardenolides and related molecules, as well as the development of new molecules derived from ouabain, could also prove useful in the fight against the oxidative and/or general cell stress triggered by neuronal pathologies.

Iron overload impact on P-ATPases.

Iron is a chemical element that is active in the fundamental physiological processes for human life, but its burden can be toxic to the body, mainly because of the stimulation of membrane lipid peroxidation. For this reason, the action of iron on many ATPases has been studied, especially on P-ATPases, such as the Na+,K+-ATPase and the Ca2+-ATPase. On the Fe2+-ATPase activity, the free iron acts as an activator, decreasing the intracellular Fe2+ and playing a protection role for the cell. On the Ca2+-ATPase activity, the iron overload decreases the enzyme activity, raising the cytoplasmic Ca2+ and decreasing the sarco/endoplasmic reticulum and the Golgi apparatus Ca2+ concentrations, which could promote an enzyme oxidation, nitration, and fragmentation. However, the iron overload effect on the Na+,K+-ATPase may change according to the tissue expressions. On the renal cells, as well as on the brain and the heart, iron promotes an enzyme inactivation, whereas its effect on the erythrocytes seems to be the opposite, directly stimulating the ATPase activity, or stimulating it by signaling pathways involving ROS and PKC. Modulations in the ATPase activity may impair the ionic transportation, which is essential for cell viability maintenance, inducing irreversible damage to the cell homeostasis. Here, we will discuss about the iron overload effect on the P-ATPases, such as the Na+,K+-ATPase, the Ca2+-ATPase, and the Fe2+-ATPase.

Properties of novel surfactin-derived biosurfactants obtained through solid-phase synthesis.

Eight molecules, four peptides (SPs) and four lipopeptides (LPs) derived by rational design from surfactin, a well-known secreted biosurfactant from Bacillus subtilis, were produced employing Fmoc-based solid-phase synthesis. These new peptides were tested to evaluate their potential biosurfactant and biological activities, aiming at possible applications in industrial, biological, pharmaceutical, and medical use. Five molecules (SP1, SP2, SP4, LP5, and LP8) presented potential for medical uses, mainly due to their drug delivery properties as suggested by their synergistic activity with the antibiotic vancomycin against Staphylococcus aureus. All synthetic peptides showed low toxicity against Vero cell cultures, in assays of hemolysis, and in different cytotoxicity assays. In addition, we found that three peptides (SP1, LP6, and LP7) had potential technological and industrial use because of their emulsifying capacity, low toxicity, and ability to physically stabilize solutions. These novel molecules retained some properties of the parental molecule (surfactin, which was originally obtained through nonribosomal synthesis in Bacillus subtilis) but have the advantage of being linear peptides, which can be produced at large scales through the use of conventional heterologous protein expression protocols.

Ouabain Modulates the Lipid Composition of Hippocampal Plasma Membranes from Rats with LPS-induced Neuroinflammation.

The effects of ouabain (OUA) and lipopolysaccharide (LPS) in vivo on hippocampal membranes (RHM) of Wistar male rats aged 3 months were analyzed. After intraperitoneal (i.p.) injection of OUA only, LPS only, OUA plus LPS, or saline, the content of proteins, phospholipids, cholesterol and gangliosides from RHM was analyzed. The total protein and cholesterol contents of RHM were not significantly affected by OUA or LPS for the experimentally paired groups. In contrast, total phospholipids and gangliosides were strongly modulated by either OUA or LPS treatments. LPS reduced the total phospholipids (roughly 23 %) and increased the total gangliosides (approximately 40 %). OUA alone increased the total phospholipids (around 23 %) and also the total gangliosides (nearly 34 %). OUA pretreatment compensated the LPS-induced changes, preserving the total phospholipids and gangliosides around the same levels of the control. Thus, an acute treatment with OUA not only modulated the composition of hippocampal membranes from 3-month-old rats, but also was apparently able to counteract membrane alterations resulting from LPS-induced neuroinflammation. This study demonstrates for the first time that the OUA capacity modulates the lipid composition of hippocampal plasma membranes from rats with LPS-induced neuroinflammation.

Ouabain-induced alterations of the apical junctional complex involve α1 and ß1 Na,K-ATPase downregulation and ERK1/2 activation independent of caveolae in colorectal cancer cells.

Studies have reported that Na,K-ATPase interacts with E-cadherin to stabilize (AJs) and regulate the expression of claudins, the main proteins present in the tight junction (TJ) in epithelial cells containing caveolae. However, the role of this ATPase in the regulation of the AJ and TJ proteins in colorectal cancer cells as well as the molecular events underlying this event in a caveolae-independent system remain undefined. In the present study, we used ouabain, a classic drug known to inhibit Na,K-ATPase, and Caco-2 cells, which are a well-established human colorectal cancer model that does not exhibit caveolae. We demonstrated that ouabain treatment resulted in a reduction of the ß1 Na,K-ATPase protein and cell redistribution of the AJ proteins E-cadherin and ß-catenin, as well as the α1 Na,K-ATPase subunit. Furthermore, ouabain increased claudin-3 protein levels, impaired the TJ barrier function and increased cell viability and proliferation during the early stages of treatment. Additionally, the observed ouabain-induced events were dependent on the activation of ERK1/2 signaling; but in contrast to previous studies, this signaling cascade was caveolae-independent. In conclusion, our findings strongly suggest that α1 and ß1 Na,K-ATPase downregulation and ERK1/2 activation induced by ouabain are interlinked events that play an important role during cell-cell adhesion loss, which is an important step during the tumor progression of colorectal carcinomas.

The effect of gamma radiation on the lipid profile of irradiated red blood cells.

An investigation into the effects of irradiation and of the storage time on aging and quality are a relevant issue to ensure the safety and the efficiency of irradiation in the prevention of transfusion-associated graft-versus-host disease (TA-GVHD). In this work, the biochemical properties and alterations presented by erythrocyte membranes, up to 28-days post-irradiation, with a dose of 25 Gy, were studied as a function of storage and post-irradiation time. There was a considerable variation in the total of phospholipid content, when comparing the control and irradiated samples, mostly from the third day onwards; and at the same time, the effect occurred as a function on the storage time of blood bags. The levels of total cholesterol decreased 3-9 days after irradiation. TBARS levels were increased after irradiation and 7 days of storage, but no increment of catalase activity was observed after the irradiation. Furthermore, the protein profile was maintained throughout the irradiation and storage time, until the 21st day, with the presence of a protein fragmentation band of around 28 kDa on the 28th day. In conclusion, although gamma irradiation is the main agent for the prevention of TA-GVHD, a better understanding of the physical and biochemical properties of erythrocytes are necessary to better assess their viability, and to be able to issue more secure recommendations on the shelf life of blood bags, and the safe use of the irradiated red cells therein.

Development and evaluation of sustained-release etoposide-loaded poly(ε-caprolactone) implants.

Poly(ε-caprolactone) implants containing etoposide, an important chemotherapeutic agent and topoisomerase II inhibitor, were fabricated by a melt method and characterized in terms of content uniformity, morphology, drug physical state, and sterility. In vitro and in vivo drug release from the implants was also evaluated. The cytotoxic activity of implants against HeLa cells was studied. The short-term tolerance of the implants was investigated after subcutaneous implantation in mice. The original chemical structure of etoposide was preserved after incorporation into the polymeric matrix, in which the drug was dispersed uniformly. Etoposide was present in crystalline form in the polymeric implant. In vitro release study showed prolonged and controlled release of etoposide, which showed cytotoxicity activity against HeLa cells. After implantation, good correlation between in vitro and in vivo drug release was found. The implants demonstrated good short-term tolerance in mice. These results tend to show that etoposide-loaded implants could be potentially applied as a local etoposide delivery system.

Antioxidant Therapy Reduces Oxidative Stress, Restores Na,K-ATPase Function and Induces Neuroprotection in Rodent Models of Seizure and Epilepsy: A Systematic Review and Meta-Analysis.

Epilepsy is a neurological disorder characterized by epileptic seizures resulting from neuronal hyperexcitability, which may be related to failures in Na,K-ATPase activity and oxidative stress participation. We conducted this study to investigate the impact of antioxidant therapy on oxidative stress, Na,K-ATPase activity, seizure factors, and mortality in rodent seizure/epilepsy models induced by pentylenetetrazol (PTZ), pilocarpine (PILO), and kainic acid (KA). After screening 561 records in the MEDLINE, EMBASE, Web of Science, Science Direct, and Scopus databases, 22 were included in the systematic review following the PRISMA guidelines. The meta-analysis included 14 studies and showed that in epileptic animals there was an increase in the oxidizing agents nitric oxide (NO) and malondialdehyde (MDA), with a reduction in endogenous antioxidants reduced glutathione (GSH) and superoxide dismutase (SO). The Na,K-ATPase activity was reduced in all areas evaluated. Antioxidant therapy reversed all of these parameters altered by seizure or epilepsy induction. In addition, there was a percentage decrease in the number of seizures and mortality, and a meta-analysis showed a longer seizure latency in animals using antioxidant therapy. Thus, this study suggests that the use of antioxidants promotes neuroprotective effects and mitigates the effects of epilepsy. The protocol was registered in the Prospective Register of Systematic Reviews (PROSPERO) CRD42022356960.

Effect of Ouabain on Glutamate Transport in the Hippocampus of Rats with LPS-Induced Neuroinflammation.

A lipopolysaccharide (LPS)-induced neuroinflammation rat model was used to study the effects of ouabain (OUA) at low concentrations, which can interact with the Na,K-ATPase, causing the modulation of intracellular signalling pathways in the Central Nervous System. Our study aimed to analyse the effects of OUA on glutamate transport in the hippocampus of rats with LPS-induced neuroinflammation. Adult male Wistar rats were divided into four groups: OUA (1.8 µg/kg), saline (CTR), LPS (200 µg/kg), and OUA + LPS (OUA 20 min before LPS). The animals were sacrificed after 2 h, and the hippocampus was collected for analysis. After treatment, we determined the activities of Na,K-ATPase and glutamine synthetase (GS). In addition, expression of the α1, α2, and α3 isoforms of Na,K-ATPase and the glutamate transporters, EAAT1 and EAAT2, were also analysed. Treatment with OUA caused a specific increase in the α2 isoform expression (~20%), whereas LPS decreased its expression (~22%), and treatment with OUA before LPS prevented the effects of LPS. Moreover, LPS caused a decrease of approximately 50% in GS activity compared with that in the CTR group; however, OUA pre-treatment attenuated this effect of LPS. Notably, it was found that treatment with OUA caused an increase in the expression of EAAT1 (~30%) and EAAT2 (~25%), whereas LPS caused a decrease in the expression of EAAT1 (~23%) and EAAT2 (~25%) compared with that in the CTR group. When treated with OUA, the effects of LPS were abrogated. In conclusion, the OUA pre-treatment abolished the effect caused by LPS, suggesting that this finding may be related to the restoration of the interaction between FXYD2 and the studied membrane proteins.

Digoxin Derivatives Sensitize a Saccharomyces cerevisiae Mutant Strain to Fluconazole by Inhibiting Pdr5p.

The poor outcome of treatments for fungal infections is a consequence of the increasing incidence of resistance to antifungal agents, mainly due to the overexpression of efflux pumps. To surpass this mechanism of resistance, a substance able to inhibit these pumps could be administered in association with antifungals. Saccharomyces cerevisiae possesses an efflux pump (Pdr5p) homologue to those found in pathogenic yeast. Digoxin is a natural product that inhibits Na+, K+-ATPase. The aim of this study was to evaluate whether digoxin and its derivatives (i.e., DGB, digoxin benzylidene) can inhibit Pdr5p, reversing the resistance to fluconazole in yeasts. An S. cerevisiae mutant strain that overexpresses Pdr5p was used in the assays. The effects of the compounds on yeast growth, efflux activity, and Pdr5p ATPase activity were measured. All derivatives enhanced the antifungal activity of fluconazole against S. cerevisiae, in comparison to fluconazole alone, with FICI values ranging from 0.031 to 0.500. DGB 1 and DGB 3 presented combined effects with fluconazole against a Candida albicans strain, with fractional inhibitory concentration index (FICI) values of 0.625 and 0.281, respectively The compounds also inhibited the efflux of rhodamine 6G and Pdr5p ATPase activity, with IC50 values ranging from 0.41 µM to 3.72 µM. The results suggest that digoxin derivatives impair Pdr5p activity. Considering the homology between Pdr5p and efflux pumps from pathogenic fungi, these compounds are potential candidates to be used in association with fluconazole to treat resistant fungal infections.

Biochemical Evaluation of the Effects of Hydroxyurea in Vitro on Red Blood Cells.

Hydroxyurea (HU) is a low-cost, low-toxicity drug that is often used in diseases, such as sickle cell anemia and different types of cancer. Its effects on the red blood cells (RBC) are still not fully understood. The in vitro effects of HU were evaluated on the biochemical parameters of the RBC from healthy individuals that were treated with 0.6 mM or 0.8 mM HU for 30 min and 1 h. After 30 min, there was a significant increase in almost all of the parameters analyzed in the two concentrations of HU, except for the pyruvate kinase (PK) activity. A treatment with 0.8 mM HU for 1 h resulted in a reduction of the levels of lipid peroxidation, Fe3+, and in the activities of some of the enzymes, such as glutathione reductase (GR), glucose-6-phosphate dehydrogenase (G6PD), and PK. After the incubation for 1 h, the levels of H2O2, lipid peroxidation, reduced glutathione (GSH), enzymatic activity (hexokinase, G6PD, and superoxide dismutase (SOD) were reduced with the treatment of 0.8 mM HU when compared with 0.6 mM. The results have suggested that a treatment with HU at a concentration of 0.8 mM seemed to be more efficient in protecting against the free radicals, as well as in treating diseases, such as sickle cell anemia. HU appears to preferentially stimulate the pentose pathway over the glycolytic pathway. Although this study was carried out with the RBC from healthy individuals, the changes described in this study may help to elucidate the mechanisms of action of HU when administered for therapeutic purposes.