Hemolysis of human erythrocytes induced by tamoxifen is related to disruption of membrane structure

The Conjugates of Indolo[2,3-b]quinoline as Anti-Pancreatic Cancer Agents: Design, Synthesis, Molecular Docking and Biological Evaluations

New amide conjugates of hydroxycinnamic acids (HCAs) and the known antineoplastic 5,11-dimethyl-5H-indolo[2,3-b]quinoline (DiMIQ), an analog of the natural alkaloid neocryptolepine, were synthesized and tested in vitro for anticancer activity. The compound 9-[((2-hydroxy)cinnamoyl)amino]-5,11-dimethyl-5H-indolo[2,3-b]quinoline (2), which contains the ortho-coumaric acid fragment, demonstrated dose-dependent effectiveness against both normal BxPC-3 and metastatic AsPC-1 pancreatic cancer cells. The IC50 values for AsPC-1 and BxPC-3 were 336.5 nM and 347.5 nM, respectively, with a selectivity index of approximately 5 for both pancreatic cancer cells compared to normal dermal fibroblasts. Conjugate 2 did not exhibit any hemolytic activity against human erythrocytes at the tested concentration. Computational studies were performed to predict the pharmacokinetic profile and potential mechanism of action of the synthesized conjugates. These studies focused on the ADME properties of the conjugates and their interactions with DNA, as well as DNA-topoisomerase alpha and beta complexes. All of the conjugates studied showed approximately one order of magnitude stronger binding to DNA compared to the reference DiMIQ, and approximately two orders of magnitude stronger binding to the topoisomerase II-DNA complex compared to DiMIQ. Conjugate 2 was predicted to have the strongest binding to the enzyme-DNA complex, with a Ki value of 2.8 nM.

Fabrication of TPGS decorated Etravirine loaded lipidic nanocarriers as a neoteric oral bioavailability enhancer for lymphatic targeting

Etravirine (ERVN) is a potential NNRTI (non-nucleoside reverse transcriptase inhibitor) in treating HIV infection. It possesses extremely low oral bioavailability. The present research aims to optimize the formulation and characterization of TPGS-enriched ERVN-loaded lipid-based nanocarriers (NLCs) for HIV-infected patients. The formulation, ERVN-TPGS-NLCs, was optimized by central composite rotational design using a modified-solvent emulsification process. Various characterization parameters of NLCs were evaluated, including globule size of 121.56 ± 2.174 nm, PDI of 0.172 ± 0.042, the zeta potential of - 7.32 ± 0.021 mV, %EE of 94.42 ± 8.65% of ERVN and %DL was 8.94 ± 0.759% of ERVN and spherical shape was revealed by TEM. PXRD was also performed to identify the crystallinity of the sample. In-vitro drug release showed % a cumulative drug release of 83.72 ± 8.35% at pH 1.2 and 90.61 ± 9.11% at pH 6.8, respectively, whereas the % cumulative drug release from drug suspension (ERVN-S) was found to be 21.13 ± 2.01% at pH 1.2 and 24.84 ± 2.51 at pH 6.8 at the end of 48 h. Further, the intestinal permeation study and confocal microscope showed approximately three-fold and  two-fold increased permeation in ERVN-TPGS-NLCs and ERVN-NLCs across the gut sac compared to ERVN-S. Hemolysis compatibility and lipolysis studies were performed to predict the in-vivo fate of the formulation. The pharmacokinetic study revealed a 3.13-fold increment in the relative bioavailability, which agrees with the ex-vivo studies, and lymphatic uptake was validated by using cycloheximide along with designed formulation, which showed the impact of lymphatic uptake in AUC. This study ensures that ERVN-TPGS-NLCs take lymphatic uptake to minimize the first-pass metabolism followed by improved oral bioavailability of ERVN. Thus, the enhanced bioavailability of ERVN can reduce the high dose of ERVN to minimize the adverse effects related to dose-related burden.

Tamoxifen induces eryptosis through calcium accumulation and oxidative stress

Chemotherapy-related anemia is a major obstacle in anticancer therapy. Tamoxifen (TAM) is an antiestrogen prescribed for breast cancer patients with hemolytic potential and apoptotic properties in nucleated cells. However, the eryptotic activity of TAM has hitherto escaped the efforts of investigators. RBCs from apparently healthy volunteers were treated with 1-50 μM of TAM for 24 h at 37 °C. Hemoglobin leakage and LDH, AST, and AChE activities were photometrically determined while K+, Na+, and Mg2+ were detected by ion-selective electrode. Flow cytometry was used to identify eryptotic cells by annexin-V-FITC, intracellular Ca2+ by Fluo4/AM, sell size and morphology by FSC and SSC signals, respectively, and oxidative stress by H2DCFDA. Whole blood was also exposed to 30 μM of TAM for 24 h at 37 °C to examine the toxicity of TAM to WBCs and platelets. TAM caused Ca2+-independent, dose-responsive hemolysis accompanied by K+, LDH, and AST leakage without improving the mechanical stability of RBCs in hypotonic environments. TAM treatment also increased the proportion of cells positive for annexin-V-FITC, Fluo4, and DCF, along with diminished FSC and SSC signals and AChE activity. Notably, TAM toxicity was aggravated by sucrose but abrogated by vitamin C, PEG 8000, and urea. Moreover, TAM exhibited distinct cytotoxic profiles against leukocytes and platelets. TAM-induced eryptosis is characterized by breakdown of membrane asymmetry, inhibition of AChE activity, Ca2+ accumulation, cell shrinkage, and oxidative stress. Vitamin C, PEG 8000, and urea may hold promise to subvert the undesirable toxic effects of TAM on RBCs.

On the Mechanism of Membrane Permeabilization by Tamoxifen and 4-Hydroxytamoxifen

Tamoxifen (TMX), commonly used in complementary therapy for breast cancer, also displays known effects on the structure and function of biological membranes. This work presents an experimental and simulation study on the permeabilization of model phospholipid membranes by TMX and its derivative 4-hydroxytamoxifen (HTMX). TMX induces rapid and extensive vesicle contents leakage in phosphatidylcholine (PC) liposomes, with the effect of HTMX being much weaker. Fitting of the leakage curves for TMX, yields two rate constants, corresponding to a fast and a slow process, whereas in the case of HTMX, only the slow process takes place. Interestingly, incorporation of phosphatidylglycerol (PG) or phosphatidylethanolamine (PE) protects PC membranes from TMXinduced permeabilization. Fourier-transform infrared spectroscopy (FTIR) shows that, in the presence of TMX there is a shift in the ν_CH2 band frequency, corresponding to an increase in gauche conformers, and a shift in the ν_C=O band frequency, indicating a dehydration of the polar region. A preferential association of TMX with PC, in mixed PC/PE systems, is observed by differential scanning calorimetry. Molecular dynamics (MD) simulations support the experimental results, and provide feasible explanations to the protecting effect of PG and PE. These findings add new information to explain the various mechanisms of the anticancer actions of TMX, not related to the estrogen receptor, and potential side effects of this drug.

Anticancer drugs tamoxifen and 4hydroxytamoxifen as effectors of phosphatidylethanolamine lipid polymorphism

The interaction of tamoxifen (TMX) and its metabolite 4-hydroxytamoxifen (HTMX) with a biomimetic membrane model system composed of 1,2-dielaidoylphosphatidylethanolamine (DEPE) has been studied using a biophysical approach. Incorporation of TMX into DEPE bilayers gives rise to a progressive broadening of the L_β/L_α phase transition and a downward temperature shift. The L_β/L_α phase transition presents multiple endotherms, indicating a lateral segregation of TMX/DEPE domains within the plane of the bilayer. TMX and HTMX also widen and shift the L_α to hexagonal-H_II transition toward lower values, the phase diagrams showing that both compounds facilitate formation of the H_II phase. TMX increases motional disorder of DEPE acyl chains in the L_β, L_α and H_II phases, whereas the effect of HTMX is clearly different. In addition, neither TMX nor HTMX significantly perturb the hydration state of the polar headgroup region of DEPE. Molecular dynamics (MD) simulations indicate that these drugs do not affect membrane thickness, area per lipid, or the conformation of DEPE molecules. As a general rule, the interaction of HTMX with DEPE is qualitatively similar to TMX but less intense. However, a significant difference shown by MD is that HTMX is mainly placed around the center of each monolayer while TMX is located mainly at the center of the membrane, also having a greater tendency to cluster formation. These results are discussed to understand the modulation of phosphatidylethanolamine lipid polymorphism carried out by these drugs, which could be of relevance to explain their effects on enzyme activity or membrane permeabilization.

Combinatorial delivery of Ribociclib and Green tea extract mediated nanostructured lipid carrier for oral delivery for the treatment of breast cancer synchronizing in silico, in vitro, and in vivo studies

Purpose: The current research investigated the development and evaluation of dual drug-loaded nanostructure lipidic carriers (NLCs) of green tea extract and Ribociclib.Method: In silico study were performed to determine the effectiveness of combinational approach. The prepared NLCs were subjected to in vitro drug release, lipolysis, haemolysis and cell line studies to assess their in vivo prospect.Results: In silico study was done to get docking score of EGCG (-8.98) close to Ribociclib (-10.78) in CDK-4 receptors. The prepared NLCs exhibited particle size (175.80 ± 3.51 nm); PDI (0.571 ± 0.012); and %EE [RBO (80.91 ± 1.66%) and GTE 75.98 ± 2.35%)] respectively. MCF-7 cell lines were used to evaluate the MTT assay, cellular uptake and antioxidant (ROS and SOD) of prepared NLCs. In vitro drug release showed the controlled release up to 72 h. In vitro lipolysis and in vitro haemolysis studies showed the availability of drugs at absorption sites and the greater in vivo prospects of NLCs respectively. Pharmacokinetic study revealed a 3.63-fold and 1.53-fold increment in RBO and GTE bioavailability in female Wistar rats respectively.Conclusion: The prominent potential of green tea extract and RBO-loaded NLCs in enhancing their therapeutic efficacy for better treatment of breast cancer.

Ribociclib Nanostructured Lipid Carrier Aimed for Breast Cancer: Formulation Optimization, Attenuating In Vitro Specification, and In Vivo Scrutinization

Purpose

The current investigation is on the explicit development and evaluation of nanostructured lipidic carriers (NLCs) through the oral route to overcome the inherent lacuna of chemotherapeutic drug, in which Ribociclib (RBO) was used for breast cancer to diminish the bioavailability issue.

Method

The RBO-NLCs were prepared using the solvent evaporation method and optimized method by the Box–Behnken design (BBD). Various assessment parameters characterized the optimized formulation and their in vivo study.

Results

The prepared NLCs exhibited mean particle size of 114.23 ± 2.75 nm, mean polydispersity index of 0.649 ± 0.043, and high entrapment efficiency of 87.7 ± 1.79%. The structural analysis by TEM revealed the spherical size of NLCs and uniform drug distribution. An in vitro drug release study was established through the 0.1 N HCl pH 1.2, acetate buffer pH 4.5, and phosphate buffer pH 6.8 with % cumulative drug release of 86.71 ± 8.14, 85.82 ± 4.58, and 70.98 ± 5.69%, was found respectively, compared with the RBO suspension (RBO-SUS). In vitro intestinal gut permeation studies unveiled a 1.95-fold gain in gut permeation by RBO-NLCs compared with RBO-SUS. In vitro lipolysis suggests the drug availability at the absorption site. In vitro haemolysis study suggests the compatibility of NLCs to red blood cells compared to the suspension of the pure drug. The confocal study revealed the depth of penetration of the drug into the intestine by RBO-NLCs which was enhanced compared to RBO-SUS. A cell line study was done in MCF-7 and significantly reduced the IC₅₀ value compared to the pure drug. The in vivo parameters suggested the enhanced bioavailability by 3.54 times of RBO-NLCs as compared to RBO-SUS.

Conclusion

The in vitro, ex vivo, and in vivo results showed a prominent potential for bioavailability enhancement of RBO and effective breast cancer therapy.

Biosynthesized Silver Nanoparticles for Cancer Therapy and In Vivo Bioimaging

In the current communication, a simple, environmentally compatible, non-toxic green chemistry process is used for the development of silver nanoparticles (AgZE) by the reaction between silver nitrate (AgNO₃) and the ethanolic leaf extract of Zinnia elegans (ZE). The optimization of AgZE is carried out using a series of experiments. Various physico-chemical techniques are utilized to characterize the nanomaterials. The cell viability assay of AgZE in normal cells (CHO, HEK-293T, EA.hy926, and H9c2) shows their biocompatible nature, which is supported by hemolytic assay using mouse RBC. Interestingly, the nanoparticles exhibited cytotoxicity towards different cancer cell lines (U-87, MCF-7, HeLa, PANC-1 and B16F10). The detailed anticancer activity of AgZE on human glioblastoma cell line (U-87) is exhibited through various in vitro assays. In vivo the AgZE illustrates anticancer activity by inhibiting blood vessel formation through CAM assay. Furthermore, the AgZE nanoparticles when intraperitoneally injected in C57BL6/J mice (with and without tumor) exhibit fluorescence properties in the NIR region (excitation: 710 nm, emission: 820 nm) evidenced by bioimaging studies. The AgZE biodistribution through ICPOES analysis illustrates the presence of silver in different vital organs. Considering all the results, AgZE could be useful as a potential cancer therapeutic agent, as well as an NIR based non-invasive imaging tool in near future.

Impact of environmental mercury exposure on the blood cells oxidative status of fishermen living around Mundaú lagoon in Maceió - Alagoas (AL), Brazil

Mercury in the aquatic environment can lead to exposure of the human population and is a known toxic metal due to its capacity for accumulation in organs. We aimed to evaluate the mercury level in the blood and urine of fishermen and correlate it with the level of oxidative stress in blood cells. We show in this case-control study that the fishermen of the exposed group (case) of Mundaú Lagoon (Maceió - Alagoas, Brazil) have higher concentrations of total mercury in the blood (0.73-48.38 μg L^-1) and urine (0.430-10.2 μg L^-1) than the total mercury concentrations in blood (0.29-17.30 μg L^-1) and urine (0.210-2.65 μg L^-1) of the control group. In the blood cells of fishermen, we observed that the lymphomononuclear cells produced high levels of reactive oxygen species (61.7%), and the erythrocytes presented increased lipid peroxidation (151%) and protein oxidation (41.0%) and a decrease in total thiol (36.5%), GSH and the REDOX state (16.5%). The activity of antioxidant system enzymes (SOD, GPx, and GST) was also reduced in the exposed group by 26.9%, 28.3%, and 19.0%, respectively. Furthermore, hemoglobin oxygen uptake was decreased in the exposed group (40.0%), and the membrane of cells presented increased osmotic fragility (154%) compared to those in the control group. These results suggest that mercury in the blood of fishermen can be responsible for causing impairments in the oxidative status of blood cells and is probably the cause of the reduction in oxygen uptake capacity and damage to the membranes of erythrocytes.

Protective effect of Terminalia arjuna against alcohol induced oxidative damage of rat erythrocyte membranes

Background

Alcohol is a widely abused drug with many health implications, mainly caused by the oxidative and nitrosative stress on different body parts. Ayurvedic herbalism authenticates the multiple therapeutic applications of Terminalia arjuna bark due to its rich phytochemical repertoire.

Objective

To observe the extent of oxidative damage caused to erythrocytes by alcohol and assess the protective ability of T. arjuna bark powder aqueous extract (AETA) against the damage.

Materials and methods

Wister albino rats were categorized into four groups of eight rats per group; first group (control) was fed with glucose, second group was given alcohol at a dose of 20% v/v; 5g alcohol/kg b. wt/day, third group was co-administered with AETA (0.5 g/kg b. wt/day) and alcohol and the fourth group was kept on bark extract alone. Blood samples were collected and evaluated for different biochemical parameters after the completion of the treatment period.

Results

Alcohol significantly increased the erythrocyte membrane protein carbonyl and malondialdehyde (MDA) contents, along with a concomitant decrease in the membrane antioxidant status, when compared to the control group. Chromatographic analysis of the alcohol-treated rat erythrocyte membranes revealed altered membrane individual phospholipid contents and fluidity properties. Alcohol-induced morphological changes in the erythrocytes and its effect on decreasing the resistance of hypotonic shock induced by NaCl are evident from the hemolysis curves. However, AETA administration to alcoholic rats beneficially modulated the membrane properties anvd protected erythrocytes from damage.

Conclusion

Results suggest that AETA protects erythrocytes from alcohol-induced oxidative stress, biophysical, and biochemical changes very effectively.

Antimicrobial Activity of Schinopsis brasiliensis Engler Extract-Loaded Chitosan Microparticles in Oral Infectious Disease

Enterococcus faecalis infections represent a health concern, mainly in oral diseases, in which treatments with chlorhexidine solution (0.2%) are often used; however, it presents high toxicity degree and several side effects. Based on this, the use of natural products as an alternative to treatment has been explored. Nonetheless, plant extracts have poor organoleptic characteristics that impair theirs in natura use. Therefore, this work aimed to evaluate the analytical profile, biological activity, and cytotoxicity in vitro of S. brasiliensis-loaded chitosan microparticles (CMSb) produced using different aspersion flow rates. The analytical fingerprint was obtained by FTIR and NIR spectra. Principal components analysis (PCA) was used to verify the similarity between the samples. The crystallinity degree was evaluated by X-ray diffraction (XRD). Phytochemical screening (PS) was performed to quantify phytocompounds. Antimicrobial activity was evaluated by minimum inhibitory concentration (MIC). Antibiofilm activity and bactericidal kinetics against E. faecalis (ATCC 29212 and MB 146-clinical isolated) were also assessed. The hemolytic potential was performed to evaluate the cytotoxicity. Data provided by FTIR, NIR, and PCA analyses revealed chemical similarity between all CMSb. Furthermore, the results from XRD analysis showed that the obtained CMSb present amorphous characteristic. Tannins and polyphenols were accurately quantified by the PS, but methodology limitations did not allow the flavonoid quantification. The low hemolytic potential assay indicates that all samples are safe. Antimicrobial assays revealed that CMSb were able to inhibit not only the E. faecalis ATCC growth but also the biofilm formation. Only one CMSb sample was able to inhibit the clinical strain. These results highlighted the CMSb antimicrobial potential and revealed this system as a promising product to treat infections caused by E. faecalis.

Antimicrobial, Antitumor and Side Effects Assessment of a Newly Synthesized Tamoxifen Analog

BACKGROUND

Tamoxifen citrate is a very prevalent drug marketed under several trade names like Apo-Tamox, Nolvadex, Tamec, Tamizam, and Tamoplex. This molecule is approved by the FDA for breast cancer treatment. Some studies have shown that tamoxifen has anti-tuberculosis and antiparasitic activities. Like any drug, tamoxifen possesses side effects, more or less dangerous.

AIMS

Basically, this work is a comparative study that aims to: primarily compare the antimicrobial and antitumor activities of tamoxifen and a newly synthesized tamoxifen analog; and to determine the molecule with lesser side effects.

METHODS

Three groups of mice were injected with tamoxifen citrate and compound 2(1,1-bis[4-(3- dimethylaminopropoxy)phenyl]-2-phenyl-but-1-ene dihydrochloride) at doses corresponding to C1 (1/10), C2 (1/50), and C3 (1/100) to compound 2 lethal dose (LD50 = 75 mg/kg) administered to adult mice. A group of noninjected mice served as a study control.

RESULTS

Experimental results suggest that compound 2 has better antitumor and antimicrobial activity than tamoxifen citrate besides its lower toxicity effects.

CONCLUSION

The results obtained from the present study confirmed the antitumor and antimicrobial effect of tamoxifen citrate and its hematological side effects. Compound 2 seems to be more effective than tamoxifen citrate for antitumor and antimicrobial treatment while having less hematological side effects and less disruption of the blood biochemical parameters. These findings encourage us to perform further studies on compound 2 and test it for other therapeutic uses for which tamoxifen was found effective.

Erythroid glucose transport in health and disease

Glucose transport is intimately linked to red blood cell physiology. Glucose is the unique energy source for these cells, and defects in glucose metabolism or transport activity are associated with impaired red blood cell morphology and deformability leading to reduced lifespan. In vertebrate erythrocytes, glucose transport is mediated by GLUT1 (in humans) or GLUT4 transporters. These proteins also account for dehydroascorbic acid (DHA) transport through erythrocyte membrane. The peculiarities of glucose transporters and the red blood cell pathologies involving GLUT1 are summarized in the present review.

A biocompatible and cathepsin B sensitive nanoscale system of dendritic polyHPMA-gemcitabine prodrug enhances antitumor activity markedly

In an attempt to improve the therapeutic indices of gemcitabine (GEM), a prodrug was designed by conjugating GEM with a stimuli-responsive dendritic polyHPMA copolymer (dendritic polyHPMA-GEM) and synthesized using the one-pot method of RAFT polymerization. The prodrug with dendritic architectures was able to aggregate and form stable nanoscale systems in the order of 46 nm. The high molecular weight (HMW, 168 kDa) dendritic prodrug could biodegrade into segments of low molecular weight (LMW, 29 kDa) for excretion. The prodrug demonstrates enzyme-responsive drug release features; over 95% GEM was released from the carrier in the presence of cathepsin B within 3 h. Investigation of the cellular mechanism underlying the dendritic prodrug suggests that cytotoxicity is associated with cellular uptake and cell apoptosis. The prodrug shows good hemocompatibility and in vivo biosafety. In particular, the dendritic polymer prodrug displays high accumulation within tumors and markedly improved in vivo antitumor activity in the 4T1 murine breast cancer model compared to free GEM. The in vivo antitumor activities are characterized by a marked suppression in tumor volumes indicating much higher tumor growth inhibition (TGI, 83%) than that in GEM treatment (TGI, 36%). In addition, some tumors were eliminated. The tumor xenograft immunohistochemistry study clearly indicates that tumor apoptosis occurs through antiangiogenic effects. These results suggest that the stimuli-responsive dendritic polymer-gemcitabine has great potential as an efficient anticancer agent.

Getting the Jump on the Development of Bullfrog Oil Microemulsions: a Nanocarrier for Amphotericin B Intended for Antifungal Treatment

Amphotericin B (AmB), a potent antifungal drug, presents physicochemical characteristics that impair the development of suitable dosage forms. In order to overcome the AmB insolubility, several lipid carriers such as microemulsions have been developed. In this context, the bullfrog oil stands out as an eligible oily phase component, since its cholesterol composition may favor the AmB incorporation. Thus, the aim of this study was to develop a microemulsion based on bullfrog oil containing AmB. Moreover, its thermal stability, antifungal activity, and cytotoxicity in vitro were evaluated. The microemulsion formulation was produced using the pseudo-ternary phase diagram (PTPD) approach and the AmB was incorporated based on the pH variation technique. The antifungal activity was evaluated by determination of minimal inhibitory concentration (MIC) against different species of Candida spp. and Trichosporon asahii. The bullfrog oil microemulsion, stabilized with 16.8% of a surfactant blend, presented an average droplet size of 26.50 ± 0.14 nm and a polydispersity index of 0.167 ± 0.006. This system was able to entrap AmB up to 2 mg mL^-1. The use of bullfrog oil as oily phase allowed an improvement of the thermal stability of the system. The MIC assay results revealed a growth inhibition for different strains of Candida spp. and were able to enhance the activity of AmB against T. asahii. The microemulsion was also able to reduce the AmB toxicity. Finally, the developed microemulsion showed to be a suitable system to incorporate AmB, improving the system's thermal stability, increasing the antifungal activity, and reducing the toxicity of this drug.

Switchable genome editing via genetic code expansion

Multiple applications of genome editing by CRISPR-Cas9 necessitate stringent regulation and Cas9 variants have accordingly been generated whose activity responds to small ligands, temperature or light. However, these approaches are often impracticable, for example in clinical therapeutic genome editing in situ or gene drives in which environmentally-compatible control is paramount. With this in mind, we have developed heritable Cas9-mediated mammalian genome editing that is acutely controlled by the cheap lysine derivative, Lys(Boc) (BOC). Genetic code expansion permitted non-physiological BOC incorporation such that Cas9 (Cas9BOC) was expressed in a full-length, active form in cultured somatic cells only after BOC exposure. Stringently BOC-dependent, heritable editing of transgenic and native genomic loci occurred when Cas9BOC was expressed at the onset of mouse embryonic development from cRNA or Cas9BOC transgenic females. The tightly controlled Cas9 editing system reported here promises to have broad applications and is a first step towards purposed, spatiotemporal gene drive regulation over large geographical ranges.

Effective cellular internalization, cell cycle arrest and improved pharmacokinetics of Tamoxifen by cholesterol based lipopolymeric nanoparticles

The present study aims at the development of cholesterol based lipopolymeric nanoparticles for improved entrapment, better cell penetration and improved pharmacokinetics of Tamoxifen (TMX). Self-assembling cholesterol grafted lipopolymer, mPEG-b-(CB-{g-chol}-co-LA) was synthesized from poly(ethyleneglycol)-block-2-methyl-2-carboxyl-propylenecarboxylic acid-co-poly (l-lactide) [mPEG-b-(CB-{g-COOH}-co-LA)] copolymer followed by carbodiimide coupling for attaching cholesterol. Lipopolymeric nanoparticles were prepared using o/w solvent evaporation technique, which were subsequently characterized to determine its particle size, entrapment efficiency, release pattern and compared with mPEG-PLA nanoparticles. Further, in order to assess the in vitro efficacy, cytotoxicity studies, uptake, apoptosis assay and cell cycle analysis were performed in breast cancer cell lines (MCF-7 and 4T1). Finally, the pharmacokinetic profile of TMX loaded mPEG-b-(CB-{g-chol}-co-LA) lipopolymeric nanoparticles was also performed. TMX loaded lipopolymeric nanoparticles of particle size 151.25 ± 3.74 (PDI 0.123) and entrapment efficiency of 73.62 ± 3.08% were formulated. The haemolytic index, protein binding and in vitro drug release of the optimized nanoparticles were found to be comparable to that of the TMX loaded mPEG-PLA nanoparticles. Lipopolymeric nanoparticles demonstrated improved IC₅₀ values in breast cancer cells (22.2 μM in 4T1; 18.8 μM in MCF-7) than free TMX (27.6 μM and 23.5 μM respectively) and higher uptake efficiency. At IC₅₀ values, TMX loaded lipopolymeric nanoparticles induced apoptosis and cell cycle arrest (G₀/G₁ phase) to similar extent as that of free drug. Pharmacokinetic studies indicated ∼2.5-fold increase in the half-life (t_1/2) (p < 0.001) and ∼2.7-fold (p < 0.001) increase in the mean residence time (MRT) of TMX following incorporation into lipopolymeric nanoparticles. Thus, mPEG-b-(CB-{g-chol}-co-LA) lipopolymeric nanoparticles offer a more promising approach for delivery of Tamoxifen in breast cancer by improving drug internalization and prolonging the mean residence time of the drug indicating possibility of dose reduction and hence bypassing the adverse effects of TMX therapy.

Antibiotic-non-antibiotic combinations for combating extremely drug-resistant Gram-negative 'superbugs'

The emergence of antimicrobial resistance of Gram-negative pathogens has become a worldwide crisis. The status quo for combating resistance is to employ synergistic combinations of antibiotics. Faced with this fast-approaching post-antibiotic era, it is critical that we devise strategies to prolong and maximize the clinical efficacy of existing antibiotics. Unfortunately, reports of extremely drug-resistant (XDR) Gram-negative pathogens have become more common. Combining antibiotics such as polymyxin B or the broad-spectrum tetracycline and minocycline with various FDA-approved non-antibiotic drugs have emerged as a novel combination strategy against otherwise untreatable XDR pathogens. This review surveys the available literature on the potential benefits of employing antibiotic-non-antibiotic drug combination therapy. The apex of this review highlights the clinical utility of this novel therapeutic strategy for combating infections caused by 'superbugs'.

Deciphering the Nongenomic, Mitochondrial Toxicity of Tamoxifens As Determined by Cell Metabolism and Redox Activity

Tamoxifen is not only considered a very potent chemotherapeutic adjuvant for estrogen receptor positive breast cancers but also a very good chemo-preventive drug. Recently, there has been a rising amount of evidence for a nongenomic cytotoxicity of tamoxifen, even in estrogen receptor negative cells, which has greatly confounded researchers. Clinically, the side effects of tamoxifen can be very serious, ranging from liver steatosis to cirrhosis, tumorigenesis, or onset of porphyrias. Herein, we deciphered the nongenomic, mitochondrial cytotoxicity of tamoxifen in estrogen receptor positive MCF7 versus triple-negative MDA-MB-231 cells, employing the mitochondrial complex III quinoloxidizing-center inhibitor myxothiazol. We showed a role for hydroxyl-radical-mediated lipid peroxidation, catalyzed by iron, stemming from the redox interactions of tamoxifen quinoid metabolites with complex III, resulting in Fenton-capable reduced quinones. The role of tamoxifen semiquinone species in mitochondrial toxicity was also shown together with evidence of mitochondrial DNA damage. Tamoxifen caused an overall metabolic (respiratory and glycolytic) rate decrease in the Pasteur type MCF cells, while in the Warburg type MDA-MB-231 cells the respiratory rate was not significantly affected and the glycolytiv rate was significantly boosted. The nongenomic cytotoxicity of tamoxifens was hence associated with the metabolic phenotype and redox activity of the cells, as in the present paradigm of Pasteur MCF7s versus Warburg MDA-MB-231 cells. Our present findings call for caution in the use of the drugs, especially as a chemopreventive and/or in cases of iron overload diseases.

Tamoxifen-loaded poly(L-lactide) nanoparticles: Development, characterization and in vitro evaluation of cytotoxicity

In this study, poly(L-lactide) (PLA) nanoparticles containing Tamoxifen (Tmx) were developed using an emulsion/solvent evaporation method, observing the influence of surfactants and their concentrations on mean particle size and drug entrapment. Nanoparticles were characterized in terms of size, morphology, polydispersity, interaction drug-polymer and in vitro drug release profile. Cytotoxicity over erythrocytes and tumor cells was assessed. The optimized formulation employed as surfactant 1% polyvinyl alcohol. Mean particle size was 155±4 nm (n=3) and Tmx encapsulation efficiency was 85±8% (n=3). The in vitro release profile revealed a biphasic release pattern diffusion-controlled with approximately 24% of drug released in 24 h followed by a sustained release up to 120 h (30% of Tmx released). PLA nanoparticles containing Tmx presented a very low index of hemolysis (less than 10%), in contrast to free Tmx that was significantly hemolytic. Tmx-loaded PLA nanoparticles showed IC50 value 2-fold higher than free Tmx, but considering the prolonged Tmx release from nanoparticles, cytotoxicity on tumor cells was maintained after nanoencapsulation. Thus, PLA nanoparticles are promising carriers for controlled delivery of Tmx with potential application in cancer treatment.

Mitochondria: the gateway for tamoxifen-induced liver injury

Tamoxifen (TAM) is routinely used in the treatment of breast carcinoma. TAM-induced liver injury remains a major concern, as TAM causes hepatic steatosis in a significant number of patients, which can progress toward steatohepatitis. Liver toxicity is generally believed to involve mitochondrial dysfunction and TAM exerts multiple deleterious effects on mitochondria, which may account for the hepatotoxicity observed in patients treated with TAM. Endoxifen (EDX), a key active metabolite of TAM that is being investigated as an alternative to TAM in breast cancer therapy, slightly affects mitochondria in comparison with TAM and this demonstration well correlates with the absence of alterations in the clinical parameters of individuals taking EDX. The steady-state plasma concentrations of TAM and its active metabolites EDX and 4-hydroxytamoxifen (OHTAM) in patients taking TAM are highly variable, reflecting genetic variants of CYP2D6 involved in TAM metabolism. Besides de genetic polymorphisms, the intake of drugs that influence the enzymatic activity of CYP2D6 compromises the therapeutic efficiency of TAM. The knowledge of the impact of the variability of TAM metabolism in the breast cancer treatment explains the discrepant outcomes observed in patients taking TAM, as well as the individual variability of idiosyncratic liver injury and other sides effects observed. Therefore, and contrarily to the clinical use of EDX, the need of therapeutic drug monitoring and a regular assessment of liver function biomarkers should be considered in patients under therapies with TAM. In this review we focus on the mitochondrial effects of TAM and its metabolites and on the role played by mitochondria in the initiating events leading to TAM-induced hepatotoxicity, as well as the clinical implications.

Uptake of Eudragit Retard L (Eudragit® RL) Nanoparticles by Human THP-1 Cell Line and Its Effects on Hematology and Erythrocyte Damage in Rats

The aim of this study was to prepare Eudragit Retard L (Eudragit RL) nanoparticles (ENPs) and to determine their properties, their uptake by the human THP-1 cell line in vitro and their effect on the hematological parameters and erythrocyte damage in rats. ENPs showed an average size of 329.0 ± 18.5 nm, a positive zeta potential value of +57.5 ± 5.47 mV and nearly spherical shape with a smooth surface. THP-1 cell lines could phagocyte ENPs after 2 h of incubation. In the in vivo study, male Sprague-Dawley rats were exposed orally or intraperitoneally (IP) with a single dose of ENP (50 mg/kg body weight). Blood samples were collected after 4 h, 48 h, one week and three weeks for hematological and erythrocytes analysis. ENPs induced significant hematological disturbances in platelets, red blood cell (RBC) total and differential counts of white blood cells (WBCs) after 4 h, 48 h and one week. ENP increased met-Hb and Co-Hb derivatives and decreased met-Hb reductase activity. These parameters were comparable to the control after three weeks when administrated orally. It could be concluded that the route of administration has a major effect on the induction of hematological disturbances and should be considered when ENPs are applied for drug delivery systems.

Naringin mitigates erythrocytes aging induced by paclitaxel: an in vitro study

In this study, the protective role of naringin (NAR) against paclitaxel (PTX)-induced erythrocytes aging has been investigated using human erythrocyte as an in vitro model. Erythrocytes were incubated with PTX in the presence and absence of NAR. Incubation of erythrocytes with PTX resulted in increased protein carbonyl content and malondialdehyde and hemolysis percentage compared with control. Furthermore, a significant increase in the ratios of glutathione peroxidase/glutathione reductase, superoxide dismutase/glutathione peroxidase, and superoxide dismutase/catalase in PTX-treated cells was observed, compared with control cells. In contrast, reduced glutathione/oxidized glutathione ratio and glucose-6-phosphate dehydrogenase activity were decreased upon PTX treatment. The simultaneous incubation of erythrocytes with PTX and NAR restored these variables to values similar to those of control erythrocytes. These results suggest that NAR inhibited PTX-induced aging by lessening the PTX-induced oxidative stress.

Effect of safeners on damage of human erythrocytes treated with chloroacetamide herbicides

Chloroacetamides are used as pre-emergent substances for growth control of annual grasses and weeds. Since they can be harmful for crop plants, protective compounds (safeners) are used along with herbicides. So far, their effects on human blood cells have not been evaluated, and this study is the very first one devoted to this subject. We examined the harmful effects of chloroacetamides, their metabolites and safeners, used alone or in combination with herbicides, on human erythrocytes measuring the extent of hemolysis, lipid peroxidation and catalase activity. Higher impact of herbicides than their metabolites on all of the investigated parameters was found. Safeners alone did not produce any damage to erythrocytes and did not elicit any changes in oxidative stress parameters. Combination of safener with herbicide did not attenuate hemolysis of erythrocytes compared to the herbicide alone. Safeners reduced lipid peroxidation induced by herbicides, which suggest the role of safeners as antioxidants.

Surface functionalization of nanoparticles to control cell interactions and drug release

Nanoparticles made from poly(dl-lactide-co-glycolide) (PLGA) are used to deliver a wide range of bioactive molecules, due to their biocompatibility and biodegradability. This study investigates the surface modification of PLGA nanoparticles via the layer-by-layer (LbL) deposition of polyelectrolytes, and the effects of these coatings on the release behavior, cytotoxicity, hemolytic activity, and cellular uptake efficiency. PLGA nanoparticles are modified via LbL adsorption of two polyelectrolyte pairs: 1) poly(allylamine hydrochloride) (PAH) and poly(styrene sulfonate) (PSS) and 2) poly(L-lysine hydrobromide) (PLL) and dextran sulfate (DES). It is demonstrated that both PAH/PSS and PLL/DES coatings suppress the burst release usually observed for unmodified PLGA nanoparticles and that the release behavior can be adjusted by changing the layer numbers, layer materials, or by crosslinking the layer constituents. Neither bare nor polyelectrolyte-modified PLGA nanoparticles show any signs of cytotoxicity. However, nanoparticles with a positively charged polyelectrolyte as the outermost layer induce hemolysis, whereas uncoated particles or particles with a negatively charged polyelectrolyte as the outermost layer show no hemolytic activity. Furthermore, particles with either PAH or PLL as the outermost layer also demonstrate a higher uptake efficiency by L929 fibroblast cells, due to a higher cell-particle affinity. This study suggests that LbL coating of PLGA nanoparticles can control the release behavior of bioactive molecules as well as the surface activity, therefore providing a promising strategy to enhance the efficiency of nanoparticulate drug-delivery systems.

Phospholipid bilayer-perturbing properties underlying lysis induced by pH-sensitive cationic lysine-based surfactants in biomembranes

Amino acid-based surfactants constitute an important class of natural surface-active biomolecules with an unpredictable number of industrial applications. To gain a better mechanistic understanding of surfactant-induced membrane destabilization, we assessed the phospholipid bilayer-perturbing properties of new cationic lysine-based surfactants. We used erythrocytes as biomembrane models to study the hemolytic activity of surfactants and their effects on cells' osmotic resistance and morphology, as well as on membrane fluidity and membrane protein profile with varying pH. The antihemolytic capacity of amphiphiles correlated negatively with the length of the alkyl chain. Anisotropy measurements showed that the pH-sensitive surfactants, with the positive charge on the α-amino group of lysine, significantly increased membrane fluidity at acidic conditions. SDS-PAGE analysis revealed that surfactants induced significant degradation of membrane proteins in hypo-osmotic medium and at pH 5.4. By scanning electron microscopy examinations, we corroborated the interaction of surfactants with lipid bilayer. We found that varying the surfactant chemical structure is a way to modulate the positioning of the molecule inside bilayer and, thus, the overall effect on the membrane. Our work showed that pH-sensitive lysine-based surfactants significantly disturb the lipid bilayer of biomembranes especially at acidic conditions, which suggests that these compounds are promising as a new class of multifunctional bioactive excipients for active intracellular drug delivery.

Definition of metabolism-dependent xenobiotic toxicity with co-cultures of human hepatocytes and mouse 3T3 fibroblasts in the novel integrated discrete multiple organ co-culture (IdMOC) experimental system: results with model toxicants aflatoxin B1, cyclophosphamide and tamoxifen

The integrated discrete multiple organ co-culture system (IdMOC) allows the co-culturing of multiple cell types as physically separated cells interconnected by a common overlying medium. We report here the application of IdMOC with two cell types: the metabolically competent primary human hepatocytes, and a metabolically incompetent cell line, mouse 3T3 fibroblasts, in the definition of the role of hepatic metabolism on the cytotoxicity of three model toxicants: cyclophosphamide (CPA), aflatoxin B1 (AFB) and tamoxifen (TMX). The presence of hepatic metabolism in IdMOC with human hepatocytes was demonstrated by the metabolism of the P450 isoform 3A4 substrate, luciferin-IPA. The three model toxicants showed three distinct patterns of cytotoxic profile: TMX was cytotoxic to 3T3 cells in the absence of hepatocytes, with slightly lower cytotoxicity towards both 3T3 cells and hepatocytes in the IdMOC. AFB was selective toxic towards the human hepatocytes and relatively noncytotoxic towards 3T3 cells both in the presence and absence of the hepatocytes. CPA cytotoxicity to the 3T3 cells was found to be significantly enhanced by the presence of the hepatocytes, with the cytotoxicity dependent of the number of hepatocytes, and with the cytotoxicity attenuated by the presence of a non-specific P450 inhibitor, 1-aminobenzotriazole. We propose here the following classification of toxicants based on the role of hepatic metabolism as defined by the human hepatocyte-3T3 cell IdMOC assay: type I: direct-acting cytotoxicants represented by TMX as indicated by cytotoxicity in 3T3 cells in the absence of hepatocytes; type II: metabolism-dependent cytotoxicity represented by AFB1 with effects localized within the site of metabolic activation (i. e. hepatocytes); and type III: metabolism-dependent cytotoxicity with metabolites that can diffuse out of the hepatocytes to cause toxicity in cells distal from the site of metabolism, as exemplified by CPA.

Interaction of tamoxifen and noise-induced damage to the cochlea

Tamoxifen has been used extensively in the treatment of breast cancer and other neoplasms. In addition to its well-known action on estrogen receptors it is also known to acutely block chloride channels that participate in cell volume regulation. Tamoxifen's role in preventing cochlear outer hair cell (OHC) swelling in vitro suggested that OHC swelling noted following noise exposure could potentially be a therapeutic target for tamoxifen in its role as a chloride channel blocker to help prevent noise-induced hearing loss. To investigate this possibility, the effects of exposure to tamoxifen on physiologic measures of cochlear function in the presence and absence of subsequent noise exposure were studied. Male Mongolian gerbils (2-4 months old) were randomly assigned to different groups. Tamoxifen at ∼10 mg/kg was administered to one of the groups. Five hours later they were exposed to a one-third octave band of noise centered at 8 kHz in a sound-isolation chamber for 30 min at 108 dB SPL. Compound action potential (CAP) thresholds and distortion product otoacoustic emission (DPOAE) levels were measured 30-35 days following noise exposure. Tamoxifen administration did not produce any changes in CAP thresholds and DPOAE levels when administered by itself in the absence of noise. Tamoxifen causes a significant increase in CAP thresholds from 8 to 15 kHz following noise exposure compared to CAP thresholds in animals exposed to noise alone. No significant differences were seen in the DPOAE levels in the f(2) = 8-15 kHz frequency range where maximum noise-induced increases in CAP thresholds were seen. Contrary to our original expectation, it is concluded that tamoxifen potentiates the degree of damage to the cochlea resulting from noise exposure.

Influence of tamoxifen on gluconeogenesis and glycolysis in the perfused rat liver

The actions of tamoxifen, a selective estrogen receptor modulator used in chemotherapy and chemo-prevention of breast cancer, on glycolysis and gluconeogenesis were investigated in the isolated perfused rat liver. Tamoxifen inhibited gluconeogenesis from both lactate and fructose at very low concentrations (e.g., 5μM). The opposite, i.e., stimulation, was found for glycolysis from both endogenous glycogen and fructose. Oxygen uptake was unaffected, inhibited or stimulated, depending on the conditions. Stimulation occurred in both microsomes and mitochondria. Tamoxifen did not affect the most important key-enzymes of gluconeogenesis, namely, phosphoenolpyruvate carboxykinase, pyruvate carboxylase, fructose 1,6-bisphosphatase and glucose 6-phosphatase. Confirming previous observations, however, tamoxifen inhibited very strongly NADH- and succinate-oxidase of freeze-thawing disrupted mitochondria. Tamoxifen promoted the release of both lactate dehydrogenase (mainly cytosolic) and fumarase (mainly mitochondrial) into the perfusate. Tamoxifen (200μM) clearly diminished the ATP content and increased the ADP content of livers in the presence of lactate with a diminution of the ATP/ADP ratio from 1.67 to 0.79. The main causes for gluconeogenesis inhibition are probably: (a) inhibition of energy metabolism; (b) deviation of intermediates (malate and glucose 6-phosphate) for the production of NADPH required in hydroxylation and demethylation reactions; (c) deviation of glucosyl units toward glucuronidation reactions; (d) secondary inhibitory action of nitric oxide, whose production is stimulated by tamoxifen; (e) impairment of the cellular structure, especially the membrane structure. Stimulation of glycolysis is probably a compensatory phenomenon for the diminished mitochondrial ATP production. The multiple actions of tamoxifen at relatively low concentrations can represent a continuous burden to the overall hepatic functions during long treatment periods.

Role of the interaction between puerarin and the erythrocyte membrane in puerarin-induced hemolysis

Adverse drug reactions (ADR), especially intravenous hemolysis, have largely limited the application of puerarin injections in clinics. This study investigated the underlying mechanisms of puerarin-induced hemolysis. Our results show that puerarin induced concentration-dependent and time-dependent hemolysis when human erythrocytes were incubated in saline solution with more than 2mM puerarin for over 2h. However, incubation in PBS or addition of 1mM of lidocaine to the saline solution completely abolished the hemolysis. Providing materials that could start ATP synthesis did not reverse the hemolysis, and puerarin did not affect Na(+)-K(+)-ATPase activity. In addition, puerarin (0.1-2mM) did not cause calcium influx or exhibited pro-oxidant activity in erythrocytes. Puerarin exhibited different influences on the membrane microviscosity of erythrocytes in saline and PBS. Moreover, 1mM lidocaine inhibited 8mM puerarin-induced reduction of membrane microviscosity in saline solution. SDS-PAGE analysis of membrane proteins revealed that 2mM puerarin treatment induced the appearance of several new protein bands but attenuated the expression of protein bands 2.1, 3, 4.1, 4.2 and 5. These results suggest that high concentrations of puerarin-induced hemolysis were associated with the changes of membrane lipids and of the composition of erythrocytes membrane proteins but not with ATP depletion, pro-oxidation and calcium influx. These changes could be related to the intercalation of amphiphilic puerarin at high concentration into the erythrocyte membrane in certain media, resulting in membrane disorganization and, eventually, cytolysis. Hence, in clinics, determining the optimal dose of puerarin is critical to avoid overdosing and ADR.

Acrylamide-induced oxidative stress in human erythrocytes

Acrylamide (AA), a widely used industrial chemical, is shown to be neurotoxic, mutagenic and carcinogenic. This study was carried out to investigate the effects of different doses of AA on lipid peroxidation (LPO), haemolysis, methaemoglobin (MetHb) and antioxidant system in human erythrocytes in vitro. Erythrocyte solutions were incubated with 0.10, 0.25, 0.50 and 1.00 mM of AA at 37°C for 1 hour. At the end of the incubation, malondialdehyde (MDA), an end product of LPO, was determined by liquid chromatography (LC) while total glutathione, reduced glutathione (GSH) levels, activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px) enzymes and the rates of haemolysis and MetHb were determined by spectrophotometric methods. All of the studied concentrations of AA increased MetHb formation and SOD activity, and induced MDA formation and haemolysis due to the destruction of erythrocyte cell membrane. AA caused a decrease in the activities of GSH-Px, CAT and GSH levels. However, these effects of AA were seen only at higher concentrations than AA intake estimated for populations in many countries. We suggest that LPO process may not be involved in the toxic effects of AA in low concentrations, although the present results showed that the studied concentrations of AA exert deteriorating effects on antioxidant enzyme activities, LPO process and haemolysis.

Protection of wheat bran feruloyl oligosaccharides against free radical-induced oxidative damage in normal human erythrocytes

The present work assessed the protective effect of water-soluble feruloyl oligosaccharides (FSH), ferulic acid ester of oligosaccharides from wheat bran, against in vitro oxidative damage of normal human erythrocytes induced by a water-soluble free radical initiator, 2,2'-azobis-2-amidinopropane dihydrochloride (AAPH). In the whole process of AAPH-initiated oxidation, hemolysis occurred quickly after the lag time. The rate of hemolysis is correlated dose-dependently with AAPH concentration. Significant decrease in reduced glutathione (GSH) levels of erythrocyte with concomitant enhancement in oxidized gluthione (GSSG) levels was noticed. It was also observed that lipid and protein peroxidation of erythrocytes induced by AAPH was significantly increased, and scanning electron microscopy observations showed that AAPH induced obvious morphological alteration in the erythrocytes from a smooth discoid to an echinocytic form. FSH suppressed depletion of GSH, lipid peroxidation, and methaemoglobin and protein carbonyl group formation of erythrocytes in concentration- and time-dependent manners, remarkably delayed AAPH-induced hemolysis. Morphological changes to erythrocyte caused by AAPH were effectively protected by FSH. It was also observed that FSH could work synergistically with endogenous antioxidants in erythrocytes. These results indicated that FSH efficiently protected normal human erythrocytes against oxidative stress, and they could be used as a potential source of natural antioxidants.

Tocopherols and tocotrienols in membranes: a critical review

The familiar role of tocols (tocopherols and tocotrienols) as lipid-soluble chain-terminating inhibitors of lipid peroxidation is currently in the midst of a reinterpretation. New biological activities have been described for tocols that apparently are not dependent on their well-established antioxidant behaviour. These activities could well be real, but there remain large gaps in our understanding of the behaviour of tocols in membranes, especially when it comes to the alpha-, beta-, gamma-, delta-chroman methylation patterns and the seemingly special nature of tocotrienols. It is inappropriate to make conclusions and develop models based on in vivo (or cell culture) results with reference to in vitro measurements of antioxidant activity. When present in biological membranes, tocols will experience a large variation in the local composition of phospholipids and the presence of neutral lipids such as cholesterol, both of which would be expected to change the efficiency of antioxidant action. It is likely that tocols are not homogeneously dispersed in a membrane, but it is still not known whether any specific combination of lipid head group and acyl chains are conferred special protection from peroxidation, nor do we currently appreciate the structural role that tocols play in membranes. Tocols may enhance curvature stress or counteract similar stresses generated by other lipids such as lysolipids. This review will outline what is known about the location and behaviour of tocols in phospholipid bilayers. We will draw mainly from the biophysical literature, but will attempt to extend the discussion to biologically relevant phenomena when appropriate. We hope that it will assist researchers when designing new experiments and when critically assessing the results, in turn providing a more thorough understanding of the biochemistry of tocols.

Molecular associations of vitamin E

To understand how vitamin E fulfills its functions in membranes and lipoproteins, it is necessary to know how it associates with the lipid components of these structures and the effects its presence has on their structure and stability. Studies of model membrane systems containing vitamin E have proved to be an informative approach to address these questions. A review of the way vitamin E interacts with phospholipid bilayers, how it distributes within the structure, its motional diffusion characteristics, and orientation has been undertaken. The effect of vitamin E on membrane stability and permeability has been described. The tendency of vitamin E to form complexes with certain phospholipids is examined as is the way modulation of protein functions takes place. Finally, recent evidence relevant to the putative role of vitamin E in protecting membranes from free radical attack and the consequences of lipid oxidation in lipoproteins and membranes is examined.

Free radical-mediated pre-hemolytic injury in human red blood cells subjected to lead acetate as evaluated by chemiluminescence

The mechanisms by which Pb(2+) induces hemolysis are not completely understood. For this reason, the involvement of oxidative stress in the mechanism of Pb(2+)-induced pre-hemolytic lesion was investigated by exposing RBC to Pb(2+) in vitro and then separating the intact non-hemolysed RBC. Oxidative stress was investigated on human RBCs by tert-butyl hydroperoxide-initiated chemiluminescence method (CL). Our results revealed that lead-induced time and concentration-dependent hemolysis and CL time curves showed a very narrow correlation each other. GSH oxidation to GSSG and the stress index also increased significantly. Treatment of lead-exposed RBC with desferrioxamine, an iron-chelating agent or the chain-breaking antioxidant, Trolox, quenched light emission and inhibited hemolysis dramatically. Mannitol and sodium formate, (*)OH scavengers, on the contrary, did not inhibit CL or hemolysis, significantly. These data indicate that lead-induced lipid peroxide formation is mediated by a metal-driven Fenton reaction but do not support the direct involvement of hydroxyl radicals in this process. By contrast, our results revealed a decrease in light emission and decreased hemolysis in the presence of histidine, a singlet oxygen scavenger. Our results suggest that membrane damage and hemolysis of RBC are mediated by Pb(2+) through free radical reactions and that singlet oxygen plays a significant role in this process.

Inhibition of monosodium urate monohydrate-mediated hemolysis by vitamin E

Microcrystals of monosodium urate monohydrate (MSUM) induce cytolysis and hemolysis in erythrocytes. In this report, we studied the effect of vitamin E on MSUM-mediated hemolysis in human erythrocytes. Vitamin E significantly inhibited hemolysis induced by MSUM. The hydroxyl group in the chromanol ring of vitamin E is dispensable for protecting erythrocytes against hemolysis induced by MSUM, indicating that the inhibitory effect of vitamin E is not due to its antioxidant properties. However, both the chromanol ring and the isoprenoid side chain are important for vitamin E to suppress MSUM-induced hemolysis. Our current study suggests that vitamin E inhibits hemolysis induced by MSUM as a membrane stabilizer.

Vitamin E inhibits hemolysis induced by hemin as a membrane stabilizer

Hemin is a potential cytolytic agent. To test the effect of vitamin E on hemin-mediated permeability in cell membranes, sheep erythrocytes were chosen as an appropriate model to study hemolysis induced by hemin. Hemin-induced hemolysis but did not elicit lipid peroxidation in sheep erythrocytes. Vitamin E was effective in inhibiting hemin-mediated hemolysis. Both chromanol ring and the isoprenoid side chain of tocopherols were essential for inhibition of hemin-induced hemolysis. There was a strong correlation between the inhibitory effects of tocopherols on hemin-induced erythrocyte hemolysis and their effects on fluorescence anisotropy of cell membranes. Our results suggested that, in contrast to its antioxidant activity, vitamin E inhibits hemolysis induced by hemin as a membrane stabilizing agent.