A new and simple method for studying the binding and ingestion steps in the phagocytosis of yeasts

Quinine and chloroquine: Potential preclinical candidates for the treatment of tegumentary Leishmaniasis

Leishmaniasis is an endemic disease in more than 90 countries, constituting a relevant public health problem. Limited treatment options, increase in resistance, and therapeutic failure are important aspects for the discovery of new treatment options. Drug repurposing may accelerate the discovery of antiLeishmanial drugs. Recent tests indicating the in vitro potential of antimalarials Leishmania resulted in the design of this study. This study aimed at evaluating the susceptibility of Leishmania (L.) amazonensis to chloroquine (CQ) and quinine (QN), alone or in combination with amphotericin B (AFT) and pentamidine (PTN). In the in vitro tests, first, we evaluated the growth inhibition of 50 % of promastigotes (IC50) and cytotoxicity for HepG2 and THP-1 cells (CC50). The IC50 values of AFT and PNT were below 1 µM, while the IC50 values of CQ and QN ranged between 4 and 13 µM. Concerning cytotoxicity, CC50 values ranged between 7 and 30 µM for AFT and PNT, and between 22 and 157 µM for the antimalarials. We also calculated the Selectivity Index (SI), where AFT and PTN obtained the highest values, while the antimalarias obtained values between 5 and 12. Both antimalarials were additive (ƩFIC 1.05-1.8) in combination with AFT and PTN. For anti-amastigote activity, the drugs obtained the following ICA50 values: AFT (0.26 µM), PNT (2.09 µM), CQ (3.77 µM) and QN (24.5 µM). In the in vivo tests, we observed that the effective dose for the death of 50 % of parasites (ED50) of AFT and CQ were 0.63 mg/kg and 27.29 mg/kg, respectively. When combining CQ with AFT, a decrease in parasitemia was observed, being statistically equal to the naive group. For cytokine quantification, it was observed that CQ, despite presenting anti-inflammatory activity was effective at increasing the production of IFN-γ. Overall, our data indicate that chloroquine will probably be a candidate for repurposing and use in drug combination therapy.

High-plasticity mineral trioxide aggregate and its effects on M1 and M2 macrophage viability and adherence, phagocyte activity, production of reactive oxygen species, and cytokines

Objectives

This study evaluated the effects of high-plasticity mineral trioxide aggregate (MTA-HP) on the activity of M1 and M2 macrophages, compared to white MTA (Angelus).

Materials and Methods

Peritoneal inflammatory M1 (from C57BL/6 mice) and M2 (from BALB/c mice) macrophages were cultured in the presence of the tested materials. Cell viability (MTT and trypan blue assays), adhesion, phagocytosis, reactive oxygen species (ROS) production, and tumor necrosis factor (TNF)-α and transforming growth factor (TGF)-β production were evaluated. Parametric analysis of variance and the non-parametric Kruskal-Wallis test were used. Results were considered significant when p < 0.05.

Results

The MTT assay revealed a significant decrease in M1 metabolism with MTA-HP at 24 hours, and with MTA and MTA-HP later. The trypan blue assay showed significantly fewer live M1 at 48 hours and live M2 at 48 and 72 hours with MTA-HP, compared to MTA. M1 and M2 adherence and phagocytosis showed no significant differences compared to control for both materials. Zymosan A stimulated ROS production by macrophages. In the absence of interferon-γ, TNF-α production by M1 did not significantly differ between groups. For M2, both materials showed higher TNF-α production in the presence of the stimulus, but without significant between-group differences. Likewise, TGF-β production by M1 and M2 macrophages was not significantly different between the groups.

Conclusions

M1 and M2 macrophages presented different viability in response to MTA and MTA-HP at different time points. Introducing a plasticizer into the MTA vehicle did not interfere with the activity of M1 and M2 macrophages.

Cytotoxicity of two self-adhesive resin cements and their interference in the phagocytic activity of murine macrophages

Objectives

This study aimed to evaluate in vitro the effects of the self-adhesive resin cements RelyX U200 (3M ESPE) and seT PP (SDI Limited) on murine macrophages and the interference of the photoactivation.

Materials and Methods

Cell viability assays, cell adherence, yeast phagocytosis of Saccharomyces boulardii and production of reactive oxygen species (ROS) were performed in the presence of capillaries containing the respective self-adhesive cement when photoactivated or not.

Results

After long periods of contact, both types of cements, when not photoactivated, are more cytotoxic for macrophages. The seT PP cement when only chemically activated seems to interfere more negatively in the process of phagocytosis of yeasts S. boulardii. Both types of cements interfere in the cell adhesion process, independent of photoactivation. None of the types of cements tested was able to induce the production of ROS.

Conclusions

Our results highlight the great importance of the photoactivation of self-adhesive resin cements in the dental clinic, since RelyX U200, when photoactivated, presented the best results within the evaluated parameters.

Antileishmanial activity evaluation of a natural amide and its synthetic analogs against Leishmania (V.) braziliensis: an integrated approach in vitro and in silico

Leishmaniasis is considered a neglected disease, which makes it an unattractive market for the pharmaceutical industry; hence, efforts in the search for biologically active substances are hampered by this lack of financial motivation. Thus, in the present study, we report the leishmanicidal activity and the possible mechanisms of action of compounds with promising activity against the species Leishmania (V.) braziliensis, the causative agent of the skin disease leishmaniasis. The natural compound 1a (piplartine) and the analog 2a were the most potent against promastigote forms with growth inhibition values for 50% of the parasite population (IC50) = 8.58 and 11.25 μM, respectively. For amastigote forms, the ICa50 values were 1.46 and 16.7 μM, respectively. In the molecular docking study, piplartine showed favorable binding energy (-7.13 kcal/mol) and with 50% inhibition of trypanothione reductase (IC50) = 91.1 μM. Preliminary investigations of the mechanism of action indicate that piplartine increased ROS levels, induced loss of cell membrane integrity, and caused accumulation of lipid bodies after 24 h of incubation at its lowest effective concentration (IC50), which was not observed for the synthetic analog 2a. The mode of action for the leishmanicidal activity of piplartine (1a) was assigned to involve affinity for the trypanothione reductase of Leishmania (V.) braziliensis TR.

Difference between the biologic and chronologic age as an individualized indicator for the skin care intensity selection: skin topography and immune system state studies, parameter correlations with age difference

Background

Present research addresses the issue of skin aging and corresponding skin treatment individualization. Particular research question was on the developing of simplified criterion supporting patient-specific decision on the necessity and intensity of skin treatment. Basing on the published results and a wide pool of experimental data, we have formulated a hypothesis that a difference between biologic and chronologic age can be used as an express criterion of skin aging.

Methods

In present paper, we report the results of studies with 80 volunteers between 15 and 65 years of age, linking parameters reflecting immune state, skin state, and topography to the difference between biologic and chronologic age. Facial skin topography, skin moisture, sebum level, and skin elasticity were studied using commercial devices. Blood immunology studies were performed using venous blood samples. Correlations between all measured parameters and age difference were calculated. Also, cross correlations between skin cell profile and blood immune profile parameters, and skin roughness parameters were calculated.

Results

Age dependencies of the blood immunological parameters on the biologic and chronologic age difference are less pronounced as compared to the changes in skin cell profile parameters. However, the changes in the tendencies when biologic age becomes equal to chronologic one are visible for all studied parameters.

All measured skin roughness parameters show correlations with age difference, but average skin roughness and depth of the deepest profile valley have the largest correlation coefficient values. Many of the measured skin cell profile and blood immunology parameters show strong correlations with average skin roughness and deepest profile valley, with some of the coefficients exceeding 0.5–0.6.

Conclusions

Basing on own experiments and published research results, it is possible to suggest using the difference between calculated biologic age and chronologic age as an individualized criterion supporting decisions on skin treatment strategy. Further research involving larger numbers of participants and aiming on optimizing the expressions for calculating biologic age could lead to reliable and easily available express criterion supporting the decision making for an individualized skin treatment.

Antileishmanial and Immunomodulatory Effect of Babassu-Loaded PLGA Microparticles: A Useful Drug Target to Leishmania amazonensis Infection

The immunological and the anti-Leishmania amazonensis activity of babassu-loaded poly(lactic-co-glycolic acid) [PLGA] microparticles was evaluated. The anti-Leishmania activity was evaluated against promastigotes or amastigotes forms, in Balb/c macrophages. The size of the microparticles ranged from 3 to 6.4 μm, with a zeta potential of −25 mV and encapsulation efficiency of 48%. The anti-Leishmania activity of the PLGA microparticles loaded with the aqueous extract of babassu mesocarp (MMP) (IC₅₀) was 10-fold higher than that free extract (Meso). MMP exhibited overall bioavailability and was very effective in eliminating intracellular parasites. MMP also reduced ex vivo parasite infectivity probably by the increased production of nitric oxide, hydrogen peroxide, and TNF-α indicating the activation of M1 macrophages. The overexpression of TNF-α did not impair cell viability, suggesting antiapoptotic effects of MMP. In conclusion, babassu-loaded microparticles could be useful for drug targeting in the treatment of leishmaniasis, due to the immunomodulatory effect on macrophage polarization and the increased efficacy as an anti-Leishmania product after the microencapsulation. These findings are of great relevance since the development of new drugs for the treatment of neglected diseases is desirable, mainly if we consider the high morbidity and mortality rates of leishmaniasis worldwide.

Assessment of the cytotoxicity of a mineral trioxide aggregate-based sealer with respect to macrophage activity

AIM

To assess the influence of co-culture with mineral trioxide aggregate (MTA) and MTA Fillapex (FLPX) on the viability, adherence, and phagocytosis activity of peritoneal macrophages from two mouse strains.

METHODOLOGY

Cellular viability, adherence, and phagocytosis of Saccharomyces boulardii were assayed in the presence of capillaries containing MTA and MTA Fillapex. The data were analyzed using parametric (Student's t) and non-parametric (Mann-Whitney) tests.

RESULTS

FLPX was severely cytotoxic and decreased cell viability, adherence, and phagocytic activity of both macrophage subtypes. Cells that were treated with MTA Fillapex remained viable (>80%) for only 4 h after stimulation. Macrophages from C57BL/6 mice presented higher adherence and higher phagocytic activity compared with macrophages from BALB/c mice.

CONCLUSION

Comparison of MTA and FLPX effects upon macrophages indicates that FLPX may impair macrophage activity and viability, while MTA seems to increase phagocytic activity.

A lupane-triterpene isolated from Combretum leprosum Mart. fruit extracts that interferes with the intracellular development of Leishmania (L.) amazonensis in vitro

BACKGROUND

3beta,6beta,16beta-trihydroxylup-20(29)-ene is a lupane triterpene isolated from Combretum leprosum fruit. The lupane group has been extensively used in studies on anticancer effects; however, its possible activity against protozoa parasites is yet poorly known. The high toxicity of the compounds currently used in leishmaniasis chemotherapy stimulates the investigation of new molecules and drug targets for antileishmanial therapy.

METHODS

The activity of 3beta,6beta,16beta-trihydroxylup-20(29)-ene was evaluated against Leishmania (L.) amazonensis by determining the cytotoxicity of the compound on murine peritoneal macrophages, as well as its effects on parasite survival inside host cells. To evaluate the effect of this compound on intracellular amastigotes, cultures of infected macrophages were treated for 24, 48 and 96 h and the percentage of infected macrophages and the number of intracellular parasites was scored using light microscopy.

RESULTS

Lupane showed significant activity against the intracellular amastigotes of L. (L.) amazonensis. The treatment with 109 μM for 96 h reduced in 80 % the survival index of parasites in BALB/c peritoneal macrophages. At this concentration, the triterpene caused no cytotoxic effects against mouse peritoneal macrophages. Ultrastructural analyses of L. (L.) amazonensis intracellular amastigotes showed that lupane induced some morphological changes in parasites, such as cytosolic vacuolization, lipid body formation and mitochondrial swelling. Bioinformatic analyses through molecular docking suggest that this lupane has high-affinity binding with DNA topoisomerase.

CONCLUSION

Taken together, our results have showed that the lupane triterpene from C. leprosum interferes with L. (L.) amazonensis amastigote replication and survival inside vertebrate host cells and bioinformatics analyses strongly indicate that this molecule may be a potential inhibitor of topoisomerase IB. Moreover, this study opens major prospects for the development of novel chemotherapeutic agents with leishmanicidal activity.

Improved innate immune responses by Frondanol A5, a sea cucumber extract, prevent intestinal tumorigenesis

Sea cucumbers are a source of antibacterial, anti-inflammatory, and anticancer compounds. We show that sea cucumber extract Frondanol A5 is capable of enhancing innate immune responses and inhibiting intestinal tumors in APC(Min/+) mice. APC(Min/+) mice were fed semi-purified diets containing 0, 250, or 500 ppm FrondanolA5 for 14 weeks before we assessed intestinal tumor inhibition. Dietary Frondanol A5 suppressed small intestinal polyp sizes and formation up to 30% (P < 0.02) in males and up to 50% (P < 0.01) in females. Importantly, 250 and 500 ppm Frondanol A5 diet suppressed colon tumor multiplicities by 65% (P < 0.007) and 75% (P < 0.0001), compared with untreated male APC(Min/+) mice. In female APC(Min/+) mice, both dose levels of Frondanol A5 suppressed colon tumor multiplicities up to 80% (P < 0.0001). Isolated peritoneal macrophages from treated mice showed increased phagocytosis efficiency (control 24% vs. treated 50%; P < 0.01) and an increase in GILT mRNA expression, indicating increased innate immune responses by these cells in treated animals. Similarly, we observed an increase in GILT expression in treated tumors, compared with untreated tumors. Furthermore, an increase in G-CSF cytokine, a decrease in inflammatory cytokines and marker 5-LOX, its regulator FLAP, proliferation (PCNA), and angiogenesis (VEGF) markers were observed in treatment groups. These data suggest that Frondanol A5 decreased inflammatory angiogenic molecules and increased GILT expression and macrophage phagocytosis. These decreases may have improved the innate immune systems of the treated mice, thus aiding in inhibition of intestinal tumor formation. These results suggest that Frondanol A5 exhibits significant chemopreventive potential against intestinal tumorigenesis.

Biodegradable microparticles containing crotamine isolated from Crotalus durissus terrificus display antileishmanial activity in vitro

BACKGROUND/AIMS

To evaluate antileishmanial activity of crotamine, a toxin isolated from Crotalus durissus terrificus, in solution form and encapsulated in biodegradable microparticles in vitro.

METHODS

Particles were analyzed on-chip by surface plasmon resonance and characterized by testing their diameters, zeta potential and encapsulation rate. The viability of promastigotes as well as murine macrophages was assessed. Furthermore, the phagocytic index was determined for macrophages, and cell supernatants were collected for the determination of TNF-α levels. An infection assay using Leishmania amazonensis-infected macrophages was also conducted.

RESULTS

The diameters and zeta potential of control particles (1.35 μm; -12.3 mV) and of those containing crotamine (3.09 μm; -20.9 mV) were adequate for the assays conducted. Crotamine-loaded particles were better captured by macrophages than control particles (increase of 12% in the phagocytic index), leading to increased TNF-α levels (196 pg/ml), and they also induced a significant decrease in the numbers of amastigotes compared to infected macrophages only.

CONCLUSION

The approach presented here opens the possibility of working with safe concentrations of encapsulated toxins to reach antileishmanial effects.

Identification of virulence factors in Leishmania infantum strains by a proteomic approach

Knowledge of Leishmania virulence is essential for understanding how the contact between the pathogen and host cells can lead to pathogenesis. Virulence in two L. infantum strains was characterized using macrophages and hamsters. Next, we used difference gel electrophoresis (DIGE) and mass spectrometry to identify the differentially expressed proteins. A total of 63 spots were identified corresponding to 36 proteins; 20 were up-regulated, in which 16 had been previously associated with Leishmania virulence. Considering our results and what has been reported before, we suggest the hypothesis that L. infatum virulence could be a result of the increased expression of KMP-11 and metallopeptidase, associated with an improved parasite-host interacting efficiency and degradation of the protective host proteins and peptides, respectively. Other factors are tryparedoxin peroxidase and peroxidoxin, which protect the parasite against the stress response, and 14-3-3 protein-like, which can prolong infected host cell lifetime. Proteins as chaperones and endoribonuclease L-PSP can increase parasite survival. Enolase is able to perform versatile functions in the cell, acting as a chaperone or in the transcription process, or as a plasminogen receptor or in cell migration events. As expected in more invasive cells with high replication rates, energy consumption and protein synthesis are higher, with up-regulation of Rieske iron-sulfur protein precursor, EF-2, S-adenosylhomocysteine, and phosphomannomutase.

Probiotic technological and functional characteristics of Lactobacillus strains isolated from chicken gut

Lactobacillus spp. isolated from different portions of chickens' gastrointestinal tract were evaluated concerning their ability to survive in a water-in-oil (W/0) emulsion containing sesame and sunflower oil. After sixty days of emulsion storage under refrigeration, three of five strains tested survived in number equal to or higher than 10(6)cfu/g. Lactobacillus reuteri 2M14C, which presented the highest survival in W/O emulsion (10(7)cfu/g), was tested for its capacity to resist throughout the passage through gnotobiotic mice gastrointestinal tract and for the ability to stimulate murine peritoneal macrophages phagocytosis. This strain remained at a number above 10(9)cfu/g feces during ten days of monoassociation, and monoassociated mice showed phagocytic activity significantly greater than the germ-free controls (P<0.05). The results suggest that the formulation can be used to incorporate viable Lactobacillus spp. cells in animal feed. Moreover, the results suggest that L. reuteri 2M14C is a strong candidate to be incorporated in probiotic formulations for use in chicken.

Liposomal-lupane system as alternative chemotherapy against cutaneous leishmaniasis: macrophage as target cell

Leishmania amazonensis causes human diseases that range from self-healing to diffusion cutaneous lesions. The chemotherapy of leishmaniasis requires long-term treatment and has been based on the use of pentavalent antimonials. Liposomes have been used as antileishmanial drug carries and have adjuvant activity in vaccines against several microorganisms, representing an important option to the development of new therapeutics for the disease. In this study, we developed a liposomal formulation containing lupane [3β,6β,16β-trihydroxylup-20(29)-ene], isolated from fruits of Combretum leprosum with pharmacological properties as antinociceptive, anti-inflammatory, antiulcerogenic and antileishmanial activities. The aim of the present study was to evaluate the efficacy of liposomal-lupane in L. amazonensis-infection model. Liposomes were prepared by the extrusion method with DPPC, DPPS and cholesterol at 5:1:4 weight ratio. The lupane (2 mg/mL) was added to the lipid mixture, solubilized in chloroform and dried under nitrogen flow. The activity of liposomal-lupane was conducted in vitro with mouse peritoneal infected macrophages. Furthermore, mice were infected in the right hind footpad with 10(5) stationary growth phase of L. amazonensis promastigotes. After 6 weeks, animals were treated with liposomal-lupane for 15 days by intraperitoneal injection. The evolution of disease was monitored weekly by measuring footpad thickness with a caliper. Three days after the treatment, peritoneal macrophages were collected, plated and production of the cytokines IL-10 and IL-12 was evaluated in supernatants of the cultures after 24 h. The results indicate that the liposomal system containing lupane achieved here is a promising tool to confer antileishmanial activity to infected macrophages.

Complement receptor 3 (CD11b/CD18) is implicated in the elimination of β-amyloid peptides

Microglia are the professional phagocytes of the brain and express phagocytic receptors such as complement receptor 3 (CR3 or CD11b/CD18). Using mimics of the amyloid deposit made of heat-killed yeasts coated with either Aβ 1-40 or Aβ 1-42, we were able to study how microglia interacted with and ingested these particles in vitro. We have shown previously that the low density lipoprotein receptor-related protein (LRP) is largely implied in the phagocytosis of Aβ 1-42-opsonized heat-killed yeasts and partly in that of Aβ 1-40-opsonized heat-killed yeasts. Here, we report that antibodies against CD11b or CD18 reduced the uptake of the artificial amyloid deposit by microglial cell showing that CR3 is involved in the mechanism. Moreover, a concomitant inhibition of LRP and CR3 completely blocked the ingestion of both kinds of particles suggesting that no other receptors participate to this mechanism.

Amyloid beta peptides trigger CD47-dependent mast cell secretory and phagocytic responses

Mast cells are found in the brain, where they contribute to immune responses. They have been implicated in multiple sclerosis, but their potential role in Alzheimers disease (AD), another inflammatory disease of the central nervous system, remains elusive. In the present study, we examined mast cell responses to amyloid beta (Abeta) peptides 1-40 and 1-42, the major components of the Alzheimer amyloid plaques. Rat peritoneal mast cells were used as experimental model for human brain serosal mast cells. Fibrillar Abeta1-40 and Ami1-42 peptides induced concentration-dependent exocytosis, as assessed by measurement of histamine secretion; exocytosis was reduced by pre-treatment with pertussis toxin and with antibodies against the CD47 receptor and the beta1-integrin subunit. Fibrillar Abeta1-40 and Abeta1- 42 peptides coated on heat-inactivated yeast particles and soluble fibrillar Abeta1-40 and Abeta1-42 peptides were also recognized and phagocyted by mast cells. Uptake of the peptides was decreased in the presence of 4N1, a peptide agonist of the CD47 receptor, but remained unchanged in the presence of 4NGG, a peptide derived from 4N1 which does not bind to CD47. Non-fibrillar forms of Abeta1-40 and 1-42 peptides were unable to elicit mast cell responses. These results show that fibrillar Abeta peptides can trigger mast cells and elicit exocytosis and phagocytosis. The Abeta-induced activation of mast cells operates through a CD47/beta1-integrin membrane complex coupled with Gi-protein. The present data support the hypothesis that mast cells, similarly to microglial cells, could play a major role in AD pathogenesis.

End-stage dying glioma cells are engulfed by mouse microglia with a strain-dependent efficacy

Microglia phagocytic activity for apoptotic glioma cells is hardly analysed inspite of its relevance to tissue damage prevention. We provide evidence for a phosphatidylserine-independent clearance of mouse glioma cells at an advanced stage of death, suggesting microglia recognition of late apoptotic markers. Dying cells were immediately cleared or stayed for hours in that stage before engulfment occurred. This phagocytic activity was restricted to a microglia subset representing 30 to 70% of the population according to the used strain. Expression of receptors involved in late apoptotic markers recognition therefore seems confined to a subpopulation of microglia and to be strain-dependent.

Cell culture and animal infection with distinct Trypanosoma cruzi strains expressing red and green fluorescent proteins

Different strains of Trypanosoma cruzi were transfected with an expression vector that allows the integration of green fluorescent protein (GFP) and red fluorescent protein (RFP) genes into the beta-tubulin locus by homologous recombination. The sites of integration of the GFP and RFP markers were determined by pulse-field gel electrophoresis and Southern blot analyses. Cloned cell lines selected from transfected epimastigote populations maintained high levels of fluorescent protein expression even after 6 months of in vitro culture of epimastigotes in the absence of drug selection. Fluorescent trypomastigotes and amastigotes were observed within Vero cells in culture as well as in hearts and diaphragms of infected mice. The infectivity of the GFP- and RFP-expressing parasites in tissue culture cells was comparable to wild type populations. Furthermore, GFP- and RFP-expressing parasites were able to produce similar levels of parasitemia in mice compared with wild type parasites. Cell cultures infected simultaneously with two cloned cell lines from the same parasite strain, each one expressing a distinct fluorescent marker, showed that at least two different parasites are able to infect the same cell. Double-infected cells were also detected when GFP- and RFP-expressing parasites were derived from strains belonging to two distinct T. cruzi lineages. These results show the usefulness of parasites expressing GFP and RFP for the study of various aspects of T. cruzi infection including the mechanisms of cell invasion, genetic exchange among parasites and the differential tissue distribution in animal models of Chagas disease.

The effect of mineral trioxide aggregate on phagocytic activity and production of reactive oxygen, nitrogen species and arginase activity by M1 and M2 macrophages

AIM

To assess the influence of co-culture with mineral trioxide aggregate (MTA) on phagocytosis and the production of reactive oxygen intermediates (ROI) and nitrogen (NO) species and the arginase activity by M1 and M2 peritoneal macrophages.

METHODOLOGY

Cellular viability, adherence and phagocytosis of Saccharomyces boulardii were assayed in the presence of MTA. Macrophages were stimulated with zymosan for ROI assays and with Fusobacterium nucleatum and Peptostreptococcus anaerobius and IFN-gamma for NO production and arginase activity, when in contact with capillaries containing MTA. Data were analysed by T, anova, Kruskall-Wallis and Mann-Whitney tests.

RESULTS

M2 macrophages displayed greater cellular viability in polypropylene tubes, greater ability to ingest yeast and smaller production of ROI and higher arginase activity when compared with M1 macrophages. Both macrophages, M1 and M2, presented similar cell adherence and NO production. The addition of bacterial preparations to macrophages interfered with NO and arginase productions. MTA did not interfere with any of the parameters measured.

CONCLUSIONS

Phagocytosis and the ability of the two macrophage subtypes to eliminate microbes were not affected by MTA.

Noninfectious entry of HIV-1 into peripheral and brain macrophages mediated by the mannose receptor

Although protein receptors on the plasma membrane involved in the initial steps of productive HIV-1 infection have been well characterized, little is known about interactions between cellular carbohydrate receptors and HIV-1. Here, we report the involvement of a carbohydrate receptor, the macrophage mannose receptor (MR), and its role in supporting HIV-1 binding and entry. HIV-1 can enter the cytoplasm of human macrophages and microglia as well as murine macrophages by MR, although no subsequent viral replication was observed. Correspondingly, HIV-1 entry into Cos-7 cells after induction of expression of MR by transfection with MR-cDNA did not demonstrate viral replication. Our studies suggest that whereas MR may serve as a binding and an entry site, the MR-mediated pathway does not lead to productive HIV-1 infection. In addition, we report that recombinant HIV-1 gp120 blocks MR-mediated phagocytosis in human and murine alveolar macrophages and microglial cells. Therefore, characterization of the HIV-1 noninfectious MR-mediated phagocytic pathway may foster advances in HIV-1 vaccine design and an improved understanding of HIV-1/AIDS pathogenesis and host defenses.

Involvement of Ssp-4-related carbohydrate epitopes in mammalian cell invasion by Trypanosoma cruzi amastigotes

We examined whether the expression of Ssp-4-related carbohydrate epitopes defined by monoclonal antibodies 1D9 and 2B7 was related to cell invasion by Trypanosoma cruzi amastigotes from different isolates and whether the highest expression of the epitope defined by MAb 1D9 would confer greater infectivity. Confocal microscopy showed that both epitopes localize to the membrane of amastigotes from 569, 588, 573, 587 and SC2005 isolates, similar to the G isolate, whereas the CL isolate showed a punctate and diffuse staining. Flow cytometry revealed inter- and intra-isolate variable expression of these epitopes. Apart from the lower expression of MAb 2B7 epitope by intracellular amastigotes of the SC2005 isolate, amastigotes from chagasic patient isolates expressed both epitopes similar to the G isolate, in contrast to CL isolate, that showed lower expression of both epitopes. MAb 1D9 did not react with CL isolate on immunoblots and reacted poorly with 588 and 587 parasites. MAb 2B7 preferentially reacted with an epitope on an 84 kDa component in G and 573 isolates. Invasion assays revealed that despite the fact that amastigotes from chagasic patient isolates displayed high levels of the epitope defined by MAb 1D9, only isolate 588 invaded host cells in levels comparable to that of isolate G. Both MAbs specifically inhibited cell invasion by G and 588, but not CL. These results suggested that the highest expression of MAb 1D9 epitope was not sufficient to confer higher infectivity on the isolate, and besides the two epitopes, other factors may modulate the invasiveness of extracellular amastigotes from the different isolates.

Effects of pravastatin on the in vitro phagocytic function and hydrogen peroxide production by monocytes of healthy individuals

Macrophages play a part in pathogenesis of atherosclerosis, oxidizing LDL-cholesterol and transforming themselves in foam cells and producing free radicals of oxygen that may also oxidize LDL-cholesterol. HMG-CoA reductase inhibitors are very efficient in long-term control of atherogenesis acting by different mechanisms not fully established. Thus, we investigated the in vitro influence of pravastatin on phagocytosis and hydrogen peroxide production by monocytes of healthy individuals. Phagocytosis of Saccharomyces erevisiae by peripheral blood monocytes of 20 healthy individuals was assessed in the absence or presence of pravastatin. Hydrogen peroxide production was assessed based on the horseradish peroxidase-dependent oxidation of phenol red method. Pravastatin had no influence on phagocytosis through scavenger receptors, while it decreased by 20% the mean+/-SD phagocytic index of monocytes through complement receptors, from 141+/-77 to 113+/-56 (p=0.017), due to a decrease in the number of particles ingested by monocytes, from 2.1+/-0.5 to 1.7+/-0.3 (p=0.003). This statin also decreased the baseline production of hydrogen peroxide, by 7.7%, from 0.098+/-0.013 to 0.091+/-0.013 (OD by 2x10(5) monocytes per hour) (p=0.025). Pravastatin was able to decrease the phagocytosis through complement receptors and caused a decrease in the production of hydrogen peroxide by monocytes. It is possible this statin may directly inhibit the development of atherosclerotic plaque and its instability dependent on phagocytosis and the presence of reactive species of oxygen.

Infection-induced respiratory burst in BALB/c macrophages kills Leishmania guyanensis amastigotes through apoptosis: possible involvement in resistance to cutaneous leishmaniasis

The immune mechanisms that underlie resistance and susceptibility to leishmaniasis are not completely understood for all species of Leishmania. It is becoming clear that the immune response, the parasite elimination by the host and, as a result, the outcome of the disease depend both on the host and on the species of the infecting Leishmania. Here, we analyzed the outcome of the infection of BALB/c mice with L. guyanensis in vivo and in vitro. We showed that BALB/c mice, which are a prototype of susceptible host for most species of Leishmania, dying from these infections, develop insignificant or no cutaneous lesions and eliminate the parasite when infected with promastigotes of L. guyanensis. In vitro, we found that thioglycollate-elicited BALB/c peritoneal macrophages, which are unable to eliminate L. amazonensis without previous activation with cytokines or lipopolysaccharide, can kill L. guyanensis amastigotes. This is the first report showing that infection of peritoneal macrophages with stationary phase promastigotes efficiently triggers innate microbicidal mechanisms that are effective in eliminating the amastigotes, without exogenous activation. We demonstrated that L. guyanensis amastigotes die inside the macrophages through an apoptotic process that is independent of nitric oxide and is mediated by reactive oxygen intermediates generated in the host cell during infection. This innate killing mechanism of macrophages may account for the resistance of BALB/c mice to infection by L. guyanensis.

Novel microtechnique for assessment of postnatal maturation of the phagocytic function of neutrophils and monocytes

We describe a simple test for the evaluation of phagocytosis and provide a chart of reference values to evaluate normal phagocytosis by age. We assessed the postnatal maturation of phagocytic function of neutrophils and monocytes. Phagocytosis was evaluated in newborn children delivered vaginally or by cesarean section, infants, preschool children, schoolchildren, and adult subjects. Two drops of blood were placed on a microscope slide and incubated with Saccharomyces cerevisiae yeasts, and phagocytosis was evaluated by microscopy. Our technique showed results comparable to or better than those obtained by other usual techniques. The neutrophils of newborn children delivered by cesarean section showed a phagocytic capacity 45% higher than those of neonates delivered vaginally, whereas neutrophils from children in the latter group showed the lowest phagocytic capacity of all age groups. Phagocytosis by neutrophils reached the levels seen in adults at about the first year of life, while there were no important variations in phagocytosis by monocytes in the different age groups. The technique described is reliable and fast, uses only a few drops of blood, and allows better preservation of cell function due to the minimal manipulation to which the cells are submitted. The delayed maturation of the phagocytic function by neutrophils may account for the high levels of susceptibility of newborn and infant children to bacterial infections. This practical method of assessment of phagocytosis may allow the diagnosis of primary or secondary phagocytic deficiencies to be made more easily and may allow better monitoring and treatment of those with dysfunctions of these cells.

Phagocytosis of Candida albicans by metastatic and non metastatic human breast cancer cell lines in vitro

Experiments were carried out to investigate the kinetic characteristics of phagocytosis of candida by metastatic (MCF-7 and ZR-75-1) and nonmetastatic (HCC70) breast cancer cell (BCC) lines. Cancer cells were mixed with candida at a ratio of 1:10 and attachment/phagocytosis were examined using cytospin preparations stained with either Giemsa or tannic acid and May-Grünwald Giemsa and by using flow cytometry. A high attachment of candida to cancer cells (29-39%) was detected as early as 10 min. Following attachment, cancer cells phagocytized yeast. The phagocytic activity of MCF-7 and ZR-75 cells was significantly higher (58-61%) than that of HCC70 cells (26%). A similar trend was observed with respect to the phagocytic index. Phagocytosis of candida by tumor cells was inhibited significantly by both cytochalasin B (50%) and by lowering temperature to 4 degrees C (66%). Phagocytosis was not associated with oxidative burst in any cell lines used. In conclusion, metastatic breast cancer cells possess phagocytic activity which may explain their invasive property.

Uptake of Abeta 1-40- and Abeta 1-42-coated yeast by microglial cells: a role for LRP

Artificial diffuse and amyloid core of neuritic plaques [beta-amyloid peptide (Abeta) deposits] could be prepared using heat-killed yeast particles opsonized with Abeta 1-40 or Abeta 1-42 peptides. Interaction and fate of these artificial deposits with microglial cells could be followed using a method of staining that allows discrimination of adherent and internalized, heat-killed yeast particles. Using this system, it was possible to show that nonfibrillar or fibrillar (f)Abeta peptides, formed in solution upon heating (aggregates), could not impair the internalization of heat-killed yeast particles opsonized with fAbeta 1-40 or fAbeta 1-42. This indicated that depending on their physical state, Abeta peptide(s) do not recognize the same receptors and probably do not follow the same internalization pathway. Using competitive ligands of class A scavenger receptors (SR-A) or low-density lipoprotein-related receptor protein (LRP), it has been shown that SR-A were not involved in the recognition of amyloid peptide deposits, whereas LRP specifically recognized deposits of fAbeta 1-42 (but not fAbeta 1-40) and mediated their phagocytosis.

Mannose receptor contribution to Candida albicans phagocytosis by murine E-clone J774 macrophages

Mannoproteins, as the main constituents of the outer layer of yeast cell walls, are able to interact with phagocytic cells in an opsonin-independent manner through the mannose receptor (MR) and to induce yeast ingestion by the professional phagocytes. Moreover, the MR also mediates endocytosis of soluble ligands through clathrin-coated pits. Here, we studied some aspects of the interaction between the MR and Candida albicans using murine E-clone macrophages and the consequences on MR trafficking. Using a pull-down assay involving mixture E-clone macrophage detergent lysate with mannosylated Sepharose beads and glutaraldehyde-fixed, heat-killed (HK) C. albicans, we found that binding of solubilized MR to mannosylated particles occurred with characteristics similar to the receptor's cell-surface mannose-binding activity. We then demonstrated that MR expressed on E-clone macrophages contributed to phagocytosis of unopsonized, HK C. albicans and that yeast phagocytosis induced a decrease in MR endocytic activity without concomitant degradation of the receptor in the time lapse studied.

A mannose-receptor is possibly involved in the phagocytosis of Saccharomyces cerevisiae by seabream (Sparus aurata L.) leucocytes

In this paper the possible involvement of the mannose-receptor on the non-specific recognition and phagocytosis of heat killed yeast cells (Saccharomyces cerevisiae) by gilthead seabream (Sparus aurata L.) head-kidney leucocytes was established by studying the ability of different sugars to inhibit the uptake of the yeast cells by leucocytes. Leucocytes were preincubated for 30min with different concentrations of sugar (alpha-mannan, d-mannose, d-fucose, l-fucose, d-glucose, d-glucosamine and n-acetyl-glucosamine, all of them described as specific ligands of the vertebrate mannose-receptor) and afterwards incubated with FITC-labelled yeast cells for phagocytosis assays. The phagocytic ability (percentage of cells with one or more ingested yeast cells within the total cell population) and capacity (number of ingested yeast cells per cell) of leucocytes was analysed by flow cytometry. The results demonstrate the potential existence of a specific receptor-sugar or receptor-yeast cell binding process, which was saturable, specific and dose-dependent. More specifically, when leucocytes were preincubated with appropriate doses of d-mannose, d- or l-fucose, d-glucose or n-acetyl-glucosamine the phagocytosis of yeast cells by head-kidney leucocytes was partially blocked. Seabream leucocytes were also preincubated with chloroquine, a lysosomotropic drug which downregulates (in a nonspecific manner) the expression of mannose-receptors in mammals, before phagocytosis assays were performed. The results demonstrated that the phagocytosis of yeast was completely blocked by this substance. The overall results seem to corroborate the presence of the mannose-receptor in seabream phagocytes, which is involved in the non-specific binding and phagocytosis of yeast cells by head-kidney leucocytes.

Low-level iron-dependent mutants of Listeria monocytogenes and their virulence in macrophages

Listeria monocytogenes is an opportunistic intracellular pathogen capable of growth that requires iron for growth within phagocytic cells and virulence expression. In the presence of an appropriate concentration tropolone, an iron-chelating agent, growth of L. monocytogenes is completely inhibited. However, this inhibition can be relieved by addition of dopamine, norepinephrine, or ferric citrate. By selection on streptonigrin medium supplemented with tropolone and norepinephrine, we have obtained two spontaneous mutants, Lm-8 and Lm-15, with the same iron dependence but lower iron dependence than the wild-type Lm-B38. The association between iron requirement and virulence of the two mutants and the wild type was studied in the J774 macrophage cell line. One hour after phagocytosis by the J774 macrophage cell line, the two mutants and the parental strain displayed no difference in the number of phagocytosed bacteria. Twenty-four hours after phagocytosis, the number of bacteria within the surviving macrophages was identical for the wild strain and the two clones. However, only 40% of macrophage cells infected with Lm-8 and 90% of those infected with Lm-15 were alive after 24 h in comparison with macrophage cells infected with the parental strain Lm-B38. These data demonstrate that there is no direct correlation between iron requirement and virulence of L. monocytogenes in the J774 macrophage cell line.

Spore diffusate isolated from some strains of Aspergillus fumigatus inhibits phagocytosis by murine alveolar macrophages

Aspergillus fumigatus is a ubiquitous fungus that grows in decaying organic matter. It can cause disease in both immunodeficient and immunocompetent patients by using virulence factors to escape the host defenses. Some of these factors, such as a diffusate, released from the spores of A. fumigatus, have previously been described. This diffusate was demonstrated to inhibit oxidative burst and phagocytosis of coated red blood cells. The present study has shown that this substance can inhibit the phagocytosis of A. fumigatus spores by murine alveolar macrophages (MALU) and evaluated the action of this substance. We quantified phagocytosis by MALU cells with and without diffusate and evaluated the inhibition of phagocytosis by testing diffusates from different strains. We conclude that the spore diffusate of some strains of A. fumigatus can reversibly decrease the ability of alveolar macrophages to ingest A. fumigatus spores.

Phagocytosis of yeast: a method for concurrent quantification of binding and internalization using differential interference contrast microscopy

In studies of phagocytosis there is a need to distinguish targets that are internalized by the cell from those that are bound to the cell surface. The present work describes a simple method by which internalized and surface-bound yeast particles can be identified by differential interference contrast microscopy, using trypan blue to stain surface-bound yeast particles. The method has the advantage that both internalized and surface-bound particles can be visualized without the need to switch the illumination source and/or filter sets, thus facilitating concurrent quantitation of binding and internalization. The method was evaluated with the phagocytosis-modulating agents horseradish peroxidase (HRP) and cytochalasin D, using adherent resident macrophages as phagocytic cells. When macrophages are challenged with a particular type of target, they usually bind many more targets than they ingest. It was shown that yeast particles were arrested in the initial binding phase of phagocytosis depending on the region of macrophage plasma membrane where binding sites were formed. Failure of surface-bound yeast particles to trigger internalization was not due to modifications of the yeast particle surface. Nor was it due to binding to non-phagocytic receptors, or low-affinity receptor-ligand interactions. The glycoprotein HRP inhibited only the binding stage of phagocytosis, whereas cytochalasin D, a drug that affects actin polymerization, inhibited both binding and internalization. However, when the yeast particles were pre-incubated in fresh mouse serum, cytochalasin D inhibited only the internalization step. The assay described here may be useful in studies concerned with the function and expression of phagocytosis-mediating surface lectins.

Disruption of filamentous actin inhibits human macrophage fusion

The foreign body reaction to implanted biomaterials, characterized by the presence of macrophages and foreign body giant cells (FBGC), can result in structural and functional failure of the implant. Recently, we have shown that interleukin-4 and interleukin-13 can independently induce human macrophage fusion to form FBGC via a macrophage mannose receptor (MR) -mediated pathway. The MR is believed to mediate both endocytosis of glycoproteins and phagocytosis of microorganisms, which bear terminal mannose, fucose, N-acetylglucosamine, or glucose residues. Polarization of microfilaments to closely apposed macrophage membranes as observed with fluorescence confocal microscopy led us to ask whether MR-mediated fusion occurred via a filamentous actin-dependent pathway. Cytochalasins B and D and latrunculin-A, agents that disrupt microfilaments, inhibited macrophage fusion in a concentration-dependent manner. The concentrations of cytochalasins D and B that inhibited fusion did not significantly decrease macrophage adhesion, spreading, or motility but did inhibit internalization of Candida albicans during interleukin-13-enhanced, MR-mediated phagocytosis. Very low concentrations of cytochalasin B (< 2 microM) induced a slight enhancement of macrophage fusion. Taken together, the results of this study suggest that cytokine-induced, MR-mediated macrophage fusion requires an intact F-actin cytoskeleton and that the mechanism of fusion is similar to phagocytosis.--DeFife, K. M., Jenney, C. R., Colton, E., Anderson, J. M. Disruption of filamentous actin inhibits human macrophage fusion.

Treatment of l(2)mbn Drosophila tumorous blood cells with the steroid hormone ecdysone amplifies the inducibility of antimicrobial peptide gene expression

Insects rely on both humoral and cellular mechanisms to defend themselves against microbial infections. The humoral response involves synthesis of a battery of potent antimicrobial peptides by the fat body and, to a lesser extent, by blood cells. The cellular response on the other hand consists of phagocytosis of small microorganisms and melanization and encapsulation of larger parasites. The l(2)mbn cell line, established from tumorous larval hemocytes, represents a system of choice to dissect the molecular events controlling cellular immunity. We report here that l(2)mbn cells can be efficiently induced to differentiate in adherent, macrophage-like cells by treatment with 20-hydroxyecdysone. Ecdysone treatment increases both the phagocytic capacity of l(2)mbn cells and their competence to express antimicrobial genes in response to immune challenge. We also report that expression of several regulatory molecules thought to be involved in the immune response is up-regulated by ecdysone in l(2)mbn cells.

Flow cytometric quantitation of attachment and phagocytosis in phenotypically-defined subpopulations of cells using PKH26-labeled Fc gamma R-specific probes

Human receptors for IgG (Fc gamma R) are characterized by diverse structure and function. We describe a flow cytometric technique to quantitate receptor-specific Fc gamma R-mediated attachment and phagocytosis in phenotypically-defined subsets of cells using erythrocytes (E) labeled with the lipophilic dye PKH26 and coupled with biotin/avidin to either human IgG (myeloma proteins) or anti-Fc gamma R mAb. Using this technique and Fc gamma RIIa as a model, (1) we demonstrate sensitive and specific quantitation of attached and internalized E coupled to receptor-specific mAb or natural ligand by monocytes within a peripheral blood leukocyte preparation; (2) we show the capacity to detect subtle allelic differences in Fc gamma R function; and (3) we demonstrate oxidant-induced enhancement of binding and internalization.

Fluorescent liposomes as quantitative markers of phagocytosis by alveolar macrophages

A new phagocytic assay based on liposome ingestion by alveolar macrophages (AMs) is described. Fluorescent microspheres were encapsulated in liposomes, which allowed rapid enumeration by fluorometry. Liposomes made in the presence of vitronectin had the protein exposed on their outer surfaces, as determined by immunolabelling. Liposomes and rat AMs were incubated under conditions favorable for phagocytosis. Observation by light and electron microscopy showed AMs engulfing liposomes, with gradual transfer of fluorescent label from liposome to cell interior. This transfer was due to bona fide phagocytosis, as evidenced by (1) fluorescence of liposome-encapsulated dihydrofluorescein (DHF)-zymosan exclusively within AMs and (2) triggering of the respiratory burst by zymosan-associated liposomes only under conditions that allowed phagocytosis. Phagocytic activity was expressed as liposomes/cell, the average number of liposomes phagocytosed per macrophage. We used this technique to follow phagocytosis over time and to measure the effects of lipopolysaccharide (LPS) and vitronectin on AM phagocytosis.

Flow cytometry distinction between adherent and phagocytized yeast particles

Our laboratory recently developed a light microscopy staining technique that provides a mean to distinguish between yeast that are simply bound to the surface of macrophages and yeast that have actually been phagocytized by macrophages (7). We adapted this technique by using fluorescent probes in order to test phagocytic activity by flow cytometry. Thus we are able to distinguish unambiguously extracellular from intracellular yeast during phagocytosis with the fast rate of flow cytometry (approximately 200 cells/s). The fluorescence quenching induced by a 1% tannic acid solution (w/v) can be applied to any FITC-labeled, heat-killed yeast cell or bacteria. The yeast cells already engulfed in the macrophage remain with their native fluorescence (internal and external pH equilibrated by 50 microM monensin 30 min/4 degrees C) protected from the action of tannic acid, a nonmembrane permeable molecule. The results presented here validate this new technique. An application is presented showing the inhibition of endocytosis by cytochalasin-B.

A new method for studying the binding and ingestion of zymosan particles by macrophages

One of the major problems encountered during quantitative studies of phagocytosis is the discrimination without ambiguity between intracellular and extracellular particles. This difficulty is especially acute when zymosan particles are used because of their poor affinity for dyes. We show in this paper that zymosan particles may be stained by a mixture of a basic dye and tannic acid in water (or in an isotonic non saline solution). Crystal violet is one of the most suitable dyes and by combining this staining step with May-Grünwald Giemsa staining, it was possible to observe two populations of macrophage-associated particles. One comprises blue violet particles (BVP), and the second consists of particles with a purple-stained core (PPC). Treating macrophages in culture with various concentrations of cytochalasin B decreases the number of PPC and increases the number of BVP, in a dose dependant manner. Moreover, treatment with alpha-mannan or laminarin decreases the number of cell-associated particles, especially that of PPC. From these observations we concludes that BVP are extracellularly located and PPC are ingested.

Functional beta-glucan receptor expression by a microglial cell line

In the central nervous system, the functions of microglia appear crucial after brain damage, when phagocytes eliminate cell debris, acting as the scavengers of the brain. Diseases where an active role for microglia has been proposed recently include Alzheimer's disease, the acquired immune deficiency syndrome (AIDS) and multiple sclerosis. Only recently has it been possible to obtain a microglial cell line retaining morphological and functional aspects of these cells and their secretory products. Sugar receptors are expressed by a variety of phagocytes in primary cultures, but in contrast, are absent on the majority of the described macrophage-like cell lines. We here establish, by 4 degrees C binding experiments, that this murine cell line, called BV-2, expresses a high level (9.86 +/- 0.91 x 10(5); n = 3) of beta-glucan receptors. At 37 degrees C, BV-2 cells show high phagocytic power that can only be inhibited by the free polysugar beta-laminarin (a poly-glucose) and not by mannan (a poly-mannose) as described for macrophages. The beta-glucan receptor expressed by the microglial cell line BV-2 is fully functional in phagocytosis of unopsonized heat-killed yeast particles.

Effects of Clostridium difficile toxin B on human monocytes and macrophages: possible relationship with cytoskeletal rearrangement

Toxin B from Clostridium difficile is cytopathic in vitro for various types of cells, including polymorphonuclear cells, lymphocytes, and monocytes. Since intestine lamina propria is rich in macrophages, we studied the effect of toxin B on human monocytes and on human macrophages generated in vitro by long-term culture of purified circulating blood monocytes. Upon addition of toxin B, human monocytes exhibited few modifications whereas macrophages adopted a stellate morphology, with rounding up of the perikaryon. Toxin B made microfilaments of actin disappear and induced an important reorganization of vimentin and a redistribution of tubulin. Membrane area increased by approximately 16%. Toxin B did not affect the viability of human mononuclear phagocytes and did not exert any significant lytic effect. It profoundly altered the phagocytic function of macrophages. When activated by gamma interferon in the presence of toxin B, monocytes were more cytotoxic for U-937 target cells than control monocytes activated in absence of toxin. Finally, the combined treatment of monocytes with gamma interferon and toxin B increased significantly the secretion of tumor necrosis factor alpha, whereas toxin B alone was unable to induce tumor necrosis factor production. These results suggest that morphological and functional alterations induced in human mononuclear phagocytes by toxin B from C. difficile are due to the disorganization of the cytoskeleton and the resulting impairment of the membrane traffic equilibrium.