Inhibition Of Phagocytic Activity Research Articles

Cytotoxicity induced by abamectin exposure in haemocytes of Chinese mitten crab, Eriocheir sinensis

Abamectin is widely utilized in both agricultural and aquaculture areas in China for pest control. However, information about toxic effects of abamectin on non-target aquatic organisms is still incomplete. The Chinese mitten crab, Erocheir sinensis has been extensively bred in the rice-crab co-culture system for years, resulting in the frequent exposure to pesticides including abamectin. In the present study, a primary haemocyte culture model was established to investigate the immune response under exposure of abamectin. The results showed that medium osmolarity ranging from 360 to 480 mOsM/Kg was optimal for primary haemocyte culture from E. sinensis. Abamectin could induce significant decrease of cell viability, inhibition of phagocytic activity, as well as decline of acid phosphatase (ACP) and alkaline phosphatase (AKP) activities. All parameters decreased in time- and dose- dependent manners throughout the experiment, indicating the remarkable immunosuppression of abamectin on E. sinensis and also the sensitivity of the cytotoxicology model of haemocytes in vitro under abamectin exposure. In addition, a dose dependent increase of intracellular reactive oxygen species (ROS) was found after 6 h exposure. It revealed that excessive generation of ROS may a main reason to the degradation of cell viability, and moreover, the decrease in immune function.

ASSESSMENT OF INDICES OF NONSPECIFIC RESISTANCE OF THE ORGANISM IN CONDITIONS OF NARROWING OF THE LUMEN OF THE TRACHEA IN AN EXPERIMENT

The narrowing of the lumen of the trachea due to cicatricial stenoses of the trachea is one of the urgent problems of the modern surgery. The processes taking place in the trachea and lungs lead to a change in the state of the immune system. Assessment of the dynamics of indices of nonspecific resistance is one of the methods for assessing the severity of the course of the disease. We studied the indices of nonspecific resistance of the organism in narrowing the lumen of the trachea in an experiment in the early postoperative period. The study was carried out on the basis of the scientific department of experimental surgery with the vivarium of Irkutsk Scientific Centre of Surgery and Traumatology, on 24 white male Wistar rats with a body weight of 300–350 g. We simulated narrowing the lumen of the trachea by placing a silicone tube in the lumen of the trachea for 14 days. The parameters of phagocytosis, the state of phagocytic activity of blood neutrophils, spontaneous NBT-test, induced NBT- test were studied. The animals were withdrawn from the experiment on the 3rd, 7th and 14th day. We revealed that as a result of narrowing of the lumen of the trachea with the original procedure, the nonspecific resistance of the organism was violated with inhibition of the phagocytic activity of leukocytes. There was inhibition of phagocytic activity of leukocytes and depletion of the functional reserve of leukocytes.

Inhibition of phagocytic activity of ARPE-19 cells by free radical mediated oxidative stress

Oxidative stress is a main factor responsible for key changes leading to the onset of age-related macular degeneration (ARMD) that occur in the retinal pigment epithelium (RPE), which is involved in phagocytosis of photoreceptor outer segments (POS). In this study, hydrogen peroxide (H2O2), H2O2 and iron ions (Fe) or rose Bengal (RB) in the presence of NADH and Fe were used to model free radical mediated oxidative stress to test if free radicals and singlet oxygen have different efficiency to inhibit phagocytosis of ARPE-19 cells. Free radical mediated oxidative stress was confirmed by HPLC-EC(Hg) measurements of cholesterol hydroperoxides in treated cells. Electron paramagnetic resonance (EPR) spin trapping was employed to detect superoxide anion. Cell survival was analyzed by the MTT assay. Specific phagocytosis of fluorescein-5-isothiocyanate-labeled POS and non-specific phagocytosis of fluorescent beads were measured by flow cytometry. HPLC analysis of cells photosensitized with RB in the presence of NADH and Fe indicated substantial increase in formation of free radical-dependent 7α/7β-hydroperoxides. EPR spin trapping confirmed the photogeneration of superoxide anion in samples enriched with RB, NADH and Fe. For all three protocols sub-lethal oxidative stress induced significant inhibition of the specific phagocytosis of POS. In contrast, non-specific phagocytosis was inhibited only by H2O2 or H2O2 and Fe treatment. Inhibition of phagocytosis was transient and recoverable by 24 h. These results suggest that free radicals may exert similar to singlet oxygen efficiency in inhibiting phagocytosis of RPE cells, and that the effect depends on the location where initial reactive species are formed.

Characterization of P2X7R and Its Function in the Macrophages of ayu, Plecoglossus altivelis

P2X purinoceptor 7 (P2X7R), an ATP-gated ion channel, plays an important role during the innate immune response in mammals. However, relatively little is known about the role of P2X7R in the fish immune system. Here, we cloned a cDNA sequence encoding ayu (Plecoglossus altivelis) P2X7R (aP2X7R). The predicted protein was composed of 574 amino acid residues with a P2X family signature, two transmembrane domains, and a long C-terminal. aP2X7R transcripts were mainly distributed in ayu immune tissues and significantly increased in all tested tissues and in macrophages after Listonella anguillarum infection. The aP2X7R protein was upregulated significantly in macrophages upon bacterial challenge. An antibody against the ectodomain of aP2X7R (aEPAb) and an antagonist (oATP) were used to block aP2X7R. aP2X7R siRNA was also used to knockdown the receptor expression in ayu macrophages. Cell death induced by ATP was significantly inhibited in ayu macrophages after aEPAb, oATP, or siRNA treatment. Moreover, aP2X7R ablation also resulted in suppression of phagocytic activity and ATP-induced bacterial killing in ayu macrophages. Our results indicated that aP2X7R was upregulated after infection and mediated cell death, phagocytosis, and bacterial killing of ayu macrophages.

Toxic effects of PCDD/Fs mixtures on Eisenia andrei earthworms

The earthworms Eisenia andrei were used to study the toxicity of PCDD/Fs mixtures to earthworms during 28 day of exposure. The experiments were performed on artificial soils contaminated with dioxins at levels of C1 (0.1ng 2, 3, 7, 8-TCDD/g soil), C2 (1ng 2, 3, 7, 8-TCDD/g soil) and C3 (1.5ng 2, 3, 7, 8-TCDD/g soil). Effects of PCDD/Fs on survival, growth rate and immune responses; phagocytosis and NK-like cell activity, were determined. No mortality was observed at the lowest concentration (C1), while mortalities of 10 and 100% were noted at the highest concentrations tested C2 and C3, respectively. A significant reduction in growth rate was obtained at C2 and no effects at C1. Additionally, an inhibition of phagocytic activity and efficiency was observed at higher concentrations. In contrast, an enhancement of NK-like cell activity was shown at lower concentrations. Based on our results, we hypothesize that the PCDD/Fs mixtures tested at levels equal or higher to C2 (1ng 2378-TCDD/g soil), lead to adverse effects on biotic potential and immune functions in E. andrei earthworms.

Degradation of Complement 3 by Streptococcal Pyrogenic Exotoxin B Inhibits Complement Activation and Neutrophil Opsonophagocytosis

Streptococcal pyrogenic exotoxin B (SPE B), a cysteine protease, is an important virulence factor in group A streptococcus (GAS) infection. The inhibition of phagocytic activity by SPE B may help prevent bacteria from being ingested. In this study, we examined the mechanism SPE B uses to enable bacteria to resist opsonophagocytosis. Using an enzyme-linked immunosorbent assay, we found that SPE B-treated serum impaired the activation of the classical, the lectin, and the alternative complement pathways. In contrast, C192S, a SPE B mutant lacking protease activity, had no effect on complement activation. Further study showed that cleavage of serum C3 by SPE B, but not C192S, blocked zymosan-induced production of reactive oxygen species in neutrophils as a result of decreased deposition of C3 fragments on the zymosan surface. Reconstitution of C3 into SPE B-treated serum unblocked zymosan-mediated neutrophil activation dose dependently. SPE B-treated, but not C192S-treated, serum also impaired opsonization of C3 fragments on the surface of GAS strain A20. Moreover, the amount of C3 fragments on the A20 cell surface, a SPE B-producing strain, was less than that on its isogenic mutant strain, SW507, after opsonization with normal serum. A20 opsonized with SPE B-treated serum was more resistant to neutrophil killing than A20 opsonized with normal serum, and SPE B-mediated resistance was C3 dependent. These results suggest a novel SPE B mechanism, one which degrades serum C3 and enables GAS to resist complement damage and opsonophagocytosis.

Inhibition of Major Histocompatibility Complex (MHC)-Restricted Presentation of Exogenous Antigen in Dendritic Cells by Korean Propolis Components

Dendritic cells (DCs) playa critical role not only in the initiation of immune responses, but also in the induction of immune tolerance. In an effort to regulate immune responses through the modulation of antigen presenting cell (APC) function of DCs, we searched for and characterized APC function modulators from natural products. Methods: DCs were cultured in the presence of propolis components, WP and CP, and then examined for their ability to present exogenous antigen in association with major histocompatibility complexes (MHC). Results: WP and CP inhibited class I MHC-restricted presentation of exogenous antigen (cross-presentation) in a DC cell line, DC2.4 cells, and DCs generated from bone marrow cells with GM-CSF and IL-4. The inhibitory activity of WP and CP appeared to be due not only to inhibition of phagocytic activity of DCs, but also to suppression of expression of MHC molecules on DCs. We also examined the effects of WP and CP on T cells. Interestingly, WP and CP increased IL-2 production from T cells. Conclusion: These results demonstrate that WP and CP inhibit MHC-restricted presentation of exogenous antigen through down-regulation of phagocytic activity and suppression of expression of MHC molecules on DCs.

Inhibition of phagocytic activity by the N-acetyl-D-galactosamine-specific lectin from Amaranthus leucocarpus.

Amaranthus leucocarpus lectin (ALL), specific for N-acetyl-D-galactosamine, induces inhibition of the erythrophagocytic activity of resident murine peritoneal macrophages and of the macrophage-like cell line J-774. This effect was observed only in macrophages that were Mac-2 (CD11c/CD18 or CR4) negative, indicating that macrophage activation induces important modification to the glycosylation (mainly O-glycosylation) of the membrane. Receptors for IgM and C3b remain unaltered after lectin treatment. Ultrastructural analysis revealed (a) that ALL induced the formation of pinocytic vacuoles, and (b) a regular distribution over the macrophage membrane as well as endosomal vesicles of the gold labeled ALL. Our results suggest that macrophage membrane glycoproteins with constitutive N-acetyl-D-galactosamine residues participate in the regulation of pinocytic-phagocytic vacuole formation.

Inhibition of phagocytosis of human macrophages induced by airborne particulates

Human monocyte-derived macrophages isolated from peripheral blood were treated with different extracts of airborne particulates collected in the highly industrialized Rhine-Ruhr area. All tested extracts showed a substantial impairment of phagocytosis by inhibition of phagocytic activity as well as phagocytic capacity, while cell viability was rather well maintained. Significant reduction of phagocytosis already appeared at a concentration equivalent to extracted particulates from 3.8 m 3 air. Having properties of alveolar macrophages, human monocyte-derived macrophage cultures may offer a reliable in vitro model for assessment of pulmonary toxicity by respirable pollutants.

Direct suppression of phagocytosis by amphipathic polymeric surfactants.

Recent studies have demonstrated that phagocytosis of colloidal particles by the mononuclear phagocytes of the liver and spleen can be controlled by either coating or stabilizing particulate carriers with the amphipathic polymeric surfactants, F108 and T908. These surfactants consist of copolymers of polypropylene oxide (PPO) and polyethylene oxide (PEO) and, when adsorbed to particulate surfaces, significantly decrease sequestration of particulates by the mononuclear phagocytes (MPS) of the liver. To evaluate these observations further, murine peritoneal macrophages were incubated for varying periods with surfactant-coated and noncoated polystyrene particles (PSPs). Phagocytosis was monitored using gamma counting and quantitative fluorescence microscopy. The data show that phagocytosis is decreased when PSPs are coated with F108 and T908. In addition, suppression of phagocytic activity was observed when cells were pretreated with the surfactant and then challenged with noncoated particles. The data confirm previous observations that polymeric surfactants consisting of PEO and PPO protect particulate carriers from rapid uptake by the MPS of the liver. Further, F108 and T908 suppress phagocytosis directly without affecting the integrity, viability, or functional state of the cell.

Letter: Selective inhibition of phagocytic activity of rabbit alveolar macrophages by cystic fibrosis serum.

Letter: Selective inhibition of phagocytic activity of rabbit alveolar macrophages by cystic fibrosis serum.

Selective inhibition of phagocytic activity of rabbit alveolar macrophages by cystic fibrosis serum.

SUMMARy _ Impaired pulmonary function associated with cystic fibrosis continues to be the principal factor responsible for morbidity and mortality. Retention of secretions and secondary infection with Staphylococcus aureus and Pseudomonas aeruginosa initially produces obstruction of the tracheo­ bronchial tree and ultimately causes irreversible lung damage. Pseudomonas aeruginosa has emerged as the major pathogen in this disease, in which the mucociliary cleaning mechanism is compromised by abnormal mucus and bacterial clearance is greatly dependent on efficient action of pulmonary alveolar macrophages. The effect of serum from patients with cystic fibrosis on alveolar macrophage activity was investigated using rabbit alveolar macrophages. A selective inhibition of phagocytic activity of these macrophages against Pseudomonas aeruginosa by fresh cystic fibrosis serum was demonstrated in which not only were fewer bacteria engulfed but also fewer engulfed bacteria were destroyed. This effect appeared to be specific for Pseudomonas aeruginosa and not for other bacteria. It appears that the decreased efficiency of alveolar phagocytic activity is due to a labile inhibitor that has no effect on blood phagocytes.

Nirogen dioxide effects on alveolar macrophages.

Rabbits were exposed to 5, 15, 25, or 50 ppm of nitrogen dioxide for three hours. Their alveolar cells were harvested and tested for phagocytic activity, rate of oxygen uptake, and hexosephosphate shunt activity. Other groups of animals were given parainfluenza 3 virus intrafracheally prior to NO2 exposure in order to measure the effect of this gas on virus-induced resistance to rabbitpox virus. Virus-induced resistance and phagocytic activity were suppressed by 15 ppm of NO2. In contrast, 50 ppm stimulated oxygen uptake and hexosephosphate shunt activity. Suppression of phagocytic activity and virus-induced resistance were observed to be the most sensitive indicators of NO2 alterations of alveolar cells.

The influence of cortisone on primate malaria.

Studies have been made of the effects of cortisone on the course of primary and developed infections with P. cynomolgi in the rhesus monkey. This investigation has shown that repetitive admmistration of the hormone in daily doses of 10 mg. per kg. during the primary attack produced striking intensification of the peripheral blood infection during the postcrisis phases of the disease. Similar administration of 10 or 50 mg. per kg. doses of the hormone during the chronic or latent stages of the infection provoked recrudescences of remarkable severity. In both early and late infections the responses induced by cortisone treatment corresponded closely to the reactions to splenectomy. Collateral studies have shown that the doses of cortisone which produced the reactions described above also evoked a lymphopenia, marked reductions in the sizes of the axillary and inguinal lymph nodes and spleen, and striking histological changes in the latter organ. These changes involved severe regression or exhaustion of lymphoid elements in both splenic nodules and pulp with almost complete obliteration of proliferative activities involved in the production of macrophages from lymphocytes. Indications are that the resulting reduction in supply of macrophages, rather than inhibition of phagocytic activity per se, was responsible for the intensification of the disease produced by cortisone.