Remodeling of the mitochondrial network is an important process in the maintenance of cellular homeostasis and is closely related to mitochondrial function. Interactions between the biogenesis of new mitochondria and the clearance of damaged mitochondria (mitophagy) is an important manifestation of mitochondrial network remodeling. Mitochondrial fission and fusion act as a bridge between biogenesis and mitophagy. In recent years, the importance of these processes has been described in a variety of tissues and cell types and under a variety of conditions. For example, robust remodeling of the mitochondrial network has been reported during the polarization and effector function of macrophages. Previous studies have also revealed the important role of mitochondrial morphological structure and metabolic changes in regulating the function of macrophages. Therefore, the processes that regulate remodeling of the mitochondrial network also play a crucial role in the immune response of macrophages. In this paper, we focus on the molecular mechanisms of mitochondrial regeneration, fission, fusion, and mitophagy in the process of mitochondrial network remodeling, and integrate these mechanisms to investigate their biological roles in macrophage polarization, inflammasome activation, and efferocytosis.
Mitochondria ; Mitophagy ; Homeostasis/physiology* ; Phagocytosis ; Macrophages/metabolism*

Free-living Naegleria fowleri leads to a fatal infection known as primary amebic meningoencephalitis in humans. Previously, the target cell death could be induced by phagocytic activity of N. fowleri as a contact-dependent mechanism. However, in this study we investigated the target cell death under a non-contact system using a tissue-culture insert. The human microglial cells, U87MG cells, co-cultured with N. fowleri trophozoites for 30 min in a non-contact system showed morphological changes such as the cell membrane destruction and a reduction in the number. By fluorescence-activated cell sorter (FACS) analysis, U87MG cells co-cultured with N. fowleri trophozoites in a non-contact system showed a significant increasse of apoptotic cells (16%) in comparison with that of the control or N. fowleri lysate. When U87MG cells were co-cultured with N. fowleri trophozoites in a non-contact system for 30 min, 2 hr, and 4 hr, the cytotoxicity of amebae against target cells was 40.5, 44.2, and 45.6%, respectively. By contrast, the cytotoxicity of non-pathogenic N. gruberi trophozoites was 10.2, 12.4, and 13.2%, respectively. These results suggest that the molecules released from N. fowleri in a contact-independent manner as well as phagocytosis in a contact-dependent manner may induce the host cell death.
Animals ; Apoptosis ; Cell Line ; Humans ; Microglia/*cytology/*parasitology ; Naegleria fowleri/*physiology ; Phagocytosis/physiology

With the acceleration of the aging society, neurodegenerative diseases, such as Alzheimer's disease (AD) and Parkinson's disease (PD), have become a rapidly growing global health crisis. Recent studies have indicated that microglia-neuron interactions are critical for maintaining homeostasis of the central nervous system. Genome-Wide Association Studies and brain imaging studies have suggested that microglia are activated in early stage of neurodegenerative diseases. Microglia are specialized phagocytes in the brain. The discovery of a new phagocytic pathway, trogocytosis, suggests that there is a close interaction between microglia and surviving neurons. In this review, we summarize the important roles of microglia in neurodegenerative diseases, and further analyze the functions and molecular mechanisms of microglia phagocytosis and trogocytosis.
Alzheimer Disease ; Genome-Wide Association Study ; Humans ; Microglia/metabolism* ; Neurodegenerative Diseases ; Phagocytosis/physiology*

Alzheimer's disease (AD) is a most common neurodegenerative disease. The mechanisms underlying AD, especially late-onset AD, remain elusive. In the past few years, results from genome-wide association studies (GWAS) and systems approaches indicated that innate immune responses mediated by microglia played critical roles in AD. Functional analysis on animal models also showed that immune receptors or proteins expressed in microglia mediated Abeta-induced inflammation, or Abeta phagocytosis by microglia. Microglia plays double sword roles in AD. More work is warranted to elucidate the exact roles of microglia in AD, which will facilitate our better understanding of the mechanisms underlying AD.
Alzheimer Disease ; pathology ; Animals ; Disease Models, Animal ; Genome-Wide Association Study ; Humans ; Inflammation ; pathology ; Microglia ; physiology ; Phagocytosis ; Receptors, Immunologic ; physiology

The purpose of this study is to provide a culture for mouse bone marrow-derived macrophages (BMDM) and peritoneal macrophages (PM) and to characterize their molecular and cellular biology. The cell number and purity from the primary culture were assessed by cell counter and flow cytometry, respectively. Morphological features were evaluated by inverted microscope. Phagocytosis by macrophages was detected by the neutral red dye uptake assay. Phenotypic markers were analyzed by real-time fluorescent quantitative PCR. Our results show that the cell number was much higher from culture of BMDM than PM, while there was no significant difference regarding the percentage of F4/80+CD11b+ cells (98.30%±0.53% vs. 94.83%±1.42%; P>0.05). The proliferation rate of BMDM was significantly higher than PM in the presence of L929 cell conditioned medium, by using CCK-8 assay. However, PM appeared to adhere to the flask wall and extend earlier than BMDM. The phagocytosis capability of un-stimulated BMDM was significantly higher than PM, as well as lipopolysaccharide (LPS)-stimulated BMDM, except the BMDM stimulated by low dose LPS (0.1 μg/mL). Furthermore, Tnfα expression was significantly higher in un-stimulated BMDM than PM, while Arg1 and Ym1 mRNA expression were significantly lower than PM. The expression difference was persistent if stimulated by LPS+IFN-γ or IL-4. Our data indicate that bone marrow can get larger amounts of macrophages than peritoneal cavity. However, it should be aware that the molecular and cellular characteristics were different between these two culture systems.
Animals ; Bone Marrow Cells ; physiology ; Cells, Cultured ; Culture Media, Conditioned ; Lipopolysaccharides ; metabolism ; Macrophages ; classification ; physiology ; Mice ; Phagocytosis

Human polymorphonuclear leukocytes (PMN) migrate into tissues in response to chemoattractants, yet it is not known whether this process alters the functional capabilities of the PMN. Using recombinant human interleukin-8 (rHIL-8, 100 ng/ml) as a stimulus, we compared a population of PMN that migrated through a polyvinylpyrrolidone-coated polycarbonate filter containing 8.0 microns diameter pores with PMN stimulated in suspension. PMN were analyzed by flow cytometry according to functional and phenotypic criteria. CD11b/CD16 expression was unaltered by chemotaxis. In contrast, chemotaxis enhanced phagocytosis of E. coli, independent of opsonization with IgG. Similarly, chemotaxis increased baseline hydrogen peroxide production. We conclude that the chemotactic motion of PMN "primes" the cell for increased oxidative burst activity and augments the ability of PMN to ingest bacteria. This increased functional capability is distinct from rHIL-8 stimulation and appears to be independent of complement-and Fc-receptor expression.
Antigens, CD/analysis ; Chemotaxis, Leukocyte/*physiology ; Escherichia coli/immunology ; Humans ; Neutrophils/physiology ; Phagocytosis/physiology ; Phenotype ; Receptors, IgG/analysis ; Respiratory Burst/physiology

BACKGROUNDTrichomonas vaginalis (T. vaginalis) belongs to a common sexually transmitted disease pathogen causing genitourinary trichomoniasis in both sexes. We investigated the pathogenetic mechanism of genitourinary trichomoniasis.

METHODSCultured T. vaginalis bodies were injected into the vaginas of rats, or incubated with genitourinary epithelial cells of female subjects, male subjects, and sperm. The ultrastructural and microscopic changes were observed via transmission and scanning electron microscopy and through microscopic histochemistry.

RESULTSGroups of T. vaginalis adhered to PAS positive columnar cells at the surface of stratified epithelium in the middle and upper portions of the vaginas. They also traversed under these cells. The parasites were shown to be PAS, cathepsin D, and actin positive, and they could release hydrolase into the cytoplasm of adhered epithelial cells. In the amebiform T. vaginalis, microfilaments were arranged into reticular formation. Similar phenomena were found during the interaction of T. vaginalis with host cells, both in vitro and in vivo. Usually several protozoa adhered to an epithelial cell and formed polymorphic pseudopodia or surface invaginations to surround and phagocytize the microvilli or other parts of the epithelial cytoplasm. Adhesion and phagocytosis of sperm by the protozoa occurred at 15 - 30 minutes of incubation. Digestion of sperm was found at 45 - 75 minutes and was complete at 90 - 105 minutes.

CONCLUSIONST. vaginalis tends to parasitize at the fornix of the vagina, because this is the site where columnar cells are rich in mucinogen granules and their microvilli are helpful for adhesion and nibbling. T. vaginalis possesses some invading and attacking abilities. Shape change, canalization, encystation, phagocytosis, digestion, the cell coat, cytoskeleton, and lysosome all play important roles in the process of adhesion. They have two methods of phagocytosis: nibbling and ingestion. Genitourinary epithelium may be injured directly by the digestive action of hydrolases, phagocytosis, and the mechanical action of pseudopodia.

Animals ; Cell Adhesion ; physiology ; Cells, Cultured ; Epithelial Cells ; physiology ; Humans ; Hydrolases ; metabolism ; Immunohistochemistry ; Male ; Phagocytosis ; physiology ; Rats ; Rats, Sprague-Dawley ; Trichomonas vaginalis ; metabolism ; ultrastructure ; Urogenital System ; cytology

The purpose of this study was to determine whether phagocytic activity is measurable by dynamic superparamagnetic iron oxide-enhanced MR imaging. For these experiments on New Zealand White rabbits, which were randomly allocated to normal and silica treated groups, we performed a dynamic MR study and radioisotope study with Tc99m-phytate. In this dynamic MR study, the ratio (Rv) of the distribution volumes of iron oxide (Vm/Ve) could be obtained by applying three- compartment model to the data obtained from the kidney and liver simultaneously. Changes in Rv caused by silica injection and by dosing superparamagnetic iron oxide, AMI-25, were evaluated. In the dynamic MR study using a Beagle dog model the input function could be calculated from data obtained from the hepatic artery and portal vein. Rv's reached maximum values at around 80 minutes after the AMI-25 injection. The Rv of the normal group was 5.06 +/- 1.53 whereas the Rv of the silica treated group was 2.13 +/- 1.20. The results were similar to tissue count data obtained by radioisope study. The Rv value was not dependent on the injected dose of AMI-25. The rate of transport constants (k1, k2, k3) could not be estimated using the 3 compartment model regardless of obtaining the input function. We conclude that Rv may be an quantitative index of decreased phagocytic activity in the liver as determined by dynamic superparamagnetic iron oxide- enhanced MRI.
Animals ; *Contrast Media ; Dogs ; *Iron ; Liver/*physiology ; *Magnetic Resonance Imaging/methods ; *Models, Biological ; Nanotechnology ; *Oxides ; Particle Size ; *Phagocytosis ; Rabbits

The Protective effect of vitamin E and selenium against peroxidative damage in white blood cells was studied. Forty-eight male rats (~100g BW) were divided into four groups and were fed with a torula yeast based diet deficient in Vit.E and Se. Vit.E (100IU/Kg diet) and Se (0.3ppm) supplementation increased the total peritoneal cell (P.C) population and cell survival rate. Selenium supplementation decreased the hydrogen peroxide generation (half of the control) significantly and Vit.E supplementation reduced the malonaldehyde production during phagocytosis in vitro. However, superoxide generation was not affected by the supplementation of Vit.E or Se. There were no significant differences in catalase activity between groups but glutathione peroxidase activity was increased about twofold by Se supplementation with no effect of Vit.E. In a separate experiment, activated alveolar macrophages were obtained from BCG infected rabbits fed a diet supplemented with Vit.E (100 IU/Kg diet) or Se (0.3 ppm). Se supplementation increased glutathione peroxidase in cells, and both Vit.E and Se increased the cell survival rate during phagocytosis as compared to the control. Both Vit.E and Se are necessary to protect host cells from peroxidative damage during phagocytosis.
Animal ; Macrophages/drug effects ; Macrophages/physiology* ; Male ; Peroxides/metabolism* ; Phagocytosis/drug effects* ; Rats ; Selenium/pharmacology* ; Vitamin E/pharmacology*

The immunocytes microglia in the central nervous system (CNS) were reported to play a crucial role in neurodegeneration. As a member of P2 receptors family, purinoceptor P2Y6 has attracted much attention recently. Previous studies showed that purinoceptor P2Y6 mainly contributed to microglia activation and their later phagocytosis in CNS, while in immune system, it participated in the secretion of interleukin (IL)-8 from monocytes and macrocytes. So there raises a question: whether purinoceptor P2Y6 also takes part in neuroinflammation? Thus, this review mainly concerns about the properties and roles of purinoceptor P2Y6, including (1) structure of purinoceptor P2Y6; (2) distribution and properties of purinoceptor P2Y6; (3) relationships between purinoceptor P2Y6 and microglia; (4) relationships between purinoceptor P2Y6 and immunoinflammation. Itos proposed that purinoceptor P2Y6 may play a role in neuroinflammation in CNS, although further research is still required.
Animals ; Humans ; Inflammation ; immunology ; metabolism ; Microglia ; drug effects ; metabolism ; Monocytes ; metabolism ; Phagocytosis ; physiology ; Receptors, Purinergic P2 ; chemistry ; genetics ; metabolism