| 1. |
- Filippini, Daniel, 1968-, et al.
(author)
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ELISA test for anti-neutrophil cytoplasm antibodies detection evaluated by a computer screen photo-assisted technique
- 2005
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In: Biosensors & bioelectronics. - : Elsevier BV. - 0956-5663 .- 1873-4235. ; 21:2, s. 266-272
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Journal article (peer-reviewed)abstract
- The computer screen photo-assisted technique (CSPT), a method for substance classification based on spectral fingerprinting, which involves just a computer screen and a web camera as measuring platform is used here for the evaluation of a prospective enzyme-linked immunosorbent assay (ELISA). A anti-neutrophil cytoplasm antibodies (ANCA-ELISA) test, typically used for diagnosing patients suffering from chronic inflammatory disorders in the skin, joints, blood vessels and other tissues is comparatively tested with a standard microplate reader and CSPT, yielding equivalent results at a fraction of the instrumental costs. The CSPT approach is discussed as a distributed measuring platform allowing decentralized measurements in routine applications, whereas keeping centralized information management due to its natural network embedded operation. © 2004 Elsevier B.V. All rights reserved.
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| 2. |
- Holm, Åsa, et al.
(author)
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Leishmania donovani lipophosphoglycan causes periphagosomal actin accumulation : correlation with impaired translocation of PKCα and defective phagosome maturation
- 2001
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In: Cellular Microbiology. - : Hindawi Limited. - 1462-5814 .- 1462-5822. ; 3:7, s. 439-447
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Journal article (peer-reviewed)abstract
- Lipophosphoglycan (LPG) is the major surface glycoconjugate of Leishmania donovani promastigotes. The repeating disaccharide–phosphate units of LPG are crucial for promastigote survival inside macrophages and establishment of infection. LPG has a number of effects on the host cell, including inhibition of PKC activity, inhibition of nitric oxide production and altered expression of cytokines. LPG also inhibits phagosomal maturation, a process requiring depolymerization of periphagosomal F-actin. In the present study, we have characterized the dynamics of F-actin during the phagocytosis of L. donovani promastigotes in J774 macrophages. We observed that F-actin accumulated progressively around phagosomes containing wild-type L. donovani promastigotes during the first hour of phagocytosis. Using LPG-defective mutants and yeast particles coated with purified LPG, we obtained evidence that this effect could be attributed to the repeating units of LPG. LPG also disturbed cortical actin turnover during phagocytosis. The LPG-dependent accumulation of periphagosomal F-actin correlated with an impaired recruitment of the lysosomal marker LAMP1 and PKCα to the phagosome. Accumulation of periphagosomal F-actin during phagocytosis of L. donovani promastigotes may contribute to the inhibition of phagosomal maturation by physically preventing vesicular trafficking to and from the phagosome.
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| 3. |
- Holm, Åsa, et al.
(author)
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Protein C α regulates phagocytosis actin dynamics and phagosomal maturation in macrophages
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Other publication (other academic/artistic)abstract
- Protein kinase C α (PKCα) participates in F-actin remodeling during phagocytosis and phagosomal maturation in macrophages. Promastigotes of the protozoan parasite Leishmania donovani cause an accumulation of periphagosomal F-actin instead of the normal decrease seen with other prey [1]. This accumulation is dependent on promastigote lipophosphoglycan (LPG), which has several detrimental effects on the cell including inhibition of PKCα activity.To directly address the role of PKCα and LPG for actin remodeling in macrophages, we investigated F-actin dynamics in RAW 264.7 macrophages overexpressing a dominant-negative mutant of PKCα (DN PKCα). We found that DN PKCα-overexpressing cells displayed increased levels of cortical F-actin and decreased phagocytic capacity, which was augmented when the cells were subjected to LPG-coated prey. The DN PKCα-overexpressing cells also showed defective breakdown of periphagosomal F-actin and inhibition of phagosomal maturation. The level of periphagosomal F-actin was similar to that of controls subjected to LPG-coated prey. Our results show that PKCα regulates phagocytosis and F-actin turnover in macrophages, and that PKCα-dependent breakdown of periphagosomal F-actin is required for normal phagosomal maturation.
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| 4. |
- Holm, Åsa, et al.
(author)
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Role of protein kinase C α for uptake of unopsonized prey and phagosomal maturation in macrophages
- 2003
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In: Biochemical and Biophysical Research Communications - BBRC. - 0006-291X .- 1090-2104. ; 302:4, s. 653-658
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Journal article (peer-reviewed)abstract
- Protein kinase C α (PKCα) participates in F-actin remodeling during phagocytosis and phagosomal maturation in macrophages. Leishmania donovani promastigotes, which inhibit phagosomal maturation, cause accumulation of periphagosomal F-actin instead of the dissassembly observed around other prey [Cell. Microbiol. 7 (2001) 439]. This accumulation is induced by promastigote lipophosphoglycan (LPG), which has several effects on macrophages including inhibition of PKCα. To investigate a possible connection between PKCα and LPG’s effects on actin dynamics, we utilized RAW264.7 macrophages overexpressing dominant-negative PKCα (DN PKCα). We found increased cortical F-actin and decreased phagocytic capacity, as well as defective periphagosomal F-actin breakdown and inhibited phagosomal maturation in the DN PKCα-overexpressing cells, effects similar to those seen in controls subjected to LPG-coated prey. The results indicate that PKCα is involved in F-actin turnover in macrophages and that PKCα-dependent breakdown of periphagosomal F-actin is required for phagosomal maturation, and endorse the hypothesis that intracellular survival of L. donovani involves inhibition of PKCα by LPG.
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| 5. |
- Tejle, Katarina, 1945-
(author)
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Effects of lipophosphoglycan on macrophage actin dynamics
- 2002
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Licentiate thesis (other academic/artistic)abstract
- Leishmania donovani is a blood-borne tropicial parasite, which infects humans through bites by Phlebotomine sandflies. The parasite survives and multiplies inside macrophages in inner organs, and causes the deadly disease visceral leishmaniasis (Kala-Azar). Lipophosphoglycan (LPG) is the major surface component of Leishmania donovani promastigotes. LPG comprises a membrane-anchoringlysophosphatidylinositol moiety and an extracellular chain of repeating disaccharide phosphates. The repeats are crucial for parasite survival inside macrophages following phagocytosis. LPG has several effects on the host cell including inhibition of protein kinase C (PKC) activity, and inhibition of phagosomal maturation, a process requiring depolymerization of periphagosomal F-actin. Confocal microscopy and image analysis was used to follow F-actin dynamics in single macrophages during phagocytosis of L. donovani promastigotes and LPG-coated particles. F-actin did not depolymerize, but instead progressively polymerized around phagosomes with LPG-containing prey. This directly correlated with reduced translocation of PKCα to the phagosome and blocked phagosomal maturation. It was also found that LPG inhibited cortical actin turnover, which may be the underlying cause of the reduced uptake of LPG-containing prey. Free calcium was necessary for phagocytosis, periphagosomal F-actin breakdown and phagosomal maturation in macrophages interacting with unopsonized prey. LPG required free calcium to exert its inhibitory effects on these processes. We also studied F -actin turnover in macrophages overexpressing dominant-negative (DN) PKCα. DN PKCα macrophages showed increased amounts of cortical F-actin, decreased phagocytic capacity, inhibition of periphagosomal F-actin breakdown and defective phagosomal maturation. When DN PKCa macrophages interacted with LPG-containing prey, phagocytosis was almost completely blocked.Together, our results indicate that blockage of F-actin breakdown through inhibition of PKCa by LPG reduces phagocytosis and is instrumental for the inhibition of phagosomal maturation induced by L. donovani promastigotes.
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| 6. |
- Tejle, Katarina, 1945-
(author)
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Leishmania donovani Lipophosphoglycan : Modulation of Macrophage and Dendritic Cell Function
- 2006
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Doctoral thesis (other academic/artistic)abstract
- Leishmania donovani is a blood-borne tropicial parasite, which infects humans through bites by Phlebotomus sandflies. The parasite survives and multiplies inside macrophages in inner organs, and causes the deadly disease visceral leishmaniasis (Kala-Azar).Macrophages and dendritic cells (DC) are professional antigen-presenting cells involved in the initiation of immune responses. Immature DC are present in all tissues where they internalise and process antigen, in response to which they migrate from tissue, into draining lymphoid organs, undergo maturation and present antigens to lymphocytes. Control measures for leishmaniasis include testing of new diagnostics and development of affordable and effective vaccines for humans.Lipophosphoglycan (LPG) is the major surface component of Leishmania donovani promastigotes. LPG comprises a membrane-anchoring lysophosphatidylinositol part and an extracellular chain of disaccharide phosphates. These repetitions are crucial for parasite survival inside macrophages following phagocytosis. LPG has several specific effects on the host cell including inhibition of protein kinase C (PKC) activity, and inhibition of phagosomal maturation, a process requiring depolymerization of periphagosomal F-actin.Confocal microscopy and image analysis were used to follow F-actin dynamics in single macrophages during phagocytosis of L. donovani promastigotes and LPG-coated particles. F-actin did not depolymerize, but instead progressively polymerized around phagosomes with LPG-containing prey. This correlated with reduced translocation of PKCα to the phagosome and blocked phagosomal maturation. LPG also inhibited cortical actin turnover, which could be the underlying cause of the reduced uptake of LPG-containing prey. Extracellular- and intracellular calcium was necessary for phagocytosis, periphagosomal F-actin breakdown and phagosomal maturation in macrophages interacting with unopsonized prey,and for the action of LPG.We also studied F-actin turnover in macrophages overexpressing dominant-negative (DN) PKCα. DN PKCα macrophages showed increased amounts of cortical F-actin, decreased phagocytic capacity, inhibition of periphagosomal F-actin breakdown and defective phagosomal maturation. When DN PKCα macrophages interacted with LPG-containing prey, phagocytosis was almost completely blocked.Moreover, we found that Leishmania promastigotes and particularly LPG inhibit DC maturation and detachment from distinct surfaces. Thus, LPG from Leishmania donovani could directly inhibit DC migration to lymphoid organs, antigen-presentation and development of immunity.
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| 7. |
- Tejle, Katarina, et al.
(author)
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Phagocytosis and phagosome maturation are regulated by calcium in J774 macrophages interacting with un-opsonized prey
- 2002
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In: Bioscience Reports. - 0144-8463 .- 1573-4935. ; 22:5-6, s. 529-540
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Journal article (peer-reviewed)abstract
- Phagocytosis by neutrophils, macrophages, and other professional phagocytes requires rapid remodeling of actin. Early phagosomes are surrounded by a rim of F-actin that is disassembled during phagosomoal maturation. Breakdown of periphagosomal F-actin and phagolysosome fusion are calcium dependent processes in neutrophils interacting with serum-opsonized prey, but appears to be calcium independent in macrophages interacting with serum- or IgG-opsonized prey. In the present study, we found that calcium was necessary for phagocytosis, breakdown of periphagosomal F-actin, and phagosomal maturation in J774 macrophages interacting with unopsonized prey. We also observed that lipophosphoglycan (LPG) from Leishmania donovani promastigotes required calcium to exert its inhibitory effect on macrophage phagocytosis and periphagosomal F-actin breakdown. We conclude that calcium is essential for phagocytosis, depolymerization of periphagosomal F-actin, and phagosomal maturation in J774 macrophages interacting with unopsonized prey, as well as for proper functioning of LPG.
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| 8. |
- Tejle, Katarina, 1945-, et al.
(author)
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Wild-type Leishmania donovani promastigotes block maturation, increase integrin expression and inhibit detachment of human monocyte-derived dendritic cells - The influence of phosphoglycans
- 2008
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In: FEMS Microbiology Letters. - : Oxford University Press (OUP). - 0378-1097 .- 1574-6968. ; 279:1, s. 92-102
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Journal article (peer-reviewed)abstract
- The protective immune response against the parasite, including the role of dendritic cells (DC) in the course of infection, plays a fundamental role. This study shows that wild-type (WT) Leishmania promastigotes and specifically the phosphoglycans family of virulence-associated antigens inhibit human monocyte-derived dendritic cells (MoDC) maturation and detachment to distinct surfaces. Immature phagocytosis of Leishmania donovani promastigotes by immature MoDC results in the increased expression of CD11b and CD51, and inhibition of cell detachment to distinct surfaces, which was dependent on the presence of phosphoglycans. These findings demonstrate that phosphoglycans of WT L. donovani might also inhibit human DC migration to lymphoid organs. © 2007 Federation of European Microbiological Societies.
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