- Email: [email protected]
Proposed role for small cytoplasmic vesicles in cytokine secretion by mouse macrophages
Medical Hypotheses (2004) 62, 911–913
http://intl.elsevierhealth.com/journals/mehy
Proposed role for small cytoplasmic vesicles in cytokine secretion by mouse macrophages Martha E. Fedorko* 510 E. 6th Street, New York, NY 10009, USA Received 10 March 2003; accepted 8 January 2004
Summary This report represents an extension of a prior report hypothesizing that cytokines in mouse macrophages are secreted by a morphologic array of small vesicles which fuse with the cell membrane and which originate in the Golgi complex [Med Hypoth 53 (1999) 107]. The Golgi complex in macrophages is distinguished by a characteristically multicentric configuration and shows budding of vesicles from the closely approximated tips of the lamellae. The location of small vesicles which extend from the Golgi complex to the cell membrane supports the hypothesis that there is one type of vesicle which fuses with the cell membrane and secretes its content of cytokines. The other type of vesicle has been shown to fuse with pinocytic vacuoles to form hydrolase positive cytoplasmic granules. Consideration of cytokines produced by macrophages will help to clarify the immunologic functions of these cells. c 2004 Elsevier Ltd. All rights reserved.
Further observations and thoughts on cytokine secretion by certain leukocytes including macrophages. Previous evidence and discussion has centered around the transport and secretion of cytokines in the small vesicle components of the cell and demonstrated that the Golgi complex is involved in cytokine production. One piece of evidence hypothesized that some of the small cytoplasmic vesicles were involved in cytokine secretion by macrophages [1]. Apart from the secretion of cytokines contained in the small vesicle system of the cell the whole process influences the membrane recycling and the membrane economy of the cell. Hypothetically the vesicular membranes in question originate in the Golgi complex and in certain cells are incorporated into the cell surface membrane during vesicular secretion process. *
Tel.: þ1-212-228-5545.
Here evidence will be put forth about cytokine secretion in several granulocytes, namely basophils and eosinophils. The morphologic evidence of the small vesicle system in macrophages will be analyzed and the intracellular journey of the small vesicle membrane will be presented. Extensive work has been performed on the production of cytokines by mast cells [2,3] and eosinophils [4]. In basophil secretion of cytokines it is apparent that TNF (tumor necrosis factor) does not depend on prior incorporation into secretion granules. Cytokine release depends on Golgi complex processing and is blocked by brefeldin A which influences Golgi processing. Eosinophils on the other hand store cytokines (preformed IL-4) in cytoplasmies granules and are able to release them at discrete cell sites. It is concluded that since brefeldin A suppresses release of IL-4 vesicular formation and transport is curtailed. There has been submitted evidence for
0306-9877/$ - see front matter c 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.mehy.2004.01.007
912
Fedorko
vesicular transport in eosinophiles from the cytoplasm to the extracellular space [5]. Macrophage cell lines have been demonstrated to produce TNF (tumor necrosis factor) [6]. The presence of cytoplasmic vesicles in mouse macrophages is distinctive in one aspect. These vesicles appear to be independent from storage granules and pinosomes although some fusion of these vesicles with lysosomes and pinosomes cannot be excluded by morphologic studies alone. A representative electron micrograph has been analyzed for presence and location of small vesicles and morphology of the Golgi complex. The morphologic appearance of a mouse macrophage in culture 48 h is shown in the accompanying figure of a published article [7], Figs. 1 and 2. Figure 2 Higher magnification of same cell shows apparent budding of Golgi vesicles from the lamellae GO label is over all area of vesicles and osmophilic cytoplasmic matrix which abuts the Golgi complex 45,000.
Figure 1 The ultrastructure of a mouse macrophage in vitro for 48 h. The Golgi complex (GO) is multicentric, composed of closely apposed lamellae which have vesicle budding from the tips of the lamellae. Vesicles extend to the cell margin (upper right margin of cell). (V3) illustrates representative Golgi vesicles. Other structures include coated vesicles (V1), varying sizes of pinocytic vesicles (V2) and PV), granules (G), mitochondria (M), and nucleus (N) 18,000 permission obtained.
Analysis of the cytoplasmic structures is as follows. There are a few coated vesicles which demonstrate the characteristic membrane structure of a spokelike appearance on the outer leaflet of the membrane. The vesicle has a lucent interior. Pinocytic vesicles and vacuoles range in size. The larger ones contain a few vesicles and clear content. The cytoplasm is replete with an abundance of small vesicles which contain an abundance of moderately electron dense content. Their location extends from the Golgi complex to the cell membrane. In certain areas vesicles are arranged in rows limited by cell membrane which shows areas of fibers beneath. Electron dense cytoplasmic granules and mitochondria are scattered throughout the cytoplasm. In view of the studies on the effect of brefeldin A which influences Golgi membrane structure and inhibits secretion of cytokines it was of interest to study the Golgi complex under conditions during which they were forming an abundance of cytoplasmic vesicles positioned from the Golgi complex to areas near the cell membrane. The Golgi complex in macrophages contrasts to that in other granule containing leukocytes [8–11]. In polymorphonuclear leukocytes and eosinophils the Golgi is unifocal with swirls of lamellae, some of which are dilated and contain apparent granule matrix. The mouse macrophage has a Golgi complex which is multifocal with no evidence of granule matrix within the lamellae. Instead there are instances where terminal areas of the lamellae bud into small vesicles containing
Proposed role for small cytoplasmic vesicles moderately dense or clear material. Of interest is the densely osmophilic areas of cytoplasmic matrix in the Golgi region abutting the closely approximated lamellae. It is hypothesized here that there are two types of cytoplasmic vesicles: one containing cytokines, the other containing acid hydrolases [12]. The macrophagic distribution extending from Golgi complex to cell membrane favors the hypothesis of existence of two types of vesicle. Cytoplasmic granule formation is driven by conditions which induces pinocytosis. This process involves fusion of acid hydrolase containing vesicles to the pinocytic vacuole. The other type of vesicle apparently contains cytokines and is described at length here. Therefore there appears to be two types of vesicle with two destinies. However, the fusability of the two types of vesicle membrane appears to be similar. Both fuse either to the cell membrane directly or to an inward extension of the cell membrane on the phagosome or lysosome. In both instances the resulting cell membrane and endocytosed membrane represent a mosaic containing Golgi vesicle membrane. The extracellular distribution of cytokines will help to further define the immunologic function of macrophages.
913
References [1] Fedorko M. Secretion of cytokines and modulation of function of immunologically competent cells. Med Hypoth 1999;53:107–9. [2] Kitauro J, Asai K. Aut-dependent cytokine production in mast cells. J Exp Med 2000;192:729–39. [3] Blank U, Blank N. Fcri-mediated induction of TNF-a gene expression in mast cell lines. Mast cell and basophils. New York: Academic Press; 2000. p. 149–61. [4] Bandiers-Milo C, Sugeyanta K. Cutting edge: cotaxin elicits rapid vesicular transport-mediated release of preformed IL-4 from human eosinophils. The J Immunol 2001;166:4813–7. [5] Dvorak A, White P. Ultrastructural analysis of human eosinophils. J. Chem Immunol. Basel: Karger 2000;76:1–28. [6] Baumgartner R, Deramo V. Constitutive and inducable mechanisms for synthesis and release of cytokines in immune cell lines. The J Immunol 1996;157:4087–93. [7] Fedorko M, Hirsch J, Cohn Z. Autophagic vacuoles produced in vitro I. J Cell Biol 1968;38:377–91. [8] Bainton D, Farquhar M. Segregation and packaging of granule enzymes in eosinophilic leukocytces. J Cell Biol 1970;45:54–73. [9] Bainton D, Farquhar M. Origin of granules in polymorphonoclear leukocytes. J Cell Biol 1966;28:277–84. [10] Fedorko M, Hirsch J. Cytoplasmic granule formation in myelocytes. J Cell Biol 1966;29:307–16. [11] Fedorko M. Formation of cytoplasmic granules in human eosinophilic myelocytes. Blood 1968;31:188–94. [12] Cohn Z. The properties of mononuclear phagocytes. Hemic cells in vitro 1969;4:59–63.
http://intl.elsevierhealth.com/journals/mehy
Proposed role for small cytoplasmic vesicles in cytokine secretion by mouse macrophages Martha E. Fedorko* 510 E. 6th Street, New York, NY 10009, USA Received 10 March 2003; accepted 8 January 2004
Summary This report represents an extension of a prior report hypothesizing that cytokines in mouse macrophages are secreted by a morphologic array of small vesicles which fuse with the cell membrane and which originate in the Golgi complex [Med Hypoth 53 (1999) 107]. The Golgi complex in macrophages is distinguished by a characteristically multicentric configuration and shows budding of vesicles from the closely approximated tips of the lamellae. The location of small vesicles which extend from the Golgi complex to the cell membrane supports the hypothesis that there is one type of vesicle which fuses with the cell membrane and secretes its content of cytokines. The other type of vesicle has been shown to fuse with pinocytic vacuoles to form hydrolase positive cytoplasmic granules. Consideration of cytokines produced by macrophages will help to clarify the immunologic functions of these cells. c 2004 Elsevier Ltd. All rights reserved.
Further observations and thoughts on cytokine secretion by certain leukocytes including macrophages. Previous evidence and discussion has centered around the transport and secretion of cytokines in the small vesicle components of the cell and demonstrated that the Golgi complex is involved in cytokine production. One piece of evidence hypothesized that some of the small cytoplasmic vesicles were involved in cytokine secretion by macrophages [1]. Apart from the secretion of cytokines contained in the small vesicle system of the cell the whole process influences the membrane recycling and the membrane economy of the cell. Hypothetically the vesicular membranes in question originate in the Golgi complex and in certain cells are incorporated into the cell surface membrane during vesicular secretion process. *
Tel.: þ1-212-228-5545.
Here evidence will be put forth about cytokine secretion in several granulocytes, namely basophils and eosinophils. The morphologic evidence of the small vesicle system in macrophages will be analyzed and the intracellular journey of the small vesicle membrane will be presented. Extensive work has been performed on the production of cytokines by mast cells [2,3] and eosinophils [4]. In basophil secretion of cytokines it is apparent that TNF (tumor necrosis factor) does not depend on prior incorporation into secretion granules. Cytokine release depends on Golgi complex processing and is blocked by brefeldin A which influences Golgi processing. Eosinophils on the other hand store cytokines (preformed IL-4) in cytoplasmies granules and are able to release them at discrete cell sites. It is concluded that since brefeldin A suppresses release of IL-4 vesicular formation and transport is curtailed. There has been submitted evidence for
0306-9877/$ - see front matter c 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.mehy.2004.01.007
912
Fedorko
vesicular transport in eosinophiles from the cytoplasm to the extracellular space [5]. Macrophage cell lines have been demonstrated to produce TNF (tumor necrosis factor) [6]. The presence of cytoplasmic vesicles in mouse macrophages is distinctive in one aspect. These vesicles appear to be independent from storage granules and pinosomes although some fusion of these vesicles with lysosomes and pinosomes cannot be excluded by morphologic studies alone. A representative electron micrograph has been analyzed for presence and location of small vesicles and morphology of the Golgi complex. The morphologic appearance of a mouse macrophage in culture 48 h is shown in the accompanying figure of a published article [7], Figs. 1 and 2. Figure 2 Higher magnification of same cell shows apparent budding of Golgi vesicles from the lamellae GO label is over all area of vesicles and osmophilic cytoplasmic matrix which abuts the Golgi complex 45,000.
Figure 1 The ultrastructure of a mouse macrophage in vitro for 48 h. The Golgi complex (GO) is multicentric, composed of closely apposed lamellae which have vesicle budding from the tips of the lamellae. Vesicles extend to the cell margin (upper right margin of cell). (V3) illustrates representative Golgi vesicles. Other structures include coated vesicles (V1), varying sizes of pinocytic vesicles (V2) and PV), granules (G), mitochondria (M), and nucleus (N) 18,000 permission obtained.
Analysis of the cytoplasmic structures is as follows. There are a few coated vesicles which demonstrate the characteristic membrane structure of a spokelike appearance on the outer leaflet of the membrane. The vesicle has a lucent interior. Pinocytic vesicles and vacuoles range in size. The larger ones contain a few vesicles and clear content. The cytoplasm is replete with an abundance of small vesicles which contain an abundance of moderately electron dense content. Their location extends from the Golgi complex to the cell membrane. In certain areas vesicles are arranged in rows limited by cell membrane which shows areas of fibers beneath. Electron dense cytoplasmic granules and mitochondria are scattered throughout the cytoplasm. In view of the studies on the effect of brefeldin A which influences Golgi membrane structure and inhibits secretion of cytokines it was of interest to study the Golgi complex under conditions during which they were forming an abundance of cytoplasmic vesicles positioned from the Golgi complex to areas near the cell membrane. The Golgi complex in macrophages contrasts to that in other granule containing leukocytes [8–11]. In polymorphonuclear leukocytes and eosinophils the Golgi is unifocal with swirls of lamellae, some of which are dilated and contain apparent granule matrix. The mouse macrophage has a Golgi complex which is multifocal with no evidence of granule matrix within the lamellae. Instead there are instances where terminal areas of the lamellae bud into small vesicles containing
Proposed role for small cytoplasmic vesicles moderately dense or clear material. Of interest is the densely osmophilic areas of cytoplasmic matrix in the Golgi region abutting the closely approximated lamellae. It is hypothesized here that there are two types of cytoplasmic vesicles: one containing cytokines, the other containing acid hydrolases [12]. The macrophagic distribution extending from Golgi complex to cell membrane favors the hypothesis of existence of two types of vesicle. Cytoplasmic granule formation is driven by conditions which induces pinocytosis. This process involves fusion of acid hydrolase containing vesicles to the pinocytic vacuole. The other type of vesicle apparently contains cytokines and is described at length here. Therefore there appears to be two types of vesicle with two destinies. However, the fusability of the two types of vesicle membrane appears to be similar. Both fuse either to the cell membrane directly or to an inward extension of the cell membrane on the phagosome or lysosome. In both instances the resulting cell membrane and endocytosed membrane represent a mosaic containing Golgi vesicle membrane. The extracellular distribution of cytokines will help to further define the immunologic function of macrophages.
913
References [1] Fedorko M. Secretion of cytokines and modulation of function of immunologically competent cells. Med Hypoth 1999;53:107–9. [2] Kitauro J, Asai K. Aut-dependent cytokine production in mast cells. J Exp Med 2000;192:729–39. [3] Blank U, Blank N. Fcri-mediated induction of TNF-a gene expression in mast cell lines. Mast cell and basophils. New York: Academic Press; 2000. p. 149–61. [4] Bandiers-Milo C, Sugeyanta K. Cutting edge: cotaxin elicits rapid vesicular transport-mediated release of preformed IL-4 from human eosinophils. The J Immunol 2001;166:4813–7. [5] Dvorak A, White P. Ultrastructural analysis of human eosinophils. J. Chem Immunol. Basel: Karger 2000;76:1–28. [6] Baumgartner R, Deramo V. Constitutive and inducable mechanisms for synthesis and release of cytokines in immune cell lines. The J Immunol 1996;157:4087–93. [7] Fedorko M, Hirsch J, Cohn Z. Autophagic vacuoles produced in vitro I. J Cell Biol 1968;38:377–91. [8] Bainton D, Farquhar M. Segregation and packaging of granule enzymes in eosinophilic leukocytces. J Cell Biol 1970;45:54–73. [9] Bainton D, Farquhar M. Origin of granules in polymorphonoclear leukocytes. J Cell Biol 1966;28:277–84. [10] Fedorko M, Hirsch J. Cytoplasmic granule formation in myelocytes. J Cell Biol 1966;29:307–16. [11] Fedorko M. Formation of cytoplasmic granules in human eosinophilic myelocytes. Blood 1968;31:188–94. [12] Cohn Z. The properties of mononuclear phagocytes. Hemic cells in vitro 1969;4:59–63.