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A new way to deplete Kupffer cells
Hepatology Research 36 (2006) 1–2
Editorial
A new way to deplete Kupffer cells The liver plays an important role in host defense system in sepsis. Kupffer cells, the resident macrophages present in the hepatic sinusoids, are responsible for bacterial scavenging, bacterial products inactivation, and inflammatory mediators clearance and production [1]. Conversely, the processes in sepsis alter the function of this organ, since hepatocytes, via receptors for many inflammatory cytokines, modify their intracellular signaling pathways. Indeed, the liver can be injured by activated Kupffer cells that release chemokines, attract blood neutrophils into the liver and activate them. Although the liver participates in host defense system through control of inflammatory and coagulation processes, the inadequate control may lead to a secondary hepatic dysfunction, and may sometimes lead to bacterial products spillover, enhanced procoagulant and inflammatory processes, and in turn, multiple organ failure and death. In addition, fulminant hepatitis is suggested to develop as a consequence of the imbalance of Th1 and Th2 immune responses. Stimulation of Th1 immune response can induce activation of Kupffer cells and macrophages to provoke massive liver necrosis through microcirculatory disturbance due to endothelial cell destruction and fibrin deposition in the hepatic sinusoids [2]. Thus, the pivotal roles of Kupffer cells are well recognized as an important player in liver injury as well as host defense system. Depletion of Kupffer cells may be useful therapeutically as well as experimental purposes. In the present issue of Hepatology Research, Hirose et al. has reported a novel method for depleting Kupffer cells [3], and I review the previous methods for Kupffer cell depletion and discuss their significance.
1. Liposome-encapsulated drugs Various compounds were used to deplete or inactivate Kupffer cells in vivo. Liposome-encapsulated clodronate was developed [4]. This method is a macrophage ‘suicide’ technique, using the liposome mediated intracellular delivery of dichloromethylene-bisphosphonate (Cl2MBP or clodronate). This method is specific with respect to phagocytic cells of the mononuclear phagocyte system (MPS) for the following reasons: (1) the natural fate of liposomes is phagocytosis. (2) Once ingested by macrophages, the phospholipids bilayers 1386-6346/$ – see front matter © 2006 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.hepres.2006.06.014
of the liposomes are disrupted under the influence of lysosomal phopholipases. (3) Cl2MBP intracellularly released in this way does not easily escape from the cell by crossing the cell membranes. (4) Cl2MBP released in the circulation from dead macrophages or by leakage from liposomes, will not easily enter non-phagocytic cells and has an extremely short half-life in the circulation and body fluids, explaining the fact that non-phagocytic cells are not affected. Liposomeencapsulated drugs including clodronate, propamidine and ethylenediaminetetraacetic acid (EDTA) were compared, since these molecules represent the drug families of bisphosphonates, diamidines and polyaminopolycarboxylic acidchelating agents, respectively [5]. Clodronate, such as bisphosphonate or alendronate, has been shown to accumulate preferentially in the bone, kills osteoclasts selectively. Bisphosphonate induces apoptosis of cultured macrophages that are ontogenetically related to osteoclasts [6]. Although liposome-delivered clodronate was used as the most efficacious drug for macrophage depletion, propamidine, an antimicrobial agent belonging to the family of aromatic polyamidines, is about 10 times as effective [6]. No substantial Kupffer cell-depleting activity of liposome-enapsulated EDTA could be demonstrated [5]. Recently, it has been shown that liposome-encapsulated bisphosphonates, but not their free forms, are taken up by macrophages and reticuloendothelial cells in the liver, lung and other tissues [7]. This study suggests that the liposome-encapsulated drugs exhibit cytotoxic effects not only on Kupffer cells but also other cells in the liver and sometimes elicit liver injury. Therefore, the administration of liposomal compounds often caused liver injury due to their non-specific distribution to the reticuloendothelial system [8].
2. Gadolinium chloride Gadolinium chloride (GdCl) hexahydrate is colloidal at pH > 6. When this colloid is administered intravenously, it is phagocytosed by Kupffer cells and inhibits Ca2+ channels, leading to Kupffer cell death. This selectively eliminates about 70–80% Kupffer cells from the liver for 2–3 days [9]. The liver begins to be repopulated by immature macrophages
2
Editorial / Hepatology Research 36 (2006) 1–2
3–4 days after injection [10]. Other macrophages pools are not significantly affected by GdCl and there is no evidence that it exerts any direct toxic effects on hepatocytes, biliary epithelial cells, endothelial cells, Ito cells or circulating monocytes. Experiments with GdCl uncovered that depletion of Kupffer cells improves early graft function and survival after liver transplantation [11]. Thus, GdCl is a useful agent for various experiments of liver pathophysiology, however, its disadvantages include incomplete depletion rate and shorter active duration.
3. Mannose-conjugated alendronate (MANA) The usefulness of MANA has been demonstrated in the paper by Hirose et al. [3], in which MANA rapidly and remarkably depleted Kupffer cells in vivo via a mannose receptor-mediated mechanism. It successfully inhibited LPSinduced liver injury, and protected animals from lethal endotoxemia. The pretreatment of animals with MANA, but not alendronate, completely inhibited the lethal effect of LPS. Kupffer cells express a number of mannose receptors that bind mannose-like glycoproteins to take up into the cells by endocytosis. The mannose receptor, unlike other receptors involved in host defense, is relatively specific for macrophages and certain macrophage-like cells. Its expression is extremely high in Kupffer cells [12]. As such, this receptor offers unique opportunities for selective targeting of therapeutic and other agents to Kupffer cells. Indeed, mannose-conjugated ligands in the circulation were rapidly and preferentially incorporated into Kupffer cells in vivo [13]. Since more than 70% of mannose-conjugated compounds were taken up by the liver, their accumulations in the spleen and other tissues including the bone marrow were as low as ∼2% of the entire dosage [3]. The major fraction of administered MANA was delivered to Kupffer cells. Alendronate markedly depletes osteoclasts and this drug has successfully been used as an antiresorptive agent for treating the patients with osteoporosis [6]. Since osteoclasts belong to a family of mononuclear phagocytes, alendronate may affect other types of macrophages including Kupffer cells. The doses of alendronates used for the depletion of osteoclasts did not affect the number of Kupffer cells [3]. Hirose et al. has reported that MANA is a safe and efficient method eliminating Kupffer cells [3]. Finally, the development of MANA may be useful not only for experiments of the pathophysiology of liver diseases, but also for the patients with Kupffer cell activation.
References [1] Dhainaut JF, Marin N, Mignon A, Vinsonneau C. Hepatic response to sepsis: interaction between coagulation and inflammatory processes. Crit Care Med 2001;29:S27–S127. [2] Arai M, Mochida S, Ohno A, Ogata I, Fujiwara K. Sinusoidal endothelial cell damage by activated hepatic macrophages in rat liver necrosis. Gastroenterology 1993;104:1466–71. [3] Hirose M, Nishikawa M, Qian W, Anwarul H, Mashimo M, Inoue M. Mannose-conjugated alendronate selectively depletes Kupffer cells and inhibits endotoxemic shock in the mice. Hepatol Res 2006;36:3– 10. [4] Rooijen NV, Sanders A. Liposome mediated depletion of macrophages: mechanism of action, preparation of liposomes and applications. J Immunol Methods 1994;174:83–93. [5] Rooijen NV, Sanders A. Kupffer cell depletion by liposome-delivered drugs: comparative activity of intracellular clodronate, propamidine, and ethylenediaminetetraacetic acid. Hepatology 1996;23:1239– 43. [6] Selander KS, Monkkonen J, Karhukorpi EK, Harkonen P, Hannuniemi R, Vaananen HK. Characteristics of clodronate-induced apoptosis in osteoclasts and macrophages. Mol Pharmacol 1996;50:1127–38. [7] Prins HA, Meijer C, Boelens PG, et al. Kupffer cell-deleted rats have a diminished acute-phase response following major liver resection. Shock 2004;21:561–5. [8] Poelstra K. Towards controlled drug release in the liver. Hepatology 2000;32:1401–2. [9] Rai RM, Yang SQ, McClain C, Karp CL, Klein AS, Diehl AM. Kupffer cell depletion by gadolinium chloride enhances liver regeneration after partial hepatectomy in rats. Am J Physiol 1996;270:G909–18. [10] Hardonk MJ, Dijkhuis FWJ, Hulstaert CE, Koudstaal J. Heterogeneity of rat liver and spleen macrophages in gadolinium chlorideinduced elimination and repopulation. J Leukocyte Biol 1992;52:296– 302. [11] von Franken M, Golling M, Mehrabi A, Nentwich H, Klar E, Kraus TW. Donor pretreatment with gadolinium chloride improves early function and survival after porcine liver transplantation. Transpl Int 2003;16:806–13. [12] Pontow SE, Kery V, Stahl PD. Mannose receptor. Int Rev Cytol 1992;137B:221–44. [13] Bijsterbosch MK, Donke W, van de Bilt H, van Weely S, van Berkel TJ, Aerts JM. Quantitative analysis of the targeting of mannose-terminal glucocerebrosidase. Predominant uptake by liver endothelial cells. Eur J Biochem 1996;237:344–9.
Goshi Shiota ∗ Division of Molecular and Genetic Medicine, Department of Genetic Medicine and Regenerative Therapeutics, Graduate School of Medicine, Tottori University, Yonago 683-8504, Japan ∗ Tel.:
+81 859 38 6431; fax: +81 859 38 6430 E-mail address: [email protected] 16 June 2006 Available online 25 July 2006
Editorial
A new way to deplete Kupffer cells The liver plays an important role in host defense system in sepsis. Kupffer cells, the resident macrophages present in the hepatic sinusoids, are responsible for bacterial scavenging, bacterial products inactivation, and inflammatory mediators clearance and production [1]. Conversely, the processes in sepsis alter the function of this organ, since hepatocytes, via receptors for many inflammatory cytokines, modify their intracellular signaling pathways. Indeed, the liver can be injured by activated Kupffer cells that release chemokines, attract blood neutrophils into the liver and activate them. Although the liver participates in host defense system through control of inflammatory and coagulation processes, the inadequate control may lead to a secondary hepatic dysfunction, and may sometimes lead to bacterial products spillover, enhanced procoagulant and inflammatory processes, and in turn, multiple organ failure and death. In addition, fulminant hepatitis is suggested to develop as a consequence of the imbalance of Th1 and Th2 immune responses. Stimulation of Th1 immune response can induce activation of Kupffer cells and macrophages to provoke massive liver necrosis through microcirculatory disturbance due to endothelial cell destruction and fibrin deposition in the hepatic sinusoids [2]. Thus, the pivotal roles of Kupffer cells are well recognized as an important player in liver injury as well as host defense system. Depletion of Kupffer cells may be useful therapeutically as well as experimental purposes. In the present issue of Hepatology Research, Hirose et al. has reported a novel method for depleting Kupffer cells [3], and I review the previous methods for Kupffer cell depletion and discuss their significance.
1. Liposome-encapsulated drugs Various compounds were used to deplete or inactivate Kupffer cells in vivo. Liposome-encapsulated clodronate was developed [4]. This method is a macrophage ‘suicide’ technique, using the liposome mediated intracellular delivery of dichloromethylene-bisphosphonate (Cl2MBP or clodronate). This method is specific with respect to phagocytic cells of the mononuclear phagocyte system (MPS) for the following reasons: (1) the natural fate of liposomes is phagocytosis. (2) Once ingested by macrophages, the phospholipids bilayers 1386-6346/$ – see front matter © 2006 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.hepres.2006.06.014
of the liposomes are disrupted under the influence of lysosomal phopholipases. (3) Cl2MBP intracellularly released in this way does not easily escape from the cell by crossing the cell membranes. (4) Cl2MBP released in the circulation from dead macrophages or by leakage from liposomes, will not easily enter non-phagocytic cells and has an extremely short half-life in the circulation and body fluids, explaining the fact that non-phagocytic cells are not affected. Liposomeencapsulated drugs including clodronate, propamidine and ethylenediaminetetraacetic acid (EDTA) were compared, since these molecules represent the drug families of bisphosphonates, diamidines and polyaminopolycarboxylic acidchelating agents, respectively [5]. Clodronate, such as bisphosphonate or alendronate, has been shown to accumulate preferentially in the bone, kills osteoclasts selectively. Bisphosphonate induces apoptosis of cultured macrophages that are ontogenetically related to osteoclasts [6]. Although liposome-delivered clodronate was used as the most efficacious drug for macrophage depletion, propamidine, an antimicrobial agent belonging to the family of aromatic polyamidines, is about 10 times as effective [6]. No substantial Kupffer cell-depleting activity of liposome-enapsulated EDTA could be demonstrated [5]. Recently, it has been shown that liposome-encapsulated bisphosphonates, but not their free forms, are taken up by macrophages and reticuloendothelial cells in the liver, lung and other tissues [7]. This study suggests that the liposome-encapsulated drugs exhibit cytotoxic effects not only on Kupffer cells but also other cells in the liver and sometimes elicit liver injury. Therefore, the administration of liposomal compounds often caused liver injury due to their non-specific distribution to the reticuloendothelial system [8].
2. Gadolinium chloride Gadolinium chloride (GdCl) hexahydrate is colloidal at pH > 6. When this colloid is administered intravenously, it is phagocytosed by Kupffer cells and inhibits Ca2+ channels, leading to Kupffer cell death. This selectively eliminates about 70–80% Kupffer cells from the liver for 2–3 days [9]. The liver begins to be repopulated by immature macrophages
2
Editorial / Hepatology Research 36 (2006) 1–2
3–4 days after injection [10]. Other macrophages pools are not significantly affected by GdCl and there is no evidence that it exerts any direct toxic effects on hepatocytes, biliary epithelial cells, endothelial cells, Ito cells or circulating monocytes. Experiments with GdCl uncovered that depletion of Kupffer cells improves early graft function and survival after liver transplantation [11]. Thus, GdCl is a useful agent for various experiments of liver pathophysiology, however, its disadvantages include incomplete depletion rate and shorter active duration.
3. Mannose-conjugated alendronate (MANA) The usefulness of MANA has been demonstrated in the paper by Hirose et al. [3], in which MANA rapidly and remarkably depleted Kupffer cells in vivo via a mannose receptor-mediated mechanism. It successfully inhibited LPSinduced liver injury, and protected animals from lethal endotoxemia. The pretreatment of animals with MANA, but not alendronate, completely inhibited the lethal effect of LPS. Kupffer cells express a number of mannose receptors that bind mannose-like glycoproteins to take up into the cells by endocytosis. The mannose receptor, unlike other receptors involved in host defense, is relatively specific for macrophages and certain macrophage-like cells. Its expression is extremely high in Kupffer cells [12]. As such, this receptor offers unique opportunities for selective targeting of therapeutic and other agents to Kupffer cells. Indeed, mannose-conjugated ligands in the circulation were rapidly and preferentially incorporated into Kupffer cells in vivo [13]. Since more than 70% of mannose-conjugated compounds were taken up by the liver, their accumulations in the spleen and other tissues including the bone marrow were as low as ∼2% of the entire dosage [3]. The major fraction of administered MANA was delivered to Kupffer cells. Alendronate markedly depletes osteoclasts and this drug has successfully been used as an antiresorptive agent for treating the patients with osteoporosis [6]. Since osteoclasts belong to a family of mononuclear phagocytes, alendronate may affect other types of macrophages including Kupffer cells. The doses of alendronates used for the depletion of osteoclasts did not affect the number of Kupffer cells [3]. Hirose et al. has reported that MANA is a safe and efficient method eliminating Kupffer cells [3]. Finally, the development of MANA may be useful not only for experiments of the pathophysiology of liver diseases, but also for the patients with Kupffer cell activation.
References [1] Dhainaut JF, Marin N, Mignon A, Vinsonneau C. Hepatic response to sepsis: interaction between coagulation and inflammatory processes. Crit Care Med 2001;29:S27–S127. [2] Arai M, Mochida S, Ohno A, Ogata I, Fujiwara K. Sinusoidal endothelial cell damage by activated hepatic macrophages in rat liver necrosis. Gastroenterology 1993;104:1466–71. [3] Hirose M, Nishikawa M, Qian W, Anwarul H, Mashimo M, Inoue M. Mannose-conjugated alendronate selectively depletes Kupffer cells and inhibits endotoxemic shock in the mice. Hepatol Res 2006;36:3– 10. [4] Rooijen NV, Sanders A. Liposome mediated depletion of macrophages: mechanism of action, preparation of liposomes and applications. J Immunol Methods 1994;174:83–93. [5] Rooijen NV, Sanders A. Kupffer cell depletion by liposome-delivered drugs: comparative activity of intracellular clodronate, propamidine, and ethylenediaminetetraacetic acid. Hepatology 1996;23:1239– 43. [6] Selander KS, Monkkonen J, Karhukorpi EK, Harkonen P, Hannuniemi R, Vaananen HK. Characteristics of clodronate-induced apoptosis in osteoclasts and macrophages. Mol Pharmacol 1996;50:1127–38. [7] Prins HA, Meijer C, Boelens PG, et al. Kupffer cell-deleted rats have a diminished acute-phase response following major liver resection. Shock 2004;21:561–5. [8] Poelstra K. Towards controlled drug release in the liver. Hepatology 2000;32:1401–2. [9] Rai RM, Yang SQ, McClain C, Karp CL, Klein AS, Diehl AM. Kupffer cell depletion by gadolinium chloride enhances liver regeneration after partial hepatectomy in rats. Am J Physiol 1996;270:G909–18. [10] Hardonk MJ, Dijkhuis FWJ, Hulstaert CE, Koudstaal J. Heterogeneity of rat liver and spleen macrophages in gadolinium chlorideinduced elimination and repopulation. J Leukocyte Biol 1992;52:296– 302. [11] von Franken M, Golling M, Mehrabi A, Nentwich H, Klar E, Kraus TW. Donor pretreatment with gadolinium chloride improves early function and survival after porcine liver transplantation. Transpl Int 2003;16:806–13. [12] Pontow SE, Kery V, Stahl PD. Mannose receptor. Int Rev Cytol 1992;137B:221–44. [13] Bijsterbosch MK, Donke W, van de Bilt H, van Weely S, van Berkel TJ, Aerts JM. Quantitative analysis of the targeting of mannose-terminal glucocerebrosidase. Predominant uptake by liver endothelial cells. Eur J Biochem 1996;237:344–9.
Goshi Shiota ∗ Division of Molecular and Genetic Medicine, Department of Genetic Medicine and Regenerative Therapeutics, Graduate School of Medicine, Tottori University, Yonago 683-8504, Japan ∗ Tel.:
+81 859 38 6431; fax: +81 859 38 6430 E-mail address: [email protected] 16 June 2006 Available online 25 July 2006