Critical role of CD11b+ macrophages and VEGF in inflammatory lymphangiogenesis, antigen clearance, and inflammation resolution

Kataru, Raghu P.,Jung, Keehoon,Jang, Cholsoon,Yang, Hanseul,Schwendener, Reto A.,Baik, Jung Eun,Han, Seung Hyun,Alitalo, Kari,Koh, Gou Young American Society of Hematology 2009 Blood Vol.113 No.22

<P>Using a bacterial pathogen-induced acute inflammation model in the skin, we defined the roles of local lymphatic vessels and draining lymph nodes (DLNs) in antigen clearance and inflammation resolution. At the peak day of inflammation, robust expansion of lymphatic vessels and profound infiltration of CD11b+/Gr-1+ macrophages into the inflamed skin and DLN were observed. Moreover, lymph flow and inflammatory cell migration from the inflamed skin to DLNs were enhanced. Concomitantly, the expression of lymphangiogenic growth factors such as vascular endothelial growth factor C (VEGF-C), VEGF-D, and VEGF-A were significantly up-regulated in the inflamed skin, DLNs, and particularly in enriched CD11b+ macrophages from the DLNs. Depletion of macrophages, or blockade of VEGF-C/D or VEGF-A, largely attenuated these phenomena, and produced notably delayed antigen clearance and inflammation resolution. Conversely, keratin 14 (K14)-VEGF-C transgenic mice, which have dense and enlarged lymphatic vessels in the skin dermis, exhibited accelerated migration of inflammatory cells from the inflamed skin to the DLNs and faster antigen clearance and inflammation resolution. Taken together, these results indicate that VEGF-C, -D, and -A derived from the CD11b+/Gr-1+ macrophages and local inflamed tissues play a critical role in promoting antigen clearance and inflammation resolution.</P>

Angiogenic Role of LYVE-1-Positive Macrophages in Adipose Tissue

Cho, Chung-Hyun,Jun Koh, Young,Han, Jinah,Sung, Hoon-Ki,Jong Lee, Hyuek,Morisada, Tohru,Schwendener, Reto A.,Brekken, Rolf A.,Kang, Guson,Oike, Yuichi,Choi, Tae-Saeng,Suda, Toshio,Yoo, Ook-Joon,Koh, G Grune & Stratton 2007 Circulation research Vol.100 No.4

<P>Here we report the discovery of a characteristic dense vascular network (DVN) in the tip portion of epididymal adipose tissue in adult mice. The DVN is formed by angiogenesis rather than by vasculogenesis, and has functional blood circulation. This DVN and its subsequent branching may provide a new functional route for adipogenesis. The recruitment, infiltration, and accumulation of bone marrow-derived LYVE-1(+) macrophages in the tip region are crucial for the formation of the DVN. Matrix metalloproteinases (MMPs) and the VEGF-VEGFR2 system are responsible not only for the formation of the DVN, but also for the recruitment and infiltration of LYVE-1(+) macrophages into the epididymal adipose tissue tip region. SDF-1, but not the MCP-1-CCR2 system, is a critical factor in recruitment and ongoing retention of macrophages in this area. We also demonstrate that the tip region of epididymal adipose tissue is highly hypoxic, and thus provides a microenvironment conducive to the high expression and enhanced activities of VEGF, VEGFR2, MMPs, and SDF-1 in autocrine and paracrine manners, to create an ideal niche for the recruitment, retention, and angiogenic action of macrophages. These findings shed light on the complex interplay between macrophage infiltration, angiogenesis, and adipogenesis in the tip region of adult epididymal adipose tissue, and provide novel insight into the regulation of alternative outgrowth of adipose tissue.</P>

Role of CD11b⁺ Macrophages in Intraperitoneal Lipopolysaccharide-Induced Aberrant Lymphangiogenesis and Lymphatic Function in the Diaphragm

Kim, K.E.,Koh, Y.J.,Jeon, B.H.,Jang, C.,Han, J.,Kataru, R.P.,Schwendener, R.A.,Kim, J.M.,Koh, G.Y. American Association of Pathologists and Bacteriol 2009 The American journal of pathology Vol.175 No.4

Lymphatic vessels in the diaphragm are essential for draining peritoneal fluid, but little is known about their pathological changes during inflammation. Here we characterized diaphragmatic lymphatic vessels in a peritonitis model generated by daily i.p. administration of lipopolysaccharide (LPS) in mice. Intraperitoneal LPS increased lymphatic density, branching, sprouts, connections, and network formation in the diaphragm in time- and dose-dependent manners. These changes were reversible on discontinuation of LPS administration. The LPS-induced lymphatic density and remodeling occur mainly through proliferation of lymphatic endothelial cells. CD11b<SUP>+</SUP> macrophages were massively accumulated and closely associated with the lymphatic vessels changed by i.p. LPS. Both RT-PCR assays and experiments with vascular endothelial growth factor-C/D blockade and macrophage-depletion indicated that the CD11b<SUP>+</SUP> macrophage-derived lymphangiogenic factors vascular endothelial growth factor-C/D could be major mediators of LPS-induced lymphangiogenesis and lymphatic remodeling through paracrine activity. Functional assays with India ink and fluorescein isothiocyanate-microspheres indicated that impaired peritoneal fluid drainage in diaphragm of LPS-induced peritonitis mice was due to inflammatory fibrosis and massive attachment of CD11b<SUP>+</SUP> macrophages on the peritoneal side of the diaphragmatic lymphatic vessels. These findings reveal that CD11b<SUP>+</SUP> macrophages play an important role in i.p. LPS-induced aberrant lymphangiogenesis and lymphatic dysfunction in the diaphragm.

Profound but Dysfunctional Lymphangiogenesis via Vascular Endothelial Growth Factor Ligands from CD11b⁺ Macrophages in Advanced Ovarian Cancer

Jeon, Bong-Hyun,Jang, Cholsoon,Han, Jinah,Kataru, Raghu P.,Piao, Lianhua,Jung, Keehoon,Cha, Hye Ji,Schwendener, Reto A.,Jang, Kyu Yun,Kim, Kwan-Sik,Alitalo, Kari,Koh, Gou Young American Association for Cancer Research 2008 Cancer Research Vol.68 No.4

<P>Severe ascites is a hallmark of advanced ovarian cancer (OVCA), yet the underlying mechanism that creates an imbalance between peritoneal vascular leakage and lymphatic drainage is unknown. Here, we identified and characterized peritoneal lymphatic vessels in OVCA mice, a model generated by implantation of human OVCA cells into athymic nude mice. The OVCA mice displayed substantial lymphangiogenesis and lymphatic remodeling, massive infiltration of CD11b(+)/LYVE-1(+) macrophages and disseminated carcinomatosis in the mesentery and diaphragm, and progressive chylous ascites formation. Functional assays indicated that the abnormally abundant lymphatic vessels in the diaphragm were not conductive in peritoneal fluid drainage. Moreover, lipid absorbed from the gut leaked out from the aberrant mesenteric lymphatic vessels. Our results indicate that vascular endothelial growth factor (VEGF)-C, VEGF-D, and VEGF-A from CD11b(+) macrophages are responsible for producing OVCA-induced dysfunctional lymphangiogenesis, although other cell types contribute to the increased ascites formation. Accordingly, the combined blockade of VEGF-C/D and VEGF-A signaling with soluble VEGF receptor-3 and VEGF-Trap, respectively, markedly inhibited chylous ascites formation. These findings provide additional therapeutic targets to ameliorate chylous ascites formation in patients with advanced OVCA.</P>

Inflammation Is Necessary for Long-Term but Not Short-Term High-Fat Diet–Induced Insulin Resistance

Lee, Yun Sok,Li, Pingping,Huh, Jin Young,Hwang, In Jae,Lu, Min,Kim, Jong In,Ham, Mira,Talukdar, Saswata,Chen, Ai,Lu, Wendell J.,Bandyopadhyay, Guatam K.,Schwendener, Reto,Olefsky, Jerrold,Kim, Jae Bum American Diabetes Association 2011 Diabetes Vol.60 No.10

<P><B>OBJECTIVE</B></P><P>Tissue inflammation is a key factor underlying insulin resistance in established obesity. Several models of immuno-compromised mice are protected from obesity-induced insulin resistance. However, it is unanswered whether inflammation triggers systemic insulin resistance or vice versa in obesity. The purpose of this study was to assess these questions.</P><P><B>RESEARCH DESIGN AND METHODS</B></P><P>We fed a high-fat diet (HFD) to wild-type mice and three different immuno-compromised mouse models (lymphocyte-deficient Rag1 knockout, macrophage-depleted, and hematopoietic cell-specific Jun NH<SUB>2</SUB>-terminal kinase–deficient mice) and measured the time course of changes in macrophage content, inflammatory markers, and lipid accumulation in adipose tissue, liver, and skeletal muscle along with systemic insulin sensitivity.</P><P><B>RESULTS</B></P><P>In wild-type mice, body weight and adipose tissue mass, as well as insulin resistance, were clearly increased by 3 days of HFD. Concurrently, in the short-term HFD period inflammation was selectively elevated in adipose tissue. Interestingly, however, all three immuno-compromised mouse models were not protected from insulin resistance induced by the short-term HFD. On the other hand, lipid content was markedly increased in liver and skeletal muscle at day 3 of HFD.</P><P><B>CONCLUSIONS</B></P><P>These data suggest that the initial stage of HFD-induced insulin resistance is independent of inflammation, whereas the more chronic state of insulin resistance in established obesity is largely mediated by macrophage-induced proinflammatory actions. The early-onset insulin resistance during HFD feeding is more likely related to acute tissue lipid overload.</P>