Promotion of lymphatic integrity by angiopoietin-1/Tie2 signaling during inflammation.
The cutaneous lymphatic system plays a major role in tissue fluid homeostasis and inflammation of the skin. Although several lymphangiogenic factors are known to be involved in the formation of lymphatic vessels, the molecular mechanisms that maintain lymphatic integrity and control the functional drainage of interstitial fluid and resolution of inflammation remain unknown. Here we show that angiopoietin-1 (Ang1) enhances lymphatic integrity and function during inflammation. Ang1 transgenic mice under the control of keratin-14 (K14-Ang1) showed attenuated edema formation and inflammation after UV B (UVB) exposure. After UVB irradiation, blood vascular permeability was inhibited in K14-Ang1 mice compared with wild-type (WT) mice. Moreover, lymphatic vessels of WT mice were markedly enlarged and leaky in inflamed skin, whereas K14-Ang1 mice showed relatively contracted lymphatic vessels together with enhanced lymphatic vascularization. Expression of endothelial-specific tight junction molecules claudin-5 and zonula occludens protein 1 (ZO-1) was strongly down-regulated in the inflamed lymphatic vessels of UVB-exposed WT mice, whereas down-regulation of both claudin-5 and ZO-1 was blocked in UVB-exposed K14-Ang1 mice. In vitro studies revealed that the stability of lymphatic endothelial cells was enhanced in the presence of Ang1, presumably via up-regulation of claudin-5, as well as ZO-1. Claudin-5 knockdown markedly increased the permeability of lymphatic endothelial cells. Overall, our data strongly support the idea that Ang1/Tie2 signaling promotes lymphatic integrity by modulating tight junction molecule expression during inflammation.
Shiseido Innovative Science Research Center, Yokohama, Japan. Electronic address: kentaro.kajiya@to.shiseido.co.jp.
Kentaro
K
Kajiya
Department of Signal Transduction, Research Institute of Microbial Diseases, Osaka University, Osaka, Japan.
Hiroyasu
H
Kidoya
Shiseido Innovative Science Research Center, Yokohama, Japan.
Mika
M
Sawane
Shiseido Innovative Science Research Center, Yokohama, Japan.
Yuuko
Y
Matsumoto-Okazaki
Shiseido Innovative Science Research Center, Yokohama, Japan.
Haruyo
H
Yamanishi
Department of Physiology and Cell Biology, Kobe University, Kobe, Japan.
Mikio
M
Furuse
Department of Signal Transduction, Research Institute of Microbial Diseases, Osaka University, Osaka, Japan.
Nobuyuki
N
Takakura
D042683:Angiopoietin-1 / Q000502:physiology*; D000818:Animals; D002465:Cell Movement; D062507:Claudin-5; D057167:Claudins / Q000378:metabolism; D004487:Edema / Q000378:metabolism; D042783:Endothelial Cells / Q000502:physiology / Q000528:radiation effects; D005260:Female; D008205:Lymphangitis / Q000503:physiopathology*; D042601:Lymphatic Vessels / Q000502:physiology* / Q000528:radiation effects; D051379:Mice; D008822:Mice, Transgenic; D010032:Otitis Externa / Q000503:physiopathology; D034741:RNA, Small Interfering / Q000494:pharmacology; D042787:Receptor, TIE-2 / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*; D019108:Tight Junctions / Q000378:metabolism; D014466:Ultraviolet Rays
D042683:Angiopoietin-1; D062507:Claudin-5; D057167:Claudins; C491511:Cldn5 protein, mouse; D034741:RNA, Small Interfering; D042787:Receptor, TIE-2