Endothelial Robo4 regulates IL-6 production by endothelial cells and monocytes via a crosstalk mechanism in inflammation

• Published in: Biochemical and biophysical research communications 2018-01, Vol.495 (1), p.801-806
• Main Authors: Shirakura, Keisuke, Ishiba, Ryosuke, Kashio, Taito, Sakai, Miki, Fukushima, Yu, Yamamoto, Nana, Manabe, Shiori, Shigesada, Naoya, Tanaka, Toru, Hino, Nobumasa, Aird, William C., Doi, Takefumi, Okada, Yoshiaki
• Format: Article
• Language: English
• Subjects: 60 APPLIED LIFE SCIENCES; ANGIOGENESIS; Endothelial cell; GM-CSF; IL-6; INFLAMMATION; LIPOPOLYSACCHARIDES; LYMPHOKINES; MICE; Monocyte; MONOCYTES; RECEPTORS; Robo4; SUBCUTANEOUS INJECTION; VEINS
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1016/j.bbrc.2017.11.067

Roundabout4 (Robo4) is an endothelial cell-specific receptor that stabilizes vasculature in pathological angiogenesis. Previous studies have shown that Robo4 is a potential therapeutic target for inflammatory diseases, but its precise roles in inflammation remain unclear. To investigate physiological Robo4 functions in inflammation, we performed a loss-of-function study in vitro and in vivo using lipopolysaccharide (LPS)-induced endotoxemia models. Subcutaneous injection of LPS into Robo4-knockout mice reduced circulating IL-6 levels. siRNA-mediated Robo4 knockdown suppressed IL-6 production induced by LPS, IL-1β, and TNFα, in human umbilical vein endothelial cells (HUVECs). Coculture experiments with HUVECs and a monocytic cell line, U937 cells, demonstrated that Robo4 knockdown suppresses IL-6 production by both endothelial cells and U937 cells. Further coculture experiments demonstrated that Robo4 knockdown inhibited a novel IL-6 amplification mechanism mediated by crosstalk between endothelial cells and U937 cells via direct interactions and two mediators, GM-CSF and IL-1β. Taken together, we demonstrated novel Robo4 functions in inflammation, i.e., it promotes IL-6 production by endothelial cells and immune cells via crosstalk. [Display omitted] •Robo4 knockout in mouse endotoxemia models reduced circulating IL-6 levels.•Robo4 knockdown suppressed IL-6 and GM-CSF production by endothelial cells (ECs).•Robo4 enhanced IL-6 production by monocytes via EC-derived GM-CSF.•Robo4 regulates cytokine production by both ECs and immune cells in inflammation.