Fig. 2

Galectin-9 medium (Gal-9 M) induces human dermal microvascular endothelial cell (HMVEC) tube formation in vitro. a Gal-9 M induced HMVEC tube formation on growth factor-reduced (GFR) Matrigel that was higher than that induced with PBS (p < 0.05). b Photomicrographs at ×20 magnification of tube formation assay with PBS, a negative control, and basic fibroblast growth factor, a positive control, and Gal-9 at various concentrations. We did not find a significant increase in HMVEC tube formation in response to Gal-9 M at 111.6, 6.97, and 3.49 nmol/L concentrations. Arrows indicate tubes formed in response to each group. c Matrigel tube formation assay with Gal-9 using various signaling inhibitors. Inhibitors of p38, Janus kinase (Jnk), and extracellular signal-regulating kinases 1/2 (Erk1/2) significantly reduced Gal-9 M-induced tube formation (p < 0.05), whereas the signaling inhibitor of phosphatidylinositol 3-kinase did not. d Photographs at ×20 magnification of tube formation assay with various signaling inhibitors. Arrows indicate HMVEC tubes formed in response to Gal-9 M with or without signaling inhibitors. e and f siRNA directed against Erk1/2 and p38 significantly reduced HMVEC tube formation on Matrigel in response to Gal-9 M compared with sham (scrambled)-transfected HMVECs. g Western blots with HMVECs stimulated with Gal-9 M. HMVECs were stimulated for 5, 15, 30, and 45 minutes with Gal-9 M (27.9 nmol/L). Shown are one of two representative blots for incremental increases in phosphorylation for Erk1/2, p38, and Jnk proportional to length of time stimulated. Western blots were performed with lysates of HMVECs stimulated with Gal-9 M in the presence or absence of signaling inhibitors. Jnk signaling inhibitor decreased Erk1/2 phosphorylation, suggesting that Jnk is upstream of Erk1/2 in the Gal-9 M-induced signaling pathway. Additionally, Jnk inhibitor did not reduce p38 phosphorylation and vice versa