Functional Analysis of Dual-Specificity Protein Phosphatases in Angiogenesis

Endothelial angiogenic activity and adipose angiogenesis is controlled by extracellular matrix protein TGFBI

Several studies have suggested that extracellular matrix (ECM) remodeling and the microenvironment are tightly associated with adipogenesis and adipose angiogenesis. In the present study, we demonstrated that transforming growth factor-beta induced (TGFBI) suppresses angiogenesis stimulated by adipocyte-conditioned medium (Ad-CM), both in vitro and in vivo. TGFBI knockout (KO) mice exhibited increased numbers of blood vessels in adipose tissue, and blood vessels from these mice showed enhanced infiltration into Matrigel containing Ad-CM. The treatment of Ad-CM-stimulated SVEC-10 endothelial cells with TGFBI protein reduced migration and tube-forming activity. TGFBI protein suppressed the activation of the Src and extracellular signaling-related kinase signaling pathways of these SVEC-10 endothelial cells. Our findings indicated that TGFBI inhibited adipose angiogenesis by suppressing the activation of Src and ERK signaling pathways, possibly because of the stimulation of the angiogenic activity of endothelial cells.

Dusp3 deletion in mice promotes experimental lung tumour metastasis in a macrophage dependent manner

Vaccinia-H1 Related (VHR) dual-specificity phosphatase, or DUSP3, plays an important role in cell cycle regulation and its expression is altered in several human cancers. In mouse model, DUSP3 deletion prevents neo-angiogenesis and b-FGF-induced microvessel outgrowth. Considering the importance of angiogenesis in metastasis formation, our study aimed to investigate the role of DUSP3 in tumour cell dissemination. Using a Lewis Lung carcinoma (LLC) experimental metastasis model, we observed that DUSP3^-/- mice developed larger lung metastases than littermate controls. DUSP3^-/- bone marrow transfer to lethally irradiated DUSP3^+/+ mice was sufficient to transfer the phenotype to DUSP3^+/+ mice, indicating that hematopoietic cells compartment was involved in the increased tumour cell dissemination to lung tissues. Interestingly, we found a higher percentage of tumour-promoting Ly6C^int macrophages in DUSP3^-/- LLC-bearing lung homogenates that was at least partially due to a better recruitment of these cells. This was confirmed by 1) the presence of higher number of the Ly6B^hi macrophages in DUSP3^-/- lung homogenates and by 2) the better migration of DUSP3^-/- bone marrow sorted monocytes, peritoneal macrophages and bone marrow derived macrophages (BMDMs), compared to DUSP3^+/+ monocytes, macrophages and BMDMs, in response to LLC-conditioned medium. Our study demonstrates that DUSP3 phosphatase plays a key role in metastatic growth through a mechanism involving the recruitment of macrophages towards LLC-bearing lungs.

Dual-Specificity Phosphatase 3 Deletion Protects Female, but Not Male, Mice from Endotoxemia-Induced and Polymicrobial-Induced Septic Shock

Dual-specificity phosphatase 3 (DUSP3) is a small phosphatase with poorly known physiological functions and for which only a few substrates are known. Using knockout mice, we recently reported that DUSP3 deficiency confers resistance to endotoxin- and polymicrobial-induced septic shock. We showed that this protection was macrophage dependent. In this study, we further investigated the role of DUSP3 in sepsis tolerance and showed that the resistance is sex dependent. Using adoptive-transfer experiments and ovariectomized mice, we highlighted the role of female sex hormones in the phenotype. Indeed, in ovariectomized females and in male mice, the dominance of M2-like macrophages observed in DUSP3^-/- female mice was reduced, suggesting a role for this cell subset in sepsis tolerance. At the molecular level, DUSP3 deletion was associated with estrogen-dependent decreased phosphorylation of ERK1/2 and Akt in peritoneal macrophages stimulated ex vivo by LPS. Our results demonstrate that estrogens may modulate M2-like responses during endotoxemia in a DUSP3-dependent manner.