IL-6/sIL-6R trans-signalling, but not TNF-α induced angiogenesis in a HUVEC and synovial cell co-culture system

Abstract

Angiogenesis in synovia is a characteristic of RA patients. We examined whether IL-6 or TNF-alpha induce tubule formation in a co-culture system of fibroblast-like synovial cells from RA patients (RA-FLS) and human umbilical vein endothelial cells (HUVEC). The effects of IL-6 and TNF-alpha on the expression of angiogenic factors in RA-FLS and HUVEC, and the proliferation of HUVEC were also studied. IL-6 + sIL-6R induced tubule formation, whereas IL-6 alone did not. IL-6/sIL-6R-induced tubule formation was completely suppressed by the addition of either anti-IL-6R or anti-VEGF antibody. TNF-alpha did not induce tubule formation. On the contrary, it decreased CD31-positive area compared with the control. IL-6 + sIL-6R augmented VEGF production in RA-FLS, whereas IL-6 alone did not. Anti-IL-6R antibody suppressed IL-6/sIL-6R-induced VEGF production, but not spontaneous VEGF production. In contrast, TNF-alpha did not induce VEGF production from RA-FLS and HUVEC. IL-6 + sIL-6R stimulation of RA-FLS strongly induced mRNA expression of VEGF, but not of other angiogenic factors, such as EGF, bFGF, TGF-beta, IL-1, TNF-alpha and IL-8. Neither IL-6 nor IL-6/sIL-6R promoted HUVEC proliferation, whereas TNF-alpha significantly inhibited VEGF-induced HUVEC proliferation. In conclusion, IL-6/sIL-6R complex showed angiogenic activity via the production of VEGF from RA-FLS, but TNF-alpha was anti-angiogenic in our experimental system.

IL-6 in Inflammation, Immunity, and Disease

“…One of these effects is that, when IL-6 is generated in bone marrow stromal cells, it stimulates the RANKL (Hashizume et al 2008), which is indispensable for the differentiation and activation of osteoclasts (Kotake et al 1996), and this leads to bone resorption and osteoporosis (Poli et al 1994). IL-6 also induces excess production of VEGF, leading to enhanced angiogenesis and increased vascular permeability, which are pathological features of inflammatory lesions and are seen in, for example, synovial tissues of rheumatoid arthritis (RA) or edema of remitting seronegative symmetrical synovitis with pitting edema (RS3PE) syndrome (Nakahara et al 2003;Hashizume et al 2009). Finally, it has been reported that IL-6 aids keratinocyte proliferation (Grossman et al 1989) or the generation of collagen in dermal fibroblasts that may account for changes in the skin of patients with systemic sclerosis (Duncan and Berman 1991).…”

A Novel IL6 Antibody Sensitizes Multiple Tumor Types to Chemotherapy Including Trastuzumab-Resistant Tumors

“…HUVEC cells do not express membrane bound IL6Ra (20), and therefore IL6 stimulation of HUVECs relies on trans-signaling (21). Adding recombinant human IL6 or sIL6R alone had only modest effects on HUVEC proliferation.…”

IL-6/IL-6 receptor system and its role in physiological and pathological conditions

“…IL-6 induced tubule formation in a co-culture system of HUVECs (human umbilical venous endothelial cells) and RA-FLS (fibroblast-like synoviocytes from RA patients), and this angiogenesis was completely inhibited by an anti-VEGF antibody, indicating that VEGF plays a crucial role in IL-6-induced angiogenesis [43]. IL-6 induces VEGF production from synovial cells [42,43], and semi-quantitative assessment by ultrasonography indicated that TCZ significantly decreases neovascularization in patients with RA [44].…”