Toll-Like Receptor 2–Blocking Antibodies Promote Angiogenesis and Induce ERK1/2 and AKT Signaling via CXCR4 in Endothelial Cells

Abstract

Objective-Toll-like receptor 2 (TLR2) inhibition by function blocking antibodies (ABs) is associated with enhanced preservation of endothelial cell function during vascular disease. In the present study, we investigated the capacity of TLR2-blocking ABs to modulate the angiogenic response of endothelial cells in vitro and in vivo. Approach and Results-Incubation of endothelial cells with mono-or polyclonal anti-TLR2 ABs resulted in increased tube formation, sprouting, and migration of endothelial cells compared with controls. In a mouse model of hindlimb ischemia, using TLR2-deficient or anti-TLR2 AB-treated wild-type mice resulted in increased new capillary formation and enhanced reperfusion. The effects of anti-TLR2 ABs were similar to those exerted by stromal cell-derived factor-1, and we show that anti-TLR2 ABs yet not TLR2 ligands lead to comparable activation of extracellular signal-regulated kinase1/2 and AKT but not p38 mitogen-activated protein kinase as activation of the CXCR4 canonical signal transduction pathways by stromal cell-derived factor-1. Immunoprecipitation of TLR2 revealed that anti-TLR2 ABs initiate an association of TLR2 with CXCR4 and mitogen-activated protein kinase activation. The proangiogenic properties of anti-TLR2 ABs were abolished by both G-protein inhibition and CXCR4 knockdown in endothelial cells. Conclusions-Our results provide evidence for a proangiogenic effect of TLR2-blocking ABs on endothelial cells in vitroand in vivo. They identify a novel molecular mechanism linking TLR2 to angiogenic processes that is independent from the activation of inflammatory cascades and further support the concept of a beneficial effect of TLR2 inhibition for endothelial cell function in vascular disease.

Elevated CD14 (Cluster of Differentiation 14) and Toll‐Like Receptor (TLR) 4 Signaling Deteriorate Periapical Inflammation in TLR2 Deficient Mice

“…In addition, infected TLR2 KO mice exhibited a pro-angiogenic response with continuous accumulation of neutrophils on Day 21 post-infection, whereas the importance of TLR2/MyD88 signal in angiogenic response to oxidative stress was previously demonstrated (West et al, 2010). Such TLR2 deficiency-dependent pro-angiogenic response was also observed in an ischemia model (Wagner et al, 2013). In a previous report, ischemiainduced tissue necrosis was observed only in TLR2 KO but not in wild-type and TLR4 KO mice (Sachdev et al, 2012).…”

The CXCL12/CXCR4 chemokine ligand/receptor axis in cardiovascular disease

“…From these data the authors conclude that TLR2 blocking might serve as a promising therapeutic approach in e.g., MI or peripheral artery disease by promoting revascularization. However, considering angiogenesis pro-atherogenic, TLR2 blocking might have detrimental consequences in the context of plaque stability and development, as already mentioned above (Wagner et al, 2013). Nevertheless, it was also shown that the inflammatory mediators IFN-γ and TNF-α decrease CXCR4 and CXCL12 expression in HUVECs, thereby decreasing their angiogenic capacity (Gupta et al, 1998; Salvucci et al, 2004).…”

Implication of Pattern-Recognition Receptors in Cardiovascular Diseases

“…Hyperlipidemia induces this regional endothelial TLR2 expression in LDLR -/-mice, which is associated with early atherosclerosis in lesion-prone areas of the mouse aorta (83). Wagner NM et al further find that inhibition of TLR2 by TLR2-blocking antibodies is beneficial to endothelial cell function in vascular disease (121). In addition, migration of VSMCs also contributes to the development of atherosclerosis.…”