Lysyl oxidase (LOX) limits VSMC proliferation and neointimal thickening through its extracellular enzymatic activity

Abstract

Lysyl oxidase (LOX) plays a critical role in extracellular matrix maturation and limits VSMC proliferation and vascular remodeling. We have investigated whether this anti-proliferative effect relies on the extracellular catalytically active LOX or on its biologically active propeptide (LOX-PP). High expression levels of both LOX and LOX-PP were detected in the vascular wall from transgenic mice over-expressing the full-length human LOX cDNA under the control of SM22α promoter (TgLOX), which targets the transgene to VSMC without affecting the expression of mouse LOX isoenzymes. TgLOX VSMC also secrete high amounts of both mature LOX and LOX-PP. Wild-type (WT) mouse VSMC exposed to VSMC supernatants from transgenic animals showed reduced proliferative rates (low [3H]-thymidine uptake and expression of PCNA) than those incubated with conditioned media from WT cells, effect that was abrogated by β-aminopropionitrile (BAPN), an inhibitor of LOX activity. Lentiviral over-expression of LOX, but not LOX-PP, decreased human VSMC proliferation, effect that was also prevented by BAPN. LOX transgenesis neither impacted local nor systemic inflammatory response induced by carotid artery ligation. Interestingly, in this model, BAPN normalized the reduced neointimal thickening observed in TgLOX mice. Therefore, extracellular enzymatically active LOX is required to limit both VSMC proliferation and vascular remodeling.

Emerging Roles of Lysyl Oxidases in the Cardiovascular System: New Concepts and Therapeutic Challenges

“…Accordingly, neointimal thickening induced by carotid artery ligation was attenuated in TgLOX VSMC mice (Figure 5C). In vivo and in vitro studies ruled out any contribution of LOX-PP to the antiproliferative activity of LOX on VSMC and evidenced the participation of extracellular and enzymatically active LOX forms [63].…”

“…Injured arteries were harvested 21 days after surgery, fixed in 4% paraformaldehyde, and embedded in paraffin. Cross-sections at 1.5 mm from the ligation site were stained with hematoxylin and eosin, as described [62,63]. This staining evidenced that LOX overexpression reduces neointimal growth (Bar: 100 µm).…”

Total Panax notoginseng saponin inhibits balloon injury-induced neointimal hyperplasia in rat carotid artery models by suppressing pERK/p38 MAPK pathways

“…Previous studies have demonstrated that, following vascular injuries, blood vessels are affected by pathological factors and cell proliferation is initiated. The proliferation and migration of VSMC from the medial to the intima layer of the artery is a key early event and the main pathological process of vascular stenosis caused by neointima formation (22 –24). Vascular stenosis may induce insufficient perfusion of tissues and organs.…”

Mechanochemical Patternable ECM‐Mimetic Hydrogels for Programmed Cell Orientation

“…[ 18,19 ] This enzyme is produced by several cell types (e.g., fibroblasts, osteoblasts, endothelial and smooth muscle cells) and plays a key role in ECM deposition and stability. [ 20–23 ] The absence or dysfunction of this process can be lethal or lead to connective tissues disease (i.e., osteolathyrism). [ 24 ] This clearly evidences the inevitable dynamic covalent crosslinks present in ECM bioarchitecture and the importance of recapitulating such processes in biomaterials design.…”