Accumulation of Advanced Oxidation Protein Products Promotes Age-Related Decline of Type H Vessels in Bone

Type H vessels have been proven to couple angiogenesis and osteogenesis. The decline of type H vessels contributes to bone loss in the aging process. Aging is accompanied by the accumulation of advanced oxidation protein products (AOPPs). However, whether AOPP accumulation is involved in age-related decline of type H vessels is unclear. Here, we show that the increase of AOPP levels in plasma and bone was correlated with the decline of type H vessels and loss of bone mass in old mice. Exposure of microvascular endothelial cells to AOPPs significantly inhibited cell proliferation, migration, and tube formation; increased NADPH oxidase activity and excessive reactive oxygen species generation; upregulated the expression of vascular cell adhesion molecule-1 and intercellular cell adhesion molecule-1; and eventually impaired angiogenesis, which was alleviated by redox modulator N-acetylcysteine and NADPH oxidase inhibitor apocynin. Furthermore, reduced AOPP accumulation by NAC treatment was able to alleviate significantly the decline of type H vessels, bone mass loss, and deterioration of bone microstructure in old mice. Collectively, these findings suggest that AOPPs accumulation contributes to the decline of type H vessels in the aging process, and illuminate a novel potential mechanism underlying age-related bone loss.