Critical Study on Tetramethylpyrazine and Paeoniflorin Inhibit Oxidized LDL-induced Angiogenesis in Human Umbilical Vein Endothelial Cells via VEGF and Notch Pathways

Atherosclerotic plaque angiogenesis is key factor inplaque instability and vulnerability, and low
concentrations of oxidized low density lipoprotein (ox-LDL)promote the in vitro angiogenesis of
endothelial cells and play an important role inplaque angiogenesis. Ligusticum chuanxiong Hort. and
Radix Paeoniae Rubra herb pair in Chinese medicine obtainsthe optimum therapeutic efficacy in
atherosclerosis, and their major active ingredientste tramethylpyrazine (TMP) and paeoniflorin (PF)
are reported to alleviate atherosclerosis. The aim of this study was to investigate the effects of TMP
and PF on ox-LDL-induced angiogenesis and the underlying mechanism. Human umbilical vein
endothelial cells (HUVECs) were incubated with ox-LDL andwere then treated with TMP, PF or a
combination of TMP and PF. Cell proliferation, migration, tube formation and the expression of
angiogenesis-related proteins were measured. Synergism was evaluated using the combination index
in cell proliferation. We found that TMP and PF attenuated the in vitro angiogenesis in ox-LDLinduced
HUVECs. In addition, the combination of TMP and PF not only inhibited the ox-LDL-induced
expression of CD31, vascular endothelial growth factor (VEGF), and VEGF receptor 2 (VEGFR2) but
also decreased the ox-LDL-induced expression of Notch1, Jagged1 and Hes1. In summary, the
combination of TMP and PF suppresses ox-LDL-induced angiogenesis in HUVECs by inhibiting both
the VEGF/VEGFR2 and the Jagged1/Notch1 signaling pathways, which might contribute to the
stability of plaques in atherosclerosis.