Research Progress on the Protective Mechanism of Ligustrazine Against Vascular Endothelial Injury

Tetramethylpyrazine (TMP), also known as Ligustrazine, is one of the main active ingredients of Chuanxiong, an active alkaloid extracted from its rhizomes. TMP has been widely used in China to treat cardiovascular diseases such as hypertension. Research has found that TMP exhibits excellent protective effects against cardiovascular diseases. In the heart, TMP can alleviate myocardial ischemia/reperfusion injury by mechanisms such as antioxidant stress, autophagy regulation, and inhibition of myocardial cell apoptosis. It can also reduce inflammatory damage to myocardial cells, reduce fibrosis and hypertrophy of infarcted myocardium, and inhibit the enlargement of the heart chamber after myocardial infarction. TMP also has a certain inhibitory effect on thrombosis. It can exert antithrombotic effects by reducing inflammatory factors and adhesion molecules, inhibiting platelet aggregation, and suppressing the expression of fibrinogen and von Willebrand factor.

The degree of vascular endothelial injury is closely related to the development of cardiovascular diseases such as hypertension. Various cardiovascular diseases, including hypertension, coronary heart disease, and atherosclerosis, can all lead to varying degrees of vascular endothelial damage. Protecting damaged endothelial cells is crucial in the prevention and treatment of cardiovascular diseases. Ligustrazine (TMP), a bioalkaloid extracted from the Chinese herbal medicine Chuanxiong, possesses biological activity and various pharmacological effects. The mechanisms of vascular endothelial injury mainly involve imbalances in vasomotor tone, endothelial cell apoptosis, angiogenesis, inflammation, and oxidative stress. However, studies have shown that TMP has multiple pharmacological effects such as delaying cell apoptosis, promoting angiogenesis, anti-inflammation, and anti-oxidation, which provide good protection for vascular endothelium. It can be used to treat changes in vascular structure and function caused by hypertension.

1. Impact on Vascular Tone Function

Endothelin and nitric oxide (NO) are the primary endothelial active substances that regulate vascular tone. Endothelin is a polypeptide composed of 21 amino acids, originating from vascular endothelial cells and smooth muscle cells, which has the effect of vasoconstriction. It includes three isomers, among which endothelin-1 (ET-1) is the strongest vasoconstrictor known so far. Research has shown that TMP can reduce stress-mediated ET-1 secretion, partially through its mechanism of reducing the production of reactive oxygen species (ROS) to decrease the phosphorylation level of extracellular signal-regulated kinases 1/2 (ERK 1/2), thereby reducing the activity of activator protein 1 (AP-1) and ultimately reducing the expression of ET-1 genes, leading to vasodilatation. Other studies have shown that TMP can protect the vascular endothelial cells of pregnant women with hypertension by downregulating ET-1 levels. NO released by vascular endothelium is an important vasodilator that can activate guanylate cyclase within vascular smooth muscle cells, increasing cyclic guanosine monophosphate levels, leading to the outflow of intracellular calcium ions, thereby causing vasodilation. TMP can increase the level of endothelial nitric oxide synthase (eNOS) during vasospasm, and the activation of eNOS can promote increased NO production and decrease phosphodiesterase V expression, which is achieved through the regulation of the NO/cGMP signaling pathway.

2. Endothelial Cell Apoptosis

The body naturally undergoes programmed cell death to eliminate senescent, damaged, and mutated cells, a process known as apoptosis. Endothelial cell apoptosis plays a significant role in the pathogenesis of various cardiovascular diseases. TMP possesses the property of inhibiting endothelial cell apoptosis. Typically, caspase, pro-apoptotic protein (Bax), and anti-apoptotic protein (Bcl-2) are considered key indicators for evaluating cell apoptosis. Research has found that TMP can delay endothelial cell apoptosis by downregulating the levels of matrix metalloproteinases 2 (MMP2), MMP9, Bax, and caspase-3. Furthermore, TMP has been observed to increase the volume and number of blood vessels, indicating that TMP can reduce the degree of nerve injury caused by spinal cord injury and facilitate the recovery of neurological function by delaying endothelial cell apoptosis and promoting angiogenesis. TMP significantly upregulates Bcl-2 levels, downregulates Bax levels, and increases the ratio of Bcl-2/Bax. In studies using CoCl2 to induce injury in human umbilical vein endothelial cells (HUVECs), TMP intervention was found to increase the expression of prolyl hydroxylase 2 (PHD2), reduce VEGF protein and mRNA expression, and decrease the protein expression of hypoxia-inducible factor-1α (HIF-1α). TMP can increase cell survival rates, reduce apoptosis rates, and activate caspase-3, caspase-8, and caspase-9, thereby protecting HUVECs from damage.

3. Angiogenesis

VEGF is a glycosylated secretory polypeptide factor that can increase vascular permeability, promote the division of vascular endothelial cells, and induce angiogenesis. TMP and paeoniflorin (PF) can inhibit the in vitro angiogenesis of HUVECs induced by oxidized low-density lipoprotein (ox-LDL). When combined, they suppress ox-LDL-induced HUVECs angiogenesis by inhibiting the VEGF/VEGFR2 and Jagged1/Notch1 signaling pathways. Research has found that TMP can increase the vascular volume, vascular surface area, percentage of vascular volume, and vascular thickness in steroid-induced femoral head necrosis, while elevating the mRNA and protein expression of VEGF and its receptor FLK1 in serum and necrotic femoral heads. This indicates that TMP inhibits steroid-induced femoral head necrosis and enhances vascular formation in the femoral head by suppressing the effects of steroids on the VEGF/FLK1 signaling pathway. HIF-1α is expressed at low levels under normal oxygen conditions but is highly expressed when tissue cells experience hypoxia. Studies have shown that when vascular endothelium is damaged, local hypoxia occurs in the tissue, leading to increased expression of HIF-1α. TMP can promote neurovascular recovery by downregulating the expression of HIF-1α and VEGF mRNA.

4. Oxidative Stress

Angiotensin II (AngⅡ) can induce endothelial cells to produce a large amount of reactive oxygen species (ROS), leading to endothelial cell damage. The addition of tetramethylpyrazine hydrochloride can significantly increase the activity of superoxide dismutase (SOD) and catalase, inhibit the phosphorylation of ERK1/2 and c-Jun N-terminal kinase in a concentration-dependent manner, enhance the expression of endothelial nitric oxide synthase (eNOS) within endothelial cells, and reduce the expression of inducible nitric oxide synthase. This protective effect mitigates AngⅡ-induced endothelial injury. TMP has a significant inhibitory effect on oxidized low-density lipoprotein (ox-LDL)-induced endothelial cell damage, primarily by significantly enhancing the activity of antioxidant enzymes SOD and glutathione peroxidase in vascular endothelial cells. Additionally, TMP can reduce the excessive expression of monocyte chemotactic protein-1 (MCP-1) and soluble intercellular adhesion molecules-1 (sICAM-1) mRNA, and improve the survival rate of lipid-peroxidized endothelial cells.

Other studies have shown that TMP can reduce ROS production, downregulate the phosphorylation level of the protein kinase B/eNOS signaling pathway, and inhibit the decrease in NO production, thus protecting against vascular endothelial injury caused by hyperglycemia. This protective mechanism is related to the promotion of uncoupling protein 2 (UCP2) mRNA/protein expression. TMP also inhibits the changes in NO and ROS levels in human umbilical vein endothelial cells (HUVECs) induced by lipopolysaccharides (LPS). TMP can inhibit the production of ROS in endothelial cells induced by H2O2, exhibiting significant hydroxyl radical scavenging ability and mitigating oxidative damage to endothelial cells. TMP also has a protective effect on pregnancy-related vascular endothelium. TMP can protect against endothelial cell damage in gestational hypertension by upregulating plasma NO levels. TMP pretreatment can inhibit the expression of endothelial nitric oxide synthase traffic inducer (NOSTRIN), which is increased by umbilical vein serum from patients with preeclampsia.

5. Inflammatory Response

TMP exerts an anti-inflammatory effect on endothelial cells by inhibiting interleukin-8 induced by LPS at both the mRNA and protein levels. This effect is achieved through the nuclear factor-κB (NF-κB)-dependent pathway. The study also demonstrated that TMP can inhibit the phosphorylation of ERK1/2 and p38 pathways. TMP inhibits tumor necrosis factor-α-induced MCP-1 mRNA expression by suppressing the p38 pathway, reducing inflammatory responses in vascular endothelium. TMP inhibits AngⅡ-induced NF-κB activation and decreased bone morphogenetic protein 2 expression, demonstrating anti-atherosclerotic effects. Related research also shows that TMP inhibits the expression of ICAM-1 and MCP-1 in vascular wall cells by inhibiting or blocking NF-κB activation and nuclear translocation induced by ox-LDL, oxidized very low-density lipoprotein, and AngⅡ, thus inhibiting monocyte adhesion to the endothelium. Another study revealed that TMP inhibits apoptosis, NF-κB nuclear translocation, and the expression of vascular endothelial cell adhesion molecule 1 in HUVECs induced by umbilical vein serum from patients with preeclampsia. TMP can reduce the increased levels of sICAM-1 and neutrophil elastase induced by extracorporeal circulation, thereby exerting protective effects on the vascular endothelium.

6. Impact on Platelets

Platelets, which possess abundant membrane glycoproteins on their surface, mediate platelet adhesion, activation, and aggregation, ultimately leading to thrombus formation. This represents one of the major pathological mechanisms of thrombotic diseases, making anti-platelet therapy a crucial approach in the prevention and treatment of cardiovascular and cerebrovascular thrombotic diseases. Research has shown that TMP can improve platelet activation and vascular endothelial function after percutaneous coronary intervention in patients with acute coronary syndrome by reducing plasma levels of CD62p, CD63, von Willebrand factor (vWF), and platelet glycoprotein Ⅱb/Ⅲa. Other related studies have also demonstrated that TMP can effectively inhibit the expression of platelet CD62p gene in elderly patients with obstructive atherosclerosis and blood stagnation syndrome.

References

[1] Zheng Sidao, Wu Hongjin. Research Progress on the Mechanism of Tetramethylpyrazine in Protecting Vascular Endothelium [J]. Chinese Journal of Integrated Traditional and Western Medicine, 2011, 31(07): 1004-1008.

[2] Li Fangfang, Zhang Qi. Research Progress on the Protective Mechanism of Tetramethylpyrazine on Vascular Endothelial Injury [J]. China Medical Herald, 2020, 17(08): 25-28.

[3] Yang Chunkun, Pan Qingquan, Ji Kui, Luo Chuanchao, Tian Zhuang, Zhou Hongyuan, Li Jun. Overview of the Protective Mechanism of Tetramethylpyrazine on Cardiovascular System [J]. China Journal of Chinese Materia Medica, 2023, 48(06): 1446-1454.

About the Author

Xiaomichong, a pharmaceutical quality researcher, has been committed to pharmaceutical quality research and drug analysis method validation for a long time. Currently employed by a large domestic pharmaceutical research and development company, she is engaged in drug inspection and analysis as well as method validation.