## 5 Discussion and Prospect  
Since the discovery of the self-activation of GPCRs, our understanding of receptor activation and disease mechanisms has dramatically changed. In this review, we summarized the related signal transduction processes of P2Y12 receptors that participate in the physiological and pathological processes of diseases in various ways. These receptors play an important role in the formation of many human diseases, especially cardiovascular diseases. P2Y12 can directly participate in the formation of thrombus and also activate Syk kinase and PI3K kinase to induce thrombus formation in the biomechanical-mediated aggregation mechanism. Antiplatelet therapy that targets ADP receptor P2Y12 has become the main strategy to prevent acute coronary events and coronary stent thrombosis. At present, the main P2Y12 inhibitors used in clinic are clopidogrel, prasugrel and ticagrelor. However, their effects are closely related to the occurrence and development of the disease. For example, P2Y12 antagonists, such as clopidogrel, effectively prevent atheorthrombotic thrombosis and are widely used. However, some studies discovered that clopidogrel has no effect on the treatment of atherosclerosis [81]. This contradictory result suggests the need for further research on P2Y12 receptor. This result prompted us to further study the therapeutic mechanism of P2Y12 receptor and explore the effect of this receptor on disease occurrence in different environments. In addition, P2Y12 participates in the physiological and pathological processes of the cardiovascular system in different ways. First, P2Y12 receptor plays an important role in LPS-induced inflammation, which may be involved in the regulation of spleen and bone marrow cell content during LPS systemic inflammation. P2Y12 can promote the release of platelet and the aggregation of inflammatory \(\alpha\)-granules and platelets. The P2Y12 inhibitor clopidogrel can inhibit platelet-related inflammation and decrease the expressions of systemic inflammatory markers. In addition, P2Y12 receptors in brain tissue are closely related to glial cell chemotaxis, inflammatory factor release, and pain regulation. At the same time, miRNAs that regulate P2Y12 signalling are also considered to be new disease biomarkers and therapeutic targets, which have attracted attention. It regulates the expression of genes after transcription to exert biological functions, thereby participating in the regulation of various physiological functions of the body, and is closely related to the pathophysiological processes of various diseases. Recent studies have found that microRNA have high expression in platelets which participation in the regulation of platelet function and play an important role in the pathophysiological process of thrombotic cardio-cerebrovascular diseases. miR-223 can regulate the expression of P2Y12 in platelets and a variety of cells. miR-223 could influence the cutting process of mRNA and affect the expression of P2Y12. With the deepening of research on microRNA, the biological function of microRNA and its target genes will be discovered more and more. The importance of microRNA for cardiovascular diseases also needs to be further discovered. Research on ion channels and G protein-coupled receptors and signalling molecules has changed our understanding of P2Y12. This activation not only affects platelet aggregation, but also regulates changes in multiple signalling pathways within the cell, such as regulating smooth muscle cytoskeletal morphology and controlling vascular tone and remodeling. At the same time, through the local release of ADP, the vascular tension and tensile stress are affected [82; 83]. Studies on P2Y12 receptors and signalling pathways have shown that P2Y12 receptors play an important role in diseases such as atherosclerosis, inflammatory diseases and neuropathy, and are potential drug targets. However, the interaction between the P2Y12 receptor and other signalling proteins and the interaction with other cell signalling pathways requires further study.