Periodic Reporting for period 1 - PAELLA (Platelet Endothelial Aggregation Receptor 1)
Période du rapport: 2020-10-01 au 2022-09-30
Cardiovascular disease is the leading cause of death world-wide, affecting both men and women. Myocardial infarction and ischemic stroke are two severe consequences of cardiovascular disease caused by formation of an occlusive thrombus. Although advances in medicine have led to a continuing decrease in the number of cardiovascular disease-related deaths over recent decades, the improvement is stagnating, especially in younger individuals and in young women. New approaches are necessary to continue this downward trend.
Blood coagulation and thrombus formation is a complex interplay between clotting factors, platelets and endothelial cells of the blood vessels that often involve interactions with leukocytes and other inflammatory cells. In a field in dire need of new treatment methods, we saw the potential importance of Platelet Endothelial Aggregation Receptor 1 (PEAR1), which is constitutively expressed on blood platelets, endothelial cells, and neurons. PEAR1 is an epidermal growth factor-like repeat receptor of uncertain function that has, repeatedly and independently, been associated with cardiovascular disease in genome wide association studies.
The overarching aim of project PAELLA was to investigate the physiological role of PEAR1 and perform in-depth studies of PEAR1 signalling using synthetic agonists, exogenous agonists, and a new potential endogenous agonist.
Blood coagulation and thrombus formation is a complex interplay between clotting factors, platelets and endothelial cells of the blood vessels that often involve interactions with leukocytes and other inflammatory cells. In a field in dire need of new treatment methods, we saw the potential importance of Platelet Endothelial Aggregation Receptor 1 (PEAR1), which is constitutively expressed on blood platelets, endothelial cells, and neurons. PEAR1 is an epidermal growth factor-like repeat receptor of uncertain function that has, repeatedly and independently, been associated with cardiovascular disease in genome wide association studies.
The overarching aim of project PAELLA was to investigate the physiological role of PEAR1 and perform in-depth studies of PEAR1 signalling using synthetic agonists, exogenous agonists, and a new potential endogenous agonist.
In project PAELLA we used pharmacological inhibitors to study the downstream signalling in PEAR1 and investigate activation by a proposed new endogenous ligand. For this purpose, we used human blood platelets.
We successfully identified that heparin and heparin proteoglycan-mimetics are ligands for PEAR1, and that PEAR1 signals via an Src family kinase - Phosphoinositide 3-kinase β pathway. In addition, we showed that PEAR1 is not activated upon platelet-platelet contact as previously proposed. We also showed that loss of effective secondary mediator-signalling had no major effect on PEAR1 activation, but it reduced aggregation. Finally, we showed that PEAR1 activation by heparin and heparin proteoglycan-mimetics can be inhibited using a novel inhibiting anti-PEAR1 nanobody which was tested for the first time in this project.
These results were disseminated in two main publications:
Kardeby C, Damaskinaki FN, Sun Y, Watson SP. Is the endogenous ligand for PEAR1 a proteoglycan: clues from the sea. Platelets. 2021 Aug 18;32(6):779-785. doi: 10.1080/09537104.2020.1863938. Epub 2020 Dec 26. PMID: 33356751.
Kardeby C, Evans A, Campos J, Moosa Al-Wahaibi, Smith CW, Slater A, Martin EM, Severin S, Brill A, Pejler G, Sun Y, Watson SP. Heparin and heparin proteoglycan-mimetic activate platelets via PEAR1 and PI3Kβ. Journal of Thrombosis and Haemostasis. 2022, accepted for publication.
The physiological role of PEAR1 was evaluated using murine in vivo models. We found that the complete absence of PEAR1 does not affect thrombus formation on thrombus size. However, we discovered that PEAR1 alters immune cell recruitment. This shows that PEAR1 is likely to play a part in inflammatory processes. Further evaluation would be required to establish if these results are translatable to humans and potentially could explain the PEAR1-Cardiovascular disease connection.
Results from this project was presented at the International Society on Thrombosis and Haemostasis Congress 2022.
We successfully identified that heparin and heparin proteoglycan-mimetics are ligands for PEAR1, and that PEAR1 signals via an Src family kinase - Phosphoinositide 3-kinase β pathway. In addition, we showed that PEAR1 is not activated upon platelet-platelet contact as previously proposed. We also showed that loss of effective secondary mediator-signalling had no major effect on PEAR1 activation, but it reduced aggregation. Finally, we showed that PEAR1 activation by heparin and heparin proteoglycan-mimetics can be inhibited using a novel inhibiting anti-PEAR1 nanobody which was tested for the first time in this project.
These results were disseminated in two main publications:
Kardeby C, Damaskinaki FN, Sun Y, Watson SP. Is the endogenous ligand for PEAR1 a proteoglycan: clues from the sea. Platelets. 2021 Aug 18;32(6):779-785. doi: 10.1080/09537104.2020.1863938. Epub 2020 Dec 26. PMID: 33356751.
Kardeby C, Evans A, Campos J, Moosa Al-Wahaibi, Smith CW, Slater A, Martin EM, Severin S, Brill A, Pejler G, Sun Y, Watson SP. Heparin and heparin proteoglycan-mimetic activate platelets via PEAR1 and PI3Kβ. Journal of Thrombosis and Haemostasis. 2022, accepted for publication.
The physiological role of PEAR1 was evaluated using murine in vivo models. We found that the complete absence of PEAR1 does not affect thrombus formation on thrombus size. However, we discovered that PEAR1 alters immune cell recruitment. This shows that PEAR1 is likely to play a part in inflammatory processes. Further evaluation would be required to establish if these results are translatable to humans and potentially could explain the PEAR1-Cardiovascular disease connection.
Results from this project was presented at the International Society on Thrombosis and Haemostasis Congress 2022.
Project PAELLA used state of the art pharmacological tools to identify the endogenous ligand for PEAR1 and to study the downstream signalling cascade. We used advanced in vivo models to investigate the physiological role of PEAR1. In our project we show that a nanobody, a novel type of drug, can inhibit PEAR1-induced platelet activation.
Our results have shown that heparin activates PEAR1, and that PEAR1 is involved in immune cell recruitment. Heparin is secreted from mast cells during inflammatory conditions, which puts PEAR1 as a key player in inflammation. The expression pattern of PEAR1 includes platelets, endothelial cells, and neurons. Therefore, we believe that PEAR1 could be of major importance in inflammatory conditions, including allergies, pathological vessel remodelling, inflammation-driven thrombosis, and neuroinflammation.
We hope that the long-term impact of the results generated in project PAELLA can help us explain the pathophysiological mechanisms behind inflammatory diseases without cures, including the progression of cardiovascular disease.
Project PAELLA has, in terms of the research fellows’ career, led to the generation of a future new research program that will study the role of PEAR1 in inflammation driven pathophysiology of disease. The training provided during the implementation of this project has provided the fellow with an excellent foundation for an independent research career.
Our results have shown that heparin activates PEAR1, and that PEAR1 is involved in immune cell recruitment. Heparin is secreted from mast cells during inflammatory conditions, which puts PEAR1 as a key player in inflammation. The expression pattern of PEAR1 includes platelets, endothelial cells, and neurons. Therefore, we believe that PEAR1 could be of major importance in inflammatory conditions, including allergies, pathological vessel remodelling, inflammation-driven thrombosis, and neuroinflammation.
We hope that the long-term impact of the results generated in project PAELLA can help us explain the pathophysiological mechanisms behind inflammatory diseases without cures, including the progression of cardiovascular disease.
Project PAELLA has, in terms of the research fellows’ career, led to the generation of a future new research program that will study the role of PEAR1 in inflammation driven pathophysiology of disease. The training provided during the implementation of this project has provided the fellow with an excellent foundation for an independent research career.