Attenuation of Atherosclerosis With PAR4 Deficiency: A Potential Role of Hematopoietically Expressed PAR4 in Atherosclerosis-Brief Report

Arterioscler Thromb Vasc Biol. 2025 Jun;45(6):901-909. doi: 10.1161/ATVBAHA.124.322068. Epub 2025 Apr 24.

Abstract

Background: Cardiovascular disease is a significant burden globally and, despite current therapeutics, remains the leading cause of death. PAR (protease-activated receptor) 4 is a receptor highly expressed by hematopoietic cells, strongly activated by thrombin, and plays a vital role in platelet activation and aggregation. However, the role of PAR4 in atherothrombotic disease remains understudied.

Methods: Mice on a low-density lipoprotein receptor-deficient (Ldlr-/-) background were bred with Par4-deficient (Par4-/-) mice to create Ldlr-/-/Par4+/+ and Ldlr-/-/Par4-/- cousin lines. Mice were fed high-fat (42%) and high-cholesterol (0.2%) Western diet for 12 weeks for all studies. Bone marrow transplant studies were conducted by irradiating Ldlr-/-/Par4+/+ and Ldlr-/-/Par4-/- mice with 550 rads (2×, 4 hours apart) and then repopulated with Par4+/+ or Par4-/- bone marrow. To determine whether the effects of thrombin were mediated solely by PAR4, the thrombin inhibitor dabigatran was added to the Western diet.

Results: We observed higher abundance of PAR4 in arteries with atherosclerosis in mouse and human lesions versus healthy controls. Using a global deletion of PAR4, we observed an attenuation in atherosclerosis versus Par4+/+ mice. Bone marrow transplant studies demonstrated these effects were due to hematopoietic cells. When observing whether PAR4 activation via thrombin contributes to atherosclerotic development, Ldlr-/-/Par4-/- mice given dabigatran did not further decrease their atherosclerotic burden. Differences between apoE-deficient (apoE-/-) and Ldlr-/- platelets were assessed for changes in reactivity. PAR4 appeared to be acting independent of PAR1, as there were no changes with the addition of dabigatran to Par4-/- mice. apoE-/- platelets were hyperreactive compared with Ldlr-/- platelets.

Conclusions: We conclude that hematopoietic-derived PAR4 plays a vital role in the development and progression of atherosclerosis. More specifically, we observe thrombin-activated PAR4 contributes to the progression. Specifically, targeting of PAR4 may be a potential therapeutic target for cardiovascular disease.

Keywords: arteries; atherosclerosis; blood platelets; cause of death; thrombin.

MeSH terms

  • Animals
  • Aortic Diseases* / genetics
  • Aortic Diseases* / metabolism
  • Aortic Diseases* / pathology
  • Aortic Diseases* / prevention & control
  • Atherosclerosis* / blood
  • Atherosclerosis* / genetics
  • Atherosclerosis* / metabolism
  • Atherosclerosis* / pathology
  • Atherosclerosis* / prevention & control
  • Blood Platelets / drug effects
  • Blood Platelets / metabolism
  • Bone Marrow Transplantation
  • Diet, Western
  • Disease Models, Animal
  • Female
  • Hematopoietic Stem Cells* / metabolism
  • Humans
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Plaque, Atherosclerotic
  • Receptors, LDL / deficiency
  • Receptors, LDL / genetics
  • Receptors, Proteinase-Activated
  • Receptors, Thrombin* / deficiency
  • Receptors, Thrombin* / genetics
  • Receptors, Thrombin* / metabolism
  • Thrombin / metabolism

Substances

  • Receptors, Thrombin
  • Receptors, LDL
  • protease-activated receptor 4, mouse
  • protease-activated receptor 4
  • Thrombin
  • Receptors, Proteinase-Activated