Roles of platelet and endothelial cell COX-1 in hypercholesterolemia-induced microvascular dysfunction

Area of Science:

• Cardiovascular Biology
• Inflammation Research
• Thrombosis Studies

Background:

• Hypercholesterolemia (HC) increases cardiovascular disease risk.
• The protective mechanisms of aspirin in HC vasculature are not fully understood.
• Inflammation and thrombosis are key pathological features in HC.

Purpose of the Study:

• To investigate the role of cyclooxygenase-1 (COX-1) in hypercholesterolemia-induced vascular inflammation and thrombosis.
• To determine the efficacy of aspirin, nitric oxide-releasing aspirin (NCX-4016), a COX-1 inhibitor (SC560), and COX-1 deficiency in preventing these pathological changes.
• To elucidate the specific cellular sources of COX-1 involved in these processes.

Main Methods:

• Utilized a murine hypercholesterolemia model with oral administration of aspirin or NCX-4016.
• Employed bone marrow transplantation in COX-1-deficient (COX-1(-/-)) and wild-type (WT) mice to create specific chimeras (WT/COX-1(-/-) and COX-1(-/-)/WT).
• Assessed platelet and leukocyte adhesion in intestinal venules using intravital fluorescence microscopy.

Main Results:

• Aspirin and NCX-4016 significantly attenuated HC-induced leukocyte and platelet adhesion.
• SC560 treatment and COX-1 deficiency in platelets (in COX-1(-/-)/WT chimeras) reduced adhesion, indicating a role for platelet COX-1.
• COX-1 deficiency in both platelets and endothelial cells (in WT/COX-1(-/-) chimeras) provided the greatest reduction in adhesion.
• NCX-4016 demonstrated protective effects independent of platelet COX-1 inhibition.

Conclusions:

• Platelet and endothelial cell-associated COX-1 contribute to microvascular inflammation and thrombosis in hypercholesterolemia.
• Aspirin's protective effects are largely mediated through COX-1 inhibition.
• Nitric oxide-releasing aspirin (NCX-4016) offers direct anti-platelet benefits independent of COX-1, suggesting a novel therapeutic mechanism.