Atherosclerosis represents a chronic inflammatory disease characterized by the accumulation of lipid-laden macrophage foam cells within arterial walls, serving as the underlying pathological basis for cardiovascular diseases including myocardial infarction and stroke. Despite significant advances in understanding the molecular mechanisms driving atherogenesis, novel therapeutic targets remain urgently needed to address the persistent global burden of cardiovascular disease. A research study by Fengchan Li and colleagues identified macrophage-derived semaphorin 7A (SEMA7A) as a critical driver of atherosclerosis progression through a previously unrecognized signaling axis involving integrin β1, c-Jun N-terminal kinase (JNK), and macrophage scavenger receptor 1 (MSR1), offering promising new targets for therapeutic intervention.
Semaphorin 7A is an immunoregulatory signaling molecule traditionally recognized for its roles in axon guidance, immune cell activation, and cellular adhesion. Previous studies have implicated SEMA7A in various pathological processes including tumor progression, pulmonary inflammation, and multiple sclerosis. In the context of cardiovascular disease, vascular endothelial SEMA7A has been shown to promote atherosclerosis through endothelial β1 integrin signaling. However, the specific contribution of macrophage-derived SEMA7A to atherogenesis remained unexplored prior to this investigation.
The research team initiated their study by analyzing gene expression profiles of human mononuclear cells from the Gene Expression Omnibus database, revealing highly expressed SEMA7A and its receptor integrin β1 in macrophages compared to monocytes. This expression pattern was further validated during the differentiation of THP-1 monocytes into macrophages, where both SEMA7A and integrin β1 protein levels progressively increased over time. Additionally, exposure to oxidized low-density lipoprotein (ox-LDL), a key pro-atherogenic factor, further upregulated SEMA7A and integrin β1 expression in macrophages, suggesting a positive feedback mechanism linking lipid accumulation to SEMA7A signaling.
To establish the causal role of macrophage SEMA7A in atherosclerosis, the investigators generated mice with macrophage-specific deletion of Sema7a and subjected them to an atherosclerosis mouse model. Remarkably, macrophage-specific SEMA7A deficiency resulted in a 57.2% reduction in atherosclerotic lesion size compared to control mice. Furthermore, plaques in SEMA7A-deficient mice exhibited improved stability characteristics, including reduced necrotic core areas and thinner fibrous caps, suggesting that targeting macrophage SEMA7A may not only limit plaque growth but also reduce the risk of plaque rupture and subsequent thrombotic events.
Mechanistic investigations revealed that macrophage SEMA7A promotes atherosclerosis through a specific signaling cascade. SEMA7A engagement with integrin β1 activated the downstream JNK signaling pathway, which in turn upregulated the expression of macrophage scavenger receptor 1 (MSR1). MSR1, also known as CD204, is a key receptor mediating the uptake of modified lipoproteins by macrophages, and its upregulation facilitates foam cell formation. The study demonstrated that SEMA7A-integrin β1 signaling enhances lipid uptake by macrophages through this JNK/MSR1 axis, thereby accelerating foam cell formation and atherosclerotic plaque development.
The therapeutic potential of targeting this pathway was validated through pharmacological intervention. The integrin receptor antagonist GLPG0187, which blocks integrin β1 signaling, effectively suppressed atherosclerosis progression when administered to atherosclerotic mice. This finding provides proof-of-concept evidence that pharmacological inhibition of the SEMA7A/integrin β1 axis represents a viable therapeutic strategy for cardiovascular disease.
The identification of macrophage SEMA7A as a key atherogenic driver has several important implications. First, it expands the understanding of SEMA7A function beyond its established roles in neuronal and immune cell biology to encompass critical contributions to metabolic and cardiovascular pathology. Second, it reveals a novel mechanism linking macrophage activation states to lipid uptake and foam cell formation, processes central to atherosclerosis pathogenesis. Third, it establishes the SEMA7A/integrin β1/JNK/MSR1 axis as a potential therapeutic target that could be modulated through multiple nodes including ligand blockade, receptor inhibition, or downstream signaling interruption.
From a translational perspective, these findings suggest that SEMA7A may serve as a biomarker for cardiovascular risk assessment and a target for therapeutic development. The observation that ox-LDL upregulates SEMA7A expression creates a positive feedback loop wherein lipid accumulation enhances SEMA7A signaling, which in turn promotes further lipid uptake through MSR1 upregulation. Interrupting this vicious cycle at the level of SEMA7A or integrin β1 could provide significant clinical benefit for patients with atherosclerotic cardiovascular disease.
Future research directions include validation of these findings in human atherosclerotic lesions, investigation of potential synergistic effects with existing lipid-lowering therapies, and development of selective SEMA7A inhibitors or integrin β1 antagonists optimized for cardiovascular indications. Additionally, the cell-specific roles of SEMA7A in different vascular and immune cell populations warrant further investigation to fully understand the complexity of SEMA7A signaling in cardiovascular pathology.
In conclusion, this study establishes macrophage-derived SEMA7A as a critical driver of atherosclerosis through the integrin β1/JNK/MSR1 signaling axis, providing novel mechanistic insights into foam cell formation and identifying potential therapeutic targets for the prevention and treatment of atherosclerotic cardiovascular disease..
