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Updated: May 21, 2025
Quantitative Analysis of Cellular Composition in Advanced Atherosclerotic Lesions of Smooth Muscle Cell Lineage-Tracing Mice
Published on: February 20, 2019
PCSK6 ablation in blood circulating cells increases atherosclerotic burden, but improves plaque stability by
Bianca E Suur1, Glykeria Karadimou2, Colin J J M Willems2
1Department of Molecular Medicine and Surgery, Karolinska Institutet and Karolinska University Hospital, Sweden; Steno Diabetes Center Aarhus, Aarhus University Hospital, Aarhus, Denmark; Department of Biomedicine, Aarhus University, Aarhus, Denmark.
Background:
Proprotein convertase subtilisins/kexins (PCSKs) have been implicated in cancers and cardiovascular disease. We have shown that PCSK6 is a key protease regulating smooth muscle cell (SMC)-mediated vascular remodeling, but also that it can be expressed by T cells and macrophages in atherosclerotic plaques. Whether PCSK6 regulates innate and adaptive immune responses in the context of vascular inflammation is still unknown.
Methods:
In this study, detailed immunophenotyping of constitutive Pcsk6-/- mice was performed. Bone marrow transplantation into high-cholesterol diet fed Ldlr-/- mice was used to investigate PCSK6-mediated immune effects in atherogenesis and plaque stability.
Results:
Compared to controls, Pcsk6-/- mice showed higher plasma levels of the chemoattractants CCL2 and CCCL3, and Th17 cytokines IL-17 A and IL-17F. Pcsk6 ablation led to increased naïve and effector-memory CD4+ and CD8+ cell numbers in the spleen, and increased release of IL-17 A, IFN-γ and IL-10 as well as proliferation by spleenocytes in vitro. Lack of Pcsk6 also affected innate immunity as macrophages from Pcsk6-/- mice secreted more cytokines, including TNF-α, CCL2, IL-6 and IL-10 upon LPS stimulation in vitro, and were more prone to oxLDL uptake. In line with a pro-inflammatory phenotype, Pcsk6-/-➔Ldlr-/- transplanted mice presented a higher atherosclerotic plaque burden compared to Ldlr-/- receiving control bone marrow. Although larger, Pcsk6-/-➔Ldlr-/- plaques showed increased stability features, including collagen deposition and SMC presence coinciding with significantly increased local levels of the fibrogenic cytokine IL-17.
Conclusions:
Global Pcsk6 ablation leads to the activation of both adaptive and innate immune systems. Interestingly, Pcsk6-/- ablation in bone marrow of hyperlipidemic mice revealed its dual role in atherogenesis, activating a Th17-SMC modulatory axis that promotes plaque stability, despite increased atherosclerotic burden.
