Abstract 4364291: Latexin Promotes Neointimal Hyperplasia by Enhancing SMC Proliferation and Macrophage Migration through Activation of MAPK Signaling

Background: Neointimal formation remains a primary cause of cardiovascular diseases such as atherosclerosis and restenosis, despite advancements with drug-eluting stents. Latexin (LXN), a novel pro-inflammatory protein, has emerged as a critical mediator in vascular remodeling. LXN expressions are elevated in neointimal hyperplasia. However, its precise role in vascular smooth muscle cell (SMC) proliferation and macrophage migration during neointimal formation remains to be fully elucidated. Objective: This study aims to determine the involvement of LXN in neointimal hyperplasia and define its underlying molecular mechanisms in VSMCs and macrophages. Methods: Using a murine model of carotid artery ligation, neointimal hyperplasia was induced, and LXN expression was evaluated through Western blot and immunohistochemical staining. Global, SMC-specific, endothelial cell-specific, and myeloid-specific LXN knockout (KO) mice were generated to assess the cell-type-specific contribution of LXN to neointimal formation. Mechanistic studies explored the role of LXN in SMC proliferation and migration in response to platelet-derived growth factor (PDGF) stimulation. Co-immunoprecipitation (Co-IP) was performed to investigate the potential role of LXN in regulating mitogen-activated protein kinase (MAPK) signaling pathway. Results: LXN expression was significantly increased in neointimal hyperplasia, predominantly localized to SMCs and macrophages. Global, SMC-specific, and myeloid-specific LXN deficiency markedly attenuated neointimal formation following arterial injury, while endothelial cell-specific knockout had no significant effect. Mechanistically, LXN deficiency in VSMCs prevented proliferation and migration by downregulating MAPK pathways. Myeloid-specific LXN deficiency inhibited MCP-1-induced macrophage migration by suppressing P38 and JNK phosphorylation. Furthermore, LXN was found to directly bind and inhibit PPM1A (protein phosphatase, Mg2+/Mn2+ Dependent 1A), a negative regulator of MAPK signaling. Loss of LXN disrupted this interaction, enhancing PPM1A activity and reducing MAPK phosphorylation. This led to attenuation of pro-proliferative and migratory signaling in both SMCs and macrophages. Conclusion: LXN promotes neointimal hyperplasia by driving SMC proliferation and macrophage migration through inhibitory interaction with PPM1A. Targeting the LXN/PPM1A axis represents a potential therapeutic strategy for mitigating proliferative vascular disease.