Abstract
Abdominal aortic aneurysm (AAA) represents a widespread vascular disorder associated with high significant mortality rates, and the phenotypic transformation of vascular smooth muscle cells (VSMCs) acts as a crucial pathological characteristic during the advancement of this condition. Recent studies suggest that metabolic reprogramming, particularly lactate accumulation, is important in modulating cellular processes in cardiovascular diseases. However, the mechanisms by which lactate influences VSMC dysfunction have not been fully elucidated. An AngII-induced VSMC injury model was established by treating VSMCs with angiotensin II (AngII). Lactate production was measured using a colorimetric assay. Fluorometric assay was conducted to analyze oxygen consumption rate (OCR). Seahorse XF Glycolysis Stress Test Kit was used to analyze extracellular acidification rate (ECAR). mRNA levels were quantified by quantitative real-time polymerase chain reaction, and protein expression was assessed by Western blotting. Reactive oxygen species (ROS) levels were measured by flow cytometry. Cell apoptosis was evaluated using flow cytometry and TUNEL assays. To detect the presence of senescent cells, SA-β-gal staining and immunofluorescence assays were employed. Enzyme-linked immunosorbent assay (ELISA) was used to quantify the levels of interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and interleukin-1β (IL-1β). Chromatin immunoprecipitation (ChIP) and dual-luciferase reporter assays were performed to examine the interactions between histone H3 lysine 18 lactylation (H3K18la), CCAAT enhancer binding protein beta (CEBPB), and target genes (CXCL12, p21, CDKN1A). In AAA patient tissues and AngII-treated VSMCs, mRNA and protein levels of p21 and CXCL12 were significantly upregulated. Silencing p21 or CXCL12 attenuated AngII-induced VSMC apoptosis. AngII treatment increased ROS production, SA-β-gal-positive cells, senescence-related P16 expression, and SASP factors (IL-6, CCL2, MMP2, CCL7), which were reversed by 2-DG treatment or p21 knockdown. AngII also promoted pro-inflammatory cytokine secretion, which was alleviated by 2-DG treatment or CXCL12 silencing. CXCL12 knockdown further reduced AngII-induced the promotion of M1 macrophage polarization and the inhibition of M2 polarization. H3K18 lactylation levels were elevated in AAA tissues and AngII-treated VSMCs. Lactate treatment increased CXCL12, p21, and CEBPB expression and H3K18 lactylation level in VSMCs. ChIP assays revealed that H3K18la was enriched at the promoter region of the CEBPB gene, upregulating its expression. The upregulated CEBPB directly bound to the promoters of CXCL12 and p21, enhancing their transcription, and this binding was further enhanced by lactate treatment. Further, overexpression of p21 or CXCL12 rescued the effects of CEBPB knockdown. In an AngII-induced VSMC injury model, histone lactylation-upregulated CEBPB transcriptionally activated CXCL12 and p21, driving VSMC senescence, inflammation, and macrophage polarization in vitro. Together with correlative findings in human AAA tissues, these results identify the lactate-CEBPB-CXCL12/p21 axis as a candidate mechanism whose contribution to AAA formation and progression requires validation in in vivo aneurysm models.