Abstract
BACKGROUND: While 5hmC features in cell-free DNA (cfDNA) show promise as early biomarkers for COVID-19 severity, myocardial injury, and long-term outcomes, their specific role in acute coronary syndrome (ACS) triggered shortly after COVID-19 infection remains unclear. METHODS: We generated genome-wide 5hmC profiles from plasma cfDNA using the 5hmC-Seal technique across three cohorts: ACS patients without prior COVID-19 infection (ACS, n = 16), patients experiencing ACS within 2 months post-COVID-19 (ACS2N, n = 24), and patients experiencing ACS beyond 2 months post-COVID-19 (ACS2W, n = 28). Differential 5hmC analysis, functional enrichment (GO, KEGG), immune cell deconvolution, and protein-protein interaction (PPI) network analysis were performed. RESULTS: Significant differences in 5hmC profiles were identified between ACS2N and ACS patients, but not between ACS2W and ACS. Functional analysis implicated immune and inflammatory pathways. Immune infiltration analysis revealed abnormal neutrophil activation specifically in the ACS2N group. PPI network analysis pinpointed phosphodiesterase 4D (PDE4D) as a key hub gene; it was highly expressed in the ACS2N group, a finding corroborated using external datasets. CONCLUSIONS: Our findings indicate that plasma cfDNA 5hmC markers can distinguish ACS occurring shortly after COVID-19 infection (ACS2N) from ACS without prior infection. We observed distinct immune dysregulation, notably abnormal neutrophil activation, in ACS2N patients. Critically, we identified PDE4D as a potential key mediator, suggesting that recent COVID-19 infection may contribute to ACS onset by abnormally upregulating PDE4D expression. This study highlights 5hmC signatures and PDE4D as potential biomarkers and therapeutic targets for post-COVID ACS.