5-hydroxymethylcytosine Epigenetic Markers in COVID-19-Associated Acute Coronary Syndrome: Insights into Neutrophil Activation and PDE4D Upregulation

Background: Studies have reported that 5hmC features in cell-free DNA (cfDNA) could serve as early warning biomarkers for the occurrence and progression of COVID-19, as well as myocardial injury. However, its roles in the occurrence and progression of acute coronary syndrome (ACS) following COVID-19 infection has not been fully studied. Methods: Firstly, we used the 5hmC-Seal technique to obtain genome-wide 5hmC profiles from plasma cfDNA of 24 ACS2N patients (individuals experiencing ACS onset within 2 months after COVID-19 infection), 28 ACS2W patients (individuals experiencing ACS onset beyond 2 months after COVID-19 infection), and 16 ACS patients (patients with ACS without COVID-19 infection). Secondly, we performed GO, KEGG analysis on the differentially expressed genes and identified a series of immune and inflammation related genes. Thirdly, the distribution of immune cells in different groups of patients was studied by immune infiltration analysis. Finally, we performed PPI network analysis on these genes to identify potential key target genes. Results: In this study, we firstly found that there was a significant difference in 5hmC levels between ACS2N patients and ACS patients, while the difference between ACS2W and ACS was not significant. Secondly, it was found that neutrophils were abnormally activated in the ACS2N group. Finally, a target gene phosphodiesterase 4D (PDE4D) was found to be highly expressed in the ACS2N group by PPI network analysis of the differential genes and validated with external datasets. Conclusions: Our study suggested that 5hmC markers extracted from plasma cfDNA could differentiate between ACS2N and ACS patients. In addition, we observed that neutrophils exhibited abnormal activation in ACS2N patients. Further analysis showed that COVID-19 infection may affect the occurrence and development of ACS by abnormally up-regulating PDE4D gene expression.