Background:

Long non-coding RNAs (lncRNAs) play a crucial role in cardiovascular biology. Improved understanding of their expression patterns and mechanisms of action is required for identification of new therapeutic targets in the era of personalized medicine. High-resolution intracoronary imaging allows one to characterize different pathological mechanisms causing acute coronary syndrome (ACS), and the differentiation of ACS with ruptured (RFC-ACS) or with intact fibrous cap (IFC-ACS). Recently a distinct T-cell driven immunological signature at the culprit lesion site was observed in IFC-ACS, suggesting a crucial role of the adaptive immunity in the pathogenesis of IFC-ACS. The current study elucidates a potential role of the lncRNA IFNG antisense 1 (IFNG-AS1) as a potential modulator of T-cell immunity and coronary immune phenotypes in patients with ACS.

Methods:

IFC-ACS patients (n=20) were matched by age and gender to patients with RFC-ACS (n=20) and a control group (n=20) consisting of patients with chronic coronary syndrome (CCS). Blood samples directly from the culprit lesion site in the ACS-patients or from a coronary artery in CCS-patients were immediately collected during acute care and peripheral blood mononuclear cells (PBMCs) were isolated and cryopreserved for measurement of IFNG-AS1. Whole-blood immunophenotyping using flow cytometry and a panel of inflammatory cytokines as measured directly at the culprit lesion were investigated.

Results:

IFNG-AS1 was significantly downregulated in IFC-ACS as compared to RFC-ACS (1.94±0.59 vs. 2.95±0.63, p=0,004) and to CCS (1.94±0.59 vs. 2.77±0.79, p=0,03). Importantly, the expression of IFNG-AS1 in IFC-ACS inversely correlated with the intracoronary enrichment of total CD3+ T Cells (r -0,68, p=0,002), as well as the major T-cell subtypes: CD4+ helper T-cells (r -0,63, p=0,005) and CD8+ cytotoxic T-cells (r -0,60, p=0,01). On the other hand, concentrations of granulocytes and neutrophils at the culprit site showed a positive correlation with IFNG-AS1 in IFC-ACS (r 0,61, p=0,008 for granulocytes and r 0,63, p=0,005 for neutrophils respectively). Finally, IFNG-AS1 expression in IFC-ACS was positively correlated with the local concentration of IP-10 (r 0,78, p=0,008), known as a specific chemoattractant for activated T-cells. Upon in vitro knockdown of IFNG-AS1 in primary T-cells, we observe a trending increase in CD8+ TEMRA-populations, suggesting immunological exhaustion and T-Cell dysregulation with higher cytotoxicity.

Conclusion:

IFNG-AS1 levels are associated with significant alterations of local inflammatory cells in patients with IFC-ACS. Given the recently described role of T-cells in IFC-ACS, these finding may provide an underlying mechanism by which a lncRNA controls immune phenotypes in patients with ACS.