Abstract 333: Tnik: A Novel Regulator Of Endothelial Interferon Signaling And Activation

Abstract

Background: Endothelial cells (ECs) are prominent cell types governing vascular tone and homeostasis. Activation of ECs is the central pathophysiological process in the initiation of atherosclerosis (AS). Interferon signaling (IFN Type I and II) is activated in ECs under inflammatory conditions such as systemic lupus erythematosus and is implicated in EC activation. But the underlying mechanisms are still unknown. Through RNA sequencing and pathway analysis, we have identified TNIK, a Ste20 family of MAP kinases (MAP4K) to regulate IFN signaling in ECs. Our study is the first to report the role and function of TNIK in IFN signaling and EC activation. Hypothesis: TNIK regulates IFNs through STAT mediated signaling and downstream interferon stimulated gene (ISG) sets Methods: Cultured Human aortic endothelial cells (HAECs) were treated with control or TNIK-targeted siRNA. Later cells were subjected to static, laminar or disturbed flow conditions. Total RNA was isolated and sequenced by mRNA-seq. The differential expression data were analyzed using CLC genomics and Ingenuity Pathway Analysis (IPA). Western blotting and qRT-PCR were performed to validate STAT activation and interferon stimulated genes (ISGs) Results: We found >450 genes differentially expressed in siTNIK vs siCTRL treated ECs (fold change>2, FDR<0.05). IPA revealed that under static (ST) and disturbed flow (DF) conditions TNIK depletion lead to inhibition IFN and upregulation of eukaryotic transcription elongation factor signaling (eIF2). In addition, under DF, TNIK depletion lead to downregulation of hyperctokinemia/hyperchemokinemia. Validation through western blotting and qRT-PCR confirmed that TNIK regulates STAT expression and IFN stimulated target genes. Conclusions: Our study elucidates the unique role of TNIK in regulating STAT mediated IFN signaling and subsequent ISGs in ECs.