JAKinibs prevent persistent, IFN gamma-autonomous endothelial cell inflammation and immunogenicity

The adhesion and subsequent activation of T cells is a critical step in local inflammatory responses, particularly of alloreactive leukocytes in rejection of transplanted donor tissue. Interferon (IFN)gamma is an adaptive cytokine that promotes endothelial cell (EC) expression of pro-adhesive factors and costimulatory molecules. We recently reported that IFN gamma-induced endothelial cell antigen-presenting capacity was protracted after cytokine withdrawal. This study sought to determine what intracellular signaling mediates this chronic endothelial activation by IFN gamma. The durability of interferon signaling in human aortic endothelial activation was tested. Pro-adhesive and costimulatory gene expression, phenotype, secretome, and Janus kinase (JAK)/STAT phosphorylation in human primary endothelial cells were measured under chronic and transient IFNc stimulation, with various JAK inhibitors. IFN gamma reporter cells were tested for STAT1 transcriptional activity with JAK inhibition and suppressors of cytokine signaling (SOCS) overexpression, under continuous and priming conditions. The consequences of even short exposure to IFN gamma were long-lasting and broad, with sustained elevation of adhesion molecules and chemokines up to 48 h later. JAK/STAT and interferon response factor expression were likewise durable, dependent on new transcription but autonomous of continuous IFN gamma. Persistent STAT new transcription and JAK signaling in the endothelium was required to maintain a pro-adhesive and proimmunogenic phenotype after IFNc withdrawal since both could be prevented by cycloheximide but only by JAKinibs with potency against JAK2. Finally, the suppressor of cytokine signaling SOCS1 failed to emerge in primed endothelial cells, which likely accounted for prolonged inflammatory gene expression. The results reveal a sustained JAK-dependent perturbation of endothelial function and suggest that JAKinibs may have therapeutic benefits in dampening vascular inflammation and allogeneic leukocyte activation. NEW & NOTEWORTHY The central question investigated in this study is why vascular endothelium remains inflamed and what underlying signaling is responsible. The new results show that the resolution of endothelial-controlled inflammation may be impaired or delayed because Janus kinase (JAK)/STAT activation is maintained autonomous of interferon (IFN)c presence, and the late phase negative regulator suppressors of cytokine signaling (SOCS)1 fails to be induced.

Automated summary

This study investigated the underlying signaling responsible for the sustained activation and inflammation of vascular endothelium. The results showed that the activation of JAK/STAT is maintained regardless of the presence of interferon (IFN), and the suppressors of cytokine signaling (SOCS)1 is not induced, suggesting the potential therapeutic benefits of JAKinibs in reducing vascular inflammation and alloreactive leukocyte activation.