Abstract 13237: Thioredoxin Interacting Protein Promotes Endothelial Cell Inflammation in Response to Disturbed Flow by Repressing Kruppel-Like Factor 2
Background: Endothelial cells (EC) at regions exposed to disturbed flow (d-flow), such as lesser curvature of aortic arch and branch points of outflow tracts, are more susceptible to inflammation associated with atherogenesis. In contrast, steady flow (s-flow) such as that present within straight segments of the vasculature is anti-inflammatory and induces Kruppel-like factor 2 (KLF2), a master regulator of atheroprotective EC functions. Previously we reported that thioredoxin interacting protein (TXNIP) expression was inhibited by s-flow, and regulates EC inflammation by modulating thioredoxin (TRX) activity. Here we hypothesize that d-flow induces TXNIP expression, which acts as a transcriptional corepressor to inhibit KLF2 promoter activity thereby promoting EC inflammation.
Methods and Results: We performed en face staining to compare TXNIP expression under different flow patterns in mouse aorta. We found a dramatic increase of TXNIP in EC at atheroprone sites exposed to d-flow as compared to s-flow. In vitro experiments utilizing a cutout chamber model to generate varying flow patterns confirmed the up-regulation of TXNIP by d-flow in human umbilical vein EC (HUVEC). Overexpression of TXNIP in EC resulted in the constitutive expression of adhesion molecules including VCAM-1, ICAM-1, and E-Selectin. Furthermore, we found that KLF2, which inhibits adhesion molecules expression in EC, was suppressed by d-flow in a TXNIP-dependent fashion. A short fragment of KLF2 promoter (-157 - +1) was responsible for TXNIP-mediated transcriptional inhibition. To confirm TXNIP as a transcriptional repressor, we showed by chromatin immunoprecipitation (CHIP) assay that TXNIP was present within a complex that occupies the KLF2 promoter in EC exposed to d-flow but not s-flow. Finally, we performed intravital microscopy of mesenteric vessels from EC-specific TXNIP knockout mouse. We found that leukocyte rolling time was decreased, while rolling speed was increased significantly compared with control littermates.
Conclusion: These findings illustrate a novel mechanism by which TXNIP acts as a pro-inflammatory factor that promotes the expression of adhesion molecules in EC by acting as a transcriptional corepressor of KLF2 in response to d-flow.
- © 2011 by American Heart Association, Inc.