Biomechanical changes in endothelial cells result from an inflammatory response*

During periods of infection and disease, the immune system induces the release of TNF-$\alpha $, an inflammatory cytokine, from a variety of cell types, such as macrophages. TNF-$\alpha $, while circulating in the vasculature, binds to the apical surface of endothelial cells and causes a wide range of biological and mechanical changes to the endothelium. While the biological changes have been widely studied, the biomechanical aspects have been largely unexplored. Here, we investigated the biomechanical changes of the endothelium as a function of TNF-$\alpha $ treatment. First, we studied the traction forces applied by the endothelium, an effect that is much less studied than others. Through the use of traction force microscopy, we found that TNF-$\alpha $ causes an increase in traction forces applied by the endothelial cells as compared to non-treated cells. Then, we investigated cell morphology, cell mechanics, migration, and cytoskeletal dynamics. We found that in addition to increasing applied traction forces, TNF-$\alpha $ causes an increase in cell area and aspect ratio on average, as well as a shift in the organization of F-actin filaments within the cell. Combining these findings together, our results show that an inflammatory response heavily impacts the morphology, cell mechanics, migration, cytoskeletal dynamics, and applied traction forces of endothelial cells.