Assessment of endoplasmic reticulum stress and the unfolded protein response in endothelial cells

In the vascular wall, the most inner cell layer that separates the blood from organelles is comprised of only a single layer of endothelial cells (ECs). This cell type is fundamental to a large variety of processes, ranging from blood coagulation and interaction with inflammatory cells to cardiovascular diseases such as hypertension, diabetes, and atherosclerosis. Dysfunction of ECs is often causally linked to these processes such that research exploring such events attracted much attention. Damage of ECs and subsequent disruption of the intact endothelial barrier can result not only from oxidative stress, but also from conditions that stress the endoplasmic reticulum (ER) and induce a signaling pathway termed unfolded protein response (UPR). While its primary goal is to alleviate ER stress, the UPR can also induce cell death. Cultured ECs are often used in in vitro approaches to understand various pathophysiological events, but they behave differently from many other cell types such that cell-type-specific procedures are needed. Here, we describe how ER stress can be induced and assessed in cultured ECs and demonstrate their specific responses to classical ER stress conditions.