Endothelial activation is a

proinflammatory Inflammation (from la, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or irritants, and is a protective response involving immune cells, blood vessels, and molec ...

and

procoagulant Coagulation, also known as clotting, is the process by which blood changes from a liquid to a gel, forming a blood clot. It potentially results in hemostasis, the cessation of blood loss from a damaged vessel, followed by repair. The mechanism o ...

state of the

endothelial cell The endothelium is a single layer of squamous endothelial cells that line the interior surface of blood vessels and lymphatic vessels. The endothelium forms an interface between circulating blood or lymph in the lumen and the rest of the vessel ...

s lining the lumen of

blood vessel The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. They also take waste and carbon dioxide away ...

s. It is most characterized by an increase in interactions with

white blood cell White blood cells, also called leukocytes or leucocytes, are the cell (biology), cells of the immune system that are involved in protecting the body against both infectious disease and foreign invaders. All white blood cells are produced and de ...

s (leukocytes), and it is associated with the early states of

atherosclerosis Atherosclerosis is a pattern of the disease arteriosclerosis in which the wall of the artery develops abnormalities, called lesions. These lesions may lead to narrowing due to the buildup of atheroma, atheromatous plaque. At onset there are usu ...

and

sepsis Sepsis, formerly known as septicemia (septicaemia in British English) or blood poisoning, is a life-threatening condition that arises when the body's response to infection causes injury to its own tissues and organs. This initial stage is follo ...

, among others. It is also implicated in the formation of

deep vein thrombosis Deep vein thrombosis (DVT) is a type of venous thrombosis involving the formation of a blood clot in a deep vein, most commonly in the legs or pelvis. A minority of DVTs occur in the arms. Symptoms can include pain, swelling, redness, and enla ...

. As a result of activation, enthothelium releases Weibel–Palade bodies.

Mechanical sensing and responses

Elevating shear stress induces a vascular response by triggering nitric oxide synthesis and mechanotransduction pathways of endothelial cells. The synthesis of nitric oxide facilitate shear stress mediated dilation in blood vessels and maintains a homeostatic status. Additionally, physiologic shear stress levels at the vessel wall upregulate the presence of antithrombotic agents through the mechano-signal transduction of mechano-recepting transmembrane proteins, junctional proteins, and subendothelial mechanosensors. Shear stress causes endothelial cell deformation which activates transmembrane ion channels Elevated wall shear stress caused by exercise is understood to promote mitochondrial biogenesis in the vascular endothelium indicating the benefits regular exercise may have on vascular function. Alignment is recognized as an important mechanism and determinant of shear-stress induced vascular response; in vivo testing of endothelial cells has demonstrated that their mechanotransductive response is direction dependent as endothelial nitric oxide synthesis is preferentially activated under parallel flow while perpendicular flows activates inflammatory pathways like reactive oxygen species production and nuclear factor-κB. Therefore, disturbed/oscillating flow and low flow conditions, which create an irregular and passive shear stress environment, result in inflammatory activation due to a limited alignment capability of the endothelial cells. Regions in the vasculature with low shear stress are vulnerable to elevated monocyte adhesion and endothelial cell apoptosis. However, unlike oscillatory flow, both laminar(steady) and pulsatile flow and shear stress environments are often considered together as mechanisms of maintaining vascular homeostasis and preventing inflammation, reactive oxygen species formation, and coagulatory pathways. High, uniform laminar shear stress is known to promote a quiescent endothelial cell state, provide anti-thrombotic effects, prevent proliferation, and decrease inflammation and apoptosis. At high shear stress levels (10 Pa), the endothelial cell response is distinct from upper normal/physiological values; high wall shear stress causes a promatrix remodeling, proliferative, anticoagulant, and anti-inflammatory state. Yet, very high wall shear stress values (28.4 Pa) prevent endothelial cell alignment and stimulate proliferation and apoptosis although the endothelial response to shear stress environments was determined to be dependent on the local wall shear stress gradient.

Mechanical sensing and responses

See also

References

Further reading