Endothelial cells functional consequences

In contrast to unfractionated heparin, LMWHs bind weakly to endothelial cells and are cleared mainly by renal excretion. A consequence of this is that their pharmacokinetics and pharmacodynamics are linear and the pharmacodynamics effect is proportional to the dose. This makes them more predictable than standard heparin, and is the main reason why routine monitoring is not needed. Because of the predominantly renal excretion there is a risk of accumulation in patients with reduced renal function. In this group of patients it may be advisable to monitor the anti-Xa activity. 

Activated neutrophils and platelets adhere to the pulmonary capillary endothelium, initiating multiple inflammatory cascades with a release a variety of toxic substances. There is diffuse pulmonary endothelial cell injury, increased capillary permeability, and alveolar epithelial cell injury. Consequently, interstitial pulmonary edema occurs and gradually progresses to alveolar flooding and collapse. The end result is loss of functional alveolar volume, impaired pulmonary compliance, and profound hypoxemia. ... 

In 1996 the exosome was discovered to have an immunological function and consequent study of the immunological role of exosomes has been extensive (Raposo et al., 1996). Exosomes have been shown to take part in both T-cell activation (Sprent, 2005) and in tolerance development (Karlsson et al., 2001). It has been shown that exosomes released from mast cells have the capacity to activate T cells and endothelial cells, and in addition to induce DC maturation. Thus, there is now extensive evidence that exosomes can mediate communication between cells over a distance. Furthermore, exosomes primed with specific tumor antigens are under clinical trials for cancer treatment. 

Endothelial cells react differently to radiation, depending on the inflammation. In inflammation endothe-Ual cells are in a special physiologic condition, rapidly prohferating, actively synthesizing many pro-inflammatory and other peptides and proteins and responding differently to radiation than resting endothelial cells. The functional consequences of radiation exposure of these activated endotheUal cells might be different from those induced in endotheUal cells in healthy normal tissues studied (Trott and Kamprad 1999). 

Other effects of irradiation on endothelial cells are cytotoxic effects that participate in the antitumor treatment. As a chronic effect of radiation exposure to blood vessels, histopathologic investigation reveals a capillary rarefication, which means a markedly reduced density of capillaries in irradiated tissues, which can occur, depending on the tissue type, even after many years. The depletion of capillaries and mircrovessels is supposed to be the consequence of an impaired cellular function leading to destruction of capiUaries. The exact mechanisms are still not known (Trott 2002). 

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