ABSTRACT
This chapter presents the basic functions of the pulmonary endothelial cell (EC) and how this is affected by viral infections. The pulmonary circulation receives the entire cardiac output and consists of a finely tuned blood vessel network. The system maintains low pressure/low resistance and forms an immense contact area with the alveolar airspace serving as the primary site of gas exchange. Among others, pulmonary endothelium in health promotes barrier integrity and hemofluidity, additionally acting as an anti-inflammatory, antiproliferative, and vasodilation promoter mainly through its paracrine and endocrine properties. Exposure of the pulmonary EC to noxious stimuli and pathogens like viruses will derange or even reverse the protective features transforming the friend to a foe and promoting lung vascular injury. ECs exert active control over the vascular tone and regulate thrombolysis and coagulation. The renin–angiotensin–aldosterone system is a potent biological system that plays a key role in pulmonary and systemic vascular homeostasis.
