FIGURE 2.

SNO or ATP exported by RBCs can interact with various cell types to produce multiple beneficial or injurious responses in paracrine fashion. Extracellular roles played by RBC-derived SNO or ATP overlap partially. ATP or SNO efflux from vehicle RBCs can be salutary: vasodilation (green); or when preventing (red) adhesion or limiting (red) endothelial (EC) permeability. Note that SNO-induced vasodilation can be endothelium-independent, acting directly on vascular smooth muscle cells (VSMCs). Alternatively these mediators can be injurious, e.g., when acting as a DAMP (damage-associated molecular pattern). ATP can act as a DAMP by promoting (green) leukocyte (WBC) adhesion and activation, driving inflammation in acute lung injury. RBC-derived SNO may oppose WBC adhesion.