S1PR3 (sphingosine-1phosphate receptor3) is a vascular barrier regulatory member of the S1P family of receptors (S1PR15) and a critical signaling molecule mediating cell proliferation, adhesion, angiogenesis, and vascular permeability. In a nitrated form protein in plasma it is found as a biomarker in patients with ALI (acute lung injury). S1PR3 plays an important role in promoting pulmonary inflammation, disrupting cell-cell junctions, and increasing lung permeability and alveolar flooding during inflammation.