SPHK1 and acute respiratory distress syndrome: Upregulated expression of the SphK-1 and S1PR-3 proteins was observed in endothelial cells, alveolar epithelial cells and alveolar macrophages in the lung tissues of ALI/ARDS group compared to control group. However, S1P in plasma and lung tissues was significantly less in ALI/ARDS group compared to control mice.