S1PR2 and pulmonary arterial hypertension: Animal experiments have confirmed the finding of increased SPHK1 protein levels and S1P production in the lung tissue of animal models of idiopathic pulmonary hypertension [151], and inhibition of SPHK1, S1P, or S1P2 slowed down the progression of PAH induced by chronic hypoxia in animals or wild lily pads [152].