S1PR5 and chronic obstructive pulmonary disease: Consistent with the alveolar macrophages from human smoker COPD subjects, we noted significantly higher relative mRNA expression of SPHK1, SPHK2, S1PR5 and S1PR2 whereas there was no increase in expression of SGPP2 and SGPL1 (n = 7experiments p<0.05, Fig 9).