SPHK1 and chronic obstructive pulmonary disease: In contrast to the findings with SPHK1, SPHK2 and S1PR2, we found that S1PR5 was higher in alveolar macrophages from both ex-smoker COPD and current smoker COPD subjects and negatively correlated with both fev1 and fev/fvc indicating a possible involvement in COPD progression that is at least to some extent independent of cigarette smoking.