SLC40A1 and chronic obstructive pulmonary disease: On the other hand, relative to healthy controls, SLC40A1 expression in COPD patients was elevated in the high intracellular iron group and reduced in those with low intracellular iron, with significantly greater expression in the high versus low group (5.38 [1.42,12.10] vs. 0.22 [0.03,0.51], p = 0.0006, Mann–Whitney test, Fig. 2b).