CYCS and chronic obstructive pulmonary disease: In line with previous studies of COPD and anoxic and oxidative stress [25], DEGs detected between our COPD and control groups were largely implicated in detection of hypoxic conditions in blood by carotid body chemoreceptor signaling, mitochondrial electron transport, cytochrome C to oxygen, and benzaldehyde dehydrogenase (NAD+) activity (Figure 4(a)).