HIF1A and chronic obstructive pulmonary disease: In cases where chronic obstructive pulmonary disease (COPD) is accompanied by hypoxemia, persistent hypoxia upregulates interleukin-6 (IL-6) expression via the hypoxia-inducible factor 1-alpha (HIF-1α) pathway, concurrently exacerbating oxidative stress and mitochondrial impairment within cerebral tissues (42).