WNK2 and chronic obstructive pulmonary disease: Administration of crocin (50 mg/kg/day, 3 times/week, for 8 weeks) to cigarette-induced COPD rats inhibited the gene expression and protein production of a nuclear factor erythroid 2-related factor 2 (Nrf2), protein kinase C (PKC), mitogen-activated protein kinase (MAPK), phosphatidylinositol 3-kinase (PI3K) and glutamate-cysteine ligase catalytic (gclc), and prevented lung damage by strengthening the anti-oxidant system (192).