CXCL8 and chronic obstructive pulmonary disease: For COPD fibroblasts, the protein levels of IL-6 and IL-8 decreased from 993.0 ± 738.9 pg/mL to 650.1 ± 421.9 pg/mL (P = 0.014) and from 703.1 ± 278.0 pg/mL to 492.0 ± 214.9 pg/mL (P = 0.001), respectively, with 5 μg/mL theophylline treatment.