CXCL1 and chronic obstructive pulmonary disease: The mRNA expression of IL-1β exhibited an ascending pattern in COPD patients compared to non-smokers (Fig. 2A), whereas IL-6, CXCL1 and CXCL8 mRNA levels were elevated in COPD patients compared to non-smokers (p < 0.01, p < 0.01 and p < 0.05 respectively, Fig. 2B–D).