CXCL8 and chronic obstructive pulmonary disease: Interestingly, three recent mRNA/protein profiling studies in quadriceps and vastus lateralis of COPD patients [36-38] failed to confirm a common hypothesis that increased expression of pro-inflammatory cytokines (IL-6, IL-8, IL-1 and TNF-α) induce muscle atrophy in COPD patients with muscle weakness.