CASP4 and chronic obstructive pulmonary disease: KEGG analysis (Fig. 4A-B) for 9 COPD-associated pyroptosis-related genes indicated that these genes were significantly enriched in NOD-like receptor signaling pathway (CASP4/CASP5/IL1B/AIM2), Lipid and atherosclerosis (IL1B/PLCG1/CASP6), Shigellosis (CASP4/IL1B/PLCG1), Salmonella (CASP4/CASP5/PLCG1) infection and so on (Fig. 4A).