PTGS2 and Constipation: Significant inflammatory responses were observed in C3 KO mice with constipation phenotypes through activation of the inducible nitric oxide synthase (iNOS)-mediated cyclooxygenase-2 (COX-2) induction pathway, apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC)-inflammasome pathway and the nuclear factor kappa B (NF-κB) signaling pathway [8].