MPO and inflammatory bowel disease: Elevated luminal levels of let-7b led to an enhanced mRNA expression of interleukin (IL)-6 and IL-1β (Figure 3(d)), known as a mRNA expression signature linked with macrophages38 and previously identified as hallmark cytokines in chronically inflamed tissues from patients with active IBD.39 On another hand, miR-21 enhanced the levels of the neutrophil marker myeloperoxidase (MPO).