CXCL8 and irritable bowel syndrome: Previous studies in humans and animals with gastroparesis, IBS, FD, and IBD have reported increased levels of pro-inflammatory cytokines such as interleukin (IL)-1β, IL-6, IL-8, and tumor necrosis factor (TNF)-α in the blood and serum (Abell et al. 2021; de Souza and Fiocchi 2016; Dinan et al. 2006; Enck et al. 2017; Liebregts et al. 2007; van Heel et al. 2002).