The distribution and localization of inflammation-related molecules in midgut of the freshwater crayfish Procambarus clarkii

ABSTRACT At present, very little is known about inflammatory mechanisms in the crustacean intestine. It could be driven by some evolutionarily conserved molecules, such as endogenous gasotransmitters (viz. NO/iNOS and H2S/CBS) and signalling components (viz. NF-кB/p65, Nrf2 and p38MAPK). To detect their tissue distribution and cellular localization in midgut, the freshwater crayfish Procambarus clarkii was used as a model organism and immunohistochemical (IHC) staining was performed. Data were representative of three independent experiments, each with n = 5. Results indicated that (1) both NO and H2S were present in midgut tissue, and iNOS and CBS could be responsible for their generation; (2) NOS-like immunoreactivity occurred primarily in the nucleus of adluminal epithelium, but the positive signals of CBS were mainly present in the cytoplasm; (3) NF-кB/p65 and p38 MAPK were diffusely distributed in the surface epithelium and lamina propria while Nrf2 densely lied in the nucleus of adluminal epithelium; (4) the positive signals of p38MAPK were more widely distributed than its phosphorylated form (p-p38MAPK), and p-p38 immunoreactivity was only observed in the nucleus but not in the cytoplasm. The epithelial cells and the molecules they produce might play a crucial part in mucosal immunity in crayfish gut.