Neuropeptide F (NPF) regulates the hepatopancreatic antimicrobial innate immune system by affecting the expression of antimicrobial peptides in Procambarus clarkii.

Neuropeptide F (NPF), a key component of the neuroendocrine-immune (NEI) system, is widely distributed in the central nervous system and peripheral immune cells and is involved in various physiological processes. In this study, the role of NPF in the NEI system of Procambarus clarkii was investigated, with a specific focus on its regulatory functions in innate immunity. We found that Pc-NPF is expressed in multiple tissues of P. clarkii, including hemocytes, hepatopancreas, gills, intestine, heart, and muscle, with higher expression levels in the hepatopancreas. Upon bacterial challenge with Staphylococcus aureus and Edwardsiella ictaluri, Pc-NPF expression levels were significantly increased, indicating its involvement in immune responses. Using RNA interference (RNAi) to knock down Pc-NPF, we observed reduced bacterial clearance and significantly decreased survival rates of P. clarkii, highlighting the critical role of Pc-NPF in defending against bacterial infections. Further investigation revealed that Pc-NPF knockdown inhibited the expression of key genes in the Toll and Imd signaling pathways, including receptor genes (Pc-toll 1 and Pc-toll 3), transcription factor genes (Pc-dorsal, Pc-relish 2, and Pc-relish 3), and antimicrobial peptide genes (Pc-crustin 1, Pc-crustin 2, Pc-ALF 1, etc.). These findings suggest that Pc-NPF regulates innate immune responses through the Toll and Imd pathways, providing new insights into the NEI system of P. clarkii and offering a theoretical basis for disease control and the development of immune strategies involving P. clarkii.