Investigating the skin response of Striped Catfish to acute ammonia stress reveals a potential exosome-based ammonia excretion system

Ammonia can rapidly accumulate in intensive aquaculture and pose serious threats to fish health. Fish skin functions as a vital immune-related organ and a significant surface barrier against ammonia; however, little is known about the skins response and to acute ammonia stress. In this study, Striped catfish were exposed to a half-lethal concentration of ammonia to evaluate skin responses. We found generalized inflammation in the liver, spleen, and skin. However, the skin tissue showed subtle signs of damage, with tissue ammonia concentration accumulating and then decreasing. Further transcriptomic analysis of skin gene function suggested a hypothesized ammonia regulation occurring within cell compartments. Cellular examination by transmission electron microscopy further showed that accumulated exosome-suspecting vesicles near the epithelial surface were associated with ammonia regulation during acute ammonia stress. Using a newly established Striped catfish skin epithelial cell line, along with an exosome inhibitor, confirms the presence of exosome vesicles and their role in ammonia excretion. In conclusion, acute ammonia stress induces inflammation in Striped catfish skin, while active ammonia excretion via exosomes may alleviate ammonia accumulation, thereby maintaining skin tissue integrity. This study explores Striped catfish skin responses to acute ammonia stress and highlights a newly identified mechanism of ammonia regulation in the skin. HighlightsO_LIFish skin can regulate ammonia concentrations and stress. C_LIO_LIExosomal vesicles are involved in the excretion of ammonia from the skin. C_LI