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Abstract: This study was aimed at investigating the toxicity mechanism of lipopolysaccharide (LPS) on Penaeus monodon haemocytes at a cellular level. Reactive oxygen species (ROS) production, nitric oxide (NO) production, non-specific esterase activity, cytoplasmic free-Ca2+ (CF-Ca2+) concentration, DNA damaged cell ratio and apoptotic cell ratio of in vitro LPS-treated haemocytes were measured by flow cytometry. Two concentrations of Escherichia coli LPS (5 and 10μgmL−1) were used. Results showed that ROS production, NO production and CF-Ca2+ concentration were significantly induced in the LPS-treated haemocytes. Ratio of DNA damaged cell and apoptotic cell increased caused by LPS, while esterase activity increased at the initial 60min and dropped later. The initial increase in esterase activity suggested that LPS activated the release of esterase, and the later decrease might result from apoptosis. These results indicated that LPS would induce oxidative stress on shrimp haemocytes, and cause Ca2+ release, DNA damage and subsequently cell apoptosis. This process of ROS/RNS-induced Ca2+-mediated apoptosis might be one of the toxicity mechanisms of LPS on shrimp haemocytes. [Copyright &y& Elsevier]

Abstract: This study investigated the in vitro effects of nitrite on reactive oxygen species (ROS) production, NO production, esterase activity and cell apoptosis of Penaeus monodon haemocytes. Haemocytes were in vitro exposed to different dose of nitrite (0, 0.1, 0.5, 1, 5 and 10μM). Cellular responses of nitrite-treated haemocytes were determined by flow cytometry. The results revealed that haemocytes treated by nitrite in vitro showed conspicuous time- and dose-dependent decreases in ROS and NO production as well as esterase activity. Additionally, 0.1 and 0.5μM nitrite did not affect the apoptotic cell ratio during the 3h experimental time, while significant increases in apoptotic cells were observed after haemocyte exposure to nitrite at 1μM for 3h, and at 5 or 10μM for 1h. These results indicated that nitrite suppresses cellular functions, including production of ROS and NO, and activity of esterase. Cell apoptosis of haemocytes would be induced by extracellular nitrite as doses exceed 1μM. [Copyright &y& Elsevier]

Abstract: This study was aimed at investigating the cytotoxicity of nitrite on haemocytes of the black tiger shrimp, Penaeus monodon. Total haemocyte count (THC), reactive oxygen species (ROS) production, DNA damaged cell ratio and apoptotic cell ratio of shrimp were determined after exposure to different concentrations of nitrite-N (0, 1, 10 and 20mgL−1) for 0, 6, 12, 24 and 48h. There was no significant effect on the analytic indicator of shrimp exposed to 1mgL−1 nitrite-N. THC decreased after 48h exposure to 10mgL−1 nitrite-N, and after 24h exposure to 20mgL−1 nitrite-N. Production of ROS was induced after 48h exposure to 10mgL−1 nitrite-N, and after 12h exposure to 20mgL−1 nitrite-N. The percentage of DNA damaged cell increased in P. monodon following 48h exposure to 10mgL−1 nitrite-N, and 24h exposure to 20mgL−1 nitrite-N. Apoptotic cell ratio increased after 48h exposure to 10mgL−1 nitrite-N, and 12h exposure to 20mgL−1 nitrite-N. These results indicated that nitrite-N would induce overproduction of ROS, and then resulted in DNA damage and cell apoptosis, and subsequently caused THC reduction. This process of oxidative stress was one of the toxicity mechanisms of nitrite on shrimp. [Copyright &y& Elsevier]