Gill damage and neurotoxicity of ammonia nitrogen on the clam Ruditapes philippinarum

Abstract

Ammonia nitrogen has been a potential menace to aquatic animals along the coastline of China. Presently, the toxicological effects of ammonia nitrogen were mainly concentrated on fishes, while little attention has been paid to molluscs. In this study, the clam Ruditapes philippinarum was used as the target animal to investigate the toxic effects of ammonia nitrogen. Our results showed that ammonia exposure could significantly reduce the integrity of lysosomes in a dose-dependent manner. Metabolite analysis revealed that exposure doses and duration time of ammonia nitrogen could affect the variation profiles of gill metabolites. In detail, branched chain amino acids, glutamate, choline and phosphocholine were significantly decreased after a one-day exposure. Inosine and phenylalanine were found significantly increased and ATP was decreased after a three-day exposure. The changes of metabolites implied that metabolisms of muscle element, neurotransmission and cell apoptosis of gill tissues would be affected by ammonia exposure. Such inferences were supported by the diminished muscle element, decreased concentrations of catecholamines and increased apoptosis rates, respectively. Therefore, we take advantage of metabolomics integrated with conventional biological assays to find out that ammonia exposure could cause lysosome instability, metabolic disturbance, aberrant gill structures and changes to neurotransmitters, and would result in mollusk gill dysfunction in feeding, respiration and immunity.

Digital gene expression analysis in the gills of Ruditapes philippinarum exposed to short- and long-term exposures of ammonia nitrogen

“…It has been suggested as a potential mediator for phospholipidosis during lysosome dysfunction (Balsinde et al, 2002). The significant variation of phospholipase A2 isozymes (PA3A/PA3B/PA5) gene after ammonia nitrogen exposure would attribute to the reduced integrity of lysosome membrane which we found in the previous study (Cong et al, 2017).…”

“…Our previous study revealed that ammonia exposure could significantly reduce the integrity of lysosome membrane, decrease the contents of glutamate and branched chain amino acid, decrease ATP supply, increase apoptosis ratios, decrease contents of neurotransmitters, reduce basal layer inside the filaments with the emergence of xenobiotic substances (Cong et al, 2017). It suggested that ammonia nitrogen exposure brought detrimental toxicity to R. philippinarum.…”

“…According to the annual reports on the environmental state of China, the actual concentration of ammonia nitrogen in the neritic China seas ranged from 0 to 19.32 mg/L with an average value of 1.82 mg/L. Based on the result of lysosomal destabilization which was an indicator of cellular damage (Keppler, 2007;Aguirre-Martínez et al, 2013), our previous study suggested that 1-day exposure of 0.1 mg/L ammonia nitrogen could cause toxic effects to the calms, and induced significant changes in neurotransmitter concentrations, lysosomal stabilization and metabolite concentrations (Cong et al, 2017). And a 30day exposure of 0.1 mg/L ammonia nitrogen didn't cause massive mortality to the clams (data not shown).…”

“…The underlying mechanism of ammonia toxicity in mollusc was not fully elucidated yet. In previous studies, we found that ammonia nitrogen exposure caused a series of adverse effects to the clam Ruditapes philippinarum, including decrease in lysosomal stability, disturbance of metabolic profiles, damage to the gill structure and variation of neurotransmitter concentrations (Cong et al, 2017). However, which genes and how many pathways were involved in the toxic reaction of R. philippinarum to ammonia nitrogen challenge?…”

High‐throughput metabolomics method based on liquid chromatography‐mass spectrometry: Insights into the underlying mechanisms of salinity–alkalinity exposure‐induced metabolites changes in Barbus capito

“…When fish are exposed to excessively high alkalinity water, a large amount of mucus is secreted on the surface of the fish, and gills bleeding at the same time, causing serious death [37]. The adaptation process of fish to the high saline‐alkali water environment mainly refers to the process of changes in blood osmotic pressure and tissue enzyme activity of the fish body under short‐term saline‐alkali stress, as well as the process of self‐regulation and restoration to the initial state of fish body, which are regulated by the gene expression associated with enzyme activity through tissues such as the kidneys and gills [38]. Gills are the main organs of fish breathing, and their structural integrity directly affects the normal operation of gas exchange, filter food, osmotic pressure regulation, and waste excretion functions [39].…”