The differential impact of iron on ferroptosis, oxidative stress, and inflammatory reaction in head-kidney macrophages of yellow catfish (Pelteobagrus fulvidraco) with and without ammonia stress.

Ammonia toxicity in fish is closely related to ferroptosis, oxidative stress, and inflammatory responses. Iron is an essential trace element that plays a key role in many biological processes for cells and organisms, including ferroptosis, oxidative stress response, and inflammation. This study aimed to investigate the effect of iron on indicators of fish exposed to ammonia, specifically on the three aspects mentioned above. The head kidney macrophages of yellow catfish were randomly assigned to one of four groups: CON (normal control), AM (0.046 mg L-1 total ammonia nitrogen), Fe (20 µg mL-1 FeSO4), and Fe + AM (20 µg mL-1 FeSO4, 0.046 mg L-1 total ammonia nitrogen). The cells were pretreated with FeSO4 for 6 h followed by ammonia for 24 h. The study found that iron supplementation led to an excessive accumulation of iron and ROS in macrophages, but it did not strongly induce ferroptosis, oxidative stress, or inflammatory responses. This was supported by a decrease in T-AOC, and the downregulation of SOD, as well as an increase in GSH levels and the upregulation of TFR1, CAT and Nrf2. Furthermore, the mRNA expression of HIF-1, p53 and the anti-inflammatory M2 macrophage marker Arg-1 were upregulated. The results also showed that iron supplementation increased the progression of some macrophages from early apoptosis to late apoptotic cells. However, the combined treatment of iron and ammonia resulted in a stronger intracellular ferroptosis, oxidative stress, and inflammatory reaction compared to either treatment alone. Additionally, there was a noticeable increase in necrotic cells in the Fe + AM and AM groups. These findings indicate that the biological functions of iron in macrophages of fish may vary inconsistently in the presence or absence of ammonia stress.

Identification and characterization of long non-coding RNAs in intestinal immune regulation of largemouth bass, Micropterus salmoides, under acute heat stress.

Long noncoding RNAs (lncRNAs), which are RNA molecules that do not code for proteins and have a length exceeding 200 base pairs, have been found to play a crucial role in regulating intestinal immunity. The high mortality of various fish species induced by high temperatures is known to be associated with enteritis. Our investigation demonstrated that acute heat stress was responsible for inducing fish enteritis. However, the specific lncRNAs involved this process remains unknown. In this current study, we utilized intestinal sequencing data from the largemouth bass species Micropterus salmoides under acute heat stress, resulting in a total of 347,351,492 clean reads obtained from six cDNA libraries. A total of 3399 novel lncRNA transcripts originating from 2488 distinct lncRNA genes were successfully identified. Consistent with previous findings in other fish species, these lncRNAs demonstrated comparatively shorter transcript lengths when compared to protein-coding genes. Furthermore, a total of 216 novel lncRNA exhibited differential expression (DE) in the intestine of largemouth bass, meeting the criteria of absolute log2 fold change exceeding 2 and a p-value below 0.05. Additionally, these DE-lncRNAs were found to regulate 210 neighboring genes in a cis-regulatory manner. An examination of GO/KEGG enrichment revealed a notable enrichment of immune regulation (p < 0.05) among these cis-genes, with lncRNA MSTRG.8573.1 playing a significant role in regulating the jak-stat signaling pathway during this process. This study presents a comprehensive inventory of novel DE-lncRNA implicated in the development of enteritis in largemouth bass under acute heat stress. These findings offer valuable insights for future investigations on the regulation of lncRNAs to mitigate heat stress-induced fish enteritis.

Temporal correlations of ferroptosis, inflammation and oxidative stress under acute ammonia exposure in brain tissue of yellow catfish (Pelteobagrus fulvidraco).

Ammonia is one of the most serious environmental stressors which severely affect fishery production. Ammonia toxicity to fish has a tight relationship with oxidative stress, inflammation and ferroptosis (a type of programmed cell death characterized by iron-dependent lipid peroxidation), but the temporal response of the above three in brain remains unclear. In the present study, yellow catfish were exposed to three concentrations of ammonia: low concentration (TA-N ˂ 0.01 mg L-1, LA), middle concentration (TA-N 5.70 mg L-1, MA), high concentration (TA-N 28.50 mg L-1, HA) for 96 h. Brain was selected as target tissues for analysis. Results showed that ammonia stress resulted in firstly increased contents of hydroxyl radical at 1 h, total iron at 12 h, malondialdehyde at 48 h, respectively, and decreased contents of GSH at 3 h. The initial high expression levels of ferroptosis (GPX4, system xc-, TFR1) and inflammatory-related factors (NF-ƙB p65, TNF, COX-2, and LOX-15B), antioxidant enzymes genes (SOD and CAT) were observed at first hour upon MA or HA stress. Combining all, it suggested that brain ferroptosis and inflammation were the first to be activated at the initial stage of ammonia stress, and then that provoked oxidative stress.