Molecular cloning, characterization and expression analysis of metallothionein in the liver of the teleost Acrossocheilus fasciatus exposed to cadmium chloride

Dietary berberine against intestinal oxidative stress, inflammation response, and microbiota disturbance caused by chronic copper exposure in freshwater grouper (Acrossocheilus fasciatus)

Berberine (BBR) is known for its strong antioxidant, anti-inflammatory, and capacity to preserve intestinal microbiota balance in fish. This study aimed to investigate the protective effects of berberine against copper-induced toxicity in the intestine of freshwater grouper Acrossocheilus fasciatus. The experiment involved four groups: a control group, a Cu group exposed to 0.02 mg/L Cu²⁺, and two BBR groups fed with 100 or 400 mg/kg of berberine diets and exposed to the same Cu²⁺ concentration. Three replicates of healthy fish (initial weight 1.56 ± 0.10 g) were subjected to their respective treatments for 30 days. Results showed that none of the treatments significantly affected the survival rate, final weight, weight gain, and feed intake (P > 0.05). However, supplementation with 100 and 400 mg/kg of BBR significantly lowered the antioxidant activities, and glutathione peroxidase (gpx) and superoxide dismutase (sod) expression levels, as well as reduced malondialdehyde (MDA) content caused by Cu²⁺ exposure (P < 0.05). Berberine inclusion significantly downregulated proinflammatory factors NLR family pyrin domain containing 3 (nlrp3), interleukin 1 beta (il1β), interleukin 6 cytokine family signal transducer (il6st) but upregulated transforming growth factor beta 1 (tgfβ1) and heat shock 70kDa protein (hsp70) expression. Moreover, berberine at both levels maintained the intestinal structural integrity and significantly improved gap junction gamma-1 (gjc1) mRNA level compared to the Cu group (P < 0.05). Based on 16S rDNA sequencing, the richness and diversity of intestinal microbiota in different groups were not significantly influenced. Berberine reduced the Firmicutes/Bacteroidota ratio and stifled the growth of some specific pathogenic bacteria such as Pseudomonas, Citrobacter, and Acinetobacter, while boosting the richness of potential probiotic bacteria, including Roseomonas and Reyranella compared with the Cu group. In conclusion, berberine showed significant protective effects against Cu²⁺-induced intestinal oxidative stress, inflammation response, and microbiota disturbance in freshwater grouper.

Integrated mRNA and miRNA Expression Profile Analysis of Female and Male Gonads in Acrossocheilus fasciatus

MicroRNAs (miRNAs) are regarded as key regulators in gonadal development and sex determination in diverse organisms. However, the functions of miRNAs in gonads of Acrossocheilus fasciatus, an economically important freshwater species in the south of China, are still unclear. Here, high-throughput sequencing was performed to investigate the mRNA and miRNAs on gonads of A. fasciatus. In total, 49,447 unigenes were obtained, including 11,635 differentially expressed genes (DEGs), among which 4147 upregulated genes and 7488 downregulated genes in the testis compared to the ovary, while 300 (237 known, and 63 novel) miRNAs with 36 differentially expressed miRNAs (DEMs) were identified, from which 17 upregulated and 19 downregulated DEMs. GO and KEGG enrichment analysis were performed to analyze the potential biological functions of DEGs and DEMs. Using qRT-PCR, 9 sex-related genes and 9 miRNAs were selected to verify the sequencing data. By dual-luciferase reporter assay, miR-22a-5p and miR-22b-5p interaction with piwil1, and miR-10d-5p interaction with piwil2 were identified. These findings could provide a reference for miRNA-regulated sex control of A. fasciatus and may reveal new insights into aquaculture and breeding concepts.

Comparative transcriptome analysis of the gills and hepatopancreas from Macrobrachium rosenbergii exposed to the heavy metal Cadmium (Cd2+)

Heavy metal Cadmium (Cd²⁺) pollution has become a severe environmental problem for aquatic organisms. In crustaceans, gills (Gi) and hepatopancreas (Hp) play a vital role in the toxicology. However, in Macrobrachium rosenbergill, there are few researches about gill and hepatopancreases responding to Cd²⁺ stress at a molecular level. In this study, transcriptomic analysis was applied to characterize gene expression profiles of gills and hepatopancreas of M. rosenbergill after Cd²⁺ exposure for 0 h, 3 h and 3 d. Six cDNA libraries (Gi 0 h, Gi 3 h, Gi 3 d, Hp 0 h, Hp 3 h, and Hp 3 d) were constructed and a total of 66,676 transcripts and 48,991 unigenes were annotated. Furthermore, differentially expressed genes (DEGs) were isolated by comparing the Cd²⁺ treated time-point libraries (3 h and 3 d group) with the control library (0 h group). The results showed that most of the DEGs were down-regulated after Cd²⁺ exposure and the number of DEGs among gill groups were significantly higher than those among hepatopancreas groups. GO functional and KEGG pathway analysis suggested many key DEGs in response to the Cd²⁺ stress, such as metallothionein and Hemocyanin. Additionally, a total of six DEGs were randomly selected to further identify their expressional profile by qPCR. The results indicated that these DEGs were involved in the response to Cd²⁺. This comparative transcriptome provides valuable molecular information on the mechanisms of responding to Cd²⁺ stress in M. rosenbergii, which lays the foundation for further understanding of heavy metal stress.

DNA methylation and gene expression alterations in zebrafish embryos exposed to cadmium

An unexplored attributing molecular mechanism of Cd toxicity is interference with the epigenetic machinery, such as DNA methylation, processes that are crucial for early fetal development. In order to investigate the effects of Cd on the expression of metallothionein (MT) and Dnmts transcripts, markers of DNA methylation, and signaling pathway gene expression, zebrafish embryos were exposed during 24 hours post-fertilization (starting at maximum 8-cell stage) to 0.0089, 0.089, and 0.89 μM Cd. The results showed that the Cd accumulation in zebrafish embryo reached a stable level after 12 hpf, and the Cd accumulation at individual time points was significantly different among different concentration groups. MT mRNA fold was significantly positive with the Cd content in embryos. We observed that the expression level of DNA methyltransferase (Dnmts) in the 0.089 μM Cd exposure group was significantly up-regulated. Dnmt1 expression was significantly up-regulated in the 0.89 μM Cd exposure group, and Dnmt3s expression and global methylation levels were significantly down-regulated. Cd up-regulated ErbB-3 gene expression, down-regulated ErbB-4 gene expression, and neutralized ErbB-1 gene expression. Cd activated Ca2+, MAPK-JUK, p38 MAP kinase, PI3K-AKT, and VEGF signaling pathway genes, indicating these pathway genes related to Cd exposure level. The results are helpful to clarify the molecular mechanism of DNA methylation in zebrafish embryo under metal pressure and further interference with the epigenetic machinery.