Toxic effects of cadmium exposure on intestinal histology, oxidative stress, microbial community, and transcriptome change in the mud crab (Scylla paramamosain).

Cadmium is one of hazardous pollutants that has a great threat to aquatic organisms and ecosystems. The intestine plays important roles in barrier function and immunity to defend against environmental stress. However, whether cadmium exposure caused the intestine injury is not well studied. Thus, the aim of this study was to explore the potential mechanisms of cadmium toxicity in the intestine of mud crab (Scylla paramamosain) via physiological, histological, microbial community, and transcriptional analyses. Mud crabs were exposed to 0, 0.01, and 0.125 mg/L cadmium. After a 21-day of cadmium exposure, 0.125 mg/L cadmium caused intestine damaged by decreasing superoxide dismutase and catalase activities, and increasing hydrogen peroxide and malondialdehyde levels. Integrated biological index analysis confirmed that the toxicity of cadmium exhibited a concentration-dependent manner. Comparative transcriptional analyses showed that the up-regulations of several genes associated with heat shock proteins, detoxification and anti-oxidant defense, and two key signaling pathways (PI3k-Akt and apoptosis) revealed an adaptive response mechanism against cadmium exposure. Transcriptomic analysis also suggested that cadmium exposure disturbed the expression of ion transport and immune-related genes, indicating that it has negative effects on the immune functions of the mud crab. Furthermore, the intestinal microbial diversity and composition were significantly influenced by cadmium exposure. The abundance of the dominant phyla Fusobacteria and Bacteroidetes significantly changed after cadmium exposure. KEGG pathway analysis demonstrated that cadmium exposure could change energy metabolism and environmental information processing. Overall, we concluded that excessive cadmium exposure could be potentially exerted adverse effects to the mud crab health by inducing oxidative damage, decreasing immune system, disrupting metabolic function, and altering intestinal microbial composition. These results provided a novel insight into the mechanism of cadmium toxicity on crustaceans.

Identification and functional characterization of glutaredoxin 5 from the mud crab (Scylla paramamosain) in response to cadmium and bacterial challenge.

Glutaredoxin (Grx) is a class molecule oxidoreductase, which plays a key role in maintaining redox homeostasis and regulating cell survival pathways. However, the expression pattern and function of Grx remain unknown in the mud crab (Scylla paramamosain). In the present study, a novel full-length of Grx 5 from the mud crab (designated as Sp-Grx 5) was cloned and characterized. The open reading frame of Sp-Grx 5 was 441 bp, which encoded a putative protein of 146 amino acids. The amino acid sequence of Sp-Grx 5 contained a typical C-G-F-S redox active motif and several GSH binding sites. Sp-Grx 5 widely existed in all tested tissues with a high-level expression in hepatopancreas. Subcellular localization showed that Sp-Grx 5 was located in the cytoplasm and nucleus. The expression of Sp-Grx 5 was significantly up-regulated after Vibrio parahaemolyticus infection and cadmium exposure, suggesting that Sp-Grx 5 was involved in innate immunity and detoxification. Furthermore, overexpression of Sp-Grx 5 could improve cells viability after H2O2 exposure. All these results indicated that Sp-Grx 5 played important roles in the redox homeostasis and innate immune response in crustaceans.

The role of caspase 3 in the mud crab (Scylla paramamosain) after Vibrio parahaemolyticus infection.

Apoptosis plays essential roles in the immune defense mechanism against pathogen infection. Caspase 3 is a family of cysteine proteases involved in apoptosis and the immune response. In this study, the full-length of mud crab (Scylla paramamosain) caspase 3 (designated as Sp-caspase 3) was cloned and characterized. The open reading frame of Sp-caspase 3 was comprised a 1035 bp, which encoded a putative protein of 344 amino acids. Sp-caspase 3 was ubiquitously expressed in various tissues with a high-level expression in hemocytes. Cellular localization analysis revealed that Sp-caspase 3 was located in the cytoplasm and nucleus. Over-expression of Sp-caspase 3 could induce cell apoptosis. In addition, V. Parahaemolyticus infection induced the relative expression of caspase-3 mRNA and increased caspase-3 activity. Knocking down Sp-caspase 3 in vivo significantly reduced cell apoptosis and increased mortality of mud crab after V. parahaemolyticus infection. These results indicated that Sp-caspase 3 played important roles in the immune response and apoptosis against bacterial infection.

The role of tumor suppressor protein p53 in the mud crab (Scylla paramamosain) after Vibrio parahaemolyticus infection.

The tumor suppressor protein p53 plays important roles in DNA repair, cell cycle and genetic stability. In the present study, a p53 gene in the mud crab (Scylla paramamosain) (designated as Sp-53) was identified and characterized. The open reading frame of Sp-53 was comprised a 1383 bp, which encoded a putative protein of 460 amino acids. Sp-53 is expressed in all examined tissues, with the highest expression in hepatopancreas and hemocytes. Vibrio parahaemolyticus infection induced oxidative stress, and led to DNA damage. The Sp-53 transcriptions in hepatopancreas were significantly up-regulated after V. parahaemolyticus infection. RNA interference (RNAi) experiment was used to understand the roles of Sp-53 in response to V. parahaemolyticus infection. Knocking down Sp-53 in vivo significantly reduced the expression of the Mn-SOD, Gpx3 and caspase 3 after V. parahaemolyticus infection. Moreover, the mortality of mud crabs and DNA damage in Sp-53-silenced mud crab challenged with V. parahaemolyticus were significantly higher than those in the control group. All these results suggested that Sp-53 played an important role in responses to V. parahaemolyticus infection through its participation in regulation of antioxidant defense, DNA repair and apoptosis.

Hsa_circ_0031288/hsa-miR-139-3p/Bcl-6 regulatory feedback circuit influences the invasion and migration of cervical cancer HeLa cells.

Circular RNA (circRNA) molecules contain microRNA (miRNA) response elements that are able to competitively bind miRNAs as well as function as miRNA sponges within cells, which can reduce miRNA inhibition of target genes, thereby increasing their expression. TargetScan and miRanda bioinformatic tools were used to analyze the binding sites between genes. The relative levels of gene expression in tissues and cells were verified using quantitative reverse transcription-polymerase chain reaction. Inhibition of cell proliferation was detected using a WST-8 method. Cell invasion ability and migration ability were assessed using a Transwell migration assay and a scratch assay, respectively. The binding of miRNA and circRNA was detected using an RNA pull-down assay. Bifluorescence reporter gene vectors were constructed to verify the binding of miRNA to messenger RNA. A tumor model of cervical cancer cell transplantation in mice was constructed to observe the effect of the genes on tumor growth. hsa_circ_0031288 and B-cell CLL/lymphoma 6 (Bcl-6) exhibited high expression in cervical cancer cells and tissue, while hsa-miR-139-3p exhibited low expression. Reducing hsa_circ_0031288 and Bcl-6 expression or increasing hsa-miR-139-3p expression significantly inhibited the migration, invasion, proliferation, and growth of xenograft and HeLa cells. hsa_circ_0031288 had a regulatory effect on hsa-miR-139-3p, and hsa-miR-139-3p targeted the 3' untranslated region of Bcl-6. Reducing hsa_circ_0031288 expression promoted hsa-miR-139-3p expression, while overexpressing miR-139-3p inhibited the transcription of Bcl-6. In the cervical cancer HeLa cell line, the hsa_circ_0031288/hsa-miR-139-3p/Bcl-6 regulatory axis affects cell migration and proliferation, and its mechanism may involve hsa_circ_0031288 acting as a sponge for hsa-miR-139-3p, thereby relieving the transcriptional inhibition of Bcl-6. This suggests an approach for elucidating the pathogenesis of cervical cancer while offering new intervention targets for cervical cancer treatment.

Curcumin regulates hepatoma cell proliferation and apoptosis through the Notch signaling pathway.

Curcumin has become a compound of interest for its antioxidant and anti-neoplastic properties. This study sought to determine the effect of curcumin administration on cell proliferation and apoptosis in hepatoma cells. SMMC-7721 hepatoma cells were treated with 10, 30, or 90 µM curcumin solution, with DMEM alone (negative control), or with 20 mg/L fluorouracil (positive control). MTT colorimetry detected significant differences in the rates of cell proliferation inhibition following curcumin treatment, with increasing inhibition accompanying increasing doses of curcumin (P < 0.05), compared to the negative control. Similarly, flow cytometry revealed significant differences in the numbers of apoptotic cells following curcumin treatment: increasing doses of curcumin produced increases in the numbers of apoptotic cells (P < 0.05). To determine whether curcumin exerts these effects by altering the Notch signaling pathway, a phenomenon reported for other cancers, relative expression of Notch1 mRNA and protein were determined in curcumin-treated cells. Both mRNA and protein expression of Notch1 decreased with increasing curcumin dose (P < 0.05). Thus, curcumin appears to inhibit proliferation and induce apoptosis in hepatoma cells by altering the Notch signaling pathway.