Transcriptome and biochemical analyses of rainbow trout (Oncorhynchus mykiss) RTG-2 gonadal cells in response to BDE-47 stress indicates effects on cell proliferation

Dietary exposure to 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) induces oxidative damage promoting cell apoptosis primarily via mitochondrial pathway in the hepatopancreas of carp, Cyprinus carpio

To investigate the mechanisms of BDE-47 on hepatotoxicity in fish, this study examined the effects of dietary exposure to BDE-47 (40 and 4000 ng/g) on carp for 42 days. The results showed that BDE-47 significantly increased carp's condition factor and hepatosomatic index. Pathological results revealed unclear hepatic cord structure, hepatocytes swelling, cellular vacuolization, and inflammatory cell infiltration in the hepatopancreas of carp. Further investigation showed that ROS levels significantly increased on days 7, 14, and 42. Moreover, the activities of antioxidant enzymes SOD, GSH, CAT, and GST increased significantly from 1 to 7 days, and the transcription levels of antioxidant enzymes CAT, Cu-Zn SOD, Mn-SOD, GST, and GPX, and antioxidant pathway genes Keap1, Nrf2, and HO-1 changed significantly at multiple time-points during the 42 days. The results of apoptosis pathway genes showed that the mitochondrial pathway genes Bax, Casp3, and Casp9 were significantly upregulated and Bcl2 was significantly downregulated, while the transcription levels of FADD and PERK were significantly enhanced. These results indicate that BDE-47 induced oxidative damage in hepatopancreas, then it promoted cell apoptosis mainly through the mitochondrial pathway. This study provides a foundation for analyzing the mechanism of hepatotoxicity induced by BDE-47 on fish.

BDE-47 Induces Immunotoxicity in RAW264.7 Macrophages through the Reactive Oxygen Species-Mediated Mitochondrial Apoptotic Pathway

Polybrominated diphenyl ethers (PBDEs) are classic and emerging pollutants that are potentially harmful to the human immune system. Research on their immunotoxicity and mechanisms suggests that they play an important role in the resulting pernicious effects of PBDEs. 2,2',4,4'-Tetrabrominated biphenyl ether (BDE-47) is the most biotoxic PBDE congener, and, in this study, we evaluated its toxicity toward RAW264.7 cells of mouse macrophages. The results show that exposure to BDE-47 led to a significant decrease in cell viability and a prominent increase in apoptosis. A decrease in mitochondrial membrane potential (MMP) and an increase in cytochrome C release and caspase cascade activation thus demonstrate that cell apoptosis induced by BDE-47 occurs via the mitochondrial pathway. In addition, BDE-47 inhibits phagocytosis in RAW264.7 cells, changes the related immune factor index, and causes immune function damage. Furthermore, we discovered a significant increase in the level of cellular reactive oxygen species (ROS), and the regulation of genes linked to oxidative stress was also demonstrated using transcriptome sequencing. The degree of apoptosis and immune function impairment caused by BDE-47 could be reversed after treatment with the antioxidant NAC and, conversely, exacerbated by treatment with the ROS-inducer BSO. These findings indicate that oxidative damage caused by BDE-47 is a critical event that leads to mitochondrial apoptosis in RAW264.7 macrophages, ultimately resulting in the suppression of immune function.

Cyt-C Mediated Mitochondrial Pathway Plays an Important Role in Oocyte Apoptosis in Ricefield Eel (Monopterus albus)

Apoptosis plays a key role in the effective removal of excessive and defective germ cells, which is essential for sequential hermaphroditism and sex change in vertebrates. The ricefield eel, Monopterus albus is a protogynous hermaphroditic fish that undergoes a sequential sex change from female to male. Previous studies have demonstrated that apoptosis is involved in sex change in M. albus. However, the apoptotic signaling pathway is unclear. In the current study, we explored the underlying mechanism of apoptosis during gonadal development and focused on the role of the mitochondrial apoptosis signaling pathway in sex change in M. albus. Flow cytometry was performed to detect apoptosis in gonads at five sexual stages and ovary tissues exposed to hydrogen peroxide (H2O2) in vitro. Then the expression patterns of key genes and proteins in the mitochondrial pathway, death receptor pathway and endoplasmic reticulum (ER) pathway were examined. The results showed that the apoptosis rate was significantly increased in the early intersexual stage and then decreased with the natural sex change from female to male. Quantitative real-time PCR revealed that bax, tnfr1, and calpain were mainly expressed in the five stages. ELISA demonstrated that the relative content of cytochrome-c (cyt-c) in the mitochondrial pathway was significantly higher than that of caspase8 and caspase12, with a peak in the early intersexual stage, while the levels of caspase8 and caspase12 peaked in the late intersexual stage. Interestingly, the Pearson’s coefficient between cyt-c and the apoptosis rate was 0.705, which suggests that these factors are closely related during the gonadal development of M. albus. Furthermore, the cyt-c signal was found to be increased in the intersexual stage by immunohistochemistry. After incubation with H2O2, the mRNA expression of mitochondrial pathway molecules such as bax, apaf-1, and caspase3 increased in ovary tissues. In conclusion, the present results suggest that the mitochondrial apoptotic pathway may play a more important role than the other apoptotic pathways in sex change in M. albus.

Guizhi Fuling pill attenuates liver fibrosis in vitro and in vivo via inhibiting TGF-β1/Smad2/3 and activating IFN-γ/Smad7 signaling pathways

Liver fibrosis resulting from chronic liver injuries (CLI) is a common health problem globally. Guizhi Fuling pill (GZFL), a modern preparation from traditional Chinese medicine, exhibited anti-dysmenorrhea, anti-inflammatory, and immune-regulative effects. However, the effect of GZFL on liver fibrosis remains unknown. In this research, LX-2 cells were stimulated with acetaldehyde for mimicking liver fibrosis progression in vitro. In addition, carbon tetrachloride (CCl₄)-induced mouse model of liver fibrosis was established as well. The data revealed GZFL obviously suppressed the proliferation and triggered the apoptosis of acetaldehyde-stimulated LX-2 cells. In addition, GZFL prevented acetaldehyde-induced activation of LX-2 cells via downregulation of TGF-β1, p-Smad2, p-Smad3, CUGBP1, and upregulation of p-STAT1 and Smad7. Meanwhile, GZFL significantly alleviated CCl₄‑induced liver fibrosis, as evidenced by the decrease of ALT and AST levels. Moreover, GZFL downregulated the expressions of TGF-β1, p-Smad2, p-Smad3, and CUGBP1 in CCl₄-treated mice. Furthermore, GZFL remarkably elevated the levels of IFN-γ, p-STAT1, and Smad7 in CCl₄-treated mice. To sum up, GZFL was able to inhibit liver fibrosis in vitro and in vivo through suppressing TGF-β1/Smad2/3-CUGBP1 signaling and activating IFN-γ/STAT1/Smad7 signaling. Thus, GZFL might have a potential to act as a therapeutic agent for anti-fibrotic therapy.