Chronic Exposure to Water of Lake Qaroun Induced Metal-Related Testicular Damage and Endocrine Disruption in Male Fish

Protein expression patterns and metal metabolites in a protogynous hermaphrodite fish, the ricefield eel (Monopterus albus)

BACKGROUND

The ricefield eel Monopterus albus undergoes a natural sex change from female to male during its life cycle, and previous studies have shown the potential mechanisms of this transition at the transcriptional and protein levels. However, the changes in protein levels have not been fully explored, especially in the intersexual stage.

RESULTS

In the present study, the protein expression patterns in the gonadal tissues from five different periods, the ovary (OV), early intersexual stage gonad (IE), middle intersexual stage gonad (IM), late intersexual stage gonad (IL), and testis (TE), were determined by untargeted proteomics sequencing. A total of 5125 proteins and 394 differentially expressed proteins (DEPs) were detected in the gonadal tissues. Of the 394 DEPs, there were 136 between the OV and IE groups, 20 between the IM and IE groups, 179 between the IL and IM groups, and 59 between the TE and IL groups. Three candidate proteins, insulin-like growth factor 2 mRNA-binding protein 3 isoform X1 (Igf2bp3), triosephosphate isomerase (Tpi), and Cu-Zn superoxide dismutase isoform X1 [(Cu-Zn) Sod1], were validated by western blotting to verify the reliability of the data. Furthermore, metal metabolite-related proteins were enriched in the IL vs. IM groups and TE vs. IL groups, which had close relationships with sex change, including Cu2+-, Ca2+-, Zn2+- and Fe2+/Fe3+-related proteins. Analysis of the combined transcriptome data revealed consistent protein/mRNA expression trends for two metal metabolite-related proteins/genes [LOC109953912 and calcium Binding Protein 39 Like (cab39l)]. Notably, we detected significantly higher levels of Cu2+ during the sex change process, suggesting that Cu2+ is a male-related metal metabolite that may have an important function in male reproductive development.

CONCLUSIONS

In summary, we analyzed the protein profiles of ricefield eel gonadal tissues in five sexual stages (OV, IE, IM, IL, and TE) and verified the plausibility of the data. After preforming the functional enrichment of metal metabolite-related DEPs, we detected the contents of the metal metabolites Zn2+, Cu2+, Ca2+, and Fe2+/Fe3+ at these five stages and screened for (Cu-Zn) Sod1 and Mmp-9 as possible key proteins in the sex reversal process.

Long-Term Exposure to the Water of Wadi El-Rayan Lakes Induced Testicular Damage and Endocrine Disruption in Mugil cephalus

This study aimed to investigate the testicular function of Mugil cephalus that inhabit Wadi El-Rayan lakes. Testes of fish inhabiting the upper lake (site 2) and the lower lake (site 3) of Wadi El-Rayan showed significant decreases in gonadosomatic index, high accumulation levels of six metals, and eight organochlorine pesticide residues. Compared to reference fish, high percentages of histological alterations as testicular degeneration, germ cell reduction, testicular inflammation, vacuolization, and loss of tubular arrangement were observed in sites 2 and 3. Moreover, endocrine disruption signs were recorded based on the percentage of ovotestis appearance and the ovotestis severity index values. The maximum defective testicular antioxidant mechanisms were recorded in site 3 as indicated by sharp decreases in catalase, superoxide dismutase, glutathione reduced levels, and high thiobarbituric acid reactive substances. Finally, long-term exposure to Wadi El-Rayan water may impair the reproductive health of fish via testicular oxidative damage and endocrine disruption.

The effective adsorbent capacity of rice husk to iron and aluminum oxides nanoparticles using Oreochromis niloticus as a bioindicator: biochemical and oxidative stress biomarkers

Metal oxide nanoparticles (NPs) have different industrial applications so it is unavoidable that NPs products could find their way into aquatic habitats. Therefore, toxic NPs must be treated sufficiently to reach the standard values before their discharge into the aquatic ecosystems. Our study aimed to investigate the adsorptive capacity of rice husk to iron and aluminum oxides from water and reducing their potential toxic effects. Fish were classified into eight groups for 7 days: Fe₂O₃ NPs (10 mg/l)-exposed group; Al₂O₃ NPs (10 mg/l)-exposed group; combined group (same concentrations of Fe₂O₃ and Al₂O₃NPs), and control group (dechlorinated water). The other four groups were the same as the above groups but with 50 mg/l rice husk in each group. Compared with control groups, our results showed a significant (p < 0.05) increase in plasma total proteins, globulin, glucose, liver enzymes, and kidney function biomarkers (creatinine and uric acid). While the recorded albumin and total lipids were significantly decreased. The oxidative biomarkers in liver and gill tissues of NPs-exposed fish showed significant (p < 0.05) reduction in glutathione-reduced content and elevation in thiobarbituric acid reactive substances, glutathione peroxidase, catalase, and superoxide dismutase. Based on our results, Fe₂O₃ NPs were more toxic than Al₂O₃ NPs. The combined doses of both NPs showed more or less toxicity compared to single doses. Therefore, this point needs more studies to show the mode of interaction. Finally, rice husk was a good adsorber to both NPs as it could improve the biochemical and antioxidant status of the studied fish.