Developmental effects of exposure to ultraviolet B radiation on the freshwater prawn Macrobrachium olfersi: Mitochondria as a target of environmental UVB radiation.

In South America, increased UVB radiation has become an important environmental issue that is potentially threatening aquatic ecosystems. Considering that species exhibit different degrees of sensitivity to UVB radiation and that embryos are more sensitive than organisms at later life stages, the aim of this study was to characterize the effects of UVB radiation on subcellular compartments of embryos of the freshwater prawn Macrobrachium olfersi. This species lives and reproduces in clear and shallow waters, where UV radiation can fully penetrates. Embryos were irradiated with a UVB 6W lamp for 30min and examined after 1h, 12h, 24h and 48h of exposure. The irradiance of the UVB used simulates the UV radiation that embryos receive in the natural environment. The subcellular compartment most affected by the UVB radiation was the mitochondria, which exhibited a circular shape, a decrease in mitochondrial cristae, rupture of membranes and a morphology compatible with fission. These impairments were observed simultaneously with increased ROS production, just after 1h of UVB exposure. Thus, we investigated proteins related to mitochondrial fission (Drp-1) and fusion (Mfn-1), which are essential to cell maintenance. We found a significant increase in Drp-1 expression at all analyzed time-points and a significant decrease in Mfn-1 expression only after 24h of UVB exposure. Additionally, a decrease in embryonic cell viability was verified via the mitochondrial integrity assay. To conclude, we observed important mitochondrial dysfunctions against the environmental stress caused by UVB radiation. Moreover, the cellular responses found are critical and should not be disregarded, because they impact embryos that can potentially compromise the aquatic ecosystems.

Assessing testicular morphofunctionality under Roundup WG® herbicide exposure in zebrafish.

Glyphosate-based herbicides, like Roundup WG® (RWG) used for a range of crops, such as corn, soybean, coffee, sugarcane, rice, apple, and citrus, can reach aquatic ecosystems and impact non-target organisms like fish. Thus, the fish were exposed to three RWG concentrations plus one negative control, which represents the concentration allowed for inland Brazilian waters and concentrations found in surface water worldwide (0.0, 0.065, 0.65, and 6.5 mg a.i./L) for 7 and 15 days. Morphological analysis revealed significant alterations in the testicular structure, particularly in Sertoli cell extensions and cytoplasmic bridges between germ cells. Subcellular compartments also displayed alterations, including dilated mitochondria and the loss of electron density and autophagic vesicles. Gene transcript levels related to autophagy and steroidogenic regulation were upregulated in exposed fish. Germ cell quality was also affected, increasing ROS (reactive oxygen species) production and DNA fragmentation. The study highlighted the RWG reproductive toxicity, providing valuable insights into understanding the morphofunctional alterations in somatic and germ cells of Danio rerio. In conclusion, the environmental relevant concentrations used in this study were toxic to male somatic and germ cells, which raises a concern about the concentrations considered safe for human and animal use.

Ultraviolet-B radiation induces transcriptional modulation of components associated with the extracellular matrix in embryos of decapod Macrobrachium olfersii.

The extracellular matrix (ECM) is a non-cellular and three-dimensional structure, constituted by a macromolecular dynamic network that involves the cells in all animal tissues, including embryonic ones. Several studies with vertebrates and cell cultures have reported deleterious effects of ultraviolet-B (UVB) radiation on the components associated with the ECM. However, studies focusing on the UVB radiation effects on ECM components of crustaceans during embryonic development are very scarce. Thus, the aim of this study was to identify the coding sequences of components associated with the ECM and to evaluate the effect of UVB radiation on embryos of the ecologically-important decapod Macrobrachium olfersii. To evaluate the modulation of these ECM components during embryonic development, the transcript levels of Col4α1, Itgß, Lamα, Mmp1 and Timp in M. olfersii embryos were analyzed at early developmental stages (E1, E3 and E4), intermediate developmental stage (E7) and late developmental stages (E10 and E14). In addition, embryos at E7, which correspond to a landmark of crustacean development, were analyzed after 12 h of UVB exposure to verify UVB effects on the ECM components. The ECM component sequences were similar to other decapods, suggesting conservation of these genes among crustaceans. The results showed modulations of the ECM components of M. olfersii embryos that reflect the need for each component in the cellular mechanisms, necessary for normal embryonic development. After UVB exposure, embryos showed opacity of embryonic tissues and it was found the overexpression of Col4α1, Itgß, Mmp1 and Timp transcript levels (1.82-, 1.52-, 2.34- and 6.27-fold, respectively). These impairments can compromise important events for normal embryonic development, such as growth of optic lobes, caudal papilla, ramification of appendages and differentiation of organic systems. The results presented here, together with the effects on morphology, cell proliferation, differentiation, and apoptosis demonstrated previously, strengthen the knowledge of the complex impacts of UVB radiation on freshwater embryos. Nevertheless, our results encourage further investigations focusing on the assessment of UVB effects on different organisms in order to better understand the myriad of UVB effects on ECM components.

Effect of UVB radiation exposure in the expression of genes and proteins related to apoptosis in freshwater prawn embryos.

Our previous studies showed that embryos of the freshwater prawn Macrobrachium olfersii exposed to ultraviolet B (UVB) radiation exhibited DNA damage, excessive ROS production, mitochondrial dysfunction and increased hsp70 expression, which are able, independently or together, to induce apoptosis. Thus, we attempted to elucidate some key apoptosis-related genes (ARG) and apoptosis-related proteins (ARP) and their expression during different stages of embryonic development, as well as to characterize the chronology of ARG expression and ARP contents after UVB radiation insult. We demonstrate that p53, Bax and Caspase3 genes are active in the embryonic cells at early embryonic developmental stages, and that the Bcl2 gene is active from the mid-embryonic stage. After UVB radiation exposure, we found an increase in ARP such as p53 and Bak after 3h of exposure. Moreover, an increase in ARG transcript levels for p53, Bax, Bcl2 and Caspase3 was observed at 6h after UVB exposure. Then, after 12h of UVB radiation exposure, an increase in Caspase3 gene expression and protein was observed, concomitantly with an increased number of apoptotic cells. Our data reveal that ARG and ARP are developmentally regulated in embryonic cells of M. olfersii and that UVB radiation causes apoptosis after 12h of exposure. Overall, we demonstrate that embryonic cells of M. olfersii are able to active the cell machinery against environmental changes, such as increased incidence of UVB radiation in aquatic ecosystems.