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Typical 2-Cys Peroxiredoxins as a Defense Mechanism against Metal-Induced Oxidative Stress in the Solitary Ascidian Ciona robusta - PubMed

  • ️Fri Jan 01 2021

Typical 2-Cys Peroxiredoxins as a Defense Mechanism against Metal-Induced Oxidative Stress in the Solitary Ascidian Ciona robusta

Laura Drago et al. Antioxidants (Basel). 2021.

Abstract

Typical 2-Cys peroxiredoxins (2-Cys Prdxs) are proteins with antioxidant properties belonging to the thioredoxin peroxidase family. With their peroxidase activity, they contribute to the homeostatic control of reactive oxygen species (ROS) and, therefore, participate in various physiological functions, such as cell proliferation, differentiation, and apoptosis. Although Prdxs have been shown to be potential biomarkers for monitoring aquatic environments, minimal scientific attention has been devoted to describing their molecular architecture and function in marine invertebrates. Our study aims to clarify the protective role against stress induced by exposure to metals (Cu, Zn, and Cd) of three Prdxs (Prdx2, Prdx3, and Prdx4) in the solitary ascidian Ciona robusta, an invertebrate chordate. Here, we report a detailed pre- and post-translational regulation of the three Prdx isoforms. Data on intestinal mRNA expression, provided by qRT-PCR analyses, show a generalized increase for Prdx2, -3, and -4, which is correlated to metal accumulation. Furthermore, the increase in tissue enzyme activity observed after Zn exposure is slower than that observed with Cu and Cd. The obtained results increase our knowledge of the evolution of anti-stress proteins in invertebrates and emphasize the importance of the synthesis of Prdxs as an efficient way to face adverse environmental conditions.

Keywords: Ciona robusta; antioxidant enzymes; metals; tunicate; typical 2-Cys peroxiredoxins.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1

Phylogenetic relationships among Prdxs of various organisms reconstructed on the basis of the cDNA coding region sequences and using both Bayesian interference (BI) and maximum likelihood (ML) methods. Bayesian posterior probability (first number) and bootstrap values higher (and equal to) than 50% are indicated on each node, respectively. The scale for branch length (3.0 substitution/site) is shown below the tree. Asterisks indicate the C. robusta Prdxs.

Figure 2
Figure 2

Relative expression levels (fold induction, f. i.) of Cr-Prdx2 (a-c), Cr-Prdx3 (d-f) and Cr-Prdx3 (g-i), during Cu, Zn and Cd exposure. Values are indicated as mean ± SD. Transcription levels were normalized with respect to controls (dashed line). Asterisks: significant differences with respect to controls (*** p < 0.001, ** p < 0.01, * p < 0.05). Different letters correspond to significant statistical differences (p < 0.05) among different treatment times (Duncan’s test).

Figure 3
Figure 3

2-Cys Prdx activity levels in the intestine of C. robusta during metal exposure (Cu, Zn and Cd). Values are indicated as mean ± SD. Protein levels were normalized with respect to controls (dashed line). Asterisks: significant differences with respect to controls (*** p < 0.001). Different letters with the same index correspond to significant statistical differences (p < 0.05) among different treatment times (Duncan’s test).

Figure 4
Figure 4

(a) Cu, (b) Zn and (c) Cd accumulation in the intestine of C. robusta (µg metal/mg total protein). Values are indicated as mean ± SD. Asterisks: significant differences with respect to controls (*** p < 0.001, ** p < 0.01). Different letters with the same index correspond to significant statistical differences (p < 0.05) among different treatment times (Duncan’s test).

Figure 5
Figure 5

ISH with anti-sense riboprobes for (a) cr-Prdx2, (b) cr-Prdx3 and (c,d) cr-Prdx4, and sense riboprobe, for (e) cr-Prdx4 as reference, on hemocyte monolayers from three-day Cd treatment. Brown color: riboprobe staining. Arrowheads: labeled hemocytes. Scale bar: 10 µm.

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