Inhibition of Diarrheal Shellfish Toxins Accumulation in the Mussel Perna viridis by Curcumin and Underlying Mechanisms

Abstract

Diarrheal shellfish toxins (DSTs) are among the most widely distributed phytotoxins, and are associated with diarrheal shellfish poisoning (DSP) events in human beings all over the world. Therefore, it is urgent and necessary to identify an effective method for toxin removal in bivalves. In this paper, we found that curcumin (CUR), a phytopolylphenol pigment, can inhibit the accumulation of DSTs (okadaic acid-eq) in the digestive gland of Perna viridis after Prorocentrum lima exposure. qPCR results demonstrated that CUR inhibited the induction of DSTs on the aryl hydrocarbon receptor (AhR), hormone receptor 96 (HR96) and CYP3A4 mRNA, indicating that the CUR-induced reduction in DSTs may be correlated with the inhibition of transcriptional induction of AhR, HR96 and CYP3A4. The histological examination showed that P. lima cells caused severe damage to the digestive gland of P. viridis, and the addition of curcumin effectively alleviated the damage induced by P. lima. In conclusion, our findings provide a potential method for the effective removal of toxins from DST-contaminated shellfish.

Keywords: AhR; CUR; CYP3A4; DSTs; HR96; Perna viridis.

Figure 1

DST content in the digestive gland of the P. lima-exposed mussels with or without curcumin. Significant differences compared to control (with 0 μmol L⁻¹ CUR) are represented by asterisks (t-test, * p < 0.05). Data are presented as mean ± SD (n = 3).

Figure 2

DST content in the digestive gland and gills of the P. lima-exposed mussels and in culture medium at different times after the addition of CUR (20 μmol L⁻¹). Control, T. subcordiformis (1 × 10⁷ cells/L); CUR, T. subcordiformis (1 × 10⁷ cells/L) + CUR (20 μmol L⁻¹); P. lima, T. subcordiformis (1 × 10⁷ cells/L) + P. lima (2 × 10⁶ cells/L); P. lima + CUR, T. subcordiformis (1 × 10⁷ cells/L) + P. lima (2 × 10⁶ cells/L) + CUR (20 μmol L⁻¹). Data are presented as mean ± SD (n = 3). Bars of the respective treatments followed by the same letters indicates that the difference is not significant at p < 0.05 (Fisher′s protected multiple comparisons LSD test).

Figure 3

Histological sections of digestive glands of Perna viridis at 12 h and 48 h (HE staining, ×400). (A) Control, T. subcordiformis (1 × 10⁷ cells/L); (B) CUR, T. subcordiformis (1 × 10⁷ cells/L) + CUR (20 μmol L⁻¹); (C) P. lima, T. subcordiformis (1 × 10⁷ cells/L) + P. lima (2 × 10⁶ cells/L); (D) P. lima + CUR, T. subcordiformis (1 × 10⁷ cells/L) + P. lima (2 × 10⁶ cells/L) + CUR (20 μmol L⁻¹); dt, alimentary canal; ct, connective tissue. Marker 1, severe atrophy of epithelial cells; Marker 2, disintegration of epithelial cells, destruction of digestive ducts, and malformation of digestive gland diverticulum.

Figure 4

Expression levels of genes associated with the metabolism of xenobiotic compounds in the digestive gland of the P. lima-exposed mussels as shown by qPCR. Control, T. subcordiformis (1 × 10⁷ cells/L); P. lima, T. subcordiformis (1 × 10⁷ cells/L) + P. lima (2 × 10⁶ cells/L); CUR, T. subcordiformis (1 × 10⁷ cells/L) + CUR (20 μmol L⁻¹); P. lima + CUR, T. subcordiformis (1 × 10⁷ cells/L) + P. lima (2 × 10⁶ cells/L) + CUR (20 μmol L⁻¹). Data presented as mean ± SD (n = 3). Bars of the respective treatments followed by the same letters indicates that the difference is not significant at p < 0.05 (Fisher′s protected multiple comparisons LSD test).