Identification of a potential tissue-specific biomarker cathepsin L-like gene from the planarian Dugesia japonica: Molecular cloning, characterization, and expression in response to heavy metal exposure

Integrated transcriptomics and metabolomics reveal the toxic mechanisms of mercury exposure to an endangered species Tachypleus tridentatus

Mercury (Hg) pollution is threatening the health of endangered Tachypleus tridentatus whereas the toxic mechanism is still unclear. This study combined transcriptomic and metabolomics technology to reveal the toxic mechanisms of mercury (Hg 2+, 0.025 mg/L) exposing to T. tridentatus larvae for 15 days. Mercury induced cellular toxicity and cardiovascular dysfunction by dysregulating the genes related to endocrine system, such as polyubiquitin-A, cathepsin B, atrial natriuretic peptide, etc. Mercury induced lipid metabolic disorder with the abnormal increase of lysoPC, leukotriene D4, and prostaglandin E2. Cytochrome P450 pathway was activated to produce anti-inflammatory substances to reconstruct the homeostasis. Mercury also inhibited arginine generation, which may affect the development of T. tridentatus by disrupting the crucial signaling pathway. The mercury methylation caused enhancement of S-adenosylmethionine to meet the need of methyl donor. The mechanisms described in present study provide new insight into the risk assessment of mercury exposure to T. tridentatus.

Identification of co-chaperone Cdc37 in Penaeus monodon: coordination with Hsp90 can reduce cadmium stress-induced lipid peroxidation

Cell division cycle 37 (Cdc37) is an important cytoplasmic phosphoprotein, which usually functions as a complex with heat shock protein 90 (Hsp90), to effectively reduce the damage caused by heavy metals, such as cadmium (Cd), in aquatic animals. The high toxicity of Cd in aquatic systems generally has a deleterious effect on healthy farming of shrimps. In the present study, a novel Cdc37 gene from Penaeus monodon was identified and designated as PmCdc37. Following exposure to Cd stress, the expression levels of PmCdc37 were upregulated at the transcriptional level in both the hepatopancreas and hemolymph. RNA interference and recombinant protein injection experiments were carried out to determine the function of PmCdc37 in P. monodon following Cd exposure. To clarify the correlations between PmCdc37 and PmHsp90, the respective recombinant proteins were expressed in vitro, and the ATPase activity of PmHsp90, with or without PmCdc37, was assessed. Moreover, a pull-down assay was conducted to detect the correlation between PmCdc37 and PmHsp90. After analyzing the expression patterns of PmHsp90 following Cd challenge, whether PmHsp90 can promote the ability of PmCdc37 to resist Cd stress or not was investigated. The results showed that formation of a PmHsp90/PmCdc37 complex protected shrimp against Cd stress-induced damage. Moreover, we also confirmed that PmSOD is involved in Cd stress, and that the PmHsp90/PmCdc37 complex can regulate SOD enzymatic activity. PmSOD was involved in decreasing the MDA content in shrimp hemolymph caused by Cd stress. We concluded that during exposure to Cd, the PmHsp90/PmCdc37 complex increases SOD enzyme activity, and in turn decreases the MDA content, thereby protecting shrimp against the damage caused by Cd stress. The present studies contribute to understanding the molecular mechanism underlying resistance to Cd stress in shrimp.

Antioxidant responses and lipid peroxidation can be used as sensitive indicators for the heavy metals risk assessment of the Wei River: a case study of planarian Dugesia Japonica

PURPOSE

To verify antioxidant responses and lipid peroxidation can be used as sensitive indicators for the risk assessment of the Wei River.

MATERIAL AND METHODS

We investigate the effects of the Wei River on oxidative stress of planarian Dugesia japonica by antioxidant parameters, and use ICP-MS to measure the heavy metals in the Wei River. Then, we observe the effects of three common heavy metal ions (Cr³⁺, Hg²⁺, Pb²⁺) on the regeneration of planarians on morphological and histological levels.

RESULTS

The significant changes of antioxidant parameters (SOD, CAT, GPx, GST, T-AOC) and MDA content indicate that oxidative stress is induced after the Wei River exposure on planarians, though the heavy metals in the Wei River are not exceeding the standards. Then, the regeneration of planarians shows different degree of morphological and histological damage after Cr³⁺, Hg²⁺ and Pb²⁺ exposure.

CONCLUSION

We speculate that the heavy metal ions in the Wei River, especially Cr³⁺, Hg²⁺ and Pb²⁺, may give rise to oxidative damage on planarians. These findings illustrate that planarian can serve as an indicator of aquatic ecosystem pollution, antioxidant responses and lipid peroxidation can also be used as sensitive indicators and provide an excellent opportunity for urban river risk assessment.

The regulation of rapamycin in planarian Dugesia japonica Ichikawa & Kawakatsu, 1964 regeneration according to TOR signaling pathway

The freshwater planarian mostly lives in the upper reaches of springs and rivers. Generally, it is realized as a suitable warning indicator of environmental toxicants. The freshwater planarian Dugesia japonica has a powerful regenerative capability and can regenerate a new individual including a complete central nervous system in one week. Rapamycin is an inhibitor of mammalian TORC1 (target of rapamycin complex-1) and used in the treatment of some diseases like cancer, cardiovascular and neurological diseases. However, the roles of rapamycin in the regulation of planarian regeneration remain to be elucidated. In present study, freshwater planarians D. japonica were firstly treated with 1 μM rapamycin for 18 h exposures and the expression patterns of Djtor was analyzed by the whole-mount in situ hybridization (WISH). Our results indicated rapamycin could strongly inhibit Djtor expression in planarian D. japonica and cause asymmetric blastemas and neuronal defects in planarians. Furthermore, knockdown of Djtor gene in planarians using RNA interference resulted in the suppression of downstream autophagy genes. These findings suggested that rapamycin might regulate freshwater planarian regeneration via Djtor signaling pathway.