ROS production in homogenate from the body wall of sea cucumber Stichopus japonicus under UVA irradiation: ESR spin-trapping study.

Sea cucumber Stichopus japonicus (S. japonicus) shows a strong ability of autolysis, which leads to severe deterioration in sea cucumber quality during processing and storage. In this study, to further characterize the mechanism of sea cucumber autolysis, hydroxyl radical production induced by ultraviolet A (UVA) irradiation was investigated. Homogenate from the body wall of S. japonicas was prepared and subjected to UVA irradiation at room temperature. Electron Spin Resonance (ESR) spectra of the treated samples were subsequently recorded. The results showed that hydroxyl radicals (OH) became more abundant while the time of UVA treatment and the homogenate concentration were increased. Addition of superoxide dismutase (SOD), catalase, EDTA, desferal, NaN3 and D2O to the homogenate samples led to different degrees of inhibition on OH production. Metal cations and pH also showed different effects on OH production. These results indicated that OH was produced in the homogenate with a possible pathway as follows: O2(-) → H2O2 → OH, suggesting that OH might be a critical factor in UVA-induced S. japonicus autolysis.

Analysis of Apoptosis in Ultraviolet-Induced Sea Cucumber (Stichopus japonicus) Melting Using Terminal Deoxynucleotidyl-Transferase-Mediated dUTP Nick End-Labeling Assay and Cleaved Caspase-3 Immunohistochemistry.

The sea cucumber body wall melting phenomenon occurs under certain circumstances, and the mechanism of this phenomenon remains unclear. This study investigated the apoptosis in the ultraviolet (UV)-induced sea cucumber melting phenomenon. Fresh sea cucumbers (Stichopus japonicus) were exposed to UV radiation for half an hour at an intensity of 0.056 mW/cm(2) and then held at room temperature for melting development. The samples were histologically processed into formalin-fixed paraffin-embedded tissues. The apoptosis of samples was analyzed with the terminal deoxynucleotidyl-transferase-mediated dUTP nick end-labeling (TUNEL) assay and cleaved caspase-3 immunohistochemistry. The emergence of TUNEL-positive cells speeds up between 0.5 and 2 h after UV irradiation. Cleaved caspase-3 positive cells were obviously detected in sample tissues immediately after the UV irradiation. These results demonstrated that sea cucumber melting induced by UV irradiation was triggered by the activation of caspase-3 followed by DNA fragmentation in sea cucumber tissue, which was attributed to apoptosis but was not a consequence of autolysis activity.

Difference in thermotolerance between green and red color variants of the Japanese sea cucumber, Apostichopus japonicus Selenka: Hsp70 and heat-hardening effect.

We studied thermal tolerance limits, heat-hardening, and Hsp70 to elucidate the difference in thermotolerance between two color variants of the sea cucumber Apostichopus japonicus. Green and Red variants occupy different habitats and have different aestivation responses to high temperature in summer. In the absence of heat-hardening, the variants showed no difference in the temperature at which 50% of the individuals died: Green, 31.49 degrees C; Red, 31.39 degrees C. However, Green specimens acquired higher thermotolerance than Red after a prior sublethal heat exposure. After 72 h of recovery from a heat-hardening treatment (30 degrees C for 2 h), the survival of Green variants was more than 50% and that of Red was less than 5% when they were treated at 33 degrees C for 2 h. Levels of mRNA and protein for Hsp70 were significantly higher in Green than Red after the heat shock of 30 degrees C, and the stability of hsp70 mRNA of Green was significantly higher than that of Red. Our findings suggest that within the same species, different variants that have similar thermal limits in the absence of heat-hardening can acquire different thermotolerances after a prior sublethal heat shock. The difference in induced thermotolerance between Green and Red is closely related to the expression pattern of Hsp70, which was partly governed by the stability of hsp70 mRNA.