Min Pang

Yessotoxin induces apoptosis in HL7702 human liver cells

The marine toxin yessotoxin (YTX) is found in numerous aquatic environments and poses a potential threat to the shellfish industry and to public health. We analyzed the toxicity of YTX on HL7702 human liver cells using optical microscopy, Hoechst 33342 chromatin staining, DNA gel electrophoresis, rhodamine 123 staining and calcium-sensitive laser scanning confocal microscopy. The results demonstrated that YTX induced the usual hallmarks of apoptosis, including chromatin condensation, DNA laddering, activity of caspase-3 deregulation and loss of mitochondrial membrane potential. Furthermore, YTX caused cytosolic calcium levels to increase in HL7702 cells. YTX may cause liver damage through hepatocyte apoptosis.

Characterization of apoptotic changes induced by yessotoxin in the Bel7402 human hepatoma cell line.

The apoptotic effects of yessotoxin (YTX) on Bel7402 human hepatoma cells have been evaluated by the combination of several methods, including optical microscopy, Hoechst 33342 staining and DNA gel electrophoresis. Rhodamine 123 staining has also been used to investigate changes in mitochondrial transmembrane potential. The results indicated that YTX has negative effects on human liver cells and induces apoptosis. Furthermore, changes in calcium concentrations were analyzed using the fluorescence probe Fluo-3 AM. The results showed that intracellular calcium concentrations increased after treatment with YTX.

Comparative study of the hemolytic and cytotoxic activities of nematocyst venoms from the jellyfish Cyanea nozakii Kishinouye and Nemopilema nomurai Kishinouye

Two species of jellyfish, Cyanea nozakii Kishinouye and Nemopilema nomurai Kishinouye, have occurred offcoastal areas of the northeastern China Sea, Yellow Sea, and Bohai Sea in recent years. They influence marine ecosystem safety and fishery production, and also pose a risk to human health. The current study examined the hemolytic and cytotoxic activities of crude venoms extracted from the nematocysts of C. nozakii and N. nomurai. The results showed that there were more nematocysts on tentacles from C. nozakii than on tentacles of the same length from N. nomurai. The protein concentration per nematocyst extracted from N. nomurai was higher than that from C. nozakii. Both nematocyst venoms showed dose- and timedependent hemolytic activity on erythrocytes from chicken, pigeon, and sheep, with sheep erythrocytes being the most sensitive, with EC50 values of 69.69 and 63.62 μg/mL over a 30-min exposure with N. nomurai and C. nozakii nematocyst venoms, respectively. A cytotoxic assay of both jellyfish venoms on A431 human epidermal carcinoma cells resulted in IC50 values of 68.6 and 40.9 μg/mL after 24-h incubation, respectively, with venom from C. nozakii showing stronger cytotoxic activity than that from N. nomurai. The results of current study indicate that nematocyst venom from C. nozakii had stronger hemolytic and cytotoxic activities than that from N. nomurai and, thus, C. nozakii might be more harmful to the health of humans and other species than are N. nomurai when they appear in coastal waters.

Effect of CO2 on growth and toxicity of Alexandrium tamarense from the East China Sea, a major producer of paralytic shellfish toxins

In recent decades, the frequency and intensity of harmful algal blooms (HABs), as well as a profusion of toxic phytoplankton species, have significantly increased in coastal regions of China. Researchers attribute this to environmental changes such as rising atmospheric CO2 levels. Such addition of carbon into the ocean ecosystem can lead to increased growth, enhanced metabolism, and altered toxicity of toxic phytoplankton communities resulting in serious human health concerns. In this study, the effects of elevated partial pressure of CO2 (pCO2) on the growth and toxicity of a strain of Alexandrium tamarense (ATDH) widespread in the East and South China Seas were investigated. Results of these studies showed a higher specific growth rate (0.31±0.05day-1) when exposed to 1000μatm CO2, (experimental), with a corresponding density of (2.02±0.19)×107cellsL-1, that was significantly larger than cells under 395μatm CO2(control). These data also revealed that elevated pCO2 primarily affected the photosynthetic properties of cells in the exponential growth phase. Interestingly, measurement of the total toxin content per cell was reduced by half under elevated CO2 conditions. The following individual toxins were measured in this study: C1, C2, GTX1, GTX2, GTX3, GTX4, GTX5, STX, dcGTX2, dcGTX3, and dcSTX. Cells grown in 1000μatm CO2 showed an overall decrease in the cellular concentrations of C1, C2, GTX2, GTX3, GTX5, STX, dcGTX2, dcGTX3, and dcSTX, but an increase in GTX1 and GTX4. Total cellular toxicity per cell was measured revealing an increase of nearly 60% toxicity in the presence of elevated CO2 compared to controls. This unusual result was attributed to a significant increase in the cellular concentrations of the more toxic derivatives, GTX1 and GTX4.Taken together; these findings indicate that the A. tamarense strain ATDH isolated from the East China Sea significantly increased in growth and cellular toxicity under elevated pCO2 levels. These data may provide vital information regarding future HABs and the corresponding harmful effects as a result of increasing atmospheric CO2.