Fisetin Protects DNA Against Oxidative Damage and Its Possible Mechanism.

PURPOSE: The paper tries to assess the protective effect of fisetin against •OH-induced DNA damage, then to investigate the possible mechanism. METHODS: The protective effect was evaluated based on the content of malondialdehyde (MDA). The possible mechanism was analyzed using various antioxidant methods in vitro, including •OH scavenging (deoxyribose degradation), •O2 (-) scavenging (pyrogallol autoxidation), DPPH• scavenging, ABTS•(+) scavenging, and Cu(2+)-reducing power assays. RESULTS: Fisetin increased dose-dependently its protective percentages against •OH-induced DNA damage (IC50 value =1535.00±29.60 µM). It also increased its radical-scavenging percentages in a dose-dependent manner in various antioxidants assays. Its IC50 values in •OH scavenging, •O2(-) scavenging, DPPH• scavenging, ABTS•(+) scavenging, and Cu(2+)-reducing power assays, were 47.41±4.50 µM, 34.05±0.87 µM, 9.69±0.53 µM, 2.43±0.14 µM, and 1.49±0.16 µM, respectively. CONCLUSION: Fisetin can effectively protect DNA against •OH-induced oxidative damage possibly via reactive oxygen species (ROS) scavenging approach, which is assumed to be hydrogen atom (H•) and/or single electron (e) donation (HAT/SET) pathways. In the HAT pathway, the 3',4'-dihydroxyl moiety in B ring of fisetin is thought to play an important role, because it can be ultimately oxidized to a stable ortho-benzoquinone form.

Zeranol stimulates proliferation and aromatase activation in human breast preadipocytes.

Aromatase is a crucial enzyme for the biosynthesis of estrogens and is involved in the process of breast carcinogenesis. Concerns have been raised regarding the effects of environmental estrogens as potential regulators of aromatase expression in human breast cells. Zeranol is a non­steroidal agent with potent estrogenic activity, which is widely used as a growth promoter for cattle in certain countries. The present study hypothesized that aromatase expression and activity may be elevated by low dose zeranol exposure, providing a source of estrogens that may stimulate cell proliferation. In the present study, primary cultured human breast preadipocytes were used as an in vitro model. The effects of zeranol on cell proliferation were measured using the MTS assay, aromatase expression levels were determined by immunocytochemical staining and reverse transcription­polymerase chain reaction, and aromatase enzyme activity and estrogen production were analyzed using corresponding assay kits. The results demonstrated that low dose zeranol (2­50 nM) was able to significantly promote cell proliferation, aromatase mRNA expression, aromatase activity and estrogen production in primary cultured human breast preadipocytes, thus suggesting that zeranol may act as an aromatase activator. The findings of the present study suggest that zeranol promotes breast cancer cell growth by stimulating aromatase activation and increasing estrogen biosynthesis in adipose tissue.

Neutralizing effect of hemolymph from the shore crab, Thalamita crenata, on paralytic shellfish toxins.

Several species of crabs are resistant to paralytic shellfish toxins (PSTs) and/or pufferfish toxin, tetrodotoxin, regardless of toxification by the toxins. The shore crab Thalamita crenata, which inhabits Leizhou Peninsula, China, is tolerant to PST toxicity, and the hemolymph has neutralizing effects against the lethal activity of PST. In the present study, we investigated the PST neutralizing factors in the hemolymph from T. crenata and successfully separated PST-binding proteins by PST-ligand affinity chromatography. The neutralization factors, obtained in the fraction with a molecular weight over 10 kDa by ultrafiltration, were susceptible to proteases such as alcalase, animal complex proteases, pancreatin, and papain. The PST-binding protein had high dose-dependent neutralization effects on PST toxicity. The PST-binding activity of the protein was stable at 25 °C and then decreased with an increase in temperature; heating at 65 °C for 60 min eliminated the initial activity by two-thirds. The PST-binding activity was strongly inhibited in the presence of Mg(2+) and Ca(2+), but not Na(+) and K(+). The PST-binding capability of the protein differed among PST components in descending order of neosaxitoxin, gonyautoxins 1 and 4, saxitoxin, and gonyautoxins 2 and 3, suggesting a structure-activity relationship in PST binding.

A novel method for preparing complete antigens of gonyautoxin 2,3 and their feature of immunogenicity.

In this paper, a novel method was proposed to prepare artificial antigens of gonyaulax parlaytic shellfish toxin 2 and 3 (GTX2,3). An intermediate GTX2,3-aldehyde was first synthesized by activating the NH2 group of the 2nd and 8th amino acid residues with three different aldehydes and two artificial complete antigens GTX2,3-aldehyde-bovine serum albumin (BSA) and GTX2,3-aldehyde- keyhole limpet hemocyanin (KLH) were then prepared by cross-linking the intermediate with BSA or KLH. The successful preparation of the two complete antigens was confirmed by UV spectral scanning, HPLC, production of antibodies with titer of 1.28 × 104 from mice immunized with the two complete antigens, indirect ELISA and Western-blot. In conclusion, the synthesized complete antigens have strong immunogenicity, which provides a solid foundation for preparing GTX2,3 monoclonal antibody and rapid detection kit.

Screening for toxicity and resistance to paralytic shellfish toxin of shore crabs inhabiting at Leizhou peninsula, China.

The situation of the environment contaminated by paralytic shellfish toxin (PST) in Leizhou peninsula, China, has attracted more attention since seafood poisoning occurred occasionally. In this study, we examined the toxicities of shore crab Leptodius exaratus, Thalamita crenata and Metopograpsus latifrons by mouse assay, resistance to PST by lethal test injection with PST, and discussed the toxicity neutralization of their hemolymph. The results showed 12% of shore crabs possessed toxicity of 4.3-4.4 MU/g. The 100% lethal dose of PST for M. latifrons was about 2 times of those for the other two crab species. The hemolymphs of the crabs were all able to neutralize PST and tetrodotoxin (TTX) toxicity in different extent. The above results indicate shore crabs at this area are exposed to an environment potentially contaminated with PST and/or TTX, and the toxicity neutralizing efficacy of their hemolymph directly affects their resistance to the toxins.