Microcystin is one of the monocyclic heptapeptides produced primarily by microcystis aeruginosa. Recent studies suggest that microcystin can induce cell apoptosis, as well as oxidative stress and mitochondrial alteration. Studies also indicate that Bcl-2 family and p53 may play an important role in the apoptosis induced by microcystin.
Animals ; Apoptosis ; physiology ; Humans ; Microcystins ; toxicity ; Microcystis ; metabolism ; Proto-Oncogene Proteins c-bcl-2 ; metabolism ; Tumor Suppressor Protein p53 ; metabolism

OBJECTIVETo explore the effects of microcystin-LR (MCLR) on the expression of base excision repair genes and genes related to apoptosis.

METHODSThe BRL-3A cells were exposed to different concentrations of MCLR for various periods of time and the cell viability was measured by MTT. The mRNA expression was determined with the quantitative real-time polymerase chain reaction (QRT-PCR).

RESULTSThe viability of BRL-3A cells significantly reduced in a concentration- and time-dependent manner. In 30 µg/ml group, the mRNA expression level (1.327 ± 0.028) of p53 increased significantly at 24 h after exposure, as compared with the other groups (1.005 ± 0.117, 0.862 ± 0.154, 1.028 ± 0.056 and 1.015 ± 0.091) (P < 0.05). The mRNA expression levels (5.080 ± 0.729, 5.820 ± 0.373, 6.018 ± 0.359 and 6.183 ± 0.515) of Bax in all exposure groups were significantly higher than that (1.024 ± 0.277) in control group at 24 h after exposure. However, the Bax mRNA expression level (0.604 ± 0.146) in the 30 µg/ml group at 72 h after exposure was significantly lower than those (1.004 ± 0.107, 0.811 ± 0.142, 0.855 ± 0.101 and 0.814 ± 0.056) in other groups (P < 0.05). When compared with control group (1.006 ± 0.132) and 1 µg/ml group (1.034 ± 0.241), the mRNA expression level (0.488 ± 0.147) of PARP1 in 30 µg/ml group at 48 h after exposure decreased significantly (P < 0.05). Furthermore, the mRNA expression levels (0.594 ± 0.180, 0.491 ± 0.015 and 0.305 ± 0.091) of JWA, XRCC1 and PARP1 in 30 µg/ml group at 72 h after exposure decreased significantly, as compared with the other groups (P < 0.05).

CONCLUSIONThe induction of gene expression is a transient phenomenon that occurred at different times of exposure for different genes. Inhibition of MCLR on the base excision repair gene expression may play important role in the course of MCLR promoting liver tumor.

Animals ; Apoptosis ; Apoptosis Regulatory Proteins ; genetics ; Base Sequence ; Cell Line ; DNA Repair ; Gene Expression ; Microcystins ; toxicity ; RNA, Messenger ; genetics ; Rats

Humans ; Male ; Semen ; Sperm Motility ; Mediation Analysis ; East Asian People ; Microcystins/toxicity* ; Spermatozoa ; Sperm Count ; Infertility, Male

OBJECTIVETo investigate the association of microcystin (MC) in drinking water with the incidence of colorectal cancer.

METHODSThe study was designed as a retrospective cohort. Eight townships or towns were randomly selected as the study sites in Haining City of Zhejiang Province, China. 408 cases of colon and rectum carcinomas diagnosed from 1977 to 1996 in the study sites were included, and a survey on types of drinking water of these patients was conducted. Samples of different water sources (well, tap, river and pond) were collected separately and microcystin concentrations were determined by indirect competitive ELISA method.

RESULTSThe incidence rate of colorectal cancer was significantly higher in population who drank river and pond water than those who drank well and tap water. Compared to well water, the relative risk (RR) for colorectal cancer was 1.88 (tap), 7.94 (river) and 7.70 (pond) respectively. The positive rate (> 50 pg/mL) of microcystin in samples of well, tap, river and pond water was 0, 0, 36.23% and 17.14% respectively. The concentration of microcystin in river and pond water was significantly higher than that in well and tap water (P < 0.01). Spearman rank correlation analysis showed that in the study sites, the microcystin concentration of river and pond water was positively associated with the incidence of colorectal cancer (rs = 0.881, P < 0.01).

CONCLUSIONSThe types of drinking water are positively associated with the incidence of colorectal cancer in the study sites, and this may be related to microcystin contamination of drinking water. Further biological study is needed to support the possible causative role of mycrocystin in carcinogenesis of colon and rectum.

Bacterial Toxins ; toxicity ; Carcinogens, Environmental ; toxicity ; China ; epidemiology ; Cohort Studies ; Colorectal Neoplasms ; chemically induced ; epidemiology ; Female ; Humans ; Male ; Microcystins ; Peptides, Cyclic ; toxicity ; Retrospective Studies ; Water ; chemistry ; Water Pollutants, Chemical ; toxicity ; Water Supply ; standards

Animals ; Gene Expression ; Genes, p53 ; Liver ; drug effects ; metabolism ; pathology ; Liver Neoplasms ; metabolism ; pathology ; Male ; Microcystins ; toxicity ; Mutation ; Rats ; Rats, Wistar

OBJECTIVETo investigate the toxicological mechanism of microcystin-LR (MCLR) on L-02 cells.

METHODSL-02 cells was treated with MCLR at different concentrations and the subsequent changes such as cell proliferation (MTT assay), morphology, lactate dehydrogenase (LDH) leakage, apoptosis rate and apoptosis-related gene expression were examined.

RESULTSMTT assay showed that MCLR mildly inhibited the cell growth within the initial 24 h of treatment but enhanced the cell viability after that till 60 h in a time- and dose-dependent manner. LDH leakage underwent no marked changes in response to 48-hour MCLR treatment but increased upon prolonged treatment for 60 h, indicating the presence of oxidative damage. After a 48-h treatment with MCLR at 50 microg/ml, obvious apoptosis of L-02 cells occurred as manifested by cell rounding, detachment from the substrate, cell shrinkage and membrane blebbing. The apoptosis rates were rather low (between 22% and 29%) after treatment with MCLR at different concentrations for 36 h, and increased to as much as 80% after a 60-h treatment with 50 microg/ml MCLR. The expressions of p53 and bcl-2 increased in the cells after treatment with high-concentration MCLR, suggesting that MCLR up-regulated the expression levels of the two proteins.

CONCLUSIONMCLR can induce apoptosis and up-regulate p53 and bcl-2 expressions in human normal liver cell line L-02.

Apoptosis ; drug effects ; Cell Line ; Hepatocytes ; cytology ; Humans ; Microcystins ; toxicity ; Proto-Oncogene Proteins c-bcl-2 ; biosynthesis ; genetics ; Tumor Suppressor Protein p53 ; biosynthesis ; genetics

OBJECTIVESTo investigate the effects of microcystins on cell cycle and expressions of c-fos and c-jun, and explore the potential carcinogenic mechanisms of Microcystins.

METHODSMicrocystic cyanobacteria extraction (MCE) purified by Sep-Pak C(18) cartridge was added into the media and co-incubated with SHE cell for various periods. Immunohistochemistry assay was applied to detect the expressions of c-fos and c-jun at 1, 3, 6 hr time point, and cell cycle at 6, 12, 24 hr point were analyzed by flow cytometry respectively.

RESULTSSustained up-regulated expression of c-fos and c-jun were induced by MCE during the experimental period, and 5 - 6 folds increased expression were observed at 6 hour point after treatment. As much as 44.8 per cent of cells were induced to entry S-phase from resting G(0)/G(1).

CONCLUSIONUp-regulating the expression of transcript factor such as c-fos and c-jun thus to induce cell abnormal proliferation may be the potential carcinogenic mechanisms of microcystins.

Animals ; Carcinogens ; toxicity ; Cell Cycle ; drug effects ; Cell Division ; drug effects ; Cells, Cultured ; Cricetinae ; Gene Expression ; drug effects ; Microcystins ; Peptides, Cyclic ; toxicity ; Proto-Oncogene Proteins c-fos ; biosynthesis ; Proto-Oncogene Proteins c-jun ; biosynthesis

OBJECTIVETo study the molecular mechanism of microcystin (MC) induced liver tumorigenesis in rats.

METHODSThe two-stage-medium-term tumorigenesis theory was applied to establish the animal model, and the effect of MC in liver tumor formation was evaluated by the Albert gamma-GT methods, and then, the immunohistochemical technique and image analysis were used to study the expression of the bcl-2 and bax genes during tumorigenesis.

RESULTS(1) MC enhanced the formation of gamma-GT foci in liver (100%), which was significantly higher than the diethylnitrosamine (DEN) control group (22.22%) (P < 0.05). (2) MC decreased the expression of bax gene. The intensity and area of bax gene expression in the pure MC toxin group were 0.028 3 AODV and 0.007 3 ( micro m(2)/ micro m(2)) and in the DEN control group were 0.065 5 AODV and 0.024 4 ( micro m(2)/ micro m(2)), respectively. The intensity and areas of bax gene expression in the pure MC toxin group were significantly lower than those in the DEN control group (P < 0.05). (3) MC increased the expression of bcl-2 gene. The intensity and area of bcl-2 gene expression in the pure MC toxin group wee 0.097 7 AODV and 0.031 5 ( micro m(2)/ micro m(2)), respectively, and in the DEN control group were 0.046 0 AODV and 0.020 5 ( micro m(2)/ micro m(2)) respectively (P < 0.05).

CONCLUSION(1) MC can strongly promote liver tumorigenesis. (2) The changes of bcl-2 and bax gene expression possibly play an important role in the MC induced liver tumor formation.

Animals ; Carcinogens ; toxicity ; Immunohistochemistry ; Liver ; drug effects ; metabolism ; pathology ; Liver Neoplasms ; chemically induced ; metabolism ; pathology ; Mice ; Microcystins ; Peptides, Cyclic ; toxicity ; Proto-Oncogene Proteins ; biosynthesis ; Proto-Oncogene Proteins c-bcl-2 ; biosynthesis ; Rats ; Rats, Wistar ; bcl-2-Associated X Protein

OBJECTIVETo deeply explore the effects of microcystins (MC-LR) on Bax and Bcl-2 during the course of MC-LR promoting liver tumor.

METHODSapplied to set up the animal model, and the effect of MC-LR promoting liver tumor was evaluated by the Albertgamma-GT methods. And then, the immunohistochemical technique, RT-PCR and image analysis were used to study the expression of the Bcl-2 and Bax during the course of promoting tumor.

RESULTS(1) MC-LR might enhance the positive reaction rate of GGT. The positive reaction rate of GGT in DEN + pure toxin group was 100%, it was significantly higher than the DEN control group 22.22% (P < 0.05). (2) The intension and areas of the protein expression of Bcl-2 in DEN + pure toxin group were 0.0977 and 0.0315, and in DEN control group were 0.0460 and 0.0205, respectively. The expression level of Bcl-2 protein in DEN + pure toxin group were significantly higher than in DEN control group (P < 0.05). Simultaneously, the protein expression of Bax was significantly decreased by MC-LR (P < 0.05). The intension and areas of the expression of Bax in DEN + pure toxin group were 0.0283 and 0.0073, and in DEN control group were 0.0655 and 0.0244 respectively. (3) The mRNA expression of Bcl-2 was significantly increased by MC-LR. The intension of Bcl-2 mRNA expression in DEN + pure toxin group was 2.244, being significantly higher than in the other groups (P < 0.05). However, the mRNA expression of Bax showed no significant difference between DEN + pure toxin and the other groups.

CONCLUSIONThe expression change of Bcl-2 and Bax should possibly play an important role in the course of MC-LR promoting liver tumor.

Animals ; Apoptosis ; Carcinogens ; toxicity ; Hepatocytes ; metabolism ; Liver Neoplasms ; chemically induced ; metabolism ; Male ; Microcystins ; toxicity ; RNA, Messenger ; genetics ; Rats ; Rats, Wistar ; bcl-2-Associated X Protein ; biosynthesis ; bcl-Associated Death Protein ; biosynthesis

OBJECTIVETo evaluate the antagonism effects of green tea (GT) against microcystin LR (MC-LR) induced hepatotoxicity and nephrotoxicity in mice.

METHODSAll 40 male mice were randomly divided into four groups. Mice in group III and IV were pretreated with green tea for free drink at doses of 2 g/L and 12 g/L prior to MC-LR intoxication, for consecutively 18 days. The toxin treatment mice were administered continually intraperitoneal injections of MC-LR at a dose of 10 microg x kg(-1) x d(-1) bw from day 6th till sacrifice, continually 13 days. Mice were sacrificed and immediately subjected to necropsy, and the body weight, relative organ weight, serum biochemical parameters, antioxidant enzyme levels (SOD and GSH), lipid peroxidation products (MDA) and histopathology were systematically evaluated.

RESULTSMC-LR exposure led to increase the oxidative stress and organ injury was significantly observed through biochemical parameters and microscopic evaluation. However, high dose of GT pretreatment caused a significant elevation in serum GSH and SOD levels, and a decrease of serum MDA level as compared with MC-LR control. The mean values of GSH and SOD activities were separately 467.29 mg/L and 139.22 U/ml in group IV. Subsequently, GT pretreatment obviously diminished the serum ALT, AST and Cr activities. Those pathological damages in liver and kidney, were to a certain extent, lessened in GT pretreatment mice in correlation with the biochemical parameters.

CONCLUSIONGT might elevate antioxidant defense system, clean up free radicals, lessen oxidative damages and protect liver and kidney against MC-LR induced toxicity.

Animals ; Antioxidants ; pharmacology ; Chemical and Drug Induced Liver Injury ; Free Radicals ; metabolism ; Kidney Diseases ; chemically induced ; metabolism ; pathology ; Liver Diseases ; metabolism ; pathology ; Male ; Mice ; Mice, Inbred Strains ; Microcystins ; toxicity ; Oxidative Stress ; Tea