Effect of microcystin-LR and cyanobacterial extract from Polish reservoir of drinking water on cell cycle progression, mitotic spindle, and apoptosis in CHO-K1 cells.
Microcystin-LR is a cyanobacterial toxin possessing a potent tumor-promoting activity mediated through inhibition of protein phosphatases PP1 and PP2A. Because these enzymes are involved in fundamental cell processes, we decided to examine the influence of microcystin-LR on cell cycle progression, onset of anaphase, segregation of chromosomes by the mitotic spindle, and apoptosis in Chinese hamster ovary (CHO-K1) cells. Cells were incubated with 25, 50, and 100 microM of pure microcystin-LR and a cyanobacterial extract for 14, 18, and 22 h. Giemsa staining of cells treated with these toxins revealed a dose- and time-dependent increase of mitotic indices, accumulation of abnormal G(2)/M figures with hypercondensed chromosomes, abnormal anaphases with defective chromosome separation, and polyploid cells. Because spindle checkpoint is a fundamental regulatory mechanism that assures the onset of anaphase and subsequent exit from mitosis, we examined the spindle organization in microcystin-treated cells. The majority of the mitotic cells showed monopolar and multipolar mitotic spindles (multiple asters). Microtubule bundles were present in interphase cells. Our results indicate that microcystin-LR induces apoptosis and necrosis in a dose- and time-dependent manner and that the frequency of dead cells cells is positively correlated with the frequency of polyploid cells.
Lankoff
Anna
A
Department of Radiobiology and Immunology, Institute of Biology, Swietokrzyska Academy, Kielce, Poland. alankoff@pu.kielce.pl
Banasik
Anna
A
Obe
Guenter
G
Deperas
Marta
M
Kuzminski
Konrad
K
Tarczynska
Malgorzata
M
Jurczak
Tomasz
T
Wojcik
Andrzej
A
D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D016466:CHO Cells; D002453:Cell Cycle / Q000187:drug effects* / Q000502:physiology; D006224:Cricetinae; D000458:Cyanobacteria / Q000302:isolation & purification; D008387:Marine Toxins; D052998:Microcystins; D010456:Peptides, Cyclic / Q000302:isolation & purification / Q000494:pharmacology*; D011044:Poland; D008941:Spindle Apparatus / Q000187:drug effects* / Q000502:physiology; D014881:Water Supply / Q000032:analysis*
D008387:Marine Toxins; D052998:Microcystins; D010456:Peptides, Cyclic; C057862:cyanoginosin LR