Involvement of caspase and reactive oxygen species in cyanobacterial toxin anatoxin-a-induced cytotoxicity and apoptosis in rat thymocytes and Vero cells.

Abstract

The hepatotoxins and neurotoxins produced by bloom-forming cyanobacteria have been the cause of human and animal health hazards and even death. The most common cyanobacterial neurotoxin is anatoxin-a, and intoxications by these toxins can be fatal through muscular paralysis causing respiratory arrest. We report here anatoxin-a-induced apoptosis in two non-neuronal cells, viz. cultured rat thymocytes and African green monkey kidney cells (Vero). Anatoxin-containing cell-free extracts (ACE) from Anabena flosaquae and purified anatoxin-a were used in the study. The toxin-induced cytotoxicity was characterized by loss of viability, lactate dehydrogenase leakage, loss of mitochondrial function, and DNA fragmentation. The toxin-induced apoptosis was characterized by plasma membrane blebbing, condensed chromatin, nuclear fragmentation and formation of apoptotic bodies. Toxin-treated thymocytes showed typical internucleosomal DNA fragmentation in agarose gel electrophoresis. Ultrastructure studies confirmed the apoptotic morphology in thymocytes. ACE and anatoxin-a showed caspase-3 activation, and pretreatment with the caspase-3-specific tetrapeptide inhibitor, acetyl-Asp-Glu-Val-Asp-aldehyde (Ac-DEVD-CHO) abolished the DNA fragmentation and reduced the incidence of apoptotic cells. The thymocytes also showed dose- and time-dependent toxin-induced generation of reactive oxygen species. The study demonstrates that anatoxin-induced apoptosis is possibly mediated by generation of reactive oxygen species and caspase activation.

• Authors: P V Lakshmana Rao, R Bhattacharya, Nidhi Gupta, M M Parida, A S B Bhaskar, Rupa Dubey
• Journal: Archives of toxicology (Arch Toxicol) Vol. 76 Issue 4 Pg. 227-35 (May 2002) ISSN: 0340-5761 [Print] Germany
• PMID: 12029386 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Bacterial Toxins
• Cyanobacteria Toxins
• Marine Toxins
• Microcystins
• Reactive Oxygen Species
• Tropanes
• anatoxin a
• Caspases

Topics

• Analysis of Variance
• Animals
• Apoptosis
• Bacterial Toxins (toxicity)
• Caspases (metabolism)
• Chlorocebus aethiops
• Cyanobacteria Toxins
• DNA Fragmentation
• Enzyme Activation
• Male
• Marine Toxins (toxicity)
• Microcystins
• Microscopy, Electron
• Rats
• Rats, Wistar
• Reactive Oxygen Species (metabolism)
• Thymus Gland (cytology, drug effects, ultrastructure)
• Time Factors
• Tropanes
• Vero Cells