Suramin inhibits beta-bungarotoxin-induced activation of N-methyl-D-aspartate receptors and cytotoxicity in primary neurons.
We demonstrated that beta-bungarotoxin (beta-BuTX), a snake presynaptic neurotoxin, exhibited a potent cytotoxic effect on cultured cerebellar granule neurons. The mechanism of action of beta-BuTX and the cytoprotective agents against beta-BuTX were studied. The neuronal death of cerebellar granule neurons induced by beta-BuTX was manifested with apoptosis and necrosis processes as revealed by neurite fragmentation, morphological alterations, and staining apoptotic bodies with the fluorescent dye Hoechst 33258. By means of microspectrofluorimetry and fura-2, we measured intracellular Ca2+ concentration, [Ca2+]i and found that [Ca2+]i was increased markedly prior to the morphological changes and cytotoxicity. The downstream pathway of the increased [Ca2+]i was investigated: there was increased production of free radicals, decreased mitochondrial membrane potential, and depleted cellular ATP content. MK801 and suramin effectively suppressed these detrimental effects of beta-BuTX. Furthermore, the [3H]MK801 binding was reduced by unlabeled MK801, beta-BuTX, and suramin. Thus, activation of N-methyl-D-aspartate (NMDA) receptors appeared to play a crucial role in the cytotoxic effects following betaBuTX exposure. In conclusion, the novel finding of this study was that a polypeptide beta-BuTX exerted a potent cytotoxic effect through sequential events, including activating NMDA receptors followed by increasing [Ca2+]i, ROS production, and impaired mitochondrial energy metabolism. Suramin, clinically used as a trypanocidal agent, was an effective antagonist against beta-BuTX. Data suggest that suramin might have value to detect the possible pathway of certain neuropathological disorders.
Tseng
Wen-Pei
WP
Institute of Pharmacology, College of Medicine, National Taiwan University, 10043, Taipei, Taiwan.
Lin-Shiau
Shoei-Yn
SY
D000818:Animals; D002038:Bungarotoxins / Q000037:antagonists & inhibitors* / Q000633:toxicity*; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D009474:Neurons / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D013498:Suramin / Q000494:pharmacology*
D002038:Bungarotoxins; D016194:Receptors, N-Methyl-D-Aspartate; D013498:Suramin