@article {Linford67, author = {Nancy J. Linford and Yaxiong Yang and David G. Cook and Daniel M. Dorsa}, title = {Neuronal Apoptosis Resulting from High Doses of the Isoflavone Genistein: Role for Calcium and P42/44 Mitogen-Activated Protein Kinase}, volume = {299}, number = {1}, pages = {67--75}, year = {2001}, publisher = {American Society for Pharmacology and Experimental Therapeutics}, abstract = {Genistein is a potent plant-derived isoflavone displaying estrogenic activity at low (nanomolar) concentrations and antiproliferative and antiangiogenic properties at higher concentrations (above 10{\textendash}50 μM). The antiproliferative potential of genistein has made it an interesting candidate for cancer chemotherapy at high concentrations; however, the potential for genistein toxicity in neurons at such concentrations has not been previously addressed. We show that genistein is toxic to rat primary cortical neurons at a concentration of 50 μM, whereas daidzein, a structural analog, shows no toxicity at similar concentrations. The dying cells display an apoptotic morphology that is characterized by fragmented nuclei, appearance of apoptotic bodies, DNA laddering, and caspase-dependent poly(ADP-ribose) polymerase cleavage. This cell death is partially dependent on caspase activity, independent of estrogen receptors, and does not result in a significant loss of Bcl-2 or Bcl-XL protein. Genistein exposure induces delayed and prolonged activation of p42/44 mitogen-activated protein kinase (MAPK) and p38 MAPK but not c-Jun NH2-terminal kinase. The specific p42/44 MAPK kinase inhibitor PD98059 (50 μM) partially blocks genistein-induced apoptosis, whereas the p38 MAPK inhibitor SB202190 (10 μM) has no effect. Genistein elevates intracellular calcium and both 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester (1 μM) and dantrolene (10 μM) inhibit genistein-induced apoptosis, suggesting a link between genistein-induced intracellular calcium release and apoptosis. The combination of dantrolene and PD98059 block genistein-induced apoptosis in an additive manner compared with either compound alone. These findings provide evidence for a proapoptotic function of p42/44 MAPK and raise caution about potential side effects in the nervous system with genistein use as a high-dose therapeutic agent. The American Society for Pharmacology and Experimental Therapeutics}, issn = {0022-3565}, URL = {https://jpet.aspetjournals.org/content/299/1/67}, eprint = {https://jpet.aspetjournals.org/content/299/1/67.full.pdf}, journal = {Journal of Pharmacology and Experimental Therapeutics} }