Anthraquinone-sensitized Ca2+ release channel from rat cardiac sarcoplasmic reticulum: possible receptor-mediated mechanism of doxorubicin cardiomyopathy.
Rat cardiac membrane vesicles enriched in biochemical markers of the junctional region of sarcoplasmic reticulum (SR) and exhibiting ruthenium red-sensitive rapid Ca2+ release have been prepared. Doxorubicin and seven congeners are shown to enhance the binding of [3H]ryanodine to the ryanodine receptor with a strong structural requirement. Doxorubicin enhances the binding of [3H]ryanodine to SR membranes and soluble receptor preparations and induces Ca2+ release from SR vesicles in a highly Ca2(+)-dependent manner, suggesting that anthraquinones promote the open state of the junctional Ca2+ release channel by increasing the affinity of the Ca2+ activator site for Ca2+. Doxorubicin reduces the Kd of [3H]ryanodine binding solely by enhancing the rat of association. Caffeine competes for the same site with anthraquinones, because the caffeine-activated binding of [3H]ryanodine is inhibited by doxorubicin and vice versa. The acute effect of doxorubicin on the cardiac Ca2+ release channel is fully reversible; however, long term treatment (up to 24 hr) with doxorubicin increases the sensitivity of the preparation to subsequent acute challenge with doxorubicin. The thiol-reductive agent dithiothreitol enhances, whereas the reactive disulfide 4,4'-dithiodipyridine reduces, the doxorubicin-enhanced binding of [3H]ryanodine. These results demonstrate that the acute and chronic cardiotoxicity of anthraquinones may be accounted for by a receptor-mediated mechanism. Our findings suggest that the chronic effects observed with the clinical use of anthraquinones may be the result of a receptor-mediated shift in the redox equilibrium of allosteric thiols at the ryanodine receptor complex, which in turn leads to long term sensitization of the Ca2+ release channel.
Pessah
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Department of Pharmacology and Toxicology, School of Veterinary Medicine, University of California, Davis 95616.
Durie
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Schiedt
M J
MJ
Zimanyi
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D000470:Alkaloids / Q000378:metabolism*; D000818:Animals; D000880:Anthraquinones / Q000633:toxicity*; D001667:Binding, Competitive; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000187:drug effects* / Q000378:metabolism; D009202:Cardiomyopathies / Q000139:chemically induced; D003630:Daunorubicin / Q000494:pharmacology; D004317:Doxorubicin / Q000633:toxicity*; D004347:Drug Interactions; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D006321:Heart / Q000187:drug effects*; D007700:Kinetics; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D011950:Receptors, Cholinergic / Q000187:drug effects* / Q000378:metabolism; D012433:Ryanodine / Q000378:metabolism*; D019837:Ryanodine Receptor Calcium Release Channel; D012519:Sarcoplasmic Reticulum / Q000187:drug effects* / Q000378:metabolism; D013329:Structure-Activity Relationship
D000470:Alkaloids; D000880:Anthraquinones; D015220:Calcium Channels; D011950:Receptors, Cholinergic; D019837:Ryanodine Receptor Calcium Release Channel; D012433:Ryanodine; D002110:Caffeine; D004317:Doxorubicin; D002118:Calcium; D003630:Daunorubicin