Biochemical and pharmacological characterization of toxins obtained from the fire coral Millepora complanata.
Millepora complanata is a normal resident of coral reefs in the Mexican Caribbean. In this study, we describe for the first time the vasoconstrictor, phospholipase A2 (PLA2), and hemolytic activities elicited by a crude extract obtained from M. complanata. This extract caused a concentration-dependent contraction of isolated rat aortic rings (EC50=22.4+/-1.1 microg protein/mL). This effect was endothelium independent and significantly reduced in the absence of extracellular Ca2+ and when the intracellular Ca2+ stores were depleted. In addition, the crude extract obtained from M. complanata showed PLA2 activity (7.231+/-0.092 mmol min(-1) mg(-1)) and hemolysis of rat erythrocytes (HU50=1.64+/-1.04 mug protein/mL). The hemolysis increased in the presence of Ca2+ and decreased in the presence of cholesterol. Furthermore, this hemolysis was significantly reduced after incubation with an inhibitor of PLA2 enzymes. The hemolytic and vasoconstrictor effects were abolished after incubating the extract under denaturing conditions. Reverse phase chromatography of the M. complanata extract afforded 19 fractions (F1 to F19). F4 induced hemolysis and contained mainly a protein of 30 kDa, probably a PLA2 enzyme, while F8 and F11, containing mainly proteins of 15 and 20 kDa respectively, produced vasoconstrictor effects mediated by different mechanisms of action.
Ibarra-Alvarado
César
C
Laboratorio de Investigación Química y Farmacológica de Productos Naturales, Facultad de Química, Universidad Autónoma de Querétaro, Centro Universitario, Querétaro 76010, Qro, Mexico. cibarra@uaq.mx
Alejandro García
J
J
Aguilar
Manuel B
MB
Rojas
Alejandra
A
Falcón
Andrés
A
Heimer de la Cotera
Edgar P
EP
D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects; D002118:Calcium / Q000494:pharmacology; D002851:Chromatography, High Pressure Liquid; D003064:Cnidarian Venoms / Q000737:chemistry / Q000201:enzymology* / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004591:Electrophoresis, Polyacrylamide Gel; D004912:Erythrocytes / Q000187:drug effects; D006461:Hemolysis / Q000187:drug effects*; D037402:Hydrozoa / Q000378:metabolism*; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology; D054467:Phospholipases A2 / Q000032:analysis / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D014661:Vasoconstriction / Q000187:drug effects; D014662:Vasoconstrictor Agents / Q000032:analysis / Q000494:pharmacology*
D003064:Cnidarian Venoms; D014662:Vasoconstrictor Agents; D054467:Phospholipases A2; D002118:Calcium