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Abstract. Caulophine is a new fluorenone alkaloid isolated from the radix of Caulophyllum robustum MAXIM and identified as 3-(2-(dimethylamino) ethyl)-4,5-dihydroxy-1,6-dimethoxy-9H-fluoren-9-one. Due to its new chemical structure, the pharmacological activities of caulophine are not well characterized. The present study evaluated the protective effect and the primary mechanisms of caulophine on cardiomyocyte injury. Viability of cardiomyocytes was assayed with the MTT method, and cell apoptosis was detected by flow cytometry. Myocardial infarction was produced by ligating the coronary artery, and myocardial ischemia was induced by isoproterenol in rats. Myocardial infarction size was estimated with p-nitro-blue tetrazolium staining. Lactate dehydrogenase (LDH), creatine kinase (CK), superoxide dismutase (SOD), malondialdehyde (MDA), and free fatty acid (FFA) were spectrophotometrically determined. Histopathological and ultrastructural changes of ischemic myocardium were observed. The results showed that pretreatment with caulophine increased the viability of H 2 O 2 -and adriamycin-injured cardiomyocytes; decreased CK, LDH, and MDA; increased SOD; and inhibited H 2 O 2 -induced cellular apoptosis. Caulophine reduced myocardial infarct size and serum CK, LDH, FFA, and MDA; raised serum SOD; and improved histopathological and ultrastructural changes of ischemic myocardium. The results demonstrate that caulophine has the ability to protect cardiomyocytes from oxidative and ischemic injury through an antioxidative mechanism that provides a basis for further study and development of caulophine as a promising agent for treating coronary heart disease.

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Caulophine is a novel fluorenone alkaloid isolated from the radix of Caulophyllum robustum Maxim. Caulophine showed high affinity for the rat myocardial cell membrane as assessed by cell membrane chromatography, suggesting that the compound may exert bioactivity in the heart. It is known that calcium plays an important role in the pathogenesis of ischaemic heart disease, and caffeine can cause calcium overload in cardiomyocytes by inducing calcium release from the sarcoplasmic reticulum. Therefore, the present study evaluated the effects of caulophine on caffeine-induced injury and calcium homeostasis in cardiomyocytes. Cardiomyocytes were pre-treated with caulophine before exposure to caffeine or potassium chloride (KCl). Cell viability was assayed using the MTT method, and lactate dehydrogenase (LDH) and malondialdehyde (MDA) were measured spectrophotometrically. Caulophine-pre-treated cardiomyocytes were incubated with Fluo-3 ⁄ AM, and then caffeine or KCl was used to induce Ca 2+ overload. The total intracellular Ca 2+ concentration was measured by flow cytometry. Fluorescence densities of single cardiomyocytes were detected using a confocal microscope. Caulophine increased the viability of caffeine-injured cardiomyocytes and decreased LDH activity and MDA level in cardiomyocytes. Furthermore, caulophine significantly decreased the total intracellular free Ca 2+ concentration and intracellular calcium release in cardiomyocytes in response to caffeine. However, the same concentrations of caulophine did not affect KCl-induced calcium influx. Our results suggest that caulophine protects cardiomyocytes from caffeine-induced injury as a result of calcium antagonism. This finding provides a basis for further study and development of caulophine as a new calcium antagonist for treating ischaemic cardiovascular diseases.Calcium plays important roles in regulating normal human cellular functions and metabolism [1]. Under physiological conditions, the free intracellular calcium concentration is tightly regulated to maintain calcium homeostasis. Intracellular calcium homeostasis is largely dependent on the regulation of calcium flowing across the plasma membrane, including Ca 2+ influx through Ca 2+ channels and the Na + -Ca 2+ exchanger, and Ca 2+ release from the sarcoplasmic reticulum mediated by the ryanodine receptor and the inositol triphosphate receptor [2]. Under pathological conditions, calcium participates in the pathogenesis of many diseases, especially ischaemic cardiocerebrovascular diseases. A number of studies have demonstrated that the concentration of free calcium in cardiomyocytes increases to result in calcium overload during myocardial ischaemia and reperfusion, which is one of the main mechanisms underlying cardiac cell injury.