The Protective Effect Of Dauricine On Cardiac Hypertrophy And Its Mechanism

Objiective: Dauricne(Dau) is a kind of bisbenzyl isoquinoline alkaloid extracted from the root of menispermun daruicum DC. It had been proved that Dau could antagonize arrhythmia,oxidative and intracellular calcium overload. In this study, we have established cardiac hypertrophy model on rats by interaperitoneal injection thyroxine, then gave Dau through intraperitoneal injection. The aim of the study is to explore the therapeutic effect of dauricine on cardiac hypertrophy induced by thyroxine and the mechanism by investigating the degree of inflammation, activity of the enzyme responsible for ionic transport, the content of nitrogen monoxidum, the activity of nitricoxide synthase and related gene expression.Methods: (1)Adult rats were given thyroxine through intraperitoneal injection (0.5mg.kg-1, once a day for 10d ) to induce cardiac hypertrophy. Several doses of dauricine (10, 40mg.kg-1) and verapamil(10mg.kg-1) were given after 3 days。10 days later, the heart and left ventricular were weighted and heart weight index was evaluated, the activities of SOD and the levels of MDA in myocardium, the activities of serum LDH and CK were measured. Hematoxylin-Eosin(HE) staining was used to determine the level of cardiac muscle injury. (2) The methods to establish the model and giving Dau and Ver were as same as those mentioned above. The effect of Dau on the ionic transport enzyme were evaluated by measuring the activities of Na+,K+-ATP enzyme and Ca2+, Mg2+-ATP enzyme. (3) The methods to establish the model and giving Dau and Ver were as same as those mentioned above. After 10d, the content of NO and the activities of NOS were measured. At the same time, the expression of Inducible Nitric Oxide Synthase(iNOS) and Endothelial Nitric Oxide Synthase(eNOS) mRNA were assayed by RT-PCR.Results: (1) In model group, HE staining showed that obviously interstitial fibrosis and cardiac muscle cells became larger; the heart weight index and MDA in myocardium significantly increased, the activity of SOD significantly reduced, activity of CK and LDH in blood serum significantly increased; except Dau-L group, the interstitial fibrosis and myocardial hypertrophy were significantly improved in high doses of Dau group(10,40 mg·kg-1·d-1) and Ver group (10 mg·kg-1·d-1) compared with model group. Dau and Ver significantly reduced the heart weight index (P<0.05 or P<0.01 vs model group). And the effects of Dau(40 mg·kg-1·d-1) and Ver (10 mg·kg-1·d-1) were better than those of Dau(10 mg·kg-1·d-1). At the meantime, Dau (40 mg·kg-1·d-1) and Ver(10 mg·kg-1·d-1) significantly reduced the MDA content, increased the activities of SOD , reduced the CK and LDH activities (P<0.05 or P<0.01 vs model group).(2) In model group ,the activities of Na+,K+-ATPase, Ca2+,Mg2+-ATPase respectively increased by 47% and 36% than those in NS group, while the activities of those were significantly reduced compared with model group (P<0.05 or P<0.01) after giving Dau(40 mg·kg-1·d-1 ) and Ver(10 mg·kg-1·d-1) at the meantime.(3)①NO content decreased obviously(P<0.01) and the activities of NOS significantly increaseed(P<0.01) in model group compared with NS group. After gave Dau(40 mg·kg-1·d-1) and Ver(10 mg·kg-1·d-1), NO content significantly increased and the activities of iNOS decreased(P<0.05);②The iNOS gene expression in model group was higher than that in NS group and eNOS gene expression was lower.(P<0.01), after giving Dau (10,40 mg·kg-1·d-1) and Ver (10 mg·kg-1·d-1), we found that the expression of iNOS gene obviously decreased in Ver group(P<0.05) while the eNOS gene expression obviously increased in Dau-H group and Ver group(P<0.05 or P<0.01).Conclusion: (1)Dau can obviously reduce the heart weight on cardiac hypertrophy rats and elevate the ability to resist on myocardium fibrosis and oxidation. Dauricine showed protective effect on thickening myocardium in the form of cardiac hypertrophy. (2) Dau could increase the activities of Na+,K+-ATPase and Ca2+,Mg2+-ATPase, these effect might work through the antagonism of calcium channel. (3) Dau can increase the NO content and reduce the NOS activities. At the same time, it can down-regulate iNOS mRNA expression and up-regulate eNOS mRNA expression. These findings on the effect of Dau on gene expression might be related to physiological and pathological mechanism of NO and NOS.