Study On Effect Of Dendrobium Officinaleon Left Ventricular Hypertrophy In Spontaneously Hypertensive Rats And Its Mechanism

Objective:To investigate the effect of Dendrobium officinale on left ventricular hypertrophy in spontaneously hypertensive rats and its possible mechanism.Methods:Eighty spontaneously hypertensive rats were randomly divided into 4 groups(model group,Dendrobium officinalelow dosage group,medium dosage group and high dosage group),with 20 rats/group.Twenty Kyoto Wistar rats with comparable age and gender were chosen as normal group.The rats in Dendrobium officinale low,medium or high dose groups were intragastrically administered with 0.25,0.5,1.0 g/kg Dendrobium officinale(equivalent to crude drug),and the rats in the model group and normal group were intragastrically administered with 2 mL distilled water for 4 weeks.The tail artery systolic pressure of rats was measured and recorded on Day 1,Day 7,Day 14,Day 21 and Day 28;after 4 weeks of administration,the rats were sacrificed and hearts were isolated.The Heart Mass Index(HMI)and Left Ventricular Hypertrophy Index(LVHI)were measured;then the hearts were sliced,and stained with Hematoxylin Eosin(HE),to observe tissue cell structure changes with microscope;the autophagosome was observed by electron microscope;the m RNA and protein expression level of Microtubule-associate Protein 1 Light Chain3-II(LC3-II)and Beclin-1 were determined with Reverse Transcription-Polymerase Chain Reaction(RT-PCR)and Western blot,respectively.All data were expressed as mean±standard deviation.SPSS 17.0 statistical software was used to analyze the data.For comparison of difference between groups,one-way ANOVA with repeated measures using SNK test wasused;P<0.05 was considered as statistically significant.Results:(1)On the 28 th day of administration,the blood pressure of Dendrobium officinale low dosage group,medium dosage group and high dosage group were(168.63±5.83)mmHg,(166.13±6.85)mm Hg and(162.25±4.65)mm Hg,respectively,which were significantly lower than that of model group(178.13±3.76)mmHg(P<0.01);the HMI and LVHI of Dendrobium officinale medium dosage group and high dosage group were(4.62±0.42)mg/g,(4.37±0.54)mg/g and(3.07±0.32)mg/g,(2.92±0.21)mg/g,respectively,which were significantly lower than those of the model(5.26±0.47)mg/g and(3.54±0.34)mg/g(all P <0.05);the mRNA level of LC3-II and Beclin-1 of Dendrobium officinale medium dosage group and high dosage group were(1.90±0.24),(1.74±0.22)and(1.46±0.20)and(1.37±0.21),respectively,which were significantly lower than those of the model group(2.30±0.33)and(1.77±0.21)(all P<0.05);the protein expression level of LC3-II and Beclin-1of Dendrobium officinale medium dosage group and high dosage group were(0.82 ± 0.07),(0.75 ± 0.08)and(0.64 ± 0.08),(0.61 ± 0.06),respectively,which were significantly lower than those of the model group(0.91±0.06)and(0.83 ± 0.08)(all P<0.05).(2)HE staining showed that: the myocardial cells of rats in normal group had regular morphology,normal volume and ordered arrangement;the myocardial cells of rats in model group were hypertrophied,with irregular morphology,not uniformly stained,with deformed and shrinking nuclei,and unclear cell wall;compared with those in model group,the hypertrophy of myocardial cells of rats in Dendrobium officinale administration groups was reduced,with more normal shape and ordered arrangement,indicating less pathological changes.(3)Electron microscope observation results showed that: the myofibrillar of rats in normal group was aligned along the long axis,with clear sarcomere,abundant mitochondria,and without obvious autophagosomes;the myofibrillar of rats in model group was arranged in disorder,with fracture,dissolution,reduction and vacuolization of mitochondrial,and formation of autophagosomes;compared with those in model group,the myofibrillar of rats inDendrobium officinale administration groups tended to be neat,with reduced mitochondrial damage,and decreased formation of autophagosomes.Conclusion:(1)Dendrobium officinale can inhibit the increase of blood pressure and delay the progression of left ventricular hypertrophy in spontaneously hypertensive rats.(2)The mechanism of Dendrobium officinale inhibiting left ventricular hypertrophy in spontaneously hypertensive rats may be associated with down-regulation of the expression of LC3-II and Beclin-1 and inhibition of myocardial cell excessive autophagy.