Quercetin inhibits necroptosis in cardiomyocytes after ischemia-reperfusion via DNA-PKcs-SIRT5-orchestrated mitochondrial quality control.

We investigated the mechanism by which quercetin preserves mitochondrial quality control (MQC) in cardiomyocytes subjected to ischemia-reperfusion stress. An enzyme-linked immunosorbent assay was employed in the in vivo experiments to assess myocardial injury markers, measure the transcript levels of SIRT5/DNAPK-cs/MLKL during various time intervals of ischemia-reperfusion, and observe structural changes in cardiomyocytes using transmission electron microscopy. In in vitro investigations, adenovirus transfection was employed to establish a gene-modified model of DNA-PKcs, and primary cardiomyocytes were obtained from a mouse model with modified SIRT5 gene. Reverse transcription polymerase chain reaction, laser confocal microscopy, immunofluorescence localization, JC-1 fluorescence assay, Seahorse energy analysis, and various other assays were applied to corroborate the regulatory influence of quercetin on the MQC network in cardiomyocytes after ischemia-reperfusion. In vitro experiments demonstrated that ischemia-reperfusion injury caused changes in the structure of the myocardium. It was seen that quercetin had a beneficial effect on the myocardial tissue, providing protection. As the ischemia-reperfusion process continued, the levels of DNA-PKcs/SIRT5/MLKL transcripts were also found to change. In vitro investigations revealed that quercetin mitigated cardiomyocyte injury caused by mitochondrial oxidative stress through DNA-PKcs, and regulated mitophagy and mitochondrial kinetics to sustain optimal mitochondrial energy metabolism levels. Quercetin, through SIRT5 desuccinylation, modulated the stability of DNA-PKcs, and together they regulated the "mitophagy-unfolded protein response." This preserved the integrity of mitochondrial membrane and genome, mitochondrial dynamics, and mitochondrial energy metabolism. Quercetin may operate synergistically to oversee the regulation of mitophagy and the unfolded protein response through DNA-PKcs-SIRT5 interaction.

Mitochondrial disorder and treatment of ischemic cardiomyopathy: Potential and advantages of Chinese herbal medicine.

Mitochondrial dysfunction is the main cause of damage to the pathological mechanism of ischemic cardiomyopathy. In addition, mitochondrial dysfunction can also affect the homeostasis of cardiomyocytes or endothelial cell dysfunction, leading to a vicious cycle of mitochondrial oxidative stress. And mitochondrial dysfunction is also an important pathological basis for ischemic cardiomyopathy and reperfusion injury after myocardial infarction or end-stage coronary heart disease. Therefore, mitochondria can be used as therapeutic targets against myocardial ischemia injury, and the regulation of mitochondrial morphology, function and structure is a key and important way of targeting mitochondrial quality control therapeutic mechanisms. Mitochondrial quality control includes mechanisms such as mitophagy, mitochondrial dynamics (mitochondrial fusion/fission), mitochondrial biosynthesis, and mitochondrial unfolded protein responses. Among them, the increase of mitochondrial fragmentation caused by mitochondrial pathological fission is the initial factor. The protective mitochondrial fusion can strengthen the interaction and synthesis of paired mitochondria and promote mitochondrial biosynthesis. In ischemia or hypoxia, pathological mitochondrial fission can promote the formation of mitochondrial fragments, fragmented mitochondria can lead to damaged mitochondrial DNA production, which can lead to mitochondrial biosynthesis dysfunction, insufficient mitochondrial ATP production, and mitochondrial ROS. Burst growth or loss of mitochondrial membrane potential. This eventually leads to the accumulation of damaged mitochondria. Then, under the leadership of mitophagy, damaged mitochondria can complete the mitochondrial degradation process through mitophagy, and transport the morphologically and structurally damaged mitochondria to lysosomes for degradation. But once the pathological mitochondrial fission increases, the damaged mitochondria increases, which may activate the pathway of cardiomyocyte death. Although laboratory studies have found that a variety of mitochondrial-targeted drugs can reduce myocardial ischemia and protect cardiomyocytes, there are still few drugs that have successfully passed clinical trials. In this review, we describe the role of MQS in ischemia/hypoxia-induced cardiomyocyte physiopathology and elucidate the relevant mechanisms of mitochondrial dysfunction in ischemic cardiomyopathy. In addition, we also further explained the advantages of natural products in improving mitochondrial dysfunction and protecting myocardial cells from the perspective of pharmacological mechanism, and explained its related mechanisms. Potential targeted therapies that can be used to improve MQS under ischemia/hypoxia are discussed, aiming to accelerate the development of cardioprotective drugs targeting mitochondrial dysfunction.

ß-tubulin contributes to Tongyang Huoxue decoction-induced protection against hypoxia/reoxygenation-induced injury of sinoatrial node cells through SIRT1-mediated regulation of mitochondrial quality surveillance.

BACKGROUND: TYHX-Tongyang Huoxue decoction has been used clinically for nearly 40 years. The ingredients of TYHX are Radix Astragali (Huangqi), Red Ginseng (Hongshen), Rehmannia Glutinosa (Dihuang), Common Yam Rhizome (Shanyao) and Cassia-bark-tree Bark (Rougui). Our previous experiments confirmed that TYHX can protect sinoatrial node cells. However, its mechanism of action is not completely understood yet. PURPOSE: The present study aimed to determine the protective effects of TYHX against Sinus node cell injury under hypoxic stress and elucidate the underlying mechanisms of protection. METHODS: Through RNA sequencing analysis and network pharmacology analysis, we found significant differences in mitochondrial-related genes before and after hypoxia-mimicking SNC, resolved the main regulatory mechanism of TYHX. Through the intervention of TYHX on SNC, a series of detection methods such as laser confocal, fluorescence co-localization, mitochondrial membrane potential and RT-PCR. The regulatory effect of TYHX on ß-tubulin in sinoatrial node cells was verified by in vitro experiments. The mechanism of action of TYHX and its active ingredient quercetin to maintain mitochondrial homeostasis and protect sinoatrial node cells through mitophagy, mitochondrial fusion/fission and mitochondrial biosynthesis was confirmed. RESULTS: Through RNA sequencing analysis, we found that there were significant differences in mitochondrial related genes before and after SNC was modeled by hypoxia. Through pharmacological experiments, we showed that TYHX could inhibit the migration of Drp1 to mitochondria, inhibit excessive mitochondrial fission, activate mitophagy and increase the mitochondrial membrane potential. These protective effects were mainly mediated by ß-tubulin. Furthermore, the active component quercetin in TYHX could inhibit excessive mitochondrial fission through SIRT1, maintain mitochondrial energy metabolism and protect SNCs. Our results showed that protection of mitochondrial function through the maintenance of ß-tubulin and activation of SIRT1 is the main mechanism by which TYHX alleviates hypoxic stress injury in SNCs. The regulatory effects of TYHX and quercetin on mitochondrial quality surveillance are also necessary. Our findings provide empirical evidence supporting the use of TYHX as a targeted treatment for sick sinus syndrome. CONCLUSION: Our data indicate that TYHX exerts protective effects against sinus node cell injury under hypoxic stress, which may be associated with the regulation of mitochondrial quality surveillance (MQS) and inhibition of mitochondrial homeostasis-mediated apoptosis.

Roles and mechanisms of quercetin on cardiac arrhythmia: A review.

Cardiac arrhythmia is one of the most prevalent cardiovascular diseases worldwide, which can occur alone or be triggered by other diseases, and it can be fatal in severe cases. Recently, Traditional Chinese Medicine has drawn the world's attention to its effective treatment. As a natural polyhydroxy flavonoid mainly isolated from a variety of plants and foods, quercetin is used for the treatment of cardiovascular disease, cancer, autoimmune diseases, and neurological disorders. A growing number of in vitro experiments and in vivo animal studies have shown that quercetin significantly inhibits mitochondrial oxidative stress, cardiac fibrosis, inflammatory responses, and apoptosis, regulates autophagic responses, improves ischemia/reperfusion injury in cardiomyocytes, and regulates gut microbiota, thereby attenuating or preventing structural and electrical remodeling in the cardiac. Based on these mechanisms, our review provides a systematic overview of the pharmacological actions and molecular targets of quercetin in cardiac arrhythmia caused by multiple etiologies, aiming to provide novel insights and therapeutic strategies to prevent or ameliorate arrhythmia.

Tongyang Huoxue Decoction (TYHX) Ameliorating Hypoxia/Reoxygenation-Induced Disequilibrium of Calcium Homeostasis and Redox Imbalance via Regulating Mitochondrial Quality Control in Sinoatrial Node Cells.

Sick sinus syndrome (SSS) is a disease with bradycardia or arrhythmia. The pathological mechanism of SSS is mainly due to the abnormal conduction function of the sinoatrial node (SAN) caused by interstitial lesions or fibrosis of the SAN or surrounding tissues, SAN pacing dysfunction, and SAN impulse conduction accompanied by SAN fibrosis. Tongyang Huoxue Decoction (TYHX) is widely used in SSS treatment and amelioration of SAN fibrosis. It has a variety of active ingredients to regulate the redox balance and mitochondrial quality control. This study mainly discusses the mechanism of TYHX in ameliorating calcium homeostasis disorder and redox imbalance of sinoatrial node cells (SANCs) and clarifies the protective mechanism of TYHX on the activity of SANCs. The activity of SANCs was determined by CCK-8 and the TUNEL method. The levels of apoptosis, ROS, and calcium release were analyzed by flow cytometry and immunofluorescence. The mRNA and protein levels of calcium channel regulatory molecules and mitochondrial quality control-related molecules were detected by real-time quantitative PCR and Western Blot. The level of calcium release was detected by laser confocal. It was found that after H/R treatment, the viability of SANCs decreased significantly, the levels of apoptosis and ROS increased, and the cells showed calcium overload, redox imbalance, and mitochondrial dysfunction. After treatment with TYHX, the cell survival level was improved, calcium overload and oxidative stress were inhibited, and mitochondrial energy metabolism and mitochondrial function were restored. However, after the SANCs were treated with siRNA (si-ß-tubulin), the regulation of TYHX on calcium homeostasis and redox balance was counteracted. These results suggest that ß-tubulin interacts with the regulation of mitochondrial function and calcium release. TYHX may regulate mitochondrial quality control, maintain calcium homeostasis and redox balance, and protect SANCs through ß-tubulin. The regulation mechanism of TYHX on mitochondrial quality control may also become a new target for SSS treatment.

Zishen Huoxue Recipe Protecting Mitochondrial Function of Hypoxic/Reoxygenated Myocardial Cells through mTORC1 Signaling Pathway.

OBJECTIVE: This study focuses on the role of Zishen Huoxue Decoction (ZSHX) in reducing mitochondrial membrane potential and reducing the proportion of apoptosis through the mTORC1 signaling pathway. METHODS: In our experiment, we first constructed an in vitro hypoxia/reoxygenation (H/R) model of H9C2 cells. Then, the cells were divided into control group, model group (hypoxia/reoxygenation, H/R), ZSHX, ZSHX + Rapa, low-dose ZSHX (100 µg/ml), and middle-dose ZSHX. High-dose ZSHX (400 µg/ml) group was treated with Zishen Huoxue Decoction (ZSHX). Western Blot was used to detect the expression of cell-related protein and RT-PCR was used to detect the expression of the cell-related gene in each group. Flow cytometry was used to assay for ROS content and the apoptotic ratio of H9C2 cells, Seahorse Live Cell Energy Meter was used to detect the Mitochondrial Respiratory Function in H9C2 Cells, and confocal laser scanning was used to detect the mitochondrial membrane potential of H9C2 cells. RESULTS: Western Blot assay showed that the relative expression of mTOR and Raptor in the H/R group was significantly lower than that in the control group (n = 3, P < 0.05). The expression of mTOR and Raptor was upregulated and the relative expression of 4E-BP1 was downregulated in the middle- and high-dose ZSHX groups (n = 3, P < 0.05). In addition, the ROS content of H9C2 cells was detected by flow cytometry, showing the ROS synthesis in H/R group (78.31 + 6.14) higher than that in the control group (34.53 + 6.10) (n = 3, P < 0.01). The ROS value was increased significantly after rapamycin inhibited mTOR (66.18 (+4.03 vs. 52.31 (+6.01), n = 3, P < 0.05). The basal mitochondrial respiration and ATP production in H/R group were significantly lower than those in the control group (38.17 + 17.76); the mitochondrial leakage in H/R model group was significantly higher than that in the control group (H/R: 40.93 + 5.18 vs. Ctrl: 27.17 + 8.92, n = 4, P < 0.05). The apoptotic rate of cardiomyocytes in the H/R model group (70.91 + 4.57) was significantly higher than that in the control group (14.52 + 2.37, n = 3, P < 0.01), and Zishen Huoxue Decoction could decrease the apoptotic rate of hypoxic-reoxygenated cardiomyocytes (ZSHX: 18.24 + 4.17 vs. H/R: 78.91 + 3.48, n = 3, P < 0.01). CONCLUSION: ZSHX Decoction has the effects of activating mTORC1, inhibiting the overexpression of 4E-BP1, inhibiting fatty acid oxidation, protecting the respiratory function of mitochondria, reducing ROS and apoptosis, and thus protecting myocardial cells from injury.

Role of Chinese Herbal Medicines in Regulation of Energy Metabolism in Treating Cardiovascular Diseases.

Recently, studying myocardial energy metabolism pathways or improving myocardial metabolism through drugs is another effective strategy for treating ischemic heart disease. Many active components of Chinese herbal medicines (CHMs) have been found to modulate energy metabolism in myocardial cells, cerebral vascular cells, endothelial cells and tumour cells. This paper reviews the advances in studies on the active components of CHMs that modulating energy metabolism in treating cardiovascular diseases over the past five years.

Effects of Yiqi Tongyang on HCN4 Protein Phosphorylation in Damaged Rabbit Sinoatrial Node Cells.

The hyperpolarization-activated cyclic nucleotide-gated cation channel (I f ) is closely associated with sinoatrial node pacing function. The present study aimed to investigate the molecular mechanisms involved in pacing function improvements of damaged sinoatrial node cells and the consequent treatment effects on sick sinus syndrome (SSS) after the use of Yiqi Tongyang. HCN4 channel protein expression and phosphorylation were measured by immunoblotting and fluorescent quantitation. After ischemia-reperfusion injury (model group), the HCN4 protein and the optical density (OD) of the phosphorylated HCN4 protein as well as intracellular PKA activity in the sinoatrial node cells decreased significantly. However, the OD values and PKA activity increased to different degrees after treatment with serum containing different doses of Yiqi Tongyang; in contrast, no significant improvement was seen in the control group compared to the model group. These findings demonstrated that the use of the traditional Chinese medicine Yiqi Tongyang could increase HCN4 protein expression and phosphorylation as well as PKA activity within sinoatrial node cells damaged by ischemia-reperfusion. The HCN4 protein is involved in the I f -related ion channel. Here, we speculated that these effects could be associated with upregulation of HCN4 protein phosphorylation, which consequently improved cell automaticity, increased heart rate, and had treatment effects on SSS.

[Effect of Zishen Huoxue Recipe on Pathomorphology in Coronary Heart Disease Rats with Shen Deficiency Blood Stasis Syndrome].

OBJECTIVE: To observe the effect of Zishen Huoxue Recipe (ZHR) on pathomorphology in coronary heart disease (CHD) rats with Shen deficiency blood stasis syndrome (SDBSS). METHODS: Totally 60 healthy Wistar rats were divided into the blank control group, the model group, high, middle, and low dose ZHR groups according to random digit table, 12 in each group. Myocardial ischemia SDBSS rat model was prepared by ligating the left anterior descending coronary artery and injecting hydrocortisone. ZHR physic liquor was administered to rats in high, middle, and low dose ZHR groups at the daily dose of 21.6, 10.8, 5.4 g/kg by gastrogavage for 7 successive days, equal volume of pure water was administered to rats in the blank control group and the model group by gastrogavage for 7 successive days. Rat heart was collected for pathomorphological observation under light microscope. RESULTS: In the model group the heart muscle fiber was swollen and deformed with widened space, loose and dropsy tissues. Blood vessels in myocardial mesenchymal were dilated, infiltrated with more inflammatory cells. Myocardial cells were markedly swollen, degenerated, or necrotic, with caryolysis or disappearance of partial nuclear. A large amount of collagen fibrous tissue became hyperplasia. Endocardial blood vessels were swollen and degenerated with infiltration of few inflammatory cells. Epicardium tissue and structure were destroyed and got hyperplasia. Swollen, degenerated, or necrotic vessels could be seen, with infiltration of more inflammatory cells and collagen deposition. Pathomorphological injuries were alleviated in each ZHR group. The higher ZHR concentration, the milder the injury degree of myocardial tissue, the more limited range of damage. CONCLUSION: ZHR could attenuate pathomorphological injuries of myocardial ischemia rats with SDBSS and regulate myocardial function, thus improving myocardial ischemia in CHD rats with SDBSS.

Comparative study between original and traditional method in establishing a chronic sinus node damage model in rabbit.

Sick Sinus Syndrome is a common and refractory arrhythmia, needing further study in which setting up a credible sinus node damage model is important. To explore the feasibility and superiority of an original formaldehyde pinpoint pressing permeation (FPPP) method for building a chronic sinus node damage (CSND) model, 5 rabbits were chosen from 35 as a sham-operation group, and the remaining were randomly divided into two groups: the formaldehyde wet compressing (FWC) group, in which models were established by applying a cotton bud dipped in 20% formaldehyde onto the sinus node (SN) area, and the FPPP group, in which models were established by injecting formaldehyde into the SN area through a self-made pinpointing and injecting electrode. We found that in both groups, the HR at 2 h, 24 h, 1 wk, and 2 wk after modeling decreased compared with premodeling; sinoatrial conduction time, sinus node recovery time, and corrected sinus node recovery time were prolonged compared with premodeling. The indexes mentioned shortened by 2 wk after modeling compared with 2 h in the FWC group, whereas they were stable after modeling in the FPPP group. The modeling achievement ratio in the FPPP group was higher and the death rate was lower. Under light microscope, paraffin sections of the SN tissue and cells showed severe injury in both groups. The results indicate that the CSND models in rabbits can be successfully established by the FPPP method, with higher achievement ratio, lower death rate, better stabilization effect, and less damaging comparing with the traditional method.

Effects of Chinese herbal medicine serum on the apoptosis of sinoatrial node cells induced by simulated ischemia-reperfusion.

OBJECTIVE: To study the effect of Chinese herbal medicine Kangxin Fumai Granule ((see text) Granule for heart diseases) serum on the primary cultured sinoatrial node (SAN) cell apoptosis induced by simulated ischemia-reperfusion (IR). METHODS: The SAN cells removed from SAN tissue of neonatal Wistar rats were cultured and purified with differential attachment and 5'-bromodeoxyuridine (BrdU) treatment. Simulated IR model was adopted. The obtained cells were morphologically observed with inverted microscopy. By using the method of serum pharmacology, the cell apoptosis was measured with TUNEL staining qualitatively and with flow cytometry quantitatively. RESULTS: Three kinds of cells were observed in the cultured SAN cells: spindle, triangle and irregular. The spindle cells comprised the greatest proportion. The SAN cells in the model group showed moderate positive brown staining in the nucleus, and the apoptosis rate increased significantly compared to that in the control group (P < 0.01). While the SAN cells in the Kangxin Fumai Granule high-dose group did not demonstrated positive staining in the nucleus, and the apoptosis rate decreased significantly compared to that in the model group (P < 0.05). CONCLUSION: Of the cells cultured from SAN, the spindle cells were pacemaker cells of SAN in rats. Blockade and/or inhibition of the SAN cell apoptosis might be one of the important mechanisms of Kangxin Fumai Granule in preventing and treating sinoatrial injury induced by simulated IR.

[Effect of kangxin fulu recipe on electrophysiological functions of the sinoatrial node in rabbits with sick sinus syndrome].

OBJECTIVE: To study the effect of Kangxin Fulu Recipe (KFR) on electrophysiological functions of the sinoatrial node in rabbits with sick sinus syndrome (SSS). METHODS: Sixty big ears white rabbits were randomly divided into six groups, i.e., the normal group, the model group, the atropine group, the high dose KFR group, the middle dose KFR group, and the low dose KFR group, ten in each group. SSS model was established by injecting formaldehyde to the sinoatrial node except those in the normal group. Changes in AA interval, the sinoatrial conduction time (SACT), the sinus node recovery time (SNRT), and the corrected sinus node recovery time (CSNRT) were measured before and after modeling, seven days before and after gastrogavage. RESULTS: (1) The AA interval and SACT could be significantly shortened in the high dose KFR group, the middle-dose KFR group, and the atropine group (P<0.05, P<0.01). Better effects were obtained in the former two groups (P<0.05). (2) SNRT and CSNRT could be shortened in the high dose KFR group and the atropine group, with no statistical difference between the two groups (P>0.05). CONCLUSION: The electrophysiological mechanism of KFR might possibly be correlated with accelerating the recovery of sinus node autorhythmicity and conduction functions.

[Effect of qiangxin fumai granule contained serum on sinoatrial node cells during Ca2+ overloading induced by simulated ischemia/reperfusion].

OBJECTIVE: To explore the effect of Qiangxin Fumai Granule (QFG, a Chinese herbal preparation for treatment of sick sinus syndrome) contained serum (QFG-S) on sinoatrial node cells during Ca2+ overloading induced by simulated ischemia/reperfusion. METHODS: Model Ca2+ overloading cells were established on sinoatrial node cells from newborn rats, with deprivation of oxygen and glucose to simulate ischemia and with restoration of them to simulate reperfusion. Cells were divided into 5 groups, those in the normal and model control groups were modeled directly and those in the treated groups were pre-cultured with UMEM containing respective medicines in aerobic environment for 30 mm before ischemia/reperfusion simulation. Cell Ca2+ concentration and morphology were observed by invert microscope and fluorescence spectrophotometer. RESULTS: Most cells in the model control group revealed cell edema and deformation, even abscission. By HE staining, many minimal vacuole appeared in cytoplasm, with crumpled nuclear membrane, partially damaged. While cells in the QFG-S treated group, either high-dose or low-dose, were attached grew well, with basically smooth and complete membrane and nuclear membrane, normal in size and shape. The intracellular Ca2+ concentration raised significantly after modeling, but it was much lower in the QFG-S treated group than in the model control group (P < 0.01) and it was not changed obviously in the atropine treated group. CONCLUSION: QFG-S could diminish the injury of cell induced by simulated ischemia/reperfusion, the acting mechanism for treatment of sick sinus syndrome might be related to its effect in relieving Ca2+ overloading and thus protecting cells from injury.

Effect of Qiangxin Fumai Granule () on electrophysiological functions of the sinoatrial node during ischemia-reperfusion of the right coronary artery in rabbits.

OBJECTIVE: To study the effect of the Chinese medicine Qiangxin Fumai Granule (, QFG) on electrophysiological functions of the sinoatrial node during ischemia-reperfusion (IR) of the right coronary artery in rabbits. METHODS: The right coronary artery IR model in rabbits was adopted. The modeled rabbits were randomly divided into 4 groups: the model group, the atropine group, the high-dose QFG group, and the low-dose QFG group, with 8 animals in each group. In addition, twelve rabbits were selected for the sham-operative group. The drugs were administered once via duodenal perfusion after modeling had been stabilized for 10 min. The changes in AA interval, the sinoatrial conduction time (SACT), the sinus node recovery time (SNRT), the corrected sinus node recovery time (CSNRT) and the index of sinus node recovery time (ISNRT) at different time points during ischemia and reperfusion were measured. RESULTS: The AA interval was prolonged for more than 40 ms in the model group during ischemia. Compared with the model group, the four electrophysiological parameters abovementioned in the high-dose QFG group and the low-dose QFG group were decreased to different extents at each time point (P<0.01 or P<0.05), and no statistically significant differences were found between the QFG groups and the atropine group (P>0.05). CONCLUSION: QFG is beneficial for accelerating the recovery of sinus node autorhythmicity and conduction function, so as to protect electrophysiological functions of the sinoatrial node. Accelerating the recovery of autorhythmicity and conduction function in the sinus node is considered its electrophysiological mechanism in the treatment of sinoatrial node injury induced by ischemia.

[Intervening effect of Qiangxin Fumai Granule on arrhythmia induced by right coronary artery ischemia/reperfusion in rabbits].

OBJECTIVE: To observe the development of arrhythmia induced by ischemia/reperfusion (I/R) of the right coronary artery in rabbits and the intervening effect of Chinese medicine Qiangxin Fumai Granule (QFG), a Chinese preparation for activating yang and promoting blood circulation, on it. METHODS: Rabbit right coronary artery I/R model was adopted. Forty healthy adult rabbits were randomly divided into 5 groups, the sham-operation group, the model group, the atropine group, the high-dose QFG group, and the low-dose QFG group, eight in each group. The drugs were administered via duodenal perfusion 10 min after ischemia. The changes of AA interval before and after medication were observed and the scores of arrhythmia were calculated. RESULTS: During ischemia period, AA interval prolonged for more than 40 ms in the model group, and the scores of arrhythmia showed a rising trend along with the prolonging of ischemia, with the presence of atrial-ventricular block (AVB) and aggravating of sinus and atrial arrhythmia; during reperfusion period, the incidence of AVB decreased, and AA interval somewhat decreased. The AA intervals and scores of arrhythmia in the high and low-dose QFG groups were significantly lower than those in the model group respectively (P < 0.01 or P < 0.05). CONCLUSION: QFG is beneficial for shortening AA interval and preventing arrhythmia induced by I/R.

[Effect of Qiangxin Fumai granule on myocyte apoptosis of sinus node and Bax, Bcl-2, Fas-L gene protein in rabbits of sinoatrial ischemia/reperfusion].

OBJECTIVE: To explore the molecular mechanism of Qiangxin Fumai granule (QFG, an effective Chinese composite drug) in preventing and treating sick sinus syndrome (SSS). METHOD: Rabbit model of sinoatrial ischemia/reperfusion was established by occluding and loosening the root of right coronary artery. Effect of QFG on cell apoptosis was observed by TUNEL method, and its effect on apoptotic related gene Bax, Bcl-2 and Fas-L gene protein expression was observed by immunohistochemical method. Average light density values of the expression of Bax, Bcl-2 and Fas-L of SAN cells was determined by Imagepro Plus image analysis system. RESULT: Sinoatrial injury induced by ischemia/reperfusion could cause evident sinoatrial cell apoptosis, enhance Fas-L gene protein expression and obviously enhance Bax gene protein expression, reduce Bcl-2/Bax ratio. QFG could significantly down-regulate Fas-L and Bax gene protein expression, up-regulate Bcl-2/Bax ratio, significantly inhibit and block the sinoatrial cell apoptosis. CONCLUSION: To inhibit and block the event of cell apoptosis through regulating Bax, Bcl-2 and Fas-L gene protein expression in sinoatrial node after ischemia/reperfusion might be one of the mechanisms of QFG in preventing and treating sinoatrial ischemia/reperfusion injury of SSS.