Zhih-Cherng Chen

Characterization of the mechanisms of the increase in PPARδ expression induced by digoxin in the heart using the H9c2 cell line

Digoxin has been used as an inotropic agent in heart failure for a long time. Troponin I (TnI) phosphorylation is related to cardiac contractility, and the genes are regulated by peroxisome proliferator‐activated receptors (PPARs). Our previous studies indicated that cardiac abnormality related to the depressed expression of PPARδ in the hearts of STZ rats is reversed by digoxin. However, the cellular mechanisms for this effect of digoxin have not been elucidated. The aim of the present study was to investigate possible mechanisms for this effect of digoxin using the H9c2 cell line cultured in high glucose (HG) conditions.

Increase of ATP-sensitive potassium (K ATP ) channels in the heart of type-1 diabetic rats

BackgroundAn impairment of cardiovascular function in streptozotocin (STZ)-diabetic rats has been mentioned within 5 days-to-3 months of induction. ATP-sensitive potassium (KATP) channels are expressed on cardiac sarcolemmal membranes. It is highly responsive to metabolic fluctuations and can have effects on cardiac contractility. The present study attempted to clarify the changes of cardiac KATP channels in diabetic disorders.MethodsStreptozotocin-induced diabetic rats and neonatal rat cardiomyocytes treated with a high concentration of glucose (a D-glucose concentration of 30 mM was used and cells were cultured for 24 hr) were used to examine the effect of hyperglycemia on cardiac function and the expression of KATP channels. KATP channels expression was found to be linked to cardiac tonic dysfunction, and we evaluated the expression levels of KATP channels by Western blot and Northern blot analysis.ResultsThe result shows diazoxide produced a marked reduction of heart rate in control group. Furthermore, the methods of Northern blotting and Western blotting were employed to identify the gene expression of KATP channel. Two subunits of cardiac KATP channel (SUR2A and kir 6.2) were purchased as indicators and showed significantly decreased in both diabetic rats and high glucose treated rat cardiac myocytes. Correction of hyperglycemia by insulin or phlorizin restored the gene expression of cardiac KATP in these diabetic rats.ConclusionsBoth mRNA and protein expression of cardiac KATP channels are decreased in diabetic rats induced by STZ for 8 weeks. This phenomenon leads to result in desensitization of some KATP channel drugs.

Activation of Peripheral Opioid µ-Receptors in Blood Vessel May Lower Blood Pressure in Spontaneously Hypertensive Rats

Background/Aims: The role of opioid receptors in the regulation of vascular function remains unclear. In the current study, we evaluated the ability of loperamide, a peripheral opioid receptor agonist, to regulate blood pressure in spontaneously hypertensive rats (SHRs) and examined the mechanism(s) by which loperamide exerts its effects. Methods: In male SHRs, mean arterial pressure (MAP) was measured and hemodynamic analysis was recorded. Additionally, the isometric tension of aortic rings isolated from SHRs was determined. Results: Loperamide dose-dependently decreased MAP in SHRs but not in the normal group of Wistar-Kyoto rats. This reduction of MAP in conscious SHRs was abolished by the selective opioid µ-receptor antagonist cyprodime, but not by naloxonazine, the µ1-opioid receptor antagonist. However, cardiac output was not altered by loperamide in anesthetized SHRs. Moreover, loperamide-induced relaxation in isolated aortic rings precontracted with phenylephrine or vasopressin. This relaxation was abolished by cyprodime, but not by naloxonazine. Loperamide-induced relaxation was also attenuated by glibenclamide, an ATP-sensitive potassium (KATP) channel blocker. Additionally, vasodilatation by loperamide was reduced by an inhibitor of protein kinase A (PKA) and enhanced by an inhibitor of phosphodiesterases. Conclusion: We suggest that loperamide can lower MAP in SHRs via µ2-opioid receptor-dependent cAMP-PKA pathway that induces vascular relaxation by opening KATP channels.

Cardiac peroxisome proliferator-activated receptor δ (PPARδ) as a new target for increased contractility without altering heart rate.

Background and Aims Agents having a positive inotropic effect on the heart are widely used for the treatment of heart failure. However, these agents have the side effect of altering heart rate. It has been established that peroxisome proliferator-activated receptor δ (PPARδ) is mediated in cardiac contraction, however the effect on heart rate is unknown. Thus, we used an agonist of PPARδ, GW0742, to investigate this issue in the present study. Methods and Results We used isolated hearts in Langendorff apparatus and hemodynamic analysis in catheterized rats to measure the actions of GW0742 extra-vivo and in vivo. In diabetic rats with heart failure, GW0742 at a dose sufficient to activate PPARδ reversed cardiac contraction without changes in heart rate. In normal rats, PPARδ enhanced cardiac contractility and hemodynamic dP/dtmax significantly more than dobutamine. Both actions were diminished by GSK0660 at a dose enough to block PPARδ. However, GW0742 at the same dose failed to modify heart rate, although it did produce a mild increase in blood pressure. Detection of intracellular calcium level and Western blotting analysis showed that the intracellular calcium concentration and troponin I phosphorylation were both enhanced by GW0742. Conclusion Activation of PPARδ by GW0742 increases cardiac contractility but not heart rate. Thus, PPARδ may be a suitable target for the development of inotropic agents to treat heart failure without changing heart rate.

Cryptotanshinone Inhibits STAT3 Signaling to Alleviate Cardiac Fibrosis in Type 1-like Diabetic Rats

Cryptotanshinone is an active principal ingredient isolated from Salvia miltiorrhiza (Danshen), a medicinal plant used in China to treat cardiac disorders. The objective of this study was to investigate the effect of cryptotanshinone on myocardial fibrosis in diabetic rats. In streptozotocin‐induced type 1 diabetic model hyperglycemic rats (STZ‐treated rats), fasting blood glucose levels and heart weight/body weight ratio were markedly increased but both were not modified by cryptotanshinone. Additionally, cardiac performance in catheterized STZ‐treated rats was improved. The histological results from Masson staining showed that cryptotanshinone attenuated cardiac fibrosis in STZ‐treated rats. Moreover, both the mRNA and protein levels of the signal transducer and activator of transcription 3 (STAT3), matrix metalloproteinase‐9, and connective tissue growth factor were reduced by cryptotanshinone in high glucose‐cultured cardiomyocytes, similar to the reductions observed in the hearts of STZ‐treated rats. In conclusion, while STAT3 regulates matrix metalloproteinase‐9 and connective tissue growth factor expression in diabetic rats with cardiac fibrosis, cryptotanshinone inhibited fibrosis to improve cardiac function by suppressing the STAT3 pathway. Cryptotanshinone is suitable as an alternative remedy for therapy of cardiac fibrosis. Copyright

Long‐Term Effects of Unprovoked Venous Thromboembolism on Mortality and Major Cardiovascular Events

Background Patients with unprovoked venous thromboembolism (VTE) are at an increased risk of mortality, but whether their cardiovascular risks also increase remains to be determined. We aimed to investigate the factors associated with overall mortality and major adverse cardiovascular events in patients with unprovoked VTE. Methods and Results We identified 2154 patients newly diagnosed with unprovoked VTE from Taiwans National Health Insurance Database between 2000 and 2013, excluding those with reversible etiologies, underlying cancer, or autoimmune diseases. These patients with VTE were compared with an age‐, sex‐, and cardiovascular risk‐matched cohort of 4308 controls. The risk of mortality and major adverse cardiovascular events in patients with VTE was 2.23 (CI, 1.93–2.57; P<0.0001) and 1.86 (CI, 1.65–2.09; P<0.0001) times, respectively, higher than that of the conditions in controls. These events mostly occurred during the first year after the diagnosis of unprovoked VTE. Among patients with VTE, advanced age, male sex, and comorbid diabetes mellitus indicated a higher incidence of mortality and major adverse cardiovascular events. Conversely, comorbid hyperlipidemia attenuated these risks. Conclusions This nation‐wide cohort study revealed that patients with unprovoked VTE, particularly older males with diabetes mellitus, had an elevated risk of both mortality and cardiovascular events. Risk of mortality and major adverse cardiovascular events were highest within the first year after diagnosis and persisted during the 10 years of follow‐up.

Ginsenoside Rh2 Improves Cardiac Fibrosis via PPARδ–STAT3 Signaling in Type 1-Like Diabetic Rats

Ginsenoside Rh2 (Rh2) is an active principal ingredient contained in ginseng (Panax ginseng Meyer), a medicinal herb used to enhance health worldwide. The present study is designed to investigate the effect of Rh2 on myocardial fibrosis in diabetic rats. In a streptozotocin-induced model of type-1 diabetic rats (STZ-diabetic rats), the increased fasting blood glucose levels and heart weight/body weight (HW/BW) ratio were substantially alleviated by Rh2. Moreover, Rh2 improved cardiac performance in STZ-diabetic rats. Histological results from Masson staining showed that Rh2 attenuated cardiac fibrosis in STZ-diabetic rats. The effects of Rh2 were reversed by GSK0660 at a dose sufficient to inhibit peroxisome proliferator-activated receptor δ (PPARδ) in STZ-diabetic rats. The role of PPARδ was subsequently investigated in vitro. Rh2 restored the decreased PPARδ expression level in high glucose-cultured cardiomyocytes. Moreover, increased protein levels of fibrotic signals, including signal transducer and activator of transcription 3 (STAT3), connective tissue growth factor (CCN2) and fibronectin, were reduced by Rh2 in high glucose-cultured cardiomyocytes. These effects of Rh2 were reversed by GSK0660 or siRNA specific for PPARδ Taken together, PPARδ activation may inhibit STAT3 activation to reduce CCN2 and fibronectin expression in diabetic rats with cardiac fibrosis. Moreover, Rh2 improves cardiac function and fibrosis by increasing PPARδ signaling. Therefore, Rh2 is suitable to develop as an alternative remedy for cardiac fibrosis.

Prognostic Factors in Patients With Pulmonary Hypertension—A Nationwide Cohort Study

Background Pulmonary hypertension (PH) is a rare but fatal condition. Large‐scale studies to examine the prognostic factors are lacking. In the present study, we aimed to investigate the factors associated with overall mortality in PH patients. Methods and Results Based on Taiwans National Health Insurance Database, we identified 1092 newly identified PH patients between 1999 and 2011. These patients were matched with 8736 healthy subjects based on propensity score calculated with age, sex, and chronic cardiovascular risk factors. Overall mortality, death incidence rate ratio, and hazard ratio were calculated. Patients with PH had a higher mortality than controls (56.45 versus 18.51 per 1000 person‐years, P<0.0001), with hazard ratio at 3.3 (95% CI: 2.92–3.73, P<0.001). The long‐term survival rates of the PH patients at 1, 5, and 10 years were 87.9%, 72.5%, and 62.6%, respectively, which were significantly lower than controls with 98.4%, 90.8%, and 83.6% at 1, 5, and 10 years, respectively. Among patients with PH, the mortality rate was higher in the older and male patients. However, after stratifying by age and sex, the younger (<50 years) and female patients had a higher risk. Regarding different etiologies of PH, chronic obstructive pulmonary disease and pulmonary embolism led to most cases of mortality (adjusted hazard ratio: 3.2, 95% CI: 2.76–3.71 and 4.64, 95% CI: 2.74–7.87, P<0.05). Conclusions PH has high mortality, especially in females, and patients with younger age and with chronic diseases. Chronic obstructive pulmonary disease and pulmonary embolism contributed to an increased risk of mortality in PH patients.

Temporal Trends of In-Hospital Mortality in Patients Treated with Intra-Aortic Balloon Pumping: A Nationwide Population Study in Taiwan, 1998-2008.

Intra-aortic balloon pumping (IABP) is widely used for hemodynamic support in critical patients with cardiogenic shock (CS). We examined whether the in-hospital mortality of patients in Taiwan treated with IABP has recently declined. We used Taiwan’s National Health Insurance Research Database to retrospectively review the in-hospital all-cause mortality of 9952 (7146 men [71.8%]) 18-year-old and older patients treated with IABP between 1998 and 2008. The mortality rate was 13.84% (n = 1377). The urbanization levels of the hospitals, and the number of days in the intensive care unit, of hospitalization, and of IABP treatment, and prior percutaneous coronary intervention (PCI) were associated with mortality. Seven thousand six hundred thirty-five patients (76.72%) underwent coronary artery bypass grafting (CABG) surgery, and 576 (5.79%) underwent high-risk PCI with IABP treatment. The number of patients treated with IABP significantly increased during this decade (ptrend < 0.0001), the in-hospital all-cause mortality for patients treated with IABP significantly decreased (ptrend = 0.0243), but the in-hospital all-cause mortality of patients who underwent CABG and PCI plus IABP did not decrease. In conclusion, the in-hospital mortality rate of IABP treatment decreased annually in Taiwan during the study period. However, high-risk patients who underwent coronary revascularization with IABP had a higher and unstable in-hospital mortality rate.

GW0742 activates peroxisome proliferator-activated receptor δ to reduce free radicals and alleviate cardiac hypertrophy induced by hyperglycemia in cultured H9c2 cells: CHENG et al.

Peroxisome proliferator‐activated receptor δ (PPARδ), the predominant PPAR subtype in the heart, is known to regulate cardiac function. PPARδ activation may inhibit cardiac hypertrophy in H9c2 cells while the potential mechanism has not been elucidated. Then, H9c2 cells incubated with high glucose to induce hypertrophy were used to investigate using GW0742 to activate PPARδ. The fluorescence assays were applied to determine the changes in cell size, cellular calcium levels, and free radicals. Western blot analyses for hypertrophic signals and assays of messenger RNA (mRNA) levels for hypertrophic biomarkers were performed. In H9c2 cells, GW0742 inhibited cardiac hypertrophy. In addition, increases in cellular calcium and hypertrophic signals, including calcineurin and nuclear factor of activated T‐cells, were reduced by GW0742. This reduction was parallel to the decrease in the mRNA levels of biomarkers, such as brain/B‐type natriuretic peptides and β‐myosin heavy chain. These effects of GW0742 were dose‐dependently inhibited by GSK0660 indicating an activation of PPARδ by GW0742 to alleviate cardiac hypertrophy. Moreover, free radicals produced by hyperglycemia were also markedly inhibited by GW0742 and were later reversed by GSK0660. GW0742 promoted the expression of thioredoxin, an antioxidant enzyme. Direct inhibition of reactive oxygen species by GW0742 was also identified in the oxidant potassium bromate stimulated H9c2 cells. Taken together, these findings suggest that PPARδ agonists can inhibit free radicals, resulting in lower cellular calcium for reduction of hypertrophic signaling to alleviate cardiac hypertrophy in H9c2 cells. Therefore, PPARδ activation can be used to develop agent(s) for treating cardiac hypertrophy.