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

<p>Abstract</p> <p>Background</p> <p>An impairment of cardiovascular function in streptozotocin (STZ)-diabetic rats has been mentioned within 5 days-to-3 months of induction. ATP-sensitive potassium (K_ATP) 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 K_ATPchannels in diabetic disorders.</p> <p>Methods</p> <p>Streptozotocin-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 K_ATPchannels. K_ATPchannels expression was found to be linked to cardiac tonic dysfunction, and we evaluated the expression levels of K_ATPchannels by Western blot and Northern blot analysis.</p> <p>Results</p> <p>The 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 K_ATPchannel. Two subunits of cardiac K_ATPchannel (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 K_ATPin these diabetic rats.</p> <p>Conclusions</p> <p>Both mRNA and protein expression of cardiac K_ATPchannels are decreased in diabetic rats induced by STZ for 8 weeks. This phenomenon leads to result in desensitization of some K_ATPchannel drugs.</p

Protective effect of transgenic expression of porcine heat shock protein 70 on hypothalamic ischemic and oxidative damage in a mouse model of heatstroke

<p>Abstract</p> <p>Background</p> <p>Transgenic mice have been used to examine the role of heat shock protein (HSP)72 in experimental heatstroke. Transgenic mice that were heterozygous for a porcine HSP70β gene ([+] HSP72) and transgene-negative littermate controls ([-] HSP72), under pentobarbital sodium anesthesia, were subjected to heat stress to induce heatstroke. It was found that the overexpression of HSP72 in multiple organs improved survival during heatstroke by reducing hypotension and cerebral ischemia and damage in mice. Herein we attempted to further assess the effect of heat exposure on thermoregulatory function, hypothalamic integration, and survival in unrestrained, unanesthetized [+]HSP72 and compare with those of [-]HSP72. In this research with the transgenic mice, we first conducted several biochemical, physiologic and histological determinations and then investigated the beneficial effects of HSP72 overexpression on the identified hypothalamic deficits, thermoregulatory dysfunction, and mortality during heatstroke.</p> <p>Results</p> <p>We report here that when [-]HSP72 mice underwent heat stress (ambient temperature 42.4°C for 1 h), the fraction survival and core temperature at 4 h after heat stress were found to be 0 of 12 and 34.2°C ± 0.4°C, respectively. Mice that survived to day 4 after heat stress were considered as survivors. In [+]HSP72 mice, when exposed to the same heat treatment, both fraction survival and core temperature values were significantly increased to new values of 12/12 and 37.4°C ± 0.3°C, respectively. Compared to [-]HSP mice, [+]HSP72 mice displayed lower hypothalamic values of cellular ischemia (e.g., glutamate and lactate-to-pyruvate ratio) and damage (e.g., glycerol) markers, pro-oxidant enzymes (e.g., lipid peroxidation and glutathione oxidation), pro-inflammatory cytokines (e.g., interleukin-1beta and tumor necrosis factor-alpha), and neuronal damage score evaluated 4 h after heat stress. In contrast, [+]HSP72 mice had higher hypothalamic values of antioxidant defences (e.g., glutathione peroxidase and glutathione reductase), ATP, and HSP72 expression.</p> <p>Conclusion</p> <p>This study indicates that HSP72 overexpression appears to be critical to the development of thermotolerance and protection from heat-induced hypothalamic ischemic and oxidative damage.</p

Doxorubicin-Induced Cardiac Toxicity Is Mediated by Lowering of Peroxisome Proliferator-Activated Receptor δ Expression in Rats

The present study investigates the changes of peroxisome proliferator-activated receptors δ (PPARδ) expression and troponin phosphorylation in heart of rats which were treated with doxorubicin (DOX). Wistar rats which were treated with DOX according to a previous method. The protein levels of PPARδ and troponin phosphorylation were measured using Western blot. The PPARδ expression in heart was markedly reduced in DOX-treated rats showing a marked decrease in cardiac dP/dT and cardiac output. Also, cardiac troponin phosphorylation was lowered in DOX-treated rats. Meanwhile, combined treatment with the agonist of PPARδ (GW0742) reversed the decrease of cardiac dP/dT and cardiac output in DOX-treated rats. Then, primary cultured cardiomyocytes from neonatal rats were used to measure the changes of calcium concentration in cells. In addition to both decrease of PPARδ expression and troponin phosphorylation in neonatal cardiomyocytes by DOX, a marked decrease of calcium concentration was also observed. Our results suggest the mediation of cardiac PPARδ in DOX-induced cardiotoxicity in rats. Thus, activation of PPARδ may restore the expression of p-TnI and the cardiac performance in DOX-induced cardio toxicity in rats

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

Andrographolide Inhibits Nuclear Factor-κB Activation through JNK-Akt-p65 Signaling Cascade in Tumor Necrosis Factor-α-Stimulated Vascular Smooth Muscle Cells

Critical vascular inflammation leads to vascular dysfunction and cardiovascular diseases, including abdominal aortic aneurysms, hypertension, and atherosclerosis. Andrographolide is the most active and critical constituent isolated from the leaves of Andrographis paniculata, a herbal medicine widely used for treating anti-inflammation in Asia. In this study, we investigated the mechanisms of the inhibitory effects of andrographolide in vascular smooth muscle cells (VSMCs) exposed to a proinflammatory stimulus, tumor necrosis factor-α (TNF-α). Treating TNF-α-stimulated VSMCs with andrographolide suppressed the expression of inducible nitric oxide synthase in a concentration-dependent manner. A reduction in TNF-α-induced c-Jun N-terminal kinase (JNK), Akt, and p65 phosphorylation was observed in andrographolide-treated VSMCs. However, andrographolide affected neither IκBα degradation nor p38 mitogen-activated protein kinase or extracellular signal-regulated kinase 1/2 phosphorylation under these conditions. Both treatment with LY294002, a phosphatidylinositol 3-kinase/Akt inhibitor, and treatment with SP600125, a JNK inhibitor, markedly reversed the andrographolide-mediated inhibition of p65 phosphorylation. In addition, LY294002 and SP600125 both diminished Akt phosphorylation, whereas LY294002 had no effects on JNK phosphorylation. These results collectively suggest that therapeutic interventions using andrographolide can benefit the treatment of vascular inflammatory diseases, and andrographolide-mediated inhibition of NF-κB activity in TNF-α-stimulated VSMCs occurs through the JNK-Akt-p65 signaling cascade, an IκBα-independent mechanism

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

Andrographolide Inhibits Nuclear Factor-B Activation through JNK-Akt-p65 Signaling Cascade in Tumor Necrosis Factor--Stimulated Vascular Smooth Muscle Cells

Critical vascular inflammation leads to vascular dysfunction and cardiovascular diseases, including abdominal aortic aneurysms, hypertension, and atherosclerosis. Andrographolide is the most active and critical constituent isolated from the leaves of Andrographis paniculata, a herbal medicine widely used for treating anti-inflammation in Asia. In this study, we investigated the mechanisms of the inhibitory effects of andrographolide in vascular smooth muscle cells (VSMCs) exposed to a proinflammatory stimulus, tumor necrosis factor-(TNF-). Treating TNF--stimulated VSMCs with andrographolide suppressed the expression of inducible nitric oxide synthase in a concentration-dependent manner. A reduction in TNF--induced c-Jun N-terminal kinase (JNK), Akt, and p65 phosphorylation was observed in andrographolide-treated VSMCs. However, andrographolide affected neither I B degradation nor p38 mitogen-activated protein kinase or extracellular signal-regulated kinase 1/2 phosphorylation under these conditions. Both treatment with LY294002, a phosphatidylinositol 3-kinase/Akt inhibitor, and treatment with SP600125, a JNK inhibitor, markedly reversed the andrographolide-mediated inhibition of p65 phosphorylation. In addition, LY294002 and SP600125 both diminished Akt phosphorylation, whereas LY294002 had no effects on JNK phosphorylation. These results collectively suggest that therapeutic interventions using andrographolide can benefit the treatment of vascular inflammatory diseases, and andrographolide-mediated inhibition of NF-B activity in TNF--stimulated VSMCs occurs through the JNK-Aktp65 signaling cascade, an I B -independent mechanism

Ubiquitin-protein ligase E3a (UBE3A) as a new biomarker of cardiac hypertrophy in cell models

Cardiac hypertrophy is widely diagnosed in clinical cardiac disorders. The pathophysiology of hypertrophy is complex and multifactorial, a series of molecular and cellular changes are participated, such as activation of different signaling pathways, a switch of fetal gene program in the myocardium, and apoptosis. Some biomarkers have been applied to assess cardiac hypertrophy including atrial natriuretic peptides (ANP), brain/B-type natriuretic peptides (BNP), and α- or β- Myosin Heavy Chain (MHC) in addition to others. Recently, ubiquitin-protein ligase E3A (UBE3A) has been observed to increase in cardiac hypertrophy. Therefore, UBE3A as a new biomarker seems valuable in the clinic. The cardiac hypertrophy is induced in rat-derived heart cell line H9c2 cells by potassium bromate (KBrO3), high glucose (HG), or isoproterenol (Iso), respectively. As an oxidizing agent, KBrO3 increased cell size at concentrations less than 250 μM. Similarly, HG and Iso also induced cardiac hypertrophy in H9c2 cells. Interestingly, each kind of the cell models promoted the gene expression of the well-known biomarkers of cardiac hypertrophy including atrial natriuretic peptides (ANP) and brain/B-type natriuretic peptides (BNP). Additionally, UBE3A is also raised with the signals involved in cardiac hypertrophy such as calcineurin and nuclear factor of activated T-cells (NFAT) determined using Western blots. KBrO3 increased the protein levels of these signals and the specific inhibitor, such as cyclosporine A and tacrolimus, attenuated the signaling in H9c2 cells at concentrations sufficient to inhibit calcineurin in addition to the reduction of mRNA levels of UBE3A, similar to ANP or BNP. Moreover, HG or Iso also significantly increased protein levels of UBE3A in H9c2 cells. Taken together, we provided a new view that UBE3A is markedly raised in cardiac hypertrophy using various cell models, mainly through the activation of the calcineurin/NFAT signaling pathway in H9c2 cells. Therefore, UBE3A could be developed as a new biomarker in the diagnosis of cardiac hypertrophy. Keywords: Hypertrophic signals, Hyperglycemia, H9c2 cells, Isoproterenol, Potassium bromat