K(ATP) activation prevents progression of cardiac hypertrophy to failure induced by pressure overload via protecting endothelial function

KATP channels are regulators of programmed cell death and targets for the creation of novel drugs against ischemia/reperfusion cardiac injury

BACKGROUND

The use of percutaneous coronary intervention (PCI) in patients with ST-segment elevation myocardial infarction (STEMI) is associated with a mortality rate of 5%-7%. It is clear that there is an urgent need to develop new drugs that can effectively prevent cardiac reperfusion injury. ATP-sensitive K+ (KATP ) channel openers (KCOs) can be classified as such drugs.

RESULTS

KCOs prevent irreversible ischemia and reperfusion injury of the heart. KATP channel opening promotes inhibition of apoptosis, necroptosis, pyroptosis, and stimulation of autophagy. KCOs prevent the development of cardiac adverse remodeling and improve cardiac contractility in reperfusion. KCOs exhibit antiarrhythmic properties and prevent the appearance of the no-reflow phenomenon in animals with coronary artery occlusion and reperfusion. Diabetes mellitus and a cholesterol-enriched diet abolish the cardioprotective effect of KCOs. Nicorandil, a KCO, attenuates major adverse cardiovascular event and the no-reflow phenomenon, reduces infarct size, and decreases the incidence of ventricular arrhythmias in patients with acute myocardial infarction.

CONCLUSION

The cardioprotective effect of KCOs is mediated by the opening of mitochondrial KATP (mitoKATP ) and sarcolemmal KATP (sarcKATP ) channels, triggered free radicals' production, and kinase activation.

Effect of ATP-sensitive Potassium Channel Openers on Intraocular Pressure in Ocular Hypertensive Animal Models

Purpose

To evaluate the effect of ATP-sensitive potassium channel openers cromakalim prodrug 1 (CKLP1) and diazoxide on IOP in three independent mouse models of ocular hypertension.

Methods

Baseline IOP was measured in TGFβ2 overexpression, steroid-induced, and iris dispersion (DBA/2J) ocular hypertension mouse models, followed by once daily eyedrop administration with CKLP1 (5 mM) or diazoxide (5 mM). The IOP was measured in conscious animals with a handheld rebound tonometer. Aqueous humor dynamics were assessed by a constant perfusion method. Effect of treatment on ocular tissues was evaluated by transmission electron microscopy.

Results

CKLP1 decreased the IOP by 20% in TGFβ2 overexpressing mice (n = 6; P < 0.0001), 24% in steroid-induced ocular hypertensive mice (n = 8; P < 0.0001), and 43% in DBA/2J mice (n = 15; P < 0.0001). Diazoxide decreased the IOP by 32% in mice with steroid-induced ocular hypertension (n = 13; P < 0.0001) and by 41% in DBA/2J mice (n = 4; P = 0.005). An analysis of the aqueous humor dynamics revealed that CKLP1 decreased the episcleral venous pressure by 29% in TGFβ2 overexpressing mice (n = 13; P < 0.0001) and by 72% in DBA/2J mice (n = 4 control, 3 treated; P = 0.0002). Diazoxide lowered episcleral venous pressure by 35% in steroid-induced ocular hypertensive mice (n = 3; P = 0.03). Tissue histology and cell morphology appeared normal when compared with controls. Accumulation of extracellular matrix was reduced in CKLP1- and diazoxide-treated eyes in the steroid-induced ocular hypertension model.

Conclusions

ATP-sensitive potassium channel openers CKLP1 and diazoxide effectively decreased the IOP in ocular hypertensive animal models by decreasing the episcleral venous pressure, supporting a potential therapeutic application of these agents in ocular hypertension and glaucoma.

Endothelial ATP-Sensitive Potassium Channel Protects Against the Development of Hypertension and Atherosclerosis

In the endothelium, ATP-sensitive potassium (KATP) channels are thought to couple cellular metabolism with membrane excitability, calcium entry, and endothelial mediator release. We hypothesized that endothelial KATP channels have a broad role protecting against high blood pressure and atherosclerosis. Endothelial-specific Kir6.1 KO mice (eKO) and eKO mice on an apolipoprotein E KO background were generated (A-eKO) to investigate the role of KATP channels in the endothelium. Basal blood pressure was not elevated in eKO mice. However, when challenged with a high-salt diet and the eNOS inhibitor L-NAME, eKO mice became more hypertensive than their littermate controls. In aorta, NO release at least partly contributes to the endothelium-dependent vasorelaxation induced by pinacidil. In A-eKO mice atherosclerotic plaque density was significantly greater than in their littermate controls when challenged with a high-fat diet, particularly in the aortic arch region. Levels of endothelial dysfunction markers were higher in eKO compared with WT mice; however, these were not significant for A-eKO mice compared with their littermate controls. Furthermore, decreased vascular reactivity was observed in the mesenteric arteries of A-eKO mice, but not in aorta when on a high-fat diet. Our data support a role for endothelial Kir6.1-containing KATP channels in the endothelial protection against environmental stressors: the maintenance of blood pressure homeostasis in response to high salt and endothelial integrity when challenged with a high-fat diet.

Exacerbated pressor and sympathoexcitatory effects of central Elabela in spontaneously hypertensive rats

Elabela (ELA) is a newly discovered peptide that acts as a novel endogenous ligand of angiotensin receptor-like 1 (APJ) receptor. This study was designed to evaluate the effects of ELA-21 in paraventricular nucleus (PVN) on blood pressure and sympathetic nerve activity in spontaneously hypertensive rats (SHR). Experiments were performed in male Wistar-Kyoto rats (WKY) and SHR. ELA expression was upregulated in PVN of SHR. PVN microinjection of ELA-21 increased renal sympathetic nerve activity (RSNA), mean arterial pressure (MAP), heart rate (HR), plasma norepinephrine, and arginine vasopressin (AVP) levels in SHR. Intravenous injection of ELA-21 significantly decreased MAP and HR in both WKY and SHR, but only induced a slight decrease in RSNA. APJ antagonist F13A in PVN abolished the effects of ELA-21 on RSNA, MAP and HR. Intravenous infusion of both ganglionic blocker hexamethonium and AVP V1a receptor antagonist SR49059 caused significant reduction in the effects of ELA-21 on RSNA, MAP and HR in SHR, while combined administration of hexamethonium and SR49059 abolished the effects of ELA-21. ELA-21 microinjection stimulated Akt and p85α subunit of phosphatidylinositol 3-kinase (PI3K) phosphorylation in PVN, whereas PI3K inhibitor LY294002 or Akt inhibitor MK-2206 almost abolished the effects of ELA-21 on RSNA, MAP, and HR. Chronic PVN infusion of ELA-21 induced sympathetic activation, hypertension, and AVP release accompanied with cardiovascular remodeling in normotensive WKY. In conclusion, ELA-21 in PVN induces exacerbated pressor and sympathoexcitatory effects in hypertensive rats via PI3K-Akt pathway.NEW & NOTEWORTHY We demonstrated that PVN microinjection of ELA-21 increases sympathetic nerve activity and blood pressure, which can be abolished by pretreatment of APJ antagonist. This is the first demonstration that central ELA can induce hypertension. The pressor effects in PVN are mediated by both sympathetic activation and vasopressin release via PI3K-Akt pathway. Our data confirm that ELA is upregulated in the PVN of SHR and so may be involved in the pressor and sympathoexcitatory effects in hypertension.

The regulatory mechanisms of Yulangsan MHBFC reversing cardiac remodeling in rats based on eNOS-NO signaling pathway

Millettia pulchra Kurz var-laxior (Dunn) Z. Wei, a wild-growing plant of the family Fabaceae is known to possess multifarious medicinal properties. 17-Methoxyl-7-hydroxy-benzene-furanchalcone (MHBFC) is a flavonoid monomer extracted from its root, which has been used in traditional Chinese medicine, with a long history as a remedy of hypertension and cardiovascular remodeling. The present study was conducted to further investigate the regulatory mechanisms of MHBFC based on the endothelial nitric oxide synthase-nitric oxide (eNOS-NO) signaling pathway. The abdominal aorta of the male Sprague-Dawley rats was narrowed to induce cardiac remodeling, and the rats were given corresponding drugs for 6 weeks after operation. At the end of the experiment, the relevant indexes were detected. The results showed that N^ω-nitro-L-arginine methyl ester (L-NAME) could increase the myocardial cell cross-section area, myocardial fibrosis, and the cardiac collagen volume fraction. The serum NO and eNOS levels and the expression of p-eNOS, p-PI₃K and p-Akt protein were decreased, and myocardial microvascular endothelial cell (MMVEC) apoptosis increased. However, the above changes were reversed after treatment with MHBFC. These results indicated that MHBFC could increase eNOS protein phosphorylation by increasing PI₃K and Akt protein phosphorylation, and activated the eNOS-NO signaling pathway, increased eNOS enzyme activity, catalyzed the generation of protective NO, and counteracted MMVEC apoptosis induced by cardiac remodeling, thereby protecting against myocardial damage and reversing cardiac remodeling.

The protective effects of polysaccharide extract from Xin-Ji-Er-Kang formula on Ang II-induced HUVECs injury, L-NAME-induced hypertension and cardiovascular remodeling in mice

Background

Xin-Ji-Er-Kang (XJEK) is a Chinese herbal formula, which has been reported to exert effective protection against cardiovascular diseases, including hypertension and myocarditis.

Methods

Cultured human umbilical vascular endothelial cells (HUVECs) were treated with angiotensin II (Ang II) and different concentrations of aqueous layer extracts (AqE). Subsequently nitric oxide (NO) and endothelial nitric oxide synthase (eNOS) expression levels were detected. In addition, fifty Kunming mice were randomized into control, Nω-nitro-L-arginine methyl ester (L-NAME), L-NAME+AqE, L-NAME+XJEK and L-NAME+fosinopril treatment groups. Following 8 weeks of treatment, the cardiac hemodynamic index was measured, relaxation of the aorta was examined and pathological changes were observed. Colorimetric analysis and enzyme linked immunosorbent assay (ELISA) were applied to determine the relevant indicators in plasma and cardiac tissues.

Results

The in vitro study results demonstrated that AqE could preserve endothelial function (NO, 21.05 ± 2.03 vs. 8.64 ± 0.59; eNOS, 1.08 ± 0.17 vs.0.73 ± 0.06). In addition, the in vivo results demonstrated that compared with the control group, treatment with AqE could enhance a high hemodynamic state (left ventricular systolic pressure, 116.76 ± 9.96 vs.114.5 ± 15.16), improve endothelial function (NO, 7.98 ± 9.64 vs. 1.66 ± 3.11; eNOS, 19.78 ± 3.18 vs.19.38 ± 3.85), suppress oxidative stress (OS) (superoxide dismutase, 178.17 ± 13.78 vs. 159.38 ± 18.86; malondialdehyde, 0.77 ± 0.13 vs.1.25 ± 0.36) and reverse cardiovascular remodeling.

Conclusion

Polysaccharide from XJEK exerts protective effects against Ang II-induced injury in HUVECs and L-NAME-induced hypertension in mice and the underlying mechanism may be attributed to improving endothelial dysfunction, OS and the inflammation status in mice.

Ferulic acid ameliorates doxorubicin-induced cardiac toxicity in rats

Ferulic acid (FA) is a phenolic compound with potent antioxidant activity. The objective of the study was to study the protective effects of FA on doxorubicin (Dox)-induced myocardial toxicity in rats. Wistar rats received vehicle (control) or Dox (20 mg/kg, i.p.) or telmisartan (Tel; 10 mg/kg, p.o.) or ferulic acid (20 mg/kg and 40 mg/kg, p.o.) for 7 days followed by treatment with Dox (20) on the fifth day of treatment, except the control group. On day 8, electrocardiographic parameters were recorded followed by blood withdrawal and then the animals were sacrificed for histopathology. Administration of Dox showed prolonged RR, QTc interval, and QRS complex. The levels of serum CK-MB, LDH, IL-1β, and IL-6 were significantly increased (p < 0.01). Similarly, levels of Ca⁺², Mg⁺² ATPase, and Ca⁺² ATPase and expression of ANP and BNP were significantly higher as compared to the control. In the FA-treated group, ECG was normal. The serum levels of CK-MB, LDH, IL-1β, and IL-6 were not elevated. Heart tissue Ca⁺², Mg⁺² ATPase, and Ca⁺² ATPase did not show a statistical difference compared to the control group. The FA treatment attenuated the expression of ANP and BNP. FA (20 and 40) augmented myocardial GSH and Na⁺/K⁺ ATPase. Histopathology of the heart confirmed the cardioprotective effect of FA.

SUR2B/Kir6.1 channel openers correct endothelial dysfunction in chronic heart failure via the miR-1-3p/ET-1 pathway

The SUR2B/Kir6.1 channel openers iptakalim and natakalim reverse cardiac remodeling and ameliorate endothelial dysfunction by re-establishing the balance between the nitric oxide and endothelin systems. In this study, we investigated the microRNAs (miRs) involved in the molecular mechanisms of SUR2B/Kir6.1 channel opening in chronic heart failure. Both iptakalim and natakalim significantly upregulated the expression of miR-1-3p, suggesting that this miR is closely associated with the therapeutic effects against chronic heart failure. Bioinformatic analysis showed that many of the 183 target genes of miR-1-3p are involved in cardiovascular diseases, suggesting that miR-1-3p plays a vital role in such diseases and vascular remodeling. Target gene prediction showed that miR-1-3p combines with the 3' untranslated region (UTR) of endothelin-1 (ET-1) mRNA. Iptakalim and natakalim upregulated miR-1-3p expression and downregulated ET-1 mRNA expression in vitro. The dual luciferase assay confirmed that there is a complementary binding sequence between miR-1-3p and the 3' UTR 158-165 sequence of ET-1 mRNA. To verify the effect of miR-1-3p on ET-1, lentiviral vectors overexpressing or inhibiting miR-1-3p were constructed for the transduction of rat primary cardiac microvascular endothelial cells. The results showed that natakalim enhanced the miR-1-3p level. miR-1-3p overexpression downregulated the expression of ET-1, whereas miR-1-3p inhibition had the opposite effect. Therefore, we verified that SUR2B/Kir6.1 channel openers could correct endothelial imbalance and ameliorate chronic heart failure through the miR-1-3p/ET-1 pathway in endothelial cells. Our study provides comprehensive insights into the molecular mechanisms behind the SUR2B/Kir6.1 channel's activity against chronic heart failure.

Effects of Xin-Ji-Er-Kang on heart failure induced by myocardial infarction: Role of inflammation, oxidative stress and endothelial dysfunction

BACKGROUND

Xin-Ji-Er-Kang (XJEK) is a Chinese herbal formula, which has been reported to exert effective protection on cardiovascular diseases like hypertension and myocarditis.

PURPOSE

To elucidate the protective effects of XJEK on heart failure (HF) induced by myocardial infarction (MI) through the amelioration of inflammation, oxidative stress (OS) and endothelial dysfunction(ED).

MATERIALS AND METHODS

Fifty-seven male KM mice were randomized into the following six groups (n = 9-10 for each): control group, model group, MI+XJEK low dose group(XJEKL) group, MI+XJEK middle dose group(XJEKM), MI+XJEK high dose group(XJEKH), and MI+fosinopril group (positive control group). After treatment for four weeks, electrocardiography (ECG) and haemodynamics were recorded. Serum and tissues were collected for further analysis. Endothelium-dependent relaxation induced by acetylcholine was assessed in isolated thoracic aorta ring experiment. Hematoxylin and eosin (HE) and Van Gieson (VG) staining were used to detect the pathological changes of heart and thoracic aorta. Colorimetric analysis was employed to determine serum nitric oxide level (NO), malondialdehyde (MDA) concentration and superoxide dismutase (SOD) activity. ELISA was used to detect serum B-type natriuretic peptide (BNP) and serum inflammatory cytokines, as well as endothelial NO synthetase (eNOS), angiotensinII (Ang II) and endothelin-1(ET-1) concentration in both serum and cardiac tissues. Immunohistochemistry and Western blotting (WB) were employed to detect eNOS and inflammatory cytokine expressions in cardiac tissues.

RESULTS

XJEK administration markedly ameliorated cardiac dysfunction and abnormal ECG manifested by decreased weight/body weight (HW/BW) ratio, BNP and remedied hypertrophy of cardiomyocytes and deposition of collagen, which might be in part attributed to the increased SOD and decreased MDA in serum. Furthermore, XJEK administration improved ED with boosted eNOS activities in serum and cardiac tissues, as well as up-regulated NO levels in serum, down-regulated Ang II and ET-1 content in serum and cardiac tissues. Lastly, protein expression of pro-inflammation cytokines significantly decreased, and anti-inflammatory cytokine was significantly enhanced in serum and cardiac tissues compared to model group.

CONCLUSION

XJEK may exert beneficial effects on HF induced by MI in mice, and the underlying mechanism may be attributable to the amelioration of ED, anti-OS and anti-inflammation effects.

Protective effect of hydrogen-rich saline on pressure overload-induced cardiac hypertrophyin rats: possible role of JAK-STAT signaling

Background

Molecular hydrogen has been shown to have antioxidant effect and have been used to prevent oxidative stress-related diseases. The goal of this study was to explore if hydrogen-rich saline (HRS) plays a cardioprotective effect on abdominal aortic constriction (AAC) induced cardiac hypertrophy in rats. 60adult Sprague–Dawley rats received surgically the AAC for 6-week. After the surgery, the rats were randomly divided into 4 groups (15 for each):1: sham-operated (sham); 2: AAC-model; 3: AAC + Low HRS (LHRS); and 4: AAC + High HRS (HHRS). The rats in sham and AAC-model groups were treated with normal saline intraperitoneally, while rats in LHRS and HHRS groups were intraperitoneally treated with 3 or 6 mL/kg HRS daily, respectively, for 6-week.

Results

The ratios of HW/BW and LVW/BW were shown in an order of Model > LHRS > HHRS > SHAM groups. The cardiac hypertrophy was also manifested with increased expressions of atrial natriuretic peptide (ANP), brain natriuretic peptides (BNP) and fibrosis of cardiac tissues in AAC-model group, which could likewise be restrained in LHRS and HHRS groups. Moreover, the JAK-STAT (Janus Kinase-Signal transducers and activators of transcription) signaling molecule expressions were decreased with HRS treatment.

Conclusions

Our results showed a protective effect of HRS on pressure overload-induced cardiac hypertrophy in rats, which may be associated to a decreasing in JAK-STAT signaling pathway.

Rosuvastatin improves myocardial hypertrophy after hemodynamic pressure overload via regulating the crosstalk of Nrf2/ARE and TGF-β/ smads pathways in rat heart

Left ventricular hypertrophy is more commonly associated with hemodynamic overload imposed by hypertension or volume overload. Transforming growth factor β (TGF-β) is involved in the cardiac hypertrophy and fibrosis of the left ventricle. The fact that TGF-β1 and the nuclear factor erythroid 2-related factor 2 (Nrf2) both become up-regulated upon persistent vessel overload suggests that these two factors may virtually impact on their signaling pathways. In this research, 40 rats were divided into sham group, model group, rosuvastatin low and high dose group. Rat models were established by incomplete constriction of abdominal aorta. After five weeks treatment, blood pressure, heart mass index (HMI), hemodynamic parameters and the average diameter of myocardium cell and collagen volume fraction (CVF) improved significantly in rosuvastatin groups, compared with the model group. Both rosuvastatin groups, increased in expression of Smad7, Nrf2, NAD (P) H dehydrogenase [quinone] 1 (Nqo1) and heme oxygenase 1(Ho1),and decreased in expression of TGF-βl、Smad3 compared with the model group. Results from co-immunoprecipitation and GST pull down showed that Nrf2 interacts with Smad7. Our results revealed the crosstalk between TGF-β1/Smads and Nrf2/ antioxidant response elements (ARE) pathways in myocardial remodeling through the interaction between Smad7 and Nrf2. Rosuvastatin can improve cardiac function and hypertrophy by regulating the crosstalk of the two signaling pathways.

Molecular and functional characterization of the endothelial ATP-sensitive potassium channel

ATP-sensitive potassium (K_ATP) channels are widely expressed in the cardiovascular system, where they regulate a range of biological activities by linking cellular metabolism with membrane excitability. K_ATP channels in vascular smooth muscle have a well-defined role in regulating vascular tone. K_ATP channels are also thought to be expressed in vascular endothelial cells, but their presence and function in this context are less clear. As a result, we aimed to investigate the molecular composition and physiological role of endothelial K_ATP channels. We first generated mice with an endothelial specific deletion of the channel subunit Kir6.1 (eKO) using cre-loxP technology. Data from qRT-PCR, patch clamp, ex vivo coronary perfusion Langendorff heart experiments, and endothelial cell Ca²⁺ imaging comparing eKO and wild-type mice show that Kir6.1-containing K_ATP channels are indeed present in vascular endothelium. An increase in intracellular [Ca²⁺], which is central to changes in endothelial function such as mediator release, at least partly contributes to the endothelium-dependent vasorelaxation induced by the K_ATP channel opener pinacidil. The absence of Kir6.1 did not elevate basal coronary perfusion pressure in eKO mice. However, vasorelaxation was impaired during hypoxia in the coronary circulation, and this resulted in greater cardiac injury during ischemia-reperfusion. The response to adenosine receptor stimulation was impaired in eKO mice in single cells in patch clamp recordings and in the intact coronary circulation. Our data support the existence of an endothelial K_ATP channel that contains Kir6.1, is involved in vascular reactivity in the coronary circulation, and has a protective role in ischemia reperfusion.

Protective effects of tannic acid on pressure overload-induced cardiac hypertrophy and underlying mechanisms in rats

Objectives

The aim of this study was to examine the cardioprotective effects and latent mechanism of tannic acid (TA) on cardiac hypertrophy.

Methods

Abdominal aortic banding (AAB) was used to induce pressure overload-induced cardiac hypertrophy in male Wistar rats, sham-operated rats served as controls. AAB rats were treated with TA (20 and 40 mg/kg) or captoril.

Key findings

Abdominal aortic banding rats that received TA showed ameliorated pathological changes in cardiac morphology and coefficients, decreased cardiac hypertrophy and apoptosis, a reduction in over expressions of angiotensin type 1 receptor (AT1R), angiotensin type 2 receptor (AT2R), phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2) and transforming growth factor-β (TGF-β) mRNA, and modified expression of matrix metal proteinase-9 (MMP-9) mRNA in AAB rat hearts. Furthermore, TA treatment contributed to a decrease in malondialdehyde (MDA) and endothelin-1 (ET-1) activities and content, while it caused an increase in superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), nitric oxide (NO) and endothelial NO synthase (e-NOS). Furthermore, TA downregulated expression of tumour necrosis factor-α (TNF-α), interleukin-1β (IL-1β), bax, caspase-3 and upregulated expression of bcl-2.

Conclusions

Tannic acid displayed obvious suppression of AAB-induced cardiac hypertrophy in rats. The cardioprotective effects of TA may be attributed to multitargeted inhibition of oxidative stress, inflammation, fibrosis and apoptosis in addition to an increase in NO levels, decrease in ET-1 levels, and downregulation of angiotensin receptors and the phosphorylation of ERK1/2.

Silencing salusin-β attenuates cardiovascular remodeling and hypertension in spontaneously hypertensive rats

Salusin-β is a bioactive peptide involved in vascular smooth muscle cell proliferation, vascular fibrosis and hypertension. The present study was designed to determine the effects of silencing salusin-β on hypertension and cardiovascular remodeling in spontaneously hypertensive rats (SHR). Thirteen-week-old male SHR and normotensive Wistar-Kyoto rats (WKY) were subjected to intravenous injection of PBS, adenoviral vectors encoding salusin-β shRNA (Ad-Sal-shRNA) or a scramble shRNA. Salusin-β levels in plasma, myocardium and mesenteric artery were increased in SHR. Silencing salusin-β had no significant effect on blood pressure in WKY, but reduced blood pressure in SHR. It reduced the ratio of left ventricle weight to body weight, cross-sectional areas of cardiocytes and perivascular fibrosis, and decreased the media thickness and the media/lumen ratio of arteries in SHR. Silencing salusin-β almost normalized plasma norepinephrine and angiotensin II levels in SHR. It prevented the upregulation of angiotensin II and AT₁ receptors, and reduced the NAD(P)H oxidase activity and superoxide anion levels in myocardium and mesenteric artery of SHR. Knockdown of salusin-β attenuated cell proliferation and fibrosis in vascular smooth muscle cells from SHR. These results indicate that silencing salusin-β attenuates hypertension and cardiovascular remodeling in SHR.

H2S as a possible therapeutic alternative for the treatment of hypertensive kidney injury

Hypertension is the most common cause of cardiovascular morbidities and mortalities, and a major risk factor for renal dysfunction. It is considered one of the causes of chronic kidney disease, which progresses into end-stage renal disease and eventually loss of renal function. Yet, the mechanism underlying the pathogenesis of hypertension and its associated kidney injury is still poorly understood. Moreover, despite existing antihypertensive therapies, achievement of blood pressure control and preservation of renal function still remain a worldwide public health challenge in a subset of hypertensive patients. Therefore, novel modes of intervention are in demand. Hydrogen sulfide (H₂S), a gaseous signaling molecule, has been established to possess antihypertensive and renoprotective properties, which may represent an important therapeutic alternative for the treatment of hypertension and kidney injury. This review discusses recent findings about H₂S in hypertension and kidney injury from both experimental and clinical studies. It also addresses future direction regarding therapeutic use of H₂S.

Pharmacological evidence: a new therapeutic approach to the treatment of chronic heart failure through SUR2B/Kir6.1 channel in endothelial cells

Both iptakalim (Ipt) and natakalim (Nat) activate the SUR2B/Kir6.1 channel, an ATP-sensitive potassium channel (KATP) subtype, with high selectivity. In this study we investigated the therapeutic effects of Ipt and Nat against isoproterenol-induced chronic heart failure (ISO-CHF) in rats, and demonstrated a new therapeutic approach to the treatment of CHF through activation of the SUR2B/Kir6.1 channel in endothelial cells. In ISO-CHF rats, oral administration of Nat (1, 3, 9 mg·kg-1·d-1) or Ipt (3 mg·kg-1·d-1) for 60 days significantly improved cardiac dysfunction, reversed cardiac remodeling, significantly attenuated the pathological increases in BNP levels, and improved endothelial dysfunction by adjusting the balance between endothelin and NO systems. The therapeutic effects of Nat were prevented by the selective KATP blocker glibenclamine (Gli, 50 mg·kg-1·d-1), confirming that these effects were mediated through activation of the SUR2B/Kir6.1 channel in endothelial cells. The molecular mechanisms underlying the therapeutic effects of Nat were further addressed using proteomic methods. We identified 724 proteins in the plasma of ISO-CHF rats; 55 proteins were related to Nat. These differentially expressed proteins were mainly involved in single-organism processes and the regulation of biological quality relative to CHF, including proteasome (Psm) and ATP protein clusters. We screened out PRKAR2β, GAS6/eNOS/NO and NO/PKG/VASP pathways involved in the amelioration of CHF among the 24 enriched pathways. We further confirmed 6 protein candidates, including PRKAR2β, GAS6 and VASP, which were involved in the endothelial mechanisms, and ATP, TIMP3 and AGT, which contributed to its cardiovascular actions. This study demonstrates a new pharmacological approach to the treatment of CHF through activation of the SUR2B/Kir6.1 channel in endothelial cells, and that the eNOS/VASP pathways are involved in its signaling mechanisms.

Cinaciguat prevents the development of pathologic hypertrophy in a rat model of left ventricular pressure overload

Pathologic myocardial hypertrophy develops when the heart is chronically pressure-overloaded. Elevated intracellular cGMP-levels have been reported to prevent the development of pathologic myocardial hypertrophy, therefore we investigated the effects of chronic activation of the cGMP producing enzyme, soluble guanylate cyclase by Cinaciguat in a rat model of pressure overload-induced cardiac hypertrophy. Abdominal aortic banding (AAB) was used to evoke pressure overload-induced cardiac hypertrophy in male Wistar rats. Sham operated animals served as controls. Experimental and control groups were treated with 10 mg/kg/day Cinaciguat (Cin) or placebo (Co) p.o. for six weeks, respectively. Pathologic myocardial hypertrophy was present in the AABCo group following 6 weeks of pressure overload of the heart, evidenced by increased relative heart weight, average cardiomyocyte diameter, collagen content and apoptosis. Cinaciguat did not significantly alter blood pressure, but effectively attenuated all features of pathologic myocardial hypertrophy, and normalized functional changes, such as the increase in contractility following AAB. Our results demonstrate that chronic enhancement of cGMP signalling by pharmacological activation of sGC might be a novel therapeutic approach in the prevention of pathologic myocardial hypertrophy.

Analysis on mechanism of ATP-sensitive K+ channel opener natakalim improving congestive heart failure after myocardial infarction

The action mechanism of natakalim, a novel ATP-sensitive potassium channel opener, was studied in ameliorating the congestive heart failure (CHF) after myocardial infarction. A total of 25 healthy Wistar male rats (age, 10 weeks; average weight, 300 g) were selected, and the CHF models after acute myocardial infarction (AMI) were prepared by ligation of left anterior descending branch. They were randomly divided into the sham operation group, the model group and the groups of 1, 3 and 9 mg/kg/day natakalims. Each group had 5 mice that were sacrificed after 8 weeks. We compared left ventricular end-diastolic diameter (LVEDD), left ventricular ejection fraction (LVEF), N-terminal prohormone of brain natriuretic peptide (NT-proBNP), left ventricular mass index, myocardial cell cross-sectional area, myocardial collagen content, plasma endothelin-1 (ET-1) and endothelial nitric oxide synthase (eNOS) levels. Compared with the sham operation, the LVEDD and NT-proBNP in the model group and each natakalim group were elevated. LVEF decreased significantly, while the left ventricular mass index, myocardial cell cross-sectional area, myocardial collagen content, plasma ET-1 and eNOS levels increased. Natakalim intervention improved the above changes and the improvement effect of 3 mg/kg/day group was the highest. The mechanism of natakalim against the endothelin system can be explained by the fact that inhibiting ET-1 synthesis can reduce the ET-1 levels in circulation leading to the release of NO and PGI2. Inhibition of the vasoconstriction effect of ET-1 can improve the hemodynamics of high-load status and ameliorate the cardiac systolic and diastolic functions. In conclusion, natakalim can improve the ventricular remodeling of CHF after AMI, and 3 mg/kg/day was the most effective dose.

ATP sensitive potassium channel openers: A new class of ocular hypotensive agents

ATP sensitive potassium (K_ATP) channels connect the metabolic and energetic state of cells due to their sensitivity to ATP and ADP concentrations. K_ATP channels have been identified in multiple tissues and organs of the body including heart, pancreas, vascular smooth muscles and skeletal muscles. These channels are obligatory hetero-octamers and contain four sulfonylurea (SUR) and four potassium inward rectifier (K_ir) subunits. Based on the particular type of SUR and K_ir present, there are several tissue specific subtypes of K_ATP channels, each with their own unique set of functions. Recently, K_ATP channels have been reported in human and mouse ocular tissues. In ex vivo and in vivo model systems, K_ATP channel openers showed significant ocular hypotensive properties with no appearance of toxic side effects. Additionally, when used in conjunction with known intraocular pressure lowering drugs, an additive effect on IOP reduction was observed. These K_ATP channel openers have also been reported to protect the retinal ganglion cells during ischemic stress and glutamate induced toxicity suggesting a neuroprotective property for this drug class. Medications that are currently used for treating ocular hypertensive diseases like glaucoma do not directly protect the affected retinal cells, are sometimes ineffective and may show significant side effects. In light of this, K_ATP channel openers with both ocular hypotensive and neuroprotective properties, have the potential to develop into a new class of glaucoma therapeutics.

Astragaloside IV improves the isoproterenol-induced vascular dysfunction via attenuating eNOS uncoupling-mediated oxidative stress and inhibiting ROS-NF-κB pathways

OBJECTIVE

Oxidative stress and inflammation are regarded as two important triggers of endothelial dysfunction and play pivotal role in progression of vascular damage associated with cardiac hypertrophy. Our previous studies demonstrated that astragaloside IV (AsIV) could protect against cardiac hypertrophy in rats induced by isoproterenol (Iso), but its effects on the aorta are not known. In present study, we aimed to assess the effects of AsIV on Isoinduced vascular dysfunction.

METHODS

Sprague-Dawley (SD) rats were treated with Iso (10mg/kg/d) alone or in combination with AsIV (50mg/kg/d).

RESULTS

Compared with Isotreated alone, AsIV significantly reduced the ratios of heart weight/body weight and left ventricular weight/body weight. AsIV ameliorated the increased vasoconstriction response to phenylephrine induced by Iso and suppressed superoxide anion generation in rat aorta, increased endothelial nitric oxide synthase (eNOS) dimer/monomer ratio and its critical cofactor tetrahydrobiopterin (BH4) content in aorta as well as the NO production in the serum, reduced the plasmatic peroxynitrite (ONOO-). Moreover, in contrast with Isotreatment alone, AsIV decreased the ratio of nuclear-to-cytosolic protein expression of the NF-κB p65 subunit while enhanced its inhibited protein expression of IκB-α, down-regulated mRNA expression of IL-1β, IL-6 and TNF-α of the aorta.

CONCLUSIONS

The present study suggested that AsIV protects against Isoinduced vascular dysfunction probably via attenuating eNOS uncoupling-mediated oxidative stress and inhibiting ROS-NF-κB pathways.

Adenosine triphosphate-sensitive potassium channels and cardiomyopathies (Review)

Cardiomyopathies have been indicated to be one of the leading causes of heart failure. Though it was indicated that genetic defects, viral infection and trace element deficiency were among the causes of cardiomyopathy, the etiology has remained to be fully elucidated. Cardiomyocytes require large amounts of energy to maintain their normal biological functions. Adenosine triphosphate-sensitive potassium channels (KATP), composed of inward-rectifier potassium ion channel and sulfonylurea receptor subunits, are present on the cell surface and mitochondrial membrane of cardiac muscle cells. As metabolic sensors sensitive to changes in intracellular energy levels, KATP adapt electrical activities to metabolic challenges, maintaining normal biological functions of myocytes. It is implied that malfunctions, mutations and altered expression of KATP are associated with the pathogenesis of conditions including c hypertrophy, diabetes as well as dilated, ischemic and endemic cardiomyopathy. However, the current knowledge is only the tip of the iceberg and the roles of KATP in cardiomyopathies largely remain to be elucidated in future studies.

Serum Amyloid P-Component Prevents Cardiac Remodeling in Hypertensive Heart Disease

The potential for serum amyloid P-component (SAP) to prevent cardiac remodeling and identify worsening diastolic dysfunction (DD) was investigated. The anti-fibrotic potential of SAP was tested in an animal model of hypertensive heart disease (spontaneously hypertensive rats treated with SAP [SHR - SAP] × 12 weeks). Biomarker analysis included a prospective study of 60 patients with asymptomatic progressive DD. Compared with vehicle-treated Wistar-Kyoto rats (WKY-V), the vehicle-treated SHRs (SHR-V) exhibited significant increases in left ventricular mass, perivascular collagen, cardiomyocyte size, and macrophage infiltration. SAP administration was associated with significantly lower left ventricular mass (p < 0.01), perivascular collagen (p < 0.01), and cardiomyocyte size (p < 0.01). Macrophage infiltration was significantly attenuated in the SHR-SAP group. Biomarker analysis showed significant decreases in SAP concentration over time in patients with progressive DD (p < 0.05). Our results indicate that SAP prevents cardiac remodeling by inhibiting recruitment of pro-fibrotic macrophages and that depleted SAP levels identify patients with advancing DD suggesting a role for SAP therapy.

Grape seed proanthocyanidins prevent DOCA-salt hypertension-induced renal injury and its mechanisms in rats

Renal dysfunction is one of the major effects of DOCA (deoxycorticosterone acetate)-salt hypertension and there is an increasing amount of evidence that oxidative stress damages the function of the kidney. Grape seed proanthocyanidins (GSPE) have been reported to be potent anti-oxidants and free radical scavengers. The present study sought to investigate the ability of GSPE to prevent renal injury in DOCA-salt hypertensive rats and to explore the molecular mechanisms underlying its protective effects. A total of 54 Sprague Dawley (SD) rats were randomly divided into 7 groups: Sham group (n = 7), UnX-sham group (n = 8), DOCA-salt group (n = 8), GSPE150 group (150 mg kg(-1), n = 7), GSPE240 group (240 mg kg(-1), n = 8), GSPE384 group (384 mg kg(-1), n = 8) and ALM (amlodipine besylate tablets) group (5 mg kg(-1), n = 8), and treated for 4 weeks. Compared to sham group rats, renal injury was observed in DOCA-salt hypertensive group rats as the urine protein, KW/BW (kidney weight/body weight), degree of renal fibrosis, renal MDA (malondialdehyde) and Hyp (hydroxyproline) contents significantly increased (P < 0.01). Moreover, SOD (Superoxide Dismutase) activities decreased in the model group (P < 0.01). In contrast, DOCA-salt hypertensive rats treated with different dose of GSPE or ALM showed a significant improvement of renal injury with decreased urine protein, KW/BW, degree of renal fibrosis, renal total MDA and Hyp contents compared to the untreated group. In addition, SOD activities increased in the treatment group. Since the experimental modeling time was short, kidney damage occurs to a lesser extent. BUN (Blood Urea Nitrogen), Scr (Serum Creatinine) and UA (Uric Acid) contents did not appear significantly changed in all groups. Finally, the activation of JNK and p38 kinases in the kidney was suppressed in rats treated with GSPEs or ALM compared to the untreated group, suggesting that the inhibition of these kinase pathways by GSPE contributes to the improvement of renal function. Taking these results together, we conclude that the anti-hypertensive and anti-oxidative stress beneficial effects of GSPE on renal injury in rats with DOCA-salt hypertension occur via the attenuation of JNK and p38 activity.

Epigenetic Therapy for the Treatment of Hypertension-Induced Cardiac Hypertrophy and Fibrosis

BACKGROUND

The development of heart failure is associated with changes in the size, shape, and structure of the heart that has a negative impact on cardiac function. These pathological changes involve excessive extracellular matrix deposition within the myocardial interstitium and myocyte hypertrophy. Alterations in fibroblast phenotype and myocyte activity are associated with reprogramming of gene transcriptional profiles that likely requires epigenetic alterations in chromatin structure. The aim of our work was to investigate the potential of a currently licensed anticancer epigenetic modifier as a treatment option for cardiac diseases associated with hypertension-induced cardiac hypertrophy and fibrosis.

METHODS AND RESULTS

The effects of DNA methylation inhibition with 5-azacytidine (5-aza) were examined in a human primary fibroblast cell line and in a spontaneously hypertensive rat (SHR) model. The results from this work allude to novel in vivo antifibrotic and antihypertrophic actions of 5-aza. Administration of the DNA methylation inhibitor significantly improved several echocardiographic parameters associated with hypertrophy and diastolic dysfunction. Myocardial collagen levels and myocyte size were reduced in 5-aza-treated SHRs. These findings are supported by beneficial in vitro effects in cardiac fibroblasts. Collagen I, collagen III, and α-smooth muscle actin were reduced in a human ventricular cardiac fibroblast cell line treated with 5-aza.

CONCLUSION

These findings suggest a role for epigenetic modifications in contributing to the profibrotic and hypertrophic changes evident during disease progression. Therapeutic intervention with 5-aza demonstrated favorable effects highlighting the potential use of this epigenetic modifier as a treatment option for cardiac pathologies associated with hypertrophy and fibrosis.

Iptakalim attenuates hypoxia-induced pulmonary arterial hypertension in rats by endothelial function protection

The present study aimed to investigate the protective effects of iptakalim, an adenosine triphosphate (ATP)-sensitive potassium channel opener, on the inflammation of the pulmonary artery and endothelial cell injury in a hypoxia-induced pulmonary arterial hypertension (PAH) rat model. Ninety-six Sprague-Dawley rats were placed into normobaric hypoxia chambers for four weeks and were treated with iptakalim (1.5 mg/kg/day) or saline for 28 days. The right ventricle systolic pressures (RVSP) were measured and small pulmonary arterial morphological alterations were analyzed with hematoxylin and eosin staining. Enzyme-linked immunosorbent assay (ELISA) was performed to analyze the content of interleukin (IL)-1β and IL-10. Immunohistochemical analysis for ED1(+) monocytes was performed to detect the inflammatory cells surrounding the pulmonary arterioles. Western blot analysis was performed to analyze the expression levels of platelet endothelial cell adhesion molecule-1 (PECAM-1) and endothelial nitric oxide synthase (eNOS) in the lung tissue. Alterations in small pulmonary arteriole morphology and the ultrastructure of pulmonary arterial endothelial cells were observed via light and transmission electron microscopy, respectively. Iptakalim significantly attenuated the increase in mean pulmonary artery pressure, RVSP, right ventricle to left ventricle plus septum ratio and small pulmonary artery wall remodeling in hypoxia-induced PAH rats. Iptakalim also prevented an increase in IL-1β and a decrease in IL-10 in the peripheral blood and lung tissue, and alleviated inflammatory cell infiltration in hypoxia-induced PAH rats. Furthermore, iptakalim enhanced PECAM-1 and eNOS expression and prevented the endothelial cell injury induced by hypoxic stimuli. Iptakalim suppressed the pulmonary arteriole and systemic inflammatory responses and protected against the endothelial damage associated with the upregulation of PECAM-1 and eNOS, suggesting that iptakalim may represent a potential therapeutic agent for PAH.

Protective effects of grape seed proanthocyanidins on cardiovascular remodeling in DOCA-salt hypertension rats

Cardiovascular remodeling, as a hallmark of hypertension-induced pathophysiology, causes substantial cardiovascular morbidity and mortality. There is increasing evidence that has demonstrated a broad spectrum of pharmacological and therapeutic benefits of grape seed proanthocyanidins (GSP) against oxidative stress and cardiovascular diseases. In this study, 180- to 200-g SD rats treated with DOCA (120 mg/week sc with 1% NaCl and 0.2% KCl in drinking water) and GSP (150, 240, 384 mg/kg) or amlodipine (ALM) (5 mg/kg) for 4 weeks were recruited. The protective effects of GSP on blood pressure and cardiovascular remodeling in rats with DOCA-salt-induced hypertension were investigated. Our results indicated that DOCA-salt could induce hypertension, cardiovascular remodeling and dysfunction, oxidative stress and the release of endothelin-1 (ET-1) and could increase JNK1/2 and p38MAPK phosphorylation. GSP or ALM treatments significantly improved hypertension, cardiovascular remodeling and dysfunction and oxidative stress, restrained the release of ET-1 and down-regulated the JNK1/2 and p38MAPK phosphorylation. These findings demonstrate that GSP has protective effects against increase of blood pressure induced by DOCA-salt hypertension and cardiovascular remodeling by inhibiting the reactive oxygen species/mitogen-activated protein kinase pathway via restraining the release of ET-1.

Effect of the angiotensin II receptor blocker valsartan on cardiac hypertrophy and myocardial histone deacetylase expression in rats with aortic constriction

The aim of the present study was to observe the myocardial expression of members of the histone deacetylase (HDAC) family (HDAC2, HDAC5 and HDAC9) in rats with or without myocardial hypertrophy (MH) in the presence and absence of the angiotensin II receptor blocker valsartan. Adult male Wistar rats were randomly divided into three groups (n=6/group): Sham-operated control rats, treated with distilled water (1 ml/day) through gavage; rats with MH (established through aortic constriction), treated with distilled water (1 ml/day) through gavage; and MH + valsartan rats, treated with 20 mg/kg/day valsartan through gavage. Treatments commenced one day after surgery and continued for eight weeks. Body weight (BW), heart weight (HW) and plasma atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) levels were determined, and the myocardial expression of HDAC2, HDAC5 and HDAC9 was analyzed through a reverse transcription semi-quantitative polymerase chain reaction. The BWs of the rats in the three groups were similar at baseline; however, after eight weeks the BW of the rats in the MH + valsartan group was significantly reduced compared with that of the MH rats. Furthermore, the HW/BW ratio and plasma ANP and BNP levels were increased, the myocardial HDAC2 expression was significantly upregulated and the HDAC5 and HDAC9 expression was significantly downregulated in the MH rats compared with those in the control rats; however, these changes were significantly attenuated by valsartan. Modulation of myocardial HDAC5, HDAC9 and HDAC2 expression may therefore be one of the anti-hypertrophic mechanisms of valsartan in this rat MH model.

Mechanical stretch promotes matrix metalloproteinase-2 and prolyl-4-hydroxylase α1 production in human aortic smooth muscle cells via Akt-p38 MAPK-JNK signaling

Hypertension can increase mechanical stretch on the vessel wall, an important stimulus that induces collagen remodeling. Prolyl-4-hydroxylaseα1 (P4Hα1) and matrix metalloproteinases (MMPs) are essential for collagen synthesis and degradation. However, the effect of mechanical strain and collagen synthesis remains largely unknown. This study aimed to identify the effect of stretch on MMPs and P4Hα1 and the involved signaling pathways. Human aortic smooth muscle cells (HASMCs) were stimulated with mechanical stretch (0, 10% and 18% strain), and production of P4Hα1 as well as production and gelatinolytic activity of MMP-2 was force-dependently increased. Mechanical stretch at 18% also increased the expression of type I and III collagen and the phosphorylation of Akt, p38 mitogen-activated protein kinase (MAPK) and c-Jun N-terminal kinase (JNK). MMP-2 production and activity enhanced by 18% stretch were inhibited by the PI3K/Akt inhibitor LY294002. Blockade of p38 MAPK or JNK inhibited the promoting effect of stretch on P4Hα1. The in vivo model of aortic banding showed increased protein levels of MMP-2, P4Hα1 and collagen I and III in the aorta. Thus, mechanical stretch increased MMP-2 and P4Hα1 expression in HASMCs via AKT-P38 MAPK-JNK signaling, thereby inducing vascular remodeling.

Natakalim improves post-infarction left ventricular remodeling by restoring the coordinated balance between endothelial function and cardiac hypertrophy

Endothelial dysfunction can lead to congestive heart failure and the activation of endothelial ATP-sensitive potassium (K_ATP) channels may contribute to endothelial protection. Therefore, the present study was carried out to investigate the hypothesis that natakalim, a novel K_ATP channel opener, ameliorates post-infarction left ventricular remodeling and failure by correcting endothelial dysfunction. The effects of myocardial infarction were assessed 8 weeks following left anterior descending coronary artery occlusion in male Wistar rats. Depressed blood pressure, cardiac dysfunction, evidence of left ventricular remodeling and congestive heart failure were observed in the rats with myocardial infarction. Treatment with natakalim at daily oral doses of 1, 3 or 9 mg/kg/day for 8 weeks prevented these changes. Natakalim also prevented the progression to cardiac failure, which was demonstrated by the increase in right ventricular weight/body weight (RVW/BW) and relative lung weight, signs of cardiac dysfunction, as well as the overexpression of atrial and brain natriuretic peptide mRNAs. Our results also demonstrated that natakalim enhanced the downregulation of endothelium-derived nitric oxide, attenuated the upregulation of inducible nitric oxide synthase-derived nitric oxide (NO), inhibited the upregulated endothelin system and corrected the imbalance between prostacyclin and thromboxane A₂. Overall, our findings suggest that natakalim prevents post-infarction hypertrophy and cardiac failure by restoring the coordinated balance between endothelial function and cardiac hypertrophy.

Effects of Xin-Ji-Er-Kang formula on 2K1C-induced hypertension and cardiovascular remodeling in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Xin-Ji-Er-Kang (XJEK), a Chinese herbal formula, is effective against hypertension induced coronary heart disease, viral myocarditis and toxic myocarditis. In this study, the effect of XJEK on cardiovascular system was investigated. To test the hypothesis that Xin-Ji-Er-Kang (XJEK) has an anti-hypertensive effect mediated through attenuation of cardiac remodeling, and amelioration of vascular endothelial dysfunction and oxidative stress.

MATERIALS AND METHODS

Hypertension was induced in Wistar rats by 2 kidney 1 clip (2K1C) treatment. The hypertensive rats were then randomly assigned into four groups and treated as follows: group 1 (Sham-operated [Sh-Op] group received only drinking water), group 2 (induced hypertensive model+no treatment), and group 3 (induced hypertensive+a single daily oral dose of 24 g kg(-1) XJEK treatment) and group 4 (induced hypertensive+a single oral dose of 15 mg kg(-1) Fosinopril treatment). The rats in all the defined groups were respectively treated for a period of 4 weeks. Cardiovascular parameter such as systolic blood pressure (SBP) was measured weekly by using tail-cuff apparatus; left ventricular systolic pressure (LVSP), left ventricular end-diastolic pressure (LVEDP) and the rate of the rise in left ventricular pressure (±dp/dt max) were measured by using a PowerLab 8/30 apparatus (AD Instruments, Australia) at the end of the 8th week; heart weight/body weight (HW/BW) was determined as an index of myocardial hypertrophy (MH). Hematoxylin and eosin (H&E) and Van Gieson (VG) stain were used to assess the cardio-histological changes. Colorimetric analysis was used to assay serum superoxide dismutase (SOD) activity, malondialdehyde (MDA), nitric oxide (NO), and hydroxyproline (Hyp) contents in cardiac tissue. Angiotensin II (Ang II) content in serum was assessed by radioimmunoassay; tetrahydrobiopterin (BH4) content in cardiac tissue, BNP and endothelial NOS (eNOS) in serum were determined by using ELISA, and the protein expressions of c-Jun NH2-terminal kinase (JNK), P-JNK, p38, P-p38, and NADPH oxidases-2 (Nox-2) were measured by western blot.

RESULTS

XJEK therapy could impair the heart systolic and diastolic function, potently improve the heart weight index, inhibit the elevation of HW/BW ratio, and markedly ameliorate hemodynamic indices and vascular remodeling index. It has blunted the decrease of SOD, NO and the increase in MDA and Ang II serum contents, myocardial cross-section area (CSA), collagen volume fraction (CVF) and perivascular circumferential collagen area (PVCA) compared to the hypertensive model group. It also reduced the serum content of Hyp while increased BH4 levels in cardiac tissue. In addition, the expressions of Nox-2, P-JNK and P-p38MAPK were all suppressed compared to the hypertensive model group. Moreover, treatment with XJEK improved endothelial dysfunction (ED) manifested by promoting eNOS activities and enhancing the NO activity in serum.

CONCLUSION

The results of the present study show that XJEK attenuates 2K1C-induced hypertension in rats, which confirms our hypothesis that XJEK has an anti-hypertensive and cardiovascular remodeling effect via attenuation of cardiac remodeling and improvement of endothelial dysfunction and oxidative stress.

Pulmonary effects of chronic elevation in microvascular pressure differ between hypertension and myocardial infarct induced heart failure

BACKGROUND

Chronic heart failure (CHF) following coronary artery ligation and myocardial infarction in the rat leads to a homeostatic reduction in surface tension with associated alveolar type II cell hyperplasia and increased surfactant content, which functionally compensates for pulmonary collagen deposition and increased tissue stiffness. To differentiate the effects on lung remodelling of the sudden rise in pulmonary microvascular pressure (Pmv) with myocardial infarction from its consequent chronic elevation, we examined a hypertensive model of CHF.

METHODS

Cardiopulmonary outcomes due to chronic pulmonary capillary hypertension were assessed at six and 15 weeks following abdominal aortic banding (AAB) in the rat.

RESULTS

At six weeks post-surgery, despite significantly elevated left ventricular end-diastolic pressure, myocardial hypertrophy and increased left ventricular internal circumference in AAB rats compared with sham operated controls (p≤0.003), lung weights and tissue composition remained unchanged, and lung compliance was normal. At 15 weeks post-surgery increased lung oedema was evident in AAB rats (p=0.002) without decreased lung compliance or evidence of tissue remodelling.

CONCLUSION

Despite chronically elevated Pmv, comparable to that resulting from past myocardial infarction (LVEDP>19mmHg), there is no evidence of pulmonary remodelling in the AAB model of CHF.

The role of ATP-sensitive potassium channels in cellular function and protection in the cardiovascular system

ATP-sensitive potassium channels (K(ATP)) are widely distributed and present in a number of tissues including muscle, pancreatic beta cells and the brain. Their activity is regulated by adenine nucleotides, characteristically being activated by falling ATP and rising ADP levels. Thus, they link cellular metabolism with membrane excitability. Recent studies using genetically modified mice and genomic studies in patients have implicated K(ATP) channels in a number of physiological and pathological processes. In this review, we focus on their role in cellular function and protection particularly in the cardiovascular system.

The effects of 17-methoxyl-7-hydroxy-benzene-furanchalcone on the pressure overload-induced progression of cardiac hypertrophy to cardiac failure

We investigated the effects of 17-methoxyl-7-hydroxy-benzene-furanchalcone (MHBFC), which was isolated from the roots of Millettia pulchra (Benth.) Kurz var. Laxior (Dunn) Z.Wei (Papilionaceae) (MKL), on the progression of cardiac hypertrophy to failure in a rat model of abdominal aortic banding (AAB)-induced pressure overloading. Endothelial dysfunction is central to pressure overload-induced cardiac hypertrophy and failure. It would be useful to clarify whether MHBFC could prevent this dysfunction. The effects of pressure overload were assessed in male Sprague-Dawley rats 6 weeks after AAB using the progression of cardiac hypertrophy to heart failure as the endpoint. The AAB-treated rats exhibited a greater progression to heart failure and had significantly elevated blood pressure, systolic and diastolic cardiac dysfunction, and evidence of left ventricular hypertrophy (LVH). LVH was characterized by increases in the ratios of heart and left ventricular weights to body weight, increased myocyte cross-sectional areas, myocardial and perivascular fibrosis, and elevated cardiac hydroxyproline. These symptoms could be prevented by treatment with MHBFC at daily oral doses of 6 and 12 mg/kg for 6 weeks. The progression to cardiac failure, which was demonstrated by increases in relative lung and right ventricular weights, cardiac function disorders and overexpression of atrial natriuretic peptide (ANP) mRNA, could also be prevented. Furthermore, MHBFC partialy rescued the downregulated nitric oxide signaling system, whereas inhibited the upregulated endothelin signaling system, normalizing the balance between these two systems. MHBFC protected the endothelium and prevented the pressure overload-induced progression of cardiac hypertrophy to cardiac failure.

ATP-sensitive potassium (K(ATP)) channel openers diazoxide and nicorandil lower intraocular pressure in vivo

PURPOSE

To evaluate the expression of ATP-sensitive potassium (K(ATP)) channel subunits and study the effect of K(ATP) channel openers diazoxide and nicorandil on intraocular pressure (IOP) in an in vivo mouse model.

METHODS

Expression of K(ATP) channel subunits in normal C57BL/6 mouse eyes was studied by immunohistochemistry and confocal microscopy. Wild-type C57BL/6 mice were treated with K(ATP) channel openers diazoxide (n = 10) and nicorandil (n = 10) for 14 days. Similar treatments with diazoxide were performed on K(ir)6.2((-/-)) mice (n = 10). IOP was recorded with a handheld tonometer 1 hour, 4 hours, and 23 hours following daily treatment. Posttreatment histology was examined by light and transmission electron microscopy.

RESULTS

The K(ATP) channel subunits SUR2B, K(ir)6.1, and K(ir)6.2 were identified in all tissues within mouse eyes. Treatment with diazoxide in wild-type mice decreased IOP by 21.5 ± 3.2% with an absolute IOP reduction of 3.9 ± 0.6 mm Hg (P = 0.002). Nicorandil also decreased IOP (18.9 ± 1.8%) with an absolute IOP reduction of 3.4 ± 0.4 mm Hg (P = 0.002). Treatment with diazoxide in K(ir)6.2((-/-)) mice had no effect on IOP. No morphological abnormalities were observed in diazoxide- or nicorandil-treated eyes.

CONCLUSIONS

K(ATP) channel openers diazoxide and nicorandil are effective regulators of IOP in mouse eyes. K(ir)6.2 appears to be a major K(ATP) channel subunit through which IOP is lowered following treatment with diazoxide.

Effects of traditional Chinese medicine Xin-Ji-Er-Kang formula on 2K1C hypertensive rats: role of oxidative stress and endothelial dysfunction

Background

XinJiErKang (XJEK), a Chinese herbal formula, is identified as an effective preparation to treat coronary heart disease and myocarditis. The aim of the study is to investigate the anti-hypertensive effects of XJEK by oral administration and also to find out whether the drug has any role in oxidative stress and vascular endothelial function.

Methods

Clipping of the renal artery resulted in gradual elevation of the systolic blood pressure (SBP) which reached a plateau after 4 weeks of surgery. Treatment of hypertensive rats (20 mmHg higher than basic systolic blood pressure) with XJEK (6, 12, 24 g/kg/day) and fosinopril (15 mg/kg/day) respectively by intragastric administration started 4 weeks after surgery and continued for 4 weeks. The sham-operated (Sh-Op) controls received drinking water. BP was monitored weekly using tail-cuff apparatus. At the end of 8 wk, left ventricular systolic pressure (LVSP), left ventricular end-diastolic pressure (LVEDP), rate of rise of left ventricular pressure (±dp/dtmax) were examined (PowerLab 8/30, AD Instruments, Australia). The myocardial hypertrophy index was expressed as heart weight/body weight (HW/BW), the histological changes were investigated by hematoxylin and eosin (HE) and Van Gieson (VG) stain. Endothelium-dependent relaxations due to acetylcholine were observed in isolated rat thoracic aortic ring preparation. Superoxide dismutase (SOD) activity, malondialdehyde (MDA) and nitric oxide (NO) content in serum, contents of hydroxyproline (Hyp) in the ventricular tissue were assayed by xanthin oxidase method, thiobarbituric acid (TBA) method, Griess method and alkaline hydrolysis method, respectively. Angiotensin II (Ang II) content in serum was detected by radioimmunoasssay method.

Results

XJEK therapy potently improved cardiac function, inhibited myocardial hypertrophy, improved cardiac pathology change, decreased the myocardial cross-section area (CSA), collagen volume fraction (CVF) and perivascular circumferential collagen area (PVCA), reduced the content of Hyp in the left ventricular tissue, inhibited the decrease of SOD activity and increase of MDA, Ang II content in serum. Moreover, treatment with XJEK improved endothelial dysfunction (ED) manifested by promoting endothelial-dependent vasodilation of thoracic aortic rings and enhancing the NO activity in serum.

Conclusions

These findings suggest that administration of XJEK possess protective effects against 2K1C induced hypertension and cardiac remodeling in rats, preserve NO activity and endothelial function.

[Effects of a compound Chinese medicine Xinji' erkang on isoproterenol-induced ventricular remodeling in mice]

OBJECTIVE

To investigate the effects of Xinji' erkang (XJEK), a compound Chinese herbal medicine, on isoproterenol-induced ventricular remodeling in mice.

METHODS

Isoproterenol was given subcutaneously (1 mg/kg, twice per day for 7 d) to induce ventricular remodeling in mice. Mice were divided into normal control group, model group, XJEK low-, medium- and high- dose groups, XJEK water layer group, XJEK n-butanol layer group and metoprolol group. All drugs were given by intragastric administration. At the end of the 7th day, the hearts of the rats were weighted, and myocardial hypertrophy index was expressed as heart weight/body weight (HW/BW). The histological changes were observed by hemotoxylin-eosin and Van Gieson staining. Colorimetric method was used to determine the content of hydroxyproline in heart, and the activity of superoxide dismutase (SOD) and the content of malondialdehyde (MDA) in serum.

RESULTS

Compared with the isoproterenol injection only, XJEK potently inhibited cardiomyocyte hypertrophy and the increase of hydroxyproline content in heart (P<0.01), improved cardiac pathology change, inhibited the decrease of SOD activity and the increase of MDA content in serum (P<0.01). XJEK water layer also inhibited the increase of cardiomyocyte hypertrophy (P<0.01) while XJEK n-butanol layer inhibited cardiomyocyte hypertrophy and fibrosis (P<0.01).

CONCLUSION

XJEK possesses protective effects against isoproterenol-induced ventricular remodeling in mice, which may be related to its actions in reducing the oxidative stress and improving the antioxidant activity of the body. XJEK water layer and XJEK n-butanol layer attenuated ventricular remodeling without significant oxidative stress state changing, which indicates that a non-antioxidative stress mechanism may exist.

Iptakalim ameliorates monocrotaline-induced pulmonary arterial hypertension in rats

OBJECTIVES

We sought to investigate the experimental therapeutic effects and mechanisms of iptakalim, a new adenosine triphosphate (ATP)-sensitive potassium channel (K(ATP)) opener, on monocrotaline (MCT)-induced pulmonary arterial hypertension (PAH) and right heart ventricle remodeling in rats.

METHODS

Rats were injected with a single dose (50 mg/kg, ip) of MCT and given iptakalim (1, 3, and 9 mg/kg·per d, orally [po]) or saline for 28 days. The hemodynamic and morphometric parameters were assessed. Tissue and plasma samples were collected for histological and molecular analysis.

RESULTS

Treatment with iptakalim at daily oral doses of 1, 3, and 9 mg/kg from the day of MCT injection attenuated the high right ventricle systolic pressure (RVSP) and the increased weight ratio of right ventricle (RV) to left ventricle (LV) plus septum (S) (RV/(LV+S)), decreased heart rate (HR) and decreased mean arterial pressure (MAP), inhibited the RV myocardial tissue cell apoptosis, and the RV myocardial cell B-type natriuretic peptide (BNP) protein expression. Iptakalim also decreased the serum levels of nitric oxide (NO), endothelin 1 (ET-1), BNP, and the levels of NO, ET-1, and tumor necrosis factor-alpha (TNF-α) in the lung tissue.

CONCLUSION

These results indicate that iptakalim prevents MCT-induced PAH and RV remodeling and its mechanisms are related to inhibiting the pathological increases in NO, ET-1, BNP, and TNF-α, and Iptakalim may be a promising candidate for the treatment of PAH.

Effects of oligomeric grape seed proanthocyanidins on heart, aorta, kidney in DOCA-salt mice: role of oxidative stress

Growing experimental and clinical data highlights the important roles of increased reactive oxygen species production in cardiovascular remodeling (CR). Oligomeric grape seed proanthocyanidins (GSPs) have been shown to be potent antioxidants and free radical scavengers. Mice were treated with DOCA-salt to induce CR and were given distilled water or oligomeric GSPs for 4 weeks. The heart weight (HW) index and kidney weight (KW) index were expressed as heart weight/body weight (HW/BW) and kidney weight/body weight (KW/BW); the histological changes were investigated by hematoxylin and eosin and Van Gieson staining.The endothelial-dependent vasodilation function induced by acetylcholine was investigated in isolated thoracic aorta ring. Colorimetric analysis was used to assay superoxide dismutase (SOD) activity, malondialdehyde (MDA) content and nitric oxide (NO) content in serum and hydroxyproline content in cardiac tissue. Administration of GSPs markedly alleviated the elevation of HW/BW ratio, KW/BW ratio and cross-sectional area of cardiomyocytes, decreased collagen deposition in heart and attenuated histopathology injury, and improves endothelial-dependent aorta ring relaxation in vitro accompany by increasing of NO content in serum. Meanwhile, treatment with GSPs significantly ameliorated oxidative stress via increasing SOD activities and decreasing MDA formation. These findings suggest that administration of GSPs has the potential to attenuate DOCA-salt induced CR and KH and preserve NO activity and endothelial function, which mechanism may contribute to its antioxidant characteristic, at least in part.

Iptakalim enhances adult mouse hippocampal neurogenesis via opening Kir6.1-composed K-ATP channels expressed in neural stem cells

BACKGROUND AND PURPOSE

Emerging evidence indicates that stimulating adult neurogenesis provides novel strategies for central nervous system diseases. Iptakalim (Ipt), a novel ATP-sensitive potassium (K-ATP) channel opener, has been demonstrated to play multipotential neuroprotective effects in vivo and in vitro. However, it remains unknown whether Ipt could regulate the adult neurogenesis.

METHODS AND RESULTS

Based on the finding that adult neural stem cells (ANSCs) in hippocampus expressed Kir6.1/SUR1-composed K-ATP channel, Kir6.1 heterozygotic (Kir6.1(+/-) ) mice were used to investigate whether and how Ipt regulates adult hippocampal neurogenesis. We showed that administration of Ipt (10 mg/kg) or fluoxetine (Flx, 10 mg/kg) for 4 weeks significantly increased newborn ANSCs in subgranular zone (SGZ) of Kir6.1(+/+) mice but failed to affect those of Kir6.1(+/-) mice. Meanwhile, ANSCs in Kir6.1(+/-) mice exhibited decreased survival rate and impaired ability of differentiation into astrocytes. We further found that Kir6.1(+/-) mice showed lower level of brain-derived neurotrophic factor (BDNF) in hippocampus compared with Kir6.1(+/+) mice. Furthermore, Ipt increased the levels of BDNF and basic fibroblast growth factor (FGF-2) throughout the hippocampus in Kir6.1(+/+) mice but not in Kir6.1(+/-) mice. Moreover, Ipt and Flx enhanced the phosphorylation of Akt and CREB in the hippocampus of Kir6.1(+/+) mice. Notably, these effects were completely abolished in Kir6.1(+/-) mice.

CONCLUSIONS

Our findings demonstrate that Ipt stimulates the adult hippocampal neurogenesis via activation of Akt and CREB signal following the opening of Kir6.1-composed K-ATP channels, which gives us an insight into the therapeutic implication of Ipt in the diseases with adult neurogenesis deficiency, such as major depression.

Simvastatin modulates remodeling of Kv4.3 expression in rat hypertrophied cardiomyocytes

Objectives: Hypertrophy has been shown to be associated with arrhythmias which can be caused by abnormal remodeling of the Kv4-family of transient potassium channels. Inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A reductase (statins) have recently been shown to exert pleiotropic protective effects in cardiovascular diseases, including anti-arrhythmias. It is hypothesized that remodeling of Kv4.3 occurs in rat hypertrophied cardiomyocytes and is regulated by simvastatin.

Methods: Male Sprague-Dawley rats and neonatal rat ventricular myocytes (NRVMs) underwent abdominal aortic banding (AAB) for 7 weeks and angiotensin II (AngII) treatment, respectively, to induce cardiac hypertrophy. Kv4.3 expression by NRVMs and myocardium (subepicardial and subendocardial) in the left ventricle was measured. The transient outward potassium current (I_to) of NRVMs was recorded using a whole-cell patch-clamp method.

Results: Expression of the Kv4.3 transcript and protein was significantly reduced in myocardium (subepicardial and subendocardial) in the left ventricle and in NRVMs. Simvastatin partially prevented the reduction of Kv4.3 expression in NRVMs and subepicardial myocardium but not in the subendocardial myocardium. Hypertrophied NRVMs exhibited a significant reduction in the I_to current and this effect was partially reversed by simvastatin.

Conclusions: Simvastatin alleviated the reduction of Kv4.3 expression, I_to currents in hypertrophied NRVMs and alleviated the reduced Kv4.3 expression in subepicardial myocardium from the hypertrophied left ventricle. It can be speculated that among the pleiotropic effects of simvastatin, the anti-arrhythmia effect is partly mediated by its effect on Kv4.3.