Right Ventricular Hypertrophy In Rats Research Articles

Bawei Chenxiang Wan ameliorates right ventricular hypertrophy in rats with high altitude heart disease by SIRT3-HIF1α-PDK/PDH signaling pathway improving fatty acid and glucose metabolism

BackgroundBawei Chenxiang Wan (BCW) is among the most effective and widely used therapies for coronary heart disease and angina pectoris in Tibet. However, whether it confers protection through a right-ventricle (RV) myocardial metabolic mechanism is unknown.MethodsMale Sprague–Dawley rats were orally administrated with BCW, which was injected concurrently with a bolus of Sugen5416, and subjected to hypoxia exposure (SuHx; 5000 m altitude) for 4 weeks. Right ventricular hypertrophy (RVH) in high-altitude heart disease (HAHD) was assessed using Fulton’s index (FI; ratio of RV to left ventricle + septum weights) and heart-weight-to-body-weight ratio (HW/BW). The effect of therapeutic administration of BCW on the RVH hemodynamics was assessed through catheterization (mean right ventricular pressure and mean pulmonary artery pressure (mRVP and mPAP, respectively)). Tissue samples were used to perform histological staining, and confirmatory analyses of mRNA and protein levels were conducted to detect alterations in the mechanisms of RVH in HAHD. The protective mechanism of BCW was further verified via cell culture.ResultsBCW considerably reduced SuHx-associated RVH, as indicated by macro morphology, HW/BW ratio, FI, mPAP, mRVP, hypertrophy markers, heart function, pathological structure, and myocardial enzymes. Moreover, BCW can alleviate the disorder of glucose and fatty acid metabolism through upregulation of carnitine palmitoyltransferase1ɑ, citrate synthase, and acetyl-CoA and downregulation of glucose transport-4, phosphofructokinase, and pyruvate, which resulted in the reduced levels of free fatty acid and lactic acid and increased aerobic oxidation. This process may be mediated via the regulation of sirtuin 3 (SIRT3)-hypoxia-inducible factor 1α (HIF1α)-pyruvate dehydrogenase kinase (PDK)/pyruvate dehydrogenase (PDH) signaling pathway. Subsequently, the inhibition of SIRT3 expression by 3-TYP (a selective inhibitor of SIRT3) can reverse substantially the anti-RVH effect of BCW in HAHD, as indicated by hypertrophy marker and serum myocardial enzyme levels.ConclusionsBCW prevented SuHx-induced RVH in HAHD via the SIRT3-HIF1ɑ-PDK/PDH signaling pathway to alleviate the disturbance in fatty acid and glucose metabolism. Therefore, BCW can be used as an alternative drug for the treatment of RVH in HAHD.

Effects of Intermittent Normoxia on Chronic Hypoxic Pulmonary Hypertension and Right Ventricular Hypertrophy in Rats.

Liu, Chunlei, Xu Chen, Ge Guo, Xiang Xu, Xin Li, Qingxia Wei, Yanying Shen, Hanlu Li, Jianxiu Hao, Ya Ping Tian, and Kunlun He. Effects of intermittent normoxia on chronic hypoxic pulmonary hypertension and right ventricular hypertrophy in rats. High Alt Med Biol. 22: 184-192, 2021. Background: Individuals with chronically low arterial oxygen tension owing to high altitude develop elevated rates of pulmonary hypertension (PH) and right ventricular (RV) hypertrophy. However, the effects of the frequency and duration of normoxic exposure on PH and RV hypertrophy have not been adequately assessed; thus, we aimed to analyze the same. Materials and Methods: PH and RV hypertrophy were induced in 60 rats using a hypobaric chamber. Of these 60 rats, every 10 were exposed to normoxic conditions for 30 minutes once (1T/D), three times (3T/D), or five times daily (5T/D), or for one 150-minute recovery daily (1LT/D). Furthermore, 10 rats were housed in a normoxic environment, and another 10 were subjected to continuous hypoxia. After 4 weeks, hemodynamic measurements were recorded, and the hearts were harvested for pathomorphological observations. Results: Average pulmonary arterial pressures (PAP) of control rats and those exposed to hypobaric hypoxia were 14.1 and 32.3 mmHg, respectively. After 30 minutes of exposure to normoxia 3T/D, 5T/D, or 1LT/D, PAP values were reduced to 27.1, 27.9, or 26.8 mmHg, respectively. Four weeks of hypoxic exposure elevated the RV/heart weight (HW) ratios, while exposure to normoxia 3T/D, 5T/D, and 1LT/D significantly reduced RV/HW. In addition, exposure to normoxia 3T/D, 5T/D, 1LT/D reduced the percentage wall thickness of the pulmonary artery as well as the hypertrophy indices of atrial natriuretic peptide, brain natriuretic peptide, and myosin heavy chain 7 (MYH-7). Conclusions: Thirty-minute exposure to normoxic conditions of 3T/D, 5T/D, or 1LT/D effectively ameliorates PH and RV thickening.

Dimethylarginine dimethylaminohydrolase 1 deficiency aggravates monocrotaline-induced pulmonary oxidative stress, pulmonary arterial hypertension and right heart failure in rats

Patients with pulmonary arterial hypertension (PAH) and right ventricular (RV) failure have a poor clinical outcome, but the mechanisms of PAH and RV failure development are not totally clear. PAH is associated with reduced NO bioavailability and increased endogenous NOS inhibitor asymmetric dimethylarginine (ADMA). Dimethylarginine dimethylaminohydrolase-1 (DDAH1) plays a critical role in ADMA degradation. Here we generated a novel DDAH1 deficiency rat strain using the CRISPR-Cas9 technique, and studied the effect of DDAH1 dysfunction on monocrotaline-induced PAH, lung vascular remodeling and RV hypertrophy. DDAH1 knockout resulted in abolished DDAH1 expression in various tissues, and significant increases of plasma and lung ADMA content. DDAH1 knockout has no detectable effect on cardiac and lung structure, and LV function under control conditions in rats. However, DDAH1 knockout significantly aggravated monocrotaline-induced lung and RV oxidative stress, lung vascular remodeling and fibrosis, pulmonary hypertension and RV hypertrophy in rats. DDAH1 KO resulted in significantly greater increases of plasma and lung ADMA content under control conditions. In the wild type rats monocrotaline resulted in significant increases of plasma and lung ADMA contents and reduction of lung eNOS protein content and these changes were more marked in DDAH1 KO rats. Together, our results demonstrated that DDAH1 plays an important role in attenuating monocrotaline-induced lung oxidative stress, pulmonary hypertension and RV hypertrophy in rats.

The intervention of ginkgo biloba extract on monocrotaline-induced right ventricular hypertrophy in rats and its mechanism

To study the protective effects of ginkgo biloba extract on the right ventricular hypertrophy. Seventy-two SD male rats were randomly divided into 3 groups: control group(CON), monocrotaline-induced right ventricular hypertrophy group (MCT) and ginkgo biloba extract treated group (EGB) (n=24 in each group). Group MCT and group EGB were intraperitoneally injected with 2%MCT at the dose of 60 mg /kg on the first day. From the second day, group MCT was injected with 2 ml 0.9% sodium chloride, and 60 mg/kg ginkgo leaf extract was administered to the stomach in group EGB. The control group was injected with 2 ml 0.9% sodium chloride on the first day. After 3 weeks, in each group,cardiac hemodynamic changes were measured, heart weight index was calculated, and myocardial pathological changes were observed by HE staining. The expression of TRPC6 was detected by real-time polymerase chain reaction (real-time -PCR) and Western blot. Compared with the control group, the right ventricular systolic pressure (RVSP) was increased significantly in the MCT group(P＜0.01), the maximum or decline rate of descent (RV ±dp/dtmax) of the right ventricle pressure was increased significantly(P＜0.01), while the EGB group had the same trend as all the indexes in the group MCT, but the amplitude of all indicators in group EGB were decreased significantly than those of group MCT(P＜0.01), and the right ventricular hypertrophy index (RVMI) in group EGB was significantly lower than that in group MCT(P＜0.01).Group MCT showed typical myocardial hypertrophy performance by HE staining, and the right ventricular myocytes in group EGB were significantly improved than that in group MCT, and the mRNA and protein expression levels of TRPC6 in the right ventricle of group MCT and group EGB were increased(P＜0.01), while the EGB group was significantly lower than that of the MCT group(P＜0.01). Ginkgo biloba extract may inhibit the signal pathway of CaN / NFAT in cardiac myocytes by reducing the expression of TRPC6 protein, and then play an early protective effect on myocardial hypertrophy.

Expression and Correlation of Hypoxia-Inducible Factor-1α (HIF-1α) with Pulmonary Artery Remodeling and Right Ventricular Hypertrophy in Experimental Pulmonary Embolism.

BackgroundWe investigated the expression of HIF-1α (hypoxia-inducible factor-1α) and its correlations with pulmonary artery remodeling and right ventricular hypertrophy in PE (pulmonary embolism) rats.Material/MethodsAfter the PE rat model was established, the dynamic changes of mPAP (mean pulmonary artery pressure), PAMT (relative medial thickness of small pulmonary arteries), WA/TA (vessel wall area/total area), and RVHI (right ventricular hypertrophy index) were detected. Then, histomorphology of pulmonary vascular was observed, followed by HIF-1α mRNA and protein for pulmonary artery and right ventricle were checked via in situ hybridization and immunohistochemistry, respectively. The correlations between HIF-1α and mPAP, PAMT, WA/TA, and RVHI were analyzed.ResultsThe mPAP level increased from the initial time to 12 weeks of PE and reached the peak at 12 weeks. After 4 weeks of PE, PAMT increased compared with the initial control group (p<0.05), and increased further after 8 weeks and 12 weeks. Changes of the vessel WA/TA were the same as PAMT. Compared with the initial control group, RVHI increased at 8 weeks (p<0.05) and 12 weeks of PE (p<0.01). HIF-1α mRNA and protein were positively correlated with mPAP, PAMT, and WA/TA in pulmonary arteries. HIF-1α mRNA and protein were positively correlated with mPAP, PAMT, WA/TA, and RVHI in right ventricles (p<0.01).ConclusionsHIF-1α mRNA and protein are expressed in the pulmonary artery and right ventricular of PE rats, and HIF-1α may correlate with pulmonary artery remodeling and right ventricular hypertrophy in rats with PE.

Phosphorylation of PTEN increase in pathological right ventricular hypertrophy in rats with chronic hypoxia induced pulmonary hypertension

Background Phosphatase and tensin homologue on chromosome ten (PTEN) acts as a convergent nodal signalling point for cardiomyocyte hypertrophy, growth and survival. However, the role of PTEN in cardiac conditions such as right ventricular hypertrophy caused by chronic hypoxic pulmonary, hypertension remains unclear. This study preliminarily discussed the role of PTEN in the cardiac response to increased pulmonary vascular resistance using the hypoxia-induced PH rats. Methods Male Sprague Dawley rats were exposed to 10% oxygen for 1, 3, 7, 14 or 21 days to induce hypertension and right ventricular hypertrophy. Right ventricular systolic pressure was measured via catheterization. Hypertrophy index was calculated as the ratio of right ventricular mass to left ventricle plus septum mass. Tissue morphology and fibrosis were measured using hematoxylin, eosin and picrosirius red staining. The expression and phosphorylation levels of PTEN in ventricles were determined by real time PCR and Western blotting. Results Hypoxic exposure of rats resulted in pathological hypertrophy, interstitial fibrosis and remodelling of the right ventricle. The phosphorylation of PTEN increased significantly in the hypertrophic right ventricle compared to the normoxic control group. There were no changes in protein expression in either ventricle. Conclusion Hypoxia induced pulmonary hypertension developed pathological right ventricular hypertrophy and remodelling probably related to an increased phosphorylation of PTEN.

Inhibitory effect of nitric oxide-induced total ginsenosides on right ventricular hypertrophy in rats

To observe the effect of total ginsenosides (TG) on right ventricular hypertrophy induced by monocrotaline (MCT) in rats, and study its relationship with the nitric oxide pathway. Male Sprague Dawley rats were randomly divided into the control group, the MCT model group, TG-treated (20, 40, 60 mg kg-1 d-1) groups, and the L-arginine (L-arg) th NO release, T + L-N and L-a + L-N groups were wi th NOS into study TG's effect 200 mg kg-1 d-1 group. Besides, and its relationship wi also set, intraperitoneally injected with TG 40 mg kg-1 d -1 and L-arg 200 mg kg-1 - d-1, and orally administered hibitor L-NAME 20 mg kg-1 d-1. After all of the groups were given drugs for 18 d, their right ventricular peak systolic pressure (RVSP) ventricular hypertrophy index (RVHI) and RVW/BW were determined. Ultra-structure of myocardial cells was observed with transmission electron microscope. The NO2 -/NO3 - content in myocardial tissues were detected with the nitrate reduction method. ANF and eNOS mRNA expressions in right ventricle tissues were detected by using real-time RT-PCR. Low, middle and high doses of TG and L-arg preventive administration could significantly reduce RVSP, RVHI, RVW/BW and ANF mRNA expressions (P < 0. 05) , and ameliorate cellular mitochondrial swelling and degeneration. L-NAME could prevent the effect of L-arg on above indexes, whereas L-NAME of the same dose could not impact the reducing effect of TG 40 mg kg -1 on above indexes. TG 60 mg kg -1 could raise eNOS mRNA expression, but TG 20 mg kg-1 and 40 mg kg-1 showed no effect. TG can significantly attenuate MCT-induced right cardiac hypertrophy in rats. Its anti-hypertrophic effect is partially realized through NO.

Antagonism role of adenosine in right ventricular hypertrophy induced by hypoxia in rat

Objective To investigate the antagonism role of adenosine and its agonists in hypoxia-induced right ventricular hypertrophy in rat. Methods Fifty-six Sprague-Dawley rats were randomly divided into 7 groups, including normoxia control group, hypoxia control group, hypoxia plus adenosine group, hypoxia plus adenosine A1 receptor agonist(CPA) group, hypoxia plus adenosine A2 receptor agonist(NECA) group, hypoxia plus CPA and adenosine A1 receptor antagonist(DPCPX) group, hypoxia plus NECA and adenosine A2b receptor antagonist(MRS1754) group.There were 8 rats in each group.Rats in all groups except normoxia group were exposed to hypoxia for 21 days(oxygen volume concentration of 95-105 mL/L). On the 7th day, agents were continuously delivered with micro osmotic pump for 14 days.At the end of the experiment, both right ventricular to left ventricular plus septum weight[RV/(LV+ S)] ratio and right ventricular to body weight(RV/BW) ratio were measured, and the expression of myosin heavy chain(β-MHC) mRNA and regulator of G protein signaling 4(RGS4) mRNA in the right ventricular myocardial tissues were detected by PCR method. Results 1.After chronic hypoxia for 21 days, the ratios of RV/(LV+ S) and RV/ BW in the hypoxia control group were significantly higher than those in the normoxia control group respectively(all P<0.001); the ratios of RV/(LV+ S) and RV/BW in the hypoxia plus adenosine group and hypoxia plus CPA group were significantly lower than those in the hypoxia control group(all P<0.05); the ratio of RV/(LV+ S) in the hypoxia plus NECA group was significantly lower than that in the hypoxia control group(P<0.05).2.The expression level of β-MHC mRNA in the hypoxia control group was higher than that in the normoxia control group(P<0.001), and the expression level of RGS4 mRNA in the hypoxia group was lower than that in the normoxia group(P<0.001); the expression levels of β-MHC mRNA in the hypoxia plus adenosine group, hypoxia plus CPA group, or hypoxia plus NECA group were lower than those in the hypoxia control group(all P<0.001); the expression levels of RGS4 mRNA in hypoxia plus adenosine group, hypoxia plus CPA group, and hypoxia plus NECA group were higher than those in the hypoxia control group(all P<0.001). Conclusions Adenosine can attenuate hypoxia-induced right ventricular hypertrophy through RGS4 mediated pathway. Key words: Adenosine; Hypoxia; Myocardial hypertrophy; Regulator of G protein signaling 4

Metabolic Gene Remodeling and Mitochondrial Dysfunction in Failing Right Ventricular Hypertrophy Secondary to Pulmonary Arterial Hypertension

Right ventricular (RV) dysfunction (RVD) is the most frequent cause of death in patients with pulmonary arterial hypertension. Although abnormal energy substrate use has been implicated in the development of chronic left heart failure, data describing such metabolic remodeling in RVD remain incomplete. Thus, we sought to characterize metabolic gene expression changes and mitochondrial dysfunction in functional and dysfunctional RV hypertrophy. Two different rat models of RV hypertrophy were studied. The model of RVD (SU5416/hypoxia) exhibited a significantly decreased gene expression of peroxisome proliferator-activated receptor-γ coactivator-1α, peroxisome proliferator-activated receptor-α and estrogen-related receptor-α. The expression of multiple peroxisome proliferator-activated receptor-γ coactivator-1α target genes required for fatty acid oxidation was similarly decreased. Decreased peroxisome proliferator-activated receptor-γ coactivator-1α expression was also associated with a net loss of mitochondrial protein and oxidative capacity. Reduced mitochondrial number was associated with a downregulation of transcription factor A, mitochondrial, and other genes required for mitochondrial biogenesis. Electron microscopy demonstrated that, in RVD tissue, mitochondria had abnormal shape and size. Lastly, respirometric analysis demonstrated that mitochondria isolated from RVD tissue had a significantly reduced ADP-stimulated (state 3) rate for complex I. Conversely, functional RV hypertrophy in the pulmonary artery banding model showed normal expression of peroxisome proliferator-activated receptor-γ coactivator-1α, whereas the expression of fatty acid oxidation genes was either preserved or unregulated. Moreover, pulmonary artery banding-RV tissue exhibited preserved transcription factor A mitochondrial expression and mitochondrial respiration despite elevated RV pressure-overload. Right ventricular dysfunction, but not functional RV hypertrophy in rats, demonstrates a gene expression profile compatible with a multilevel impairment of fatty acid metabolism and significant mitochondrial dysfunction, partially independent of chronic pressure-overload.

Enhanced Ca 2+ -Sensing Receptor Function in Idiopathic Pulmonary Arterial Hypertension

A rise in cytosolic Ca(2+) concentration ([Ca(2+)](cyt)) in pulmonary arterial smooth muscle cells (PASMC) is an important stimulus for pulmonary vasoconstriction and vascular remodeling. Increased resting [Ca(2+)](cyt) and enhanced Ca(2+) influx have been implicated in PASMC from patients with idiopathic pulmonary arterial hypertension (IPAH). We examined whether the extracellular Ca(2+)-sensing receptor (CaSR) is involved in the enhanced Ca(2+) influx and proliferation in IPAH-PASMC and whether blockade of CaSR inhibits experimental pulmonary hypertension. In normal PASMC superfused with Ca(2+)-free solution, addition of 2.2 mmol/L Ca(2+) to the perfusate had little effect on [Ca(2+)](cyt). In IPAH-PASMC, however, restoration of extracellular Ca(2+) induced a significant increase in [Ca(2+)](cyt). Extracellular application of spermine also markedly raised [Ca(2+)](cyt) in IPAH-PASMC but not in normal PASMC. The calcimimetic R568 enhanced, whereas the calcilytic NPS 2143 attenuated, the extracellular Ca(2+)-induced [Ca(2+)](cyt) rise in IPAH-PASMC. Furthermore, the protein expression level of CaSR in IPAH-PASMC was greater than in normal PASMC; knockdown of CaSR in IPAH-PASMC with siRNA attenuated the extracellular Ca(2+)-mediated [Ca(2+)](cyt) increase and inhibited IPAH-PASMC proliferation. Using animal models of pulmonary hypertension, our data showed that CaSR expression and function were both enhanced in PASMC, whereas intraperitoneal injection of the calcilytic NPS 2143 prevented the development of pulmonary hypertension and right ventricular hypertrophy in rats injected with monocrotaline and mice exposed to hypoxia. The extracellular Ca(2+)-induced increase in [Ca(2+)](cyt) due to upregulated CaSR is a novel pathogenic mechanism contributing to the augmented Ca(2+) influx and excessive PASMC proliferation in patients and animals with pulmonary arterial hypertension.

Effects of a Pure .ALPHA./.BETA.-Adrenergic Receptor Blocker on Monocrotaline-Induced Pulmonary Arterial Hypertension With Right Ventricular Hypertrophy in Rats

It is unclear how much the sympathetic nervous system is involved in the development of pulmonary arterial hypertension (PAH). The present study examined whether or not a pure alpha/beta-adrenergic receptor blocker (arotinolol) could prevent the development of PAH and right ventricular hypertrophy (RVH) in a rat model of monocrotaline (MCT)-induced PAH. The heart rate, arterial blood pressure (BP), left ventricular pressure, pulmonary artery pressure (PAP), and right ventricular pressure (RVP) were measured after administration of arotinolol or saline for 2 weeks. Ventricular weight and myocyte size were also measured. Mean PAP was increased less in the arotinolol group (n=6), (53 +/-9 vs 21 +/-2 mmHg in the control (n=6); P<0.01). Systolic RVP was also less in the arotinolol group (41 +/-3 vs 91 +/-14 mmHg in the control, P<0.05) without differences in BP. It also significantly reduced the RV/body weight ratio (0.58 +/-0.01 vs 0.77 +/-0.04 mg/g; P<0.01). Furthermore, the myocyte width was significantly decreased in the arotinolol group. The pure alpha/beta-blocker arotinolol prevented the progression of MCT-induced PAH and RVH in rats, suggesting that sympathetic nervous activation might play a role in the development of PAH.

Captopril Attenuates Matrix Metalloproteinase-2 and -9 in Monocrotaline-Induced Right Ventricular Hypertrophy in Rats

Little is known about the influence of angiotensin converting enzyme (ACE) inhibitors on matrix metalloproteinase (MMP) in right ventricular remodeling. We investigated the effect of captopril, an ACE inhibitor, on MMP-2 and MMP-9 in monocrotaline-induced right ventricular hypertrophy. Six-week-old male Wistar rats were injected intraperitoneally with monocrotaline (60 mg/kg) or saline. The rats were administrated captopril (30 mg/kg per day) or a vehicle orally for 24 days from the day of monocrotaline injection. At day 25, echocardiography was performed and hearts were excised. Expressions and activities of MMP-2 and MMP-9 were measured by Western blotting and by gelatin zymography, respectively. In monocrotaline-injected rats, right ventricular weight/tail length ratio increased significantly. Histological analysis revealed cardiomyocyte hypertrophy and fibrosis in right ventricular sections. Echocardiography showed right ventricular dysfunction compared with saline-injected rats. The right ventricular hypertrophy, fibrosis, and dysfunction were inhibited by captopril. However, captopril did not attenuate an increase in pulmonary artery pressure. MMP-2 and MMP-9 expressions and activities in right ventricles increased significantly in monocrotaline-injected rats and captopril inhibited them. These findings indicate that captopril attenuates the development of monocrotaline-induced right ventricular hypertrophy in association with inhibition of MMP-2 and MMP-9 in rats.

Preservation of diastolic function in monocrotaline-induced right ventricular hypertrophy in rats

During ischemic heart diseases and when heart failure progresses depletion of myocardial energy stores occurs. D-Ribose (R) has been shown to improve cardiac function and energy status after ischemia. Folic acid (FA) is an essential cofactor in the formation of adenine nucleotides. Therefore, we assessed whether chronic R-FA administration during the development of hypertrophy resulted in an improved cardiac function and energy status. In Wistar rats (n = 40) compensatory right ventricular (RV) hypertrophy was induced by monocrotaline (30 mg/kg; MCT), whereas saline served as control. Both groups received a daily oral dose of either 150 mg.kg(-1).day(-1) dextrose (placebo) or R-FA (150 and 40 mg.kg(-1).day(-1), respectively). In Langendorff-perfused hearts, RV and left ventricular (LV) pressure development and collagen content as well as total RV adenine nucleotides (TAN), creatine content, and RV and LV collagen content were determined. In the control group R-FA had no effect. In the MCT-placebo group, TAN and creatine content were reduced, RV and LV diastolic pressure-volume relations were steeper, RV systolic pressures were elevated, RV and LV collagen content was increased, and RV-LV diastolic interaction was altered compared with controls. In the MCT-R-FA group, TAN, RV and LV diastolic stiffness, RV and LV collagen content, and RV-LV diastolic interaction were normalized to the values in the control group while creatine content remained depressed and RV systolic function remained elevated. In conclusion, the depression of energy status in compensated hypertrophic myocardium observed was partly prevented by chronic R-FA administration and accompanied by a preservation of diastolic function and collagen deposition.

Temporal Response of Na+/H+ exchanger 1(NHE1) Expression and Right Ventricular Hypertrophy in Rats Exposed to Chronic Hypoxia (CH)

Temporal Response of Na+/H+ exchanger 1(NHE1) Expression and Right Ventricular Hypertrophy in Rats Exposed to Chronic Hypoxia (CH)

Mechanism of Garlic Protection Against Coronary Endothelial Dysfunction and Right Ventricular Hypertrophy (RVH) in Pulmonary Hypertensive (PH) Rats: Comparisons among Fresh, Boiled and Aged Garlics

We recently found that coronary endothelial (EC) dysfunction associated and preceded the development of MCT-induced PH and RVH. Preliminary data showed a protective effect of garlic against this EC dysfunction and RVH. To investigate the possible mechanism for garlic effect, we pretreated the rats with either 1% fresh garlic powder (GQ), boiled GQ (BGQ) or aged garlic (Kyolic-KYO) prior to MCT injection. Mass spectrometric (LC/MS with ESI) analyses of GQ extracts showed a distinct allicin (163 M+H+) peak. Only allicin precursor, alliin, was found after heart inactivation of allicin synthesis in BGQ (Figure 1). KYO does not contain allicin either. Significant PH (34±4 mmHg) and RVH (40±2% of septum+LV weight) were found 3 weeks after MCT injection (vs. 19±2 mmHg and 25±1% of S+LV in controls, respectively). GQ treatment prevented PH (20±2 mmHg) and RVH (27±1% of S+LV), but BGQ (30±2 mmHg and 46±3% of S+LV) and KYO (28±2 mmHg and 47±5% of S+LV) treatments did not. In isolated right coronary arteries (RCA) acetylcholine (Ach) -induced NO dilation showed a marked decrease in MCT rats (Figure 2), which was prevented in the GQ, but not the BGQ and KYO rats. L-NAME induced constriction, an estimate of the spontaneous EC NO mediated dilation, was decreased in the MCT rats (−18±3% vs. −27±3% in controls), preserved in the GQ (−29±4%) but not the BGQ (−14±2%) and KYO (−20±5%) rats. A marked increase to U46619-induced constriction was also found in all RCA of MCT, BGQ, and KYO rats, but not the GQ. Taken together, these findings show that active ingredient allicin in garlic provides a protective effect against the development of RVH in rats, and that preservation of coronary EC function may represent an important underlying mechanism of the observed effect. Figure 1Open in figure viewerPowerPoint LC/MS Analyses of GQ and Boiled GQ Figure 2Open in figure viewerPowerPoint GQ prevents decreased Ach dilation in MCT rats

Time- and subunit-dependent differential mRNA expression of L-type Ca2+ channel during progression of right ventricular hypertrophy.

To clarify the molecular basis for changes in L-type calcium channel (VLCC) density in ventricular hypertrophy, we analyzed the mRNA expression of all the subunits including the main subunit alpha1c and auxiliary subunits (alpha2delta, beta2 and beta3) composing VLCC in rat right ventricular hypertrophy (RVH) induced by monocrotaline injection. To test the hypothesis that the expression of each subunit might change differently during progression of RVH, leading to an altered electrophysiologic outcome for VLCC, we investigated the ratio of the mRNA level of each auxiliary subunit to the main subunit. After monocrotaline injection, alpha1c mRNA showed a transient decrease on the 14th day and thereafter significantly increased to reach approximately 1.8 fold that of the control level on the 21st day. The auxiliary subunit alpha2delta mRNA showed a pattern similar to that of alpha1c. The beta3 mRNA increased rapidly after monocrotaline injection and increased approximately 4.1 fold. On the other hand, beta2 mRNA showed no significant changes. Accordingly, only the mRNA ratio of beta3 to alpha1c showed a significant increase among the auxiliary subunits after the monocrotaline injection. The ratio increased to a maximum of approximately 5.7 fold on the 14th day and thereafter decreased. These results suggest that VLCC density may be modified not only by alpha1c but also by its auxiliary subunit expression in ventricular hypertrophy, and provide a clue for understanding the controversial electrophysiologic results on VLCC density in hypertrophied hearts.

Endothelin-A-Receptor Antagonist and Oral Prostacyclin Analog are Comparably Effective in Ameliorating Pulmonary Hypertension and Right Ventricular Hypertrophy in Rats

Summary: Pulmonary hypertension (PH) has a poor prognosis and is a drug-resistant disease. Recently, it has been reported that continuous intravenous prostacyclin (PGI2) administration is effective for PH. In this study, we compared the effects of chronic treatment with an endothelin-A- (ETA) receptor antagonist with an oral PGI2 analog on PH in rats. We administered the ETA-receptor antagonist TA-0201 or beraprost sodium (BPS), which is an orally active PGI2 analog, to monocrotaline- (MCT) induced PH rats. Each drug was given orally for 19 days. The rats were divided into the following four groups: (1) normal rats with vehicle (control); (2) PH rats with vehicle treatment (PH + vehicle); (3) PH rats with TA-0201 treatment (0.5 mg/kg/day) (PH + TA-0201); (4) PH rats with BPS treatment (100 μg/kg/day) (PH + BPS). Nineteen days after MCT injection, Pp/Ps [the ratio of right ventricular (RV) systolic pressure to systemic systolic blood pressure) and the ratio of the RV weight to the body weight (RV/BW), indicators of PH and RV hypertrophy, were markedly higher in the PH + vehicle group than in the control (healthy) group. The increase in Pp/Ps and RV/BW was significantly depressed in the PH + TA-0201 group and PH + BPS group to a similar extent. The expression of β-myosin heavy chain (MHC) mRNA, a molecular marker for cardiac hypertrophy, in the RV was greatly increased in the PH + vehicle group and this increase was inhibited in the PH + TA-0201 group and PH + BPS group to a similar effect. In conclusion, treatment with an ETA-receptor antagonist or an oral PGI2 analog is comparably effective in the prevention of progression of PH and RV hypertrophy.

Effects of the endothelin ET A receptor antagonist, TA-0201, on pulmonary arteries isolated from hypoxic rats

To investigate the roles of endothelin-1 in the pathogenesis of hypoxic pulmonary hypertension, we studied the effects of a selective endothelin ET A receptor antagonist, TA-0201 ( N-(6-(2-(5-Bromopyrimidin-2-yloxy) ethoxy)-5-(4-methylphenyl) pyrimidin-4-yl)-4-(2-hydroxy-1,1-dimethylethyl) benzensulfonamide sodium salt sesquihydrate), on helical strips of pulmonary arteries isolated from hypoxia-induced pulmonary hypertensive rats as compared with those of normoxic rats. Endothelin-1-induced maximum contractions were significantly inhibited by exposure to hypoxia in the pulmonary arterial strips, but not in the mesenteric arterial strips. The hypoxia also induced right ventricular hypertrophy in rats. Addition of TA-0201 to the bath inhibited the endothelin-1-induced contraction of pulmonary arterial strips isolated from hypoxic rats more effectively than in those of normoxic rats. Oral administration of TA-0201 to hypoxic rats inhibited the hypoxia-induced right ventricular hypertrophy, and decreased the maximum contractile response to endothelin-1 in pulmonary arterial strips isolated from these rats. Those inhibitory effects induced by the oral administration of TA-0201 were not observed in the pulmonary arteries from normoxic rats or in the mesenteric arteries from both hypoxic and normoxic rats. These results suggest that endothelin-1 has important pathophysiological roles in hypoxia-induced pulmonary hypertension, and that TA-0201 may inhibit the endothelin-1-induced contraction through a change in the function of endothelin ET A receptor as well as competitive inhibition for endothelin ET A receptor.

Effects of Angiotensin II Receptor Blockade on Hypoxia-induced Right Ventricular Hypertrophy in Rats

It was the aim of the present study to characterize the hemodynamic, biochemical and morphologic effect of angiotensin II receptor blockade on hypoxia-induced right ventricular hypertrophy in rats. Isolated right ventricular hypertrophy was induced in female Sprague–Dawley rats by intermittent hypoxia (IH; 10% O2, 8 h/day, 5 days/week, 20 days of exposition,n=15). After completion of IH, left- (LV) and right-ventricular (RV) hemodynamic parameters were measured under room air conditions in the intact, thiopental-anesthetized animals with special Millar ultraminiature tipcatheter-manometers. Cardiac output was determined using the thermodilution method. Cell volume (CV) of isolated cardiomyocytes was measured with a Coulter Channellyzer after collagenase cell isolation. The specific activities of the myocardial pentose phosphate pathway enzymes glucose-6-phosphate-dehydrogenase (G-6-PD) and 6-phosphogluconate-dehydrogenase (6-PGD) were determined using a spectrophotometric assay. IH caused a rise in right ventricular systolic pressure (RVSP) from 38.1±0.83 to 58.1±1.42 mmHg and an increase in the RV weight/body weight ratio (RVW/BW) from 0.884±0.053 to 1.166±0.049 mg/g. The activities of G-6-PD and 6-PGD were significantly increased after IH in the RV, but not in the LV. CV was increased from 24 248±1193 to 29 541±1765μm3, myocardial cell length was unchanged. IH had no influence on the LV parameters or cardiac output. Co-infusion of the angiotensin II receptor antagonist losartan (LO; 12 mg/kg/d i.p.,n=14) during the IH period reduced the rises in RVSP (49.4±2.06 mmHg), RVW/BW (0.99±0.072 mg/g), G-6-PD and 6-PGD significantly, but not completely. The increase in CV, however, was prevented (24 524±2370μm3) entirely. We conclude from these data that the IH-induced RV-hypertrophy was primarily of the concentric type. LO attenuated the hypoxia-induced isolated RV hypertrophy and significantly reduced the metabolic response of the RV. The LO effect was most potent with regard to the increase in cardiomyocyte volume.

Endogenous endothelin-1 mediates cardiac hypertrophy and switching of myosin heavy chain gene expression in rat ventricular myocardium

We investigated the role of endogenous endothelin-1 in the development of cardiac hypertrophy in vivo under pressure overload conditions. Endothelin-1, a potent vasoconstrictor peptide, has recently been shown to act as a growth factor of myocardial cells in culture. We examined the effect of an endothelin-A receptor antagonist (FR139317) on the development of right ventricular hypertrophy in rats with monocrotaline-induced pulmonary hypertension. Three groups of rats were studied: those given monocrotaline alone or monocrotaline plus FR139317 and those given vehicle alone (control group). The ratio of right ventricular systolic pressure to aortic systolic pressure was similarly elevated in rats treated with monocrotaline and monocrotaline plus FR139317. The right ventricular/left ventricular weight ratio was increased in monocrotaline-treated rats but lower in rats treated with monocrotaline plus FR139317 than in those treated with monocrotaline alone (p < 0.01). As a biochemical marker of hypertrophy, the isoform ratio of beta-myosin heavy chain protein was determined for the right ventricular tissue samples. This ratio was increased in all monocrotaline-treated rats but was lower (p < 0.01) in rats given monocrotaline plus FR139317 than in those given monocrotaline alone. The isoform ratio of beta-myosin heavy chain messenger ribonucleic acid quantitated by S1 nuclease mapping also was lower (p < 0.025) in rats receiving monocrotaline plus FR139317 than in those receiving monocrotaline alone. These data suggest that blocking the action of endothelin-1 with a receptor antagonist ameliorates cardiac hypertrophy in this model system, and that this action is not mediated by ameliorating hemodynamic changes.