Temporal relation of cardiac hypertrophy, oxidative stress, and fatty acid metabolism in spontaneously hypertensive rat

Acute poisoning by chlorpyrifos differentially impacts survival and cardiorespiratory function in normotensive and hypertensive rats

Hypertension is the most important and well-known risk factor for cardiovascular disease (CVD). Recently, acute organophosphate (OP) poisoning has also been pointed as a CVD risk factor. Despite this evidence, no studies have contrasted the acute toxicosis and cardiovascular (CV) effects of OP poisoning under conditions of normotension and hypertension. In this work, adult male normotensive Wistar and Spontaneously Hypertensive rats (SHR) were intraperitoneally injected with saline or chlorpyrifos (CPF), an OP compound, monitored for acute toxicosis signs and 24-h survival. After poisoning, blood pressure, heart rate and ventilation were recorded, the Bezold-Jarisch Reflex (BJR), the Chemoreflex (CR) were chemically activated, as well as the cardiac autonomic tone (AUT) was assessed. Erythrocyte and brainstem acetylcholinesterase and plasmatic butyrylcholinesterase (BuChE) activities were measured as well as lipid peroxidation, advanced oxidation protein products (AOPP), nitrite/nitrate levels, expression of catalase, TNFα and angiotensin-I converting enzyme (ACE-1) within the brainstem. CPF induced a much more pronounced acute toxicosis and 33 % lethality in SHR. CPF poisoning impaired ventilation in SHR, the BJR reflex responses in Wistar rats, and the chemoreflex tachypneic response in both strains. CPF inhibited activity of cholinesterases in both strains, increased AOPP and nitrite/nitrate levels and expression of TNFα and ACE-1 in the brainstem of Wistar rats. Interestingly, SHR presented a reduced intrinsic BuChE activity, an important bioscavenger. Our findings show that, CPF at sublethal doses in normotensive rats lead to lethality and much more pronounced acute toxicity signs in the SHR. We also showed that cardiorespiratory reflexes were differentially impacted after CPF poisoning in both strains and that the cardiorespiratory disfunction seems to be associated with interference in cholinergic transmission, oxidative stress and inflammation. These results points to an increased susceptibility to acute toxicosis in hypertension, which may impose a significant risk to vulnerable populations.

Apitherapy combination improvement of blood pressure, cardiovascular protection, and antioxidant and anti-inflammatory responses in dexamethasone model hypertensive rats

Hypertension-induced ventricular and vascular remodeling causes myocardial infarction, heart failure, and sudden death. Most available pharmaceutical products used to treat hypertension lead to adverse effects on human health. Limited data is available on apitherapy (bee products) combinations for treatment of hypertension. This study aims to evaluate the antihypertensive effects of combinations of natural apitherapy compounds used in the medical sector to treat a variety of diseases. Rats were assigned into six groups consisting of one control group and five hypertensive groups where hypertension (blood pressure > 140/90) was induced with dexamethasone. One of these groups was used as a hypertension model, while the remaining four hypertensive groups were treated with a propolis, royal jelly, and bee venom combination (PRV) at daily oral doses of 0.5, 1.0, and 2.0 mg/kg, and with losartan 10 mg/kg. The PRV combination at all doses decreased arterial blood pressure below the suboptimal value (p < 0.001), and PRV combination treatment improved dexamethasone-induced-ECG changes. The same treatment decreased angiotensin-II, endothelin-1, and tumor growth factor β serum levels in hypertensive rats. Additionally, PRV combination improved histopathological structure, and decreased serum levels of NF-kB and oxidative stress biomarkers. We concluded that PRV combination therapy may be used as a potential treatment for a variety of cardiovascular diseases.

Transcriptomic profile analysis of the left atrium in spontaneously hypertensive rats in the early stage

Left atrial remodeling, characterized by enlargement and hypertrophy of the left atrium and increased fibrosis, was accompanied by an increased incidence of atrial fibrillation. While before morphological changes at the early stage of hypertension, how overloaded hypertension influences the transcriptomic profile of the left atrium remains unclear. Therefore, RNA-sequencing was performed to define the RNA expressing profiles of left atrium in spontaneously hypertensive rats (SHRs) and normotensive Wistar-Kyoto (WKY) rats as a control group. We also compared the changes in the RNA expression profiles in SHRs treated with an angiotensin receptor blocker (ARB) and angiotensin receptor-neprilysin inhibitor (ARNI) to assess the distinct effects on the left atrium. In total, 1,558 differentially expressed genes were found in the left atrium between WKY rats and SHRs. Bioinformatics analysis showed that these mRNAs could regulate upstream pathways in atrial remodeling through atrial fibrosis, inflammation, electrical remodeling, and cardiac metabolism. The regulated transcripts detected in the left atrial tissue in both the ARB-treated and ARNI-treated groups were related to metabolism. In contrast to the ARB-treated rates, the transcripts in ARNI-treated rats were mapped to the cyclic guanosine monophosphate-protein kinase G signaling pathway.

Alterations of Lipid Metabolism in the Heart in Spontaneously Hypertensive Rats Precedes Left Ventricular Hypertrophy and Cardiac Dysfunction

Disturbances in cardiac lipid metabolism are associated with the development of cardiac hypertrophy and heart failure. Spontaneously hypertensive rats (SHRs), a genetic model of primary hypertension and pathological left ventricular (LV) hypertrophy, have high levels of diacylglycerols in cardiomyocytes early in development. However, the exact effect of lipids and pathways that are involved in their metabolism on the development of cardiac dysfunction in SHRs is unknown. Therefore, we used SHRs and Wistar Kyoto (WKY) rats at 6 and 18 weeks of age to analyze the impact of perturbations of processes that are involved in lipid synthesis and degradation in the development of LV hypertrophy in SHRs with age. Triglyceride levels were higher, whereas free fatty acid (FA) content was lower in the LV in SHRs compared with WKY rats. The expression of de novo FA synthesis proteins was lower in cardiomyocytes in SHRs compared with corresponding WKY controls. The higher expression of genes that are involved in TG synthesis in 6-week-old SHRs may explain the higher TG content in these rats. Adenosine monophosphate-activated protein kinase phosphorylation and peroxisome proliferator-activated receptor α protein content were lower in cardiomyocytes in 18-week-old SHRs, suggesting a lower rate of β-oxidation. The decreased protein content of α/β-hydrolase domain-containing 5, adipose triglyceride lipase (ATGL) activator, and increased content of G0/G1 switch protein 2, ATGL inhibitor, indicating a lower rate of lipolysis in the heart in SHRs. In conclusion, the present study showed that the development of LV hypertrophy and myocardial dysfunction in SHRs is associated with triglyceride accumulation, attributable to a lower rate of lipolysis and β-oxidation in cardiomyocytes.

Mito-targeted antioxidant prevents cardiovascular remodelling in spontaneously hypertensive rat by modulation of energy metabolism

Hypertension induced left ventricular hypertrophy (LVH) augments the risk of cardiovascular anomalies. Mitochondrial alterations result in oxidative stress, accompanied by decrease in fatty acid oxidation, leading to the activation of the hypertrophic program. Targeted antioxidants are expected to reduce mitochondrial reactive oxygen species more effectively than general antioxidants. This study was designed to assess whether the mito-targeted antioxidant, Mito-Tempol (Mito-TEMP) is more effective than the general oxidant, Tempol (TEMP) in reduction of hypertension and hypertrophy and prevention of shift in cardiac energy metabolism. Spontaneously hypertensive rats were administered either TEMP (20 mg/kg/day) or Mito-TEMP (2 mg/kg/day) intraperitoneally for 30 days. Post treatment, animals were subjected to 2D-echocardiography. Myocardial lysates were subjected to RPLC - LTQ-Orbitrap-MS analysis. Mid-ventricular sections were probed for markers of energy metabolism and fibrosis. The beneficial effect on cardiovascular structure and function was significantly higher for Mito-TEMP. Increase in mitochondrial antioxidants and stimulation of fatty acid metabolism; with significant improvement in cardiovascular function was apparent in spontaneously hypertensive rats (SHR) treated with Mito-TEMP. The study indicates that Mito-TEMP is superior to its non- targeted isoform in preventing hypertension induced LVH, and the beneficial effects on heart are possibly mediated by reversal of metabolic remodelling.

Management of oxidative stress and inflammation in cardiovascular diseases: mechanisms and challenges

Cardiovascular diseases (CVDs) have diverse physiopathological mechanisms with interconnected oxidative stress and inflammation as one of the common etiologies which result in the onset and development of atherosclerotic plaques. In this review, we illustrate this strong crosstalk between oxidative stress, inflammation, and CVD. Also, mitochondrial functions underlying this crosstalk, and various approaches for the prevention of redox/inflammatory biological impacts will be illustrated. In part, we focus on the laboratory biomarkers and physiological tests for the evaluation of oxidative stress status and inflammatory processes. The impact of a healthy lifestyle on CVD onset and development is displayed as well. Furthermore, the differences in oxidative stress and inflammation are related to genetic susceptibility to cardiovascular diseases and the variability in the assessment of CVDs risk between individuals; Omics technologies for measuring oxidative stress and inflammation will be explored. Finally, we display the oxidative stress-related microRNA and the functions of the redox basis of epigenetic modifications.

Targeted Metabolic Profiling and PRM Analysis of Proteins Revealed Impaired Polyunsaturated Fatty Acid Metabolism and GTP Metabolism in the Brainstem of Spontaneously Hypertensive Rats

An untargeted multi-omics study implicated the potential dysregulation of fatty acid, nucleotide, and energy metabolism in the brainstems of spontaneously hypertensive rats (SHRs). A further quantitative exploration of the alterations in the metabolic pathways is necessary for a deep understanding of the central nervous system in SHRs. Targeted metabolic profiling of 40 fatty acids (PeptideAtlas: PASS01671) and 32 metabolites of nucleotides and energy metabolism (PeptideAtlas: PASS01672) and parallel reaction monitoring analysis of 5 proteins (PeptideAtlas: PASS01673) were performed on the brainstems of SHRs (n = 8, 11 weeks old) and normotensive Wistar rats (n = 8, age-matched) using gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-tandem MS. The targeted profiling results of metabolites and proteins revealed decreased polyunsaturated fatty acid (PUFA) synthesis with a significant downregulation of cis-11,14-eicosadienoic acid, cis-13,16-docosadienoic acid, and docosatetraenoate and impaired PUFA oxidation with the accumulation of γ-linolenate induced by the significantly downregulated expression of 2,4-dienoyl-CoA reductase (p < 0.05). Dysregulated GTP and ATP metabolism was observed, with significantly decreased GDP and ADP (p < 0.05) correlated with reduced GTPases of guanine nucleotide-binding protein subunit beta-1 (GNB1), transforming protein RhoA (RHOA), and Rho-related GTP-binding protein RhoB (RHOB) in the brainstem of SHRs. In addition, protein-arginine deiminase type-2 was significantly reduced in the brainstems of SHRs (p < 0.05). The aberrant PUFA and energy metabolism might help to explain the alterations in the brainstem of SHRs. The findings on both metabolites and proteins could provide systemic insights into the pathology basis of altered PUFA and energy metabolism in hypertension, especially in the central nervous system.

PDE5 inhibition improves cardiac morphology and function in SHR by reducing NHE1 activity: Repurposing Sildenafil for the treatment of hypertensive cardiac hypertrophy

Previously, we have shown that an increased cGMP-activated protein Kinase (PKG) activity after phosphodiesterase 5 (PDE5) inhibition by Sildenafil (SIL), leads to myocardial Na+/H+ exchanger (NHE1) inhibition preserving its basal homeostatic function. Since NHE1 is hyperactive in the hypertrophied myocardium of spontaneous hypertensive rats (SHR), while its inhibition was shown to prevent and revert this pathology, the current study was aimed to evaluate the potential antihypertrophic effect of SIL on adult SHR myocardium. We initially tested the inhibitory capability of SIL on NHE1 in isolated cardiomyocytes of SHR by comparing H+ efflux during the recovery from an acid load. After confirmed that effect, eight-month-old SHR were chronically treated for one month with SIL through drinking water. Compared to their littermate controls, SIL-treated rats presented a decreased NHE1 activity, which correlated with a reduction in its phosphorylation level assigned to activation of a PKG-p38 MAP kinase-PP2A signaling pathway. Moreover, treated animals showed a decreased oxidative stress that appears to be a consequence of a decreased mitochondrial NHE1 phosphorylation. Treated SHR showed a significant reduction in the pro-hypertrophic phosphatase calcineurin, despite slight tendency to decrease hypertrophy was detected. When SIL treatment was prolonged to three months, a significant decrease in myocardial hypertrophy and interstitial fibrosis that correlated with a lower myocardial stiffness was observed. In conclusion, the current study provides evidence concerning the ability of SIL to revert established cardiac hypertrophy in SHR, a clinically relevant animal model that resembles human essential hypertension.

Remote transplantation of human adipose-derived stem cells induces regression of cardiac hypertrophy by regulating the macrophage polarization in spontaneously hypertensive rats

Left ventricular hypertrophy (LVH) in hypertension has prognostic significance on cardiovascular mortality and morbidity. Recently, we have shown that n-butylidenephthalide (BP) improves human adipose-derived stem cell (hADSC) engraftment via attenuated reactive oxygen species (ROS) production. This prompted us to investigate whether remote transplantation of BP-pretreated hADSCs confers attenuated LVH at an established phase of hypertension. Male spontaneously hypertensive rats (SHRs) aged 12 weeks were randomly allocated to receive right hamstring injection of vehicle, clinical-grade hADSCs, and BP-preconditioned hADSCs for 8 weeks. As compared with untreated SHRs, naïve hADSCs decreased the ratio of LV weight to tibia, cardiomyocyte cell size, and collagen deposition independent of hemodynamic changes. These changes were accompanied by attenuated myocardial ROS production and increased p-STAT3 levels. Compared with naïve hADSCs, BP-preconditioned hADSCs provided a further decrease of ROS and LVH and an increase of local hADSC engraftment, STAT3 phosphorylation, STAT3 activity, STAT3 nuclear translocation, myocardial IL-10 levels, and the percentage of M2 macrophage infiltration. SIN-1 or S3I-201 reversed the effects of BP-preconditioned ADSCs increase on myocardial IL-10 levels. Furthermore, SIN-1 abolished the phosphorylation of STAT3, whereas superoxide levels were not affected following the inhibition of STAT3. Our results highlighted the feasibility of remote transplantation of hADSCs can be considered as an alternative procedure to reverse cardiac hypertrophy even at an established phase of hypertension. BP-pretreated hADSCs polarize macrophages into M2 immunoregulatory cells more efficiently than naïve hADSCs via ROS/STAT3 pathway.

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Hypertension was associated with left ventricular hypertrophy.

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Compared with untreated SHRs, naïve hADSCs injected at the right hamstring decreased LV mass and cardiomyocyte cell size.

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BP-preconditioned ADSCs provided a further increase of the M2 macrophage infiltration.

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The beneficial effects of BP-preconditioned stem cell administration can be abolished by exogenous SIN-1 or 3SI-201.

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Remote transplantation of hADSCs can be considered as an alternative procedure to reverse cardiac hypertrophy.

Association of histamine with hypertension-induced cardiac remodeling and reduction of hypertrophy with the histamine-2-receptor antagonist famotidine compared with the beta-blocker metoprolol

The association of histamine with adverse cardiac remodeling in chronic pressure overload has not received much attention. A pilot study in spontaneously hypertensive rats (SHRs) indicated a reduction of left ventricular hypertrophy (LVH) with a histamine-2-receptor (H2R) antagonist (famotidine). This finding prompted a detailed investigation of temporal variation in myocardial histamine and H2R expression and the cardiovascular response to H2R antagonism compared with that of the conventional beta-blocker metoprolol. Reduction of LVH is known to reduce the risk of adverse cardiovascular events. The myocardial histamine content and H2R expression increased with age in SHRs but not in normotensive Wistar rats. The cardiovascular response to famotidine (30 mg kg^-1) was compared with that of metoprolol (50 mg kg^-1) in 6-month-old male SHRs treated for 60 days. The decrease in diastolic blood pressure and improvement in cardiac function induced by famotidine and metoprolol were comparable. Both treatments caused the regression of LVH as assessed from the hypertrophy index, histomorphometry, B type natriuretic peptide (BNP), pro-collagen 1, and hydroxyproline levels. Calcineurin-A expression (marker of pathological remodeling) decreased, and Peroxiredoxin-3 expression (mitochondrial antioxidant) increased in response to the treatments. The myocardial histamine levels decreased with the treatments. The age-dependent increase in myocardial histamine and H2R in the SHRs signifies their association with progressive cardiac remodeling. The regression of LVH and improvement in cardiac function by famotidine further demonstrates the role of histamine in cardiac remodeling. Hypertrophy of cultured cardiac cells upon exposure to histamine and the H2R agonist amthamine substantiates the role of histamine in cardiac remodeling. The cardiovascular response to famotidine is comparable to that of metoprolol, suggesting repurposing of H2R antagonists for the management of hypertensive heart disease.

JIP3 deficiency attenuates cardiac hypertrophy by suppression of JNK pathway

Pathological cardiac hypertrophy is a leading cause of morbidity and mortality worldwide; however, our understanding of the molecular mechanisms revealing the disease is still unclear. In the present study, we suggested that c-Jun N-terminal kinase (JNK)-interacting protein 3 (JIP3), involved in various cellular processes, played an essential role in regulating pathological cardiac hypertrophy through in vivo and in vitro studies. JIP3 was highly expressed in human hearts with hypertrophic cardiomyopathy (HCM), and in mouse hypertrophic hearts. Following, the wild type (WT) and JIP3-knockout (KO) mice subjected to aortic banding (AB) challenge were used as animal models with cardiac hypertrophy. The results showed that JIP3-KO mice after AB operation exhibited attenuated cardiac function, reduced fibrosis levels and decreased hypertrophic marker proteins, including atrial natriuretic peptides (Anp) and brain/B-type natriuretic peptides (Bnp) and β-myosin heavy chain (β-Mhc). Loss of JIP3 also ameliorated oxidative stress, inflammatory response, apoptosis and endoplasmic reticulum (ER) stress in hearts of mice after AB surgery. Consistently, the expressions of ER stress-related molecules, such as phosphorylated-α-subunit of the eukaryotic initiation factor-2 (eIF2α), glucose-regulated protein (GRP) 78 and C/-EBP homologous protein (CHOP), were markedly decreased by JIP3-deficiency in hearts of AB-operated mice. JNK and its down-streaming signal of p90rsk was highly activated by AB operation in WT mice, while being significantly reversed by JIP3-ablation. Intriguingly, the in vitro results showed that promoting JNK activation by using its activator of anisomycin enhanced AngII-stimulated ER stress, oxidative stress, apoptosis and inflammatory response in cardiomyocytes isolated from WT mice. However, JIP3-KO-attenuated these pathologies was rescued by anisomycin treatment in AngII-incubated cardiomyocytes. Together, the findings indicated that blockage of JIP3 could alleviate cardiac hypertrophy via inactivating JNK pathway, and thus might be a promising strategy to prevent pathological cardiac hypertrophy.

Modulation of cardiac stem cell characteristics by metoprolol in hypertensive heart disease

Cardiac stem cells (CSCs) play a vital role in cardiac remodeling. Uncontrolled hypertension leads to cardiac hypertrophy, followed by cardiac failure. Pathological remodeling is associated with enhanced oxidative stress. Decreased cardiac stem cell efficiency is speculated in heart diseases. Maintaining a healthy stem cell population is essential for preventing progressive cardiac remodeling. Some anti-hypertensive drugs are cardioprotective. However, the effect of these drugs on CSCs has not been investigated. Metoprolol is a cardioprotective anti-hypertensive agent. To examine whether metoprolol can prevent the deterioration of CSC efficiency, spontaneously hypertensive rats (SHRs) were treated with this drug, and the effects on stem cell function were evaluated. Six-month-old male SHRs were treated with metoprolol (50 mg × kg^-1per day) for 2 months. The effectiveness of the treatment at reducing blood pressure and reducing hypertrophy was ensured, and the animals were killed. Cardiac stem cells were isolated from the atrial tissue, and the effect of metoprolol on stem cell migration, proliferation, differentiation, and survival was evaluated by comparing the treated SHRs with untreated SHRs and normotensive Wistar rats. Compared to the Wistar rats, the SHR rats presented with a decrease in stem cell migration and proliferation and an increase in intracellular oxidative stress and senescence. Treating SHRs with metoprolol increased CSC migration and proliferation potential and stemness retention. Cellular senescence and oxidative stress were reduced. The attributes of stem cells from the metoprolol-treated SHRs were comparable to those of the Wistar rats. The restoration of stem cell efficiency is expected to prevent hypertension-induced progressive cardiac remodeling.

Accelerated decline in cardiac stem cell efficiency in Spontaneously hypertensive rat compared to normotensive Wistar rat

Cardiac hypertrophy is recognized as an independent risk factor for cardiac failure. Efficient management of hypertensive heart disease requires identification of factors that can possibly mediate the transition from hypertrophy to failure. Resident cardiac stem cells have a prominent role in the maintenance of cardiac tissue homeostasis. Decline in the proportion of healthy cardiac stem cells (CSCs) can affect tissue regeneration. In pathological conditions, apart from natural aging, an adverse microenvironment can lead to decrease in efficiency of CSCs. A systematic analysis of cardiac stem cell characteristics in pathological conditions has not been reported so far. Therefore, this study was designed with the objective of examining the age associated variation in stem cell attributes of Spontaneously hypertensive rat (SHR) in comparison with normotensive Wistar rat. Spontaneously hypertensive rat was used as the experimental model since the cardiac remodeling resembles the clinical course of hypertensive heart disease. CSCs were isolated from atrial explants. Stem cell attributes were assessed in 1-week, 6, 12 and 18-month-old male SHR, in comparison with age matched Wistar rats. In 1-week-old pups, stem cell attributes of SHR and Wistar were comparable. Migration potential, proliferative capacity, TERT expression, telomerase activity and the proportion of c-kit⁺ cells decreased with age, both in SHR and Wistar. DNA damage and the proportion of senescent CSCs increased with age both in SHR and Wistar rats. Age associated increase was observed in the oxidative stress of stem cells, possibly mediated by the enhanced oxidative stress in the microenvironment. The changes were more pronounced in SHR, and as early as six months of age, there was significant decrease in efficiency of CSCs of SHR compared to Wistar. The density of healthy CSCs determined as a fraction of the differentiated cells was remarkably low in 18-month-old SHR. Age associated decrease in functionally efficient CSCs was therefore accelerated in SHR. Considering the vital role of CSCs in the maintenance of a healthy myocardium, decrease in functionally efficient CSCs can be a precipitating factor in pathological cardiac remodeling. Elevated ROS levels in CSCs of SHR lends scope for speculation that decrease in efficiency of CSCs is mediated by oxidative stress; and that modulation of the microenvironment by therapeutic interventions can restore a healthy stem cell population and facilitate maintenance of cardiac homeostasis and prevent cardiac decompensation.

Dronedarone produces early regression of myocardial remodelling in structural heart disease

Background and aims

Left ventricular hypertrophy (LVH) in hypertension is associated with a greater risk of sustained supraventricular/atrial arrhythmias. Dronedarone is an antiarrhythmic agent that was recently approved for the treatment of atrial fibrillation. However, its effect on early regression of LVH has not been reported. We tested the hypothesis that short-term administration of dronedarone induces early regression of LVH in spontaneously hypertensive rats (SHR_s).

Methods

Ten-month-old male SHR_s were randomly assigned to an intervention group (SHR-D), where animals received dronedarone treatment (100 mg/kg) for a period of 14 days, or to a control group (SHR) where rats were given vehicle. A third group with normotensive control rats (WKY) was also added. At the end of the treatment with dronedarone we studied the cardiac anatomy and function in all the rats using transthoracic echocardiogram, cardiac metabolism using the PET/CT study (2-deoxy-2[18F]fluoro-D-glucose) and cardiac structure by histological analysis of myocyte size and collagen content.

Results

The hypertensive vehicle treated SHR rats developed the classic cardiac pattern of hypertensive cardiomyopathy as expected for the experimental model, with increases in left ventricular wall thickness, a metabolic shift towards an increase in glucose use and increases in myocyte and collagen content. However, the SHR-D rats showed statistically significant lower values in comparison to SHR group for septal wall thickness, posterior wall thickness, ventricular mass, glucose myocardial uptake, size of left ventricular cardiomyocytes and collagen content. All these values obtained in SHR-D rats were similar to the values measured in the normotensive WKY control group.

Conclusion

The results suggest by three alternative and complementary ways (analysis of anatomy and cardiac function, metabolism and histological structure) that dronedarone has the potential to reverse the LVH induced by arterial hypertension in the SHR model of compensated ventricular hypertrophy.

Anti-hypertensive and cardioprotective effects of a novel apitherapy formulation via upregulation of peroxisome proliferator-activated receptor-α and -γ in spontaneous hypertensive rats

Ventricular remodeling is associated with many heart diseases, and ventricular remodeling induced by hypertension can be fatal independent of hypertension. In this study, we prepared a novel apitherapy formulation, designated Bao-Yuan-Ling (BYL), which contained propolis, royal jelly, and bee venom, to treat spontaneous hypertensive rats (SHRs). We then evaluated the pharmacology of BYL and the potential mechanisms through which BYL affects hypertension and ventricular remodeling. We found that BYL treatment could reduce blood pressure in SHRs. Thereafter, we found that BYL treatment reduced serum levels of angiotensin II, endothelin 1, and transforming growth factor-β and improved the myocardial structure. Moreover, the results of quantitative real-time polymerase chain reaction indicated that BYL treatment could upregulate the mRNA expression of peroxisome proliferator-activated receptor (PPAR)-α and PPAR-γ. Thus, we could conclude that BYL had hypotensive and cardioprotective effects in SHRs, potentially through improvement of myocardial energy metabolism.

Histamine-2 receptor antagonist famotidine modulates cardiac stem cell characteristics in hypertensive heart disease

BACKGROUND

Cardiac stem cells (CSCs) play a vital role in cardiac homeostasis. A decrease in the efficiency of cardiac stem cells is speculated in various cardiac abnormalities. The maintenance of a healthy stem cell population is essential for the prevention of adverse cardiac remodeling leading to cardiac failure. Famotidine, a histamine-2 receptor antagonist, is currently used to treat ulcers of the stomach and intestines. In repurposing the use of the drug, reduction of cardiac hypertrophy and improvement in cardiac function of spontaneously hypertensive rats (SHR) was reported by our group. Given that stem cells are affected in cardiac pathologies, the effect of histamine-2 receptor antagonism on CSC characteristics was investigated.

METHODS

To examine whether famotidine has a positive effect on CSCs, spontaneously hypertensive rats (SHR) treated with the drug were sacrificed; and CSCs isolated from atrial appendages was evaluated. Six-month-old male SHRs were treated with famotidine (30 mg/kg/day) for two months. The effect of famotidine treatment on migration, proliferation and survival of CSCs was compared with untreated SHRs and normotensive Wistar rats.

RESULTS

Functional efficiency of CSCs from SHR was compromised relative to that in Wistar rat. Famotidine increased the migration and proliferation potential, along with retention of stemness of CSCs in treated SHRs. Cellular senescence and oxidative stress were also reduced. The expression of H2R was unaffected by the treatment.

DISCUSSION

As anticipated, CSCs from SHRs were functionally impaired. Stem cell attributes of famotidine-treated SHRs was comparable to that of Wistar rats. Therefore, in addition to being cardioprotective, the histamine 2 receptor antagonist modulated cardiac stem cells characteristics. Restoration of stem cell efficiency by famotidine is possibly mediated by reduction of oxidative stress as the expression of H2R was unaffected by the treatment. Maintenance of healthy stem cell population is suggested as a possible mechanism underlying the cardioprotective effect of famotidine.

Apigenin ameliorates hypertension-induced cardiac hypertrophy and down-regulates cardiac hypoxia inducible factor-lα in rats

Apigenin is a natural flavonoid compound that can inhibit hypoxia-inducible factor (HIF)-1α expression in cultured tumor cells under hypoxic conditions. Hypertension-induced cardiac hypertrophy is always accompanied by abnormal myocardial glucolipid metabolism due to an increase of HIF-1α. However, whether or not apigenin may ameliorate the cardiac hypertrophy and abnormal myocardial glucolipid metabolism remains unknown. This study aimed to examine the effects of apigenin. Rats with cardiac hypertrophy induced by renovascular hypertension were treated with apigenin 50-100 mg kg(-1) (the doses can be achieved by pharmacological or dietary supplementation for an adult person) by gavage for 4 weeks. The results showed that after treatment with apigenin, the blood pressure, heart weight, heart weight index, cardiomyocyte cross-sectional area, serum angiotensin II, and serum and myocardial free fatty acids were reduced. It is important to note that apigenin decreased the expression level of myocardial HIF-1α protein. Moreover, apigenin simultaneously increased the expression levels of myocardial peroxisome proliferator-activated receptor (PPAR) α, carnitine palmitoyltransferase (CPT)-1, and pyruvate dehydrogenase kinase (PDK)-4 proteins and decreased the expression levels of myocardial PPARγ, glycerol-3-phosphate acyltransferase genes (GPAT), and glucose transporter (GLUT)-4 proteins. These findings demonstrated that apigenin could improve hypertensive cardiac hypertrophy and abnormal myocardial glucolipid metabolism in rats, and its mechanisms might be associated with the down-regulation of myocardial HIF-1α expression and, subsequently increasing the expressions of myocardial PPARα and its target genes CPT-1 and PDK-4, and decreasing the expressions of myocardial PPARγ and its target genes GPAT and GLUT-4.

Mitoprotective antioxidant EUK-134 stimulates fatty acid oxidation and prevents hypertrophy in H9C2 cells

Oxidative stress is an important contributory factor for the development of cardiovascular diseases like hypertension-induced hypertrophy. Mitochondrion is the major source of reactive oxygen species. Hence, protecting mitochondria from oxidative damage can be an effective therapeutic strategy for the prevention of hypertensive heart disease. Conventional antioxidants are not likely to be cardioprotective, as they cannot protect mitochondria from oxidative damage. EUK-134 is a salen-manganese complex with superoxide dismutase and catalase activity. The possible role of EUK-134, a mitoprotective antioxidant, in the prevention of hypertrophy of H9C2 cells was examined. The cells were stimulated with phenylephrine (50 μM), and hypertrophy was assessed based on cell volume and expression of brain natriuretic peptide and calcineurin. Enhanced myocardial lipid peroxidation and protein carbonyl content, accompanied by nuclear factor-kappa B gene expression, confirmed the presence of oxidative stress in hypertrophic cells. Metabolic shift was evident from reduction in the expression of medium-chain acyl-CoA dehydrogenase. Mitochondrial oxidative stress was confirmed by the reduced expression of mitochondria-specific antioxidant peroxiredoxin-3 and enhanced mitochondrial superoxide production. Compromised mitochondrial function was apparent from reduced mitochondrial membrane potential. Pretreatment with EUK-134 (10 μM) was effective in the prevention of hypertrophic changes in H9C2 cells, reduction of oxidative stress, and prevention of metabolic shift. EUK-134 treatment improved the oxidative status of mitochondria and reversed hypertrophy-induced reduction of mitochondrial membrane potential. Supplementation with EUK-134 is therefore identified as a novel approach to attenuate cardiac hypertrophy and lends scope for the development of EUK-134 as a therapeutic agent in the management of human cardiovascular disease.

Systemic leukotriene B4 receptor antagonism lowers arterial blood pressure and improves autonomic function in the spontaneously hypertensive rat

KEY POINTS

Evidence indicates an association between hypertension and chronic systemic inflammation in both human hypertension and experimental animal models. Previous studies in the spontaneously hypertensive rat (SHR) support a role for leukotriene B₄ (LTB₄ ), a potent chemoattractant involved in the inflammatory response, but its mode of action is poorly understood. In the SHR, we observed an increase in T cells and macrophages in the brainstem; in addition, gene expression profiling data showed that LTB₄ production, degradation and downstream signalling in the brainstem of the SHR are dynamically regulated during hypertension. When LTB₄ receptor 1 (BLT1) receptors were blocked with CP-105,696, arterial pressure was reduced in the SHR compared to the normotensive control and this reduction was associated with a significant decrease in systolic blood pressure (BP) indicators. These data provide new evidence for the role of LTB₄ as an important neuro-immune pathway in the development of hypertension and therefore may serve as a novel therapeutic target for the treatment of neurogenic hypertension.

ABSTRACT

Accumulating evidence indicates an association between hypertension and chronic systemic inflammation in both human hypertension and experimental animal models. Previous studies in the spontaneously hypertensive rat (SHR) support a role for leukotriene B₄ (LTB₄ ), a potent chemoattractant involved in the inflammatory response. However, the mechanism for LTB₄ -mediated inflammation in hypertension is poorly understood. Here we report in the SHR, increased brainstem infiltration of T cells and macrophages plus gene expression profiling data showing that LTB₄ production, degradation and downstream signalling in the brainstem of the SHR are dynamically regulated during hypertension. Chronic blockade of the LTB₄ receptor 1 (BLT1) receptor with CP-105,696, reduced arterial pressure in the SHR compared to the normotensive control and this reduction was associated with a significant decrease in low and high frequency spectra of systolic blood pressure, and an increase in spontaneous baroreceptor reflex gain (sBRG). These data provide new evidence for the role of LTB₄ as an important neuro-immune pathway in the development of hypertension and therefore may serve as a novel therapeutic target for the treatment of neurogenic hypertension.

Ligand specific variation in cardiac response to stimulation of peroxisome proliferator-activated receptor-alpha in spontaneously hypertensive rat

Left ventricular hypertrophy (LVH) is an independent risk factor for cardiac failure. Reduction of LVH has beneficial effects on the heart. LVH is associated with shift in energy substrate preference from fatty acid to glucose, mediated by down regulation of peroxisome proliferator-activated receptor-alpha (PPAR-α). As long-term dependence on glucose can promote adverse cardiac remodeling, it was hypothesized that, prevention of metabolic shift by averting down regulation of PPAR-α can reduce cardiac remodeling in spontaneously hypertensive rat (SHR). Cardiac response to stimulation of PPAR-α presumably depends on the type of ligand used. Therefore, the study was carried out in SHR, using two different PPAR-α ligands. SHR were treated with either fenofibrate (100 mg/kg/day) or medium-chain triglyceride (MCT) Tricaprylin (5% of diet) for 4 months. Expression of PPAR-α and medium-chain acylCoA dehydrogenase served as markers, for stimulation of PPAR-α. Both ligands stimulated PPAR-α. Decrease of blood pressure was observed only with fenofibrate. LVH was assessed from heart-weight/body weight ratio, histology and brain natriuretic peptide expression. As oxidative stress is linked with hypertrophy, serum and cardiac malondialdehyde and cardiac 3-nitrotyrosine levels were determined. Compared to untreated SHR, LVH and oxidative stress were lower on supplementation with MCT, but higher on treatment with fenofibrate. The observations indicate that reduction of blood pressure is not essentially accompanied by reduction of LVH, and that, progressive cardiac remodeling can be prevented with decrease in oxidative stress. Contrary to the notion that reactivation of PPAR-α is detrimental; the study substantiates that cardiac response to stimulation of PPAR-α is ligand specific.

Changes in short-chain acyl-coA dehydrogenase during rat cardiac development and stress

This study was designed to investigate the expression of short-chain acyl-CoA dehydrogenase (SCAD), a key enzyme of fatty acid β-oxidation, during rat heart development and the difference of SCAD between pathological and physiological cardiac hypertrophy. The expression of SCAD was lowest in the foetal and neonatal heart, which had time-dependent increase during normal heart development. In contrast, a significant decrease in SCAD expression was observed in different ages of spontaneously hypertensive rats (SHR). On the other hand, swim-trained rats developed physiological cardiac hypertrophy, whereas SHR developed pathological cardiac hypertrophy. The two kinds of cardiac hypertrophy exhibited divergent SCAD changes in myocardial fatty acids utilization. In addition, the expression of SCAD was significantly decreased in pathological cardiomyocyte hypertrophy, however, increased in physiological cardiomyocyte hypertrophy. SCAD siRNA treatment triggered the pathological cardiomyocyte hypertrophy, which showed that the down-regulation of SCAD expression may play an important role in pathological cardiac hypertrophy. The changes in peroxisome proliferator-activated receptor α (PPARα) was accordant with that of SCAD. Moreover, the specific PPARα ligand fenofibrate treatment increased the expression of SCAD and inhibited pathological cardiac hypertrophy. Therefore, we speculate that the down-regulated expression of SCAD in pathological cardiac hypertrophy may be responsible for 'the recapitulation of foetal energy metabolism'. The deactivation of PPARα may result in the decrease in SCAD expression in pathological cardiac hypertrophy. Changes in SCAD are different in pathological and physiological cardiac hypertrophy, which may be used as the molecular markers of pathological and physiological cardiac hypertrophy.

Systemic and renal oxidative stress in the pathogenesis of hypertension: modulation of long-term control of arterial blood pressure by resveratrol

Hypertension affects over 25% of the global population and is associated with grave and often fatal complications that affect many organ systems. Although great advancements have been made in the clinical assessment and treatment of hypertension, the cause of hypertension in over 90% of these patients is unknown, which hampers the development of targeted and more effective treatment. The etiology of hypertension involves multiple pathological processes and organ systems, however one unifying feature of all of these contributing factors is oxidative stress. Once the body's natural anti-oxidant defense mechanisms are overwhelmed, reactive oxygen species (ROS) begin to accumulate in the tissues. ROS play important roles in normal regulation of many physiological processes, however in excess they are detrimental and cause widespread cell and tissue damage as well as derangements in many physiological processes. Thus, control of oxidative stress has become an attractive target for pharmacotherapy to prevent and manage hypertension. Resveratrol (trans-3,5,4'-Trihydroxystilbene) is a naturally occurring polyphenol which has anti-oxidant effects in vivo. Many studies have shown anti-hypertensive effects of resveratrol in different pre-clinical models of hypertension, via a multitude of mechanisms that include its function as an anti-oxidant. However, results have been mixed and in some cases resveratrol has no effect on blood pressure. This may be due to the heavy emphasis on peripheral vasodilator effects of resveratrol and virtually no investigation of its potential renal effects. This is particularly troubling in the arena of hypertension, where it is well known and accepted that the kidney plays an essential role in the long term regulation of arterial pressure and a vital role in the initiation, development and maintenance of chronic hypertension. It is thus the focus of this review to discuss the potential of resveratrol as an anti-hypertensive treatment via amelioration of oxidative stress within the framework of the fundamental physiological principles of long term regulation of arterial blood pressure.

Can 18F-FDG-PET show differences in myocardial metabolism between Wistar Kyoto rats and spontaneously hypertensive rats?

Positron emission tomography (PET) is useful for evaluating the cardiac metabolism of free fatty acid, glucose and oxygen both in human clinical practice and in experimental animal models. However, no data are available for such an evaluation in a model of stable compensated left ventricular hypertrophy in 14-month-old spontaneously hypertensive rats (SHRs). This study was designed to assess the metabolism of myocardial glucose in SHRs using 2-deoxy-2-[18F]fluoro-D-glucose ((18)F-FDG) using PET. The study was performed on 14-month-old male SHRs (n = 4) and age-matched Wistar Kyoto (WKY) rats (n = 4). PET scans were performed after the administration of anaesthesia with isoflurane and injection of a bolus of 39.37 ± 3.25 (mean ± SD) MBq (1.06 mCi) of (18)F-FDG. The standardized uptake value (SUV) was used to evaluate (18)F-FDG uptake by the heart. The analysis of SUV showed increased metabolism in the left ventricle of SHRs compared with WKY rats. Our results show that small animal PET using (18)F-FDG can be performed in 14-month-old SHRs to evaluate new therapies in the regression of left ventricular hypertrophy in SHRs because pathological myocardial metabolism in the SHR differs from the normal metabolism of the WKY rat.

Reduced hemodynamic load aids low-dose resveratrol in reversing cardiovascular defects in hypertensive rats

Cardiac hypertrophy and associated myocardial remodeling is one of the main complications of hypertension resulting in the development of heart failure. It is of great significance to explore novel treatments to reverse cardiac hypertrophy in hypertensives with or without affecting blood pressure. In the present study, we investigated whether low-dose resveratrol alone or in a combination with a blood pressure-lowering agent can reverse hypertension-induced cardiovascular dysfunction. Twenty-week-old male spontaneously hypertensive rats (SHRs) and Wistar-Kyoto rats were treated with resveratrol (2.5 mg kg⁻¹ per day) and/or hydralazine (25 mg kg⁻¹ per day) for 8 weeks. Blood pressure, cardiac structure and function, and electrocardiogram measurements were examined. Pressure myography of resistance arteries, histological examinations of heart tissues, oxidative stress and inflammatory measurements were also preformed to assess the efficacy of the treatment. Although resveratrol treatment alone was ineffective in reducing systolic blood pressure, diastolic blood pressure, diastolic dysfunction and vascular remodeling, it significantly prevented the systolic impairment and reduced myocardial fibrosis, and reduced oxidative stress and inflammation in hypertensive rats. Furthermore, a combination of resveratrol with hydralazine treatment significantly reduced blood pressure, improved systolic and diastolic function, decreased fibrosis and improved vascular geometry. In summary, low-dose resveratrol itself was unable to reduce systolic blood pressure, diastolic blood pressure, diastolic dysfunction and vascular remodeling. However, resveratrol alone alleviated cardiac fibrosis and some of the functional abnormalities in SHRs. And a combination of resveratrol with hydralazine was more effective than resveratrol or hydralazine alone in improving overall cardiovascular parameters.

Reduction of rat cardiac hypertrophy by osthol is related to regulation of cardiac oxidative stress and lipid metabolism

The objective of this study was to examine the therapeutic effect of osthol, a coumarin compound isolated from the fruit of Cnidium monnieri (L.) Cusson, on cardiac hypertrophy in rats and investigate its potential mechanisms. The rats with cardiac hypertrophy induced by renovascular hypertension were given osthol orally by gavage for 4 weeks. The results showed that in the osthol 20 mg/kg group, the blood pressure, heart weight index and myocardial malondialdehyde content were lowered (p < 0.001, p = 0.002 and p = 0.025, respectively), the myocardial superoxide dismutase and glutathione peroxidase contents were increased (p < 0.001), and the elevated unesterified fatty acids and triacylglycerols in myocardial tissues were decreased (p = 0.017 and p = 0.004, respectively). At the same time, the myocardial peroxisome proliferator-activated receptor (PPAR)-α and carnitine palmitoyltransferase (CPT)-1a mRNA expressions were increased and the myocardial diacylglycerol acyltransferase (DGAT) mRNA expression was decreased in the osthol 20 mg/kg group (p < 0.001). Osthol treatment was associated with a decreased cross-sectional area of cardiomyocytes (p < 0.001). These findings suggest that osthol may exert a therapeutic effect on cardiac hypertrophy in rats, and its mechanisms may be related to the improvement of myocardial oxidative stress and lipid metabolism via regulation of PPARα-mediated target gene expressions including an increase in CPT-1a mRNA expression and a decrease in DGAT mRNA expression.

The association of oxidative stress with hypertensive retinopathy

This study was designed to answer the following questions: (i) Do levels of serum gamma-glutamyl transferase (GGT), a marker of oxidative stress, change in hypertensive retinopathy (HR)? (ii) Is there any relation between degree of HR and GGT levels? This study included 80 hypertensive patients with HR. Group 1 comprised 40 patients with grade I HR, and group 2 comprised 40 patients with grade II HR. We selected 40 healthy subjects for the control group. Level of GGT in group 2 was significantly higher than in group 1 (P = 0.005) and control group (P = 0.001); it was also higher in group 1 than in control group (P = 0.025). Our study suggests that oxidative stress, mechanisms known to be involved in vascular lesions, may promote the development of HR.

Cardoguard, an Ayurvedic antihypertensive formulation, prevents cardiac remodeling in spontaneously hypertensive rats by inhibition of ERK and PKCε signaling pathways

Ayurveda is an Indian system of medicine. Despite clinical efficacy, lack of scientific validation has limited the effective use of Ayurvedic drugs. Cardoguard is an Ayurvedic antihypertensive drug formulated by Nagarjuna Herbal Concentrates Ltd., Kerala, India. Left ventricular hypertrophy (LVH) is a modifiable risk factor, and regression of LVH reduces the propensity for adverse cardiovascular events. This study was taken up with the objective of evaluating the efficacy of Cardoguard in the prevention of cardiac remodeling. Cardoguard was administered orally to 2-month-old spontaneously hypertensive rats for 4 months at a dose of 5 mg·day(-1). The dose corresponds to the therapeutic dose calculated on the basis of body surface area. Lower hypertrophy index, decrease in cardiomyocyte area, and reduction of interstitial fibrosis in treated spontaneously hypertensive rats indicate amelioration of cardiac hypertrophy by Cardoguard. Cardiac output increased in response to treatment. Immunostaining for the phosphorylated components of major signaling pathways associated with hypertrophy suggests that prevention of LVH by Cardoguard is possibly mediated through inhibition of extracellular signal-regulated kinases and protein kinase C-ε signaling pathways. Reduced expression of 3-nitrotyrosine in response to the treatment suggests that prevention of cardiac remodeling by Cardoguard is mediated by reduction of oxidative stress.

Molecular mechanisms of hypertension--reactive oxygen species and antioxidants: a basic science update for the clinician

Many factors have been implicated in the pathophysiology of hypertension such as upregulation of the renin-angiotensin-aldosterone system, activation of the sympathetic nervous system, perturbed G protein-coupled receptor signalling, inflammation, and altered T-cell function. Common to these processes is increased bioavailability of reactive oxygen species (ROS) (termed oxidative stress) due to excess ROS generation, decreased nitric oxide (NO) levels, and reduced antioxidant capacity in the cardiovascular, renal, and nervous systems. Although oxidative stress may not be the sole etiology of hypertension, it amplifies blood pressure elevation in the presence of other prohypertensive factors. In the cardiovascular system ROS play a physiological role in controlling endothelial function, vascular tone, and cardiac function, and a pathophysiological role in inflammation, hypertrophy, proliferation, apoptosis, migration, fibrosis, angiogenesis, and rarefaction, all of which are important processes contributing to endothelial dysfunction and cardiovascular remodelling in hypertension. A major source for cardiovascular ROS is a family of nonphagocytic nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (Nox1, Nox2, Nox4, and Nox5). Other sources include mitochondrial enzymes, xanthine oxidase, and uncoupled NO synthase (NOS). Although convincing data from animal studies support a causative role for oxidative stress in the pathogenesis of hypertension, there is still no solid evidence that oxidative stress causes hypertension in humans. However, biomarkers of excess ROS are increased in patients with hypertension and oxidative damage is important in the molecular mechanisms associated with cardiovascular and renal injury in hypertension. Although clinical trials failed to show beneficial antihypertensive effects of antioxidants, strategies that combat oxidative stress by targeting Noxs in an isoform-specific manner may have therapeutic potential.

Proteome changes in the myocardium of experimental chronic diabetes and hypertension: role of PPARα in the associated hypertrophy

Diabetes with or without the presence of hypertension damages the heart. However, there is currently a lack of information about these associated pathologies and the alteration of linked proteins. For these reasons, we were interested in the potential synergistic interaction of diabetes and hypertension in the heart, focusing on the proteome characterization of the pathological phenotypes and the associated hypertrophic response. We treated normotensive and spontaneously hypertensive (SHR) rats with either streptozotocin or vehicle. After 22weeks, type-I diabetic (DM1), SHR, SHR/DM1 and control left-ventricles were studied using proteomic approaches. Proteomics revealed that long-term DM1, SHR and SHR/DM1 rats exhibited 24, 53 and 53 altered proteins in the myocardia, respectively. DM1 myocardium showed over-expression of apoptotic and cytoskeleton proteins, and down-regulation of anti-apoptotic and mitochondrial metabolic enzymes. In both SHR and SHR/DM1 these changes were exacerbated and free fatty-acid (FFA) ß-oxidation enzymes were additionally decreased. Furthermore, SHR/DM1 hearts exhibited a misbalance of specific pro-hypertrophic, anti-apoptotic and mitochondrial ATP-carrier factors, which could cause additional damage. Differential proteins were validated and then clustered into different biological pathways using bioinformatics. These studies suggested the implication of FFA-nuclear receptors and hypertrophic factors in these pathologies. Although key ß-oxidation enzymes were not stimulated in DM1 and hypertensive hearts, peroxisome proliferator-activated receptors-α (PPARα) were potentially activated for other responses. In this regard, PPARα stimulation reduced hypertrophy and pro-hypertrophic factors such as annexin-V in high-glucose and angiotensin-II induced cardiomyocytes. Thus, activation of PPARα could reflect a compensatory response to the metabolic-shifted, apoptotic and hypertrophic status of the hypertensive-diabetic cardiomyopathy.