Prolongation of life span in hypertensive rats by dietary interventions. Effects of garlic and linseed oil

Right Ventricular Hypertrophy in Spontaneously Hypertensive Rats (SHR/NHsd) Is Associated with Inter-Individual Variations of the Pulmonary Endothelin System

Spontaneously hypertensive rats (SHRs) develop severe hypertension and subsequently left ventricular hypertrophy. Whether they also develop right ventricular hypertrophy is not clear. We analyzed 76 female SHRs (strain SHR/NHsd) and observed severe right ventricular hypertrophy in 7% of these rats (SHR-RVH). Right ventricular hypertrophy did not correlate with the age of the rats and was already seen in one rat at the pre-hypertensive state. The current study investigated the molecular fingerprint of the lung and right ventricle from SHR-RVH and compared this first to SHRs that did develop left but not right ventricular hypertrophy, and second to normotensive rats without hypertrophy. Rats with right ventricular hypertrophy had a decreased expression of the endothelin-B receptor (EDNRB) in the lung, together with an increased protein content of endothelin-1 and an increased expression of ACTA2A. Furthermore, in the right ventricle, a down-regulation of the endothelin-A receptor (EDNRA) was found, consistent with a mild phenotype. The data suggest that in a sub-group of SHR/NHsd rats, low expression of the endothelin clearance receptor (endothelin-B receptor) in the lung triggers an increase in vascular resistance to the right ventricle that then triggers hypertrophy. Our study is the first description of a genetic variant in a defined SHR strain.

Importance of Flaxseed and its Components in the Management of Hypertension

This review paper describes the effects of flaxseed and its components (flax oil, secoisolariciresinol diglucoside [SDG], flax lignan complex [FLC], and flaxseed protein hydrolysate [FPH]) on blood pressure (BP) in Sprague Dawley rats (SDR), spontaneously hypertensive rats (SHR), and humans. Flaxseed, flax oil, and FLC had variable effects on BP in humans, while SDG and FPH significantly reduced the BP in SDR and SHR. The effect of SDG was dose-dependent and long lasting. The lowering of BP is mediated through inhibition of soluble epoxide by α -linolenic acid in flax oil, stimulation of guanylate cyclase and inhibition of angiotensin converting enzyme (ACE) by SDG, and inhibition of renin and ACE activity by FPH. Flaxseed, flax oil, and FLC have variable effects on BP (none, slight, and significant). They are effective in lowering BP in individuals with hypertension and metabolic syndrome but ineffective in healthy individuals' ineffectiveness of flaxseed and its compounds in lowering BP may be due to their low doses, long interval of dosing, short duration of consumption, and patient status. In conclusion, the data at present suggest that flaxseed, flax oil, and FLC cannot serve as therapeutic agents for the treatment of hypertension. However, they can be used as an adjunct in the treatment of hypertension. A clinical trial should be conducted of these agents with higher doses which would be given twice daily for long duration. Pure SDG and FPS may serve as therapeutic agents for the treatment of hypertension but they have not been tried in humans.

Garlic and cardioprotection: insights into the molecular mechanisms

Garlic is widely recognized for its immense therapeutic potential. Garlic has been shown to exert its beneficial effects against a wide spectrum of diseases, including cancer, diabetes, and microbial infections, as well as immunological and cardiovascular disorders. Most of the research on garlic has indicated that garlic and its active compounds are effective in reducing cardiovascular and metabolic risk by normalizing abnormal plasma lipids, oxidized low density lipoproteins, abnormal platelet aggregation, high blood pressure, and cardiac injury. Some of the beneficial effects of dietary garlic against cardiovascular disorders are mediated via the generation of hydrogen sulfide and nitric oxide in cardiomyocytes and endothelial cells. Garlic has the potential to protect the heart against myocardial infarction, doxorubicin-induced cardiotoxicity, arrhythmia, hypertrophy, and ischemia-reperfusion injury. The induction of cardiac endogenous antioxidants and the reduction of lipid peroxidation by garlic has been reported by several different groups. Other mechanisms, such as regulating ion channels, modulating Akt signaling pathways, histone deacetylase inhibition, and cytochrome P450 inhibition, could be responsible for the cardioprotective effect of garlic. Although several mechanisms have been identified for the cardioprotective effect of garlic, there is a need for further research to identify the specific molecular mechanism of cardioprotection in different cardiac diseases.

Garlic extracts prevent oxidative stress, hypertrophy and apoptosis in cardiomyocytes: a role for nitric oxide and hydrogen sulfide

Background

In ancient times, plants were recognized for their medicinal properties. Later, the arrival of synthetic drugs pushed it to the backstage. However, from being merely used for food, plants are now been widely explored for their therapeutic value. The current study explores the potential of skin and flesh extracts from a hard-necked Rocambole variety of purple garlic in preventing cardiomyocyte hypertrophy and cell death.

Methods

Norepinephrine (NE) was used to induce hypertrophy in adult rat cardiomyocytes pretreated with garlic skin and flesh extracts. Cell death was measured as ratio of rod to round shaped cardiomyocytes. Fluorescent probes were used to measure apoptosis and oxidative stress in cardiomyocytes treated with and without extracts and NE. Pharmacological blockade of nitric oxide (NO) and hydrogen sulfide (H₂S) were used to elucidate the mechanism of action of garlic extracts. Garlic extract samples were also tested for alliin and allicin concentrations.

Results

Exposure of cardiomyocytes to NE induced an increase in cell size and cell death; this increase was significantly prevented upon treatment with garlic skin and flesh extracts. Norepinephrine increased apoptosis and oxidative stress in cardiomyocytes which was prevented upon pretreatment with skin and flesh extracts; NO, and H₂S blockers significantly inhibited this beneficial effect. Allicin and alliin concentration were significantly higher in garlic flesh extract when compared to the skin extract.

Conclusion

These results suggest that both skin and flesh garlic extracts are effective in preventing NE induced cardiomyocyte hypertrophy and cell death. Reduction in oxidative stress may also play an important role in the anti-hypertrophic and anti-apoptotic properties of garlic extracts. These beneficial effects may in part be mediated by NO and H₂S.

Reduced ischemic brain injury by partial rejuvenation of bone marrow cells in aged rats

Circulating bone marrow-derived immature cells, including endothelial progenitor cells, have been implicated in homeostasis of the microvasculature. Decreased levels of circulating endothelial progenitor cells, associated with aging and/or cardiovascular risk factors, correlate with poor clinical outcomes in a range of cardiovascular diseases. Herein, we transplanted bone marrow cells from young stroke-prone spontaneously hypertensive rats (SHR-SP) into aged SHR-SP, the latter not exposed to radiation or chemotherapy. Analysis of recipient peripheral blood 28 days after transplantation revealed that 5% of circulating blood cells were of donor origin. Cerebral infarction was induced on day 30 posttransplantation. Animals transplanted with bone marrow from young SHR-SP displayed an increase in density of the microvasculature in the periinfarction zone, reduced ischemic brain damage and improved neurologic function. In vitro analysis revealed enhanced activation of endothelial nitric oxide synthase and reduced activation p38 microtubule-associated protein (MAP) kinase, the latter associated with endothelial apoptosis, in cultures exposed to bone marrow-derived mononuclear cells from young animals versus cells from aged counterparts. Our findings indicate that partial rejuvenation of bone marrow from aged rats with cells from young animals enhances the response to ischemic injury, potentially at the level of endothelial/vascular activation, providing insight into a novel approach ameliorate chronic vascular diseases.

Determination of percent area density of epithelial and stromal components in development of prostatic hyperplasia in spontaneously hypertensive rats

OBJECTIVES

To determine the percent area density of epithelial and stromal components in the development of prostatic hyperplasia in spontaneously hypertensive (SH) rats.

METHODS

The ventral lobes of prostates obtained from male SH rats and their normotensive counterparts, Wistar Kyoto (WKY) rats, were examined histopathologically at 15, 29, 40, and 54 weeks of age (5 SH and WKY rats each at each age group). The degree of prostatic hyperplasia was evaluated with a score-chart protocol, histoscore. The percent area density of epithelium and stroma of the ventral prostate were determined using a computerized image analysis system.

RESULTS

Definite lesions of hyperplastic changes were demonstrated in the ventral prostate of SH rats from 15 to 54 weeks. In comparison with WKY rats, SH rats showed a significantly increased degree of prostatic hyperplasia as reflected by the histoscore values. Furthermore, the histoscore of the ventral prostate of SH rats increased with age (from 21.7 +/- 0.7 at 15 weeks to 26.1 +/- 0.4 at 54 weeks). The percent area density of epithelium and stroma were significantly increased in SH rats, and the ratio of stroma to epithelium ranged from 1:2.94 to 1:3.50 in SH rats but was maintained at 1:1.15 to 1:1.19 in WKY rats during the observation period.

CONCLUSIONS

The hyperplastic changes of the ventral prostate may develop with advancing age in SH rats. The development of prostatic hyperplasia may result from both epithelial and stromal proliferation and may be predominantly expressed as a glandular type in SH rats.

Effect of garlic on cardiovascular disorders: a review

Garlic and its preparations have been widely recognized as agents for prevention and treatment of cardiovascular and other metabolic diseases, atherosclerosis, hyperlipidemia, thrombosis, hypertension and diabetes. Effectiveness of garlic in cardiovascular diseases was more encouraging in experimental studies, which prompted several clinical trials. Though many clinical trials showed a positive effect of garlic on almost all cardiovascular conditions mentioned above, however a number of negative studies have recently cast doubt on the efficacy of garlic specially its cholesterol lowering effect of garlic. It is a great challenge for scientists all over the world to make a proper use of garlic and enjoy its maximum beneficial effect as it is the cheapest way to prevent cardiovascular disease. This review has attempted to make a bridge the gap between experimental and clinical study and to discuss the possible mechanisms of such therapeutic actions of garlic.

Garlic and its active metabolite allicin produce endothelium- and nitric oxide-dependent relaxation in rat pulmonary arteries

1. The aims of the present study were to investigate the effects of fresh garlic and one of its active metabolites, allicin, on rat isolated pulmonary arteries (RPA). 2. In endothelium-intact and phenylephrine-precontracted RPA, the addition of a water or a 5% ethanol extract of fresh garlic (1-500 microg/mL) resulted in a dose-dependent relaxation reaching a maximum (mean +/- SEM) of -91 +/- 3 and -93 +/- 2%, respectively, with an ED(50) of 113 +/- 12 and 106 +/- 10 microg/mL, respectively. The vasorelaxation was readily reversible upon washing and no tachyphylaxis was noted. 3. An extract of the external garlic storage leaf produced a significantly greater relaxation than the inner stem. Microfiltration of extracts with a 10,000 molecular sieve did not attenuate relaxation. Inactivation of alliinase and allicin formation, with either boiling of the garlic clove for 30 min or 100% ethanol treatment, completely abolished relaxation. In contrast, similar treatment of crushed garlic with formed allicin retained the relaxation response. 4. Pure allicin produced a similar relaxation as garlic extract, with an EC(50) of approximately 0.8 microg/mL. Disruption of endothelium or N(G)-nitro-L-arginine methyl ester pretreatment attenuated the relaxation, whereas indomethacin had no effect. 5. Prior garlic (500 microg/mL) treatment enhanced acetylcholine relaxation by shifting the response curve to the left, but had no effect on nitric oxide (NO) donor-induced responses. 6. These results demonstrate that garlic and the active metabolite allicin are capable of eliciting a NO-dependent relaxation in RPA and that this response is likely to be mediated via garlic activation of NO formation rather than its stabilization.

Garlic and onions: their effect on eicosanoid metabolism and its clinical relevance

Garlic (Allium sativum) and onion (Allium cepa) are among the oldest of all cultivated plants. Additionally, both plants have been used as medicinal agents for thousands of years. Both garlic and onion have been shown to have applications as antimicrobial, antithrombotic, antitumor, hypolipidaemic, antiarthritic and hypoglycemic agents. In recent years, extensive research has focussed on the beneficial and medicinal properties of garlic and onions. In particular, the use of these agents in the treatment and prevention of cardiovascular disease and cancer is an area of considerable investigation and interest.