Pulse pressure, aortic reactivity, and endothelium dysfunction in old hypertensive rats

Decreased sympathetic nerve activity in young hypertensive rats reared by normotensive mothers

AIMS

Early postnatal development can be significantly compromised by changes in factors provided by the mother, leading to increased vulnerability to hypertension in her offspring. TGR(mRen-2)27 (TGR) mothers, characterised by an overactivated renin-angiotensin system, exhibit altered ion composition in their breast milk. Therefore, we aimed to analyse the impact of cross-fostering on cardiovascular parameters in hypertensive TGR and normotensive Hannover Sprague-Dawley (HanSD) offspring.

MATERIALS AND METHODS

We measured cardiovascular parameters in 5- to 10-week-old male offspring by telemetry. The expression of proteins related to vascular function was assessed by western blotting in the aortic samples obtained from 6- to 12-week-old male offspring. Plasma renin activity and plasma angiotensin II (Ang II) levels were evaluated by radioimmunoassay (RIA).

KEY FINDINGS

The development of hypertension was in TGR accompanied by increased low-to-high frequency ratio (LF/HF; a marker of sympathovagal balance; 0.51 ± 0.16 in week 10). Furthermore, TGR exhibited increased aortic expression of mineralocorticoid receptor (MR; p < 0.05) and transforming growth factor beta type 1 (TGF-β1; p = 0.002) compared to HanSD offspring. Fostering significantly decreased sympathovagal balance (0.23 ± 0.10 in week 10) and, transiently, plasma Ang II levels and MR expression in TGR offspring reared by HanSD mothers.

SIGNIFICANCE

These findings highlight the importance of understanding the complex interplay between early life experiences, maternal factors, and later cardiovascular function. Understanding the mechanisms behind the observed effects may help to identify potential interventions to prevent the development of hypertension later in life.

Aging of the Arterial System

Aging of the vascular system is associated with deep changes of the structural proprieties of the arterial wall. Arterial hypertension, diabetes mellitus, and chronic kidney disease are the major determinants for the loss of elasticity and reduced compliance of vascular wall. Arterial stiffness is a key parameter for assessing the elasticity of the arterial wall and can be easily evaluated with non-invasive methods, such as pulse wave velocity. Early assessment of vessel stiffness is critical because its alteration can precede clinical manifestation of cardiovascular disease. Although there is no specific pharmacological target for arterial stiffness, the treatment of its risk factors helps to improve the elasticity of the arterial wall.

Home-measured pulse pressure is a predictor of cardiovascular disease in type 2 diabetes: The KAMOGAWA-HBP study

BACKGROUND AND AIMS

Pulse pressure (PP) is a prognostic predictor of cardiovascular mortality. This retrospective cohort study aimed to investigate the association between home PP measurements and cardiovascular disease in patients with type 2 diabetes.

METHODS AND RESULTS

Home blood pressure was measured for 14 consecutive days in 1082 patients with type 2 diabetes, and pulse pressure was calculated. A 10 mmHg increase in morning PP was associated with a 1.30-fold increase in the risk of cardiovascular disease. The risk of cardiovascular disease was 1.88 times higher in the morning in the higher PP group than in the lower PP group. In the receiver operating characteristic analysis, the areas under the curve (95% confidence interval) corresponding to the PP (morning, evening, and clinic) for new-onset cardiovascular disease were 0.63 (0.58-0.69), 0.62 (0.57-0.67), and 0.59 (0.54-0.64), respectively. The area under the curve for PP measured in the morning was significantly greater than that for PP measured in the clinic (P = 0.032).

CONCLUSION

Home-measured PP is a better predictor of new-onset cardiovascular disease than clinic-measured PP, in patients with type 2 diabetes.

Sacubitril/Valsartan Improves Sexual Function and Fibrosis of the Clitoral and Vaginal Tissues in Female Spontaneously Hypertensive Rats

ABSTRACT

Female sexual dysfunction is common in hypertension. The effects of sacubitril/valsartan (SAC/VAL) as a potential therapy for hypertension and heart failure have not been studied in relation to sexual function and genital fibrosis in female spontaneously hypertensive rats (SHRs). Thirty female SHRs were administered VAL, SAC/VAL, or saline. Ten normotensive female Wistar-Kyoto (WKY) rats were included in the control group. We assessed estrous cyclicity and sexual behavior in the female rats. In addition, the morphology of clitoral and vaginal tissues was evaluated by histological analyses. Western blotting and enzyme-linked immunosorbent assays were used to assess the levels of fibrotic markers in vaginal and clitoral tissues. Furthermore, the protein levels of phosphatase and tensin homolog deleted from chromosome 10 (PTEN), phosphoinositide-3-kinase (PI3K), and AKT expression were measured by Western blotting. SAC/VAL treatment improved hypertension-induced sexual dysfunction, exhibited as a prolonged estrus phase, increased receptivity and proceptive events, and decreased aggressive events, compared with those of VAL treatment and control SHRs without treatments. In addition, SAC/VAL-treated SHRs had lower levels of fibrotic markers, estradiol, and estrogen receptor α/β than the levels of VAL-treated SHRs or SHRs without treatment. Moreover, SAC/VAL decreased p-PTEN expression and increased p-PI3K and p-AKT expression at the protein level compared with those in VAL treatment alone. VAL and SAC/VAL treatments have significantly increased sexual receptivity and proceptivity, decreased aggressiveness, and improved the fibrosis of vaginal and clitoral tissues in female SHRs. However, SAC/VAL treatment shows more effective results compared with VAL treatment, which may be related to the PTEN/PI3K/AKT pathway.

Vascular Stiffness in Aging and Disease

The goal of this review is to provide further understanding of increased vascular stiffness with aging, and how it contributes to the adverse effects of major human diseases. Differences in stiffness down the aortic tree are discussed, a topic requiring further research, because most prior work only examined one location in the aorta. It is also important to understand the divergent effects of increased aortic stiffness between males and females, principally due to the protective role of female sex hormones prior to menopause. Another goal is to review human and non-human primate data and contrast them with data in rodents. This is particularly important for understanding sex differences in vascular stiffness with aging as well as the changes in vascular stiffness before and after menopause in females, as this is controversial. This area of research necessitates studies in humans and non-human primates, since rodents do not go through menopause. The most important mechanism studied as a cause of age-related increases in vascular stiffness is an alteration in the vascular extracellular matrix resulting from an increase in collagen and decrease in elastin. However, there are other mechanisms mediating increased vascular stiffness, such as collagen and elastin disarray, calcium deposition, endothelial dysfunction, and the number of vascular smooth muscle cells (VSMCs). Populations with increased longevity, who live in areas called “Blue Zones,” are also discussed as they provide additional insights into mechanisms that protect against age-related increases in vascular stiffness. Such increases in vascular stiffness are important in mediating the adverse effects of major cardiovascular diseases, including atherosclerosis, hypertension and diabetes, but require further research into their mechanisms and treatment.

Finger Millet Ethanol Extracts Prevent Hypertension by Inhibiting the Angiotensin-Converting Enzyme Level and Enhancing the Antioxidant Capacity in Spontaneously Hypertensive Rats

Finger millet (Eleusine coracana) contains high levels of calcium and polyphenols, which have a variety of beneficial functions. We tested the hypothesis that finger millet ethanol extracts (FEs) have an antihypertensive effect in spontaneously hypertensive rats (SHRs). The study groups were assigned as follows: (1) Wistar Kyoto rats (normal); (2) SHRs treated with saline (negative control); (3) SHRs treated with captopril 50 mg/kg bw (positive control); (4) SHRs treated with FE 250 mg/kg bw (FE250); and (5) SHRs treated with FE 500 mg/kg bw (FE500). FE supplementation improved the lipid profiles, including the triglyceride, total cholesterol, and low-density lipoprotein cholesterol levels, without deterioration in liver function. The thiobarbituric acid reactive substance concentration and superoxide dismutase activity significantly improved after the application of FE250 and FE500. Interestingly, FE250 and FE500 application dramatically reduced the systolic blood pressure. FE supplementation exhibited powerful control over the renin-angiotensin system by reducing the angiotensin-converting enzyme levels and renin mRNA expression in the kidney. Additionally, FE500 application ameliorated vascular remodeling, reversed the thickening media, and decreased the media thickness/lumen diameter ratio of the aorta. These results imply that FEs are a potent antihypertensive nutraceutical for regulating the renin-angiotensin system and simultaneously inhibiting oxidative stress.

Central Blood Pressure and Subclinical Atherosclerotic Risk in Young Hispanic American Women

Background

The incidence of younger women being hospitalized from cardiovascular disease (CVD) events is on the rise. Hispanic women are generally thought to have higher CVD risk factor burden than non-Hispanic White (NHW) women yet Hispanic Americans have lower mortality from CVD. Traditional measures of CVD may not accurately capture CVD risk in Hispanic Americans. Hence, the purpose of this study was to assess the impact of ethnicity on vascular reactivity and central hemodynamic load to gain insight into subclinical CVD risk in young women.

Methods

Brachial flow-mediated dilation (FMD), low-flow mediated constriction (L-FMC), carotid-femoral pulse wave velocity (cfPWV), and pulse wave analysis (from synthesized aortic pressure waveforms) were measured in 25 Hispanic women and 31 NHW women aged between 18-35 years. FMD and L-FMC were combined to provide an index of total vessel reactivity.

Results

NHW and Hispanic women did not differ in age or traditional CVD risk factors (P>.05 for all). Compared with NHW women, Hispanic women had greater vascular reactivity (8.7±4.1 vs 11.7±4.1 %, P=.011), lower central pulse pressure (28±5 vs 24±3 mm Hg, P=.001) and lower pressure from wave reflections (12±2 vs 10±1 mm Hg, P=.001). There were no differences in cfPWV between NHW women and Hispanic women (5.4±0.7 vs 5.3±0.7 m/s, P=.73).

Conclusion

Young Hispanic women have greater vascular reactivity and lower central pulsatile hemodynamic load compared with NHW women, suggesting lower subclinical CVD risk.

Prenatal exercise reprograms the development of hypertension progress and improves vascular health in SHR offspring

BACKGROUND

Upregulation of L-type voltage-gated Ca²⁺ (Ca_V1.2) channel in the arterial myocytes is a hallmark feature of hypertension. However, whether maternal exercise during pregnancy has a sustained beneficial effect on the offspring of spontaneously hypertensive rats (SHRs) through epigenetic regulation of Ca_V1.2 channel is largely unknown.

METHODS

Pregnant SHRs and Wistar-Kyoto rats were subjected to swimming and the vascular molecular and functional properties of male offspring were evaluated at embryonic (E) 20.5 day, 3 months (3 M), and 6 months (6 M).

RESULTS

Exercise during pregnancy significantly decreased the resting blood pressure at 3 M but not 6 M in the offspring of SHR. Prenatal exercise significantly reduced the cardiovascular reactivity, the contribution of Ca_V1.2 channel to the vascular tone, and the whole-cell current density of Ca_V1.2 channel in both 3 M and 6 M offspring of SHR. Moreover, maternal exercise triggered hypermethylation of the promoter region of the Ca_V1.2 α1C gene (CACNA1C), with a concomitant decrease in its protein and mRNA expressions in SHR offspring at E20.5, 3 M, and 6 M. Tissue culture experiments further confirmed that 5-Aza-2'-deoxycytidine increased the structure and functional expression of Ca_V1.2 channel by inhibiting the DNA methylation of CACNA1C. However, the improvement of prenatal exercise on the blood pressure, function, and expression of Ca_V1.2 channel was attenuated in the offspring of SHRs at 6 M compared to the 3 M readout.

CONCLUSIONS

These data suggest that prenatal exercise improves the vascular function by the hypermethylation of CACNA1C in the arterial myocytes and delays the development of hypertension in the offspring of SHRs. However, these effects fade out with age.

Time-of-Day-Dependent Effects of Bromocriptine to Ameliorate Vascular Pathology and Metabolic Syndrome in SHR Rats Held on High Fat Diet

The treatment of type 2 diabetes patients with bromocriptine-QR, a unique, quick release micronized formulation of bromocriptine, improves glycemic control and reduces adverse cardiovascular events. While the improvement of glycemic control is largely the result of improved postprandial hepatic glucose metabolism and insulin action, the mechanisms underlying the drug's cardioprotective effects are less well defined. Bromocriptine is a sympatholytic dopamine agonist and reduces the elevated sympathetic tone, characteristic of metabolic syndrome and type 2 diabetes, which potentiates elevations of vascular oxidative/nitrosative stress, known to precipitate cardiovascular disease. Therefore, this study investigated the impact of bromocriptine treatment upon biomarkers of vascular oxidative/nitrosative stress (including the pro-oxidative/nitrosative stress enzymes of NADPH oxidase 4, inducible nitric oxide (iNOS), uncoupled endothelial nitric oxide synthase (eNOS), the pro-inflammatory/pro-oxidative marker GTP cyclohydrolase 1 (GTPCH 1), and the pro-vascular health enzyme, soluble guanylate cyclase (sGC) as well as the plasma level of thiobarbituric acid reactive substances (TBARS), a circulating marker of systemic oxidative stress), in hypertensive SHR rats held on a high fat diet to induce metabolic syndrome. Inasmuch as the central nervous system (CNS) dopaminergic activities both regulate and are regulated by CNS circadian pacemaker circuitry, this study also investigated the time-of-day-dependent effects of bromocriptine treatment (10 mg/kg/day at either 13 or 19 h after the onset of light (at the natural waking time or late during the activity period, respectively) among animals held on 14 h daily photoperiods for 16 days upon such vascular biomarkers of vascular redox state, several metabolic syndrome parameters, and mediobasal hypothalamic (MBH) mRNA expression levels of neuropeptides neuropeptide Y (NPY) and agouti-related protein (AgRP) which regulate the peripheral fuel metabolism and of mRNA expression of other MBH glial and neuronal cell genes that support such metabolism regulating neurons in this model system. Such bromocriptine treatment at ZT 13 improved (reduced) biomarkers of vascular oxidative/nitrosative stress including plasma TBARS level, aortic NADPH oxidase 4, iNOS and GTPCH 1 levels, and improved other markers of coupled eNOS function, including increased sGC protein level, relative to controls. However, bromocriptine treatment at ZT 19 produced no improvement in either coupled eNOS function or sGC protein level. Moreover, such ZT 13 bromocriptine treatment reduced several metabolic syndrome parameters including fasting insulin and leptin levels, as well as elevated systolic and diastolic blood pressure, insulin resistance, body fat store levels and liver fat content, however, such effects of ZT 19 bromocriptine treatment were largely absent versus control. Finally, ZT 13 bromocriptine treatment reduced MBH NPY and AgRP mRNA levels and mRNA levels of several MBH glial cell/neuronal genes that code for neuronal support/plasticity proteins (suggesting a shift in neuronal structure/function to a new metabolic control state) while ZT 19 treatment reduced only AgRP, not NPY, and was with very little effect on such MBH glial cell genes expression. These findings indicate that circadian-timed bromocriptine administration at the natural circadian peak of CNS dopaminergic activity (that is diminished in insulin resistant states), but not outside this daily time window when such CNS dopaminergic activity is naturally low, produces widespread improvements in biomarkers of vascular oxidative stress that are associated with the amelioration of metabolic syndrome and reductions in MBH neuropeptides and gene expressions known to facilitate metabolic syndrome. These results of such circadian-timed bromocriptine treatment upon vascular pathology provide potential mechanisms for the observed marked reductions in adverse cardiovascular events with circadian-timed bromocriptine-QR therapy (similarly timed to the onset of daily waking as in this study) of type 2 diabetes subjects and warrant further investigations into related mechanisms and the potential application of such intervention to prediabetes and metabolic syndrome patients as well.

Guidelines for the measurement of vascular function and structure in isolated arteries and veins

The measurement of vascular function in isolated vessels has revealed important insights into the structural, functional, and biomechanical features of the normal and diseased cardiovascular system and has provided a molecular understanding of the cells that constitutes arteries and veins and their interaction. Further, this approach has allowed the discovery of vital pharmacological treatments for cardiovascular diseases. However, the expansion of the vascular physiology field has also brought new concerns over scientific rigor and reproducibility. Therefore, it is appropriate to set guidelines for the best practices of evaluating vascular function in isolated vessels. These guidelines are a comprehensive document detailing the best practices and pitfalls for the assessment of function in large and small arteries and veins. Herein, we bring together experts in the field of vascular physiology with the purpose of developing guidelines for evaluating ex vivo vascular function. By using this document, vascular physiologists will have consistency among methodological approaches, producing more reliable and reproducible results.

Home-Measured Blood Pressure Is Associated with Handgrip Strength in Patients with Type 2 Diabetes: The KAMOGAWA-HBP Study

The association between blood pressure measured at home and handgrip strength in patients with diabetes has not been investigated. Therefore, in this study, we aimed to assess this association among patients with type 2 diabetes. In this cross-sectional study, 157 patients with type 2 diabetes underwent muscle tests and morning and evening blood-pressure measurements at home in triplicate for 14 consecutive days throughout the study period. Univariate and multivariate regression analyses were conducted to analyze the relationship between home blood-pressure parameters and handgrip strength. The average age and hemoglobin A1c of the patients were 70.5 years and 7.1%, respectively. Morning diastolic blood pressure of [β (95% confidence interval; CI): 0.20 (0.03, 0.37)] was associated with handgrip strength in men, while morning systolic blood pressure of [−0.09 (−0.15, −0.04)], morning pulse pressure of [−0.14 (−0.21, −0.08)], and evening pulse pressure of [−0.12 (−0.19, −0.04)] were associated with handgrip strength in women. Home-measured blood pressure was associated with handgrip strength. Sex differences were found in the relationship between home blood-pressure parameters and handgrip strength.

Increased urinary excretion of hedgehog interacting protein (uHhip) in early diabetic kidney disease

Glomerular endothelial cell (GEC) dysfunction occurs in diabetic kidney disease (DKD) and generally precedes albuminuria. We recently reported that hedgehog interacting protein (Hhip), highly expressed in GECs, contributes to DKD development in diabetic mice. Here, we hypothesized that urinary Hhip (uHhip) could identify early DKD; we tested uHhip in mice and humans with diabetes (DM). In both type 1 (Akita) and type 2 (db/db) DM mice, uHhip is elevated prior to the development of albuminuria, while non-DM controls excrete minimal amount of uHhip. In 87 type 2 DM patients and 39 healthy controls, the uHhip/creatinine (Cr) ratio provides a significant discrimination between non-DM and DM groups; 0 [0-69.5] in non-DM, 9.9 [1.7-39.5] in normoalbuminuric DM, 167.7 [95.7-558.7] in microalbuminuric DM, and 207.9 [0-957.2] in macroalbuminuric DM (median [IQR] ng/mmol, P < 0.0001). The log-uHhip/Cr is positively correlated with urine albumin/Cr ratio (UACR) (spearman correlation coefficient 0.47, P < 0.0001). The log-uHhip/Cr is also associated with eGFR, pulse pressure, and urinary cytokines (IL-1β, IL-6, IL-8, and TGFβ1) independent of UACR. By immunostaining, Hhip is localized in glomeruli and tubules, and is increased in human DM kidneys compared with non-DM kidneys. TGFβ1 shares the similar staining pattern as Hhip in human DM kidneys. Thus, uHhip appears to be a novel indicator of diabetic GEC injury and is elevated in early DKD before the development of microalbuminuria in mice and humans. Clinical value for detecting early DKD warrants further investigation.

Mechanical pressure unloading therapy reverses thoracic aortic structural and functional changes in a hypertensive rat model

OBJECTIVES

Hypertension can impair structure and function of blood vessels. Experimental data describing the reverse remodeling process after a mechanical pressure unloading therapy in the vasculature is limited. We studied the influence of pressure unloading on both the structural and functional alterations of the aorta in a hypertensive rat model.

METHODS

Using isolated thoracic aortic rings in an in-vitro organ bath system, endothelium-dependent and endothelium-independent vasorelaxation were studied 6-weeks or 12-weeks after abdominal aortic banding (aortic banding-6-week or aortic banding-12-week), and 6-weeks after an aortic debanding procedure performed after the sixth experimental week of aortic banding (aortic banding + debanding-12-week). Age-matched rats were sham-operated (sham-6-week or sham-12-week). The aortic morphometry and histological fibrosis were studied, and the mRNA-expression of metalloproteinase (MMP)-2, tissue inhibitor of metalloproteinase (TIMP)-2, and soluble guanylate cyclase subunits GUCY1a3 and GUCY1b3 were determined.

RESULTS

Aortic banding significantly increased systolic, diastolic, and pulse pressures. Structural changes (increased intima-media thickness and area normalized to body weight, aortic collagen content, higher MMP-2 and TIMP-2, and lower GUCY1a3 and GUCY1b3 mRNA-levels) and functional alterations (impaired endothelium-dependent and endothelium-independent vasorelaxation) have already taken place after 6 weeks of aortic banding. Pressure unloading, after established vascular changes, improved vascular function, resulted in reduced collagen content, and decreased both MMP-2 and TIMP-2 mRNA-expression.

CONCLUSION

Pressure-overload-induced vascular changes regressed due to mechanical unloading. Furthermore, debanding leads to a reductive tendency in fibrosis-associated gene expression and collagen accumulation. Collectively, the addition of drugs that target fibrosis to existing hypertensive treatment may present an attractive therapy against vascular remodeling.

Effects of acute footbath before and after glucose ingestion on arterial stiffness

The present study investigated the acute effect of a footbath on increases in arterial stiffness after glucose ingestion in healthy young women. Nine healthy young women (aged 18.4 ± 0.2 years; mean ± SE) completed three trials in random order. They started a footbath before 75-g oral glucose ingestion, a footbath after 75-g oral glucose ingestion and no footbath (control) trials. Aortic (carotid-femoral) and leg (femoral-ankle) pulse wave velocity, the carotid augmentation index, carotid, brachial and ankle blood pressure, heart rate, blood glucose levels, insulin levels and sublingual temperature were measured before (baseline) and at 15, 30, 60 and 90 min after the 75-g oral glucose ingestion. Aortic pulse wave velocity and brachial systolic blood pressure did not change from baseline to after the 75-g oral glucose ingestion in all trials. Leg pulse wave velocity and ankle systolic blood pressure were increased from baseline to after the 75-g oral glucose ingestion in the footbath after glucose ingestion and control trials, but not in the footbath before glucose ingestion trial. These results suggest that a footbath effectively suppresses the increase in leg arterial stiffness after glucose ingestion when implemented before glucose ingestion.

Elastin, arterial mechanics, and cardiovascular disease

Large, elastic arteries are composed of cells and a specialized extracellular matrix that provides reversible elasticity and strength. Elastin is the matrix protein responsible for this reversible elasticity that reduces the workload on the heart and dampens pulsatile flow in distal arteries. Here, we summarize the elastin protein biochemistry, self-association behavior, cross-linking process, and multistep elastic fiber assembly that provide large arteries with their unique mechanical properties. We present measures of passive arterial mechanics that depend on elastic fiber amounts and integrity such as the Windkessel effect, structural and material stiffness, and energy storage. We discuss supravalvular aortic stenosis and autosomal dominant cutis laxa-1, which are genetic disorders caused by mutations in the elastin gene. We present mouse models of supravalvular aortic stenosis, autosomal dominant cutis laxa-1, and graded elastin amounts that have been invaluable for understanding the role of elastin in arterial mechanics and cardiovascular disease. We summarize acquired diseases associated with elastic fiber defects, including hypertension and arterial stiffness, diabetes, obesity, atherosclerosis, calcification, and aneurysms and dissections. We mention animal models that have helped delineate the role of elastic fiber defects in these acquired diseases. We briefly summarize challenges and recent advances in generating functional elastic fibers in tissue-engineered arteries. We conclude with suggestions for future research and opportunities for therapeutic intervention in genetic and acquired elastinopathies.

Different Structural Alterations in Individual Conduit Arteries of SHRs Compared to Wistar Rats From the Prehypertensive Period to Late Adulthood

Structural changes of thoracic aorta (TA), carotid (CA) and iliac artery (IA) were assessed in Wistar and spontaneously hypertensive rats (SHR) aged 3, 17, and 52 weeks. Systolic blood pressure (sBP) was measured by plethysmography weekly. After perfusion fixation the arteries were processed for electron microscopy. The wall thickness (WT), cross-sectional area (CSA), inner diameter (ID), and WT/ID in all arteries and volume densities of endothelial cells (ECs), muscle cells (SMCs), and extracellular matrix (ECM) in TA were measured and their CSAs were calculated. In 3-week-old SHR compared to Wistar rats, sBP did not differ; in the TA, all parameters (WT, CSA, ID, WT/ID, CSA of SMCs, CSA of ECs, and CSA of ECM) were decreased; in CA, WT and CSA did not differ, ID was decreased, and WT/ID was increased; in IA, WT, CSA, and ID were increased. In 17- and 52-week-old SHRs, sBP and all parameters in all arteries were increased, only ID in IE in 52-week-old SHRs and CSA of ECs in the TA in 17-week-old SHRs did not change. Disproportionality between BP increase and structural alterations during ontogeny in SHR could reflect the flexibility of the arterial tree to the different needs of supplied areas.

Lecithin derived from ω-3 PUFA fortified eggs decreases blood pressure in spontaneously hypertensive rats

Hypertension is the most common risk factor for stroke, coronary heart disease and heart failure, which are the leading causes of death worldwide. Dietary patterns and supplements intakes are becoming important factors in the hypertension. The aim of this study was to estimate the effects of new generation egg yolk phospholipids rich in lecithin (SL) esterified with omega-3 and omega-6 fatty acids on blood pressure in hypertensive rats (SHR). Here we have reported that lecithin (SL) derived from egg yolk lowers blood pressure in pathology of hypertension. The SHR rats treated with SL had significantly lower blood pressure than control group (157/104 vs. 178/121 mmHg; P < 0.05) and down-regulated mesenteric artery over-response to norepinephrine and potassium chloride, giving similar arterial response as for normotensive Wistar Kyoto rats (WKY). Hypertensive rats treated by SL demonstrated significantly lower serum level of inflammatory factors. This work also indicates that SL treatment lowers heart rate and reduces the serum level of oxidative stress marker - nitrotyrosine - by 30–34% in both hypertensive and normotensive animals. Phospholipids with lecithin derived from PUFA fortified eggs may be a valuable dietary supplement in prophylaxis of hypertension and in patients with hypertension, however, this requires further studies on humans.

Danhong injection reduces vascular remodeling and up-regulates the Kallikrein-kinin system in spontaneously hypertensive rats

Although Danhong injection (DHI) is one of the most prescribed cardiovascular medicines in China, its therapeutic indications and mechanisms remain partially defined. We now identify molecular targets of DHI in resistance vasculatures and demonstrate its role in vascular function and blood pressure (BP) regulation. BP was determined in DHI, Losartan, and placebo- treated Spontaneously Hypertensive Rats (SHR) by both noninvasive and invasive measurements. Vasorelaxation was examined both in conduit and resistance vasculature by ex vivo aortic rings. Microarray analysis was performed and gene expression changes were verified by RT-qPCR and ELISA. Diastolic, systolic and mean BPs were significantly lower in DHI-treated SHR than controls by both tail-cuff and invasive BP measurements. In ex vivo rings, aortic and mesenteric vessels from SHR treated with DHI exhibited significantly greater acetylcholine-mediated relaxation. Among the 282 genes that are differentially expressed in microarray analysis, DHI treatment up-regulated the expression of kallikrein and plasma kallikrein B genes. DHI also significantly increased serum kallikrein content in SHR. Treatment with DHI significantly increased the ratio of aortic lumen to outer diameter. Therefore, the reduction of vascular remodeling and the up-regulation of Kallikrein-kinin system contribute, at least in part, to the antihypertensive effect of DHI in SHR.

From Newborn to Senescence Morphological and Functional Remodeling Leads to Increased Contractile Capacity of Arteries

Aging induces substantial morphological and functional changes in vessels. We hypothesized that due to morphological remodeling the total contractile forces of arteries increase, especially in older age as a function of age. Mean arterial blood pressure of rats and morphological and functional characteristics of isolated carotid arteries rats, from newborn to senescent, were assessed. The arterial blood pressure of rats increased significantly from 0.25 to the age of 6 months, and then it reached a level, which was maintained until age of 30 months. Wall lumen and wall thickness increased with age, mostly due to media (smooth muscle) thickening, whereas wall tension gradually reduced with age. Contractions of arteries to nonreceptor-mediated vasomotor agent (KCl, 60mM) increased in three consecutive age groups, whereas contractility first increased (until 2 months), then it did not change further with aging. Norepinephrine-induced contractions initially increased in young age and then did not change further in older age. These findings suggest that during normal aging due to remodeling of arterial wall (smooth muscle) the contractile capacity of arteries increases, which seems to be independent from systemic blood pressure. Thus, arterial remodeling can favor the development of increased circulatory resistance in older age.

Acute effects of aerobic exercise intensity on arterial stiffness after glucose ingestion in young men

Arterial stiffness increases after glucose ingestion. Acute low- and moderate-intensity aerobic exercise decreases arterial stiffness. However, the acute effects of 30 min of cycling at low- and moderate-intensity [25% (LE trial) and 65% (ME trial) peak oxygen uptake, respectively] on arterial stiffness at 30, 60 and 120 min of a postexercise glucose ingestion. Ten healthy young men (age, 22·4 ± 0·5 years) performed LE and ME trials on separate days in a randomized controlled crossover fashion. Carotid-femoral (aortic) pulse wave velocity (PWV), femoral-ankle (leg) PWV, carotid augmentation index (AIx) and carotid blood pressure (BP) (applanation tonometry), brachial and ankle BP (oscillometric device), heart rate (HR) (electrocardiography), blood glucose (UV-hexokinase method) and blood insulin (CLEIA method) levels were measured at before (baseline) and at 30, 60 and 120 min after the 75-g OGTT. Leg PWV, ankle pulse pressure and BG levels significantly increased from baseline after the 75-g OGTT in the LE trial (P<0·05), but not in the ME trial. Insulin levels and HR significantly increased from baseline after the 75-g OGTT in both trials (P<0·05). Aortic PWV, carotid AIx, brachial BP and carotid BP did not change from baseline after the 75-g OGTT in both trials. The present findings indicate that aerobic exercise at moderate intensity before glucose ingestion suppresses increases leg arterial stiffness after glucose ingestion.

Extracellular Matrix Disarray as a Mechanism for Greater Abdominal Versus Thoracic Aortic Stiffness With Aging in Primates

OBJECTIVE

Increased vascular stiffness is central to the pathophysiology of aging, hypertension, diabetes mellitus, and atherosclerosis. However, relatively few studies have examined vascular stiffness in both the thoracic and the abdominal aorta with aging, despite major differences in anatomy, embryological origin, and relation to aortic aneurysm.

APPROACH AND RESULTS

The 2 other unique features of this study were (1) to study young (9±1 years) and old (26±1 years) male monkeys and (2) to study direct and continuous measurements of aortic pressure and thoracic and abdominal aortic diameters in conscious monkeys. As expected, aortic stiffness, β, was increased P<0.05, 2- to 3-fold, in old versus young thoracic aorta and augmented further with superimposition of acute hypertension with phenylephrine. Surprisingly, stiffness was not greater in old thoracic aorta than in young abdominal aorta. These results can be explained, in part, by the collagen/elastin ratio, but more importantly, by disarray of collagen and elastin, which correlated best with vascular stiffness. However, vascular smooth muscle cell stiffness was not different in thoracic versus abdominal aorta in either young or old monkeys.

CONCLUSIONS

Thus, aortic stiffness increases with aging as expected, but the most severe increases in aortic stiffness observed in the abdominal aorta is novel, where values in young monkeys equaled, or even exceeded, values of thoracic aortic stiffness in old monkeys. These results can be explained by alterations in collagen/elastin ratio, but even more importantly by collagen and elastin disarray.

Tributyltin chloride increases phenylephrine-induced contraction and vascular stiffness in mesenteric resistance arteries from female rats

Tributyltin chloride (TBT) is an organotin compound that reduces estrogen levels in female rats. We aimed to investigate the effects of TBT exposure on vascular tonus and vascular remodelling in the resistance arteries of female rats. Rats were treated daily with TBT (500 ng/kg) for 15 days. TBT did not change arterial blood pressure but did modify some morpho-physiological parameters of third-order mesenteric resistance arteries in the following ways: (1) decreased lumen and external diameters; (2) increased wall/lm ratio and wall thickness; (3) decreased distensibility and increased stiffness; (4) increased collagen deposition; and (5) increased pulse wave velocity. TBT exposure increased the phenylephrine-induced contractile response in mesenteric resistance arteries. However, vasodilatation responses induced by acetylcholine and sodium nitroprusside were not modified by TBT. It is suggested that TBT exposure reduces vascular nitric oxide (NO) production, because:(1) L-NAME incubation did not cause a leftward shift in the concentration-response curve for phenylephrine; (2) both eNOS protein expression; (3) in situ NO production were reduced. Incubation with L-NAME; and (4) SOD shifted the phenylephrine response curve to the left in TBT rats. Tiron, catalase, ML-171 and VAS2870 decreased vascular reactivity to phenylephrine only in TBT rats. Moreover, increased superoxide anion production was observed in the mesenteric resistance arteries of TBT rats accompanied by an increase in gp91phox, catalase, AT1 receptor and total ERK1/2 protein expression. In conclusion, these findings show that TBT induced alterations are most likely due to a reduction of NO production combined with increased O2(-) production derived from NADPH oxidase and ERK1/2 activation. These findings offer further evidence that TBT is an environmental risk factor for cardiovascular disease.

Effect of docosahexaenoic acid monoacylglyceride on systemic hypertension and cardiovascular dysfunction

ω-3 Fatty acid supplementation has been associated with lower blood pressure. Cardiovascular diseases are also known to be linked directly to an increase in ω-6 and a reduction in ω-3 fatty acid levels in blood circulation and tissues. To determine the effect of docosahexaenoic acid monoglycerides (MAG-DHA) on blood pressure, lipid profiles, and vascular remodeling in rats fed a high-fat/high-carbohydrate (HFHC) diet. Studies were performed in male rats subjected to 8 wk of HFHC diet supplemented or not with 3 g/day MAG-DHA. After 8 wk of daily MAG-DHA treatment, rats in the HFHC + MAG-DHA group had lower arterial blood pressure and heart rate compared with the HFHC group. Moreover, MAG-DHA prevented the increase aortic wall thickness, whereas lipid analysis of aortic tissues revealed an increase in DHA/AA ratio correlated with the production of resolvin D2 and D3 metabolites. Histological analysis revealed that MAG-DHA prevented the development of LVH in the HFHC group. Serum lipid profile analysis further showed a decrease in total cholesterol (TC) and LDL, including very low-density lipoprotein (VLDL) and triglyceride (TG) levels, together with an increase in HDL levels after 8 wk of MAG-DHA treatment compared with the HFHC group. Furthermore, daily MAG-DHA treatment resulted in reduced proinflammatory marker levels such as CRP, IL-6, TNFα, and IL-1β. Altogether, these findings revealed that per os administration of MAG-DHA prevents HFHC-diet induced hypertension and LVH in rats.

Resveratrol prevents cardiovascular complications in the SHR/STZ rat by reductions in oxidative stress and inflammation

The cardioprotective effects of resveratrol are well established in animal models of metabolic disease but are yet to be investigated in a combined model of hypertension and diabetes. This study investigated the ability of resveratrol's antioxidant and anti-inflammatory effects to prevent cardiovascular complications in the spontaneously hypertensive streptozotocin-induced diabetic rat. Diabetes was induced in eight-week-old male spontaneously hypertensive rats via a single intravenous injection of streptozotocin. Following this, resveratrol was administered orally for an eight-week period until the animals were sixteen weeks of age. Upon completion of the treatment regime assessments of oxidative stress, lipid peroxidation, inflammation, and cardiovascular function were made. Resveratrol administration to hypertensive-diabetic animals did not impact upon blood glucose or haemodynamics but significantly reduced oxidative stress, lipid peroxidation, and inflammatory cytokines. Reductions in systemic levels of oxidative stress and inflammation conferred improvements in vascular reactivity and left ventricular pump function and electrophysiology. This study demonstrates that resveratrol administration to hypertensive diabetic animals can elicit cardioprotective properties via antioxidant and anti-inflammatory effects. The observed preservation of cardiovascular function was independent of changes in blood glucose concentration and haemodynamics, suggesting that oxidative stress and inflammation are key components within the pathological cascade associated with hypertension and diabetes.

Augmented vascular smooth muscle cell stiffness and adhesion when hypertension is superimposed on aging

Hypertension and aging are both recognized to increase aortic stiffness, but their interactions are not completely understood. Most previous studies have attributed increased aortic stiffness to changes in extracellular matrix proteins that alter the mechanical properties of the vascular wall. Alternatively, we hypothesized that a significant component of increased vascular stiffness in hypertension is due to changes in the mechanical and adhesive properties of vascular smooth muscle cells, and that aging would augment the contribution from vascular smooth muscle cells when compared with the extracellular matrix. Accordingly, we studied aortic stiffness in young (16-week-old) and old (64-week-old) spontaneously hypertensive rats and Wistar-Kyoto wild-type controls. Systolic and pulse pressures were significantly increased in young spontaneously hypertensive rats when compared with young Wistar-Kyoto rats, and these continued to rise in old spontaneously hypertensive rats when compared with age-matched controls. Excised aortic ring segments exhibited significantly greater elastic moduli in both young and old spontaneously hypertensive rats versus Wistar-Kyoto rats. were isolated from the thoracic aorta, and stiffness and adhesion to fibronectin were measured by atomic force microscopy. Hypertension increased both vascular smooth muscle cell stiffness and vascular smooth muscle cell adhesion, and these increases were both augmented with aging. By contrast, hypertension did not affect histological measures of aortic collagen and elastin, which were predominantly changed by aging. These findings support the concept that stiffness and adhesive properties of vascular smooth muscle cells are novel mechanisms contributing to the increased aortic stiffness occurring with hypertension superimposed on aging.

In vivo assessment of arterial stiffness in the isoflurane anesthetized spontaneously hypertensive rat

Background

Rodent models are increasingly used to study the development and progression of arterial stiffness. Both the non-invasive Doppler derived Pulse Wave Velocity (PWV) and the invasively determined arterial elastance index (EaI) have been used to assess arterial stiffness in rats and mice, but the need for anesthetic agents to make these in vivo estimates may limit their utility. Thus, we sought to determine: 1) if known differences in arterial stiffness in spontaneously hypertensive rats (SHR) are detectable by PWV and EaI measurements when made under isoflurane anesthesia, and 2) if these two uniquely acquired assessments of arterial elasticity correlate.

Methods

We obtained PWV and EaI measurements in isoflurane anesthetized young and old SHRs, which are known to have significant differences in arterial stiffness. Doppler pulse waves were recorded from carotid and iliac arteries and the distance (D) between probe applantation sites was recorded. Simultaneously, an EKG was obtained, and the time intervals between the R-wave of the EKG to the foot of the Doppler waveforms were measured and averaged over three cardiac cycles. Pulse-transit time (T) of the carotid to iliac artery was determined, and PWV was calculated as Distance (D)/Time (T), where D = the distance from the carotid to the iliac notch and T = (R to iliac foot) - (R to carotid foot). EaI was subsequently determined from pressure volumes loops obtained via left ventricle catheterization.

Results

PWV and EaI were found to be significantly faster in the older rats (13.2 ± 2.0 vs. 8.0 ± 0.8 m/sec, p < 0.001; 120 ± 20 vs. 97 ± 16 mmHg/μl/g, p <0.05). Bland-Altman analyses of intra- and inter-observer measures demonstrate a statistically significant relationship between readings (p < 0.0001). PWV and EaI measurements were found to be significantly and positively correlated with a correlation coefficient of 0.53 (p < 0.05).

Conclusion

Our study suggests that isoflurane administration does not limit Doppler PWV or EaI measures in their ability to provide accurate, in vivo assessments of relative arterial stiffness in isoflurane anesthetised SHR rats. Furthermore, PWV data obtained in these rats correlate well with invasively determined EaI.

Sex-specific alterations in NOS regulation of vascular function in aorta and mesenteric arteries from spontaneously hypertensive rats compared to Wistar Kyoto rats

The present study tested the hypothesis that spontaneously hypertensive rats (SHR) have impaired nitric oxide synthase (NOS)‐mediated regulation of vascular function versus Wistar‐Kyoto rats (WKY). Aorta and small mesenteric arteries were studied from male and female SHR (M SHR and F SHR) and WKY (M WKY and F WKY). Phenylephrine (PE)‐induced vasoconstriction was greater in aorta of M SHR versus all others (P < 0.05); there were neither sex nor strain differences in PE contraction in mesenteric arteries. The NOS inhibitor l‐Nitro‐Arginine Methyl Ester (l‐NAME) increased PE‐induced vasoconstriction in all rats, although the increase was the least in male SHR (P < 0.05), revealing a blunted vasoconstrictor buffering capacity of NOS. l‐NAME increased sensitivity to PE‐induced constriction only in mesenteric arteries of SHR, although, the maximal percent increase in contraction was comparable among groups. ACh‐induced relaxation was also less in aorta from M SHR versus all others (P < 0.05). ACh relaxation was comparable among groups in mesenteric arteries, although SHR exhibited a greater NOS component to ACh‐induced relaxation than WKY. To gain mechanistic insight into sex and strain differences in vascular function, NOS activity and NOS3 protein expression were measured. Aortic NOS activity was comparable between groups and M SHR had greater NOS3 expression than M WKY. In contrast, although vascular function was largely maintained in mesenteric arteries of SHR, NOS activity was less in SHR versus WKY. In conclusion, M SHR exhibit a decrease in NOS regulation of vascular function compared to F SHR and WKY, although this is not mediated by decreases in NOS activity and/or expression.

The present study tested the hypothesis that spontaneously hypertensive rats (SHR) have impaired nitric oxide synthase (NOS)‐mediated regulation of vascular function versus Wistar‐Kyoto rats (WKY). Aorta and small mesenteric arteries were studied from male and female SHR and WKY. Male SHR showed a decreased NOS regulation of vascular function compared to F SHR and WKY, although this was not mediated by decreases in NOS activity and/or expression.

Contractile force is enhanced in Aortas from pendrin null mice due to stimulation of angiotensin II-dependent signaling

Pendrin is a Cl⁻/HCO₃⁻ exchanger expressed in the apical regions of renal intercalated cells. Following pendrin gene ablation, blood pressure falls, in part, from reduced renal NaCl absorption. We asked if pendrin is expressed in vascular tissue and if the lower blood pressure observed in pendrin null mice is accompanied by reduced vascular reactivity. Thus, the contractile responses to KCl and phenylephrine (PE) were examined in isometrically mounted thoracic aortas from wild-type and pendrin null mice. Although pendrin expression was not detected in the aorta, pendrin gene ablation changed contractile protein abundance and increased the maximal contractile response to PE when normalized to cross sectional area (CSA). However, the contractile sensitivity to this agent was unchanged. The increase in contractile force/cross sectional area observed in pendrin null mice was due to reduced cross sectional area of the aorta and not from increased contractile force per vessel. The pendrin-dependent increase in maximal contractile response was endothelium- and nitric oxide-independent and did not occur from changes in Ca²⁺ sensitivity or chronic changes in catecholamine production. However, application of 100 nM angiotensin II increased force/CSA more in aortas from pendrin null than from wild type mice. Moreover, angiotensin type 1 receptor inhibitor (candesartan) treatment in vivo eliminated the pendrin-dependent changes contractile protein abundance and changes in the contractile force/cross sectional area in response to PE. In conclusion, pendrin gene ablation increases aorta contractile force per cross sectional area in response to angiotensin II and PE due to stimulation of angiotensin type 1 receptor-dependent signaling. The angiotensin type 1 receptor-dependent increase in vascular reactivity may mitigate the fall in blood pressure observed with pendrin gene ablation.

Mechanisms of improved aortic stiffness by arotinolol in spontaneously hypertensive rats

OBJECTIVES

This study investigates the effects on aortic stiffness and vasodilation by arotinolol and the underlying mechanisms in spontaneously hypertensive rats (SHR).

METHODS

The vasodilations of rat aortas, renal and mesenteric arteries were evaluated by isometric force recording. Nitric oxide (NO) was measured in human aortic endothelial cells (HAECs) by fluorescent probes. Sixteen-week old SHRs were treated with metoprolol (200 mg·kg-1·d⁻¹), arotinolol (30 mg·kg-1·d⁻¹) for 8 weeks. Central arterial pressure (CAP) and pulse wave velocity (PWV) were evaluated via catheter pressure transducers. Collagen was assessed by immunohistochemistry and biochemistry assay, while endothelial nitric oxide synthase (eNOS) and eNOS phosphorylation (p-eNOS) of HAECs or aortas were analyzed by western blotting.

RESULTS

Arotinolol relaxed vascular rings and the relaxations were attenuated by Nω-nitro-L-arginine methyl ester (L-NAME, NO synthase inhibitor) and the absence of endothelium. Furthermore, arotinolol-induced relaxations were attenuated by 4-aminopyridine (4-AP, Kv channels blocker). Arotinolol produced more nitric oxide compared to metoprolol and increased the expression of p-eNOS in HAECs. These results indicated that arotinolol-induced vasodilation involves endothelium-derived NO and Kv channels. The treatement with arotinolol in 8 weeks, but not metoprolol, markedly decreased CAP and PWV. Biochemistry assay and immunohistochemistry showed that aortic collagen depositions in the arotinolol groups were reduced compared with SHRs with metoprolol. Moreover, eNOS phosphorylation was significantly increased in aortinolol-treated SHR compared with SHRs with metoprolol.

CONCLUSIONS

Arotinolol improves arterial stiffness in SHR, which involved in increasing NO and decreasing collagen contents in large arteries.

Attenuation of alpha-adrenergic-induced vasoconstriction by dietary wild blueberries (Vaccinium angustifolium) is mediated by the NO-cGMP pathway in spontaneously hypertensive rats (SHRs)

The role of wild blueberries (WB) on key signaling steps of nitric oxide (NO) and cyclooxygenase (COX) pathways was examined in spontaneously hypertensive rats (SHRs) after eight weeks on a control (C) or an 8% w/w WB diet. Aortic rings from SHRs were stimulated with phenylephrine (Phe) in the absence or presence of inhibitors of: soluble guanylyl cyclase (sGC), phosphodiesterase-5 (PDE(5)), prostaglandin I(2) (PGI(2)) synthase and thromboxane A(2) (TXA(2)) synthase. Additionally, enzymatic activities in these pathways were determined by the concentration of NO, cyclic guanosine monophosphate (cGMP), PGI(2) and TXA(2). In the WB-fed SHR, attenuation of Phe-induced vasoconstriction was mediated by an increased synthesis or preservation of cGMP. Despite an increased release of PGI(2) in the WB group, neither inhibition of PGI(2) or TXA(2) synthase resulted in a different response to Phe between the control and the WB rings. Hence, in the SHR, WB decrease Phe-mediated vasoconstriction under basal conditions by enhancing NO-cGMP signaling without a significant involvement of the COX pathway.

Pioglitazone enhances the blood pressure-lowering effect of losartan via synergistic attenuation of angiotensin II-induced vasoconstriction

INTRODUCTION

This study was designed to investigate the underlying mechanisms of synergistic antihypertensive effect produced by combination therapy of losartan and pioglitazone in metabolic syndrome (MS) rats.

MATERIALS AND METHODS

An MS model was induced by feeding rats a high-fat, high-sodium diet and 20% sucrose solution. Losartan (20 mg/kg/day), pioglitazone (10 mg/kg/day), and their combination were orally administered for eight consecutive weeks. Systolic blood pressure (SBP) and mean arterial pressure (MAP) were measured using the tail-cuff method and carotid arterial catheterization, respectively. The aortas were isolated and in vitro vascular reactivity studies were performed. The protein expression of angiotensin type 1 receptor (AT1), endothelial nitric oxide synthase (eNOS), phosphorylated eNOS and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase subunit p47(phox), level of nitrotyrosine as well as activity of eNOS and NADPH oxidase in aortas of MS rats were detected.

RESULTS

After eight weeks of treatment, the SBP and MAP in the losartan (115 ± 5 and 106 ± 6 mmHg), pioglitazone (130 ± 6 and 118 ± 6 mmHg), and combination therapy (105 ± 6 and 98 ± 5 mmHg) groups were lower than those in the model group (150 ± 8 and 136 ± 9 mmHg). Combination therapy of losartan and pioglitazone reduced BP more than either monotherapy, and showed additive effects on improving endothelial dysfunction and abolishing the increased vascular responsiveness to angiotensin II. These synergistic effects were associated with further reductions in protein expression of p47(phox) and AT1, NADPH oxidase activity, and nitrotyrosine level.

CONCLUSIONS

Our data indicate that combined treatment exerts more beneficial effects on lowering BP and improving vascular lesions.

Sex-specific programming of hypertension in offspring of late-gestation diabetic rats

BACKGROUND

The intrauterine environment strongly influences adult disease susceptibility. We used a rat model of third-trimester maternal diabetes to test the hypothesis that adult offspring exposed to hyperglycemia in utero display increased blood pressure and alterations in vascular responsiveness.

METHODS

Diabetes was induced by streptozotocin injection to pregnant rats on gestation day 13 (term 21 d) and partially controlled with insulin injections. Hemodynamic function was evaluated in 6-12-mo-old offspring.

RESULTS

Male but not female offspring of diabetic mothers (ODM) had significantly increased blood pressure as compared with controls; heart rate (HR) was similar. For both sexes, HR baroreflex responses were similar as were in vivo hemodynamic responses to angiotensin II, nitric oxide synthase inhibition, and ganglionic blockade. Aortic contractility to angiotensin II was similar in the two groups. Nitric oxide synthase inhibition and the Cu/Zn superoxide dismutase inhibitor diethyldithiocarbamate, but not the superoxide dismutase-mimetic Tempol, significantly increased contractile responses to angiotensin II in controls but not ODM. Reduced nicotinamide adenine dinucleotide phosphate-stimulated superoxide production was greater in male ODM than in controls (P < 0.05).

CONCLUSION

Exposure to hyperglycemia in utero results in sex-specific cardiovascular changes in adult offspring. Impaired nitric oxide-reactive oxygen species signaling may play a significant role in the hemodynamic phenotype of ODM.

Aortic stiffness in vivo in hypertensive rat via echo-tracking: analysis of the pulsatile distension waveform

Large-artery stiffening is a major risk factor in aging and hypertension. Elevated blood pressure (BP) and vascular wall properties participate in arterial stiffening; we aimed to evaluate their respective role by combining echo-tracking and the spontaneously hypertensive rats (SHR) treated with low doses of a nitric oxide synthase inhibitor, shown to have arterial stiffening. Normotensive [Wistar-Kyoto (WKY)], SHR, and SHR treated for 2 wk with NG-nitro-l-arginine methyl ester (SHRLN) were anesthetized; BP and distension (pulsatile displacement) of the aortic walls with the ArtLab echo-tracking device were measured. Stiffness index increased in SHRLN vs. SHR; compliance, distensibility, and the slopes and area of the distension-pressure loop curve decreased. The pulsatile distension and pressure waveforms were strongly altered in SHRLN. Maximal values were decreased and increased, respectively, and the waveform kinetics also differed. Thus the area under the curve adjusted to heart rate (AUC/ms) was calculated. Acute BP reductions were induced by diltiazem in SHR and SHRLN, to levels similar to those of WKY. In SHR, compliance, distensibility, stiffness index, and the ascending slope of the distension-pressure loop reached the values of WKY, whereas they were only partially improved in SHRLN. Aortic distension (maximal value and AUC/ms) and the area of the distension-pressure loop were improved in SHR, but not in SHRLN. These data confirm the aortic stiffening induced by nitric oxide reduction in SHR. They show that the ArtLab system analyzes aortic stiffness in rats, and that the aortic pulsatile distension waveform is a parameter strongly dependent on the vascular wall properties.

Endothelial dysfunction in spontaneously hypertensive rats: focus on methodological aspects

Despite the apparent consensus on the existence of endothelial dysfunction in conduit and resistance arteries of spontaneously hypertensive rats (SHR), a commonly employed experimental model of hypertension, there are a number of reports showing that endothelium-dependent vasodilatory responses are similar, or even increased, in SHR compared with their normotensive counterparts. The present paper aims to discuss the rationale for these apparent discrepancies, including the effect of age, type of artery and methodological aspects. Data from the literature indicate that the age of the animal is a contributing factor and that endothelial dysfunction is likely to be a consequence of hypertension. In addition, the use of antioxidant additives, such as ascorbic acid or ethylene diaminetetraacetic acid, and differences in the level of initial arterial stretch, might also be of importance because they may modify the oxidative status of the artery and the levels of vasoactive factors released by the endothelium.

Effects of dietary fish oil and trans fat on rat aorta histopathology and cardiovascular risk markers

Fish oil and shortening have been suggested to have opposite effects on cardiovascular disease (CVD). This study investigated the effect of shortening and fish oil on CVD risk factors and aorta histopathology, and the association between risk factors and aorta histopathology. Male Wister rats (n=30) were fed an AIN-93G diet containing 20% fat in the form of fish oil, shortening, or soybean oil for 4 weeks. Total cholesterol (TC), triacylglyceride (TG), and C-reactive protein levels were significantly (P<0.001) lower in the fish oil than in soybean oil and shortening groups. HDL-cholesterol concentrations were significantly different (P<0.001) between groups. In addition, LDL-cholesterol levels were significantly (P<0.001) lower in the fish oil and shortening groups than in the soybean oil group. Insulin and glucose concentrations did not differ among groups. Effect of dietary fat on tissue fatty acid composition significantly differed in abdominal fat and brain compared with RBC, heart, kidney and liver. The aortic wall was significantly (P=0.02) thinner in the fish oil group than in the soybean oil and shortening groups. The aortic wall thickness was positively correlated with TG and TC, but negatively with EPA + DHA levels of all tissues. These results suggested that fish oil had protective effects on aorta histopathology by hypolipidemic action in this rat model.

Intravascular ultrasound allows a hyperplasia diagnosis in vivo in rat as accurate as histomorphometry

OBJECTIVE AND MOTIVATION

Intravascular ultrasound (IVUS) allows in vivo invasive intra-luminal real-time examination of the arterial wall structure. In this study, we aimed to validate for the first time the in vivo IVUS performing as a diagnostic tool by comparison to the well-established histomorphometry approach, in the largely used rat model of carotid angioplasty model that mimics the angioplasty procedure in humans.

METHODS

Atherosclerotic lesions were allowed to develop during four weeks after balloon catheter inflation of the left carotid artery, whereas the intact right carotid artery was used as control. Four weeks after injury, a Boston Scientific 40MHz device to perform IVUS exams in vivo on both carotid arteries. Then, both carotid arteries were examined in vitro by histomorphometry and correlation between IVUS and histomorphometric parameters (plaque plus media cross-sectional areas [CSA] and eccentricity index) were researched.

RESULTS

After ANOVA analysis, comparative statistical analysis showed significant correlations between IVUS and histomorphometry when examining the intact right carotid artery (r=0.662 with p<0.003 for plaque plus media CSA; r=0.774 with p<0.002 for eccentricity index), but also when exploring the injured left carotid artery (r=0.805 with p<0.0001 for plaque plus media CSA; r=0.775 with p<0.002 for eccentricity index).

CONCLUSIONS AND OUTCOME

We report here for the first time the ability of IVUS to study therapeutic vascular effects in vivo in alive rats. This result is of major importance since it will allow this device to be used for restenosis drug testing in rat model of carotid angioplasty.

Aortic stiffness and pulse pressure amplification in Wistar-Kyoto and spontaneously hypertensive rats

In humans, increased body weight and arterial stiffness are significantly associated, independently of blood pressure (BP) level. The finding was never investigated in rodents devoid of metabolic disorders as spontaneously hypertensive rats (SHR). Using simultaneous catheterization of proximal and distal aorta, we measured body weight, intra-arterial BP, heart rate and their variability (spectral analysis), aortic pulse wave velocity (PWV), and systolic and pulse pressure (PP) amplifications in unrestrained conscious Wistar-Kyoto (WKY) rats and SHR between 6 and 24 wk of age. Aortic proximal systolic and diastolic pressure, PP, and mean BP were significantly higher in SHR than in WKY rats and increased significantly with age (with the exception of PP). PP amplification increased with age but did not differ between strains. PWV was significantly associated with heart rate variability. PWV was significantly higher (via two-way variance analysis) in SHR than in WKY rats (strain effect) and increased markedly with age in both strains (age effect). Adjustment of PWV to mean BP attenuated markedly both the age and the strain effects. After adjustment for body weight, either alone or associated with mean BP, the age effect was not more significant, but the strain effect was markedly enhanced. In conscious unanesthetized SHR and WKY rats, aortic stiffness is consistently associated with body weight independent of age and mean BP. An intervention study should consider in the objectives systolic BP and PP amplifications measured in conscious animals, central control of body weight, and autonomic nervous system.

Increased intracavernosal pressure response in hypertensive rats after chronic hemin treatment

INTRODUCTION

Erectile dysfunction (ED) is increased in prevalence in patients with arterial hypertension. Whether upregulation of heme oxygenase (HO) expression could improve penile erection has been unknown.

AIMS

To correlate altered expression profiles of HO-1 and soluble guanylyl cyclase (sGC) in penile tissues with low intracavernosal pressure (ICP) in adult spontaneously hypertensive rats (SHR); and to investigate therapeutic effect of hemin-induced upregulation of HO-1 in penile tissues on ED developed in adult SHR.

METHODS AND MAIN OUTCOME MEASURES

Intracavernosal pressure changes after electrical stimulation were monitored in adult SHR and age-matched normotensive Sprague-Dawley (SD) rats after chronic administration of either hemin or hydralazine. Expression levels of HO-1, HO-2, sGC, and phosphodiesterase type 5 (PDE5) were examined with Western blot.

RESULTS

Frequency-dependent ICP changes were reduced in adult SHR. Three weeks after hemin treatment, high blood pressure of SHR was normalized and ICP responses to electrical stimulations in SHR were significantly increased to the level of normotensive rats. Hydralazine-treated SHR had normalized blood pressure but unaltered low ICP response. Expression of HO-1 and sGC was upregulated and that of PDE5 downregulated in hemin-treated, but not hydralazine-treated, SHR.

CONCLUSIONS

Decreased erectile responses in adult SHR can be improved through chronic hemin treatment. Prolonged upregulation of HO-1 and sGC as well as lowered expression of PDE5 may at least partially explain the effect of hemin treatment on ICP. Upregulation of HO-1 may represent a novel therapeutic approach to treat ED.

Respective contribution of age, mean arterial pressure, and body weight on central arterial distensibility in SHR

In spontaneously hypertensive rats (SHR), carotid and aortic distensibilities measured at operational blood pressure (BP) are reduced. Increased body weight and mean arterial pressure (MAP) are both known to reduce distensibility independently. However, whether, after adjustment to body weight and mean BP, distensibility remains reduced in SHR has never been investigated. Carotid and abdominal aorta distensibilities were measured under anesthesia in SHR at 5, 12, 52, and 78 wk of age, and measurements were compared with age-matched normotensive Wistar rats. Each age group was composed of 9 or 10 animals. We determined distensibility using echo-tracking techniques of high resolution. Compared with Wistar rats, carotid and aortic distensibilities measured at operational MAP are reduced in SHR. This reduction is accentuated with age, particularly for the carotid artery. After adjustment to body weight and MAP, carotid and aortic distensibilities become identical in Wistar and SHR (or even slightly increased in SHR) but continue to be reduced with age, mainly for the carotid artery. In conclusion, in SHR, age and high BP do not have a parallel and similar influence on the reduction of arterial distensibility. Aging constantly reduces arterial distensibility, whereas MAP levels contribute to maintenance of arterial function.

Effect of pressure overload and its recovery on the rat carotid artery: change of vascular reactivity and remodeling process

Compared to chronic hypertension, little is known about the pathophysiology of acute hypertension and its recovery. To characterize this, we investigated the functional and structural properties of the common carotid arteries (CCA) from 35 rats. We established a unilateral and reversible carotid arterial hypertension model using the partial transverse aortic constriction (TAC) technique. By TAC, the right CCAs were made to endure a pressure-overload environment, while the left CCAs remained under normotension. The TACs were removed 2 weeks later, which unloaded the hypertensive effects. We compared the contractile, histological, and molecular responses of the CCA before TAC, during TAC (the hypertension period), and after removal of TAC (the recovery period). Vessel contractility was nearly abolished during 2 weeks of TAC. The recovery process from hypertension showed an initial hypercontractile period within a week. The relaxation response due to acetylcholine, as measured during the recovery period, showed a longer time course than the contractility for recovering its magnitude. During the hypertension period, the media thickness increased and this persisted throughout the recovery period. Apoptosis of the endothelial layer was significantly increased during the hypertension period and this disappeared 2 weeks after recovery. Expression of endothelial NO synthase was not detectable at the end of the hypertension period, but this gradually returned to the basal level after 2 weeks of recovery. Although increased contractility is usually expected in chronic hypertensive vessels, an abrupt pressure overload decreases contractility and the endothelium-dependent relaxation. It also increases endothelial apoptosis and the media thickness. These findings have clinical relevance, and they could be applied to human acute and severe hypertension and its recovery.

Antihypertensive Potential and Mechanism of Action of Astaxanthin: III. Antioxidant and Histopathological Effects in Spontaneously Hypertensive Rats

We investigated the effects of a dietary astaxanthin (ASX-O) on oxidative parameters in spontaneously hypertensive rats (SHR), by determination of the level of nitric oxide (NO) end products nitrite/nitrate (NO2-/NO3-) and lipid peroxidation in ASX-O-treated SHR. Oral administration of the ASX-O significantly reduced the plasma level of NO2-/NO3- compared to the control vehicle (p<0.05). The lipid peroxidation level, however, was reduced in both ASX-O- and olive oil-treated groups. We also analyzed the post-treatment effects of ASX-O on the vascular tissues by examining the changes in the aorta and coronary arteries and arterioles. The dietary ASX-O showed significant reduction in the elastin bands in the rat aorta (p<0.05). It also significantly decreased the [wall : lumen] aerial ratio of the coronary arteries. These results suggest that ASX-O can modulate the oxidative condition and may improve vascular elastin and arterial wall thickness in hypertension.

L-carnitine and propionyl-L-carnitine improve endothelial dysfunction in spontaneously hypertensive rats: Different participation of NO and COX-products

L-carnitine and propionyl-L-carnitine are supplements to therapy in cardiovascular pathologies. Their effect on endothelial dysfunction in hypertension was studied after treatment with either 200 mg/kg of L-carnitine or propionyl-L-carnitine during 8 weeks of spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto rats (WKY). Endothelial function was assessed in aortic rings by carbachol-induced relaxation (CCh 10(-8) to 10(-4) M) and factors involved were characterized in the presence of the inhibitors: L-NAME, indomethacin, the TXA2/PGH2 Tp receptor antagonist ICI-192,605 and the thromboxane synthetase inhibitor-Tp receptor antagonist, Ro-68,070. The effect on phenylephrine-induced contractions was also observed. To identify the nature of vasoactive COX-derived products, enzyme-immunoassay of incubation media was assessed. Involvement of reactive oxygen species was evaluated by incubating with superoxide dismutase and catalase. Nitric oxide production was evaluated by serum concentration of NO2+NO3.Treatment with both compounds improved endothelial function of rings from SHR without blood pressure change. Propionyl-L-carnitine increased NO participation in WKY and SHR. L-carnitine reduced endothelium-dependent responses to CCh in WKY due to an increase of TXA2 production. In both SHR and WKY, L-carnitine enhanced concentration of PGI2 and increased participation of NO. Results in the presence of SOD plus catalase show that it might be related to antioxidant properties of L-carnitine and propionyl-L-carnitine. Comparison between the effect of both compounds shows that both may reduce reactive oxygen species and increase NO participation in endothelium-dependent relaxations in SHR. However, only L-carnitine was able to increase the release of the vasodilator PGI2 and even enhanced TXA2 production in normotensive rats.

Systolic hypertension in the elderly: arterial wall mechanical properties and the renin-angiotensin-aldosterone system

BACKGROUND

Systolic hypertension in the elderly involves an increase of arterial stiffness and early wave reflections, both of them causing a predominant or selective increase of systolic blood pressure. The mechanisms for such alterations remain largely unknown.

DESCRIPTION AND RESULTS

The development of systolic hypertension includes constantly an age-related increase of sodium sensitivity and of endothelial dysfunction, both responsible for phenotypic changes of aortic smooth muscle cells with collagen accumulation and increased stiffness. In the presence of a high sodium diet and under the influence of angiotensin II and aldosterone, a higher number of attachments between vascular smooth muscle cells and collagen fibers develop, causing a supplementary increase in stiffness independent of the mean blood pressure together with the occurrence of early wave reflections. Gene polymorphisms related to the renin-angiotensin system may participate in this evolution.

CONCLUSION

This process contributes to accelerating the increase in pulse pressure and arterial stiffness with age, and therefore to the development of cardiovascular risk.