Treatment with valsartan stimulates endothelial progenitor cells and renal label-retaining cells in hypertensive rats. J Hypertens. 2011;29:91-101. [PMID: 20935578 DOI: 10.1097/hjh.0b013e32834000e2]

Gut-Microbiota Dysbiosis in Stroke-Prone Spontaneously Hypertensive Rats with Diet-Induced Steatohepatitis

Metabolic-dysfunction-associated fatty-liver disease (MAFLD) is the principal worldwide cause of liver disease. Individuals with nonalcoholic steatohepatitis (NASH) have a higher prevalence of small-intestinal bacterial overgrowth (SIBO). We examined gut-microbiota isolated from 12-week-old stroke-prone spontaneously hypertensive-5 rats (SHRSP5) fed on a normal diet (ND) or a high-fat- and high-cholesterol-containing diet (HFCD) and clarified the differences between their gut-microbiota. We observed that the Firmicute/Bacteroidetes (F/B) ratio in both the small intestines and the feces of the SHRSP5 rats fed HFCD increased compared to that of the SHRSP5 rats fed ND. Notably, the quantities of the 16S rRNA genes in small intestines of the SHRSP5 rats fed HFCD were significantly lower than those of the SHRSP5 rats fed ND. As in SIBO syndrome, the SHRSP5 rats fed HFCD presented with diarrhea and body-weight loss with abnormal types of bacteria in the small intestine, although the number of bacteria in the small intestine did not increase. The microbiota of the feces in the SHRSP5 rats fed HFCD was different from those in the SHRP5 rats fed ND. In conclusion, there is an association between MAFLD and gut-microbiota alteration. Gut-microbiota alteration may be a therapeutic target for MAFLD.

Preserved endothelial progenitor cell angiogenic activity in African American essential hypertensive patients

Background

African American (AA) subjects with essential hypertension (EH) have greater inflammation and cardiovascular complications than Caucasian EH. An impaired endogenous cellular repair system may exacerbate vascular injury in hypertension, yet whether these differ between AA EH and Caucasian EH remains unknown. Vascular repair by circulating endothelial progenitor cells (EPCs) is controlled by regulators of EPC mobilization, homing, adhesion and new vessel formation, but can be hindered by various cytokines. We hypothesized that EPC levels and function would be impaired in AA EH compared with Caucasian EH, in association with increased levels of inflammatory mediators and EPC regulators.

Methods

CD34+/KDR+ EPCs were isolated from inferior vena cava and renal vein blood samples of AA EH and Caucasian EH patients (n = 18 each) and from peripheral veins of 17 healthy volunteers (HVs) and enumerated using fluorescence-activated cell sorting. Angiogenic function of late-outgrowth endothelial cells expanded from these samples for 3 weeks was tested in vitro. Levels of inflammatory mediators, angiogenic factors and EPC regulators were measured by Luminex.

Results

EPC levels were decreased in both AA and Caucasian EH compared with HVs, whereas their late-outgrowth endothelial cell angiogenic function was comparable. Levels of several inflammatory mediators were elevated in AA EH compared with Caucasian EH and HVs. Contrarily, vascular endothelial growth factor and its receptor-2 were lower. EPC levels inversely correlated with blood pressure in all hypertensive patients and estimated glomerular filtration rate with inflammatory mediators only in AA EH.

Conclusions

Despite lower EPC numbers, decreased vascular endothelial growth factor signaling and inflammation, EPC function is preserved in AA EH compared with Caucasian EH and HVs, suggesting compensatory mechanisms for vascular repair.

Association of mRNA expression of iron metabolism-associated genes and progression of non-alcoholic steatohepatitis in rats

Background

Excess iron is associated with non-alcoholic steatohepatitis (NASH).

Results

mRNA expression of duodenal cytochrome b, divalent metal transporter 1, ferroportin 1, hepcidin, hephaestin and transferrin receptor 1 in liver were higher in high fat, high cholesterol-containing diet (HFCD) group than in normal diet (ND) group. mRNA levels of divalent metal transporter 1 and transferrin receptor 1, which stimulate iron absorption and excretion, were enhanced in small intestine. Epithelial mucosa of small intestine in HFCD group was characterized by plasma cell and eosinophil infiltration and increased vacuoles. Iron absorption was enhanced in this NASH model in the context of chronic inflammation of small intestinal epithelial cells, consequences of intestinal epithelial cell impairment caused by HFCD. Iron is transported to hepatocytes via portal blood, and abnormalities in iron absorption and excretion occur in small intestine from changes in iron transporter expression, which also occurs in NASH liver. Knockdown of hepcidin antimicrobial peptide led to enhanced heavy chain of ferritin expression in human hepatocytes, indicating association between hepcidin production and iron storage in hepatocytes.

Conclusions

Iron-related transporters in liver and lower/upper portions of small intestine play critical roles in NASH development.

Methods

Expression of iron metabolism-related genes in liver and small intestine was analyzed in stroke-prone spontaneously hypertensive rats (SHR-SP), which develop NASH. Five-week-old SHR-SP fed ND or HFCD were examined. mRNA and protein levels of iron metabolism-related genes in liver and small intestine from 12- and 19-week-old rats were evaluated by real-time RT-PCR and immunohistochemistry or Western blot.

Intrauterine growth restriction-induced deleterious adaptations in endothelial progenitor cells: possible mechanism to impair endothelial function

Intrauterine growth restriction (IUGR) can induce deleterious changes in the modulatory ability of the vascular endothelium, contributing to an increased risk of developing cardiovascular diseases in the long term. However, the mechanisms involved are not fully understood. Emerging evidence has suggested the potential role of endothelial progenitor cells (EPCs) in vascular health and repair. Therefore, we aimed to evaluate the effects of IUGR on vascular reactivity and EPCs derived from the peripheral blood (PB) and bone marrow (BM) in vitro. Pregnant Wistar rats were fed an ad libitum diet (control group) or 50% of the ad libitum diet (restricted group) throughout gestation. We determined vascular reactivity, nitric oxide (NO) concentration, and endothelial nitric oxide synthase (eNOS) protein expression by evaluating the thoracic aorta of adult male offspring from both groups (aged: 19-20 weeks). Moreover, the amount, functional capacity, and senescence of EPCs were assessed in vitro. Our results indicated that IUGR reduced vasodilation via acetylcholine in aorta rings, decreased NO levels, and increased eNOS phosphorylation at Thr495. The amount of EPCs was similar between both groups; however, IUGR decreased the functional capacity of EPCs from the PB and BM. Furthermore, the senescence process was accelerated in BM-derived EPCs from IUGR rats. In summary, our findings demonstrated the deleterious changes in EPCs from IUGR rats, such as reduced EPC function and accelerated senescence in vitro. These findings may contribute towards elucidating the possible mechanisms involved in endothelial dysfunction induced by fetal programming.

Progenitor Cells for Arterial Repair: Incremental Advancements towards Therapeutic Reality

Coronary revascularization remains the standard treatment for obstructive coronary artery disease and can be accomplished by either percutaneous coronary intervention (PCI) or coronary artery bypass graft surgery. Considerable advances have rendered PCI the most common form of revascularization and improved clinical outcomes. However, numerous challenges to modern PCI remain, namely, in-stent restenosis and stent thrombosis, underscoring the importance of understanding the vessel wall response to injury to identify targets for intervention. Among recent promising discoveries, endothelial progenitor cells (EPCs) have garnered considerable interest given an increasing appreciation of their role in vascular homeostasis and their ability to promote vascular repair after stent placement. Circulating EPC numbers have been inversely correlated with cardiovascular risk, while administration of EPCs in humans has demonstrated improved clinical outcomes. Despite these encouraging results, however, advancing EPCs as a therapeutic modality has been hampered by a fundamental roadblock: what constitutes an EPC? We review current definitions and sources of EPCs as well as the proposed mechanisms of EPC-mediated vascular repair. Additionally, we discuss the current state of EPCs as therapeutic agents, focusing on endogenous augmentation and transplantation.

Angiotensin II type 1 receptor antagonists in animal models of vascular, cardiac, metabolic and renal disease

We have reviewed the effects of angiotensin II type 1 receptor antagonists (ARBs) in various animal models of hypertension, atherosclerosis, cardiac function, hypertrophy and fibrosis, glucose and lipid metabolism, and renal function and morphology. Those of azilsartan and telmisartan have been included comprehensively whereas those of other ARBs have been included systematically but without intention of completeness. ARBs as a class lower blood pressure in established hypertension and prevent hypertension development in all applicable animal models except those with a markedly suppressed renin-angiotensin system; blood pressure lowering even persists for a considerable time after discontinuation of treatment. This translates into a reduced mortality, particularly in models exhibiting marked hypertension. The retrieved data on vascular, cardiac and renal function and morphology as well as on glucose and lipid metabolism are discussed to address three main questions: 1. Can ARB effects on blood vessels, heart, kidney and metabolic function be explained by blood pressure lowering alone or are they additionally directly related to blockade of the renin-angiotensin system? 2. Are they shared by other inhibitors of the renin-angiotensin system, e.g. angiotensin converting enzyme inhibitors? 3. Are some effects specific for one or more compounds within the ARB class? Taken together these data profile ARBs as a drug class with unique properties that have beneficial effects far beyond those on blood pressure reduction and, in some cases distinct from those of angiotensin converting enzyme inhibitors. The clinical relevance of angiotensin receptor-independent effects of some ARBs remains to be determined.

Distinct populations of label-retaining cells in the adult kidney are defined temporally and exhibit divergent regional distributions

DNA label-retention, or retention of a thymidine analog, is a characteristic of slow cycling cells and has been used to identify stem cells in several organ systems. Recent findings have demonstrated inconsistent localization of label-retaining cells (LRCs) in the kidney. Differences in the dose and timing of administration of deoxyuridine, the length of the chase period, and the species of animal used have made understanding the distinctions between these findings difficult. In the present studies, we utilized a dual loading scheme in the same animal to demonstrate that the cells labeled at different ages identified independent populations of LRC that distributed globally in an anti-parallel manner in the kidney. Loading with a DNA label in neonates identified LRC more often in the papilla, while administering the DNA label in adult mice identified LRC prominently in the cortex and the outer medulla. Furthermore, the tissue compartment distribution (epithelial-endothelial-interstitial) as well as the specific distribution within the nephron epithelia differed for these populations. These findings highlighted the complexity of the dynamics of cell proliferation in the kidney throughout the postnatal and adult period and call attention to the confusion associated with the term "label-retaining cells" for different timings of the loading and chase periods. This study indicated that the results of previous studies should be viewed as nonoverlapping and that further studies are needed to ascertain the role of each of these populations in the steady-state maintenance and injury recovery of the kidney.

Endothelial progenitor cells in cardiovascular diseases

Endothelial dysfunction has been associated with the development of atherosclerosis and cardiovascular diseases. Adult endothelial progenitor cells (EPCs) are derived from hematopoietic stem cells and are capable of forming new blood vessels through a process of vasculogenesis. There are studies which report correlations between circulating EPCs and cardiovascular risk factors. There are also studies on how pharmacotherapies may influence levels of circulating EPCs. In this review, we discuss the potential role of endothelial progenitor cells as both diagnostic and prognostic biomarkers. In addition, we look at the interaction between cardiovascular pharmacotherapies and endothelial progenitor cells. We also discuss how EPCs can be used directly and indirectly as a therapeutic agent. Finally, we evaluate the challenges facing EPC research and how these may be overcome.

Effects of an angiotensin II receptor blocker on the impaired function of endothelial progenitor cells in patients with essential hypertension

BACKGROUND

Endothelial progenitor cells (EPCs) induce neovascularization and repair vascular damage. We have demonstrated that EPC function is impaired in hypertensive rats with increases in oxidative stress and that angiotensin II receptor blockers improved the impaired function of EPCs. In this study, we investigated basal EPC functions in normotensive control subjects and patients with essential hypertension and the effect of losartan on EPC function in hypertensive patients.

METHODS

Eighteen normotensive control subjects and 36 patients with essential hypertension who were undergoing treatment participated in the study. Hypertensive patients were randomly selected to receive 50mg of losartan or 4 mg of trichlormethiazide daily for 4 weeks. Peripheral blood mononuclear cells were isolated and cultured to assay EPC colony formation. Blood pressure, biological examination, and oxidative stress were evaluated in all subjects.

RESULTS

The number of EPC colonies was significantly lower in patients with essential hypertension than in normotensive control subjects. EPC colony number was significantly and inversely correlated with systolic and diastolic blood pressure in all subjects. EPC colony number was significantly increased by treatment with losartan in patients with essential hypertension but not affected by treatment with trichlormethiazide.

CONCLUSIONS

EPC function was inversely correlated with blood pressure and was impaired in essential hypertension. Losartan significantly improved the impaired EPC function in hypertensive patients. Impaired EPC function may determine the cardiovascular complications in essential hypertension. The improvement of EPC function with the administration of angiotensin II receptor blockers is considered to be one of the cardiovascular protective effects.

The renin–angiotensin system, bone marrow and progenitor cells

Modulation of the RAS (renin–angiotensin system), in particular of the function of the hormones AngII (angiotensin II) and Ang-(1–7) [angiotensin-(1–7)], is an important target for pharmacotherapy in the cardiovascular system. In the classical view, such modulation affects cardiovascular cells to decrease hypertrophy, fibrosis and endothelial dysfunction, and improves diuresis. In this view, excessive stimulation of AT1 receptors (AngII type 1 receptors) fulfils a detrimental role, as it promotes cardiovascular pathogenesis, and this is opposed by stimulation of the AT2 receptor (angiotensin II type 2 receptor) and the Ang-(1–7) receptor encoded by the Mas proto-oncogene. In recent years, this view has been broadened with the observation that the RAS regulates bone marrow stromal cells and stem cells, thus involving haematopoiesis and tissue regeneration by progenitor cells. This change of paradigm has enlarged the field of perspectives for therapeutic application of existing as well as newly developed medicines that alter angiotensin signalling, which now stretches beyond cardiovascular therapy. In the present article, we review the role of AngII and Ang-(1–7) and their respective receptors in haematopoietic and mesenchymal stem cells, and discuss possible pharmacotherapeutical implications.

Reduction of age-associated arterial wall changes by low-dose valsartan

BACKGROUND

Functional and morphological arterial wall impairment progresses with ageing. Angiotensin II in the arterial wall is involved in this process. Appropriate early intervention might theoretically slow the progress of age-related changes. Herein, we investigated a new approach to this issue: whether arterial wall changes present in middle-aged males could be reduced by low-dose valsartan intervention.

METHODS

Forty apparently healthy, middle-aged males (42.9 ± 0.9 years) were recruited for a double-blind randomized study and received either placebo or valsartan (20 mg daily) for 30 days. Brachial artery flow-mediated dilation (FMD), pulse wave velocity (PWV), and β-stiffness of the common carotid artery were measured using an Aloka alfa-10 Prosound with an integrated eTracking system at inclusion, after 30 days, and after 3 and 8 months.

RESULTS

Intervention resulted in FMD increase (154.2 ± 20.1 %; p < 0.001) and PWV and β-stiffness decrease compared to initial values (-6.9 ± 1.0 % and -13.2 ± 1.4 %; both p < 0.01) whereas values in the untreated group (p < 0.001 for all parameters) remained unchanged throughout the study. The advantageous effects decreased over the months following valsartan discontinuation, but were still significant after 3 months (largely in FMD and less in PWV and β-stiffness), and negligible after 8 months. The beneficial effects were ascribed to valsartan's pleiotropic effects, as no blood pressure changes were recorded.

CONCLUSIONS

We showed that age-related arterial wall changes in middle-aged males are reversible and could be reduced by a low-dose, short-term valsartan intervention. The new approach merits detailed investigation in future studies.

Angiotensin II and the vascular phenotype in hypertension

Hypertension is associated with vascular changes characterised by remodelling, endothelial dysfunction and hyperreactivity. Cellular processes underlying these perturbations include altered vascular smooth muscle cell growth and apoptosis, fibrosis, hypercontractility and calcification. Inflammation, associated with macrophage infiltration and increased expression of redox-sensitive pro-inflammatory genes, also contributes to vascular remodelling. Many of these features occur with ageing, and the vascular phenotype in hypertension is considered a phenomenon of ‘premature vascular ageing’. Among the many factors involved in the hypertensive vascular phenotype, angiotensin II (Ang II) is especially important. Ang II, previously thought to be the sole effector of the renin–angiotensin system (RAS), is converted to smaller peptides [Ang III, Ang IV, Ang-(1-7)] that are biologically active in the vascular system. Another new component of the RAS is the (pro)renin receptor, which signals through Ang-II-independent mechanisms and might influence vascular function. Ang II mediates effects through complex signalling pathways on binding to its G-protein-coupled receptors (GPCRs) AT1R and AT2R. These receptors are regulated by the GPCR-interacting proteins ATRAP, ARAP1 and ATIP. AT1R activation induces effects through the phospholipase C pathway, mitogen-activated protein kinases, tyrosine kinases/phosphatases, RhoA/Rhokinase and NAD(P)H-oxidase-derived reactive oxygen species. Here we focus on recent developments and new research trends related to Ang II and the RAS and involvement in the hypertensive vascular phenotype.

Effects of the renin angiotensin system on vasculogenesis-related progenitor cells

The current concept is that there are both cells that integrate into the vasculature, true endothelial progenitor cells (EPC), and cells with hematopoietic markers that support neovascularisation. As identification of the EPC is controversial and studies refer cells that might fall into either pools, we will use the term, vasculogenesis-related progenitor cells (VRPC), for this review. VRPC are considered to be an important target for the treatment of cardiovascular diseases (CVD). Angiotensin II is known to be an important player in neovascularisation and the modulation of renin angiotensin system (RAS) is one of the major pharmacotherapeutic strategies for the treatment of CVD. We will review the effects of different components of the RAS on such VRPC under physiological conditions and in CVD. The reviewed research strongly supports a critical role of the RAS in vasculogenesis and vascular regeneration. Therefore, pharmacological intervention on the components of the RAS does not only target directly end-organ remodelling and blood pressure but also influence tissue healing and/or regeneration by influencing specific progenitor cells. Thus, the interrogation of RAS effects on VRPC will be important in the optimisation of RAS intervention or regenerative therapy.