Structure and mechanical properties of resistance arteries in hypertension: role of adhesion molecules and extracellular matrix determinants

Calycosin and Formononetin Induce Endothelium-Dependent Vasodilation by the Activation of Large-Conductance Ca2+-Activated K+ Channels (BKCa)

Calycosin and formononetin are two structurally similar isoflavonoids that have been shown to induce vasodilation in aorta and conduit arteries, but study of their actions on endothelial functions is lacking. Here, we demonstrated that both isoflavonoids relaxed rat mesenteric resistance arteries in a concentration-dependent manner, which was reduced by endothelial disruption and nitric oxide synthase (NOS) inhibition, indicating the involvement of both endothelium and vascular smooth muscle. In addition, the endothelium-dependent vasodilation, but not the endothelium-independent vasodilation, was blocked by BK_Ca inhibitor iberiotoxin (IbTX). Using human umbilical vein endothelial cells (HUVECs) as a model, we showed calycosin and formononetin induced dose-dependent outwardly rectifying K⁺ currents using whole cell patch clamp. These currents were blocked by tetraethylammonium chloride (TEACl), charybdotoxin (ChTX), or IbTX, but not apamin. We further demonstrated that both isoflavonoids significantly increased nitric oxide (NO) production and upregulated the activities and expressions of endothelial NOS (eNOS) and neuronal NOS (nNOS). These results suggested that calycosin and formononetin act as endothelial BK_Ca activators for mediating endothelium-dependent vasodilation through enhancing endothelium hyperpolarization and NO production. Since activation of BK_Ca plays a role in improving behavioral and cognitive disorders, we suggested that these two isoflavonoids could provide beneficial effects to cognitive disorders through vascular regulation.

Galectin-3 contributes to vascular fibrosis in monocrotaline-induced pulmonary arterial hypertension rat model

Galectin-3 (Gal-3) plays a critical role in vascular inflammation and fibrosis. The role of TGF-β1 in mediating pulmonary vascular fibrosis is well documented; thus, we suspected that Gal-3 could be an important factor in TGF-β1-induced fibrosis in pulmonary adventitial fibroblasts (PAFs). We treated rats with monocrotaline (MCT) and cultured PAFs with TGF-β1 to stimulate fibrosis. We found that MCT injection induced vessel thickening and extracellular matrix deposition in vivo. TGF-β1 stimulated the production of collagen and fibronectin (Fn) protein in vitro. TGF-β1 promoted the expression of Gal-3 and its translocation, while silencing Gal-3 reduced Col-1a deposition. Blockage of STAT3 decreased the expression of Gal-3 induced by TGF-β1. Gal-3 increased Col-1a accumulation and downregulated matrix metallopeptidase 9 (MMP-9) expression in PAFs, but it did not affect Fn expression. These findings demonstrate that Gal-3 is required for TGF-β1-stimulated vascular fibrosis via a STAT3 signaling cascade and that MMP-9 is also involved in TGF-β1/Gal-3-induced vascular fibrosis.

Vascular structural and functional changes: their association with causality in hypertension: models, remodeling and relevance

Essential hypertension is a complex multifactorial disease process that involves the interaction of multiple genes at various loci throughout the genome, and the influence of environmental factors such as diet and lifestyle, to ultimately determine long-term arterial pressure. These factors converge with physiological signaling pathways to regulate the set-point of long-term blood pressure. In hypertension, structural changes in arteries occur and show differences within and between vascular beds, between species, models and sexes. Such changes can also reflect the development of hypertension, and the levels of circulating humoral and vasoactive compounds. The role of perivascular adipose tissue in the modulation of vascular structure under various disease states such as hypertension, obesity and metabolic syndrome is an emerging area of research, and is likely to contribute to the heterogeneity described in this review. Diversity in structure and related function is the norm, with morphological changes being causative in some beds and states, and in others, a consequence of hypertension. Specific animal models of hypertension have advantages and limitations, each with factors influencing the relevance of the model to the human hypertensive state/s. However, understanding the fundamental properties of artery function and how these relate to signalling mechanisms in real (intact) tissues is key for translating isolated cell and model data to have an impact and relevance in human disease etiology. Indeed, the ultimate aim of developing new treatments to correct vascular dysfunction requires understanding and recognition of the limitations of the methodologies used.

Impact of apocynin on vascular disease in hypertension

Reactive oxygen species (ROS) are generated by cell metabolism of oxygen and represent signaling molecules playing an active role in vascular biology. In pathological conditions, including hypertension, a ROS excess, together with reduced endogenous antioxidant defenses, occurs, determining a state of oxidative stress. NAD(P)H oxidase (Nox) is a major ROS source within the vasculature. A large body of literature has demonstrated that hypertension-associated vascular functional and structural changes are attributable to Nox-driven intravascular ROS generation. Apocynin is a methoxy-catechol discovered as an inhibitor of superoxide. It has been utilized in several laboratories and in different models of hypertension as an inhibitor of Nox. Recent evidence proposes that apocynin predominantly acts as an antioxidant. The present review will discuss the role of ROS in vascular disease in hypertension and the impact of apocynin on these vascular changes.

Experimental reduction of miR-92a mimics arterial aging

MicroRNAs (miRs) are small non-coding RNAs that are important regulators of aging and cardiovascular diseases. MiR-92a is important in developmental vascular growth and tumorigenesis and two of its putative targets, tumor necrosis factor alpha receptor 1 (TNFR1) and collagen type 1, play a role in age-related arterial dysfunction. We hypothesized that reduced miR-92a expression contributes to age-related arterial dysfunction characterized by endothelial dysfunction and increased large artery stiffness. MiR-92a is reduced 39% (RT-PCR, p<0.05) in arteries of older adults compared to young adults. Similarly, there was a 40% reduction in miR-92a in aortas of old (29months, n=13) compared to young (6months, n=11) B6D2F1 mice, an established model of vascular aging. To determine if reduced miR-92a contributes to arterial dysfunction; miR-92a was inhibited in vivo in young mice using antagomirs (I.P., 4wks). Antagomir treatment was associated with a concomitant 48% increase in TNFR1 (Western blot, p<0.05), 19% increase in type 1 collagen (immunohistochemistry, p<0.01), and a reduction in endothelial dependent dilation (max dilation: 93±1 vs. 73±5%, p<0.01) in response to acetylcholine (ACh, 10(-9) to 10(-4)M). Treatment with the nitric oxide (NO) synthase inhibitor, L-NAME (10(-4)M), revealed that impaired ACh dilation after antagomir treatment resulted from reduced NO bioavailability. Inhibition of miR-92a also increased arterial stiffness (pulse wave velocity, 309±13 vs. 484±52cm/s, p<0.05). Together, these results suggest that experimental reductions in arterial miR-92a partially mimic the arterial aging phenotype and we speculate that modulating miR-92a may provide a therapeutic strategy to improve age-related arterial dysfunction.

Correlation Between the Reduction in Lenticulostriate Arteries Caused by Hypertension and Changes in Brain Metabolism Detected With MRI

OBJECTIVE

Hypertension can alter the vascular structure, mechanics, and function of small arteries and arterioles. It remains unknown whether microvascular changes are associated with brain metabolism. The purpose of this study was to analyze the correlation between the reduction in small arteries and changes in brain metabolism in patients with hypertension.

SUBJECTS AND METHODS

The study population comprised 50 patients with hypertension and 50 volunteers without hypertension. The two groups underwent 3-T 3D time-of-flight MR angiography, and the numbers of lenticulostriate arteries (LSAs) were determined for both groups. Single-voxel proton MR spectroscopic data on the basal ganglia regions were also acquired. The ratios of N-acetylaspartate to creatine (NAA/Cr), myo-inositol to creatine (Mi/Cr), and choline to creatine (Cho/Cr) were measured. Statistical analysis was performed to evaluate the differences between the two groups with respect to metabolite ratios.

RESULTS

The average total number of LSA stems on both sides in patients with hypertension was 5.12 ± 0.98 compared with 6.10 ± 0.95 in volunteers without hypertension (p < 0.0001). The NAA/Cr ratio decreased according to a reduction in the number of LSAs in the hypertension group, which was significantly reduced when the number of LSAs was 3 or fewer.

CONCLUSION

Hypertension can lead to a statistically significant reduction in NAA/Cr ratio in the basal ganglia regions when the number of LSAs decreases to a certain extent. Reduced numbers of LSAs correlated with brain metabolism changes caused by hypertension, which can provide important insights for understanding the pathophysiologic mechanism of hypertension and may be valuable in evaluating this disease.

Maternal Hyperleptinemia Is Associated with Male Offspring's Altered Vascular Function and Structure in Mice

Children of mothers with gestational diabetes have greater risk of developing hypertension but little is known about the mechanisms by which this occurs. The objective of this study was to test the hypothesis that high maternal concentrations of leptin during pregnancy, which are present in mothers with gestational diabetes and/or obesity, alter blood pressure, vascular structure and vascular function in offspring. Wildtype (WT) offspring of hyperleptinemic, normoglycemic, Leprdb/+ dams were compared to genotype matched offspring of WT-control dams. Vascular function was assessed in male offspring at 6, and at 31 weeks of age after half the offspring had been fed a high fat, high sucrose diet (HFD) for 6 weeks. Blood pressure was increased by HFD but not affected by maternal hyperleptinemia. On a standard diet, offspring of hyperleptinemic dams had outwardly remodeled mesenteric arteries and an enhanced vasodilatory response to insulin. In offspring of WT but not Leprdb/+ dams, HFD induced vessel hypertrophy and enhanced vasodilatory responses to acetylcholine, while HFD reduced insulin responsiveness in offspring of hyperleptinemic dams. Offspring of hyperleptinemic dams had stiffer arteries regardless of diet. Therefore, while maternal hyperleptinemia was largely beneficial to offspring vascular health under a standard diet, it had detrimental effects in offspring fed HFD. These results suggest that circulating maternal leptin concentrations may interact with other factors in the pre- and post -natal environments to contribute to altered vascular function in offspring of diabetic pregnancies.

Matrix metalloproteinases are possible targets in monocrotaline-induced pulmonary hypertension: investigation of anti-remodeling effects of alagebrium and everolimus

Objective:

In our study, sildenafil alone and everolimus or alagebrium in combination with sildenafil were investigated in terms of their additional therapeutic and anti-remodeling activity in monocrotaline-induced pulmonary hypertension (PH) model in rats. In particular, the inter-relationships between PH and matrix metalloproteinases (MMPs) were investigated.

Methods:

The pulmonary artery responses of male Sprague Dawley rats were recorded using myography, and the quantities and activities of MMPs were analyzed in homogenates of the pulmonary arteries and lungs by enzyme-linked immunosorbent assays, activity assays, and gelatin zymography techniques.

Results:

Our results indicated that the therapeutic effects of sildenafil were accompanied by its suppressor effects on MMP activity. It was also shown that everolimus or alagebrium in combination with sildenafil showed additional regulatory effects on MMPs as well as functional responses on pulmonary artery pressure. Therefore, the enzymes in the MMP superfamily are likely to be target molecules for the treatment of PH.

Conclusion:

In conclusion, MMPs were involved in the pathogenesis of PH, and our results suggested that the addition of everolimus or alagebrium to sildenafil therapy may be beneficial in PH. Our results indicated that agents that limit pulmonary vascular hypertrophy and inflammation via their anti-remodeling effects significantly ameliorate mortality and morbidity in PH.

Mechanisms of Vascular Smooth Muscle Contraction and the Basis for Pharmacologic Treatment of Smooth Muscle Disorders

The smooth muscle cell directly drives the contraction of the vascular wall and hence regulates the size of the blood vessel lumen. We review here the current understanding of the molecular mechanisms by which agonists, therapeutics, and diseases regulate contractility of the vascular smooth muscle cell and we place this within the context of whole body function. We also discuss the implications for personalized medicine and highlight specific potential target molecules that may provide opportunities for the future development of new therapeutics to regulate vascular function.

Regression of cardiovascular remodeling in hypertension: Novel relevant mechanisms

Asymptomatic organ damage due to progressive kidney damage, cardiac hypertrophy and remodeling put hypertensive patients at high risk for developing heart and renal failure, myocardial infarction and stroke. Current antihypertensive treatment normalizes high blood pressure, partially reverses organ damage, and reduces the incidence of heart and renal failure. Activation of the renin-angiotensin system (RAS) is a primary mechanism of progressive organ damage and, specifically, a major cause of both renal and cardiovascular fibrosis. Currently, inhibition of the RAS system [mainly with angiotensin I converting enzyme inhibitors or angiotensin II (Ang II) receptor antagonists] is the most effective antihypertensive strategy for normalizing blood pressure and preventing target organ damage. However, residual organ damage and consequently high risk for cardiovascular events and renal failure still persist. Accordingly, in hypertension, it is relevant to develop new therapeutic perspectives, beyond reducing blood pressure to further prevent/reduce target organ damage by acting on pathways that trigger and maintain cardiovascular and renal remodeling. We review here relevant novel mechanisms of target organ damage in hypertension, their role and evidence in prevention/regression of cardiovascular remodeling and their possible clinical impact as well. Specifically, we focus on the signaling pathway RhoA/Rho kinase, on the impact of the vasodilatory peptides from the RAS and some insights on the role of estrogens and myocardial chymase in cardiovascular hypertensive remodeling.

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.

Intracerebral hemorrhage and deep microbleeds associated with cnm-positive Streptococcus mutans; a hospital cohort study

Oral infectious diseases are epidemiologically associated with stroke. We previously showed that oral Streptococcus mutans with the cnm gene encoding a collagen-binding Cnm protein induced intracerebral hemorrhage (ICH) experimentally and was also associated with cerebral microbleeds (CMBs) in our population-based cohort study. We therefore investigated the roles of cnm-positive Streptococcus mutans in this single hospital-based, observational study that enrolled 100 acute stroke subjects. The cnm gene in Streptococcus mutans isolated from saliva was screened using PCR techniques and its collagen-binding activities examined. CMBs were evaluated on T2* gradient-recalled echo MRI. One subject withdrew informed consent and 99 subjects (63 males) were analyzed, consisting of 67 subjects with ischemic stroke, 5 with transient ischemic attack, and 27 with ICH. Eleven cases showed Streptococcus mutans strains positive for cnm. The presence of cnm-positive Streptococcus mutans was significantly associated with ICH [OR vs. ischemic stroke, 4.5; 95% CI, 1.17–19.1] and increased number of deep CMBs [median (IQR), 3 (2–9) vs. 0 (0–1), p = 0.0002]. In subjects positive for Streptococcus mutans, collagen binding activity was positively correlated with the number of deep CMBs (R² = 0.405; p < 0.0001). These results provide further evidence for the key role of oral health in stroke.

Vascular reactivity of rabbit isolated renal and femoral resistance arteries in renal wrap hypertension

In rabbits with cellophane renal wrap hypertension, hindquarter and total vascular resistance changes to pressor and depressor agents are amplified compared to those of normotensive rabbits. The aim of the present study was to evaluate the in vitro pharmacodynamics of hypertensive and normotensive rabbit small artery segments isolated from the renal and hindquarter vascular beds. Using wire myography, the full range (Emax) and sensitivity (EC50) to a range of agonists of segments of renal interlobar (≈ 600 µm i.d.), renal arcuate (≈ 250 µm i.d.) and deep femoral branch (≈ 250 µm i.d.) arteries were assessed under normalised conditions of passive tension. Interlobar arteries from hypertensive rabbits were more sensitive (EC50) than those from normotensive rabbits to noradrenaline (6-fold), methoxamine (3-fold) and angiotensin II (3-fold). Arcuate artery reactivity was largely unaffected by hypertension. Deep femoral arteries from hypertensive rabbits had enhanced sensitivity only to noradrenaline (2-fold) and methoxamine (4-fold). Sensitivity to relaxation by acetylcholine was unaffected by hypertension in all arteries. Deep femoral arteries from hypertensive rabbits were more sensitive to sodium nitroprusside than normotensive counterparts. Adenosine caused little relaxation in renal arteries, but full relaxation in deep femoral arteries, unaltered by hypertension. This study found substantial heterogeneity in the pharmacodynamic profile of vessels isolated from different vascular beds and between arterial segments within the kidney. These profiles were differentially affected by hypertension suggesting that hypertension per se is not a resultant of general vascular dysfunction.

Progressive vascular remodelling, endothelial dysfunction and stiffness in mesenteric resistance arteries in a rodent model of chronic kidney disease

Chronic kidney disease (CKD) and hypertension are co-morbid conditions both associated with altered resistance artery structure, biomechanics and function. We examined these characteristics in mesenteric artery together with renal function and systolic blood pressure (SBP) changes in the Lewis polycystic kidney (LPK) rat model of CKD. Animals were studied at early (6-weeks), intermediate (12-weeks), and late (18-weeks) time-points (n=21), relative to age-matched Lewis controls (n=29). At 12 and 18-weeks, LPK arteries exhibited eutrophic and hypertrophic inward remodelling characterised by thickened medial smooth muscle, decreased lumen diameter, and unchanged or increased media cross-sectional area, respectively. At these later time points, endothelium-dependent vasorelaxation was also compromised, associated with impaired endothelium-dependent hyperpolarisation and reduced nitric oxide synthase activity. Stiffness, elastic-modulus/stress slopes and collagen/elastin ratios were increased in 6 and 18-week-old-LPK, in contrast to greater arterial compliance at 12weeks. Multiple linear regression analysis highlighted SBP as the main predictor of wall-lumen ratio (r=0.536, P<0.001 n=46 pairs). Concentration-response curves revealed increased sensitivity to phenylephrine but not potassium chloride in 18-week-LPK. Our results indicate that impairment in LPK resistance vasculature is evident at 6weeks, and worsens with hypertension and progression of renal disease.

Perturbations of the cerebrovascular matrisome: A convergent mechanism in small vessel disease of the brain?

The term matrisome refers to the ensemble of proteins constituting the extracellular matrix (ECM) (core matrisome) as well as the proteins associated with the ECM. Every organ has an ECM with a unique composition that not only provides the support and anchorage for cells, but also controls fundamental cellular processes as diverse as differentiation, survival, proliferation, and polarity. The current knowledge of the matrisome of small brain vessels is reviewed with a focus on the basement membrane (BM), a specialized form of ECM located at the interface between endothelial cells, contractile cells (smooth muscle cells and pericytes), and astrocyte endfeet—a very strategic location in the communication pathway between the cerebral microcirculation and astrocytes. We discuss some of the most recent genetic data and relevant findings from experimental models of nonamyloid cerebral small vessel disease (SVD). We propose the concept that perturbations of the cerebrovascular matrisome is a convergent pathologic pathway in monogenic forms of SVD, and is likely relevant to the sporadic disease.

Efficacy of flavonoids in the management of high blood pressure

Plant compounds such as flavonoids have been reported to exert beneficial effects in cardiovascular disease, including hypertension. Information on the effects of isolated individual flavonoids for management of high blood pressure, however, is more limited. This review is focused on the flavonoids, as isolated outside of the food matrix, from the 5 main subgroups consumed in the Western diet (flavones, flavonols, flavanones, flavan-3-ols, and anthocyanins), along with their effects on hypertension, including the potential mechanisms for regulating blood pressure. Flavonoids from all 5 subgroups have been shown to attenuate a rise in or to reduce blood pressure during several pathological conditions (hypertension, metabolic syndrome, and diabetes mellitus). Flavones, flavonols, flavanones, and flavanols were able to modulate blood pressure by restoring endothelial function, either directly, by affecting nitric oxide levels, or indirectly, through other pathways. Quercetin had the most consistent blood pressure-lowering effect in animal and human studies, irrespective of dose, duration, or disease status. However, further research on the safety and efficacy of the flavonoids is required before any of them can be used by humans, presumably in supplement form, at the doses required for therapeutic benefit.

Vasopeptidase Inhibition Corrects the Structure and Function of the Small Arteries in Experimental Renal Insufficiency

BACKGROUND

We studied whether vasopeptidase inhibition corrects the structure and function of the small arteries in experimental chronic renal insufficiency (CRI).

METHODS

After 5/6 nephrectomy (NX) surgery was performed on rats, there was a 14-week follow-up, allowing CRI to become established. Omapatrilat (40 mg/kg/day in chow) was then given for 8 weeks, and the small mesenteric arterial rings were investigated in vitro using wire and pressure myographs.

RESULTS

Plasma and ventricular B-type natriuretic peptide (BNP) concentrations were increased 2- to 2.7-fold, while systolic blood pressure (BP) increased by 32 mm Hg after NX. Omapatrilat treatment normalized the BNP and reduced the BP by 45 mm Hg in the NX rats. Endothelium-dependent vasorelaxation was impaired but the response to acetylcholine was normalized after omapatrilat treatment. Vasorelaxations induced by nitroprusside, isoprenaline and levcromakalim were enhanced after omapatrilat, and the responses were even more pronounced than in untreated sham-operated rats. Arterial wall thickness and wall-to-lumen ratio were increased after NX, whereas omapatrilat normalized these structural features and improved the strain-stress relationship in the small arteries; this suggests improved arterial elastic properties.

CONCLUSION

Omapatrilat treatment reduced BP, normalized volume overload, improved vasorelaxation and corrected the dimensions and passive elastic properties of the small arteries in the NX rats. Therefore, we consider vasopeptidase inhibition to be an effective treatment for CRI-induced changes in the small arteries.

Vascular function, insulin action, and exercise: an intricate interplay

Insulin enhances the compliance of conduit arteries, relaxes resistance arterioles to increase tissue blood flow, and dilates precapillary arterioles to expand muscle microvascular blood volume. These actions are impaired in the insulin resistant states. Exercise ameliorates endothelial dysfunction and improves insulin responses in insulin resistant patients, but the precise underlying mechanisms remain unclear. The microvasculature critically regulates insulin action in muscle by modulating insulin delivery to the capillaries nurturing the myocytes and trans-endothelial insulin transport. Recent data suggest that exercise may exert its insulin-sensitizing effect via recruiting muscle microvasculature to increase insulin delivery to and action in muscle. The current review focuses on how the interplay among exercise, insulin action, and the vasculature contributes to exercise-mediated insulin sensitization in muscle.

Mechanisms of the inward remodeling process in resistance vessels: is the actin cytoskeleton involved?

The resistance arteries and arterioles are the vascular components of the circulatory system where the greatest drop in blood pressure takes place. Consequently, these vessels play a preponderant role in the regulation of blood flow and the modulation of blood pressure. For this reason, the inward remodeling process of the resistance vasculature, as it occurs in hypertension, has profound consequences on the incidence of life-threatening cardiovascular events. In this manuscript, we review some of the most prominent characteristics of inwardly remodeled resistance arteries including their changes in vascular passive diameter, wall thickness, and elastic properties. Then, we explore the known contribution of the different components of the vascular wall to the characteristics of inwardly remodeled vessels, and pay particular attention to the role the vascular smooth muscle actin cytoskeleton may play on the initial stages of the remodeling process. We end by proposing potential ways by which many of the factors and mechanisms known to participate in the inward remodeling process may be associated with cytoskeletal modifications and participate in reducing the passive diameter of resistance vessels.

The role of mechanotransduction on vascular smooth muscle myocytes' [corrected] cytoskeleton and contractile function

Smooth muscle (SM) exhibits a highly organized structural hierarchy that extends over multiple spatial scales to perform a wide range of functions at the cellular, tissue, and organ levels. Early efforts primarily focused on understanding vascular SM (VSM) function through biochemical signaling. However, accumulating evidence suggests that mechanotransduction, the process through which cells convert mechanical stimuli into biochemical cues, is requisite for regulating contractility. Cytoskeletal proteins that comprise the extracellular, intercellular, and intracellular domains are mechanosensitive and can remodel their structure and function in response to external mechanical cues. Pathological stimuli such as malignant hypertension can act through the same mechanotransductive pathways to induce maladaptive remodeling, leading to changes in cellular shape and loss of contractile function. In both health and disease, the cytoskeletal architecture integrates the mechanical stimuli and mediates structural and functional remodeling in the VSM.

TonEBP/NFAT5 regulates ACTBL2 expression in biomechanically activated vascular smooth muscle cells

Cytoskeletal reorganization and migration are critical responses which enable vascular smooth muscle cells (VSMCs) cells to evade, compensate, or adapt to alterations in biomechanical stress. An increase in wall stress or biomechanical stretch as it is elicited by arterial hypertension promotes their reorganization in the vessel wall which may lead to arterial stiffening and contractile dysfunction. This adaptive remodeling process is dependent on and driven by subtle phenotype changes including those controlling the cytoskeletal architecture and motility of VSMCs. Recently, it has been reported that the transcription factor nuclear factor of activated T-cells 5 (TonEBP/NFAT5) controls critical aspects of the VSMC phenotype and is activated by biomechanical stretch. We therefore hypothesized that NFAT5 controls the expression of gene products orchestrating cytoskeletal reorganization in stretch-stimulated VSMCs. Automated immunofluorescence and Western blot analyses revealed that biomechanical stretch enhances the expression and nuclear translocation of NFAT5 in VSMCs. Subsequent in silico analyses suggested that this transcription factor binds to the promotor region of ACTBL2 encoding kappa-actin which was shown to be abundantly expressed in VSMCs upon exposure to biomechanical stretch. Furthermore, ACTBL2 expression was inhibited in these cells upon siRNA-mediated knockdown of NFAT5. Kappa-actin appeared to be aligned with stress fibers under static culture conditions, dispersed in lamellipodia and supported VSMC migration as its knockdown diminishes lateral migration of these cells. In summary, our findings delineated biomechanical stretch as a determinant of NFAT5 expression and nuclear translocation controlling the expression of the cytoskeletal protein ACTBL2. This response may orchestrate the migratory activity of VSMCs and thus promote maladaptive rearrangement of the arterial vessel wall during hypertension.

Beneficial effects of renal sympathetic denervation on cardiovascular inflammation and remodeling in essential hypertension

BACKGROUND

Renal sympathetic denervation (RSD) represents a potential treatment option for certain patients with resistant arterial hypertension (HT). HT is associated with chronic vascular inflammation and remodeling, contributing to progressive vascular damage, and atherosclerosis. The present study aimed to evaluate the influence of RSD on cardiovascular inflammation and remodeling by determining serum levels of interleukin-6 (IL-6), high-sensitive C-reactive protein (hsCRP), matrix metalloproteinases (MMP), and tissue inhibitor of metalloproteinases (TIMP).

METHODS

A total of 60 consecutive patients (age 67.9 ± 9.6 years) undergoing RSD were included. A therapeutic response was defined as an office systolic blood pressure (SBP) reduction of >10 mmHg 6 months after RSD. Venous serum samples for measurement of hsCRP, IL-6, MMP-2, MMP-9, and TIMP-1 were collected prior to and 6 months after RSD.

RESULTS

A significant reduction in office SBP of 26.4 mmHg [SBPbaseline 169.3 mmHg (SD 11.3), p < 0.001] was documented 6 months after RSD. The serum levels of hsCRP (p < 0.001) and the pro-inflammatory cytokine IL-6 (p < 0.001) were significantly decreased compared to baseline values. The levels of MMP-9 (p = 0.024) and MMP-2 (p < 0.01) were significantly increased compared to baseline values.

CONCLUSION

In addition to the effective blood pressure reduction in response to RSD, this study demonstrates a positive effect of RSD on biomarkers reflecting vascular inflammation and remodeling. These results suggest a possible prognostic benefit of RSD in high-risk patients for endothelial dysfunction and cardiovascular remodeling as well as end-organ damage.

Dynamic resistant hypertension patterns as predictors of cardiovascular morbidity: a 4-year prospective study

OBJECTIVE

Little is known regarding the clinical course and prognosis of resistant hypertension (RHT). We evaluated predictors of persistent RHT and the associated cardiovascular risk.

METHODS

We studied 1911 treated hypertensive patients (aged 59±11 years, 49% men) for a mean period of 3.9 years. At baseline, clinical data were collected and patients underwent echocardiographic measurements, routine blood testing and additional workup for exclusion of secondary causes of RHT (office-based uncontrolled hypertension under at least three drugs including a diuretic or controlled hypertension under four or more drugs). Endpoint of interest was the composite of coronary artery disease and stroke.

MAIN RESULTS

Four groups were identified depending on presence or absence of RHT at baseline and follow-up: 1153 patients (60%) never having RHT, 189 (10%) with resolved RHT, 204 (11%) with incident RHT and 365 (19%) with persistent RHT. Two-thirds of the patients with RHT at baseline remained resistant at the end of the study. Independent variables associated with both incident and persistent RHT were diabetes mellitus, history of cardiovascular disease, hypertension duration, SBP, left ventricular hypertrophy and glomerular filtration rate. Persistent RHT compared with never-having RHT was associated with a 2.2-fold increased risk for cardiovascular morbidity (95% CI: 1.21-4.05, P = 0.01) after adjustment for risk factors.

CONCLUSION

In treated hypertensive patients, among prospective RHT dynamic patterns, persistent RHT is frequent and independently associated with adverse cardiovascular prognosis.

Heterogeneity in arterial remodeling among sublines of spontaneously hypertensive rats

OBJECTIVES

Spontaneously hypertensive rats (SHR) have been used frequently as a model for human essential hypertension. However, both the SHR and its normotensive control, the Wistar Kyoto rat (WKY), consist of genetically different sublines. We tested the hypothesis that the pathophysiology of vascular remodeling in hypertension differs among rat sublines.

METHODS AND RESULTS

We studied mesenteric resistance arteries of WKY and SHR from three different sources, at 6 weeks and 5 months of age. Sublines of WKY and SHR showed differences in blood pressure, body weight, vascular remodeling, endothelial function, and vessel ultrastructure. Common features in small mesenteric arteries from SHR were an increase in wall thickness, wall-to-lumen ratio, and internal elastic lamina thickness.

CONCLUSIONS

Endothelial dysfunction, vascular stiffening, and inward remodeling of small mesenteric arteries are not common features of hypertension, but are subline-dependent. Differences in genetic background associate with different types of vascular remodeling in hypertensive rats.

Rosuvastatin prevents angiotensin II-induced vascular changes by inhibition of NAD(P)H oxidase and COX-1

BACKGROUND AND PURPOSE

NAD(P)H oxidase and COX-1 participate in vascular damage induced by angiotensin II. We investigated the effect of rosuvastatin on endothelial dysfunction, vascular remodelling, changes in extracellular matrix components and mechanical properties of small mesenteric arteries from angiotensin II-infused rats.

EXPERIMENTAL APPROACH

Male rats received angiotensin II (120 ng·kg⁻¹ ·min⁻¹ , subcutaneously) for 14 days with or without rosuvastatin (10 mg·kg⁻¹ ·day⁻¹ , oral gavage) or vehicle. Vascular functions and morphological parameters were assessed by pressurized myography.

KEY RESULTS

In angiotensin II-infused rats, ACh-induced relaxation was attenuated compared with controls, less sensitive to L-NAME, enhanced by SC-560 (COX-1 inhibitor) or SQ-29548 (prostanoid TP receptor antagonist), and normalized by the antioxidant ascorbic acid or NAD(P)H oxidase inhibitors. After rosuvastatin, relaxations to ACh were normalized, fully sensitive to L-NAME, and no longer affected by SC-560, SQ-29548 or NAD(P)H oxidase inhibitors. Angiotensin II enhanced intravascular superoxide generation, eutrophic remodelling, collagen and fibronectin depositions, and decreased elastin content, resulting in increased vessel stiffness. All these changes were prevented by rosuvastatin. Angiotensin II increased phosphorylation of NAD(P)H oxidase subunit p47phox and its binding to subunit p67phox, effects inhibited by rosuvastatin. Rosuvastatin down-regulated vascular Nox4/NAD(P)H isoform and COX-1 expression, attenuated the vascular release of 6-keto-PGF1α , and enhanced copper/zinc-superoxide dismutase expression.

CONCLUSION AND IMPLICATIONS

Rosuvastatin prevents angiotensin II-induced alterations in resistance arteries in terms of function, structure, mechanics and composition. These effects depend on restoration of NO availability, prevention of NAD(P)H oxidase-derived oxidant excess, reversal of COX-1 induction and its prostanoid production, and stimulation of endogenous vascular antioxidant defences.

Animal models of stroke: translational potential at present and in 2050

Translation from basic science bench research in ischemic stroke to bedside treatment of patients suffering ischemic stroke remains a difficult challenge. Despite literally hundreds of compounds and interventions that provide benefit in experimental models of cerebral ischemia, efficacy in humans remains to be demonstrated. The reasons for failure to translate the extensive positive basic science findings to successful clinical trials have been the focus of discussion for years. Some attribute the failure to flaws in clinical trial design, others question the predictive value of current animal models and some question the quality of preclinical data. It is likely that a combination of all these shortcomings have ultimately led to the failure. The purpose of this review is to analyze the commonly used animal models used in the field today, provide a framework for understanding the current state of basic science research in the ischemic stroke field and discuss a path forward.

Microfluidic techniques for development of 3D vascularized tissue

Development of a vascularized tissue is one of the key challenges for the successful clinical application of tissue engineered constructs. Despite the significant efforts over the last few decades, establishing a gold standard to develop three dimensional (3D) vascularized tissues has still remained far from reality. Recent advances in the application of microfluidic platforms to the field of tissue engineering have greatly accelerated the progress toward the development of viable vascularized tissue constructs. Numerous techniques have emerged to induce the formation of vascular structure within tissues which can be broadly classified into two distinct categories, namely (1) prevascularization-based techniques and (2) vasculogenesis and angiogenesis-based techniques. This review presents an overview of the recent advancements in the vascularization techniques using both approaches for generating 3D vascular structure on microfluidic platforms.

Hypotensive and antihypertensive potential of 4-[(1-phenyl-1H-pyrazol-4-yl) methyl]1-piperazine carboxylic acid ethyl ester: a piperazine derivative

AIMS

Clinical complaints on the first-line of cardiovascular medications make continuous search for new drugs a necessity. This study evaluated the cardiovascular effects and mechanism of 4-[(1-phenyl-1H-pyrazol-4-yl)methyl]1-piperazine carboxylic acid ethyl ester (LQFM008).

MAIN METHODS

Normotensive male Wistar or spontaneously hypertensive rats (anesthetized or conscious) were used to evaluate the effect of LQFM008 on the mean arterial pressure (MAP), heart rate (HR), arterial blood flow (ABF), arterial vascular conductance (AVC), baroreflex effectiveness index (BI), systolic blood pressure (SBP), diastolic blood pressure (DBP) and vascular function.

KEY FINDINGS

In anesthetized normotensive rats, LQFM008 (7.3, 14.3 or 28.6 μmol/kg, i.v.) reduced MAP (-21.1±2.7; -23.9±4.7 or -32.4±8.3 mmHg, respectively) and AVC (22%, 32% or 38%) in a dose-dependent manner. LQFM008 elicited a temporal reduction in the SBP and DBP without changes to the BI of conscious normotensive rats. In hypertensive rats, LQFM008 (7.3, 14.3 or 28.6 μmol/kg, i.v.) reduced MAP (-2.3±2.6; -29.3±2.7 or -38.4±2.8 mmHg, respectively) and increased HR (1.6±3.7; 15.4±4.9 or 25.5±6.2 bmp, respectively) in a dose-dependent manner. A week of oral administration of LQFM008 47.7 μmol/kg elicited a temporal reduction in SBP of hypertensive rats. Pretreatments with atropine, WAY-100635 or L-NAME blocked the effect of LQFM008. In addition, LQFM008-induced endothelium-dependent vascular relaxation was inhibited by L-NAME.

SIGNIFICANCE

Our findings showed hypotensive, antihypertensive and vasorelaxant effects of LQFM008 and suggest the participation of nitric oxide, 5-HT1A and muscarinic receptors.

Vascular wall extracellular matrix proteins and vascular diseases

Extracellular matrix proteins form the basic structure of blood vessels. Along with providing basic structural support to blood vessels, matrix proteins interact with different sets of vascular cells via cell surface integrin or non-integrin receptors. Such interactions induce vascular cell de novo synthesis of new matrix proteins during blood vessel development or remodeling. Under pathological conditions, vascular matrix proteins undergo proteolytic processing, yielding bioactive fragments to influence vascular wall matrix remodeling. Vascular cells also produce alternatively spliced variants that induce vascular cell production of different matrix proteins to interrupt matrix homeostasis, leading to increased blood vessel stiffness; vascular cell migration, proliferation, or death; or vascular wall leakage and rupture. Destruction of vascular matrix proteins leads to vascular cell or blood-borne leukocyte accumulation, proliferation, and neointima formation within the vascular wall; blood vessels prone to uncontrolled enlargement during blood flow diastole; tortuous vein development; and neovascularization from existing pathological tissue microvessels. Here we summarize discoveries related to blood vessel matrix proteins within the past decade from basic and clinical studies in humans and animals - from expression to cross-linking, assembly, and degradation under physiological and vascular pathological conditions, including atherosclerosis, aortic aneurysms, varicose veins, and hypertension.

Vitamin D induces increased systolic arterial pressure via vascular reactivity and mechanical properties

Background/Aims

The aim of this study was to evaluate whether supplementation of high doses of cholecalciferol for two months in normotensive rats results in increased systolic arterial pressure and which are the mechanisms involved. Specifically, this study assesses the potential effect on cardiac output as well as the changes in aortic structure and functional properties.

Methods

Male Wistar rats were divided into three groups: 1) Control group (C, n = 20), with no supplementation of vitamin D, 2) VD3 (n = 19), supplemented with 3,000 IU vitamin D/kg of chow; 3) VD10 (n = 21), supplemented with 10,000 IU vitamin D/kg of chow. After two months, echocardiographic analyses, measurements of systolic arterial pressure (SAP), vascular reactivity, reactive oxygen species (ROS) generation, mechanical properties, histological analysis and metalloproteinase-2 and -9 activity were performed.

Results

SAP was higher in VD3 and VD10 than in C rats (p = 0.001). Echocardiographic variables were not different among groups. Responses to phenylephrine in endothelium-denuded aortas was higher in VD3 compared to the C group (p = 0.041). Vascular relaxation induced by acetylcholine (p = 0.023) and sodium nitroprusside (p = 0.005) was impaired in both supplemented groups compared to the C group and apocynin treatment reversed impaired vasodilation. Collagen volume fraction (<0.001) and MMP-2 activity (p = 0.025) was higher in VD10 group compared to the VD3 group. Elastin volume fraction was lower in VD10 than in C and yield point was lower in VD3 than in C.

Conclusion

Our findings support the view that vitamin D supplementation increases arterial pressure in normotensive rats and this is associated with structural and functional vascular changes, modulated by NADPH oxidase, nitric oxide, and extracellular matrix components.

Altered matrix metalloproteinase-2 and -9 expression/activity links placental ischemia and anti-angiogenic sFlt-1 to uteroplacental and vascular remodeling and collagen deposition in hypertensive pregnancy

Preeclampsia is a complication of pregnancy manifested as maternal hypertension and often fetal growth restriction. Placental ischemia could be an initiating event, but the linking mechanisms leading to hypertension and growth restriction are unclear. We have shown an upregulation of matrix metalloproteinases (MMPs) during normal pregnancy (Norm-Preg). To test the role of MMPs in hypertensive-pregnancy (HTN-Preg), maternal and fetal parameters, MMPs expression, activity and distribution, and collagen and elastin content were measured in uterus, placenta and aorta of Norm-Preg rats and in rat model of reduced uteroplacental perfusion pressure (RUPP). Maternal blood pressure was higher, and uterine, placental and aortic weight, and the litter size and pup weight were less in RUPP than Norm-Preg rats. Western blots and gelatin zymography revealed decreases in amount and gelatinase activity of MMP-2 and MMP-9 in uterus, placenta and aorta of RUPP compared with Norm-Preg rats. Immunohistochemistry confirmed reduced MMPs in uterus, placenta and aortic media of RUPP rats. Collagen, but not elastin, was more abundant in uterus, placenta and aorta of RUPP than Norm-Preg rats. The anti-angiogenic factor soluble fms-like tyrosine kinase-1 (sFlt-1) decreased MMPs in uterus, placenta and aorta of Norm-Preg rats, and vascular endothelial growth factor (VEGF) reversed the decreases in MMPs in tissues of RUPP rats. Thus placental ischemia and anti-angiogenic sFlt-1 decrease uterine, placental and vascular MMP-2 and MMP-9, leading to increased uteroplacental and vascular collagen, and growth-restrictive remodeling in HTN-Preg. Angiogenic factors and MMP activators may reverse the decrease in MMPs and enhance growth-permissive remodeling in preeclampsia.

Arterial wall stress controls NFAT5 activity in vascular smooth muscle cells

Background

Nuclear factor of activated T‐cells 5 (NFAT5) has recently been described to control the phenotype of vascular smooth muscle cells (VSMCs). Although an increase in wall stress or stretch (eg, elicited by hypertension) is a prototypic determinant of VSMC activation, the impact of this biomechanical force on the activity of NFAT5 is unknown. This study intended to reveal the function of NFAT5 and to explore potential signal transduction pathways leading to its activation in stretch‐stimulated VSMCs.

Methods and Results

Human arterial VSMCs were exposed to biomechanical stretch and subjected to immunofluorescence and protein‐biochemical analyses. Stretch promoted the translocation of NFAT5 to the nucleus within 24 hours. While the protein abundance of NFAT5 was regulated through activation of c‐Jun N‐terminal kinase under these conditions, its translocation required prior activation of palmitoyltransferases. DNA microarray and ChiP analyses identified the matrix molecule tenascin‐C as a prominent transcriptional target of NFAT5 under these conditions that stimulates migration of VSMCs. Analyses of isolated mouse femoral arteries exposed to hypertensive perfusion conditions verified that NFAT5 translocation to the nucleus is followed by an increase in tenascin‐C abundance in the vessel wall.

Conclusions

Collectively, our data suggest that biomechanical stretch is sufficient to activate NFAT5 both in native and cultured VSMCs where it regulates the expression of tenascin‐C. This may contribute to an improved migratory activity of VSMCs and thus promote maladaptive vascular remodeling processes such as hypertension‐induced arterial stiffening.

Smooth muscle cell mineralocorticoid receptors are mandatory for aldosterone-salt to induce vascular stiffness

Arterial stiffness is recognized as a risk factor for many cardiovascular diseases. Aldosterone via its binding to and activation of the mineralocorticoid receptors (MRs) is a main regulator of blood pressure by controlling renal sodium reabsorption. Although both clinical and experimental data indicate that MR activation by aldosterone is involved in arterial stiffening, the molecular mechanism is not known. In addition to the kidney, MR is expressed in both endothelial and vascular smooth muscle cells (VSMCs), but the specific contribution of the VSMC MR to aldosterone-induced vascular stiffness remains to be explored. To address this question, we generated a mouse model with conditional inactivation of the MR in VSMC (MR(SMKO)). MR(SMKO) mice show no alteration in renal sodium handling or vascular structure, but they have decreased blood pressure when compared with control littermate mice. In vivo at baseline, large vessels of mutant mice presented with normal elastic properties, whereas carotids displayed a smaller diameter when compared with those of the control group. As expected after aldosterone/salt challenge, the arterial stiffness increased in control mice; however, it remained unchanged in MR(SMKO) mice, without significant modification in vascular collagen/elastin ratio. Instead, we found that the fibronectin/α5-subunit integrin ratio is profoundly altered in MR(SMKO) mice because the induction of α5 expression by aldosterone/salt challenge is prevented in mice lacking VSMC MR. Altogether, our data reveal in the aldosterone/salt hypertension model that MR activation specifically in VSMC leads to the arterial stiffening by modulation of cell-matrix attachment proteins independent of major vascular structural changes.

Differential mechanical response and microstructural organization between non-human primate femoral and carotid arteries

Unique anatomic locations and physiologic functions predispose different arteries to varying mechanical responses and pathologies. However, the underlying causes of these mechanical differences are not well understood. The objective of this study was to first identify structural differences in the arterial matrix that would account for the mechanical differences between healthy femoral and carotid arteries and second to utilize these structural observations to perform a microstructurally motivated constitutive analysis. Femoral and carotid arteries were subjected to cylindrical biaxial loading and their microstructure was quantified using two-photon microscopy. The femoral arteries were found to be less compliant than the carotid arteries at physiologic loads, consistent with previous studies, despite similar extracellular compositions of collagen and elastin ([Formula: see text]). The femoral arteries exhibited significantly less circumferential dispersion of collagen fibers ([Formula: see text]), despite a similar mean fiber alignment direction as the carotid arteries. Elastin transmural distribution, in vivo axial stretch, and opening angles were also found to be distinctly different between the arteries. Lastly, we modeled the arteries' mechanical behaviors using a microstructural-based, distributed collagen fiber constitutive model. With this approach, the material parameters of the model were solved using the experimental microstructural observations. The findings of this study support an important role for microstructural organization in arterial stiffness.

Retinal arterial hypertrophy: the new LVH?

Prevention of target organ damage represents the El Dorado for clinicians who treat hypertension. Although many of the cardiovascular sequelae of chronic hypertension are due to large artery atherosclerosis, an equal number are due to small artery dysfunction. These microvascular complications include eye disease (retinopathy), kidney failure, diastolic dysfunction of the heart and small vessel brain disease leading to stroke syndromes, dementia and even depression. Examination of the retinal vasculature represents the only way to reliably derive information regarding small arteries responsible for these diverse pathologies. This review aims to summarise the rapidly accruing evidence indicating that easily observable abnormalities of retinal arteries reflect target organ damage elsewhere in the body of hypertensive patients. In tandem, we also present putative mechanisms by which hypertension and diabetes fundamentally change small artery structure and function and how these processes may lead to target organ damage.

Blood pressure regulation V: in vivo mechanical properties of precapillary vessels as affected by long-term pressure loading and unloading

Recent studies are reviewed, concerning the in vivo wall stiffness of arteries and arterioles in healthy humans, and how these properties adapt to iterative increments or sustained reductions in local intravascular pressure. A novel technique was used, by which arterial and arteriolar stiffness was determined as changes in arterial diameter and flow, respectively, during graded increments in distending pressure in the blood vessels of an arm or a leg. Pressure-induced increases in diameter and flow were smaller in the lower leg than in the arm, indicating greater stiffness in the arteries/arterioles of the leg. A 5-week period of intermittent intravascular pressure elevations in one arm reduced pressure distension and pressure-induced flow in the brachial artery by about 50 %. Conversely, prolonged reduction of arterial/arteriolar pressure in the lower body by 5 weeks of sustained horizontal bedrest, induced threefold increases of the pressure-distension and pressure-flow responses in a tibial artery. Thus, the wall stiffness of arteries and arterioles are plastic properties that readily adapt to changes in the prevailing local intravascular pressure. The discussion concerns mechanisms underlying changes in local arterial/arteriolar stiffness as well as whether stiffness is altered by changes in myogenic tone and/or wall structure. As regards implications, regulation of local arterial/arteriolar stiffness may facilitate control of arterial pressure in erect posture and conditions of exaggerated intravascular pressure gradients. That increased intravascular pressure leads to increased arteriolar wall stiffness also supports the notion that local pressure loading may constitute a prime mover in the development of vascular changes in hypertension.

Copper transporter ATP7A protects against endothelial dysfunction in type 1 diabetic mice by regulating extracellular superoxide dismutase

Oxidative stress and endothelial dysfunction contribute to vascular complication in diabetes. Extracellular superoxide dismutase (SOD3) is one of the key antioxidant enzymes that obtains copper via copper transporter ATP7A. SOD3 is secreted from vascular smooth muscles cells (VSMCs) and anchors at the endothelial surface. The role of SOD3 and ATP7A in endothelial dysfunction in type 1 diabetes mellitus (T1DM) is entirely unknown. Here we show that the specific activity of SOD3, but not SOD1, is decreased, which is associated with increased O2(•-) production in aortas of streptozotocin-induced and genetically induced Ins2(Akita) T1DM mice. Exogenous copper partially rescued SOD3 activity in isolated T1DM vessels. Functionally, acetylcholine-induced, endothelium-dependent relaxation is impaired in T1DM mesenteric arteries, which is rescued by SOD mimetic tempol or gene transfer of SOD3. Mechanistically, ATP7A expression in T1DM vessels is dramatically decreased whereas other copper transport proteins are not altered. T1DM-induced endothelial dysfunction and decrease of SOD3 activity are rescued in transgenic mice overexpressing ATP7A. Furthermore, SOD3-deficient T1DM mice or ATP7A mutant T1DM mice augment endothelial dysfunction and vascular O2(•-) production versus T1DM mice. These effects are in part due to hypoinsulinemia in T1DM mice, since insulin treatment, but not high glucose, increases ATP7A expression in VSMCs and restores SOD3 activity in the organoid culture of T1DM vessels. In summary, a decrease in ATP7A protein expression contributes to impaired SOD3 activity, resulting in O2(•-) overproduction and endothelial dysfunction in blood vessels of T1DM. Thus, restoring copper transporter function is an essential therapeutic approach for oxidant stress-dependent vascular and metabolic diseases.

Molecular biology of atherosclerosis

At least 468 individual genes have been manipulated by molecular methods to study their effects on the initiation, promotion, and progression of atherosclerosis. Most clinicians and many investigators, even in related disciplines, find many of these genes and the related pathways entirely foreign. Medical schools generally do not attempt to incorporate the relevant molecular biology into their curriculum. A number of key signaling pathways are highly relevant to atherogenesis and are presented to provide a context for the gene manipulations summarized herein. The pathways include the following: the insulin receptor (and other receptor tyrosine kinases); Ras and MAPK activation; TNF-α and related family members leading to activation of NF-κB; effects of reactive oxygen species (ROS) on signaling; endothelial adaptations to flow including G protein-coupled receptor (GPCR) and integrin-related signaling; activation of endothelial and other cells by modified lipoproteins; purinergic signaling; control of leukocyte adhesion to endothelium, migration, and further activation; foam cell formation; and macrophage and vascular smooth muscle cell signaling related to proliferation, efferocytosis, and apoptosis. This review is intended primarily as an introduction to these key signaling pathways. They have become the focus of modern atherosclerosis research and will undoubtedly provide a rich resource for future innovation toward intervention and prevention of the number one cause of death in the modern world.

Aerobic exercise reduces oxidative stress and improves vascular changes of small mesenteric and coronary arteries in hypertension

BACKGROUND AND PURPOSE

Regular physical activity is an effective non-pharmacological therapy for prevention and control of hypertension. We investigated the effects of aerobic exercise training in vascular remodelling and in the mechanical and functional alterations of coronary and small mesenteric arteries from spontaneously hypertensive rats (SHR).

EXPERIMENTAL APPROACH

Normotensive Wistar Kyoto (WKY), SHR and SHR trained on a treadmill for 12 weeks were used to evaluate vascular structural, mechanical and functional properties.

KEY RESULTS

Exercise did not affect lumen diameter, wall thickness and wall/lumen ratio but reduced vascular stiffness of coronary and mesenteric arteries from SHR. Exercise also reduced collagen deposition and normalized altered internal elastic lamina organization and expression of MMP-9 in mesenteric arteries from SHR. Exercise did not affect contractile responses of coronary arteries but improved the endothelium-dependent relaxation in SHR. In mesenteric arteries, training normalized the increased contractile responses induced by U46619 and by high concentrations of acetylcholine. In vessels from SHR, exercise normalized the effects of the NADPH oxidase inhibitor apocynin and the NOS inhibitor l-NAME in vasodilator or vasoconstrictor responses, normalized the increased O(2) (-) production and the reduced Cu/Zn superoxide dismutase expression and increased NO production.

CONCLUSIONS AND IMPLICATIONS

Exercise training of SHR improves endothelial function and vascular stiffness in coronary and small mesenteric arteries. This might be related to the concomitant decrease of oxidative stress and increase of NO bioavailability. Such effects demonstrate the beneficial effects of exercise on the vascular system and could contribute to a reduction in blood pressure.

TIMP3 is the primary TIMP to regulate agonist-induced vascular remodelling and hypertension

AIMS

Hypertension is accompanied by structural remodelling of vascular extracellular matrix (ECM). Tissue inhibitor of metalloproteinases (TIMPs) inhibits matrix metalloproteinases (MMPs) that degrade the matrix structural proteins. In response to a hypertensive stimulus, the balance between MMPs and TIMPs is altered. We examined the role of TIMPs in agonist-induced hypertension.

METHODS AND RESULTS

We subjected TIMP-knockout mice to angiotensin II (Ang II) infusion, and found that Ang-II-induced hypertension in TIMP1(-/-), TIMP2(-/-), and TIMP4(-/-) mice was comparable to wild-type (WT) mice, but significantly suppressed in TIMP3(-/-) mice. Ex vivo pressure myography analyses on carotid and mesenteric arteries revealed that Ang-II-infused TIMP3(-/-) arteries were more distensible with impaired elastic recoil compared with the WT group. The acute response to vasoconstriction and vasodilation was intact in TIMP3(-/-) mesenteric and carotid arteries. Mesenteric arteries from TIMP3(-/-)-Ang II mice exhibited a reduced media-to-lumen ratio, suppressed collagen and elastin levels, elevated elastase and gelatinase proteolytic activities compared with WT-Ang II. TIMP3(-/-)-Ang II carotid arteries also showed adverse structural remodelling. Treatment of mice with doxycycline, a matrix metalloproteinase inhibitor, improved matrix integrity in mesenteric and carotid arteries in TIMP3(-/-)-Ang II and differentially regulated elastin and collagen levels in WT-Ang II vs. TIMP3(-/-)-Ang II.

CONCLUSION

Our study demonstrates a critical role for TIMP3, among all TIMPs, is preserving arterial ECM in response to Ang II. It is critical to acknowledge that the suppressed Ang-II-induced hypertension in TIMP3(-/-) mice is not a protective mechanism but owing to adverse remodelling in arterial matrix.

A new multiscale model for the mechanical behavior of vein walls

The purpose of the present work is to propose a new multiscale model for the prediction of the mechanical behavior of vein walls. This model is based on one of our previous works which considered scale transitions applied to undulated collagen fibers. In the present work, the scale below was added to take the anisotropy of collagen fibrils into account. One scale above was also added, modeling the global reorientation of collagen fibers inside the vessel wall. The model was verified on experimental data from the literature, leading to a satisfactory agreement. The proposed multiscale approach also allows the extraction of local stresses and strains at each scale. This approach is presented here in the case of vein walls, but can easily be extended to other tissues which contain similar constituents.

Prolonged vasoconstriction of resistance arteries involves vascular smooth muscle actin polymerization leading to inward remodelling

AIMS

Inward remodelling of the resistance vasculature is predictive of hypertension and life-threatening cardiovascular events. We hypothesize that the contractile mechanisms responsible for maintaining a reduced diameter over time in response to prolonged stimulation with vasoconstrictor agonists are in part responsible for the initial stages of the remodelling process. Here we investigated the role of vascular smooth muscle (VSM) actin polymerization on agonist-induced vasoconstriction and development of inward remodelling.

METHODS AND RESULTS

Experiments were conducted in Sprague-Dawley rat resistance vessels isolated from the cremaster and mesentery. Within blood vessels, actin dynamics of VSM were monitored by confocal microscopy after introduction of fluorescent actin monomers through electroporation and by differential centrifugation to probe globular (G) and filamentous (F) actin content. Results indicated that 4 h of agonist-dependent vasoconstriction induced inward remodelling and caused significant actin polymerization, elevating the F-/total-actin ratio. Inhibition of actin polymerization prevented vessels from maintaining prolonged vasoconstriction and developing inward remodelling. Activation of the small GTPases Rho/Rac/Cdc42 also increased the F-/total-actin ratio and induced inward remodelling, while inhibition of Rho kinase or Rac-1 prevented inward remodelling. Disruption of the actin cytoskeleton reversed the inward remodelling caused by prolonged vasoconstriction, but did not affect the passive diameter of freshly isolated vessels.

CONCLUSION

These results indicate that vasoconstriction-induced inward remodelling is in part caused by the polymerization of actin within VSM cells through activation of small GTPases.