Symphony of vascular contraction: how smooth muscle cells lose harmony to signal increased vascular resistance in hypertension

Enhancing Vascular Health and Lowering Blood Pressure in Spontaneously Hypertensive Rats through Syrah Grape (Vitis vinifera) Pomace: The Role of Phenolic Compounds

BACKGROUND

The beneficial properties of wine by-products include actions that help prevent and treat cardiovascular conditions such as hypertension, primarily due to their antioxidant effects. Novel pharmacotherapies are being developed to treat arterial hypertension, including investigations into natural products exhibiting biological activity, necessitating rigorous evaluation of their efficacy and safety. This study aimed to identify and quantify phenolic compounds in Syrah (Vitis vinifera) grapes grown in the Brazilian Cerrado and their presence in winemaking by-products. It also examined the effects of grape pomace on blood pressure.

METHODS

Fresh grapes, pomace, and lees, were subjected to spectrophotometric determination of total phenolic compounds, followed by identification and quantification using HPLC-DAD-ESI-MSn. Normotensive male rats (Wistar) and spontaneously hypertensive rats (SHR) received grape pomace-enriched (150 or 300 mg/kg/day, 14 days) or standard chow. Indirect arterial pressure was assessed, while vascular reactivity was evaluated in mesenteric resistance arteries.

RESULTS

Pomace samples exhibited higher total phenolic compound concentrations than grapes or lees. Seven derivatives of hydroxycinnamic acids and twenty-one flavonols were identified. Quercetin-3-glucoside and ethyl caffeate were the most abundant phenolic compounds. Grape pomace-enriched chow demonstrated a dose-dependent hypotensive effect in rats.

CONCLUSION

the abundance of flavonols and hydroxycinnamic acids, combined with their hypotensive effects, underscores the therapeutic potential of fine wine-making by-products produced in the Brazilian Cerrado.

Nardilysin in vascular smooth muscle cells controls blood pressure via the regulation of calcium dynamics

Blood pressure is a crucial physiological parameter and its abnormalities can cause a variety of health problems. We have previously reported that mice with systemic deletion of nardilysin (NRDC), an M16 family metalloprotease, exhibit hypotension. In this study, we aimed to clarify the role of NRDC in vascular smooth muscle cell (VSMC) by generating VSMC-specific Nrdc knockout (VSMC-KO) mice. Our findings reveal that VSMC-KO mice also exhibit hypotension. Aortas isolated from VSMC-KO mice exhibited a weakened contractile response to phenylephrine, accompanied by reduced phosphorylation of myosin light chain 2 and decreased rhoA expression. VSMC isolated from VSMC-KO aortas showed a reduced increase in intracellular Ca2+ concentration induced by α-stimulants. These findings suggest that NRDC in VSMC regulates vascular contraction and blood pressure by modulating Ca2+ dynamics.

Calcium signaling in endothelial and vascular smooth muscle cells: sex differences and the influence of estrogens and androgens

Calcium signaling in vascular endothelial cells (ECs) and smooth muscle cells (VSMCs) is essential for the regulation of vascular tone. However, the changes to intracellular Ca2+ concentrations are often influenced by sex differences. Furthermore, a large body of evidence shows that sex hormone imbalance leads to dysregulation of Ca2+ signaling and this is a key factor in the pathogenesis of cardiovascular diseases. In this review, the effects of estrogens and androgens on vascular calcium-handling proteins are discussed, with emphasis on the associated genomic or nongenomic molecular mechanisms. The experimental models from which data were collected were also considered. The review highlights 1) in female ECs, transient receptor potential vanilloid 4 (TRPV4) and mitochondrial Ca2+ uniporter (MCU) enhance Ca2+-dependent nitric oxide (NO) generation. In males, only transient receptor potential canonical 3 (TRPC3) plays a fundamental role in this effect. 2) Female VSMCs have lower cytosolic Ca2+ levels than males due to differences in the activity and expression of stromal interaction molecule 1 (STIM1), calcium release-activated calcium modulator 1 (Orai1), calcium voltage-gated channel subunit-α1C (CaV1.2), Na+-K+-2Cl- symporter (NKCC1), and the Na+/K+-ATPase. 3) When compared with androgens, the influence of estrogens on Ca2+ homeostasis, vascular tone, and incidence of vascular disease is better documented. 4) Many studies use supraphysiological concentrations of sex hormones, which may limit the physiological relevance of outcomes. 5) Sex-dependent differences in Ca2+ signaling mean both sexes ought to be included in experimental design.

Role of TRPV4 on vascular tone regulation in pathophysiological states

Vascular tone regulation is a key event in controlling blood flow in the body. Endothelial cells (ECs) and vascular smooth muscle cells (VSMCs) help regulate the vascular tone. Abnormal vascular responsiveness to various stimuli, including constrictors and dilators, has been observed in pathophysiological states although EC and VSMC coordinate to maintain the exquisite balance between contraction and relaxation in vasculatures. Thus, investigating the mechanisms underlying vascular tone abnormality is very important in maintaining vascular health and treating vasculopathy. Increased intracellular free Ca2+ concentration ([Ca2+]i) is one of the major triggers initiating each EC and VSMC response. Transient receptor potential vanilloid family member 4 (TRPV4) is a Ca2+-permeable non-selective ion channel, which is activated by several stimuli, and is presented in both ECs and VSMCs. Therefore, TRPV4 plays an important role in vascular responses. Emerging evidence indicates the role of TRPV4 on the functions of ECs and VSMCs in various pathophysiological states, including hypertension, diabetes, and obesity. This review focused on the link between TRPV4 and the functions of ECs/VSMCs, particularly its role in vascular tone and responsiveness to vasoactive substances.

Aortic smooth muscle TRPV4 channels regulate vasoconstriction in high salt-induced hypertension

Recent studies have focused on the contribution of vascular endothelial transient receptor potential vanilloid 4 (TRPV4) channels to hypertension. However, in hypertension, TRPV4 channels in vascular smooth muscle remain unexplored. In the present study, we performed wire myograph experiments in isolated aortas from endothelial cell specific TRPV4 channel knockout (TRPV4EC-/-) mice to demonstrate that GSK1016790A (a specific TRPV4 channel agonist) triggered aortic smooth muscle-dependent contractions from mice on a normal-salt diet, and the contractions were enhanced in high-salt diet (HSD) mice. Intracellular Ca2+ concentration ([Ca2+]i) and Ca2+ imaging assays showed that TRPV4-induced [Ca2+]i was significantly higher in aortic smooth muscle cells (ASMCs) from HSD-induced hypertensive mice, and application of an inositol trisphosphate receptor (IP3R) inhibitor markedly attenuated TRPV4-induced [Ca2+]i. IP3R2 expression was enhanced in ASMCs from HSD-induced hypertensive mice and the contractile response induced by TRPV4 was inhibited by the IP3R inhibitor. Whole-transcriptome analysis by RNA-seq and western blot assays revealed the involvement of interferon regulatory factor 7 (IRF7) in TRPV4-IRF7-IP3R2 signaling in HSD-induced hypertension. These results suggested that TRPV4 channels regulate smooth muscle-dependent contractions in high salt-induced hypertension, and this contraction involves increased [Ca2+]i, IP3R2, and IRF7 activity. Our study revealed a considerable effect of TRPV4 channels in smooth muscle-dependent contraction in mice during high-salt induced hypertension.

p90RSK2, a new MLCK mediates contractility in myosin light chain kinase null smooth muscle

Introduction: Phosphorylation of smooth muscle (SM) myosin regulatory light chain (RLC20) is a critical switch leading to SM contraction. The canonical view held that only the short isoform of myosin light chain kinase (MLCK1) catalyzed this reaction. It is now accepted that auxiliary kinases may contribute to vascular SM tone and contractility. We have previously reported that p90 ribosomal S6 kinase (RSK2) functions as such a kinase, in parallel with MLCK1, contributing ∼25% of the maximal myogenic force in resistance arteries. Thus, RSK2 may be instrumental in the regulation of basal vascular tone and blood pressure. Here, we take advantage of a MLCK1 null mouse (mylk1 -/-) to further test our hypothesis that RSK2 can function as an MLCK, playing a significant physiological role in SM contractility. Methods: Using fetal (E14.5-18.5) SM tissues, as embryos die at birth, we investigated the necessity of MLCK for contractility and fetal development and determined the ability of RSK2 kinase to compensate for the lack of MLCK and characterized its signaling pathway in SM. Results and Discussion: Agonists induced contraction and RLC20 phosphorylation in mylk1 -/- SM was attenuated by RSK2 inhibition. The pCa-tension relationships in permeabilized strips of bladder showed no difference in Ca2+ sensitivity in WT vs mylk1 -/- muscles, although the magnitude of force responses was considerably smaller in the absence of MLCK. The magnitude of contractile responses was similar upon addition of GTPγS to activate the RhoA/ROCK pathway or calyculinA to inhibit the myosin phosphatase. The Ca2+-dependent tyrosine kinase, Pyk2, contributed to RSK2-mediated contractility and RLC20 phosphorylation. Proximity-ligation and immunoprecipitation assays demonstrated an association of RSK2, PDK1 and ERK1/2 with MLCK and actin. RSK2, PDK1, ERK1/2 and MLCK formed a signaling complex on the actin filament, positioning them for interaction with adjacent myosin heads. The Ca2+-dependent component reflected the agonist mediated increases in Ca2+, which activated the Pyk2/PDK1/RSK2 signaling cascade. The Ca2+-independent component was through activation of Erk1/2/PDK1/RSK2 leading to direct phosphorylation of RLC20, to increase contraction. Overall, RSK2 signaling constitutes a new third signaling pathway, in addition to the established Ca2+/CaM/MLCK and RhoA/ROCK pathways to regulate SM contractility.

p90RSK2, a new MLCK, rescues contractility in myosin light chain kinase null smooth muscle

Background

Phosphorylation of smooth muscle (SM) myosin regulatory light chain (RLC 20 ) is a critical switch leading to contraction or cell migration. The canonical view held that the only kinase catalyzing this reaction is the short isoform of myosin light chain kinase (MLCK1). Auxiliary kinases may be involved and play a vital role in blood pressure homeostasis. We have previously reported that p90 ribosomal S6 kinase (RSK2) functions as such a kinase, in parallel with the classical MLCK1, contributing ∼25% of the maximal myogenic force in resistance arteries and regulating blood pressure. Here, we take advantage of a MLCK1 null mouse to further test our hypothesis that RSK2 can function as an MLCK, playing a significant physiological role in SM contractility.

Methods

Fetal (E14.5-18.5) SM tissues were used as embryos die at birth. We investigated the necessity of MLCK for contractility, cell migration and fetal development and determined the ability of RSK2 kinase to compensate for the lack of MLCK and characterized it's signaling pathway in SM.

Results

Agonists induced contraction and RLC 20 phosphorylation in mylk1 -/- SM, that was inhibited by RSK2 inhibitors. Embryos developed and cells migrated in the absence of MLCK. The pCa-tension relationships in WT vs mylk1 -/- muscles demonstrated a Ca 2+ -dependency due to the Ca 2+ -dependent tyrosine kinase Pyk2, known to activate PDK1 that phosphorylates and fully activates RSK2. The magnitude of contractile responses was similar upon addition of GTPγS to activate the RhoA/ROCK pathway. The Ca 2+ -independent component was through activation of Erk1/2/PDK1/RSK2 leading to direct phosphorylation of RLC 20 , to increase contraction. RSK2, PDK1, Erk1/2 and MLCK formed a signaling complex on the actin filament, optimally positioning them for interaction with adjacent myosin heads.

Conclusions

RSK2 signaling constitutes a new third signaling pathway, in addition to the established Ca 2+ /CAM/MLCK and RhoA/ROCK pathways to regulate SM contractility and cell migration.

Translational potential of targeting Anoctamin-1-Encoded Calcium-Activated chloride channels in hypertension

Calcium-activated chloride channels (CaCC) provide a depolarizing stimulus to a variety of tissues through chloride efflux in response to a rise in internal Ca²⁺ and voltage. One of these channels, Anoctamin-1 (ANO1 or TMEM16A) is now recognized to play a central role in promoting smooth muscle tone in various types of blood vessels. Its role in hypertension, and thus the therapeutic promise of targeting ANO1, is less straightforward. This review gives an overview of our current knowledge about the potential role ANO1 may play in hypertension within the systemic, portal, and pulmonary vascular systems and the importance of this information when pursuing potential treatment strategies. While the role of ANO1 is well-established in several forms of pulmonary hypertension, its contributions to both the generation of vascular tone and its role in hypertension within the systemic and portal systems are much less clear. This, combined with ANO1's various roles throughout a multitude of tissues throughout the body, command caution when targeting ANO1 as a therapeutic target and may require tissue-selective strategies.

Reduced blood circulating calcium level is an outstanding biomarker for preeclampsia among 48 types of human diseases

BACKGROUND

Calcium ion (Ca2+) is essential for human physiology by regulating various signal transduction pathways inside all cells and in the blood circulation.

AIM

We compared circulating Ca2+ levels in the healthy control against 48 different types of human diseases.

DESIGN

A total of 144 201 independent test results of Ca2+ levels from 48 clinically defined diseases and 141 679 independent test results of Ca2+ from healthy individuals who came to the hospital for annual physical examination were retrieved during the past 5 years.

METHODS

Ca2+ was determined by the standard 'Arsenazo III method' in the clinical laboratory of Affiliated Hospital of Qingdao University. We analyzed all data using RStudio V.1.3.1073 and python libraries 3.8.

RESULTS

All 48 types of diseases had decreased Ca2+ levels than the healthy control based on either mean or median values. Patients suffering from preeclampsia had the lowest Ca2+ levels among all 48 diseases. The perfect area under the curve, sensitivity, and specificity values of 1.0, 0.96 and 0.96 indicated that Ca2+ was an excellent biomarker for diagnosing preeclampsia. Extremely low Ca2+ was present in patients suffering kidney-related diseases. Since the correlation between each disease on the statistical features is proportional to their vector distance, the two-component analysis revealed that preeclampsia, sepsis and chronic obstructive pulmonary disease were closely related among 48 diseases.

CONCLUSIONS

All human diseases were associated with reduced circulating Ca2+ levels, where the decreased Ca2+ was a perfect biomarker for preeclampsia. Kidney-related conditions were related to over-down-regulation of Ca2+ levels. The resemblance of preeclampsia to sepsis and chronic obstructive pulmonary disease based on two-component analysis suggested that the three unrelated diseases might share a similar mechanism of the circulating Ca2+ regulation.

Dissecting the Polygenic Basis of Primary Hypertension: Identification of Key Pathway-Specific Components

Introduction and Objectives

Genome-wide association studies have identified a high number of genetic loci associated with hypertension suggesting the presence of an underlying polygenic architecture. In this study, we aimed to dissect the polygenic component of primary hypertension searching also for pathway-specific components.

Methods

The polygenic risk score (PRS) models, based on the UK biobank genetic signals for hypertension status, were obtained on a target Italian case/control cohort including 561 cases and 731 hyper-normal controls from HYPERGENES, and were then applied to an independent validation cohort composed by multi-countries European-based samples including 1,284 cases and 960 hyper-normal controls.

Results

The resulting genome-wide PRS was capable of stratifying the individuals for hypertension risk by comparing between individuals in the last PRS decile and the median decile: we observed an odds ratio (OR) of 3.62, CI = [2.01, 6.32] (P = 9.01E-07) and 3.22, 95% CI = [2.06, 5.10] (P = 6.47E-08) in the target and validation cohorts, respectively. The relatively high case/control ORs across PRS quantiles corroborates the presence of strong polygenic components which could be driven by an enrichment of risk alleles within the cases but also by potential enrichment of protective alleles in the old normotensive controls. Moreover, novel pathway-specific PRS revealed an enrichment of the polygenic signal attributable to specific biological pathways. Among those the most significantly associated with hypertension status was the calcium signaling pathway together with other mainly related such as the phosphatidylinositol/inositol phosphate pathways.

Conclusions

The development of pathway-specific PRS could prioritize biological mechanisms, according to their contribution to the genetic susceptibility, whose regulations might be a potential pharmacological preventive target.

Chronic 3D Vascular-Immune Interface Established by Coculturing Pressurized Resistance Arteries and Immune Cells

[Figure: see text].

Crosstalk of TLR4, vascular NADPH oxidase, and COVID-19 in diabetes: What are the potential implications?

Toll-like receptor 4 (TLR4) contributes to the pathophysiology of diabetes. This happens, at least in part, because TLR4 modulates the enzyme NADPH oxidase, a primary source of ROS in vascular structures. Increased oxidative stress disrupts key vascular signaling mechanisms and drives the progression of diabetes, elevating the likelihood of cardiovascular diseases. Recently, it has been shown that patients with diabetes are also at a higher risk of developing severe coronavirus disease 2019 (COVID-19). Given the importance of the interaction between TLR4 and NADPH oxidase to the disrupted diabetic vascular system, we put forward the hypothesis that TLR4-mediated NADPH oxidase-derived ROS might be a critical mechanism to help explain why this disparity appears in diabetic patients, but unfortunately, conclusive experimental evidence still lacks in the literature. Herein, we focus on discussing the pathological implications of this signaling communication in the diabetic vasculature and exploring this crosstalk in the context of diabetes-associated severe COVID-19.

Distinct signatures of calcium activity in brain mural cells

Pericytes have been implicated in various neuropathologies, yet little is known about their function and signaling pathways in health. Here, we characterized calcium dynamics of cortical mural cells in anesthetized or awake Pdgfrb-CreERT2;Rosa26< LSL-GCaMP6s > mice and in acute brain slices. Smooth muscle cells (SMCs) and ensheathing pericytes (EPs), also named as terminal vascular SMCs, revealed similar calcium dynamics in vivo. In contrast, calcium signals in capillary pericytes (CPs) were irregular, higher in frequency, and occurred in cellular microdomains. In the absence of the vessel constricting agent U46619 in acute slices, SMCs and EPs revealed only sparse calcium signals, whereas CPs retained their spontaneous calcium activity. Interestingly, chemogenetic activation of neurons in vivo and acute elevations of extracellular potassium in brain slices strongly decreased calcium activity in CPs. We propose that neuronal activation and an extracellular increase in potassium suppress calcium activity in CPs, likely mediated by Kir2.2 and KATP channels.

Male and female high-fat diet-fed Dahl SS rats are largely protected from vascular dysfunctions: PVAT contributions reveal sex differences

Vascular dysfunctions are observed in the arteries from hypertensive subjects. The establishment of the Dahl salt-sensitive (SS) male and female rat models to develop a reproducible hypertension with high-fat (HF) diet feeding from weaning allows addressing the question of whether HF diet-associated hypertension results in vascular dysfunction similar to that of essential hypertension in both sexes. We hypothesized that dysfunction of three distinct vascular layers, i.e., endothelial, smooth muscle, and perivascular adipose tissue (PVAT), would be present in the aorta from HF diet-fed versus control diet-fed male and female rats. Dahl SS rats were fed a control (10% kcal of fat) or HF (60%) diet from weaning for 24 wk. Male and female Dahl SS rats became equally hypertensive when placed on a HF diet. For male and female rats, the thoracic aorta exhibited medial hypertrophy in HF diet-induced hypertension versus control, but neither displayed a hyperresponsive contraction to the α-adrenergic agonist phenylephrine nor an endothelial cell dysfunction as measured by acetylcholine-induced relaxation. A beneficial PVAT function, support of stress relaxation, was reduced in the male versus female rats fed a HF diet. PVAT in the aorta of males but not in females retained the anticontractile activity. We conclude that this HF model does not display the same vascular dysfunctions observed in essential hypertension. Moreover, both male and female show significantly different vascular dysfunctions in this HF feeding model.NEW & NOTEWORTHY Although the aorta exhibits medial hypertrophy in response to HF diet-induced hypertension, it did not exhibit hyperresponsive contraction to an α-adrenergic agonist nor endothelial cell dysfunction; this was true for both sexes. Unlike other hypertension models, PVAT around aorta from (male) rats on the HF diet retained significant anticontractile activity. PVAT around aorta of the male on a HF diet was modestly more fibrotic and lost the ability to assist in arterial stress relaxation.

Role of Rho in Salt-Sensitive Hypertension

A high amount of salt in the diet increases blood pressure (BP) and leads to salt-sensitive hypertension in individuals with impaired renal sodium excretion. Small guanosine triphosphatase (GTP)ase Rho and Rac, activated by salt intake, play important roles in the pathogenesis of salt-sensitive hypertension as key switches of intracellular signaling. Focusing on Rho, high salt intake in the central nervous system increases sodium concentrations of cerebrospinal fluid in salt-sensitive subjects via Rho/Rho kinase and renin-angiotensin system activation and causes increased brain salt sensitivity and sympathetic nerve outflow in BP control centers. In vascular smooth muscle cells, Rho-guanine nucleotide exchange factors and Rho determine sensitivity to vasoconstrictors such as angiotensin II (Ang II), and facilitate vasoconstriction via G-protein and Wnt pathways, leading to increased vascular resistance, including in the renal arteries, in salt-sensitive subjects with high salt intake. In the vascular endothelium, Rho/Rho kinase inhibits nitric oxide (NO) production and function, and high salt amounts further augment Rho activity via asymmetric dimethylarginine, an endogenous inhibitor of NO synthetase, causing aberrant relaxation and increased vascular tone. Rho-associated mechanisms are deeply involved in the development of salt-sensitive hypertension, and their further elucidation can help in developing effective protection and new therapies.

Low-Frequency (20 kHz) Ultrasonic Modulation of Drug Action

We tested the effect of low-frequency ultrasound (LUS, 20 kHz, 4 W/cm²) on the function of rat mesentery and human pulmonary arteries with wire myography. The vessels were induced to contract with either noradrenaline or physiologic saline solution (PSS) with a high potassium concentration (KPSS) and then incubated with capsaicin (2.1 × 10^-7 M, TRPV1 [transient receptor potential vanilloid 1] activator), dopamine (1 × 10^-4 M, dopamine and α₂-receptor activator), or fenoldopam (dopamine_A1 receptor agonist, 1 × 10^-4 M) with and without glibenclamide (1 μM, KATP [adenosine triphosphate {sensitive potassium channel (ATP)}-sensitive potassium channel] inhibitor and α₂-receptor modulator), and insonated. Vessels were incubated in Ca²⁺-free PSS and induced to contract with added extracellular Ca²⁺ and noradrenaline. Pulmonary arteries were induced to contract with KPSS and dopamine. Then the vessels were insonated. LUS inhibited the influx of external Ca²⁺, inhibited the dopamine-induced vasoconstriction in the KPSS (glibenclamide reversible), reduced the capsaicin-induced vasorelaxation, increased the gentamicin-induced vasorelaxation and increased the dopamine-induced contraction in the KPSS in human pulmonary arteries.

Serum calcium-magnesium ratio in women with pre-eclampsia at a tertiary hospital in Nigeria

OBJECTIVE

To determine the serum calcium-magnesium ratio in pre-eclampsia and compare with normotensives.

METHODS

A case-control study was conducted in a tertiary hospital between October 2017 and March 2018 among 81 pregnant women (27 cases and 54 controls matched for age, gestational age, and parity). An interviewer-administered questionnaire was used to obtain data on demography/clinical history. Venous blood was collected without stasis and sent for biochemical analysis. Statistical analysis used IBM SPSS 21.0.

RESULTS

The levels of serum Ca²⁺ (7.73 + 1.24 vs 9.17 + 0.77; P<0.001), Ca²⁺ -Mg²⁺ ratio (3.36 + 0.60 vs 3.83 + 0.41; P=0.001), and Mg²⁺ (2.35 + 0.35 vs 2.41 + 0.16; P=0.469) were lower among cases. Serum Ca²⁺ level correlated negatively with systolic (r=0.45, P=0.05) and diastolic blood pressure (r=0.50, P=0.010) among the cases. Hypocalcemia was a risk factor (adjusted odds ratio [AOR] 7.63, 95% confidence interval [CI] 1.64-35.37) while social classes 2 and 3 were protective factors (AOR 0.01, 95% CI 0.00-0.46 and AOR 0.01, 95% CI 0.00-0.24, respectively) against pre-eclampsia.

CONCLUSION

The result of this research supported the implication of micronutrients in pre-eclampsia and may help to understand the pathophysiological process of pre-eclampsia. It will also help to establish and enhance existing preventive strategies for the condition. The recommendation by WHO on calcium supplementation in pregnancy as a step in preventing the occurrence of pre-eclampsia should be practiced.

Vascular smooth muscle contraction in hypertension

Hypertension is a major risk factor for many common chronic diseases, such as heart failure, myocardial infarction, stroke, vascular dementia, and chronic kidney disease. Pathophysiological mechanisms contributing to the development of hypertension include increased vascular resistance, determined in large part by reduced vascular diameter due to increased vascular contraction and arterial remodelling. These processes are regulated by complex-interacting systems such as the renin-angiotensin-aldosterone system, sympathetic nervous system, immune activation, and oxidative stress, which influence vascular smooth muscle function. Vascular smooth muscle cells are highly plastic and in pathological conditions undergo phenotypic changes from a contractile to a proliferative state. Vascular smooth muscle contraction is triggered by an increase in intracellular free calcium concentration ([Ca²⁺]_i), promoting actin–myosin cross-bridge formation. Growing evidence indicates that contraction is also regulated by calcium-independent mechanisms involving RhoA-Rho kinase, protein Kinase C and mitogen-activated protein kinase signalling, reactive oxygen species, and reorganization of the actin cytoskeleton. Activation of immune/inflammatory pathways and non-coding RNAs are also emerging as important regulators of vascular function. Vascular smooth muscle cell [Ca²⁺]_i not only determines the contractile state but also influences activity of many calcium-dependent transcription factors and proteins thereby impacting the cellular phenotype and function. Perturbations in vascular smooth muscle cell signalling and altered function influence vascular reactivity and tone, important determinants of vascular resistance and blood pressure. Here, we discuss mechanisms regulating vascular reactivity and contraction in physiological and pathophysiological conditions and highlight some new advances in the field, focusing specifically on hypertension.

Vascular Smooth Muscle Remodeling in Conductive and Resistance Arteries in Hypertension

Cardiovascular disease is a leading cause of death worldwide and accounts for >17.3 million deaths per year, with an estimated increase in incidence to 23.6 million by 2030. ¹ Cardiovascular death represents 31% of all global deaths ² -with stroke, heart attack, and ruptured aneurysms predominantly contributing to these high mortality rates. A key risk factor for cardiovascular disease is hypertension. Although treatment or reduction in hypertension can prevent the onset of cardiovascular events, existing therapies are only partially effective. A key pathological hallmark of hypertension is increased peripheral vascular resistance because of structural and functional changes in large (conductive) and small (resistance) arteries. In this review, we discuss the clinical implications of vascular remodeling, compare the differences between vascular smooth muscle cell remodeling in conductive and resistance arteries, discuss the genetic factors associated with vascular smooth muscle cell function in hypertensive patients, and provide a prospective assessment of current and future research and pharmacological targets for the treatment of hypertension.

Selective inhibition of histone deacetylase 8 improves vascular hypertrophy, relaxation, and inflammation in angiotensin II hypertensive mice

Background

The dysregulation of histone deacetylase (HDAC) protein expression or its enzyme activity is implicated in a variety of diseases. Cardiac HDAC6 and HDAC8 enzyme activity induced by deoxycorticosterone acetate (DOCA) hypertension was attenuated by sodium valproate, a pan-HDAC inhibitor. However, the HDAC6-selective inhibitor, tubastatin A, did not attenuate angiotensin II-induced hypertension. The purpose of this study was to investigate whether PCI34051, an HDAC8-selective inhibitor, can modulate angiotensin II-induced hypertension and its regulatory mechanism.

Methods

An angiotensin II-regulated mouse model was used in this study. Animals received vehicle or PCI34051 (3 mg·kg - ¹·day- ¹) via intraperitoneal injection. Systolic blood pressure was measured by the tail-cuff method. Blood vessel thickness was measured following hematoxylin and eosin staining, VCAM-1 immunohistochemistry was performed in the aortas, and mRNA expression of renin-angiotensin system components, inflammation markers, and NADPH oxidase (Nox) was determined by RT-PCR. The effect of PCI34051 on vasorelaxation was studied in rat aortic rings, and its effect on nitric oxide (NO) production was determined using DAF-FM DA, a fluorescent dye, in human umbilical vascular endothelial cells (HUVECs).

Results

PCI34051 administration reduced systolic blood pressure via downregulation of angiotensin II receptor type 1 (AT1) mRNA expression. PCI34051 treatment attenuated vascular hypertrophy by decreasing E2F3 and GATA6 mRNA expression. Vascular relaxation after PCI34051 treatment was more dependent on vascular endothelial cells and it was blocked by an NO synthase (NOS) inhibitor. In addition, NO production increased in HUVECs after PCI34051 treatment; this was decreased by the NOS inhibitor. The expression of inflammatory molecules and adhesion molecules VCAM-1 and ICAM-1 decreased in the aortas of angiotensin II-infused mice after PCI34051 administration. However, PCI34051 did not affect Nox or its regulatory subunits.

Conclusions

PCI34051 lowered high blood pressure through modulation of arterial remodeling, vasoconstriction, and inflammation in an angiotensin II-induced hypertension model. We suggest that HDAC8 could be a potential therapeutic target for hypertension.

Angiotensin II-Regulated Autophagy Is Required for Vascular Smooth Muscle Cell Hypertrophy

Hypertension is a disease associated to increased plasma levels of angiotensin II (Ang II). Ang II can regulate proliferation, migration, ROS production and hypertrophy of vascular smooth muscle cells (VSMCs). However, the mechanisms by which Ang II can affect VSMCs remain to be fully elucidated. In this context, autophagy, a process involved in self-digestion of proteins and organelles, has been described to regulate vascular remodeling. Therefore, we sought to investigate if Ang II regulates VSMC hypertrophy through an autophagy-dependent mechanism. To test this, we stimulated A7r5 cell line and primary rat aortic smooth muscle cells with Ang II 100 nM and measured autophagic markers at 24 h by Western blot. Autophagosomes were quantified by visualizing fluorescently labeled LC3 using confocal microscopy. The results showed that treatment with Ang II increases Beclin-1, Vps34, Atg-12-Atg5, Atg4 and Atg7 protein levels, Beclin-1 phosphorylation, as well as the number of autophagic vesicles, suggesting that this peptide induces autophagy by activating phagophore initiation and elongation. These findings were confirmed by the assessment of autophagic flux by co-administering Ang II together with chloroquine (30 μM). Pharmacological antagonism of the angiotensin type 1 receptor (AT1R) with losartan and RhoA/Rho Kinase inhibition prevented Ang II-induced autophagy. Moreover, Ang II-induced A7r5 hypertrophy, evaluated by α-SMA expression and cell size, was prevented upon autophagy inhibition. Taking together, our results suggest that the induction of autophagy by an AT1R/RhoA/Rho Kinase-dependent mechanism contributes to Ang II-induced hypertrophy in VSMC.

Inhibition of endoplasmic reticulum stress protected DOCA-salt hypertension-induced vascular dysfunction

Hypertension has complex vascular pathogenesis and therefore the molecular etiology remains poorly elucidated. Endoplasmic reticulum stress (ERS), which is a condition of the unfolded/misfolded protein accumulation in the endoplasmic reticulum, has been defined as a potential target for cardiovascular disease. In the present study, the effects of ERS inhibition on hypertension-induced alterations in the vessels were investigated. In male Wistar albino rats, hypertension was induced through unilateral nephrectomy, deoxycorticosterone-acetate (DOCA) injection (20 mg/kg, twice a week) and 1% NaCl with 0.2% KCI added to drinking water for 12 weeks. An ERS inhibitor, tauroursodeoxycolic acid (TUDCA) (150 mg/kg/day, i.p.), was administered for the final four weeks. ERS inhibition in DOCA-salt induced hypertension was observed to have reduced systolic blood pressure, improved endothelial dysfunction, enhanced plasma nitric oxide (NO) level, reduced protein expressions of phosphorylated-double-stranded RNA-activated protein kinase-like endoplasmic reticulum kinase (pPERK), 78 kDa glucose-regulated protein (GRP78), Inositol trisphosphate receptor1 (IP₃R1) and Epidermal growth factor receptor (EGFR), increased expressions of endoplasmic reticulum Ca²⁺-ATPase2 (SERCA2) and B cell lymphoma2 (Bcl2) in vessels. These findings suggest that the beneficial effects of ERS inhibition on hypertension may be related to protection of vessel functions through restoration of endoplasmic reticulum calcium homeostasis, and apoptotic and mitotic pathways.

Effects of hypoestrogenism and/or hyperaldosteronism on myocardial remodeling in female mice

We investigated the potential adverse effects of hyperaldosteronism and/or hypoestrogenism on cardiac phenotype, and examined their combined effects in female mice overexpressing cardiac aldosterone synthase (AS). We focused on some signaling cascades challenging defensive responses to adapt and/or to survive in the face of double deleterious stresses, such as Ca2+ -homeostasis, pro/anti-hypertrophic, endoplasmic reticulum stress (ER stress), pro- or anti-apoptotic effectors, and MAP kinase activation, and redox signaling. These protein expressions were assessed by immunoblotting at 9 weeks after surgery. Female wild type (FWT) and FAS mice were fed with phytoestrogen-free diet; underwent ovariectomy (Ovx) or sham-operation (Sham). Ovx increased gain weight and hypertrophy index. Transthoracic echocardiograghy was performed. Both Ovx-induced heart rate decrease and fractional shortening increase were associated with collagen type III shift. Cardiac estrogen receptor (ERα, ERβ) protein expression levels were downregulated in Ovx mice. Hypoestrogenism increased plasma aldosterone and MR protein expression in FAS mice. Both aldosterone and Ovx played as mirror effects on up and downstream signaling effectors of calcium/redox homeostasis, apoptosis, such as concomitant CaMKII activation and calcineurin down-regulation, MAP kinase inhibition (ERK1/2, p38 MAPK) and Akt activation. The ratio Bcl2/Bax is in favor to promote cell survivor. Finally, myocardium had dynamically orchestrated multiple signaling cascades to restore tolerance to hostile environment thereby contributing to a better maintenance of Ca2+ /redox homeostasis. Ovx-induced collagen type III isoform shift and its upregulation may be important for the biomechanical transduction of the heart and the recovery of cardiac function in FAS mice. OVX antagonized aldosterone signaling pathways.

The effects of LXR agonist GW3965 on vascular reactivity and inflammation in hypertensive rat aorta

AIMS

Liver X receptors (LXRs) play an important role in the regulation of cholesterol, fatty acid and glucose metabolisms together with inflammatory processes. In the present study, the effects of LXR agonist GW3965 on vascular reactivity and expression of functional proteins in DOCA-Salt induced hypertension were examined.

MAIN METHODS

Hypertension was induced through unilateral nephrectomy and deoxycorticosterone-acetate (DOCA) injection (20 mg/kg, twice a week) for 6 weeks in male Wistar albino rats (8 weeks old). An LXR agonist GW3965 (10 mg/kg/day, i.p.) was administered to animals for last seven days.

KEY FINDINGS

GW3965 treatment reduced systolic blood pressures in hypertensive rats. Acetylcholine-induced endothelium-dependent and sodium nitroprusside-induced endothelium-independent vasorelaxations were decreased in hypertensive rats but not affected by GW3965. GW3965 treatment enhanced plasma nitrite levels in normotensive rats. KCl and phenylephrine (Phe)-induced vasocontractions were reduced in hypertensive groups and increased with GW3965 treatment. Decreased sarco/endoplasmic reticulum Ca²⁺-ATPase2 (SERCA2) expression in the hypertensive aorta was not changed by GW3965 treatment. Expression of inositoltrisphosphate receptor1 (IP3R1) was increased by GW3965 in normotensive animals. The nuclear factor kappaB (NF-κB) and tumor necrosis factor alpha (TNF-α) expressions were increased in hypertensive rats and reduced by GW3965 treatment.

SIGNIFICANCE

The results of study indicate that the LXR agonist, GW3965, exhibited a beneficial effect on increased blood pressure and improved hypertension-induced impairment in contractile activity of vessel and inflammatory markers in vascular tissue. Therefore, these effects of LXR agonists on vessel should be taken into account in experimental or therapeutic approaches to hypertension.

Targeting Pim Kinases and DAPK3 to Control Hypertension

Sustained vascular smooth muscle hypercontractility promotes hypertension and cardiovascular disease. The etiology of hypercontractility is not completely understood. New therapeutic targets remain vitally important for drug discovery. Here we report that Pim kinases, in combination with DAPK3, regulate contractility and control hypertension. Using a co-crystal structure of lead molecule (HS38) in complex with DAPK3, a dual Pim/DAPK3 inhibitor (HS56) and selective DAPK3 inhibitors (HS94 and HS148) were developed to provide mechanistic insight into the polypharmacology of hypertension. In vitro and ex vivo studies indicated that Pim kinases directly phosphorylate smooth muscle targets and that Pim/DAPK3 inhibition, unlike selective DAPK3 inhibition, significantly reduces contractility. In vivo, HS56 decreased blood pressure in spontaneously hypertensive mice in a dose-dependent manner without affecting heart rate. These findings suggest including Pim kinase inhibition within a multi-target engagement strategy for hypertension management. HS56 represents a significant step in the development of molecularly targeted antihypertensive medications.

Cardiovascular and Hemostatic Disorders: Role of STIM and Orai Proteins in Vascular Disorders

Store-operated Ca²⁺ entry (SOCE) mediated by STIM and Orai proteins is a highly regulated and ubiquitous signaling pathway that plays an important role in various cellular and physiological functions. Endoplasmic reticulum (ER) serves as the major site for intracellular Ca²⁺ storage. Stromal Interaction Molecule 1/2 (STIM1/2) sense decrease in ER Ca²⁺ levels and transmits the message to plasma membrane Ca²⁺ channels constituted by Orai family members (Orai1/2/3) resulting in Ca²⁺ influx into the cells. This increase in cytosolic Ca²⁺ in turn activates a variety of signaling cascades to regulate a plethora of cellular functions. Evidence from the literature suggests that SOCE dysregulation is associated with several pathophysiologies, including vascular disorders. Interestingly, recent studies have suggested that STIM proteins may also regulate vascular functions independent of their contribution to SOCE. In this updated book chapter, we will focus on the physiological role of STIM and Orai proteins in the vasculature (endothelial cells and vascular smooth muscle cells). We will further retrospect the literature implicating a critical role for these proteins in vascular disease.

Mineralocorticoid regulation of cell function: the role of rapid signalling and gene transcription pathways

The mineralocorticoid receptor (MR) and mineralocorticoids regulate epithelial handling of electrolytes, and induces diverse effects on other tissues. Traditionally, the effects of MR were ascribed to ligand-receptor binding and activation of gene transcription. However, the MR also utilises a number of intracellular signalling cascades, often by transactivating unrelated receptors, to change cell function more rapidly. Although aldosterone is the physiological mineralocorticoid, it is not the sole ligand for MR. Tissue-selective and mineralocorticoid-specific effects are conferred through the enzyme 11β-hydroxysteroid dehydrogenase 2, cellular redox status and properties of the MR itself. Furthermore, not all aldosterone effects are mediated via MR, with implication of the involvement of other membrane-bound receptors such as GPER. This review will describe the ligands, receptors and intracellular mechanisms available for mineralocorticoid hormone and receptor signalling and illustrate their complex interactions in physiology and disease.

Age-Related Reduction of Contractile Responses to Urotensin II Is Seen in Aortas from Wistar Rats but Not from Type 2 Diabetic Goto-Kakizaki Rats

Vascular dysfunction is a common finding in type 2 diabetes, although the response to urotensin II (UII), a potent vasoconstrictor peptide, remains unclear. We investigated whether a UII-induced contraction was increased in the aortas from type 2 diabetic Goto-Kakizaki (GK) rats at the chronic stage. At 36 or 37 weeks of age (older group), a UII-induced contraction was seen in GK rats and was reduced by a Rho kinase inhibitor or urotensin receptor (UT) antagonist, whereas UII failed to induce a contraction in aortas from age-matched Wistar rats. In UII-stimulated aortas, the expression of Rho kinases, Rho A, and phosphorylated myosin phosphatase target subunit 1 did not change between the two groups; however, phosphorylation of extracellular-regulated kinase 1/2 and p38 mitogen-activated protein kinase (MAPK) was greater in GK than in Wistar rats. Compared to intact aortas, UII-induced contractions were slightly, but not significantly, increased by endothelial denudation of the aortas of Wistar rats at 24 weeks of age. At 6 weeks of age (young group), the UII-induced contractions were seen in GK and Wistar groups. The total expression and the membrane-to-cytosol ratio of the UT protein slightly decreased in Wistar aortas with aging but not in GK aortas. These results demonstrate that the UII-induced contraction gradually decreased with aging in Wistar rats and was preserved in type 2 diabetes. Although alterations of UII-induced contractions during aging and type 2 diabetes may be associated with kinase activities (MAPKs or Rho kinase) or receptor profiles, further investigations are necessary to clarify the mechanisms.

Endothelium- and smooth muscle-dependent vasodilator effects of Citrus aurantium L. var. amara: Focus on Ca(2+) modulation

Neroli, the essential oil of Citrus aurantium L. var. amara, is a well-characterized alleviative agent used to treat cardiovascular symptoms. However, because it has been found to have multiple effects, its mechanism of action requires further exploration. We sought to clarify the mechanism underlying the actions of neroli in mouse aorta. In aortic rings from mice precontracted with prostaglandin F2 alpha, neroli induced vasodilation. However, relaxation effect of neroli was decreased in endothelium-denuded ring or pre-incubation with the nitric oxide synthase inhibitor NG-Nitro-l-arginine-methyl ester (L-NAME). And also, neroli-induced relaxation was also partially reversed by 1H-[1,2,4] oxadiazolo [4,3-a] quinoxalin-1-one (ODQ), a soluble guanylyl cyclase (sGC) inhibitor. In addition, neroli inhibited extracellular Ca(2+)-dependent, depolarization-induced contraction, an effect that was concentration dependent. Pretreatment with the non-selective cation channel blocker, Ni(2+), attenuated neroli-induced relaxation, whereas the K(+) channel blocker, tetraethylammonium chloride, had no effect. In the presence of verapamil, added to prevent Ca(2+) influx via smooth muscle voltage-gated Ca(2+) channels, neroli-induced relaxation was reduced by the ryanodine receptor (RyR) inhibitor ruthenium red. Our findings further indicate that the endothelial component of neroli-induced vasodilation is partly mediated by the NO-sGC pathway, whereas the smooth muscle component involves modulation of intracellular Ca(2+) concentration through inhibition of cation channel-mediated extracellular Ca(2+) influx and store-operated Ca(2+) release mediated by the RyR signaling pathway.

Multiple activation mechanisms of serotonin-mediated contraction in the carotid arteries obtained from spontaneously hypertensive rats

Serotonin (5-hydroxytryptamine, 5-HT) is an important endogenous substance that regulates the vascular tone, and the abnormal signaling of 5-HT has been observed in the arteries under several pathophysiological conditions such as diabetes and hypertension. However, signaling pathways of 5-HT-mediated vasocontraction in hypertension remain unclear. Therefore, we tested the hypothesis that 5-HT-mediated contraction and contributions of various kinases such as mitogen-activated protein kinases (MAPKs), phosphoinositide 3-kinase (PI3K), Rho kinase (ROCK), and 3-phosphoinositide-dependent kinase 1 (PDK1) to the contraction would be altered in the carotid arteries obtained from spontaneously hypertensive rats (SHR) compared to control Wistar Kyoto (WKY) rats. In the carotid arteries from SHR (vs. those from WKY), (1) the 5-HT-mediated contraction was increased, whereas the norepinephrine-mediated contraction was not; (2) 5-HT-mediated contractions were partly inhibited by each kinase (extracellular signal-regulated kinase 1/2 (ERK1/2), p38 MAPK, c-Jun N-terminal kinase (JNK), PI3K, ROCK, and PDK1) inhibitor; and (3) 5-HT-stimulated phosphorylation of ERK1/2, p38 MAPK, JNK, myosin phosphatase target subunit 1 (MYPT1), and PDK1 was increased. The expression of ROCK2 but not ROCK1 was increased in the carotid arteries from SHR compared to WKY. The expression of 5-HT2A receptor, a major receptor of 5-HT-mediated contraction in rat carotid artery, was similar in carotid arteries between the two groups. These results suggest that 5-HT-mediated contraction was utilized multiple signaling pathways such as ERK1/2, p38 MAPK, JNK, PI3K, ROCK, and PDK1. Although 5-HT-mediated contraction was increased in the carotid arteries obtained from SHR, further studies are necessary to clarify how each kinase may integrate in the vascular smooth muscles under hypertension.

Insulin augments serotonin-induced contraction via activation of the IR/PI3K/PDK1 pathway in the rat carotid artery

Hyperinsulinemia associated with type 2 diabetes may contribute to the development of vascular diseases. Although we recently reported that enhanced contractile responses to serotonin (5-hydroxytryptamine, 5-HT) are observed in the arteries of type 2 diabetes models, the causative factors and detailed signaling pathways involved remain unclear. The purpose of this study was to investigate whether high insulin would be an amplifier of 5-HT-induced contraction in rat carotid arteries and whether the contraction involves phosphoinositide 3-kinase (PI3K)/3-phosphoinositide-dependent protein kinase 1 (PDK1) signaling, an insulin-mediated signaling pathway. In rat carotid arteries organ-cultured with insulin (for 24 h), (1) the contractile responses to 5-HT were significantly greater (vs. vehicle), (2) the insulin-induced enhancement of 5-HT-induced contractions was largely suppressed by inhibitors of the insulin receptor (IR) (GSK1838705A), PI3K (LY294002), and PDK1 (GSK2334470), and (3) the levels of phosphorylated forms of both PDK1 and myosin phosphatase target subunit 1 (MYPT1) were greater upon 5-HT stimulation. In addition, in rat carotid arteries organ-cultured with an activator of PDK1 (PS48), the 5-HT-induced contraction was greater, and this was suppressed by PDK1 inhibition but not PI3K inhibition. In addition, MYPT1 and PDK1 phosphorylation upon 5-HT stimulation was enhanced (vs. vehicle). These results suggest that high insulin levels amplify 5-HT-induced contraction. Moreover, the present results indicated the direct linkage between IR/PI3K/PDK1 activation and 5-HT-induced contraction in rat carotid arteries for the first time.

The COP9 signalosome and vascular function: intriguing possibilities?

Disorders of vascular function contribute importantly to cardiovascular disease which represents a substantial cause of morbidity and mortality worldwide. An emerging paradigm in the study of cardiovascular diseases is that protein ubiquitination and turnover represent key pathological mechanisms. Our understanding of these processes in the vasculature is growing but remains incomplete. Since protein ubiquitination and turnover can represent a terminal event in the life of a given protein, entry into these pathways must be highly regulated. However, at present understanding of these regulatory mechanisms, particularly in the vasculature, is fragmentary. The COP9 (constitutive photomorphogenic mutant 9) signalosome (CSN) is a heteromeric protein complex implicated in the control of protein degradation. The CSN participates critically in the control of Cullin Ring Ligases (CRLs), at least in part via the detachment of a small protein, Nedd8 (deneddylation). CRLs are one of the largest groups of ubiquitin ligases, which represent the most selective control point for protein ubiquitination. Thus, the CSN by virtue of its ability to control the CRLs ubiquitin ligase activity is ideally positioned to effect selective modulation of protein turnover. This review surveys currently available data regarding the potential role of the CSN in control of vascular function. Data potentially linking the CSN to control of regulatory proteins involved in vascular smooth muscle proliferation and to vascular smooth muscle contraction are presented with the intent of providing potentially intriguing possibilities for future investigation.