Vascular Myocytes Research Articles

Cardiovascular Changes Among Healthy Elderly

World Health Organization (WHO) defines health as a complete physical, mental, and social well-being and not merely the absence of disease or infirmity. Health is one of the important and valuable values among the elderly. Aging is a progress of life in each individual. Unlike pathological conditions, the aging process will occurs in each individual. Elderly tend to experience physical, mental, and spiritual deterioration. The health status of each individual can have an impact on changes in cardiovascular function in the elderly. After each individual reaches the age of 30, heart-lung fitness decreases by 1% for each age, which increases by one year. At the age of 60, heart-lung fitness will decrease until 35%. The aim of conducting this literature review is to provide an understanding of the cardiovascular changes among healthy elderly. The main effects aging on the cardiovascular system are a changes in vascular structure, a decrease in vascular function, myocytes and atrial pacemaker cells, an increase in cardiac fibrous tissue, a decrease in the function of the ventricular, myocardial contraction, and cardiac output which results in impaired cardiovascular fitness among elderly.

Androgen Effects on the Adrenergic System of the Vascular, Airway, and Cardiac Myocytes and Their Relevance in Pathological Processes.

Introduction Androgen signaling comprises nongenomic and genomic pathways. Nongenomic actions are not related to the binding of the androgen receptor (AR) and occur rapidly. The genomic effects implicate the binding to a cytosolic AR, leading to protein synthesis. Both events are independent of each other. Genomic effects have been associated with different pathologies such as vascular ischemia, hypertension, asthma, and cardiovascular diseases. Catecholamines play a crucial role in regulating vascular smooth muscle (VSM), airway smooth muscle (ASM), and cardiac muscle (CM) function and tone. Objective The aim of this review is an updated analysis of the role of androgens in the adrenergic system of vascular, airway, and cardiac myocytes. Body. Testosterone (T) favors vasoconstriction, and its concentration fluctuation during life stages can affect the vascular tone and might contribute to the development of hypertension. In the VSM, T increases α1-adrenergic receptors (α1-ARs) and decreases adenylyl cyclase expression, favoring high blood pressure and hypertension. Androgens have also been associated with asthma. During puberty, girls are more susceptible to present asthma symptoms than boys because of the increment in the plasmatic concentrations of T in young men. In the ASM, β2-ARs are responsible for the bronchodilator effect, and T augments the expression of β2-ARs evoking an increase in the relaxing response to salbutamol. The levels of T are also associated with an increment in atherosclerosis and cardiovascular risk. In the CM, activation of α1A-ARs and β2-ARs increases the ionotropic activity, leading to the development of contraction, and T upregulates the expression of both receptors and improves the myocardial performance. Conclusions Androgens play an essential role in the adrenergic system of vascular, airway, and cardiac myocytes, favoring either a state of health or disease. While the use of androgens as a therapeutic tool for treating asthma symptoms or heart disease is proposed, the vascular system is warmly affected.

TRPV1 expressed throughout the arterial circulation regulates vasoconstriction and blood pressure.

The functional roles of the capsaicin receptor, TRPV1, outside of sensory nerves are unclear. We mapped TRPV1 in the mouse circulation, revealing extensive expression in the smooth muscle of resistance arterioles supplying skeletal muscle, heart and adipose tissue. Activation of TRPV1 in vascular myocytes constricted arteries, reduced coronary flow in isolated hearts and increased systemic blood pressure. These functional effects were retained after sensory nerve ablation, indicating specific signalling by arterial TRPV1. TRPV1 mediated the vasoconstrictive and blood pressure responses to the endogenous inflammatory lipid lysophosphatidic acid. These results show that TRPV1 in arteriolar myocytes modulates regional blood flow and systemic blood pressure, and suggest that TRPV1 may be a target of vasoactive inflammatory mediators. The capsaicin receptor, TRPV1, is a key ion channel involved in inflammatory pain signalling. Although mainly studied in sensory nerves, there are reports of TRPV1 expression in isolated segments of the vasculature, but whether the channel localizes to vascular endothelium or smooth muscle is controversial and the distribution and functional roles of TRPV1 in arteries remain unknown. We mapped functional TRPV1 expression throughout the mouse arterial circulation. Analysis of reporter mouse lines TRPV1PLAP-nlacZ and TRPV1-Cre:tdTomato combined with Ca2+ imaging revealed specific localization of TRPV1 to smooth muscle of terminal arterioles in the heart, adipose tissue and skeletal muscle. Capsaicin evoked inward currents (current density ∼10% of sensory neurons) and raised intracellular Ca2+ levels in arterial smooth muscle cells, constricted arterioles ex vivo and in vivo and increased systemic blood pressure in mice and rats. Further, capsaicin markedly and dose-dependently reduced coronary flow. Pharmacological and/or genetic disruption of TRPV1 abolished all these effects of capsaicin as well as vasoconstriction triggered by lysophosphatidic acid, a bioactive lipid generated by platelets and atherogenic plaques. Notably, ablation of sensory nerves did not affect the responses to capsaicin revealing a vascular smooth muscle-restricted signalling mechanism. Moreover, unlike in sensory nerves, TRPV1 function in arteries was resistant to activity-induced desensitization. Thus, TRPV1 activation in vascular myocytes enables a persistent depolarizing current, leading to constriction of coronary, skeletal muscle and adipose arterioles and a sustained increase in systemic blood pressure.

TRPML channel activation partially rescues Ca2+ spark activity in sheep fetal pulmonary arterial myocytes following intrauterine long‐term hypoxia

Ca2+ sparks result from the activation of ryanodine receptors located on the sarcoplasmic reticulum of pulmonary arterial smooth muscle cells. These Ca2+ sparks activate potassium channels on the plasma membrane and are important to arterial vasodilation and increases in vascular blood flow. Previous studies showed that long‐term high altitude hypoxia restricted membrane depolarization elicited Ca2+ spark activity in fetal lamb pulmonary arterial myocytes, but had little effect on pulmonary myocytes in adult sheep. Moreover, the studies also indicated that there was preservation of the sarcoplasmic reticulum Ca2+ stores in pulmonary arterial myocytes of both fetuses and adults as determined through direct activation of ryanodine receptors with caffeine. Given that the sarcoplasmic reticulum Ca2+ stores are intact and have functional ryanodine receptors we hypothesize that aberrations to the canonical membrane depolarization Ca2+ spark triggering pathway in fetal pulmonary arterial myocytes due to intrauterine hypoxia can be resolved through activation of alternate pathways. Recent studies illustrated that Ca2+ sparks were triggered in various vascular myocytes by releasing Ca2+ from lysosomes through activation of TRPML (transient receptor potential cation channel, mucolipin subfamily) channels. To evaluate the potential that TRPML activation may elicit Ca2+ sparks in fetal and adult pulmonary arterial myocytes we studied isolated pulmonary arteries from near term fetal and adult sheep from low altitude (700 m) or those that had been exposed to high altitude (3801 m) for 110+ days. Ca2+ sparks were recorded using laser scanning confocal microscopy while 10 μM MLSA1 was used to activate TRPML channels. MLSA1 enhanced the activity of Ca2+ sparks in myocytes of adult pulmonary arteries to a greater extent than those from fetuses, suggesting developmental changes in the communication of lysosomes with the sarcoplasmic reticulum. Of importance, TRPML activation by MLSA1 partially recovered the aberrant Ca2+ spark activity in fetal pulmonary arterial myocytes caused by hypoxia. The findings suggest that ryanodine receptor activation through pathways alternate to membrane depolarization may hold promise for improving pulmonary vascular function following intrauterine hypoxic exposure.Support or Funding InformationImaging was performed in the LLUSM Advanced Imaging and Microscopy Core with support of NSF Grant MRI‐DBI 0923559 (SMW) and the Loma Linda University School of Medicine. Additional support provided through NIH grant HD083132 (LZ).

Effect of Natural Cytokine Complex on Metabolism of Smooth Muscle Cells in Myocardial Arteries under Normal Conditions and during Hemodynamic Overload.

Histoenzymological methods were employed to examine the effects of systemically administered natural cytokine complex including IL-1, IL-2, IL-6, TNFα, MIF, and TGFβ on metabolism of smooth muscle cells in intramural myocardial arteries under physiological conditions and during acute hemodynamic overload of the heart. Natural cytokine complex markedly inhibited metabolism of vascular smooth muscle cells under control conditions and during acute experimental aortal stenosis. In vascular smooth muscle cells, deceleration of tricarboxylic acid cycle, redistribution of the fluxes in glycolytic cascade and its inhibition, down-regulation of oxidation of free fatty acids and their metabolites, and inhibition of the shuttle systems and biosynthetic processes were observed. Inhibition of metabolism in the vascular wall of myocardial arteries correlated with a decrease in their tone and could be partially determined by a decrease in contractile activity of smooth muscle cells. These findings do not exclude the involvement of other factors and mechanisms in down-regulation of metabolism in vascular myocytes in response to increased cytokines levels of in the blood, including their direct effect on biochemical processes in cells.

Thyroid and Cardiovascular Disease: A Focused Review on the Impact of Hyperthyroidism in Heart Failure.

The association between thyroid hormones and cardiovascular conditions has been well studied, specifically, the effects of hypothyroidism on cardiomyopathy, and hyperthyroidism with arrhythmias. Nonetheless, an explicit correlation between hyperthyroidism and cardiomyopathy has yet to be established. Medical databases MEDLINE and PubMed were accessed and queried as primary sources for data acquisition. Search criteria consisted of “hyperthyroidism”, “heart failure”, and “thyroid and cardiovascular system”, which allowed the retrieval of relevant and recent works. From these sources, a consensus was developed and employed to yield an updated review of the etiology of heart failure in the setting of hyperthyroidism. It is rare for patients with hyperthyroidism to remain in a chronic hyperthyroid state, making it difficult to analyze subsequent long-term effects on the cardiovascular system. Related to heart failure, some studies have demonstrated no change in ejection fraction, while others have shown an acute change along with diastolic dysfunction, with or without an underlying rhythm abnormality. Further investigation is warranted to elucidate the mechanism driving such cardiac dysfunction, and whether it is due to vascular changes, tachyarrhythmias, or myocyte remodeling and fibrosis. The intent of this review article is to improve our understanding of how a hyperthyroid state affects cardiovascular function. An enhanced understanding of the effects on cardiovascular physiology will afford physicians the ability to provide more comprehensive care in consideration of both endocrine and cardiovascular pathologies.

Concentration-Dependent Effects of N-3 Long-Chain Fatty Acids on Na,K-ATPase Activity in Human Endothelial Cells.

N-3 eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) seem to prevent endothelial dysfunction, a crucial step in atherogenesis, by modulating the levels of vasoactive molecules and by influencing Na,K-ATPase activity of vascular myocytes. The activity of endothelial Na,K-ATPase controls the ionic homeostasis of the neighboring cells, as well as cell function. However, controversy exists with respect to the vascular protective effect of EPA and DHA. We argue that this dispute might be due to the use of different concentrations of EPA and DHA in different studies. Therefore, this study was designed to define an optimal concentration of EPA and DHA to investigate endothelial function. For this purpose, human endothelial cells were exposed for 24 h to different concentrations of DHA or EPA (0–20 μM) to study membrane fluidity, peroxidation potential and Na,K-ATPase activity. EPA and DHA were linearly incorporated and this incorporation was mirrored by the linear increase of unsaturation index, membrane fluidity, and peroxidation potential. Na,K-ATPase activity peaked at 3.75 μM of EPA and DHA and then gradually decreased. It is noteworthy that DHA effects were always more pronounced than EPA. Concluding, low concentrations of EPA and DHA minimize peroxidation sensitivity and optimize Na,K-ATPase activity.

A novel function of calcium sensing receptor in chronic hypoxia-induced pulmonary venous smooth muscle cells proliferation.

Chronic hypoxia (CH) causes remodeling not only in pulmonary arteries but also in pulmonary veins. Pulmonary vascular remodeling stems from increased pulmonary vascular myocyte proliferation. However, the pathogenesis of CH-induced proliferation of pulmonary venous smooth muscle cells (PVSMCs) remains unknown. The present study aimed to explore the mechanisms by which CH affects PVSMCs proliferation. PVSMCs were isolated from rat distal pulmonary veins and exposed to CH (4% O2 for 60 h). The expression of calcium sensing receptor (CaSR) was determined by immunofluorescence, real-time quantitative PCR and Western blotting. Cell proliferation was assessed by cell counting, CCK-8 assay, and BrdU incorporation. Apoptosis analysis was examined by flow cytometry. In rat distal PVSMCs, CH increased the cell number and cell viability and enhanced DNA synthesis, which is accompanied by upregulated mRNA and protein expression levels of CaSR. Two negative CaSR modulators (NPS2143, NPS2390) not only attenuated CH-induced CaSR upregulation but also inhibited CH-induced increases in cell number, cell viability and the proliferation index of PVSMCs, whereas two positive modulators (spermine, R568) not only amplified CH-induced CaSR upregulation but also intensified CH-induced increases in cell number, cell viability and the proliferation index of PVSMCs. Silencing CaSR with siRNA similarly attenuated the CH-induced enhancement of cell number, cell viability and DNA synthesis in PVSMCs. Neither CH nor downregulation of CaSR with siRNA had an effect on apoptosis in PVSMCs. These results suggest that CaSR mediating excessive proliferation is a new pathogenic mechanism involved in the initiation and progression of distal PVSMCs proliferation under CH conditions.

The cGMP-Degrading Enzyme Phosphodiesterase-5 (PDE5) in Cerebral Small Arteries of Older People.

Cerebral small vessel disease in deep penetrating arteries is a major cause of lacunar infarcts, white matter lesions and vascular cognitive impairment. Local cerebral blood flow in these small vessels is controlled by endothelial-derived nitric oxide, which exerts a primary vasodilator stimulus on vascular myocytes, via cytoplasmic cyclic GMP. Here, we investigated whether the cGMP-degrading enzyme phosphodiesterase-5 (PDE5) is present in small penetrating arteries in the deep subcortical white matter of older people. Frontal cortical tissue blocks were examined from donated brains of older people (n = 42, 24 male: 18 female, median age 81, range: 59-100 years). PDE5, detected by immunohistochemical labeling, was graded as absent, sparse, or abundant in vascular cells within small arteries in subcortical white matter (vessel outer diameter: 20-100 µm). PDE5 labeling within arterial myocytes was detected in all cases. Degree of PDE5 expression (absent, sparse, or abundant) was not associated with age or with neuropathological diagnosis of small vessel disease. In conclusion, PDE5 is present in vascular myocytes within small penetrating arteries in older people. This is a potential molecular target for pharmacological interventions.

Nuclear abnormalities in vascular myocytes in cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL).

Cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a stroke and dementia syndrome with degeneration and loss of vascular smooth muscle cells (VSMCs). The disease is due to mutations in NOTCH3 playing an important role in VSMC differentiation, proliferation and apoptosis. Searching for a possible cause of VSMC dysfunction in CADASIL, we investigated morphology and proliferative activity the affected myocytes. In material from autopsy brains and skin-muscle biopsies of patients with CADASIL diagnosis, assessment of VSMCs in arterial vessels at the level of light and electron microscopy was performed. Proliferative activity of VSMCs was evaluated in immune reactions to proliferative markers: proliferating cell nuclear antigen, and cyclins B1 and D. In CADASIL, abnormal morphology of VSMC nuclei was observed in 18.1%, 11.5%, and 6.9% of the cerebral, skin, and skeletal muscle vessels, respectively. The affected myocytes showed variability in nuclear size, irregularity in nuclear shape, and abnormal chromatin appearance. Frequently, double nuclei of equal size or micronuclei were observed. Sometimes, even multinuclear myocytes were found. In some of the nuclei immune reactions to the examined proliferative markers were positive. Aberrant structure and number of VSCM nuclei, and their immunoreactivity to proliferative markers suggest mitotic instability of vascular myocytes in CADASIL. We speculate that mutant NOTCH3 which is unable to control properly VSMC proliferation, and may be responsible for their premature or inappropriate entry into mitosis, irreversible arrest of the cell cycle, senescence or degeneration and loss.

Eosinophilic inflammation in spontaneous coronary artery dissection: A potential therapeutic target?

Spontaneous coronary artery dissection (SCAD), defined as non-traumatic, non-iatrogenic dissociation of coronary vessel wall resulting from intimal disruption or intramural hemorrhage, represents an important cause of sudden death and myocardial infarction among young or middle-aged women without conventional risk factors for atherosclerosis. On histopathological examination, SCAD is featured by prominent eosinophilic infiltration of the adventitia or periadventitial layer of coronary artery. It has been estimated that approximately 15–30% of SCAD patients experience recurrent episodes of dissection despite medical therapy. Preliminary evidence suggests that injury to the vascular endothelium and myocytes in the arterial wall may be explained by cytotoxic products released from eosinophils in response to inflammatory mediators. In addition, neovascularization of vasa vasorum and dilatation of intimal capillaries may be stimulated by localized eosinophils. Newly formed fragile vasa vasorum may disrupt due to high intraluminal pressure from the interconnected capillary network, leading to the expansion of intramural hemorrhage. It is hypothesized that anti-inflammatory therapy targeting eosinophilic coronary periarteritis would be effective in preventing the recurrence of SCAD by promoting the healing of dissection. The article delineates the biological plausibility, empirical data, and future perspective regarding eosinophilic inflammation as a potential therapeutic target for SCAD.

Large conductance voltage- and calcium-gated potassium channels (BK) in cerebral artery myocytes of perinatal fetal primates share several major characteristics with the adult phenotype.

Large conductance voltage- and calcium-gated channels (BK) control fundamental processes, including smooth muscle contractility and artery diameter. We used a baboon (Papio spp) model of pregnancy that is similar to that of humans to characterize BK channels in the middle cerebral artery and its branches in near-term (165 dGa) primate fetuses and corresponding pregnant mothers. In cell-attached patches (K+pipette = 135 mM) on freshly isolated fetal cerebral artery myocytes, BK currents were identified by large conductance, and voltage- and paxilline-sensitive effects. Their calcium sensitivity was confirmed by a lower Vhalf (transmembrane voltage needed to reach half-maximal current) in inside-out patches at 30 versus 3 μM [Ca2+]free. Immunostaining against the BK channel-forming alpha subunit revealed qualitatively similar levels of BK alpha protein-corresponding fluorescence in fetal and maternal myocytes. Fetal and maternal BK currents recorded at 3 μM [Ca2+]free from excised membrane patches had similar unitary current amplitude, and Vhalf. However, subtle differences between fetal and maternal BK channel phenotypes were detected in macroscopic current activation kinetics. To assess BK function at the organ level, fetal and maternal artery branches were pressurized in vitro at 30 mmHg and probed with the selective BK channel blocker paxilline (1 μM). The degree of paxilline-induced constriction was similar in fetal and maternal arteries, yet the constriction of maternal arteries was achieved sooner. In conclusion, we present a first identification and characterization of fetal cerebral artery BK channels in myocytes from primates. Although differences in BK channels between fetal and maternal arteries exist, the similarities reported herein advance the idea that vascular myocyte BK channels are functional near-term, and thus may serve as pharmacological targets during the perinatal-neonatal period.

Regulation of nitric oxide synthases by intracellular oxidants

The activity of nitric oxide synthases (NOS) is dynamically regulated by calcium-calmodulin, and further modulated by a wide range of differentially-targeted reversibly oxidized protein kinases and phosphoprotein phosphatases. This presentation will review the roles of intracellular oxidants in the regulation of NOS activity in vascular endothelial cells and cardiac myocytes and will present the results of recent studies using informative hydrogen peroxide biosensors and novel chemogenetic approaches.

Hypoxic conditioning in blood vessels and smooth muscle tissues: effects on function, mechanisms, and unknowns.

Hypoxic preconditioning, the protective effect of brief, intermittent hypoxic or ischemic episodes on subsequent more severe hypoxic episodes, has been known for 30 yr from studies on cardiac muscle. The concept of hypoxic preconditioning has expanded; excitingly, organs beyond the heart, including the brain, liver, and kidney, also benefit. Preconditioning of vascular and visceral smooth muscles has received less attention despite their obvious importance to health. In addition, there has been no attempt to synthesize the literature in this field. Therefore, in addition to overviewing the current understanding of hypoxic conditioning, in the present review, we consider the role of blood vessels in conditioning and explore evidence for conditioning in other smooth muscles. Where possible, we have distinguished effects on myocytes from other cell types in the visceral organs. We found evidence of a pivotal role for blood vessels in conditioning and for conditioning in other smooth muscle, including the bladder, vascular myocytes, and gastrointestinal tract, and a novel response in the uterus of a hypoxic-induced force increase, which helps maintain contractions during labor. To date, however, there are insufficient data to provide a comprehensive or unifying mechanism for smooth muscles or visceral organs and the effects of conditioning on their function. This also means that no firm conclusions can be drawn as to how differences between smooth muscles in metabolic and contractile activity may contribute to conditioning. Therefore, we have suggested what may be general mechanisms of conditioning occurring in all smooth muscles and tabulated tissue-specific mechanistic findings and suggested ideas for further progress.

Chronic Prenatal Hypoxia Down-Regulated BK Channel Β1 Subunits in Mesenteric Artery Smooth Muscle Cells of the Offspring

Background/Aims: Chronic hypoxia in utero could impair vascular functions in the offspring, underlying mechanisms are unclear. This study investigated functional alteration in large-conductance Ca²⁺-activated K⁺ (BK) channels in offspring mesenteric arteries following prenatal hypoxia. Methods: Pregnant rats were exposed to normoxic control (21% O₂, Con) or hypoxic (10.5% O₂, Hy) conditions from gestational day 5 to 21, their 7-month-old adult male offspring were tested for blood pressure, vascular BK channel functions and expression using patch clamp and wire myograh technique, western blotting, and qRT-PCR. Results: Prenatal hypoxia increased pressor responses and vasoconstrictions to phenylephrine in the offspring. Whole-cell currents density of BK channels and amplitude of spontaneous transient outward currents (STOCs), not the frequency, were significantly reduced in Hy vascular myocytes. The sensitivity of BK channels to voltage, Ca²⁺, and tamoxifen were reduced in Hy myocytes, whereas the number of channels per patch and the single-channel conductance were unchanged. Prenatal hypoxia impaired NS1102- and tamoxifen-mediated relaxation in mesenteric arteries precontracted with phenylephrine in the presence of N^ω-nitro-L-arginine methyl ester. The mRNA and protein expression of BK channel β1, not the α-subunit, was decreased in Hy mesenteric arteries. Conclusions: Impaired BK channel β1-subunits in vascular smooth muscle cells contributed to vascular dysfunction in the offspring exposed to prenatal hypoxia.

Abstract P508: Inhibition of Big-conductance Calcium-activated Potassium Channels in Vascular Myocytes is a Key Novel Mechanism for Tacrolimus-induced Hypertension

Background and Purpose: Tacrolimus (TAC, also called FK506), a common immunosuppressive drug, causes hypertension. In this study, we tested a novel hypothesis that TAC inhibits big-conductance Ca 2+ -activated K + (BK) channels in artery smooth muscle cells (SMCs), leading to hypertension. Experimental Approach: Noninvasive and invasive blood pressure measurements were used to determine hypertension; organ bath technique and live videomicroscopy to assess vasoconstriction; fluorescence imaging and confocal microscope to detect whole-cell and local intracellular Ca 2+ concentration; patch-clamp techniques to record channel activity; Western blot analysis and real-time RT-PCR to evaluate channel expression; and gene knockout mice to determine its functions. Key Results: Intraperitoneal injection of TAC once a day for a week causes hypertension with a peak at 4 weeks. Application of norepinephrine (NE) induces a larger vasoconstriction in arteries and increase in [Ca 2+ ] i in artery SMCs from mice treated with TAC for 4 weeks. Whole-cell BK channel activity is significantly decreased in SMCs from TAC-treated mice, whereas Ca 2+ spark activity is increased. The voltage sensitivity, Ca 2+ sensitivity and open time of single BK channels are all decreased in TAC-administrated mouse cells. BK channel β1, but not α, subunit protein and mRNA expression levels are significantly decreased in arteries from TAC-treated mice. Chronic administration of TAC fails to further increase blood pressure in BK channel β1 knockout mice with hypertension. Conclusion and Implications: Our findings provide novel evidence that TAC inhibits BK channel β1 subunit expression and functions in artery SMCs, thereby leading to enhanced vasoconstriction and hypertension.

Abstract 266: Phosphodiesterase 9A Deficiency Does Not Attenuate Chronic-hypoxic Pulmonary Hypertension

Background: Phosphodiesterase (PDE) inhibition is a cornerstone of therapy for pulmonary arterial hypertension. A novel role for PDE9A in natriuretic peptide-mediated left ventricular cyclic guanosine monophosphate (cGMP) signaling and remodeling has recently been described. Since cGMP-signaling can promote vaso-relaxation and prevent vascular smooth muscle cell proliferation and cardiac myocyte hypertrophy, we hypothesized that PDE9A deficiency would attenuate right ventricular (RV) and pulmonary vascular remodeling during chronic RV pressure overload. Methods: Chronic-hypoxic pulmonary hypertension (CH-PH) was induced in mice lacking PDE9A expression ( Pde9a -/- ) and wild-type littermates ( Pde9a +/+ ) by exposure to normobaric hypoxia (FiO2 = 10%) for 3 weeks. RV systolic pressures were measured to quantify PH, and RV hypertrophy was quantified as the ratio of RV free wall mass to LV/septal mass (RV/LV+S). Heart, lung, and serum were flash frozen for biochemical analyses. Results: In wild-type mice, exposure to chronic hypoxia resulted in significant increases in RV pressure (30 ± 2.4 vs. 20 ± 3.2 mm Hg; P = 0.0006) and RV hypertrophy (0.34 ± 0.04 vs. 0.25 ± 0.02; P < 0.0001). Serum ANP levels were increased 5-fold with CH-PH ( P = <0.0001), associated with a 72% reduction in lung Npr3 receptor expression (responsible for ANP clearance; P < 0.0001) but no increase in RV Nppa expression. After 3 weeks of CH-PH, tissue levels of cGMP were not increased in lung (993 ± 502 pg/mg vs. 667 ± 210 pg/mg; P = 0.27) or RV (47 ± 18 pg/mg vs. 49 ± 13 pg/mg; P = 0.88) homogenates. Accordingly, serine-239 phosphorylation of vasodilatory-stimulated phosphoprotein (VASP; a surrogate for protein kinase G activation) was not increased by CH-PH in lung or RV. Expression of Pde9a RNA was not increased by CH-PH in lung or RV. Pde9a -/- mice did not have attenuated CH-PH induced increases in RVH ( P = 0.27, 2-way ANOVA) or RVSP ( P = 0.23, 2-way ANOVA) when compared to Pde9a +/+ mice. In both Pde9a -/- and Pde9a +/+ mice, CH-PH was associated with significant increases in lung PDE5A expression. Conclusions: In a murine model of chronic RV pressure overload, PDE9A deficiency does not attenuate RV remodeling or PH, despite robust increases in circulating natriuretic peptide levels.

Role of Epicardial Adipose Tissue in Health and Disease: A Matter of Fat?

Epicardial adipose tissue (EAT) is a small but very biologically active ectopic fat depot that surrounds the heart. Given its rapid metabolism, thermogenic capacity, unique transcriptome, secretory profile, and simply measurability, epicardial fat has drawn increasing attention among researchers attempting to elucidate its putative role in health and cardiovascular diseases. The cellular crosstalk between epicardial adipocytes and cells of the vascular wall or myocytes is high and suggests a local role for this tissue. The balance between protective and proinflammatory/profibrotic cytokines, chemokines, and adipokines released by EAT seem to be a key element in atherogenesis and could represent a future therapeutic target. EAT amount has been found to predict clinical coronary outcomes. EAT can also modulate cardiac structure and function. Its amount has been associated with atrial fibrillation, coronary artery disease, and sleep apnea syndrome. Conversely, a beiging fat profile of EAT has been identified. In this review, we describe the current state of knowledge regarding the anatomy, physiology and pathophysiological role of EAT, and the factors more globally leading to ectopic fat development. We will also highlight the most recent findings on the origin of this ectopic tissue, and its association with cardiac diseases. © 2017 American Physiological Society. Compr Physiol 7:1051-1082, 2017.

Nifedipine Inhibition of High-Voltage Activated Calcium Channel Currents in Cerebral Artery Myocytes Is Influenced by Extracellular Divalent Cations.

Voltage-dependent calcium channels (VDCCs) play an essential role in regulating cerebral artery diameter and it is widely appreciated that the L-type VDCC, CaV1.2, encoded by the CACNA1C gene, is a principal Ca2+ entry pathway in vascular myocytes. However, electrophysiological studies using 10 mM extracellular barium ([Ba2+]o) as a charge carrier have shown that ~20% of VDCC currents in cerebral artery myocytes are insensitive to 1,4-dihydropyridine (1,4-DHP) L-type VDDC inhibitors such as nifedipine. Here, we investigated the hypothesis that the concentration of extracellular divalent cations can influence nifedipine inhibition of VDCC currents. Whole-cell VDCC membrane currents were obtained from freshly isolated rat cerebral artery myocytes in extracellular solutions containing Ba2+ and/or Ca2+. In the absence of [Ca2+]o, both nifedipine-sensitive and -insensitive calcium currents were observed in 10 mM [Ba2+]o. However, VDCC currents were abolished by nifedipine when using a combination of 10 mM [Ba2+]o and 100 μM [Ca2+]o. VDCC currents were also completely inhibited by nifedipine in either 2 mM [Ba2+]o or 2 mM [Ca2+]o. The biophysical characteristics of all recorded VDCC currents were consistent with properties of a high-voltage activated VDCC, such as CaV1.2. Further, VDCC currents recorded in 10 mM [Ba2+]o ± 100 μM [Ca2+]o or 2 mM [Ba2+]o exhibited similar sensitivity to the benzothiazepine L-type VDCC blocker, diltiazem, with complete current inhibition at 100 μM. These data suggest that nifedipine inhibition is influenced by both Ca2+ binding to an external site(s) on these channels and surface charge effects related to extracellular divalent cations. In sum, this work demonstrates that the extracellular environment can profoundly impact VDCC current measurements.

Caveolar remodeling is a critical mechanotransduction mechanism of the stretch-induced L-type Ca2+ channel activation in vascular myocytes.

Activation of L-type voltage-dependent Ca2+ channels (VDCCL) by membrane stretch contributes to many biological responses such as myogenic contraction of arteries. However, mechanism for the stretch-induced VDCCL activation is unclear. In this study, we examined the hypothesis that caveolar remodeling and its related signaling cascade contribute to the stretch-induced activation of VDCCL in rat mesenteric arterial smooth muscle cells. The VDCCL currents were recorded with nystatin-perforated or with conventional whole-cell patch-clamp technique. Hypotonic (~230mOsm) swelling-induced membrane stretch reversibly increased the VDCCL currents. Electron microscope and confocal imaging analysis revealed that both hypotonic swelling and cholesterol depletion by methyl-β-cychlodextrin (MβCD) similarly disrupted the caveolae structure and translocated caveolin-1 (Cav-1) from membrane to cytosolic space. Accordingly, MβCD also increased VDCCL currents. Moreover, subsequent hypotonic swelling after MβCD treatment failed to increase the VDCCL currents further. Western blotting experiments revealed that hypotonic swelling phosphorylated Cav-1 and JNK. Inhibitors of tyrosine kinases (genistein) and JNK (SP00125) prevented the swelling-induced facilitation of VDCCL currents. Knockdown of Cav-1 by small interfering RNA blocked both the VDCCL current facilitation by stretch and the related phosphorylation of JNK. Taken together, the results suggest that membrane stretch is transduced to the facilitation of VDCCL currents via caveolar structure-dependent tyrosine phosphorylation of Cav-1 and subsequent activation of JNK in rat mesenteric arterial myocytes.