Compartmentalized nitric oxide signaling in the resistance vasculature

Soluble guanylyl cyclase, the NO-receptor, regulates endothelium-dependent vascular relaxation via its transnitrosation activity

We previously demonstrated that the NO-receptor soluble guanylyl cyclase (GC1) has the ability to transnitrosate other proteins in a reaction that involves, in some cases, oxidized Thioredoxin 1 (oTrx1). This transnitrosation cascade was established in vitro and we identified by mass spectrometry and mutational analysis Cys 610 (C610) of GC1 α-subunit as a major donor of S-nitrosothiols (SNO). To assay the relevance of GC1 transnitrosation under physiological conditions and in oxidative pathologies, we studied a knock-in mouse in which C610 was replaced with a serine (KI αC 610S ) under basal or angiotensin II (Ang II)-treated conditions. Despite similar GC1 expression and NO-stimulated cGMP-forming activity, the Ang II-treated KI mice displayed exacerbated oxidative pathologies including higher mean arterial pressure and more severe cardiac dysfunctions compared to the Ang II-treated WT. These phenotypes were associated with a drastic decrease in global S-nitrosation and in levels of SNO-Trx1 and SNO-RhoA in the KI mice. To investigate the mechanism underlying the dysregulation of blood pressure despite an intact NO-cGMP axis, pressure myography and in vivo intravital microscopy were conducted to analyze the vascular resistance tone. Both approaches indicated that, even in the absence of oxidative stress, the single mutation C610S led to a significant deficiency in acetylcholine-induced vasorelaxation while smooth muscle relaxation in response to NO remained unchanged. These findings indicate that the C610S mutation uncoupled the two NO signaling pathways involved in the endothelium and smooth muscle vasorelaxation and suggest that GC1-dependent S-nitrosation is a key player in endothelium-derived hyperpolarization.

Cooling-induced cutaneous vasodilatation is mediated by small-conductance, calcium-activated potassium channels in tail arteries from male mice

Cooling causes cutaneous dilatation to restrain cold-induced constriction and prevent tissue injury. Cooling increases communication through myoendothelial gap junctions (MEGJs), thereby increasing endothelium-derived hyperpolarization (EDH)-type dilatation. EDH is initiated by calcium-activated potassium channels (KCa ) activated by endothelial stimuli or muscle-derived mediators traversing MEGJs (myoendothelial feedback). The goal of this study was to determine the individual roles of KCa with small (SK3) and intermediate (IK1) conductance in cooling-induced dilatation. Vasomotor responses of mice isolated cutaneous tail arteries were analyzed by pressure myography at 37°C and 28°C. Cooling increased acetylcholine-induced EDH-type dilatation during inhibition of NO and prostacyclin production. IK1 inhibition did not affect dilatations to acetylcholine, whereas SK3 inhibition inhibited dilatation at both temperatures. Cooling uncovered myoendothelial feedback to inhibit constrictions in U46619. IK1 inhibition did not affect U46619 constrictions, whereas SK3 inhibition abolished the inhibitory effect of cooling without affecting U46619 constriction at 37°C. Immunoblots confirmed SK3 expression, which was localized (immunofluorescence) to holes in the internal elastic lamina consistent with myoendothelial projections. Immunoblots and Immunofluorescence did not detect IK1. Studies in non-cutaneous arteries have highlighted the predominant role of IK1 in EDH-type dilatation. Cutaneous arteries are distinctly reliant on SK3, which may enable EDH-type dilation to be amplified by cooling.

Connexin 40-Mediated Regulation of Systemic Circulation and Arterial Blood Pressure

Vascular system is a complex network in which different cell types and vascular segments must work in concert to regulate blood flow distribution and arterial blood pressure. Although paracrine/autocrine signaling is involved in the regulation of vasomotor tone, direct intercellular communication via gap junctions plays a central role in the control and coordination of vascular function in the microvascular network. Gap junctions are made up by connexin (Cx) proteins, and among the four Cxs expressed in the cardiovascular system (Cx37, Cx40, Cx43, and Cx45), Cx40 has emerged as a critical signaling pathway in the vessel wall. This Cx is predominantly found in the endothelium, but it is involved in the development of the cardiovascular system and in the coordination of endothelial and smooth muscle cell function along the length of the vessels. In addition, Cx40 participates in the control of vasomotor tone through the transmission of electrical signals from the endothelium to the underlying smooth muscle and in the regulation of arterial blood pressure by renin-angiotensin system in afferent arterioles. In this review, we discuss the participation of Cx40-formed channels in the development of cardiovascular system, control and coordination of vascular function, and regulation of arterial blood pressure.

Antenatal Dexamethasone Exposure Impairs Vascular Contractile Functions via Upregulating IP3 Receptor 1 and Cav1.2 in Adult Male Offspring

BACKGROUND

Administration of antenatal glucocorticoids remains common practice for treating preterm delivery. Antenatal glucocorticoid exposure increased the risk of developing vascular diseases in later life, but the precise mechanisms remain unclear. This study aimed to explore the effects and mechanisms of antenatal exposure to clinically relevant doses of dexamethasone (synthetic glucocorticoids) on vascular functions in adult male offspring.

METHODS

Pregnant Sprague-Dawley rats received dexamethasone or vehicle during the last week of pregnancy. Male offspring were killed at gestational day 21 (Fetus) or postnatal day 120 (adult offspring). Mesenteric arteries were collected for vascular function, electrophysiology, target gene expression, and promotor methylation studies.

RESULTS

Antenatal dexamethasone exposure increased phenylephrine-mediated vascular contractility in offspring, which was resulted by the activated inositol 1,4,5-trisphosphate (IP3) receptor and L-type Ca²⁺ channels. Specifically, increases of IP3R1 (IP3 receptor 1) and Cav1.2 (L-type Ca²⁺ channels subunit alpha1 C) were responsible for an activated IP3-Ca²⁺ pathway in the vasculature, and eventually predisposed the antenatal dexamethasone offspring to vascular hypercontractility. In addition, IP3R1 and Cav1.2 was upregulated through transcriptional mechanism; the overall changes in promotor histone modifications were consistent with the corresponding changes in transcriptional levels of the 2 genes, suggesting that antenatal dexamethasone exposure activated the transcription of IP3R1 and Cav1.2 via altering promotor histone modifications.

CONCLUSIONS

Taken together, this study demonstrated that antenatal dexamethasone exposure resulted in vascular adverse outcomes in male offspring that is linked to the increases of IP3R1 and Cav1.2 mediated by epigenetic modifications in the vasculature.

Hypertension and human immunodeficiency virus: A paradigm for epithelial sodium channels?

Hypertension is a risk factor for end organ damage and death and is more common in persons with HIV compared to the general population. Several mechanisms have been studied in the pathogenesis of hypertension. Current evidence suggests that the epithelial sodium channel (ENaC) plays a key role in regulating blood pressure through the transport of sodium and water across membranes in the kidney tubules, resulting in retention of sodium and water and an altered fluid balance. However, there is scarcity of information that elucidates the role of ENaC in HIV as it relates to increasing the risk for development or pathogenesis of hypertension. This review summarized the evidence to date implicating a potential role for altered ENaC activity in contributing to hypertension in patients with HIV.

Femoral Pulse Pressure Variation Is Not Interchangeable with Radial Pulse Pressure Variation during Living Donor Liver Transplantation

The radial artery is commonly used as the site measuring pulse pressure variation (PPV) during surgery. Accurate measurement of circulating blood volume and timely interventions to maintain optimal circulating blood volume is important to deliver sufficient oxygen to tissues and organs. It has not rather than never studied in patients undergoing liver transplantation whether PPV measured at peripheral sites, such as the radial artery, do represent central PPV for evaluating blood volume. In this retrospective study, 51 liver transplant recipients were enrolled. The two PPVs had been automatically recorded every minute in electrical medical records. A total 1878 pairs of the two PPVs were collected. The interchangeability of PPV measured at the radial and the femoral artery was analyzed by using the Bland−Altman plot, four-quadrant plot, Cohen’s kappa (k), and receiver operating curve. The bias and limits of agreement of the two PPVs were −1.3% and −8.8% to 6.2%, respectively. The percentage error was 75%. The concordance rate was 65%. The Kappa of PPV-radial determining whether PPV-femoral was >13% or ≤13% was 0.64. We found that PPV-radial is not interchangeable with PPV-femoral during liver transplantation. Additionally, PPV-radial failed to reliably track changes of PPV-femoral. Lastly, the clinical decision regarding blood volume status (depletion or not) is significantly different between the two PPVs. Therefore, PPV-femoral may help maintain blood volume circulating to major organs including the newly transplanted liver graft for liver transplant recipients.

The Effects of Acidosis on eNOS in the Systemic Vasculature: A Focus on Early Postnatal Ontogenesis

The activity of many vasomotor signaling pathways strongly depends on extracellular/intracellular pH. Nitric oxide (NO) is one of the most important vasodilators produced by the endothelium. In this review, we present evidence that in most vascular beds of mature mammalian organisms metabolic or respiratory acidosis increases functional endothelial NO-synthase (eNOS) activity, despite the observation that direct effects of low pH on eNOS enzymatic activity are inhibitory. This can be explained by the fact that acidosis increases the activity of signaling pathways that positively regulate eNOS activity. The role of NO in the regulation of vascular tone is greater in early postnatal ontogenesis compared to adulthood. Importantly, in early postnatal ontogenesis acidosis also augments functional eNOS activity and its contribution to the regulation of arterial contractility. Therefore, the effect of acidosis on total peripheral resistance in neonates may be stronger than in adults and can be one of the reasons for an undesirable decrease in blood pressure during neonatal asphyxia. The latter, however, should be proven in future studies.

Deletion of the Gamma Subunit of ENaC in Endothelial Cells Does Not Protect against Renal Ischemia Reperfusion Injury

Acute kidney injury due to renal ischemia-reperfusion injury (IRI) may lead to chronic or end stage kidney disease. A greater understanding of the cellular mechanisms underlying IRI are required to develop therapeutic options aimed at limiting or reversing damage from IRI. Prior work has shown that deletion of the α subunit of the epithelial Na+ channel (ENaC) in endothelial cells protects from IRI by increasing the availability of nitric oxide. While canonical ENaCs consist of an α, β, and γ subunit, there is evidence of non-canonical ENaC expression in endothelial cells involving the α subunit. We therefore tested whether the deletion of the γ subunit of ENaC also protects mice from IRI to differentiate between these channel configurations. Mice with endothelial-specific deletion of the γ subunit and control littermates were subjected to unilateral renal artery occlusion followed by 48 h of reperfusion. No significant difference was noted in injury between the two groups as assessed by serum creatinine and blood urea nitrogen, levels of specific kidney injury markers, and histological examination. While deletion of the γ subunit did not alter infiltration of immune cells or cytokine message, it was associated with an increase in levels of total and phosphorylated endothelial nitric oxide synthase (eNOS) in the injured kidneys. Our studies demonstrate that even though deletion of the γ subunit of ENaC may allow for greater activation of eNOS, this is not sufficient to prevent IRI, suggesting the protective effects of α subunit deletion may be due, in part, to other mechanisms.

Functional implications of vascular endothelium in regulation of endothelial nitric oxide synthesis to control blood pressure and cardiac functions

The endothelium is the innermost vascular lining performing significant roles all over the human body while maintaining the blood pressure at physiological levels. Malfunction of endothelium is thus recognized as a biomarker linked with many vascular diseases including but not limited to atherosclerosis, hypertension and thrombosis. Alternatively, prevention of endothelial malfunctioning or regulating the functions of its associated physiological partners like endothelial nitric oxide synthase can prevent the associated vascular disorders which account for the highest death toll worldwide. While many anti-hypertensive drugs are available commercially, a comprehensive description of the key physiological roles of the endothelium and its regulation by endothelial nitric oxide synthase or vice versa is the need of the hour to understand its contribution in vascular homeostasis. This, in turn, will help in designing new therapeutics targeting endothelial nitric oxide synthase or its interacting partners present in the cellular pool. This review describes the central role of vascular endothelium in the regulation of endothelial nitric oxide synthase while outlining the emerging drug targets present in the vasculature with potential to treat vascular disorders including hypertension.

Of neurons and pericytes: The neuro-vascular approach to diabetic retinopathy

Diabetic retinopathy (DR) is a frequent complication of diabetes mellitus and an increasingly common cause of visual impairment. Blood vessel damage occurs as the disease progresses, leading to ischemia, neovascularization, blood-retina barrier (BRB) failure and eventual blindness. Although detection and treatment strategies have improved considerably over the past years, there is room for a better understanding of the pathophysiology of the diabetic retina. Indeed, it has been increasingly realized that DR is in fact a disease of the retina's neurovascular unit (NVU), the multi-cellular framework underlying functional hyperemia, coupling neuronal computations to blood flow. The accumulating evidence reveals that both neurochemical (synapses) and electrical (gap junctions) means of communications between retinal cells are affected at the onset of hyperglycemia, warranting a global assessment of cellular interactions and their role in DR. This is further supported by the recent data showing down-regulation of connexin 43 gap junctions along the vascular relay from capillary to feeding arteriole as one of the earliest indicators of experimental DR, with rippling consequences to the anatomical and physiological integrity of the retina. Here, recent advancements in our knowledge of mechanisms controlling the retinal neurovascular unit will be assessed, along with their implications for future treatment and diagnosis of DR.

Inosine, an endogenous purine nucleoside, avoids early stages of atherosclerosis development associated to eNOS activation and p38 MAPK/NF-kB inhibition in rats

Atherosclerosis is a multifactorial chronic disease, initiated by an endothelial dysfunction. Adenosine and its analogs can change a variety of inflammatory diseases and has shown important effects at different disease models. Inosine is a stable analogous of adenosine, but its effects in inflammatory diseases, like atherosclerosis, have not yet been studied. The aim of this study was to evaluate the pharmacological properties of inosine, administered sub chronically in a hypercholesterolemic model. Male Wistar rats were divided into four groups: control group (C) and control + inosine (C + INO) received standard chow, hypercholesterolemic diet group (HCD) and HCD + inosine (HCD + INO) were fed a hypercholesterolemic diet. At 31st experimentation day, the treatment with inosine was performed for C + INO and HCD + INO groups once daily in the last 15 days. We observed that the hypercholesterolemic diet promoted an increase in lipid levels and inflammatory cytokines production, while inosine treatment strongly decreased these effects. Additionally, HCD group presented a decrease in maximum relaxation acetylcholine induced and an increase in contractile response phenylephrine induced when compared to the control group, as well as it has presented an enhancement in collagen and ADP-induced platelet aggregation. On the other hand, inosine treatment promoted a decrease in contractile response to phenylephrine, evoked an improvement in endothelium-dependent vasorelaxant response and presented antiplatelet properties. Moreover, inosine activated eNOS and reduced p38 MAPK/NF-κB pathway in aortic tissues. Taken together, the present results indicate inosine as a potential drug for the treatment of cardiovascular disorders such as atherosclerosis.

The pericyte connectome: spatial precision of neurovascular coupling is driven by selective connectivity maps of pericytes and endothelial cells and is disrupted in diabetes

Functional hyperemia, or the matching of blood flow with activity, directs oxygen and nutrients to regionally firing neurons. The mechanisms responsible for this spatial accuracy remain unclear but are critical for brain function and establish the diagnostic resolution of BOLD-fMRI. Here, we described a mosaic of pericytes, the vasomotor capillary cells in the living retina. We then tested whether this net of pericytes and surrounding neuroglia predicted a connectivity map in response to sensory stimuli. Surprisingly, we found that these connections were not only selective across cell types, but also highly asymmetric spatially. First, pericytes connected predominantly to other neighboring pericytes and endothelial cells, and less to arteriolar smooth muscle cells, and not to surrounding neurons or glia. Second, focal, but not global stimulation evoked a directional vasomotor response by strengthening connections along the feeding vascular branch. This activity required local NO signaling and occurred by means of direct coupling via gap junctions. By contrast, bath application of NO or diabetes, a common microvascular pathology, not only weakened the vascular signaling but also abolished its directionality. We conclude that the exclusivity of neurovascular interactions may thus establish spatial accuracy of blood delivery with the precision of the neuronal receptive field size, and is disrupted early in diabetes.

Fast relaxation and desensitization of angiotensin II contraction in the pulmonary artery via AT1R and Akt-mediated phosphorylation of muscular eNOS

Angiotensin II (AngII) triggers a transient contraction of pulmonary arteries (PAs) followed by protracted desensitization. Based on the unconventional eNOS expression in PA smooth muscle cells (PASMCs), we hypothesized that activation of smooth muscle eNOS by AngII might be responsible for fast relaxation and tachyphylaxis. Using dual-wire myograph, mechanically endothelium-denuded rat PA [E(-)PA] showed AngII concentration-dependent transient contractions (ΔT_AngII, 95% decay within 1 min), which were abolished by losartan (AT1R antagonist). Neither PD123319 (AT2R antagonist) nor A779 (MasR antagonist) affected ΔT_AngII. When the vessels were pretreated with L-NAME (NOS inhibitor), ODQ (guanylate cyclase inhibitor), or KT5823 (PKG inhibitor), ΔT_AngII of E(-)PA became larger and sustained, whereas nNOS or iNOS inhibitors had no such effect. Immunoblotting of human PASMCs (hPASMCs) also showed eNOS expression, and AngII treatment induced activating phosphorylations of Ser¹¹⁷⁷ in eNOS and of Ser⁴⁷³ in Akt (Ser/Thr protein kinase B), an upstream signal of eNOS phosphorylation. In addition, L-NAME co-treatment promoted AngII-induced Ser¹⁹ phosphorylation of myosin light chain. In hPASMCs, AngII abolished plasma membrane expression of AT1R, and recovery by washout took more than 1 h. Consistent with the data from hPASMCs, the second application of AngII to E(-)PA did not induce contraction, and significant recovery of ΔT_AngII required prolonged washout (> 2 h) in the myography study. L-NAME treatment before the second application facilitated recovery of ΔT_AngII. Muscular eNOS plays an auto-inhibitory role in ΔT_AngII of PAs. The molecular changes investigated in hPASMCs revealed eNOS phosphorylation and internalization of AT1R by AngII. We propose that the rat PA smooth muscle eNOS-induced lusitropy and slow recovery of AT1R from tachyphylaxis might counterbalance the excessive contractile response to AngII, contributing to the distinctive low-pressure pulmonary circulation.

The role of NO-cGMP pathway inhibition in vascular endothelial-dependent smooth muscle relaxation disorder of AT1-AA positive rats: protective effects of adiponectin

Angiotensin II type 1 receptor autoantibodies (AT1-AA) cause endothelial-dependent smooth muscle relaxation disorder. It is well understood that impairment of the NO-cGMP signaling pathway is one of the mechanisms of endothelial-dependent smooth muscle relaxation disorder. However, it is still unclear whether AT1-AA induces endothelial-dependent smooth muscle relaxation disorder via the impairment of the NO-cGMP signaling pathway. In addition, adiponectin exerts vascular endothelial protection through the NO-cGMP signaling pathway. Therefore, the purpose of this investigation was to assess the mechanism of vascular endothelial-dependent smooth muscle relaxation disorder induced by AT1-AA and the role of adiponectin in attenuating this dysregulation. Serum endothelin-1 (ET-1), adiponectin and AT1-AA were detected by enzyme-linked immunosorbent assay. In preeclamptic patients, there was an increased level of AT1-AA, which was positively correlated with ET-1 and negatively correlated with adiponectin, as elevated levels of ET-1 suggested endothelial injury. AT1-AA-positive animal models were actively immunized with the second extracellular loop of the angiotensin II type 1 receptor (AT1R-ECII) for eight weeks. In thoracic aortas of AT1-AA positive rats, ET-1 was elevated, endothelium-dependent vasodilation was decreased. Paradoxically, as the upstream element of the NO-cGMP signaling pathway, NO production was not decreased but increased, and the ratio of p-VASP/VASP, an established biochemical endpoint of NO-cGMP signaling pathway, was reduced. Moreover, the levels of nitrotyrosine and gp91phox which indicate the presence of peroxynitrite (ONOO^-) and superoxide anion (O₂·^-) were increased. Pretreatment with the ONOO^- scavenger FeTMPyP or O₂·^-scavenger Tempol normalized vasorelaxation. Key enzymes responsible for NO synthesis were also assessed. iNOS protein expression was increased, but p-eNOS(Ser1177)/eNOS was reduced. Preincubation with the iNOS inhibitor 1400 W or eNOS agonist nebivolol restored vasorelaxation. Further experiments showed levels of p-AMPKα (Thr172)/AMPKα, which controls iNOS expression and eNOS activity, to have been reduced. Furthermore, levels of the upstream component of AMPK, adiponectin, was reduced in sera of AT1-AA positive rats and supplementation of adiponectin significantly decreased ET-1 contents, improved endothelial-dependent vasodilation, reduced NO production, elevated p-VASP/VASP, inhibited protein expression of nitrotyrosine and gp91phox, reduced iNOS overexpression, and increased eNOS phosphorylation at Ser1177 in the thoracic aorta of AT1-AA positive rats. These results established that impairment NO-cGMP pathway may aggravate the endothelial-dependent smooth muscle relaxation disorder in AT1-AA positive rats and adiponectin improved endothelial-dependent smooth muscle relaxation disorder by enhancing NO-cGMP pathway. This discovery may shed a novel light on clinical treatment of vascular diseases associated with AT1-AA.

Endothelium-dependent responses in the microcirculation observed in vivo

Endothelium-dependent responses were first demonstrated 40 years ago in the aorta. Since then, extensive research has been conducted in vitro using conductance vessels and materials derived from them. However, the microcirculation controls blood flow to vital organs and has been the focus of in vivo studies of endothelium-dependent dilation beginning immediately after the first in vitro report. Initial in vivo studies employed a light/dye technique for selectively damaging the endothelium to unequivocally prove, in vivo, the existence of endothelium-dependent dilation and in the microvasculature. Endothelium-dependent constriction was similarly proven. Endothelium-dependent agonists include acetylcholine (ACh), bradykinin, arachidonic acid, calcium ionophore A-23187, calcitonin gene-related peptide (CGRP), serotonin, histamine and endothelin-1. Normal and disease states have been studied. Endothelial nitric oxide synthase, cyclooxygenase and cytochrome P450 have been shown to generate the mediators of the responses. Some of the key enzyme systems generate reactive oxygen species (ROS) like superoxide which may prevent EDR. However, one ROS, namely H₂ O₂ , is one of a number of hyperpolarizing factors that cause dilation initiated by endothelium. Depending upon microvascular bed, a single agonist may use different pathways to elicit an endothelium-dependent response. Interpretation of studies using inhibitors of eNOS is complicated by the fact that these inhibitors may also inhibit ATP-sensitive potassium channels. Other in vivo observations of brain arterioles failed to establish nitric oxide as the mediator of responses elicited by CGRP or by ACh and suggest that a nitrosothiol may be a better fit for the latter.

Long-term hypoxia uncouples Ca2+ and eNOS in bradykinin-mediated pulmonary arterial relaxation

Bradykinin-induced activation of the pulmonary endothelium triggers a rise in intracellular Ca²⁺ that activates nitric oxide (NO)-dependent vasorelaxation. Chronic hypoxia is commonly associated with increased pulmonary vascular tone, which can cause pulmonary hypertension in responsive individuals. In the present study, we tested the hypothesis that long-term high-altitude hypoxia (LTH) diminishes bradykinin-induced Ca²⁺ signals and inhibits endothelial nitric oxide synthase (eNOS), prostacyclin (PGI₂), and large-conductance K⁺ (BK_Ca) channels in sheep, which are moderately responsive to LTH, resulting in decreased pulmonary arterial vasorelaxation. Pulmonary arteries were isolated from ewes kept near sea level (720 m) or at high altitude (3,801 m) for >100 days. Vessel force was measured with wire myography and endothelial intracellular Ca²⁺ with confocal microscopy. eNOS was inhibited with 100 μM N^G-nitro-l-arginine methyl ester (l-NAME), PGI₂ production was inhibited with 10 µM indomethacin that inhibits cyclooxygenase, and BK_Ca channels were blocked with 1 mM tetraethylammonium. Bradykinin-induced endothelial Ca²⁺ signals increased following LTH, but bradykinin relaxation decreased. Furthermore, some vessels contracted in response to bradykinin after LTH. l-NAME sensitivity decreased, suggesting that eNOS dysfunction played a role in uncoupling Ca²⁺ signals and bradykinin relaxation. The Ca²⁺ ionophore A-23187 (10 µM) elicited an enhanced Ca²⁺ response following LTH while relaxation was unchanged although l-NAME sensitivity increased. Additionally, BK_Ca function decreased during bradykinin relaxation following LTH. Western analysis showed that BK_Ca α-subunit expression was increased by LTH while that for the β₁ subunit was unchanged. Overall, these results suggest that those even moderately responsive to LTH can have impaired endothelial function.

Effects of a simple prototype respiratory muscle trainer on respiratory muscle strength, quality of life and dyspnea, and oxidative stress in COPD patients: a preliminary study

Background

The aim of this study was to evaluate the efficiency of a simple prototype device for training respiratory muscles in lung function, respiratory muscle strength, walking capacity, quality of life (QOL), dyspnea, and oxidative stress in patients with COPD.

Methods

Thirty COPD patients with moderate severity of the disease were randomized into three groups: control (n=10, 6 males and 4 females), standard training (n=10, 4 males and 6 females), and prototype device (n=10, 5 males and 5 females). Respiratory muscle strength (maximal inspiratory pressure [PImax] and maximal expiratory pressure [PEmax]), lung function (forced vital capacity [FVC], percentage of FVC, forced expiratory volume in 1 second [FEV₁], percentage of FEV₁ [FEV₁%], and FEV₁/FVC), 6-minute walking distance (6MWD), QOL, and oxidative stress markers (total antioxidant capacity [TAC]), glutathione (GSH), malondialdehyde (MDA), and nitric oxide (NO) were evaluated before and after 6 weeks of training. Moreover, dyspnea scores were assessed before; during week 2, 4, and 6 of training; and at rest after training.

Results

All parameters between the groups had no statistical difference before training, and no statistical change in the control group after week 6. FVC, FEV₁/FVC, PImax, PEmax, QOL, MDA, and NO showed significant changes after 6 weeks of training with either the standard or prototype device, compared to pre-training. FEV₁, FEV₁%, 6MWD, TAC, and GSH data did not change statistically. Furthermore, the results of significant changes in all parameters were not statistically different between training groups using the standard and prototype device. The peak dyspnea scores increased significantly in week 4 and 6 when applying the standard or prototype device, and then lowered significantly at rest after 6 weeks of training, compared to pre-training.

Conclusion

This study proposes that a simple prototype device can be used clinically in COPD patients as a standard device to train respiratory muscles, improving lung function and QOL, as well as involving MDA and NO levels.

There is blood in the water: hemolysis, hemoglobin, and heme in acute lung injury

The major role of red blood cells (RBCs) is to deliver oxygen and remove carbon dioxide within organisms through the unique properties of hemoglobin. Although beneficial within RBCs, when outside hemoglobin and its breakdown products (heme, iron) induce proinflammatory responses affecting various cellular responses. Although these effects are considered to be prominent in disorders with increased hemolysis, recent evidence suggests that this process may be active in nonhemolytic disorders such as acute lung injury/acute respiratory distress syndrome. This perspectives article focuses on data related to red cell products in nonhemolytic disorders and the potential to target these factors in acute lung injury/acute respiratory distress syndrome.

Two functionally distinct pools of eNOS in endothelium are facilitated by myoendothelial junction lipid composition

In resistance arteries, endothelial cells (EC) make contact with smooth muscle cells (SMC), forming myoendothelial junctions (MEJ). Endothelial nitric oxide synthase (eNOS) is present in the luminal side of the EC (apical EC) and the basal side of the EC (MEJ). To test if these eNOS pools acted in sync or separately, we co-cultured ECs and SMCs, then stimulated SMCs with phenylephrine (PE). Adrenergic activation causes inositol [1,4,5] triphosphate (IP3) to move from SMC to EC through gap junctions at the MEJ. PE increases MEJ eNOS phosphorylation (eNOS-P) at S1177, but not in EC. Conversely, we used bradykinin (BK) to increase EC calcium; this increased EC eNOS-P but did not affect MEJ eNOS-P. Inhibiting gap junctions abrogated the MEJ eNOS-P after PE, but had no effect on BK eNOS-P. Differential lipid composition between apical EC and MEJ may account for the compartmentalized eNOS-P response. Indeed, DAG and phosphatidylserine are both enriched in MEJ. These lipids are cofactors for PKC activity, which was significantly increased at the MEJ after PE. Because PKC activity also relies on endoplasmic reticulum (ER) calcium release, we used thapsigargin and xestospongin C, BAPTA, and PKC inhibitors, which caused significant decreases in MEJ eNOS-P after PE. Functionally, BK inhibited leukocyte adhesion and PE caused an increase in SMC cGMP. We hypothesize that local lipid composition of the MEJ primes PKC and eNOS-P for stimulation by PE, allowing for compartmentalized function of eNOS in the blood vessel wall.

Advanced age decreases local calcium signaling in endothelium of mouse mesenteric arteries in vivo

Aging is associated with vascular dysfunction that impairs tissue perfusion, physical activity, and the quality of life. Calcium signaling in endothelial cells (ECs) is integral to vasomotor control, exemplified by localized Ca(2+) signals within EC projections through holes in the internal elastic lamina (IEL). Within these microdomains, endothelium-derived hyperpolarization is integral to smooth muscle cell (SMC) relaxation via coupling through myoendothelial gap junctions. However, the effects of aging on local EC Ca(2+) signals (and thereby signaling between ECs and SMCs) remain unclear, and these events have not been investigated in vivo. Furthermore, it is unknown whether aging affects either the number or the size of IEL holes. In the present study, we tested the hypothesis that local EC Ca(2+) signaling is impaired with advanced age along with a reduction in IEL holes. In anesthetized mice expressing a Ca(2+)-sensitive fluorescent protein (GCaMP2) selectively in ECs, our findings illustrate that for mesenteric arteries controlling splanchnic blood flow the frequency of spontaneous local Ca(2+) signals in ECs was reduced by ∼85% in old (24-26 mo) vs. young (3-6 mo) animals. At the same time, the number (and total area) of holes per square millimeter of IEL was reduced by ∼40%. We suggest that diminished signaling between ECs and SMCs contributes to dysfunction of resistance arteries with advanced age.Listen to this article's corresponding podcast at http://ajpheart.podbean.com/e/aging-impairs-endothelial-ca2-signaling/.

Endothelial nitric oxide weakens arterial contractile responses and reduces blood pressure during early postnatal development in rats

OBJECTIVE

During maturation the vascular system undergoes structural and functional remodeling. At the systemic level it results in a gradual increase of arterial blood pressure during postnatal ontogenesis. The mechanisms of maintaining the blood pressure at a comparatively low level during the early postnatal development are not completely understood. Recently we showed that the hindlimb arteries of young (1-2 wk-old) rats exhibited an enhanced endothelial NO-pathway activity, which weakened their contractile responsiveness compared to the arteries of adult rats. Here we tested the hypothesis that an increased tonic endothelial NO production can take place in the whole vascular system leading to a decreased level of systemic blood pressure in young rats.

DESIGN AND METHODS

Segments of small mesenteric, saphenous, sural and intrarenal arteries were isolated from the young (2 wk-old), juvenile (4 wk-old) and adult (10-12 wk-old) male rats and tested in a wire isometric myograph. Anticontractile effect of NO was evaluated by the effects of NOS inhibitor L-NNA on both arterial spontaneous tone and constrictor responses to methoxamine (α1-adrenoceptor agonist). In addition, eNOS and arginase-2 mRNA expression in arterial preparations by qPCR and serum nitrite/nitrate levels by Griess reaction were estimated. Blood pressure with an intra-carotid artery catheter was measured in conscious rats.

RESULTS

In all arteries of 2 wk rats except the renal ones, L-NNA exposure resulted in a considerable tonic contraction and a remarkable enhancement of contractile responses to methoxamine. The effect of L-NNA gradually decreased with age and by 10-12 weeks became very small in the mesenteric arteries and disappeared in the sural and saphenous arteries. Although no difference in eNOS mRNA expression was found, the content of arginase-2 mRNA was significantly lower in young rats compared to adults. Serum levels of NO metabolites were two-fold higher in 2 wk-old rats than in adult rats. Along with that, arterial blood pressure was by half lower but rose more prominently after administration of l-NAME in young rats than in adults.

CONCLUSIONS

In young rats, tonic release of NO by the endothelium considerably weakens contractile responses of arteries supplying intestine, skin and skeletal muscles, which receive a high proportion of the cardiac output. Such anticontractile effect of NO can be an important mechanism responsible for the blood pressure reduction in immature circulatory system.

A novel nitro-dexamethasone inhibits agr system activity and improves therapeutic effects in MRSA sepsis models without antibiotics

Methicillin-resistant Staphylococcus aureus (MRSA) sepsis is a life-threatening medical condition that involves systemic inflammation throughout the body. Glucocorticoids are widely used in combination with antibiotics in the treatment of MRSA sepsis to fight the overwhelming inflammation. Here, we describe the improved anti-inflammatory properties of a nitric oxide (NO)-releasing derivative of dexamethasone, ND8008. ND8008 affected MRSA biofilm formation, caused biofilm cell death, and reduced the effects of virulence factors, such as α-toxin, by inhibiting the activity of the Staphylococcus aureus accessory gene regulator (agr) system. Dosing of mice with ND8008 (127.4 nmol/kg, i.p.) alone greatly reduced the inflammatory response caused by MRSA blood stream infection and considerably increased the survival rate of septic mice. These findings suggest that this novel NO-releasing derivative of dexamethasone ND8008 could be helpful in the treatment of MRSA sepsis.

Developmental acceleration of bradykinin-dependent relaxation by prenatal chronic hypoxia impedes normal development after birth

Bradykinin-induced activation of the pulmonary endothelium triggers nitric oxide production and other signals that cause vasorelaxation, including stimulation of large-conductance Ca(2+)-activated K(+) (BKCa) channels in myocytes that hyperpolarize the plasma membrane and decrease intracellular Ca(2+). Intrauterine chronic hypoxia (CH) may reduce vasorelaxation in the fetal-to-newborn transition and contribute to pulmonary hypertension of the newborn. Thus we examined the effects of maturation and CH on the role of BKCa channels during bradykinin-induced vasorelaxation by examining endothelial Ca(2+) signals, wire myography, and Western immunoblots on pulmonary arteries isolated from near-term fetal (∼ 140 days gestation) and newborn, 10- to 20-day-old, sheep that lived in normoxia at 700 m or in CH at high altitude (3,801 m) for >100 days. CH enhanced bradykinin-induced relaxation of fetal vessels but decreased relaxation in newborns. Endothelial Ca(2+) responses decreased with maturation but increased with CH. Bradykinin-dependent relaxation was sensitive to 100 μM nitro-L-arginine methyl ester or 10 μM 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, supporting roles for endothelial nitric oxide synthase and soluble guanylate cyclase activation. Indomethacin blocked relaxation in CH vessels, suggesting upregulation of PLA2 pathways. BKCa channel inhibition with 1 mM tetraethylammonium reduced bradykinin-induced vasorelaxation in the normoxic newborn and fetal CH vessels. Maturation reduced whole cell BKCa channel α1-subunit expression but increased β1-subunit expression. These results suggest that CH amplifies the contribution of BKCa channels to bradykinin-induced vasorelaxation in fetal sheep but stunts further development of this vasodilatory pathway in newborns. This involves complex changes in multiple components of the bradykinin-signaling axes.

Consumption of star fruit juice on pro-inflammatory markers and walking distance in the community dwelling elderly

PURPOSE

This study aimed to evaluate the effect of star fruit juice supplementation on tumor necrosis factor-alpha (TNF-α), interleukin-23 (IL-23) and interleukin-2 (IL-2), nitric oxide (NO), and 6 min walking distance (6MWD) in a group of elderly individuals.

METHODS

Twenty-nine individuals (20 males, 9 females) with a mean age of 72.4±8.3 years completed this study. A two-week control period was followed by four weeks of 100g fresh star fruit juice consumption twice per day after meals.

RESULTS

Plasma TNF-α, IL-23, IL-2, NO and the 6MWD were evaluated twice during the control period (weeks 0 and 2) and once after the star fruit juice consumption (week 6).

RESULTS

The results showed that all parameters in the blood did not change significantly during the control period. After 4 weeks of star fruit juice consumption, a significant reduction in NO, TNF-α and IL-23 was found; however, there was no change in IL-2. Moreover, the 6MWD increased significantly at week 6, when compared to that at week 0 and 2. Furthermore, the results also showed a significantly positive and negative correlation of NO and TNF-α to the 6MWD, but no correlation of IL-23 and IL-2.

CONCLUSION

This preliminary study concluded that consumption of star fruit juice at 100g twice daily for one month can significantly depress the pro-inflammation cytokines: TNF-α, IL-23, and NO, while increasing walking distance. Low TNF-α and high NO also present a significant correlation to walking capacity in elderly individuals.