c-Src, ERK1/2 and Rho kinase mediate hydrogen peroxide-induced vascular contraction in hypertension: role of TXA2, NAD(P)H oxidase and mitochondria

NADPH oxidase derived ROS promote arterial contraction in early postnatal rats by activation of L-type voltage-gated Ca2+ channels

Reactive oxygen species (ROS) produced by NADPH oxidase promote contraction of peripheral arteries, which is especially pronounced in early postnatal period in comparison to adulthood, but the mechanisms of such vasomotor influence are poorly understood. We tested the hypothesis that Rho-kinase and protein kinase C (PKC) mediate procontractile influence of NADPH oxidase derived ROS in peripheral artery of early postnatal rats. In addition, we evaluated the involvement Src-kinase and L-type voltage-gated Ca2+ channels (LTCC) into procontractile influence of ROS, produced by NADPH oxidase, because of their known interplay with Rho-kinase and PKC pathways. Saphenous arteries from 11- to 15-day-old male rats were studied using quantitative PCR, isometric myography and lucigenin-enhanced chemiluminescence. Arterial tissue of early postnatal rats contained Nox2, Nox4, Duox1 and Duox2 mRNAs, among which Nox2 mRNA was the most abundant. Pan-NADPH oxidase inhibitor VAS2870 (10 µM) significantly reduced arterial contractile responses to methoxamine. The inhibitors of Rho-kinase (Y27632, 3 µM), PKC (GF109203X, 10 µM) and Src-kinase (PP2, 10 µM), as well as LTCC blockers (nimodipine, 0.1 µM, and verapamil, 0.1 μM) also reduced methoxamine-induced contraction. Importantly, the effect of VAS2870 persisted in the presence of Rho-kinase, PKC or Src-kinase inhibitors, but not in the presence of LTCC blocker. Notably, the blockade of LTCC did not affect either basal or NADPH-induced O2•- production. Our data show that LTCC, but not Rho-kinase, PKC or Src-kinase are involved into procontractile effect of ROS, produced by NADPH oxidase, in saphenous artery of young rats. Сalcium influx through LTCC does not activate ROS production by NADPH oxidase.

Oxidative Stress Participates in Age-Related Cataract Formation by Disrupting Connection between Lens Epithelial Cells through c-Src/VEGF Pathway

PURPOSE

To observe the effects of oxidative stress on vascular endothelial growth factor (VEGF) and connections of lens epithelial cells.

METHODS

Human lens epithelium of patients with age-related cataract (ARC), both SRA01/04 cells and whole mice lens stimulated by H2O2 were employed. VEGF in human aqueous humor of ARC-patients and the supernatant of SRA01/04 cells was determined by ELISA. The expressions of VEFG in human lens epithelium were detected by immunofluorescence staining. Multiple linear regression analysis and spearman rank-order correlation were used to determine the associations between VEGF and parameters of ARC individuals. In H2O2-induced SRA01/04 cells, Catalase (CAT), PP1 (inhibitor of c-Src kinase) and Avastin (VEGF antibody) were used to inhibit the effects of H2O2, activation of c-Src kinase and VEGF, which were detected by Western blot. The alterations of ZO-1 and N-cadherin were tested by immunofluorescence staining and Western blot. In H2O2-induced whole lens, the changes of opacification area in different treatment of inhibitors were observed.

RESULTS

The secretion of VEGF in aqueous humor and expression of VEGF in the lens epithelium of ARC patients increased significantly with age. In H2O2-induced SRA01/04 cells, the VEGF in the supernatant was increased with the culture duration and the dose of H2O2. The expressions of p-Src418 and VEGF were also up-regulated, whereas the expressions of ZO-1 and N-cadherin were down-regulated. CAT effectively prevented these changes induced by H2O2, while PP1 inhibited not only p-Src418 but also up-regulation of VEGF, Avastin partially inhibited VEGF up-regulation. Both PP1 and Avastin prevented down-regulation of ZO-1 and N-cadherin, respectively, but Avastin combined with PP1 had no significant synergistic effects. In H2O2-induced cataract, CAT prevented development of opacification area effectively, and PP1 and Avastin did partially.

CONCLUSIONS

Oxidative stress disrupts connections of lens epithelial cells by activating c-Src/VEGF, inhibiting which may prevent cataract.

Maximakinin reduced intracellular Ca2+ level in vascular smooth muscle cells through AMPK/ERK1/2 signaling pathways

We detect the antihypertensive effects of maximakinin (MK) on renal hypertensive rats (RHRs) and further research the influence of MK on vascular smooth muscle cells (VSMCs) to explore its hypotensive mechanism. The effects of MK on arterial blood pressure were observed in RHRs. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide (MTT) assays were performed to detect the effect of MK on VSMC viability. Western blot and flow cytometry were used to investigate the influence of MK on intracellular Ca2+ levels and protein expression changes in VSMCs. In addition, specific protein inhibitors were applied to confirm the involvement of Ca2+-related signaling pathways induced by MK in VSMCs. MK showed a more significant antihypertensive effect than bradykinin in RHRs. MK significantly decreased intracellular Ca2+ concentrations. Furthermore, MK significantly induced the phosphorylation of signaling molecules, including extracellular signal-regulated kinase 1/2 (ERK1/2), P38, AMP-activated protein kinase (AMPK) and Akt in VSMCs. Moreover, only ERK1/2 inhibitor U0126 and AMPK inhibitor Compound C completely restored the decreased intracellular Ca2+ level induced by MK, and further research demonstrated that AMPK functioned upstream of ERK1/2 following exposure to MK. Finally, HOE-140, an inhibitor of the bradykinin B2 receptors (B2Rs), was applied to investigate the potential targets of MK in VSMCs. HOE-140 significantly blocked the AMPK/ERK1/2 pathway induced by MK, suggesting that the B2Rs might play an important role in MK-induced AMPK and ERK1/2 activation. MK significantly reduces blood pressure in RHRs. MK exerts its antihypertensive effect by activating the B2Rs and downstream AMPK/ERK1/2 pathways, leading to significantly reduced Ca2+ levels in VSMCs.

Signaling pathways in vascular function and hypertension: molecular mechanisms and therapeutic interventions

Hypertension is a global public health issue and the leading cause of premature death in humans. Despite more than a century of research, hypertension remains difficult to cure due to its complex mechanisms involving multiple interactive factors and our limited understanding of it. Hypertension is a condition that is named after its clinical features. Vascular function is a factor that affects blood pressure directly, and it is a main strategy for clinically controlling BP to regulate constriction/relaxation function of blood vessels. Vascular elasticity, caliber, and reactivity are all characteristic indicators reflecting vascular function. Blood vessels are composed of three distinct layers, out of which the endothelial cells in intima and the smooth muscle cells in media are the main performers of vascular function. The alterations in signaling pathways in these cells are the key molecular mechanisms underlying vascular dysfunction and hypertension development. In this manuscript, we will comprehensively review the signaling pathways involved in vascular function regulation and hypertension progression, including calcium pathway, NO-NOsGC-cGMP pathway, various vascular remodeling pathways and some important upstream pathways such as renin-angiotensin-aldosterone system, oxidative stress-related signaling pathway, immunity/inflammation pathway, etc. Meanwhile, we will also summarize the treatment methods of hypertension that targets vascular function regulation and discuss the possibility of these signaling pathways being applied to clinical work.

Oxidative Regulation of Vascular Cav1.2 Channels Triggers Vascular Dysfunction in Hypertension-Related Disorders

Blood pressure is determined by cardiac output and peripheral vascular resistance. The L-type voltage-gated Ca²⁺ (Ca_v1.2) channel in small arteries and arterioles plays an essential role in regulating Ca²⁺ influx, vascular resistance, and blood pressure. Hypertension and preeclampsia are characterized by high blood pressure. In addition, diabetes has a high prevalence of hypertension. The etiology of these disorders remains elusive, involving the complex interplay of environmental and genetic factors. Common to these disorders are oxidative stress and vascular dysfunction. Reactive oxygen species (ROS) derived from NADPH oxidases (NOXs) and mitochondria are primary sources of vascular oxidative stress, whereas dysfunction of the Ca_v1.2 channel confers increased vascular resistance in hypertension. This review will discuss the importance of ROS derived from NOXs and mitochondria in regulating vascular Ca_v1.2 and potential roles of ROS-mediated Ca_v1.2 dysfunction in aberrant vascular function in hypertension, diabetes, and preeclampsia.

Thromboxane-dependent coronary vasoconstriction in obese mice: Role of peroxynitrite

Obesity leads to chronic oxidative stress promoting the development of cardiovascular diseases including coronary artery disease and endothelial dysfunction. Increased reactive oxygen species production associated with obesity might lead to endothelial dysfunction through cyclooxygenase (COX) pathway. We evaluated arachidonic acid (AA)-dependent coronary vascular responses and explored COX metabolism in obese C57BL/6 mice. In response to arachidonic acid (AA), isolated hearts from obese mice showed increased vasoconstriction compared with control mice. Released thromboxane (TX) A2 during AA-induced vasoconstriction phase was increased in heart perfusates from obese mice. Indomethacin and 1-benzylimidazole, both reduced vasoconstriction response in control and obese mice. Vasoconstriction response to TXA2 mimetic analog U46619 was 2.7 higher in obese mice. Obesity increased COX-2, TXS and TX receptor protein expression as well as oxidative stress evaluated by nitrotyrosine and peroxynitrite levels, compared with control mice. Obese mice treated with FeTMPyP, a peroxynitrite scavenger, reversed all these parameters to control levels. These data suggest that alterations in COX pathway may be associated with increased generation of free radicals, including peroxynitrite, that result from the oxidative stress observed in obesity.

Central role of c-Src in NOX5- mediated redox signalling in vascular smooth muscle cells in human hypertension

AIMS

NOX-derived reactive oxygen species (ROS) are mediators of signalling pathways implicated in vascular smooth muscle cell (VSMC) dysfunction in hypertension. Among the numerous redox-sensitive kinases important in VSMC regulation is c-Src. However, mechanisms linking NOX/ROS to c-Src are unclear, especially in the context of oxidative stress in hypertension. Here, we investigated the role of NOX-induced oxidative stress in VSMCs in human hypertension focusing on NOX5, and explored c-Src, as a putative intermediate connecting NOX5-ROS to downstream effector targets underlying VSMC dysfunction.

METHODS AND RESULTS

VSMC from arteries from normotensive (NT) and hypertensive (HT) subjects were studied. NOX1,2,4,5 expression, ROS generation, oxidation/phosphorylation of signalling molecules, and actin polymerization and migration were assessed in the absence and presence of NOX5 (melittin) and Src (PP2) inhibitors. NOX5 and p22phox-dependent NOXs (NOX1-4) were down-regulated using NOX5 siRNA and p22phox-siRNA approaches. As proof of concept in intact vessels, vascular function was assessed by myography in transgenic mice expressing human NOX5 in a VSMC-specific manner. In HT VSMCs, NOX5 was up-regulated, with associated oxidative stress, hyperoxidation (c-Src, peroxiredoxin, DJ-1), and hyperphosphorylation (c-Src, PKC, ERK1/2, MLC20) of signalling molecules. NOX5 siRNA reduced ROS generation in NT and HT subjects. NOX5 siRNA, but not p22phox-siRNA, blunted c-Src phosphorylation in HT VSMCs. NOX5 siRNA reduced phosphorylation of MLC20 and FAK in NT and HT. In p22phox- silenced HT VSMCs, Ang II-induced phosphorylation of MLC20 was increased, effects blocked by melittin and PP2. NOX5 and c-Src inhibition attenuated actin polymerization and migration in HT VSMCs. In NOX5 transgenic mice, vascular hypercontractilty was decreased by melittin and PP2.

CONCLUSION

We define NOX5/ROS/c-Src as a novel feedforward signalling network in human VSMCs. Amplification of this system in hypertension contributes to VSMC dysfunction. Dampening the NOX5/ROS/c-Src pathway may ameliorate hypertension-associated vascular injury.

Early manifestation of aging-related vascular dysfunction in human penile vasculature-A potential explanation for the role of erectile dysfunction as a harbinger of systemic vascular disease

Advanced age is related to functional alterations of human vasculature, but erectile dysfunction precedes systemic manifestations of vascular disease. The current study aimed to simultaneously evaluate the influence of aging on vascular function (relaxation and contraction responses) in systemic human vascular territories: aorta (HA) and resistance mesenteric arteries (HMA) and human corpus cavernosum (HCC) and penile resistance arteries (HPRA). Associations of oxidative stress and inflammation circulating biomarkers with age and functional responses were also determined. Vascular specimens were obtained from 76 organ donors (age range 18-87). Four age-groups were established: < 40, 40-55, 56-65 and > 65 years old. Increasing age was associated with a decline in endothelium-dependent relaxation induced by BK in HMA (r = -0.597, p = 0.0001), or by ACh in HCC (r = -0.505, p = 0.0022), and HPRA (r = -0.601, p = 0.0012). Significant impairment was detected at > 65 years old in HMA but earlier in penile vasculature (> 55 years old). Age-related reduction to H2O2-vasodilatory response started before in HCC (56-65 years old) than in HA (> 65 years old). In contrast to relaxation responses, aging-related hypercontractility to adrenergic stimulation was homogeneous: contractions significantly increased in subjects > 55 years old in all tested vessels. Although not significantly age related, circulating levels of ADMA (r = -0.681, p = 0.0052) and TNF-α (r = -0.537, p = 0.0385) were negatively correlated with endothelial vasodilation in HMA but not in HCC or HPRA. Penile vasculature exhibits an early impairment of endothelium-dependent and H2O2-induced vasodilations when compared to mesenteric microcirculation and aorta. Therefore, functional susceptibility of penile vasculature to the aging process may account for anticipation of erectile dysfunction to systemic manifestations of vascular disease.

Signalling pathway of U46619-induced vascular smooth muscle contraction in mouse coronary artery

BACKGROUND

Thromboxane A2 (TXA2 ) participates in many pathophysiological processes of coronary artery disease. However, its mechanism of TXA2 -induced contraction in the coronary artery remains to be clarified. A multi myograph system was used to measure the isometric tension of the mouse coronary arteries and identify the effect and pathway of TXA2 analogues U46619. Confocal laser scanning microscopy was used to measure the intracellular calcium concentration ([Ca2+ ]i ) in mouse coronary artery smooth muscle cells. Results from the experiment had shown that contraction in coronary artery was generated by U46619 in a concentration-dependent manner, which was completely abolished by a specific TXA2 receptor blocker, GR32191. PI-PLC inhibitors U73122 and D609 and Rho-Kinase inhibitor Y-27632 can block the U46619 elicited coronary artery contraction in a dose-dependent manner. Then, the vasoconstriction response to U46619 was obviously inhibited by two pan-PKC inhibitors chelerythrine or Gӧ6983, and a selective PKCδ inhibitor rottlerin, but was not blocked by a selective PKCζ inhibitor PKC-PS or a selective PKCβ inhibitor hispidin. Meanwhile, the PKC activator PDBu-induced vasoconstriction was significantly inhibited by 1 μmol/L nifedipine, then mostly inhibited by 100 μmol/L 2-APB and 10 μmol/L Y27632. We further found that the response to U46619 was inhibited, respectively, by three calcium channel blockers nifedipine, SKF96356 or 2-APB in a concentration-dependent manner. Although Store-operated Ca2+ (SOC) channels generated the increase of [Ca2+ ]i in mouse coronary artery smooth muscle cells, SOC channels did not contribute to the vasoconstriction in mouse coronary arteries. Caffeine-induced sarcoplasmic reticulum (SR) Ca2+ release could obviously induce coronal vasoconstriction. In addition, NPPB, a cell membrane Ca2+ activated C1- channel blocker, could obviously inhibit the U46619-induced vasoconstriction. The U46619-induced mouse coronary artery contraction was involved in the increase in [Ca2+ ]i mediated by Cav1.2, TRPC channels and SR release through the activation of G-protein-coupled TP receptors and the kinases signalling pathway in TP downstream proteins, while SOC channels did not participate in the vasoconstriction.

Androgen Deprivation Therapy in Patients With Prostate Cancer Increases Serum Levels of Thromboxane A2: Cardiovascular Implications

Introduction: Androgens have been described as important players in the regulation of vascular function/structure through their action on the release and effect of vasoactive factors, such as prostanoids. Patients with prostate cancer (PCa) under androgen deprivation therapies (ADTs) present increased risk of cardiovascular mortality. Since thromboxane A₂ (TXA₂) is one of the most studied prostanoids and its involvement in different cardiovascular diseases has been described, the aim of this study was to investigate: (i) the effect of ADT on the serum levels of TXA₂ in PCa patients and its possible link to the redox status and (ii) the effect of the non-hydrolyzable TXA₂ analog U-46619 on the function of the aorta of male rats.

Methods: The levels of TXA₂ and total antioxidant status in 50 healthy subjects, 54 PCa patients, and 57 PCa under ADT were evaluated. These determinations were accompanied by levels of testosterone and C-reactive protein as an inflammation marker. In aortic segments from male rats, the U46619-induced effects on: (i) the vasomotor responses to acetylcholine (ACh), to the NO donor sodium nitroprusside (SNP), to the carbon monoxide-releasing molecule-3 (CORM-3), and to noradrenaline (NA) and (ii) the expression of cyclooxygenase-2 (COX-2), heme oxygenase-1 (HO-1), and phosphorylated ERK1/2 were analyzed.

Results: The serum level of TXA₂ in patients with PCa was increased with respect to healthy subjects, which was further increased by ADT. There was no modification in the total antioxidant status among the three experimental groups. In aortic segments from male rats, the TXA₂ analog decreased the endothelium-dependent relaxation and the sensitivity of smooth muscle cells to NO, while it increased the vasoconstriction induced by NA; the expression of COX-2, HO-1, and pERK1/2 was also increased.

Conclusions: ADT increased, along with other inflammatory/oxidative markers, the serum levels of TXA₂. The fact that TXA₂ negatively impacts the vascular function of the aorta of healthy male rats suggests that inhibition of TXA₂-mediated events could be considered a potential strategy to protect the cardiovascular system.

Oxidative Stress and Hypertension

A link between oxidative stress and hypertension has been firmly established in multiple animal models of hypertension but remains elusive in humans. While initial studies focused on inactivation of nitric oxide by superoxide, our understanding of relevant reactive oxygen species (superoxide, hydrogen peroxide, and peroxynitrite) and how they modify complex signaling pathways to promote hypertension has expanded significantly. In this review, we summarize recent advances in delineating the primary and secondary sources of reactive oxygen species (nicotinamide adenine dinucleotide phosphate oxidases, uncoupled endothelial nitric oxide synthase, endoplasmic reticulum, and mitochondria), the posttranslational oxidative modifications they induce on protein targets important for redox signaling, their interplay with endogenous antioxidant systems, and the role of inflammasome activation and endoplasmic reticular stress in the development of hypertension. We highlight how oxidative stress in different organ systems contributes to hypertension, describe new animal models that have clarified the importance of specific proteins, and discuss clinical studies that shed light on how these processes and pathways are altered in human hypertension. Finally, we focus on the promise of redox proteomics and systems biology to help us fully understand the relationship between ROS and hypertension and their potential for designing and evaluating novel antihypertensive therapies.

Perspective: Prospects for Nutraceutical Support of Intestinal Barrier Function

Impairment of intestinal barrier function is linked to certain pathologies and to aging, and can be a cause of bacterial infections, systemic and hepatic inflammation, food allergies, and autoimmune disorders. The formation and maintenance of intestinal tight junctions is supported by glucagon-like peptide-2 (GLP-2), which via insulin-like growth factor I activity boosts phosphoinositide 3-kinase/Akt/mammalian target of rapamycin complex 1 (PI3K/Akt/mTORC1) signaling in enterocytes. 5'-AMP-activated protein kinase (AMPK) activity as well as estrogen receptor-β (ERβ) activity are also protective in this regard. Conversely, activation of mitogen-activated protein kinases (MAPKs) and cellular Src (c-Src) under inflammatory conditions can induce dissociation of tight junctions. Hence, nutraceuticals that promote GLP-2 secretion from L cells-effective pre/probiotics, glycine, and glutamine-as well as diets rich in soluble fiber or resistant starch, can support intestinal barrier function. AMPK activators-notably berberine and the butyric acid produced by health-promoting microflora-are also beneficial in this regard, as are soy isoflavones, which function as selective agonists for ERβ. The adverse impact of MAPK and c-Src overactivation on the intestinal barrier can be combatted with various antioxidant measures, including phycocyanobilin, phase 2-inducer nutraceuticals, and N-acetylcysteine. These considerations suggest that rationally designed functional foods or complex supplementation programs could have clinical potential for supporting and restoring healthful intestinal barrier function.

Downregulation of Soluble Guanylate Cyclase and Protein Kinase G With Upregulated ROCK2 in the Pulmonary Artery Leads to Thromboxane A2 Sensitization in Monocrotaline-Induced Pulmonary Hypertensive Rats

Thromboxane A2 (TXA2) promotes various physiological responses including pulmonary artery (PA) contraction, and pathophysiological implications have been suggested in cardiovascular diseases including pulmonary hypertension. Here, we investigated the role of TXA2 receptor (TP)-mediated signaling in the pathophysiology of pulmonary arterial hypertension (PAH). The sensitivity of PA to the contractile agonist could be set by relaxing signals such as the nitric oxide (NO), soluble guanylate cyclase (sGC), and cGMP-dependent kinase (PKG) pathways. Changes in the TP agonist (U46619)-induced PA contraction and its modulation by NO/cGMP signaling were analyzed in a monocrotaline-induced PAH rat model (PAH-MCT). In the myograph study, PA from PAH-MCT showed higher responsiveness to U46619, that is decreased EC50. Immunoblot analysis revealed a lower expression of eNOS, sGC, and PKG, while there was a higher expression of RhoA-dependent kinase 2 (ROCK2) in the PA from PAH-MCT than in the control. In PAH-MCT, the higher sensitivity to U46619 was reversed by 8-Br-cGMP, a membrane-permeable cGMP analog, but not by the NO donor, sodium nitroprusside (SNP 30 μM). In contrast, in the control PA, inhibition of sGC by its inhibitor (1H- [1,2,4] oxadiazolo [4,3-a] quinoxalin-1-one (ODQ), 10 μM) lowered the threshold of U46619-induced contraction. In the presence of ODQ, SNP treatment had no effect whereas the addition of 8-Br-cGMP lowered the sensitivity to U46619. The inhibition of ROCK by Y-27632 attenuated the sensitivity to U46619 in both control and PAH-MCT. The study suggests that the attenuation of NO/cGMP signaling and the upregulation of ROCK2 increase the sensitivity to TXA2 in the PAH animal, which might have pathophysiological implications in patients with PAH.

Activated ROCK/Akt/eNOS and ET-1/ERK pathways in 5-fluorouracil-induced cardiotoxicity: modulation by simvastatin

5-Fluorouracil (5-FU) is used in the treatment of different solid tumors; however, its use is associated with rare, but serious cardiotoxicity. Nevertheless, the involvement of ROCK/NF-κB, Akt/eNOS and ET-1/ERK1/2 trajectories in the cardiotoxic effect and in the potential cardioprotective upshot of simvastatin has been elusive. Male Wistar rats were allocated into 5-FU (50 mg/kg/week; i.p, 6 weeks), simvastatin (15 mg/kg/day; p.o, 8 weeks) treated groups and simvastatin + 5-FU, besides the normal control group. 5-FU-induced cardiotoxicity boosted the serum level of N-terminal pro-brain (B-type) natriuretic peptide (NT-proBNP), aortic contents of endothelin (ET)-1 and thromboxane (TX) A2, as well as cardiac contents of NADPH oxidases (Nox), cyclooxygenase (COX)-2, malondialdehyde (MDA), phosphorylated Akt (p-Akt), phosphorylated extracellular signal-regulated kinase (p-ERK)1/2 and the protein expressions of rho-kinase (ROCK) and caspase-3. On the other hand, it suppressed cardiac reduced glutathione (GSH) and phosphorylated endothelial nitric oxide synthase (p-eNOS). Contrariwise, co-administration with simvastatin overcame these disturbed events and modulated the ROCK/NF-κB, Akt/eNOS and ET-1/ERK1/2 signaling pathways. This study highlights other mechanisms than coronary artery spasm in the 5-FU cardiotoxicity and reveals that NT-proBNP is a potential early marker in this case. Moreover, the cross-talk between ROCK/ NF-κB, ROS/COX-2/TXA2, Akt/eNOS and ET-1/ERK1/2 pathways contributes via different means to upsetting the vasoconstriction/vasodilatation equilibrium as well as endothelial cell function and finally leads to cardiomyocyte stress and death-the modulation of these trajectories offers simvastatin its potential cardio-protection against 5-FU.

Oxidative Stress: A Unifying Paradigm in Hypertension

The etiology of hypertension involves complex interactions among genetic, environmental, and pathophysiologic factors that influence many regulatory systems. Hypertension is characteristically associated with vascular dysfunction, cardiovascular remodelling, renal dysfunction, and stimulation of the sympathetic nervous system. Emerging evidence indicates that the immune system is also important and that activated immune cells migrate and accumulate in tissues promoting inflammation, fibrosis, and target-organ damage. Common to these processes is oxidative stress, defined as an imbalance between oxidants and antioxidants in favour of the oxidants that leads to a disruption of oxidation-reduction (redox) signalling and control and molecular damage. Physiologically, reactive oxygen species (ROS) act as signalling molecules and influence cell function through highly regulated redox-sensitive signal transduction. In hypertension, oxidative stress promotes posttranslational modification (oxidation and phosphorylation) of proteins and aberrant signalling with consequent cell and tissue damage. Many enzymatic systems generate ROS, but NADPH oxidases (Nox) are the major sources in cells of the heart, vessels, kidneys, and immune system. Expression and activity of Nox are increased in hypertension and are the major systems responsible for oxidative stress in cardiovascular disease. Here we provide a unifying concept where oxidative stress is a common mediator underlying pathophysiologic processes in hypertension. We focus on some novel concepts whereby ROS influence vascular function, aldosterone/mineralocorticoid actions, and immunoinflammation, all important processes contributing to the development of hypertension.

Proteomics and phosphoproteomics study of LCMT1 overexpression and oxidative stress: overexpression of LCMT1 arrests H2O2-induced lose of cells viability

Objectives: Protein phosphatase 2A (PP2A), a major serine/threonine phosphatase, is also known to be a target of ROS. The methylation of PP2A can be catalyzed by leucine carboxyl methyltransferase-1 (LCMT1), which regulates PP2A activity and substrate specificity.

Methods: In the previous study, we have showed that LCMT1-dependent PP2Ac methylation arrests H₂O₂-induced cell oxidative stress damage. To explore the possible protective mechanism, we performed iTRAQ-based comparative quantitative proteomics and phosphoproteomics studies of H₂O₂-treated vector control and LCMT1-overexpressing cells.

Results: A total of 4480 non-redundant proteins and 3801 unique phosphopeptides were identified by this means. By comparing the H₂O₂-regulated proteins in LCMT1-overexpressing and vector control cells, we found that these differences were mainly related to protein phosphorylation, gene expression, protein maturation, the cytoskeleton and cell division. Further investigation of LCMT1 overexpression-specific regulated proteins under H₂O₂ treatment supported the idea that LCMT1 overexpression induced ageneral dephosphorylation of proteins and indicated increased expression of non-erythrocytic hemoglobin, inactivation of MAPK3 and regulation of proteins related to Rho signal transduction, which were known to be linked to the regulation of the cytoskeleton.

Discussion: These data provide proteomics and phosphoproteomics insights into the association of LCMT1-dependent PP2Ac methylation and oxidative stress and indirectly indicate that the methylation of PP2A plays an important role against oxidative stress.

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.

NADPH oxidase 1/4 inhibition attenuates the portal hypertensive syndrome via modulation of mesenteric angiogenesis and arterial hyporeactivity in rats

AIM

NADPH oxidase (NOX)-derived reactive oxygen species (ROS) plays key roles in the development of portal hypertension (PHT) and represents a potential therapeutic method. The objective of this study was to investigate whether pharmacological inhibition of NADPH oxidase activity could ameliorate PHT in rats.

METHOD

PHT model was established by partial portal vein ligation (PPVL). Rats were treated with 30 mg/kg GKT137831 (the most specific Nox1/4 inhibitor) or vehicle daily by gavage for 14 days beginning at the day of PPVL or sham operation (SO). Hemodynamics, severity of portal-systemic shunting, vascular contractility, vascular endothelial growth factor (VEGF), VEGFR-2, CD31, AKT, phospho-AKT (p-AKT, at Ser473), endothelial nitric oxide synthase (eNOS), and phospho-eNOS (p-eNOS, at Ser1177) expressions were evaluated. Nitric oxide (NO) production and oxidative stress in mesenteric arteries, and hydrogen peroxide (H2O2) in both mesenteric tissues and arteries were measured.

RESULT

Inhibition of NOX1/4 with GKT137831 significantly decreased cardiac index, increased portal flow resistance, reduced portal pressure (PP), portal blood flow, mesenteric angiogenesis and portal-systemic shunting (PSS) in PPVL rats. GKT137831 reduced the production of H2O2, down regulated mesenteric angiogenesis markers (CD31, vascular endothelial growth factor (VEGF) and VEGFR-2 expression. Compared with controls), the mesenteric artery contraction to norepinephrine (NE) was impaired in PPVL rats, which was reversed by exposure to GKT137831. In addition, GKT137831 markedly decrease NADPH oxidase activity and ROS production in mesenteric arteries, and reduced NO production by decreasing the level of phosphor-AKT and eNOS.

CONCLUSION

Inhibition of NOX1/4 decreased PP, ameliorated hyperdynamic circulation, mesenteric angiogenesis and arterial hyporesonse in portal hypertensive rats. Pharmacological inhibition of NOX1/4 activity may be a potential treatment for PHT-related complications.

Mechanisms of U46619-induced contraction in mouse intrarenal artery

Thromboxane A₂ (TXA₂ ) has been implicated in the pathogenesis of vascular complications, but the underlying mechanism remains unclear. The contraction of renal arterial rings in mice was measured by a Multi Myograph System. The intracellular calcium concentration ([Ca²⁺ ]_i ) in vascular smooth muscle cells (VSMCs) was obtained by using a fluo-4/AM dye and a confocal laser scanning microscopy. The results show that the U46619-induced vasoconstriction of renal artery was completely blocked by a TXA₂ receptor antagonist GR32191, significantly inhibited by a selective phospholipase C (PI-PLC) inhibitor U73122 at 10 μmol/L and partially inhibited by a Phosphatidylcholine - specific phospholipase C (PC-PLC) inhibitor D609 at 50 μmol/L. Moreover, the U46619-induced vasoconstriction was inhibited by a general protein kinase C (PKC) inhibitor chelerythrine at 10 μmol/L, and a selective PKCδ inhibitor rottlerin at 10 μmol/L. In addition, the PKC-induced vasoconstriction was partially inhibited by a Rho-kinase inhibitor Y-27632 at 10 μmol/L and was further completely inhibited together with a putative IP₃ receptor antagonist and store-operated Ca²⁺ (SOC) entry inhibitor 2-APB at 100 μmol/L. On the other hand, U46619-induced vasoconstriction was partially inhibited by L-type calcium channel (Cav1.2) inhibitor nifedipine at 1 μmol/L and 2-APB at 50 and 100 μmol/L. Last, U46619-induced vasoconstriction was partially inhibited by a cell membrane Ca²⁺ activated C1^- channel blocker 5-Nitro-2-(3-phenylpropylamino) benzoic acid (NPPB) at 50 and 100 μmol/L. Our results suggest that the U46619-induced contraction of mouse intrarenal arteries is mediated by Cav1.2 and SOC channel, through the activation of thromboxane-prostanoid receptors and its downstream signaling pathway.

Regulation of Spontaneous Contractions in Intact Rat Bladder Strips and the Effects of Hydrogen Peroxide

Enhanced spontaneous contractions are associated with overactive bladder. Elevated levels of reactive oxygen species might contribute to enhanced spontaneous contractions. We investigated the regulation of spontaneous contractions and the effects of hydrogen peroxide (H₂O₂) in intact rat bladder strips. The spontaneous contractions were measured using a tissue bath system. The vehicle or the specific activators/blockers were applied and followed by the application of 0.003 g% H₂O₂. The basal tension, amplitude, and frequency of spontaneous contractions were quantified. Nisoldipine and bisindolylmaleimide 1 had no effects on spontaneous contractions. SKF96365 and Y27632 decreased basal tension and amplitude. Ryanodine slightly increased frequency. Both iberiotoxin and NS-1619 increased amplitude. Apamin reduced frequency but increased amplitude. NS-309 inhibited both the amplitude and frequency. The basal tension and amplitude increased when H₂O₂ was applied. Pretreatment with NS-309 inhibited H₂O₂-elicited augmented amplitude and frequency, while pretreatment with Y-27632 inhibited the augmented basal tension. The combined application of NS-309 and Y27632 almost eliminated spontaneous contractions and its augmentation induced by H₂O₂. In conclusion, Ca²⁺ influx, Rho kinase activation, and SK channel inactivation play important roles in spontaneous contractions in intact bladder strips, whereas only latter two mechanisms may be involved in H₂O₂-elicited increased spontaneous contractions.

Role of thromboxane A2 signaling in endothelium-dependent contractions of arteries

Thromboxane A₂ (TxA₂) plays a very important role in various cardiovascular diseases through its action on platelet aggregation, vasoconstriction, and proliferation. The present article focuses on the role of TxA₂ signaling in endothelium-dependent contractions of arteries. Arachidonic acid (AA) is metabolized by cyclooxygenase (COX) to form the unstable prostaglandin H₂ which is further converted into TxA₂. After being produced by thromboxane synthase (TxAS), TxA₂ ultimately stimulates TxA₂/prostanoid (TP) receptor to induce vasoconstriction. The calcium ionophore A23187, the prostanoid precursor AA, or the muscarinic receptor agonist acetylcholine (ACh) can evoke endothelium-dependent contractions associated with TxA₂. The endothelium-dependent contractions shown in hypertension, diabetes, atherogenesis, and other cardiovascular diseases have been significantly reduced by antagonism of COX, TxAS, or TP receptor. So inhibition of the bioavailability and/or effect of TxA₂ may be promising therapeutic targets to prevent these diseases. Especially some bioactive compounds isolated from medicinal plants will provide new pharmacological approaches to promote vascular health.

Integrin CD11b mediates α-synuclein-induced activation of NADPH oxidase through a Rho-dependent pathway

The activation of microglial NADPH oxidase (NOX2) induced by α-synuclein has been implicated in Parkinson's disease (PD) and other synucleinopathies. However, how α-synuclein activates NOX2 remains unclear. Previous study revealed that both toll-like receptor 2 (TLR2) and integrin play important roles in α-synuclein-induced microglial activation. In this study, we found that blocking CD11b, the α chain of integrin α_Mβ₂, but not TLR2 attenuated α-synuclein-induced NOX2 activation in microglia. The involvement of CD11b in α-synuclein-induced activation of NOX2 was further confirmed in CD11b^-/- microglia by showing reduced membrane translocation of NOX2 cytosolic subunit p47^phox and superoxide production. Mechanistically, α-synuclein bound to CD11b and subsequently activated Rho signaling pathway. α-Synuclein induced activation of RhoA and downstream ROCK but not Rac1 in a CD11b-dependent manner. Moreover, siRNA-mediated knockdown of RhoA impeded NOX2 activation in response to α-synuclein. Furthermore, we found that inhibition of NOX2 failed to interfere with the activation of RhoA signaling and interactions between α-synuclein and CD11b, further confirming that NOX2 was the downstream target of CD11b. Finally, we found that genetic deletion of CD11b abrogated α-synuclein-induced NOX2 activatoin in vivo. Taken together, our results indicated that integrin CD11b mediates α-synuclein-induced NOX2 activation through a RhoA-dependent pathway, providing not only a novel mechanistic insight but also a new potential therapeutic target for synucleinopathies.

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Blocking CD11b, the α chain of integrin α_Mβ₂, but not TLR2 attenuates α-synuclein-induced NOX2 activation.

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α-Synuclein binds to CD11b.

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CD11b regulates NOX2 activation induced by α-synuclein through a RhoA-dependent pathway.

Thrombospondin-1, Free Radicals, and the Coronary Microcirculation: The Aging Conundrum

SIGNIFICANCE

Successful matching of cardiac metabolism to perfusion is accomplished primarily through vasodilation of the coronary resistance arterioles, but the mechanism that achieves this effect changes significantly as aging progresses and involves the contribution of reactive oxygen species (ROS). Recent Advances: A matricellular protein, thrombospondin-1 (Thbs-1), has been shown to be a prolific contributor to the production and modulation of ROS in large conductance vessels and in the peripheral circulation. Recently, the presence of physiologically relevant circulating Thbs-1 levels was proven to also disrupt vasodilation to nitric oxide (NO) in coronary arterioles from aged animals, negatively impacting coronary blood flow reserve.

CRITICAL ISSUES

This review seeks to reconcile how ROS can be successfully utilized as a substrate to mediate vasoreactivity in the coronary microcirculation as "normal" aging progresses, but will also examine how Thbs-1-induced ROS production leads to dysfunctional perfusion and eventual ischemia and why this is more of a concern in advancing age.

FUTURE DIRECTIONS

Current therapies that may effectively disrupt Thbs-1 and its receptor CD47 in the vascular wall and areas for future exploration will be discussed. Antioxid. Redox Signal. 27, 785-801.

Lysyl Oxidase Induces Vascular Oxidative Stress and Contributes to Arterial Stiffness and Abnormal Elastin Structure in Hypertension: Role of p38MAPK

AIMS

Vascular stiffness, structural elastin abnormalities, and increased oxidative stress are hallmarks of hypertension. Lysyl oxidase (LOX) is an elastin crosslinking enzyme that produces H2O2 as a by-product. We addressed the interplay between LOX, oxidative stress, vessel stiffness, and elastin.

RESULTS

Angiotensin II (Ang II)-infused hypertensive mice and spontaneously hypertensive rats (SHR) showed increased vascular LOX expression and stiffness and an abnormal elastin structure. Mice over-expressing LOX in vascular smooth muscle cells (TgLOX) exhibited similar mechanical and elastin alterations to those of hypertensive models. LOX inhibition with β-aminopropionitrile (BAPN) attenuated mechanical and elastin alterations in TgLOX mice, Ang II-infused mice, and SHR. Arteries from TgLOX mice, Ang II-infused mice, and/or SHR exhibited increased vascular H2O2 and O2.- levels, NADPH oxidase activity, and/or mitochondrial dysfunction. BAPN prevented the higher oxidative stress in hypertensive models. Treatment of TgLOX and Ang II-infused mice and SHR with the mitochondrial-targeted superoxide dismutase mimetic mito-TEMPO, the antioxidant apocynin, or the H2O2 scavenger polyethylene glycol-conjugated catalase (PEG-catalase) reduced oxidative stress, vascular stiffness, and elastin alterations. Vascular p38 mitogen-activated protein kinase (p38MAPK) activation was increased in Ang II-infused and TgLOX mice and this effect was prevented by BAPN, mito-TEMPO, or PEG-catalase. SB203580, the p38MAPK inhibitor, normalized vessel stiffness and elastin structure in TgLOX mice.

INNOVATION

We identify LOX as a novel source of vascular reactive oxygen species and a new pathway involved in vascular stiffness and elastin remodeling in hypertension.

CONCLUSION

LOX up-regulation is associated with enhanced oxidative stress that promotes p38MAPK activation, elastin structural alterations, and vascular stiffness. This pathway contributes to vascular abnormalities in hypertension. Antioxid. Redox Signal. 27, 379-397.

Vascular lysyl oxidase over-expression alters extracellular matrix structure and induces oxidative stress

INTRODUCTION

Lysyl oxidase (LOX) participates in the assembly of collagen and elastin fibres. The impact of vascular LOX over-expression on extracellular matrix (ECM) structure and its contribution to oxidative stress has been analysed.

METHODS

Studies were conducted on mice over-expressing LOX (Tg), specifically in smooth muscle cells (VSMC). Gene expression was assessed by real-time PCR analysis. Sirius Red staining, H₂O₂ production and NADPH oxidase activity were analysed in different vascular beds. The size and number of fenestra of the internal elastic lamina were determined by confocal microscopy.

RESULTS

LOX activity was up-regulated in VSMC of transgenic mice compared with cells from control animals. At the same time, transgenic cells deposited more organised elastin fibres and their supernatants induced a stronger collagen assembly in in vitro assays. Vascular collagen cross-linking was also higher in Tg mice, which showed a decrease in the size of fenestrae and an enhanced expression of Fibulin-5. Interestingly, higher H₂O₂ production and NADPH oxidase activity was detected in the vascular wall from transgenic mice. The H₂O₂ scavenger catalase attenuated the stronger deposition of mature elastin fibres induced by LOX transgenesis.

CONCLUSIONS

LOX over-expression in VSMC was associated with a change in the structure of collagen and elastin fibres. LOX could constitute a novel source of oxidative stress that might participate in elastin changes and contribute to vascular remodelling.

Regulation of Na+-K+-ATPase effected high glucose-induced myocardial cell injury through c-Src dependent NADPH oxidase/ROS pathway

Depressed Na⁺/K⁺-ATPase activity has long been reported to be involved in diabetic-related cardiomyocyte death and cardiac dysfunction. However, the nature of directly regulating Na⁺-K⁺-ATPase in diabetic-related myocardial diseases remains unknown. Hyperglycemia is believed as one of major factors responsible for diabetic-related myocardial apoptosis and dysfunction. In this study, whether inhibiting Na⁺-K⁺-ATPase by ouabain or activating Na⁺-K⁺-ATPase by DRm217 has functions on high glucose (HG) -induced myocardial injury was investigated. Here we found that addition of DRm217 or ouabain to HG-treated cells had opposite effects. DRm217 decreased but ouabain increased HG-induced cell injury and apoptosis. This was mediated by changing Na⁺-K⁺-ATPase activity and Na⁺-K⁺-ATPase cell surface expression. The inhibition of Na⁺-K⁺-ATPase endocytosis alleviated HG-induced ROS accumulation. Na⁺-K⁺-ATPase·c-Src dependent NADPH oxidase/ROS pathway was also involved in the effects of ouabain and DRm217 on HG-induced cell injury. These novel results may help us to understand the important role of the Na⁺-K⁺-ATPase in diabetic cardiovascular diseases.

Increased mitochondrial ROS generation mediates the loss of the anti-contractile effects of perivascular adipose tissue in high-fat diet obese mice

BACKGROUND AND PURPOSE

Obesity is associated with structural and functional changes in perivascular adipose tissue (PVAT), favouring release of reactive oxygen species (ROS), vasoconstrictor and proinflammatory factors. The cytokine TNF-α induces vascular dysfunction and is produced by PVAT. We tested the hypothesis that obesity-associated PVAT dysfunction was mediated by augmented mitochondrial ROS (mROS) generation due to increased TNF-α production in this tissue.

EXPERIMENTAL APPROACH

C57Bl/6J and TNF-α receptor-deficient mice received control or high fat diet (HFD) for 18 weeks. We used pharmacological tools to determine the participation of mROS in PVAT dysfunction. Superoxide anion (O₂^.- ) and H₂ O₂ were assayed in PVAT and aortic rings were used to assess vascular function.

KEY RESULTS

Aortae from HFD-fed obese mice displayed increased contractions to phenylephrine and loss of PVAT anti-contractile effect. Inactivation of O₂^.- , dismutation of mitochondria-derived H₂ O₂ , uncoupling of oxidative phosphorylation and Rho kinase inhibition, decreased phenylephrine-induced contractions in aortae with PVAT from HFD-fed mice. O₂^.- and H₂ O₂ were increased in PVAT from HFD-fed mice. Mitochondrial respiration analysis revealed decreased O₂ consumption rates in PVAT from HFD-fed mice. TNF-α inhibition reduced H₂ O₂ levels in PVAT from HFD-fed mice. PVAT dysfunction, i.e. increased contraction to phenylephrine in PVAT-intact aortae, was not observed in HFD-obese mice lacking TNF-α receptors. Generation of H₂ O₂ was prevented in PVAT from TNF-α receptor deficient obese mice.

CONCLUSION AND IMPLICATIONS

TNF-α-induced mitochondrial oxidative stress is a key and novel mechanism involved in obesity-associated PVAT dysfunction. These findings elucidate molecular mechanisms whereby oxidative stress in PVAT could affect vascular function.

LINKED ARTICLES

This article is part of a themed section on Molecular Mechanisms Regulating Perivascular Adipose Tissue - Potential Pharmacological Targets? To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.20/issuetoc.

c-Src Inhibition Improves Cardiovascular Function but not Remodeling or Fibrosis in Angiotensin II–Induced Hypertension

c-Src plays an important role in angiotensin II (Ang II) signaling. Whether this member of the Src family kinases is involved in the development of Ang II–induced hypertension and associated cardiovascular damage in vivo remains unknown. Here, we studied Ang II–infused (400 ng/kg/min) mice in which c-Src was partially deleted ( c-Src +/− ) and in wild-type (WT, c-Src +/+ ) mice treated with a c-Src inhibitor (CGP077675; 25 mg/kg/d). Ang II increased blood pressure and induced endothelial dysfunction in WT mice, responses that were ameliorated in c-Src +/− and CGP077675-treated mice. Vascular wall thickness and cross-sectional area were similarly increased by Ang II in WT and c-Src +/− mice. CGP077675 further increased cross-sectional area in hypertensive mice. Cardiac dysfunction (ejection fraction and fractional shortening) in Ang II–infused WT mice was normalized in c-Src +/− mice. Increased oxidative stress (plasma thiobarbituric acid–reactive substances, hydrogen peroxide, and vascular superoxide generation) in Ang II–infused WT mice was attenuated in c-Src–deficient and CGP077675-treated mice. Hyperactivation of vascular c-Src, ERK1/2 (extracellular signal–regulated kinase 1/2), and JNK (c-Jun N-terminal kinase) in hypertensive mice was normalized in CGP077675-treated and c-Src +/− mice. Vascular fibronectin was increased by Ang II in all groups and further augmented by CGP077675. Cardiac fibrosis and inflammation induced by Ang II were amplified in c-Src +/− and CGP-treated mice. Our data indicate that although c-Src downregulation attenuates development of hypertension, improves endothelial and cardiac function, reduces oxidative stress, and normalizes vascular signaling, it has little beneficial effect on fibrosis. These findings suggest a divergent role for c-Src in Ang II–dependent hypertension, where c-Src may be more important in regulating redox-sensitive cardiac and vascular function than fibrosis and remodeling.

Augmented oxidative stress and preserved vasoconstriction induced by hydrogen peroxide in coronary arteries in obesity: role of COX-2

BACKGROUND AND PURPOSE

Oxidative stress plays a key role in the vascular and metabolic abnormalities associated with obesity. Herein, we assessed whether obesity can increase coronary vasoconstriction induced by hydrogen peroxide (H₂ O₂ ) and the signalling pathways involving COX-2 and superoxide (O₂^.- ) generation.

EXPERIMENTAL APPROACH

Contractile responses to H₂ O₂ and O₂^.- generation were measured in coronary arteries from genetically obese Zucker rats (OZR) and compared to lean Zucker rats (LZR).

KEY RESULTS

Both basal and H₂ O₂ -stimulated O₂^.- production were enhanced in coronary arteries from OZR, but H₂ O₂ -induced vasoconstriction was unchanged. The selective COX-2 inhibitor NS398 significantly reduced H₂ O₂ -induced contractions in endothelium-denuded arteries from LZR and OZR, but only in endothelium-intact arteries from LZR. PGI₂ (IP) receptor antagonism modestly reduced the vasoconstrictor action of H₂ O₂ while antagonism of the PGE₂ receptor 4 (EP₄ ) enhanced H₂ O₂ contractions in arteries from OZR but not LZR. Basal release of COX-2-derived PGE₂ was higher in coronary arteries from OZR where the selective agonist of EP₄ receptors TCS 2519 evoked potent relaxations. COX-2 was up-regulated after acute exposure to H₂ O₂ in coronary endothelium and vascular smooth muscle (VSM) and inhibition of COX-2 markedly reduced H₂ O₂ -elicited O₂^.- generation in coronary arteries and myocardium. Expression of Nox subunits in VSM and NADPH-stimulated O₂^.- generation was enhanced and contributed to H₂ O₂ vasoconstriction in arteries from obese rats.

CONCLUSION AND IMPLICATIONS

COX-2 contributes to cardiac oxidative stress and to the endothelium-independent O₂^.- -mediated coronary vasoconstriction induced by H₂ O₂ in obesity, which is offset by the release of COX-2-derived endothelial PGE₂ acting on EP₄ vasodilator receptors.

Constrictor prostanoids and uridine adenosine tetraphosphate: vascular mediators and therapeutic targets in hypertension and diabetes

Vascular dysfunction plays a pivotal role in the development of systemic complications associated with arterial hypertension and diabetes. The endothelium, or more specifically, various factors derived from endothelial cells tightly regulate vascular function, including vascular tone. In physiological conditions, there is a balance between endothelium-derived factors, that is, relaxing factors (endothelium-derived relaxing factors; EDRFs) and contracting factors (endothelium-derived contracting factors; EDCFs), which mediate vascular homeostasis. However, in disease states, such as diabetes and arterial hypertension, there is an imbalance between EDRF and EDCF, with a reduction of EDRF signalling and an increase of EDCF signalling. Among EDCFs, COX-derived vasoconstrictor prostanoids play an important role in the development of vascular dysfunction associated with hypertension and diabetes. Moreover, uridine adenosine tetraphosphate (Up4 A), identified as an EDCF in 2005, also modulates vascular function. However, the role of Up4 A in hypertension- and diabetes-associated vascular dysfunction is unclear. In the present review, we focused on experimental and clinical evidence that implicate these two EDCFs (vasoconstrictor prostanoids and Up4 A) in vascular dysfunction associated with hypertension and diabetes.