Antioxidant effect of adrenomedullin on angiotensin II-induced reactive oxygen species generation in vascular smooth muscle cells

Adrenomedullin Improves Hypertension and Vascular Remodeling partly through the Receptor-Mediated AMPK Pathway in Rats with Obesity-Related Hypertension

Adrenomedullin (ADM) is a novel cardiovascular peptide with anti-inflammatory and antioxidant properties. Chronic inflammation, oxidative stress and calcification play pivotal roles in the pathogenesis of vascular dysfunction in obesity-related hypertension (OH). Our study aimed to explore the effects of ADM on the vascular inflammation, oxidative stress and calcification in rats with OH. Eight-week-old Sprague Dawley male rats were fed with either a Control diet or a high fat diet (HFD) for 28 weeks. Next, the OH rats were randomly subdivided into two groups as follows: (1) HFD control group, and (2) HFD with ADM. A 4-week treatment with ADM (7.2 μg/kg/day, ip) not only improved hypertension and vascular remodeling, but also inhibited vascular inflammation, oxidative stress and calcification in aorta of rats with OH. In vitro experiments, ADM (10 nM) in A7r5 cells (rat thoracic aorta smooth muscle cells) attenuated palmitic acid (PA, 200 μM) or angiotensin II (Ang II, 10 nM) alone or their combination treatment-induced inflammation, oxidative stress and calcification, which were effectively inhibited by the ADM receptor antagonist ADM22-52 and AMP-activated protein kinase (AMPK) inhibitor Compound C, respectively. Moreover, ADM treatment significantly inhibited Ang II type 1 receptor (AT1R) protein expression in aorta of rats with OH or in PA-treated A7r5 cells. ADM improved hypertension, vascular remodeling and arterial stiffness, and attenuated inflammation, oxidative stress and calcification in OH state partially via receptor-mediated AMPK pathway. The results also raise the possibility that ADM will be considered for improving hypertension and vascular damage in patients with OH.

Kinetics of Biomarkers of Oxidative Stress in Septic Shock: A Pilot Study

Septic shock is a major cause of mortality in ICU patients, its pathophysiology is complex and not properly understood. Oxidative stress seems to be one of the most important mechanisms of shock progression to multiple organ failure. In the present pilot study, we have analysed eight oxidative-stress-related biomarkers in seven consecutive time points (i.e., the first seven days) in 21 septic shock patients admitted to the ICU. Our objective was to describe the kinetics of four biomarkers related to pro-oxidative processes (nitrite/nitrate, malondialdehyde, 8-oxo-2′-deoxyguanosine, soluble endoglin) compared to four biomarkers of antioxidant processes (the ferric reducing ability of plasma, superoxide dismutase, asymmetric dimethylarginine, mid-regional pro-adrenomedullin) and four inflammatory biomarkers (CRP, IL-6, IL-10 and neopterin). Furthermore, we analysed each biomarker’s ability to predict mortality at the time of admission and 12 h after admission. Although a small number of study subjects were recruited, we have identified four promising molecules for further investigation: soluble endoglin, superoxide dismutase, asymmetric dimethylarginine and neopterin.

Effects of Melatonin and Adrenomedullin in Reducing the Cardiotoxic Effects of Doxorubicin in Rats

The main disadvantage of doxorubicin (DOX) is that it has cardiotoxic side effects. Our aim is to evaluate the cardioprotective effects of adrenomedullin (ADM) and to compare these effects with melatonin (MEL), it's cardioprotective effects are well known. Rats were divided into four groups: Control group (0.9% NaCl solution, intravenously), Doxorubicin group (45 mg/kg DOX, intravenously), Doxorubicin + Melatonin group (DOX + MEL, 10 mg/kg melatonin, intraperitoneally), Doxorubicin + Adrenomedullin group (DOX + ADM, 12 µg/kg adrenomedullin, intraperitoneally). A single dose of DOX was injected to the experimental groups on day 5, and a single dose of 0.9% NaCl solution was injected to the control group through the tail vein. The animals were anesthetized and ECG recordings were obtained on day 8. For the purpose of biochemical and histological analysis, cardiac tissue biopsy was obtained after ECG recordings. Compared to the control group, the DOX group had significantly increased duration of QRS complex, PR interval, QT interval and QTc interval. QRS complex, QT interval and QTc interval were prolonged with the administration of DOX and shortened with the administration of ADM. MEL weakened the toxic effects of DOX on the cardiac tissue and it is shown histologically. DOX increased interleukins (IL-1α, IL-6, IL-18), tumor necrosis factor-α (TNF-α), hypoxia-inducible factor 1-alpha (HIF-1α), malondialdehyde (MDA), nitric oxide (NO), creatine kinase myocardial band (CK-MB), and total oxidant status (TOS) levels in cardiac tissue, while reducing total antioxidant status (TAS), superoxide dismutase (SOD) and catalase (CAT) levels. MEL administration decreased the levels of CK-MB, MDA, IL-1α, IL-6, IL-18, NO, and TNF-α, whereas ADM only decreased IL-1α, IL-18, MDA and TNF-α levels. In summary, these results show that DOX has toxic effects on rat cardiac tissue which is documented histologically, electrocardiographically and biochemically. MEL alleviated histological damage and showed improvement on the several biochemical parameters of cardiac tissue. ADM brought several electrocardiographic and biochemical parameters closer to normal values.

Uremic Toxins and Vascular Calcification-Missing the Forest for All the Trees

The cardiorenal syndrome relates to the detrimental interplay between the vascular system and the kidney. The uremic milieu induced by reduced kidney function alters the phenotype of vascular smooth muscle cells (VSMC) and promotes vascular calcification, a condition which is strongly linked to cardiovascular morbidity and mortality. Biological mechanisms involved include generation of reactive oxygen species, inflammation and accelerated senescence. A better understanding of the vasotoxic effects of uremic retention molecules may reveal novel avenues to reduce vascular calcification in CKD. The present review aims to present a state of the art on the role of uremic toxins in pathogenesis of vascular calcification. Evidence, so far, is fragmentary and limited with only a few uremic toxins being investigated, often by a single group of investigators. Experimental heterogeneity furthermore hampers comparison. There is a clear need for a concerted action harmonizing and standardizing experimental protocols and combining efforts of basic and clinical researchers to solve the complex puzzle of uremic vascular calcification.

Protective Effects of Adrenomedullin on Rat Cerebral Tissue After Transient Bilateral Common Carotid Artery Occlusion and Reperfusion

Objective

We aimed to investigate the protective effect of adrenomedullin (ADM) on cerebral tissue of rats with cerebral ischemia/reperfusion (I/R) injury.

Methods

Thirty-two Wistar rats were randomized into four groups (n=8). In the I/R Group, bilateral common carotid arteries were clamped for 30 minutes and, subsequently, reperfused for 120 minutes. In the ADM Group, rats received 12 µg/kg of ADM. In the I/R+ADM Group, bilateral common carotid arteries were clamped for 30 minutes and, subsequently, the rats received 12 µg/ kg of ADM. Then, reperfusion was performed for 120 minutes. The Control Group underwent no procedure. Blood and brain tissue samples were collected for biochemical and histopathological analysis. Serum malondialdehyde (MDA), superoxide dismutase (SOD), and glutathione peroxidase (GPx) were analysed. Brain tissue was evaluated histopathologically and neuronal cells were counted in five different fields, at a magnification of ×400.

Results

Brain MDA in I/R Group was significantly higher than in ADM Group. Brain GPx and SOD in I/R+ADM Group were significantly higher than in I/R Group. The number of neurons was decreased in I/R Group compared to the Control Group. The number of neurons in I/R+ADM Group was significantly higher than in I/R Group, and lower than in Control Group. Apoptotic changes decreased significantly in I/R+ADM Group and the cell structure was similar in morphology compared to the Control Group.

Conclusion

We demonstrated the cerebral protective effect of ADM in the rat model of cerebral I/R injury after bilateral carotid artery occlusion.

Oral Resolvin D1 attenuates early inflammation but not intimal hyperplasia in a rat carotid angioplasty model

Inflammation ensuing from vascular injury promotes intimal hyperplasia (IH) and restenosis. Resolvin D1 (RvD1) is a lipid mediator that attenuates IH in vivo when delivered locally to the vessel wall in animal models. We tested the hypothesis that peri-procedural oral administration of RvD1 could blunt the local inflammatory response to angioplasty, and attenuate downstream IH. Carotid angioplasty was performed on rats fed with either RvD1 or vehicle through oral gavage, starting one day prior to injury until post-operative day (POD) 3 or 14 when arteries were harvested. To study pharmacokinetics and bioactivity of oral RvD1, we measured plasma RvD1 by ELISA, whole blood phagocytosis activity using flow cytometry, and cAMP levels in the thoracic aorta by ELISA. Carotid arteries were harvested on POD3 for staining (anti-CD45, anti-Myeloperoxidase (MPO), anti-Ki67 or dihydroethidium (DHE) for reactive oxygen species), mRNA expression of target genes (quantitative RT-PCR), or on POD14 for morphometry (elastin stain). RvD1 plasma concentration peaked 3 h after gavage in rats, at which point we concurrently observed an increase in circulating monocyte phagocytosis activity and aortic cAMP levels in RvD1-treated rats vs. vehicle. Oral RvD1 attenuated local arterial inflammation after angioplasty by reducing CD45+, MPO+, Ki67+ cells, and DHE staining intensity. Oral RvD1 also reduced the expression of several pro-inflammatory genes within the injured vessels. However, oral RvD1 did not significantly reduce IH. Oral RvD1 attenuated acute inflammation within the arterial wall after angioplasty in rats, but did not significantly affect IH.

Effect of Valsartan on Cerebellar Adrenomedullin System Dysregulation During Hypertension

Adrenomedullin (AM) and its receptors components, calcitonin-receptor-like receptor (CRLR), and receptor activity-modifying protein (RAMP1, RAMP2, and RAMP3) are expressed in cerebellum. Cerebellar AM, AM binding sites and receptor components are altered during hypertension, suggesting a role for cerebellar AM in blood pressure regulation. Thus, we assessed the effect of valsartan, on AM and its receptor components expression in the cerebellar vermis of Wistar Kyoto (WKY) and spontaneously hypertensive (SHR) rats. Additionally, we evaluated AM action on superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) activity, and thiobarbituric acid reactive substances (TBARS) production in cerebellar vermis. Animals were treated with valsartan or vehicle for 11 days. Rats were sacrificed by decapitation; cerebellar vermis was dissected; and AM, CRLR, RAMP1, RAMP2, and RAMP3 expression was quantified by Western blot analysis. CAT, SOD, and GPx activity was determined spectrophotometrically and blood pressure by non-invasive plethysmography. We demonstrate that AM and RAMP2 expression was lower in cerebellum of SHR rats, while CRLR, RAMP1, and RAMP3 expression was higher than those of WKY rats. AM reduced cerebellar CAT, SOD, GPx activities, and TBARS production in WKY rats, but not in SHR rats. Valsartan reduced blood pressure and reversed the altered expression of AM and its receptors components, as well the loss of AM capacity to reduce antioxidant enzyme activity and TBARS production in SHR rats. These findings demonstrate that valsartan is able to reverse the dysregulation of cerebellar adrenomedullinergic system; and they suggest that altered AM system in the cerebellum could represent the primary abnormality leading to hypertension.

Molecular Mechanisms Underlying Renin-Angiotensin-Aldosterone System Mediated Regulation of BK Channels

Large-conductance calcium-activated potassium channels (BK channels) belong to a family of Ca²⁺-sensitive voltage-dependent potassium channels and play a vital role in various physiological activities in the human body. The renin-angiotensin-aldosterone system is acknowledged as being vital in the body's hormone system and plays a fundamental role in the maintenance of water and electrolyte balance and blood pressure regulation. There is growing evidence that the renin-angiotensin-aldosterone system has profound influences on the expression and bioactivity of BK channels. In this review, we focus on the molecular mechanisms underlying the regulation of BK channels mediated by the renin-angiotensin-aldosterone system and its potential as a target for clinical drugs.

Dysregulation of Cerebellar Adrenomedullin Signaling During Hypertension

Adrenomedullin (AM) is a peptide involved in blood pressure regulation. AM activates three different receptors, the AM type 1 (AM1), type 2 (AM2), and calcitonin gene-related peptide 1 (CGRP1) receptors. AM triggers several signaling pathways such as adenylyl cyclase (AC), guanylyl cyclase (GC), and extracellular signal-regulated kinases (ERK) and modulates reactive oxygen species (ROS) metabolism. Cerebellar AM, AM-binding sites, and its receptor components are altered during hypertension, although it is unknown if these alterations are associated with changes in AM signaling. Thus, we assessed AM signaling pathways in cerebellar vermis of 16-week-old Wistar Kyoto (WKY) and spontaneously hypertensive rats (SHR). Animals were sacrificed by decapitation, and cerebellar vermis was microdissected under stereomicroscopic control. Tissue was stimulated in vitro with AM. Then the production of cyclic guanosine monophosphate (cGMP), nitric oxide (NO) and cyclic adenosine monophosphate (cAMP) were assessed along with ERK1/2 activation and three antioxidant enzymes' activity: glutathione peroxidase (GPx), catalase (CAT), and superoxide dismutase (SOD). Our findings demonstrate that in the cerebellar vermis of normotensive rats, AM increases cGMP, NO, cAMP production, and ERK1/2 phosphorylation, while decreases basal antioxidant enzyme activity. In addition, AM antagonizes angiotensin II (ANG II)-induced increment of antioxidant enzyme activity. Hypertension blunts AM-induced cGMP and NO production and AM-induced decrease of antioxidant enzyme activity. Meanwhile, AM-induced effects on cAMP production, ERK1/2 activation, and AM-ANG II antagonism were not altered in SHR rats. Our results support a dysregulation of several AM signaling pathways during hypertension in cerebellar vermis.

Neuropeptides and Microglial Activation in Inflammation, Pain, and Neurodegenerative Diseases

Microglial cells are responsible for immune surveillance within the CNS. They respond to noxious stimuli by releasing inflammatory mediators and mounting an effective inflammatory response. This is followed by release of anti-inflammatory mediators and resolution of the inflammatory response. Alterations to this delicate process may lead to tissue damage, neuroinflammation, and neurodegeneration. Chronic pain, such as inflammatory or neuropathic pain, is accompanied by neuroimmune activation, and the role of glial cells in the initiation and maintenance of chronic pain has been the subject of increasing research over the last two decades. Neuropeptides are small amino acidic molecules with the ability to regulate neuronal activity and thereby affect various functions such as thermoregulation, reproductive behavior, food and water intake, and circadian rhythms. Neuropeptides can also affect inflammatory responses and pain sensitivity by modulating the activity of glial cells. The last decade has witnessed growing interest in the study of microglial activation and its modulation by neuropeptides in the hope of developing new therapeutics for treating neurodegenerative diseases and chronic pain. This review summarizes the current literature on the way in which several neuropeptides modulate microglial activity and response to tissue damage and how this modulation may affect pain sensitivity.

Adrenomedullin and angiotensin II signaling pathways involved in the effects on cerebellar antioxidant enzymes activity

Human adrenomedullin (AM) is a 52-amino acid peptide involved in cardiovascular control. AM has two specific receptors formed by the calcitonin-receptor-like receptor (CRLR) and receptor activity-modifying protein (RAMP) 2 or 3, known as AM1 and AM2 receptors, respectively. In addition, AM has appreciable affinity for the calcitonin gene-1 related peptide receptor (CGRP1), composed of CRLR/RAMP1. In brain, AM and their receptors are expressed in several localized areas, including the cerebellum. AM has been reported as an antioxidant. Little is known about the role of AM in the regulation of cerebellar reactive oxygen species (ROS) metabolism. We assessed the effect of AM on three antioxidant enzymes activity: catalase (CAT), glutathione peroxidase (GPx) and superoxide dismutase (SOD) and on thiobarbituric acid reactive substances (TBARS) production in rat cerebellar vermis, as well the receptor subtypes involved in AM actions. Additionally, we evaluated the role of angiotensin II (ANG II), protein kinase A (PKA) activity, and protein kinase C/nicotinamide adenine dinucleotide phosphate oxidase (PKC/NAD(P)H) (oxidase) pathway. Sprague-Dawley rats were sacrificed by decapitation and cerebellar vermis was microdissected under stereomicroscopic control. CAT, GPx, SOD activity and TBARS production was determined spectrophotometrically. Our findings demonstrated that in cerebellar vermis, AM decreased and ANG II increased CAT, GPx and SOD activity and TBARS production. Likewise, AM antagonized ANG II-induced increase antioxidant enzyme activity. AM(22-50) and CGRP(8-37) blunted AM-induced decrease of antioxidant enzymes activity and TBARS production indicating that these actions are mediated through AM and CGRP₁ receptors. Further, PKA inhibitor (PKAi) blunted AM action and apocynin and chelerythrine reverted ANG II action, suggesting that AM antioxidant action is mediated through stimulation of PKA activity, while ANG II-induced stimulation through PKC/NAD(P)H oxidase pathway. Our results support the role of AM in the regulation of cerebellar antioxidant enzymes activity and suggest a physiological role for AM in cerebellum.

Cerebellar Adrenomedullinergic System. Role in Cardiovascular Regulation

Adrenomedullin (AM) is a multifunctional peptide which exerts numerous biological activities through the activation of AM1 (CRLR + RAMP2) and AM2 (CRLR + RAMP3) receptors. AM immunoreactivity, AM binding sites and CRLR, RAMP1, RAMP2 and RAMP3 are expressed in rat cerebellar vermis. AM binding sites are discretely and differentially distributed in the rat cerebellar cortex with higher levels detected in SHR when compared with WKY rats. In addition, there is an up-regulation of cerebellar CGRP1 (CRLR + RAMP1) and AM2 (CRLR + RAMP3) receptors and a down-regulation of AM1 (CRLR + RAMP2) receptor during hypertension associated with a decreased AM expression. These changes may constitute a mechanism which contributes to the development of hypertension, and supports the notion that cerebellar AM is involved in the regulation of blood pressure. Cerebellar AM activates ERK, increases cAMP, cGMP and nitric oxide, and decreases antioxidant enzyme activity. These effects are mediated through AM₁ receptor since they are blunted by AM(22-52). AM-stimulated cAMP production is mediated through AM2 and CGRP receptors. In vivo administration of AM into the cerebellar vermis caused a profound, specific and dose-dependent hypotensive effect in SHR, but not in normotensive WKY rats. This effect was mediated through AM1 receptor since it was abolished by AM(22-52). In addition, AM injected into the cerebellar vermis reduced vasopressor response to footshock stress. These findings demonstrate dysregulation of cerebellar AM system during hypertension, and suggest that cerebellar AM plays an important role in the regulation of blood pressure. Likewise, they constitute a novel mechanism of blood pressure control which has not been described so far.

Cyclo(phenylalanine-proline) induces DNA damage in mammalian cells via reactive oxygen species

Cyclo(phenylalanine‐proline) is produced by various organisms such as animals, plants, bacteria and fungi. It has diverse biological functions including anti‐fungal activity, anti‐bacterial activity and molecular signalling. However, a few studies have demonstrated the effect of cyclo(phenylalanine‐proline) on the mammalian cellular processes, such as cell growth and apoptosis. In this study, we investigated whether cyclo(phenylalanine‐proline) affects cellular responses associated with DNA damage in mammalian cells. We found that treatment of 1 mM cyclo(phenylalanine‐proline) induces phosphorylation of H2AX (S139) through ATM‐CHK2 activation as well as DNA double strand breaks. Gene expression analysis revealed that a subset of genes related to regulation of reactive oxygen species (ROS) scavenging and production is suppressed by the cyclo(phenylalanine‐proline) treatment. We also found that cyclo(phenylalanine‐proline) treatment induces perturbation of the mitochondrial membrane, resulting in increased ROS, especially superoxide, production. Collectively, our study suggests that cyclo(phenylalanine‐proline) treatment induces DNA damage via elevation of ROS in mammalian cells. Our findings may help explain the mechanism underlying the bacterial infection‐induced activation of DNA damage response in host mammalian cells.

Plasma Adrenomedullin and Allelic Variation in the ADM Gene and Kidney Disease in People With Type 2 Diabetes

Production of adrenomedullin (ADM), a vasodilator peptide, increases in response to ischemia and hypoxia in the vascular wall and the kidney. This may be an adaptive response providing protection against organ damage. We investigated the hypothesis that ADM has a nephroprotective effect in two prospective cohorts of patients with type 2 diabetes recruited in France. The highest tertile of plasma MR-proADM (a surrogate for ADM) concentration at baseline was associated with the risk of renal outcomes (doubling of plasma creatinine concentration and/or progression to end-stage renal disease) during follow-up in both cohorts. Four SNPs in the ADM gene region were associated with plasma MR-proADM concentration at baseline and with eGFR during follow-up in both cohorts. The alleles associated with lower eGFR were also associated with lower plasma MR-proADM level. In conclusion, plasma MR-proADM concentration was associated with renal outcome in patients with type 2 diabetes. Our data suggest that the ADM gene modulates the genetic susceptibility to nephropathy progression. Results are consistent with the hypothesis of a reactive rise of ADM in diabetic nephropathy, blunted in risk alleles carriers, and with a nephroprotective effect of ADM. A possible therapeutic effect of ADM receptor agonists in diabetic renal disease would be worth investigating.

Genome-wide gene expression profiling of ischemia-reperfusion injury in rat kidney, intestine and skeletal muscle implicate a common involvement of MAPK signaling pathway

The mechanisms of ischemia‑reperfusion (I/R) injury have not been fully elucidated to date. In order to determine the genetic involvement across different organs during I/R injury, a DNA microarray approach was used to analyze the gene expression profiles of the kidney, intestine, and skeletal muscle in a rat model of I/R injury. Fifteen male Lewis rats were divided randomly into three different organ groups; a sham operation (control group), 60‑min‑ischemia (Is group) only, and 60‑min‑ischemia plus 60‑min‑reperfusion (I/R group), respectively. The target genes were identified by DNA microarray and studied by quantitative polymerase chain reaction (qPCR). By comparing the I/R group with the control group, a 2‑fold upregulation of 467, 172, and 3932 and a 2‑fold downregulation of 437, 416, and 4203 genes were identified in the kidney, small intestine, and skeletal muscle, respectively. Several commonly upregulated genes associated with mitogen‑activated protein kinase (MAPK) pathways, including Jun, Atf3, junB, Fos, Adm and Dusp 1, were differentially expressed in the I/R group. The mRNA expression levels of the target genes were confirmed by qPCR. The present study hypothesized that the MAPK pathway may function in a common pathway of I/R injury and regulate the pathogenesis through activator protein 1. The findings of the present study contributed to the understanding of the molecular pathways associated with I/R injury.

Study of the association of adrenomedullin and basic-fibroblast growth factors with the peripheral arterial blood flow and endothelial dysfunction biomarkers in type 2 diabetic patients with peripheral vascular insufficiency

Background

Progressive micro-vascular vaso-degeneration is the major factor in progression of diabetic complications. Adrenomedullin (AM) and basic-Fibroblast growth factor (b-FGF) are strongly correlated with angiogenesis in vascular diseases. This study aims to provide base line data regarding the vascular effects and correlation of AM, and b-FGF with the peripheral blood flow in diabetic patients with peripheral vascular disease (PVD), and their effect on endothelial dysfunction markers. Ninety age- and sex matched females were enrolled in the study: 30 were controls, 30 had diabetes without complications (group II) and 30 had diabetes with PVD (group III) diagnosed by ankle/ brachial index (A/BI). Plasma levels of AM, b-FGF, intercellular adhesion molecule −1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) were measured by indirect enzyme immunoassay (ELISA).

Results

There was a significant increase in plasma AM, VCAM-1and ICAM-1, while a significant decrease in plasma b-FGF in diabetic patients with PVD (p < 0.05). A positive correlation was observed between plasma AM, b-FGF and A/BI and a negative correlation with VCAM −1 and ICAM in diabetic PVD. AM was not a predictor, while b-FG, VCAM-1 and ICAM-1 could be predictors for peripheral blood flow in diabetic PVD.

Conclusion

This study elucidates for the first time that AM and b-FGF are correlated and have a direct impact on the peripheral blood flow, the rise of AM in diabetic PVD may be a consecutive and compensatory vasculo-protective effect as its angiogenic and anti-inflammatory properties act to relief the endothelial insult. Down expression of b-FGF may be a predisposing factor for micro-vascular derangement. It is not clear if the rise of AM and the decline of b- FGF levels may be consequences or predisposing factors for VCAM-1 and ICAM-1 elevation as these endothelial dysfunction biomarkers could reduce peripheral blood flow and vascular integrity. It is optimistic to believe that drug intervention through AM and b-FGF administration together with reversing the endothelial inflammatory process by targeting VCAM and ICAM could reduce the prevalence of diabetic vascular complications, reduce the risk of cerebrovascular and cardiovascular morbidity in diabetes through normalizing vascular endothelium function and peripheral blood flow.

Deficiency of growth factor midkine exacerbates necrotizing glomerular injuries in progressive glomerulonephritis

Inflammatory cell infiltration and fibrin deposition play important roles in the development of crescentic glomerulonephritis (GN). In particular, activation of coagulation is an indispensable factor in crescent formation. However, the mechanisms underlying the pathogenesis of crescent formation have not been completely elucidated. We identified the growth factor midkine (MK) as a novel key molecule in the progression of crescentic GN induced by anti-glomerular basement membrane antibody. Despite the lack of significant differences in autologous and heterologous reactions, MK-deficient (Mdk(-/-)) mice unexpectedly showed a greater number of necrotizing glomerular injuries than wild-type (Mdk(+/+)) mice. Likewise, more tubulointerstitial damage was observed in Mdk(-/-) mice, and this damage positively correlated with glomerular injury. Plasminogen activator inhibitor (PAI)-1 was strongly induced in the injured glomerulus of Mdk(-/-) mice, particularly in crescents and endothelial cells. This enhanced PAI-1 production was associated with an increase in inflammatory cell infiltration and matrix deposition in the glomerulus and the interstitium of Mdk(-/-) mice. In line with these in vivo data, primary cultured endothelial cells derived from Mdk(-/-) mice exhibited higher PAI-1 mRNA expression on fibrin challenge and less fibrinolysis than Mdk(+/+) mice. In contrast, the expression of plasminogen activators was not affected. Our combined data suggest that MK leads to a blockade of PAI-1, which is closely associated with the suppression of crescentic GN.

Adrenomedullin and cardiovascular diseases

The cardiovascular system is regulated by the autonomic nervous system, the renin-angiotensin-aldosterone system, nitric oxide (NO) and other factors including neuropeptides. Research in neurohumoral factors has led to the development of many cardiovascular drugs. Adrenomedullin (ADM), initially isolated from the adrenal gland, has diverse physiological and pathophysiological functions in the cardiovascular system. It is produced in many organs and tissues including the vasculature. ADM has numerous actions, including vasodilation, natriuresis, antiapoptosis and stimulation of NO production. It might play a protective role in various cardiovascular pathologies, and its plasma level is elevated in patients with hypertension and heart failure. Administration of ADM is a possible therapeutic approach for treating cardiovascular diseases. A number of studies have investigated the infusion of ADM in humans, which seems to be benficial in heart failure and myocardial infarction. Instead of ADM infusion, augmentation of its endogenous level is another possible strategy. Gene therapy is feasible in animal models, but its application in humans is limited. At present, the most promising clinical application of ADM is the use of the plasma level of mid-regional proadrenomedullin as a biomarker in cardiovascular diseases. It is a good marker of prognosis and survival in patients with coronary aretery disease or heart failure.

8-Hydroxy-2-deoxyguanosine prevents plaque formation and inhibits vascular smooth muscle cell activation through Rac1 inactivation

8-Hydroxy-2-deoxyguanosine (8-OHdG), a marker of oxidative stress, has been recently rediscovered to inhibit Rac1 in neutrophils and macrophages, thereby inhibiting Rac1-linked functions of these cells, including reactive oxygen species production through NADPH oxidase activation, phagocytosis, chemotaxis, and cytokine release. In vascular smooth muscle cells (VSMCs), reactive oxygen species also induce abnormal proliferation and migration leading to progression of atherosclerosis. Based upon the involvement of reactive oxygen species in phagocytic cells and VSMCs during the atherosclerotic process, we hypothesized that 8-OHdG could have antiatherosclerotic action and tested this hypothesis in an experimentally induced atherosclerosis in mice. Partially ligated ApoE knockout mice, a more physiologically relevant model of low and oscillatory flow, developed an advanced lesion in 2 weeks, and orally administered 8-OHdG significantly reduced plaque formation along with reduced superoxide formation, monocyte/macrophage infiltration, and extracellular matrix (ECM) accumulation. The effects of 8-OHdG observed in primary VSMCs were consistent with the in vivo effects of 8-OHdG and were inhibitory to angiotensin II or platelet-derived growth factor-induced production of reactive oxygen species, proliferation, migration, and ECM production. Also, angiotensin II-induced Rac1 activity in VSMCs was significantly inhibited by 8-OHdG, and transfection of constitutively active Rac1 reversed the inhibitory effect of 8-OHdG on VSMC activation. Molecular docking study showed that 8-OHdG stabilizes Rac1-GEF complex, indicating the physical contact of 8-OHdG with Rac1. These findings highly suggest that the antiatherosclerotic effect of 8-OHdG is mediated by inhibition of Rac1 activity. In conclusion, our results show a novel action of orally active 8-OHdG in suppressing atherosclerotic plaque formation in vivo and VSMC activation in vitro through inhibition of Rac1, which emphasizes a new therapeutic avenue to benefit atherosclerosis.

Impact of the additive effect of angiotensin-converting enzyme inhibitors and /or statins with antiplatelet medication on mortality after acute ischaemic stroke

There has been recent interest in combining antiplatelets, angiotensin-converting enzyme inhibitors (ACEIs) and statins in primary and secondary ischaemic stroke prevention. This observational study was performed to evaluate the impact of adding ACEIs and/or statins to antiplatelets on post-stroke in-hospital mortality. Ischaemic stroke patients attending a hospital in Malaysia over an 18-month period were evaluated. Patients were categorized according to their vital status at discharge. Data included demographic information, risk factors, clinical characteristics and previous medications with particular attention on antiplatelets, ACEIs and statins. In-hospital mortality was compared among patients who were not taking antiplatelets, ACEIs or statins before stroke onset versus those who were taking antiplatelets alone or in combination with either ACEIs, statins or both. Data analysis was performed using SPSS version 15. Overall, 637 patients met the study inclusion criteria. After controlling for the effects of confounders, adding ACEIs or statins to antiplatelets significantly decreased the incidence of death after stroke attack by 68% (p = 0.036) and 81% (p = 0.010), respectively, compared to patients on antiplatelets alone or none of these medications. Additionally, the addition of both ACEIs and statins to antiplatelet medication resulted in the highest reduction (by 94%) of the occurrence of death after stroke attack (p < 0.001). Our results suggest that adding ACEIs and/or statins to antiplatelets for patients at risk of developing stroke, either as a primary or as a secondary preventive regimen, was associated with a significant reduction in the incidence of mortality after ischaemic stroke than antiplatelets alone. These results might help reduce the rate of ischaemic stroke morbidity and mortality by enhancing the application of specific therapeutic and management strategies for patients at a high risk of acute stroke.

An ontogenic study of adrenomedullin gene expression in the rat lung, adrenal, kidney, and heart

In this study, the gene expression of adrenomedullin (Adm) in the peripheral tissues which include lung, adrenal, kidney, and heart during development was investigated in the rat. The preproadrenomedullin (preproAdm) mRNA and mRNAs of its related receptor components, calcitonin receptor-like receptor (Crlr), and receptor activity-modifying proteins (Ramp1, 2 and 3) of the lung, adrenal, kidney, and heart were measured by real-time RT-PCR and the ADM peptide measured by radioimmunoassay in 1-, 7-, 21-day-old rats and the adult rats. From day 1 to 21, preproAdm mRNA levels increased with age in the lung, the kidney, and the heart but decreased with age in the adrenal. ADM levels, however, increased with age in the lung but decreased with age in the kidney, the adrenal, and the heart. The preproAdm levels in the lung, in the kidney, and in the adrenal all increased in the adult rat. ADM peptide levels, however, decreased in the adult rat. Crlr and Ramp2 gene expression increased with age in the lung, in the kidney, and in the heart but decreased with age in the adrenal in the prepubertal rats. The results indicate that the levels of preproAdm mRNA, ADM peptide and its receptor component mRNAs in different tissues followed different patterns of changes during development.

Antioxidant and anti-inflammatory potential of hesperetin metabolites obtained from hesperetin-administered rat serum: an ex vivo approach

In recent years much attention has been focused on the pharmaceutical relevance of bioflavonoids, especially hesperidin and its aglycon hesperetin in terms of their antioxidant and anti-inflammatory actions. However, the bioactivity of their metabolites, the real molecules in vivo hesperetin glucuronides/sulfates produced after ingestion, has been poorly understood. Thus, the study using an ex vivo approach is aimed to compare the antioxidant and anti-inflammatory activities of hesperidin/hesperetin or hesperetin metabolites derived from hesperetin-administered rat serum. We found that hesperetin metabolites (2.5-20 μM) showed higher antioxidant activity against various oxidative systems, including superoxide anion scavenging, reducing power, and metal chelating effects, than that of hesperidin or hesperetin. The data also showed that pretreatment of hesperetin metabolites (1-10 μM) within the range of physiological concentrations, compared to hesperetin, significantly inhibited nitric oxide (NO) and prostaglandin E(2) (PGE(2)) production, as evidenced by the inhibition of their precursors, inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) protein levels without appreciable cytotoxicity on LPS-activated RAW264.7 macrophages or A7r5 smooth muscle cells. Concomitantly, hesperetin metabolites dose-dependently inhibited LPS-induced intracellular reactive oxygen species (ROS). Furthermore, hesperetin metabolites significantly downregulate LPS-induced nuclear factor-κB (NF-κB) activation followed by the suppression of inhibitor-κB (I-κB) degradation and phosphorylation of c-Jun N-terminal kinase1/2 (JNK1/2) and p38 MAPKs after challenge with LPS. Hesperetin metabolites ex vivo showed potent antioxidant and anti-inflammatory activity in comparison with hesperidin/hesperetin.

Adrenomedullin attenuates aortic cross-clamping-induced myocardial injury in rats

BACKGROUND

In this study we investigate the effects of adrenomedullin on myocardial injury after ischemia-reperfusion (I/R) after abdominal aortic surgery.

METHODS

Thirty-two Wistar rats were randomized into 4 groups (n = 8) as follows: control group (sham laparotomy), the aortic I/R group, aortic I/R plus adrenomedullin group (underwent aortic I/R periods, and received a bolus intravenous injection of .05 μg/kg/min adrenomedullin), and the control plus adrenomedullin group.

RESULTS

Biochemical analysis showed that aortic I/R significantly increased (P < .05) the plasma levels of troponin-I and tumor necrosis factor-α, and the myocardial tissue levels of malondialdehyde, superoxide dismutase, catalase, and angiotensin II, whereas aortic I/R plus adrenomedullin significantly decreased these same factors (P < .05). Aortic I/R significantly increased (P < .05) myocardial tissue levels of nitric oxide whereas aortic I/R plus adrenomedullin significantly increased the same factor (P < .05).

CONCLUSIONS

These results indicate that adrenomedullin has protective effects against myocardial injury induced by abdominal aortic I/R in rats.

Relationship of increased circulating adrenomedullin with cardiac dysfunction, inflammation, oxidative stress and volume overload in hemodialysis patients

Adrenomedullin (AM) is a peptide involved in cardiovascular homeostasis. The aim of our study was to investigate whether circulating AM might be related to cardiac function, volume overload, oxidative stress and inflammation in hemodialysis patients. Plasma adrenomedullin, C-reactive protein (CRP), oxidized LDL (ox-LDL), lipoprotein (a), systolic and diastolic cardiac functions were assessed before hemodialysis in 80 patients as well as in 40 healthy control subjects. Plasma adrenomedullin levels were significantly higher in the hemodialysis group compared to the control group. Plasma adrenomedullin levels were negatively correlated with systolic and diastolic blood pressure, S/D ratio, deceleration time, left ventricular ejection fraction, ox-LDL and lipoprotein (a). However, it was positively correlated with CRP, delta body weight, mitral E/A wave, and inferior vena cava diameter. Higher plasma adrenomedullin levels may provide a possible index of cardiac dysfunction, systemic inflammation, and volume overload conditions in haemodialysis patients with concomitant cardiovascular disease. In addition, the negative correlation between ox-LDL, lipoprotein (a) and adrenomedullin may suggest that endogenous AM is an important protective factor in anti-atherosclerosis and might be useful as a new target for prevention and therapy for the disease.

Aldosterone stimulates superoxide production in macula densa cells

Two major factors which regulate tubuloglomerular feedback (TGF)-mediated constriction of the afferent arteriole are release of superoxide (O(2)(-)) and nitric oxide (NO) by macula densa (MD) cells. MD O(2)(-) inactivates NO; however, among the factors that increase MD O(2)(-) release, the role of aldosterone is unclear. We hypothesize that aldosterone activates the mineralocorticoid receptor (MR) on MD cells, resulting in increased O(2)(-) production due to upregulation of cyclooxygenase-1 (COX-2) and NOX-2, and NOX-4, isoforms of NAD(P)H oxidase. Studies were performed on MMDD1 cells, a renal epithelial cell line with properties of MD cells. RT-PCR and Western blotting confirmed the expression of MR. Aldosterone (10(-8) mol/l for 30 min) doubled MMDD1 cell O(2)(-) production, and this was completely blocked by MR inhibition with 10(-5) mol/l eplerenone. RT-PCR, real-time PCR, and Western blotting demonstrated aldosterone-induced increases in COX-2, NOX-2, and NOX-4 expression. Inhibition of COX-2 (NS398), NADPH oxidase (apocynin), or a combination blocked aldosterone-induced O(2)(-) production to the same degree. These data suggest that aldosterone-stimulated MD O(2)(-) production is mediated by COX-2 and NADPH oxidase. Next, COX-2 small-interfering RNA (siRNA) specifically decreased COX-2 mRNA without affecting NOX-2 or NOX-4 mRNAs. In the presence of the COX-2 siRNA, the aldosterone-induced increases in COX-2, NOX-2, and NOX-4 mRNAs and O(2)(-) production were completely blocked, suggesting that COX-2 causes increased expression of NOX-2 and NOX-4. In conclusion 1) MD cells express MR; 2) aldosterone increases O(2)(-) production by activating MR; and 3) aldosterone stimulates COX-2, which further activates NOX-2 and NOX-4 and generates O(2)(-). The resulting balance between O(2)(-) and NO in the MD is important in modulating TGF.

Clinicopathological features of primary aldosteronism associated with subclinical Cushing's syndrome

Primary aldosteronism (PA), an autonomous aldosterone hypersecretion from adrenal adenoma and/or hyperplasia, and subclinical Cushing syndrome (SCS), a mild but autonomous cortisol hypersecretion from adrenal adenoma without signs or symptoms of Cuhing's syndrome, are now well-recognized clinical entities of adrenal incidentaloma. However, the clinicopathological features of PA associated with SCS (PA/SCS) remain unknown. The present study was undertaken to study the prevalence of PA/SCS among PA patients diagnosed at our institute, and characterize their clinicopathlogical features. The prevalence of PA/SCS was 8 of 38 PA patients (21%) studied. These 8 PA/SCS patients were significantly older and had larger tumor, higher serum potassium levels, lower basal plasma levels of aldosterone, ACTH and DHEA-S as well as lower response of aldosterone after ACTH stimulation than those in 12 patients with aldosterone-producing adenoma without hypercortisolism. All 8 PA/SCS patients showed unilateral uptake by adrenal scintigraphy at the ipsilateral side, whereas the laterality of aldosterone hypersecretion as determined by adrenal venous sampling varied from ipsilateral (3), contralateral (2), and bilateral side (2). 6 PA/SCS patinets who underwent adrenalectomy required hydrocortisone replacement postoperatively. Histopathological analysis of the resected adrenal tumors from 5 PA/SCS patients revealed a single adenoma in 3, and double adenomas in 2, with varying degrees of positive immunoreactivities for steroidgenic enzymes (3β-HSD, P450(C17)) by immunohistochemical study as well as CYP11B2 mRNA expression as measured by real-time RT-PCR. In conclusion, PA/SCS consists of a variety of adrenal pathologies so that therapeutic approach differs depending on the disease subtype.

Impact of angiotensin-converting enzyme inhibitors administration prior to acute ischemic stroke onset on in-hospital mortality

INTRODUCTION

Angiotensin-converting enzyme inhibitors (ACEIs) have shown promising results in decreasing the incidence and the severity of ischemic stroke in populations at risk and in improving ischemic stroke outcomes.

OBJECTIVES

The objectives of this study were to investigate the impact of ACEI use before ischemic stroke onset on in-hospital mortality and to identify the independent predictors of in-hospital mortality among patients with ischemic stroke.

METHODS AND MATERIALS

A retrospective cohort study of all patients with acute ischemic stroke attending the hospital from June 1, 2008 to November 30, 2008 was performed. Data were collected from medical records and included demographic information, diagnostic information, risk factors, previous ACEI use, and vital discharge status. Statistical Package for Social Sciences (SPSS) version 15 was used for data analysis.

RESULTS

A total of 327 patients with acute ischemic stroke were studied, of which 119 (36.4%) had documented previous ACEI use. During the study period, 52 (15.9%) of the patients with acute ischemic stroke died in hospital. In-hospital mortality was significantly lower among patients who were on ACEI before the attack (P = 0.002). The independent predictors for in-hospital mortality among patients with ischemic stroke were age >or=65 years (P < .001), the presence of diabetes mellitus (P = .012), renal impairment (P = .002), and heart failure (P = .001). Moreover, prior use of ACEI was an independent predictor for survival after ischemic stroke attack (P < .001).

CONCLUSION

This study provides evidence that the prophylactic administration of ACEI before ischemic stroke may be a potential life-saving strategy. Furthermore, knowledge of in-hospital mortality predictors is necessary to improve survival rate after acute stroke.

Adrenomedullin ameliorates the development of atherosclerosis in apoE-/- mice

Adrenomedullin (ADM) is a multifunctional peptide regulating cardiovascular homeostasis. We studied the role of ADM in the pathogenesis of atherosclerosis by investigating changes in ADM and its receptors - calcitonin receptor-like receptor (CRLR) and receptor activity-modifying proteins (RAMPs) - in aorta of apoE-/- mice and the effect of exogenous ADM administration. ApoE-/- mice were fed an atherogenic diet for 4 weeks, and apoE-/-+ADM mice were additionally given subcutaneous injections of ADM, 300ng/kg/h, for 4 weeks. ApoE-/- mice fed an atherogenic diet showed hyperlipidemia, a large plaque area and increased vessel wall thickness. The mRNA expression and protein level of ADM/ADM receptors were increased in the aorta, compared with C57BL/6J mice. The elevated mRNA level of CRLR and RAMPs correlated positively with ADM mRNA level. Radioimmunoassay revealed a higher plasma and aorta ADM content, by 61.6% and 285% (both P<0.01), respectively, in apoE-/- mice than that in C57BL/6J mice. Exogenous ADM significantly ameliorated dyslipidemia in apoE-/- mice. ADM-treated mice showed fewer aortic plaques, decreased plaque area, by 76% (P<0.01), and reduced ratio of plaque area to luminal area, by 65% (P<0.01), and ultrasonography revealed significantly reduced intima-media thickness of the ascending branch and abdominal aorta. The results suggest that atherosclerotic apoE-/- mice fed an atherogenic diet showed upregulated endogenous ADM and its receptors, and exogenous ADM treatment ameliorated the dyslipidemia and vascular atherosclerotic lesions. ADM/ADM receptors might be an important protective system against atherosclerosis and could become a new target of prevention and therapy for atherosclerosis.

Regulation of coronary arterial BK channels by caveolae-mediated angiotensin II signaling in diabetes mellitus

RATIONALE

The large conductance Ca(2+)-activated K(+) (BK) channel, a key determinant of vascular tone, is regulated by angiotensin II (Ang II) type 1 receptor signaling. Upregulation of Ang II functions and downregulation of BK channel activities have been reported in diabetic vessels. However, the molecular mechanisms underlying Ang II-mediated BK channel modulation, especially in diabetes mellitus, have not been thoroughly examined.

OBJECTIVES

The aim in this study was to determine whether caveolae-targeting facilitates BK channel dysfunction in diabetic vessels.

METHODS AND RESULTS

Using patch clamp techniques and molecular biological approaches, we found that BK channels, Ang II type 1 receptor, G(alphaq/11) (G protein q/11 alpha subunit), nonphagocytic NAD(P)H oxidases (NOX-1), and c-Src kinases (c-Src) were colocalized in the caveolae of rat arterial smooth muscle cells and the integrity of caveolae in smooth muscle cells was critical for Ang II-mediated BK channel regulation. Most importantly, membrane microdomain targeting of these proteins was upregulated in the caveolae of streptozotocin-induced rat diabetic vessels, leading to enhanced Ang II-induced redox-mediated BK channel modification and causing BK channel and coronary dysfunction. The absence of caveolae abolished the effects of Ang II on vascular BK channel activity and preserved BK channel function in diabetes.

CONCLUSIONS

These results identified a molecular scheme of receptor/enzyme/channel/caveolae microdomain complex that facilitates the development of vascular BK channel dysfunction in diabetes.

NADPH oxidases: functions and pathologies in the vasculature

Reactive oxygen species are ubiquitous signaling molecules in biological systems. Four members of the NADPH oxidase (Nox) enzyme family are important sources of reactive oxygen species in the vasculature: Nox1, Nox2, Nox4, and Nox5. Signaling cascades triggered by stresses, hormones, vasoactive agents, and cytokines control the expression and activity of these enzymes and of their regulatory subunits, among which p22phox, p47phox, Noxa1, and p67phox are present in blood vessels. Vascular Nox enzymes are also regulated by Rac, ClC-3, Poldip2, and protein disulfide isomerase. Multiple Nox subtypes, simultaneously present in different subcellular compartments, produce specific amounts of superoxide, some of which is rapidly converted to hydrogen peroxide. The identity and location of these reactive oxygen species, and of the enzymes that degrade them, determine their downstream signaling pathways. Nox enzymes participate in a broad array of cellular functions, including differentiation, fibrosis, growth, proliferation, apoptosis, cytoskeletal regulation, migration, and contraction. They are involved in vascular pathologies such as hypertension, restenosis, inflammation, atherosclerosis, and diabetes. As our understanding of the regulation of these oxidases progresses, so will our ability to alter their functions and associated pathologies.

The renin-angiotensin system, adrenomedullins and urotensin II in the kidney: possible renoprotection via the kidney peptide systems

The incidence of chronic kidney disease, such as diabetic nephropathy, is increasing throughout the world. Many biologically active peptides play important roles in the kidney. The classical example is the renin-angiotensin system (RAS). Angiotensin II plays critical roles in the progression of chronic kidney disease through its vasoconstrictor action, stimulatory action on cell proliferation, and reactive oxygen-generating activity. A renin inhibitor, aliskiren, has recently been shown to be a clinically effective drug to reduce proteinuria in patients with diabetic nephropathy. (Pro)renin receptor, a specific receptor for renin and prorenin, was newly identified as a member of the RAS. When bound to prorenin, (pro)renin receptor activates the angiotensin I-generating activity of prorenin in the absence of cleavage of the prosegment, and directly stimulates the pathway of mitogen-activated protein kinase independently from the RAS. The kidney peptides that antagonize the intrarenal RAS may have renoprotective actions. Adrenomedullins, potent vasodilator peptides, have been shown to have renoprotective actions. On the other hand, urotensin II, a potent vasoconstrictor peptide, may promote the renal dysfunction in chronic kidney disease together with the renal RAS. Thus, in addition to the renin inhibitor and (pro)renin receptor, adrenomedullins and urotensin II may be novel targets to develop therapeutic strategies against chronic kidney disease.

The role of plasminogen activator inhibitor 1 in renal and cardiovascular diseases

The 50 kDa glycoprotein plasminogen activator inhibitor 1 (PAI-1) is the major physiological inhibitor of tissue-type and urokinase-type plasminogen activator. These two molecules convert inactive plasminogen into its fibrin-degrading form, plasmin. Plasma and tissue concentrations of PAI-1 are extremely low under normal circumstances but increase under pathologic conditions. This increase is mediated by many factors, including reactive oxygen species. Increased PAI-1 activity is associated with an increased risk of ischemic cardiovascular events and tissue fibrosis. Whereas the antifibrinolytic property of PAI-1 derives mainly from its inhibition of serine proteases, its profibrotic actions seem to derive from a capacity to stimulate interstitial macrophage recruitment and increase transcription of profibrotic genes, as well as from inhibition of serine proteases. Despite studies in mice that lack or overexpress PAI-1, the biological effects of this molecule in humans remain incompletely understood because of the complexity of the PAI-1-plasminogen-activator-plasmin system. The cardioprotective and renoprotective properties of some currently available drugs might be attributable in part to inhibition of PAI-1. The development of an orally active, high-affinity PAI-1 inhibitor will provide a potentially important pharmacological tool for further investigation of the role of PAI-1 and might offer a novel therapeutic strategy in renal and cardiovascular diseases.

Effect of adrenomedullin on hepatic damage in hepatic ischaemia/reperfusion injury in rats

AIMS

Adrenomedullin (AM) is a multifunctional peptide with a putative beneficial role after an ischaemic insult. The aim of this study was to evaluate the effect of AM on partial hepatic ischaemia reperfusion (I/R) injury.

METHODS

Rats were subjected to 1 h of 70% hepatic ischaemia, followed by reperfusion or sham. At the end of ischaemia, vehicle (phosphate-buffered saline solution), N-nitro-L-arginine methyl ester (L-NAME) and AM with or without L-NAME were infused via the portal vein. Analysis was performed at pre-ischaemia, ischaemia onset and 1, 2 and 4 h after reperfusion. Hepatic tissue blood flow (HTBF) was evaluated by laser Doppler.

RESULTS

Plasma AM levels in the I/R groups were significantly lower than the levels in the sham group. AM treatment significantly reduced levels of aspartate transaminase and tissue arginase (P<0.05). Significant decreases of tumour necrosis factor-alpha, interleukin-1beta and endothelin-1 levels were also found in the serum. Endothelin-1, malondialdehyde and necrosis were observed more frequently in liver tissue in the AM group than the control (P<0.05). Tissue nitric oxide, energy charge and HTBF were significantly increased in AM treatment experiments (P<0.05).

CONCLUSION

The improved HTBF, energy charge and nitric oxide and the reduction of hepatic necrosis, oxidative stress, liver enzymes, endotelin-1 and pro-inflammatory cytokines demonstrate that treatment with AM attenuates liver I/R injury.

Characterization of the acute temporal changes in excisional murine cutaneous wound inflammation by screening of the wound-edge transcriptome

This work represents a maiden effort to systematically screen the transcriptome of the healing wound-edge tissue temporally using high-density GeneChips. Changes during the acute inflammatory phase of murine excisional wounds were characterized histologically. Sets of genes that significantly changed in expression during healing could be segregated into the following five sets: up-early (6-24 h; cytokine-cytokine receptor interaction pathway), up-intermediary (12-96 h; leukocyte-endothelial interaction pathway), up-late (48-96 h; cell-cycle pathway), down-early (6-12 h; purine metabolism) and down-intermediary (12-96 h; oxidative phosphorylation pathway). Results from microarray and real-time PCR analyses were consistent. Results listing all genes that were significantly changed at any specific time point were further mined for cell-type (neutrophils, macrophages, endothelial, fibroblasts, and pluripotent stem cells) specificity. Candidate genes were also clustered on the basis of their functional annotation, linking them to inflammation, angiogenesis, reactive oxygen species (ROS), or extracellular matrix (ECM) categories. Rapid induction of genes encoding NADPH oxidase subunits and downregulation of catalase in response to wounding is consistent with the fact that low levels of endogenous H2O2 is required for wound healing. Angiogenic genes, previously not connected to cutaneous wound healing, that were induced in the healing wound-edge included adiponectin, epiregulin, angiomotin, Nogo, and VEGF-B. This study provides a digested database that may serve as a valuable reference tool to develop novel hypotheses aiming to elucidate the biology of cutaneous wound healing comprehensively.

Aldosterone induces superoxide generation via Rac1 activation in endothelial cells

Currently, aldosterone is believed to be involved in the development of cardiovascular injury as a potential cardiovascular risk hormone. However, its exact cellular mechanisms remain obscure. This study was undertaken to examine the effect of aldosterone on superoxide production in cultured rat aortic endothelial cells with possible involvement of the small GTP-binding (G) protein Rac1. The aldosterone levels showed a time-dependent (6-24 h) and dose-dependent (10(-8) to 10(-6) m) increase in superoxide generation, whose effect was abolished by mineralocorticoid receptor antagonist (eplerenone), Src inhibitor (PP2), and reduced nicotinamide adenine dinucleotide phosphate [NAD(P)H] oxidase inhibitor (apocynin). Aldosterone activated NADP(H) oxidase and Rac1, whose effects were abolished by eplerenone. The aldosterone-induced superoxide generation was abolished either by nonselective small G protein inhibitor (Clostridium difficile toxin A) or dominant-negative Rac1. Dominant-negative Rac1 also inhibited aldosterone-induced ACE gene expression. Thus, the present study is the first to demonstrate that aldosterone induces superoxide generation via mineralocorticoid receptor-mediated activation of NAD(P)H-oxidase and Rac1 in endothelial cells, thereby contributing to the development of aldosterone-induced vascular injury.

Adiponectin inhibits vascular endothelial growth factor-induced migration of human coronary artery endothelial cells

AIMS

Vascular endothelial growth factor (VEGF)-induced endothelial cell migration and angiogenesis are associated with the vascular complications of diabetes mellitus, and adiponectin is an abundant plasma adipokine that exhibits salutary effects on endothelial function. We investigated whether adiponectin suppresses VEGF-induced migration and related signal transduction responses in human coronary artery endothelial cells (HCAECs).

METHODS AND RESULTS

Using a modified Boyden chamber technique and a monolayer 'wound-healing' assay, both the recombinant adiponectin globular domain and full-length adiponectin protein potently suppressed the migration of HCAEC induced by VEGF. Adiponectin did not increase endothelial cell apoptosis, as measured by terminal deoxynucleotidyl transferase biotin-dUTP Nick End Labelling assay. Adiponectin also suppressed VEGF-induced reactive oxygen species generation, activation of Akt, the mitogen-activated protein kinase ERK and the RhoGTPase RhoA, and induction of the formation of actin stress fibres and focal cellular adhesions. VEGF-stimulated cell migration was inhibited by activation of adenylyl cyclase with forskolin, and adiponectin treatment increased cellular cyclic adenosine monophosphate (cAMP) levels and protein kinase A (PKA) enzymatic activity. Pharmacological inhibition of either adenylyl cyclase or PKA significantly abrogated the effect of adiponectin globular domain to suppress VEGF-induced cell migration.

CONCLUSION

Adiponectin suppresses VEGF-stimulated HCAEC migration via cAMP/PKA-dependent signalling, an important effect with implications for a regulatory role of adiponectin in vascular processes associated with diabetes and atherosclerosis.

Oxidative stress, plasminogen activator inhibitor 1, and lung fibrosis

Fibrosis is characterized by excessive accumulation of extracellular matrix (ECM) in basement membranes and interstitial tissues, resulting from increased synthesis or decreased degradation of ECM or both. The plasminogen activator/plasmin system plays an important role in ECM degradation, whereas the plasminogen activator inhibitor 1 (PAI-1) is a physiologic inhibitor of plasminogen activators. PAI-1 expression is increased in the lung fibrotic diseases and in experimental fibrosis models. The deletion of the PAI-1 gene reduces, whereas the overexpression of PAI-1 enhances, the susceptibility of animals to lung fibrosis induced by different stimuli, indicating an important role of PAI-1 in the development of lung fibrosis. Many growth factors, including transforming growth factor beta (TGF-beta) and tumor necrosis factor alpha (TNF-alpha), as well as other chemicals/agents, induce PAI-1 expression in cultured cells and in vivo. Reactive oxygen and nitrogen species (ROS/RNS) have been shown to mediate the induction of PAI-1 by many of these stimuli. This review summarizes some recent findings that help us to understand the role of PAI-1 in the development of lung fibrosis and ROS/RNS in the regulation of PAI-1 expression during fibrogenesis.

The effect of adrenomedullin on rats exposed to lead

Adrenomedullin (AdM) was originally discovered as a vasorelaxant peptide. The antioxidative properties of AdM have been reported recently. Through its antioxidative effect, adrenomedullin can protect organs from damage induced by stressors. Lead, commonly detected in air, soil, water and food, is a major source of oxidative stress. The effect of AdM in the liver of rats exposed to lead was investigated. Twenty-four female Wistar rats were divided into four groups: a control group (C), adrenomedullin group (AdM), lead (Pb) group and lead + adrenomedullin (Pb + AdM) group. In the Pb-treated groups, the animals were exposed to lead in drinking water containing 250 ppm PbCl2 for 4 weeks. In the AdM-treated group, the animals received an i.p. injection of AdM (3000 ng kg(-1) body weight) in the third week of lead treatment for 1 week. The activities of catalase (CAT), glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) and the level of malondialdehyde (MDA) were determined in the liver of rats. Histological changes in the liver were examined by light and electron microscopy as well. The MDA levels were increased significantly in the Pb-treated groups, but in the Pb + AdM group the MDA levels were decreased significantly when compared with the Pb group. AdM reduced hepatic damage in the Pb + AdM group, but the difference in the total histopathological scores between the Pb and Pb + AdM groups was not significant. When the results are taken together, it can be concluded that AdM may have protective or compensating effects in lead toxicity.

Chronic blockade of nitric oxide synthesis reduces adiposity and improves insulin resistance in high fat-induced obese mice

Genetic deletion of inducible nitric oxide synthase (NOS) in mice has been shown to improve high-fat diet (HFD)-induced insulin resistance. However, a pathophysiological role of endogenous nitric oxide (NO) in obesity-related insulin resistance remains controversial. To address this issue, we examined the metabolic phenotypes in HFD-induced obese mice with chronic blockade of NO synthesis by a NOS inhibitor, N(G)-nitro-l-arginine methyl ester (L-NAME). Six-week-old male C57BL/6j mice were provided free access to either a standard diet (SD) or a HFD and tap water with or without L-NAME (100 mg/kg.d) for 12 wk. L-NAME treatment significantly attenuated body weight gain of mice fed either SD or HFD without affecting calorie intake. L-NAME treatment in HFD-fed mice improved glucose tolerance and insulin sensitivity. HFD feeding induced inducible NOS mRNA expression, but not the other two NOS isoforms, in white adipose tissue (WAT) and skeletal muscle. L-NAME treatment up-regulated uncoupling protein-1 in brown adipose tissue of HFD-fed mice but down-regulated monocyte chemoattractant protein-1 and CD68 mRNAs levels in WAT. HFD feeding up-regulated leptin mRNA levels but conversely down-regulated adiponectin mRNA levels in WAT, but these effects were unaffected by L-NAME treatment. Moreover, L-NAME treatment also increased peroxisome proliferator-uncoupling protein-3 mRNA levels in skeletal muscles of HFD-fed mice. Increased urinary excretion of norepinephrine after HFD feeding was augmented in L-NAME-treated mice. Insulin-stimulated tyrosine phosphorylation of insulin receptor substrate-1 and serine phosphorylation of Akt/Akt2 in soleus muscle was markedly impaired in HFD-fed mice but reversed by L-NAME treatment. In conclusion, chronic NOS blockade by L-NAME in mice ameliorates HFD-induced adiposity and glucose intolerance, accompanied by reduced adipose inflammation and improved insulin signaling in skeletal muscle, suggesting that endogenous NO plays a modulatory role in the development of obesity-related insulin resistance.

Receptor-independent intracellular radical scavenging activity of an angiotensin II receptor blocker

OBJECTIVES

Angiotensin II plays a crucial role in the induction of oxidative stress and the pathogenesis of cardiovascular and renal diseases, and the beneficial mechanisms of angiotensin II receptor 1 blockers (ARBs) are multifactorial. We investigated the receptor-independent protective role of an ARB using primary-cultured mesangial cells from angiotensin II receptor 1 knockout or wild-type mice and a highly lipophilic ARB, telmisartan.

METHODS AND RESULTS

Intracellular reactive oxygen species were estimated using a fluorogenic probe, CM-H2DCFDA. Non-angiotensin II-induced reactive oxygen species production was generated by exposing cells to hydrogen peroxide alone or after treatment with telmisartan. Flow cytometry analysis showed that angiotensin II induced an increase in oxidant production in a dose-dependent manner in wild-type cells, but not in knockout cells. In contrast, hydrogen peroxide induced oxidative stress in both wild-type and knockout cells. Interestingly, telmisartan attenuated the oxidative stress induced by hydrogen peroxide in both cells, suggesting that it acted via a receptor-independent antioxidant effect. Intracellular concentrations of telmisartan were confirmed by high-performance liquid chromatography analysis. Expression of plasminogen activator inhibitor 1, which is stimulated by oxidative stress, was also attenuated by telmisartan in a receptor-independent as well as receptor-dependent manner. Telmisartan did not change expression levels of antioxidative enzymes such as catalase or glutathione peroxidase. Furthermore, the amelioration of oxidative stress by telmisartan did not involve the peroxisome proliferator-activated receptor-gamma pathway.

CONCLUSIONS

Telmisartan inhibits intracellular oxidative stress, at least in part, in a receptor-independent manner, possibly owing to its lipophilic and antioxidant structure.

Aortic cross-clamping-induced spinal cord oxidative stress in rabbits: the role of a novel antioxidant adrenomedullin

BACKGROUND

Spinal cord injury remains a devastating complication of thoracic and thoracoabdominal aortic operations. We aim to investigate the neuro-protective role of adrenomedullin (AM) administered to rabbits before ischemia and during reperfusion against ischemia-reperfusion (I/R) injury.

MATERIALS AND METHODS

Occlusion of the abdominal aorta was applied to adult rabbits, followed by removal of aortic clamp and reperfusion. The abdominal aortas of New Zealand white albino rabbits were occluded for 30 min. Experimental groups were as follows: control group (sham operation group, n = 10), I/R group (n = 9) undergoing occlusion but receiving no pharmacologic intervention, AM-treated group (n = 8) receiving 0.05 microg/kg/min AM intravenously 10 min before ischemia and during reperfusion. Neurological status was assessed at 6, 24, and 48 h after the operation. All animals were killed at 48 h after the operation. Spinal cords were harvested for histopathologic and biochemical analyses.

RESULTS

According to Tarlov's scale, neurological status of the rabbits at postoperative hour 48 was better in the AM-treated group compared to the I/R group (P < 0.05). Decreased tissue and serum malondialdehyde levels and increased tissue and serum glutathione levels were observed in the AM-treated group (P < 0.05). In the same group tissue and serum nitrate levels were decreased (P < 0.05). Histopathologic analyses demonstrated typical morphological changes characteristic of necrosis in the I/R group. AM attenuated ischemia-induced necrosis.

CONCLUSION

To our knowledge, this is the first study that shows the effects of AM administered both preischemic and during reperfusion on induced oxidative damage to injured spinal cords. AM administration may significantly reduce the incidence of spinal cord injury following temporary aortic occlusion.

Aldosterone as a cardiovascular risk hormone

The pathophysiological role of aldosterone in the development of cardiovascular disease has long been considered to be due its potent volume expansion/hypertensive effect mainly via mineralocorticoid receptor (MR) expressed in renal tubular epithelial cells. However, recent accumulating lines of evidence from clinical and experimental studies have suggested that direct cardiovascular effect of aldosterone contributes to the development of cardiovascular injury via MRs in non-epithelial tissue. A series of recent clinical studies have revealed that patients with primary aldosteronism have higher incidence of cardiovascular and renal complications than those with essential hypertension, and that aldosterone antagonism has cardiovascular protective effect in patients with heart failure independent from blood pressure. Numerous experimental studies have shown that both inflammation and oxidative stress play an initial and key role in the development of aldosterone-induced cardiovascular injury via non-epithelial MR activation. In this review, we discuss recent research progress in aldosterone and MR effects, with special emphasis on the pathophysiological role of aldosterone in cardiovascular diseases and the possible molecular mechanism(s) of cardiovascular injury by non-epithelial MR activation.

Angiotensin II receptor type 1-mediated vascular oxidative stress and proinflammatory gene expression in aldosterone-induced hypertension: the possible role of local renin-angiotensin system

Recently, aldosterone has been shown to activate local renin-angiotensin system in vitro. To elucidate the potential role of local renin-angiotensin system in aldosterone-induced cardiovascular injury, we investigated the effects of selective mineralocorticoid receptor (MR) antagonist eplerenone (EPL), angiotensin (Ang) II type 1 receptor antagonist candesartan (ARB), and superoxide dismutase mimetic tempol (TEM) on the development of hypertension, vascular injury, oxidative stress, and inflammatory-related gene expression in aldosterone-treated hypertensive rats. The increased systolic blood pressure and vascular inflammatory changes were attenuated by cotreatment either with EPL, ARB, or TEM. Aldosterone increased angiotensin-converting enzyme expression in the aortic tissue; its effects were blocked by EPL but not by ARB or TEM. Aldosterone also increased Ang II contents in the aortic tissue in the presence of low circulating Ang II concentrations. Aldosterone induced expression of various inflammatory-related genes, whose effects were abolished by EPL, whereas the inhibitory effects of ARB and TEM varied depending on the gene. Aldosterone caused greater accumulation of the oxidant stress marker 4-hydroxy-2-neonenal in the endothelium; its effect was abolished by EPL, ARB, or TEM. Aldosterone increased mRNA levels of reduced nicotinamide adenine dinucleotide phosphate oxidase components; their effect was abolished by EPL, whereas ARB and TEM decreased only the p47phox mRNA level but not that of p22phox or gp91phox. The present findings suggest that the Ang II-dependent pathway resulting from vascular angiotensin-converting enzyme up-regulation and Ang II-independent pathway are both involved in the underlying mechanisms resulting in the development of hypertension, vascular inflammation, and oxidative stress induced by aldosterone.

Adrenomedullin antagonizes angiotensin II-stimulated proliferation of human aortic smooth muscle cells

The vasodilating peptide adrenomedullin has been reported to regulate vascular tone as well as proliferation and differentiation of various cell types in an autocrine/paracrine manner. Conflicting data have been reported on the adrenomedullin (AM) effect on vascular smooth muscle cell proliferation, a process involved in the progression of vascular remodeling and atherosclerotic lesion. In this paper we investigate the effect of AM on proliferation of human aorta smooth muscle cell (HASMC). AM showed a potent dose-dependent inhibiting effect on angiotensin II (AngII) induced-proliferation and a stimulatory effect on proliferation of quiescent cells. The cAMP/PKA pathway was involved in the AM inhibitory effect of AngII-induced proliferation in HASMC. PI3K/Akt and ERK pathways were involved in the proliferative effect exerted by AM per se. Our results suggest that AM plays a role in the regulation of HASMC growth antagonizing the AngII effect and may be involved in conditions of altered regulation of the blood vessels.

Adrenomedullin inhibits angiotensin II-induced oxidative stress via Csk-mediated inhibition of Src activity

We have demonstrated that adrenomedullin (AM) protects against angiotensin II (ANG II)-induced cardiovascular damage through the attenuation of increased oxidative stress observed in AM-deficient mice. However, the mechanism(s) that underlie this activity remain unclear. To address this question, we investigated the effect of AM on ANG II-stimulated reactive oxygen species (ROS) production in cultured rat aortic vascular smooth muscle cells (VSMCs). ANG II markedly increased ROS production through activation of NADPH oxidase. This effect was significantly attenuated by AM in a concentration-dependent manner. This effect was mimicked by dibutyl-cAMP and blocked by pretreatment with N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide hydrochloride (H-89), a protein kinase A inhibitor, and CGRP(8-37), an AM/CGRP receptor antagonist. This inhibitory effect of AM was also lost following the expression of a constitutively active Src. Moreover, AM intersected ANG II signaling by inducing COOH-terminal Src kinase (Csk) activation that, in turn, inhibits Src activation. These data, for the first time, demonstrate that AM attenuates the ANG II-induced increase in ROS in VSMCs via activation of Csk, thereby inhibiting Src activity.