CyA and OxLDL cause endothelial dysfunction in isolated arteries through endothelin-mediated stimulation of O(2)(-) formation

Selective gene expression profiling contributes to a better understanding of the molecular pathways underlying the histological changes observed after RHMVL

Background

In previous studies, five vasoactive drugs were investigated for their effect on the recovery process after extended liver resection without observing relevant improvements. We hypothesized that an analysis of gene expression could help to identify potentially druggable pathways and could support the selection of promising drug candidates.

Methods

Liver samples obtained from rats after combined 70% partial hepatectomy and right median hepatic vein ligation (n = 6/group) sacrificed at 0 h, 24 h, 48 h, and 7days were selected for this study. Liver samples were collected from differentially perfused regions of the median lobe (obstruction-zone, border-zone, normal-zone). Gene expression profiling of marker genes regulating hepatic hemodynamics, vascular remodeling, and liver regeneration was performed with microfluidic chips. We used 3 technical replicates from each sample. Raw data were normalized using LEMming and differentially expressed genes were identified using LIMMA.

Results

The strongest differences were found in obstruction-zone at 24 h and 48 h postoperatively compared to all other groups. mRNA expression of marker genes from hepatic hemodynamics pathways (iNOS,Ptgs2,Edn1) was most upregulated.

Conclusion

These upregulated genes suggest a strong vasoconstrictive effect promoting arterial hypoperfusion in the obstruction-zone. Reducing iNOS expression using selective iNOS inhibitors seems to be a promising approach to promote vasodilation and liver regeneration.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12920-022-01364-z.

The Causal Relationship between Endothelin-1 and Hypertension: Focusing on Endothelial Dysfunction, Arterial Stiffness, Vascular Remodeling, and Blood Pressure Regulation

Hypertension (HTN) is one of the most prevalent diseases worldwide and is among the most important risk factors for cardiovascular and cerebrovascular complications. It is currently thought to be the result of disturbances in a number of neural, renal, hormonal, and vascular mechanisms regulating blood pressure (BP), so crucial importance is given to the imbalance of a number of vasoactive factors produced by the endothelium. Decreased nitric oxide production and increased production of endothelin-1 (ET-1) in the vascular wall may promote oxidative stress and low-grade inflammation, with the development of endothelial dysfunction (ED) and increased vasoconstrictor activity. Increased ET-1 production can contribute to arterial aging and the development of atherosclerotic changes, which are associated with increased arterial stiffness and manifestation of isolated systolic HTN. In addition, ET-1 is involved in the complex regulation of BP through synergistic interactions with angiotensin II, regulates the production of catecholamines and sympathetic activity, affects renal hemodynamics and water–salt balance, and regulates baroreceptor activity and myocardial contractility. This review focuses on the relationship between ET-1 and HTN and in particular on the key role of ET-1 in the pathogenesis of ED, arterial structural changes, and impaired vascular regulation of BP. The information presented includes basic concepts on the role of ET-1 in the pathogenesis of HTN without going into detailed analyses, which allows it to be used by a wide range of specialists. Also, the main pathological processes and mechanisms are richly illustrated for better understanding.

Attenuation of oxidative stress and hypertension in an animal model of HELLP syndrome

HELLP (hemolysis elevated liver enzyme low platelet) syndrome is associated with hypertension, inflammation, oxidative stress and endothelial activation. The objective of this study was to determine if oxygen scavenging or endothelin A receptor antagonism improved hypertension and oxidative stress. sFlt-1 and sEndoglin were infused via mini-osmotic pump into normal pregnant rats (NP) on gestational day 12 to create HELLP syndrome. On gestational day 18 arterial catheters were inserted and on gestational day 19 mean arterial pressure was analyzed in rats; serum, urine and tissues were collected for molecular analysis. HELLP rats had significantly increased MAP compared to control normal pregnant rats (P < 0.0005). Endothelin A receptor antagonism via ABT-627 and Tempol, superoxide dismutase mimetic, were administered to a subset of normal pregnant and HELLP rats beginning on gestational day 13 and attenuated mean arterial pressure in HELLP rats (P < 0.05; P < 0.005). There were no statistically significant differences in mean arterial pressure between NP+ET_A Receptor or NP+Tempol treated rats and NP rats (P = 0.22). Endothelin A receptor blockade significantly decreased HELLP induced isoprostane excretion (P < 0.0005), placental and hepatic reactive oxygen species (P < 0.05; P < 0.0005) and increased placental total antioxidant capacity (P < 0.005) compared to untreated HELLP rats. Similar results in isoprostane (P < 0.005), hepatic reactive oxygen species (P < 0.05) and placental total antioxidant capacity (P < 0.05) were seen in HELLP rats treated with Tempol or Endothelin A receptor antagonist vs. untreated HELLP rats. These data demonstrated a role for oxidative stress in contributing to the hypertension, placental and liver damage that is seen in HELLP syndrome.

Increased Advanced Oxidation Protein Products Generation by Cyclosporine-A and Angiotensin II in Human Gingival Fibroblasts - Ex-vivo Study

INTRODUCTION

Cyclosporin-A (CsA), an immunosuppressant, induces renal fibrosis and Renin Angiotensin System (RAS) is known to play a major role. CsA has the potential to increase the oxidative stress; specifically through the Advanced Oxidation Protein Products (AOPP) which could possibly stimulate fibrosis. A similar type of pathology occurs even in the gingiva known as CsA Induced Gingival Overgrowth (CIGO).

AIM

This study was undertaken to estimate the AOPP generation by Human Gingival Fibroblasts (HGF) under the influence of CsA and Angiotensin II (Ang II).

MATERIALS AND METHODS

Six healthy gingival tissue samples were obtained during crown lengthening procedure and primary HGF were cultured using enzymatic digestion method. The ideal non-cytotoxic concentrations of CsA and Ang II were identified using cytotoxicity assay. Later, HGF were incubated with CsA and Ang II for 12 hours and AOPP assay was performed at zero and one hour interval.

RESULTS

There was a statistically significant increase in AOPP production in both the CsA and Ang II when compared to the control group with a p value<0.05.

CONCLUSION

CsA can induce oxidative stress and preventing/controlling it may be necessary to prevent untoward effect of the drug.

Serum Concentrations of Endothelin-1 and Matrix Metalloproteinases-2, -9 in Pre-Hypertensive and Hypertensive Patients with Type 2 Diabetes

Endothelin-1 (ET-1) is one of the most potent vasoconstrictors known to date. While its plasma or serum concentrations are elevated in some forms of experimental and human hypertension, this is not a consistent finding in all forms of hypertension. Matrix metalloproteinases -2 and -9 (MMP-2 and MMP-9), which degrade collagen type IV of the vascular basement membrane, are responsible for vascular remodeling, inflammation, and atherosclerotic complications, including in type 2 diabetes (T2D). In our study, we compared concentrations of ET-1, MMP-2, and MMP-9 in pre-hypertensive (PHTN) and hypertensive (HTN) T2D patients with those of healthy normotensive controls (N). ET-1, MMP-2, and MMP-9 were measured by ELISA. Concentrations of ET-1 in PHTN and N were very similar, while those in HTN were significantly higher. Concentrations of MMP-2 and MMP-9 in PHTN and HTN were also significantly higher compared to N. An interesting result in our study is that concentrations of MMP-2 and MMP-9 in HTN were lower compared to PHTN. In conclusion, we showed that increased production of ET-1 in patients with T2D can lead to long-lasting increases in blood pressure (BP) and clinical manifestation of hypertension. We also demonstrated that increased levels of MMP-2 and MMP-9 in pre-hypertensive and hypertensive patients with T2D mainly reflect the early vascular changes in extracellular matrix (ECM) turnover.

Prevention of nephrotoxicity induced by cyclosporine-A: role of antioxidants

Cyclosporine A (CsA) is a powerful immunosuppressive drug used to prevent allograft rejection after organ transplantation as well as in human and veterinary medicine. Unfortunately, its use is hampered by its nephrotoxic effects. The mechanisms of CsA-induced hypertension and nephrotoxicity are not clear, but several studies suggest the possible involvement of free radicals. In this review we have summarized the effect of some antioxidants that we have used in the recent years, in combination with CsA, to better understand the exact mechanism of action of CsA and to try to open new perspectives in the treatment of CsA nephrotoxicity.

oxLDL induces injury and defenestration of human liver sinusoidal endothelial cells via LOX1

Non-alcoholic fatty liver disease is associated with hepatic microangiopathy and liver inflammation caused by type 2 diabetes mellitus. Oxidised LDL (oxLDL) is involved in proinflammatory and cytotoxic events in various microcirculatory systems. The lectin-like oxLDL receptor 1 (LOX1) plays a crucial role in oxLDL-induced pathological transformation. However, the underlying mechanism of oxLDL's effects on liver microcirculation disturbances remains unclear. In this study, we investigated the effects of oxLDL on LOX1 (OLR1) expression and function, as well as on the fenestration features of human liver sinusoidal endothelial cells (HLSECs) in vitro. Primary HLSECs were obtained and cultured. The cells were treated with various concentrations of oxLDL (25, 50, 100 and 200  μg/ml), and the cytotoxicity and expression of LOX1 were examined. Furthermore, LOX1 knockdown was performed using siRNA technology, and the changes in intracellular reactive oxygen species (ROS), NFκB, p65, (p65), endothelin 1 (ET1 (EDN1)), eNOS (NOS3) and caveolin 1 (CAV1) levels were measured. Cells were treated with 100  μg/ml oxLDL, and the fenestra morphology was visualised using scanning electron microscopy. oxLDL significantly increased LOX1 expression at both the mRNA and protein levels in HLSECs in a dose- and time-dependent manner. oxLDL stimulation increased ROS generation and NFκB activation, upregulated ET1 and caveolin 1 expression, downregulated eNOS expression and reduced the fenestra diameter and porosity. All of these oxLDL-mediated effects were inhibited after LOX1 knockdown. These results reveal a mechanism by which oxLDL stimulates the production of LOX1 through the ROS/NFκB signalling pathway and by which LOX1 mediates oxLDL-induced endothelial injury and the defenestration of HLSECs.

Serum and tissue endothelin-1 are independent from intima-media thickness of peripheral arteries in patients with chronic kidney disease

AIM

We aimed to study the relationship of peripheral arteries' atherosclerosis with serum and tissue endothelin-1 in chronic kidney disease patients.

METHODS

Ninety patients were enrolled, including 35 patients with chronic kidney disease (case group), 31 patients with coronary artery diseases who were candidates for coronary artery bypass grafting (positive control group), and 24 living kidney donors (negative control group). Intima-media thickness of the common carotid and femoral arteries was determined by ultrasonography. Serum and tissue endothelin-1 were measured by ELISA method.

RESULTS

The mean serum and tissue endothelin-1 levels in the donor group were significantly lower than other groups (p < 0.001 for both). The coronary artery bypass grafting group had higher carotid and femoral intima-media thickness than other groups (p < 0.001), and the chronic kidney disease group had higher carotid and femoral intima-media thickness than the donor group (p < 0.001). Regression analysis in all groups did not reveal any correlation between the carotid intima-media thickness/femoral intima-media thickness and the serum/tissue endothelin-1. There was a direct linear correlation between the carotid and femoral intima-media thickness (p < 0.001) in all groups.

CONCLUSIONS

Endothelin-1 level and intima-media thickness were higher in the chronic kidney disease patients and coronary artery bypass grafting candidates, without any correlation between endothelin-1 and peripheral arteries' intima-media thickness of both groups. Perhaps endothelin-1 rises and remains high upon endothelial damage and initiation of atherosclerosis.

Ginkgo biloba extract inhibits oxidized low-density lipoprotein (oxLDL)-induced matrix metalloproteinase activation by the modulation of the lectin-like oxLDL receptor 1-regulated signaling pathway in human umbilical vein endothelial cells

BACKGROUND

The overexpression of matrix metalloproteinases (MMPs) induced by oxidized low-density lipoprotein (oxLDL) has been found in atherosclerotic lesions. Previous reports have identified that oxLDL, via the upregulation of lectin-like ox-LDL receptor 1 (LOX-1), modulates the expression of MMPs in endothelial cells. Ginkgo biloba extract (GbE), from Ginkgo biloba leaves, has often been considered as a therapeutic compound for cardiovascular and neurologic diseases. However, further investigation is needed to ascertain the probable molecular mechanisms underlying the antiatherogenic effects of GbE. The aim of this study was to investigate the effects of GbE on oxLDL-activated MMPs of human endothelial cells and to test the involvement of LOX-1 and protein kinase C (PKC)-α, extracellular signal-regulated kinase (ERK), and peroxisome proliferator-activated receptor-γ (PPAR-γ).

METHODS

Human umbilical vein endothelial cells were stimulated with oxLDL, with or without GbE treatment. LOX-1 signaling and MMPs expression were tested by Western blotting or activity assay. Further, protein expression levels of PKC-α, ERK, nuclear factor-κB, and PPAR-γ were investigated by Western blotting.

RESULTS

GbE inhibited the oxLDL-caused upregulation of MMP-1, MMP-2, and MMP-3. Pretreating with GbE reduced oxLDL-activated LOX-1 expression. Furthermore, pharmacologic inhibitors of free radicals, Ca(++), PKC, and GbE, inhibited the oxLDL-induced ERK and nuclear factor-κB activation. Lastly, GbE ameliorated the oxLDL-inhibited PPAR-γ function.

CONCLUSIONS

Data obtained in this study indicate that GbE actives its protective effects by regulating the LOX-1-mediated PKC-α/ERK/PPAR-γ/MMP pathway, resulting in the suppression of reactive oxygen species formation and, ultimately, the reduction of MMPs expression in endothelial cells treated with oxLDL.

ComparativeIn VitroEffects of Calcineurin Inhibitors on Functional Vascular Relaxations of Both Rat Thoracic and Abdominal Aorta

Background and Aim. Calcineurin inhibitors (CNIs) have shown to develop hypertension in transplant patients. The in vitro incubation effects of cyclosporine (CsA) and tacrolimus (Tac) on vascular relaxations of rat thoracic aorta (TA) and abdominal aorta (AA) need to be investigated. Methods. The optimal concentrations of CsA (1.0 mg/mL) and Tac (0.1 mg/mL) used to compare endothelium-dependent (acetylcholine (ACh)) and endothelium-independent (sodium nitroprusside (SNP)) vascular relaxation against the agonists in phenylephrine (PE-) constricted TA and AA of 13-week-old male Sprague Dawley rats (n = 6). Results. In TA, the maximal vasodilator response elicited by ACh (control: I_max 98%) was significantly (P < 0.01) inhibited by CsA (I_max 10%) but not by Tac (I_max 97%). In AA, (control: IC₅₀ 50 nM; I_max 100%) CsA (IC₅₀ 7 μM; (P < 0.01) showed strong sensitivity to inhibit ACh-dependent vascular relaxation than Tac (IC₅₀ 215 nM (P < 0.05); I_max 98%). CsA and Tac failed to affect the inhibitory responses to SNP in both TA and AA. Conclusion. CsA exerts profound inhibitory effect on endothelium-dependent vasodilatation as compared to Tac in both TA and AA. Aortic rings from the thoracic region are more sensitive to CNIs, since the vasodilator response to ACh is solely mediated by NO while in the AA, ACh likely recruits other endothelial mediators besides NO to maintain vasodilatation.

Redox imbalances incite the hypertensive, baroreflex, and autonomic effects of cyclosporine in rats

Previous studies including ours showed that cyclosporine (CSA) causes baroreflex dysfunction and hypertension. Here we tested the hypothesis that oxidative damage in central and peripheral tissues underlies the hypertensive, baroreflex and autonomic actions elicited by CSA in rats. We investigated the effects of individual and combined 7-day treatments with CSA (25 mg/kg/day, n=7) and 4-hydroxy-2,2,6,6-tetramethyl piperidinoxyl (tempol, superoxide dismutase mimetic, 100 mg/kg/day, n=7) on blood pressure, reflex heart rate responses to peripherally mediated pressor and depressor responses, and biomarkers of oxidative stress. CSA elevated blood pressure and reduced reflex bradycardic (phenylephrine) and tachycardic (sodium nitroptrusside) responses. The ability of muscarinic (atropine, 1 mg/kg i.v.) or β-adrenoceptor blockade (propranolol, 1 mg/kg i.v.) to reduce reflex heart rate responses was reduced in CSA-treated rats, suggesting the impairment by CSA of reflex cardiac autonomic control. Concurrent administration of tempol abolished CSA-induced hypertension and normalized the associated impairment in baroreflex gain and cardiac autonomic control. Tempol also reversed the CSA-induced increases in aortic and brainstem nitrite/nitrate and malondialdehyde (MDA) and decreases in aortic superoxide dismutase (SOD). These findings implicate oxidative stress in peripheral and central cardiovascular sites in the deleterious actions of CSA on blood pressure and baroreceptor control of heart rate.

New perspectives on endothelin-1 in atherosclerosis and diabetes mellitus

Endothelin-1 (ET-1) is a vasoconstrictor, proinflammatory and proliferative endothelial cell-derived peptide that is of significant importance in the regulation of vascular function. It is involved in the development of endothelial dysfunction including important interactions with nitric oxide. The expression and functional effects of ET-1 and its receptors are markedly altered during development of cardiovascular disease. Increased production of ET-1 and its receptors mediate many pathophysiological events contributing to the development of atherosclerosis and vascular complications in diabetes mellitus. The present review focuses on the pathophysiological role of ET-1 and the potential importance of ET receptors as a therapeutic target for treatment of these conditions.

Suppression of low-density lipoprotein oxidation, vascular smooth muscle cell proliferation and migration by a herbal extract of Radix Astragali, Radix Codonopsis and Cortex Lycii

Background

Atherosclerosis is a major cause of death in developed world. Atherosclerosis is characterized by low-density lipoprotein deposition in the arterial wall which ultimately begets the formation of lesions. Rupture of lesions finally leads to clinical events such as heart attack and stroke. Atherosclerosis is a complication associated with diabetes. In patients with diabetes, the risk of atherosclerosis is three to five folds greater than in non-diabetics. Our previous study showed that a herbal extract of Radix Astragali, Radix Codonopsis and Cortex Lycii, namely SR10, could improve glucose homeostasis both in vitro and in vivo. In this study, we want to further investigate the efficacy of SR10 in treating atherosclerosis.

Method

The inhibitory effect of SR10 on low-density lipoprotein oxidation was investigated using free radical-induced erythrocyte hemolysis model and copper ion-induced low-density lipoprotein oxidation model. Since vascular smooth muscle cell proliferation and migration are important processes in atherogenesis, we also examined the effect of SR10 in inhibiting these events.

Results

Our results showed that SR10 inhibited erythrocyte hemolysis with IC₅₀ value at 0.25 mg/ml and significantly prolonged low-density lipoprotein oxidation in vitro. SR10 attenuated platelet derived growth factor-BB-induced vascular smooth muscle cell proliferation by promoting cell cycle arrest at G₀/G₁ phase as well as inhibiting vascular smooth muscle cell migration.

Conclusion

The potential application of SR10 in treating atherosclerosis has been implied in this study. Animal model will be needed to further verify the efficacy of SR10 in future.

Reactive oxygen species are indispensable in ovulation

Ovulation is stimulated by the preovulatory surge of the pituitary luteinizing hormone (LH). Because the ovulatory response is commonly identified with inflammation, we explored the involvement of reactive oxygen species (ROS) in this process. Our experiments show that administration of broad-range scavengers of oxidative species into the ovarian bursa of mice, hormonally induced to ovulate, significantly reduced the rate of ovulation. LH-induced cumulus mucification/expansion, a necessary requirement for ovulation, was prevented by antioxidants both in vivo and in an ex vivo system of isolated intact ovarian follicles. Along this line, H(2)O(2) fully mimicked the effect of LH, bringing about an extensive mucification/expansion of the follicle-enclosed cumulus-oocyte complexes. Impaired progesterone production was observed in isolated follicles incubated with LH in the presence of the antioxidant agents. Furthermore, LH-stimulated up-regulation of genes, the expression of which is crucial for ovulation, was substantially attenuated upon ROS ablation. This system was also used for demonstrating the role of ROS in phosphorylation and activation of the EGF receptor as well as its downstream effector, p42/44 MAPK. Together, our results provide evidence that ovarian production of ROS is an essential preovulatory signaling event, most probably transiently triggered by LH.

Phosphodiesterases as targets for intermittent claudication

Intermittent claudication (IC) is one of the most frequent forms of lower extremity peripheral arterial disease (PAD) and is most commonly caused by arterial atherosclerosis. Its clinical manifestation includes fatigue, discomfort, or pain occurring in limb muscles due to exercise-induced ischemia, thus limiting the ability of IC patients to walk and exercise. In addition to lifestyle changes (diet, exercise, and smoking cessation), pharmacological treatments are needed. Pathologically, atherosclerotic lesions cause a mismatch in oxygen supply and metabolic demand in the leg muscles during walking/exercise. This subjects the muscles to repeated ischemia and reperfusion injury that can alter structure and oxidative metabolism, resulting in insufficient utilization of oxygen supply. Despite extensive research efforts, cilostazol and pentoxifylline are the only drugs indicated for relieving the symptoms of IC, with cilostazol demonstrating significant improvement in walking distance and quality of life in these patients. Originally developed as a PDE3 inhibitor, cilostazol was later found to have several other pharmacological actions, and its success has been attributed to its multifactorial actions on platelets, endothelium, smooth muscle, and lipid profiles. Using cilostazol as an example, we discuss the rationales and pitfalls of targeting PDEs in IC, and potential strategies for the development of new and more effective pharmacological treatments.

Pioglitazone abrogates cyclosporine-evoked hypertension via rectifying abnormalities in vascular endothelial function

In addition to insulin sensitization, the thiazolidenedione drug pioglitazone exhibits favorable circulatory effects. Here, we hypothesized that pioglitazone protects against the hypertension and related vascular derangements caused by the immunosuppressant drug cyclosporine (CSA). Compared with vehicle (olive oil)-treated rats, chronic treatment with CSA (20mg/kg/day s.c., for 14 days) increased blood pressure (BP), reduced the aortic protein expression of phosphorylated eNOS (p-eNOS), and impaired responsiveness of isolated aortas to endothelium-dependent vasorelaxations induced by carbachol. The effects of CSA on BP, aortic p-eNOS, and carbachol relaxations were abolished upon concurrent administration of pioglitazone (2.5mg/kg/day). Serum levels of adiponectin, an adipose tissue-derived adipokine, were not altered by CSA but showed significant elevations in rats treated with pioglitazone or pioglitazone plus CSA. The possibility that alterations in the antioxidant and/or lipid profile contributed to the CSA-pioglitazone BP interaction was investigated. Pioglitazone abrogated the oxidative (aortic superoxide dismutase), lipid peroxidation (aortic malondialdyde), and dyslipidemic (serum LDL levels and LDL/HDL ratio) effects of CSA. Histologically, CSA caused focal disruption in the endothelial lining of the aorta and this effect disappeared in rats co-treated with pioglitazone. Collectively, pioglitazone abrogates the hypertensive effect of CSA via ameliorating detrimental changes in vascular endothelial NOS/NO pathway and oxidative and lipid profiles caused by CSA.

Danshen protects endothelial progenitor cells from oxidized low-density lipoprotein induced impairment

In this study, we examined the protective effects of Danshen both on endothelial progenitor cells (EPCs) in patients with hypercholesterolemia and on in-vitro EPCs of healthy volunteers. In the clinical study, we randomly divided 24 subjects with hypercholesterolemia into two groups (the control group and the Danshen-treated group). At the end of two weeks of treatment, the EPC cellular functions of both groups were tested. The results indicated that, compared to the control group, EPCs in the Danshen-treated group showed significantly better cellular functions, which was manifested in the cloning number, the proliferation capacity, the number of EPC adhesions, and cell migration. In the subsequent in-vitro experiments, EPCs were treated with vehicle, oxidized low-density lipoprotein (Ox-LDL, 100 microg/ml), or Ox-LDL (100 microg/ml) plus different concentrations of Danshen (Danshensu 2, 10, or 50 microg/ml, respectively) for 24 h. The results showed that Danshen treatments can prevent the detrimental effects of Ox-LDL on EPC cellular functions measured by proliferation capacity (0.24+/-0.08, 0.37+/-0.11, 0.30+/-0.04 vs. 0.13+/-0.02, P<0.05, P<0.01, and P<0.01, respectively), and adhesion ability (63.00+/-11.60, 70.00+/-10.80, 85.50+/-11.41 vs. 40.50+/-6.85, all P<0.01). Compared to the group treated with Ox-LDL alone, Danshen treatment significantly decreased the lipid peroxidation end product malondialdehyde (MDA) [(4.34+/-0.54), (3.98+/-0.47), (3.46+/-0.31) vs. (5.57+/-0.64) nmol/ml, all P<0.01], increased the production of superoxide dismutase (SOD) [(29.74+/-0.71), (31.09+/-0.83), (30.41+/-0.65) vs. (14.76+/-3.99) U/ml, all P<0.01], and lowered the expression of interleukin-6 (IL-6) [(24.62+/-7.69), (27.04+/-3.14), (33.38+/-18.86) vs. (230.67+/-33.53) pg/ml, all P<0.01] and tumor necrosis factor-alpha (TNF-alpha) [(41.72+/-6.10), (17.02+/-6.82), (3.73+/-2.26) vs. (228.71+/-41.53) pg/ml, all P<0.01] in Ox-LDL treated EPCs. These results suggest that Danshen may exert a protective effect through its antioxidant and anti-inflammatory features.

Role of oxidative stress in erythropoietin-induced hypertension in uremic rats

BACKGROUND

Erythropoietin (EPO) administration in uremic rats leads to an increase in blood pressure (BP). Because chronic renal failure has been associated with oxidative stress, we hypothesize that EPO treatment could accentuate this condition and contribute to hypertension. The present study was designed to investigate the role of reactive oxygen species in EPO-induced hypertension and the effect of tempol, a superoxide dismutase-mimetic.

METHODS

Renal failure was induced by a two-stage 5/6 nephrectomy followed by a 3-week stabilization period. Uremic rats were divided into four groups and received for 4 weeks: vehicle; EPO (100 U/kg, subcutaneously, three times per week); vehicle + tempol (1 mmol/l in drinking water); and EPO + tempol. Systolic BP and biochemical parameters were assessed before and at the end of the treatment. Renal histology, creatinine clearance rate, endothelin-1 (ET-1) concentrations and superoxide anion production were assessed at the end of the study.

RESULTS

The uremic rats developed anemia and hypertension. ET-1 concentrations and superoxide anion production were increased. EPO administration corrected anemia, but accentuated hypertension and renal injuries such as glomerulosclerosis, interstitial fibrosis, and inflammation. EPO therapy further increased tissue levels of ET-1 and superoxide anion production. Tempol treatment improved hypertension and renal injury, and reduced ET-1 concentrations and superoxide anion production.

CONCLUSION

Oxidative stress contributes to the development of hypertension and to the progression of renal injuries in uremic rats. EPO administration further increases oxidative stress, which might partly account for the accentuation of hypertension and renal injury.

Sirolimus as primary immunosuppression is associated with improved coronary vasomotor function compared with calcineurin inhibitors in stable cardiac transplant recipients

AIMS

The aim of this study was to evaluate coronary vasomotor function in cardiac transplant recipients maintained on sirolimus (SRL)- or cyclosporin (CyA)-based immunosuppression.

METHODS AND RESULTS

Endothelium-independent response to intracoronary nitroglycerin and adenosine and endothelium-dependent response to intracoronary acetylcholine (Ach) were assessed in 15 SRL- and 21 CyA- treated subjects with angiographically normal coronary arteries. Baseline mean blood pressure was lower in the SRL group (85.6 +/- 10.3 vs. 105.2 +/- 8.7 mmHg, P = 0.002). There was no difference between the groups in coronary flow reserve after adenosine administration in multivariable analysis (P = 0.34). Nitroglycerin administration resulted in increase in coronary artery diameter in the SRL compared with the CyA groups (2.79 +/- 0.54 vs. 2.57 +/- 0.61, P = 0.0036). In 13 SRL-treated subjects without evidence of cardiac allograft vasculopathy (CAV), Ach administration resulted in less epicardial vasoconstriction compared with CyA-treated subjects (2.7 +/- 17.7 vs. -15.6 +/- 17.2%, P = 0.005). Two SRL-treated subjects with three-dimensional intravascular ultrasound evidence of CAV developed coronary spasm in response to Ach 10(-4). Microvascular endothelial function did not differ between the groups.

CONCLUSION

Sirolimus immunosuppression is associated with less pronounced coronary epicardial endothelial dysfunction compared with CyA immunosuppression. Improvement of coronary vasomotor function with SRL may be an important mechanism for the prevention of CAV.

Features of cardiac allograft coronary endothelial dysfunction

The aim of the study was to evaluate the features and mechanism of cardiac allograft coronary endothelial dysfunction. Coronary blood flow and epicardial coronary artery diameter response to intracoronary acetylcholine and N(G)-monomethyl-l-arginine were assessed in 19 cyclosporine-treated heart transplant recipients with normal coronary angiograms (3.8 +/- 2.3 years after transplantation) and compared with 19 age-, gender-, and cardiovascular risk factor-matched nontransplantation control patients with normal coronary angiograms. Heart transplant recipients had more epicardial vasoconstriction in response to intracoronary acetylcholine (mean -16 +/- 19% [SD] vs 4 +/- 10%; p = 0.036). Microvascular endothelial function was similar between groups. Coronary flow reserve in response to adenosine was higher in the transplant group (3.6 +/- 0.8 vs 3.1 +/- 0.7; p = 0.04). The effect of N(G)-monomethyl-l-arginine (64 micromol/min) on coronary blood flow (-16 +/- 21% vs -37 +/- 19%; p = 0.018), coronary artery diameter (-10 +/- 13% vs -21 +/- 11%; p = 0.04), and coronary vascular resistance (34 +/- 40% vs 73 +/- 63%; p = 0.047) was significantly attenuated in the transplant group compared with controls. In conclusion, cardiac allograft epicardial coronary endothelial function was abnormal and may be related to an impaired endogenous NO synthetase pathway and reduced endothelial nitric oxide production in transplant recipients.

Protective effects of antithrombin on puromycin aminonucleoside nephrosis in rats

We investigated the effects of antithrombin, a plasma inhibitor of coagulation factors, in rats with puromycin aminonucleoside-induced nephrosis, which is an experimental model of human nephrotic syndrome. Antithrombin (50 or 500 IU/kg/i.v.) was administered to rats once a day for 10 days immediately after the injection of puromycin aminonucleoside (50 mg/kg/i.v.). Treatment with antithrombin attenuated the puromycin aminonucleoside-induced hematological abnormalities. Puromycin aminonucleoside-induced renal dysfunction and hyperlipidemia were also suppressed. Histopathological examination revealed severe renal damage such as proteinaceous casts in tubuli and tubular expansion in the kidney of control rats, while an improvement of the damage was seen in antithrombin-treated rats. In addition, antithrombin treatment markedly suppressed puromycin aminonucleoside-induced apoptosis of renal tubular epithelial cells. Furthermore, puromycin aminonucleoside-induced increases in renal cytokine content were also decreased. These findings suggest that thrombin plays an important role in the pathogenesis of puromycin aminonucleoside-induced nephrotic syndrome. Treatment with antithrombin may be clinically effective in patients with nephrotic syndrome.

IGF-1 reduces inflammatory responses, suppresses oxidative stress, and decreases atherosclerosis progression in ApoE-deficient mice

OBJECTIVE

Whereas growth factors, via their ability to stimulate vascular smooth muscle cell (VSMC) proliferation and migration, have been thought to play a permissive role in atherosclerosis initiation and progression, the role of insulin-like growth factor-1 (IGF-1) is unknown. Here we report for the first time that IGF-1 infusion decreased atherosclerotic plaque progression in ApoE-deficient mice on a Western diet.

METHODS AND RESULTS

ApoE-null mice (8 weeks) were infused with vehicle or recombinant human IGF-1 and fed a high-fat diet for 12 weeks. Analysis of aortic sinuses revealed that IGF-1 infusion decreased atherosclerotic plaque progression and macrophage infiltration into lesions. Furthermore, IGF-1 decreased vascular expression of the proinflammatory cytokines interleukin-6 and tumor necrosis factor-alpha, reduced aortic superoxide formation and urinary 8-isoprostane levels, and increased aortic pAkt and eNOS expression and circulating endothelial progenitor cells, consistent with an antiinflammatory, antioxidant, and prorepair effect on the vasculature.

CONCLUSIONS

Our data indicate that an increase in circulating IGF-1 reduces vascular inflammatory responses, systemic and vascular oxidant stress and decreases atherosclerotic plaque progression. These findings have major implications for the treatment of atherosclerosis.

Oxidized low density lipoprotein receptor-1 mediates oxidized low density lipoprotein-induced apoptosis in human umbilical vein endothelial cells: Role of reactive oxygen species

Studies have shown that oxidized low density lipoprotein (ox-LDL) elicits both necrotic and apoptotic cell death and several mechanisms have been proposed. Ox-LDL induces reactive oxygen species (ROS), a second messenger that might be involved in apoptosis, formation in different types of cells including endothelial cells (ECs) and smooth muscle cells (SMCs). As lectin-like ox-LDL receptor-1 (LOX-1) was the main receptor for ox-LDL, this study was designed to determine whether the apoptosis induced by ox-LDL was mediated by LOX-1 in cultured human umbilical vein endothelial cells (HUVECs) and whether there is an association between LOX-1 mediated apoptosis and the production of ROS. After exposure to ox-LDL (50,100, and 150 microg/ml for 18 h), HUVECs exhibit typical apoptotic characteristics as determined by transmission electron microscopy and flow cytometry analysis in a dose-dependent pattern. Ox-LDL increases intracellular ROS formation including superoxide anion (O2-) and hydrogen peroxide (H2O2) in a dose-dependent and time-dependent manner. Pretreatment with anti-LOX-1 mAb, Vitamin C, apocynin or catalase significantly reduced ROS production and prevented ox-LDL-induced apoptosis, while indomethacin or allopurinol had no effect. These results suggest that LOX-1 mediates ox-LDL-induced apoptosis in endothelial cells and that ROS production and NADPH oxidase might play an important role in ox-LDL-induced apoptosis.

Pharmacological and physicochemical factors in the pressor effects of conjugated haemoglobin-based oxygen carriers in vivo

BACKGROUND

The hypertension induced by haemoglobin-based oxygen carriers could be a result of different pharmacological and physicochemical factors.

OBJECTIVE

To investigate whether production of superoxide anion (O2*-) and release of endothelin could be the factors responsible.

METHODS

We studied the variation in mean arterial pressure (MAP) in guinea pigs by carrying out a 50% isovolaemic exchange transfusion with conjugated oxyhaemoglobin (non-oxidized form) or conjugated methaemoglobin (fully oxidized form) in the presence or absence of BQ-788 (5 nmol/l), an endothelin receptor type B (ETR-B) antagonist. At key timepoints of variation in MAP, the plasma concentrations of O2*- were measured. The presence of conjugated oxyhaemoglobin and increases in ETR-B concentrations inside the vascular wall were investigated in different vessels, using western blotting.

RESULTS

We found that the administration of conjugated oxyhaemoglobin induced a significant increase in MAP, whereas conjugated methaemoglobin had no significant haemodynamic effect. Pretreatment with BQ-788 attenuated the increase in MAP induced by conjugated oxyhaemoglobin. This haemoglobin induced the production of high concentrations of O2*- that declined towards control values after 120 min and decreased in the presence of BQ-788. Western blot analysis showed that the presence of conjugated oxyhaemoglobin inside the vascular wall was time-dependent and correlated with increased ETR-B.

CONCLUSION

These results show that the release of O2*- during auto-oxidation of conjugated oxyhaemoglobin is associated with the observed increase in MAP, which may be a result of the vasoconstriction caused by an increase in activation of ETR-B. This activation may be caused by the massive release of endothelin induced by the production of O2*-.

Endothelin-A and -B receptors, superoxide, and Ca2+ signaling in afferent arterioles

It is unknown if endothelin-A and -B receptors (ET(A)R and ET(B)R) activate the production of superoxide via NAD(P)H oxidase and subsequently stimulate the formation of cyclic adenine diphosphate ribose (cADPR) in afferent arterioles. Vessels were isolated from rat kidney and loaded with fura 2. Endothelin-1 (ET-1) rapidly increased cytosolic Ca(2+) concentration ([Ca(2+)](i)) by 303 nM. The superoxide dismutase mimetic tempol, the NAD(P)H oxidase inhibitor apocynin, and nicotinamide, an inhibitor of ADPR cyclase, diminished the response by approximately 60%. The ET(B)R agonist sarafotoxin 6c (S6c) increased peak [Ca(2+)](i) by 117 nM. Subsequent addition of ET-1 in the continued presence of S6c caused an additional [Ca(2+)](i) peak of 225 nM. Neither nicotinamide or 8-bromo- (8-Br) cADPR nor apocynin decreased the [Ca(2+)](i) response to S6c, but inhibited the subsequent [Ca(2+)](i) response to ET-1. The ET(B)R blockers BQ-788 and A-192621 prevented the S6c [Ca(2+)](i) peak and reduced the ET-1 response by more than one-half, suggesting an ET(B)R/ET(A)R interaction. In contrast, the ET(A)R blocker BQ-123 had no effect on the S6c [Ca(2+)](i) peak and obliterated the subsequent ET-1 response. ET-1 immediately stimulated superoxide formation (measured with TEMPO-9-AC, 68 arbitrary units) that was inhibited 95% by apocynin or diphenyl iodonium. S6c or IRL-1620 increased superoxide by 8% of that caused by subsequent ET-1 addition. We conclude that ET(A)R activation of afferent arterioles increases the formation of superoxide that accounts for approximately 60% of subsequent Ca(2+) signaling. ET(B)R activation appears to result in only minor increases in superoxide production. Nicotinamide and 8-Br-cADPR results suggest that ET-1 (and primarily ET(A)R) causes the activation of vascular smooth muscle cell-ADPR cyclase.

Vitamin C blocks vascular dysfunction and release of interleukin-6 induced by endothelin-1 in humans in vivo

OBJECTIVE

Inflammation of the vessel wall is of importance in atherosclerosis. Endothelin-1 (ET-1) exerts pro-inflammatory effects and contributes to endothelial dysfunction. The objective was to test whether ET-1 impairs vascular function by increasing oxidative stress and release of pro-inflammatory cytokines in humans.

METHODS

Forearm blood flow (FBF) was determined in 12 young healthy males with venous occlusion plethysmography.

RESULTS

Intra-brachial infusion of ET-1 (20 pmol/min) decreased both endothelium-dependent and -independent vasodilatation (P<0.001). ET-1 also increased venous IL-6 levels (0.96+/-0.14-1.40+/-0.15 ng/ml; P<0.001). Administration of Vitamin C (24 mg/min) following the ET-1 infusion did not restore vascular function. However, pre-treatment with Vitamin C before ET-1 prevented the decrease in endothelium-dependent and -independent vasodilatation as well as the increase in IL-6 levels (1.20+/-0.28 versus 1.29+/-0.27 ng/ml; P=0.57). Infusion of a control vasoconstrictor substance, noradrenaline (80 ng/min) for 30 min did not affect IL-6 levels.

CONCLUSIONS

ET-1 impairs endothelium-dependent and -independent vasodilatation and stimulates release of IL-6 in humans in vivo. These effects are inhibited by pre-treatment with the antioxidant Vitamin C. This suggests that the mechanism by which ET-1 impairs vascular function and stimulates release of IL-6 involves increased oxidative stress.

Endothelin mediates superoxide production and vasoconstriction through activation of NADPH oxidase and uncoupled nitric-oxide synthase in the rat aorta

Experiments were designed to test the hypothesis that elevated levels of endothelin 1 (ET-1) in the vasculature activate NADPH oxidase and/or uncoupled nitric-oxide synthase (NOS), resulting in O2-* production, and mediate increased constriction. Rat aortic rings were incubated with ET-1 or vehicle in the presence and absence of superoxide dismutase (SOD), ebselen (glutathione peroxidase mimetic), apocynin (NADPH oxidase inhibitor), L-NAME (Nomega-nitro-L-arginine methyl ester) (NOS inhibitor), tetrahydrobiopterin (BH4) (NOS cofactor), or selective ETA and ETB receptor antagonists (BQ-123 [cyclo(D-Asp-Pro-D-Val-Leu-D-Trp)] and A-192621 [[2R-(4-propoxyphenyl)-4S-(1,3-benzodioxol-5-yl)-1-(N-(2,6-diethylphenyl)aminocarbonyl-methyl)-pyrrolidine-3R-carboxylic acid]], respectively). O2-* production was monitored by oxidized dihydroethidine staining and/or lucigenin chemiluminescence. ET-1 significantly increased O2-* production compared with vehicle. SOD, ebselen, and apocynin inhibited the ET-1-induced increase in O2-* in intact and endothelium-denuded aorta. L-NAME and BH4 inhibited the ET-1-induced increase in O2-* in intact tissue, whereas these two compounds had no effect on ET-1-induced O2-* in endothelium-denuded aorta. Preincubation with BQ-123 or A-192621, individually, had no effect on ET-1-induced O2-*; however combining both antagonists inhibited the ET-1-stimulated increase in O2-*. Rat aortic rings were incubated with ET-1 or vehicle in the presence or absence of sepiapterin (BH4 synthesis substrate) or apocynin and mounted on wire myographs to determine isometric force generation in response to increasing KCl concentrations. ET-1 increased the contractile response to KCl compared with vehicle. Treatment with either sepiapterin or apocynin attenuated the ET-1-mediated increase with no effect of sepiapterin or apocynin alone. These data support the hypothesis that ET-1 increases vascular tone, in part, through ETA/ETB receptor activation of O2-* production from NADPH oxidase and NOS uncoupling.

Cyclosporine-induced coronary endothelial dysfunction: is tetrahydrobiopterin the solution?

BACKGROUND

Coronary endothelial dysfunction after heart transplantation is predictive of cardiac allograft vasculopathy. Immunosuppressive drugs, particularly cyclosporine may contribute to this dysfunction by a direct effect. Tetrahydrobiopterin (BH(4)) is a potent antioxidant and an essential cofactor of nitric oxide biosynthesis. The purpose of this study was to investigate whether BH(4) could reverse the endothelial dysfunction induced by cyclosporine.

METHODS

A previously described in vitro model of drug incubation in Krebs-bicarbonate solution (4 degrees C, 48 hours) of porcine epicardial coronary arteries was used. Coronary endothelial function studies were performed in organ chamber experiments after incubation with cyclosporine (10(-4) mol/L) in the presence or absence of 6-methyltetrahydropterin (MH(4) [0.1 mol/L], a BH(4) analog) to assess its effect on the cyclosporine-induced endothelial dysfunction.

RESULTS

The average doses of PGF2(alpha) required to attain 50% of the maximal contraction to KCl was significantly lower (P < .001) in the cyclosporine group (8.6 +/- 1.94 x 10(-6) mol/L) compared to the control group (24.8 +/- 5.2 x 10(-6) mol/L). Exposure to cyclosporine induced a significant decrease in endothelium-dependent relaxations to serotonin (5HT) (% E(max) [5HT]: 77% +/- 4%; P < .05). Addition of MH(4) significantly reversed this impaired response (% E(max) [5HT]: 62% +/- 4%; P < .05). No alterations of relaxation were observed with bradykinin in both groups. Endothelium-independent relaxations to sodium nitroprussiate were fully preserved.

CONCLUSIONS

These results suggest a significant protective role of BH(4) on coronary endothelial function following exposure to cyclosporine, which could reduce the incidence of endothelial dysfunction and cardiac allograft vasculopathy following cardiac transplantation.

The endothelin-1 receptor antagonist bosentan protects against ischaemia/reperfusion-induced endothelial dysfunction in humans

Endothelial dysfunction may contribute to the extent of ischaemia/reperfusion injury. ET (endothelin)-1 receptor antagonism protects against myocardial ischaemia/reperfusion injury in animal models. The present study investigated whether oral administration of an ET(A)/ET(B) receptor antagonist protects against ischaemia/reperfusion-induced endothelial dysfunction in humans. FBF (forearm blood flow) was measured with venous occlusion plethysmography in 13 healthy male subjects. Forearm ischaemia was induced for 20 min followed by 60 min of reperfusion. Using a cross-over protocol, the subjects were randomized to oral administration of 500 mg of bosentan or placebo 2 h before ischaemia. Endothelium-dependent and -independent vasodilatation were determined by intra-brachial infusion of acetylcholine (1-10 microg/min) and nitroprusside (0.3-3 microg/min) respectively, before and after ischaemia. Compared with pre-ischaemia, the endothelium-dependent increase in FBF was significantly impaired at 15 and 30 min of reperfusion when the subjects received placebo (P<0.01). When the subjects received bosentan, the endothelium-dependent increase in FBF was not affected by ischaemia/reperfusion. Endothelium-independent vasodilatation was not affected during reperfusion compared with pre-ischaemia. The vaso-constrictor response induced by intra-arterial infusion of ET-1 was attenuated significantly by bosentan (P<0.001). The results suggest that the dual ET(A)/ET(B) receptor antagonist bosentan attenuates ischaemia/reperfusion-induced endothelial dysfunction in humans in vivo. Bosentan may thus be a feasible therapeutic agent in the treatment of ischaemia/reperfusion injury in humans.

Endothelin-1, superoxide and adeninediphosphate ribose cyclase in shark vascular smooth muscle

In vascular smooth muscle (VSM) of Squalus acanthias, endothelin-1(ET-1) signals via the ETB receptor. In both shark and mammalian VSM, ET-1 induces a rise in cytosolic Ca2+ concentration([Ca2+]i) via activation of the inositol trisphosphate (IP3) receptor (IP3R) and subsequent release of Ca2+ from the sarcoplasmic reticulum (SR). IP3R-mediated release of SR Ca2+ causes calcium-induced calcium release (CICR) via the ryanodine receptor (RyR), which can be sensitized by cyclic adeninediphosphate ribose (cADPR). cADPR is synthesized from NAD+ by a membrane-bound bifunctional enzyme, ADPR cyclase. We have previously shown that the antagonists of the RyR, Ruthenium Red, high concentrations of ryanodine and 8-Br cADPR, diminish the[Ca2+]i response to ET-1 in shark VSM. To investigate how ET-1 might influence the activity of the ADPR cyclase, we employed inhibitors of the cyclase. To explore the possibility that ET-1-induced production of superoxide (O2.-) might activate the cyclase, we used an inhibitor of NAD(P)H oxidase (NOX), DPI and a scavenger of O2.-, TEMPOL. Anterior mesenteric artery VSM was loaded with fura-2AM to measure [Ca2+]i. In Ca2+-free shark Ringers, ET-1 increased[Ca2+]i by 104±8 nmol l-1. The VSM ADPR cyclase inhibitors, nicotinamide and Zn2+, diminished the response by 62% and 72%, respectively. Both DPI and TEMPOL reduced the response by 63%. The combination of the IP3R antagonists, 2-APB or TMB-8, with DPI or TEMPOL further reduced the response by 83%. We show for the first time that in shark VSM, inhibition of the ADPR cyclase reduces the[Ca2+]i response to ET-1 and that superoxide may be involved in the activation of the cyclase.

Cyclosporin A does not affect platelets in children with idiopathic nephrotic syndrome

The immunosuppressive agents administered to maintain the remission of idiopathic nephrotic syndrome (INS) may have a deleterious effect on several cell types. The aim of this study was to analyze platelet activation and reactivity in children with INS treated with cyclosporin A (CyA). The study groups comprised 16 children with remission of INS induced by CyA and 16 children with glucocorticosteroid-induced remission 8 weeks from the onset of INS relapse. Fifteen healthy children served as controls. Surface expression of CD61, CD62P, and CD42b on resting and thrombin-stimulated platelets was analyzed with flow cytometry. No differences between groups were found in CD61, CD62P, and CD42b surface expression, but markers of the coagulation cascade and fibrinolysis or endothelial injury (F1+2 prothrombin fragments, tissue plasminogen activator inhibitor 1) were elevated in patients treated with CyA compared with children on steroids and healthy controls. No correlations between markers of platelet function and CyA concentration were found. We postulate that CyA administration in nephrotic patients causes an activation of thrombinogenesis but does not influence platelet activation and reactivity in INS.

NADPH oxidase inhibition attenuates oxidative stress but not hypertension produced by chronic ET-1

Experiments were conducted to test the hypothesis that hypertension produced by chronic ET-1 infusion is mediated by NADPH oxidase-dependent superoxide production. Mean arterial pressure (MAP) was continuously monitored in male Sprague Dawley rats by telemetry. After baseline measurements, rats were placed on a high-salt diet (8% NaCl) and osmotic minipumps were implanted to infuse ET-1 (5 pmol/kg per minute intravenous) for 12 days. Control rats were maintained on the high-salt diet only. Separate groups of rats were also infused with ET-1 and given the superoxide dismutase mimetic, tempol (1 mmol/L), or the NADPH oxidase inhibitor, apocynin (1.5 mmol/L), in the drinking water. Infusion of ET-1 significantly increased MAP when compared with baseline values (132+/-3 versus 114+/-2 mm Hg, P<0.05). Neither tempol nor apocynin treatment had any effect on the increase in MAP produced by ET-1 when compared with baseline values (127+/-5 versus 113+/-2 and 130+/-3 versus 115+/-2 mm Hg, respectively). Plasma 8-isoprostane, an indicator of oxidative stress, was significantly increased in ET-1-infused rats compared with rats on a high-salt diet alone (128+/-33 versus 51+/-5 pg/mL; P<0.05). Both tempol and apocynin treatment significantly attenuated the ET-1-induced increase in plasma 8-isoprostane (72+/-10 and 61+/-6 pg/mL, respectively). Similarly, ET-1 infusion also significantly increased aortic superoxide production (chemiluminescence and dihydroethidium staining techniques), which was prevented by both tempol and apocynin. These data provide evidence that chronic ET-1 infusion increases vascular NADPH oxidase-dependent superoxide production but does not account for chronic ET-1-induced hypertension.

Effect of immunosuppressive agents on long-term survival of renal transplant recipients: focus on the cardiovascular risk

In the control of acute rejection, attention is being focused more and more on the long-term adverse effects of the immunosuppressive agents used. Since cardiovascular disease is the main cause of death in renal transplant recipients, optimal control of cardiovascular risk factors is essential in the long-term management of these patients. Unfortunately, several commonly used immunosuppressive drugs interfere with the cardiovascular system. In this review, the cardiovascular adverse effects of the immunosuppressive agents currently used for maintenance immunosuppression are thoroughly discussed. Optimising immunosuppression means finding a balance between efficacy and safety. Corticosteroids induce endothelial dysfunction, hypertension, hyperlipidaemia and diabetes mellitus, and impair fibrinolysis. The use of corticosteroids in transplant recipients is undesirable, not only because of their cardiovascular effects, but also because they induce such adverse effects as osteoporosis, obesity, and atrophy of the skin and vessel wall. Calcineurin inhibitors are the most powerful agents for maintenance immunosuppression. The calcineurin inhibitor ciclosporin (cyclosporine) not only induces these same adverse effects as corticosteroids but is also nephrotoxic. Tacrolimus has a more favourable cardiovascular risk profile than ciclosporin and is also less nephrotoxic. It has little or no effect on blood pressure and serum lipids; however, its diabetogenic effect is more prominent in the period immediately following transplantation, although at maintenance dosages, the diabetogenic effect appears to be comparable to that of ciclosporin. The diabetogenic effect of tacrolimus can be managed by reducing the dose of tacrolimus and early corticosteroid withdrawal. The effect of tacrolimus on endothelial function has not been completely elucidated. The proliferation inhibitors azathioprine and mycophenolate mofetil (MMF) have little effect on the cardiovascular system. Yet, indirectly, by inducing anaemia, they may lead to left ventricular hypertrophy. MMF is an attractive alternative to azathioprine because of its higher potency and possibly lower risk of malignancies. Sirolimus also induces anaemia, but may be promising because of its antiproliferative features. Whether the hyperlipidaemia induced by sirolimus counteracts its beneficial effects is, as yet, unknown. It may be combined with MMF, however, initial attempts resulted in severe mouth ulcers.

Oxidized LDLs affect nitric oxide and radical generation in brain endothelial cells

There is an increase in the generation of reactive oxygen species and nitric oxide in the cerebral microcirculation in Alzheimer's disease. The factors that cause this increase in oxidative stress have not been identified. Increasing evidence suggests that there are common mechanisms in atherosclerosis and Alzheimer's disease. The objective of this study was to determine the effects of oxidized low density lipoproteins (LDLs) on brain endothelial cells. Cultured rat brain endothelial cells were treated with either native LDL (10 microg/ml) or LDL oxidized in vitro using 4-hydroxy-2-nonenal (HNE-LDL) (10 microg/ml), for 24h. The results showed that HNE-LDL significantly increased production of nitric oxide (p<0.01), decreased membrane fluidity (p<0.05), and increased reactive oxygen species generation (p<0.01). These data demonstrate that oxidized LDLs affect nitric oxide and radical generation in brain endothelial cells and could contribute to cerebrovascular dysfunction in Alzheimer's disease.

Up-regulation of kidney NAD(P)H oxidase and calcineurin in SHR: Reversal by lifelong antioxidant supplementation

BACKGROUND

Spontaneously hypertensive rats (SHR) are born normotensive and develop hypertension (HTN) later in life (age 4 to 5 weeks). HTN in SHR is associated with and caused in part, by oxidative stress and renal interstitial inflammation. This study tested the hypothesis that lifelong antioxidant supplementation beginning at prenatal period may delay the onset and reduce the severity of HTN in SHR. The study further sought to explore the effect of diet modification on renal tissue NAD(P)H oxidase and calcineurin abundance.

METHODS

Pregnant SHR and their offspring were fed either an antioxidant-fortified diet (a chow containing alpha-tocopherol 5000 IU/kg, ascorbic acid 500 ppm, selenium 2.76 ppm, and zinc 350 ppm) or regular diet (alpha-tocopherol 40 IU/kg, selenium 0.2 ppm, and zinc 70 ppm). Animals were observed for 24 weeks. Wistar-Kyoto rats fed either a regular or antioxidant diet served as control.

RESULTS

Onset of HTN was delayed and severity of HTN was reduced in antioxidant-treated compared with untreated SHR. Markers of oxidative stress (i.e., plasma hydrogen peroxide, renal tissue malondialdehyde, and nitrotyrosine abundance) were elevated in untreated but not in antioxidant-treated SHR. gp91phox and p22phox subunits of NAD(P)H oxidase were markedly elevated in the renal cortex of untreated SHR and partially restored in the treated SHR. Similarly, renal calcineurin Aalpha and B subunits were elevated in untreated SHR and were partially restored in the treated SHR. Antioxidant therapy had no effect on the measured parameters in the WKY control.

CONCLUSION

Lifelong consumption of antioxidant-rich diet ameliorates HTN and oxidative stress in SHR. This is associated with the reduction of superoxide-generating enzyme, NAD(P)H oxidase, and immunoregulatory factor calcineurin. Antioxidant-rich diet appears to attenuate oxidative stress, not only by fortifying antioxidant defense capacity but also by lowering NAD(P)H oxidase, which is a major source of reactive oxygen species.

Vasopressin type 1A receptor up-regulation by cyclosporin A in vascular smooth muscle cells is mediated by superoxide

Based on our previous results, we investigated whether cyclosporin A (CsA)-induced vasopressin type 1A receptor up-regulation was mediated by free radicals. We report that CsA analogues with different affinities for cyclophilin and calcineurin were able to up-regulate vasopressin type 1A receptor and to generate free radicals in smooth muscle cells independently of calcineurin. Further, we demonstrate that the antioxidant N-acetyl-L-cysteine blocked the increase in vasopressin type 1A receptor mRNA and protein levels induced by CsA and that low concentrations of prooxidants were able to directly increase vasopressin type 1A receptor mRNA and protein levels. In addition, short exposure to CsA or pro-oxidants was sufficient to significantly increase vasopressin type 1A receptor mRNA and protein levels. Using cell-permeable forms of superoxide dismutase and catalase, we finally show that superoxide mediates the CsA-induced effects on vasopressin type 1A receptor. These results provide strong evidence that CsA-induced superoxide generation is causally involved in vasopressin type 1A receptor expression and demonstrate for the first time that low physiological concentrations of radicals, most probably superoxide, are able to directly affect cellular signaling to increase vasopressin type 1A receptor expression in rat aortic smooth muscle cells.

Role of angiotensin II and reactive oxygen species in cyclosporine A-dependent hypertension

Treatment with cyclosporine A (CysA), a potent immunosuppressive agent, is associated with systemic and renal vasoconstriction, leading to hypertension. The present study was conducted to elucidate the contribution of angiotensin II (Ang II) to CysA-induced hypertension and reactive oxygen species (ROS) generation. CysA (30 mg/kg per day SC), given for 3 weeks in rats, increased systolic blood pressure (SBP) from 119+/-2 to 145+/-3 mm Hg (n=7). Plasma and kidney Ang II levels were significantly higher in CysA-treated rats (136+/-10 fmol/mL and 516+/-70 fmol/g) than in vehicle-treated (1 mL olive oil) rats (76+/-10 fmol/mL and 222+/-21 fmol/g, n=7). CysA treatment increased AT1 receptor protein expression in the aorta (by 251+/-35%), whereas it was reduced in the kidney (by -32+/-4%). Superoxide anion production in aortic segments and kidney thiobarbituric acid-reactive substance (TBARS) contents were higher in CysA-treated rats (26+/-2 counts/min per milligram and 37+/-3 nmol/g) than in vehicle-treated rats (17+/-1 counts/min per milligram and 24+/-3 nmol/g). Concurrent administration of an AT1 receptor antagonist, valsartan (30 mg/kg per day, in drinking water), to CysA-treated rats (n=7) significantly decreased SBP (113+/-4 mm Hg) and prevented increases in vascular superoxide (16+/-2 counts/min per milligram) and kidney TBARS contents (21+/-3 nmol/g). Similarly, treatment with a superoxide dismutase mimetic, 4-hydroxy-2,2,6,6,-tetramethylpiperidine-N-oxyl (Tempol; 3 mmol/L in drinking water, n=7), prevented CysA-induced increases in SBP (115+/-3 mm Hg), vascular superoxide (16+/-1 counts/min per milligram), and kidney TBARS contents (19+/-2 nmol/g). These data suggest that ROS generation induced by augmented Ang II levels contributes to the development of CysA-induced hypertension.

Role of reactive oxygen species in endothelin-induced hypertension

Recent reports have indicated that endothelin-induced vasoconstriction in isolated aortic vascular rings may be mediated by the production of superoxide anion. The purpose of this study was to determine the role of superoxide anion in mediating the chronic renal and hypertensive actions of endothelin. Endothelin-1 (5 pmol/kg per minute) was chronically infused into the jugular vein by use of mini-osmotic pump for 9 days in male Sprague-Dawley rats and in rats treated with the superoxide anion scavenger tempol (30 mg/kg per day). Mean arterial pressure in the endothelin-1-treated rats was 141+/-3 mm Hg, compared with 125+/-2 mm Hg in control rats. Endothelin-1 increased renal vascular resistance (15.3+/-2.5 versus 10+/-1.3 mm Hg/mL per minute) and decreased renal plasma flow (6.5+/-0.9 versus 8.7+/-0.7 mL/min) in control rats. Endothelin-1 also significantly increased TBARS in the kidney and urinary 8-isoprostaglandin F2alpha excretion. The increase in arterial pressure in response to endothelin-1 was completely abolished by tempol (127+/-4 versus 127+/-4 mm Hg). Tempol also markedly attenuated the renal plasma flow and renal vascular resistance response to endothelin-1. Tempol also significantly decreased the level of 8-isoprostaglandin F2alpha in the endothelin-1-treated rats. Tempol had no effect on arterial pressure or renal hemodynamics in control rats. These data indicate that formation of reactive oxygen species may play an important role in mediating hypertension induced by chronic elevations in endothelin.

Effect of atorvastatin on postcardiac transplant increase in low-density lipoprotein cholesterol reduces development of intimal hyperplasia and progression of endothelial dysfunction

Following cardiac transplantation, accelerated coronary disease limits long-term survival. Because statins may reduce the progression of the disease in part by their anti-inflammatory effects, this study was designed to assess if atorvastatin prevented neointimal hyperplasia and endothelial dysfunction independently of baseline cholesterol levels. Patients were randomized to usual therapy (n = 13) or to 10 to 20 mg of atorvastatin (n = 12). Control subjects received niacin when their low-density lipoprotein (LDL) cholesterol levels were >130 mg/dl (n = 4). Neointimal hyperplasia by intracoronary ultrasonography, endothelial dependent vascular reactivity, and coronary flow reserve were measured at baseline and 1 year. Control group total cholesterol (203 +/- 11 to 200 +/- 13 mg/dl) and LDL (116 +/- 10 to 119 +/- 11 mg/dl) remained stable, whereas there was a nonsignificant reduction at 12 months in the atorvastatin group (total cholesterol 216 +/- 28 to 178 +/- 21 mg/dl; LDL 126 +/- 17 to 100 +/- 18 mg/dl). At 2 to 3 months there was a significant increase in total cholesterol and LDL cholesterol that was reduced with atorvastatin. At 1 year, patients taking atorvastatin showed a decrease in new or progressing lesions (2.5 +/- 1.7 vs 4.2 +/- 1.8 lesions/patient, p = 0.02), progression of maximal intimal thickness (0.12 +/- 0.07 vs 0.52 +/- 0.17 mm, p = 0.04), and percent area stenosis (5.9 +/- 2.2% vs 19.0 +/- 5.5%, p = 0.04). Atorvastatin ameliorated progressive endothelial dysfunction, whereas coronary flow reserve was unchanged in both groups. Atorvastatin administered to patients with normal or mild hypercholesterolemia in the initial year after transplant reduced the initial increase in LDL cholesterol, and, by doing so, prevented the development and progression of coronary artery lesions and endothelial dysfunction with only mild long-term decreases in cholesterol levels.

Alteration in the redox state of plasma in heart-transplant patients with moderate hyperhomocysteinemia

Hyperhomocysteinemia has recently been suggested to contribute to the progression of the so-called chronic rejection or cardiac allograft vasculopathy (CAV) in heart-transplant patients in which the major determinant of the increase in homocysteine (Hcy) was the progressive decline of renal function. The exact mechanisms of tissue injury by Hcy is unknown, but some aspects of its toxicity have been related to its capacity for altering the redox state of plasma and forming protein adducts by intermediate lactone. To study the relationships between Hcy levels and variations in the redox state governed by thiols, plasma levels of Hcy, cysteine, glutathione, cysteinylglycine, and corresponding disulfides and protein-mixed disulfides were evaluated in subjects with moderate hyperhomocysteinemia represented by heart-transplant patients with (HTRF) and without (HT) renal failure, as well as patients with renal failure of different origin (RF), and compared with those of a control group (C) of normal subjects matched for age and sex. Plasma levels of Hcy and the corresponding protein mixed disulfides increased progressively in HTs, RFs, and HTRFs with respect to control. These changes were correlated with cysteine variations (as cystine and protein-mixed disulfides) but not with glutathione or cysteinylglycine that varied only as disulfides with a similar tendency. Moreover, an alteration in the plasma redox was evidenced by the decrease in thiol/disulfide ratios of cysteine, Hcy, and cysteinylglycine. In all groups, cysteine was directly correlated with Hcy but not with glutathione or cysteinylglycine, which in turn were correlated each other. Therefore levels of plasma cysteine were more linked to Hcy than to metabolism of glutathione. The clinical meaning of cysteine changes remains undefined and requires further study.

Oxidized low-density lipoprotein inhibits endothelium-dependent vasodilation by an antioxidant-sensitive, lysophosphatidylcholine-independent mechanism

Previous studies have shown that oxidized low-density lipoprotein (LDL) can impair endothelial function and that this can be overcome in vivo by administration of vitamin E. However, it is unclear whether this effect of oxidized LDL is due to lysophosphatidylcholine or other components of oxidized LDL, and it is also uncertain if the protective effect of vitamin E is related to its antioxidant action. The objectives of the current study were to define how much of the effect of extensively oxidized LDL on endothelium-dependent relaxation (EDR) was in fact due to lysophosphatidylcholine, to determine if the effect of oxidized LDL involved oxidant stress to the endothelium, and, if so, to ascertain if this could be blocked by oxyradical scavengers or antioxidants. Endothelial function was assessed by measuring vasodilation in preconstricted rat mesenteric artery rings in response to acetylcholine. In the presence of 100 microg/mL oxidized LDL, 25-fold higher concentrations of acetylcholine were required for the same degree of vasorelaxation. Similar concentrations of native LDL or acetyl LDL had no effect, but 100 microg/mL phospholipase A(2)-treated LDL or 20 microM lysophosphatidylcholine produced a similar inhibition of EDR. Removal of more than 90% of lysophosphatidylcholine from oxidized LDL did not affect its ability to inhibit EDR, nor did treatment of oxidized LDL with borohydride. This effect of oxidized LDL was blocked by preincubation of arterial rings with vitamin E, probucol, or BO-653 (a potent lipophilic antioxidant), but not by superoxide dismutase. In contrast, the inhibition of EDR by lysophosphatidylcholine was unaffected by antioxidants. Calphostin C prevented the inhibition of EDR by oxidized LDL and lysophosphatidylcholine. These studies demonstrate that at least part of the effect of oxidized LDL on EDR is independent of lysophosphatidylcholine, lipid peroxides, and superoxide release but appears to involve intracellular oxidative stress and protein kinase C activation.

NADPH oxidase in endothelial cells: impact on atherosclerosis

An elevated vascular superoxide anion formation has been implicated in the initiation and progression of hypertension and atherosclerosis. In this review, we would like to discuss the generation of superoxide anions by an NADPH oxidase complex in vascular cells. Special focus is on the induction of endothelial NADPH oxidase by proatherosclerotic stimuli. We propose a proatherosclerotic vicious cycle of increased NADPH oxidase-dependent superoxide anion formation, augmented generation and uptake of oxidatively modified low-density lipoprotein, and further potentiation of oxidative stress by oxidized low-density lipoprotein itself, angiotensin II, and endothelin-1 in endothelial cells. Furthermore, novel homologues of NADPH oxidase subunit gp91(phox) are summarized. Future directions of research for a better understanding of the role of NADPH oxidase in the pathogenesis of atherosclerosis and clinical implications are discussed.

Atrial natriuretic peptide reduces cyclosporin toxicity in renal cells: role of cGMP and heme oxygenase-1

Using cultured proximal renal tubular epithelial cells (LLC-PK1), the present study investigates the effect of atrial natriuretic peptide (ANP) on cytotoxicity induced by cyclosporin A (CsA). Preincubation with ANP (1-100 nM) protected LLC-PK1 cells from CsA-induced toxicity in a concentration-dependent manner. A cytoprotective effect comparable to ANP was observed when preincubating the cells with 8-bromo cGMP (1-100 microM) or the antioxidant heme oxygenase (HO) metabolite bilirubin (0.1-10 microM). ANP or cGMP produced increases in HO-1 protein levels at concentrations that were also effective in cellular protection. Moreover, incubation with ANP or 8-bromo cGMP led to increased HO activity, i.e., formation of bilirubin in the cell lysate (up to 3-fold over basal). Tin protoporphyrin-IX (SnPP; 19 microM), an inhibitor of HO activity, completely abolished ANP-induced cytoprotection. Our results demonstrate that HO-1 is a cellular target of ANP and cGMP in renal cells. HO-1 induction and ensuing formation of antioxidant metabolites may be a novel pathway by which ANP protects from CsA-dependent nephrotoxicity and preserves renal function.