Angiotensin II increases plasminogen activator inhibitor type 1 and tissue-type plasminogen activator messenger RNA in cultured rat aortic smooth muscle cells

A Hypertrophic Spinal Pachymeningitis Patient With Factor V Leiden (G1691A), MTHFR C677T, MTHFR A1298C, PAI-1 4G-5G, Glycoprotein IIIa L33P Gene Mutations

Hypertrophic pachymeningitis (HP) is a rare clinical entity of diverse etiology, characterized by a chronic inflammation that causes dura thickening. Reports of Idiopathic hypertrophic cranial pachymeningitis (IHCP) were related to infections, trauma, tumors, and rheumatologic conditions. It was first described by Charcot and Joffroy regarding spinal meninges in 1869. HP has three stages; progressive radicular symptoms begin first, then muscle weakness and atrophy start. Findings such as paraplegia, loss of bladder and bowel control, and respiratory distress caused by intercostal and diaphragmatic denervation are considered the third stage of the disease. Especially in the cranial form of the disease, nerve ischemia and various cranial neuropathic findings may occur.

Factor V Leiden (G1691A), MTHFR C677T, MTHFR A1298C, and PAI-1 4G-5G gene mutation analysis were measured with an ABI Prism. In this case report, the authors present a case of hypertrophic mutations pachymeningitis with Factor V Leiden (G1691A), MTHFR C677T, MTHFR A1298C, PAI-1 4G-5G, Glycoprotein IIIa L33P gene.

In conclusion, we report a case of HP with Factor V Leiden (G1691A), MTHFR C677T, MTHFR A1298C, PAI-1 4G-5G, and Glycoprotein IIIa L33P gene mutations. We emphasize that the identification of pachymeningitis can be easily bypassed with the application of limited laboratory techniques. As in this case report, we think that these mutations should be analyzed in patients diagnosed with pachymeningitis.

The mechanistic basis linking cytokine storm to thrombosis in COVID-19

It is now well established that infection with SARS-CoV-2 resulting in COVID-19 disease includes a severely symptomatic subset of patients in whom an aggressive and/or dysregulated host immune response leads to cytokine storm syndrome (CSS) that may be further complicated by thrombotic events, contributing to the severe morbidity and mortality observed in COVID-19. This review provides a brief overview of cytokine storm in COVID-19, and then presents a mechanistic discussion of how cytokine storm affects integrated pathways in thrombosis involving the endothelium, platelets, the coagulation cascade, eicosanoids, auto-antibody mediated thrombosis, and the fibrinolytic system.

A Vicious Cycle: In Severe and Critically Ill COVID-19 Patients

The coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus, is one of the fastest-evolving viral diseases that has instigated a worldwide pandemic. Severe inflammatory syndrome and venous thrombosis are commonly noted in COVID-19 patients with severe and critical illness, contributing to the poor prognosis. Interleukin (IL)-6, a major complex inflammatory cytokine, is an independent factor in predicting the severity of COVID-19 disease in patients. IL-6 and tumor necrosis factor (TNF)-α participate in COVID-19-induced cytokine storm, causing endothelial cell damage and upregulation of plasminogen activator inhibitor-1 (PAI-1) levels. In addition, IL-6 and PAI-1 form a vicious cycle of inflammation and thrombosis, which may contribute to the poor prognosis of patients with severe COVID-19. Targeted inhibition of IL-6 and PAI-1 signal transduction appears to improve treatment outcomes in severely and critically ill COVID-19 patients suffering from cytokine storms and venous thrombosis. Motivated by studies highlighting the relationship between inflammatory cytokines and thrombosis in viral immunology, we provide an overview of the immunothrombosis and immunoinflammation vicious loop between IL-6 and PAI-1. Our goal is that understanding this ferocious circle will benefit critically ill patients with COVID-19 worldwide.

Obesity and its impact on COVID-19

The severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) pandemic has proven a challenge to healthcare systems since its first appearance in late 2019. The global spread and devastating effects of coronavirus disease 2019 (COVID-19) on patients have resulted in countless studies on risk factors and disease progression. Overweight and obesity emerged as one of the major risk factors for developing severe COVID-19. Here we review the biology of coronavirus infections in relation to obesity. In particular, we review literature about the impact of adiposity-related systemic inflammation on the COVID-19 disease severity, involving cytokine, chemokine, leptin, and growth hormone signaling, and we discuss the involvement of hyperactivation of the renin-angiotensin-aldosterone system (RAAS). Due to the sheer number of publications on COVID-19, we cannot be completed, and therefore, we apologize for all the publications that we do not cite.

The Impact of the Renin-Angiotensin-Aldosterone System on Inflammation, Coagulation, and Atherothrombotic Complications, and to Aggravated COVID-19

Atherosclerosis is considered a disease caused by a chronic inflammation, associated with endothelial dysfunction, and several mediators of inflammation are up-regulated in subjects with atherosclerotic disease. Healthy, intact endothelium exhibits an antithrombotic, protective surface between the vascular lumen and vascular smooth muscle cells in the vessel wall. Oxidative stress is an imbalance between anti- and prooxidants, with a subsequent increase of reactive oxygen species, leading to tissue damage. The renin-angiotensin-aldosterone system is of vital importance in the pathobiology of vascular disease. Convincing data indicate that angiotensin II accelerates hypertension and augments the production of reactive oxygen species. This leads to the generation of a proinflammatory phenotype in human endothelial and vascular smooth muscle cells by the up-regulation of adhesion molecules, chemokines and cytokines. In addition, angiotensin II also seems to increase thrombin generation, possibly via a direct impact on tissue factor. However, the mechanism of cross-talk between inflammation and haemostasis can also contribute to prothrombotic states in inflammatory environments. Thus, blocking of the renin-angiotensin-aldosterone system might be an approach to reduce both inflammatory and thrombotic complications in high-risk patients. During COVID-19, the renin-angiotensin-aldosterone system may be activated. The levels of angiotensin II could contribute to the ongoing inflammation, which might result in a cytokine storm, a complication that significantly impairs prognosis. At the outbreak of COVID-19 concerns were raised about the use of angiotensin converting enzyme inhibitors and angiotensin receptor blocker drugs in patients with COVID-19 and hypertension or other cardiovascular comorbidities. However, the present evidence is in favor of continuing to use of these drugs. Based on experimental evidence, blocking the renin-angiotensin-aldosterone system might even exert a potentially protective influence in the setting of COVID-19.

Cerebral venous thrombosis in COVID-19

BACKGROUND AND AIMS

Initially, novel severe acute respiratory syndrome coronavirus (SARS-CoV-2) was considered primarily a respiratory pathogen. However, with time it has behaved as a virus with the potential to cause multi-system involvement, including neurological manifestations. Cerebral venous sinus thrombosis (CVT) has increasingly been reported in association with coronavirus infectious disease of 2019 (COVID-19). Here, we have shed light upon CVT and its possible mechanisms in the backdrop of the ongoing COVID-19 pandemic.

METHODS

In this review, data were collected from PubMed, EMBASE and Web of Science, until March 30, 2021, using pre-specified searching strategies. The search strategy consisted of a variation of keywords of relevant medical subject headings and keywords, including "COVID-19", "SARS-CoV-2", "coronavirus", and "cerebral venous sinus thrombosis".

RESULTS

COVID-19 has a causal association with a plethora of neurological, neuropsychiatric and psychological effects. CVT has gained particular importance in this regard. The known hypercoagulable state in SARS-CoV-2 infection is thought to be the main mechanism in COVID-19 related CVT. Other plausible mechanisms may include vascular endothelial dysfunction and altered flow dynamics.

CONCLUSIONS

Although there are no specific clinical characteristics, insidious or acute onset headache, seizures, stroke-like, or encephalopathy symptoms in a patient with, or who has suffered COVID-19, should prompt the attending physician to investigate for CVT. The treatment of COVID-19 associated CVT does not differ radically from the therapy of CVT without the infection, i.e. urgent initiation of parenteral unfractionated heparin or low molecular weight heparin followed by conventional or mostly newer oral anticoagulants.

Thromboembolic Complications in Covid-19: From Clinical Scenario to Laboratory Evidence

SARS-Cov-2 infection, a pandemic disease since March 2020, is associated with a high percentage of cardiovascular complications mainly of a thromboembolic (TE) nature. Although clinical patterns have been described for the assessment of patients with increased risk, many TE complications occur in patients with apparently moderate risk. Notably, a recent statement from the European Society of Cardiology (ESC) atherosclerosis and vascular biology working group pointed out the key role of vascular endothelium for the recruitment of inflammatory and thrombotic pathways responsible for both disseminated intravascular coagulation and cardiovascular complications. Therefore, a better understanding of the pathophysiological process linking infection to increased TE risk is needed in order to understand the pathways of this dangerous liaison and possibly interrupt it with appropriate treatment. In this review, we describe the histological lesions and the related blood coagulation mechanisms involved in COVID-19, we define the laboratory parameters and clinical risk factors associated with TE events, and propose a prophylactic anticoagulation treatment in relation to the risk category. Finally, we highlight the concept that a solid risk assessment based on prospective multi-center data would be the challenge for a more precise risk stratification and more appropriate treatment.

From angiotensin-converting enzyme 2 disruption to thromboinflammatory microvascular disease: A paradigm drawn from COVID-19

We concisely review clinical, autopsy, experimental and molecular data of 2019 coronavirus disease (COVID-19). Angiotensin-converting enzyme 2 disruption and thromboinflammatory microangiopathy emerge as distinctive features. Briefly, entry of the virus into microvessels can profoundly disrupt the local renin-angiotensin system, cause endothelial injury, activate the complement cascade and induce powerful thromboinflammatory reactions, involving, in particular, von Willebrand factor, that, if widespread, may lead to microvascular plugging, ischemia and, ultimately, organ failure. We believe the current COVID-19 data consolidate a widely unrecognised paradigm of potentially fatal thromboinflammatory microvascular disease.

COVID-19: the role of excessive cytokine release and potential ACE2 down-regulation in promoting hypercoagulable state associated with severe illness

The novel coronavirus disease (COVID-19) has become a universally prevalent infectious disease. The causative virus of COVID-19 is severe acute respiratory syndrome coronavirus type 2. Recent retrospective clinical studies have established a significant association between the incidence of vascular thrombotic events and the severity of COVID-19. The enhancement in serum levels of markers that reflect a hypercoagulable state has been suggested to indicate a poor prognosis. Therefore, at present, it is crucial to understand the mechanisms that foster the hypercoagulable state in COVID-19. Over-activated inflammatory response, which is manifested as excessive cytokine release in COVID-19 patients, is also associated with COVID-19 severity. This review discusses the immuno-pathological basis of the excessive cytokine release in COVID-19. Besides, this article reviews the role of pro-inflammatory or anti-inflammatory cytokines, whose significant elevations in their serum levels have been consistently detected in multiple different clinical studies, in promoting the hypercoagulable state. Since the expression of angiotensin-converting enzyme 2 (ACE2) is potentially down-regulated in COVID-19, as proposed by a recent bio-informatic analysis, mechanisms through which reduced ACE2 expressions promote vascular thrombosis are summarized. In addition, the reciprocal-enhancing effects of the excessive cytokine release and the downregulated ACE2 expression on their pro-thrombotic activities are further discussed. Here, based on currently available evidence, we review the pathogenic mechanisms of the hypercoagulable state associated with severe cases of COVID-19 to give insights into prevention and treatment of the vascular thrombotic events in COVID-19.

ACE2 in the renin-angiotensin system

In 2020 we are celebrating the 20th anniversary of the angiotensin-converting enzyme 2 (ACE2) discovery. This event was a landmark that shaped the way that we see the renin-angiotensin system (RAS) today. ACE2 is an important molecular hub that connects the RAS classical arm, formed mainly by the octapeptide angiotensin II (Ang II) and its receptor AT1, with the RAS alternative or protective arm, formed mainly by the heptapeptides Ang-(1-7) and alamandine, and their receptors, Mas and MrgD, respectively. In this work we reviewed classical and modern literature to describe how ACE2 is a critical component of the protective arm, particularly in the context of the cardiac function, coagulation homeostasis and immune system. We also review recent literature to present a critical view of the role of ACE2 and RAS in the SARS-CoV-2 pandemic.

Are losartan and imatinib effective against SARS-CoV2 pathogenesis? A pathophysiologic-based in silico study

Proposing a theory about the pathophysiology of cytokine storm in COVID19, we were to find the potential drugs to treat this disease and to find any effect of these drugs on the virus infectivity through an in silico study. COVID-19-induced ARDS is linked to a cytokine storm phenomenon not explainable solely by the virus infectivity. Knowing that ACE2, the hydrolyzing enzyme of AngII and SARS-CoV2 receptor, downregulates when the virus enters the host cells, we hypothesize that hyperacute AngII upregulation is the eliciting factor of this ARDS. We were to validate this theory through reviewing previous studies to figure out the role of overzealous activation of AT1R in ARDS. According to this theory losartan may attenuate ARDS in this disease. Imatinib, has previously been elucidated to be promising in modulating lung inflammatory reactions and virus infectivity in SARS and MERS. We did an in silico study to uncover any probable other unconsidered inhibitory effects of losartan and imatinib against SARS-CoV2 pathogenesis. Reviewing the literature, we could find that over-activation of AT1R could explain precisely the mechanism of cytokine storm in COVID19. Our in silico study revealed that losartan and imatinib could probably: (1) decline SARS-CoV2 affinity to ACE2. (2) inhibit the main protease and furin, (3) disturb papain-like protease and p38MAPK functions. Our reviewing on renin-angiotensin system showed that overzealous activation of AT1R by hyper-acute excess of AngII due to acute downregulation of ACE2 by SARS-CoV2 explains precisely the mechanism of cytokine storm in COVID-19. Besides, based on our in silico study we concluded that losartan and imatinib are promising in COVID19.

Thrombosis in Coronavirus disease 2019 (COVID-19) through the prism of Virchow's triad

The pathogenesis of Coronavirus disease 2019 (COVID-19) is gradually being comprehended. A high number of thrombotic episodes are reported, along with the mortality benefits of heparin. COVID-19 can be viewed as a prothrombotic disease. We overviewed the available evidence to explore this possibility. We identified various histopathology reports and clinical case series reporting thromboses in COVID-19. Also, multiple coagulation markers support this. COVID-19 can be regarded as a risk factor for thrombosis. Applying the principles of Virchow's triad, we described abnormalities in the vascular endothelium, altered blood flow, and platelet function abnormalities that lead to venous and arterial thromboses in COVID-19. Endothelial dysfunction, activation of the renin-angiotensin-aldosterone system (RAAS) with the release of procoagulant plasminogen activator inhibitor (PAI-1), and hyperimmune response with activated platelets seem to be significant contributors to thrombogenesis in COVID-19. Stratifying risk of COVID-19 thromboses should be based on age, presence of comorbidities, D-dimer, CT scoring, and various blood cell ratios. Isolated heparin therapy may not be sufficient to combat thrombosis in this disease. There is an urgent need to explore newer avenues like activated protein C, PAI-1 antagonists, and tissue plasminogen activators (tPA). These should be augmented with therapies targeting RAAS, antiplatelet drugs, repurposed antiinflammatory, and antirheumatic drugs. Key Points • Venous and arterial thromboses in COVID-19 can be viewed through the prism of Virchow's triad. • Endothelial dysfunction, platelet activation, hyperviscosity, and blood flow abnormalities due to hypoxia, immune reactions, and hypercoagulability lead to thrombogenesis in COVID-19. • There is an urgent need to stratify COVID-19 patients at risk for thrombosis using age, comorbidities, D-dimer, and CT scoring. • Patients with COVID-19 at high risk for thrombosis should be put on high dose heparin therapy.

Targeted gene expression study using TaqMan low density array to gain insights into venous thrombo-embolism (VTE) pathogenesis at high altitude

Venous thrombo-embolism (VTE) is multi-factorial disease involving several genetic and acquired risk factors responsible for its onset. It may occur spontaneously upon climbing at High Altitude (HA). Several studies demonstrated that hypoxic conditions prevailing at HA pose an independent risk factor for VTE; however, molecular mechanism remains unknown. Present study aims to identify genes associated with HA-induced VTE pathophysiology using real time TaqMan Low-Density Array (TLDA) of known candidate genes. Gene expression of total 93 genes were studied and analyzed in patients of VTE from HA (HA-VTE) and from sea level (SL-VTE) in comparison to respective controls. Both HA-VTE and SL-VTE patients showed up-regulation of 37 genes involved in blood coagulation cascade, clot formation, platelet formation, endothelial response, angiogenesis, cell adhesion and calcium channel activity. Seven genes including ACE, EREG, C8A, DLG2, USF1, F2 and PCDHA7 were up-regulated in both HA-controls and VTE patients (both HA-VTE and SL-VTE) indicating their role during VTE event and also upon HA exposure. Ten genes; CDH18, FGA, EDNBR, GATA2, MAPK9, BCAR1, FRK, F11, PCDHA1 and ST8SIA4 were uniquely up-regulated in HA-VTE. The differentially expressed genes from the present study could be determining factors for HA-VTE susceptibility and provide insights into VTE occurrence at HA.

Combined Treatment With Angiotensin-Converting Enzyme Inhibitors and Angiotensin II Receptor Blockers: A Review of the Current Evidence

Several studies have shown that angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers are useful in the treatment of hypertension, cardiovascular disease, chronic heart failure, and some types of nephropathy. In this context, dual renin-angiotensin system blockade with both angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers may be more effective than treatment with each agent alone. Many clinical trials have demonstrated the beneficial effect of this combined treatment on proteinuria, hypertension, heart failure, and cardiovascular events. Moreover, these studies demonstrated that dual renin-angiotensin system blockade is generally safe and well tolerated. Long-term studies are under way to confirm these effects and also investigate the effectiveness of dual reninangiotensin system blockade on cerebrovascular disease and prevention of type 2 diabetes mellitus. These studies are expected to define the optimal use of combination treatment in everyday clinical practice. This review considers the most important clinical trials that evaluated the effect of dual renin-angiotensin system blockade on blood pressure, heart failure, and renal function.

Imperatorin derivative OW1 inhibits the upregulation of TGF-β and MMP-2 in renovascular hypertension-induced cardiac remodeling

Chronic hypertension induces vascular and cardiac remodeling. OW1 is a novel imperatorin derivative that was previously reported to inhibit vascular remodeling and improve kidney function affected by hypertension. In the present study, the effect of OW1 on the cardiac remodeling induced by hypertension was investigated. OW1 inhibited vascular smooth muscle cell (VSMC) proliferation and the phenotypic modulation of VSMCs induced by angiotensin II (Ang II). The OW1-induced vasodilatation of rat cardiac arteries was evaluated in vitro. Renovascular hypertensive rats were developed using the two-kidney one-clip method and treated with OW1 (40 or 80 mg/kg/day) or nifedipine (30 mg/kg per day) for 5 weeks. OW1 markedly reduced the systolic and diastolic blood pressure compared with that in the hypertension group or the respective baseline value during the first week. OW1 also reduced cardiac weight, and the concentrations of Ang II, aldosterone and transforming growth factor-β1 (TGF-β1). Histological examination demonstrated that OW1 exerted an inhibitory effect on vascular and cardiac remodeling. These inhibitory effects were associated with decreased cardiac levels of Ang II, matrix metalloproteinase-2 and TGF-β₁ in the hypertensive rats. In summary, OW1 exhibited a clear antihypertensive effect. More importantly, it inhibited vascular and cardiovascular remodeling, which may reduce the risk of hypertension-induced cardiovascular diseases. These results have potential implications in the development of new antihypertensive drugs.

Antihypertensive and vascular remodelling effects of the imperatorin derivative OW1 in renovascular hypertension rats

OW1 is a novel imperatorin derivative that exhibits vasodilator activity. In the present study, the antihypertensive effect of and inhibition of vascular remodelling by OW1 were investigated in two-kidney, one-clip (2K1C) renovascular hypertensive rats. Rats were subjected to the 2K1C procedure and treated with OW1 (40 or 80 mg/kg per day) for 8 weeks. Blood pressure was measured in conscious rats. Microalbumin (mALB) and total protein (U-TP) concentrations were determined in the urine, as were plasma concentrations of angiotensin (Ang) II, calcitonin gene-related peptide (CGRP) and angiotensin-converting enzyme 1 (ACE). The unclipped kidney was stained with haematoxylin and eosin and Masson trichrome, whereas aortic sections were stained with Masson trichrome. In addition, OW1-induced vasodilatation was evaluated in vitro in rat mesenteric and renal arteries. Immunohistochemical analysis was used to quantify collagen I and III expression. OW1 relaxed rat mesenteric and renal arterial rings in vitro. Treatment of 2K1C hypertensive rats with OW1 (40 and 80 mg/kg per day) for 8 weeks significantly decreased blood pressure. In addition, OW1 reduced plasma AngII and ACE concentrations and increased plasma CGRP concentrations. At 80 mg/kg per day, OW1 decreased blood urea nitrogen, mALB and U-TP levels. Histological analysis revealed that OW1 reduced renal arteriolar thickness and relieved the structural hypertrophic arteries. Moreover, OW1 had an inhibitory effect on vascular remodelling and renal lesions in hypertensive rats. In conclusion, the results suggest that OW1 could potentially be a novel candidate for hypertension intervention.

Update on the role of angiotensin in the pathophysiology of coronary atherothrombosis

BACKGROUND

Coronary atherothrombosis due to atherosclerotic plaque rupture or erosion is frequently associated with acute coronary syndromes (ACS). Significant efforts have been made to elucidate the pathophysiological mechanisms underlying acute coronary events.

MATERIALS AND METHODS

This narrative review is based on the material searched for and obtained via PubMed up to August 2014. The search terms we used were as follows: 'angiotensin, acute coronary syndromes, acute myocardial infarction' in combination with 'atherosclerosis, vulnerability, clinical trial, ACE inhibitors, inflammation'.

RESULTS

Among several regulatory components, the renin-angiotensin system (RAS) was shown as a key pathway modulating coronary atherosclerotic plaque vulnerability. Indeed, these molecules are involved in all stages of atherogenesis. Classically, the RAS is composed by a series of enzymatic reactions leading to the angiotensin (Ang) II generation and activity. However, the knowledge of RAS has expanded and become more complex. The discovery of novel components and their functions has revealed additional pathways that contribute to or counterbalance the actions of Ang II. In this review, we discussed on recent findings concerning the role of different angiotensin peptides in the pathophysiology of ACS and coronary atherothrombosis, exploring the link between these molecules and atherosclerotic plaque vulnerability.

CONCLUSIONS

Treatments selectively targeting angiotensins (including Mas and AT2 agonists, ACE2 recombinant, or Ang-(1-7) and almandine in oral formulations) have been tested in animal studies or in small human subgroups, expanding the perspective in the ACS prevention. These novel strategies, especially in the counter-regulatory axis ACE2/Ang-(1-7)/Mas, might be promising to reduce plaque vulnerability and inflammation.

Angiotensin II upregulates endothelial lipase expression via the NF-kappa B and MAPK signaling pathways

BACKGROUND

Angiotensin II (AngII) participates in endothelial damage and inflammation, and accelerates atherosclerosis. Endothelial lipase (EL) is involved in the metabolism and clearance of high density lipoproteins (HDL), the serum levels of which correlate negatively with the onset of cardiovascular diseases including atherosclerosis. However, the relationship between AngII and EL is not yet fully understood. In this study, we investigated the effects of AngII on the expression of EL and the signaling pathways that mediate its effects in human umbilical vein endothelial cells (HUVECs).

METHODS AND FINDINGS

HUVECs were cultured in vitro with different treatments as follows: 1) The control group without any treatment; 2) AngII treatment for 0 h, 4 h, 8 h, 12 h and 24 h; 3) NF-κB activation inhibitor pyrrolidine dithiocarbamate (PDTC) pretreatment for 1 h before AngII treatment; and 4) mitogen-activated protein kinase (MAPK) p38 inhibitor (SB203580) pretreatment for 1 h before AngII treatment. EL levels in each group were detected by immunocytochemical staining and western blotting. HUVECs proliferation was detected by MTT and proliferating cell nuclear antigen (PCNA) immunofluorescence staining. NF-kappa B (NF-κB) p65, MAPK p38, c-Jun N-terminal kinase (JNK), extracellular signal-regulated kinase (ERK) and phosphorylated extracellular signal-regulated kinase (p-ERK) expression levels were assayed by western blotting. The results showed that the protein levels of EL, NF-κB p65, MAPK p38, JNK, and p-ERK protein levels, in addition to the proliferation of HUVECs, were increased by AngII. Both the NF-kB inhibitor (PDTC) and the MAPK p38 inhibitor (SB203580) partially inhibited the effects of AngII on EL expression.

CONCLUSION

AngII may upregulate EL protein expression via the NF-κB and MAPK signaling pathways.

The PAI-1 4G/5G and ACE I/D polymorphisms and risk of recurrent pregnancy loss: a case-control study

PROBLEM

Thrombophilia has been postulated to be a contributor to the pathophysiology of recurrent pregnancy loss (RPL). We investigated the role of the plasminogen activator inhibitor type 1 (PAI-1) 4G/5G and angiotensin converting enzyme (ACE) I/D polymorphisms in Korean patients with RPL.

METHOD OF STUDY

Genotyping was performed using the TaqMan assay in 227 RPL patients and 304 controls.

RESULTS

The genotype distributions of both polymorphisms in the RPL group did not differ from those of controls. Because the frequency of being homozygous for ACE D/D and the PAI-I 4G/4G combination has been reported to be significantly higher in RPL patients, this was also analyzed. However, no significant difference was noted; 3.1% of RPL patients had both ACE D/D and PAI-I 4G/4G, as did 4.9% of controls (P = 0.791).

CONCLUSION

The current study suggests that both polymorphisms, either alone or in combination, are not major determinants of the development of RPL in Korean women.

Impact of lysophosphatidylcholine on the plasminogen activator system in cultured vascular smooth muscle cells

The balance between tissue-type plasminogen activator (t-PA) and plasminogen activator inhibitor type 1 (PAI-1) regulates fibrinolysis. PAI-1 expression increases in atherosclerotic arteries and vascular smooth muscle cells (VSMCs) are one of major constituents of atheroma. We investigated the impact of lysophosphatidylcholine (lysoPC), an active component of oxidized low-density lipoprotein, on the plasminogen activator system of the rat VSMCs. The lysoPC stimulated the protein and gene expressions of PAI-1 but did not affect the protein expression of t-PA. Fibrin overlay zymography revealed that lysoPC increased the activity of PAI-1 in the conditioned media, while concurrently decreasing that of free t-PA. Vitamin E inhibited the lysoPC-induced PAI-1 expression. Further, lysoPC increased the intracellular reactive oxygen species (ROS) formation. Caffeic acid phenethyl ester, an inhibitor of NF-κB, blocked this lysoPC effect. Indeed, lysoPC induced the NF-κB-mediated transcriptional activity as measured by luciferase reporter assay. In addition, genistein, an inhibitor of protein-tyrosine kinase (PTK), diminished the lysoPC effect, while 7,12-dimethylbenz[a]anthracene, a stimulator of PTK, stimulated PAI-1 production. In conclusion, lysoPC does not affect t-PA expression but induces PAI-1 expression in the VSMC by mediating NF-κB and the genistein-sensitive PTK signaling pathways via oxidative stress. Importantly, lysoPC stimulates the enzyme activity of PAI-1 and suppresses that of t-PA.

Apelin protects against angiotensin II-induced cardiovascular fibrosis and decreases plasminogen activator inhibitor type-1 production

OBJECTIVE

To test the hypothesis that apelin protects against angiotensin II (Ang II)-induced cardiovascular fibrosis and vascular remodeling.

METHODS AND RESULTS

Wild-type mice administered apelin or apelin along with Ang II exhibited less cardiovascular fibrosis and decreased plasminogen activator inhibitor type-1 (PAI-1) gene expression than mice receiving Ang II, N-nitro-L-arginine methyl ester (L-NAME), apelin plus L-NAME or apelin plus Ang II plus L-NAME. In-vitro analysis using a luciferase construct driven by 3.1 kb of the human PAI-1 promoter revealed that apelin blocked Ang II-mediated PAI-1 gene expression. Immunoblotting for phosphorylated myosin phosphatase subunit and myosin light chain revealed that apelin blocked Ang II activation of the Rho kinase pathway, which is associated with induction of PAI-1 gene expression by Ang II. In addition, treatment of human aortic smooth muscle cells with apelin reduced PAI-1 mRNA and protein production in the presence and absence of Ang II. Conversely, L-NAME treatment attenuated the downregulation of PAI-1 by apelin in cells.

CONCLUSION

Apelin protects against cardiac fibrosis and vascular remodeling through direct regulation of PAI-1 gene expression. This protective effect is mediated through the synergistic inhibition of Ang II signaling and increased production of nitric oxide by apelin. Our data extend previous findings and provide new insight into the molecular mechanisms by which apelin elicits a cardioprotective effect.

Phase I, pharmacokinetic, and biological studies of TSU-68, a novel multiple receptor tyrosine kinase inhibitor, administered after meals with solid tumors

PURPOSE

TSU-68 is a low molecular weight inhibitor of the tyrosine kinases for vascular endothelial growth factor receptor 2, platelet-derived growth factor receptor β, and fibroblast growth factors receptor 1. In this study, we assessed the recommended dose with TSU-68 administration of twice-daily (b.i.d.) or thrice-daily (t.i.d.) after meals for 4 weeks in Japanese patients with solid tumors based on the safety and tolerability and investigated the relationship between angiogenesis biomarker and clinical outcomes.

METHODS

The study design was a dose-escalation method with alternating enrollment of b.i.d. administration and t.i.d. administration after meal by traditional three-patient cohort.

RESULTS

We enrolled 24 patients at doses of 200, 400, and 500 mg/m(2) b.i.d. or 200 and 400 mg/m(2) t.i.d. No dose-limiting toxicity (DLT) occurred in the 200 mg/m(2) b.i.d. or t.i.d., and 3 patients experienced DLTs at 400 mg/m(2) b.i.d. or 400 mg/m(2) t.i.d. As main toxicity, blood albumin decreased, malaise, diarrhea, alkaline phosphatase increased, anorexia, abdominal pain, nausea, and vomiting were observed as almost all grade 1-2. There were no apparent differences in pharmacokinetic parameters between days 2 and 28 after the repeated b.i.d. and t.i.d. doses. Although tumor shrinkage was not observed, the disease control rate was 41.7%. As an angiogenesis-related factor of stratified analysis, plasma vascular endothelial growth factor and plasminogen activator inhibitor-1 were detected as a significant increase with progressive disease patients.

CONCLUSIONS

A recommended dosage of TSU-68 for this administration schedules was estimated to be 400 mg/m(2) or less b.i.d.

Targeting orphan nuclear receptor SHP in the treatment of metabolic diseases

IMPORTANCE OF THE FIELD

The orphan nuclear receptor small heterodimer partner (SHP; NR0B2) is an atypical nuclear receptor that contains a ligand-binding domain, but lacks the conserved DNA-binding domain. Since its discovery, SHP has been identified as a key transcriptional regulatory factor of genes involved in diverse metabolic pathways.

AREAS COVERED IN THIS REVIEW

We performed a Medline/Pubmed search to find published studies on the role of SHP in the regulation of metabolism in the liver, pancreatic islets, blood vessel, and kidney and on the feasibility of using SHP as a therapeutic target in metabolic disease.

WHAT THE READER WILL GAIN

In this review, we discuss the function of SHP as regulator of cholesterol, lipid and glucose metabolism, and the role of SHP in metabolic and fibrotic diseases.

TAKE HOME MESSAGE

The reviewed studies suggested that SHP could be a major target for therapeutic intervention in metabolic and fibrotic diseases, including metabolic syndrome and its complications. However, for SHP-targeted therapy, there are some outstanding issues, including the small number of known inducers of SHP and the lack of sufficient data in humans.

Orphan nuclear receptor small heterodimer partner inhibits angiotensin II- stimulated PAI-1 expression in vascular smooth muscle cells

Angiotensin II is a major effector molecule in the development of cardiovascular disease. In vascular smooth muscle cells (VSMCs), angiotensin II promotes cellular proliferation and extracellular matrix accumulation through the upregulation of plasminogen activator inhibitor-1 (PAI-1) expression. Previously, we demonstrated that small heterodimer partner (SHP) represses PAI-1 expression in the liver through the inhibition of TGF-beta signaling pathways. Here, we investigated whether SHP inhibited angiotensin II-stimulated PAI-1 expression in VSMCs. Adenovirus-mediated overexpression of SHP (Ad- SHP) in VSMCs inhibited angiotensin II- and TGF-beta-stimulated PAI-1 expression. Ad-SHP also inhibited angiotensin II-, TGF-beta- and Smad3-stimulated PAI-1 promoter activity, and angiotensin II-stimulated AP-1 activity. The level of PAI-1 expression was significantly higher in VSMCs of SHP(-/-) mice than wild type mice. Moreover, loss of SHP increased PAI-1 mRNA expression after angiotensin II treatment. These results suggest that SHP inhibits PAI-1 expression in VSMCs through the suppression of TGF-beta/Smad3 and AP-1 activity. Thus, agents that target the induction of SHP expression in VSMCs might help prevent the development and progression of atherosclerosis.

The mechanism of distinct diurnal variations of renin-angiotensin system in aorta and heart of spontaneously hypertensive rats

Diurnal variations in plasminogen activator inhibitor-1 mRNA expression are different between the spontaneously hypertensive rats (SHRs) and the Wistar-Kyoto (WKY) rats, and between the aorta and the heart. To elucidate the mechanisms, we examined diurnal changes in the circulating renin-angiotensin system in the SHR and WKY rats. Diurnal variations in plasma renin activity (PRA), plasma angiotensin I, and aldosterone concentrations were similar between the SHR and WKY rats. On the other hand, plasma angiotensin II (Ang II) concentration in the SHR was lower than that in the WKY rats at most time points, but increased to the level of the WKY rats in the late light phase. Treatment with AT1 receptor antagonist candesartan increased plasma Ang II concentration except at ZT 8 and lessened its diurnal variation in the SHR. At the peak in plasma Ang II in the SHR, Ang II regulated genes such as transforming growth factor-beta1 and p22phox were upregulated in the aorta. On the other hand, these genes were upregulated throughout the day in the heart of SHR. Candesartan treatment increased AT1a receptor mRNA expression in the heart but not in the aorta of SHR. These findings suggest that an AT1 receptor-mediated mechanism might cause a surge in plasma Ang II concentration at the late light phase in the SHR. Homologous down-regulation of AT1a receptor by Ang II may dampen the effect of a surge in plasma Ang II concentration in the heart of SHR.

ACE2 activation promotes antithrombotic activity

The aim of the present study was to test the hypothesis that the activation of the angiotensin-converting enzyme (ACE)2/angiotensin-(1-7)/Mas receptor axis by use of a novel ACE2 activator (XNT) would protect against thrombosis. Thrombi were induced in the vena cava of spontaneously hypertensive rats (SHR) and Wistar Kyoto (WKY) rats, and ACE2 and ACE activity in the thrombus was determined. Real-time thrombus formation was viewed through intravital microscopy of vessels in nude mice. Thrombus weight was 40% greater in the SHR (4.99 +/- 0.39 versus 7.04 +/- 0.66 mg). This weight increase was associated with a 20% decrease in ACE2 activity in the thrombus. In contrast, there were no differences between the WKY and SHR in ACE2 protein and ACE activity in the thrombi. ACE2 inhibition (DX600; 0.1 micromol/L/kg) increased thrombus weight by 30% and XNT treatment (10 mg/kg) resulted in a 30% attenuation of thrombus formation in the SHR. Moreover, XNT reduced platelet attachment to injured vessels, reduced thrombus size, and prolonged the time for complete vessel occlusion in mice. Thus, a decrease in thrombus ACE2 activity is associated with increased thrombus formation in SHR. Furthermore, ACE2 activation attenuates thrombus formation and reduces platelet attachment to vessels. These results suggest that ACE2 could be a novel target for the treatment of thrombogenic diseases.

Effects of losartan versus hydrochlorothiazide on indices of endothelial damage/dysfunction, angiogenesis and tissue factor in essential hypertension

BACKGROUND

Abnormalities in endothelial function, angiogenesis and thrombogenesis are found in essential hypertension. Angiotensin II has been postulated as an agent involved in these processes. We hypothesized that the treatment of essential hypertension with the angiotensin II receptor antagonist, losartan, would affect endothelial damage/dysfunction, angiogenesis and coagulation, when compared to treatment with a diuretic.

METHODS

Forty hypertensive patients (28 male, mean age 56 +/- 11.8 years) were randomized to treatment with losartan 50-100 mg o.d. or hydrochlorothiazide 12.5-25 mg o.d. over a 12-week period. Patients were assessed at week 0, 4 and 12. Endothelial damage/dysfunction was assessed using plasma levels of von Willebrand factor (vWf) and changes in flow-mediated dilation of the brachial artery (FMD). Vascular endothelial growth factor (VEGF) and its soluble receptor Flt-1 (sFlt-1) were measured as indices of angiogenesis, and plasma tissue factor (TF) as an index of coagulation. Baseline results in hypertensives were compared to 20 healthy controls (13 male, mean age 61.1 +/- 10.1 years).

RESULTS

Mean patient BP was 161/95 +/- 21/18 mmHg compared to 134/81 +/- 11/7 mmHg in controls (p<0.002). Plasma levels of TF (p=0.023) were significantly higher in patients compared to controls, and FMD was significantly lower (p<0.001). There were no significant differences in baseline blood pressures, plasma indices or FMD between patients randomized to losartan and hydrochlorothiazide. There were no significant changes in levels of plasma indices or FMD over 12 weeks of treatment in either patient group. Significant correlations between levels of VEGF with sFlt-1 (Spearman p<0.001) and TF (p=0.009) and sFlt-1 and TF (p=0.035) were seen in the untreated state, amongst the patient group only.

CONCLUSION

We have confirmed previous observations of increased levels of TF and decreased FMD in hypertensive patients compared to healthy controls. Contrary to previous observations in higher-risk hypertensive patient groups, the treatment of essential hypertension with either losartan or hydrochlorothiazide did not affect indices of endothelial damage/dysfunction, angiogenesis or coagulation.

Cilostazol inhibits high glucose- and angiotensin II-induced type 1 plasminogen activator inhibitor expression in artery wall and neointimal region after vascular injury

Increased expression of plasminogen activator inhibitor-1 (PAI-1) in vascular tissues is a potential factor linking diabetes to restenosis after percutaneous coronary intervention. Recent studies have shown that cilostazol, a selective type 3 phosphodiesterase inhibitor, prevents neointimal hyperplasia and in-stent thrombosis in patients with diabetes after coronary angioplasty and stent implantation. However, the molecular mechanism of this drug has not been fully elucidated. We examined whether cilostazol inhibits PAI-1 expression in vascular smooth muscle cells (VSMCs) and neointimal hyperplasia. We found that cilostazol effectively inhibits angiotensin II-, high glucose- and TGF-beta-stimulated PAI-1 expression in vivo and in vitro. Cilostazol attenuated PAI-1 expression in neointimal regions and inhibited neointimal hyperplasia after balloon injury. Cilostazol inhibited PAI-1 expression by multiple mechanisms including downregulation of TGF-beta, JNK and p38 signaling pathways. Cilostazol also inhibited transactivating activity at the PAI-1 promoter by Smad3, leading to a suppression of PAI-1 gene transcription. Taken together with its antiproliferative effect on VSMCs, this may explain how cilostazol exerts its antithrombogenic effects after angioplasty and stent implantation.

Receptor-dependent prorenin activation and induction of PAI-1 expression in vascular smooth muscle cells

Although elevated plasma prorenin levels are commonly found in diabetic patients and correlate with microvascular complications, the pathological role of these increases, if any, remains unclear. Prorenin/renin binding to the prorenin/renin receptor [(p)RR] enhances the efficiency of angiotensinogen cleavage by renin and unmasks prorenin catalytic activity. We asked whether plasma prorenin could be activated in local vascular tissue through receptor binding. Immunohistochemical staining showing localization of the (p)RR in the aorta to vascular smooth muscle cells (VSMCs). After cultured rat VSMCs were incubated with 10(-7) M inactive prorenin, cultured supernatant acquired the ability to generate ANG I from angiotensinogen, indicating that prorenin had been activated. Activated prorenin facilitated angiotensin generation in cultured VSMCs when exogenous angiotensinogen was added. Small interfering RNA (siRNA) against the (p)RR blocked this activation and subsequent angiotensin generation. Prorenin alone induced dose- and time-dependent increases in mRNA and protein for the profibrotic molecule plasminogen activator inhibitor (PAI)-1, effects that were blocked by siRNA, but not by the ANG II receptor antagonist saralasin. When inactive prorenin and angiotensinogen were incubated with cells, PAI-1 mRNA increased a striking 54-fold, 8-fold higher than the increase seen with prorenin alone. PAI-1 protein increased 2.75-fold. These effects were blocked by treatment with siRNA + saralasin. We conclude that prorenin at high concentration binds the (p)RR on VSMCs and is activated. This activation leads to increased expression of PAI-1 via ANG II-independent and -dependent mechanisms. These data provide a mechanism by which elevated prorenin levels in diabetes may contribute to the progression of fibrotic disease.

Correlation of angiotensin converting enzyme activity and the genotypes of the I/D polymorphism in the ACE gene with preterm birth and birth weight

OBJECTIVE

Preterm birth remains one of the most challenging areas in obstetrics. The pathogenesis of preterm labor is multifactorial and research on preterm birth has focused principally on infection and inflammatory markers. Recently the focus has turned to potential genetic factors influencing preterm birth. Uteroplacental insufficiency and thrombotic vasculopathy are considered part of the pathogenesis of preterm labor. Investigating the gene expression in the maternal/fetal interface seems of importance to expand our knowledge of the pathophysiology of preterm birth. The renin-angiotensin system (RAS) appears to play an important role in fetal/placental development and uteroplacental circulation. Hence, the aim of this study was to investigate angiotensin converting enzyme (ACE) activity and I/D polymorphisms in the ACE gene in mothers and infants with appropriately grown infants in relation to preterm birth and infant birth weight.

STUDY DESIGN

We conducted a cross-sectional study of 113 term pregnancies (> or =37 weeks) and 18 preterm pregnancies (<37 weeks). Umbilical cord bloods (venous and arterial) were obtained from the placenta immediately after delivery for serum ACE activity, ACE genotype analysis of the I/D polymorphism and the acid-base status. Maternal venous samples were obtained just after delivery for analysis of ACE activity and ACE genotype.

RESULTS

The distribution of the maternal ACE genotypes was similar for preterm and term births as was maternal ACE activity. Preterm infants were more likely to be of the DD genotype than term infants (7/18 (39%) vs. 11/83 (13%), p=0.02) (adjusted p=0.04). There was no correlation between ACE activity and birth weight (r(2) 0.00, p=0.82).

CONCLUSIONS

These findings suggest that the ACE genotype of the infant may influence the risk of preterm birth among appropriately grown fetuses.

The antithrombotic effect of angiotensin-(1-7) involves mas-mediated NO release from platelets

The antithrombotic effect of angiotensin(Ang)-(1-7) has been reported, but the mechanism of this effect is not known. We investigated the participation of platelets and receptor Mas-related mechanisms in this action. We used Western blotting to test for the presence of Mas protein in rat platelets and used fluorescent-labeled FAM-Ang-(1-7) to determine the specific binding for Ang-(1-7) and its displacement by the receptor Mas antagonist A-779 in rat platelets and in Mas(-/ -) and Mas(+/+) mice platelets. To test whether Ang-(1-7) induces NO release from platelets, we used the NO indicator DAF-FM. In addition we examined the role of Mas in the Ang-(1-7) antithrombotic effect on induced thrombi in the vena cava of male Mas(-/ -) and Mas(+/+) mice. The functional relevance of Mas in hemostasis was evaluated by determining bleeding time in Mas(+/+) and Mas(-/ -) mice. We observed the presence of Mas protein in platelets, as indicated by Western Blot, and displacement of the binding of fluorescent Ang-(1-7) to rat platelets by A-779. Furthermore, in Mas(+/+) mouse platelets we found specific binding for Ang-(1-7), which was absent in Mas(-/ -) mouse platelets. Ang-(1-7) released NO from rat and Mas(+/+) mouse platelets, and A-779 blocked this effect. The NO release stimulated by Ang-(1-7) was abolished in Mas(-/ -) mouse platelets. Ang-(1-7) inhibited thrombus formation in Mas(+/+) mice. Strikingly, this effect was abolished in Mas(-) (/) (-)mice. Moreover, Mas deficiency resulted in a significant decrease in bleeding time (8.50 +/- 1.47 vs. 4.28 +/- 0.66 min). This study is the first to show the presence of Mas protein and specific binding for Ang-(1-7) in rat and mouse platelets. Our data also suggest that the Ang-(1-7) antithrombotic effect involves Mas-mediated NO release from platelets. More importantly, we showed that the antithrombotic effect of Ang-(1-7) in vivo is Mas dependent and that Mas is functionally important in hemostasis.

Angiotensin II activates plasminogen activator inhibitor-I promoter in renal tubular epithelial cells via the AT1receptor

BACKGROUND

Plasminogen activator inhibitor-1 (PAI-1) regulates normal extracellular matrix (ECM) metabolism and it is a key regulator of the fibrotic process. Both angiotensin II (Ang II) and angiotensin IV (Ang IV) have been reported to stimulate PAI-1 expression. It is not known how PAI-1 expression is regulated by the renin-angiotensin system (RAS) in renal tubular cells.

METHODS

To dissect signaling mechanisms contributing to the up-regulation of the PAI-1 promoter, porcine proximal tubular cells stably expressing the rabbit AT1 receptor (LLC-PK/AT1) were transiently transfected with a luciferase reporter construct containing the PAI-1 promoter. Promoter activation was assessed by measuring luciferase activity from cell lysates.

RESULTS

Ang II dose-dependently stimulated the transcriptional activity of the PAI-1 promoter in renal proximal tubular cells whereas Ang IV had no consistent effect on the promoter activity. Neither inhibition of the Extracellular Signal Regulated Kinase (ERK) cascade nor inhibition of the c-Jun-N-terminal Kinase (JNK) pathway did reduce the stimulation of the PAI-1 promoter by Ang II. However, genistein, a tyrosine kinase inhibitor blocked the effect of Ang II.

CONCLUSION

Ang II but not Ang IV activates the PAI-1 promoter in renal proximal tubular cells and this effect is mediated by tyrosine kinases.

ANGIOTENSIN II INCREASES TISSUE-SPECIFIC INHIBITOR OF METALLOPROTEINASE-2 EXPRESSION IN RAT AORTIC SMOOTH MUSCLE CELLS IN VIVO: EVIDENCE OF A PRESSURE-INDEPENDENT EFFECT

1. Angiotensin (Ang) II plays a major role in vascular remodelling. Matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) are involved in the tissue remodelling processes. The aim of the present study was to investigate whether AngII modulates TIMP-2 expression in rat aortic smooth muscle cells in vivo. 2. Angiotensin II (200 ng/kg per min, s.c.) or AngII + losartan (10 mg/kg per day, s.c.) or normal saline was administered continuously by osmotic minipumps to Sprague-Dawley rats for 1 week. In addition, the effect of endogenous AngII on TIMP-2 expression was evaluated in renovascular hypertensive rats (two kidney, one clip (2K1C) and one kidney, one clip (1K1C) models). Control rats (sham 2K1C and sham 1K1C rats) underwent sham-clipping of the left renal artery. At the end of the treatment, plasma renin activity was measured by radioimmunoassay, aortic TIMP-2 mRNA expression was evaluated by real-time polymerase chain reaction and/or northern blotting and protein expression was evaluated by immunohistochemistry. Systolic blood pressure (SBP) was measured twice a week by the tail-cuff method. 3. Exogenous AngII administration produced the expected increase in SBP (P = 0.02) compared with the control saline-treated group. The increase in SBP was abolished in AngII + losartan-treated rats. Administration of AngII caused a significant increase in TIMP-2 expression (P = 0.01) in rat aortic smooth muscle cells that was abolished in AngII + losartan-treated rats. In renovascular hypertensive rats, SBP was higher (P < 0.0001) in 2K1C and 1K1C rats compared with the corresponding sham-operated rats. Plasma renin activity was higher (P < 0.01) in 2K1C rats compared with the other groups. The expression of TIMP-2 was significantly (P < 0.05) increased only in 2K1C rats. 4. Our in vivo data demonstrate that exogenous and endogenous AngII increases TIMP-2 expression in rat aortic smooth muscle cells. This effect is not dependent on the AngII-induced increase in blood pressure and is mediated by angiotensin AT1 receptors.

Systemic inhibition of the angiotensin-converting enzyme limits lipopolysaccharide-induced lung neutrophil recruitment through both bradykinin and angiotensin II-regulated pathways

Recruitment of neutrophils to the lung is a sentinel event in acute lung inflammation. Identifying mechanisms that regulate neutrophil recruitment to the lung may result in strategies to limit lung damage and improve clinical outcomes. Recently, the renin angiotensin system (RAS) has been shown to regulate neutrophil influx in acute inflammatory models of cardiac, neurologic, and gastrointestinal disease. As a role for the RAS in LPS-induced acute lung inflammation has not been described, we undertook this study to examine the possibility that the RAS regulates neutrophil recruitment to the lung after LPS exposure. Pretreatment of mice with the angiotensin-converting enzyme (ACE) inhibitor enalapril, but not the anti-hypertensive hydralazine, decreased pulmonary neutrophil recruitment after exposure to LPS. We hypothesize that inhibition of LPS-induced neutrophil accumulation to the lung with enalapril occurred through both an increase in bradykinin, and a decrease in angiotensin II (ATII), mediated signaling. Bradykinin receptor blockade reversed the inhibitory effect of enalapril on neutrophil recruitment. Similarly, pretreatment with bradykinin receptor agonists inhibited IL-8-induced neutrophil chemotaxis and LPS-induced neutrophil recruitment to the lung. Inhibition of ATII-mediated signaling, with the ATII receptor 1a inhibitor losartan, decreased LPS-induced pulmonary neutrophil recruitment, and this was suggested to occur through decreased PAI-1 levels. LPS-induced PAI-1 levels were diminished in animals pretreated with losartan and in those deficient for the ATII receptor 1a. Taken together, these results suggest that ACE regulates LPS-induced pulmonary neutrophil recruitment via modulation of both bradykinin- and ATII-mediated pathways, each regulating neutrophil recruitment by separate, but distinct, mechanisms.

CX3CR1 receptor is up-regulated in monocytes of coronary artery diseased patients: Impact of pre-inflammatory stimuli and renin–angiotensin system modulators

Fractalkine/CX3CR1 pathway is considered a major modulator of atherosclerosis. In the present study, expression of CX3CR1 on PBMCs/monocytes of healthy individuals and coronary artery diseased patients was initially assessed by flow cytometry. Effects of pre-inflammatory cytokines interferon (INF)-gamma and tumor necrosis factor (TNF)-alpha on expression of CX3CR1 and a single representative of each major chemokine family (CCR5 and CXCR4) were further assessed in three cell models: THP-1 monocytes, Jurkat T lymphocytes and primary monocytes isolated from healthy donors. Finally, effects of angiotensin-converting enzyme (ACE) inhibitors captopril, lisinopril and angiotensin receptor blocker (ARB) losartan on chemokine receptor expression were evaluated in the same cell models either in a naive or stimulated state. INF-gamma significantly affected the chemokine receptor phenotype of THP-1 cells by increasing the rate of CX3CR1-positive cells. Pre-treatment with the ACE inhibitors, captopril and lisinopril, and the ARB, losartan, did not influence these effects. Captopril and lisinopril similarly had no effect on either stimulated or naive primary monocytes. Yet, a small but repeatable increase in CX3CR1 expression after treatment with losartan was noted. Nevertheless, the latter observation did not retain statistical significance after applying the Bonferroni correction. In conclusion, our data did not indicate any significant effect of the ACE inhibitors on the chemokine receptor phenotype of monocytes.

Review of the molecular pharmacology of Losartan and its possible relevance to stroke prevention in patients with hypertension

BACKGROUND

The Losartan Intervention For End-point reduction in hypertension (LIFE) study found that a losartan-based regimen, compared with an atenolol-based regimen, resulted in a significantly lower risk of stroke in hypertensive patients with left ventricular hypertrophy, despite similar reductions in blood pressure.

OBJECTIVE

The purpose of this review was to examine the molecular and pharmacologic mechanisms that may be associated with the different outcomes observed in the LIFE study.

METHODS

A PubMed/MEDLINE search of English-language articles (1990 to February 2006) with the terms angiotensin II antagonists or AIIAs or angiotensin receptor blockers or losartan or atenolol or beta blocker and terms including, but not limited to, atherosclerosis, left ventricular hypertrophy, carotid artery hypertrophy, fatty streaks, atrial fibrillation, arrhythmias, endothelial function, myocyte hypertrophy, myocardial fibrosis, platelet aggregation, tissue factor, plasminogen activator inhibitor-1, PAI-1, anti-inflammatory, uric acid, or oxidative stress.

RESULTS

Losartan's significant effect on stroke may be related to several possible mechanisms that are independent of blood-pressure reductions. These include improvements in endothelial function and vascular structure; decreases in vascular oxidative stress; reductions in left ventricular hypertrophy, reductions in myocardial fibrosis, or both; and modulation of atherosclerotic disease progression. Although some of these effects may be shared by other angiotensin II receptor antagonists (AIIAs), and perhaps other anti-hypertensive classes (eg, angiotensin-converting enzyme inhibitors), the ability of losartan to lower serum uric acid levels-a proposed independent risk factor for cardiovascular disease-appears to be a molecule-specific effect. Alternative explanations of the results of the LIFE study have also been hypothesized, including inappropriate choice of atenolol as an active comparator and differences in central pulse pressures between study groups.

CONCLUSIONS

This review of the literature suggests that losartan (and perhaps other AIIAs) may possess a number of properties, independent of its antihypertensive effects, that may be associated with decreased vulnerability of the plaque, myocardium, and blood.

Angiotensin II stimulates phosphorylation of an ectodomain-truncated platelet-derived growth factor receptor-beta and its binding to class IA PI3K in vascular smooth muscle cells

PI3K (phosphoinositide 3-kinase) activity is involved in Ang (angiotensin) II-stimulated VSMC (vascular smooth muscle cell) growth and hypertrophy. In the present study, we demonstrate that the inhibition of PI3K in VSMCs by expression of a dominant-negative p85alpha mutant lacking the p110-binding domain (Deltap85), or by treatment of cells with LY294002, inhibited Ang II-stimulated PAI-1 (plasminogen activator inhibitor-1) mRNA expression. Using a GST (glutathione S-transferase) fusion protein containing the p85 N-terminal SH2 (Src homology 2) domain as 'bait' followed by MS/MS (tandem MS), we identified a 70 kDa fragment of the p70 PDGFR-beta (platelet-derived growth factor receptor-beta) as a signalling adapter that is phosphorylated and recruits the p85 subunit of PI3K after Ang II stimulation of AT1 (Ang II subtype 1) receptors on VSMCs. This fragment of the PDGFR-beta, which has a truncation of its extracellular domain, accounted for approx. 15% of the total PDGFR-beta detected in VSMCs with an antibody against its cytoplasmic domain. Stimulation of VSMCs with Ang II increased tyrosine-phosphorylation of p70 PDGFR-beta at Tyr751 and Tyr1021 and increased its binding to p85. PDGF also induced phosphorylation of p70 PDGFR-beta, a response inhibited by the PDGF tyrosine kinase selective inhibitor, AG1296. By contrast, Ang II-induced phosphorylation of the 70 kDa receptor was not affected by AG1296. Ang II-stimulated phosphorylation of the p70 PDGFR-beta was blocked by the AT1 receptor antagonist, candesartan (CV 11974) and was partially inhibited by PP2 {4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine}, an Src family kinase inhibitor. Our result suggests that the p70 PDGFR-beta functions as an adapter that recruits PI3K to the membrane upon AT1 receptor stimulation.

Angiotensin-converting enzyme insertion/deletion polymorphism and retinal artery occlusion

PURPOSE

An insertion/deletion (I/D) polymorphism of the gene for angiotensin-converting enzyme (ACE) is associated with higher ACE plasma levels and activity. This enzyme is known to play an important role in blood pressure regulation and the ACE I/D gene polymorphism has been suggested as a risk factor for atherosclerotic vascular diseases. The purpose of the present study was to investigate a hypothesized association between the ACE I/D polymorphism and retinal artery occlusion (RAO).

METHODS

A total of 159 patients with RAO and 304 control subjects were enrolled in the present retrospective case-control study. ACE I/D genotypes were determined by polymerase chain reaction.

RESULTS

Allelic frequencies and genotype distribution of the ACE I/D polymorphism did not significantly differ between patients and control subjects (ACE DD 25.8% versus 28.0%; p = 0.36). A logistic regression analysis predicted the presence of RAO by arterial hypertension and current smoking status, but not by ACE I/D genotypes.

CONCLUSION

Our data suggest that the ACE I/D polymorphism is not a major risk factor for RAO.

Impaired fibrinolytic activity in type II diabetes: Correlation with urinary albumin excretion and progression of renal disease

Progression of renal disease and cardiovascular complications in type II diabetes mellitus have been shown to correlate with control of blood glucose, lipids, blood pressure, and smoking. These factors, however, do not appear to totally explain these diabetic complications. Renal disease and cardiovascular complications in type II diabetes are associated with vascular abnormalities and fibrosis, both of which may occur with impaired fibrinolysis. A cross-sectional study was therefore performed in 107 type II diabetic patients recruited from the Denver Metropolitan Area to examine the effect of impaired fibrinolysis, as assessed by the ratio of plasminogen activator inhibitor (PAI-1) to tissue-type plasminogen activator (t-PA). With urinary albumin excretion (UAE) as a risk factor for both renal disease progression and cardiovascular complications, the patients were analyzed with respect to UAE less than and greater than 1 gm/day. The age, blood glucose, hemoglobin A1C, duration of diabetes, lipids, body mass index, and smoking were no different between the groups. As expected, the group with greater UAE had worse renal function, the serum creatinine (1.98 +/- 0.24 vs 1.21 +/- 0.05 mg/dl, P < 0.001) and creatinine clearance (55.5 +/- 6.0 vs 76.8 +/- 2.7 ml/min, P < 0.001) were significantly different. The type II diabetic patients with greater UAE exhibited significantly higher PAI-1/t-PA (2.43 +/- 0.26 vs 1.85 +/- 0.07, P < 0.03). The past history of cardiac complications was also higher (87.5 vs 72.3%, P < 0.07) in the diabetic patients with more impaired fibrinolysis and greater UAE. Thus a prospective, randomized clinical trial in type II diabetes with PAI-1 inhibitors is needed.

Endothelial dysfunction and oxidative stress in arterial hypertension

A large body of evidence indicates that endothelial dysfunction is a characteristic of patients with essential hypertension. By definition, endothelial dysfunction is a functional and reversible alteration of endothelial cells, resulting from impairment in nitric oxide (NO) availability and oxidative stress. Superoxide anion is a major determinant of NO biosynthesis and also acts as a vasoconstrictor. In addition, NO synthase (NOS) can generate superoxide rather than NO in response to atherogenic stimuli ("NOS uncoupling"). Under these circumstances, NOS may become a peroxynitrite generator, leading to a dramatic increase in oxidative stress, since peroxynitrite has additional detrimental effects on vascular function by lipid peroxidation. Increased levels of biomarkers of lipid peroxidation and oxidative stress have been found in patients with hypertension. In particular, patients with hypertension-related microvascular changes showed increased lipid peroxidation and platelet activation when compared with patients with absent or early signs of retinopathy. Furthermore, oxidant stress has been shown to play an important role in promoting a prothrombotic state in the vascular system. For all these reasons, endothelial dysfunction is evoked in hypertensive patients as promotor of vascular progressive damage and atherosclerotic and thrombotic complications through the enhanced oxidative stress of arterial walls. This broadens the cardiovascular risk of hypertensive patients and explains the insufficient role of the strict BP reduction in the prevention of vascular complications, thus opening up new perspectives on the antioxidant properties of currently available antihypertensive drugs and supplementation with antioxidant principles.

Transcriptional profiling after bile duct ligation identifies PAI-1 as a contributor to cholestatic injury in mice

Extrahepatic cholestasis leads to complex injury and repair processes that result in bile infarct formation, neutrophil infiltration, cholangiocyte and hepatocyte proliferation, extracellular matrix remodeling, and fibrosis. To identify early molecular mechanisms of injury and repair after bile duct obstruction, microarray analysis was performed on liver tissue 24 hours after bile duct ligation (BDL) or sham surgery. The most upregulated gene identified encodes plasminogen activator inhibitor 1 (PAI-1, Serpine 1), a protease inhibitor that blocks urokinase plasminogen activator (uPA) and tissue-type plasminogen activator (tPA) activity. Because PAI-1, uPA, and tPA influence growth factor and cytokine processing as well as extracellular matrix remodeling, we evaluated the role of PAI-1 in cholestatic liver injury by comparing the injury and repair processes in wild-type (WT) and PAI-1-deficient (PAI-1-/-) mice after BDL. PAI-1-/- mice had fewer and smaller bile infarcts, less neutrophil infiltration, and higher levels of cholangiocyte and hepatocyte proliferation than WT animals after BDL. Furthermore, PAI-1-/- mice had higher levels of tPA activation and mature hepatocyte growth factor (HGF) after BDL than WT mice, suggesting that PAI-1 effects on HGF activation critically influence cholestatic liver injury. This was further supported by elevated levels of c-Met and Akt phosphorylation in PAI-1-/- mice after BDL. In conclusion, PAI-1 deficiency reduces liver injury after BDL in mice. These data suggest that inhibiting PAI-1 might attenuate liver injury in cholestatic liver diseases.

Salutary effects of attenuation of angiotensin II on coronary perivascular fibrosis associated with insulin resistance and obesity

Obesity and insulin resistance confer increased risk for accelerated coronary disease and cardiomyopathic phenomena. We have previously shown that inhibition of angiotensin-converting enzyme (ACE) prevents coronary perimicrovascular fibrosis in genetically obese mice that develop insulin resistance. This study was performed to elucidate mechanism(s) implicated and to determine the effects of attenuation of angiotensin II (Ang) II. Genetically obese ob/ob mice were given ACE inhibitor (temocapril) or Ang II type 1 (AT(1)) receptor blocker (olmesartan) from 10 to 20 weeks. Cardiac expressions of plasminogen activator inhibitor (PAI)-1, the major physiologic inhibitor of fibrinolysis, and transforming growth factor (TGF)-beta(1), a prototypic profibrotic molecule, were determined and extent of perivascular coronary fibrosis was measured. Twenty-week-old obese mice exhibited increased plasma levels of PAI-1 and TGF-beta(1) compared with the values in lean counterpart. Perivascular coronary fibrosis in arterioles and small arteries was evident in obese mice that also showed increased left ventricular collagen as measured by hydroxyproline assay. Immunohistochemistry confirmed the deposition of perivascular type 1 collagen. Markedly increased PAI-1 and TGF-beta were seen immunohistochemically in coronary vascular wall and confirmed by western blotting. When obese mice were treated with temocapril or olmesartan from 10 to 20 weeks, both were equally effective and prevented increases in perivascular fibrosis, plasma PAI-1 and TGF-beta(1), left ventricular collagen and mural immunoreactivity for PAI-1, TGF-beta and collagen type 1. The c-Jun NH(2)-terminal kinase (JNK) activity was elevated in the left ventricle of obese mice (western) and blocked by temocapril and olmesartan. Ang II-mediated upregulation of PAI-1 and TGF-beta(1) with collagen deposition may explain the mechanism of perivascular fibrosis in obese mice. ACE inhibition and blockade of AT(1) receptor may prevent coronary perivascular fibrosis and collagen deposition even before development of overt diabetes. JNK activation may be a mediator of obesity-related cardiac dysfunction and a potential therapeutic target.

Reduced cardiac expression of plasminogen activator inhibitor 1 and transforming growth factor beta1 in obese Zucker rats by perindopril

OBJECTIVE

To determine whether angiotensin converting enzyme inhibition by perindopril can reduce cardiac transforming growth factor beta1 (TGFbeta1) and plasminogen activator inhibitor 1 (PAI-1) and therefore control collagen accumulation in an animal model with the metabolic syndrome such as the obese Zucker rat (OZR).

ANIMALS

Male OZR (group 1, n = 10); OZR treated with perindopril (group 2, n = 10); and lean Zucker rats (group 3, n = 10).

METHODS

During six months, group 2 received 3 mg/kg/day of perindopril orally and group 1 and group 3 were given a vehicle. Hearts were processed for pathology studies including immunohistochemical analysis with antibodies to PAI-1, TGFbeta1, collagen type I, and collagen type III.

RESULTS

Group 2 had lower blood pressure (126.7 (2) v 148.6 (2.7) mm Hg, p < 0.01) than untreated OZR and had decreased cardiac PAI-1 (3.6 (0.4) v 13.5 (1.7)% of positive area/field, p < 0.01), TGFbeta1 in myocytes (0.13 (0.1) v 9.14 (4.7)%/area, p < 0.01) and in interstitium (19.8 (6.8) v 178.9 (27.4) positive cells/area, p < 0.01), collagen I (3 (0.8) v 13.3 (1)%/area, p < 0.01), collagen III (5 (0.6) v 9.5 (0.9)%/area, p < 0.01), and collagen I to collagen III ratio (0.59 (0.13) v 1.40 (0.15) p < 0.01) compared with untreated OZR.

CONCLUSION

These results suggest that perindopril reduces cardiac PAI-1 and TGFbeta1 and ameliorates cardiac fibrosis in a rat model with multiple cardiovascular risk factors.