Angiotensin, fibrinolysis, and vascular homeostasis

Blood hypercoagulability and thrombosis mechanisms in cancer patients -A brief review

Patients with malignant tumors are prone to present hypercoagulability of blood and form thrombosis, and its pathogenesis is complex involving various factors from clinical and histopathological to genetic influences. Current studies on the potential mechanism of blood hypercoagulability in patients with malignant tumors focus on the following aspects but are not limited: (1) tumor cells release coagulant-promoting substances, (2) tumor cells interact with the fibrinolytic system, (3) tumor cell-mediated platelet activation, (4) tumor-associated complement activation, and (5) genetic factors and clinical factors. Especially, the pathogenesis of blood hypercoagulability is in-depth analyzed covering tumor cells' release of procoagulant substances, the interplay of cancer cells and fibrinolytic system, platelet activation mediated by cancer cells, cancer-associated complement activation, and the action of genetic and clinical factors. We review the pathogenesis of blood hypercoagulability in patients with malignant tumors, which will assist in the research and development of new drugs and providing theoretical support for the formulation of the best treatment plan for patients, to prolong the survival of patients.

Anticoagulant therapy in COVID-19: A narrative review

Coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), can manifest itself in several ways, including coagulopathy and thrombosis. These complications can be the first and sometimes only manifestations of SARS-CoV-2 infection and can occur early or late in the course of the disease. However, these symptoms are more prevalent in hospitalized patients with venous thromboembolism, particularly those admitted to intensive care units. Moreover, various forms of arterial and venous thrombosis, or micro- or macro-vasculature embolisms, have been reported during the current pandemic. They have led to harmful consequences, such as neurological and cardiac events, nearly all resulting from the hypercoagulable state caused by this viral infection. The severe hypercoagulability observed in patients with COVID-19 accounts for most cases of the disease that become critical. Therefore, anticoagulants seem to be one of the most vital therapeutics for treating this potentially life-threatening condition. In the current paper, we present a thorough review of the pathophysiology of COVID-19-induced hypercoagulable state and the use of anticoagulants to treat SARS-CoV-2 infections in different patient groups, as well as their pros and cons.

The antagonistic effect of magnesium hydroxide particles on vascular endothelial activation induced by acidic PLGA degradation products

Although drug-eluting stents (DESs) are mainly coated with biodegradable polymers such as PLGA and PLLA, their acidic degradation products can alter the local microenvironment and affect the homeostasis of adjacent tissue. Previously, we developed anti-inflammatory PLGA-based materials including magnesium hydroxide (MH) to relieve the side effects caused by PLGA degradation. However, the underlying molecular mechanism of its protective effects has not yet been clarified. Here, we demonstrated the pathological mechanism of vascular endothelial activation caused by PLGA by-products. The PLGA by-products accumulated in HCAECs through MCT1, followed by oxidative stress and the activation of the MAPK/NF-κB signaling pathway. Finally, the PLGA by-products increased the expression of VCAM-1 as well as the secretion of proinflammatory cytokines. However, the addition of MH particles significantly diminished the activation of this molecular pathway and the expression of inflammation-related factors induced by acidic PLGA degradation products. Furthermore, Mg2+ released from MH particles restored endothelial function in both intracellular and extracellular spaces. Taken together, MH particles prevent the accumulation of PLGA degradation products in HCAECs, thereby repressing the associated vascular endothelial activation. These findings on the biochemical mechanisms are expected to provide important clues for addressing the safety issues in nearly all biodegradable polymer-based implants.

ACE2, the kidney and the emergence of COVID-19 two decades after ACE2 discovery

Angiotensin-converting enzyme II (ACE2) is a homologue of angiotensin-converting enzyme discovered in 2000. From the initial discovery, it was recognized that the kidneys were organs very rich on ACE2. Subsequent studies demonstrated the precise localization of ACE2 within the kidney and the importance of this enzyme in the metabolism of Angiotensin II and the formation of Angiotensin 1–7. With the recognition early in 2020 of ACE2 being the main receptor of severe acute respiratory syndrome Coronavirus 2 (SARS-CoV-2), the interest in this protein has dramatically increased. In this review, we will focus on kidney ACE2; its localization, its alterations in hypertension, diabetes, the effect of ACE inhibitors and angiotensin type 1 receptor blockers (ARBs) on ACE2 and the potential use of ACE2 recombinant proteins therapeutically for kidney disease.

We also describe the emerging kidney manifestations of COVID-19, namely the frequent development of acute kidney injury. The possibility that binding of SARS-CoV-2 to kidney ACE2 plays a role in the kidney manifestations is also briefly discussed.

Coagulation dysfunction in COVID-19: The interplay between inflammation, viral infection and the coagulation system

COVID-19 is a new pandemic, caused by Severe Acute Respiratory Syndrome-CoronaVirus-2 (SARS-Cov2) infection and characterized by a broad spectrum of clinical manifestations.

Inflammation and the innate immune system have been recently recognized as pivotal players in the most severe forms, characterized by significantly elevated levels of pro-inflammatory cytokines. In this setting, several studies have also reported the presence of abnormalities in coagulation parameters and platelets count, possibly identifying a subgroup of patients with poor prognosis. Some reports of full-blown thromboembolic events are emerging.

Among the possible mechanisms underlying coagulation dysfunction, the so-called "cytokine storm" seems to play a pivotal role. Other candidate factors include virus-specific mechanisms, related to the virus interaction with renin angiotensin system (RAS) and the fibrinolytic pathway, but also comorbidities affecting these patients.

Coagulation dysfunction is therefore a candidate risk factor for adverse outcomes in COVID-19 and should be carefully addressed in clinical practice.

A Role of Inflammation and Immunity in Essential Hypertension-Modeled and Analyzed Using Petri Nets

Recent studies have shown that the innate and adaptive immune system, together with low-grade inflammation, may play an important role in essential hypertension. In this work, to verify the importance of selected factors for the development of essential hypertension, we created a Petri net-based model and analyzed it. The analysis was based mainly on t-invariants, knockouts of selected fragments of the net and its simulations. The blockade of the renin-angiotensin (RAA) system revealed that the most significant effect on the emergence of essential hypertension has RAA activation. This blockade affects: (1) the formation of angiotensin II, (2) inflammatory process (by influencing C-reactive protein (CRP)), (3) the initiation of blood coagulation, (4) bradykinin generation via the kallikrein-kinin system, (5) activation of lymphocytes in hypertension, (6) the participation of TNF alpha in the activation of the acute phase response, and (7) activation of NADPH oxidase-a key enzyme of oxidative stress. On the other hand, we found that the blockade of the activation of the RAA system may not eliminate hypertension that can occur due to disturbances associated with the osmotically independent binding of Na in the interstitium. Moreover, we revealed that inflammation alone is not enough to trigger primary hypertension, but it can coexist with it. We believe that our research may contribute to a better understanding of the pathology of hypertension. It can help identify potential subprocesses, which blocking will allow better control of essential hypertension.

PAI-1 is a critical regulator of FGF23 homeostasis

Elevated levels of fibroblast growth factor 23 (FGF23), a bone-derived phosphaturic hormone, are associated with a number of pathologic conditions including chronic kidney disease, cardiac hypertrophy, and congestive heart failure. Currently, there are no specific treatments available to lower plasma FGF23 levels. We have recently reported that genetic plasminogen activator inhibitor-1 (PAI-1) deficiency provided a significant reduction in circulating FGF23 levels while simultaneously prolonging the life span of Klotho-deficient mice. We extend our investigations into the effect of PAI-1 on FGF23 homeostasis. Transgenic overexpression of PAI-1 resulted in threefold increase in FGF23 levels compared to wild-type littermates. Moreover, pharmacological modulation of PAI-1 activity with the small-molecule PAI-1 antagonist TM5441 significantly reduced FGF23 levels in PAI-1 transgenic and Klotho-deficient mice. In addition, TM5441 treatment or PAI-1 deficiency significantly accelerated the clearance of endogenous FGF23 and recombinant human FGF23 from circulation in mice with acute kidney injury. On the basis of these observations, we studied the effects of plasminogen activators (PAs), tissue-type PA (tPA) and urokinase-type PA (uPA), on FGF23. We demonstrate that both PAs directly cleave FGF23; however, it is not known whether the PA-generated FGF23 peptides retain or acquire functions that affect binding and/or signaling properties of intact FGF23. PAI-1 inhibits the PA-dependent cleavage of FGF23, and TM5441 inhibition of PAI-1 restores the proteolysis of FGF23. Furthermore, top-down proteomic analysis indicates that tPA cleaves FGF23 at multiple arginines including the proconvertase sensitive site R176. In summary, our results indicate that PAI-1 prevents the PA-driven proteolysis of FGF23 and PAI-1 inhibition provides a novel therapeutic approach to prevent the pathologic consequences of increased FGF23.

Angiotensin-converting enzyme insertion/deletion polymorphism is not associated with vasoocclusive complications of sickle cell anemia

CONTEXT

Sickle cell anemia (SCA) is a group of hemoglobin disorders in which the sickle β-globin gene is inherited. It is associated with many complications; most of them are related to thrombotic events.

AIM

This study aimed to investigate the association between angiotensin converting enzyme (ACE) insertion/deletion polymorphism and complications of SCA.

SETTINGS AND DESIGN

A case-control study was conducted in Khartoum state.

SUBJECTS AND METHODS

A total of 50 patients with SCA and 40 healthy volunteers as a control group were enrolled in this study. Three milliliters of ethylenediamine tetraacetic acid anticoagulated blood were collected from each subject, DNA was extracted by salting-out method, and target DNA regions of the ACE gene were amplified using allele-specific polymerase chain reaction.

STATISTICAL ANALYSIS USED

Data of this study was analyzed by Statistical Package for Social Sciences. Frequency of qualitative variables was calculated, and correlation was tested by Chi-square test. Regression was used to investigate the association between the polymorphism and complications of SCA.

RESULTS

The frequencies of the DD, ID, and II genotypes were 42%, 50%, and 8%, respectively, for patients, whereas in the control group, it was 80% for DD genotype and 20% for ID, while II genotype was totally absent. The regression analysis showed no statistically significant association between the disease complications and each of the ACE polymorphic genotypes.

CONCLUSION

No statistically significant association was found between ACE polymorphism and complications of SCA.

Mineralocorticoid receptor blockade: new insights into the mechanism of action in patients with cardiovascular disease

Mineralocorticoid receptor (MR) blockade is effective in reducing total mortality and the incidence of heart failure in patients with systolic left ventricular dysfunction (SLVD) associated with chronic heart failure or post myocardial infarction.

Pre-clinical and clinical studies in SLVD have shown that MR blockade reduces sudden cardiac death, left ventricular remodelling, left ventricular hypertrophy, endothelial dysfunction, autonomic imbalance, renal dysfunction and improves fibrinolysis.

While MR blockade promotes sodium excretion and the combination of an angiotensin-converting enzyme inhibitor and a MR blocker have been shown to be more effective than either alone in causing natriuresis, it is unlikely that their beneficial effects can be explained solely on this basis.

Aldosterone has been shown to have a number of adverse effects, including activation of other neurohumeral mediators, stimulation of active reactive oxygen species (ROS), activation of the NF-κβ and AP-1 signalling pathways, vascular inflammation and fibrosis, myocardial hypertrophy, autonomic imbalance, and a decrease in fibrinolysis. MR blockade is, however, effective both in situations with and without an increase in serum aldosterone level, since the MR can be occupied and activated by cortisol as well as by aldosterone.

In view of these mechanisms, MR blockade may play an important role not only on SLVD, but also in essential hypertension with normal systolic function, diastolic heart failure, valvular heart disease, vascular stiffening with ageing, progression of renal disease, and diabetes mellitus. This hypothesis will, however, require further prospective evaluation.

Impact of Nutrition on Cerebral Circulation and Cognition in the Metabolic Syndrome

The increasing prevalence of Metabolic Syndrome (MetS), defined as the clustering of abdominal obesity, dyslipidemia, hypertension, and hyperglycemia, appears to be driving the global epidemics cardiovascular disease (CVD) and type 2 diabetes mellitus (T2DM). Nutrition has a major impact on MetS and plays an important role in the prevention, development, and treatment of its features. Structural and functional alterations in the vasculature, associated with MetS, might form the link between MetS and the increased risk of developing CVD and T2DM. Not only does the peripheral vasculature seem to be affected, but the syndrome has a profound impact on the cerebral circulation and thence brain structure as well. Furthermore, strong associations are shown with stroke, cognitive impairment, and dementia. In this review the impact of nutrition on the individual components of MetS, the effects of MetS on peripheral and cerebral vasculature, and its consequences for brain structure and function will be discussed.

Relationship between angiotensin I-converting enzyme insertion/deletion gene polymorphism and retinal vein occlusion

To evaluate the association between angiotensin I-converting enzyme insertion/deletion (ACE I/D) gene polymorphism and retinal vein occlusion (RVO). A total of 80 patients with retinal vein occlusion who was admitted to the Eye Department of Kartal Training and Research Hospital between 2008 and 2011, and 80 subjects were enrolled in this retrospective case–control study. Patients who experienced RVO within one week to six months of study enrolment were included, and those with coronary artery diseases, prior myocardial infarction history and coagulation disturbances were excluded from the study. The diagnosis was made by ophthalmoscopic fundus examination and fluorescein angiography. The ACE gene I/D polymorphism was determined by polymerase chain reaction, and the ACE gene was classified into three types: I/I, I/D and D/D. In multivariate logistic regression analysis, ACE D/D genotype (p = 0.035), diabetes-mellitus (p = 0.019) and hypertension (p = 0.001) were found to be independent predictive factors for RVO. The results of the present study reveal that ACE D/D polymorphism is an independent predictive factor for RVO. However, one cannot definitely conclude that ACE gene polymorphism is a risk factor for retinal vein occlusion.

PAI-1 and t-PA/PAI-1 complex potential markers of fibrinolytic bleeding after cardiac surgery employing cardiopulmonary bypass

Background

Enhanced bleeding remains a serious problem after cardiac surgery, and fibrinolysis is often involved. We speculate that lower plasma concentrations of plasminogen activator inhibitor – 1 (PAI-1) preoperatively and tissue plasminogen activator/PAI-1 (t-PA/PAI-1) complex postoperatively might predispose for enhanced fibrinolysis and increased postoperative bleeding.

Methods

Totally 88 adult patients (mean age 66 ± 10 years) scheduled for cardiac surgery, were enrolled into a prospective study. Blood samples were collected pre-operatively, on admission to the recovery and at 6 and 24 hours postoperatively. Patients with a surgical bleeding that was diagnosed during reoperation were discarded from the study. The patients were allocated to two groups depending on the 24-hour postoperative chest tube drainage (CTD): Group I > 500ml, Group II ≤ 500ml. Associations between CTD, PAI-1, t-PA/PAI-1 complex and D-dimer were analyzed with SPSS.

Results

Nine patients were excluded because of surgical bleeding. Of the 79 remaining patients, 38 were allocated to Group I and 41 to Group II. The CTD volumes correlated with the preoperative plasma levels of PAI-1 (r = − 0.3, P = 0.009). Plasma concentrations of preoperative PAI-1 and postoperative t-PA/PAI-1 complex differed significantly between the groups (P < 0.001 and P = 0.012, respectively). Group I displayed significantly lower plasma concentrations of fibrinogen and higher levels of D-dimer from immediately after the operation and throughout the first 24 hours postoperatively.

Conclusions

Lower plasma concentrations of PAI-1 preoperatively and t-PA/PAI-1 complex postoperatively leads to higher plasma levels of D-dimer in association with more postoperative bleeding after cardiac surgery.

Angiotensin II type 1 receptor, but no type 2 receptor, interferes with the insulin-induced nitric oxide production in HUVECs

OBJECTIVE

Two subtypes of angiotensin II (ATII) receptor have been defined on the basis of their differential pharmacological and biochemical properties: ATII-type1 receptors (AT(1)-R) and ATII-type2 receptors (AT(2)-R). It has been hypothesized that part of the protective effects on the cardiovascular system of AT(1)-R blockers is mediated by an ATII-mediated overstimulation of AT(2)-R. We hypothesized that the inhibition of AT(1)-R has a stronger impact on insulin-induced nitric oxide (NO) production than ATII-mediated overstimulation of AT(2)-R. Therefore we studied the effect of the inhibition of AT(1)-R and AT(2)-R on ATII-mediated actions in Human Umbilical Vein Endothelial Cells (HUVECs).

METHODS

We analyzed the phosphorylation state of IRS1 at Ser(616) and Ser(312) and on tyrosines after preincubation with PD123319, an inhibitor of AT(2)-R, alone and in combination with losartan, an inhibitor of AT(1)-R. In addition we measured eNOS and Akt activation through the evaluation of their phosphorylation at Ser(1177) and Ser(473) sites respectively.

RESULTS

ATII induces IRS-1 phosphorylation at Ser(312) and Ser(616) through the activation of JNK and ERK 1/2, resulting in the inhibition of the insulin-induced phosphorylation of IRS1 tyrosines, Akt and eNOS. Treatment of HUVECs with AT(1)-R inhibitor restored the insulin signaling leading to NO production, whereas AT(2)-R inhibitor did not have effects on NO production in presence of ATII.

CONCLUSION

Our results demonstrate that in presence of AT(1)-R antagonist, the AT(2)-R blockage does not modify the effect obtained with the AT(1)-R inhibition alone. Therefore, a possible positive role of an AT(2)-R overstimulation in condition of AT(1)-R antagonism seems to be irrelevant.

Role of angiotensin II in plasma PAI-1 changes induced by imidapril or candesartan in hypertensive patients with metabolic syndrome

To evaluate the relationship between plasma plasminogen activator inhibitor-1 (PAI-1) and angiotensin II (Ang II) changes during treatment with imidapril and candesartan in hypertensive patients with metabolic syndrome. A total of 84 hypertensive patients with metabolic syndrome were randomized to imidapril 10 mg or candesartan 16 mg for 16 weeks. At weeks 4 and 8, there was a dose titration to imidapril 20 mg and candesartan 32 mg in nonresponders (systolic blood pressure (SBP) >140 and/or diastolic blood pressure (DBP) >90 mm Hg). We evaluated, at baseline and after 2, 4, 8, 12 and 16 weeks, clinic blood pressure, Ang II and PAI-1 antigen. Both imidapril and candesartan induced a similar SBP/DBP reduction (-19.4/16.8 and -19.5/16.3 mm Hg, respectively, P<0.001 vs. baseline). Both drugs decreased PAI-1 antigen after 4 weeks of treatment, but only the PAI-1 lowering effect of imidapril was sustained throughout the 16 weeks (-9.3 ng ml(-1), P<0.01 vs. baseline), whereas candesartan increased PAI-1 (+6.5 ng ml(-1), P<0.05 vs. baseline and P<0.01 vs. imidapril). Imidapril significantly decreased Ang II levels (-14.6 pg ml(-1) at week 16, P<0.05 vs. baseline), whereas candesartan increased them (+24.2 pg ml(-1), P<0.01 vs. baseline and vs. imidapril). In both groups there was a positive correlation between Ang II and PAI-1 changes (r=0.61, P<0.001 at week 16 for imidapril, and r=0.37, P<0.005 at week 16 for candesartan). Imidapril reduced plasma PAI-1 and Ang II levels, whereas candesartan increased them. This suggests that the different effect of angiotensin-converting enzyme inhibitors and Ang II blockers on Ang II production has a role in their different influence on fibrinolysis.

Direct renin inhibition: update on clinical investigations with aliskiren

The renin–angiotensin–aldosterone system (RAAS) plays a pivotal role in regulating blood pressure, volume, and electrolytes. The final product of RAAS cascade is angiotensin II, which exerts diverse biological activities via binding to one of three known receptor types, with different binding consequences. Despite the success with conventional strategies to limit angiotensin II production and action, these agents promote a reflex rise in plasma renin activity, which is thought to be associated with an increased incidence of cardiovascular events. Several renin inhibitors have been synthesized in order to counteract deleterious consequences of renin activity and RAAS activation; aliskiren is the first of these new non-peptide direct renin inhibitors to be approved for the treatment of hypertension. The paper reviews pharmacokinetics of aliskiren and its role in hypertension, with particular regard to those studies that compared clinical efficacy of aliskiren in comparison and in addition to other antihypertensive drug strategies.

Angiotensin-Converting Enzyme Inhibition Augments Coronary Release of Tissue Plasminogen Activator in Women But Not in Men

The renin-angiotensin system regulates the vascular fibrinolytic balance. In the human forearm vasculature, angiotensin-converting enzyme (ACE) inhibitors (ACE-Is) increase the release of t-PA through endogenous bradykinin. We tested the hypothesis that ACE inhibition and sex modulate the endogenous coronary release of tissue plasminogen activator (t-PA) in hypertensive patients. Seventy-three patients underwent diagnostic coronary angiography and had normal coronary angiograms. Thirty-three patients (21 men and 12 women) were treated with imidapril (5 mg/day) for 4 weeks (ACE-I group), and 40 (23 men and 17 women) were not treated with ACE-I (non–ACE-I group). All of the women were postmenopausal. Coronary blood flow in the left anterior descending artery was evaluated by measuring Doppler flow velocity. Net coronary t-PA release was determined as (coronary sinus−aorta gradient of t-PA)×(coronary blood flow)×[(100−hematocrit)/100]. Age, arterial pressure, heart rate, lipid levels, coronary flow, and the plasma level of t-PA at either aorta or coronary sinus were comparable among the 4 groups. In women, net t-PA release in the ACE-I group was significantly higher than that in the other groups ( P <0.05; man non–ACE-I group: 1.4±2.6 ng/mL; woman non–ACE-I group: 1.4±3.1 ng/mL; man ACE-I group: −1.8±2.8 ng/mL; woman ACE-I group: 14.8±3.6 ng/mL). Correction for smoking status gave similar results. There was a significant negative correlation between serum ACE activity and coronary t-PA release in women ( r =−0.38; P <0.05) but not in men. ACE inhibition increases coronary release of t-PA in women but not in men.

Position of fixed‐dose combinations containing an AT1‐receptor blocker and a thiazide diuretic

Treatment of hypertension remains a difficult task despite the availability of different types of medications lowering blood pressure by different mechanisms. In order to reach the target blood pressures recommended today combination therapy is required in most patients. The co-administration of two drugs with different impacts on the cardiovascular system markedly increases the antihypertensive effectiveness without altering adversely tolerability. Fixed low-dose combinations are becoming a valuable option not only as second-line, but also as first-line therapy. In this respect the co-administration of thiazide diuretic with an AT(1)-receptor blocker is particularly appealing. The diuretic-induced decrease in total body sodium activates the renin-angiotensin system, thus rendering blood pressure maintenance angiotensin II-dependent. During blockade of the renin-angiotensin system low doses of thiazides generally suffice, allowing the prevention of undesirable metabolic effects. Also, blockade of the AT(1)-receptor, particularly when angiotensin II production is enhanced in response to diuretic therapy, is expected to be beneficial, since angiotensin II seems to contribute importantly to the pathogenesis of cardiovascular and renal complications of hypertension.

Shadows of complexity: what biological networks reveal about epistasis and pleiotropy

Pleiotropy, in which one mutation causes multiple phenotypes, has traditionally been seen as a deviation from the conventional observation in which one gene affects one phenotype. Epistasis, or gene-gene interaction, has also been treated as an exception to the Mendelian one gene-one phenotype paradigm. This simplified perspective belies the pervasive complexity of biology and hinders progress toward a deeper understanding of biological systems. We assert that epistasis and pleiotropy are not isolated occurrences, but ubiquitous and inherent properties of biomolecular networks. These phenomena should not be treated as exceptions, but rather as fundamental components of genetic analyses. A systems level understanding of epistasis and pleiotropy is, therefore, critical to furthering our understanding of human genetics and its contribution to common human disease. Finally, graph theory offers an intuitive and powerful set of tools with which to study the network bases of these important genetic phenomena.

Beneficial effects of spironolactone on glomerular injury in streptozotocin-induced diabetic rats

INTRODUCTION

To investigate the beneficial effects of spironolactone (SPL) on glomerular injury in streptozotocin (STZ)-induced diabetic rats and the possible mechanism.

METHODS AND RESULTS

STZ-induced diabetic rats were divided into control group, STZ group, and SPL group. Glomerular morphology was observed by light microscopy after the rats were sacrificed after 30 days treatment. The mRNA expressions of transforming growth factor-beta 1 (TGF-beta1) and type-1 plasminogen activator inhibitor (PAI-1) in renal cortex were measured by transcription-polymerase chain reaction (RT-PCR). The protein expressions of PAI-1, fibronectin (FN) and TGF-beta1 were detected by western blotting and immunohistochemistry respectively. In addition, levels of malondialdehyde (MDA) and the activity of antioxidants including superoxide diamutase (SOD), glutathione peroxidase (GSH-PX) in the cortex of kidney were measured.

RESULTS

In untreated diabetic rats, the glomerular volume, the expression of FN and the urinary albumin excretion increased. The mRNA and protein expression of PAI-1 and TGF-beta1 significantly increased in the STZ group. Treatment with SPL partially reversed these changes. Meanwhile, elevated MDA levels as well as decreased SOD and GSH-PX activities in the cortex of kidney were significantly ameliorated in the treated group.

CONCLUSION

SPL ameliorates the glomerular injury in STZ-induced early diabetic renal injury, which is closely related with the reduction of PAI-1 and TGF-beta1 expression and the attenuation of oxidative stress.

Differential effects of AT1 receptor and Ca2+ channel blockade on atherosclerosis, inflammatory gene expression, and production of reactive oxygen species

Angiotensin II receptor blockade has been shown to inhibit atherosclerosis in several different animal models. We sought to determine if this effect was the result of blood pressure reduction per se or a result of the anti-inflammatory effects of receptor blockade. ApoE-deficient mice were fed a high fat diet and treated with either an angiotensin II receptor antagonist, candesartan (0.5 mg/kg/day, s.c.) or a calcium channel blocker, amlodipine (7.5 mg/kg/day, mixed with food). Atherosclerotic lesion area, aortic inflammatory gene expression as well as aortic H2O2 and superoxide production were assayed. We found that candesartan but not amlodipine treatment dramatically attenuated the development of atherosclerosis despite a similar reduction in blood pressure. Similarly, candesartan treatment inhibited aortic expression of inflammatory genes and production of reactive oxygen species, effects not seen with amlodipine. These data demonstrate that angiotensin II receptor blockade inhibits atherosclerosis by reducing vascular oxidative stress and inflammatory gene production independent of blood pressure reduction.

Serpins in thrombosis, hemostasis and fibrinolysis

Hemostasis and fibrinolysis, the biological processes that maintain proper blood flow, are the consequence of a complex series of cascading enzymatic reactions. Serine proteases involved in these processes are regulated by feedback loops, local cofactor molecules, and serine protease inhibitors (serpins). The delicate balance between proteolytic and inhibitory reactions in hemostasis and fibrinolysis, described by the coagulation, protein C and fibrinolytic pathways, can be disrupted, resulting in the pathological conditions of thrombosis or abnormal bleeding. Medicine capitalizes on the importance of serpins, using therapeutics to manipulate the serpin-protease reactions for the treatment and prevention of thrombosis and hemorrhage. Therefore, investigation of serpins, their cofactors, and their structure-function relationships is imperative for the development of state-of-the-art pharmaceuticals for the selective fine-tuning of hemostasis and fibrinolysis. This review describes key serpins important in the regulation of these pathways: antithrombin, heparin cofactor II, protein Z-dependent protease inhibitor, alpha(1)-protease inhibitor, protein C inhibitor, alpha(2)-antiplasmin and plasminogen activator inhibitor-1. We focus on the biological function, the important structural elements, their known non-hemostatic roles, the pathologies related to deficiencies or dysfunction, and the therapeutic roles of specific serpins.

Effects of Candesartan and Lisinopril on the Fibrinolytic System in Hypertensive Patients

The effects of the angiotensin II receptor blocker candesartan and the angiotensin-converting enzyme inhibitor lisinopril on the fibrinolytic system were investigated in a double-blinded, prospective, randomized study. Seventy-seven hypertensive patients taking candesartan (n=41) and lisinopril (n=36) with a systolic blood pressure >130 mm Hg and/or a diastolic blood pressure >80 mm Hg obtained by 24-hour ambulatory blood pressure measurement were included in the study. Blood pressure, plasminogen activator inhibitor 1 (PAI-1), tissue plasminogen activator (tPA), and the molar ratio of PAI-1/tPA were determined before treatment and 6 weeks later. Blood pressure decreased in both groups (candesartan, 155/85 mm Hg to 140/84 mm Hg; P<.05; lisinopril, 152/85 mm Hg to 138/83 mm Hg; P<.05). The fibrinolytic balance was significantly different between treatment groups (molar ratio of PAI-1/tPA: candesartan, 3.66 [2.2;] lisinopril, 5.44 [2.6;] P<.05). In contrast to lisinopril, the balance between coagulation and fibrinolytic activity shifted toward fibrinolysis during candesartan treatment.

Aldosterone up-regulates production of plasminogen activator inhibitor-1 by renal mesangial cells

In vivo studies have demonstrated that aldosterone is an independent contributor to glomerulosclerosis. In the present study, we have investigated whether aldosterone itself mediated glomerulosclerosis, as angiotensin II (Ang II) did, by inducing cultured renal mesangial cells to produce plasminogen activator inhibitor-1 (PAI-1), and whether these effects were mediated by aldosterone-induced increase in transforming growth factor beta(1) (TGF-beta(1)) expression and cellular reactive oxygen species (ROS) activity. Quiescent rat mesangial cells were treated by aldosterone alone or by combination of aldosterone and spironolactone, Ang II, neutralizing antibody to TGF-beta(1) or antioxidant Nacetylcysteme (NAC). This study indicate that aldosterone can increase PAI-1 mRNA and protein expression by cultured mesangial cells alone, which is independent of aldosterone-induced increases in TGF-beta(1) expression and cellular ROS. The effects on PAI-1, TGF-beta(1) and ROS generation were markedly attenuated by spironolactone, a mineralocorticoid receptor antagonist, which demonstrate that mineralocorticoid receptor (MR) may play a role in mediating these effects of aldosterone.

Factors associated with excessive bleeding in cardiopulmonary bypass patients: a nested case-control study

Introduction

Excessive bleeding (EB) after cardiopulmonary bypass (CPB) may lead to increased mortality, morbidity, transfusion requirements and re-intervention. Less than 50% of patients undergoing re-intervention exhibit surgical sources of bleeding. We studied clinical and genetic factors associated with EB.

Methods

We performed a nested case-control study of 26 patients who did not receive antifibrinolytic prophylaxis. Variables were collected preoperatively, at intensive care unit (ICU) admission, at 4 and 24 hours post-CPB. EB was defined as 24-hour blood loss of >1 l post-CPB. Associations of EB with genetic, demographic, and clinical factors were analyzed, using SPSS-12.2 for statistical purposes.

Results

EB incidence was 50%, associated with body mass index (BMI)< 26.4 (25–28) Kg/m², (P = 0.03), lower preoperative levels of plasminogen activator inhibitor-1 (PAI-1) (P = 0.01), lower body temperature during CPB (P = 0.037) and at ICU admission (P = 0.029), and internal mammary artery graft (P = 0.03) in bypass surgery. We found a significant association between EB and 5G homozygotes for PAI-1, after adjusting for BMI (F = 6.07; P = 0.02) and temperature during CPB (F = 8.84; P = 0.007). EB patients showed higher consumption of complement, coagulation, fibrinolysis and hemoderivatives, with significantly lower leptin levels at all postoperative time points (P = 0.01, P < 0.01 and P < 0.01).

Conclusion

Excessive postoperative bleeding in CPB patients was associated with demographics, particularly less pronounced BMI, and surgical factors together with serine protease activation.

Inflammation in coronary artery disease: potential role for immunomodulatory therapy

Understanding of the mechanisms underlying atherosclerotic disorders has evolved beyond the view of a progressive collection of lipids and cellular debris in the vascular wall. Current evidence has implicated inflammatory pathways as an important pathogenic mechanism in atherogenesis and plaque destabilization. Although not necessarily the primary event, inflammation and cytokine activation during plaque formation and destabilization may represent a common final pathway to various stimuli. Thus, it seems that not only 'new' risk factors, such as infections with various microorganisms, but also classic risk factors for cardiovascular disease, such as hyperlipidemia, hypertension and diabetes, may promote their atherogenic effects through inflammatory responses. Indeed, recent reports have suggested that traditional cardiovascular medications may attenuate atherogenesis and enhance plaque stability, at least partly through anti-inflammatory mechanisms. However, uncovering the inflammatory pathways in atherosclerosis has raised the possibility that newer treatment modalities should be more directly targeted against inflammatory mediators. Recently, a series of experimental studies have reported reduction of atherosclerosis by immunomodulatory therapy, such as chemokine blockade, interleukin-10 and immunization/vaccination against oxidized low-density lipoprotein and heat-shock protein. It is conceivable that some of these approaches will be tested clinically and, if successful, they could provide novel treatment strategies in coronary artery disease in humans.

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.

Angiotensin-converting enzyme II in the heart and the kidney

The renin-angiotensin system (RAS) has been recognized for many years as critical pathway for blood pressure control and kidney functions. Although most of the well-known cardiovascular and renal effects of RAS are attributed to angiotensin-converting enzyme (ACE), much less is known about the function of ACE2. Experiments using genetically modified mice and inhibitor studies have shown that ACE2 counterbalances the functions of ACE and that the balance between these two proteases determines local and systemic levels of RAS peptides such as angiotensin II and angiotensin1-7. Ace2 mutant mice exhibit progressive impairment of heart contractility at advanced ages, a phenotype that can be reverted by loss of ACE, suggesting that these enzymes directly control heart function. Moreover, ACE2 is also found to be upregulated in failing hearts. In the kidney, ACE2 protein levels are significantly decreased in hypertensive rats, suggesting a negative regulatory role of ACE2 in blood pressure control. Moreover, ACE2 expression is downregulated in the kidneys of diabetic and pregnant rats and ACE2 mutant mice develop late onset glomerulonephritis resembling diabetic nephropathy. Importantly, ACE2 not only controls angiotensin II levels but functions as a protease on additional molecular targets that could contribute to the observed in vivo phenotypes of ACE2 mutant mice. Thus, ACE2 seems to be a molecule that has protective roles in heart and kidney. The development of drugs that could activate ACE2 function would allow extending our treatment options in diabetic nephropathy, heart failure, or hypertension.

Serial analysis of gene expression in mouse kidney following angiotensin II administration

As a new line of inquiry into the molecular mechanisms underlying pathophysiological processes associated with angiotensin (ANG II)-dependent hypertension, we applied the method of serial analysis of gene expression (SAGE) to examine genome-wide transcription changes in the kidneys of mice that developed hypertension in response to chronic ANG II administration. Mice were infused subcutaneously via osmotic minipumps with ANG II for 7 days, and systolic blood pressure was measured by tail-cuff plethysmography. Subsequently, mice were euthanized, and the total RNA isolated from the kidneys was used to construct SAGE libraries. Comparison of 11,447 SAGE tags from the hypertensive kidneys, representing 5,740 unique transcripts, and 11,273 tags from the control kidneys, corresponding to 5,619 different transcripts, identified genes that are significantly ( P < 0.05) down- or upregulated in the hypertensive kidney. Our assessment of the genome-wide influence of ANG II resulted in the detection of several novel genes and in a recognition of potential new roles for the previously characterized genes, thus providing new probes with which to further explore the ANG II effects in normal and disease states.

Angiotensin-converting enzyme inhibition but not angiotensin II type 1 receptor antagonism augments coronary release of tissue plasminogen activator in hypertensive patients

OBJECTIVES

We compared the effects of perindopril and losartan on endothelium-dependent coronary vasomotor and fibrinolytic function.

BACKGROUND

The renin-angiotensin system regulates the vascular fibrinolytic balance. However, the effects of angiotensin-converting enzyme inhibitors and angiotensin II type 1 receptor antagonists on coronary fibrinolytic function have not been compared in hypertensive patients.

METHODS

Forty-five patients with hypertension were randomly assigned to three groups: 16 patients were treated with perindopril (4 mg/day) for four weeks; 15 were treated with losartan (50 mg/day) for four weeks; and 14 were not treated with either perindopril or losartan (control group). Graded doses of bradykinin (BK) (0.2, 0.6, and 2.0 microg/min) were administered into the left coronary artery. Coronary blood flow (CBF) was evaluated by Doppler flow velocity measurement.

RESULTS

Bradykinin induced dose-dependent increases in CBF in all groups. The increases in CBF induced by BK in the perindopril and losartan groups were significantly greater than those in the control group. Net coronary tissue-type plasminogen activator (t-PA) release was enhanced by BK in all groups, and the increase in the perindopril group was greater than that in the losartan and control groups. Bradykinin did not alter plasminogen activator inhibitor type 1 levels in any of the groups.

CONCLUSIONS

Perindopril and losartan similarly augment BK-induced coronary vasodilation. Perindopril may have a greater potential to enhance the BK-induced coronary release of t-PA than losartan.

Use of ACE Inhibitors for Secondary Prevention

The role of the renin-angiotensin system as a regulator of blood pressure, body fluids, electrolytes, and neurohormonal activation has been established for more than two decades. The dramatic benefits of angiotensin-converting enzyme (ACE) inhibition on overall mortality, progression to heart failure, and major cardiovascular events were first demonstrated in patients with congestive heart failure (CHF) or left ventricular dysfunction. ACE inhibitors should be prescribed for all patients with symptomatic CHF and for all asymptomatic patients with a left ventricular ejection fraction less than 35% to 40%, unless contraindicated or not tolerated, and therapy should be continued indefinitely. Data have shown that ACE inhibition improves oxidative stress, endothelial and ventricular function, and reduces ventricular remodeling as well as progression of carotid intimal and medial thickening. Current evidence suggests that ACE inhibitors should be prescribed as early as possible for all patients with acute myocardial infarction, unless contraindicated or not tolerated, and that they should be continued for at least 6 weeks; moreover, because these patients automatically qualify as high-risk individuals, indefinite therapy should be considered. Likewise, individuals at increased risk for major cardiovascular events (diabetic patients with additional risk factors and patients with known vascular disease) should be prescribed ACE inhibitors, unless contraindicated or not tolerated, and therapy should be continued indefinitely. There is not sufficient evidence at present to recommend the use of ACE inhibitors after coronary revascularization for the specific goal of preventing restenosis or graft disease, in the absence of decreased ejection fraction, CHF, or a new myocardial infarction.

Improved prognosis of patients presenting with clinical markers of spontaneous reperfusion during acute myocardial infarction

OBJECTIVE

To describe the clinical features, management, and prognosis of patients presenting with clinical markers of spontaneous reperfusion (SR) during acute myocardial infarction (AMI).

DESIGN

Cohort study.

SETTING

National registry of 26 coronary care units.

PATIENTS

2382 consecutive patients with AMI.

MAIN OUTCOME MEASURES

Patient characteristics, management, and mortality.

RESULTS

The incidence of SR was 4% of patients (n = 98) compared with thrombolytic treatment (n = 1163, 49%), primary angioplasty (n = 102, 4%), and non-reperfusion (n = 1019, 43%). SR patients were more likely to develop less or no myocardial damage as indicated by a higher percentage of non-Q wave AMI (58% v 32%, 47%, and 44%, respectively, p < 0.0001), aborted AMI (25% v 9%, 8%, and 12%, p < 0.001), and lower peak creatine kinase (503 v 1384, 1519, and 751 IU, p < 0.0001). SR patients, however, were more likely to develop recurrent ischaemic events (35% v 17%, 12%, and 16%, respectively; p < 0.001) and subsequently were more likely to be referred to coronary angiography (67%), angioplasty (41%), or bypass surgery (16%, p < 0.001). Mortality at 30 days (1% v 8%, 7%, and 13%, respectively, p < 0.0001) and one year (6% v 11%, 12%, and 19%, p < 0.0001) was significantly lower for SR patients than for the other subgroups. By multivariate analysis, SR remained a strong determinant of 30 day survival (odds ratio (OR) 0.16, 95% confidence interval (CI) 0.01 to 0.74). At one year, the association between SR and survival decreased (OR 0.49, 95% CI 0.18 to 1.13).

CONCLUSIONS

Clinical markers of SR are associated with greater myocardial salvage and favourable prognosis. The vulnerability of SR patients to recurrent ischaemic events suggests that they need close surveillance and may benefit from early intervention.

A comparison of combinatorial partitioning and linear regression for the detection of epistatic effects of the ACE I/D and PAI-1 4G/5G polymorphisms on plasma PAI-1 levels

The detection and characterization of epistasis or non-additive gene-gene interactions remains a statistical challenge in genetic epidemiology. The recently developed combinatorial partitioning method (CPM) may overcome some of the limitations of linear regression for the exploratory analysis of non-additive epistatic effects. The goal of this study was to compare CPM with linear regression analysis for the exploratory analysis of non-additive interactive effects of the angiotensin converting enzyme (ACE) insertion/deletion (I/D) and plasminogen activator inhibitor 1 (PAI-1) 4G/5G polymorphisms on plasma PAI-1 levels in a sample of 50 unrelated African Americans and 117 unrelated Caucasians. Using linear regression, we documented the additive effects of the ACE and PAI-1 genes on plasma PAI-1 levels in African American females (R(2) = 0.10), African American males (R(2) = 0.16), Caucasian females (R(2) = 0.11), and Caucasian males (R2 = 0.09). Using CPM, we found evidence for non-additive effects of the ACE and PAI-1 genes in both African American females (R(2) = 0.22) and African American males (R(2) = 0.24) but not in Caucasian females (R(2) = 0.10) or Caucasian males (R(2) = 0.11). The results of this exploratory data analysis support previous experimental, clinical, and epidemiological studies that have proposed as a working hypothesis that the ACE gene mediates interaction effects of the fibrinolytic and renin-angiotensin systems on plasma levels of PAI-1.

The relationship between plasma t-PA and PAI-1 levels is dependent on epistatic effects of the ACE I/D and PAI-1 4G/5G polymorphisms

Thrombus formation and degradation is partly due to a complex interplay between tissue-type plasminogen activator (t-PA) and plasminogen activator inhibitor 1 (PAI-1). There is accumulating evidence that plasma levels of t-PA and PAI-1 may be influenced by an interaction between the fibrinolytic and renin-angiotensin systems. The goal of this study was to conduct an exploratory data analysis to determine whether there is evidence that the relationship (i.e. correlation) between plasma t-PA and PAI-1 is influenced by interactive effects of the angiotensin converting enzyme (ACE) insertion/deletion (I/D) and plasminogen activator inhibitor 1 (PAI-1) 4G/5G polymorphisms in a sample of 50 unrelated African Americans and 117 unrelated Caucasians. In a single-locus analysis, no evidence for heterogeneity of plasma t-PA and PAI-1 correlations among either ACE I/D or PAI-1 4G/5G genotypes was detected. However, using the combinatorial partitioning method for exploratory data analysis, we identified evidence that is suggestive of heterogeneity of plasma t-PA and PAI-1 correlations among multilocus ACE I/D and PAI-1 4G/5G genotypes in African American females, Caucasian females, Caucasian males, but not African American males. From these results, we propose as a working hypothesis that the correlation between plasma t-PA and PAI-1 may be dependent on epistatic effects of the ACE I/D and PAI-1 4G/5G polymorphisms. This study supports the idea that interactions between the fibrinolytic and renin-angiotensin systems play an important role in the genetic architecture of plasma t-PA and PAI-1.

Atherothrombosis: plaque instability and thrombogenesis

Hemostasis involves a carefully regulated balance between circulating and endothelium-derived prothrombotic and antithrombotic factors. The unstable or vulnerable plaque facilitates thrombosis, clinically manifest as an acute coronary syndrome (ACS), by creating an environment that favors thrombus formation over prevention of lysis. Endothelial cell dysfunction is integral to both the development of the atherosclerotic lesion as well as its destabilization. The transformation of a stable plaque to an unstable one involves complex interactions among T lymphocytes, macrophages, endothelial cells, and smooth muscle cells. Degradation of the fibrous cap of the atherosclerotic lesion as well as the overexpression of prothrombotic and underexpression of antithrombotic factors by cells within the plaque precede thrombus formation. Accordingly, pharmacological interventions for the treatment of ACS are directed against the initiation and propagation of thrombosis, as well as toward improvement of endothelial function.

Release and degradation of angiotensin I and angiotensin II from angiotensinogen by neutrophil serine proteinases

Cathepsin G, elastase, and proteinase 3 are serine proteinases released by activated neutrophils. Cathepsin G can cleave angiotensinogen to release angiotensin II, but this activity has not been previously reported for elastase or proteinase 3. In this study we show that elastase and proteinase 3 can release angiotensin I from angiotensinogen and release angiotensin II from angiotensin I and angiotensinogen. The relative order of potency in releasing angiotensin II by the three proteinases at equivalent concentrations is cathepsin G > elastase > proteinase 3. When all three proteinases are used together, the release of angiotensin II is greater than the sum of the release when each proteinase is used individually. Cathepsin G and elastase can also degrade angiotensin II, reactions which might be important in regulating the activity of angiotensin II. The release and degradation of angiotensin II by the neutrophil proteinases are reactions which could play a role in the local inflammatory response and wound healing.

Clinical studies of CS-866, the newest angiotensin II receptor antagonist

Angiotensin II receptor blockers have shown widespread efficacy as antihypertensive medications. These agents bind selectively to angiotensin II type 1 (AT(1)) receptors, specifically blocking the renin-angiotensin system at the last step in its cascade. CS-866 is the most recently introduced drug in this class. This article presents integrated safety and efficacy data from 7 randomized, double-blind, placebo-controlled, parallel group studies in which once-daily CS-866 monotherapy was used in the treatment of patients with essential hypertension (sitting diastolic blood pressure > or =100 mm Hg and < or =115 mm Hg). Data from a total of 2,145 CS-866-treated patients were included in the efficacy analysis. Safety data were available from 2,540 CS-866-treated patients, with a cumulative exposure of 5,888 patient-months. The antihypertensive efficacy of the drug was assessed using both cuff blood pressure measurements and 24-hour ambulatory blood pressure monitoring. The data show that CS-866 is effective and safe for the treatment of hypertension. Dose-dependent reductions in both diastolic and systolic blood pressures occurred within 1 week of initiating treatment, and the response was almost maximal within 2 weeks. There was no difference in efficacy between younger (<65 years) and older (> or =65 years) groups of patients. Trough-to-peak ratios showed that CS-866 retains the majority of its peak effect 24 hours after treatment, and is therefore suitable for once-daily dosing. Dizziness was the only treatment-emergent adverse event with which CS-866 was associated.