Tissue factor, protease activated receptors and pathologic heart remodelling

Rivaroxaban, a direct inhibitor of coagulation factor Xa, attenuates adverse cardiac remodeling in rats by regulating the PAR-2 and TGF-β1 signaling pathways

Background

Factor Xa (FXa) not only plays an active role in the coagulation cascade but also exerts non-hemostatic signaling through the protease-activated receptors (PARs). This study aimed to investigate whether the FXa inhibitor, Rivaroxaban (RIV), attenuates adverse cardiac remodeling in rats with myocardial infarction (MI) and to identify the underlying molecular mechanisms it uses.

Methods

An MI model was induced in eight-week-old, male Wistar rats, by permanent ligation of the left anterior descending coronary artery. MI rats were randomly assigned to receive RIV or protease-activated receptors 2-antagonist (PAR-2 antagonist, FSLLRY) treatment for four weeks. Histological staining, echocardiography and hemodynamics were used to assess the cardioprotective effects of RIV. Meanwhile, pharmacological approaches of agonist and inhibitor were used to observe the potential pathways in which RIV exerts antifibrotic effects in neonatal rat cardiac fibroblasts (CFs). In addition, real-time PCR and western blot analysis were performed to examine the associated signaling pathways.

Results

RIV presented favorable protection of left ventricular (LV) cardiac function in MI rats by significantly reducing myocardial infarct size, ameliorating myocardial pathological damage and improving left ventricular (LV) remodeling. Similar improvements in the PAR-2 antagonist FSLLRY and RIV groups suggested that RIV protects against cardiac dysfunction in MI rats by ameliorating PAR-2 activation. Furthermore, an in vitro model of fibrosis was then generated by applying angiotensin II (Ang II) to neonatal rat cardiac fibroblasts (CFs). Consistent with the findings of the animal experiments, RIV and FSLLRY inhibited the expression of fibrosis markers and suppressed the intracellular upregulation of transforming growth factor β1 (TGFβ1), as well as its downstream Smad2/3 phosphorylation effectors in Ang II-induced fibrosis, and PAR-2 agonist peptide (PAR-2 AP) reversed the inhibition effect of RIV.

Conclusions

Our findings demonstrate that RIV attenuates MI-induced cardiac remodeling and improves heart function, partly by inhibiting the activation of the PAR-2 and TGF-β1 signaling pathways.

MicroRNA-19 upregulation attenuates cardiac fibrosis via targeting connective tissue growth factor

BACKGROUND

Previous studies have shown the role of microRNA (miR)-19 in aging-related heart failure. The present study aimed to verify the effects of miR-19 on cardiac fibrosis and its target.

METHODS

Cardiac fibrosis was induced by myocardial infarction (MI)-induced heart failure and angiotensin (Ang) II-treated rats in vivo, and was induced in Ang II-treated cardiac fibroblasts (CFs) in vitro.

RESULTS

The expression of miR-19 was reduced in the heart tissue of MI and Ang II-treated rats, and Ang II-treated CFs. The impaired cardiac function in rats was repaired after miR-19 administration. The levels of collagen I, collagen III and transforming growth factor-beta (TGF-β) increased in the heart tissue of MI and Ang II-treated rats, and Ang II-treated CFs. These increases were reversed by miR-19 agomiR. Moreover, the bioinformatic analysis and luciferase reporter assays demonstrated that connective tissue growth factor (CTGF) was a direct target of miR-19. MiR-19 treatment inhibited CTGF expression in CFs, while CTGF overexpression inhibited miR-19 agomiR to attenuate the Ang II-induced increases of collagen I and collagen III in CFs. The increases of p-ERK, p-JNK and p-p38 in the CFs induced by Ang II were repressed by miR-19 agomiR.

CONCLUSIONS

Upregulating miR-19 can improve cardiac function and attenuate cardiac fibrosis by inhibiting the CTGF and MAPK pathways.

Novel Mechanisms of Anthracycline-Induced Cardiovascular Toxicity: A Focus on Thrombosis, Cardiac Atrophy, and Programmed Cell Death

Anthracycline antineoplastic agents such as doxorubicin are widely used and highly effective component of adjuvant chemotherapy for breast cancer and curative regimens for lymphomas, leukemias, and sarcomas. The primary dose-limiting adverse effect of anthracyclines is cardiotoxicity that typically manifests as cardiomyopathy and can progress to the potentially fatal clinical syndrome of heart failure. Decades of pre-clinical research have explicated the complex and multifaceted mechanisms of anthracycline-induced cardiotoxicity. It is well-established that oxidative stress contributes to the pathobiology and recent work has elucidated important central roles for direct mitochondrial injury and iron overload. Here we focus instead on emerging aspects of anthracycline-induced cardiotoxicity that may have received less attention in other recent reviews: thrombosis, myocardial atrophy, and non-apoptotic programmed cell death.

Alamandine protects against renal ischaemia-reperfusion injury in rats via inhibiting oxidative stress

OBJECTIVE

This study was to determine whether alamandine (Ala) could reduce ischaemia and reperfusion (I/R) injury of kidney in rats.

METHODS

Renal I/R was induced by an occlusion of bilateral renal arteries for 70 min and a 24-h reperfusion in vivo, and rat kidney proximal tubular epithelial cells NRK52E were exposed to 24 h of hypoxia and followed by 3-h reoxygenation (H/R) in vitro.

RESULTS

The elevated serum creatinine (Cr), blood cystatin C (CysC) and blood urea nitrogen (BUN) levels in I/R rats were inhibited by Ala treatment. Tumour necrosis factor alpha (TNF)-α, IL-1β, IL-6, cleaved caspase-3, cleaved caspase-8 and Bax were increased, and Bcl2 was reduced in the kidney of I/R rats, which were reversed by Ala administration. Ala reversed the increase of TNF-α, IL-1β, IL-6, cleaved caspase-3, cleaved caspase-8 and Bax and the decrease of Bcl2 in the H/R NRK52E cells. Ala could also inhibit the increase of oxidative stress levels in the kidney of I/R rats. NADPH oxidase 1 (Nox1) overexpression reversed the improving effects of Ala on renal function, inflammation and apoptosis of I/R rats.

CONCLUSION

These results indicated that Ala could improve renal function, attenuate inflammation and apoptosis in the kidney of I/R rats via inhibiting oxidative stress.

Rivaroxaban attenuates cardiac hypertrophy by inhibiting protease-activated receptor-2 signaling in renin-overexpressing hypertensive mice

Rivaroxaban (Riv), a direct factor Xa (FXa) inhibitor, exerts anti-inflammatory effects in addition to anticoagulation. However, its role in cardiovascular remodeling is largely unknown. We tested the hypothesis that Riv attenuates the progression of cardiac hypertrophy and fibrosis induced by continuous activation of the renin-angiotensin system (RAS) in renin-overexpressing hypertensive transgenic (Ren-Tg) mice. We treated 12-week-old male Ren-Tg and wild-type (WT) mice with a diet containing Riv (12 mg/kg/day) or a regular diet for 4 weeks. After this, FXa in plasma significantly increased in Ren-Tg mice compared with WT mice, and Riv inhibited this increase. Left ventricular wall thickness (LVWT) and the area of cardiac fibrosis evaluated by Masson's trichrome staining were greater in Ren-Tg mice than in WT mice, and Riv decreased them. Cardiac expression levels of the protease-activated receptor (PAR)-2, tumor necrosis factor-α, transforming growth factor (TGF)-β1, and collagen type 3 α1 (COL3A1) genes were all greater in Ren-Tg mice than in WT mice, and Riv attenuated these increases. To investigate the possible involvement of PAR-2, we treated Ren-Tg mice with a continuous subcutaneous infusion of 10 μg/kg/day of the PAR-2 antagonist FSLLRY for 4 weeks. FSLLRY significantly decreased LVWT and cardiac expression of PAR-2, TGF-β1, and COL3A1. In isolated cardiac fibroblasts (CFs), Riv or FSLLRY pretreatment inhibited the FXa-induced increase in the phosphorylation of extracellular signal-regulated kinases. In addition, Riv or FSLLRY inhibited FXa-stimulated wound closure in CFs. Riv exerts a protective effect against cardiac hypertrophy and fibrosis development induced by continuous activation of the RAS, partly by inhibiting PAR-2.

Vascular Protective Effects of New Oral Anticoagulants in Patients with Atrial Fibrillation

This study was designed to determine the efficacy of a new oral anticoagulant (NOAC) therapy for the prevention of endothelial dysfunction and atherosclerosis progression in patients with atrial fibrillation (AF). Sixty-five AF patients with a CHA2DS2-VASc score ≥2 without previous history of cardiovascular disease were registered and randomly assigned to either an NOAC group (dabigatran or rivaroxaban) or the warfarin group. Reactive hyperemia peripheral arterial tonometry (RH-PAT) measurements reflecting endothelial function were taken using Endo-PAT2000. Carotid intima–media thickness (IMT) was measured at baseline, 12 months, and 24 months, and several biomarkers were also analyzed. For the primary end point, the reactive hyperemia index (RHI) for the NOAC group was 1.5 ± 0.4 and that for the warfarin group was 1.6 ± 0.5. The left and right carotid IMT was 0.7 mm in the NOAC groups and 0.8 mm in the warfarin group. At 12 months, RHI was 1.6 ± 0.3 for the dabigatran group, 1.6 ± 0.5 for the rivaroxaban group, and 1.6 ± 0.3 for the warfarin group. The three groups did not differ statistically with respect to change in left and right carotid IMT at 12 and 24 months, respectively. The biomarkers for endothelial function and atherosclerosis were not significantly different. There was a trend of reduced P-selectin levels in the NOAC group compared to the warfarin group. In patients with AF, there were no significant differences in the prevention of endothelial dysfunction and atherosclerosis progression between the NOAC and warfarin groups.

Sphingosine-1-phosphate: A mediator of the ARB-MI paradox?

BACKGROUND

Angiotensin converting enzyme inhibitors (ACEI) and angiotensin II receptor blockers (ARB) are important in the prevention of cardiovascular disease. The "ARB-MI paradox" implies that no risk reduction of myocardial infarction (MI) was found in ARB-treated patients despite target blood pressure control. Sphingosine-1-phosphate (S1P) is a cardioprotective sphingolipid which is released by platelets during activation. In this study we aimed to investigate differences of S1P homeostasis mediated by bradykinin and sphingosine kinases during ACEI/ARB treatment.

METHODS

In this hypothesis generating pilot study, we investigated S1P plasma concentrations in 34 patients before and 3 months after ARB/ACEI medication. S1P levels were measured via liquid chromatography-tandem mass spectrometry. Bradykinin levels were measured by an enzyme-linked immunosorbent assay.

RESULTS

Patient characteristics were not different between the ACEI and ARB group. Baseline S1P plasma concentrations were similar before ARB and ACEI treatment (7.4 SD 1.9 pmol vs. 7.8 SD 2.7 pmol, p = 0.54). After 3 months, S1P plasma levels were significantly higher in ACEI (9.3 SD 2.2 pmol) as compared to ARB treated patients (7.4 SD 2.4 pmol, p = 0.001). Pearson correlation showed no significant association between bradykinin and S1P levels before (r = -0.219; 95% CI [-0.54-0.15]; p = 0.245) or after three months of treatment with ACEI or ARB (r = -0.015; 95% CI [-0.48-0.45]; p = 0.95).

CONCLUSIONS

S1P plasma concentrations are higher in ACE treated patients as compared to ARB treatment. This leads to the hypothesis, that differences in S1P metabolism might partially explain the ARB-MI paradox. This needs to be tested in clinical trials.

Mechanisms of Pulmonary Hypertension in Acute Respiratory Distress Syndrome (ARDS)

Background: Acute respiratory distress syndrome (ARDS) is a severe and often fatal disease. The causes that lead to ARDS are multiple and include inhalation of salt water, smoke particles, or as a result of damage caused by respiratory viruses. ARDS can also arise due to systemic complications such as blood transfusions, sepsis, or pancreatitis. Unfortunately, despite a high mortality rate of 40%, there are limited treatment options available for ARDS outside of last resort options such as mechanical ventilation and extracorporeal support strategies. Aim of review: A complication of ARDS is the development of pulmonary hypertension (PH); however, the mechanisms that lead to PH in ARDS are not fully understood. In this review, we summarize the known mechanisms that promote PH in ARDS. Key scientific concepts of review: (1) Provide an overview of acute respiratory distress syndrome; (2) delineate the mechanisms that contribute to the development of PH in ARDS; (3) address the implications of PH in the setting of coronavirus disease 2019 (COVID-19).

Alamandine attenuates angiotensin II-induced vascular fibrosis via inhibiting p38 MAPK pathway

Alamandine attenuates hypertension and cardiac remodeling in spontaneously hypertensive rats (SHRs). We examined whether alamandine attenuates vascular remodeling in mice, and regulates angiotensin II (Ang II)-induced fibrosis in rat vascular smooth muscle cells (VSMCs). Alamandine attenuated hypertension in mice induced by Ang II. Ang II increased the fibrosis of thoracic aorta in mice, which was attenuated by alamandine treatment. Increased levels of collagen I, transforming growth factor-β (TGF-β), and connective tissue growth factor (CTGF) levels in thoracic aortas after Ang II treatment in mice were inhibited by alamandine. Ang II-stimulated collagen I, TGF-β, and CTGF level increases were inhibited by alamandine in rat VSMCs. This could be reversed by Mas-related G protein-coupled receptor, member D (MrgD) antagonist D-Pro⁷-Ang-(1-7) but not Mas receptor antagonist A779. MrgD expression was increased in the thoracic aortas of mice or VSMCs treatment with Ang II. Ang II increased p-p38 and cAMP levels in rat VSMCs, and alamandine blocked Ang II-induced these increases. Cyclic adenosine monophosphate (cAMP) reversed the inhibitory effects of alamandine on the Ang II-induced increases in collagen I, TGF-β, and CTGF levels. These results demonstrate alamandine attenuates vascular fibrosis by stimulating MrgD expression and decreases arterial fibrosis by blocking p-p38 expression. Alamandine/MrgD axis is a potential target for the treatment of vascular remodeling.

A novel mechanism of ACE inhibition-associated enhanced platelet reactivity: disproof of the ARB-MI paradox?

PURPOSE

ACE inhibitors (ACEI) and angiotensin II receptor blockers (ARB) are important drugs in cardiovascular disease. However, little is known about which of these drug class is to be preferred. First analyses show that the blockade of the renin-angiotensin-aldosterone system (RAAS) influences platelet reactivity. Therefore, we evaluated the effects of ACEI and ARB on platelet reactivity and thrombin generation.

METHODS

We conducted a time series analysis in 34 patients. We performed light transmission aggregometry (LTA) to evaluate platelet reactivity. Results are given as maximum of aggregation (MoA). Thrombin generation was measured as endogenous thrombin potential (ETP) via calibrated automated thrombogram. Flow cytometry was used to analyze protease-activated receptor (PAR)-1 expression.

RESULTS

ACEI treatment significantly increased platelet reactivity already 4 h after initiation of treatment (prior vs. 4 h post ACEI: MoA 41.9 ± 16.2% vs. 55.2 ± 16.7%; p = 0.003). After switching from ACEI to ARB treatment, platelet reactivity decreased significantly (3 months after switching: MoA 34.7 ± 20.9%; p = 0.03). ACEI reduced endogenous thrombin potential significantly from before to 3 months after ACEI (ETP 1527 ± 437 nM × min vs. 1088 ± 631 nM × min; p = 0.025). Platelet thrombin receptor (PAR1) expression increased from 37.38 ± 10.97% before to 49.53 ± 6.04% after ACEI treatment (p = 0.036).

CONCLUSION

ACEI enhanced platelet reactivity. This can be reversed by changing to ARB. The mechanism behind RAAS influencing platelet function seems to be associated with PAR-1 expression.

Cardiac Expression of Factor X Mediates Cardiac Hypertrophy and Fibrosis in Pressure Overload

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Factor X expression was increased in the heart following pressure overload and in isolated cardiac myocytes and fibroblasts.

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Rivaroxaban treatment at doses that do not affect thrombin generation, blood coagulation or cardiac hemostasis attenuated cardiac inflammation, hypertrophy, and fibrosis caused by pressure overload and improved cardiac diastolic function.

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Activated coagulation factor X induced PAR-1/-2–mediated elongated cardiomyocyte hypertrophy and PAR1-mediated cardiac fibroblast proliferation, migration and differentiation.

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Activated coagulation factor X derived from a cardiac source may represent an important physiologic and pathophysiologic activator of PAR-1/PAR-2.

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Non-anticoagulation dosage of rivaroxaban could provide an effective therapy to attenuate early phases of heart failure development.

Activated factor X is a key component of the coagulation cascade, but whether it directly regulates pathological cardiac remodeling is unclear. In mice subjected to pressure overload stress, cardiac factor X mRNA expression and activity increased concurrently with cardiac hypertrophy, fibrosis, inflammation and diastolic dysfunction, and responses blocked with a low coagulation-independent dose of rivaroxaban. In vitro, neurohormone stressors increased activated factor X expression in both cardiac myocytes and fibroblasts, resulting in activated factor X-mediated activation of protease-activated receptors and pro-hypertrophic and -fibrotic responses, respectively. Thus, inhibition of cardiac-expressed activated factor X could provide an effective therapy for the prevention of adverse cardiac remodeling in hypertensive patients.

Hemostatic function in Cavalier King Charles Spaniels assessed using thromboelastography

BACKGROUND

Macrothrombocytopenia is a well-known anomaly in Cavalier King Charles Spaniels (CKCSs), a breed also highly predisposed to develop myxomatous mitral valve disease (MMVD). Thromboelastography (TEG) has been shown to be a valuable instrument for whole blood hemostatic evaluation in dogs and correlates well with different physiologic and pathologic situations.

OBJECTIVES

We aimed to assess the influence of macrothrombocytopenia and the severity of MMVD on hemostatic function as measured by TEG.

METHODS

Associations between TEG variables (R, K, α, MA, and G) and dog characteristics, heart rates, systolic blood pressures, MMVD severities (healthy, mild or moderate, and severe), echocardiographic variables, platelet variables (platelet count, mean platelet volume [MPV], and plateletcrit), and hematocrits were evaluated in 47 prospectively recruited privately owned CKCSs. Blood samples were analyzed using a computerized thromboelastograph and an Advia 2120 hematology analyzer.

RESULTS

Univariable and multiple regression analyses showed an effect of left ventricular (LV) fractional shortening (FS%) on all TEG variables, an effect of LV FS% and age on TEG α, and an effect of LV FS% and MPV on TEG MA and TEG G. TEG MA and G increased with increasing MPV, but the associations were generally weak. No significant differences were detected in the TEG variables between the MMVD severity groups.

CONCLUSION

Macrothrombocytopenia and increased LV FS%, of which the latter commonly increases in various positive inotropic states, were both associated with a more hypercoagulable hemostatic system, according to the TEG results, in the present study.

The microRNA in ventricular remodeling: the miR-30 family

Ventricular remodeling (VR) is a complex pathological process of cardiomyocyte apoptosis, cardiac hypertrophy, and myocardial fibrosis, which is often caused by various cardiovascular diseases (CVDs) such as hypertension, acute myocardial infarction, heart failure (HF), etc. It is also an independent risk factor for a variety of CVDs, which will eventually to damage the heart function, promote cardiovascular events, and lead to an increase in mortality. MicroRNAs (miRNAs) can participate in a variety of CVDs through post-transcriptional regulation of target gene proteins. Among them, microRNA-30 (miR-30) is one of the most abundant miRNAs in the heart. In recent years, the study found that the miR-30 family can participate in VR through a variety of mechanisms, including autophagy, apoptosis, oxidative stress, and inflammation. VR is commonly found in ischemic heart disease (IHD), hypertensive heart disease (HHD), diabetic cardiomyopathy (DCM), antineoplastic drug cardiotoxicity (CTX), and other CVDs. Therefore, we will review the relevant mechanisms of the miR-30 in VR induced by various diseases.

Protease-activated receptor 4 protects mice from Coxsackievirus B3 and H1N1 influenza A virus infection

PAR4 is expressed by a variety of cells, including platelets, cardiac, lung and immune cells. We investigated the contribution of PAR4 to viral infections of the heart and lung. Toll-like receptor (TLR) 3-dependent immune responses were analyzed after co-stimulation of PAR4 in murine bone-marrow derived macrophages, embryonic fibroblasts and embryonic cardiomyocytes. In addition, we analyzed Coxsackievirus B3 (CVB3) or H1N1 influenza A virus (H1N1 IAV) infection of PAR4^-/- (ΔPAR4) and wild-type (WT) mice. Lastly, we investigated the effect of platelet inhibition on H1N1 IAV infection. In vitro experiments revealed that PAR4 stimulation enhances the expression of TLR3-dependent CXCL10 expression and decreases TLR3-dependent NFκB-mediated proinflammatory gene expression. Furthermore, CVB3-infected ΔPAR4 mice exhibited a decreased anti-viral response and increased viral genomes in the heart leading to more pronounced CVB3 myocarditis compared to WT mice. Similarly, H1N1 IAV-infected ΔPAR4 mice had increased immune cell numbers and inflammatory mediators in the lung, and increased mortality compared with infected WT controls. The study showed that PAR4 protects mice from viral infections of the heart and lung.

Straight to the heart: Pleiotropic antiarrhythmic actions of oral anticoagulants

Mechanistic understanding of atrial fibrillation (AF) pathophysiology and the complex bidirectional relationship with thromboembolic risk remains limited. Oral anticoagulation is a mainstay of AF management. An emerging concept is that anticoagulants may themselves have potential pleiotropic disease-modifying effects. We here review the available evidence for hemostasis-independent actions of the oral anticoagulants on electrical and structural remodeling, and the inflammatory component of the vulnerable substrate.

Cross-Talk between Neurohormonal Pathways and the Immune System in Heart Failure: A Review of the Literature

Heart failure is a complex clinical syndrome involving a multitude of neurohormonal pathways including the renin-angiotensin-aldosterone system, sympathetic nervous system, and natriuretic peptides system. It is now emerging that neurohumoral mechanisms activated during heart failure, with both preserved and reduced ejection fraction, modulate cells of the immune system. Indeed, these cells express angiotensin I receptors, adrenoceptors, and natriuretic peptides receptors. Ang II modulates macrophage polarization, promoting M2 macrophages phenotype, and this stimulation can influence lymphocytes Th1/Th2 balance. β-AR activation in monocytes is responsible for inhibition of free oxygen radicals production, and together with α2-AR can modulate TNF-α receptor expression and TNF-α release. In dendritic cells, activation of β2-AR inhibits IL-12 production, resulting in the inhibition of Th1 and promotion of Th2 differentiation. ANP induces the activation of secretion of superoxide anion in polymorphonucleated cells; reduces TNF-α and nitric oxide secretion in macrophages; and attenuates the exacerbated TH1 responses. BNP in macrophages can stimulate ROS production, up-regulates IL-10, and inhibits IL-12 and TNF-α release by dendritic cells, suggesting an anti-inflammatory cytokines profile induction. Therefore, different neurohormonal-immune cross-talks can determine the phenotype of cardiac remodeling, promoting either favorable or maladaptive responses. This review aims to summarize the available knowledge on neurohormonal modulation of immune responses, providing supportive rational background for further research.

Protease-activated receptor 1 activation enhances doxorubicin-induced cardiotoxicity

OBJECTIVE

The anti-cancer anthracycline drug Doxorubicin (Dox) causes cardiotoxicity. We investigated the role of protease-activated receptor 1 (PAR-1) in Dox-induced cardiotoxicity.

METHODS AND RESULTS

In vitro experiments revealed that PAR-1 enhanced Dox-induced mitochondrial dysfunction, reactive oxygen species and cell death of cardiac myocytes and cardiac fibroblasts. The contribution of PAR-1 to Dox-induced cardiotoxicity was investigated by subjecting PAR-1^-/- mice and PAR-1^+/+ mice to acute and chronic exposure to Dox. Heart function was measured by echocardiography. PAR-1^-/- mice exhibited significant less cardiac injury and dysfunction compared to PAR-1^+/+ mice after acute and chronic Dox administration. PAR-1^-/- mice had reduced levels of nitrotyrosine, apoptosis and inflammation in their heart compared to PAR-1^+/+ mice. Furthermore, inhibition of PAR-1 in wild-type mice with vorapaxar significantly reduced the acute Dox-induced cardiotoxicity.

CONCLUSION

Our results indicate that activation of PAR-1 contributes to Dox-induced cardiotoxicity. Inhibition of PAR-1 may be a new approach to reduce Dox-induced cardiotoxicity in cancer patients.

Alamandine attenuates hypertension and cardiac hypertrophy in hypertensive rats

Oral administration of the peptide alamandine has antihypertensive and anti-fibrotic effects in rats. This work aimed to determine whether subcutaneous alamandine injection would attenuate hypertension and cardiac hypertrophy, and improve the function of a major target of hypertension-related damage, the left ventricle (LV), in spontaneously hypertensive rats (SHRs). This was examined in vivo in SHRs and normotensive rats subjected to 6-week subcutaneous infusion of alamandine or saline control, and in vitro in H9C2-derived and primary neonatal rat cardiomyocytes treated with angiotensin (Ang) II to model cardiac hypertrophy. Tail artery blood pressure measurement and transthoracic echocardiography showed that hypertension and impaired LV function in SHRs were ameliorated upon alamandine infusion. Alamandine administration also decreased the mass gains of heart and lung in SHRs, suppressed cardiomyocyte cross-sectional area expansion, and inhibited the mRNA levels of atrial natriuretic peptide and brain natriuretic peptide. The expression of alamandine receptor Mas-related G protein-coupled receptor, member D was increased in SHR hearts and in cardiomyocytes treated with Ang II. Alamandine inhibited the increases of protein kinase A (PKA) levels in the heart in SHRs and in cardiomyocytes treated with Ang II. In conclusion, the present study showed that alamandine administration attenuates hypertension, alleviates cardiac hypertrophy, and improves LV function. PKA signaling may be involved in the mechanisms underlying these effects.

The coagulation system in host defense

The blood coagulation system and immune system of higher organisms are thought to have a common ancestral origin. During infections, the blood coagulation system is activated and components of the hemostatic system are directly involved in the immune response and immune system modulations. The current view is that the activation of coagulation is beneficial for infections with bacteria and viruses. It limits pathogen dissemination and supports pathogen killing and tissue repair. On the other hand, over-activation can lead to thrombosis with subsequent depletion of hemostatic factors and secondary bleeding. This review will summarize the current knowledge on blood coagulation and pathogen infection with focus on most recent studies of the role of the different parts of the blood coagulation system in selected bacterial and viral infections.

Aucubin Protects against Myocardial Infarction-Induced Cardiac Remodeling via nNOS/NO-Regulated Oxidative Stress

Whether aucubin could protect myocardial infarction- (MI-) induced cardiac remodeling is not clear. In this study, in a mouse model, cardiac remodeling was induced by left anterior descending coronary artery ligation surgery. Mice were intraperitoneally injected with aucubin (10 mg/kg) 3 days post-MI. Two weeks post-MI, mice in the aucubin treatment group showed decreased mortality, decreased infarct size, and improved cardiac function. Aucubin also decreased cardiac remodeling post-MI. Consistently, aucubin protected cardiomyocytes against hypoxic injury in vitro. Mechanistically, we found that aucubin inhibited the ASK1/JNK signaling. These effects were abolished by the JNK activator. Moreover, we found that the oxidative stress was attenuated in both in vivo aucubin-treated mice heart and in vitro-treated cardiomyocytes, which caused decreased thioredoxin (Trx) consumption, leading to ASK1 forming the inactive complex with Trx. Aucubin increased nNOS-derived NO production in vivo and vitro. The protective effects of aucubin were reversed by the NOS inhibitors L-NAME and L-VINO in vitro. Furthermore, nNOS knockout mice also reversed the protective effects of aucubin on cardiac remodeling. Taken together, aucubin protects against cardiac remodeling post-MI through activation of the nNOS/NO pathway, which subsequently attenuates the ROS production, increases Trx preservation, and leads to inhibition of the ASK1/JNK pathway.

Protease-Activated Receptor 1 Contributes to Angiotensin II-Induced Cardiovascular Remodeling and Inflammation

BACKGROUND

Angiotensin II (Ang II) plays an important role in cardiovascular disease. It also leads to the activation of coagulation. The coagulation protease thrombin induces cellular responses by activating protease-activated receptor 1 (PAR-1). We investigated whether PAR-1 contributes to Ang II-induced cardiovascular remodeling and inflammation.

METHODS AND RESULTS

PAR-1+/+ (wild-type; WT) and PAR-1-/- mice were infused with Ang II (600 ng/kg/min) for up to 4 weeks. In WT mice, this dose of Ang II did not cause a significant increase in blood pressure but it did cause pathological changes in both the aorta and the heart. Ang II infusion resulted in vascular remodeling of the aorta, demonstrated by a significant increase in medial wall thickening and perivascular fibrosis. Importantly, both parameters were significantly attenuated by PAR-1 deficiency. Furthermore, perivascular fibrosis around coronary vessels was reduced in Ang II-treated PAR-1-/- mice compared to WT mice. In addition, PAR-1 deficiency significantly attenuated Ang II induction of inflammatory cytokines and profibrotic genes in the aortas compared to WT mice. Finally, PAR-1 deficiency had no effect on Ang II-induced heart hypertrophy. However, the heart function measured by fractional shortening was less impaired in PAR-1-/- mice than in WT mice.

CONCLUSION

Our data indicate that PAR-1 plays a significant role in cardiovascular remodeling mediated by a blood pressure-independent action of Ang II.