Spironolactone suppresses aldosterone-induced Kv1.5 expression by attenuating mineralocorticoid receptor-Nox1/2/4-mediated ROS generation in neonatal rat atrial myocytes.

Our previous investigation indicated that angiotensin II (Ang II) enhances the expression of Kv1.5, a promising target for the treatment of atrial fibrillation (AF), by activating reactive oxygen species (ROS)-dependent phosphorylation of Smad 2/3 (forming P-Smad 2/3) and ERK 1/2 (forming P-ERK 1/2). A recent study indicated that aldosterone (Aldo) upregulates atrial Kv1.5 protein in a rat AF model, but the mechanism remains unknown. The present study aimed to clarify the mechanism underlying Aldo-induced Kv1.5 expression and to test whether spironolactone may modulate atrial Kv1.5. Our Western blot analysis indicated that the Aldo/mineralocorticoid receptor (MR) interacts with Ang II/AT1R in upregulating Kv1.5 expression in cultured neonatal atrial myocytes (NRAMs). Blockade of MR with spironolactone and of AT1R with losartan significantly suppressed Kv1.5 expression induction by combined Aldo and Ang II treatment. Aldo increased the protein expression of Nox1, Nox2 and Nox4, but this effect was abolished by spironolactone pretreatment. The Aldo-induced upregulation of Kv1.5 was also reversed by the Src protein tyrosine kinase family inhibitor PP2, the Nox2 inhibitor gp91ds-tat and the Nox1/Nox4 inhibitor GKT137831 but not by the Rac GTPase inhibitor NSC23766. Flow cytometry showed that the Aldo-induced ROS production was inhibited by spironolactone, PP2, gp91ds-tat and GKT137831. Spironolactone suppressed the Aldo-induced protein expression phosphorylated Src (P-Src), P-Smad 2/3 and P-ERK 1/2. In conclusion, we have demonstrated that spironolactone suppresses Aldo-induced Kv1.5 expression by attenuating MR-Nox1/2/4-mediated ROS generation in NRAMs.

Inhibition of perivascular mast cell activation is involved in the atheroprotective effect of rosiglitazone in apolipoprotein E-deficient mice.

Activation of perivascular mast cells (MCs) and subsequent release of their abundant inflammatory mediators have been well documented to induce excessive inflammation and subsequent rupture of atherosclerotic plaques. Previous studies have suggested that rosiglitazone affects the stability of plaques, although the precise mechanism of action is not clearly understood. In this study, we evaluated the effects of rosiglitazone on MCs in vivo and in vitro. Apolipoprotein E-deficient (ApoE-/-) mice were fed a high-fat diet (HFD), with or without rosiglitazone supplemented in the drinking water (1.5 mg/kg/day). Compared with the HFD group, rosiglitazone did not affect blood glucose levels, but it attenuated serum levels of tumor necrosis factor alpha (TNFα) and interleukin-6 (IL-6), ameliorated plaque lipid accumulation and the expression of matrix metalloproteinases-2 and -9, increased the collagen content of plaques, and inhibited perivascular MC degranulation and chymase expression. The in vitro experiments showed that rosiglitazone treatment repressed the expression of TNFα and IL-6 induced by antigen-challenged RBL-2H3 cells in a peroxisome proliferator-activated receptor γ (PPARγ)-independent manner, which was related to the repression of protein kinase C (PKC)-ß1 activation. Combined, these results suggest that the plaque-stabilizing effect of rosiglitazone is attributable to its ability to inhibit the activation of perivascular MCs.

H2S inhibits angiotensin II-induced atrial Kv1.5 upregulation by attenuating Nox4-mediated ROS generation during atrial fibrillation.

Our previous study demonstrated that angiotensin II (Ang II) upregulates the expression of Kv1.5, a promising target for atrial fibrillation (AF) therapy, by activating ROS-dependent P-Smad2/3 and P-ERK 1/2. A recent study showed that hydrogen sulfide (H2S) may modulate the effects of angiotensin II (Ang II) by inhibiting the NADPH oxidase 4 (Nox4)-ROS signaling in the heart. The present study aimed to determine whether H2S is involved in the regulation of atrial Kv1.5 via ROS-related mechanisms in AF. Cultured neonatal rat atrial myocytes and a beagle model of AF were used for this study. In the neonatal rat atrial myocytes, quantitative PCR and enzyme immunoassays revealed that the mRNA expression levels of angiotensinogen, angiotensin-converting enzyme, and Ang II type I receptor (AT1R) and the Ang II supernatant concentration were significantly increased by hydrogen peroxide (H2O2) incubation, and these H2O2-induced alterations were reversed by diphenyleneiodonium, apocynin and H2S supplementation. Flow cytometry and Western blotting revealed that blockade of H2S biosynthesis using dl-propargylglycine increased ROS production and the expression of Ang II and Kv1.5. Sodium hydrosulfide (an exogenous H2S donor) and Nox4 siRNA inhibited Ang II-induced ROS production and Ang II-induced expression of Kv1.5, P-Smad2/3, P-ERK 1/2. Sodium hydrosulfide suppressed the Ang II-induced upregulation of Nox4. In our beagle AF model, 24 h of rapid atrial pacing (RAP) increased the atrial Ang II concentration, ROS production and the protein expression of Nox4, Kv1.5, P-Smad2/3 and P-ERK 1/2. These RAP-induced changes were inhibited by H2S supplementation and losartan (an AT1R blocker) pretreatment. In conclusion, our study indicates that H2S downregulates Ang II-induced atrial Kv1.5 expression by attenuating Nox4-related ROS-triggered P-Smad2/3 and P-ERK 1/2 activation during AF. H2S supplementation would be beneficial for AF treatment via the suppression of atrial Kv1.5 expression.

Shedding of Syndecan-1/CXCL1 Complexes by Matrix Metalloproteinase 7 Functions as an Epithelial Checkpoint of Neutrophil Activation.

Although neutrophils play critical roles in innate immunity, in excess these cells cause severe tissue damage. Thus, neutrophil activation must be tightly regulated to prevent indiscriminant damage. Previously, we reported that mice lacking matrix metalloproteinase (MMP) 7 are protected from lung injury owing to markedly impaired neutrophil movement from the interstitium into mucosal lumenal spaces. This phenotype resulted from a lack of MMP7 shedding of syndecan-1, a heparan sulfate proteoglycan that carries the neutrophil chemokine CXCL1 as cargo. Here, we assessed if shedding syndecan-1/CXCL1 complexes affects neutrophil activation. Whereas injured monolayers of wild-type alveolar type II cells potently stimulated neutrophil activation, as gauged by release of myeloperoxidase, cells from Mmp7(-/-) or syndecan-1-null (Sdc1(-/-)) mice or human cells with MMP7 knockdown did not. In vivo, we observed reduced myeloperoxidase release relative to neutrophil numbers in bleomycin-injured Mmp7(-/-) and Sdc1(-/-) mice. Furthermore, we determined that soluble syndecan-1 directly stimulated neutrophil activation in the absence of cellular damage. These data indicate that MMP7 shedding of syndecan-1/CXCL1 complexes functions as a checkpoint that restricts neutrophil activation at sites of epithelial injury.

Protective effect of uridine on atrial fibrillation: a Mendelian randomisation study.

Uridine, a pyrimidine nucleoside, is crucial in the synthesis of metabolites. According to observational studies, a higher plasma uridine level is associated with a lower risk of atrial fibrillation (AF). However, the casual relationship between uridine and AF is still unknown. In this study, we used the Mendelian randomisation (MR) approach to explore causality. Three genetic variants associated with uridine were identified from the Metabolomics GWAS server (7824 participants); summary-level datasets associated with AF were acquired from a genome-wide association study (GWAS) meta-analysis with 1,030,836 European participants (60,620 AF cases). We duplicated the MR analyses using datasets from AF HRC studies and the FinnGen Consortium, and then conducted a meta-analysis which combined the main results. The risk of AF was significantly associated with the genetically determined plasma uridine level (odds ratio [OR] 0.27; 95% confidence interval [CI] 0.16, 0.47; p = 2.39 × 10-6). The association remained consistent in the meta-analysis of the various datasets (OR 0.27; 95% CI 0.17, 0.42; p = 1.34 × 10-8). In conclusion, the plasma uridine level is inversely associated with the risk of AF. Raising the plasma uridine level may have prophylactic potential against AF.

CD51 distinguishes a subpopulation of bone marrow mesenchymal stem cells with distinct migratory potential: a novel cell-based strategy to treat acute myocardial infarction in mice.

BACKGROUND: Experimental and clinical trials have demonstrated the efficiency of bone marrow-derived mesenchymal stromal/stem cells (bMSCs) in the treatment of myocardial infarction. However, after intravenous injection, the ineffective migration of engrafted bMSCs to the hearts remains an obstacle, which has an undesirable impact on the efficiency of cell-based therapy. Therefore, we attempted to identify a marker that could distinguish a subpopulation of bMSCs with a promising migratory capacity. METHODS: Here, CD51-negative and CD51-positive cells were isolated by flow cytometry from Ter119-CD45-CD31-bMSCs and cultured in specifically modified medium. The proliferation ability of the cells was evaluated by 5-ethynyl-2'-deoxyuridine (EdU) staining or continuously monitored during culture, and the differentiation potential was assessed by culturing the cells in the appropriate conditioned media. Wound healing assays, transwell assays and quantitative polymerase chain reaction (qPCR) were used to measure the migratory ability. The mice were subjected to a sham operation or myocardial infarction (MI) by permanently occluding the coronary artery, and green fluorescent protein (GFP)-labelled cells were transplanted into the mice via intravenous infusion immediately after MI. Heart function was measured by echocardiography; infarct myocardium tissues were detected by triphenyl tetrazolium chloride (TTC) staining. Additionally, immunofluorescence staining was used to verify the characteristics of CD51+bMSCs and inflammatory responses in vivo. Statistical comparisons were performed using a two-tailed Student's t test. RESULTS: In this study, the isolated CD51-bMSCs and CD51+bMSCs, especially the CD51+ cells, presented a favourable proliferative capacity and could differentiate into adipocytes, osteocytes and chondrocytes in vitro. After the cells were transplanted into the MI mice by intravenous injection, the therapeutic efficiency of CD51+bMSCs in improving left ventricular ejection fraction (LVEF) and left ventricular fractional shortening (LVFS) was better than that of CD51-bMSCs. Compared with CD51-bMSCs, CD51+bMSCs preferentially migrated to and were retained in the infarcted hearts at 48 h and 8 days after intravenous injection. Accordingly, the migratory capacity of CD51+bMSCs exceeded that of CD51-bMSCs in vitro, and the former cells expressed higher levels of chemokine receptors or ligands. Interestingly, the retained CD51+bMSCs retained in the myocardium possessed proliferative potential but only differentiated into endothelial cells, smooth muscle cells, fibroblasts or cardiomyocytes. Transplantation of CD51+bMSCs partially attenuated the inflammatory response in the hearts after MI, while the potential for inflammatory suppression was low in CD51-bMSC-treated mice. CONCLUSIONS: These findings indicated that the CD51-distinguished subpopulation of bMSCs facilitated proliferation and migration both in vitro and in vivo, which provided a novel cell-based strategy to treat acute MI in mice by intravenous injection.

Selenium modulates MMP2 expression through the TGFß1/Smad signalling pathway in human umbilical vein endothelial cells and rabbits following lipid disturbance.

BACKGROUND: A high-fat diet is a major risk factor for coronary heart diseases. Matrix metalloprotease (MMP) expression is changed in many cardiovascular diseases. Selenium, which is an important trace element in animals, has a close relationship with cardiovascular diseases. The TGFß1/Smad signalling pathway is ubiquitous in diverse tissues and cells, and it is also associated with the occurrence and development of cardiovascular diseases. Therefore, in this study, we aimed to determine selenium's effect on lipid metabolism, atherosclerotic plaque formation, and MMP2 expression, as well as the underlying functional mechanism. METHODS AND RESULTS: In vivo tests: 24 male New Zealand white rabbits were randomly divided into 4 groups: regular diet, high-fat diet, high-fat diet+selenium and regular diet+selenium groups. The high-fat diet induced the lipid disturbances of rabbits at week 12. Selenium supplementation lowered total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C) and triglyceride (TG) levels (p<0.01). Selenium supplementation also suppressed MMP2 over-expression in thoracic aortas. In vitro tests: Human umbilical vein endothelial cells (HUVECs) were treated with different concentrations of selenium or ox-LDL. Ox-LDL promoted MMP2 expression by increasing TGFß1, pSmad2, pSmad3 and Smad3 expression (p<0.01). Selenium attenuated MMP2 over-expression by regulating the TGFß1/Smad signalling pathway. CONCLUSIONS: Selenium suppressed high-fat diet-induced MMP2 over-expression in vivo by improving lipid metabolism. In vitro, selenium attenuated MMP2 over-expression through the TGFß1/Smad signalling pathway.

The secretion patterns and roles of cardiac and circulating arginine vasopressin during the development of heart failure.

OBJECTIVE: The aim of this study is to investigate local cardiac and circulating AVP secretion during heart failure and to determine whether AVP mediates ventricular remodeling. METHODS: We assessed cardiac function and AVP levels of post-myocardial infarction (MI) heart-failure rats 3 weeks (n = 10), 4 weeks (n = 10), 6 weeks (n = 10), 9 weeks (n = 15) after the proximal left anterior descending coronary artery (LAD) ligation. Ten sham-operated rats were used as the control group. In vitro, cardiac microvascular endothelial cells (CMECs) were initiated from isolated Wistar rat hearts and subjected to Ang II to induce AVP expression and secretion. Besides, the effects of AVP stimulation on CMECs and cardiac fibroblasts (CFs) were studied using methylthiazol tetrazolium assay, Western blotting and real-time PCR. RESULTS: With cardiac dysfunction, plasma and local cardiac AVP, aldosterone levels increased over time, peaking at 9 weeks post-MI. AVP levels were negatively correlated with serum Na(+) and LVEF but positively correlated with LVEDD and myocardial hydroxyproline. In CMECs treated with Ang II, AVP mRNA and protein expression increased. In addition, AVP promoted CFs proliferation and up-regulated the expression of endothelin-1 and connective tissue growth factor. CONCLUSION: CMECs are the cellular sources of elevated local heart AVP stimulated with Ang II/AT1. An intrinsic cardiac AVP system exists. Local cardiac and circulating AVP secretion were enhanced by deteriorating cardiac function. AVP may promote ventricular remodeling. Thus, AVP could be an important mediator of myocardial fibrosis in late-stage heart failure.

Zinc Regulates Lipid Metabolism and MMPs Expression in Lipid Disturbance Rabbits.

Lipid disturbance induced by high-fat diet is a worldwide problem, and it can induce inflammation and oxidative stress in vivo. Zinc is considered as an antioxidant, anti-inflammatory agent. Since matrix metalloprotease 2 (MMP2) and matrix metalloprotease 9 (MMP9)'s expressions are changed under many pathological conditions, we would like to know how zinc affects lipid metabolism and MMP2, MMP9's expressions in the lipid disturbance rabbits. Twenty-four male New Zealand white rabbits were randomly divided into four groups. Each group had six rabbits, and they were fed with regular diet, high-fat diet, high-fat diet+zinc, and regular diet+zinc separately for 12 weeks. High-fat diet induced lipid disturbance significantly which raised the level of aspartate aminotransferase (p<0.01) and alanine transaminase (p<0.05) in the high-fat diet group, but zinc supplement reversed this phenomenon (p<0.05). Zinc did not reduce total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) (p>0.05), but it lowered triglyceride (TG) and raised high-density lipoprotein cholesterol (HDL-C) (p<0.01). Zinc also reduced high-sensitivity C-reactive protein (hs-CRP) (p<0.01) and interleukin-6 (IL-6)'s expressions (p<0.05). Zinc reduced the epicardial adipose tissue and alleviated the hepatic steatosis. Zinc suppressed MMP2 and MMP9's expressions in vivo, but it did not alleviate the aorta fatty streak's severity in the lipid disturbance rabbits. Zinc protected the liver, reduced TG, hs-CRP, and IL-6 and raised HDL-C in the lipid disturbance rabbits. Zinc suppressed MMP2 and MMP9's expressions in vivo, but it did not alleviate the severity of aorta fatty streak induced by the high-fat diet.

[Clinical observation on effect of taizhi'an capsule in treating 150 patients with hyperlipidemia].

OBJECTIVE: To grasp the therapeutic effect of Taizhi'an (TZA) in lowering blood lipid level. METHODS: Three hundred patients with hyperlipidemia were randomly divided adopting numerical table method into 7 groups, the Taizhi'an group (A, n = 90), the half-dose Fenofibrate plus Taizhi'an group (B, n = 30), the full-dose Fenofibrate group (C, n = 30), the half-dose Simvastatin plus Taizhi'an group (D, n = 30), the full-dose Simvastatin group (E, n = 30), the Zhibituo group (F, n = 60) and the Xuezhikang group (G, n = 30). The effect in different groups were compared after 8 weeks treatment. RESULTS: In group A, the total cholesterol (TC) lowered by 12.7%, triglyceride (TG) lowered by 22.1% and the high density lipoprotein cholesterol (HDL-C) increased by 13.1%, the total effective rate being 82%. The therapeutic effect in group B was similar to that in group C, and that in group D was similar to that in group E (P > 0.05). The therapeutic effect of Taizhi'an was similar to that of Xuezhikang and Zhibituo, but was better than Zhibituo in lowering TG, LDL-C and increasing HDL-C, and better than Xuezhikang in lowering TG and increasing HDL-C (P < 0.05). CONCLUSION: When Taizhi'an used in combination with half-dose Simvastatin, it could not only enhance the blood lipid regulatory effect of Simvastatin but also reduce the dosage used and alleviate its adverse reaction. Compared with Xuezhikang and Zhibituo, Taizhi'an got the similar therapeutic effect, but was superior in regulating blood lipids.

MMP7 shedding of syndecan-1 facilitates re-epithelialization by affecting alpha(2)beta(1) integrin activation.

BACKGROUND: Lung injury promotes the expression of matrix metalloproteinase-7 (MMP7, matrilysin), which is required for neutrophil recruitment and re-epithelialization. MMP7 governs the lung inflammatory response through the shedding of syndecan-1. Because inflammation and repair are related events, we evaluated the role of syndecan-1 shedding in lung re-epithelialization. METHODOLOGY/PRINCIPAL FINDING: Epithelial injury induced syndecan-1 shedding from wild-type epithelium but not from Mmp7(-/-) mice in vitro and in vivo. Moreover, cell migration and wound closure was enhanced by MMP7 shedding of syndecan-1. Additionally, we found that syndecan-1 augmented cell adhesion to collagen by controlling the affinity state of the alpha(2)beta(1) integrin. CONCLUSION/SIGNIFICANCE: MMP7 shedding of syndecan-1 facilitates wound closure by causing the alpha(2)beta(1) integrin to assume a less active conformation thereby removing restrictions to migration. MMP7 acts in the lungs to regulate inflammation and repair, and our data now show that both these functions are controlled through the shedding of syndecan-1.

[Study on the therapeutic status of 1242 hospitalized acute myocardial infarction patients in Beijing].

OBJECTIVE: To investigate and analyze the therapeutic level and the existing problems on acute myocardial infarction (AMI) management in Beijing. METHODS: We collected clinic data of 1242 AMI patients from 12 hospitals in Beijing, from January 2000 to March 2001, using a uniformed questionnaire, and evaluated the status of the diagnosis and treatment of AMI according to the Chinese guidelines issued on Decmeber 2001. Corresponding factors which influencing the mortality were also analyzed by one-way factor and multiple factors analysis methodologies. RESULTS: The mean age of the 1242 AMI patients was 63.0 years old and about one third of them were under 55 years old. In hospitals, the total mortality was 9.10%. 37.9% of the patients had received therapy of the intravenous thrombolysis and emergency PCI with a total rate of reperfusion therapy as 56.0%. The in-hospital rates of drug use were as follows: Nitrates 90.0%, Aspirin 87.8%, heparin 88.7%, beta-blockers 73.4%, angiotensin converting enzyme inhibitors(ACEI) 77.6%, lipid regulating agents 43.6%. The rate of intravenous therapy of TCM by promoting the blood circulation and supplementing the vital energy was 30.5%. Results from multiple factors analysis showed that the compositive factors which could lower the mortality were reperfusion therapy,lipid regulating agents, intravenous therapy of TCM, beta-blockers, ACEI, lower molecule heparin and digitalis. CONCLUSION: Data from this study showed that there still existed a gap between clinical management on AMI and the guideline in Beijing. To set up a straightway passage of reperfusion therapy, to become more standardized to follow the guideline in undertaking the medical treatment practice, and to go deep into discuss the status of TCM on AMI management seemed the important tasks we are facing.

Matrix metalloproteinases promote inflammation and fibrosis in asbestos-induced lung injury in mice.

Inhalation of asbestos fibers causes pulmonary inflammation and eventual pulmonary fibrosis (asbestosis). Although the underlying molecular events are poorly understood, protease/antiprotease and oxidant/antioxidant imbalances are believed to contribute to the disease. Implicated in other forms of pulmonary fibrosis, the matrix metalloproteinases (MMPs) have not been examined in asbestosis. We therefore hypothesized that MMPs play a pathogenic role in asbestosis development. Wild-type C57BL/6 mice were intratracheally instilled with 0.1 mg crocidolite asbestos, causing an inflammatory response at 1 d and a developing fibrotic response at 7, 14, and 28 d. Gelatin zymography demonstrated an increase in MMP-9 (gelatinase B) during the inflammatory phase, while MMP-2 (gelatinase A) was profoundly increased in the fibrotic phase. Immunohistochemistry revealed MMP-9 in and around bronchiolar and airspace neutrophils that were often associated with visible asbestos fibers. MMP-2 was found in fibrotic regions at 7, 14, and 28 d. No increases in RNA levels of MMP-2, MMP-9, or MMP-8 were found, but levels of MMP-7, MMP-12, and MMP-13 RNA did increase at 14 d. The MMP inhibitors, TIMP-1 and TIMP-2, were also increased at 7-28 d after asbestos exposure. To confirm the importance of MMP activity in disease progression, mice exposed to asbestos were given daily injections of the MMP inhibitor, GM6001. MMP inhibition reduced inflammation and fibrosis in asbestos-treated mice. Collectively, these data suggest that MMPs contribute to the pathogenesis of asbestosis through effects on inflammation and fibrosis development.

Matrilysin (matrix metalloproteinase-7) mediates E-cadherin ectodomain shedding in injured lung epithelium.

Matrilysin (matrix metalloproteinase-7) is highly expressed in lungs of patients with pulmonary fibrosis and other conditions associated with airway and alveolar injury. Although matrilysin is required for closure of epithelial wounds ex vivo, the mechanism of its action in repair is unknown. We demonstrate that matrilysin mediates shedding of E-cadherin ectodomain from injured lung epithelium both in vitro and in vivo. In alveolar-like epithelial cells, transfection of activated matrilysin resulted in shedding of E-cadherin and accelerated cell migration. In vivo, matrilysin co-localized with E-cadherin at the basolateral surfaces of migrating tracheal epithelium, and the reorganization of cell-cell junctions seen in wild-type injured tissue was absent in matrilysin-null samples. E-cadherin ectodomain was shed into the bronchoalveolar lavage fluid of bleomycin-injured wild-type mice, but was not shed in matrilysin-null mice. These findings identify E-cadherin as a novel substrate for matrilysin and indicate that shedding of E-cadherin ectodomain is required for epithelial repair.

Matrilysin shedding of syndecan-1 regulates chemokine mobilization and transepithelial efflux of neutrophils in acute lung injury.

The influx of inflammatory cells to sites of injury is largely directed by signals from the epithelium, but how these cells form chemotactic gradients is not known. In matrilysin null mice, neutrophils remained confined in the interstitium of injured lungs and did not advance into the alveolar space. Impaired transepithelial migration was accompanied by a lack of both shed syndecan-1, a heparan sulfate proteoglycan, and KC, a CXC chemokine, in the alveolar fluid. KC was bound to shed syndecan-1, and it was not detected in the lavage of syndecan-1 null mice. In vitro, matrilysin cleaved syndecan-1 from the surface of cells. Thus, matrilysin-mediated shedding of syndecan-1/KC complexes from the mucosal surface directs and confines neutrophil influx to sites of injury.