Metformin Directly Binds to MMP-9 to Improve Plaque Stability.

Vulnerable atherosclerotic plaque rupture is the principal mechanism that accounts for myocardial infarction and stroke. High matrix metalloproteinase-9 (MMP-9) expression and activity have been proven to lead to plaque instability. Metformin, a first-line treatment for type 2 diabetes, is beneficial to plaque vulnerability. However, the mechanism underlying its anti-atherogenic effect remains unclear. Molecular docking and surface plasmon resonance experiments showed that metformin directly interacts with MMP-9, and incubated MMP-9 overexpressing HEK293A cells with metformin (1 µmol·L-1) significantly attenuates MMP-9's activity using zymography and MMP activity assays. Moreover, metformin treatment drives MMP-9 degradation. Next, we constructed a carotid artery atherosclerotic plaque model and administered consecutive 14-day metformin (200 mg·kg-1·d-1) treatment by intragastric gavage. Immunofluorescence staining of the right carotid common artery and serum MMP activity assay results showed that metformin treatment decreased local plaque MMP-9 protein level and circulating MMP-9 activity, respectively. Histochemical staining revealed that after metformin treatment, the collagen content in plaque was significantly preserved, and the plaque vulnerability index decreased. These findings suggested that metformin improved atherosclerotic plaque stability by directly binding to MMP-9 and driving its degradation.

Galectin-3-centered paracrine network mediates cardiac inflammation and fibrosis upon ß-adrenergic insult.

Rapid over-activation of ß-adrenergic receptors (ß-AR) following acute stress initiates cardiac inflammation and injury by activating interleukin-18 (IL-18), however, the process of inflammation cascades has not been fully illustrated. The present study aimed to determine the mechanisms of cardiac inflammatory amplification following acute sympathetic activation. With bioinformatics analysis, galectin-3 was identified as a potential key downstream effector of ß-AR and IL-18 activation. The serum level of galectin-3 was positively correlated with norepinephrine or IL-18 in patients with chest pain. In the heart of mice treated with ß-AR agonist isoproterenol (ISO, 5 mg kg-1), galectin-3 expression was upregulated markedly later than IL-18 activation, and Nlrp3-/- and Il18-/- mice did not show ISO-induced galectin-3 upregulation. It was further revealed that cardiomyocyte-derived IL-18 induced galectin-3 expression in macrophages following ISO treatment. Moreover, galectin-3 deficiency suppressed ISO-induced cardiac inflammation and fibrosis without blocking ISO-induced IL-18 increase. Treatment with a galectin-3 inhibitor, but not a ß-blocker, one day after ISO treatment effectively attenuated cardiac inflammation and injury. In conclusion, galectin-3 is upregulated to exaggerate cardiac inflammation and injury following acute ß-AR activation, a galectin-3 inhibitor effectively blocks cardiac injury one day after ß-AR insult.

Composite protective effect of benzotriazole and 2-mercaptobenzothiazole on electroplated copper coating.

Benzotriazole (BTAH) and 2-mercaptobenzothiazole (MBT) are mixed to passivate electroplated copper coatings. The growth process of passive films is comprehensively analyzed from the surface potential, microstructure and chemical composition by potential-time curve, FESEM and XPS. Meanwhile, the corrosion resistance of copper coatings with different passivation treatments is evaluated by potentiodynamic polarization curves and electrochemical impedance spectroscopy. During the composite passivation process of BTAH and MBT, the copper coating undergoes the following steps: chemical dissolution of the copper coating, preferential adsorption of MBT, formation of Cu(i)-BTA complex film and Cu2O, and synergistic growth of Cu(i)-BTA and Cu(i)-MBT. A protective film with a thickness of about 233 nm, containing the inner layer of BTA-Cu(i) and MBT-Cu(i) and the outer layer of MBT-Cu(i) and Cu2O, is formed on the copper coating after composite passivation. The composite passivation film significantly improves the corrosion resistance of copper coatings, and its corrosion inhibition efficiency for copper coatings reaches 90.7%, which is far better than that produced by using BTAH or MBT alone.

IMM-H007 attenuates isoprenaline-induced cardiac fibrosis through targeting TGFß1 signaling pathway.

Upon chronic stress, ß-adrenergic receptor activation induces cardiac fibrosis and leads to heart failure. The small molecule compound IMM-H007 has demonstrated protective effects in cardiovascular diseases via activation of AMP-activated protein kinase (AMPK). This study aimed to investigate IMM-H007 effects on cardiac fibrosis induced by ß-adrenergic receptor activation. Because adenosine analogs also exert AMPK-independent effects, we assessed AMPK-dependent and -independent IMM-H007 effects in murine models of cardiac fibrosis. Continual subcutaneous injection of isoprenaline for 7 days caused cardiac fibrosis and cardiac dysfunction in mice in vivo. IMM-H007 attenuated isoprenaline-induced cardiac fibrosis, diastolic dysfunction, α-smooth muscle actin expression, and collagen I deposition in both wild-type and AMPKα2-/- mice. Moreover, IMM-H007 inhibited transforming growth factor ß1 (TGFß1) expression in wild-type, but not AMPKα2-/- mice. By contrast, IMM-H007 inhibited Smad2/3 signaling downstream of TGFß1 in both wild-type and AMPKα2-/- mice. Surface plasmon resonance and molecular docking experiments showed that IMM-H007 directly interacts with TGFß1, inhibits its binding to TGFß type II receptors, and downregulates the Smad2/3 signaling pathway downstream of TGFß1. These findings suggest that IMM-H007 inhibits isoprenaline-induced cardiac fibrosis via both AMPKα2-dependent and -independent mechanisms. IMM-H007 may be useful as a novel TGFß1 antagonist.

Membrane nanotubes facilitate the propagation of inflammatory injury in the heart upon overactivation of the ß-adrenergic receptor.

Acute sympathetic stress quickly induces cardiac inflammation and injury, suggesting that pathogenic signals rapidly spread among cardiac cells and that cell-to-cell communication may play an important role in the subsequent cardiac injury. However, the underlying mechanism of this response is unknown. Our previous study demonstrated that acute ß-adrenergic receptor (ß-AR) signaling activates inflammasomes in the heart, which triggers the inflammatory cascade. In the present study, ß-AR overactivation induced inflammasome activation in both the cardiomyocytes and cardiac fibroblasts (CFs) of mice hearts following a subcutaneous injection of isoproterenol (ISO, 5 mg/kg body weight), a selective agonist of ß-AR. In isolated cardiac cells, ISO treatment only activated the inflammasomes in the cardiomyocytes but not the CFs. These results demonstrated that inflammasome activation was propagated from cardiomyocytes to CFs in the mice hearts. Further investigation revealed that the inflammasomes were activated in the cocultured CFs that connected with cardiomyocytes via membrane nanotubes (MNTs), a novel membrane structure that mediates distant intercellular connections and communication. Disruption of the MNTs with the microfilament polymerization inhibitor cytochalasin D (Cyto D) attenuated the inflammasome activation in the cocultured CFs. In addition, the MNT-mediated inflammasome activation in the CFs was blocked by deficiency of the inflammasome component NOD-like receptor protein 3 (NLRP3) in the cardiomyocytes, but not NLRP3 deficiency in the CFs. Moreover, ISO induced pyroptosis in the CFs cocultured with cardiomyocytes, and this process was inhibited by disruption of the MNTs with Cyto D or by the NLRP3 inhibitor MCC950 and the caspase-1 inhibitor Z-YVAD-FMK (FMK). Our study revealed that MNTs facilitate the rapid propagation of inflammasome activation among cardiac cells to promote pyroptosis in the early phase of ß-adrenergic insult. Therefore, preventing inflammasome transfer is a potential therapeutic strategy to alleviate acute ß-AR overactivation-induced cardiac injury.

Paired box 6 inhibits cardiac fibroblast differentiation.

Cardiac fibroblast (CF) differentiation plays a crucial role in cardiac fibrosis, which is a specific manifestation distinguishing pathological cardiac hypertrophy from physiological hypertrophy. The DNA-binding activity of paired box 6 (Pax6) has been shown to be oppositely regulated in physiological and pathological hypertrophy; however, it remains unclear whether Pax6 is involved in CF differentiation during cardiac fibrosis. We found that Pax6 is expressed in the heart of and CFs isolated from adult mice. Moreover, angiotensin II (Ang II) induced the downregulation of Pax6 mRNA and protein expression in fibrotic heart tissue and cardiac myofibroblasts. Pax6 knockdown in CFs promoted the expression of the myofibroblast marker α-smooth muscle actin (α-SMA) and the synthesis of the extracellular matrix (ECM) proteins collagen I and fibronectin. Furthermore, we validated the ability of Pax6 to bind to the promoter regions of Cxcl10 and Il1r2 and the intronic region of Tgfb1. Pax6 knockdown in CFs decreased CXC chemokine 10 (CXCL10) and interleukin-1 receptor 2 (IL-1R2) expression and increased transforming growth factor ß1 (TGFß1) expression, mimicking the effects of Ang II. In conclusion, Pax6 exerts an inhibitory effect on CF differentiation and ECM synthesis by transcriptionally activating the expression of the anti-fibrotic factors CXCL10 and IL-1R2 and repressing the expression of the pro-fibrotic factor TGFß1. Therefore, maintaining Pax6 expression in CFs is essential for preventing CF differentiation, and provides a new therapeutic target for cardiac fibrosis.

Determination of Iron Valence States Around Pits and the Influence of Fe3+ on the Pitting Corrosion of 304 Stainless Steel.

Potassium ferricyanide and potassium ferrocyanide were used to observe and monitor the pitting corrosion of 304 stainless steel (SS) at anodic polarization in situ. The results show that there are Fe3+ ions around the corrosion pit when pitting occurs on 304 SS in NaCl aqueous solution. The effect of Fe3+ surrounded pits on the pitting corrosion was also studied by testing the electrochemical behavior of 304 SS in different Fe3+/Fe2+ solutions. The presence of Fe3+ leads to the positive shift of corrosion potential and the increase of corrosion rate of 304 SS. There are two possible reasons for this phenomenon. On the one hand, Fe3+ hydrolysis results in the decrease of pH value of solution. At the same iron ion concentration, the higher the Fe3+ ion concentration, the lower the solution pH value. On the other hand, Fe3+ may reduce on the electrode surface. The decrease of solution pH and the reduction of Fe3+ resulted in the acceleration of the corrosion rate.

α1-AR overactivation induces cardiac inflammation through NLRP3 inflammasome activation.

Acute sympathetic stress causes excessive secretion of catecholamines and induces cardiac injuries, which are mainly mediated by ß-adrenergic receptors (ß-ARs). However, α1-adrenergic receptors (α1-ARs) are also expressed in the heart and are activated upon acute sympathetic stress. In the present study, we investigated whether α1-AR activation induced cardiac inflammation and the underlying mechanisms. Male C57BL/6 mice were injected with a single dose of α1-AR agonist phenylephrine (PE, 5 or 10 mg/kg, s.c.) with or without pretreatment with α-AR antagonist prazosin (5 mg/kg, s.c.). PE injection caused cardiac dysfunction and cardiac inflammation, evidenced by the increased expression of inflammatory cytokine IL-6 and chemokines MCP-1 and MCP-5, as well as macrophage infiltration in myocardium. These effects were blocked by prazosin pretreatment. Furthermore, PE injection significantly increased the expression of NOD-like receptor protein 3 (NLRP3) and the cleavage of caspase-1 (p20) and interleukin-18 in the heart; similar results were observed in both Langendorff-perfused hearts and cultured cardiomyocytes following the treatment with PE (10 µM). Moreover, PE-induced NLRP3 inflammasome activation and cardiac inflammation was blocked in Nlrp3-/- mice compared with wild-type mice. In conclusion, α1-AR overactivation induces cardiac inflammation by activating NLRP3 inflammasomes.

Coupling Effects of pH and Dissolved Oxygen on the Corrosion Behavior and Mechanism of X80 Steel in Acidic Soil Simulated Solution.

In an acidic red soil environment, the corrosion mechanism of X80 steel may be closely related to the pH value and oxygen content, but it has not yet formed a systematic understanding. In this paper, the coupling effects of pH and dissolved oxygen on the corrosion behavior and mechanism of X80 steel in an acidic soil simulated solution were further analyzed by electrochemical methods and three-dimensional video microscope. Results showed that the hydrogen reduction reaction was almost the only cathode process in the anoxic and low pH system, and small and dense pits were present on the electrode surface. pH value increased, the pits decreased, but the size of pits increased. In the oxygen-adequate system, oxygen-consuming (OC) corrosion preferentially occurred, and a protective corrosion product layer (including FeOOH, Fe3O4, etc.) might be formed accordingly, but the proportion of hydrogen evolution (HE) increased and the product layer had defects at a low pH environment. The specific corrosion mechanism of X80 steel in an acidic soil simulated solution is described in the relevant models.

Metformin attenuates renal fibrosis in both AMPKα2-dependent and independent manners.

Metformin is a well-known AMP-activated protein kinase (AMPK) activator, and it has been shown to inhibit organ fibrosis. Whether AMPKα2 mediates metformin protection against renal fibrosis remains unknown. Here, we aimed to investigate the role of the AMPKα2 isoform in mediating the inhibitory effect of metformin on renal fibrosis. Unilateral ureteral obstruction (UUO) was used to induce renal fibrosis in wild-type (WT) and AMPKα2 knockout (AMPKα2-/- ) mice. Metformin treatment was initiated 3 days before UUO and was continued until 7 days after UUO. In WT mice, metformin significantly inhibited UUO-induced renal fibrosis. In AMPKα2-/- mice, metformin also tended to inhibit UUO-induced renal fibrosis. Specifically, metformin significantly reduced UUO-induced transforming growth factor ß1 (TGFß1) mRNA and protein expression in WT mice but not in AMPKα2-/- mice. In contrast, metformin reduced UUO-induced TGFß1 downstream Smad3 phosphorylation in both WT and AMPKα2-/- mice, suggesting that this regulation occurs in an AMPKα2-independent manner. In conclusion, the underlying mechanisms for the protective effects of metformin against renal fibrosis include AMPKα2-dependent targeting of TGFß1 production and AMPKα2-independent targeting of TGFß1 downstream signalling. In this regard, metformin has an advantage over other AMPK activators for the treatment of renal fibrosis.

A portable system for on-site quantification of formaldehyde in air based on G-quadruplex halves coupled with A smartphone reader.

A portable colorimetric determination system based on G-quadruplex DNAzyme integrated with a smartphone was developed to quantitatively detect formaldehyde (FA). The method is based on the oxidation of FA by H2O2, which prevents the 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS)­H2O2 reaction catalyzed by G-quadruplex halves. With the addition of FA, the amount of the blue-green-colored free-radical cation (ABTS+) was reduced. The concentration of FA can be determined by monitoring this competitive reaction with a UV-vis spectrometer. Response surface methodology (RSM) and Box-Behnken design (BBD) were applied for optimization of the colorimetric assay. A smartphone-based colorimetric reader was also developed, which could display FA responses and report the concentration in real-time. The system could detect FA as low as 0.01 µM with a linear range of 1-600 µM. Taking advantages of smartphone and DNAzyme, the assay provides great potential for its practical application as a home testing or on-site analysis with high sensitivity and selectivity.

A one-step approach to the large-scale synthesis of functionalized MoS2 nanosheets by ionic liquid assisted grinding.

A prerequisite for exploiting most proposed applications for MoS2 is the availability of water-dispersible functionalized MoS2 nanosheets in large quantities. Here we report one-step synthesis and surface functionalization of MoS2 nanosheets by a facile ionic liquid assisted grinding method in the presence of chitosan. The selected ionic liquid with suitable surface energy could efficiently overcome the van der Waals force between the MoS2 layers. Meanwhile, chitosan molecules bind to the plane of MoS2 sheets non-covalently, which prevents the reassembling of exfoliated MoS2 sheets and facilitates the exfoliation progress. The obtained chitosan functionalized MoS2 nanosheets possess favorable stability and biocompatibility, which renders them as promising and biocompatible near-infrared agents for photothermal ablation of cancer. This contribution provides a facile way for the green, one-step and large-scale synthesis of advanced functional MoS2 materials.