Specific α7 nicotinic acetylcholine receptor agonist ameliorates isoproterenol-induced cardiac remodelling in mice through TGF-ß1/Smad3 pathway.

It is well-accepted that inflammation plays an important role in the development of cardiac remodelling and that therapeutic approaches targeting inflammation can inhibit cardiac remodelling. Although a large amount of evidence indicates that activation of α7 nicotinic acetylcholine receptor (α7nAChR) causes an anti-inflammatory effect, the role of α7nAChR in cardiac remodelling and the underlying mechanism have not been established. To investigate the effect of the specific α7nAChR agonist, PNU282987, on cardiac remodelling induced by isoproterenol (ISO 60 mg/kg per day) in mice, the cardiomyocyte cross-sectional area (CSA) and collagen volume fraction were evaluated by hematoxylin and eosin (HE) and Masson staining, respectively. Cardiac function and ventricular wall thickness were measured by echocardiography. The protein expressions of collagen I, matrix metalloproteinase 9 (MMP-9), transforming growth factor ß1 (TGF-ß1), and Smad3 were analyzed by Western blot. ISO-induced cardiac hypertrophy, characterized by an increase in the heart weight/body weight ratio, CSA and ventricular wall thickness. Moreover, cardiac fibrosis indices, such as collagen volume fraction, MMP-9 and collagen I protein expression, were also increased by ISO. PNU282987 not only attenuated cardiac hypertrophy but also decreased the cardiac fibrosis induced by ISO. Furthermore, PNU282987 suppressed TGF-ß1 protein expression and the phosphorylation of Smad3 induced by ISO. In conclusion, PNU282987 ameliorated the cardiac remodelling induced by ISO, which may be related to the TGF-ß1/Smad3 pathway. These data imply that the α7nAChR may represent a novel therapeutic target for cardiac remodelling in many cardiovascular diseases.

Acetylcholine Inhibits LPS-Induced MMP-9 Production and Cell Migration via the α7 nAChR-JAK2/STAT3 Pathway in RAW264.7 Cells.

BACKGROUND: Excessive activation of matrix metalloproteinase 9 (MMP-9) has been found in several inflammatory diseases. Previous studies have shown that acetylcholine (ACh) reduced the levels of pro-inflammatory cytokines and decreased tissue damage. Therefore, this study was designed to explore the potential effects and mechanisms of ACh on MMP-9 production and cell migration in response to lipopolysaccharide (LPS) stimulation in RAW264.7 cells. METHODS: MMP-9 expression and activity were induced by LPS in RAW264.7 cells, and examined by real-time PCR, western blotting and gelatin zymography, respectively. ELISA was used to determine the changes in MMP-9 secretion among the groups. Macrophage migration was evaluated using transwell migration assay. Knockdown of α7 nicotinic acetylcholine receptor (α7 nAChR) expression was performed using siRNA transfection. RESULTS: Pre-treatment with ACh inhibited LPS-induced MMP-9 production and macrophage migration in RAW264.7 cells. These effects were abolished by the α7 nAChR antagonist methyllycaconitine (MLA) and α7 nAChR siRNA. The α7 nAChR agonist PNU282987 was found to have an effect similar to that of ACh. Moreover, ACh enhanced the expression of JAK2 and STAT3, and the JAK2 inhibitor AG490 and the STAT3 inhibitor static restored the effect of ACh. Meanwhile, ACh decreased the phosphorylation and nuclear translocation of NF-κB, and this effect was abrogated in the presence of MLA. In addition, the JAK2 and STAT3 inhibitor abolished the inhibitory effects of ACh on phosphorylation of NF-κB. CONCLUSIONS: Activation of α7 nAChR by ACh inhibited LPS-induced MMP-9 production and macrophage migration through the JAK2/STAT3 signaling pathway. These results provide novel insights into the anti-inflammatory effects and mechanisms of ACh.