Loss of α7nAChR enhances endothelial-to-mesenchymal transition after myocardial infarction via NF-κB activation.

The myocardial fibrosis in response to myocardial infarction (MI) is closely related to the dysbalance of endothelial-to-mesenchymal transition (EndMT). Although numerous reports indicate that α7 nicotinic acetylcholine receptor (α7nAChR) activates the cholinergic anti-inflammatory pathway (CAP) to regulate the magnitude of inflammatory responses, the role of α7nAChR in myocardial fibrosis, as well as the underlying mechanisms, have not been elucidated. In this study, we evaluated cardiac function, fibrosis, and EndMT signaling using a mouse model of MI and interleukin (IL)-1ß-induced human cardiac microvascular endothelial cells (HCMECs). In vivo, α7nAChR deletion increased cardiac dysfunction, exacerbated the cardiac inflammatory response, and NF-κB activation, and enhanced EndMT, as shown by higher expression levels of fibroblast markers (FSP-1, α-SMA, collagen I, Snail) and decreased levels of the FGFR1, glucocorticoid receptor (GR) and endothelial marker (CD31) compared to wild-type mice. In vitro, the pharmacological activation of α7nAChR with PNU282987 significantly inhibited IL-1ß-induced EndMT, as shown by a reduced transition to the fibroblast-like phenotype and the expression of fibrotic markers. Moreover, the IL-1ß-mediated activation of NF-κB pathway was suppressed by PNU282987. This anti-EndMT effect of α7nAChR was associated with regulation of Snail. Furthermore, Western blot analysis further revealed that the GR antagonist RU38486 could partially counteract the effect of PNU282987 on NF-κB expression. In conclusion, our results show that α7nAChR is involved in cardiac fibrosis by inhibiting EndMT, providing a novel approach to the treatment of MI.

Activation of the alpha 7 nicotinic acetylcholine receptor mitigates osteoarthritis progression by inhibiting NF-κB/NLRP3 inflammasome activation and enhancing autophagy.

Osteoarthritis (OA) is a chronic degenerative joint disease characterized by cartilage degradation. Alpha 7 nicotinic acetylcholine receptor (α7nAChR) is associated with inflammatory and metabolic responses in OA. However, the mechanisms underlying the pathological process of OA remain unclear. The aim of the present study was to examine the role and mechanisms of α7nAChR-mediated autophagy and anti-inflammatory response in chondroprotection. Monosodium iodoacetate (MIA)-induced Wistar rat OA model was used to assess the in vivo effects of the ɑ7nAChR agonist (PNU-282987). The histopathological characteristics of OA were evaluated by immunohistochemistry (IHC), and the levels of autophagy markers were determined by western blotting and transmission electron microscopy. The anti-inflammatory effect of the ɑ7nAChR agonist was assessed by IHC, quantitative real-time polymerase chain reaction, and western blotting. Parallel experiments to determine the molecular mechanisms through which the ɑ7nAChR agonist prevents OA were performed using interleukin-1ß (IL-1ß)-treated chondrocytes. Our results showed that PNU-282987 reduced cartilage degeneration and matrix metalloproteinase (MMP)-1 and MMP-13 expressions. Activating α7nAChR with PNU-282987 significantly promoted MIA/IL-1ß-induced chondrocyte autophagy, as demonstrated by the increase in LC3-II/LC3-I ratio, Beclin-1 levels, and autophagosome number. Furthermore, treating chondrocyte with ULK1 siRNA attenuated the PNU282987-induced enhancement of LC3-II/LC3-I ratio and Beclin-1 level. Additionally, PNU282987 suppressed NF-κB/NLRP3 inflammasome activation by inhibiting the ROS/TXNIP pathway and suppressed tumor necrosis factor-ɑ and IL-1ß secretion in MIA/IL-1ß-treated chondrocytes. Our results demonstrate that the activation of α7nAChR promotes chondrocyte autophagy and attenuates inflammation to mitigate OA progression, providing a novel target for the treatment of OA.

Protective effects of Notch1 signaling activation against high glucose-induced myocardial cell injury: Analysis of its mechanisms of action.

Notch1 plays an important role in cardiomyocyte apoptosis and cardiac fibrosis. However, the effects of Notch1 on diabetic cardiomyopathy (DCM) and its mechanisms of action remain unclear. In the present study, we sought to investigate the role of Notch1 in, and its effects on high glucose (HG)­induced myocardial cell apoptosis and myocardial fibrosis. H9c2 cells exposed to HG were used to establish an in vitro model of myocardial injury. The H9c2 cells were cultured with normal glucose (NG; 5.5 mmol/L­ NG), and were then epxosed to HG (33 mmol/L­ HG), a γ­secretase inhibitor (DAPT), and were transfected with a lentiviral vector containing the Notch1 intracellular domain (N1ICD; lentivirus­N1ICD). At 72 h following exposure to HG, DAPT or transfection with lentivirus­N1ICD, myocardial cell viability was assessed using a Cell Counting kit­8 (CCK­8) assay. Cell apoptosis was measured using Annexin V/propidium iodide (PI) double staining and flow cytometry. The mRNA expression levels of hairy/enhancer of split­1 (Hes­1) and hairy/enhancer-of-split related with YRPW motif­1 (Hey­1) were measured by quantitative PCR (qPCR), while the protein expression of N1ICD, Bax, Bcl­2, transforming growth factor­ß1 (TGF­ß1) and connective tissue growth factor (CTGF), and the levels of phosphorylated (p-)AKT, total (t-)AKT, p­phosphoinositide 3-kinase (PI3K) and t­AKT were measured by western blot analysis. Our results revealed that exposure to HG induced apoptosis and upregulated TGF­ß1 and CTGF expression in the H9c2 cardiomyocytes. Furthermore, the Notch1 and PI3K/AKT signaling pathways were activated following transfection with lentivirus­N1ICD, and this activation enhanced myocardial cell viability, prevented cardiomyocyte apoptosis and decreased TGF­ß1 and CTGF expression. On the whole, our data demonstrate that the overexpression of Notch1 prevents HG­induced cardiomyocyte apoptosis and decreases CTGF expression in H9c2 cells exposed to HG. Thus, Notch1 may be used to prevent the development of DCM and to inhibit cardiac fibrosis. The findings of our study may prove to be of use in the development of novel therapeutic strategies for DCM.