Objective: Hydrogen sulfide (H 2 S) has been reported to be a gasotransmitter which regulates cardiovascular homeostasis. The present study aims to examine the hypothesis that hydrogen sulfide is able to promote angiogenesis. Methods: Angiogenesis was assessed using in vitro parameters (i.e. endothelial cell proliferation, adhesion, transwell migration assay, scratched wound healing and formation of tube-like structure) and in vivo by assessing neovascularization in mice. Phosphorylation of Akt was measured using Western blot analysis. Results: Exogenously administered NaHS (H 2 S donor) concentration-dependently (10-20 μmol/l) increased cell growth, migration, scratched wound healing and tube-like structure formation in cultured endothelial cells. These effects of NaHS on endothelial wound healing and tube-like structure formation were prevented by either the phosphatidylinositol 3-kinase (PI3K) inhibitor LY 294002 (5 μmol/l) or transfection of a dominant-negative mutant of Akt. NaHS increased Akt phosphorylation and this effect was also blocked by either LY 294002 or wortmannin (25 nmol/l). NaHS did not significantly alter the levels of vascular endothelial growth factor, mRNA expression of fibroblast growth factor and angiopoietin-1, or nitric oxide metabolites. NaHS treatment (10 and 50 μmol kg − 1 day − 1 ) significantly promoted neovascularization in vivo in mice. Conclusion:The present study reports a novel proangiogenic role of H 2 S which is dependent on activation of Akt.

H(2)S (hydrogen sulfide), regarded as the third gaseous transmitter, is implicated in ulcerative colitis and colorectal cancers. The present study investigates the effects of H(2)S on cell proliferation in human colon cancer HCT 116 cells and SW480 cells. We identified the two key enzymes, CBS and CSE, for H(2)S synthesis in HCT 116 cells. An exogenously administered H(2)S donor NaHS induced cell proliferation in a concentration-dependent manner, with optimal proliferative concentration at 200 micromol/l. NaHS administration increased Akt and ERK phosphorylation. Blockade of Akt and ERK activation attenuated NaHS-induced cell proliferation. Cell-cycle analysis showed that NaHS treatment for 6 h decreased the proportion of cells in G(0)-G(1) phase and increased the proportion of cells in S phase. Protein expressions of Cyclin D1 and PCNA (proliferating cell nuclear antigen) were not altered, but the cyclin-dependent kinase inhibitor p21(Waf1/Cip1) was inhibited significantly by NaHS treatment. NaHS significantly reduced NO metabolite levels. In conclusion, NaHS induced human colon cancer cell proliferation. This effect might be mediated by the increase of Akt and ERK phosphorylation and the decrease of p21(Waf1/Cip1) expression and NO production. The results suggested a role for H(2)S in human colonic cancer development.

It is not known whether H(2)S can promote angiogenesis with improvement of regional blood flow in ischemic organs. Sodium hydrosulfide (NaHS, a H(2)S donor) was administered once a day for 4 w following femoral artery ligation. Collateral vessel growth, capillary density, regional tissue blood flow, the expression of endothelial growth factor (VEGF), VEGF receptor 2 (VEGFR2) and Akt were examined during or at the end of the treatment period. NaHS treatment significantly increased collateral vessel growth, capillary density, and regional tissue blood flow in ischemic hind limb muscles compared with the controls. These effects were associated with an increase in VEGF expression in the skeletal muscles and VEGFR2 phosphorylation in the neighboring vascular endothelial cells, suggesting a role of VEGF in mediating the NaHS effects in a cell-cell interaction pattern. Moreover, NaHS treatment also resulted in an increase in Akt phosphorylation in ischemic hind limb muscles. In conclusion, our observations with NaHS strongly suggest that H(2)S is a proangiogenic factor in chronic ischemia. The proangiogenic effect of NaHS may be mediated by interaction between the upregulated VEGF in the skeletal muscle cells and the VEGFR2 as well as its downstream signaling element Akt in the vascular endothelial cells.

Aims: The potential receptor for hydrogen sulfide (H 2 S) remains unknown. Results: H 2 S could directly activate vascular endothelial growth factor receptor 2 (VEGFR2) and that a small interfering RNA (siRNA)-mediated knockdown of VEGFR2 inhibited H 2 S-induced migration of human vascular endothelial cells. H 2 S promoted angiogenesis in Matrigel plug assay in mice and this effect was attenuated by a VEGF receptor inhibitor. Using tandem mass spectrometry (MS), we identified a new disulfide complex located between Cys1045 and Cys1024 within VEGFR2 that was labile to H 2 S-mediated modification. Kinase activity of the mutant VEGFR2 (C1045A) devoid of the Cys1045-Cys1024 disulfide bond was significantly higher than wild-type VEGFR2. Transfection with vectors expressing VEGFR2 (C1045A) caused a significant increase in cell migration, while the migrationpromoting effect of H 2 S disappeared in the cells transfected with VEGFR2 (C1045A). Therefore, the Cys1045-Cys1024 disulfide bond serves as an intrinsic inhibitory motif and functions as a molecular switch for H 2 S. The formation of the Cys1045-Cys1024 disulfide bond disrupted the integrity of the active conformation of VEGFR2. Breaking the Cys1045-Cys1024 disulfide bond recovered the active conformation of VEGFR2. This motif was prone to a nucleophilic attack by H 2 S via an interaction of their frontier molecular orbitals. siRNA-mediated knockdown of cystathionine c-lyase attenuated migration of vascular endothelial cells induced by VEGF or moderate hypoxia.

Objective: Accurate QRS complex detection is essential for electrocardiography (ECG) diagnosis. Many proposed algorithms don't perform satisfactorily on noisy and arrhythmia ECGs. The purpose of this study is to develop a noise resistant and generalizable method to detect QRS complexes accurately. Methods: Two deep learning models based on multi-dilated convolutional blocks are proposed. One model (CNN) is mainly composed of convolutional blocks and Squeeze-and-Excitation networks (SENet). The other model (CRNN) contains a hybrid convolutional and recurrent neural network. With 5-fold cross-validation approach the models are trained and tested on four open-access ECG databases: the China Physiological Signal Challenge (2019) database (CPSCDB), the MIT-BIH Noise Stress Test Database (NSTDB), the MIT-BIH Arrhythmia Database (MITDB) and the QT Database (QTDB). Results: The F1 score of CNN model on CPSCDB, NSTDB, MITDB and QTDB are 0.9929, 0.9892, 0.9994 and 0.9998 respectively. The F1 score of CRNN model on these four databases are 0.9947, 0.9953, 0.9995 and 0.9998 respectively. The ensemble of both models scored the first place in the China Physiological Signal Challenge (2019). Conclusion: The proposed models achieve state-of-the-art performance in QRS complex detection and show good generalization on different databases. This work might help make better ECG diagnosis. INDEX TERMS Convolutional neural network, deep learning, electrocardiography, QRS complex, recurrent neural network.