Cystathionine γ-lyase-derived H2S negatively regulates thymic egress via allosteric inhibition of sphingosine-1-phosphate lyase.

Thymic egress is a crucial process for thymocyte maturation, strictly regulated by sphingosine-1-phosphate lyase (S1PL). Recently, cystathionine γ-lyase (CSE), one of the enzymes producing hydrogen sulfide (H2S), has emerged as a vital immune process regulator. However, the molecular connection between CSE, H2S and thymic egress remains largely unexplored. In this study, we investigated the regulatory function of CSE in the thymic egress of immune cells. We showed that genetic knockout of CSE or pharmacological inhibition by CSE enzyme inhibitor NSC4056 or D,L-propargylglycine (PAG) significantly enhanced the migration of mature lymphocytes and monocytes from the thymus to the peripheral blood, and this redistribution effect could be reversed by treatment with NaHS, an exogenous donor of H2S. In addition, the CSE-generated H2S significantly increased the levels of S1P in the peripheral blood, thymus and spleen of mice, suppressed the production of proinflammatory cytokines and rescued pathogen-induced sepsis in cells and in vivo. Notably, H2S or polysulfide inhibited S1PL activity in cells and an in vitro purified enzyme assay. We found that this inhibition relied on a newly identified C203XC205 redox motif adjacent to the enzyme's active site, shedding light on the biochemical mechanism of S1PL regulation. In conclusion, this study uncovers a new function and mechanism for CSE-derived H2S in thymic egress and provides a potential drug target for treating S1P-related immune diseases.

Design and fabrication of an integrated heart-on-a-chip platform for construction of cardiac tissue from human iPSC-derived cardiomyocytes and in situ evaluation of physiological function.

In vitro model of the human cardiac tissues generated from human induced pluripotent stem cells (hiPSCs) could facilitate drug discovery and patient-specific studies of physiology and disease. However, the immature state of hiPSC-derived cardiomyocytes (hiPSC-CMs) compared to adult myocardium is a key defect that must be overcome to enable the potential applications of hiPSC-CMs in drug testing. For this purpose, we developed a heart-on-a-chip device that contains microfluidic channels for long-term dynamic culture of cells, platinum wire electrodes for electrical stimulation of hiPSC-CMs, and gold electrode arrays as acquisition electrodes for real-time recording electrophysiological signals of cardiac tissues. Human iPSC-CMs cultured on biocompatible hydrogels in the chip chamber can be electrically stimulated to prompt the maturation of cardiomyocytes (CMs) and generate functional cardiac tissues. Drug tests were performed with calcium transient measurements to evaluate drug responsiveness of electrical stimulated and unstimulated cardiac tissues. The results show that only the electrical-stimulated cardiac tissues respond correctly to drug treatment of verapamil and isoprenaline, indicating the reliability of this engineered cardiac tissues for drug testing. The above integrated heart-on-a-chip device provides a promising platform for drug efficacy testing and cardiactoxicity.

[Determination of HLA-DRB1 gene polymorphism by PCR-SBT in Lahu ethnic group of Yunnan, China].

The HLA-DRB1 gene polymorphism in Lahu ethnic of Yunnan, China was the first time investigated using high resolution PCR-SBT method, which is based on sequences of HLA-DRB1 Intron 1 and Intron 2 and with our improvement. From 55 individuals of Lahu ethnic 16 DRB1 alleles were detected. The three most common alleles were HLA-DRB1 * 12021(30.909%), 09012(15.455%), 15011(13.636%), and they covered 60% of the total alleles detected from Lahu ethnic.HLA-DRB1 * 1413, * 11081, * 1312, * 1418, * 1504 were the first time detected in the Chinese, and were very rare in worldwide ethnic groups. With comparison of HLA-DRB1 gene frequencies between various ethnic groups we analyzed the characteristics of HLA-DRB1 gene distribution in worldwide populations,and constructed the phylogenetic tree by Neighbor-joining method and Nei measure of genetic distance. The result showed Lahu ethnic obviously belong to the Chinese South ethnic groups and can't trace its origin from northern groups with the HLA-DRB1 genetic data. The preliminary explanations about the contradiction were given in this paper.