Hydrogen sulfide is an endogenous potentiator of T cell activation.

H(2)S is an endogenous signaling molecule that may act via protein sulfhydrylation to regulate various physiological functions. H(2)S is also a byproduct of dietary sulfate metabolism by gut bacteria. Inflammatory bowel diseases such as ulcerative colitis are associated with an increase in the colonization of the intestine by sulfate reducing bacteria along with an increase in H(2)S production. Consistent with its increased production, H(2)S is implicated as a mediator of ulcerative colitis both in its genesis or maintenance. As T cells are well established mediators of inflammatory bowel disease, we investigated the effect of H(2)S exposure on T cell activation. Using primary mouse T lymphocytes (CD3+), OT-II CD4+ T cells, and the human Jurkat T cell line, we show that physiological levels of H(2)S potentiate TCR-induced activation. Nanomolar levels of H(2)S (50-500 nM) enhance T cell activation assessed by CD69 expression, interleukin-2 expression, and CD25 levels. Exposure of T cells to H(2)S dose-dependently enhances TCR-stimulated proliferation with a maximum at 300 nM (30% increase, p < 0.01). Furthermore, activation increases the capacity of T cells to make H(2)S via increased expression of cystathionine γ-lyase and cystathionine ß-synthase. Disrupting this response by silencing these H(2)S producing enzymes impairs T cell activation, and proliferation and can be rescued by the addition of 300 nM H(2)S. Thus, H(2)S represents a novel autocrine immunomodulatory molecule in T cells.

Cystathionine ß-synthase mediated PRRX2/IL-6/STAT3 inactivation suppresses Tregs infiltration and induces apoptosis to inhibit HCC carcinogenesis.

BACKGROUND: Hepatocellular carcinoma (HCC) is characterized by inflammation and immunopathogenesis. Accumulating evidence has shown that the cystathionine ß-synthase/hydrogen sulfide (CBS/H2S) axis is involved in the regulation of inflammation. However, roles of CBS in HCC development and immune evasion have not been systematically investigated, and their underlying mechanisms remain elusive. Here, we investigated the roles of CBS in tumor cells and tumor microenvironment of HCC. METHODS: 236 HCC samples were collected to detect the expression of CBS, cleaved Caspase-3 and paired related homeobox 2 (PRRX2) and the number of immune cells. HCC cell lines were employed to examine the effects of CBS on cellular viability, apoptosis and signaling in vitro. Cbs heterozygous knockout mice, C57BL/6 mice, nude mice and non-obese diabetic severe combined immunodeficiency mice were used to investigate the in vivo functions of CBS. RESULTS: Downregulation of CBS was observed in HCC, and low expression of CBS predicted poor prognosis in HCC patients. CBS overexpression dramatically promoted cellular apoptosis in vitro and inhibited tumor growth in vivo. Activation of the Cbs/H2S axis also reduced the abundance of tumor-infiltrating Tregs, while Cbs deficiency promoted Tregs-mediated immune evasion and boosted tumor growth in Cbs heterozygous knockout mice. Mechanistically, CBS facilitated the expression cleaved Caspase-3 in tumor cells, and on the other hand, suppressed Foxp3 expression in Tregs via inactivating IL-6/STAT3 pathway. As a transcription factor of IL-6, PRRX2 was reduced by CBS. Additionally, miR-24-3p was proven to be an upstream suppressor of CBS in HCC. CONCLUSIONS: Our results indicate the antitumor function of CBS in HCC by inactivation of the PRRX2/IL-6/STAT3 pathway, which may serve as a potential target for HCC clinical immunotherapy.

Trophoblast H2S Maintains Early Pregnancy via Regulating Maternal-Fetal Interface Immune Hemostasis.

CONTEXT: Dysregulated immune hemostasis occurs in unexplained recurrent spontaneous abortion (URSA). Synthesized by cystathionine ß-synthase (CBS) and cystathionine γ-lyase (CSE), hydrogen sulfide (H2S) promotes regulatory T-cell differentiation and regulates immune hemostasis; yet, its role in URSA is elusive. OBJECTIVE: To determine if H2S plays a role in early pregnancy and if dysregulated H2S signaling results in recurrent spontaneous abortion. DESIGN: First trimester placenta villi and decidua were collected from normal and URSA pregnancies. Protein expression was examined by immunohistochemistry and immunoblotting. Human trophoblast HTR8/SVneo and JEG3 cells were treated with H2S donors; HTR8/SVneo cells were transfected with CBS ribonucleic acid interference (RNAi) or complementary deoxyribonucleic acid. Cell migration and invasion were determined by transwell assays; trophoblast transcriptomes were determined by RNA sequencing (RNA-seq). Wild-type, CBS-deficient, and CBA/J × DBA/2 mice were treated with CBS and CSE inhibitors or H2S donors to determine the role of H2S in early pregnancy in vivo. RESULTS: CBS and CSE proteins showed cell-specific expressions, but only CBS decreased in the villous cytotrophoblast in URSA versus normal participants. H2S donors promoted migration and invasion and MMP-2 and VEGF expression in human placenta trophoblast cells that contain SV40 viral deoxyribonucleic acid sequences (HTR8/SVneo) and human placenta trophoblast cells (JEG3 cells), similar to forced CBS expression in HTR8/SVneo cells. The CBS-responsive transcriptomes in HTR8/SVneo cells contained differentially regulated genes (ie, interleukin-1 receptor and prostaglandin-endoperoxide synthase 2) that are associated with nuclear factor-κB-mediated inflammatory response. In vivo, dysregulated CBS/H2S signaling significantly increased embryonic resorption and decidual T-helper 1/T-helper 2 imbalance in mice, which was partially rescued by H2S donors. CONCLUSION: CBS/H2S signaling maintains early pregnancy, possibly via regulating maternal-fetal interface immune hemostasis, offering opportunities for H2S-based immunotherapies for URSA.

Down-regulation of endogenous hydrogen sulphide pathway in nasal mucosa of allergic rhinitis in guinea pigs.

BACKGROUND: The present study was designed to explore the possible changes in endogenous hydrogen sulphide (H(2)S), a novel gasotransmitter, on the pathogenesis of allergic rhinitis (AR). METHODS: AR guinea pig model was established by nasal ovalbumin sensitisation. Guinea pigs were divided into four groups: Saline control, AR sensitised, sodium hydrosulphide (NaHS) treated, and propargylglycine (PPG) treated group. The frequency of sneezing and nose rubbing was recorded. Leukocyte infiltration in nasal lavage fluid (NLF) and plasma H(2)S level were measured. Expression of Cystathionine-beta-synthase (CBS) and Cystathionine-gamma-lyase (CSE) mRNA as H(2)S-producing enzymes in nasal mucosa was determined by real time Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR). RESULTS: The frequency of sneezing and nose rubbing, and levels of leukocyte infiltration in NLF were higher than those of control (P<0.01), but plasma H(2)S in sensitised guinea pigs was lower than those of control (P<0.05). From the results of RT-PCR, it was found that the expression of CSE was higher than CBS in nasal mucosa, and in sensitised guinea pigs it was lower than that of control (P<0.05). NaHS successfully increased the level of H(2)S and alleviated the symptoms of AR accompanied by up-regulation of CSE as compared with AR group (P<0.05). PPG significantly suppressed the expression of CSE and decreased the H(2)S level, yet also aggravated the symptoms of AR. CONCLUSION: H(2)S level may be negatively correlated with the process of inflammation and positively correlated with expression of CSE in nasal mucosa. The endogenous H(2)S pathway is down-regulated in AR.

Immunochemical studies on cultured fibroblasts from patients with homocystinuria due to cystathionine beta-synthase deficiency.

Fibroblast extracts from 20 individuals with homocystinuria due to cystathionine beta-synthase deficiency were analyzed for the presence of immunoreactive synthase antigen as cross-reacting material (CRM). CRM was quantitated by competitive and direct immunotitration using rabbit antiserum against homogeneous human liver synthase. The lower limit of sensitivity for detection of CRM was 1.5% of the amount of synthase antigen in control extracts. Each of 14 mutant extracts with detectable synthase activity had detectable CRM ranging from 5% to 100% of the amount found in control extracts. No statistically significant correlation was observed between the percent residual activity and the percent CRM. Of six mutant extracts without measurable catalytic activity, three had no detectable CRM, while three had 13%, 17%, and 26% CRM, respectively. These results extend our information about the biochemical heterogeneity previously found in synthase deficiency, and emphasize that such deficiency is caused by a wide array of mutations affecting the structural locus for cystathionine beta-synthase.