Sulfide induces apoptosis and Rho kinase-dependent cell blebbing in Jurkat cells

Intracellular hydrogen sulfide induces stress granule formation and translational repression through eIF2α phosphorylation

Acute exposure to high concentrations of hydrogen sulfide (H2S), a toxic gaseous substance, can cause potentially lethal respiratory damages. Stress granules (SGs) are cytoprotective membrane-less intracellular organelles formed transiently in response to various stressors. We examined SG formation and the underlying molecular mechanism following exposure to high concentrations of H2S using human bronchial BEAS-2B (BEAS) and GFP-tagged G3BP1-stably transfected CHO cells. We first examined the changes in intracellular H2S concentration by NaHS exposure. Qualitative and quantitative analyses revealed that intracellular H2S levels rapidly increased after NaHS exposure and accumulated in cells dose dependently. In terms of the response to H2S taken up after exposure to 2.5-10 mM NaHS, both cell lines formed discrete SG assemblies within 1 h. SG formation induced by NaHS exposure was enhanced by treatment with glutathione (GSH) or thioredoxin (Trx) inhibitor but suppressed by treatment with a PERK inhibitor or integrated stress response inhibitor. Levels of phosphorylation of eIF2 α, which is essential for canonical SG formation, were significantly and dose-dependently increased in NaHS-exposed BEAS cells. Phosphorylation of eIF2α was further increased by GSH or Trx inhibitor treatment. These results suggest that GSH and Trx play protective roles in H2S-induced SG formation. PERK, a kinase of eIF2α, might activate the pathway partially. Levels of newly synthesized proteins were markedly reduced in NaHS-exposed cells. In summary, when humans inhale high concentrations of H2S, H2S is rapidly taken up by pulmonary cells and induces SG formation and translational repression via eIF2α phosphorylation, thereby protecting against cell death.

A narrative review of multiple mechanisms of progranulin in cancer: a potential target for anti-cancer therapy

Progranulin (PGRN) is an autocrine growth factor and has important effects on regulation of cell growth, motility, tissue repair and embryonic development. Recent years, several researches found the expression of PGRN was at higher levels in a number of cancer cells and its high levels are associated with poor outcome of patients. More and more studies investigated the role of PGRN in cancer and found PGRN exerted various biological functions in cancer cells, such as promoting proliferation, inhibiting apoptosis, inducing migration and invasion of cells, accelerating angiogenesis and enhancing the effectiveness of chemoresistance and radiation. Now the effects of PGRN have been demonstrated in several cancers, including breast cancer, lung cancer, and bladder cancer. In addition, several signaling pathways and molecules are involved in the effects of PGRN on cancer cells, including Akt, mitogen-activated protein kinase (MAPK), vascular endothelial growth factor (VEGF) and cyclin D1. Therefore, PGRN is probably a significant diagnostic and prognostic biomarker for cancer and may be a potential target for anti-cancer therapy. Here, we reviewed the advancing field of PGRN in cancer as well as several signaling pathways activated by PGRN and confirmed PGRN is a key role in cancer. Moreover, future studies are still necessary to elucidate the biological functions and signaling pathways of PGRN in cancer.

Hydrogen sulfide inhalation-induced immune damage is involved in oxidative stress, inflammation, apoptosis and the Th1/Th2 imbalance in broiler bursa of Fabricius

Hydrogen sulfide (H₂S) is widely accepted to be a signaling molecule that exhibits some potentially beneficial therapeutic effects at physiological concentrations. At elevated levels, H₂S is highly toxic and has a negative effect on human health and animal welfare. Studies have shown that H₂S exposure induces an immune function in mice, but there are few studies of the effect of continuous H₂S exposure on immune organs in poultry. In this study, one-day-old broilers were selected and exposed to 4 or 20 ppm of H₂S gas for 14, 28 and 42 days of age. After exposure, the bursa of Fabricius (BF) was harvested. The results showed that continuous H₂S exposure reduced the body weight, abdominal fat percentage, and antibody titer in broilers. H₂S exposure also decreased mRNA expression of IgA, IgM and IgG in the broiler BF. A histological study revealed obvious nuclear debris, and a few vacuoles in the BF, and an ultrastructural study revealed mitochondrial and nuclear damage to BF cells after H₂S exposure for 42 d. Terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) assay suggested H₂S exposure remarkably increased the number of TUNEL positive nuclei and significantly increased apoptotic index. The expression of apoptotic genes also confirmed that H₂S inhalation damaged the broiler BF. Increased cytokines and reduced antioxidant responses were detected in the BF after exposure to H₂S. Cytokines promoted inflammation and caused a Th1/Th2 imbalance. We suggest that continuous H₂S intoxication triggers oxidative stress, inflammation, apoptosis and a Th1/Th2 imbalance in the BF, leading to immune injury in broilers.

Regulation of Cellular Redox Signaling by Matricellular Proteins in Vascular Biology, Immunology, and Cancer

SIGNIFICANCE

In contrast to structural elements of the extracellular matrix, matricellular proteins appear transiently during development and injury responses, but their sustained expression can contribute to chronic disease. Through interactions with other matrix components and specific cell surface receptors, matricellular proteins regulate multiple signaling pathways, including those mediated by reactive oxygen and nitrogen species and H2S. Dysregulation of matricellular proteins contributes to the pathogenesis of vascular diseases and cancer. Defining the molecular mechanisms and receptors involved is revealing new therapeutic opportunities. Recent Advances: Thrombospondin-1 (TSP1) regulates NO, H2S, and superoxide production and signaling in several cell types. The TSP1 receptor CD47 plays a central role in inhibition of NO signaling, but other TSP1 receptors also modulate redox signaling. The matricellular protein CCN1 engages some of the same receptors to regulate redox signaling, and ADAMTS1 regulates NO signaling in Marfan syndrome. In addition to mediating matricellular protein signaling, redox signaling is emerging as an important pathway that controls the expression of several matricellular proteins.

CRITICAL ISSUES

Redox signaling remains unexplored for many matricellular proteins. Their interactions with multiple cellular receptors remains an obstacle to defining signaling mechanisms, but improved transgenic models could overcome this barrier.

FUTURE DIRECTIONS

Therapeutics targeting the TSP1 receptor CD47 may have beneficial effects for treating cardiovascular disease and cancer and have recently entered clinical trials. Biomarkers are needed to assess their effects on redox signaling in patients and to evaluate how these contribute to their therapeutic efficacy and potential side effects. Antioxid. Redox Signal. 27, 874-911.

Hydrogen Sulfide Regulates Homeostasis of Mesenchymal Stem Cells and Regulatory T Cells

Hydrogen sulfide (H2S) has long been known as a toxic gas. However, recently accumulated evidence suggests that H2S contributes to a variety of physiologic and pathologic processes. Endogenous H2S production is regulated by multiple enzymes that are differentially expressed in the cardiovascular, neuronal, immune, renal, respiratory, gastrointestinal, reproductive, liver, and endocrine systems. Alteration of H2S metabolism may affect multiple signaling pathways and tissue homeostasis. The growing number of diverse targets for which H2S serves as a gasotransmitter has been extensively reviewed elsewhere. In this review, the authors discuss current emerging evidence that H2S regulates mesenchymal stem cell and T-cell functions.

Lidocaine induces ROCK-dependent membrane blebbing and subsequent cell death in rabbit articular chondrocytes

Local anesthetics are administered intraarticularly for pain control in orthopedic clinics and surgeries. Although previous studies have shown that local anesthetics can be toxic to chondrocytes, the underlying cellular mechanisms remain unclear. The present study investigates acute cellular responses associated with lidocaine-induced toxicity to articular chondrocytes. Rabbit articular chondrocytes were exposed to lidocaine and their morphological changes were monitored with live cell microscopy. The viability of chondrocytes was evaluated using a fluorescence based LIVE/DEAD assay. Acute treatment of chondrocytes with lidocaine (3-30 mM) induced spherical protrusions on the cell surface (so called "membrane blebbing") in a time- and concentration-dependent manner. The concentration-response relationship for the lidocaine effect was shifted leftward by elevating extracellular pH, as expected for the non-ionized lidocaine being involved in the bleb formation. ROCK (Rho-kinase) inhibitors Y-27632 and fasudil completely prevented the lidocaine-induced membrane blebbing, suggesting that ROCK activation is required for bleb formation. Caspase-3 levels were unchanged by 10 mM lidocaine (p = 0.325) and a caspase inhibitor z-VAD-fmk did not affect the lidocaine-induced blebbing (p = 0.964). GTP-RhoA levels were significantly increased (p < 0.001), but Rho inhibitor-1 failed to suppress the membrane blebbing (p = 0.875). Lidocaine (30 mM) reduced the cell viability of isolated chondrocytes (p < 0.001) and in situ chondrocytes (p < 0.001). The chondrotoxicity was attenuated by pretreatment of cells with ROCK inhibitors or a myosin-II inhibitor blebbistatin (p < 0.001). These findings suggest that lidocaine induces ROCK-dependent membrane blebbing and thereby produces a cytotoxic effect on chondrocytes. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:754-762, 2016.

CD47-dependent regulation of H₂S biosynthesis and signaling in T cells

Pharmacological concentrations of H2S donors inhibit some T cell functions by inhibiting mitochondrial function, but evidence is also emerging that H2S at physiological concentrations produced via chemical sources and endogenously is a positive physiological mediator of T cell function. Expression of the H2S biosynthetic enzymes cystathionine γ-lyase (CSE) and cystathionine β-synthase (CBS) is induced in response to T cell receptor signaling. Inhibiting the induction of these enzymes limits T cell activation and proliferation, which can be overcome by exposure to exogenous H2S at submicromolar concentrations. Exogenous H2S at physiological concentrations increases the ability of T cells to form an immunological synapse by altering cytoskeletal actin dynamics and increasing the reorientation of the microtubule-organizing center. Downstream, H2S enhances T cell receptor-dependent induction of CD69, CD25, and Interleukin-2 (IL-2) gene expression. The T cell stimulatory activity of H2S is enhanced under hypoxic conditions that limit its oxidative metabolism by mitochondrial and nonenzymatic processes. Studies of the receptor CD47 have revealed the first endogenous inhibitory signaling pathway that regulates H2S signaling in T cells. Binding of the secreted protein thrombospondin-1 to CD47 elicits signals that block the stimulatory activity of exogenous H2S on T cell activation and limit the induction of CSE and CBS gene expression. CD47 signaling thereby inhibits T cell receptor-mediated T cell activation.

Dexamethasone ameliorates H₂S-induced acute lung injury by alleviating matrix metalloproteinase-2 and -9 expression

Acute lung injury (ALI) is one of the fatal outcomes after exposure to high levels of hydrogen sulfide (H₂S), and the matrix metalloproteinases (MMPs) especially MMP-2 and MMP-9 are believed to be involved in the development of ALI by degrading the extracellular matrix (ECM) of blood-air barrier. However, the roles of MMP-2 and MMP-9 in H₂S-induced ALI and the mechanisms of dexamethasone (DXM) in treating ALI in clinical practice are still largely unknown. The present work was aimed to investigate the roles of MMP-2 and MMP-9 in H₂S-induced ALI and the protective effects of DXM. In our study, SD rats were exposed to H₂S to establish the ALI model and in parallel, A549 cells were incubated with NaHS (a H₂S donor) to establish cell model. The lung HE staining, immunohistochemisty, electron microscope assay and wet/dry ratio were used to identify the ALI induced by H₂S, then the MMP-2 and MMP-9 expression in both rats and A549 cells were detected. Our results revealed that MMP-2 and MMP-9 were obviously increased in both mRNA and protein level after H₂S exposure, and they could be inhibited by MMP inhibitor doxycycline (DOX) in rat model. Moreover, DXM significantly ameliorated the symptoms of H₂S-induced ALI including alveolar edema, infiltration of inflammatory cells and the protein leakage in BAFL via up-regulating glucocorticoid receptor(GR) to mediate the suppression of MMP-2 and MMP-9. Furthermore, the protective effects of DXM in vivo and vitro study could be partially blocked by co-treated with GR antagonist mifepristone (MIF). Our results, taken together, demonstrated that MMP-2 and MMP-9 were involved in the development of H₂S-induced ALI and DXM exerted protective effects by alleviating the expression of MMP-2 and MMP-9. Therefore, MMP-2 and MMP-9 might represent novel pharmacological targets for the treatment of H₂S and other hazard gases induced ALI.